TWI716513B - Adhesive composition, adhesive layer and surface protective sheet - Google Patents

Abstract

An object of the present invention is to provide an adhesive composition which is capable of suppressing denaturation and adhesion enhancement under severe environments and forming an adhesive layer that prevents the occurrence of adhesive residue on an adherend during peeling.

The adhesive composition comprises a (meth)acrylic polymer (A) and an isocyanate compound (B) having an isocyanate group number of 2 or more in one molecule, and has a gel fraction of 85% by mass or more when an adhesive layer is formed. The (meth)acrylic polymer (A) comprises a (meth)acrylic acid ester polymer molecule (a) having a trithiocarbonate structure and hydroxyl groups at both ends of the molecule and in the molecular chain, and has a weight average molecular weight (Mw) of 300,000 to 600,000, a molecular weight distribution (Mw/Mn) of 4.0 or less and a hydroxyl value of 4 to 80 mg KOH/g as measured by gel permeation chromatography;

Description

Adhesive composition, adhesive layer and surface protection sheet

The present invention relates to an adhesive composition, an adhesive layer and a surface protection sheet.

The bonding of electronic materials and the bonding of surface protection sheets temporarily used in the manufacturing steps of electronic devices using the electronic materials are widely used adhesives mainly composed of (meth)acrylic polymers.

The recent electronic equipment system requires that even in the harsh environment of high temperature and high humidity, it will not produce abnormally high durability and reliability. Therefore, it can be used as an adhesive for the components of the electronic equipment, and it also requires durability and reliability under harsh environments. In addition, the adhesives used for the surface protection sheets temporarily used in the manufacturing steps of electronic devices also require durability and reliability that can withstand the temporary high temperature and high humidity environment in the manufacturing steps of electronic devices. It is required to be peelable from the adherend without residual glue.

As an adhesive composed of a (meth)acrylic polymer, for example, Patent Document 1 discloses an adhesive layer containing: a polymer component containing a specific acrylic polymer, and a rosin-based tackifying resin or Terpene series tackifying resin. In addition, Patent Document 2 discloses an adhesive layer composed of an adhesive composition containing a specific (meth)acrylate polymer and a polyfunctional isocyanate compound.

However, these adhesives will produce residual glue (contamination of the adherend) caused by the modification in harsh environments and the excessive increase in adhesion.

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Application Publication No. 2015-110724.

Patent Document 2: International Publication No. 2014/192492.

The subject of the present invention is to provide an adhesive composition that can form an adhesive layer, which can suppress modification and excessive increase in adhesive force even in severe environments, and prevent adhesion to the adherend during peeling. Produce residual glue.

The inventors of the present invention devoted themselves to the review in order to solve the above-mentioned problems. As a result, it was found that the above-mentioned problem can be solved by a composition for an adhesive containing a specific (meth)acrylic polymer and a specific isocyanate compound, and the present invention has been completed.

The present invention is, for example, the following [1] to [5].

[1]. An adhesive composition containing a (meth)acrylic polymer (A) and an isocyanate compound having an isocyanate group number of 2 or more per molecule (B), and the gel fraction when forming the adhesive layer is 85% by mass or more. The aforementioned (meth)acrylic polymer (A) includes the structure represented by formula (a1) and is at both ends of the molecule and the molecule The (meth)acrylate polymer molecule (a) with a hydroxyl group in the chain has a weight average molecular weight (Mw) of 300,000 to 600,000 as measured by colloidal permeation chromatography, a molecular weight distribution (Mw/Mn) of 4.0 or less, and a hydroxyl group The value is 4 to 80 mgKOH/g.

[2]. The adhesive composition as described in [1], wherein the (meth)acrylic polymer (A) is a reversible addition cleavage of a polymerizable double bond-containing monomer containing a hydroxyl-containing monomer Chain transfer (RAFT) polymer.

[3]. The adhesive composition according to [1] or [2], wherein the (meth)acrylate polymer molecule (a) is a polymer represented by formula (A1-1).

In the formula (A1-1), R ^{1 is} each independently a divalent organic group, and (A) is each independently a divalent group derived from a polymer of a polymerizable double bond-containing monomer containing a hydroxyl-containing monomer .

[4]. An adhesive layer obtained from the adhesive composition described in any one of [1] to [3].

[5]. A surface protection sheet having the adhesive layer described in [4].

According to the present invention, it is possible to provide an adhesive composition capable of forming an adhesive layer. The adhesive layer can suppress modification and excessive increase in adhesive force even in severe environments, and prevent generation of the adherend during peeling. Residue.

The adhesive composition, adhesive, and surface protection sheet of the present invention will be described below.

In addition, in this specification, "polymer" includes homopolymers and copolymers, and "polymerization" includes homopolymerization and copolymerization.

In addition, acrylic acid and methacrylic acid are collectively referred to as "(meth)acrylic acid".

〔Composition for Adhesive〕

The adhesive composition system of the present invention contains the characteristic of containing specific (meth)acrylate polymer molecules (a) (hereinafter referred to as "polymer molecules (a)") A predetermined (meth)acrylic polymer (A) and an isocyanate compound (B) having an isocyanate group number of 2 or more in a molecule (hereinafter referred to as "polyfunctional isocyanate compound (B)").

<(Meth)acrylic polymer (A)>

The (meth)acrylic polymer (A) contains polymer molecules (a).

<(Meth)acrylate polymer molecule (a)>

The polymer molecule (a) has a structure represented by formula (a1) and has hydroxyl groups at both ends of the molecule and in the molecular chain.

The polymer molecule (a) has a structure represented by formula (a1) (hereinafter referred to as "trithiocarbonate structure").

Since the polymer molecule (a) has hydroxyl groups at both ends of the molecule, it has excellent reactivity with the polyfunctional isocyanate compound (B). The reason is that compared with the hydroxyl group existing in the molecular chain, the hydroxyl group existing at the molecular end has a higher degree of freedom of movement, so there are more opportunities to approach the isocyanate group. In addition, it is considered that the reactivity is improved as described above, and therefore the polymer molecules (a) are more likely to enter the cross-linked structure. As a result, the resulting adhesive layer has fewer polymer molecules that are unintentionally released, thereby preventing adhesion. Body produces residual glue. In addition, the polymer molecule (a) has a hydroxyl group in the molecular chain, thereby adjusting the adhesive force of the adhesive layer Adjusting within an appropriate range can also suppress the increase in the adhesive force of the adhesive layer after high-temperature heating.

From the viewpoint of productivity, the hydroxyl group in the molecular chain of the polymer molecule (a) is preferably introduced by random copolymerization of a polymerizable double bond-containing monomer containing a hydroxyl group-containing monomer.

The weight average molecular weight (Mw) of the polymer molecule (a) measured by colloidal permeation chromatography (GPC) is preferably 300,000 to 600,000, more preferably 320,000 to 550,000, and still more preferably 330,000 to 500,000.

The molecular weight distribution (Mw/Mn) of the polymer molecule (a) is preferably 4.0 or less, more preferably 1.5 to 3.8, and still more preferably 1.8 to 3.5.

Mw and Mw/Mn can be measured, for example, by the method described in the Examples.

The polymer molecule (a) is preferably a polymer: in the compound represented by the formula (A1) (hereinafter referred to as "compound (A1)"), a monomer containing a polymerizable double bond such as (meth)acrylate The polymer is polymerized by reversible addition fragmentation chain transfer (RAFT) polymerization method.

In formula (A1), R ^{1 is} each independently a divalent organic group.

The compound (A1) has a trithiocarbonate structure in the molecule and has hydroxyl groups at both ends of the molecule. Compound (A1) can be synthesized in accordance with the method described in JP 2007-230947 A, for example. By using The compound (A1) having the aforementioned structure can form a telechelic structure without containing harmful organic metals.

By carrying out RAFT polymerization, the repeating structural units derived from monomers containing polymerizable double bonds are almost evenly bonded on both sides of the trithiocarbonate structure in the molecule, and high symmetry of the hydroxyl groups at both ends of the molecule can be obtained.的chain polymer.

The compound (A1) includes, for example, a compound represented by formula (A2) (hereinafter referred to as "compound (A2)") and a compound represented by formula (A3) (hereinafter referred to as "compound (A3)").

The compound (A2) has a trithiocarbonate structure in the molecule, and has one hydroxyl group at each end of the molecule. The compound (A2) includes, for example, RAFT-NT manufactured by Nippon Terpene Chemicals Co., Ltd.

In formula (A2), X is each independently -COO-, -CONR ³ -or a direct bond, and R ^{3 is} each independently an alkyl group, and the carbon number of the alkyl group is preferably 1 to 4, more preferably 1 To 3; R ^{2 is} each independently an alkylene group, the carbon number of the alkylene group is preferably 1 to 12, more preferably 1 to 6; Ar is each independently a phenylene group, a naphthylene group, or substituted with A group substituted for at least one of the aromatic ring hydrogens contained in the phenylene and naphthylene groups. Examples of the substituent include an alkyl group and an alkoxy group. In addition, in X, the carbonyl group in -COO- and -CONR ³ -is bonded to Ar. Two Xs are preferably the same group, two R ^{2 are} preferably the same group, two R ^{3 are} preferably the same group, and two Ar are preferably the same group.

The compound (A3) has a trithiocarbonate structure in the molecule and has two hydroxyl groups at both ends of the molecule. The compound (A3) may be RAFT-DiOH manufactured by Nippon Terpene Chemicals Co., Ltd., for example.

In formula (A3), X and Ar are synonymous with the same symbols in formula (A2); R ^{4 is} each independently an alkylene group, and R ^{5 is} each independently a direct bond or an alkylene group. The carbon number is preferably 1 to 12, more preferably 1 to 6. Two Xs are preferably the same group, two R ^{4 are} preferably the same group, and two R ^{5 are} preferably the same group, 2 Each Ar is preferably the same base.

Specific examples of the compound (A1) are shown below.

In RAFT polymerization, in the presence of compound (A1), a polymer containing a polymerizable double bond Monomer polymerization. The amount of the compound (A1) used is usually 0.05 to 20 parts by mass, preferably 0.05 to 10 parts by mass, relative to 100 parts by mass of the total amount of polymerizable double bond-containing monomers. If the use amount of the compound (A1) is more than the lower limit of the aforementioned range, it is easy to control the reaction, and if it is less than the upper limit of the aforementioned range, it is easy to adjust the weight average molecular weight of the obtained polymer to the aforementioned range.

For example, it reacts by inserting a monomer containing a polymerizable double bond between the sulfur atom in the compound (A1) and the methylene group adjacent to the sulfur atom to produce a polymer represented by formula (A1-1) (hereinafter referred to as Is "polymer (A1-1)"), and specific examples are polymers represented by formula (A2-1) or formula (A3-1) (hereinafter referred to as "polymer (A2-1)", "polymer ( A3-1)”).

In formula (A1-1), R ¹ is synonymous with the same symbol in formula (A1), and (A) is each independently derived from a polymer of a polymerizable double bond-containing monomer containing a hydroxyl-containing monomer Divalent groups (polymer chains of monomers containing polymerizable double bonds).

In formula (A2-1), X, R ² and Ar are synonymous with the same symbols in formula (A2), and (A) are independently polymerizable double bond-containing monomers derived from hydroxyl-containing monomers The divalent group of the polymer (polymer chain of monomer containing polymerizable double bond).

In formula (A3-1), X, R ⁴ , R ⁵ and Ar are synonymous with the same symbols in formula (A3), and (A) is each independently a polymerizable double bond derived from a monomer containing a hydroxyl group The divalent group of the polymer of the monomer (the polymer chain of the monomer containing polymerizable double bonds).

In formulas (A1-1) to (A3-1), the aforementioned A (derived from the divalent group of the polymer) is a copolymer structure of a monomer containing a polymerizable double bond. From the viewpoint of productivity, the copolymer The structure is preferably a random copolymer structure of monomers containing polymerizable double bonds.

In formulas (A1-1) to (A3-1), the number of repeating structural units derived from monomers containing polymerizable double bonds in A (derived from a divalent polymer group) is (meth)acrylic acid The Mw of the polymer (A) is in the above range.

The polymer molecules (a) may be used singly or in two or more types.

The (meth)acrylic polymer (A) may further contain polymers other than the polymer molecule (a) in addition to the polymer molecule (a). Examples of polymers other than polymer molecule (a) include when RAFT polymerization is used to produce polymer molecule (a) By-product of RAFT polymerization.

In the (meth)acrylic polymer (A), the content of the polymer molecule (a) is not specifically defined, as long as the (meth)acrylic polymer (A) contains the polymer molecule (a).

The (meth)acrylic polymer (A) is preferably a RAFT polymer of a polymerizable double bond-containing monomer containing a hydroxyl-containing monomer.

The polymerizable double bond-containing monomer used to form the (meth)acrylic polymer (A) is preferably the same as the polymerizable double bond-containing monomer used to form the aforementioned polymer molecule (a) the same. That is, the polymer molecule (a) and the polymer other than the polymer molecule (a) contained in the (meth)acrylic polymer (A) are preferably composed of the same polymerizable double bond-containing single The polymer formed by the body.

The Mw of the (meth)acrylic polymer (A) measured by GPC is 300,000 to 600,000, preferably 320,000 to 550,000, more preferably 330,000 to 500,000. By using acrylic polymer (A) with Mw in the aforementioned range, an adhesive layer can be obtained. The adhesive layer can inhibit modification and excessive increase in adhesion under severe environments, and prevent generation of adherends during peeling Residue.

The Mw/Mn of the (meth)acrylic polymer (A) is 4.0 or less, preferably 1.5 to 3.8, more preferably 1.8 to 3.5. The (meth)acrylic polymer (A) with Mw/Mn in the aforementioned range has a uniform molecular weight and a small amount of low-molecular-weight compounds. Therefore, the resulting cross-linked body has excellent heat resistance and, when the surface protective sheet is peeled off under low to high temperature conditions, It can prevent the residual glue caused by low molecular weight in the adherend.

Mw and Mw/Mn can be measured, for example, by the method described in the Examples.

In addition, the effect of preventing adhesive residues can be evaluated by, for example, measuring the water contact angle of the adherend before and after the surface protection sheet is attached and after peeling off, and evaluating the smaller change.

The (meth)acrylic polymer (A) has a hydroxyl value of 4 to 80 mgKOH/g, preferably 7 to 60 mgKOH/g, more preferably 10 to 40 mgKOH/g. The hydroxyl value can be measured, for example, by the method described in the Examples. By making the hydroxyl value of the (meth)acrylic polymer (A) within the aforementioned range, the adhesive force of the adhesive layer can be adjusted within an appropriate range. In addition, it can suppress the increase in the adhesive force of the adhesive layer after high-temperature heating, and prevent the generation of glue residue on the adherend.

In the adhesive composition, the content of the (meth)acrylic polymer (A) is usually 10 to 95% by mass in 100% by mass of the adhesive composition.

"Monomers Containing Polymeric Double Bonds"

The (meth)acrylic polymer (A) containing the polymer molecule (a) can be obtained by RAFT polymerization of the monomer containing a polymerizable double bond. As the polymerizable double bond-containing monomer, at least (meth)acrylate and hydroxyl-containing monomers are used. However, the aforementioned (meth)acrylates do not include (meth)acrylates containing hydroxyl groups, (meth)acrylates containing carboxyl groups, and (meth)acrylates containing amino groups, etc. )Acrylate.

In addition, as the polymerizable double bond-containing monomer, at least one selected from a monomer containing a functional group other than a hydroxyl group and a copolymerizable monomer other than these can be used.

<(Meth)acrylate>

In order for the polymer molecule (a) to have a structural unit derived from (meth)acrylate, (meth)acrylate is used as a polymerizable double bond-containing monomer.

(Meth) acrylates include, for example, alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, alkoxypolyalkylene glycol mono(meth)acrylates, containing alicyclic groups or Aromatic (meth)acrylate.

The carbon number of the alkyl group in the alkyl (meth)acrylate is preferably 1-20. The alkyl (meth)acrylate can include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-propyl (meth)acrylate Butyl ester, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, (meth)acrylate 2-ethylhexyl acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, Oil (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, didecyl (meth)acrylate.

The alkoxyalkyl (meth)acrylate includes, for example, methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxypropyl (meth)acrylate, 3-ethoxypropyl (meth)acrylate, 4-methoxybutyl (meth)acrylate, 4-ethoxybutyl (meth)acrylate ester.

Alkoxy polyalkylene glycol mono (meth) acrylate can include, for example, methoxy diethylene glycol mono (meth) acrylate, methoxy dipropylene glycol mono (Meth)acrylate, ethoxytriethylene glycol mono(meth)acrylate, ethoxydiethylene glycol mono(meth)acrylate, methoxytriethylene glycol mono(meth)acrylic acid ester.

Examples of (meth)acrylates containing an alicyclic group or aromatic ring include cyclohexyl (meth)acrylate, benzyl (meth)acrylate, and phenyl (meth)acrylate.

(Meth)acrylate can be used individually by 1 type or in 2 or more types.

The amount of (meth)acrylate used is usually 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more with respect to 100% by mass of all polymerizable double bond-containing monomers.

<Hydroxy-containing monomer>

In order for the polymer molecule (a) to have a hydroxyl group in the molecular chain, a hydroxyl group-containing monomer is used as a polymerizable double bond-containing monomer.

The hydroxyl-containing monomers include, for example, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate Hydroxy-containing (meth)acrylates such as esters and 8-hydroxyoctyl (meth)acrylate.

The hydroxyl group-containing monomer can be used singly or in two or more types.

The usage amount of the hydroxyl group-containing monomer is usually 0.5 to 15% by mass, preferably 1 to 12% by mass, and more preferably 3 to 10% by mass relative to 100% by mass of the total polymerizable double bond-containing monomer.

<Monomers containing functional groups other than hydroxyl>

Examples of monomers containing functional groups other than hydroxyl groups include acid group-containing monomers, amine group-containing monomers, amide group-containing monomers, nitrogen-containing heterocyclic ring monomers, and cyano group-containing monomers. Examples of acid groups include carboxyl groups, acid anhydride groups, phosphoric acid groups, and sulfuric acid groups.

The acid group-containing monomers include, for example, β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylate, mono(meth)acryloxyethyl succinate, and ω-carboxyl Carboxyl-containing (meth)acrylates such as caprolactone mono(meth)acrylate; (meth)acrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid and other carboxyl-containing monomers; phthalic acid Acid anhydride, maleic anhydride and other acid anhydride group-containing monomers; phosphoric acid group-containing monomers such as (meth)acrylic monomers having a phosphoric acid group in the side chain; (meth)acrylic monomers having a sulfuric acid group in the side chain Body and other monomers containing sulfuric acid groups.

Examples of the amine group-containing monomer include amine group-containing (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate.

The monomer containing an amide group can include, for example, (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(methyl) Acrylamide, N-hexyl(meth)acrylamide. Examples of the nitrogen-containing heterocyclic monomer include vinylpyrrolidone, acrylomorpholine, and vinylcaprolactam. Examples of the cyano group-containing monomer include cyano (meth)acrylate and (meth)acrylonitrile.

Monomers containing functional groups other than hydroxyl groups may be used alone or in two or more types.

The usage amount of monomers containing functional groups other than hydroxyl is usually 2% by mass or less, preferably 1% by mass or less, and more preferably 0.8% by mass or less with respect to 100% by mass of all polymerizable double bond monomers.

<Copolymerizable monomer>

Copolymerizable monomers include, for example, styrene, methyl styrene, dimethyl styrene, trimethyl styrene, propyl styrene, butyl styrene, hexyl styrene, heptyl styrene and octyl styrene Alkyl styrenes; styrene monomers such as fluorostyrene, chlorostyrene, bromostyrene, dibromostyrene, iodostyrene, nitrostyrene, acetylstyrene and methoxystyrene; Vinyl acetate.

The copolymerizable monomer may be used singly or in two or more types.

"Polymerization initiator"

RAFT polymerization is preferably carried out in the presence of a polymerization initiator. Examples of polymerization initiators include general organic polymerization initiators, and specific examples include peroxides such as benzyl peroxide and lauryl peroxide, and azo compounds such as 2,2'-azobisisobutyronitrile. Compound. Among these, azo compounds are preferred.

The azo compound may include, for example, 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azo Azobis(2-cyclopropylpropionitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1 ,1'-Azobis(cyclohexane-1-carbonitrile), 2-(aminomethanoylazo)isobutyronitrile, 2-phenylazo-4-methoxy-2,4-bis Methylvaleronitrile, 2,2'-azobis(2-carboxamidinopropane) dihydrochloride, 2,2'-azobis(N,N'-dimethylene iso Butyl amidine), 2,2'-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide], 2,2'-azobis(isobutylamide) two Hydrate, 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-cyanopropanol), dimethyl-2,2'-azobis( 2-methyl propionate).

A polymerization initiator can be used individually by 1 type or in 2 or more types.

The amount of the polymerization initiator used is usually 0.001 to 2 parts by mass, preferably 0.002 to 1 part by mass, relative to 100 parts by mass of the monomer containing polymerizable double bonds. If the amount of polymerization initiator used is more than the lower limit of the aforementioned range, it is easy to control the reaction, and if it is less than the upper limit of the aforementioned range, it is easy to adjust the weight average molecular weight of the (meth)acrylic polymer (A) For the above range.

"Aggregation Conditions"

The reaction temperature in RAFT polymerization is usually 60 to 120°C, preferably 70 to 110°C, usually under an inert gas atmosphere such as nitrogen, and the reaction can be carried out under any conditions of normal pressure, increased pressure and reduced pressure , Usually carried out under normal pressure. In addition, the reaction time is usually 1 to 20 hours, preferably 2 to 14 hours. For the polymerization conditions, refer to, for example, Japanese Patent Application Publication No. 2007-230947 and Japanese Patent Application Publication No. 2011-52057.

In addition, RAFT polymerization can be reacted without using a reaction solvent, but a reaction solvent may be used as needed. Examples of reaction solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and n-octane; cyclopentane, cyclohexane, cycloheptane, and cyclohexane. Alicyclic hydrocarbons such as octane; diethyl ether, diisopropyl ether, 1,2-dimethoxyethane, dibutyl ether, tetrahydrofuran, dioxane, anisole, phenylethyl Ether, diphenyl Base ethers and other ethers; chloroform, carbon tetrachloride, 1,2-dichloroethane, chlorobenzene and other halogenated hydrocarbons; ethyl acetate, propyl acetate, butyl acetate, methyl propionate and other esters; acetone , Methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, cyclohexanone and other ketones; N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl Amines such as pyrrolidone; Nitriles such as acetonitrile and benzonitrile; Subsidiary such as dimethyl sulfinium and cyclobutane etc. These solvents may be used singly or in two or more types.

<Multifunctional isocyanate compound (B)>

The polyfunctional isocyanate compound (B) is an isocyanate compound in which the number of isocyanate groups in one molecule is 2 or more. The number of isocyanate groups in one molecule of the polyfunctional isocyanate compound (B) is preferably from 2 to 8, and more preferably from 3 to 5. If the number of isocyanate groups is in the aforementioned range, it is preferable from the viewpoint of the efficiency of the crosslinking reaction between the polymer molecule (a) and the isocyanate compound and the viewpoint of easy availability.

Examples of the diisocyanate compound in which the number of isocyanate groups in one molecule is 2 include aliphatic diisocyanates, alicyclic diisocyanates, and aromatic diisocyanates. Aliphatic diisocyanates include ethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 2-methyl-1,5-pentane diisocyanate, 3- Aliphatic diisocyanates with 4 to 30 carbon atoms such as methyl-1,5-pentane diisocyanate and 2,2,4-trimethyl-1,6-hexamethylene diisocyanate. The cycloaliphatic diisocyanate may include isophorone diisocyanate, cyclopentyl diisocyanate, cyclohexyl diisocyanate, hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethyl Benzyl Alicyclic diisocyanates with 7 to 30 carbon atoms such as diisocyanates. Aromatic diisocyanates include, for example, phenylene diisocyanate, toluene diisocyanate, xylylene diisocyanate, naphthalene diisocyanate, diphenyl ether diisocyanate, diphenylmethane diisocyanate, diphenylpropane diisocyanate, etc., carbon number 8 Aromatic diisocyanate up to 30.

Examples of isocyanate compounds having an isocyanate group number of 3 or more in one molecule include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates. Specific examples include 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, and 4,4',4"-triphenylmethane triisocyanate.

In addition, the isocyanate compound may include, for example, a polymer of the above-mentioned isocyanate compound having an isocyanate group of 2 or 3 or more (e.g., dimer or trimer, biuret, trimeric isocyanate), derivatives (e.g., polyol and Addition reaction products of 2 or more diisocyanate compounds), polymers. Examples of polyols in the aforementioned derivatives include low-molecular-weight polyols such as trimethylolpropane, glycerin, neopentylerythritol, and other trivalent or higher alcohols; high-molecular-weight polyols include, for example, polyether polyols and polyester polyols. Alcohol, acrylic polyol, polybutadiene polyol, polyisoprene polyol.

Examples of such isocyanate compounds include diphenylmethane diisocyanate trimer, polymethylene polyphenyl polyisocyanate, hexamethylene diisocyanate or toluene diisocyanate biuret or trimer isocyanate; trihydroxy The reaction product of methyl propane and toluene diisocyanate or xylylene diisocyanate (for example, the 3-molecular adduct of toluene diisocyanate or xylylene diisocyanate); trimethylol propane and hexamethylene diisocyanate Cyanide Reaction products of acid esters (for example, 3-molecular adducts of hexamethylene diisocyanate), polyether polyisocyanates, and polyester polyisocyanates.

The polyfunctional isocyanate compound (B) can be used individually by 1 type or in 2 or more types.

The content of the polyfunctional isocyanate compound (B) in the adhesive composition is preferably 1 to 15 parts by mass, more preferably 1.5 to 12 parts by mass, relative to 100 parts by mass of the (meth)acrylic polymer (A), It is more preferably 2 to 10 parts by mass. When the content of the compound (B) is within the aforementioned range, the cohesiveness of the obtained composition does not decrease, and the balance of the adhesive properties of the obtained composition is excellent. In particular, it is preferable to use the compound (B) above the aforementioned lower limit to increase the reaction rate between the hydroxyl group and the isocyanate group and to be sufficiently hardened, so that the adhesive performance can be exhibited.

<Additives>

In addition to the above-mentioned components, the adhesive composition of the present invention may further contain selected from organic solvents, antistatic agents, ultraviolet absorbers, antioxidants, tackifying resins, plasticizers, etc. within the range that does not impair the effects of the present invention. One or more of defoamers, fillers, stabilizers, softeners, and wettability modifiers.

The organic solvent can be the reaction solvent described in section B of "Polymerization Conditions" for RAFT polymerization. For example, a polymer solution containing a (meth)acrylic polymer (A) and a reaction solvent obtained by RAFT polymerization and a polyfunctional isocyanate compound (B) can be mixed to prepare an adhesive composition. In 100% by mass of the adhesive composition of the present invention, the content of the organic solvent is usually 0 to 90% by mass, preferably 10 to 80% by mass.

〔Adhesive layer〕

The adhesive layer formed from the adhesive composition of the present invention can be cross-linked by crosslinking the adhesive composition, specifically, by adding (meth)acrylate polymer molecules (a) ( The meth)acrylic polymer (A) is obtained by crosslinking the polyfunctional isocyanate compound (B). The adhesive layer obtained as described above suppresses modification and excessive increase in adhesion even in severe environments, and prevents the generation of glue residue on the adherend during peeling.

The thickness of the adhesive layer is usually 3 to 100 μm, preferably 5 to 50 μm.

From the viewpoint of suppressing the deformation of the polarizing plate, improving the cohesive force, adhesive force, and repeelability, the gel fraction of the adhesive layer is 85% by mass or more, preferably 90% by mass, and more preferably 95% by mass or more . The gel fraction can be measured, for example, by the method described in the Examples.

The formation conditions of the adhesive layer are as follows. For example, the aforementioned composition is coated on a support at a temperature of usually 60 to 120°C, preferably 70 to 110°C, and dried for usually 1 to 5 minutes, preferably 2 to 4 minutes, to form a coating film.

Preferably, the adhesive layer is formed under the following conditions. After coating the aforementioned composition on a support and attaching a protective film on the coating film formed under the above conditions, it usually takes more than 3 days, preferably 7 to 10 days, usually 5 to 60°C, preferably It is aged at 15 to 40°C, usually 30 to 70% RH, preferably 40 to 70% RH. If the cross-linking is performed under the above-mentioned maturation conditions, the cross-linked body (network polymer) can be effectively formed.

Examples of the support and the protective film include plastic films made of polyester such as polyethylene terephthalate, polyethylene, polypropylene, and ethylene/vinyl acetate copolymer.

〔Surface protection sheet〕

The surface protection sheet of the present invention has an adhesive layer composed of the above-mentioned adhesive composition. The surface protection sheet preferably has a base material, and may have a separation film on the adhesive layer.

The thickness of the adhesive layer is usually 3 to 100 μm, preferably 5 to 50 μm. The thickness of the substrate and the protective film is not particularly limited, and is usually 10 to 100 μm, preferably 25 to 50 μm.

Examples of the substrate and the separation film include plastic films made of polyester such as polyethylene terephthalate, polyethylene, polypropylene, and ethylene/vinyl acetate copolymer.

The formation conditions and gel fraction of the adhesive layer are the same as the conditions described in section B of [Adhesive layer].

The surface protection sheet of the present invention can be used, for example, as a surface protection sheet temporarily used in the manufacturing steps of electronic equipment using electronic materials.

The surface protection sheet of the present invention has an adhesive layer, which suppresses modification and excessive increase in adhesion even in severe environments, and prevents the generation of glue residue on the adherend during peeling, so it can withstand electrons Durability and reliability under temporary high temperature and high humidity environment in the manufacturing process of the machine.

The surface protection sheet of the present invention is mainly adhered to the liquid crystal display device The surface of electronic equipment such as placement, plasma display, surface conduction electron emission device (SED) display, etc., can protect the surface of the above-mentioned electronic equipment. In addition, it is pasted on the surface of the parts constituting the electronic material, such as the polarizing plate, the phase difference plate, the liquid crystal cell, the transparent electrode plate and the like constituting the electronic device, so as to protect the surface of the electronic material.

(Example)

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. In the description of the following examples and the like, "parts" means "parts by mass" unless otherwise specified.

The measurement values in the examples were obtained by the following methods.

〔Weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn)〕

The (meth)acrylic polymer is based on the colloid permeation chromatography (GPC) method and the weight average molecular weight (Mw) and molecular weight distribution (Mw/Mn) in terms of standard polystyrene are obtained under the following conditions.

. Measuring device: HLC-8120GPC (manufactured by TOSOH Co., Ltd.).

. GPC string composition: The following 5 strings (all manufactured by TOSOH Co., Ltd.).

(1) TSK-GEL HXL-H (protection string).

(2) TSK-GEL G7000HXL.

(3) TSK-GEL GMHXL.

(4) TSK-GEL GMHXL.

(5) TSK-GEL G2500HXL.

. Sample concentration: diluted with tetrahydrofuran to 1.0 mg/cm ³ .

. Mobile phase solvent: tetrahydrofuran.

. Flow rate: 1.0cm ³ /min.

. Column temperature: 40℃.

〔Determination of hydroxyl value〕

The hydroxyl value is based on the JISK0070 method. After the hydroxyl group of the (meth)acrylic polymer contained in the polymer solution is acetylated with acetic anhydride, the excess acetic acid in the polymer solution is neutralized and titrated with potassium hydroxide. The obtained value is divided by the heating residue to obtain the hydroxyl value of the (meth)acrylic polymer.

[Measurement of heating residue]

After adding 1 g of (meth)acrylic polymer solution to a finely weighed tin-plated petri dish (mass: n1), weighing the total mass (n2), heating at 105°C for 3 hours. After that, the tin-plated petri dish was placed in a desiccator at room temperature for 1 hour, and then weighed again to measure the total mass (n3) after heating. Using the obtained mass measurement values (n1 to n3), the heating residue was calculated from the following formula.

Heating residue (mass%)=100×[mass after heating (n3-n1)/mass before heating (n2-n1)].

<(Meth) Acrylic Polymer>

[Manufacturing Example A1]

Add 44.9 parts of n-butyl acrylate, 50 parts of 2-ethylhexyl acrylate, 5 parts of 4-hydroxybutyl acrylate, 0.1 part of acrylic acid, and double [4] into a flask equipped with a stirring device, nitrogen introduction tube, thermometer and reflux cooling tube. -{Ethyl-(2- Hydroxyethyl)aminocarbonyl}-benzyl)trithiocarbonate (manufactured by Nippon Terpene Chemicals Co., Ltd.) (hereinafter also referred to as "RAFT agent-1") 0.15 parts, while introducing nitrogen into the flask, the contents of the flask The material was heated to 80°C.

After visually confirming the dissolution of the RAFT agent, 0.02 parts of 2,2'-azobisisobutyronitrile was added to the flask under stirring, and the temperature of the contents in the flask was maintained at 80°C for 1 hour. Next, while keeping the temperature of the contents in the flask at 80°C, 65 parts of ethyl acetate was dropped over 1 hour, and then heating and cooling were performed for 10 hours in a manner that could maintain the temperature of the contents in the flask at 80°C , And finally add 20 parts of ethyl acetate.

In the above manner, a polymer solution containing acrylic polymer (A1) is obtained. The molecular weight of the acrylic polymer (A1) contained in the obtained polymer solution was measured by GPC, Mw: 360,000, Mw/Mn: 3.0, and hydroxyl value 18.0 mgKOH/g. The heating residue of the obtained polymer solution was 53% by mass.

[Manufacturing Examples A2 to A5 and B1 to B4]

Except that the blending composition in Production Example A1 was changed to be as described in Table 1, a polymer solution containing acrylic polymers A2 to A5 or B1 to B4 was obtained in the same manner as in Production Example A1. Also, in Production Example A5, 80 parts of ethyl acetate was dropped over 1 hour while keeping the temperature of the contents in the flask at 80°C, and finally 20 parts were added.

The components described in Table 1 are as follows.

BA: n-butyl acrylate.

2-EHA: 2-ethylhexyl acrylate.

2-HEA: 2-hydroxyethyl acrylate.

4-HBA: 4-hydroxybutyl acrylate.

AA: Acrylic.

RAFT agent-1: Bis[4-{ethyl-(2-hydroxyethyl)aminocarbonyl}-benzyl] trithiocarbonate.

RAFT agent-2: S,S-dibenzyl trithiocarbonate.

<Composition for Adhesive and Surface Protection Sheet>

[Example 1]

Combine the polymer solution containing acrylic polymer (A1) obtained above and isocyanate compound Y-75 (manufactured by Soken Chemical Co., hexamethylene diisocyanate-based crosslinking agent, the number of isocyanate groups per molecule is about 3), The blending amount of Y-75 was 7 parts (solid ratio) with respect to 100 parts of acrylic polymer (A1) and mixed to obtain an adhesive composition.

After the adhesive composition is deaerated, a polyethylene terephthalate (PET) separation membrane (trade name: cerapeel MFA; manufactured by TORAY FILM Co., Ltd.) is applied with a doctor blade so that the dry film thickness becomes 25 μm. It was immediately dried at 80°C for 3 minutes, thereby forming a coating film on the PET separation film. After the aforementioned drying, a PET film with a thickness of 25μm is stuck on the surface of the coating film on the opposite side of the PET separation film, and it is allowed to stand for 7 days at a room temperature of 23°C and a humidity of 65% to obtain a PET separation film/adhesive layer /Surface protection sheet composed of PET film.

[Examples 2 to 6 and Comparative Examples 1 to 5]

Except that the compounding composition in Example 1 was changed to what is described in Table 1, the adhesive composition and the surface protection sheet were obtained in the same manner as in Example 1.

<evaluation>

〔Gel fraction〕

About 0.1 g of the adhesive layer obtained in the examples were collected in a sampling bottle, 30 mL of ethyl acetate was added and shaken for 4 hours, the contents of the sample bottle were filtered with a 200-mesh stainless steel filter, and the residue on the filter was filtered Dry at 100°C for 2 hours and measure the dry quality. The gel fraction of the adhesive layer is obtained by the following formula.

Gel fraction (mass%)=(dry mass/collected mass of adhesive layer)×100(%).

〔Rise ratio of adhesion〕

After cutting the surface protection sheet obtained in the examples to a width of 25 mm, the PET separation film was peeled off, and the exposed adhesive coating surface was crimped and pasted to a glass plate with a thickness of 1 mm using a 2 kg roller to form a test piece. After sticking for 20 minutes, the surface protection sheet was peeled from the glass plate at a peeling angle of 180° and a peeling speed of 30m/min under an environment of 23°C and 50%RH, and the initial adhesion was measured.

The test piece made under the same conditions was allowed to stand in a 150°C/drying oven for 1 hour. After slowly heating, the adhesive force after heating was measured under the same conditions as the initial adhesive force.

Divide the above-mentioned "adhesion after heating" by the "initial adhesion" to calculate the adhesion increase ratio. The results are shown in Table 1. In Table 1, "NG" means that the adhesive force is too high to peel off, and the adhesive force cannot be measured. Also, the adhesion rise ratio is Those below 4.0 are qualified (AA), and all others are not qualified (CC).

〔Poor water contact angle〕

The surface protection sheet obtained in the examples etc. was cut into a size of 50 mm×50 mm, and two test pieces were produced. The PET separation film on one side of the test piece was peeled off, and adhered to the non-easy-adhesive surface of the deposited PET film (DIAFOIL T680E100: manufactured by Mitsubishi Plastics Corporation) fixed on the support, and pressed back and forth 3 times with a 2kg roller. After standing for 20 minutes, the test piece was peeled off the deposited PET film, and the ion exchange water filled in the syringe was dropped on the exposed surface of the deposited PET film at a flow rate of 1 μL and a flow rate of 0.5 μL/s. The contact angle was measured at 23°C ( OCA15EC manufactured by Dataphysics Corporation) measured the contact angle (initial contact angle) of the deposited PET film.

The other side of the test piece was peeled off the PET separation film, and adhered to the surface of the deposited PET film (DIAFOIL T680E100: manufactured by Mitsubishi Plastics Corporation) fixed on the support without easy bonding treatment, and press-bonded back and forth three times with a 2kg roller. After standing for 20 minutes, heat treatment was performed at 150°C for 1 hour. After further standing at 23°C for 1 hour, the test piece was peeled from the deposited PET film, and the ion exchange water filled in the syringe was dropped on the exposed surface of the deposited PET film at a flow rate of 1μL and a flow rate of 0.5μL/s, and contacted at 23°C. A goniometer measures the contact angle of the deposited PET film (contact angle after heat treatment).

The absolute value of the difference between the "initial contact angle" and the "contact angle after heat treatment" is shown in Table 1. If the absolute value of the difference is less than 5.0, it is qualified (AA), and everything else is not qualified (CC).

Claims (5)

An adhesive composition containing a (meth)acrylic polymer (A) and an isocyanate compound (B) with an isocyanate group number of 2 or more in one molecule, and the gel fraction when forming an adhesive layer is 85 mass % Or more, the aforementioned (meth)acrylic polymer (A) contains a (meth)acrylate polymer molecule (a) having a structure represented by formula (a1) and having hydroxyl groups at both ends of the molecule and in the molecular chain, to The weight average molecular weight (Mw) measured by colloidal permeation chromatography is 300,000 to 600,000, the molecular weight distribution (Mw/Mn) is 4.0 or less, and the hydroxyl value is 4 to 80 mgKOH/g, the aforementioned (meth)acrylic polymer (A) The content is 10 to 95% by mass in 100% by mass of the adhesive composition, and the content of the isocyanate compound (B) is 1 to 15 parts by mass relative to 100 parts by mass of the (meth)acrylic polymer (A) ,

The adhesive composition described in the first item of the scope of patent application, wherein the aforementioned (meth)acrylic polymer (A) is a polymerizable double bond-containing monomer containing a hydroxyl group-containing monomer by reversible addition and fragmentation of the chain Transfer (RAFT) polymer. The adhesive composition described in item 1 or 2 of the scope of patent application, wherein the aforementioned (meth)acrylate polymer molecule (a) is a polymer represented by formula (A1-1),

In the formula (A1-1), R ^{1 is} each independently a divalent organic group, and (A) is each independently a divalent group derived from a polymer of a polymerizable double bond-containing monomer containing a hydroxyl-containing monomer . An adhesive layer is obtained from the adhesive composition described in any one of items 1 to 3 in the scope of the patent application. A surface protection sheet having the adhesive layer described in item 4 of the scope of patent application.