JP7400572B2 - Active energy ray-curable peelable adhesive composition and peelable adhesive sheet - Google Patents

Description

The present invention relates to an active energy ray-curable release adhesive composition and a release adhesive sheet using the same. The present invention relates to an active energy ray-curable releasable adhesive composition and a releasable adhesive sheet used in an adhesive layer of a releasable adhesive sheet for temporary surface protection when processing a member.

Conventionally, in processing processes such as fabricating integrated circuits on semiconductor wafers or drilling holes, the above-mentioned methods are temporarily used to prevent contamination or damage to the semiconductor wafer, which is the workpiece. A surface protection adhesive sheet is used to protect the surface of a workpiece.
In recent years, due to the miniaturization of processing technology and the thinning of films on workpieces, the above-mentioned adhesive sheets are required to have an appropriate adhesive strength to workpieces. It is required that the adhesive can be removed with light force without leaving any adhesive residue. Such adhesive sheets are used not only in semiconductor wafers but also in the processing of various members.

The adhesive used in the adhesive layer of the above-mentioned adhesive sheet contains an acrylic resin and a polyfunctional unsaturated group-containing compound, and has active energy that cures the adhesive by irradiation with active energy rays and provides removability. Line-curable release adhesives are known.

As shown in Patent Document 1, the acrylic resin used in the composition forming the active energy ray-curable release adhesive includes polyfunctional monomers, polyfunctional urethane (meth)acrylate, etc. In consideration of compatibility with polyfunctional unsaturated group-containing compounds, it is known that the main component is an alkyl (meth)acrylate whose alkyl group has 1 to 4 carbon atoms as a polymerization component.
In addition, as shown in Patent Document 2, the adhesive sheet is an active energy ray-curable release type that is a blend of a (meth)acrylic acid ester polymer containing 2-ethylhexyl acrylate as a main component and a polyfunctional (meth)acrylate. It is known that the adhesive layer is formed from an adhesive composition.

Japanese Patent Application Publication No. 2000-44894 Japanese Patent Application Publication No. 2011-225706

However, in the adhesive sheet for surface protection using the active energy ray-curable peelable adhesive composition containing the acrylic resin of Patent Document 1, when used on a thinned workpiece, it is difficult to irradiate the workpiece with active energy rays. There is a concern that the adhesive strength after applying the adhesive strength may be insufficiently reduced and the workpiece may be damaged, so there has been a demand for an even lower adhesive strength.

In addition, in the active energy ray curable peelable adhesive composition shown in Patent Document 2, a polyfunctional (meth)acrylate is used as the active energy ray curable component as a result of prioritizing compatibility with the acrylic resin. Therefore, compared to the case where urethane (meth)acrylate is used, there is a problem that the adhesive strength is less likely to decrease when irradiated with active energy rays, and it is not easy to peel the adhesive sheet from the workpiece. In addition, there is also the problem that uncured polyfunctional (meth)acrylate tends to remain on the workpiece, which is unsatisfactory.

In the present invention, even when an acrylic resin and a urethane (meth)acrylate compound are mixed, a highly transparent coating film with uniform physical properties can be obtained, and furthermore, it is possible to obtain a highly transparent coating film that is resistant to active energy ray irradiation. An active energy ray-curable peelable adhesive composition and a peelable adhesive sheet that have the desired adhesive strength before and after irradiation with active energy rays, have extremely low adhesive strength especially after irradiation with active energy rays, and exhibit very little change in physical properties even after long-term storage. The purpose is to provide

As a result of extensive research in view of the above circumstances, the present inventors have found that, in an active energy ray-curable release adhesive composition containing an acrylic resin and a urethane (meth)acrylate compound, the acrylic resin has a polar By using an acrylic resin that has a gradient structure in which the polarity changes, especially an acrylic resin that has a structure in which the polarity is gradient from a block with high polarity to a block with low polarity or from a block with low polarity to a block with high polarity. , a highly transparent coating film with uniform physical properties can be obtained, and it also has the desired adhesive strength before and after irradiation with active energy rays, and in particular, has extremely low adhesive strength after irradiation with active energy rays, and can be used for a long period of time. It has been found that it is possible to obtain an active energy ray-curable peelable adhesive composition that exhibits extremely small changes in physical properties even when stored.
Note that the gradient structure in which the polarity changes includes cases in which the polarity changes intermittently and cases in which the polarity changes continuously.

That is, triblock resins, diblock resins, and the like having a block structure are conventionally known as acrylic resins. The above-mentioned triblock resin, diblock resin, etc. are also used as compatibilizers by connecting block structures with different polarities.
However, when an acrylic resin having such a block structure is used as a binder resin, it tends to form a phase separation structure (sea-island structure) due to the polarity difference between the block structures when other materials are mixed. There is a concern that the coating film may become cloudy or have poor uniformity, but the present inventors have developed a method for changing from a block structure with high polarity to a block structure with low polarity or from a block structure with low polarity to a block structure with high polarity. By creating a polarity gradient in They have discovered that even when a urethane (meth)acrylate compound is mixed in the adhesive composition, it has excellent compatibility and excellent adhesive properties before and after irradiation with active energy rays.

In order to achieve the above object, the present invention has the following [1] to [6] as its gist.
[1] An active energy ray-curable peelable adhesive composition containing an acrylic resin (Ac) having a gradient structure in which polarity changes and a urethane (meth)acrylate compound (U).
[2] The acrylic resin (Ac) is an acrylic resin having a weight average molecular weight of 100,000 or more, and contains a functional group-containing monomer (α) (excluding the polar group-containing monomer described below). a structural site derived from at least one monomer (β) selected from the group consisting of an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms and a polar group-containing monomer, and an alkyl Contains a structural moiety derived from at least one monomer (γ) selected from alkyl (meth)acrylates having at least one of straight chain and branched alkyl (meth)acrylates having at least one of straight chain and branched carbon atoms of the group having 4 to 18 carbon atoms, and having the following general formula: The active energy ray-curable peelable adhesive composition of [1], which has the block structure shown in (1).
ABC...(1)
In the formula, A, B and C satisfy the following requirements (i) to (iii).
(i) A indicates a polymerized block A containing the above monomer (β), and the content (β _A ) of the above monomer (β) with respect to all the monomers constituting the above block A is 40 ~99% by weight.
(ii) C indicates a polymerized block C containing the above monomer (γ), and the content (γ _C ) of the above monomer (γ) with respect to all monomers constituting the above block C is 40 ~99% by weight.
(iii) B indicates a polymerized block B containing the monomer (β) and the monomer (γ), and the ratio of the monomer (β) to all the monomers constituting the block B is The content (β _B ) is smaller than the content (β _A ) of the block A, and the content (γ B ) of the monomer (γ) with respect to all monomers constituting the block _B is the block C. content (γ _C ).
[3] The active energy ray-curable peelable adhesive composition of [1] or [2], wherein the acrylic resin (Ac) has a glass transition temperature of -10°C or lower.
[4] The active energy ray-curable peelable adhesive composition according to any one of [1] to [3], further containing a crosslinking agent (Cr).
[5] The active energy ray-curable peelable adhesive composition according to any one of [1] to [4], further containing a photopolymerization initiator (P).
[6] The active energy ray-curable peelable adhesive composition according to any one of [1] to [5] is characterized in that it has an adhesive layer made of an adhesive crosslinked with a crosslinking agent (Cr). Peelable adhesive sheet.

The present invention provides a coating film that is uniform and highly transparent, has the desired adhesive strength before and after irradiation with active energy rays, has extremely low adhesive strength especially after irradiation with active energy rays, and is suitable for long-term storage. The effect is that the change in physical properties is extremely small even in the case of
The active energy ray-curable release adhesive composition can be used as a release adhesive sheet for temporary surface protection when processing semiconductor wafers, printed circuit boards, glass products, metal plates, plastic plates, etc. It can be suitably used.

FIG. 2 is a diagram illustrating a block structure of an acrylic resin used in the present invention. It is a figure explaining the method of manufacturing the above-mentioned acrylic resin. It is a figure explaining the block structure of the acrylic resin of a manufacturing example.

Hereinafter, embodiments for carrying out the present invention will be specifically described, but the present invention is not limited thereto.
In the present invention, "(meth)acrylic" means acrylic or methacrylic, "(meth)acryloyl" means acryloyl or methacryloyl, and "(meth)acrylate" means acrylate or methacrylate. . Moreover, "acrylic resin" is a resin obtained by polymerizing a polymerization component containing at least one type of (meth)acrylate monomer.

The active energy ray-curable releasable pressure-sensitive adhesive composition of the present invention is generally used mainly for the pressure-sensitive adhesive layer of a releasable pressure-sensitive adhesive sheet that is intended to be peeled off after being bonded to a workpiece. The above-mentioned releasable adhesive sheet is used with an active energy ray-curable releasable adhesive composition coated on a base sheet. The adhesive layer hardens and its adhesive strength decreases, allowing it to be easily peeled off from the workpiece.

The active energy ray-curable peelable adhesive composition contains an acrylic resin (Ac) having a gradient structure in which polarity changes and a urethane (meth)acrylate compound (U). . Each component will be explained below.

<Acrylic resin (Ac)>
Figure 1 shows an example of the block structure of acrylic resin (Ac) used in the present invention, in which a block C with low polarity is provided on the right hand side in the paper, and a block A with high polarity is provided on the left hand side in the paper. A block B having an intermediate polarity is provided between the blocks A and C. In addition, in the figure, the code|symbol Ac has shown the acrylic resin (Ac).

The acrylic resin (Ac) used in the present invention may be any acrylic resin having a gradient structure in which polarity changes, but the following acrylic resins are particularly preferred.
That is, the acrylic resin (Ac) has a weight average molecular weight of 100,000 or more, and has a structural moiety derived from a functional group-containing monomer (α) (excluding the polar group-containing monomer described later), A structural moiety derived from at least one monomer (β) selected from the group consisting of an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms and a polar group-containing monomer, and the number of carbon atoms in the alkyl group is It contains a structural moiety derived from at least one monomer (γ) selected from alkyl (meth)acrylates having at least one of straight chain and branched alkyl (meth)acrylates of 4 to 18, and has the following general formula (1). It has a block structure shown in .
ABC...(1)
In the above general formula (1), A, B and C satisfy the following requirements (i) to (iii).
(i) A indicates a polymerized block A containing the above monomer (β), and the content (β _A ) of the above monomer (β) with respect to all the monomers constituting the above block A is 40 ~99% by weight. (ii) C indicates a polymerized block C containing the above monomer (γ), and the content (γ _C ) of the above monomer (γ) with respect to all monomers constituting the above block C is 40 ~99% by weight.
(iii) B indicates a polymerized block B containing the monomer (β) and the monomer (γ), and the ratio of the monomer (β) to all the monomers constituting the block B is The content (β _B ) is smaller than the content (β _A ) of the block A, and the content (γ B ) of the monomer (γ) with respect to all monomers constituting the block _B is the block C. content (γ _C ).

Hereinafter, the structure of this acrylic resin (Ac) will be explained in detail.
It should be noted that containing structural sites derived from the monomers (α), (β), and (γ) mentioned above means that these are used as materials for block polymerization.

[Functional group-containing monomer (α)]
First, the functional group-containing monomer (α) will be explained. The above-mentioned functional group-containing monomer (α) has a polymerizable unsaturated group and a functional group, but in the present invention, it refers to a monomer excluding the polar group-containing monomer described below.

Examples of such functional group-containing monomers (α) include hydroxyl group-containing monomers, carboxy group-containing monomers, amino group-containing monomers, acetoacetyl group-containing monomers, and sulfonic group-containing monomers. and glycidyl group-containing monomers. Among these, hydroxyl group-containing monomers and carboxyl group-containing monomers are preferred from the viewpoint of copolymerizability, and when used in combination with a crosslinking agent, preferred from the viewpoint of reactivity with the crosslinking agent. These can be used alone or in combination of two or more.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxy Acrylic acid hydroxyalkyl esters such as octyl (meth)acrylate; caprolactone-modified monomers such as caprolactone-modified 2-hydroxyethyl (meth)acrylate; hydroxyl group-containing acrylamide monomers such as N-(hydroxymethyl)acrylamide; diethylene glycol (meth)acrylate; ) Oxyalkylene-modified monomers such as acrylate and polyethylene glycol (meth)acrylate; Other monomers containing primary hydroxyl groups such as 2-acryloyloxyethyl-2-hydroxyethylphthalic acid; 2-hydroxypropyl (meth) Secondary hydroxyl group-containing monomers such as acrylate, 2-hydroxybutyl (meth)acrylate, and 3-chloro 2-hydroxypropyl (meth)acrylate; tertiary hydroxyl group-containing monomers such as 2,2-dimethyl 2-hydroxyethyl (meth)acrylate Containing monomers can be mentioned. Among these, it is usually preferable to use monomers having 4 to 30 carbon atoms, more preferably 4 to 8 carbon atoms, and (meth)acrylic monomers, which are particularly excellent in copolymerizability and polymerization stability. It is particularly preferred to use 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate.

Examples of the carboxy group-containing monomer include (meth)acrylic acid, (meth)acrylic acid dimer, crotonic acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid, glutaconic acid, itaconic acid, acrylamide N- Examples include glycolic acid and cinnamic acid. Among them, (meth)acrylic acid is preferably used from the viewpoint of copolymerizability.

Examples of the amino group-containing monomer include primary amino group-containing monomers such as aminomethyl (meth)acrylate and aminoethyl (meth)acrylate; and secondary amino group-containing monomers such as t-butylaminoethyl (meth)acrylate. Amino group-containing monomers; Examples include tertiary amino group-containing monomers such as ethylaminoethyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and diethylaminoethyl (meth)acrylate.

Examples of the acetoacetyl group-containing monomer include 2-(acetoacetoxy)ethyl (meth)acrylate, allyl acetoacetate, and the like.

Examples of the sulfonic group-containing monomer include olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and meta-allylsulfonic acid, 2-acrylamido-2-methylolpropanesulfonic acid, styrene sulfonic acid, or salts thereof. It will be done.

Examples of the glycidyl group-containing monomer include glycidyl methacrylate, allylglycidyl methacrylate, and the like.

[At least one monomer (β) selected from the group consisting of an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms and a polar group-containing monomer]
The alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms and the polar group-containing monomer will be explained.

Examples of the alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and the like. These can be used alone or in combination of two or more.

Examples of the polar group-containing monomer include 2-methoxyethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxytriethylene glycol (meth)acrylate, and ethoxydiethylene glycol (meth)acrylate. ) acrylate, methoxypolyethylene glycol (meth)acrylate, polypropylene glycol-mono(meth)acrylate, and other alkoxy or oxyalkylene group-containing monomers; methoxymethyl (meth)acrylamide, ethoxymethyl (meth)acrylamide, propoxymethyl (meth)acrylate; ) alkoxyalkyl (meth)acrylamide monomers such as acrylamide, isopropoxymethyl (meth)acrylamide, n-butoxymethyl (meth)acrylamide, isobutoxymethyl (meth)acrylamide; dimethyl (meth)acrylamide, diethyl (meth)acrylamide Dialkyl(meth)acrylamide monomers such as acrylamide; heterocyclic amide monomers such as (meth)acryloylmorpholine; and the like. Among them, 2-methoxyethyl (meth)acrylate and methoxytriethylene glycol (meth)acrylate are preferably used, and 2-methoxyethyl (meth)acrylate is more preferably used. These can be used alone or in combination of two or more.
In addition, as the monomer (β), a polar group-containing monomer is preferably used.

[At least one monomer (γ) selected from alkyl (meth)acrylates having at least one of linear and branched alkyl groups having 4 to 18 carbon atoms]
The at least one monomer (γ) selected from alkyl (meth)acrylates having at least one of linear and branched alkyl groups having 4 to 18 carbon atoms is not particularly limited. , Specifically, as alkyl (meth)acrylates having a straight chain in which the alkyl group has 4 to 18 carbon atoms, examples include n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl ( meth)acrylate, n-heptyl(meth)acrylate, n-octyl(meth)acrylate, n-nonyl(meth)acrylate, n-decyl(meth)acrylate, lauryl(meth)acrylate, myristyl(meth)acrylate, cetyl( Examples include meth)acrylate, stearyl (meth)acrylate, and the like.
In addition, examples of alkyl (meth)acrylates having branches in which the alkyl group has 4 to 18 carbon atoms include iso-butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, Examples include iso-octyl acrylate, iso-nonyl (meth)acrylate, iso-decyl (meth)acrylate, iso-tridecyl (meth)acrylate, and iso-stearyl acrylate.
Among these, those in which the alkyl group has 4 to 10 carbon atoms are preferred, and from the viewpoints of excellent durability, copolymerizability, ease of handling, and ease of obtaining raw materials, n-butyl (meth)acrylate, Preferably, 2-ethylhexyl (meth)acrylate is used. These can be used alone or in combination of two or more.

<Other copolymerizable monomers>
In the acrylic resin (Ac), in addition to the monomers (α), (β), and (γ), other copolymerizable monomers (δ) can also be used in combination.
Other copolymerizable monomers (δ) include (meth)acrylates containing an alicyclic structure such as cyclohexyl (meth)acrylate and isobornyl acrylate; phenyl (meth)acrylate, benzyl (meth)acrylate , phenoxyethyl (meth)acrylate, phenyldiethylene glycol (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, styrene, α-methylstyrene, and other monomers containing one aromatic ring; biphenyloxyethyl (meth)acrylic acid ester monomers containing biphenyloxy structure such as (meth)acrylate; acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, Examples include vinylpyridine, vinylpyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol, acryl chloride, methyl vinyl ketone, allyltrimethylammonium chloride, dimethylallyl vinyl ketone, and the like.
Further, as the copolymerizable monomer (δ), a (meth)acrylate containing an active energy ray crosslinkable structural moiety can also be used. Examples of such (meth)acrylates containing active energy ray crosslinkable structural moieties include (meth)acrylates having a benzophenone structure, specifically (meth)acryloylbenzophenone, 4-(meth)acryloyloxybenzophenone, etc. It will be done.

The acrylic resin (Ac) preferably contains 0.1 to 40% by weight of the functional group-containing monomer (α) based on all the monomers constituting the acrylic resin, The content is more preferably 1 to 30% by weight, and even more preferably 3 to 20% by weight. If the content is too small, the crosslinking density and cohesive force will tend to decrease when a crosslinking agent (Cr) is used in combination with the adhesive composition, and if it is too large, the compatibility with various materials will decrease. and polymerization stability tends to decrease.
Further, it is preferable that the monomer (β) is contained in an amount of 0.1 to 60% by weight, more preferably 1 to 50% by weight, based on all the monomers constituting the acrylic resin (Ac). It is more preferable that the content is 5 to 40% by weight. If the content is too small or too large, there is a tendency for the compatibility with various materials to decrease and the adhesive properties when used as an adhesive layer to decrease.
The monomer (γ) is preferably contained in an amount of 40 to 99.9% by weight, more preferably 50 to 99% by weight, based on all the monomers constituting the acrylic resin (Ac). More preferably, the content is 60 to 95% by weight. If the content is too low or too high, the compatibility with various materials tends to decrease.
The content of other copolymerizable monomers (δ) is preferably 50% by weight or less, more preferably 30% by weight or less with respect to all monomers constituting the acrylic resin (Ac). , more preferably 20% by weight or less. If this content is too large, the compatibility with various materials tends to decrease.

Next, each block (blocks A to C) of the block structure represented by the general formula (1) will be explained below in the order of block A, block C, and block B.

[Block A]
The above-mentioned block A is usually contained in an amount of 1 to 90% by weight based on the weight of the entire block of acrylic resin (Ac), and from the viewpoint of compatibility with various materials, it is preferably contained in an amount of 5 to 80% by weight. is preferred, and more preferably 10 to 70% by weight.

The content (α _A ) of the monomer (α) relative to all the monomers constituting the block A is preferably 0 to 30% by weight, and preferably 0.1 to 20% by weight. More preferred. If the content is too large, the adhesive properties after crosslinking will tend to decrease when used as an adhesive, and if the content is too small, the cohesive force will tend to decrease. Further, when used in binder resin applications, if the amount is too small, the compatibility tends to decrease, and if the amount is too large, the storage stability tends to decrease.
Further, the content (β _A ) of the monomer (β) based on all the monomers constituting the block A is 40 to 99% by weight. Furthermore, from the viewpoint of compatibility with various materials, the content is more preferably 50 to 99% by weight, and even more preferably 60 to 99% by weight.
Further, the content (γ _A ) of the monomer (γ) based on all the monomers constituting the block A is preferably less than 50% by weight, more preferably less than 30% by weight. If this content is too large, the polarity of block A tends to decrease and the compatibility tends to decrease.

The glass transition temperature of the structural site of block A is preferably less than 25°C, more preferably in the range of -80 to 15°C, particularly preferably -75 to 0°C. It is preferable that the glass transition temperature of the structural part of the block A is within the above temperature range from the viewpoint of adhesive properties when used as an adhesive.

The glass transition temperature (Tg) of the structural site of the block A can be calculated, for example, from the content ratio of the monomers constituting the block A using the Fox equation described below.

[Block C]
The above-mentioned block C is usually contained in an amount of 10 to 90% by weight based on the weight of the entire block of acrylic resin (Ac), and from the viewpoint of compatibility with various materials, it is contained in an amount of 20 to 80% by weight. The content is preferably 30 to 70% by weight, and more preferably 30 to 70% by weight.

The content (α _C ) of the monomer (α) relative to all the monomers constituting the block C is preferably 0.1 to 40% by weight, and preferably 0.5 to 20% by weight. It is more preferable. If this content is too small, the cohesive force tends to decrease, and if it is too large, the polarity of block C becomes too high, which tends to cause a decrease in compatibility and a decrease in adhesive properties when used as an adhesive. There is a tendency to
Further, the content (β _C ) of the monomer (β) relative to all the monomers constituting the block C is preferably less than 50% by weight, more preferably less than 30% by weight. If the content is too large, the polarity of block C increases, which tends to reduce compatibility and reduce adhesive properties when used as an adhesive.
Furthermore, the content (γ _C ) of the monomer (γ) based on all the monomers constituting the block C is 40 to 99% by weight. More preferably, it is 50 to 99% by weight, and still more preferably 60 to 98% by weight. If the content is too small, the compatibility tends to decrease and the adhesive properties when used as an adhesive tend to decrease, while if the content is too large, the cohesive force decreases.

[Block B]
The above block B is usually contained in an amount of 5 to 80% by weight based on the total weight of the acrylic resin block, and from the viewpoint of compatibility with various materials, it may be contained in an amount of 10 to 70% by weight. It is preferably contained in an amount of 20 to 60% by weight.

The content (β _B ) of monomer (β) relative to all the monomers constituting the block B is smaller than the content (β A ) of the block A, and is usually smaller than the content (β _A ) of the block A. content (β _C ).
Further, the content (γ _B ) of monomer (γ) relative to all monomers constituting the block B is smaller than the content (γ C ) of the block C, and is usually smaller than the content (γ _C ) of the block A. content (γ _A ).
In addition, the content of the monomer (α) with respect to all the monomers constituting the above block B is preferably 0.1 to 40% by weight, and 0.5% by weight from the viewpoint of compatibility with various materials. More preferably, it is 20% by weight.

The acrylic resin (Ac) having such blocks A, B, and C has a weight average molecular weight of 100,000 or more, preferably 150,000 to 1,500,000, more preferably 200,000 to 1,200,000, and even more preferably It is 300,000 to 1 million. If the weight average molecular weight is too small, the cohesive force tends to decrease and the contamination of the workpiece tends to increase. If the weight average molecular weight is too large, the coatability tends to decrease and it also tends to be disadvantageous in terms of cost. be.

Further, the acrylic resin (Ac) used in the present invention preferably has a dispersity of 15 or less, more preferably 12 or less, particularly preferably 8 or less. If the degree of dispersion is too high, the cohesive force tends to decrease. Note that the lower limit of the degree of dispersion is usually 1.1.

The weight average molecular weight of the above acrylic resin (Ac) is the weight average molecular weight in terms of standard polystyrene molecular weight, and is determined by high performance liquid chromatograph (Japan Waters Co., Ltd., "Waters 2695 (main body)" and "Waters 2414 (detector)"). Column: Shodex GPC KF-806L (exclusion limit molecular weight: 2 x 10 ⁷ , separation range: 100 to 2 x 10 ⁷ , number of theoretical plates: 10,000 plates/piece, packing material: styrene-divinylbenzene copolymer) , filler particle size: 10 μm) are used in series. Further, the number average molecular weight is also measured in the same manner.

The glass transition temperature of the acrylic resin (Ac) used in the present invention is preferably -10°C or lower, more preferably -25°C or lower, and even more preferably -40°C or lower. It is preferable for the glass transition temperature of the acrylic resin to be within the above range from the viewpoint of adhesion to adherends. Note that the lower limit of the glass transition temperature is usually -80°C.

Ｔｇ：アクリル系樹脂のガラス転移温度（Ｋ）
Ｔga：単量体（ａ）のホモポリマーのガラス転移温度（Ｋ）
Ｗａ：単量体（ａ）の重量分率
Ｔgb：単量体（ｂ）のホモポリマーのガラス転移温度（Ｋ）
Ｗｂ：単量体（ｂ）の重量分率
Ｔgn：単量体（ｎ）のホモポリマーのガラス転移温度（Ｋ）
Ｗｎ：単量体（ｎ）の重量分率
（Ｗａ＋Ｗｂ＋・・・＋Ｗｎ＝１） The glass transition temperature (Tg) is calculated from the following Fox formula.

Tg: Glass transition temperature (K) of acrylic resin
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: Glass transition temperature (K) of homopolymer of monomer (n)
Wn: weight fraction of monomer (n) (Wa+Wb+...+Wn=1)

In other words, the glass transition temperature (Tg) of an acrylic resin is calculated by applying the glass transition temperature and weight fraction of each monomer constituting the acrylic resin to the Fox equation above. It is a value.
The glass transition temperature of a homopolymer of monomers constituting an acrylic resin is usually measured using a differential scanning calorimeter (DSC), and is specified in JIS K7121-1987 and JIS K 6240. Can be measured using a compliant method.

As described above, in the block structure of the acrylic resin (Ac) used in the present invention, block B always exists between block A and block C, and blocks A and C, which have extremely different polarities, are directly connected. They are not adjacent to each other, and when looking at the acrylic resin as a whole, the polarity gradually changes (decreases) from one end to the other. Therefore, even when mixed with the urethane (meth)acrylate compound (U) to form an active energy ray-curable release adhesive composition, a phase separation structure (sea-island structure) is difficult to form, and cloudiness does not occur, resulting in a uniform A coating film with excellent properties can be obtained.
Since the hydrophilic monomer is localized within the acrylic resin, it has excellent compatibility with various compounds.

Such acrylic resin (Ac) can be produced, for example, as follows.
That is, monomers used in each block that satisfy requirements (i) to (iii) of the general formula (1) are prepared, and first, a mixture of monomers containing a large amount of highly polar monomers is charged and polymerized. Then, a mixture of high polarity and low polarity components was prepared so that there was no extreme difference in the amount, and polymerization was carried out to create block B. Block C can be obtained by preparing a mixture of monomers in large amounts and polymerizing the mixture.

The above acrylic resin (Ac) is produced using living radical polymerization because it is easy to control the structure of the acrylic resin to be produced, and the reaction is easy to control, especially when polymerizing without using a solvent (bulk polymerization). Preferably, it is manufactured by

Examples of the above-mentioned living radical polymerization methods include the nitroxyl method (TEMPO), atom transfer radical polymerization (ATRP) method, and reversible addition-fragmentation chain transfer polymerization (RAFT) method, among which the selection of polymerization monomers is important. The ATRP method and the RAFT method are preferable from the viewpoint of performance and ease of control, and the RAFT method is preferably used from the viewpoint of being excellent in simplicity and not using a metal catalyst.
As the RAFT agent used in the above RAFT method, commonly known dithiocarbonyl-based, trithiocarbonyl-based, etc. can be used.

Note that the above acrylic resin (Ac) has a block structure of ABC, and each block is formed one by one, but each block may be formed in plural numbers. For example, the block structure may be ABCB, ABCB, etc.

Furthermore, as shown in FIG. 2(c), the acrylic resin (Ac) used in the present invention has a block structure of acrylic resin that is formed symmetrically like ABCB-A. Good too. An acrylic resin having such a block structure can be produced in the following manner, for example, by appropriately selecting a polymerization method, a polymerization initiator, and the like.
That is, first, block A is prepared, and then, as shown in FIG. 2(a), a polymerization initiator is applied to the center of block A (the location indicated by the black arrow) so that the polymer extends outward. , block B is produced. Next, as shown in FIG. 2(b), a polymerization initiator is applied to the central portion of the block B (indicated by the black arrow) to produce a block C such that the polymer extends outward.

In the acrylic resin (Ac) shown in FIG. 2(c), the polarity is high at both ends, and the polarity gradually decreases from both ends toward the center. It is more compatible with U).

In the above acrylic resin (Ac), the block structure is ABCB-A, and each block is formed in one step, but each block may be formed in multiple steps. . For example, the block B may be formed into two stages of blocks B1 and B2, and the block structure of the acrylic resin may be like AB1-B2-C-B2-B1-A.
When each block is formed in multiple stages, the change in polarity becomes even more gradual, and further, compatibility with the urethane (meth)acrylate compound (U) is observed. Among these, it is preferable that the blocks B are formed in multiple stages because the aggregation (phase separation) of each block is further alleviated and the transparency of the acrylic resin (Ac) itself tends to be high.

Furthermore, in the above acrylic resin (Ac), the polarity is high at both ends and low at the center, but for example, as in the block structure CBABC, the polarity at both ends is low and the center is low. The part may be higher.

In addition, when the block structure of acrylic resin (Ac) is formed symmetrically like ABCB-A or C-BABC-B-C, as mentioned above, In addition to producing it by applying a polymerization initiator as shown in 2(a) and 2(b), it can also be produced, for example, in the following manner. That is, first, blocks are sequentially formed from A or C to produce an acrylic resin having a block structure ABC. Next, by reacting the acrylic resin having a functional group at either end of A or C with a compound having two functional groups that can react with the functional group, ABC An acrylic resin having a structure of -(z)-C-B-A or C-B-A-(z)-ABC can be produced. The above (z) indicates a compound having two functional groups that can react with the above functional group.

However, as for the acrylic resin (Ac) used in the present invention, the block structure of the acrylic resin is ABC, such as ABC, where a block A with high polarity and a block C with low polarity are adjacent to each other. I don't like the configurations to match. That is, in the block structure of the acrylic resin described above, block A and block C are directly adjacent to each other near the center, but in this way, a structure in which block A with high polarity and block C with low polarity are adjacent to each other In this case, even if the other portions are formed with a gradual change in polarity, the compatibility with the urethane (meth)acrylate compound (U) tends to be poor.

<Urethane (meth)acrylate compound (U)>
The urethane (meth)acrylate (U) used together with the acrylic resin (Ac) in the present invention is a compound having a urethane bond and a (meth)acryloyl group.

The urethane (meth)acrylate compound (U) is a urethane (meth)acrylate compound (UI) that is a reaction product of a hydroxyl group-containing (meth)acrylate compound (u1) and a polyvalent isocyanate compound (u2). It may be a urethane (meth)acrylate compound (UII) which is a reaction product of a hydroxyl group-containing (meth)acrylate compound (u1), a polyvalent isocyanate compound (u2) and a polyol compound (u3). You can. Among these, in the present invention, it is preferable to use urethane (meth)acrylate compounds (UI) in terms of releasability after irradiation with active energy rays.
In addition, in the present invention, only one type of urethane (meth)acrylate compound (U) may be used, or two or more types may be used in combination.

The urethane (meth)acrylate compound (U) can be produced by reacting with a known reaction method.
Usually, in the case of a urethane (meth)acrylate compound (UI), the hydroxyl group-containing (meth)acrylate compound (u1) and the polyvalent isocyanate compound (u2) are combined into a urethane (meth)acrylate compound (UII). ), the polyol compound (u3) can be further produced by charging the polyol compound (u3) into a reactor all at once or separately and carrying out a urethane reaction using a known reaction method. In addition, when producing a urethane (meth)acrylate compound (UII), a reaction product obtained by reacting a polyol compound (u3) and a polyvalent isocyanate compound (u2) in advance has a hydroxyl group-containing ( The method of reacting the meth)acrylate compound (u1) is useful in terms of stability of the urethanization reaction, reduction of by-products, and the like.

The urethane (meth)acrylate compound (U) preferably contains 4 or more ethylenically unsaturated groups, more preferably 4 to 20, particularly preferably The number is 5 to 18, particularly preferably 6 to 15.
If the number of such ethylenically unsaturated groups is too large, the crosslinking density after irradiation with active energy rays becomes too large, and cracks tend to occur in the adhesive layer, whereas if the number is too small, sufficient crosslinking density cannot be obtained. , it tends to become difficult to peel off after irradiation with active energy rays.

The weight average molecular weight of the urethane (meth)acrylate compound (U) is usually 500 to 10,000, preferably 750 to 5,000, more preferably 1,000 to 4,000. If the weight average molecular weight is too large, the viscosity of the urethane (meth)acrylate compound (U) will increase, the compatibility with the acrylic resin (Ac) will decrease, and adhesive will tend to remain on the workpiece. There is. If the weight average molecular weight is too small, the urethane (meth)acrylate compound (U) tends to bleed from the pressure-sensitive adhesive sheet, resulting in adhesive residue.

Note that the above weight average molecular weight is the weight average molecular weight in terms of standard polystyrene molecular weight, and a high performance liquid chromatograph (Waters, "ACQUITY APC System") was equipped with columns: ACQUITY APC XT 450 x 1, ACQUITY APC XT 200 It is measured by connecting four ACQUITY APC XT 45 x 2 units in series.

The viscosity of the urethane (meth)acrylate compound (U) used in the present invention at 60° C. is preferably 500 to 100,000 mPa·s, particularly preferably 1,000 to 50,000 mPa·s. When the viscosity is outside the above range, coating properties tend to decrease. Note that the viscosity can be measured using an E-type viscometer.

The content of the urethane (meth)acrylate compound (U) in the active energy ray-curable peelable adhesive composition of the present invention is 10 to 200 parts by weight per 100 parts by weight of the acrylic resin (Ac). , preferably 15 to 160 parts by weight, particularly preferably 20 to 120 parts by weight. If the content of the urethane (meth)acrylate compound (U) is too low, the releasability after irradiation with active energy rays will tend to decrease, and if it is too high, the adhesive will become plasticized and the adhesive strength and retention before irradiation with active energy rays will decrease. This may result in a decrease in strength, adhesive residue, or cracks in the adhesive layer after irradiation with active energy rays.

In addition to the acrylic resin (Ac) and the urethane (meth)acrylate compound (U), the active energy ray-curable peelable adhesive composition preferably further contains a crosslinking agent (Cr) described below, a photopolymerization initiator, and a photopolymerization initiator. agent (P), and if necessary, a monofunctional monomer, a polyfunctional monomer, and other optional components such as an antistatic agent, an antioxidant, a plasticizer, a filler, a pigment, and a diluent. The composition may further contain additives such as anti-aging agents, ultraviolet absorbers, ultraviolet stabilizers, and tackifying resins. In addition to the additives, a small amount of impurities etc. contained in the manufacturing raw materials of the constituent components of the adhesive composition may be contained.

<Crosslinking agent (Cr)>
In the present invention, it is preferable to include a crosslinking agent (Cr) because it forms a crosslinked structure with the acrylic resin (Ac) and has excellent adhesive strength before irradiation with active energy rays. Examples of the crosslinking agent (Cr) include isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, oxazoline crosslinking agents, melamine crosslinking agents, aldehyde crosslinking agents, and amine crosslinking agents. Among these, it is preferable to use an isocyanate-based crosslinking agent from the viewpoint of improving the adhesiveness with the base sheet of the peelable pressure-sensitive adhesive sheet and the reactivity with the acrylic resin (Ac).
Further, these crosslinking agents (Cr) 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 xylylene diisocyanate, hexamethylene diisocyanate, and diphenylmethane-4,4-diisocyanate. , isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, and these polyisocyanate compounds and polyol compounds such as trimethylolpropane. Examples include adduct forms of these polyisocyanate compounds, buret forms and isocyanurate forms of these polyisocyanate compounds.
Among these, in terms of drug resistance and reactivity with functional groups, isocyanurates of hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,4-tolylene diisocyanate, or 2,6-tolylene diisocyanate and trimethylol are preferred. Adducts with propane, isocyanurates of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, and adducts of tetramethylxylylene diisocyanate with trimethylolpropane are preferred.

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

Examples of the aziridine-based crosslinking 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 crosslinking agents include 2,2'-bis(2-oxazoline), 1,2-bis(2-oxazolin-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-oxazolin-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. Examples include polymers of one or more types of oxazolines.

Examples of the melamine-based crosslinking agent include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexabutoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins.

Examples of the aldehyde crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, maleic dialdehyde, glutardialdehyde, formaldehyde, acetaldehyde, benzaldehyde, and the like.

Examples of the amine crosslinking agent include hexamethylene diamine, triethyl diamine, polyethylene imine, hexamethylene tetraamine, diethylene triamine, triethyl tetraamine, isophorone diamine, amino resin, polyamide, and the like.

The content of the crosslinking agent (Cr) is usually preferably 0.01 to 20 parts by weight, particularly preferably 0.1 to 15 parts by weight, based on 100 parts by weight of the acrylic resin (Ac). More preferably, it is 0.2 to 10 parts by weight. If the amount of crosslinking agent (Cr) is too low, the cohesive force of the adhesive will decrease, which tends to cause adhesive residue; if it is too high, the adhesive strength will decrease, and there will be a tendency for floating between the adhesive and the workpiece. There is.

<Photopolymerization initiator (P)>
The active energy ray-curable peelable adhesive composition of the present invention preferably contains a photopolymerization initiator (P) because it has excellent releasability after irradiation with active energy rays.
The photopolymerization initiator (P) may be one that generates radicals by the action of light, such as diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, benzyldimethyl Ketal, 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-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-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, benzoin isobutyl ether; benzophenone, methyl o-benzoylbenzoate, 4-phenylbenzophenone , 4-benzoyl-4'-methyl-diphenyl sulfide, 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, benzophenones such as (4-benzoylbenzyl)trimethylammonium chloride; 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 Thioxanthone such as chloride; 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethyl-pentylphosphine oxide, bis(2,4,6-trimethyl Acyl phosphone oxides such as (benzoyl)-phenylphosphine oxide; and the like. Among these, acetophenones, especially 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, thioxanthone, Particularly 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.
Note that these photopolymerization initiators (P) can be used alone or in combination of two or more.

The content of the photopolymerization initiator (P) should be 0.01 to 20 parts by weight based on 100 parts by weight of the urethane (meth)acrylate compound (U) and other photopolymerizable compounds. The amount is preferably from 0.1 to 15 parts by weight, particularly preferably from 0.5 to 10 parts by weight. If the content of the photopolymerization initiator (P) is too small, the curing properties upon irradiation with active energy rays will be low, and the peelability after irradiation with active energy rays will tend to decrease. Contamination tends to increase.

In addition, as an auxiliary agent for these photopolymerization initiators (P), 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, etc. can also be used in combination. These auxiliaries can also be used alone or in combination of two or more.

As the monofunctional monomer, polyfunctional monomer, and additives, those commonly used in adhesive compositions containing acrylic resins can be used.

In the active energy ray-curable releasable pressure-sensitive adhesive composition of the present invention, the acrylic resin (Ac) is usually contained in an amount of 5 to 99% by weight of the entire pressure-sensitive adhesive composition. From the viewpoint of cohesive strength, the content is preferably 10 to 97% by weight, more preferably 15 to 95% by weight.

When using the above-mentioned other optional components, the content thereof is preferably 5 parts by weight or less, particularly preferably 1 part by weight or less, and even more preferably 0.5 parts by weight, based on 100 parts by weight of the acrylic resin (Ac). Parts by weight or less. If this content is too large, there is a tendency for the adherend to be easily contaminated.

Thus, by mixing the acrylic resin (Ac), the urethane (meth)acrylate compound (U), preferably the crosslinking agent (Cr), the photopolymerization initiator (P), and other components as necessary, the present invention can be made. The active energy ray-curable peelable adhesive composition of the invention is obtained.

The active energy ray-curable peelable adhesive composition of the present invention is usually crosslinked with the above-mentioned crosslinking agent (Cr) and exhibits performance as an adhesive. The meth)acrylate compound (U) polymerizes, hardens the adhesive, and exhibits removability due to a decrease in adhesive strength.

The adhesive crosslinked with the active energy ray-curable peelable adhesive composition of the present invention is usually used temporarily when processing workpieces such as electronic substrates, semiconductor wafers, glass products, metal plates, and plastic plates. It is preferably used as an adhesive layer of a releasable adhesive sheet to protect the surface. Furthermore, the removable pressure-sensitive adhesive sheet of the present invention exhibits excellent releasability by irradiating active energy rays after adhering it to the surface of a workpiece.
The above-mentioned releasable pressure-sensitive adhesive sheet will be explained below.

The above-mentioned peelable adhesive sheet has an adhesive layer made of the active energy ray-curable peelable adhesive composition of the present invention, a sheet serving as a base material, and, if necessary, a release film. As a method for producing such a releasable adhesive sheet, first, the active energy ray-curable releasable adhesive composition of the present invention is applied as it is, or the concentration is adjusted with an appropriate organic solvent, and then applied onto a release film or a base sheet. Apply directly to. Thereafter, it is dried by heat treatment, for example, at 80 to 120°C for 0.5 to 10 minutes, and is attached to a base sheet or a release film to obtain a releasable pressure-sensitive adhesive sheet. Further, in order to balance the adhesive properties, aging may be further performed after drying.

Examples of the base sheet include polyester resins such as polyethylene naphthalate, polyethylene terephthalate, polybutylene terephthalate, and polyethylene terephthalate/isophthalate copolymers; polyolefin resins such as polyethylene, polypropylene, and polymethylpentene; polyvinyl fluoride; , polyvinylidene fluoride, polyfluorinated ethylene 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 copolymers, 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; Synthetic resin sheets such as polyimide, metal foils of aluminum, copper, and iron, paper such as high-quality paper and glassine paper, woven and non-woven fabrics made of glass fiber, natural fiber, synthetic fiber, etc. It will be done. These base sheets can be used as a single layer or as a multilayer in which two or more types are laminated. Among these, synthetic resin sheets are preferred from the viewpoint of weight reduction.

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

The method for applying the above-mentioned active energy ray-curable release adhesive composition is not particularly limited as long as it is a general coating method, such as roll coating, die coating, gravure coating, comma coating, screen coating, etc. Examples include methods such as printing.

The thickness of the adhesive layer of the above-mentioned peelable adhesive sheet is usually preferably 1 to 200 μm, more preferably 5 to 100 μm.

The aging conditions are usually room temperature (23°C) to 70°C, and time is usually 1 to 30 days. Specifically, for example, 23°C for 1 to 20 days, 23°C for 3 to 30 days. It may be carried out under conditions such as 10 days or 1 to 7 days at 40°C.

The adhesive strength of the peelable adhesive sheet of the present invention is reduced by irradiation with active energy rays as described above, and the active energy rays are usually far ultraviolet rays, ultraviolet rays, near ultraviolet rays, and infrared rays. In addition to electromagnetic waves such as light rays, X-rays, and γ-rays, electron beams, proton beams, neutron beams, etc. can be used. Among these, ultraviolet rays are preferred from the viewpoint of curing speed, availability of irradiation equipment, cost, etc.

The cumulative irradiation amount when irradiating the above ultraviolet rays is usually 50 to 3,000 mJ/cm ² , preferably 100 to 1,000 mJ/cm ² . Although 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, it is usually several seconds, and may be a fraction of a second in some cases.

The adhesive force of the above-mentioned peelable adhesive sheet varies depending on the type of base sheet, the type of workpiece, etc., but before irradiation with active energy rays, it is preferably 4.0 N/25 mm or more, more preferably 6.0 N/25 mm. It is preferably at least 8.0 N/25 mm, particularly preferably at least 8.0 N/25 mm.

The peelable adhesive sheet preferably has an adhesive strength of 0.8 N/25 mm or less when heated at 150° C. for 1 hour and then irradiated with ultraviolet rays (total irradiation amount: 250 mJ/cm ² ). It is preferably 0.5 N/25 mm or less, particularly preferably 0.3 N/25 mm or less, and furthermore, it is preferable that no adhesive residue is observed on the adherend after peeling.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, in the examples, "parts" and "%" mean weight basis.

First, various acrylic resins (Ac) or (Ac') and urethane (meth)acrylate compounds (U) were synthesized as shown below, and other raw materials for adhesive compositions were prepared. The monomer composition ratio, etc. of the synthesized acrylic resin are also shown in [Table 1] below.
The weight average molecular weight, degree of dispersion, and glass transition temperature of the acrylic resins (Ac) and (Ac') were measured according to the method described above, and the viscosity was measured at 25°C using a B-type viscometer. did. Moreover, the weight average molecular weight of the urethane (meth)acrylate compound (U) was measured according to the method described above.

<Production Example 1 [Synthesis of acrylic resin (Ac-1) solution]>
In a 2L round bottom 4-neck flask, 100 g of ethyl acetate, 1.008 g of trithiocarbonate bis[[4-[[ethyl-(2-acetoxyethyl)amino]carbonyl]phenyl]methyl]ester (Nippon Terpene Kagaku Co., Ltd.), and block As structural components of A, 7.25 g of 2-ethylhexyl acrylate (2EHA), 40.0 g of 2-methoxyethyl acrylate (MEA), 2.5 g of 2-hydroxyethyl acrylate (HEA), 0.25 g of acrylic acid (AAc), polymerization 0.054 g of azobisisobutyronitrile (AIBN) was charged as an initiator, and the temperature was raised. The start of reflux is taken as the reaction start point, and one hour after the start of the reaction, as block B structural components (first stage), 33.4 g of 2EHA, 37.5 g of MEA, 3.75 g of HEA, 0.375 g of AAc, and 20 g of ethyl acetate are added. , 0.081 g of AIBN was added dropwise over 30 minutes, and 2 hours after the start of the reaction, as block B structural components (second stage), 93.1 g of 2EHA, 25.0 g of MEA, 6.25 g of HEA, 0.625 g of AAc, and acetic acid were added. 20 g of ethyl and 0.081 g of AIBN were added dropwise over 1 hour, and 4 hours after the start of the reaction, 236.3 g of 2EHA, 12.5 g of HEA, 1.25 g of AAc, 80 g of ethyl acetate, and 0.27 g of AIBN were added as block C structural components. The mixture was added dropwise over 5 hours, and 6 hours after the start of the reaction, 40 g of ethyl acetate and 0.18 g of AIBN were added, and the reaction was continued for another 2 hours to complete the reaction. After that, the solid content was adjusted with ethyl acetate to obtain an acrylic resin (Ac-1) solution having a block structure of A-B1-B2-C-B2-B1-A as shown in Figure 3. Ta.
The overall composition of the obtained acrylic resin (Ac-1) was MEA/HEA/AAc/2EHA=20.5/5/0.5/74 (weight ratio), and the solid content was 45.5%. The viscosity was 4100 mPa·s/25°C, the glass transition temperature was -63.4°C, and the weight average molecular weight was 500,000.

<Production Example 2 [Synthesis of acrylic resin (Ac'-1) solution]>
180 g of ethyl acetate and 0.22 g of AIBN were placed in a 2L round-bottomed 4-necked flask, and the temperature was raised. While refluxing, 223.5 g of 2EHA, 60.0 g of MEA, 15.0 g of HEA, and 1.5 g of AAc were added dropwise over 2 hours, ethyl acetate and AIBN were added as appropriate, the reaction was allowed to proceed for 7 hours, and the reaction was completed. . The solid content was adjusted with ethyl acetate to obtain an acrylic resin (Ac'-1) solution having a random structure.
The composition of the obtained acrylic resin (Ac'-1) is MEA/HEA/AAc/2EHA=20/5/0.5/74.5 (weight ratio), and the solid content is 53.6%. The viscosity was 800 mPa·s/25°C, the glass transition temperature was -63.5°C, and the weight average molecular weight was 260,000.

<Production Example 3 [Synthesis of acrylic resin (Ac'-2) solution]>
105 g of ethyl acetate and 0.13 g of AIBN were placed in a 2 L round-bottomed 4-necked flask, and the temperature was raised. While refluxing, 180 g of 2EHA, 295 g of butyl acrylate (BA), and 25 g of HEA were added dropwise over 2 hours, toluene and AIBN were added as appropriate, and the reaction was completed for 7.5 hours. The solid content was adjusted with toluene to obtain an acrylic resin (Ac'-2) solution having a random structure.
The composition of the obtained acrylic resin (Ac'-2) is BA/HEA/2EHA=59/5/36 (weight ratio), the solid content is 40%, the viscosity is 6500 mPa・s/25°C, and the glass The transition temperature was -59.6°C, and the weight average molecular weight was 820,000.

<Production Example 4 [Synthesis of urethane acrylate compound (U-1) solution]>
In a four-necked flask equipped with a thermometer, stirrer, water-cooled condenser, and nitrogen gas inlet, 23.87 parts of isophorone diisocyanate, 5.59 parts of neopentyl glycol, and 2,6-di-tert-butyl as a polymerization inhibitor were added. 0.06 part of cresol, 0.01 part of dibutyltin dilaurate as a reaction catalyst, and 20 parts of ethyl acetate as a solvent were charged, and the reaction was carried out at 60°C. Next, 50.54 parts of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value: 119 mgKOH/g) was added to this system, and the reaction was terminated when the remaining isocyanate groups became 0.3% or less, and the urethane An acrylate compound (U-1) was obtained. The obtained urethane acrylate compound (U-1) had a weight average molecular weight of 2000, a resin concentration of 80%, and 6 ethylenically unsaturated groups.

<Production Example 5 [Synthesis of urethane acrylate compound (U-2) solution]>
In a four-neck flask equipped with a thermometer, stirrer, water-cooled condenser, and nitrogen gas inlet, 27.76 parts of isophorone diisocyanate trimer, a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value 119 mgKOH/g) The reaction was carried out at 60°C. . Next, 5.99 parts of 1-decanol was added to this system, and the reaction was terminated when the remaining isocyanate groups became 0.3% or less, to obtain a urethane acrylate compound (U-2). The resulting urethane acrylate compound (U-2) had a weight average molecular weight of 2,700, a resin concentration of 70%, and 6 ethylenically unsaturated groups.

<Production Example 6 [Synthesis of urethane acrylate compound (U-3) solution]>
In a four-necked flask equipped with a thermometer, stirrer, water-cooled condenser, and nitrogen gas inlet, 15.87 parts of isophorone diisocyanate, 0.06 part of 2,6-di-tert-butylcresol as a polymerization inhibitor, and a reaction catalyst were placed. 0.01 part of dibutyltin dilaurate and 30 parts of ethyl acetate were added as a solvent. Next, 30.62 parts of polyoxypropylene glycol (ADEKA Co., Ltd., "ADEKA Polyether P-700") in which 0.50 part of neopentyl glycol was dissolved was added to this system, and the reaction was carried out at 60°C. Next, 23.01 parts of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (hydroxyl value: 119 mgKOH/g) was charged into this system, and the reaction was terminated when the remaining isocyanate groups became 0.3% or less. An acrylate compound (U-3) was obtained. The resulting urethane acrylate compound (U-3) had a weight average molecular weight of 5,700, a resin concentration of 70%, and 6 ethylenically unsaturated groups.

Other ingredients are as follows.
<Crosslinking agent>
・Coronate L-55E (isocyanate crosslinking agent, Tosoh Corporation)
<Photopolymerization initiator>
・Omnirad184 (IGMRESIN)

Next, using these prepared components, adhesive compositions (coating liquids) and coating sheets of Examples 1 to 3 and Comparative Examples 1 to 5 shown below were prepared, and according to the criteria described below, "Coating film haze", "adhesive strength of the releasable adhesive sheet after aging", and "adhesive strength of the releasable adhesive sheet after being left still for two months after aging" were evaluated. The obtained results are also shown in [Table 2] below.

[Example 1]
(Preparation of active energy ray-curable peelable adhesive composition)
100 parts (solid content) of the above acrylic resin (Ac-1), 100 parts (solid content) of urethane acrylate compound (U-1), 4.0 parts (active ingredient) of crosslinking agent (Coronate L-55E), light 4.2 parts of a polymerization initiator (Omnirad 184) was mixed and the solid content was adjusted to 45% using ethyl acetate as a diluting solvent to obtain an active energy ray-curable peelable adhesive composition.

(Preparation of peelable adhesive sheet)
The obtained active energy ray-curable peelable adhesive composition was applied as a base sheet onto an easily adhesive polyethylene terephthalate film (film thickness 50 μm) (Toray Industries, Lumirror T60) using an applicator, and then heated at 100°C. After drying for 3 minutes at I got it.

[Examples 2 and 3, Comparative Examples 1 to 5]
A peelable pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 using the types and amounts of the acrylic resin and urethane (meth)acrylate compound shown in Table 2.

<Paint film haze>
The diffuse transmittance and total light transmittance of the removable pressure-sensitive adhesive sheet from which the release film was peeled off were measured using HAZE MATER NDH2000 (Nippon Denshoku Kogyo Co., Ltd.), and the values of the obtained diffuse transmittance and total light transmittance were was substituted into the following formula to determine the haze value, and evaluated based on the following criteria. Note that the higher the haze value, the less uniform the components in the active energy ray-curable peelable adhesive composition. Further, the haze value is a value including the base sheet.
Haze value (%) = (diffuse transmittance/total light transmittance) x 100
(Evaluation criteria)
◎...Less than 3% 〇...3% or more and less than 10% ×...10% or more

<Adhesive strength of peelable adhesive sheet after aging>
[Adhesive strength before ultraviolet (UV) irradiation]
A test piece with a size of 25 mm x 100 mm was prepared from the peelable adhesive sheet obtained above, and after peeling off the release film, it was placed on a stainless steel plate (SUS304BA plate) at 23°C in an atmosphere of 50% relative humidity. The adhesive was pasted under pressure by moving a rubber roller with a mass of 2 kg back and forth twice, and after being allowed to stand for 30 minutes in the same atmosphere, the 180 degree peel strength (N/25 mm) was measured at a peeling speed of 300 mm/min. It was evaluated.
(Evaluation criteria)
◎...5N/25mm or more 〇...3N/25mm or more but less than 5N/25mm ×...less than 3N/25mm

[Adhesive strength after ultraviolet (UV) irradiation]
A test piece with a size of 25 mm x 100 mm was prepared from the peelable adhesive sheet obtained above, and after peeling off the release film, it was placed on a stainless steel plate (SUS304BA plate) at 23°C in an atmosphere of 50% relative humidity. After applying pressure by making two reciprocations of a rubber roller with a mass of 2 kg, and leaving it for 30 minutes in the same atmosphere, the conveyor speed was 5.1 m/min from a height of 18 cm using one 80 W high-pressure mercury lamp. Ultraviolet irradiation (cumulative irradiation amount: 200 mJ/cm ² ) was performed. Next, after being allowed to stand 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 based on the following criteria.
(Evaluation criteria)
◎...0.05N/25mm or more 〇...More than 0.05N/25mm but less than 0.10N/25mm ×...More than 0.10N/25mm

<Adhesive strength of releasable adhesive sheet after being left for two months after aging>
The adhesive strength before ultraviolet (UV) irradiation and the ultraviolet (UV) The adhesive strength after irradiation was measured and evaluated using the same criteria.

From the above results, Examples 1 to 3 using acrylic resins (Ac) with specific structures have excellent compatibility with urethane (meth)acrylate compounds (U), and therefore have excellent coating film transparency. You can see that it will be a good thing. Moreover, while it has high adhesive strength before irradiation with ultraviolet rays, the adhesive strength decreases after irradiation with ultraviolet rays, and it has excellent removability. Furthermore, even when the peelable pressure-sensitive adhesive sheet is stored for a long period of time, there is very little change in the physical properties of the adhesive, indicating that it is very useful as an active energy ray-curable peelable pressure-sensitive adhesive.
On the other hand, in Comparative Examples 1 and 2 in which acrylic resin (Ac'), which is a random copolymer without a block structure, was used, the compatibility with the urethane (meth)acrylate compound (U) was poor and the coating film could not be formed. In addition, in Comparative Examples 3 to 5, although a coating film was formed, the transparency was poor, the adhesive properties before and after UV irradiation were not satisfactory, and the adhesive properties were not satisfactory when stored for a long period of time.
From the above, it is clear that the adhesive composition containing the acrylic resin (Ac) with a specific structure and the urethane (meth)acrylate compound (U) has excellent transparency and is very excellent as a peelable adhesive sheet. Recognize.

The active energy ray-curable peelable adhesive composition of the present invention has excellent compatibility between the acrylic resin and the urethane (meth)acrylate compound, and is particularly suitable for semiconductor wafers, printed circuit boards, glass processed products, metal plates, etc. It is useful for the adhesive layer of a releasable adhesive sheet and a releasable adhesive sheet for temporary surface protection when processing workpieces such as plastic plates.

A Block A
B Block B
C Block C

Claims (5)

Contains an acrylic resin (Ac) and a urethane (meth)acrylate compound (U) having a gradient structure with changing polarity,
The acrylic resin (Ac) is an acrylic resin with a weight average molecular weight of 100,000 or more, and has a structure derived from a functional group-containing monomer (α) (excluding the polar group-containing monomer described later). a structural site derived from at least one monomer (β) selected from the group consisting of an alkyl (meth)acrylate having an alkyl group having 1 to 3 carbon atoms and a polar group-containing monomer, and a carbon of the alkyl group. Contains a structural moiety derived from at least one monomer (γ) selected from alkyl (meth)acrylates having at least one of linear and branched alkyl (meth)acrylates having a number of 4 to 18, and having the following general formula (1) An active energy ray-curable peelable pressure-sensitive adhesive composition having a block structure represented by the following formula, wherein the polarity of each block is such that block A>block B>block C.
ABC...(1)
In the formula, A, B and C satisfy the following requirements (i) to (iii).
(i) A indicates a polymerized block A containing the above monomer (β), and the content (β A ) of the above monomer (β) with respect to all the monomers constituting the above block A _is 40 ~99% by weight. (ii) C indicates a polymerized block C containing the above monomer (γ), and the content (γ C ) of the above monomer (γ) with respect to all monomers constituting the above block C _is 40 ~99% by weight. (iii) B indicates a polymerized block B containing the monomer (β) and the monomer (γ), and the ratio of the monomer (β) to all the monomers constituting the block B is The content (β _B ) is smaller than the content (β _A ) of the block A, and the content (γ B ) of the monomer (γ) with respect to all monomers constituting the block B _is the block C. content (γ _C ). The active energy ray-curable peelable adhesive composition according to claim 1, wherein the acrylic resin (Ac) has a glass transition temperature of -10°C or lower. The active energy ray-curable peelable adhesive composition according to claim 1 or 2, further comprising a crosslinking agent (Cr). The active energy ray-curable peelable adhesive composition according to any one of claims 1 to 3 , further comprising a photopolymerization initiator (P). A release agent characterized in that the active energy ray-curable release adhesive composition according to any one of claims 1 to 4 has an adhesive layer made of an adhesive crosslinked with a crosslinking agent (Cr). Type adhesive sheet.

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