TWI824013B - Adhesive composition for surface protection sheet and surface protective sheet - Google Patents

Abstract

The invention provides an adhesive composition for surface protection sheet which has low haze, is easy to be laminated on an adherend, is easy to be peeled off, and can prevent adhesive residue on the adherend after peeling, has no cracks during cutting. The adhesive composition includes 30 to 60% by mass of polyurethane (A), 2 to 10% by mass of polyfunctional monomer (B), 30 to 68% by mass of other monomers (C) polymerizable with the polyurethane (A) and the polyfunctional monomer (B), and 0.1 to 5 parts by mass of photopolymerization initiator (D) with respect to 100 parts by mass of the total amount of (A) to (C). The polyurethane (A) has a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, has (meth) acryloyl groups at a plurality of terminals, and has a weight average molecular weight of 30,000 to 200,000.

Description

Adhesive composition for surface protection sheet and surface protection sheet

The present invention relates to an adhesive composition for surface protection sheets and a surface protection sheet. In particular, it relates to an adhesive composition for surface protection sheets containing a compound having a (meth)acrylyl group, and an adhesive composition for surface protection sheets having the same. Surface protection sheet of hardened material of composition.

Various optical films are used in optical components such as liquid crystal displays and touch panels in smartphones, personal computers, and televisions. The surface of these optical films is generally laminated with a protective sheet (surface protection sheet) for the purpose of preventing contamination or damage during transportation steps, manufacturing steps, and inspection steps. This protective sheet is peeled off after the assembly step or the like. Various urethane adhesives have been proposed as adhesives for protecting sheets.

For example, Patent Document 1 describes a photocurable composition for transparent adhesive sheets, which contains a polyoxyalkylene polyol as a skeleton and has a (meth)acrylyl group at the end and a weight average molecular weight of 10,000. ~300,000 polyurethane, (meth)acrylate with hydroxyl group, other photopolymerizable monomers and photopolymerization initiators.

Furthermore, Patent Document 2 describes a photocurable composition for a transparent adhesive sheet, which contains a poly(meth)acrylyl group bonded to the terminal end of a polyoxyalkylene chain through a urethane bond. Urethane, (meth)acrylate having a hydroxyl group, (meth)acrylate having an aromatic ring, other polymerizable monomers and photopolymerization initiators.

In the optical element inspection step, there are situations where it is required to fully discover or detect minute foreign matter or damage to the product or part while a protective sheet is laminated on the product or part. Therefore, the protective sheet is required to have low turbidity, that is, low haze.

In addition, in the manufacturing process of optical elements, the protective sheet may be repeatedly laminated and peeled off. Therefore, the protective sheet is required to be easy to laminate to the adherend (high wettability to the adherend) and easy to peel off. Furthermore, recently, as displays become larger and panel components become thinner, optical elements themselves become prone to cracks. Therefore, protective sheets are required to have moderate adhesion (peel strength) and to be able to be peeled off with a lighter force (light peelability). In addition, it is also required that after the protective sheet is peeled off, a part of the adhesive layer on the surface of the product (adherent) will not remain, which is the so-called adhesive residue (re-peelability). [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2014-210895 [Patent Document 2] Japanese Patent Application Publication No. 2016-20477

[Problem to be solved by the invention]

However, the compositions described in Patent Document 1 and Patent Document 2 are not intended to be used as protective sheets for peeling during the manufacturing process. The adhesive sheets using these compositions have high peel strength.

Therefore, the present inventors made careful examinations to solve the above-mentioned problems. By having a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and having (meth)acrylyl groups at the plural terminals, The polyurethane has a weight average molecular weight of 30,000~200,000; a multifunctional monomer with plural (meth)acrylyl groups; it can be combined with polyurethane and multifunctional monomers Other monomers for bulk polymerization; and the photopolymerization initiator of the photocurable surface protection sheet are hardened with the adhesive composition to obtain low haze, easy lamination, easy peeling, and can suppress adhesive residue after peeling. Surface protection sheet. However, since the adhesive layer of the surface protection sheet obtained from the adhesive composition for photocurable surface protection sheets is slightly hard, it is known that when the sheet with a thickened adhesive layer is laser-cut or knife-cut, the adhesive layer Cracks occur on the end surface.

Therefore, an object of the present invention is to provide a surface protection sheet that has low haze, is easy to laminate, is easy to peel off, can suppress adhesive residue after peeling, and does not cause cracks in the adhesive layer during cutting. Use adhesive compositions. Another object of the present invention is to provide a surface protection sheet that has low haze, is easy to laminate and peel off, can suppress adhesive residue after peeling, and does not cause cracks in the adhesive layer during cutting. [Means used to solve problems]

The structure of the present invention used to solve the above-mentioned problems is as follows. [1] An adhesive composition for surface protection sheets, which contains polyurethane (A), multifunctional monomer (B), polyurethane (A) and multifunctional monomer (B) An adhesive composition for surface protection sheets polymerized with other monomers (C) and photopolymerization initiator (D), Wherein the aforementioned polyurethane (A) is a polyurethane having a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, The aforementioned polyurethane (A) includes polyurethane (a1), The polyurethane (a1) has a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and the plural terminals of the polyurethane (a1) have (methyl )acrylyl, The weight average molecular weight of the aforementioned polyurethane (A) is 30,000~200,000, The aforementioned multifunctional monomer (B) is a compound having plural (meth)acrylyl groups, Relative to 100% by mass of the total amount of the aforementioned polyurethane (A), the aforementioned polyfunctional monomer (B), and the aforementioned other monomer (C), The content of the aforementioned polyurethane (A) is 30~60% by mass, The content of the aforementioned multifunctional monomer (B) is 2 to 10% by mass, The content of the aforementioned other monomers (C) is 30 to 68% by mass, Relative to 100 parts by mass of the total amount of the aforementioned polyurethane (A), the aforementioned polyfunctional monomer (B), and the aforementioned other monomer (C), The content of the photopolymerization initiator (D) is 0.1 to 5 parts by mass. [2] The adhesive composition for surface protection sheets according to [1], wherein the polyurethane (A) contains a structure derived from the polyoxyalkylene polyol having a number average molecular weight of 500 to 5,000 The structure of polyoxyalkylene polyol. [3] The adhesive composition for surface protection sheets according to [1] or [2], wherein the polyurethane (A) contains a copolymer whose skeleton is a polyoxyalkylene glycol and a diisocyanate. [4] The adhesive composition for surface protection sheets according to any one of [1] to [3], wherein the aforementioned polyoxyalkylene glycol is polypropylene glycol, The aforementioned diisocyanate is a hydrogenated product of diphenylmethane diisocyanate. [5] The adhesive composition for surface protection sheets according to any one of [1] to [4], wherein the (meth)acrylyl group in the polyurethane (A) is (meth) ) part of the acryloxy group. [6] The adhesive composition for surface protection sheets according to any one of [1] to [5], wherein the polyfunctional monomer (B) has three or more (meth)acrylyl groups. [7] The adhesive composition for surface protection sheets according to [6], wherein the polyfunctional monomer (B) is trimethylolpropane triacrylate. [8] The adhesive composition for surface protection sheets according to [7], wherein the aforementioned other monomer (C) has a (meth)acrylyl group. [9] The adhesive composition for surface protection sheets according to [8], wherein the aforementioned other monomer (C) contains alkyl (meth)acrylate. [10] The adhesive composition for surface protection sheets according to any one of [1] to [9], wherein the aforementioned polyurethane (A) further contains polyurethane (a2), The polyurethane (a2) has a skeleton having a structure derived from a polyoxyalkylene polyol and a polyisocyanate, and only one terminal of the polyurethane (a2) has a (methyl ) acryl-based polyurethane (a2). [11] The adhesive composition for surface protection sheets according to any one of [1] to [10], wherein on a numerical basis, the polyurethane contained in the aforementioned polyurethane (A) 90~100% of the ends of the molecule are introduced into (meth)acrylyl groups. [12] A surface protection sheet having a sheet-like base material and an adhesive layer formed on the base material, The aforementioned adhesive layer is made of a photohardened product of the adhesive composition for surface protection sheets according to any one of [1] to [11]. [Effects of the invention]

According to the present invention, it is possible to provide a surface protection sheet that has low haze, is easy to laminate and peel off, can suppress adhesive residue after peeling, and does not cause cracks in the adhesive layer during cutting processing. Adhesive composition. Furthermore, according to the present invention, it is possible to provide a surface protection sheet that has low haze, is easy to laminate and peel off, can suppress adhesive residue after peeling, and does not cause cracks in the adhesive layer during cutting.

[Form of carrying out the invention]

An embodiment of the present invention will be described below. Here, (meth)acrylyl group refers to one or more types selected from the group represented by the chemical formula CH ₂ =CH-CO- and the functional group represented by the chemical formula CH ₂ =C(CH ₃ )-CO-, (Meth)acryloxy group refers to one selected from the group represented by the chemical formula CH ₂ =CH-CO-O- and the functional group represented by the chemical formula CH ₂ =C(CH ₃ )-CO-O- above. In addition, the isocyanate group refers to a functional group represented by the chemical formula -N=C=O.

<1. Adhesive composition for surface protection sheets> The adhesive composition for surface protection sheets of this embodiment (hereinafter sometimes referred to as "adhesive composition") contains polyurethane (A), a multifunctional monomer (B), and a polyamine group. Formate (A) and polyfunctional monomer (B) are polymerized with other monomers (C) and photopolymerization initiator (D). The polyurethane (A) is a polyurethane having a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate. The aforementioned polyurethane (A) contains polyurethane (a1). The aforementioned polyurethane (a1) has a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and the plural terminals of the aforementioned polyurethane (a1) have (methane) base) acrylic group. The weight average molecular weight of the aforementioned polyurethane (A) is 30,000~200,000. The polyfunctional monomer (B) is a compound having plural (meth)acrylyl groups. Relative to 100% by mass of the total amount of the aforementioned polyurethane (A), the aforementioned polyfunctional monomer (B), and the aforementioned other monomer (C), the content of the aforementioned polyurethane (A) is 30 to 60 mass%, the content of the aforementioned multifunctional monomer (B) is 2 to 10 mass%, and the content of the aforementioned other monomers (C) is 30 to 68 mass%. Moreover, the content of the photopolymerization initiator (D) is 0.1~5 parts by mass is characteristic. In addition, the adhesive composition of this embodiment may contain additives such as fatty acid esters if necessary. In addition, the adhesive composition of this embodiment may not contain a solvent, and may contain a solvent if necessary. Each component contained in the adhesive composition is described below. In addition, in the following description, components composed of polyurethane (A), polyfunctional monomer (B), and other monomers (C) may be referred to as "components (A) to (C). )".

<1-1. Polyurethane (A)> Polyurethane (A) is a polyurethane having a skeleton including a structure derived from polyoxyalkylene polyol and polyisocyanate. Polyurethane (A) contains polyurethane (a1) described below. In order to adjust the cohesive force of the hardened|cured material of an adhesive composition, the polyurethane (A) may further contain the polyurethane (a2) mentioned later.

[Polyurethane (a1)] Polyurethane (a1) has a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and has a (meth)acrylyl group at the plural terminals. . Moreover, the (meth)acrylyl group at the terminal of the polyurethane (a1) is preferably a part of the (meth)acryloxy group.

[Polyurethane (a2)] The polyurethane (a2) has a skeleton containing a structure derived from a polyoxyalkylene polyol and a polyisocyanate, and is a polyurethane having a (meth)acrylyl group at only one terminal. Furthermore, the (meth)acrylyl group at the terminal of the polyurethane (a2) is preferably a part of the (meth)acryloxy group. Moreover, the content of the polyurethane (a1) and the polyurethane (a2) contained in the polyurethane (A), that is, the content of the polyurethane (A) The method for adjusting the number of (meth)acrylyl groups at the terminals of the polyurethane is described in the method for producing the polyurethane (A). An example of the method is described below.

In the present invention, "plural terminals" means two terminals in the case of a linear polymer, and two or more terminals in the case of a branched polymer, the same number of terminals as the number of branches of each branch. The polyurethane (A) does not contain components other than the polyurethane (a1) and the polyurethane (a2).

The polyurethane (a1) contained in the polyurethane (A) is based on the number, preferably 80~100% of the polyurethane (A), and more preferably 90~100% %, and preferably 100%. The polyurethane (a2) contained in the polyurethane (A) is based on the number, preferably 0 to 20% of the polyurethane (A), and more preferably 0 to 10 %, preferably 0%. When the polyurethane (a1) contained in the polyurethane (A) is 80% or more, the cohesive force of the cured product of the adhesive composition becomes sufficiently large.

"Polyoxyalkylene polyol" The polyoxyalkylene polyol is preferably one having an alkylene chain having 2 to 4 carbon atoms. Specific examples of the polyoxyalkylene polyol include polyoxyethylene polyol, polyoxypropylene polyol, and polyoxypropylene polyol. Butyl polyol, etc. Moreover, among the polyoxyalkylene polyols, polyoxyalkylene glycol is preferably used, and polypropylene glycol is particularly preferably used.

In addition, the polyoxyalkylene polyol may contain two or more types of alkylene chains. Furthermore, as the polyurethane (A), the structures derived from two or more different polyoxyalkylene polyols may be a structure in which polyisocyanate is sandwiched and bonded.

The number average molecular weight of the polyoxyalkylene polyol is preferably 500 to 5,000, more preferably 800 to 4,000, and still more preferably 1,000 to 3,000. When the number average molecular weight is 500 or more, the peeling strength of the adhesive layer obtained by hardening the adhesive composition is improved. When the number average molecular weight is 5,000 or less, the polyurethane contains a sufficient amount of urethane bonds, so the cohesion of the adhesive layer increases.

The polyoxyalkylene polyol preferably has two or three hydroxyl groups at the terminal (diol or triol type polyoxyalkylene polyol). For example, in the case of glycol-type polypropylene glycol, the hydroxyl value is preferably 20 to 120 mgKOH/g, more preferably 30 to 100 mgKOH/g, and still more preferably 40 to 80 mgKOH/g. Specific examples of polypropylene glycol include ACTCOL D-2000 (manufactured by Mitsui Chemicals, number average molecular weight 2000, diol type) which has a hydroxyl value of 56 mgKOH/g and a hydroxyl group at the terminal. Here, the hydroxyl value refers to the hydroxyl value of the polyoxyalkylene polyol measured in accordance with JISK0070. When 1 g of the polyoxyalkylene polyol is acetylated, the free acetic acid and the hydrogenation required for neutralization are mg of potassium. Specifically, acetic anhydride is used to acetylate the hydroxyl group in the sample, and the free acetic acid generated at this time can be determined by titration with a potassium hydroxide solution.

"Polyisocyanate" The polyisocyanate is not particularly limited as long as it is a compound having a plurality of isocyanate groups, but diisocyanate is preferred. Examples of diisocyanates include tolylene diisocyanate and its hydrogenated product, xylylene diisocyanate and its hydrogenated product, diphenylmethane diisocyanate and its hydrogenated product, and 1,5-naphthylene diisocyanate. Isocyanates and their hydrogenated products, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexyl diisocyanate , 1,3-bis(isocyanatemethyl)cyclohexane, norbornane diisocyanate, etc.

Among these exemplified compounds, from the viewpoint of control of light resistance and reactivity, the hydrogenated product of isophorone diisocyanate or diphenylmethane diisocyanate is preferred, and from the viewpoint of reactivity, diphenyl is more preferred. Hydrogenated compound of methane diisocyanate. The polyisocyanate-derived structure contained in the polyurethane (A) may be one type, or may include two or more types of structures. Specific examples of the polyisocyanate include hydrogenated products of diphenylmethane diisocyanate (Desmodur W, manufactured by Sumika Covestro Urethane), isophorone diisocyanate (Desmodur I, manufactured by Sumika Covestro Urethane), and the like.

The weight average molecular weight of the polyurethane (A) is 30,000 to 200,000, preferably 50,000 to 150,000, and more preferably 70,000 to 100,000. When the weight average molecular weight of the polyurethane (A) is less than 30,000, the adhesive layer obtained by hardening the adhesive composition will not have sufficient flexibility, and the surface protection sheet containing the adhesive layer will not be easily laminated. In addition, when the weight average molecular weight of the polyurethane (A) exceeds 200,000, the adhesive composition becomes more viscous and becomes difficult to handle, resulting in reduced workability.

The content of polyurethane (A) is 30 to 60 mass%, preferably 35 to 55 mass%, more preferably 40 to 50 mass% relative to the total amount of components (A) to (C). When the content of polyurethane (A) is less than 30% by mass, the cohesion of the hardened material of the adhesive composition is insufficient, and the adhesive layer becomes too soft, causing friction between the adhesive surface (the adhesive layer and the adherend). time), there is a concern about entrapment of air bubbles. When the content of polyurethane (A) exceeds 60% by mass, the cohesion of the hardened material of the adhesive composition is too high, the flexibility of the adhesive layer is insufficient, and the wettability of the adhesive layer to the adherend is reduced. doubts.

＜1-2.Polyfunctional monomer (B)＞ The multifunctional monomer (B) adjusts the peel strength of the adhesive layer (surface protection sheet) of the cured product using the adhesive composition. The polyfunctional monomer (B) is a compound having a plurality of (meth)acrylyl groups, except for the polyurethane (A). When the number of (meth)acrylyl groups is 2 or more, there is no particular limitation. From the viewpoint of curability, the polyfunctional monomer (B) preferably has 3 or more (meth)acrylyl groups.

The polyfunctional monomer (B) is preferably a poly(meth)acrylate of a polyol compound, and examples thereof include polyethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate , 1,3-bis(hydroxyethyl)-5,5-dimethylhydantoin di(meth)acrylate, α,ω-di(meth)acrylyl bisdiethylene glycol benzene Formate, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate Ester, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, diacryloyloxyethyl phosphate, dipentaerythritol trihydroxy(methyl) Acrylate, pentaerythritol tetra(meth)acrylate, etc.

Among these, from the viewpoint that the peel strength of the surface protection sheet using the adhesive composition can be easily reduced and adjusted, 1,6-hexanediol di(meth)acrylate and trimethylolpropane tri(meth)acrylate are more preferred. base) acrylate, dipentaerythritol trihydroxy(meth)acrylate, pentaerythritol tetra(meth)acrylate, and more preferably trimethylolpropane tri(meth)acrylate. In addition, the polyfunctional monomer (B) may be composed of one type of compound, or may be composed of two or more types of compounds.

The content of the polyfunctional monomer (B) is 2 to 10 mass %, preferably 3 to 9 mass %, more preferably 4 to 8 mass % relative to the total amount of components (A) to (C). When the content is less than 2% by mass, the peeling strength of the surface protection sheet is too high and the light peelability is poor. When the content exceeds 10% by mass, the adhesive layer of the cured product using the adhesive composition becomes hard, and cracks may easily occur during cutting of the sheet. In addition, when the content exceeds 10% by mass, the surface protection sheet tends to have high haze.

＜1-3. Other monomers (C)＞ Other monomers (C) are compounds other than polyurethane (A) and polyfunctional monomer (B), which can be combined with polyurethane (A) and multifunctional monomer (B). In the case of polymerization, there is no particular limitation. However, the other monomer (C) serves as a functional group for polymerization with the polyurethane (A) and the multifunctional monomer (B), and preferably has an ethylenically unsaturated bond that can be radically polymerized, wherein , more preferably one having a vinyl group or a (meth)acrylyl group, and still more preferably one having a (meth)acrylyl group.

Other monomers (C) are not particularly limited, and examples thereof include alkyl (meth)acrylate, cyclic alkyl (meth)acrylate, alkoxyalkyl (meth)acrylate, alkoxy ( Polyalkylene glycol (meth)acrylate, hydroxyl-containing (meth)acrylate, carboxyl-containing (meth)acrylate, fluorinated alkyl (meth)acrylate, dialkylaminoalkane (meth)acrylate, (meth)acrylamide, (meth)acrylate containing epoxy group, unsaturated carboxylic acid, etc.

Examples of alkyl (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, and n-butyl (meth)acrylate. ester, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-hexyl (meth)acrylate acrylate, isooctyl (meth)acrylate, isoctadecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, etc.

Examples of cyclic alkyl (meth)acrylates include cyclohexyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, and norbornyl (meth)acrylate. ) Acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentyloxyethyl ( Meth)acrylate, etc.

Examples of alkoxyalkyl (meth)acrylates include ethoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, and butoxyethyl (meth)acrylate. , 2-methoxyethoxyethyl (meth)acrylate, 2-ethoxyethoxyethyl (meth)acrylate, etc.

Alkoxy (poly) alkylene glycol (meth)acrylate includes, for example, methoxy diethylene glycol (meth)acrylate, ethoxy diethylene glycol (meth)acrylate, methoxy diethylene glycol (meth)acrylate, Dipropylene glycol (meth)acrylate, etc.

Examples of (meth)acrylates containing hydroxyl groups include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1 ,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate, 3-methylpentane Alcohol mono(meth)acrylate, etc.

Examples of carboxyl group-containing (meth)acrylates include β-carboxyethyl (meth)acrylate.

Examples of fluorinated alkyl (meth)acrylates include octafluoropentyl (meth)acrylate and the like.

Examples of dialkylaminoalkyl (meth)acrylates include N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate. Acrylic etc.

Examples of (meth)acrylamide include (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, and N-propyl(methyl)acrylamide. ) Acrylamide, N-isopropylacrylamide, N-hexyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(methyl ) acrylamide, (meth)acrylamide, diacetone acrylamide, etc.

Examples of the epoxy group-containing (meth)acrylate include glycidyl (meth)acrylate. Examples of unsaturated carboxylic acids include (meth)acrylic acid, maleic acid, itaconic acid, and the like.

In addition, other monomers (C), excluding the above-mentioned compounds, include, for example, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, Vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, N-vinylpyridine, N-vinylpyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol, Hydroxybutyl vinyl ether, hydroxyethyl vinyl ether, 4-hydroxymethylcyclohexyl methyl vinyl ether, triethylene glycol monovinyl ether or diethylene glycol monovinyl ether, methyl vinyl ketone, N-acrylamide Aminomethyltrimethylammonium chloride, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, etc.

Among these exemplified compounds, from the viewpoint of compatibility with polyurethane (A), viscosity of the adhesive composition, and adjustment of peel strength, alkyl (meth)acrylate is preferred, and more preferred is alkyl (meth)acrylate. Preferably, it is 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isostearyl (meth)acrylate, isobornyl (meth)acrylate, and more preferably 2-Ethylhexyl(meth)acrylate. Moreover, the other monomer (C) may be composed of one type of compound, or may be composed of two or more types of compounds.

The content of other monomers (C) is 30 to 68 mass %, preferably 35 to 62 mass %, more preferably 40 to 56 mass % relative to the total amount of components (A) to (C). When the content is less than 30% by mass, the cohesion of the hardened material of the adhesive composition is too high, the flexibility of the adhesive layer is insufficient, and the wettability of the adherend may be reduced. When the content is higher than 68% by mass, the cohesion of the hardened material of the adhesive composition becomes smaller, the adhesive layer is too soft, and there is a concern that bubbles may be trapped on the adhesive surface (between the adhesive layer and the adherend).

<1-4. Photopolymerization initiator (D)> The photopolymerization initiator (D) is not particularly limited, and examples thereof include carbonyl-based photopolymerization initiators, sulfur-based photopolymerization initiators, acyl-based phosphorus oxide-based photopolymerization initiators, and quinone-based photopolymerization initiators. Sulfonyl chloride photopolymerization initiator, thioxanthone photopolymerization initiator, etc.

Examples of carbonyl-based photopolymerization initiators include benzophenone, diphenylethylenedione, benzoin, ω-bromoacetophenone, chloroacetone, acetophenone, and 2,2-diethoxybenzene. Ethyl ketone, 2,2-dimethoxy-2-phenylacetophenone, p-dimethylaminoacetophenone, p-dimethylaminoacetophenone, 2-chlorobenzophenone, 4 ,4'‐dichlorobenzophenone, 4,4'‐bisdiethylaminobenzophenone, Michler's ketone, benzoin methyl ether, benzoin isobutyl ether, benzoin‐n ‐Butyl ether, benzyl methyl acetal, 1‐hydroxycyclohexyl phenyl ketone, 2‐hydroxy‐2‐methyl‐1‐phenyl‐propan‐1‐one, 1‐(4‐isopropylphenyl )‐2‐Hydroxy‐2‐Methylpropane‐1‐one, Toluylcarbamate, 2,2‐diethoxyacetophenone, 4‐N,N'‐Dimethylphenyl ketone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane-1-one, etc.

Examples of the sulfur-based photopolymerization initiator include diphenyl disulfide, bibenzyl disulfide, tetraethylthiuram disulfide, tetramethylammonium monosulfide, and the like.

Phosphine oxide is a photopolymerization initiator, and examples thereof include 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,4,6 - trimethylbenzoyldiphenylphosphine oxide. Phenylethoxyphosphine oxide, etc.

Examples of the quinone-based photopolymerization initiator include quinone-based photopolymerization initiators such as benzoquinone and anthraquinone.

Sulfonyl chloride is a photopolymerization initiator, and examples thereof include 2-naphthalene sulfonyl chloride and the like.

Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, and the like.

Among these exemplified compounds, from the viewpoint of the transparency of the adhesive layer obtained by hardening the adhesive composition, 1-hydroxycyclohexyl phenyl ketone and 2,4,6-trimethylbenzoyl ketone are preferred. diphenylphosphine oxide. Moreover, the photopolymerization initiator (D) may be composed of one type of compound, or may be composed of two or more types of compounds.

The content of the photopolymerization initiator (D) is 0.1~5 parts by mass, preferably 0.2~3 parts by mass, more preferably 0.3~2 parts by mass relative to 100 parts by mass of the total amount of components (A)~(C) share. When the content of the photopolymerization initiator (D) is less than 0.1 parts by mass, the adhesive composition is not sufficiently photohardened. When it exceeds 5 parts by mass, many low molecular weight components are generated, and the peelability of the resulting surface protection sheet is deteriorated. tendency.

＜1-5.Additive＞ In the adhesive composition, fatty acid esters may be added when necessary in order to improve the lamination properties (wetting properties) and defoaming properties (ease of removing air bubbles trapped during lamination) of the surface protection sheet obtained. Examples of fatty acid esters include monobasic acids with 8 to 18 carbon atoms, esters of polybasic acids and branched alcohols with 18 or less carbon atoms, unsaturated fatty acids with 14 to 18 carbon atoms, or branched fatty acids. Esters of acids and 4-valent alcohols, etc. Preferred specific examples of the fatty acid ester include isopropyl myristate. The amount of fatty acid ester added is preferably 1 to 40 parts by mass, more preferably 3 to 35 parts by mass, and still more preferably 5 to 30 parts by mass relative to 100 parts by mass of the total amount of components (A) to (C). share.

In addition, other additives may be added to the adhesive composition if necessary as long as the transparency is not impaired. Examples of additives include plasticizers, surface lubricants, flattening agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, light stabilizers such as benzotriazole series, and phosphate ester series. And other flame retardants, such as surfactants, antistatic agents, dyes, etc.

＜1-6. Solvent＞ Since the adhesive composition contains the polyfunctional monomer (B) and other monomers (C) as low molecular weight components, it can be adjusted to a coatable viscosity even without adding a solvent. That is, the adhesive composition must be composed of the aforementioned polyurethane (A), the aforementioned multifunctional monomer (B), the aforementioned other monomers (C) and the photopolymerization initiator (D). In addition to the ingredients, it may not substantially contain solvents. In this case, when manufacturing the surface protection sheet, the step of heating and drying the solvent can be omitted, thereby improving productivity. Especially when producing a surface protection sheet with a film thickness exceeding 50 μm, it is preferable that the adhesive composition substantially does not contain this solvent. The term “substantially free” in the present invention means that the content of the aforementioned solvent in the adhesive composition of the present invention is 0 to 1 mass %, preferably 0 to 0.5 mass %, and more preferably 0 to 0.1 mass %. A solvent may also be added to the adhesive composition to adjust the viscosity during coating. The solvent can be appropriately selected depending on other components contained in the adhesive composition, and is preferably an organic solvent. Organic solvents that can be used are not particularly limited, and examples include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol, and isopropanol. Propanol etc. These organic solvents may be used individually or in mixture of two or more types. The solvent-based adhesive composition is preferably applied to a base material, etc., and then removed by drying, and then photocured.

＜2. Manufacturing method of adhesive composition for surface protection sheet＞ Moreover, here, an example of the synthesis method of the polyurethane (A) is explained, but the polyfunctional monomer (B) and other monomers (C) and other components contained in the adhesive composition for surface protection sheets The ingredients are easy to purchase as commercial products, and there are various synthesis methods depending on the types of compounds used, so the description of the synthesis method is omitted.

<2-1. Synthesis method of polyurethane (A)> An example of a preferred synthesis method of the polyurethane (A) contained in the adhesive composition of this embodiment will be described below. However, the synthesis method of the polyurethane (A) is not limited to this, because the synthesis method is The conditions of raw materials or equipment can be changed appropriately. Furthermore, in this example, in any step of the reaction between the hydroxyl group and the isocyanate group, dibutyltin dilaurate, dibutyltin diethylhexanoate, dibutyltin dilaurate, and dibutyltin dilaurate are used in any step in the presence of an organic solvent inert to the isocyanate group. Carbamate catalyst such as octyltin dilaurate is used for the reaction. The reaction is preferably continued at 30 to 100°C for 1 to 5 hours. The usage amount of the urethanization catalyst is relative to the total mass of the reactants, and is preferably 50 to 500 ppm by mass.

First, polyoxyalkylene polyol and polyisocyanate are added in a ratio such that the amount of isocyanate groups (on a numerical basis, the same below) is greater than the amount of hydroxyl groups (on a numerical basis, the same below), and these reactions are carried out to synthesize an isocyanate group at the end. of polyurethane. Specific examples of the polyoxyalkylene polyol and the polyisocyanate are as exemplified by the polyurethane (A).

At this time, the molecular weight (polymerization degree) can be adjusted by adjusting the amount of isocyanate groups relative to the amount of hydroxyl groups. Specifically, the smaller the excess amount of isocyanate groups relative to the amount of hydroxyl groups, the greater the molecular weight of the polyurethane having isocyanate groups, and the larger the excess amount of isocyanate groups relative to the amount of hydroxyl groups, the greater the molecular weight of the polyurethane having isocyanate groups. The molecular weight of the polyurethane is smaller.

Next, a polyurethane having an isocyanate group at the end is reacted with a compound having a hydroxyl group and a (meth)acrylyl group to synthesize a polyurethane having a (meth)acrylyl group at the end of the molecular chain. (A). Furthermore, the (meth)acrylyl group contained in this compound is preferably a part of the (meth)acryloxy group.

The compound having a hydroxyl group and a (meth)acrylyl group is not particularly limited, and examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Hydroxyalkyl (meth)acrylate such as acrylate; 1,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 1,6- Monols having (meth)acrylyl groups derived from various polyols, such as hexanediol mono(meth)acrylate, 3-methylpentanediol mono(meth)acrylate, etc. These can be used individually or in combination of two or more types. Among them, 2-hydroxyethyl (meth)acrylate is preferred from the viewpoint of reactivity with isocyanate groups and photocurability.

Furthermore, in addition to the compound having a hydroxyl group and a (meth)acrylyl group, an alkyl alcohol having one hydroxyl group and a polyurethane having an isocyanate group at the terminal is used in combination, without having a (meth)acrylyl group. reaction, the amount of (meth)acrylyl group introduced can be adjusted. The alkyl alcohol is not particularly limited, and examples thereof include linear, branched, and alicyclic alkyl alcohols. These may be used alone or in combination of two or more types. Thereby, a polyurethane having a structure derived from the above-mentioned alkyl alcohol at at least either terminal is produced. At this time, the polyurethane (A) includes a polyurethane that does not have a (meth)acryl group at at least one terminal. Therefore, a polyurethane (a2) having a (meth)acrylyl group at only one terminal may be included.

On a numerical basis, it is preferable that 90 to 100% of the terminal ends of the polyurethane contained in the polyurethane (A) are introduced with (meth)acrylyl groups, and more preferably 95 to 100%. And even better is 100%. When the introduced amount of (meth)acryl groups is 90% or more on a numerical basis relative to the isocyanate group, the cohesive force of the adhesive layer obtained by curing the adhesive composition can be sufficiently obtained. The ratio of the number of terminals introduced with (meth)acrylyl groups relative to the number of terminals of the entire polyurethane molecular chain can be measured by IR, NMR, etc.

<2-2. Modification of the synthesis method of polyurethane (A)> Modifications of the synthesis method of polyurethane (A) will be described. In addition, this example is the same as the above example. In any step of the reaction between the hydroxyl group and the isocyanate group, dibutyltin dilaurate, dibutyltin diethylhexanoate, The reaction is carried out with a urethanation catalyst such as dioctyltin dilaurate. The reaction is preferably continued at 30 to 100°C for 1 to 5 hours. The usage amount of the urethanization catalyst is relative to the total mass of the reactants, and is preferably 50 to 500 ppm by mass. In this modification, first, polyoxyalkylene polyol and polyisocyanate are reacted in a ratio in which the amount of hydroxyl groups is greater than the amount of isocyanate groups, thereby synthesizing a polyurethane having a hydroxyl group at the terminal.

In this case, as in the above example, the molecular weight can be adjusted by adjusting the amount of hydroxyl groups relative to the amount of isocyanate groups. Specifically, the smaller the excess amount of hydroxyl groups relative to the amount of isocyanate groups, the greater the molecular weight of the polyurethane having hydroxyl groups, and the larger the excess amount of hydroxyl groups relative to the amount of isocyanate groups, the greater the molecular weight of the polyurethane having hydroxyl groups. The molecular weight of urethane is smaller.

Next, a polyurethane having a hydroxyl group at the end is reacted with a compound having an isocyanate group and a (meth)acrylyl group to synthesize a polyurethane having a (meth)acrylyl group at the end of the molecular chain. (A). Furthermore, the (meth)acrylyl group contained in this compound is preferably a part of the (meth)acryloxy group.

The compound having an isocyanate group and a (meth)acrylyl group is not particularly limited, and examples thereof include 2-(meth)acryloxyethyl isocyanate, 2-(meth)acryloxypropyl isocyanate, and 1, 1-Bis(acrylyloxymethyl)ethyl isocyanate, etc. Examples of commercially available compounds having an isocyanate group and a (meth)acrylyl group include Karenz MOI (registered trademark) or KarenzAOI (registered trademark) manufactured by Showa Denko Co., Ltd. These can be used individually or in combination of two or more types. Among them, from the viewpoint of reactivity with hydroxyl groups and photocurability, 2-(meth)acryloxyethyl isocyanate is preferred.

Furthermore, in addition to the compound having an isocyanate group and a (meth)acrylyl group, an alkyl isocyanate having one isocyanate group and a polyaminomethyl group having a hydroxyl group at the terminal is used in combination, which does not have a (meth)acrylyl group. Acid ester reaction can adjust the amount of (meth)acrylyl group introduced. The alkyl isocyanate is not particularly limited, and examples thereof include linear, branched, and alicyclic alkyl isocyanates. These may be used alone or in combination of two or more types. Thereby, a polyurethane having a structure derived from the above-mentioned alkyl isocyanate at at least one terminal is produced. In this case, the polyurethane (A) includes a polyurethane that does not have a (meth)acrylyl group at at least one terminal. Therefore, in this case, the polyurethane (A) may contain a polyurethane having a (meth)acrylyl group at only one terminal.

On a numerical basis, it is preferable that (meth)acrylyl groups are introduced into 90 to 100% of the ends of the polyurethane contained in the polyurethane (A), and more preferably 95 to 100%. Better is 100%. When the introduced amount of (meth)acryl groups is 90% or more on a numerical basis relative to the isocyanate group, the cohesive force of the adhesive layer obtained by curing the adhesive composition can be sufficiently obtained.

<2-3. Mixing method of each component contained in the adhesive composition for surface protection sheets> By mixing polyurethane (A), multifunctional monomer (B), other monomers (C), photopolymerization initiator (D), fatty acid ester added if necessary, and other additives , and organic solvents to produce adhesive compositions. The mixing method is not particularly limited. For example, a homogeneous disperser or a stirring device equipped with a stirring blade such as a blade or the like can be used.

In addition, all the components may be added at once and mixed, or each component may be divided into multiple times and added and mixed repeatedly. In addition, if there is a solid component at room temperature, it can be added in a form that is dissolved in a solvent or dispersed in a dispersion medium, or added in a form that is melted by heating. This component can easily be added with high uniformity in the adhesive composition. Sex is mixed.

＜3. Surface protection sheet＞ ＜3-1. Composition of surface protection sheet＞ The surface protection sheet of this embodiment has an adhesive layer including a cured product of the above-mentioned adhesive composition formed on one side of the base material. The thickness of the adhesive layer is preferably 3~150 μm, more preferably 5~130 μm, and more preferably 10~100 μm. When the film thickness of the adhesive layer is 3 μm or more, the strength of the adhesive layer is sufficient. When the film thickness is less than 150 μm, the control of the film thickness of the adhesive layer is easy. In addition, when the function of protecting the adherend from impact (impact resistance) is to be imparted to the surface protection sheet, the film thickness of the adhesive layer is preferably 50 μm or more.

The gel fraction of the hardened material of the adhesive composition contained in the adhesive layer is preferably 85 to 100 mass %, more preferably 90 to 100 mass %, and still more preferably 95 to 100 mass %. Here, the gel fraction refers to the mass fraction of the insoluble components extracted by the solvent. Here, the solvent is selected as an uncrosslinked component that can be dissolved in the hardened material of the adhesive composition. In addition, examples of specific measurement methods of the gel fraction will be described later in the Examples. When the gel fraction of the hardened material of the adhesive composition is 85 to 100% by mass, when the surface protection sheet is peeled off, part of the adhesive layer remains on the adherend, so-called adhesive residue can be suppressed.

The material of the base material can be appropriately selected according to the purpose of the surface protection sheet, and examples thereof include resin films. The surface protection sheet is used, for example, as a protective sheet in the manufacturing process. When inspecting the adherend, that is, when the product is sometimes damaged or has foreign matter, it is better to make the base material transparent when the protective sheet is laminated. Examples of the transparent base material include polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, cellulose, and the like.

The thickness of the base material can be appropriately selected according to the use of the surface protection sheet, and is not particularly limited. In the case of a resin film, the thickness of the base material is preferably 5 μm or more, more preferably 10 μm or more, and more preferably from the viewpoint of operability and strength. Preferably, it is above 20 μm. In addition, when considering the flexibility of the resin film, the thickness of the base material is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

Moreover, as a base material, it is preferable to use the thing which has been antistatically treated. The antistatic treatment applied to the base material is not particularly limited, and a method of providing an antistatic layer on at least one side of the base material, a method of mixing an antistatic agent into the base material, etc. can be used. In addition, on the surface of the base material on which the adhesive layer is formed, easy adhesion treatments such as acid treatment, alkali treatment, primer treatment, corona treatment, plasma treatment, ultraviolet treatment, and ozone treatment can be performed when necessary.

For the surface protection sheet, for the purpose of protecting the adhesive layer, a separator can be laminated on the surface of the adhesive layer. As the material of the separator, for example, paper, plastic film, etc. can be used. From the viewpoint of excellent surface smoothness, plastic film is preferred. The plastic film used as a separator is not particularly limited as long as it can protect the adhesive layer, and examples thereof include polyethylene, polypropylene, polyethylene terephthalate, and polybutylene.

＜3-2. Manufacturing method of surface protection sheet＞ The surface protection sheet of this embodiment can be manufactured by, for example, coating an adhesive composition on a base sheet, laminating a separator, and then irradiating the coated adhesive composition with ultraviolet rays to cure it by light.

The method of applying the adhesive composition to the base material is not particularly limited and can be appropriately selected. For example, methods for coating the adhesive composition on the substrate include gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, coating rod, and blade coating. machine, spray coater, notch wheel coater, direct coater, various coating machine methods, screen printing method, etc.

In addition, examples of the light source for photohardening the adhesive composition include black light, low-pressure mercury lamp, high-pressure mercury lamp, ultra-high-pressure mercury lamp, metal halide lamp, xenon lamp, and the like. The intensity of light irradiation is sufficient as long as it can fully harden the adhesive composition, for example, 50~3000mW/ ^cm2 is preferred. In addition, when the intensity of light irradiation is weak, hardening takes time, so productivity decreases. When irradiating light to make it transparent, it can be from either the separator side or the base material side.

＜3-3. Purpose and required performance of surface protection sheet＞ During the inspection step, it is required that minute foreign matter or damage to the product or parts can be adequately discovered or detected while the protective sheet is laminated on the product or part. In addition, the protective sheet is also suitable for use to protect optical elements such as polarizers, wavelength plates, phase difference plates, optical compensation films, reflective sheets, brightness enhancement films, etc. used in liquid crystal displays of smartphones, personal computers, televisions, etc. The surface of the plastic film used.

When the surface protection sheet of this embodiment is used as such a protective sheet, the surface protection sheet is required to have low turbidity, that is, low haze. At this time, the haze value of the surface protection sheet is preferably 2.0% or less, more preferably 1.5% or less, and still more preferably 1.0% or less. The specific method of measuring the haze value of the surface protection sheet will be described later in the Examples.

Furthermore, when the surface protection sheet of this embodiment is used as the above-mentioned protective sheet, the surface protection sheet requires a minimum peel strength in order to avoid peeling off from the product or part during transportation and other processes. When peeling the surface protection sheet from a product or part, it is necessary to reduce the peel strength in order to facilitate the peeling operation or to prevent the product or part from being deformed or damaged during peeling. From this point of view, when the peeling speed is 3.0m/min, the peeling strength of the surface protection sheet varies depending on the thickness of the base material and the adhesive layer. When the adhesive layer is 50~100μm, it is preferably 1~50gf. /25mm, preferably 2~45gf/25mm, and even better 3~40gf/25mm. The specific method for measuring the peel strength of the surface protection sheet is as described in the Examples. [Example]

The present invention will be described in detail below through examples. The present invention is not limited to the examples shown below. Moreover, in the following examples, the weight average molecular weight of the obtained polyurethane (A) was determined by colloidal permeation chromatography (Shodex (registered trademark) GPC-101 manufactured by Showa Denko Co., Ltd., hereinafter referred to as GPC). The measured polystyrene converted value. The measurement conditions of GPC are as follows. Pipe string: LF-804 made by Showa Denko Co., Ltd. Tube string temperature: 40℃ Sample: 0.2 mass% tetrahydrofuran solution of polyurethane (A) Flow rate: 1ml/minute Eluate: Tetrahydrofuran Detector: RI detector (differential refractive index detector)

＜Synthesis of polyurethane (A)＞ (A-1) Into a reactor equipped with a thermometer, a stirrer, a dropping funnel, and a condenser tube with a drying tube, 5.5 kg (21 mol) of hydride of diphenylmethane diisocyanate (Desmodur W, manufactured by Sumika Covestro Urethane) and hydroxyl group were added. It was 56 mgKOH/g, and 40.1 kg (20 mol) of polypropylene glycol ACTCOL D-2000 (manufactured by Mitsui Chemicals, number average molecular weight 2000) having a hydroxyl group at the terminal. Then, the temperature of the reactor was raised to 60°C, and the reaction was carried out for 4 hours to obtain a polyurethane having isocyanate groups at both ends.

Next, 232.2 g (2 mol) of 2-hydroxyethyl acrylate was added to the reactor, the temperature was raised to 70°C, and the reaction was carried out for 2 hours to obtain 45.8 kg of polyurethane (A-1) having an acryl group at the end. By IR analysis of this polyurethane (A-1), it was confirmed that the peak derived from the isocyanate group disappeared. The weight average molecular weight of the obtained polyurethane (A-1) was 70,000. Since it was confirmed by IR that the peak originating from the isocyanate group disappeared, 2-hydroxyethyl acrylate was added to all terminals of the polyurethane having isocyanate groups at both terminals. That is, on a numerical basis, 100% of the terminals of the polyurethane molecules contained in the polyurethane (A-1) are introduced with acryl groups.

(A-2) In addition to using isophorone diisocyanate (DesmodurI, manufactured by Sumika Covestro Urethane) instead of the hydrogenated product of diphenylmethane diisocyanate, a polyurethane having propylene at both ends is obtained by the same synthesis method as the polyurethane (A-1). Carboxylic polyurethane (A-2). The weight average molecular weight of the obtained polyurethane (A-2) was 67,000.

(A-3) In addition to changing the hydride of diphenylmethane diisocyanate to 8 mol, and the polypropylene glycol ACTCOL D-2000 (manufactured by Mitsui Chemicals, number average molecular weight 2000) with a hydroxyl group at the end of the hydroxyl value of 56 mgKOH/g to 7 mol, The synthesis method of urethane (A-1) also obtains polyurethane (A-3) having acryl groups at both ends. The weight average molecular weight of the obtained polyurethane (A-3) was 35,000.

(A-4) In addition to changing the hydride of diphenylmethane diisocyanate to 4 mol, and the polypropylene glycol ACTCOL D-2000 (Mitsui Chemical Co., Ltd.) with a hydroxyl group at the end of the hydroxyl value of 56 mgKOH/g to 3 mol, the same as the polyurethane ( The synthesis method of A-1) also obtains polyurethane (A-4) having an acryl group at the terminal. The weight average molecular weight of the obtained polyurethane (A-4) was 12,000.

(A-5) In addition to using 1.8 mol of 2-hydroxyethyl acrylate and 0.2 mol of 1-octanol, replacing 2 mol of 2-hydroxyethyl acrylate, the synthesis method of polyurethane (A-1) is the same as that of polyurethane (A-1). Or polyurethane (A-5) of a polyurethane mixture having an acryl group at one end. The weight average molecular weight of the obtained polyurethane (A-5) was 69,000. Since the peak originating from the isocyanate group disappeared when confirmed by IR, 2-hydroxyethyl acrylate or 1-octanol was added to all terminals of the polyurethane having isocyanate groups at both terminals. That is, on a numerical basis, acryl groups are introduced into 90% of the ends of the polyurethane molecules contained in the polyurethane (A-5). At this time, the polyurethane (a1) contained in the polyurethane (A-5) is 80% of the polyurethane (A) on a numerical basis, and the polyurethane (a1) a2) On a numerical basis, it is 20% of polyurethane (A).

＜Preparation of adhesive composition for surface protection sheets＞ Polyurethane resin (A), polyfunctional monomer (B), other monomers (C), photopolymerization initiator (D) and additives were prepared with the composition listed in Table 1, at 25°C. , mixed using a disperser to prepare adhesive compositions of Examples 1 to 9 and Comparative Examples 1 to 4.

<Preparation of Surface Protection Sheet> For Examples 1 to 9 and Comparative Examples 1 to 4, a surface protection sheet having a base material of an optical PET film on one side was produced in the same manner. First, use an applicator to apply the prepared adhesive composition on an optical PET film (A4300 manufactured by Toyobo Co., Ltd.) with a thickness of 75 μm as a separator, and cover the coated adhesive composition with a thickness of 75 μm. Peeling PET film (E7006 manufactured by Toyobo Co., Ltd.). Next, an ultraviolet irradiation device (made by EYE GRAPHICS Co., Ltd., UV irradiation device 3kW, high-pressure mercury lamp) was used to irradiate the sheet covered with the peeled PET film with ultraviolet rays from the side of the peeled PET film to light-harden the adhesive composition. The irradiation distance of ultraviolet rays is 25cm, the moving speed of the lamp is 1.0m/min, and the irradiation amount is 1000mJ/cm ² . The thickness of the hardened adhesive layer is calculated by using a dial gauge to measure the thickness of the surface protection sheet after peeling off the separator, and then subtracting 75 μm from the base material thickness from the measured value. The measuring surface of the thickness gauge is a circular plane with a diameter of 5mm, and the measuring force is 0.8N. Examples 1 to 9 and Comparative Examples 1 to 4 are all 75 μm.

<Evaluation of adhesive compositions for surface protection sheets and surface protection sheets> Regarding the adhesive compositions and surface protection sheets of Examples 1 to 9 and Comparative Examples 1 to 4, the gel fraction, transparency (haze value), peel strength, and lamination property (moisturizing properties) were evaluated by the methods described below. Moisture), adhesive residue on the adherend, and cracks in the adhesive layer when cutting. The results are shown in Table 1.

(gel fraction) First, the adhesive compositions of Examples 1 to 9 and Comparative Examples 1 to 4 were applied to a 50 μm thick release PET film (HY-S10 manufactured by Toyama Film Co., Ltd.) using an applicator and allowed to harden. The thickness of the adhesive layer was 75 μm. In addition, the method for confirming the thickness of the adhesive layer is the same as the above-mentioned measurement method for the production of surface protection sheets.

Next, the adhesive composition on the peeled PET film was covered with a 75 μm thick peeled PET film (E7006 manufactured by Toyobo Co., Ltd.). Next, an ultraviolet irradiation device (made by EYE GRAPHICS Co., Ltd., UV irradiation device 3kW, high-pressure mercury lamp) was used to irradiate ultraviolet rays from the surface of the 75 μm-thick peeled PET film side of the adhesive composition covered with the peelable PET film on both sides, so that the adhesive The composition is photohardened. The irradiation distance of ultraviolet rays is 25cm, the moving speed of the lamp is 1.0m/min, and the irradiation amount is 1000mJ/cm ² .

The prepared sheet was cut into a size of 100 mm × 100 mm, and the PET film was peeled off from both sides of the hardened material of the adhesive composition to serve as a sample for measurement. This measurement sample was immersed in 50 ml of toluene at 25°C for 24 hours, and then dried at 80°C for 5 hours. From the mass of the measurement sample before and after toluene immersion, the gel fraction was calculated by the following formula (1) . The results are shown in Table 1. Gel fraction (mass %)=[A/B]×100 (1) A: The dry mass of the sample for measurement after immersion in toluene (mass without toluene) B: The mass of the sample for measurement before immersion in toluene

(Haze value) The surface protection sheets with separators prepared in Examples 1 to 9 and Comparative Examples 1 to 4 were cut into a size of 50 mm × 50 mm, and the peeled PET film was peeled off. Then, the entire exposed adhesive layer was laminated on the glass plate, and a rubber roller (diameter: 85mm, width: 50mm) with a mass of 2kg (load: 19.6N) was reciprocated once to prepare a sample for measurement. Regarding this measurement sample, the haze value was measured using a haze meter (NM-150 (manufactured by Murakami Color Technology Research Institute, Inc.)). The haze value (%) is calculated by dividing the diffusion transmittance by the total light transmittance and multiplying by 100. In addition, the measurement was performed on the same sample at three locations, and the average value was used as the haze value.

(peel strength) The surface protection sheets with separators produced in Examples 1 to 9 and Comparative Examples 1 to 4 were cut into sizes of 25 mm × 150 mm, and the peeled PET films were peeled off. Then, the entire exposed adhesive layer was laminated on the glass plate, and a rubber roller (diameter: 85mm, width: 50mm) with a mass of 2kg (load: 19.6N) was reciprocated once to prepare a sample for measurement. The obtained measurement sample was placed in an environment with a temperature of 23°C and a relative humidity of 50% for 1 hour. Then, in accordance with JIS K 6854-2, a tensile test in the 180° direction was performed at peeling speeds of 0.3m/min and 3.0m/min to measure the peeling strength of the surface protection sheet to the glass plate (gf/25mm).

(Stacked) FIG. 1 is a plan view showing a method for evaluating the lamination properties of the surface protection sheet 10 , and FIG. 2 is a cross-sectional view taken along line A-A in FIG. 1 . Cut the surface protection sheet 10 with the separator into a size of 20 mm × 100 mm, and peel off the PET film. Secondly, the adhesive layer 12 is attached to the glass plate 30 in the range from one end of the length direction of the surface protection sheet 10 to 15 mm, and the adhesive part is fixed to the glass plate 30. As shown in Figure 2, lift up the surface protection sheet 10. the other end. The fixing method of the adhesive part is as shown in Figure 1, in the range from the above-mentioned end of the surface protection sheet 10 to 15mm, so that the top surface of the surface protection sheet 10 and both outer sides of the width direction of the surface protection sheet cover the glass plate. Method 20. Apply cellophane tape.

From this state, release the other end of the surface protection sheet 10, measure the time until the entire adhesive layer adheres to the glass plate 30 based on the weight of the surface protection sheet 10, and evaluate Examples 1 to 9 and comparison using the following criteria. Lamination properties of surface protection sheets in Examples 1 to 4. (Evaluation criteria for layering properties) ◎: Less than 5 seconds until close adhesion ○: More than 5 seconds and less than 10 seconds until close adhesion △: Until close adhesion, more than 10 seconds, less than 15 seconds ×: It takes more than 15 seconds to become tightly adhered, or it is not tightly adhered.

(adhesive residue) The surface protection sheets with separators prepared in Examples 1 to 9 and Comparative Examples 1 to 4 were cut into a size of 50 mm × 50 mm, and the peeled PET film was peeled off. Then, the exposed adhesive area was laminated on a glass plate to serve as a sample. After this sample was left at 85°C and a relative humidity of 85% for 3 days, the surface protective sheet was peeled off from the glass plate to visually confirm the adhesive residue on the surface of the glass plate, and the following criteria were used for evaluation.

(Evaluation criteria for adhesive residue) ○: The surface of the glass plate is unchanged from before lamination. △: It is confirmed that there is slight adhesive residue on the surface of the glass plate. ×: On the surface of the glass plate, it is confirmed that there is obvious adhesive residue.

(Cracks in the adhesive layer when cutting) The surface protection sheets produced in each of Examples 1 to 9 and Comparative Examples 1 to 4 were cut using a serrated knife (blade height: 0.80 mm, knife angle: 50° (manufactured by Tsukatani Knife Seisakusho Co., Ltd.)), and the adhesion after cutting was The end surface of the agent layer was evaluated using a microscope (magnification: 800 times (RH-2000 manufactured by Hirox Corporation)) using the following criteria.

(Evaluation criteria for cracks) ○: Cracks were confirmed in the adhesive layer. ×: No cracks were confirmed in the adhesive layer.

<Evaluation results of Examples and Comparative Examples> According to the above Examples and Comparative Examples, the composition of Comparative Example 1 in which the content of polyurethane (A) is 10% by mass shows adhesive residue. Moreover, the composition of Comparative Example 2 using polyurethane (A-4) with a weight average molecular weight of 12,000 as the polyurethane (A) had insufficient lamination properties and residual adhesive was observed. In addition, the composition of Comparative Example 3, which did not contain the polyfunctional monomer (B), had too high peel strength and insufficient lamination properties. The polyfunctional monomer (B) was 15% by mass of the composition of Comparative Example 4. The adhesive layer was hard and cracked when cut.

10: Surface protection sheet 12: Adhesive layer 14:Substrate 20: Cellophane tape 30:Glass plate

[Fig. 1] A plan view showing a method for evaluating lamination properties of surface protection sheets. [Figure 2] A-A cross-sectional view in Figure 1.

Claims (13)

An adhesive composition for surface protection sheets, which contains polyurethane (A), multifunctional monomer (B), polyurethane (A) and multifunctional monomer (B) An adhesive composition for surface protection sheets polymerized with other monomers (C) and photopolymerization initiator (D), characterized in that: the aforementioned polyurethane (A) is composed of polyoxyalkanes derived from The polyurethane has the structure of a polyol and a skeleton derived from the structure of polyisocyanate. The aforementioned polyurethane (A) includes polyurethane (a1), and the aforementioned polyurethane (A) a1) has a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and the plural terminals of the aforementioned polyurethane (a1) have (meth)acryl groups, and the aforementioned polyamine The weight average molecular weight of the polyurethane ester (A) is 30,000~200,000, and the aforementioned multifunctional monomer (B) is a compound with a plurality of (meth)acrylyl groups. Compared with the aforementioned polyurethane ester (A) With the total amount of the aforementioned multifunctional monomer (B) and the aforementioned other monomer (C) being 100% by mass, the content of the aforementioned polyurethane (A) is 30 to 60% by mass, and the aforementioned multifunctional monomer ( The content of B) is 4 to 8 mass%, and the content of the aforementioned other monomers (C) is 30 to 68 mass%. Compared with the aforementioned polyurethane (A) and the aforementioned multifunctional monomer (B) and The total amount of the aforementioned other monomers (C) is 100 parts by mass, and the content of the photopolymerization initiator (D) is 0.1 to 5 parts by mass. The adhesive composition for surface protection sheets according to claim 1, wherein the structure derived from the polyoxyalkylene polyol contained in the polyurethane (A) is derived from a polyoxyalkylene polyol with a number average molecular weight of 500 to 5,000. Structure of alkylene polyols. The adhesive composition for surface protection sheets according to claim 1 or 2, wherein the polyurethane (A) contains a copolymer of polyoxyalkylene glycol and diisocyanate as the skeleton. The adhesive composition for surface protection sheets of claim 1 or 2, wherein the polyoxyalkylene glycol is polypropylene glycol, and the diisocyanate is a hydrogenated product of diphenylmethane diisocyanate. The adhesive composition for surface protection sheets according to claim 1 or 2, wherein the (meth)acrylyl group in the polyurethane (A) is part of the (meth)acryloxy group. For example, the adhesive composition for surface protection sheets according to claim 1 or 2, wherein the aforementioned polyfunctional monomer (B) has three or more (meth)acrylyl groups. Such as the adhesive composition for surface protection sheets of claim 6, wherein the aforementioned multifunctional monomer (B) is trimethylolpropane triacrylate. For example, the adhesive composition for surface protection sheets according to claim 1 or 2, wherein the aforementioned other monomer (C) has only one (meth)acrylyl group. The adhesive composition for surface protection sheets of claim 1 or 2, wherein the aforementioned other monomer (C) includes alkyl (meth)acrylic acid ester. The adhesive composition for surface protection sheets of claim 1 or 2, wherein the aforementioned polyurethane (A) further includes polyurethane (a2), and the aforementioned polyurethane (a2) is It has a skeleton including a structure derived from polyoxyalkylene polyol and polyisocyanate, and only one terminal of the polyurethane (a2) has a (meth)acrylyl group. The adhesive composition for surface protection sheets according to claim 1 or 2, wherein on a numerical basis, 90 to 100% of the ends of the polyurethane molecules contained in the polyurethane (A) are covered Introduce (meth)acrylyl group. The adhesive composition for surface protection sheets of claim 1 or 2, wherein relative to the total amount of the aforementioned polyurethane (A), the aforementioned multifunctional monomer (B), and the aforementioned other monomers (C) 100 parts by mass further contains 1 to 40 parts by mass of fatty acid ester. A surface protection sheet having a sheet-like base material and an adhesive layer formed on the base material, wherein the aforementioned adhesive layer is an adhesive for surface protection sheets according to any one of claims 1 to 12 The composition is made of light-hardened matter.

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