JP6325538B2 - Adhesive composition for polarizing plate, adhesive sheet for polarizing plate, polarizing plate with adhesive layer, laminate and flat panel display - Google Patents

Description

  The present invention is used for adhesion between a polarizing plate and an optical member, for example, a thin transparent substrate, is an adhesive having excellent processing characteristics at room temperature and excellent stress relaxation properties when heated, and warping of the optical member. Sufficiently suppressed pressure-sensitive adhesive composition for polarizing plate, pressure-sensitive adhesive sheet for polarizing plate having a pressure-sensitive adhesive layer containing the composition, a polarizing plate with a pressure-sensitive adhesive layer in which the pressure-sensitive adhesive layer is formed on at least one side, the pressure-sensitive adhesive The present invention relates to a laminate in which a transparent substrate is laminated on an adhesive layer of a polarizing plate with an adhesive layer, and a flat panel display having the polarizing plate or laminate with the adhesive layer.

  With respect to adhesives for the flat panel display (FPD) field, the demands for high image quality, high quality, and high durability are increasing as the size of displays increases, the LED system spreads, and the display devices become thinner.

  For example, a liquid crystal display (LCD) classified as an FPD is formed of a liquid crystal panel, a backlight, and a peripheral circuit. This liquid crystal panel typically includes a polarizing plate, a glass substrate having a transparent electrode, a color filter, and other layers. The glass substrate includes a liquid crystal cell sandwiching a liquid crystal.

  The polarizing plate is composed of a multilayer structure of different materials (such as a polarizing film made of a polyvinyl alcohol film in which iodine or a dichroic dye is adsorbed and oriented, or a protective film made of triacetyl cellulose). Has different physical and chemical properties. For this reason, especially in the manufacture of FPD, there are processes carried out in a high-temperature and high-humidity environment, and in the case of LCD, the temperature rises to about 40-60 ° C. due to the heat from the backlight. Under the environment, the degree of dimensional change of each layer constituting the polarizing plate due to shrinkage or swelling is different, and the degree of the difference is large. For this reason, the polarizing plate as a whole has poor dimensional stability.

  This dimensional change causes various influences on various performances represented by light leakage and durability as the entire polarizing plate. In addition, it is known that the light leakage, durability, and the like may be affected by the type of pressure-sensitive adhesive used for bonding between optical films such as polarizing plates and bonding between the liquid crystal cell (glass substrate) and the polarizing plate. ing.

  At present, the combination of polarizing plate type and adhesive type supports the above various required performances. However, the required performance is such as high image quality and high durability as display screens become larger and thinner. It is required to be more advanced.

  Here, in order to solve the light leakage caused by the dimensional change of the polarizing plate and the peeling in a high temperature and high humidity environment, the adhesive type is focused on various characteristics of the polymer constituting the adhesive, Studies have been made to realize leakage prevention performance and ensuring high durability.

  For example, in Patent Documents 1 and 2, regarding the polarizing plate, the amount of creep of the pressure-sensitive adhesive layer that bonds the polarizing plate and the predetermined optical member is increased by a load at normal temperature or high temperature, and the pressure-sensitive adhesive layer becomes the polarizing plate. By following the above, a technique has been proposed in which stress acting on the optical member due to a dimensional change of the polarizing plate is relieved, thereby improving display unevenness and the like of the liquid crystal display device. However, particularly when the creep amount is large at room temperature, the processing characteristics are inferior, such as the occurrence of contamination due to paste sticking, stringing, sticking to the blade, and the like in operations such as punching and bonding.

  Therefore, as a pressure-sensitive adhesive that reduces the sticking of the pressure-sensitive adhesive from the cut surface, a pressure-sensitive adhesive that has a small creep amount at room temperature and has a certain amount of increase in creep amount due to an increase in temperature in a certain temperature range has been proposed. (Patent Document 3).

  Patent Document 4 includes 70% by weight or more of n-butyl (meth) acrylate and no carboxyl group-containing monomer or less than 2% by weight with respect to the adhesive used for bonding the touch panel constituent members. A double-sided pressure-sensitive adhesive tape using an acrylic pressure-sensitive adhesive layer obtained by polymerizing monomer components has been proposed. In this document, since there are no studies on the hard characteristics of the adhesive layer and the cross-linking design, when the adhesive tape having the adhesive layer is used for bonding a polarizing plate and a liquid crystal cell (of the glass substrate), There are concerns that the durability and processing characteristics are insufficient and light leakage occurs.

  Patent Document 5 discloses a linear or branched alkyl group carbon as a durable pressure-sensitive adhesive that can suppress warping of an optical film such as a polarizing plate even in a low-temperature environment. A weight average molecular weight of 30 to 2,500,000, comprising a monomer unit of (meth) acrylic acid alkyl ester of 2 to 18 as a main skeleton and a copolymer monomer copolymerized with the (meth) acrylic acid alkyl ester as a monomer unit. An optical pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer and having a Tg of −35 ° C. or less has been proposed.

In addition, Patent Document 6 discloses an acrylic polymer (A) composed of the following monomer components (a1) to (a4) having a weight average molecular weight of 1 million or more, an ionic compound (B), and a crosslinking agent (C). An optical film pressure-sensitive adhesive composition having a gel fraction after crosslinking of 60% by weight or more is disclosed: monomer component (a1); n-butyl (meth) acrylate 10 to 89.9% by weight monomer component (A2); specific (meth) acrylic acid alkyl ester monomer 5-50% by weight monomer component (a3); monomer having alkylene oxide group 5-40% by weight monomer component (a4); hydroxyl group-containing monomer 0.1 10% by mass:
Patent Document 7 discloses (A) an acrylic copolymer containing 0.1 to 1% by weight of repeating units having a carboxyl group in the molecule and 0.01 to 0.5% by weight of repeating units having a hydroxyl group ( However, the weight of the acrylic copolymer is 100% by weight), and the acrylic copolymer 100 has a weight average molecular weight (Mw) of 800,000 or more and a glass transition temperature (Tg) of −40 ° C. or less. Based on parts by weight, (B) 0.3 to 3 parts by weight of a polyisocyanate compound, and (C) 0.05 to 5 parts by weight of a mercapto group or alicyclic epoxy group-containing silane coupling agent are contained as essential components. A pressure sensitive adhesive composition for polarizing film is disclosed,
Patent Document 8 discloses an adhesive tape having at least one layer of a polyacrylate pressure-sensitive adhesive having a weight average molecular weight _{Mw in} a range of 200,000 ≦ M _w ≦ 1 million g / mol, The acrylate is (a) one or more acrylic monomers of the general formula CH ₂ ═CH—COOR _{1 in} an amount of 55 to 92% by weight (R ₁ means a hydrocarbon residue of C4 to C14; (A) monomer homopolymer glass transition temperature _{TG, aH} is −20 ° C. or lower) and (b) 5 to 30% by weight of one or more copolymerizable monomers (component (b) promoting the glass transition temperature T _G of the _{homopolymer, bH} is the 0 ℃ higher than that), (c) 3 to 15 weight% of one or more copolymerizable, cross-linking reaction of the polyacrylate monomer By radical copolymerization with monomers Obtained Te, where the polyacrylates meets certain parameters, the adhesive tape is disclosed.

JP 2001-272541 A JP 2003-50313 A JP 2001-350020 A JP 2010-215794 A Japanese Patent Application Laid-Open No. 2011-17709 JP 2012-131963 A JP 2004-224873 A Special table 2012-531498 gazette

  As described above, with the increase in size and thickness of display devices and the widespread use of LED systems, demands for various characteristics have become higher.

  Especially for thinning, the transparent substrate used in the liquid crystal cell with the dimensional change when the polarizing plate contracts due to the thermal environment (the constituent layer of the liquid crystal cell laminated on the polarizing plate through the adhesive, It is known that Bending occurs in the glass substrate. In recent years, the thickness of the transparent substrate has become very thin, for example, 0.4 mm or less, and the warp is more likely to occur.

  For this reason, even if it uses the adhesive proposed by patent documents 1-3, when a polarizing plate is bonded together with such a thin transparent substrate, the curvature of the said board | substrate cannot fully be suppressed, for example. , Light leakage will occur.

  Therefore, the present invention can be suitably used for laminating a polarizing plate and various optical members (particularly a thin transparent substrate), and can effectively suppress warping of the member in a thermal environment, thereby preventing light leakage. An object of the present invention is to provide a pressure-sensitive adhesive composition excellent in processing characteristics, such as being effectively prevented and difficult to adhere to a tool.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have (meth) acrylic resin constituting the pressure-sensitive adhesive so that it exhibits excellent hard characteristics at room temperature and exhibits excellent processing characteristics. In addition, it is designed to be flexible so that stress applied to optical members (especially thin transparent substrates) can be reduced when heated, and the degree of cross-linking is within a certain range by combining such (meth) acrylic resin with a certain amount of cross-linking agent. It was found that the above-mentioned problems can be solved by adding a silane coupling agent to improve the adhesiveness of the adhesive to the optical member, thereby completing the present invention.

  That is, the present invention comprises (A): a (meth) acrylic resin containing structural units derived from the following monomers (a1) to (a4) in the following proportions; and (a1) a homopolymer having a Tg of 0 ° C. or higher (meta ) Acrylic monomer 5 to 50% by weight (a2) (meth) acrylic monomer 43 to 93.9% by weight of Tg of homopolymer of −60 ° C. or more and less than 0 ° C. (a3) (meth) acrylic having a carboxyl group 1.1 to 7% by weight of monomer (a4) 0 to 10% by weight of other monomer (B): 0.15 to 1.5 parts by weight of a crosslinking agent with respect to 100 parts by weight of the (meth) acrylic resin, C): A pressure-sensitive adhesive composition for a polarizing plate containing a silane coupling agent.

  From the viewpoint of achieving both hard properties at room temperature and flexibility during heating, the (meth) acrylic monomer (a1) is a (meth) acrylic monomer having a branched C 3-8 alkyl group. Preferably, it is t-butyl (meth) acrylate and / or isobutyl methacrylate.

  The gel fraction of the pressure-sensitive adhesive composition for polarizing plates of the present invention is usually in the range of 50 to 80%.

The pressure-sensitive adhesive composition for polarizing plates of the present invention has a certain hardness at room temperature and is excellent in processing characteristics. Specifically, when the following minute creep test is conducted on the composition, the creep value at 23 ° C. is preferably 0.3 mm or less:
The pressure-sensitive adhesive composition for polarizing plate is applied and dried on a peeled polyester film to prepare a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 25 μm;
The pressure-sensitive adhesive sheet is bonded to a polarizing plate so that the pressure-sensitive adhesive layer is in contact with the polarizing plate to prepare a pressure-sensitive adhesive processed polarizing plate for evaluation, and is aged in a dark place at 23 ° C./50% RH for 7 days;
Aged adhesive polarizing plate for evaluation was cut into a width of 10 mm and a length of 100 mm, the peeled polyester film was peeled off, and the pressure-sensitive adhesive layer was in contact with the glass on the alkali-treated glass and 10 mm. Bonded to have a bonding area of × 10 mm to obtain an adhesive-coated polarizing plate test piece for evaluation;
The pressure-sensitive adhesive-processed polarizing plate test piece for evaluation was autoclaved (50 ° C., 5 atm) and allowed to stand in a 23 ° C./50% RH atmosphere for 24 hours;
Next, the test piece is set in the chamber BOX of the micro creep measuring machine with the length of the fixing chuck portion being 15 mm;
The inside of the chamber BOX is heated to the measurement temperature, and after standing at the measurement temperature for 40 minutes, the laminate of the pressure-sensitive adhesive layer and the polarizing plate in the test piece is obtained with a tensile load of 800 g and a tensile time of 1000 seconds. Pulling in parallel to the bonding surface between the laminate and the glass and in the length direction of the laminate;
The distance of displacement (mm) of the bonded portion between the glass and the laminate in the test piece is measured as a creep value.

  Furthermore, since the pressure-sensitive adhesive composition for polarizing plates of the present invention exhibits good flexibility when heated, the ratio between the creep value at 60 ° C. and the creep value at 23 ° C. (60 ° C. creep) Value / 23 ° C. creep value) is preferably 1.4 or more.

  In the (meth) acrylic resin (A), the proportion of structural units derived from the (meth) acrylic monomer (a1) is preferably 5 to 45% by weight, and the (meth) acrylic monomer (a2) The proportion of structural units derived from is 49.5 to 90% by weight, the proportion of structural units derived from the (meth) acrylic monomer (a3) is 1.5 to 5.5% by weight, and the others The proportion of structural units derived from the monomer (a4) is 0 to 5% by weight.

  From the viewpoint of good hard properties at room temperature of the pressure-sensitive adhesive composition for polarizing plates of the present invention, the (meth) acrylic resin (A) preferably has a weight average molecular weight of 500,000 to 2,000,000.

  The pressure-sensitive adhesive sheet for polarizing plates of the present invention is formed by forming a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition for polarizing plates of the present invention on a base film.

  The polarizing plate with the pressure-sensitive adhesive layer of the present invention is obtained by forming a pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition for a polarizing plate of the present invention on at least one surface of the polarizing plate.

  The pressure-sensitive adhesive composition of the present invention is particularly suitably used for bonding a polarizing plate and a transparent substrate having a thickness of 0.3 mm or less, and the polarizing plate with the pressure-sensitive adhesive layer obtained by performing such bonding. A laminate in which a transparent substrate having a thickness of 0.3 mm or less is laminated on the adhesive layer is also included in the present invention.

  For example, a flat panel display is manufactured by passing through various manufacturing processes using the polarizing plate or laminated body with an adhesive layer demonstrated above.

  The pressure-sensitive adhesive composition for a polarizing plate of the present invention can be suitably used for bonding a polarizing plate and various optical members. The composition exhibits excellent hard characteristics at room temperature, and thus has excellent processing characteristics. In addition, the composition exhibits flexibility during heating, and the stress applied to the optical member is relieved by the dimensional change of the polarizing plate. As a result, the member, particularly a thin transparent substrate In this case, warping during heating is satisfactorily suppressed.

FIG. 1 shows the light leakage size R on the screen of a 19-inch size liquid crystal panel used for the evaluation of the light leakage characteristics in the example, and the luminance measurement parts (La, Lb, Lc, Ld in the area of 1 cm diameter near each corner). ) And a luminance measurement portion (Lcenter) in a 1 cm diameter region in the central portion of the monitor.

Hereinafter, the present invention will be described in detail.
[Adhesive composition for polarizing plate]
As described above, the pressure-sensitive adhesive composition for polarizing plates of the present invention (hereinafter also simply referred to as “the composition of the present invention”) includes a specific (meth) acrylic resin (A), a specific amount of a crosslinking agent (B), and And a silane coupling agent (C). Hereinafter, each of these components will be described. In the present specification, (meth) acryl means methacryl or acryl, and (meth) acrylate means methacrylate or acrylate.

[(A) (meth) acrylic resin]
The (meth) acrylic resin (A) constituting the composition of the present invention contains structural units derived from the specific monomers (a1) to (a4) at a specific ratio as described above (other monomers (a4)). The structural unit derived from may not be included). Hereinafter, the monomer which becomes each structural unit is demonstrated.

<(A1) (Meth) acrylic monomer>
The (meth) acrylic resin (A) includes a structural unit derived from a (meth) acrylic monomer (a1) having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or higher. The Tg of the homopolymer of the (meth) acrylic monomer (a1) is usually 200 ° C. or lower. Thus, the structural unit derived from the monomer having a high Tg of the homopolymer contributes to the excellent hard properties at room temperature of the (meth) acrylic resin (A) and thus the composition of the present invention containing the same.

In the present specification, unless otherwise specified, Tg is used to raise the temperature of a test piece (homopolymer) for measuring Tg at a rate of 10 ° C./min in a range of −60 ° C. to 180 ° C. in an N ₂ atmosphere. , DSC (differential scanning calorimeter DSC8230) is a glass transition temperature obtained by calorimetric measurement. The measurement is performed in accordance with JIS K7121 (plastic transition temperature measurement method).

  Moreover, about the glass transition temperature (Tg (degreeC)) of a homopolymer, the glass transition temperature (homopolymer) of various homopolymers described in "POLYMERHANDBOOK 3rd edition" (John Wiley & Sons, Inc. issue) Tg (K)) may be referred to. For reference, the Tg of homopolymers of several various monomers (including monomers other than (meth) acrylic monomers) is shown in Table 1 below (expressed in ° C.).

  The (meth) acrylic monomer (a1) is not particularly limited as long as it satisfies the above Tg requirements. Examples thereof include (meth) acrylates having an alkyl group having 1 to 20 carbon atoms. The number of carbon atoms is preferably 3 to 8 from the viewpoint of achieving both good hard characteristics at room temperature and good flexibility during heating.

  From the same viewpoint, the (meth) acrylic monomer (a1) is preferably a (meth) acrylate having a branched alkyl group.

  Specific examples of such (meth) acrylic monomer (a1) include methyl (meth) acrylate, ethyl methacrylate, propyl (meth) acrylate, i-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl ( Examples include meth) acrylate, pentyl acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, tetradecyl acrylate, hexadecyl (meth) acrylate, and stearyl (meth) acrylate.

  Among these, t-butyl (meth) acrylate and isobutyl methacrylate are preferable from the above viewpoint, and t-butyl (meth) acrylate is particularly preferable. Moreover, in this invention, the (meth) acrylic-type monomer (a1) demonstrated above may be used individually by 1 type, or may be used in combination of 2 or more type.

<(A2) (Meth) acrylic monomer>
The (meth) acrylic resin (A) used in the present invention contains a structural unit derived from a (meth) acrylic monomer (a2) having a Tg of homopolymer of −60 ° C. or higher and lower than 0 ° C. Thus, the structural unit derived from the monomer having a low Tg of the homopolymer contributes to the (meth) acrylic resin (A), and thus the excellent flexibility at the time of heating of the pressure-sensitive adhesive composition for polarizing plate of the present invention containing the same. To do.

  The (meth) acrylic monomer (a2) is not particularly limited as long as the Tg of the homopolymer is within the above range, but is preferably a (meth) acrylate that does not have a rigid structure such as an aromatic ring. . In the present specification, the aromatic ring is a structure in which atoms having π electrons are arranged in a ring, satisfies the Hückel rule, the π electrons are delocalized, and the ring has a planar structure. Point to.

  Specific examples of such (meth) acrylic monomer (a2) include ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-pentyl methacrylate, isopentyl acrylate, hexyl (meth) acrylate, and heptyl acrylate. , Isoamyl acrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl (meth) acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-lauryl acrylate and n- A tridecyl (meth) acrylate is mentioned.

  Among these, n-butyl acrylate is preferable from the viewpoint of achieving excellent flexibility during heating for the composition of the present invention. Moreover, in this invention, the (meth) acrylic-type monomer (a2) demonstrated above may be used individually by 1 type, or may be used in combination of 2 or more type.

<(A3) (Meth) acrylic monomer>
The (meth) acrylic resin (A) used for this invention contains the structural unit derived from the (meth) acrylic-type monomer (a3) which has a carboxyl group. In the (meth) acrylic resin (A) in the composition of the present invention, a part of the carboxyl group of the structural unit derived from the monomer (a3) is involved in crosslinking by the action of the crosslinking agent (B) described later. It is considered that the part is not crosslinked and forms a hydrogen bond (a carboxyl group that is neither crosslinked nor formed with a hydrogen bond is considered to exist). When heated, this hydrogen bond is broken, so that the flexibility of the (meth) acrylic resin (A) containing the structural unit is considered to increase.

  In addition, formation of a cross-link by a carboxyl group (and formation of a hydrogen bond) is important for exerting the effect of the present invention. For example, the effect of the present invention cannot be obtained by cross-linking by a hydroxyl group.

  The (meth) acrylic monomer (a3) is not particularly limited as long as it has a carboxyl group. Specific examples thereof include (meth) acrylic acid, β-carboxylethyl (meth) acrylate, and (meth) acrylic. Examples include carboxyl group-containing (meth) acrylates such as acid β-carboxyethyl, 5-carboxypentyl (meth) acrylate, succinic acid mono (meth) acryloyloxyethyl ester, and ω-carboxypolycaprolactone mono (meth) acrylate. .

  Among these, acrylic acid is preferable from the viewpoint of achieving excellent flexibility during heating. In the present invention, the (meth) acrylic monomer (a3) may be used alone or in combination of two or more.

<(A4) Other monomer>
In the present invention, a structural unit derived from another monomer (a4) other than the monomer components (a1) to (a3) is used in order to adjust various properties within a range not impairing the effects of the present invention. It can be included in the (meth) acrylic resin (A).

Examples of such other monomers (a4) include
Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and 8-hydroxyoctyl (meta ) Hydroxyl group-containing (meth) acrylates such as acrylates;
Examples of amino group-containing monomers include amino group-containing (meth) acrylates such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate;
Examples of amide group-containing monomers include (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-hexyl (meth) acrylamide and (meth) acrylic acid. Dimethylaminoethyl;
Examples of nitrogen-based heterocyclic ring-containing monomers include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactam.

  In addition, in a monomer having a (meth) acrylic structure, if the ester moiety has an alkylene oxide group, the side chain tends to move, and the hard characteristics at room temperature of the pressure-sensitive adhesive composition for polarizing plates of the present invention tend to deteriorate. The (meth) acrylic resin (A) used in the composition preferably does not contain a structural unit derived from a (meth) acrylic monomer having an alkylene oxide group.

  In the present invention, the other monomer (a4) described above may be used alone or in combination of two or more.

<Production method of (meth) acrylic resin (A)>
The (meth) acrylic resin (A) described above comprises the monomer components (a1) to (a3) and, if necessary, other monomers (a4), a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method. It can manufacture by superposing | polymerizing by conventionally well-known polymerization methods, such as a turbid polymerization method. Among these methods, it is preferable to employ a solution polymerization method because the molecular weight of the resin can be easily adjusted and impurities are hardly mixed into the reaction system.

  In the solution polymerization method, an organic solvent is used as a reaction solvent, and a mixture of monomer components forming the (meth) acrylic resin (A) is dissolved or dispersed in the reaction solvent, and a polymerization initiator is added with stirring. Thus, the copolymerization reaction is performed.

  Examples of the organic solvent include ester solvents such as ethyl acetate; ketone solvents such as methyl ethyl ketone, formaldehyde and acetaldehyde; ether solvents such as dimethyl ether; aromatic solvents such as toluene and xylene; alicyclic systems such as cyclohexane Solvents; and aliphatic solvents such as hexane and octane. These solvents may be used alone or as a mixed solvent of two or more.

  Examples of the polymerization initiator include 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis (4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis. Azo compounds such as -2,4-dimethylvaleronitrile and 1,1'-azobiscyclohexane-1-carbonitrile; isobutyryl peroxide, α, α'-bis (neodecanoylperoxy) diisopropylbenzene, cumylper Oxyneodecanoate, di-n-propylperoxydicarbonate, diisopropylperoxydicarbonate, di-sec-butylperoxydicarbonate, 1,1,3,3-tetramethylbutylperoxyneodecanoate Bis (4-butylcyclohexyl) peroxydicarbonate, benzoyl peroxide, di-t rt- butyl peroxide, lauroyl peroxide and tert- butyl - such as 2-ethyl hexanoate and the like. These can be used alone or in combination of two or more.

  In the solution polymerization method, the reaction temperature of the copolymerization reaction using these reaction solvent and polymerization initiator is usually in the range of 50 to 90 ° C, preferably 60 to 85 ° C, and the reaction time is usually 1 to 1. It is 10 hours, preferably 2 to 8 hours, and the reaction pressure is usually atmospheric pressure to 0.1 MPa.

  By changing the charged amount of each monomer component in these polymerizations and various conditions, the proportion of each structural unit in the (meth) acrylic resin (A) described later, the weight average molecular weight, the molecular weight distribution, and the like can be adjusted.

<Characteristics of (meth) acrylic resin (A)>
For example, the (meth) acrylic resin (A) produced by the above-described method has a structural unit derived from a (meth) acrylic monomer (a1) having a homopolymer Tg of 0 ° C. or higher. The adhesive composition for polarizing plates of the present invention is excellent in processing characteristics. The (meth) acrylic resin (A) has a structural unit derived from a (meth) acrylic monomer (a2) having a Tg of homopolymer of −60 ° C. or higher and lower than 0 ° C. The portion of the structural unit is Flexibility is exhibited at the time of heating, and bending of an optical member such as a transparent substrate due to a heating dimension change of the polarizing plate is suppressed, and good light leakage prevention performance is achieved. Further, the (meth) acrylic resin (A) has a structural unit derived from the (meth) acrylic monomer (a3) having a carboxyl group, and a part of the carboxyl group is formed by a crosslinking agent (B) described later. Cross-linking enhances the hard properties at room temperature of the composition of the present invention, resulting in enhanced processing properties. On the other hand, it is considered that the hydrogen bond formed by the carboxyl group is broken at the time of heating, whereby the structural unit derived from the monomer (a3) at the time of heating gives the composition of the present invention flexibility during heating, It is thought that it contributes to suppression of the warp of the optical member and improves the light leakage prevention performance.

  In such a (meth) acrylic resin (A), the structural unit derived from the (meth) acrylic monomer (a1) accounts for 5 to 50% by weight of the total structural unit of 100% by weight, and the (meth) acrylic The structural unit derived from the system monomer (a2) accounts for 43 to 93.9% by weight out of 100% by weight of the total structural unit, and the structural unit derived from the (meth) acrylic monomer (a3) It occupies 1.1-7 weight% in weight%. The total of structural units derived from these monomers (a1) to (a3) is 90% by weight or more and 100% by weight or less. Moreover, the (meth) acrylic resin (A) may contain the structural unit derived from said other monomer (a4), The ratio shall be 0 to 10 weight% in 100 weight% of all structural units.

  When the proportion of the structural unit derived from the (meth) acrylic monomer (a1) is less than 5% by weight, the (meth) acrylic resin (A) cannot exhibit sufficient hard properties at room temperature, When the composition of the invention is inferior in processing characteristics, and exceeds 50% by weight, the hard characteristics become excessive, the flexibility during heating becomes insufficient, and it becomes difficult to suppress warping of the optical member. From such a point, the proportion of the structural unit derived from the (meth) acrylic monomer (a1) is preferably 5 to 48% by weight, more preferably 5 to 45% by weight.

  When the proportion of the structural unit derived from the (meth) acrylic monomer (a2) is less than 43% by weight, the flexibility during heating becomes insufficient, while when it exceeds 93.9% by weight, the adhesive is flexible. As a result, the pressure-sensitive adhesive sticks out, the dents are generated on the surface, the suitability for punching is reduced, and the like. From such a point, the proportion of the structural unit derived from the (meth) acrylic monomer (a2) is preferably 46 to 92% by weight, more preferably 49.5 to 90% by weight.

  When the proportion of structural units derived from the (meth) acrylic monomer (a3) is less than 1.1% by weight, a sufficient crosslinking rate cannot be achieved, and the hard characteristics at room temperature become insufficient. The composition of the present invention is inferior in processing characteristics. On the other hand, if the ratio exceeds 7% by weight, the crosslinking rate becomes too high, the flexibility during heating becomes insufficient, and it becomes difficult to suppress warping of the optical member. From such a point, the proportion of the structural unit derived from the (meth) acrylic monomer (a3) is preferably 1.3 to 6% by weight, more preferably 1.5 to 5.5% by weight. .

  When the proportion of the structural unit derived from the other monomer (a4) is 0 to 10% by weight, various characteristics of the composition of the present invention can be adjusted without impairing the effects of the present invention. The proportion of structural units derived from the other monomer (a4) is preferably 0 to 5% by weight.

  The amount of structural units derived from these (meth) acrylic monomers (a1) to (a4) reflects the charged weight ratio of each monomer component when the (meth) acrylic resin (A) is produced.

  The weight average molecular weight of the (meth) acrylic resin (A) containing the various structural units described above is usually 500,000 or more. By setting to such a weight average molecular weight, the (meth) acrylic resin (A) is imparted with good hard properties at room temperature, and the composition of the present invention has good processing properties.

  In this specification, the weight average molecular weight refers to the weight average molecular weight in terms of standard polystyrene measured by GPC, and the weight average molecular weight of the (meth) acrylic resin (A) is preferably 500,000 from the above viewpoint. ~ 2 million, more preferably 1 million to 2 million.

  In addition, the molecular weight distribution (Mw / Mn) of the (meth) acrylic resin (A) is a viewpoint of contamination on the adherend during reworking and processing characteristics generated because the pressure-sensitive adhesive composition becomes flexible. Therefore, it is usually 2 to 10, preferably 4 to 8, and Tg is usually −55 to 0 ° C. from the viewpoint of appropriate wettability, adhesive property, and hard property.

[(B) Crosslinking agent]
Next, the crosslinking agent (B) contained in the pressure-sensitive adhesive composition for polarizing plates of the present invention will be described. The crosslinking agent (B) causes a crosslinking reaction with the carboxyl group of the (meth) acrylic monomer (a3) and, when present, the crosslinking group in the structural unit derived from the other monomer (a4). The gel fraction of the product is adjusted to a predetermined range described later. As a result, while ensuring good adhesion between the polarizing plate and its adherend, the composition exhibits good flexibility during heating and suppresses warping of the optical member, thus providing good light leakage prevention performance. It is thought that this is achieved. Examples of the crosslinkable group include a hydroxyl group, a carboxyl group, an epoxy group, an amino group, an amide group, and a tertiary amino group.

  The cross-linking agent (B) is not particularly limited as long as it can cause a cross-linking reaction with the (meth) acrylic resin (A). Examples thereof include an isocyanate cross-linking agent, a metal chelate cross-linking agent, and an epoxy cross-linking agent. Can be mentioned.

  Specific examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, and the like. Isocyanurate compounds; isocyanate compounds obtained by adding these isocyanate monomers to trimethylolpropane; isocyanurate compounds; burette type compounds; and addition reactions with known polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, etc. Mention of a urethane prepolymer type of isocyanate Kill.

  As the metal chelate-based crosslinking agent, isopropyl alcohol, acetylacetone, ethyl acetoacetate or the like is arranged on a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium or zirconium. And the like.

  Specific examples thereof include aluminum isopropylate, diisopropoxybisacetylacetone titanate and aluminum triethylacetoacetate.

  Specific examples of the epoxy crosslinking agent include ethylene glycol glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, N , N, N ′, N′-tetraglycidyl-m-xylylenediamine, N, N, N ′, N′-tetraglycidylaminophenylmethane, triglycidyl isocyanurate, m-N, N-diglycidylaminophenylglycidyl Mention may be made of ether, N, N-diglycidyltoluidine and N, N-diglycidylaniline.

  The crosslinking agent (B) described above may be used singly or in combination of two or more. Such a crosslinking agent (B) is contained in 0.15-1.5 weight part with respect to 100 weight part of (meth) acrylic resin (A) in the adhesive composition for polarizing plates of this invention.

  Thus, by containing a certain amount of the crosslinking agent (B), an appropriate degree of crosslinking (gel fraction) is achieved for the composition of the present invention, and good hard properties at room temperature (this is good processing properties). And good flexibility at the time of heating (this leads to suppression of warpage of the adherend of the polarizing plate and good light leakage prevention performance is achieved). From such a viewpoint, the content of the crosslinking agent (B) is preferably 0.3 to 1.2 parts by weight with respect to 100 parts by weight of the (meth) acrylic resin (A).

[(C) Silane coupling agent]
The pressure-sensitive adhesive composition for polarizing plates of the present invention contains a silane coupling agent (C). The silane coupling agent (C) forms a bond such as a chemical bond with various adherends and improves the adhesion between the polarizing plate and the adherend. It is particularly effective for bonding with a glass substrate.

  Examples of the silane coupling agent (C) include polymerizable unsaturated group-containing silicon compounds such as vinyltrimethoxysilane, vinyltriethoxysilane, and methacryloxypropyltrimethoxysilane; 3-glycidoxypropyltrimethoxysilane, 3- Silicon compounds having an epoxy structure such as glycidoxypropylmethyldimethoxysilane and 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N- (2-aminoethyl) 3-amino Examples include amino group-containing silicon compounds such as propyltrimethoxysilane and N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane; and 3-chloropropyltrimethoxysilane; oligomer type silane coupling agents.

  Among these, when a silane coupling agent having a functional group that reacts with a functional group (such as a carboxyl group) contained in the (meth) acrylic resin (A) is used, the polarizing plate is deposited in a humid heat environment. It is preferable in that it is difficult to cause peeling from the body.

  The compounding quantity of the silane coupling agent (C) in the composition of this invention is 0.01-0.3 weight part normally with respect to 100 weight part of (meth) acrylic resin (A), Preferably it is 0.00. 05 to 0.25 parts by weight. Moreover, a silane coupling agent (C) may be used individually by 1 type, or may be used in combination of 2 or more type.

[Other ingredients]
In the pressure-sensitive adhesive composition for polarizing plate of the present invention, an antistatic agent, an antioxidant, an ultraviolet absorber, a colorant, a pigment, a dye, a tackifier resin, a surface lubricant, a leveling agent, a softener, if necessary. You may contain other components, such as anti-aging agent, a light stabilizer, a photoinitiator, a polymerization inhibitor, a filler, an organic particle, an inorganic particle, or a plasticizer. The composition of the present invention contains, as the softening agent, an acrylic copolymer containing no crosslinkable functional group and having a weight average molecular weight Mw of less than 100,000 based on 100 parts by weight of the (meth) acrylic resin (A). Part may be contained. Furthermore, the composition of the present invention may contain the solvent or other solvent used in the production of the (meth) acrylic resin (A).

[Adhesive composition for polarizing plate]
The pressure-sensitive adhesive composition for polarizing plates of the present invention comprises the (meth) acrylic resin (A) described above, a specific amount of a crosslinking agent (B), and a silane coupling agent (C).

  The (meth) acrylic resin (A) is considered that its various structural units exhibit good hard properties at room temperature and flexibility during heating. The composition of the present invention containing such a (meth) acrylic resin (A) is excellent in processing characteristics.

  Further, due to the presence of the specific amount of the crosslinking agent (B), the gel fraction of the composition of the present invention is usually 50 to 80%, and this also achieves good hard properties at room temperature, and further the gel fraction is reduced. Since it is not too high, the composition becomes flexible upon heating. As a result, it is presumed that the stress applied to the adherend (optical member such as a transparent substrate) is relieved by the dimensional change of the polarizing plate during heating, and as a result, the warpage of the adherend is suppressed and good light is obtained. Leak prevention performance is achieved.

  Furthermore, in the specific composition of the present invention, since the gel fraction is adjusted to the specific range, the cohesive strength of the composition is sufficient, and the stress relaxation property during heating is excellent. Therefore, the composition of the present invention is also excellent in wet heat durability. For example, even when the pressure-sensitive adhesive layer described later is placed in a wet heat environment, the pressure-sensitive adhesive layer is less likely to foam or tear.

  Moreover, since the composition of this invention contains the silane coupling agent (C), a polarizing plate and a to-be-adhered body can fully be adhere | attached.

  Since the composition of the present invention has good hard properties at room temperature as described above, the creep value at 23 ° C. in the following minute creep test is 0.5 mm or less. Considering practicality such as processing characteristics, the creep value at 23 ° C. is preferably 0.3 mm or less.

(Small creep test)
The pressure-sensitive adhesive composition for polarizing plates of the present invention is applied and dried on a release-treated polyester film to produce a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a thickness of 25 μm.
This pressure-sensitive adhesive sheet is bonded to a polarizing plate so that the pressure-sensitive adhesive layer is in contact with the polarizing plate to prepare a pressure-sensitive adhesive processed polarizing plate for evaluation, and is aged in a dark place at 23 ° C./50% RH for 7 days.
Aged adhesive polarizing plate for evaluation was cut into a width of 10 mm and a length of 100 mm, the peeled polyester film was peeled off, and the pressure-sensitive adhesive layer was in contact with the glass on the alkali-treated glass and 10 mm. It sticks together so that it may become a bonding area of * 10 mm, and it is set as the adhesive-processed polarizing plate test piece for evaluation.
The pressure-sensitive adhesive-processed polarizing plate test piece for evaluation is subjected to autoclave treatment (50 ° C., 5 atm) and left to stand in a 23 ° C./50% RH atmosphere for 24 hours.
Next, the test piece is set in the chamber BOX of the minute creep measuring machine with a fixing chuck portion length of 15 mm.
The inside of the chamber BOX is heated to the measurement temperature, and after standing at the measurement temperature for 40 minutes, the laminate of the pressure-sensitive adhesive layer and the polarizing plate in the test piece is obtained with a tensile load of 800 g and a tensile time of 1000 seconds. The laminate is pulled in the length direction of the laminate in parallel with the bonding surface between the laminate and the glass.
The distance (mm) of the misalignment of the bonded portion between the glass and the laminate in the test piece is measured, and this is used as the creep value.

  Furthermore, since the composition of the present invention exhibits good flexibility when heated as described above, the creep value at 60 ° C. is 0.2 mm or more when the above-described minute creep test is performed. From the viewpoint of effectively preventing warpage of the optical member and achieving good light leakage prevention performance, the creep value at 60 ° C. is preferably 0.3 mm or more.

  In order to effectively prevent warping of the optical member, it is also important that the flexibility of the composition of the present invention rises above a certain level when the temperature rises from room temperature to a heated state. It is necessary that the ratio of the creep value at 23 ° C. to the creep value at 23 ° C. (60 ° C. creep value / 23 ° C. creep value) is 1.3 or more. In consideration of actual use, the ratio is preferably 1.4 or more, more preferably 1.5 or more, and usually the ratio is 25 or less.

<Use of pressure-sensitive adhesive composition for polarizing plate>
The polarizing plate pressure-sensitive adhesive composition of the present invention described above is excellent in both hard properties at room temperature and flexibility during heating, has excellent processing characteristics, and suppresses warpage of the adherend of the polarizing plate, and has excellent light. Shows leakage prevention performance.

  For this reason, the composition of this invention is suitable for the bonding use of a polarizing plate and various optical members. In particular, the composition of the present invention is used for laminating a polarizing plate having a very thin optical member, for example, a transparent substrate (in a liquid crystal cell) having a thickness of 0.4 mm or less, which has been recently adopted in the field of display devices. Even so, it is possible to suppress warping during heating of the transparent substrate.

  In particular, in recent years, further thinning has been carried out, and a transparent substrate having a thickness of 0.3 mm or less has been used, but the composition of the present invention is also used for bonding such a very thin transparent substrate and a polarizing plate. A thing is suitable and it is hard to produce the curvature of a transparent substrate at the time of a heating.

<Method for producing pressure-sensitive adhesive composition for polarizing plate>
The manufacturing method in particular of the adhesive composition for polarizing plates of this invention is not restrict | limited, The composition of this invention is obtained by mixing the various component of the composition mentioned above by a well-known method. A solvent may be used for smooth mixing.

  The produced composition of the present invention is usually cured for a certain period (for example, 3 to 7 days at room temperature (23 ° C. and 50% RH), 2 to 5 days under accelerated heating (40 ° C. and 90% RH)). Aging), the crosslinking reaction is allowed to proceed to a certain extent, adjusted to the appropriate gel fraction, and used.

[Adhesive sheet]
When the pressure-sensitive adhesive composition for polarizing plates of the present invention is used as a pressure-sensitive adhesive, it is convenient and convenient to form a pressure-sensitive adhesive layer on a substrate film to form a pressure-sensitive adhesive sheet.

  The base film is preferably a release film in consideration of handling properties such as when the pressure-sensitive adhesive sheet is used in the production process of a flat panel display. Examples of the material include polyester, polyolefin, and polyether. Can be mentioned.

  The pressure-sensitive adhesive sheet of the present invention forms a pressure-sensitive adhesive layer having a desired thickness by, for example, applying and drying a coating liquid containing the composition of the present invention on a base film to evaporate a solvent contained in the coating liquid. It can produce by doing. Although the thickness of the said adhesive layer is not specifically limited, The range of 5-100 micrometers is preferable and the range of 10-50 micrometers is more preferable. When the thickness of the pressure-sensitive adhesive layer is less than 5 μm, predetermined performance (wet heat durability, etc.) may not be exhibited, and when it exceeds 100 μm, the processing characteristics when cutting the pressure-sensitive adhesive sheet may be deteriorated.

  Moreover, in the adhesive sheet of this invention, the surface which is not in contact with the said base film surface of the said adhesive layer may be coat | covered with a peeling film, and the said peeling film may be peeled off at the time of use.

[Polarizing plate with adhesive layer]
By forming the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition for a polarizing plate of the present invention on at least one side of the polarizing plate, it has excellent processing characteristics as described above and achieves excellent light leakage prevention performance even in a thermal environment. The obtained polarizing plate with an adhesive layer is obtained.

  Since the composition of the present invention is excellent in flexibility during heating as described above, a transparent substrate (preferably having a thickness of 0.4 mm or less, preferably a glass substrate) on the pressure-sensitive adhesive layer of the polarizing plate with the pressure-sensitive adhesive layer. In a laminate having a thickness of preferably 0.3 mm or less, stress due to dimensional change of the polarizing plate is not easily applied to the transparent substrate even under heating, and warpage is unlikely to occur.

<Method for producing polarizing plate with pressure-sensitive adhesive layer>
The polarizing plate with an adhesive layer of the present invention is produced, for example, by the following methods (1) to (3).

(1) A coating solution containing the pressure-sensitive adhesive composition for polarizing plates of the present invention is applied to a release layer of a release film by a known method (die coating method, knife coating method, etc.), and contained in the coating solution by heat drying. A solvent or the like is vaporized to form a pressure-sensitive adhesive layer having a desired thickness, and this is bonded to a polarizing plate.

(2) A coating solution containing the composition of the present invention is applied to a polarizing plate by a known method (die coating method, knife coating method, etc.), and the solvent contained in the coating solution is vaporized by heat drying. A pressure-sensitive adhesive layer having a thickness is formed, and this is bonded to the release layer of the release film.

(3) A coating solution containing the composition of the present invention is applied to the release layer of the first release film by a known method (die coating method, knife coating method, etc.), and the solvent contained in the coating solution by heat drying. Is vaporized to form a pressure-sensitive adhesive layer having a desired thickness, and this is bonded to the release layer of the second release film (usually having a lower peel strength than the first release film) to form a non-carrier pressure-sensitive adhesive film Is made. Thereafter, the second release film is peeled off, and the pressure-sensitive adhesive layer is bonded to the polarizing plate.

  Moreover, the thickness of the adhesive layer in the polarizing plate with an adhesive layer obtained is although it does not specifically limit, The range of 5-100 micrometers is preferable and the range of 10-50 micrometers is more preferable. When the thickness of the pressure-sensitive adhesive layer is less than 5 μm, the predetermined performance may not be exhibited. When the thickness exceeds 100 μm, the processing characteristics when cutting the polarizing plate with the pressure-sensitive adhesive layer may be deteriorated.

  In the composition of this invention, as above-mentioned, after formation of the said adhesive layer, it is made to age for a fixed period and a crosslinking reaction is advanced. And after adjusting to an appropriate gel fraction, the said adhesive layer can be affixed on the structural layer etc. of the flat panel display mentioned later.

[Flat panel display]
For example, by using the pressure-sensitive adhesive composition for a polarizing plate of the present invention, a polarizing plate and a transparent substrate and the like are bonded together (resulting in the laminate described in the above section [Polarizing plate with pressure-sensitive adhesive layer]). ), The light leakage prevention performance based on the superior bending prevention performance as described above is achieved.

  It is possible to produce a flat panel display using such a polarizing plate and the composition of the present invention, and FPDs thus produced are also included in the scope of the present invention.

  Examples of the FPD include a liquid crystal display (LCD), a plasma display (PDP), a field emission display (FED), and the like.

  In LCDs, the liquid crystal layer is generally sandwiched between glass substrates having transparent electrodes, an alignment film or a color filter is provided between the glass substrate and the liquid crystal layer, and the surface opposite to the surface of the glass substrate close to the liquid crystal layer. It has the structure which has the laminated body structure in which the polarizing plate was provided on the surface.

  In general, a PDP is a laminate in which a phosphor layer exists between opposing glass substrates, and various dielectric layers, electrodes, and other functional layers are provided on the surface of the glass substrate close to the phosphor layer. It has a configuration having a body structure.

  The FED generally has a glass substrate, an anode electrode (anode) formed on the substrate, a phosphor layer formed on the electrode, a vacuum space, and a phosphor layer across the space. The glass substrate has a laminated structure in which a cathode electrode (cathode) is provided.

  The polarizing plate with an adhesive layer of the present invention or a laminate in which a transparent substrate is laminated constitutes a part of the constituent layers of these FPDs. Moreover, it is also possible to laminate | stack at least one part of the structure layer of FPD sequentially using the adhesive sheet of this invention.

Hereinafter, the present invention will be described in detail by way of examples.
<Weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of (meth) acrylic resin>
The weight average molecular weight of the (meth) acrylic resin is determined by standard polystyrene conversion under GPC (gel permeation chromatography) under the following conditions.

<GPC measurement conditions>
Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)
GPC column configuration: The following five columns (all manufactured by Tosoh Corporation)
(1) TSK-GEL HXL-H (guard column)
(2) TSK-GEL G7000HXL
(3) TSK-GEL GMHXL
(4) TSK-GEL GMHXL
(5) TSK-GEL G2500HXL
Diluted with tetrahydrofuran so that the sample concentration is 1.0 mg / cm ³ Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0 cm ³ / min
Column temperature: 40 ° C

[Production example of (meth) acrylic resin]
In a reaction apparatus equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen introduction tube, a (meth) acrylic monomer (a1), a (meth) acrylic monomer (a2), a (meth) acrylic monomer (a3) and The other monomer (a4) is charged in accordance with the blending ratio shown in the following Tables 2 and 3 (in the table, the unit of numerical values regarding the monomer is parts by weight), and then ethyl acetate is added at a monomer concentration of 50 wt%. It was charged with a blending amount.

  Next, 0.1 part by weight of 2,2′-azobisisobutyronitrile is added to 100 parts by weight of the monomer components, and the temperature is raised to 60 ° C. with stirring while replacing the air in the reaction vessel with nitrogen gas. After warming, the reaction was allowed to proceed for 4 hours. After completion of the reaction, it was diluted with ethyl acetate to obtain a (meth) acrylic resin solution.

In addition, the meaning of the symbol in Table 1 and 2 is as follows.
AA: acrylic acid BA: n-butyl acrylate t-BA: t-butyl acrylate MMA: methyl methacrylate MA: methyl acrylate i-BMA: isobutyl methacrylate HEA: 2-hydroxyethyl acrylate

[Preparation of adhesive processing polarizing plate for evaluation]
Using the (meth) acrylic resin solution obtained in the above production example, the blending of Tables 4 to 6 (solid blending, numerical values are parts by weight with respect to 100 parts by weight of (meth) acrylic resin (expressed as “adhesive”) ) To obtain a pressure-sensitive adhesive composition solution.

  The pressure-sensitive adhesive composition solution was applied to the surface of the peeled polyester film and dried to obtain a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 25 μm. After sticking this pressure-sensitive adhesive sheet on one side of a polarizing film (TAC (triacetylcellulose) -PVA (polyvinyl alcohol) -TAC configuration), it is aged for 7 days in the dark at 23 ° C / 50% RH. A polarizing plate was obtained.

[Evaluation]
Various evaluations described below were performed using the obtained adhesive processed polarizing plate for evaluation. These evaluation results are also shown in Tables 4 to 6 below.

<Gel fraction>
The obtained pressure-sensitive adhesive composition was applied to the surface of the PET film subjected to the peeling treatment and dried so that the thickness after drying was 20 μm. Thereafter, a PET film that had been similarly subjected to a peeling treatment was bonded to the other surface of the applied pressure-sensitive adhesive composition to obtain a test piece. Store the test piece at 23 ° C, 50% RH, and immediately after the start of storage (0 day), collect approximately 0.1 g of adhesive from the test piece into a sample bottle, add 30 cc of ethyl acetate and let it infiltrate for 24 hours. After that, the content of the sample bottle was filtered with a 200 mesh stainless steel wire mesh, and the weight of the residue after drying on the wire mesh at 100 ° C. for 2 hours was defined as the dry weight. Based on these values, the gel fraction was measured by the following formula.

Gel fraction (%) = (dry weight / weight of collected adhesive) × 100
In addition, the gel fraction in Tables 4-6 shows the gel fraction measured value after aging is completed and stabilized.

<Small creep test>
The evaluation pressure-sensitive adhesive polarizing plate was cut to a width of 10 mm and a length of 100 mm, and the peel-treated polyester film was peeled off so that the evaluation pressure-sensitive adhesive polarizing plate was placed on alkali-treated glass and the pressure-sensitive adhesive layer was in contact with the glass In addition, they were laminated so as to have a bonding area of 10 mm × 10 mm, autoclaved (50 ° C., 5 atm), and then allowed to stand in a 23 ° C./50% RH atmosphere for 24 hours. This was used as a sample for a minute creep test.

  A test sample was set with a length of 15 mm of the fixing chuck portion in the chamber BOX of a micro creep measuring machine (model name: TA.TX.PLUS manufactured by Eiko Seiki Co., Ltd.). After heating the inside of the chamber BOX to the measurement temperature and allowing to stand at the measurement temperature for 40 minutes, the laminate of the pressure-sensitive adhesive layer and the polarizing film in the sample for the minute creep test was obtained at a tensile load of 800 g and a tensile time of 1000 seconds. The laminate was pulled in parallel with the bonding surface between the laminate and the glass and in the length direction of the laminate. The distance (mm) of the misalignment between the glass and the laminated body after being pulled was confirmed (measured) to obtain a minute creep test result.

<Light leakage characteristics>
(Light leakage size R)
A 19-inch-size liquid crystal panel is peeled off from the peeled polyester film, and the adhesive-coated polarizing plate for evaluation is in contact with the glass substrate of the liquid crystal panel, and the polarizing plate and the liquid crystal panel are crossed Nicols. After being bonded to each other and left in an 80 ° C. atmosphere for 240 hours, it was left in a 23 ° C./50% RH atmosphere for 2 hours.

  Thereafter, the liquid crystal panel on which the polarizing plate was bonded was connected to a personal computer in a dark room to display a full screen black. In this state, the part where the light leakage occurs is visually confirmed, and the distance from the corner of the screen of the light leakage occurrence part is measured as shown in FIG. 1, and this is the light leakage size R (mm). did. If R is 30 mm or less, it can be used as a liquid crystal display panel.

(ΔL (Cd / m ² ))
In the above-mentioned full screen black display state, the luminance (La, Lb, Lc, Ld) in the 1 cm diameter region near each corner and the luminance (Lcenter) in the 1 cm diameter region in the center of the monitor are luminance meters (manufactured by Highland Corporation). (RISA-COLOR / CD8) and light leakage (ΔL) was determined by the following formula.

          Formula: ΔL = (La + Lb + Lc + Ld) / 4-Lcenter

The smaller ΔL (Cd / m ² ), the smaller the light leakage (from the backlight). Usually, if it is less than 2.0, it can be used as a liquid crystal display panel.

<Bending>
A 130 mm × 230 mm adhesive polarizing plate for evaluation was bonded to 0.3 mm × 150 mm × 250 mm borosilicate glass so as to be crossed Nicol, and Auto Clave treatment (50 ° C., 5 atm) was performed. After Auto Clave treatment, it was allowed to stand in a 70 ° C. atmosphere for 72 hours.

  Thereafter, the degree of warpage of the glass was measured using a steel ruler, and the result was evaluated as Bending. If it is usually 2 mm or less, preferably 1 mm or less, more preferably 0.5 mm or less, it can be used without any practical problem.

<Processing characteristics>
The evaluation processed adhesive polarizing plate was punched into a predetermined mold 10,000 times, and adhesion of the adhesive to the blade was visually determined. The evaluation criteria are as follows.
○: No adhesion, △: Some adhesion, ×: Adhesion

<Foaming and tearing>
A 19-inch-size non-alkali-treated glass is attached with an evaluation adhesive polarizing plate from which the peeled polyester film has been peeled off to form a test plate, which is left in the test environment (60 ° C / 95% RH) for 500 hr. Thereafter, the appearance change of foaming and tearing was visually confirmed and evaluated according to the following criteria. Foaming is caused by insufficient cohesive force due to low crosslinking degree, and tearing is caused by insufficient stress relaxation force due to too high crosslinking degree.

Foam-size)
○: No foaming is observed Δ: Foam diameter is 1 mm or less ×: Foam diameter is greater than 1 mm

Foaming amount generated)
○: No foaming is observed Δ: The number of foams is 10 or less ×: The number of foams is more than 10

Rupture-size)
◯: Not seen at all △: Generated area is the entire bonded portion of the test plate (10
Less than 5% with respect to 0%) x: The generated area is the entire bonded portion of the test plate (10
0%) over 5%

Rupture-position)
○: Not at all Δ: There is a defect only at a position less than 0.5 mm from the end part ×: There is a defect at a position of 0.5 mm or more from the end part.

The compositions of the pressure-sensitive adhesive compositions of Examples , Reference Examples and Comparative Examples and the various evaluation results are summarized in Tables 4 to 6 below.

In addition, the meaning of the symbol in Tables 4-6 is as follows.
L-45: TDI-based isocyanate compound (L-45 manufactured by Soken Chemical Co., Ltd.)
TD: XDI isocyanate compound (TD-75 manufactured by Mitsui Takeda Pharmaceutical Co., Ltd.)
Al chelate: Al chelate compound (E-5XM manufactured by Soken Chemical Co., Ltd.)
Tetrad C: 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company)
KBM-403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)

  In Comparative Example 1, the amount of the cross-linking agent used was less than the lower limit specified in the present invention, and the gel fraction was very low and firing occurred due to insufficient cohesive force. Therefore, it was impossible to measure light leakage and bending. Met.

  In Comparative Example 2, the amount of the crosslinking agent used exceeds the upper limit specified in the present invention, the gel fraction is very high, and the ratio of the 60 ° C. creep value to the 23 ° C. creep value is about 1, The stress due to the dimensional change of the polarizing plate was not relaxed, and the warp was large and light leakage occurred.

  Comparative Example 3 uses a resin that does not contain a structural unit derived from the (meth) acrylic monomer (a1), has a large 23 ° C. creep value, inferior hard characteristics at room temperature, and inferior processing characteristics. Light leakage also occurred.

  Comparative Example 4 does not include a structural unit derived from the (meth) acrylic monomer (a1) and the (meth) acrylic monomer (a3), and uses a resin including a structural unit derived from a monomer having a hydroxyl group. The warpage was great.

  In Comparative Example 5, the proportion of the structural unit derived from the (meth) acrylic monomer (a3) is less than the lower limit of the proportion defined in the present invention, and a resin containing a structural unit derived from a monomer having a hydroxyl group is used. As a result, the processing characteristics were insufficient, the warp was large, and tearing was also observed. It can be seen that the hydroxyl group also reacts with the cross-linking agent to form a cross-link, but this does not provide the effect of the present invention.

  Comparative Example 6 uses the same resin as Comparative Example 5 and doubles the amount of crosslinking agent used. Although the processing characteristics and tearing were improved by increasing the amount of crosslinking, it was considered that stress relaxation during heating was insufficient, and warping and light leakage occurred.

  Comparative Example 7 is an example in which a pressure-sensitive adhesive composition having substantially the same composition as the pressure-sensitive adhesive produced in Production Example 1 of Patent Document 3 was used. Although the hard characteristics at room temperature are excellent, it showed good processing characteristics, but when used for bonding a glass substrate with a thickness of 0.3 mm and a polarizing plate, stress relaxation is considered insufficient, warping and light leakage Occurred and tearing was also observed.

Claims (11)

(A): a (meth) acrylic resin containing structural units derived from the following monomers (a1) to (a4) in the following proportions;
(A1) Tg of homopolymer is 0 ° C. or higher , and 5 to 50% by weight of (meth) acrylic monomer having a branched C 3-8 alkyl group
(A2) (meth) acrylic monomer having a Tg of -60 ° C. or more and less than 0 ° C. of 43 to 93.9% by weight
(A3) 1.1 to 7% by weight of a (meth) acrylic monomer having a carboxyl group
(A4) 0-10% by weight of other monomers
(B): 0.15 to 1.5 parts by weight of a crosslinking agent with respect to 100 parts by weight of the (meth) acrylic resin,
(C): A pressure-sensitive adhesive composition for a polarizing plate comprising a silane coupling agent. The pressure-sensitive adhesive composition for polarizing plates according to claim 1 , wherein the gel fraction is 50 to 80%. The pressure-sensitive adhesive composition for polarizing plates according to claim 1 or 2 , wherein a creep value at 23 ° C is 0.3 mm or less when the following micro creep test is performed on the pressure-sensitive adhesive composition for polarizing plates:
The pressure-sensitive adhesive composition for polarizing plate is applied and dried on a peeled polyester film to prepare a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a thickness of 25 μm;
The pressure-sensitive adhesive sheet is bonded to a polarizing plate so that the pressure-sensitive adhesive layer is in contact with the polarizing plate to prepare a pressure-sensitive adhesive processed polarizing plate for evaluation, and is aged in a dark place at 23 ° C./50% RH for 7 days;
Aged adhesive polarizing plate for evaluation was cut into a width of 10 mm and a length of 100 mm, the peeled polyester film was peeled off, and the pressure-sensitive adhesive layer was in contact with the glass on the alkali-treated glass and 10 mm. Bonded to have a bonding area of × 10 mm to obtain an adhesive-coated polarizing plate test piece for evaluation;
The pressure-sensitive adhesive-processed polarizing plate test piece for evaluation was autoclaved (50 ° C., 5 atm) and allowed to stand in a 23 ° C./50% RH atmosphere for 24 hours;
Next, the test piece is set in the chamber BOX of the micro creep measuring machine with the length of the fixing chuck portion being 15 mm;
The inside of the chamber BOX is heated to the measurement temperature, and after standing at the measurement temperature for 40 minutes, the laminate of the pressure-sensitive adhesive layer and the polarizing plate in the test piece is obtained with a tensile load of 800 g and a tensile time of 1000 seconds. Pulling in parallel to the bonding surface between the laminate and the glass and in the length direction of the laminate;
The distance of displacement (mm) of the bonded portion between the glass and the laminate in the test piece is measured as a creep value. 4. The polarized light according to claim 3 , wherein a ratio of a creep value at 60 ° C. to a creep value at 23 ° C. (60 ° C. creep value / 23 ° C. creep value) is 1.4 or more when the micro creep test is performed. Adhesive composition for board. In the (meth) acrylic resin (A), the proportion of the structural unit derived from the (meth) acrylic monomer (a1) is 5 to 45% by weight, and is derived from the (meth) acrylic monomer (a2). The proportion of structural units is 49.5 to 90% by weight, the proportion of structural units derived from the (meth) acrylic monomer (a3) is 1.5 to 5.5% by weight, and the other monomers ( proportion of the structural unit derived from a4) is 0 to 5 wt%, a polarizing plate pressure-sensitive adhesive composition according to any one of claims 1-4. The (meth) acrylic monomer (a1) is a t- butyl (meth) acrylate and / or isobutyl methacrylate, polarizing plates for pressure-sensitive adhesive composition according to any one of claims 1-5. The (meth) weight average molecular weight of the acrylic resin (A) is 500,000 2,000,000 polarizing plate pressure-sensitive adhesive composition according to any one of claims 1-6. Polarizing plate adhesive sheet for pressure-sensitive adhesive layer is formed comprising a polarizing plate for a pressure-sensitive adhesive composition according to any one of claims 1 to 7 on a substrate film. And at least the pressure-sensitive adhesive layer-carrying pressure-sensitive adhesive layer formed on one side polarizing plate of the polarizing plate includes a polarizing plate for a pressure-sensitive adhesive composition according to any one of the pressure-sensitive adhesive layer according to claim 1 to 7 , Polarizing plate with adhesive layer. The laminated body by which the transparent substrate of thickness 0.3mm or less is laminated | stacked on the adhesive layer of the polarizing plate with an adhesive layer of Claim 9 . The flat panel display which has a polarizing plate with an adhesive layer of Claim 9 , or the laminated body of Claim 10 .