JP2018100399A - Pressure-sensitive adhesive composition, and pressure-sensitive adhesive for polarizing plate obtained using the same, polarizing plate with pressure-sensitive adhesive layer, and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive which is used for bonding a polarizing plate (protective film) and liquid crystal cell (glass), has small variation in reworkability, durability, antistatic properties and tacky force during rework, and has uniform tacky force.SOLUTION: The pressure-sensitive adhesive composition is provided, containing an acrylic resin (A) obtained by copolymerization of (a1) 5-75 wt.% of normal butyl acrylate, (a2) 20-80 wt.% of at least one monomer selected from an aromatic ring-containing monomer and C1-2 alkyl(meth)acrylate, (a3) 1-30 wt.% of a polar group-containing monomer selected from at least one of a carboxyl group-containing monomer and a hydroxyl group-containing monomer, and a nitrogen atom-containing monomer, and (a4) 10 wt.% or less of a monomer other than (a1) to (a3), an ionic compound (B) having fluorine-containing anion, a silane coupling agent (C) having a weight average molecular weight of 4,000 or more, and a crosslinking agent (D).SELECTED DRAWING: None

Description

  The present invention relates to a pressure-sensitive adhesive composition. More specifically, the present invention satisfies various performances required for bonding a polarizing plate used in a liquid crystal display device and the like to a liquid crystal cell, and further exhibits variations in adhesive strength. The present invention relates to a pressure-sensitive adhesive composition capable of obtaining a small and uniform pressure-sensitive adhesive, and a pressure-sensitive adhesive for polarizing plates, a polarizing plate with a pressure-sensitive adhesive layer, and an image display device using the same.

  Conventionally, a polarizing plate in which both sides of a polarizer composed of a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film having a polarizing property is protected with a protective film is aligned between two glass plates. A liquid crystal display panel is manufactured by laminating the liquid crystal cell with the liquid crystal component sandwiched therebetween. The lamination of the polarizing plate on the surface of the liquid crystal cell is to produce a polarizing plate with an adhesive layer provided with an adhesive layer on the surface of the protective film of the polarizing plate, and the adhesive layer is brought into contact with and pressed against the liquid crystal cell surface. Usually, it is performed by.

  The pressure-sensitive adhesive used for laminating the polarizing plate (protective film) and the liquid crystal cell (glass) has durability that does not cause floating or peeling even in an environment such as high temperature or wet heat, and when exposed to such conditions. However, non-uniformity of display to prevent light leakage from the backlight, reworkability to prevent damage to the liquid crystal cell and generation of adhesive residue when the polarizing film is peeled off from the liquid crystal cell, external Various performances such as antistatic properties for preventing failure of the liquid crystal cell due to static electricity are required.

  Many studies have been made in order to obtain pressure-sensitive adhesives satisfying such various performances. For example, Patent Document 1 discloses monomers and aromatics having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or higher. An acrylic resin containing a ring-containing monomer and a pressure-sensitive adhesive composed of an ionic compound are described, and it is described that it is excellent in durability, light leakage resistance, and antistatic properties in a humid heat environment.

  Patent Document 2 describes that an adhesive having excellent heat resistance can be obtained by using an acrylic resin obtained by copolymerizing an aromatic ring-containing monomer.

  Patent Document 3 proposes to add an oligomer type silane coupling agent in order to improve the reworkability.

International Publication WO2013 / 0996683 JP 59-11114 A JP 7-331206 A

  However, even the pressure-sensitive adhesive described in Patent Document 1 or 2 above does not satisfy all the required performances. In addition, referring to Patent Documents 1 and 2, homopolymers are used to satisfy various performances. When a monomer having a high glass transition temperature or an aromatic ring-containing monomer is used in combination, there has been a problem that the glass transition temperature of the acrylic resin becomes too high and the reworkability is lowered.

  Furthermore, in the technique disclosed in Patent Document 3 for improving the reworkability, even if an oligomer type silane coupling agent is simply used, the average value of the adhesive force tends to decrease, but the acrylic having a high glass transition temperature. When using resin, the adhesive strength varies greatly when peeled off. When used on a glass substrate or liquid crystal cell with a thin film in recent years, the liquid crystal cell may not be smoothly peeled off during rework. There was a fear.

  Therefore, in the present invention, under such a background, a monomer having a high glass transition temperature of a homopolymer, particularly an aromatic ring-containing monomer or an alkyl (meth) acrylate having 1 to 2 carbon atoms is used at the time of manufacturing a liquid crystal display device. Durability, reworkability, and antistatic performance when used as an adhesive for bonding a polarizing plate (protective film) and a liquid crystal cell (glass) even when using acrylic resin with high heat resistance It is an object of the present invention to provide a pressure-sensitive adhesive composition that can provide a pressure-sensitive adhesive that is excellent in the reworking, has a small variation in the pressure-sensitive adhesive force during reworking, has a uniform pressure-sensitive adhesive force, and can perform reworking work efficiently. It is what.

  However, as a result of intensive studies in view of such circumstances, the present inventor has found that in the adhesive composition, as the acrylic resin, normal butyl acrylate, an aromatic ring-containing monomer, and an alkyl group having 1 to 2 carbon atoms (meta) A) an acrylic resin having a specific composition containing at least one monomer selected from acrylates and at least one polar group-containing monomer selected from a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a nitrogen atom-containing monomer; Uses an acrylic resin containing a monomer component having a high glass transition temperature of a homopolymer by containing an ionic compound having a specific structure and a silane coupling agent having a weight average molecular weight larger than that usually used. Reworkability, durability, antistatic properties, etc. It was found that an adhesive capable of satisfying various required performances in a well-balanced manner, and having small variations in adhesive strength, uniform adhesive strength, and capable of performing rework work efficiently can be obtained. Completed the invention.

That is, the gist of the present invention is as follows.
Acrylic resin (A)
Ionic compound (B)
Silane coupling agent (C)
A pressure-sensitive adhesive composition containing a crosslinking agent (D),
The acrylic resin (A) is obtained by copolymerizing the following monomers (a1) to (a4) with respect to the whole monomer components in the following proportions:
(A1) Normal butyl acrylate 5 to 75% by weight
(A2) 20-80% by weight of at least one monomer selected from aromatic ring-containing monomers and alkyl (meth) acrylates having 1 to 2 carbon atoms in the alkyl group
(A3) At least one polar group-containing monomer selected from a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a nitrogen atom-containing monomer 1 to 30% by weight
(However, it contains at least one of a carboxyl group-containing monomer and a hydroxyl group-containing monomer.)
(A4) Monomers other than (a1) to (a3) 10 wt% or less The ionic compound (B) is an ionic compound having a fluorine-containing anion,
The present invention relates to a pressure-sensitive adhesive composition wherein the silane coupling agent (C) has a weight average molecular weight of 4,000 or more.

  Furthermore, this invention relates to the adhesive for polarizing plates which uses the said adhesive composition, the polarizing plate with an adhesive layer, and an image display apparatus.

  When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive used for laminating a polarizing plate (protective film) and a liquid crystal cell (glass substrate), various rework properties, durability, antistatic properties, etc. Adhesives satisfying the required performance in a well-balanced manner can be obtained, and furthermore, adhesives with small variations in adhesive strength and uniform adhesive strength can be obtained. Therefore, the liquid crystal display device can be manufactured efficiently.

FIG. 1 shows measurement results of variations in adhesive strength in Example 1 and Comparative Example 2.

The present invention is described in detail below.
In the present invention, (meth) acryl means acryl or methacryl, (meth) acryloyl means acryloyl or methacryloyl, and (meth) acrylate means acrylate or methacrylate. The acrylic resin is a resin obtained by polymerizing a polymerization component containing at least one (meth) acrylate monomer.

  The pressure-sensitive adhesive composition of the present invention contains an acrylic resin (A), an ionic compound (B), a silane coupling agent (C) and a crosslinking agent (D) as essential components.

<Acrylic resin (A)>
The acrylic resin (A) used in the present invention is obtained by copolymerizing the following monomer components. That is,
(A1) normal butyl acrylate (a2) at least one monomer selected from an aromatic ring-containing monomer and an alkyl (meth) acrylate having 1 to 2 carbon atoms in the alkyl group (a3) a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and nitrogen At least one polar group-containing monomer selected from atom-containing monomers (however, it contains at least one of a carboxyl group-containing monomer and a hydroxyl group-containing monomer).
(A4) Monomers other than (a1) to (a3)

  The content ratio of the normal butyl acrylate (a1) is 5 to 75% by weight, preferably 20 to 75% by weight, particularly preferably, based on the whole monomer component (total of (a1) to (a4)). 30 to 70% by weight. If the content is too small, the glass transition temperature of the acrylic resin (A) becomes too high, so that the tack when used as an adhesive tends to be lowered and workability tends to be lowered. There is a tendency.

  In the monomer (a2), examples of the aromatic ring-containing monomer include phenyl (meth) acrylate; benzyl (meth) acrylate; phenoxyalkyl (meth) acrylate such as phenoxyethyl (meth) acrylate and phenoxypropyl (meth) acrylate; Phenoxydialkylene glycol (meth) acrylates such as phenoxydiethylene glycol (meth) acrylate and phenoxydipropylene glycol (meth) acrylate; phenoxypolyethylene glycol (meth) acrylate; phenoxypolyethylene glycol-polypropylene glycol- (meth) acrylate and the like. These may be used alone or in combination of two or more.

  Among these, benzyl (meth) acrylate and phenoxyalkyl (meth) acrylate are advantageous in that the birefringence of the acrylic resin (A) can be adjusted efficiently and the glass transition temperature of the acrylic resin (A) does not become too high. Phenoxy dialkylene glycol (meth) acrylate is preferred, and the monomer remaining during polymerization does not remain in the pressure-sensitive adhesive layer when drying the pressure-sensitive adhesive composition, and benzyl (meth) acrylate does not cause odor or outgassing. In particular, benzyl acrylate and phenoxyethyl acrylate are preferable in that the glass transition point of the acrylic resin is not excessively increased.

Moreover, in the said monomer (a2), as a C1-C2 alkyl (meth) acrylate of an alkyl group, methyl acrylate (carbon number 1), methyl methacrylate (carbon number 1), ethyl acrylate (carbon number 2), Ethyl methacrylate (carbon number 2). These may be used alone or in combination of two or more.
Among these, methyl acrylate and ethyl acrylate are preferable because they are excellent in copolymerizability with other monomers and can easily increase the weight average molecular weight.

  The content ratio of the monomer (a2) is 20 to 80% by weight, preferably 25 to 70% by weight, and particularly preferably 30 to 80% by weight with respect to the whole monomer components (total of (a1) to (a4)). 60% by weight. If the content is too small, the heat resistance tends to decrease, and if it is too large, the glass transition temperature of the acrylic resin (A) increases, and the tack when used as a pressure-sensitive adhesive is decreased, resulting in a decrease in workability. is there.

  The polar group-containing monomer (a3) is at least one selected from a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a nitrogen atom-containing monomer, and further contains at least one of a carboxyl group-containing monomer and a hydroxyl group-containing monomer. is there.

  Examples of the carboxyl group-containing monomer include dimer acid of acrylic acid such as (meth) acrylic acid, β-carboxyethyl acrylate, etc. Among them, acrylic acid from the viewpoint of moist heat whitening resistance and stability during polymerization. Is preferred.

Examples of the hydroxyl group-containing monomer include primary hydroxyl groups such as hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, hydroxyhexyl (meth) acrylate, and hydroxyoctyl (meth) acrylate ( (Meth) acrylate; 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 3-chloro-2-hydroxypropyl (meth) acrylate, 2- Secondary hydroxyl group-containing (meth) acrylates such as hydroxy-3-phenoxypropyl (meth) acrylate; Tertiary hydroxyl group-containing (meth) acrylates such as 2,2-dimethyl-2-hydroxyethyl (meth) acrylate Over preparative; N-(hydroxymethyl) (meth) hydroxyl group-containing (meth) acrylamide monomers such as acrylamide, and the like. These may be used alone or in combination of two or more.
In the present invention, a monomer having both a hydroxyl group and a nitrogen atom is included in the hydroxyl group-containing monomer as described above.

  Among the above hydroxyl group-containing monomers, it has excellent reactivity with cross-linking agents, improved heat-and-moisture whitening resistance, excellent reactivity with cross-linking agents, and has a solid cross-linking structure that makes it easy to stabilize adhesive strength. Primary hydroxyl group-containing monomers are preferable, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferably used because they have few impurities such as di (meth) acrylate and are easy to produce. .

  As the hydroxyl group-containing monomer, it is also preferable to use an impurity having a content ratio of di (meth) acrylate of 0.5% or less, particularly preferably 0.2% or less, and more preferably 0.1%. % Or less.

  Examples of the nitrogen atom-containing monomer include an amino group-containing monomer, an amide group-containing monomer, and other nitrogen atom-containing monomers.

  Examples of amino group-containing monomers include primary amino group-containing monomers such as aminoalkyl (meth) acrylates such as aminomethyl (meth) acrylate and aminoethyl (meth) acrylate; t-butylaminoethyl (meth) acrylate and the like. Secondary amino group-containing monomer; Tertiary amino group-containing monomer such as dialkylaminoethyl (meth) acrylate such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; Heterocyclic amine such as (meth) acryloylmorpholine Examples include structure-containing monomers. These may be used alone or in combination of two or more.

Among these, a tertiary amino group-containing monomer is preferable in terms of high crosslinking promoting effect, high storage stability of the resin, excellent durability, and excellent adhesion to metals and metal oxides. In view of the above, a heterocyclic amine structure-containing monomer such as (meth) acryloylmorpholine is preferred.
Among these, dimethylaminoethyl (meth) acrylate and (meth) acryloylmorpholine are particularly preferable.

  Examples of the amide group-containing monomer include (meth) acrylamide; N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, and N-isopropoxymethyl (meth). N-alkoxyalkyl (meth) acrylamides such as acrylamide, Nn-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meta ) N, N-dialkyl (meth) acrylamide such as acrylamide. These may be used alone or in combination of two or more.

  Among these, (meth) acrylamide, N-alkoxyalkyl (in terms of the stability of the resin solution, the suppression of the migration of the antistatic agent, and the great effect of suppressing the precipitation of crystals in a moist heat environment. (Meth) acrylamide and N, N-dialkyl (meth) acrylamide are preferable, and acrylamide, methacrylamide, N-ethoxymethylacrylamide, N-butoxymethylacrylamide, and N-iso are particularly preferable in view of copolymerization with other monomers. Butoxymethylacrylamide, N, N-dimethylacrylamide, N, N-diethylacrylamide, and N, N-dipropylacrylamide are preferable, and N, N-dimethylacrylamide and N, N-diethylacrylamide are more preferable.

  Among the nitrogen atom-containing monomers, N, N-dialkyl (meth) acrylamide is most preferable because it is excellent in storage stability.

  The content of the polar group-containing monomer (a3) is 1 to 30% by weight, preferably 2 to 25% by weight, particularly preferably based on the whole monomer component (total of (a1) to (a4)). Is 3 to 15% by weight. If the content is too small, the durability and heat-and-whitening resistance (suppressing the whitening phenomenon of the pressure-sensitive adhesive layer that occurs in a moist and heat environment) tends to be reduced. If the content is too large, the storage stability and reworkability of the resin are reduced. It tends to decrease.

  Examples of the monomer (a4) other than the above (a1) to (a3) include various ethylenically unsaturated group-containing monomers. From the viewpoint of the effect of the present invention, the content ratio is 10 with respect to the whole monomer components. % By weight or less, preferably 5% by weight or less.

  Examples of the ethylenically unsaturated monomer (a4) include iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-propyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl ( (Meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, isotridecyl (meth) acrylate, myristyl (meth) Carbon number of alkyl groups such as acrylate, isomyristyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate is usually 3 to 24 (preferably (Meth) acrylic acid alkyl ester (except for n-butyl acrylate (a1)); cyclohexyl (meth) acrylate, isovol. 3-20, particularly preferably 3-18, more preferably 3-12) Nyl acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, 2-adamantyl (meth) acrylate, etc. (Meth) acrylic acid ester having an alicyclic structure; 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 3-methoxybutyl (meth) acrylate, 2-butoxyethyl (meth) acrylate, 2- Butoxydiethylene Cole (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytriethylene glycol (meth) acrylate, ethoxydiethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, octoxypolyethylene glycol -(Meth) acrylic acid ester containing an alkoxy group and an oxyalkylene group such as polypropylene glycol mono (meth) acrylate, lauroxypolyethylene glycol mono (meth) acrylate, stearoxypolyethylene glycol mono (meth) acrylate, etc. . These may be used alone or in combination of two or more.

  As the method for producing the acrylic resin (A), conventionally known methods such as solution radical polymerization, suspension polymerization, bulk polymerization, and emulsion polymerization can be used. For example, in an organic solvent, a monomer component, polymerization initiation An agent is mixed or dropped and polymerized under predetermined polymerization conditions. Among these, solution radical polymerization and bulk polymerization are preferable, and solution radical polymerization is particularly preferable in that an acrylic resin (A) can be obtained stably.

  Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene, aliphatic hydrocarbons such as hexane, esters such as ethyl acetate and butyl acetate, n-propyl alcohol, and isopropyl alcohol. Aliphatic alcohols such as acetone, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone.

  Among these organic solvents, ethyl acetate, acetone, methyl ethyl ketone, butyl acetate, toluene, and methyl isobutyl ketone are used for ease of polymerization reaction, chain transfer effect, ease of drying during adhesive coating, and safety. Particularly preferred are ethyl acetate, acetone, and methyl ethyl ketone.

  Examples of the polymerization initiator used for such radical polymerization include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, which are ordinary radical polymerization initiators, Azo initiators such as 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (methylpropionic acid), benzoyl peroxide, laurolyl peroxide, di-t-butyl peroxide, cumene Examples thereof include organic peroxides such as hydroperoxide, which can be appropriately selected according to the monomer used. These polymerization initiators can be used alone or in combination of two or more.

  The acrylic resin (A) preferably has a weight average molecular weight of 200,000 to 2,500,000, particularly preferably 600,000 to 2,000,000, and more preferably 1,000,000 to 1,800,000. If the weight average molecular weight is too small, the durability tends to decrease. If the weight average molecular weight is too large, gelation tends to occur at the time of polymerization, or a large amount of a diluent solvent is required at the time of manufacture, and the drying property is reduced. Residual solvent increases and heat resistance tends to decrease.

  The degree of dispersion (weight average molecular weight / number average molecular weight) of the acrylic resin (A) is preferably 15 or less, particularly preferably 10 or less, and further preferably 6 or less. If the degree of dispersion is too high, the cohesive force is lowered, and reworkability tends to be lowered or durability tends to be lowered. Note that the lower limit of the degree of dispersion is usually 1.

In addition, the weight average molecular weight of said acrylic resin (A) is a weight average molecular weight by standard polystyrene molecular weight conversion, high performance liquid chromatography (Nippon Waters company make, "Waters 2695 (main body)" and "Waters 2414 (detection). Column): Shodex GPC KF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates / piece, filler material: styrene-divinyl The number average molecular weight can be measured by the same method as described above by using three series of benzene copolymer and filler particle size: 10 μm. The degree of dispersion is determined from the weight average molecular weight and the number average molecular weight.

  The glass transition temperature (Tg) of the acrylic resin (A) is preferably −45 to 10 ° C., particularly preferably −40 to 0 ° C., and further preferably −39 to −10 ° C. When such a glass transition temperature is too high, tack tends to be lowered and workability at the time of bonding tends to be lowered, and when too low, durability tends to be lowered.

The glass transition temperature is calculated from the following Fox equation.
Tg: Glass transition temperature of copolymer (K)
Tga: Glass transition temperature (K) of monomer A homopolymer Wa: Weight fraction of monomer A Tgb: Glass transition temperature of homopolymer of monomer B (K) Wb: Weight fraction of monomer B Tgn: Homogeneity of monomer N Glass transition temperature (K) of polymer Wn: weight fraction of monomer N (Wa + Wb +... + Wn = 1)

  That is, it is a value calculated by applying the glass transition temperature and the weight fraction to the Fox equation when the homopolymer of each monomer constituting the acrylic resin is used.

  In addition, the glass transition temperature at the time of setting it as the homopolymer of the monomer which comprises acrylic resin is normally measured with a differential scanning calorimeter (DSC), and was based on JISK7121-1987 and JISK6240. Can be measured by the method.

The glass transition temperature (Tg) of the homopolymer of the main monomer is shown below. Tg of the acrylic resin (A) in the present invention is calculated from the following value.
(A1):
Normal butyl acrylate -56 ° C
(A2):
Methyl acrylate 8 ℃
Methyl methacrylate 105 ° C
Ethyl methacrylate 65 ° C
Benzyl acrylate 6 ° C
Phenoxyethyl acrylate -22 ° C
(A3):
Acrylic acid 106 ℃
2-hydroxyethyl acrylate -15 ° C
2-Hydroxyethyl methacrylate 55 ° C
Dimethylacrylamide 119 ° C
Acryloylmorpholine 145 ° C

In the present invention, the refractive index of the acrylic resin (A) is usually from 1.440 to 1.600, preferably from 1.460 to 1.550, particularly preferably from 1.470 to 1.500. For such a refractive index, it is preferable to reduce the difference in refractive index of each member to be laminated, because the optical loss at the member interface is reduced.
The refractive index is a value obtained by measuring the acrylic resin (A) formed into a thin film of about 10 μm to 100 μm with a NaD line using a refractive index measuring device (“Abbe refractometer 1T” manufactured by Atago Co., Ltd.).

  The haze when the acrylic resin (A) is layered is preferably 1.0 or less, particularly preferably 0.8 or less, and further preferably 0.5 or less. If the haze is too high, the image quality of the display tends to deteriorate.

For such haze, diffuse transmittance and total light transmittance are measured using HAZE MATER NDH2000 (manufactured by Nippon Denshoku Industries Co., Ltd.), and the values of the obtained diffuse transmittance and total light transmittance are substituted into the following formula. Calculated. This machine complies with JIS K7361-1.
Haze (%) = (diffuse transmittance / total light transmittance) × 100

<Ionic compound (B)>
The ionic compound (B) of the present invention is required to be an ionic compound comprising a cation and an anion and having a fluorine-containing anion as the anion.

  Examples of the fluorine-containing anion include fluorine-containing inorganic anions such as tetrafluoroborate anion, hexafluorophosphate anion, N, N-bis (fluorosulfonyl) imide; N, N-bis (trifluoromethanesulfonyl) imide, N, N Examples include fluorine-containing organic anions such as -bis (pentafluoroethanesulfonyl) imide, N, N-bis (heptafluoropropanesulfonyl) imide, and N, N-bis (nonafluorobutanesulfonyl) imide.

  Among these, N, N-bis (fluorosulfonyl) imide, N, N-bis (trifluoromethanesulfonyl) imide, N, N-bis (pentafluoro) are used in that the variation in antistatic performance and adhesive strength is reduced. Fluorine-containing imide anions such as ethanesulfonyl) imide are preferred.

The cation may be a cation selected from an inorganic cation and an organic cation.
Examples of the inorganic cation include non-metallic inorganic cations such as a phosphonium cation and a sulfonium cation, and metal inorganic cations such as a lithium cation, a sodium cation, a calcium cation, and a potassium cation.
Examples of the organic cation include a cation having a nitrogen atom such as a quaternary ammonium cation, an imidazolium cation, a pyridinium cation, a piperidinium cation, and a pyrrolidinium cation.

  Among these, non-metal cations such as organic cations are preferable because they are excellent in corrosion prevention, excellent in reworkability, and small in variation in adhesive strength. Among them, quaternary ammonium cations (particularly acyclic quaternary ammonium cations) are preferable. ), Nitrogen atom-containing cations such as imidazolium cation, pyridinium cation, piperidinium cation and pyrrolidinium cation, particularly quaternary ammonium cation nitrogen atom-containing cations are preferred.

  Moreover, it is preferable that melting | fusing point of the ionic compound (B) of this invention is 10-80 degreeC, Most preferably, it is 25-50 degreeC. If the melting point is too high, precipitation tends to occur at low temperatures, and if it is too low, color loss of the polarizing plate tends to occur in a moist heat environment.

  In the present invention, the content of the ionic compound (B) is preferably 1 to 20 parts by weight, particularly preferably 2 to 15 parts by weight, more preferably 2 to 2 parts by weight with respect to 100 parts by weight of the acrylic resin (A). 10 parts by weight. If the amount is too large, the durability tends to decrease, the hydrolysis of the substrate or the adherend is promoted, and when used as a polarizing plate, the degree of polarization tends to decrease. The variation tends to increase.

<Silane coupling agent (C)>
The silane coupling agent (C) used in the present invention is required to have a weight average molecular weight of 4,000 or more, more preferably 4,500 or more, particularly preferably 5,000 or more, and further preferably 7. , 500 or more, particularly preferably 10,000 or more. In addition, as an upper limit of a weight average molecular weight, 100,000 is preferable, More preferably, it is 80,000, Especially preferably, it is 50,000, More preferably, it is 30,000. If the weight average molecular weight is too small, the reworkability tends to decrease, and if it is too large, the compatibility with the acrylic resin (A) decreases, bleeding out and the durability tends to decrease.

In addition, said weight average molecular weight is a weight average molecular weight by standard polystyrene molecular weight conversion, and is measured by the following method.
Apparatus: Gel permeation chromatography detector: Differential refractive index detector RI (RI-8020 manufactured by Tosoh Corporation, sensitivity 32)
Column: TSK guard column H _HR -H (1) (φ6 mm × 4 cm), (TSKgelGMH _HR -N (2) (φ7.8 mm × 30 cm), manufactured by Tosoh Corporation
Solvent: tetrahydrofuran (THF)
Column temperature: 23 ° C. Flow rate: 1.0 mL / min

  The silane coupling agent (C) is an organosilicon compound containing one or more reactive functional groups other than alkoxy groups and one or more alkoxy groups bonded to silicon atoms in the structure.

  Examples of the reactive functional group include an epoxy group, a (meth) acryloyl group, a mercapto group, a hydroxyl group, a carboxyl group, an amino group, an amide group, and an isocyanate group. Among these, durability and reworkability are mentioned. From the viewpoint of balance, a mercapto group and an epoxy group are preferable.

  The alkoxy group bonded to the silicon atom preferably contains an alkoxy group having 1 to 8 carbon atoms, particularly preferably an alkoxy group having 1 to 2 carbon atoms, from the viewpoint of durability and storage stability. Specifically, they are a methoxy group and an ethoxy group.

  The alkoxy group content of the silane coupling agent (C) is preferably 1 to 30% by weight, particularly preferably 3 to 20% by weight, and further preferably 5 to 15% by weight. When the content of the alkoxy group bonded to the silicon atom is too small, the adhesion to the liquid crystal cell tends to be lowered and the durability tends to be lowered, and when too much, the reworkability tends to be lowered.

  Moreover, it is preferable that the reactive functional group equivalent of a silane coupling agent (C) is 1000 g / mol or less, Most preferably, it is 100-650 g / mol, More preferably, it is 300-600 g / mol. If the reactive functional group equivalent is too small, the reworkability tends to decrease, and if it is too large, the durability under wet heat conditions tends to decrease.

  In addition, the silane coupling agent (C) may have organic substituents other than a reactive functional group and an alkoxy group, for example, an alkyl group, a phenyl group, etc.

As a silane coupling agent (C) used by this invention, a weight average molecular weight should just be 40,000 or more, for example,
3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 2- (3,4 epoxycyclohexyl) Some of the silane compounds such as ethyltrimethoxysilane may undergo hydrolytic condensation polymerization, or the above silane compounds and alkyl group-containing silane compounds such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, and ethyltrimethoxysilane Oligomer-type epoxy group-containing silane coupling agent which is a co-condensed silane compound;
Some of the silane compounds such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, γ-mercaptopropyldimethoxymethylsilane, 3-mercaptopropylmethyldimethoxysilane may undergo hydrolysis condensation polymerization, An oligomeric mercapto group-containing silane coupling agent, which is a silane compound obtained by cocondensation of an alkyl group-containing silane compound such as methyltriethoxysilane, ethyltriethoxysilane, methyltrimethoxysilane, or ethyltrimethoxysilane;
Is mentioned.
Examples of the silane coupling agent other than the above include those substituted with an alkyl group or a polyether group.
These may be used alone or in combination of two or more.

  As the silane coupling agent (C) used in the present invention, specifically, “X-24-9590” manufactured by Shin-Etsu Chemical Co., Ltd. (weight average molecular weight; 13,700, contained alkoxy group; methoxy) Group, alkoxy content: 9.5 wt%, reactive functional group; epoxy group, epoxy equivalent 592 g / mol), “X-24-9589” (weight-average molecular weight 4,700-containing alkoxy group ethoxy group, alkoxy group-containing 14.5% by weight, reactive functional group epoxy group, epoxy equivalent 1509 g / mol).

  Moreover, in this invention, 0.001-5 weight part is preferable with respect to 100 weight part of acrylic resin (A), and, as for content of a silane coupling agent (C), 0.005-1 weight part is especially. Preferably, 0.01 to 0.3 part by weight is more preferable. When the content is too large, bleeding out tends to decrease the heat resistance, and when the content is too small, the adhesive strength tends to increase or the heat and humidity resistance tends to decrease.

  In addition, although the silane coupling agent other than the said silane coupling agent (C) can be used for the acrylic adhesive composition of this invention in the range which does not inhibit the effect of this invention, this silane coupling agent. If the total amount is too large, the durability tends to decrease due to bleeding. Specifically, the amount is preferably 1 part by weight or less, more preferably 0 parts per 100 parts by weight of the acrylic resin (A). .5 parts by weight or less.

<Crosslinking agent (D)>
The crosslinking agent (D) reacts with a functional group in the acrylic resin (A) to form a crosslinked structure. For example, an isocyanate crosslinking agent, an epoxy crosslinking agent, an aziridine crosslinking agent, a melamine crosslinking agent. Agents, aldehyde crosslinking agents, amine crosslinking agents, metal chelate crosslinking agents, and carbodiimide crosslinking agents. Among these, it is preferable to use an isocyanate-based cross-linking agent from the viewpoint of improving the adhesion to the base material and the excellent reactivity with the base polymer.

  Examples of the isocyanate crosslinking agent include, for example, tolylene diisocyanate crosslinking agents such as 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, xylylene diisocyanate crosslinking agents such as 1,3-xylylene diisocyanate, Diphenylmethane-based crosslinkers such as diphenylmethane-4,4-diisocyanate, aromatic isocyanate-based crosslinkers such as naphthalene diisocyanate-based crosslinkers such as 1,5-naphthalene diisocyanate; isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 4,4 '-Dicyclohexylmethane diisocyanate, methylcyclohexane diisocyanate, isopropylidene dicyclohexyl-4,4'-diisocyanate, 1,3-diisocyanatomethylcyclohexane, And alicyclic isocyanate crosslinking agents such as bornane diisocyanate; aliphatic isocyanate crosslinking agents such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; and adducts, burettes and isocyanurates of the above isocyanate compounds. It is done. These may be used alone or in combination of two or more.

  Among these, tolylene diisocyanate crosslinking agents are preferable in terms of pot life and durability, and non-aromatic isocyanate crosslinking agents are preferable in terms of yellowing resistance. Among these, specifically, tolylene diisocyanate, xylylene diisocyanate, adduct body of hexamethylene diisocyanate and trimethylolpropane, and nurate body are preferable in terms of excellent balance of durability, pot life, and crosslinking speed. .

  The said crosslinking agent (D) may be used independently and may use 2 or more types together.

  The content of the crosslinking agent (D) is preferably 0.01 to 5 parts by weight, more preferably 0.05 to 3 parts by weight, particularly preferably 100 parts by weight of the acrylic resin (A). Is 0.1 to 1.5 parts by weight. If the content is too small, the durability tends to decrease or adhesive residue may be generated during reworking. If the content is too large, the stress relaxation property decreases and the liquid crystal cell tends to warp, causing uneven display on the liquid crystal display. It tends to occur easily.

  Furthermore, the pressure-sensitive adhesive composition of the present invention includes, as other components, resin components other than the acrylic resin (A), acrylic monomers, polymerization inhibitors, antioxidants, as long as the effects of the present invention are not impaired. Further, various additives such as corrosion inhibitors, crosslinking accelerators, radical generators, peroxides, radical scavengers, metals, resin particles and the like can be blended. In addition to the above, a small amount of impurities and the like contained in the raw materials for producing the constituent components of the pressure-sensitive adhesive composition may be contained.

  The content of the other components is preferably 5 parts by weight or less, particularly preferably 1 part by weight or less, and further preferably 0.5 parts by weight or less with respect to the acrylic resin (A). When there is too much this content, compatibility with acrylic resin (A) will fall, and there exists a tendency for durability to fall.

Thus, the pressure-sensitive adhesive composition of the present invention can be obtained.
The pressure-sensitive adhesive composition of the present invention can be made into a pressure-sensitive adhesive by crosslinking with a crosslinking agent (D), and further, a pressure-sensitive adhesive layer made of such a pressure-sensitive adhesive is laminated on a polarizing plate (optical laminate). Thereby, a polarizing plate with an adhesive layer can be obtained.
The pressure-sensitive adhesive layer-attached polarizing plate is preferably provided with a release sheet on the surface opposite to the pressure-sensitive adhesive layer.

As a manufacturing method of the said polarizing plate with an adhesive layer, [1] After apply | coating an adhesive composition and drying on a polarizing plate, a release sheet is bonded and at least the aging in normal temperature or a heating state is carried out. Method of performing treatment by one, [2] Method of applying a pressure-sensitive adhesive composition on a release sheet, drying, pasting a polarizing plate, and performing treatment by at least one of aging at room temperature or in a heated state Etc.
Among these, the method of aging at room temperature by the method [2] is preferable in that it does not damage the polarizing plate and is excellent in adhesion to the substrate.

  This aging treatment is performed to balance the physical properties of the adhesive as the reaction time of the chemical crosslinking of the adhesive. As the aging conditions, the temperature is usually from room temperature to 70 ° C., and the time is usually from 1 day to 30 days. Specifically, for example, the treatment may be performed under conditions such as 23 ° C. for 1 day to 20 days, 23 ° C. for 3 to 10 days, 40 ° C. for 1 day to 7 days, and the like.

  In the application of the pressure-sensitive adhesive composition, it is preferable to dilute the pressure-sensitive adhesive composition with a solvent, and the dilution concentration is preferably 5 to 60% by weight, particularly preferably 10% as a heating residue concentration. ~ 30% by weight.

The solvent is not particularly limited as long as it dissolves the pressure-sensitive adhesive composition. For example, ester solvents such as methyl acetate, ethyl acetate, methyl acetoacetate, and ethyl acetoacetate, acetone, methyl ethyl ketone, A ketone solvent such as methyl isobutyl ketone, an aromatic solvent such as toluene and xylene, and an alcohol solvent such as methanol, ethanol and propyl alcohol can be used. Among these, ethyl acetate and methyl ethyl ketone are preferably used from the viewpoints of solubility, drying property, price, and the like.

  Moreover, regarding application | coating of the said adhesive composition, it is performed by conventional methods, such as roll coating, die coating, gravure coating, comma coating, screen printing, for example.

Moreover, 5-100 micrometers is preferable, as for the thickness of the adhesive layer in the polarizing plate with an adhesive layer obtained, 10-50 micrometers is especially preferable, Furthermore, 10-30 micrometers is preferable.
If the thickness of the pressure-sensitive adhesive layer is too thin, the pressure-sensitive adhesive for polarizing plates does not have sufficient stress relaxation properties, and the durability tends to decrease. There is a tendency to decrease.

  The gel fraction of the pressure-sensitive adhesive layer produced by the above method is preferably 30 to 100%, particularly preferably 40 to 95%, more preferably 50 from the viewpoint of durability performance and suppression of polarization degree reduction. ~ 90%. If the gel fraction is too low, the durability tends not to be sufficiently obtained or the reworkability tends to be lowered. If the gel fraction is too high, there is a tendency that floating and peeling are likely to occur.

  The gel fraction is a measure of the degree of crosslinking (curing degree), and is calculated, for example, by the following method. That is, the pressure-sensitive adhesive is picked from a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer formed on a base material, wrapped in a 200-mesh SUS wire mesh, immersed in ethyl acetate at 23 ° C. for 24 hours, and placed in the wire mesh. The weight percentage of the remaining insoluble pressure-sensitive adhesive component is defined as the gel fraction.

  The pressure-sensitive adhesive layer produced by the above method preferably has a good tack feeling when touched with a finger, because it has good wettability when actually attached to an adherend, and therefore tends to improve workability. .

As an electrical property of the pressure-sensitive adhesive layer obtained using the pressure-sensitive adhesive composition of the present invention, a low surface resistance value is preferable as a countermeasure against static electricity, particularly preferably 1 × 10 ¹² Ω / □ or less, more preferably 5 ×. 10 ¹¹ Ω / □ or less, particularly preferably 1 × 10 ¹¹ Ω / □ or less. If the surface resistance is too high, it is difficult to obtain antistatic performance, and the display failure of the liquid crystal display due to static electricity tends to be difficult to recover.

  The polarizing plate with the pressure-sensitive adhesive layer of the present invention has a release sheet directly or after peeling off the release sheet, and then the adhesive layer surface is bonded to the glass substrate of the liquid crystal cell, for example, for a liquid crystal display plate. Then, an image display device is manufactured.

When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive sheet having a cross-linked pressure-sensitive adhesive layer, the average adhesive strength is appropriately determined according to the material of the adherend, but glass such as a liquid crystal cell. When sticking to a board | substrate, it is preferable to have the adhesive force of 0.1-20N / 25mm, Most preferably, it is 0.1-10N / 25mm.

Further, in terms of reducing breakage of the adherend, it is preferable that there is little variation in the adhesive strength of the pressure-sensitive adhesive layer, and the coefficient of variation of the adhesive strength calculated from the following formula (1) is preferably less than 4%. More preferably, it is less than 3%.
Coefficient of variation of adhesive strength = standard deviation of adhesive strength / average value of adhesive strength × 100 (1)

Average adhesive strength: The average adhesive strength for a measured value of 1600 points per 0.05 mm, with the peel distance 30 mm to 110 mm when the peel start point is 0 mm and the peel end point is 120 mm. Values were used. The measured values near the peeling start point and the peeling end point were excluded from the measurement as noise.

Standard deviation of adhesive force: When the peeling start point is 0 mm and the peeling end point is 120 mm, the measuring distance is 30 mm to 110 mm, and the standard deviation value for 1600 measured values every 0.05 mm is Using.
The measured values near the peeling start point and the peeling end point were excluded from the measurement as noise.

The average value of the adhesive strength (average adhesive strength) is measured as follows.
That is, the polarizing plate with the pressure-sensitive adhesive layer was cut to a width of 25 mm, the release sheet was peeled off, the pressure-sensitive adhesive layer surface was washed with methanol, and then dried at 50 ° C. for 20 minutes, under conditions of 23 ° C. and 50% RH. And pressed against a non-alkali glass plate (Corning Co., “Eagle XG”) after standing for 3 hours to bond the polarizing plate and the glass plate. Then, after autoclaving (50 ° C., 0.5 MPa, 20 minutes), after leaving still at 23 ° C. and 50% RH for 24 hours, a 180 ° peel test was performed, and the average value was calculated from the above 1600 points of adhesive strength. calculate.

  The pressure-sensitive adhesive obtained by using the pressure-sensitive adhesive composition of the present invention is excellent in balance of various performances such as rework resistance, durability, and antistatic property, and further, variation in pressure-sensitive adhesive force during rework is small and uniform. Therefore, it is useful as an adhesive for polarizing plates that bonds a polarizing plate and a glass substrate.

  Examples of the protective film constituting the polarizing plate include a triacetyl cellulose film, an acrylic film, a polyethylene film, a polypropylene film, a cycloolefin film, and the like. Also suitable for use.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. In the examples, “parts” and “%” mean weight basis.

In addition, the weight average molecular weight of the acrylic resin (A), the degree of dispersion, the glass transition temperature, the weight average molecular weight of the silane coupling agent, and the gel fraction of the pressure-sensitive adhesive were measured according to the methods described above.
The glass transition temperature of the acrylic resin (A) is calculated using the above-described Fox equation, and the glass transition temperature when the homopolymer of the monomer constituting the acrylic resin (A) is usually measured by DSC. The literature values and catalog values described were used.
The viscosity was measured according to the JIS K5400 (1990) 4.5.3 rotational viscometer method.

[Manufacture of acrylic resin (A-1)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 64.5 parts of normal butyl acrylate (a1), 30 parts of methyl acrylate (a2), 2-hydroxyethyl acrylate (A3) 5 parts, acrylic acid (a3) 0.5 part, ethyl acetate 83 parts, acetone 42 parts, and azobisisobutyronitrile (AIBN) 0.0126 part as a polymerization initiator were charged, and 2,2′- Azobis-2,4-dimethylvaleronitrile (ADVN) acetic acid solution (ADVN: 0.0126 parts, 30 parts of ethyl acetate) was added dropwise and reacted at reflux temperature for 3.25 hours, then diluted with ethyl acetate and acrylic. Resin (A-1) solution (solid content 17.4%, viscosity 4,120 mPa · s / 25 ° C .; acrylic resin (A-1): glass transition temperature −37.5 ° C., weight average An average molecular weight of 141,000 and a degree of dispersion of 4.0) were obtained (see Table 1).

[Manufacture of acrylic resin (A-2)]
In a 4-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 59.5 parts of normal butyl acrylate (a1), 25 parts of methyl acrylate (a2), benzyl acrylate (a2) 10 parts, 2-hydroxyethyl acrylate (a3) 5 parts, acrylic acid (a3) 0.5 parts, ethyl acetate 83 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0.0126 parts as a polymerization initiator Was added, and 2,2′-azobis-2,4-dimethylvaleronitrile (ADVN) acetic acid solution (ADVN: 0.0126 parts, ethyl acetate 30 parts) was added dropwise at a reflux temperature for 3.25 hours, followed by acetic acid. Acrylic resin (A-1) solution diluted with ethyl (solid content 16.4%, viscosity 2,620 mPa · s / 25 ° C .; acrylic resin (A-1 ): A glass transition temperature of −34.7 ° C., a weight average molecular weight of 1.4 million, and a dispersity of 3.5) were obtained (see Table 1).

[Production of acrylic resin (A-3)]
In a four-neck round bottom flask equipped with a reflux condenser, a stirrer, a nitrogen gas inlet and a thermometer, 52.3 parts of normal butyl acrylate (a1), 20 parts of methyl acrylate (a2), benzyl acrylate (a2) 19 parts, 2-hydroxyethyl acrylate (a3) 8 parts, acrylic acid (a3) 0.7 parts, ethyl acetate 54.9 parts, acetone 42 parts, azobisisobutyronitrile (AIBN) 0. 013 parts were charged, and azobisisobutyronitrile acetic acid solution was added dropwise, followed by reaction at reflux temperature for 3.25 hours, and then diluted with ethyl acetate to obtain an acrylic resin (A-1) solution (solid content 22.9%). Viscosity: 8,600 mPa · s / 25 ° C .; acrylic resin (A-1): glass transition temperature—31.0 ° C., weight average molecular weight of 1.4 million, dispersity 4.3) was obtained ( Reference 1).

<Ionic compounds>
The following were prepared as ionic compounds.
Ionic compound (B-1) having fluorine as anion: ionic compound composed of ammonium cation and N, N-bis (fluorosulfonyl) imidobi (Daiichi Kogyo Seiyaku “MP-402”, melting point 47 ° C.)
(B-2): Tri-n-butylmethylammonium N, N- (trifluoromethanesulfonyl) imide (“FC-4400” manufactured by 3M, melting point 27.5 ° C.)

<Silane coupling agent>
The following were prepared as silane coupling agents.
(C-1): “X-24-9590” manufactured by Shin-Etsu Chemical Co., Ltd. (weight average molecular weight: 13,700, alkoxy group content: 9.5% by weight, reactive functional group; epoxy group, epoxy equivalent 592 g / Mol, containing alkoxy group; methoxy group)
(C′-1): “X-41-1059A” manufactured by Shin-Etsu Chemical Co., Ltd. (weight average molecular weight; 2,300, alkoxy group content; 42% by weight, reactive functional group; epoxy group, epoxy equivalent 350 g / mol, contained alkoxy group; methoxy group, ethoxy group)
(C′-2): “X-41-1805” manufactured by Shin-Etsu Chemical Co., Ltd. (weight average molecular weight 3,450; alkoxy group content; 50% by weight, reactive functional group; mercapto group, mercapto equivalent 800 g / mol, contained alkoxy group; methoxy group, ethoxy group)

<Crosslinking agent>
The following were prepared as a crosslinking agent.
(D-1): Adduct body of tolylene diisocyanate and trimethylolpropane ("Coronate L55E" manufactured by Tosoh Corporation)

<Examples 1-3, Comparative Examples 1-3>
The components (A) to (D) prepared and prepared as described above were blended as shown in Table 2 below, and the resulting mixture was adjusted to a solid content concentration of 12.5% with ethyl acetate. I got a thing.

[Preparation of polarizing plate with adhesive layer]
The obtained pressure-sensitive adhesive composition was applied to a 38 μm polyester release sheet (“Therapy WZ” manufactured by Toray Industries Inc.) so that the thickness after drying was 20 μm, dried at 100 ° C. for 3 minutes, and then triacetyl cellulose ( TAC) Adhesive layer on the opposite side of the release sheet is pasted on one TAC film surface of the polarizing plate laminated on both sides, and cured for 7 days in an environment of 23 ° C x 50% RH, with adhesive layer A polarizing plate was obtained (layer constitution; release sheet / adhesive layer / TAC film / polarizer / TAC film).
Using the obtained polarizing plate with the pressure-sensitive adhesive layer, the gel fraction, antistatic performance, reworkability (average adhesive strength, variation in adhesive strength), and durability were evaluated as follows. The results are shown in Table 2.
Moreover, about Example 1 and Comparative Example 2, the measurement result of the dispersion | variation in adhesive force is shown in FIG.

<Antistatic property>
[Surface resistance value]
The polarizing plate with the pressure-sensitive adhesive layer was allowed to stand for 24 hours in an atmosphere of 23 ° C. × 50% RH, and then the release sheet of the pressure-sensitive adhesive layer was removed, and a surface resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd., “device name” The surface resistance value of the pressure-sensitive adhesive layer was measured using “Hiresta-UP MCP-HT450”) and evaluated according to the following criteria.
◎ ・ ・ ・ less than 1 × 10 ¹¹ Ω / □,
〇 ・ ・ ・ 1 × 10 ¹¹ Ω / □ or more, less than 5 × 10 ¹¹ Ω / □ △ ・ ・ ・ 5 × 10 ¹¹ Ω / □ or more, less than 1 × 10 ¹² Ω / □ × ・ ・ ・ 1 × 10 ¹² Ω / □ or more.

<Durability>
The obtained polarizing plate with the pressure-sensitive adhesive layer was cut into 15 cm × 20 cm cm × 160 cm, the release sheet was peeled off, and the pressure-sensitive adhesive layer surface was pressed against alkali-free glass (Corning “Eagle XG”: thickness 0.7 mm) 2 kg After reciprocating two times with a roller, autoclave treatment (0.5 Mpa × 50 ° C. × 20 minutes) was performed to prepare a sample for durability test.
Using the obtained durability test samples, the following durability tests were performed and evaluated.

[Heat resistance test]
250 hours in 85 ° C atmosphere [Moisture and heat resistance test]
Durability test for 250 hours under 60x90 ° C atmosphere (evaluation criteria)
○ ・ ・ ・ No floating was observed between the polarizing plate and the glass × ・ ・ ・ Floating was observed between the polarizing plate and the glass

<Reworkability>
[Average adhesive strength]
The polarizing plate with the pressure-sensitive adhesive layer obtained above was cut to a width of 25 mm, the release sheet was peeled off, and the pressure-sensitive adhesive layer surface was pressed against alkali-free glass (Corning “Eagle XG”: thickness 1.1 mm). And then autoclaving (0.5 Mpa × 50 ° C. × 20 minutes), then left to stand at 23 ° C. × 50% RH for 1 day and 15 days, then peeled off to 180 °, peel distance Of 120 mm, an average value of 1600 points of adhesive strength every 0.05 mm at a separation distance of 30 mm to 110 mm was obtained. The same measurement was performed twice, the average value was calculated, and evaluated according to the following criteria.
(Evaluation criteria)
◎ ・ ・ ・ less than 5N / 25mm ○ ・ ・ ・ 5N / 25mm or more and less than 10N / 25mm △ ・ ・ ・ 10N / 25mm or more and less than 20N / mm × ・ ・ ・ 20N / 25mm or more

[Variation of adhesive strength]
In the above rework test, the coefficient of variation of the adhesive strength of 1600 points of adhesive strength every 0.05 mm at a separation distance of 30 mm to 110 mm was obtained from the following equation. The same measurement was performed twice, the average value was calculated, and evaluated according to the following criteria.
Coefficient of variation = (standard deviation of adhesive force of 1600 points with a separation distance of 30 mm to 110 mm) / average adhesive force (evaluation criteria)
◎ ... less than 2.5 ○ ... 2.5 or more but less than 4 △ ... 4 or more but less than 5 × ... 5 or more

From the results shown in Table 2, in Examples using an adhesive composition containing an ionic compound (B) having a fluorine-containing anion and a high molecular weight silane coupling agent (C), a highly durable glass transition temperature is obtained. It can be seen that even when an acrylic resin obtained by copolymerizing a high polymerization component is used, in addition to the reworkability, the variation in adhesive force is small and a stable peeling force can be exhibited.
This is because the ionic compound and the silane coupling agent are segregated on the surface of the pressure-sensitive adhesive by containing both the ionic compound having a fluorine-containing anion and the high molecular weight silane coupling agent in the pressure-sensitive adhesive layer. Since wetting to the adherend is improved, it is considered that variation in adhesive force is small and uniform adhesive force can be expressed.

On the other hand, in Comparative Examples 1 and 2 using the pressure-sensitive adhesive composition containing no silane coupling agent having a weight average molecular weight of 4,000 or more, the coefficient of variation of the pressure-sensitive adhesive force is large, and the pressure-sensitive adhesive force varies. I understand.
Moreover, it can be seen that Comparative Example 3 not using an ionic compound having a fluorine-containing anion has not only antistatic performance, but also a large coefficient of variation in adhesive force, resulting in variations in adhesive force.
About the dispersion | variation in adhesive force, it turns out that the difference is clear from FIG. 1 which showed the measurement result of Example 1 and Comparative Example 2. FIG.

  When the pressure-sensitive adhesive composition of the present invention is used as a pressure-sensitive adhesive used for laminating a polarizing plate (protective film) and a liquid crystal cell (glass substrate), various rework properties, durability, antistatic properties, etc. It is possible to obtain a pressure-sensitive adhesive that satisfies the required performance in a well-balanced manner, and further, it is possible to obtain a pressure-sensitive adhesive layer not only having a low average pressure-sensitive adhesive force but also having a small variation in pressure-sensitive adhesive force and showing a uniform pressure-sensitive adhesive force. . Therefore, damage to the liquid crystal cell and the substrate during rework can be prevented, and a liquid crystal display device can be produced efficiently, which is very useful as an adhesive for polarizing plates.

Claims (4)

Acrylic resin (A)
Ionic compound (B)
Silane coupling agent (C)
A pressure-sensitive adhesive composition containing a crosslinking agent (D),
The acrylic resin (A) is obtained by copolymerizing the following monomers (a1) to (a4) with respect to the whole monomer components in the following proportions:
(A1) Normal butyl acrylate 5 to 75% by weight
(A2) 20-80% by weight of at least one monomer selected from aromatic ring-containing monomers and alkyl (meth) acrylates having 1 to 2 carbon atoms in the alkyl group
(A3) At least one polar group-containing monomer selected from a carboxyl group-containing monomer, a hydroxyl group-containing monomer, and a nitrogen atom-containing monomer 1 to 30% by weight
(However, it contains at least one of a carboxyl group-containing monomer and a hydroxyl group-containing monomer.)
(A4) Monomers other than (a1) to (a3) 10 wt% or less The ionic compound (B) is an ionic compound having a fluorine-containing anion,
A pressure-sensitive adhesive composition, wherein the silane coupling agent (C) has a weight average molecular weight of 4,000 or more.   A pressure-sensitive adhesive for polarizing plates, wherein the pressure-sensitive adhesive composition according to claim 1 is crosslinked with a crosslinking agent (D).   It has an adhesive layer which consists of an adhesive for polarizing plates of Claim 2, The polarizing plate with an adhesive layer characterized by the above-mentioned.   An image display device comprising the polarizing plate with the pressure-sensitive adhesive layer according to claim 3.

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