CN113825635A - Adhesive sheet, method for producing adhesive sheet, and method for producing semiconductor device - Google Patents

Adhesive sheet, method for producing adhesive sheet, and method for producing semiconductor device Download PDF

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Publication number
CN113825635A
CN113825635A CN202080024544.5A CN202080024544A CN113825635A CN 113825635 A CN113825635 A CN 113825635A CN 202080024544 A CN202080024544 A CN 202080024544A CN 113825635 A CN113825635 A CN 113825635A
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CN
China
Prior art keywords
pressure
sensitive adhesive
adhesive layer
adhesive sheet
energy ray
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202080024544.5A
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Chinese (zh)
Inventor
阿久津高志
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Lintec Corp
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Lintec Corp
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Publication of CN113825635A publication Critical patent/CN113825635A/en
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/30—Adhesives in the form of films or foils characterised by the adhesive composition
    • C09J7/38—Pressure-sensitive adhesives [PSA]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J11/00—Features of adhesives not provided for in group C09J9/00, e.g. additives
    • C09J11/02—Non-macromolecular additives
    • C09J11/06—Non-macromolecular additives organic
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J201/00—Adhesives based on unspecified macromolecular compounds
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J5/00—Adhesive processes in general; Adhesive processes not provided for elsewhere, e.g. relating to primers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J7/00—Adhesives in the form of films or foils
    • C09J7/20—Adhesives in the form of films or foils characterised by their carriers
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J9/00—Adhesives characterised by their physical nature or the effects produced, e.g. glue sticks
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J2203/00—Applications of adhesives in processes or use of adhesives in the form of films or foils
    • C09J2203/326—Applications of adhesives in processes or use of adhesives in the form of films or foils for bonding electronic components such as wafers, chips or semiconductors

Abstract

The present invention relates to an adhesive sheet comprising a substrate (Y), and an adhesive layer (X1) comprising a polymer containing an energy ray-polymerizable component and thermally expandable particles having an expansion starting temperature (t) of 50 to 110 ℃, wherein the adhesive layer (X1) is a layer formed by irradiating a polymerizable composition containing the energy ray-polymerizable component and the thermally expandable particles with an energy ray to form the polymer of the energy ray-polymerizable component.

Description

Adhesive sheet, method for producing adhesive sheet, and method for producing semiconductor device
Technical Field
The invention relates to an adhesive sheet, a method for manufacturing the adhesive sheet, and a method for manufacturing a semiconductor device.
Background
The pressure-sensitive adhesive sheet is used not only for the purpose of semi-permanently fixing a member, but also as a temporary fixing sheet for temporarily fixing a member (hereinafter, also referred to as an "adherend") to be processed or inspected when processing or inspecting a building material, an interior material, an electronic component, or 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 a manufacturing process of a semiconductor device, a semiconductor wafer is processed into semiconductor chips through a grinding process for reducing the thickness by grinding, a singulation process for singulation by cutting and separation, 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 subjected to a predetermined process are separated from the temporary fixing sheet, a spreading step of spreading the intervals between the semiconductor chips, a rearranging step of arranging the plurality of semiconductor chips with the spread intervals, an inverting step of inverting the front and back surfaces of the semiconductor chips, and the like are appropriately performed as necessary, and then the semiconductor chips are mounted on the substrate. In each of the steps described above, a temporary fixing sheet suitable for each application may be used.
Patent document 1 discloses a heat-peelable pressure-sensitive adhesive sheet for temporary fixation when an electronic component is cut, the pressure-sensitive adhesive sheet having a heat-expandable pressure-sensitive adhesive layer containing heat-expandable microspheres on at least one surface of a substrate. This document describes the following: the heat-peelable pressure-sensitive adhesive sheet can secure a contact area of a predetermined size with respect to an adherend when an electronic component is cut, and therefore can exhibit adhesiveness that can prevent poor adhesion such as chip splash, while can reduce the contact area with the adherend when the heat-expandable microspheres expand by heating after use, thereby achieving easy peeling.
Documents of the prior art
Patent document
Patent document 1: japanese patent No. 3594853
Disclosure of Invention
Problems to be solved by the invention
On the other hand, when mounting a semiconductor chip on a substrate, a process of attaching the semiconductor chip to the substrate via a film-like adhesive having thermosetting property called a die attach film (hereinafter, also referred to as "DAF") has been adopted.
The DAF is attached to one surface of the semiconductor wafer or the plurality of singulated semiconductor chips, and is divided into the same shape as the semiconductor chips simultaneously with or after the singulation of the semiconductor wafer. The semiconductor chip with DAF obtained by singulation is attached (die-bonded) to a substrate from the DAF side, and then the DAF is thermally cured to bond the semiconductor chip and the substrate. In this case, the DAF needs to have a property of being adhered by pressure or heat until it is attached to the substrate.
The heat-peelable pressure-sensitive adhesive sheet disclosed in patent document 1 is a material that is peeled from an adherend by forming irregularities on the pressure-sensitive adhesive surface by expanding thermally expandable microspheres. Since the adhesive sheet can reduce the contact area between the adhesive layer and the semiconductor chip by forming the irregularities, the adhesive sheet has an advantage that the adhesive sheet can be peeled from an adherend with a smaller force than a temporary fixing sheet in which the adhesive layer is cured by irradiation with an energy ray to reduce the adhesive strength.
However, when the semiconductor chip with DAF is an adherend of a heat-peelable adhesive sheet, the DAF may be cured immediately before die bonding due to heating when the thermally expandable microspheres are expanded, and the adhesion of the DAF to the substrate may be reduced. The decrease in the adhesive strength of the DAF causes a decrease in the bonding reliability between the semiconductor chip and the substrate, and therefore needs to be suppressed.
On the other hand, when a material having a low expansion start temperature is used as the thermally expandable microspheres of the heat-peelable adhesive sheet for the purpose of heat peeling at a low temperature in order to suppress the progress of curing of DAF before die attachment, there is a case where unexpected expansion of the thermally expandable microspheres occurs during the production of the adhesive sheet. As a result, the performance as a temporary fixing sheet may be impaired, for example, by a decrease in adhesive strength or by air intrusion during application (air entering between the adherend and the adhesive sheet).
The present invention has been made in view of the above problems, and an object of the present invention is to provide a pressure-sensitive adhesive sheet that can be peeled off at low temperature by heating despite having sufficient adhesive force at the time of temporary fixing, a method for producing the pressure-sensitive adhesive sheet, and a method for producing a semiconductor device using the pressure-sensitive adhesive sheet.
Means for solving the problems
The present inventors have found that the above problems can be solved by a pressure-sensitive adhesive sheet comprising a substrate, a pressure-sensitive adhesive layer comprising a polymer containing an energy ray-polymerizable component and heat-expandable particles having an expansion initiation temperature in a specific range, and a layer obtained by irradiating a polymerizable composition containing the energy ray-polymerizable component and the heat-expandable particles with an energy ray to form the polymer of the energy ray-polymerizable component.
That is, the present invention relates to the following [1] to [15 ].
[1] An adhesive sheet, comprising: a base material (Y), a binder layer (X1) comprising a polymer containing an energy ray-polymerizable component and heat-expandable particles having an expansion initiation temperature (t) of 50 to 110 ℃,
wherein the pressure-sensitive adhesive layer (X1) is a layer formed by irradiating a polymerizable composition containing the energy ray-polymerizable component and the thermally expandable particles with an energy ray to form a polymer of the energy ray-polymerizable component.
[2] The pressure-sensitive adhesive sheet according to item [1], wherein the content of the thermally expandable particles is 1 to 30% by mass based on the total mass (100% by mass) of the pressure-sensitive adhesive layer (X1).
[3] The adhesive sheet according to the above [1] or [2], wherein the adhesive layer (X1) has a thickness of 5 to 150 μm at 23 ℃.
[4] The adhesive sheet according to any one of the above [1] to [3], wherein the adhesive strength of the adhesive layer (X1) at 23 ℃ is 0.1 to 12.0N/25 mm.
[5] The adhesive sheet according to any one of the above [1] to [4], wherein the thermally expandable particles have an average particle diameter of 1 to 30 μm at 23 ℃.
[6] The adhesive sheet according to any one of [1] to [5], which comprises: a base material (Y), an adhesive layer (X1) provided on one surface side of the base material (Y), and an adhesive layer (X2) provided on the other surface side of the base material (Y).
[7] The pressure-sensitive adhesive sheet according to item [6], wherein the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer which is cured by irradiation with an energy ray and has a reduced adhesive strength.
[8] A method for producing a pressure-sensitive adhesive sheet according to any one of the above [1] to [7],
wherein the method of forming the adhesive layer (X1) comprises: and a step of irradiating the polymerizable composition containing the energy ray-polymerizable component and the thermally expandable particles with an energy ray to form a polymer of the energy ray-polymerizable component.
[9] The method for producing a pressure-sensitive adhesive sheet according to [8], wherein the method for forming the pressure-sensitive adhesive layer (X1) comprises the following steps I and II.
Step I: a step of forming a polymerizable composition layer on one surface side of the base material (Y), the polymerizable composition layer being formed from the polymerizable composition
And a step II: a step of irradiating the polymerizable composition layer with an energy ray to form a polymer of the energy ray-polymerizable component, thereby forming a pressure-sensitive adhesive layer (X1) containing the polymer and the thermally expandable particles
[10] The method for producing an adhesive sheet according to [8] or [9], wherein the polymerizable composition does not contain a solvent.
[11] The method for producing a pressure-sensitive adhesive sheet according to any one of [8] to [10], which does not include a step of heating the polymerizable composition.
[12] A method for manufacturing a semiconductor device, comprising the steps of:
the adhesive sheet according to any one of [1] to [7] wherein an object to be processed is adhered to the adhesive sheet,
subjecting the object to at least one treatment selected from grinding treatment and singulation treatment,
after the treatment, the adhesive sheet is heated to the expansion start temperature (t) or higher and 120 ℃ or lower to expand the adhesive layer (X1).
[13] A method for manufacturing a semiconductor device includes the following steps 1A to 5A.
Step 1A: a step of attaching an object to be processed to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet according to [6], and a step of attaching a support to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet
Step 2A: a step of subjecting the object to at least one treatment selected from grinding and singulation
Step 3A: a step of attaching a thermosetting film having thermosetting properties to the surface of the processed object on the opposite side of the pressure-sensitive adhesive layer (X2)
Step 4A: a step of heating the pressure-sensitive adhesive sheet to the expansion initiation temperature (t) or higher and 120 ℃ or lower to separate the pressure-sensitive adhesive layer (X1) from the support
Step 5A: separating the pressure-sensitive adhesive layer (X2) from the object
[14] The method for manufacturing a semiconductor device according to item [13], wherein,
the adhesive layer (X2) is an adhesive layer which is cured by irradiation of energy rays and thus undergoes a decrease in adhesive force,
the step 5A is a step of irradiating the pressure-sensitive adhesive layer (X2) with an energy ray to cure the pressure-sensitive adhesive layer (X2), thereby separating the pressure-sensitive adhesive layer (X2) from the object.
[15] A method for manufacturing a semiconductor device includes the following steps 1B to 4B.
Step 1B: a step of attaching an object to be processed to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet according to [6], and a step of attaching a support to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet
Step 2B: a step of subjecting the object to at least one treatment selected from grinding and singulation
Step 3B: a step of attaching a thermosetting film having thermosetting properties to the surface of the object subjected to the treatment opposite to the pressure-sensitive adhesive layer (X1)
Step 4B: a step of separating the pressure-sensitive adhesive layer (X1) from the object by heating the pressure-sensitive adhesive sheet to a temperature of not less than the expansion initiation temperature (t) and not more than 120 DEG C
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, it is possible to provide an adhesive sheet that can be peeled off at low temperature by heating despite having sufficient adhesive force at the time of temporary fixing, a method for producing the adhesive sheet, and a method for producing a semiconductor device using the adhesive sheet.
Drawings
Fig. 1 is a sectional view showing an example of the structure of the pressure-sensitive adhesive sheet of the present invention.
Fig. 2 is a sectional view showing an example of the structure of the pressure-sensitive 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 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.
Description of the symbols
1a, 1b, 2a, 2b adhesive sheet
10. 10a, 10b release material
3 support body
4 laser irradiation device
5 modified region
6 grinding machine
7 thermosetting film
8 supporting sheet
W semiconductor wafer
W1 semiconductor wafer and circuit surface of semiconductor chip
W2 semiconductor wafer and semiconductor chip back surface
CP semiconductor chip
Detailed Description
In the present specification, the "active ingredient" refers to a component other than the diluting solvent among the components contained in the target composition.
In the present specification, the weight average molecular weight (Mw) is a value in terms of standard polystyrene measured by a Gel Permeation Chromatography (GPC) method, specifically, a value measured by the method described in examples.
In the present specification, for example, "(meth) acrylic acid" means both "acrylic acid" and "methacrylic acid", and other similar terms are also used.
In the present specification, regarding a preferable numerical range (for example, a range of contents or the like), lower limit values and upper limit values described hierarchically may be independently combined. 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, "energy ray" means a ray having an energy quantum in an electromagnetic wave or a charged particle beam, and examples thereof include ultraviolet rays, radiation, electron beams, and the like. For example, an electrodeless lamp, a high-pressure mercury lamp, a metal halide lamp, a UV-LED, or the like may be used as the ultraviolet light source to irradiate ultraviolet light. As 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" indicates a property of causing polymerization by irradiation with an energy ray.
In the present specification, whether the "layer" is the "non-thermal expandable layer" or the "thermal expandable layer" is determined as follows.
When the layer to be evaluated contains the thermally expandable particles, the layer is subjected to a heating treatment at the expansion start temperature (t) of the thermally expandable particles for 3 minutes. When the volume change rate calculated from the following formula is less than 5%, the layer is determined to be a "non-thermally expandable layer", and when the volume change rate is 5% or more, the layer is determined 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 referred to as a "non-thermally expandable layer".
In this specification, the "front surface" of the semiconductor wafer and the semiconductor chip means a surface on which a circuit is formed (hereinafter, also referred to as "circuit surface"), and the "back surface" of the semiconductor wafer and the semiconductor chip means a surface on which no circuit is formed.
[ adhesive sheet ]
An adhesive sheet according to one embodiment of the present invention is an adhesive sheet comprising a substrate (Y), and an adhesive layer (X1) comprising a polymer containing an energy ray-polymerizable component and thermally expandable particles having an expansion start temperature (t) of 50 to 110 ℃, wherein the adhesive layer (X1) is a layer formed by irradiating a polymerizable composition containing the energy ray-polymerizable component and the thermally expandable particles with an energy ray to form the polymer containing the energy ray-polymerizable component.
In the psa sheet according to one embodiment of the present invention, the thermally expandable particles contained in the psa layer (X1) are expanded by heating to the expansion initiation temperature (t) or higher, thereby forming irregularities on the adhesive surface of the psa layer (X1) and causing the adhesive to peel off from the adherend. In the pressure-sensitive adhesive sheet according to one embodiment of the present invention, the uneven portions are formed, whereby the contact area between the pressure-sensitive adhesive layer (X1) and the adherend can be reduced, and therefore the adhesiveness between the pressure-sensitive adhesive sheet and the adherend can be significantly reduced. Thus, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be peeled from an adherend by the own weight of the pressure-sensitive adhesive sheet or the own weight of the adherend without applying a peeling force during thermal peeling. Specifically, for example, when the pressure-sensitive adhesive sheet according to one embodiment of the present invention is peeled from an adherend by heating, the pressure-sensitive adhesive sheet can be peeled by allowing the pressure-sensitive adhesive sheet side to face downward and allowing the pressure-sensitive adhesive sheet to fall from the adherend by gravity.
In the present specification, a state in which the pressure-sensitive adhesive sheet is peeled from an adherend without applying a peeling force to the pressure-sensitive adhesive sheet, or a case in which peeling occurs is referred to as "self-peeling". Such a property is referred to as "self-peelability".
As described above, the pressure-sensitive adhesive sheet according to one embodiment of the present invention is a material that reduces the contact area between the pressure-sensitive adhesive layer (X1) and an adherend during heat peeling, and therefore has superior self-peeling properties compared to a temporary fixing sheet in which the pressure-sensitive adhesive layer is cured by irradiation with energy rays and the adhesive strength is reduced.
Further, since the expansion start temperature (t) of the heat-expandable particles contained in the pressure-sensitive adhesive layer (X1) is a low temperature of 110 ℃ or lower, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be peeled off by heating at a low temperature. Thus, when a material that is likely to undergo thermal change, such as a semiconductor chip with DAF, is used as the adherend, thermal change due to heating during thermal peeling can be suppressed. On the other hand, by setting the expansion start temperature (t) of the thermally expandable particles to 50 ℃ or higher, it is possible to suppress the thermally expandable particles from expanding due to a temperature increase in the case of grinding or the like of the adherend.
The pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet according to one embodiment of the present invention is a layer obtained by irradiating a polymerizable composition containing an energy ray-polymerizable component and thermally expandable particles with an energy ray to form a polymer of the energy ray-polymerizable component. Since the polymerizable composition can be made to have a high molecular weight by the subsequent energy ray polymerization, the energy ray polymerizable component having a low molecular weight can be contained in the layer formation. Therefore, the polymerizable composition can be adjusted to a viscosity suitable for coating without using a solvent such as a diluent. As a result, when the pressure-sensitive adhesive layer (X1) is formed using the polymerizable composition, heat drying for removing the solvent can be omitted, and the unexpected expansion of the heat-expandable particles during heat drying can be suppressed.
The psa sheet according to one embodiment of the present invention may be configured to include the substrate (Y) and the psa layer (X1), but may include layers other than the substrate (Y) and the psa layer (X1) 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 adherend, from the viewpoint of improving the processability of the adherend, it is preferably a configuration (that is, a configuration of a double-sided pressure-sensitive adhesive sheet) having a substrate (Y), a pressure-sensitive adhesive layer (X1) provided on one surface side of the substrate (Y), and a pressure-sensitive adhesive layer (X2) provided on the other surface side of the substrate (Y). With this configuration, the adherend can be attached to the adhesive layer on one side of the adhesive layer (X1) or the adhesive layer (X2), and the support can be attached to the adhesive layer on the other side. By fixing the adherend to the support via the adhesive sheet, vibration, displacement, damage to a fragile object to be processed, and the like of the adherend can be suppressed during processing of the adherend, and the processing accuracy and processing speed can be improved.
In the following description, unless otherwise specified, "double-sided adhesive sheet" refers to an adhesive sheet having a substrate (Y), an adhesive layer (X1) provided on one surface side of the substrate (Y), and an adhesive layer (X2) provided on the other surface side of the substrate (Y).
The pressure-sensitive adhesive sheet according to one embodiment of the present invention may have a release agent on the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1). In the case where the pressure-sensitive adhesive sheet according to one embodiment of the present invention has a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer (X1) and/or the pressure-sensitive adhesive layer (X2) may have a release agent on the adhesive surface thereof.
Hereinafter, a structure of a pressure-sensitive adhesive sheet according to an embodiment of the present invention will be described in more detail with reference to the drawings.
[ constitution of adhesive sheet ]
As an example of the pressure-sensitive adhesive sheet according to an embodiment of the present invention, a pressure-sensitive adhesive sheet 1a having a pressure-sensitive adhesive layer (X1) on a substrate (Y) as shown in fig. 1(a) is mentioned.
The pressure-sensitive adhesive sheet according to one embodiment of the present invention may be configured to further include a release agent 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 a pressure-sensitive adhesive sheet according to another embodiment of the present invention, a pressure-sensitive adhesive sheet having the above-described double-sided pressure-sensitive adhesive sheet structure can be mentioned.
As an example of the pressure-sensitive adhesive sheet having such a structure, a double-sided pressure-sensitive adhesive sheet 2a having a structure in which a substrate (Y) is sandwiched between a pressure-sensitive adhesive layer (X1) and a pressure-sensitive adhesive layer (X2) is shown in fig. 2 (a).
As in the double-sided adhesive sheet 2b shown in fig. 2(b), the pressure-sensitive adhesive layer (X1) may further have a release liner 10a on the pressure-sensitive adhesive surface and the pressure-sensitive adhesive layer (X2) may further have a release liner 10b on the pressure-sensitive adhesive surface.
In the double-sided adhesive sheet 2b shown in fig. 2(b), when the peeling force when peeling the peeling member 10a from the adhesive layer (X1) and the peeling force when peeling the peeling member 10b from the adhesive layer (X2) are of the same level, the adhesive layer may be peeled off with the peeling members on both sides being cut off when the peeling members on both sides are pulled outward. From the viewpoint of suppressing such a phenomenon, it is preferable to use 2 types of release materials designed to have different release forces from the pressure-sensitive adhesive layers to be bonded to each other, as the release materials 10a and 10b on both sides.
As another embodiment of the psa sheet, the double-sided psa sheet 2a shown in fig. 2(a) may be a double-sided psa sheet having a structure in which a release material, both sides of which have been subjected to a release treatment, is laminated on the adhesive surface of one of the psa layer (X1) and the psa layer (X2) and then rolled up into a roll.
In the psa sheet according to one embodiment of the present invention, other layers may or may not be present between the substrate (Y) and the psa 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 or may not be provided between the substrate (Y) and the pressure-sensitive adhesive layer (X2), in addition to the above layers.
Among these, the pressure-sensitive adhesive layer (X1) is preferably one in which a layer capable of suppressing swelling on the surface opposite to the pressure-sensitive adhesive surface is directly laminated, and more preferably one in which the substrate (Y) is directly laminated.
< substrate (Y) >
Examples of the material for forming the substrate (Y) include resin, metal, and paper, and can be appropriately selected according to the use of the psa sheet according to one embodiment of the present invention.
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 copolymers, and ethylene-vinyl alcohol copolymers; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polystyrene; acrylonitrile-butadiene-styrene copolymers; cellulose triacetate; a polycarbonate; urethane resins such as polyurethane and acrylic-modified polyurethane; polymethylpentene; polysulfones; polyether ether ketone; polyether sulfone; polyphenylene sulfide; polyimide resins such as polyetherimide and polyimide; a polyamide-based resin; 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: thin paper, medium paper, high-quality paper, impregnated paper, coated paper, art paper, parchment paper, glassine paper and the like.
Among these, polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate are preferable.
These forming materials may be composed of one kind, or two or more kinds may be used in combination.
Examples of the base material (Y) using two or more kinds of forming materials in combination include: a material obtained by laminating a paper material with a thermoplastic resin such as polyethylene, a material obtained by forming a metal layer on the surface of a resin film or sheet containing a resin, or the like.
Examples of the method for forming the metal layer include: a method of depositing metal by a PVD method such as vacuum deposition, sputtering, or ion plating, a method of attaching a metal foil using a conventional adhesive, or the like.
From the viewpoint of improving the interlayer adhesiveness between the substrate (Y) and the other layer to be laminated, the surface of the substrate (Y) may be subjected to a surface treatment such as an oxidation method or a roughening method, an easy adhesion treatment, an undercoating treatment, or the like.
Examples of the oxidation method include: corona discharge treatment, plasma discharge treatment, chromic acid treatment (wet type), hot air treatment, ozone irradiation treatment, ultraviolet irradiation treatment, and the like. Examples of the method of forming the concavities and convexities include: sand blasting, solvent treatment, and the like.
The substrate (Y) may contain, as additives for substrates, for example, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, slip agents, antiblocking agents, colorants, and the like in addition to the above-mentioned resins. These additives for base materials may be used alone or in combination of two or more.
When the base material (Y) contains the resin and the additive for base material, the content of the additive for base material is preferably 0.0001 to 20 parts by weight, more preferably 0.001 to 10 parts by weight, based on 100 parts by weight of the resin.
The substrate (Y) is preferably a non-thermal expandable layer.
When the substrate (Y) is a non-thermally expandable layer, the volume change (%) of the substrate (Y) 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%, and still more preferably less than 0.01%.
The base material (Y) may contain thermally expandable particles within a range not departing from the object of the present invention, but preferably does not contain thermally expandable particles.
When the substrate (Y) contains the thermally expandable particles, the smaller the content thereof, the more preferable the content is, the less is 3 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, and still more preferably 0.001 mass% or less, based on the total mass (100 mass%) of the substrate (Y).
(storage modulus at 23 ℃ of base Material (Y) E' (23))
The storage modulus E' (23) of the base material (Y) at 23 ℃ is preferably 5.0X 107～5.0×109Pa, more preferably 5.0X 108～4.5×109Pa, more preferably 1.0X 109～4.0×109Pa。
The storage modulus E' (23) of the base material (Y) was 5.0X 107When Pa or more is used, the expansion of the surface of the pressure-sensitive adhesive layer (X1) on the substrate (Y) side can be effectively suppressed, and the deformation resistance of the pressure-sensitive adhesive sheet can be improved. On the other hand, the storage modulus E' (23) of the base material (Y) was 5.0X 109When Pa is less, the workability of the pressure-sensitive adhesive sheet can be improved.
In the present specification, the storage modulus E' (23) of the base material (Y) represents a value measured by the method described in examples.
(storage modulus E' (t) of base Material (Y) at expansion initiation temperature (t))
The storage modulus E' (t) of the base material (Y) at the expansion initiation temperature (t) of the thermally expandable particles is preferably 5.0 × 106～4.0×109Pa, more preferably 2.0X 108～3.0×109Pa, more preferably 5.0X 108～2.5×109Pa。
The storage modulus E' (t) of the base material (Y) was 5.0X 106When Pa or more is used, the expansion of the surface of the pressure-sensitive adhesive layer (X1) on the substrate (Y) side can be effectively suppressed, and the deformation resistance of the pressure-sensitive adhesive sheet can be improved. On the other hand, the storage modulus E' (t) of the base material (Y) was 4.0X 109When Pa is less, the workability of the pressure-sensitive adhesive sheet can be improved.
In the present specification, the storage modulus E' (t) of the base material (Y) represents a value measured by the method described in examples.
(thickness of base Material (Y))
The thickness of the base material (Y) is preferably 5 to 500. mu.m, more preferably 15 to 300. mu.m, and still more preferably 20 to 200. mu.m. When the thickness of the substrate (Y) is 5 μm or more, the deformation resistance of the adhesive sheet can be improved. On the other hand, when the thickness of the substrate (Y) is 500 μm or less, the workability of the adhesive sheet can be improved.
In the present specification, the thickness of the base material (Y) represents a value measured by the method described in examples.
< adhesive layer (X1) >
The pressure-sensitive adhesive layer (X1) contains a polymer of an energy ray-polymerizable component and thermally expandable particles.
Among the above polymers, the energy ray-polymerizable component is a polymer obtained by irradiating a polymerizable composition (hereinafter, also referred to as "polymerizable composition (x-1)") containing a monomer (a1) (hereinafter, also referred to as "component (a 1)") having an energy ray-polymerizable functional group and a prepolymer (a2) (hereinafter, also referred to as "component (a 2)") having an energy ray-polymerizable functional group with an energy ray.
In the present specification, the prepolymer refers to a compound that is obtained by polymerizing a monomer and that can be further polymerized to form a polymer.
(polymerizable composition (x-1))
The energy ray-polymerizable component contained in the polymerizable composition (x-1) is a component that is polymerized by irradiation with an energy ray, 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) acryloyl group, vinyl group, and allyl group. In the present specification, a functional group partially including a vinyl group or a substituted vinyl group, such as a (meth) acryloyl group, an allyl group, or the like, and a vinyl group or a substituted vinyl group itself are sometimes collectively referred to as a "vinyl group-containing group".
Hereinafter, each component contained in the polymerizable composition (x-1) will be described.
[ monomer (a1) having an energy ray-polymerizable functional group ]
The monomer (a1) 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 the energy ray-polymerizable functional group.
Examples of the hydrocarbon group contained in the component (a1) 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 may be an alicyclic hydrocarbon group.
Examples of the linear or branched aliphatic hydrocarbon group include: and aliphatic hydrocarbon groups having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a n-propyl group, an isopropyl group, a n-butyl group, a tert-butyl group, a sec-butyl group, a n-pentyl group, a n-hexyl group, a 2-ethylhexyl group, a n-octyl group, an isooctyl group, a n-decyl group, a n-dodecyl group, a n-myristyl group, a n-palmityl group, and a n-stearyl group.
Examples of the alicyclic hydrocarbon group include: alicyclic hydrocarbon groups having 3 to 20 carbon atoms such as cyclopentyl, cyclohexyl, isobornyl, and the like.
Examples of the aromatic hydrocarbon group include a phenyl group.
Examples of the group formed by combining an aliphatic hydrocarbon group and an aromatic hydrocarbon group include: phenoxyethyl, benzyl.
Among these hydrocarbon groups, the component (a1) preferably contains a monomer (a1-1) having an energy ray-polymerizable functional group and a linear or branched aliphatic hydrocarbon group (hereinafter, also referred to as the component (a 1-1)), a monomer (a1-2) having an energy ray-polymerizable functional group and an alicyclic hydrocarbon group (hereinafter, also referred to as the component (a 1-2)), and the like, from the viewpoint of further improving the adhesive strength of the adhesive layer (X1).
When the component (a1) contains the component (a1-1), the content thereof is preferably 20 to 80% by mass, more preferably 40 to 70% by mass, and still more preferably 50 to 60% by mass, based on the total (100% by mass) of the components (a 1).
When the component (a1) contains the component (a1-2), the content thereof is preferably 5 to 60% by mass, more preferably 10 to 40% by mass, and still more preferably 20 to 30% by mass, based on the total (100% by mass) of the components (a 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 functional group other than the energy ray-polymerizable functional group, such as a hydroxyl group, a carboxyl group, a thiol group, a primary amino group, or a secondary amino group. Among these functional groups, the component (a1) preferably contains a monomer (a1-3) having an energy ray-polymerizable functional group and a hydroxyl group (hereinafter also referred to as "component (a 1-3)") from the viewpoint of further improving the formability of the pressure-sensitive adhesive layer (X1).
When the component (a1) contains the component (a1-3), the content thereof is preferably 1 to 60% by mass, more preferably 5 to 30% by mass, and still more preferably 10 to 20% by mass, based on the total (100% by mass) of the components (a 1).
(a1) The number of the energy ray-polymerizable functional groups contained in the component (a) may be 1, or 2 or more. From the viewpoint of further improving the self-releasability of the pressure-sensitive adhesive layer (X1), the component (a1) preferably contains a monomer (a1-4) having 3 or more energy ray-polymerizable functional groups (hereinafter, also referred to as a "component (a 1-4)").
When the component (a1) contains the component (a1-4), the content thereof is preferably 1 to 20% by mass, more preferably 2 to 15% by mass, and still more preferably 3 to 10% by mass, based on the total (100% by mass) of the components (a 1).
The monomer having 1 energy ray-polymerizable functional group is preferably a monomer having 1 vinyl group (hereinafter, also referred to as "polymerizable vinyl monomer").
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 "polyfunctional (meth) acrylate monomer"). When the component (a1) contains the above-mentioned compound, the cohesive force of the adhesive obtained by polymerizing the compound is improved, and a pressure-sensitive adhesive layer (X1) with less contamination of an adherend after peeling can be formed.
Polymerizable vinyl monomer
The polymerizable vinyl monomer is not particularly limited as long as it is a monomer having a vinyl group, 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 component (a1-1) 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, and stearyl (meth) acrylate; compounds corresponding to the above-mentioned component (a1-2), such as cyclohexyl (meth) acrylate and isobornyl (meth) acrylate; and (meth) acrylates having no functional group other than a vinyl group in a molecule, such as phenoxyethyl (meth) acrylate, benzyl (meth) acrylate, and polyoxyalkylene-modified (meth) acrylate. 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 component (a1-3) 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, and the like. Further, as the polymerizable vinyl monomer having a carboxyl group, there can be mentioned: and 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 preferred.
Examples of the 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 alpha-methylstyrene; diene monomers such as butadiene, isoprene and chloroprene; nitrile monomers such as acrylonitrile and methacrylonitrile; amide monomers such as acrylamide, methacrylamide, N-methylmethacrylamide, N-dimethyl (meth) acrylamide, N-diethyl (meth) acrylamide, and N-vinylpyrrolidone; and tertiary amino group-containing monomers such as N, N-diethylaminoethyl (meth) acrylate and N- (meth) acryloylmorpholine.
Polyfunctional (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 alone or in combination of two or more.
As the polyfunctional (meth) acrylate monomer, for example, there can be mentioned: 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, hydroxypivalic acid neopentyl glycol di (meth) acrylate, dicyclopentyl di (meth) acrylate, caprolactone-modified dicyclopentyl di (meth) acrylate, ethylene oxide-modified phosphoric acid di (meth) acrylate, di (acryloyloxyethyl) isocyanurate, allylated cyclohexyl di (meth) acrylate, and ethylene oxide-modified isocyanurate; 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 (acryloyloxyethyl) isocyanurate, bis (acryloyloxyethyl) hydroxyethyl isocyanurate, polyfunctional (meth) acrylate monomers corresponding to the component (a1-4) described above, such as isocyanuric acid ethylene oxide-modified triacrylate, epsilon-caprolactone-modified tris (acryloyloxyethyl) isocyanurate, diglycerin tetra (meth) acrylate, pentaerythritol tetra (meth) acrylate, propionic acid-modified dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, and caprolactone-modified dipentaerythritol hexa (meth) acrylate.
(content of component (a 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 still 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 still more preferably 2 to 5% 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 component (a1) in the polymerizable composition (x-1) is preferably 15 to 90 mass%, more preferably 35 to 80 mass%, and still more preferably 55 to 75 mass%, based on the total amount (100 mass%) of the active ingredients in the polymerizable composition (x-1).
[ prepolymer (a2) having energy ray-polymerizable functional group ]
Examples of the energy ray-polymerizable functional group-containing prepolymer (a2) include: 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, the component (a2) 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, from the viewpoint of forming an adhesive layer excellent in self-releasability and less contamination of adherends after release.
The component (a2) preferably contains a prepolymer having 2 or more (meth) acryloyl groups as the energy ray-polymerizable functional group (hereinafter, also referred to as "polyfunctional (meth) acrylate prepolymer"). When the component (a2) contains the above-mentioned compound, the cohesive force of the pressure-sensitive adhesive obtained by polymerizing the compound is improved, and a pressure-sensitive adhesive layer (X1) which is excellent in self-releasability and is less contaminated with an adherend after peeling can be formed.
Polyfunctional (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 prepolymers can be suitably used.
The polyfunctional (meth) acrylate prepolymer may be used alone 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.
The urethane acrylate based prepolymer can be obtained by esterifying a polyurethane prepolymer, which is obtained by reacting a polyisocyanate with a compound such as a polyalkylene polyol, a polyether polyol, a polyester polyol, hydrogenated isoprene having a hydroxyl terminal, or hydrogenated butadiene having a hydroxyl terminal, with (meth) acrylic acid or a (meth) acrylic acid derivative.
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 preferred. When 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, or the like may be appropriately combined.
Examples of the polyisocyanate usable for the production of the urethane acrylate prepolymer include: aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylene diisocyanate; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, and diphenyl diisocyanate; and alicyclic diisocyanates such as dicyclohexylmethane diisocyanate and isophorone diisocyanate, and among these polyisocyanates, aliphatic diisocyanates are preferred, and hexamethylene diisocyanate is more preferred. The polyisocyanate is not limited to a bifunctional one, and a trifunctional or higher polyisocyanate 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; 2-isocyanoethyl acrylate, 2-isocyanoethyl methacrylate, 1-bis (acryloyloxymethyl) ethyl isocyanate, etc., and among these (meth) acrylic acid derivatives, 2-isocyanoethyl acrylate is preferred.
Other methods for producing urethane acrylate prepolymers include: 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 terminal, or hydrogenated butadiene having a hydroxyl terminal with a-N ═ C ═ O moiety of an isocyanoalkyl (meth) acrylate. In this case, as the isocyanoalkyl (meth) acrylate, for example: 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. Alternatively, the hydroxyl group at the end of a prepolymer obtained by adding an alkylene oxide to a polycarboxylic acid may be esterified with (meth) acrylic acid.
The epoxy acrylate prepolymer can be obtained by, for example, esterifying epoxy rings of a relatively low molecular weight bisphenol epoxy resin, a novolak epoxy resin, or the like by reacting them with (meth) acrylic acid. In addition, a carboxyl-modified epoxy acrylate prepolymer obtained by partially modifying an epoxy acrylate prepolymer with a dicarboxylic acid 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 acryloyl group at the side chain, or may have an acryloyl group at both or one of the ends. The polyacryl acrylate prepolymer having an acryloyl group in a side chain thereof can be obtained, for example, by adding glycidyl methacrylate to a carboxyl group of polyacrylic acid. The polyacrylate prepolymer having acryloyl groups at both ends can be obtained by introducing acryloyl groups at both ends by utilizing a polymerized long-end structure of a polyacrylate prepolymer synthesized by an ATRP (Atom Transfer Radical Polymerization) method, for example.
(a2) The weight average molecular weight (Mw) of the component (B) is preferably 10,000 to 350,000, more preferably 15,000 to 200,000, and still more preferably 20,000 to 50,000.
(content of component (a 2))
The total content of the polyfunctional (meth) acrylate prepolymers in the polymerizable composition (x-1) is preferably 10 to 60 mass%, more preferably 15 to 55 mass%, and still more preferably 20 to 30 mass% with respect to the total amount (100 mass%) of the active ingredients in the polymerizable composition (x-1).
The total content of the component (a2) 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 ingredients in the polymerizable composition (x-1).
The content ratio [ (a2)/(a1) ] of the component (a2) and the component (a1) in the polymerizable composition (x-1) is preferably 10/90 to 70/30, more preferably 20/80 to 50/50, and further preferably 25/75 to 40/60 on a mass basis.
Among the 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, further preferably 95% by mass or more, further 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 mass%, more preferably 75 to 97 mass%, even more preferably 80 to 96 mass%, and even more preferably 82 to 95 mass%, based on the total amount (100 mass%) of the active ingredients in the polymerizable composition (x-1).
[ Heat-expandable particles ]
The thermally expandable particles have an expansion initiation temperature (t) adjusted to 50 to 110 ℃.
The expansion start temperature (t) of the heat-expandable particles may be appropriately adjusted within the above range depending on the application of the pressure-sensitive adhesive sheet, and is preferably 55 ℃ or higher, more preferably 60 ℃ or higher, and even more preferably 70 ℃ or higher, for example, from the viewpoint of suppressing expansion of the heat-expandable particles due to temperature rise in the case of grinding or the like of the adherend, and is preferably 105 ℃ or lower, more preferably 100 ℃ or lower, and even more preferably 95 ℃ or lower, from the viewpoint of suppressing thermal change of the adherend when heat peeling is performed.
In the present specification, the expansion start temperature (t) of the thermally expandable particles is a value measured by the following method.
[ measurement method of expansion initiation temperature (t) of Heat-expansible particles ]
A sample was prepared by adding 0.5mg of the thermally expandable particles to be measured to an aluminum cup having a diameter of 6.0mm (inner diameter of 5.65mm) and a depth of 4.8mm, and covering the aluminum cup with an aluminum cover (diameter of 5.6mm and thickness of 0.1 mm).
The height of the sample was measured using a dynamic viscoelasticity measuring apparatus 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 sample was heated from 20 ℃ to 300 ℃ at a temperature rising rate of 10 ℃/min while a force of 0.01N was applied by the indenter, and the amount of displacement of the indenter in the vertical direction was measured, and the displacement start temperature in the positive direction was defined as the expansion start temperature (t).
The thermally expandable particles are preferably a microencapsulated blowing agent containing an outer shell made of a thermoplastic resin and an encapsulated component encapsulated by the outer shell and vaporized when heated to a predetermined temperature.
The thermoplastic resin constituting the shell of the microencapsulated blowing agent is not particularly limited, and a material and a composition which can be melted, dissolved, cracked or the like at the expansion starting temperature (t) of the thermally expandable particles, that is, 50 to 110 ℃ may be appropriately selected.
Examples of the thermoplastic resin include: vinylidene chloride-acrylonitrile copolymers, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, and the like. These thermoplastic resins may be used alone or in combination of two or more.
The encapsulated component, which is a component encapsulated by the shell of the microencapsulated blowing agent, may be any component that expands at 50 to 110 ℃ which is the expansion starting temperature (t) of the thermally expandable particles, and examples thereof include: and low-boiling point liquids such as propane, propylene, butene, n-butane, isobutane, isopentane, neopentane, n-pentane, n-hexane, isohexane, n-heptane, n-octane, cyclopropane, cyclobutane, and petroleum ether.
These inclusion components may be used alone or in combination of two or more.
The expansion start temperature (t) of the thermally expandable particles can be adjusted by appropriately selecting the type of the encapsulated component.
The average particle diameter of the thermally expandable particles before thermal expansion at 23 ℃ is preferably 1 to 30 μm, more preferably 4 to 25 μm, still more preferably 6 to 20 μm, and still more preferably 10 to 15 μm.
The average particle diameter (D) of the thermally expandable particles50) Means 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, a product name "Mastersizer 3000" manufactured by Malvern), the cumulative volume frequency calculated from particles having a small particle size corresponds to a particle size of 50%.
90% particle diameter (D) of thermally expandable particles at 23 ℃ before thermal expansion90) Preferably 2 to 60 μm, more preferably 8 to 50 μm, further preferably 12 to 40 μm, and further preferably 20 to 30 μm.
The heat-expandable particles have a particle diameter (D) of 90%90) The term "particle size distribution" refers to a particle size at which the cumulative volume frequency calculated from particles having a small particle size in the particle distribution of the thermally expandable particles before expansion, measured by the laser diffraction particle size distribution measuring apparatus, corresponds to 90%.
The maximum volume expansion ratio when the thermally expandable particles are heated to a temperature not lower 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, and still more preferably 3 to 100 times.
The content of the thermally expandable particles is preferably 1 to 30% by mass, more preferably 2 to 25% by mass, and still more preferably 3 to 20% by mass, based on the total amount (100% by mass) of the active ingredients in the polymerizable composition (X-1) or the total mass (100% by mass) of the pressure-sensitive adhesive layer (X1).
When the content of the thermally expandable particles is 1% by mass or more, the releasability at the time of thermal release tends to be improved. When the content of the thermally expandable particles is 30% by mass or less, the adhesive force of the adhesive layer (X1) tends to be good, and the adhesive sheet tends to be inhibited from warping during thermal peeling, thereby improving the handling properties.
[ other ingredients ]
The polymerizable composition (x-1) may contain other components in addition to the energy ray polymerizable component and the thermally expandable particles.
Examples of the other components include a photopolymerization initiator, a tackifier, and an additive for adhesives other than the above components, which is generally used for adhesives. Of these components, the polymerizable composition (x-1) preferably contains a photopolymerization initiator.
Photopolymerization initiator
By containing a photopolymerization initiator in the polymerizable composition (x-1), the polymerization of the energy ray-polymerizable component can be more efficiently performed.
Examples of the photopolymerization initiator include: benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, 2-dimethoxy-2-phenylacetophenone, 2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl ] -2-morpholinyl-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4' -diethylaminobenzophenone, Dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2, 4-dimethylthioxanthone, 2, 4-diethylthioxanthone, benzoin dimethyl ether, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligo [ 2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl ] acetone ], 2,4, 6-trimethylbenzoyl-diphenyl-phosphine oxide, and the like. The photopolymerization initiator may be used alone or in combination of two or more.
When the polymerizable composition (x-1) contains a photopolymerization initiator, the content thereof is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, and still more preferably 0.3 to 1 part by weight, based on 100 parts by weight of the energy ray polymerizable component.
When the content of the photopolymerization initiator is 0.1 parts by weight or more, the polymerization of the energy ray-polymerizable component can be more efficiently performed. On the other hand, when the content is 10 parts by weight or less, the residual photopolymerization initiator remaining unreacted can be eliminated or reduced, and the resulting pressure-sensitive adhesive layer (X1) can be easily adjusted to desired physical properties.
Tackifier
The tackifier is a component used as needed for the purpose of further improving the adhesive force.
In the present specification, the "tackifier" refers to a component having a weight average molecular weight (Mw) of less than 1 ten thousand, and is a component different from the adhesive resin described later.
The tackifier has a weight average molecular weight (Mw) of less than 1 ten thousand, preferably 400 to 9,000, more preferably 500 to 8,000, and further preferably 800 to 5,000.
Examples of the tackifier 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, which are produced by thermal decomposition of naphtha, C9-based petroleum resins obtained by copolymerizing C9 fractions such as indene and vinyl toluene, which are produced by thermal decomposition of naphtha, hydrogenated resins obtained by hydrogenating these resins, and the like.
The softening point of the thickener is preferably 60 to 170 ℃, more preferably 65 to 160 ℃, and further preferably 70 to 150 ℃.
In the present specification, the "softening point" of the thickener means a value measured in accordance with JIS K2531.
The tackifier may be used alone, or two or more different in softening point, structure, and the like may be used in combination. In the case where two or more tackifiers are used, it is preferable that the weighted average of the softening points of these multiple tackifiers fall within the above range.
When the polymerizable composition (x-1) contains a thickener, the content thereof 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, based on the total amount (100% by mass) of the active ingredients of the polymerizable composition (x-1).
Additive for adhesive
Examples of the additive for adhesives include: silane coupling agents, antioxidants, softeners (plasticizers), rust inhibitors, pigments, dyes, retarders, reaction promoters (catalysts), ultraviolet absorbers, and the like. These additives for adhesives may be used alone or in combination of two or more.
When the polymerizable composition (x-1) contains the additive for adhesives, the content of each additive for adhesives is preferably 0.0001 to 20 parts by weight, more preferably 0.001 to 10 parts by weight, based on 100 parts by weight of the energy ray polymerizable component.
The polymerizable composition (x-1) may contain a solvent such as a diluent, but preferably does not contain a solvent, within a range not departing from the object of the present invention. That is, the polymerizable composition (x-1) is preferably a solvent-free polymerizable composition.
By using the solvent-free polymerizable composition as the polymerizable composition (X-1), the heat drying of the solvent can be omitted when the pressure-sensitive adhesive layer (X1) is formed, and therefore the expansion of the heat-expandable particles during the heat drying can be suppressed. In addition, when a solvent is used, the thermally expandable particles may be unevenly present on one surface side with a decrease in volume during drying, and adhesion to the substrate (Y) or adhesive force of the adhesive surface may be reduced. On the other hand, the solvent-free polymerizable composition is not likely to cause the above-mentioned problems because the pressure-sensitive adhesive layer (X1) can be formed by polymerizing while maintaining the state in which the thermally expandable particles are uniformly dispersed in the energy ray polymerizable component.
When the polymerizable composition (x-1) contains a solvent, the smaller the content thereof, the more preferable the content is 10% by mass or less, more preferably 1% by mass or less, further preferably 0.1% by mass or less, and still further preferably 0.01% by mass or less with respect to the total amount (100% by mass) of the active ingredients of the polymerizable composition (x-1).
The polymerizable composition (x-1) can be produced by mixing the energy ray polymerizable component, the thermally expandable particles, and other components contained as needed. Since the resultant polymerizable composition (x-1) has a high molecular weight by the subsequent energy ray polymerization, the viscosity can be adjusted to an appropriate level by the low molecular weight energy ray polymerizable component when forming a layer. Therefore, the polymerizable composition can be used for forming the pressure-sensitive adhesive layer (X1) as 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 a wide variety of polymers polymerized from 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 the number of the polymers by the structure and physical properties.
(adhesive force at 23 ℃ C. of adhesive layer (X1) before thermal expansion)
The adhesive strength of the adhesive layer (X1) before thermal expansion at 23 ℃ 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, and still more preferably 1.2 to 7.5N/25 mm.
When the adhesive strength of the pressure-sensitive adhesive layer (X1) at 23 ℃ before thermal expansion is 0.1N/25mm or more, the occurrence of unintended peeling or displacement of the adherend relative to the adherend during temporary fixation can be more effectively suppressed. On the other hand, when the adhesive strength is 12.0N/25mm or less, the peelability at the time of heat peeling can be further improved.
In this specification, the adhesive force of the adhesive layer means the adhesive force of the mirror surface with respect to the silicon mirror surface wafer.
In the present specification, the adhesive force of the pressure-sensitive adhesive layer (X1) at 23 ℃ before thermal expansion is specifically a value measured by the method described in examples.
(adhesive force at 23 ℃ C. of adhesive layer (X1) after thermal expansion)
The adhesive strength of the pressure-sensitive adhesive layer (X1) at 23 ℃ after thermal expansion is preferably 1.5N/25mm or less, more preferably 0.05N/25mm or less, still more preferably 0.01N/25mm or less, and still more preferably 0N/25 mm. The adhesive force of 0N/25mm means an adhesive force not more than the measurement limit in the method of measuring an adhesive force at 23 ℃ after thermal expansion described later, and includes a case where the adhesive force is too small and peeling occurs unexpectedly when the adhesive sheet is fixed for measurement.
In the present specification, the adhesive force at 23 ℃ after thermal expansion of the adhesive layer (X1) is specifically a value measured by the method described in examples.
(shear storage modulus at 23 ℃ G' (23) of adhesive layer (X1))
The adhesive layer (X1) preferably has a storage modulus at 23 ℃ in shear G' (23) of 1.0X 104～5.0×107Pa, more preferably 5.0X 104～1.0×107Pa, more preferably 1.0X 105～5.0×106Pa。
The shear storage modulus G' (23) of the adhesive layer (X1) was 1.0X 104When Pa or more is used, displacement of the adherend at the time of temporary fixation, excessive sinking of the adherend into the adhesive layer (X1), and the like can be suppressed. On the other hand, the shear storage modulus G' (23) was 5.0X 107When Pa is less, unevenness tends to be formed on the surface of the pressure-sensitive adhesive layer (X1) by expansion of the thermally expandable particles, and the releasability at the time of thermal release tends to be improved.
In the present specification, the shear storage modulus G' (23) of the pressure-sensitive adhesive layer (X1) at 23 ℃ represents a value measured by the method described in examples.
The adhesive layer (X1) is a layer containing thermally expandable particles, and the shear storage modulus G' of the adhesive layer (X1) may be affected by the thermally expandable particles. From the viewpoint of measuring the shear storage modulus G ' after excluding the influence of the thermally expandable particles, a pressure-sensitive adhesive layer having the same configuration as that of the pressure-sensitive adhesive layer (X1) (hereinafter, also referred to as "non-expandable pressure-sensitive adhesive layer (X1 ')") except that the thermally expandable particles are not contained, and the shear storage modulus G ' of the pressure-sensitive adhesive layer can be measured.
(shear storage modulus G '(23) at 23 ℃ of non-expandable adhesive layer (X1'))
The shear storage modulus G '(23) at 23 ℃ of the non-expandable adhesive layer (X1') is preferably 1.0X 104～5.0×107Pa, more preferably 5.0X 104～1.0×107Pa, more preferably 1.0X 105～5.0×106Pa。
The shear storage modulus G '(23) of the non-expandable adhesive layer (X1') was 1.0X 104When Pa or more is used, displacement of the adherend during temporary fixation, excessive sinking of the adherend into the adhesive layer (X1), and the like can be suppressed. On the other hand, the shear storage modulus G' (23) was 5.0X 107When Pa is less, unevenness tends to be formed on the surface of the pressure-sensitive adhesive layer (X1) by expansion of the thermally expandable particles, and the releasability at the time of thermal release tends to be improved.
(shear storage modulus G '(t) at expansion onset temperature (t) of non-expandable adhesive layer (X1'))
The shear storage modulus G '(t) of the non-expandable adhesive layer (X1') at the expansion initiation temperature (t) of the thermally expandable particles is preferably 5.0 × 103～1.0×107Pa, more preferably 1.0X 104～5.0×106Pa, more preferably 5.0X 104～1.0×106Pa。
The non-expandable adhesive layer (X1 ') had a shear storage modulus G' (t) of 5.0X 103When Pa or more is used, the adhesive sheet tends to be prevented from warping during heat peeling and to improve workability, while preventing displacement of the adherend during temporary fixing, excessive sinking of the adherend into the adhesive layer (X1), and the like. On the other hand, the shear storage modulus G' (t) was 1.0X 107When Pa is less, unevenness tends to be formed on the surface of the pressure-sensitive adhesive layer (X1) by expansion of the thermally expandable particles, and the releasability at the time of thermal release tends to be improved.
In the present specification, the shear storage modulus G 'of the non-expandable adhesive layer (X1') at a given temperature represents a value measured by the method described in examples.
(thickness of adhesive layer (X1) at 23 ℃ C.)
The thickness of the pressure-sensitive adhesive layer (X1) at 23 ℃ is preferably 5 to 150 μm, more preferably 10 to 100 μm, and still more preferably 20 to 80 μm.
When the thickness of the pressure-sensitive adhesive layer (X1) is 5 μm or more at 23 ℃, sufficient adhesive force is easily obtained, and unexpected peeling from the adherend, displacement of the adherend, and the like during temporary fixation tend to be suppressed. On the other hand, when the thickness of the pressure-sensitive adhesive layer (X1) at 23 ℃ is 150 μm or less, the peelability during heat peeling tends to be improved, and the occurrence of warpage in the pressure-sensitive adhesive sheet during heat peeling tends to be suppressed, thereby improving the workability.
In the present specification, the thickness of the pressure-sensitive adhesive layer represents a value measured by the method described in examples. The thickness of the pressure-sensitive adhesive layer (X1) is a value before the thermal expansion particles expand.
< adhesive layer (X2) >
The adhesive layer (X2) is a layer optionally provided on the other surface side of the substrate (Y).
The adhesive layer (X2) may be a thermally expandable layer or a non-thermally expandable layer, but is preferably a non-thermally expandable layer. By making the mechanism of action of the pressure-sensitive adhesive layer (X1) and the pressure-sensitive adhesive layer (X2) to decrease the adhesive force of the pressure-sensitive adhesive layers different from each other, it is possible to suppress the unintended decrease in the adhesive force of the other pressure-sensitive adhesive layer when the treatment to decrease the adhesive force of either pressure-sensitive adhesive layer is performed.
In the case where the adhesive layer (X2) is a non-thermally expandable layer, the volume change (%) of the adhesive layer (X2) calculated from the above formula is less than 5%, preferably less than 2%, more preferably less than 1%, further preferably less than 0.1%, and still further preferably less than 0.01%.
The adhesive layer (X2) preferably does not contain 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 the thermally expandable particles, the smaller the content thereof, the more preferable the content is, the less 3 mass%, more preferably less 1 mass%, still more preferably less 0.1 mass%, still more preferably less 0.01 mass%, and still more preferably less 0.001 mass% of the total mass (100 mass%) of the pressure-sensitive adhesive layer (X2).
The adhesive layer (X2) is preferably formed from an adhesive composition (X-2) containing an adhesive resin. Hereinafter, each component contained in the pressure-sensitive adhesive composition (x-2) will be described.
(adhesive composition (x-2))
The pressure-sensitive adhesive composition (x-2) is a composition containing a pressure-sensitive adhesive resin, and may contain, if necessary, a crosslinking agent, a tackifier, a polymerizable compound, a polymerization initiator, and additives for pressure-sensitive adhesives generally used for pressure-sensitive adhesives other than the above components.
[ adhesive resin ]
The adhesive resin may be a polymer having adhesive properties and a weight average molecular weight (Mw) of 1 ten thousand or more.
From the viewpoint of further improving the adhesive force of the adhesive layer (X2), the weight average molecular weight (Mw) of the adhesive resin is preferably 1 to 200 ten thousand, more preferably 2 to 150 ten thousand, and even more preferably 3 to 100 ten thousand.
Examples of the adhesive resin include: rubber-based resins such as acrylic resins, urethane-based resins and polyisobutylene-based resins, polyester-based resins, olefin-based resins, silicone-based resins, and polyvinyl ether-based resins.
These adhesive resins may be used alone or in combination of two or more.
When the adhesive resin is a copolymer having two or more kinds of structural units, the form of the copolymer may be any of a block copolymer, a random copolymer, and a graft copolymer.
The pressure-sensitive adhesive composition (X-2) containing a pressure-sensitive adhesive resin is preferably a pressure-sensitive adhesive composition that is cured by irradiation with an energy ray, and the pressure-sensitive adhesive resin is more preferably a resin having an energy ray-polymerizable functional group in a side chain of the pressure-sensitive adhesive resin, from the viewpoint of making the mechanism of action of reducing the pressure-sensitive adhesive force with the pressure-sensitive adhesive layer (X1) different. By forming the pressure-sensitive adhesive composition, the pressure-sensitive adhesive layer (X2) can be a pressure-sensitive adhesive layer which is cured by irradiation with an energy ray and has a reduced adhesive force.
Examples of the energy ray-polymerizable functional group include: functional groups having a carbon-carbon double bond such as (meth) acryloyl group, vinyl group, and allyl group.
Among the above-mentioned energy rays, ultraviolet rays which are easy to handle are preferable as the energy rays.
The pressure-sensitive adhesive composition (x-2) may contain an energy ray-polymerizable functional group-containing pressure-sensitive adhesive resin, and may contain a monomer or prepolymer having an energy ray-polymerizable functional group instead of the energy ray-polymerizable functional group-containing pressure-sensitive adhesive resin.
Examples of the monomer or prepolymer having an energy ray-polymerizable functional group include those similar to the energy ray-polymerizable component contained in the polymerizable composition (x-1).
When the pressure-sensitive adhesive composition (x-2) is a pressure-sensitive adhesive composition which is cured by irradiation with an energy ray, the pressure-sensitive adhesive composition preferably further contains a photopolymerization initiator.
By containing a photopolymerization initiator, the polymerization of the energy ray-polymerizable component can be more efficiently performed.
Examples of the photopolymerization initiator include those similar to those optionally contained in the polymerizable composition (x-1).
The content of the photopolymerization initiator is preferably 0.01 to 10 parts by weight, more preferably 0.03 to 5 parts by weight, and still more preferably 0.05 to 2 parts by weight, based on 100 parts by weight of the total amount of the adhesive resin having an energy ray-polymerizable functional group, the monomer, and the prepolymer.
The adhesive resin preferably contains an acrylic resin from the viewpoint of exhibiting excellent adhesive force.
The content of the acrylic resin in the adhesive composition (x-2) 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-2).
The content of the adhesive resin in the adhesive composition (x-2) is preferably 35 to 100 mass%, more preferably 50 to 100 mass%, even more preferably 60 to 98 mass%, and even more preferably 70 to 95 mass% with respect to the total amount (100 mass%) of the active ingredients in the adhesive composition (x-2).
[ crosslinking agent ]
In one embodiment of the present invention, when the adhesive composition (x-2) contains an adhesive resin having a functional group, the adhesive composition (x-2) preferably further contains a crosslinking agent.
The crosslinking agent is a component that reacts with an adhesive resin having a functional group to crosslink the adhesive resins with each other with the functional group as a crosslinking starting point.
Examples of the crosslinking agent include: isocyanate crosslinking agents, epoxy crosslinking agents, aziridine crosslinking agents, metal chelate crosslinking agents, and the like.
One kind of the crosslinking agent may be used alone, or two or more kinds may be used in combination.
Among these crosslinking agents, isocyanate-based crosslinking agents are preferable from the viewpoint of improving cohesive force to improve adhesive force, and from the viewpoint of easiness in acquisition.
The content of the crosslinking agent may be appropriately adjusted depending on the number of functional groups contained in 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, based on 100 parts by mass of the adhesive resin having functional groups.
[ tackifier ]
In one embodiment of the present invention, the pressure-sensitive adhesive composition (x-2) may further contain a tackifier from the viewpoint of further improving the adhesive strength.
As the tackifier optionally contained in the adhesive composition (x-2), those equivalent to the tackifier optionally contained in the polymerizable composition (x-1) can be used.
[ additive for adhesive agent ]
Examples of the adhesive additive include those similar to those optionally contained in the polymerizable composition (x-1).
When the pressure-sensitive adhesive composition (x-2) does not contain the thermally expandable particles, the pressure-sensitive adhesive composition (x-2) may contain a solvent as needed because it is not necessary to avoid the heat drying that would reach the expansion starting temperature (t) of the thermally expandable particles or higher.
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, which are used as needed.
[ adhesive force of adhesive layer (X2) ]
The adhesive force of the adhesive surface of the adhesive layer (X2) is preferably 0.1 to 10.0N/25mm, more preferably 0.2 to 8.0N/25mm, still more preferably 0.4 to 6.0N/25mm, and still more preferably 0.5 to 4.0N/25 mm.
When the adhesive force of the adhesive surface of the pressure-sensitive adhesive layer (X2) is 0.1N/25mm or more, it is possible to more effectively suppress unintended peeling from the adherend at the time of temporary fixation, displacement of the adherend, and the like. On the other hand, when the adhesive strength is 10.0N/25mm or less, peeling is easily performed without damaging the adherend.
[ shear storage modulus G' (23) of adhesive layer (X2) at 23 ℃ ]
The shear storage modulus G' (23) of the adhesive layer (X2) at 23 ℃ is preferably 5.0X 103～1.0×107Pa, more preferably 1.0X 104～5.0×106Pa, more preferably 5.0X 104～1.0×106Pa。
The shear storage modulus G' (23) of the adhesive layer (X2) was 5.0X 103When Pa or more, there is a case where temporary fixation can be suppressedDisplacement of the adherend, excessive sinking of the adherend into the adhesive layer (X2), and the like. On the other hand, the shear storage modulus G' (23) was 1.0X 107When Pa is less, the adhesion to the adherend tends to be improved.
In the present specification, the shear storage modulus G '(23) of the pressure-sensitive adhesive layer (X2) at 23 ℃ can be measured by the same method as the shear storage modulus G' of the pressure-sensitive adhesive layer (X1) at 23 ℃.
[ thickness of adhesive layer (X2) at 23 ℃ ]
The thickness of the adhesive layer (X2) at 23 ℃ is preferably 5 to 150 μm, more preferably 8 to 100 μm, still more preferably 12 to 70 μm, and still more preferably 15 to 50 μm.
When the thickness of the pressure-sensitive adhesive layer (X2) is 5 μm or more at 23 ℃, sufficient adhesive force is easily obtained, and unexpected peeling from the adherend, displacement of the adherend, and the like during temporary fixation tend to be suppressed. On the other hand, when the thickness of the pressure-sensitive adhesive layer (X2) at 23 ℃ is 150 μm or less, handling of the pressure-sensitive adhesive sheet tends to be easy.
< Release Material >
As the release material, 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 obtained by coating a release agent 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 resins, polybutylene terephthalate resins, and polyethylene naphthalate resins; olefin resin films such as polypropylene resins and polyethylene resins, and examples of the paper include: high quality paper, cellophane, kraft paper, and the like.
Examples of the release agent include: rubber elastomers such as silicone resins, olefin resins, isoprene resins, and butadiene resins; long-chain alkyl resins, alkyd resins, fluorine resins, and the like. The releasing agent may be used alone or in combination of two or more.
The thickness of the release material is preferably 10 to 200 μm, more preferably 20 to 150 μm, and further preferably 35 to 80 μm.
[ method for producing adhesive sheet ]
In a method for producing a pressure-sensitive adhesive sheet according to an embodiment of the present invention, a method for forming a pressure-sensitive adhesive layer (X1) includes the steps of: and a step of irradiating the polymerizable composition (x-1) containing the energy ray polymerizable component and the thermally expandable particles with an energy ray to form a polymer of the energy ray polymerizable component.
The method for forming the pressure-sensitive adhesive layer (X1) preferably includes the following steps I and II.
Step I: a step of forming a polymerizable composition layer made of the polymerizable composition (x-1) on one surface side of the base material (Y);
and a step II: and a step of irradiating the polymerizable composition layer with an energy ray to form a polymer of the energy ray polymerizable component, thereby forming a pressure-sensitive adhesive layer (X1) containing the polymer and the thermally expandable particles.
< Process I >
The step I is not particularly limited as long as it is a step of forming a polymerizable composition layer on one surface side of the substrate (Y), but preferably includes the following steps I-1 to I-3.
Step I-1: a step of applying a polymerizable composition (x-1) to the release-treated surface of the release material to form a polymerizable composition layer;
step I-2: a step of irradiating the polymerizable composition layer with a first energy ray to prepolymerize the energy ray-polymerizable component in the polymerizable composition layer;
step I-3: and (d) a step of attaching a base material (Y) to the polymerizable composition layer after the first energy ray irradiation.
(Process I-1)
The step I-1 is a step of applying the polymerizable composition (x-1) to the release-treated surface of the release material to form a polymerizable composition layer.
In the step I-1, examples of the method for applying the polymerizable composition (x-1) to the release material include: spin coating, spray coating, wire bar coating, blade coating, roll coating, blade coating, die coating, gravure coating, and the like.
The polymerizable composition (x-1) is preferably a solventless polymerizable composition, as described above. When the polymerizable composition (x-1) is a solvent-free polymerizable composition, the heating and drying step of the solvent may not be performed in this step. On the other hand, in the case where the polymerizable composition (x-1) contains a solvent within a range not departing from the object of the present invention, the polymerizable composition (x-1) may be applied and then dried by heating, but the heating temperature in this case is set to be lower than the expansion starting temperature (t) of the thermally expandable particles.
(Process I-2)
The step I-2 is a step of irradiating the polymerizable composition layer formed in the step I-1 with a first energy ray to prepolymerize the energy ray-polymerizable component in the polymerizable composition layer.
The first energy ray irradiation is performed for the purpose of: the energy ray-polymerizable component is prepolymerized to increase the viscosity of the polymerizable composition, thereby improving the shape retention of the polymerizable composition layer.
In the first energy ray irradiation, the energy ray-polymerizable component is not completely polymerized, but remains only in the prepolymerization. This improves the adhesion between the polymerizable composition layer and the base (Y) in the step I-3.
Among the energy rays, ultraviolet rays which are easy to handle are preferable as the energy rays used for the first energy ray irradiation in the step I-2.
The preferred illuminance of ultraviolet rays in the first energy ray irradiation is 70-250 mW/cm2More preferably 100-200 mW/cm2More preferably 130 to 170mW/cm2. The amount of ultraviolet light in the first energy ray irradiation is preferably 40 to 200mJ/cm2More preferably 60 to 150mJ/cm2More preferably 80 to 120mJ/cm2。
The first energy ray irradiation may be performed once or may be performed in a plurality of times. In addition, in order to suppress the temperature increase of the polymerizable composition layer due to the heat of polymerization or the like, the irradiation may be performed while cooling the polymerizable composition layer.
(Process I-3)
The step I-3 is a step of bonding the base material (Y) to the polymerizable composition layer after the first energy ray irradiation.
The method for adhering the base material (Y) to the polymerizable composition layer is not particularly limited, and examples thereof include: a method of laminating the substrate (Y) on the side where the polymerizable composition layer is exposed.
The lamination may be performed while heating or without heating, but is preferably performed without heating from the viewpoint of suppressing expansion of the thermally expandable particles. In this case, the polymerizable composition layer which is prepolymerized by the irradiation with the first energy ray has good adhesion to the substrate (Y) even without heating.
< Process II >
The step II is a step of irradiating the polymerizable composition layer formed in the step I with an energy ray to form a polymer of an energy ray polymerizable component, and forming a pressure-sensitive adhesive layer (X1) containing the polymer and thermally expandable particles.
Here, in the case where the first energy ray irradiation is performed in the step I, the energy ray irradiation in the step II is the second energy ray irradiation performed on the polymerizable composition layer after the preliminary polymerization.
The irradiation with energy rays in the step II is preferably performed to such an extent that the polymerization of the energy ray-polymerizable component does not proceed substantially any more even if the energy rays are further irradiated, unlike the irradiation with the first energy rays.
The energy ray-polymerizable component is polymerized by the irradiation with the energy ray in step II, thereby forming a polymer of the energy ray-polymerizable component constituting the pressure-sensitive adhesive layer (X1).
Among the energy rays, ultraviolet rays which are easy to handle are preferable as the energy rays used for the irradiation of the energy rays in the step II.
The illuminance of ultraviolet rays in the energy ray irradiation in the step II is preferablyIs 100-350 mW/cm2More preferably 150-300 mW/cm2More preferably 180 to 250mW/cm2。
The amount of ultraviolet light in the energy ray irradiation in the step (II) is preferably 500 to 4,000mJ/cm2More preferably 1,000 to 3,000mJ/cm2More preferably 1,500 to 2,500mJ/cm2。
The energy ray irradiation in step II may be performed once or in multiple steps. In addition, in order to suppress the temperature increase of the polymerizable composition layer due to the heat of polymerization or the like, the irradiation may be performed while cooling the polymerizable composition layer.
When the step I includes the above-mentioned steps I-1 to I-3, the polymerizable composition layer is obtained as an intermediate layer of a laminate in which a release material, the polymerizable composition layer, and the substrate (Y) are sequentially laminated. In this case, the second energy ray irradiation may be performed on the laminate having the above configuration. In this case, from the viewpoint of sufficiently irradiating the energy ray to the polymerizable composition layer present as the intermediate layer of the laminate, it is preferable that at least one selected from the release material and the substrate (Y) has energy ray transparency.
In view of suppressing expansion of the thermally expandable particles, it is preferable that all of the steps included in the above-mentioned steps I and II do not include a step of heating the polymerizable composition.
The term "heating" as used herein means, for example, intentionally heating at the time of drying, laminating, or the like, and does not include a temperature rise due to heat applied to the polymerizable composition by energy ray irradiation, polymerization heat generated by polymerization of the energy ray polymerizable composition, or the like.
When the step of heating the polymerizable composition is included if necessary, the heating temperature is preferably "a temperature lower than the expansion start temperature (t)", more preferably "the expansion start temperature (t) -5 ℃ or lower", still more preferably "the expansion start temperature (t) -10 ℃ or lower", and still more preferably "the expansion start temperature (t) -15 ℃ or lower". When the temperature of the polymerizable composition is unexpectedly increased, it is preferable to cool the polymerizable composition so that the temperature of the polymerizable composition falls within the above temperature range.
When the pressure-sensitive adhesive sheet according to an embodiment of the present invention has the above-described configuration of the double-sided pressure-sensitive adhesive sheet, the method for producing a pressure-sensitive adhesive sheet according to an embodiment of the present invention preferably further includes the following step III.
< step III >
And a step III: a step of forming an adhesive layer (X2) on the other surface side of the substrate (Y)
The method for forming the pressure-sensitive adhesive layer (X2) may be appropriately determined depending on the type of the composition constituting the pressure-sensitive adhesive layer (X2). For example, when the pressure-sensitive adhesive layer (X2) is formed using the pressure-sensitive adhesive composition (X-2), the step III preferably includes the following steps III-1 and III-2.
Step III-1: a step of applying the pressure-sensitive adhesive composition (X-2) to one side of a release material to form a pressure-sensitive adhesive layer (X2)
Step III-2: a step of adhering the pressure-sensitive adhesive layer (X2) formed in step III-1 to the other surface side of the substrate (Y)
In the step III-1, the same method as that described for the step I-1 of applying the polymerizable composition (x-1) can be used as the method of applying the adhesive composition (x-2). When the pressure-sensitive adhesive layer (X2) contains a solvent, the pressure-sensitive adhesive composition (X-2) may be applied and then the coating film may be dried.
As described above, it is preferable to design the release material used in step III-1 and the release material used in step I-1 so that the release forces are different from each other in order to suppress the phenomenon in which the pressure-sensitive adhesive layer is separated and peeled off by being cut off together with the two release materials.
In the step III-2, as a method for attaching the pressure-sensitive adhesive layer (X2) to the base material (Y), the same method as the method for attaching the base material (Y) to the polymerizable composition layer in the step I-3 can be used, and the same is applied to the preferred embodiment.
[ use and method of Using adhesive sheet ]
The pressure-sensitive adhesive sheet according to one embodiment of the present invention has sufficient adhesive force at the time of temporary fixation and can be peeled off by heating at low temperature, and therefore, is applicable to various applications. Specifically, it is applicable to, for example: a dicing sheet used when dicing an adherend such as a semiconductor wafer, a back grinding sheet used in a step of grinding the adherend, a spreading tape for extending a distance between adherends such as semiconductor chips singulated by dicing, a transfer tape for inverting the front and back surfaces of the adherend such as semiconductor chips, a temporary fixing sheet used when temporarily fixing the adherend for inspection of an inspection object, 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, panel substrates, and the like. The pressure-sensitive adhesive sheet according to one embodiment of the present invention can be peeled off by heating at a low temperature, and is therefore suitable for temporarily fixing an adherend such as a semiconductor chip with DAF, which is likely to be thermally changed.
The heating temperature at the time of heat peeling the pressure-sensitive adhesive sheet of one embodiment of the present invention from an adherend is not less than the expansion start temperature (t) of the heat-expandable particles, preferably "a temperature higher than the expansion start temperature (t)", more preferably "the expansion start temperature (t) +2 ℃", still more preferably "the expansion start temperature (t) +4 ℃", and yet more preferably "the expansion start temperature (t) +5 ℃". From the viewpoints of energy saving and suppression of thermal change of the adherend during heat peeling, the expansion start temperature (t) +50 ℃ ", more preferably the expansion start temperature (t) +40 ℃", and still more preferably the expansion start temperature (t) +20 ℃ ", are preferably not higher.
In addition, from the viewpoint of suppressing thermal change of the adherend, the heating temperature at the time of heat peeling is within a range of not less than the expansion start temperature (t), preferably not more than 120 ℃, more preferably not more than 115 ℃, further preferably not more than 110 ℃, and still further preferably not more than 105 ℃.
The heating method is not particularly limited as long as it is a method capable of heating to a temperature at which the thermally expandable particles expand, and for example: an electric heater; induction heating; magnetic heating; heating by electromagnetic waves such as near infrared rays, intermediate infrared rays, and infrared rays such as far infrared rays. The heating method may be any of a contact heating method such as a heating roller and a heating press, a non-contact heating method such as an atmosphere heating device and 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 can be mentioned: an embodiment in which the adhesive sheet according to one embodiment of the present invention is used as a temporary fixing sheet for processing an adherend (hereinafter, also referred to as "method for manufacturing a semiconductor device according to the first embodiment").
< method for manufacturing semiconductor device of first embodiment >
As a more specific aspect of the method for manufacturing a semiconductor device according to the first aspect, there is provided a method for manufacturing a semiconductor device including the steps of: the pressure-sensitive adhesive sheet according to one embodiment of the present invention is obtained by sticking an object to be processed to a pressure-sensitive adhesive sheet, subjecting the object to one or more treatments (hereinafter, also referred to as "processing treatments") selected from a grinding treatment and a singulation treatment, and thereafter heating the pressure-sensitive adhesive sheet to the expansion start temperature (t) or higher and 120 ℃ or lower to expand the pressure-sensitive adhesive layer (X1).
In this specification, the term "semiconductor device" refers to all devices that can function by utilizing semiconductor characteristics. Examples thereof include: a wafer provided with an integrated circuit, a thinned wafer provided with an integrated circuit, a chip provided with an integrated circuit, a thinned chip provided with an integrated circuit, an electronic component including these chips, an electronic device provided with the electronic component, and the like.
In the method for manufacturing a semiconductor device according to the first aspect, the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet to which the object to be processed is to be attached may be the pressure-sensitive adhesive layer (X1), or in the case where the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, the pressure-sensitive adhesive layer may be the pressure-sensitive adhesive layer (X2).
When the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, the object to be processed is preferably attached to one pressure-sensitive adhesive layer and the support is preferably attached to the other pressure-sensitive adhesive layer. By fixing the object to be processed to the support via the adhesive sheet, vibration, displacement, damage to the fragile object, and the like of the object can be suppressed during processing, and processing accuracy and processing speed can be improved. In this case, the support may be attached to the adhesive layer (X1) and the object may be attached to the adhesive layer (X2), or the object may be attached to the adhesive layer (X1) and the support may be attached to the adhesive layer (X2).
In the case of the form in which the support is attached to the pressure-sensitive adhesive layer (X1) and the object is attached to the pressure-sensitive adhesive layer (X2), by attaching the support to the pressure-sensitive adhesive layer (X1) having excellent peelability after the heat treatment, even if the support is made of a hard material, the pressure-sensitive adhesive sheet and the support can be peeled off by heating without causing bending. The composition of the pressure-sensitive adhesive layer (X2) may be appropriately selected depending on the type of the object, and for example, when the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer whose adhesive force is reduced by irradiation with energy rays, the pressure-sensitive adhesive layer can be peeled without contaminating the object with residues derived from the thermally expandable particles.
On the other hand, in the case of the form in which the object is attached to the pressure-sensitive adhesive layer (X1) and the support is attached to the pressure-sensitive adhesive layer (X2), by attaching the object to the pressure-sensitive adhesive layer (X1) having excellent peelability after the heat treatment, the object can be peeled from the pressure-sensitive adhesive sheet by self-peeling when the object is thermally peeled after processing, and therefore, damage to the object can be reduced.
When a double-sided adhesive sheet is used as the adhesive sheet according to one embodiment of the present invention, the method for manufacturing a semiconductor device according to the first embodiment preferably includes the following steps 1A to 5A (hereinafter also referred to as "manufacturing method a").
Step 1A: a step of attaching the object to be processed to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet and attaching the support to the pressure-sensitive adhesive layer (X1)
Step 2A: a step of subjecting the object to at least one treatment selected from grinding and singulation
Step 3A: a step of attaching a thermosetting film to the surface of the object subjected to the above-described treatment, which is opposite to the pressure-sensitive adhesive layer (X2)
Step 4A: a step of heating the adhesive sheet to the expansion initiation temperature (t) or higher and 120 ℃ or lower to separate the adhesive layer (X1) from the support
Step 5A: separating the pressure-sensitive adhesive layer (X2) from the object
Hereinafter, a method for manufacturing a semiconductor device including steps 1A to 5A will be described with reference to the drawings. In the following description, an example in which a semiconductor wafer is used as an object to be processed will be mainly described, but the same applies to other objects to be processed.
(Process 1A)
Step 1A is a step of attaching the object to be processed to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet and attaching the support to the pressure-sensitive adhesive layer (X1).
Fig. 3 is a cross-sectional view illustrating a step of attaching the semiconductor wafer W to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet 2a and attaching the support 3 to the pressure-sensitive adhesive layer (X1).
The semiconductor wafer W is bonded so that the front surface W1, which is a circuit surface, is on the side of the pressure-sensitive adhesive layer (X2).
The semiconductor wafer W may be a silicon wafer, or a wafer or a glass wafer such as gallium arsenide, silicon carbide, sapphire, lithium tantalate, lithium niobate, gallium nitride, or indium phosphide.
The thickness of the semiconductor wafer W before grinding is usually 500 to 1000 μm.
The circuit provided on the front surface W1 of the semiconductor wafer W can be formed by a conventional general method such as an etching method or a lift-off method.
The material of the support 3 may be appropriately selected in consideration of required characteristics such as mechanical strength and heat resistance, depending on the type of the object to be processed, the content of processing, and the like.
Examples of the material of the support 3 include: metal materials such as SUS; non-metallic inorganic materials such as glass and silicon wafers; epoxy resin, ABS resin, acrylic resin, engineering plastic, special engineering plastic, polyimide resin, polyamide-imide resin and other resin materials; and composite materials such as glass epoxy resins, and of these materials, SUS, glass, and silicon wafers are preferable.
Examples of the engineering plastics include: nylon, Polycarbonate (PC), polyethylene terephthalate (PET), and the like.
Examples of the special engineering plastics include: polyphenylene Sulfide (PPS), polyether sulfone (PES), polyether ether ketone (PEEK), and the like.
The support 3 is preferably attached to the entire surface of the adhesive layer (X1). Therefore, the surface of the support 3 stuck to the pressure-sensitive adhesive layer (X1) on the pressure-sensitive adhesive surface side is preferably equal to or larger than the area of the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer (X1). The surface of the support 3 attached to the adhesive surface side of the adhesive layer (X1) is preferably flat.
The shape of the support 3 is not particularly limited, but is preferably plate-like.
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, and more preferably 60 μm or more and 20mm or less.
(step 2A)
The step 2A is a step of applying one or more treatments selected from grinding treatment and singulation treatment to the object.
Examples of the one or more treatments selected from the grinding treatment and the singulation treatment include: grinding treatment using a grinder or the like; singulation processing by a blade Dicing method, a laser Dicing method, a steadh Dicing (registered trademark) method, a blade tip Dicing method, an invisible tip Dicing method, or the like.
Among these, the singulation process by the Stealth Dicing method, the grinding process and singulation process by the blade tip Dicing method, and the grinding process and singulation process by the invisible tip Dicing method are preferable, and the grinding process and singulation process by the blade tip Dicing method, and the grinding process and singulation process by the invisible tip Dicing method are more preferable.
The Stealth Dicing method is a method of forming a modified region in a semiconductor wafer by irradiating the semiconductor wafer with laser light, and singulating the semiconductor wafer with the modified region as a dividing starting point. The modified region formed in the semiconductor wafer is a portion which is embrittled by multiphoton absorption, and the semiconductor wafer is subjected to a stress in a direction parallel to the wafer surface and in which the wafer is expanded by expanding, whereby cracks are extended toward the front surface and the back surface of the semiconductor wafer from the modified region as a starting point, and the semiconductor wafer is singulated into semiconductor chips. That is, the modified region is formed along the dividing line in the singulation.
The modified region is formed inside the semiconductor wafer by irradiating the semiconductor wafer with laser light having a focal point focused inside the semiconductor wafer. The laser light incidence surface may be the front surface or the back surface of the semiconductor wafer. In addition, the laser light entrance surface may be a surface to which an adhesive sheet is attached, in which case laser light is irradiated to the semiconductor wafer via the adhesive sheet.
The blade tip cutting method is also called a DBG method (cutting Before Grinding). The blade tip dicing method is a method in which a groove is formed in advance on a semiconductor wafer along a line to be divided to a depth shallower than the thickness thereof, and then the semiconductor wafer is subjected to back grinding for thinning the semiconductor wafer until the ground surface reaches at least the groove, and is singulated. The grooves where the grinding surfaces have reached become cuts penetrating the semiconductor wafer, and the semiconductor wafer is divided into individual semiconductor chips by the cuts. The groove formed in advance is 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 provided with a dicing blade.
The Stealth tip cutting method is also called an SDBG method (Stealth cutting Before Grinding). The Stealth tip Dicing method is one of methods for forming a modified region in a semiconductor wafer by laser irradiation and singulating the semiconductor wafer with the modified region as a division starting point, similarly to the Stealth Dicing method, but is different from the Stealth Dicing method in that the semiconductor wafer is thinned while the semiconductor wafer is diced into semiconductor chips. Specifically, the semiconductor wafer having the modified region is thinned by back grinding, and the semiconductor wafer is singulated into semiconductor chips by stretching the crack toward the bonding surface of the adhesive layer to the semiconductor wafer from the modified region as a starting point by a pressure applied to the semiconductor wafer at this time.
The grinding thickness after the formation of the reformed region may be a thickness reaching the reformed region, but may be a thickness not reaching the reformed region precisely, and may be cut by a machining pressure such as a grinding stone after grinding to a position near the reformed region.
When the semiconductor wafer W is singulated by the blade tip dicing method, a groove is preferably formed in advance in the front surface W1 of the semiconductor wafer W to be bonded to the pressure-sensitive adhesive layer (X2) in step 1A.
On the other hand, when the semiconductor wafer W is singulated by the stealth tip dicing method, the semiconductor wafer W to be bonded to the pressure-sensitive adhesive layer (X2) in step 1A may be irradiated with a laser beam to form a reformed region in advance, or the semiconductor wafer W bonded to the pressure-sensitive adhesive layer (X2) may be irradiated with a laser beam to form a reformed region.
Fig. 4 is a cross-sectional view illustrating a step of forming a plurality of modified regions 5 on the semiconductor wafer W attached to the pressure-sensitive adhesive layer (X2) by using the laser irradiation apparatus 4.
The rear surface W2 of the semiconductor wafer W is irradiated with laser light, so that a plurality of modified regions 5 are formed at substantially equal intervals inside the semiconductor wafer W.
Fig. 5 is a cross-sectional view illustrating a process of grinding the rear surface W2 of the semiconductor wafer W on which the reformed region 5 is formed by the grinder 6, and thinning the semiconductor wafer W while cutting from the reformed region 5 as a starting point to singulate the semiconductor wafer W into a plurality of semiconductor chips CP.
The semiconductor wafer W having the modified region 5 formed thereon is ground with its back surface W2 in a state where the support body 3 supporting the semiconductor wafer W is fixed to a fixing table such as a chuck table, for example.
The thickness of the semiconductor chip CP after grinding is preferably 5 to 100 μm, more preferably 10 to 45 μm. In addition, when the grinding process and the singulation process are performed by the stealth tip dicing method, it is easy to set the thickness of the semiconductor chip CP obtained by grinding to 50 μm or less, more preferably 10 to 45 μm.
The size of the ground semiconductor chip CP in plan view is preferably less than 600mm2More preferably below 400mm2More preferably less than 300mm2. The plan view is a view seen in the thickness direction.
The shape of the singulated semiconductor chip CP in a plan view may be a rectangular shape or an elongated shape such as a rectangular shape.
(step 3A)
Step 3A is a step of attaching a thermosetting film to the surface of the object subjected to the above treatment opposite to the pressure-sensitive adhesive layer (X2).
Fig. 6 is a cross-sectional view illustrating a step of attaching the thermosetting film 7 including the supporting sheet 8 to the surface of the plurality of semiconductor chips CP obtained by the above-described treatment opposite to the pressure-sensitive adhesive layer (X2).
The thermosetting film 7 is a film having thermosetting properties obtained by forming a resin composition containing at least a thermosetting resin, and is used as an adhesive when the semiconductor chip CP is mounted 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 needed.
As the thermosetting film 7, a thermosetting film generally used as, for example, a die bonding 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, and more preferably 5 to 50 μm.
The support sheet 8 may be made of any material that supports the thermosetting film 7, and examples thereof include: examples of the substrate (Y) of the psa sheet according to one embodiment of the present invention include resins, metals, and paper materials.
As a method of attaching the thermosetting film 7 to the plurality of semiconductor chips CP, for example, a method by lamination is cited.
The lamination may be performed while heating or may be performed without heating. In the case of laminating the heat-expandable particles while heating, the heating temperature is preferably "a temperature lower than the expansion start temperature (t)", more preferably "the expansion start temperature (t) -5 ℃", even more preferably "the expansion start temperature (t) -10 ℃", and even more preferably "the expansion start temperature (t) -15 ℃" from the viewpoint of suppressing the expansion of the heat-expandable particles and the thermal change of the adherend.
(step 4A)
Step 4A is a step of heating the pressure-sensitive adhesive sheet to the expansion start temperature (t) or higher and 120 ℃ or lower to separate the pressure-sensitive adhesive layer (X1) from the support.
Fig. 7 is a 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 step 4A is in the range of not less than the expansion starting temperature (t) of the thermally expandable particles and not more than 120 ℃, preferably "a temperature higher than the expansion starting temperature (t)", more preferably "the expansion starting temperature (t) +2 ℃", still more preferably "the expansion starting temperature (t) +4 ℃", and yet still more preferably "the expansion starting temperature (t) +5 ℃". In addition, from the viewpoint of energy saving and suppression of thermal change of the adherend during heat peeling, the expansion starting temperature (t) +50 ℃ is preferably 120 ℃ or lower, more preferably "expansion starting temperature (t) +40 ℃ or lower", and still more preferably "expansion starting temperature (t) +20 ℃ or lower".
The heating temperature in step 4A is in the range of not less than the expansion start temperature (t), preferably not more than 115 ℃, more preferably not more than 110 ℃, and still more preferably not more than 105 ℃ from the viewpoint of suppressing the thermal change of the adherend.
(step 5A)
Step 5A is a step of separating the pressure-sensitive adhesive layer (X2) from the object.
Fig. 8 is a cross-sectional view illustrating a process of separating the adhesive layer (X2) and 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 pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer whose adhesive strength is reduced by irradiation with energy rays, the pressure-sensitive adhesive layer (X2) may be irradiated with energy rays to reduce the adhesive strength and then separated.
Through the above steps 1A to 5A, a plurality of semiconductor chips CP attached to the thermosetting film 7 can be obtained.
Next, it is preferable to obtain the semiconductor chip CP with the thermosetting film 7 by dividing the thermosetting film 7 to which the plurality of semiconductor chips CP are attached into the same shape as the semiconductor chip CP. As a method for dividing the thermosetting film 7, for example: laser cutting, sheet expanding, fusing, etc. by laser.
Fig. 9 shows the semiconductor chip CP with the thermosetting film 7 divided into the same shape as the semiconductor chip CP.
The semiconductor chips CP with the thermosetting film 7 are further subjected to a spreading step of spreading the intervals between the semiconductor chips CP, a rearranging step of arranging the plurality of semiconductor chips CP with the spread intervals, an inverting step of inverting the front and back surfaces of the plurality of semiconductor chips CP, and the like as necessary, and then bonded (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 fixed together.
In the manufacturing method according to one embodiment of the present invention, the step 3A may not be included in the manufacturing method a. When the step 3A is not included, the following step 4A' may be included instead of the step 4A.
Step 4A': a step of heating the pressure-sensitive adhesive sheet to the expansion initiation temperature (t) or higher to separate the pressure-sensitive adhesive layer (X1) from the support
In the case of using a double-sided adhesive sheet as the adhesive sheet according to one embodiment of the present invention, the method for manufacturing a semiconductor device according to the first embodiment may be a manufacturing method including the following steps 1B to 4B (hereinafter, also referred to as "manufacturing method B").
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 subjecting the object to at least one treatment selected from grinding and singulation
Step 3B: a step of attaching a thermosetting film having thermosetting properties to the surface of the processed object on the opposite side of the pressure-sensitive adhesive layer (X1)
Step 4B: a step of separating the pressure-sensitive adhesive layer (X1) from the object by heating the pressure-sensitive adhesive sheet to a temperature of not less than the expansion initiation temperature (t) and not more than 120 DEG C
In the steps 1B to 3B, the pressure-sensitive adhesive layer (X1) and the pressure-sensitive adhesive layer (X2) in the descriptions of the steps 1A to 3A are replaced with the pressure-sensitive adhesive layer (X2) and the pressure-sensitive adhesive layer (X1), respectively.
Step 4B is a step of heating the pressure-sensitive adhesive sheet to the expansion start temperature (t) or higher and 120 ℃ or lower to separate the pressure-sensitive adhesive layer (X1) from the object.
The heating conditions such as the heating temperature of the adhesive sheet in step 4B are the same as those described in step 4A.
In step 4B, a plurality of semiconductor chips attached to the thermosetting film can be obtained. Thereafter, as in the case of the above-described manufacturing method a, the thermosetting film is divided to obtain semiconductor chips with thermosetting films.
The production method B may include a step 5B of separating the pressure-sensitive adhesive layer (X2) from the support after the step 4B.
The method for separating the pressure-sensitive adhesive layer (X2) from the support may be appropriately selected depending on the type of the pressure-sensitive adhesive layer (X2). For example, in the case where the pressure-sensitive adhesive layer (X2) is a pressure-sensitive adhesive layer whose adhesive strength is reduced by irradiation with energy rays, the pressure-sensitive adhesive layer (X2) may be irradiated with energy rays to reduce the adhesive strength and then separated.
In the manufacturing method according to one embodiment of the present invention, the step 3B may not be included in the manufacturing method B. When step 3B is not included, step 4B' may be included instead of step 4B.
Step 4B': a step of separating the pressure-sensitive adhesive layer (X1) from the object by heating the pressure-sensitive adhesive sheet to the expansion initiation temperature (t) or higher
< method for manufacturing semiconductor device of another embodiment >
The method for manufacturing a semiconductor device of the present invention is not limited to the method for manufacturing a semiconductor device of the first embodiment, and may be a method for manufacturing a semiconductor device of another embodiment different from the first embodiment.
As an example of a method for manufacturing a semiconductor device according to another aspect, there is a method in which the adhesive sheet according to one aspect of the present invention is used as a temporary fixing sheet for inspecting an inspection target as one part of a manufacturing process. Examples of the inspection object include: optical microscopes, defect inspections using laser light (for example, dust inspection, surface scratch inspection, wiring pattern inspection, and the like), surface inspections by visual inspection, and the like.
Examples of the object to be examined include: semiconductor chips, semiconductor wafers, compound semiconductors, semiconductor packages, electronic components, LED elements, sapphire substrates, displays, panel substrates, and the like.
When the pressure-sensitive adhesive sheet according to one embodiment of the present invention is used as a temporary fixing sheet for inspecting an inspection object, the inspection can be performed in a state where a plurality of inspection objects are attached to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet. After the inspection, for example, a part of the pressure-sensitive adhesive layer (X1) to which the plurality of inspection objects are attached may be locally heated, and a specific inspection object attached to the part may be selectively peeled off by heating. In this case, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be heat-peeled at a low temperature, and therefore, the workability and energy saving performance of the heat-peeling operation are excellent, and even if the inspection object is a material that is susceptible to thermal change, thermal change of the inspection object caused by heating at the time of heat peeling can be suppressed.
As another example of the method for manufacturing a semiconductor device according to another embodiment, a method for separating an object to be processed, which is stuck to another sheet, from the other sheet by using the adhesive sheet according to one embodiment of the present invention is given.
For example, a plurality of semiconductor chips with enlarged intervals on the tape are stuck to the adhesive surface of the tape, but the operation of picking up the 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 attached to the exposed surfaces of the plurality of semiconductor chips attached to the tape spreader, and then the tape spreader is peeled off from the plurality of semiconductor chips, whereby the plurality of semiconductor chips can be separated from the tape spreader at one time.
Through the above steps, a plurality of semiconductor chips can be obtained which are adhered to the adhesive sheet according to one embodiment of the present invention. The plurality of semiconductor chips can be easily separated by subsequently heating the adhesive layer (X1) to above the expansion start temperature (t) of the thermally-expansible particles. In this case, the pressure-sensitive adhesive sheet according to one embodiment of the present invention can be heat-peeled at a low temperature, and therefore, is excellent in workability and energy saving performance in the heat-peeling operation, and can suppress thermal change of the adherend due to heating at the time of heat peeling even when the adherend is likely to thermally change.
The plurality of semiconductor chips after separation 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 described in more detail with reference to the following examples, but the present invention is not limited to the following examples.
In the following description, the "non-expandable pressure-sensitive adhesive layer (X1 ')" means a pressure-sensitive adhesive layer containing no thermally expandable particles, and the pressure-sensitive adhesive layer included in the pressure-sensitive adhesive sheet produced in the comparative example described later and the pressure-sensitive adhesive layer containing no thermally expandable particles produced for measuring the shear storage modulus G ' belong to the non-expandable pressure-sensitive adhesive layer (X1 ').
The physical property values in the following synthesis examples and examples are values measured by the following methods.
[ weight average molecular weight (Mw) ]
The measurement was carried out under the following conditions using a gel permeation chromatography apparatus (product name "HLC-8020" available from Tosoh corporation) and the value was measured in terms of standard polystyrene.
(measurement conditions)
Column chromatography: a column comprising TSK guard column HXL-L, TSK gel G2500HXL, TSK gel G2000HXL and TSK gel G1000HXL (all available from Tosoh Corp.) successively connected
Column temperature: 40 deg.C
Developing solvent: tetrahydrofuran (THF)
Flow rate 1.0mL/min
[ thickness of each layer ]
The measurement was carried out using a constant-pressure thickness gauge (model: "PG-02J", Standard: based on JIS K6783, Z1702 and Z1709) manufactured by TECCLOCK.
[ average particle diameter (D) of thermally expandable particles50) 90% particle diameter (D)90)]
The particle distribution of the thermally expandable particles before expansion at 23 ℃ was measured using a laser diffraction particle size distribution measuring apparatus (for example, product name "Mastersizer 3000" manufactured by Malvern corporation).
Further, the particle diameters corresponding to 50% and 90% of the cumulative volume frequency of particles having a small particle diameter in the particle distribution were defined as "average particle diameter of thermally expandable particles" (D)50)”And "90% particle diameter of thermally expandable particles (D)90)”。
[ storage modulus E' of base Material (Y) ]
A base material (Y) cut into a length of 5mm X a width of 30mm was used as a test sample, and a storage modulus E' at a predetermined temperature was measured using a dynamic viscoelasticity measuring apparatus (product name "DMAQ 800" manufactured by TA INSTRUMENTS Co., Ltd.) under conditions of a test start temperature of 0 ℃, a test end temperature of 200 ℃, a temperature rise rate of 3 ℃/min, a frequency of 1Hz, and an amplitude of 20 μm.
[ shear storage modulus G' (23) of adhesive layer (X1) at 23 ℃ ]
The adhesive layer (X1) was formed to have a diameter of 8mm × a thickness of 3mm, and used as a test sample, and the shear storage modulus G' (23) at 23 ℃ was measured by a torsional shear method using a viscoelasticity measuring apparatus (manufactured by Anton Paar, Inc., under the apparatus name "MCR 300") under conditions of a test initiation temperature of 0 ℃, a test termination temperature of 300 ℃, a temperature rise rate of 3 ℃/min, and a frequency of 1 Hz.
[ shear storage modulus G 'of non-expandable adhesive layer (X1') ]
In order to measure the shear storage modulus G ' excluding the influence of the thermally expandable particles, a non-expandable pressure-sensitive adhesive layer (X1 ') having the same configuration as the pressure-sensitive adhesive layer (X1) except that the thermally expandable particles were not contained in each example was prepared as a sample for measuring the shear storage modulus corresponding to the pressure-sensitive adhesive layer (X1) in each example, and the shear storage modulus G ' was measured.
The shear storage modulus G 'of the non-expandable pressure-sensitive adhesive layer (X1') prepared in the comparative example was also measured by the present evaluation method.
The non-expandable pressure-sensitive adhesive layer (X1 ') was prepared to have a diameter of 8mm × a thickness of 3mm, and used as a test sample, and the shear storage modulus G ' (23) at 23 ℃ and the shear storage modulus G ' (t) at the expansion start temperature (t) of the thermally expandable particles were measured by the torsional shear method using a viscoelasticity measuring apparatus (manufactured by Anton Paar, apparatus name "MCR 300") under conditions of a test start temperature of 0 ℃, a test end temperature of 300 ℃, a temperature rise rate of 3 ℃/min, and a frequency of 1 Hz.
The expansion start temperature (t) of the thermally expandable particles in the non-expandable pressure-sensitive adhesive layer (X1') as the sample for measuring the shear storage modulus is the expansion start temperature (t) of the thermally expandable particles contained in the pressure-sensitive adhesive layer (X1) of the example corresponding to the sample for measuring the shear storage modulus, and in this example, it is 88 ℃.
In addition, since the psa sheet produced in the comparative example did not have the expansion initiation temperature (t), the shear storage modulus G' at 88 ℃ was measured, which was the same as that of the psa sheet of the example.
Synthesis example 1
(Synthesis of urethane acrylate prepolymer)
100 parts by mass (solid content equivalent; the same applies hereinafter) of polypropylene glycol having a weight average molecular weight (Mw) of 3,000, 4 parts by mass of hexamethylene diisocyanate, and 0.02 part by mass of dioctyltin dilaurate were mixed and stirred at 80 ℃ for 6 hours, whereby a reaction product was obtained. As a result of IR spectroscopy of the obtained reaction product by infrared spectroscopy, it was confirmed that the isocyanate group had substantially disappeared.
Then, 1 part by mass of 2-isocyanoethyl acrylate was mixed with respect to the total amount of the obtained reaction product, and the mixture was stirred at 80 ℃ for 3 hours, thereby obtaining a urethane acrylate prepolymer. As a result of IR spectrum measurement of the obtained urethane acrylate prepolymer by infrared spectroscopy, it was confirmed that the isocyanate group had substantially disappeared. The weight average molecular weight (Mw) of the resulting urethane acrylate prepolymer was 25,000.
Examples 1 to 22
(production of polymerizable composition)
The components shown in table 1 were mixed in the compounding composition shown in table 1 to obtain a solvent-free polymerizable composition. The details of each component described in table 1 are as follows.
[ polymerizable vinyl monomer ]
2 EHA: 2-ethylhexyl acrylate ((a1-1) component)
IBXA: isobornyl acrylate ((a1-2) component)
HEA: 2-hydroxyethyl acrylate ((a1-3) component)
4 HBA: acrylic acid 4-hydroxybutyl ester ((a1-3) component)
[ polyfunctional (meth) acrylate monomer ]
Trifunctional monomer: ethylene oxide isocyanurate-modified triacrylate (component (a 1-4))
[ polyfunctional (meth) acrylate prepolymer ]
Urethane acrylate prepolymer: synthesis of the component prepared in Synthesis example 1 (component (a 2))
Polyacryl acrylate prepolymer: "KANEKA XMAP (registered trademark) RC 100C" (polyacrylic prepolymer having acryloyl groups at both ends, manufactured by Kameka corporation, weight average molecular weight (Mw):21,500) (component (a 2))
[ photopolymerization initiator ]
1-hydroxycyclohexyl phenyl ketones
[ Heat-expandable particles ]
Manufactured by Akzo Nobel, under the product name "Expancel (registered trademark) 031-40" (DU type), an expansion initiation temperature (t) of 88 ℃ and an average particle diameter (D)50) 12.6 μm, 90% particle diameter (D)90)＝26.2μm
In the composition of the pressure-sensitive adhesive layer (X1) or the non-expandable pressure-sensitive adhesive layer (X1') "in table 1," - "indicates that the component was not blended.
(production of adhesive sheet)
A pressure-sensitive adhesive sheet was produced using the solvent-free polymerizable composition produced above in the following procedure.
The solvent-free type polymerizable composition was applied to a release-treated surface of a polyethylene terephthalate (PET) release film (product name "SP-PET 381031" manufactured by Lingdeko Co., Ltd., thickness: 38 μm) to form a polymerizable composition layer. The resultant polymer composition layer was irradiated with an illumination of 150mW/cm2Light quantity 100mJ/cm2The prepolymer was carried out by irradiating the resulting mixture with ultraviolet light. The thickness of the obtained pressure-sensitive adhesive layer (X1) was adjusted so that the thickness of the pressure-sensitive adhesive layer was as shown in table 1.
Then, a polyethylene terephthalate film (product of Toyo Boseki Co., Ltd., Cosmo Shine (registered trademark), product number "A4300", thickness: 50 μm) as a substrate (Y) was bonded to the exposed surface of the polymer composition layer to obtain a laminate in which a release film, a polymer composition layer, and a substrate (Y) were laminated in this order. The storage modulus E' (23) of the base material (Y) at 23 ℃ was 3.0X 109Pa, and a storage modulus E' (t) of the base material (Y) at an expansion initiation temperature (t) of the thermally-expansible particles of 2.4X 109Pa。
The laminate thus obtained was irradiated from the side of the release film with an illuminance of 200mW/cm2Light quantity 2,000mJ/cm2(at 500mJ/cm2Irradiation with ultraviolet light 4 times) was performed to form a pressure-sensitive adhesive layer (X1), and a pressure-sensitive adhesive sheet in which a release film, a pressure-sensitive adhesive layer (X1), and a substrate (Y) were laminated in this order was obtained.
The illuminance and the amount of light in the ultraviolet irradiation are measured by using an illuminance/light meter (product name "UV Power Puck II" manufactured by EIT corporation).
Comparative examples 1 to 5
A psa sheet was produced in the same manner as in example 1, with the exception that the composition of the psa layer (X1) in example 1 was changed to the composition described in table 1, and a release film, a non-expandable psa layer (X1'), and a substrate (Y) were laminated in this order.
Next, the pressure-sensitive adhesive sheets produced in the respective examples were evaluated as follows. The evaluation results are shown in table 2.
[ measurement of adhesive force at 23 ℃ of adhesive layer (X1) before thermal expansion ]
The release film was removed from the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet cut into 25 mm. times.250 mm, and the exposed surface of the pressure-sensitive adhesive layer (X1) was bonded to the mirror surface of the silicon mirror wafer by means of a 2kg rubber roller based on JIS Z0237:2000, followed by immediately leaving to stand in an atmosphere of 23 ℃ and 50% RH (relative humidity) for 20 minutes.
After standing under the above conditions, the adhesive force was measured at a tensile rate of 300 mm/min by a 180 ° peel method in an environment of 23 ℃ and 50% RH (relative humidity) using a tensile tester (product name "TENSILON (registered trademark)" made by a & D corporation) in accordance with JIS Z0237: 2000.
[ measurement of adhesive force of adhesive layer (X1) at 23 ℃ after thermal expansion ]
The test sample was placed on a hot plate so that the silicon mirror wafer was in contact with the hot plate and the pressure-sensitive adhesive sheet was not in contact with the hot plate, heated at 100 ℃ or higher, the temperature at which the thermally expandable particles start to expand, for 1 minute, and allowed to stand in a standard environment (23 ℃ and 50% RH (relative humidity)) for 60 minutes, and then the pressure-sensitive adhesive strength of the pressure-sensitive adhesive layer (X1) was measured by a 180 ° peel method based on JIS Z0237:2000 at a tensile rate of 300 mm/min.
When the adhesive strength was too small to cause unexpected peeling when the adhesive sheet was fixed for measurement, and the measurement of the adhesive strength was difficult, the adhesive strength was considered to be 0N/25 mm.
[ evaluation of self-peelability ]
The release film was removed from the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet cut into 50mm × 50mm pieces, and the exposed surface of the pressure-sensitive adhesive layer (X1) was bonded to the mirror surface of the silicon mirror wafer by a 2kg rubber roller based on JIS Z0237:2000, and immediately thereafter, it was left to stand in an environment of 23 ℃ and 50% RH (relative humidity) for 20 minutes, and then it was used as a test sample. Next, the test sample was placed on a hot plate so that the silicon mirror wafer was in contact with the hot plate and the adhesive sheet was not in contact with the hot plate, and was heated at 100 ℃ or higher, which was the expansion start temperature of the thermally expandable particles, for 60 seconds at the maximum. The ratio (%) of the peeled area of the adhesive sheet at the time of 60 seconds heating (peeled area × 100/area of the entire adhesive sheet) was determined and evaluated according to the following criteria.
A: the adhesive sheet was peeled off entirely within 60 seconds.
B: the area peeled off by heating for 60 seconds was 30% or more and less than 100%.
C: the area where peeling occurred by heating for 60 seconds was less than 30%.
In addition, the time (seconds) required until the entire surface was peeled off was measured for the sample evaluated as "a".
[ method for measuring the adhesive force and self-releasability of the non-expandable adhesive layer (X1') at 23 ]
The adhesive strength and self-releasability at 23 ℃ of the non-expandable adhesive layer (X1 ') prepared in comparative examples 1 to 5 were measured by replacing the adhesive layer (X1) with the non-expandable adhesive layer (X1') in the description of the method for measuring the adhesive strength and self-releasability at 23 ℃ of the adhesive layer (X1).
In table 2, "before thermal expansion" and "after thermal expansion" in "the adhesive strength at 23 ℃ of the non-expandable adhesive layer (X1'), comparative examples 1 to 5 are" before heat treatment corresponding to the thermal expansion treatment in examples "and" after heat treatment corresponding to the thermal expansion treatment in examples ", and" after heat treatment corresponding to the thermal expansion treatment in examples "are the heat treatment described in [ measurement of the adhesive strength at 23 ℃ of the adhesive layer (X1) after thermal expansion ].
[ Table 1]
Figure BDA0003279493960000481
[ Table 2]
Figure BDA0003279493960000491
As is clear from Table 2, the pressure-sensitive adhesive sheets of examples 1 to 22 were all capable of being heat-peeled at a low temperature (100 ℃ C.) although they had sufficient adhesive strength before heat-peeling. It is also known that the adhesive strength and self-peelability of these pressure-sensitive adhesive sheets can be adjusted by adjusting the composition of the polymerizable composition, the thickness of the pressure-sensitive adhesive layer (X1), and the like. On the other hand, the pressure-sensitive adhesive sheets of comparative examples 1 to 5 were not peeled off by heating.

Claims (15)

1. An adhesive sheet, comprising:
base material (Y), and
a binder layer (X1) comprising a polymer containing an energy ray-polymerizable component and thermally expandable particles having an expansion initiation temperature (t) of 50 to 110 ℃,
wherein the pressure-sensitive adhesive layer (X1) is a layer formed by irradiating a polymerizable composition containing the energy ray-polymerizable component and the thermally expandable particles with an energy ray to form a polymer of the energy ray-polymerizable component.
2. The adhesive sheet according to claim 1, wherein the content of the thermally expandable particles is 1 to 30% by mass relative to 100% by mass of the total mass of the adhesive layer (X1).
3. The adhesive sheet according to claim 1 or 2, wherein the thickness of the adhesive layer (X1) at 23 ℃ is 5 to 150 μm.
4. The adhesive sheet according to any one of claims 1 to 3, wherein the adhesive layer (X1) has an adhesive force at 23 ℃ of 0.1 to 12.0N/25 mm.
5. The adhesive sheet according to any one of claims 1 to 4, wherein the average particle diameter of the thermally expandable particles at 23 ℃ is 1 to 30 μm.
6. The adhesive sheet according to any one of claims 1 to 5, which comprises:
a base material (Y),
An adhesive layer (X1) provided on one surface side of the substrate (Y), and
and an adhesive layer (X2) provided on the other surface side of the substrate (Y).
7. The adhesive sheet according to claim 6, wherein the adhesive layer (X2) is an adhesive layer which is cured by irradiation with energy rays and thus undergoes a decrease in adhesive force.
8. A method for producing the adhesive sheet according to any one of claims 1 to 7,
wherein the method of forming the adhesive layer (X1) comprises:
and a step of irradiating the polymerizable composition containing the energy ray-polymerizable component and the thermally expandable particles with an energy ray to form a polymer of the energy ray-polymerizable component.
9. The method for producing an adhesive sheet according to claim 8, wherein the method for forming the adhesive layer (X1) comprises the following steps I and II,
step I: a step of forming a polymerizable composition layer on one surface side of a base material (Y), the polymerizable composition layer being formed from the polymerizable composition;
and a step II: and a step of irradiating the polymerizable composition layer with an energy ray to form a polymer of the energy ray-polymerizable component, thereby forming a pressure-sensitive adhesive layer (X1) containing the polymer and the thermally expandable particles.
10. The method for producing an adhesive sheet according to claim 8 or 9, wherein the polymerizable composition does not contain a solvent.
11. The method for producing an adhesive sheet according to any one of claims 8 to 10, wherein a step of heating the polymerizable composition is not included.
12. A method for manufacturing a semiconductor device, comprising the steps of:
the adhesive sheet according to any one of claims 1 to 7, wherein an object to be processed is adhered to the adhesive sheet,
subjecting the object to one or more treatments selected from grinding treatment and singulation treatment,
after the treatment, the adhesive sheet is heated to the expansion start temperature (t) or higher and 120 ℃ or lower to expand the adhesive layer (X1).
13. A method for manufacturing a semiconductor device, comprising the following steps 1A to 5A,
step 1A: a step of attaching an object to be processed to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet according to claim 6 and attaching a support to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet;
step 2A: performing one or more treatments selected from grinding and singulation on the object to be processed;
step 3A: a step of attaching a thermosetting film having thermosetting properties to the surface of the processed object opposite to the pressure-sensitive adhesive layer (X2);
step 4A: a step of heating the pressure-sensitive adhesive sheet to the expansion start temperature (t) or higher and 120 ℃ or lower to separate the pressure-sensitive adhesive layer (X1) from the support;
step 5A: and a step of separating the pressure-sensitive adhesive layer (X2) from the object.
14. The method for manufacturing a semiconductor device according to claim 13,
the adhesive layer (X2) is an adhesive layer which is cured by irradiation of energy rays and thus undergoes a decrease in adhesive force,
the step 5A is a step of irradiating the pressure-sensitive adhesive layer (X2) with an energy ray to cure the pressure-sensitive adhesive layer (X2), thereby separating the pressure-sensitive adhesive layer (X2) from the object.
15. A method for manufacturing a semiconductor device includes the following steps 1B to 4B,
step 1B: a step of attaching an object to be processed to the pressure-sensitive adhesive layer (X1) of the pressure-sensitive adhesive sheet according to claim 6 and attaching a support to the pressure-sensitive adhesive layer (X2) of the pressure-sensitive adhesive sheet;
step 2B: performing one or more treatments selected from grinding and singulation on the object to be processed;
step 3B: a step of attaching a thermosetting film having thermosetting properties to the surface of the processed object opposite to the pressure-sensitive adhesive layer (X1);
step 4B: and a step of separating the pressure-sensitive adhesive layer (X1) from the object by heating the pressure-sensitive adhesive sheet to a temperature of not less than the expansion initiation temperature (t) but not more than 120 ℃.
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