TW201510143A - Adhesive composition for polarizing plate, adhesive sheet for polarizing plate, polarizing plate with adhesive layer, laminate and flat panel display - Google Patents

Abstract

The object of this invention is to provide a adhesive composition suitable for lamination of polarizing plate with various optical members (especially thin transparent substrates), capable of suppressing bending of the members under heat environment, capable of preventing light leakage, and excellent in workability such as not easy to be attached on tools. The present adhesive composition for polarizing plate comprises: (A) a (meth) acrylate resin comprising the structure units derived from the following monomer (a1) to (a4) in the following ratio: (a1) a (meth) acrylic monomer of 5 to 50 weight %, the homopolymer thereof having a Tg of 0 DEG C or more, (a2) a (meth) acrylic monomer of 43 to 93.9 weight %, the homopolymer thereof having a Tg of -60 DEG C or more and under 0DEG C, (a3) a (meth) acrylic monomer having carboxyl group of 1.1 to 7 weight %, (a4) other monomers of 0 to 10 weight %, (B) a crosslinker of 0.15 to 1.5 parts by weight with respect to the (meth) acrylic acid resin 100 parts by weight, and (C) a silane coupling.

Description

Adhesive composition for polarizing plate, adhesive sheet for polarizing plate, polarizing plate with adhesive layer, laminated body, and flat panel display

The present invention relates to an adhesive which can be used for adhesion between a polarizing plate and an optical member, for example, a thin transparent substrate, has excellent processing properties at room temperature, and is excellent in stress relaxation property upon heating, and sufficiently suppresses warpage of the optical member. An adhesive composition for a polarizing plate; an adhesive sheet for a polarizing plate having an adhesive layer containing the composition; the adhesive layer formed on at least one of a polarizing plate with an adhesive layer on one side, and a polarizing plate with the adhesive layer a laminate formed by laminating a transparent substrate on the adhesive layer; and a flat panel display having the above-mentioned polarizing plate or laminate with an adhesive layer.

In the field of flat panel display (FPD), the demand for high image quality, high quality, and high durability has been increasing with the increase in the size of the display, the spread of the LED system, and the reduction in the thickness of the display device.

For example, a liquid crystal display classified as an FPD is formed by a liquid crystal panel, a backlight, and a peripheral circuit, and the liquid crystal panel is typically biased. Each of the light plate, the glass substrate having the transparent electrode, and the color filter is configured to include a liquid crystal cell in which the liquid crystal cell is sandwiched between the glass substrate.

The polarizing plate is composed of a multilayer structure of a dissimilar material (a polarizing film made of a polyvinyl alcohol-based film in which iodine or a dichroic dye is adsorbed and aligned, or a protective film made of triacetyl cellulose). The materials have different physical/chemical properties. Therefore, the manufacture of FPD in particular has a step of being carried out in a high-temperature/high-humidity environment, and in the case of an LCD, since the heat-induced temperature from the backlight rises to about 40 to 60 ° C, but in such a thermal environment, The dimensional changes of the layers constituting the polarizing plate due to shrinkage and expansion are different, and the degree of the difference is also large. Therefore, the polarizing plate as a whole lacks dimensional stability.

Then, due to the dimensional change, various effects are exerted on various performances such as light leakage of the polarizing plate or durability. Further, it is known that even if the optical films such as a polarizing plate are adhered to each other or the type of the adhesive used for the liquid crystal cell (glass substrate) and the polarizing plate, the light leakage, durability, and the like are affected.

In the current situation, the combination of the type of the polarizer and the type of the adhesive is required to meet the various requirements described above, but the required performance is required to be large screen/thinness of the display device, and it is required to have a high image quality/high durability. height.

In order to solve the problem of leakage of light due to dimensional change of the polarizing plate and peeling in a high-temperature and high-humidity environment, attention has been paid to various types of properties of the polymer constituting the adhesive, and it has been found that excellent light leakage prevention performance can be exhibited. Ensure high durability.

For example, in Patent Documents 1 and 2, it has been proposed that the amount of creep generated by the load of the polarizer and the adhesive layer of the polarizing plate and the predetermined optical member at normal temperature or high temperature is increased due to the adhesive layer. With the polarizing plate, the stress acting on the optical member due to the dimensional change of the polarizing plate is alleviated, thereby improving the display unevenness of the liquid crystal display device and the like. However, if the submersible variable is particularly large at room temperature, contamination such as bleed out of the slurry, drawing, and adhesion to the knives may occur in the working steps such as pressing and laminating, and the processing characteristics may be deteriorated.

Here, in order to reduce the bleed out of the adhesive from the cross section, an adhesive having a small latent variable at room temperature and a rise in the latent variable due to an increase in temperature in a certain temperature range has been proposed (patent Document 3).

Further, Patent Document 4 proposes an adhesive for use in bonding a touch panel constituting member, which comprises 70% by weight or more of n-butyl (meth) acrylate, and contains or contains no The monomer component of 2% by weight of the carboxyl group-containing monomer is adhered to both sides of the acrylic adhesive layer obtained by polymerization. In this document, due to the hard characteristics of the adhesive layer or the cross-linking design, the adhesive tape having the above-mentioned adhesive layer is used for bonding the polarizing plate and the liquid crystal cell (glass substrate), and the adhesive layer is durable. Insufficient sexual or processing characteristics, or fear of light leakage.

Patent Document 5 proposes a durable adhesive which can suppress warpage of an optical film such as a polarizing plate even when placed in a low-temperature environment, and is a linear or branched alkyl carbon. a monomer unit of 2 to 18 alkyl (meth) acrylate as a main skeleton, further The (meth)acrylic acid alkyl ester-copolymerized copolymerized monomer is used as a monomer unit, and an acrylic polymer having a weight average molecular weight of 300 to 2.5 million is used as a matrix polymer, and the Tg is -35 ° C or less for optical use. Adhesive layer.

In addition, Patent Document 6 discloses an acrylic polymer (A) and an ionic compound (B) which are composed of the following monomer components (a1) to (a4) and have a weight average molecular weight of 1,000,000 or more. The crosslinking agent (C), and the gel fraction after cross-linking is 60% by weight or more of the adhesive composition for an optical film; the monomer component (a1): n-butyl (meth)acrylate is 10 to 89.9% by mass; Body component (a2): 5 to 50% by mass of the specific (meth)acrylic acid alkyl ester monomer; monomer component (a3): 5 to 40% by mass of the monomer having an alkylene oxide group; monomer component (a4): The hydroxyl group-containing monomer is 0.1 to 10% by mass. Patent Document 7 discloses that (A) contains: 0.1 to 1% by weight of a repeating unit having a carboxyl group in a molecule; and 0.01 to 0.5% by weight of an acrylic copolymer having a repeating unit of a hydroxyl group (but the weight of the acrylic copolymer is 100% by weight), based on 100 parts by weight of the acrylic copolymer having a weight average molecular weight (Mw) of 800,000 or more and a glass transition temperature (Tg) of -40 ° C or less, containing (B) a polyisocyanate compound of 0.3 to 3 by weight. And (C) a pressure-sensitive adhesive composition for a polarizing film in which 0.05 to 5 parts by weight of a decane coupling agent containing a mercapto group and an alicyclic epoxy group are essential components, and Patent Document 8 discloses a weight average molecular weight. M _w is an adhesive tape of at least one layer of polyacrylate having a range of 200,000 ≦M _w ≦ 1 million g/mol, and the polyacrylate is one or more kinds of formulas of (a) 55 to 92% by weight. The acrylic monomer of CH ₂ =CH-COOR ₁ (R ₁ means a hydrocarbon residue of C4 to C14, and the homopolymer of the monomer of component (a) has a glass transition temperature of T _{G and aH} of -20 ° C (b) 5 to 30% by weight of one or more kinds of copolymerizable monomers (the homopolymerization of the monomers of the component (b) Radical monomer glass transition temperature thereof is T _{G, bH} 0 deg.] C or higher) and (c) 3 to 15 weight% of one or a plurality of kinds of promoting copolymerizable polyacrylate co-crosslinking reaction of It is obtained by polymerization, where the aforementioned polyacrylate meets the specific parameters of the adhesive tape.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Laid-Open Patent Publication No. 2001-272541

[Patent Document 2] Japanese Laid-Open Patent Publication No. 2003-50313

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2001-350020

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2010-215794

[Patent Document 5] Japanese Laid-Open Patent Publication No. 2011-17009

[Patent Document 6] Japanese Laid-Open Patent Publication No. 2012-131963

[Patent Document 7] Japanese Laid-Open Patent Publication No. 2004-224873

[Patent Document 8] Japanese Laid-Open Patent Publication No. 2012-531498

As described above, with the increase in size and thickness of display devices and the spread of LED systems, demands for various characteristics are becoming higher.

In particular, regarding the thinning, it is known that the dimensional change of the polarizing plate when shrinking with a thermal environment is used for a transparent substrate of a liquid crystal cell (a constituent layer of a liquid crystal cell laminated on a polarizing plate via an adhesive, typically glass) The substrate) produces a bending. Then, in recent years, the thickness of the transparent substrate has become For example, a very thin one of 0.4 mm or less is more likely to cause the aforementioned warpage.

Therefore, for example, even when the polarizing plate is bonded to such a thin transparent substrate by using the adhesives proposed in Patent Documents 1 to 3, warpage of the substrate cannot be sufficiently suppressed, and light leakage occurs.

Accordingly, it is an object of the present invention to provide a suitable combination for use in a polarizing plate and various optical members (especially a thin transparent substrate), which can effectively suppress warpage of the aforementioned members in a hot environment, and effectively prevent light leakage. Moreover, it is not easy to adhere to an adhesive composition having a good processing property such as a tool.

In order to solve the above problems, the present inventors have found that the (meth)acrylic resin constituting the adhesive exhibits good hard properties at room temperature and exhibits good workability, and exhibits flexibility during heating. To alleviate the stress applied to the optical member (especially a thin transparent substrate), such a (meth)acrylic resin is combined with a certain amount of a crosslinking agent, and the degree of crosslinking is suppressed within a certain range, and then the coupling of the butane couple is performed. The composition can solve the above problems by improving the adhesion of the adhesive to the optical member, and thus the present invention has been completed.

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

The (meth)acrylic monomer (a1) is preferably an alkyl group having a branched carbon number of 3 to 8 from the viewpoint of the combination of the hard property at room temperature and the flexibility at the time of heating. The acrylic monomer is more preferably a third butyl (meth) acrylate and/or an isobutyl (meth) acrylate.

The gel fraction of the adhesive composition for a polarizing plate of the present invention is generally in the range of 50 to 80%.

The adhesive composition for a polarizing plate of the present invention has a certain hardness at room temperature and has excellent processing properties. Specifically, when the composition is subjected to the following subliminal test, the latent value at 23 ° C is preferably 0.3 mm or less: a polyester film applied to the above-mentioned adhesive composition for a polarizing plate by a release treatment, And drying the adhesive sheet to prepare an adhesive sheet having a film thickness of 25 μm ; bonding the adhesive sheet to the polarizing plate so that the adhesive layer is in contact with the polarizing plate, and preparing an adhesive processing for evaluation The polarizing plate was immersed in a dark room at 23 ° C / 50% RH for 7 days; the adhesive-processed polarizing plate was cut into a width of 10 mm × a length of 100 mm, and the release-treated polyester film was peeled off and treated with alkali. The glass was bonded to the glass so as to be in contact with the glass, and was bonded to a bonding area of 10 mm × 10 mm as a test sheet for evaluation of an adhesive processing polarizing plate; The test piece of the plate was subjected to autoclave treatment (50 ° C, 5 atm), and allowed to stand in an environment of 23 ° C / 50% RH for 24 hours; then, the test piece was attached to the micro-submersible with a length of 15 mm for fixing the chuck portion. Change the cavity of the test machine BOX; heating After the chamber BOX is allowed to stand at the measurement temperature for 40 minutes, the tensile load is 800 g and the stretching time is 1000 seconds, and the laminate of the adhesive layer and the polarizing plate of the test piece is parallel to the temperature. The laminated body and the contact surface of the glass were stretched in the longitudinal direction of the laminated body, and the distance (mm) of the offset of the bonded portion of the glass and the laminated body of the test piece was measured as a latent change value.

Further, since the adhesive composition for a polarizing plate of the present invention exhibits good flexibility upon heating, the ratio of the latent value of 60 ° C to the latent value of 23 ° C when the aforementioned creep test is performed (60) The latent value of °C / the latent value of 23 ° C is preferably 1.4 or more.

The ratio of the structural unit derived from the (meth)acrylic monomer (a1) to the (meth)acrylic resin (A) is preferably 5 to 45% by weight based on the (meth)acrylic monomer. The ratio of the structural unit of (a2) is 49.5 to 90% by weight, and the ratio of the structural unit derived from the aforementioned (meth)acrylic monomer (a3) is 1.5 to 5.5% by weight, and the structure derived from the aforementioned other monomer (a4) The ratio of the units is from 0 to 5% by weight.

The weight average molecular weight of the (meth)acrylic resin (A) is preferably from 500,000 to 2,000,000 from the viewpoint of good hard properties at room temperature of the adhesive composition for a polarizing plate of the present invention.

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

The polarizing plate with an adhesive layer of the present invention is formed by forming an adhesive layer containing the adhesive composition for a polarizing plate of the present invention on at least one side of the polarizing plate.

The adhesive composition of the present invention is particularly suitable for use in bonding a polarizing plate to a transparent substrate having a thickness of 0.3 mm or less, and the thickness of the adhesive layer of the polarizing plate with the adhesive layer obtained by the bonding is 0.3 mm. A laminate comprising the following transparent substrate is also included in the present invention.

For example, a flat panel display is manufactured by various manufacturing steps by using the polarizing plate or laminated body with the adhesive layer described above.

The adhesive composition for a polarizing plate of the present invention can be suitably used for bonding a polarizing plate to various optical members. Since the composition exhibits good hard characteristics at room temperature, it is excellent in workability and exhibits flexibility during heating, and the stress applied to the optical member by the dimensional change of the polarizing plate can be alleviated, and as a result, the member is particularly thin and transparent. The warpage at the time of heating can be favorably suppressed.

Fig. 1 is a view showing a light leakage R of a screen of a 19-inch liquid crystal panel used for evaluation of light leakage characteristics of the embodiment, and a straight line near each corner. The luminance measuring portion (La, Lb, Lc, Ld) of the region having a diameter of 1 cm and the luminance measuring portion (Lcenter) of the region having a diameter of 1 cm in the central portion of the monitor.

Hereinafter, the present invention will be described in detail.

[Adhesive Composition for Polarizing Plate]

The adhesive composition for a polarizing plate of the present invention (hereinafter also referred to simply as "the composition of the present invention") is as described above, and includes a specific (meth)acrylic resin (A) and a specific amount of a crosslinking agent (B). And decane coupling agent (C). Hereinafter, each component will be described. In the present specification, the term "(meth)acrylic" means methacrylic acid or acrylic acid, and the term "(meth)acrylate" means methacrylate or acrylate.

[(A) (meth)acrylic resin]

The (meth)acrylic resin (A) constituting the composition of the present invention, as described above, contains structural units derived from specific monomers (a1) to (a4) in a specific ratio (may not include other monomers (a4)) Construction unit). Hereinafter, a single unit that becomes each structural unit will be described.

<(a1) (meth)acrylic monomer>

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

In the present specification, the aforementioned Tg, unless otherwise specified, is to measure the Tg test piece (the homopolymer) in a range of -60 ° C to 180 ° C in an N ₂ atmosphere, and to increase the temperature at a rate of 10 ° C / min. The glass transition temperature determined by the heat was measured by DSC (differential scanning calorimeter DSC8230). Further, the measurement was carried out in accordance with JIS K7111 (Method for Measuring Transformation Temperature of Plastics).

Moreover, the glass transition temperature (Tg (°C)) of the homopolymer can also be referred to the glass transition temperature of various individual polymers (homopolymers) described in "Polymer Handbook 3rd Edition" (issued by John Wiley & Sons). (Tg(K)). For reference only, the Tg of some of the homopolymers of various monomers (including monomers other than (meth)acrylic monomers) is shown in Table 1 below (in °C units).

The (meth)acrylic monomer (a1) is not particularly limited as long as it satisfies the requirements of the above Tg, and examples thereof include, for example, a (meth) acrylate having an alkyl group having 1 to 20 carbon atoms, and the alkyl group described above. The carbon number is preferably from 3 to 8 from the viewpoint of both the hard characteristics at room temperature and the good softness at the time of heating.

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

Specific examples of such a (meth)acrylic monomer (a1) include methyl (meth)acrylate, ethyl methacrylate, propyl (meth)acrylate, isopropyl methacrylate, and methyl group. N-butyl acrylate, isobutyl methacrylate, 3 butyl (meth) acrylate, amyl acrylate, cyclohexyl (meth) acrylate, isodecyl (meth) acrylate, tetradecyl acrylate, Cetyl (meth) acrylate and stearyl (meth) acrylate.

Among these, from the above viewpoints, preferred are 3,butyl (meth)acrylate and isobutyl methacrylate, and particularly preferred is 3,butyl (meth)acrylate. Furthermore, in the present invention, the (meth)acrylic monomer (a1) described above may be used alone or in combination of two or more.

<(a2) (meth)acrylic monomer>

The (meth)acrylic resin (A) used in the present invention comprises a (meth)acrylic monomer (a2) having a glass transition temperature (Tg) of from -60 ° C or more and less than 0 ° C from a homopolymer. Construction unit. The structural unit of the monomer having a low Tg from the homopolymer thus contributes to the excellent softness of the (meth)acrylic resin (A) and the adhesive composition for a polarizing plate of the present invention containing the same. .

The (meth)acrylic monomer (a2) is not particularly limited as long as the Tg of the above-mentioned homopolymer is within the above range, and is preferably a (meth)acrylate having a rigid structure such as an aromatic ring. In the present specification, the term "aromatic ring" as used herein refers to a structure in which atoms having π electrons are arranged in a ring shape, satisfying the Huckel criterion, and the aforementioned π electrons are non-instrumental. The ring is a planar structure.

Specific examples of such a (meth)acrylic monomer (a2) include ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl methacrylate, and isoamyl acrylate. Hexyl (meth)acrylate, heptyl acrylate, isoamyl acrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl (meth)acrylate, n-decyl acrylate, acrylic acid An oxime ester, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl acrylate and n-tridecyl acrylate.

Among these, the composition of the present invention is preferably n-butyl acrylate from the viewpoint of achieving good flexibility at the time of heating. Furthermore, in the present invention, the (meth)acrylic monomer (a2) described above may be used alone or in combination of two or more.

<(a3) (meth)acrylic monomer>

The (meth)acrylic resin (A) used in the present invention contains a structural unit derived from a (meth)acrylic monomer (a3) having a carboxyl group. In the (meth)acrylic resin (A) of the composition of the present invention, a part of the carboxyl group derived from the structural unit of the monomer (a3) participates in crosslinking by the action of the crosslinking agent (B) described later, and a part thereof Hydrogen bonds are formed without crosslinking (it is also considered that there are also carboxyl groups which do not crosslink and do not form hydrogen bonds). At the time of heating, the hydrogen bond is cut, and the softness of the (meth)acrylic resin (A) containing the structural unit is considered to be increased.

Further, crosslinking by formation of a carboxyl group (and formation of a hydrogen bond) is important in exerting the effects of the present invention, and for example, crosslinking by a carboxyl group does not provide the effects of the present invention.

The aforementioned (meth)acrylic monomer (a3) has a carboxyl group Further, it is not particularly limited, and specific examples thereof include (meth)acrylic acid, β-carboxyethyl (meth)acrylate, β-carboxyethyl (meth)acrylate, and 5-carboxypentyl (meth)acrylate. A carboxyl group-containing (meth) acrylate such as succinic acid mono(methyl) propylene methoxyethyl ester or ω-carboxy polycaprolactone mono (meth) acrylate.

Among these, acrylic acid is preferred from the viewpoint of achieving good flexibility at the time of heating. Furthermore, in the present invention, the (meth)acrylic monomer (a3) may be used alone or in combination of two or more.

<(a4) Other monomers>

In the present invention, in order to adjust various characteristics, the (meth)acrylic resin (A) may contain other monomers than the above monomer components (a1) to (a3) insofar as the effects of the present invention are not impaired. Construction unit of (a4).

As an example of such another monomer (a4), as a monomer containing a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxyl (meth)acrylate a hydroxyl group-containing (meth) acrylate such as butyl ester, 6-hydroxyhexyl (meth) acrylate or 8-hydroxyoctyl (meth) acrylate; and an amino group-containing monomer such as (meth) acrylate An amino group-containing (meth) acrylate such as methylaminoethyl ester or diethylaminoethyl (meth) acrylate; and a guanamine group-containing monomer such as (meth) acrylamide, N -Methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-propyl (meth) acrylamide, N-hexyl (meth) acrylamide and (methyl) Dimethylaminoethyl acrylate; Examples of the monomer containing a nitrogen-based heterocyclic ring include vinyl pyrrolidone, acryloyl morpholine, and vinyl caprolactone.

Further, in the monomer having a (meth)acrylic structure, if the ester moiety has an alkylene oxide group, the side chain is easily moved, and the hardening property of the adhesive composition for a polarizing plate of the present invention changes at room temperature. The (meth)acrylic resin (A) used in the composition is preferably a structural unit which does not contain 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.

<Method for Producing (Meth)Acrylic Resin (A)>

The (meth)acrylic resin (A) described above can be obtained by solution polymerization, bulk polymerization, emulsion polymerization of each monomer component (a1) to (a3) and other monomers (a4) as needed. It is produced by polymerization of a conventional polymerization method such as a method or a suspension polymerization method. In these methods, since it is easy to adjust the molecular weight of the resin and to mix less impurities into the reaction system, a solution polymerization method is preferred.

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

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

Further, as the polymerization initiator, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), An azo compound such as 2,2'-azobis-2,4-dimethylvaleronitrile or 1,1'-azobiscyclohexane-1-carbonitrile; diisobutyl peroxide, α, α' - bis(new fluorenyl peroxide) diisopropylbenzene, cumene peroxy neodecanoate, di-n-propyl peroxydicarboxylate, di-isopropyl peroxydicarboxylate, dicarboxylic acid dicarboxylic acid 2nd butyl ester, 1,1,3,3-tetramethylbutyl peroxy neodecanoate, bis(4-butylhexyl) dicarboxylate, benzoyl peroxide, and 3rd peroxide Butyl, dodecyl peroxide, and butyloxy-2-ethyl hexanoate. These may be used alone or in combination of two or more.

In the solution polymerization method, the reaction temperature of the copolymerization reaction using the reaction solvent and the polymerization initiator is generally 50 to 90 ° C, preferably 60 to 85 ° C, and the reaction time is usually 1 to 10 hours. Preferably, it is 2 to 8 hours, and the reaction pressure is usually from normal pressure to 0.1 MPa.

The ratio of each structural unit of the (meth)acrylic resin (A), the weight average molecular weight, the molecular weight distribution, and the like of the (meth)acrylic resin (A) can be adjusted by the amount of each monomer component of the polymerization or by changing various conditions.

<Characteristics of (Meth)Acrylic Resin (A)>

For example, the (meth)acrylic resin (A) produced by the above method has a structural unit of a (meth)acrylic monomer (a1) having a Tg of 0 ° C or higher from a homopolymer, thereby being in a chamber. The hard characteristics under the temperature are good, and the adhesive composition of the polarizing plate of the present invention has excellent processing characteristics. Further, the (meth)acrylic resin (A) has a structural unit derived from a homopolymer such as a (meth)acrylic monomer (a2) having a Tg of -60 ° C or more and less than 0 ° C. The partial softness is exhibited during heating, and warpage of an optical member such as a transparent substrate due to a change in heating size of the polarizing plate is suppressed, and good light leakage prevention performance can be achieved. Further, the (meth)acrylic resin (A) has a structural unit derived from a (meth)acrylic monomer (a3) having a carboxyl group, and a part of the carboxyl group is crosslinked by a crosslinking agent (B) to be described later. The hard characteristics at room temperature of the composition of the present invention are improved, and as a result, the processing characteristics are improved. On the other hand, it is considered that the hydrogen bond formed by the carboxyl group is cut during heating, whereby the structural unit derived from the monomer (a3) during heating imparts flexibility to the composition of the present invention upon heating, which is helpful The suppression of the warpage of the optical member improves the performance of preventing light leakage.

In such a (meth)acrylic resin (A), the structural unit derived from the above (meth)acrylic monomer (a1) accounts for 5 to 50% by weight in 100% by weight of all structural units, from the above (methyl) The structural unit of the acrylic monomer (a2) accounts for 43 to 93.9% by weight of 100% by weight of all structural units, and the structural unit derived from the above (meth)acrylic monomer (a3) is 100% by weight of all structural units. % accounted for 1.1 to 7% by weight. Further, the total amount of the structural units derived from the monomers (a1) to (a3) is 90% by weight or more and 100% by weight or less. Further, the (meth)acrylic resin (A) may contain the above-mentioned structural unit derived from the other monomer (a4) in a proportion of from 0 to 10% by weight based on 100% by weight of all the structural units.

When the ratio of the structural unit derived from the (meth)acrylic monomer (a1) is less than 5% by weight, sufficient hard characteristics of the (meth)acrylic resin (A) at room temperature cannot be exhibited, and the composition of the present invention The processing characteristics of the material are poor. On the other hand, if it exceeds 50% by weight, the hard characteristics are excessive and the softness is heated. The softness is insufficient, and it is difficult to suppress the warpage of the optical member. From such a point, the proportion of the structural unit derived from the aforementioned (meth)acrylic monomer (a1) is preferably from 5 to 48% by weight, more preferably from 5 to 45% by weight.

When the ratio of the structural unit derived from the (meth)acrylic monomer (a2) is less than 43% by weight, the flexibility at the time of heating becomes insufficient, and when it exceeds 93.9 wt%, the adhesive becomes too soft. It causes bleed out of the adhesive, dents on the surface, and reduced applicability of press processing. From such a point, the proportion of the structural unit derived from the aforementioned (meth)acrylic monomer (a2) is preferably from 46 to 92% by weight, more preferably from 49.5 to 90% by weight.

When the ratio of the structural unit derived from the (meth)acrylic monomer (a3) is less than 1.1% by weight, a sufficient crosslinking ratio cannot be obtained, and hard properties at room temperature become insufficient, and the composition of the present invention is processed. The characteristics are deteriorated. On the other hand, when the ratio exceeds 7% by weight, the crosslinking ratio becomes too high, and the flexibility at the time of heating becomes insufficient, and it becomes difficult to suppress warpage of the optical member. From such a point, the proportion of the structural unit derived from the aforementioned (meth)acrylic monomer (a3) is preferably from 1.3 to 6% by weight, more preferably from 1.5 to 5.5% by weight.

When the ratio of the structural unit derived from the other monomer (a4) is from 0 to 10% by weight, the effects of the present invention are not impaired, and various characteristics of the composition of the present invention can be adjusted. The proportion of the structural unit derived from the aforementioned other monomer (a4) is preferably from 0 to 5% by weight.

The amount of the structural unit derived from the (meth)acrylic monomers (a1) to (a4) is reflected in the 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 various structural units described above is generally 500,000 or more. By setting 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 characteristics.

In the present specification, the weight average molecular weight means the weight average molecular weight of the converted standard polystyrene measured by GPC, and the weight average molecular weight of the (meth)acrylic resin (A). From the above viewpoint, it is preferred. It is 500,000 to 2 million, and more preferably 1 million to 2 million.

Further, the molecular weight distribution (Mw/Mn) of the (meth)acrylic resin (A) is generally 2 to 2 from the viewpoint of the contamination property of the adherend at the time of rework or the processing property which is softened for the adhesive composition. 10, preferably 4 to 8, the Tg is generally from -55 to 0 °C from the viewpoint of suitable wettability/adhesion characteristics/hard characteristics.

[(B) Crosslinker]

Next, the crosslinking agent (B) contained in the adhesive composition for a polarizing plate of the present invention will be described. The crosslinking agent (B) causes a crosslinking reaction with a carboxyl group of the (meth)acrylic monomer (a3) or a crosslinkable group derived from a structural unit of the other monomer (a4), and adjusts the present invention. The gel fraction of the composition is a predetermined range described later. Thereby, good adhesion of the polarizing plate to the adherend is ensured, and the composition exhibits good flexibility at the time of heating, suppresses warpage of the optical member, and achieves excellent light leakage prevention performance. Further, examples of the crosslinkable group include a hydroxyl group, a carboxyl group, an epoxy group, an amine group, a guanamine group, and a tertiary amine group.

The crosslinking agent (B) is not particularly limited as long as it can cause a crosslinking reaction with the (meth)acrylic resin (A), and examples thereof include an isocyanate crosslinking agent and a metal chelate crosslinking agent and a ring. Oxygen crosslinker.

Specific examples of the isocyanate crosslinking agent include tolyl diisocyanate, chlorophenyl diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, and xylylene diisocyanate. Isocyanate monomer such as diphenylmethane diisocyanate or hydrogenated diphenylmethane diisocyanate; isocyanate compound added to trimethylolpropane or the like; isocyanuric acid compound; biuret type compound Further, a polyamine ester prepolymer type isocyanate which is added and reacted with a conventional polyether polyol, a polyester polyol, an acrylic polyol, a polybutadiene polyol, a polyisoprene polyol or the like.

The metal chelate-based crosslinking agent is, for example, a polyvalent metal such as aluminum, iron, copper, zinc, tin, titanium, nickel, ruthenium, magnesium, vanadium, chromium or zirconium, and is coordinated with isopropyl alcohol or acetamidine. A compound such as acetone or ethyl acetate.

As specific examples thereof, for example, aluminum isopropoxide, diisopropoxy bisacetoacetone titanate, and ethyl triacetate ethyl acetate.

Specific examples of the epoxy-based crosslinking agent include, for example, ethylene glycol epoxypropyl ether, polyethylene glycol diepoxypropyl ether, glycerin diepoxypropyl ether, and glycerol triepoxypropyl Ether, 1,3-bis(N,N-diepoxypropylaminomethyl)cyclohexane, N,N,N',N'-tetraepoxypropyl-m-extended xylylenediamine ,N,N,N',N'-tetraepoxypropylaminophenylmethane, triepoxypropyl isocyanurate, mN,N-diepoxypropylaminophenyl epoxide Ether, N, N- Di-epoxypropyl toluidine and N,N-diepoxypropyl aniline.

The crosslinking agent (B) described above may be used alone or in combination of two or more. The crosslinking agent (B) is contained in the adhesive composition for a polarizing plate of the present invention in an amount of 0.15 to 1.5 parts by weight based on 100 parts by weight of the (meth)acrylic resin (A).

Thus, by containing a certain amount of the crosslinking agent (B), a moderate degree of crosslinking (gel ratio) is achieved for the composition of the present invention, and good hard characteristics at room temperature can be achieved (this is associated with good processing). Characteristics) and good flexibility during heating (this is related to prevention of warpage of the adherend of the polarizing plate). From such a viewpoint, the content of the crosslinking agent (B) is preferably from 0.3 to 1.2 parts by weight based on 100 parts by weight of the (meth)acrylic resin (A).

[(C) decane coupling agent]

The adhesive composition for a polarizing plate of the present invention comprises a decane coupling agent (C). The decane coupling agent (C) forms a bond such as a chemical bond with various adherends, thereby improving the adhesion between the polarizing plate and the adherend. In particular, it is effective for the subsequent attachment of a glass substrate.

As the decane coupling agent (C), for example, a fluorene compound containing a polymerizable unsaturated group such as vinyl trimethoxy decane, vinyl triethoxy decane or methacryl methoxy trimethoxy decane; 3-epoxy Propyloxypropyltrimethoxydecane, 3-glycidoxypropylmethyldimethoxydecane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxydecane have epoxy Base structure of hydrazine compound; 3-aminopropyltrimethoxydecane, N-(2-aminoethyl) 3-aminopropyltrimethoxydecane and N-(2-aminoethyl)-3 - an amine group-containing hydrazine compound such as aminopropylmethyldimethoxydecane; and 3-chloropropyl Trimethoxy decane; oligomeric decane coupling agent, and the like.

Among these, a decane coupling agent having a functional group reactive with a functional group (carboxyl group or the like) contained in the (meth)acrylic resin (A) is not easily produced from a polarizing plate in a moist heat environment. The point at which the adherend is peeled off is preferred.

The compounding amount of the decane coupling agent (C) of the composition of the present invention is usually 0.01 to 0.3 parts by weight, preferably 0.05 to 0.25 parts by weight, based on 100 parts by weight of the (meth)acrylic resin (A). Further, the decane coupling agent (C) may be used alone or in combination of two or more.

[Other ingredients]

The adhesive composition for a polarizing plate of the present invention may further contain an antistatic agent, an antioxidant, an ultraviolet absorber, a colorant, a pigment, a dye, a tackifying resin, a surface lubricant, a leveling agent, a softening agent, and the like, if necessary. Other components such as an anti-aging agent, a photostabilizer, a photoinitiator, a polymerization inhibitor, a filler, organic particles, inorganic particles or a plasticizer. The composition of the present invention may contain, as the softening agent, an acrylic copolymer having a weight average molecular weight Mw of not less than 100,000, which does not contain a crosslinkable functional group, and 100 parts by weight based on the (meth)acrylic resin (A). It is 5 to 50 parts by weight. Further, the composition of the present invention may contain a solvent other than the solvent used for the production of the (meth)acrylic resin (A).

[Adhesive Composition for Polarizing Plate]

The adhesive composition for a polarizing plate of the present invention comprises the (meth)acrylic resin (A) described above, a specific amount of a crosslinking agent (B), and a decane coupling agent (C).

It is considered that (meth)acrylic resin (A) is a variety of structural singles. The element exhibits good hard properties at room temperature or flexibility at the time of heating. The composition of the present invention containing such a (meth)acrylic resin (A) has excellent processing properties.

Moreover, by the presence of a specific amount of the crosslinking agent (B), the gel fraction of the composition of the present invention is generally from 50 to 80%, whereby good hard characteristics at room temperature can be attained, and gel The rate is not too high, and the aforementioned composition becomes soft when heated. In this way, it is estimated that the stress applied to the adherend (optical member such as a transparent substrate) due to the dimensional change of the polarizing plate during heating can be alleviated, and as a result, warpage of the adherend can be suppressed, and good light leakage prevention performance can be achieved. .

Further, in the specific composition of the present invention, the gel fraction can be adjusted to the above specific range, and the cohesive force of the composition is sufficient and the stress relaxation property upon heating is also good. Therefore, the composition of the present invention is also excellent in moist heat durability. For example, when it is placed in a hot and humid environment as an adhesive layer to be described later, the adhesive layer is less likely to be foamed or broken.

Further, since the composition of the present invention contains the decane coupling agent (C), the polarizing plate and the adherend can be sufficiently adhered.

As described above, since the composition of the present invention has good hard characteristics at room temperature, the following subtle creep test is carried out, and the latent value at 23 ° C is 0.5 mm or less. When considering the practicability of processing characteristics and the like, the latent value at 23 ° C is preferably 0.3 mm or less.

(small creep test)

The adhesive composition applied to the polarizing plate of the present invention was subjected to a release-treated polyester film and dried to prepare an adhesive sheet having an adhesive layer having a film thickness of 25 μm .

The adhesive sheet and the polarizing plate were bonded to each other so that the pressure-sensitive adhesive layer was in contact with the polarizing plate, and an adhesive-processed polarizing plate for evaluation was prepared and cooked in a dark room at 23 ° C / 50% RH for 7 days.

The cured evaluation adhesive sheet was cut into a width of 10 mm × a length of 100 mm, and the release-treated polyester film was peeled off from the alkali-treated glass so that the adhesive layer was in contact with the glass. In addition, it was bonded so as to be a bonding area of 10 mm × 10 mm, and it was used as a test sheet for evaluation of an adhesive processing polarizing plate.

For the evaluation, an adhesive processing polarizing plate test piece was subjected to autoclaving (50 ° C, 5 atm), and allowed to stand in an environment of 23 ° C / 50% RH for 24 hours.

Then, the aforementioned test piece was mounted in the cavity BOX of the minimal creep tester with a length of 15 mm of the chuck portion for fixing.

The inside of the cavity BOX is heated to the measurement temperature, and after standing at the measurement temperature for 40 minutes, the laminate of the adhesive layer and the polarizing plate of the test piece is parallel to the tensile load of 800 g and the stretching time of 1000 seconds. The laminated body and the surface of the glass are stretched in the longitudinal direction of the laminated body.

The distance (mm) of the offset of the bonding portion of the glass and the laminated body of the test piece was measured, and this was used as a latent value.

Further, since the composition of the present invention exhibits good flexibility upon heating as described above, the creep value at 60 ° C is 0.2 mm or more when the above-described subtle creep test is carried out. From the viewpoint of effectively preventing warpage of the optical member and achieving good performance of preventing light leakage, the creep value at 60 ° C is 0.3. Above mm is preferred.

Further, in order to effectively prevent the warpage of the optical member, when the temperature is raised from the room temperature to the heated state, it is important that the flexibility of the composition of the present invention also rises to a certain degree or more, specifically, the latent value at 60 ° C and 30 ° C. The ratio of the latent value (the latent value of 60 ° C / the latent value of 23 ° C) must be 1.3 or more. Further, in consideration of actual use, the ratio is preferably 1.4 or more, more preferably 1.5 or more, and generally the ratio is 25 or less.

<Use of Adhesive Composition for Polarizing Plate>

The adhesive composition for a polarizing plate of the present invention described above is excellent in both hard properties at room temperature and flexibility at the time of heating, and has good processing properties, suppresses warpage of the adherend of the polarizing plate, and exhibits good display. The ability to prevent light leakage.

Therefore, the composition of the present invention is suitable for the bonding application of a polarizing plate and various optical members. In particular, the composition of the present invention is used in a case where the optical member is extremely thin. For example, in the past, the transparent substrate having a thickness of 0.4 mm or less (liquid crystal cell) used in the field of display devices and the polarizing plate can be bonded to each other, thereby suppressing heating of the transparent substrate. Warp.

In particular, a transparent substrate which is further reduced in thickness and has a thickness of 0.3 mm or less in recent years is used. However, the use of such a very thin transparent substrate and a polarizing plate is also suitable for the composition of the present invention, and warpage of the transparent substrate is less likely to occur during heating.

<Method for Producing Adhesive Composition for Polarizing Plate>

The method for producing the adhesive composition for a polarizing plate of the present invention is not particularly limited, and various constituent components of the above composition are mixed by a known method. The composition of the present invention can be obtained, and in order to carry out the mixing smoothly, a solvent can be used.

Furthermore, the composition of the present invention produced generally has a health (cooking) for a certain period of time (for example, room temperature (23 ° C, 50% RH) for 3 to 7 days, heating promotion (40 ° C, 90% RH). The crosslinking reaction is carried out to a certain extent for about 2 to 5 days, and is adjusted to the above-mentioned suitable gel fraction for use.

[adhesive sheet]

When the adhesive composition for a polarizing plate of the present invention is used as an adhesive, when the adhesive layer is formed on the base film and used as an adhesive sheet, the treatment is simple and convenient.

When the substrate film is used for the treatment of the flat panel display in the production step of the flat panel display, the release film is preferably used as a material such as polyester, polyolefin, or polyether.

In the adhesive sheet of the present invention, for example, a coating liquid containing the composition of the present invention is applied/dried on a base film, and a solvent or the like contained in the coating liquid is vaporized to form an adhesive of a desired thickness. Made with layers. The thickness of the aforementioned adhesive layer is not particularly limited, and is preferably in the range of 5 to 100 μm , more preferably in the range of 10 to 50 μm . When the thickness of the adhesive layer is less than 5 μm , the predetermined performance may not be exhibited. When the thickness exceeds 100 μm , the processing characteristics when the adhesive sheet is cut may be lowered.

Further, in the pressure-sensitive adhesive sheet of the present invention, the surface of the pressure-sensitive adhesive layer which is not in contact with the surface of the base material film is covered with a release film, and the release film is peeled off during use.

[Polarizer with Adhesive Layer]

The adhesive layer containing the adhesive composition for a polarizing plate of the present invention is formed on at least one side of the polarizing plate, and as described above, it is possible to obtain an adhesive property which is excellent in processing characteristics and can achieve good light leakage prevention performance even in a hot environment. a polarizing plate of the agent layer.

In the composition of the present invention, since the flexibility is good at the time of heating, a transparent substrate such as a glass substrate is preferably laminated on the adhesive layer of the polarizing plate with the adhesive layer (preferably having a thickness of 0.4 mm or less, more preferably In the laminate of a thickness of 0.3 mm or less, the stress generated by the dimensional change of the polarizing plate is not easily applied to the transparent substrate, and warpage is less likely to occur.

<Method for Producing Polarizing Plate with Adhesive Layer>

The polarizing plate with an adhesive layer of the present invention can be produced by the following methods (1) to (3).

(1) A coating liquid containing the adhesive composition for a polarizing plate of the present invention is applied to a release layer of a release film by a conventional method (slit coating method, knife coating method, etc.) by heat After drying, the solvent or the like contained in the coating liquid is vaporized to form an adhesive layer having a desired thickness, and is bonded to the polarizing plate.

(2) The coating liquid containing the composition of the present invention is applied to a polarizing plate by a conventional method (slit coating method, knife coating method, etc.), and the solvent contained in the coating liquid is thermally dried. The gas is equalized to form an adhesive layer having a desired thickness, which is bonded to the release layer of the release film.

(3) The coating liquid containing the composition of the present invention is applied to the release layer of the first release film by a conventional method (slit coating method, knife coating method, etc.), and is dried by heat. a solvent or the like contained in the coating liquid is vaporized to form The adhesive layer having a desired thickness is bonded to the release layer of the second release film (generally lower than the release force of the first release film) to form a carrier-free adhesive film. Then, the second release film is peeled off, and the adhesive layer is bonded to the polarizing plate.

Further, the thickness of the adhesive layer of the obtained polarizing plate with the adhesive layer is not particularly limited, and is preferably in the range of 5 to 100 μm , more preferably in the range of 10 to 50 μm . When the thickness of the adhesive layer is less than 5 μm , the predetermined performance may not be exhibited. When the thickness exceeds 100 μm , the processing characteristics when the polarizing plate with the adhesive layer is cut may be lowered.

In the composition of the present invention, as described above, after the pressure-sensitive adhesive layer is formed, the treatment is carried out for a predetermined period of time to carry out a crosslinking reaction. Then, after adjusting to a suitable gel fraction, the adhesive layer can be adhered to a constituent layer of a flat panel display to be described later.

[flat panel display]

For example, the polarizer for a polarizing plate of the present invention is used, and a polarizing plate and a transparent substrate are bonded together (the result is that the laminated body described in the item of "the polarizing plate with an adhesive layer" described above) can be obtained as described above. The performance of preventing bending is achieved to prevent light leakage.

A flat panel display can be produced by using such a polarizing plate and the composition of the present invention, and the FPD manufactured is also included in the scope of the present invention.

As the FPD, for example, a liquid crystal display (LCD), a plasma display (PDP), and a field emission type display (FED).

The LCD generally has a liquid crystal layer sandwiched between a glass substrate having a transparent electrode and a liquid crystal layer. A laminated body structure of a polarizing plate is provided on the film or the color filter, and on the opposite surface of the surface of the glass substrate close to the liquid crystal layer.

The PDP is generally configured to have a phosphor layer interposed between the opposing glass substrates, and a laminate structure of various dielectric layers, electrodes, and other functional layers is provided on the surface of the glass substrate close to the phosphor layer.

The FED is generally composed of a glass substrate, an anode formed on the substrate, a phosphor layer formed on the electrode, a vacuum space, and a cathode sandwiching the space and facing the phosphor layer. The laminated structure of the glass substrate.

The polarizing plate with an adhesive layer of the present invention or a laminate having a transparent substrate laminated thereon constitutes a part of the constituent layers of the FPD. Further, at least a part of the constituent layers of the FPD can be sequentially laminated by using the adhesive sheet of the present invention.

[Examples]

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 was determined by GPC (gel permeation chromatography) under the following conditions by standard polystyrene conversion.

<GPC measurement conditions>

Measuring device: HLC-8120GPC (manufactured by Tosoh Corporation)

The composition of the GPC column: the following five strings (all manufactured by Tosoh Corporation)

(1) TSK-GEL HXL-H (protective column)

(2)TSK-GEL G7000HXL

(3)TSK-GEL GMHXL

(4)TSK-GEL GMHXL

(5)TSK-GEL G2500HXL

Sample concentration: diluted to 1.0 mg/cm ³ with tetrahydrofuran

Mobile phase solvent: tetrahydrofuran

Flow rate: 1.0cm 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 gas introduction tube, according to the mixing ratio of Table 2 and Table 3 below (the unit of the numerical value of the monomer in the table is part by weight), (M) is placed. Acrylic monomer (a1), (meth)acrylic monomer (a2), (meth)acrylic monomer (a3) and other monomer (a4), and then placed in ethyl acetate to make monomer concentration It became a blending amount of 50% by weight.

Then, 0.1 part by weight of 2,2'-azobisisobutyronitrile was added to 100 parts by weight of the total of the monomer components, and the air in the reaction vessel was stirred with nitrogen, and the mixture was stirred and heated to 60 ° C. It was allowed to react for 4 hours. After completion of the reaction, it was diluted with ethyl acetate to obtain a (meth)acrylic resin solution.

Furthermore, the meanings of the abbreviations of Tables 2 and 3 are as follows.

AA: Acrylic

BA: n-butyl acrylate

t-BA: 3 Butyl Acrylate

MMA: Methyl methacrylate

BMA: isobutyl methacrylate

HEA: 2-hydroxyethyl acrylate

[Production of Adhesive Polarized Plate for Evaluation]

The (meth)acrylic resin solution obtained by the above production example was used, and the blending ratios of the following Tables 4 to 6 (solid content ratio, the value is 100 weight with respect to the (meth)acrylic resin (indicated as "adhesive"). Parts by weight) The ingredients were mixed to obtain a solution of the adhesive composition.

A solution of the adhesive composition was applied onto the surface of the release-treated polyester film and dried to obtain an adhesive sheet having an adhesive layer having a thickness of 25 μm . The adhesive sheet was adhered to one side of a polarizing film (a composition of TAC (triethyl fluorenyl cellulose)-PVA (polyvinyl alcohol)-TAC), and then immersed in a dark room at 23 ° C / 50% RH for 7 days. An adhesive processing polarizing plate for evaluation was obtained.

〔Evaluation〕

The evaluations described below were carried out using the obtained adhesive-processed polarizing plate. The results of these evaluations are also shown in Tables 4 to 6 which will be described later.

<gel rate>

The obtained adhesive composition was applied to the surface of the release-treated PET film so as to have a thickness of 20 μm after drying, and dried. Then, on the other side of the surface on which the adhesive composition was applied, the release-treated PET film was applied in the same manner to form a test piece. The test piece was stored at 23 ° C, 50% RH, and after the start of storage (0 days), about 0.1 g of the adhesive was taken from the test piece to the sample bottle every day, and 30 cc of ethyl acetate was added to allow it to permeate for 24 hours. The contents of the vial were filtered through a 200 mesh stainless steel metal mesh and dried on a metal mesh at 100 ° C for 2 hours as the dry weight. The equivalent value was determined by the following formula.

Gel fraction (%) = (dry weight / weight of adhesive taken) × 100

Further, the gel fractions in Tables 4 to 6 indicate the measured values of the gel fraction after completion of aging and stabilization.

<Miniature creep test>

The above evaluation was cut into a width of 10 mm × length by an adhesive processing polarizing plate. 100 mm, the pressure-sensitive adhesive polarizing plate for peeling off the release-treated polyester film, and the adhesive layer is placed in contact with the glass so as to be bonded to the bonding area of 10 mm × 10 mm. The glass was treated with alkali, and autoclaved (50 ° C, 5 atm), and allowed to stand in an environment of 23 ° C / 50% RH for 24 hours. It was used as a sample for minimal creep test.

The test sample was mounted by using a length of 15 mm for the fixing chuck portion in the cavity BOX of the micro-leakage tester (Model name: TA.TX.PLUS). After heating the inside of the cavity BOX to the measurement temperature, after standing at the measurement temperature for 40 minutes, the tensile load was 800 g and the stretching time was 1000 seconds, and the laminate of the adhesive layer of the sample for the latent creep test and the polarizing plate was slightly The laminate is stretched in the longitudinal direction of the laminate in parallel with the subsequent surface of the glass. The distance (mm) from the offset of the bonded portion of the glass and the laminated body after the stretching was confirmed (measured) as a result of the little creep test.

<Light leakage characteristics>

(Light leakage size R)

In a liquid crystal panel of a size of 19 inches, an adhesive-processed polarizing plate for evaluation of peeling off of the release-treated polyester film is bonded, and the adhesive layer is bonded to the glass substrate of the liquid crystal panel, and the polarizing plate and the liquid crystal panel are Nikol. The Nicole Cross was placed in an environment of 80 ° C for 240 hours and then placed in a 23 ° C / 50% RH environment for 2 hours.

Then, the liquid crystal panel that is bonded to the polarizing plate is connected to the computer in the dark room to make the full screen black display. In this state, the portion where light leakage occurred was visually confirmed, and as shown in Fig. 1, the portion where light leakage occurred was measured to separate the aforementioned The distance from the corner of the screen is taken as the light leakage size R. When R is 30 mm or less, it can be used as a panel for liquid crystal display.

(△L(Cd/m ² ))

In the state where the full screen black is displayed, the luminance (La, Lb, Lc, Ld) of the region having a diameter of 1 cm in the vicinity of each corner and the diameter of the central portion of the monitor were measured using a luminance meter (RISA-COLOR/CD8 manufactured by Highland). In the luminance measuring portion (Lcenter) of the region of 1 cm, the light leakage property was obtained by the following formula.

Formula: △L=(La+Lb+Lc+Ld)/4-Lcenter

△ L (Cd / m ²⁾ smaller light leakage means (from the back) the less, typically less than 2.0, can be used as the liquid crystal display panel used.

<bending>

The borax silicate glass of 0.3 mm × 150 mm × 250 mm was bonded to a 130 mm × 230 mm adhesive-processed polarizing plate to be a Nicole Cross, and subjected to autoclave treatment (50 ° C, 5 atm). . After autoclaving, it was allowed to stand at 70 ° C for 72 hours.

Then, the degree of warpage of the glass was measured using an iron ruler as a result of evaluation of bending. Generally, it is 2 mm or less, preferably 1 mm or less, and more preferably 0.5 mm or less, and it is practically used without problems.

<Processing characteristics>

For the evaluation of the adhesive-processed polarizing plate, the predetermined mold was punched 10,000 times, and the adhesion of the adhesive to the blade was visually determined. The evaluation criteria are as follows.

○: no adhesion, △: a little adhesion, X: adhesion

<foaming and breaking>

For the 19-inch untreated glass, the adhesive-processed polarizing plate for the release of the release-treated polyester film was used as a test plate, and it was allowed to stand in the test environment (60 ° C / 95% RH) for 500 hours. After that, the change in appearance of foaming/fracture was visually confirmed, and it was evaluated based on the following criteria. Further, the foaming system has insufficient cohesive force due to a low degree of crosslinking, and the fracture system is insufficient in stress relaxation due to a too high degree of crosslinking.

Foaming - size)

○: No foaming at all

△: The diameter of the foaming is 1 mm or less.

X: The diameter of the foam is larger than 1mm.

Foaming-production amount)

○: No foaming at all

△: The number of foaming is 10 or less

X: The number of foaming is more than 10

Break-size

○: I can't see it at all.

△: The total area (100%) of the bonding area for the test board was less than 5%.

X: The area to be produced is 5% or more for the entire bonding portion (100%) of the test board.

Fracture-location

○: Nothing at all

△: Defect only at a position less than 0.5 mm from the end

X: Defective at a position 0.5 mm or more from the end

The compositions of the adhesive compositions of the examples and the comparative examples and the above various evaluation results are summarized in the following Tables 4 to 6.

Furthermore, the meanings of the abbreviations of Tables 4 to 6 are as follows.

L-45: TDI isocyanate compound (L-45, manufactured by Soken Chemical Co., Ltd.)

TD: XDI isocyanate compound (TD-75, 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-diepoxypropylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Co., Ltd.)

KBM-403: 3-glycidoxypropyltrimethoxydecane (manufactured by Shin-Etsu Chemical Co., Ltd.)

In Comparative Example 1, the amount of the crosslinking agent used did not reach the lower limit defined by the present invention, the gel fraction was extremely low, the cohesive force was insufficient, foaming occurred, and light leakage or bending could not be measured.

In Comparative Example 2, the amount of the crosslinking agent used exceeds the upper limit value specified in the present invention, and the gel fraction is very high. The ratio of the latent value of 60 ° C to the latent value of 23 ° C is about 1, and the polarized light during heating cannot be alleviated. The stress caused by the change in the size of the plate, and the warpage is large, causing light leakage.

Comparative Example 3 is based on the use of (meth)acrylic acid Since the resin of the structural unit of the monomer (a1) has a large latent value at 23 ° C, the hard characteristics at room temperature are poor, and the processing characteristics are poor. It also produces light leakage.

In Comparative Example 4, a resin containing a structural unit derived from a monomer having a hydroxyl group, which does not include a structural unit derived from the (meth)acrylic monomer (a1) and the (meth)acrylic monomer (a3), is used. Therefore, the warpage is large.

In Comparative Example 5, since the ratio of the structural unit derived from the (meth)acrylic monomer (a3) was less than the lower limit of the ratio specified in the present invention, and the resin derived from the structural unit of the monomer having a hydroxyl group was used, The processing characteristics are insufficient, the warpage is large, and the fracture is also seen. It was found that although the hydroxyl group reacted with the crosslinking agent to form a crosslinking, the effects of the present invention could not be obtained.

In Comparative Example 6, the same resin as in Comparative Example 5 was used, and the amount of the crosslinking agent used was twice. When the amount of crosslinking increases, the processing characteristics or the fracture are increased, but the stress relaxation during heating is insufficient to cause warpage or light leakage.

In Comparative Example 7, an example of an adhesive composition having substantially the same composition as the adhesive manufactured in Production Example 1 of Patent Document 3 was used. Since it has good hard characteristics at room temperature, it exhibits good processing characteristics. When it is used for bonding a glass substrate having a thickness of 0.3 mm to a polarizing plate, it is considered that stress relaxation is insufficient, warpage or light leakage occurs, and fracture is also observed.

Claims (12)

An adhesive composition for a polarizing plate comprising: (A): a (meth)acrylic resin containing a structural unit of a monomer derived from the following (a1) to (a4) in the following ratio; (a1) homopolymerization The Tg of the material is 5 to 50% by weight of the (meth)acrylic monomer above 0 ° C; (a2) the Tg of the homopolymer is -60 ° C or more and the (meth)acrylic monomer is less than 0 ° C To 93.9 wt%; (a3) 1.1 to 7% by weight of the (meth)acrylic monomer having a carboxyl group; and (a4) 0 to 10% by weight of the other monomer; (B): relative to the aforementioned (meth)acrylic acid 100 parts by weight of the resin is 0.15 to 1.5 parts by weight of a crosslinking agent; and (C): a decane coupling agent. The adhesive composition for a polarizing plate according to claim 1, wherein the (meth)acrylic monomer (a1) is a (meth)acrylic acid having a branched alkyl group having 3 to 8 carbon atoms. monomer. The adhesive composition for a polarizing plate according to claim 1 or 2, which has a gel fraction of 50 to 80%. The adhesive composition for a polarizing plate according to any one of the items 1 to 3, wherein the adhesive for the polarizing plate is subjected to the following subtle creep test, and the dive at 23 ° C The change value is 0.3 mm or less: the polarizing plate is coated with the adhesive composition on the release treatment And drying the polyester film to prepare an adhesive sheet having an adhesive layer having a thickness of 25 μm; and bonding the adhesive sheet and the polarizing plate so that the adhesive layer is in contact with the polarizing plate, and making an adhesion for evaluation The polarizing plate was processed and cooked in a dark room at 23 ° C / 50% RH for 7 days; the adhesive processing polarizing plate was cut into a width of 10 mm × a length of 100 mm, and the release-treated polyester film was peeled off to alkali. The treatment glass was bonded to the glass so that the adhesive layer was in contact with the glass, and was bonded to a bonding area of 10 mm × 10 mm to serve as a test sheet for evaluation of an adhesive processing polarizing plate; The test piece of the plate was subjected to autoclave treatment (50 ° C, 5 atm), and allowed to stand in an environment of 23 ° C / 50% RH for 24 hours; then, the test piece was attached to the micro-submersible with a length of 15 mm for fixing the chuck portion. In the cavity BOX of the test machine; heating the cavity BOX to the measured temperature, and after standing at the measurement temperature for 40 minutes, the adhesive layer of the test piece is formed with a tensile load of 800 g and a stretching time of 1000 seconds. Layered body of polarizing plate The laminate was stretched in the longitudinal direction of the laminated body in parallel with the laminated surface of the laminated body, and the distance (mm) of the offset of the bonded portion of the glass and the laminated body of the test piece was measured as a latent change value. The adhesive composition for a polarizing plate according to the fourth aspect of the invention, wherein the creeping value of 60 ° C is used when performing the aforementioned creep test. The ratio of the latent value at 23 ° C (the latent value at 60 ° C / the latent value at 23 ° C) was 1.4 or more. The adhesive composition for a polarizing plate according to any one of claims 1 to 5, wherein the (meth)acrylic resin (A) is derived from the (meth)acrylic monomer. The proportion of the structural unit of (a1) is 5 to 45% by weight, and the ratio of the structural unit derived from the aforementioned (meth)acrylic monomer (a2) is 49.5 to 90% by weight derived from the aforementioned (meth)acrylic monomer The proportion of the structural unit of (a3) is from 1.5 to 5.5% by weight, and the proportion of the structural unit derived from the aforementioned other monomer (a4) is from 0 to 5% by weight. The adhesive composition for a polarizing plate according to any one of claims 1 to 6, wherein the (meth)acrylic monomer (a1) is a (butyl) (meth)acrylate and / or isobutyl (meth)acrylate. The adhesive composition for a polarizing plate according to any one of claims 1 to 7, wherein the (meth)acrylic resin (A) has a weight average molecular weight of 500,000 to 2,000,000. An adhesive sheet for a polarizing plate, which is formed on a base film, and which is formed by an adhesive layer comprising the adhesive composition for a polarizing plate according to any one of the first to eighth aspects of the invention. A polarizing plate with an adhesive layer, wherein an adhesive layer is formed on at least one side of the polarizing plate, wherein the adhesive layer comprises the polarizing plate according to any one of claims 1 to 8. Use an adhesive composition. A laminate body attached as described in claim 10 of the scope of the patent application On the adhesive layer of the polarizing plate of the adhesive layer, a transparent substrate having a thickness of 0.3 mm or less is laminated. A flat panel display comprising a polarizing plate with an adhesive layer as described in claim 10 or a laminate according to claim 11 of the patent application.