JP2022160306A - Active energy ray-curable peelable adhesive composition and peelable adhesive sheet - Google Patents

Abstract

To provide a solventless type active energy ray curable peelable adhesive composition which is not cured before coating even when exposed to a high temperature for a long time (thermal stability), which is excellent in a coating property to a base material sheet in forming an adhesive sheet, further which has desired adhesive force before and after irradiation of an object with an active energy ray, in particular which has an adhesive property of being peeled off without an adhesive residue because the adhesive force after irradiation with the active energy ray is extremely low, and to provide a peelable adhesive sheet.SOLUTION: An active energy ray curable peelable adhesive composition contains an active energy ray curable composition (X) containing a (meth)acrylic resin (A) and an active energy ray curable compound (B) in which the active energy ray curable composition (X) satisfies all of requirements (α)-(ω). A requirement (α): the active energy ray curable compound (B) contains an urethane (meth)acrylic compound (b), a requirement (β): a content of a solvent in the active energy ray curable composition (X) is less than 1 wt.%, a requirement (γ): a content of a thermal polymerization initiator in the active energy ray curable composition (X) is less than 200 ppm, and a requirement (ω): melt viscosity of the active energy ray curable composition (X) at 100°C is 120 Pa s or less.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to an active energy ray-curable peelable pressure-sensitive adhesive composition and a peelable pressure-sensitive adhesive sheet using the same, and more particularly to a semiconductor wafer, a printed circuit board, a processed glass product, a metal plate, a plastic plate, and the like. The present invention relates to an active energy ray-curable peelable pressure-sensitive adhesive composition and a peelable pressure-sensitive adhesive sheet used in the pressure-sensitive adhesive layer of a peelable pressure-sensitive adhesive sheet for temporary protection during processing of members.

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 (peelable adhesive sheet) is used to protect the member to be processed.

As such a protective pressure-sensitive adhesive sheet, a pressure-sensitive adhesive sheet using an emulsion-type acrylic resin whose adhesive strength is reduced 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 curable emulsion pressure-sensitive adhesive using a urethane (meth)acrylate compound having a self-emulsifying action have been disclosed (see, for example, Patent Document 2).
Furthermore, a pressure-sensitive adhesive sheet having a solvent-free acrylic pressure-sensitive adhesive layer containing an acrylic polymer, an acrylic monomer and a photopolymerization initiator on a substrate film is disclosed (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 peelable adhesive sheet for temporary protection is required to have an appropriate adhesive strength to the processed materials, but it can be peeled off after completing its role of protection. When peeling, it is required to be able to peel off with an extremely light force without leaving any 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.
Therefore, in Patent Document 2, a self-emulsifying type urethane (meth)acrylate was used as an emulsion type adhesive to obtain an adhesive without using a surfactant. The reduction in adhesive strength after linear curing was insufficient.

In addition, since the adhesive sheet of Patent Document 3 is not an adhesive sheet whose adhesive strength is reduced by irradiation with active energy rays, it could not be applied to miniaturized and thin-film processed members.

Against this background, the present invention does not cure even when exposed to high temperatures for a long time before coating (thermal stability), and has excellent coating properties on a base sheet when used as an adhesive sheet. Furthermore, an active energy ray-curable peelable pressure-sensitive adhesive composition having a desired adhesive strength before and after irradiation with an active energy ray, in particular, an extremely low adhesive strength after irradiation with an active energy ray, and an adhesive property that allows the composition to be peeled off without adhesive residue; An object of the present invention is to provide a peelable pressure-sensitive adhesive sheet.

However, the inventor of the present invention generally believes that an active energy ray-curable peelable pressure-sensitive adhesive composition containing an acrylic resin and an active energy ray-curable compound is exposed to a high temperature to cause thermal polymerization initiation that remains in the acrylic resin. Due to the decomposition of the agent, the curing of the active energy ray-curable compound started and it was not even possible to heat it to the temperature required for hot melt coating. Thermal stability and coatability are improved by adjusting the melt viscosity of the acrylic resin and the amount of the residual thermal polymerization initiator within a predetermined range by using an active energy ray-curable release-type adhesive composition containing a chemical compound. It has been found that an active energy ray-curable peelable pressure-sensitive adhesive composition can be obtained which has excellent adhesive properties before and after irradiation with active energy rays and excellent stain resistance after peeling even when made into a peelable pressure-sensitive adhesive sheet.

That is, the present invention contains an active energy ray-curable composition (X) containing a (meth)acrylic resin (A) and an active energy ray-curable compound (B),
An active energy ray-curable peelable pressure-sensitive adhesive composition characterized in that the active energy ray-curable composition (X) satisfies all of the following requirements (α) to (ω).
Requirement (α): The active energy ray-curable compound (B) contains a urethane (meth)acrylate compound (b) Requirement (β): The solvent content in the active energy ray-curable composition (X) is 1 Less than wt% Requirement (γ): The content of the thermal polymerization initiator in the active energy ray-curable composition (X) is less than 200 ppm Requirement (ω): Melting of the active energy ray-curable composition (X) at 100 ° C. Viscosity of 120 Pa·s or less The present invention also provides a release-type pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which the above active energy ray-curable release-type pressure-sensitive adhesive composition is crosslinked.

The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention does not harden even when exposed to high temperatures for a long time before coating (thermal stability), and is suitable for use as a base sheet when forming a pressure-sensitive adhesive sheet. Active energy ray-curable release with excellent coatability and desired adhesive strength before and after active energy ray irradiation. It can be a type adhesive composition.

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 acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate, respectively.
In the present invention, the term "sheet" is not particularly distinguished from "film" and "tape", but is used to include these.

The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention is a pressure-sensitive adhesive for a peelable pressure-sensitive adhesive sheet that is normally peeled off after being bonded to a workpiece such as a metal plate, a plastic plate, or a semiconductor wafer. Used for layers. The peelable pressure-sensitive adhesive sheet is formed by coating an active energy ray-curable peelable pressure-sensitive adhesive composition on a base sheet to form a pressure-sensitive adhesive layer. By irradiating the active energy ray, the pressure-sensitive adhesive layer is cured and the adhesive force is lowered, so that the pressure-sensitive adhesive layer can be easily peeled off from the workpiece.

Hereinafter, the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention is
(Meth) contains an active energy ray-curable composition (X) containing an acrylic resin (A) and an active energy ray-curable compound (B),
An active energy ray-curable peelable pressure-sensitive adhesive composition characterized in that the active energy ray-curable composition (X) satisfies all of the following requirements (α) to (ω).
Requirement (α): The active energy ray-curable compound (B) contains a urethane (meth)acrylate compound (b) Requirement (β): The solvent content in the active energy ray-curable composition (X) is 1 Less than wt% Requirement (γ): The content of the thermal polymerization initiator in the active energy ray-curable composition (X) is less than 200 ppm Requirement (ω): Melting of the active energy ray-curable composition (X) at 100 ° C. The viscosity is 120 Pa·s or less.

[(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. and acrylic resins obtained by polymerizing a polymerizable component containing other various polymerizable monomers.

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, methoxypolyethylene glycol (meth) acrylate, ethyl carbitol (meth) acrylate, phenoxyethyl (meth) acrylate, alkylphenoxy polyethylene glycol (meth) acrylate or other alkoxy group or phenoxy group-containing ( 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 these, n-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and n-lauryl methacrylate have a glass transition temperature (Tg) of −30° C. or less when made into a homopolymer and easily lower the melt viscosity. 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, a photocrosslinkable monomer may be contained as the other polymerizable monomer. Such photocrosslinkable monomers are those that generate radicals by the action of light.
Examples of the above photocrosslinkable monomers include 4-acryloyloxybenzophenone, 4-acryloyloxyethoxybenzophenone, 4-acryloyloxy-4'-methoxybenzophenone, 4-acryloyloxyethoxy-4'-methoxybenzophenone, 4-acryloyloxy- 4'-bromobenzophenone, 4-acryloyloxyethoxy-4'-bromobenzophenone, 4-methacryloyloxybenzophenone, 4-methacryloyloxyethoxybenzophenone, 4-methacryloyloxy-4'-methoxybenzophenone, 4-methacryloyloxyethoxy-4' -methoxybenzophenone, 4-methacryloyloxy-4'-bromobenzophenone, 4-methacryloyloxyethoxy-4'-bromobenzophenone, and mixtures thereof.
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 monomer 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, 2-hydroxyethyl (meth)acrylate and (meth)acrylic acid are particularly preferred.

The above-mentioned alkyl group-containing (meth)acrylate monomer is usually contained in an amount of 40% by weight or more, preferably 50% by weight or more, and more preferably 60% by weight or more based on the total polymerized components of the (meth)acrylic resin (A). is preferred. 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 preferable, and 5 to 30% by weight is even more preferable. If the amount of the functional group-containing monomer is too small, the cohesive force tends to decrease when the pressure-sensitive adhesive layer is formed, and the reworkability tends to decrease. On the other hand, if it is too large, the melt viscosity tends to increase and the pot life tends to be shortened.

Other polymerizable monomers are preferably contained in an amount of usually 0 to 30% by weight, preferably 0 to 20% by weight, based on the total polymerizable components of the (meth)acrylic resin (A).
Among other polymerizable monomers, the photocrosslinkable monomer is usually contained in an amount of 0 to 10% by weight, preferably 0 to 5% by weight, based on the total polymerizable components of 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. Among them, solution radical polymerization and bulk polymerization are preferred. Solution radical polymerization is particularly preferable in that acrylic resin can be stably obtained.
An example of a preferred method for producing the (meth)acrylic resin (A) used in the present invention is shown below.

First, the above-described copolymerization component and thermal polymerization initiator are mixed or added dropwise into an organic solvent, followed by solution polymerization to obtain an 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. and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone. These can be used alone or in combination of two or more. Among these solvents, an organic solvent having a boiling point of 80° C. or less is used because solvent-free acrylic resin can be efficiently produced by distilling off the solvent from the acrylic resin solution obtained by solution polymerization. is preferred.

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.), methyl ethyl ketone (80 ° C.), ketone solvents such as acetone (56 ° C.), diethyl ether (35 ° C.), methylene chloride (40 ° C.), tetrahydrofuran (66 ° C.), etc. Among them, ethyl acetate, acetone and methyl acetate are preferably used from the viewpoint of versatility and safety, and ethyl acetate and acetone are particularly preferably used.
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 polymerization reaction, an azo polymerization initiator, a peroxide polymerization initiator, or the like, which is a normal radical polymerization initiator, can be used. , 2,2′-azobis(2-methylbutyronitrile), 2,2′-azobisisobutyronitrile, (1-phenylethyl)azodiphenylmethane, 2,2′-azobis(2,4-dimethylvalero nitrile), 2,2'-azobis (2-cyclopropylpropionitrile), 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile) and the like, and peroxide polymerization initiators Examples include benzoyl peroxide, di-t-butyl peroxide, cumene hydroperoxide, lauroyl peroxide, t-butylperoxypivalate, t-hexylperoxypivalate, t-hexylperoxyneodecanoate, diisopropyl peroxycarbonate, diisobutyryl peroxide and the like. These can be used alone or in combination of two or more.

In the production of the above 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 carry out polymerization at a relatively low temperature. When an initiator 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 acrylic resin solution and the step of heating the active energy ray-curable peelable pressure-sensitive adhesive composition, which will be described later.

Therefore, in the present invention, the step of distilling off the solvent from the acrylic resin solution obtained by solution polymerization and the step of heating as an active energy ray-curable peelable pressure-sensitive adhesive composition are performed stably. Among thermal polymerization initiators, it is preferable to use a thermal polymerization initiator having a 10-hour half-life temperature of 60° C. or less, and particularly preferably 2,2′-azobis(2,4-dimethylvaleronitrile) ( 52° C.), 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), t-hexyl peroxyneodecanoate (44.5°C), diisopropyl peroxycarbonate (40.5°C), Diisobutyryl peroxide (32.7°C), more preferably 2,2'-azobis(2,4-dimethylvaleronitrile) (52°C), t-hexylperoxypivalate (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, and particularly preferably 0.5 to 6 parts by weight, per 100 parts by weight of the polymerization component. , more preferably 1 to 4 parts by weight, particularly preferably 1.5 to 3 parts by weight, most 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 acrylic resin tends to decrease, the amount of residual monomers increases, and the weight average molecular weight of the acrylic resin tends to increase. If the amount used is too large, it will take a long time for the after-mentioned run-up heating, which is not productive.

(Polymerization conditions, etc.)
Polymerization conditions for solution polymerization may be polymerized 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., particularly preferably 55 to 75° C., more preferably 60 to 70° C., from the viewpoint of stable reaction. °C. If the polymerization temperature is too high, the acrylic resin tends to gel easily, and if it is too low, the activity of the thermal polymerization initiator decreases, resulting in a decrease in polymerization rate and an increase in residual monomers.

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. , particularly preferably 1 hour or longer, more preferably 2 hours or longer, particularly preferably 5 hours or longer. 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 acrylic resin, in order to reduce the amount of the residual thermal radical 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 75 to 95°C is particularly preferred. If the run-in heating temperature is too high, the acrylic resin tends to yellow. . Thus, an acrylic resin solution can be obtained.

Since the acrylic resin used in the present invention is preferably a solvent-free acrylic resin containing no solvent, the solvent is then distilled off from the acrylic resin solution.

The step of distilling off the solvent from the acrylic resin solution can be carried out by a known general method. There is a method of distilling off the solvent, and the method of distilling off by heating under reduced pressure is preferable from the point of efficiently distilling off the solvent.

The temperature for distilling off the solvent by heating is preferably 60 to 150°C, and in particular, the reaction solution after polymerization of the 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 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, particularly after distilling off the solvent in the reaction solution by keeping it in the range of 50 to 101.3 kPa. , 0 to 50 kPa to distill off the residual solvent is preferable from the viewpoint of extremely reducing the amount of the residual solvent. Thus, the (meth)acrylic resin (A) used in the present invention can be produced.

[Physical properties of (meth)acrylic resin (A)]
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, particularly preferably less than 200 ppm, more preferably less than 100 ppm, especially less than 100 ppm. preferably 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 content 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 more preferably 90,000 to 1,500,000. 1,000,000, particularly preferably 100,000 to 500,000. If the weight-average molecular weight is too small, the cohesive strength of the resulting pressure-sensitive adhesive layer tends to be low, and the pressure-sensitive adhesive performance before curing with active energy rays and reworkability 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 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 × 107, separation range: 100 to 2 × 107, number of theoretical plates: 10000 plates / book, packing material: styrene-divinylbenzene copolymer, packing particle size : 10 μm) can be measured by connecting three in series, and the number average molecular weight can also be measured by the same method. Further, the degree of dispersion can be obtained from the measured values of the weight average molecular weight and the number average molecular weight.

The (meth)acrylic resin (A) used in the present invention has a melt viscosity at 100° C. of less than 1000 Pa·s, preferably 800 to 0.1 Pa·s, more preferably 500 to 1 Pa·s. If this value is too small, the cohesive force of the adhesive layer will be insufficient, and the adhesive properties before the active energy ray irradiation will tend to deteriorate.
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, still more preferably -68°C to -10°C, particularly preferably -65 to -30°C. If the glass transition temperature is too low, the cohesive strength of the pressure-sensitive adhesive layer is reduced, and the adhesive properties before irradiation with active energy rays tend to be reduced. 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 of homopolymer of monomer A (K) Wa: weight fraction of monomer A Tgb: glass transition temperature of homopolymer of monomer B (K) Wb: weight fraction of monomer B Tgn: homopolymer of monomer N Polymer glass transition temperature (K) Wn: Weight fraction of monomer N (Wa + Wb + ... + Wn = 1)

That is, it is a value calculated by applying the glass transition temperature and weight fraction of each homopolymer of each monomer constituting the acrylic resin to the Fox formula.
The glass transition temperature of a homopolymer of the monomers constituting the acrylic resin is usually measured by a differential scanning calorimeter (DSC), and is measured by a method conforming to JISK7121-1987 or JISK6240. can do.

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 is a value obtained by measuring the (meth)acrylic resin (A) made into a thin film at 23° C. with a NaD line using a refractive index measuring device (“Abbe refractometer 1T” manufactured by Atago Co., Ltd.). .

The solvent content in the (meth)acrylic resin (A) is preferably less than 1% by weight, 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 reworkability before active energy ray curing tend to decrease.
The content is measured by gas chromatography-mass spectrometry (GC-MS).

[Active energy ray-curable compound (B)]
A requirement (α) of the present invention is that the active energy ray-curable compound (B) contains a urethane (meth)acrylate compound (b).
The active energy ray-curable compound (B) used in the present invention contains a urethane (meth)acrylate compound (b). In addition, monofunctional (meth)acrylates, polyfunctional (meth)acrylates, and the like may be contained.

The urethane (meth)acrylate compound (b) is a urethane (meth)acrylate compound (b-1 ), or a urethane (meth)acrylate compound (b- 2), or a urethane (meta ) may be an acrylate compound (b-3).

Among them, in the present invention, the hydroxyl group-containing (meth)acrylate compound (b1) is used as the hydroxyl group-containing (meth)acrylate compound (b1) because it is easily compatible with the (meth)acrylic resin (A) and has good releasability and stain resistance after irradiation with an active energy ray. A urethane (meth)acrylate compound (b-2) or a hydroxyl group-containing (meth)acrylate compound (b1) that is a reaction product with a polyvalent isocyanate compound (b2), a polyvalent isocyanate compound (b2), a monofunctional alcohol A urethane (meth)acrylate compound (b-3) which is a reactant with (b4) and, if necessary, 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.

For example, the hydroxyl group-containing (meth)acrylate compound (b1) has one hydroxyl group, the polyvalent isocyanate compound (b2) has two isocyanate groups, and the polyol compound (b3) has two hydroxyl groups. In the case where the monofunctional alcohol (b4) has one hydroxyl group, the hydroxyl group-containing (meth)acrylate compound (b1) and the polyvalent isocyanate when synthesizing the urethane (meth)acrylate compound (b-2) The reaction molar ratio of the polyol compound (b2) and the polyol compound (b3) is usually a polyvalent isocyanate compound (b2): polyol compound (b3): hydroxyl group-containing (meth)acrylate compound (b1) in a molar ratio. It is about 2:1:2. Further, when the urethane (meth)acrylate compound (b-3) is used, the reaction molar ratio of the hydroxyl group-containing (meth)acrylate compound (b1), the polyvalent isocyanate compound (b2), and the monofunctional alcohol (b4) is usually a polyvalent isocyanate compound (b2): hydroxyl group-containing (meth)acrylate compound (b1): monofunctional alcohol (b4) is about 1:1:1 in molar ratio, and when a polyol is used in combination is usually polyvalent isocyanate compound (b2): polyol compound (b3): hydroxyl group-containing (meth)acrylate compound (b1): monofunctional alcohol (b4) at a molar ratio of about 2:1:1:1. be.

The hydroxyl group-containing (meth)acrylate compound (b1) preferably has one hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate ) acrylate, hydroxyalkyl (meth)acrylates such as 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 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- Hydroxy group-containing (meth)acrylate compounds containing one ethylenically unsaturated group such as 3-(meth)acryloyloxypropyl (meth)acrylate; glycerin di(meth)acrylate, 2-hydroxy-3-acryloyl-oxy Hydroxyl group-containing (meth)acrylate compounds containing two ethylenically unsaturated groups such as propyl 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 and other hydroxyl group-containing (meth)acrylates containing 3 or more ethylenically unsaturated groups ) acrylate compounds and the like.
These hydroxyl group-containing (meth)acrylate compounds (b1) can be used alone or in combination of two or more.

The hydroxyl group-containing (meth)acrylate compound (b1) is, among others, a hydroxyl group-containing (meth)acrylate compound (b1) containing 3 or more ethylenically unsaturated groups in terms of excellent reactivity and versatility. Pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate are particularly preferred.

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; Alicyclic compounds such as hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate and norbornene diisocyanate family-based polyisocyanates; or isocyanurates or polymeric compounds of these polyisocyanates, allophanate-type polyisocyanates, biret-type polyisocyanates, water-dispersed polyisocyanates (e.g., "Aquanate 100" manufactured by Nippon Polyurethane Industry Co., Ltd., "Aquanate 110", "Aquanate 200", "Aquanate 210", etc.).

Among these, aliphatic diisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, and lysine diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate, isophorone diisocyanate, and norbornene are preferred for their excellent reactivity and versatility. Alicyclic diisocyanates such as diisocyanate are preferred, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated xylylene diisocyanate and hexamethylene diisocyanate are particularly preferred, and isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate are more 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 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 polyols include cyclohexanediols such as 1,4-cyclohexanediol and cyclohexyldimethanol, hydrogenated bisphenols such as hydrogenated bisphenol A, and 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 combinations of these polyalkylene glycols. A polymer 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 those having at least two hydroxyl groups in the molecule of a (meth)acrylic acid ester polymer or copolymer. are, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, hexyl (meth)acrylate, octyl (meth)acrylate, (meth)acrylic (Meth)acrylic acid alkyl esters such as 2-ethylhexyl acid, 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 from the viewpoint of cost, and polyester-based polyols, polyether-based polyols and polycarbonate-based polyols are preferably used from the viewpoint of versatility.

The weight average molecular weight of the polyol-based compound (b3) is preferably 60-10,000, particularly preferably 100-5,000, further preferably 200-4,000. If the weight average molecular weight of the polyol compound (b3) is too large, the resulting urethane (meth)acrylate compound (b) and (meth)acrylic resin (A) will be difficult to mix uniformly, and after the active energy ray irradiation Releasability tends to decrease. 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 above monofunctional alcohol (b4) is not particularly limited, but includes linear or branched alkyl group-containing alcohols having 1 to 36 carbon atoms, aromatic ring-containing alcohols, alicyclic group-containing alcohols, heterocyclic ring-containing alcohols, etc., and is preferably is a linear or branched alkyl group-containing alcohol having 1 to 36 carbon atoms, more preferably a linear or branched alkyl group-containing alcohol having 4 to 18 carbon atoms, from the viewpoint of versatility. These can be used singly or in combination of two or more.

The urethane (meth)acrylate compound (b) can be produced by reacting the components as described above by a known reaction means.
An example is shown below.
(1) When obtaining a urethane (meth)acrylate compound (b-1) Method of subjecting the hydroxyl group-containing (meth)acrylate compound (b1) and polyvalent isocyanate compound (b2) to a urethanization reaction (2) Urethane When obtaining a (meth)acrylate compound (b-2), the hydroxyl group-containing (meth)acrylate compound (b1), the polyvalent isocyanate compound (b2), and the polyol compound (b3) are subjected to a urethanization reaction. Method (3) When obtaining a urethane (meth)acrylate compound (b-3) Method for urethanization reaction of functional alcohol (b4) The above urethanization reaction can be carried out by charging the above components into a reactor collectively or separately and carrying out the urethanization reaction by a known reaction means. Further, when producing the urethane (meth)acrylate compound (b-2) or the urethane (meth)acrylate compound (b-3), the polyol compound (b3) and the polyvalent isocyanate compound (b2) A method of reacting a hydroxyl group-containing (meth)acrylate compound (b1) or a monofunctional alcohol (b4) with the reaction product obtained by reacting in advance is to improve the stability of the urethanization reaction and the reduction of by-products. useful in that respect.

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 a reaction catalyst include dibutyl organometallic compounds such as tin dilaurate, trimethyltin hydroxide and tetra-n-butyltin; metal salts such as zinc octenoate, tin octenoate, tin octoate, cobalt naphthenate, stannous chloride and stannic chloride; triethylamine, benzyldiethylamine, 1,4-diazabicyclo[2,2,2]octane, 1,8-diazabicyclo[5,4,0]undecene, N,N,N',N'-tetramethyl-1,3- Amine catalysts such as butanediamine and N-ethylmorpholine, bismuth nitrate, bismuth bromide, bismuth iodide, bismuth sulfide, organic bismuth compounds such as dibutylbismuth dilaurate and dioctylbismuth dilaurate, and bismuth 2-ethylhexanoate Salt, bismuth naphthenate, bismuth isodecanoate, bismuth neodecanoate, bismuth laurate, bismuth maleate, bismuth stearate, bismuth oleate, bismuth linoleate, bismuth acetate, bismuth bismuth neodeca Bismuth-based catalysts such as organic acid bismuth salts such as noate, bismuth disalicylate, and bismuth digallate, zirconium-based catalysts such as inorganic zirconium, organic zirconium, and simple zirconium, zinc 2-ethylhexanoate/zirconium tetraacetylacetoate Examples thereof include catalysts using two or more kinds of catalysts such as nitrate, and among them, dibutyltin dilaurate and organic bismuth compounds are preferable. These catalysts can be used singly or in combination of two or more.

In the above urethanization reaction, an organic solvent having no functional group that reacts with an isocyanate group, for example, esters such as ethyl acetate and butyl acetate, ketones such as methyl ethyl ketone and methyl isobutyl ketone, and aromatics such as toluene and xylene. Organic solvents, such as organic solvents, 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 urethane (meth)acrylate compound (b) is obtained by terminating the above urethanization reaction when the residual isocyanate group content in the reaction system becomes 0.5% by weight or less.

The (meth)acryloyl group concentration of the urethane (meth)acrylate compound (b) thus obtained is 0.5 mmol/g or more. It is preferably 1.0 to 35 mmol/g, more preferably 1.5 to 20 mmol/g, and particularly preferably 2.0 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.

In addition, the urethane (meth)acrylate compound (b) preferably has three or more ethylenically unsaturated groups from the viewpoint of releasability after irradiation with active energy rays. If the number of ethylenically unsaturated 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) become difficult to mix uniformly, and the adhesive properties before and after the active energy ray irradiation tend to deteriorate. If the weight-average molecular weight is too small, the cohesive strength of the pressure-sensitive adhesive layer tends to decrease and the pressure-sensitive adhesive properties tend to decrease.

The above weight-average molecular weight is the weight-average molecular weight in terms of standard polystyrene molecular weight. It is measured by using two in series with four.

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.

In addition, the active energy ray-curable compound (B) may also contain monofunctional (meth)acrylates and polyfunctional (meth)acrylates.

[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 acrylic (Meth)acrylate monomers such as alkyl ether acrylate, 2-hydroxyethylacrylamide, N-methylol(meth)acrylamide, N-vinylpyrrolidone, 2-vinylpyridine, vinyl acetate and the like.

[Polyfunctional (meth)acrylate]
Examples of polyfunctional (meth)acrylates include bifunctional (meth)acrylates and trifunctional or higher acrylates.
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, Michael adducts of acrylic acid or 2-acryloyloxyethyldicarboxylic acid monoesters can also be used in combination. Such Michael adducts of acrylic acid include (meth)acrylic acid dimer, (meth)acrylic acid trimer, (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, other oligoester acrylates and the like can be mentioned.
These monofunctional (meth)acrylates and polyfunctional (meth)acrylates may 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 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, 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 reworkability before active energy ray curing tend to decrease.
The content is measured by gas chromatography-mass spectrometry (GC-MS).

[Active energy ray-curable composition (X)]
In the active energy ray-curable composition (X) of the present invention, the content of the active energy ray-curable compound (B) is 10 to 200 parts by weight with respect to 100 parts by weight of the (meth)acrylic resin (A). is. It is preferably 30 to 150 parts by weight, particularly preferably 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 amount of the active energy ray-curable compound (B) is reduced before and after the active energy ray. Adhesive properties tend to decrease.

Requirement (β) of the present invention is that the solvent content in the active energy ray-curable composition (X) is less than 1% by weight, preferably 0.5% by weight or less, and particularly preferably 0.1% by weight or less. is.
If the content is too large, the cohesive force of the obtained adhesive layer tends to decrease, and the adhesive performance and reworkability before active energy ray curing tend to decrease.
The content is measured by gas chromatography-mass spectrometry (GC-MS).

A requirement (γ) of the present invention is that the content of the thermal polymerization initiator in the active energy ray-curable composition (X) is less than 200 ppm.
The content of such a thermal polymerization initiator is less than 200 ppm, preferably less than 100 ppm, more 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 amount of the thermal polymerization initiator in the (meth)acrylic resin (A).

The amount of thermal polymerization initiator is measured by liquid chromatography-mass spectrometry (LC-MS).

Furthermore, the requirement (ω) of the present invention is that the melt viscosity at 100° C. of the active energy ray-curable composition (X) is 120 Pa·s or less, preferably less than 100 Pa·s. If it is higher than the above range, the coatability tends to be remarkably lowered.
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 peelable pressure-sensitive adhesive composition of the present invention may further contain a cross-linking agent (C) in addition to the active energy ray-curable composition (X). 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) may be used alone or in combination of two or more.

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 these, isocyanurate form of hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,6-tolylene diisocyanate and trimethylol are used in terms of chemical resistance and reactivity with functional groups. Adducts with propane, isocyanurates of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, and adducts of tetramethylxylylene diisocyanate 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.

The content of the crosslinking agent (C) is generally preferably 0.1 to 30 parts by weight, particularly preferably 0.2 to 20 parts by weight, with respect to 100 parts by weight of the (meth)acrylic resin (A). parts by weight, more preferably 0.3 to 15 parts by weight. If the amount of the cross-linking agent (C) is too small, the cohesive strength of the adhesive layer tends to decrease and the adhesive properties tend to deteriorate. There is a tendency for floating and peeling to occur between the material to be processed.

[Photoinitiator (D)]
The photopolymerization initiator (D) used in the present invention may be one that generates radicals by the action of light. When the (meth)acrylic resin contains a photocrosslinkable monomer, the photopolymerization initiator may not be contained.
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 or can use 2 or more types together.

Further, as an auxiliary agent for these photopolymerization initiators (D), for example, triethanolamine, triisopropanolamine, 4,4'-dimethylaminobenzophenone (Michler's ketone)
, 4,4′-diethylaminobenzophenone, 2-dimethylaminoethylbenzoic acid, ethyl 4-dimethylaminobenzoate, (n-butoxy)ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, 4-dimethylamino 2-Ethylhexyl benzoate, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. can also be used in combination. These auxiliaries can also be used alone or in combination of two or more.

The content of the photopolymerization initiator (D) is preferably 0.1 to 20 parts by weight, particularly preferably 0.5 to 15 parts by weight, relative to 100 parts by weight of the active energy ray-curable compound (B). parts, particularly preferably 1 to 10 parts by weight. If the content of the photopolymerization initiator (D) is too small, the peelability after irradiation with active energy rays tends to decrease, and if it is too large, the contamination resistance of the workpiece after irradiation with active energy rays tends to decrease. There is

[Other ingredients]
The active energy ray-curable peelable 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, as long as the effects of the present invention are not impaired. Additives such as diluents, anti-aging agents, UV absorbers, and UV stabilizers may be further contained, and these additives may be used alone 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 relative to the active energy ray-curable peelable pressure-sensitive adhesive composition. In addition to the additives described above, the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention contains impurities, etc. contained in raw materials for manufacturing the constituent components of the active energy ray-curable peelable pressure-sensitive adhesive composition. may be contained in a small amount.

In addition, since the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention has low contamination resistance to a workpiece after irradiation with active energy rays, It is preferable not to contain tackifying resins such as resins, styrene-based resins, and petroleum-based resins.

[Active energy ray-curable peelable pressure-sensitive adhesive composition]
Thus, a (meth)acrylic resin (A), an active energy ray-curable composition (X) containing an active energy ray-curable compound (B), optionally a cross-linking agent (C), a photopolymerization initiator By mixing optional components such as (D), an ethylenically unsaturated compound, and other components, the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention can be obtained.

Moreover, the solvent content in the active energy ray-curable peelable pressure-sensitive adhesive composition is less than 1.5% by weight, preferably less than 1% by weight.
If this value is too large, a large amount of solvent remains in the adhesive layer, which tends to reduce the cohesion and adhesive properties.
Solvent content is measured by gas chromatography-mass spectrometry (GC-MS).

The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention is crosslinked with the crosslinking agent (C), and is suitably used as a pressure-sensitive adhesive layer of a peelable pressure-sensitive adhesive sheet. Then, after this peelable pressure-sensitive adhesive sheet is attached to a member to be processed, the active energy ray-curable composition (X) is polymerized and the pressure-sensitive adhesive layer is cured by irradiating the active energy ray, thereby increasing the adhesive strength. Releasability is demonstrated by the occurrence of a decrease. Utilizing this property, it is used to temporarily protect the surface of various workpieces during machining.
The peelable pressure-sensitive adhesive sheet will be described below.

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 comprising the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention, and a release film. As a method for producing such a peelable pressure-sensitive adhesive sheet, first, the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention is directly applied on a release film or a base sheet after adjusting the concentration with an appropriate organic solvent. to coat. 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 Resin; polystyrene; polycarbonate; polyarylate; sheet made of at least one synthetic resin selected from the group consisting of polyimide, etc.; , woven fabrics and non-woven fabrics made of synthetic fibers and the like. 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.

Furthermore, as the release film, for example, release-treated various synthetic resin sheets, paper, woven fabrics, non-woven fabrics, etc. exemplified in the base sheet can be used.

In addition, the method for applying the active energy ray-curable peelable pressure-sensitive adhesive composition is not particularly limited as long as it is a general coating method, and examples thereof include roll coating, die coating, gravure coating, and comma coating. , screen printing, and the like.

The thickness of the pressure-sensitive adhesive layer in the peelable pressure-sensitive adhesive sheet is generally 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 rays because of the availability and price of equipment.

The cumulative irradiation dose of the ultraviolet rays is usually 50 to 3000 mJ/cm2, preferably 100 to 1000 mJ/cm2. 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 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, 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 1 N/25 mm or less, preferably 0.5 N/25 mm or less.

A peelable pressure-sensitive adhesive sheet using the active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention as a pressure-sensitive adhesive layer is adhered to a member to be processed, and after temporarily protecting the surface of the member to be processed, By irradiating the active energy ray, the pressure-sensitive adhesive layer is cured and the adhesive force is lowered, so that the pressure-sensitive adhesive layer can be easily peeled off from the member to be processed.

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.

<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), 9.10 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, 3 hours after the start of the reaction, a solution of 3.3 parts of methyl ethyl ketone and 0.083 parts of ADVN was added, and 4.5 hours after 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, and the acrylic resin (A-1) solution had a glass transition temperature of −51.4° C., a resin content of 62.2%, and a viscosity of 1500 mPa s (25° C.). ], a weight average molecular weight Mw of 122,000 was obtained.
Next, the obtained acrylic resin (A-1) solution was put into a flask equipped with a reflux liquid discharge tube, and the pressure was reduced to 10 kPa and held at 90° C. for 3 hours at 90° C. for 1 hour. The solvent was distilled off to obtain acrylic resin (A-1) (melt viscosity at 100° C.: 120 Pa·s).

[Acrylic resin (A'-1)]
An acrylic resin (A'-1) was obtained in the same manner as the above acrylic resin (A-1) except that the amount of ADVN (thermal polymerization initiator) added was increased.

[Acrylic resin (A'-2)]
A reactor equipped with a temperature controller, a thermometer, a stirrer, a dropping funnel and a reflux condenser was charged with 75 parts of methyl ethyl ketone and 0.042 parts of ADVN as a polymerization catalyst. , 52 parts of n-butyl acrylate (a1), 20 parts of methyl methacrylate, 28 parts of 2-hydroxyethyl methacrylate (a2), 0.083 parts of ADVN, and 3.3 parts of methyl ethyl ketone as copolymer components were mixed and dissolved. The resulting mixture 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 0.042 parts of ADVN were dissolved was added, and after 4.5 hours from the start of the reaction, a solution in which 3.3 parts of methyl ethyl ketone and 0.042 parts of ADVN were dissolved was added. was added, and the reaction was terminated after 9 hours from the start of the reaction. , and a weight average molecular weight Mw of 231,000.
Next, the obtained acrylic resin (A'-2) solution was put into a flask equipped with a reflux liquid discharge tube, and the pressure was reduced to 10 kPa and held at 90° C. for 3 hours at 90° C. for 1 hour. The solvent was removed by distillation to obtain an acrylic resin (A'-2) having a melt viscosity of 2000 Pa·s or more.

*
2EHA: 2-ethylhexyl acrylate BA: n-butyl acrylate MMA: methyl methacrylate HEA: 2-hydroxyethyl acrylate VAc: vinyl acetate

<Preparation of active energy ray-curable compound (B)>
[Urethane acrylate (B-1)] Isophorone diisocyanate (isocyanate group content: 37.8%) (Evonik・ Made in Japan) 9.4 parts, Sannics PP-2000 43.3 parts (hydroxyl value: 54.9 mgKOH / g) (manufactured by Sanyo Chemical Industries), a mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (hydroxyl Value: 51 mg KOH/g) 47.3 parts, 0.04 parts of 2,6-di-tert-butylcresol as a polymerization inhibitor, and 0.02 parts of dibutyltin dilaurate, which is a tin compound as a reaction catalyst, were charged at 60°C. The reaction was terminated when the residual isocyanate groups became 0.3% or less, and urethane acrylate (B) (10 ethylenically unsaturated groups, weight average molecular weight of 7,500, acryloyl group concentration of 4.73 mmol /g) mixture was obtained.

[Urethane acrylate (B-2)]
Dicyclohexylmethane 4,4'--diisocyanate (isocyanate group content: 32.0%) (Evonik・ Made in Japan) 25.8 parts, pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value: 119.1 mgKOH / g) 46.2 parts, Fine Oxocol 180T (hydroxyl value: 203.0 mgKOH / g) (Nissan Chemical 28.0 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 groups became 0.3% or less, and a mixture of urethane acrylate (B) (3 ethylenically unsaturated groups, weight average molecular weight of 1,400, acryloyl group concentration of 4.87 mmol/g) got

[Polyfunctional (meth)acrylate (B-3)]
Trimethylolpropane triacrylate (manufactured by Toagosei Chemical Co., Ltd.: Aronix M-309)

[Preparation of active energy ray-curable composition (X)]
The acrylic resin (A) and the urethane acrylate (b) were mixed (requirement (α)) at the contents shown in Table 2 to obtain an active energy ray-curable composition (X).

[Requirement (β): Solvent content]
The solvent content in the obtained active energy ray-curable composition (X) was measured. Table 2 shows the results.

[Requirement (γ): content of thermal polymerization initiator]
The amount of thermal polymerization initiator in the obtained active energy ray-curable composition (X) was measured using LC-MS. The detection limit of the thermal polymerization initiator was 5 ppm.

[Requirement (ω): 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 ×: More than melt viscosity 120 Pa · s

(Thermal stability)
After the obtained active energy ray-curable composition (X) was allowed to stand at 100° C. for 24 hours, the appearance was visually observed and evaluated according to the following evaluation criteria.
◯: Neither thickening nor gelling was observed.
x: Thickening or gelation was observed.

<Examples 1 to 6, Comparative Examples 1 to 3>
The active energy ray-curable composition (X) prepared above and the following components are blended in the amounts shown in Table 3 to obtain an active energy ray-curable peelable pressure-sensitive adhesive composition, which is a peelable pressure-sensitive adhesive. A sheet was produced.

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

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

[Production of peelable adhesive sheet]
After blending each component shown in Table 3 using the obtained active energy ray-curable peelable pressure-sensitive adhesive composition and adjusting the temperature to 100 ° C., a polyethylene terephthalate film (thickness 38 μm) (Toray company, "T60 Lumirror"), dried at 100 ° C. for 2 minutes, cooled to room temperature, and then a release film (Mitsui Chemicals Tocello, "SP-PET3801-BU") and aged at 40° C. for 7 days to obtain a peelable pressure-sensitive adhesive sheet (thickness of pressure-sensitive adhesive layer: 25 μm).
The following evaluation was performed using the obtained peelable pressure-sensitive adhesive sheet. Table 3 shows the results.

(Coatability)
The appearance of the obtained peelable pressure-sensitive adhesive sheet was visually observed and evaluated according to the following criteria.
○: Uniform coating film with no unevenness or streaks in the coating film ×: Non-uniform coating film with unevenness or streaks in the coating film

(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%. The rubber roller was reciprocated twice to apply pressure, and after standing for 30 minutes in the same atmosphere, the 180 degree peel strength (N/25 mm) was measured at a peel speed 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%. The rubber roller was reciprocated twice to attach it under pressure, left for 30 minutes in an atmosphere of 23 ° C. and a relative humidity of 50%, and then using one 80 W high-pressure mercury lamp, 51.0 m / min from a height of 18 cm. was irradiated with ultraviolet rays (accumulated irradiation amount: 250 mJ/cm2) at a conveyor speed of . Further, after standing for 30 minutes in an atmosphere of 23° C. and 50% relative humidity, the 180° peel strength (N/25 mm) was measured at a peel speed of 300 mm/min.
○: 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

*Comparative Example 1: Adhesive strength could not be evaluated because it gelled during heating and could not be applied. Comparative Example 2: Adhesive strength could not be evaluated because unevenness and streaks occurred in the coating film.

Example 1 shows excellent thermal stability of the active energy ray-curable composition (X), excellent coatability of the active energy ray-curable peelable pressure-sensitive adhesive composition, and adhesive strength before and after active energy ray irradiation. was also excellent.
On the other hand, in Comparative Example 1, in which the amount of the thermal polymerization initiator remaining in the active energy ray-curable peelable pressure-sensitive adhesive composition exceeded a predetermined amount, gelation was observed during heating and the thermal stability was poor, so evaluation was not possible. Interrupted.
In addition, in Comparative Example 2 in which the melt viscosity of the active energy ray-curable peelable pressure-sensitive adhesive composition exceeds 200 Pa s, the viscosity at the time of coating is too high, causing unevenness and streaks in the coating film, resulting in poor coating properties. evaluation was discontinued.
Furthermore, Comparative Example 3, which does not contain urethane (meth)acrylate as the active energy ray-curable compound (B), was excellent in thermal stability and melt viscosity, but inferior in adhesive strength before active energy ray curing.

From the above results, the active energy ray-curable compound contains urethane (meth)acrylate (b) (requirement (α)) and the active energy ray-curable composition (X) (requirement (β )) is used as a release-type adhesive sheet, the amount of thermal polymerization initiator in the active-energy-ray-curable composition (X) is less than 200 ppm ( Requirement (γ)) and that the viscosity of the active energy ray-curable composition (X) at 100 ° C. is 120 Pa s or less (requirement (ω)), excellent coatability, and a peelable pressure-sensitive adhesive sheet It can be seen that a pressure-sensitive adhesive composition having excellent adhesive strength before and after irradiation with active energy rays and excellent stain resistance after peeling can be obtained.

The active energy ray-curable peelable pressure-sensitive adhesive composition of the present invention is a temporary surface protective pressure-sensitive adhesive sheet (peeling pressure-sensitive adhesive sheet ) can be suitably used.

Claims (6)

(Meth) contains an active energy ray-curable composition (X) containing an acrylic resin (A) and an active energy ray-curable compound (B),
An active energy ray-curable peelable pressure-sensitive adhesive composition characterized in that the active energy ray-curable composition (X) satisfies all of the following requirements (α) to (ω).
Requirement (α): The active energy ray-curable compound (B) contains a urethane (meth)acrylate compound (b) Requirement (β): The solvent content in the active energy ray-curable composition (X) is 1 Less than wt% Requirement (γ): The content of the thermal polymerization initiator in the active energy ray-curable composition (X) is less than 200 ppm Requirement (ω): Melting of the active energy ray-curable composition (X) at 100 ° C. Viscosity of 120 Pa s or less 2. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic resin (A) has a weight average molecular weight of 50,000 or more. 3. The active energy ray-curable peelable pressure-sensitive adhesive composition according to claim 1, wherein the (meth)acrylic resin (A) has a glass transition temperature of −30° C. or lower. 4. The active energy ray-curable peelable 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 peelable 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 peelable pressure-sensitive adhesive composition according to any one of claims 1 to 6 is crosslinked.