JP2012067275A - Adhesive for polarizing plate, and polarizing plate with adhesive using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive for a polarizing plate excellent in antistatic performance, as well as in durability and in prevention of light leakage.SOLUTION: The adhesive for a polarizing plate is obtained from an adhesive composition comprised of 100 pts.mass of a (meth)acryl polymer (A), 0.01-10 pts.mass of a fluorine-containing anionic compound (B) or 0.1-5 pts.mass of an isocyanate-based crosslinking agent (C), wherein, the polymer (A) is made by performing copolymerization of 79-97.9 mass% of at least (meth)acryl alkoxy ethyl ester (a1) whose added mole number of ethylene oxide group is one, 0.05-10 mass% of a hydroxy group-containing monomer (a2), 0.1-10 mass% of a carboxyl group-containing monomer (a3), or 1-10 mass% of a (meth)acryl alkyl ester (a4), and whose weight average molecular weight is 500,000-2,000,000, wherein, when (a2) is ≥1 mass%, (a3) is <3 mass%, and when (a2) is <1 mass%, (a3) is ≥3 mass%, and the photoelastic coefficient of the adhesive for polarizing plate measured at a wavelength of 600 nm is from -300×10to 0 (m/N).

Description

  The present invention relates to a pressure-sensitive adhesive for polarizing plates, and more particularly relates to a pressure-sensitive adhesive for polarizing plates having excellent antistatic performance, high light leakage prevention properties and durability, and a polarizing plate with a pressure-sensitive adhesive using the same. Is.

  The liquid crystal element has a structure in which a liquid crystal material is sandwiched between two glass substrates, and a polarizing plate is attached to the surface of the glass substrate via an adhesive layer. In recent years, the use of liquid crystal elements for mounting on vehicles, for outdoor instruments, personal computer displays, televisions, and the like has been expanded, and the usage environment has become very severe.

  The polarizing plate has a multilayer structure of different materials, and is poor in dimensional stability due to the characteristics of the constituent materials. In particular, in a high temperature, high humidity environment, stress concentrates due to the contraction of the polarizing plate and induces birefringence of the polarizing plate. Light leakage occurs at the concentrated end, and the display quality deteriorates. In such an environment, problems such as foaming at the interface between the polarizing plate and glass and peeling of the polarizing plate are likely to occur. Therefore, excellent light leakage prevention and durability are required for the pressure-sensitive adhesive for polarizing plates.

  In addition, a separator is attached to the pressure-sensitive adhesive layer formed on the polarizing plate, and when manufacturing the liquid crystal element, the separator is peeled off to expose the pressure-sensitive adhesive layer, and then the polarizing plate is attached to the glass substrate. In this case, static electricity is generated due to the high insulating properties of the separator and the polarizing plate, which adversely affects liquid crystal alignment and damages electronic components. For this reason, the pressure-sensitive adhesive for polarizing plates is also required to have antistatic performance, but in recent years, the amount of charge to be charged has increased with the increase in the size of the liquid crystal display, and thus the required level has become much higher than before. ing.

  So far, various technologies have been proposed for the purpose of improving the light leakage prevention property, antistatic property, durability and the like in the optical adhesive. For example, in Patent Document 1, an adhesive material containing a (meth) acrylic acid ester copolymer, a polyfunctional active energy ray-curable compound, and an antistatic agent is irradiated with active energy rays to obtain a photoelastic coefficient and a loss tangent ( By adjusting the temperature showing the maximum value of tan δ to a certain range, the light leakage prevention property, the antistatic property and the like are improved. In Patent Documents 2 and 3, an acrylic polymer obtained by copolymerizing an alkylene oxide (meth) acrylate such as ethoxy-diethylene glycol acrylate, and an alkali metal salt such as lithium iodide or an ionic liquid as an antistatic agent. The antistatic adhesive used is disclosed. The present applicant has also already reported a display pressure-sensitive adhesive sheet having improved moisture resistance by using a pressure-sensitive adhesive polymer mainly composed of (meth) acrylic acid alkoxyalkyl ester and a low molecular weight polymer (Patent Document 4). However, with these technologies, it has been extremely difficult to achieve the required high antistatic performance while achieving both durability and light leakage prevention.

JP 2009-242633 A JP 2005-314579 A JP 2006-063311 A JP 2002-327160 A

  Therefore, a pressure-sensitive adhesive for a polarizing plate having high antistatic performance and excellent durability and light leakage prevention is desired, and the present invention provides such a pressure-sensitive adhesive for a polarizing plate. Let it be an issue.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have, as a main monomer, an alkoxyethyl (meth) acrylate having an addition mole number of ethylene oxide groups of 1, a hydroxyl group-containing monomer and a carboxyl group-containing monomer. By using a (meth) acrylic polymer copolymerized with (meth) acrylic acid alkyl ester and adjusting the photoelastic coefficient to a certain range, any of antistatic property, durability and light leakage preventing property can be obtained. It has been found that excellent performance can be obtained, and the present invention has been completed.

That is, the present invention provides the following components (A) to (C):
(A) At least the following components (a1) to (a4)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Cyethyl 79-97.9% by mass
(A2) Hydroxyl group-containing monomer 0.05 to 10% by mass
(A3) Carboxyl group-containing monomer 0.1 to 10% by mass
(A4) 1 to 10% by mass of (meth) acrylic acid alkyl ester
(Meth) acrylic polymer having a weight average molecular weight of 500,000 to 2,000,000 (provided that when (a2) is 1% by mass or more, (a3) is less than 3% by mass, and (a2 )
(A3 is 3% by mass or more) 100 parts by mass (B) Ion compound containing fluorine-containing anion 0.01 to 10 parts by mass (C) Isocyanate-based crosslinking agent 0.1 to 5 parts by mass The pressure-sensitive adhesive for polarizing plates is characterized in that the photoelastic coefficient at a measurement wavelength of 600 nm is −300 × 10 ^{−12 to} 0 (m ² / N).

The present invention also includes the following components (A1), (B) and (C)
(A1) At least the following components (a1) to (a4)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Siethyl 80-97.9% by mass
(A2) Hydroxyl group-containing monomer 1 to 10% by mass
(A3) carboxyl group-containing monomer 0.1% by mass or more and less than 3% by mass (a4) (meth) acrylic acid alkyl ester 1 to 10% by mass
(Meth) acrylic polymer having a weight average molecular weight of 500,000 to 2,000,000 100 parts by mass (B) ionic compound containing fluorine-containing anion 0.01 to 10 parts by mass (C) Isocyanate-based crosslinking A polarizing plate obtained from a pressure-sensitive adhesive composition containing 0.1 to 5 parts by mass of an agent and having a photoelastic coefficient at a measurement wavelength of 600 nm of −300 × 10 ^{−12 to} 0 (m ² / N). It is an adhesive.

Furthermore, the present invention provides the following components (A2), (B) and (C)
(A2) At least the following components (a1) to (a4)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Cyethyl 79-95.95 mass%
(A2) hydroxyl group-containing monomer 0.05% by mass or more and less than 1% by mass (a3) carboxyl group-containing monomer 3 to 10% by mass
(A4) 1 to 10% by mass of (meth) acrylic acid alkyl ester
(Meth) acrylic polymer having a weight average molecular weight of 500,000 to 2,000,000 100 parts by mass (B) ionic compound containing fluorine-containing anion 0.01 to 10 parts by mass (C) Isocyanate-based crosslinking A polarizing plate obtained from a pressure-sensitive adhesive composition containing 0.1 to 5 parts by mass of an agent and having a photoelastic coefficient at a measurement wavelength of 600 nm of −300 × 10 ^{−12 to} 0 (m ² / N). It is an adhesive.

  Moreover, this invention is a polarizing plate with an adhesive which has the layer which consists of the said adhesive for polarizing plates in the at least one surface of a polarizing plate.

  The pressure-sensitive adhesive for polarizing plates of the present invention is excellent in light leakage prevention and durability, and can prevent appearance defects such as light leakage, foaming and peeling even under high temperature and high humidity environment. In addition, the antistatic performance is high, and it is possible to effectively prevent the generation of static electricity when the separator is peeled off. Furthermore, by using an ionic compound of an organic anion and a fluorine-containing cation as an antistatic agent and using an isocyanate-based and metal chelate-based crosslinking agent in combination, the durability can be further improved and the aging period can be shortened.

  The (meth) acrylic polymer of component (A) used for the polarizing plate pressure-sensitive adhesive of the present invention contains at least (a1) alkoxyethyl (meth) acrylate having an ethylene oxide group addition mole number of 1, and (a2) containing a hydroxyl group. It is obtained by copolymerizing a monomer, (a3) a carboxyl group-containing monomer, and (a4) (meth) acrylic acid alkyl ester.

  Examples of (ethyl) alkoxyethyl (meth) acrylate having 1 added mole number of ethylene oxide group (a1) include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, (meth) acrylic acid 2 -Butoxyethyl, 2-propoxyethyl (meth) acrylate, etc. can be mentioned. Of these, 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, and the like are preferably used because they can be stably polymerized and the molecular weight can be easily adjusted.

  Examples of the hydroxyl group-containing monomer of the component (a2) include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- Examples thereof include hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 1,4-cyclohexanedimethanol mono (meth) acrylate, chloro-2-hydroxypropyl acrylate, etc. Among these, 2-hydroxyethyl acrylate, 4 -Hydroxybutyl acrylate is preferred because it is readily available and has good copolymerizability.

  As the carboxyl group-containing monomer of the component (a3), (meth) acrylic acid, 2-carboxyethyl (meth) acrylate, 3-carboxypropyl (meth) acrylate, 4-carboxybutyl (meth) acrylate, itaconic acid, croton Examples thereof include acid, maleic acid, fumaric acid, maleic anhydride, etc. Among them, (meth) acrylic acid is preferably used because it is easily available and has good copolymerizability.

  As said component (a4) (meth) acrylic-acid alkylester, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate , Pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, lauryl (meth) acrylate Etc. Of these, butyl acrylate, methyl acrylate, and the like are preferably used from the viewpoint of adjusting adhesive properties.

  Component (A) The content of component (a1) is 79 to 97.9% by mass (hereinafter referred to as “%”) and component (a2) 0.05 with respect to the entire constituent monomers of the (meth) acrylic polymer. 10%, component (a3) 0.1-10%, and component (a4) 1-10%, but the content of component (a3) defines the content of component (a3). When component (a2) is 1% or more of the above range, the content of component (a3) is less than 3%, and when component (a2) is less than 1%, the content of component (a3) is 3% or more. Along with this, the content of the component (a1) is also defined. That is, the component (A) used in the present invention includes (meth) acrylic polymers (A1) and (A2) composed of monomers having the following composition.

(A1)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Siethyl 80-97.9%
(A2) Hydroxyl group-containing monomer 1 to 10%
(A3) carboxyl group-containing monomer 0.1% or more and less than 3% (a4) (meth) acrylic acid alkyl ester 1 to 10%

(A2)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Cyethyl 79-95.95%
(A2) Hydroxyl group-containing monomer 0.05% or more and less than 1% (a3) Carboxyl group-containing monomer 3 to 10%
(A4) (Meth) acrylic acid alkyl ester 1 to 10%

In the (meth) acrylic polymer (A1), when the content of the component (a1) is out of the range of 80 to 97.9%, the photoelastic coefficient described later is −300 × 10 ^{−12 to} 0 (m ² / N). ) Is not preferable because it is difficult to adjust the range. A more preferable content of the component (a1) is 85 to 95%.

  In (A1), if the content of the component (a2) is less than 1%, sufficient cohesive force cannot be obtained and the durability is inferior. If more than 10%, the pot life is shortened and workability is deteriorated. Moreover, there exists a possibility that a coating film may become hard by excess bridge | crosslinking formation and light leak property may deteriorate. More preferably, it is 1 to 5%.

  In (A1), when the content of the component (a3) is less than 0.1%, the effect of promoting the crosslinking between the hydroxyl group and the isocyanate group cannot be obtained sufficiently, resulting in insufficient cohesive force and 3% or more. Further, the pot life is shortened due to excessive crosslinking promotion, so that workability is deteriorated, and the coating film becomes hard due to the crosslinking formation by the reaction between the carboxyl group and the crosslinking agent, and the light leakage may be deteriorated. A more preferable range is 0.1 to 2%.

  In (A1), when the content of the component (a4) is less than 1%, the durability performance may be insufficient, and when it is more than 10%, the antistatic performance is insufficient. Preferably it is 5 to 10%.

On the other hand, in the (meth) acrylic polymer (A2), when the content of the component (a1) deviates from the range of 79 to 95.95%, the photoelastic coefficient described later is −300 × 10 ^{−12 to} 0 (m ^2). / N), it is difficult to adjust to the range. A more preferable range of the content of the component (a1) is 85 to 95%.

  In (A2), if the content of component (a2) is less than 0.05%, sufficient cohesive force cannot be obtained and durability is inferior. If it is 1% or more, pot life is shortened and workability is poor. Moreover, there exists a possibility that a coating film may become hard by excess bridge | crosslinking formation, and light leak property may deteriorate. More preferably, it is 0.1 to 0.5%.

  In (A2), if the content of component (a3) is less than 3%, the effect of promoting crosslinking between hydroxyl groups and isocyanate groups cannot be obtained sufficiently, resulting in insufficient cohesive force. Since the pot life is shortened due to the promotion of crosslinking, the workability is deteriorated, and the coating film is hardened by the crosslinking formation by the reaction between the carboxyl group and the crosslinking agent, so that the light leakage may be deteriorated. More preferably, it is 3 to 5%.

  In (A2), when the content of the component (a4) is less than 1%, the durability performance may be insufficient, and when it is more than 10%, the antistatic performance is insufficient. Preferably it is 5 to 10%.

  The component (A) can be produced by polymerizing a mixture of the above monomer components by a conventionally known polymerization method such as a solution polymerization method, a bulk polymerization method, an emulsion polymerization method, a suspension polymerization method or the like. Among these, those produced by a solution polymerization method are preferable in that reaction control is easy and impurities such as an emulsifier are not included.

  The weight average molecular weight (Mw) of the component (A) obtained as described above is 500 to 2,000,000, preferably 800 to 1.6 million. When the weight average molecular weight is less than 500,000, the durability becomes insufficient, while when it is larger than 2 million, production is difficult, and it is necessary to dilute with a large amount of solvent at the time of coating, which is not preferable in the environment. Workability also deteriorates.

  Moreover, it is preferable that the ratio (Mw / Mn; dispersion index) of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of a component (A) is 7-40, and 15-30 are more preferable. In addition, in this specification, a weight average molecular weight (Mw) and a number average molecular weight (Mn) mean the value calculated | required by the measuring method described in the Example.

In this invention, the ionic compound containing a component (B) fluorine-containing anion is used as an antistatic agent. Examples of the ionic compound containing a fluorinated anion include an ionic compound comprising an organic cation and a fluorinated anion, and an ionic compound comprising an alkali metal cation and a fluorinated anion. Fluorine-containing anions include BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (SO ₂ F) ₂ N ⁻ , C ₄ F ₉ SO ₃ ⁻ Etc.

  Examples of the organic cation include a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline ring, a cation having a pyrrole ring, an imidazolium cation, and a tetraalkylammonium cation. Specifically, 1-ethylpyridinium cation, 1-butylpyridinium cation, 1-hexylpyridinium cation, 1-butyl-3-methylpyridinium cation, 1-butyl-4-methylpyridinium cation, 1-hexyl-3 -Pyridinium cations such as methylpyridinium cation and 1-hexyl-4-methylpyridinium cation; 1-propylpiperidinium cation, 1-pentylpiperidinium cation, 1,1-dimethylpiperidinium cation, 1-methyl- 1-ethylpiperidinium cation, 1-methyl-1-propylpiperidinium cation, 1-methyl-1-butylpiperidinium cation, 1-methyl-1-pentylpiperidinium cation, 1-methyl-1- Piper such as hexyl piperidinium cation Lidinium cation; 1,1-dimethylpyrrolidinium cation, 1-ethyl-1-methylpyrrolidinium cation, 1-methyl-1-propylpyrrolidinium cation, 1-methyl-1-butylpyrrolidinium cation, 1-methyl-1-pentylpyrrolidinium cation, 1-methyl-1-hexylpyrrolidinium cation, 1-methyl-1-heptylpyrrolidinium cation, 1-ethyl-1-propylpyrrolidinium cation, 1 -Pyrrolidinium cations such as ethyl-1-butylpyrrolidinium cation, 1-ethyl-1-pentylpyrrolidinium cation, 1-ethyl-1-hexylpyrrolidinium cation; 2-methyl-1-pyrroline cation A cation having a pyrroline ring such as 1-ethyl-2-phenylindole cation Cation having a pyrrole ring such as 1,2-dimethylindole cation, 1-ethylcarbazole cation; 1,3-dimethylimidazolium cation, 1,3-diethylimidazolium cation, 1-ethyl-3-methylimidazolium cation Imidazolium cations such as 1-butyl-3-methylimidazolium cation and 1-hexyl-3-methylimidazolium cation; tetramethylammonium cation, tetraethylammonium cation, tetrabutylammonium cation, tetrahexylammonium cation, triethylmethyl Examples thereof include tetraalkylammonium cations such as ammonium cation, tributylethylammonium cation, and trimethyldecylammonium cation.

  Specific examples of the ionic compound comprising an organic cation and a fluorine-containing anion include 1-butyl-4-methylpyridinium tetrafluoroborate, 1-butyl-4-methylpyridinium hexafluorophosphate, and 1-butyl-3-methylpyridinium bis. (Trifluoromethanesulfonyl) imide; 1-butyl-1-methylpyrrolidinium bis (trifluoromethanesulfonyl) imide, 1-butyl-1-methylpyrrolidinium tetrafluoroborate; 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-2,3-dimethylimidazolium tetrafluoroborate, 1-butyl-2,3-dimethylimidazolium hexafluorophosphate 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-methyl-3-octylimidazolium trifluoromethanesulfonate, 1,2,3-trimethylimidazolium trifluoromethanesulfonate, 1-hexyl-3-methylimidazole Examples include lithium trifluoromethanesulfonate; tetraethylammonium trifluoroacetate, tetrahexylammonium tetrafluoroborate and the like. Of these, 1-butyl-4-methylpyridinium hexafluorophosphate and 1-butyl-2,3-dimethylimidazolium hexafluorophosphate have high stability in component (A) and good antistatic performance. preferable.

On the other hand, examples of the alkali metal cation include K ⁺ , Li ⁺ , and Na ⁺ . Among the ionic compounds composed of alkali metal cations and fluorine-containing anions, LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (SO ₂ F) ₂ N, LiC ₄ F ₉ SO ₃ Lithium salts such as are preferable because they have high stability in the component (A) and good antistatic performance.

  The compounding quantity of the component (B) in the adhesive composition used for this invention is 0.01-10 parts with respect to 100 mass parts (henceforth "part") of a component (A), Preferably 0.1 to 8 parts. If it is less than 0.01 part, sufficient antistatic performance cannot be obtained, and if it is more than 10 parts, durability is lowered by bleeding of the antistatic agent, which is not preferable.

  Component (C) Isocyanate-based cross-linking agent includes two in the molecule such as tolylene diisocyanate, xylylene diisocyanate, chlorophenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, etc. A compound having an isocyanate group of: an isocyanate compound obtained by subjecting them to an addition reaction with a polyhydric alcohol such as trimethylolpropane or pentaerythritol, an isocyanurate compound, a burette type compound, and a known polyether polyol, polyester polyol, acrylic polyol, Urethane prepolymer subjected to addition reaction with polybutadiene polyol, polyisoprene polyol, etc. It can be mentioned types derivatives such as isocyanate compounds. Among these, xylylene diisocyanate and its derivatives are preferably used.

  The compounding quantity of the component (C) in an adhesive composition is 0.1-5 parts with respect to 100 parts of components (A).

  In this invention, crosslinking agents other than the said component (C) can also be used together. Examples of such a crosslinking agent include (D1) an epoxy-based crosslinking agent and (D2) a metal chelate-based crosslinking agent.

  As the component (D1) epoxy crosslinking agent, ethylene diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, di 2 in a molecule such as glycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N′-diamine glycidylaminomethyl) cyclohexane The compound which has the above epoxy groups is mentioned.

  The compounding quantity of (D1) in an adhesive composition is 0.01-5 parts with respect to 100 parts of components (A), Preferably it is 0.1-2 parts. A blending amount within this range is preferable in that the durability can be adjusted to a favorable range.

  Examples of the component (D2) chelate-based crosslinking agent include polyvalent metals such as aluminum, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, zirconium, and acetylacetone, ethyl acetoacetate, and the like. Examples include coordinated compounds. Of these, aluminum triacetyl acetate is preferably used in that it is highly stable against hydrolysis.

  In addition to component (C) isocyanate-based crosslinking agent, (D2) metal chelate-based crosslinking agent is used in combination to further improve the durability and shorten the time required for aging, thus increasing productivity. It becomes possible to reduce the stock quantity.

  The compounding quantity of the component (D2) in an adhesive composition is 0.01-1 part with respect to 100 parts of components (A), Preferably it is 0.1-0.5 part. If the amount is less than 0.01 part, the effect of improving the durability cannot be obtained. If the amount is more than 1 part, the stability over time may be deteriorated. Moreover, it is preferable to mix | blend so that a compounding mass ratio may become 1: 0.5-1: 2 with respect to a component (C). When the blending ratio is within such a range, the durability can be further improved and the aging time can be shortened.

  The pressure-sensitive adhesive composition used in the present invention preferably further contains a component (E) silane coupling agent. By using this, the pressure-sensitive adhesive can be firmly adhered to the glass, and peeling can be prevented in a humid heat environment. Specifically, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4 epoxy cyclohexyl) ethyltrimethoxysilane, etc. And an amino group-containing silane coupling agent such as 3-aminopropyltrimethoxysilane and N-2 (aminoethyl) 3-aminopropyltrimethoxysilane.

The compounding quantity of the silane coupling agent (E) in an adhesive composition is 0.1-5 parts with respect to 100 parts of components (A), Preferably it is 0.1-1 part. If the amount is less than 0.1 part, sufficient adhesion to glass may not be obtained. If the amount is more than 5 parts, the silane coupling agent may bleed and durability may be deteriorated.

  The pressure-sensitive adhesive composition is prepared by blending the above components (A) to (C) with components (D1), (D2) and (E) and other optional components as necessary, and mixing them according to a conventional method. Done. Examples of optional components that can be used include antioxidants, ultraviolet absorbers, plasticizers, tackifying resins, inorganic particles, and organic particles. These can be blended within a range that does not impair the effects of the present invention.

  The pressure-sensitive adhesive composition of the present invention can be obtained by coating the pressure-sensitive adhesive composition thus obtained on at least one surface of the support according to a conventional method, drying and crosslinking. The thickness of the pressure-sensitive adhesive layer to be formed is usually about 5 to 50 μm, preferably about 10 to 30 μm.

The pressure-sensitive adhesive for polarizing plates of the present invention has a photoelastic coefficient of −300 × 10 ^{−12 to} 0 (m ² / N), and further −250 × 10 ^{−12 to} 0 (m ² / N). preferable. If it deviates from the range of −300 × 10 ^{−12 to} 0 (m ² / N), light leakage cannot be sufficiently suppressed. In addition, in this specification, a photoelastic coefficient is a value measured by the method as described in an Example.

In addition, the pressure-sensitive adhesive for polarizing plate of the present invention has high compatibility between the acrylic polymer and the antistatic agent, and does not bleed out even when the antistatic agent is added at a high concentration, so that high antistatic properties can be imparted. For example, the surface resistance value can be adjusted to about 1.0 × 10 ^{7 to} 1.0 × 10 ⁹ Ω / □. The surface resistance value is a value measured by the method described in the examples.

  Furthermore, the polarizing plate with an adhesive of this invention can be obtained by providing the layer which consists of an adhesive for polarizing plates of this invention in the at least one surface of a polarizing plate. The thickness of the pressure-sensitive adhesive layer provided on the polarizing plate is usually 5 to 50 μm, preferably about 10 to 30 μm.

  In providing the pressure-sensitive adhesive layer on the polarizing plate, the pressure-sensitive adhesive composition is applied on the polarizing plate and dried or aged, or the coated and dried coating film is laminated on the polarizing plate, An adhesive layer can be formed by aging this.

  Moreover, as a polarizing plate used for this invention, the layer which has another function may be laminated | stacked, and an elliptically polarizing plate, a phase difference plate, etc. are specifically included.

  The type of the liquid crystal element in which the polarizing plate of the present invention obtained as described above is used is not particularly limited, and any of TN mode, VA mode, IPS mode, OCB mode, and the like may be used.

The pressure-sensitive adhesive for polarizing plate of the present invention has high antistatic performance, effectively prevents the generation of static electricity when the separator is peeled off, and has excellent light leakage prevention and durability, under a high temperature and high humidity environment. However, light leakage does not occur and the occurrence of foaming and peeling can be prevented. The reason is considered as follows.
Alkoxyethyl (meth) acrylate having an ethylene oxide group addition mole number of 1 has a negative value of intrinsic birefringence close to 0, and the monomer is copolymerized at a ratio of 79 to 97.9%. As a result, the photoelastic coefficient of the (meth) acrylic polymer at a measurement wavelength of 600 nm is adjusted to a range of −300 × 10 ^{−12 to} 0 (m ² / N), and light leakage due to contraction of the polarizing plate is suppressed. I can do it.
Furthermore, a (meth) acrylic polymer obtained by copolymerizing a specific amount of alkoxyethyl (meth) acrylate having an ethylene oxide group addition mole number of 1 has an effect of stabilizing an ionic compound, and particularly has an electronegativity. High antistatic performance is exhibited by adding a highly dissociated ionic compound containing a high fluorine anion.
In addition, by using a hydroxyl group-containing monomer and a carboxyl group-containing monomer in combination and crosslinking with a relatively large amount of an isocyanate-based crosslinking agent, a sufficient cohesive force is imparted, and an adhesive having good durability is obtained.

  EXAMPLES Next, although an Example etc. are given and this invention is demonstrated in more detail, this invention is not restrict | limited at all by these Examples.

Manufacturing example 1
Acrylic polymer production:
In a flask equipped with a stirrer, a nitrogen gas inlet tube, a thermometer and a reflux condenser, 7.8 parts of butyl acrylate, 0.2 part of acrylic acid, 2 parts of 2-hydroxyethyl acrylate, 90 parts of 2-methoxyethyl acrylate Then, 120 parts of ethyl acetate was charged, and the contents of the flask were heated to 66 ° C. while introducing nitrogen gas into the flask. Next, azobisisobutyronitrile (AIBN) sufficiently substituted with nitrogen gas was added to the flask under stirring with 0.05 part. Heating and cooling were performed for 3 hours so that the temperature of the contents in the flask could be maintained at 65-66 ° C. 160 parts of ethyl acetate was added dropwise, heated to 75 ° C. and refluxed for 5 hours, and finally 120 parts of ethyl acetate was added to obtain an acrylic polymer A1 solution. About this acrylic polymer A1, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were measured according to the following gel permeation chromatography (GPC) measurement conditions, and the dispersion index (Mw / Mn) was determined. Further, the heating residue (nV) and viscosity at 105 ° C. were also measured by the following method. The measurement results are shown in Table 1 together with the monomer composition.

<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

<Measurement method of 105 ° C. heating residue (nV)>
About 1 g of the acrylic copolymer solution was placed in a precisely weighed tin plate (n1), the total weight (n2) was precisely weighed, and then heated at 105 ° C. for 3 hours. Thereafter, the tin plate was allowed to stand in a desiccator at room temperature for 1 hour, and then precisely weighed again to measure the total weight (n3) after heating. The heating residue (nV) was calculated from the following formula using the obtained weight measurement values (n1 to n3).
Residual heating (%) = 100 × [weight after heating (n3-n1) / weight before heating (n2-n1)]

<Measurement method of viscosity>
Measurement was performed at 23 ° C. using a B-type viscometer.

Manufacturing example 2-4
Except having replaced with the monomer composition shown in Table 1, it carried out similarly to manufacture example 1, and obtained acrylic polymer A2-A4 solution. Mw, Mn, 105 ° C. heating residue (nV) and viscosity of this polymer were measured in the same manner as in Production Example 1. The results are shown in Table 1.

Comparative production example 1-3
Except having replaced with the monomer composition shown in Table 1, it carried out similarly to manufacture example 1, and obtained acrylic polymer B1-B3 solution. Mw, Mn, 105 ° C. heating residue (nV) and viscosity of this polymer were measured in the same manner as in Production Example 1. The results are shown in Table 1.

Example 1
Production of polarizing plate with adhesive:
(Preparation of adhesive composition)
For 100 parts of the acrylic polymer A1 (solid content) in the acrylic polymer A1 solution obtained in Production Example 1, bis (trifluoromethanesulfonyl) imide lithium salt (Li (CF ₃ SO ₂ ) ₂ N as an antistatic agent. ) 2.5 parts, 0.7 parts of TD-75 (manufactured by Soken Chemical Co., Ltd.) which is an xylylene diisocyanate trimethylolpropane adduct as an isocyanate cross-linking agent, and A-50 (manufactured by Soken Chemical Co., Ltd.) as a silane coupling agent .2 parts was added and these were mixed well to obtain a pressure-sensitive adhesive composition.

(Preparation of polarizing plate)
After defoaming, it was applied to a PET separator that had been peeled off using a doctor blade, and immediately dried at 90 ° C. for 3 minutes. After drying, it was bonded to a polarizing plate and allowed to stand for 1 to 7 days under conditions of a room temperature of 23 ° C. and a humidity of 65% to obtain a polarizing plate with an adhesive.

Examples 2-8
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the acrylic polymer, antistatic agent, crosslinking agent and silane coupling agent were changed as shown in Table 2 below. Moreover, the polarizing plate with an adhesive was produced like Example 1 using the obtained adhesive composition.

Comparative Examples 1-7
A pressure-sensitive adhesive composition was obtained in the same manner as in Example 1 except that the acrylic polymer, antistatic agent, crosslinking agent and silane coupling agent were changed as shown in Table 3 below. Moreover, the polarizing plate with an adhesive was produced like Example 1 using the obtained adhesive composition.

Test example 1
About the polarizing plate with an adhesive obtained in Examples 1-8 and Comparative Examples 1-7, the performance was evaluated by the following method. These results are summarized in Tables 2 and 3.

<Heat and humidity resistance test>
The polarizing plate with an adhesive is cut into a size of 310 mm × 385 mm, stuck on one side of a glass plate using a laminator roll, and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes, A test plate was prepared. Two similar test plates were prepared and left for 500 hours under the conditions of 60 ° C. and 95% RH (humidity resistance) and 80 ° C. (heat resistance), respectively. It was visually observed and evaluated.
(Standard)
○: Appearance defects such as peeling were not observed.
Δ: A slight appearance defect such as peeling was observed.
X: Appearance defects such as peeling were clearly observed.

<Shock test>
A polarizing plate with an adhesive is cut into a size of 310 mm × 385 mm, adhered to one side of a glass plate using a laminator roll, and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes. Created. The test plate was allowed to stand for 24 hours under conditions of a temperature of 60 ° C. and a humidity of 95% RH, and then left for 96 hours under a condition of a temperature of 60 ° C., and the occurrence of peeling or foaming was visually confirmed on the following criteria.
(Standard)
A: No appearance defect such as peeling was observed.
○: Appearance defects such as peeling are observed only slightly, but there is no problem.
Δ: A slight appearance defect such as peeling was observed.
X: Appearance defects such as peeling were clearly observed.

<Light leakage test>
Two pressure-sensitive adhesive polarizing plates are cut into 310 mm x 385 mm, stuck on both sides of the glass plate using a laminator roll, and then held in an autoclave adjusted to 50 ° C. and 5 atm for 20 minutes. A test plate was prepared. This test plate was allowed to stand for 500 hours at a temperature of 80 ° C., and light leakage was observed according to the following criteria.
(Standard)
○: No light leakage was observed.
Δ: Slight light leakage was observed.
X: Light leakage was clearly observed.

<Aging days>
The aging days is the number of days until the last measurement time when the gel fraction value is measured every 24 hours and no increase in the gel fraction value is observed from the previous measurement value. The gel fraction was measured by the following method.
(Measurement method of gel fraction)
About 0.1 g of the obtained adhesive is collected in a sample bottle, 30 g of ethyl acetate is added to the sample bottle, and left at room temperature for 24 hours, and then the contents of the sample bottle are filtered through a 200-mesh stainless steel wire mesh. Then, the residue on the wire mesh was dried at 100 ° C. for 2 hours, and the dry weight was measured.
Gel fraction (%) = (Dry weight / Adhesive sampling weight) × 100

<Measurement of surface resistance value>
About the polarizing plate with an adhesive cut | judged to 90 mm x 90 mm, the surface resistance value was measured using R8252 digital electrometer (made by ADC Co., Ltd.).

<Photoelastic coefficient>
The adhesive layer cut to 50 mm × 10 mm × 1 mm (length × width × thickness) was measured for the photoelastic coefficient at a measurement wavelength of 600 nm using an M-220 automatic wavelength scanning ellipsometer (manufactured by JASCO Corporation). .

In Comparative Example 1 in which 15 parts of the antistatic agent bis (trifluoromethanesulfonyl) imide lithium salt was added, the durability was remarkably lowered due to bleeding of the antistatic agent, and no antistatic agent was added. In Comparative Example 2, the surface resistance value is high and antistatic performance cannot be obtained.
In Comparative Example 3 using a (meth) acrylic polymer obtained by copolymerizing 50% of an alkoxyethyl (meth) acrylate having an addition mole number of ethylene oxide group of 1, the value of the photoelastic coefficient is −300 × 10 ^−. It cannot be adjusted to a range of ^{12 to} 0 (m ² / N), and light leakage is poor.
Further, in Comparative Example 4 using ethoxydiethylene glycol acrylate having an addition mole number of ethylene oxide groups of 2, the photoelastic coefficient cannot be adjusted to the above range, so light leakage is poor, and the hygroscopicity of ethylene oxide groups is also low. The durability tends to deteriorate due to its high value.
Furthermore, in Comparative Examples 5 and 6 in which an alkoxyethyl (meth) acrylate having an ethylene oxide group addition mole number of 1 is not copolymerized, the antistatic agent is used as an adhesive layer because of poor compatibility with the antistatic agent. Bleeding at the interface results in poor durability, and the photoelastic coefficient is not in the above range, so light leakage is poor.
In Comparative Example 7 in which an ionic compound containing no fluorine anion is used as an antistatic agent, the compatibility with the (meth) acrylic polymer of the present invention is insufficient, and the ionic compound bleeds, so that the durability is sufficient. Is not obtained.

The polarizing plate pressure-sensitive adhesive of the present invention effectively prevents the generation of static electricity when the separator is peeled off, and has excellent light leakage prevention and durability. Light leakage, foaming, peeling, etc. even under high temperature and high humidity conditions Is not useful and is very useful.
more than

Claims (12)

Next component (A) thru | or (C)
(A) At least the following components (a1) to (a4)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Cyethyl 79-97.9% by mass
(A2) Hydroxyl group-containing monomer 0.05 to 10% by mass
(A3) Carboxyl group-containing monomer 0.1 to 10% by mass
(A4) 1 to 10% by mass of (meth) acrylic acid alkyl ester
(Meth) acrylic polymer having a weight average molecular weight of 500,000 to 2,000,000 (provided that when (a2) is 1% by mass or more, (a3) is less than 3% by mass, and (a2 )
(A3 is 3% by mass or more) 100 parts by mass (B) Ion compound containing fluorine-containing anion 0.01 to 10 parts by mass (C) Isocyanate-based crosslinking agent 0.1 to 5 parts by mass A pressure-sensitive adhesive for a polarizing plate, which is obtained from a pressure-sensitive adhesive composition containing a photoelastic coefficient of −300 × 10 ^{−12 to} 0 (m ² / N) at a measurement wavelength of 600 nm. The following components (A1), (B) and (C)
(A1) At least the following components (a1) to (a4)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Siethyl 80-97.9% by mass
(A2) Hydroxyl group-containing monomer 1 to 10% by mass
(A3) carboxyl group-containing monomer 0.1% by mass or more and less than 3% by mass (a4) (meth) acrylic acid alkyl ester 1 to 10% by mass
(Meth) acrylic polymer having a weight average molecular weight of 500,000 to 2,000,000 100 parts by mass (B) ionic compound containing fluorine-containing anion 0.01 to 10 parts by mass (C) Isocyanate-based crosslinking The polarizing plate according to claim 1, wherein the polarizing plate is obtained from a pressure-sensitive adhesive composition containing 0.1 to 5 parts by mass of an agent, and has a photoelastic coefficient at a measurement wavelength of 600 nm of -300 × 10 ^{-12 to} 0 (m ² / N). Adhesive. Next components (A2), (B) and (C)
(A2) At least the following components (a1) to (a4)
(A1) Alkoxy (meth) acrylate having 1 added mole of ethylene oxide group
Cyethyl 79-95.95 mass%
(A2) Hydroxyl group-containing monomer 0.05 mass% or more and less than 1 mass% (a3) Carboxyl group-containing monomer 3 to 10 mass (a4) (Meth) acrylic acid alkyl ester 1 to 10 mass%
(Meth) acrylic polymer having a weight average molecular weight of 500,000 to 2,000,000 100 parts by mass (B) ionic compound containing fluorine-containing anion 0.01 to 10 parts by mass (C) Isocyanate-based crosslinking The polarizing plate according to claim 1, wherein the polarizing plate is obtained from a pressure-sensitive adhesive composition containing 0.1 to 5 parts by mass of an agent, and has a photoelastic coefficient at a measurement wavelength of 600 nm of -300 × 10 ^{-12 to} 0 (m ² / N). Adhesive.   (B) The adhesive for polarizing plates according to any one of claims 1 to 3, wherein the ionic compound containing a fluorine-containing anion comprises an alkali metal cation and a fluorine-containing anion.   The pressure-sensitive adhesive for polarizing plates according to claim 4, wherein the alkali metal cation is selected from the group consisting of potassium ion, lithium ion and sodium ion. The fluorine-containing anion is BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (SO ₂ F) ₂ N ⁻ and C ₄ F ₉ SO ₃ ^−. The pressure-sensitive adhesive for polarizing plates according to claim 4 or 5, which is selected from the group consisting of:   (B) The adhesive for polarizing plates according to any one of claims 1 to 3, wherein the ionic compound containing a fluorine-containing anion comprises an organic cation and a fluorine-containing anion.   The organic cation is selected from the group consisting of a pyridinium cation, a piperidinium cation, a pyrrolidinium cation, a cation having a pyrroline ring, a cation having a pyrrole ring, an imidazolium cation and a tetraalkylammonium cation. Adhesive for polarizing plate. The fluorine-containing anion is BF ₄ ⁻ , PF ₆ ⁻ , CF ₃ COO ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (SO ₂ F) ₂ N ⁻ and C ₄ F ₉ SO ₃ ^−. The pressure-sensitive adhesive for polarizing plates according to claim 7 or 8, which is selected from the group consisting of:   The pressure-sensitive adhesive composition further comprises 0.01 to 1 part by mass of component (D2) metal chelate-based crosslinking agent with respect to 100 parts by mass of component (A). The adhesive for polarizing plates of description.   Furthermore, the adhesive for polarizing plates in any one of Claim 1 thru | or 10 containing a component (E) silane coupling agent.   The polarizing plate with an adhesive which has the layer which consists of an adhesive in any one of Claims 1 thru | or 11 in the at least one surface of a polarizing plate.