JP2023087882A - Re-peelable type adhesive sheet - Google Patents

Abstract

To provide a re-peelable type adhesive sheet which has sufficient adhesive force to an adherend, obtains excellent easy peelability even when the adherend to which the adhesive sheet is set to be a high temperature state of 250°C or higher, is returned to room temperature, is irradiated with UV from the base material surface, and then is peeled, and prevents deformation of a base material and adhesive residues.SOLUTION: A re-peelable type adhesive sheet has a transparent polyamide-based sheet-like base material, and an adhesive layer formed on one surface of the base material, wherein the adhesive layer contains an adhesive composition containing an acrylic resin (A) having a (meth)acrylic group, a photopolymerization initiator (B) and a crosslinking agent (C), the acrylic resin (A) is composed of alkyl (meth)acrylate having 1 to 16 carbon atoms, alicyclic hydrocarbon group or aromatic hydrocarbon group-containing (meth)acrylate, and (meth)acrylate having a COOH group, and a gel fraction of the adhesive layer is 80-99 mass%.SELECTED DRAWING: None

Description

The present invention relates to a removable pressure-sensitive adhesive sheet.

2. Description of the Related Art Conventionally, various adhesive sheets have been used in semiconductor manufacturing processes and the like. Specifically, there are a protective sheet for protecting the wafer in the back grinding process of the semiconductor wafer, and a fixing sheet used in the process of cutting and dividing the semiconductor wafer into element pieces (dicing). These pressure-sensitive adhesive sheets are re-peelable pressure-sensitive adhesive sheets that are attached to a semiconductor wafer, which is an adherend, and are peeled off from the adherend after a predetermined processing step is completed.

As a pressure-sensitive adhesive composition used for the pressure-sensitive adhesive layer of a removable pressure-sensitive adhesive sheet, one containing an ethylenically unsaturated group in the molecule and containing a UV (ultraviolet) curable resin is known.

In Patent Document 1, a (meth)acrylic polymer having two or more hydroxyl groups in the side chain and a compound having an isocyanato group are reacted in the presence of a first catalyst to produce a (meth)acrylic polymer having a urethane bond. A step of forming a polymer, and a (meth)acrylic polymer having urethane bonds and a compound having two or more isocyanato groups in one molecule are reacted in the presence of a second catalyst to form an adhesive layer. A method for producing a pressure-sensitive adhesive sheet is disclosed, wherein the first catalyst is a complex of at least one metal selected from zirconium, titanium and aluminum, and the second catalyst is an amine-based catalyst.

Japanese Patent No. 5996985

Removable pressure-sensitive adhesive sheets must have sufficient adhesive strength to the adherend when performing a predetermined processing step, and can be easily peeled off from the adherend after the predetermined processing step (easy to peel off). It is required that the adhesive layer of the adhesive sheet is not transferred to the adherend after peeling (no adhesive residue).

However, conventional pressure-sensitive adhesive sheets did not satisfy all of the above conditions. In particular, when the adhesive sheet is attached to the adherend, the adherend is processed at a high temperature of 250 ° C or higher such as a solder reflow process, and then peeled off by UV irradiation, deformation of the base material or adhesive residue may occur. The problem was that it was likely to occur.

In the present invention, the adherend having sufficient adhesion to the adherend and having the pressure-sensitive adhesive sheet attached thereto is brought to a high temperature state of 250° C. or higher, returned to room temperature, and then peeled off after being irradiated with UV from the substrate surface. An object of the present invention is to provide a re-peelable pressure-sensitive adhesive sheet in which excellent easy peelability can be obtained and deformation of the base material and adhesive residue are less likely to occur.

The present inventors have found that the above problems can be solved by forming a pressure-sensitive adhesive layer having a specific chemical structure on one side of a transparent polyamide-based sheet-like substrate.

（式（１－１）において、ｋ、ｌ、ｍ及びｎは、ｋ＋ｌ＋ｍ＋ｎ＝１００としたときのモル組成比を示す。ｋは０超～９２以下である。ｌは０～５０である。ｍは０超～９０以下である。ｋ、ｌ及びｍの合計は６５～９５である。ｎは５～３５である。Ｒ^１～Ｒ^４は－Ｈ又は－ＣＨ_３である。Ｒ^５は炭素原子数１～１６のアルキル基である。Ｒ^６は炭素原子数３～３０の脂環式炭化水素基又は炭素原子数６～２０の芳香族炭化水素基である。Ｒ^７は－Ｈ又は－（ＣＨ_２）_ｊ－ＣＯＯＨ（式中のｊは１又は２である。）である。Ｒ^８は上記一般式（１－２）又は（１－３）で示される基である。式（１－２）及び（１－３）において、ｐ及びｑは０、１及び２から選ばれるいずれかである。ｓはｐが０のときは０であり、ｐが１又は２のときは１である。Ｒ^９は－Ｈ又は－ＣＨ_３である。）
［２］
前記透明ポリアミド系シート状基材の厚さが１０～１００μｍであり、前記透明ポリアミド系シート状基材の４００ｎｍにおける光線透過率が７０％以上である［１］に記載の再剥離型粘着シート。
［３］
前記架橋剤（Ｃ）がエポキシ系化合物である［１］又は［２］に記載の再剥離型粘着シート。 The present invention includes the following aspects.
[1]
A removable pressure-sensitive adhesive sheet having a transparent polyamide sheet-like base material and a pressure-sensitive adhesive layer formed on one side of the base material,
The pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive composition containing a resin (A) represented by the following general formula (1-1), a photopolymerization initiator (B), and a cross-linking agent (C),
A removable pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a gel fraction of 80 to 99% by mass.

(In formula (1-1), k, l, m and n represent the molar composition ratio when k + l + m + n = 100. k is more than 0 to 92 or less. l is 0 to 50. m is greater than 0 to 90. The sum of k, l and m is 65 to 95. n is 5 to 35. R ¹ to R ⁴ are —H or —CH _3. R ⁵ is carbon. an alkyl group having 1 to 16 atoms, R ⁶ being an alicyclic hydrocarbon group having 3 to 30 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and R ⁷ being -H or - (CH ₂ ) _j —COOH (in the formula, j is 1 or 2.) R ⁸ is a group represented by the general formula (1-2) or (1-3). -2) and (1-3), p and q are any selected from 0, 1 and 2. s is 0 when p is 0 and 1 when p is 1 or 2 and R ⁹ is —H or —CH _3. )
[2]
The removable pressure-sensitive adhesive sheet according to [1], wherein the transparent polyamide-based sheet-like substrate has a thickness of 10 to 100 μm and a light transmittance at 400 nm of the transparent polyamide-based sheet-like substrate is 70% or more.
[3]
The removable pressure-sensitive adhesive sheet according to [1] or [2], wherein the cross-linking agent (C) is an epoxy compound.

According to the present invention, the adherend having sufficient adhesion to the adherend and having the pressure-sensitive adhesive sheet adhered thereto is brought to a high temperature state of 250° C. or higher, returned to room temperature, and irradiated with UV from the substrate surface. It is possible to provide a re-peelable pressure-sensitive adhesive sheet that exhibits excellent easy peelability even when peeled later, and that hardly causes deformation of the base material and adhesive residue.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the embodiments shown below.

[Removable adhesive sheet]
A removable pressure-sensitive adhesive sheet of one embodiment has a transparent polyamide-based sheet-like substrate and a pressure-sensitive adhesive layer formed on one side of the substrate.

The removable pressure-sensitive adhesive sheet may be, for example, strip-shaped, rectangular, or disk-shaped, and the shape is not particularly limited. The removable pressure-sensitive adhesive sheet may be used as a pressure-sensitive adhesive sheet formed into a shape corresponding to the shape of the adherend by a punching method or the like. The removable pressure-sensitive adhesive sheet may be used as a roll-shaped pressure-sensitive adhesive sheet by winding and cutting.

<Transparent polyamide sheet base material>
A transparent polyamide-based sheet-like substrate is a transparent substrate containing polyamide as a main component. Examples of polyamides contained in the transparent polyamide-based sheet-like substrate include aliphatic polyamides and aromatic polyamides. Aliphatic polyamides include, for example, polyamide 6 and polyamide 66. Aromatic polyamides include semi-aromatic polyamides and wholly aromatic polyamides. Semi-aromatic polyamides include, for example, polyamide 6T, polyamide 9T, and polyamide 10T. Wholly aromatic polyamides are obtained from aromatic dicarboxylic acids and aromatic diamines. It is preferred to use aliphatic polyamides with high light transmission at 400 nm. The aliphatic polyamide may have alicyclic groups in addition to the aliphatic groups.

The light transmittance at 400 nm of the transparent polyamide-based sheet-like substrate is preferably 70% or more, more preferably 80% or more. If the light transmittance at 400 nm is 70% or more, the removable pressure-sensitive adhesive sheet can be easily peeled off from the adherend by UV irradiation for a short period of time.

The light transmittance at 400 nm of the transparent polyamide-based sheet-like base material is obtained by measuring the light transmittance of the base material in a wavelength range of 300 nm to 800 nm using a UV-visible spectrophotometer, and from the obtained measurement results, the light transmittance at 400 nm. Determined by reading the rate Tr (%).

The thickness of the transparent polyamide-based sheet-like substrate can be appropriately selected depending on the application, but is preferably 10 to 100 μm, more preferably 20 to 80 μm. When the thickness of the base material is 10 μm or more, the rigidity (resilience) of the removable pressure-sensitive adhesive sheet increases. Therefore, when the removable pressure-sensitive adhesive sheet is attached to or peeled from an adherend, wrinkles and lifting tend to be less likely to occur in the removable pressure-sensitive adhesive sheet. When the thickness of the substrate is 100 µm or less, the removable pressure-sensitive adhesive sheet can be easily peeled from the adherend, and good workability (handleability, handling) can be obtained.

As a method for molding the transparent polyamide-based sheet-like substrate, conventionally known general sheet molding methods (e.g., extrusion molding, T-die molding, inflation molding, uniaxial or biaxial stretching molding, etc.) can be appropriately employed. .

As the transparent polyamide-based sheet-like base material, one subjected to antistatic treatment may be used. The antistatic treatment is not particularly limited, but a method of providing an antistatic layer on at least one surface of the substrate or a method of kneading an antistatic agent into the substrate can be used.

Furthermore, the surface of the base material on which the adhesive layer is formed is subjected, if necessary, to an easy-adhesion treatment such as acid treatment, alkali treatment, primer treatment, corona treatment, plasma treatment, ultraviolet treatment, ozone treatment, or the like. may

<Adhesive layer>
The pressure-sensitive adhesive layer contains the pressure-sensitive adhesive composition described below and is formed on one side of the substrate.

When a removable pressure-sensitive adhesive sheet is applied to an adherend and then peeled off, the pressure-sensitive adhesive layer should fix the removable pressure-sensitive adhesive sheet to the surface of the adherend with sufficient adhesive strength. Therefore, it has a role to protect the surface of the adherend during the process at high temperature. The pressure-sensitive adhesive layer can be easily peeled off from the adherend by UV irradiation after the processing step, and no adhesive residue is left on the adherend after peeling.

The thickness of the adhesive layer is preferably 5 to 100 μm, more preferably 8 to 80 μm, even more preferably 10 to 50 μm. When the thickness of the pressure-sensitive adhesive layer is 5 µm or more, the adhesive strength to the adherend is good. When the thickness of the adhesive layer is 100 μm or less, it is easy to control the thickness of the adhesive layer when forming the adhesive layer. Can be easily removed.

The pressure-sensitive adhesive layer may have a single layer structure, or a multilayer structure in which the pressure-sensitive adhesive layer of one embodiment and one or more other pressure-sensitive adhesive layers different from the pressure-sensitive adhesive layer are laminated. good too. As another adhesive layer, a conventionally known adhesive layer can be used. When the pressure-sensitive adhesive layer has a multilayer structure, the pressure-sensitive adhesive layer of one embodiment should be present on the outermost surface. In the removable pressure-sensitive adhesive sheet, a layer other than the pressure-sensitive adhesive layer may exist between the pressure-sensitive adhesive layer and the substrate. The pressure-sensitive adhesive layer preferably has a single-layer structure from the viewpoint of shortening the manufacturing process of the removable pressure-sensitive adhesive sheet.

The adhesive layer has a gel fraction of 80 to 99% by mass, preferably 85 to 99% by mass. When the gel fraction of the pressure-sensitive adhesive layer is 80 to 99% by mass, it is possible to more effectively suppress the occurrence of adhesive residue when the removable pressure-sensitive adhesive sheet attached to the adherend is peeled off. The gel fraction is a value measured by the method described in Examples.

The glass transition temperature of the pressure-sensitive adhesive layer is preferably -80 to 0°C, more preferably -60 to -5°C, still more preferably -40 to -10°C. The glass transition temperature (Tg) was determined by taking a 10 mg sample from the adhesive layer and using a differential scanning calorimeter (DSC) to raise the temperature of the sample from -100°C to 200°C at a rate of 10°C/min. is the onset temperature of the endotherm due to the glass transition observed by differential scanning calorimetry. When two or more endothermic onset temperatures are observed, Tg is a simple average value of two or more endothermic onset temperatures. When the glass transition temperature is -80°C to 0°C, the adhesive strength of the adhesive layer before UV irradiation is good.

For the purpose of protecting the pressure-sensitive adhesive layer of the removable pressure-sensitive adhesive sheet, a separator may be provided on the surface of the pressure-sensitive adhesive layer opposite to the substrate. The separator is preferably laminated on the surface of the adhesive layer. As a material for the separator, for example, paper, plastic film, or the like can be used, and it is preferable to use a plastic film from the viewpoint of excellent surface smoothness. The material of the plastic film used as the separator is not particularly limited as long as it can protect the pressure-sensitive adhesive layer, and examples thereof include polyethylene, polypropylene, polyethylene terephthalate, and polybutene.

When a plastic film is used as the separator, the thickness of the separator is preferably 5-300 μm, more preferably 10-200 μm, and still more preferably 25-100 μm.

The release surface of the separator (the surface placed in contact with the adhesive layer) is subjected to a release treatment using a conventionally known release agent such as a silicone-based, long-chain alkyl-based, or fluorine-based release agent, if necessary. good too.

(Adhesive composition)
The pressure-sensitive adhesive composition of one embodiment contains a resin (A), a photoinitiator (B), and a cross-linking agent (C).

(Resin (A))
The resin (A) contained in the adhesive composition of one embodiment is a compound represented by the following general formula (1-1).

（式（１－１）において、ｋ、ｌ、ｍ及びｎは、ｋ＋ｌ＋ｍ＋ｎ＝１００としたときのモル組成比を示す。ｋは０超～９２以下である。ｌは０～５０である。ｍは０超～９０以下である。ｋ、ｌ及びｍの合計は６５～９５である。ｎは５～３５である。Ｒ^１～Ｒ^４は－Ｈ又は－ＣＨ_３である。Ｒ^５は炭素原子数１～１６のアルキル基である。Ｒ^６は炭素原子数３～３０の脂環式炭化水素基又は炭素原子数６～２０の芳香族炭化水素基である。Ｒ^７は－Ｈ又は－（ＣＨ_２）_ｊ－ＣＯＯＨ（式中のｊは１又は２である。）である。Ｒ^８は上記一般式（１－２）又は（１－３）で示される基である。式（１－２）及び（１－３）において、ｐ及びｑは０、１及び２から選ばれるいずれかである。ｓはｐが０のときは０であり、ｐが１又は２のときは１である。Ｒ^９は－Ｈ又は－ＣＨ_３である。）

(In formula (1-1), k, l, m and n represent the molar composition ratio when k + l + m + n = 100. k is more than 0 to 92 or less. l is 0 to 50. m is greater than 0 to 90. The sum of k, l and m is 65 to 95. n is 5 to 35. R ¹ to R ⁴ are —H or —CH _3. R ⁵ is carbon. an alkyl group having 1 to 16 atoms, R ⁶ being an alicyclic hydrocarbon group having 3 to 30 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and R ⁷ being -H or - (CH ₂ ) _j —COOH (in the formula, j is 1 or 2.) R ⁸ is a group represented by the general formula (1-2) or (1-3). -2) and (1-3), p and q are any selected from 0, 1 and 2. s is 0 when p is 0 and 1 when p is 1 or 2 and R ⁹ is —H or —CH _3. )

In formula (1-1), k, l, m and n represent molar composition ratios when k+l+m+n=100. k is greater than 0 to 92 or less. l is 0-50. m is from more than 0 to 90 or less. The sum of k, l and m is 65-95. When the sum of k, l and m is 65 or more, a pressure-sensitive adhesive layer having sufficient adhesiveness to an adherend can be formed before UV irradiation. The sum of k, l and m is preferably 70-85.

In formula (1-1), a repeating unit shown in parentheses surrounded by k (hereinafter referred to as “repeating unit k”) is an essential repeating unit. The repeating unit k contributes to the adhesive strength of the adhesive composition before UV irradiation. The repeating number k of the repeating unit k is from more than 0 to 92 or less, preferably from 45 to 90, more preferably from 60 to 88.

In formula (1-1), the repeating unit shown in parentheses enclosed by l (hereinafter referred to as “repeating unit l”) may be omitted. In other words, the repeating number of repeating unit l may be zero. The repeating unit l contributes to the heat resistance of the pressure-sensitive adhesive composition. The repeating number l of the repeating unit l is 0-50, preferably 5-40, more preferably 10-30.

In formula (1-1), a repeating unit shown in parentheses surrounded by m (hereinafter referred to as “repeating unit m”) is an essential repeating unit. The repeating unit m imparts cohesion to the pressure-sensitive adhesive layer by reacting with a cross-linking agent having a functional group that reacts with a carboxyl group. The repeating number m of the repeating unit m is from more than 0 to 90 or less, preferably from 1 to 15, more preferably from 1 to 5.

In formula (1-1), a repeating unit shown in parentheses surrounded by n (hereinafter referred to as “repeating unit n”) is an essential repeating unit. The repeating unit n contributes to heat resistance of the pressure-sensitive adhesive composition. The repeating number n of repeating unit n is 5 to 35, preferably 10 to 33, more preferably 10 to 20. When the repeating unit n is 35 or less, the unsaturated bonds in the resin (A) are cured by UV irradiation to form a three-dimensional crosslinked structure, resulting in a pressure-sensitive adhesive layer whose adhesive strength is reduced to an appropriate range. can be formed. When n is 5 or more, the effect of improving heat resistance due to the structure derived from the alicyclic compound can be obtained.

Due to the synergistic effect of the functions contributed by these repeating units, the pressure-sensitive adhesive composition containing the resin (A) has a better balance between the adhesive strength before ultraviolet (UV) irradiation and the adhesive strength after UV irradiation. Become. As a result, it is possible to obtain a pressure-sensitive adhesive composition that exhibits sufficient adhesive strength to an adherend before UV irradiation, and that exhibits reduced adhesive strength after UV irradiation, thereby providing superior easy peelability. . Moreover, this pressure-sensitive adhesive composition does not excessively increase its adhesive strength even when it is brought to a high temperature state before UV irradiation and then returned to room temperature, and excellent easy peelability can be obtained after UV irradiation, and the adhesive composition can be easily peeled off after peeling. Adhesive residue on the body is less likely to occur.

In repeating unit k, R ¹ is -H or -CH ₃ , preferably -H. R ⁵ is an alkyl group having 1 to 16 carbon atoms, preferably an alkyl group having 1 to 8 carbon atoms, particularly preferably an alkyl group having 2, 4 or 8 carbon atoms.

Repeating unit k may be a plurality of repeating units with different R ¹ and/or R ⁵ . When the repeating unit k contains multiple types of repeating units, the repeating number k of the repeating unit k indicates the total number of repeating units of the multiple types of repeating units. For example, if repeating unit k contains repeating units A and B with different R ¹ and/or R ⁵ , and contains two repeating units A and three repeating units B, then the number of repeating units k is the number of A and B The numbers add up to 5.

In repeating unit l, R ² is -H or -CH ₃ , preferably -H. R ⁶ is an alicyclic hydrocarbon group having 3 to 30 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms.

Repeating unit 1 may be a plurality of repeating units with different R ² and/or R ⁶ . When the repeating unit 1 contains multiple types of repeating units, the repeating number 1 of the repeating unit 1 indicates the sum of the repeating numbers of the multiple types of repeating units.

In repeating unit m, R ³ is -H or -CH ₃ , preferably -H. R ⁷ is -H or -(CH ₂ ) _j -COOH (where j is 1 or 2), preferably -H.

Repeating unit m may be a plurality of repeating units with different R ³ and/or R ⁷ . When the repeating unit m contains multiple types of repeating units, the repeating number m of the repeating unit m indicates the total number of repeating units of the multiple types of repeating units.

In repeating unit n, R ⁴ is -H or -CH ₃ , preferably -H. R ⁸ is a group represented by formula (1-2) or (1-3). Each group represented by formula (1-2) or (1-3) contains a structure derived from an alicyclic compound and has the function of improving the heat resistance of the pressure-sensitive adhesive composition. In formula (1-2) or (1-3), p and q are any selected from 0, 1 and 2. s is 0 when p is 0 and 1 when p is 1 or 2; R ⁹ is -H or -CH ₃ .

Repeating unit n may be a plurality of repeating units with different R ⁴ and/or R ⁸ . When the repeating unit n contains multiple types of repeating units, the repeating number n of the repeating unit n indicates the total number of repeating units of the multiple types of repeating units.

The resin (A) represented by formula (1-1) is a random copolymer, block copolymer, or alternating copolymer composed of repeating unit k, repeating unit l, repeating unit m, and repeating unit n. may be either. The resin (A) represented by formula (1-1) may not contain the repeating unit l, and may be a random copolymer or a block copolymer consisting of a repeating unit k, a repeating unit m, and a repeating unit n. , alternating copolymers.

The weight average molecular weight of resin (A) is preferably 200,000 to 1,000,000, more preferably 300,000 to 800,000. When the weight average molecular weight of the resin (A) is 200,000 or more, when the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer containing the pressure-sensitive adhesive composition is attached to an adherend and then peeled off, the pressure-sensitive adhesive layer is removed from the adherend. It becomes even more difficult to survive. When the weight average molecular weight of the resin (A) is 1,000,000 or less, the viscosity of the resin (A) does not become too high, and the workability of the pressure-sensitive adhesive composition can be improved. The weight average molecular weight of resin (A) is a standard polystyrene conversion value measured by gel permeation chromatography (GPC).

The acid value of resin (A) is preferably 1 to 20 mgKOH/g, more preferably 3 to 10 mgKOH/g. When the acid value of the resin (A) is in the range of 1 to 20 mgKOH/g, the resin (A) reacts with the cross-linking agent to effectively increase the cohesive strength of the pressure-sensitive adhesive composition, resulting in adhesion after heating. Body contamination (adhesive residue) can be further reduced. The acid value is a value measured according to JIS K 0070:1992.

(Method for producing resin (A))
Resin (A) can be produced, for example, by the method shown below.

First, raw material monomers containing a carboxy group-containing ethylenically unsaturated monomer (a) and an ethylenically unsaturated monomer (d) are polymerized to produce a carboxy group-containing resin (b). The ethylenically unsaturated monomer (d) contains a monomer that forms the repeating unit k after polymerization, and may contain a monomer that forms the skeleton of the repeating unit l.

Next, the resin (A) can be produced by the addition reaction of the carboxy group-containing resin (b) and the specific alicyclic epoxy group-containing ethylenically unsaturated compound (c).

(Carboxy group-containing ethylenically unsaturated monomer (a))
The carboxy group-containing ethylenically unsaturated monomer (a) used when producing the carboxy group-containing resin (b) is a monomer that forms a skeleton of the repeating unit m by polymerizing. The carboxy group-containing ethylenically unsaturated monomer (a) has one carboxy group.

Carboxy group-containing ethylenically unsaturated monomers (a) include, for example, (meth)acrylic acid, carboxymethyl (meth)acrylate, and β-carboxyethyl (meth)acrylate.

Among these, (meth)acrylic acid and/or β-carboxyethyl (meth)acrylate are preferably used as the carboxy group-containing ethylenically unsaturated monomer (a) from the viewpoint of reactivity.

In the present disclosure, (meth)acryl means “acryl” or “methacryl”. (Meth)acrylate means "acrylate" or "methacrylate".

(Carboxy group-containing resin (b))
The carboxy group-containing resin (b) is a carboxy group-containing ethylenically unsaturated monomer (a) and an ethylenically unsaturated monomer copolymerizable with the carboxy group-containing ethylenically unsaturated monomer (a) ( It is obtained by copolymerizing raw material monomers containing at least d).

The carboxy group-containing resin (b) is a component that forms the skeleton of the resin (A) represented by formula (1-1). Repeating unit k, repeating unit l, and repeating unit m are all repeating units derived from the carboxy group-containing resin (b).

As the ethylenically unsaturated monomer (d), one or more monomers that form the skeleton of the repeating unit k when polymerized are used. As the ethylenically unsaturated monomer (d), at least one monomer that forms the skeleton of the repeating unit k by polymerization and a monomer that forms the skeleton of the repeating unit l by polymerization are used. good too.

The ethylenically unsaturated monomer (d) that forms the skeleton of the repeating unit k by polymerization is an alkyl (meth)acrylate having 1 to 16 carbon atoms, from the viewpoint of adjusting the peel strength of the pressure-sensitive adhesive composition. Therefore, it preferably contains an alkyl (meth)acrylate having 2 to 16 carbon atoms, more preferably an alkyl (meth)acrylate having 4 to 12 carbon atoms. Specific examples of alkyl (meth)acrylates having 1 to 16 carbon atoms include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, tert- Butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isodecyl (meth)acrylate, n-hexyl (meth)acrylate, isooctyl (meth)acrylate, and lauryl (meth)acrylate. Among these, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isooctyl (meth)acrylate are preferred.

Examples of the ethylenically unsaturated monomer (d) that forms the skeleton of the repeating unit l by polymerization include (meth)acrylates containing a cyclic alkyl group having 3 to 30 carbon atoms, and 6 to 20 carbon atoms. of aromatic group-containing (meth)acrylates.

The (meth)acrylate containing a cyclic alkyl group having 3 to 30 carbon atoms used as the ethylenically unsaturated monomer (d) that forms the skeleton of the repeating unit l by polymerization includes, for example, cyclohexyl (meth)acrylate , norbornyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and dicyclopentanyloxyethyl (meth)acrylate Acrylates are mentioned. Among these, it is particularly preferable to use isobornyl (meth)acrylate. When a cyclic alkyl group-containing (meth)acrylate is contained in the raw material monomer of the carboxy group-containing resin (b), the pressure-sensitive adhesive composition containing the resin (A) produced using the carboxy group-containing resin (b) It can increase the heat resistance of the object.

The aromatic group-containing (meth)acrylate having 6 to 20 carbon atoms used as the ethylenically unsaturated monomer (d) that forms the skeleton of the repeating unit l by polymerization includes, for example, benzyl (meth)acrylate , phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, phenoxypropyl (meth)acrylate, and phenoxypolypropylene glycol (meth)acrylate. Among these, it is particularly preferable to use benzyl (meth)acrylate. When aromatic group-containing (meth)acrylate is contained in the raw material monomer of the carboxy group-containing resin (b), the pressure-sensitive adhesive composition containing the resin (A) produced using the carboxy group-containing resin (b) It can increase the heat resistance of the object.

Among the raw material monomers of the carboxy group-containing resin (b), not only the above carboxy group-containing ethylenically unsaturated monomer (a) and the above ethylenically unsaturated monomer (d), but also the above A monomer copolymerizable with the carboxy group-containing ethylenically unsaturated monomer (a) other than the ethylenically unsaturated monomer (d) may also be included.

Examples of the ethylenically unsaturated monomer copolymerizable with the carboxy group-containing ethylenically unsaturated monomer (a) other than the above ethylenically unsaturated monomer (d) include, for example, alkoxyalkyl (meth) Acrylates, alkoxy(poly)alkylene glycol (meth)acrylates, hydroxy group-containing (meth)acrylates, fluorinated alkyl (meth)acrylates, dialkylaminoalkyl (meth)acrylates, and (meth)acrylamide compounds.

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

Alkoxy(poly)alkylene glycol (meth)acrylates include, for example, methoxydiethylene glycol (meth)acrylate, ethoxydiethylene glycol (meth)acrylate, and methoxydipropylene glycol (meth)acrylate.

Examples of hydroxy group-containing (meth)acrylates include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 1,3-butanediol (meth)acrylate, 1,4-butanediol (meth)acrylate, 1,6-hexanediol (meth)acrylate, and 3-methylpentanediol (meth)acrylate.

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

Dialkylaminoalkyl (meth)acrylates include, for example, N,N-dimethylaminoethyl (meth)acrylate and N,N-diethylaminoethyl (meth)acrylate.

(Meth)acrylamide compounds include, for example, (meth)acrylamide, N-methyl(meth)acrylamide, N-ethyl(meth)acrylamide, N-propyl(meth)acrylamide, N-isopropylacrylamide, N-hexyl(meth) Acrylamide, N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, (meth)acryloylmorpholine, and diacetoneacrylamide.

Specific examples of the monomer copolymerizable with the carboxy group-containing ethylenically unsaturated monomer (a) other than the ethylenically unsaturated monomer (d) include acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, vinyl propionate, vinyl stearate, vinyl chloride, vinylidene chloride, alkyl vinyl ether, vinyl toluene, N-vinylpyridine, N-vinylpyrrolidone, dialkyl itaconate, dialkyl fumarate, allyl alcohol , hydroxybutyl vinyl ether, hydroxyethyl vinyl ether, 4-hydroxymethylcyclohexylmethyl vinyl ether, triethylene glycol monovinyl ether, diethylene glycol monovinyl ether, methyl vinyl ketone, allyltrimethylammonium chloride, and dimethyl allyl vinyl ketone.

The method for producing the carboxy group-containing resin (b) is not particularly limited. For example, raw material monomers containing a carboxy group-containing ethylenically unsaturated monomer (a) and an ethylenically unsaturated monomer (d), which are constituent components of the carboxy group-containing resin (b), are subjected to known polymerization. Carboxy group-containing resin (b) can be obtained by copolymerizing according to the method. Specifically, as the polymerization method, a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, an alternating copolymerization method, or the like can be used. Among these polymerization methods, considering the addition reaction between the carboxy group-containing resin (b) obtained after polymerization and the alicyclic epoxy group-containing ethylenically unsaturated compound (c), solution polymerization is preferred in terms of ease of reaction. It is preferred to use law.

When producing the carboxy group-containing resin (b) by a solution polymerization method, a radical polymerization initiator and/or a solvent are used as necessary.

The radical polymerization initiator is not particularly limited, and can be appropriately selected from known ones and used.

Examples of radical polymerization initiators include 2,2′-azobis(isobutyronitrile), 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis(2 ,4-dimethylvaleronitrile), 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile), 2,2′-azobis(2,4,4 -trimethylpentane), dimethyl-2,2'-azobis (2-methylpropionate) and other azo polymerization initiators; and benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t -butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, etc. Examples include oil-soluble polymerization initiators such as oxide polymerization initiators.

These radical polymerization initiators may be used alone or in combination of two or more.

The amount of the radical polymerization initiator used is the carboxy group-containing ethylenically unsaturated monomer (a) and the carboxy group-containing ethylenically unsaturated monomer (a) and the ethylenically unsaturated monomer copolymerizable with It is preferably 0.01 to 5 parts by mass, more preferably 0.02 to 4 parts by mass, and even more preferably 0.03 to 3 parts by mass, with respect to the total 100 parts by mass.

Various general solvents can be used as the solvent for polymerization used when producing the carboxy group-containing resin (b). Examples of solvents include esters such as ethyl acetate, n-propyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene, xylene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as methylcyclohexane; ketones such as methyl ethyl ketone and methyl isobutyl ketone; glycols such as ethylene glycol, propylene glycol and dipropylene glycol; glycol ethers such as methyl cellosolve, propylene glycol monomethyl ether and dipropylene glycol monomethyl ether; and glycol esters such as ethylene glycol diacetate and propylene glycol monomethyl ether acetate.

These solvents may be used alone or in combination of two or more.

When producing the carboxy group-containing resin (b), the carboxy group-containing ethylenically unsaturated monomer (a), the ethylenically unsaturated monomer (d), and other optionally contained The content of the carboxy group-containing ethylenically unsaturated monomer (a) in the raw material monomer containing the monomer is preferably 5 to 40% by mass, and may be 7 to 30% by mass. More preferably, it is 10 to 25% by mass. By setting the content of the carboxy group-containing ethylenically unsaturated monomer (a) in the raw material monomer to the above range, the carboxy group-containing resin (b) and the alicyclic epoxy group-containing ethylenically unsaturated compound ( The pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition containing the resin (A) produced by the addition reaction with c) has good adhesive strength before UV irradiation.

(Alicyclic epoxy group-containing ethylenically unsaturated compound (c))
The alicyclic epoxy group-containing ethylenically unsaturated compound (c) is an ethylenically unsaturated group-containing compound having an alicyclic epoxy group and represented by general formula (1-2) or general formula (1-3). It is the compound that gives the structure. An alicyclic epoxy group in the present disclosure refers to an epoxy group formed by bonding one oxygen to two adjacent carbon atoms on the ring of an alicyclic hydrocarbon compound.

The alicyclic epoxy group-containing ethylenically unsaturated compound (c) is used to add R ⁸ in the repeating unit n of the resin (A) represented by formula (1-1). R ⁸ in repeating unit n in formula (1-1) contains a group derived from the alicyclic epoxy group-containing ethylenically unsaturated compound (c).

Examples of the alicyclic epoxy group-containing ethylenically unsaturated compound (c) include compounds represented by the following formula (1) or (2).

（式（１）において、Ｒ^９は－Ｈ又は－ＣＨ_３である。ｑは０、１及び２から選ばれるいずれかである。）
（式（２）において、Ｒ^９は－Ｈ又は－ＣＨ_３である。ｑは０、１及び２から選ばれるいずれかである。）

(In formula (1), R ⁹ is —H or —CH _3. q is any one selected from 0, 1 and 2.)
(In formula (2), R ⁹ is —H or —CH _3. q is any one selected from 0, 1 and 2.)

In formula (1), R ⁹ is -H or -CH ₃ . q is any one selected from 0, 1 and 2, preferably q is 1;

In formula (2), R ⁹ is -H or -CH ₃ . q is any one selected from 0, 1 and 2, preferably q is 1;

The alicyclic epoxy group-containing ethylenically unsaturated compound (c) is preferably a compound represented by formula (1), particularly preferably 3,4-epoxycyclohexylmethyl (meth)acrylate.

The alicyclic epoxy group-containing ethylenically unsaturated compound (c) may be used alone or in combination of two or more.

The resin (A) can be produced by addition reaction of the carboxy group of the carboxy group-containing resin (b) with the alicyclic epoxy group of the alicyclic epoxy group-containing ethylenically unsaturated compound (c).

The amount of the resin (A) is preferably 0.2 to 1.0 mol, more preferably 0.3 to 0.95 mol, still more preferably 0.6 to 0.95 mol, per 1 mol of the carboxy group of the carboxy group-containing resin (b). It is preferably produced by addition reaction of 95 mol of the alicyclic epoxy group-containing ethylenically unsaturated compound (c). The pressure-sensitive adhesive composition containing the resin (A) obtained by using the carboxyl group-containing resin (b) and the alicyclic epoxy group-containing ethylenically unsaturated compound (c) in the above ratio, before UV irradiation It exhibits sufficient adhesiveness to adherends, and its adhesive strength decreases after UV irradiation, resulting in more excellent easy peelability. In addition, this pressure-sensitive adhesive composition does not easily increase its adhesive strength even when it is brought to a high temperature state before UV irradiation and then returned to room temperature, and excellent easy peelability can be obtained after UV irradiation. The adhesive residue can be prevented more effectively.

The temperature of the addition reaction in producing the resin (A) is preferably 80 to 130°C, particularly preferably 90 to 120°C. When the addition reaction temperature is 80° C. or higher, a sufficient reaction rate can be obtained. When the temperature of the addition reaction is 130° C. or lower, it is possible to prevent the formation of a gelled product due to cross-linking of double bonds due to thermal radical polymerization.

A known catalyst can be used for the addition reaction in producing the resin (A), if necessary. Examples of catalysts include primary amines such as n-butylamine, n-hexylamine and benzylamine; triethylamine, tributylamine, dimethylbenzylamine, 1,8-diazabicyclo[5.4.0]undec-7-ene, Tertiary amines such as 1,5-diazabicyclo[4.3.0]non-5-ene, 1,4-diazabicyclo[2.2.2]octane; aniline, toluidine, phenylenediamine, 1,8-diaminonaphthalene aromatic amines such as; pyridine, 2,6-lutidine, 4-N,N-dimethylaminopyridine and other pyridine compounds; Alkyl ureas such as methyl urea; Alkyl guanidines such as tetramethyl guanidine; Phosphines such as (2,6-dimethylphenyl)phosphine, tris(2,6-dimethoxyphenyl)phosphine, tris(2,4,6-trimethylphenyl)phosphine and tris(2,4,6-trimethoxyphenyl)phosphine compound. Among the above catalysts for the addition reaction, it is preferable to use a tertiary amine, a pyridine compound, or a phosphine compound from the viewpoint of reactivity.

The amount of the catalyst used in the addition reaction is preferably 0.01 to 30 parts by mass with respect to a total of 100 parts by mass of the carboxy group-containing resin (b) and the alicyclic epoxy group-containing ethylenically unsaturated compound (c). , more preferably 0.05 to 5 parts by mass, and most preferably 0.1 to 2 parts by mass.

Furthermore, during the addition reaction, a gas having a polymerization inhibitory effect may be introduced into the reaction system, or a polymerization inhibitor may be added. Gelation during the addition reaction can be prevented by introducing a gas having a polymerization inhibitory effect into the reaction system or by adding a polymerization inhibitor.

Gases having an effect of inhibiting polymerization include gases containing oxygen to such an extent that they do not fall within the explosive range of substances in the system, such as air.

As the polymerization inhibitor, known ones can be used without particular limitation. 4-methyl-6-t-butylphenol), and phenothiazine. These polymerization inhibitors may be used alone or in combination of two or more.

The amount of the polymerization inhibitor used is preferably 0.005 to 5 parts by mass with respect to a total of 100 parts by mass of the carboxy group-containing resin (b) and the alicyclic epoxy group-containing ethylenically unsaturated compound (c). More preferably 0.03 to 3 parts by mass, most preferably 0.05 to 1.5 parts by mass. If the amount of polymerization inhibitor is too small, the effect of inhibiting polymerization may not be sufficient. On the other hand, if the amount of the polymerization inhibitor is too large, the exposure sensitivity of the resin (A) during UV irradiation may decrease.

It is more preferable to use a gas having a polymerization inhibiting effect in combination with a polymerization inhibitor because the amount of the polymerization inhibitor to be used can be reduced and the polymerization inhibiting effect can be enhanced.

(Photoinitiator (B))
Examples of the photopolymerization initiator (B) contained in the adhesive composition include benzophenone, benzyl, benzoin, ω-bromoacetophenone, chloroacetone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2 -phenylacetophenone, p-dimethylaminoacetophenone, p-dimethylaminopropiophenone, 2-chlorobenzophenone, 4,4'-dichlorobenzophenone, 4,4'-bisdiethylaminobenzophenone, Michler's ketone, benzoin methyl ether, benzoin isobutyl ether, Benzoin-n-butyl ether, benzyl methyl ketal, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-isopropylphenyl)-2-hydroxy-2- methylpropan-1-one, methylbenzoylformate, 2,2-diethoxyacetophenone, 4-N,N'-dimethylacetophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropane Carbonyl-based photopolymerization initiators such as -1-one can be mentioned.

Examples of the photopolymerization initiator (B) include sulfide photopolymerization initiators such as diphenyl disulfide, dibenzyl disulfide, tetraethylthiuram disulfide, and tetramethylammonium monosulfide; 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4 Acylphosphine oxides such as ,6-trimethylbenzoylphenylethoxyphosphine oxide; quinone photopolymerization initiators such as benzoquinone and anthraquinone; sulfochloride photopolymerization initiators; A system photoinitiator may be used.

Among these photopolymerization initiators (B), 1-hydroxycyclohexylphenyl ketone and/or 2,4,6-trimethylbenzoyldiphenylphosphine oxide are preferably used from the viewpoint of solubility in the adhesive composition.

These photopolymerization initiators (B) may be used alone or in combination of two or more.

The photopolymerization initiator (B) contained in the adhesive composition is preferably 0.1 to 5.0 parts by mass, and 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the resin (A). Part is more preferred. When the content of the photopolymerization initiator (B) with respect to 100 parts by mass of the resin (A) is 0.1 parts by mass or more, the adhesive composition can be cured at a sufficiently high curing rate by UV irradiation. , so that the adhesive strength of the adhesive composition after UV irradiation can be sufficiently reduced. When the content of the photopolymerization initiator (B) is 5.0 parts by mass or less with respect to 100 parts by mass of the resin (A), the adhesive sheet having the adhesive layer containing the adhesive composition is attached to the adherend. When the adhesive layer is peeled off after application, the adhesive layer is less likely to remain on the adherend. Even if the content of the photoinitiator (B) with respect to 100 parts by mass of the resin (A) exceeds 5.0 parts by mass, the effect corresponding to the content of the photoinitiator (B) is not seen, so the same content By setting the amount to 5.0 parts by mass or less, the pressure-sensitive adhesive composition can be produced economically.

(Crosslinking agent (C))
The pressure-sensitive adhesive composition contains a cross-linking agent (C). By containing the cross-linking agent (C), it is possible to obtain a PSA composition having a good balance between the adhesive strength before UV irradiation and the adhesive strength after UV irradiation.

The cross-linking agent (C) is not particularly limited, but is preferably a compound having two or more functional groups reactive with the hydroxyl group of repeating unit n, or the hydroxyl group of repeating unit n and the carboxy group of repeating unit m.

Examples of the cross-linking agent (C) include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hydrogenated tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, diphenylmethane- 4,4-diisocyanate, isophorone diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, isocyanurate of hexamethylene diisocyanate, tetramethylxylylene diisocyanate, 1,5-naphthalene diisocyanate, tolylene diisocyanate addition of trimethylolpropane xylylene diisocyanate adduct of trimethylolpropane, triphenylmethane triisocyanate, isocyanate compounds such as methylenebis(4-phenylmethane) triisocyanate; 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane , bisphenol A/epichlorohydrin type epoxy resin, N,N'-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-ylmethyl)amine], 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 epoxy-based compounds such as; 1-aziridinecarboxamide), N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide) and other aziridine compounds; and hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexa Melamine-based compounds such as butoxymethylmelamine, hexapentyloxymethylmelamine, and hexahexyloxymethylmelamine are included.

Among these cross-linking agents (C), it is preferable to use an epoxy-based compound and/or an isocyanate-based compound, and more preferably to use an epoxy-based compound, because of their good reactivity with the resin (A). .

These cross-linking agents (C) may be used alone or in combination of two or more.

The cross-linking agent (C) contained in the adhesive composition is preferably 0.1 to 10 parts by mass, more preferably 0.1 to 5 parts by mass, with respect to 100 parts by mass of the resin (A). It is preferably 0.1 to 1.0 parts by mass, more preferably. When the content of the cross-linking agent (C) is 0.1 parts by mass or more relative to 100 parts by mass of the resin (A), a three-dimensional cross-linked structure is sufficiently formed in the pressure-sensitive adhesive composition. As a result, the adhesive strength of the adhesive composition after UV irradiation can be sufficiently reduced. When the content of the cross-linking agent (C) is 10 parts by mass or less with respect to 100 parts by mass of the resin (A), the adhesive strength of the pressure-sensitive adhesive composition before UV irradiation is good.

(other ingredients)
The pressure-sensitive adhesive composition may contain components other than the resin (A), the photopolymerization initiator (B), and the cross-linking agent (C) described above, if necessary. Other ingredients include, for example, tackifiers, solvents, and various additives.

(Tackifier)
As the tackifier, conventionally known ones can be used without particular limitation. Examples of tackifiers include terpene-based tackifying resins, phenol-based tackifying resins, rosin-based tackifying resins, aliphatic petroleum resins, aromatic petroleum resins, copolymer petroleum resins, and alicyclic petroleum resins. , xylene resins, epoxy tackifier resins, polyamide tackifier resins, ketone tackifier resins, and elastomer tackifier resins. These tackifiers may be used alone or in combination of two or more.

When the pressure-sensitive adhesive composition contains a tackifier, the content thereof is preferably 30 parts by mass or less, more preferably 5 to 20 parts by mass, based on 100 parts by mass of the resin (A).

(solvent)
A solvent can be used to dilute the adhesive composition for the purpose of adjusting the viscosity of the adhesive composition when the adhesive composition is applied.

Examples of the solvent include organic solvents such as methyl ethyl ketone, methyl isobutyl ketone, acetone, ethyl acetate, n-propyl acetate, tetrahydrofuran, dioxane, cyclohexanone, n-hexane, toluene, xylene, n-propanol and isopropanol. can. These solvents may be used alone or in combination of two or more.

(Additive)
Additives include, for example, plasticizers, surface lubricants, leveling agents, softeners, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, light stabilizers such as benzotriazoles, phosphorus Acid ester and other flame retardants, surfactants, and antistatic agents are included.

(Method for producing pressure-sensitive adhesive composition)
An adhesive composition can be manufactured by a conventionally well-known method. The pressure-sensitive adhesive composition can be produced by mixing the resin (A), the photopolymerization initiator (B), the cross-linking agent (C), and other components added as necessary. The method of mixing each component contained in the adhesive composition is not particularly limited. Mixing can be carried out using, for example, a stirring device equipped with stirring blades such as Homodisper and paddle blades.

[Manufacturing method of removable pressure-sensitive adhesive sheet]
The removable pressure-sensitive adhesive sheet can be produced, for example, by the method described below.

First, an adhesive solution is prepared by dissolving or dispersing the above-mentioned adhesive composition in a solvent. You may use the adhesive composition mentioned above as an adhesive solution as it is.

Next, a pressure-sensitive adhesive solution is applied onto the base material, and if the solution contains a solvent, the solvent is removed by heating and drying to form a pressure-sensitive adhesive layer. After that, a release sheet is pasted on the pressure-sensitive adhesive layer, if necessary. Furthermore, if necessary, the obtained sheet is cured in an oven for a certain period of time to form a crosslinked structure, whereby a removable pressure-sensitive adhesive sheet can be obtained.

Another method for producing a removable pressure-sensitive adhesive sheet is to apply the above pressure-sensitive adhesive solution onto a release sheet, and if it contains a solvent, dry it by heating to remove the solvent to form a pressure-sensitive adhesive layer. Thereafter, a release sheet having an adhesive layer is placed on the substrate with the adhesive layer side facing the substrate, and the adhesive layer is transferred (transferred) onto the substrate. A method of curing in an oven for a certain period of time to form a crosslinked structure can be used.

A known method can be used as a method of applying the adhesive solution on the substrate (or on the release sheet). Specific examples include a method of coating using a conventional coater such as gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, direct coater, and the like. be done.

The conditions for heat drying the applied adhesive solution are not particularly limited, but usually 25 to 180 ° C., preferably 60 to 150 ° C., usually 1 to 20 minutes, preferably 1 to 10 minutes. I do. The solvent contained in the adhesive solution can be removed by performing heat drying under the above conditions. The conditions for curing the pressure-sensitive adhesive sheet after heat drying in an oven for a certain period of time are not particularly limited, but the curing is usually carried out at 25 to 100° C., preferably 30 to 80° C., for usually 1 to 7 days, preferably 1 to 3 days. . By curing under the above conditions, the resin (A) and the cross-linking agent (C) are cross-linked, and the gel fraction of the pressure-sensitive adhesive layer can be adjusted within a desired range.

[Applications of Removable Adhesive Sheet]
The removable pressure-sensitive adhesive sheet can be used, for example, when manufacturing electronic components. Specifically, in each process of manufacturing electronic parts, the adhesive sheet is used to fix an adherend, subject it to various processing steps, and then irradiate ultraviolet (UV) rays to peel off the adherend. , used for recovery purposes. Therefore, the adhesive sheet can be used as a backgrinding tape, a dicing tape, or the like when processing a semiconductor wafer. The pressure-sensitive adhesive sheet can be suitably used as a supporting tape or the like for fragile members such as ultra-thin glass substrates, or members that easily warp such as FPC substrates. In particular, the adhesive sheet is suitable as a dicing tape that protects the adherend during the heating process.

When a removable adhesive sheet is used as a wafer dicing tape, the adhesive sheet is attached to a wafer having a plurality of components before the dicing process. Next, the wafer is cut and cut (diced) into individual parts to form element pieces (chips). After that, the adhesive sheet attached on each element piece is irradiated with UV. As a result, the pressure-sensitive adhesive layer is irradiated with UV through the base material of the pressure-sensitive adhesive sheet, and the unsaturated bonds in the pressure-sensitive adhesive form a three-dimensional crosslinked structure and are cured. As a result, the adhesive strength of the adhesive layer is lowered. After that, the adhesive sheet is peeled off from each element piece.

Examples of the light source used for UV irradiation of the adhesive sheet before peeling attached to the adherend include high-pressure mercury lamps, ultra-high-pressure mercury lamp carbon arc lamps, xenon lamps, metal halide lamps, chemical lamps, and black light.

The amount of UV irradiation applied to the adhesive sheet is preferably 50-3000 mJ/cm ² , more preferably 100-600 mJ/cm ² . When the amount of UV irradiation applied to the adhesive sheet is 50 mJ/cm ² or more, the adhesive layer can be cured at a sufficiently high curing rate by UV irradiation, thereby improving the adhesion of the adhesive layer after UV irradiation. The force can be made sufficiently small. Even if the amount of UV irradiation applied to the adhesive sheet exceeds 3000 mJ/cm ² , the corresponding effect cannot be obtained ^. The pressure-sensitive adhesive sheet can be removed economically while reducing the effects of UV irradiation.

EXAMPLES The present invention will now be described more specifically with reference to examples and comparative examples. In addition, the present invention is not limited only to the following examples.

[Production Example 1: Production of resin (A)]
<Preparation of first mixed solution>
As shown in Table 1, 23.9 parts by mass of acrylic acid, which is a carboxy group-containing ethylenically unsaturated monomer (a), and an ethylenically unsaturated monomer (d) copolymerizable with the above (a) A raw material monomer containing 71.8 parts by mass of n-butyl acrylate and 143.6 parts by mass of 2-ethylhexyl acrylate, and 0.2'-azobis(isobutyronitrile) as a polymerization initiator. A first mixed solution containing 1 part by mass was prepared.

<Preparation of second mixed solution>
As shown in Table 1, 59.8 parts by mass of 3,4-epoxycyclohexylmethyl methacrylate, which is an alicyclic epoxy group-containing ethylenically unsaturated compound (c), and tris(4-methylphenyl)phosphine ( TPTP), 100.0 parts by mass of n-butyl acetate and 91.1 parts by mass of toluene as solvents were prepared.

A four-necked flask equipped with a stirrer, a dropping funnel, a condenser tube and a nitrogen inlet tube was charged with 175.6 parts by mass of n-butyl acetate as a solvent, and the temperature was raised to 80° C. under a nitrogen gas atmosphere. Then, while maintaining the reaction temperature at 80 ° C. ± 2 ° C., the first mixed solution is uniformly added dropwise to the four-necked flask over 4 hours. Polymerization was carried out while stirring to obtain a carboxy group-containing resin (b). After that, 0.15 parts by mass of 4-methoxyphenol was added as a polymerization inhibitor to the reaction system.

The temperature of the reaction system to which 4-methoxyphenol was added was raised to 100° C., and the second mixed solution was added dropwise over 0.5 hours, followed by continued stirring at a temperature of 100° C. for 8 hours to obtain resin (A-1). was synthesized and cooled to room temperature (23° C.).

Resin (A-1) was identified by a nuclear magnetic resonance method (NMR method) and found to be a compound represented by general formula (2-1). The repeating unit k of the compound represented by the general formula (2-1) is two kinds of repeating units (k-1, k-2) with different ^R5 .

（式（２－１）において、ｋ－１は３４であり、ｋ－２は４７であり、ｍは１であり、ｋ－１、ｋ－２及びｍの合計は８２である。ｎは１８である。）

(In formula (2-1), k-1 is 34, k-2 is 47, m is 1, and the sum of k-1, k-2 and m is 82. n is 18 is.)

[Production Examples 2 to 4, 6]
The content (parts by mass) shown in Table 1, except for using a carboxyl group-containing ethylenically unsaturated monomer (a), an ethylenically unsaturated monomer (d), and a polymerization initiator, A first mixed solution was prepared in the same manner as in Production Example 1.

The content (parts by mass) shown in Table 1, except that the alicyclic epoxy group-containing ethylenically unsaturated compound (c) (glycidyl methacrylate (GMA) in Production Example 4) and the catalyst were used. A second mixed solution was prepared in the same manner as in Example 1.

Resins (A-2) to (A-4) and (A-6) were obtained in the same manner as in Production Example 1 except that the first mixed solution and the second mixed solution were used.

As a result of identifying resins (A-2) to (A-4) and (A-6) in the same manner as in Production Example 1, general formulas (2-2) to (2-4) and (2- 6). The repeating unit k of the compounds represented by formulas (2-2) to (2-4) is two different repeating units (k-1, k-2) of R ⁵ .

Resin (A-2) is a compound represented by the following general formula (2-2).

Resin (A-3) is a compound represented by the following general formula (2-3).

Resin (A-4) is a compound represented by the following general formula (2-4).

Resin (A-6) is a compound represented by the following general formula (2-6).

（式（２－２）において、ｋ－１は５２であり、ｋ－２は３４であり、ｍは３であり、ｋ－１、ｋ－２及びｍの合計は８９である。ｎは１１である。）
（式（２－３）において、ｋ－１は１１であり、ｋ－２は５２であり、ｍは４であり、ｋ－１、ｋ－２及びｍの合計は６７であり、ｎは３３である。）

(In formula (2-2), k-1 is 52, k-2 is 34, m is 3, and the sum of k-1, k-2 and m is 89. n is 11 is.)
(In formula (2-3), k-1 is 11, k-2 is 52, m is 4, the sum of k-1, k-2 and m is 67, and n is 33 is.)

（式（２－４）において、ｋ－１は３７であり、ｋ－２は４４であり、ｍは２であり、ｋ－１、ｋ－２及びｍの合計は８３である。ｎ’は１７である。）

(In formula (2-4), k-1 is 37, k-2 is 44, m is 2, and the sum of k-1, k-2 and m is 83. n' is 17.)

（式（２－６）において、ｋは７４であり、ｌは９であり、ｍは１であり、ｋ、ｌ及びｍの合計は８４である。ｎは１６である。）

(In formula (2-6), k is 74, l is 9, m is 1, and the sum of k, l and m is 84. n is 16.)

[Production Example 5]
The content (parts by mass) shown in Table 1, except for using a carboxyl group-containing ethylenically unsaturated monomer (a), an ethylenically unsaturated monomer (d), and a polymerization initiator, A first mixed solution was prepared in the same manner as in Production Example 1.

A four-necked flask equipped with a stirrer, a dropping funnel, a condenser tube and a nitrogen inlet tube was charged with 175.6 parts by mass of n-butyl acetate as a solvent, and heated under reflux. After heating under reflux, the first mixed solution was uniformly added dropwise over 4 hours, and after the completion of the dropwise addition, stirring was continued under heating under reflux for 6 hours. After that, the reaction system was cooled to 60° C., 100 parts by mass of n-butyl acetate as a solvent, 91.1 parts by mass of toluene, 0.15 parts by mass of 4-methoxyphenol as a polymerization inhibitor, and dioctyltin dilaurate as a catalyst. was added in an amount of 0.3 parts by mass.

After 4-methoxyphenol was dissolved, 47.8 parts by mass of 2-methacryloxyethyl isocyanate (MOI) was added to the reaction system, and stirring was continued at 60°C for 8 hours to synthesize resin (A-5). 23° C.).

As a result of identifying resin (A-5) in the same manner as in Production Example 1, it was a compound represented by general formula (2-5). The repeating unit k of the compound represented by the general formula (2-5) is two different repeating units (k-1, k-2) of R ⁵ .

（式（２－５）において、ｋ－１は４８であり、ｋ－２は３２であり、ｍは１であり、ｋ－１、ｋ－２及びｍの合計は８１である。ｎ”は１９である。）

(In formula (2-5), k-1 is 48, k-2 is 32, m is 1, and the sum of k-1, k-2 and m is 81. n" is 19.)

Table 1 shows the carboxyl group-containing ethylenically unsaturated monomer (a) used in the production of resins (A-1) to (A-6), the ethylenically unsaturated monomer copolymerizable with the above (a) Polymer (d), polymerization initiator, alicyclic epoxy group-containing ethylenically unsaturated compound (c), catalyst, polymerization inhibitor and type and amount of solvent used (parts by mass), glycidyl methacrylate (GMA) and 2 - Indicates the amount (parts by mass) of isocyanatoethyl acrylate (MOI) used.

[Preparation of adhesive composition]
Ethyl acetate as a diluent solvent was added to the reaction solution of the resins (A-1) to (A-6) synthesized in Production Examples 1 to 6, and the contents of the resins (A-1) to (A-6) were determined. was adjusted to 30% by mass. Using a resin (A-1) to (A-6) solution containing 30% by mass of the resins (A-1) to (A-6), a pressure-sensitive adhesive composition was obtained by the method shown below. .

The resin (A), the photopolymerization initiator (B), and the cross-linking agent (C) shown in Table 2 are added to a plastic container in a room shielded from actinic radiation, with the contents (parts by mass) shown in Table 2, respectively. In addition, they were stirred to obtain adhesive compositions (B-1) to (B-9).

The numerical values of resins (A-1) to (A-6) in Table 2 are resins (A-1) to (A-6) in which the content of resins (A-1) to (A-6) is 30% by mass -6) The solid content of the solution, that is, the amount (parts by mass) of the resins (A-1) to (A-6) used. The numerical value of the photopolymerization initiator (B) is the amount (parts by mass) of the photopolymerization initiator (B) used with respect to 100 parts by mass of the resin (A). The numerical value of the cross-linking agent (C) is the amount (parts by mass) of the cross-linking agent (C) used with respect to 100 parts by mass of the resin (A).

"TETRAD-C", "TETRAD-X", "HX" and "TPO" in Table 2 are as follows.
"TETRAD-C": 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name: TETRAD-C)
“TETRAD-X”: N,N′-[1,3-phenylenebis(methylene)]bis[bis(oxiran-2-ylmethyl)amine] (manufactured by Mitsubishi Gas Chemical Company, Inc., trade name: TETRAD-X)
"HX": isocyanurate form of hexamethylene diisocyanate (manufactured by Tosoh Corporation, trade name: Coronate (registered trademark) HX)
"TPO": 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by BASF, trade name: L-TPO)

[Example 1: Preparation of removable pressure-sensitive adhesive sheet]
A 25 μm thick transparent polyamide sheet (manufactured by Unitika Ltd., product name: Uniamide EX-25, light transmittance at 400 nm: 83%) was prepared as a sheet-like base material. Then, the pressure-sensitive adhesive composition (B-1) is applied to the corona-treated surface of the substrate using an applicator so that the thickness after curing is 20 μm, and dried by heating at 100° C. for 2 minutes. , to form an adhesive layer.

Next, on the exposed surface of the pressure-sensitive adhesive layer, a 25 μm thick silicone-based light release PET film (manufactured by Toyobo Co., Ltd., product name: E7006) was laminated as a separator using a rubber roller. The adhesive layer was cured in an oven for 3 days, and the adhesive layer was cross-linked and cured to obtain a removable adhesive sheet of Example 1.

(Examples 2 to 7, Comparative Examples 1 to 6)
Using the pressure-sensitive adhesive composition and substrate shown in Table 3, the removable pressure-sensitive adhesive sheets of Examples 2 to 7 and Comparative Examples 1 to 6 shown in Table 3 were produced in the same manner as in Example 1.

"CPA", "PI", "PEN" and "PET" in Table 3 are as follows.
"CPA": transparent polyamide sheet (manufactured by Unitika Ltd., product name: Uniamide EX-25 (25 μm), Uniamide EX-50 (50 μm), light transmittance at 400 nm: 83%)
"PI": polyimide sheet (manufactured by DuPont-Toray, product name: Kapton (trademark) polyimide film, light transmittance at 400 nm: 0%)
“PEN”: polyethylene naphthalate sheet (manufactured by Toyobo Co., Ltd., product name: Teonex Q53, light transmittance at 400 nm: 61%)
“PET”: polyethylene terephthalate sheet (manufactured by Toyobo Co., Ltd., product name: E5100, light transmittance at 400 nm: 82%)

The removable pressure-sensitive adhesive sheets of Examples 1 to 7 and Comparative Examples 1 to 6 thus obtained were evaluated for the items shown below by the methods shown below. Table 3 shows the results.

[Measurement of Gel Fraction of Adhesive Layer]
The measurement of the gel fraction of the pressure-sensitive adhesive layer was performed by the following method. First, a sheet having a size of about 1 g was cut out from a removable pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer was peeled off from the substrate to obtain a measurement sample, and the mass thereof was measured. Subsequently, the measurement sample was immersed in 50 mL of THF and allowed to stand at room temperature for 72 hours. After that, the sample for measurement was taken out from THF, dried at 80° C. for 5 hours, and weighed again. The gel fraction was determined based on the following formula.
Gel fraction (%) = [A/B] x 100
A: Mass of measurement sample after immersion in THF (not including THF mass)
B: Mass of measurement sample before immersion in THF

[Peel strength before UV irradiation]
The removable pressure-sensitive adhesive sheet was cut into a size of 25 mm long and 100 mm wide, and the separator was peeled off to expose the pressure-sensitive adhesive layer. Next, the adhesive sheet is attached to the glass plate so that the exposed adhesive layer (measurement surface) is in contact with the glass plate, and a 2 kg rubber roller (width: about 50 mm) is reciprocated once on the substrate side. , a sample for measuring the peel strength before UV irradiation was obtained.

The obtained measurement sample was left for 24 hours in an environment with a temperature of 23° C. and a humidity of 50%. After that, according to JIS Z 0237:2009, a tensile test in a 180° direction was performed at a peel rate of 300 mm/min to measure the peel strength (N/25 mm) of the adhesive sheet to the glass plate.

[Peel strength after UV irradiation]
Prepare the same sample for measuring the peel strength before UV irradiation, irradiate ultraviolet (UV) from the surface of the adhesive sheet on the substrate side at an irradiation amount of 500 mJ / cm ² , and measure the peel strength after UV irradiation. Got a sample. For UV irradiation, a conveyor type ultraviolet irradiation device (manufactured by Eye Graphics, 2 KW lamp, 80 W/cm) was used.

For the obtained measurement sample, the peel strength (N/25 mm) of the adhesive sheet to the glass plate was measured in the same manner as the "peeling strength before UV irradiation".

[Peel strength after heat-resistant UV irradiation]
The same sample as for measuring the peel strength before UV irradiation was prepared, heated at 260 ° C for 20 minutes, cooled to room temperature (23 ° C), and UV was applied under the same conditions as "peeling strength after UV irradiation". was irradiated to obtain a sample for measurement of peel strength after heat-resistant UV irradiation.

The peel strength (N/25 mm) of the pressure-sensitive adhesive sheet to the glass plate was measured in the same manner as the "peeling strength after UV irradiation" for the obtained measurement sample.

[Adhesive residue]
After measuring the peel strength after UV irradiation, the glass plate was visually observed and evaluated according to the following criteria.
(Evaluation criteria)
A: No adhesive remains on the glass plate.
B: The adhesive remained on a very small portion of the glass plate.
C: Adhesive remained on the entire surface of the glass plate.

As shown in Table 3, the adhesive sheets of Examples 1 to 7 all had "adhesive residue" of A or B. In addition, the "peel strength after heat-resistant UV irradiation" was less than 1.0 N/25 mm, and the peelability after the heating test was good.

The pressure-sensitive adhesive sheets of Comparative Examples 1 to 5 all had C in "adhesive residue". The "peeling strength after heat-resistant UV irradiation" was 1.0 N/25 mm or more, indicating insufficient heat resistance. In Comparative Example 6, deformation of the base material was observed, and it was found that it is not suitable for high-temperature processes.

Claims (3)

A removable pressure-sensitive adhesive sheet having a transparent polyamide sheet-like base material and a pressure-sensitive adhesive layer formed on one side of the base material,
The pressure-sensitive adhesive layer comprises a pressure-sensitive adhesive composition containing a resin (A) represented by the following general formula (1-1), a photopolymerization initiator (B), and a cross-linking agent (C),
A removable pressure-sensitive adhesive sheet, wherein the pressure-sensitive adhesive layer has a gel fraction of 80 to 99% by mass.

(In formula (1-1), k, l, m and n represent the molar composition ratio when k + l + m + n = 100. k is more than 0 to 92 or less. l is 0 to 50. m is greater than 0 to 90. The sum of k, l and m is 65 to 95. n is 5 to 35. R ¹ to R ⁴ are —H or —CH _3. R ⁵ is carbon. an alkyl group having 1 to 16 atoms, R ⁶ being an alicyclic hydrocarbon group having 3 to 30 carbon atoms or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and R ⁷ being -H or - (CH ₂ ) _j —COOH (in the formula, j is 1 or 2.) R ⁸ is a group represented by the general formula (1-2) or (1-3). -2) and (1-3), p and q are any selected from 0, 1 and 2. s is 0 when p is 0 and 1 when p is 1 or 2 and R ⁹ is —H or —CH _3. ) 2. The removable pressure-sensitive adhesive sheet according to claim 1, wherein the transparent polyamide-based sheet-like substrate has a thickness of 10 to 100 μm and a light transmittance at 400 nm of the transparent polyamide-based sheet-like substrate is 70% or more. 3. The removable pressure-sensitive adhesive sheet according to claim 1, wherein the cross-linking agent (C) is an epoxy compound.