JP4437632B2 - Pressure-sensitive adhesive composition for optical member surface protective film - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure-sensitive adhesive composition for a protective film used for primary protection of the surface of an optical member such as a liquid crystal display panel. Specifically, the composition contains at least a hydroxyl group as a reactive functional group. Acrylic copolymer (A) in the glass transition temperature (Tg) range, and specific chemical structural formulaThe uretdione structure shown byHavetwoFunctional isocyanate compound (b₁ ) Including two or morePolyisocyanate compoundThe present invention relates to a pressure-sensitive adhesive composition for an optical member surface protective film comprising a polyisocyanate compound (B) as an essential component.
[0002]
[Prior art]
In recent years, liquid crystal display panels have been used as screen display devices for various information-related devices such as word processors and notebook personal computers because they are thin and light and consume less power. In such a liquid crystal display plate, an optical member such as a polarizing plate or a retardation plate is used together with a glass cell (liquid crystal cell) containing liquid crystal as a main body. Among these optical members, for example, a polarizing plate is usually a polarizing element made of a polyvinyl alcohol (PVA) film, and a saponified triacetyl cellulose bonded to both surfaces of the polarizing element to maintain its mechanical strength. (TAC) Consists of a protective layer made of a film, and the surface of the polarizing plate on the front side of the liquid crystal display panel is to protect the polarizing plate from scratches and contamination, and to provide functions according to its use. In many cases, a functional layer is formed. This functional layer has an anti-glare layer that forms fine irregularities on the surface in order to diffuse the reflected image of a fluorescent lamp on the polarizing plate and make the display easy to see; scratch resistance by increasing the surface hardness of the polarizing plate A hard coat layer that imparts a property; an anti-reflection layer that suppresses reflection of external light on the surface of the polarizing plate to make the display easier to see. The polarizing plate is attached to the liquid crystal cell via a pressure sensitive adhesive.
[0003]
These optical members are usually further coated with a surface protective film so that the surface is not contaminated or damaged during each process such as punching, inspection, transportation, and assembly of the liquid crystal display panel. And formed as a long optical member laminate, and after these steps, the surface protective film is peeled off from the optical member when surface protection is no longer necessary. In addition, in the process of assembling the liquid crystal display panel or the like, a heating and pressing process called an autoclave process is often performed for the purpose of stabilizing the adhesion state between the optical member and the liquid crystal cell. In order to release the distortion generated in the autoclave process, an aging process is performed at a certain high temperature such as 90 ° C. for several hours.
[0004]
In such a surface protection film, while the surface protection of the optical member is required, the surface protection film is adhered to the surface to such an extent that the optical member does not shift or fall off from the surface. In addition, it is highly transparent and does not have defects in the adhesive layer such as bulge, tunneling, peeling, and the interface between the adhesive layer and the optical member so as not to hinder various inspections such as liquid crystal performance. Is required. When such a defective portion exists, the surface of the optical member in that portion often has spider or contamination. When the film is peeled from the optical member, the optical member and the liquid crystal cell are not damaged by the distortion caused by the peeling, and the inconvenience such as peeling of the optical member from the liquid crystal cell does not occur. It must be easily peelable.
[0005]
Occurrence of the above-mentioned swelling, tunneling, peeling, etc. is caused by heating in the liquid crystal display panel assembly process, etc. due to gas from the inside of moisture-absorbing and moisture-permeable polarizing plates, surface moisture, etc., or surface protection This is due to shrinkage of the base film, but in the case of a polarizing plate provided with a layer having fine irregularities such as an antiglare layer on the surface, the antiglare layer of the pressure-sensitive adhesive layer of the surface protective film The degree of wetting on the surface becomes a problem. If this wetting is insufficient, the encapsulated air expands due to autoclaving or the like, causing bulge between the antiglare layer of the polarizing plate and the pressure-sensitive adhesive layer of the surface protective film, and the autoclave under pressure. Even if the pressure-sensitive adhesive is so wet that the blisters are not visible in the treatment, the compressed high-temperature air bubbles expand by the release of pressure and heating in the subsequent high-temperature aging treatment. Often appear. Further, swelling, tunneling, peeling, etc. are particularly likely to occur when the adhesive force of the adhesive layer to the optical member is too weak.
[0006]
In addition, when many of the conventional surface protective films have sufficient adhesiveness for protecting the surface of the optical member in the above-described processing steps, the adhesive strength to the optical member is increased over time and peeled off. The adhesive force during the process tends to be too high, the work efficiency for peeling is poor, and the distortion caused by peeling may cause inconveniences such as disordered alignment of the optical member and liquid crystal cell, and even expansion of the cell gap. is there. Especially in the polarizing plate provided with the anti-glare layer and the like, the adhesive force is likely to increase, and in particular, when the wetting is sufficient to prevent the occurrence of bulge by the aging treatment, the adhesive force tends to be too high, Furthermore, the surface protective film is often peeled off manually, and a larger peeling force is generally applied than at a peeling speed used in a normal test such as 300 mm / min.
[0007]
Many proposals have been known in the past to solve one or several of these problems. For example, Japanese Patent Laid-Open No. 9-208910 discloses a pressure-sensitive adhesive composition and a surface protective film using the same that have moderate adhesive strength and excellent removability, and do not cause swelling or tunneling. It is disclosed. The pressure-sensitive adhesive in this proposal is mainly composed of an acrylic acid alkyl ester having 1 to 9 carbon atoms in the alkyl group, a copolymerizable unsaturated monomer containing a hydroxyl group and / or a carboxyl group, and the carbon number of the alkyl group. Is obtained by blending a specific amount of a crosslinking agent such as an isocyanate into an acrylic copolymer obtained by copolymerizing a specific amount of each of 16 to 22 (meth) acrylic acid alkyl esters and reactive emulsifiers.
[0008]
However, with the surface protective film using the above-mentioned pressure-sensitive adhesive, it was possible to suppress the occurrence of swelling and tunneling, but the re-peelability is not always sufficient, especially as an adherend. It has been found that when a polarizing plate having an antiglare layer is used, the peeling force becomes so large that it cannot be practically used.
[0009]
Furthermore, for example, Japanese Patent Laid-Open No. 2001-33624 satisfies the basic performance that it does not peel off from the optical member due to environmental changes such as temperature and humidity, and can be peeled off from the optical member without any adhesive residue at the time of peeling. It is a surface protective film for the purpose of obtaining a surface protective film that can be easily peeled and separated without damage to the optical member or peeling from the liquid crystal cell even after heat treatment such as aging, with a peeling speed of 300 mm / min. In the case of 180 ° peeling, a surface protective film is disclosed in which the adhesive strength at 80 ° C. is within 1.3 times the adhesive strength at normal temperature. Specific examples of the second proposal include a tetrafunctional epoxy crosslinking agent for 100 parts by weight of an acrylic copolymer of 2-ethylhexyl acrylate / vinyl acetate / acrylic acid = 54.1 / 43.2 / 2.7 (% by weight). An acrylic pressure-sensitive adhesive composed of 3 parts by weight is described.
[0010]
However, according to the results of a further test by the present inventors, the above-mentioned pressure-sensitive adhesive of the above-mentioned second proved that the adhesive strength test using a stainless steel plate as an adherend is an adhesive that is allowed to stand at 80 ° C. Although it was within 1.3 times the force, for example, when a polarizing plate having an antiglare layer on the surface was used as an adherend, an aging treatment was performed at 90 ° C. for 2 hours after the autoclave treatment. It has been found that there are problems such as the occurrence of numerous blisters between the surface protective film.
[0011]
[Problems to be solved by the invention]
In order to solve the problems of the conventional pressure-sensitive adhesive composition for a surface protective film for an optical member, the present inventors have conducted an improvement study on an acrylic pressure-sensitive adhesive. As a result, for example, 2-ethylhexyl acrylate was used as a main component, and 4-hydroxybutyl acrylate and acrylic acid were copolymerized therewith. The weight average molecular weight (Mw) was about 600,000, the weight average molecular weight (Mw) and the number average molecular weight (Mn ) And an acrylic copolymer having a molecular weight distribution of Mw / Mn of about 10Uretodione structure represented by a specific chemical structural formulaA bifunctional isocyanate compound (b)₁ ) Including two or morePolyisocyanate compoundIt was found that the acrylic pressure-sensitive adhesive composition obtained by blending the composition is an excellent pressure-sensitive adhesive composition that can solve all of the above-mentioned problems, and further research is completed to complete the present invention. did.
[0012]
[Means for Solving the Problems]
According to the present invention, the following (A) and (B):
(A) an acrylic copolymer containing at least a hydroxyl group as a reactive functional group and having a glass transition temperature (Tg) of −30 ° C. or lower; and
[0013]
(B) The following structural formula (1),
[0014]
[Chemical 2]
(Where R¹Represents an alkylene group having 4 to 8 carbon atoms)
[0015]
The uretdione structure shown byA bifunctional isocyanate compound (b)₁ )A polyisocyanate compound having an isocyanurate structure based on a trimer of HMDI, a polyisocyanate compound having a biuret structure based on HMDI, a polyisocyanate compound comprising an adduct of HMDI and trimethylolpropane, and a prepolymer structure based on HMDI Aliphatic polyisocyanate compounds selected from polyisocyanate compounds having an oxadiazine trione structure based on HMDI (b) ₂ )A pressure-sensitive adhesive composition for an optical member surface protective film, comprising: a polyisocyanate compound as an essential component is provided.
[0016]
The present invention will be described in detail below.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The acrylic copolymer (A) used in the present invention is an acrylic ester or an acrylic ester and a methacrylic ester as a main component, for example, a total of 50 weights based on the weight of the acrylic copolymer (A). % Is copolymerized and contains a hydroxyl group in the molecule. In addition, the acrylic copolymer (A) may further contain a functional group other than a hydroxyl group, for example, a carboxyl group, in the molecule, if necessary.
[0018]
Specifically, the acrylic copolymer (A) that is particularly preferably used in the present invention, as an essential component, the following monomers (a1) and (a2),
[0019]
(a1) The following general formula (2),
H₂C = CHCOOR¹           (2)
(Where R¹Represents a linear or branched alkyl group having 4 to 10 carbon atoms)
An acrylic ester having a glass transition temperature (Tg) of the homopolymer of −50 ° C. or lower (hereinafter sometimes referred to as an acrylic ester (a1) or simply a monomer (a1)), and
[0020]
(a2) copolymerized with a monomer having a hydroxyl group in the molecule (hereinafter sometimes referred to as a hydroxyl group-containing monomer (a2) or simply a monomer (a2)), and if necessary Together with these monomers (a1) and (a2), the following monomers (a3) and / or (a4)
[0021]
(a3) a monomer having a carboxyl group in the molecule (hereinafter sometimes referred to as a carboxyl group-containing monomer (a3) or simply monomer (a3)), and / or
[0022]
(a4) copolymerizable with the above monomers (a1) to (a3), and a comonomer other than the monomers (a1) to (a3) (hereinafter referred to as comonomer (a4) or simply The monomer (sometimes referred to as amer (a4)) is preferably copolymerized.
[0023]
The acrylic ester (a1) of the general formula (2) 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. or lower. Specific examples of the acrylic ester include n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, and isononyl acrylate. Among these, n -Butyl acrylate, 2-ethylhexyl acrylate and isooctyl acrylate are preferred. 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 acid ester (a1) is generally 50 to 99.5 based on the total 100% by weight of the monomer components (a1) to (a4) constituting the acrylic acid copolymer (A). It should be in the range of wt%, preferably 70-99 wt%, more preferably 80-97.9 wt%. If the copolymerization amount of the acrylate ester (a1) is less than or equal to the above upper limit value, the adhesive force at the time of re-peeling will not be excessively increased, especially from the damage of the optical member or the liquid crystal cell even when heat treatment is performed. The surface protective film can be easily peeled off without causing inconvenience such as peeling of the optical member. On the other hand, if it is at least the lower limit value, the surface of the polarizing plate and the surface protective film can be obtained by autoclaving or aging treatment. This is preferable because no swelling occurs between the pressure-sensitive adhesive layer.
[0026]
Specific examples of the hydroxyl group-containing monomer (a2) include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, polyethylene glycol monoacrylate, 2-hydroxyethyl methacrylate. , 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, polyethylene glycol monomethacrylate, allyl alcohol, methallyl alcohol, and the like. From the viewpoint of polymerizability, it is preferable to use a hydroxyl group-containing (meth) acrylic acid ester, and it is particularly preferable to use 4-hydroxybutyl acrylate. These monomers (a2) may be used alone or in combination of two or more.
[0027]
The copolymerization amount of these hydroxyl group-containing monomers (a2) is generally 0.5 to 10% by weight, preferably 1 to 7% by weight, based on the total of 100% by weight of the monomer components (a1) to (a4). %, More preferably in the range of 2 to 5% by weight. If the copolymerization amount of the monomer (a2) is equal to or greater than the lower limit, the adhesive force at the time of re-peeling does not become too large, especially when heat treatment is performed, from damage to the optical member or from the liquid crystal cell. The surface protective film can be easily peeled off without causing inconvenience such as peeling of the optical member. On the other hand, if it is not more than the upper limit value, the surface of the polarizing plate and the surface protective film can be obtained by autoclaving or aging treatment. This is preferable because no swelling occurs between the pressure-sensitive adhesive layer.
[0028]
Specific examples of the carboxyl group-containing monomer (a3) used together with these monomers (a1) and (a2) in the present invention include acrylic acid, methacrylic acid, itaconic acid, maleic acid. , Fumaric acid, crotonic acid, citraconic acid, maleic anhydride, and the like, may include α, β-unsaturated mono- or dicarboxylic acids having 3 to 5 carbon atoms. Among these, acrylic acid and methacrylic acid Use is preferred. These monomers (a3) may be used alone or in combination of two or more.
[0029]
The copolymerization amount of these carboxyl group-containing monomers (a3) is generally 0 to 5% by weight, preferably 0.1 to 3% by weight, based on the total of 100% by weight of the monomer components (a1) to (a4). %, More preferably in the range of 0.1 to 2% by weight. If the copolymerization amount of the monomer (a3) is less than or equal to the upper limit, it is preferable because the pot life of the pressure-sensitive adhesive composition after blending the polyisocyanate compound is sufficient to withstand use, while the If it is above the lower limit value, the adhesive force at the time of re-peeling will not become too large, and in particular, even when heat treatment etc. are performed, there will be no inconvenience such as damage to the optical member or peeling of the optical member from the liquid crystal cell It is preferable because the surface protective film can be easily peeled off.
[0030]
In the present invention, specific examples of the comonomer (a4) used together with the monomers (a1) and (a2) or with the monomers (a1) to (a3) as necessary include the above-mentioned Acrylic esters other than (a1), such as methyl acrylate, ethyl acrylate, n-propyl acrylate, i-propyl acrylate, i-butyl acrylate, t-butyl acrylate, tridecyl acrylate, stearyl acrylate, oleyl acrylate, etc. (preferably 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. Preferably Methyl methacrylate); 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 -Methyl styrene, vinyl toluene and the like; and vinyl cyanide monomers such as acrylonitrile, methacrylonitrile and the like.
[0031]
Examples of the comonomer (a4) include dimethyl malate, di-n-butyl malate, di-2-ethylhexyl malate, di-n-octyl malate, dimethyl fumarate, and di-n-butyl fumarate. , Diesters of maleic acid or fumaric acid such as di-2-ethylhexyl fumarate and di-n-octyl fumarate can also be used.
[0032]
Further, the comonomer (a4) is a monomer having at least one functional group in addition to one radical polymerizable unsaturated group in the molecule, if necessary, Monomers other than (a2) and (a3) (hereinafter sometimes referred to as functional comonomers) can also be copolymerized.
[0033]
Examples of such a functional comonomer include 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 as a functional group, A monomer having two or more radically polymerizable unsaturated groups in the molecule can also be used.
[0034]
Specific examples of these functional comonomers include acrylamide, methacrylamide, diacetone acrylamide, N-methylol acrylamide, N-methylol methacrylamide, Nn-butoxymethyl acrylamide, Ni-butoxymethyl acrylamide, N, N-dimethyl. Amide group or substituted amide group-containing monomers such as acrylamide and N-methylacrylamide (preferably acrylamide and methacrylamide); for example, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, Amino group-containing or substituted amino group-containing monomers such as N, N-dimethylaminoethyl methacrylate and N, N-diethylaminoethyl methacrylate;
[0035]
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, etc. Lower alkoxyl group-containing monomers; for example, glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, glycidyl methallyl ether Epoxy group-containing monomers;
[0036]
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, 2,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, etc. A monomer group such as a monomer having one or more radically polymerizable unsaturated groups;
[0037]
The copolymerization amount of these comonomers (a4) is generally 0 to 49.5 wt%, preferably 0 to 30 wt%, based on the total 100 wt% of the monomer components (a1) to (a4). More preferably, it is in the range of 0 to 20% by weight. If the copolymerization amount of the monomer (a4) is less than or equal to the upper limit value, there will be no swelling between the polarizing plate surface and the pressure-sensitive adhesive layer of the surface protective film even by autoclaving or aging treatment. preferable.
[0038]
The acrylic copolymer used in the present invention is also required to have a glass transition temperature (Tg) of −30 ° C. or lower, preferably −40 ° C. or lower, more preferably −50 ° C. or lower. Is good. If the Tg is too high above the temperature, the pressure-sensitive adhesive layer is hard and difficult to flow, especially when used for a polarizing plate having an anti-glare layer on the surface, the pressure-sensitive adhesive has sufficient anti-glare layer unevenness. Therefore, the air remaining slightly between the pressure-sensitive adhesive layer and the anti-glare layer is expanded by autoclaving or aging treatment, and the pressure-sensitive adhesive layer of the polarizing plate surface and the surface protective film This is not preferable because a bulge may occur between the two.
[0039]
In the present invention, the glass transition temperature (Tg) of the acrylic copolymer is a value determined and measured by the following.
[0040]
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 1 minute 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.
[0041]
The acrylic copolymer used in the present invention has a weight average molecular weight (Mw) of generally 300,000 or more, preferably 350,000 or more, and more preferably 400,000 to 800,000. If the weight average molecular weight (Mw) is equal to or greater than the lower limit value, the adhesive force during re-peeling does not become excessively large. This is preferable because the surface protective film can be easily peeled without causing inconvenience such as peeling. On the other hand, if it is less than or equal to the upper limit value, the resulting pressure-sensitive adhesive layer has excellent fluidity, and even when used in a polarizing plate having minute irregularities on the surface, the pressure-sensitive adhesive sufficiently covers the polarizing plate surface. Since it can be wetted, it is preferable that no swelling occurs between the polarizing plate surface and the pressure-sensitive adhesive layer of the surface protective film even by autoclaving or aging.
[0042]
The acrylic copolymer suitably used in the present invention generally has a molecular weight distribution represented by a ratio Mw / Mn of weight average molecular weight (Mw) and number average molecular weight (Mn) of generally 15 or less, preferably 2 to 2. It should be in the range of 12. If the value of Mw / Mn is less than or equal to the above upper limit value, the adhesive force at the time of re-peeling will not be too great, especially damage to the optical member or peeling of the optical member from the liquid crystal cell even if heat treatment etc. This is preferable because the surface protective film can be easily peeled off without causing the above disadvantages.
[0043]
In addition, the value measured by the gel permeation chromatography (GPC) method according to a usual method is used for the value of the said weight average molecular weight (Mw) and number average molecular weight (Mn) in this specification.
[0044]
The polymerization method of the acrylic copolymer (A) used in the present invention is not particularly limited and can be polymerized by a known method such as solution polymerization, emulsion polymerization, suspension polymerization, etc., but obtained by polymerization. In producing the pressure-sensitive adhesive composition of the present invention using a copolymer mixture, it is preferable to perform polymerization by solution polymerization since the treatment process is relatively simple and can be performed in a short time.
[0045]
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 and / or the polymerization initiator may be sequentially added.
[0046]
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; for example, ethylene glycol monomethyl ester Glycol ethers such as ter, 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-propyl alcohol, n -Alcohols such as butyl alcohol, i-butyl alcohol, s-butyl alcohol and t-butyl alcohol; These organic solvents can be used alone or in admixture of two or more.
[0047]
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.
[0048]
As said polymerization initiator, it is possible to use the organic peroxide, an azo compound, etc. which can be used by normal solution polymerization.
[0049]
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, etc. As a compound For example, 2,2'-azobis-i-butyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, etc. Can do.
[0050]
Among these organic peroxides, when the acrylic copolymer (A) is polymerized, a polymerization initiator that does not cause a graft reaction during the polymerization reaction is preferable, and an azobis type is particularly preferable. 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.
[0051]
Further, in the production of the acrylic copolymer (A) used in the present invention, it is normal not to use a chain transfer agent, as long as it does not impair the purpose and effect of the present invention. It is possible to use.
[0052]
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; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromotrichloro Halogenated hydrocarbons such as methane, tribromomethane, 3-chloro-1-propene; chloral, Aldehydes such as furaldehyde: alkyl mercaptans having 1 to 18 carbon atoms; aromatic mercaptans such as thiophenol and toluene mercaptan; mercaptoacetic acid, alkyl esters having 1 to 10 carbon atoms of mercaptoacetic acid; And hydroxyalkyl mercaptans; terpenes such as vinylene and terpinolene; and the like.
[0053]
The polymerization temperature is generally in the range of about 30 to 180 ° C, preferably 40 to 150 ° C, more preferably 50 to 90 ° C.
[0054]
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.
[0055]
The pressure-sensitive adhesive composition for an optical member surface protective film of the present invention, as an essential component, together with the acrylic copolymer (A) described above, the following structural formula (1),
[0056]
[Chemical Formula 3]
(Where R¹Represents an alkylene group having 4 to 8 carbon atoms)
[0057]
The uretdione structure shown byA bifunctional isocyanate compound (b)₁ )A polyisocyanate compound having an isocyanurate structure based on a trimer of HMDI, a polyisocyanate compound having a biuret structure based on HMDI, a polyisocyanate compound comprising an adduct of HMDI and trimethylolpropane, and a prepolymer structure based on HMDI Aliphatic polyisocyanate compounds selected from polyisocyanate compounds having an oxadiazine trione structure based on HMDI (b) ₂ 2 or more types of polyisocyanate compoundsThe polyisocyanate compound (B) is contained as an essential component.
[0058]
The present inventors are the most important property of the pressure-sensitive adhesive composition for optical member surface protective film, and the removability from an optical member such as a polarizing plate, in particular heat such as autoclave treatment and high-temperature aging treatment together with the optical member. Research has been conducted on the improvement of removability after receiving a history. As a result, it is represented by the above structural formula (1).Bifunctional isocyanate compounds having uretdione structure2 or more types includingPolyisocyanate compoundIt has been found that the removability can be remarkably improved by using.
[0059]
It has a uretdione structure represented by the structural formula (1) that can be used in the present invention.Bifunctional isocyanate compound (b ₁ )Examples thereof include a polyisocyanate compound based on a hexamethylene diisocyanate (HMDI) dimer, and this compound is sold as, for example, “Desmodur N3400” (manufactured by Sumika Bayer Urethane Co., Ltd.). .
[0060]
In the present invention, it is represented by the structural formula (1).Bifunctional isocyanate compound (b ₁ )Used with,Polyisocyanate compound having isocyanurate structure based on HMDI trimer, polyisocyanate compound having biuret structure based on HMDI, polyisocyanate compound comprising adduct of HMDI and trimethylolpropane, prepolymer structure based on HMDI Aliphatic polyisocyanate compounds selected from polyisocyanate compounds and polyisocyanate compounds having an oxadiazine trione structure based on HMDI (b ₂ )As those having an isocyanurate structure based on a trimer of HMDI, for example, “Coronate HX”, “Coronate HK”, “Coronate 2096”, “Coronate 2230”, “Coronate 2092” [above Nippon Polyurethane Co., Ltd. Made, Takenate D-170N, Takenate D-170HN, Takenate D-172N, Takenate D-175HN, Takenate D-177N (Takeda Pharmaceutical Co., Ltd.), Duranate TPA-100, Duranate THA-100, Duranate TSA-100 (manufactured by Asahi Kasei Kogyo Co., Ltd.), Sumijour N3390EA, Sumijoule N3300 (manufactured by Sumika Bayer Urethane Co., Ltd.) ; Having a biuret structure based on HMDI, for example, "Takenate D-165N90PX" (manufactured by Takeda Pharmaceutical Co., Ltd.), "Duranate 24A-100", "Duranate 22A-75PX" (manufactured by Asahi Kasei Kogyo Co., Ltd.) , "Death Module N100" , "Desmodule N75", "Desmodule N3200" (manufactured by Sumika Bayer Urethane Co., Ltd.); adducts of HMDI and trimethylolpropane (TMP), such as "Coronate HL", "Coronate 2094", " "Coronate HL-S" (manufactured by Nippon Polyurethane Co., Ltd.), "Takenate D-160N" (manufactured by Takeda Pharmaceutical Co., Ltd.), "Duranate P301-75E" (manufactured by Asahi Kasei Kogyo Co., Ltd.), "Sumijoule HT [Made by Sumika Bayer Urethane Co., Ltd.]; having a prepolymer structure based on HMDI, for example, “Desmodule TPLS2010 / 1”, “Desmodule E-3265” (manufactured by Sumika Bayer Urethane Co., Ltd.) A bifunctional and / or trifunctional polyisocyanate compound having an oxadiazine trione structure based on HMDI, for example, “Takenate D-190N” (manufactured by Takeda Pharmaceutical Co., Ltd.);
[0061]
Use amount of these polyisocyanate compounds (B) [Bifunctional isocyanate compound(b ₁ )as well asAliphatic polyisocyanate compound(b ₂ ) Is generally in the range of 0.1 to 6 equivalents, preferably 0.3 to 4 and particularly preferably 0.5 to 2 with respect to 1 equivalent of the reactive functional group in the acrylic copolymer (A). Good. If the amount used is greater than or equal to the lower limit value, the adhesive force during re-peeling does not become excessively large, and inconveniences such as damage to the optical member and peeling of the optical member from the liquid crystal cell even when heat treatment is performed. It is preferable because the surface protective film can be easily peeled off without causing slag, and if it is less than or equal to the upper limit value, the surface of the polarizing plate and the pressure-sensitive adhesive layer of the surface protective film can be obtained by autoclaving or aging treatment. It is preferable because no blisters are generated between them.
[0062]
In addition, the bifunctional isocyanate compound (b₁) And aliphatic polyisocyanate compounds (b)₂) Equivalent ratio (b₁/ b₂) Is generally in the range of 0.01 to 10, preferably 0.05 to 5, particularly preferably 0.1 to 3. If the amount ratio is less than or equal to the upper limit value, the adhesive force at the time of re-peeling will not be excessive, and inconveniences such as damage to the optical member and peeling of the optical member from the liquid crystal cell even if heat treatment is performed. It is preferable because the surface protective film can be easily peeled off without causing odor, and on the other hand, if it is at least the lower limit value, the surface of the polarizing plate and the pressure-sensitive adhesive layer of the surface protective film can be obtained by autoclave treatment or aging treatment. It is preferable because no blisters are generated between them.
[0063]
In addition to the acrylic copolymer (A) and the polyisocyanate compound (B) described above, the pressure-sensitive adhesive composition for an optical member surface protective film of the present invention, if necessary, a pressure-sensitive adhesive for a protective film. For example, a weather resistance stabilizer, a tackifier, a plasticizer, a softening agent, a dye, a pigment, an inorganic filler, and the like can be appropriately blended in the adhesive composition.
[0064]
The pressure-sensitive adhesive composition for an optical member surface protective film of the present invention thus obtained is prepared on at least one surface of an appropriate transparent surface protective base film by a conventionally known method in order to produce an optical member surface protective film. Used to form a pressure sensitive adhesive layer.
[0065]
The surface protective base film is not particularly limited, but from the viewpoint of inspection and management of optical members through fluoroscopy, for example, polyester-based resin, acetate-based resin, polyethersulfone-based resin, polycarbonate-based resin, Examples thereof include films made of polyamide resin, polyimide resin, polyolefin resin, acrylic resin, and the like. Although the thickness of the base film is also not particularly limited, a thickness of generally about 500 μm or less, preferably 5 to 300 μm, more preferably about 10 to 200 μm can be exemplified. An antistatic layer may be provided on one side or both sides of these base films for the purpose of preventing charging during peeling. Further, the surface of the base film on the side where the pressure-sensitive adhesive layer is provided may be subjected to corona discharge treatment or the like in order to improve the adhesion with the pressure-sensitive adhesive layer.
[0066]
The thickness of the pressure-sensitive adhesive layer to be formed can be appropriately set according to the required adhesive strength of the protective film, the surface roughness of the optical member, etc., and generally 1 to 500 μm, preferably 5 to 200 μm, more preferably Can be exemplified by a thickness of about 10-100 μm.
[0067]
As a method for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition of the present invention is used as it is or diluted with an appropriate solvent as necessary, and this is directly applied to a surface protective base film and dried to obtain a solvent. It is possible to adopt a method of removing In addition, first, the pressure-sensitive adhesive composition of the present invention is applied on a release sheet made of an appropriate film such as paper or polyester film that has been subjected to a release treatment with a silicone resin or the like, and then heat-dried for pressure-sensitive adhesion. An adhesive layer may be formed, and then the adhesive layer side of the release sheet may be pressed against a surface protective base film to transfer the adhesive layer to the protective film.
[0068]
The protective film thus obtained is laminated on the surface of the optical member to protect the surface of the optical member from being contaminated or damaged, and when the optical member is processed into a liquid crystal display panel or the like, While the protective film is laminated on the optical member, it is used in various processes such as punching, inspection, transportation, and assembly of the liquid crystal display panel. If necessary, heat and pressure such as autoclaving and high-temperature aging When the surface treatment is no longer necessary, the optical member is peeled off and removed.
[0069]
Next, the surface protective film and the optical member in which it is used in the present invention will be described.
[0070]
In general, the optical member in which the surface protective film in the present invention is used includes a polarizing plate and a retardation plate.
[0071]
As a specific example of the polarizing plate, the main component of the polarizer is usually a hydrophilic polymer such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or an ethylene / vinyl acetate copolymer partially saponified film. It is formed by a polyene oriented film such as a film obtained by adsorbing iodine and / or a dichroic dye to the film and stretched, a polyvinyl alcohol dehydrated product, a polyvinyl chloride dehydrochlorinated product, etc. For example, a transparent protective layer similar to that used for the surface protective base film may be provided on one or both surfaces of the polarizer. Although the thickness of a transparent protective layer is not specifically limited, Generally it is 500 micrometers or less, Preferably it is 5-300 micrometers, More preferably, the thickness of about 10-200 micrometers can be illustrated.
[0072]
In addition, the surface on the viewing side of the transparent protective layer contains, as necessary, transparent fine particles of about 0.5 to 20 μm in order to impart light diffusibility, antiglare properties, etc. Further, the surface on the viewing side of the transparent protective layer may be roughened by buffing or the like. Furthermore, an anti-glare layer having a fine concavo-convex structure on the surface or having a roughened surface may be further laminated on the surface on the viewing side of the transparent protective layer.
[0073]
Specific examples of the retardation plate include a birefringent film obtained by stretching a film of polyolefin such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, and polypropylene, polyarylate, and polyamide, and an alignment film of a liquid crystal polymer. Can be mentioned.
[0074]
The retardation plate has an appropriate retardation according to the purpose of use, such as various wavelength plates such as 1/2, 1/4, etc., and those for the purpose of compensation such as coloring or vision due to birefringence of the liquid crystal layer. It may be a thing, and the inclination orientation film which controlled the refractive index of the thickness direction may be sufficient. Moreover, what laminated | stacked 2 or more types of phase difference plates may be used.
[0075]
In the surface protective film of the present invention, the pressure-sensitive adhesive layer comprising the pressure-sensitive adhesive composition of the present invention is formed on the surface of the surface protective base film that is in contact with the optical member (opposite to the viewing side). Conventional surface protection except that the pressure-sensitive adhesive layer for adhering the surface protective film to the surface of the optical member is formed of the pressure-sensitive adhesive composition of the present invention described above. It is comprised similarly to a film. That is, for example, as shown in FIG. 1, the surface protective film 1 in the present invention is composed of a surface protective base film 2 and a pressure-sensitive adhesive layer 3 formed on the surface of the base film.
[0076]
The pressure-sensitive adhesive layer 3 has a dry thickness of 10 to 50 μm, particularly preferably 15 to 30 μm.
[0077]
The surface protective film is affixed to the optical member 4 by the pressure-sensitive adhesive layer 3, and the optical member 4 is bonded to a glass cell (not shown) such as a liquid crystal cell by the pressure-sensitive adhesive layer 5. Before being applied, the surface of the pressure-sensitive adhesive layer 5 is usually protected by the release paper 6.
[0078]
【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.
[0079]
(1) Creation of pressure-sensitive adhesive sheet for testing
On a release paper surface-treated with a silicone release agent, the coating amount after drying is 25 g / m.²The pressure-sensitive adhesive composition was applied so that the pressure-sensitive adhesive layer was formed by drying with a hot air circulation dryer at 100 ° C. for 60 seconds, and then a polyethylene terephthalate (PET) film [trade name; E5001; manufactured by Toyobo Co., Ltd.] so that the pressure-sensitive adhesive layer surface is in contact with each other, pressed through a pressure nip roll and bonded together, and then cured at 23 ° C. and 65% RH for 10 days. A test surface protective film was obtained.
[0080]
(2) Measurement of initial adhesive strength
After cutting the test surface protective film prepared in the above (1) to 25 mm x 150 mm, this surface protective film piece was antiglare-treated with a desktop laminator [trade name; SQ-1852AP- AG6; manufactured by Sumitomo Chemical Co., Ltd.] (AG) and a polarizing film without anti-glare treatment [trade name; SQ-1852AP-HC; manufactured by Sumitomo Chemical Co., Ltd.] (HC) were used as test samples. This sample was allowed to stand for 24 hours under conditions of 23 ° C. and 65% RH (conditioning treatment), and then the adhesive force at 180 ° peeling (peeling speed: 300 mm / min) was measured.
[0081]
The initial adhesive strength of the surface protective film to both polarizing films is preferably, for example, 0.3 N / 25 mm or less, further 0.25 N / 25 mm or less, and particularly 0.1 to 0.2 N / 25 mm.
[0082]
(3) Measurement of adhesive force change over time and observation of surface condition of polarizing film after peeling
The test sample prepared in the same manner as in the previous (2) was heat-treated at 40 ° C for 1 week, then left at 23 ° C and 65% RH for about 1 hour, and then the adhesive strength at 180 ° peeling (peeling) Speed: 300 mm / min).
[0083]
The adhesive strength of the surface protective film after the heat history to both polarizing films is, for example, 0.3 N or less, more preferably 0.25 N / 25 mm or less, and particularly preferably 0.1 to 0.2 N / 25 mm.
[0084]
Moreover, the state of the polarizing film surface after peeling was observed visually and evaluated according to the following reference | standard.
[0085]
(Evaluation criteria)
○: Contamination and adhesive residue are not seen on the peeled surface.
X: Contamination or adhesive residue is observed on the peeled surface.
[0086]
(Four) Autoclave suitability evaluation
After cutting the test surface protective film prepared in the previous item (1) into 60 mm × 80 mm, the surface protective film piece was pressure-bonded to the same two kinds of polarizing films in the same manner as in the previous item (2). Next, using a commercially available pressure-sensitive adhesive composition [Nissetsu Q-1851: manufactured by Nippon Carbide Industries Co., Ltd.], a pressure-sensitive adhesive having a thickness of about 25 μm on the release paper in the same manner as in the previous item (1). After forming a layer and transferring this pressure-sensitive adhesive layer to the back surface of each polarizing film, these were pressure-bonded to a glass plate having a thickness of about 2 mm using a table laminating machine to prepare a test sample. This sample was allowed to stand for 1 week at 23 ° C. and 65% RH, and then autoclaved (70 ° C., 490 kPa). , 30 minutes), and the occurrence of bubbles and peeling of the pressure-sensitive adhesive layer of the surface protective film were evaluated by visual observation from the surface of the test sample on the surface protective film side. The evaluation criteria are as follows.
[0087]
(Evaluation criteria)
A: Generation of bubbles is not recognized at all.
○: Air bubbles are slightly observed in the test sample (width of about 5 mm).
Δ: Many bubbles are observed in the test sample (width of about 5 mm).
X: A small amount of bubbles is observed on the entire surface of the test sample.
XX: A large amount of bubble generation or tunneling is observed on the entire surface of the test sample.
[0088]
(Five) Evaluation of heat resistance
After autoclaving the test sample prepared in the same manner as in the previous (4), heat treatment was further performed at 90 ° C. for 2 hours, and the surface protection film was visually observed from the surface of the test sample on the surface protection film side. The pressure adhesive layer was evaluated for bubble generation and peeling. The evaluation criteria are as follows.
[0089]
(Evaluation criteria)
A: Generation of bubbles is not recognized at all.
○: Air bubbles are slightly observed in the test sample (width of about 5 mm).
Δ: Many bubbles are observed in the test sample (width of about 5 mm).
X: A small amount of bubbles is observed on the entire surface of the test sample.
XX: A large amount of bubble generation or tunneling is observed on the entire surface of the test sample.
[0090]
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, 32.5 parts by weight of ethyl acetate was placed, and in another container, 96.5% of 2-ethylhexyl acrylate (EHA) as the monomer (a1). Part, 4-hydroxybutyl acrylate (HBA) 3.0 parts by weight as monomer (a2) and acrylic acid (AA) 0.5 parts by weight as monomer (a3) are mixed to form a monomer mixture. 25 parts by weight was added to the reaction vessel, and then the air in the reaction vessel was replaced with nitrogen gas. Then, 0.015 part by weight of 1,1′-azobis-1-cyclohexanecarbonitrile (ACHN) was added as a polymerization initiator. The initial reaction was started by raising the temperature of the mixture in the reaction vessel to 80 ° C. in a nitrogen atmosphere with stirring. After the completion of the initial reaction, the remaining monomer mixture (75 parts by weight) and ethyl acetate (25 parts by weight) and ACHN (0.2 part by weight) were respectively added to the reaction mixture at reflux for about 1.5 hours. Reacted for hours. Thereafter, a solution in which 0.25 parts by weight of azobisisobutyronitrile (AIBN) was dissolved in 25 parts by weight of toluene was added dropwise over 1 hour, and the mixture was further reacted for 1.5 hours. After completion of the reaction, the reaction mixture was diluted with 57.5 parts by weight of toluene and 37.5 parts by weight of t-butyl alcohol to obtain an acrylic copolymer solution having a solid content of 35.4% by weight.
[0091]
The viscosity of the obtained acrylic copolymer solution is 760 mPa · s, and the acrylic copolymer has a glass transition temperature (Tg) of about −75 ° C., a weight average molecular weight (Mw) of about 530,000 and a weight average molecular weight. The ratio of (Mw) to number average molecular weight (Mn) was about 9.8 Mw / Mn.
[0092]
Production Examples 2 to 4
In Production Example 1, instead of using 96.5 parts by weight of EHA as the monomer (a1), as shown in Table 1, the monomer (a4) was used together with the monomer (a1), and the monomer (a1) ) And / or the monomer (a4) and / or the amount used, and the glass transition temperature (Tg) was changed to obtain an acrylic copolymer solution in the same manner as in Production Example 1. Table 1 shows the viscosity, solid content, Tg, Mw and Mw / Mn of the resulting acrylic copolymer solution.
[0093]
Production Examples 5-6
In Production Example 1, an acrylic copolymer having a different Mw and / or Mw / Mn is used in the same manner as in Production Example 1 except that the amount of the polymerization initiator used is changed and the addition timing of the solvent is changed as necessary. A solution was obtained. Table 1 shows the viscosity, solid content, Tg, Mw and Mw / Mn of the resulting acrylic copolymer solution.
[0094]
Production Examples 7-10
In Production Example 1, as shown in Table 1, instead of using 3.0 parts by weight of HBA as the monomer (a2), the amount used is changed, or this is not used, or the type of the monomer (a2) is changed. An acrylic copolymer solution was obtained in the same manner as in Production Example 1 except that the amount of the EHA used as the monomer (a1) was changed as necessary. Table 1 shows the viscosity, solid content, Tg, Mw and Mw / Mn of the resulting acrylic copolymer solution.
[0095]
Production Examples 11-12
In Production Example 1, as shown in Table 1, instead of using 0.5 part by weight of AA as the monomer (a3), the amount of the monomer (a1) can be changed as necessary, or the amount used can be changed or not used. An acrylic copolymer solution was obtained in the same manner as in Production Example 1 except that the amount of EHA used was changed. Table 1 shows the viscosity, solid content, Tg, Mw and Mw / Mn of the resulting acrylic copolymer solution.
[0096]
Production Example 13
In Production Example 1, instead of using 96.5 parts by weight of EHA as the monomer (a1), 3.0 parts by weight of HBA as the monomer (a2) and 0.5 parts by weight of AA as the monomer (a3), the monomer (a1 ) 54.1 parts by weight of EHA, 2.7 parts by weight of AA as monomer (a3) and 43.2 parts by weight of vinyl acetate (VAc) as monomer (a4), without using monomer (a2), and further acetic acid An acrylic copolymer solution was obtained in the same manner as in Production Example 1 except that toluene was used instead of ethyl. Table 1 shows the viscosity, solid content, Tg, Mw and Mw / Mn of the resulting acrylic copolymer solution.
[0097]
Production Example 14
In the same reactor as used in Production Example 1, 44.0 parts by weight of EHA and 43.0 parts by weight of BA as monomer (a1), 5.0 parts by weight of HEA as monomer (a2), and stearyl acrylate as monomer (a4) (StA) 5.0 parts by weight and reactive surfactant “Adekaria soap SE-10N” [1-allyl-2-nonylphenyl-3-polyoxyethylene (n = 10) sulfate ammonium salt; Asahi Denka Co., Ltd. [Production] 3.0 parts by weight, 150 parts by weight of ethyl acetate and 0.2 parts by weight of azobisisobutyronitrile (AIBN) were charged, and a polymerization reaction was carried out at 68 ° C. for 8 hours in a nitrogen gas stream. After completion of the reaction, the reaction mixture was diluted with 35.5 parts by weight of t-butyl alcohol to obtain an acrylic copolymer solution. Table 1 shows the viscosity, solid content, Tg, Mw and Mw / Mn of the resulting acrylic copolymer solution.
[0098]
In addition, the symbol of the monomer in Table 1 is as follows.
EHA: 2-ethylhexyl acrylate
BA: Butyl acrylate
MA: Methyl acrylate
StA: Stearyl acrylate
MMA: Methyl methacrylate
VAc: Vinyl acetate
AA: Acrylic acid
HBA: 4-hydroxybutyl acrylate
HEA: 2-hydroxyethyl acrylate
Surf *: Reactive surfactant “Adekaria Soap SE-10N” 1-allyl-2-nonylphenyl-3-polyoxyethylene (n = 10) sulfate ammonium salt (Asahi Denka Co., Ltd.)
[0099]
[Table 1]
[0100]
Preparation of pressure-sensitive adhesive composition for surface protective film
Example 1
As the acrylic copolymer (A), 284 parts by weight of the acrylic copolymer solution of Production Example 1 (about 100 parts by weight as a copolymer; 0.02083 equivalent part of hydroxyl group + 0.00694 equivalent part of carboxyl group: where "equivalent part Is the value equivalent to “equivalent” when “parts by weight” is read as “g”).Polyisocyanate compound (B)As a bifunctional isocyanate compound (b₁) [Product name: Death module N3400; HMDI uretdione type, active ingredient 100% by weight, isocyanate (NCO) content 21.8% by weight; manufactured by Sumika Bayer Urethane Co., Ltd.] (N3400) 1.41 parts by weight (NCO
0.00732 equivalent parts) and an aliphatic polyisocyanate compound (b₂) [Product name: Sumidur N3300; HMDI trimmer type, active ingredient 100% by weight, NCO content 21.8% by weight; manufactured by Sumika Bayer Urethane Co., Ltd.] (N3300) 4.24 parts by weight (NCO
0.0220 equivalent part) was added and stirred well to obtain a solution of the pressure-sensitive adhesive composition for optical member surface protective film. The obtained pressure-sensitive adhesive composition has a solid content of about 36.7% by weight and a viscosity of 780 mPa · s. The polyisocyanate is used with respect to 1 equivalent of the reactive functional group of the acrylic copolymer (A).Compound(B) [(b₁) + (b₂)] Containing about 1.06 equivalents of a bifunctional isocyanate compound (b₁) And aliphatic polyisocyanate compounds (b)₂) Equivalent ratio ((b₁) / (b₂)] Was about 0.333.
[0101]
Using this pressure-sensitive adhesive composition, a test surface protective film was prepared according to the above-described method for preparing a test pressure-sensitive adhesive sheet, and the above-described various physical property tests were conducted. The obtained results are shown in Table 3.
[0102]
Examples 2-6 and Comparative Examples 1-2
In Example 1, the bifunctional isocyanate compound (b₁) And aliphatic polyisocyanate compounds (b)₂) Is used as shown in Table 2, or these polyisocyanate compounds (b)₁) And (b₂The solution of the pressure sensitive adhesive composition for optical member surface protection films was obtained like Example 1 except not using any one of these. Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and the characteristic values such as solid content and viscosity thereof.
[0103]
Using this pressure-sensitive adhesive composition, a test surface protective film was prepared according to the above-described method for preparing a test pressure-sensitive adhesive sheet, and the above-described various physical property tests were conducted. The obtained results are shown in Table 3.
[0104]
Examples 7-8
In Example 1, an aliphatic polyisocyanate compound (b₂) Instead of using 4.24 parts by weight of [N3300] [NCO 0.0220 equivalents] [DURANATE 24A-100] [HMDI biuret type, active ingredient 100% by weight, NCO content 23.5% by weight; manufactured by Asahi Kasei Kogyo Co., Ltd. ] (24A100) 3.93 parts by weight (NCO 0.0220 equivalent part) or "Desmodur TPLS2010 / 1" [HMDI prepolymer type, active ingredient 100% by weight, NCO content 10.9% by weight; manufactured by Sumika Bayer Urethane Co., Ltd.] A solution of the pressure-sensitive adhesive composition for an optical member surface protective film was obtained in the same manner as in Example 1 except that 8.48 parts by weight (2010/1) (NCO 0.0220 equivalent parts) was used. Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and the characteristic values such as solid content and viscosity thereof.
[0105]
Using this pressure-sensitive adhesive composition, a test surface protective film was prepared according to the above-described method for preparing a test pressure-sensitive adhesive sheet, and the above-described various physical property tests were conducted. The obtained results are shown in Table 3.
[0106]
Examples 9-17 and Comparative Examples 3-4
In Example 1, instead of using the acrylic copolymer solution of Production Example 1 as the acrylic copolymer (A), the acrylic copolymer solution of any of Production Examples 2 to 12 was used, and Production Example 8 was used. Is used, the amount of the polyisocyanate compound (B) used is changed to 4.0 equivalents per 1 equivalent of the functional group of the acrylic copolymer (A), and when the production example 9 is used, the acrylic copolymer is used. Except for changing the amount of polyisocyanate compound (B) used to 0.5 equivalent to 1 equivalent of the functional group of (A), other production examples are equivalent to the functional group of the acrylic copolymer (A). Without changing the equivalent of the polyisocyanate compound (B) to the difunctional isocyanate compound (b₁) And aliphatic polyisocyanate compounds (b)₂) Equivalent ratio ((b₁) / (b₂)] Was changed in the same manner as in Example 1 except that the amount of these polyisocyanate compounds was changed so that a solution of the pressure-sensitive adhesive composition for optical member surface protective film was obtained.
Table 2 shows the blended composition of the obtained pressure-sensitive adhesive composition and the characteristic values such as solid content and viscosity thereof.
[0107]
Using this pressure-sensitive adhesive composition, a test surface protective film was prepared according to the above-described method for preparing a test pressure-sensitive adhesive sheet, and the above-described various physical property tests were conducted. However, for the pressure-sensitive adhesive sheet for test of Example 16 using Production Example 11, instead of performing curing for 10 days at 23 ° C. and 65% RH in the method for producing the pressure-sensitive adhesive sheet for test, 35 Curing was performed at 65 ° C. and 65% RH for 20 days. The obtained results are shown in Table 3.
[0108]
The abbreviations of the polyisocyanate compound (B) in Table 2 and other polyfunctional compounds used for comparison are as follows.
N3400: "Death module N3400" HMDI uretdione type polyisocyanate,
100% active ingredient, 21.8% NCO content (manufactured by Sumika Bayer Urethane Co., Ltd.)
N3300: “Sumijour N3300” HMDI trimer type polyisocyanate, active ingredient 100% by weight, NCO content 21.8% by weight (manufactured by Sumika Bayer Urethane Co., Ltd.)
24A100: “Duranate 24A-100” HMDI biuret type polyisocyanate,
Active ingredient 100% by weight, NCO content 23.5% by weight (manufactured by Asahi Kasei Kogyo Co., Ltd.)
2010/1: "Desmodule TPLS2010 / 1" HMDI prepolymer type polyisocyanate, active ingredient 100% by weight, NCO content 10.9% by weight (manufactured by Sumika Bayer Urethane Co., Ltd.)
C-L: “Coronate L” tolylene diisocyanate / trimethylolpropane adduct, 75% by weight of active ingredient, NCO content of 13.2% by weight (manufactured by Nippon Polyurethane Co., Ltd.)
TET-C: “TETRAD-C” 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane, active ingredient 100% by weight, epoxy equivalent 100 (Mitsubishi Gas Chemical Co., Ltd.)
[0109]
[Table 2]
[0110]
[Table 3]
[0111]
【The invention's effect】
The pressure-sensitive adhesive composition for an optical member surface protective film of the present invention comprises at least a hydroxyl group as a reactive functional group, an acrylic copolymer (A) in a specific glass transition temperature (Tg) range, and a specific Chemical structural formulaThe uretdione structure shown byHavetwoFunctional isocyanate compound (b₁)
A polyisocyanate compound having an isocyanurate structure based on a trimer of HMDI, a polyisocyanate compound having a biuret structure based on HMDI, a polyisocyanate compound comprising an adduct of HMDI and trimethylolpropane, and a prepolymer structure based on HMDI Aliphatic polyisocyanate compounds selected from polyisocyanate compounds having an oxadiazine trione structure based on HMDI (b) ₂ 2 or more types of polyisocyanate compoundsThe polyisocyanate compound (B) is contained as an essential component.
[0112]
By being configured in this manner, the surface protective film of the present invention has the surface protection and high transparency of the optical member, which are essential properties, and a layer having fine irregularities such as an antiglare layer on the surface. Even when used for an optical member such as a polarizing plate provided, even after passing through a heat history in autoclave treatment and subsequent work and use, occurrence of adhesive layer defects such as swelling, tunneling, peeling, etc. is not seen, Further, even when the film is peeled off from such an optical member, it is easy to cause inconveniences such as disorder of the alignment of the optical member and the liquid crystal cell, expansion of the cell gap, and peeling of the optical member from the liquid crystal cell. Can be peeled off.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an example of a polarizing film protected by a surface protective film having a pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive composition of the present invention.
[Explanation of symbols]
1: Surface protective film
2: Surface protection base film
3: Pressure sensitive adhesive layer
4: Optical member
5: Pressure sensitive adhesive layer
6: Release material

Claims (9)

Below (A) and (B):
(A) an acrylic copolymer containing at least a hydroxyl group as a reactive functional group and having a glass transition temperature (Tg) of −30 ° C. or lower; and
(B) The following structural formula (1),
(Wherein R1 represents an alkylene group having 4 to 8 carbon atoms) and a bifunctional isocyanate compound (b ₁ ) having a uretdione structure ,
Polyisocyanate compound having isocyanurate structure based on HMDI trimer, polyisocyanate compound having biuret structure based on HMDI, polyisocyanate compound consisting of adduct of HMDI and trimethylolpropane, prepolymer structure based on HMDI It comprises two or more polyisocyanate compounds consisting of a polyisocyanate compound and an aliphatic polyisocyanate compound (b ₂ ) selected from polyisocyanate compounds having an oxadiazinetrione structure based on HMDI, as essential components. and,
The content of the polyisocyanate compound (B) is in the range of 0.1 to 6 equivalents with respect to 1 equivalent of the reactive functional group in the acrylic copolymer (A),
The equivalent ratio (b ₁ / b ₂ ) between the difunctional isocyanate compound (b ₁ ) and the aliphatic polyisocyanate compound (b ₂ ) of the polyisocyanate compound (B ) is in the range of 0.01 to 10.
Pressure-sensitive adhesive composition for optical member surface protective film. The acrylic copolymer (A) is obtained by copolymerizing acrylic acid ester or acrylic acid ester and methacrylic acid ester in total of 50% by weight or more based on the weight of the acrylic copolymer (A). The pressure-sensitive adhesive composition according to claim 1. The weight average molecular weight (Mw) of the acrylic copolymer (A) is 300,000 or more, and the molecular weight distribution represented by the ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) is 15 or less. The pressure-sensitive adhesive composition according to claim 1. The pressure-sensitive adhesive composition according to claim 1, wherein the acrylic copolymer (A) further contains a carboxyl group. Acrylic copolymer (A), the following monomers (a1) to (a4),
(a1) The following general formula (2),
H ₂ C = CHCOOR ¹
(2)
(Wherein R ¹ represents a linear or branched alkyl group having 4 to 10 carbon atoms), and its homopolymer has a glass transition temperature (Tg) of −50 ° C. or lower. ~ 99.5% by weight,
(a2) Monomer having a hydroxyl group in the molecule
0.5-10% by weight,
(a3) 0 to 5% by weight of a monomer having a carboxyl group in the molecule,
(a4) copolymerizable with the monomers (a1) to (a3), and 0 to 49.5% by weight of a comonomer other than the monomers (a1) to (a3),
The pressure-sensitive adhesive composition according to claim 1, wherein the pressure-sensitive adhesive composition is obtained by copolymerizing [wherein the total of the monomers (a1) to (a4) is 100% by weight]. The pressure-sensitive adhesive composition according to claim 5, wherein the monomer (a2) containing a hydroxyl group is a hydroxyl group-containing (meth) acrylic ester. The pressure-sensitive adhesive composition according to claim 6, wherein the hydroxyl group-containing acrylic acid ester is 4-hydroxybutyl acrylate. The pressure-sensitive adhesive composition according to claim 5, wherein the monomer (a3) containing a carboxyl group is an α, β-unsaturated mono- or di-carboxylic acid having 3 to 5 carbon atoms. The aliphatic polyisocyanate compound (b ₂ ) other than the difunctional isocyanate compound (b ₁ ) in the polyisocyanate compound (B) is one or more difunctional and / or trifunctional polyisocyanate compounds. The pressure-sensitive adhesive composition described in 1.