JP6403936B2 - Polarizing plate and liquid crystal display panel using the same - Google Patents

Description

  The present invention relates to a polarizing plate in which a transparent protective film is bonded to a polarizer having a thickness of 1 to 10 μm and a liquid crystal display panel in which the polarizing plate is bonded to a liquid crystal cell.

  A polarizing plate is an optical element that converts incident natural light into linearly polarized light, and is often used in liquid crystal display panels and liquid crystal display devices. Traditionally, a polarizing plate is a typical example of triacetyl cellulose as a polarizer obtained by subjecting a polyvinyl alcohol resin film to uniaxial stretching and dyeing treatment with a dichroic material to adsorb and align the dichroic material. A protective film was bonded and manufactured.

  Such a polarizer obtained by using a polyvinyl alcohol-based resin film as a raw film and uniaxially stretching and dyeing with a dichroic material has a limit in reducing its thickness. Therefore, for example, a polarizing plate in which a protective film made of triacetyl cellulose is bonded to both surfaces of the polarizer must have a thickness of at least about 100 μm, and the liquid crystal display panel, Has become a bottleneck for thinning liquid crystal display devices.

  Therefore, a polyvinyl alcohol resin coating layer is formed on the base film, and the resulting laminated film is uniaxially stretched, and the uniaxially stretched polyvinyl alcohol resin layer is dyed with a dichroic substance, There has been proposed a method of manufacturing a polarizing plate in which a polarizer comprising a polyvinyl alcohol-based resin layer subjected to the above uniaxial stretching and dyeing is thinner than in the past by applying a transparent protective film to the substrate.

  For example, in Japanese Patent Application Laid-Open No. 2000-338329 (Patent Document 1), a polyvinyl alcohol resin layer having a thickness of 6 μm to 30 μm is formed on one side of a thermoplastic resin film, and then stretched by 2 times to 5 times. Then, the polyvinyl alcohol-based resin layer is used as a transparent film element layer, and then the transparent film element layer is dyed and fixed to form a composite film composed of two layers of a thermoplastic resin film layer using the transparent film element layer as a polarizing element layer. Then, after the transparent protective film is bonded to the polarizing element layer side of the obtained composite film through an adhesive, the thermoplastic resin film layer is peeled and removed, and the transparent protective film layer and the polarizing element layer are separated. A method for producing a polarizing plate comprising layers is disclosed. It is said that the obtained polarizing plate is less curled and deformed and can be easily bonded to the liquid crystal cell.

  In JP 2001-343521 (Patent Document 2), a step of applying a polyvinyl alcohol-based resin to a base resin film, and the resulting laminated film are prepared so that the thickness of the polyvinyl alcohol-based resin layer is 10 μm or less. A step of uniaxial stretching, a step of bonding a protective film via an adhesive to the side of the polyvinyl alcohol resin layer having a thickness of 10 μm or less, and a base resin film is peeled off after the protective film is bonded A manufacturing method of a polarizing plate including a process is disclosed. In that example, a polyvinyl alcohol resin layer is formed on a polyethylene terephthalate sheet, and the resulting laminated sheet is stretched laterally uniaxially by a tenter stretching machine to prepare a dyeing web, and this dyeing web is subjected to iodine dyeing and boric acid treatment. Then, washing with water and drying are sequentially performed to obtain a polarizer with a base film, a triacetyl cellulose film is bonded to the polarizer surface, and then the stretched polyethylene terephthalate film is peeled off to obtain a polarizing plate. Manufactured.

  In JP-A-2009-93074 (Patent Document 3) and JP-A-2009-98653 (Patent Document 4), a hydrophilic polymer-containing solution, typically polyvinyl alcohol, is applied on a base material layer. , Drying to form a laminate having a hydrophilic polymer layer formed on the base material layer, stretching step for subjecting the laminate to stretching treatment, and dichroism to the hydrophilic polymer layer of the laminate A technique for manufacturing a polarizing plate through a dyeing process for adsorbing a substance is disclosed. The hydrophilic polymer layer to which the dichroic substance is adsorbed becomes a polarizer, and the occurrence of curling is suppressed even though the polarizer is thinned. In Patent Document 3, a biaxially stretched acrylic resin film is used as a base material layer, a polyvinyl alcohol aqueous solution is applied thereon, and dried to form a hydrophilic polymer layer. The example which manufactured the polarizing plate which is a laminated body by which the free end uniaxial stretching was carried out to the width direction, and the polyvinyl alcohol iodine type polarizer was formed on the acrylic resin film is shown. On the other hand, in Patent Document 4, a longitudinally uniaxially stretched acrylic resin film is used as a base material layer, a polyvinyl alcohol aqueous solution is applied thereon, and dried to form a hydrophilic polymer layer, and the resulting laminate is obtained. The example which manufactured the polarizing plate which is a laminated body by which the body was extended uniaxially in the width direction and the polyvinyl alcohol-iodine type polarizer was formed on the acrylic resin film is shown.

  JP 2012-13764 A (Patent Document 5) discloses a polarizer made of a polyvinyl alcohol-based resin that is uniaxially stretched and adsorbed and oriented with a dichroic substance, and has a thickness of 10 μm or less. A polarizing plate having a bonded protective film and having a dimensional shrinkage rate of 0.3% or less when the temperature is raised from 20 ° C. to 84 ° C. is disclosed. In that example, a polypropylene film is used as a base film, and a laminated film obtained by coating an aqueous solution of polyvinyl alcohol on the polypropylene film and drying is stretched uniaxially at the free end in the longitudinal direction, and then the laminated film remains as an iodine film. Dyeing, boric acid treatment, washing with water and drying are carried out to obtain a polarizer with a base film, and after a protective film is bonded to the polarizer surface, the base film is peeled off to produce a polarizing plate. Yes.

JP 2000-338329 A (Claim 2, Example 2) JP 2001-343521 A (Claim 6, Example 1) JP 2009-93074 A (Claim 1, Example 1) JP 2009-98653 A (Claim 1, Example 1) JP 2012-13764 A (Claim 1, Example 1)

  According to the techniques disclosed in these Patent Documents 1 to 5, it is possible to manufacture a thinned polarizer having a thickness of 10 μm or less. The present inventor has further studied the technique of attaching a polarizing plate having such a thinned polarizer to a liquid crystal cell to form a liquid crystal panel. As a result, for example, the polarizing plate obtained by pasting the transparent protective film on the opposite side of the base film of the polarizer that has been uniaxially stretched on the base film and prepared in a thin state, peels off the base film When the obtained polarizing plate or a polarizing plate obtained by pasting another transparent protective film on the polarizer surface after peeling off the substrate film is attached to a liquid crystal cell, the resulting liquid crystal panel is then put into a high temperature environment. It has become clear that warping tends to increase when exposed to high temperatures and high humidity.

  Accordingly, one of the problems of the present invention is a polarizing plate in which a transparent protective film is bonded to a thinned polarizer having a thickness of 10 μm or less, and the polarizing plate is bonded to a liquid crystal cell to obtain a liquid crystal. When it is set as a panel, it is providing the polarizing plate which can make curvature small even if it exposes to a high temperature environment and a high temperature, high humidity environment. Another object of the present invention is to provide a liquid crystal panel having a small warp even when the polarizing plate is attached to a liquid crystal cell and exposed to a high temperature environment or a high temperature and high humidity environment.

  As a result of research, it is possible to prevent the warpage of the liquid crystal panel by laminating the stretched acrylic resin film so that the stretch axes thereof are orthogonal to the uniaxially stretched polarizer having a thickness of 1 to 10 μm. The present invention has been found to be effective, and various studies have been made to complete the present invention.

  That is, according to the present invention, a polarizer comprising a polyvinyl alcohol-based resin film that is uniaxially stretched and has a thickness of 1 to 10 μm, and a dichroic substance is adsorbed and oriented, and a stretched acrylic resin film; However, the polarizing plate bonded so that the extending axes of both are orthogonal to each other is provided.

  The polarizer constituting the polarizing plate can be produced by longitudinal uniaxial stretching or lateral uniaxial stretching, and the acrylic resin film has uniaxial or biaxial stretching in which the longitudinal direction is the stretching axis or the stretching direction in the lateral direction. Although it can manufacture by uniaxial or biaxial stretching, it is important to bond so that both extending axes may be orthogonal. In particular, a polarizer produced by longitudinal uniaxial stretching and an acrylic resin film produced by transverse uniaxial stretching were bonded by roll-to-roll, and the stretching axes of both were made orthogonal. The form is advantageous both in terms of polarization performance and productivity.

  The acrylic resin film can be constituted by forming an acrylic resin composition containing 10 to 50% by weight of rubber particles in an acrylic base resin and stretching it. The stretched acrylic resin film preferably has a thickness of 15 to 60 μm. In addition, the stretched acrylic resin film is cut into squares each having a length of 100 mm in the direction of the stretching axis and in the direction perpendicular to the stretching axis, and contracted in the direction of the stretching axis after being heated at a temperature of 80 ° C. for 24 hours. It is preferable that the rate is 1.5% or more, particularly 1.5 to 5%.

  In these polarizing plates, an optical film can be bonded to the polarizer surface opposite to the surface bonded to the acrylic resin film. It is preferable that the acrylic resin film and the polarizer are bonded with an ultraviolet curable adhesive. When bonding an optical film on the opposite side to the surface where the acrylic resin film of a polarizer is bonded, it is preferable that the optical film and the polarizer are also bonded by the ultraviolet curable adhesive.

  Moreover, according to the present invention, any one of the above polarizing plates and a liquid crystal cell are provided, and the polarizing plate has a polarizer surface opposite to the surface bonded to the acrylic resin film, the liquid crystal cell side. Thus, a liquid crystal display panel in which both are attached is also provided.

  In this liquid crystal display panel, the polarizing plate of the present invention described above is attached to one side of the liquid crystal cell, and a second polarizing plate different from the polarizing plate of the present invention is attached to the other surface of the liquid crystal cell. Can take the form. Moreover, it can also take the form by which the polarizing plate of this invention is affixed on both surfaces of a liquid crystal cell, respectively. In any case, the polarizing plate is preferably attached to the liquid crystal cell via the pressure-sensitive adhesive layer. In either case, the polarizing plate of the present invention has a configuration in which an optical film is bonded to the polarizer surface opposite to the surface bonded to the acrylic resin film, and the optical film side is It is preferable to be bonded to the liquid crystal cell via an adhesive layer.

  When the polarizing plate of the present invention is adhered to a liquid crystal cell to form a liquid crystal panel, even if it is exposed to a high temperature environment or a high temperature and high humidity environment, the warpage is small. Therefore, the liquid crystal panel of the present invention is also less warped when exposed to a high temperature environment or a high temperature and high humidity environment.

It is a cross-sectional schematic diagram which shows the suitable example of a layer structure in the case of arrange | positioning the polarizing plate of this invention to the visual recognition side of a liquid crystal panel. It is a cross-sectional schematic diagram which shows the suitable example of a layer structure in the case of arrange | positioning the polarizing plate of this invention to the back side of a liquid crystal panel. It is a cross-sectional schematic diagram which shows the suitable bonding order when manufacturing the polarizing plate of this invention. It is a cross-sectional schematic diagram which shows an example of the liquid crystal display panel which concerns on this invention. It is a cross-sectional schematic diagram which shows another example of the liquid crystal display panel which concerns on this invention. It is a cross-sectional schematic diagram which shows another example of the liquid crystal display panel which concerns on this invention. It is a cross-sectional schematic diagram which shows another example of the liquid crystal display panel which concerns on this invention. It is a cross-sectional schematic diagram which shows another example of the liquid crystal display panel which concerns on this invention. It is a top view which shows the measurement location of the height position data of the liquid crystal panel equivalent in an Example. It is a perspective view which shows typically one curvature state of the liquid crystal panel equivalent in an Example. It is a perspective view which shows typically the other curvature state of the liquid crystal panel equivalent in an Example.

  Hereinafter, the present invention will be described in detail with reference to the drawings as appropriate. In the present invention, a polarizer made of a polyvinyl alcohol-based resin film that is uniaxially stretched and has a thickness of 1 to 10 μm, and a dichroic material is adsorbed and oriented, and a stretched acrylic resin film, The polarizing axes are configured by pasting so that the stretching axes of the two are orthogonal to each other.

  Examples of the layer structure of the polarizing plate according to the present invention are shown in cross-sectional schematic views in FIGS. FIG. 1 shows a preferred layer configuration example together with a liquid crystal cell when the polarizing plate of the present invention is disposed on the viewing side of a liquid crystal panel. In (A) of FIG. 1, the stretched acrylic resin film 12 is bonded to one surface of the polarizer 11, and the optical film 14 is bonded to the other surface of the polarizer 11. A polarizing plate 10 is configured. It is bonded to the liquid crystal cell 30 by the pressure-sensitive adhesive layer 18 provided outside the optical film 14.

  In FIG. 1B, the stretched acrylic resin film 12 is bonded to one surface of the polarizer 11, the optical film 14 is bonded to the other surface of the polarizer 11, and the optical The second optical film 15 is bonded to the outside of the film 14 via the interlayer pressure-sensitive adhesive layer 17 to constitute the viewing side polarizing plate 10. It is bonded to the liquid crystal cell 30 by the pressure-sensitive adhesive layer 18 provided outside the second optical film 15.

  FIG. 2 shows a preferred layer configuration example together with the liquid crystal cell when the polarizing plate of the present invention is disposed on the back side of the liquid crystal panel. 2A, the stretched acrylic resin film 22 is bonded to one surface of the polarizer 21, the optical film 24 is bonded to the other surface of the polarizer 21, and the back side. A polarizing plate 20 is configured. The liquid crystal cell 30 is bonded by an adhesive layer 28 provided outside the optical film 24.

  In FIG. 2B, the stretched acrylic resin film 22 is bonded to one surface of the polarizer 21, and the back-side polarizing plate 20 is constituted by these two layers. The pressure-sensitive adhesive layer 28 is directly provided on the opposite side of the surface of the polarizer 21 to which the acrylic resin film 22 is bonded, and the pressure-sensitive adhesive layer 28 is bonded to the liquid crystal cell 30.

  In any example, the polarizer 11 and the acrylic resin film 12, the polarizer 11 and the optical film 14, the polarizer 21 and the acrylic resin film 22, and the polarizer 21 and the optical film 24 are adhesives. The adhesive layer is not shown in FIG. The same applies to FIGS. 3 to 8 described later. A separate film that temporarily protects the surface of the adhesive layers 18 and 28 is provided until just before being bonded to the liquid crystal cell 30, but this separate film is also not shown.

  In the present invention, the polarizers 11 and 21 and the stretched acrylic resin films 12 and 22 are bonded so that the stretch axes thereof are orthogonal to each other. In this way, by laminating the polarizer and the acrylic resin film so that the stretching axes are orthogonal to each other, it suppresses the warping when it is pasted on a liquid crystal cell to make a liquid crystal panel, and the display quality is lowered. Can be suppressed.

  The stretching axis defined in the present invention will be described. In the case of uniaxial stretching, the stretching axis means the direction of stretching. In the case of biaxial stretching, the stretching axis means a direction having a large stretching ratio among the two stretching directions. In other words, when heated, for example, when heated for 24 hours under drying at 80 ° C., the direction in which the shrinkage rate becomes maximum in the plane becomes the stretching axis. As can be seen from this description, an acrylic resin film having the same stretch ratio in the longitudinal stretching and the lateral stretching is not the subject of the present invention even in the case of biaxial stretching. In this case, the shrinkage rate is almost the same in two stretching directions orthogonal to each other in the film plane, and even if such a film is bonded to a polarizer, the liquid crystal display panel cannot be prevented from warping.

  Since the polarizer is manufactured by uniaxial stretching, the stretching direction is the stretching axis. In the polarizer, the dichroic substance is oriented in the stretching direction, and the stretching axis has a small light transmittance, that is, a large absorption axis. Therefore, it is also called an absorption axis.

  On the other hand, resins (polymers) generally include a resin having a positive refractive index anisotropy and a resin having a negative refractive index anisotropy due to its molecular structure. A substance exhibiting optical anisotropy whose refractive index in the orientation direction is greater than the refractive index in the direction perpendicular thereto is called positive optical anisotropy, and conversely the refractive index in the orientation direction is If the refractive index is smaller than the refractive index in the direction perpendicular thereto, the optical anisotropy is called negative. When the resin (polymer) film is uniaxially stretched, the stretch direction is the orientation direction. In addition, in the case of biaxial stretching, the direction of stretching so that the orientation becomes larger becomes the orientation direction. Especially for resins (polymers), those having a higher refractive index in the orientation direction are called resins having positive refractive index anisotropy, and those having a lower refractive index in the orientation direction are negative refractive indexes. It is called a resin having anisotropy. Whether a certain resin has a positive refractive index anisotropy or a negative refractive index anisotropy is obtained by determining the expression state of the refractive index anisotropy when the film made of the resin is uniaxially stretched. Easily determined.

  The direction in which the refractive index is maximum in the film plane is called the slow axis, and the direction in which the refractive index is minimum in the plane perpendicular to the film plane is called the fast axis. In the case of uniaxial stretching, the refractive index increases in the stretching direction, that is, in a resin film having positive refractive index anisotropy, the stretching direction is the slow axis, and the direction orthogonal to this is the fast axis, while stretching In a resin film having a refractive index that is small in the direction, that is, a negative refractive index anisotropy, the stretching direction is the fast axis, and the direction orthogonal thereto is the slow axis. Even in the case of biaxial stretching, if the direction in which the draw ratio is relatively large is a resin having a positive refractive index anisotropy, it becomes the slow axis, and if the resin has a negative refractive index anisotropy, the phase is advanced. It becomes an axis.

  In acrylic resins, many have negative refractive index anisotropy due to the ester moiety of (meth) acrylic acid ester, which is the main monomer, particularly the alkyl ester moiety. However, when the main chain has a cyclic structure, such as an acrylic resin having a lactone ring in the main chain described later, the ratio of the cyclic structure in the main chain, specifically, the cyclic structure is formed. Although it is influenced by the copolymerization ratio and the cyclization rate of the monomer, it may show positive refractive index anisotropy. Therefore, in the case of an acrylic resin having negative refractive index anisotropy, the stretching axis referred to in the present invention is a fast axis, and in the case of an acrylic resin having positive refractive index anisotropy, it is referred to in the present invention. The stretching axis is the slow axis.

  Hereinafter, each member constituting the polarizing plate of the present invention will be described, and then the description will proceed to a method for manufacturing the polarizing plate, a liquid crystal display panel using the polarizing plate, and a liquid crystal display device.

[Polarizer]
The polarizers 11 and 21 are made of a polyvinyl alcohol-based resin film that is uniaxially stretched and has a dichroic substance adsorbed and oriented. The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. The polyvinyl acetate resin may be not only polyvinyl acetate, which is a homopolymer of vinyl acetate, but also a copolymer of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  A film formed of such a polyvinyl alcohol resin becomes a raw film of the polarizers 11 and 21. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. However, in order to obtain a thin polarizer as defined in the present invention, a solution of the polyvinyl alcohol-based resin is used. A method of forming a film by coating on a material film is preferably employed.

  The polarizers 11 and 21 have a thickness of 10 μm or less, preferably 7 μm or less, from the viewpoint of thinning. By setting the thickness of the polarizer to 10 μm or less, a thin polarizing plate and further a liquid crystal display panel can be obtained. The polarizers 11 and 21 are stretched and oriented, and a dichroic substance is adsorbed thereto, thereby exhibiting a function as a polarizer, that is, a function of extracting linearly polarized light from natural light. The draw ratio is preferably more than 5 times, more preferably more than 5 times and 17 times or less.

  The polyvinyl alcohol resin used for the polarizers 11 and 21 preferably has a saponification degree of 80 mol% or more, more preferably 90 mol% or more, and particularly 94 mol% or more. If the degree of saponification is too low, the water resistance and heat-and-moisture resistance after making the polarizing plate may not be sufficient. Also, it may be a completely saponified product, but if the degree of saponification is too high, the dyeing speed will be slow and the production time will be longer to give sufficient polarization performance, or in some cases sufficient polarization performance In some cases, a saponification degree is 99.5 mol% or less, and more preferably 99 mol% or less.

The degree of saponification referred to here is expressed as a unit ratio (mol%) in which the ratio of acetic acid groups (acetoxy groups) contained in polyvinyl acetate resin, which is a raw material for polyvinyl alcohol resins, to hydroxyl groups by saponification treatment. Defined by the following formula.
Degree of saponification (mol%) = [(number of hydroxyl groups) / (number of hydroxyl groups + number of acetate groups)] × 100

  The higher the degree of saponification, the higher the proportion of hydroxyl groups, and hence the lower the proportion of acetate groups that inhibit crystallization. The saponification degree can be determined by a method specified in JIS K 6726-1994 “Testing method for polyvinyl alcohol”.

  The average degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of about 100 to 10,000, preferably 1,500 to 8,000, and more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol resin can also be determined by the method specified in JIS K 6726-1994 “Testing method for polyvinyl alcohol”.

  The dichroic substance adsorbed on the polarizer can be iodine or a dichroic organic dye. Examples of dichroic organic dyes include red BR, red LR, red R, pink LB, Rubin BL, Bordeaux GS, sky blue LG, lemon yellow, blue BR, blue 2R, navy RY, green LG, violet LB, Violet B, Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky blue, direct first orange S, first black and the like. These dyes are commercially available. A dichroic substance may be used independently, respectively, and may be used in combination of 2 or more type.

[Acrylic resin film]
In the present invention, the acrylic resin films 12 and 22 are bonded to the polarizers 11 and 21 described above to obtain polarizing plates 10 and 20. The acrylic resin films 12 and 22 are stretched, and are bonded so that their stretch axes are orthogonal to the stretch axes of the polarizers 11 and 21.

  The acrylic resin used as the raw material for the acrylic resin films 12 and 22 is usually a polymer having (meth) acrylic acid ester and (meth) acrylic acid alkyl ester as main constituent monomers. This resin may be a homopolymer of (meth) acrylic acid ester or a copolymer using two or more kinds of (meth) acrylic acid ester, and can be copolymerized with (meth) acrylic acid ester. It may be a copolymer with a monomer. In the present specification, (meth) acrylic acid means acrylic acid and / or methacrylic acid. Similarly, (meth) acrylic acid ester means acrylic acid ester and / or methacrylic acid ester.

  Specific examples of (meth) acrylic acid ester which is the main raw material of acrylic resin are methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, sec-butyl acrylate Alkyl acrylates such as tert-butyl acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, and dodecyl acrylate; methyl methacrylate, ethyl methacrylate, methacryl Propyl acid, isopropyl methacrylate, butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate And alkyl methacrylates such as decyl methacrylate and dodecyl methacrylate.

  These (meth) acrylic acid alkyl esters may have an arbitrary substituent such as a hydroxyl group or a halogen atom at the alkyl site. Examples of (meth) acrylic acid alkyl esters having such substituents are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, methacrylic acid. Examples include 2-hydroxypropyl, 4-hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, and glycidyl methacrylate.

  Among these (meth) acrylic acid esters, methyl methacrylate is suitably used as the main raw material for acrylic resins. That is, as will be described in detail later, a methyl methacrylate homopolymer, methyl methacrylate as a main constituent monomer, a copolymer of it with other (meth) acrylic acid esters, and methyl methacrylate as a main monomer. Constituent monomer, copolymer of it and monomers other than (meth) acrylic acid ester, or methyl methacrylate as main constituent monomer, and other than (meth) acrylic acid ester and (meth) acrylic acid ester Copolymers with these monomers are suitable as acrylic resins.

  Examples of monomers copolymerizable with (meth) acrylic acid esters include α, β-ethylenically unsaturated carboxylic acid esters and α, β-ethylenically unsaturated compounds other than the (meth) acrylic acid esters described above. Examples thereof include carboxylic acids, alkenyl aromatic compounds, conjugated dienes, non-conjugated dienes, vinyl cyanide, α, β-ethylenically unsaturated carboxylic acid amides, carboxylic acid unsaturated alcohol esters, and olefins.

  Specific examples of α, β-ethylenically unsaturated carboxylic acid esters other than (meth) acrylic acid esters include dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, dimethyl itaconate, monoethyl maleate, fumaric acid And monobutyl. Further, the α, β-ethylenically unsaturated carboxylic acid may be any of monocarboxylic acid, polyvalent carboxylic acid, and polyvalent carboxylic acid anhydride, and specific examples thereof include acrylic acid, methacrylic acid, crotonic acid, Mention may be made of maleic acid, fumaric acid, itaconic acid, maleic anhydride, itaconic anhydride and the like.

  Specific examples of the alkenyl aromatic compound include styrene, α-methylstyrene, α-methyl-2-,-3- or -4-methylstyrene, vinyltoluene, divinylbenzene, and the like. Specific examples of conjugated dienes include 1,3-butadiene, 2-methyl-1,3-butadiene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, and 2-chloro-1,3-butadiene. And cyclopentadiene. Specific examples of the non-conjugated diene include 1,4-hexadiene, dicyclopentadiene, ethylidene norbornene and the like.

  Specific examples of vinyl cyanide include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like. Specific examples of the α, β-ethylenically unsaturated carboxylic acid amide include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-dimethylacrylamide and the like. Specific examples of the carboxylic acid unsaturated alcohol ester include vinyl acetate. Specific examples of olefins include ethylene, propylene, butene and pentene.

  When monomers other than (meth) acrylic acid esters are copolymerized, only one type of comonomer may be copolymerized, or two or more types may be copolymerized. When such a monomer other than (meth) acrylic acid ester is copolymerized, the content of structural units derived from these monomers in the acrylic resin is preferably 50% by weight or less, more preferably 15%. % By weight or less, more preferably 10% by weight or less.

  Specific examples of preferred acrylic resins for use in the present invention include poly (methyl methacrylate), methyl methacrylate / methyl acrylate copolymer, methyl methacrylate / methyl acrylate / butyl acrylate / styrene copolymer. Examples thereof include a polymer, a copolymer of methyl methacrylate / styrene / butyl acrylate, and a copolymer of methyl methacrylate / ethylene. Among these, a polymer in which the structural unit derived from methyl methacrylate is 70% by weight or more, more preferably 80% by weight or more, and particularly 90% by weight or more in all the structural units is preferable. One type of acrylic resin may be used alone, or two or more types may be used in combination. The molecular weight of the acrylic resin is a polystyrene-reduced weight average molecular weight, for example, about 50,000 to 500,000. When the weight average molecular weight is within this range, a homogeneous film is easily obtained when the film is formed by the melt extrusion method.

  The acrylic resin can also have a ring structure in the main chain. When the acrylic resin has a ring structure in its main chain, the heat resistance and hardness of the finally obtained acrylic resin film can be improved. When the acrylic resin has a ring structure in the main chain, the content of the ring structure in the resin may generally be in the range of 5 to 90% by weight, but is 10 to 70% by weight, more preferably 10 to 60% by weight. In particular, the range of 10 to 50% by weight is preferable for improving the heat resistance and hardness while maintaining the stretchability and handling properties of the acrylic resin film. If the content of the ring structure is excessively large, the stretchability and handling properties of the acrylic resin film are lowered.

  Examples of the ring structure that the acrylic resin may have in the main chain include a lactone ring structure, a succinic anhydride structure, a succinimide structure, and a glutarimide structure. From the viewpoint of the heat resistance of the finally obtained film, the ring structure is preferably a lactone ring structure. This lactone ring structure is usually a 4- to 8-membered ring, and a 5- to 6-membered ring is preferable and a 6-membered ring is more preferable from the viewpoint of the stability of the ring structure. Examples of the 6-membered ring structure are as shown in the following formula (I).

Wherein, R _1, R ₂ and R _3, independently of one another, an organic group having a hydrogen atom or a C 1-20. This organic group may be a group containing an atom other than carbon and hydrogen, such as an oxygen atom, in addition to a hydrocarbon group. Examples of the organic group include an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, and a propyl group; an unsaturated aliphatic hydrocarbon group having 2 to 20 carbon atoms such as an ethenyl group and a propenyl group; An aromatic hydrocarbon group having 6 to 20 carbon atoms such as a phenyl group and a naphthyl group; one or more of hydrogen atoms in the alkyl group, the unsaturated aliphatic hydrocarbon group, or the aromatic hydrocarbon group are a hydroxyl group, There are groups substituted by a carboxyl group, an alkoxy group, an alkoxyalkyl group, an alkoxycarbonyl group, and the like.

  The acrylic resin having a ring structure in the main chain can be produced by a known method. For example, a method of introducing a ring structure into the main chain of the acrylic resin by allowing a monomer mixture containing a (meth) acrylic acid ester to copolymerize and then proceeding with a cyclization reaction can be employed. In this case, the acrylic resin to be used for the cyclization reaction contains a monomer having a hydroxyl group, a monomer having a carboxyl group, or a monomer containing both of them in (meth) acrylic acid alkyl ester. It is preferably formed by polymerization. Examples of the monomer having a hydroxyl group include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, and 2- (hydroxymethyl) acrylic acid. It can be butyl, methyl 2- (hydroxyethyl) acrylate, methallyl alcohol, or allyl alcohol. The monomer having a carboxyl group can be, for example, acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, or 2- (hydroxyethyl) acrylic acid. Two or more of these monomers may be used. These monomers constitute a ring structure located in the main chain of the acrylic resin by a cyclization reaction, but it is not necessary for all of the monomers to change into a ring structure during the cyclization reaction, and the cyclization reaction The later acrylic resin may have a structural unit derived from these monomers.

For example, the lactone ring structure represented by the above formula (I) is adjacent to a copolymer obtained by copolymerizing a monomer mixture containing methyl methacrylate and methyl 2- (hydroxymethyl) acrylate. It can be formed by dealcoholization cyclocondensation of methyl methacrylate units and 2- (hydroxymethyl) methyl acrylate units. At this time, R ₁ in the formula (I) is H, R ₂ is CH ₃ , and R ₃ is CH ₃ . This cyclization condensation reaction can be caused by a method of heating the reaction mixture obtained in the acrylic resin polymerization step as it is. You may heat using a cyclization catalyst as needed. For example, any of organic phosphorus compounds such as 2-ethylhexyl phosphate, octyl phosphate, and dioctyl phosphate, or a mixture thereof is added as a cyclization catalyst, heated under reflux conditions for 2 hours, and then added by an autoclave. A method of heating for 30 minutes under pressure is used. This causes intramolecular dealcohol condensation of the polymer, and a lactone ring structure is formed in the main chain of the polymer.

  The acrylic resin generally has a Vicat softening temperature in the range of 85 ° C. or more and 140 ° C. or less, and preferably has a Vicat softening temperature of 90 ° C. or more and 130 ° C. or less, particularly 95 ° C. or more and 120 ° C. or less. The Vicat softening temperature is a value determined by the B50 method defined in JIS K 7206: 1999 “Plastic—Thermoplastic—Vicat Softening Temperature (VST) Test Method”. When the Vicat softening temperature is within this range, sufficient heat resistance can be achieved, and breakage during film molding can be prevented.

  The acrylic resin usually has a tensile fracture strain in the range of 2% to 75%, and preferably has a tensile fracture strain of 5% to 40%, particularly 5% to 20%. Tensile fracture strain can be determined by the method specified in JIS K 7162-1994 "Plastics-Test method for tensile properties, Part 2: Test conditions for molding, extrusion molding and cast plastic". If the tensile fracture strain is in this range, sufficient heat resistance can be realized, and breakage during film molding can be prevented.

  It is also effective that the acrylic resin contains rubber particles. That is, according to the present invention, a film formed from an acrylic resin composition in which rubber particles are blended with the acrylic base resin described above is stretched and bonded to a polarizer according to one preferred embodiment. One. Examples of the rubber particles that can be blended include a rubber-like polymer having acrylate as a main constituent monomer, a rubber-like polymer having butadiene as a main constituent monomer, and an ethylene-vinyl acetate copolymer. Among these, acrylic rubber particles that are rubbery polymers having acrylic acid ester as a main constituent monomer are preferable. Of course, acrylic rubber particles and other rubber particles may be used in combination.

  The acrylic rubber particles may be ones mainly composed of an acrylic acid alkyl ester having a large number of carbon atoms in the alkyl group, for example, about 4 to 8 carbon atoms, such as butyl acrylate and 2-ethylhexyl acrylate. . Among these, an elastic polymer having butyl acrylate as a main constituent monomer is preferable. Although rubber particles having a single-layer structure made of an elastic polymer containing an alkyl acrylate as a main constituent monomer may be used, rubber particles having a multilayer structure including the elastic polymer layer are also effective. As a representative example of the latter, an acrylic elastic polymer layer such as a grafted elastic polymer of alkyl acrylate such as butyl acrylate and styrene, and a hard polymer layer mainly composed of methyl methacrylate, However, rubber particles forming a layer with a core-shell structure may be mentioned. More specifically, it has a two-layer structure in which the hard polymer layer is formed on the outside of the acrylic elastic body, or the hard polymer layer is formed on the inside of the acrylic elastic body. There is also a three-layer structure in which the hard polymer layer is formed on the outside of the elastic body.

  In particular, a blend of such acrylic rubber particles having a multilayer structure is a suitable example. When blended with acrylic rubber particles with a multilayer structure, the value of tensile fracture strain is adjusted without lowering the Vicat softening point of the acrylic resin more than necessary to prevent breakage during film molding without reducing heat resistance. be able to.

  The rubber particles preferably have a number average particle size of 1,000 nm or less, more preferably in the range of 100 to 1,000 nm, and particularly in the range of 100 to 500 nm when dispersed in the acrylic base resin. When the number average particle diameter of the rubber particles is large, the haze (cloudiness) of the film becomes too large and the light transmittance is lowered. On the other hand, when the number average particle size is too small, the flexibility of the film tends to be lowered.

  The average particle diameter of the acrylic rubber particles containing the acrylic elastic polymer is measured as follows. That is, when such rubber particles are blended into an acrylic base resin to form a film and the cross section is dyed with an aqueous solution of ruthenium oxide, only the acrylic elastic polymer layer is colored and observed in a substantially circular shape, The acrylic resin of the mother layer is not dyed. Therefore, from the cross section of the film dyed in this way, a thin piece is prepared using a microtome or the like, and this is observed with an electron microscope. And after extracting 100 dye | stained elastic polymer particles at random and calculating each particle diameter, let the number average value be an average particle diameter. In order to measure by such a method, the average particle diameter of the rubber particles defined here is the number average particle diameter.

  When the outermost layer is a hard polymer mainly composed of methyl methacrylate and the rubber particles in which the acrylic elastic polymer is encapsulated are used, the rubber particles are mixed with the acrylic matrix resin. The outermost layer of is mixed with the acrylic base resin. Therefore, when the cross section is dyed with ruthenium oxide and observed with an electron microscope, the rubber particles are observed as particles in a state excluding the outermost layer. Specifically, when rubber particles having a two-layer structure in which the inner layer is an acrylic elastic polymer and the outer layer is a hard polymer mainly composed of methyl methacrylate, the acrylic elastic polymer portion of the inner layer is used. Are observed as particles having a single layer structure, the innermost layer is a hard polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is mainly composed of methyl methacrylate. In the case of using rubber particles having a three-layer structure that is a hard polymer, particles having a two-layer structure in which the innermost layer is not dyed but only the acrylic elastic polymer portion of the intermediate layer is dyed. Will be observed as.

  The amount of rubber particles added to the acrylic base resin is preferably 10 to 50% by weight, more preferably 10 to 40% by weight, based on the total amount of the acrylic resin composition in which the rubber particles are blended. If the amount of rubber particles is too small, the slipperiness and flexibility of the film are not sufficient, and conversely if too large, the heat resistance of the film is not sufficiently realized.

The rubber particles preferably have a small difference between the refractive index n _a (λ) at a wavelength of 380 to 780 nm and the refractive index n _b (λ) at a wavelength of 380 to 780 nm of the acrylic resin as a matrix. Here, n _a (λ) and n _b (λ) are average values of the main refractive indexes at the wavelength λ. For example, it is preferable that both satisfy the following relationship.
| N _a (λ) −n _b (λ) | ≦ 0.05

When | n _a (λ) −n _b (λ) | exceeds 0.05, transparency may be impaired due to interface reflection caused by a difference in refractive index at the interface.

  The acrylic resin film can contain an ultraviolet absorber. What is necessary is just to select a ultraviolet absorber from what is mix | blended with general resin. For example, there are hydroxybenzophenone compounds, benzotriazole compounds, triazine compounds, salicylic acid ester compounds, and the like. Among them, 2,2'-methylenebis [4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol], 2- (2-hydroxy-3-tert Benzotriazole compounds such as -butyl-5-methylphenyl) -5-chlorobenzotriazole and 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol; Hydroxybenzophenone compounds such as '-dihydroxy-4,4'-dimethoxybenzophenone and 2,2', 4,4'-tetrahydroxybenzophenone are preferred.

  In order to form an acrylic resin film containing an ultraviolet absorber, the following method can be employed. That is, (A) a method in which an ultraviolet absorber is blended with an acrylic resin, and a film is formed from the blend; (B) an ultraviolet absorber is directly supplied to the molten resin during melt extrusion molding of the acrylic resin. For example, a film is formed from the compound using a twin screw extruder. Especially, since it is easy to suppress the dispersion | variation in the density | concentration of the ultraviolet absorber in the film obtained, the method of (A) is preferable.

  The amount of the ultraviolet absorber contained in the acrylic resin film is preferably 0.5 to 6 parts by weight, more preferably 0.5 to 5 parts by weight, especially 1 to 5 parts by weight with respect to 100 parts by weight of the acrylic resin. Is more preferable. By making the content of the ultraviolet absorber within the above-mentioned range, it is possible to efficiently block ultraviolet rays without deteriorating the color tone of the display screen, and in particular, it is applied to a liquid crystal panel or a liquid crystal display device in a state of being attached to a polarizer. In some cases, it is possible to prevent a decrease in alignment characteristics of liquid crystal molecules in the liquid crystal cell over a long period of time. If the content of the ultraviolet absorber in the acrylic resin film is too small, the light transmittance in the vicinity of a wavelength of 370 to 380 nm increases, and the liquid crystal molecules in the liquid crystal cell may deteriorate the alignment characteristics.

  Next, a method for producing an acrylic resin film, that is, a method for producing an acrylic resin raw film used for stretching will be described. The raw film is preferably produced by a melt extrusion method using a T die from the viewpoint of excellent productivity and thickness accuracy.

  The raw film preferably has a small variation in thickness. For example, the following method can be adopted as means for reducing the variation in thickness of the raw film. That is, 1) A method of covering up to the cast roll to which the sheet-like melt extruded from the opening of the T die first adheres with a surrounding member; 2) Edge pinning of both ends of the film on the cast roll, and the second roll A method of performing air blasting above; 3) a method of setting the distance between the die slip and the cast part of the extruded film to 200 mm or less. The thickness of the raw film is arbitrary, but is preferably 20 to 120 μm, more preferably 30 to 100 μm.

  In this invention, it is set as the film for extending | stretching the raw film obtained in this way to at least one direction, and bonding to a polarizer.

  A step of heating in advance (preheating step) may be provided before stretching the raw film. Examples of means for heating the raw film in the preheating step include oven-type heating, radiation heating, and heating by dipping in a liquid. Among these, it is preferable to use an oven-type heating device. The heating temperature in the preheating step is generally in the range of (stretching temperature −40 ° C.) to (stretching temperature + 20 ° C.), preferably (stretching temperature −30 ° C.) to (stretching temperature + 15 ° C.). The temperature here means a set temperature of the heating device.

  There is no special restriction | limiting in the method of extending | stretching, A conventionally well-known method is applicable. Specifically, uniaxial stretching such as a method of uniaxially stretching in the longitudinal direction using a peripheral speed difference between rolls or a method of uniaxially stretching in the lateral direction using a tenter, or while opening a gap between clips to be fixed. After stretching in the longitudinal direction using the simultaneous biaxial stretching method that stretches in the longitudinal direction and also in the lateral direction depending on the spread angle of the guide rail and the difference in peripheral speed between the rolls, both ends in the width direction are clipped Biaxial stretching such as a sequential biaxial stretching method in which the film is held and stretched in the transverse direction using a tenter can be employed.

  The stretching temperature is generally (Tg-30 ° C) to (Tg + 30 ° C), preferably (Tg-20 ° C), where Tg is the glass transition temperature of the resin having the lowest glass transition temperature among the resins constituting the film. To (Tg + 20 ° C.).

  The draw ratio is 1.2 to 6 times, preferably 1.3 to 5 times, and more preferably 1.5 to 3 times. By setting the draw ratio within this range, the shrinkage in the draw direction after heating for 24 hours under drying at 80 ° C., which will be described later, can be adjusted to a range of 1.5 to 5%, and the draw ratio is 6 times or less. By doing so, tearing in the stretching step of the acrylic resin film can be prevented. In the present invention, uniaxial stretching is preferred. A biaxially stretched film can also be used as the stretched film. In that case, one of the stretching ratios in the orthogonal direction is in the range of 1.2 to 6 times, and the other is 1-2 times. Furthermore, it is preferable to make it smaller than said one draw ratio in the range of 1 to 1.5 times, especially 1 to 1.3 times. By setting the draw ratio in the direction perpendicular to this range, the warpage of the liquid crystal display panel to which the polarizing plate using the acrylic resin film is bonded can be reduced, and deterioration of display quality can be prevented.

  After the stretching step, a step of relaxing the stretched state, that is, a heat setting step may be provided. The relaxation temperature in the heat setting step is generally room temperature to (stretching temperature + 30 ° C.), preferably (stretching temperature−40 ° C.) to (stretching temperature + 20 ° C.). In the heat setting step, the temperature may not be set and the stretching temperature may be maintained.

  The acrylic resin film thus stretched preferably has a thickness of 15 to 60 μm. In addition, the acrylic resin film preferably has a shrinkage ratio in the stretching axis direction of 1.5% or more, particularly 1.5 to 5% after being heated for 24 hours under drying at a temperature of 80 ° C. The shrinkage rate here is obtained from the dimensional change before and after heating a test piece cut into a square having a length of 100 mm each in the direction of the stretching axis and the direction perpendicular thereto. When the heat shrinkage ratio is in this range, a polarizer comprising a polyvinyl alcohol-based resin film and a polarizing plate bonded with the stretching axis orthogonally manufactured are manufactured, and when this polarizing plate is used in a liquid crystal display panel, the warpage is caused. Can be reduced.

  The acrylic resin film can be provided with functional layers generally employed for optical films, such as a hard coat layer, an antiglare layer, and a low refractive index layer.

  The hard coat layer is a layer having a function of increasing the surface hardness of the film. JIS K 5600-5-4: 1999 “Paint General Test Method—Part 5: Mechanical Properties of Coating Film—Section 4: Scratch Hardness In a pencil hardness test (a test plate uses a glass plate) performed according to “(Pencil method)”, it is preferable to show H or a value harder than that. It is more preferable that the film provided with the hard coat layer has a pencil hardness of 4H or higher. The material for forming the hard coat layer (hard coat material) is preferably one that can be cured by heat or light, for example, organic hard such as organic silicone, melamine, epoxy, acrylic, and urethane acrylate. Coat material; inorganic hard coat material such as silicon dioxide. Among these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesive strength and excellent productivity. The hard coat layer is for the purpose of adjusting the refractive index, improving the flexural modulus, and / or stabilizing the volume shrinkage, if desired, and improving the heat resistance, antistatic properties, antiglare properties, etc. Various fillers can be contained. Furthermore, the hard coat layer may contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent.

  The antiglare layer is a layer that prevents reflection of external light by scattering and reflecting light. The antiglare layer generally has a fine uneven shape on the surface. The antiglare layer preferably has a haze in the range of 0.1 to 50%. The haze is measured by a method defined in JIS K 7136: 2000 “Plastics—How to determine haze of transparent material”. The antiglare layer can be formed using a resin composition containing one or more kinds of light-transmitting fine particles in the light-transmitting resin. More specifically, for example, a translucent resin solution in which translucent fine particles as a filler are dispersed is applied onto an acrylic resin film, and the coating film thickness is adjusted to project the translucent fine particles. Can be formed. In addition, after forming a coating film from a translucent resin solution on an acrylic resin film, it can be formed by embossing the surface.

  The translucent resin is preferably an ultraviolet curable resin, and a commercially available resin can be used. For example, “Irgacure 907” or “Irgacure 184” (both trade names sold by BASF) are used alone or in combination of two or more polyfunctional acrylate compounds such as trimethylolpropane triacrylate and pentaerythritol tetraacrylate. A mixture with such a photopolymerization initiator can be used as an ultraviolet curable resin. After the translucent fine particles were dispersed in such an ultraviolet curable resin, the translucent fine particles were dispersed in the translucent resin by applying the resin composition on the film and irradiating with ultraviolet rays. An antiglare layer can be formed.

  Here, the polyfunctional acrylate compound is a compound having at least two acryloyloxy groups or methacryloyloxy groups in the molecule, and specifically includes ethylene glycol diacrylate, diethylene glycol diacrylate, and 1,6-hexane. Diol diacrylate, Neopentyl glycol diacrylate, Trimethylol propane triacrylate, Trimethylol ethane triacrylate, Tetramethylol methane triacrylate, Tetramethylol methane tetraacrylate, Pentaglycerol triacrylate, Pentaerythritol triacrylate, Pentaerythritol tetraacrylate, Glycerin Triacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate Rate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tris (acryloyloxyethyl) isocyanurate; ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentylglycol dimethacrylate, trimethylolpropane Trimethacrylate, trimethylolethane trimethacrylate, tetramethylolmethane trimethacrylate, tetramethylolmethane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerin trimethacrylate, dipentaerythritol trimethacrylate, dipe Taerythritol tetramethacrylate, Dipentaerythritol pentamethacrylate, Dipentaerythritol hexamethacrylate, Tris (methacryloyloxyethyl) isocyanurate Methacrylate compound; urethane acrylate compound or urethane methacrylate compound obtained by reaction of polyisocyanate having at least two isocyanate groups in the molecule and polyol compound having at least one acryloyloxy group or methacryloyloxy group and hydroxyl group, in the molecule At least two carboxylic acid halides and at least one acryloyl Examples thereof include polyester acrylate or polyester methacrylate compounds obtained by a reaction with a polyol compound having an oxy group or a methacryloyloxy group and a hydroxyl group; oligomers such as dimers and trimers of the above-mentioned respective compounds. These compounds are used alone or in combination of two or more.

  In addition to the polyfunctional (meth) acrylate described above, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) An acrylate and a monofunctional (meth) acrylate such as glycidyl (meth) acrylate may be blended preferably in the range of 10% by weight or less based on the resin solid content at the time of curing. Of course, these monofunctional (meth) acrylates can be used alone or in admixture of two or more.

  A polymerizable oligomer can be added to the ultraviolet curable resin for the purpose of adjusting the hardness. Such oligomers include terminal (meth) acrylate polymethyl methacrylate, terminal styryl poly (meth) acrylate, terminal (meth) acrylate polystyrene, terminal (meth) acrylate polyethylene glycol, terminal (meth) acrylate acrylonitrile-styrene copolymer, Examples thereof include macromonomers such as terminal (meth) acrylate styrene-methyl (meth) acrylate copolymer. The blending amount is preferably 5 to 50% by weight based on the solid content at the time of curing of the composition.

In general, the refractive index of ultraviolet curable resin is about 1.5, which is about the same as glass. When the refractive index of the translucent resin is small in comparison with the refractive index of the translucent fine particles, the translucent resin contains TiO ₂ (refractive index 2.3 to 2.7) which is fine particles having a large refractive index. ), Y ₂ O ₃ (refractive index 1.87), La ₂ O ₃ (refractive index 1.95), ZrO ₂ (refractive index 2.05), Al ₂ O ₃ (refractive index 1.63), etc. In addition to maintaining the diffusibility of the film, it can also be adjusted by increasing the refractive index.

  The ultraviolet curable resin may be used as a solution mixed with a solvent. The ultraviolet curable resin or the solution thereof may be a commercially available hard coat agent. Specific examples of commercially available hard coating agents include “NK Hard M101”, a urethane acrylate compound sold by Shin-Nakamura Chemical Co., Ltd., and “NK Ester A-TMM-3L”, a tetramethylol methane triacrylate. , And dipentaerythritol hexaacrylate “NK ester A-9530”, dipentaerythritol hexaacrylate derivative “KAYARAD DPCA series” sold by Nippon Kayaku Co., Ltd., sold by Toa Gosei Co., Ltd. Examples thereof include “Aronix M-8560” which is a polyester acrylate compound.

  From the viewpoint of facilitating application of the ultraviolet curable resin to the acrylic resin film, the ultraviolet curable resin is preferably diluted with an appropriate solvent. Solvents include aliphatic hydrocarbons such as hexane and octane, aromatic hydrocarbons such as toluene and xylene, alcohols such as ethanol, 1-propanol, isopropanol and 1-butanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, acetic acid Examples thereof include esters such as ethyl and butyl acetate, cellosolves and the like. Preferably, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and esters such as ethyl acetate and butyl acetate are used. These organic solvents may be used in combination of several kinds as required. Since it is necessary to evaporate the organic solvent after coating, a solvent having a boiling point in the range of 70 to 200 ° C. is preferable. The type and amount of the solvent used are appropriately selected according to the type and amount of the ultraviolet curable compound to be used, the material and shape of the film to be applied, the coating method, the desired thickness of the hard coat layer, and the like.

  As previously mentioned, some photopolymerization initiators include, for example, acetophenone, acetophenone benzyl ketone, anthraquinone, 1- (4-isopropylphenyl-2-hydroxy-2-methylpropan-1-one Carbazole, xanthone, benzophenone, 4-chlorobenzophenone, 4,4'-diaminobenzophenone, 1,1-dimethoxydeoxybenzoin, 3,3'-dimethyl-4-methoxybenzophenone, thioxanthone, 2,2-dimethoxy-2- Phenylacetophenone, 1- (4-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one , Triphenylamine, 2,4,6-trimethylbenzoyldiphenylphos Oxide, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 3-methylacetophenone, 3,3 ′, 4,4′-tetra-tert-butylperoxycarbonylbenzo Examples include phenone, 2- (dimethylamino) -1- [4- (morpholinyl) phenyl] -2-phenylmethyl) -1-butanone, 4-benzoyl-4′-methyldiphenyl sulfide. The photopolymerization initiator may be used in combination with a dye sensitizer. Examples of the dye sensitizer include xanthene, thioxanthene, coumarin, and ketocoumarin. As a combination of a photopolymerization initiator and a dye sensitizer, for example, the above 3,3 ′, 4,4′-tetra-tert-butylperoxycarbonylbenzophenone is used as a photopolymerization initiator, , Combinations with thioxanthene, combinations with coumarin, combinations with ketocoumarin, and the like.

  When using a photoinitiator, the usage-amount is 0.1 weight part or more per 100 weight part of ultraviolet curable compounds. If the amount is small, the effect of increasing the curing rate is less likely to be exhibited as compared with the case where no photopolymerization initiator is used. The upper limit of the amount of the photopolymerization initiator used is sufficient up to about 10 parts by weight per 100 parts by weight of the ultraviolet curable compound.

  The translucent fine particles are silica-based fine particles or resin fine particles having a particle diameter in the range of 0.5 to 5 μm and a difference in refractive index from the translucent resin in the range of 0.02 to 0.2. preferable. More preferably, the particle diameter is 1 to 4 μm, and the refractive index difference is 0.04 to 0.1. When the particle size of the light-transmitting fine particles is too small, it is difficult to obtain a light diffusion effect unless the amount of the light-transmitting fine particles to be added to the light-transmitting resin is significantly increased. As a result, it is difficult to form irregularities on the surface of the film, and it is difficult to obtain a sufficient antiglare effect. On the other hand, when the particle size of the light-transmitting fine particles is too large, the surface shape of the antiglare layer becomes rough and the haze increases significantly, which is not preferable. If the refractive index difference is too small, it is difficult to obtain a sufficient light diffusion effect. Moreover, when the refractive index difference is too large, the light diffusing ability becomes too high and the entire acrylic resin film is whitened, which is not preferable.

  The translucent fine particles are blended at a ratio of 3 to 30 parts by weight with respect to 100 parts by weight of the translucent resin. More preferably, it is 5 to 20 parts by weight. When the addition amount is less than 3 parts by weight, it is difficult to obtain a sufficient light diffusion effect. Moreover, since the whole acrylic resin film will whiten when the addition amount exceeds 30 weight part, it is unpreferable.

  The translucent fine particles preferably have a specific gravity close to that of the translucent resin and hardly settle, and the surface free energy is preferably small and relatively easy to disperse. From such a viewpoint, resin fine particles are preferably used. . As resin fine particles, melamine beads (refractive index 1.57), polymethyl methacrylate beads (refractive index 1.49), methyl methacrylate / styrene copolymer resin beads (refractive index 1.50 to 1.59), Polystyrene beads are used. On the other hand, examples of the silica-based fine particles include agglomerated silica. Agglomerated silica is obtained by agglomerating tens to hundreds of colloidal silica particles. The temporary particle diameter of silica is 30 nm or less, preferably about 5 to 25 nm, and the aggregated particle diameter is about 1 to 5 μm.

  By regulating the refractive index, particle size, and blending amount of the translucent fine particles as described above, it is possible to prevent glare on the surface without reducing the transmission sharpness even in a high haze region of the antiglare layer. Further, glare can be prevented even in a low haze region while maintaining high transmission clarity.

  When the translucent fine particles are blended with the translucent resin, the translucent fine particles may settle depending on the viscosity of the resin composition. In this case, it is also effective to add an inorganic filler such as silica as an anti-settling agent. The inorganic filler exhibits a remarkable anti-settling effect as the addition amount increases, but decreases the transparency of the antiglare layer. For this reason, it is preferable to make the particle size of the inorganic filler 0.5 μm or less and 0.1% by weight or less.

  The antiglare layer may contain an antistatic agent. By containing an antistatic agent, an antiglare layer having antistatic performance and antistatic performance can be obtained. Examples of the antistatic agent include a surfactant, an antistatic agent composed of a conductive polymer, and conductive particles. Examples of the conductive particles include particles of indium-tin-composite oxide (ITO), tin oxide doped with antimony, and the like. These antistatic agents are used alone or in combination of two or more. In addition, such a composition contains organic compounds containing bromine atoms, fluorine atoms, sulfur atoms, benzene rings, inorganic oxide fine particles such as tin oxide, antimony oxide, titanium oxide, zirconium oxide, zinc oxide, and silicon oxide. When it contains, the refractive index of the hard-coat layer obtained can be adjusted.

  By dispersing the translucent fine particles in the translucent resin, a desired antiglare layer-forming coating solution can be obtained. The antiglare layer can be formed by applying this antiglare layer-forming coating solution onto the surface of the acrylic resin film and drying it. The coating can be performed by a usual method such as a micro gravure coating method, a roll coating method, a dipping coating method, a spin coating method, a die coating method, a cast transfer method, a flow coating method, or a spray coating method. Thereafter, the ultraviolet curable resin is cured by irradiating ultraviolet rays to obtain an antiglare layer. The intensity of ultraviolet rays to be irradiated, the irradiation time, and the like are appropriately selected according to the type of the curable compound used, the thickness of the layer containing the curable compound, and the like. Ultraviolet rays may be irradiated in an inert gas atmosphere. In order to irradiate ultraviolet rays in an inert gas atmosphere, for example, activation energy ray irradiation may be performed in a container sealed with an inert gas, and nitrogen gas, argon gas, or the like can be used as the inert gas.

  Next, a method of forming an antiglare layer by forming a translucent resin coating film on an acrylic resin film and then embossing the surface thereof will be described. In this method, a translucent resin is applied to the surface of the acrylic resin film, and an ultraviolet ray is irradiated while an embossing roll of 50 ° C. or higher is brought into contact with the translucent resin thus coated. It includes a curing step (first curing step) for curing the resin layer to form an antiglare layer, and a peeling step for peeling the resulting antiglare layer from the embossing roll. At this time, the translucent resin is preferably an ultraviolet curable resin, as described above, and a commercially available one can be used. After peeling off the antiglare layer from the embossing roll, it is also effective to perform a second curing step of irradiating ultraviolet rays again from the antiglare layer side for the purpose of further promoting the curing reaction of the antiglare layer. The coating process, the curing process (first curing process), the peeling process, and the optional second curing process described here will be described in order.

  In the coating process, an ultraviolet curable resin is coated on one surface of the acrylic resin film to form a coating layer. The coating method at this time is the wire bar coating method, roll coating method, gravure coating method, knife coating method, slot die coating method, spin coating method, spray coating method, slide coating method, curtain coating method, ink jet method as described above. Etc., and can be appropriately selected from known various methods.

  In the curing step (first curing step), the coating layer obtained in the previous coating step is brought into contact with an embossing roll whose surface temperature is maintained at 50 ° C. or higher, and irradiated with ultraviolet rays to the above-described coating layer. The coating layer is cured. Thereby, the surface shape of the embossing roll is transferred to the coating layer, and an antiglare layer is formed. The upper limit of the contact temperature may be a temperature at which the acrylic resin film cannot be melted, but is preferably set to 100 ° C. or less from the heat resistance of the resin film.

  In order to set the contact temperature to 50 ° C. or higher, the embossing roll may be provided with a heating mechanism, or the embossing roll may have the contact temperature described above by the heat generated from the light source that irradiates ultraviolet rays without providing the heating mechanism. May be. As a heating mechanism provided in the embossing roll, for example, a pipe that circulates a fluid serving as a heat medium is installed inside the embossing roll, and this is connected to a device that heats the fluid outside the embossing roll. And a method of incorporating a heating mechanism such as a heating wire inside the embossing roll. With such a heating mechanism, it is possible to heat the surface of the embossing roll, thereby adjusting the contact temperature to the above-described temperature.

  The embossing roll is preferably provided with a cooling mechanism in order to achieve the contact temperature described above or to protect it from overheating due to ultraviolet irradiation. Examples of the cooling mechanism include a structure in which a cooling pipe is provided inside the embossing roll, the cooling pipe inside the embossing roll is connected to a refrigerant unit installed outside, and the refrigerant is circulated. By such a cooling mechanism, it becomes possible to cool the surface of the embossing roll, and thereby, the contact temperature is adjusted to the above-described contact temperature.

  Although there is no special restriction | limiting in the method of sticking a coating layer and an embossing roll, In order to prevent that a bubble mixes between both, it is preferable to use crimping apparatuses, such as a nip roll. When using a nip roll, the nip pressure is preferably 0.05 MPa or more and 1 MPa or less. If the nip pressure is too small, bubbles tend to be mixed between the coating layer and the embossing roll. On the other hand, if the nip pressure is too large, the film may be broken due to slight deviation when the film is conveyed, or the coating layer may protrude from the end of the film and cause contamination.

  The light source for irradiating ultraviolet rays may be anything that emits ultraviolet rays. Can be used. Among these, an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a xenon arc lamp, and a metal halide lamp can be preferably used.

The cumulative amount of ultraviolet light is determined by ultraviolet light having a wavelength suitable for the photopolymerization initiator to be used. For example, it is preferably 40 mJ / cm ² or more, more preferably 70 mJ / cm ² or more. . If the integrated light quantity is too small, the UV curable resin may be insufficiently cured, and the uncured UV curable resin may adhere to the embossing roll. The upper limit of the integrated light amount is not particularly limited as long as the contact temperature described above is maintained.

  The ultraviolet irradiation may be performed only once or may be performed twice or more. Moreover, there is no special restriction | limiting in the number of the ultraviolet irradiation apparatus and light sources used in a hardening process, One lamp may be sufficient and two or more lamps may be sufficient. In the curing step, it is preferable to fill an inert gas between the coating layer on the film and the irradiation device in order to prevent the curing of the ultraviolet curable resin from being inhibited by oxygen. The inert gas may be appropriately selected from nitrogen, argon, neon, etc., but nitrogen is preferable from the viewpoint of ease of handling and cost. In the inert gas layer, the oxygen concentration is preferably 0.1% by volume or less.

  In the peeling step subsequent to the first curing step, the laminate of the acrylic resin film and the antiglare layer is peeled from the embossing roll. Although the method of peeling is not particularly limited, for example, at the separation point between the laminate of the acrylic resin film and the antiglare layer and the embossing roll, a pressure bonding device such as a peeling roll is installed, and this pressure bonding device is used as a fulcrum. A method of peeling the acrylic resin film on which the antiglare layer is formed from the embossing roll is preferably used. This effectively prevents the film from being peeled off from the embossing roll during the irradiation of ultraviolet rays, maintains the close contact state between the embossing roll and the film, and efficiently and stably peels off the film that has reached the fulcrum. It becomes possible to do.

  Thus, by embossing the coating film surface of the translucent resin, an acrylic resin film having an antiglare layer can be obtained. As described above, the curing reaction of the antiglare layer is performed. For the purpose of further promotion, it is preferable to irradiate ultraviolet rays once more from the antiglare layer side. This process is called a second curing process and will be described below.

As the light source used for the ultraviolet irradiation in the second curing step, the same light source as mentioned in the previous first curing step can be used. Moreover, the ultraviolet irradiation device and the light source may be the same combination or a plurality of different combinations may be used. The type of ultraviolet irradiation device or light source used in the second curing step may be different from that in the first curing step as long as the photopolymerization initiator contained in the ultraviolet curable resin layer functions effectively. . For example, a metal halide lamp may be used in the first curing step, and a high pressure mercury lamp may be used in the second curing step. The cumulative amount of ultraviolet light in the second curing step is preferably 200 mJ / cm ² or more, more preferably 300 mJ / cm ² or more. The upper limit of the integrated light quantity is not particularly limited.

  The irradiation of ultraviolet rays in the second curing step may be performed only once or may be performed twice or more. Also. There are no particular restrictions on the number of ultraviolet irradiation devices or light sources used in the second curing step, and there may be only one lamp or two or more lamps. When performing ultraviolet irradiation twice or more in the second curing step, the above-described integrated light quantity is the total value of ultraviolet rays irradiated in the second curing step. Also in the second curing step, it is preferable to fill an inert gas between the antiglare layer and the irradiation device in order to prevent the curing of the ultraviolet curable resin from being inhibited by oxygen. As the inert gas, the same one as described for the first curing step can be used, and the oxygen concentration in the inert gas is preferably 0.1% by volume or less.

  There is no particular limitation on the specific irradiation method of ultraviolet rays in the second curing step, for example, a method of irradiating the acrylic resin film side on a roll such as a backup roll, A method of irradiating with an ultraviolet irradiation device installed in the middle of the guide roll can be adopted. Among these, from the viewpoint of preventing thermal damage to the acrylic resin film caused by ultraviolet rays and generation of hot soot, an irradiation method using a backup roll equipped with a cooling mechanism is preferable. The surface temperature of the cooled backup roll is generally in the range of 10 to 70 ° C, preferably in the range of 20 to 60 ° C. When using a backup roll, a scraping device for preventing wrinkles from entering the acrylic resin film may be installed on the inlet side of the second curing step or on both the inlet side and the outlet side. .

  The thickness of the antiglare layer may be appropriately adjusted so that the haze of the antiglare layer is within the above-described range, but is preferably in the range of 2 to 12 μm. If the thickness of the antiglare layer is too small, a sufficient antiglare effect cannot be obtained. On the other hand, if the thickness is too large, the film tends to break or the antiglare layer curls due to cure shrinkage of the antiglare layer, and the productivity tends to decrease.

  The antiglare layer may have an antireflection layer composed of a low reflection layer on the outermost surface, that is, the uneven surface side. Although a sufficient antiglare function is exhibited even without an antireflection layer, the antiglare property can be further improved by providing an antireflection layer on the outermost surface.

  The antireflection layer is a layer for preventing reflection of external light and eliminating the reflection, and directly on the surface of the acrylic resin film (surface exposed to the outside) or through another layer such as a hard coat layer. Are stacked. The thickness of the antireflection layer is preferably from 0.01 to 1 [mu] m, more preferably from 0.02 to 0.5 [mu] m. The antireflection layer comprises a low refractive index layer having a refractive index smaller than the refractive index of the layer on which the antireflection layer is laminated, specifically a refractive index of 1.3 to 1.45; an inorganic compound For example, a plurality of thin film low refractive index layers and inorganic thin film high refractive index layers may be alternately stacked.

  The material for forming the low refractive index layer is not particularly limited as long as it has a low refractive index. Examples thereof include a resin material such as an ultraviolet curable acrylic resin, a hybrid material in which inorganic fine particles such as colloidal silica are dispersed in the resin, and a sol-gel material using a metal alkoxide such as tetraethoxysilane. The material for forming these low refractive index layers may be a polymerized polymer, or may be a monomer or oligomer serving as a precursor. Each material preferably contains a fluorine-containing compound in order to impart antifouling properties.

  Examples of the fluorine-containing compound include a fluorinated polymer having a crosslinkable functional group in addition to a sol-gel material having a fluorine group.

An example of the sol-gel material having a fluorine group is fluoroalkylalkoxysilane. Fluoroalkylalkoxysilanes can be represented, for example, by the formula:
CF ₃ (CF ₂ ) nCH ₂ CH ₂ Si (OR) ₃
(In the formula, R represents an alkyl group having 1 to 5 carbon atoms, and n represents an integer of 0 to 12). Specific fluoroalkylalkoxysilanes include trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane, heptadeca Fluorodecyltriethoxysilane and the like can be mentioned. Among these, the compound whose said n is 2-6 is preferable.

  The fluorine-containing polymer having a crosslinkable functional group is obtained by copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or a fluorine-containing monomer and a monomer having a functional group. It can be obtained by copolymerization and then adding a compound having a crosslinkable functional group to a functional group in the polymer.

  Fluorine-containing monomers include fluoroolefins such as fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, and perfluoro-2,2-dimethyl-1,3-dioxole; Osaka (Meth) acrylic acid such as a compound sold under the trade name “Biscoat 6FM” by Organic Chemical Industry Co., Ltd. and a compound sold under the product name “M-2020” from Daikin Industries, Ltd. Or partially fluorinated alkyl ester derivatives, or fully or partially fluorinated vinyl ethers.

  The monomer having a crosslinkable functional group or the compound having a crosslinkable functional group includes a monomer having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate; a monomer having a carboxyl group such as acrylic acid and methacrylic acid. Monomers: Monomers having a hydroxyl group such as hydroxyalkyl acrylates such as hydroxymethyl acrylate and hydroxyalkyl methacrylates such as hydroxymethyl methacrylate; such as allyl acrylate and allyl methacrylate And a monomer having a vinyl group; a monomer having an amino group; a monomer having a sulfonic acid group.

  As a material for forming the low refractive index layer, a material containing a sol in which fine particles such as silica, alumina, titania, zirconia, magnesium fluoride and the like are dispersed in an alcohol solvent is used from the viewpoint of improving the scratch resistance. be able to. From the viewpoint of antireflection properties, these fine particles are preferably those having a lower refractive index. These fine particles may have voids, and silica hollow fine particles are particularly preferable. The average particle diameter of the hollow fine particles is preferably 5 to 2,000 nm, more preferably 20 to 100 nm. Here, the average particle diameter is a number average particle diameter obtained by observation with a transmission electron microscope.

  In addition to the above, the functional layer may be other general layers employed in optical films, such as an antifouling layer, a gas barrier layer, a transparent antistatic layer, a primer layer, an electromagnetic wave shielding layer, and an undercoat layer. Good.

[Optical film]
As described with reference to FIGS. 1 and 2, the optical films 14, 15, and 24 can be bonded to the opposite surfaces of the polarizers 11 and 21 to which the acrylic resin films 12 and 22 are bonded. . Although not shown in FIG. 2, in the polarizing plate 20 disposed on the back side of the liquid crystal cell 30, an optical film is bonded to the outside of the acrylic resin film 22 located on the side far from the liquid crystal cell 30. You can also The optical films 14, 15, and 24 positioned between the polarizers 11 and 21 and the liquid crystal cell 30 are also called retardation films formed of a stretched resin film, and are formed by coating and orientation of an optically anisotropic material. What is called an optical compensation film, and what is generally called a protective film can also be used. Moreover, in the back side polarizing plate 20, an example of an optical film that can be disposed outside the acrylic resin film 22 is a brightness enhancement film.

The retardation film formed by stretching the resin film can be composed of a polycarbonate-based resin, a cycloolefin-based resin, an acetylcellulose-based resin such as triacetylcellulose as a representative example, and the like. These resins exhibit appropriate in-plane retardation Re and thickness direction retardation Rth by uniaxial stretching or biaxial stretching. The biaxial index is represented by an Nz coefficient. The refractive index of in-plane slow axis direction n _x of the birefringent film, the direction perpendicular to the slow axis in the plane, that is, the refractive index of the fast axis direction n _y, the refractive index in the thickness direction n _z, When the film thickness is d, the in-plane retardation Re, the thickness direction retardation Rth, and the Nz coefficient are defined by the following equations (1), (2), and (3), respectively.

_{Re = (n x -n y)} × d (1)
Rth = _{[(n x + n y) /} 2-n z ] × d (2)
_{Nz = (n x -n z)} / (n x -n y) (3)

  These in-plane retardation Re, thickness direction retardation Rth, and Nz coefficient can be measured using a commercially available retardation measuring apparatus. Examples of commercially available phase difference measuring devices include the “KOBRA” series sold by Oji Scientific Instruments, such as “KOBRA-21ADH” and “KOBRA WR”.

  As the retardation film made of the resin exemplified above, those having various optical properties are commercially available from respective resin manufacturers. Examples of commercially available products corresponding to retardation films made of cycloolefin resins are “Arton Film” sold by JSR Co., Ltd. and “Essina” sold by Sekisui Chemical Co., Ltd. There are “retardation film” and “Zeonor film” sold by ZEON Corporation.

  An optical compensation film formed by applying and orienting an optically anisotropic substance is one in which an optically anisotropic substance such as a liquid crystalline compound is applied to the surface of a base film, oriented, and the orientation is fixed. It is. Examples of commercially available products corresponding to such optical compensation films include “WV film” sold by FUJIFILM Corporation and “NH sold by JX Nippon Mining & Energy Corporation. There are “film” and “NV film”.

  Other examples of the protective film for the polarizer include acetylcellulose-based resin films, cycloolefin-based resin films, and the like, with triacetylcellulose as a representative example.

  In addition, the brightness enhancement film disposed on the side farther from the liquid crystal cell (backlight side) of the back-side polarizing plate, for example, is a reflective type that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties. It can be a polarizing plate or the like. An example of a commercial product corresponding to a reflective polarizing plate that transmits one linearly polarized light and reflects the linearly polarized light orthogonal to it is manufactured and sold by 3M. In Japan, Sumitomo 3M Limited. There is "DBEF" available from

[Adhesion between Polarizer, Acrylic Resin Film and Optical Film]
Generally, an adhesive is used for bonding the polarizers 11 and 21 and the acrylic resin films 12 and 22 and bonding the polarizers 11 and 21 and the optical films 14 and 24. The adhesive is not particularly limited as long as it can join the polarizer and these films, but an adhesive satisfying sufficient adhesive force and transparency is selected. From these points, an ultraviolet curable adhesive is preferably used for bonding the polarizer and the acrylic resin film. In addition, the polarizer and the acetylcellulose-based resin film are bonded to each other in addition to the above-described ultraviolet curable resin, an aqueous adhesive, for example, an aqueous solution of a polyvinyl alcohol-based resin, or an aqueous solution in which a crosslinking agent is blended. Urethane emulsion adhesives can also be used.

  In order to improve adhesiveness, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment may be appropriately performed on the adhesion surface of the film to be adhered. The saponification treatment is performed by immersing the film in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

  The ultraviolet curable adhesive may be a mixture of an acrylic compound and a photo radical polymerization initiator, a mixture of an epoxy compound and a photo cationic polymerization initiator, or the like. Alternatively, a cationic polymerizable epoxy compound and a radical polymerizable acrylic compound may be used in combination, and a photo cationic polymerization initiator and a photo radical polymerization initiator may be used in combination as an initiator.

  When an ultraviolet curable adhesive is used, the adhesive is cured by irradiating ultraviolet rays after laminating the films. Although the light source of ultraviolet rays is not particularly limited, those having a light emission distribution at a wavelength of 400 nm or less are preferable. Specifically, low pressure mercury lamp, medium pressure mercury lamp, high pressure mercury lamp, ultrahigh pressure mercury lamp, chemical lamp, black light lamp, microwave excitation Mercury lamps and metal halide lamps are preferably used.

The light irradiation intensity for curing the ultraviolet curable adhesive is appropriately determined depending on the composition of the adhesive and is not particularly limited. However, the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6, 000 mW / cm ² is preferable. By appropriately selecting the irradiation intensity from this range, the reaction time does not become too long, and the yellowing of the adhesive and the deterioration of the polarizer due to the heat radiated from the light source and the heat generated when the adhesive is cured are suppressed. Can do. The light irradiation time is also selected according to the adhesive to be cured and is not particularly limited. However, the integrated light amount expressed as the product of the irradiation intensity and the irradiation time is 10 to 10,000 mJ / cm ² . It is preferable to set so as to be. By appropriately selecting the integrated light quantity from this range, it is possible to generate a sufficient amount of active species derived from the polymerization initiator to surely advance the curing reaction, and it is possible to maintain good productivity without excessively extending the irradiation time.

  When curing UV curable adhesives for films containing polarizers and protective films by UV irradiation, the polarizing plate functions, such as the degree of polarization, transmittance and hue of the polarizer, and the transparency of the protective film, do not deteriorate. It is preferable to perform curing under conditions.

  When using a water-based adhesive, for example, apply the adhesive uniformly on the surface of the film, or pour it between two films, overlap the two films through the coating layer, and bond them with a roll. Then, a drying method can be adopted. After drying, it may be further cured at room temperature or slightly higher temperature, for example, about 20 to 45 ° C.

  The thickness of the adhesive layer is appropriately selected from the range of about 0.001 to 5 μm depending on the type of adhesive and the combination of two films to be bonded. Preferably, it is 0.01 μm or more, and preferably 2 μm or less.

[Adhesive layer]
As shown in FIGS. 1 and 2, pressure-sensitive adhesive layers 18 and 28 are formed on the surfaces of the polarizing plates 10 and 20 to be bonded to the liquid crystal cell 30. An adhesive layer is formed from the adhesive shown below. That is, the pressure-sensitive adhesive is usually composed of a composition in which an acrylic resin, a styrene resin, a silicone resin or the like is used as a base polymer and a crosslinking agent such as an isocyanate compound, an epoxy compound, or an aziridine compound is added thereto. Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property.

  The thickness of the pressure-sensitive adhesive layer is generally in the range of about 1 to 40 μm, but it is preferable to make it thin as long as the workability and durability are not impaired, for example, in the range of about 3 to 25 μm. If the pressure-sensitive adhesive layer is too thin, the adhesiveness is lowered, and if it is too thick, problems such as the pressure-sensitive adhesive protruding easily occur.

  For example, the pressure-sensitive adhesive layer is formed on the optical film or the polarizer by, for example, applying an organic solvent solution containing each component including the above-mentioned base polymer to the optical film surface or the polarizer surface, and then drying the pressure-sensitive adhesive layer. After forming a layer, it can be performed by a method of pasting a separate film, a method of forming a pressure-sensitive adhesive layer on a separate film, and then transferring it to an optical film surface or a polarizer surface. When the pressure-sensitive adhesive layer is formed on the optical film or the polarizer surface, an easy adhesion treatment such as a corona treatment may be applied to the surface of the optical film or the polarizer surface and / or the pressure-sensitive adhesive layer as necessary.

  As shown in FIG. 1B, when two optical films 14 and 15 are sequentially laminated on one surface of a polarizer 11, an interlayer pressure-sensitive adhesive layer is also used for bonding these two optical films 14 and 15. 17 is preferably used. The adhesive described here is also used for forming the interlayer adhesive layer 17 in this case. In FIG. 1B, the interlayer pressure-sensitive adhesive layer 17 is used for bonding the optical films 14 and 15, but an ultraviolet curable adhesive may be used instead of the pressure-sensitive adhesive layer.

[Production method of polarizing plate]
The polarizing plate of the present invention is an acrylic resin separately stretched on a polarizer obtained by subjecting a polyvinyl alcohol resin film to uniaxial stretching, dyeing with a dichroic material, and crosslinking treatment with boric acid according to a conventional method. It can manufacture by the method of bonding a film. However, since the polarizer is made as thin as 1 to 10 μm, a polyvinyl alcohol-based resin layer is formed on the base film as shown in the above-mentioned Patent Documents 1 to 5, and uniaxially stretched and bicolored in the laminated state. It is preferable to first produce a polarizer by a method using the polyvinyl alcohol-based resin layer as a polarizer by performing dyeing with a functional substance and crosslinking treatment with boric acid.

  What is necessary is just to bond the acrylic resin film extended | stretched separately to the polarizer side of the laminated film which consists of a base film and a polarizer obtained in this way. When laminating an optical film on the surface of the polarizer opposite to the acrylic resin film, peel off the substrate film from the substrate film / polarizer / acrylic resin film laminate obtained as described above. What is necessary is just to paste an optical film there. The pasting order in this case is shown in a schematic cross-sectional view in FIG. That is, first, as illustrated in FIG. 3A, the polarizer 11 is formed on the base film 40, and the acrylic resin film 12 is bonded to the surface of the polarizer 11. Next, as shown in FIG. 3B, the base film 40 is peeled off from the polarizer 11 to expose the surface of the polarizer 11 opposite to the surface on which the acrylic resin film 12 is bonded. Then, as shown to (C) of FIG. 3, the optical film 14 is bonded to the exposed surface of the polarizer 11, and a polarizing plate is manufactured. The order of bonding of the acrylic resin film 12 to the polarizer 11 and bonding of the optical film 14 may be reversed.

  As the base film 40, cellulose ester resin, polyester resin, polyethersulfone resin, polysulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyolefin resin, acrylic resin, cycloolefin resin A thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like, such as polyarylate resin, polystyrene resin, and polyvinyl alcohol resin may be used.

In this case, a polarizing plate is basically manufactured through the following steps.
1. A polyvinyl alcohol-based resin layer forming step in which a polyvinyl alcohol-based resin layer is formed on a base film to form a laminated film;
2. A polarizer conversion treatment step in which the polyvinyl alcohol resin layer is subjected to a polarizer conversion treatment including the following steps 2-1 to 2-3 to obtain a polarizer,
2-1. A uniaxial stretching step of uniaxially stretching the laminated film,
2-2. A dyeing process for dyeing a polyvinyl alcohol resin layer with a dichroic material;
2-3. A cross-linking step of performing cross-linking treatment with boric acid on the polyvinyl alcohol resin layer after dyeing,
3. 3. Acrylic resin film laminating step for laminating an acrylic resin film on the surface of the polarizer opposite to the base film. A base film peeling process for peeling the base film from the laminated film,
5. The optical film bonding process which bonds an optical film to the polarizer surface after peeling a base film.

  Each of these steps can basically be performed according to the disclosure of Patent Documents 1 to 5. The uniaxial stretching process and the dyeing process in the above-described polarizer treatment process may be performed in this order, or may be performed in the reverse order, that is, the uniaxial stretching process after the dyeing process, or both may be performed simultaneously. Hereinafter, the above steps will be briefly described.

1. Polyvinyl alcohol-based resin layer forming step In this step, a solution containing a polyvinyl alcohol-based resin is applied to one surface of the base film and dried to form a polyvinyl alcohol-based resin layer. The polyvinyl alcohol resin used is as described above. Coating of a solution containing a polyvinyl alcohol resin is a known method such as a wire bar coating method, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, or a spray method. Can be selected as appropriate. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. The drying time is, for example, 5 to 30 minutes. In this step, it is also possible to form a polyvinyl alcohol-based resin layer by sticking a raw film made of a polyvinyl alcohol-based resin to a base film.

2. 2. Polarization process step 2-1. Uniaxial Stretching Step In the uniaxial stretching step, a laminated film composed of a base film and a polyvinyl alcohol-based resin layer is uniaxially drawn so that the draw ratio is preferably more than 5 times the original length of the laminated film. More preferably, it is uniaxially stretched so that the draw ratio is more than 5 times and not more than 17 times. In the polarizing plate of the present invention, the stretching direction at this time is in a positional relationship orthogonal to the stretching direction of the acrylic resin film. When the draw ratio is 5 times or less, the orientation of the polyvinyl alcohol-based resin layer is not sufficient, and as a result, the degree of polarization of the polarizer tends not to be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the laminated film is likely to break during stretching, and the thickness of the laminated film becomes unnecessarily thin, which may reduce workability and handling properties in subsequent steps. is there. Of course, the stretching treatment in the uniaxial stretching step is not limited to stretching in one stage, and can be performed in multiple stages. When performing in multiple stages, the stretching process is carried out so that the stretching ratio of all stages of the stretching process is preferably more than 5 times.

  In the uniaxial stretching step, horizontal uniaxial stretching that stretches in the width direction of the laminated film can be adopted, and longitudinal uniaxial stretching that stretches in the longitudinal direction can also be adopted, but the optical performance of the obtained polarizer From this aspect, longitudinal uniaxial stretching is preferred. Examples of the longitudinal stretching method include an inter-roll stretching method and a compression stretching method. For stretching, either a wet stretching method or a dry stretching method can be adopted. However, dry stretching is preferred because the temperature at which the laminated film is stretched can be selected from a wide range.

2-2. Dyeing process In the dyeing process, the polyvinyl alcohol resin layer of the laminated film is dyed with a dichroic substance. A dyeing process is performed by immersing the whole laminated film which consists of a substrate film and a polyvinyl alcohol system resin layer in the solution (dyeing bath) containing the dichroic substance explained previously, for example. As the dyeing bath, a solution in which a dichroic substance is dissolved in a solvent is used. The solvent constituting the dyeing bath is generally water, but an organic solvent compatible with water may be further added. The concentration of the dichroic material is preferably 0.01 to 10% by weight, more preferably 0.07 to 7% by weight, and particularly preferably 0.025 to 5% by weight.

  When iodine is used as the dichroic substance, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. The addition ratio of these iodides is preferably 0.01 to 10% by weight in the dyeing bath. Of the iodides, potassium iodide is preferably used. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100 by weight, in the range of 1: 6 to 1:80, and more preferably 1: 7. More preferably in the range of ˜1: 70.

  The immersion time of the laminated film in the dyeing bath is usually in the range of 15 seconds to 15 minutes, and preferably in the range of 1 to 3 minutes. The temperature of the dyeing bath is preferably in the range of 10 to 60 ° C, and more preferably in the range of 20 to 40 ° C.

  In the dyeing step, the dichroic substance is adsorbed on the resin layer made of the polyvinyl alcohol resin of the laminated film, and the dichroic substance is oriented. The dyeing step (step 2-2) can be performed before, simultaneously with, or after the uniaxial stretching step (step 2-1), but the dichroic material adsorbed on the resin layer made of polyvinyl alcohol resin is satisfactorily used. From the viewpoint of orientation, it is preferable to carry out the uniaxial stretching step (step 2-1) on the laminated film.

2-3. Crosslinking step After the uniaxial stretching step and the dyeing step, the crosslinking step is performed. The crosslinking step can be performed, for example, by a method of immersing a laminated film that has been uniaxially stretched and dyed in a solution (crosslinking bath) containing boric acid as a crosslinking agent. As the crosslinking bath, a solution obtained by dissolving boric acid in a solvent is used. As the solvent, water is generally used, but it may further contain an organic solvent compatible with water. The concentration of boric acid in the crosslinking bath is, for example, 1 to 10% by weight, preferably 2 to 6% by weight.

  The crosslinking bath may contain iodide. By adding iodide, the in-plane polarization characteristics of the polyvinyl alcohol-based resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Etc. The iodide content is usually 0.05 to 15% by weight, preferably 0.5 to 8% by weight. The immersion time of the laminated film in the crosslinking bath is usually 15 seconds to 20 minutes, but preferably 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a crosslinking bath exists in the range of 10-80 degreeC.

  By blending the crosslinking agent in the dyeing bath, the crosslinking step and the dyeing step can be performed simultaneously, but it is preferable not to perform these simultaneously. Moreover, it is preferable not to extend | stretch at a bridge | crosslinking process, and when it extends here, it will become easy to generate | occur | produce a neck-in in a laminated | multilayer film.

2-4. Other Steps that can be Adopted in the Polarizing Process Step In the polarizing process step, it is preferable to finally perform a washing step and a drying step. In the washing step, washing with water is performed. Washing with water can usually be performed by using pure water such as ion-exchanged water or distilled water, and immersing the laminated film subjected to uniaxial stretching, dyeing and crosslinking therein. The temperature of the water washing is usually 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time is usually 2 to 300 seconds, preferably 5 seconds to 240 seconds. In the washing step, washing with an iodide solution and washing with water may be combined, and a solution appropriately blended with liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like can also be used.

  It is preferable to perform a drying process after the washing process. In the drying step, for example, natural drying, air drying, heat drying, or the like can be employed. The drying temperature in the case of heat drying is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes.

  By the above polarizing treatment process, the polyvinyl alcohol-based resin layer has a function as a polarizer. In this specification, the polyvinyl alcohol-type resin layer after passing through a polarizer formation process may be called a polarizer or a polarizer layer.

3. Acrylic resin film bonding step In the acrylic resin film bonding step, the stretched acrylic resin film is bonded to the surface of the polarizer opposite to the base film. The adhesive mentioned above is used for bonding.

4). Base film peeling process In a base film peeling process, a base film is peeled from the laminated body of a base film, a polarizer, and an acrylic resin film. The peeling method is not particularly limited, and a method similar to the peeling film peeling step performed in a normal pressure-sensitive adhesive polarizing plate can be employed. After the acrylic resin film laminating step, the base film may be peeled off as it is, or after the acrylic resin film laminating step, it is wound up into a roll and then peeled off while unwinding. May be.

5. Optical film bonding process In an optical film bonding process, the optical film demonstrated previously is bonded to the surface on the opposite side to the bonding surface of the acrylic resin film of a polarizer. Although the adhesive agent demonstrated previously is normally used for bonding of an optical film, an adhesive can also be used depending on the case.

  As described above, the uniaxial stretching step for producing the polarizer may be performed by fixed-end lateral uniaxial stretching or by free-end longitudinal uniaxial stretching. When a polarizer is produced by fixed-end lateral uniaxial stretching, an acrylic resin film that has been stretched so as to increase the longitudinal stretching ratio is bonded. When a polarizer is produced by free-end longitudinal uniaxial stretching, an acrylic resin film that has been stretched so as to increase the lateral stretching ratio is bonded. In terms of optical properties of the obtained polarizer, it is preferable to produce the polarizer by free-end longitudinal uniaxial stretching. Therefore, a polarizing plate in which a polarizer produced by longitudinal uniaxial stretching and an acrylic resin film produced by lateral uniaxial stretching are bonded is a preferred embodiment of the present invention.

[Liquid crystal display panel and liquid crystal display device]
The polarizing plate of this invention is used suitably for the liquid crystal display panel which comprises a liquid crystal display device. The liquid crystal display panel is configured by sticking a viewing-side polarizing plate and a back-side polarizing plate to both surfaces of a liquid crystal cell, respectively. As the viewing side polarizing plate and / or the back side polarizing plate, the polarizing plate of the present invention can be used. Accordingly, the liquid crystal display panel according to the present invention includes the polarizing plate described above and a liquid crystal cell, and the polarizing plate has a liquid crystal surface opposite to the surface bonded to the acrylic resin film. Both are attached so as to be on the cell side.

  FIG. 4 to FIG. 8 show cross-sectional schematic diagrams of layer configuration examples of the liquid crystal display panel according to the present invention. FIG. 4 is an example in which the viewing side polarizing plate 10 is configured with the one shown in FIG. 1A and the back side polarizing plate is configured with the one shown in FIG. FIG. 5 is an example in which the viewing side polarizing plate 10 is configured with the one shown in FIG. 1B and the back side polarizing plate is configured with the one shown in FIG. FIG. 6 is an example in which the viewing side polarizing plate 10 is configured by the one shown in FIG. 1B and the back side polarizing plate is configured by the one shown in FIG. FIG. 7 shows the viewing-side polarizing plate 50 similar to that shown in FIG. 1B, except that the outermost protective film 55 is a resin film other than a stretched acrylic resin film. In this example, the back-side polarizing plate 20 is configured with the one shown in FIG. FIG. 8 shows the viewing side polarizing plate 10 as shown in FIG. 1B, and the back side polarizing plate 52 is similar to that shown in FIG. In this example, the protective film 57 is made of a resin film other than a stretched acrylic resin film. In each figure, a backlight unit 70 is drawn on the back side of the liquid crystal panel 60.

  As shown in FIGS. 7 and 8, a liquid crystal display panel in which the polarizing plate of the present invention is attached to one side of a liquid crystal cell, and a polarizing plate that does not satisfy the provisions of the present invention is attached to the other side of the liquid crystal cell. Is also an embodiment of the present invention. Of course, as shown in FIG. 4 and FIG. 5, the polarizing plate of the present invention in which both sides of the liquid crystal cell have an optical film bonded to the surface opposite to the surface on which the acrylic resin film of the polarizer is bonded. The polarizing plate on the front side is attached to the liquid crystal cell 30 via the first pressure-sensitive adhesive layer 18 on the optical film side, and the polarizing plate on the back side is also the second pressure-sensitive adhesive layer 28 on the optical film side. A liquid crystal display panel attached to the liquid crystal cell 30 via the liquid crystal panel is also an embodiment of the present invention.

  The liquid crystal display panel and the liquid crystal display device can be assembled according to a conventionally known method. That is, the liquid crystal display device is generally formed by assembling other constituent members such as a liquid crystal cell, a polarizing plate, and an illumination system as needed, and further incorporating a drive circuit. And a liquid crystal display panel and also a liquid crystal display device can be assembled according to the former except that the polarizing plate of the present invention is used as a polarizing plate on the viewing side and / or the back side. As the liquid crystal cell, any type such as a TN type, a VA type, and an IPS type can be used. Among these, the polarizing plate of this invention expresses the outstanding effect especially with respect to VA type and IPS type with which a liquid crystal cell is thin.

  A liquid crystal display panel can be formed by disposing a polarizing plate on one side or both sides of a liquid crystal cell, and a backlight or a reflecting plate can be used for an illumination system. In such a liquid crystal display device, at least one of the polarizing plates disposed on one side or both sides of the liquid crystal cell is a polarizing plate defined in the present invention. The liquid crystal display device can be further configured by combining appropriate elements such as a diffusion plate, an antireflection film, a protective plate, a prism array, and a lens array sheet.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

Reference Example 1 Production of Acrylic Resin Raw Film A ratio of 30 parts of acrylic rubber particles to 70 parts of acrylic matrix resin consisting of a copolymer of methyl methacrylate / methyl acrylate in a weight ratio of 96/4. The pellets of the acrylic resin composition blended in (1) were used. The acrylic rubber particles have a hard polymer in which the innermost layer is copolymerized with methyl methacrylate and a small amount of allyl methacrylate, the intermediate layer is mainly composed of butyl acrylate, and styrene and a small amount of allyl methacrylate are mixed. Polymerized soft elastic body, the outermost layer is a three-layer rubber elastic body particle made of a hard polymer in which a small amount of ethyl acrylate is copolymerized with methyl methacrylate, up to the elastic body as an intermediate layer Have an average particle size of 240 nm. It was 102 degreeC when the Vicat softening temperature of this acrylic resin composition was measured. Moreover, it was 105 degreeC when the glass transition temperature (Tg) was measured.

  The above pellets are put into a 65 mmφ single screw extruder, extruded through a T die set at a temperature of 275 ° C., and both sides of the extruded film-like molten resin have mirror surfaces set at 45 ° C. 2 An acrylic resin raw film having a thickness of 80 μm was prepared by sandwiching between two polishing rolls and cooling. This is designated as “80 μm thick original film”.

  Moreover, although it was the same method as the above, the raw film of the acrylic resin which has a thickness of 40 micrometers was produced by changing the slit space | interval of a T-type die. This is referred to as “40 μm thick original film”.

[Reference Example 2] Stretching of acrylic resin raw film Using a tenter horizontal stretching machine, the 80 μm thick raw film produced in Reference Example 1 was stretched twice in the horizontal direction at a temperature of 100 ° C. to have a thickness of 40 μm. A stretched acrylic resin film was produced. This is referred to as a “40 μm thick stretched film”.

Reference Example 3 Film Shrinkage Measurement The 40 μm-thick stretched film produced in Reference Example 2 was subjected to measurement of the shrinkage rate in the direction of the drawing axis. First, square samples each having a length of 100 mm in the direction of the stretching axis (width direction, TD) and the direction orthogonal to it (longitudinal direction, MD) are cut from this film, and the length in the direction of the stretching axis is accurately determined. It was. Next, this sample was put into an oven at 80 ° C. and kept in a heated state for 24 hours, then removed from the oven, left to stand at a temperature of 23 ° C. and a relative humidity of 50% for 1 minute, and the length in the direction of the stretching axis was again obtained. It was. And the shrinkage | contraction rate was calculated | required by the following formula | equation from the initial length and the length after a heating.
Shrinkage rate (%) = [(initial length−length after heating) / initial length] × 100

  Similarly, the 40 μm thick raw film produced in Reference Example 1 was also cut before and after heating when a square sample with a length of 100 mm in the width direction (TD) and the length direction (MD) was cut at 80 ° C. for 24 hours. From the length, the shrinkage in the width direction (TD) was determined.

  For comparison, the following films, which are all commercially available, were cut into 100 mm × 100 mm square samples, heated at 80 ° C. for 24 hours, and the shrinkage in the width direction was determined from the length before and after heating. . The results are shown in Table 1 together with the results for the above acrylic resin film.

Cycloolefin resin film:
A retardation film having a thickness of 25 μm (in-plane retardation of 90 nm, thickness direction retardation of 79 nm),
An unstretched film having a thickness of 23 μm.
Triacetyl cellulose film:
A film with a thickness of 40 μm.

[Reference Example 4] Production of Polarizing Laminated Film (a) Base Film First, an aqueous polyvinyl alcohol solution was applied on the base film and dried to produce a laminated film as a raw material for producing a polarizer. Here, a polypropylene film having a thickness of 110 μm and a melting point of 163 ° C. was used as the base film.

(B) Formation of primer layer Acetacetyl group-modified polyvinyl alcohol powder (trade name “Gosefimer Z-200” having an average polymerization degree of 1,100 and a saponification degree of 99.5 mol% obtained from Nippon Synthetic Chemical Industry Co., Ltd. )) Was dissolved in hot water at 95 ° C. to prepare a 3% strength aqueous solution. As a crosslinking agent, water-soluble polyamide epoxy resin obtained from Taoka Chemical Co., Ltd. (trade name “Smileze Resin 650”, aqueous solution with a solid content of 30%) was added to this aqueous solution as a crosslinking agent at a solid content of 5 parts per 6 parts of polyvinyl alcohol. The mixture was mixed at a ratio of parts to obtain a primer coating solution.

  After applying the corona treatment to the above-mentioned base film made of polypropylene, the above primer coating liquid is applied to the corona-treated surface with a micro gravure coater and dried at 80 ° C. for 10 minutes to obtain a thickness of 0 A 2 μm primer layer was formed.

(C) Formation of polyvinyl alcohol layer Polyvinyl alcohol powder (trade name “PVA124”) having an average polymerization degree of 2,400 and a saponification degree of 98.0 to 99.0 mol% obtained from Kuraray Co., Ltd. It melt | dissolved in hot water and prepared 8% concentration polyvinyl alcohol aqueous solution. The obtained aqueous solution was coated on the primer layer of the base film using a lip coater at room temperature and dried at 80 ° C. for 20 minutes to obtain a laminated film consisting of the base film / primer layer / polyvinyl alcohol layer. Produced. The thickness of the polyvinyl alcohol layer was 10 μm.

(D) Stretching of laminated film The resulting laminated film was stretched 5.8 times at a free end in a longitudinal direction at a temperature of 160 ° C. The total thickness of the laminated stretched film thus obtained was 28.5 μm, and the thickness of the polyvinyl alcohol layer was 4.2 μm.

(E) Dyeing of polyvinyl alcohol layer The obtained laminated stretched film was dyed by immersing it in an aqueous solution having a water / iodine / potassium iodide weight ratio of 100 / 0.35 / 10 at 26 ° C. for 90 seconds, followed by 10 ° C. Washed with pure water. Next, this laminated film was immersed in an aqueous solution having a weight ratio of water / boric acid / potassium iodide of 100 / 9.5 / 5 at 76 ° C. for 300 seconds to crosslink the polyvinyl alcohol. Subsequently, the substrate was washed with pure water at 10 ° C. for 10 seconds, and finally dried at 80 ° C. for 200 seconds. By the above operation, a polarizing laminated film in which a polarizer composed of a polyvinyl alcohol layer on which iodine was adsorbed and oriented was formed on a polypropylene base film was produced.

[Example 1] Preparation of viewing-side polarizing plate (a) Bonding of acrylic resin film to polarizer On the surface (polarizer surface) opposite to the base film of the polarizing laminated film prepared in Reference Example 4, A 40 μm-thick stretched film made of the acrylic resin prepared in Reference Example 2 was bonded. First, a corona treatment is applied to one side of the 40 μm thick stretched film, and an ultraviolet curable adhesive containing an epoxy compound and a photocationic polymerization initiator is applied to the corona treatment surface, and then the adhesive coating surface is applied. The film is sandwiched between nip rolls from both sides so that the polarizing axis of the polarizing laminate film prepared in Reference Example 4 is roll-to-roll, that is, the stretching axis of the 40 μm thick stretched film and the stretching axis of the polarizer are perpendicular to each other. Pasted together. And the ultraviolet-ray was irradiated from the base film side of the polarizing laminated film, and the adhesive agent was hardened. Thus, a second laminated film having a layer structure of 40 μm-thick stretched film / polyvinyl alcohol-based polarizer / polypropylene base film made of acrylic resin was produced.

(B) Bonding of retardation film to other surface of polarizer A 25 μm-thick retardation film (in-plane retardation 90 nm, thickness direction retardation 79 nm) made of a cycloolefin resin was prepared in a long roll shape. This retardation film has a slow axis in the width direction. One side of the retardation film was subjected to corona treatment, and the same ultraviolet curable adhesive as above was applied to the corona treatment surface. On the other hand, from the second laminated film prepared in (a) above, the polypropylene base film is peeled off and wound, and the adhesive coating surface of the retardation film is applied to the polarizer surface after the base film is peeled off. They were overlapped with roll-to-roll, and sandwiched from both sides with nip rolls. At this time, the slow axis of the retardation film and the absorption axis of the polarizer are orthogonal to each other. And the ultraviolet-ray was irradiated from the phase difference film side, and the adhesive agent was hardened. Thus, a polarizing plate having a layer structure of 40 μm thick stretched film made of acrylic resin / polyvinyl alcohol polarizer / cycloolefin retardation film was produced.

[Example 2] Bonding of second retardation film to polarizing plate and formation of pressure-sensitive adhesive layer The polarizing plate produced in Example 1 is bonded to the liquid crystal cell on the side of the retardation film via the pressure-sensitive adhesive. In this case, a second retardation film was further bonded to the retardation film side. First, as a second retardation film, it has a three-layer structure in which a styrene resin is used as a core layer and both surfaces thereof are sandwiched between acrylic resin layers containing acrylic rubber. The total thickness is 46 μm, the in-plane retardation is 60 nm, The thing of Nz coefficient-1.0 was prepared in the shape of a long roll. This second retardation film has a slow axis in the width direction. Next, the second retardation film was bonded to the cycloolefin phase difference film side of the polarizing plate produced in Example 1 through a 20 μm thick acrylic pressure-sensitive adhesive layer with a roll-to-roll. Next, an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm formed on a separate film was provided outside the second retardation film. Thus, a layer structure of 40 μm-thick stretched film made of acrylic resin / polyvinyl alcohol polarizer / cycloolefin retardation film / interlayer adhesive layer / 3-layer second retardation film / adhesive layer / separate film A viewing-side polarizing plate with an adhesive was prepared. The slow axis of the cycloolefin retardation film and the slow axis of the second retardation film are both orthogonal to the absorption axis of the polarizer.

[Example 3] Production of back side polarizing plate (a) Production of polarizing plate In (b) of Example 1, a 25 μm thick retardation film made of cycloolefin resin was unstretched and had a thickness of 23 μm. A polarizing plate having a layer structure of a 40 μm-thick stretched film composed of an unstretched cycloolefin resin film / polyvinyl alcohol polarizer / acrylic resin was prepared in the same manner as in Example 1 except that the olefin resin film was changed. .

(B) Bonding of optical film to polarizing plate and formation of pressure-sensitive adhesive layer On the 40 μm-thick stretched film side made of an acrylic resin of the polarizing plate prepared above, an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm is interposed. A brightness enhancement film (trade name “DBEF”) obtained from Sumitomo 3M Limited was bonded. Further, an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm formed on a separate film was provided on the unstretched cycloolefin-based resin film side. Thus, the back side with pressure-sensitive adhesive comprising the layer structure of separate film / pressure-sensitive adhesive layer / unstretched cycloolefin-based resin film / polyvinyl alcohol-based polarizer / acrylic resin, 40 μm thick stretched film / interlayer pressure-sensitive adhesive / brightness enhancement film A polarizing plate was produced.

[Reference Example 5] Production of viewing-side polarizing plate with no acrylic resin bonded In Example 1 (a), instead of a 40 μm thick stretched film made of acrylic resin, obtained from Konica Minolta Opto Co., Ltd. A 40 μm thick triacetylcellulose film was used, and an adhesive composed of a 3% polyvinyl alcohol aqueous solution was used to bond it to a polyvinyl alcohol polarizer, and both were bonded via the adhesive, followed by heat drying. A polarizing plate having a layer structure of triacetyl cellulose film / polyvinyl alcohol polarizer / cycloolefin retardation film was produced in the same manner as in Example 1 except that both were bonded together.

  Further, an operation according to Example 2 was performed on the polarizing plate, and the second retardation of the triacetyl cellulose film / polyvinyl alcohol-based polarizer / cycloolefin-based retardation film / interlayer pressure-sensitive adhesive layer / 3-layer structure. A viewing-side polarizing plate with a pressure-sensitive adhesive comprising a layer configuration of film / pressure-sensitive adhesive layer / separate film was prepared.

[Reference Example 6] Preparation of back-side polarizing plate to which acrylic resin is not bonded (a) Preparation of polarizing plate In (a) of Example 1, instead of the 40 μm thick stretched film made of acrylic resin, Konica Using a 40 μm thick triacetylcellulose film obtained from Minolta Opto Co., Ltd., and using an adhesive made of a 3% polyvinyl alcohol aqueous solution for laminating it with a polyvinyl alcohol polarizer, After pasting, both were adhered by heating and drying, and a laminated film having a layer configuration of triacetyl cellulose film / polyvinyl alcohol polarizer / polypropylene base film was produced.

  An unstretched 23 μm thick cycloolefin resin film is prepared in the form of a long roll, and one side thereof is subjected to corona treatment, and the same UV curing as that used in (a) of Example 1 is applied to the corona treatment surface. A mold adhesive was applied. On the other hand, the polypropylene base film is peeled off from the laminated film and wound up, and the adhesive-coated surface of the cycloolefin resin film is overlapped with a roll-to-roll on the polarizer surface after the base film is peeled off. Then, they were sandwiched by nip rolls from both sides. And the ultraviolet-ray was irradiated from the cycloolefin type-resin film side, and the adhesive agent was hardened according to (b) of Example 1 others. Thus, a polarizing plate having a layer structure of unstretched cycloolefin resin film / polyvinyl alcohol polarizer / triacetyl cellulose film was produced.

(B) Bonding of optical film to polarizing plate and formation of pressure-sensitive adhesive layer The polarizing plate obtained in this manner was subjected to an operation according to (b) of Example 3 to produce a separate film / pressure-sensitive adhesive layer / unstretched cyclohexane. A back-side polarizing plate with an adhesive comprising a layer structure of olefin resin film / polyvinyl alcohol polarizer / triacetyl cellulose film / interlayer adhesive / brightness enhancement film was prepared.

[Example 4] Manufacture of liquid crystal panel equivalent and evaluation of warpage A viewing side polarizing plate with an adhesive having a 40 μm-thick stretched film made of acrylic resin prepared in Example 2 on its outermost surface has a long absorption axis. It was cut into a rectangle with a size of 200 mm × 150 mm. Moreover, the back side polarizing plate with the adhesive having the brightness enhancement film pasted on the outside of the 40 μm-thick stretched film made of the acrylic resin prepared in Example 3 has a size of 200 mm × 150 mm so that the absorption axis is a short side. Cut into rectangles.

  Then, a glass plate (trade name “EAGLE XG” obtained from Corning Inc.) having a rectangular shape of 206 mm × 156 mm and a thickness of 400 μm was peeled off from the polarizing plate on the viewing side with the adhesive. On the other side, the separation film was peeled off from the above-mentioned pressure-sensitive adhesive-backed polarizing plate so that a margin of about 3 mm was formed from each side of the glass plate. This was put into an autoclave and subjected to a pressure heat treatment at a temperature of 50 ° C. and a pressure of 5 MPa for 20 minutes, and then cured for 24 hours under the conditions of a temperature of 23 ° C. and a relative humidity of 55%. In this way, a liquid crystal panel equivalent product in which polarizing plates were bonded to both surfaces of a glass plate with crossed Nicols was produced. This liquid crystal panel equivalent has the layer structure shown in FIG. 7, but an interlayer adhesive layer (not shown) is provided outside the stretched acrylic resin film 22 constituting the back-side polarizing plate 20 in FIG. The brightness improvement film is bonded through.

  This liquid crystal panel equivalent 60 was placed in an oven at 80 ° C. and kept in a heated state for 24 hours, then taken out and left in an atmosphere at a temperature of 23 ° C. and a relative humidity of 55% for 1 minute. This was placed on a sample table of a three-dimensional measuring instrument (trade name “VMR12072”) manufactured by Nikon Corporation so that the viewing-side polarizing plate 10 was on top, and the amount of warpage was measured. The amount of warpage is positive (+) when concave on the viewing side polarizing plate 10 side and convex on the back side polarizing plate side 20, conversely convex on the viewing side polarizing plate 10 side, and concave on the back side polarizing plate 20 side. The minus time (−) was used. And as shown in FIG. 9, a total of 25 places (P01-P25 in FIG. 9) of 5 rows of long side directions and 5 rows of short side directions including the four sides of the viewing side polarizing plate 10 which comprises the liquid crystal panel equivalent 60. The height position data on the outermost surface of the viewing side polarizing plate was determined. In addition, the difference between the maximum value and the minimum value of the data at the five central points in the long side direction (P11, P12, P13, P14 and P15 in Fig. 9) is taken as the amount of warpage in the long side direction, and the center 5 in the short side direction. The difference between the maximum value and the minimum value of the points (P03, P08, P13, P18 and P23 in Fig. 9) was taken as the amount of warpage in the short side direction. As a result, the warpage amount in the long side direction was +1,600 μm, and the warpage amount in the short side direction was +113 μm.

  FIG. 10 is a schematic perspective view showing a warped state of the liquid crystal panel equivalent 60. In this figure, the upper side of the liquid crystal panel equivalent 60 is the viewing side polarizing plate 10 (not shown). Then, on the reference surface 62, the outermost surface position of the viewing side polarizing plate 10 when it is assumed that the liquid crystal panel equivalent 60 is not warped is a virtual surface 63 corresponding to a virtual quadrilateral ABCD with a one-dot chain line. It is displayed. One corner A on the virtual surface 63 is actually at the position A1, and similarly, the corners B, C, and D on the virtual surface 63 are actually at the positions B1, C1, and D1, respectively. P03, P11, P13, P15 and P23 in the figure correspond to the measurement positions of the height position data shown in FIG. In this example, the measurement points P11 and P15 at the center of the short side and the measurement points P03 and P23 at the center of the long side are both lifted from the reference plane 62, so that the amount of warpage is positive in both the long side direction and the short side direction. It has become.

  Here, the warpage in the long side direction and the short side direction was obtained from the measurement data of 5 points in the long side direction and 5 points in the short side direction, but from P11 to P15 in the center of the long side direction in FIGS. The same result can be obtained by calculating the position data in the height direction of more points from P03 to P23 in the middle of the short side direction and calculating the amount of warpage from them.

[Example 5] Preparation of another liquid crystal panel equivalent and evaluation of warpage In Example 4, the visual recognition side polarizing plate with an adhesive having the triacetyl cellulose film prepared in Reference Example 5 on the outermost surface was used. A liquid crystal panel equivalent was prepared according to Example 4 and the warpage was evaluated by changing to the side polarizing plate. As a result, the warpage amount in the long side direction was +1,462 μm, and the warpage amount in the short side direction was −127 μm. FIG. 11 is a schematic perspective view showing a warped state of the liquid crystal panel equivalent 60 in this example. The display format in FIG. 11 is the same as in FIG. In this example, the measurement points P11 and P15 in the middle of the short side were in a state of being lifted from the reference plane, but the measurement points P03 and P23 in the center of the long side were in a state of being lowered from the reference plane. The amount of warpage is negative.

[Comparative Example 1]
In Example 4, the viewing-side polarizing plate with an adhesive was changed to the viewing-side polarizing plate with an adhesive having the triacetyl cellulose film prepared in Reference Example 5 on the outermost surface, and the back-side polarizing plate with an adhesive was Change to a back-side polarizing plate with a pressure-sensitive adhesive with a brightness enhancement film pasted on the outer side of the triacetylcellulose film produced in Reference Example 6, and otherwise produce a liquid crystal panel equivalent according to Example 4 to evaluate warpage. Went. As a result, the warpage amount in the long side direction was +2,062 μm, and the warpage amount in the short side direction was −112 μm. The warp state of the liquid crystal panel equivalent 60 in this example is substantially the same as in FIG. 11, but the warp amount in the long side direction is particularly large.

  For Examples 4 and 5 and Comparative Example 1 above, the summary of the layer structure and the measurement results of the amount of warpage are summarized in Table 2.

  As described above, in Comparative Example 1, the amount of warpage in the long side direction is particularly large, whereas Examples 4 and 5 in which both or one of the protective films on the side far from the liquid crystal cell is composed of a stretched acrylic resin film are The amount of warpage has been improved.

10, 20 ... Polarizing plate,
11, 21 ... Polarizer,
12, 22 ... A stretched acrylic resin film,
14, 24 ... Optical film,
15 ... Second optical film,
17 …… Interlayer adhesive layer,
18, 28 ... Adhesive layer for application to the liquid crystal cell,
30 ... Liquid crystal cell,
40 …… Base film,
50, 52... (Without a stretched acrylic resin film) Polarizing plate,
55, 57 ...... Protective film (other than stretched acrylic resin film),
60 …… Liquid crystal display panel or equivalent,
62 …… Reference plane for measuring warpage,
63 …… A virtual surface on the reference surface when it is assumed that the liquid crystal display panel is not warped,
70 …… Backlight unit.

Claims (5)

A resin film is bonded to one surface of the polarizer, and an optical film and a second optical film are bonded to the other surface of the polarizer in order from the polarizer, and on the outside of the second optical film. A pressure-sensitive adhesive layer is laminated, and the optical film closer to the polarizer is a viewing-side polarizing plate composed of a cycloolefin resin,
A set of polarizing plates having a pressure-sensitive adhesive layer on one side of the polarizer, a brightness enhancement film disposed on the other side, and a back side polarizing plate further having a resin film,
The optical film and the second optical film provided on the viewing side polarizing plate are each independently a retardation film or an optical compensation film,
At least one of the resin films is a stretched film of a single layer acrylic resin,
Has a thickness of 1 to 10 [mu] m, a polarizer dichroic material comprises a stretched film of a polyvinyl alcohol-based resin is adsorbed and oriented, and oriented film of the acrylic resin of the monolayer, both 80 ° C. When heated for 24 hours under the dry condition, the direction in which the shrinkage rate becomes maximum in the plane is bonded so as to be orthogonal,
The stretched film of the single-layer acrylic resin (excluding the case where the acrylic resin film contains a cellulose ester resin) has a length in the direction in which the shrinkage rate is maximum in the plane and a direction perpendicular thereto. Are each cut into squares so as to be 100 mm, and after being heated for 24 hours under drying at a temperature of 80 ° C., the shrinkage in the direction in which the shrinkage becomes maximum in the plane is in the range of 1.5 to 5%. A set of polarizing plates characterized by being. The set of polarizing plates according to claim 1, wherein the stretched film of the single-layer acrylic resin is formed from an acrylic resin composition containing 10 to 50% by weight of rubber particles in an acrylic base resin. The set of polarizing plates according to claim 1, wherein the stretched film of the single-layer acrylic resin has a thickness of 15 to 60 μm.
The set of polarizing plates according to any one of claims 1 to 3 , wherein the stretched film of the single-layer acrylic resin and the polarizer are bonded with an ultraviolet curable adhesive. A set of polarizing plates according to any one of claims 1 to 4 and a liquid crystal cell, wherein the viewing side polarizing plate and the back side polarizing plate are attached to the liquid crystal cell via the pressure-sensitive adhesive layer . A liquid crystal display panel characterized by that.

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