CN116171220A

CN116171220A - Pressure-sensitive adhesive sheet and method for manufacturing semiconductor device

Info

Publication number: CN116171220A
Application number: CN202180062506.3A
Authority: CN
Inventors: 垣内康彦; 渡边康贵
Original assignee: Lintec Corp
Current assignee: Lintec Corp
Priority date: 2020-09-14
Filing date: 2021-09-10
Publication date: 2023-05-26
Also published as: TW202216445A; WO2022054889A1; JPWO2022054889A1; KR20230069910A

Abstract

The invention provides an adhesive sheet and a method for manufacturing a semiconductor device using the same, wherein the adhesive sheet has a laminated structure comprising an adhesive layer (X1) and a base material layer (Y), at least one of the adhesive layer (X1) and the base material layer (Y) is a thermally expandable layer containing thermally expandable particles, and the surface (S1) of the adhesive layer (X1) _X1 ) Has an arithmetic average waviness (Wa) of 0.090 μm or less, and the surface (S _X1 ) Is the surface opposite to the surface facing the substrate layer (Y).

Description

Pressure-sensitive adhesive sheet and method for manufacturing semiconductor device

Technical Field

The present invention relates to an adhesive sheet and a method for manufacturing a semiconductor device using the same.

Background

The pressure-sensitive adhesive sheet is used not only for semi-permanently fixing members, but also as a temporary fixing sheet for temporarily fixing members (hereinafter, also referred to as "adherends") to be subjected to processing, inspection, and the like when processing or inspecting building materials, interior materials, electronic components, and the like. For example, in the manufacturing process of a semiconductor device, a temporary fixing sheet is used when a semiconductor wafer is processed.

In the manufacturing process of a semiconductor device, a semiconductor wafer is processed into semiconductor chips through a grinding process for thinning by grinding, a singulation process for cutting and separating to singulate, and the like. At this time, the semiconductor wafer is subjected to a predetermined process in a state of being temporarily fixed to the temporary fixing sheet. After the semiconductor chips obtained by the predetermined process are separated from the temporary fixing sheet, a dicing step of expanding the intervals between the semiconductor chips, a rearranging step of arranging the plurality of semiconductor chips after the intervals are expanded, a flip step of flip the front and back surfaces of the semiconductor chips, and the like are appropriately performed as needed, and then mounted on the substrate. In each of the above steps, a temporary fixing sheet suitable for the respective applications may be used. As such a temporary fixing sheet, a single-sided adhesive sheet or a double-sided adhesive sheet may be used, and in the case of the double-sided adhesive sheet, a predetermined process may be performed in a state in which the object to be processed is adhered to one side and the other side is adhered to the support.

Patent document 1 discloses a heat-peelable adhesive sheet for temporary fixation at the time of cutting an electronic component, in which at least one surface of a base material is provided with a heat-expandable adhesive layer containing heat-expandable microspheres. In this document the following is described: the heat-peelable pressure-sensitive adhesive sheet can ensure a predetermined contact area with respect to an adherend when cutting an electronic component, and thus can exhibit adhesiveness that can prevent adhesion failure such as chip splash, and can easily achieve peeling by reducing the contact area with the adherend when heating and expanding the heat-expandable microspheres after use.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 3594853

Disclosure of Invention

Problems to be solved by the invention

When the temporary fixing sheet is used in a mode of performing a predetermined process on a work object in a state in which the work object is attached to one surface and the support is attached to the other surface, a hard material may be attached to both surfaces of the temporary fixing sheet. In this case, for example, when a hard support is attached to a temporary fixing sheet attached to a hard object, it is necessary to attach the temporary fixing sheet and the support in a state where the attaching surfaces are kept substantially parallel to each other.

In comparison with the method of bonding the temporary fixing sheet while bending the temporary fixing sheet, the method of bonding the temporary fixing sheet and the adherend in a state of being kept substantially parallel is likely to cause air stagnation at the bonding interface of the temporary fixing sheet and the adherend. Air stagnation at the bonding interface causes vibration, displacement, and the like of the adherend, and causes degradation in processing accuracy such as breakage and occurrence of defects when processing the object. On the other hand, in the case of adhering an adherend to a temporary fixing sheet, it is preferable to avoid setting the adhering condition to be severe in order to improve the adhesion, and to adhere under a mild condition as much as possible, from the viewpoints of productivity and suppression of breakage and deterioration of the adherend due to pressurization and heating. Therefore, although excellent adhesiveness is required for the temporary fixing sheet itself, the heat-peelable adhesive sheet of patent document 1 is not an adhesive sheet that sufficiently satisfies this requirement.

The present invention has been made in view of the above-described problems, and an object thereof is to provide an adhesive sheet excellent in adhesion and a method for manufacturing a semiconductor device using the adhesive sheet.

Means for solving the problems

The present inventors have found that the above problems can be solved by adjusting the arithmetic average waviness (Wa) to a specific range, and have completed the present invention.

That is, the present invention relates to the following [1] to [13].

[1] An adhesive sheet having a laminated structure comprising an adhesive layer (X1) and a base material layer (Y),

at least one of the adhesive layer (X1) and the base layer (Y) is a thermally expandable layer containing thermally expandable particles,

a surface (S) of the adhesive layer (X1) _X1 ) Has an arithmetic average waviness (Wa) of 0.090 μm or less, and the surface (S _X1 ) Is the surface opposite to the surface facing the base material layer (Y).

[2] The pressure-sensitive adhesive sheet according to [1], wherein the thickness of the thermally expandable layer before thermal expansion is 30 to 300. Mu.m.

[3] The pressure-sensitive adhesive sheet according to the item [1] or [2], wherein the content of the thermally expandable particles in the thermally expandable layer is 1 to 25% by mass relative to the total mass (100% by mass) of the thermally expandable layer.

[4] The pressure-sensitive adhesive sheet according to any one of the above [1] to [3], wherein the expansion initiation temperature (t) of the thermally expandable particles is 50℃or higher and lower than 125 ℃.

[5] The pressure-sensitive adhesive sheet according to any one of the above [1] to [4], wherein the base material layer (Y) is a base material laminate in which a thermally expandable base material layer (Y1) containing thermally expandable particles is laminated with a non-thermally expandable base material layer (Y2), and the pressure-sensitive adhesive sheet has a laminated structure in which the pressure-sensitive adhesive layer (X1), the thermally expandable base material layer (Y1), and the non-thermally expandable base material layer (Y2) are arranged in this order.

[6] The pressure-sensitive adhesive sheet according to any one of the above [1] to [5], further comprising a pressure-sensitive adhesive layer (X2), wherein the pressure-sensitive adhesive sheet has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are arranged in this order.

[7] The pressure-sensitive adhesive sheet according to item [6], wherein the pressure-sensitive adhesive layer (X2) is an energy-ray-curable pressure-sensitive adhesive layer which is cured by irradiation with energy rays and has a reduced adhesive force.

[8] A method for manufacturing a semiconductor device, wherein the adhesive sheet of [6] or [7] is used, and the method comprises the following steps 1A, 2A, first and second separation steps.

Step 1A: a step of adhering the object to be processed to the adhesive layer (X2) of the adhesive sheet and adhering the support to the adhesive layer (X1) of the adhesive sheet

Step 2A: a step of performing one or more treatments selected from grinding treatment and singulation treatment on the object

A first separation process: a step of separating the pressure-sensitive adhesive layer (X1) from the support by heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles

And a second separation procedure: a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed

[9] The method of manufacturing a semiconductor device according to item [8], wherein the expansion initiation temperature (t) of the thermally expandable particles is 50℃or higher and lower than 125 ℃,

after the step 2A, a step 3A of adhering a thermosetting film to the surface of the object subjected to the treatment opposite to the adhesive layer (X2) is included,

the first separation step is a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) and lower than 125 ℃ to separate the pressure-sensitive adhesive layer (X1) from the support.

[10]Above [8]]Or [9]]In the method for manufacturing a semiconductor device, the step of adhering the support to the adhesive layer (X1) of the adhesive sheet in the step 1A is performed by forming the adhesive layer (X1) on a surface (S _X1 ) A surface of the adhesive sheet to be adhered to the support (S _s ) The surface (S) _s ) Is adhered to the surface (S) of the adhesive layer (X1) _X1 ) Is a step of (a) a step of (b).

[11] A method for manufacturing a semiconductor device, wherein the adhesive sheet of [6] or [7] is used, and the method comprises the following steps 1B, 2B, first and second separation steps.

Step 1B: a step of adhering the object to be processed to the adhesive layer (X1) of the adhesive sheet and adhering the support to the adhesive layer (X2) of the adhesive sheet

Step 2B: a step of performing one or more treatments selected from grinding treatment and singulation treatment on the object

A first separation process: a step of separating the pressure-sensitive adhesive layer (X1) from the object by heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles

And a second separation procedure: a step of separating the adhesive layer (X2) from the support

[12] The method of manufacturing a semiconductor device according to item [11], wherein the expansion initiation temperature (t) of the thermally expandable particles is 50℃or higher and lower than 125 ℃,

after the step 2B, a step 3B of adhering a thermosetting film to the surface of the object subjected to the treatment opposite to the adhesive layer (X1) is included,

The first separation step is a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion start temperature (t) and lower than 125 ℃ to separate the pressure-sensitive adhesive layer (X1) from the object.

[13]Above [11 ]]Or [12 ]]In the method for manufacturing a semiconductor device, the step of adhering the object to be processed to the adhesive layer (X1) of the adhesive sheet in the step 1B is performed by forming the adhesive layer (X1) on a surface (S _X1 ) A surface of the adhesive sheet to be adhered to the object (S _w ) The surface of the object is kept substantially parallel (S _w ) Is adhered to the surface (S) of the adhesive layer (X1) _X1 ) Is a step of (a) a step of (b).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an adhesive sheet excellent in adhesion and a method for manufacturing a semiconductor device using the adhesive sheet can be provided.

Drawings

Fig. 1 is a cross-sectional view showing an example of the structure of an adhesive sheet of the present invention.

Fig. 2 is a cross-sectional view showing another example of the structure of the adhesive sheet of the present invention.

Fig. 3 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 4 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 5 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 6 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 7 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 8 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 9 is a cross-sectional view illustrating an example of a process of the method for manufacturing a semiconductor device according to the present invention.

Fig. 10 is a three-dimensional surface shape image of the adhesive sheet produced in example 1.

Fig. 11 is a three-dimensional surface shape image of the adhesive sheet produced in comparative example 9.

Fig. 12 is an example of an appearance photograph of a test sample corresponding to evaluation a in the adhesion evaluation.

Fig. 13 is an example of an appearance photograph of a test sample corresponding to evaluation F in the adhesion evaluation.

Symbol description

1a, 1b, 2a, 2b adhesive sheet

10. 10a, 10b release material

3. Support body

4. Laser irradiation apparatus

5. Modified region

6. Grinding machine

7. Thermosetting film

8. Supporting sheet

W semiconductor wafer

Circuit surface of W1 semiconductor wafer

Back surface of W2 semiconductor wafer

CP semiconductor chip

(X1) adhesive layer (X1)

(X2) adhesive layer (X2)

(Y) substrate layer (Y)

(S _x1 ) A face (S) of the adhesive layer (X1) _x1 )

(S _s ) The surface of the support to which the adhesive sheet is to be adhered (S _s )

Detailed Description

In the present specification, the term "active ingredient" refers to a component other than a diluent solvent among components contained in the composition to be subjected to the formulation.

In the present specification, the weight average molecular weight (Mw) is a value converted to standard polystyrene measured by Gel Permeation Chromatography (GPC), and specifically, a value measured by the method described in examples.

In the present specification, "(meth) acrylic acid" means both "acrylic acid" and "methacrylic acid", for example, and other similar expressions are also used.

In the present specification, the lower limit value and the upper limit value described in a hierarchical manner may be independently combined with respect to a preferable numerical range (for example, a range of content or the like). For example, according to the description of "preferably 10 to 90, more preferably 30 to 60", the "preferable lower limit value (10)" and the "more preferable upper limit value (60)" may be combined to obtain "10 to 60".

In the present specification, the term "energy ray" means a ray having energy in an electromagnetic wave or a charged particle beam, and examples thereof include ultraviolet rays, radiation rays, and electron beams. For example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, or the like may be used as an ultraviolet light source to irradiate ultraviolet rays. As for the electron beam, an electron beam generated by an electron beam accelerator or the like may be irradiated.

In the present specification, "energy ray polymerizability" means a property of polymerization by irradiation with energy rays. The term "energy ray curability" means a property of curing by irradiation with energy rays.

In the present specification, whether the "layer" is the "non-thermally-expansive layer" or the "thermally-expansive layer" is determined as follows.

When the layer to be evaluated contains thermally expandable particles, the layer is subjected to a heating treatment for 3 minutes at the expansion initiation temperature (t) of the thermally expandable particles. When the volume change rate calculated from the following formula is less than 5%, the layer is judged to be a "non-thermally expandable layer", and when it is 5% or more, the layer is judged to be a "thermally expandable layer".

■ Volume change rate (%) = { (volume of the layer after heat treatment-volume of the layer before heat treatment)/volume of the layer before heat treatment } ×100

The layer containing no thermally expandable particles is regarded as a "non-thermally expandable layer".

In the present specification, the "front surface" of a semiconductor wafer and a semiconductor chip means a surface on which a circuit is formed (hereinafter, also referred to as a "circuit surface"), and the "back surface" of a semiconductor wafer and a semiconductor chip means a surface on which a circuit is not formed.

In the present specification, the thickness of each layer is a thickness at 23 ℃, and represents a value measured by the method described in examples.

In the present specification, the adhesion of each layer means adhesion to the mirror surface of a silicon mirror wafer, and means adhesion measured at a stretching speed of 300mm/min by 180 ° peeling method based on JIS Z0237:2000 in an environment of 23℃and 50% RH (relative humidity).

[ adhesive sheet ]

An adhesive sheet according to one embodiment of the present invention has a laminated structure including an adhesive layer (X1) and a base material layer (Y),

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the heat-expandable particles contained in the heat-expandable layer, which is at least one of the pressure-sensitive adhesive layer (X1) and the base layer (Y), are heated to a temperature equal to or higher than the expansion initiation temperature (t) to expand the heat-expandable particles, so that irregularities are formed on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1), and the contact area between the adherend adhered to the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1) and the pressure-sensitive adhesive surface is greatly reduced. This significantly reduces the adhesion between the adhesive surface of the adhesive layer (X1) and the adherend, and can easily separate the adhesive sheet from the adherend.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the pressure-sensitive adhesive layer (X1) is formed by a surface (S) opposite to the surface facing the base layer (Y) _X1 ) The arithmetic average waviness (Wa) of the adhesive sheet is 0.090 mu m or less, and the adhesive sheet is excellent in adhesion.

As a factor affecting the adhesion of the adhesive sheet, there is a case where attention is paid to the arithmetic average roughness (Ra) of the adhesive surface. However, the present inventors have found that, in the case of an adhesive sheet containing thermally expandable particles, particularly in the case of adhering the adhesive sheet in such a state that the adhering surfaces are kept substantially parallel to each other, sufficient adhesion cannot be obtained by merely suppressing the arithmetic average roughness (Ra) to be small. This is considered to be because, although the local adhesion is improved by improving the microscopic smoothness characterized by the arithmetic average roughness (Ra), the adhesive sheet containing the thermally expandable particles may cause air stagnation at the adhesive interface due to the presence of the thermally expandable particles or the presence of a plurality of undulations in the adhesive surface. On the other hand, in the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the arithmetic average waviness (Wa) representing a more microscopic surface shape is adjusted to a specific range of 0.090 μm or less, whereby occurrence of air stagnation can be suppressed, and excellent adhesion can be exhibited.

< construction of adhesive sheet >

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, at least one of the pressure-sensitive adhesive layer (X1) and the base layer (Y) may be a thermally expandable layer containing thermally expandable particles.

As the adhesive sheet in the case where the base material layer (Y) is a thermally expandable layer containing thermally expandable particles, the following adhesive sheets can be mentioned: the base material layer (Y) is a base material laminate in which a thermally expandable base material layer (Y1) containing thermally expandable particles and a non-thermally expandable base material layer (Y2) are laminated, and the adhesive sheet has a laminated structure in which an adhesive layer (X1), a thermally expandable base material layer (Y1), and a non-thermally expandable base material layer (Y2) are arranged in this order. Hereinafter, the pressure-sensitive adhesive sheet having such a configuration may be referred to as "pressure-sensitive adhesive sheet of mode 1".

In the adhesive sheet according to one embodiment of the present invention, when the adhesive layer (X1) is a thermally expandable layer containing thermally expandable particles, an adhesive sheet having a laminated structure including the adhesive layer (X1) and the base layer (Y) as thermally expandable layers is exemplified. Hereinafter, the pressure-sensitive adhesive sheet having such a configuration may be referred to as "pressure-sensitive adhesive sheet of mode 2".

The pressure-sensitive adhesive sheet according to one embodiment of the present invention may have a laminated structure including the pressure-sensitive adhesive layer (X1) and the base layer (Y), or may have a layer other than the pressure-sensitive adhesive layer (X1) and the base layer (Y) depending on the application.

For example, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used for processing an object to be processed, the pressure-sensitive adhesive sheet according to one embodiment of the present invention preferably has the following structure from the viewpoint of improving the processability of the object to be processed: further has an adhesive layer (X2), and has a laminated structure (i.e., a double-sided adhesive sheet) in which an adhesive layer (X1), a base layer (Y), and an adhesive layer (X2) are disposed in this order. With this configuration, the object can be attached to one of the adhesive layers (X1) and (X2), and the support can be attached to the other adhesive layer. By fixing the object to be processed to the support via the adhesive sheet, vibration, displacement, breakage of the fragile object to be processed, and the like of the object to be processed can be suppressed at the time of processing the object to be processed, and the processing accuracy and processing speed can be improved.

In the following description, unless otherwise specified, the "double-sided pressure-sensitive adhesive sheet" refers to a pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive layer (X1), a base layer (Y), and a pressure-sensitive adhesive layer (X2) are disposed in this order.

The pressure-sensitive adhesive sheet according to one embodiment of the present invention may have a release material on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1). In addition, in the case where the adhesive sheet according to one embodiment of the present invention has a double-sided adhesive sheet structure, a release material may be provided on the adhesive surface of at least one of the adhesive layer (X1) and the adhesive layer (X2).

Hereinafter, the structure of the pressure-sensitive adhesive sheet according to one embodiment of the present invention will be described in more detail with reference to the drawings.

As an adhesive sheet according to an embodiment of the present invention, an adhesive sheet 1a having an adhesive layer (X1) on a base layer (Y) as shown in fig. 1 (a) is exemplified. The pressure-sensitive adhesive sheet 1a has a surface (S) having an arithmetic average waviness (Wa) of 0.090 [ mu ] m or less on the side opposite to the surface of the pressure-sensitive adhesive layer (X1) facing the substrate layer (Y) _X1 )。

The pressure-sensitive adhesive sheet according to one embodiment of the present invention may be formed to further have a release material 10 on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1), as in the pressure-sensitive adhesive sheet 1b shown in fig. 1 (b).

As an adhesive sheet according to another embodiment of the present invention, an adhesive sheet having the above-described configuration of a double-sided adhesive sheet is exemplified.

As the pressure-sensitive adhesive sheet having such a constitution, for example, a double-sided pressure-sensitive adhesive sheet 2a having a constitution in which a base layer (Y) is sandwiched between a pressure-sensitive adhesive layer (X1) and a pressure-sensitive adhesive layer (X2) as shown in fig. 2 (a) is exemplified. The double-sided adhesive sheet 2a has a surface (S) having an arithmetic average waviness (Wa) of 0.090 [ mu ] m or less on the opposite side of the surface of the adhesive layer (X1) to the substrate layer (Y) _X1 )。

Further, as in the double-sided adhesive sheet 2b shown in fig. 2 (b), the adhesive layer (X1) may have a structure in which a release material 10a is further provided on the adhesive surface, and the release material 10b is further provided on the adhesive surface of the adhesive layer (X2).

In the double-sided adhesive sheet 2b shown in fig. 2 (b), when the peeling force of the release material 10a from the adhesive layer (X1) and the peeling force of the release material 10b from the adhesive layer (X2) are equal, the adhesive layer may be peeled off with the release material on both sides being cut when the release material on both sides is to be pulled outward. From the viewpoint of suppressing such a phenomenon, it is preferable to use 2 kinds of release materials having different release forces from the adhesive layers to be adhered to each other for the

release materials

10a and 10b on both sides.

As another embodiment of the pressure-sensitive adhesive sheet, the double-sided pressure-sensitive adhesive sheet 2a shown in fig. 2 (a) may have a structure in which a release material having release treated on both sides thereof is laminated on the pressure-sensitive adhesive surface of one of the pressure-sensitive adhesive layers (X1) and (X2) and then rolled up.

The pressure-sensitive adhesive sheet according to one embodiment of the present invention may or may not have another layer between the base layer (Y) and the pressure-sensitive adhesive layer (X1). In the case where the pressure-sensitive adhesive sheet according to one embodiment of the present invention is the double-sided pressure-sensitive adhesive sheet, other layers may be provided between the base layer (Y) and the pressure-sensitive adhesive layer (X2) or may be omitted, in addition to the above.

In the pressure-sensitive adhesive sheet according to embodiment 1, from the viewpoint of suppressing expansion on the surface, it is preferable that the non-heat-expandable base material layer (Y2) is directly laminated on the surface of the heat-expandable base material layer (Y1) opposite to the pressure-sensitive adhesive layer (X1). In the pressure-sensitive adhesive sheet according to aspect 2, a layer capable of suppressing expansion on the surface of the pressure-sensitive adhesive layer (X1) opposite to the pressure-sensitive adhesive surface is preferably directly laminated on the surface, and more preferably the base layer (Y) is directly laminated on the surface.

< arithmetic mean waviness (Wa) >)

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the surface (S) of the pressure-sensitive adhesive layer (X1) opposite to the surface facing the base layer (Y) _X1 ) The arithmetic average waviness (Wa) of the composition is 0.090 μm or less.

By making the surface (S) of the adhesive layer (X1) _X1 ) The arithmetic average waviness (Wa) of 0.090 μm or less, and excellent adhesion can be obtained.

On the other handWhen the surface (S) of the adhesive layer (X1) _X1 ) When the arithmetic average waviness (Wa) exceeds 0.090 μm, sufficient adhesion may not be obtained.

In the present specification, the arithmetic mean waviness (Wa) is measured based on JIS B0601:2013, and more specifically, can be measured by the method described in examples described later.

Further, from the viewpoint of improving the adhesion of the pressure-sensitive adhesive sheet, the surface (S _X1 ) The arithmetic average waviness (Wa) of (a) is preferably 0.089 μm or less, more preferably 0.088 μm or less, still more preferably 0.087 μm or less, still more preferably 0.086 μm or less. In addition, the surface (S) of the adhesive layer (X1) _X1 ) The lower limit of the arithmetic mean waviness (Wa) is not particularly limited, and may be 0 μm, but from the viewpoint of keeping a good balance of releasability from the pressure-sensitive adhesive layer (X1), it is preferably 0.010 μm or more, more preferably 0.020 μm or more, still more preferably 0.030 μm or more, still more preferably 0.040 μm or more.

For the face (S) of the adhesive layer (X1) _X1 ) The arithmetic average waviness (Wa) of (a) may be adjusted to the above range depending on, for example, the thicknesses of the adhesive layer (X1) and the base layer (Y), the content of the thermally expandable particles in the thermally expandable layer, the adhesive composition (X-1) as a material for forming the adhesive layer (X1) described later, the production conditions of the resin composition (Y-1) as a material for forming the base layer (Y), and the like.

< thermally-expansive particles >

The thermally expandable particles used in the pressure-sensitive adhesive sheet according to one embodiment of the present invention may be any particles that expand by heating, and the expansion initiation temperature (t) may be appropriately selected depending on the application of the pressure-sensitive adhesive sheet.

Meanwhile, in recent years, when mounting a semiconductor chip on a substrate, a step of adhering the semiconductor chip to the substrate via a film-like adhesive having thermosetting properties called a die attach film (hereinafter, also referred to as "DAF") has been employed.

The DAF is bonded to one surface of the semiconductor wafer or the singulated semiconductor chips, and is divided into the same shape as the semiconductor chips simultaneously with singulation of the semiconductor wafer or after bonding to the semiconductor chips. The singulated semiconductor chip with DAF is bonded (die-attached) to a substrate from the DAF side, and thereafter, the semiconductor chip is bonded to the substrate by thermally curing the DAF. In this case, the DAF needs to maintain the property of being bonded by pressure sensing or heating until it is bonded to the substrate. However, when the semiconductor chip with the DAF is an adherend of a heat-peelable adhesive sheet, the DAF may be cured immediately before die attach due to heating at the time of expanding the thermally expandable microspheres, and the adhesion of the DAF to the substrate may be lowered. The decrease in the adhesive force of the DAF causes a decrease in the bonding reliability of the semiconductor chip and the substrate, and therefore needs to be suppressed. That is, it is desirable to suppress thermal changes in the adherend when heat peeling is performed.

From such a viewpoint, in the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the expansion initiation temperature (t) of the thermally expandable particles is preferably 125 ℃ or lower, more preferably 120 ℃ or lower, still more preferably 115 ℃ or lower, still more preferably 110 ℃ or lower, and still more preferably 105 ℃ or lower.

In addition, when particles having a low expansion initiation temperature are used as the thermally expandable particles of the heat peelable adhesive sheet, the thermally expandable particles may expand due to a temperature rise in the case of grinding or the like of an adherend. Such unexpected expansion of the thermally expandable particles is desirable to suppress such unexpected separation and displacement of the adherend.

From such a viewpoint, in the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the expansion initiation temperature (t) of the thermally expandable particles is preferably 50 ℃ or higher, more preferably 55 ℃ or higher, still more preferably 60 ℃ or higher, still more preferably 70 ℃ or higher.

In the present specification, the expansion initiation temperature (t) of the thermally expandable particles represents a value measured by the following method.

(measurement of the expansion initiation temperature (t) of thermally-expansive particles)

A sample was prepared by adding 0.5mg of thermally expandable particles to be measured to an aluminum cup having a diameter of 6.0mm (inner diameter of 5.65 mm) and a depth of 4.8mm, and covering the cup with an aluminum cap (diameter of 5.6mm and thickness of 0.1 mm) from above.

The height of the sample was measured using a dynamic viscoelasticity measuring device in a state where a force of 0.01N was applied to the sample from the upper part of the aluminum cap by a indenter. Then, the displacement amount of the indenter in the vertical direction was measured by heating the material from 20 to 300℃at a heating rate of 10℃per minute with a force of 0.01N applied thereto by the indenter, and the displacement start temperature in the positive direction was defined as the expansion start temperature (t).

The heat-expandable particles are preferably a microencapsulated foaming agent comprising an outer shell made of a thermoplastic resin and an inner-shell component which is encapsulated by the outer shell and which is gasified when heated to a predetermined temperature.

Examples of the thermoplastic resin constituting the shell of the microencapsulated foaming agent include: polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, or a copolymer obtained by polymerizing two or more monomers forming a structural unit contained in these thermoplastic resins.

As the component encapsulated by the shell of the microencapsulated foaming agent, i.e., the inner package component, there may be mentioned, for example: propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, n-heptane, n-octane, cyclopropane, cyclobutane, petroleum ether, and the like.

Among these components, from the viewpoint of suppressing thermal change of the adherend at the time of heat release and suppressing unexpected expansion of the thermally expandable particles caused by a temperature rise in the case of grinding or the like of the adherend, propane, isobutane, n-pentane and cyclopropane are preferable as the inclusion component when the expansion initiation temperature (t) of the thermally expandable particles is 50 ℃ or higher and lower than 125 ℃.

These inner package components may be used singly or in combination of two or more.

The expansion initiation temperature (t) of the thermally expandable particles can be adjusted by appropriately selecting the type of the inner package component.

The average particle diameter of the thermally expandable particles used in one embodiment of the present invention before expansion at 23℃is preferably 3 to 100. Mu.m, more preferably 4 to 70. Mu.m, still more preferably 6 to 60. Mu.m, still more preferably 10 to 50. Mu.m.

The average particle diameter of the thermally expandable particles before expansion means the volume median particle diameter (D ₅₀ ) In the particle distribution of the thermally expandable particles before expansion measured by a laser diffraction particle size distribution measuring apparatus (for example, manufactured by Malvern corporation under the product name "Mastersizer 3000"), the cumulative volume frequency calculated from the particles having a small particle diameter among the thermally expandable particles before expansion corresponds to 50% of the particle diameter.

As the heat-expandable particles used in one embodiment of the present invention, the particles having a particle diameter (D) of 90% before expansion at 23 ℃ ₉₀ ) Preferably 10 to 150. Mu.m, more preferably 15 to 100. Mu.m, still more preferably 20 to 90. Mu.m, still more preferably 25 to 80. Mu.m.

The particles before expansion had a particle diameter of 90% (D ₉₀ ) The term "particle size distribution" refers to a particle size distribution of thermally expandable particles before expansion measured by a laser diffraction particle size distribution measuring apparatus (for example, manufactured by Malvern corporation under the product name "Mastersizer 3000"), wherein the cumulative volume frequency calculated from particles having a small particle size among the thermally expandable particles before expansion is 90%.

The volume maximum expansion ratio of the thermally expandable particles used in one embodiment of the present invention when heated to a temperature equal to or higher than the expansion initiation temperature (t) is preferably 1.5 to 200 times, more preferably 2 to 150 times, still more preferably 2.5 to 120 times, still more preferably 3 to 100 times.

The content of the thermally-expansive particles in the thermally-expansive layer is preferably 1 mass% or more, more preferably 2 mass% or more, still more preferably 3 mass% or more, still more preferably 4 mass% or more, relative to the total mass (100 mass%) of the thermally-expansive layer. The content of the thermally-expandable particles in the thermally-expandable layer is preferably 25 mass% or less, more preferably 23 mass% or less, further preferably 22 mass% or less, and further preferably 21 mass% or less, relative to the total mass (100 mass%) of the thermally-expandable layer.

When the content of the thermally expandable particles is 1 mass% or more, the releasability at the time of heat release tends to be improved. When the content of the thermally expandable particles is 25 mass% or less, the generation of irregularities due to the thermally expandable particles before thermal expansion is suppressed, and the surface (S) of the adhesive layer (X1) can be further reduced _x1 ) Tends to improve the arithmetic average waviness (Wa) and the adhesiveness.

< thickness of thermally-expansive layer >

In one embodiment of the present invention, the thickness of the thermally expandable layer before thermal expansion is preferably 30 to 300. Mu.m, more preferably 40 to 270. Mu.m, still more preferably 50 to 240. Mu.m, still more preferably 55 to 220. Mu.m.

When the thickness of the thermally expandable layer before thermal expansion is 30 μm or more, the generation of irregularities due to thermally expandable particles before thermal expansion is suppressed, and the surface (S) of the adhesive layer (X1) can be further reduced _x1 ) Tends to improve the arithmetic average waviness (Wa) and the adhesiveness. In addition, when the thickness of the thermally expandable layer before thermal expansion is 300 μm or less, the handling of the adhesive sheet tends to be easy.

Next, a preferred embodiment of each layer of the pressure-sensitive adhesive sheet according to one embodiment of the present invention will be described.

Hereinafter, preferred embodiments will be described with respect to the adhesive sheet according to embodiment 1 and the adhesive sheet according to embodiment 2, respectively, but the present invention is not limited to these embodiments.

[ pressure-sensitive adhesive sheet of embodiment 1 ]

The pressure-sensitive adhesive sheet according to embodiment 1 is a pressure-sensitive adhesive sheet having a laminated structure in which a pressure-sensitive adhesive layer (X1), a thermally expandable base material layer (Y1), and a non-thermally expandable base material layer (Y2) are disposed in this order.

In the adhesive sheet according to embodiment 1, since the thermally expandable particles are contained in the base material layer (Y), the recesses caused by the thermally expandable particlesThe convex part is not easy to be used as the surface (S) of the adhesive layer (X1) _x1 ) Is present. Further, since the pressure-sensitive adhesive layer (X1) may not contain thermally expandable particles, the degree of freedom in design such as thickness and resin composition is high, and the arithmetic average waviness (Wa) can be further reduced, so that the adhesiveness tends to be improved.

< adhesive layer (X1) >)

The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of embodiment 1 may be a thermally expandable layer or a non-thermally expandable layer, but is preferably a non-thermally expandable layer.

When the pressure-sensitive adhesive layer (X1) is a non-thermally-expansive layer, the volume change rate (%) of the pressure-sensitive adhesive layer (X1) calculated by the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, even more preferably less than 0.1%, and still more preferably less than 0.01%.

The pressure-sensitive adhesive layer (X1) in the pressure-sensitive adhesive sheet of embodiment 1 preferably contains no thermally expandable particles, but may contain thermally expandable particles within a range not departing from the object of the present invention. When the pressure-sensitive adhesive layer (X1) contains thermally expandable particles, the content thereof is preferably smaller, and is preferably less than 3 mass%, more preferably less than 1 mass%, further preferably less than 0.1 mass%, further preferably less than 0.01 mass%, further preferably less than 0.001 mass%, relative to the total mass (100 mass%) of the pressure-sensitive adhesive layer (X1).

The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of embodiment 1 may be formed of a pressure-sensitive adhesive composition (X-1) containing a pressure-sensitive adhesive resin.

The components contained in the adhesive composition (x-1) will be described below.

(adhesive resin)

The adhesive resin may be a polymer having adhesive properties alone and having a weight average molecular weight (Mw) of 1 ten thousand or more.

The weight average molecular weight (Mw) of the adhesive resin is preferably 1 to 200 tens of thousands, more preferably 2 to 150 tens of thousands, and still more preferably 3 to 100 tens of thousands, from the viewpoint of improving the adhesive force of the adhesive layer (X1).

Specific examples of the adhesive resin include: rubber-based resins such as acrylic resins, urethane resins and polyisobutylene resins, polyester resins, olefin resins, silicone resins and polyvinyl ether resins.

These adhesive resins may be used singly or in combination of two or more.

In the case where these adhesive resins are copolymers having two or more structural units, the form of the copolymer is not particularly limited, and any form of block copolymer, random copolymer, and graft copolymer may be used.

Here, in one embodiment of the present invention, the adhesive resin preferably contains an acrylic resin from the viewpoint of making the adhesive layer (X1) exhibit excellent adhesive force.

The content of the acrylic resin in the adhesive resin is preferably 30 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 70 to 100 mass%, and even more preferably 85 to 100 mass% with respect to the total amount (100 mass%) of the adhesive resin contained in the adhesive composition (X-1) or the adhesive layer (X1).

In one embodiment of the present invention, examples of the acrylic resin that can be used as the adhesive resin include: polymers comprising structural units derived from alkyl (meth) acrylates having straight or branched alkyl groups, polymers comprising structural units derived from (meth) acrylates having cyclic structures, and the like.

The weight average molecular weight (Mw) of the acrylic resin is preferably 10 to 150 million, more preferably 20 to 130 million, still more preferably 35 to 120 million, still more preferably 50 to 110 million.

The acrylic resin used in one embodiment of the present invention is more preferably an acrylic copolymer (A1) having a structural unit (A1) derived from an alkyl (meth) acrylate (A1 ') (hereinafter, also referred to as "monomer (A1')") and a structural unit (a 2) derived from a functional group-containing monomer (a 2 ') (hereinafter, also referred to as "monomer (a 2')").

The number of carbon atoms of the alkyl group in the monomer (a 1') is preferably 1 to 24, more preferably 1 to 12, still more preferably 2 to 10, still more preferably 4 to 8, from the viewpoint of providing excellent adhesion to the adhesive layer (X1).

The alkyl group contained in the monomer (a 1') may be a linear alkyl group or a branched alkyl group.

Examples of the monomer (a 1') include: methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, sec-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, stearyl (meth) acrylate, and the like.

These monomers (a 1') may be used singly or in combination of two or more.

As the monomer (a 1'), n-butyl acrylate and 2-ethylhexyl acrylate are preferable.

The content of the structural unit (A1) is preferably 50 to 99.9% by mass, more preferably 60 to 99.0% by mass, still more preferably 70 to 97.0% by mass, and still more preferably 80 to 95.0% by mass, relative to the total structural units (100% by mass) of the acrylic copolymer (A1).

Examples of the functional group of the monomer (a 2') include: hydroxyl, carboxyl, amino, epoxy, and the like.

That is, examples of the monomer (a 2') include: hydroxyl group-containing monomers, carboxyl group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, and the like.

These monomers (a 2') may be used singly or in combination of two or more.

Among these monomers, the monomer (a 2') is preferably a hydroxyl group-containing monomer and a carboxyl group-containing monomer, and more preferably a hydroxyl group-containing monomer.

Examples of the hydroxyl group-containing monomer include: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, butyl 2-hydroxy (meth) acrylate, butyl 3-hydroxy (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; hydroxyl-containing compounds such as unsaturated alcohols including vinyl alcohol and allyl alcohol.

Examples of the carboxyl group-containing monomer include: ethylenically unsaturated monocarboxylic acids such as (meth) acrylic acid and crotonic acid; ethylenically unsaturated dicarboxylic acids such as fumaric acid, itaconic acid, maleic acid and citraconic acid, anhydrides thereof, 2- (acryloyloxy) ethyl succinate, 2-carboxyethyl (meth) acrylate, and the like.

The content of the structural unit (a 2) is preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, still more preferably 1.0 to 15% by mass, and still more preferably 3.0 to 10% by mass, relative to the total structural units (100% by mass) of the acrylic copolymer (A1).

The acrylic copolymer (A1) may further have a structural unit (a 3) derived from a monomer (a 3 ') other than the monomers (A1 ') and (a 2 ').

In the acrylic copolymer (A1), the total content of the structural units (A1) and (a 2) is preferably 70 to 100% by mass, more preferably 80 to 100% by mass, still more preferably 90 to 100% by mass, and still more preferably 95 to 100% by mass, based on the total structural units (100% by mass) of the acrylic copolymer (A1).

Examples of the monomer (a 3') include: olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; diene monomers such as butadiene, isoprene, and chloroprene; (meth) acrylic esters having a cyclic structure such as cyclohexyl (meth) acrylate, benzyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentyl (meth) acrylate, dicyclopentenyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, and imide (meth) acrylate; styrene, alpha-methylstyrene, vinyl toluene, vinyl formate, vinyl acetate, acrylonitrile, (meth) acrylamide, (meth) acrylonitrile, (meth) acryloylmorpholine, N-vinylpyrrolidone, and the like.

The content of the adhesive resin in the adhesive composition (x-1) is preferably 35 to 100 mass%, more preferably 50 to 100 mass%, still more preferably 60 to 100 mass%, and still more preferably 70 to 99.5 mass% with respect to the total amount (100 mass%) of the active ingredient of the adhesive composition (x-1).

(crosslinking agent)

In one embodiment of the present invention, when the adhesive composition (x-1) contains an adhesive resin having a functional group as in the acrylic copolymer (A1), it is preferable to further contain a crosslinking agent.

The crosslinking agent is a component that reacts with the adhesive resin having a functional group to crosslink the adhesive resins with each other with the functional group as a crosslinking origin.

Examples of the crosslinking agent include: isocyanate-based crosslinking agents, epoxy-based crosslinking agents, aziridine-based crosslinking agents, metal chelate-based crosslinking agents, and the like.

These crosslinking agents may be used singly or in combination of two or more.

Among these crosslinking agents, isocyanate-based crosslinking agents are preferable from the viewpoints of improving cohesive force and thus improving adhesive force, ease of acquisition, and the like.

Examples of the isocyanate-based crosslinking agent include: aromatic polyisocyanates such as toluene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; alicyclic polyisocyanates such as dicyclohexylmethane-4, 4' -diisocyanate, dicyclohexyl triisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, methylcyclohexylene diisocyanate, methylenebis (cyclohexyl isocyanate), 3-isocyanatomethyl-3, 5-trimethylcyclohexyl isocyanate, and hydrogenated xylylene diisocyanate; non-cyclic aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate and lysine diisocyanate; and the like.

The isocyanate-based crosslinking agent may be: a trimethylolpropane adduct type modified product of the polyvalent isocyanate compound, a biuret type modified product obtained by reacting with water, an isocyanurate type modified product containing an isocyanurate ring, and the like.

Among these isocyanate-based crosslinking agents, from the viewpoint of suppressing the decrease in the elastic modulus of the adhesive layer (X1) at the time of heating and the adhesion of residues derived from the adhesive layer (X1) to an adherend, a trimethylolpropane adduct type modified product of a polyvalent isocyanate compound is preferably used, a trimethylolpropane adduct type modified product of an aromatic polyisocyanate compound is more preferably used, and a trimethylolpropane adduct type modified product of toluene diisocyanate is more preferably used.

The content of the crosslinking agent may be appropriately adjusted depending on the number of functional groups of the adhesive resin, but is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 7 parts by mass, and still more preferably 0.05 to 5 parts by mass, relative to 100 parts by mass of the adhesive resin having functional groups.

(tackifier)

In one embodiment of the present invention, the adhesive composition (x-1) may further contain a tackifier from the viewpoint of further improving the adhesive force.

In the present specification, the "tackifier" refers to those having a weight average molecular weight (Mw) of less than 1 ten thousand among components for assisting in improving the adhesive force of the adhesive resin, and is distinguished from the above-described components of the adhesive resin.

The weight average molecular weight (Mw) of the tackifier is less than 1 ten thousand, preferably 400 to 9,000, more preferably 500 to 8,000, still more preferably 800 to 5,000.

Examples of the thickener include: rosin-based resins, terpene-based resins, styrene-based resins, C5-based petroleum resins obtained by copolymerizing C5 fractions such as pentene, isoprene, piperine and 1, 3-pentadiene obtained by thermal decomposition of naphtha, C9-based petroleum resins obtained by copolymerizing C9 fractions such as indene and vinyl toluene obtained by thermal decomposition of naphtha, hydrogenated resins obtained by hydrogenation of these resins, and the like.

The softening point of the tackifier is preferably 60 to 170 ℃, more preferably 65 to 160 ℃, and still more preferably 70 to 150 ℃.

In the present specification, the "softening point" of the tackifier means a value measured based on JIS K2531.

The tackifier may be used alone or in combination of two or more kinds different in softening point, structure and the like. In the case where two or more tackifiers are used, it is preferable that the weighted average of softening points of these various tackifiers falls within the above range.

The content of the tackifier is preferably 0.01 to 65% by mass, more preferably 0.1 to 50% by mass, still more preferably 1 to 40% by mass, and still more preferably 2 to 30% by mass, relative to the total amount (100% by mass) of the active ingredient of the adhesive composition (x-1).

(additive for adhesive)

In one embodiment of the present invention, the adhesive composition (x-1) may contain, in addition to the above-mentioned additives, conventional additives for adhesives used for adhesives within a range not impairing the effects of the present invention.

Examples of such an additive for adhesives include: antioxidants, softeners (plasticizers), rust inhibitors, pigments, dyes, retarders, reaction accelerators (catalysts), ultraviolet absorbers, energy ray-curable compounds described later, photopolymerization initiators, and the like.

These additives for adhesives may be used alone or in combination of two or more.

When these additives for adhesives are contained, the content of each additive for adhesives is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, per 100 parts by mass of the adhesive resin.

(adhesive force of adhesive layer (X1) before thermally expanding the thermally-expansive base material layer (Y1))

The adhesive force of the adhesive layer (X1) before the heat-expandable base material layer (Y1) is thermally expanded is preferably 0.1 to 12.0N/25mm, more preferably 0.5 to 9.0N/25mm, still more preferably 1.0 to 8.0N/25mm, still more preferably 1.2 to 7.5N/25mm.

When the adhesive force of the adhesive layer (X1) before the thermal expansion of the thermally expandable base material layer (Y1) is 0.1N/25mm or more, the occurrence of unexpected peeling from the adherend, displacement of the adherend, and the like during temporary fixation can be more effectively suppressed. On the other hand, when the adhesive force is 12.0N/25mm or less, the peelability at the time of heat peeling can be further improved.

The adhesive force of the adhesive layer (X1) at 23 ℃ before thermal expansion can be measured by the above-described method.

(adhesive force of adhesive layer (X1) at 23 ℃ after thermally expanding Heat-Expandable base layer (Y1))

The adhesive force of the adhesive layer (X1) at 23℃after the heat-expandable base material layer (Y1) is thermally expanded is preferably 1.5N/25mm or less, more preferably 0.05N/25mm or less, still more preferably 0.01N/25mm or less, still more preferably 0N/25mm. The adhesive force of 0N/25mm means an adhesive force below the measurement limit in the method of measuring an adhesive force after thermal expansion described later, and also includes a case where unexpected peeling occurs due to an excessively small adhesive force when the adhesive sheet is fixed for measurement.

The adhesive force of the adhesive layer (X1) at 23 ℃ after the heat-expandable base material layer (Y1) is thermally expanded can be measured by the above-described method with respect to the adhesive sheet heated for 1 minute at +22 ℃ which is the expansion initiation temperature of the heat-expandable particles contained in the heat-expandable base material layer (Y1).

(thickness of adhesive layer (X1))

The thickness of the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of embodiment 1 is preferably 3 to 10 μm, more preferably 3 to 8 μm, and even more preferably 3 to 7 μm in terms of exhibiting good adhesive force and forming irregularities on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1) when the thermally expandable particles are expanded by heating.

By adjusting the thickness of the adhesive layer (X1) to the above range, the adhesive layer (X1) can be easily formed, and irregularities can be easily formed on the adhesive surface of the adhesive layer (X1).

< thermally-expansive base material layer (Y1) >)

The thermally expandable base layer (Y1) of the adhesive sheet according to the embodiment 1 is a thermally expandable layer containing thermally expandable particles in a resin material, and is a layer provided between the adhesive layer (X1) and the non-thermally expandable base layer (Y2).

The thermally expandable base material layer (Y1) is preferably a non-adhesive base material.

The probe tack value of the surface of the thermally expandable base material layer (Y1) is usually less than 50mN/5 mm. Phi., preferably less than 30mN/5 mm. Phi., more preferably less than 10mN/5 mm. Phi., still more preferably less than 5mN/5 mm. Phi.

In the present specification, the probe tack value of the substrate surface indicates a value measured by the following method.

< probe tack value >

After cutting a base material to be measured into a square having a side length of 10mm, the resultant was allowed to stand in an atmosphere of 50% RH (relative humidity) at 23℃for 24 hours, and the resultant material was used as a test sample, and the probe tack value of the surface of the test sample was measured in an atmosphere of 50% RH (relative humidity) at 23℃using a tack tester (product name "NTS-4800" manufactured by Japanese Seiki Seisaku-ku-Sho-Ltd.), based on JIS Z0237:1991. Specifically, a probe made of stainless steel having a diameter of 5mm was brought into contact with a load of 0.98N/cm for 1 second ² After contact with the surface of the test sample, the force required to move the probe away from the surface of the test sample at a speed of 10 mm/sec was measured, and the obtained value was used as the probe tack value of the test sample.

From the viewpoint of improving the interlayer adhesion between the heat-expandable base material layer (Y1) and other layers to be laminated, the surface of the heat-expandable base material layer (Y1) may be subjected to a surface treatment by an oxidation method, a concavity and convexity method, or the like, an easy-to-adhere treatment, or a primer treatment.

Examples of the oxidation method include corona discharge treatment, plasma discharge treatment, chromic acid treatment (wet type), hot air treatment, ozone, and ultraviolet irradiation treatment; examples of the rugged surface treatment include a sand blasting method and a solvent treatment method.

The thermally expandable base material layer (Y1) is preferably formed of a resin composition (Y-1) containing a resin and thermally expandable particles.

Hereinafter, a preferred embodiment of the resin composition (y-1) will be described. The preferable mode of the thermally expandable particles is as described above.

(resin)

The resin contained in the resin composition (y-1) may be a non-adhesive resin or an adhesive resin.

That is, even if the resin contained in the resin composition (Y-1) is an adhesive resin, the adhesive resin and the polymerizable compound are polymerized in the process of forming the thermally expandable base material layer (Y1) from the resin composition (Y-1), and the resulting resin may be a non-adhesive resin, and the thermally expandable base material layer (Y1) containing the resin may be non-adhesive.

The weight average molecular weight (Mw) of the resin contained in the resin composition (y-1) is preferably 1,000 to 100 tens of thousands, more preferably 1,000 to 70 tens of thousands, still more preferably 1,000 to 50 tens of thousands.

In the case where the resin is a copolymer having two or more structural units, the form of the copolymer is not particularly limited, and any form of a block copolymer, a random copolymer and a graft copolymer may be used.

The content of the resin is preferably 50 to 99% by mass, more preferably 60 to 95% by mass, still more preferably 65 to 90% by mass, and still more preferably 70 to 85% by mass, relative to the total amount (100% by mass) of the active ingredient of the resin composition (y-1).

The resin contained in the resin composition (y-1) preferably contains one or more selected from the group consisting of acrylic urethane resins and olefin resins, from the viewpoint of easily forming irregularities on the adhesive surface of the adhesive layer (X1) and from the viewpoint of improving the sheet shape retention after thermal expansion. That is, the thermally expandable base material layer (Y1) preferably contains at least one selected from the group consisting of an acrylic urethane resin and an olefin resin.

The acrylic urethane resin is preferably the following resin (U1).

■ An acrylic urethane resin (U1) obtained by polymerizing a Urethane Prepolymer (UP) with a vinyl compound containing a (meth) acrylic ester.

In the present specification, a prepolymer refers to a compound that is polymerized from a monomer and can constitute a polymer by only further polymerization.

[ acrylic urethane resin (U1) ]

As the Urethane Prepolymer (UP) forming the main chain of the acrylic urethane resin (U1), a reaction product of a polyol and a polyisocyanate is exemplified.

The Urethane Prepolymer (UP) is preferably a prepolymer obtained by further performing a chain extension reaction using a chain extender.

Examples of the polyol to be a raw material of the Urethane Prepolymer (UP) include: alkylene polyols, ether polyols, ester amide polyols, ester-ether polyols, carbonate polyols, and the like.

These polyols may be used singly or in combination of two or more.

The polyhydric alcohol used in one embodiment of the present invention is preferably a diol, more preferably an ester-type diol, an alkylene-type diol, and a carbonate-type diol, and still more preferably an ester-type diol and a carbonate-type diol.

Examples of the ester-type diol include polycondensates of one or more selected from the group consisting of the following diols including: alkane diols such as 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, neopentyl glycol, and 1, 6-hexanediol, alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, and dipropylene glycol; the dicarboxylic acid comprises: phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, 4-diphenyldicarboxylic acid, diphenylmethane-4, 4' -dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, chlorobridge acid, maleic acid, fumaric acid, itaconic acid, cyclohexane-1, 3-dicarboxylic acid, cyclohexane-1, 4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, methylhexahydrophthalic acid, and the like.

Specific examples thereof include: polyethylene glycol adipate glycol, polybutylene glycol adipate glycol, 1, 6-hexanediol isophthalate glycol, neopentyl glycol adipate glycol, polyethylene glycol propylene glycol adipate glycol, polyethylene glycol butylene glycol adipate glycol, polybutylene 1, 6-hexanediol adipate glycol, polyethylene glycol adipate glycol, poly (polytetramethylene ether) adipate glycol, poly (3-methylpentanedioate) glycol, polyethylene azelate glycol, polyethylene sebacate glycol, polybutylene azelate glycol, polybutylene sebacate glycol, and polyethylene glycol terephthalate.

Examples of the alkylene glycol include: alkane diols such as 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, neopentyl glycol, and 1, 6-hexanediol; alkylene glycols such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, and the like; polyalkylene glycols such as polyethylene glycol, polypropylene glycol and polytetramethylene glycol; polyoxyalkylene glycols such as polytetramethylene glycol; etc.

Examples of the carbonate diol include: 1, 4-tetramethylene carbonate diol, 1, 5-pentamethylene carbonate diol, 1, 6-hexamethylene carbonate diol, 1, 2-propylene carbonate diol, 1, 3-propylene carbonate diol, 2-dimethylpropylene carbonate diol, 1, 7-heptamethylene carbonate diol, 1, 8-octamethylene carbonate diol, 1, 4-cyclohexane carbonate diol, and the like.

Examples of the polyisocyanate used as a raw material of the Urethane Prepolymer (UP) include aromatic polyisocyanates, aliphatic polyisocyanates, and alicyclic polyisocyanates.

These polyisocyanates may be used singly or in combination of two or more.

These polyisocyanates may be trimethylolpropane adduct type modified products, biuret type modified products obtained by reacting with water, or isocyanurate type modified products containing an isocyanurate ring.

Among these, the polyisocyanate used in one embodiment of the present invention is preferably a diisocyanate, and more preferably at least one selected from the group consisting of 4,4' -diphenylmethane diisocyanate (MDI), 2, 4-toluene diisocyanate (2, 4-TDI), 2, 6-toluene diisocyanate (2, 6-TDI), hexamethylene diisocyanate (HMDI), and alicyclic diisocyanate.

Examples of the alicyclic diisocyanate include: 3-isocyanate methyl-3, 5-trimethylcyclohexyl isocyanate (isophorone diisocyanate, IPDI), 1, 3-cyclopentane diisocyanate, 1, 3-cyclohexane diisocyanate, 1, 4-cyclohexane diisocyanate, methyl-2, 6-cyclohexane diisocyanate, etc., preferably isophorone diisocyanate (IPDI).

In one embodiment of the present invention, the Urethane Prepolymer (UP) forming the main chain of the acrylic urethane resin (U1) is preferably a linear urethane prepolymer having an ethylenically unsaturated group at both ends and a reaction product of a diol and a diisocyanate.

As a method of introducing an ethylenically unsaturated group into both ends of the linear urethane prepolymer, there is a method of reacting an NCO group at the end of a linear urethane prepolymer obtained by reacting a diol and a diisocyanate compound with a hydroxyalkyl (meth) acrylate.

Examples of the hydroxyalkyl (meth) acrylate include: 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and the like.

The vinyl compound forming the side chain of the acrylic urethane resin (U1) contains at least (meth) acrylate.

The (meth) acrylic acid ester is preferably at least one selected from the group consisting of alkyl (meth) acrylates and hydroxyalkyl (meth) acrylates, and more preferably, alkyl (meth) acrylates and hydroxyalkyl (meth) acrylates are used in combination.

When the alkyl (meth) acrylate and the hydroxyalkyl (meth) acrylate are used in combination, the blending ratio of the hydroxyalkyl (meth) acrylate to 100 parts by mass of the alkyl (meth) acrylate is preferably 0.1 to 100 parts by mass, more preferably 0.5 to 30 parts by mass, still more preferably 1.0 to 20 parts by mass, and still more preferably 1.5 to 10 parts by mass.

The number of carbon atoms of the alkyl group of the alkyl (meth) acrylate is preferably 1 to 24, more preferably 1 to 12, still more preferably 1 to 8, and still more preferably 1 to 3.

In addition, as the hydroxyalkyl (meth) acrylate, those same as those described above for the hydroxyalkyl (meth) acrylate used for introducing an ethylenically unsaturated group to both ends of the linear urethane prepolymer can be mentioned.

Examples of the vinyl compound other than the (meth) acrylate include: aromatic hydrocarbon vinyl compounds such as styrene, α -methylstyrene, and vinyltoluene; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether; polar group-containing monomers such as vinyl acetate, vinyl propionate, (meth) acrylonitrile, N-vinylpyrrolidone, (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, and (meth) acrylamide; etc.

These compounds may be used singly or in combination of two or more.

The content of the (meth) acrylic acid ester in the vinyl compound is preferably 40 to 100% by mass, more preferably 65 to 100% by mass, still more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass, based on the total amount (100% by mass) of the vinyl compound.

The total content of the alkyl (meth) acrylate and the hydroxyalkyl (meth) acrylate in the vinyl compound is preferably 40 to 100% by mass, more preferably 65 to 100% by mass, still more preferably 80 to 100% by mass, and still more preferably 90 to 100% by mass, based on the total amount (100% by mass) of the vinyl compound.

The acrylic urethane resin (U1) used in one embodiment of the present invention can be obtained by mixing a Urethane Prepolymer (UP) and a vinyl compound containing a (meth) acrylate, and polymerizing both.

In this polymerization, it is preferable to further add a radical initiator.

In the acrylic urethane resin (U1) used in one embodiment of the present invention, the content ratio [ (U11)/(U12) ] of the structural unit (U11) derived from the Urethane Prepolymer (UP) to the structural unit (U12) derived from the vinyl compound is preferably 10/90 to 80/20, more preferably 20/80 to 70/30, still more preferably 30/70 to 60/40, still more preferably 35/65 to 55/45 in terms of mass ratio.

[ olefin-based resin ]

As the olefin-based resin suitably used as the resin contained in the resin composition (y-1), a polymer having at least a structural unit derived from an olefin monomer is used.

The olefin monomer is preferably an α -olefin having 2 to 8 carbon atoms, and specific examples thereof include: ethylene, propylene, butene, isobutylene, 1-hexene, and the like.

Among these, ethylene and propylene are preferable.

Specific examples of the olefin-based resin include: ultra low density polyethylene (VLDPE, density: 880 kg/m) ³ Above and below 910kg/m ³ ) Low density polyethylene (LDPE, density: 910kg/m ³ Above and below 915kg/m ³ ) Medium density polyethylene (MDPE, density: 915kg/m ³ Above and below 942kg/m ³ ) High density polyethylene (HDPE, density: 942kg/m ³ Above), linear low density polyethylene and other polyethylene resins; polypropylene resin (PP); polybutene resin (PB); an ethylene-propylene copolymer; olefinic elastomers (TPOs); poly (4-methyl-1-pentene) (PMP); ethylene vinyl acetate copolymer (EVA); ethylene vinyl alcohol copolymer (EVOH); olefin terpolymers such as ethylene-propylene- (5-ethylidene-2-norbornene); etc.

In one embodiment of the present invention, the olefin-based resin may be a modified olefin-based resin in which one or more modifications selected from the group consisting of acid modification, hydroxyl modification and acrylic modification are further performed.

For example, as an acid-modified olefin resin obtained by acid-modifying an olefin resin, there is mentioned a modified polymer obtained by graft-polymerizing an unsaturated carboxylic acid or an anhydride thereof to the above-mentioned unmodified olefin resin.

Examples of the unsaturated carboxylic acid or anhydride thereof include: maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, tetrahydrophthalic acid, aconitic acid, (meth) acrylic acid, maleic anhydride, itaconic anhydride, glutaconic anhydride, citraconic anhydride, aconitic anhydride, norbornene dicarboxylic anhydride, tetrahydrophthalic anhydride, and the like.

The unsaturated carboxylic acid or its anhydride may be used alone or in combination of two or more.

As the acrylic-modified olefin-based resin obtained by acrylic-modifying an olefin-based resin, there may be mentioned a modified polymer obtained by graft-polymerizing an alkyl (meth) acrylate as a side chain to the above-mentioned unmodified olefin-based resin as a main chain.

The number of carbon atoms of the alkyl group of the alkyl (meth) acrylate is preferably 1 to 20, more preferably 1 to 16, and still more preferably 1 to 12.

Examples of the alkyl (meth) acrylate include the same compounds as those mentioned above as the compounds optionally used as the monomer (a 1').

As the hydroxyl-modified olefin-based resin obtained by modifying an olefin-based resin with a hydroxyl group, there can be mentioned a modified polymer obtained by graft polymerizing a hydroxyl group-containing compound to the above-mentioned unmodified olefin-based resin as a main chain.

The hydroxyl group-containing compound mentioned above may be the same as the hydroxyl group-containing compound mentioned above.

[ resins other than acrylic urethane resins and olefin resins ]

In one embodiment of the present invention, the resin composition (y-1) may contain a resin other than the acrylic urethane resin and the olefin resin within a range that does not impair the effects of the present invention.

Examples of such resins include: vinyl resins such as polyvinyl chloride, polyvinylidene chloride and polyvinyl alcohol; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; a polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; a polycarbonate; polyurethane which is not an acrylic urethane resin; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyether imide and polyimide; polyamide resin; an acrylic resin; fluorine-based resins, and the like.

Among them, from the viewpoint of easily forming irregularities on the adhesive surface of the adhesive layer (X1) and from the viewpoint of making the sheet shape retention after thermal expansion good, the content of the resin other than the urethane acrylate resin and the olefin resin in the resin composition (y-1) is preferably small.

The content of the resin other than the acrylic urethane resin and the olefin resin is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, still more preferably less than 10 parts by mass, still more preferably less than 5 parts by mass, and still more preferably less than 1 part by mass relative to 100 parts by mass of the total amount of the resin contained in the resin composition (y-1).

(additive for substrate)

The resin composition (y-1) may contain a base material additive as required within a range not to impair the effects of the present invention.

Examples of the additive for a substrate include: ultraviolet light absorbers, light stabilizers, antioxidants, antistatic agents, slip agents, antiblocking agents, colorants, and the like.

These additives for a substrate may be used alone or in combination of two or more.

When these base material additives are contained, the content of each base material additive is preferably 0.0001 to 20 parts by mass, more preferably 0.001 to 10 parts by mass, per 100 parts by mass of the resin.

(solvent-free resin composition (y-1 a))

As one embodiment of the resin composition (y-1) used in one embodiment of the present invention, there is mentioned a solvent-free resin composition (y-1 a) which is obtained by blending an oligomer having an ethylenically unsaturated group and having a weight average molecular weight (Mw) of 50,000 or less, an energy ray-polymerizable monomer, and the above-mentioned heat-expandable particles, and which is free of a solvent.

The solvent-free resin composition (y-1 a) does not contain a solvent, but the energy ray-polymerizable monomer contributes to improvement of the plasticity of the oligomer.

By irradiating the solvent-free resin composition (Y-1 a) with energy rays, an oligomer having an ethylenically unsaturated group, an energy ray polymerizable monomer, or the like can be polymerized to form the thermally expandable base material layer (Y1).

The weight average molecular weight (Mw) of the oligomer contained in the solvent-free resin composition (y-1 a) is 50,000 or less, preferably 1,000 to 50,000, more preferably 2,000 to 40,000, still more preferably 3,000 to 35,000, and still more preferably 4,000 to 30,000.

The oligomer may be any resin having an ethylenically unsaturated group, the weight average molecular weight of which is 50,000 or less, of the resins contained in the resin composition (y-1), and is preferably the Urethane Prepolymer (UP), more preferably a linear urethane prepolymer having ethylenically unsaturated groups at both ends.

As the oligomer, a modified olefin resin having an ethylenically unsaturated group may be used.

The total content of the oligomers and the energy ray-polymerizable monomers in the solvent-free resin composition (y-1 a) is preferably 50 to 99% by mass, more preferably 60 to 95% by mass, still more preferably 65 to 90% by mass, and still more preferably 70 to 85% by mass, based on the total amount (100% by mass) of the solvent-free resin composition (y-1 a).

Examples of the energy ray polymerizable monomer include: alicyclic polymerizable compounds such as isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentanyloxy (meth) acrylate, cyclohexyl (meth) acrylate, adamantyl (meth) acrylate, and tricyclodecane acrylate; aromatic polymerizable compounds such as phenylpropyl acrylate, benzyl acrylate, and phenol ethylene oxide-modified acrylate; and heterocyclic polymerizable compounds such as tetrahydrofurfuryl (meth) acrylate, morpholinoacrylate, N-vinylpyrrolidone and N-vinylcaprolactam. Among these, isobornyl (meth) acrylate and phenyl hydroxypropyl acrylate are preferable.

These energy ray polymerizable monomers may be used singly or in combination of two or more.

The content ratio of the oligomer to the energy ray-polymerizable monomer [ oligomer/energy ray-polymerizable monomer ] in the solvent-free resin composition (y-1 a) is preferably 20/80 to 90/10, more preferably 30/70 to 85/15, and still more preferably 35/65 to 80/20 in terms of mass ratio.

In one embodiment of the present invention, the solvent-free resin composition (y-1 a) is preferably further blended with a photopolymerization initiator.

By containing the photopolymerization initiator, the curing reaction can be sufficiently performed by irradiation with energy rays of relatively low energy.

Examples of the photopolymerization initiator include: 1-hydroxycyclohexyl phenyl ketone, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzyl phenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, dibenzyl, butanedione, beta-chloroanthraquinone, phenyl bis (2, 4, 6-trimethylbenzoyl) phosphine oxide, and the like.

These photopolymerization initiators may be used singly or in combination of two or more.

The amount of the photopolymerization initiator to be blended is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 4 parts by mass, and still more preferably 0.02 to 3 parts by mass, based on the total amount (100 parts by mass) of the oligomer and the energy ray polymerizable monomer.

The resin composition (y-1) can be produced by mixing the above-mentioned components.

The method for mixing the components is not particularly limited, and may be appropriately selected from known mixing methods according to the types of the components used, the viscosity of the resin composition, and the like.

Since the resin composition (y-1) is a composition containing thermally expandable particles, a dispersion treatment for improving the dispersibility of the thermally expandable particles may be performed. By improving the dispersibility of the thermally expandable particles in the resin composition (Y-1), the surface of the thermally expandable base material layer (Y1) becomes smoother, and the surface (S) of the adhesive layer (X1) formed on the thermally expandable base material layer (Y1) can be further reduced _x1 ) Is a combination of the arithmetic mean waviness (Wa).

Examples of the method for dispersing the thermally expandable particles include: a stirring treatment of applying shear using a high-speed stirrer such as a homomixer, a homogenizer, a planetary mixer, a ball mill, etc.; ultrasonic treatment; filtering treatment for removing the condensate by a filter, and the like. Among these dispersion treatment methods, a method and conditions that can improve dispersibility while maintaining the function of the thermally expandable particles are preferably appropriately determined.

The dispersion treatment of the thermally expandable particles may be performed after mixing the thermally expandable particles with other components, or may be performed in a dispersion medium before mixing with other components.

(thickness of thermally-expansive base material layer (Y1))

In one embodiment of the present invention, the thickness of the thermally expandable base material layer (Y1) before thermal expansion is preferably 30 to 300 μm, more preferably 40 to 270 μm, still more preferably 50 to 240 μm, still more preferably 55 to 220 μm.

When the thickness of the heat-expandable base material layer (Y1) before heat expansion is 30 μm or more, the occurrence of irregularities due to heat-expandable particles before heat expansion is suppressed, and the surface (S) of the adhesive layer (X1) can be further reduced _x1 ) Arithmetic mean waviness of (2)(Wa) and the adhesiveness tends to be improved. In addition, when the thickness of the heat-expandable base material layer (Y1) before thermal expansion is 300 μm or less, the handling of the adhesive sheet tends to be easy.

< non-thermally-expansive base material layer (Y2) >)

The non-heat-expandable base material layer (Y2) of the adhesive sheet according to claim 1 is provided on the surface of the heat-expandable base material layer (Y1) opposite to the lamination surface of the adhesive layer (X1).

The non-heat-expandable base material layer (Y2) is preferably a non-adhesive base material. The probe tack value of the surface of the non-heat-expandable base material layer (Y2) is usually less than 50mN/5mm phi, preferably less than 30mN/5mm phi, more preferably less than 10mN/5mm phi, still more preferably less than 5mN/5mm phi.

Examples of the material for forming the non-thermally-expansive base material layer (Y2) include: the resin, metal, paper, etc. may be appropriately selected according to the use of the adhesive sheet.

Examples of the resin include: polyolefin resins such as polyethylene and polypropylene; vinyl resins such as polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl acetate copolymer and ethylene-vinyl alcohol copolymer; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; a polystyrene; acrylonitrile-butadiene-styrene copolymer; cellulose triacetate; a polycarbonate; polyurethane resins such as polyurethane and acrylic modified polyurethane; polymethylpentene; polysulfone; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyether imide and polyimide; polyamide resin; an acrylic resin; fluorine-based resins, and the like.

Examples of the metal include: aluminum, tin, chromium, titanium, and the like.

Examples of the paper include: tissue paper, medium paper, quality paper, impregnated paper, coated paper, art paper, sulfuric acid paper, glass paper, and the like.

Among these, polyester resins such as polyethylene terephthalate, polybutylene terephthalate and polyethylene naphthalate are preferable.

These forming materials may be formed of one kind, or two or more kinds may be used in combination.

The non-heat-expandable base material layer (Y2) in which two or more kinds of forming materials are used in combination includes a material in which paper is laminated with a thermoplastic resin such as polyethylene, a material in which a metal film is formed on the surface of a resin film or sheet containing a resin, and the like.

The method for forming the metal layer includes, for example: a method of vapor-depositing the above metal by PVD such as vacuum vapor deposition, sputtering, ion plating, or a method of adhering a metal foil made of the above metal using a conventional adhesive.

In the case where the non-heat-expandable base material layer (Y2) contains a resin, the surface of the non-heat-expandable base material layer (Y2) may be subjected to a surface treatment by an oxidation method, a concavity and convexity method, or an adhesion-facilitating treatment, or a primer treatment, similarly to the above-described heat-expandable base material layer (Y1), from the viewpoint of improving the interlayer adhesion between the non-heat-expandable base material layer (Y2) and other layers to be laminated.

In the case where the non-thermally expandable base material layer (Y2) contains a resin, the resin may be contained, and the base material additive may be contained in the resin composition (Y-1).

The non-thermally-expansive base material layer (Y2) is a non-thermally-expansive layer determined based on the above method.

Therefore, the volume change rate (%) of the non-thermally-expansive base material layer (Y2) which can be calculated from the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, still more preferably less than 0.1%, still more preferably less than 0.01%.

The non-thermally expandable base material layer (Y2) may contain thermally expandable particles as long as the volume change rate is within the above range. For example, by selecting the resin contained in the non-thermally expandable base material layer (Y2), the volume change rate can be adjusted to the above range even when the thermally expandable particles are contained.

The smaller the content of the thermally expandable particles in the non-thermally expandable base material layer (Y2), the more preferable.

The content of the thermally expandable particles is usually less than 3 mass%, preferably less than 1 mass%, more preferably less than 0.1 mass%, even more preferably less than 0.01 mass%, and even more preferably less than 0.001 mass% based on the total mass (100 mass%) of the non-thermally expandable base material layer (Y2). Further preferably, the heat-expandable particles are not contained.

(storage modulus E' (23) of the non-thermally-expansive base material layer (Y2) at 23 ℃ C.)

The storage modulus E' (23) of the non-heat-expandable base material layer (Y2) at 23℃is preferably 5.0X10 ⁷ ～5.0×10 ⁹ Pa, more preferably 5.0X10 ⁸ ～4.5×10 ⁹ Pa, more preferably 1.0X10 ⁹ ～4.0×10 ⁹ Pa。

The storage modulus E' (23) of the non-heat-expandable base material layer (Y2) was 5.0X10 ⁷ When Pa is equal to or greater, the deformation resistance of the adhesive sheet is easily improved. On the other hand, the storage modulus E' (23) of the non-thermally-expansive base material layer (Y2) was 5.0X10 ⁹ When Pa is less than or equal to Pa, the handling property of the pressure-sensitive adhesive sheet is easily improved.

In the present specification, the storage modulus E' (23) of the non-thermally-expansive base material layer (Y2) represents a value measured by the method described in examples.

(thickness of non-thermally-expansive base material layer (Y2))

The thickness of the non-heat-expandable base material layer (Y2) is preferably 5 to 500. Mu.m, more preferably 15 to 300. Mu.m, still more preferably 20 to 200. Mu.m. When the thickness of the non-heat-expandable base material layer (Y2) is 5 μm or more, the deformation resistance of the adhesive sheet is easily improved. On the other hand, when the thickness of the non-heat-expandable base material layer (Y2) is 500 μm or less, the handleability of the adhesive sheet is easily improved.

< adhesive layer (X2) >)

The pressure-sensitive adhesive sheet of embodiment 1 may have a pressure-sensitive adhesive layer (X2) on the side of the non-heat-expandable base layer (Y2) opposite to the lamination surface of the heat-expandable base layer (Y1). Specifically, the pressure-sensitive adhesive sheet according to embodiment 1 may have a laminated structure in which the pressure-sensitive adhesive layer (X1), the thermally expandable base material layer (Y1), the non-thermally expandable base material layer (Y2), and the pressure-sensitive adhesive layer (X2) are disposed in this order.

The adhesive layer (X2) is preferably a non-thermally expandable layer.

When the pressure-sensitive adhesive layer (X2) is a non-thermally-expansive layer, the volume change rate (%) of the pressure-sensitive adhesive layer (X2) calculated by the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, still more preferably less than 0.1%, still more preferably less than 0.01%.

The pressure-sensitive adhesive layer (X2) preferably contains no thermally expandable particles, but may contain thermally expandable particles within a range not departing from the object of the present invention.

When the pressure-sensitive adhesive layer (X2) contains thermally expandable particles, the content thereof is preferably smaller, and is preferably less than 3 mass%, more preferably less than 1 mass%, further preferably less than 0.1 mass%, further preferably less than 0.01 mass%, further preferably less than 0.001 mass%, relative to the total mass (100 mass%) of the pressure-sensitive adhesive layer (X2).

The adhesive layer (X2) is preferably an energy ray-curable adhesive layer cured by irradiation with energy rays, and thus the adhesive force is reduced. By setting the pressure-sensitive adhesive layer (X2) to an energy ray-curable pressure-sensitive adhesive layer, the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1) can be set to a form in which the pressure-sensitive adhesive force is reduced by heating, and the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X2) can be set to a form in which the pressure-sensitive adhesive force is reduced by irradiation with energy rays, whereby the mechanisms of action of the pressure-sensitive adhesive layers to each other to reduce the pressure-sensitive adhesive force can be made different. Thus, when the adhesive force of one of the adhesive layers is reduced, it is possible to avoid the adhesive force of the other adhesive layer from being reduced unintentionally.

The adhesive layer (X2) is preferably formed of an adhesive composition (X-2) containing an adhesive resin. The components contained in the adhesive composition (x-2) will be described below.

The adhesive composition (x-2) is a composition containing an adhesive resin, and may contain a crosslinking agent, a tackifier, a polymerizable compound, a polymerization initiator, an adhesive additive other than the above components, which is generally used for adhesives, and the like, as required.

(adhesive resin)

The adhesive resin may be any polymer having adhesive properties alone and having a weight average molecular weight (Mw) of 1 ten thousand or more.

The weight average molecular weight (Mw) of the adhesive resin is preferably 1 to 200 tens of thousands, more preferably 2 to 150 tens of thousands, and still more preferably 3 to 100 tens of thousands, from the viewpoint of further improving the adhesive force of the adhesive layer (X2).

As the adhesive resin, those same as the adhesive resin contained in the adhesive composition (x-1) can be mentioned.

These adhesive resins may be used singly or in combination of two or more.

In the case where these adhesive resins are copolymers having two or more structural units, the form of the copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer.

The adhesive resin contained in the adhesive composition (X-2) is preferably an adhesive resin having an energy ray polymerizable functional group in a side chain, from the viewpoint that the adhesive layer (X2) obtained is an adhesive layer cured by irradiation with energy rays and the adhesive force is reduced.

Examples of the energy ray polymerizable functional group include: functional groups having a carbon-carbon double bond such as (meth) acryl, vinyl, allyl, and the like.

From the viewpoint of exhibiting excellent adhesion, the adhesive resin preferably contains an acrylic resin.

The content of the acrylic resin in the adhesive composition (x-2) is preferably 30 to 100% by mass, more preferably 50 to 100% by mass, still more preferably 70 to 100% by mass, and still more preferably 85 to 100% by mass, relative to the total amount (100% by mass) of the adhesive resin contained in the adhesive composition (x-2).

The content of the adhesive resin in the adhesive composition (x-2) is preferably 35 to 100% by mass, more preferably 50 to 100% by mass, still more preferably 60 to 98% by mass, and still more preferably 70 to 95% by mass, relative to the total amount (100% by mass) of the active ingredient of the adhesive composition (x-2).

(energy ray-curable Compound)

The adhesive composition (x-2) may contain, as the energy ray-curable compound, a monomer or oligomer which can be polymerized and cured by irradiation with energy rays, together with the adhesive resin.

Examples of such an energy ray-curable compound include: a polyvalent (meth) acrylate monomer such as trimethylolpropane tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1, 4-butanediol di (meth) acrylate, and 1, 6-hexanediol (meth) acrylate; oligomers such as multifunctional urethane (meth) acrylates, multifunctional polyester (meth) acrylates, multifunctional polyether (meth) acrylates, and multifunctional epoxy (meth) acrylates.

Among these, the multifunctional urethane (meth) acrylate oligomer is preferable from the viewpoint of having a relatively high molecular weight and being less likely to cause a decrease in the elastic modulus of the adhesive layer (X2).

The molecular weight (weight average molecular weight (Mw) in the case of the oligomer) of the energy ray-curable compound is preferably 100 to 12,000, more preferably 200 to 10,000, still more preferably 400 to 8,000, and still more preferably 600 to 6,000.

(photopolymerization initiator)

The adhesive composition (x-2) preferably further contains a photopolymerization initiator.

By containing the photopolymerization initiator, polymerization of the energy ray polymerizable component can be performed more efficiently.

As the photopolymerization initiator, the same ones as those shown in the explanation of the solvent-free resin composition (y-1 a) can be exemplified. Among them, 1-hydroxycyclohexyl phenyl ketone is preferable.

The content of the photopolymerization initiator is preferably 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.05 to 2 parts by mass, relative to 100 parts by mass of the total amount of the adhesive resin having the energy ray polymerizable functional group.

(crosslinking agent)

In one embodiment of the present invention, when the adhesive resin having a functional group is contained in the adhesive composition (x-2), the adhesive composition (x-2) preferably further contains a crosslinking agent.

The crosslinking agent optionally contained in the adhesive composition (x-2) may be the same as or equivalent to the crosslinking agent optionally contained in the adhesive composition (x-1), but isocyanate-based crosslinking agents are preferable from the viewpoints of improving the cohesive force and thus improving the adhesive force, ease of acquisition, and the like.

(tackifier)

In one embodiment of the present invention, the adhesive composition (x-2) may further contain a tackifier from the viewpoint of further improving the adhesive force.

As the tackifier optionally contained in the adhesive composition (x-2), those identical or equivalent to those optionally contained in the adhesive composition (x-1) can be used.

(additive for adhesive)

As the additive for an adhesive, the same ones as those optionally contained in the adhesive composition (x-1) can be mentioned.

The adhesive composition (x-2) can be produced by mixing an adhesive resin, a crosslinking agent, a tackifier, an additive for adhesives, and the like, as needed.

(adhesive force of adhesive layer (X2) before irradiation with energy ray)

The adhesive force of the adhesive layer (X2) before irradiation with energy rays is preferably 1.1 to 30.0N/25mm, more preferably 3.0 to 25.0N/25mm, still more preferably 5.0 to 20.0N/25mm.

When the adhesive force of the adhesive layer (X2) before irradiation with energy rays is 1.1N/25mm or more, unexpected peeling from the adherend, dislocation of the adherend, and the like can be more effectively suppressed. On the other hand, when the adhesive force is 30.0N/25mm or less, the peelability after irradiation with energy rays can be further improved.

The adhesive force of the adhesive layer (X2) before irradiation with energy rays can be measured by the above-described method.

(adhesive force of adhesive layer (X2) after irradiation with energy ray)

The adhesive force of the adhesive layer (X2) after irradiation with energy rays is preferably 1.0N/25mm or less, more preferably 0.9N/25mm or less, still more preferably 0.8N/25mm or less, still more preferably 0.7N/25mm or less. The lower limit of the adhesive layer (X2) after irradiation with energy rays is not particularly limited, but may be 0N/25mm or more.

When the adhesive force of the adhesive layer (X2) after irradiation of energy rays is 1.0N/25mm or less, the layer is more excellent in releasability from the adherend.

The adhesive force of the adhesive layer (X2) after irradiation with energy rays may be obtained by irradiating the adhesive layer (X2) with an illuminance of 230mW/cm ² Light quantity 90mJ/cm ² The adhesive sheet obtained by the ultraviolet ray was measured by the method described above.

(thickness of adhesive layer (X2))

The pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet of embodiment 1 preferably has a thickness of 5 to 150. Mu.m, more preferably 8 to 100. Mu.m, still more preferably 12 to 70. Mu.m, still more preferably 15 to 50. Mu.m.

When the thickness of the adhesive layer (X2) is 5 μm or more, sufficient adhesive force is easily obtained, and unexpected peeling from the adherend, displacement of the adherend, and the like tend to be suppressed at the time of temporary fixation. On the other hand, when the thickness of the pressure-sensitive adhesive layer (X2) is 150 μm or less, the handling of the pressure-sensitive adhesive sheet tends to be easy.

< method for producing an adhesive sheet according to embodiment 1 >

The method for producing the pressure-sensitive adhesive sheet according to embodiment 1 is not particularly limited, and examples thereof include the following steps (1 a) to (3 a).

■ Step (1 a): and a step of forming an adhesive layer (X1) by applying the adhesive composition (X-1) to the release treated surface of the release material.

■ Step (2 a): and a step of forming a base laminate comprising a non-heat-expandable base layer (Y2) and a heat-expandable base layer (Y1) laminated by applying the resin composition (Y-1) to one side of the non-heat-expandable base layer (Y2).

■ Step (3 a): and (2) bonding the bonding surface of the adhesive layer (X1) formed in the step (1 a) to the surface of the heat-expandable substrate layer (Y1) side of the substrate laminate formed in the step (2 a) to obtain the adhesive sheet.

In addition, in the case where the pressure-sensitive adhesive sheet of claim 1 has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are disposed in this order, the pressure-sensitive adhesive sheet can be produced by a method further including the following steps (4 a) and (5 a).

■ Step (4 a): and a step of forming an adhesive layer (X2) by applying the adhesive composition (X-2) to the release treated surface of the release material.

■ Step (5 a): and (3) bonding the adhesive surface of the adhesive layer (X2) formed in the step (4 a) to the surface of the adhesive sheet on the non-heat-expandable substrate layer (Y2) side formed in the step (3 a).

In the above method for producing an adhesive sheet, the resin composition (y-1), the adhesive composition (x-1), and the adhesive composition (x-2) may be further mixed with a diluting solvent to prepare a solution.

Examples of the coating method include: spin coating, spray coating, bar coating, doctor blade coating, roll coating, blade coating, die coating, gravure coating, and the like.

In addition, the step of drying the coating film formed of the resin composition (y-1), the binder composition (x-1) and the binder composition (x-2) is preferably performed under a condition that the drying temperature is lower than the expansion initiation temperature (t) of the thermally expandable particles from the viewpoint of suppressing expansion of the thermally expandable particles.

[ pressure-sensitive adhesive sheet of mode 2 ]

The adhesive sheet according to embodiment 2 is an adhesive sheet having a laminated structure including a base layer (Y) and an adhesive layer (X1) as a thermally expandable layer.

The pressure-sensitive adhesive sheet of claim 2 may have the pressure-sensitive adhesive layer (X2) on the surface of the base layer (Y) opposite to the lamination surface of the pressure-sensitive adhesive layer (X1). That is, the pressure-sensitive adhesive sheet according to claim 2 may have a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are disposed in this order as the heat-expandable layer.

The explanation of the base material layer (Y) of the adhesive sheet according to claim 2 is the same as the explanation of the non-heat-expandable base material layer (Y2) of the adhesive sheet according to claim 1. The description of the adhesive layer (X2) optionally included in the adhesive sheet according to embodiment 2 is the same as the description of the adhesive layer (X2) optionally included in the adhesive sheet according to embodiment 1.

< adhesive layer (X1) >)

The pressure-sensitive adhesive layer (X1) of claim 2 is a heat-expandable layer containing heat-expandable particles, and preferably contains a polymer containing an energy ray-polymerizable component and heat-expandable particles.

The energy ray polymerizable component in the polymer is a polymer obtained by irradiating an energy ray to a polymerizable composition (hereinafter, also referred to as "polymerizable composition (x-1')") containing a monomer (b 1) having an energy ray polymerizable functional group (hereinafter, also referred to as "component b 1") and a prepolymer (b 2) having an energy ray polymerizable functional group (hereinafter, also referred to as "component b 2").

In the present specification, a prepolymer means a compound which is polymerized from a monomer and can be further polymerized to form a polymer.

The energy ray polymerizable component contained in the polymerizable composition (x-1') is a component that is polymerized by irradiation with energy rays, and has an energy ray polymerizable functional group.

Examples of the energy ray polymerizable functional group include: functional groups having a carbon-carbon double bond such as (meth) acryl, vinyl, allyl, and the like. In the following description, a functional group partially containing a vinyl group or a substituted vinyl group, such as a (meth) acryloyl group or an allyl group, and a vinyl group or a substituted vinyl group itself are sometimes collectively referred to as a "vinyl group".

The components contained in the polymerizable composition (x-1) will be described below.

(monomer (b 1) having an energy ray-polymerizable functional group)

The monomer (b 1) having an energy ray polymerizable functional group may be any monomer having an energy ray polymerizable functional group, and may have a hydrocarbon group, a functional group other than an energy ray polymerizable functional group, or the like in addition to an energy ray polymerizable functional group.

Examples of the hydrocarbon group contained in the component (b 1) include: aliphatic hydrocarbon groups, aromatic hydrocarbon groups, groups formed by combining these hydrocarbon groups, and the like.

The aliphatic hydrocarbon group may be a linear or branched aliphatic hydrocarbon group or an alicyclic hydrocarbon group.

Examples of the linear or branched aliphatic hydrocarbon group include: aliphatic hydrocarbon groups having 1 to 20 carbon atoms such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, t-butyl group, sec-butyl group, n-pentyl group, n-hexyl group, 2-ethylhexyl group, n-octyl group, isooctyl group, n-decyl group, n-dodecyl group, n-myristyl group, n-palmityl group, and n-stearyl group.

Examples of the alicyclic hydrocarbon group include: alicyclic hydrocarbon groups having 3 to 20 carbon atoms such as cyclopentyl, cyclohexyl and isobornyl.

Examples of the aromatic hydrocarbon group include phenyl groups.

Examples of the group formed by combining an aliphatic hydrocarbon group and an aromatic hydrocarbon group include: phenoxyethyl, benzyl.

Among these hydrocarbon groups, from the viewpoint of further improving the adhesive force of the adhesive layer (X1), the component (b 1) preferably contains a monomer (b 1-1) having an energy ray polymerizable functional group and a linear or branched aliphatic hydrocarbon group (hereinafter also referred to as a "component (b 1-1)"), a monomer (b 1-2) having an energy ray polymerizable functional group and an alicyclic hydrocarbon group (hereinafter also referred to as a "component (b 1-2)"), and the like.

When component (b 1) contains component (b 1-1), the content thereof is preferably 20 to 80% by mass, more preferably 40 to 70% by mass, and even more preferably 50 to 60% by mass, based on the total (100% by mass) of component (b 1).

When component (b 1) contains component (b 1-2), the content thereof is preferably 5 to 60% by mass, more preferably 10 to 40% by mass, and even more preferably 20 to 30% by mass, based on the total (100% by mass) of component (b 1).

Examples of the monomer having an energy ray polymerizable functional group and a functional group other than the energy ray polymerizable functional group include: a monomer having a hydroxyl group, a carboxyl group, a thiol group, a primary amino group, a secondary amino group, or the like as a functional group other than the energy ray polymerizable functional group. Among these functional groups, from the viewpoint of further improving the formability of the adhesive layer (X1), it is preferable that the component (b 1) contains a monomer (b 1-3) having an energy ray polymerizable functional group and a hydroxyl group (hereinafter, also referred to as a "(b 1-3 component").

When component (b 1) contains component (b 1-3), the content thereof is preferably 1 to 60% by mass, more preferably 5 to 30% by mass, and even more preferably 10 to 20% by mass, based on the total (100% by mass) of component (b 1).

(b1) The number of the energy ray polymerizable functional groups included in the component (a) may be 1 or 2 or more. In addition, from the viewpoint of further improving the releasability of the pressure-sensitive adhesive layer (X1), it is preferable that the component (b 1) contains a monomer (b 1-4) having 3 or more energy ray-polymerizable functional groups (hereinafter, also referred to as a "(b 1-4 component").

When component (b 1) contains component (b 1-4), the content thereof is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and even more preferably 3 to 10% by mass, relative to the total (100% by mass) of component (b 1).

As the monomer having 1 energy ray polymerizable functional group, a monomer having 1 vinyl group-containing (hereinafter, also referred to as "polymerizable vinyl monomer") is preferable.

The monomer having 2 or more energy ray polymerizable functional groups is preferably a monomer having 2 or more (meth) acryloyl groups (hereinafter, also referred to as "multifunctional (meth) acrylate monomer"). By containing the compound in the component (b 1), the cohesive force of the adhesive obtained by polymerizing the compound increases, and an adhesive layer (X1) with little contamination of the adherend after peeling can be formed.

[ polymerizable vinyl monomer ]

The polymerizable vinyl monomer is not particularly limited as long as it has a vinyl group-containing monomer, and conventionally known ones can be suitably used.

The polymerizable vinyl monomer may be used alone or in combination of two or more.

Examples of the polymerizable vinyl monomer include: compounds corresponding to the above component (b 1-1), such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate; a compound corresponding to the component (b 1-2) such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, polyoxyalkylene modified (meth) acrylate, and other (meth) acrylates having no functional group other than a vinyl group in the molecule. Among them, 2-ethylhexyl acrylate and isobornyl acrylate are preferable.

The polymerizable vinyl monomer may be a monomer having a functional group other than a vinyl group in the molecule. Examples of the functional group include: hydroxyl, carboxyl, thiol, primary or secondary amino, and the like. Among these functional groups, a polymerizable vinyl monomer having a hydroxyl group corresponding to the above component (b 1-3) is preferable.

Examples of the polymerizable vinyl monomer having a hydroxyl group include: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate; hydroxyl-containing acrylamides such as N-methylolacrylamide and N-methylolmethacrylamide. Further, examples of the polymerizable vinyl monomer having a carboxyl group include: ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these monomers, 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate are preferable.

Further, examples of other polymerizable vinyl monomers include: vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, and isobutylene; halogenated olefins such as vinyl chloride and vinylidene chloride; styrene monomers such as styrene and α -methylstyrene; diene monomers such as butadiene, isoprene, and chloroprene; nitrile monomers such as acrylonitrile and methacrylonitrile; amide monomers such as acrylamide, methacrylamide, N-methylacrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, and N-vinylpyrrolidone; tertiary amino group-containing monomers such as N, N-diethylaminoethyl (meth) acrylate and N- (meth) acryloylmorpholine.

[ multifunctional (meth) acrylate monomer ]

The polyfunctional (meth) acrylate monomer is not particularly limited as long as it has 2 or more (meth) acryloyl groups in one molecule, and conventionally known ones can be suitably used.

The polyfunctional (meth) acrylate monomer may be used singly or in combination of two or more.

Examples of the polyfunctional (meth) acrylate monomer include: difunctional (meth) acrylate monomers such as 1, 4-butanediol di (meth) acrylate, 1, 6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, neopentyl glycol adipate di (meth) acrylate, hydroxypivalate neopentyl glycol di (meth) acrylate, dicyclopentanyl di (meth) acrylate, caprolactone-modified dicyclopentanyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, di (acryloyloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, and isocyanuric acid ethylene oxide-modified diacrylate; trimethylolpropane tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, propionic acid modified dipentaerythritol tri (meth) acrylate, pentaerythritol tri (meth) acrylate, propylene oxide modified trimethylolpropane tri (meth) acrylate, tris (acryloxyethyl) isocyanurate, bis (acryloxyethyl) hydroxyethyl isocyanurate, isocyanuric ethylene oxide modified triacrylate, epsilon-caprolactone modified tris (acryloxyethyl) isocyanurate, diglycerol tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, propionic acid modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, and the like.

Content of component (b 1)

The total content of the polymerizable vinyl monomers in the polymerizable composition (x-1 ') is preferably 10 to 80% by mass, more preferably 30 to 75% by mass, and even more preferably 50 to 70% by mass, based on the total amount (100% by mass) of the active ingredients in the polymerizable composition (x-1').

The total content of the polyfunctional (meth) acrylate monomers in the polymerizable composition (x-1 ') is preferably 0.5 to 15% by mass, more preferably 1 to 10% by mass, and even more preferably 2 to 5% by mass, relative to the total amount (100% by mass) of the active ingredient in the polymerizable composition (x-1').

The total content of the component (b 1) in the polymerizable composition (x-1 ') is preferably 15 to 90% by mass, more preferably 35 to 80% by mass, and still more preferably 55 to 75% by mass, based on the total amount (100% by mass) of the active components in the polymerizable composition (x-1').

(prepolymer (b 2) having an energy ray-polymerizable functional group)

The prepolymer (b 2) having an energy ray polymerizable functional group includes: a prepolymer having 1 energy ray polymerizable functional group, a prepolymer having 2 or more energy ray polymerizable functional groups, and the like. Among these prepolymers, from the viewpoint of forming an adhesive layer excellent in releasability and less in contamination of an adherend after release, the component (b 2) preferably contains a prepolymer having 2 or more energy ray polymerizable functional groups, more preferably contains a prepolymer having 2 energy ray polymerizable functional groups, and still more preferably contains a prepolymer having 2 energy ray polymerizable functional groups and having the energy ray polymerizable functional groups at both ends.

The component (b 2) preferably contains a prepolymer having 2 or more (meth) acryloyl groups as energy ray-polymerizable functional groups (hereinafter, also referred to as "multifunctional (meth) acrylate prepolymer"). By containing the compound as the component (b 2), the cohesive force of the adhesive obtained by polymerizing the compound is improved, and an adhesive layer (X1) having excellent peelability and less contamination of the adherend after peeling can be formed.

[ multifunctional (meth) acrylate prepolymer ]

The polyfunctional (meth) acrylate prepolymer is not particularly limited as long as it has 2 or more (meth) acryloyl groups in one molecule, and conventionally known ones can be suitably used.

The polyfunctional (meth) acrylate prepolymer may be used singly or in combination of two or more.

Examples of the polyfunctional (meth) acrylate prepolymer include: urethane acrylate prepolymers, polyester acrylate prepolymers, epoxy acrylate prepolymers, polyether acrylate prepolymers, polybutadiene acrylate prepolymers, silicone acrylate prepolymers, polyacryl acrylate prepolymers, and the like.

Urethane acrylate prepolymers are obtained by esterifying urethane prepolymers obtained by reacting polyisocyanates with compounds such as polyalkylene polyols, polyether polyols, polyester polyols, hydrogenated isoprene having hydroxyl ends, hydrogenated butadiene having hydroxyl ends, or the like with (meth) acrylic acid or (meth) acrylic acid derivatives.

Examples of the polyalkylene polyol that can be used for producing the urethane acrylate prepolymer include polypropylene glycol, polyethylene glycol, polybutylene glycol, and polyhexamethylene glycol, and among these, polypropylene glycol is preferable. In the case where the number of functional groups of the urethane acrylate prepolymer to be obtained is 3 or more, for example, glycerin, trimethylolpropane, triethanolamine, pentaerythritol, ethylenediamine, diethylenetriamine, sorbitol, sucrose, and the like may be appropriately combined.

Examples of the polyisocyanate that can be used for producing the urethane acrylate prepolymer include: aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as toluene diisocyanate, xylene diisocyanate, and diphenyl diisocyanate; among these polyisocyanates, aliphatic diisocyanates are preferable, and hexamethylene diisocyanate is more preferable. The polyisocyanate is not limited to difunctional, and trifunctional or more may be used.

Examples of the (meth) acrylic acid derivative that can be used for producing the urethane acrylate prepolymer include: hydroxyalkyl (meth) acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; among these (meth) acrylic acid derivatives, 2-isocyanoethyl acrylate, 2-isocyanoethyl methacrylate, 1-bis (acryloyloxymethyl) ethyl isocyanate and the like are preferable.

As another method for producing the urethane acrylate prepolymer, there can be mentioned: a method of reacting a hydroxyl group of a compound such as a polyalkylene polyol, a polyether polyol, a polyester polyol, hydrogenated isoprene having a hydroxyl end, and hydrogenated butadiene having a hydroxyl end with a moiety of-n=c=o of an isocyanoalkyl (meth) acrylate. In this case, as the isocyanatoalkyl (meth) acrylate, for example, it is possible to use: the above-mentioned 2-isocyanoethyl acrylate, 2-isocyanoethyl methacrylate, 1-bis (acryloyloxymethyl) ethyl isocyanate and the like.

The polyester acrylate prepolymer can be obtained, for example, by esterifying the hydroxyl groups of a polyester prepolymer having hydroxyl groups at both ends, which is obtained by condensing a polycarboxylic acid and a polyhydric alcohol, with (meth) acrylic acid. Further, the prepolymer may be obtained by esterifying a terminal hydroxyl group of a prepolymer obtained by adding an alkylene oxide to a polycarboxylic acid with (meth) acrylic acid.

The epoxy acrylate prepolymer can be obtained, for example, by reacting an epoxy ring of a bisphenol epoxy resin, a novolac epoxy resin or the like having a relatively low molecular weight with (meth) acrylic acid to esterify the epoxy ring. Further, a carboxyl group-modified epoxy acrylate prepolymer obtained by modifying an epoxy acrylate prepolymer partially with a dicarboxylic anhydride may be used.

The polyether acrylate prepolymer can be obtained, for example, by esterifying the hydroxyl groups of a polyether polyol with (meth) acrylic acid.

The polyacryl-acrylate prepolymer may have an acryl group in a side chain, or may have acryl groups at both ends or one end. The polyacryl-acrylate prepolymer having an acryl group in a side chain can be obtained, for example, by adding glycidyl methacrylate to a carboxyl group of polyacrylic acid. The polyacrylate acrylate prepolymer having an acryl group at both ends can be obtained by introducing an acryl group into both ends by using a polymerization-grown terminal structure of a polyacrylate prepolymer synthesized by an ATRP (atom transfer radical polymerization ) method, for example.

(b2) The weight average molecular weight (Mw) of the component is preferably 10,000 ～ 350,000, more preferably 15,000 ～ 200,000, and further preferably 20,000 ～ 50,000.

Content of component (b 2)

The total content of the polyfunctional (meth) acrylate prepolymer in the polymerizable composition (x-1 ') is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, and even more preferably 20 to 30% by mass, based on the total amount (100% by mass) of the active ingredient in the polymerizable composition (x-1').

The total content of the component (b 2) in the polymerizable composition (x-1 ') is preferably 10 to 60% by mass, more preferably 15 to 55% by mass, and still more preferably 20 to 30% by mass, based on the total amount (100% by mass) of the active components in the polymerizable composition (x-1').

The content ratio [ (b 2)/(b 1) ] of the component (b 2) and the component (b 1) in the polymerizable composition (x-1') is preferably 10/90 to 70/30, more preferably 20/80 to 50/50, still more preferably 25/75 to 40/60, in terms of mass.

Among the above-mentioned energy ray polymerizable components, the polymerizable composition (x-1') preferably contains a polymerizable vinyl monomer, a polyfunctional (meth) acrylate monomer and a polyfunctional (meth) acrylate prepolymer.

The total content of the polymerizable vinyl monomer, the polyfunctional (meth) acrylate monomer, and the polyfunctional (meth) acrylate prepolymer in the energy ray polymerizable component contained in the polymerizable composition (x-1') is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 99% by mass or more, and may be 100% by mass, based on the total amount (100% by mass) of the energy ray polymerizable component.

The total content of the energy ray polymerizable components in the polymerizable composition (x-1 ') is preferably 70 to 98% by mass, more preferably 75 to 97% by mass, still more preferably 80 to 96% by mass, and still more preferably 82 to 95% by mass, relative to the total amount (100% by mass) of the active components in the polymerizable composition (x-1').

(other Components)

The polymerizable composition (x-1') may contain other components than the energy ray polymerizable component and the heat expandable particles.

Examples of the other components include a photopolymerization initiator, a tackifier, and an adhesive additive which is usually used for adhesives other than the above components.

These components are the same as those described in the adhesive sheet of embodiment 1.

The polymerizable composition (x-1') may contain a solvent such as a diluent within a range not departing from the object of the present invention, but preferably contains no solvent. That is, the polymerizable composition (x-1') is preferably a solvent-free polymerizable composition.

By making the polymerizable composition (X-1') a solvent-free polymerizable composition, the heat drying of the solvent can be omitted when forming the pressure-sensitive adhesive layer (X1), and therefore expansion of the heat-expandable particles during heat drying can be suppressed.

When the polymerizable composition (x-1') contains a solvent, the content thereof is preferably 10 mass% or less, more preferably 1 mass% or less, still more preferably 0.1 mass% or less, still more preferably 0.01 mass% or less, based on the total amount (100 mass%) of the active ingredients of the polymerizable composition (x-1).

The polymerizable composition (x-1') can be produced by mixing an energy ray polymerizable component, thermally expandable particles, and other components if necessary.

Since the polymerizable composition (x-1 ') is a composition containing thermally expandable particles, a dispersion treatment for improving the dispersibility of the thermally expandable particles in the polymerizable composition (x-1') may be performed. By improving the dispersibility of the thermally expandable particles, the surface of the adhesive layer (X1) becomes smoother, and the surface (S) of the adhesive layer (X1) can be further reduced _x1 ) A kind of electronic deviceArithmetic mean waviness (Wa).

The dispersion treatment method of the heat-expandable particles is the same as that described in the description of the "resin composition (y-1)" of the "adhesive sheet according to the above-mentioned" 1 st aspect ".

Since the polymerizable composition (x-1') is polymerized to have a high molecular weight by the subsequent energy ray polymerization, the composition can be adjusted to have a proper viscosity by using an energy ray polymerizable component having a low molecular weight when forming a layer. Therefore, the polymerizable composition (X-1') can be used directly for forming the adhesive layer (X1) in the form of a coating solution without adding a solvent such as a diluent.

The pressure-sensitive adhesive layer (X1) formed by irradiating the polymerizable composition (X-1') with energy rays contains various polymers obtained by polymerizing energy ray polymerizable components and thermally expandable particles dispersed in the polymers, but in some cases, it is impossible or almost impractical to directly limit them by structure and physical properties.

(adhesive force of adhesive layer (X1))

The adhesive force before thermal expansion and the adhesive force after thermal expansion of the adhesive layer (X1) in the adhesive sheet according to claim 2 are the same as the adhesive force before thermal expansion of the adhesive layer (X1) and the adhesive force after thermal expansion of the adhesive layer (X1) in the adhesive sheet according to claim 1.

(thickness of adhesive layer (X1))

The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet of claim 2 preferably has a thickness before thermal expansion of 20 to 270. Mu.m, more preferably 30 to 240. Mu.m, still more preferably 40 to 220. Mu.m, still more preferably 50 to 200. Mu.m.

When the thickness of the adhesive layer (X1) before thermal expansion is 20 μm or more, the occurrence of irregularities due to thermally expandable particles before thermal expansion is suppressed, and the surface (S) of the adhesive layer (X1) can be further reduced _x1 ) Arithmetical average waviness (Wa) and adhesionHigh tendency. In addition, when the thickness of the adhesive layer (X1) before thermal expansion is 270 μm or less, the handling of the adhesive sheet tends to be easy.

< method for producing an adhesive sheet according to embodiment 2 >

The method for producing the adhesive sheet according to the 2 nd aspect is preferably a method for producing an adhesive sheet comprising a step of irradiating a polymerizable composition (X-1') containing the energy ray polymerizable component and the thermally expandable particles with energy rays to form a polymer of the energy ray polymerizable component, and more preferably a method for producing an adhesive sheet comprising the following steps (1 b) and (2 b).

Step (1 b): a step of forming a polymerizable composition layer formed of a polymerizable composition (x-1') on one surface side of the substrate (Y)

Step (2 b): a step of forming a pressure-sensitive adhesive layer (X1) containing the polymer and the thermally expandable particles by irradiating the polymerizable composition layer with energy rays to form a polymer of the energy ray polymerizable component, thereby obtaining a pressure-sensitive adhesive sheet

In the case where the pressure-sensitive adhesive sheet of claim 2 has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are disposed in this order, the pressure-sensitive adhesive sheet can be produced by a method further including the following step (3 b).

Step (3 b): a step of forming an adhesive layer (X2) on the surface of the base layer (Y) of the adhesive sheet formed in the step (2 b) opposite to the lamination surface of the adhesive layer (X1)

The step (1 b) may be, for example, the following method: the release material is coated with a polymerizable composition (x-1') on a release treated surface thereof to form a polymerizable composition layer, and the polymerizable composition layer is irradiated with a first energy ray to prepolymerize an energy ray polymerizable component in the polymerizable composition layer, and then a base material (Y) is bonded to the polymerized polymerizable composition layer after the prepolymerization.

The polymerizable composition (x-1') is preferably a solvent-free polymerizable composition as described above. In the case where the polymerizable composition (x-1') is a solvent-free polymerizable composition, the step of heating and drying the solvent may not be performed in this step, and expansion of the thermally expandable particles can be suppressed.

The step (2 b) is a step of forming an adhesive layer (X1) containing the polymer and thermally expandable particles by irradiating the polymerizable composition layer formed in the step (1 b) with energy rays to form a polymer of an energy ray polymerizable component.

Here, when the first energy ray irradiation is performed in the step (1 b), the energy ray irradiation in the step (2 b) is performed as the second energy ray irradiation to the prepolymerized polymerizable composition layer.

The irradiation with energy rays in the step (2 b) is preferably performed to such an extent that the polymerization of the energy ray polymerizable component is not substantially performed even if the energy rays are further irradiated, unlike the first energy ray irradiation. The energy ray irradiation in the step (2 b) causes polymerization of the energy ray polymerizable component to proceed, thereby forming a polymer of the energy ray polymerizable component constituting the adhesive layer (X1).

The step (3 b) may be a method of forming an adhesive layer (X2) by applying the adhesive composition (X-2) to one surface of the release material and adhering the adhesive layer (X2) to the other surface side of the substrate (Y).

From the viewpoint of suppressing expansion of the thermally expandable particles, it is preferable that the step of heating the polymerizable composition is not included in any of the above steps.

The term "heating" used herein means heating intentionally performed, for example, during drying or lamination, and does not include heat applied to the polymerizable composition by irradiation with energy rays, or a temperature increase due to polymerization heat generated by polymerization of the energy ray-polymerizable composition.

< Release Material >

As the release material optionally included in the pressure-sensitive adhesive sheet according to one embodiment of the present invention, a release sheet subjected to double-sided release treatment, a release sheet subjected to single-sided release treatment, or the like can be used, and examples thereof include a material in which a release agent is coated on a base material for a release material.

Examples of the base material for the release material include plastic films and papers. Examples of the plastic film include: polyester resin films such as polyethylene terephthalate resin, polybutylene terephthalate resin, and polyethylene naphthalate resin; examples of the paper include olefin resin films such as polypropylene resin and polyethylene resin: high quality paper, cellophane, kraft paper, etc.

Examples of the release agent include: rubber-based elastomers such as silicone-based resins, olefin-based resins, isoprene-based resins, and butadiene-based resins; long chain alkyl resins, alkyd resins, fluorine resins, and the like. The stripping agent may be used alone or in combination of two or more.

The thickness of the release material is preferably 10 to 200. Mu.m, more preferably 20 to 150. Mu.m, still more preferably 35 to 80. Mu.m.

[ use of pressure-sensitive adhesive sheet and method of use ]

The pressure-sensitive adhesive sheet according to one embodiment of the present invention can be used for various applications because the temporarily fixed adherend can be easily peeled off by heating. Specifically, the present invention is applicable to, for example: a dicing sheet used for dicing an adherend such as a semiconductor wafer, a back grinding sheet used in a process of grinding the adherend, a dicing tape for expanding a distance between the adherend such as a semiconductor chip singulated by dicing, a transfer tape for turning the front and back surfaces of the adherend such as a semiconductor chip, a temporary fixing sheet for temporarily fixing an inspection object and inspecting the same, and the like.

The adherend of the pressure-sensitive adhesive sheet according to one embodiment of the present invention is not particularly limited, and examples thereof include: semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, sapphire substrates, displays, substrates for panels, and the like.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, when the expansion initiation temperature (t) of the thermally expandable particles is lower than 125 ℃, the heat release at a low temperature can be realized, and therefore, the pressure-sensitive adhesive sheet is suitable for temporarily fixing an adherend such as a semiconductor chip with DAF, which is susceptible to thermal change.

In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, when the expansion initiation temperature (t) of the thermally expandable particles is 50 ℃ or higher, unexpected expansion of the thermally expandable particles due to a temperature rise in the case of grinding an adherend or the like can be suppressed, and therefore, the pressure-sensitive adhesive sheet is suitably used as a back sheet for use in a process of grinding an adherend.

The heating temperature at which the pressure-sensitive adhesive sheet according to one embodiment of the present invention is peeled off from the adherend by heating is not less than the expansion start temperature (t) of the thermally expandable particles, preferably not less than the expansion start temperature (t), more preferably not less than the expansion start temperature (t) +2deg.C, still more preferably not less than the expansion start temperature (t) +4deg.C, still more preferably not less than the expansion start temperature (t) +5deg.C. In addition, from the viewpoints of energy saving and suppression of thermal change of the adherend at the time of heat peeling, it is preferably "expansion start temperature (t) +50 ℃ or less", more preferably "expansion start temperature (t) +40 ℃ or less", and still more preferably "expansion start temperature (t) +20 ℃ or less".

In addition, from the viewpoint of suppressing thermal change of the adherend, the heating temperature at the time of heat release is preferably lower than 125 ℃, more preferably 120 ℃ or lower, still more preferably 115 ℃ or lower, still more preferably 110 ℃ or lower, still more preferably 105 ℃ or lower, in the range of the expansion initiation temperature (t) or higher.

The heating method is not particularly limited as long as it can be heated to a temperature equal to or higher than the temperature at which the thermally expandable particles expand, and for example, it is possible to suitably use: an electric heater; induction heating; magnetically heating; heating by electromagnetic waves, such as infrared rays, such as near infrared rays, mid infrared rays, and far infrared rays. The heating method may be a contact heating method such as a heating roller and a heating press; an atmosphere heating device, and a noncontact heating system such as infrared irradiation.

[ method for manufacturing semiconductor device ]

The present invention also provides a method for manufacturing a semiconductor device using the adhesive sheet according to one embodiment of the present invention.

As one embodiment of the method for manufacturing a semiconductor device of the present invention, there is given: the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a temporary fixing sheet for processing or inspecting an adherend (hereinafter, also referred to as "method for manufacturing a semiconductor device according to embodiment 1").

In the present specification, the term "semiconductor device" refers to all devices that can function by utilizing semiconductor characteristics. Examples include: wafer having integrated circuits, thinned wafer having integrated circuits, chip having integrated circuits, thinned chip having integrated circuits, electronic component including these chips, electronic device including the electronic component, and the like.

< method for manufacturing a semiconductor device according to embodiment 1 >

As a more specific embodiment of the method for manufacturing a semiconductor device according to claim 1, a method for manufacturing a semiconductor device including the steps of: an object to be inspected is stuck to an adhesive sheet according to one embodiment of the present invention, and after one or more selected from the group consisting of processing and inspection is performed on the object to be inspected, the adhesive sheet is heated to the expansion initiation temperature (t) or higher.

Examples of the object to be processed include: semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, LED elements, sapphire substrates, displays, substrates for panels, and the like.

The processing performed on the object to be processed is not particularly limited, and examples thereof include: grinding, singulation, and the like.

The inspection of the object to be inspected is not particularly limited, and examples thereof include: optical microscopy, defect inspection using laser (e.g., dust inspection, surface scratch inspection, wiring pattern inspection, etc.), surface inspection based on visual inspection, and the like.

In the method for manufacturing a semiconductor device according to claim 1, the adhesive layer of the adhesive sheet to be bonded to the object to be inspected may be the adhesive layer (X1), or the adhesive layer (X2) in the case where the adhesive sheet is a double-sided adhesive sheet.

When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable to adhere the object to be processed to the pressure-sensitive adhesive layer on one side and adhere the support to the pressure-sensitive adhesive layer on the other side. By fixing the object to be processed to the support via the adhesive sheet, vibration, displacement, breakage of the fragile object to be processed can be suppressed during processing, and processing accuracy and processing speed can be improved. Further, the pressure-sensitive adhesive sheet according to one embodiment of the present invention is excellent in adhesiveness, and therefore can more effectively suppress vibration, displacement, breakage of a work object, and the like caused by air stagnation at the bonding interface between the pressure-sensitive adhesive sheet and the work object. In this case, the support may be attached to the adhesive layer (X1) or the object to be inspected may be attached to the adhesive layer (X2), or the object to be inspected may be attached to the adhesive layer (X1) or the support may be attached to the adhesive layer (X2).

When the support is adhered to the adhesive layer (X1) and the object to be processed is adhered to the adhesive layer (X2), the support is adhered to the adhesive layer (X1) having excellent peeling property after the heat treatment, and thus the support can be peeled by heating without bending the adhesive sheet and the support even if the support is made of a hard material. The composition of the adhesive layer (X2) may be appropriately selected according to the type of the object to be processed, and for example, when the adhesive layer (X2) is an adhesive layer in which the adhesive force is reduced by irradiation with energy rays, the object to be processed can be peeled off without being contaminated by residues derived from thermally expandable particles or the like.

On the other hand, in the case of the form in which the object to be inspected is adhered to the adhesive layer (X1) and the support is adhered to the adhesive layer (X2), the object to be inspected is adhered to the adhesive layer (X1) excellent in peelability after the heat treatment, and the object to be inspected can be easily peeled from the adhesive sheet after the processing, so that damage to the object to be inspected can be reduced.

< method for manufacturing a semiconductor device according to claim 2 >

The method for manufacturing the semiconductor device according to claim 2 includes: an adhesive sheet having a laminated structure in which an adhesive layer (X1), a base layer (Y), and an adhesive layer (X2) are sequentially disposed is used as an adhesive sheet according to one embodiment of the present invention, and includes a manufacturing method (hereinafter, also referred to as "manufacturing method a") including the following steps 1A, 2A, a first separation step, and a second separation step.

The following description will be given of the manufacturing method a with reference to the drawings. In the following description, the case of using a semiconductor wafer as a processing object will be mainly described, but the same applies to other processing objects. The other objects to be processed include the same objects as those listed above as objects to be processed.

(Process 1A)

Step 1A is a step of adhering the object to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet and adhering the support to the pressure-sensitive adhesive layer (X1).

Fig. 3 (a) and (b) show the surface (S) of the support 3 on the adhesive layer (X2) of the adhesive sheet 2a for adhering the semiconductor wafer W _s ) A surface (S) adhered to the adhesive layer (X1) _x1 ) A cross-sectional view illustrating the steps of (a)。

The semiconductor wafer W is bonded such that the surface W1 as a circuit surface is on the side of the adhesive layer (X2).

The semiconductor wafer W may be a silicon wafer, or may be a wafer such as gallium arsenide, silicon carbide, sapphire, lithium tantalate, lithium niobate, gallium nitride, or indium phosphide, or a glass wafer.

The thickness of the semiconductor wafer W before grinding is usually 500 to 1000. Mu.m.

The circuit provided on the front surface W1 of the semiconductor wafer W can be formed by a conventional general-purpose method such as an etching method or a lift-off (lift-off) method.

The material of the support 3 may be appropriately selected in consideration of the required characteristics such as mechanical strength and heat resistance, depending on the type of the object to be processed, the processing content, and the like.

Examples of the material of the support 3 include: metal materials such as SUS; nonmetallic inorganic materials such as glass and silicon wafers; resin materials such as epoxy resin, ABS resin, acrylic resin, engineering plastic, special engineering plastic, polyimide resin, and polyamideimide resin; among these materials, SUS, glass, and silicon wafers are preferable, for example, composite materials such as glass epoxy resin.

Examples of the engineering plastic include: nylon, polycarbonate (PC), polyethylene terephthalate (PET), and the like.

Examples of the special engineering plastic include: polyphenylene Sulfide (PPS), polyethersulfone (PES), polyetheretherketone (PEEK), and the like.

The support 3 is preferably adhered to the entire surface of the adhesive layer (X1). Therefore, the surface area of the support 3 attached to the adhesive surface side of the adhesive layer (X1) is preferably equal to or larger than the adhesive surface area of the adhesive layer (X1). The surface of the support 3 to be adhered to the adhesive surface side of the adhesive layer (X1) is preferably planar.

The shape of the support 3 is not particularly limited, and is preferably a plate shape.

The thickness of the support 3 may be appropriately selected in consideration of the required characteristics, and is preferably 20 μm or more and 50mm or less, more preferably 60 μm or more and 20mm or less.

The step of adhering the support 3 to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet 2a in step 1A is preferably performed on the surface (S) of the pressure-sensitive adhesive layer (X1) _X1 ) A surface to be bonded with the adhesive sheet 2a of the support 3 (S _s ) The surface of the support body 3 is kept substantially parallel (S _s ) A surface (S) adhered to the adhesive layer (X1) _X1 ) (hereinafter, also referred to as "surface adhering step a").

Since the adhesive sheet according to one embodiment of the present invention has excellent adhesion, air stagnation at the adhesive interface between the adhesive sheet 2a and the support 3 can be suppressed even when the surface adhesion step a is performed.

The surface adhering step a includes, for example, the following steps: after the object is adhered to the adhesive layer (X2) of the adhesive sheet 2a, the surface (S) of the adhesive layer (X1) of the adhesive sheet 2a adhered to the object _X1 ) A surface to be bonded with the adhesive sheet 2a of the support 3 (S _s ) Bonding the surface (Ss) of the support 3 to the surface (S) of the adhesive layer (X1) while maintaining the substantially parallel state _X1 ) Is a step of (a) a step of (b).

In the present specification, "substantially parallel" means a state in which the degree of parallelism is 0 degrees±10 degrees or less, preferably 0 degrees±5 degrees or less, and more preferably 0 degrees±1 degrees or less.

The bonding in step 1A may be performed while performing lamination, heating, decompression, or the like, as needed.

The pressing pressure is preferably 0.12 to 1.0MPa, more preferably 0.15 to 0.7MPa, and even more preferably 0.17 to 0.5MPa, from the viewpoints of adhesion and productivity. When the pressing pressure is 0.12MPa or more, more excellent adhesion tends to be obtained. In addition, when the pressing pressure is 1.0MPa or less, more excellent productivity tends to be obtained. The pressing may be performed by pressing on a flat surface, or may be performed by loading a wire by a roller. The pressing pressure here means a pressure applied to the object to be adhered, and for example, when both the pressing force of the pressing mechanism of the apparatus and the atmospheric pressure are applied to the object to be adhered, the total pressure of the pressing force of the pressing mechanism of the apparatus and the atmospheric pressure is the pressing pressure.

The heating temperature is preferably 40 to 88 ℃, more preferably 45 to 80 ℃, and even more preferably 50 to 70 ℃ from the viewpoint of adhesion and productivity. When the heating temperature is 40 ℃ or higher, more excellent adhesion tends to be obtained. In addition, when the heating temperature is 88 ℃ or lower, more excellent productivity tends to be obtained.

The pressing or heating time is preferably 5 to 120 seconds, more preferably 10 to 60 seconds, and even more preferably 20 to 40 seconds from the viewpoints of adhesion and productivity. When the pressing time is 5 seconds or longer, more excellent adhesion tends to be obtained. In addition, when the press-fit time is 120 seconds or less, more excellent productivity tends to be obtained.

The atmospheric pressure in the case of reducing the pressure during the adhesion is preferably 50hPa or less, more preferably 10hPa or less, and still more preferably 5hPa or less from the viewpoints of adhesion and productivity. The lower limit of the atmospheric pressure is not particularly limited, and may be 0hPa.

(Process 2A)

The step 2A is a step of performing one or more treatments selected from grinding and singulation on the object.

Examples of one or more treatments selected from the grinding treatment and the singulation treatment include: grinding treatment using a grinder or the like; singulation based on a blade cutting method, a laser cutting method, a steph cutting (registered trademark) method; grinding treatment and singulation treatment based on a blade cutting-first method and a stealth cutting-first method; etc.

Among these, the singulation process by the sealth Dicing method, the grinding process and singulation process by the blade-first Dicing method, the grinding process and singulation process by the Stealth-first Dicing method are preferable, and the grinding process and singulation process by the blade-first Dicing method, and the grinding process and singulation process by the Stealth-first Dicing method are more preferable.

The sealth differentiation method is a method of forming a modified region in a semiconductor wafer by irradiating the inside of the semiconductor wafer with laser light, and Dicing the semiconductor wafer using the modified region as a Dicing origin. The modified region formed in the semiconductor wafer is a portion which is embrittled by multiphoton absorption, and after dicing, the semiconductor wafer is subjected to stress in a direction parallel to the wafer surface and in which the wafer expands, whereby the modified region is stretched toward the front and rear surface cracks of the semiconductor wafer from the start point, and the semiconductor wafer is singulated into semiconductor chips. That is, the modified region is formed along the dividing line when the singulation is performed.

The modified region is formed in the semiconductor wafer by irradiating laser light having a focal point focused in the semiconductor wafer. The incidence surface of the laser light may be the front surface or the back surface of the semiconductor wafer. In this case, the laser beam is irradiated to the semiconductor wafer through the adhesive sheet.

The blade-first-cut method is also referred to as the DBG method (Dicing Before Grinding, cutting-first-grinding-then-grinding). The dicing method is a method of forming grooves in advance along predetermined lines of dicing at a depth shallower than the thickness of the semiconductor wafer, and thereafter, back grinding the semiconductor wafer to make the ground surface at least up to the grooves, thereby thinning the semiconductor wafer, and simultaneously singulating the semiconductor wafer. The grooves reaching the ground surface are slits penetrating the semiconductor wafer, and the semiconductor wafer is divided by the slits to be singulated into semiconductor chips. The preformed grooves are usually provided on the surface (circuit surface) of the semiconductor wafer, and can be formed by dicing using a conventionally known wafer dicing apparatus or the like having dicing blades, for example.

The stealth pre-cut method is also known as the SDBG method (Stealth Dicing Before Grinding, stealth cut followed by grinding). The Stealth Dicing method is a method of forming a modified region in a semiconductor wafer by irradiating the inside of the semiconductor wafer with laser light and Dicing the semiconductor wafer using the modified region as a Dicing origin, similar to the Stealth Dicing method, but is different from the Stealth Dicing method in that the semiconductor wafer is thinned and diced into semiconductor chips while the semiconductor wafer is subjected to a grinding process. Specifically, the semiconductor wafer having the modified region is thinned by back grinding, and the semiconductor wafer is singulated into semiconductor chips by stretching a crack toward the adhesion surface of the adhesive layer to the semiconductor wafer starting from the modified region by the pressure applied to the semiconductor wafer at this time.

The thickness of the ground material after forming the modified region may be a thickness reaching the modified region, but even if the ground material does not exactly reach the modified region, the ground material may be cut by a working pressure of grinding stone or the like after reaching a position near the modified region.

When dicing the semiconductor wafer W by the blade dicing method, grooves are preferably formed in advance on the surface W1 of the semiconductor wafer W to be bonded to the adhesive layer (X2) in step 1A.

On the other hand, in the case of dicing the semiconductor wafer W by the stealth dicing method, the semiconductor wafer W to be bonded to the adhesive layer (X2) in step 1A may be irradiated with laser light to form the modified region in advance, or the semiconductor wafer W bonded to the adhesive layer (X2) may be irradiated with laser light to form the modified region.

Fig. 4 is a cross-sectional view illustrating a process of forming a plurality of modified regions 5 on a semiconductor wafer W bonded to an adhesive layer (X2) by using the laser irradiation apparatus 4.

Laser light is irradiated from the back surface W2 side of the semiconductor wafer W, whereby a plurality of modified regions 5 are formed substantially at equal intervals inside the semiconductor wafer W.

Fig. 5 (a) and (b) are cross-sectional views illustrating a process of thinning a semiconductor wafer W and singulating the wafer into a plurality of semiconductor chips CP.

As shown in fig. 5 (a), the rear surface W2 of the semiconductor wafer W on which the modified region 5 is formed is ground by the grinder 6, and at this time, the semiconductor wafer W is subjected to pressure so that the cleavage starting from the modified region 5 occurs. As a result, as shown in fig. 5 (b), a plurality of semiconductor chips CP obtained by thinning and singulating the semiconductor wafer W can be obtained.

For example, the back surface W2 of the semiconductor wafer W having the modified region 5 formed thereon is ground in a state in which the support 3 supporting the semiconductor wafer W is fixed to a fixing table such as a chuck table.

The thickness of the semiconductor chip CP after grinding is preferably 5 to 100 μm, more preferably 10 to 45 μm. In addition, in the case of performing the grinding treatment and the singulation treatment by the stealth dicing method, it is easy to make the thickness of the semiconductor chip CP obtained by grinding 50 μm or less, more preferably 10 to 45 μm.

The size of the semiconductor chip CP after grinding in plan view is preferably less than 600mm ² More preferably below 400mm ² Further preferably less than 300mm ² . The plane view means a view in the thickness direction.

The singulated semiconductor chips CP may have a rectangular shape in a plan view or may have a rectangular shape or other elongated shape.

(Process 3A)

The production method a preferably further includes the following step 3A.

Step 3A: a step of adhering a thermosetting film to the surface of the object subjected to the treatment on the side opposite to the adhesive layer (X2)

In the manufacturing method a, the step 3A is an arbitrary step, and may be a method not including the step 3A.

In the case of performing step 3A, the expansion initiation temperature (t) of the thermally expandable particles contained in the pressure-sensitive adhesive sheet used in the production method a is preferably 50 ℃ or higher and lower than 125 ℃. This can prevent the thermosetting film from being cured unexpectedly when the first separation step described later is performed.

Fig. 6 is a cross-sectional view illustrating a process of attaching the thermosetting film 7 provided with the support sheet 8 to the surface of the plurality of semiconductor chips CP on the opposite side of the adhesive layer (X2) obtained by the above-described process.

The thermosetting film 7 is a film having thermosetting properties obtained by forming a film of a resin composition containing at least a thermosetting resin, and is used as an adhesive in mounting the semiconductor chip CP on a substrate. The thermosetting film 7 may contain a curing agent for the thermosetting resin, a thermoplastic resin, an inorganic filler, a curing accelerator, and the like, as necessary.

As the thermosetting film 7, a thermosetting film which is generally used as, for example, a die bonding film, a die attach film, or the like can be used.

The thickness of the thermosetting film 7 is not particularly limited, but is usually 1 to 200. Mu.m, preferably 3 to 100. Mu.m, more preferably 5 to 50. Mu.m.

The support sheet 8 may be any material that supports the thermosetting film 7, and examples thereof include: the non-heat-expandable base material layer (Y2) included in the pressure-sensitive adhesive sheet according to one embodiment of the present invention is exemplified by a resin, a metal, a paper, or the like.

As a method of adhering the thermosetting film 7 to the plurality of semiconductor chips CP, for example, a method based on lamination is cited.

Lamination may be performed with or without heating. In the case of laminating while heating, the heating temperature is preferably "a temperature lower than the expansion start temperature (t)" and more preferably "an expansion start temperature (t) -5 ℃ or lower, further preferably" an expansion start temperature (t) -10 ℃ or lower, and still further preferably "an expansion start temperature (t) -15 ℃ or lower, from the viewpoint of suppressing expansion of the thermally expandable particles and suppressing thermal change of the adherend.

(first separation step)

The first separation step is a step of heating the adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles to separate the adhesive layer (X1) from the support.

Fig. 7 is a cross-sectional view illustrating a step of separating the pressure-sensitive adhesive layer (X1) from the support 3 by heating the pressure-sensitive adhesive sheet 2 a.

The heating temperature in the first separation step is preferably not less than the expansion initiation temperature (t) of the thermally expandable particles, more preferably not less than the expansion initiation temperature (t), still more preferably not less than the expansion initiation temperature (t) +2deg.C, still more preferably not less than the expansion initiation temperature (t) +4deg.C, still more preferably not less than the expansion initiation temperature (t) +5deg.C). In addition, from the viewpoints of energy saving and suppression of thermal change of the adherend during heat peeling, the heating temperature in the first separation step is in the range of 125 ℃ or lower, preferably "expansion start temperature (t) +50 ℃ or lower", more preferably "expansion start temperature (t) +40 ℃ or lower", and still more preferably "expansion start temperature (t) +20 ℃ or lower".

From the viewpoint of suppressing thermal change of the adherend, the heating temperature in the first separation step is preferably lower than 125 ℃, more preferably 120 ℃ or lower, still more preferably 115 ℃ or lower, still more preferably 110 ℃ or lower, still more preferably 105 ℃ or lower, in the range of the expansion initiation temperature (t) or higher. In particular, when the heating temperature in the first separation step is lower than 125 ℃, unexpected curing of the thermosetting film can be suppressed in the case of performing step 3A described above.

(second separation step)

The second separation step is a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed.

Fig. 8 is a cross-sectional view illustrating a process of separating the adhesive layer (X2) from the plurality of semiconductor chips CP.

The method of separating the adhesive layer (X2) from the plurality of semiconductor chips CP may be appropriately selected according to the type of the adhesive layer (X2). For example, in the case where the adhesive layer (X2) is an adhesive layer whose adhesive force is reduced by irradiation with energy rays, the adhesive layer (X2) may be separated after the adhesive force is reduced by irradiation with energy rays.

Through the above steps, a plurality of semiconductor chips CP adhered to the thermosetting film 7 can be obtained.

Next, the thermosetting film 7 to which the plurality of semiconductor chips CP are attached is preferably divided into the same shape as the semiconductor chips CP to obtain the semiconductor chips CP with the thermosetting film 7. As a method of dividing the thermosetting film 7, for example, there can be employed: laser cutting, expanding and fusing by laser.

Fig. 9 shows a semiconductor chip CP with a thermosetting film 7 divided into the same shape as the semiconductor chip CP.

The semiconductor chips CP with the thermosetting film 7 are further suitably subjected to a dicing step of expanding the intervals between the semiconductor chips CP, a rearranging step of arranging the plurality of semiconductor chips CP after the intervals are expanded, a flipping step of flipping the front and rear surfaces of the plurality of semiconductor chips CP, and the like, as necessary, and then attached (die-attached) to the substrate from the thermosetting film 7 side. Then, the thermosetting film is thermally cured, whereby the semiconductor chip and the substrate can be bonded.

The method for manufacturing the semiconductor device according to claim 2 may be as follows: an adhesive sheet having a laminated structure in which an adhesive layer (X1), a base layer (Y), and an adhesive layer (X2) are sequentially disposed is used as an adhesive sheet according to one embodiment of the present invention, and includes the following steps 1B to 2B, and a method for manufacturing the adhesive sheet (hereinafter, also referred to as "manufacturing method B") by the following first and second separation steps.

The production method B preferably further includes the following step 3B.

Step 3B: a step of adhering a thermosetting film to the surface of the object subjected to the treatment, which is opposite to the adhesive layer (X1)

In the manufacturing method B, the step 3B is an arbitrary step, or may be a method not including the step 3B.

In the case of performing step 3B, the expansion initiation temperature (t) of the thermally expandable particles contained in the pressure-sensitive adhesive sheet used in the production method B is preferably 50 ℃ or higher and lower than 125 ℃. This can prevent the thermosetting film from being cured unexpectedly when the first separation step described later is performed.

The step of adhering the object to be processed to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet 2a in step 1B is preferably performed on the surface (S) of the pressure-sensitive adhesive layer (X1) _X1 ) A surface of the adhesive sheet 2a to be adhered to the object (S _w ) The surface of the object to be processed is kept substantially parallel (S _w ) A surface (S) adhered to the adhesive layer (X1) _X1 ) (hereinafter, also referred to as "surface adhering step B").

The surface bonding step B may be, for example, the following steps: after the support 3 is adhered to the adhesive layer (X2) of the adhesive sheet 2a, the surface (S) of the adhesive layer (X1) of the adhesive sheet 2a to be adhered to the support 3 _X1 ) A surface of the adhesive sheet 2a to be adhered to the object (S _w ) The surface of the object to be processed is kept substantially parallel (S _w ) A surface (S) adhered to the adhesive layer (X1) _X1 ) And (3) working procedure.

Since the adhesive sheet according to one embodiment of the present invention has excellent adhesion, air stagnation at the adhesion interface between the adhesive sheet 2a and the object can be suppressed even when the surface adhesion step B is performed.

The bonding in step 1B may be performed while pressurizing, heating, depressurizing, etc. as needed, and the preferable conditions are the same as those described in step 1A.

The steps 1B to 3B can be described by replacing the adhesive layer (X1) with the adhesive layer (X2) and replacing the adhesive layer (X2) with the adhesive layer (X1) in the description of the steps 1A to 3A.

The first separation step is a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) to separate the pressure-sensitive adhesive layer (X1) from the object.

The heating conditions such as the heating temperature of the adhesive sheet in the first separation step are the same as those described in the production method a. In particular, in the case of performing step 3B, the first separation step is preferably a step of heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) and lower than 125 ℃ to separate the pressure-sensitive adhesive layer (X1) from the object.

In the first separation step, a plurality of semiconductor chips attached to the thermosetting film can be obtained. Thereafter, the thermosetting film can be divided to obtain semiconductor chips with thermosetting films, as in the case of the above-described manufacturing method a.

The second separation step is a step of separating the pressure-sensitive adhesive layer (X2) from the support.

The method of separating the adhesive layer (X2) from the support may be appropriately selected according to the type of the adhesive layer (X2). For example, in the case where the adhesive layer (X2) is an adhesive layer whose adhesive force is reduced by irradiation with energy rays, the adhesive layer (X2) may be separated after the adhesive force is reduced by irradiation with energy rays.

The production method B may include a second separation step.

< method for manufacturing semiconductor device according to other embodiment >

The method for manufacturing a semiconductor device according to the present invention is not limited to the method for manufacturing a semiconductor device according to the above-described 1 st and 2 nd modes, and may be a method for manufacturing a semiconductor device according to another mode different from the 1 st and 2 nd modes.

As another example of a method for manufacturing a semiconductor device according to another aspect, a method in which an object to be processed attached to another sheet is separated from the other sheet using the pressure-sensitive adhesive sheet according to one aspect of the present invention is given.

For example, a plurality of semiconductor chips, which are spread on a dicing tape, are stuck to the adhesive surface of the dicing tape, but the operation of picking up these chips one by one is very troublesome. In the method for manufacturing a semiconductor device according to one embodiment of the present invention, the adhesive layer (X1) of the adhesive sheet according to one embodiment of the present invention is adhered to the exposed surfaces of the plurality of semiconductor chips adhered to the dicing tape, and then the dicing tape is peeled off from the plurality of semiconductor chips, whereby the plurality of semiconductor chips can be separated from the dicing tape at one time.

Through the above steps, a plurality of semiconductor chips attached to the adhesive sheet according to one embodiment of the present invention can be obtained. The plurality of semiconductor chips can be easily separated by subsequently heating the adhesive layer (X1) to a temperature higher than the expansion initiation temperature (t) of the thermally expandable particles.

The separated plurality of semiconductor chips may be transferred to another adhesive sheet, or may be subjected to a rearrangement step of aligning the plurality of semiconductor chips after temporary separation.

Examples

The present invention will be specifically described with reference to the following examples, but the present invention is not limited to the following examples. The physical properties in each example were measured by the following method.

[ weight average molecular weight (Mw) ]

The values obtained by measuring the resultant sample under the following conditions using a gel permeation chromatography apparatus (product name "HLC-8020" manufactured by Tosoh Co., ltd.) and converting the sample into standard polystyrene were used.

(measurement conditions)

■ Chromatographic column: chromatographic columns comprising "TSK guard column HXL-L", "TSK gel G2500HXL", "TSK gel G2000HXL", "TSK gel G1000HXL" (manufactured by Tosoh Co., ltd.) connected in this order

■ Column temperature: 40 DEG C

■ Developing solvent: tetrahydrofuran (THF)

■ Flow rate 1.0mL/min

[ thickness of layers ]

The measurement was performed at 23℃using a constant pressure thickness gauge (model: PG-02J, standard: JIS K6783, Z1702, Z1709) manufactured by TECLOCK, inc.

[ average particle diameter of thermally-expansive particles (D ₅₀ ) 90% particle diameter (D) ₉₀ )]

The particle distribution of the thermally expandable particles before expansion at 23℃was measured using a laser diffraction type particle size distribution measuring apparatus (for example, manufactured by Malvern Co., ltd., product name "Mastersizer 3000").

Further, the cumulative volume frequency of the particles with small particle diameters in the particle distribution is calculatedThe particle diameters corresponding to 50% and 90% were used as "average particle diameter of thermally expandable particles (D ₅₀ ) 90% of the particle diameter (D ₉₀ )”。

[ method for measuring arithmetical average waviness (Wa) ]

The arithmetic average waviness (Wa) was measured based on JIS B0601:2013 using a scanning white light interference microscope (Hitachi Hi-Tech, product name "VS-1550", co., ltd.). To the surface (S) of the adhesive layer (X1) under the conditions of the measurement mode PSI and the objective lens of 10 times _X1 ) An image of a total of 100 sheets (overlapping ratio with the adjacent image of 10%) was obtained in a grid shape of 10 sheets in the vertical direction×10 sheets in the horizontal direction. Next, synthesis was performed by combining each image with an adjacent image, and the height data of the obtained synthesized image was processed with a gaussian filter having a cut-off value of 100 μm and a vibration transmission rate of 50%, to obtain a value of arithmetic average waviness (Wa).

In the following examples, details of materials used to form the respective layers are as follows.

< adhesive resin >

■ Acrylic copolymer (A1): a solution comprising an acrylic copolymer having a Mw of 60 tens of thousands, a diluent solvent: ethyl acetate, solid content concentration: 40 mass%, wherein the acrylic copolymer has a structural unit derived from a raw material monomer consisting of n-Butyl Acrylate (BA)/Methyl Methacrylate (MMA)/Acrylic Acid (AA)/2-hydroxyethyl acrylate (HEA) =86/8/1/5 (mass ratio)

< crosslinking agent >

■ Isocyanate-based crosslinking agent (i): the solution and solid content concentration of trimethylolpropane-modified toluene diisocyanate were contained under the product name "Coronate L" manufactured by Tosoh Corp: 75 mass%

< photopolymerization initiator >

■ Photopolymerization initiator (i): 1-hydroxycyclohexyl phenyl ketone

< additive >

■ Phthalocyanine pigment

< thermally-expansive particles >

■ Thermal expansion ofSex particles: nouryon company product name "Expancel (registered trademark) 031-40" (DU type), expansion initiation temperature (t) =88℃and average particle diameter (D ₅₀ ) =12.6 μm, 90% particle size (D ₉₀ )＝26.2μm

< Release Material >

■ Heavy release film: product name "SP-PET382150" of Lindeke, inc., film having a release agent layer formed of an organosilicon release agent provided on one side of a polyethylene terephthalate (PET) film, and having a thickness of 38 μm

Examples 1 to 10 and comparative examples 1 to 10: formation of adhesive sheet

(1) Formation of adhesive layer (X1)

1.38 parts by mass (solid content ratio) of an isocyanate-based crosslinking agent (i) was blended with 100 parts by mass of the solid content of the acrylic copolymer (A1), diluted with toluene, and stirred uniformly to prepare an adhesive composition (x-1) having a solid content concentration (active ingredient concentration) of 25% by mass.

Then, the prepared adhesive composition (X-1) was applied to the release surface of the re-release film to form a coating film, and the coating film was dried at 100℃for 60 seconds to form an adhesive layer (X1) having a thickness of 5. Mu.m.

(2) Preparation of solvent-free resin composition (y-1 a)

Reacting 2-hydroxyethyl acrylate with a terminal isocyanate urethane prepolymer obtained by reacting an ester type diol with isophorone diisocyanate (IPDI) gives an oligomer of weight average molecular weight (Mw) 5,000, which is a linear urethane prepolymer having ethylenically unsaturated groups at both terminals.

Then, 40 parts by mass (solid content ratio) of isobornyl acrylate (IBXA) as an energy ray polymerizable monomer and 20 parts by mass (solid content ratio) of phenyl hydroxypropyl acrylate (HPPA) were blended into 40 parts by mass (solid content ratio) of the above-described synthetic urethane prepolymer, and 2.0 parts by mass (solid content ratio) of a photopolymerization initiator (i), 0.2 parts by mass (solid content ratio) of a phthalocyanine pigment as an additive and 20 parts by mass of cyclohexyl acrylate (CHA) were further blended with respect to the total amount (100 parts by mass) of the urethane prepolymer and the energy ray polymerizable monomer, to prepare an energy ray curable composition.

Next, the energy ray-curable composition was mixed with thermally expandable particles, and the content of the thermally expandable particles was set to the content shown in table 1 with respect to the total mass (100 mass%) of the obtained thermally expandable base material layer (Y1). Then, any of the dispersion treatments shown in Table 1 was carried out to prepare a solvent-free resin composition (y-1 a) containing no solvent. Details of the dispersing process shown in table 1 are as follows.

(dispersion treatment)

Stirring: a cylindrical stirring bar (product name "PE05", 30 mm. Phi. Times.300 mm, manufactured by Kyowa Co., ltd.) was used to stir at 200rpm for 5 minutes.

And (3) filtering: filtration was performed using a tetron Mesh (# 200).

And (3) high-speed stirring treatment: a stirring apparatus (manufactured by Primix Co., ltd., product name "LABOLION") was equipped with a stirring paddle (manufactured by Primix Co., ltd., product name "Homomixer MARKII") and was cooled with water at 10℃for 20 minutes at 10,000 rpm.

(3) Formation of a substrate laminate comprising a thermally-expansive substrate layer (Y1) and a non-thermally-expansive substrate layer (Y2) laminated

As the non-heat-expandable base material layer (Y2), a PET film (product name "COSMESINE A4300", manufactured by Toyo Kabushiki Kaisha, thickness: 50 μm) was prepared.

Next, a solvent-free resin composition (Y-1 a) was applied to one side of the PET film so that the thickness of the thermally expandable base material layer (Y1) formed became the thickness shown in table 1, thereby forming a coating film.

Then, the irradiation was performed with an ultraviolet irradiation apparatus (product name "ECS-401GX" manufactured by Eye Graphics Co., ltd.) and a high-pressure mercury lamp (product name "H04-L41" manufactured by Eye Graphics Co., ltd.) at an illuminance of 160mW/cm ² Light quantity 500mJ/cm ² Ultraviolet rays were irradiated under the conditions of (a) to cure the coating film, and a thermal film having the thickness shown in Table 1 was formed on a PET film as a non-thermally-expansive base material layer (Y2)A base material laminate of an expandable base material layer (Y1). The illuminance and the light amount at the time of ultraviolet irradiation were measured using an illuminance/light meter (manufactured by EIT corporation, product name "UV Power Puck II").

(4) Formation of adhesive sheet

An adhesive sheet having the following structure was produced by bonding the adhesive surface of the adhesive layer (X1) formed in (1) to the surface of the thermally expandable base layer (Y1) of the base laminate formed in (2).

< heavy release film >/< adhesive layer (X1), thickness: 5 μm >/< thermally expandable substrate layer (Y1), thickness: thickness >/< non-thermally expandable substrate layer (Y2) described in Table 1, thickness: 50 μm >

FIG. 10 shows a face (S) obtained for calculating the arithmetic average waviness (Wa) of the adhesive sheet of example 1 _X1 ) FIG. 11 shows a plane (S) obtained for calculating the arithmetic average waviness (Wa) of the adhesive sheet of comparative example 9 _X1 ) Is a three-dimensional surface shape image of (a). Fig. 10 and 11 each show a region of about 16mm in the x-axis direction and about 12mm in the y-axis direction, and the scale in the z-axis direction is the same as that in fig. 10 and 11.

As can be seen from fig. 10 and 11, the surface (S) of the adhesive sheet of example 1 (fig. 10) having smaller arithmetic average waviness (Wa) than that of the adhesive sheet of example 1 _X1 ) The face (S) of the adhesive sheet of comparative example 9 (fig. 11) having a large arithmetic average waviness (Wa) _X1 ) There is a larger heave.

[ storage modulus E' (23) at 23℃of non-thermally-expansive base material layer (Y2) ]

As a test sample, a non-heat-expandable base material layer (Y2) cut into 30mm in the longitudinal direction and 5mm in the transverse direction was measured for storage modulus E' at 23℃under the conditions of a test initiation temperature of 0℃and a test termination temperature of 200℃and a temperature rise rate of 3℃per minute, a frequency of 1Hz and an amplitude of 20. Mu.m using a dynamic viscoelasticity measuring apparatus (product name "DMAQ800" manufactured by TA INSTRUMENTS Co.). As a result, the PET film as the non-heat-expandable base material layer (Y2) had a storage modulus E' (23) at 23℃of 2.27X10 ⁹ Pa。

[ evaluation of adhesion ]

The pressure-sensitive adhesive sheets obtained in each example were cut to a diameter of 300mm, and the re-release film was removed so that the surface (S) of the pressure-sensitive adhesive layer (X1) was exposed _x1 ) The plate rests on a flat surface in an upward manner. A silicon mirror wafer having a diameter of 300mm is placed thereon, and the mirror surface is made to be a surface (S) with the adhesive layer (X1) _x1 ) On the side in contact, the surface (S) holding the adhesive layer (X1) _x1 ) Is placed in a state substantially parallel to the mirror surface. A test sample was prepared by pressurizing the sample under a condition that the pressurizing temperature was 60℃and the set value of the pressurizing force of the pressurizing means was 0.2MPa for 30 seconds while the atmospheric pressure was reduced to 2hPa or less by using a vacuum laminator (product name "V-130" manufactured by Nikko Materials Co., ltd.). In the vacuum laminator, the total pressure of 0.3MPa, which is the total pressure of 0.2MPa and 0.1MPa, which is the pressure applied by the pressurizing mechanism of the apparatus, is the lamination pressure.

For the test samples obtained in each example, the presence of air retention at the bonding interface between the adhesive layer (X1) and the silicon mirror wafer was evaluated as "a" and the presence of air retention was evaluated as "F" when the presence of air retention was visually observed from the non-thermally expandable substrate layer (Y2) side. Since a material having transmittance is used as the thermally expandable base material layer (Y1) and the non-thermally expandable base material layer (Y2), the state of the adhesion interface between the silicon mirror wafer and the adhesive layer (X1) can be confirmed by the naked eye from the non-thermally expandable base material layer (Y2) side.

The evaluation results of each example are shown in table 1. Fig. 12 (a) and (b) show examples of the appearance photographs of the test sample corresponding to the evaluation "a", and fig. 13 (a) and (b) show examples of the appearance photographs of the test sample corresponding to the evaluation "F".

In fig. 12 and 13, fig. (b) is an enlarged photograph of the region outlined with a black dotted line in fig. (a). It is clear that in fig. 12, the presence of air stagnation was not confirmed, whereas in fig. 13, a plurality of island-like air stagnation (a portion having a relatively bright color) was present.

TABLE 1

The symbol "-" in the table indicates that the treatment is not performed

As is clear from Table 1, the adhesive layers (X1) of the adhesive sheets of examples 1 to 10 had surfaces (S _X1 ) The arithmetic average waviness (Wa) was 0.090 μm or less, and it was found that the adhesiveness was excellent. In contrast, the adhesive layers (X1) of the adhesive sheets of comparative examples 1 to 10 had a surface (S _X1 ) The arithmetic average waviness (Wa) of (C) was more than 0.090. Mu.m, and it was found that the adhesiveness was poor.

Claims

1. An adhesive sheet having a laminated structure comprising an adhesive layer (X1) and a base material layer (Y),

at least one of the adhesive layer (X1) and the base material layer (Y) is a thermally expandable layer containing thermally expandable particles,

a face (S) of the adhesive layer (X1) _X1 ) Has an arithmetic average waviness (Wa) of 0.090 μm or less, and the surface (S _X1 ) Is the surface opposite to the surface facing the substrate layer (Y).

2. The adhesive sheet according to claim 1, wherein the thickness of the thermally expandable layer before thermal expansion is 30 to 300 μm.

3. The adhesive sheet according to claim 1 or 2, wherein the content of the thermally expandable particles in the thermally expandable layer is 1 to 25 mass% relative to the total mass (100 mass%) of the thermally expandable layer.

4. The adhesive sheet according to any one of claims 1 to 3, wherein the expansion initiation temperature (t) of the thermally expandable particles is 50 ℃ or more and less than 125 ℃.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the base material layer (Y) is a base material laminate in which a thermally expandable base material layer (Y1) containing thermally expandable particles and a non-thermally expandable base material layer (Y2) are laminated, and the pressure-sensitive adhesive sheet has a laminated structure in which the pressure-sensitive adhesive layer (X1), the thermally expandable base material layer (Y1), and the non-thermally expandable base material layer (Y2) are arranged in this order.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, further comprising a pressure-sensitive adhesive layer (X2), wherein the pressure-sensitive adhesive sheet has a laminated structure in which the pressure-sensitive adhesive layer (X1), the base layer (Y), and the pressure-sensitive adhesive layer (X2) are disposed in this order.

7. The adhesive sheet according to claim 6, wherein the adhesive layer (X2) is an energy ray curable adhesive layer cured by irradiation of energy rays so that a decrease in adhesive force occurs.

8. A method for manufacturing a semiconductor device using the adhesive sheet according to claim 6 or 7, comprising the following steps 1A, 2A, first and second separating steps,

step 1A: a step of adhering a processing object to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet and adhering a support to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet;

step 2A: a step of performing one or more treatments selected from a grinding treatment and a singulation treatment on the object to be processed;

a first separation process: a step of separating the pressure-sensitive adhesive layer (X1) from the support by heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles;

and a second separation procedure: and a step of separating the pressure-sensitive adhesive layer (X2) from the object to be processed.

9. The method for manufacturing a semiconductor device according to claim 8, wherein an expansion start temperature (t) of the thermally expandable particles is 50 ℃ or higher and lower than 125 ℃,

After the step 2A, a step 3A of adhering a thermosetting film to the surface of the object subjected to the treatment on the opposite side of the pressure-sensitive adhesive layer (X2) is included,

the first separation step is a step of heating the adhesive sheet to a temperature equal to or higher than the expansion start temperature (t) and lower than 125 ℃ to separate the adhesive layer (X1) from the support.

10. The method for manufacturing a semiconductor device according to claim 8 or 9, wherein the step of adhering the support to the adhesive layer (X1) of the adhesive sheet in the step 1A is performed by applying the adhesive layer (X1) on a surface (S _X1 ) A surface to be bonded with the adhesive sheet of the support (S _s ) Maintaining the surfaces of the support body in a substantially parallel state (S _s ) Is adhered to the surface (S) of the adhesive layer (X1) _X1 ) Is a step of (a) a step of (b).

11. A method for manufacturing a semiconductor device using the adhesive sheet according to claim 6 or 7, comprising the following steps 1B, 2B, first and second separating steps,

step 1B: a step of adhering a processing object to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet and adhering a support to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet;

Step 2B: a step of performing one or more treatments selected from a grinding treatment and a singulation treatment on the object to be processed;

a first separation process: a step of separating the pressure-sensitive adhesive layer (X1) from the object by heating the pressure-sensitive adhesive sheet to a temperature equal to or higher than the expansion initiation temperature (t) of the thermally expandable particles;

and a second separation procedure: and a step of separating the adhesive layer (X2) from the support.

12. The method for manufacturing a semiconductor device according to claim 11, wherein an expansion start temperature (t) of the thermally expandable particles is 50 ℃ or higher and lower than 125 ℃,

after the step 2B, a step 3B of adhering a thermosetting film to the surface of the object subjected to the treatment on the opposite side of the pressure-sensitive adhesive layer (X1) is included,

13. The method for manufacturing a semiconductor device according to claim 11 or 12, wherein the step of adhering the object to be processed to the adhesive layer (X1) of the adhesive sheet in the step 1B is performed by forming the adhesive layer (X1) on a surface (S _X1 ) A surface of the adhesive sheet to be adhered to the object (S _w ) The surface of the object is kept substantially parallel (S _w ) Is adhered to the surface (S) of the adhesive layer (X1) _X1 ) Is a step of (a) a step of (b).