JP4236148B2 - Pressure-sensitive adhesive composition for polarizing film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure-sensitive adhesive composition for a polarizing film for attaching a polarizing film used for a liquid crystal display panel or the like to a glass cell such as a liquid crystal cell, and more specifically, a weight average of 800,000 or more Based on 100 parts by weight of the acrylic copolymer (A) having a molecular weight and a glass transition temperature (Tg) of −45 ° C. or less and containing a carboxyl group in the molecule, the acrylic copolymer (A) Polarizing film feeling comprising 0.001 to 5 parts by weight of a polyfunctional compound (B) having reactivity with components and 0.15 to 1 part by weight of a mercapto group or alicyclic epoxy group-containing silane coupling agent (C) The present invention relates to a pressure-sensitive adhesive composition.
[0002]
[Prior art]
A liquid crystal display panel used in a wide range of fields as a display device is usually composed of a liquid crystal cell in which a liquid crystal component oriented in a predetermined direction is sandwiched between two supporting substrates such as glass, and a supporting substrate of the liquid crystal cell. It is comprised from the polarizing film stuck on the surface using the pressure sensitive adhesive.
[0003]
In recent years, liquid crystal display panels have been used as display devices for personal computers, wall-mounted televisions, car navigation systems, and the like, and thus high pressure transparency is required for the pressure-sensitive adhesive used. In addition, such a liquid crystal display panel is often used under severe conditions such as high temperature and high humidity, and in that case, peeling and bubbles are generated at the interface between the pressure sensitive adhesive layer and the support substrate, and pressure sensitive. There is a problem of the so-called white spot phenomenon, in which light leaks from the peripheral portion of the liquid crystal display panel which occurs because the adhesive layer cannot follow the contraction of the polarizing film and becomes white. The occurrence of such peeling, bubbles, and white spots is caused by insufficient adhesive force, insufficient cohesive force, insufficient flexibility, and the like of the pressure-sensitive adhesive for attaching the polarizing film to the support substrate.
[0004]
Furthermore, in this technical field, when a polarizing film having such a pressure-sensitive adhesive layer is stuck to a liquid crystal cell, if foreign matter is mixed, damaged, or an adhesion error occurs, the polarizing film is peeled off and re-applied. At that time, problems such as ease of operation and partial remaining of pressure-sensitive adhesive on the adherend surface such as glass cell after peeling of the polarizing film, generation of spider (reworkability) ) Exists. Recently, in order to recycle and use expensive liquid crystal cells, peeling of the polarizing film from the used liquid crystal display plate is often performed. Characteristics (recyclability) such as no damage and no contamination of the glass cell surface have been demanded as a new problem to be solved.
[0005]
Various proposals have been made in order to prevent the occurrence of the above-mentioned peeling, bubbles, white spots, etc. For example, JP-A-9-145925 discloses an alkyl (meth) acrylate having 2 to 12 carbon atoms. An alkoxysilyl group-containing thiol compound as a chain transfer agent with respect to 100 parts by weight of a monomer mixture mainly composed of 70 to 99.5% by weight and at least one of 0.3 to 30% by weight of carboxyl group, amide group or hydroxyl group Acrylic copolymer having a weight average molecular weight Mw of 80 to 1,500,000 and a ratio Mw / Mn of Mw to number average molecular weight Mn of 1.5 to 3.5, obtained by copolymerization using 0.001 to 0.1 parts by weight A pressure-sensitive adhesive polarizing plate is disclosed in which a cross-linked acrylic pressure-sensitive adhesive composition containing a combination as a main component is formed on at least one surface of a polarizer.
[0006]
In the above-mentioned proposed adhesive type polarizing plate, the occurrence of peeling, bubbles, white spots, etc. is suppressed to some extent, but this is mainly due to the regulation of the molecular weight of the acrylic copolymer by the alkoxysilyl group-containing thiol compound used as a chain transfer agent. It is thought to be due to action. This is because if the alkoxysilyl group-containing thiol compound is too much, the molecular weight of the acrylic copolymer is lowered and bubbles are likely to be formed (right column [0024] on page 4 of the above-mentioned publication). It is clear from the fact that the effect can be achieved by using a hydroxyl group-containing thiol compound instead of the alkoxysilyl group-containing thiol compound (page 4, right column [0025] of the same publication).
[0007]
The proposed publication does not mention anything such as reworkability and recyclability.
[0008]
Furthermore, when the present inventors further tested the proposed examples, the pressure-sensitive adhesive obtained had a problem in reworkability because its initial adhesive strength was too high, and the glass cell was removed when the polarizing film was peeled off. It was found that the surface was not recyclable due to contamination.
[0009]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a pressure-sensitive adhesive composition for a polarizing film that can sufficiently prevent the occurrence of peeling, bubbles and white spots, and is excellent in reworkability and recyclability. .
[0010]
As a result of intensive studies to solve the above problems, the present inventors have, for example, a weight average molecular weight of 1,200,000 and a glass transition temperature (Tg) of −55 ° C., and acrylic acid is based on all monomers. 1 wt% copolymerized high molecular weight acrylic copolymer, polyisocyanate derived from hexamethylene diisocyanate (HMDI), 1,3-bis (N, N'-diglycidylaminomethyl) cyclohexane Based on 100 parts by weight of the acrylic copolymer, 1.5 parts by weight, 0.005 parts by weight and 0.3 parts by weight of a polyepoxy compound such as γ-mercaptopropyltrimethoxysilane The blended pressure-sensitive adhesive composition for polarizing film is soft and strong in viscoelasticity, and has the above problems as a pressure-sensitive adhesive for polarizing film. As found to be those capable of solving, the present invention has been completed to continue further studies.
[0011]
[Means for Solving the Problems]
Therefore, according to the present invention, the following (A) to (C):
[0012]
(A) Based on 100 parts by weight of an acrylic copolymer having a weight average molecular weight of 800,000 or more and a glass transition temperature (Tg) of −45 ° C. or less and containing a carboxyl group in the molecule,
[0013]
(B) 0.001 to 5 parts by weight of a polyfunctional compound containing two or more functional groups capable of reacting with the acrylic copolymer (A) component to form a crosslinked structure; and
[0014]
(C) 0.15-1 part by weight of a silane coupling agent containing a mercapto group or alicyclic epoxy group,
Is provided as an essential component, and a pressure-sensitive adhesive composition for polarizing film is provided.
[0015]
Hereinafter, the pressure-sensitive adhesive composition for polarizing film of the present invention will be described in detail.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The acrylic copolymer (A) used in the present invention has a repeating unit derived from an acrylate ester and a methacrylate ester as a main component, for example, a total of 50% by weight or more based on the acrylic copolymer (A). And a carboxyl group in the molecule. In addition, the acrylic copolymer (A) may further contain a functional group other than a carboxyl group, for example, a hydroxyl group, in the molecule as necessary.
[0017]
Specifically, the acrylic copolymer (A) that is particularly preferably used in the present invention, as an essential component, the following monomers (a-1) and (a-2),
[0018]
(a-1) The following general formula (1),
H₂C = CHCOOR¹           (1)
[0019]
(Where R¹Represents a linear or branched alkyl group having 4 to 10 carbon atoms)
An acrylic ester whose homopolymer has a glass transition temperature (Tg) of −50 ° C. or lower (hereinafter sometimes referred to as an acrylic ester or simply a monomer (a-1)), and
[0020]
(a-2) copolymerized with a monomer having a carboxyl group in the molecule (hereinafter sometimes referred to as a carboxyl group-containing monomer or simply monomer (a-2)), and if necessary Together with these monomers (a-1) and (a-2), the following monomers (a-3) and / or (a-4),
[0021]
(a-3) A monomer having at least one functional group in addition to one radical-polymerizable unsaturated group in the molecule, the monomer other than the monomer (a-2) [ Hereinafter, functional monomer or simply monomer (a-3)), and / or
[0022]
(a-4) copolymerizable with the above monomers (a-1) to (a-3), and a comonomer other than the monomers (a-1) to (a-3) [hereinafter, It is preferably a copolymer obtained by copolymerizing a monomer or a monomer (a-4).
[0023]
The acrylic ester (a-1) of the general formula (1) has a linear or branched alkyl group having 4 to 10 carbon atoms, and the homopolymer has a glass transition temperature (Tg) of −50 ° C. Specific examples of the acrylate ester are n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, and the like. N-butyl acrylate, 2-ethylhexyl acrylate, and isooctyl acrylate are preferable. These acrylic acid esters may be used alone or in combination of two or more.
[0024]
As used herein, “glass transition temperature (Tg) of homopolymer” refers to the monomer glass described in LE Nielsen, translated by Nojiharu Onoki, “Mechanical Properties of Polymers” on pages 11-35. A transition temperature is applied.
[0025]
The copolymerization amount of the acrylic ester (a-1) is based on a total of 100% by weight of the monomer components (a-1) to (a-4) constituting the acrylic acid copolymer (A). In general, the range is 69.5 to 99.5% by weight, preferably 79.5 to 99.3% by weight, and more preferably 89.5 to 99.1% by weight. If the copolymerization amount of the acrylate ester (a-1) is less than or equal to the upper limit value, it is preferable because the generation of bubbles due to insufficient cohesive force is suppressed, while if the copolymerization amount is greater than or equal to the lower limit value, excessive cohesion force and the like This is preferable because inconveniences such as peeling and white spotting phenomenon hardly occur.
[0026]
Specific examples of the carboxyl group-containing monomer (a-2) include acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride and the like. Among these, acrylic acid and methacrylic acid. Use is preferred. These monomers (a-2) may be used alone or in combination of two or more.
[0027]
The copolymerization amount of these carboxyl group-containing monomers (a-2) is generally 0.5 to 1.5% by weight based on the total 100% by weight of the monomer components (a-1) to (a-4), Preferably it is 0.7 to 1.3% by weight, more preferably 0.7 to 1.1% by weight. If the copolymerization amount of the monomer (a-2) is less than or equal to the upper limit value, it is preferable because inconveniences such as peeling and white spots due to excessive cohesive force are unlikely to occur, and on the other hand, if the copolymerization amount is greater than or equal to the lower limit value, This is preferable because the generation of bubbles due to insufficient cohesion is suppressed.
[0028]
In the present invention, the functional monomer (a-3) used as necessary together with these monomers (a-1) and (a-2), as a functional group, for example, a hydroxyl group, A monomer having an amide group or a substituted amide group, an amino group or a substituted amino group, a lower alkoxyl group, an epoxy group, or the like, and a monomer having two or more radically polymerizable unsaturated groups in the molecule The body can also be used.
[0029]
Specific examples of these functional comonomers include, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate. Hydroxyl group-containing monomers such as (preferably 2-hydroxyethyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate); for example, acrylamide, methacrylamide, diacetone acrylamide, N-methylol acrylamide, N-methylol methacryl Amides, Nn-butoxymethylacrylamide, Ni-butoxymethylacrylamide, N, N-dimethylacrylamide, N-methylacrylamide (preferably acrylamide, methacrylamide) Amide group or a substituted amide group-containing monomers;
[0030]
For example, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-diethylaminoethyl methacrylate (preferably N, N-dimethylaminoethyl methacrylate) Amino group or substituted amino group-containing monomers such as N, N-diethylaminoethyl methacrylate);
[0031]
For example, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-n-butoxyethyl acrylate, 2-methoxyethoxyethyl acrylate, 2-ethoxyethoxyethyl acrylate, 2-n-butoxyethoxyethyl acrylate, 2-methoxyethyl methacrylate 2-ethoxyethyl methacrylate, 2-n-butoxyethyl methacrylate, 2-methoxyethoxyethyl methacrylate, 2-ethoxyethoxyethyl methacrylate, 2-n-butoxyethoxyethyl methacrylate, methoxypolyethylene glycol monoacrylate, methoxypolyethylene glycol monomethacrylate ( Preferably 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2-methoxyethyl methacrylate, 2-ethoxyethyl methacrylate, methoxypolyester Lower alkoxyl group-containing monomers such as ethylene glycol monoacrylate and methoxypolyethylene glycol monomethacrylate);
[0032]
For example, epoxy group-containing monomers such as glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, glycidyl methallyl ether (preferably glycidyl acrylate, glycidyl methacrylate); for example, divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate , Ethylene glycol di (meth) acrylate, 1,2-propylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexane Monomers having two or more radically polymerizable unsaturated groups such as diol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and allyl (meth) acrylate; It can be mentioned monomers group.
[0033]
These functional monomers (a-3) may be used alone or in combination of two or more, but the generation of bubbles due to insufficient cohesive force is suppressed, reworkability From the viewpoint of excellent recyclability and the like, it is preferable to use a hydroxyl group-containing monomer.
[0034]
The copolymerization amount of these functional monomers (a-3) is generally 0 to 1% by weight, preferably based on the total of 100% by weight of the monomer components (a-1) to (a-4). Is in the range of 0.05 to 0.8% by weight, more preferably 0.1 to 0.6% by weight. If the copolymerization amount of the monomer (a-3) is less than or equal to the upper limit value, it is preferable because inconveniences such as peeling and white spot phenomenon due to excessive cohesive force and the like are less likely to occur, while by using more than the lower limit value, This is preferable because the generation of bubbles due to insufficient cohesion is suppressed.
[0035]
In the present invention, the comonomer (a) used together with the monomers (a-1) and (a-2) or with the monomers (a-1) to (a-3) as necessary. Specific examples of -4) include acrylic esters other than the above (a-1), such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, i-butyl acrylate, t-butyl acrylate, Decyl acrylate, stearyl acrylate, oleyl acrylate, etc. (preferably methyl acrylate); methacrylic acid esters such as ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, i-butyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, cyclohexyl methacrylate, benzyl methacrylate, etc. (preferred Ku methyl methacrylate);
[0036]
Saturated fatty acid vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, “vinyl versatate” (trade name), etc. (preferably vinyl acetate); aromatic vinyl monomers such as styrene, α-methylstyrene, And vinyl cyanide monomers such as acrylonitrile and methacrylonitrile (preferably acrylonitrile).
[0037]
Examples of the comonomer (a-4) include dimethyl malate, di-n-butyl malate, di-2-ethylhexyl malate, di-n-octyl malate, dimethyl fumarate, and di-n-butyl. It is also possible to use maleic acid or fumaric acid diesters such as fumarate, di-2-ethylhexyl fumarate, di-n-octyl fumarate.
[0038]
The copolymerization amount of these comonomers (a-4) is generally 0 to 30% by weight, preferably based on the total 100% by weight of the monomer components (a-1) to (a-4). It is good to be in the range of 0 to 25% by weight, more preferably 0 to 20% by weight. If the copolymerization amount of the monomer (a-4) is less than or equal to the upper limit value, it is preferable because inconveniences such as peeling and white spot phenomenon due to excessive cohesive force and the like are less likely to occur, while by using more than the lower limit value, This is preferable because the generation of bubbles due to insufficient cohesion is suppressed.
[0039]
The acrylic copolymer (A) used in the present invention needs to have a weight average molecular weight (Mw) of 800,000 or more, preferably 1 million or more, more preferably 1.1 to 1.5 million. Is good. If the weight average molecular weight (Mw) is too low, being less than the lower limit value, bubbles are generated due to insufficient cohesion, etc., which is not preferable. On the other hand, if it is below this upper limit, it is preferable because an acrylic copolymer having a low branching structure is easily obtained.
[0040]
The ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic copolymer (A) suitably used in the present invention is generally 20 or less, preferably in the range of 5-15. There should be. If the value of Mw / Mn is less than or equal to the upper limit value, it is preferable because inconveniences such as generation of bubbles and a decrease in reworkability due to insufficient cohesive force are unlikely to occur.
[0041]
The weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic copolymer are values measured by the following method.
[0042]
Average molecular weight ( Mw as well as Mn ) Measuring method
Measure according to (1) to (3) below.
(1) An acrylic copolymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The film-like acrylic copolymer obtained in the above (1) is dissolved in tetrahydrofuran so as to have a solid content of 0.2%.
(3) Under the following conditions, the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the acrylic copolymer are measured using gel permeation chromatography (GPC).
[0043]
(conditions)
GPC: HLC-8220 GPC [manufactured by Tosoh Corporation]
Column: Use 4 TSK-GEL GMHXL
Mobile phase solvent: Tetrahydrofuran
Flow rate: 0.6ml / min
Column temperature: 40 ° C
[0044]
The acrylic copolymer (A) used in the present invention is also required to have a glass transition temperature (Tg) of −45 ° C. or lower, preferably −50 ° C. or lower. If the Tg is too high above the temperature, the adhesive strength to the support substrate becomes too high, so that the reworkability is lowered, which is not preferable.
[0045]
In the present invention, the glass transition temperature (Tg) of the acrylic copolymer is a value determined and measured by the following.
[0046]
Glass-transition temperature( Tg )
Measure according to (1) to (3) below.
(1) An acrylic copolymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) About 10 mg of the sample obtained in (1) is weighed in a cylindrical cell made of aluminum foil with a thickness of about 0.05 mm and an inner diameter of about 5 mm and a depth of about 5 mm.
(3) Using a SSC-5000 differential scanning calorimeter manufactured by Seiko Denshi Kogyo Co., Ltd., the temperature is measured from −150 ° C. at a heating rate of 10 ° C./min.
[0047]
Further, the acrylic copolymer (A) used in the present invention is preferably a low branching degree polymer.
[0048]
In general, a polymer has the general formula [η] = KM_r ^aIt is known that it is expressed by [Mark-Houwink formula]. Where [η] is the intrinsic viscosity, M_rIs the molecular weight of the polymer, and K and a are constants depending on the type of polymer and solvent and the temperature. This equation is log [η] = alogM_r+ LogK can be rewritten, and at this time, a is logM_rIs the gradient when plotting with X axis and log [η] as Y axis (gradient of Mark Hoink plot), and logK is the Y-edge.
[0049]
The degree of polymer branching can be determined by the slope (a) of the Mark-Houwink plot, where a polymer with a large value has a low degree of branching structure and a small polymer has a high degree of branching structure. Have. The value of a in the acrylic copolymer (A) used in the present invention is preferably in the range of 0.3 to 1.5, particularly 0.5 to 1.0. By using such a low-branching acrylic copolymer (A), a pressure-sensitive adhesive layer having further excellent viscoelasticity can be obtained. If the gradient is less than or equal to the upper limit, there is no inconvenience such as a decrease in the smoothness of the coated surface after applying the solution of the pressure sensitive adhesive composition, and if the gradient is greater than or equal to the lower limit, This is preferable because an effect of improving durability can be obtained.
[0050]
The Mark Hoink plot is measured by the following method.
[0051]
How to measure the slope of a Mark Hoink plot
Measure according to (1) to (6) below.
(1) An acrylic copolymer solution is applied to release paper and dried at 100 ° C. for 2 minutes to obtain a film-like acrylic copolymer.
(2) The obtained film-like acrylic copolymer is dissolved in tetrahydrofuran so that the solid content is 1% by weight, 2% by weight, 3% by weight, and 4% by weight.
(3) Using a high-sensitivity differential refractometer (DRM-1021, manufactured by Otsuka Electronics Co., Ltd.) at 25 ° C, the ratio of the refractive index change (dn) to the concentration change (dc) ( dn / dc).
(4) The film-like acrylic copolymer obtained in (1) above is dissolved in tetrahydrofuran so that the solid content is 0.2% by weight.
[0052]
(5) The intrinsic viscosity ([η]) and weight average molecular weight (Mw) of the acrylic copolymer were determined using a refraction / differential pressure viscosity detector [T60A, manufactured by Asahi Techneion Co., Ltd.] under the following conditions. taking measurement.
In the measurement, the measured value obtained in (3) above was used as the dn / dc of the acrylic copolymer.
(6) Calculate the slope of the Mark Hoink plot using the following formula.
Mark Hoink plot slope (a) = Log [η] / Log (Mw)
[0053]
The acrylic copolymer (A) used in the present invention is not particularly limited to the polymerization method, and can be polymerized by known methods such as solution polymerization, emulsion polymerization, suspension polymerization, etc., but can be obtained by polymerization. When the pressure-sensitive adhesive composition of the present invention is produced using a mixture of copolymers, the polymerization is preferably performed by solution polymerization since the treatment process is relatively simple and can be performed in a short time.
[0054]
In solution polymerization, a predetermined organic solvent, a monomer, a polymerization initiator, and a chain transfer agent used as needed are generally charged in a polymerization tank, and stirred in a nitrogen stream or at the reflux temperature of the organic solvent. The reaction is performed by heating for several hours. In this case, at least a part of the organic solvent, the monomer, the polymerization initiator and / or the chain transfer agent may be sequentially added.
[0055]
Examples of the organic solvent for polymerization include aromatics such as benzene, toluene, ethylbenzene, n-propylbenzene, t-butylbenzene, o-xylene, m-xylene, p-xylene, tetralin, decalin, and aromatic naphtha. Hydrocarbons; for example, aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, i-octane, n-decane, dipentene, petroleum spirit, petroleum naphtha, turpentine oil; Esters such as ethyl acetate, n-butyl acetate, n-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate; for example, acetone, methyl ethyl ketone, methyl-i- Ketones such as butyl ketone, isophorone, cyclohexanone, methylcyclohexanone;
[0056]
For example, glycol ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether; for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, i And alcohols such as -propyl alcohol, n-butyl alcohol, i-butyl alcohol, s-butyl alcohol, t-butyl alcohol; These organic solvents can be used alone or in admixture of two or more.
[0057]
Of these organic solvents for polymerization, when the acrylic copolymer (A) is polymerized, it is preferable to use an organic solvent that hardly causes chain transfer during the polymerization reaction, for example, esters and ketones. In view of the solubility of the acrylic copolymer (A) and the ease of the polymerization reaction, it is preferable to use ethyl acetate, methyl ethyl ketone, acetone or the like.
[0058]
As said polymerization initiator, it is possible to use the organic peroxide, an azo compound, etc. which can be used by normal solution polymerization.
[0059]
Examples of such organic peroxides include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, and di-i-propyl peroxydicarbonate. , Di-2-ethylhexyl peroxydicarbonate, t-butyl peroxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis (4,4- Di-t-amylperoxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) propane, 2,2-bis (4,4-di-α-cumylperoxycyclohexyl) ) Propane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) butane, 2,2-bis (4,4-di-t-octylperoxycyclohexyl) butane, and the like.
[0060]
Examples of the azo compound include 2,2′-azobis-i-butylnitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 2,2′-azobis-4-methoxy-2,4-dimethyl. Examples include valeronitrile.
[0061]
Among these organic peroxides, when the acrylic copolymer (A) is polymerized, it is preferable to use a polymerization initiator that does not cause a graft reaction during the polymerization reaction, and particularly preferably an azobis type. The amount used is usually 0.01 to 2 parts by weight, preferably 0.1 to 1.0 parts by weight, based on 100 parts by weight of the total amount of monomers.
[0062]
Further, in the production of the acrylic copolymer (A) used in the present invention, it is normal not to use a chain transfer agent, but it is used as necessary as long as the object and effect of the present invention are not impaired. It is possible to do.
[0063]
Examples of such chain transfer agents include cyanoacetic acid; alkyl esters having 1 to 8 carbon atoms of cyanoacetic acid; bromoacetic acid; alkyl esters having 1 to 8 carbon atoms of bromoacetic acid; anthracene, phenanthrene, fluorene, 9 -Aromatic compounds such as phenylfluorene; aromatic nitro compounds such as p-nitroaniline, nitrobenzene, dinitrobenzene, p-nitrobenzoic acid, p-nitrophenol, p-nitrotoluene; benzoquinone, 2,3,5, Benzoquinone derivatives such as 6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane;
[0064]
Halogenated hydrocarbons such as carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloromethane, tribromomethane, 3-chloro-1-propene; Aldehydes such as chloral and furaldehyde: alkyl mercaptans having 1 to 18 carbon atoms; aromatic mercaptans such as thiophenol and toluene mercaptan; mercaptoacetic acids and alkyl esters having 1 to 10 carbon atoms of mercaptoacetic acid; 12 hydroxyalkyl mercaptans; terpenes such as binene and terpinolene;
[0065]
The polymerization temperature is generally in the range of about 30 to 180 ° C, preferably 50 to 150 ° C, more preferably 50 to 90 ° C, and still more preferably 50 to 80 ° C.
[0066]
When an unreacted monomer is contained in a polymer obtained by a solution polymerization method or the like, it can be purified by a reprecipitation method using methanol or the like in order to remove the monomer.
[0067]
The pressure-sensitive adhesive composition for polarizing film of the present invention has, as an essential component, a functional group capable of forming a crosslinked structure by reacting with the acrylic copolymer (A) together with the acrylic copolymer (A). It comprises two or more, preferably 2 to 4 polyfunctional compounds (B).
[0068]
The polyfunctional compound (B) is not particularly limited as long as it reacts with the acrylic copolymer (A) to form a crosslinked structure, and is not limited to polyisocyanate compounds, polyaziridine compounds, poly An epoxy compound, a melamine formaldehyde condensate, a metal salt, a metal chelate compound, and the like can be mentioned. From the viewpoint of adhesion with a polarizing film, stability after blending with an acrylic copolymer (A), etc. Preference is given to using isocyanate compounds (b-1), polyaziridine compounds (b-2) and / or polyepoxy compounds (b-3). These polyfunctional compounds (B) can be used alone or in combination of two or more.
[0069]
The amount of these polyfunctional compounds (B) used is usually in the range of 0.001 to 5 parts by weight, preferably 0.005 to 3 parts by weight, based on 100 parts by weight of the acrylic copolymer (A). If the amount of the polyfunctional compound (B) used is too small and less than the lower limit value, bubbles due to insufficient cohesive force are likely to occur, and the adherend surface contamination is reduced. If the amount is too much, it is not preferable because peeling or white spot phenomenon easily occurs due to excessive cohesion.
[0070]
Examples of the polyisocyanate compound (b-1) that can be suitably used as the polyfunctional compound (B) include aromatics such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate. A polyisocyanate; for example, an aliphatic or alicyclic polyisocyanate such as hexamethylene diisocyanate, isophorone diisocyanate, a hydrogenated product of the aromatic polyisocyanate compound; a dimer or trimer of these polyisocyanates, or a polyisocyanate thereof; Mention may be made of polyisocyanate compounds derived from various polyisocyanates such as adducts with polyols such as trimethylolpropane.
[0071]
Among these polyisocyanate compounds, hexamethylene diisocyanate or xylylene dimer or trimer, or adducts of hexamethylene diisocyanate or xylylene diisocyanate and a polyol such as trimethylolpropane, etc. Polyisocyanate compounds derived from isocyanate are preferred, and trimers of hexamethylene diisocyanate and adducts of xylylene diisocyanate and trimethylolpropane are particularly preferred.
[0072]
These polyisocyanate compounds are, for example, `` Coronate HX '', `` Coronate HL-S '', `` Coronate 2234 '' (manufactured by Nippon Polyurethane Co., Ltd.), `` Desmodur N3400 '' (manufactured by Sumitomo Bayer Urethane Co., Ltd.), `` Duranate E-405-80T, Duranate TSE-100 (Asahi Kasei Kogyo Co., Ltd.), Takenate D-110N, Takenate D-120N, Takenate M-631N (Mitsui Takeda Chemical Co., Ltd. A product commercially available under a trade name such as) can be suitably used.
[0073]
The amount of the polyisocyanate compound (b-1) used is in the range of 0.15 to 3 parts by weight, particularly 0.5 to 2 parts by weight as an active ingredient, based on 100 parts by weight of the acrylic copolymer (A). It is preferable.
[0074]
As the polyaziridine compound (b-2), a reaction product of a polyisocyanate compound and ethyleneimine can be used, and as the polyisocyanate compound, those exemplified above can be used. Also known is a compound obtained by adding ethyleneimine to a polyvalent ester of (meth) acrylic acid or the like with a polyol such as trimethylolpropane or pentaerythritol, and is used as the polyfunctional compound (B) of the present invention. Can do.
[0075]
Examples of such polyaziridine compounds include N, N′-hexamethylenebis (1-aziridinecarboxamide), methylenebis [N- (1-aziridinylcarbonyl) -4-aniline], tetramethylolmethane-tris. (β-aziridinylpropionate), trimethylolpropane-tris (β-aziridinylpropionate) and the like. Among these, for example, “TAZO”, “TAZM” The product commercially available under the trade name such as “Chemite PZ-33” (manufactured by Nippon Shokubai Co., Ltd.) can be suitably used.
[0076]
The amount of these polyaziridine compounds (b-2) used is in the range of 0.001 to 0.1 parts by weight, particularly 0.001 to 0.05 parts by weight, as an active ingredient, based on 100 parts by weight of the acrylic copolymer (A). It is preferable.
[0077]
Examples of the polyepoxy compound (b-3) include ethylene glycol diglycidyl ether, diethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, Neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, polytetramethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, resorcin diglycidyl Ether, 2,2-dibromoneopentyl glycol diglycidyl ether Ter, trimethylolpropane triglycidyl ether, pentaerythritol polyglycidyl ether, sorbitol polyglycidyl ether, adipic acid diglycidyl ester, phthalic acid diglycidyl ester, tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1 , 3-bis (N, N-glycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and the like.
[0078]
Of these polyepoxy compounds, polyepoxy compounds containing three or more epoxy groups are preferred, among which tris (glycidyl) isocyanurate, tris (glycidoxyethyl) isocyanurate, 1,3-bis (N, N More preferred is the use of a polyepoxy compound such as cycloglycidylaminomethyl) cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine, 1,3-bis (N, N-glycidylaminomethyl) The use of cyclohexane, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine is particularly preferred. As such a polyepoxy compound, for example, those commercially available under trade names such as “TETRAD-C” and “TETRAD-X” (manufactured by Mitsubishi Gas Chemical Co., Inc.) can be suitably used.
[0079]
The amount of these polyepoxy compounds (b-3) used is in the range of 0.005 to 0.3 parts by weight, particularly 0.01 to 0.2 parts by weight as an active ingredient, based on 100 parts by weight of the acrylic copolymer (A). Is preferred.
[0080]
In the present invention, the polyfunctional compound (B) can be used in combination of two or more as described above, and the polyisocyanate compound (b-1) and the polyaziridine compound (b-2), or the polyisocyanate compound. It is preferable to combine (b-1) with the polyepoxy compound (b-3). In that case, the polyisocyanate compound (b-1), the polyaziridine compound (b-2), and the polyepoxy compound (b-3) can be appropriately selected within the above-mentioned usage amount ranges, preferably, In any case, the polyisocyanate compound (b-1): polyaziridine compound (b-2) = 1 to 500: 1, particularly 10 to 300: 1 or the polyisocyanate compound (b-1): The polyepoxy compound (b-3) is preferably used in a range of 1 to 300: 1, particularly 10 to 100: 1.
[0081]
The pressure-sensitive adhesive composition for polarizing film of the present invention has, as essential components, 2 functional groups capable of forming a crosslinked structure by reacting with the acrylic copolymer (A) and the acrylic copolymer (A). Along with the polyfunctional compound (B) containing two or more,Contains mercapto groupIt comprises a silane coupling agent (C).
[0082]
The present inventors have examined the influence of the silane coupling agent often used in the pressure-sensitive adhesive composition for polarizing films on the physical properties of the pressure-sensitive adhesive composition, particularly the durability and rework properties. I went. as a result,Mercapto groupIt has been found that silane coupling agents containing can significantly improve their performance compared to other silane coupling agents such as 3-triethoxysilylpropyl succinic acid (anhydride).
[0083]
Examples of the mercapto group-containing silane coupling agent (C) that can be used in the present invention include mercapto such as γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, and γ-mercaptopropyldimethoxymethylsilane. Examples thereof include a group-containing silane compound.
[0084]
The amount of the silane coupling agent (C) used should be 0.15 to 1 part by weight, preferably 0.2 to 0.8 part by weight, based on 100 parts by weight of the acrylic copolymer (A). . When the amount used is less than the lower limit value, it is not preferable because inconvenience such as peeling tends to occur. On the other hand, when it exceeds the upper limit value, it is not preferable because inconvenience such as peeling easily occurs.
[0085]
In the pressure-sensitive adhesive composition of the present invention, the acrylic copolymer (A), polyfunctional compound (B) andContains mercapto groupIn addition to the silane coupling agent (C), if necessary, a formulation usually blended in the pressure-sensitive adhesive composition for polarizing film, for example, a silane coupling agent other than the silane coupling agent (C), weather resistance Stability stabilizers, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers and the like can be appropriately blended.
[0086]
Examples of silane coupling agents that can be used in combination include 3-triethoxysilylpropyl succinic acid (anhydride), 3-trimethoxysilylpropyl succinic acid (anhydride), and 3-methyldimethoxysilylpropyl succinic acid (anhydrous anhydride). Products), carboxyl group-containing silane compounds such as methyldiethoxysilylpropyl succinic acid (anhydride), 1-carboxy-3-triethoxysilylpropyl succinic acid (anhydride); for example, N- (β-aminoethyl) -γ-aminopropylmethyldimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltrimethoxysilane, N- (β-aminoethyl) -γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane , Γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane and other amino group-containing silane systems Compound; for example, hydroxyl group-containing silane compound such as γ-hydroxypropyltrimethoxysilane; amide group-containing silane compound such as γ-amidopropyltrimethoxysilane; for example, γ-isocyanatopropyltrimethoxysilane Examples include isocyanate group-containing silane compounds.
[0087]
The pressure-sensitive adhesive composition for a polarizing film of the present invention has a gel content of 40 to 40 after a crosslinked structure is formed between the acrylic copolymer (A) and the polyfunctional compound (B). It is preferably 80% by weight, particularly 50 to 75% by weight. If the gel content is equal to or higher than the lower limit value, it is preferable because inconveniences such as generation of bubbles can be suppressed, and if the gel content is equal to or lower than the upper limit value, problems such as peeling and white spots are hardly generated. The gel content is measured by the following method.
[0088]
Measurement of gel content of pressure sensitive adhesive composition
Measure according to (1) to (7) below.
(1) A pressure-sensitive adhesive composition solution is applied onto release paper, air-dried at room temperature for 30 minutes, and finally dried at 100 ° C. for 5 minutes to form a film-like pressure-sensitive adhesive layer.
(2) The pressure sensitive adhesive layer is cured for 10 days at 23 ° C and 65% relative humidity.
(3) About 1 g of the film-like pressure-sensitive adhesive layer is applied to a precisely weighed glass rod (diameter 5 mm × 30 mm) and dried in a desiccator for 1 hour. Thereafter, the weight is accurately measured with a precision balance to prepare a sample.
(4) Place the sample obtained in (3) into a cylindrical filter paper (No. 84).
[0089]
(5) About 100 ml of solvent (ethyl acetate) is put into a 200 ml round bottom flask accurately weighed by a Soxhlet extractor, and Soxhlet extraction is performed for 4 hours.
(6) After cooling, the solvent (ethyl acetate) in the round bottom flask is volatilized by a rotary evaporator, and then the round bottom flask containing the above extract is dried at 100 ° C. for 3 hours and in a desiccator for 1 hour. Thereafter, the weight is accurately measured with a precision balance.
(7) Calculate the gel content by the following formula.
Gel content (% by weight) = 100 − [(A−B) / (C−D)] × 100
However, A is the weight (g) of the round bottom flask after extraction, B is the weight (g) of the round bottom flask, C is the weight (g) of the sample, and D is the weight (g) of the glass rod.
[0090]
Further, the pressure-sensitive adhesive composition for polarizing film of the present invention preferably has a logarithmic decay rate of 30 to 100 ° C. of 0.1 to 0.5, particularly 0.15 to 0.4. If the logarithmic decay rate is equal to or higher than the lower limit value, it is preferable because peeling and white spotting can be prevented. It is preferable because inconveniences hardly occur. The logarithmic decay rate is a value measured by the following method.
[0091]
Measurement of logarithmic decay rate of pressure sensitive adhesive composition
Measure according to (1) to (3) below.
(1) A pressure-sensitive adhesive composition solution is applied to a polyester release film and dried at 100 ° C. for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 25 μm.
(2) A polarizing film is pressure-bonded to the pressure-sensitive adhesive layer, cured at 23 ° C. and 65% relative humidity for 10 days, and then cut into a size of 10 mm × 20 mm.
(3) The logarithmic decay rate is measured using a rigid pendulum tester [TEIC RPT-α100, manufactured by A & D Co., Ltd.] under the following conditions.
[0092]
Next, the polarizing film in the present invention will be described.
[0093]
In the polarizing film of the present invention, the pressure-sensitive adhesive layer comprising the above-mentioned pressure-sensitive adhesive composition of the present invention is formed on at least one surface of the polarizing base film. The pressure sensitive adhesive layer for adhering to the surface of a support substrate is comprised similarly to the conventional polarizing film except being formed with the above-mentioned pressure sensitive adhesive composition of this invention. . That is, for example, as shown in FIG. 1, the polarizing film 1 in the present invention comprises a polarizing base film 2 comprising a polarizer 2a and protective layers 2b and 2c laminated on both sides of the polarizer 2a, and the protective layer 2c. The pressure-sensitive adhesive layer 3 is formed on the surface, and the release paper 4 is affixed via the pressure-sensitive adhesive layer 3.
[0094]
The pressure-sensitive adhesive layer 3 has a dry thickness of 10 to 50 μm, particularly preferably 15 to 30 μm.
[0095]
Moreover, in the polarizing film in this invention shown in FIG. 1, although the pressure sensitive adhesive layer 3 and the release paper 4 were provided only in the protective layer 2c side, it was pressure sensitive adhesive to both the protective layer 2b side and the protective layer 2c side. You may provide the agent layer 3 and the release paper 4, respectively. Further, the protective layers 2b and 2c may or may not be provided, and a layer having other functions such as a reflective layer and an antiglare layer may be provided instead of or together with the protective layer.
[0096]
【Example】
EXAMPLES Examples and comparative examples will be described below to specifically describe the effects of the present invention, but the present invention is not limited to these examples. In addition, preparation of a test piece and various test methods and evaluation methods used in Examples and Comparative Examples are as follows.
[0097]
(1) Creating a polarizing film for testing
On a release paper surface-treated with a silicone release agent, the coating amount after drying is 20 g / m.²After applying the pressure-sensitive adhesive composition so as to form a pressure-sensitive adhesive layer by drying with a hot air circulating dryer at 100 ° C. for 90 seconds, a polarizing base film [polyvinyl alcohol (PVA) film A cellulose triacetate (TAC) film laminated on both sides of a polarizer mainly composed of the above; about 190 μm] was bonded to the pressure-sensitive adhesive layer surface and pressed through a pressure nip roll to obtain a polarizing film .
[0098]
(2) Initial adhesion strength measurement and evaluation of adherend surface contamination (reworkability evaluation)
After cutting the polarizing film prepared according to the item (1) into 25 mm × 150 mm, this polarizing film piece is pressure-bonded to a soda glass plate with a thickness of 1.1 mm using a table laminating machine to obtain a test sample. The sample was autoclaved (50 ° C, 5 kg / cm²20 minutes) and left for 24 hours under the conditions of 23 ° C. and 65% RH (conditioning treatment), and then the adhesive strength at 180 ° peeling (peeling speed: 300 mm / min) is measured.
[0099]
Moreover, the state of the glass plate surface after peeling is observed visually and evaluated according to the following criteria.
(Evaluation criteria)
A: Appearance abnormality such as spider cannot be confirmed.
○: A thin spider can be confirmed at the peeling start portion.
Δ: A thin spider can be confirmed on the entire surface.
X: A dark spider can be confirmed on the entire surface.
[0100]
Among the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive composition for polarizing films, those having such a high adhesive force that they cannot be peeled off from the liquid crystal cell (glass cell) are in terms of reworkability. It is not preferable. The adhesive strength measured by the above method is preferably 1200 g / 25 mm or less, particularly 1000 g / 25 mm or less because it has excellent reworkability. In addition, there is a problem in reworkability when adhesive residue or spider is generated on the glass surface after peeling.
[0101]
(3) Adhesion measurement after heat treatment and evaluation of adherend surface contamination (recyclability evaluation)A test sample prepared and autoclaved as in the previous section (2) is left for 1 hour under conditions of 23 ° C and 65% RH, then heat-treated at 70 ° C for 3 hours, After conditioning as in (1), measure the adhesive strength at 180 ° peeling (peeling speed: 300 mm / min).
[0102]
Moreover, the state of the glass plate surface after peeling is observed visually and evaluated according to the following criteria.
(Evaluation criteria)
A: Appearance abnormality such as spider cannot be confirmed.
○: A thin spider can be confirmed at the peeling start portion.
Δ: A thin spider can be confirmed on the entire surface.
X: A dark spider can be confirmed on the entire surface.
[0103]
Among the pressure-sensitive adhesive layers formed from the pressure-sensitive adhesive composition for polarizing films, those having such a high adhesive force that they cannot be peeled off from the liquid crystal cell (glass cell) are recyclable. It is not preferable. An adhesive strength measured by the above method is preferably 1500 g / 25 mm or less, particularly 1000 g / 25 mm or less because of excellent recyclability. Also, there is a problem in recyclability when adhesive residue is left on the glass surface after peeling.
[0104]
(Four) Durability evaluation
A test sample is prepared and autoclaved in the same manner as in the previous section (2) except that a 70 mm x 140 mm (long side) polarizing film piece cut so that the long side is 45 ° to the absorption axis is used. Then, after conditioning the same as in the previous item (2), it is left for 1000 hours under the following temperature and humidity conditions, and the state of bubble formation and peeling is evaluated by visual observation. The evaluation criteria are as follows.
[0105]
a) 100 ℃, dry ( 100 ℃, dry evaluation criteria)
A: Generation of bubbles is not recognized.
○: Generation of bubbles having a diameter of less than 100 μm is slightly observed.
Δ: Many bubbles with a diameter of 100 to 200 μm are observed.
X: Many bubbles with a diameter of 200 μm or more are observed.
[0106]
b) 65 ℃, 95% RH ( 65 ℃, 95 % RH Evaluation criteria)
A: There is no peeling.
○: Peeling within 500 μm.
Δ: Peeling less than 2 mm.
X: Peeling of 2 mm or more.
[0107]
(Five) Evaluation test of white spot phenomenon
In the same manner as in the previous (4), a test sample was prepared by attaching a polarizing film on both surfaces of a soda glass plate so that the polarization axes thereof were orthogonal to each other, and after conditioning treatment as in the previous (4), 90 Leave for 24 hours under dry condition at ℃. Next, using the simple photometric apparatus shown in FIG. 2, the brightness is measured for each point on the surface of the polarizing film shown in FIG. 3 while moving the test sample. The evaluation of white spotting is based on the average value of luminosity at the measurement points (2), (4), (6) and (8), and the measurement points (1), (3), (5), (7) and It is represented by the value divided by the average value of luminance at 9 ▼. At that time, the light intensity of the backlight is adjusted so that the luminance at the measurement point (5) is 0.05 or less, and the luminance is measured.
[0108]
The value measured by the above method is ideally 1.0, but in practice, if the value is 2.5 or less, particularly 2.0 or less, the white spot phenomenon is not substantially observed and there is no problem in use. However, if this value exceeds 2.5, a white spot phenomenon is visually recognized and a problem occurs.
[0109]
Acrylic copolymer (A) Manufacturing of
Production Example 1
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, 99 parts by weight of n-butyl acrylate (BA), 1 part by weight of acrylic acid (AA), 100 parts by weight of ethyl acetate and azobisisobutyrate After adding 0.2 parts by weight of nitrile (AIBN) and replacing the air in the reaction vessel with nitrogen gas, the contents of the reaction vessel were raised to 65 ° C. in a nitrogen atmosphere with stirring and reacted for 6 hours. The mixture was further heated to 70 ° C. and reacted for 2 hours. Thereafter, a solution in which 0.4 part by weight of azobisisobutyronitrile was dissolved in 20 parts by weight of ethyl acetate was added dropwise over 1 hour, and the mixture was further reacted for 2 hours. After completion of the reaction, the reaction mixture was diluted with toluene to obtain an acrylic copolymer solution having a solid content of 20% by weight.
[0110]
The viscosity of the obtained acrylic copolymer solution is 6500 mPa · s, and the acrylic copolymer has a glass transition point (Tg) of about −55 ° C., a weight average molecular weight (Mw) of about 1.2 million, and a weight average. It had a ratio of molecular weight (Mw) to number average molecular weight (Mn) Mw / Mn of about 6.7 and a Mark-Hoink plot slope value (a) of 0.75.
[0111]
Production Examples 2-3
In Production Example 1, the initial reaction temperature of 65 ° C. was changed to 70 ° C., and the amount of initial AIBN added was changed from 0.2 parts by weight to 0.35 parts by weight or 0.25 parts by weight. Each polymer solution was obtained. Viscosity of the resulting acrylic copolymer solution, and glass transition point (Tg), weight average molecular weight (Mw), ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer Mw Table 1 shows the slope value (a) of / Mn and the Mark-Hoink plot.
[0112]
Production Examples 4-8
In Production Example 1, instead of using 99 parts by weight of BA and 1 part by weight of AA as a monomer, an acrylic copolymer solution was prepared in the same manner as in Production Example 1 except that the monomers shown in Table 1 were used. Obtained. Viscosity of the resulting acrylic copolymer solution, and glass transition point (Tg), weight average molecular weight (Mw), ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer Mw Table 1 shows the slope value (a) of / Mn and the Mark-Hoink plot.
[0113]
Production Example 9
An acrylic copolymer solution was produced in the same manner as in Example 1 of JP-A-9-145925. That is, in the same reactor as used in Production Example 1, 94 parts by weight of BA, 6 parts by weight of AA, 100 parts by weight of ethyl acetate and γ-mercaptopropyltrimethoxysilane which is a silane coupling agent (C) (Name: Sila Ace S810; manufactured by Chisso Corporation) (S810) was charged with 0.0097 parts by weight, and nitrogen publishing was performed for 30 minutes to substantially remove dissolved oxygen. Next, the temperature of the contents of the reaction vessel was raised to 60 ° C. in a nitrogen atmosphere with stirring, and 0.03 part by weight of AIBN was added and reacted for 7 hours. After completion of the reaction, the reaction mixture was diluted with toluene to obtain an acrylic copolymer solution having a solid content of 20% by weight. Viscosity of the resulting acrylic copolymer solution, and glass transition point (Tg), weight average molecular weight (Mw), ratio of weight average molecular weight (Mw) and number average molecular weight (Mn) of the copolymer Mw Table 1 shows the slope value (a) of / Mn and the Mark-Hoink plot.
[0114]
In addition, the symbol of the monomer in Table 1 is as follows.
EHA: 2-ethylhexyl acrylate
BA: Butyl acrylate
EA: Ethyl acrylate
MA: Methyl acrylate
MMA: Methyl methacrylate
AA: Acrylic acid
HEA: 2-hydroxyethyl acrylate
[0115]
[Table 1]
[0116]
Manufacture of pressure sensitive adhesive composition for polarizing film
Example 1
As the acrylic copolymer (A), 500 parts by weight of the acrylic copolymer solution of Production Example 1 (about 100 parts by weight as a copolymer) is used, and a polyisocyanate compound (B) is added to the polyisocyanate compound (B). b-1) “Coronate L” (trade name: tolylene diisocyanate / trimethylolpropane adduct; manufactured by Nippon Polyurethane Co., Ltd.) 3.0 parts by weight (approximately 2.25 parts by weight as an active ingredient), and a silane coupling agent ( As C), 0.3 part by weight of γ-mercaptopropyltrimethoxysilane [trade name: Silaace S810; manufactured by Chisso Corporation] (S810) was added and stirred sufficiently to prepare a solution of the pressure-sensitive adhesive composition for polarizing film. Obtained. Using this pressure-sensitive adhesive composition, the logarithmic decay rate and the gel content were measured. Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and its characteristic values, that is, the viscosity of the solution of the composition, the logarithmic decay rate of the pressure-sensitive adhesive layer after crosslinking, and the gel content.
[0117]
Next, the solution of the obtained pressure-sensitive adhesive composition for polarizing film was applied to a polyester release film and then dried. The coating thickness after drying at this time was adjusted to 25 μm. Next, the pressure-sensitive adhesive layer applied on the release film was transferred onto a polarizing base film, and aged for 10 days at a temperature of 23 ° C. and 65% RH to obtain a polarizing film.
[0118]
The obtained polarizing film was evaluated for reworkability, recyclability, durability, and white spot phenomenon according to the test methods described above. The obtained results are shown in Table 3.
[0119]
Example 23And Comparative Examples 1-4
As shown in Table 2, instead of using 3.0 parts by weight of the polyisocyanate compound “Coronate L” as the polyfunctional compound (B) and 0.3 parts by weight of “Silaace S810” as the silane coupling agent (C) in Example 1. In addition, the same procedure as in Example 1 was conducted except that the type and / or amount of the polyfunctional compound (B) was changed and / or the type and / or amount of the silane coupling agent (C) was changed or not used. Thus, a pressure-sensitive adhesive solution for a polarizing film was obtained. Using these pressure-sensitive adhesive compositions, logarithmic decay rate and gel content were measured in the same manner as in Example 1. Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and its characteristic values, that is, the viscosity of the solution of the composition, the logarithmic decay rate of the pressure-sensitive adhesive layer after crosslinking, and the gel content.
[0120]
In addition, using these pressure-sensitive adhesive solutions, polarizing films were obtained in the same manner as in Example 1, and reworkability, recyclability, durability, and white spots were evaluated according to the above test methods. The obtained results are shown in Table 3.
[0121]
Example4-8And Comparative Examples 5-6
In Example 1, as the acrylic copolymer (A), instead of using the acrylic copolymer solution of Production Example 1, Example 1 except that the acrylic copolymer solution of Production Examples 2 to 8 is used. Similarly, a pressure-sensitive adhesive solution for a polarizing film was obtained. Using these pressure-sensitive adhesive compositions, logarithmic decay rate and gel content were measured in the same manner as in Example 1. Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and its characteristic values, that is, the viscosity of the solution of the composition, the logarithmic decay rate of the pressure-sensitive adhesive layer after crosslinking, and the gel content.
[0122]
In addition, using these pressure-sensitive adhesive solutions, polarizing films were obtained in the same manner as in Example 1, and reworkability, recyclability, durability, and white spots were evaluated according to the above test methods. The obtained results are shown in Table 3.
[0123]
Comparative Example 7
In Example 1, instead of using the acrylic copolymer solution of Production Example 1 as the acrylic copolymer (A), the acrylic copolymer solution of Production Example 9 was used, and the polyfunctional compound (B) Instead of using 3.0 parts by weight of “Coronate L” (2.25 parts by weight as an active ingredient), 3.5 parts by weight (about 2.63 parts by weight as an active ingredient) was added, 0.5 parts by weight of tributylamine was further added, and a silane coupling agent ( A solution of a pressure sensitive adhesive for polarizing film was obtained in the same manner as in Example 1 except that C) was not used. Using this pressure-sensitive adhesive composition, logarithmic decay rate and gel content were measured in the same manner as in Example 1. Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and its characteristic values, that is, the viscosity of the solution of the composition, the logarithmic decay rate of the pressure-sensitive adhesive layer after crosslinking, and the gel content.
[0124]
In addition, using these pressure-sensitive adhesive solutions, polarizing films were obtained in the same manner as in Example 1, and reworkability, recyclability, durability, and white spots were evaluated according to the above test methods. The obtained results are shown in Table 3.
[0125]
In addition, the abbreviations of the polyfunctional compound (B) and the silane coupling agent (C) in Table 2 are as follows.
[0126]
TET-C: “TETRAD-C” 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, active ingredient about 100% by weight (manufactured by Mitsubishi Gas Chemical Co., Inc.)
TAZO: “TAZO” tetramethylolmethane-tris (β-aziridinylpropionate), active ingredient about 100% by weight (manufactured by Mutual Pharmaceutical Co., Ltd.)
[0127]
S810: “Syra Ace S810” γ-mercaptopropyltrimethoxysilane, approximately 100% by weight of active ingredient [manufactured by Chisso Corporation]
S510: “Syra Ace S510” γ-glycidoxypropyltrimethoxysilane, active ingredient about 100% by weight [manufactured by Chisso Corporation]
[0128]
[Table 2]
[0129]
[Table 3]
[0130]
【The invention's effect】
The pressure-sensitive adhesive composition for a polarizing film of the present invention has a weight average molecular weight and glass transition temperature (Tg) in a specific range, and is based on an acrylic copolymer (A) containing a carboxyl group in the molecule. A polyfunctional compound (B) having reactivity with the component (A) andContains mercapto groupEach of the silane coupling agents (C) contains a specific amount range.
[0131]
The pressure-sensitive adhesive composition for polarizing film of the present invention having the above-described configuration can sufficiently prevent the occurrence of peeling, foaming and white spotting, and is excellent in reworkability and recyclability. Further, the adherend is not contaminated.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of a polarizing film having a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention.
FIG. 2 is a conceptual diagram of an apparatus used for an evaluation test of a white spot phenomenon.
FIG. 3 is a conceptual diagram showing measurement points in an evaluation test of a white spot phenomenon.
[Explanation of symbols]
1: Polarizing film
2: Polarized base film
2a: Polarizer
2b, 2c: protective layer
3: Pressure sensitive adhesive layer
4: Release paper
5: Simple photometric device
6: Light source
7: Diffuser
8: Luminance meter
9: Glass plate
10: Test sample
11: Shading plate

Claims (13)

The following (A) to (C): (A) 100 parts by weight of an acrylic copolymer having a weight average molecular weight of 800,000 or more and a glass transition temperature (Tg) of −45 ° C. or less and containing a carboxyl group in the molecule. Based on (B) acrylic copolymer (A) 0.001 to 5 parts by weight of a polyfunctional compound containing two or more functional groups capable of reacting with component (A) to form a crosslinked structure, and (C) containing a mercapto group A pressure-sensitive adhesive composition for a polarizing film, comprising 0.15 to 1 part by weight of a silane coupling agent as an essential component. The acrylic copolymer (A) contains a total of 50% by weight or more of repeating units derived from an acrylic ester and a methacrylic ester based on the acrylic copolymer. Pressure-sensitive adhesive composition. Acrylic copolymer (A), the following monomers (a-1) to (a-4),
(a-1) The following general formula (1),
H ₂ C = CHCOOR ¹ (1)
(Wherein R ¹ represents a linear or branched alkyl group having 4 to 10 carbon atoms)
69.5-99.5% by weight of an acrylate ester having a glass transition temperature (Tg) of the homopolymer of not more than −50 ° C.
(a-2) 0.5 to 1.5% by weight of a monomer having a carboxyl group in the molecule,
(a-3) A monomer having at least one functional group in addition to one radical polymerizable unsaturated group in the molecule, and a monomer other than the monomer (a-2) 0 ~ 1% by weight
(a-4) Comonomers other than the monomers (a-1) to (a-3), which can be copolymerized with the monomers (a-1) to (a-3). weight%,
[However, the total of monomers (a-1) to (a-4) is 100% by weight]
The pressure-sensitive adhesive composition according to claim 1, which is obtained by copolymerizing A monomer having at least one functional group in addition to one radical polymerizable unsaturated group in the molecule, wherein the monomer (a-3) other than the monomer (a-2) is The pressure-sensitive adhesive composition according to claim 3, which is a monomer having a hydroxyl group in the molecule. The pressure-sensitive adhesive composition according to claim 1 or 3, wherein the acrylic copolymer (A) is a low branching degree polymer. The pressure-sensitive adhesive composition according to claim 1, 3 or 5, wherein the gradient (a) of the Mark Hoink plot of the acrylic copolymer (A) is in the range of 0.3 to 1.5. The pressure-sensitive adhesive composition according to claim 1, wherein the polyfunctional compound (B) component comprises a polyisocyanate compound (b-1), a polyaziridine compound (b-2) and / or a polyepoxy compound (b-3). object. The pressure-sensitive adhesive composition according to claim 7, wherein the amount of the polyisocyanate compound (b-1) used is in the range of 0.15 to 3 parts by weight as an active ingredient based on 100 parts by weight of the acrylic copolymer. The pressure-sensitive adhesive composition according to claim 7, wherein the amount of the polyaziridine compound (b-2) used is in the range of 0.001 to 0.1 parts by weight as an active ingredient based on 100 parts by weight of the acrylic copolymer. The pressure-sensitive adhesive composition according to claim 7, wherein the polyepoxy compound (b-3) is used in an amount of 0.01 to 0.3 parts by weight as an active ingredient based on 100 parts by weight of the acrylic copolymer. The pressure-sensitive adhesive composition according to claim 7 or 10, wherein the polyepoxy compound (b-3) is a polyepoxy compound containing three or more epoxy groups in the molecule. The pressure sensitive adhesive layer formed from the pressure sensitive adhesive composition has a gel content of 40 to 80% by weight based on the weight after the crosslinked structure is formed. The pressure-sensitive adhesive composition according to item. The pressure-sensitive adhesive composition according to any one of claims 1 to 12, wherein the pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition has a logarithmic decay rate at 30 to 100 ° C of 0.1 to 0.5. .