JP2009091406A - Pressure-sensitive adhesive composition and surface protection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure-sensitive adhesive composition which does not transfer and attach a part of broken pressure sensitive adhesive layer on an optical member which is a material to be bonded, on peeling a surface protective film even if the part of the pressure sensitive adhesive layer is broken by having a large external stress on the surface of the surface protection film, requires a small peeling force on a high speed peeling in a large surface area, and does not cause zipping and is excellent in bonding power on low speed peeling, and an optical member surface-protecting film. <P>SOLUTION: This pressure sensitive adhesive composition is characterized by containing (A) an acrylic copolymer containing at least 0.1 to 10 wt.% hydroxy group-containing monomer as a copolymerizing component and having -76 to -50°C glass transition point (Tg), and (B) 0.01 pt.wt. to 2.0 pts.wt. polyoxyalkylene-modified dimethylsilicon compound based on 100 pts.wt. (A) the acrylic copolymer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pressure-sensitive adhesive composition and a surface protective film using the same, and more specifically, a pressure-sensitive adhesive for a surface protective film used for primary protection on the surface of an optical member such as a liquid crystal display panel. The present invention relates to a composition and a surface protective film using the composition.

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 tri-layer bonded to both surfaces of the polarizing element in order to maintain its mechanical strength. It is composed of a protective layer made of acetyl cellulose (TAC) film, and the surface on the front side of the liquid crystal display panel of the polarizing plate protects the polarizing plate from scratches and contamination, and further functions according to its use. In many cases, a functional layer is formed in order to impart the.

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. The surface protection film is peeled and removed from the optical member when the surface protection is no longer necessary. Furthermore, in the process of assembling the liquid crystal display panel, a heat and pressure treatment called autoclave treatment may be 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 process, an aging process is performed at a high temperature such as 90 ° C. for several hours.

Such a surface protective film has a pot life sufficient for coating work, and while the surface protection of the optical member is required, the surface of the member is displaced or dropped from the surface. Adhering to the surface to such an extent that it does not interfere with various inspections such as the performance of the liquid crystal, it must be highly transparent and within the adhesive layer such as bulge, tunneling, peeling, etc. It is required that the interface between the agent layer and the optical member is free from defects. When peeling the film from the optical member, in order not to damage the optical member or the liquid crystal cell due to the distortion caused by the peeling, and so as not to cause inconvenience such as the optical member peeling from the liquid crystal cell, It must be easily peelable.
In recent years, the speed of peeling of the surface protective film tends to be increased for the purpose of improving working efficiency, and workability in high-speed peeling has been required as a characteristic of the adhesive.

Many of the conventional surface protective films are peeled off by increasing the adhesive force to the optical member over time when the above-mentioned processing steps have sufficient adhesiveness for protecting the surface of the optical member. There is a tendency that the adhesive force at the time becomes too high. For this reason, when the separation is performed at a particularly high speed, the working efficiency is poor, and in addition, the distortion associated with the separation may cause inconveniences such as disorder of the alignment of the optical member and the liquid crystal cell and expansion of the cell gap. In particular, the polarizing plate provided with the anti-glare layer or the like tends to increase the adhesive force. In particular, the adhesive force tends to be too high when wetting is sufficient to prevent the occurrence of blistering even by an aging treatment. Furthermore, if the peeling of the surface protective film is mechanized and speeded up, a larger peeling force is applied than at the conventional peeling speed.

In order to solve these problems, many proposals have been known. For example, Patent Document 1 (Japanese Patent Application Laid-Open No. 9-208910) describes a copolymerizable alkyl ester having an alkyl group having 1 to 9 carbon atoms as a main component and containing a hydroxyl group and / or a carboxyl group. A cross-linking agent such as isocyanate based on an unsaturated copolymer, an acrylic copolymer obtained by copolymerizing a specific amount of a (meth) acrylic acid alkyl ester having 16 to 22 carbon atoms in the alkyl group and a reactive emulsifier. Discloses a pressure-sensitive adhesive composition comprising a specific amount and a surface protective film using the same.

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.

For example, in Patent Document 2 (Japanese Patent Laid-Open No. 2001-33624), there is basically no separation from an optical member due to environmental changes such as temperature and humidity, and separation and separation from the optical member without any adhesive residue at the time of separation. A surface protective film intended to obtain 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 while satisfying the performance, A surface protective film is disclosed in which the adhesive strength when left at 80 ° C. is within 1.3 times the adhesive strength when left at room temperature at 180 ° peeling at a peeling speed of 300 mm / min.

However, the adhesive of the second proposal has an adhesive strength test using a stainless steel plate as an adherend, and the adhesive strength after standing at 80 ° C. is within 1.3 times the adhesive strength when left at room temperature. For example, when a polarizing plate having an antiglare layer on the surface is used as the adherend, an aging treatment is performed at 90 ° C. for 2 hours after the autoclave treatment. It turned out that there was a problem such as.

The inventors of the present invention have made researches on improving acrylic pressure-sensitive adhesives, and in Japanese Patent Application Laid-Open No. 2003-41229, Japanese Patent Application Laid-Open No. 2005-97451, etc. A pressure sensitive adhesive composition for film is proposed.

The composition proposed in Patent Document 4 showed good properties in a good balance when used in a liquid crystal display member having a small area, but the large area due to the increase in the size of the liquid crystal display member. In the application for protecting the display member, the adhesive force at high-speed peeling is too large, which hinders the peeling work. Therefore, it is necessary to reduce the peeling force at high speed while maintaining a sufficient adhesive force (peeling force at low speed) in the protective film protecting a large area.

As described above, the surface protective film needs to reduce the peeling force. For this reason, the resin that is the main component of the pressure-sensitive adhesive layer is highly crosslinked and has brittle properties.
On the other hand, the surface protective film is attached to protect the optical member so that the surface of the optical member is not contaminated or damaged, and the surface of the protective film is easily subjected to external stresses such as collision and bonding of articles. In the environment. By receiving such external stress, a part of the pressure-sensitive adhesive layer of the surface protective film is also destroyed, and a part of the pressure-sensitive adhesive layer destroyed when the surface protective film is peeled off is on the surface of the optical member. A remaining defect occurred.

JP-A-9-208910 JP 2001-33624 A JP 2003-41229 A JP-A-2005-97451

The problem to be solved by the present application is that when the surface protective film is peeled off even if a large external stress is applied to the surface of the surface protective film and a part of the pressure sensitive adhesive layer is broken, A pressure-sensitive adhesive that does not transfer part of the pressure-sensitive adhesive layer destroyed on the member, has a small peeling force in high-speed peeling in a large area, and has excellent adhesion in low-speed peeling without causing zipping It is to provide a composition and an optical member surface protective film.

As a result of intensive research to solve the above problems, it was found that the present invention can be solved by including a specific acrylic copolymer and a specific silicon compound in the pressure-sensitive adhesive composition. It came to complete.
That is, the present invention is as follows.
1. An acrylic copolymer (A) having at least 0.1 to 10% by weight of a hydroxyl group-containing monomer as a copolymerization component and having a glass transition point (Tg) of −76 to −50 ° C .;
0.01 to 2.0 parts by weight of a polyoxyalkylene-modified dimethylsilicone compound (B) with respect to 100 parts by weight of the acrylic copolymer (A);
A pressure-sensitive adhesive composition comprising:
2. The pressure-sensitive adhesive composition further contains an isocyanate compound (C),
When the sum of the hydroxyl group equivalent and the carboxyl group equivalent in the acrylic copolymer (A) is n, the content of the isocyanate compound (C) is 0.1 to 1.5 n equivalent in terms of isocyanate equivalent. The pressure-sensitive adhesive composition as described.

3. An acrylic copolymer (A) having at least 0.1 to 10% by weight of a hydroxyl group-containing monomer as a copolymerization component and having a glass transition point (Tg) of −76 to −50 ° C .;
0.01 to 2.0 parts by weight of a polyoxyalkylene-modified dimethylsilicone compound (B) with respect to 100 parts by weight of the acrylic copolymer (A);
A surface protective film having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing
4). The pressure-sensitive adhesive composition further contains an isocyanate compound (C),
When the sum of the hydroxyl group equivalent and the carboxyl group equivalent in the acrylic copolymer (A) is n, the content of the isocyanate compound (C) is 0.1 to 1.5 n equivalent in terms of isocyanate equivalent. The surface protective film as described.

The pressure-sensitive adhesive composition of the present invention contains a specific acrylic copolymer (A) and a specific silicon compound in the pressure-sensitive adhesive composition. When the agent composition transfer preventing component is bred to form a transfer inhibition layer, transfer of the pressure sensitive adhesive composition can be prevented.

Moreover, the surface protective film using the pressure-sensitive adhesive composition of the present invention by being configured in this way has surface protection and high transparency of the optical member, and, for example, an antiglare layer on the surface, etc. Even when used for optical members such as polarizing plates provided with a layer with fine irregularities, adhesive layer defects such as bulge, tunneling, peeling, etc., even after undergoing autoclave treatment and subsequent work and use heat history Furthermore, even when a large compressive stress is applied to the surface of the optical member protective film and the pressure-sensitive adhesive composition causes cohesive failure, the cohesive failure of the pressure-sensitive adhesive composition is transferred to the optical member. It shows good peeling properties and easily peels off without causing inconveniences such as disordered alignment of the optical member or liquid crystal cell, expansion of the cell gap, peeling of the optical member from the liquid crystal cell, etc. Rukoto can.

The pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive composition containing a specific acrylic copolymer (A) and a specific silicon compound (B).

The acrylic copolymer (A) contains 0.1 to 10% by weight of a hydroxyl group-containing monomer as a copolymer component in the molecule, and an acrylic resin having a glass transition point (Tg) of −76 to −50 ° C. It is a copolymer.

The type of the hydroxyl group-containing monomer is not particularly limited as long as it is a monomer containing a hydroxyl group, and examples thereof include an acrylic monomer, a methacryl monomer and other monomers containing a hydroxyl group ( Hereinafter, when an acrylic monomer and a methacrylic monomer are used together, they may be referred to as a (meth) acrylic monomer).
Examples of the (meth) acrylic monomer containing a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) ) Acrylate, 3-methyl-3-hydroxybutyl (meth) acrylate, 1,1-dimethyl-3-butyl (meth) acrylate, 1,3-dimethyl-3-hydroxybutyl (meth) acrylate, 2,2,4 -Trimethyl-3-hydroxypentyl (meth) acrylate, 2-ethyl-3-hydroxyhexyl (meth) acrylate, glycerin mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, poly ( Ethylene glycol-propylene glycol) mono (meth) acrylic Over DOO, mention may be made of N- methylolacrylamide.

Examples of the other monomers include allyl alcohol and methallyl alcohol.

Among these monomers, good compatibility and copolymerizability with other monomers when copolymerizing with other monomers to synthesize acrylic copolymer (A), and From the viewpoint of good crosslinking reactivity with the crosslinking agent, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are preferred, and 4-hydroxybutyl (meth) acrylate is more preferred.

The content of the hydroxyl group-containing monomer as a copolymerization component in the acrylic copolymer (A) molecule is 0.1 to 10% by weight with respect to the acrylic copolymer (A), preferably 1 to 8% by weight, more preferably 3 to 6% by weight.

  If the content contained as a copolymerization component of the hydroxyl group-containing monomer is less than the above lower limit value, contamination to the adherend occurs when the surface protective film is peeled, whereas if the content exceeds the upper limit value, Since the agent layer becomes hard, a problem arises in the conformability (wetting property) when the surface protective film is applied to the adherend.

In the present invention, the acrylic copolymer (A) means that the copolymer contains 70% by weight or more of a (meth) acrylic monomer as a copolymer component, preferably 90% by weight or more. It is good to be.
If the (meth) acrylic monomer contained in the copolymer (A) as a copolymerization component is less than the above lower limit, the heat resistance of the pressure-sensitive adhesive is reduced, and therefore, by autoclaving or aging treatment Also, a swelling occurs between the polarizing plate surface and the pressure-sensitive adhesive layer of the surface protective film.

Moreover, what is a (meth) acrylic acid ester among the said hydroxyl-containing monomers is also counted as the quantity of a (meth) acryl monomer as a copolymerization component contained in the said copolymer (A).

The acrylic monomer is not particularly limited as long as it has an acrylate structure. For example, methyl acrylate, ethyl acrylate, n-butyl acrylate, i-butyl acrylate, n-octyl acrylate, i- C1-C18 linear or branched alkyl esters of acrylic acid such as octyl acrylate, 2-ethylhexyl acrylate, n-nonyl acrylate, i-nonyl acrylate, n-decyl acrylate, n-dodecyl acrylate, stearyl acrylate, etc. It is done.

The methacrylic monomer is not particularly limited as long as it has a methacrylic ester structure. For example, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, n-dodecyl methacrylate, stearyl A linear or branched alkyl ester having 1 to 18 carbon atoms of methacrylic acid such as methacrylate, or one or more of these various derivatives can be selected.

The said acrylic copolymer (A) can contain monomers other than a (meth) acryl monomer as a copolymerization component in the range which does not exceed the definition of the said acrylic copolymer (A).
As monomers other than (meth) acrylic monomers, for example, 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, vinyl toluene, etc .; vinyl cyanide monomers such as acrylonitrile, methacrylonitrile; diesters of maleic acid or fumaric acid such as dimethyl maleate Di-N-butyl maleate, di-2-ethylhexyl maleate, di-N-octyl maleate, dimethyl fumarate, di-N-butyl fumarate, di-2-ethylhexyl maleate, di- N-octyl fumarate and the like can be mentioned.

The acrylic copolymer (A) may contain a carboxyl group-containing monomer as a copolymerization component, and a crosslinking catalyst when the pressure-sensitive adhesive composition of the present invention is crosslinked to form a surface protective sheet. When not used, the carboxyl group-containing monomer component acts as a crosslinking catalyst, which is effective.

The carboxyl group-containing monomer is not particularly limited as long as it is a monomer having a carboxyl group. For example, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid Citraconic acid, cinnamic acid, monohydroxyethyl (meth) acrylate succinate, monohydroxyethyl (meth) acrylate maleate, monohydroxyethyl (meth) acrylate fumarate, monohydroxyethyl (meth) acrylate phthalate, 1, Examples thereof include 2-dicarboxycyclohexane monohydroxyethyl (meth) acrylate, (meth) acrylic acid dimer, ω-carboxy-polycaprolactone mono (meth) acrylate and the like.

  When the carboxyl group-containing monomer is copolymerized to exert the effect of the crosslinking catalyst, the content of the carboxyl group-containing monomer as a copolymer component in the acrylic copolymer (A) is 0. 0.1 to 2.0% by weight, preferably 0.3 to 1.0% by weight, and more preferably 0.4 to 0.8% by weight.

When the content of the carboxyl group-containing monomer as a copolymerization component in the acrylic copolymer (A) exceeds the upper limit value, the pot life of the pressure-sensitive adhesive composition after blending the isocyanate compound (C) On the other hand, if the cross-linking catalyst is not present if the wettability is less than the lower limit value, the adhesive force at the time of re-peeling becomes too large. Inconvenience such as peeling of the optical member from the cell occurs, and the surface protective film cannot be easily peeled off.

Furthermore, as a monomer which may be contained as a copolymerization component in the acrylic copolymer (A), if necessary, in addition to one radical polymerizable unsaturated group in the molecule, at least one It is a monomer unit having a functional group, and can contain monomers other than the hydroxyl group-containing monomer and the carboxyl group-containing monomer.

Examples of the monomer include monomers having a functional group such as an amide group or a substituted amide group, an amino group or a substituted amino group, a lower alkoxyl group, or an epoxy group. A monomer having two or more radically polymerizable unsaturated groups can also be used.

Specific examples of the monomer having an amide group or a substituted amide group, an amino group or a substituted amino group as the functional group include, for example, acrylamide, methacrylamide, diacetone acrylamide, N-methylol acrylamide, and N-methylo. An amide group or a substituted amide group-containing amide group such as -methacrylamide, NN-butoxymethylacrylamide, Ni-butoxymethylacrylamide, N, N-dimethylacrylamide, N-methylacrylamide (preferably acrylamide, methacrylamide) For example, aminoethyl acrylate, N, N-dimethylaminoethyl acrylate, N, N-diethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N -Diethylaminoethyl methacrylate, etc. And an amino group or substituted amino group-containing monomer.

Examples of the monomer having a lower alkoxyl group or an epoxy group as the functional group include 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, Contains lower alkoxyl groups such as methoxypolyethylene glycol monomethacrylate Mer; for example, glycidyl acrylate Le - and epoxy group-containing monomers such as ether - DOO, glycidyl methacrylate - DOO, glycidyl allyl et - ether, glycidyl methallyl Rue.

Examples of the monomer having two or more radically polymerizable unsaturated groups in the molecule include divinylbenzene, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, ethylene glycol di (meta ) Acrylate, 1,2-propylene glycol di (meth) acrylate, 1,3-propylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1 Two or more radical polymerizations such as 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, allyl (meth) acrylate, etc. And a monomer having a polymerizable unsaturated group.

The glass transition point (Tg) of the acrylic copolymer (A) is an acrylic copolymer of −76 to −50 ° C., and if the Tg exceeds the temperature, the pressure-sensitive adhesive layer is hard. It becomes difficult to flow, especially when it is used for a polarizing plate with an anti-glare layer on the surface, the pressure-sensitive adhesive cannot sufficiently wet the unevenness of the anti-glare layer, so that pressure sensitivity is reduced by autoclaving or aging treatment. This is not preferable because air slightly remaining between the adhesive layer and the antiglare layer may expand to cause swelling between the polarizing plate surface and the pressure-sensitive adhesive layer of the surface protective film.

In addition, in this invention, Tg is calculated | required by following Formula using Tg of the homopolymer of each monomer component which comprises a copolymer (A).

1 / Tg = w1 / Tg1 + w2 / Tg2 ++ ... + wk / Tgk

Where Tg is the glass transition temperature of the copolymer (A), Tg1, Tg2,... Tgk is the Tg of the homopolymer of each monomer component, w1, w2,. ... wk represents the weight fraction of each monomer component, and w1 + w2 + ... + wk = 1.

The acrylic copolymer (A) 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 less than the lower limit value, the adhesive force at the time of re-peeling becomes too large. Especially when heat treatment is performed, damage to the optical member or peeling of the optical member from the liquid crystal cell, etc. Inconvenience occurs and the surface protective film cannot be easily peeled off. On the other hand, when the upper limit is exceeded, the fluidity of the resulting pressure-sensitive adhesive layer decreases, and when used for a polarizing plate having minute irregularities on the surface, the pressure-sensitive adhesive may sufficiently wet the polarizing plate surface. This is not preferable because a bulge is generated between the polarizing plate surface and the pressure-sensitive adhesive layer of the surface protective film by autoclaving or aging.

The acrylic copolymer (A) suitably used in the present invention generally has a molecular weight distribution expressed by a ratio Mw / Mn of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of generally 15 or less, preferably It should be in the range of 12 or less. If the value of Mw / Mn exceeds the upper limit value, the adhesive strength at the time of re-peeling becomes too large. Especially when heat treatment is performed, inconveniences such as damage to the optical member and peeling of the optical member from the liquid crystal cell may occur. The surface protective film cannot be easily peeled off.
In addition, the value measured by the gel permeation chromatography (GPC) method according to the usual method is used for the value of the said weight average molecular weight (Mw) and number average molecular weight (Mn) in this specification.

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 or the like. In producing the pressure-sensitive adhesive composition of the present invention using a polymer, it is preferable to perform polymerization by solution polymerization because the treatment process is relatively simple and can be performed in a short time.

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.

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; , Ethyl acetate, N-butyl acetate, N-amyl acetate, 2-hydroxyethyl acetate, 2-butoxyethyl acetate, 3-methoxybutyl acetate, methyl benzoate, etc .; for example, acetone, methyl ethyl ketone, methyl-i- Keto such as butyl ketone, isophorone, cyclohexanone, methylcyclohexanone 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 Alcohols such as -propyl alcohol, i-propyl alcohol, N-butyl alcohol, i-butyl alcohol, s-butyl alcohol, t-butyl alcohol; and the like. These organic solvents can be used alone or in admixture of two or more.

Among 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, such as esters and ketones. In view of the solubility of the copolymer (A) and the ease of the polymerization reaction, use of ethyl acetate, methyl ethyl ketone, acetone, or the like is preferable.

As said polymerization initiator, it is possible to use the organic peroxide, an azo compound, etc. which can be used by normal solution polymerization.
Examples of such organic peroxides include t-butyl hydroperoxide, cumene hydroxide, dicumyl peroxide, benzoyl peroxide, lauroyl peroxide, caproyl peroxide, di-i-propyl peroxide-dicarbonate. , Di-2-ethylhexylperoxydicarbonate, t-butylperoxybivalate, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) propane, 2,2-bis ( 4,4-di-t-amylpa-oxycyclohexyl) propane, 2,2-bis (4,4-di-t-octylpa-oxycyclohexyl) propane, 2,2-bis (4,4-di-α-) Cumylpa-oxycyclohexyl) propane, 2,2-bis (4,4-di-t-butylperoxycyclohexyl) ) Butane, 2,2-bis (4,4-di-t-octylpa-oxycyclohexyl) butane and the like. Examples of the azo compound include 2,2′-azobis-i-butyronitrile, 2,2 ′. -Azobis-2,4-dimethylvaleronitrile, 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, etc. can be mentioned.

  Among these organic peroxides, in the polymerization of the acrylic copolymer (A), 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 2.0 parts by weight, preferably 0.1 to 1.0 parts by weight, based on 100 parts by weight of the total amount of monomers.

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 within the range not impairing the object and effect of the present invention. It is possible.
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 1,6-tetramethyl-p-benzoquinone; borane derivatives such as tributylborane; carbon tetrabromide, carbon tetrachloride, 1,1,2,2-tetrabromoethane, tribromoethylene, trichloroethylene, bromo Trichloromethane, tribromomethane, 3-chloro-1-propyl Halogenated hydrocarbons such as pens; Aldehydes such as chloral and fulleraldehyde: Alkyl mercaptans having 1 to 18 carbon atoms; Aromatic mercaptans such as thiophenol and toluene mercaptan; Carbon number of mercaptoacetic acid and mercaptoacetic acid 1-10 alkyl esters; C1-C12 hydroxyalkyl mercaptans; terpenes such as vinylene and terpinolene; and the like.

  The polymerization temperature is generally about 30 to 180 ° C, preferably 40 to 150 ° C, more preferably 50 to 90 ° C.

  In addition, when an unreacted monomer is contained in a polymer obtained by a solution polymerization method, it can be purified by a reprecipitation method using methanol or the like in order to remove the monomer. is there.

The pressure-sensitive adhesive composition of the present invention contains 0.01 to 2.0 parts by weight of the polyoxyalkylene-modified dimethylsilicon compound (B) with respect to 100 parts by weight of the acrylic copolymer (A).

As the polyoxyalkylene-modified dimethyl silicon compound (B),
A compound obtained by substituting the side chain of dimethylsilicon represented by the following chemical formula 1 with a polyoxyalkylene group (described as an organic group in the chemical formula, the same shall apply hereinafter) [Chemical formula 1]

A compound in which the terminal portion of dimethylsilicon represented by the following chemical formula 2 is substituted with a polyoxyalkylene group [Chemical formula 2]

A compound in which both ends of dimethylsilicon represented by the following chemical formula 3 are substituted with polyoxyalkylene groups [Chemical formula 3]

A compound in which the side chain and both ends of dimethyl silicon represented by the following chemical formula 4 are substituted with polyoxyalkylene groups [Chemical formula 4]
Etc.

Examples of the polyoxyalkylene group include polyoxyethylene, polyoxypropylene, polyoxybutylene, and block compounds thereof.

The polyoxyalkylene-modified dimethyl silicon compound (B) is, for example, “KF-96-1000”, “KF-351”, “KF-353”, “KF-410”, “KF-412”, “KF” -851 "," KF-858 "," KF-859 "," X-22-161A "," X-22-161B "," KF-6001 "," KF-6002 "," KF-6003 " “X-22-160AS”, “X-22-170B”, “X-22-170D”, “X-41-1810”, “KF-50-100”, “KF-54”, “KF-995” ”,“ KF-945 ”,“ KF-6004 ”,“ FL-100-450 ”,“ KF-905 ”,“ KS-707 ”,“ SEPA-COAT ”,“ KP-301 ”,“ KP-323 ” ”,“ KP-354 ”,“ KP-355 ”[Shin-Etsu Chemical Manufactured by Co., Ltd.], “BY-16-201”, “FZ-77”, “FZ-2101”, “FZ-2104”, “FZ-2110”, “FZ-2118”, “FZ-2162”, “FZ-2203”, “FZ-2207”, “FZ-2208”, “L-7001”, “L-7002”, “SF-8427”, “SF-8428”, “SH-3749”, “SH” -3773 "," SH-8400 "(manufactured by Dow Corning Toray)," TSF-4440 "," TSF-4445 "," TSF-4450 "," TSF-4442 "," TSF-4460 "[ Momentive Performance Materials Japan G.K.) and other commercial names.

Moreover, according to the objective, you may mix | blend suitably silicone oil in addition to the polyoxyalkylene modified dimethylsilicon compound (B).

The polyoxyalkylene-modified dimethyl silicon compound (B) is contained in the pressure-sensitive adhesive composition in an amount of 0.01 to 2.0 parts by weight with respect to 100 parts by weight of the acrylic copolymer (A). Yes, preferably 0.05 to 1.0 part by weight, more preferably 0.1 to 0.5 part by weight.

When the amount of the polyoxyalkylene-modified dimethylsilicon compound (B) contained in the pressure-sensitive adhesive composition is less than the lower limit, the surface of the protective film is subjected to external stress and pressure-sensitive to the surface protective film. When a part of the adhesive layer is destroyed, there is a problem that a part of the pressure-sensitive adhesive layer destroyed when the surface protective film is peeled remains on the surface of the optical member.
When the amount of the polyoxyalkylene-modified dimethylsilicon compound (B) contained in the pressure-sensitive adhesive composition exceeds the upper limit, the adhesiveness of the surface protective film changes with time, and the optical member Excess dimethylsilicon compound (B) remains on the surface of the substrate, causing surface contamination.

The pressure-sensitive adhesive composition is added with an isocyanate compound (C) as a crosslinking catalyst when forming a surface protective film, thereby forming an adhesive layer.

Examples of the isocyanate compound (C) that can be used in the present invention include fragrances such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate. Aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated aromatic polyisocyanate compounds, etc .; Polyisocyanate compounds derived from various polyisocyanates such as adducts of dimers or trimers or polyisocyanates thereof and polyols such as trimethylolpropane can be mentioned, but these isocyanates can be mentioned. Among hexagonal compounds, hexamethylene diisocyanate is special. Preferred.

  These isocyanate compounds include, for example, “Colonate HX”, “Colonate HL-S”, “Colonate 2234”, “Aquanet 200”, “Aquanet 210” [Nippon Polyurethane Co., Ltd. )], "Desmodur N3400" (manufactured by Sumitomo Bayer Urethane Co., Ltd.), "Duranet E-405-80T", "Duranet 24A-100", "Duranet TSE-100" [Asahi Kasei Industrial Co., Ltd.], “Takenet D-110N”, “Takenet D-120N”, “Takenet M-631N”, “MT-Oresta-NP1200” (manufactured by Mitsui Takeda Chemical Co., Ltd.) What is marketed with a brand name, such as, can be used conveniently.

  The amount of the isocyanate compound (C) used is 0.1 to 1.5 n equivalent as an isocyanate group when the sum of the hydroxyl equivalent and carboxyl group equivalent of the acrylic copolymer (A) is n equivalent. Is preferable, 0.3 to 1.2 n equivalent is more preferable, and 0.5 to 1.0 n equivalent is particularly preferable. When the amount of the isocyanate compound (C) is 1 equivalent to the sum of the hydroxyl group equivalent and the carboxyl group equivalent of the acrylic copolymer (A), if the amount exceeds the above upper limit as an isocyanate group, the conformability (wetting property) is increased. When it is extremely deteriorated and is less than the above lower limit, the high-speed adhesive strength is too high.

The pressure-sensitive adhesive composition of the present invention may contain a crosslinking catalyst in addition to the isocyanate compound (C) as a crosslinking agent. As described above, a carboxyl group-containing monomer can be used as a crosslinking catalyst, but when a carboxyl group-containing monomer is not used, a metal catalyst can be used.
A general isocyanate crosslinking catalyst such as a Sn (tin) catalyst can be used as the metal catalyst, and dibutyltin dilaurate can be preferably used from the viewpoint of pot life and catalytic effect.

In addition to the acrylic copolymer (A), polyoxyalkylene-modified dimethylsilicon compound (B) and isocyanate compound (C) described above, the pressure-sensitive adhesive composition of the present invention, if necessary, Formulations to be blended in the pressure sensitive adhesive composition for protective film, for example, solvents, weather resistance stabilizers, tackifiers, plasticizers, softeners, dyes, pigments, inorganic fillers and the like can be blended as appropriate. .
Range of blending amount of weathering stabilizer, tackifier, plasticizer, softener, dye, pigment, inorganic filler, etc. The amount is preferably 30 parts by weight or less, more preferably 100 parts by weight of acrylic copolymer (A). Is 20 parts by weight or less, and most preferably 10 parts by weight or less. When the blending amount is more than the upper limit, the balance of adhesive strength, wettability, heat resistance, and paste transferability is lost, and various physical properties deteriorate.

A solvent can be contained in the pressure-sensitive adhesive composition of the present invention, and the non-volatile content of the pressure-sensitive adhesive composition can be set to a viscosity suitable for coating by about 20 to 50%.
The solvent does not react with the components of the pressure-sensitive adhesive composition, and when the acrylic copolymer (A) is dissolved to form a surface protective film, it is dried at an appropriate speed after coating. There are no particular restrictions.
The viscosity of the pressure-sensitive adhesive composition of the present invention is preferably about 300 to 5000 mPa · s from the viewpoint of coating properties and the like.

The surface protective film of the present invention can be produced by forming the above pressure sensitive adhesive composition on at least one surface of an appropriate transparent surface protective substrate by forming a pressure sensitive adhesive layer.
Specifically, as a method for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition of the present invention is directly or diluted with an appropriate solvent as needed, and this is directly applied to a surface protective base film and dried. Thus, a method of removing the solvent can be employed. First, the pressure-sensitive adhesive composition of the present invention is applied onto a release sheet made of an appropriate film such as paper or polyester film that has been subjected to a release treatment with a silicon resin or the like, followed by drying by heating. It is also possible to form a pressure adhesive layer, and then press the adhesive layer side of the release sheet against the surface protective base film to transfer the adhesive layer to the protective film.

The substrate for the surface protective film must be a substrate to which a pressure sensitive adhesive can be applied. From the viewpoint of inspection and management of optical members through fluoroscopy, the resin used as the raw material of the base material is, for example, polyester resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin. Examples thereof include films made of polyimide resins, polyolefin resins, acrylic resins, etc., but polyester resins are preferable from the viewpoint of surface protection performance, and polyethylene terephthalate resins are particularly preferable in view of practicality.

  The thickness of the substrate is generally 500 μm or less, preferably 5 to 300 μm, more preferably about 10 to 200 μm. An antistatic layer may be provided on one or both surfaces of these base materials for the purpose of preventing antistatic during peeling. The surface of the substrate on the side where the pressure-sensitive adhesive layer is provided may be subjected to a corona discharge treatment or the like in order to improve the adhesion with the pressure-sensitive adhesive layer.

The pressure-sensitive adhesive composition applied on the substrate can be dried and crosslinked with a hot air dryer under heating conditions of 70 to 120 ° C. for about 1 to 3 minutes.

The thickness of the pressure-sensitive adhesive layer formed on the substrate can be appropriately set according to the adhesive force required for the protective film, the surface roughness of the optical member, etc., and preferably 5 to 50 μm in dry thickness. More preferably, a thickness of about 15 to 30 μm can be exemplified. When the thickness of the pressure-sensitive adhesive layer is equal to or greater than the upper limit value, the adhesive is likely to protrude and the adhesive force is increased. When the thickness of the pressure-sensitive adhesive layer is equal to or less than the lower limit value, the adhesive force is decreased. , Wettability also deteriorates. Further, when a large stress is applied to the surface of the optical member protective film, the cushioning property is lowered when the thickness of the pressure-sensitive adhesive layer is not more than the lower limit value, so that the optical member is easily damaged.

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.

(1) Preparation of pressure-sensitive adhesive sheet for test The pressure-sensitive adhesive composition was applied on a release paper surface-treated with a silicon-based release agent so that the coating amount after drying was 21 g / m2. After coating and drying with a hot air circulating drier at 70 ° C. for 60 seconds to form a pressure sensitive adhesive layer, a polyethylene terephthalate (PET) film [trade name; E5001; manufactured by Toyobo Co., Ltd.] The pressure-sensitive adhesive layer surface is placed on top and bonded through pressure nip rolls, followed by curing at 23 ° C. and 50% RH for 10 days to obtain a test surface protection film. It was.

(2) Evaluation of removability
After the test surface protective film prepared in the preceding item (1) was cut to 25 mm × 150 mm, the surface protective film piece was antiglare-treated using a table laminating machine [trade name; SQ- 1852AP-AG6; manufactured by Sumitomo Chemical Co., Ltd.] was used as a test sample. After leaving this sample under conditions of 23 ° C. and 50% RH for 24 hours (conditioning treatment), the adhesive strength at 180 ° peeling was peeled off at a peeling speed of 30 m / min (high-speed peeling conditions), and applied to the adherend. Evaluate the adhesive residue.

(Evaluation criteria)
A: Adhesive residue on the adherend is not recognized.
○: Almost no adhesive residue on the adherend is observed, but a thin mark is observed.
Δ: Some adhesive residue on the adherend is observed.
X: Adhesive residue on the adherend is observed.

(3) Evaluation of heat resistance After cutting the test surface protective film prepared in the previous item (1) into 60 mm × 80 mm, the same two kinds of polarized light were applied to the surface protective film piece in the same manner as in the previous item (2). Crimped to film. Next, using a commercially available pressure-sensitive adhesive composition [Nissetsu Q-1851: manufactured by Nippon Carbide Industries Co., Ltd.], a pressure-sensitive layer having a thickness of about 25 μm is formed on the release paper in the same manner as in the previous item (1). After forming an adhesive layer and transferring this pressure-sensitive adhesive layer to the back of each polarizing film, these were pressure-bonded to a glass plate having a thickness of about 2 mm using a table laminating machine. It was. The sample was allowed to stand for 1 week under conditions of 23 ° C. and 50% RH, and then autoclaved (70 ° C., 490 kPa).
, 20 minutes), further heat treatment at 90 ° C. for 2 hours, and by visual observation from the surface of the surface protective film side of this test sample, generation of bubbles in the pressure-sensitive adhesive layer of the surface protective film, The state of peeling was evaluated. The evaluation criteria are as follows.

(Evaluation criteria)
A: Generation of bubbles is not recognized at all.
○: Some bubbles are observed in the test sample (width of about 5 mm).
Δ: Bubbles are observed in the test sample (width of about 5 mm), but there is no peeling.
X: Bubbles are observed on the entire surface of the test sample.

(4) Evaluation method of adhesive transfer After the surface protective film for test prepared in the previous item (1) was cut into 20 mm × 150 mm, this surface protective film piece was used as a clear polarizing film using a table laminating machine. A test sample was prepared by pressure bonding (not surface-treated). A ballpoint pen was fixed vertically on the surface of the protective film of this sample, a load of 500 g was applied, and a distance of 30 mm of the sample was scratched with 3 reciprocating ballpoint pens at a speed of 1 mm / s, and a scratch test was performed. After the test, the protective film of the sample was peeled off, and the transfer state of the pressure-sensitive adhesive composition was evaluated by visual observation from the surface of the clear polarizing film. The evaluation criteria are as follows.

(Evaluation criteria)
A: No transfer of the pressure-sensitive adhesive composition is observed.
○: Almost no transfer of the pressure-sensitive adhesive composition is observed, but a thin trace of transfer is observed.
Δ: Some transfer of the pressure-sensitive adhesive composition is observed.
X: Transfer of the pressure-sensitive adhesive composition is observed.

Production Example 1 of Acrylic Copolymer (A) Solution
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, 80 parts by weight of acetone and 40 parts by weight of toluene were placed, and in another container, 2-ethylhexyl acrylate (2EHA) 96. 0 parts by weight and 4.0 parts by weight of 4-hydroxybutyl acrylate (4HBA) were mixed to form a monomer mixture, and 25% of the monomer mixture was added to the reaction vessel, and then the reaction After replacing the air in the vessel with nitrogen gas, 0.05 part by weight of azobisbutyronitrilo (hereinafter referred to as AIBN) is added as a polymerization initiator, and the temperature of the mixture in the reaction vessel in a nitrogen atmosphere with stirring is added. Was heated to 70 ° C. to initiate the initial reaction. After the heat generation due to the initial reaction was almost completed, the remaining monomer mixture 75%, and 80 parts by weight of acetone, 40 parts by weight of toluene and 0.5 parts by weight of AIBN were reacted for 1.5 hours while sequentially adding each. Subsequently, the mixture was further reacted for 1.5 hours. Thereafter, a solution in which 1.0 part by weight of perbutyl PV was dissolved in 100 parts by weight of toluene was dropped over 1 hour, and the reaction was further performed for 1.5 hours. After completion of the reaction, the reaction mixture was diluted with 200 parts by weight of toluene and 180 parts by weight of ethyl acetate to obtain an acrylic copolymer solution having a solid content of 35.8% by weight.

Production Example 2
In a reactor equipped with a thermometer, a stirrer, a nitrogen introducing tube and a reflux condenser, 46.7 parts by weight of acetone and 73.3 parts by weight of toluene were placed, and in another container, 2-ethylhexyl acrylate ( 2EHA) 47.2 parts by weight, butyl acrylate (BA) 47.2 parts by weight, 4-hydroxybutyl acrylate (4HBA) 5.0 parts by weight, acrylic acid (AA) 0.6 parts by weight and mixed. Then, 25% of the monomer mixture was added to the reaction vessel, the air in the reaction vessel was replaced with nitrogen gas, and then azobisbutyronitrilo (hereinafter referred to as AIBN) was used as a polymerization initiator. 0.05 parts by weight were added, and the temperature of the mixture in the reaction vessel was raised to 70 ° C. in a nitrogen atmosphere with stirring to initiate an initial reaction. After the heat generation due to the initial reaction was almost completed, the remaining monomer mixture 75%, and 80 parts by weight of acetone, 40 parts by weight of toluene and 0.5 parts by weight of AIBN were reacted for 1.5 hours while sequentially adding each. Subsequently, the mixture was further reacted for 1.5 hours. Thereafter, a solution in which 1.0 part by weight of perbutyl PV was dissolved in 100 parts by weight of toluene was dropped over 1 hour, and the reaction was further performed for 1.5 hours. After completion of the reaction, the reaction mixture was diluted with 33.3 parts by weight of acetone and 166.7 parts by weight of toluene to obtain an acrylic copolymer solution having a solid content of 42.7% by weight.

Production Example 3
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, 116.3 parts by weight of acetone was placed, and in another container, 98.5 parts by weight of 2-ethylhexyl acrylate (2EHA). 4-hydroxybutyl acrylate (4HBA) 1.0 part by weight and acrylic acid (AA) 0.5 part by weight are mixed to form a monomer mixture, and 31.25% in the monomer mixture Then, the air in the reaction vessel was replaced with nitrogen gas, 0.067 parts by weight of azobisbutyronitrilo (hereinafter referred to as AIBN) was added as a polymerization initiator, and nitrogen was stirred with stirring. The initial reaction was started by raising the temperature of the mixture in the reaction vessel to 67 ° C. in the atmosphere. After the exothermic reaction from the initial reaction was almost completed, the remaining monomer mixture (68.75%) and acetone (125 parts by weight) and AIBN (0.16 part by weight) were respectively added and reacted for 1.17 hours, followed by The reaction was further continued for 1.33 hours. Thereafter, 129.2 parts by weight of ethyl acetate was added dropwise over 1 hour, and the reaction was further continued for 0.5 hour. Thereafter, 150 parts by weight of acetone was added dropwise over 0.67 hours and reacted for another 2 hours. After completion of the reaction, the reaction mixture was diluted with 346.7 parts by weight of methyl ethyl ketone to obtain an acrylic copolymer solution having a solid content of 27.7% by weight.

Production Example 4
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, 55 parts by weight of acetone and 65 parts by weight of toluene are placed, and in another container, 2-ethylhexyl acrylate (2EHA) 68. 0 parts by weight, 29.5 parts by weight of methyl acrylate and 2.5 parts by weight of 4-hydroxybutyl acrylate (4HBA) were mixed to form a monomer mixture, and 25% of the monomer mixture was reacted. After adding to the vessel and then replacing the air in the reaction vessel with nitrogen gas, 0.05 part by weight of azobisbutyronitrilo (hereinafter referred to as AIBN) was added as a polymerization initiator, and the mixture was stirred in a nitrogen atmosphere. The temperature of the mixture in the reaction vessel was raised to 70 ° C. to initiate the initial reaction. After the heat generation due to the initial reaction was almost completed, the remaining monomer mixture 75%, and 80 parts by weight of acetone, 40 parts by weight of toluene and 0.5 parts by weight of AIBN were reacted for 1.5 hours while sequentially adding each. Subsequently, the mixture was further reacted for 1.5 hours. Thereafter, a solution in which 1.0 part by weight of perbutyl PV was dissolved in 100 parts by weight of toluene was dropped over 1 hour, and the reaction was further performed for 1.5 hours. After completion of the reaction, the reaction mixture was diluted with 200 parts by weight of toluene and 180 parts by weight of ethyl acetate to obtain an acrylic copolymer solution having a solid content of 35.8% by weight.

Production Example 5
In a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser, 80 parts by weight of acetone and 40 parts by weight of toluene were placed, and in another container, 2-ethylhexyl acrylate (2EHA) 99. 5 parts by weight and 0.5 part by weight of acrylic acid (AA) are mixed to form a monomer mixture. 25% of the monomer mixture is added to the reaction vessel, and then the air in the reaction vessel is nitrogen gas. Then, 0.05 parts by weight of azobisbutyronitrilo (hereinafter referred to as AIBN) is added as a polymerization initiator, and the temperature of the mixture in the reaction vessel is raised to 70 ° C. in a nitrogen atmosphere with stirring. To start the initial reaction. After the heat generation due to the initial reaction was almost completed, the remaining monomer mixture 75%, and 80 parts by weight of acetone, 40 parts by weight of toluene and 0.5 parts by weight of AIBN were reacted for 1.5 hours while sequentially adding each. Subsequently, the mixture was further reacted for 1.5 hours. Thereafter, a solution in which 1.0 part by weight of perbutyl PV was dissolved in 100 parts by weight of toluene was dropped over 1 hour, and the reaction was further performed for 1.5 hours. After completion of the reaction, the reaction mixture was diluted with 498 parts by weight of toluene and 193.3 parts by weight of ethyl acetate to obtain an acrylic copolymer solution having a solid content of 28.0% by weight.

Composition of monomers used in Production Examples 1 to 5 above, viscosity of the obtained acrylic copolymer (A) solution, solid content, glass transition point (Tg), weight average molecular weight (Mw), weight average molecular weight ( Mw) is shown in Table 1.

Table 1

In addition, the symbol of the monomer in Table 1 is as follows.
2EHA: 2-ethylhexyl acrylate
BA: Butyl acrylate
MA: methyl acrylate 4HBA: 4-hydroxybutyl acrylate
AA: Acrylic acid

Preparation Example 1 of Pressure-Sensitive Adhesive Composition for Surface Protection Film
285.7 parts by weight (100 parts by weight of solid content) of the acrylic copolymer (A) solution prepared in Production Example 1 as the acrylic copolymer (A), and KP-355 (Shin-Etsu Chemical Co., Ltd.) as the silicon compound (B) 0.1 parts by weight of polyoxyalkylene-modified silicone oil, trade name: KP-355, active ingredient 100%, manufactured by Toray Dow Co., Ltd., polyoxyalkylene-modified silicone oil, trade name: SH8400, active ingredient 100%) is used as an isocyanate compound (C) in an amount of 0.1 part by weight, and hexamethylene diisocyanate-based crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name: Coronate HX, NCO content 21. 3%) with respect to 100 parts by weight of the acrylic copolymer (A), 5.48 parts by weight (the sum of the hydroxyl group equivalent and carboxyl group equivalent of the acrylic copolymer (A) is n equivalent) NCO equivalent number = 1.0 n equivalent) was added and stirred well to obtain a solution of the pressure-sensitive adhesive composition for the optical member surface protective film. The obtained pressure-sensitive adhesive composition had a solid content of about 35.8% by weight and a viscosity of 980 mPa · s. 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 2.

Example 2 to Example 4
A surface protective film for testing was prepared in the same manner as in Example 1 except that the compounding was carried out under the compounding conditions of each Example shown in Table 2 instead of the compounding conditions of Example 1, and each physical property was measured by the test method described above. Table 2 shows the measurement results.

Comparative Example 1
In Example 1, the pressure-sensitive adhesive composition for an optical member surface protective film was used in the same manner as in Example 1 except that the acrylic copolymer (A) solution produced in Production Example 5 was used as the acrylic copolymer (A). Solution was obtained.
Using this pressure-sensitive adhesive composition, a test surface protective film was prepared according to the above-described test surface protective film preparation method, and the physical properties measured by the test method described above are shown in Table 2.

Comparative Examples 2-6
A surface protective film for testing was prepared in the same manner as in Example 1 except that the compounding was performed under the compounding conditions of each comparative example shown in Table 2 instead of the compounding conditions of Example 1, and each physical property was measured by the test method described above. Table 2 shows the measurement results.

In addition, the symbol of the compound in Table 2 is as follows.
KP-355: Polyoxyalkylene-modified silicon, 100% active ingredient
Product name: KP-355, manufactured by Shin-Etsu Chemical Co., Ltd.
SH8400: polyoxyalkylene-modified silicon, active ingredient 100%
Product name: SH8400, manufactured by Toray Dow Corning Co., Ltd.
FZ-2208: polyoxyalkylene-modified silicon, active ingredient 100%
Toray Dow Corning Co., Ltd., trade name: FZ-2208
KF96-1000: Dimethyl silicon, active ingredient 100%
Product name: KF96-1000, manufactured by Shin-Etsu Chemical Co., Ltd.
KF-858: amino-modified silicon, active ingredient 100%
Product name: KF-858, manufactured by Shin-Etsu Chemical Co., Ltd.
KF-6001: Carbinol-modified silicon, 100% active ingredient
Product name: KF-6001, manufactured by Shin-Etsu Chemical Co., Ltd.
KF-412: Alkyl-modified silicon, active ingredient 100%
Product name: KF-412, manufactured by Shin-Etsu Chemical Co., Ltd.
Coronate HX: Hexamethylene diisocyanate crosslinking agent
NCO content 21.3%, manufactured by Nippon Polyurethane Co., Ltd.
Product Name: Coronate HX

A surface protective film having a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive composition of the present invention is laminated on the surface of an optical member to protect the surface of the optical member from being contaminated or damaged. When the optical member is processed into a liquid crystal display panel or the like, it is used for each process such as punching, inspection, transportation, and assembly of the liquid crystal display panel while the protective film is laminated on the optical member. If necessary, a heat and pressure treatment such as an autoclave treatment or a high temperature aging treatment is performed, and the surface is no longer required to be peeled off and used.

Claims (4)

An acrylic copolymer (A) having at least 0.1 to 10% by weight of a hydroxyl group-containing monomer as a copolymerization component and having a glass transition point (Tg) of −76 to −50 ° C .;
0.01 to 2.0 parts by weight of a polyoxyalkylene-modified dimethylsilicone compound (B) with respect to 100 parts by weight of the acrylic copolymer (A);
A pressure-sensitive adhesive composition comprising: The pressure-sensitive adhesive composition further contains an isocyanate compound (C),
2. The content of the isocyanate compound (C) is 0.1 to 1.5 n equivalent in terms of isocyanate equivalent, where n is the sum of the hydroxyl equivalent and carboxyl group equivalent in the acrylic copolymer (A). The pressure-sensitive adhesive composition described in 1. An acrylic copolymer (A) having at least 0.1 to 10% by weight of a hydroxyl group-containing monomer as a copolymerization component and having a glass transition point (Tg) of −76 to −50 ° C .;
0.01 to 2.0 parts by weight of a polyoxyalkylene-modified dimethylsilicone compound (B) with respect to 100 parts by weight of the acrylic copolymer (A);
A surface protective film having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing The pressure-sensitive adhesive composition further contains an isocyanate compound (C),
4. The content of the isocyanate compound (C) is 0.1 to 1.5 n equivalent in terms of isocyanate equivalent, where n is the sum of the hydroxyl equivalent and carboxyl group equivalent in the acrylic copolymer (A). The surface protective film as described in 2.