WO2022054789A1

WO2022054789A1 - Adhesive sheet

Info

Publication number: WO2022054789A1
Application number: PCT/JP2021/032810
Authority: WO
Inventors: 直宏加藤; 匡崇西脇; 一樹箕浦; 俊輝伊神
Original assignee: 日東電工株式会社
Priority date: 2020-09-14
Filing date: 2021-09-07
Publication date: 2022-03-17
Also published as: JP7681955B2; JP2022047705A; KR20230066445A; CN116209728A

Abstract

The present invention provides an adhesive sheet in which both high-temperature holding power and an ability to follow a complex shape can be achieved. The adhesive sheet has an adhesive layer. The adhesive layer includes: a polymer having a weight-average molecular weight exceeding 70×10⁴; and at least one selected from oligomers and tackifier resins with a softening point of less than 145°C. The adhesive layer has a storage modulus G' (25°C) at 25°C of less than 0.15 MPa.

Description

Adhesive sheet

The present invention relates to an adhesive sheet. This application claims priority under Japanese Patent Application No. 2020-153622 filed on September 14, 2020, the entire contents of which are incorporated herein by reference.

Generally, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive; the same applies hereinafter) exhibits a soft solid state (viscous elastic body) in a temperature range near room temperature, and has a property of easily adhering to an adherend by pressure. Taking advantage of these properties, the pressure-sensitive adhesive is, for example, in the form of a pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on a support base material, or in the form of a base material-less pressure-sensitive adhesive sheet without a support base material, such as a smartphone or the like. It is widely used for the purpose of joining, fixing, and protecting members in portable electronic devices. Patent Documents 1 and 2 are listed as technical documents relating to adhesive tapes used for fixing members of portable electronic devices.

Japanese Patent Application Publication No. 2019-70102 Japanese Patent Application Publication No. 2018-28051

Adhesive sheets used in environments exposed to high temperatures are required to have good adhesive properties even at high temperatures. For example, the above-mentioned portable electronic device may be used in a high temperature environment, and the internal space thereof may be heated by the heat generated by the electronic component. Therefore, the adhesive sheet used for the purpose is in a high temperature state. However, it is necessary to have sufficient adhesive reliability. Further, since the adhesive area of the member fixing in the portable electronic device is usually small due to the limitation of size, weight, etc., the adhesive sheet used for the application can realize good fixing even in a small area. It is necessary to have the property, and its required performance has become higher level due to the demand for weight reduction and miniaturization. In particular, mobile electronic devices equipped with a touch panel display, such as smartphones, are becoming smaller and thinner, while the screens are becoming larger from the viewpoint of display visibility and operability. The applied pressure-sensitive adhesive is required to have adhesive fixing performance under more severe conditions. For fixing members in portable electronic devices, it is desirable to use an adhesive sheet having excellent adhesive fixing performance (for example, high temperature holding power) not only in a normal temperature range but also in a high temperature range.

In recent years, in addition to the above-mentioned miniaturization and thinning, the development of portable electronic device products having curved surface shapes such as three-dimensional shapes has been progressing, and the shapes of the constituent members tend to be complicated. Adhesives that are attached to the complicated shape are required to have the ability to follow the shape well and adhere to it. For example, in the above-mentioned portable electronic device, the adhesive for fixing a member such as a cover glass having a complicated surface shape (which may be a curved surface shape) is good while maintaining a state of following the complicated shape without a gap. It is necessary to exert a fixed function. If a gap is created between the adherend and the adherend without following the curved surface shape of the adherend, water may enter through the gap and the waterproof property may be impaired. The ability of the adherend to follow the complex surface shape can be improved by utilizing the flexibility of the adhesive sheet, but the highly flexible adhesive has the above-mentioned adhesive fixing performance at high temperature (particularly high temperature). Holding power) tends to decrease, and it is not easy to achieve both. It would be beneficial to provide an adhesive sheet that can achieve both followability to a complicated adherend shape and high temperature holding power.

The present invention has been created in view of the above circumstances, and an object of the present invention is to provide an adhesive sheet capable of achieving both followability to a complicated shape and high temperature holding power.

According to the present specification, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer is provided. The pressure-sensitive adhesive layer contains a polymer having a weight ^average molecular weight of more than 70 × 104, and at least one selected from an oligomer and a tackifier resin having a softening point of less than 145 ° C. The pressure-sensitive adhesive layer has a storage elastic modulus G'(25 ° C.) at 25 ° C. of less than 0.15 MPa. As the polymer contained in the pressure ^- sensitive adhesive, a polymer having a weight average molecular weight (Mw) of more than 70 × 104 is used, and at least one selected from an oligomer and a tackifier resin having a softening point of less than 145 ° C. is used. By forming a pressure-sensitive adhesive layer having a storage elasticity G'(25 ° C.) of less than 0.15 MPa at 25 ° C., the cohesive force based on the entanglement of the polymer and the effect of adding the oligomer and the low softening point pressure-sensitive adhesive resin can be obtained. By utilizing it, it is possible to realize a good high temperature holding force while maintaining the flexibility to follow a complicated adherend shape. That is, an adhesive sheet capable of achieving both followability to a complicated shape and high temperature holding power is provided.

In some preferred embodiments, the adhesive layer has a gel fraction greater than 35% by weight. By setting the gel fraction of the pressure-sensitive adhesive layer to more than 35% by weight, the high-temperature holding power can be improved.

In some preferred embodiments, the pressure-sensitive adhesive layer comprises a ratio of a storage modulus G'(25 ° C.) at 25 ° C. to a storage modulus G'(80 ° C.) at 80 ° C. (G'(80 ° C.) / G. ´ (25 ° C.)) is greater than 0.20. According to the pressure-sensitive adhesive in which the ratio of the 25 ° C. storage elastic modulus and the 80 ° C. storage elastic modulus is within a predetermined range as described above, both complex shape followability and high temperature holding power can be preferably compatible.

In some embodiments, the polymer dispersity (Mw / Mn) is 40 or less. By setting the dispersity of the polymer to a predetermined value or less, a cohesive action having a predetermined flexibility is preferably exhibited based on the entanglement of the high molecular weight sol of the polymer.

In some preferred embodiments, the polymer is an acrylic polymer. The pressure-sensitive adhesive layer disclosed herein may be an acrylic pressure-sensitive adhesive layer containing an acrylic-based polymer as a polymer. By using an acrylic polymer that has a wide range of molecular design options and is relatively easy to design, it is easy to obtain a polymer that is suitable for both complex shape followability and high temperature holding power. The techniques disclosed herein are preferably practiced in configurations with an acrylic pressure-sensitive adhesive layer.

In some preferred embodiments, the pressure-sensitive adhesive layer comprises both the oligomer and the pressure-imparting resin. In the composition containing a high molecular weight polymer, by using the tackifier resin having a softening point of less than 145 ° C. and the oligomer in combination, it is possible to achieve both complex shape followability and high temperature holding power in a more balanced manner.

In some embodiments, the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent. By using an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent in combination as the cross-linking agent, it is possible to preferably realize flexibility and cohesive power that achieve both complex shape followability and high-temperature holding power.

In some preferred embodiments, the pressure-sensitive adhesive sheet is a substrate-less double-sided adhesive pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer. The base material-less double-sided adhesive sheet can be made thinner because it does not have a base material, and can contribute to miniaturization and space saving of products to which the double-sided pressure-sensitive adhesive sheet is applied. Further, according to the base material-less pressure-sensitive adhesive sheet, the action of the pressure-sensitive adhesive layer such as flexibility and holding power can be maximized. Both the complex shape followability and the high temperature holding power by the techniques disclosed herein are preferably realized in the base material-less adhesive sheet.

The adhesive sheet disclosed herein has good high temperature holding power, so that it may be used in a high temperature environment, and the internal space thereof may become hot due to heat generation of electronic parts in a portable electronic device. It is suitable for the purpose of fixing a member. Further, since a portable electronic device such as a smartphone may include a member having a three-dimensional curved surface shape, it is suitable for the member fixing application in such a portable electronic device. The pressure-sensitive adhesive sheet disclosed herein is suitable for use in a portable electronic device to be attached to the step and / or curved surface of a member having a step and / or curved surface shape.

It is sectional drawing which shows typically one structural example of the pressure-sensitive adhesive sheet. It is an exploded perspective view which shows the structural example of a display device schematically.

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 the 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 schematically modeled for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product. ..

As described above, the term "adhesive" as used herein refers to a material that exhibits a soft solid state (viscoelastic body) in a temperature range near room temperature and has the property of easily adhering to an adherend by pressure. .. As defined in "C. A. Dahlquist," Adhesion: Fundamentals and Practice ", McLaren & Sons, (1966) P. 143", the pressure-sensitive adhesive here is generally a complex tensile modulus E ^* (1 Hz). It can be a material having a property of satisfying < ¹⁰⁷ dyne / cm ² (typically, a material having the above-mentioned property at 25 ° C.).

<Structure example of adhesive sheet>
The pressure-sensitive adhesive sheet disclosed herein may be a pressure-sensitive adhesive sheet with a base material having the pressure-sensitive adhesive layer on one side or both sides of a non-peelable base material (supporting base material), and the pressure-sensitive adhesive layer may be peeled off. It may be a base material-less pressure-sensitive adhesive sheet (that is, a pressure-sensitive adhesive sheet having no non-peelable base material) such as a form held on a liner. 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. The pressure-sensitive adhesive sheet disclosed herein 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.

FIG. 1 shows a configuration example of a double-sided adhesive type base material-less adhesive sheet (base material-less double-sided adhesive sheet). The pressure-sensitive adhesive sheet 1 shown in FIG. 1 has a structure in which both

sides

21A and 21B of the base-less pressure-sensitive adhesive layer 21 are protected by at least

release liners

31 and 32 having the pressure-sensitive adhesive layer side as a peel-off surface. Alternatively, the adhesive sheet has a structure in which one surface (adhesive surface, first adhesive surface) of the adhesive layer without a base material is protected by a release liner having both sides as release surfaces, and the adhesive sheet is wound. When turned, the other surface (adhesive surface, second adhesive surface) of the adhesive layer abuts on the back surface of the release liner, so that the second adhesive surface of the adhesive layer is also protected by the release liner. It may be configured. The technique disclosed herein can be preferably carried out in such a substrate-less form from the viewpoint of reducing the thickness of the pressure-sensitive adhesive sheet. The base material-less pressure-sensitive adhesive sheet is also advantageous in that it can be easily thinned and can maximize the pressure-sensitive adhesive properties such as adhesive strength, impact resistance, flexibility, and holding power.

<Adhesive layer>
(25 ° C storage elastic modulus)
The pressure-sensitive adhesive layer disclosed herein is characterized by a storage elastic modulus G'(25 ° C.) at 25 ° C. of less than 0.15 MPa. The pressure-sensitive adhesive having G'(25 ° C.) can be flexible enough to follow a complicated adherend shape. The G'(25 ° C.) is preferably less than 0.14 MPa, more preferably 0.12 MPa or less, and may be 0.11 MPa or less. Further, the G'(25 ° C.) is preferably 0.03 MPa or more, preferably 0.05 MPa or more, more preferably 0.09 MPa or more, still more preferably, from the viewpoint of compatibility with high temperature holding power. Is 0.10 MPa or more, and may be, for example, 0.11 MPa or more.

(25 ° C loss elastic modulus)
Further, although not particularly limited, the pressure-sensitive adhesive layer disclosed herein usually has a loss elastic modulus G "(25 ° C.) at 25 ° C. of 2.0 MPa or less. "(25 ° C.) is preferably 1.0 MPa or less, more preferably 0.50 MPa or less, still more preferably 0.30 MPa or less (for example, 0.20 MPa or less) from the viewpoint of cohesive force. The G "(25 ° C.) may be 0.10 MPa or less (for example, 0.07 MPa or less), and it is usually appropriate that the G" (25 ° C.) is larger than 0.01 MPa. From the viewpoint of wettability to the surface of the adherend and, by extension, followability to the shape of the adherend, it is preferably 0.03 MPa or more, more preferably 0.05 MPa or more, still more preferably 0.07 MPa or more, for example. It may be 0.08 MPa or more.

(25 ° C tan δ)
Further, the tan δ (25 ° C.) of the pressure-sensitive adhesive layer disclosed here at 25 ° C. can be appropriately set in consideration of adhesion to the adherend at room temperature, followability, cohesive force and the like. Here, the tan δ (tangent loss) of the pressure-sensitive adhesive (layer) means the ratio of the loss elastic modulus G ″ to the storage elastic modulus G ′ of the pressure-sensitive adhesive (layer), that is, tan δ = G ″ / G ′. be. It is appropriate that the tan δ (25 ° C.) is, for example, about 0.1 or more, preferably about 0.3 or more, more preferably about 0.5 or more, and about 0. It may be 7 or more. Further, the tan δ (25 ° C.) is suitable, for example, about 3 or less, and from the viewpoint of improving the cohesive force, it is preferably about 1.5 or less, more preferably about 1.2 or less, and further preferably about 1.0 or less. (For example, 0.90 or less), and may be approximately 0.80 or less (for example, 0.60 or less).

(80 ° C storage elastic modulus)
In some embodiments, the storage elastic modulus G'(80 ° C.) of the pressure-sensitive adhesive layer at 80 ° C. can be 0.01 MPa or more. The pressure-sensitive adhesive layer having a G'(80 ° C.) of a predetermined value or more tends to have excellent high-temperature holding power. The G'(80 ° C.) is preferably 0.020 MPa or more, more preferably 0.025 MPa or more, still more preferably about 0.030 MPa or more (for example, 0.035 MPa or more), and particularly preferably 0.040 MPa or more. It may be 0.045 MPa or more (for example, 0.050 MPa or more). The G'(80 ° C.) is usually preferably less than 0.10 MPa, for example, less than 0.08 MPa, less than 0.06 MPa, or less than 0.05 MPa.

(80 ° C. loss elastic modulus)
Further, although not particularly limited, it is appropriate that the loss elastic modulus G "(80 ° C.) of the pressure-sensitive adhesive layer at 80 ° C. is 1.0 MPa or less. The above G" (80 ° C.) is high temperature. From the viewpoint of cohesive force, it is preferably 0.30 MPa or less, more preferably 0.10 MPa or less, still more preferably 0.05 MPa or less, and particularly preferably 0.03 MPa or less (for example, less than 0.02 MPa). Further, the G "(80 ° C.) is usually preferably larger than 0.001 MPa, and may be 0.005 MPa or more, or 0.010 MPa or more.

(80 ° C. tan δ)
Further, the tan δ (80 ° C.) of the pressure-sensitive adhesive layer disclosed here at 80 ° C. can be appropriately set in consideration of adhesion to the adherend at high temperature, followability, cohesive force and the like. It is appropriate that the tan δ (80 ° C.) is, for example, about 0.03 or more, preferably about 0.08 or more, more preferably 0.10 or more, still more preferably 0.20 or more (for example, 0.30 or more). ). Further, for tan δ (80 ° C.), for example, about 1.0 or less is suitable, preferably about 0.80 or less, more preferably about 0.60 or less, still more preferably 0.50 MPa or less (for example, about 0.40). Below).

((G'(80 ° C) / G'(25 ° C))
In some preferred embodiments, the pressure-sensitive adhesive layer comprises a ratio of storage modulus G'(25 ° C.) at 25 ° C. to storage modulus G'(80 ° C.) at 80 ° C. (G'(80 ° C.) / G'. (25 ° C.)) is greater than 0.20. As described above, the adhesive having a ratio of the 25 ° C. storage elastic modulus and the 80 ° C. storage elastic modulus within a predetermined range has relatively high flexibility at room temperature and relatively high cohesive force at high temperature. Tends to stay high. Therefore, according to the pressure-sensitive adhesive that satisfies the above-mentioned characteristics, both complex shape followability and high temperature holding power can be preferably compatible. The ratio (G'(80 ° C.) / G'(25 ° C.)) may be 0.22 or more, 0.25 or more, 0.27 or more, and more preferably 0.30 or more. It is more preferably 0.35 or more, and particularly preferably 0.40 or more (for example, 0.42 or more). The upper limit of the above ratio (G'(80 ° C.) / G'(25 ° C.)) is not particularly limited, and is usually 0.80 or less, for example, 0.60 or less, or 0.50 or less. good.

Although not particularly limited, it is appropriate that the glass transition temperature (Tg) of the pressure-sensitive adhesive layer is controlled to about 20 ° C. or lower from the viewpoint of adhesion to the adherend. The pressure-sensitive adhesive layer having Tg tends to have excellent impact resistance. The Tg of the pressure-sensitive adhesive layer is preferably about 10 ° C. or lower, more preferably about 5 ° C. or lower, and may be about 0 ° C. or lower, and may be −5 ° C., from the viewpoint of followability to a complicated adherend shape. It may be ℃ or less (for example, -10 ℃ or less). The Tg of the pressure-sensitive adhesive layer is preferably about -25 ° C. or higher from the viewpoint of improving the cohesive force, and preferably about -15 ° C. or higher, more preferably about-from the viewpoint of obtaining a good high-temperature holding power. It is 12 ° C. or higher, may be approximately −7 ° C. or higher, or may be approximately -3 ° C. or higher (for example, -1 ° C. or higher). The Tg of the pressure-sensitive adhesive layer in the present specification means the glass transition temperature obtained from the peak temperature of tan δ in the dynamic viscoelasticity measurement.

Viscoelastic properties of the above-mentioned pressure-sensitive adhesive layer (25 ° C storage elastic modulus, 25 ° C loss elastic modulus, 25 ° C. tanδ, 80 ° C. storage elastic modulus, 80 ° C. loss elastic modulus, 80 ° C. tanδ and Tg (peak top temperature of tanδ)) The specific numerical range of) is that when the pressure-sensitive adhesive sheet is a substrate-less pressure-sensitive adhesive sheet consisting substantially only of a pressure-sensitive adhesive layer, the elastic modulus of the pressure-sensitive adhesive sheet (25 ° C. storage elastic modulus, 25 ° C. loss elastic modulus). , 25 ° C. tan δ, 80 ° C. storage elastic modulus, 80 ° C. loss elastic modulus, 80 ° C. tan δ and Tg (peak top temperature of tan δ)).

The viscoelastic property of the above-mentioned pressure-sensitive adhesive layer is at least one selected from a polymer having a Mw of more than 70 × ¹⁰⁴ and an oligomer and a tackifier resin having a softening point of less than 145 ° C., based on the contents described in the present specification. Using seeds, further adjusting their usage ratio, and appropriately setting the pressure-sensitive adhesive composition containing other components (crosslinking agent, etc.) as necessary, polymer polymerization conditions and pressure-sensitive adhesive layer production conditions. It can be adjusted by such as.

In the techniques disclosed herein, the pressure-sensitive adhesive layer has a 25 ° C. storage modulus, a 25 ° C. loss modulus, a 25 ° C. tanδ, an 80 ° C. storage modulus, an 80 ° C. loss modulus, a peak top of 80 ° C. tanδ and Tg (tanδ). Temperature) can be determined by dynamic viscoelastic modulus measurement. Specifically, a pressure-sensitive adhesive layer having a thickness of about 2 mm is produced by stacking a plurality of pressure-sensitive adhesive layers (adhesive sheets in the case of a base material-less pressure-sensitive adhesive sheet) to be measured. A sample punched into a disk shape having a diameter of 7.9 mm is sandwiched between parallel plates to fix the pressure-sensitive adhesive layer, and a viscoelasticity tester (for example, manufactured by TA Instruments, ARES or its equivalent) is used to determine the following. Dynamic viscoelasticity measurement was performed under the conditions of 25 ° C. storage elastic modulus, 25 ° C. loss elastic modulus, 25 ° C. tanδ, 80 ° C. storage elastic modulus, 80 ° C. loss elastic modulus, 80 ° C. tanδ and Tg (peak top temperature of tanδ). ).
-Measurement mode: Shear mode-Temperature range: -70 ° C to 150 ° C
・ Temperature rise rate: 5 ° C / min
・ Measurement frequency: 1Hz
Also in the examples described later, the measurement is performed by the above method. The pressure-sensitive adhesive layer to be measured can be formed by applying the corresponding pressure-sensitive adhesive composition in a layered manner and drying or curing the pressure-sensitive adhesive layer.

(Adhesive)
In the technique disclosed herein, the type of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesives include acrylic polymers, rubber-based polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester-based polymers, urethane-based polymers, polyether polymers, silicone-based polymers, which can be used in the field of pressure-sensitive adhesives. One or more of various rubber-like polymers such as polyamide-based polymers and fluoropolymers may be contained as an adhesive polymer (hereinafter, also referred to as "base polymer" in the sense of a structural polymer forming an adhesive). .. From the viewpoint of adhesive performance, cost, and the like, a pressure-sensitive adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably adopted. Of these, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) using an acrylic polymer as a base polymer is preferable. The technique disclosed herein is preferably carried out in an embodiment using an acrylic pressure-sensitive adhesive.

Hereinafter, the pressure-sensitive adhesive layer composed of the acrylic pressure-sensitive adhesive, that is, the pressure-sensitive adhesive sheet having the acrylic-based pressure-sensitive adhesive layer will be mainly described, but the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein is composed of the acrylic pressure-sensitive adhesive. It is not intended to be limited to acrylic.

(polymer)
The pressure-sensitive adhesive layer disclosed herein is characterized by containing polymers with Mw greater than 70 × ¹⁰⁴ . By using the polymer having Mw, the cohesive force based on the entanglement of the polymer is exhibited, and it is easy to obtain a good high temperature holding force. In addition, the cohesive force based on the high molecular weight body of the polymer has a higher degree of freedom in molecular structure as compared with general chemical cross-linking, and can maintain a predetermined flexibility. Therefore, it tends to be easy to realize good followability to a complicated adherend shape while maintaining a high temperature holding force. The Mw of the polymer is preferably about 90 × 10 ⁴ or more, more preferably 100 × 10 ⁴ or more (for example, more than 100 × 10 ⁴ ), still more preferably about 110 × 10 ⁴ or more, and particularly preferably about 120 × 10 ⁴ or more. (For example, about 130 × ¹⁰⁴ or more). Further, the above Mw is usually about 500 × ¹⁰⁴ or less, and about 300 × ¹⁰⁴ or less is appropriate. From the viewpoint of improving flexibility, the Mw is preferably about 200 × ¹⁰⁴ or less, and may be about 150 × 104 or less ⁽ for example, about 140 × ¹⁰⁴ or less). As the polymer, one or more of various polymers exemplified as the above-mentioned rubber-like polymer can be used. For example, in the case of an acrylic polymer obtained by a solution polymerization method, it is preferable to set Mw in the above range.

The above polymer is a component typically used as a base polymer in the pressure-sensitive adhesive layer. The polymer is preferably an acrylic polymer. Here, the "base polymer" of the pressure-sensitive adhesive refers to the main component of the rubber-like polymer contained in the pressure-sensitive adhesive, and is not interpreted in any limitation other than this. The rubber-like polymer refers to a polymer that exhibits rubber elasticity in a temperature range near room temperature. Further, in this specification, the “main component” refers to a component contained in an amount of more than 50% by weight, unless otherwise specified.

Further, the "acrylic polymer" refers to a polymer containing a monomer unit derived from a monomer having at least one (meth) acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth) acryloyl group in one molecule is also referred to as an “acrylic monomer”. Therefore, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. A typical example of the acrylic polymer is an acrylic polymer in which the proportion of the acrylic monomer in the total monomer components used in the synthesis of the acrylic polymer is more than 50% by weight.
In addition, "(meth) acryloyl" means acryloyl and methacryloyl comprehensively. Similarly, "(meth) acrylate" means acrylate and methacrylate, and "(meth) acrylic" means acrylic and methacrylic, respectively.

(Acrylic polymer)
In the technique disclosed herein, as the acrylic polymer used as a polymer, for example, polymerization of a monomer raw material containing an alkyl (meth) acrylate as a main monomer and further containing a submonomer having copolymerizability with the main monomer. The thing is preferable. Here, the main monomer means a component that occupies more than 50% by weight of the monomer composition in the above-mentioned monomer raw material.

As the alkyl (meth) acrylate, for example, a compound represented by the following formula (1) can be preferably used.
CH ₂ = C (R ¹ ) COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, such a range of the number of carbon atoms may be expressed as "C _1-20 ". From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive, the main monomer is an alkyl (meth) acrylate in which R ² is a chain alkyl group of C _1-14 (for example, C _1-10 , typically C _4-8 ). It is appropriate to do. Alkyl (meth) acrylates in which R ² is a butyl group or a 2-ethylhexyl group are preferred. Further, from the viewpoint of adhesive properties, an alkyl acrylate in which R ¹ is a hydrogen atom and R ² is a chain alkyl group of C _4-8 (hereinafter, also simply referred to as C _4-8 alkyl acrylate) is used as a main monomer. It is preferable to do so.

Specific examples of the alkyl (meth) acrylate in which R ² is a C _1-20 chain alkyl group are not particularly limited, but are, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and isopropyl. (Meta) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-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, Eikosyl (meth) acrylate and the like. These alkyl (meth) acrylates can be used alone or in combination of two or more. Preferable examples of alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). Particularly preferred alkyl (meth) acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

The proportion of alkyl (meth) acrylate in the monomer component constituting the acrylic polymer is typically more than 50% by weight, for example, 70% by weight or more, 85% by weight or more, and 90% by weight. It may be% by weight or more. The upper limit of the proportion of the alkyl (meth) acrylate is not particularly limited, but is preferably 99.5% by weight or less (for example, 99% by weight or less), or characteristics based on an accessory monomer such as a carboxy group-containing monomer (for example, agglomeration). From the viewpoint of preferably exerting force), it may be 98% by weight or less (for example, less than 97% by weight). Alternatively, the acrylic polymer may be substantially obtained by polymerizing only an alkyl (meth) acrylate.

When C _4-8 alkyl acrylate is used as the monomer component, the proportion of C _4-8 alkyl acrylate in the alkyl (meth) acrylate contained in the monomer component is preferably 70% by weight or more. More preferably, it is 90% by weight or more.

In the technique disclosed herein, the monomer component constituting the acrylic polymer contains at least one of BA and 2EHA, and the total amount of BA and 2EHA among the alkyl (meth) acrylates contained in the monomer component is 75 weight by weight. It can be preferably carried out in an embodiment of% or more (usually 85% by weight or more, for example, 90% by weight or more, further 95% by weight or more). The technique disclosed herein can be carried out, for example, in a mode in which the alkyl (meth) acrylate contained in the above-mentioned monomer component is BA alone, a mode in which 2EHA is alone, a mode in which BA and 2EHA are contained, and the like.

In some preferred embodiments, the monomer component constituting the acrylic polymer contains 50% by weight or more of C _1-6 alkyl (meth) acrylate. In other words, the polymerization ratio of C _1-6 alkyl (meth) acrylate in the acrylic polymer is preferably 50% by weight or more. By using C _1-6 alkyl (meth) acrylate as the main monomer in this way, the storage elastic modulus at 80 ° C. can be preferably improved, thereby improving the high-temperature cohesive force and achieving both flexibility. It can be realized. In this embodiment, the ratio of C _1-6 alkyl (meth) acrylate to the monomer components (in other words, the polymerization ratio) is preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 92% by weight or more (more preferably 92% by weight or more). For example, over 95% by weight). The upper limit of the ratio of C _1-6 alkyl (meth) acrylate to the monomer component is not particularly limited, and is usually 99% by weight or less, and 98% by weight or less due to the relationship with the usage ratio of other copolymerizable monomers. It is appropriate that there is, preferably 97% by weight or less, and may be less than 95% by weight. The C _1-6 alkyl (meth) acrylate may be used alone or in combination of two or more. As the C _1-6 alkyl (meth) acrylate, C _1-6 alkyl acrylate is preferable, C _2-6 alkyl acrylate is more preferable, and C _4-6 alkyl acrylate is further preferable. In some other embodiments, the C _1-6 alkyl (meth) acrylate is preferably a C _1-4 alkyl acrylate, more preferably a C _2-4 alkyl acrylate. BA is mentioned as a preferable example of C _1-6 alkyl (meth) acrylate.

In some other preferred embodiments, the monomer component constituting the acrylic polymer contains 50% by weight or more of C _7-10 alkyl (meth) acrylate. In other words, the copolymerization ratio of the C _7-10 alkyl (meth) acrylate in the acrylic polymer is preferably 50% by weight or more. By using C _7-10 alkyl (meth) acrylate as the main monomer in this way, the storage elastic modulus at 25 ° C. can be preferably lowered, thereby increasing the flexibility and improving the followability with the adherend. However, it is possible to achieve both high temperature holding power. The ratio of C _7-10 alkyl (meth) acrylate to the monomer component (in other words, the copolymerization ratio) may be more than 60% by weight, more than 70% by weight, and more preferably more than 80% by weight. More preferably, it is 90% by weight or more, and particularly preferably 92% by weight or more (for example, 95% by weight or more). The upper limit of the ratio of C _7-10 alkyl (meth) acrylate to the monomer component is not particularly limited, and is usually 99% by weight or less, and is related to the ratio of other copolymerizable monomers (for example, acid group-containing monomers) used. Therefore, it is appropriate that the content is 97% by weight or less, and preferably 96% by weight or less. The C _7-10 alkyl (meth) acrylate may be used alone or in combination of two or more. Preferable examples of the C _7-10 alkyl (meth) acrylate include C _7-10 alkyl acrylates such as 2EHA, isooctyl acrylate and isononyl acrylate. Of these, 2EHA is preferable.

Acrylic polymers in the techniques disclosed herein may be copolymerized with submonomers. A carboxy group-containing monomer and a hydroxyl group (OH group) -containing monomer (2-hydroxyethyl (meth) acrylate, 4 -Hydroxybutyl (meth) acrylate, etc.), acid anhydride group-containing monomer, amide group-containing monomer ((meth) acrylamide, N, N-dimethyl (meth) acrylamide, etc.), amino group-containing monomer (aminoethyl (meth) acrylate, etc.) , N, N-dimethylaminoethyl (meth) acrylate, etc.), epoxy group-containing monomer, cyano group-containing monomer, keto group-containing monomer, monomer having a nitrogen atom-containing ring (N-vinyl-2-pyrrolidone, N- (meth) ) Acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, imide group-containing monomers, and the like. As the submonomer, one type may be used alone or two or more types may be used in combination.

When the monomer component constituting the acrylic polymer contains the above-mentioned functional group-containing monomer, the content of the functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the effect of using the functional group-containing monomer, the content of the functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, and 0.5% by weight or more. Is appropriate, and may be 1% by weight or more. Further, from the viewpoint of facilitating the balance of adhesive performance in relation to the main monomer, it is appropriate that the content of the functional group-containing monomer in the monomer component is 40% by weight or less, and 20% by weight or less. Is preferable, and it may be 10% by weight or less (for example, 5% by weight or less).

In some preferred embodiments, an acidic group-containing monomer is used as a monomer copolymerizable with the main monomer, alkyl (meth) acrylate. The acidic group-containing monomer can exhibit an improvement in cohesiveness based on its polarity and a good binding force to a polar adherend. When a cross-linking agent such as an isocyanate-based or epoxy-based cross-linking agent is used, the acidic group (typically, a carboxy group) serves as a cross-linking point of the acrylic polymer. Due to these actions, it is possible to suitably realize the followability to a complicated adherend shape and the high temperature holding power.

As the acidic group-containing monomer, a carboxy group-containing monomer is preferably used. Examples of the carboxy group-containing monomer include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth) acrylate, crotonic acid and isocrotonic acid; maleic acid, itaconic acid and citraconic acid. Such as ethylenically unsaturated dicarboxylic acid and its anhydride (maleic anhydride, itaconic anhydride, etc.) can be mentioned. Further, the acidic group-containing monomer may be a monomer having a metal salt of a carboxy group (for example, an alkali metal salt). Among them, AA and MAA are preferable, and AA is more preferable.

In the technique disclosed herein, the content of the acidic group-containing monomer (typically the carboxy group-containing monomer) in the monomer component (in other words, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer) is 1. It is appropriate to set it to 0% by weight or more. By using an acidic group-containing monomer in a predetermined amount or more, the cohesive force (particularly high temperature cohesive force) of the pressure-sensitive adhesive layer can be improved. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is preferably 1.5% by weight or more, more preferably 2.0% by weight or more, still more preferably 2.5% by weight or more, and particularly preferably 3.0% by weight. % Or more. In some preferred embodiments, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is 4.0% by weight or more, may be more than 5.0% by weight, or may be 6.0% by weight or more. , 6.5% by weight or more may be used. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is usually 20% by weight or less, and is preferably 10% by weight from the viewpoint of improving the adhesion to the adherend and the followability. Less than, more preferably less than 8.0% by weight, even more preferably less than 7.0% by weight, particularly preferably less than 6.0% by weight, even less than 5.0% by weight (eg, less than 4.0% by weight). good.

The acrylic polymer preferably used in the technique disclosed herein may be a copolymer obtained by copolymerizing an alkyl (meth) acrylate as a main monomer and an acidic group-containing monomer as a submonomer. In such an acrylic polymer, the proportion of the copolymerization component other than the alkyl (meth) acrylate and the acidic group-containing monomer may be less than 10% by weight, less than 3% by weight, or less than 1% by weight. It may be less than 0.1% by weight and less than 0.03% by weight (for example, less than 0.01% by weight). The monomer component constituting the acrylic polymer may be substantially free of a functional group-containing monomer other than the acidic group-containing monomer. According to the acrylic polymer substantially composed of the alkyl (meth) acrylate and the acidic group-containing monomer, the action of the alkyl (meth) acrylate and the acidic group-containing monomer can be maximized.

Alternatively, in some embodiments, the monomer component forming the acrylic polymer may contain, for example, a hydroxyl group-containing monomer as a functional group-containing monomer other than the acidic group-containing monomer. The ratio of the hydroxyl group-containing monomer to the monomer component may be, for example, 0.01% by weight or more and less than 1% by weight, may be less than 0.5% by weight, or may be less than 0.1% by weight. ..

The monomer component constituting the acrylic polymer may contain a copolymerization component other than the above-mentioned submonomer for the purpose of improving the cohesive force and the like. Examples of other copolymerization components include vinyl ester-based monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth) such as cyclohexyl (meth) acrylate, cyclopentyl (meth) acrylate, and isobornyl (meth) acrylate. ) Acrylate; aryl (meth) acrylate (eg, phenyl (meth) acrylate), aryloxyalkyl (meth) acrylate (eg, phenoxyethyl (meth) acrylate), arylalkyl (meth) acrylate (eg, benzyl (meth) acrylate), etc. Aromatic ring-containing (meth) acrylate; olefin-based monomer; chlorine-containing monomer; isocyanate group-containing monomer such as 2- (meth) acryloyloxyethyl isocyanate; alkoxy such as methoxyethyl (meth) acrylate and ethoxyethyl (meth) acrylate. Group-containing monomers; vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; and the like can be mentioned. The above-mentioned other copolymerization components may be used alone or in combination of two or more.

The amount of the other copolymerization component may be appropriately selected depending on the purpose and application, and is not particularly limited, but is appropriately set to 0.05% by weight or more from the viewpoint of appropriately exerting the effect of use. , 0.5% by weight or more may be used. Further, from the viewpoint of facilitating the balance of adhesive performance, it is appropriate that the content of the other copolymerization component in the monomer component is 20% by weight or less, and 10% by weight or less (for example, 5% by weight or less). May be good. The technique disclosed herein may also be preferably carried out in an embodiment in which the monomer component is substantially free of other copolymerization components. Here, the fact that the monomer component does not substantially contain other copolymerization components means that the other copolymerization components are not used at least intentionally, and the other copolymerization components are, for example, 0.01% by weight or less. To some extent, unintentional inclusion is acceptable.

Acrylic polymers have polyfunctionality having at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth) acryloyl group and vinyl group as other monomer components. It may contain a monomer. By using a polyfunctional monomer as the monomer component, the cohesive force of the pressure-sensitive adhesive layer can be enhanced. The polyfunctional monomer can be used as a cross-linking agent. The polyfunctional monomer is not particularly limited, and is, for example, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, neopentyl glycol di (meth) acrylate. And so on. The polyfunctional monomer may be used alone or in combination of two or more.

The amount of the polyfunctional monomer used is not particularly limited, and can be appropriately set so that the purpose of use of the polyfunctional monomer is achieved. The amount of the polyfunctional monomer used can be about 3% by weight or less of the above-mentioned monomer component, preferably about 2% by weight or less, and more preferably about 1% by weight or less (for example, about 0.5% by weight or less). When the polyfunctional monomer is used, the lower limit of the amount used may be larger than 0% by weight and is not particularly limited. Usually, by setting the amount of the polyfunctional monomer to be used in an amount of about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component, the effect of using the polyfunctional monomer can be appropriately exhibited.

The composition of the monomer components constituting the acrylic polymer shall be designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately −15 ° C. or lower (for example, approximately −70 ° C. or higher and −15 ° C. or lower). Is appropriate. Here, the Tg of the acrylic polymer means the Tg obtained by the Fox formula based on the composition of the above-mentioned monomer component. 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 obtained by homopolymerizing each of the monomers constituting the copolymer.
1 / Tg = Σ (Wi / Tgi)
In the above 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 the publicly known material 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
2-Hydroxyethyl acrylate -15 ° C
4-Hydroxybutyl acrylate -40 ° C
Vinyl acetate 32 ° 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. For monomers for which multiple types of values are described in this document, the highest value is adopted. If it is not described in the Polymer Handbook, the value obtained by the measurement method described in Japanese Patent Application Publication No. 2007-51271 shall be used.

Although not particularly limited, from the viewpoint of adhesiveness and flexibility, it is advantageous that the Tg of the acrylic polymer is about −25 ° C. or lower, preferably about −35 ° C. or lower, and more preferably about −35 ° C. It may be 40 ° C. or lower, more preferably −45 ° C. or lower, for example, −50 ° C. or lower, or −55 ° C. or lower. Further, from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer is usually about −75 ° C. or higher, preferably about −70 ° C. or higher. In some embodiments, the Tg of the acrylic polymer may be −60 ° C. or lower, or −62 ° C. or lower (for example, −64 ° C. or lower). Further, from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer may be about −65 ° C. or higher, or about −60 ° C. or higher (for example, about −55 ° C. or higher). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type and amount ratio of the monomers used in the synthesis of the polymer).

The dispersity (Mw / Mn) of the polymer disclosed here (preferably an acrylic polymer) is not particularly limited. The degree of dispersion (Mw / Mn) here means the degree of dispersion (Mw / Mn) expressed by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In some preferred embodiments, the polymer dispersity (Mw / Mn) is 40 or less, may be less than 20, may be less than 15 (eg, 12 or less), may be less than 10, and may be less than 7.0. good. By limiting the molecular weight distribution within an appropriate range, stable characteristics can be easily obtained. In a polymer having a Mw of more than 700,000 (preferably an acrylic polymer), by setting Mw / Mn in the above range, the cohesive force and flexibility based on the entanglement of the high molecular weight polymer in the polymer tend to be accurately expressed. .. The lower limit of Mw / Mn is not particularly limited, and may be, for example, 3.0 or more, 5.0 or more, or 7.0 or more. By having a certain degree of molecular weight distribution, the actions of the low molecular weight body and the high molecular weight body tend to be expressed in a well-balanced manner. Such polymers also tend to be highly productive.

In addition, Mw, Mn and Mw / Mn are polymerized based on the polymerization conditions (time, temperature, etc.), the concentration of the non-volatile component (monomer component) at the time of polymerization, the amount of the polymerization initiator used, the use of the chain transfer agent, and the chain transfer constant. It can be adjusted by selecting a solvent or the like. Further, Mw and Mn are obtained from the standard polystyrene-equivalent values obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, a model name “HLC-8320GPC” (column: TSKgelGMH-H (S), manufactured by Tosoh Corporation) can be used.

The method for obtaining a polymer (for example, an acrylic polymer) is not particularly limited, and various methods known as polymer synthesis methods such as a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a suspension polymerization method, and a photopolymerization method are used. A polymerization method can be appropriately adopted. For example, a solution polymerization method can be preferably adopted. The polymerization temperature at the time of solution polymerization can be appropriately selected depending on the type of the monomer and solvent used, the type of the polymerization initiator and the like, and is, for example, about 20 ° C. to 170 ° C. (typically 40 ° C. to 140 ° C.). ℃).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). The initiator used for the polymerization may be an azo-based polymerization initiator such as a conventionally known polymerization initiator (for example, 2,2'-azobisisobutyronitrile (AIBN)) or a peroxide-based initiator, depending on the type of the polymerization method. It can be appropriately selected from the initiator, etc.). The amount of the polymerization initiator used may be a normal amount, for example, about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) with respect to 100 parts by weight of the monomer component. ) Can be selected.

(Adhesive-imparting resin)
The pressure-sensitive adhesive layer in the technique disclosed herein may contain a pressure-sensitive adhesive resin. This makes it possible to increase the peel strength of the adhesive sheet. Examples of the pressure-sensitive adhesive resin include phenol-based pressure-sensitive adhesive resin, terpene-based pressure-sensitive adhesive resin, modified terpen-based pressure-sensitive adhesive resin, rosin-based pressure-sensitive adhesive resin, hydrocarbon-based pressure-sensitive adhesive resin, epoxy-based pressure-sensitive adhesive resin, and polyamide-based pressure-sensitive adhesive resin. One or more selected from tackifier resins such as elastomer-based tackifier resins and ketone-based tackifier resins can be used. Among them, a phenol-based tackifier resin, a terpene-based tackifier resin, and a modified terpene-based tackifier resin are preferable, and a phenol-based tackifier resin (preferably a terpene phenol resin) is more preferable.

Examples of phenol-based tackifier resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins and rosinphenolic resins.
The terpene phenolic resin refers to a polymer containing a terpene residue and a phenol residue, and is a copolymer of terpene and a phenol compound (terpene-phenol copolymer resin) and a homopolymer or copolymer of terpene. Is a concept that includes both phenol-modified products (phenol-modified terpene resin). Preferable examples of terpenes constituting such a terpene phenolic resin are monoterpenes such as α-pinene, β-pinene, and limonene (including d-form, l-form, and d / l-form (dipentene)). Can be mentioned. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is also called hydrogenated terpene phenolic resin.
The alkylphenol resin is a resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include novolak type and resol type.
The rosin phenolic resin is typically a phenolic variant of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid modified rosins and unsaturated fatty acid modified rosin esters). Examples of the rosin phenol resin include a rosin phenol resin obtained by adding phenol to rosins or the above-mentioned various rosin derivatives with an acid catalyst and thermally polymerizing the resin.

Examples of terpene-based tackifier resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one kind of terpenes or a copolymer of two or more kinds of terpenes. Examples of the homopolymer of one kind of terpenes include α-pinene polymer, β-pinene polymer, dipentene polymer and the like. Examples of the modified terpene resin include modified terpene resins. Specific examples thereof include styrene-modified terpene resin and hydrogenated terpene resin.

The concept of rosin-based tackifier resin here includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosins, wood rosins, and tall oil rosins; modified rosins obtained by modifying these unmodified rosins by hydrogenation, disproportionation, polymerization, etc. (hydrogen-added rosins, non-modified rosins). Normalized rosins, polymerized rosins, other chemically modified rosins, etc.); are included.

The rosin derivative resin is typically a derivative of rosins as described above. The concept of a rosin-based resin as used herein includes derivatives of unmodified rosins and derivatives of modified rosins (including hydrogenated rosins, disproportionated rosins and polymerized rosins). For example, rosin esters such as unmodified rosin esters, which are esters of unmodified rosins and alcohols, and modified rosin esters, which are esters of modified rosins and alcohols; for example, unmodified rosins modified with unsaturated fatty acids. Saturated fatty acid-modified rosins; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; for example, rosins or various rosin derivatives described above (rosin esters, unsaturated fatty acid-modified rosins and unsaturated fatty acids). Examples include rosin alcohols obtained by reducing the carboxy group of fatty acid-modified rosin esters; for example, metal salts of rosins or various rosin derivatives described above; and the like. Specific examples of the rosin esters include methyl esters of unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.), triethylene glycol esters, glycerin esters, pentaerythritol esters and the like.

Examples of hydrocarbon-based tackifier resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.). ), Various hydrocarbon-based resins such as aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, kumaron-based resins, and kumaron-inden-based resins.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving the cohesive force, a tackifier resin having a softening point (softening temperature) of about 80 ° C. or higher (preferably about 100 ° C. or higher) can be preferably adopted. For example, a phenol-based tackifier resin (terpene phenol resin or the like) having such a softening point can be preferably used. In some embodiments, a terpene phenolic resin having a softening point of about 135 ° C. or higher (further, about 140 ° C. or higher) can be used. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of adhesion to the adherend and the substrate, a tackifier resin having a softening point of about 200 ° C. or lower (more preferably about 180 ° C. or lower) can be preferably used. The softening point of the tackifier resin can be measured based on the softening point test method (ring ball method) specified in JIS K2207.

In some preferred embodiments, as the tackifier resin, a tackifier resin _TL having a softening point of less than 145 ° C. is used. By using the tackifier resin _TL having a softening point of less than 145 ° C., it is possible to preferably form a pressure-sensitive adhesive that better balances high-temperature holding power and complex shape followability. The softening point of the tackifier resin _TL is preferably less than 135 ° C., more preferably less than 125 ° C., and may be 120 ° C. or lower. The lower limit of the softening point of the tackifier resin _TL is not particularly limited, for example, 60 ° C. or higher (hence, solid state at 30 ° C.), 80 ° C. or higher is appropriate, and high temperature holding power and complex shape followability. From the viewpoint of achieving both, it is preferably 90 ° C. or higher, more preferably 100 ° C. or higher, and may be 110 ° C. or higher. In the following, the tackifier resin _TL having a softening point of 60 ° C. or higher and lower than 145 ° C. may be referred to as a tackifier resin _TL1 . As the tackifier resin _TL (specifically, the tackifier resin _TL1 ), an appropriate type can be selected and used from the above-mentioned tackifier resin types, and among them, the terpene phenol resin is preferably used. .. The tackifier resin _TL may be used alone or in combination of two or more.

When the pressure-sensitive adhesive layer contains the pressure-sensitive adhesive resin _TL1 , the content of the pressure-sensitive adhesive resin _TL1 is a polymer (for example, acrylic) in the pressure-sensitive adhesive layer from the viewpoint of preferably exhibiting the effect of using the pressure-sensitive adhesive resin _TL1 . It is appropriate that the amount is 1 part by weight or more with respect to 100 parts by weight of the polymer), preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and further preferably 15 parts by weight or more (for example, more than 15 parts by weight). Particularly preferably, it is 18 parts by weight or more. Further, from the viewpoint of cohesive force, it is appropriate that the amount of the tackifier resin _TL1 with respect to 100 parts by weight of the polymer is less than 50 parts by weight, and from the viewpoint of high temperature holding power, it is preferably less than 40 parts by weight, more preferably. Is less than 30 parts by weight and may be less than 25 parts by weight.

Further, as the tackifier resin TL, a liquid _tackifier resin (liquid resin) _TL2 which is liquid at 30 ° C. can be used. By using the liquid resin _TL2 , the storage elastic modulus at 25 ° C. of the pressure-sensitive adhesive layer can be preferably reduced. The liquid resin _TL2 may be, for example, a tackifier resin having a softening point of less than 60 ° C., preferably about 50 ° C. or lower, and more preferably about 40 ° C. or lower. As the liquid resin _TL2 , an appropriate type can be selected and used from the above-mentioned tackifier resin types, and among them, rosin-based, terpene-based, hydrocarbon-based and other tackifier-imparting resins are preferable, for example, hydrogen. A rosin-based tackifier resin such as an added rosin methyl ester is particularly preferable. The liquid resin _TL2 may be used alone or in combination of two or more. The liquid resin _TL2 is preferably used in combination with the tackifier resin _TL1 .

When the pressure-sensitive adhesive layer contains the liquid resin _TL2 , the content of the liquid resin _TL2 is a polymer (for example, an acrylic polymer) in the pressure-sensitive adhesive layer from the viewpoint of preferably exhibiting the effect of using the liquid resin _TL2 . It is appropriate that the amount is 0.1 parts by weight or more with respect to 100 parts by weight, preferably 1 part by weight or more, more preferably 2 parts by weight or more, and further preferably 3 parts by weight or more. Further, from the viewpoint of cohesive force, it is appropriate that the amount of the liquid resin _TL2 with respect to 100 parts by weight of the polymer is less than 20 parts by weight, and from the viewpoint of high temperature holding power, it is preferably less than 10 parts by weight, more preferably. It is less than 8 parts by weight and may be 5 parts by weight or less.

When the pressure-sensitive adhesive layer contains the pressure-sensitive adhesive resin _TL , the total content of the pressure-sensitive adhesive resin _TL is a polymer (for example, for example) in the pressure-sensitive adhesive layer from the viewpoint of preferably exhibiting the effect of using the pressure-sensitive adhesive resin _TL . It is appropriate that the amount is 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, preferably 5 parts by weight or more, more preferably 10 parts by weight or more, and further preferably 15 parts by weight or more (for example, 18 parts by weight or more). ), Particularly preferably 20 parts by weight or more (for example, 22 parts by weight or more). Further, from the viewpoint of cohesive force, it is appropriate that the amount of the tackifier resin with respect to 100 parts by weight of the polymer is 60 parts by weight or less, and from the viewpoint of high temperature holding power, it is preferably 50 parts by weight or less, more preferably 40 parts by weight. It may be 30 parts by weight or less (for example, 28 parts by weight or less).

In an embodiment in which the tackifier resin _TL having a softening point of less than 145 ° C. is used, the pressure-sensitive adhesive layer is a high softening point tackifier resin (typically, which does not correspond to the tackifier resin _TL having a softening point of less than 145 ° C.). The tackifier resin) _TH having a softening point of 145 ° C. or higher may or may not be contained. When the pressure-sensitive adhesive layer contains the pressure-sensitive adhesive resin _TH in addition to the pressure-sensitive adhesive resin _TL , the content of the pressure-sensitive adhesive resin _TH shall be less than 100 parts by weight with respect to 100 parts by weight of the pressure-sensitive adhesive resin _TL . Is suitable, preferably less than 50 parts by weight, more preferably less than 30 parts by weight, still more preferably less than 10 parts by weight, less than 1 part by weight, or less than 0.1 parts by weight. By limiting the amount of the _tackifier resin TH with respect to the amount of the tackifier resin _TL , it is easy to reduce the 25 ° C. storage elastic modulus of the pressure-sensitive adhesive layer.

As some preferred embodiments, the tackifier resin contains one or more phenol-based tackifier resins (typically terpene phenolic resins). The technique disclosed herein can be preferably carried out, for example, in an embodiment in which the total amount of the tackifier resin is 100% by weight, of which about 25% by weight or more (more preferably about 30% by weight or more) is a terpene phenol resin. Approximately 50% by weight or more of the total amount of the tackifier resin may be terpene phenol resin, and approximately 70% by weight or more (for example, approximately 80% by weight or more) may be terpene phenol resin. Substantially all of the tackifier resin (eg, about 95-100% by weight, even about 99-100% by weight) may be terpene phenolic resin.

Although not particularly limited, in some embodiments, the tackifier resin may include a tackifier resin having a hydroxyl value higher than 20 mgKOH / g. Of these, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more is preferable. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more may be referred to as a “high hydroxyl value resin”. According to the tackifier resin containing such a high hydroxyl value resin, a pressure-sensitive adhesive layer having excellent adhesion to an adherend and high cohesive force can be realized. The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the polymer and the like, the hydroxyl value of the high hydroxyl value resin is preferably about 200 mgKOH / g or less, preferably about 100 mgKOH / g or less, and may be about 70 mgKOH / g or less. It may be about 65 mgKOH / g or less. As the high hydroxyl value resin, one type can be used alone or two or more types can be used in combination. The technique disclosed herein is preferably an embodiment in which the tackifier resin contains a high hydroxyl value resin having a hydroxyl value of more than 20 mgKOH / g (for example, 30 to 65 mgKOH / g) (for example, a phenol-based tackifier resin, preferably a terpene phenol resin). Can be carried out. In some preferred embodiments, the high hydroxyl value resin may be a tackifier resin _TL with a softening point of less than 145 ° C.

Here, as the value of the hydroxyl value, the value measured by the potentiometric titration method specified in JIS K0070: 1992 can be adopted. The specific measurement method is as shown below.
[Measurement method of hydroxyl value]
1. 1. Reagent (1) As the acetylation reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, pyridine is added thereto to make the total volume 50 mL, and the reagent is sufficiently stirred. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to this to make the total volume 100 mL, and use the one that has been sufficiently stirred.
(2) As a measurement reagent, a 0.5 mol / L potassium hydroxide ethanol solution is used.
(3) In addition, prepare toluene, pyridine, ethanol and distilled water.
2. 2. Operation (1) Weigh about 2 g of a sample into a flat-bottomed flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air cooling tube.
(2) The flask is heated in a bath at 100 ° C. for 70 minutes, allowed to cool, 35 mL of toluene is added as a solvent from the upper part of the cooling tube and stirred, and then 1 mL of distilled water is added and stirred to obtain acetic anhydride. Disassemble. Heat again in the bath for 10 minutes to complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Then, 50 mL of pyridine as a solvent is added and stirred.
(4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a whole pipette.
(5) Potentiometric titration is performed with a 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is used as the end point.
(6) In the blank test, perform the above (1) to (5) without inserting a sample.
3. 3. Calculation Calculate the hydroxyl value by the following formula.
Hydroxy group value (mgKOH / g) = [(BC) x f x 28.05] / S + D
here,
B: Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test,
C: Amount (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the sample,
f: Factor of 0.5 mol / L potassium hydroxide ethanol solution,
S: Sample weight (g),
D: Acid value,
28.05: 1/2 of the molecular weight of potassium hydroxide 56.11,
Is.

When the pressure-sensitive adhesive layer contains a pressure-sensitive adhesive resin, the amount (total amount) of the pressure-sensitive adhesive resin used is not particularly limited, and may be appropriately set in the range of, for example, about 1 to 100 parts by weight with respect to 100 parts by weight of the polymer. From the viewpoint of preferably exerting the effect of improving the peel strength, it is appropriate that the amount of the tackifier resin used for 100 parts by weight of the polymer (for example, acrylic polymer) is 5 parts by weight or more, and 10 parts by weight or more. It is preferable to use 15 parts by weight or more. Further, from the viewpoint of impact resistance and cohesive force, it is appropriate that the amount of the tackifier resin used for 100 parts by weight of the polymer (for example, acrylic polymer) is 50 parts by weight or less, and may be 40 parts by weight or less. , 30 parts by weight or less may be used.

(Oligomer)
In some preferred embodiments, the pressure-sensitive adhesive layer contains an oligomer. By including the oligomer in the pressure-sensitive adhesive layer, in addition to the effect of improving the pressure-sensitive adhesive properties such as the improvement of the adhesive strength, the high-temperature holding power and the complex shape followability can be preferably compatible with each other. The type of oligomer is not particularly limited, and is appropriately selected in consideration of compatibility and the like according to the type of polymer. The oligomer is typically an acrylic oligomer. The acrylic oligomer is preferably used in an embodiment in which an acrylic polymer is used as the polymer. The oligomer is more than the Tg of the copolymer corresponding to the composition of the monomer component of the polymer (typically, the Tg of the acrylic polymer contained in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition). It is preferable to use a polymer having a high Tg. By containing the oligomer, the adhesive strength of the pressure-sensitive adhesive can be improved. The oligomer may be used alone or in combination of two or more.

It is desirable that the oligomer (typically an acrylic oligomer) has a Tg of about 0 ° C. or higher and about 300 ° C. or lower, preferably about 20 ° C. or higher and about 300 ° C. or lower, and more preferably about 40 ° C. or higher and about 300 ° C. or lower. .. When Tg is within the above range, the adhesive strength can be suitably improved. In some preferred embodiments, the Tg of the oligomer is about 30 ° C. or higher, more preferably about 50 ° C. or higher (for example, about 60 ° C. or higher) from the viewpoint of cohesiveness of the pressure-sensitive adhesive, and from the viewpoint of adhesiveness and the like. Therefore, it is preferably about 200 ° C. or lower, more preferably about 150 ° C. or lower, still more preferably about 100 ° C. or lower (for example, about 80 ° C. or lower). The Tg of the oligomer is a value calculated based on the Fox formula, like the Tg of the copolymer corresponding to the composition of the monomer component.

The weight average molecular weight (Mw) of the oligomer (typically an acrylic oligomer) is typically about 1000 or more and less than about 30,000, preferably about 1500 or more and less than about 20,000, and more preferably about 2000 or more and less than about 10,000. obtain. When Mw is within the above range, good adhesive strength and holding characteristics can be obtained, which is preferable. In some preferred embodiments, the oligomer has a Mw of about 2,500 or more (eg, about 3,000 or more) from the viewpoint of high temperature holding power, and is preferably about 7,000 or less, more preferably about 5,000, from the viewpoint of adhesiveness and the like. The following (for example, about 4500 or less, typically about 4000 or less). The Mw of the oligomer can be measured by gel permeation chromatography (GPC) and determined as a standard polystyrene-equivalent value. Specifically, it is measured by using TSKgelGMH-H (20) × 2 as a column on HPLC8020 manufactured by Tosoh Co., Ltd. under the condition of a flow rate of about 0.5 mL / min in a tetrahydrofuran solvent.

Examples of the monomers constituting the acrylic oligomer used as the oligomer include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, and isobutyl (meth) acrylate. , S-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, heptyl (meth) acrylate, octyl Alkyl such as (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate. (Meta) Acrylate; Ester of (meth) acrylic acid such as cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate and alicyclic alcohol (containing alicyclic hydrocarbon group) Meta) acrylates); aryl (meth) acrylates such as phenyl (meth) acrylates, benzyl (meth) acrylates; (meth) acrylates obtained from terpene compound derivative alcohols; and the like. Such (meth) acrylates can be used alone or in combination of two or more.

Examples of the acrylic oligomer include alkyl (meth) acrylates in which an alkyl group has a branched structure such as isobutyl (meth) acrylate and t-butyl (meth) acrylate; cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, and dicyclopenta. Esters of (meth) acrylic acids such as nyl (meth) acrylates and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth) acrylates); aryls such as phenyl (meth) acrylates and benzyl (meth) acrylates. The inclusion of an acrylic monomer having a relatively bulky structure as a monomer unit, typified by a (meth) acrylate having a cyclic structure such as (meth) acrylate, further improves the adhesiveness of the pressure-sensitive adhesive layer. It is preferable from the viewpoint of being able to. Further, when ultraviolet rays are used when synthesizing an acrylic oligomer or when forming an adhesive layer, those having a saturated bond are preferable in that polymerization inhibition is unlikely to occur, and the alkyl group has a branched structure. An alkyl (meth) acrylate or an ester with an alicyclic alcohol (an alicyclic hydrocarbon group-containing (meth) acrylate) can be suitably used as a monomer constituting an acrylic oligomer. The above-mentioned branched chain alkyl (meth) acrylate, alicyclic hydrocarbon group (meth) acrylate, and aryl (meth) acrylate all correspond to the (meth) acrylate monomer in the technique disclosed herein. The alicyclic hydrocarbon group can be a saturated or unsaturated alicyclic hydrocarbon group.

The ratio of the (meth) acrylate monomer (for example, alicyclic hydrocarbon group-containing (meth) acrylate) to all the monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight. % Or more, more preferably 70% by weight or more (for example, 80% by weight or more, further 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting substantially exclusively of (meth) acrylate monomers.

As the constituent monomer component of the acrylic oligomer, a functional group-containing monomer can be used in addition to the above (meth) acrylate monomer. Preferable examples of the functional group-containing monomer are monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholin; N, N-dimethylamino. Amino group-containing monomers such as ethyl (meth) acrylate; amide group-containing monomers such as N, N-diethyl (meth) acrylamide; carboxy group-containing monomers such as AA and MAA; hydroxyl groups such as 2-hydroxyethyl (meth) acrylate Monomer; These functional group-containing monomers may be used alone or in combination of two or more. Of these, a carboxy group-containing monomer is preferable, and AA is particularly preferable.

When all the monomer components constituting the acrylic oligomer contain a functional group-containing monomer, the ratio of the functional group-containing monomer (for example, a carboxy group-containing monomer such as AA) to the total monomer components is approximately 1% by weight or more. It is appropriate, preferably 2% by weight or more, more preferably 3% by weight or more, and more preferably about 15% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less. It is as follows.

Oligomers (typically acrylic oligomers) can be formed by polymerizing their constituent monomer components. The polymerization method and the polymerization mode are not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization and the like) can be adopted as appropriate. The types of polymerization initiators (for example, azo-based polymerization initiators such as AIBN) that can be used as needed are generally as exemplified in the synthesis of acrylic polymers, and the amount of the polymerization initiator and arbitrarily used. Since the amount of the chain transfer agent such as n-dodecyl mercaptan is appropriately set based on the common technical knowledge so as to have a desired molecular weight, detailed description thereof will be omitted here.

From the above viewpoint, suitable acrylic oligomers include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), and dicyclopentanyl. In addition to each homopolymer of acrylate (DCPA), 1-adamantyl methacrylate (ADAM), 1-adamantyl acrylate (ADA), a copolymer of CHMA and isobutyl methacrylate (IBMA), a copolymer of CHMA and IBXMA, Polymer of CHMA and acryloylmorpholine (ACMO), polymer of CHMA and diethylacrylamide (DEAA), polymer of CHMA and AA, polymer of ADA and methylmethacrylate (MMA), DCPMA and IBXMA And the copolymer of DCPMA and MMA, and the like.

When the pressure-sensitive adhesive layer disclosed herein contains an oligomer (preferably an acrylic oligomer), the content thereof is, for example, 0.1 part by weight with respect to 100 parts by weight of the polymer (typically an acrylic polymer). It is appropriate to set the above (for example, 1 part by weight or more). From the viewpoint of better exerting the effect of the oligomer, the content of the oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, and may be 12 parts by weight or more. Further, from the viewpoint of compatibility with a polymer (typically an acrylic polymer), the content of the oligomer (typically an acrylic oligomer) is preferably less than 50 parts by weight, and is preferable. It may be less than 30 parts by weight, more preferably less than 20 parts by weight, and less than 15 parts by weight (for example, less than 12 parts by weight).

In some preferred embodiments, the pressure-sensitive adhesive layer comprises one or more of the above-mentioned pressure-imparting resins (typically a pressure-imparting resin _TL with a softening point of less than 145 ° C.) and an oligomer (preferably acrylic). Includes one or more of (oligomers). By using the tackifier resin and the oligomer in combination, it is possible to preferably achieve both high-temperature holding power and followability to an adherend while exhibiting desired adhesive properties. The ratio of the content _CT of the tackifier resin (typically the tackifier resin T _L having a softening point of less than 145 ° C.) to the content _CO of the oligomer is not particularly limited, and for example, C _T / _CO is. Approximately 0.2 or more is suitable, preferably approximately 1 or more (for example, more than 1), more preferably 1.2 or more, still more preferably 1.5 or more, and may be 2.0 or more. It may be 3 or more. Further, the C _T / _CO is preferably about 20 or less, preferably 10 or less, more preferably 5 or less, still more preferably 3 or less. Within the above ratio range, the effect of the combined use of the tackifier resin and the oligomer can be preferably exhibited.

The total amount (total amount) of the tackifier resin and the oligomer (preferably acrylic oligomer) contained in the pressure-sensitive adhesive layer according to some preferred embodiments is a polymer from the viewpoint of preferably exerting the effect of the technique disclosed herein. (Preferably an acrylic polymer) It is appropriate to have about 1 part by weight or more with respect to 100 parts by weight, preferably about 10 parts by weight or more, more preferably about 20 parts by weight or more, still more preferably 30 parts by weight. More than parts, particularly preferably 35 parts by weight or more, and less than 120 parts by weight (for example, about 80 parts by weight or less), preferably less than 60 parts by weight, more preferably about 50 parts by weight or less. More preferably, it is about 45 parts by weight or less.

(Crosslinking agent)
In the techniques disclosed herein, the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer may contain a cross-linking agent, if necessary. The type of the cross-linking agent is not particularly limited, and a conventionally known cross-linking agent can be appropriately selected and used. Examples of such a cross-linking agent include an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, an oxazoline-based cross-linking agent, an aziridine-based cross-linking agent, a melamine-based cross-linking agent, a peroxide-based cross-linking agent, a urea-based cross-linking agent, and a metal alkoxide-based cross-linking agent. Examples thereof include a cross-linking agent, a metal chelate-based cross-linking agent, a metal salt-based cross-linking agent, a carbodiimide-based cross-linking agent, a hydrazine-based cross-linking agent, an amine-based cross-linking agent, and a silane coupling agent. Of these, isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, and melamine-based cross-linking agents are preferable, isocyanate-based cross-linking agents and epoxy-based cross-linking agents are more preferable, and isocyanate-based cross-linking agents are particularly preferable. .. By appropriately selecting and using a cross-linking agent, it is possible to obtain the cohesive force of the pressure-sensitive adhesive layer and improve the followability to the adherend, the adhesive force, etc. while having a good high-temperature holding force. .. The pressure-sensitive adhesive layer in the technique disclosed herein is obtained by using the above-mentioned cross-linking agent in a form after the cross-linking reaction, a form before the cross-linking reaction, a form in which the cross-linking reaction is partially carried out, an intermediate or a composite form thereof, or the like. May contain. The cross-linking agent is typically contained in the pressure-sensitive adhesive layer exclusively in the form after the cross-linking reaction.

As the isocyanate-based cross-linking agent, polyfunctional isocyanate (a compound having an average of two or more isocyanate groups per molecule, including one having an isocyanurate structure) can be preferably used. The isocyanate-based cross-linking agent may be used alone or in combination of two or more.

Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates and the like.
Specific examples of aliphatic polyisocyanes include 1,2-ethylene diisocyanate; 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, 1,4-tetramethylene diisocyanate and other tetramethylene diisocyanates; 1,2. -Hexamethylene diisocyanate such as hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 2,5-hexamethylene diisocyanate; Examples thereof include 2-methyl-1,5-pentanediisocyanate, 3-methyl-1,5-pentanediisocyanate and lysine diisocyanate.

Specific examples of the alicyclic polyisocyanates include isophorone diisocyanates; 1,2-cyclohexyldiisocyanates, 1,3-cyclohexyldiisocyanates, 1,4-cyclohexyldiisocyanates and other cyclohexyldiisocyanates; 1,2-cyclopentyldiisocyanates, 1,3. -Cyclopentyl diisocyanate such as cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate and the like.

Specific examples of aromatic polyisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 2,2'-diphenylmethane diisocyanate. , 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate , 4,4'-diphenylpropane diisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate , Xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate and the like.

As a preferable polyfunctional isocyanate, a polyfunctional isocyanate having an average of 3 or more isocyanate groups per molecule is exemplified. Such trifunctional or higher functional isocyanates are bifunctional or trifunctional or higher functional isocyanate multimers (typically dimers or trimers), derivatives (eg, polyhydric alcohols and two or more molecules of polyfunctional isocyanates). It can be an addition reaction product), a polymer, or the like. For example, diphenylmethane diisocyanate dimer or trimer, hexamethylene diisocyanate isocyanurate (isocyanurate structure trimer adduct), reaction product of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexa. Examples thereof include reaction products with methylene diisocyanate, polyfunctional isocyanates such as polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of such polyfunctional isocyanates include the trade name "Duranate TPA-100" manufactured by Asahi Kasei Chemicals, the trade name "Coronate L", the same "Coronate HL", the same "Coronate HK", and the same "Coronate" manufactured by Tosoh Corporation. "HX", "Coronate 2096" and the like can be mentioned.

The amount of the isocyanate-based cross-linking agent used is not particularly limited. For example, the amount may be approximately 0.1 parts by weight or more with respect to 100 parts by weight of the polymer. From the viewpoint of achieving both cohesive force and adhesion and impact resistance, the amount of the isocyanate-based cross-linking agent used per 100 parts by weight of the polymer can be, for example, more than 0.5 parts by weight, and more than 1.0 parts by weight. Is suitable, preferably 1.5 parts by weight or more, more preferably more than 2.0 parts by weight, still more preferably more than 2.5 parts by weight (for example, 2.8 parts by weight or more). By adopting the amount of the isocyanate-based cross-linking agent in the above range, it is possible to preferably achieve both high temperature holding power and complex shape followability. On the other hand, from the viewpoint of improving the adhesion to the adherend and the followability, it is appropriate that the amount of the isocyanate-based cross-linking agent used is 10 parts by weight or less with respect to 100 parts by weight of the polymer, preferably 5 parts by weight. Less than parts, more preferably less than 4.5 parts by weight, even more preferably less than 4.0 parts by weight, particularly preferably less than 3.5 parts by weight (eg, 3.0 parts by weight or less).

In some preferred embodiments, the isocyanate-based cross-linking agent is used in combination with an isocyanate-based cross-linking agent and at least one cross-linking agent having a different type of cross-linking functional group from the isocyanate-based cross-linking agent. According to the technique disclosed herein, a cross-linking agent other than the isocyanate-based cross-linking agent (that is, a cross-linking agent having a different type of cross-linking reactive group from the isocyanate-based cross-linking agent; hereinafter also referred to as "non-isocyanate-based cross-linking agent"). By using it in combination with an isocyanate-based cross-linking agent, it is possible to suitably achieve both high temperature holding power and complex shape followability.

The type of non-isocyanate-based cross-linking agent that can be used in combination with the isocyanate-based cross-linking agent is not particularly limited, and can be appropriately selected and used from the above-mentioned cross-linking agents. The non-isocyanate cross-linking agent may be used alone or in combination of two or more.

In some preferred embodiments, an epoxy-based cross-linking agent can be adopted as the non-isocyanate-based cross-linking agent. For example, by using an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent in combination, it is easy to achieve both cohesiveness and impact resistance. As the epoxy-based cross-linking agent, a compound 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. The epoxy-based cross-linking agent may be used alone or in combination of two or more.

Although not particularly limited, specific examples of the epoxy-based cross-linking agent include, for example, N, N, N', N'-tetraglycidyl-m-xylenediolamine, 1,3-bis (N, N-diglycidylaminomethyl). ) Cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like can be mentioned. Commercially available epoxy-based cross-linking agents include the product name "TETRAD-C" and product name "TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, the product name "Epicron CR-5L" manufactured by DIC, and Nagase ChemteX. The product name "Denacol EX-512", the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like can be mentioned.

The amount of epoxy cross-linking agent used is not particularly limited. The amount of the epoxy-based cross-linking agent used may be, for example, more than 0 parts by weight and about 1 part by weight or less (typically about 0.001 to 0.5 parts by weight) with respect to 100 parts by weight of the polymer. can. From the viewpoint of suitably exhibiting the effect of improving the cohesive force, it is appropriate that the amount of the epoxy-based cross-linking agent used is about 0.005 part by weight or more with respect to 100 parts by weight of the polymer, and about 0.01 part by weight. The above is preferable, and about 0.02 part by weight or more is more preferable. Further, from the viewpoint of improving the adhesion to the adherend and the followability, it is appropriate that the amount of the epoxy-based cross-linking agent used is about 0.2 parts by weight or less with respect to 100 parts by weight of the polymer, and is about 0. It is preferably 1 part by weight or less, and more preferably less than about 0.05 part by weight. By reducing the amount of the epoxy-based cross-linking agent used, it tends to follow the complicated adherend shape well and improve the impact resistance.

In the technique disclosed here, the relationship between the content of the isocyanate-based cross-linking agent and the content of the non-isocyanate-based cross-linking agent (for example, epoxy-based cross-linking agent) is not particularly limited. The content of the non-isocyanate-based cross-linking agent can be, for example, approximately 1/50 or less of the content of the isocyanate-based cross-linking agent. From the viewpoint of more preferably achieving both adhesion to the adherend and cohesive force, the content of the non-isocyanate-based cross-linking agent should be about 1/75 or less of the content of the isocyanate-based cross-linking agent on a weight basis. It is appropriate, preferably about 1/100 or less, and may be 1/120 or less. Further, from the viewpoint of preferably exerting the effect of using the isocyanate-based cross-linking agent and the non-isocyanate-based cross-linking agent (for example, epoxy-based cross-linking agent) in combination, the content of the non-isocyanate-based cross-linking agent is the same as that of the isocyanate-based cross-linking agent. It is appropriate that the content is about 1/1000 or more, for example, about 1/500 or more, preferably 1/300 or more, and more preferably 1/150 or more.

The total amount (total amount) of the cross-linking agent used is not particularly limited. For example, the amount may be about 10 parts by weight or less with respect to 100 parts by weight of the polymer (preferably acrylic polymer), preferably about 0.005 to 10 parts by weight, and more preferably about 0.01 to 5 parts by weight. You can choose from the range of.

(anti-rust)
The pressure-sensitive adhesive layer according to some embodiments may contain a rust preventive. The rust preventive is not particularly limited, and is not particularly limited, and is an azole rust preventive, an amine compound, nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate. Examples thereof include acid salts, urea, urotropin, thiourea, phenylcarbamate, cyclohexylammonium-N-cyclohexylcarbamate (CHC) and the like. The rust preventive may be used alone or in combination of two or more.

As the rust preventive, an azole-based rust preventive can be preferably used. As the azole-based rust preventive agent, a five-membered ring aromatic compound containing two or more heteroatoms, wherein an azole-based compound in which at least one of the heteroatoms is a nitrogen atom is preferably used as an active ingredient. Can be. A preferable example of a compound that can be used as an azole-based rust inhibitor is a benzotriazole-based rust inhibitor containing a benzotriazole-based compound as an active ingredient. Preferable examples of the benzotriazole-based compound include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, carboxybenzotriazole and the like.

The content of the rust inhibitor is not particularly limited, and can be, for example, 0.01 part by weight or more (typically 0.05 part by weight or more) with respect to 100 parts by weight of the polymer. From the viewpoint of obtaining a better metal corrosion prevention effect, the content may be 0.1 parts by weight or more, 0.3 parts by weight or more, or 0.5 parts by weight or more. On the other hand, from the viewpoint of enhancing the cohesive force of the pressure-sensitive adhesive, the content of the rust inhibitor is appropriately less than 8 parts by weight with respect to 100 parts by weight of the polymer, and may be 5 parts by weight or less, and may be 2 parts by weight. It may be as follows.

(Other additives)
The pressure-sensitive adhesive composition may include a leveling agent, a cross-linking aid, a plasticizer, a softening agent, a filler, a colorant, an antioxidant, an antioxidant, an ultraviolet absorber, an antioxidant, and a light stabilizer, if necessary. Various additives that are common in the field of adhesives such as these may be contained. The pressure-sensitive adhesive layer disclosed herein may contain a colorant such as a black colorant (for example, carbon black particles) that can help improve the light-shielding property, and the above-mentioned colorant may be used from the viewpoint of optical properties such as light transmission. It does not have to be contained. As the above-mentioned various additives, conventionally known ones can be used by a conventional method and do not particularly characterize the present invention, and therefore detailed description thereof will be omitted.

The pressure-sensitive adhesive layer (layer composed of a pressure-sensitive adhesive) disclosed herein is a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt type pressure-sensitive adhesive composition, and active energy rays such as ultraviolet rays and electron beams. It can be a pressure-sensitive adhesive layer formed from an active energy ray-curable pressure-sensitive adhesive composition that cures by irradiation. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in which a pressure-sensitive adhesive (sticking agent layer-forming component) is contained in a solvent containing water as a main component (water-based solvent), and is typically water-dispersed. A type pressure-sensitive adhesive composition (a composition in which at least a part of the pressure-sensitive adhesive is dispersed in water) or the like is included. Further, the solvent-type pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive is contained in an organic solvent. As the organic solvent contained in the solvent-type pressure-sensitive adhesive composition, one kind or two or more kinds exemplified as the organic solvent (toluene, ethyl acetate, etc.) that can be used in the above-mentioned solution polymerization can be used without particular limitation. The technique disclosed herein can be preferably carried out in an embodiment including a pressure-sensitive adhesive layer formed from a solvent-type pressure-sensitive adhesive composition from the viewpoint of pressure-sensitive adhesive properties and the like. In the embodiment including the solvent-type pressure-sensitive adhesive layer formed from the solvent-type pressure-sensitive adhesive composition, the effects of the techniques disclosed herein are preferably realized.

The pressure-sensitive adhesive layer disclosed here can be formed by a conventionally known method. For example, a method of forming a pressure-sensitive adhesive layer by applying a pressure-sensitive adhesive composition to a peelable surface (peeling surface) and drying it can be adopted. For the pressure-sensitive adhesive sheet having a base material, for example, a method (direct method) of directly applying (typically applying) a pressure-sensitive adhesive composition to the base material and drying it to form a pressure-sensitive adhesive layer can be adopted. can. Further, a method (transfer method) in which a pressure-sensitive adhesive composition is applied to a peelable surface (peeling surface) and dried to form a pressure-sensitive adhesive layer on the surface, and the pressure-sensitive adhesive layer is transferred to a substrate (transfer method). May be adopted. As the peeling surface, for example, the surface of a peeling liner described later can be preferably used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form, and may have a regular or random pattern such as a dot shape or a striped shape. It may be a formed pressure-sensitive adhesive layer.

The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, or a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation, a curtain coating method, or the like.
From the viewpoint of promoting the crosslinking reaction and improving the production efficiency, it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 to 150 ° C., preferably about 60 to 130 ° C. After the pressure-sensitive adhesive composition is dried, aging may be further performed for the purpose of adjusting the component transfer in the pressure-sensitive adhesive layer, advancing the crosslinking reaction, alleviating the strain that may exist in the pressure-sensitive adhesive layer, and the like.

The pressure-sensitive adhesive layer disclosed here may have a single-layer structure or may have a multi-layer structure of two or more layers. From the viewpoint of productivity and the like, the pressure-sensitive adhesive layer preferably has a single-layer structure.

The thickness of the adhesive layer is not particularly limited. The thickness of the pressure-sensitive adhesive layer is usually about 300 μm or less, preferably about 150 μm or less, preferably about 100 μm or less, more preferably about 70 μm or less, and about 60 μm or less (for example, 55 μm or less). May be good. The thickness-limited pressure-sensitive adhesive layer can well meet the demand for thinner and lighter weight. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesiveness and adherend followability, for example, it is about 3 μm or more, and about 10 μm or more is appropriate. In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is about 20 μm or more, more preferably about 30 μm or more, and may be about 40 μm or more. By increasing the thickness of the pressure-sensitive adhesive layer, it is easy to obtain more excellent pressure-sensitive adhesive properties, and there is a tendency that the followability to an adherend having a complicated shape is excellent. In the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer (first pressure-sensitive adhesive layer and second pressure-sensitive adhesive layer) on each surface of the base material, the thickness of each pressure-sensitive adhesive layer may be the same or different.

(Gel fraction)
Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein can be, for example, 20% or more on a weight basis, and usually 30% or more is appropriate, 35. It is preferably larger than%. By increasing the gel fraction of the pressure-sensitive adhesive layer in an appropriate range, it is possible to improve the high-temperature holding power while maintaining the followability to the adherend. In the technique disclosed herein, the gel fraction is more preferably 45% or more, still more preferably 50% or more, particularly preferably 55% or more, and may be 60% or more. On the other hand, from the viewpoint of followability to the adherend, the gel fraction of the pressure-sensitive adhesive layer is preferably 90% or less, preferably 70% or less (for example, 65% or less), and may be less than 60%. ..

Here, the "gel fraction of the pressure-sensitive adhesive layer" means a value measured by the following method. The gel fraction can be grasped as the weight ratio of the ethyl acetate insoluble content in the pressure-sensitive adhesive layer.
[Gel fraction measurement method]
About 0.1 g of the pressure-sensitive adhesive sample (weight Wg ₁ ) is wrapped in a porous polytetrafluoroethylene film (weight Wg ₂ ) having an average pore diameter of 0.2 μm in a purse-like shape, and the mouth is tied with octopus thread (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) film, the trade name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) available from Nitto Denko Co., Ltd. or its equivalent. Use the item.
This package is immersed in 50 mL of ethyl acetate and held at room temperature (typically 23 ° C.) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer out of the film, and then the package is taken out and placed on the outer surface. The attached ethyl acetate is wiped off, the package is dried at 130 ° C. for 2 hours, and the weight of the package (Wg ₄ ) is measured. The gel fraction _FG of the pressure-sensitive adhesive layer can be obtained by substituting each value into the following equation. The same method is adopted in the examples described later.
Gel fraction _FG (%) = [(Wg ₄ -Wg ₂ -Wg ₃ ) / Wg ₁ ] x 100

<Base material>
In the embodiment in which the pressure-sensitive adhesive sheet disclosed herein is in the form of a single-sided pressure-sensitive adhesive type or double-sided pressure-sensitive adhesive sheet with a base material, the base material for supporting (lining) the pressure-sensitive adhesive layer is a resin film or a foam film (foaming). Body base material), paper, cloth, metal foil, composites thereof and the like can be used.

The technique disclosed herein can be carried out in the form of a pressure-sensitive adhesive sheet with a base material having the pressure-sensitive adhesive layer on at least one surface of the base material (support). For example, it can be carried out in the form of a double-sided pressure-sensitive adhesive sheet with a base material having the above-mentioned pressure-sensitive adhesive layer on one surface of the base material and the other surface.

As the base film, a base film containing a resin film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The substrate in the techniques disclosed herein may be substantially composed of such a base film. Alternatively, the substrate may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an undercoat layer, an antistatic layer, a colored layer and the like provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (a component contained in the resin film in an amount of more than 50% by weight). Examples of resin films include polyethylene (PE), polypropylene (PP), ethylene / propylene copolymer and other polyolefin resin films; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN) and the like. Polyethylene resin film; vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; cellophane; and the like. The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. Among them, a polyester film is preferable from the viewpoint of handleability and processability, and a PET film is particularly preferable.

The resin film may have a single-layer structure or may have a multi-layer structure of two layers, three layers or more. From the viewpoint of shape stability, the resin film preferably has a single-layer structure. In the case of a multi-layer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the above resin (for example, a polyester resin). The method for producing the resin film may appropriately adopt a conventionally known method, and is not particularly limited. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calendar roll molding can be appropriately adopted.

In some other embodiments, paper or cloth is used as the base material. Examples of paper that can be used as a base material include Japanese paper, kraft paper, glassin paper, high-quality paper, synthetic paper, top-coated paper and the like. Examples of the cloth include woven cloths and non-woven fabrics made by spinning various fibrous substances alone or by blending them. Examples of the fibrous material include cotton, sufu, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber and the like.

The non-woven fabric referred to here is a concept that mainly refers to a non-woven fabric for an adhesive sheet used in the field of adhesive tape and other adhesive sheets, and is typically a non-woven fabric produced by using a general paper machine. (Sometimes called "paper"). Further, the resin film referred to here is typically a non-porous resin sheet, and is a concept that is distinguished from, for example, a non-woven fabric (that is, does not include a non-woven fabric). The resin film may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film. Further, the surface of the base material on which the pressure-sensitive adhesive layer is provided may be subjected to surface treatment such as application of an undercoat agent, corona discharge treatment, and plasma treatment.

The base material (for example, a resin film such as PET film) may contain a filler (inorganic filler, organic filler, etc.), a colorant, a dispersant (surfactant, etc.), an antistatic agent, and an oxidation, if necessary. Various additives such as an inhibitor, an ultraviolet absorber, an antistatic agent, a lubricant, and a plasticizer may be blended. The blending ratio of the various additives is usually about less than about 30% by weight (for example, less than about 20% by weight, preferably less than about 10% by weight).

The surface of the base material may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat agent. Such a surface treatment may be a treatment for improving the adhesion between the base material and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer on the base material.

The thickness of the base material disclosed here is not particularly limited. The thickness of the base material (for example, the resin film) can be, for example, about 200 μm or less, preferably about 100 μm or less, and more preferably about 50 μm or less. Depending on the purpose and mode of use of the pressure-sensitive adhesive sheet, the thickness of the base material may be about 30 μm or less, about 15 μm or less, or about 10 μm or less (for example, about 5 μm or less). By reducing the thickness of the base material, the thickness of the pressure-sensitive adhesive layer can be further increased even if the total thickness of the pressure-sensitive adhesive sheets is the same. This can be advantageous from the viewpoint of improving the adhesion to the adherend. The lower limit of the thickness of the base material is not particularly limited. From the viewpoint of handleability (handleability) and processability of the pressure-sensitive adhesive sheet, the thickness of the base material is usually about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example, about 4 μm or more. In some embodiments, the thickness of the substrate may be approximately 10 μm or greater.

<Peeling liner>
In the technique disclosed herein, a release liner can be used when forming an adhesive layer, producing an adhesive sheet, storing an adhesive sheet before use, distributing it, processing a shape, and the like. The release liner is not particularly limited, and for example, a release liner having a release treatment layer on the surface of a liner base material such as a resin film or paper, a fluoropolymer (polytetrafluoroethylene, etc.) or a polyolefin resin (PE, A release liner or the like made of a low adhesive material such as PP) can be used. The peeling treatment layer may be formed by surface-treating the liner base material with a peeling treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Adhesive sheet>
The pressure-sensitive adhesive sheet according to some preferred embodiments is a base-less double-sided adhesive pressure-sensitive adhesive sheet (base-less double-sided pressure-sensitive adhesive sheet) substantially composed of only a pressure-sensitive adhesive layer. Since such a base material-less adhesive sheet has excellent followability, it can adhere well to an adherend having a step, for example, and can exhibit excellent adhesive performance. In particular, it can exhibit good followability to an adherend having a complicated surface such as a three-dimensional curved surface shape. Since the entire thickness of the base material-less double-sided adhesive sheet is composed of an adhesive layer, it is possible to exhibit more excellent adhesive properties (particularly high temperature holding power) in a limited thickness space. Therefore, the thickness tends to be limited, and it can be particularly preferably used for member fixing applications of portable electronic devices that can be exposed to high temperatures.

The total thickness of the adhesive sheet (excluding the release liner) disclosed here is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet can be, for example, about 500 μm or less, usually about 350 μm or less, and preferably about 250 μm or less (for example, about 200 μm or less). The technique disclosed herein is preferably in the form of an adhesive sheet (typically a double-sided adhesive sheet) having a total thickness of about 150 μm or less (more preferably about 100 μm or less, still more preferably less than about 60 μm, for example about 55 μm or less). Can be carried out. The lower limit of the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, and is usually about 10 μm or more, preferably about 20 μm or more, more preferably about 30 μm or more, and about 40 μm from the viewpoint of adhesiveness and adherend followability. The above is more preferable. By increasing the thickness of the pressure-sensitive adhesive sheet, it is easy to obtain better pressure-sensitive adhesive properties, and the followability to an adherend having a complicated shape tends to be improved. When the pressure-sensitive adhesive sheet comprises a foam base material, the upper limit of the total thickness of the pressure-sensitive adhesive sheet is usually preferably 1.5 mm or less, preferably 1 mm or less, and more preferably 0.5 mm or less. be.

<Use>
The pressure-sensitive adhesive sheet disclosed herein has a good high-temperature holding power and can follow the surface of an adherend having a complicated shape well. Taking advantage of these characteristics, the adhesive sheet can be used in various applications where high temperature holding power and adherend followability are required. For example, it is suitable for fixing members of various portable electronic devices having members having a curved surface shape such as a three-dimensional shape. Since portable electronic devices may be used in a high temperature environment and the internal space thereof may be heated by the heat generated by electronic components, the adhesive sheet disclosed here is used to provide high temperature holding power. The benefits of improvement are great. Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, laptop computers, various wearable devices (for example, wristwatch-type wristwatches, clips, straps, etc.). Modular type to be attached to a part of, eyewear type including glasses type (monocular type and binocular type, including head mount type), clothes type to be attached to shirts, socks, hats, etc. in the form of accessories, earphones (Earwear type, etc. attached to the ear), digital camera, digital video camera, audio equipment (portable music player, IC recorder, etc.), computer (computer, etc.), portable game equipment, electronic dictionary, electronic notebook, electronic book, in-vehicle Includes information devices, mobile radios, mobile TVs, mobile printers, mobile scanners, mobile modems, etc. In addition, in this specification, "portable" means that it is not enough to be portable, but to have a level of portability that an individual (standard adult) can carry relatively easily. It shall mean.

Further, the adhesive sheet disclosed herein is preferably used in a portable electronic device for fixing a member such as a cover glass having a three-dimensional shape (typically a curved surface shape) constituting the portable electronic device. .. It is also suitable for fixing the surface of an adherend having a step. Since the pressure-sensitive adhesive sheet disclosed here has excellent followability to the adherend, it can well follow and adhere to the above-mentioned three-dimensional shape or a complicated shape having a step. For products that require waterproofness (for example, electronic devices such as portable electronic devices) while exhibiting a good fixing function by closely adhering to the surface of an adherend having such a three-dimensional shape or a step. On the other hand, excellent waterproofness can be imparted.

The adhesive sheet disclosed here (typically a double-sided adhesive sheet) can be used for fixing a member constituting a portable electronic device as described above in the form of a bonding material processed into various outer shapes. Among them, it can be preferably used for an electronic device (typically a portable electronic device) provided with an organic EL display device or a liquid crystal display device. For example, an adhesive sheet disclosed here for fixing a member of an electronic device having a display unit such as a touch panel type display (typically, a portable electronic device such as a smartphone) and having a display unit having a large screen. Is preferably used.

FIG. 2 is an exploded perspective view schematically showing a configuration example of a display device to which the adhesive sheet disclosed herein can be applied. As shown in FIG. 2, the display device 200 included in the portable electronic device 100 includes a display unit 220 composed of a cover member, an organic EL unit, and the like, and a support unit 240. The display device 200 is configured to further include an adhesive sheet 230. In this configuration example, the adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided adhesive sheet) for fixing the members constituting the display portion 220 and the support portion 240. The support portion 240 includes a substrate (a metal plate such as a stainless steel plate or an aluminum plate) and the like. Alternatively, the adhesive sheet disclosed herein may be a member such as a cover member or one for fixing an organic EL unit. The pressure-sensitive adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

The matters disclosed herein include:
[1] A portable electronic device including a display unit including a cover member and an organic EL unit, and a support unit.
An adhesive sheet is joined to the cover member.
The adhesive sheet has an adhesive layer and has an adhesive layer.
The pressure-sensitive adhesive layer is
Polymers with a weight ^average molecular weight of more than 70 × 104 and
At least one selected from oligomers and tackifier resins with a softening point of less than 145 ° C.
Including
The pressure-sensitive adhesive layer is a portable electronic device having a storage elastic modulus G'(25 ° C.) at 25 ° C. of less than 0.15 MPa.
[2] The portable electronic device according to the above [1], comprising a touch panel in which the display unit also functions as an input unit.
[3] The portable electronic device according to the above [1] or [2], wherein the cover member has a three-dimensional curved surface shape.
[4] The portable electronic device according to any one of [1] to [3] above, wherein the gel content of the pressure-sensitive adhesive layer is larger than 35% by weight.
[5] In the pressure-sensitive adhesive layer, the ratio of the storage elastic modulus G'(25 ° C.) at 25 ° C. to the storage elastic modulus G'(80 ° C.) at 80 ° C. (G'(80 ° C.) / G'(25 ° C.) )) Is larger than 0.20, according to any one of the above [1] to [4].
[6] The portable electronic device according to any one of [1] to [5] above, wherein the polymer has a dispersity (Mw / Mn) of 40 or less.
[7] The portable electronic device according to any one of [1] to [6] above, wherein the polymer is an acrylic polymer.
[8] The portable electronic device according to any one of [1] to [7] above, wherein the pressure-sensitive adhesive layer contains both the oligomer and the pressure-sensitive adhesive resin.
[9] The portable electronic device according to any one of [1] to [8] above, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent.
[10] The portable electronic device according to any one of [1] to [9] above, which is a base material-less double-sided adhesive adhesive sheet composed of the pressure-sensitive adhesive layer.

[11] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer.
The pressure-sensitive adhesive layer is
Polymers with a weight ^average molecular weight of more than 70 × 104 and
At least one selected from oligomers and tackifier resins with a softening point of less than 145 ° C.
Including
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a storage elastic modulus G'(25 ° C.) at 25 ° C. of less than 0.15 MPa.
[12] The pressure-sensitive adhesive sheet according to the above [11], wherein the gel content of the pressure-sensitive adhesive layer is larger than 35% by weight.
[13] In the pressure-sensitive adhesive layer, the ratio of the storage elastic modulus G'(25 ° C.) at 25 ° C. to the storage elastic modulus G'(80 ° C.) at 80 ° C. (G'(80 ° C.) / G'(25 ° C.) )) Is larger than 0.20, according to the above [11] or [12].
[14] The pressure-sensitive adhesive sheet according to any one of [11] to [13] above, wherein the polymer has a dispersity (Mw / Mn) of 40 or less.
[15] The pressure-sensitive adhesive sheet according to any one of [11] to [14] above, wherein the polymer is an acrylic polymer.
[16] The pressure-sensitive adhesive sheet according to any one of [11] to [15] above, wherein the pressure-sensitive adhesive layer contains both the oligomer and the pressure-sensitive adhesive resin.
[17] The pressure-sensitive adhesive sheet according to any one of [11] to [16] above, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent.
[18] The pressure-sensitive adhesive sheet according to any one of [11] to [17] above, which is a base-less double-sided adhesive pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer.
[19] The adhesive sheet according to any one of the above [11] to [18], which is used for fixing a member in a portable electronic device.
[20] The adhesive sheet according to any one of [11] to [19] above, which is attached to the step and / or curved surface of a member having a step and / or curved surface shape in a portable electronic device.

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.

<Example 1>
(Preparation of acrylic polymer)
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel, 95 parts of 2-ethylhexyl acrylate (2EHA) and 5 parts of acrylic acid (AA) as monomer components were used as a polymerization solvent. Ethyl acetate was charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.1 part of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60 ° C. for 6 hours to carry out acrylic. A solution of the system polymer (P1) was obtained. The above polymerization reaction was carried out by adjusting the amount of the polymerization solvent to control the concentration of the non-volatile component (monomer component). The Mw of the acrylic polymer (P1) was 126 × ¹⁰⁴ , and the Mw / Mn was 8.7.

(Preparation of adhesive composition)
20 parts of the tackifier resin (T1), 5 parts of the tackifier resin (T2), and 10 parts of the oligomer are crosslinked with 100 parts of the acrylic polymer (P1) contained in the acrylic polymer solution. Three parts of an isocyanate-based cross-linking agent and 0.03 part of an epoxy-based cross-linking agent as agents were added and mixed by stirring to prepare a pressure-sensitive adhesive composition. As the tackifier resin (T1), a terpene phenol resin (trade name "YS Polystar T-115", manufactured by Yasuhara Chemical Co., Ltd., softening point of about 115 ° C., hydroxyl value of 30 to 60 mgKOH / g) was used. As the tackifying resin (T2), a liquid resin (manufactured by Nissei Forestry Chemical Industry Co., Ltd., trade name "M-HDR", hydrogenated rosin methyl ester resin) was used. As the isocyanate-based cross-linking agent, trade name "Coronate L" (75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct manufactured by Tosoh Corporation) was used. As the epoxy-based cross-linking agent, the trade name “TETRAD-C” (manufactured by Mitsubishi Gas Chemical Company, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane) was used.
As the oligomer, an acrylic oligomer prepared by the following method was used. Specifically, in a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser, and a dropping funnel, 95 parts of cyclohexyl methacrylate (CHMA) and 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and 10 parts of AIBN as a polymerization initiator. After adding toluene as a polymerization solvent and stirring in a nitrogen stream for 1 hour to remove oxygen in the polymerization system, the temperature is raised to 85 ° C. and the reaction is carried out for 5 hours to obtain an acrylic oligomer having a solid content concentration of 50%. Obtained. The Mw of the obtained acrylic oligomer was 3600.

(Making an adhesive sheet)
As the peeling liner A, a polyester peeling film (trade name "Diafoil MRV", thickness 75 μm, manufactured by Mitsubishi Polyester Co., Ltd.) whose one side is peeled and treated as a peeling surface is used as a peeling liner B and one side is peeled. A polyester peeling film (trade name "Diafoil MRF", thickness 38 μm, manufactured by Mitsubishi Polyester Co., Ltd.) that has been peeled off was prepared. The pressure-sensitive adhesive composition obtained above was applied to the peel-off surface of the peel-off liner A and dried at 100 ° C. for 2 minutes to form a pressure-sensitive adhesive layer having a thickness of 50 μm. A release liner B was placed on the exposed adhesive surface of the pressure-sensitive adhesive layer so that the peel-off surface was on the pressure-sensitive adhesive layer side to prepare a base-less double-sided adhesive pressure-sensitive adhesive sheet according to this example.

<Example 2>
The monomer composition was changed to 93 parts of n-butyl acrylate (BA), 7 parts of AA and 0.05 part of 4-hydroxybutyl acrylate (4HBA), and the amount of the polymerization solvent was adjusted to control the concentration of the non-volatile component (monomer component). Acrylic polymer (P2) was synthesized in the same manner as in the synthesis of acrylic polymer (P1) to obtain a solution of acrylic polymer (P2). The Mw of the acrylic polymer (P2) was 132 × ¹⁰⁴ , and the Mw / Mn was 5.85. 20 parts of the tackifier resin (T1), 5 parts of the tackifier resin (T2), and 15 parts of the oligomer are crosslinked with 100 parts of the acrylic polymer (P2) contained in the acrylic polymer solution. 1.5 parts of an isocyanate-based cross-linking agent and 0.01 part of an epoxy-based cross-linking agent as agents were added and mixed by stirring to prepare a pressure-sensitive adhesive composition. As the tackifier resins (T1) and (T2), oligomers, isocyanate-based cross-linking agents, and epoxy-based cross-linking agents, those of the same type as those used in Example 1 were used.
A substrateless double-sided pressure-sensitive adhesive sheet having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive composition was used, and both sides were protected by the above two polyester release liners.

<Example 3>
The monomer composition was changed to BA97 part and AA3 part, and the amount of the polymerization solvent was adjusted to control the concentration of the non-volatile component (monomer component). An acrylic polymer (P3) was synthesized to obtain a solution of the acrylic polymer (P3). The Mw of the acrylic polymer (P3) was 100 × 104, and the Mw / Mn was ^4.5 . In this acrylic polymer solution, with respect to 100 parts of the acrylic polymer (P3) contained in the solution, 20 parts of the tackifier resin (T1), 3 parts of the isocyanate-based cross-linking agent as a cross-linking agent, and 0 of the epoxy-based cross-linking agent. .02 parts were added, and the mixture was stirred and mixed to prepare a pressure-sensitive adhesive composition. As the tackifier resin (T1), the isocyanate-based cross-linking agent, and the epoxy-based cross-linking agent, those of the same type as those used in Example 1 were used.
A substrateless double-sided pressure-sensitive adhesive sheet having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive composition was used, and both sides were protected by the above two polyester release liners.

<Example 4>
A reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel is charged with BA70 part, 2EHA30 part and AA3 part as a monomer component, and ethyl acetate as a polymerization solvent, and nitrogen gas is charged. The mixture was stirred for 2 hours while being introduced. After removing oxygen in the polymerization system in this manner, 0.2 parts of AIBN was added as a polymerization initiator and solution-polymerized at 60 ° C. for 8 hours to obtain a solution of an acrylic polymer (P4). The Mw of the acrylic polymer (P4) was 44 × ¹⁰⁴ , and the Mw / Mn was 8.8. To 100 parts of the acrylic polymer (P4) contained in the acrylic polymer solution, 30 parts of the tackifier resin (T3) and 3 parts of the isocyanate-based cross-linking agent as a cross-linking agent are added and mixed by stirring. To prepare a pressure-sensitive adhesive composition. As the tackifier resin (T3), a polymerized rosin ester having a softening point of 125 ° C. (manufactured by Arakawa Chemical Industry Co., Ltd., trade name “Pencel D125”) was used. As the isocyanate-based cross-linking agent, the same type as that used in Example 1 was used.
A substrateless double-sided pressure-sensitive adhesive sheet having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive composition was used, and both sides were protected by the above two polyester release liners.

<Example 5>
Acrylic polymer (P5) is synthesized by the same method as the synthesis of acrylic polymer (P4) except that the monomer composition is changed to BA95 part and AA5 part, and a solution of acrylic polymer (P5) is obtained. rice field. The Mw of the acrylic polymer (P5) was 68 × 10 ⁴ , and the Mw / Mn was 4.4. In this acrylic polymer solution, with respect to 100 parts of the acrylic polymer (P5) contained in the solution, 30 parts of the tackifier resin (T4), 2 parts of the isocyanate-based cross-linking agent as a cross-linking agent, and 0 parts of the epoxy-based cross-linking agent. A mixture of 0.01 parts was added, and the mixture was stirred and mixed to prepare a pressure-sensitive adhesive composition. As the isocyanate-based cross-linking agent and the epoxy-based cross-linking agent, those of the same type as those used in Example 1 were used. As the tackifier resin (T4), a terpene phenol resin (trade name "YS Polystar S-145" manufactured by Yasuhara Chemical Co., Ltd., softening point of about 145 ° C., hydroxyl value of 70 to 110 mgKOH / g) was used.
A substrateless double-sided pressure-sensitive adhesive sheet having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the obtained pressure-sensitive adhesive composition was used, and both sides were protected by the above two polyester release liners.

<Evaluation>
[High temperature holding power test]
A high temperature holding power test was conducted under a temperature condition of 80 ° C. according to JIS Z0237: 2009. That is, in an environment of 23 ° C. and 50% RH, a PET film having a thickness of 50 μm was attached to one of the adhesive surfaces of the double-sided adhesive sheet, lined with the adhesive, and cut into a width of 10 mm to prepare a measurement sample. The other adhesive surface of the measurement sample was attached to a bakelite plate as an adherend by reciprocating a 2 kg roller once. The adhesive area between the measurement sample and the adherend was 10 mm wide and 20 mm long. The measurement sample attached to the adherend in this way was hung in an environment of 80 ° C. and left for 30 minutes, and then a load of 1 kg was applied to the free end of the measurement sample, and the load was applied. The state was left in an environment of 80 ° C. for 1 hour. When the measurement sample was held by the adherend even after 1 hour, it was judged as "pass", and when the measurement sample was peeled off from the adherend and dropped within 1 hour, it was judged as "fail". In the case of a single-sided adhesive sheet, the PET film does not need to be lined.

[Step waterproof test]
The adhesive sheet (double-sided adhesive sheet) had a square outer edge of 24.5 mm × 24.5 mm and was cut into a window frame shape (frame shape) having a width of 2 mm to obtain a window frame-shaped adhesive sheet. This window frame-shaped adhesive sheet was attached to a 50 mm × 50 mm square acrylic plate having a thickness of 2 mm to prepare an acrylic plate with a window frame-shaped adhesive sheet.
A polycarbonate plate having a size larger than that of the acrylic plate was prepared, and a step tape (width 5 mm, height 20 μm) was attached to the surface of the polycarbonate plate. This step tape is used for the purpose of providing a convex (step) on the surface of the polycarbonate plate. Here, as the step tape, an adhesive sheet having an adhesive layer on one side of the PET base material was used. Then, on the polycarbonate plate, the acrylic plate with the window frame-shaped adhesive sheet produced above is placed so that the central portions of the two parallel sides of the window frame-shaped adhesive sheet cross the step tape (the parallel of the window frame-shaped adhesive sheet). The two sides of the tape were arranged so as to intersect (orthogonally) the stepped tape), and the pressure was applied under the condition of 0.2 MPa for 1 minute. In this way, an evaluation sample was obtained. In the obtained evaluation sample, when the window frame-shaped adhesive sheet is in close contact with the adherend (acrylic plate, polycarbonate plate and step tape), the inside thereof becomes a space sealed from the outside.
To evaluate the step waterproofness, the evaluation sample was submerged in water in an autoclave, and pressure was applied at 25 ° C. and 0.5 MPa for 30 minutes in the autoclave to inside the evaluation sample (window frame-like adhesion). This was done by visually observing the presence or absence of water ingress into the inside of the sheet. When inundation into the evaluation sample was observed, it was judged as "fail", and when it was not observed, it was judged as "pass".
The step waterproof test was performed after aging the evaluation sample in a standard state (23 ° C., 50% RH) for 30 minutes.

Outline of the pressure-sensitive adhesive according to each example, G'(25 ° C.) [MPa], G "(25 ° C.) [MPa], tanδ (25 ° C.), G'(80 ° C.) [MPa], G of the pressure-sensitive adhesive layer. "(80 ° C) [MPa], tanδ (80 ° C), glass transition temperature (Tg) (temperature of peak top of tanδ) [° C], G'(80 ° C) / G'(25 ° C), high temperature holding power Table 1 shows the evaluation results of the step waterproofness.

As shown in Table 1, a polymer having an Mw of more than 70 × 10 ⁴ is used, and at least one of an oligomer and a low softening point tackifier resin (softening point <145 ° C.) is used, and a 25 ° C. storage modulus G is used. In Examples 1 to 3 using the pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer in which ′ (25 ° C.) was less than 0.15 MPa, the evaluation results of high-temperature holding power and step waterproofness were both acceptable. ^On the other hand, a polymer having an Mw of more than 70 × 104 was used, a low softening point tackifier resin (softening point less than 145 ° C.) was used, and the G'(25 ° C.) of the pressure-sensitive adhesive layer was less than 0.15 MPa. In Example 4, the step waterproofness was acceptable, but the evaluation result of the high temperature holding power was unacceptable. Further, the pressure-sensitive adhesive sheet according to Example 5 in which the G'(25 ° C.) of the pressure-sensitive adhesive layer was 0.15 MPa or more passed the evaluation result of the high temperature holding power, but failed the step waterproof property. .. The pressure-sensitive adhesive layer according to Example ⁵ did not contain a polymer having a Mw of more than 70 × 104 and did not contain a low softening point pressure-sensitive adhesive resin.
From the above results, a polymer having a Mw of more than 70 × 10 ⁴ and at least one selected from an oligomer and a low softening point tackifier resin (softening point <145 ° C.) are included, and the storage elastic modulus at 25 ° C. is included. According to the pressure-sensitive adhesive sheet having the pressure-sensitive adhesive layer in which G'(25 ° C.) is less than 0.15 MPa, it can be seen that both the followability to a complicated shape and the high-temperature holding power can be achieved at the same time.

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 exemplified above.

1 Adhesive sheet 21

Adhesive layer

31, 32 Peeling liner

Claims

An adhesive sheet having an adhesive layer,
The pressure-sensitive adhesive layer is
Polymers with a weight average molecular weight of more than 70 × 104 and
At least one selected from oligomers and tackifier resins with a softening point of less than 145 ° C.
Including
The pressure-sensitive adhesive layer is a pressure-sensitive adhesive sheet having a storage elastic modulus G'(25 ° C.) at 25 ° C. of less than 0.15 MPa.
The pressure-sensitive adhesive sheet according to claim 1, wherein the gel content of the pressure-sensitive adhesive layer is larger than 35% by weight.
The pressure-sensitive adhesive layer has a ratio (G'(80 ° C.) / G'(25 ° C.)) of a storage elastic modulus G'(25 ° C.) at 25 ° C. and a storage elastic modulus G'(80 ° C.) at 80 ° C. The adhesive sheet according to claim 1 or 2, which is larger than 0.20.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the polymer has a dispersity (Mw / Mn) of 40 or less.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the polymer is an acrylic polymer.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer contains both the oligomer and the pressure-sensitive adhesive resin.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer contains an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent.
The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, which is a base-less double-sided adhesive pressure-sensitive adhesive sheet composed of the pressure-sensitive adhesive layer.
The adhesive sheet according to any one of claims 1 to 8, which is used for fixing a member in a portable electronic device.
The adhesive sheet according to any one of claims 1 to 9, which is attached to the step and / or curved surface of a member having a step and / or curved surface shape in a portable electronic device.