JPWO2013099683A1 - Adhesive composition for optical member, adhesive sheet using the same, optical member with adhesive layer, and flat panel display - Google Patents

Abstract

An object of this invention is to provide the adhesive composition for optical members which is excellent in dimensional stability, and exhibits the outstanding light leakage prevention performance and durability also in a humid heat environment. The present invention provides a specific amount of (meth) acrylic copolymer (A) obtained by copolymerizing specific monomer components (a-1) to (a-4) at a specific ratio and a crosslinking agent (B). It is related with the adhesive composition for optical members characterized by including.

Description

  The present invention provides an adhesive composition for optical members which is excellent in dimensional stability and wet heat durability and can effectively prevent light leakage and peeling in a high temperature and high humidity environment, and an adhesive sheet and an adhesive layer using the same. The present invention relates to an attached optical member and a flat panel display.

  With respect to adhesives for the flat panel display (FPD) field, the demand for high quality such as high image quality and high durability has been increasing with the increase in the size of displays and the spread of LED systems.

  For example, a liquid crystal display (LCD) classified as an FPD is formed of a liquid crystal panel, a backlight, and peripheral circuits. This liquid crystal panel is typically composed of layers such as a polarizing plate, a glass substrate having a transparent electrode, and a color filter, and the glass substrate sandwiches the liquid crystal.

  The polarizing plate has a multi-layer structure of different materials, and each material has different physical and chemical characteristics. Therefore, particularly in a high temperature and high humidity environment, the dimensions of each layer due to shrinkage and swelling. The degree of change is different, and the degree of 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. It is also known that the light leakage and durability are affected by the type of pressure-sensitive adhesive used for bonding between optical films such as polarizing plates and bonding between a glass substrate and a polarizing plate.

  At present, the combination of polarizing plate type and pressure sensitive adhesive type supports various performance requirements such as light leakage and durability. Along with this, there is a demand for further sophistication such as higher image quality and higher durability.

  Here, for the pressure-sensitive adhesive type, various properties such as hard characteristics and optical characteristics of the polymer constituting the pressure-sensitive adhesive are used to solve light leakage caused by dimensional change of the polarizing plate and peeling in a high-temperature and high-humidity environment. In order to realize good light leakage prevention performance and ensure high durability, etc. are being studied.

  For example, pressure sensitive adhesives that focus on hard properties are not easily deformed even in a humid heat environment and are less likely to cause foaming. Therefore, they have excellent stress resistance and durability when contracting a polarizing plate, and relatively good light leakage prevention properties and durability. It was easy to get sex. However, when the FPD is increased in size, light leakage and slight foaming, which were not a problem in the previous size, become more noticeable, which is a problem. For this reason, conventional pressure-sensitive adhesives cannot sufficiently cope with the sophistication of required characteristics.

  As such an adhesive, for example, Patent Document 1 discloses a specific (meth) acrylic acid ester (A-1), an unsaturated monomer having an aromatic ring (A-2), and an unsaturated monomer having a polar functional group. Disclosed is a pressure-sensitive adhesive composition containing a (meth) acrylic copolymer (A) obtained by copolymerizing a monomer (A-3), an ionic compound (B), and a crosslinking agent (C). ing.

  The composition is used, for example, for adhesion of a polarizing plate. Examples of (A-1) include n-butyl acrylate. Examples of (A-2) include 2-phenoxyethyl (meth) acrylate. Examples of the (A-3) include acrylic acid and 2-hydroxyethyl (meth) acrylate.

Patent Document 2 discloses a (meth) acrylic acid ester monomer (a ₁ ) having a homopolymer Tg of less than −30 ° C., a compound (a ₂ ) having a vinyl group having a homopolymer Tg of −30 ° C. or more, and Polarized light having an adhesive layer comprising an adhesive containing a (meth) acrylic copolymer (A) comprising a specific functional group-containing monomer (a ₃ ) and a polyfunctional compound (B) capable of forming a crosslinked structure A board is disclosed.

Examples of (a ₁ ) include n-butyl acrylate, examples of (a ₂ ) include t-butyl acrylate, and examples of (a ₃ ) include (meth) acrylic acid and 2 -Hydroxyethyl (meth) acrylate is mentioned.

  However, as described above, the pressure-sensitive adhesives disclosed in these documents cannot cope with the advanced characteristics currently required.

JP 2010-66755 A JP 2006-301572 A

  Then, an object of this invention is to provide the adhesive composition for optical members which is excellent in dimensional stability, and exhibits the outstanding light leakage prevention performance and durability also in a wet heat environment.

  The inventors of the present invention have studied the pressure-sensitive adhesive composition focusing on the hard characteristics and the optical compensation function and the crosslinking system of the pressure-sensitive adhesive, and found useful for adjusting the monomer and the polymer hardness that impart flexibility to the polymer. Monomers are used in a specific ratio to set the hard characteristics of the polymer in an appropriate region, and monomers that can provide an optical compensation function and monomers that give the polymer crosslinkability are used in a specific ratio. Optically capable of effectively preventing light leakage and peeling in high temperature and high humidity environments by cross-linking the obtained (meth) acrylic copolymer with an appropriate degree of cross-linking to ensure excellent dimensional stability and wet heat durability. It discovered that the adhesive composition for members could be provided.

That is, the present invention includes (A): a (meth) acrylic copolymer obtained by copolymerizing the following (a-1) to (a-4) at the following ratio:
(A-1) The glass transition temperature of the homopolymer is −40 ° C. or less and (meth) acrylic acid ester having no aromatic ring is 40 to 94.9% by weight.
(A-2) The glass transition temperature of the homopolymer is 0 ° C. or higher and the (meth) acrylic acid ester having no aromatic ring is 0.1 to 50% by weight.
(A-3) 0.1 to 25% by weight of (meth) acrylic acid ester having an aromatic ring
(A-4) (Meth) acrylic monomer having two or more types of polar functional groups and / or (meth) acrylic monomer having one or more different types of polar functional groups of 0.1 to 6% by weight
(However, the sum of (a-2) and (a-3) is 5 to 59.9% by weight,
The polar functional group is selected from a carboxyl group, a hydroxyl group, an amino group, an amide group and an epoxy group,
(The sum of (a-1) to (a-4) is 100% by weight)
(B): A pressure-sensitive adhesive composition for an optical member comprising 0.01 to 3 parts by weight of a crosslinking agent with respect to 100 parts by weight of the (meth) acrylic copolymer (A).

  The copolymerization ratio of the (meth) acrylic acid ester (a-2) is preferably 10 to 40% by weight.

  The (meth) acrylic acid ester (a-2) is selected from the group consisting of methyl (meth) acrylate, i-butyl methacrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate and isobornyl (meth) acrylate. It is preferable that there is at least one.

  The (meth) acrylic acid ester (a-2) is preferably t-butyl (meth) acrylate.

  The copolymerization ratio of the (meth) acrylic acid ester (a-1) is preferably 50 to 90% by weight.

  The (meth) acrylic acid ester (a-1) is n-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl. Acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl methacrylate, n-tridecyl (meth) acrylate, methoxyethyl acrylate, methoxypolyethylene glycol acrylate and ethoxyethoxyethyl It is preferably at least one selected from the group consisting of acrylates.

  The (meth) acrylic acid ester (a-3) is at least one selected from the group consisting of benzyl (meth) acrylate, phenoxyethyl (meth) acrylic acid ester represented by the following general formula (1), and derivatives thereof. It is preferable that

In Formula (1), R ₀ is hydrogen or a methyl group, R ₁ is a group represented by (CH ₂ CH ₂ O) _n (n is an integer of 1 to 20), and m is 1 to R ₂ is hydrogen, an alkyl group having 1 to 9 carbon atoms, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 11 carbon atoms, and when m is 2 or more, a plurality of R ₂ are present. R ₂ may be the same or different.

  The copolymerization ratio of the (meth) acrylic monomer (a-4) is preferably 1 to 6% by weight.

  When the following minute creep test is performed on the pressure-sensitive adhesive composition for optical members, the ratio of the measured value at 60 ° C./measured value at 23 ° C. is preferably 1.05 to 2.00.

(Small creep test)
The pressure-sensitive adhesive composition for optical members 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;
The pressure-sensitive adhesive sheet is bonded to a polarizing plate having a TAC (triacetyl cellulose) -PVA (polyvinyl alcohol) -TAC configuration and the pressure-sensitive adhesive layer is in contact with the polarizing plate to produce a pressure-sensitive adhesive processed polarizing plate for evaluation;
The pressure-sensitive adhesive processing polarizing plate for evaluation is cut into a width of 10 mm × a length of 100 mm, the peel-treated polyester film is peeled off, and the pressure-sensitive adhesive layer is in contact with the glass on the alkali-treated glass and 10 mm × 10 mm. Are bonded so as to have a bonding area of 2 to obtain an adhesive-coated polarizing plate test piece for evaluation;
The test piece for the pressure-sensitive adhesive processed polarizing plate 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 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 evaluation-treated pressure-sensitive adhesive polarizing plate in the test piece is separated from the polarizing plate at a tensile load of 800 g and a tensile time of 1000 seconds. Pulling in parallel to the adhesive surface with the glass and in the length direction of the polarizing plate;
The distance (mm) of the deviation of the bonded portion between the glass and the polarizing plate in the test piece is measured.

  It is preferable that the pressure-sensitive adhesive composition for an optical member of the present invention further contains 0.01 to 0.5 parts by weight of a silane coupling agent with respect to 100 parts by weight of the (meth) acrylic copolymer (A).

  Moreover, it is preferable that the said composition contains 0.01-3 weight part of antistatic agents with respect to 100 weight part of said (meth) acrylic-type copolymers (A) further.

  By using the pressure-sensitive adhesive composition for optical members of the present invention as a component of a pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is formed on a substrate film can be obtained.

  An optical member with an adhesive layer in which an adhesive layer is formed on at least one surface of the optical member, wherein the adhesive layer contains the adhesive composition for optical members of the present invention. The attached optical member is also included in the scope of the present invention.

  The flat panel display of this invention has the said optical member with an adhesive layer, It is characterized by the above-mentioned.

  ADVANTAGE OF THE INVENTION According to this invention, it is excellent in dimensional stability and wet heat durability, and can effectively prevent light leakage and peeling in a high temperature and high humidity environment, and an adhesive using the composition. A sheet, an optical member with an adhesive layer, and an FPD are provided.

It is a schematic diagram which shows the distance d from the corner | corner of the light leak generation | occurrence | production part in the measurement of the light leak size in an Example. It is a schematic diagram which shows the measuring method of the photoelastic coefficient in an Example.

  Hereinafter, the pressure-sensitive adhesive composition for optical members of the present invention (hereinafter also simply referred to as “the composition of the present invention”), the pressure-sensitive adhesive sheet using the same, the optical member with a pressure-sensitive adhesive layer, and a flat panel display will be described in detail in order. To do. In the present specification, (meth) acryl means methacryl or acryl, and (meth) acrylate means methacrylate or acrylate.

[Adhesive composition for optical members]
[(A) (Meth) acrylic copolymer]
The (meth) acrylic copolymer (A), which is a constituent component of the composition of the present invention, is obtained by copolymerizing specific monomer components (a-1) to (a-4) at a specific ratio as described above. . Hereinafter, each of these monomers will be described.

<(A-1) (Meth) acrylic acid ester having a glass transition temperature of −40 ° C. or less and having no aromatic ring>
About the (meth) acrylic acid ester (a-1) used for this invention, the glass transition temperature (henceforth Tg) of the homopolymer is -40 degrees C or less.

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 manufactured by Rigaku Corporation) is used for calorimetric measurement. The measurement is performed in accordance with JIS K7121 (plastic transition temperature measurement method).

  If only the hard properties are improved, the crosslinked product obtained by crosslinking the pressure-sensitive adhesive composition for optical members of the present invention may have problems such as insufficient tackiness, so the Tg of the homopolymer is -40 ° C. By using the following (meth) acrylic acid ester (a-1), the (meth) acrylic copolymer (A) is imparted with appropriate flexibility and balanced.

  Moreover, the said (meth) acrylic acid ester (a-1) does not have an aromatic ring. If an aromatic ring is present, flexibility may not be imparted to the (meth) acrylic copolymer (A), and in balance with adjustment of the optical compensation function by the (meth) acrylic acid ester (a-3) described later. May cause problems.

  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.

  As such (meth) acrylic acid ester (a-1), n-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate , Isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl methacrylate, n-tridecyl (meth) acrylate, methoxyethyl acrylate, methoxypolyethylene glycol acrylate and And ethoxyethoxyethyl acrylate.

  Among these, n-butyl acrylate and 2-ethylhexyl acrylate are preferable from the viewpoint of achieving excellent stress resistance by balancing hard characteristics and flexibility.

  The (meth) acrylic acid ester (a-1) described above can be used alone or in combination of two or more.

<(A-2) (Meth) acrylic acid ester having a glass transition temperature of 0 ° C. or higher and no aromatic ring>
About (meth) acrylic acid ester (a-2) used for this invention, Tg of the homopolymer is 0 degreeC or more. Thus, (meth) acrylic acid ester (a-2) having a high Tg of homopolymer imparts excellent hard properties to (meth) acrylic copolymer (A), and the pressure-sensitive adhesive composition for optical members of the present invention. Contributes to high dimensional stability.

  Moreover, (meth) acrylic acid ester (a-2) does not have an aromatic ring. If an aromatic ring is present, there may be a problem in balance with the adjustment of the optical compensation function by the (meth) acrylic acid ester (a-3) described later.

  As such (meth) acrylic acid ester (a-2), methyl (meth) acrylate, propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, Examples include isobornyl (meth) acrylate and stearyl (meth) acrylate.

  Among these, from the viewpoint of achieving excellent hard properties, methyl (meth) acrylate, i-butyl methacrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate and isobornyl (meth) acrylate are preferable, and t- Butyl (meth) acrylate is particularly preferred.

  (Meth) acrylic acid ester (a-2) demonstrated above can be used individually by 1 type or in combination of 2 or more types.

<(A-3) (Meth) acrylic acid ester having aromatic ring>
The (meth) acrylic acid ester (a-3) has an aromatic ring, and by including a structural unit derived therefrom in the (meth) acrylic copolymer (A), the copolymer (A) The optical compensation function can be appropriately controlled. Thereby, even if an optical member is adhere | attached using the adhesive composition for optical members of this invention, and light leakage arises in a humid heat environment, this light leakage is suppressed by the said optical compensation function.

  Examples of such (meth) acrylic acid ester (a-3) include benzyl (meth) acrylate, phenoxyethyl (meth) acrylic acid ester represented by the following general formula (1), and derivatives thereof.

In Formula (1), R ₀ is hydrogen or a methyl group, R ₁ is a group represented by (CH ₂ CH ₂ O) _n (n is an integer of 1 to 20), and m is 1 to R ₂ is hydrogen, an alkyl group having 1 to 9 carbon atoms, an aryl group having 6 to 10 carbon atoms or an aralkyl group having 7 to 11 carbon atoms, and when m is 2 or more, a plurality of R ₂ are present. R ₂ may be the same or different.

  Specific examples of the phenoxyethyl (meth) acrylate represented by the general formula (1) and derivatives thereof include phenoxyethyl (meth) acrylate, phenoxydiethylene glycol (meth) acrylate, and phenoxy (poly) ethylene glycol (meth). Examples include acrylate, nonylphenol ethylene oxide adduct (meth) acrylate, ethoxylated o-phenylphenol (meth) acrylate, and the like.

  Among these, benzyl (meth) acrylate and phenoxyethyl (meth) acrylate are preferable from the viewpoint of achieving an excellent optical compensation function.

  The (meth) acrylic acid ester (a-3) described above can be used alone or in combination of two or more.

<(A-4) (Meth) acrylic monomer having two or more types of polar functional groups and / or (meth) acrylic monomer having one or more different types of polar functional groups>
The (meth) acrylic monomer (a-4) used in the present invention has a polar functional group, and a crosslinking reaction occurs between this and the crosslinking agent (B) described later, and the optical member of the present invention. Excellent adhesive properties are achieved for the pressure-sensitive adhesive composition. The polar functional group is a carboxyl group, a hydroxyl group, an amino group, an amide group, and an epoxy group. Among these, a hydroxyl group is preferable from the viewpoint of good durability in a moist heat environment.

  Further, the (meth) acrylic monomer (a-4) has two or more types of polar functional groups, and the presence of a plurality of different types of polar functional groups makes it possible to use the (meth) acrylic copolymer ( It is considered that the crosslinking between A) proceeds appropriately and a good degree of crosslinking is achieved.

  The above-mentioned “having two or more types of polar functional groups” means that two or more types of polar functional groups are present when the whole (meth) acrylic monomer (a-4) composed of a plurality of molecules is viewed. It is.

  Therefore, the (meth) acrylic monomer (a-4) is one type of monomer, and two or more types of polar functional groups may be present in one molecule of the monomer, or the (meth) acrylic monomer (a -4) is composed of two or more different monomers, and each of the monomers may have one type of polar functional group. The latter includes two or more types of monomers having different structures, but the case where the polar functional groups they have is the same is not included.

  In the (meth) acrylic copolymer (A), as the monomer (a-4), only a monomer having two or more types of polar functional groups in one monomer molecule may be used. First, two or more monomers having one type of polar functional group may be used, or both of them may be used.

  Moreover, in this specification, what corresponds to any of (meth) acrylic acid ester (a-1)-(a-3), and corresponds to a (meth) acrylic-type monomer (a-4), It is regarded as a (meth) acrylic monomer (a-4).

  Examples of the (meth) acrylic monomer having two or more types of polar functional groups described above include hydroxyethyl acrylamide and t-butyl acrylamide sulfonic acid.

  Moreover, the following monomers are mentioned as a (meth) acrylic-type monomer which has one type of polar functional group demonstrated above.

(I) (meth) acrylic monomer having a carboxyl group: (meth) acrylic acid, β-carboxylethyl (meth) acrylate

(Ii) (meth) acrylic monomer having a hydroxyl group: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, glycerin mono (meth) acrylate, (poly ) Ethylene glycol mono (meth) acrylate, (poly) propylene glycol mono (meth) acrylate)

(Iii) (meth) acrylic monomer having amino group: aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate

(Iv) (Meth) acrylic monomer having an amide group: (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-butyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methylolpropane ( (Meth) acrylamide

(V) (Meth) acrylic monomer having an epoxy group: glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether.

<Other monomers>
In the present invention, structural units derived from other monomers other than the above monomer components (a-1) to (a-4) are used for adjusting various properties within a range that does not impair the effects of the present invention. It can be included in the (meth) acrylic copolymer (A).

  Examples of such other monomers include styrene, α-methylstyrene, vinyl acetate, vinyl propionate, ethyl acrylate, isobutyl acrylate, 2-ethylhexyl methacrylate, lauryl acrylate, and the like.

<Method for producing (meth) acrylic copolymer (A)>
(Copolymerization ratio of each monomer)
The (meth) acrylic copolymer (A), which is a constituent component of the pressure-sensitive adhesive composition for optical members of the present invention, includes the monomer components (a-1) to (a-4) described above, and others as necessary. Is obtained by copolymerization at a specific ratio described below.

  The copolymerization ratio of the (meth) acrylic acid ester (a-1) in the (meth) acrylic copolymer (A) is 40 to 94.9% by weight from the viewpoint of a balance between hard properties and flexibility, preferably 50 to 90% by weight.

  The copolymerization ratio of the (meth) acrylic acid ester (a-2) in the (meth) acrylic copolymer (A) is 0.1 to 50% by weight, preferably 10 to 40% by weight from the viewpoint of hard properties. More preferably, it is 10 to 25% by weight.

  The copolymerization ratio in the (meth) acrylic copolymer (A) of the (meth) acrylic acid ester (a-3) is 0.1 to 25% by weight, preferably 5 to 20% from the viewpoint of the optical compensation function. %.

  The copolymerization ratio of the (meth) acrylic monomer (a-4) in the (meth) acrylic copolymer (A) is 0.1 to 6% by weight, preferably 1 to 6% from the viewpoint of an appropriate degree of crosslinking. % By weight.

  In addition, the sum total of the copolymerization ratio of each monomer component (a-1)-(a-4) is 100 weight%.

  In addition, in order to effectively prevent light leakage by simultaneously setting the hard characteristics and the optical compensation function in an appropriate region, the total of the copolymerization ratio of (meth) acrylic acid esters (a-2) and (a-3) Is 5 to 59.9% by weight, preferably 10 to 50% by weight.

  Furthermore, the copolymerization ratio of the other monomers is usually 0 to 5 parts by weight with respect to a total of 100 parts by weight of the monomers (a-1) to (a-4).

(Method for producing (meth) acrylic copolymer (A))
In the (meth) acrylic copolymer (A), each of the monomer components (a-1) to (a-4), and other monomers as necessary, solution polymerization method, bulk polymerization method, emulsion polymerization method, suspension It can manufacture by superposing | polymerizing by conventionally well-known polymerization methods, such as a polymerization method. Among these methods, it is preferable to employ a solution polymerization method because the molecular weight of the polymer 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, each monomer component forming the (meth) acrylic copolymer (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; and 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.

  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 normal pressure to 0.5 MPa.

<(A) (Meth) acrylic copolymer>
Since the (meth) acrylic copolymer (A) is crosslinked using a crosslinking agent (B) described later, a crosslinked product excellent in hard characteristics and optical compensation function is formed. Therefore, the pressure-sensitive adhesive for optical members of the present invention When the agent composition is used, it is possible to achieve excellent dimensional stability, light leakage prevention performance, and durability under a wet heat environment.

  The weight average molecular weight Mw measured by GPC of the (meth) acrylic copolymer (A) is usually 500,000 to 2,000,000, preferably 800,000 to 1,800,000, and the copolymer (A) has excellent adhesive strength. have.

  The (meth) acrylic copolymer (A) preferably has a glass transition temperature of 0 ° C. or lower, more preferably −10 ° C. or lower, and particularly preferably −15 to −60 ° C. When the glass transition temperature is higher than 0 ° C., the adhesion of the resulting pressure-sensitive adhesive to the adherend and the flexibility of the pressure-sensitive adhesive layer may decrease, and peeling or floating may occur from the adherend. The glass transition temperature of the (meth) acrylic copolymer (A) is a value calculated by the following FOX equation.

(Form of FOX)
1 / Tg = Wa / Tga + Wb / Tgb + ...
Tg: Glass transition temperature of (meth) acrylic copolymer (A) Tga, Tgb,...: Glass transition temperatures of homopolymers of monomer a, monomer b,... Wa, Wb,. ..: Weight fraction of (meth) acrylic copolymer (A) of structural units derived from each of monomer a, monomer b,... * (Meth) acrylic monomer (a-1) to (A-4) and other monomers can be arbitrarily assigned to monomer a, monomer b,.

  The (meth) acrylic copolymer (A) may be a random copolymer of the above monomer components or a block copolymer.

  In the present invention, the (meth) acrylic copolymer (A) may be used alone or in combination of two or more.

[(B) Crosslinking agent]
The pressure-sensitive adhesive composition for an optical member of the present invention contains a crosslinking agent (B) together with the (meth) acrylic copolymer (A) described above.

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

  Specific examples of the isocyanate-based crosslinking agent include isocyanate monomers such as tolylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate; Isocyanurate compound; isocyanurate compound; burette type compound; and urethane prepolymer type that is addition-reacted with known polyether polyol, polyester polyol, acrylic polyol, polybutadiene polyol, polyisoprene polyol, etc. To mention the 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 alone or in combination of two or more.
Such a crosslinking agent (B) is contained in 0.01 to 3 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer (A) in the pressure-sensitive adhesive composition for optical members of the present invention.

  By including a certain amount of the cross-linking agent (B) in this way, it is possible to achieve an appropriate degree of cross-linking, and to achieve excellent tackiness, dimensional stability, light leakage prevention performance and durability in a humid heat environment. it can. From such a viewpoint, the content of the crosslinking agent (B) is preferably 0.03 to 2.5 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer (A).

[Other ingredients]
In the pressure-sensitive adhesive composition for an optical member of the present invention, a silane coupling agent, an antistatic agent, an antioxidant, an ultraviolet absorber, a colorant, a pigment, a dye, a tackifying resin, a surface lubricant, and a leveling as necessary. Other components such as an agent, a softening agent, an anti-aging agent, a light stabilizer, a photoinitiator, a polymerization inhibitor, a filler, organic particles, inorganic particles, or a plasticizer 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 copolymer (A). Below, the said silane coupling agent and antistatic agent are demonstrated.

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

  Among these, the use of a silane coupling agent having a functional group that reacts with a functional group contained in the (meth) acrylic copolymer (A) is preferable in that it is difficult to cause peeling in a humid heat environment. .

  The compounding amount of the silane coupling agent in the pressure-sensitive adhesive composition for optical members of the present invention is usually 0.01 to 0.5 parts by weight, preferably 100 parts by weight of (meth) acrylic copolymer (A). Is 0.05 to 0.3 parts by weight.

<Antistatic agent>
An antistatic agent is used in order to reduce the surface resistance value of the adhesive composition for optical members of this invention. In the present invention, known antistatic agents can be used, and the antistatic agents can be roughly classified into (i) surfactants, (ii) ionic compounds, and (iii) conductive polymers.

(I) As the surfactant, the following can be used. Quaternary ammonium salts, amide quaternary ammonium salts, pyridium salts, cationic surfactants having a cationic group such as primary to tertiary amino groups;
An anionic surfactant having an anionic group such as sulfonate group, sulfate ester base, phosphate ester base;
Amphoteric surfactants such as alkylbetaines, alkylimidazolinium betaines, alkylamine oxides, amino acid sulfates,
Nonionic interfaces such as glycerin fatty acid esters, sorbitan fatty acid esters, polyoxyethylene alkylamines, polyoxyethylene alkylamine fatty acid esters, N-hydroxyethyl-N-2-hydroxyalkylamines, alkyldiethanolamides Activator.

  Moreover, the reactive type emulsifier which has a polymeric group is also mentioned as surfactant, The polymeric surfactant which made high molecular weight the monomer component containing said surfactant or reactive emulsifier can also be used.

(Ii) The ionic compound is composed of a cation part and an anion part, and may be solid or liquid at room temperature (23 ° C. 50% RH).

  The cation moiety may be either an inorganic cation or an organic cation, or both.

As the inorganic cation, alkali metal ions and alkaline earth metal ions are preferable, and Li ⁺ , Na ⁺ and K ⁺ having excellent antistatic properties are more preferable.

  Examples of the organic cation include pyridinium cation, piperidinium cation, pyrrolidinium cation, pyrroline cation, pyrrole cation, imidazolium cation, tetrahydropyrimidinium cation, dihydropyrimidinium cation, pyrazolium cation, and pyrazolinium cation. , Tetraalkylammonium cation, trialkylsulfonium cation, tetraalkylphosphonium cation and derivatives thereof.

On the other hand, the anion portion constituting the ionic compound is not particularly limited as long as it can form an ionic compound by ionic bonding with the cation. Specifically, F ⁻ , Cl ⁻ , Br ⁻ , I ⁻ , AlCl ₄ ⁻ , Al ₂ Cl ₇ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , SCN ⁻ , ClO ₄ ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , CF ₃ COO ⁻ , CH ₃ SO ₃ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (F ₂ SO ₂ ) ₂ N ⁻ , (CF ₃ SO ₂ ) ₃ C ⁻ , AsF ₆ ⁻ , SbF ₆ ⁻ , NbF ₆ ⁻ , TaF ₆ ⁻ , F (HF) _n ⁻ , (CN) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , C ₃ F ₇ COO ^-, and _{(CF 3 SO 2) (CF} 3 CO) N - , and the like. Among these, an anion containing a fluorine atom is preferable because it gives an ionic compound having a low melting point, and (F ₂ SO ₂ ) ₂ N ⁻ and (CF ₃ SO ₂ ) ₂ N ⁻ are particularly preferable.

  Examples of ionic compounds used as an antistatic agent in the present invention include lithium bis (trifluoromethanesulfonyl) imide, lithium bis (difluorosulfonyl) imide, lithium tris (trifluoromethanesulfonyl) methane, potassium bis (trifluoromethanesulfonyl) imide, potassium Bis (difluorosulfonyl) imide, 1-ethylpyridinium hexafluorophosphate, 1-butylpyridinium hexafluorophosphate, 1-hexyl-4-methylpyridinium hexafluorophosphate, 1-octyl-4-methylpyridinium hexafluorophosphate, 1-octyl -4-methylpyridinium bis (fluorosulfonyl) imide, (N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium teto Fluoroborate, N, N-diethyl-N-methyl-N- (2-methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide, 1-octylpyridinium fluorosphoniumimide, 1-octyl3-methylpyridinium and trifluorosulfonium An imide or the like is preferable.

(Iii) Examples of the conductive polymer include polythiophene, polyaniline, polypyrrole, and derivatives thereof.

  The compounding amount of the antistatic agent in the pressure-sensitive adhesive composition for optical members of the present invention is usually 0.01 to 3 parts by weight, preferably 0.05 to 100 parts by weight with respect to 100 parts by weight of the (meth) acrylic copolymer (A). 2.5 parts by weight.

[Adhesive composition for optical members]
The pressure-sensitive adhesive composition for optical members of the present invention contains the (meth) acrylic copolymer (A) and the crosslinking agent (B) described above as essential components, and may optionally contain the above-mentioned other components.

  And in the said (meth) acrylic-type copolymer (A), since the (meth) acrylic acid ester (a-2) and (a-3) are copolymerized in a specific ratio, the outstanding hard characteristic and optical Since the compensation function is compatible and (meth) acrylic acid ester (a-1) is also copolymerized, not only the hard properties are simply strengthened, but also the (meth) acrylic copolymer (A) has a suitable flexibility. Excellent dimensional stability has been achieved by introducing the properties.

  Further, in the (meth) acrylic copolymer (A), the (meth) acrylic monomer (a-4) is also copolymerized, and this and a certain amount of the crosslinking agent (B) cause a crosslinking reaction. Thus, moderate crosslinking occurs, and excellent adhesiveness and excellent dimensional stability and durability in a moist heat environment are realized.

  Since the composition of the present invention is excellent in dimensional stability and durability in a wet heat environment, the deformation is very small even in a wet heat environment, and a phenomenon of reducing the product value such as foaming is very unlikely to occur.

  For example, when a minute creep test is performed using the composition of the present invention under the conditions described below, the ratio between the measured value performed at 60 ° C. and the measured value performed at 23 ° C. (measured value at 60 ° C. / 23 ° C. measured value) is usually 1.05 to 2.00, preferably 1.05 to 1.95.

-Micro creep test The pressure-sensitive adhesive composition for optical members of the present invention is applied to a release-treated polyester film and dried 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 (plain polarizing plate) having a layer structure of TAC (triacetyl cellulose) -PVA (polyvinyl alcohol) -TAC so that the pressure-sensitive adhesive layer is in contact with the polarizing plate. A polarizing plate is produced.

  The prepared pressure-sensitive adhesive processed polarizing plate 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 × 10 mm. Laminate to make the bonding area.

  Thereafter, the pressure-sensitive adhesive processing polarizing plate bonded to the glass was subjected to autoclave treatment (50 ° C., 5 atm), and allowed to stand for 24 hours in a 23 ° C./50% RH atmosphere. To do.

  The test sample is set with a length of 15 mm of the fixing chuck portion in the chamber BOX of the micro creep measuring machine, and the inside of the chamber BOX is heated to the measurement temperature (23 ° C. or 60 ° C.). After standing for 40 minutes at the measurement temperature, the pressure-sensitive adhesive processing polarizing plate for evaluation in the test sample was parallel to the adhesive surface between the polarizing plate and the glass at a tensile load of 800 g and a tensile time of 1000 seconds. Pull in the length direction of the board.

  After pulling, the distance (mm) of the gap between the bonded portions of the glass and the polarizing plate is measured to obtain a minute creep test result (measured value).

The measured value at 23 ° C. in the micro creep test is usually 0.05 to 1.00 mm, preferably 0.08 to 0.50 mm, more preferably 0.10 to 0.30 mm.
The measured value at 60 ° C. in the minute creep test is preferably 0.15 to 1.00 mm, and more preferably 0.15 to 0.50 mm.

  That is, the composition of the present invention hardly deforms even in a humid heat environment and has excellent dimensional stability, and the degree of deformation does not change much depending on the temperature change.

  The measured values in these micro creep tests are mainly defined by the hard characteristics of the composition of the present invention, and the measured values change by adjusting these characteristics. In general, the hard characteristics are improved, that is, the copolymerization ratio of (meth) acrylic acid ester (a-2) in (meth) acrylic copolymer (A) is increased, or (meth) having a polar functional group When the copolymerization ratio of the acrylic monomer (a-4) is increased or the amount of the crosslinking agent (B) is increased, the measured value tends to decrease. Moreover, the copolymerization ratio of the (meth) acrylic acid ester (a-2) in the (meth) acrylic copolymer (A) is lowered, or the (meth) acrylic monomer (a-4) having a polar functional group is used. When the copolymerization ratio is decreased or the amount of the crosslinking agent (B) is decreased, the measured value tends to increase.

  As described above, since the deformation in the wet heat environment is very small, the composition of the present invention exhibits stress resistance when the optical member to which it is bonded exhibits deformation such as shrinkage, floating, and strain in the wet heat environment. Such deformation can be prevented satisfactorily.

  As a result, light leakage caused by the deformation can be prevented well. Even if light leakage is not completely prevented, slight light leakage is suppressed by the optical compensation function derived from the (meth) acrylic copolymer (A).

[Adhesive sheet]
When the pressure-sensitive adhesive composition for optical members 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 handleability when the pressure-sensitive adhesive sheet is used in the production process of a flat panel display, and examples of the material include polyester, polyolefin, and polyether. It is done.

  The pressure-sensitive adhesive sheet of the present invention has a desired thickness, for example, by applying and drying a coating liquid containing the pressure-sensitive adhesive composition for optical members of the present invention on a substrate film to evaporate the solvent contained in the coating liquid. It can be produced by forming an adhesive layer. 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. If the thickness of this pressure-sensitive adhesive layer is less than 5 μm, it may not be possible to exhibit the prescribed performance (wet heat durability, etc.). If it exceeds 100 μm, the adhesive sheet tends to protrude when the pressure-sensitive adhesive sheet is cut. May decrease.

  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.

[Optical member with adhesive layer]
By forming the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition for optical members of the present invention on at least one surface of the optical member, excellent light leakage prevention performance and durability were achieved even in a humid heat environment as described above. An optical member with an adhesive layer is obtained.

  The optical member in the present invention is not particularly limited, and is an optical film suitably used for a flat panel display, for example, a polarizing plate, a retardation plate, an elliptical polarizing plate, an optical compensation film, a brightness enhancement film, an infrared / electromagnetic wave. Examples thereof include a cut film, an antireflection film for the front surface, a surface protective film, and those in which these are laminated.

  Among these, the polarizing plate, in particular, has different degrees of deformation of the constituent layers in a wet and heat environment, and thus birefringence occurs due to optical distortion and physical distortion. This birefringence causes light leakage and becomes a serious problem. The composition of the present invention suppresses deformation of the polarizing plate with hard characteristics, can suppress optical distortion, that is, light leakage, and is excellent in durability such as peeling prevention. Moreover, even if slight optical distortion occurs, the optical compensation function can suppress light leakage, so that it is suitable for a bonding application of a polarizing plate and a glass substrate.

  In addition, the composition of the present invention can be applied to a liquid crystal panel for TV use having a relatively large size because the deformation of the polarizing plate can be suppressed by hard characteristics. In particular, it is suitable for use in bonding a polarizing plate and a glass substrate used in a VA mode liquid crystal panel.

<Method for producing optical member with adhesive layer>
The optical member with the pressure-sensitive adhesive layer is produced, for example, by the following methods (1) to (3).

(1) A coating solution containing the pressure-sensitive adhesive composition for an optical member 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 is bonded to the optical member.

(2) A coating solution containing the pressure-sensitive adhesive composition for an optical member of the present invention is applied to the optical member by a known method (die coating method, knife coating method, etc.), and a solvent contained in the coating solution is dried by heat drying. Vaporization is performed to form a pressure-sensitive adhesive layer having a desired thickness, which is then bonded to the release layer of the release film.

(3) A coating solution containing the pressure-sensitive adhesive composition for optical members 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 coating solution is dried by heat drying. The adhesive contained in the film is vaporized to form a pressure-sensitive adhesive layer having a desired thickness, and bonded to the release layer of the second release film (usually having a lower release force than the first release film). A carrier adhesive film is prepared. Thereafter, the second release film is peeled off and bonded to the optical member.

  The pressure-sensitive adhesive composition for an optical member of the present invention is 3 to 7 days at room temperature (23 ° C., 50% RH) after formation of the pressure-sensitive adhesive layer, and 2 under heat-promoting conditions (40 ° C., 90% RH). It is crosslinked in about 5 days, and can be applied to the constituent layer of a flat panel display described later.

  Moreover, the thickness of the adhesive layer in the optical member with an adhesive layer obtained is not specifically limited, However, The range of 5-100 micrometers is preferable and the range of 10-50 micrometers is more preferable. If the thickness of the pressure-sensitive adhesive layer is less than 5 μm, the prescribed performance (wet heat durability, etc.) may not be exhibited. If the thickness exceeds 100 μm, the adhesive sticks out when the optical member with the pressure-sensitive adhesive layer is cut. It becomes easy and processing suitability may fall.

Furthermore, when the composition of this invention is used in manufacture of FPD, the adhesive layer which consists of the said composition is formed as a structural layer of FPD. The pressure-sensitive adhesive layer contains a crosslinked (meth) acrylic copolymer (A) having an optical compensation function, and the photoelastic coefficient of the pressure-sensitive adhesive layer is preferably −320 to 0 (× 10 ⁻¹² m ^2). / N). The method for measuring the photoelastic coefficient will be described in the [Example] section.

[Flat panel display]
A flat panel display can be manufactured using at least one optical member with an adhesive layer of the present invention, and an FPD manufactured in this manner is 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 optical member with an adhesive layer of the present invention 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.
<Production example of acrylic copolymer used in Examples 1 to 13 and Comparative Examples 1 to 8>
In a reactor equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen introduction tube, acrylic esters (a-1) to (a-3) and acrylic monomers (a-4) shown in the following Tables 1 to 3 Were charged in accordance with the blending ratio (parts by weight) shown in Tables 1 to 3, and then ethyl acetate was charged in a blending amount so that the monomer concentration was 50 wt%.

  Next, 0.1 part by weight of 2,2′-azobisisobutyronitrile is added to 100 parts by weight of the total of acrylic acid esters (a-1) to (a-3) and acrylic monomer (a-4). In addition, stirring was performed while replacing the air in the reaction apparatus with nitrogen gas, the temperature was raised to 60 ° C., and the reaction was performed at a pressure of 1 atm for 4 hours. After completion of the reaction, the obtained acrylic copolymer was diluted with ethyl acetate to obtain an acrylic copolymer solution.

<Preparation of evaluation polarizing plate for evaluation>
Using the acrylic copolymer solution obtained by the production example, each component was added according to the formulations shown in Tables 1 to 3 to obtain a solution of the pressure-sensitive adhesive composition. 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. This pressure-sensitive adhesive sheet was affixed to one side of a polarizing film having a layer structure of TAC-PVA-TAC and then aged for 7 days under the condition of 23 ° C./50% RH in the dark to obtain a pressure-sensitive adhesive processed polarizing plate for evaluation.

  The evaluation processed adhesive polarizing plates were evaluated for microcreep, light leakage, floating / foaming, cracking, and peeling as shown in Tables 1 to 3 below.

* Contents of abbreviations and the like in Tables 1 to 3 are as follows.
BA: n-butyl acrylate t-BA: tertiary butyl acrylate POA: phenoxyethyl acrylate HEA: 2-hydroxyethyl acrylate MA: methyl acrylate CHA: cyclohexyl acrylate IBOA: isobornyl acrylate AA: acrylic acid TD: XDI isocyanate compound (TD-75: manufactured by Soken Chemical Co., Ltd.)
L: TDI adduct type isocyanate compound (Coronate L: manufactured by Nippon Polyurethane Co., Ltd.)
KBM-403: 3-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.)
Antistatic agent: 1-octyl-4-methylpyridinium bis (fluorosulfonyl) imide

[Tg measurement]
Measurement of Tg of homopolymers of various acrylic monomers (a-1) to (a-3) shown in Tables 1 to 3 was performed as follows.

Various homopolymers shown in Table 4 below were prepared by solution polymerization and used as test pieces.
The test piece was heated at a rate of 10 ° C./min in the range of −60 ° C. to 180 ° C. in an N ₂ atmosphere, and JISK7121 (plastic transition temperature of the differential scanning calorimeter DSC8230 manufactured by Rigaku Corporation) was used. The calorific value was measured according to the measurement method.

[Mw, PDI measurement]
For the acrylic copolymers prepared in Examples and Comparative Examples, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured according to the following GPC measurement conditions to obtain a polydispersity index (PDI = Mw / Mn).

<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 ml / min
Column temperature: 40 ° C

[Evaluation methods]
Various evaluations shown in Tables 1 to 3 were performed by the following methods.

<Small creep>
Adhesion processing polarizing plate for evaluation, which was cut into a width of 10 mm and a length of 100 mm, and the peeled polyester film was peeled off, was bonded to an alkali-treated glass so that the adhesive layer was in contact with the glass and 10 mm × 10 mm. After bonding to an area and autoclaving (50 ° C., 5 atm), the mixture was 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 it to stand at the measurement temperature for 40 minutes, the pressure-sensitive adhesive processing polarizing plate for evaluation in the test sample is applied to the polarizing plate and the glass at a tensile load of 800 g and a tensile time of 1000 seconds. And pulled in the length direction of the polarizing plate in parallel with the adhesive surface. The distance (mm) of the misalignment between the glass and the polarizing plate after being pulled was confirmed (measured) to obtain a minute creep test result.

<Light leakage>
A pressure-sensitive adhesive processing polarizing plate for evaluation, in which a peeled polyester film was peeled off on a 19-inch VA type liquid crystal panel (made by I / O DATA, model: LCD-A191EW), The adhesive-coated polarizing plate for evaluation and the liquid crystal panel were bonded so as to be in contact with the liquid crystal panel and crossed Nicol, and allowed to stand in an 80 ° C. atmosphere for 240 hours, and then in a 23 ° C./50% RH atmosphere. Left for 2 hours.

  Thereafter, the VA 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. For this display monitor displaying black on the full screen, 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 measured with a luminance meter (Highland Corporation). Measurement was performed using RISA-COLOR / CD8), and light leakage (ΔL) was determined by the following formula. Smaller ΔL means less light leakage (from the backlight), and if it is less than 2.0, it can be used as a liquid crystal display panel.

  ΔL = (La + Lb + Lc + Ld) / 4−Lcenter

  With respect to the light leakage size, a portion where light leakage occurred was visually confirmed in the above-described black display on the entire screen, and the distance d from the corner of the light leakage occurrence portion was measured as shown in FIG. If the distance is 30 mm or less, it can be used as a liquid crystal display panel.

  As for Comparative Examples 1 and 3 to 6, when the display monitor was confirmed after being left for 240 hours in an atmosphere at 80 ° C., appearance defects derived from the pressure-sensitive adhesive layer such as foaming and peeling occurred, and the light leakage test was measured. Was impossible.

<Damp heat durability>
The evaluation-adhesive polarizing plate from which the peeled polyester film was peeled off was cut into a 15-inch size (233 mm × 309 mm), and a pressure-sensitive adhesive layer was applied to the glass plate on one surface of a 0.5 mm-thick alkali-free glass plate. It stuck using the laminator roll so that it might contact | connect. After pasting, a test plate was obtained by pressurizing in an autoclave (manufactured by Kurihara Seisakusho) under conditions of 0.5 MPa, 50 ° C., and 20 minutes.

  The test plate thus obtained was left under conditions of 60 ° C./90% RH for 500 hours. After completion of the test, the test plate is taken out from the test environment and allowed to stand in an atmosphere of 23 ° C./50% RH for 2 hours. Then, the adhesive layer is visually observed for foaming, peeling, and cracking according to the following evaluation criteria. evaluated.

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: Number of foams is 10 or less ×: Number of foams is more than 10

(Kiretsu, peeling-size)
○: No floating / peeling is observed Δ: Lifting / peeling area is less than 5% with respect to the entire bonded portion (100%) in the test plate x: Lamination / peeling area is bonded on the test plate 5% or more for the entire part (100%)

(Kiretsu, peeling-position)
○: There is no defect (floating or peeling). Δ: There is a defect only at a position less than 0.5 mm from the end. ×: There is a defect at a position of 0.5 mm or more from the end.

  The “edge” in the evaluation of the sharpness / peeling position means the shortest vertical line and the side of the test plate when the vertical line is dropped on each side of the test plate from the position where the sharpness / peeling occurred. The point of intersection.

  In Comparative Examples 5 and 6, when the test plate was checked after being left for 500 hours under the conditions of 60 ° C./90% RH, many floats and foams derived from the pressure-sensitive adhesive layer were generated. Was impossible.

<Photoelastic coefficient measurement>
As shown below, a 15 mm × 50 mm × 1 mm thick adhesive test piece was prepared and used as a measurement sample.

  A crosslinking agent, a silane coupling agent, and an antistatic agent were added to the acrylic copolymer solution obtained in the production example in the proportions shown in Tables 1 to 3 to obtain an adhesive composition solution. This pressure-sensitive adhesive composition solution was coated and dried on a PET film that had been subjected to a release treatment so that the thickness after drying was 1 mm. After drying, it was cut into 15 mm × 50 mm to obtain an adhesive test piece 12, which was used as a measurement sample.

  The measurement sample was set in a measurement apparatus (Spectroscopic Ellipsometer M-220 manufactured by JASCO Corporation), and measurement was performed in an atmosphere at 23 ° C.

In FIG. 2, the stress generated when the sample is pulled in the X direction is controlled in the range of 0 to 0.15 N, and the relationship between wavelength and transmitted light phase difference (* 1) for each stress was measured. . From (* 1), the phase difference of transmitted light at a wavelength of 600 nm was plotted with the relationship of phase difference-stress, and the inclination was obtained. Furthermore, the photoelastic coefficient was ^{calculated |} required from the relationship of inclination = (-1) x photoelastic coefficient (10 < ^-12 > m < ² > / N).

12 Adhesive test piece 14 Sample fixing jig 16 Light source 18 Slit 20 Analyzer

Claims (14)

(A): a (meth) acrylic copolymer obtained by copolymerizing the following (a-1) to (a-4) at the following ratio:
(A-1) The glass transition temperature of the homopolymer is −40 ° C. or less and (meth) acrylic acid ester having no aromatic ring is 40 to 94.9% by weight.
(A-2) The glass transition temperature of the homopolymer is 0 ° C. or higher and the (meth) acrylic acid ester having no aromatic ring is 0.1 to 50% by weight.
(A-3) 0.1 to 25% by weight of (meth) acrylic acid ester having an aromatic ring
(A-4) (Meth) acrylic monomer having two or more types of polar functional groups and / or (meth) acrylic monomer having one or more different types of polar functional groups of 0.1 to 6% by weight
(However, the sum of (a-2) and (a-3) is 5 to 59.9% by weight,
The polar functional group is selected from a carboxyl group, a hydroxyl group, an amino group, an amide group and an epoxy group,
(The sum of (a-1) to (a-4) is 100% by weight)
(B): A pressure-sensitive adhesive composition for an optical member comprising 0.01 to 3 parts by weight of a crosslinking agent with respect to 100 parts by weight of the (meth) acrylic copolymer (A).   The pressure-sensitive adhesive composition for an optical member according to claim 1, wherein the copolymerization ratio of the (meth) acrylic acid ester (a-2) is 10 to 40% by weight.   The (meth) acrylic acid ester (a-2) is selected from the group consisting of methyl (meth) acrylate, i-butyl methacrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate and isobornyl (meth) acrylate. The pressure-sensitive adhesive composition for an optical member according to claim 1 or 2, wherein the pressure-sensitive adhesive composition is at least one.   The said (meth) acrylic acid ester (a-2) is t-butyl (meth) acrylate, The adhesive composition for optical members of Claim 1 or 2 characterized by the above-mentioned.   The pressure-sensitive adhesive composition for an optical member according to any one of claims 1 to 4, wherein a copolymerization ratio of the (meth) acrylic acid ester (a-1) is 50 to 90% by weight.   The (meth) acrylic acid ester (a-1) is n-butyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, isoamyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl. Acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl methacrylate, n-tridecyl (meth) acrylate, methoxyethyl acrylate, methoxypolyethylene glycol acrylate and ethoxyethoxyethyl It is at least 1 sort (s) chosen from the group which consists of acrylates, The adhesive composition for optical members in any one of Claims 1-5 characterized by the above-mentioned. The (meth) acrylic acid ester (a-3) is at least one selected from the group consisting of benzyl (meth) acrylate, phenoxyethyl (meth) acrylic acid ester represented by the following general formula (1), and derivatives thereof. The pressure-sensitive adhesive composition for optical members according to any one of claims 1 to 6, wherein:
(In Formula (1), R ₀ is hydrogen or a methyl group, R ₁ is a group represented by (CH ₂ CH ₂ O) _n (n is an integer of 1 to 20), and m is 1. Is an integer of -5, R ₂ is hydrogen, an alkyl group having 1 to 9 carbon atoms, an aryl group having 6 to 10 carbon atoms, or an aralkyl group having 7 to 11 carbon atoms, and when m is 2 or more, a plurality of R ₂ are present. R ₂ may be the same or different.)   The pressure-sensitive adhesive composition for an optical member according to any one of claims 1 to 7, wherein a copolymerization ratio of the (meth) acrylic monomer (a-4) is 1 to 6% by weight. The ratio of 60 ° C. measured value / 23 ° C. measured value is 1.05 to 2.00 when the following minute creep test is performed on the pressure-sensitive adhesive composition for optical members. The adhesive composition for optical members according to any one of 1 to 8:
The pressure-sensitive adhesive composition for optical members 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;
The pressure-sensitive adhesive sheet is bonded to a polarizing plate having a TAC (triacetyl cellulose) -PVA (polyvinyl alcohol) -TAC configuration and the pressure-sensitive adhesive layer is in contact with the polarizing plate to produce a pressure-sensitive adhesive processed polarizing plate for evaluation;
The pressure-sensitive adhesive processing polarizing plate for evaluation is cut into a width of 10 mm × a length of 100 mm, the peel-treated polyester film is peeled off, and the pressure-sensitive adhesive layer is in contact with the glass on the alkali-treated glass and 10 mm × 10 mm. Adhesive processing polarizing plate test piece for evaluation by bonding so that the bonding area becomes
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 evaluation-treated pressure-sensitive adhesive polarizing plate in the test piece is separated from the polarizing plate at a tensile load of 800 g and a tensile time of 1000 seconds. Pulling in parallel to the adhesive surface with the glass and in the length direction of the polarizing plate;
The distance (mm) of the deviation of the bonded portion between the glass and the polarizing plate in the test piece is measured.   Furthermore, 0.01-0.5 weight part of silane coupling agents are included with respect to 100 weight part of the said (meth) acrylic-type copolymer (A), The optical in any one of Claims 1-9 characterized by the above-mentioned. A pressure-sensitive adhesive composition for members.   Furthermore, 0.01-3 weight part of antistatic agents are contained with respect to 100 weight part of said (meth) acrylic-type copolymers (A), The adhesive for optical members in any one of Claims 1-10 characterized by the above-mentioned. Agent composition.   The adhesive sheet in which the adhesive layer containing the adhesive composition for optical members in any one of Claims 1-11 is formed on a base film.   It is an optical member with an adhesive layer in which an adhesive layer is formed on at least one surface of the optical member, and the adhesive layer contains the adhesive composition for optical members according to any one of claims 1 to 11. An optical member with a pressure-sensitive adhesive layer.   A flat panel display comprising the optical member with an adhesive layer according to claim 13.