JP2021095451A - Pressure sensitive adhesive sheet - Google Patents

Abstract

To provide a pressure sensitive adhesive sheet useful in improving cleanliness on a surface after peeling.SOLUTION: A pressure sensitive adhesive sheet includes an adhesive layer composing an adhesive face, and has a cleaning degree of 20% or higher calculated by an expression below: cleaning degree=1-(B/A). Here, the B in the expression is a carbon amount B [atomic%] on a surface of a SiN wafer after water-peeling of the pressure sensitive adhesive sheet from the SiN wafer. The A in the expression is a carbon amount A [atomic%] on the surface of the SiN wafer before adhering the pressure sensitive adhesive sheet.SELECTED DRAWING: Figure 1

Description

The present invention relates to an adhesive sheet.

In the process of manufacturing a semiconductor element, a process of grinding, cutting, or the like on a circuit-formed semiconductor wafer is generally performed on the circuit-forming surface side of the semiconductor wafer (adhesive body) in order to protect or fix the semiconductor wafer. This is performed with an adhesive sheet (adhesive sheet for semiconductor processing) attached to the wafer. For example, when grinding (back grinding) the back surface of a semiconductor wafer, a back grind tape is used to protect the circuit forming surface (front surface) of the semiconductor wafer and to hold (fix) the semiconductor wafer. (For example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-212441

An adhesive sheet used in a mode of being temporarily attached to an adherend in a product manufacturing process, such as the above-mentioned adhesive sheet for semiconductor processing, is peeled off from the adherend after fulfilling its intended purpose. At this time, if the cleanliness of the adherend surface after the adhesive tape is peeled off is low, this may cause problems in the downstream process, or reduce the performance and quality stability of the final product (semiconductor element, etc.). It can be a factor that causes it. Therefore, an object of the present invention is to provide an adhesive sheet that is useful for improving the cleanliness of the surface after peeling.

The degree of surface cleanliness can be grasped by using the amount of carbon on the surface as an index. According to this specification, an adhesive sheet containing an adhesive layer constituting an adhesive surface and having a cleaning degree of 20% or more calculated by the following formula is provided.
Cleaning degree = 1- (B / A)
Here, B in the above formula is the amount of carbon B [atomic%] on the surface of the SiN wafer after the pressure-sensitive adhesive sheet is water-peeled from the silicon nitride (SiN) wafer. A in the above formula is the amount of carbon A [atomic%] on the surface of the SiN wafer before the adhesive sheet is attached. Hereinafter, the carbon amount A may be referred to as "initial carbon amount A", and the carbon amount B may be referred to as "carbon amount B after water exfoliation". When the cleaning degree of the adhesive sheet is 20% or more, the carbon amount [atomic%] on the surface of the SiN wafer is in the initial state (the state before the adhesive sheet is attached) by peeling the adhesive sheet from the SiN wafer with water. This means that the cleanliness of the SiN wafer surface is improved by 20% or more. The pressure-sensitive adhesive sheet exhibiting such a degree of cleaning can be used in a mode in which water is peeled off from a SiN wafer or other various adherends, and can exert an effect of enhancing the cleanliness of the adherend surface.

In the pressure-sensitive adhesive sheet according to some preferred embodiments, the carbon amount B can be, for example, 10 atomic% or less. Such an adhesive sheet is used in a mode in which water is peeled off from various adherends, and high cleanliness can be realized on the surface of the adherend after peeling.

The pressure-sensitive adhesive sheet according to some preferred embodiments has a water peeling force from the SiN wafer of 1.5 N / 20 mm or less. As described above, the pressure-sensitive adhesive sheet having a low water peeling force can be easily peeled from the adherend, and the cleanliness of the surface of the adherend can be improved by the water peeling.

In the pressure-sensitive adhesive sheet according to some preferred embodiments, the water peeling force [N / 20 mm] from the SiN wafer is 40% or less of the normal peeling force [N / 20 mm] from the SiN wafer. According to such an adhesive sheet, the peeling force can be significantly reduced by applying the water peeling method, and the cleanliness of the surface of the adherend can be improved by the water peeling.

In some embodiments, the pressure-sensitive adhesive layer comprises, as a water stripping additive, at least one compound A selected from the group consisting of surfactants and compounds having a polyoxyalkylene skeleton. When the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface contains the compound A, the water releasability can be improved.

In some embodiments, the pressure-sensitive adhesive layer comprises a surfactant as compound A. When the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface contains a surfactant as the compound A, the water releasability can be improved and the degree of cleaning can be preferably realized.

In some embodiments, as the compound A, a compound that exhibits a liquid state at 25 ° C. can be preferably adopted. This can be advantageous from the viewpoint of compatibility of the compound A in the pressure-sensitive adhesive layer, ease of preparation of the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, and the like.

In some preferred embodiments, the pressure-sensitive adhesive layer is an active energy ray-curable pressure-sensitive adhesive layer. The degree of cleaning can be preferably realized in a pressure-sensitive adhesive sheet having an adhesive surface composed of an active energy ray-curable pressure-sensitive adhesive layer. Of these, an active energy ray-curable pressure-sensitive adhesive layer configured so that the peeling force is reduced by irradiation with active energy rays is preferable. The pressure-sensitive adhesive sheet having such an adhesive layer is attached to the adherend, then irradiated with active energy rays to reduce the peeling force, and further peeled by applying the water peeling method to the adherend at the time of peeling. The applied load can be effectively reduced.

It should be noted that an appropriate combination of the above-mentioned elements may be included in the scope of the invention for which protection by the patent is sought by the present patent application.

It is sectional drawing which shows typically one structural example of the pressure-sensitive adhesive sheet. It is sectional drawing which shows typically another structural example of the adhesive sheet. It is sectional drawing which shows typically another structural example of the adhesive sheet. It is sectional drawing which shows typically another structural example of the adhesive sheet. It is sectional drawing which shows typically another structural example of the adhesive sheet. It is sectional drawing which shows typically another structural example of the adhesive sheet.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in the present specification and necessary for the implementation of the present invention are based on the teachings regarding the implementation of the invention described in the present specification and the common general knowledge at the time of filing. Can be understood by those skilled in the art. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art. Further, in the following drawings, members / parts having the same function may be described with the same reference numerals, and duplicate description may be omitted or simplified. Further, the embodiments described in the drawings are modeled for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the actually provided product.

In this specification, the adhesive sheet is peeled from the adherend by using an aqueous stripping solution such as water (typically, the aqueous stripping solution is supplied to the peeling front from the adherend to peel off). May be referred to as "water peeling" or "water peeling method". Water is used as the water-based stripping liquid for stripping the pressure-sensitive adhesive sheet from the SiN wafer in order to evaluate the degree of cleaning.

In this specification, the main chain of a polymer refers to a chain structure forming the skeleton of the polymer. Further, the side chain of the polymer refers to a group (pendant, side group) that binds to the main chain or a molecular chain that can be regarded as a pendant.

As used herein, the term "acrylic polymer" refers to a polymer derived from a monomer raw material containing more than 50% by weight (preferably more than 70% by weight, for example, more than 90% by weight) of an acrylic monomer. The acrylic monomer means a monomer having at least one (meth) acryloyl group in one molecule. Further, in this specification, "(meth) acryloyl" means a comprehensively referring to acryloyl and methacryloyl. Similarly, "(meth) acrylate" means acrylate and methacrylate, and "(meth) acrylic" means acrylic and methacryl, respectively.

Further, in this specification, the "active energy ray" includes light such as ultraviolet rays, visible rays and infrared rays, and radiation such as α rays, β rays, γ rays, electron rays, neutron rays and X-rays. It is a concept to do.

<Structure example of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein comprises a pressure-sensitive adhesive layer. This pressure-sensitive adhesive layer typically constitutes at least one surface of the pressure-sensitive adhesive sheet. The pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet with a base material having an adhesive layer on one side or both sides of the base material (support), and may be a pressure-sensitive adhesive sheet without a base material (base material-less pressure-sensitive adhesive sheet). There may be.
The concept of the pressure-sensitive adhesive sheet as used herein may include what is called an pressure-sensitive adhesive tape, a pressure-sensitive adhesive label, a pressure-sensitive adhesive film, or the like. Further, the pressure-sensitive adhesive layer is typically formed continuously, but is not limited to such a form, and the pressure-sensitive adhesive layer is formed in a regular or random pattern such as a dot shape or a stripe shape. It may be. In addition, the pressure-sensitive adhesive sheet provided by the present specification may be in the form of a roll or in the form of a single leaf. Alternatively, the pressure-sensitive adhesive sheet may be further processed into various shapes.

The pressure-sensitive adhesive sheet disclosed herein may have, for example, the cross-sectional structure schematically shown in FIGS. 1 to 6. Of these, FIGS. 1 and 2 are configuration examples of a single-sided adhesive base-attached pressure-sensitive adhesive sheet (base-based single-sided pressure-sensitive adhesive sheet). In the pressure-sensitive adhesive sheet 1 shown in FIG. 1, a pressure-sensitive adhesive layer 21 is provided on one surface 10A (non-peelable) of the base material 10, and the surface (adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is peeled off at least on the pressure-sensitive adhesive layer side. It has a structure protected by a release liner 31 which is a surface. The pressure-sensitive adhesive sheet 2 shown in FIG. 2 has a structure in which the pressure-sensitive adhesive layer 21 is provided on one surface 10A (non-peelable) of the base material 10. In this pressure-sensitive adhesive sheet 2, the other surface 10B of the base material 10 is a peeling surface, and when the pressure-sensitive adhesive sheet 2 is wound, the pressure-sensitive adhesive layer 21 comes into contact with the other side surface 10B, and the surface of the pressure-sensitive adhesive layer (adhesive). Surface) 21A is protected by the other surface 10B of the base material 10.

3 and 4 are configuration examples of a double-sided adhesive type pressure-sensitive adhesive sheet with a base material (double-sided pressure-sensitive adhesive sheet with a base material). The pressure-sensitive adhesive sheet 3 shown in FIG. 3 has a pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer) 21 and a pressure-sensitive adhesive layer (second pressure-sensitive adhesive) on the first surface 10A and the second surface 10B (both non-peelable) of the base material 10. The agent layer) 22 is provided, and the surface of the first adhesive layer 21 (first adhesive surface) and the surface of the second adhesive layer 22 (second adhesive surface) are at least the peeling surface on the adhesive layer side. It has a structure protected by the release liners 31 and 32, respectively. In the pressure-sensitive adhesive sheet 4 shown in FIG. 4, a first pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive layer 22 are provided on the first surface 10A and the second surface 10B (both are non-peelable) of the base material 10, respectively. Of these, the surface (first adhesive surface) of the first pressure-sensitive adhesive layer 21 has a structure protected by a release liner 31 having both sides as release surfaces. The adhesive sheet 4 is wound around the adhesive sheet 4 so that the front surface (second adhesive surface) of the second adhesive layer 22 is brought into contact with the back surface of the release liner 31, so that the second adhesive surface is also formed by the release liner 31. It can be a protected configuration.

5 and 6 are configuration examples of a base material-less double-sided adhesive adhesive sheet (base material-less double-sided adhesive sheet). In the pressure-sensitive adhesive sheet 5 shown in FIG. 5, one surface (first adhesive surface) 21A and the other surface (second adhesive surface) 21B of the base material-less pressure-sensitive adhesive layer 21 have at least the pressure-sensitive adhesive layer side as a peeling surface. It has a structure protected by the release liners 31 and 32, respectively. The pressure-sensitive adhesive sheet 6 shown in FIG. 6 has a structure in which one surface (first pressure-sensitive adhesive surface) 21A of the pressure-sensitive adhesive layer 21 is protected by a release liner 31 having both sides as release surfaces, and the adhesive sheet 6 is wound around the adhesive sheet 6. Then, the other surface (second adhesive surface) 21B of the pressure-sensitive adhesive layer 21 comes into contact with the back surface of the release liner 31, so that the other surface 21B can also be protected by the release liner 31.
A double-sided pressure-sensitive adhesive sheet without a base material or with a base material can be used as a single-sided pressure-sensitive adhesive sheet with a base material by laminating a non-peelable base material on one of the pressure-sensitive adhesive surfaces.

The pressure-sensitive adhesive sheet before use (before sticking to the adherend) may be in the form of a pressure-sensitive adhesive sheet with a release liner whose adhesive surface is protected by a release liner, for example, as shown in FIGS. 1 to 6. The release liner is not particularly limited, and is, for example, a release liner in which the surface of a liner base material such as a resin film or paper is peeled off, a fluoropolymer (polytetrafluoroethylene, etc.), a polyolefin resin (polyethylene, polypropylene, etc.). ), A release liner made of a low-adhesive material or the like can be used. For the peeling treatment, for example, a silicone-based peeling agent, a long-chain alkyl-based peeling agent, or the like can be used. In some embodiments, the stripped resin film can be preferably used as the strip liner.

When the pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet with a base material or a double-sided pressure-sensitive adhesive sheet without a base material, the pressure-sensitive adhesive (first pressure-sensitive adhesive) constituting the first pressure-sensitive adhesive surface and the second pressure-sensitive adhesive surface are formed. The pressure-sensitive adhesive (second pressure-sensitive adhesive) may have the same composition or different compositions. A base-less double-sided pressure-sensitive adhesive sheet having different compositions on the first adhesive surface and the second adhesive surface is, for example, a multi-layered pressure-sensitive adhesive in which two or more pressure-sensitive adhesive layers having different compositions are directly laminated (without interposing a base material). It can be realized by layers.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive surface composed of a pressure-sensitive adhesive layer having active energy ray-curable (active energy ray-curable pressure-sensitive adhesive layer). The pressure-sensitive adhesive sheet according to some other aspects has a pressure-sensitive surface composed of a pressure-sensitive adhesive layer (non-active energy ray-curable pressure-sensitive adhesive layer) having no active energy ray-curable property. In the case of a double-sided adhesive sheet having a first adhesive surface and a second adhesive surface, both the first adhesive surface and the second adhesive surface may be adhesive surfaces composed of an active energy ray-curable adhesive layer. Each may be an adhesive surface composed of an inactive energy ray-curable pressure-sensitive adhesive layer, one is an adhesive surface composed of an active energy ray-curable pressure-sensitive adhesive layer, and the other is an inactive energy ray-curable adhesive surface. It may be an adhesive surface composed of an adhesive layer. The pressure-sensitive adhesive sheet disclosed herein can be preferably implemented in the form of a single-sided pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive surface composed of an active energy ray-curable pressure-sensitive adhesive layer containing the compound A described later.

<Cleaning degree>
The pressure-sensitive adhesive sheet disclosed herein is characterized by a degree of cleaning defined by the following formula of 20% or more. The pressure-sensitive adhesive sheet having a cleaning degree of 20% or more can be used in a mode in which water is peeled off from a SiN wafer or other various adherends, and can contribute to improving the cleanliness of the adherend surface.
Cleaning degree = 1- (B / A)
Here, B in the above formula is the carbon amount B (carbon amount B after water peeling) [atomic%] on the surface of the SiN wafer after the pressure-sensitive adhesive sheet is peeled from the SiN wafer by the water peeling method. A in the above formula is the carbon amount A (initial carbon amount A) [atomic%] on the surface of the SiN wafer before the adhesive sheet is attached.

The initial carbon amount A is narrowed by X-ray photoelectron spectroscopy (ESCA) for the four elements of carbon (carbon), nitrogen, oxygen, and silicon, with the surface of an unused SiN wafer (before attaching the adhesive sheet) as the measurement target. By performing scan analysis, it can be obtained as the element ratio [atomic%] of carbon in the total amount of the above four elements. As the analyzer, "Quantum 2000" manufactured by ULVAC-PHI or an equivalent product thereof can be used. More specifically, the initial carbon amount A can be obtained by the method described in Examples described later.
The carbon amount B after water peeling is obtained as follows. That is, after the pressure-sensitive adhesive sheet to be measured is attached to the unused SiN wafer (adhesion body), the pressure-sensitive adhesive sheet is peeled off from the adherend by water. Water peeling of the pressure-sensitive adhesive sheet is performed under the conditions of a tensile speed of 300 mm / min and a peeling angle of 180 degrees after supplying 20 μL of water (preferably distilled water) to a portion where the pressure-sensitive adhesive sheet starts to separate from the SiN wafer. For the surface of the SiN wafer after water peeling, the element ratio [atomic%] of carbon is calculated in the same manner as the initial carbon amount A, and this is defined as the carbon amount B after water peeling. More specifically, the carbon amount B after water peeling can be obtained by the method described in Examples described later. When the pressure-sensitive adhesive sheet is attached to the adherend or peeled off from the adherend, an appropriate treatment (heat-pressurization treatment, ultraviolet irradiation treatment, etc.) is performed according to the structure of the pressure-sensitive adhesive sheet and the expected usage mode. ) Can be performed at an appropriate timing as needed.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the degree of cleaning may be, for example, 25% or higher, 30% or higher, 35% or higher, or 40% or higher. Adhesive sheets with a higher degree of cleanliness evaluated using SiN wafers are more clean in a usage mode in which water is peeled off from SiN wafers and other various adherends (for example, semiconductor wafers such as SiN wafers and silicon wafers). It tends to exert a chemical effect (cleaning effect). The upper limit of the cleaning degree is 100% in principle.

In the evaluation of the degree of cleaning, the carbon amount B after water peeling is not particularly limited, and may be a value 20% or more lower than the initial carbon amount A. In adhesive sheets for applications where a high level of cleanliness is required on the surface after peeling (for example, adhesive sheets for semiconductor processing, adhesive sheets for optics), in some embodiments, the amount of carbon B after water peeling is approximately 30 atomic. It is appropriate that it is% or less, preferably 15 atomic% or less, more preferably less than 12 atomic%, and even more preferably less than 10 atomic%. The lower limit of the carbon amount B after water exfoliation is 0 atomic%. From a practical point of view such as cost and productivity, in some embodiments, the carbon amount B after water exfoliation may be, for example, 1 atomic% or more, 3 atomic% or more, or 5 atomic% or more. May be good.

Although not particularly limited, the initial carbon amount A of the SiN wafer used for evaluating the degree of cleaning is appropriately in the range of about 5 to 30 atomic% from the viewpoint of evaluation accuracy, and is about 5 to 20 atomic%. It is preferably in the range of about 10 to 20 atomic%, and more preferably in the range of about 10 to 20 atomic%. A SiN wafer having a higher carbon content is prepared so that the carbon content A is within the above range by performing a known appropriate pretreatment (cleaning treatment, etc.), and then used for the evaluation of the cleaning degree. May be good.

<Adhesive layer>
The pressure-sensitive adhesive layer (for example, the active energy ray-curable pressure-sensitive adhesive layer) constituting the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet disclosed herein includes an acrylic pressure-sensitive adhesive and a rubber-based pressure-sensitive adhesive (natural rubber type, synthetic rubber type, these. 1 or 2 selected from various known adhesives such as mixed adhesives), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, fluorine adhesives, etc. It can be a pressure-sensitive adhesive layer composed of more than a seed of pressure-sensitive adhesive. Here, the acrylic pressure-sensitive adhesive refers to a pressure-sensitive adhesive using an acrylic polymer as a base polymer. The same meaning applies to rubber-based pressure-sensitive adhesives and other pressure-sensitive adhesives.
In this specification, the "base polymer" of the pressure-sensitive adhesive means the main component of the polymer contained in the pressure-sensitive adhesive. Further, in this specification, the “main component” refers to a component contained in an amount of more than 50% by weight unless otherwise specified.

(Acrylic adhesive layer)
In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer may be an acrylic pressure-sensitive adhesive layer containing an acrylic pressure-sensitive adhesive as a main component. In an adhesive sheet provided with an acrylic adhesive layer, adhesive properties suitable for use in a mode of being temporarily attached to an adherend during the manufacturing process of a product (for example, use in semiconductor processing applications), and the above-mentioned cleaning property. Can be preferably compatible with each other. The acrylic pressure-sensitive adhesive layer is also preferable from the viewpoint of easily imparting active energy ray curability, which will be described later.

The acrylic pressure-sensitive adhesive preferably contains, for example, a polymer of a monomer raw material containing an alkyl (meth) acrylate or an acrylic polymer which is a modified product thereof by chemical modification or the like as a base polymer. As a constituent component of the monomer raw material, an alkyl (meth) acrylate having a linear or branched alkyl group having 1 to 20 carbon atoms at the ester terminal can be preferably used. Hereinafter, an alkyl (meth) acrylate having an alkyl group having an number of carbon atoms of X or more and Y or less at the ester terminal _{may be referred to as “CXY} alkyl (meth) acrylate”. Since it is easy to obtain appropriate adhesive properties according to the application (for example, semiconductor processing application), the C _1-20 alkyl (meth) acrylate is a C _1-14 (for example, C _1-12 ) alkyl (meth) acrylate. Is preferable. Further, as the C _1-20 alkyl acrylate, a C _1-20 (for example, C _1-14 , typically C _1-12 ) alkyl acrylate is preferable.

Non-limiting specific examples of C _1-20 alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. , Isobutyl (meth) acrylate, s-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) ) Acrylate, Isooctyl (meth) acrylate, Nonyl (meth) acrylate, Isononyl (meth) acrylate, Decyl (meth) acrylate, Isodecyl (meth) acrylate, Undecyl (meth) acrylate, Dodecyl (meth) acrylate, Tridecyl (meth) acrylate , Tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, nonadecil (meth) acrylate, ecocil (meth) acrylate and the like. These alkyl (meth) acrylates may be used alone or in combination of two or more. Preferred alkyl (meth) acrylates include ethyl acrylate (EA), n-butyl acrylate (BA), 2-ethylhexyl acrylate (2EHA) and lauryl acrylate (LA). In some embodiments, the monomer raw material comprises at least one of EA, BA, 2EHA and LA, preferably at least one of EA, BA and 2EHA, and preferably at least one of BA and 2EHA. More preferable.

_{In some embodiments, the proportion of C 1-20} alkyl (meth) acrylate in the monomer raw material is usually 40% by weight or more, and 50% by weight, because it is easy to balance the characteristics. It is preferably more than%, for example, 55% by weight or more, 60% by weight or more, 65% by weight or more, or 70% by weight or more. _{For the same reason, the ratio of C 1-20} alkyl (meth) acrylate in the above-mentioned monomer raw material is usually preferably 99.9% by weight or less, may be 99% by weight or less, or 98% by weight or less. Good. _{In some embodiments, the proportion of C 1-20} alkyl (meth) acrylate in the monomer raw material may be, for example, 95% by weight or less, and 85 by weight, from the viewpoint of facilitating the cleaning effect by water peeling. It may be less than 80% by weight, less than 80% by weight, less than 70% by weight, or less than 65% by weight.

In some preferred embodiments, the alkyl (meth) acrylate comprises an alkyl (meth) acrylate A1 (ie, C _1-9 alkyl (meth) acrylate) having an alkyl group having 9 or less carbon atoms at the ester terminal. Alkyl (meth) acrylate A1 can be used alone or in combination of two or more. According to the structure in which the length of the side chain alkyl group is limited as described above, a high cohesive force capable of highly preventing adhesive residue tends to be obtained. For example, in a configuration having a carbon-carbon double bond in the side chain (typically the end of the side chain) of the polymer, the length of the side chain alkyl group is limited, so that carbon-carbon dicarbonate is used during the curing treatment. The double bond reaction can proceed smoothly. Further, due to the limitation of the length of the side chain alkyl group, the pressure-sensitive adhesive sheet provided with the pressure-sensitive adhesive layer containing the polymer obtained from the monomer has an aqueous stripping solution such as water on the stripping front from the adherend. Can be efficiently peeled from the adherend by the peeling method of supplying.

The ratio of the alkyl (meth) acrylate A1 to the entire monomer raw material is preferably about 30% by weight or more, and is preferably about 40% by weight from the viewpoint of better expressing the action of the alkyl (meth) acrylate A1. % Or more, more preferably about 55% by weight or more. In some embodiments, the proportion of the alkyl (meth) acrylate A1 may be, for example, about 65% by weight or more, about 75% by weight or more, or about 80% by weight or more. In some other embodiments, the proportion of the alkyl (meth) acrylate A1 may be, for example, approximately 85% by weight or more, approximately 90% by weight or more, or approximately 95% by weight or more. Good. The upper limit of the ratio of the alkyl (meth) acrylate A1 in the monomer raw material is not particularly limited, and is usually 99.5% by weight or less, and can be, for example, 99% by weight or less. In some embodiments, the alkyl (meth) in the entire monomer raw material, for example, from the viewpoint of preferably exhibiting the action of the carbon-carbon double bond in the pressure-sensitive adhesive layer containing a polymer having a carbon-carbon double bond. The proportion of the acrylate A1 is preferably about 95% by weight or less, more preferably about 90% by weight or less, may be about 85% by weight or less, may be about 75% by weight or less, or may be about 70% by weight or less.

The ratio of the alkyl (meth) acrylate A1 to the entire alkyl (meth) acrylate is preferably about 50% by weight or more, and is preferably about 70 from the viewpoint of preferably expressing the action of the alkyl (meth) acrylate A1. By weight% or more, more preferably about 80% by weight or more, about 90% by weight or more, about 95% by weight or more, or about 99% by weight or more. The upper limit of the ratio of the alkyl (meth) acrylate A1 to the total alkyl (meth) acrylate is 100% by weight.

In some embodiments, the alkyl (meth) acrylate A1 may contain one or more alkyl (meth) acrylates A3 having an alkyl group having less than 7 carbon atoms at the ester terminal. A pressure-sensitive adhesive containing a polymer obtained from a monomer raw material containing an alkyl (meth) acrylate A3 can easily provide a pressure-sensitive adhesive sheet that is efficiently peeled by a peeling method that supplies a stripping liquid such as water to a stripping front from an adherend. .. Further, in an active energy ray-curable pressure-sensitive adhesive containing a polymer obtained from a monomer raw material containing an alkyl (meth) acrylate A3, the curing reaction by irradiation with active energy rays can proceed preferably. From such a viewpoint, the number of carbon atoms of the alkyl group in the alkyl (meth) acrylate A3 is preferably 6 or less, more preferably 4 or less, and may be 3 or less or 2 or less. Further, the number of carbon atoms of the alkyl group in the alkyl (meth) acrylate A3 may be 1 or more, and is preferably 2 or more from the viewpoint of adhesiveness to the adherend.

In the embodiment in which the monomer raw material contains an alkyl (meth) acrylate A3, the ratio of the alkyl (meth) acrylate A3 to the entire monomer raw material may be, for example, about 1% by weight or more, and usually about 5% by weight or more. From the viewpoint of preferably expressing the action of the alkyl (meth) acrylate A3, it is preferably about 20% by weight or more, more preferably about 30% by weight or more, still more preferably about 40% by weight or more, particularly preferably. Is about 50% by weight or more, for example, 60% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. The upper limit of the ratio of the alkyl (meth) acrylate A3 to the entire monomer raw material is not particularly limited, and it is usually appropriate to be about 99% by weight or less, for example, 90% by weight or less. In some embodiments, an alkyl (meth) acrylate occupying the entire monomer raw material, for example, from the viewpoint of preferably exhibiting the action of the carbon-carbon double bond in a pressure-sensitive adhesive layer containing a polymer having a carbon-carbon double bond. The proportion of A3 is preferably about 80% by weight or less, more preferably about 70% by weight or less, still more preferably about 60% by weight or less. The above embodiment may be, for example, an embodiment in which a reactive group for a curing treatment or a functional group serving as a cross-linking point is introduced into the polymer.

The ratio of the alkyl (meth) acrylate A3 to the entire alkyl (meth) acrylate is preferably about 5% by weight or more, and is preferably about 20 from the viewpoint of preferably expressing the action of the alkyl (meth) acrylate A3. By weight% or more, more preferably about 35% by weight or more, still more preferably about 45% by weight or more, particularly preferably about 55% by weight or more, for example, about 65% by weight or more, about 75% by weight or more. However, it may be about 85% by weight or more, and may be about 90% by weight or more. The upper limit of the ratio of the alkyl (meth) acrylate A3 to the entire alkyl (meth) acrylate is 100% by weight, and may be, for example, about 98% by weight or less. In some embodiments, for example, when alkyl (meth) acrylate A2, which will be described later, is used in combination with alkyl (meth) acrylate A3, the effect of alkyl (meth) acrylate A2 is preferably exhibited. The proportion of acrylate A3 may be, for example, about 90% by weight or less, about 85% by weight or less, about 75% by weight or less, about 60% by weight or less, about 45% by weight or less, and about 45% by weight. It may be 30% by weight or less, and may be about 15% by weight or less. Alkyl (meth) acrylate A3 may not be used.

In some embodiments, the alkyl (meth) acrylate comprises an alkyl (meth) acrylate A2 having an alkyl group having 7 or more carbon atoms at the ester terminal as the alkyl (meth) acrylate A1 or an alkyl (meth) acrylate. It can be contained as a monomer different from A1. The use of alkyl (meth) acrylate A2 can be advantageous, for example, from the viewpoint of adhesion to an adherend. The number of carbon atoms of the alkyl group in the alkyl (meth) acrylate A2 is preferably 8 or more, and may be 9 or more. Further, from the viewpoint of adhesive properties such as adhesive strength, the number of carbon atoms of the alkyl group in the alkyl (meth) acrylate A2 is preferably 14 or less, more preferably 12 or less, still more preferably 10 or less, for example, 9 or less. Yes, it may be less than 9.

In the embodiment in which the monomer raw material contains an alkyl (meth) acrylate A2, the ratio of the alkyl (meth) acrylate A2 to the entire monomer raw material may be, for example, about 1% by weight or more, and usually about 5% by weight or more. From the viewpoint of better expressing the action of the alkyl (meth) acrylate A2, it is preferably about 20% by weight or more, more preferably about 30% by weight or more, still more preferably about 40% by weight or more, in particular. It is preferably about 50% by weight or more, for example, 60% by weight or more, about 70% by weight or more, about 80% by weight or more, or about 90% by weight or more. The upper limit of the ratio of the alkyl (meth) acrylate A2 to the entire monomer raw material is not particularly limited, and it is usually appropriate to be about 99.5% by weight or less, for example, about 99% by weight or less. .. In some embodiments, the alkyl (meth) in the entire monomer raw material, for example, from the viewpoint of preferably exhibiting the action of the carbon-carbon double bond in the pressure-sensitive adhesive layer containing a polymer having a carbon-carbon double bond. The proportion of the acrylate A2 is preferably about 95% by weight or less, may be about 90% by weight or less, may be about 85% by weight or less, may be about 75% by weight or less, or may be about 70% by weight or less.

The ratio of the alkyl (meth) acrylate A2 to the total amount of the alkyl (meth) acrylate contained in the monomer raw material is appropriately about 5% by weight or more, and the viewpoint of preferably expressing the action of the alkyl (meth) acrylate A2. Therefore, it is preferably about 20% by weight or more, more preferably about 35% by weight or more, still more preferably about 45% by weight or more, for example, about 55% by weight or more, about 65% by weight or more, about 65% by weight or more. It may be 75% by weight or more, about 85% by weight or more, about 90% by weight or more, or about 95% by weight or more. The upper limit of the ratio of the alkyl (meth) acrylate A2 to the entire alkyl (meth) acrylate is 100% by weight. In some embodiments, the alkyl (meth) acrylate A2 occupies the entire alkyl (meth) acrylate, for example, from the viewpoint of preferably exhibiting its action when the alkyl (meth) acrylate A3 is used in combination with the alkyl (meth) acrylate A2. The ratio may be, for example, about 95% by weight or less, about 90% by weight or less, about 80% by weight or less, about 70% by weight or less, about 60% by weight or less, about 45% by weight. % Or less, about 30% by weight or less, about 20% by weight or less, about 10% by weight or less, or about 5% by weight or less. Alkyl (meth) acrylate A2 may not be used.

The monomer raw material used in the synthesis of the acrylic polymer may further contain a submonomer having copolymerizability with the alkyl (meth) acrylate as described above. The submonomer can be useful for introducing cross-linking points into the acrylic polymer and increasing the cohesive force of the acrylic polymer. Further, for example, a monomer raw material used for synthesizing a polymer having a carbon-carbon double bond can react with a functional group (hereinafter, also referred to as “functional group B”) of a carbon-carbon double bond-containing monomer described later. It is preferable to use a monomer having a functional group (hereinafter, also referred to as “functional group A”) as a submonomer.

As the submonomer, for example, the following functional group-containing monomers can be used alone or in combination of two or more.
Hydroxy group-containing monomers: For example, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, (4-hydroxymethylcyclohexyl). Hydroxyalkyl (meth) acrylates such as methyl (meth) acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; ether compounds such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and diethylene glycol monovinyl ether.
Carboxy group-containing monomer: Ethylene unsaturated monocarboxylic acid such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid, isocrotonic acid; ethylenically non-ethylic acid such as maleic acid, fumaric acid, itaconic acid, citraconic acid Saturated dicarboxylic acid.
Acid anhydride group-containing monomer: For example, maleic anhydride, itaconic anhydride.
Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, methyl-N-vinylpyrrolidone, vinylpyridine, vinylpyrazine, vinylpyrimidine, N-vinylpiperidone, N-vinylpiperazine, N-vinylpyrol, N-vinyl. Imidazole, N-vinyloxazole, N-vinylmorpholin, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl-1,3-oxazine-2-one, N-vinyl-3,5- Morpholindione, N-vinylpyrazole, N-vinylisoxazole, N-vinylthiazole, N-vinylisothiazole, N- (meth) acryloyl morpholine, N- (meth) acryloyl-2-pyrrolidone, N- (meth) acryloyl Piperidine, N- (meth) acryloylpyrrolidin, etc.
Amide group-containing monomers: For example, (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth). N, N-dialkyl (meth) acrylamide such as acrylamide, N, N-di (n-butyl) (meth) acrylamide, N, N-di (t-butyl) (meth) acrylamide; N-ethyl (meth) acrylamide , N-alkyl (meth) acrylamide such as N-isopropyl (meth) acrylamide, N-butyl (meth) acrylamide, Nn-butyl (meth) acrylamide; N-vinylcarboxylic acid amides such as N-vinylacetamide; Monomers having a hydroxyl group and an amide group, for example, N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-Hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) N-Hydroxyalkyl (meth) acrylamide such as acrylamide; monomers having an alkoxy group and an amide group, for example, N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide. N-alkoxyalkyl (meth) acrylamide such as N, N-dialkylaminoalkyl (meth) acrylamide such as N, N-dimethylaminopropyl (meth) acrylamide and the like.
Amino group-containing monomer: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having a succinimide skeleton: for example, N- (meth) acryloyloxymethylene succinimide, N- (meth) acryloyl-6-oxyhexamethylene succinimide, N- (meth) acryloyl-8-oxyhexamethylene succinimide and the like.
Maleimides: For example, N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide, N-phenylmaleimide and the like.
Itaconimides: For example, N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide, N-octylitaconimide, N-2-ethylhexylitaconimide, N-cyclohexylitaconimide, N-lauryl. Itaconimide, etc.
Epoxy group-containing monomers: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile.
Keto group-containing monomer: For example, diacetone (meth) acrylamide, diacetone (meth) acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.
Alkoxysilyl group-containing monomers: for example, 3- (meth) acryloxypropyltrimethoxysilane, 3- (meth) acryloxypropyltriethoxysilane, 3- (meth) acryloxipropylmethyldimethoxysilane, 3- (meth) acryloxy. Alkoxysilyl group-containing (meth) acrylates such as propylmethyldiethoxysilane, alkoxysilyl group-containing vinyl compounds such as vinyltrimethoxysilane and vinyltriethoxysilane, and the like.
Amino group-containing monomer: for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate.
Monomers having an epoxy group: for example, glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, allyl glycidyl ether.
Monomers containing sulfonic acid groups or phosphoric acid groups: for example, styrene sulfonic acid, allyl sulfonic acid, sodium vinyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfo. Propyl (meth) acrylate, (meth) acryloyloxynaphthalene sulfonic acid, 2-hydroxyethylacryloyl phosphate, etc.
Isocyanate group-containing monomers: for example, 2-isocyanatoethyl (meth) acrylate, (meth) acryloyl isocyanate, m-isopropenyl-α, α-dimethylbenzyl isocyanate.

The amount of the functional group-containing monomer may be appropriately selected so as to achieve a desired cohesive force, and is not particularly limited. Usually, from the viewpoint of achieving a good balance between cohesive force and other properties (for example, adhesiveness), the amount of functional group-containing monomers (when two or more kinds of functional group-containing monomers are used, the total amount thereof) is a monomer. It is suitable to be 0.1% by weight or more of the whole raw material, preferably 0.3% by weight or more, for example, 1% by weight or more. The amount of the functional group-containing monomer may be, for example, 50% by weight or less, preferably 40% by weight or less, for example, 35% by weight or less, 30% by weight or less, and 25% by weight or less of the total monomer raw material. However, it may be 20% by weight or less.

In some embodiments, the monomer raw material may include a hydroxyl group-containing monomer as the functional group-containing monomer. When a hydroxyl group-containing monomer is used, the amount used is not particularly limited, and may be, for example, 0.01% by weight or more, 0.1% by weight or more, or 0.5% by weight or more of the entire monomer raw material. It may be 1% by weight or more, 5% by weight or more, or 10% by weight or more. In some embodiments, the amount of the hydroxyl group-containing monomer used can be, for example, 50% by weight or less of the total monomer raw material, and is usually preferably 40% by weight or less from the viewpoint of suppressing water absorption of the pressure-sensitive adhesive. It may be 30% by weight or less, 25% by weight or less, or 20% by weight or less. Further, in some embodiments, the amount of the hydroxyl group-containing monomer used may be 15% by weight or less of the total monomer raw material, 10% by weight or less, or 5% by weight or less. Alternatively, it is not necessary to use a hydroxyl group-containing monomer.

In some embodiments, the monomer raw material may include a carboxy group-containing monomer as the functional group-containing monomer. The ratio of the carboxy group-containing monomer to the total monomer raw material used for synthesizing the acrylic polymer may be, for example, 15% by weight or less, 10% by weight or less, and 7% by weight from the viewpoint of suppressing water absorption of the pressure-sensitive adhesive layer. % Or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, 0.5% by weight or less, 0.1% by weight. It may be less than. The monomer raw material does not have to contain substantially no carboxy group-containing monomer. Here, the fact that the carboxy group-containing monomer is substantially not contained means that the carboxy group-containing monomer is not used at least intentionally. For example, in a monomer raw material used for preparing a polymer having a carbon-carbon double bond in a side chain, a configuration in which the proportion of a carboxy group monomer is limited for vapor can be preferably adopted.

In some embodiments, the monomer raw material may include, as the functional group-containing monomer, a monomer having a nitrogen atom. The use of a monomer having a nitrogen atom can impart appropriate polarity to the pressure-sensitive adhesive. This can be advantageous in realizing an adhesive sheet suitable for light peeling by supplying an aqueous stripping liquid such as water. A preferred example of a monomer having a nitrogen atom is a monomer having a nitrogen atom-containing ring. Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-type compounds such as N-vinyl-2-pyrrolidone (N-vinyl cyclic amide and the like) and N- (meth) acryloylmorpholine and the like from the viewpoint of compatibility and the like. -(Meta) acryloyl type compounds can be preferably adopted.

When a monomer having a nitrogen atom (for example, a monomer having a nitrogen atom-containing ring) is used, the amount used is not particularly limited, and may be, for example, 1% by weight or more of the entire monomer raw material, or 2% by weight or more. It may be 3% by weight or more, 5% by weight or more, or 7% by weight or more. From the viewpoint of obtaining a higher effect, in some embodiments, the amount of the monomer having a nitrogen atom used may be 10% by weight or more, 15% by weight or more, or 20% by weight or more of the total monomer raw material. Good. Further, from the viewpoint of facilitating the balance of characteristics, it is usually appropriate that the amount of the monomer having a nitrogen atom used is, for example, 40% by weight or less of the entire monomer raw material, and may be 35% by weight or less. It may be 50% by weight or less, or 25% by weight or less. In some embodiments, the amount of the monomer having a nitrogen atom used may be, for example, 20% by weight or less, 15% by weight or less, 10% by weight or less, or 5% by weight or less of the total monomer raw material. May be good. Alternatively, it is not necessary to use a monomer having a nitrogen atom.

When the above-mentioned monomer raw material is used for preparing a polymer having a carbon-carbon double bond, a functional group capable of reacting with a functional group (functional group B) of a compound having a carbon-carbon double bond, which will be described later, as an accessory monomer. It is preferable to use a functional group-containing monomer having (functional group A). In such a case, the type of the functional group-containing monomer is determined by the above compound type. As the submonomer having the functional group A, for example, a hydroxyl group-containing monomer, a carboxy group-containing monomer, an epoxy group-containing monomer, and an isocyanate group-containing monomer are preferable, and a hydroxyl group-containing monomer is particularly preferable. By using a hydroxyl group-containing monomer as a sub-monomer, the acrylic polymer has a hydroxyl group. On the other hand, by using an isocyanate group-containing monomer as a compound having a carbon-carbon double bond, the hydroxyl group (functional group A) of the acrylic polymer reacts with the isocyanate group (functional group B) of the compound. , The carbon-carbon double bond derived from the above compound is introduced into the acrylic polymer.

When a submonomer is used for the purpose of reacting with a compound having a carbon-carbon double bond, the amount of the submonomer (preferably a hydroxyl group-containing monomer) facilitates obtaining a pressure-sensitive adhesive layer suitable for water peeling. From the viewpoint, it is appropriate to use about 1% by weight or more in the total monomer raw material, preferably about 5% by weight or more, more preferably about 10% by weight or more, still more preferably about 12% by weight or more, for example, about 14% by weight. Weight% or more. Further, from the viewpoint of maintaining good adhesive properties such as adhesiveness, it is appropriate that the amount of the submonomer is about 40% by weight or less in the total monomer raw material, preferably about 30% by weight or less, more preferably. Is about 20% by weight or less, and may be, for example, about 15% by weight or less.

The monomer raw material used for preparing the acrylic polymer contains an accessory monomer (hereinafter, also referred to as a copolymerizable monomer) other than the above-mentioned functional group-containing monomer for the purpose of enhancing the cohesiveness of the acrylic polymer. You may.
Non-limiting specific examples of the above-mentioned copolymerizable monomer include the following.
Alkoxy group-containing monomer: Alkoxyalkyl (meth) acrylate such as 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate (alkoxyalkyl (meth) acrylate) Classes: Alkoxy (poly) alkylene glycol (meth) acrylates such as methoxyethylene glycol (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate.
Vinyl esters: For example, vinyl acetate, vinyl propionate and the like.
Vinyl ethers: For example, vinyl alkyl ethers such as methyl vinyl ether and ethyl vinyl ether.
Aromatic vinyl compounds: for example, styrene, α-methylstyrene, vinyltoluene and the like.
Olefins: For example, ethylene, butadiene, isoprene, isobutylene and the like.
(Meta) acrylic acid ester having an alicyclic hydrocarbon group: For example, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate and the like. Alicyclic hydrocarbon group-containing (meth) acrylate.
Aromatic ring-containing (meth) acrylate: For example, aryl (meth) acrylate such as phenyl (meth) acrylate, aryloxyalkyl (meth) acrylate such as phenoxyethyl (meth) acrylate, and arylalkyl (meth) acrylate such as benzyl (meth) acrylate. ) Acrylate.
In addition, heterocyclic (meth) acrylates such as tetrahydrofurfuryl (meth) acrylate, halogen atom-containing monomers such as vinyl chloride and fluorine atom-containing (meth) acrylates, and organosiloxane chain-containing monomers such as silicone (meth) acrylates. Terpen compound derivative (meth) acrylic acid ester obtained from alcohol, etc.
Such copolymerizable monomers may be used alone or in combination of two or more. The amount of the other copolymerizable monomer may be appropriately selected depending on the intended purpose and application, and is not particularly limited. For example, 20% by weight or less (for example, 2 to 20% by weight) of the total monomer raw material of the acrylic polymer. Typically, it is preferably 3 to 10% by weight).

In a preferred embodiment, the monomer raw material preferably has a total ratio of alkoxyalkyl (meth) acrylate and alkoxypolyalkylene glycol (meth) acrylate limited to less than 20% by weight from the viewpoint of suppressing gelation. The total proportion of the alkoxyalkyl (meth) acrylate and the alkoxypolyalkylene glycol (meth) acrylate is more preferably less than 10% by weight, further preferably less than 3% by weight, particularly preferably less than 1% by weight, in one embodiment. The monomer raw material is substantially free of alkoxyalkyl (meth) acrylate and alkoxypolyalkylene glycol (meth) acrylate (content 0 to 0.3% by weight).
Similarly, in one embodiment, the monomer raw material may or may not contain an alkoxy group-containing monomer in a proportion of less than 20% by weight. The amount of the alkoxy group-containing monomer in the monomer raw material is preferably less than 10% by weight, more preferably less than 3% by weight, still more preferably less than 1% by weight, and in a particularly preferable aspect, the monomer raw material has an alkoxy group. It contains substantially no monomer (content 0 to 0.3% by weight).

The method for polymerizing the monomer raw material is not particularly limited, and various polymerization methods known as synthetic polymers of acrylic polymers such as a solution polymerization method, an emulsion polymerization method, a massive polymerization method, and a suspension polymerization method are appropriately adopted. be able to. For example, a solution polymerization method can be preferably adopted. As a monomer supply method for solution polymerization, a batch charging method, a continuous supply (dropping) method, a divided feeding (dropping) method, or the like in which all the monomer raw materials are supplied at once can be appropriately adopted. The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds such as toluene (typically aromatic hydrocarbons); esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; 1,2- Alkane halides such as dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc. Any one solvent or a mixed solvent of two or more can be used. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and may be, for example, about 20 ° C. to 120 ° C. (typically 40 ° C. to 80 ° C.). it can. By solution polymerization, a polymerization reaction solution in which the polymer of the monomer raw material is dissolved in the polymerization solvent can be obtained. The pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer can be preferably produced by using the above-mentioned polymerization reaction solution. Producing a pressure-sensitive adhesive composition using the above-mentioned polymerization reaction solution may include, for example, chemically modifying the polymer contained in the above-mentioned polymerization reaction solution, such as introducing a carbon-carbon double bond.

In the polymerization, a known or commonly used thermal polymerization initiator or photopolymerization initiator may be used depending on the polymerization method, polymerization mode and the like. Examples of the thermal polymerization initiator include an azo-based polymerization initiator, a peroxide-based initiator, a redox-based initiator obtained by combining a peroxide and a reducing agent, a substituted ethane-based initiator, and the like. Examples of photopolymerization initiators include α-ketor photoinitiators, acetophenone photoinitiators, benzoin ether photoinitiators, ketal photoinitiators, aromatic sulfonyl chloride photoinitiators, photoactive oxime photoinitiators. Examples thereof include an initiator, a benzophenone-based photoinitiator, a thioxanthone-based photoinitiator, and an acylphosphinoxide-based photoinitiator. As the polymerization initiator, one type may be used alone or two or more types may be used in combination as appropriate.

The amount of the polymerization initiator used may be a normal amount, for example, about 0.005 to 1 part by weight (typically 0.01 to 1 part by weight) with respect to 100 parts by weight of the total monomer raw material. You can choose from a range. When the polymerization initiator is also used as a photoinitiator, the amount of the polymerization initiator used can be set in consideration of this.

For the above polymerization, various conventionally known chain transfer agents (which can also be grasped as a molecular weight adjuster or a degree of polymerization adjuster) can be used, if necessary. As the chain transfer agent, mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, thioglycolic acid, and α-thioglycerol can be used. Alternatively, a chain transfer agent containing no sulfur atom (non-sulfur chain transfer agent) may be used. Specific examples of the non-sulfur chain transfer agent include anilins such as N, N-dimethylaniline and N, N-diethylaniline; terpenoids such as α-pinene and turpinolene; α-methylstyrene and α-methylstyrene dimer. Such as styrenes; compounds having a benzylidenyl group such as dibenzylidene acetone, cinnamyl alcohol, cinnamyl aldehyde; hydroquinones such as hydroquinone and naphthohydroquinone; quinones such as benzoquinone and naphthoquinone; 2,3-dimethyl-2-butene , 1,5-Cyclooctadiene and the like; alcohols such as phenol, benzyl alcohol and allyl alcohol; benzyl hydrogens such as diphenylbenzene and triphenylbenzene; and the like.
The chain transfer agent may be used alone or in combination of two or more. When a chain transfer agent is used, the amount used can be, for example, about 0.01 to 1 part by weight with respect to 100 parts by weight of the monomer raw material. The techniques disclosed herein may also be preferably practiced in aspects that do not use chain transfer agents.

The molecular weight of the acrylic polymer is not particularly limited and can be set in an appropriate range according to the required performance. The weight average molecular weight (Mw) of an acrylic polymer is usually about 10 × 10 ⁴ or more (for example, 20 × 10 ^{4 or more), and is more than 30 × 10 4} from the viewpoint of achieving a good balance between cohesive force and adhesive force. and it is appropriate to, is preferably about 40 × 10 ⁴ or more, may be approximately 50 × 10 ⁴ or more, may be approximately 55 × 10 ⁴ or more. The upper limit of Mw of the acrylic polymer is not particularly limited. From the viewpoint of coatability of the pressure-sensitive adhesive composition, the Mw of the acrylic polymer, usually suitably be at about 500 × 10 ⁴ or less, for example may be at about 0.99 × 10 ⁴ or less, approximately 75 × 10 ⁴ may be less. The Mw may be the Mw of the acrylic polymer in either the pressure-sensitive adhesive composition or the pressure-sensitive adhesive layer.
Here, Mw refers to a standard polystyrene-equivalent value obtained by gel permeation chromatography (GPC). As the GPC apparatus, for example, a model name "HLC-8320GPC" (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used. The same applies to the examples described later.

The acrylic pressure-sensitive adhesive layer may further contain a polymer other than the acrylic polymer as a subpolymer, if necessary. As the above-mentioned subpolymer, among various polymers exemplified as polymers that can be contained in the pressure-sensitive adhesive layer, those other than the acrylic polymer can be mentioned as a preferable example. When the pressure-sensitive adhesive layer disclosed herein is an acrylic pressure-sensitive adhesive layer containing a subpolymer in addition to the acrylic polymer, the content of the subpolymer is less than 100 parts by weight with respect to 100 parts by weight of the acrylic polymer. It is appropriate, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and further preferably 10 parts by weight or less. The content of the subpolymer may be 5 parts by weight or less with respect to 100 parts by weight of the acrylic polymer, or may be 1 part by weight or less. The technique disclosed herein can be preferably carried out, for example, in an embodiment in which 99.5 to 100% by weight of the polymer contained in the pressure-sensitive adhesive layer is an acrylic polymer.

(Adhesive layer other than acrylic)
The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface in the pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive layer using a polymer other than the acrylic-based polymer as a base polymer, that is, a pressure-sensitive adhesive layer other than the acrylic-based polymer. The non-acrylic pressure-sensitive adhesive layer may further contain a subpolymer other than the base polymer in addition to the base polymer, if necessary. In this case, the content of the subpolymer in the non-acrylic pressure-sensitive adhesive layer can be selected from the above-mentioned contents exemplified as the content of the subpolymer in the acrylic pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer other than the acrylic-based adhesive layer may be a pressure-sensitive adhesive layer containing an acrylic-based polymer as a secondary polymer.

(Glass-transition temperature)
The glass transition temperature (Tg) of the base polymer (for example, an acrylic polymer) of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface is preferably about 15 ° C. or lower. In some embodiments, the Tg is preferably 10 ° C. or lower, and is 0 ° C. or lower, from the viewpoint of adhesion to the adherend (for example, followability to the surface shape of the adherend). The temperature is preferably −10 ° C. or lower, or −20 ° C. or lower. Further, from the viewpoint of the cohesiveness of the pressure-sensitive adhesive and the ease of light peeling due to water peeling, the Tg of the base polymer may be, for example, −75 ° C. or higher, −60 ° C. or higher, or −50 ° C. or higher. In some embodiments, the Tg of the base polymer may be −45 ° C. or higher, or −40 ° C. or higher.

Here, the glass transition temperature (Tg) of the polymer in the present specification means the glass transition temperature obtained by the Fox formula based on the composition of the monomer raw material constituting the polymer. As shown below, the Fox formula is a relational formula between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer in which each of the monomers constituting the copolymer is homopolymerized.
1 / Tg = Σ (Wi / Tgi)
In the Fox formula, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on the weight), and Tgi is the monomer i. Represents the glass transition temperature (unit: K) of the homopolymer.

As the glass transition temperature of the homopolymer used for calculating Tg, the value described in publicly known materials shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.
2-Ethylhexyl acrylate-70 ° C
n-Butyl acrylate -55 ° C
Isostearyl acrylate -18 ° C
Methyl methacrylate 105 ° C
Methyl acrylate 8 ℃
Ethyl acrylate-22 ° C
N-Vinyl-2-pyrrolidone 54 ° C
N-Acryloyl Morpholine 145 ° C
2-Hydroxyethyl acrylate -15 ° C
4-Hydroxybutyl acrylate-40 ° C
Acrylic acid 106 ℃
Methacrylic acid 228 ° C

For the glass transition temperature of homopolymers of monomers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple types of values are described in this document, the highest value is adopted.

For the monomer in which the glass transition temperature of the homopolymer is not described in the Polymer Handbook, the value obtained by the following measurement method shall be used (see JP-A-2007-51271). Specifically, in a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux condenser, 100 parts by weight of a monomer, 0.2 parts by weight of azobisisobutyronitrile and 200 parts by weight of ethyl acetate as a polymerization solvent were added. Add and stir for 1 hour while circulating nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63 ° C. and the reaction is carried out for 10 hours. Then, the mixture is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and subjected to shear strain at a frequency of 1 Hz using a viscoelasticity tester (ARES, manufactured by Leometrics) in a temperature range of −70 to 150 ° C. The viscoelasticity is measured in a shear mode at a heating rate of 5 ° C./min, and the peak top temperature of tan δ is defined as Tg of the homopolymer.

(Compound A)
The pressure-sensitive adhesive layer may contain a water-stripping additive, if necessary. As the water stripping additive, at least one compound A selected from the group consisting of a surfactant and a compound having a polyoxyalkylene skeleton is used. According to the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer containing such a water-stripping additive, the light peeling effect by water-stripping can be preferably exhibited. The reason is not particularly limited, but both the surfactant and the compound having a polyoxyalkylene skeleton have a hydrophilic region, whereby they are appropriately unevenly distributed on the surface of the pressure-sensitive adhesive layer and are aqueous. It is considered that the peeling force is effectively reduced when it comes into contact with the stripping liquid. As the compound having a surfactant and a polyoxyalkylene skeleton, one or more of known surfactants and compounds having a polyoxyalkylene skeleton can be used without particular limitation. Compound A is typically preferably contained in the pressure-sensitive adhesive layer in free form. Needless to say, some of the above-mentioned surfactants have a compound having a polyoxyalkylene skeleton, and vice versa.

As the surfactant that can be used as compound A, known nonionic surfactants, anionic surfactants, cationic surfactants and the like can be used. Of these, nonionic surfactants are preferable. The surfactant may be used alone or in combination of two or more.

Examples of nonionic surfactants are polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, and polyoxyethylene oleyl ether; polyoxyethylene octylphenyl ether, polyoxy. Polyoxyethylene alkyl phenyl ethers such as ethylene nonylphenyl ether; polyoxyethylene fatty acid esters such as polyoxyethylene monolaurate, polyoxyethylene monostearate, polyoxyethylene monooleate; sorbitan monolaurate, sorbitan monopalmitate , Solbitan monostearate, sorbitan fatty acid esters such as sorbitan monooleate; polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxy Polyoxyethylene sorbitan fatty acid esters such as ethylene sorbitan triisostearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate; polyoxyethylene glyceryl ether fatty acid esters; polyoxyelene-polyoxypropylene block copolymers; etc. Can be mentioned. Nonionic surfactants include reactive surfactants having radically polymerizable functional groups such as propenyl group, (meth) allyl group, vinyl group and (meth) acryloyl group (eg, polyoxyethylene nonylpropenylphenyl ether and the like). , Nonionic reactive surfactant). These nonionic surfactants can be used alone or in combination of two or more. From the viewpoint of preferably exerting the effect of the compound A being appropriately unevenly distributed on the surface of the pressure-sensitive adhesive layer and enhancing the performance stability of the pressure-sensitive adhesive sheet, it does not have the above-mentioned radically polymerizable functional group (non-reactive). ) A nonionic surfactant can be preferably adopted.

Examples of anionic surfactants include alkylbenzene sulfonates such as nonylbenzene sulfonate, dodecylbenzene sulfonate (eg sodium dodecylbenzene sulfonate); lauryl sulfate (eg sodium lauryl sulfate, ammonium lauryl sulfate), etc. Alkyl sulfate such as octadecyl sulfate; fatty acid salt; polyoxyethylene alkyl ether sulfate such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate (for example, sodium polyoxyethylene alkyl ether sulfate), polyoxy Polyoxyethylene alkyl phenyl ether sulfate such as ethylene lauryl phenyl ether sulfate (for example, sodium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, etc.), polyoxyethylene styrene phenyl ether sulfate, etc. Polyether sulfate; polyoxyethylene alkyl ether phosphate such as polyoxyethylene stearyl ether phosphate, polyoxyethylene lauryl ether phosphate, etc .; sodium salt, potassium salt, etc. of the above polyoxyethylene alkyl ether phosphate, etc. Polyoxyethylene alkyl ether phosphate ester salts; sulfosuccinates such as lauryl sulfosuccinate, polyoxyethylene lauryl sulfosuccinate (eg, sodium polyoxyethylene alkyl sulfosuccinate); polyoxyethylene alkyl ether acetate; etc. Can be mentioned. When the anionic surfactant forms a salt, the salt may be, for example, a metal salt such as a sodium salt, a potassium salt, a calcium salt or a magnesium salt (preferably a monovalent metal salt), an ammonium salt, an amine salt or the like. Can be. The anionic surfactant may be used alone or in combination of two or more. From the same viewpoint as the nonionic surfactant, a non-reactive anionic surfactant can be preferably adopted.

Examples of cationic surfactants include polyether amines such as polyoxyethylene lauryl amine and polyoxyethylene stearyl amine. The cationic surfactant may be used alone or in combination of two or more.

Examples of the compound having a polyoxyalkylene skeleton that can be used as compound A include polyalkylene glycols such as polyethylene glycol (PEG) and polypropylene glycol (PPG); polyethers containing polyoxyethylene units, and polyoxypropylene units. Compounds containing polyethers, oxyethylene units and oxypropylene units (the sequences of these units may be random or block-like); derivatives thereof; and the like can be used. Further, among the above-mentioned nonionic, anionic and cationic surfactants, compounds having a polyoxyalkylene skeleton can also be used. As the compound having a polyoxyalkylene skeleton, one kind may be used alone or two or more kinds may be used in combination. Among them, it is preferable to use a compound containing a polyoxyethylene skeleton (also referred to as a polyoxyethylene segment), and PEG is more preferable.

The molecular weight (chemical formula) of the compound having a polyoxyalkylene skeleton (for example, polyethylene glycol) is not particularly limited. From the viewpoint of uniform mixing, it is suitable, for example, less than 1000, and preferably about 600 or less (for example, 500 or less). The lower limit of the molecular weight of the compound having a polyoxyalkylene skeleton (for example, polyethylene glycol) is not particularly limited, and a compound having a molecular weight of about 100 or more (for example, about 200 or more, further about 300 or more) is preferably used.

In the pressure-sensitive adhesive sheet according to some preferred embodiments, the pressure-sensitive adhesive layer contains at least a surfactant as the compound A. This can increase the degree of cleaning of the adhesive sheet. The reason is not particularly limited, but a predetermined amount of water (peeling water) supplied when the pressure-sensitive adhesive sheet is water-striped from the SiN wafer comes into contact with the pressure-sensitive adhesive layer to form the pressure-sensitive adhesive layer. A part of the contained surfactant dissolves in the peeling water, and the peeling water moves on the adherend as the peeling of the adhesive sheet from the adherend progresses, whereby the surface of the adherend adheres. It is considered that the amount of carbon is reduced by cleaning in the peeling direction of the sheet. A similar effect can be exhibited when the pressure-sensitive adhesive sheet is water-striped from SiN or other various adherends using an aqueous stripping solution.

The pressure-sensitive adhesive layer containing compound A is typically formed from a pressure-sensitive adhesive composition containing the compound A. The pressure-sensitive adhesive composition containing Compound A can be preferably prepared by a method comprising adding Compound A in the form of no solvent or in the form of an organic solvent solution. The solvent-free form refers to a form that is not diluted with an organic solvent or water that does not form a pressure-sensitive adhesive layer, and may be, for example, a form composed of compound A. The organic solvent used for preparing the organic solvent solution can be appropriately selected from conventionally known organic solvents. Specific examples of such an organic solvent include the same solvents as those used for solution polymerization described later. Preferable examples include a mixed solvent containing ethyl acetate and ethyl acetate (which may be a mixed solvent of ethyl acetate and toluene), and a mixed solvent containing toluene and toluene. For example, a mixed solvent containing ethyl acetate or ethyl acetate as a main component can be preferably adopted. The solvent-based or active energy ray-curable pressure-sensitive adhesive composition is substantially water-free in some embodiments (eg, 100 parts by weight of Compound A) from the viewpoint of preventing water from being brought into the pressure-sensitive adhesive composition. It is preferred that Compound A be added in the form of an organic solvent solution (with a water content of less than 10 parts by weight or less than 5 parts by weight or less than 1 part by weight). As a result, a more homogeneous pressure-sensitive adhesive layer can be formed.

In some embodiments, as the compound A, a nonionic compound is preferably used because it can be easily blended into the pressure-sensitive adhesive composition with good uniformity. According to the pressure-sensitive adhesive composition in which the compound A is uniformly blended, a pressure-sensitive adhesive layer in which the compound A is uniformly present on the surface tends to be formed. This is preferable from the viewpoint of allowing the adhesive sheet to be peeled off from the adherend more smoothly and reducing the load on the adherend due to fluctuations in the peeling force (for example, vibration or impact accompanying the fluctuations).

The HLB of compound A is not particularly limited. The HLB of compound A can be, for example, 1 or more or 3 or more. The HLB of compound A is preferably 5 or more, 6 or more, 8 or more, or 9 or more. As a result, water releasability tends to be preferably exhibited. The HLB of compound A is more preferably 10 or more, still more preferably 11 or more, still more preferably 12 or more, particularly preferably 13 or more, and may be 14 or more, 15 or more, or even 16 or more. According to the compound A having an HLB in the above range, the light exfoliation property due to water exfoliation can be more effectively exhibited. The upper limit of the HLB is 20 or less, and may be 18, for example. In some embodiments, the HLB of compound A may be 16 or less, for example 15 or less, for example in terms of compatibility.

The HLB in the present specification is a Hydrophilic-Lipophile Balance by Griffin, which is a value indicating the degree of affinity of the surfactant with water or oil, and the ratio of hydrophilicity to lipophilicity is between 0 and 20. It is expressed by the numerical value of. The definition of HLB is W. C. Griffin: J. Soc. Cosmetic Chemists, 1,311 (1949), Koshimitsu Takahashi, Yoshiro Namba, Motoo Koike, Masao Kobayashi, "Surfactant Handbook", 3rd Edition, Kogaku Shosha Publishing, November 25, 1972, p179- As described in 182 and the like. The compound A having the above HLB can be selected based on the common general technical knowledge of those skilled in the art by referring to the above references as necessary.

In some correspondences, the compound A preferably has 2 or more hydroxyl groups in one molecule, and more preferably has 3 or more hydroxyl groups in one molecule, from the viewpoint of affinity with the aqueous stripping solution. .. Examples of compound A having 2 or 3 or more hydroxyl groups in one molecule include sorbitan monoester, polyoxyalkylene sorbitan monoester, polyoxyalkylene glyceryl ether, polyoxyalkylene diglyceryl ether, polyoxyalkylene glyceryl ether monoester and the like. Can be mentioned. The upper limit of the number of hydroxyl groups contained in one molecule of compound A is not particularly limited, but it is usually appropriate to be 10 or less from the viewpoint of solubility in an organic solvent and ease of preparation of a pressure-sensitive adhesive composition. It is preferably 8 or less, 6 or less, or 4 or less.

In some correspondences, as the compound A, a nonionic compound having a fatty acid ester structure can be preferably selected from the viewpoint of solubility in an organic solvent (for example, esters such as ethyl acetate). Compound A having a fatty acid ester structure can also be advantageous in terms of compatibility in the pressure-sensitive adhesive layer. For example, as the compound A to be contained in the acrylic pressure-sensitive adhesive layer, a compound having a fatty acid ester structure can be preferably adopted. Examples of nonionic compounds having a fatty acid ester structure include sorbitan fatty acid ester, polyoxyalkylene fatty acid ester, polyoxyalkylene fatty acid monoester and the like.

In some embodiments, the compound A is preferably in the form of 100% solid content and is liquid at room temperature (25 ° C. in this case) from the viewpoint of ease of preparation of the organic solvent solution.
Further, in some embodiments, the compound A is preferably one that dissolves without phase separation in Test II below, and more preferably one that dissolves without phase separation in Test I below. The following tests I and II shall be carried out in an environment of room temperature (23 to 25 ° C.) using compound A in the form of 100% solid content.
[Test I]
90 g of ethyl acetate and 10 g of compound A are placed in a container having a capacity of 200 ml (mL), stirred for 1 minute using a glass rod, allowed to stand, and visually observed for phase separation after 5 minutes.
[Test II]
90 g of ethyl acetate and 10 g of compound A are placed in a container having a capacity of 200 mL, stirred for 1 minute using a glass rod, treated at 35 kHz for 10 minutes using an ultrasonic disperser, and further stirred for 1 minute using a glass rod. After 5 minutes, visually observe the presence or absence of phase separation.
As the ultrasonic disperser, (manufactured by AS ONE, model name "ULTRASONIC CLEANER") or an equivalent product thereof can be used.

The amount of compound A used is not particularly limited, and can be set so as to appropriately exert the effect of use according to the purpose (for example, one or both of improvement in cleaning degree and reduction in water peeling power). In some embodiments, the amount of Compound A used may be, for example, approximately 5 parts by weight or less relative to 100 parts by weight of the base polymer, such as bonding reliability and water resistance to the adherend at a stage not intended for peeling. From the viewpoint of reliability, it is appropriate to be about 3 parts by weight or less, preferably less than 2 parts by weight, more preferably less than 1 part by weight, less than 0.8 parts by weight, and 0.6 parts by weight. It may be less than 0.4 parts by weight, less than 0.2 parts by weight, or less than 0.1 parts by weight. Compound A having a high HLB (for example, 5 or more, preferably 10 or more) tends to exhibit good water peelability even when added in a small amount. Further, the amount of the compound A with respect to 100 parts by weight of the base polymer can be, for example, 0.001 part by weight or more, and the compound A is uniformly present on the surface of the pressure-sensitive adhesive layer so that the pressure-sensitive adhesive sheet can be peeled off from the adherend. From the viewpoint of smoother progress, it is usually appropriate to set the amount to 0.01 parts by weight or more, preferably 0.03 parts by weight or more (for example, 0.1 parts by weight or more). In a composition that emphasizes water releasability, the amount of compound A with respect to 100 parts by weight of the base polymer may be 0.3 parts by weight or more (for example, 0.5 parts by weight or more).

(Crosslinking agent)
A cross-linking agent may be used for the pressure-sensitive adhesive layer (which may be an active energy ray-curable pressure-sensitive adhesive layer) for the purpose of adjusting the cohesive force or the like. The cross-linking agent may be contained in the pressure-sensitive adhesive layer in the form after the cross-linking reaction, or may be contained in the form before the cross-linking reaction. The type of the cross-linking agent is not particularly limited, and is selected from the conventionally known cross-linking agents so that the cross-linking agent exhibits an appropriate cross-linking function in the pressure-sensitive adhesive layer, for example, depending on the composition of the pressure-sensitive adhesive composition. be able to. Examples of the cross-linking agent that can be used include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, carbodiimide-based cross-linking agents, melamine-based cross-linking agents, urea-based cross-linking agents, metal alkoxide-based cross-linking agents, and metals. Examples thereof include a chelate-based cross-linking agent, a metal salt-based cross-linking agent, a hydrazine-based cross-linking agent, and an amine-based cross-linking agent. These can be used alone or in combination of two or more. In some preferred embodiments, at least an isocyanate-based crosslinker is used as the crosslinker. An isocyanate-based cross-linking agent and another cross-linking agent (for example, an epoxy-based cross-linking agent) may be used in combination.

As the isocyanate-based cross-linking agent, a polyfunctional isocyanate compound having two or more functionalities can be used. For example, aromatic isocyanates such as tolylene diisocyanate, xylene diisocyanate, polymethylene polyphenyl diisocyanate, tris (p-isocyanatophenyl) thiophosphate, diphenylmethane diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate. Isocyanate; etc. Commercially available products include trimethylolpropane / tolylene diisocyanate adduct (manufactured by Toso Co., Ltd., trade name "Coronate L") and trimethylolpropane / hexamethylene diisocyanate adduct (manufactured by Toso Co., Ltd., trade name "Coronate L"). Examples thereof include isocyanate adducts such as "Coronate HL") and isocyanurates of hexamethylene diisocyanate (manufactured by Toso Co., Ltd., trade name "Coronate HX").

As the epoxy-based cross-linking agent, one having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferable. Specific examples of the epoxy-based cross-linking agent include N, N, N', N'-tetraglycidyl-m-xylene diamine, 1,3-bis (N, N-diglycidyl aminomethyl) cyclohexane, and 1,6-hexane. Examples thereof include diol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy cross-linking agents include Mitsubishi Gas Chemical's product names "TETRAD-X" and "TETRAD-C", DIC's product name "Epicron CR-5L", and Nagase ChemteX's products. Examples thereof include the name "Denacol EX-512" and the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

As the oxazoline-based cross-linking agent, those having one or more oxazoline groups in one molecule can be used without particular limitation.
Examples of the aziridine-based cross-linking agent include trimethylolpropane tris [3- (1-aziridinyl) propionate], trimethylolpropane tris [3- (1- (2-methyl) aziridinyl propionate)], and the like. Be done.
As the carbodiimide-based cross-linking agent, a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used.

The metal chelate-based cross-linking agent can typically have a structure in which a polyvalent metal is covalently or coordinated to an organic compound. Examples of the polyvalent metal atom include Al, Zr, Co, Cu, Fe, Ni, V, Zn, In, Ca, Mg, Mn, Y, Ce, Ba, Mo, La, Sn, Ti and the like. Of these, Al, Zr, and Ti are preferable. Examples of the organic compound include an alkyl ester, an alcohol compound, a carboxylic acid compound, an ether compound, and a ketone compound. The metal chelate-based cross-linking agent can typically be a compound having a structure in which an oxygen atom in the organic compound is bonded (covalent bond or coordinate bond) to the polyvalent metal.

Peroxides may be used as the cross-linking agent in some embodiments. Peroxides include di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate, di-sec-butylperoxydicarbonate, and t-butylperoxyneodecanoate. , T-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxyisobutyrate, di Examples thereof include benzoyl peroxide. Among these, peroxides having particularly excellent cross-linking reaction efficiency include di (4-t-butylcyclohexyl) peroxydicarbonate, dilauroyl peroxide, dibenzoyl peroxide and the like. When a peroxide is used as the polymerization initiator, the peroxide remaining without being used in the polymerization reaction can also be used in the crosslinking reaction. In that case, the residual amount of peroxide may be quantified, and if the ratio of peroxide is less than a predetermined amount, the peroxide may be added so as to be a predetermined amount, if necessary. The quantification of peroxide can be carried out by the method described in Japanese Patent No. 4971517.

The amount of the cross-linking agent used (when two or more cross-linking agents are used, the total amount thereof) is not particularly limited, and can be appropriately set so as to obtain a desired effect of use. From the viewpoint of adhesion to the adherend and bond reliability at a stage where peeling is not intended, the amount of the cross-linking agent used with respect to 100 parts by weight of the base polymer (for example, acrylic polymer) is usually about 15 parts by weight or less. Is appropriate, preferably about 12 parts by weight or less, more preferably about 10 parts by weight or less, less than 7.0 parts by weight, less than 5.0 parts by weight, less than 4.0 parts by weight. It may be less than 3.0 parts by weight, less than 2.0 parts by weight, less than 1.0 parts by weight, or less than 0.5 parts by weight. In an embodiment containing a certain amount of compound A (for example, more than 0.2 parts by weight with respect to 100 parts by weight of the base polymer), the fact that the amount of the cross-linking agent used is not too large means that the compound A is excessive on the surface of the pressure-sensitive adhesive layer. It can also be advantageous from the viewpoint of avoiding contamination of the adherend due to uneven distribution.
Further, for example, in the pressure-sensitive adhesive sheet having an adhesive surface composed of an active energy ray-curable pressure-sensitive adhesive layer, the base polymer (for example, an acrylic polymer) 100 is exhibited from the viewpoint of exhibiting appropriate cohesiveness before the curing treatment by the active energy ray. The amount of the cross-linking agent used with respect to parts by weight is usually preferably about 0.005 parts by weight or more, preferably about 0.01 parts by weight or more, and may be about 0.05 parts by weight or more, and is about about 0.05 parts by weight. It may be 0.1 parts by weight or more, and may be about 0.2 parts by weight or more. In some embodiments, the amount of the cross-linking agent used relative to 100 parts by weight of the base polymer is preferably more than 0.3 parts by weight, more preferably more than 0.5 parts by weight, and may be more than 1.0 parts by weight. It may be over 5.5 parts by weight, over 2.0 parts by weight, over 3.0 parts by weight, or over 4.0 parts by weight. In the pressure-sensitive adhesive sheet that can be used in a mode in which water is peeled off after the curing treatment with active energy rays, when the amount of the cross-linking agent used is large, the strain due to curing shrinkage is easily maintained until the water-based stripping solution is supplied. The effect of light peeling by application can be more exerted.

In the embodiment in which the isocyanate-based cross-linking agent is used as the cross-linking agent, the amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the base polymer is usually about 0.005 parts by weight from the viewpoint of exhibiting appropriate cohesiveness before the curing treatment. The above is appropriate, preferably about 0.01 parts by weight or more, may be about 0.05 parts by weight or more, may be about 0.1 parts by weight or more, and may be about 0.2 parts by weight or more. , More than 0.3 parts by weight, more than 0.5 parts by weight, more than 1.0 parts by weight, more than 1.5 parts by weight, more than 2.0 parts by weight, 3.0 parts by weight. It may be more than 4.0 parts by weight. In the pressure-sensitive adhesive sheet that can be used in a mode in which water is peeled off after the curing treatment with active energy rays, the effect of light peeling by applying the water peeling method can be better exhibited by increasing the amount of the isocyanate-based cross-linking agent used.
Further, it is usually appropriate that the amount of the isocyanate-based cross-linking agent used with respect to 100 parts by weight of the base polymer is about 15 parts by weight or less, and the adhesion to the adherend and the bonding reliability at a stage where peeling is not intended. From the viewpoint of the above, it is preferably about 12 parts by weight or less, more preferably about 10 parts by weight or less, it may be less than 7.0 parts by weight, it may be less than 5.0 parts by weight, or it may be less than 4.0 parts by weight. , Less than 3.0 parts by weight, less than 2.0 parts by weight, less than 1.0 parts by weight, less than 0.5 parts by weight. In an embodiment containing a certain amount of compound A (for example, more than 0.2 parts by weight with respect to 100 parts by weight of the base polymer), the fact that the amount of the isocyanate-based cross-linking agent used is not too large means that the compound A is on the surface of the pressure-sensitive adhesive layer. It can also be advantageous from the viewpoint of avoiding contamination of the adherend due to excessive uneven distribution.

A cross-linking catalyst may be used to allow the cross-linking reaction to proceed more effectively. Examples of the cross-linking catalyst include metal-based cross-linking catalysts such as tetra-n-butyl titanate, tetraisopropyl titanate, ferric nasem, butyl tin oxide, and dioctyl tin dilaurate. Of these, tin-based cross-linking catalysts such as dioctyl tin dilaurate are preferable. The amount of the cross-linking catalyst used is not particularly limited. The amount of the cross-linking catalyst used with respect to 100 parts by weight of the base polymer may be, for example, approximately 0.0001 parts by weight or more and 1 part by weight or less, 0.001 parts by weight or more and 0.1 parts by weight or less, and 0.005 parts by weight or more. It may be 0.5 parts by weight or less.

(Polyfunctional monomer)
A polyfunctional monomer can be used for the pressure-sensitive adhesive layer, if necessary. The polyfunctional monomer can be used in place of or in combination with the cross-linking agent as described above, and may be useful for purposes such as adjusting the cohesive force. As the polyfunctional monomer, a compound having two or more carbon-carbon double bonds (for example, an ethylenically unsaturated group such as a (meth) acryloyl group) can be used. The polyfunctional monomer may be contained in the pressure-sensitive adhesive layer in an unreacted form, or may be contained in the pressure-sensitive adhesive layer in a post-reaction (post-crosslinking) form. The pressure-sensitive adhesive layer containing the unreacted polyfunctional monomer is formed by irradiating the pressure-sensitive adhesive layer with an active energy ray such as ultraviolet rays to react the polyfunctional monomer to form a crosslinked structure. It can be a curable pressure-sensitive adhesive layer.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) acrylate, and the like. Pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 1,12-dodecane Didioldi (meth) acrylate, trimethylolpropantri (meth) acrylate, tetramethylolmethanetri (meth) acrylate, allyl (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, butyl Examples thereof include diol (meth) acrylate and hexyldiol di (meth) acrylate. Of these, trimethylolpropane tri (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and dipentaerythritol hexa (meth) acrylate can be preferably used. The polyfunctional monomer may be used alone or in combination of two or more.

When a polyfunctional monomer is used, the appropriate amount to be used varies depending on its molecular weight, the number of functional groups, etc., but is usually 0.01 parts by weight to 3.3 parts by weight with respect to 100 parts by weight of the base polymer (for example, an acrylic polymer). It is appropriate that the range is about 0 parts by weight. In some embodiments, the amount of the polyfunctional monomer used relative to 100 parts by weight of the base polymer may be, for example, 0.02 parts by weight or more, 0.1 parts by weight or more, or 0.5 parts by weight. As mentioned above, it may be 1.0 part by weight or more or 2.0 parts by weight or more. Higher cohesive force tends to be obtained by increasing the amount of the polyfunctional monomer used. On the other hand, from the viewpoint of avoiding a decrease in adhesion to the adherend and a decrease in storage stability of the pressure-sensitive adhesive sheet due to excessive improvement in cohesive force, the amount of the polyfunctional monomer used with respect to 100 parts by weight of the base polymer is, for example, 10 parts by weight or less. It may be 5.0 parts by weight or less, or 3.0 parts by weight or less. Alternatively, it is not necessary to use a polyfunctional monomer. For example, a pressure-sensitive adhesive layer containing a polymer having a structure (carbon-carbon double bond, benzophenone structure, etc.) that causes a cross-linking reaction by irradiation with active energy rays is a pressure-sensitive adhesive that is substantially free of unreacted polyfunctional monomers. It can be a layer or a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition that is substantially free of polyfunctional monomers. Here, the fact that the pressure-sensitive adhesive composition does not substantially contain the polyfunctional monomer means that the amount of the polyfunctional monomer with respect to 100 parts by weight of the base polymer is less than 0.05 parts by weight (for example, less than 0.01 parts by weight). Say that.

(Other optional ingredients)
The pressure-sensitive adhesive layer (which may be an active energy ray-curable pressure-sensitive adhesive layer) is provided with a pressure-imparting resin (for example, a rosin-based, petroleum-based, terpene-based, phenol-based, ketone-based) tackifier resin, if necessary. ), Viscosity modifiers (eg thickeners), leveling agents, plasticizers, fillers, colorants such as pigments and dyes, stabilizers, preservatives, antioxidants, anti-aging agents, etc. Various common additives may be included as other optional ingredients. As for such various additives, conventionally known ones can be used by a conventional method and do not particularly characterize the present invention, and thus detailed description thereof will be omitted.
From the viewpoint of enhancing the cleaning effect by water peeling, in some embodiments, the content of the tackifier resin in the pressure-sensitive adhesive layer is, for example, less than 5 parts by weight, further less than 3 parts by weight, based on 100 parts by weight of the base polymer. It may be less than 1 part by weight, less than 0.5 parts by weight, or less than 0.1 parts by weight. The pressure-sensitive adhesive layer may be substantially free of the tack-imparting resin (for example, the content of the pressure-sensitive adhesive layer with respect to 100 parts by weight of the base polymer is 0 to 0.05 parts by weight). Limiting the content of the tackifier resin in this way can be advantageous from the viewpoint of improving the curability of the active energy ray-curable pressure-sensitive adhesive layer, for example.

In some preferred embodiments, the pressure-sensitive adhesive layer may have a composition in which the content of the polymer (typically the base polymer) accounts for approximately 80% by weight or more of the total weight of the pressure-sensitive adhesive layer. As a result, the effect of applying water peeling to reduce the peeling force (light peeling effect) can be preferably realized. From such a viewpoint, the content of the polymer is preferably about 85% by weight or more, more preferably about 90% by weight or more, and may be about 92% by weight or more based on the total weight of the pressure-sensitive adhesive layer. , It may be about 95% by weight or more.

(Active energy ray-curable adhesive layer)
In some embodiments, the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface is preferably a pressure-sensitive adhesive layer (active energy ray-curable pressure-sensitive adhesive layer) composed of an active energy ray-curable pressure-sensitive adhesive. The pressure-sensitive adhesive sheet having such a pressure-sensitive adhesive layer is irradiated with active energy rays after being attached to the adherend to cure the active energy ray-curable pressure-sensitive adhesive layer, and then water-based such as water is applied to the peeling front from the adherend. By supplying the peeling liquid and peeling (water peeling), a good cleaning effect can be exhibited and the peeling force from the adherend can be particularly effectively reduced.

In some embodiments, the active energy ray-curable pressure-sensitive adhesive layer is cured by irradiating it with active energy rays after being attached to the adherend, so that the peeling force from the adherend is reduced as compared with that before irradiation. It is preferable that it is configured to do so. The pressure-sensitive adhesive sheet having such an active energy ray-curable pressure-sensitive adhesive layer has good bonding reliability to the adherend before irradiation with active energy rays, and is peeled off with an aqueous stripping solution after irradiation with active energy rays. As a result, the peeling force can be significantly reduced.
As described above, the reason why the peeling force can be effectively reduced by peeling with an aqueous stripping solution after irradiation with active energy rays is not particularly limited, but is attached to the adherend. When the active energy ray-curable pressure-sensitive adhesive layer in the attached state is irradiated with active energy rays, micro-floating from the adherend occurs due to rapid curing shrinkage of the pressure-sensitive adhesive layer, or distortion occurs in the pressure-sensitive adhesive layer. It is considered that when the aqueous stripping solution is supplied in this state, the aqueous stripping solution rapidly penetrates into the interface between the pressure-sensitive adhesive layer and the adherend, and the peeling force is effectively reduced. By peeling the pressure-sensitive adhesive sheet, which is configured so that the pressure-sensitive adhesive layer is hardened by irradiation with active energy rays and the peeling power is reduced, by the water peeling method after irradiation with active energy rays, the peeling power due to curing of the pressure-sensitive adhesive layer Due to the synergistic effect of the decrease in water peeling force due to the above-mentioned rapid curing shrinkage, a particularly remarkable light peeling effect can be exhibited.

A preferred example of the active energy ray-curable pressure-sensitive adhesive layer is one that exhibits curability by containing a carbon-carbon double bond in the pressure-sensitive adhesive layer. The carbon-carbon double bond is chemically stable without reacting with moisture, acidity, etc. in the air in a normal storage environment that can be applied industrially. On the other hand, when radicals are generated by irradiating with active energy rays, they react (for example, polymerization reaction or cross-linking reaction) and harden. Light (for example, ultraviolet rays) is mentioned as a preferable active energy ray from the viewpoint of ease of handling.

In the pressure-sensitive adhesive layer that exhibits curability by containing a carbon-carbon double bond, the existence form of the carbon-carbon double bond in the pressure-sensitive adhesive layer is not particularly limited. The carbon-carbon double bond is, for example, a polymer having a carbon-carbon double bond (for example, a base polymer) or a monomer having a carbon-carbon double bond (for example, an unreacted polyfunctional monomer as described above). ) Etc., which can be contained in the pressure-sensitive adhesive layer. These may be used individually by 1 type, and may be used in combination of 2 or more type.

The form of the carbon-carbon double bond contained in the polymer and the form of the carbon-carbon double bond contained in the monomer are not particularly limited. For example, carbon-carbon double bonds can be present in polymers or monomers in the form of ethylenically unsaturated groups. Examples of the ethylenically unsaturated group include a (meth) acryloyl group, a vinyl group, an allyl group, a metharyl group and the like. From the viewpoint of reactivity, a (meth) acryloyl group is preferable.

(Polymer with carbon-carbon double bond)
In some embodiments, the active energy ray-curable pressure-sensitive adhesive layer preferably comprises a polymer having a carbon-carbon double bond. Hereinafter, the polymer having a carbon-carbon double bond is also referred to as "polymer (PD)". For example, a polymer (PD) having a carbon-carbon double bond in the form of an ethylenically unsaturated group is preferred. In some preferred embodiments, the polymer (PD) may be included in the active energy ray-curable pressure-sensitive adhesive layer as the base polymer for the pressure-sensitive adhesive layer. In some other embodiments, the polymer (PD) may be included in the active energy ray-curable pressure-sensitive adhesive layer as an accessory component used in addition to the carbon-carbon double bond-free base polymer. It may be an active energy ray-curable pressure-sensitive adhesive layer containing a polymer (PD) as a base polymer and further containing a monomer having a carbon-carbon double bond (for example, an unreacted polyfunctional monomer) as an accessory component.

The form of the carbon-carbon double bond of the polymer (PD) is not particularly limited. The polymer (PD) may be a polymer having a carbon-carbon double bond in the side chain or a polymer having a carbon-carbon double bond in the main chain. Here, having a carbon-carbon double bond in the main chain means that the carbon-carbon double bond is present in the main chain skeleton of the polymer (PD), and that the carbon-carbon double bond is present at the end of the main chain. Including what to do. From the viewpoint of the reactivity of the carbon-carbon double bond, a polymer (PD) having a carbon-carbon double bond in the side chain can be preferably adopted. The method of including the carbon-carbon double bond in the polymer (PD) is not particularly limited, and an appropriate method can be selected from the methods known to those skilled in the art.

The polymer (PD) is not particularly limited, and an appropriate polymer can be selected and used in consideration of the characteristics of the pressure-sensitive adhesive layer and the like. As a polymer (PD), a carbon-carbon double bond is chemically modified for a polymer (primary polymer) that does not contain a carbon-carbon double bond or has a carbon-carbon double bond content lower than that of the target product. Those introduced by a method such as modification (secondary polymer) can be preferably used.

As a specific example of the method for introducing a carbon-carbon double bond into a primary polymer, a primary polymer in which a monomer having a functional group (functional group A) is copolymerized is prepared, and the above-mentioned primary polymer is used in one molecule. A polymer having a functional group (functional group B) capable of reacting with the functional group A and a carbon-carbon double bond (hereinafter, also referred to as "functional group B-containing unsaturated compound") loses the carbon-carbon double bond. There is a method of reacting so as not to. The reaction between the functional group A and the functional group B is preferably a reaction that does not involve radical generation, such as a condensation reaction or an addition reaction.

Examples of the combination of the functional group A and the functional group B include a combination of a carboxy group and an epoxy group, a combination of a carboxy group and an aziridyl group, a combination of a hydroxyl group and an isocyanate group, and the like. Of these, a combination of a hydroxyl group and an isocyanate group is preferable from the viewpoint of reaction traceability. Further, as for the combination of the functional groups A and B, if a polymer having a carbon-carbon double bond can be obtained, one functional group in the combination may be a functional group A and the other may be a functional group B. Well, or one of the above functional groups may be a functional group B and the other may be a functional group A. For example, in the case of a combination of a hydroxyl group and an isocyanate group, the functional group A may be a hydroxyl group (in that case, the functional group B becomes an isocyanate group) or an isocyanate group (in that case, functional). Group B becomes a hydroxyl group.). Of these, a combination in which the primary polymer has a hydroxyl group and the above compound has an isocyanate group is preferable. This combination is particularly preferable when the primary polymer is an acrylic polymer.

Further, a vinyl alcohol-based polymer (typically polyvinyl alcohol) is used as the primary polymer, and vinyl bromide or the like is used as the vinyl alcohol-based polymer (typically, a vinyl alcohol-based polymer containing no carbon-carbon double bond). A method of reacting an allyl halide such as vinyl halide or allyl bromide is also mentioned as a preferable example of a method of obtaining a polymer having a carbon-carbon double bond. In this method, the above reaction is carried out under appropriate basic conditions, and the reaction gives a vinyl alcohol-based polymer containing a vinyl group in the side chain. Further, for example, a method of preparing a polymer having a carbon-carbon double bond may be adopted by utilizing a microorganism that produces a polymer as disclosed in Japanese Patent No. 4502363. Various conditions such as microbial species and microbial culture conditions in this method may be set by adopting the conditions described in the above patent gazette or appropriately modifying within the range of common general technical knowledge of those skilled in the art.

Molar ratio of the moles _{(M B)} of the molar _{(M A)} and the functional group B of the above functional groups A _(M A / M _B), from the viewpoint of both the reactive and usually be 0.2 or more Is appropriate, and may be 0.5 or more, 0.7 or more, or 1.0 or more. In some embodiments, the molar ratio _(M A / M _B) is 1.0 super but good, 1.5 super but may be 2.0 greater. For example, when utilizing a functional group A in (crosslinking reaction of the crosslinking agent) other reaction, it is preferable to molar ratio (M A _{/ M B)} and greater than 1.0. The molar ratio _(M A / M _B) may be, for example, 20 or less. In some embodiments, the molar ratio is from the viewpoint of achieving a good balance between adhesion to the adherend before light irradiation and peelability from the adherend after light irradiation (for example, peelability due to water peeling). _(M a / _{M B)} is preferably 10 or less, may be 5.0 or less, may be 2.5 or less, may be 1.8 or less, may be 1.5 or less, even 1.3 or less Good.

Functional groups B and the carbon - compound having a carbon double bond (. Hereinafter, also referred to as "functional group B-containing unsaturated compound") used in an amount of in the range satisfying the molar ratio of the above-mentioned (M A _{/ M B)} , For example, 1.0 part by weight or more, 3.0 parts by weight or more, 5.0 parts by weight or more, and 7.0 parts by weight with respect to 100 parts by weight of the primary polymer having a functional group A. It may be more than one copy. From the viewpoint of achieving both adhesion before light irradiation and peelability after light irradiation (for example, peelability by water peeling) at a higher level, in some embodiments, the functional group B is contained with respect to 100 parts by weight of the primary polymer. The amount of the unsaturated compound used is preferably 9.0 parts by weight or more, more preferably 10 parts by weight or more, 12 parts by weight or more, 14 parts by weight or more, or 16 parts by weight or more. The amount of the functional group B-containing unsaturated compound used with respect to 100 parts by weight of the primary polymer can be, for example, less than 40 parts by weight, usually less than 35 parts by weight, and less than 30 parts by weight. It may be less than 25 parts by weight, and may be less than 20 parts by weight. In some embodiments, the amount of the functional group B-containing unsaturated compound used relative to 100 parts by weight of the primary polymer may be less than 18 parts by weight, less than 16 parts by weight, less than 13 parts by weight, or less than 10 parts by weight. However, it may be less than 7 parts by weight.

A preferred example of a polymer having a carbon-carbon double bond is an acrylic polymer in which a (meth) acryloyl group is introduced into a side chain. Such an acrylic polymer includes, for example, an acrylic primary polymer in which a hydroxyl group (functional group A) has been introduced by copolymerization, and a compound having a carbon-carbon double bond and an isocyanate group (functional group B). It can be obtained by reacting so that the carbon-carbon double bond does not disappear.

Further, the polymer having a carbon-carbon double bond may be, for example, a diene-based polymer (typically, a conjugated diene-based polymer). A diene-based polymer (typically a conjugated diene-based polymer) is a polymer obtained by polymerizing or copolymerizing a diene (typically a conjugated diene). Examples of the diene polymer (typically, a conjugated diene polymer) include a butadiene polymer such as polybutadiene and a styrene butadiene copolymer; an isoprene polymer such as a polyisoprene and a styrene isoprene copolymer; and a chloroprene polymer such as polychloroprene. ; Etc. can be mentioned.

Another example of the active energy ray-curable pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer containing a polymer having a structure that causes a cross-linking reaction by irradiation with active energy rays and having a structure other than a carbon-carbon double bond. For example, a pressure-sensitive adhesive containing a polymer having a benzophenone structure in a side chain can exhibit active energy ray curability by photocrosslinking using the benzophenone structure. As the polymer having a benzophenone structure in the side chain, an acrylic polymer having a benzophenone structure in the side chain can be preferably adopted.

(Light initiator)
When ultraviolet rays are used as active energy rays for curing the active energy ray-curable pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer may contain a light initiator from the viewpoint of promoting a reaction or improving the utilization efficiency of light energy. preferable.
Examples of the photoinitiator include benzoin ether-based photoinitiator, acetophenone-based photoinitiator, α-hydroxyketone-based photoinitiator, aromatic sulfonyl chloride-based photoinitiator, photoactive oxime-based photoinitiator, and benzoin-based. Examples thereof include a photoinitiator, a benzyl-based photoinitiator, a benzophenone-based photoinitiator, a ketal-based photoinitiator, a thioxanthone-based photoinitiator, an α-aminoketone-based photoinitiator, and an acylphosphine oxide-based photoinitiator. The photoinitiator may be used alone or in combination of two or more.

Examples of the benzoin ether-based photoinitiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one, and anisole methyl. Examples include ether. Examples of the acetophenone-based photoinitiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxy-cyclohexyl-phenylketone, 4-phenoxydichloroacetophenone, and 4-t-butyl-. Examples thereof include dichloroacetophenone. Examples of the α-hydroxyketone-based photoinitiator include 2-hydroxy-2-methyl-1-phenyl-propan-1-one and 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-. Examples thereof include 2-methyl-1-propane-1-one. Examples of the aromatic sulfonyl chloride-based photoinitiator include 2-naphthalene sulfonyl chloride and the like. Examples of the photoactive oxime-based photoinitiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like. Examples of the benzoin-based photoinitiator include benzoin and the like. Examples of the benzyl-based photoinitiator include benzyl and the like. Examples of the benzophenone-based photoinitiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone and the like. Examples of the ketal-based photoinitiator include benzyldimethyl ketal and the like. Examples of the thioxanthone-based photoinitiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4-. Diisopropylthioxanthone, dodecylthioxanthone and the like can be mentioned. Examples of the α-aminoketone-based photoinitiator include 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1-one and 2-benzyl-2-dimethylamino-1- (4). -Morphorinophenyl) -butanone-1 and the like. Examples of the acylphosphine oxide-based photoinitiator include 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and the like.

A commercially available product may be used as the photoinitiator. For example, the trade names "Omnirad 651", "Omnirad 184", "Omnirad 2959", "Omnirad 907", "Omnirad 369", "Omnirad 1173", "Omnirad TPO", etc. manufactured by IGM Regins can be mentioned.

In some embodiments, the photoinitiator may be a photoinitiator that is difficult to decompose or radicalize by heating. For example, as the photoinitiator, a heat-resistant photoinitiator having a 10% by weight reduction temperature of 200 ° C. or higher can be used. By using such a heat-resistant photoinitiator, even if it is exposed to a high temperature before the curing treatment, the effect of reducing the peeling force due to the curing treatment by the active energy ray is not easily impaired. Can be done. The 10% by weight reduction temperature means that when the photoinitiator is placed in a nitrogen atmosphere and the environmental temperature is raised from 23 ° C. to 300 ° C. at a heating rate of 2 ° C./min, the weight of the photoinitiator is increased. It means the environmental temperature at the time when the weight before the temperature rise is reduced by 10% by weight (that is, the weight of the photoinitiator is 90% by weight with respect to the weight before the temperature rise). The 10% by weight reduction temperature of the photoinitiator is more preferably 210 ° C. or higher, still more preferably 220 ° C. or higher. Examples of the photoinitiator having a 10% by weight reduction temperature in such a range include the trade names "Omnirad 369", "Omnirad 127", "Omnirad 379", and "Omnirad 819" manufactured by IGM Regins, Inc.; Product name "Irgacure OXE02"; Product name "Esacure one", "Esacure 1001m" manufactured by Lamberti; Product name "Adeka Putmer N-1414", "Adeka Putmer N-1606" manufactured by Asahi Denka Kogyo Co., Ltd. , "Adeka Putmer N-1717" and the like.

The pressure-sensitive adhesive layer containing the photoinitiator can be formed by using the pressure-sensitive adhesive composition containing the photoinitiator. The method of incorporating the photoinitiator in the pressure-sensitive adhesive composition is not particularly limited. For example, it is preferable to add and mix a photoinitiator in a pressure-sensitive adhesive composition, typically in a polymer (polymerized polymer) -containing liquid. In this method, the photoinitiator can be added to the composition along with other additive components (eg, cross-linking agent, etc.). As another method, a method of adding a polymerization initiator capable of functioning as a photoinitiator at the time of polymer polymerization is exemplified. In this method, the polymerization initiator is added so that a predetermined amount remains even after the polymerization. The residual amount of the polymerization initiator (absence amount of the photoinitiator) can be adjusted not only by the amount of the polymerization initiator added, but also by the polymer polymerization conditions, the drying conditions at the time of forming the pressure-sensitive adhesive layer, the curing conditions, and the like.

When the pressure-sensitive adhesive layer contains a photoinitiator, the content of the photoinitiator in the pressure-sensitive adhesive layer is not particularly limited and can be set so as to appropriately exert a desired effect. In some embodiments, the content of the photoinitiator may be, for example, approximately 0.05 parts by weight or more, and approximately 0.1 parts by weight or more, based on 100 parts by weight of the base polymer of the pressure-sensitive adhesive layer. Is preferable, and more preferably about 0.5 parts by weight or more. As the content of the photoinitiator increases, the active energy ray curability of the pressure-sensitive adhesive layer tends to improve. In some embodiments, the content of the photoinitiator with respect to 100 parts by weight of the base polymer may be, for example, approximately 1.0 part by weight or more, may be approximately 2.0 parts by weight or more, and may be approximately 2.5 parts by weight or more. It may be. By increasing the content of the photoinitiator, the active energy ray curability of the pressure-sensitive adhesive layer is improved. The content of the photoinitiator with respect to 100 parts by weight of the base polymer can be, for example, about 20 parts by weight or less, usually about 10 parts by weight or less, and about 8 parts by weight or less. It is preferable that the amount is about 6 parts by weight or less, and the amount may be about 4 parts by weight or less. It is preferable that the content of the photoinitiator is not too large from the viewpoint of storage stability of the pressure-sensitive adhesive layer pressure-sensitive adhesive sheet (for example, performance of suppressing performance change due to storage of the pressure-sensitive adhesive sheet before use).

<Formation of adhesive layer>
The pressure-sensitive adhesive layer (eg, active energy ray-curable pressure-sensitive adhesive layer) constituting the pressure-sensitive surface of the pressure-sensitive adhesive sheet disclosed herein includes a base polymer (for example, an acrylic polymer) and, if necessary, other optional components. It can be a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive composition containing. The pressure-sensitive adhesive composition is a solvent-type pressure-sensitive adhesive composition in which a pressure-sensitive adhesive (adhesive component) is contained in an organic solvent, and is prepared so as to be cured by active energy rays such as ultraviolet rays and radiation to form a pressure-sensitive adhesive. Active energy ray-curable pressure-sensitive adhesive composition, water-dispersed pressure-sensitive adhesive composition in which the pressure-sensitive adhesive is dispersed in water, hot-melt type pressure-sensitive adhesive that is applied in a heat-melted state and forms a pressure-sensitive adhesive when cooled to around room temperature. It can be in various forms such as a composition. The active energy curable pressure-sensitive adhesive composition typically exhibits fluidity that can be applied at room temperature (approximately 0 ° C. to 40 ° C., for example, about 25 ° C.), and is cured by irradiation with active energy. It is a liquid composition that forms a pressure-sensitive adhesive (viscoelastic body).
The pressure-sensitive adhesive sheet according to some aspects may have a structure having a pressure-sensitive adhesive layer formed by using a solvent-type pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition. As the pressure-sensitive adhesive composition for forming the active energy ray-curable pressure-sensitive adhesive layer, a solvent-type pressure-sensitive adhesive composition can be preferably adopted from the viewpoint of easy control of the active energy ray-curable pressure.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein can be formed by applying (for example, coating) the pressure-sensitive adhesive composition to an appropriate surface and then appropriately performing a curing treatment (drying, cross-linking, polymerization, etc.). When performing two or more types of curing treatments, these can be performed simultaneously or in multiple stages. The pressure-sensitive adhesive layer having a multi-layer structure of two or more layers can be produced by laminating the pressure-sensitive adhesive layers formed in advance. Alternatively, the pressure-sensitive adhesive composition may be applied onto the first pressure-sensitive adhesive layer formed in advance, and the pressure-sensitive adhesive composition may be cured to form a second pressure-sensitive adhesive layer.

The pressure-sensitive adhesive composition can be applied using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, or a spray coater. In the pressure-sensitive adhesive sheet having a support, as a method of providing the pressure-sensitive adhesive layer on the support, a direct method of directly applying the pressure-sensitive adhesive composition to the support to form the pressure-sensitive adhesive layer may be used, and peeling may be used. A transfer method may be used in which the pressure-sensitive adhesive layer formed on the surface is transferred to the support.

In the pressure-sensitive adhesive sheet disclosed herein, the thickness of the pressure-sensitive adhesive layer is not particularly limited, and can be appropriately selected depending on the intended purpose. Usually, the thickness of the pressure-sensitive adhesive layer is preferably about 5 to 200 μm, preferably about 10 μm or more (for example, 15 μm or more), 25 μm or more, and preferably 150 μm or less from the viewpoint of adhesion and the like. , More preferably 100 μm or less, still more preferably 80 μm or less (for example, 60 μm or less, typically 40 μm or less), and may be 35 μm or less or less than 30 μm. When the pressure-sensitive adhesive sheet disclosed herein is a double-sided pressure-sensitive adhesive sheet having pressure-sensitive adhesive layers on both sides of a base material, the thickness of each pressure-sensitive adhesive layer may be the same or different.

<Additional adhesive layer>
In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet is configured such that an additional pressure-sensitive adhesive layer is laminated on the back side (opposite side of the pressure-sensitive adhesive surface) of the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface. There may be. It is preferable that the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface and the additional pressure-sensitive adhesive layer are directly in contact with each other and laminated. That is, it is preferable that a separator layer (for example, a resin film such as a polyester film) that completely separates the two pressure-sensitive adhesive layers is not interposed between the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface and the additional pressure-sensitive adhesive layer. Additional adhesive layers include, for example, acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixed systems, etc.), silicone adhesives, polyester adhesives, urethane adhesives, poly. The pressure-sensitive adhesive layer may be composed of one or more types of pressure-sensitive adhesives selected from various known pressure-sensitive adhesives such as ether-based pressure-sensitive adhesives, polyamide-based pressure-sensitive adhesives, and fluorine-based pressure-sensitive adhesives. From the viewpoint of transparency, weather resistance, and the like, an acrylic pressure-sensitive adhesive may be preferably adopted as a constituent material of the additional pressure-sensitive adhesive layer in some embodiments. For other matters of the additional pressure-sensitive adhesive layer, the same structure as the pressure-sensitive adhesive layer described above can be adopted, or an appropriate structure is adopted according to the application and purpose based on known or commonly used techniques and common general knowledge. Therefore, detailed description thereof will be omitted here.

<Base material>
In a single-sided adhesive type or double-sided adhesive type pressure-sensitive adhesive sheet with a base material, examples of the base material that supports (backs) the pressure-sensitive adhesive layer include a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, and a composite thereof. Various sheet-like base materials such as a body can be used. The base material may be a single layer, or may be a laminate of the same type or different types of base materials. In addition, in this specification, a single layer means a layer having the same composition, and includes the form in which a plurality of layers having the same composition are laminated.

In a preferred embodiment, a base material having a resin sheet as a main component (resin film base material) can be used. Examples of the resin constituting the base material include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, ultra-low-density polyethylene, random copolymerized polypropylene, block copolymerized polypropylene, homopolyprolene, and polybutene. , Polymethylpentene, ethylene-vinyl acetate copolymer (EVA), ionomer, ethylene- (meth) acrylic acid copolymer, ethylene- (meth) acrylic acid ester (random, alternating) copolymer, ethylene-butene Polypropylene resins such as polymers, ethylene-hexene copolymers; polyurethane; polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, polybutylene terephthalate (PBT); polycarbonate; polyimide; polyether ether ketone; polyetherimide; aramid , Polypropylene such as total aromatic polyamide; polyphenyl sulfide; fluororesin; polyvinyl chloride; polyvinylidene chloride; cellulose resin; silicone resin; and the like. The above resins may be used alone or in combination of two or more to form all or part of a substrate (eg, any layer in a substrate having a laminated structure of two or more layers). When the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface is an active energy ray-curable pressure-sensitive adhesive layer, it is preferable that the base material has active energy ray-transmitting property. In some embodiments, a substrate having an ultraviolet transmittance of 40% to 100% (more preferably 60% to 100%) at a wavelength of 365 nm can be preferably adopted. When a highly permeable base material is used, the pressure-sensitive adhesive layer can be easily cured.

As required, fillers (inorganic fillers, organic fillers, etc.), antioxidants, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, colorants (pigments, dyes, etc.) are used for the base material. Etc.) and other various additives may be blended.

The base material can be produced by any suitable method. For example, it can be produced by a known method such as a calendar method, a casting method, an inflation extrusion method, or a T-die extrusion method. Further, if necessary, it may be produced by performing a stretching treatment.

For the purpose of improving the adhesion to the pressure-sensitive adhesive layer and the retention of the pressure-sensitive adhesive layer on the surface of the base material on the pressure-sensitive adhesive layer side, for example, corona discharge treatment, plasma treatment, sand mat processing treatment, ozone exposure treatment, etc. Known or commonly used, such as physical treatments such as flame exposure treatment, high piezoelectric impact treatment, ionizing radiation treatment; chemical treatments such as acid treatment, alkali treatment, and chromium acid treatment; easy adhesion treatment with a coating agent (undercoating agent); Surface treatment may be applied. Further, a conductive vapor-deposited layer containing a metal, an alloy, an oxide thereof, or the like may be provided on the surface of the base material for the purpose of imparting antistatic ability.

In some preferred embodiments, an undercoat layer is provided on the pressure-sensitive surface of the substrate. In other words, an undercoat layer may be placed between the substrate and the pressure-sensitive adhesive layer. The undercoat layer forming material is not particularly limited, and is urethane (polyisocyanate) resin, polyester resin, acrylic resin, polyamide resin, melamine resin, olefin resin, polystyrene resin, epoxy resin, and phenol resin. One or more kinds of resins, isocyanurate-based resins, polyvinyl acetate-based resins and the like can be used. When an acrylic-based adhesive layer is provided on the resin film base material via an undercoat layer, a polyester-based, urethane-based, or acrylic-based undercoat layer is preferable. When an acrylic pressure-sensitive adhesive layer is provided on a polyester-based substrate such as a PET film via an undercoat layer, a polyester-based undercoat layer is particularly preferable. The thickness of the undercoat layer is not particularly limited and may generally be in the range of approximately 0.1 μm to 10 μm (eg, 0.1 μm to 3 μm, typically 0.1 μm to 1 μm). The undercoat layer can be formed using a known or conventional coater such as a gravure roll coater or a reverse roll coater.

When the pressure-sensitive adhesive sheet disclosed herein is a single-sided adhesive pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided on one side of the base material, a release treatment agent (back surface treatment) is applied to the non-formation surface (back surface) of the pressure-sensitive adhesive layer of the base material. The peeling treatment may be performed by the agent). The back treatment agent that can be used for forming the back treatment layer is not particularly limited, and is intended for silicone-based back treatment agents, fluorine-based back treatment agents, long-chain alkyl-based back treatment agents, and other known or conventional treatment agents. It can be used according to the application.

The thickness of the base material is not particularly limited and can be appropriately selected depending on the intended purpose, but generally it can be about 3 μm to 800 μm. From the viewpoint of processability and handleability of the pressure-sensitive adhesive sheet (for example, workability at the time of sticking or peeling to an adherend), it is appropriate that the thickness of the base material is 5 μm or more, and 10 μm or more. From the viewpoint of enhancing the protection of the adherend, it is preferably 20 μm or more, and may be 30 μm or more, or 40 μm or more. In some embodiments where protection is more important, the thickness of the substrate can be, for example, 55 μm or greater, 75 μm or greater, or 90 μm or greater. Further, from the viewpoint of reducing the load on the adherend at the time of peeling from the adherend, the thickness of the base material is usually preferably 300 μm, preferably 200 μm or less, and is preferably 150 μm. It may be 125 μm or less, 80 μm or less, or 60 μm or less.

The total thickness of the pressure-sensitive adhesive sheet (which may include the pressure-sensitive adhesive layer and the base material but does not include the release liner) disclosed herein is not particularly limited, and is appropriately in the range of approximately 10 μm to 1000 μm. The total thickness of the pressure-sensitive adhesive sheet is preferably in the range of about 15 μm to 300 μm, more preferably in the range of about 20 μm to 300 μm, and may be in the range of 20 μm to 200 μm in consideration of adhesion and handleability. .. Further, from the viewpoint of enhancing the protection of the adherend, it is advantageous that the total thickness of the adhesive sheet is about 30 μm or more, preferably about 40 μm or more, and about 50 μm or more (for example, 60 μm or more). Is more preferable. In some embodiments where protection is more important, the total thickness of the pressure-sensitive adhesive sheet may be greater than 65 μm, greater than 80 μm, or greater than 100 μm.

<Characteristics of adhesive sheet>
_{The pressure-sensitive adhesive sheet disclosed here preferably has a normal peeling force Fd 0} of 0.20 N / 20 mm or more, which is measured with a SiN wafer as an adherend by the method described in Examples described later. As a result, the adhesive sheet has good adhesion reliability to the adherend at a stage where peeling is not intended. Such an adhesive sheet can be preferably used as, for example, an adhesive sheet for semiconductor processing (back grind tape, dicing tape, etc.) used in a mode of being temporarily attached to an adherend in a process of manufacturing a semiconductor element. From the viewpoint of adhesion to the adherend, protection, etc., the normal peeling force Fd ₀ is preferably 0.50 N / 20 mm or more, may be 1.0 N / 20 mm or more, or 2.0 N / 20 mm or more. It may be 3.0 N / 20 mm or more, or 4.0 or more. Normally, the upper limit of the peeling force Fd _{0 is not particularly limited.} From the viewpoint of facilitating the reduction of the water peeling force Fw _{1, which will be described later, the normal peeling force Fd 0} may be, for example, 20.0 N / 20 mm or less, 15.0 N / 20 mm or less, or 10.0 N / 20 mm or less. It may be 7.0 N / 20 mm or less. Usually, the peeling force Fd ₀ is adjusted by selecting a base polymer, selecting the type and amount of the compound A when using compound A, selecting the type and amount of the cross-linking agent when using a cross-linking agent, and the like. be able to.

_{In the pressure-sensitive adhesive sheet disclosed here, the water peeling force Fw 1} after irradiation with active energy rays measured by the method described in Examples described later with the SiN wafer as an adherend is, for example, 4.0 N / 20 mm or less. It may be 3.0 N / 20 mm or less, or 2.0 N / 20 mm or less. According to the pressure-sensitive adhesive sheet having a smaller water peeling force Fw _1, the load applied to the adherend at the time of peeling can be further reduced by water peeling after irradiation with active energy rays. In some embodiments, the water peeling force Fw ₁ may be 1.5N / 20mm or less, 1.0N / 20mm or less, 0.50N / 20mm or less, 0.20N / 20mm or less, 0. It may be 10 N / 20 mm or less. The lower limit of the water peeling force Fw _{1 is not particularly limited, and the smaller the water peeling force Fw 1,} the more advantageous it is from the viewpoint of reducing the load on the adherend. On the other hand, from the viewpoint of bonding reliability to the adherend at a stage where peeling is not intended, the water peeling force Fw ₁ may be, for example, 0.001N / 20mm or more, and 0.005N / It may be 20 mm or more, 0.008 N / 20 mm or more, 0.01 N / 20 mm or more, or 0.005 N / 20 mm or more. The water peeling force Fw ₁ is adjusted by selecting a base polymer, selecting the type and amount of the compound A when using compound A, selecting the type and amount of the cross-linking agent when using a cross-linking agent, and the like. be able to.

_{In the pressure-sensitive adhesive sheet disclosed herein, the normal peeling force Fd 1} after irradiation with active energy rays measured by the method described in Examples described later with the SiN wafer as an adherend is the normal peeling force before irradiation with active energy rays. It is preferably lower than Fd _0. That is, it is preferable that _{Fd 0} <Fd _1. In some embodiments, the normal peeling force Fd ₁ may be, for example, less than 2.50 N / 20 mm, preferably less than 1.50 N / 20 mm, more preferably less than 1.00 N / 20 mm. It may be less than 0.50 N / 20 mm and may be less than 0.30 N / 20 mm. _{A pressure-sensitive adhesive sheet having a normal peeling force Fd 1} after irradiation with active energy rays is preferable because the peeling force can be further reduced by water peeling. Usually, the peeling force Fd ₁ is adjusted by selecting a base polymer, selecting the type and amount of the compound A when using compound A, selecting the type and amount of the cross-linking agent when using a cross-linking agent, and the like. be able to.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet has _{a water-peeling force Fw 0} measured in the same manner as the _{water-peeling force Fw 1 except that it is not irradiated with active energy rays.} It is suitable that it is .08N / 20mm or more, and it is preferable that it is 0.10N / 20mm or more. A larger water peeling force Fw ₀ may be advantageous from the viewpoint of bonding reliability (particularly, water resistance reliability) to the adherend at a stage where peeling is not intended. From this point of view, in some embodiments, the water peeling force Fw ₀ may be 0.70 N / 20 mm or more, 1.2 N / 20 mm or more, or 1.7 N / 20 mm or more. In some embodiments, the water peeling force Fw ₀ may be, for example, 7.0 N / 20 mm or less, 5.0 N / 20 mm or less, or 3.0 N / 20 mm or less. For example, when the pressure-sensitive adhesive layer constituting the adhesive surface does not have active energy ray-curable (non-active energy ray-curable), the water peeling force Fw ₀ is not too high when the pressure-sensitive adhesive sheet is removed from the adherend. It can be advantageous from the viewpoint of reducing the load applied to the adherend when the water is peeled off. The water peeling force Fw ₀ is adjusted by selecting the base polymer, selecting the type and amount of the compound A when using compound A, selecting the type and amount of the cross-linking agent when using a cross-linking agent, and the like. be able to.

As the tensile tester used for measuring the normal peeling forces Fd ₀ and Fd ₁ and the water peeling forces Fw ₀ and Fw ₁ , a precision universal testing machine "Autograph EZ-S" manufactured by Shimadzu Corporation or an equivalent product thereof shall be used. Can be done. In the measurement, if necessary, an appropriate backing material (for example, a PET film having a thickness of about 25 μm) can be attached to the adhesive sheet to be measured to reinforce it.

In the examples described later, the measurement of the normal peeling force and the measurement of the water peeling force were continuously performed for each test piece, but the measurement of the normal peeling force and the measurement of the water peeling force are different test pieces. May be done by. For example, when it is difficult to prepare a test piece having a sufficient length for carrying out continuous measurement, a mode in which measurement is performed using different test pieces can be adopted.

In a preferred embodiment of the pressure-sensitive adhesive sheet disclosed herein, the ratio of the water peeling force Fw _{1 [N / 20 mm] to the normal peeling force Fd 0} [N / 20 mm], that is, Fw ₁ / Fd ₀ (hereinafter, “peeling force residual rate”). ”) Can be, for example, less than 10.0%. In a usage mode in which such an adhesive sheet is temporarily attached to an adherend during the manufacturing process of a product, it exhibits good adhesion and protection to the adherend at a stage where peeling is not intended, and at the time of peeling. The load applied to the adherend can be effectively reduced. The peeling force residual rate is preferably less than 5.0%, more preferably less than 3.0%, less than 2.0%, or less than 1.0%. The lower limit of Fw ₁ / Fd _{0 is not particularly limited, and the smaller Fw 1} / Fd ₀ is, the more advantageous it is from the viewpoint of reducing the load on the adherend. On the other hand, from a practical point of view such as cost, in the pressure-sensitive adhesive sheet according to some aspects, Fw ₁ / Fd ₀ may be, for example, 0.01% or more, 0.05% or more, and 0.10. It may be% or more.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface is an active energy ray-curable pressure-sensitive adhesive layer, and the normal peeling force Fd _{1 after irradiation with active energy rays.} It is preferable that the reduction rate of the water peeling force Fw ₁ [N / 20 mm] with respect to [N / 20 mm] is more than 30%. That is, it is preferable that the rate of decrease in water peeling force calculated by the following formula is more than 30%.
Water peeling force reduction rate = 1- (Fw ₁ / Fd ₁ )
An adhesive sheet having a high rate of decrease in water peeling power is peeled off by a water peeling method after irradiating an active energy ray to cure the pressure-sensitive adhesive layer, thereby cleaning the surface of the adherend and peeling by a normal peeling method. By significantly reducing the peeling force as compared with the case where the peeling force is applied, the load applied to the adherend at the time of peeling can be significantly reduced. In the pressure-sensitive adhesive sheet according to some preferred embodiments, the rate of decrease in water peeling power may be more than 50%, 60% or more, 70% or more, or 80% or more. The upper limit of the rate of decrease in water peeling power is not particularly limited, but is usually 100% or less, and may be, for example, 95% or less or 90% or less from a practical point of view.

In some aspects of the pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive sheet has the above-mentioned carbon content B [atomic%] after water peeling and the SiN wafer after peeling the pressure-sensitive adhesive sheet from the SiN wafer by a normal peeling method. The degree of water peeling cleaning calculated by the following formula: 1- (B / C); from the amount of carbon C [atomic%] on the surface of the surface can be, for example, 10% or more. Here, the amount of carbon C is determined by a normal peeling method for peeling the test piece from the SiN wafer (when the pressure-sensitive adhesive layer constituting the adhesive surface is an active energy ray-curable pressure-sensitive adhesive layer, the normal peeling force Fd ₁ and so on. In the case of an inactive energy ray-curable pressure-sensitive adhesive layer, it is usually _{measured in the same manner as the measurement of the peeling force Fd 0} ), and is measured in the same manner as the measurement of the carbon amount B after water peeling described in Examples described later. To. Hereinafter, the carbon amount C may be referred to as "usually the carbon amount C after peeling".

The adhesive sheet having a water peeling cleaning degree of 10% or more is used in a mode of water peeling from a SiN wafer or other various adherends, and has a surface surface as compared with the case where the adherend is peeled off by a normal peeling method. Cleanliness can be improved. From the viewpoint of exerting a higher cleaning effect, in some embodiments, the degree of water peeling cleaning may be, for example, 15% or more, 20% or more, 25% or more, or 30% or more. It may be 35% or more, or 40% or more. In principle, the upper limit of the water peeling cleaning degree is 100%.

The pressure-sensitive adhesive sheet disclosed herein is characterized by having a water peeling cleaning degree of at least one of the above-mentioned lower limits (for example, 10%), and as long as this feature is provided, the formula: 1- (B / A) The degree of cleaning calculated by; may not be limited. Therefore, the matters disclosed in this specification are the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface, and the amount of carbon B on the surface of the SiN wafer after the pressure-sensitive adhesive sheet is water-peeled from the SiN wafer. It is calculated by the following formula: 1- (B / C); from [atomic%] and the carbon amount C [atomic%] on the surface of the SiN wafer after the adhesive sheet is usually peeled from the SiN wafer. An adhesive sheet having a water peeling cleaning degree of 10% or more is included. The pressure-sensitive adhesive sheet having a water peeling cleaning degree of a predetermined value or more can be implemented in the same manner as any of the above-mentioned pressure-sensitive adhesive sheets, for example.

<Use>
The pressure-sensitive adhesive sheet disclosed herein can be stripped of water from the adherend to improve the cleanliness of the surface of the adherend. Taking advantage of these features, the pressure-sensitive adhesive sheet can be preferably used as a pressure-sensitive adhesive sheet for applications that require a high level of cleanliness on the surface after peeling, such as a pressure-sensitive adhesive sheet for semiconductor processing and an optical pressure-sensitive adhesive sheet.

The aqueous stripping solution in the techniques disclosed herein (including pressure-sensitive adhesive sheets, pressure-sensitive adhesive compositions, semiconductor device manufacturing methods, pressure-sensitive adhesive sheet peeling methods, cleaning methods, etc.) contains water or water as a main component. A mixed solvent containing a small amount of additives, if necessary, can be used. As the solvent other than water constituting the mixed solvent, a lower alcohol (for example, ethyl alcohol) or a lower ketone (for example, acetone) that can be uniformly mixed with water can be used. As the additive, a known surfactant, pH adjuster, or the like can be used. From the viewpoint of surface cleanliness after peeling, in some embodiments, an aqueous stripping solution that is substantially free of additives may be used. From the viewpoint of environmental hygiene, it is particularly preferable to use water as the aqueous stripping solution. The water is not particularly limited, and for example, distilled water, ion-exchanged water, tap water, or the like can be used in consideration of the purity and availability required according to the application.

The pressure-sensitive adhesive sheet disclosed herein can be peeled off from the adherend while highly suppressing the load on the adherend by using an aqueous stripping solution, and thus is a hard and brittle material (for example, a silicon wafer or the like). The hard, brittle and thin portion (for example, 150 μm or less, 100 μm) of an adherend having a thin portion (hereinafter, also referred to as a hard, brittle and thin portion) composed of a constituent material of a semiconductor wafer, various ceramic materials such as sapphire, glass, etc. Hereinafter, it is suitable as an adhesive sheet that can be used in a mode of being peeled off from a portion of 50 μm or less or 30 μm or less. The pressure-sensitive adhesive sheet disclosed herein is preferably used as a pressure-sensitive adhesive sheet that is temporarily attached to such an adherend, and cracks or chips occur in the hard, brittle and thin portion due to a load when the pressure-sensitive adhesive sheet is peeled off. It is possible to prevent such an event. The hard, brittle and thin portion may be a portion formed by processing the adherend after attaching the adhesive sheet to the adherend.

The pressure-sensitive adhesive sheet disclosed herein is, for example, in a mode of being bonded to the semiconductor wafer formed by a circuit in a previous step in a process of manufacturing a semiconductor element (for example, a semiconductor chip) from various semiconductor wafers. , The semiconductor wafer can be preferably used as a semiconductor processing pressure-sensitive adhesive sheet for protecting and / or fixing the semiconductor wafer during processing. The semiconductor wafer may be, for example, a silicon wafer, a silicon carbide (SiC) wafer, a nitride semiconductor wafer (silicon nitride (SiN), gallium nitride (GaN), etc.), a compound semiconductor wafer such as a gallium hydride wafer, or the like. .. Examples of processing that can be performed on the semiconductor wafer after the pressure-sensitive adhesive sheets disclosed herein are bonded and before the pressure-sensitive adhesive sheets are peeled off include, but are not limited to, back grind processing and dicing processing. In this specification, even if the shape of the semiconductor wafer to be processed changes due to processing (for example, thinning of the whole or part by back grind processing, individual pieces by dicing processing, etc.), the processed article is continued. Sometimes called a semiconductor wafer.

Further, the adhesive sheet (optical adhesive sheet) attached to the optical member may be required to have reworkability. The above-mentioned rework is, for example, when the adhesive sheet is attached to the adherend due to failure (positional deviation, wrinkles, bubbles, foreign matter, etc.), or after the adhesive sheet is attached to the adherend. When a defect is found, the adhesive sheet attached to the adherend is peeled off and reattached. The pressure-sensitive adhesive sheet disclosed herein can be easily peeled off from the adherend by using a water peeling method, and the surface of the adherend after peeling has good cleanliness. Can be preferably used as. For example, it can be used for fixing, joining, molding, decorating, protecting, supporting, and the like in a manner of being attached to an optical member constituting various portable devices (portable devices), automobiles, home appliances, and the like.

The material constituting at least the surface of the optical member is, for example, glass such as an alkali glass plate or non-alkali glass; a metal material such as stainless steel (SUS) or aluminum; a ceramic material such as alumina or silica; an acrylic resin or an ABS resin. , Polycarbonate resin, polystyrene resin, transparent polyimide resin and other resin materials; etc. The optical member may be, for example, a member made of glass, acrylic resin, polycarbonate, polyethylene terephthalate, a metal thin film, or the like (for example, a sheet-shaped, film-shaped, or plate-shaped member). Preferable examples of the adherend include inorganic materials such as the above-mentioned glass, the above-mentioned ceramic material, and the above-mentioned metal material. The pressure-sensitive adhesive sheet disclosed herein includes, for example, an optical member whose surface is at least partially made of such a material and the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet is bonded to the surface of the optical member. It can be a component of an optical member with an adhesive sheet.

Examples of optical applications in the technology disclosed herein include applications for bonding optical members (for bonding optical members), applications for manufacturing products using the above optical members (optical products), and the like. As the optical pressure-sensitive adhesive sheet used for such applications, the pressure-sensitive adhesive sheet disclosed herein can be preferably used.

The optical member is a member having optical characteristics (for example, polarization, light refraction, light scattering, light reflection, light transmission, light absorption, light diffraction, optical rotation, visibility, etc.). obtain. Examples of the optical member include a member constituting a display device (image display device), a device (optical device) such as an input device, a member used for these devices, and the like, and specific examples thereof include a polarizing plate. Wavelength plate, retardation plate, optical compensation film, brightness improvement film, light guide plate, reflective film, antireflection film, hard coat (HC) film, shock absorbing film, antifouling film, photochromic film, light control film, transparent conductive film (ITO film), design film, decorative film, surface protective plate, prism, lens, color filter, transparent substrate, and members in which these are laminated (these may be collectively referred to as "functional film"). ), Etc., but are not limited to these. The above-mentioned "plate" and "film" shall include a plate-like, a film-like, a sheet-like form, respectively, and for example, the "polarizing film" shall include a "polarizing plate", a "polarizing sheet" and the like. Examples of the display device include a liquid crystal display device, an organic EL (electroluminescence) display device, a PDP (plasma display panel), electronic paper, and the like, and in particular, an expensive display device such as a foldable display device and an in-vehicle display device. The techniques disclosed herein are preferably applied when the components are included. Further, examples of the input device include a touch panel and the like. The "optical member" in this specification also includes a member (design film, decorative film, surface protective film, etc.) that plays a role of decoration and protection while maintaining the visibility of the display device and the input device.

The mode in which the optical members are bonded using the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and examples thereof include (1) a mode in which the optical members are bonded to each other via the pressure-sensitive adhesive sheet disclosed here, and (2). ) The optical member may be attached to a member other than the optical member via the pressure-sensitive adhesive sheet disclosed here, or (3) the pressure-sensitive adhesive sheet disclosed here includes the optical member. The adhesive sheet may be attached to an optical member or a member other than the optical member. In the aspect of (3) above, the pressure-sensitive adhesive sheet including the optical member may be, for example, a pressure-sensitive adhesive sheet in which the support is an optical member (for example, an optical film). The pressure-sensitive adhesive sheet including the optical member as the support can also be grasped as a pressure-sensitive optical member (for example, a pressure-sensitive optical film). Further, when the pressure-sensitive adhesive sheet disclosed herein is a type of pressure-sensitive adhesive sheet having a support and the above-mentioned functional film is used as the above-mentioned support, the pressure-sensitive adhesive sheet is provided on at least one side of the functional film. It can also be grasped as a "adhesive type functional film" having an adhesive layer disclosed in.

Adhesion of the pressure-sensitive adhesive sheet disclosed herein to an adherend (for example, a SiN wafer used for measuring the amount of carbon, a semiconductor wafer when used as a pressure-sensitive adhesive sheet for semiconductor processing, an optical member, etc.) is arbitrarily appropriate. It can be done by any method. The temperature at which the adhesive sheets are bonded may be around room temperature (for example, 10 ° C. to 35 ° C.), or may be higher than the room temperature range (for example, over 35 ° C., preferably 60 ° C. to 90 ° C.). .. Adhering the pressure-sensitive adhesive sheets at a temperature higher than the room temperature range may be advantageous from the viewpoint of improving the adhesion of the pressure-sensitive adhesive sheets to the adherend. After laminating the adhesive sheet in the room temperature range, the temperature is higher than the room temperature range (for example, 40 ° C. to 90 ° C., preferably 40 ° C. to 60 ° C.) and the pressure is higher than the atmospheric pressure (for example, 1.5 to 10 atm, preferably 3 to 3 to 3 to A heat-pressurizing treatment for imparting 7 atm) may be performed. The time for performing the heat and pressurization treatment is not particularly limited, and can be set so that an appropriate treatment effect can be obtained. In some embodiments, the time for performing the heat-pressurizing treatment can be set to 3 minutes to 1 hour (for example, 5 minutes to 30 minutes) in consideration of the balance between the stability of the treatment effect and the productivity.

When the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet disclosed herein is an active energy ray-curable pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet is attached to an adherend and then irradiated with active energy rays and water. It can be preferably used in an aspect of performing peeling. The irradiation conditions of the active energy rays are not particularly limited, and can be set so that the curing of the active energy ray-curable pressure-sensitive adhesive layer can proceed appropriately. A person skilled in the art can set appropriate irradiation conditions without undue burden based on the common general technical knowledge in the field, and therefore detailed description thereof will be omitted. As an example, the case of using ultraviolet rays as the active energy ray irradiation conditions of the ultraviolet rays, for example, approximately 50mJ ^/ cm ² ~5000mJ ^/ cm 2 in the range of integrated light quantity, of approximately 50mJ ^/ cm ² ~2000mJ ^/ cm 2 range or about 100 mJ ^/ cm 2 can be in the range of ~2000mJ / cm ^2, also can range approximately of 1 second to 30 minutes irradiation time.

<Semiconductor device manufacturing method>
An embodiment of a semiconductor device manufacturing method including using the pressure-sensitive adhesive sheet disclosed herein as a pressure-sensitive adhesive sheet for semiconductor processing will be described below. The semiconductor element manufacturing method of this embodiment includes a step (1) of adhering an adhesive surface of an adhesive sheet for semiconductor processing to the circuit forming surface side of a semiconductor wafer having a circuit forming surface, and the semiconductor to which the adhesive sheet is attached. The wafer includes a step (2) of processing the wafer from the side opposite to the pressure-sensitive adhesive sheet, and a step (3) of peeling the pressure-sensitive adhesive sheet from the processed semiconductor wafer.

Here, it is preferable that the step (3) is performed by supplying an aqueous peeling liquid to the peeling front of the pressure-sensitive adhesive sheet from the processed semiconductor wafer (adhesion). By peeling the adhesive sheet with water in this way, the effect of improving the cleanliness of the surface of the adherend can be exhibited. In addition, the pressure-sensitive adhesive sheet can be lightly peeled off, and the pressure-sensitive adhesive sheet can be efficiently peeled off while avoiding damage to the adherend. In some embodiments, the step (3) can be preferably carried out by the pressure-sensitive adhesive sheet peeling method described later.

When the pressure-sensitive adhesive layer constituting the adhesive surface is an active energy ray-curable pressure-sensitive adhesive layer, the active energy ray-curable pressure-sensitive adhesive layer is cured by irradiating with active energy rays before peeling off the pressure-sensitive adhesive sheet. Perform processing. Typically, the curing treatment reduces the peeling force of the pressure-sensitive adhesive sheet. By peeling the adhesive sheet with water after the curing treatment, the load applied to the adherend (semiconductor wafer after processing) at the time of peeling can be more effectively reduced. From the viewpoint of achieving both the reliability of adhesion to the adherend in the step (2) and the light peelability in the step (3), the curing treatment is preferably performed after the step (2).

In some embodiments, the step (2) can be a backgrinding step. In this case, the adhesive sheet is used as a back grind tape. The backgrinding process can be performed by any suitable method. The backgrinding step may be a step of thinning the semiconductor wafer to which the adhesive sheet is bonded until the thickness of the semiconductor wafer is, for example, 150 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. In the aspect of thinning in this way, the effect of peeling the pressure-sensitive adhesive sheet by the water peeling method in the step (3) can be preferably exhibited. The back grind step may be performed so that the inside of the annular convex portion becomes a concave portion (that is, a TAIKO (registered trademark) wafer can be obtained). In this case, the thickness of the thinned semiconductor wafer means the thickness of the recess. Further, although not particularly limited, the thickness of the semiconductor wafer before backgrinding may be, for example, about 500 μm to 1000 μm.

The semiconductor device manufacturing method disclosed herein may further include any suitable steps. Examples of such an optional step include, but are not limited to, an etching step, a photolithograph step, an ion injection step, a dicing step, a die bonding step, a wire bonding step, a packaging step, and the like. Each of the steps exemplified above may be performed in the step (2), after the step (2), before the step (3), or after the step (3). It may be done.

The pressure-sensitive adhesive sheet disclosed here can be water-striated from the adherend to improve the cleanliness of the surface of the adherend, which means that the pressure-sensitive adhesive sheet is water-striated from the adherend. It does not prevent the application of other cleaning means at any time. For example, the adherend after the pressure-sensitive adhesive sheet is peeled off with water may be washed with an appropriate cleaning liquid. In a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface contains compound A (preferably a surfactant), a trace amount of compound A may remain on the surface of the pressure-sensitive adhesive sheet after water peeling, and the remaining compound. A can contribute to the improvement of detergency when the adherend after water peeling is washed with an aqueous liquid (for example, water).

<Adhesive sheet peeling method>
According to this specification, there is provided a pressure-sensitive adhesive sheet peeling method for peeling a pressure-sensitive adhesive sheet attached to an adherend from the adherend. The method is such that the aqueous stripping liquid follows the movement of the stripping front in a state where the aqueous stripping solution is present at the interface between the adherend and the adhesive sheet in the peeling front of the adhesive sheet from the adherend. It may include a water stripping step of stripping the pressure-sensitive adhesive sheet from the adherend while advancing the liquid's entry into the interface. Here, the peeling front refers to a portion where the adhesive surface of the pressure-sensitive adhesive sheet begins to separate from the adherend when the pressure-sensitive adhesive sheet is peeled off from the adherend. According to the water peeling step, the adhesive sheet can be peeled from the adherend by effectively utilizing the aqueous stripping liquid. The peeling method can be preferably carried out, for example, by peeling any of the pressure-sensitive adhesive sheets disclosed herein from the adherend.

The adherend in the peeling method disclosed herein can be various semiconductor wafers exemplified above. The semiconductor wafer may be a circuit-formed semiconductor wafer. The peeling method disclosed herein can be preferably used as a method for peeling the pressure-sensitive adhesive sheet attached to the circuit-forming surface of the circuit-formed semiconductor wafer from the circuit-forming surface.

As the pressure-sensitive adhesive sheet to be peeled off from the adherend by the above-mentioned peeling method, any of the pressure-sensitive adhesive sheets disclosed herein can be preferably used. Therefore, the peeling method is suitable as a peeling method for any of the pressure-sensitive adhesive sheets disclosed herein.

In some embodiments, the peeling method comprises forming an initial peeling front by forcibly lifting the adhesive sheet from the adherend at one end of the outer edge of the adhesive sheet attached to the adherend. The above-mentioned adhesion is carried out while supplying the aqueous release liquid to the peeling front and advancing the invasion of the aqueous peeling liquid into the interface between the adhesive sheet and the adherend following the movement of the peeling front. It can be preferably carried out in a mode including peeling the pressure-sensitive adhesive sheet from the body. The initial peeling front is formed, for example, by inserting the tip of a jig such as a cutter knife or a needle into the interface between the adhesive sheet and the adherend, scratching the adhesive sheet with a hook or a nail, and lifting the adhesive sheet. A strong adhesive tape, a suction cup, or the like is attached to the back surface of the adhesive sheet to lift the edge of the adhesive sheet. By forming the initial peeling front in this way and then supplying the water-based stripping liquid to the peeling front to start water peeling, the water-based stripping liquid can be efficiently supplied to the peeling front. Further, in the peeling method and the pressure-sensitive adhesive sheet used in the peeling method, good water peelability after the operation of forcibly forming the initial peeling front to create a trigger for peeling and such an operation are not performed. It is possible to preferably achieve both high water resistance and reliability in some cases.

In some embodiments, the stripping method supplies a new aqueous stripping solution after supplying the aqueous stripping solution to the initial stripping front (ie, after supplying the aqueous stripping solution at the start of water stripping). It can be preferably carried out in a manner in which the peeling of the pressure-sensitive adhesive sheet is promoted without any trouble. Alternatively, if the aqueous stripping liquid that follows the movement of the stripping front and enters the interface between the adhesive sheet and the adherend is exhausted or insufficient during the progress of water stripping, the water stripping is started. Later, an additional aqueous stripping solution may be supplied intermittently or continuously. For example, when the length of the peeling front increases as the peeling progresses (for example, when water peeling proceeds from one end of the outer edge of the disk-shaped adherend in the radial direction of the circle), or on the surface of the adherend. When the aqueous stripping solution is likely to remain, a mode in which the aqueous stripping solution is additionally supplied after the start of water stripping can be preferably adopted. Further, the position for supplying the aqueous stripping solution may be one place or a plurality of places. When an additional aqueous stripping solution is supplied after the start of water stripping, the number of positions for supplying the aqueous stripping solution may be increased or decreased after the start of water stripping.

<Cleaning method>
According to this specification, a cleaning method including a step of water-stripping the adhesive sheet from the adherend (water-stripping step) is provided. In the water peeling step, the peeling front accompanying the progress of peeling of the pressure-sensitive adhesive sheet in a state where the aqueous stripping liquid is present at the interface between the adherend and the pressure-sensitive adhesive sheet in the peeling front of the pressure-sensitive adhesive sheet from the adherend. It is preferable to carry out the process in such a manner that the water-based stripping solution enters the interface in accordance with the movement of the water-based stripper. According to the water peeling step performed in such an embodiment, as the peeling front moves as the peeling of the pressure-sensitive adhesive sheet progresses, the aqueous peeling liquid moves on the adherend in the peeling direction of the pressure-sensitive adhesive sheet due to its cohesive force. .. As a result, the effect of cleaning the surface of the adherend with the aqueous release liquid in the release direction of the pressure-sensitive adhesive sheet can be exhibited. In the cleaning method, the carbon amount b [atomic%] on the surface of the adherend after the water peeling step is 5% as compared with the carbon amount a [atomic%] before the adhesive sheet is attached to the adherend. It is preferable that the amount is reduced by 10% or more, more preferably 20% or more, for example, 30% or more or 50% or more.

The cleaning method can be carried out using various pressure-sensitive adhesive sheets capable of improving the cleanliness of the surface of the adherend by being stripped of water from the adherend. For example, the adhesive layer constituting the adhesive surface of the adhesive sheet used in the above cleaning method is an acrylic adhesive, a rubber adhesive, a silicone adhesive, a polyester adhesive, a urethane adhesive, or a polyether adhesive. The pressure-sensitive adhesive layer may be composed of one or more types of pressure-sensitive adhesives selected from various known pressure-sensitive adhesives such as agents, polyamide-based pressure-sensitive adhesives, and fluorine-based pressure-sensitive adhesives. The pressure-sensitive adhesive layer may be an active energy ray-curable pressure-sensitive adhesive layer or a non-active energy ray-curable pressure-sensitive adhesive layer. Further, the pressure-sensitive adhesive layer may or may not contain the above-mentioned compound A. When the pressure-sensitive adhesive layer contains compound A, a surfactant (for example, a nonionic surfactant) can be preferably used as the compound A. The above cleaning method can be preferably carried out in an embodiment in which the pressure-sensitive adhesive layer constituting the pressure-sensitive surface uses a pressure-sensitive adhesive sheet containing at least a surfactant as compound A. In such an embodiment, a better cleaning effect can be exhibited.

In some embodiments, the cleaning method can be preferably carried out using any of the pressure-sensitive adhesive sheets disclosed herein. The pressure-sensitive adhesive sheet used may satisfy at least one of the above-mentioned preferable cleaning degree (1- (B / A)) and water peeling cleaning degree (1- (B / C)).

In some aspects of the cleaning method disclosed herein, the amount of aqueous stripping solution supplied to the initial stripping front (ie, the amount of aqueous stripping fluid supplied at the start of water stripping) is, for example, 5 μL or more. Usually, it is suitable to be 10 μL or more, and may be 20 μL or more. There is no particular limitation on the upper limit of the amount of aqueous stripping liquid to be supplied at the start of water stripping. In some embodiments, the amount of the aqueous stripping solution may be, for example, less than 10 mL or less than 5 mL from the viewpoint of improving workability and the like. This makes it possible to omit or simplify the operation of removing the aqueous liquid by drying, wiping, or the like after the pressure-sensitive adhesive sheet is peeled off. Also, in some embodiments, the amount of aqueous stripping solution supplied at the start of stripping may be, for example, less than 1 mL, less than 0.5 mL, less than 0.3 mL, 0.1 mL. It may be less than, and may be less than 0.05 mL. By limiting the amount of the aqueous stripping liquid used, the cleaning effect due to the movement of the aqueous stripping liquid in the peeling direction of the pressure-sensitive adhesive sheet as the peeling of the pressure-sensitive adhesive sheet progresses can be more efficiently exhibited. This is particularly significant in the embodiment of using a pressure-sensitive adhesive sheet having a pressure-sensitive surface composed of a pressure-sensitive adhesive containing compound A (preferably a surfactant).

From the viewpoint of operability when water is peeled off from the adherend, the cleaning method can be preferably carried out using a pressure-sensitive adhesive sheet having the form of a single-sided pressure-sensitive adhesive sheet with a base material (for example, a resin film base material). The cleaning method may include, in addition to the water peeling step, a step of adhering the adhesive sheet to the adherend. When the pressure-sensitive adhesive sheet is attached to the adherend or peeled off from the adherend, appropriate treatment (heat-pressurization treatment, ultraviolet irradiation treatment, etc.) according to the configuration and usage mode of the pressure-sensitive adhesive sheet is performed. It can be done at the right time as needed.

The adherend (object to be cleaned) to which the above cleaning method is applied may be, for example, the above-mentioned semiconductor wafer, optical member, or the like, but is not limited thereto. The cleaning method disclosed herein can be applied to various adherends capable of exhibiting a cleaning effect by applying the method.

The matters disclosed in this specification include the following.
[1] An adhesive sheet containing an adhesive layer constituting an adhesive surface.
The carbon amount B [atomic%] on the surface of the silicon nitride wafer after the pressure-sensitive adhesive sheet is water-peeled from the silicon nitride wafer, and the carbon amount A [atomic%] on the surface of the silicon nitride wafer before the pressure-sensitive adhesive sheet is attached. ], And the degree of cleaning calculated by the following formula: 1- (B / A); is 20% or more, the adhesive sheet.
[2] An adhesive sheet containing an adhesive layer constituting an adhesive surface.
The carbon amount B [atomic%] on the surface of the silicon nitride wafer after the pressure-sensitive adhesive sheet is water-peeled from the silicon nitride wafer, and the surface of the silicon nitride wafer after the pressure-sensitive adhesive sheet is peeled off from the silicon nitride wafer by a normal peeling method. An adhesive sheet having a water peeling cleaning degree of 10% or more calculated by the following formula: 1- (B / C); from the carbon amount C [atomic%] of.
[3] The adhesive sheet according to the above [1] or [2], wherein the carbon amount B is 10 atomic% or less.
[4] The pressure-sensitive adhesive sheet according to any one of [1] to [3] above, wherein the pressure-sensitive adhesive sheet has a water peeling force of 1.5 N / 20 mm or less from the silicon nitride wafer.
[5] In the pressure-sensitive adhesive sheet, the water peeling force [N / 20 mm] from the silicon nitride wafer is 40% or less of the normal peeling force [N / 20 mm] from the silicon nitride wafer. The adhesive sheet according to any one of [4].
[6] The above-mentioned [1] to [5], wherein the pressure-sensitive adhesive sheet contains at least one compound A selected from the group consisting of a surfactant and a compound having a polyoxyalkylene skeleton as a water-stripping additive. Adhesive sheet described in any.
[7] The pressure-sensitive adhesive sheet according to [6] above, which contains a surfactant as the compound A.
[8] The pressure-sensitive adhesive sheet according to the above [6] or [7], wherein the compound A is liquid at 25 ° C.
[9] The pressure-sensitive adhesive sheet according to any one of [1] to [8] above, wherein the pressure-sensitive adhesive layer is an active energy ray-curable pressure-sensitive adhesive layer.
[10] The pressure-sensitive adhesive sheet according to any one of [1] to [9] above, wherein the pressure-sensitive adhesive layer contains a photoinitiator.
[11] The pressure-sensitive adhesive sheet according to any one of [1] to [10] above, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer.
[12] The pressure-sensitive adhesive sheet according to any one of [1] to [11] above, which comprises a base material that supports the pressure-sensitive adhesive layer.
[13] The pressure-sensitive adhesive sheet according to any one of the above [1] to [12], which is used as a pressure-sensitive adhesive sheet for semiconductor processing.
[14] A pressure-sensitive adhesive composition used for forming the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet according to any one of the above [1] to [13].

[15] A method for cleaning the surface of an adherend.
Including a water peeling step of water stripping the adhesive sheet from the adherend.
Compared with the carbon amount b [atomic%] on the surface of the adherend before the adhesive sheet is attached to the adherend, the carbon amount b [atomic%] on the surface of the adherend after the water peeling step is 5% or more. How to reduce.
[16] In the water peeling step, the peeling of the pressure-sensitive adhesive sheet proceeds in a state where the aqueous stripping liquid is present at the interface between the adherend and the pressure-sensitive adhesive sheet at the peeling front of the pressure-sensitive adhesive sheet from the adherend. The method according to [15] above, wherein the approach of the aqueous stripping liquid to the interface proceeds following the movement of the stripping front.
[17] The method according to [15] or [16] above, further comprising a step of attaching the pressure-sensitive adhesive sheet to the adherend.
[18] The method according to any one of [15] to [17] above, wherein the adherend is a semiconductor wafer.
[19] The method according to any one of [15] to [18], wherein the adhesive sheet according to any one of [1] to [13] is used as the adhesive sheet.

Hereinafter, some examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples. In the following description, "part" and "%" are based on weight unless otherwise specified.

<Evaluation method>
(Normal measurement of peeling force Fd ₀₎
A test piece is prepared by cutting the adhesive sheet to be measured into a strip having a width of 20 mm. Silicon nitride wafer with the adhesive surface of the test piece as an adherend in an environment of 23 ° C. and 50% RH (6 inch wafer with LP-CVD nitride film 0.015 μm manufactured by KST World). It is attached to the wafer with a hand roller and left for 30 minutes to prepare a sample for evaluation.
Then, in an environment of 23 ° C. and 50% RH, a cutter knife is inserted into the interface between the test piece of the evaluation sample and the adherend to peel off one end s of the test piece in the longitudinal direction from the adherend. According to JIS Z0237: 2009 "10.4.1 Method 1: 180 ° peeling adhesive strength to test plate", specifically, a tensile tester (precision universal tester manufactured by Shimadzu Corporation) at a test temperature of 23 ° C. "Autograph EZ-S") is used to measure the peel strength under the conditions of a tensile speed of 300 mm / min and a peel angle of 180 degrees. The peel strength is measured so that the test piece attached to the adherend is peeled from the bottom to the top. The measurement is performed three times, and the average value thereof is usually set to a peeling force Fd ₀ [N / 20 mm].

(Measurement of water peeling force Fw ₀₎
In the measurement of the normal peeling force Fd ₀ , 20 μL of distilled water is supplied to a portion (peeling front) where the test piece begins to separate from the adherend while the test piece is being peeled from the adherend, and the distilled water is supplied. Measure the peel strength after supply. The measurement is performed for each measurement of each peel strength Fd ₀ (that is, three times), and the average value thereof is defined as the water peel strength Fw ₀ [N / 20 mm].

(Normal measurement of peeling force Fd ₁₎
An evaluation sample prepared in the same manner as the above-mentioned measurement of the normal peeling force Fd ₀ was subjected to the following conditions under the following conditions on the base material side of the pressure-sensitive adhesive sheet (the side opposite to the measurement pressure-sensitive adhesive surface. , Also referred to as "back side"), using a UV irradiator manufactured by Nitto Seiki Co., Ltd., trade name "NEL SYSTEM UM810" (high-pressure mercury lamp light source) or its equivalent, irradiation amount: illuminance 60 mW / cm ² , integration Ultraviolet rays are irradiated under the condition of a light amount of 300 mJ / cm ^2.
Then, in an environment of 23 ° C. and 50% RH, a cutter knife is inserted into the interface between the test piece of the evaluation sample and the adherend to peel off one end of the test piece in the longitudinal direction from the adherend. Normally, the peeling strength is measured in the same manner as the measurement of the _{peeling force Fd 0.} The measurement is performed three times, and the average value thereof is usually set to a peeling force Fd ₁ [N / 20 mm].

(Measurement of water peeling force Fw ₁₎
In the measurement of the normal peeling force Fd ₁ , 20 μL of distilled water is supplied to a portion (peeling front) where the test piece begins to separate from the adherend while the test piece is being peeled from the adherend, and the distilled water is supplied. Measure the peel strength after supply. The measurement is performed for each measurement of each peel strength Fd ₁ (that is, three times), and the average value thereof is defined as the water peel strength Fw ₁ [N / 20 mm].

(Measurement of carbon content)
The amount of carbon on the surface of the SiN wafer is determined by the following method based on X-ray photoelectron spectroscopy (ESCA).
[Measurement of initial carbon amount A]
An unused SiN wafer is fixed to a sample table, and qualitative analysis is performed by wide scan measurement. In addition, narrow scan measurements are performed on the four elements of carbon, nitrogen, oxygen, and silicon, and the element ratio of carbon [atomic%] out of the total amount of these four elements is calculated, and this is used as the initial carbon amount A. ..
[Measurement of carbon amount B after water peeling]
A test piece is prepared by cutting the adhesive sheet to be evaluated into a strip having a width of 20 mm. In an environment of 23 ° C. and 50% RH, the adhesive surface of the test piece is attached to an unused SiN wafer with a hand roller, and then left at room temperature for 2 hours.
Next, when the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet to be evaluated is an active energy ray-curable pressure-sensitive adhesive layer, it is usually irradiated with ultraviolet rays under the same conditions as the measurement of the _{peeling force Fd 1, and then the above water.} The test piece is peeled from the SiN wafer in the same manner as in the measurement of the peeling force Fw _1.
On the other hand, when the pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive surface of the pressure-sensitive adhesive sheet to be evaluated is a non-active energy ray-curable pressure-sensitive adhesive layer, the water peeling force is not performed after being left at room temperature for 2 hours without irradiation with ultraviolet rays. The test piece is peeled off from the SiN wafer in the same manner as in the measurement of Fw _0.
Then, using the SiN wafer surface in the range where the test piece was peeled off by water peeling as a measurement target, the elemental ratio of carbon [atomic%] was calculated in the same manner as the initial carbon amount A, and this was referred to as the carbon amount B after water peeling. To do.

The analyzer and measurement conditions used to measure the amount of carbon are shown below.
-Device :: ULVAC-PHI, Quantum 2000
・ X-ray source: Monochrome AlKα
-X Ray setting: 200 μmφ [15 kV, 30 W]
-Correction of binding energy: Corrects the peak caused by CC bond to 285.0 eV-Charge neutralization condition: Combined use of neutralization gun and Ar ion gun (neutralization mode)

<Example 1>
(Preparation of adhesive composition)
100 parts of n-butyl acrylate (BA) as a monomer raw material, 78 parts of ethyl acrylate (EA) and 40 parts of 2-hydroxyl ethyl acrylate (HEA) are mixed with 0.3 parts of BPO and toluene as a polymerization solvent. , Monomer composition was prepared. The above monomer composition is put into a 1L round bottom separable flask into an experimental apparatus for polymerization equipped with a separable cover, a separating funnel, a thermometer, a nitrogen introduction tube, a Liebig condenser, a vacuum seal, a stirring rod, and a stirring blade. The mixture was charged and replaced with nitrogen at room temperature for 6 hours with stirring. Then, the polymer was polymerized by holding at 60 ° C. for 6 hours and further at 78 ° C. for 1 hour with stirring under a nitrogen stream to obtain a solution of polymer Q1 (Mw: about 500,000). The Tg calculated from the Fox formula based on the composition of the monomer raw material is −37.2 ° C.

After cooling the solution of the above polymer Q1 to room temperature, 43.6 parts of 2-isocyanatoethyl methacrylate (manufactured by Showa Denko, trade name "Karenzu MOI") was added, and further dibutyltin (IV) dilaurate (Wako Pure Chemical Industries, Ltd.) was added. (Manufactured) 0.2 parts was added, and MOI was added to the polymer P1 by stirring at 50 ° C. for 24 hours in an air atmosphere to obtain a solution of the polymer P1 having a carbon-carbon double bond. Incidentally, amount of the MOI, the moles of the hydroxyl moles of the (functional group A) _{(M A)} and the isocyanate groups contained in the MOI (functional group B) contained in the HEA used in the synthesis of the polymer Q1 _{(M B} ) ratio of _(M a / M _B) is an amount which is about 1.2.

In a solution of the above polymer P1, per 100 parts of the polymer P1 in the solution, an isocyanate-based cross-linking agent (trimethylolpropane / tolylene diisocyanate trimer adduct, manufactured by Toso Co., Ltd., trade name "Coronate L", solid content concentration (75% by weight) was added in an amount of 0.2 parts based on the solid content, and further 3 parts of a photoinitiator H1 (manufactured by IGM Regins, trade name “Omnirad 651”) was added and mixed to prepare a pressure-sensitive adhesive composition C1. did.

(Making an adhesive sheet)
The pressure-sensitive adhesive composition C1 is applied to the peeling surface of a 38 μm-thick peeling film R1 (MRF38, manufactured by Mitsubishi Resin Co., Ltd.) in which one side of the polyethylene terephthalate (PET) film is a peeling surface by silicone treatment, and at 140 ° C. It was dried for 2 minutes to form a 20 μm thick pressure-sensitive adhesive layer. After the above-mentioned pressure-sensitive adhesive layer was bonded to the easy-adhesion surface of an easily-adhesive-treated PET film (thickness 50 μm) as a base material, it was aged at 50 ° C. for 2 days to obtain an adhesive sheet according to this example. This pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet with a base material having an adhesive surface composed of an active energy ray-curable pressure-sensitive adhesive layer.

<Example 2>
Nonionic surfactant A1 (polyoxyethylene sorbitan monolaure) that dissolves in the solution of the polymer P1 in 100 parts of the polymer P1 in the solution as a water-stripping additive in ethyl acetate without phase separation in the above-mentioned Test I. Rate, sorbitan fatty acid ester manufactured by Kao, trade name "Leodor TW-L 120", number of moles of ethylene oxide added 20, HLB 16.7) 0.10 part were further added. The pressure-sensitive adhesive composition C2 was prepared in the same manner as in the preparation of the pressure-sensitive adhesive composition C1 except for the above points. The pressure-sensitive adhesive sheet according to this example was obtained in the same manner as in the production of the pressure-sensitive adhesive sheet according to Example 1 except that the pressure-sensitive adhesive composition C2 was used. This pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet with a base material having an adhesive surface composed of an active energy ray-curable pressure-sensitive adhesive layer.
The nonionic surfactant A1 was used in the form of an ethyl acetate solution so that the above amount was added based on the solid content.

<Measurement and evaluation>
For the pressure-sensitive adhesive sheet according to each example, the initial carbon amount A [atomic%] and the carbon amount B [atomic%] after water peeling were obtained and substituted into 1- (B / A) to calculate the cleaning degree [%]. Further, for the adhesive sheet according to each example, the normal peeling force Fd ₀ [N / 20 mm] _{before UV irradiation and the water peeling force Fw 0,} and the normal peeling force Fd ₁ [N / 20 mm] and water peeling force Fw after UV irradiation. ₁ [N / 20 mm] was measured. The results are shown in Table 1.

As shown in Table 1, the pressure-sensitive adhesive sheet of Example 2 had a higher degree of cleaning than the pressure-sensitive adhesive sheet of Example 1, and was more suitable for cleaning the surface of the adherend by water peeling. In addition, the adhesive sheets of Examples 1 and 2 all showed good water releasability. Compared with the pressure-sensitive adhesive sheet of Example 1, the pressure-sensitive adhesive sheet of Example 2 _{had a lower water peeling force Fw 1} and was excellent in light peelability from an adherend.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

1,2,3,4,5,6 Adhesive sheet 10 Base material 10A First surface 10B Second surface 21,22 Adhesive layer 21A First adhesive surface 21B Second adhesive surface 31,32 Peeling liner

Claims (9)

An adhesive sheet containing an adhesive layer constituting an adhesive surface.
The carbon amount B [atomic%] on the surface of the silicon nitride wafer after the pressure-sensitive adhesive sheet is water-peeled from the silicon nitride wafer, and the carbon amount A [atomic%] on the surface of the silicon nitride wafer before the pressure-sensitive adhesive sheet is attached. ], And the degree of cleaning calculated by the following formula: 1- (B / A); is 20% or more, the adhesive sheet. The adhesive sheet according to claim 1, wherein the carbon amount B is 10 atomic% or less. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive sheet has a water peeling force from the silicon nitride wafer of 1.5 N / 20 mm or less. The pressure-sensitive adhesive sheet has any of claims 1 to 3 in which the water peeling force [N / 20 mm] from the silicon nitride wafer is 40% or less of the normal peeling force [N / 20 mm] from the silicon nitride wafer. The adhesive sheet described in item 1. The pressure-sensitive adhesive layer according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer contains at least one compound A selected from the group consisting of a surfactant and a compound having a polyoxyalkylene skeleton as a water-stripping additive. The described adhesive sheet. The pressure-sensitive adhesive sheet according to claim 5, which contains a surfactant as the compound A. The pressure-sensitive adhesive sheet according to claim 5 or 6, wherein the compound A is liquid at 25 ° C. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive layer is an active energy ray-curable pressure-sensitive adhesive layer. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, which comprises a base material that supports the pressure-sensitive adhesive layer.

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