JP2022182471A - Active energy ray-curable pressure-sensitive adhesive composition and peelable pressure-sensitive adhesive sheet - Google Patents

Abstract

To provide an active energy ray-curable pressure-sensitive adhesive composition which is excellent in coating property, and is excellent in pressure-sensitive adhesive characteristics before and after irradiation with active energy rays, peelability and stain resistance after peeling when a pressure-sensitive adhesive layer of a peelable pressure-sensitive adhesive sheet is formed.SOLUTION: An active energy ray-curable pressure-sensitive adhesive composition is provided, contains at least an active energy ray-curable composition (X) containing a (meth)acrylic resin (A) and an active energy ray-curable compound (B), and satisfies all of the following requirements (α), (β) and (γ). Requirement (α): A solvent content in the active energy ray-curable composition (X) is less than 1 wt.%. Requirement (β): The active energy ray-curable compound (B) contains urethane (meth)acrylate (b). Requirement (γ): The urethane (meth)acrylate (b) has structure represented by general formula (1) and/or polyol-derived structure, and has three or more (meth)acryloyl groups in one molecule. General formula (1): -U-A. In the general formula (1), U represents an urethane bond, and A represents at least one selected from straight chain or branched alkyl, an alicyclic structure, an aromatic ring structure and heterocyclic structure.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an active energy ray-curable pressure-sensitive adhesive composition and a peelable pressure-sensitive adhesive sheet. The present invention relates to a peelable pressure-sensitive adhesive sheet which is used for protection against damage and then peeled off, and an active energy ray-curable pressure-sensitive adhesive composition suitably used for the pressure-sensitive adhesive layer of this peelable pressure-sensitive adhesive sheet.

Conventionally, in processing processes such as manufacturing integrated circuits in semiconductor wafers and drilling holes, etc., the above-mentioned temporary cleaning agent was used to prevent contamination and damage to the semiconductor wafer, which is the member to be processed. A protective adhesive sheet is used to protect the workpiece.

As a pressure-sensitive adhesive to be used in such a protective pressure-sensitive adhesive sheet, an emulsion-type acrylic pressure-sensitive adhesive that is easily released by heating has been proposed (see, for example, Patent Document 1).
In addition, an acrylic emulsion polymerized without using an emulsifier (dispersant) and a UV-curing emulsion pressure-sensitive adhesive using a urethane (meth)acrylate compound having a self-emulsifying action have been proposed (see, for example, Patent Documents 2).
Furthermore, a pressure-sensitive adhesive sheet having a non-solvent acrylic pressure-sensitive adhesive layer containing an acrylic polymer, an acrylic monomer and a photopolymerization initiator on a base film has been proposed (see, for example, Patent Document 3).

JP 2013-201263 A JP 2012-001615 A JP 2004-269796 A

Due to the miniaturization of processing technology and the thinning of processed materials, the above adhesive sheet is required to have an appropriate adhesive strength to the processed materials. It is required to be able to peel off with a light force without leaving an adhesive residue.
Furthermore, in recent years, the emission of greenhouse gases has become a problem from the viewpoint of global environmental pollution. Therefore, attempts have been made to suppress the above problems by using water-based materials or non-solvent-based materials instead of conventional solvent-based materials.

However, the technique of Patent Document 1 has problems such as insufficient reduction in adhesive strength due to heating and surfactant remaining on the wafer surface.
On the other hand, in Patent Document 2, self-emulsifying urethane (meth)acrylate can be cured without using a surfactant, so the problem of surfactant remaining on the wafer surface is solved, As with the technique of Patent Document 1, the reduction in adhesive strength after curing with active energy rays was insufficient. In addition, the adhesive sheet of Patent Document 3 is not an adhesive sheet that can be easily peeled off by irradiation with active energy rays, so it cannot be applied to fine or thin processed members.

Under such circumstances, the present invention provides a solvent-free active energy ray-curable pressure-sensitive adhesive composition that can be suitably used for the pressure-sensitive adhesive layer of a peelable pressure-sensitive adhesive sheet, and is suitable for hot-melt coating. Although it has a melt viscosity, it has excellent compatibility between the (meth)acrylic resin (A) and the active energy ray-curable compound (B), and further has a desired adhesive strength before and after irradiation with an active energy ray, especially It is an object of the present invention to provide a pressure-sensitive adhesive composition having a very low adhesive force after irradiation with active energy rays and having adhesive properties that allow peeling without adhesive residue. Another object of the present invention is to provide a peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the active energy ray-curable pressure-sensitive adhesive composition is crosslinked.

In general, a solvent-free active energy ray-curable pressure-sensitive adhesive composition containing a (meth)acrylic resin and an active energy ray-curable compound remains in the (meth)acrylic resin when exposed to high temperatures. As a result of decomposition of the thermal polymerization initiator, curing of the active energy ray-curable compound was initiated, and even heating to the temperature required for hot-melt coating was impossible.
Therefore, the present inventors dared to use a solvent-free active energy ray-curable pressure-sensitive adhesive composition containing a (meth)acrylic resin (A) and an active energy ray-curable compound (B). The urethane (meth)acrylate (b) is contained as the energy ray-curable compound (B), and the urethane (meth)acrylate (b) has a predetermined structure, thereby forming a phase with the (meth)acrylic resin (A). It was found to have excellent solubility. In addition, as a result, even though it has a melt viscosity suitable for hot-melt coating, it is a solvent-free type that has excellent adhesive properties before and after irradiation of active energy rays and excellent stain resistance after peeling when used as an adhesive for peelable adhesive sheets. It has also been found that an active energy ray-curable pressure-sensitive adhesive composition can be obtained.

That is, the present invention contains at least an active energy ray-curable composition (X) containing a (meth)acrylic resin (A) and an active energy ray-curable compound (B), and satisfies the following requirements (α), ( The gist of the present invention is an active energy ray-curable pressure-sensitive adhesive composition that satisfies both β) and (γ).
Requirement (α): The solvent content in the active energy ray-curable composition (X) is less than 1% by weight.
Requirement (β): The active energy ray-curable compound (B) contains urethane (meth)acrylate (b).
Requirement (γ): The urethane (meth)acrylate (b) has a structure represented by general formula (1) and/or a polyol-derived structure, and has 3 or more (meth)acryloyl groups per molecule.
-UA general formula (1)
[U is a urethane bond, A is at least one selected from linear or branched alkyl, an alicyclic structure, an aromatic ring structure and a heterocyclic structure. ]

The present invention also provides a peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the active energy ray-curable pressure-sensitive adhesive composition is crosslinked.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention is excellent in coatability, and when the pressure-sensitive adhesive layer of a peelable pressure-sensitive adhesive sheet is formed, it exhibits adhesive properties before and after irradiation with active energy rays, peelability, and stain resistance after peeling. It can be made to have excellent properties.
In the present invention, "releasability" means the degree of ease of peeling when the peelable pressure-sensitive adhesive sheet is peeled off from the adherend after irradiation with active energy rays, and good peelability means the adhesiveness at the time of peeling. It means less force.
In the present invention, "stain resistance" means that when the peelable pressure-sensitive adhesive sheet is peeled off from the adherend after irradiation with active energy rays, all or part of the pressure-sensitive adhesive of the peelable pressure-sensitive adhesive sheet remains on the surface of the adherend. Good contamination resistance means that little or all or part of the adhesive remains on the surface of the adherend.

EMBODIMENT OF THE INVENTION Hereinafter, although the form for implementing this invention is demonstrated concretely, this invention is not limited to these.
In the present invention, "(meth)acryl" means acryl or methacryl, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate.
In the present invention, the term "sheet" is not particularly distinguished from "film" and "tape", but is defined as including these.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention is usually used for forming a pressure-sensitive adhesive layer of a peelable pressure-sensitive adhesive sheet. It is assumed that the peelable pressure-sensitive adhesive sheet is attached to an adherend, such as a metal plate, a plastic plate, or a semiconductor wafer, and then peeled off after being irradiated with active energy rays. The peelable pressure-sensitive adhesive sheet is formed by coating an active energy ray-curable pressure-sensitive adhesive composition on a base sheet to form a pressure-sensitive adhesive layer, and after bonding to a member to be processed, the active energy By irradiating with rays, the pressure-sensitive adhesive layer is cured and the adhesive strength is lowered, so that it can be easily peeled off from the workpiece.

Hereinafter, the active energy ray-curable pressure-sensitive adhesive composition of the present invention (hereinafter also simply referred to as “the pressure-sensitive adhesive composition of the present invention”) comprises a (meth)acrylic resin (A) and an active energy ray-curable compound (B ) contains at least an active energy ray-curable composition (X) containing
Hereinafter, each component will be described in order.

[(Meth) acrylic resin (A)]
The (meth)acrylic resin (A) is a resin obtained by polymerizing a polymerizable component containing at least one (meth)acrylic monomer. (Meth)acrylic resins obtained by polymerizing a polymerization component containing other various polymerizable monomers.
In addition, in this invention, only 1 type may be used for the (meth)acrylic resin (A), and 2 or more types may be used together.

Incidentally, the (meth)acrylic monomer "as a main component" means that the (meth)acrylic monomer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight, based on the total polymerization components. It means that it contains more than

Examples of the (meth)acrylic monomer include (meth)acrylic acid or derivatives thereof, (meth)acrylamide or derivatives thereof, and the like.

Derivatives of the above (meth)acrylic acid include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, 2-methyl-2-nitropropyl (meth) Acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, n-pentyl (meth)acrylate, t-pentyl (meth)acrylate, 3- Pentyl (meth)acrylate, 2,2-dimethylbutyl (meth)acrylate, n-hexyl (meth)acrylate, cetyl (meth)acrylate, n-octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 4-methyl -Alkyl group-containing (meth)acrylates such as 2-propylpentyl (meth)acrylate and n-octadecyl (meth)acrylate.

Other examples of derivatives of (meth)acrylic acid include cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate and cyclopentyl (meth)acrylate; aralkyl (meth)acrylates such as benzyl (meth)acrylate. ;biphenyloxy structure-containing (meth)acrylates such as biphenyloxyethyl (meth)acrylate; 2-isobornyl (meth)acrylate, 2-norbornylmethyl (meth)acrylate, 5-norbornen-2-yl-methyl (meth) Acrylate, 3-methyl-2-norbornylmethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, etc. polycyclic (meth)acrylates; 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-methoxymethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate ) Acrylate, ethoxydiethylene glycol (meth) acrylate, methoxy polyethylene glycol (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, alkylphenoxy polyethylene glycol (meth) acrylate, etc. containing alkoxy or phenoxy groups ( meth) acrylate; and the like.

Furthermore, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxy Hydroxyalkyl (meth)acrylates such as hexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, [4-(hydroxymethyl)cyclohexyl] Hydroxyl group-containing (meth)acrylates such as methyl acrylate, cyclohexanedimethanol mono (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate; glycidyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate glycidyl ether, etc. Epoxy group-containing (meth)acrylates; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,2-trifluoroethylethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl ( Halogen-containing (meth)acrylates such as meth)acrylate, octafluoropentyl (meth)acrylate, heptadecafluorodecyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate; dimethylaminoethyl (meth)acrylate, etc. 3-oxetanylmethyl (meth)acrylate, 3-methyl-oxetanylmethyl (meth)acrylate, 3-ethyl-oxetanylmethyl (meth)acrylate, 3-butyl-oxetanylmethyl (meth)acrylate , oxetane group-containing (meth)acrylates such as 3-hexyl-oxetanylmethyl (meth)acrylate;

Derivatives of the above (meth)acrylamide include, for example, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, N-isopropyl(meth)acrylamide, N- N-alkyl group-containing (meth)acrylamide derivatives such as butyl (meth)acrylamide and N-hexyl (meth)acrylamide; N-methylol (meth)acrylamide, N-hydroxyethyl (meth)acrylamide, N-methylol-N-propane (Meth) N-hydroxyalkyl group-containing (meth)acrylamide derivatives such as acrylamide; N-aminoalkyl group-containing (meth)acrylamide derivatives such as aminomethyl (meth)acrylamide and aminoethyl (meth)acrylamide; N-methoxymethyl ( N-alkoxy group-containing (meth)acrylamide derivatives such as meth)acrylamide and N-ethoxymethyl (meth)acrylamide; N-mercaptoalkyl group-containing (meth)acrylamides such as mercaptomethyl (meth)acrylamide and mercaptoethyl (meth)acrylamide Derivatives; heterocycle-containing (meth)acrylamide derivatives such as N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine, N-acryloylpyrrolidine, and the like.

These (meth)acrylic monomers may be used singly or in combination of two or more. Among these (meth)acrylic monomers, alkyl group-containing (meth)acrylates are preferably used. The number of carbon atoms in the alkyl group in the alkyl group-containing (meth)acrylate is generally 1-20, preferably 4-18, more preferably 8-12. Among them, the glass transition temperature (Tg) when forming a homopolymer is -30 ° C. or less, and the melt viscosity can be easily lowered. Lauryl methacrylate is preferred.

Moreover, the polymerizable component constituting the (meth)acrylic resin (A) may contain a polymerizable monomer (hereinafter referred to as “other polymerizable monomer”) other than the (meth)acrylic monomer.
Examples of the other polymerizable monomers include unsaturated carboxylic acids such as crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamido-N-glycolic acid, and cinnamic acid; Carboxylic acid vinyl ester monomers such as vinyl acetate, vinyl propionate, vinyl stearate and vinyl benzoate; aromatic ring-containing monomers such as styrene and α-methylstyrene; acrylonitrile, methacrylonitrile, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, vinyl pyridine, vinyl pyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol, acryl chloride, methyl vinyl ketone, allyl trimethyl ammonium chloride, dimethyl allyl vinyl ketone and the like. These may be used independently and may use 2 or more types together.

Moreover, you may contain a photocrosslinkable monomer as said other polymerizable monomer. Such photocrosslinkable monomers generate radicals by the action of light.
As the photocrosslinkable monomer, for example, a (meth)acrylate monomer having a benzophenone structure can be used. Specifically, 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4' -methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy-4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxy benzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4'-methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone and these A mixture etc. are mentioned.
By using such a photocrosslinkable monomer as a copolymerization component, a photocrosslinkable structural site can be formed in the (meth)acrylic resin (A).

The polymerizable component constituting the (meth)acrylic resin (A) preferably contains an alkyl group-containing (meth)acrylate and a functional group-containing monomer. As such a functional group-containing monomer, it is preferable to contain at least one functional group-containing monomer selected from hydroxyl group-containing monomers and carboxy group-containing monomers. Among them, a functional group-containing monomer containing a (meth)acryloyl group is preferred. Among these, hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl (meth)acrylate and (meth)acrylic acid are particularly preferred.

The content of the alkyl group-containing (meth)acrylate is usually 40% by weight or more, preferably 50% by weight or more, relative to the total polymerization components constituting the (meth)acrylic resin (A). , more preferably 60% by weight or more. The upper limit is usually 100% by weight.
The content of the above-mentioned functional group-containing monomer is preferably 0.1 to 40% by weight, preferably 1 to 35% by weight, based on the total polymerization components constituting the (meth)acrylic resin (A). is more preferred, and 5 to 30% by weight is particularly preferred. If the amount of the above-mentioned functional group-containing monomer is too small, the cohesive force of the pressure-sensitive adhesive layer formed tends to be low, and the pressure-sensitive adhesive performance and releasability before curing by active energy rays tend to be low. On the other hand, if it is too large, the melt viscosity tends to increase and the pot life tends to be shortened.

The content of other polymerizable monomers is usually 0 to 30% by weight, preferably 0 to 20% by weight, with respect to the total polymerizable components constituting the (meth)acrylic resin (A). .
Among other polymerizable monomers, the content of the photocrosslinkable monomer in particular is usually 0 to 10% by weight, and 0 to 5% by weight, based on the total polymerization components constituting the (meth)acrylic resin (A). %.

[Method for producing (meth)acrylic resin (A)]
As a method for polymerizing the (meth)acrylic resin (A) used in the present invention, conventionally known methods such as solution (radical) polymerization, suspension polymerization, bulk polymerization and emulsion polymerization can be used. Examples thereof include a method of polymerizing under predetermined polymerization conditions by mixing or dropping appropriately selected polymerization components and a thermal polymerization initiator into an organic solvent. Solution (radical) polymerization is particularly preferred in that a (meth)acrylic resin can be stably obtained.

A preferred method for producing the (meth)acrylic resin (A) used in the present invention will be described below using solution (radical) polymerization as an example.
First, the above copolymerization component and thermal polymerization initiator are mixed or added dropwise into an organic solvent, followed by solution radical polymerization to obtain a (meth)acrylic resin solution.

(Organic solvent)
Examples of the organic solvent used in the polymerization reaction include aromatic hydrocarbons such as toluene and xylene; aliphatic hydrocarbons such as hexane; esters such as ethyl acetate and butyl acetate; N-propyl alcohol and isopropyl alcohol. ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and the like. These can be used alone or in combination of two or more. Among these solvents, solvent-free (meth)acrylic resin can be efficiently produced by distilling off the solvent from the (meth)acrylic resin solution obtained by solution polymerization, and the boiling point is 80° C. or less. It is preferable to use an organic solvent which is

Examples of organic solvents having a boiling point of 80° C. or lower include hydrocarbon solvents such as n-hexane (67° C.); alcohol solvents such as methanol (65° C.); ethyl acetate (77° C.) and methyl acetate. ester solvents such as (54 ° C.); ketone solvents such as methyl ethyl ketone (80 ° C.) and acetone (56 ° C.); diethyl ether (35 ° C.), methylene chloride (40 ° C.), tetrahydrofuran (66 ° C.), etc. Of these, ethyl acetate, acetone, and methyl acetate are preferred, and ethyl acetate and acetone are more preferred, from the viewpoint of versatility and safety.
The numerical value in parentheses following each organic solvent name is the boiling point of each organic solvent.

(Thermal polymerization initiator)
As the thermal polymerization initiator used in the above polymerization reaction, an azo polymerization initiator, a peroxide polymerization initiator, or the like, which is a normal radical polymerization initiator, can be used. Examples of azo polymerization initiators include 2,2′-azobis(2-methylbutyronitrile), 2,2′-azobisisobutyronitrile, (1-phenylethyl)azodiphenylmethane, 2,2′ -azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-cyclopropylpropionitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) and the like. be done. Examples of peroxide polymerization initiators include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, lauroyl peroxide, t-butylperoxypivalate, t-hexylperoxypivalate, t-hexyl peroxyneodecanoate, diisopropyl peroxycarbonate, diisobutyryl peroxide and the like. These can be used alone or in combination of two or more.

In the production of the (meth)acrylic resin, it is preferable to use an organic solvent having a boiling point of 80° C. or less as a reaction solvent for solution polymerization, and to carry out the polymerization at a relatively low temperature. If a thermal polymerization initiator with a high .sup.2 is used, the thermal polymerization initiator tends to remain. If the thermal polymerization initiator remains, gelation tends to occur in the step of distilling off the solvent from the (meth)acrylic resin solution and the step of heating the active energy ray-curable pressure-sensitive adhesive composition, which will be described later.

Therefore, in the present invention, the step of distilling off the solvent from the (meth)acrylic resin solution obtained by solution polymerization and the step of heating as an active energy ray-curable pressure-sensitive adhesive composition are stably performed, Among the above thermal polymerization initiators, it is preferable to use a thermal polymerization initiator having a 10-hour half-life temperature of 60° C. or lower. Among such thermal polymerization initiators, particularly preferred are 2,2′-azobis(2,4-dimethylvaleronitrile) (52° C.) and 2,2′-azobis(2-cyclopropylpropionitrile) (49. 6° C.), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile) (30° C.), t-butyl peroxypivalate (54.6° C.), t-hexyl peroxypivalate (53.2° C.) ° C.), t-hexylperoxyneodecanoate (44.5° C.), diisopropyl peroxycarbonate (40.5° C.), diisobutyryl peroxide (32.7° C.), more preferably 2,2′-azobis (2,4-dimethylvaleronitrile) (52°C), t-hexyl peroxypivalate (53.2°C).
The numerical value in parentheses following each compound name is the 10-hour half-life temperature of each compound.

The amount of the thermal polymerization initiator used is usually 0.001 to 10 parts by weight, preferably 0.1 to 8 parts by weight, more preferably 0.5 to 6 parts by weight, per 100 parts by weight of the polymerization component. , particularly preferably 1 to 4 parts by weight, more preferably 1.5 to 3 parts by weight, particularly preferably 2 to 2.5 parts by weight. If the amount of the thermal polymerization initiator used is too small, the polymerization rate of the (meth)acrylic resin tends to decrease, the amount of residual monomer increases, and the weight average molecular weight of the (meth)acrylic resin tends to increase. If the amount used is too large, the time required for run-in heating, which will be described later, tends to take a long time and the production efficiency tends to decrease.

(Polymerization conditions, etc.)
Polymerization conditions for solution polymerization may be according to conventionally known polymerization conditions. For example, polymerization components and a thermal polymerization initiator can be mixed or dropped into a solvent and polymerized under predetermined polymerization conditions.

The polymerization temperature in the above polymerization reaction is usually 40 to 120° C., but in the present invention, it is preferably 50 to 90° C., more preferably 55 to 75° C., and particularly preferably 60 to 70° C. from the viewpoint of stable reaction. °C. If the polymerization temperature is too high, the (meth)acrylic resin tends to gel easily, and if it is too low, the activity of the thermal polymerization initiator decreases, so that the polymerization rate decreases and the residual monomer tends to increase.

In addition, the polymerization time in the polymerization reaction (the time until the start of the final heating when the later-described final heating is performed) is not particularly limited, but it is preferably 0.5 hours or more from the last addition of the thermal polymerization initiator. , more preferably 1 hour or more, particularly preferably 2 hours or more, and still more preferably 5 hours or more. The upper limit of polymerization time is usually 72 hours.
Incidentally, the polymerization reaction is preferably carried out while refluxing the solvent in order to facilitate heat removal.

In the production of the (meth)acrylic resin, in order to reduce the residual amount of the thermal polymerization initiator, it is preferable to thermally decompose the thermal polymerization initiator by run-in heating.
The run-in heating temperature is preferably carried out at a temperature higher than the 10-hour half-life temperature of the thermal polymerization initiator. is preferred, and more preferably 75 to 95°C. If the run-in heating temperature is too high, the (meth)acrylic resin tends to yellow. tends to decrease. Thus, a (meth)acrylic resin solution can be obtained.

The (meth)acrylic resin used in the present invention is preferably a solvent-free (meth)acrylic resin containing no solvent. Therefore, it is preferable to then distill off the solvent from the (meth)acrylic resin solution.

The step of distilling off the solvent from the (meth)acrylic resin solution can be performed by a known general method. Examples of the method of distilling off the solvent include a method of distilling off the solvent by heating and a method of distilling off the solvent by reducing the pressure. A method of distilling off the solvent by heating under reduced pressure is preferred.

The temperature for distilling off the solvent by heating is preferably 60 to 150° C., and in particular, the reaction solution after polymerizing the (meth)acrylic resin is kept at 60 to 80° C. to distill off the solvent. and then distilling off the solvent at 80 to 150° C. is preferable from the viewpoint of extremely reducing the amount of residual solvent. In order to suppress gelation of the (meth)acrylic resin, it is preferable not to perform the solvent distillation at a temperature exceeding 150°C.

The pressure when distilling off the solvent by reducing the pressure is preferably 20 to 101.3 kPa, and in particular, the pressure is maintained in the range of 50 to 101.3 kPa to distill off the solvent in the reaction solution. Distilling the residual solvent at 50 kPa is preferable in terms of extremely reducing the amount of residual solvent. Thus, the (meth)acrylic resin (A) used in the present invention can be produced.

The content of the thermal polymerization initiator remaining in the (meth)acrylic resin (A) used in the present invention is usually preferably less than 400 ppm, more preferably less than 200 ppm, particularly preferably less than 100 ppm, and even more preferably less than 100 ppm. less than 50 ppm. The lower limit is 0 ppm.
If this value is too large, the thermal stability tends to decrease during coating.
The thermal polymerization initiator content is measured by liquid chromatography-mass spectrometry (LC-MS).
In order to adjust the residual amount of the thermal polymerization initiator to the above amount, it is preferable to thermally decompose the thermal polymerization initiator by run-in heating.

[Physical properties of (meth)acrylic resin (A)]
The weight average molecular weight (Mw) of the (meth)acrylic resin (A) obtained as described above is preferably 50,000 or more, more preferably 70,000 to 1,500,000, and particularly preferably 90,000 to 1,000,000. 100,000 to 500,000 is more preferable. If the weight-average molecular weight is too small, the cohesive strength of the pressure-sensitive adhesive layer to be obtained tends to be low, and the pressure-sensitive adhesive performance and peelability before curing by active energy rays tend to be low. On the other hand, if the weight average molecular weight is too large, the melt viscosity of the acrylic resin tends to increase and the coatability tends to deteriorate.

Further, the (meth)acrylic resin (A) has a degree of dispersion [weight average molecular weight (Mw)/number average molecular weight (Mn)] of preferably 10 or less, more preferably 7 or less. If the degree of dispersion is too high, the cohesion tends to decrease. The lower limit of the degree of dispersion is usually 1.

The weight-average molecular weight (Mw) of the (meth)acrylic resin (A) is the weight-average molecular weight in terms of standard polystyrene molecular weight. Column: Shodex GPCKF-806L (exclusion limit molecular weight: 2 × 10 ⁷ , separation range: 100 to 2 × 10 ⁷ , theoretical plate number: 10,000 plates/line, packing material: styrene-divinylbenzene co- Polymer, filler particle size: 10 μm) can be measured by connecting three in series, and the number average molecular weight (Mn) can also be measured by the same method. The degree of dispersion can be obtained from the measured values of the weight average molecular weight (Mw) and number average molecular weight (Mn).

The (meth)acrylic resin (A) used in the present invention has a melt viscosity at 100° C. of usually less than 1000 Pa·s, preferably 0.1 to 800 Pa·s, more preferably 1 to 500 Pa·s. . If this value is too small, the cohesive force when the adhesive layer is formed tends to decrease, and the adhesive performance and releasability before curing by active energy rays tend to decrease.
The melt viscosity at 100°C is measured with a B-type rotational viscometer.

The glass transition temperature (Tg) of the (meth)acrylic resin (A) is preferably 20° C. or less, more preferably −70° C. to 0° C., particularly preferably −68° C. to −10° C., still more preferably -65 to -30°C. If the glass transition temperature is too low, the cohesive force when forming the adhesive layer tends to decrease, and the adhesive performance and releasability before curing by active energy rays tend to decrease. On the other hand, if the glass transition temperature is too high, the melt viscosity of the active energy ray-curable pressure-sensitive adhesive composition tends to increase and the coatability tends to deteriorate.

Ｔｇ：重合体のガラス転移温度（Ｋ）
Ｔga：モノマーＡのホモポリマーのガラス転移温度（Ｋ） Ｗａ：モノマーＡの重量分率
Ｔgb：モノマーＢのホモポリマーのガラス転移温度（Ｋ） Ｗｂ：モノマーＢの重量分率
Ｔgn：モノマーＮのホモポリマーのガラス転移温度（Ｋ） Ｗｎ：モノマーＮの重量分率
（Ｗａ＋Ｗｂ＋・・・＋Ｗｎ＝１） The glass transition temperature is calculated from the following Fox formula.

Tg: glass transition temperature of the polymer (K)
Tga: glass transition temperature (K) of homopolymer of monomer A Wa: weight fraction of monomer A Tgb: glass transition temperature (K) of homopolymer of monomer B Wb: weight fraction of monomer B Tgn: homopolymer of monomer N Glass transition temperature of polymer (K) Wn: Weight fraction of monomer N (Wa + Wb + ... + Wn = 1)

That is, the glass transition temperature (Tg) of the (meth)acrylic resin (A) is the glass transition temperature and the weight fraction when a homopolymer is formed from each monomer constituting the (meth)acrylic resin (A). is a value calculated by applying to Fox's formula.
The glass transition temperature when a homopolymer is formed from each monomer constituting the (meth)acrylic resin (A) is usually measured by a differential scanning calorimeter (DSC), and is JIS K7121-1987. Alternatively, it can be measured by a method conforming to JISK6240.

The (meth)acrylic resin (A) generally has a refractive index of 1.440 to 1.600. It is preferable to reduce the difference in refractive index between the laminated member and the member to reduce the optical loss at the member interface.
The above refractive index was measured at 23° C. with NaD line using a refractive index measuring device (“Abbe Refractometer 1T” manufactured by Atago Co., Ltd.) for a thin film obtained from the (meth)acrylic resin (A). value.

The solvent content in the (meth)acrylic resin (A) is preferably less than 1% by weight, more preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less.
If the content is too large, the cohesive strength of the obtained adhesive layer tends to decrease, and the adhesive performance and peelability before curing by active energy rays tend to decrease.
The method for measuring the solvent content is gas chromatography-mass spectrometry (GC-MS).

[Active energy ray-curable compound (B)]
The active energy ray-curable compound (B) used in the present invention contains urethane (meth)acrylate (b). The urethane (meth)acrylate (b) has a structure represented by general formula (1) and/or a polyol-derived structure.
-UA general formula (1)
[U is a urethane bond (--NHCOO--), and A is at least one selected from linear or branched alkyl groups, alicyclic structures, aromatic ring structures and heterocyclic structures. ]

In the present invention, the urethane (meth)acrylate (b) is a hydroxyl group-containing (meth)acrylate that is compatible with the (meth)acrylic resin (A) and has good peelability and stain resistance after irradiation with an active energy ray. A urethane (meth)acrylate compound (b-1) or a hydroxyl group-containing (meth)acrylate compound that is a reaction product of a compound (b1), a polyvalent isocyanate compound (b2), and a polyol compound (b3) A urethane (meth)acrylate compound (b-2) which is a reaction product of (b1), a polyvalent isocyanate compound (b2), a monool (b4), and optionally a polyol compound (b3) is preferred.
In the present invention, the urethane (meth)acrylate compound (b) may be used alone or in combination of two or more.
The urethane (meth)acrylate (b) obtained using the polyol compound (b3) has at least a polyol-derived structure.

Regarding the reaction molar ratio of each component when synthesizing the urethane (meth)acrylate compound (b), the number of hydroxyl groups in the hydroxyl group-containing (meth)acrylate compound (b1) is one, and the polyvalent isocyanate compound (b2 ) has two isocyanate groups, the polyol compound (b3) has two hydroxyl groups, and the monool (b4) has one hydroxyl group.
In the urethane (meth)acrylate compound (b-1), the reaction molar ratio of the hydroxyl group-containing (meth)acrylate compound (b1), the polyvalent isocyanate compound (b2) and the polyol compound (b3) is usually large. The ratio of polyisocyanate compound (b2): polyol compound (b3): hydroxyl group-containing (meth)acrylate compound (b1) is about 2:1:2.
In the urethane (meth)acrylate compound (b-2), the reaction molar ratio of the hydroxyl group-containing (meth)acrylate compound (b1), the polyvalent isocyanate compound (b2) and the monool (b4) is usually Polyvalent isocyanate compound (b2): hydroxyl group-containing (meth)acrylate compound (b1): monool (b4) is about 1:1:1, and the reaction moles when the polyol compound (b3) is used in combination The ratio of polyvalent isocyanate compound (b2): polyol compound (b3): hydroxyl group-containing (meth)acrylate compound (b1): monool (b4) is usually about 2:1:1:1.

The hydroxyl group-containing (meth)acrylate compound (b1) preferably has one hydroxyl group, such as 2-hydroxyethyl acryloyl phosphate, 2-(meth) acryloyloxyethyl-2-hydroxypropyl phthalate, caprolactone. Modified 2-hydroxyethyl (meth) acrylate, dipropylene glycol (meth) acrylate, fatty acid-modified glycidyl (meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, 2-hydroxy-3-( Meth) acryloyloxypropyl (meth) acrylate, and hydroxyl group-containing (meth) acrylate compounds containing one ethylenically unsaturated group such as hydroxyalkyl (meth) acrylate. , For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and the like. be done.
Also, hydroxyl group-containing (meth)acrylate compounds containing two ethylenically unsaturated groups such as glycerin di(meth)acrylate, 2-hydroxy-3-acryloyl-oxypropyl methacrylate; pentaerythritol tri(meth)acrylate, caprolactone Modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate Examples include hydroxyl group-containing (meth)acrylate compounds containing 3 or more ethylenically unsaturated groups such as acrylates.
These hydroxyl group-containing (meth)acrylate compounds (b1) can be used singly or in combination of two or more.

Among them, the hydroxyl group-containing (meth)acrylate compound (b1) is preferably a hydroxyl group-containing (meth)acrylate compound containing 3 or more ethylenically unsaturated groups in terms of excellent reactivity and versatility. Particularly preferred are pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate.
In other words, the urethane (meth)acrylate (b) preferably has 3 or more (meth)acryloyl groups per molecule.

Examples of the polyvalent isocyanate compound (b2) include aromatic compounds such as tolylene diisocyanate, diphenylmethane diisocyanate, polyphenylmethane polyisocyanate, modified diphenylmethane diisocyanate, xylylene diisocyanate, tetramethylxylylene diisocyanate, phenylene diisocyanate, and naphthalene diisocyanate. Aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, and lysine triisocyanate; hydrogenated diphenylmethane diisocyanate (dicyclohexylmethane 4,4'-diisocyanate, etc.), hydrogenated Alicyclic polyvalent isocyanates such as xylylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate; isocyanurate or polymer compounds of these polyvalent isocyanates; allophanate-type polyisocyanates; buret-type polyisocyanates; "Aquanate 100", "Aquanate 110", "Aquanate 200", "Aquanate 210" manufactured by Nippon Polyurethane Industry Co., Ltd.) and the like.

Among these, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate; hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene are Alicyclic diisocyanates such as diisocyanate are preferred, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate and hexamethylene diisocyanate are more preferred, and isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate are particularly preferred. .

The polyol-based compound (b3) may be any compound containing two or more hydroxyl groups. Examples include aliphatic polyols, alicyclic polyols, polyether polyols, polyester polyols, polycarbonate polyols, and polyolefins. polyols, polybutadiene-based polyols, polyisoprene-based polyols, (meth)acrylic-based polyols, polysiloxane-based polyols, and the like. These polyol compounds (b3) can be used singly or in combination of two or more.

Examples of the aliphatic polyols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, dimethylolpropane, neopentyl glycol, 2,2-diethyl-1,3-propanediol, and 2-butyl. -2-ethyl-1,3-propanediol, 1,4-tetramethylenediol, 1,3-tetramethylenediol, 2-methyl-1,3-trimethylenediol, 1,5-pentamethylenediol, 1, 6-hexamethylenediol, 3-methyl-1,5-pentamethylenediol, 2,4-diethyl-1,5-pentamethylenediol, pentaerythritol diacrylate, 1,9-nonanediol, 2-methyl-1, Aliphatic alcohols containing two hydroxyl groups such as 8-octanediol; Sugar alcohols such as xylitol and sorbitol; Aliphatic alcohols containing three or more hydroxyl groups such as glycerin, trimethylolpropane and trimethylolethane Alcohols etc. are mentioned.

Examples of the alicyclic polyol include cyclohexanediols such as 1,4-cyclohexanediol and cyclohexyldimethanol; hydrogenated bisphenols such as hydrogenated bisphenol A; tricyclodecanedimethanol;

Examples of the polyether-based polyol include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polybutylene glycol, polypentamethylene glycol, and polyhexamethylene glycol, and random or block copolymerization of these polyalkylene glycols. A coalescence etc. are mentioned.

Examples of the polyester-based polyol include three types of components: a condensation polymer of a polyhydric alcohol and a polycarboxylic acid; a ring-opening polymer of a cyclic ester (lactone); a polyhydric alcohol, a polycarboxylic acid, and a cyclic ester. and the like.
Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, 1,4-tetramethylenediol, 1,3-tetramethylenediol, 2-methyl-1,3-tri methylenediol, 1,5-pentamethylenediol, neopentyl glycol, 1,6-hexamethylenediol, 3-methyl-1,5-pentamethylenediol, 2,4-diethyl-1,5-pentamethylenediol, glycerin , trimethylolpropane, trimethylolethane, cyclohexanediols (1,4-cyclohexanediol, etc.), bisphenols (bisphenol A, etc.), sugar alcohols (xylitol, sorbitol, etc.), and the like.
Examples of polyvalent carboxylic acids include aliphatic dicarboxylic acids such as malonic acid, maleic acid, fumaric acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; -alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid; and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, 2,6-naphthalenedicarboxylic acid, paraphenylenedicarboxylic acid and trimellitic acid.
Examples of the cyclic ester include propiolactone, β-methyl-δ-valerolactone, ε-caprolactone and the like.

Examples of the polycarbonate-based polyols include reaction products of polyhydric alcohols and phosgene; ring-opening polymers of cyclic carbonates (alkylene carbonates, etc.);
Examples of the polyhydric alcohol include the polyhydric alcohols exemplified in the description of the polyester-based polyol, and examples of the alkylene carbonate include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, and hexamethylene carbonate. be done.
Incidentally, the polycarbonate-based polyol may be a compound having a carbonate bond in the molecule and a terminal hydroxyl group, and may have an ester bond together with the carbonate bond.

Examples of the above-mentioned polyolefin-based polyols include those having a homopolymer or copolymer of ethylene, propylene, butene, etc. as a saturated hydrocarbon skeleton and hydroxyl groups at the molecular terminals thereof.

Examples of the polybutadiene-based polyols include those having a butadiene copolymer as a hydrocarbon skeleton and hydroxyl groups at the ends of the molecules. The polybutadiene-based polyol may be a hydrogenated polybutadiene polyol in which all or part of the ethylenically unsaturated groups contained in its structure are hydrogenated.

Examples of the polyisoprene-based polyols include those having an isoprene copolymer as a hydrocarbon skeleton and hydroxyl groups at the molecular terminals thereof. The polyisoprene-based polyol may be a hydrogenated polyisoprene polyol in which all or part of the ethylenically unsaturated groups contained in its structure are hydrogenated.

Examples of the (meth)acrylic polyol include (meth)acrylic acid ester polymers or copolymers having at least two hydroxyl groups in the molecule. Such (meth)acrylic acid esters include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, (meth) (Meth)acrylic acid alkyl esters such as octyl acrylate, 2-ethylhexyl (meth)acrylate, decyl (meth)acrylate, dodecyl (meth)acrylate and octadecyl (meth)acrylate.

Examples of the polysiloxane-based polyol include dimethylpolysiloxane polyol and methylphenylpolysiloxane polyol.

Among these, aliphatic polyols and alicyclic polyols are preferably used in terms of cost, and polyether polyols, polyester polyols and polycarbonate polyols are preferably used in terms of versatility.

The weight average molecular weight of the polyol compound (b3) is preferably 60-10,000, more preferably 100-5,000, and particularly preferably 200-4,000. If the weight average molecular weight of the polyol compound (b3) is too large, the resulting urethane (meth)acrylate (b) and (meth)acrylic resin (A) will be difficult to mix uniformly, resulting in peeling after irradiation with active energy rays. tend to be less sexual. On the other hand, if the weight average molecular weight of the polyol compound (b3) is too small, the pressure-sensitive adhesive layer tends to crack easily after irradiation with active energy rays.
The weight average molecular weight of the polyol compound (b3) is measured by the same method as for the weight average molecular weight (Mw) of the (meth)acrylic resin (A).

Examples of the monool (b4) include aliphatic monools, aromatic monools, alicyclic monools, polyoxyalkylene glycol monoalkyl ethers, and the like. The above monool (b4) may be used alone or in combination of two or more.
Examples of the aliphatic monools include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 1-hexanol, 2-methyl-1-pentanol, 4- Methyl-2-pentanol, 2-ethyl-1-butanol, 1-heptanol, 1-octanol, 2-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol, 1-hexadecanol, 1 - Linear saturated aliphatic monools such as heptadecanol, 1-octadecanol, 1-nonadecanol, 1-eicosanol, 1-hexacosanol, 1-heptatricontanol, 2-octyldodecanol; 1-oleyl alcohol linear unsaturated aliphatic monools such as; branched chain saturated aliphatic monools such as 6-dimethyl-4-heptanol;
Examples of the aromatic monool include phenol, cresol, benzyl alcohol and the like.
Examples of the alicyclic monool include cyclohexanol and methylcyclohexanol.
Examples of the polyoxyalkylene glycol monoalkyl ether include reaction products of the above aliphatic monool and polyoxypropylene glycol. Specifically, polyoxypropylene methyl ether, polyoxypropylene ethyl ether, polyoxypropylene Propylene butyl ether, polyoxypropylene-2-ethylhexyl ether, polyoxypropylene oleyl ether, polyoxypropylene-2-octyl dodecaether and the like.
From the viewpoint of versatility, the monool (b4) is preferably a linear or branched alkyl-containing alcohol having 1 to 36 carbon atoms, more preferably a linear or branched alkyl-containing alcohol having 4 to 18 carbon atoms.
These monools (b4) can be used singly or in combination of two or more.
By using a monool (b4) having at least one selected from linear or branched alkyl, alicyclic structure, aromatic ring structure and heterocyclic structure, A in general formula (1) is linear or branched alkyl , an alicyclic structure, an aromatic ring structure and a heterocyclic structure.

The urethane (meth)acrylate compound (b) can be produced by reacting the above components by known reaction means.
Examples of each of the compounds (b-1) and (b-2) are shown below.
(1) When obtaining a urethane (meth)acrylate compound (b-1) The hydroxyl group-containing (meth)acrylate compound (b1), the polyvalent isocyanate compound (b2), and the polyol compound (b3) are Method of urethanization reaction (2) When obtaining a urethane (meth)acrylate compound (b-2) The hydroxyl group-containing (meth)acrylate compound (b1), the polyvalent isocyanate compound (b2), and a monool ( Method of subjecting b4) to a urethanization reaction with a polyol-based compound (b3) as necessary The above urethanization reaction can be carried out by a known reaction means in which the above components are charged collectively or separately in a reactor.
Further, when producing the urethane (meth)acrylate compound (b-1), the reaction product obtained by pre-reacting the polyol compound (b3) and the polyvalent isocyanate compound (b2) is added with hydroxyl groups. A method of reacting the contained (meth)acrylate compound (b1) is useful in terms of stability of the urethanization reaction, reduction of by-products, and the like.
For the same reason, when producing the urethane (meth)acrylate compound (b-2) using the polyol compound (b3), the polyol compound (b3) and the polyvalent isocyanate compound (b2) are A method of reacting a hydroxyl group-containing (meth)acrylate compound (b1) and a monool (b4) with a reaction product obtained by reacting in advance is useful.

In the reaction between the hydroxyl group-containing (meth)acrylate compound (b1) and the polyvalent isocyanate compound (b2), it is preferable to use a reaction catalyst for the purpose of promoting the reaction. Examples of such reaction catalysts include organometallic compounds such as dibutyltin dilaurate, trimethyltin hydroxide, tetra-n-butyltin; Metal salts such as stannic chloride; triethylamine, benzyldiethylamine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undecene, N,N,N',N Amine catalysts such as '-tetramethyl-1,3-butanediamine and N-ethylmorpholine; inorganic bismuth compounds such as bismuth nitrate, bismuth bromide, bismuth iodide and bismuth sulfide; Organic bismuth compounds; bismuth 2-ethylhexanoate, bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate Bismuth-based catalysts such as organic acid bismuth salts such as salts, bismuth acetate, bismuth bis-neodecanoate, bismuth disalicylate, and bismuth digallate; zirconium-based catalysts such as inorganic zirconium, organic zirconium, and simple zirconium; - Zinc ethylhexanoate/zirconium tetraacetylacetonate, etc., which use two or more catalysts in combination, among which dibutyltin dilaurate and organic bismuth compounds are preferred. In addition, these catalysts can be used individually by 1 type or in combination of 2 or more types.

In the above urethanization reaction, an organic solvent having no functional group that reacts with an isocyanate group, such as esters such as ethyl acetate and butyl acetate; ketones such as methyl ethyl ketone and methyl isobutyl ketone; aromatics such as toluene and xylene. can be used.

The reaction temperature for the urethanization reaction is usually 30 to 90° C., preferably 40 to 80° C., and the reaction time is usually 2 to 10 hours, preferably 3 to 8 hours.

The above urethanization reaction is preferably terminated when the residual isocyanate group content in the reaction system becomes 0.5% by weight or less, whereby the urethane (meth)acrylate compound (b) is efficiently obtained in

The (meth)acryloyl group concentration of the urethane (meth)acrylate compound (b) thus obtained is usually 0.5 mmol/g or more, preferably 1 to 35 mmol/g, more preferably 1.5 to 35 mmol/g. 20 mmol/g, particularly preferably 2 to 15 mmol/g. By setting the (meth)acryloyl group concentration of the urethane (meth)acrylate compound (b) within the above range, it is possible to achieve excellent peelability after irradiation with active energy rays.

Moreover, the urethane (meth)acrylate compound (b) preferably has three or more (meth)acryloyl groups from the viewpoint of releasability after irradiation with active energy rays. If the number of such (meth)acryloyl groups is too small, a sufficient cross-linking density cannot be obtained, which tends to reduce the peelability after irradiation with active energy rays.

The weight average molecular weight of the urethane (meth)acrylate compound (b) is generally 200-10,000, preferably 400-5,000, more preferably 600-4,000. If the weight-average molecular weight is too large, the active energy ray-curable compound (B) and the (meth)acrylic resin (A) will be difficult to mix uniformly, and the adhesive properties before and after the active energy ray irradiation will tend to deteriorate. . Also, if the weight-average molecular weight is too small, the cohesive force of the pressure-sensitive adhesive layer tends to decrease, and the pressure-sensitive adhesive performance and peelability before curing by active energy rays tend to decrease.

The above weight average molecular weight is the weight average molecular weight in terms of standard polystyrene molecular weight. : Shodex GPC KF-806L (exclusion limit molecular weight: 2×10 ⁷ , separation range: 100 to 2×10 ⁷ , number of theoretical plates: 10,000 plates/line, filler material: styrene-divinylbenzene copolymer, filler Particle size: Measured by using 3 in series of 10 μm).

The urethane (meth)acrylate compound (b) used in the present invention preferably has a viscosity at 60° C. of 50 to 10,000 mPa·s, more preferably 100 to 7,000 mPa·s, and particularly preferably 200 to 4,000. . If the viscosity is too low, the cohesive force tends to decrease, and if it is too high, the coatability tends to decrease. The viscosity can be measured with an E-type viscometer.

The active energy ray-curable compound (B) used in the present invention may be composed of a monofunctional (meth)acrylate and a polyfunctional (meth)acrylate in addition to the urethane (meth)acrylate compound (b).

[Monofunctional (meth)acrylate]
Such monofunctional (meth)acrylates include, for example, methyl (meth)acrylate, ethyl (meth)acrylate, acrylonitrile, 2-methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, ) acrylate, 2-hydroxybutyl (meth)acrylate, phenoxyethyl (meth)acrylate, 2-phenoxy-2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-chloro-2 - hydroxypropyl (meth)acrylate, glycerol mono(meth)acrylate, glycidyl (meth)acrylate, lauryl (meth)acrylate, cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, dicyclodecanyl (meth)acrylate pentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)-methyl (meth) acrylates, cyclohexanespiro-2-(1,3-dioxolan-4-yl)-methyl (meth)acrylate, 3-ethyl-3-oxetanylmethyl (meth)acrylate, γ-butyrolactone (meth)acrylate, n-butyl ( meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, dodecyl (meth)acrylate, n-stearyl ( meth) acrylate, benzyl (meth) acrylate, phenol ethylene oxide-modified (n=2) (meth) acrylate, nonylphenol propylene oxide-modified (n=2.5) (meth) acrylate, 2-(meth) acryloyloxyethyl acid phosphate , 2-(meth)acryloyloxy-2-hydroxypropyl phthalate and other half (meth)acrylates of phthalic acid derivatives, furfuryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, carbitol (meth)acrylate, benzyl (meth)acrylate ) acrylate, butoxyethyl (meth)acrylate, allyl (meth)acrylate, (meth)acryloylmorpholine, polyoxyethylene secondary (Meth)acrylate monomers such as alkyl ether acrylate, 2-hydroxyethylacrylamide, N-methylol(meth)acrylamide, N-vinylpyrrolidone, 2-vinylpyridine, vinyl acetate and the like.
Incidentally, n in the above compound names represents the average number of added moles of alkylene oxide.

[Polyfunctional (meth)acrylate]
Polyfunctional (meth)acrylates include bifunctional (meth)acrylates, trifunctional (meth)acrylates, and the like.
Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, and propylene glycol di(meth)acrylate. , dipropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, butylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethylene oxide-modified bisphenol A type di(meth)acrylate, propylene oxide-modified Bisphenol A type di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, ethoxylated cyclohexanedimethanol di(meth)acrylate, dimethyloldicyclopentane di(meth)acrylate, tricyclodecanedimethanol di(meth)acrylate , 1,6-hexanediol di(meth)acrylate, glycerin di(meth)acrylate, pentaerythritol di(meth)acrylate, ethylene glycol diglycidyl ether di(meth)acrylate, diethylene glycol diglycidyl ether di(meth)acrylate, phthalate Acid diglycidyl ester di(meth)acrylate, hydroxypivalic acid-modified neopentyl glycol di(meth)acrylate, isocyanuric acid ethylene oxide-modified diacrylate, and the like.

Trifunctional or higher acrylates include, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth) ) acrylate, tri(meth)acryloyloxyethoxytrimethylolpropane, glycerin polyglycidyl ether poly(meth)acrylate, isocyanuric acid ethylene oxide-modified triacrylate, caprolactone-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol hexa( meth)acrylate, caprolactone-modified pentaerythritol tri(meth)acrylate, caprolactone-modified pentaerythritol tetra(meth)acrylate, ethylene oxide-modified dipentaerythritol penta(meth)acrylate, ethylene oxide-modified dipentaerythritol hexa(meth)acrylate, ethylene oxide Modified pentaerythritol tri(meth)acrylate, ethylene oxide-modified pentaerythritol tetra(meth)acrylate, ethoxylated 15-glycerin triacrylate and the like can be mentioned.

In addition, the active energy ray-curable compound (B) can also be used in combination with a Michael adduct of acrylic acid or 2-acryloyloxyethyldicarboxylic acid monoester as other constituent compounds.
Examples of the Michael adduct of acrylic acid include (meth)acrylic acid dimer, (meth)acrylic acid trimer, (meth)acrylic acid tetramer, and the like.
The 2-acryloyloxyethyldicarboxylic acid monoester is a carboxylic acid having a specific substituent, such as 2-acryloyloxyethylsuccinic acid monoester, 2-methacryloyloxyethylsuccinic acid monoester, 2-acryloyloxy ethyl phthalate monoester, 2-methacryloyloxyethyl phthalate monoester, 2-acryloyloxyethyl hexahydrophthalate monoester, 2-methacryloyloxyethyl hexahydrophthalate monoester, and the like.
Furthermore, oligoester acrylate etc. can be mentioned as another constituent compound.

These monofunctional (meth)acrylates, polyfunctional (meth)acrylates, and other constituent compounds can be used singly or in combination of two or more.

The content of the urethane (meth)acrylate compound (b) in the active energy ray-curable compound (B) is usually 50% by weight or more, preferably 80% by weight or more, and the upper limit is 100% by weight. . If the content is too small, there is a tendency that the releasability and stain resistance after irradiation with active energy rays are lowered.

Moreover, the solvent content in the active energy ray-curable compound (B) is preferably less than 1% by weight, more preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less.
If the content is too large, the cohesive force of the obtained adhesive layer tends to decrease, and the adhesive performance and peelability before curing with active energy rays tend to decrease.
The method for measuring the solvent content is gas chromatography-mass spectrometry (GC-MS).

[Active energy ray-curable composition (X)]
The active energy ray-curable composition (X) contains a (meth)acrylic resin (A) and an active energy ray-curable compound (B). The content of the active energy ray-curable compound (B) is usually 10 to 200 parts by weight, preferably 30 to 150 parts by weight, more preferably 100 parts by weight of the (meth)acrylic resin (A). 50 to 120 parts by weight. If the content of the active energy ray-curable compound (B) is too small, the peelability after irradiation with the active energy ray tends to be lowered, and if it is too large, the cohesive force of the adhesive layer is lowered and the content of the active energy ray-curable compound (B) is reduced before and after the active energy ray. The adhesive properties of the adhesive tend to decrease.

The requirement (α) of the present invention is that the solvent content in the active energy ray-curable composition (X) is less than 1% by weight, and the solvent content is preferably 0.5% by weight or less, more preferably is 0.1% by weight or less.
If the content is too large, the cohesive force of the adhesive layer obtained tends to be low, and the adhesive performance and peelability before curing with active energy rays tend to be low.
The method for measuring the solvent content is gas chromatography-mass spectrometry (GC-MS).

The content of the thermal polymerization initiator in the active energy ray-curable composition (X) is preferably less than 200 ppm, more preferably less than 100 ppm, particularly preferably less than 50 ppm.
If the content is too large, the thermal stability tends to decrease. Such content can be reduced by reducing the content of the thermal polymerization initiator of the (meth)acrylic resin (A).
The thermal polymerization initiator content is measured by liquid chromatography-mass spectrometry (LC-MS).

Furthermore, the melt viscosity of the active energy ray-curable composition (X) at 100° C. is preferably 120 Pa·s or less, more preferably less than 100 Pa·s. If the melt viscosity is too high, there is a tendency for the coatability to significantly deteriorate.
The melt viscosity of the active energy ray-curable composition (X) at 100°C is measured with a B-type rotational viscometer.

[Crosslinking agent (C)]
The active energy ray-curable pressure-sensitive adhesive composition of the present invention contains at least the active energy ray-curable composition (X) and may further contain a cross-linking agent (C).
Examples of the cross-linking agent (C) include isocyanate cross-linking agents, epoxy cross-linking agents, aziridine cross-linking agents, oxazoline cross-linking agents, melamine cross-linking agents, aldehyde cross-linking agents, and amine cross-linking agents. Among these, it is preferable to use an isocyanate cross-linking agent from the viewpoint of improving the adhesiveness of the peelable pressure-sensitive adhesive sheet to the base sheet and the reactivity with the (meth)acrylic resin (A). Moreover, these crosslinking agents (C) can be used individually by 1 type or in combination of 2 or more types.

Examples of the isocyanate-based crosslinking agent include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated xylene diisocyanate, hexamethylene diisocyanate, diphenylmethane-4,4-diisocyanate, and isophorone. Diisocyanates, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and adducts of these polyisocyanate compounds with polyol compounds such as trimethylolpropane polyisocyanate compounds, burettes and isocyanurates of these polyisocyanate compounds. Among them, isocyanurate of hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,6-tolylene diisocyanate and tri Adducts with methylolpropane, isocyanurates of 2,4-tolylenediisocyanate and 2,6-tolylenediisocyanate, and adducts of tetramethylxylylenediisocyanate and trimethylolpropane are preferred.

Examples of the epoxy-based cross-linking agent include bisphenol A/epichlorohydrin type epoxy resin, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether. , trimethylolpropane triglycidyl ether, sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, pentaerythritol polyglycidylerythritol, diglycerol polyglycidyl ether, 1,3′-bis(N,N-diglycidylaminomethyl)cyclohexane, N , N,N',N'-tetraglycidyl-m-xylenediamine and the like.

Examples of the aziridine-based cross-linking agent include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4 '-bis(1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide) and the like.

Examples of the oxazoline-based cross-linking agent include 2,2′-bis(2-oxazoline), 1,2-bis(2-oxazoline-2-yl)ethane, 1,4-bis(2-oxazoline-2- yl)butane, 1,8-bis(2-oxazolin-2-yl)butane, 1,4-bis(2-oxazolin-2-yl)cyclohexane, 1,2-bis(2-oxazolin-2-yl) Bisoxazoline compounds containing aliphatic or aromatic compounds such as benzene, 1,3-bis(2-oxazoline-2-yl)benzene, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, Addition polymerization of 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, etc. and polymers of one or more of oxazolines.

Examples of the melamine-based cross-linking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins. .

Examples of the aldehyde cross-linking agent include glyoxal, malondialdehyde, succindialdehyde, maleinedialdehyde, glutaredialdehyde, formaldehyde, acetaldehyde, and benzaldehyde.

Examples of the amine cross-linking agent include hexamethylenediamine, triethyldiamine, polyethyleneimine, hexamethylenetetramine, diethylenetriamine, triethyltetramine, isophoronediamine, amino resins, and polyamides.

When the active energy ray-curable pressure-sensitive adhesive composition of the present invention further contains a cross-linking agent (C), the content of the cross-linking agent (C) is usually On the other hand, it is preferably 0.1 to 30 parts by weight, more preferably 0.2 to 20 parts by weight, and particularly preferably 0.3 to 15 parts by weight. If the content of the cross-linking agent (C) is within the above range, the cohesive force of the adhesive layer is further improved, the adhesive properties are improved, and the adhesive strength before irradiation with the active energy ray is also good, so that it is possible to use the material to be processed. There is a tendency that lifting and peeling from the adherend are less likely to occur.

[Photoinitiator (D)]
The active energy ray-curable pressure-sensitive adhesive composition of the present invention may further contain a photopolymerization initiator (D).
The photopolymerization initiator (D) used in the present invention may be one that generates radicals by the action of light. In addition, when the (meth)acrylic resin (A) has a photocrosslinkable monomer, it may not contain a photopolymerization initiator.

Such photopolymerization initiators (D) include, for example, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethylketal, 4-(2-hydroxyethoxy)phenyl-(2 -hydroxy-2-propyl)ketone, 1-hydroxycyclohexylphenylketone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-methyl -2-morpholino(4-thiomethylphenyl)propan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 2-hydroxy-2-methyl-1-[4-( Acetophenones such as 1-methylvinyl)phenyl]propanone oligomer; Benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, and benzoin isobutyl ether; Benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone , 4-benzoyl-4′-methyl-diphenylsulfide, 3,3′,4,4′-tetra(tert-butylperoxycarbonyl)benzophenone, 2,4,6-trimethylbenzophenone, 4-benzoyl-N,N -Dimethyl-N-[2-(1-oxo-2-propenyloxy)ethyl]benzenemethanaminium bromide, (4-benzoylbenzyl)trimethylammonium chloride and other benzophenones; 2-isopropylthioxanthone, 4-isopropylthioxanthone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, 2-(3-dimethylamino-2-hydroxy)-3,4-dimethyl-9H-thioxanthone-9-one meso Thioxanthones such as chloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, bis(2,4,6 -trimethylbenzoyl)-phenylphosphine oxide; and the like.
Among them, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone, 1 -[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one and the like are preferred.
In addition, these photoinitiators (D) can be used individually by 1 type or in combination of 2 or more types.

Further, as auxiliary agents for these photopolymerization initiators (D), for example, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone), 4,4'-diethylaminobenzophenone, 2-dimethylaminoethyl Benzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 2-ethylhexyl 4-dimethylaminobenzoate, 2,4-diethylthioxanthone , 2,4-diisopropylthioxanthone and the like can also be used in combination. These auxiliaries may also be used singly or in combination of two or more.

When the active energy ray-curable pressure-sensitive adhesive composition of the present invention further contains a photopolymerization initiator (D), the content of the photopolymerization initiator (D) is 100 weight of the active energy ray-curable compound (B) It is preferably 0.1 to 20 parts by weight, more preferably 0.5 to 15 parts by weight, and particularly preferably 1 to 10 parts by weight. If the content of the photopolymerization initiator (D) is within the above range, there is a tendency that the releasability after irradiation with active energy rays and the contamination resistance to an adherend such as a member to be processed are further improved.

[Other ingredients]
The active energy ray-curable pressure-sensitive adhesive composition of the present invention contains, for example, a small amount of a monofunctional monomer, an antistatic agent, an antioxidant, a plasticizer, a filler, a pigment, a diluent within a range that does not impair the effects of the present invention. , an anti-aging agent, an ultraviolet absorber, an ultraviolet stabilizer, and the like, and these additives may be used singly or in combination of two or more.
Antioxidants are particularly effective in maintaining the stability of the pressure-sensitive adhesive layer. The content of the antioxidant when blended is not particularly limited, but is preferably 0.01 to 5% by weight based on the active energy ray-curable pressure-sensitive adhesive composition.
In addition to the above additives, the active energy ray-curable pressure-sensitive adhesive composition of the present invention contains a small amount of impurities contained in raw materials for manufacturing the constituent components of the active energy ray-curable pressure-sensitive adhesive composition. may be

In addition, since the pressure-sensitive adhesive composition of the present invention may have low contamination resistance to adherends such as workpieces after irradiation with active energy rays, terpene-based resins, rosin-based resins, chroman-based resins, and phenol It is preferable not to contain tackifying resins such as tackifying resins, styrene resins, and petroleum resins.

[Active energy ray-curable adhesive composition]
Thus, by containing at least the active energy ray-curable composition (X) and, if necessary, further containing optional components such as a cross-linking agent (C), a photopolymerization initiator (D), and other components, , the active energy ray-curable pressure-sensitive adhesive composition of the present invention is obtained.

Moreover, the solvent content in the active energy ray-curable pressure-sensitive adhesive composition is preferably less than 1.5% by weight, more preferably less than 1% by weight.
If the solvent content is too high, a large amount of the solvent will remain in the pressure-sensitive adhesive layer, which tends to lower the cohesive force and lower the adhesive properties.
The solvent content is measured by gas chromatography-mass spectrometry (GC-MS).

The active-energy-ray-curable pressure-sensitive adhesive composition of the present invention can be crosslinked, for example, by the cross-linking agent (C) described above to form a peelable pressure-sensitive adhesive, and thus is suitably used as the pressure-sensitive adhesive layer of a peel-type pressure-sensitive adhesive sheet. After laminating this peelable pressure-sensitive adhesive sheet to a member to be processed, by irradiating the active energy ray, the active energy ray-curable composition (X) in the pressure-sensitive adhesive layer is polymerized and the pressure-sensitive adhesive layer is cured, Decrease in adhesive force occurs and exhibits releasability. Using this property, the peelable pressure-sensitive adhesive sheet is used to temporarily protect the surface of various workpieces when the workpieces are processed.
The peelable pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the active energy ray-curable pressure-sensitive adhesive composition of the present invention is crosslinked will be described below.

[Removable adhesive sheet]
The peelable pressure-sensitive adhesive sheet of the present invention is adhered to an adherend such as a member to be processed, and then irradiated with active energy rays to cure the pressure-sensitive adhesive layer to reduce the adhesive strength of the pressure-sensitive adhesive layer. It facilitates detachment from the body.

Examples of workpieces protected by the peelable pressure-sensitive adhesive sheet include semiconductor wafers, printed circuit boards, processed glass products, metal plates, and plastic plates.

The peelable pressure-sensitive adhesive sheet usually has a base sheet, a pressure-sensitive adhesive layer containing the active energy ray-curable pressure-sensitive adhesive composition of the present invention, and a release film.
A method for producing such a peelable pressure-sensitive adhesive sheet will be briefly described. First, the active energy ray-curable pressure-sensitive adhesive composition of the present invention is directly coated on a release film or a base sheet after adjusting the concentration with an appropriate organic solvent. After that, it is dried by heat treatment at 80 to 105° C. for 0.5 to 10 minutes, and is attached to a base sheet or release film to obtain a peelable pressure-sensitive adhesive sheet. Further aging may be performed after drying in order to balance adhesive properties.

Examples of the base sheet include polyester-based resins such as polyethylene naphtate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymer; polyolefin-based resins such as polyethylene, polypropylene, and polymethylpentene; and polyvinyl fluoride. , polyvinylidene fluoride, polyethylene fluoride resins such as polyethylene fluoride; polyamides such as nylon 6, nylon 6,6; polyvinyl chloride, polyvinyl chloride / vinyl acetate copolymer, ethylene-vinyl acetate copolymer, ethylene- vinyl polymers such as vinyl alcohol copolymer, polyvinyl alcohol, and vinylon; cellulose resins such as cellulose triacetate and cellophane; acrylics such as polymethyl methacrylate, polyethyl methacrylate, polyethyl acrylate and polybutyl acrylate Polystyrene; Polycarbonate; Polyarylate; Sheet made of at least one synthetic resin selected from the group consisting of polyimide, etc.; Metal foil of aluminum, copper, and iron; , woven fabrics and non-woven fabrics made of synthetic fibers, etc.;
These base sheets can be used as a single-layer body or as a multi-layer body in which two or more types are laminated. Among these, a sheet made of synthetic resin is preferable from the viewpoint of weight reduction and the like.

As the release film, for example, a sheet made of various synthetic resins exemplified in the base sheet; a sheet having a release treatment on the surface thereof such as paper, woven fabric, or non-woven fabric can be used.

As a method for coating the active energy ray-curable pressure-sensitive adhesive composition, a general coating method can be employed, and examples thereof include roll coating, die coating, gravure coating, comma coating, screen printing, and the like. mentioned.
When the active energy ray-curable pressure-sensitive adhesive composition is dissolved or dispersed in a suitable organic solvent, the organic solvent described in the section [Method for producing (meth)acrylic resin (A)] can be used. It is preferable to use an organic solvent having a boiling point of 80° C. or lower.

The thickness of the pressure-sensitive adhesive layer in the peelable pressure-sensitive adhesive sheet is preferably 1 to 200 μm, more preferably 10 to 100 μm.

As active energy rays, in addition to light rays such as far ultraviolet rays, ultraviolet rays, near ultraviolet rays and infrared rays, electromagnetic waves such as X-rays and gamma rays, electron beams, proton beams, neutron beams and the like can be used. It is advantageous to use ultraviolet light because of the availability of equipment, the price, and the like.

The cumulative irradiation dose of the ultraviolet rays is usually 50 to 3000 mJ/cm ² , preferably 100 to 1000 mJ/cm ² . The irradiation time varies depending on the type of light source, the distance between the light source and the adhesive layer, the thickness of the adhesive layer, and other conditions. good.

The adhesive strength of the peelable pressure-sensitive adhesive sheet varies depending on the composition of the pressure-sensitive adhesive, the type of base sheet, the type of member to be processed, etc., but the 180-degree peel strength before irradiation with active energy rays is usually 1 N/25 mm or more. Yes, preferably 3 N/25 mm or more.

The peelable pressure-sensitive adhesive sheet usually has a lower peel strength after irradiation with active energy than before irradiation with active energy rays.
The 180-degree peel strength of the peelable pressure-sensitive adhesive sheet after irradiation with active energy rays is usually less than 1 N/25 mm, preferably 0.5 N/25 mm or less.
The 180 degree peel strength in the present invention is measured by the method described in Examples.

When the release type pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the active energy ray-curable pressure-sensitive adhesive composition of the present invention is crosslinked has a release film, after peeling the release film, the member to be processed which is an adherend The surface of the member to be processed can be temporarily protected by laminating it on the surface of the workpiece. In addition, by irradiating the active energy ray, the adhesive layer of the peelable adhesive sheet is cured and the adhesive strength is lowered, so that the peelable adhesive sheet can be easily peeled off from the member to be processed.
In addition, the peelable pressure-sensitive adhesive sheet of the present invention is not limited to the one in the form of a sheet, and may be in the form of a roll, or may be processed into various shapes. A roll-shaped peelable pressure-sensitive adhesive sheet may not have a release film, and in this case, the back surface of the base sheet (the surface opposite to the pressure-sensitive adhesive layer) is preferably release-treated.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.
In addition, "%" and "parts" hereinafter mean weight standards. The glass transition temperature (Tg), weight average molecular weight (Mw), solvent content, and melt viscosity (Pa·s (100°C)) are values measured according to the methods described herein. Viscosity (Pa·s (25°C)) is a value measured by a B-type rotational viscometer.

<Preparation of (meth)acrylic resin (A) solution>
[Acrylic resin (A-1)]
In a reactor equipped with a temperature controller, a thermometer, a stirrer, a dropping funnel and a reflux condenser, 50 parts of methyl ethyl ketone and 2,2′-azobis(2,4-dimethylvaleronitrile) (ADVN (thermal 0.042 parts of polymerization initiator)) was charged, and the temperature was raised while stirring. When the internal temperature was stabilized at 78° C., 65.45 parts of 2-ethylhexyl acrylate (a1) and 2-hydroxyethyl were used as copolymer components. A mixture prepared by mixing and dissolving 25.45 parts of methacrylate (a2), 9.1 parts of vinyl acetate, 0.083 parts of ADVN and 3.3 parts of methyl ethyl ketone was added dropwise over 2 hours and reacted under reflux. Then, after 3 hours from the start of the reaction, a solution in which 3.3 parts of methyl ethyl ketone and 0.083 parts of ADVN were dissolved was added, and after 4.5 hours from the start of the reaction, 3.3 parts of ethyl acetate and 0.083 parts of ADVN were dissolved. After 7 hours from the start of the reaction, the reaction was terminated to obtain an acrylic resin (A-1) solution.
The obtained acrylic resin (A-1) had a glass transition temperature (Tg) of −51.4° C., a resin content in the solution of 62.2%, a viscosity of 1500 mPa s (25° C.), and a weight average molecular weight ( Mw) was 122,000.
Next, the obtained acrylic resin (A-1) solution was put into a flask equipped with a reflux liquid discharge tube, and the temperature was reduced to 10 kPa for 1 hour, and the pressure was reduced to 10 kPa and held at 90° C. for 3 hours. The solvent was distilled off to obtain acrylic resin (A-1) (melt viscosity at 100° C.: 120 Pa·s).

<Preparation of active energy ray-curable compound (B)>
[Urethane acrylate (B-1)]
25.9 parts of isophorone diisocyanate (isocyanate group content: 37.8%) (manufactured by Evonik Japan) was added to a four-necked flask equipped with a temperature controller, a thermometer, a stirrer, a water-cooled condenser and a nitrogen gas inlet, Pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value: 119.1 mgKOH/g) 54.9 parts, decyl alcohol (hydroxyl value: 350.9 mgKOH/g) (Carcol 1098, manufactured by Kao Corporation) 19.2 parts, polymerization 0.04 parts of 2,6-di-tert-butylcresol as an inhibitor and 0.02 parts of dibutyltin dilaurate, a tin-based compound, as a reaction catalyst were charged and reacted at 60° C. until the residual isocyanate group content was 0.00. The reaction was terminated when the content became 3% or less, and urethane acrylate (B-1) (3 (meth)acryloyl groups, weight average molecular weight 900, urethane acrylate having a structure of general formula (1), solvent content 0 .1% or less and acryloyl group concentration of 5.79 mmol/g) mixture was obtained.

[Urethane acrylate (B-2)]
Dicyclohexylmethane 4,4'-diisocyanate (isocyanate group content: 32%) (manufactured by Evonik Japan Co., Ltd.) ) 25.8 parts, pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value: 119.1 mgKOH/g) 46.2 parts, branched alcohol having 17 carbon atoms (hydroxyl value: 203 mgKOH/g) (Fine Oxocol 180T, Nissan Chemical Co., Ltd.) 28 parts, 0.04 parts of 2,6-di-tert-butyl cresol as a polymerization inhibitor, and 0.02 parts of dibutyltin dilaurate, which is a tin compound as a reaction catalyst, were charged and reacted at 60°C. , The reaction was terminated when the residual isocyanate group content was 0.3% or less, and urethane acrylate (B-2) ((meth)acryloyl group number: 3, weight average molecular weight: 1,400, general formula (1) A mixture of urethane acrylate having the structure of, a solvent content of 0.1% or less, and an acryloyl group concentration of 4.87 mmol/g) was obtained.

[Urethane acrylate (B-3)]
9.4 parts of isophorone diisocyanate (isocyanate group content: 37.8%) (manufactured by Evonik Japan) was added to a four-necked flask equipped with a temperature controller, thermometer, stirrer, water-cooled condenser and nitrogen gas inlet. 43.3 parts of polypropylene glycol (hydroxyl value: 54.9 mgKOH/g) (Sannics PP-2000, manufactured by Sanyo Chemical Industries, Ltd.), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl value: 51 mgKOH/g) ) 47.3 parts, 0.04 parts of 2,6-di-tert-butyl cresol as a polymerization inhibitor, and 0.02 parts of dibutyltin dilaurate, which is a tin-based compound as a reaction catalyst, were charged, reacted at 60° C., and residual The reaction was terminated when the isocyanate group content was 0.3% or less, and urethane acrylate (B-3) ((meth)acryloyl group number: 10, weight average molecular weight: 7,500, urethane having a polyol-derived structure A mixture of acrylate, solvent content <0.1% acryloyl group concentration 4.73 mmol/g) was obtained.

[Urethane acrylate (B-4)]
12.0 parts of hexamethylene diisocyanate (isocyanate group content: 50%) (manufactured by Asahi Kasei Co., Ltd.), polypropylene glycol 36, and .1 part (hydroxyl value: 111 mgKOH/g) (Sannix PP-1000, manufactured by Sanyo Chemical Industries, Ltd.), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl value: 48 mgKOH/g) 41.7 parts , branched alcohol having 17 carbon atoms (Fine Oxocol 180T, manufactured by Nissan Chemical Industries, Ltd., hydroxyl value: 203 mgKOH / g) 10.2 parts, 2,6-di-tert-butyl cresol 0.04 parts as a polymerization inhibitor, reaction 0.02 parts of dibutyltin dilaurate, which is a tin-based compound, was charged as a catalyst and reacted at 60°C. ) (5 (meth)acryloyl groups, weight average molecular weight of 1,600, urethane acrylate having a polyol-derived structure, solvent content of 0.1% or less, acryloyl group concentration of 0.99 mmol/g) mixture was obtained.

[Urethane acrylate (B'-1)]
6.6 parts of isophorone diisocyanate (isocyanate group content: 37.8%) (manufactured by Evonik Japan), dipentaerythritol penta 93.4 parts of a mixture of acrylate and dipentaerythritol hexaacrylate (hydroxyl value 48 mgKOH/g), 0.06 parts of 2,6-di-tert-butyl cresol as a polymerization inhibitor, and 0.02 parts of dibutyltin dilaurate as a reaction catalyst. Charged, reacted at 60 ° C., the reaction was terminated when the residual isocyanate group content was 0.3% or less, urethane acrylate (B'-1) (number of (meth)acryloyl groups: 10, weight average molecular weight: 1270 , a solvent content of 0.1% or less and an acryloyl group concentration of 9.3 mmol/g).

[Urethane acrylate (B'-2)]
16.3 parts of isophorone diisocyanate (isocyanate group content: 37.8%) (manufactured by Evonik Japan) was added to a four-necked flask equipped with a temperature controller, thermometer, stirrer, water-cooled condenser and nitrogen gas inlet, 75 parts of polypropylene glycol (hydroxyl value: 54.9 mgKOH/g) (Sannix PP-2000, manufactured by Sanyo Chemical Industries, Ltd.), 8.7 parts of 2-hydroxyethyl acrylate (hydroxyl value: 483.2 mgKOH/g), polymerization prohibited 0.04 parts of 2,6-di-tert-butylcresol as an agent and 0.02 parts of dibutyltin dilaurate, a tin compound as a reaction catalyst, were charged and reacted at 60° C. to give a residual isocyanate group content of 0.3. % or less, the reaction was terminated, and urethane acrylate (B′-2) (two (meth)acryloyl groups, weight average molecular weight of 5,700, urethane acrylate having a polyol-derived structure, solvent content of 0.000). 1% or less, acryloyl group concentration 0.74 mmol/g) mixture was obtained.

[Polyfunctional acrylate (B'-3)]
A mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl value 48 mgKOH/g)

[Polyfunctional acrylate (B'-4)]
Trimethylolpropane triacrylate (Aronix M-309, manufactured by Toagosei Co., Ltd.)

[Preparation of active energy ray-curable composition (X) <X-1 to 4, X'-1 to 4>]
The acrylic resin (A) and the active energy ray-curable compound (B) are mixed at the contents shown in Table 1, and the active energy ray-curable composition (X) <X-1 to 4, X'-1. ~4> was obtained.

[Requirement (α): Solvent content (% by weight)]
The solvent content in the obtained active energy ray-curable composition (X) was measured, and the results are shown in Table 1.

[Requirement (β): Presence or absence of urethane (meth)acrylate in compound (B)]
When the active energy ray-curable compound (B) used contains urethane (meth)acrylate (b), it is marked with “○” in Table 1, and when it does not contain urethane (meth)acrylate (b), Table 1 "x" was written in.

[Requirement (γ): Presence or absence of specific structure of urethane (meth)acrylate (b)]
When the urethane (meth)acrylate (b) has the structure described in general formula (1) and/or the structure derived from a polyol and has 3 or more (meth)acryloyl groups per molecule, it is marked with "○" in Table 1. was described, and "x" was described in Table 1 in other cases. In Table 1, "-" is indicated when not applicable to urethane (meth)acrylate.

[Compatibility]
The appearance of the obtained active energy ray-curable composition (X) was visually observed and evaluated according to the following criteria.
○: Uniform and transparent △: Uniform and slightly cloudy ×: Non-uniform (separation) or cloudy

[Melt viscosity]
After the obtained active energy ray-curable composition (X) was allowed to stand at 100° C. for 24 hours, the viscosity at 100° C. was measured using a B-type rotational viscometer and evaluated according to the following evaluation criteria.
○: Melt viscosity 120 Pa s or less ×: Melt viscosity exceeds 120 Pa s

<Examples 1 to 4, Comparative Examples 1 to 4>
The acrylic resin (A) prepared above, the active energy ray-curable compound (B), and the following components were blended in the amounts shown in Table 2 to obtain an active energy ray-curable pressure-sensitive adhesive composition. . Furthermore, using this pressure-sensitive adhesive composition, a release-type pressure-sensitive adhesive sheet was produced.

[Crosslinking agent (C)]
- Isocyanate-based cross-linking agent (C-1): trimethylolpropane adduct of tolylene diisocyanate (Coronate L-55E, manufactured by Tosoh Corporation)

[Photopolymerization initiator (D)]
- Photopolymerization initiator (D-1): 2-dimethylamine-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)-butanone (OMNIRAD379, manufactured by IGM Resins)

[Production of peelable adhesive sheet]
Using the obtained active energy ray-curable pressure-sensitive adhesive composition, each component shown in Table 2 was blended and the temperature was adjusted to 100° C., and then a polyethylene terephthalate film (thickness: 38 μm) as a base sheet (T60 Lumirror, manufactured by Toray Industries, Inc.) with an applicator. After drying at 100 ° C. for 2 minutes and cooling to room temperature, it was attached to a release film (SP-PET3801-BU, manufactured by Mitsui Chemicals Tohcello) and aged at 40 ° C. for 7 days to obtain a peelable adhesive sheet ( A pressure-sensitive adhesive layer having a thickness of 25 μm was obtained.
The following evaluation was performed using the obtained peelable pressure-sensitive adhesive sheet. The results are also shown in Table 2.

(Adhesive strength before active energy ray irradiation)
A test piece of 25 mm × 100 mm was prepared from the peelable pressure-sensitive adhesive sheet obtained above, and after peeling off the release film, it was placed on a stainless steel plate (SUS304BA plate) at 23 ° C. and a relative humidity of 50%. A rubber roller was reciprocated twice to apply pressure. After standing for 30 minutes in the same atmosphere, the 180 degree peel strength (N/25 mm) was measured at a peel rate of 300 mm/min and evaluated according to the following criteria.
○: 5 N / 25 mm or more △: 1 N / 25 mm or more, less than 5 N / 25 mm ×: less than 1 N / 25 mm

(Adhesive strength after irradiation with active energy rays)
A test piece of 25 mm × 100 mm was prepared from the peelable pressure-sensitive adhesive sheet obtained above, and after peeling off the release film, it was placed on a stainless steel plate (SUS304BA plate) at 23 ° C. and a relative humidity of 50%. A rubber roller was reciprocated twice to apply pressure. After standing for 30 minutes in the same atmosphere, ultraviolet irradiation was performed from a height of 18 cm at a conveyor speed of 51 m/min using one 80 W high-pressure mercury lamp (accumulated irradiation amount: 250 mJ/cm ² ). Furthermore, after standing for 30 minutes in an atmosphere of 23° C. and 50% relative humidity, the 180 degree peel strength (N/25 mm) was measured at a peel rate of 300 mm/min and evaluated according to the following criteria.
○: Less than 0.1 N/25 mm △: 0.1 N/25 mm or more, less than 1.0 N/25 mm ×: 1.0 N/25 mm or more

The active energy ray-curable compositions (X-1 to 4) shown in Table 1 have good or excellent compatibility between the acrylic resin (A) and the active energy ray-curable compound (B). The peelable pressure-sensitive adhesive sheets of Examples 1 to 4 obtained using the compositions (X-1 to 4) had excellent adhesive strength before and after irradiation with active energy rays.
On the other hand, Comparative Example 1 using urethane acrylate (B'-1) not containing general formula (1) and/or polyol structure as the active energy ray-curable compound (B), and active energy ray-curable compound (B) In Comparative Example 3 using the mixture (B'-3) of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate as the compound, the compatibility with the acrylic resin (A) was poor, so it was difficult to obtain a peelable pressure-sensitive adhesive sheet. I couldn't do it.
Further, the active energy ray-curable composition (X'-2) using urethane acrylate (B'-2) having only two acryloyl groups as the active energy ray-curable compound (B) has compatibility and melt viscosity However, the peelable pressure-sensitive adhesive sheet of Comparative Example 2 obtained using this composition (X'-2) was inferior in adhesive strength after curing with active energy rays.
Furthermore, the active energy ray-curable composition (X'-4) using trimethylolpropane triacrylate (B'-4) as the active energy ray-curable compound (B) is also excellent in compatibility and melt viscosity, and this composition The peelable pressure-sensitive adhesive sheet of Comparative Example 4 obtained using the product (X'-4) was excellent in adhesive strength after irradiation with active energy rays, but inferior in adhesive strength before curing with active energy rays. .

From the above results, the active energy ray-curable compound (B) contains urethane (meth)acrylate (b), and the urethane (meth)acrylate (b) is derived from the structure and/or polyol described in general formula (1) and having 3 or more (meth)acryloyl groups per molecule, the compatibility with the acrylic resin (A) and the melt viscosity are excellent. In addition, when a peelable pressure-sensitive adhesive sheet is produced using this composition, it is found that the adhesive strength before and after irradiation with active energy rays and the stain resistance and peelability after peeling are excellent.

The active energy ray-curable pressure-sensitive adhesive composition of the present invention can be suitably used as a temporary surface-protecting pressure-sensitive adhesive sheet for processing semiconductor wafers, printed circuit boards, processed glass products, metal plates, plastic plates, and the like. .

Claims (6)

It contains at least an active energy ray-curable composition (X) containing a (meth)acrylic resin (A) and an active energy ray-curable compound (B), and satisfies the following requirements (α), (β) and (γ ), an active energy ray-curable pressure-sensitive adhesive composition characterized by satisfying all.
Requirement (α): The solvent content in the active energy ray-curable composition (X) is less than 1% by weight.
Requirement (β): The active energy ray-curable compound (B) contains urethane (meth)acrylate (b).
Requirement (γ): The urethane (meth)acrylate (b) has a structure represented by general formula (1) and/or a polyol-derived structure, and has 3 or more (meth)acryloyl groups per molecule.
-UA general formula (1)
[U is a urethane bond, A is at least one selected from linear or branched alkyl, an alicyclic structure, an aromatic ring structure and a heterocyclic structure. ] 2. The active energy ray-curable pressure-sensitive adhesive composition according to claim 1, wherein the active energy ray-curable composition (X) has a melt viscosity at 100° C. of 120 Pa·s or less. 3. The active energy ray according to claim 1, wherein the urethane (meth)acrylate (b) has at least one structural unit selected from isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate and hexamethylene diisocyanate. A curable adhesive composition. 4. The active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 3, further comprising a cross-linking agent (C). 5. The active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 4, further comprising a photopolymerization initiator (D). A peelable pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer in which the active energy ray-curable pressure-sensitive adhesive composition according to any one of claims 1 to 5 is crosslinked.