TW202026385A - 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 a surface protection sheet and a surface protection sheet, and particularly relates to an adhesive composition for a surface protection sheet containing a compound having a (meth)acryloyl group, and an adhesive for the surface protection sheet The surface protection sheet of the hardened material of the composition.

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

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

In addition, Patent Document 2 describes a photocurable composition for a transparent adhesive sheet, which contains a polyoxyalkylene chain terminal via a urethane bond to which a (meth)acrylic acid group is bonded. Urethane, (meth)acrylate having a hydroxyl group, (meth)acrylate having an aromatic ring, other polymerizable monomers, and photopolymerization initiators.

In the inspection step of optical components, in the state where the protective sheet is laminated on the product or part, it is required to fully detect or detect the fine foreign matter or injury of the product or part. Therefore, the protective sheet is required to have low haze, that is, low haze.

In addition, in the manufacturing process of the optical element, the protective sheet may be repeatedly laminated and peeled off. Therefore, the protection sheet requires the ease of stacking the adherend (high wettability to the adherend) and the ease of peeling. In addition, recently, as the display screen becomes larger and the panel parts become thinner, the optical element itself becomes prone to cracks. Therefore, the protective sheet is required to have moderate adhesion (peel strength), and at the same time, it can be peeled off with a lighter force (light peelability). In addition, it is also required that the so-called adhesive residue (re-peelability) does not occur after the peeling of the protective sheet and a part of the adhesive layer on the surface of the product (adhesive). [Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2014-210895 A [Patent Document 2] JP 2016-20477 A

[The problem to be solved by the invention]

However, the composition described in Patent Document 1 and Patent Document 2 is not intended to be used as a protective sheet for peeling in the manufacturing process, and an adhesive sheet using these compositions has high peel strength.

Therefore, in order to solve the above-mentioned problems, the present inventors conducted a careful review by including: a skeleton having a structure derived from polyoxyalkylene polyol and polyisocyanate, and including a (meth)acryloyl group at plural ends Polyurethane with a weight average molecular weight of 30,000~200,000; a polyfunctional monomer with plural (meth)acrylic groups; can be combined with polyurethane and polyfunctional mono Other monomers that are polymerized in bulk; and the adhesive composition for photocurable surface protection sheets of photopolymerization initiator is hardened to obtain low haze, easy build-up, easy peeling, and can prevent adhesive residue after peeling Surface protection sheet. However, the surface protection sheet obtained from the adhesive composition for photocurable surface protection sheet has a slightly harder adhesive layer. Therefore, it is known that the adhesive layer is Cracks occurred on the end face.

Therefore, the object of the present invention is to provide a surface protection sheet for a surface protection sheet that has low haze, is easy to build up, easy to peel, can prevent adhesive residue after peeling, and does not crack the adhesive layer during cutting processing Use adhesive composition. In addition, another object of the present invention is to provide a surface protection sheet that has low haze, is easy to build up, is easy to peel, can prevent adhesive residue after peeling, and does not crack the adhesive layer during cutting. [Means to solve the problem]

The structure of the present invention for solving the above-mentioned problems is as follows. [1] An adhesive composition for a surface protection sheet, which contains polyurethane (A), a polyfunctional monomer (B), and can be combined with polyurethane (A) and a polyfunctional monomer (B) An adhesive composition for surface protection sheets of polymerized other monomers (C) and photopolymerization initiator (D), Wherein the aforementioned polyurethane (A) is a polyurethane having a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, The aforementioned polyurethane (A) includes polyurethane (a1), The aforementioned polyurethane (a1) has a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and the plural ends of the aforementioned polyurethane (a1) have (methyl ) Acrylic, The weight average molecular weight of the aforementioned polyurethane (A) is 30,000~200,000, The aforementioned polyfunctional monomer (B) is a compound having plural (meth)acrylic groups, 100% by mass relative to the total amount of the polyurethane (A), the polyfunctional monomer (B), and the other monomer (C), The content of the aforementioned polyurethane (A) is 30-60% by mass, The content of the aforementioned multifunctional monomer (B) is 2-10% by mass, The content of the aforementioned other monomer (C) is 30~68% by mass, With respect to 100 parts by mass of the total amount of the polyurethane (A), the polyfunctional monomer (B), and the other monomer (C), The content of the photopolymerization initiator (D) is 0.1 to 5 parts by mass. [2] The adhesive composition for a surface protection sheet according to [1], wherein the structure derived from the polyoxyalkylene polyol contained in the polyurethane (A) is derived from a number average molecular weight of 500 to 5,000 The structure of polyoxyalkylene polyol. [3] The adhesive composition for a surface protection sheet according to [1] or [2], wherein the skeleton contained in the polyurethane (A) is a copolymer of polyoxyalkylene glycol and diisocyanate. [4] The adhesive composition for a surface protection sheet 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 a surface protection sheet according to any one of [1] to [4], wherein the (meth)acryloyl group in the polyurethane (A) is (methyl) ) A part of the propylene oxy group. [6] The adhesive composition for a surface protection sheet according to any one of [1] to [5], wherein the multifunctional monomer (B) has 3 or more (meth)acrylic groups. [7] The adhesive composition for a surface protection sheet according to [6], wherein the multifunctional monomer (B) is trimethylolpropane triacrylate. [8] The adhesive composition for a surface protection sheet according to [7], wherein the aforementioned other monomer (C) has a (meth)acryloyl group. [9] The adhesive composition for a surface protection sheet according to [8], wherein the aforementioned other monomer (C) contains an alkyl (meth)acrylate. [10] The adhesive composition for a surface protection sheet according to any one of [1] to [9], wherein the aforementioned polyurethane (A) further comprises polyurethane (a2), The aforementioned polyurethane (a2) comprises: a skeleton having a structure derived from polyoxyalkylene polyol and polyisocyanate, and only any one end of the aforementioned polyurethane (a2) has (methyl) ) Acrylic-based polyurethane (a2). [11] The adhesive composition for a surface protection sheet 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 end of the molecule is introduced into (meth)acrylic acid groups. [12] A surface protection sheet, which has a sheet-like substrate and an adhesive layer formed on the substrate, Wherein, the aforementioned adhesive layer is formed by the photocured material of the adhesive composition for surface protection sheet as in any one of [1] to [11]. [Invention Effect]

According to the present invention, it is possible to provide a surface protection sheet for a surface protection sheet that has low haze, is easy to build up, and is easy to peel off, can suppress the adhesive residue after peeling, and the adhesive layer does not crack during cutting processing. Adhesive composition. In addition, according to the present invention, it is possible to provide a surface protection sheet that has low haze, is easy to build up, easy to peel, and can prevent adhesive residue after peeling, and does not crack the adhesive layer during cutting.

[The form of implementing the invention]

An embodiment of the present invention will be described below. Here, the (meth)acryloyl group refers to one or more 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-, The (meth)acryloxy group refers to a group 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- the 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 sheet＞ The adhesive composition for surface protection sheets of this embodiment (hereinafter sometimes referred to as "adhesive composition") contains polyurethane (A), polyfunctional monomer (B), and a Other monomers (C) and photopolymerization initiator (D) in which the formate (A) and the polyfunctional monomer (B) are polymerized. The aforementioned polyurethane (A) is a polyurethane having a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate. The aforementioned polyurethane (A) includes polyurethane (a1). The aforementioned polyurethane (a1) has a skeleton comprising a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and the plural ends of the aforementioned polyurethane (a1) have (former Base) Acrylic acid base. The weight average molecular weight of the aforementioned polyurethane (A) is 30,000 to 200,000. The aforementioned polyfunctional monomer (B) is a compound having plural (meth)acrylic groups. The content of the polyurethane (A) is 100% by mass relative to the total amount of the polyurethane (A), the polyfunctional monomer (B), and the other monomer (C) 30-60% by mass, the content of the aforementioned multifunctional monomer (B) is 2-10% by mass, and the content of the aforementioned other monomer (C) is 30-68% by mass. In addition, the content of the photopolymerization initiator (D) relative to 100 parts by mass of the total amount of the polyurethane (A), the polyfunctional monomer (B), and the other monomer (C) is 0.1 to 5 parts by mass is characteristic. In addition, the adhesive composition of the present 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. The components contained in the adhesive composition will be described below. In addition, in the following description, the components composed of polyurethane (A), polyfunctional monomer (B), and other monomers (C) may be referred to as "components (A) ~ (C) )".

＜1-1. Polyurethane (A)＞ Polyurethane (A) is a polyurethane having a skeleton containing a structure derived from polyoxyalkylene polyol and polyisocyanate. The polyurethane (A) includes the polyurethane (a1) described later. In order to adjust the cohesive force of the cured product of the adhesive composition, the polyurethane (A) may further include the polyurethane (a2) described later.

[Polyurethane (a1)] Polyurethane (a1) is a polyurethane having a skeleton including a structure derived from a polyoxyalkylene polyol and a structure derived from a polyisocyanate, and a plurality of ends having a (meth)acrylic acid group . Furthermore, the (meth)acryloyl group at the terminal of the polyurethane (a1) is preferably a part of the (meth)acryloyloxy group.

[Polyurethane (a2)] The polyurethane (a2) is a polyurethane having a skeleton containing a structure derived from a polyoxyalkylene polyol and a polyisocyanate, and having a (meth)acryloyl group at only one end. Moreover, the (meth)acryloyl group at the terminal of the polyurethane (a2) is preferably a part of the (meth)acryloyloxy group. In addition, the content of polyurethane (a1) and polyurethane (a2) contained in polyurethane (A), that is, the content of polyurethane (A) The method of adjusting the number of (meth)acrylic groups at the end of the polyurethane is in the section of the method for producing polyurethane (A), and an example is described later.

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

The polyurethane (a1) contained in the polyurethane (A) is based on the number, preferably 80-100% of the polyurethane (A), more preferably 90-100 %, more preferably 100%. The polyurethane (a2) contained in the polyurethane (A) is on a numerical basis, preferably 0-20% of the polyurethane (A), more preferably 0-10 %, more 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 with a carbon number of 2 to 4. The specific examples include polyoxyethylene polyol, polyoxypropylene polyol, polyoxyethylene Butyl polyol and so on. Moreover, among polyoxyalkylene polyols, it is preferable to use polyoxyalkylene glycol, and it is especially preferable to use polypropylene glycol.

In addition, as the polyoxyalkylene polyol, two or more kinds of alkylene chains may be contained. In addition, as the polyurethane (A), the structure derived from two or more different polyoxyalkylene polyols may be a structure in which polyisocyanate is interposed 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 peel strength of the adhesive layer obtained by curing the adhesive composition is improved. When the number average molecular weight is 5,000 or less, since a sufficient amount of urethane bonds are contained in the polyurethane, the cohesive force of the adhesive layer increases.

The polyoxyalkylene polyol preferably has 2 or 3 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, glycol type) of polypropylene glycol having a hydroxyl value of 56 mgKOH/g and a hydroxy group at the end. 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 is used to neutralize the required hydroxide The mg of potassium. Specifically, acetic anhydride is used to acetylate the hydroxyl group in the sample, and the free acetic acid produced at this time can be obtained by titration with potassium hydroxide solution.

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

Among these exemplified compounds, from the viewpoint of light resistance and reactivity control, isophorone diisocyanate or diphenylmethane diisocyanate hydride is preferred, and from the viewpoint of reactivity, diphenyl is more preferred Hydrogenated methane diisocyanate. The polyisocyanate-derived structure contained in the polyurethane (A) may be one type, or may include two or more types. Specific examples of the polyisocyanate include hydrogenated diphenylmethane diisocyanate (manufactured by Desmodur W, Sumika Covestro Urethane), isophorone diisocyanate (manufactured by Desmodur I, 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 curing the adhesive composition has insufficient flexibility, and the surface protection sheet containing the adhesive layer is not easy to be laminated. In addition, when the weight average molecular weight of the polyurethane (A) is greater than 200,000, the adhesive composition becomes difficult to handle, such as increased viscosity, and workability decreases.

The content of the polyurethane (A) is 30-60% by mass, preferably 35-55% by mass, and more preferably 40-50% by mass relative to the total amount of components (A) to (C). When the content of polyurethane (A) is less than 30% by mass, the cohesive force of the hardened material of the adhesive composition is insufficient, the adhesive layer becomes too soft, and the adhesive surface (between the adhesive layer and the adherend) Intermittently) There is a doubt about air bubbles. When the content of polyurethane (A) is greater than 60% by mass, the cohesive force 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 decreases Doubts.

＜1-2. Multifunctional monomer (B)＞ The polyfunctional monomer (B) adjusts the peel strength of the adhesive layer (surface protection sheet) of the hardened product of the adhesive composition. The polyfunctional monomer (B) is a compound having a plurality of (meth)acrylic groups except for the polyurethane (A). When the number of (meth)acryloyl groups is 2 or more, it is not particularly limited. From the viewpoint of curability, the polyfunctional monomer (B) preferably has 3 or more (meth)acryloyl groups.

The multifunctional monomer (B) is preferably a poly(meth)acrylate of a polyol compound, for example, 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-bis(meth)acryloyl bis-diethylene glycol benzene two Formate, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylic acid Esters, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, dipropylene oxyethyl 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 is easy to be reduced and adjusted, it is more preferably 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(methyl) Yl)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 2-10% by mass, preferably 3-9% by mass, more preferably 4-8% by mass relative to the total amount of components (A) to (C). When the content is less than 2% by mass, the peel strength of the surface protection sheet is too high and the light peelability is poor. When the content is more than 10% by mass, the adhesive layer of the hardened product using the adhesive composition becomes hard, and cracks are likely to occur when the sheet is cut. Moreover, when the content is more than 10% by mass, the haze tends to increase as a surface protection sheet.

＜1-3. Other monomers (C)＞ Other monomers (C) are excluding polyurethane (A), and compounds other than polyfunctional monomer (B) can be combined with polyurethane (A) and polyfunctional monomer (B) At the time of polymerization, there is no particular limitation. However, other monomers (C) are used as functional groups for polymerization with polyurethane (A) and polyfunctional monomers (B), and preferably have a radically polymerizable ethylenic unsaturated bond. , More preferably having a vinyl group or (meth)acrylic acid group, and still more preferably having a (meth)acrylic acid group.

Other monomers (C) are not particularly limited, and examples include alkyl (meth)acrylates, cyclic alkyl (meth)acrylates, alkoxyalkyl (meth)acrylates, and alkoxy ( Poly)alkylene glycol (meth)acrylate, hydroxyl-containing (meth)acrylate, carboxyl-containing (meth)acrylate, fluorinated alkyl (meth)acrylate, dialkylamino alkane (Meth)acrylate, (meth)acrylamide, epoxy-containing (meth)acrylate, unsaturated carboxylic acid, etc.

Alkyl (meth)acrylates, for example, meth (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylic acid Ester, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-hexyl (meth)acrylate, Yl)acrylate, isooctyl (meth)acrylate, isooctadecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, etc.

Cyclic alkyl (meth)acrylates include, for example, cyclohexyl (meth)acrylate, norbornyl (meth)acrylate, isobornyl (meth)acrylate, norbornyl (meth)acrylate. )Acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentyloxyethyl ( Meth) acrylate and the like.

Alkoxyalkyl (meth)acrylates include, for example, ethoxyethyl (meth)acrylate, methoxyethyl (meth)acrylate, butoxyethyl (meth)acrylate , 2-Methoxyethoxyethyl (meth)acrylate, 2-ethoxyethoxyethyl (meth)acrylate, etc.

Alkoxy (poly)alkylene glycol (meth)acrylate, for example, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, methoxy Dipropylene glycol (meth)acrylate and the like.

Hydroxy-containing (meth)acrylates include, for example, 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-methylpentadiene Alcohol mono(meth)acrylate etc.

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

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

Dialkylaminoalkyl (meth)acrylates, for example, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth) Acrylic etc.

(Meth)acrylamide, for example (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(methyl) )Acrylamide, N-isopropylacrylamide, N-hexyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(methyl) ) Acrylamide, (meth)acrylamide morpholine, diacetone acrylamide, etc.

The epoxy group-containing (meth)acrylate includes, for example, glycidyl (meth)acrylate. Examples of unsaturated carboxylic acids include (meth)acrylic acid, maleic acid, and itaconic acid.

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 itconate, dialkyl fumarate, allyl alcohol, Hydroxybutyl vinyl ether, hydroxyethyl vinyl ether, 4-hydroxymethyl cyclohexyl methyl vinyl ether, triethylene glycol monovinyl ether or diethylene glycol monovinyl ether, methyl vinyl ketone, N-acrylic acid Aminomethyl trimethyl ammonium chloride, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone, etc.

Among these exemplified compounds, from the viewpoint of the compatibility with the polyurethane (A), the viscosity of the adhesive composition, and the adjustment of the peel strength, the alkyl (meth)acrylate is more preferred, and Preferably it is 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isooctadecyl (meth)acrylate, isobornyl (meth)acrylate, and more preferably 2-Ethylhexyl (meth)acrylate. In addition, 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% by mass, preferably 35 to 62% by mass, and more preferably 40 to 56% by mass relative to the total amount of components (A) to (C). When the content is less than 30% by mass, the cohesive force of the hardened material of the adhesive composition is too high, the flexibility of the adhesive layer is insufficient, and there is a concern about the wettability of the adherend. When the content is higher than 68% by mass, the cohesive force of the hardened material of the adhesive composition becomes small, the adhesive layer is too soft, and there is a concern that air bubbles may occur 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 include carbonyl-based photopolymerization initiators, sulfur-based photopolymerization initiators, oxyphosphorus-based photopolymerization initiators, quinone-based photopolymerization initiators, Sulfonyl chloride (sulfonyl chloride)-based photopolymerization initiator, thioxanthone-based photopolymerization initiator, etc.

Carbonyl-based photopolymerization initiators include, for example, benzophenone, diphenylethylenedione, benzidine, ω-bromoacetophenone, chloroacetone, acetophenone, and 2,2-diethoxybenzene Ethyl ketone, 2,2-dimethoxy-2-phenylacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4 ,4'-Dichlorobenzophenone, 4,4'-Diethylaminobenzophenone, Michlerone, Benzene methyl ether, Benzene isobutyl ether, Benzene-n -Butyl ether, benzyl methyl acetal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propane-1-ketone, 1-(4-isopropylphenyl) )-2-Hydroxy-2-methylpropane-1-ketone, methylbenzyl formate, 2,2-diethoxyacetophenone, 4-N,N'-dimethyl styrene 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, and tetramethylammonium monosulfide.

Phosphine oxide ( phosphine oxide ) is a photopolymerization initiator, for example 2,4,6-trimethylbenzyl diphenyl phosphine oxide, 2,4,6-trimethylbenzyl Phenyl ethoxy phosphine oxide and so on.

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

Sulfonyl chloride (sulfonyl chloride)-based photopolymerization initiators include, for example, 2-naphthalenesulfonyl chloride.

The thioxanthone-based photopolymerization initiator includes, for example, thioxanthone, 2-chlorothiaxanthone, 2-methylthioxanthone, and the like.

Among these exemplified compounds, from the viewpoint of the transparency of the adhesive layer obtained by curing the adhesive composition, 1-hydroxycyclohexyl phenyl ketone, 2,4,6-trimethylbenzyl are preferred Diphenyl phosphine oxide. In addition, 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 to 5 parts by mass, preferably 0.2 to 3 parts by mass, more preferably 0.3 to 2 parts by mass relative to 100 parts by mass of the total amount of components (A) to (C) Copies. When the content of the photopolymerization initiator (D) is less than 0.1 parts by mass, the adhesive composition is not sufficiently photocured, and when it is greater than 5 parts by mass, many low molecular weight components are formed, and the peelability of the resulting surface protection sheet deteriorates Propensity.

＜1-5. Additives＞ In the adhesive composition, in order to improve the layering properties (wettability) and defoaming properties (easy to remove bubbles entrapped during bonding) of the obtained surface protection sheet, fatty acid esters may be added if necessary. Examples of fatty acid esters include monobasic acids with 8 to 18 carbons, or esters of polybasic acids and branch alcohols with carbons of 18 or less, unsaturated fatty acids with 14 to 18 carbons, or branched Esters of acids and tetravalent alcohols, etc. Preferred specific examples of fatty acid esters include isopropyl myristate. Relative to 100 parts by mass of the total amount of components (A) to (C), the amount of fatty acid ester added is preferably 1-40 parts by mass, more preferably 3~35 parts by mass, and still more preferably 5-30 parts by mass Copies.

In addition, in the adhesive composition, other additives may be added as necessary within a range that does not impair transparency. Additives include, for example, plasticizers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, benzotriazole-based light stabilizers, phosphate ester-based And other flame retardants, such as surfactants, antistatic agents, dyes, etc.

＜1-6. Solvent＞ Since the adhesive composition contains a polyfunctional monomer (B) as a low molecular weight component and other monomers (C), even if a solvent is not added, the viscosity can be adjusted to be coatable. That is, the adhesive composition is in addition to the aforementioned polyurethane (A), the aforementioned multifunctional monomer (B), the aforementioned other monomers (C) and the photopolymerization initiator (D). Except for the ingredients, it may be substantially free of solvent. In this case, when manufacturing the surface protection sheet, the step of heating and drying the solvent can be omitted, and the productivity is improved. In particular, when manufacturing a surface protection sheet having a film thickness of more than 50 μm, it is preferable that the adhesive composition does not substantially contain the solvent. The meaning of "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% by mass, preferably 0 to 0.5% by mass, and more preferably 0 to 0.1% by mass. In order to adjust the viscosity of the adhesive composition during application, a solvent may be added. The solvent can be appropriately selected due to other components contained in the adhesive composition, and an organic solvent is preferred. The usable organic solvent is not particularly limited, and examples include methyl ethyl ketone, acetone, ethyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol, iso Propanol and so on. These organic solvents may be used alone or in combination of two or more kinds. The solvent is preferably used for photo-curing after coating the adhesive composition on a substrate or the like and then removing it by drying.

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

<2-1. Synthesis method of polyurethane (A)> The following describes an example of a preferable synthesis method of polyurethane (A) contained in the adhesive composition of this embodiment, but the synthesis method of polyurethane (A) is not limited to this, because it is used for synthesis The conditions of raw materials or equipment can be changed as appropriate. Also, in this example, the reaction between the hydroxyl group and the isocyanate group, in any of the steps, is also used in the presence of an organic solvent inert to the isocyanate group, using dibutyltin dilaurate, dibutyltin diethylhexanoate, and Carbamate catalysts such as octyltin dilaurate react. It is better to keep the reaction system at 30~100℃ for 1~5 hours. The usage amount of the urethane catalyst is relative to the total mass of the reactants, and is preferably 50 to 500 mass ppm.

First, the polyoxyalkylene polyol and the polyisocyanate are charged in a ratio in which the amount of isocyanate groups (on the basis of numbers, the same below) is greater than the amount of hydroxyl groups (on the basis of numbers, the same below), and these are reacted to synthesize having isocyanate groups at the ends. Of polyurethane. Specific examples of polyoxyalkylene polyol and polyisocyanate are as illustrated in the section of polyurethane (A).

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

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

The compound having a hydroxy group and a (meth)acryloyl group is not particularly limited, and examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Yl) acrylate and other hydroxyalkyl (meth)acrylates; 1,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 1,6- Hexanediol mono(meth)acrylate, 3-methylpentanediol mono(meth)acrylate, etc., are derived from various polyols and have (meth)acrylic acid monools. These can be used alone or in combination of two or more types. Among them, from the viewpoint of reactivity with an isocyanate group and photocurability, 2-hydroxyethyl (meth)acrylate is preferred.

Also, in addition to the compound having a hydroxyl group and a (meth)acryloyl group, an alkyl alcohol having no (meth)acryloyl group but one hydroxyl group is used in combination with a polyurethane having an isocyanate group at the end In the reaction, the introduction amount of (meth)acryloyl group can be adjusted. The alkyl alcohol is not particularly limited, and examples 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 on at least any one end is produced. In this case, the polyurethane (A) includes a polyurethane that does not have a (meth)acryl group at at least any terminal. Therefore, polyurethane (a2) having a (meth)acryloyl group at only one end may be included.

On a numerical basis, 90-100% of the ends of the polyurethane contained in the polyurethane (A) is preferably introduced with (meth)acrylic groups, more preferably 95-100%, More preferably, it is 100%. When the introduced amount of the (meth)acryloyl group 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 (meth)acrylic acid groups introduced with respect to the number of ends of the entire polyurethane molecular chain can be measured by IR, NMR, etc.

＜2-2. Modification of the synthetic method of polyurethane (A)＞ A modification example of the synthesis method of polyurethane (A) is explained. 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, and dibutyltin diethylhexanoate are used in the presence of an organic solvent that is inactive to isocyanate groups. Carbamate catalysts such as dioctyltin dilaurate react. It is better to keep the reaction system at 30~100℃ for 1~5 hours. The usage amount of the urethane catalyst is relative to the total mass of the reactants, and is preferably 50 to 500 mass ppm. In this modification, first, the polyoxyalkylene polyol and the polyisocyanate are reacted at a ratio in which the amount of hydroxyl groups is greater than the amount of isocyanate groups to synthesize a polyurethane having a hydroxyl group at the terminal.

At this time, 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 larger the molecular weight of the polyurethane having hydroxyl groups, and the greater the excess amount of hydroxyl groups relative to the amount of isocyanate groups, and the greater the excess amount of hydroxyl groups relative to the amount of isocyanate groups. The smaller the molecular weight of the urethane.

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

The compound having an isocyanate group and a (meth)acryloyl group is not particularly limited, and examples include 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxypropyl isocyanate, 1, 1-bis(acryloxymethyl)ethyl isocyanate and the like. In addition, examples of commercially available products of compounds having isocyanate groups and (meth)acryloyl groups include Karenz MOI (registered trademark) or Karenz AOI (registered trademark) manufactured by Showa Denko Corporation. These can be used alone or in combination of two or more types. Among them, from the viewpoint of reactivity with a hydroxyl group and photocurability, 2-(meth)acryloxyethyl isocyanate is preferred.

In addition, in addition to compounds having isocyanate groups and (meth)acrylic groups, the combination of alkyl isocyanates that do not have (meth)acrylic groups but one isocyanate group, and polyurethanes having hydroxyl groups at the end The acid ester reaction can adjust the introduction amount of (meth)acryloyl group. The alkyl isocyanate is not particularly limited, and examples include linear, branched, and alicyclic alkyl isocyanates. These may be used alone or in combination of two or more types. As a result, a polyurethane having a structure derived from the above-mentioned alkyl isocyanate at at least any one end is produced. In this case, the polyurethane (A) includes a polyurethane that does not have a (meth)acryloyl group at at least any terminal. Therefore, in this case, the polyurethane (A) may contain a polyurethane having a (meth)acryloyl group at only one terminal.

On a numerical basis, it is better to introduce (meth)acrylic groups at 90-100% of the ends of the polyurethane contained in the polyurethane (A), and more preferably 95-100%, and More preferably, it is 100%. When the introduced amount of the (meth)acryloyl group 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. How to mix the components contained in the adhesive composition for surface protection sheets> By mixing polyurethane (A), multifunctional monomer (B), other monomers (C), photopolymerization initiator (D), fatty acid esters added if necessary, and other additives , And organic solvents to make adhesive compositions. The mixing method is not particularly limited. For example, it can be performed using a homogenizer or a stirring device equipped with a stirring blade such as a paddle and a blade.

In addition, all the components may be added and mixed at once, or the addition and mixing may be repeated multiple times for each component. In addition, when there is a solid component at room temperature, it can be added with a solvent or dispersed in a dispersion medium or by heating and melting. This component is easy to be highly uniform 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 is formed on one side of the base material to form an adhesive layer containing a cured product of the adhesive composition. The thickness of the adhesive layer is preferably 3 to 150 μm, more preferably 5 to 130 μm, and still more preferably 10 to 100 μm. When the film thickness of the adhesive layer is 3 μm or more, the strength of the adhesive layer is sufficient, and when the film thickness is 150 μm or less, the control of the film thickness of the adhesive layer is easy. In addition, when the function of protecting the adherend from impact (shock 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 cured product of the adhesive composition contained in the adhesive layer is preferably 85-100% by mass, more preferably 90-100% by mass, and still more preferably 95-100% by mass. Here, the gel fraction refers to the mass fraction of the solvent-extracted insoluble fraction. Here, the solvent is selected to be a non-crosslinked component that can be dissolved in the hardened substance of the adhesive composition. In addition, an example of a specific method for measuring the gel fraction is described later in the examples. When the gel fraction of the hardened substance of the adhesive composition is 85-100% by mass, when the surface protection sheet is peeled off, a part of the adhesive layer remains on the adherend, so-called adhesive residue can be suppressed.

The material of the substrate can be appropriately selected according to the purpose of the surface protection sheet, and for example, a resin film can be mentioned. The surface protection sheet is used, for example, as a protection sheet in the manufacturing process. When inspecting adherends, that is, when the product is sometimes injured or foreign, when the protection sheet is laminated, the base material is preferably transparent. Examples of transparent substrates include polyethylene terephthalate, polyethylene, polypropylene, polystyrene, polyimide, polyvinyl alcohol, polyvinyl chloride, and cellulose.

The thickness of the substrate can be appropriately selected according to the application of the surface protection sheet, and is not particularly limited. In the case of a resin film, the thickness of the substrate is preferably 5 μm or more, more preferably 10 μm or more, and more from the viewpoint of handleability and strength. It is preferably 20 μm or more. Furthermore, when considering the flexibility of the resin film, the thickness of the substrate is preferably 200 μm or less, more preferably 150 μm or less, and still more preferably 100 μm or less.

Furthermore, as the substrate, it is preferable to use an antistatic treatment. The antistatic treatment applied to the substrate is not particularly limited, and a method of providing an antistatic layer on at least one side of the substrate, a method of mixing an antistatic agent on the substrate, and the like can be used. In addition, on the substrate surface where the adhesive layer is formed, easy bonding treatments such as acid treatment, alkali treatment, primer treatment, corona treatment, plasma treatment, ultraviolet treatment, ozone treatment, etc. can be carried out if necessary.

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

＜3-2. Manufacturing method of surface protection sheet＞ The manufacturing method of the surface protection sheet of this embodiment can be obtained by coating an adhesive composition on a substrate sheet, laminating a separator, and irradiating the coated adhesive composition with ultraviolet rays and curing by light.

The method of coating the adhesive composition on the substrate is not particularly limited and can be appropriately selected. For example, the method of coating the adhesive composition on the substrate includes the use of a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a coating bar, and a knife coating. Various coating machine methods such as spray coating machine, cut-off wheel coating machine, direct coating machine, screen printing method, etc.

In addition, the light source when the adhesive composition is cured by light includes 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 the adhesive composition can be sufficiently hardened, for example, 50 to 3000 mW/cm ^{2 is} preferred. In addition, when the intensity of light irradiation is weak, hardening takes time, so productivity is reduced. When the light irradiation is transparent, it can be either on the side of the separator or the side of the substrate.

＜3-3. Use of surface protection sheet and required performance＞ In the inspection step, it is required to fully detect or detect fine foreign objects or injuries of the product or part in the state where the protective sheet is laminated on the product or part. In addition, the protective sheet is also suitable for protecting optical elements such as polarizing plates, wave plates, retardation plates, optical compensation films, reflective sheets, brightness enhancement films, etc. used in liquid crystal displays of smart phones, personal computers, televisions, etc. The surface of the plastic film used.

When the surface protection sheet of this embodiment is used as such a protection sheet, it is required that the surface protection sheet has a low haze, that is, a 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 measurement method of the haze value of the surface protection sheet is described later in the examples.

In addition, when the surface protection sheet of this embodiment is used as the above-mentioned protection sheet, the surface protection sheet needs the minimum peel strength in order to prevent the product or parts from peeling during processing such as transportation. 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 avoid deformation or damage of the product or part during peeling. From this point of view, the peel strength of the surface protection sheet when the peel speed is 3.0m/min, although it varies with the thickness of the substrate and the adhesive layer, when the adhesive layer is 50-100μm, preferably 1-50gf /25mm, more preferably 2~45gf/25mm, still more preferably 3~40gf/25mm. The specific measurement method of the peel strength of the surface protection sheet is as described in the examples. [Example]

The following examples illustrate the present invention in detail. The present invention is not limited by the examples shown below. In addition, in the following examples, the weight average molecular weight of the polyurethane (A) obtained is measured by a colloidal permeation chromatography (Shodex (registered trademark) GPC-101 manufactured by Showa Denko Co., Ltd., hereinafter referred to as GPC) The measured polystyrene conversion value. The measurement conditions of GPC are as follows. Column: Showa Denko Corporation LF-804 Column temperature: 40℃ Sample: 0.2% by mass tetrahydrofuran solution of polyurethane (A) Flow rate: 1ml/min Eluent: Tetrahydrofuran Detector: RI detector (differential refractive index detector)

＜Synthesis of Polyurethane (A)＞ (A-1) In a reactor equipped with a thermometer, a stirrer, a dropping funnel, and a condenser tube with a drying tube, put in the hydride of diphenylmethane diisocyanate (manufactured by Desmodur W, Sumika Covestro Urethane) 5.5 kg (21 mol), and hydroxyl value It is 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 reactor was heated to 60° C. and reacted 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 performed for 2 hours to obtain 45.8 kg of polyurethane (A-1) having an acryl group at the terminal. The IR analysis of this polyurethane (A-1) 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 peaks derived from the isocyanate group disappeared, 2-hydroxyethyl acrylate was added to all the ends of the polyurethane having isocyanate groups at both ends. That is, on a numerical basis, 100% of the ends of the polyurethane molecules contained in the polyurethane (A-1) are introduced with acryl groups.

(A-2) Except for the use of isophorone diisocyanate (Desmodur I, Sumika Covestro Urethane) to replace the hydrogenated diphenylmethane diisocyanate, the same method as the synthesis of polyurethane (A-1) is obtained with propylene at both ends Polyurethane of acyl group (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 8mol, and the polypropylene glycol ACTCOL D-2000 (manufactured by Mitsui Chemicals, number average molecular weight 2000) with a hydroxyl value of 56mgKOH/g and a hydroxyl value of 56mgKOH/g to 7mol, The method of synthesizing the urethane (A-1) similarly obtains the 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 4mol, the hydroxyl value of 56mgKOH/g of polypropylene glycol ACTCOL D-2000 (manufactured by Mitsui Chemicals) with a hydroxyl group at the end was changed to 3mol, and polyurethane ( The synthesis method of A-1) similarly obtained 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) Except for using 1.8 mol of 2-hydroxyethyl acrylate and 0.2 mol of 1-octanol, and 2 mol of substituted 2-hydroxyethyl acrylate, the same method as the synthesis of polyurethane (A-1) is obtained at both ends Or a polyurethane (A-5) which is a mixture of polyurethanes with an acrylic group at one end. The weight average molecular weight of the obtained polyurethane (A-5) was 69,000. Since it was confirmed by IR that the peaks derived from the isocyanate group disappeared, 2-hydroxyethyl acrylate or 1-octanol was added to all the ends of the polyurethane having isocyanate groups at both ends. That is, on a numerical basis, 90% of the ends of the polyurethane molecules contained in the polyurethane (A-5) are introduced with acryl groups. 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 ( a2) 20% of polyurethane (A) on a numerical basis.

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

<Production of surface protection sheet> In the same manner as in Examples 1 to 9 and Comparative Examples 1 to 4, a surface protection sheet having a substrate of a PET film for optics on one side was produced. First, use an applicator to apply the prepared adhesive composition on a 75μm-thick optical PET film (A4300 manufactured by Toyobo Co., Ltd.) as a separator, and cover the coated adhesive composition with a thickness of 75μm Peeling PET film (E7006 manufactured by Toyobo Co., Ltd.). Next, using an ultraviolet irradiation device (manufactured by EYE GRAPHICS Co., Ltd., UV irradiation device 3kW, high-pressure mercury lamp), the sheet covered with the peeled PET film was irradiated with ultraviolet rays from the side of the peeled PET film to light-cur 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 adhesive layer after curing is calculated by using a dial gauge to measure the thickness of the surface protection sheet after peeling off the separator, and subtracting the thickness of the base material from 75 μm 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 composition for surface protection sheet and surface protection sheet> 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 layering properties (moisturizing) were evaluated by the methods described below. Wetness), the adhesive residue on the adherend, and the cracking of the adhesive layer during cutting. The results are shown in Table 1.

(Gel fraction) First, using an applicator, the adhesive composition of each of Examples 1 to 9 and Comparative Examples 1 to 4 was applied to a 50μm thick peeling PET film (HY-S10 manufactured by Higashiyama Film Co., Ltd.), and cured. The thickness of the adhesive layer was 75 μm. In addition, the method of confirming the thickness of the adhesive layer is the same as the above-mentioned measuring method in the production of the surface protection sheet.

Next, the adhesive composition on the peelable PET film was covered with a 75 μm thick peelable PET film (E7006 manufactured by Toyobo Co., Ltd.). Next, using an ultraviolet irradiation device (manufactured by EYE GRAPHICS Co., Ltd., UV irradiation device 3kW, high-pressure mercury lamp), the adhesive composition covered with peeling PET film on both sides was irradiated with ultraviolet light from the surface of the peeling PET film with a thickness of 75 μm to make the adhesive The composition is photocured. 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 produced sheet was cut into a size of 100mm×100mm, and the PET film was peeled off from both sides of the hardened product of the adhesive composition, as a sample for measurement. The sample for measurement was immersed in 50 ml of toluene for 24 hours at 25°C, and then dried at 80°C for 5 hours. From the mass of the sample for measurement before and after the 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 measuring sample after immersion in toluene (the mass without toluene) B: The mass of the measuring sample before immersion in toluene

(Haze value) The surface protection sheets with separators produced in Examples 1 to 9 and Comparative Examples 1 to 4 were cut into a size of 50 mm×50 mm, and the peeling PET film was peeled off. Then, the entire area of the exposed adhesive layer was layered on the glass plate, and a rubber roller (diameter: 85 mm, width: 50 mm) with a mass of 2 kg (load 19.6 N) 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 Co., Ltd.)). The haze value (%) is calculated by dividing the diffuse transmittance by the total light transmittance and multiplying by 100. In addition, the measurement system measures 3 places on the same sample, and their average value is used as the haze value.

(Peel strength) The separator-attached surface protection sheets produced in each of Examples 1 to 9 and Comparative Examples 1 to 4 were cut into a size of 25 mm×150 mm, and the peeling PET film was peeled off. Then, the entire area of the exposed adhesive layer was layered on the glass plate, and a rubber roller (diameter: 85 mm, width: 50 mm) with a mass of 2 kg (load 19.6 N) was reciprocated once to prepare a sample for measurement. Place the resulting measurement sample 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 180° direction tensile test was performed at a peeling speed of 0.3 m/min and 3.0 m/min, and the peel strength (gf/25mm) of the surface protection sheet to the glass plate was measured.

(Layered) Fig. 1 is a plan view showing a method of evaluating the layering 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 separator into a size of 20mm×100mm, and peel off the peeling PET film. Next, in the range from one end of the surface protection sheet 10 in the longitudinal direction to 15 mm, the adhesive layer 12 is attached to the glass plate 30, and the adhesive part is fixed to the glass plate 30. As shown in FIG. 2, the surface protection sheet 10 is lifted The other end. The method of fixing the adhesive part is shown in Figure 1. In the range from the above-mentioned end of the surface protection sheet 10 to 15 mm, the upper surface of the surface protection sheet 10 and the two outer sides of the width direction of the surface protection sheet are covered with the glass plate. Way to paste cellophane tape 20.

From this state, the other end of the surface protection sheet 10 was released, and the time until the entire adhesive layer was adhered to the glass plate 30 by the weight of the surface protection sheet 10 was measured, and the following criteria were used to evaluate Examples 1-9 and comparison Examples 1 to 4 of the layered surface protection sheet. (Multi-layered evaluation criteria) ◎: Less than 5 seconds until close ○: 5 seconds or more, less than 10 seconds until close △: Until close, more than 10 seconds, less than 15 seconds ×: until close, 15 seconds or more, or not close

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

(Evaluation criteria for adhesive residue) ○: The surface of the glass plate has no change compared with that before bonding. △: On the surface of the glass plate, a slight adhesive residue was confirmed. ×: On the surface of the glass plate, the adhesive residue was confirmed.

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

(Crack evaluation criteria) ○: The adhesive layer was cracked. ×: The adhesive layer has no cracks.

<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 the polyurethane (A) is 10% by mass, the adhesive remains. In addition, the composition of Comparative Example 2 in which a polyurethane (A-4) with a weight average molecular weight of 12,000 was used as the polyurethane (A) had insufficient layering properties, and adhesive residue was also seen. In addition, the composition of Comparative Example 3 that does not contain the polyfunctional monomer (B) had too high peel strength and insufficient layering properties. The polyfunctional monomer (B) was 15% by mass in the composition of Comparative Example 4, and the adhesive layer was hard, and cracks occurred in the adhesive layer during cutting.

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

[Figure 1] A plan view showing a method for evaluating the layering properties of a surface protection sheet. [Figure 2] A-A section view in Figure 1.

Claims (12)

An adhesive composition for surface protection sheets, which contains polyurethane (A), multifunctional monomer (B), and can be combined with polyurethane (A) and multifunctional monomer (B) The adhesive composition for surface protection sheet of polymerized other monomer (C) and photopolymerization initiator (D), It is characterized in that the aforementioned polyurethane (A) is a polyurethane having a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, The aforementioned polyurethane (A) includes polyurethane (a1), The aforementioned polyurethane (a1) has a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and the plural ends of the aforementioned polyurethane (a1) have (methyl ) Acrylic, The weight average molecular weight of the aforementioned polyurethane (A) is 30,000~200,000, The aforementioned polyfunctional monomer (B) is a compound having plural (meth)acrylic groups, 100% by mass relative to the total amount of the polyurethane (A), the polyfunctional monomer (B), and the other monomer (C), The content of the aforementioned polyurethane (A) is 30-60% by mass, The content of the aforementioned multifunctional monomer (B) is 2-10% by mass, The content of the aforementioned other monomer (C) is 30~68% by mass, With respect to 100 parts by mass of the total amount of the polyurethane (A), the polyfunctional monomer (B), and the other monomer (C), The content of the photopolymerization initiator (D) is 0.1 to 5 parts by mass. The adhesive composition for a surface protection sheet according to claim 1, wherein the structure derived from the polyoxyalkylene polyol contained in the polyurethane (A) is derived from a polyoxyethylene having a number average molecular weight of 500 to 5,000 The structure of alkylene polyols. The adhesive composition for a surface protection sheet according to claim 1 or 2, wherein the skeleton contained in the polyurethane (A) is a copolymer of polyoxyalkylene glycol and diisocyanate. The adhesive composition for a surface protection sheet of claim 1 or 2, wherein the aforementioned polyoxyalkylene glycol is polypropylene glycol, The aforementioned diisocyanate is a hydrogenated product of diphenylmethane diisocyanate. The adhesive composition for a surface protective sheet according to claim 1 or 2, wherein the (meth)acryloyl group in the polyurethane (A) is a part of the (meth)acryloyloxy group. The adhesive composition for a surface protection sheet according to claim 1 or 2, wherein the polyfunctional monomer (B) has 3 or more (meth)acrylic groups. The adhesive composition for a surface protection sheet according to claim 6, wherein the aforementioned multifunctional monomer (B) is trimethylolpropane triacrylate. The adhesive composition for a surface protection sheet according to claim 1 or 2, wherein the aforementioned other monomer (C) has only one (meth)acrylic group. The adhesive composition for a surface protection sheet according to claim 1 or 2, wherein the aforementioned other monomer (C) contains an alkyl (meth)acrylate. The adhesive composition for a surface protection sheet according to claim 1 or 2, wherein the aforementioned polyurethane (A) further comprises polyurethane (a2), The aforementioned polyurethane (a2) has a skeleton containing a structure derived from polyoxyalkylene polyol and polyisocyanate, and only either end of the aforementioned polyurethane (a2) has (methyl) Acrylic based. The adhesive composition for a surface protection sheet of claim 1 or 2, wherein on a numerical basis, 90-100% of the ends of the polyurethane molecules contained in the aforementioned polyurethane (A) are Introduce (meth)acrylic acid groups. A surface protection sheet, which has a sheet-like substrate and an adhesive layer formed on the aforementioned substrate, Wherein, the aforementioned adhesive layer is made of a photocured product of the adhesive composition for a surface protection sheet according to any one of claims 1 to 11.

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