KR102241901B1 - Optical laminate and display device using same - Google Patents

Abstract

A transparent front plate (COV), an ultraviolet curable adhesive layer (ADH), a polarizing plate (POL2), a pressure sensitive adhesive layer (not shown), and a transparent substrate (SUB2) are arranged in this order, and the ultraviolet curable adhesive layer (ADH) is , The ester moiety is formed of an ultraviolet curable adhesive composition containing an acrylic acid ester monomer having 6 to 11 carbon atoms, and the pressure-sensitive adhesive layer is bonded to an alkali-free glass substrate in an area of 25 mm × 25 mm, at a temperature of 23° C. When a load of 3 kg is applied under the condition of 55% relative humidity, an optical laminate having a creep amount after 3,000 seconds in the range of 90 to 1,000 µm is provided.

Description

Optical laminated body and a display device using the same TECHNICAL FIELD

The present invention relates to an optical laminate used in a liquid crystal display (LCD) or an organic electro-luminescence display (OLED).

BACKGROUND ART Display devices such as LCDs are widely used in mobile phones, televisions, navigation systems for automobiles, electronic books, and other various portable terminals. In addition, optical films, such as a polarizing plate and a retardation plate, and a pressure-sensitive adhesive layer for bonding them, are laminated and used in display devices such as LCDs. In particular, recently, in order to provide an input function on a display screen, a touch panel type with a touch sensor module has been developed. In this touch panel type, since a human finger touches and inputs the screen of a display device such as an LCD, a cover glass or the like is used on the display surface to prevent damage due to friction or the like.

For example, in Japanese Patent Laid-Open No. 2009-69321 (Patent Document 1), in a display device in which a transparent cover is adhered to the observer side through an adhesive of a liquid crystal display panel having a polarizing plate on the observer side surface, a transparent cover on the display panel It is disclosed that the adhesive for adhering to is configured to cover the entire side surface of the polarizing plate. Thereby, the exposure of the side surface of the polarizing plate is prevented, and the problem that atmospheric moisture enters from the side surface of the polarizing plate and the vicinity of the end portion of the polarizing plate expands is solved. However, in the case of applying the adhesive, since the uncured adhesive component comes into contact with the pressure-sensitive adhesive (pressure-sensitive adhesive) that adheres the polarizing plate to the substrate, photocuring is insufficient while the adhesive is cured or under the light-shielding film. In the discarded place, there is a problem that the pressure-sensitive adhesive layer bonding the polarizing plate to the substrate is deformed.

Due to such deformation of the pressure-sensitive adhesive layer, linear or dotted reflection unevenness may be observed at the end of the display screen of the display device. In Fig. 1, an example of the occurrence of such linear or dotted reflection unevenness 4 is shown in a schematic front view. In Fig. 1, the display device 1 has a display screen 2 in the center, the periphery of the display screen 2 is covered with a frame-shaped light-shielding film 3, and a speaker ( 5) A microphone 6 is arranged. In the display device 1 configured as described above, there was a case where a linear or dotted reflection unevenness 4 was observed at the end of the display screen 2. In particular, since the printed width (distance from the outermost side of the display device 1 to the display screen 2) of the frame-shaped light-shielding film 3 has become smaller in recent years, reflection unevenness due to deformation of the pressure-sensitive adhesive layer (4) This became noticeable.

An object of the present invention is to provide an optical laminate in which a transparent front plate is laminated on a display device such as an LCD through an ultraviolet curable adhesive layer, and the deformation in the portion of the polarizing plate is suppressed. In addition, another object of the present invention is to provide a display device such as an LCD in which linear or dotted reflection unevenness at the end of the display screen of the display device is prevented from occurring due to the deformation of the polarizing plate.

The present inventors, as a result of repeated intensive research in order to solve the above problems, in a display device such as an LCD in which a transparent front plate is laminated through an ultraviolet curable adhesive layer, a composition for forming an ultraviolet curable adhesive layer, a polarizing plate, etc. Due to the properties of the pressure-sensitive adhesive for bonding the optical film to the substrate of the display device, it is possible to suppress the deformation of the end of the optical film and suppress the linear or dotted reflection unevenness that tends to occur at the end of the display screen of the display device. The present invention was completed by discovering a new fact that there is.

That is, the present invention is an optical laminate in which a transparent front plate, an ultraviolet curable adhesive layer, a polarizing plate, a pressure sensitive adhesive layer, and a transparent substrate are arranged in this order, wherein the ultraviolet curable adhesive layer is acrylic acid having 6 to 11 carbon atoms in the ester moiety. It is formed of an ultraviolet curable adhesive composition containing an ester monomer, and the pressure-sensitive adhesive layer is bonded to an alkali-free glass substrate in an area of 25 mm × 25 mm, and 3 kg under conditions of a temperature of 23° C. and a relative humidity of 55%. It is to provide an optical laminate having a creep amount in the range of 90 to 1,000 µm after 3,000 seconds when a load of is applied.

The transparent front plate is composed of a frame-shaped light-shielding film printed, and the optical laminate of the present invention is particularly effective when the width of the portion overlapping with the polarizing plate is within 2 mm. In addition, the transparent front plate preferably has a thickness in the range of 0.25 mm to 2 mm.

The present invention also provides a display device in which any of these optical laminates are disposed on a display surface.

A method of manufacturing an optical laminate by attaching a polarizing plate to a glass substrate through a pressure-sensitive adhesive and then attaching a transparent front plate to the surface of the polarizing plate through an ultraviolet-curable adhesive, wherein the ultraviolet-curable adhesive layer has an ester moiety of carbon number. Formed from an ultraviolet curable adhesive composition containing an acrylic acid ester monomer of 6 to 11, and the pressure-sensitive adhesive layer was bonded to an alkali-free glass substrate in an area of 25 mm×25 mm, and had a temperature of 23°C and a relative humidity of 55%. Also disclosed is a method for producing an optical laminate selected from those in which the creep amount after 3,000 seconds is in the range of 90 to 1,000 µm when a load of 3 kg is applied under the conditions. The optical laminate produced by this method can also be applied to a display surface of a display device.

Advantageous Effects of Invention According to the present invention, in an optical laminate having a structure in which a transparent front plate is laminated on a display device such as an LCD through an ultraviolet curable adhesive layer, it is possible to suppress deformation at the end of the polarizing plate. In addition, it is possible to provide a display device such as an LCD in which linear or dotted reflection unevenness, which tends to occur at the end of the display screen of the display device due to the deformation of the polarizing plate, is prevented.

1 is a front view schematically illustrating a conventional display device with a transparent front plate in which a linear or dotted reflection unevenness occurs.
2 is a schematic cross-sectional view showing a layer structure of an optical laminate.
3 is a perspective view schematically showing a state in which a transparent front plate is bonded to a liquid crystal cell via an ultraviolet curable adhesive.
4 is a plan view schematically showing a state in which a chemical is adhered to a cut end surface of a polarizing plate with a pressure-sensitive adhesive bonded to glass.
5 is a plan view and a cross-sectional view schematically showing a state in which a chemical attached to a cut end surface of a polarizing plate with a pressure-sensitive adhesive bonded to glass is covered with a cover glass.
6 is a plan view and a cross-sectional view schematically showing a state in which a change in height in the in-plane center direction from the cut end surface of the polarizing plate is measured after a chemical is attached to the cut end surface of the polarizing plate.
7 is a graph showing an example of the measurement result of the height change from the cut end surface A of the polarizing plate toward the in-plane center direction A'.

[Optical laminate]

The optical laminate of the present invention is a transparent front plate, an ultraviolet curable adhesive layer, a polarizing plate, a pressure sensitive adhesive layer, and a transparent substrate arranged in this order, and is used for LCD and OLED. Regarding the present invention, a case where the display device is an LCD will be described in detail below with reference to Fig. 2, but the present invention is not particularly limited thereto.

[LCD]

In Fig. 2, in the LCD, a liquid crystal compound (LC) is sealed between two substrates SUB1 and SUB2 on which pixel electrodes are formed, a voltage is applied between the electrodes of the two substrates, and the encapsulated liquid crystal compound is The orientation is controlled to display an image. In this way, a structure in which a liquid crystal compound is enclosed between two substrates is usually referred to as a liquid crystal cell. The circumference of the liquid crystal cell is sealed with a sealing material (SEAL). This LCD itself does not emit light by itself, and uses the light emitted from a light source such as the backlight unit (BL) to polarize the light through a polarizing plate (POL1) on the incident side first, and pass through the liquid crystal compound (LC). While controlling the amplitude surface of the light, the image is displayed by passing or absorbing the light through another polarizing plate POL2 arranged on the display surface. In the present invention, a display device in which a transparent front plate (COV) is bonded to the outside (outermost surface) of a polarizing plate (POL2) disposed on the display surface side through an ultraviolet curable adhesive layer (ADH), or an optical laminate used therein It targets. A frame-shaped light-shielding film BLK corresponding to the light-shielding film 3 for partitioning the display screen 2 in FIG. 1 is printed on the outer periphery of the surface of the transparent front plate COV bonded to the polarizing plate POL2.

The polarizing plates POL1 and POL2 are usually bonded to the substrates SUB1 and SUB2 of the LCD through a pressure-sensitive adhesive. However, in FIG. 2, the layer formed from this pressure-sensitive adhesive (pressure-sensitive adhesive layer) is omitted. By using a pressure-sensitive adhesive, when the polarizing plate is adhered to the liquid crystal cell, even if the polarizing plate cannot be adhered in the correct direction or when dust enters between the polarizing plate and the liquid crystal cell, the polarizing plate is peeled off and a new polarizing plate is adhered. This enables the manufacture of LCDs without discarding expensive liquid crystal cells.

[Polarizing plate (POL1, POL2)]

Polarizing plates (POL1, POL2) are usually uniaxially stretched, and a polarizing film made of a polyvinyl alcohol-based film in which a dichroic substance is adsorbed and oriented, and a transparent resin film such as a triacetyl cellulose (TAC) film, which is a protective film, is an adhesive. It is manufactured by bonding with. Hereinafter, a polarizing film, a protective film, and an adhesive are further described in order.

The polarizing film is uniaxially stretched and is made of a polyvinyl alcohol-based resin film in which a dichroic substance is adsorbed and oriented. The polyvinyl alcohol-based resin is obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and other monomers copolymerizable therewith in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

What formed such a polyvinyl alcohol-type resin into a film becomes the original film of a polarizing film. The method of forming a film of the polyvinyl alcohol-based resin is not particularly limited, and it can be formed by a known method. It is preferable that the thickness of a polarizing film is 30 micrometers or less from a viewpoint of thinning. By making the thickness of a polarizing film 30 micrometers or less, it can be set as a thin polarizing plate and furthermore a liquid crystal display panel. The polarizing film is stretched and oriented, and a dichroic substance is adsorbed thereto, thereby exhibiting a function as a polarizing film, 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-based resin used for the polarizing film preferably has a degree of saponification of 80 mol% or more, further 90 mol% or more, particularly 94 mol% or more. If the degree of saponification is too low, there is a possibility that water resistance and moist heat resistance after setting as a polarizing plate will not be sufficient. In addition, it may be a completely saponified product, but if the degree of saponification is too high, the dyeing speed becomes slow, and in order to provide sufficient polarization performance, the manufacturing time may be lengthened, or in some cases, a polarizing film having sufficient polarization performance may not be obtained. Therefore, the degree of saponification is preferably 99.5 mol% or less, and further preferably 99 mol% or less.

Here, the degree of saponification is the ratio of the acetic acid group (acetoxy group) contained in the polyvinyl acetate-based resin, which is a raw material of the polyvinyl alcohol-based resin, to a hydroxyl group by saponification treatment, expressed as a unit ratio (mol%), and the following formula Is defined as

Saponification degree (mol%) = [number of hydroxyl groups/(number of hydroxyl groups + number of acetic acid groups)] × 100

The higher the degree of saponification, the greater the proportion of hydroxyl groups, and thus, the smaller the proportion of acetic acid groups that inhibit crystallization. The saponification degree can be calculated|required by the method prescribed|regulated in JIS K 6726-1994 "Polyvinyl alcohol test method." 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, more preferably 2,000 to 5,000. The average degree of polymerization of the polyvinyl alcohol-based resin can also be determined by the method prescribed in JIS K 6726-1994 "Polyvinyl Alcohol Test Method".

The dichroic material adsorbed on the polarizing film may be iodine or a dichroic organic dye. Dichroic organic dyes include, for example, 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, etc. are mentioned. These dyes are available on the market. The dichroic substances may be used individually or in combination of two or more.

The protective film of the polarizing film is an acetyl cellulose resin film, an olefin resin film, a cycloolefin resin film, a polymethyl methacrylate film, etc., using triacetyl cellulose as a representative example, and has a high transmittance, thin, and uniform thickness. It is excellent in durability, optical properties such as retardation are preferable, mechanical properties such as shrinkage at the time of heating are also preferable, and a sufficient supply amount is obtained. Triacetyl cellulose film is a representative one. As a triacetyl cellulose film, "Fuji Tac Film" sold by Fuji Film Co., Ltd. as a commercial product, and "Konica Minolta TAC film" sold by Konica Minolta Advanced Layer Co., Ltd. are mentioned. As an olefin resin film, a polypropylene film, a polyethylene film, etc. are mentioned. As a cycloolefin resin film, "ZEONOR" sold by Nippon Xeon Co., Ltd. is mentioned. As a polymethyl methacrylate-based film, it is a polymer containing an alkyl methacrylate ester as a main constituent monomer, and may be a homopolymer of methacrylic acid ester, a copolymer using two or more methacrylic acid esters, or methacrylic acid ester. It may be a copolymer of an acid ester and a monomer copolymerizable therewith.

An adhesive is used for adhesion between the polarizing film and the protective film. The adhesive is not particularly limited as long as it can bond the polarizing film and the protective film, but those satisfying sufficient adhesive strength and transparency are selected. From this point of view, an ultraviolet curable adhesive is preferably used for bonding of the polarizing film and the protective film. In addition, in addition to the ultraviolet-curable resin, an aqueous adhesive, such as an aqueous solution of a polyvinyl alcohol-based resin, or an aqueous solution in which a crosslinking agent is added, or a urethane emulsion adhesive may be used for bonding the polarizing film and the acetyl cellulose resin film. . The adhesion surface of the film to be bonded may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, frame (flame) treatment, and saponification treatment in order to improve adhesion. The saponification treatment is performed by immersing the film in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

For the adhesion of the polarizing film and the protective film, an ultraviolet curable adhesive is preferably used, but this is different from the ultraviolet curable adhesive used to laminate the transparent front plate and the polarizing plate. The ultraviolet curable adhesive used for bonding the polarizing film and the protective film will be referred to as an ultraviolet curable adhesive (B). This ultraviolet curable adhesive (B) can be a mixture of an acrylic compound and a photoradical polymerization initiator, or a mixture of an epoxy compound and a photocationic polymerization initiator. Further, a cationic polymerizable epoxy compound and a radical polymerizable acrylic compound may be used in combination, and a photocationic polymerization initiator and a photoradical polymerization initiator may be used together as an initiator.

In the case of using an ultraviolet curable adhesive (B), the adhesive is cured by irradiating ultraviolet rays after laminating the film. The ultraviolet light source is not particularly limited, but it is preferable to have a light emission distribution at a wavelength of 400 nm or less, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, Metal halide lamps and the like are preferably used.

The light irradiation intensity for curing the ultraviolet curable adhesive (B) is appropriately determined according to the composition of the adhesive, and is not particularly limited, but the irradiation intensity in the wavelength region effective for activation of the photopolymerization initiator is 0.1 to 6000 mW/cm2. It is desirable to do it. By appropriately selecting the irradiation intensity within this range, the reaction time is not too long, and yellowing of the adhesive due to heat radiated from the light source and heat generated during curing of the adhesive, and deterioration of the polarizing film can be suppressed. The light irradiation time is also selected depending on the adhesive to be cured and is not particularly limited, but it is preferable that the accumulated light amount expressed as the product of the irradiation intensity and the irradiation time is set to be 10 to 10,000 mJ/cm 2. By appropriately selecting the accumulated amount of light within this range, a sufficient amount of active species derived from the photopolymerization initiator is generated, the curing reaction reliably proceeds, and the irradiation time is not too long, so that good productivity can be maintained. When the ultraviolet-curable adhesive (B) of a polarizing film or a film containing a protective film is cured by irradiation with ultraviolet rays, various functions of the polarizing plate such as polarization degree, transmittance and color of the polarizing film, and transparency of the protective film are not deteriorated. It is preferable to perform curing under conditions that do not. In addition, an acrylic compound and a photo radical polymerization initiator can also be used in combination for the ultraviolet curable adhesive (B).

In the case of using a water-based adhesive, for example, a method of uniformly applying the adhesive to the surface of the film or flowing the adhesive between two films, overlapping the two films through the coating layer, bonding with a roll, etc. to dry. Can be employed. After drying, it may also be cured at room temperature or at a temperature slightly higher than that, such as about 20 to 45°C. The thickness of the adhesive layer is appropriately selected in the range of about 0.001 to 5 µm, depending on the type of adhesive or a combination of the two films to be adhered. This thickness is preferably 0.01 µm or more, and preferably 2 µm or less.

[Phase difference film and optical compensation film]

In addition, in an LCD, since light passes through the liquid crystal compound layer enclosed between two substrates and is emitted from the display surface, when observed from an oblique direction, the outgoing light changes to normal light and abnormal light, resulting in a phase difference. have. At this time, it is known that a phenomenon called a color shift occurs because the phase difference is different for each wavelength of light depending on the thickness of the liquid crystal compound layer, and an image cannot be displayed in a normal color. In addition, in order to eliminate and compensate for the retardation occurring in the liquid crystal compound layer of such a liquid crystal cell, a film formed by stretching a resin film or an optically anisotropic material using a separate liquid crystal compound as a representative example is applied and aligned. A method of arranging a layer to be formed and passing through it to display an image is known. These stretch-oriented resin films and films having layers of optically anisotropic substances are usually referred to as retardation films or optical compensation films. These retardation films and optical compensation films may be used by bonding to a polarizing film as a protective film of a polarizing plate, or may be used by bonding to a polarizing plate through a pressure-sensitive adhesive or an adhesive.

The retardation film formed by stretching of a resin film can be composed of a polycarbonate-based resin, a cycloolefin-based resin, an acetyl cellulose-based resin using triacetyl cellulose as a representative example, or the like. These resins express appropriate in-plane retardation Re and thickness direction retardation Rth by uniaxial stretching or biaxial stretching, and by addition of an additive for expressing a retardation. The index of biaxiality is expressed by the Nz coefficient. When the refractive index of the birefringent film in the in-plane slow axis direction is n _x , in the direction perpendicular to the slow axis in the plane, that is, the refractive index in the fast axis direction is n _y , the refractive index in the thickness direction is n _z , and the thickness of the film is d , In-plane retardation Re, thickness direction retardation Rth, and Nz coefficients 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 coefficients can be measured using a commercially available retardation measuring device. Examples of commercially available phase difference measuring devices include the "KOBRA" series sold by Oji Measuring Instruments Co., Ltd., such as "KOBRA-21 ADH" and "KOBRA WR".

As for the retardation film made of the above-exemplified resin, those having various optical properties are commercially available from respective resin manufacturers. Examples of commercially available products corresponding to the retardation film made of a cycloolefin resin as a brand name include "Aton Film" sold by JSR Corporation, and "Zeonoa Film" sold by Nippon Xeon Corporation.

An optical compensation film formed by coating and orientation of an optically anisotropic substance is one in which an optically anisotropic substance such as a liquid crystal compound is applied to the surface of a base film and aligned, and the orientation is fixed. Examples of commercially available products equivalent to such optical compensation films as brand names are "WV film" sold by Fujifilm Co., Ltd., "NH film" and "NV film" sold by JX Nikko Nisseki Energy Co., Ltd. Etc.

[Pressure-sensitive adhesive layer]

A pressure-sensitive adhesive layer is formed on the bonding surface of the polarizing plate to be bonded to the transparent substrate of the liquid crystal cell. This pressure-sensitive adhesive layer is usually made 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. Among these, a pressure-sensitive adhesive made of an acrylic resin excellent in transparency, weather resistance, heat resistance and the like as a base polymer is preferably used. In particular, it is preferable to select and use those that maintain adequate wettability and cohesion, are excellent in adhesion to a transparent protective film or a polarizing film, and do not cause peeling problems such as lifting or peeling under conditions of heating or humidification. Moreover, a pressure-sensitive adhesive called an energy ray curable type may be used. Moreover, it can also be set as the pressure-sensitive adhesive layer which contains fine particles and exhibits light scattering property.

The pressure-sensitive adhesive layer used in the present invention is formed on the surface of a suitable substrate, such as a polarizing plate, and bonded to an alkali-free glass substrate in an area of 25 mm×25 mm, and weighing 3 kg under conditions of a temperature of 23°C and a relative humidity of 55%. When a load is applied, it is assumed that the creep amount after 3,000 seconds is in the range of 90 to 1,000 µm. This creep amount is measured, for example, by cutting a polarizing plate provided with a pressure-sensitive adhesive layer into a short side of 25 mm x a long side of 100 mm, and bonding the pressure-sensitive adhesive layer to an alkali-free glass substrate with an area of 25 mm x 25 mm therein. , It can be done by applying a load of 3 kg at the above temperature and relative humidity. The creep amount at this time is preferably in the range of 90 to 700 µm, more preferably 90 to 500 µm. Since the pressure-sensitive adhesive layer has the above-described predetermined creep amount, even in the case where the ultraviolet-curable resin is adhered to the end of the polarizing plate in the optical laminate of the present invention, deformation at the end of the polarizing plate in the laminate can be suppressed. In addition, it is possible to prevent linear or dotted reflection unevenness that tends to occur at the end of the display screen of the display device due to the deformation of the polarizing plate. In particular, even when a frame-shaped light-shielding film (BLK) is printed on the transparent front plate (COV) and the width (d) of the overlapping portion of the light-shielding film (BLK) and the polarizing plate (POL2) is within 2 mm, the polarizing plate in the laminated body This is preferable because it is possible to suppress the deformation at the end of (POL2) and to prevent linear or dotted reflection unevenness that tends to occur at the end of the display screen of the display device.

The acrylic resin used to form the pressure-sensitive adhesive layer is, for example, a polymer of (meth)acrylic acid ester such as butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. The composed base polymer or a copolymerized base polymer using two or more of these (meth)acrylic acid esters is preferably used. Further, a polar monomer is copolymerized with these base polymers. As a polar monomer, for example, (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, 2-(N,N-dimethylamino)ethyl (meth) Monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like as a polar functional group, such as acrylate and glycidyl (meth)acrylate, are mentioned. In particular, in the case where the touch panel function is provided on the glass substrate, or in the case where the ITO film is formed for the purpose of providing the antistatic function, the content of the carboxyl group is adjusted by adjusting the content of the hydroxyl group-containing acrylic monomer constituting the base polymer. It is preferable to make it a small composition.

These acrylic resins can be used alone as a pressure-sensitive adhesive, but a crosslinking agent is usually blended. As a crosslinking agent, an isocyanate compound having at least two isocyanate groups (-NCO) in a molecule, forming a urethane bond between a carboxyl group or a hydroxyl group, and an ester between a carboxyl group as a divalent or polyvalent epoxy compound Forming a bond, forming a metal salt between a carboxyl group or a hydroxyl group as a divalent or polyvalent metal ion, and the like are exemplified. Among them, isocyanate compounds are widely used as organic crosslinking agents.

Specific examples of the crosslinking agent composed of an isocyanate compound include tolylene diisocyanate, 4,4-diphenylmethane diisocyanate, hexamethylene diisocyanate, xylylene diisocyanate, metaxylylene diisocyanate, 1,5-naphthalene diisocyanate, hydrogenation Diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, and tolylene diisocyanate adducts of trimethylolpropane. Further, a block isocyanate compound in which the isocyanate group in these compounds has undergone condensation reaction is also used as a crosslinking agent.

Examples of commercially available isocyanate-based crosslinking agents include adduct polyisocyanate compounds, such as "Sumizul L" manufactured by Sumika Bayer Urethane Co., Ltd., "Colonate HL" manufactured by Nihon Polyurethane Co., Ltd., and as a biuret polyisocyanate compound. , As a polyisocyanate compound having an isocyanurate ring, "Smizul N", "Death module IL", "Death module HL" manufactured by Sumika Bayer Urethane Co., Ltd., "Colonate manufactured by Nippon Polyurethane Co., Ltd. EH" and the like.

Moreover, as another crosslinking agent, there exists a thing which forms an ester bond with a carboxyl group as a divalent or polyvalent epoxy compound. For example, N,N-diglycidylaniline, N,N-diglycidyltoluidine, mN,N-diglycidylaminophenylglycidyl ether, triglycidyl isocyanurate, polyethylene glycol diglyci Dyl ether, N,N,N',N'-tetraglycidylaminodiphenylmethane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, N,N,N' And N'-tetraglycidyl-m-cyclohexenediamine. Examples of commercially available products of such an epoxy crosslinking agent are polyethylene glycol diglycidyl ether, "Denacol EX-832" and "Denacol EX-841" (all brand names) manufactured by Nagase Chemtex Co., Ltd., N,N. As ,N',N'-tetraglycidyl-m-xylenediamine, "TETRAD-X" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd. is N,N,N',N'-tetraglycidyl- As m-cyclohexenediamine, there is "TETRAD-C" (trade name) manufactured by Mitsubishi Gas Chemical Co., Ltd.

As another crosslinking agent, there is one that forms a metal salt between a carboxyl group or a hydroxyl group as a divalent or polyvalent metal ion. Examples of the metals include aluminum, magnesium, zinc, and calcium, and hydroxides, oxides, and halides such as chloride and bromide of these metals are crosslinking agents. Specific compound names include, for example, aluminum sulfate, aluminum hydroxide, aluminum chloride, and potassium alum.

In addition, it is also effective to blend a silane coupling agent together with a crosslinking agent in the acrylic resin. The silane coupling agent is a compound in which a hydrolyzable group such as an alkoxy group is bonded to a silicon atom, and an organic group having a reactive functional group such as an amino group, an epoxy group, a (meth)acryloyl group, a vinyl group, a halogeno group, or a mercapto group is bonded. I can. As a specific example, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-( 2-Aminoethyl)-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyl Triethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylethoxydimethylsilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-chloropropylmethyldime Toxoxysilane, 3-chloropropyl trimethoxysilane, 3-methacryloyloxypropyl trimethoxysilane, 3-mercaptopropyl trimethoxysilane, etc. are mentioned. Furthermore, an oligomer type silane coupling agent may be used. In the case of an oligomer type, a condensation product of two or more types of monomers may be used.

The creep amount of the pressure-sensitive adhesive layer is appropriately selected by appropriately selecting the type of acrylic resin constituting the pressure-sensitive adhesive composition (adhesive composition) used to form the pressure-sensitive adhesive layer, the type and amount of the crosslinking agent, and the type and amount of the silane coupling agent. It can be controlled by combining. For example, it is one of the preferred embodiments to use a pressure-sensitive adhesive composition in which a high molecular weight acrylic resin (1) and a low molecular weight acrylic resin (2) shown below are combined, and a crosslinking agent and a silane coupling agent are added thereto. Such a preferable pressure-sensitive adhesive composition is described in Japanese Unexamined Patent Application Publication No. 2006-316256.

High molecular weight acrylic resin (1): the following formula (I)

(In the formula, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group or aralkyl group having 1 to 14 carbon atoms, but _{the hydrogen atom constituting R 2} may be substituted with an alkoxy group having 1 to 10 carbon atoms. )

A (meth)acrylic structural unit (a) derived from a (meth)acrylic acid ester represented by and a polar functional group-containing structural unit derived from a polar functional group-containing monomer having at least one polar functional group and one olefinic double bond in the molecule ( b), and a weight average molecular weight of 1 million to 2 million acrylic resins.

Low molecular weight acrylic resin (2): An acrylic resin containing the (meth)acrylic structural unit (a) and the polar functional group-containing structural unit (b) and having a weight average molecular weight of 50,000 to 500,000.

The polar functional group constituting the polar functional group-containing monomer is specifically selected from the group consisting of a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, an oxetanyl group, an aldehyde group (-CHO), and an isocyanate group (-NCO). do. It is preferable that the polar functional group-containing monomer is also (meth)acrylic, that is, (meth)acrylic acid itself or a derivative thereof. In particular, a monomer having a carboxyl group such as acrylic acid or methacrylic acid, and a monomer having a hydroxyl group such as 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate, are preferably used as a polar functional group-containing monomer. do.

The low molecular weight acrylic resin (2) is preferably mixed and used in a ratio of 5 to 40 parts by weight, further 10 to 30 parts by weight, particularly 10 to 20 parts by weight, based on 100 parts by weight of the high molecular weight acrylic resin (1). .

The crosslinking agent blended in the acrylic resin, which is a mixture of the high molecular weight acrylic resin (1) and the low molecular weight acrylic resin (2), is an acrylic resin (a high molecular weight acrylic resin (1) and a low molecular weight acrylic resin (2)). Total) It is preferably used in an amount of 0.1 to 10 parts by weight, further 0.5 to 5 parts by weight, particularly 1 to 3 parts by weight, based on 100 parts by weight. As the crosslinking agent in this case, the isocyanate compound described above, the divalent or polyvalent epoxy compound, and the divalent or polyvalent metal ion may be used alone, or they may be appropriately mixed and used. In the case of mixing and using two or more types of crosslinking agents, it is preferable to make the total amount thereof within the above range in the pressure-sensitive adhesive composition.

The silane coupling agent may be used alone or in combination of two or more of those described above. The silane coupling agent is 0.01 to 3 parts by weight, further 0.05 to 2 parts by weight, based on 100 parts by weight of an acrylic resin (the sum of the high molecular weight acrylic resin (1) and the low molecular weight acrylic resin (2)) in the pressure-sensitive adhesive composition, In particular, it is preferably used in a proportion of 0.1 to 1 part by weight.

[Method of forming pressure sensitive adhesive layer]

For the formation of the pressure-sensitive adhesive layer, a conventionally known method may be employed. For example, (1) a method of applying the above-described pressure-sensitive adhesive composition to the surface of a polarizing plate, drying it, and curing it by irradiating energy rays as necessary, or (2) ) A method of transferring the pressure-sensitive adhesive layer to the surface of a polarizing plate from the laminate in which the pressure-sensitive adhesive layer was previously formed on the surface of the separator, etc. are mentioned. When a pressure-sensitive adhesive layer is formed by the former method, it is preferable to bond a separator to protect the pressure-sensitive adhesive layer. Further, from the viewpoint of enhancing the adhesion between the adherend surface of the polarizing plate and the pressure-sensitive adhesive layer, it is preferable to perform corona treatment on the adherend surface.

In the pressure-sensitive adhesive layer, a pressure-sensitive adhesive composition obtained by dissolving or dispersing each of the above components in an organic solvent such as toluene or ethyl acetate to obtain a solid content concentration of about 10 to 40% by weight is applied on a substrate and dried to form organic solvents. It can be formed by removing a solvent. In the case of an energy ray-curable pressure-sensitive adhesive, a desired cured product can be obtained by irradiating the thus formed coating film with energy rays such as ultraviolet rays or electron beams.

The thickness of the pressure-sensitive adhesive layer is usually about 1 to 40 µm, but in order to reduce the thickness of the polarizing plate without impairing workability or durability, it is preferably 3 to 25 µm, and more preferably 15 to 25 µm. When the pressure-sensitive adhesive layer is too thin, the adhesiveness decreases, and when the pressure-sensitive adhesive layer is too thick, problems such as protruding of the pressure-sensitive adhesive are likely to occur. In the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer, in addition to the base polymer, the crosslinking agent and the silane coupling agent, if necessary, in order to adjust the adhesion, cohesive force, viscosity, elastic modulus, glass transition temperature, etc. of the pressure-sensitive adhesive, for example, a natural product. In addition, suitable additives such as synthetic resins, tackifier resins, antioxidants, dyes, pigments, antifoaming agents, corrosive agents, photopolymerization initiators, and ultraviolet absorbers may also be blended. Examples of the ultraviolet absorber include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, and nickel complex salt compounds. Moreover, it can also be set as the pressure-sensitive adhesive layer which contains fine particles and exhibits light scattering property. Further, a filler made of glass fibers, glass beads, resin beads, metal powders, other inorganic powders, or the like may be blended.

The energy ray-curable pressure-sensitive adhesive described above has a property of curing by irradiation with energy rays such as ultraviolet rays or electron beams, and has adhesiveness even before irradiation with energy rays, adheres to an adherend such as a film, and cures by irradiation of energy rays. It is a pressure-sensitive adhesive with properties that can be adjusted. As the energy ray-curable pressure-sensitive adhesive, it is particularly preferable to use an ultraviolet-curable pressure-sensitive adhesive. In general, an energy ray-curable pressure-sensitive adhesive has the above-described acrylic resin and an energy ray-polymerizable compound as main components. Usually, a crosslinking agent is further blended, and a photoinitiator, a photosensitizer, etc. may be further blended if necessary.

[Transparent substrate]

The transparent substrates SUB1 and SUB2 shown in FIG. 2 constitute a liquid crystal cell and sandwich the liquid crystal. The transparent substrate may be glass or plastic, but glass, particularly alkali-free glass or acrylic resin plate, is preferable. These glass plates and acrylic resin plates have excellent surface smoothness, and their average surface roughness is usually 1.0 nm or less. The transparent substrate constituting the optical laminate of the present invention is SUB2 in FIG. 2.

[Transparent front panel]

The transparent front plate (COV) shown in Fig. 2 may also be made of glass or plastic, and may be one in which a touch panel function is integrated. The transparent front plate is preferably a frame-shaped light-shielding film (BLK) printed, and a polarizing plate (POL2) and a pressure-sensitive adhesive layer (not shown) between the light-shielding film (BLK) of the transparent front plate (COV) and the transparent substrate (SUB2). It is more preferable that the end of) is disposed, and the width d of the portion where the light-shielding film BLK and the polarizing plate POL2 overlap is within 2 mm. In particular, the present invention is preferably used when the area of the light shielding film BLK is narrow. The thickness of the transparent front plate (COV) is preferably in the range of 0.25 mm to 2 mm, and more preferably in the range of 0.5 mm to 1.5 mm, particularly 0.7 mm to 1 mm.

[UV curable adhesive layer]

The transparent front plate COV is bonded to the polarizing plate POL2 on the display surface of the LCD through an ultraviolet curable adhesive layer ADH. The ultraviolet-curable adhesive used to form the ultraviolet-curable adhesive layer (ADH) has a predetermined elastic property even after curing, and has an effect of alleviating the impact even when subjected to an impact. In the present invention, as the ultraviolet-curable adhesive composition before curing, the ester moiety may contain an acrylic acid ester monomer having a bulky group (side chain) having 6 to 11 carbon atoms. The ultraviolet curable adhesive may have both ultraviolet curing properties and thermosetting properties, but an ultraviolet curing component is essential. The thickness of the ultraviolet curable adhesive layer is usually 50 to 800 µm, preferably 70 to 500 µm, and more preferably 100 to 300 µm.

It is preferable that the ultraviolet-curable adhesive layer (ADH) has a refractive index of 1.45 or more and 1.55 or less, particularly 1.51 or more and 1.52 or less, and has a transmittance of 90% or more in the visible light region when the thickness is 100 µm. In addition, it is preferable that this ultraviolet-curable adhesive layer has a shrinkage ratio of 5% or less, further 4.5% or less, particularly 4% or less, at the time of curing by ultraviolet rays. It is still more preferable that the shrinkage rate at this time is 0 to 2%. By using such a low shrinkage ratio, internal stress accumulated when the UV curable adhesive layer (ADH) is cured can be reduced, and the UV curable adhesive layer (ADH) and a polarizing plate (POL2) on the display panel or a transparent front panel (COV) can be reduced. ), it can prevent distortion at the interface.

The ultraviolet-curable adhesive layer (ADH) is composed of oligomers or polymers, acrylate monomers, and photopolymerization initiators as main agents, and other additives such as sensitizers, plasticizers, transparent particles, etc., are added within the scope of the purpose of the present invention. It is obtained by forming a coating layer of an ultraviolet curable adhesive and curing it by irradiating ultraviolet rays thereon. Here, as the oligomer or polymer, polyurethane acrylate, polybutadiene acrylate, polyisoprene acrylate or esterified products thereof, terpene-based hydrogenated resins, butadiene polymers, epoxy acrylate oligomers, and the like can be preferably used. As an acrylate monomer, isobornyl acrylate, dicyclopentenyloxyethyl methacrylate, hydroxymethyl methacrylate, hydroxypropyl methacrylate, hydroxybutyl methacrylate, lauryl acrylate, benzyl acryl Rate and the like can be preferably used.

As a photoinitiator, 1-hydroxycyclohexylphenyl ketone (trade name "IRGACURE 184": manufactured by BASF), 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl) Benzyl}phenyl]-2-methyl-propan-1-one (trade name "IRGACURE 127": manufactured by BASF), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (trade name "DAROCUR1173": BASF company make) etc. can be used suitably. In addition, in order to protect the display panel from ultraviolet rays of sunlight, the transparent front plate COV may be provided with a function of cutting light in the ultraviolet region. In this case, it is preferable to use a photopolymerization initiator that can be cured even in a visible light region (for example, brand name "Speed Cure TPO": manufactured by Nippon Sibel Hegna Co., Ltd.).

[Method of manufacturing optical laminate]

The optical laminate of the present invention is manufactured by the following method. First, a polarizing plate POL2 is bonded to the surface of a transparent substrate SUB2 such as glass constituting a display device such as an LCD or OLED through a pressure-sensitive adhesive. Next, an ultraviolet-curable adhesive is applied to the transparent front plate COV, and is bonded to the surface of the polarizing plate POL2 of the display panel. Then, ultraviolet rays are irradiated from the transparent front plate (COV) side to cure the ultraviolet curable adhesive, thereby manufacturing the optical laminate of the present invention. In the following description, among the display devices, a glass substrate is used as the transparent substrate included in the laminate of the present invention.

In order to bond the polarizing plate POL2 to the surface of the glass substrate SUB2 constituting a display device such as an LCD or OLED through a pressure-sensitive adhesive, a polarizing plate with a pressure-sensitive adhesive layer is bonded to the glass substrate SUB2. As a polarizing plate with a pressure-sensitive adhesive layer, a commercially available polarizing plate can be used, and examples thereof include a polarizing plate "Sumikaran" manufactured by Sumitomo Chemical Co., Ltd., a polarizing plate "Nitto Polarizing Film (NPF)" manufactured by Nitto Denko Corporation, and the like.

In order to bond the display panel or the polarizing plate (POL2) to the transparent front plate (COV) through an ultraviolet curable adhesive, a known method can be used, and problems such as bubbles entering or the ultraviolet curable adhesive protruding from the substrate can be solved. There is no particular limitation as long as it can be suppressed. In general, for example, a transparent front plate (COV) is disposed on a polarizing plate (POL2) of a display panel, and the back surface of the transparent front plate (COV) is brought into contact with an ultraviolet curable adhesive, so that the polarizing plate (POL2) and the transparent front plate (COV) are ) It is possible to adopt a method of interposing an ultraviolet curable adhesive in the voids between. In addition, for example, as shown in FIG. 3, an ultraviolet curable adhesive layer (ADH) is formed on the surface of the transparent front plate (COV), and through the ultraviolet curable adhesive layer, the transparent substrate (SUB1)/liquid crystal layer (not shown) A method of bonding the transparent front plate COV to the polarizing plate POL2 surface of the display panel DIS, which is a stack of transparent substrate SUB2/polarizing plate POL2, may also be employed. At this time, in order to prevent air bubbles from entering or the ultraviolet curable adhesive from protruding from the substrate, the application location and the amount of the ultraviolet curable adhesive are optimized. Thereafter, ultraviolet rays are irradiated from the transparent front plate COV side to the UV-curable adhesive layer on the display panel corresponding to the light-shielding portion non-formation region of the transparent front plate COV.

In this case, for example, as disclosed in Japanese Patent Laid-Open No. 2012-128247, the viscosity of the optical resin constituting the UV-curable adhesive is increased so that the surface of the liquid UV-curable adhesive applied in a dam type does not form a solid peel. To form a dam shape by performing thickening treatment to form a dam shape, an inner dam and an outer dam positioned outside the dam are formed, and the liquid UV-curable adhesive is supplied to the central region of at least one of the bonding surfaces, and the display panel and A method of bonding a transparent front plate or the like can also be employed. The liquid UV-curable adhesive supplied to the central region is extended between the bonding surfaces to cross the inner dam, and the liquid UV-curable adhesive that has crossed the inner dam is transferred from the outermost dam. It is also possible to adopt a method of curing and bonding all liquid UV-curable adhesives interposed between the bonding surfaces by making the gaps between the bonding surfaces and making the gaps between the bonding surfaces predetermined.

In order to cure the ultraviolet curable adhesive by irradiating ultraviolet rays from the transparent front plate (COV) side, an ultraviolet irradiation lamp having a light emission distribution at a wavelength of 400 nm or less is preferably used, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, and a high pressure A mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp, a metal halide lamp, and the like are preferable. The light irradiation intensity for curing the ultraviolet curable adhesive is appropriately determined according to the composition of the adhesive, and is not particularly limited, and is similar to the ultraviolet curable adhesive (B). By appropriately selecting the irradiation intensity, the reaction time is not too long, and yellowing of the adhesive or deterioration of the polarizing plate due to heat radiated from the light source and heat generated during curing of the adhesive can be suppressed. The light irradiation time is also selected depending on the adhesive to be cured, and is not particularly limited, but it is preferable that the accumulated light amount expressed as the product of the irradiation intensity and the irradiation time is set to 10 to 10,000 mJ/cm 2. By appropriately selecting the accumulated amount of light within this range, the active species derived from the photopolymerization initiator are generated in a sufficient amount to reliably advance the curing reaction, and the irradiation time is not too long, so that good productivity can be maintained. In addition, the irradiation direction of ultraviolet rays is not particularly limited, but in order to uniformly cure the ultraviolet curable adhesive layer on the display panel, it is preferable to irradiate the surface of the transparent front plate COV from a perpendicular direction.

Example

Next, examples of the present invention will be described in detail, but the present invention is not limited by these examples. In the examples,% and parts indicating the content to the amount used are based on weight unless otherwise specified.

(Production Example 1)

(A) Preparation of a water-based adhesive used for bonding a polarizing film and a protective film

With respect to 100 parts of water, 3 parts of carboxyl-modified polyvinyl alcohol ["KL-318" obtained from Kuraray Co., Ltd.) is dissolved, and a water-soluble epoxy resin polyamide epoxy resin additive [Taoka Chemical Co., Ltd.] is dissolved in the aqueous solution. ), a brand name "Sumirez resin 650(30)" obtained from ), an aqueous solution having a solid content concentration of 30%] was added to 1.5 parts to obtain a water-based adhesive.

(B) Preparation of polarizing plate

A polyvinyl alcohol film having an average polymerization degree of about 2,400, a saponification degree of 99.9 mol% or more, and a thickness of 75 μm was uniaxially stretched by about 5 times in a dry manner, and immersed in pure water at 60° C. for 1 minute while maintaining a tension state, and then iodine/ It was immersed in an aqueous solution having a weight ratio of potassium iodide/water of 0.05/5/100 at 28°C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 at 72°C for 300 seconds. Subsequently, after washing with pure water at 26° C. for 20 seconds, it was dried at 65° C. to prepare a polarizing film in which iodine is adsorbed and oriented to polyvinyl alcohol.

To one side of this polarizing film, a 40 μm-thick triacetyl cellulose film (trade name "Konica Tac KC4UYW" obtained from Konica Minolta Advanced Layer Co., Ltd.) was bonded to the surface of which saponification was applied, and the other side was , Corona discharge treatment was performed on one side of a 23 µm-thick cyclic olefin resin film [brand name "Zeonoa film ZF14-023" obtained from Nippon Xeon Co., Ltd.], and the corona discharge treated side was bonded to form a polarizing plate. Made. For bonding, the aqueous adhesive shown above was used, and dried at 80° C. for 5 minutes after bonding to bond the triacetyl cellulose film and the cyclic olefin resin film to the polarizing film. The obtained polarizing plate was then cured at 40°C for 168 hours.

(C) Preparation of pressure-sensitive adhesive sheet

Pressure sensitive adhesive sheet A:

<Preparation of high molecular weight acrylic resin (1)>

In a reaction vessel equipped with a cooling tube, a nitrogen inlet tube, a thermometer and a stirrer, a mixed solution of 80 parts of ethyl acetate as a solvent, 99 parts of butyl acrylate as a monomer (A-1) and 1 part of acrylic acid was put, and air in the apparatus with nitrogen gas. The internal temperature was increased to 55° C. while replacing and not including oxygen. Thereafter, a total amount of a solution in which 0.14 parts of azobisisobutyronitrile (polymerization initiator) was dissolved in 10 parts of ethyl acetate was added. After the initiator was added, the temperature was maintained at this temperature for 1 hour, and then ethyl acetate was continuously added into the reaction vessel at an addition rate of 17.3 parts/hr while maintaining the internal temperature at 54 to 56°C, and the concentration of the acrylic copolymer was reduced to 35%. At this point, the addition of ethyl acetate was stopped, and the temperature was kept at this temperature until 12 hours had elapsed from the start of addition of ethyl acetate. Finally, ethyl acetate was added to adjust the concentration of the acrylic copolymer to 20%, to prepare an ethyl acetate solution of the acrylic copolymer. In the obtained acrylic copolymer, the weight average molecular weight Mw in terms of polystyrene by gel permeation chromatography (GPC) was 1.3 million, and the ratio Mw/Mn of the weight average molecular weight Mw and the number average molecular weight Mn was 3.7. Let this be a high molecular weight acrylic resin (1).

<Preparation of low molecular weight acrylic resin (2)>

230 parts of ethyl acetate were put in the same reaction vessel as that used in the preparation of the high molecular weight acrylic resin (1), and the air in the apparatus was replaced with nitrogen gas to make it oxygen-free, and then the internal temperature was raised to 75°C. After adding the total amount of the solution in which 0.50 parts of azobisisobutyronitrile was dissolved in 10.0 parts of ethyl acetate, and maintaining the internal temperature at 74 to 76°C, as monomers 35 parts of butyl acrylate, 44 parts of butyl methacrylate, 20 parts of methyl acrylate And a mixed solution of 1 part of 2-hydroxyethyl acrylate was dripped into the reaction system over 3 hours. After that, the mixture was kept at an internal temperature of 74 to 76°C for 5 hours to complete the reaction. The obtained acrylic copolymer had a weight average molecular weight Mw of 100,000 in terms of polystyrene by GPC. Let this be a low molecular weight acrylic resin (2).

<Production of pressure sensitive adhesive sheet A>

70 parts of the high molecular weight acrylic resin (1) and 30 parts of the low molecular weight acrylic resin (2) (100 parts in total) were added to the adduct body of tolylene diisocyanate as a crosslinking agent (trade name: Colonate L, Nippon Polyurethane Industrial Co., Ltd.) Manufacture) 3 parts and silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed with 0.3 parts, diluted with methyl ethyl ketone so that the concentration was 15%, and the pressure-sensitive adhesive composition (pressure-sensitive adhesive A) was prepared. Got it. This pressure-sensitive adhesive composition was coated on a 38 µm-thick polyethylene terephthalate film (separator) with a bar coater so that the thickness after drying was 25 µm, and then dried to obtain a pressure-sensitive adhesive sheet A.

Pressure-sensitive adhesive sheets B and C used the following obtained from a pressure-sensitive adhesive manufacturer.

Pressure-sensitive adhesive sheet B: A pressure-sensitive adhesive layer having a thickness of 25 µm made of an acrylic acid ester copolymer containing a hydroxyl group is formed on a polyethylene terephthalate film (separator) having a thickness of 38 µm.

Pressure-sensitive adhesive sheet C: An acrylic resin containing butyl acrylate as a main component and a small amount of 2-hydroxyethyl acrylate and acrylic acid is copolymerized with an isocyanate crosslinking agent and a silane compound having a thickness of 25 µm, having a thickness of 38 What is formed on a µm polyethylene terephthalate film (separator).

(D) Preparation of polarizing plate with pressure sensitive adhesive

Corona discharge treatment was performed on the side of the cyclic olefin resin film of the polarizing plate produced in the above (B), and a pressure-sensitive adhesive sheet A was bonded to the corona discharge treatment surface to obtain a polarizing plate A with a pressure-sensitive adhesive.

In addition, in bonding the pressure-sensitive adhesive sheet to each film, while moving each film or sheet at a speed of 10 m/min, corona discharge treatment was performed on each bonding surface at an output strength of 280 W, and the pressure-sensitive adhesive sheet and It bonded after improving the adhesiveness of a film.

<Corona discharge device>

In this example, all of them are manufactured by Kasuga Electric Co., Ltd., and a corona discharge device having a corona surface treatment frame of "STR-1764", a high-frequency power supply "CT-0212", and a high-voltage transformer "CT-T02W" was used. .

(Production Example 2)

Except having changed the pressure-sensitive adhesive sheet A to the pressure-sensitive adhesive sheet B, it carried out similarly to Example 1, and produced the polarizing plate B with a pressure-sensitive adhesive.

(Production Example 3)

Except having changed pressure-sensitive adhesive sheet A to pressure-sensitive adhesive sheet C, it carried out similarly to Example 1, and produced the polarizing plate C with a pressure-sensitive adhesive.

(Measurement of creep amount of pressure sensitive adhesive)

A pressure-sensitive adhesive is bonded to a polarizing plate "SRW062A" (trade name) manufactured by Sumitomo Chemical Co., Ltd. At this time, corona discharge treatment was performed on the pressure-sensitive adhesive layer side and the polarizing plate side under the conditions of 280 W and 10 m/min. Then, after cutting into a size of 25 mm x 100 mm, this was bonded to an alkali-free glass ("Eagle-XG" manufactured by Corning), and then autoclaved under the conditions of 0.5 MPa, 50°C and 20 minutes. , Prepare a test piece for measuring the amount of creep. After curing the prepared sample piece in an environment of 23°C x 55% for 24 hours, a load of 3 kg is applied so that it becomes parallel to the long side of the test piece. The amount of displacement of the pressure-sensitive adhesive layer from the initial stage to 3000 seconds is measured with a laser displacement meter ("LK-G15" manufactured by KEYENCE Corporation), and is taken as the amount of creep. The creep amount measured for each pressure-sensitive adhesive sheet produced in the above Production Example is summarized in Table 1.

(Measurement of storage modulus of pressure sensitive adhesive)

Two 25±1 mg spherical samples are prepared from a pressure-sensitive adhesive sheet, and each of these samples is placed between three plate jigs to prepare a sample piece. Storage modulus (G') at 23°C and 80°C for the sample piece by using a dynamic viscoelasticity measuring device "DVA-200" manufactured by Haiti Measuring Control Co., Ltd. by a non-resonant forced vibration method with a frequency of 10 Hz. Measure The storage modulus of the pressure-sensitive adhesive layer obtained at 23°C and 80°C was taken as a measurement value. Table 1 summarizes the storage modulus (G') measured for each pressure-sensitive adhesive sheet used in the above production example.

(Example 1)

After cutting the polarizing plate A with a pressure-sensitive adhesive prepared in Preparation Example 1 to a size of 50 mm × 50 mm, this was bonded to an alkali-free glass ("Eagle-XG" manufactured by Corning), followed by 0.5 MPa, 50°C, 20 An autoclave treatment is performed on the condition of minutes, and a test piece for measuring the deformation of a polarizing plate is prepared.

Place the polarizing plate A with pressure-sensitive adhesive bonded to the glass on a horizontal laboratory table, add 0.01 mL of each of the following chemicals to the cut end surface of the polarizing plate A with pressure-sensitive adhesive, and attach the chemicals to the cut surface to prevent volatilization of the chemicals. In order to do this, a cover glass was covered and left to stand for 1 hour in an environment of 23°C and 55% relative humidity (see Figs. 4 and 5).

<Chemicals used in the test for measuring the amount of deformation of the polarizing plate>

2HEA: 2-hydroxyethyl acrylate (manufactured by Kanto Chemical Co., Ltd.), the ester moiety is 2-hydroxyethyl, and its carbon number is 2.

4HBA: 4-hydroxybutyl acrylate (manufactured by Nippon Kasei Co., Ltd.), the ester moiety is 4-hydroxybutyl, and its carbon number is 4.

2PEA: 2-phenoxyethyl acrylate (manufactured by Nippongo Sei Chemical Co., Ltd.), the ester moiety is 2-phenoxyethyl, and its carbon number is 8.

2EHA: 2-ethylhexyl acrylate (manufactured by Nippon Shokubai Co., Ltd.), the ester moiety is 2-ethylhexyl, and its carbon number is 8.

After removing the cover glass, the remaining chemical was wiped off with a cloth, and left to stand for 24 hours in an environment of 23°C and 55% relative humidity, and then the height change from the cut end surface of the polarizing plate toward the in-plane center direction was measured. Further, as a reference, the change in height from the cut end surface of the polarizing plate immediately after the glass cover was removed and the remaining chemical was wiped off with a cloth was also performed.

For the measurement, "Imaging Profiler PLμ2300" manufactured by SENSOFAR was used, and the height change was calculated from the cut end surface (A) of the polarizing plate A to the in-plane center direction (A') with a width of 3,000 µm by confocal mode ( See Fig. 6). From the obtained results, the height of the cut end was set as the "cutting edge deformation height", and the distance from the region where the deformation height became 1 µm or more to the cut end was set as the "deformation occurrence width from the cut end". Fig. 7 shows an example of the measurement result of the height change from the cut end surface A of the polarizing plate toward the in-plane center direction A'. In addition, the inclination of the deformed portion was determined as "calculated inclination angle" by the following equation.

(Example 2)

In the same manner, except that the polarizing plate A with a pressure-sensitive adhesive in Example 1 was changed to the polarizing plate B with a pressure-sensitive adhesive, the height change from the cut end surface (A) of the polarizing plate B to the in-plane center direction (A') of 3,000 µm was changed. It measured and calculated|required the "cutting edge deformation height", the "deformation generation width from the cut edge", and "calculated inclination angle" which are the height of a cut end.

(Comparative Example 1)

In the same manner, except that the polarizing plate A with a pressure-sensitive adhesive in Example 1 was changed to the polarizing plate C with a pressure-sensitive adhesive, the height change from the cut end surface (A) of the polarizing plate C to the width of 3,000 µm in the in-plane center direction (A') was changed. It measured and calculated|required the "cutting edge deformation height", the "deformation generation width from the cut edge", and "calculated inclination angle" which are the height of a cut end.

In Tables 2 to 7 below, the "cutting edge strain height", "the strain generation width from the cut edge" and "calculated inclination angle" in each of the Examples and Comparative Examples were collectively shown.

As described above, in the comparative example, the diffusion of the drug is small, and it has an inclination of 0.44° or more from the cut end to 1.4 mm. In the optical laminate disposed within 2 mm from the end of the polarizing plate and the pressure-sensitive adhesive layer, the inclined portion is visually recognized, whereas in Examples, the inclination angle becomes small due to diffusion of the chemical, and the inclined portion is not visible in the reflection inspection (especially , See the columns of "2PEA" and "2EHA" in Tables 3 and 4).

Advantageous Effects of Invention According to the present invention, in an optical laminate having a structure in which a transparent front plate is laminated on a display device such as an LCD through an ultraviolet curable adhesive layer, it is possible to suppress deformation at the end of the polarizing plate. Further, according to the deformation of the polarizing plate, it is possible to provide a display device such as an LCD in which linear or dotted reflection irregularities that tend to occur at the end of the display screen of the display device are prevented.

1: display device,
2: display screen of the display device,
3: shading film,
4: Linear or dotted reflection unevenness occurring at the end,
5: speaker,
6: microphone,
SUB1, SUB2: transparent substrate,
SEAL: Seal material,
LC: liquid crystal layer,
POL1, POL2: polarizer,
COV: Transparent cover (transparent front panel),
BLK: shading film,
ADH: adhesive layer,
DSP: display panel,
d: width of the portion where the light-shielding film overlaps the polarizing plate,
BL: Backlight.

Claims (4)

As an optical laminate in which a transparent front plate, an ultraviolet curable adhesive layer, a polarizing plate, a pressure sensitive adhesive layer, and a transparent substrate are arranged in this order,
The ultraviolet curable adhesive layer is formed of an ultraviolet curable adhesive composition containing an acrylic acid ester monomer having 6 to 11 carbon atoms in the ester moiety, and
The pressure-sensitive adhesive layer was bonded to an alkali-free glass substrate with an area of 25 mm×25 mm, and when a load of 3 kg was applied under conditions of a temperature of 23°C and a relative humidity of 55%, the creep amount after 3,000 seconds was 90 to 1,000 μm Optical laminate, characterized in that in the range of. The optical laminate of claim 1, wherein the transparent front plate has a frame-shaped light-shielding film printed on it, and the light-shielding film has a width of a portion overlapping with the polarizing plate within 2 mm. The optical laminate according to claim 1 or 2, wherein the transparent front plate has a thickness in the range of 0.25 mm to 2 mm. A display device, wherein the optical laminate according to claim 1 or 2 is disposed on a display surface.

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