KR102587767B1 - Adhesive sheets and adhesive compositions - Google Patents

Abstract

It has a sheet-like substrate and an adhesive layer formed on one side of the substrate, the adhesive layer is made of a cured product of the adhesive composition, the gel fraction is 50 to 65% by mass, and the adhesive composition includes polyurethane (A), ( It contains a (meth)acrylic monomer (B) made of a compound having a meth)acryloyloxy group, a chain transfer agent (C), and a photopolymerization initiator (D), and the polyurethane (A) is derived from polyoxyalkylene polyol. It is an adhesive sheet containing polyurethane (a1), which has a structure and a skeleton containing a polyisocyanate-derived structure and has (meth)acryloyl groups at two or more terminals.

Description

Adhesive sheets and adhesive compositions

The present invention relates to adhesive sheets and adhesive compositions.

This application claims priority based on Patent Application No. 2019-138812 filed in Japan on July 29, 2019, and uses the content here.

In response to the demand for thinner semiconductor devices, a backgrind process for semiconductor wafers is being performed in the semiconductor device manufacturing process. In the semiconductor wafer backgrinding process, the surface of the semiconductor wafer is protected with an adhesive sheet, and then the back surface is ground to reduce the thickness of the semiconductor wafer.

Conventionally, various adhesive sheets used to protect the surface of a semiconductor wafer have been proposed. In recent years, as an adhesive sheet, a semiconductor wafer having uneven portions on the surface, such as a semiconductor wafer with bumps (electrodes) made of solder or the like, has been required to have sufficient unevenness absorbency.

For example, in Patent Document 1, there is a backgrind sheet having an uneven absorption layer on a substrate, wherein the uneven absorption layer contains (A) urethane (meth)acrylate and (B) polymerizable monomers other than component (A). A backgrind sheet is disclosed, which is a layer formed from a composition for film formation containing a layer that satisfies a specific range of loss tangent, relaxation rate, and storage modulus.

International Publication No. 2014/046096

When performing a backgrind process for a semiconductor wafer having bumps on the surface, the adhesive sheet used to protect the surface is required to have sufficient adhesive strength. However, when a pressure-sensitive adhesive sheet with high adhesive strength is attached to a semiconductor wafer having bumps on the surface and a back-grind process is performed, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is transferred around the bumps of the semiconductor wafer from which the pressure-sensitive adhesive sheet was peeled after the back-grind process. Adhesive residue is generated.

Additionally, when performing a backgrind process on a semiconductor wafer having bumps on the surface, if the pressure-sensitive adhesive sheet protecting the surface has insufficient absorbency for unevenness of the semiconductor wafer, voids are generated around the bumps. If water used in the backgrind process enters this gap, there is a possibility that the semiconductor wafer will be contaminated.

In this way, the adhesive sheet used for applications that are attached to an adherend having an uneven surface and then peeled off is required to have sufficient adhesive strength, be less likely to generate adhesive residue, and have excellent unevenness absorbency. there is.

However, conventional pressure-sensitive adhesive sheets did not have sufficient adhesive strength, did not easily generate adhesive residue, and were not excellent in absorbing irregularities. For this reason, when using a conventional adhesive sheet, in order to obtain sufficient adhesion to the semiconductor wafer and uneven absorption, it is necessary to provide an uneven absorption layer separately from the adhesive layer of the adhesive sheet, or to heat and soften the adhesive layer. there was.

The present invention has been made in consideration of the above circumstances, and aims to provide an adhesive sheet that has sufficient adhesive strength, is less likely to generate adhesive residue that transfers the adhesive layer to the adherend after peeling off the adhesive sheet, and is also excellent in irregularity absorbent properties. The purpose.

Another object of the present invention is to provide a pressure-sensitive adhesive composition that has sufficient adhesive strength, is less likely to generate adhesive residue, and is excellent in absorbing irregularities and convexities, thereby obtaining a cured product that is suitable as a material for the pressure-sensitive adhesive layer of a pressure-sensitive adhesive sheet.

The first aspect of the present invention is the following adhesive sheet.

[1] An adhesive sheet having at least a sheet-like substrate and an adhesive layer formed on one side of the substrate,

The adhesive layer is made of a cured product of the adhesive composition and has a gel fraction of 50 to 65% by mass,

The adhesive composition includes polyurethane (A), a (meth)acrylic monomer (B) made of a compound having a (meth)acryloyloxy group, a chain transfer agent (C), and a photopolymerization initiator (D),

The polyurethane (A) has a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and includes polyurethane (a1) having (meth)acryloyl groups at two or more terminals. Featured adhesive sheet.

The pressure-sensitive adhesive sheet of the first aspect of the present invention preferably includes the following features [2] to [3]. Two or more of the following features may be combined.

[2] The adhesive layer has a storage modulus of 1.0×10 ⁴ to 1.0×10 ⁵ at 25°C measured at a frequency of 1 Hz,

Additionally, the adhesive sheet according to [1], wherein the loss tangent at 25°C measured at a frequency of 1 Hz is 0.25 to 0.55.

[3] The adhesive sheet according to [1] or [2], wherein the adhesive layer has a thickness of 50 to 500 μm.

The second aspect of the present invention is the following adhesive composition.

[4] Polyurethane (A), a (meth)acrylic monomer (B) made of a compound having a (meth)acryloyloxy group, a chain transfer agent (C), and a photopolymerization initiator (D),

The polyurethane (A) has a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and includes polyurethane (a1) having (meth)acryloyl groups at two or more terminals,

An adhesive composition, characterized in that the gel fraction of the cured product photocured at an irradiation dose of 1000 mJ/cm2 is 50 to 65% by mass.

The adhesive composition of the second aspect of the present invention preferably includes the following features [5] to [10]. Two or more of the following features may be combined.

[5] The cured product has a storage modulus of 1.0×10 ⁴ to 1.0×10 ⁵ at 25°C measured at a frequency of 1 Hz,

Additionally, the adhesive composition according to [4], which has a loss tangent of 0.25 to 0.55 at 25°C measured at a frequency of 1 Hz.

[6] The pressure-sensitive adhesive composition according to [4] or [5], wherein the (meth)acrylic monomer (B) contains monofunctional (meth)acrylate and polyfunctional (meth)acrylate.

[7] When the total of the (meth)acrylic monomer (B) is 100 mol%, the monofunctional (meth)acrylate is 85 to 99 mol% and the polyfunctional (meth)acrylate is 1 to 15 mol%. % of the adhesive composition described in [6].

[8] The adhesive composition according to any one of [4] to [7], wherein the chain transfer agent (C) is a polyfunctional thiol.

[9] 20 to 50% by mass of the polyurethane (A),

49 to 79% by mass of the (meth)acrylic monomer (B),

0.5 to 5% by mass of the chain transfer agent (C),

The pressure-sensitive adhesive composition according to any one of [4] to [8], comprising 0.01 to 5% by mass of the photopolymerization initiator (D).

[10] The adhesive composition according to any one of [4] to [9], further containing fatty acid ester (E).

The pressure-sensitive adhesive sheet of the present invention has a pressure-sensitive adhesive layer on one side of the sheet-like substrate, which is made of a cured product of a specific pressure-sensitive adhesive composition and has a gel fraction of 50 to 65% by mass. For this reason, the adhesive sheet of the present invention has sufficient adhesive strength, is less likely to generate adhesive residue that transfers the adhesive layer to the adherend after peeling off the adhesive sheet, and is also excellent in uneven absorption. Therefore, when the adhesive sheet of the present invention is used for an application in which it is attached to an adherend having an uneven portion on the surface and then peeled off, an uneven absorption layer is provided separately from the adhesive layer, as in the case of using a conventional adhesive sheet. There is no need to prepare or heat the adhesive layer to soften it. Therefore, the adhesive sheet of the present invention is suitable for applications in which it is attached to an adherend having uneven portions on the surface and is then peeled off.

The adhesive composition of the present invention has a specific composition and gel fraction. For this reason, by curing the adhesive composition of the present invention, a cured product is obtained that has sufficient adhesive strength, is less likely to generate adhesive residue, and is excellent in uneven absorption. Therefore, the pressure-sensitive adhesive composition of the present invention is suitable as a material for the pressure-sensitive adhesive layer in a pressure-sensitive adhesive sheet that is attached to an adherend having uneven portions on the surface and is then peeled off.

Hereinafter, the adhesive sheet and adhesive composition of the present invention will be described in detail. Additionally, the present invention is not limited to the embodiments described below. Within the scope of the present invention, it is also possible to omit, change, exchange, and/or add the type, amount, composition, ratio, number, value, position, and size, etc., as necessary.

<Adhesive sheet>

The adhesive sheet of this embodiment has a sheet-like substrate and an adhesive layer formed on one side of the substrate. The adhesive layer consists of a cured product of the adhesive composition described later.

The material of the base material can be selected appropriately, and examples include resin materials. Resin materials include polyolefins such as polyethylene (PE) and polypropylene (PP); Polyester sheets such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate; polyvinyl chloride (PVC); polyimide (PI); polyphenylene sulfide (PPS); ethylene vinyl acetate (EVA); Polytetrafluoroethylene (PTFE), etc. can be mentioned. Among these resin materials, it is preferable to use PE, PP, and PET because sheets with appropriate flexibility can be obtained. One type of resin material may be used individually, or two or more types may be mixed and used.

When using a resin sheet made of a resin material as a base material, the resin sheet may be a single layer or a multilayer structure of two or more layers (for example, a three-layer structure). In a resin sheet having a multilayer structure, the resin material constituting each layer may be a resin material containing only one type, or may be a resin material containing two or more types.

As a base material, one that has been subjected to antistatic treatment may be used. The antistatic treatment applied to the substrate is not particularly limited, but methods such as providing an antistatic layer on at least one side of the substrate, mixing an antistatic agent into the substrate, etc. can be used.

Additionally, the surface of the substrate on which the adhesive layer is formed may be subjected to adhesion facilitation treatment, such as acid treatment, alkali treatment, primer treatment, corona treatment, plasma treatment, ultraviolet treatment, or ozone treatment, as necessary.

The thickness of the base material can be appropriately selected depending on the material of the base material, etc. An adhesive sheet is used to protect a semiconductor wafer having an uneven portion on the surface in a semiconductor wafer processing process, and when a resin sheet is used as a base material, the thickness of the base material is, for example, 10 to 1000 μm. is preferred, and is preferably 50 to 300㎛. When the thickness of the base material is 10 μm or more, the rigidity (viscosity) of the adhesive sheet increases. Therefore, when the adhesive sheet is attached to or peeled off from a semiconductor wafer, which is an adherend, it tends to be difficult for the adhesive sheet to wrinkle or float. Additionally, if the thickness of the base material is 1000 μm or less, it becomes easy to peel the adhesive sheet attached to the semiconductor wafer from the semiconductor wafer, and workability (handleability, handling) becomes good.

The thickness of the adhesive layer is preferably 50 to 500 μm, more preferably 60 to 400 μm, and still more preferably 70 to 300 μm. If the thickness of the adhesive layer is 50 μm or more, the irregularity absorbency of the adhesive sheet becomes even better. Additionally, if the thickness of the adhesive layer is 500 μm or less, it becomes easy to control the film thickness of the adhesive layer.

When the adhesive sheet of this embodiment is a adhesive sheet attached to an adherend having an uneven portion on the surface, the thickness of the adhesive layer largely depends on the height of the uneven portion on the surface. The thickness of the adhesive layer is preferably greater than or equal to the height of the uneven portion of the surface so as to obtain sufficient unevenness and absorption. Therefore, for example, when the irregularities on the surface are bumps formed on a semiconductor wafer, it is desirable that the thickness of the adhesive layer be at least twice the height dimension of the bump. The height of the bump is usually 30 to 200㎛. For example, when the height of the bump is 100㎛, the thickness of the adhesive layer is preferably 200㎛ or more, and when the height of the bump is 200㎛, the adhesive layer It is desirable that the thickness is 400㎛ or more.

The adhesive layer of the adhesive sheet of this embodiment has a gel fraction in the range of 50 to 65 mass%. For this reason, the pressure-sensitive adhesive sheet of the present embodiment has sufficient adhesive strength, is less likely to generate adhesive residue, and is excellent in irregularity absorbency. The gel fraction of the adhesive layer is preferably 52% by mass or more. Additionally, the gel fraction of the adhesive layer is preferably 63% by mass or less.

On the other hand, if the gel fraction is less than 50% by mass, adhesive residue is likely to be generated when the adhesive sheet is peeled off after attaching it to an adherend. Additionally, if the gel fraction exceeds 65% by mass, the fluidity tends to become insufficient when used as an adhesive layer of a pressure-sensitive adhesive sheet. For this reason, when the adhesive sheet is sent to an adherend having an uneven portion on the surface, a gap is likely to occur between the adhesive sheet and the uneven portion of the adherend.

(Measurement of gel fraction of adhesive layer)

The gel fraction of the adhesive layer can be measured, for example, by the method shown below.

A square sheet of 8 cm in length and 8 cm in width is cut from the adhesive sheet, and the base material is peeled from the adhesive layer of the obtained square sheet. Then, the adhesive layer peeled from the square sheet is used as a sample for measurement. The obtained sample for measurement can be measured using a method similar to the method for measuring the gel fraction of a sample for measurement consisting of a cured product of an adhesive composition described later.

The adhesive layer of the adhesive sheet of this embodiment has a storage modulus of 1.0×10 ⁴ to 1.0×10 ⁵ at 25°C measured at a frequency of 1 Hz, and a loss tangent at 25°C measured at a frequency of 1 Hz. It is preferable that this is 0.25 to 0.55. An adhesive layer with a storage modulus and loss tangent in the above ranges has good flexibility and fluidity. For this reason, when the adhesive sheet is attached to a work (adherent body) such as a semiconductor wafer having uneven portions such as bumps, it is possible to prevent voids from occurring between the uneven portions and the adhesive sheet.

The storage elastic modulus of the adhesive layer is more preferably 2.0×10 ⁴ or more, and even more preferably 3.0×10 ⁴ or more. Moreover, the storage elastic modulus is more preferably 9.0×10 ⁴ or less, and even more preferably 8.0×10 ⁴ or less.

The pressure-sensitive adhesive layer having a storage modulus of 1.0×10 ⁴ or more is not excessively flexible. For this reason, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a storage modulus of 1.0×10 ⁴ or more is preferable because it is more difficult to generate adhesive residue even when peeled off after being attached to an adherend. Additionally, the pressure-sensitive adhesive layer having a storage modulus of 1.0×10 ⁵ or less has good flexibility. For this reason, when a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer having a storage modulus of ^1.0 desirable.

It is more preferable that the loss tangent of the adhesive layer is 0.30 or more. Moreover, it is more preferable that the loss tangent is 0.50 or less.

The adhesive layer with the loss tangent of 0.25 or more has good fluidity. For this reason, when a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a loss tangent of 0.25 or more is attached to an adherend having an uneven portion on the surface, it is difficult to create a gap between the adhesive and the uneven portion of the adherend, which is preferable. Additionally, the adhesive layer with the loss tangent of 0.55 or less does not have excessive fluidity. For this reason, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer with a loss tangent of 0.55 or less is preferable because adhesive residue is unlikely to be generated even when peeled off after being attached to an adherend.

(Measurement of storage modulus and loss tangent of adhesive layer)

The storage modulus and loss tangent of the adhesive layer can be measured, for example, by the method shown below. First, the substrate is peeled from the adhesive sheet. Then, the adhesive layer obtained by peeling off the base material is laminated to form a laminated sheet with a thickness within the range of 1 to 2 mm. A square sheet of 8 mm in length and 8 mm in width was cut from the obtained laminated sheet to serve as a sample for measurement. The obtained sample for measurement can be measured using a method similar to the method for measuring the storage modulus and loss tangent of a sample for measurement consisting of a cured product of an adhesive composition described later.

For the purpose of protecting the adhesive layer, the adhesive sheet may be provided with a transparent separator on the surface opposite to the base material of the adhesive layer. The separator is preferably laminated to the surface of the adhesive layer. As a material for the separator, for example, paper, plastic film, etc. can be used, and it is preferable to use plastic film because it has excellent surface smoothness. The plastic film used as a separator is not particularly limited as long as it can protect the adhesive layer, and examples include polyethylene, polypropylene, polyethylene terephthalate, and polybutene.

<Adhesive composition>

The adhesive layer of the adhesive sheet of this embodiment consists of a cured product of the adhesive composition. Hereinafter, the adhesive composition used as a material for the adhesive layer of the adhesive sheet of this embodiment will be described in detail.

The adhesive composition of this embodiment contains polyurethane (A), (meth)acrylic monomer (B), chain transfer agent (C), and photopolymerization initiator (D).

(Polyurethane (A))

Polyurethane (A) includes polyurethane (a1). Polyurethane (A) may contain not only polyurethane (a1) but also polyurethane (a2), which will be described later, for the purpose of controlling the cohesive force in the cured product of the adhesive composition. It is preferable that polyurethane (A) does not contain components other than polyurethane (a1) and polyurethane (a2) contained as necessary.

[Polyurethane (a1)]

Polyurethane (a1) has a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate. In addition, polyurethane (a1) has two or more (meth)acryloyl groups at a plurality of terminals. The terminal (meth)acryloyl group of polyurethane (a1) is preferably a part of a (meth)acryloyloxy group.

In the present invention, “plural terminals” of polyurethane means two terminals when polyurethane is a straight-chain polymer, and two or more terminals of the same number of terminals as the number of each branched chain when polyurethane is a branched polymer. It is terminal.

In addition, in the present invention, the (meth)acryloyl group is one or more types selected from the functional group represented by the formula CH ₂ =CH-CO- and the functional group represented by the formula CH ₂ =C(CH ₃ )-CO- means.

[Polyurethane (a2)]

Polyurethane (a2), like polyurethane (a1), has a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate. Polyurethane (a2), unlike polyurethane (a1), has a (meth)acryloyl group at only one terminal. The terminal (meth)acryloyl group of polyurethane (a2) is preferably a part of a (meth)acryloyloxy group. The terminal that does not have a (meth)acryloyl group of polyurethane (a2) preferably has one selected from an isocyanato group, an alkyl alcohol-derived structure, and an alkyl isocyanate-derived structure, and an alkyl alcohol-derived structure. It is more desirable to have.

“Structure derived from polyoxyalkylene polyol”

The polyoxyalkylene polyol whose structure is derived from the polyoxyalkylene polyol contained in the skeleton of polyurethane (a1) and polyurethane (a2) is preferably one having an alkylene chain having 2 to 4 carbon atoms. Specific examples include polyoxyethylene polyol, polyoxypropylene polyol, and polyoxybtylene polyol.

The polyoxyalkylene polyol whose structure is derived from polyoxyalkylene polyol may contain one type of alkylene chain or may contain two or more types of alkylene chains.

The polyoxyalkylene polyol whose structure is derived from polyoxyalkylene polyol is preferably one having 2 or 3 hydroxyl groups at the terminal (diol type or triol type polyoxyalkylene polyol). Glycol (diol type) is more preferable, and polypropylene glycol having an alkylene chain of 3 carbon atoms is particularly preferable.

For example, when the polyoxyalkylene polyol is polypropylene glycol, the hydroxyl value is preferably 20 to 120 mgKOH/g, more preferably 30 to 100 mgKOH/g, and 40 to 80 mgKOH/g. It is more preferable that it is g. As a specific example of polypropylene glycol, for example, polypropylene glycol (Actcol D-2000; manufactured by Mitsui Chemicals, number average molecular weight 2000, diol type) having a hydroxyl group (hydroxy group) at the terminal with a hydroxyl value of 56 mgKOH/g. etc. can be mentioned.

Here, the hydroxyl value of polyoxyalkylene polyol is the hydroxyl value of polyoxyalkylene polyol measured according to JISK0070. In other words, it means the number of mg of potassium hydroxide required to neutralize free acetic acid when 1g of polyoxyalkylene polyol is acetylated. Specifically, it can be obtained by acetylating the hydroxyl group in a sample (polyoxyalkylene polyol) using acetic anhydride and titrating the free acetic acid generated at that time with a potassium hydroxide solution.

The number average molecular weight of the polyoxyalkylene polyol is preferably 500 to 5,000, more preferably 800 to 4,000, and still more preferably 1,000 to 3,000. If the number average molecular weight of the polyoxyalkylene polyol is 500 or more, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of a cured product of a pressure-sensitive adhesive composition containing polyurethane (A) synthesized using this will have a high peel strength. In addition, if the number average molecular weight of the polyoxyalkylene polyol is 5,000 or less, the polyurethane (A) synthesized using it contains a sufficient amount of urethane bonds. For this reason, the cured product obtained by curing the adhesive composition containing polyurethane (A) has good cohesion.

There may be only one type of structure derived from polyoxyalkylene polyol contained in the skeleton of polyurethane (a1) and polyurethane (a2), or a structure containing two or more types may be used.

Polyurethane (a1) and polyurethane (a2) may have a structure in which two or more structures derived from different polyoxyalkylene polyols are bonded across a structure derived from polyisocyanate.

The structure derived from the polyoxyalkylene polyol contained in the skeleton of polyurethane (a1) and the structure derived from the polyoxyalkylene polyol contained in the skeleton of polyurethane (a2) may be the same or different.

“Structure derived from polyisocyanate”

As the polyisocyanate whose structure is derived from the polyisocyanate contained in the skeleton of polyurethane (a1) and polyurethane (a2), a compound having a plurality of isocyanato groups is used, and diisocyanate is preferably used.

As diisocyanate, for example, tolylene diisocyanate and its hydrogenated product, xylylene diisocyanate and its hydrogenated product, diphenylmethane diisocyanate and its hydrogenated product, 1,5-naphthylene diisocyanate and its hydrogenated product, and hexamethylene. Diisocyanate, trimethylhexamethylene diisocyanate, tetramethylxylylene diisocyanate, isophorone diisocyanate, 4,4'-dicyclohexyl diisocyanate, 1,3-bis(isocyanate methyl)cyclohexane, norbornane diisocyanate, etc. I can hear it.

Among these polyisocyanates, it is better to use a hydrogenated product of isophorone diisocyanate or diphenylmethane diisocyanate from the viewpoint of controlling the light resistance of polyurethane (A) synthesized using it and the reactivity with polyoxyalkylene polyol. desirable. From the viewpoint of reactivity with polyoxyalkylene polyol, it is more preferable to use a hydrogenated product of diphenylmethane diisocyanate.

Specific examples of polyisocyanate having a structure derived from polyisocyanate include hydrogenated diphenylmethane diisocyanate (Desmodule W, manufactured by Sumica Covestro Urethane) and isophorone diisocyanate (Desmodule I, manufactured by Sumica Covestro Urethane). etc. can be mentioned.

The polyisocyanate-derived structure contained in the skeleton of polyurethane (a1) and polyurethane (a2) may be of only one type, or may be a structure containing two or more types.

In addition, the structure derived from the polyisocyanate contained in the skeleton of polyurethane (a1) and the structure derived from the polyisocyanate contained in the skeleton of polyurethane (a2) may be the same or different.

If the polyisocyanate-derived structure and the polyoxyalkylene polyol-derived structure included in the skeleton of polyurethane (a1) and polyurethane (a2) are the same, polyurethane (a1) and polyurethane (a2) can be synthesized simultaneously. This is preferable because polyurethane (A) can be produced efficiently.

The proportion of polyurethane (a1) contained in polyurethane (A) is preferably 80 to 100% of polyurethane (A), more preferably 90 to 100%, and even more preferably 100%, based on the number of molecules. .

The proportion of polyurethane (a2) contained in polyurethane (A) is preferably 0 to 20% of polyurethane (A), more preferably 0 to 10%, and even more preferably 0%, based on the number of molecules. .

If the ratio of polyurethane (a1) contained in polyurethane (A) is 80% or more, the cured product of the adhesive composition containing polyurethane (A) has sufficiently high cohesive force, which is preferable.

Of all the number of terminals contained in polyurethane (A) (the total number of terminals of polyurethane (a1) and the number of terminals of polyurethane (a2) contained as necessary), 90 to 100% (based on the number of molecules) It is preferable that a meth)acryloyl group is introduced, 95 to 100% is more preferable, and 100% is still more preferable. Among all the number of terminals contained in polyurethane (A), if the amount of (meth)acryloyl group introduced is 90% or more based on the number of molecules, the cohesion of the cured product obtained by curing the adhesive composition containing polyurethane (A) is sufficiently high. It becomes a thing.

Among all the number of terminals contained in polyurethane (A), the ratio of the number of terminals into which a (meth)acryloyl group is introduced based on the number of molecules is determined by using infrared absorption spectrum (IR) method, nuclear magnetic resonance spectrum (NMR) method, etc. It can be calculated using the results of analyzing polyurethane (A).

The ratio of the content of polyurethane (a1) and polyurethane (a2) contained in polyurethane (A), that is, among all the number of terminals contained in polyurethane (A), (meth)acryloyl group is based on the number of molecules. The ratio of the introduced terminal water can be adjusted by the method for producing polyurethane (A) described later.

The mass average molecular weight of polyurethane (A) is preferably 30,000 to 200,000, more preferably 50,000 to 150,000, and still more preferably 60,000 to 100,000. If the mass average molecular weight of polyurethane (A) is 30,000 or more, the cured product obtained by curing the adhesive composition containing polyurethane (A) will have good flexibility. Additionally, if the mass average molecular weight of polyurethane (A) is 200,000 or less, the adhesive composition containing polyurethane (A) is easy to handle and has good workability.

(Method for measuring mass average molecular weight of polyurethane (A))

The mass average molecular weight of polyurethane (A) is a polystyrene conversion value measured by gel/permeation/chromatography (GPC-101; Shodex (registered trademark) manufactured by Showa Denko Co., Ltd.) (hereinafter referred to as GPC). am. The measurement conditions of GPC are as follows.

Column: LF-804 (manufactured by Showa Denko Co., Ltd.)

Column temperature: 40℃

Sample: 0.2% by mass tetrahydrofuran solution of polyurethane (A)

Flow rate: 1ml/min

Eluent: Tetrahydrofuran

Detector: RI detector (differential refractive index detector)

The content of polyurethane (A) in the adhesive composition of this embodiment is preferably 20 to 50 mass%, more preferably 25 to 45 mass%, and even more preferably 30 to 40 mass%. When the content of polyurethane (A) is 20% by mass or more, the cured product obtained by curing the adhesive composition has sufficient cohesive strength and excellent adhesive strength is obtained. In addition, in the adhesive sheet using this cured product as the adhesive layer, the flexibility of the adhesive layer is within an appropriate range, and it is difficult for air bubbles to be inserted between the adhesive layer and the adherend. Additionally, if the content of polyurethane (A) is 50% by mass or less, the cured product obtained by curing the adhesive composition will have sufficient flexibility. Therefore, the adhesive sheet using this cured product as the adhesive layer has good wettability to the adherend.

((meth)acrylic monomer (B))

The (meth)acrylic monomer (B) may be a compound having a (meth)acryloyloxy group and is not particularly limited. As the (meth)acrylic monomer (B), one type of compound having a (meth)acryloyloxy group may be used individually, or two or more types may be used in mixture. As the (meth)acrylic monomer (B), monofunctional (meth)acrylate may be used, polyfunctional (meth)acrylate may be used, or a combination of monofunctional (meth)acrylate and polyfunctional (meth)acrylate may be used. You can use both sides.

In the present invention, “monofunctional” in monofunctional (meth)acrylate means (meth)acrylate with only one (meth)acryloyloxy group.

In addition, in this invention, "polyfunctional" in polyfunctional (meth)acrylate means (meth)acrylate in which the number of (meth)acryloyloxy groups is 2 or more.

As the (meth)acrylic monomer (B), it is preferable to use a combination of monofunctional (meth)acrylate and polyfunctional (meth)acrylate from the viewpoint of the cohesion of the cured product obtained by curing the adhesive composition and the curability of the adhesive composition. , it is more preferable to contain a monofunctional (meth)acrylate and a trifunctional or higher (meth)acrylate, especially a monofunctional (meth)acrylate and a trifunctional (meth)acrylate having three (meth)acryloyloxy groups. ) It is most preferable to contain acrylate.

Examples of monofunctional (meth)acrylates include alkyl (meth)acrylates, cyclic alkyl (meth)acrylates such as isobornyl (meth)acrylate, alkoxyalkyl (meth)acrylates, and alkoxy (poly)acrylates. Alkylene glycol (meth)acrylate, hydroxy group-containing (meth)acrylate, carboxyl group-containing (meth)acrylate, fluorinated alkyl (meth)acrylate, dialkylaminoalkyl (meth)acrylate, (meth)acrylamide, epoxy group Containing (meth)acrylate, (meth)acryloylmorpholine, etc. are mentioned.

Among these monofunctional (meth)acrylates, the adhesive strength (peel strength) of the cured product obtained by curing the adhesive composition, the storage modulus, loss tangent, and gel fraction described later are, when the cured product is used as the adhesive layer of an adhesive sheet, Since it is likely to fall into a more appropriate range, it is preferable to contain alkyl (meth)acrylate.

As the alkyl (meth)acrylate, it is more preferable to use an alkyl (meth)acrylate having an alkyl group having 4 to 10 carbon atoms. Specifically, examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Among these, it is particularly preferable to use 2-ethylhexyl (meth)acrylate and/or n-butyl (meth)acrylate.

Polyfunctional (meth)acrylate is a compound other than polyurethane (A) and has multiple (meth)acryloyloxy groups. As the polyfunctional (meth)acrylate, it is preferable to use poly(meth)acrylate of a polyol compound.

As polyfunctional (meth)acrylate, specifically, polyethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, and triethylene glycol di(meth)acrylate. Latex, tripropylene glycol di(meth)acrylate, hydroxypivalic acid esterneopentyl glycol di(meth)acrylate, 1,3-bis(hydroxyethyl)-5,5-dimethylhydant (meth) Acrylate, α,ω-di(meth)acrylic bisdiethylene glycol phthalate, trimethylolpropane tri(meth)acrylate, ethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, 1,4 -Butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, diacryloxyethyl phosphate, and pentaerythritol tetra(meth)acrylate. Among these, it is preferable to use trimethylolpropane tri(meth)acrylate as the polyfunctional (meth)acrylate from the viewpoint of curability of the adhesive composition.

When the (meth)acrylic monomer (B) contains both monofunctional (meth)acrylate and polyfunctional (meth)acrylate, when the total amount of (meth)acrylic monomer (B) is 100 mol%, It is preferable to contain 85 to 99 mol% of monofunctional (meth)acrylate and 1 to 15 mol% of polyfunctional (meth)acrylate. In this case, the content of monofunctional (meth)acrylate is more preferably 90 to 99 mol%, and even more preferably 95 to 98 mol%. Moreover, the content of polyfunctional (meth)acrylate is more preferably 1 to 10 mol%, and even more preferably 2 to 5 mol%.

When containing monofunctional (meth)acrylate and polyfunctional (meth)acrylate, if the content of monofunctional (meth)acrylate is 85 mol% or more, the fluidity of the cured product obtained by curing the adhesive composition is This is a preferable range when used as an adhesive layer of an adhesive sheet. Therefore, a pressure-sensitive adhesive sheet using this cured product as an adhesive layer is preferable because it has sufficient irregularity-absorbing properties and, when attached to an adherend having uneven portions on the surface, it is difficult to create voids between the uneven portions of the adherend. do. Additionally, it is preferable that the content of monofunctional (meth)acrylate is 99 mol% or less because no adhesive remains when a pressure-sensitive adhesive sheet using a cured product of the pressure-sensitive adhesive composition as an pressure-sensitive adhesive layer is peeled from the adherend.

When containing monofunctional (meth)acrylate and polyfunctional (meth)acrylate, it is preferable that the content of polyfunctional (meth)acrylate is 1 mol% or more because the fluidity of the cured product obtained by curing the adhesive composition does not become too large. do. In addition, if the content of polyfunctional (meth)acrylate is 15 mol% or less, the fluidity of the cured product obtained by curing the adhesive composition falls within a preferable range when the cured product is used as an adhesive layer of an adhesive sheet. Therefore, the adhesive sheet using the cured product as the adhesive layer is preferable because it has sufficient unevenness and water absorption, and when it is attached to an adherend having uneven portions on the surface, it is difficult for voids to occur between the uneven portions of the adherend. do.

The content of the (meth)acrylic monomer (B) in the adhesive composition of this embodiment is preferably 49 to 79% by mass, more preferably 53 to 73% by mass, and even more preferably 56 to 66% by mass. desirable. It is preferable that the content of the (meth)acrylic monomer (B) is 49% by mass or more because the viscosity of the adhesive composition does not become too high and coating properties are excellent. Additionally, if the content of the (meth)acrylic monomer (B) is 79% by mass or less, the viscosity of the adhesive composition does not become too low and the thickness of the coating film made of the adhesive composition is easy to control, so it is preferable.

(Chain transfer agent (C))

The chain transfer agent (C) is contained in the adhesive composition for the purpose of controlling the storage modulus, loss tangent, and gel fraction of the cured product obtained by curing the adhesive composition.

As the chain transfer agent (C), for example, polyfunctional thiol can be preferably used. A polyfunctional thiol is a compound having two or more mercapto groups in the molecule.

The polyfunctional thiol is not particularly limited, but examples include 1,2-ethanedithiol, 1,4-bis(3-mercaptobutyryloxy)butane, and tetraethylene glycol bis(3-mercaptopropionate). ), trimethylol ethane tris (3-mercaptobutyrate), trimethylol propane tris (3-mercaptobutylate), trimethylol propane tris (3-mercaptopropionate), pentaerythritol tetrakis (3- mercaptobutyrate), pentaerythritol tetrakis (3-mercaptopropionate, 1,3,5-tris (3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4, 6(1H, 3H, 5H)-trione, tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate,, dipentaethyritol hexas(3-mercaptopropionate) etc. As the chain transfer agent (C), among the above, it is preferable to use pentaerythritol tetrakis (3-mercaptobutyrate) from the viewpoint of the reactivity of the adhesive composition.

The content of the chain transfer agent (C) in the adhesive composition of this embodiment is preferably 0.5 to 5% by mass, more preferably 1 to 5% by mass, and even more preferably 3 to 4.5% by mass. When the content of the chain transfer agent (C) is 0.5% by mass or more, the fluidity of the cured product obtained by curing the adhesive composition falls within a preferable range when the cured product is used as an adhesive layer of an adhesive sheet. Therefore, a pressure-sensitive adhesive sheet using the cured product as a pressure-sensitive adhesive layer is preferable because it has sufficient unevenness-absorbing properties and prevents voids from forming between the uneven portions of the adherend. If the content is 5% by mass or less, it is preferable that no adhesive remains when the adhesive sheet using the cured product of the adhesive composition as the adhesive layer is peeled from the adherend.

(Photopolymerization initiator (D))

The photopolymerization initiator (D) is not particularly limited, but a radical photopolymerization initiator is preferable. As the photopolymerization initiator (D), for example, a carbonyl-based photopolymerization initiator, a sulfide-based photopolymerization initiator, an acylphosphine oxide-based photopolymerization initiator, a quinone-based photopolymerization initiator, a sulfo chloride-based photopolymerization initiator, a thioxanthone-based photopolymerization initiator, etc. You can use it. Among these photopolymerization initiators (D), from the viewpoint of transparency of the cured product obtained by photocuring the adhesive composition, it is preferable to use an acylphosphine oxide-based photopolymerization initiator, and specifically, 2,4,6-trimethylbenzoyldi. It is preferred to use phenylphosphine oxide.

The content of the photopolymerization initiator (D) in the adhesive composition of this embodiment is preferably 0.01 to 5% by mass, more preferably 0.05 to 3% by mass, and even more preferably 0.1 to 2% by mass. If the content of the photopolymerization initiator (D) is 0.01% by mass or more, photocuring of the adhesive composition proceeds sufficiently. Additionally, if the content of the photopolymerization initiator (D) is 5% by mass or less, the low molecular weight component does not increase excessively during photocuring of the adhesive composition. For this reason, it is preferable that no adhesive remains when a pressure-sensitive adhesive sheet using a cured product of the pressure-sensitive adhesive composition as the pressure-sensitive adhesive layer is peeled from the adherend.

(Fatty acid ester (E))

The adhesive composition of this embodiment contains polyurethane (A), (meth)acrylic monomer (B), chain transfer agent (C), and photopolymerization initiator (D), and, if necessary, fatty acid ester (E ) may be included.

The fatty acid ester (E) not only controls the adhesive strength of the adhesive sheet using the cured product of the adhesive composition as the adhesive layer, but also controls the lamination properties (wetting properties) and bubble leakage properties of the adhesive layer (when the adhesive sheet is bonded to the adherend). It is contained for the purpose of improving the ease of discharge of trapped air bubbles.

As the fatty acid ester (E), an ester of a fatty acid and an alkyl alcohol can be used. From the viewpoint of compatibility with other components, an ester of a fatty acid with 8 to 18 carbon atoms and a monofunctional alcohol having a branched hydrocarbon group with 3 to 18 carbon atoms and a carbon number of It is preferable to use a fatty acid ester selected from esters of 14 to 18 unsaturated fatty acids and 2 to 4 functional alcohols.

Examples of esters of a fatty acid having 8 to 18 carbon atoms and a monofunctional alcohol having a branched hydrocarbon group having 3 to 18 carbon atoms include isostearyl laurate, isopropyl myristate, isocetyl myristate, octyldodecyl myristate, and palmitic acid. Isopropyl, isostearyl palmitate, isocetyl stearate, 2-ethylhexyl stearate, octyldodecyl oleate, diisostearyl adipate, diisocetyl sebacate, trioleyl trimellitate and triisocetyl trimellitate. etc. can be mentioned. Among these, it is preferable to use isopropyl myristate, isopropyl palmitate, and 2-ethylhexyl stearate, and it is especially preferable to use isopropyl myristate and/or 2-ethylhexyl stearate.

Examples of esters of unsaturated fatty acids having 14 to 18 carbon atoms and alcohols having 2 to 4 functions include unsaturated fatty acids such as myristrenic acid, oleic acid, linoleic acid, linolenic acid, isopalmitic acid, and isostearic acid, ethylene glycol, propylene glycol, glycerin, and trimethylolpropane. , esters of alcohols such as pentaerythritol and sorbitan.

The content of fatty acid ester (E) in the adhesive composition of this embodiment is preferably 3 to 18 mass%, and more preferably 5 to 15 mass%. If the content of fatty acid ester (E) is 3% by mass or more, the adhesive strength of the adhesive sheet using the cured product of the adhesive composition as the adhesive layer will be within a range desirable for the adhesive sheet, and the lamination properties and bubble leakage properties of the adhesive layer will be improved. It gets better. If the content of fatty acid ester (E) is 18% by mass or less, adhesive residue containing fatty acid ester (E) is unlikely to be generated when the adhesive sheet using the cured product of the adhesive composition as the adhesive layer is peeled from the adherend, which is preferable. do.

(solvent)

Although the adhesive composition of this embodiment may contain a solvent, it is more preferable that it is a solvent-free thing which does not substantially contain a solvent.

When the pressure-sensitive adhesive composition of the present embodiment contains a solvent, the solvent can be used as a leveling agent and/or softener, for example.

When the adhesive composition of this embodiment is solvent-free, when using it to form the adhesive layer of an adhesive sheet, the step of heating and drying the solvent can be omitted, resulting in excellent productivity. In particular, when using the pressure-sensitive adhesive composition of the present embodiment to manufacture a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer whose thickness exceeds 50 μm, the effect of improving productivity by omitting the step of heating and drying the solvent becomes significant. It is preferable that it is solvent-free.

In the present invention, the meaning that the adhesive composition "does not substantially contain a solvent" means that the solvent content in the adhesive composition is 0 to 1% by mass, preferably 0 to 0.5% by mass, More preferably, it is 0 to 0.1 mass%.

(etc)

The adhesive composition of this embodiment may contain other additives as needed within the range that does not impair the effect of the present invention. Additives include, for example, plasticizers, surface lubricants, antioxidants, anti-aging agents, light stabilizers, ultraviolet absorbers, polymerization inhibitors, light stabilizers such as benzotriazoles, phosphoric acid esters and other flame retardants, and antistatic agents such as surfactants. , dyes, etc.

(gel fraction)

The adhesive composition of this embodiment is photocurable, and the gel fraction of the cured product cured at an irradiation dose of 1000 mJ/cm2 is in the range of 50 to 65 mass% so that the thickness after curing is 150 μm. The gel fraction of the cured product cured at an irradiation dose of 1000 mJ/cm2 is the adhesive of the present embodiment containing polyurethane (A), (meth)acrylic monomer (B), chain transfer agent (C), and photopolymerization initiator (D). In the composition, it can be adjusted by controlling the content of the chain transfer agent (C) and/or the photopolymerization initiator (D). More specifically, as the content of the chain transfer agent (C) and/or photopolymerization initiator (D) increases, the gel fraction decreases, and as the content of the chain transfer agent (C) and/or photopolymerization initiator (D) decreases, the gel fraction decreases. It gets higher.

A cured product with a gel fraction of 50 to 65% by mass obtained by curing the adhesive composition of the present embodiment at an irradiation dose of 1000 mJ/cm2 has sufficient adhesive strength, is less likely to generate adhesive residue, and is excellent in irregularity absorption. For this reason, the pressure-sensitive adhesive composition of the present embodiment is suitable as a material for the pressure-sensitive adhesive layer in a pressure-sensitive adhesive sheet used for applications in which the adhesive composition is adhered to an adherend having uneven portions on the surface and then peeled off. The gel fraction of the cured product obtained by curing the adhesive composition of this embodiment at an irradiation dose of 1000 mJ/cm2 is preferably 52% by mass or more. Additionally, the gel fraction of the cured product is preferably 63% by mass or less.

On the other hand, an adhesive sheet using a cured product with a gel fraction of less than 50% by mass as an adhesive layer is likely to generate adhesive residue when peeled off after being attached to an adherend. In addition, the cured product with a gel fraction exceeding 65% by mass has insufficient fluidity when used as an adhesive layer of an adhesive sheet. For this reason, when a pressure-sensitive adhesive sheet using a cured product with a gel fraction exceeding 65 mass% as the pressure-sensitive adhesive layer is attached to an adherend having uneven portions on the surface, voids are likely to occur between the uneven portions of the adherend. easy.

(Measurement of gel fraction)

In the present invention, the gel fraction of the cured product obtained by curing the adhesive composition at an irradiation dose of 1000 mJ/cm2 is measured as follows.

First, the adhesive composition was applied using an applicator to a peelable PET film with a thickness of 75 ㎛ (manufactured by Higashiyama Film Co., Ltd., product name: Clean Sepa (trademark) HY-S10-2) so that the thickness after curing was 150 ㎛. do. Next, the surface to which the adhesive composition is applied is covered with a silicone-based cemented carbide peelable PET film (manufactured by Toyobo Co., Ltd., product name: E7006) with a thickness of 75 μm.

Subsequently, using an ultraviolet irradiation device (manufactured by Eye Graphics Co., Ltd., UV irradiation device 3 kW, high-pressure mercury lamp), carbide exfoliation was carried out under the conditions of irradiation distance of 25 cm, lamp movement speed of 1.0 m/min, and irradiation amount of 1000 mJ/cm2. The adhesive composition is cured by irradiating ultraviolet rays through the PET film to form a cured product (adhesive layer).

Next, a square sheet of 8 cm in length and 8 cm in width is cut from the sheet having the cured product (adhesive layer), and the peeled PET film and the cemented carbide peeled PET film are peeled from the adhesive layer of the obtained square sheet. Then, the adhesive layer peeled from the square sheet is used as a sample for measurement, and its mass is measured. Subsequently, the sample for measurement is immersed in 50 ml of toluene and left to stand at room temperature for 72 hours. After that, the sample for measurement is taken out from the toluene, dried at 80°C for 5 hours, and the mass is measured again. Then, the gel fraction is measured based on the following formula.

Gel fraction (%)=[A/B]×100

A: Mass of sample for measurement after immersion in toluene (mass of toluene is not included)

B: Mass of sample for measurement before immersion in toluene

(Storage modulus and loss tangent)

The cured product of the adhesive composition of this embodiment cured at an irradiation dose of 1000 mJ/cm2 so that the thickness after curing is 150 ㎛ has a storage modulus at 25°C measured at a frequency of 1 Hz of 1.0×10 ⁴ to 1.0×10 ⁵ and the loss tangent is preferably 0.25 to 0.55.

The storage modulus and loss tangent at 25°C of the cured product cured at an irradiation dose of 1000 mJ/cm2 measured at a frequency of 1 Hz control the content of the chain transfer agent (C) and/or photopolymerization initiator (D) contained in the adhesive composition. You can adjust it by doing this. More specifically, as the content of the chain transfer agent (C) and/or photopolymerization initiator (D) increases, the storage modulus decreases and the loss tangent increases. Additionally, when the content of the chain transfer agent (C) and/or the photopolymerization initiator (D) is reduced, the storage modulus increases and the loss tangent decreases.

The cured product obtained by curing the adhesive composition of the present embodiment at an irradiation dose of 1000 mJ/cm 2 and having a storage modulus of 1.0×10 ⁴ to 1.0×10 ⁵ and a loss tangent of 0.25 to 0.55 has good flexibility and fluidity. . For this reason, when an adhesive sheet using this cured product as an adhesive layer is attached to a work (adherent) such as a semiconductor wafer having uneven portions such as bumps, voids are prevented from occurring between the uneven portions and the adhesive sheet. can do.

The storage modulus of the cured product obtained by curing the adhesive composition of the present embodiment at an irradiation dose of 1000 mJ/cm2 at 25°C measured at a frequency of 1 Hz is more preferably 2.0×10 ⁴ or more, and still more preferably 3.0×10 ⁴ or more. . Moreover, the storage elastic modulus is more preferably 9.0×10 ⁴ or less, and even more preferably 8.0×10 ⁴ or less.

The cured product having a storage modulus of 1.0×10 ⁴ or more is not excessively flexible when used as an adhesive layer of an adhesive sheet. For this reason, an adhesive sheet using a cured product with a storage modulus of 1.0×10 ⁴ or more as an adhesive layer is preferable because adhesive residue is unlikely to be generated even when peeled off after being attached to an adherend. Additionally, the cured product having a storage modulus of 1.0×10 ⁵ or less has good flexibility when used as an adhesive layer of an adhesive sheet. For this reason, when a pressure-sensitive adhesive sheet using a cured product with a storage modulus of ^1.0 It is difficult and desirable.

The loss tangent at 25°C measured at a frequency of 1 Hz of the cured product obtained by curing the adhesive composition of the present embodiment at an irradiation dose of 1000 mJ/cm2 is more preferably 0.30 or more. Moreover, it is more preferable that the loss tangent is 0.50 or less.

The cured product having the loss tangent of 0.25 or more has good fluidity when used as an adhesive layer of an adhesive sheet. For this reason, when a pressure-sensitive adhesive sheet using a cured product with a loss tangent of 0.25 or more as an adhesive layer is attached to an adherend having uneven portions on the surface, it is difficult for voids to occur between the uneven portions of the adherend, which is preferable. . In addition, the cured product having the loss tangent of 0.55 or less does not have excessive fluidity when used as an adhesive layer of an adhesive sheet. For this reason, an adhesive sheet using a cured product with a loss tangent of 0.55 or less as an adhesive layer is preferable because adhesive residue is unlikely to be generated even when peeled off after being attached to an adherend.

(Measurement of storage modulus and loss tangent)

In the present invention, the storage modulus and loss tangent at 25°C measured at a frequency of 1 Hz of the cured product obtained by curing the adhesive composition at an irradiation dose of 1000 mJ/cm2 are measured by the following method.

First, in the same manner as the method of measuring the gel fraction described above, the adhesive composition is cured to produce a sheet having a cured product (adhesive layer) with a thickness of 150 μm. The peeled PET film and the cemented carbide peeled PET film are peeled from the adhesive layer of the sheet having the cured product (adhesive layer). Then, 10 peeled adhesive layers with a thickness of 150 μm are laminated to form a laminated sheet with a thickness of 1.5 mm. A square sheet of 8 mm in length and 8 mm in width was cut from the obtained laminated sheet to serve as a sample for measurement.

Thereafter, the obtained measurement sample was stored at -20 to 120°C at a frequency of 1 Hz (6.28 rad/sec) using a rotational viscoelasticity measurement device (rheometer) (manufactured by TA Instruments, product name "AR2000"). The elastic modulus and loss modulus are measured in shear mode, and the storage modulus and loss tangent at 25°C are calculated.

<Method for producing adhesive composition>

Next, the manufacturing method of the adhesive composition of this embodiment is explained in detail with an example.

Hereinafter, among the components contained in the pressure-sensitive adhesive composition of the present embodiment, polyurethane (A) will be described by way of example, and a preferred synthesis method will be given. Among the components contained in the adhesive composition of this embodiment, (meth)acrylic monomer (B), chain transfer agent (C), photopolymerization initiator (D), fatty acid ester (E), etc., each component except polyurethane (A) Regarding this, commercial products can be easily purchased, and since each synthesis method is different depending on the type of compound used as each component, description of the synthesis method is omitted.

<Method for synthesizing polyurethane (A)>

Hereinafter, an example of a preferred method for synthesizing polyurethane (A) contained in the pressure-sensitive adhesive composition of the present embodiment will be described. In addition, the method for synthesizing polyurethane (A) is not limited to the synthesis method shown below, and can be appropriately changed depending on conditions such as raw materials and equipment used for synthesis.

In the method for synthesizing polyurethane (A) shown below, the reaction between a hydroxy group and an isocyanato group is carried out in the presence of an organic solvent inert to the isocyanato group in any step, such as dibutyltin dilaurate, This is carried out using a urethanization catalyst such as butyltin ethylhexoate and dioctyltin dilaurate. In addition, the reaction between the hydroxy group and the isocyanato group is preferably carried out continuously at 30 to 100°C for 1 to 5 hours in any process. The amount of the urethanization catalyst used is preferably 50 to 500 ppm by mass based on the total mass of reactants (raw materials).

In order to synthesize polyurethane (A), first, polyoxyalkylene polyol and polyisocyanate are mixed in a ratio such that the isocyanato group amount (based on the number of molecules, hereinafter the same) is greater than the hydroxyl group amount (based on the number of molecules, hereinafter the same). Put in. Thereafter, polyoxyalkylene polyol and polyisocyanate are reacted to synthesize polyurethane having an isocyanato group at the terminal as a precursor of polyurethane (A). Specific examples of polyoxyalkylene polyol and polyisocyanate that can be used as raw materials are as exemplified in the section on polyurethane (A).

At this time, the molecular weight (degree of polymerization) of the polyurethane having an isocyanato group at the terminal can be adjusted by adjusting the ratio of the amount of isocyanato group to the amount of hydroxy group contained in the raw material. Specifically, the smaller the excess amount of the isocyanato group relative to the hydroxy group, the greater the molecular weight of the polyurethane having an isocyanato group at the terminal. In addition, the larger the excess amount of isocyanato group relative to the hydroxy group, the smaller the molecular weight of the polyurethane having an isocyanato group at the terminal. In this embodiment, the mass average molecular weight of the target polyurethane (A) is adjusted by adjusting the molecular weight of the polyurethane having an isocyanato group at the terminal.

Next, polyurethane having an isocyanato group at the terminal and a compound having a hydroxy group and a (meth)acryloyl group are reacted to form a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate. , producing polyurethane (A) containing polyurethane (a1) having a (meth)acryloyl group at a plurality of terminals. It is preferable that the terminal (meth)acryloyl group of the produced polyurethane (A) is a part of a (meth)acryloyloxy group.

The compound having a hydroxy group and a (meth)acryloyl group is not particularly limited, but includes 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. hydroxyalkyl (meth)acrylates such as; 1,3-butanediol mono(meth)acrylate, 1,4-butanediol mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate, 3-methylpentanediol mono(meth)acrylate, etc. Monools having a (meth)acryloyl group derived from various polyols, etc. can be mentioned. The compounds having these hydroxy groups and (meth)acryloyl groups may be used individually, or may be used in combination of two or more types. Among these compounds having a hydroxy group and a (meth)acryloyl group, 2-hydroxyethyl (meth) is preferred because of its reactivity with the isocyanato group of polyurethane having an isocyanato group at the terminal and the photocurability of the adhesive composition. It is preferred to use acrylates.

In addition, polyurethane (A) uses a compound having a hydroxy group and a (meth)acryloyl group together with an alkyl alcohol having no (meth)acryloyl group and one hydroxy group, and has an isocyanato group at the terminal. It may be produced by reacting with polyurethane.

The alkyl alcohol may be one that does not have a (meth)acryloyl group and has one hydroxy group, and straight-chain, branched, or alicyclic alkyl alcohols can be used, and are not particularly limited. The said alkyl alcohol may be used individually by 1 type, or may be used in combination of 2 or more types.

By reacting a compound having a hydroxy group and a (meth)acryloyl group, an alkyl alcohol having no (meth)acryloyl group and one hydroxy group, and polyurethane having an isocyanato group at the terminal, polyurethane (A ), the amount of (meth)acryloyl group introduced into the polyurethane having an isocyanato group at the terminal can be adjusted.

More specifically, according to the above reaction, polyurethane (A) containing multiple types of polyurethanes with different amounts of terminal (meth)acryloyl groups introduced is produced. Among the multiple types of polyurethanes, polyurethane (a1) having (meth)acryloyl groups at multiple terminals is included. Moreover, among the plural types of polyurethanes, not only polyurethane (a1) but also polyurethanes in which at least some of the plurality of terminals have a structure derived from the alkyl alcohol are included. Therefore, among the plurality of types of polyurethanes produced, polyurethanes in which at least some of the plurality of terminals do not have a (meth)acryloyl group are included. In addition, among the plurality of types of polyurethanes produced, polyurethane (a2) having a (meth)acryloyl group at only one terminal may also be included.

<Other examples of methods for synthesizing polyurethane (A)>

Next, another example of a preferred method for synthesizing polyurethane (A) will be described.

In the method for synthesizing polyurethane (A) shown below, as in the example of the above-mentioned synthesis method, the reaction between a hydroxy group and an isocyanato group is carried out in the presence of an organic solvent inert to the isocyanato group in any step, This is carried out using a urethanization catalyst such as dibutyltin dilaurate, dibutyltin ethylhexoate, and dioctyltin dilaurate. In addition, the reaction between the hydroxy group and the isocyanato group is preferably carried out continuously at 30 to 100°C for 1 to 5 hours in any process. The amount of the urethanization catalyst used is preferably 50 to 500 ppm by mass based on the total mass of reactants (raw materials).

When synthesizing polyurethane (A) using this synthesis method, unlike the example of the above synthesis method, polyurethane having a hydroxy group at the terminal is synthesized as a precursor of polyurethane (A).

Specifically, first, polyoxyalkylene polyol and polyisocyanate are added in a ratio such that the amount of hydroxyl group (based on the number of molecules, hereinafter the same will apply) is greater than the amount of isocyanato group (based on the number of molecules, hereinafter the same will apply). Thereafter, polyoxyalkylene polyol and polyisocyanate are reacted to synthesize polyurethane having a hydroxy group at the terminal as a precursor of polyurethane (A).

At this time, the molecular weight (degree of polymerization) of polyurethane having a hydroxy group at the terminal can be adjusted by adjusting the ratio of the amount of hydroxy group to the amount of isocyanato group contained in the raw material. Specifically, the smaller the excess amount of the hydroxyl group relative to the isocyanato group, the larger the molecular weight of the polyurethane having a hydroxyl group at the terminal. In addition, the larger the excess amount of the hydroxyl group relative to the isocyanato group, the smaller the molecular weight of the polyurethane having a hydroxyl group at the terminal. In this embodiment, the mass average molecular weight of the target polyurethane (A) is adjusted by adjusting the molecular weight of the polyurethane having a hydroxy group at the terminal.

Next, polyurethane having a hydroxy group at the terminal is reacted with a compound having an isocyanato group and a (meth)acryloyl group to obtain a skeleton containing a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate. , producing polyurethane (A) containing polyurethane (a1) having a (meth)acryloyl group at a plurality of terminals. It is preferable that the terminal (meth)acryloyl group of the produced polyurethane (A) is a part of a (meth)acryloyloxy group.

The compound having an isocyanato group and a (meth)acryloyl group is not particularly limited, but includes 2-(meth)acryloyloxyethyl isocyanate, 2-(meth)acryloyloxypropyl isocyanate, and 1,1-bis. (acryloyloxymethyl)ethyl isocyanate, etc. are mentioned. In addition, commercially available compounds having an isocyanato group and a (meth)acryloyl group include, for example, Karenz MOI (registered trademark) and Karenz AOI (registered trademark) manufactured by Showa Denko Co., Ltd. You can. The compounds having these isocyanato groups and (meth)acryloyl groups may be used individually, or may be used in combination of two or more types. Among these compounds having an isocyanato group and a (meth)acryloyl group, 2-(meth)acryloyloxyethyl is preferred because of its reactivity with the hydroxy group of polyurethane having a hydroxy group at the terminal and the photocurability of the adhesive composition. It is preferred to use isocyanate.

In addition, polyurethane (A) is prepared by using a compound having an isocyanato group and a (meth)acryloyl group together with an alkyl isocyanate having no (meth)acryloyl group and one isocyanato group, It may be produced by reacting with polyurethane having a hydroxy group.

The alkyl isocyanate may be one that does not have a (meth)acryloyl group and has one isocyanato group, and straight-chain, branched, or alicyclic alkyl isocyanates can be used, and are not particularly limited. The said alkyl isocyanate may be used individually by 1 type, or may be used in combination of 2 or more types.

By reacting a compound having an isocyanato group and a (meth)acryloyl group, an alkyl isocyanate having no (meth)acryloyl group and one isocyanato group, and polyurethane having a hydroxy group at the terminal, polyurethane is produced. By producing urethane (A), the amount of (meth)acryloyl group introduced into the polyurethane having a hydroxy group at the terminal can be adjusted.

More specifically, according to the above reaction, polyurethane (A) containing multiple types of polyurethanes with different amounts of terminal (meth)acryloyl groups introduced is produced. Among the multiple types of polyurethanes, polyurethane (a1) having (meth)acryloyl groups at multiple terminals is included. Moreover, among the multiple types of polyurethanes, not only polyurethane (a1) but also polyurethanes in which at least some of the terminals have a structure derived from the alkyl isocyanate are included. Therefore, among the plurality of types of polyurethanes produced, polyurethanes in which at least some of the plurality of terminals do not have a (meth)acryloyl group are included. In addition, among the plurality of types of polyurethanes produced, polyurethane (a2) having a (meth)acryloyl group at only one terminal may also be included.

<Method of mixing each component included in the adhesive composition>

The adhesive composition of the present embodiment includes polyurethane (A) obtained by the above synthesis method, (meth)acrylic monomer (B), chain transfer agent (C), and photopolymerization initiator (D), and added as necessary. It can be manufactured by mixing fatty acid ester (E) and other additives.

The method of mixing each component contained in the adhesive composition of this embodiment is not particularly limited, and can be performed, for example, using a stirring device provided with stirring blades such as homo disper or paddle blades.

The adhesive composition of this embodiment includes polyurethane (A), (meth)acrylic monomer (B), chain transfer agent (C), and photopolymerization initiator (D), and polyurethane (A) is polyoxyalkyl A gel of a cured product containing a polyurethane (a1) having a skeleton containing a structure derived from renpolyol and a structure derived from polyisocyanate and having a (meth)acryloyl group at a plurality of terminals, and photocured at an irradiation dose of 1000 mJ/cm2. The fraction is 50 to 65 mass%. For this reason, by curing the adhesive composition of the present embodiment, a cured product is obtained that has sufficient adhesive strength, is less likely to generate adhesive residue, and is excellent in uneven absorption. Therefore, the pressure-sensitive adhesive composition of the present embodiment is suitable as a material for the pressure-sensitive adhesive layer in a pressure-sensitive adhesive sheet used for applications where it is attached to an adherend having an uneven portion on the surface and is then peeled off.

<Method for manufacturing adhesive sheet>

Next, the manufacturing method of the adhesive sheet of this embodiment is explained.

The manufacturing method of the adhesive sheet of this embodiment is not particularly limited, and can be manufactured using a known method.

For example, an adhesive composition is applied onto a sheet-like substrate, and a separator is laminated to form a laminate. Thereafter, ultraviolet rays are irradiated to the adhesive composition through a separator to photocure the adhesive composition. In this way, a pressure-sensitive adhesive sheet is obtained in which a pressure-sensitive adhesive layer consisting of a cured product of the pressure-sensitive adhesive composition is formed on a base material.

The method of applying the adhesive composition to the substrate is not particularly limited and can be selected appropriately. For example, as a method of applying the adhesive composition to the substrate, various coaters such as gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, spray coater, comma coater, and direct coater are used. method, screen printing method, etc.

Light sources for photocuring the adhesive composition include black lights, low-pressure mercury lamps, high-pressure mercury lamps, ultra-high pressure mercury lamps, metal halide lamps, and xenon lamps.

The irradiation intensity of light is sufficient as long as the pressure-sensitive adhesive composition can be sufficiently cured and the gel fraction of the cured product is within the range of 50 to 65% by mass. For example, it is preferably 50 to 3000 mW/cm2. If the irradiation intensity of light is low, curing takes time and productivity decreases. In addition, it is more preferable to adjust the light irradiation intensity so that the storage modulus and loss tangent values of the cured product at 25°C measured at a frequency of 1 Hz are within the desired range.

In this embodiment, ultraviolet rays are irradiated to the adhesive composition through a transparent separator, but when the substrate and the separator are transparent, ultraviolet rays may be irradiated from either the separator side or the substrate side.

<Use of adhesive sheet and obtained performance>

The adhesive sheet of this embodiment can be used for applications in which it is attached to an adherend having uneven portions on the surface and is then peeled off. Specifically, it can be suitably used as an adhesive sheet that is attached to the bumped surface of a semiconductor wafer, protects the surface of the semiconductor wafer, and is peeled off after a predetermined processing step.

When the adhesive sheet of this embodiment is used to protect the bump formation surface of a semiconductor wafer, the peel strength (adhesive force) of the adhesive sheet is determined by It needs to be strong enough to be securely fixed to the adhesive sheet. On the other hand, when the adhesive sheet is peeled from the semiconductor wafer after a predetermined processing process, it needs to be strong enough not to damage the components of the semiconductor device.

From these viewpoints, the peel strength of the adhesive sheet used for the above application is preferably 10 to 300 gf/25 mm when the peel speed is 0.3 m/min and the thickness of the adhesive layer is 50 to 200 μm. , more preferably 15 to 200 gf/25 mm, and even more preferably 20 to 150 gf/25 mm. The specific method of measuring the peel strength of the adhesive sheet will be described later in the Examples.

The adhesive sheet of this embodiment has an adhesive layer made of a cured product of the adhesive composition of this embodiment on one side of the sheet-like substrate. For this reason, the pressure-sensitive adhesive sheet of this embodiment has sufficient adhesive strength, it is difficult to generate adhesive residue that transfers the pressure-sensitive adhesive layer to the adherend after peeling off the pressure-sensitive adhesive sheet, and it is also excellent in uneven absorption. Therefore, the adhesive sheet of this embodiment is suitable for applications in which it is attached to an adherend having uneven portions on the surface and is then peeled off.

The adhesive sheet of this embodiment can be suitably used, for example, as an adhesive sheet that is attached when performing a backgrind process on a semiconductor wafer having uneven portions made of bumps on the surface and is peeled off after the backgrind process. In this case, the semiconductor wafer is fixed with sufficient adhesive force by the adhesive sheet of this embodiment, and furthermore, a gap is unlikely to occur between the adhesive sheet attached to the semiconductor wafer and the periphery of the bump. Therefore, water used in the backgrind process can be prevented from entering the gap between the adhesive sheet and the bump periphery and contaminating the semiconductor wafer. In addition, it is preferable that adhesive residue is unlikely to be generated around the bumps of the semiconductor wafer from which the adhesive sheet has been peeled after the backgrind process.

Example

Hereinafter, the present invention will be described in more detail through examples and comparative examples. Additionally, the present invention is not limited to the following examples.

<Synthesis of polyurethane (A-1)>

In a reactor equipped with a thermometer, a stirrer, a dropping lot, and a cooling tube with a drying tube, 0.55 kg (2.1 mol) of a hydrogenated product of diphenylmethane diisocyanate (Desmodule W, manufactured by Sumica Covestro Urethane) and a hydroxyl value of 4.01 kg (2.0 mol) of polypropylene glycol (Actcol D-2000; manufactured by Mitsui Chemicals, number average molecular weight 2000) having a hydroxyl group at the terminal of 56 mg KOH/g, and dioctyltin (Neostane U) as a urethanization catalyst. 0.8 g of -810 (manufactured by Nitto Chemical Industries, Ltd.) was added.

Thereafter, the reactor was heated to 60°C and reacted for 4 hours to obtain polyurethane having isocyanato groups at both ends as a precursor of polyurethane (A). Subsequently, 23.22 g (0.2 mol) of 2-hydroxyethyl acrylate was added to the reactor, the temperature was raised to 70°C and reaction was performed for 2 hours, and 4.58 kg of polyurethane (A-1) with a mass average molecular weight of 67,000 was obtained.

The obtained polyurethane (A-1) was analyzed using an infrared absorption spectrum (IR) method. As a result, no peak derived from the isocyanate group was observed. Therefore, it was confirmed that polyurethane (A-1) was polyurethane (a1) with acryloyloxy groups introduced at all terminals.

<Synthesis of polyurethane (A-2)>

The mass average method was the same as the synthesis method for polyurethane (A-1), except that 2.1 mol of isophorone diisocyanate (Desmodul I, manufactured by Sumica Covestro Urethane) was used instead of the hydrogenated diphenylmethane diisocyanate. Polyurethane (A-2) with a molecular weight of 66,000 was obtained.

The obtained polyurethane (A-2) was analyzed using an infrared absorption spectrum (IR) method. As a result, no peak derived from the isocyanate group was observed. Accordingly, it was confirmed that polyurethane (A-2) was polyurethane (a1) with acryloyloxy groups introduced at all terminals.

<Preparation of adhesive composition>

Polyurethane (A-1) or (A-2) obtained in this way, (meth)acrylic monomer (B), chain transfer agent (C), photopolymerization initiator (D), and fatty acid ester (E) shown in Table 1 or 2. ) were mixed in the ratios shown in Table 1 or 2 and mixed using a disper at 25°C to obtain the adhesive compositions of Examples 1 to 5 and Comparative Examples 1 to 5.

The following symbols shown in Table 1 or 2 indicate the compounds shown below.

2EHA: 2-ethylhexyl acrylate (manufactured by Toagosei Co., Ltd.)

BUA:n-butylacrylate (manufactured by Toa Gosei Co., Ltd.)

ACMO: Acryloylmorpholine (manufactured by Shinnakamura Chemical Industry Co., Ltd.)

IBOA: Isobornyl acrylate (manufactured by Osaka Yuki Chemical High School Co., Ltd.)

TMPTA: Trimethylolpropane triacrylate (manufactured by Toagosei Co., Ltd.)

PE1: Pentaerythritol tetrakis (3-mercaptobutyrate) (manufactured by Showa Denko Co., Ltd.)

NR1: 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H, 3H, 5H)-trione (Showa Denko Co., Ltd. manufacturing)

TPO (Omnirad TPO H): 2,4,6-trimethylbenzoyldiphenylphosphine oxide (manufactured by IGM Resins B.V.)

Exepal IPM: Isopropyl myristate (manufactured by Gao Co., Ltd.)

Exepal EH-S: 2-ethylhexyl stearate (manufactured by Gao Co., Ltd.)

<Measurement of gel fraction>

By the above-described method, samples for measurement were prepared using the adhesive compositions of Examples 1 to 5 and Comparative Examples 1 to 5, and the gel fraction of the cured product photocured at an irradiation dose of 1000 mJ/cm2 was measured. The results are shown in Table 1 or 2.

<Measurement of storage modulus and loss tangent>

By the method described above, samples for measurement were prepared using the adhesive compositions of Examples 1 to 5 and Comparative Examples 1 to 5, and the cured product photocured at an irradiation dose of 1000 mJ/cm2 was measured at a frequency of 1 Hz. The storage modulus and loss tangent at 25°C were measured. The results are shown in Table 1 or 2.

<Production of adhesive sheet>

As a sheet-like substrate, a 50-μm-thick PET film (manufactured by Toyobo Co., Ltd., brand name: Ester (trademark) film E5100) was prepared. Then, the adhesive composition of Example 1 was applied onto the corona-treated surface of the substrate using an applicator so that the thickness after curing was 150 μm.

Next, a 75-μm-thick silicone-based cemented carbide peelable PET film (manufactured by Toyobo Co., Ltd., product name: E7006) was bonded to the surface to which the adhesive composition was applied as a separator using a rubber roller.

Thereafter, an ultraviolet irradiation device (made by Eye Graphics Co., Ltd., UV irradiation device 3 kW, high-pressure mercury lamp) was applied to the adhesive composition through a separator, with an irradiation distance of 25 cm, a lamp moving speed of 1.0 m/min, and an irradiation amount of 1000 mJ. The adhesive composition was photocured by irradiating ultraviolet rays under the conditions of /cm2. As a result, the adhesive sheet of Example 1 was obtained in which an adhesive layer, which is a cured product of the adhesive composition, and a separator were laminated on a base material.

Next, instead of the adhesive composition of Example 1, the adhesive compositions of Examples 2 to 5 and Comparative Examples 1 to 5 were used, respectively, to produce an adhesive sheet in the same manner as the adhesive sheet of Example 1. . As a result, the adhesive sheets of Examples 2 to 5 and Comparative Examples 2 to 4 were obtained.

However, with respect to the adhesive compositions of Comparative Examples 1 and 5, the adhesive layer consisting of the cured product of the adhesive composition could not be formed due to poor curing.

Next, the items shown below were evaluated for the adhesive sheets of Examples 1 to 5 and Comparative Examples 2 to 4.

<Peel force (peel strength)>

The adhesive sheet was cut to a size of 25 mm in length and 150 mm in width, and the separator was peeled off to expose the adhesive layer. After that, the entire surface of the exposed adhesive layer was laminated to a glass plate, and a rubber roller (diameter: 85 mm, width: 50 mm) with a mass of 2 kg (load: 19.6 N) was rotated once to obtain a sample for measurement. The obtained measurement sample was left for 30 minutes in an environment with a temperature of 23°C and a relative humidity of 50% RH. Thereafter, in accordance with JIS K 6854-2, a tensile test was performed in the 180° direction at a peeling speed of 0.3 m/min. to measure the peeling strength (gf/25 mm) for the glass plate. The results are shown in Table 1 or 2.

<Irregularity Absorbency>

The adhesive sheet was cut into pieces measuring 25 mm in length and 50 mm in width, and the separator was peeled off to expose the adhesive layer. After that, the exposed surface of the adhesive layer was installed with the bumps of a bump-equipped wafer (WALTS-TEG FC150SCJY LF(PI) manufactured by Waltz, bump height: 75 μm, bump size: 90 μm in diameter) facing each other. Then, on the base of the adhesive sheet, a rubber roller (diameter: 85 mm, width: 50 mm) with a mass of 2 kg (load: 19.6 N) is moved back and forth three times at a speed of 10 mm/sec to bond the adhesive sheet and the bump-equipped wafer. did.

The bump-equipped wafer bonded to the adhesive sheet was observed from the substrate side of the adhesive sheet using a digital optical microscope (RH-2000, manufactured by Hyrox Corporation, Inc.), and the irregularity absorbency of the bump was evaluated based on the following criteria. did. The results are shown in Table 1 or 2.

"standard"

○ (possible): There is no gap between the adhesive layer of the adhesive sheet and the area around the bump of the bump-equipped wafer.

× (not possible): There is a gap between the adhesive layer of the adhesive sheet and the bump periphery of the bump-equipped wafer.

<Adhesive residue>

The adhesive sheet was cut into pieces measuring 25 mm in length and 50 mm in width, and the separator was peeled off to expose the adhesive layer. After that, the surface of the exposed adhesive layer was installed so as to face the bump of a bump-equipped wafer (WALTS-TEG FC150SCJY LF(PI) manufactured by Waltz, bump height: 75 μm, bump size: 90 μm in diameter). Then, on the base of the adhesive sheet, a rubber roller (diameter: 85 mm, width: 50 mm) with a mass of 2 kg (load: 19.6 N) is moved back and forth three times at a speed of 10 mm/sec to bond the adhesive sheet and the bump-equipped wafer. did.

After the bump-equipped wafer bonded to the adhesive sheet was left at 23°C for 24 hours, the adhesive sheet was moved at approximately 2 m/min. It was peeled off by hand at a moderate speed. Then, the surface of the bump-equipped wafer was observed using a digital optical microscope (RH-2000, manufactured by Hyrox Co., Ltd.), and the presence or absence of adhesive residue was evaluated based on the following criteria. The results are shown in Table 1 or 2.

"standard"

○ (possible): There is no adhesive residue around the bump.

× (No): There is adhesive residue around the bump.

As shown in Table 1 or 2, the adhesive sheets of Examples 1 to 5 with a gel fraction of 50 to 65 mass% all had a peeling force of 10 gf/25 mm or more and had sufficient adhesive strength. In addition, the pressure-sensitive adhesive sheets of Examples 1 to 5 were all evaluated as “○ (possible)” in terms of irregularity absorbency and adhesive residue.

On the other hand, the adhesive sheets of Comparative Example 2 and Comparative Example 4, where the gel fraction was less than 50% by mass, both had uneven water absorption evaluated as “○ (possible)”, but the adhesive residue evaluation was “× (impossible).”

In addition, the adhesive sheet of Comparative Example 3 with a gel fraction exceeding 65% by mass had an adhesive residue evaluation of “○ (good)”, but an uneven water absorbency evaluation of “× (possible)”.

The present invention can provide a pressure-sensitive adhesive sheet that has sufficient adhesive strength, is less likely to generate adhesive residue that transfers the pressure-sensitive adhesive layer to the adherend after peeling off the pressure-sensitive adhesive sheet, and is also excellent in uneven absorption.

Claims (10)

It is an adhesive sheet having at least a sheet-like substrate and an adhesive layer formed on one side of the substrate,
The adhesive layer is made of a cured product of the adhesive composition and has a gel fraction of 50 to 65% by mass,
The adhesive composition includes polyurethane (A), a (meth)acrylic monomer (B) made of a compound having a (meth)acryloyloxy group, a chain transfer agent (C), and a photopolymerization initiator (D),
The polyurethane (A) has a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and includes polyurethane (a1) having (meth)acryloyl groups at two or more terminals,
The (meth)acrylic monomer (B) contains monofunctional (meth)acrylate and polyfunctional (meth)acrylate,
When the total of the (meth)acrylic monomers (B) is 100 mol%, it contains 85 to 99 mol% of the monofunctional (meth)acrylate and 1 to 15 mol% of the polyfunctional (meth)acrylate. An adhesive sheet characterized in that. According to paragraph 1,
The adhesive layer has a storage modulus of 1.0×10 ⁴ to 1.0×10 ⁵ Pa at 25°C measured at a frequency of 1 Hz,
Additionally, the adhesive sheet has a loss tangent of 0.25 to 0.55 at 25°C measured at a frequency of 1 Hz. According to claim 1 or 2,
An adhesive sheet wherein the adhesive layer has a thickness of 50 to 500 μm. It contains polyurethane (A), a (meth)acrylic monomer (B) made of a compound having a (meth)acryloyloxy group, a chain transfer agent (C), and a photopolymerization initiator (D),
The polyurethane (A) has a skeleton including a structure derived from polyoxyalkylene polyol and a structure derived from polyisocyanate, and includes polyurethane (a1) having (meth)acryloyl groups at two or more terminals,
An adhesive composition, characterized in that the gel fraction of the cured product photocured at an irradiation dose of 1000 mJ/cm2 is 50 to 65% by mass. According to paragraph 4,
The cured product has a storage modulus of 1.0×10 ⁴ to 1.0×10 ⁵ Pa at 25°C measured at a frequency of 1 Hz,
Additionally, the adhesive composition has a loss tangent of 0.25 to 0.55 at 25°C measured at a frequency of 1 Hz. delete delete According to clause 4 or 5,
An adhesive composition wherein the chain transfer agent (C) is a polyfunctional thiol. According to clause 4 or 5,
20 to 50% by mass of the polyurethane (A),
49 to 79% by mass of the (meth)acrylic monomer (B),
0.5 to 5% by mass of the chain transfer agent (C),
An adhesive composition containing 0.01 to 5% by mass of the photopolymerization initiator (D). According to clause 4 or 5,
An adhesive composition further containing fatty acid ester (E).