WO2023027092A1

WO2023027092A1 - Laminate

Info

Publication number: WO2023027092A1
Application number: PCT/JP2022/031804
Authority: WO
Inventors: 一樹箕浦; 直宏加藤; 康武蔵島
Original assignee: 日東電工株式会社
Priority date: 2021-08-27
Filing date: 2022-08-24
Publication date: 2023-03-02
Also published as: CN117836386A; JP2023032966A; KR20240055780A

Abstract

Provided is a laminate that is capable of satisfying both ability to follow complicated profiles and ability to tolerate strain. Provided is a laminate comprising: a core body; a first pressure-sensitive adhesive sheet that contains a pressure-sensitive adhesive agent layer and is disposed on one surface of the core body; and a second pressure-sensitive adhesive sheet that contains a pressure-sensitive adhesive agent layer and is disposed on other surface of the core body. The product (EA×TA) between the Young's modulus EA [MPa] of the core body and the thickness TA [μm] thereof is 500,000 or more. The first pressure-sensitive adhesive sheet and/or the second pressure-sensitive adhesive sheet has a thickness TB of greater than 10 μm and a storage elastic modulus G' (25°C) of less than 0.20 MPa at 25°C.

Description

laminate

The present invention relates to a laminate including a core and adhesive sheets arranged on each surface of the core. This application claims priority based on Japanese Patent Application No. 2021-139359 filed on August 27, 2021, the entire contents of which are incorporated herein by reference.

In general, pressure-sensitive adhesives (also called pressure-sensitive adhesives; the same shall apply hereinafter) exhibit a soft solid (viscoelastic) state in a temperature range near room temperature, and have the property of easily adhering to adherends under pressure. Taking advantage of such properties, pressure-sensitive adhesives are widely used in various industrial fields such as home electric appliances, automobiles, and OA equipment as bonding means with good workability and high adhesion reliability. For example, pressure-sensitive adhesives are widely used for purposes such as joining, fixing, and protecting members in smartphones and other mobile electronic devices. Patent Documents 1 and 2 are cited 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

In recent years, in addition to miniaturization and thinning, the development of mobile electronic equipment products with curved surfaces such as three-dimensional shapes is progressing, and the shapes of their constituent members tend to be complicated. The pressure-sensitive adhesive that is applied to the above-mentioned complicated shape is required to have the ability to follow the shape well and adhere to it. For example, in the portable electronic device, the adhesive for fixing a member having a complicated surface shape (which may be a curved surface shape) exhibits a good fixing function while maintaining a state in which the complicated shape is followed without gaps. There is a need to. If the adhesive does not adhere to the curved surface of the adherend and a gap is formed between the adherend and the adherend, water may enter through the gap and water resistance may be impaired.

In addition, the adhesive is required to have the ability to protect the adherend. In particular, mobile electronic devices tend to be easily subjected to impacts and loads from the outside due to their portability. The performance of suppressing deformation (distortion) of a member, etc., placed on the back side of the body is required. For example, if the adherend is a flexible printed wiring board to which an electronic component is fixed, the electronic component may be deformed and damaged by an external impact or the like, if the adhesive is poor in protecting the adherend. malfunction may occur. Therefore, the pressure-sensitive adhesive is required to have the performance of suppressing deformation (distortion) of other members due to impact or the like (such performance is hereinafter referred to as "distortion resistance").

It is not easy to improve both the conformability to complex shapes and the protection of the adherend with the structure of conventional adhesives. The present invention has been created in view of the above circumstances, and an object of the present invention is to provide a structure (laminated body) capable of achieving both conformability to a complicated shape and resistance to distortion.

With a structure composed of a single element, such as a sheet-shaped pressure-sensitive adhesive sheet with only one pressure-sensitive adhesive layer, it tends to be difficult to combine two or more different properties at a high level. . The inventors adopted a laminate composed of two or more constituent elements laminated at least including an adhesive layer, thereby improving both the followability to a complicated shape and the above-mentioned strain resistance. found to get.

According to this specification, a laminate comprising a core, a first adhesive sheet arranged on one surface of the core, and a second adhesive sheet arranged on the other surface of the core is provided. Here, the first adhesive sheet and the second adhesive sheet each include an adhesive layer. In this laminate, the product (E _A ×T _A ) of Young's modulus E _A [MPa] and thickness T _A [μm] of the core is 500,000 or more. By using such a core, even if the laminate has a relatively thin thickness _TA , excellent strain resistance is likely to be achieved. In addition, one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet have a thickness T _B of more than 10 μm and a storage elastic modulus G′ at 25° C. (25° C.) of less than 0.20 MPa. be. Such a pressure-sensitive adhesive sheet was used in a manner in which the side of the pressure-sensitive adhesive sheet having the above thickness T _B and storage elastic modulus G′ (25° C.) is attached to an adherend having a complicated shape (e.g., steps). In this case, there is a tendency that followability to a complicated shape (for example, steps) of the laminate is improved. Therefore, the product of the Young's modulus E _A [MPa] and the thickness T _A [μm] (E _A ×T _A ) is 500000 or more, and _the storage elastic modulus G′ ( 25° C.) is less than 0.20 MPa, it is possible to achieve both conformability to complex shapes and distortion resistance.

In some preferred embodiments, one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet have a storage elastic modulus G' at 25°C (85°C) of less than 0.05 MPa. By using such a pressure-sensitive adhesive sheet, there is a tendency that the conformability to a complicated shape of the laminate is improved.

In some preferred embodiments, one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet have a storage elastic modulus G' at 120°C (120°C) of less than 0.03 MPa. By using such a pressure-sensitive adhesive sheet, there is a tendency that the conformability to a complicated shape of the laminate is improved.

In some preferred embodiments, the thickness _TA of the core is 10 μm or more and 300 μm or less. According to such a configuration, it becomes easier to achieve thinning of the laminate and excellent strain resistance.

In some preferred embodiments, the Young's modulus _EA of the core is 3000 MPa or higher. According to such a configuration, it becomes easier to achieve thinning of the laminate and excellent strain resistance.

In some preferred embodiments, the laminate has a light transmittance C _total of 10% or less. Such a laminate is used in products including a light source such as a backlight module, and tends to be excellent in suppressing light leakage from the light source (light shielding property) and imparting design properties.

In some preferred embodiments, the laminate has a total thickness T _total of 50 μm or more and 400 μm or less. Such laminates tend to have excellent conformability to complex shapes.

The laminate disclosed here can be preferably used for electronic equipment. In particular, the laminate disclosed herein utilizes the features of being excellent in conformability to complex shapes and in distortion resistance, and includes members having complex shapes, and is subject to impact and load from the outside. It is preferably used for portable electronic devices that are easy to wear. Since the laminate disclosed herein has a limited thickness, from this point of view as well, it is preferably used in portable electronic devices that are becoming thinner and lighter.

Any appropriate combination of the elements described in this specification may also be included in the scope of the invention for which patent protection is sought by this patent application.

1 is a schematic cross-sectional view showing the configuration of a laminate according to one embodiment; FIG. FIG. 4 is a schematic cross-sectional view showing the configuration of a laminate according to another embodiment; FIG. 4 is a schematic cross-sectional view showing the configuration of a laminate according to another embodiment; It is a schematic diagram explaining the method of a strain resistance test.

A preferred embodiment of the present invention will be described below. Matters other than the matters specifically mentioned in the present specification, which are necessary for the implementation of the present invention, are based on the teaching of 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 implemented based on the contents disclosed in this specification and common general technical knowledge in the field. Further, in the following drawings, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified. In addition, the embodiments described in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the laminate or pressure-sensitive adhesive sheet of the present invention that is actually provided as a product. not a thing

As used herein, the term “adhesive” refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has the property of easily adhering to an adherend under pressure, as described above. . The adhesive as used herein generally has a complex tensile modulus E ^* (1 Hz), as defined in "C. A. Dahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) P. 143". It may be a material having properties satisfying <10 ⁷ dyne/cm ² (typically, a material having the above properties at 25°C).

<Structure Example of Laminate>
The laminate disclosed herein includes a non-releasable core, a first adhesive sheet disposed on one surface of the core, and a second adhesive sheet disposed on the other surface of the core. Including sheet. Here, the first adhesive sheet is an adhesive sheet containing an adhesive layer, and the second adhesive sheet is also an adhesive sheet containing an adhesive layer. The first pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet with a substrate in the form of having pressure-sensitive adhesive layers on both sides of a non-releasable substrate (supporting substrate). It may be a material-less pressure-sensitive adhesive sheet. Further, the second pressure-sensitive adhesive sheet may be a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on both sides of a non-releasable substrate (supporting substrate), and has a non-releasable substrate. It may be a substrate-less pressure-sensitive adhesive sheet.

The concept of laminate here can include what is called a pressure-sensitive adhesive sheet with a substrate. Further, the concept of the laminate as used herein may include what is called an adhesive sheet, adhesive tape, adhesive label, adhesive film, and the like. The laminate disclosed herein is typically in the form of a sheet, may be in the form of a roll, or may be in the form of a sheet. Alternatively, it may be a laminated body processed into various shapes.

FIG. 1 shows a configuration example of a laminate in which both the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet are double-sided pressure-sensitive adhesive sheets without a base material (double-sided pressure-sensitive adhesive sheet without a base material). A laminate 1 shown in FIG. are provided respectively. Here, the first adhesive sheet 11 is composed of an adhesive layer. The second adhesive sheet 12 is also composed of an adhesive layer. As shown in FIG. 1, the laminate 1 before use (before being attached to an adherend) is spirally wound with the front surface 21A and the back surface 21B superimposed on the release liner 21, which is a release surface. can be in the form In the laminate 1 having such a configuration, the adhesive surface 12A of the second adhesive sheet 12 is protected by the front surface 21A of the release liner 21, and the adhesive surface 11A of the first adhesive sheet 11 is protected by the back surface 21B of the release liner 21. there is Alternatively, the adhesive surface 11A and the adhesive surface 12A may be protected by two separate release liners.

The first pressure-sensitive adhesive sheet is a double-sided adhesive type substrate-less pressure-sensitive adhesive sheet (base-less double-sided pressure-sensitive adhesive sheet), and the second pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive type pressure-sensitive adhesive sheet with a substrate (double-sided pressure-sensitive adhesive sheet with substrate). FIG. 2 shows a configuration example of the laminate in the case of . The laminate 1 shown in FIG. 2 includes a core 15, and a first adhesive sheet 11 and a second adhesive sheet 12 are attached to the first surface 15A and the second surface 15B (both of which are non-releasable) of the core 15. are provided respectively. The first adhesive sheet 11 is composed of an adhesive layer. The second adhesive sheet 12 includes a substrate 35, and

adhesive layers

32 and 34 are provided on the first surface and the second surface (both of which are non-releasable) of the substrate 35, respectively. As shown in FIG. 2, the laminate 1 before use (before being attached to an adherend) is spirally wound with the front surface 21A and the back surface 21B superimposed on the release liner 21, which is a release surface. can be in the form In the laminate 1 having such a configuration, the surface (adhesive surface 34A) of the adhesive layer 34 is protected by the front surface 21A of the release liner 21, and the adhesive surface 11A of the first adhesive sheet 11 is protected by the back surface 21B of the release liner 21. ing. Alternatively, the adhesive surface 11A and the adhesive surface 34A may be protected by two separate release liners.

FIG. 3 shows a configuration example of a laminate in which both the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet are double-sided pressure-sensitive adhesive sheets with a substrate (double-sided pressure-sensitive adhesive sheet with a substrate). A laminate 1 shown in FIG. are provided respectively. The first adhesive sheet 11 includes a substrate 25, and

adhesive layers

36 and 38 are provided on the first surface and the second surface (both of which are non-releasable) of the substrate 25, respectively. The second adhesive sheet 12 includes a substrate 35, and

adhesive layers

32 and 34 are provided on the first surface and the second surface (both of which are non-releasable) of the substrate 35, respectively. As shown in FIG. 3, the laminate 1 before use (before being attached to an adherend) is spirally wound with the front surface 21A and the back surface 21B superimposed on the release liner 21, which is a release surface. can be in the form In the laminate 1 having such a configuration, the surface of the adhesive layer 34 (adhesive surface 34A) is protected by the front surface 21A of the release liner 21, and the surface of the adhesive layer 36 (adhesive surface 36A) is protected by the back surface 21B of the release liner 21. It is Alternatively, the adhesive surface 34A and the adhesive surface 36A may be protected by two separate release liners.

<Core body>
The core disclosed here is a support member that supports the first adhesive sheet and the second adhesive sheet. In the technology disclosed herein, the core body is characterized in that the product of Young's modulus and thickness is equal to or greater than a predetermined value. Specifically, the value _EA calculated by multiplying the Young's modulus value _EA of the core when the unit is MPa and the thickness value _TA of the core when the unit is μm. _xTA is 500,000 or more. The use of such a core tends to improve the strain resistance of the laminate.

In some preferred embodiments, E _A ×T _A is 70×10 ⁴ or more, more preferably 90×10 ⁴ or more (eg 100×10 ⁴ or more, 110×10 ⁴ or more or 120×10 ⁴ or more) and more preferably 130×10 ⁴ or more. The upper limit of E _A × _TA is not particularly limited. From the viewpoint of thinning and weight reduction of the laminate, it is preferably 1500×10 ⁴ or less, more preferably 1000×10 ⁴ or less (for example, 800×10 ⁴ or more, 600×10 ⁴ or more, or 500×10 ⁴ or less), more preferably 400×10 ⁴ or less.

The Young's modulus _EA of the core is not particularly limited as long as the product of it and the thickness _TA of the core is equal to or greater than a predetermined value. From the viewpoint of improving the strain resistance of the laminate, the Young's modulus _EA of the core is preferably 3000 MPa or more, more preferably 5000 MPa or more (for example, 7000 MPa or more, 8000 MPa or more, or 9000 MPa or more). It is preferably 10000 MPa or more. From the viewpoint of achieving a higher level of strain resistance, the Young's modulus _EA of the core is preferably 60,000 MPa or more, more preferably 70,000 MPa or more (for example, 90,000 MPa or more, 100,000 MPa or more, or 130,000 MPa or more), More preferably, it is 150000 MPa or more. The upper limit of the Young's modulus _EA of the core is not particularly limited. From the viewpoint of workability and handleability, the Young's modulus _EA of the core is preferably 650000 MPa or less, more preferably 400000 MPa or less (for example, it may be 300000 MPa or less, may be 280000 MPa or less, and may be 250000 MPa or less. may be

The thickness _TA of the core is not particularly limited as long as the product of the thickness TA of the core and the Young's modulus _EA of the core is equal to or greater than a predetermined value. From the viewpoint of strain resistance, the thickness _TA of the core is preferably 10 μm or more, more preferably 12 μm or more (for example, 15 μm or more), and still more preferably 20 μm or more. The upper limit of the thickness _TA of the core is not particularly limited. From the viewpoint of thinning and weight reduction of the laminate, the thickness _TA of the core is preferably 500 μm or less (for example, 300 μm or less), more preferably 270 μm or less, or 250 μm or less. 150 μm or less.

The material of the core included in the laminate disclosed here is not particularly limited. For example, as the core, metal foil, resin film, foam film, paper, cloth, composites thereof, and the like can be used.

From the viewpoint of improving the strain resistance of the laminate, a metal foil can be preferably used as the core. Common metal foils such as stainless steel foil, aluminum foil, copper foil, titanium foil, and zinc foil can be used as the metal foil. Among them, stainless steel foil, aluminum foil, and copper foil can be preferably used from the viewpoint of cost and workability. The metal foil may have the form of a single layer, or may have a multi-layered structure of two, three or more layers. For example, it may be a plated foil in which different kinds of metals are plated on the surface of a metal foil. Alternatively, it may have a multi-layer structure including a metal layer and a layer made of another material (eg, paper).

Alternatively, a core containing a resin film as a base film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The core in the technique disclosed here can be substantially composed of such a base film. Alternatively, the core may contain an auxiliary layer in addition to the base film. Examples of the auxiliary layer include an undercoat layer, an antistatic layer, a colored layer, etc. provided on the surface of the base film. From the viewpoint of reducing the light transmittance of the laminate, a core having a colored layer disposed on the surface of the base polymer can be preferably used. As the colorant contained in the colored layer, the same colorant as used in the pressure-sensitive adhesive sheet described later can be preferably employed.

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

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 multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (for example, polyester resin). The method for producing the resin film is not particularly limited, and a conventionally known method may be appropriately adopted. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be employed as appropriate.

If necessary, the core including the resin film (PET film, etc.) may contain fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, etc. Various additives such as agents, ultraviolet absorbers, antistatic agents, lubricants and plasticizers may be blended. The blending ratio of various additives is usually less than about 30% by weight (for example, less than about 20% by weight, preferably less than about 10% by weight).

In some embodiments, a foam film can be used as the core material. The foam film used for the core is a film having a portion with cells (cell structure), typically a film containing at least one stratified foam (foam layer). Although not particularly limited, a preferred example of the foam film in the technology disclosed herein is a foam film composed of a single (one) foam layer.

In some other embodiments, paper or cloth is used as the core material. Examples of paper that can be used for the core include Japanese paper, kraft paper, glassine paper, woodfree paper, synthetic paper, top coat paper, and the like. Examples of fabrics include woven fabrics and non-woven fabrics obtained by spinning various fibrous materials alone or by blending them. Examples of the fibrous substance include cotton, staple fiber, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber.

The nonwoven fabric referred to here is a concept that refers to a nonwoven fabric for adhesive sheets that is mainly used in the field of adhesive tapes and other adhesive sheets, and is typically a nonwoven fabric that is produced using a general paper machine. (sometimes referred to as so-called "paper"). The term "resin film" as used herein is typically a non-porous resin sheet, which is distinguished from, for example, non-woven fabrics (that is, does not include non-woven fabrics). The resin film may be a non-stretched film, a uniaxially stretched film, or a biaxially stretched film. In addition, the surface of the substrate on which the pressure-sensitive adhesive layer is to be provided may be subjected to surface treatment such as application of an undercoat, corona discharge treatment, plasma treatment, or the like.

The surface of the core may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, and the like. Such a surface treatment can be a treatment for improving the adhesion between the core and the adhesive sheet (adhesive layer), in other words, the anchoring property of the adhesive sheet (adhesive layer) to the core.

<Adhesive sheet>
(25°C storage modulus)
The pressure-sensitive adhesive sheet (one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet; the same shall apply hereinafter) contained in the laminate disclosed herein has a storage elastic modulus G' at 25°C of the pressure-sensitive adhesive sheet (25°C) is characterized by being less than 0.20 MPa. When a pressure-sensitive adhesive sheet having a G' (25°C) of less than a predetermined value is used, the conformability of the laminate to steps tends to be improved. The G' (25°C) is preferably less than 0.19 MPa, more preferably less than 0.18 MPa, still more preferably less than about 0.17 MPa (e.g., less than 0.15 MPa), particularly preferably less than 0.14 MPa, It may be less than 0.1 MPa. The lower limit of the G' (25 ° C.) is not particularly limited, but from the viewpoint of adhesion, the G' (25 ° C.) is preferably 0.02 MPa or more, more preferably 0.035 MPa or more. 0.05 MPa or more, 0.1 MPa or more, or 0.12 MPa or more.

(85°C storage modulus)
In some embodiments, the PSA sheet may have a storage modulus G'(85°C) at 85°C of less than 0.08 MPa. When a pressure-sensitive adhesive sheet having a G' (85°C) of less than a predetermined value is used, the conformability of the laminate to steps tends to be improved. The G′ (85° C.) is preferably less than 0.07 MPa, more preferably less than 0.06 MPa, even more preferably less than about 0.05 MPa (for example, less than 0.045 MPa). The lower limit of the G' (85 ° C.) is not particularly limited, but from the viewpoint of adhesion, the G' (85 ° C.) is usually 0.01 MPa or more, preferably 0.02 MPa or more. Yes, it may be 0.03 MPa or more, or 0.04 MPa or more.

(120°C storage modulus)
In some aspects, the storage modulus G'(120°C) at 120°C of the PSA sheet can be less than 0.04 MPa. When a pressure-sensitive adhesive sheet having a G' (120°C) of less than a predetermined value is used, the conformability of the laminate to unevenness tends to be improved. The G′ (120° C.) is preferably less than 0.035 MPa, more preferably less than 0.033 MPa, still more preferably less than 0.03 MPa (for example, less than 0.028 MPa). The lower limit of the G' (120 ° C.) is not particularly limited, but from the viewpoint of adhesion, the G' (120 ° C.) is usually 0.01 MPa or more, preferably 0.015 MPa or more. , more preferably 0.02 MPa or more, and still more preferably 0.023 MPa or more.

The viscoelastic properties of the above-mentioned pressure-sensitive adhesive sheet can be obtained by adjusting the monomer composition of the base polymer contained in the pressure-sensitive adhesive layer and, if necessary, by appropriately adjusting the type and amount of the tackifying resin based on the contents described in this specification. It can be adjusted by selecting, appropriately setting the pressure-sensitive adhesive composition containing other components (such as a cross-linking agent) as necessary, polymer polymerization conditions, pressure-sensitive adhesive layer manufacturing conditions, and the like.

In the technology disclosed herein, the 25° C. storage modulus, 85° C. storage modulus and 120° C. storage modulus of the PSA sheet can be determined by dynamic viscoelasticity measurement. Specifically, a test piece having a thickness of about 2 mm is prepared by stacking a plurality of adhesive sheets to be measured. This test piece was punched into a disk shape with a diameter of 7.9 mm. A dynamic viscoelasticity measurement is performed under the conditions to obtain a 25°C storage modulus, an 85°C storage modulus and a 120°C storage modulus.
・Measurement mode: Shear mode ・Temperature range: -70°C to 150°C
・Temperature increase rate: 5°C/min
・Measurement frequency: 1Hz
It is also measured by the above method in the examples described later.

The thickness T _B of the pressure-sensitive adhesive sheet (not including a release liner) disclosed herein is suitably 3 μm or more, preferably 5 μm or more, more preferably over 10 μm, and still more preferably 15 μm or more. By increasing the thickness _TB of the pressure-sensitive adhesive sheet, it is easy to improve both the conformability to irregularities and the pressure-sensitive adhesive properties. The thickness T _B of the pressure-sensitive adhesive sheet can be, for example, 500 μm or less, preferably 350 μm or less, and preferably 270 μm or less (for example, 250 μm or less) from the viewpoint of thinning.

When the pressure-sensitive adhesive sheet is a substrate-less pressure-sensitive adhesive sheet that does not contain a substrate, the thickness T _B1 of the substrate-less pressure-sensitive adhesive sheet is usually appropriately 3 μm or more, preferably 5 μm or more, and more preferably 10 μm or more. , more preferably 15 μm or more. By increasing the thickness _TB1 of the substrate-less pressure-sensitive adhesive sheet, it is easy to improve both the step conformability and the pressure-sensitive adhesive properties. The thickness T _B1 of the substrate-less pressure-sensitive adhesive sheet is usually appropriately 200 μm or less, and from the viewpoint of thinning, it is preferably 100 μm or less, more preferably 70 μm or less (e.g., 60 μm or less), and still more preferably 50 μm or less. .

When the pressure-sensitive adhesive sheet is a pressure-sensitive adhesive sheet with a substrate containing a substrate, the thickness T _B2 of the pressure-sensitive adhesive sheet with a substrate is preferably more than 10 μm, more preferably 20 μm or more, and still more preferably 25 μm or more, Especially preferably, it is 30 μm or more. By increasing the thickness _TB2 of the pressure-sensitive adhesive sheet with a substrate, it is easy to improve both the conformability to irregularities and the pressure-sensitive adhesive properties. The thickness T _B2 of the pressure-sensitive adhesive sheet with a substrate is usually suitably 500 μm or less, preferably 300 μm or less, more preferably 270 μm or less (for example, 260 μm or less), and 150 μm or less from the viewpoint of thinning. good too.

The light transmittance _CB of the adhesive sheet is not particularly limited. In the technology disclosed herein, from the viewpoint of imparting designability and improving the light shielding property of the laminate, the light transmittance _CB is 20% or less (preferably 10% or less, more preferably 5% or less, especially (preferably 1.5% or less) may be used. The lower limit of the light transmittance _CB is not particularly limited, and may be substantially 0%, that is, the detection limit or less, 1% or more, 5% or more, or 15% or more. In some other embodiments, the light transmittance C _B of the adhesive sheet may be greater than 30%, may be greater than 50%, or may be 70% or more (eg, 75% or more).

In the technique disclosed here, the light transmittance _CB of the pressure-sensitive adhesive sheet can be measured by the following method. Also in the examples described later, it is measured by the following method.

[Light transmittance C _B ]
The light transmittance _CB [%] of the adhesive sheet is the light transmittance in the thickness direction of the adhesive sheet peeled off from the release liner (light transmittance at a wavelength of 550 nm). is measured using a transmissometer. As the transmittance meter, a spectrophotometer manufactured by Hitachi (apparatus name “U4150 type spectrophotometer”) or an equivalent thereof is used.

(adhesive)
In the technology disclosed herein, the type of adhesive that constitutes the adhesive layer contained in the adhesive sheet is not particularly limited. The adhesives include acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, which can be used in the field of adhesives. It may contain one or more of various rubber-like polymers such as polyamide-based polymers and fluorine-based polymers as an adhesive polymer (in the sense of a structural polymer that forms an adhesive, hereinafter also referred to as "base polymer"). . From the viewpoint of adhesive performance, cost, etc., a pressure-sensitive adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably employed. Among them, a pressure-sensitive adhesive having an acrylic polymer as a base polymer (acrylic pressure-sensitive adhesive) is preferable. The technique disclosed here is preferably implemented in a mode using an acrylic pressure-sensitive adhesive.

A pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive, that is, a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer will be mainly described below. It is not intended to be limited to

Here, the "base polymer" of the adhesive refers to the main component of the rubber-like polymer contained in the adhesive, and is not to be construed as being limited to anything other than this. The term "rubber-like polymer" refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.

Further, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as "acrylic monomer". Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomeric units derived from an acrylic monomer. A typical example of an acrylic polymer is an acrylic polymer containing more than 50% by weight of the acrylic monomer in the total monomer components used to synthesize the acrylic polymer.
In addition, "(meth)acryloyl" is a generic term for acryloyl and methacryloyl. Similarly, "(meth)acrylate" is a generic term for acrylate and methacrylate, and "(meth)acrylic" is generic for acrylic and methacrylic.

(acrylic polymer)
In the technique disclosed herein, the acrylic polymer used as the polymer includes, for example, an alkyl (meth)acrylate as a main monomer, and may further include a sub-monomer copolymerizable with the main monomer. things are preferred. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the monomer raw material.

As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.
_CH2 =C( ^R1 ) ^COOR2 (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, such a carbon atom number range may be expressed as "C _1-20 ". From the viewpoint of the storage elastic modulus of the adhesive, an alkyl (meth)acrylate in which R ² is a C _1-14 (for example, C _1-10 , typically C _4-8 ) chain alkyl group is used as the main monomer. It is appropriate to Alkyl (meth)acrylates in which R ² is a butyl group or a 2-ethylhexyl group are preferred. In addition, from the viewpoint of adhesive properties, an alkyl acrylate in which R ¹ is a hydrogen atom and R ² is a C _4-8 chain alkyl group (hereinafter also simply referred to as C _4-8 alkyl acrylate) is used as the main monomer. preferably.

Specific examples of alkyl (meth)acrylates in which R ² is a C _1-20 chain alkyl group include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth) 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 ) 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 , nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like. These alkyl (meth)acrylates may be used singly or in combination of two or more. Suitable 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 ratio of the alkyl (meth)acrylate to the monomer components constituting the acrylic polymer is typically more than 50% by weight, and can be, for example, 70% by weight or more, and may be 85% by weight or more, or 90% by weight. % by weight or more. The upper limit of the ratio of alkyl (meth)acrylate is not particularly limited, but it is preferably 99.5% by weight or less (for example, 99% by weight or less), or properties based on submonomers such as carboxy group-containing monomers (for example, aggregation 98% by weight or less (for example, less than 97% by weight) from the viewpoint of preferably exerting force). Alternatively, the acrylic polymer may be obtained by polymerizing substantially only alkyl (meth)acrylate.

Further, when C _4-8 alkyl acrylate is used as a 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, It is more preferably 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 in the alkyl (meth)acrylate contained in the monomer component is 75 wt. % or more (usually 85 wt% or more, for example 90 wt% or more, further 95 wt% or more). The technology disclosed herein can be practiced, for example, in a mode in which the alkyl (meth)acrylate contained in the monomer component is BA alone, 2EHA alone, BA and 2EHA, 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 the C _1-6 alkyl (meth)acrylate as the main monomer in this way, the storage modulus can be moderately improved. In this embodiment, the ratio of C _1-6 alkyl (meth)acrylate in the monomer component (in other words, polymerization ratio) is preferably 80% by weight or more, more preferably 90% by weight or more, and still more preferably 92% by weight or more ( for example greater than 95% by weight). The upper limit of the ratio of C _1-6 alkyl (meth)acrylate in the monomer component is not particularly limited, and is usually 99% by weight or less, and 98% by weight or less in relation to the proportion of other copolymerizable monomers used. 97% by weight or less is preferable, and it may be less than 95% by weight. The C _1-6 alkyl (meth)acrylates may be used singly or in combination of two or more. The C _1-6 alkyl (meth)acrylate is preferably a C _1-6 alkyl acrylate, more preferably a C _2-6 alkyl acrylate, and even more preferably a C _4-6 alkyl acrylate. In some other aspects, the C _1-6 alkyl (meth)acrylate is preferably a C _1-4 alkyl acrylate, more preferably a C _2-4 alkyl acrylate. Preferred examples of C _1-6 alkyl (meth)acrylates include BA.

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 C _7-10 alkyl (meth)acrylate in the acrylic polymer is preferably 50% by weight or more. By using a _C7-10 alkyl (meth)acrylate as a main monomer in this way, the 25°C storage elastic modulus can be preferably lowered, thereby increasing the flexibility and improving the conformability to the adherend. can be made The ratio of C _7-10 alkyl (meth)acrylate in the monomer component (in other words, copolymerization ratio) may be greater than 60% by weight, may be greater than 70% by weight, and more preferably greater than 80% by weight. , more preferably 90% by weight or more, 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 in the monomer component is not particularly limited, and is usually 99% by weight or less, and the relationship with the ratio of other copolymerizable monomers (eg, acidic group-containing monomers). Therefore, it is suitable that the content is 97% by weight or less, and preferably 96% by weight or less. The C _7-10 alkyl (meth)acrylates can be used singly or in combination of two or more. Suitable examples of C _7-10 alkyl (meth)acrylates include C _7-10 alkyl acrylates such as 2EHA, isooctyl acrylate, isononyl acrylate. Among them, 2EHA is preferable.

The acrylic polymer in the technology disclosed here may be copolymerized with a sub-monomer. A carboxy group-containing monomer, a hydroxyl group (OH group)-containing monomer (2-hydroxyethyl (meth) acrylate, 4 - hydroxybutyl (meth) acrylate, etc.), acid anhydride group-containing monomers, amide group-containing monomers ((meth) acrylamide, N,N-dimethyl (meth) acrylamide, etc.), amino group-containing monomers (aminoethyl (meth) acrylate , N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers 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. The said submonomer can be used individually by 1 type or in combination of 2 or more types.

When the monomer component constituting the acrylic polymer contains the functional group-containing monomer described above, the content of the functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exhibiting 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 should be 0.5% by weight or more. is suitable, and it may be 1% by weight or more. In addition, from the viewpoint of easily balancing the adhesion performance in relation to the main monomer, the content of the functional group-containing monomer in the monomer component is appropriately 40% by weight or less, and is 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 improve cohesiveness based on its polarity and exhibit good bonding strength to polar adherends. When using a cross-linking agent such as an isocyanate-based or epoxy-based cross-linking agent, the acidic group (typically a carboxyl group) becomes a cross-linking point of the acrylic polymer.

A carboxy group-containing monomer is preferably used as the acidic group-containing monomer. Examples of carboxy group-containing monomers 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; ethylenically unsaturated dicarboxylic acids such as and anhydrides thereof (maleic anhydride, itaconic anhydride, etc.). The acidic group-containing monomer may also be a monomer having a metal salt (for example, an alkali metal salt) of a carboxy group. Among them, AA and MAA are preferred, and AA is more preferred.

In the technology disclosed herein, the content of an acidic group-containing monomer (typically a 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. A content of 0% by weight or more is appropriate. By using a predetermined amount or more of the acidic group-containing monomer, the cohesive strength 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. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is usually 20% by weight or less, and preferably 10% by weight from the viewpoint of improving the adhesion to the adherend and thus the followability. less than, more preferably less than 8.0 wt%, more preferably less than 7.0 wt%, particularly preferably less than 6.0 wt%, even less than 5.0 wt% (e.g. less than 4.0 wt%) good.

The acrylic polymer preferably used in the technology disclosed herein can be a copolymer obtained by copolymerizing an alkyl (meth)acrylate as a main monomer and an acidic group-containing monomer as a sub-monomer. In such an acrylic polymer, the proportion of copolymer components 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. Well, less than 0.1 wt%, less than 0.03 wt% (eg less than 0.01 wt%). The monomer component constituting the acrylic polymer may be substantially free of functional group-containing monomers other than the above acidic group-containing monomers. An acrylic polymer substantially composed of an alkyl (meth)acrylate and an acidic group-containing monomer can maximize the effects of the alkyl (meth)acrylate and the acidic group-containing monomer.

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 above-mentioned acidic group-containing monomer. The proportion of the hydroxyl group-containing monomer in the monomer component may be, for example, about 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 that constitutes the acrylic polymer may contain other copolymerization components other than the sub-monomers described above for the purpose of improving the cohesive force. Examples of other copolymerization components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; ) acrylate; aryl (meth)acrylate (e.g. phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (e.g. phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylate (e.g. benzyl (meth)acrylate), etc. Aromatic ring-containing (meth)acrylates; olefinic monomers; chlorine-containing monomers; isocyanate group-containing monomers 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; The above-mentioned other copolymerization components can be used singly or in combination of two or more.

The amount of such other copolymerization components may be appropriately selected according to the purpose and application and is not particularly limited, but from the viewpoint of appropriately exhibiting the effects of use, it is suitable to be 0.05% by weight or more. , 0.5% by weight or more. In addition, from the viewpoint of easily balancing adhesive performance, the content of other copolymerization components in the monomer component is suitably 20% by weight or less, and 10% by weight or less (for example, 5% by weight or less). good too. The technology disclosed herein can also be preferably practiced in a mode in which the monomer component does not substantially contain other copolymerization components. Here, the monomer component does not substantially contain other copolymerization components means that other copolymerization components are not used at least intentionally, and other copolymerization components are, for example, 0.01 wt% or less. To some extent, unintentional inclusion is acceptable.

Acrylic polymers are polyfunctional having at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth)acryloyl groups and vinyl groups 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 increased. Polyfunctional monomers can be used as cross-linking agents. Polyfunctional monomers are not particularly limited, and examples include 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and neopentyl glycol di(meth)acrylate. etc. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types.

The amount of 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 approximately 3% by weight or less, preferably approximately 2% by weight or less, and more preferably approximately 1% by weight or less (for example, approximately 0.5% by weight or less) based on the above monomer components. The lower limit of the amount used when using a polyfunctional monomer is not particularly limited as long as it is greater than 0% by weight. Usually, by setting the amount of the polyfunctional monomer used to 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 is 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 refers to the Tg determined by the Fox formula based on the composition of the monomer components. The Fox equation is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio based on weight), and Tgi is the content of the monomer i. It represents the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer used for calculating the Tg, the value described in the known materials shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
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°C
Methacrylic acid 228°C

For the glass transition temperatures 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 values are listed in this document, the highest value is adopted. If it is not described in the above 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, the Tg of the acrylic polymer is advantageously about −25° C. or less, preferably about −35° C. or less, more preferably about − The temperature is 40° C. or lower, more preferably -45° C. or lower, and may be -50° C. or lower, or -55° C. or lower. From the viewpoint of the cohesive strength 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 (eg, −64° C. or lower). From the viewpoint of the cohesive strength 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 types and usage ratios of the monomers used in synthesizing the polymer).

The weight average molecular weight Mw of the base polymer disclosed herein is preferably about 30×10 ⁴ or more, more preferably 40×10 ⁴ or more (e.g. 45×10 ⁴ or more), still more preferably It is about 50×10 ⁴ or more, particularly preferably about 55×10 ⁴ or more (for example, about 58×10 ⁴ or more). Moreover, the above Mw is usually about 300×10 ⁴ or less, and about 200×10 ⁴ or less is suitable. From the viewpoint of improving flexibility, Mw is preferably about 100×10 ⁴ or less, and may be about 70×10 ⁴ or less (for example, about 65×10 ⁴ or less). As the base polymer, one or more of the various polymers exemplified as the rubber-like polymer can be used. For example, an acrylic polymer obtained by a solution polymerization method preferably has Mw within the above range.

The dispersion (Mw/Mn) of the base polymer (preferably acrylic polymer) disclosed herein is not particularly limited. The dispersity (Mw/Mn) here means the dispersity (Mw/Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In some preferred embodiments, the dispersity (Mw/Mn) of the base polymer is 50 or less, may be less than 45, may be less than 40 (e.g., 38 or less), may be less than 35, or may be less than 32. . By restricting the molecular weight distribution within an appropriate range, stable properties can be easily obtained. 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, there is a tendency for the actions of the low-molecular-weight and high-molecular-weight substances to be exhibited in a well-balanced manner. Such polymers also tend to be highly manufacturable.

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

The method for obtaining the base polymer (for example, an acrylic polymer) is not particularly limited, and various known polymer synthesis methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization can be used. can be appropriately adopted polymerization method. For example, a solution polymerization method can be preferably employed. The polymerization temperature at the time of solution polymerization can be appropriately selected according to the type of monomer and solvent used, the type of polymerization initiator, etc. ° C.).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). Depending on the type of polymerization method, the initiator used for polymerization may be a conventionally known polymerization initiator (for example, an azo polymerization initiator such as 2,2'-azobisisobutyronitrile (AIBN) or a peroxide polymerization initiator). 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) per 100 parts by weight of the monomer component. ).

(tackifying resin)
The adhesive layer in the technology disclosed herein can contain a tackifying resin. Thereby, the peel strength of the adhesive sheet can be increased. Examples of tackifying resins include phenol-based tackifying resins, terpene-based tackifying resins, modified terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, One or more selected from tackifier resins such as elastomer-based tackifier resins and ketone-based tackifier resins can be used. Among them, phenol-based tackifying resins, terpene-based tackifying resins, and modified terpene-based tackifying resins are preferable, and phenol-based tackifying resins (preferably terpene phenolic resins) are more preferable.

Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins and rosin phenolic resins.
Terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin), and a homopolymer or copolymer of terpenes is a concept that includes both phenol-modified (phenol-modified terpene resin). Preferred examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l- and d/l-forms (dipentene)). is mentioned. A hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes called a hydrogenated terpene phenolic resin.
Alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oily phenolic resins). Examples of alkylphenol resins include novolac and resole types.
Rosin phenolic resins are typically rosins or phenol-modified products of the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosin phenol resins include rosin phenol resins obtained by a method of adding phenol to rosins or various rosin derivatives described above with an acid catalyst and thermally polymerizing the mixture.

Examples of terpene-based tackifying 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. One type of terpene homopolymer includes α-pinene polymer, β-pinene polymer, dipentene polymer and the like. Examples of modified terpene resins include those obtained by modifying the above terpene resins. Specific examples include styrene-modified terpene resins and hydrogenated terpene resins.

The concept of rosin-based tackifying resins here includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (fresh rosins) such as gum rosin, wood rosin and tall oil rosin; homogenized rosin, polymerized rosin, other chemically modified rosins, etc.);

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

Examples of hydrocarbon tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc. ), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesive strength, a tackifier resin having a softening point (softening temperature) of about 80° C. or higher (preferably about 100° C. or higher) can be preferably used. For example, a phenol-based tackifying resin (terpene phenol resin, etc.) having such a softening point can be preferably used. In some embodiments, terpene phenolic resins with softening points of about 135° C. or higher (or even about 140° C. or higher) can be used. There is no particular upper limit for the softening point of the tackifying resin. A tackifying resin having a softening point of about 200° C. or lower (more preferably about 180° C. or lower) can be preferably used from the viewpoint of adhesion to adherends and substrates. The softening point of the tackifying resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207.

Some preferred embodiments include embodiments in which the tackifying resin contains one or more phenolic tackifying resins (typically terpene phenolic resins). The technology disclosed herein can be preferably implemented in a mode in which, for example, about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of tackifying resin is 100% by weight is a terpene phenol resin. About 50% by weight or more of the total amount of tackifying resin may be the terpene phenolic resin, and about 70% by weight or more (eg, about 80% by weight or more) may be the terpene phenolic resin. Substantially all of the tackifying resin (eg, about 95-100 wt%, or even about 99-100 wt%) may be a terpene phenolic resin.

Although not particularly limited, in some embodiments, the tackifying resin may include a tackifying resin having a hydroxyl value higher than 20 mgKOH/g. Among them, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more is preferable. Hereinafter, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more may be referred to as a "high hydroxyl value resin". A tackifying resin containing such a high hydroxyl value resin (e.g., a phenolic tackifying resin, preferably a terpene phenolic resin) can provide a pressure-sensitive adhesive layer with excellent adhesion to adherends and high cohesion. . The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the base polymer, the hydroxyl value of the high hydroxyl value resin is suitably about 200 mgKOH/g or less, preferably about 100 mgKOH/g or less, and may be about 70 mgKOH/g or less. , approximately 65 mg KOH/g or less. High hydroxyl value resin can be used individually by 1 type or in combination of 2 or more types.

Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method specified in JIS K0070:1992 can be adopted. A specific measuring method is as follows.
[Method for measuring hydroxyl value]
1. Reagent (1) As the acetylation reagent, approximately 12.5 g (approximately 11.8 mL) of acetic anhydride is taken, pyridine is added to bring the total amount to 50 mL, and the mixture is thoroughly stirred and used. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to bring the total amount to 100 mL, and use the mixture after thorough stirring.
(2) A 0.5 mol/L potassium hydroxide ethanol solution is used as a measurement reagent.
(3) In addition, prepare toluene, pyridine, ethanol and distilled water.
2. Operation (1) About 2 g of a sample is accurately weighed and collected in a flat-bottomed flask, 5 mL of an acetylation reagent and 10 mL of pyridine are added, and an air cooling tube is attached.
(2) After heating the flask in a bath at 100°C for 70 minutes, allowing it to cool, adding 35 mL of toluene as a solvent from the top of the cooling tube and stirring, then adding 1 mL of distilled water and stirring to obtain acetic anhydride. decompose. Heat again in the bath for 10 minutes for complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove. Then, 50 mL of pyridine is added as a solvent and stirred.
(4) Add 25 mL of 0.5 mol/L potassium hydroxide ethanol solution using a whole pipette.
(5) Perform potentiometric titration with 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is taken as the end point.
(6) In the blank test, the above (1) to (5) are performed without any sample.
3. Calculation Calculate the hydroxyl value by the following formula.
Hydroxyl 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: weight of sample (g),
D: acid value,
28.05: ½ of the molecular weight of potassium hydroxide, 56.11;
is.

When the pressure-sensitive adhesive layer contains a tackifying resin, the amount (total amount) of the tackifying resin used is not particularly limited, and can be appropriately set, for example, in the range of about 1 to 100 parts by weight with respect to 100 parts by weight of the base polymer. . From the viewpoint of suitably exhibiting the effect of improving the peel strength, the amount of the tackifying resin to be used with respect to 100 parts by weight of the base polymer (for example, an acrylic polymer) is suitably 5 parts by weight or more, and 10 parts by weight or more. , and may be 15 parts by weight or more. From the viewpoint of impact resistance and cohesive strength, the amount of tackifying resin to be used with respect to 100 parts by weight of the base polymer (for example, an acrylic polymer) is preferably 50 parts by weight or less, and may be 40 parts by weight or less. Well, it may be 30 parts by weight or less.

(crosslinking agent)
In the technique disclosed here, the adhesive composition used for forming the adhesive layer may contain a cross-linking agent as needed. The type of cross-linking agent is not particularly limited, and can be appropriately selected from conventionally known cross-linking agents. Examples of such cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, peroxide-based cross-linking agents, urea-based cross-linking agents, and metal alkoxide-based cross-linking agents. Cross-linking agents, metal chelate-based cross-linking agents, metal salt-based cross-linking agents, carbodiimide-based cross-linking agents, hydrazine-based cross-linking agents, amine-based cross-linking agents, silane coupling agents, and the like. Among them, 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, the cohesive force of the pressure-sensitive adhesive layer can be obtained, and the conformability to the adherend, adhesive force, and the like can be improved. The pressure-sensitive adhesive layer in the technology disclosed herein contains the cross-linking agent in the form after the cross-linking reaction, the form before the cross-linking reaction, the form after the cross-linking reaction, the intermediate or composite form thereof, and the like. can 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, a polyfunctional isocyanate (meaning a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based cross-linking agents may be used singly or in combination of two or more.

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

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

Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene 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-phenylene diisocyanate, p-phenylene diisocyanate, 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.

Examples of preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of 3 or more isocyanate groups per molecule. Such tri- or more functional isocyanates are polymers (typically dimers or trimers) of di- or tri- or more functional isocyanates, derivatives (for example, polyhydric alcohols and two or more molecules of polyfunctional isocyanates). addition reaction products), polymers, and the like. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurate of hexamethylene diisocyanate (trimer adduct of isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexa Polyfunctional isocyanates such as reaction products with methylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate and polyester polyisocyanate can be mentioned. Commercially available polyfunctional isocyanates include "Duranate TPA-100" (trade name) manufactured by Asahi Kasei Chemicals, "Coronate L" (trade name), "Coronate HL", "Coronate HK" (trade name) and "Coronate HK" (trade names) manufactured by Tosoh Corporation. HX", "Coronate 2096", and the like.

The amount of the isocyanate-based cross-linking agent used is not particularly limited. For example, it can be about 0.1 part by weight or more with respect to 100 parts by weight of the base polymer. From the viewpoint of compatibility between cohesive strength and adhesion, impact resistance, etc., the amount of the isocyanate-based cross-linking agent used relative to 100 parts by weight of the base polymer can be, for example, more than 0.3 parts by weight, preferably 0.5 parts by weight. It is at least 0.75 parts by weight, more preferably at least 1.0 parts by weight (for example, at least 1.2 parts by weight). On the other hand, from the viewpoint of improving the adhesion to the adherend and the followability, the amount of the isocyanate-based cross-linking agent used is appropriately 10 parts by weight or less, preferably 7 parts by weight, per 100 parts by weight of the base polymer. Less than 5 parts by weight, more preferably less than 4.5 parts by weight, particularly preferably less than 4 parts by weight.

In some preferred embodiments, an isocyanate-based cross-linking agent and at least one cross-linking agent having a different type of cross-linkable functional group from the isocyanate-based cross-linking agent are used in combination as the cross-linking agent. In the technology disclosed herein, a cross-linking agent other than an isocyanate-based cross-linking agent (that is, a cross-linking agent having a different type of cross-linkable reactive group from the isocyanate-based cross-linking agent; hereinafter also referred to as a “non-isocyanate cross-linking agent”) and an isocyanate It can be used in combination with a system cross-linking agent.

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 from the above-described cross-linking agents. The non-isocyanate-based cross-linking agents may be used singly or in combination of two or more.

In some preferred embodiments, an epoxy-based cross-linking agent can be employed 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 preferred. Epoxy-based cross-linking agents may be used singly or in combination of two or more.

Specific examples of epoxy-based cross-linking agents include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercially available epoxy-based cross-linking agents include Mitsubishi Gas Chemical Co., Ltd.'s trade name "TETRAD-C" and trade name "TETRAD-X", DIC's trade name "Epiclon CR-5L", and Nagase ChemteX Corp. and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd. under the trade name of "Denacol EX-512".

The amount of epoxy-based cross-linking agent used is not particularly limited. The amount of the epoxy-based cross-linking agent used is, 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 base polymer. can be done. From the viewpoint of suitably exhibiting the effect of improving the cohesive strength, the amount of the epoxy-based cross-linking agent to be used is preferably about 0.005 parts by weight or more per 100 parts by weight of the base polymer. In addition, from the viewpoint of improving the adhesion to the adherend and the followability, the amount of the epoxy-based cross-linking agent used is appropriately about 0.2 parts by weight or less with respect to 100 parts by weight of the base polymer. It is preferably 0.1 part by weight or less, more preferably less than about 0.05 part by weight.

The total amount (total amount) of the cross-linking agent used is not particularly limited. For example, it can be about 10 parts by weight or less, preferably about 0.005 to 10 parts by weight, more preferably about 0.01 to 5 parts by weight, based on 100 parts by weight of the base polymer (preferably acrylic polymer). can be selected from a range of

(coloring agent)
The pressure-sensitive adhesive layer disclosed herein may or may not contain a coloring agent that can help reduce light transmittance. Conventionally known pigments and dyes can be used as the colorant. As the color of the coloring agent, colored is preferable. The color of the coloring agent can be, for example, black, gray, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent, and the like. A colored coloring agent can impart light-shielding properties and design properties. The coloring agent may or may not contain a colorless coloring agent in combination with a colored coloring agent. The pressure-sensitive adhesive layer according to one typical aspect disclosed herein may be substantially free of colorless coloring agents. In addition, in this specification, "colored" is a meaning including black and metallic color. In addition, the term “colorless” is meant to include white. The pressure-sensitive adhesive layer may have a multilayer structure including a colored layer containing a coloring agent. Alternatively, the pressure-sensitive adhesive layer may contain the colorant in a substantially dispersed state (it may be in a dissolved state).

Various pigments and dyes can be used as the coloring agent. Examples of pigments include zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide, and iron hydroxide. , Chromium oxide type, Spinel type firing type, Chromic acid type, Chromium vermillion type, Prussian blue type, Aluminum powder type, Bronze powder type, Silver powder type, Inorganic pigment such as calcium phosphate, Phthalocyanine type, Azo type, Condensed azo type , azo lake-based, anthraquinone-based, perylene/perinone-based, indigo-based, thioindigo-based, isoindolinone-based, azomethine-based, dioxazine-based, quinacridone-based, aniline black-based, triphenylmethane-based, and carbon black-based organic pigments. be done. Examples of dyes include azo dyes, anthraquinone, quinophthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine. Colorants may be used singly or in appropriate combination of two or more.

A black coloring agent can be preferably used because the light-shielding property can be efficiently adjusted with a small amount of the coloring agent. In a preferred aspect of the technology disclosed herein, the pressure-sensitive adhesive layer contains a black colorant. As the black colorant contained in the adhesive layer, an organic or inorganic colorant (pigment, dye, etc.) can be used. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, and cyanine. Black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone colorants, and the like. Among them, carbon black is preferred. As the carbon black particles, it is also possible to use surface-modified carbon black particles having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, silicon-containing groups (e.g., alkoxysilyl groups and alkylsilyl groups). . Such surface-modified carbon black particles are also called self-dispersing carbon black, and the addition of a dispersant becomes unnecessary or the amount thereof can be reduced. The carbon black particles may be used singly or in combination of two or more.

The black colorant is not particularly limited, and a particulate colorant (pigment) can be preferably used. In one preferred embodiment, a black colorant (eg, a black pigment such as carbon black) having an average particle size of about 10 nm or more (eg, about 50 nm or more) can be used. The upper limit of the average particle size of the black colorant is not particularly limited, and is usually about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, for example 200 nm or less (for example, about 120 nm or less). In addition, unless otherwise specified, the "average particle size" in this specification means the particle size at 50% of the integrated value in the particle size distribution measured based on the particle size distribution measuring device based on the laser scattering/diffraction method (50% volume mean particle diameter; hereinafter sometimes abbreviated as _D50 ).

The amount of the coloring agent (solid content) used in the pressure-sensitive adhesive layer is not particularly limited, and the amount can be appropriately adjusted so as to impart the desired light-shielding properties. The amount of the black colorant used is usually about 0.1 to 30% by weight of the total weight of the adhesive layer, for example 0.1 to 25% by weight (typically 0.1 to 30% by weight). 20% by weight).

(anti-rust)
The pressure-sensitive adhesive layer according to some embodiments may contain an antirust agent. Rust inhibitors are not particularly limited, and include azole rust inhibitors, amine compounds, nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, and dicyclohexylamine benzoate. acid salts, urea, urotropine, thiourea, phenyl carbamate, cyclohexylammonium-N-cyclohexylcarbamate (CHC) and the like. The rust preventives can be used singly or in combination of two or more.

As the rust inhibitor, an azole-based rust inhibitor can be preferably used. As the azole-based rust preventive agent, a five-membered ring aromatic compound containing two or more heteroatoms, in which at least one of the heteroatoms is a nitrogen atom, is preferably used as an active ingredient. can be Preferred examples of compounds that can be used as azole rust inhibitors include benzotriazole rust inhibitors containing benzotriazole compounds as active ingredients. Preferable examples of benzotriazole compounds 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 parts by weight or more (typically 0.05 parts by weight or more) with respect to 100 parts by weight of the base 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 increasing the cohesive strength of the pressure-sensitive adhesive, the content of the rust inhibitor is preferably less than 8 parts by weight with respect to 100 parts by weight of the base polymer. It may be less than part.

(Other additives)
The pressure-sensitive adhesive composition may optionally contain adhesive agents such as leveling agents, cross-linking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, and the like. Various additives common in the pharmaceutical field may be included. As for the various additives mentioned above, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

The pressure-sensitive adhesive layer (layer made of pressure-sensitive adhesive) disclosed herein is a water-based pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, and active energy rays such as ultraviolet rays and electron beams. It may be a pressure-sensitive adhesive layer formed from an active energy ray-curable pressure-sensitive adhesive composition that is cured by irradiation. The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in the form of containing a pressure-sensitive adhesive (adhesive layer-forming component) in a water-based solvent (aqueous solvent), typically water-dispersed. Also included are so-called type adhesive compositions (compositions in which at least part of the adhesive is dispersed in water) and the like. Moreover, the solvent-type adhesive composition refers to an adhesive composition in the form of containing an adhesive in an organic solvent. As the organic solvent contained in the solvent-based pressure-sensitive adhesive composition, one or two or more of the organic solvents (toluene, ethyl acetate, etc.) exemplified as the organic solvent (toluene, ethyl acetate, etc.) that can be used in the above solution polymerization can be used without particular limitation. From the viewpoint of adhesive properties, the technology disclosed herein can be preferably practiced in a mode comprising a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition. In an embodiment having a solvent-based pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition, the effects of the technique disclosed herein are preferably achieved.

The 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 surface having releasability (release surface) and drying can be employed. For a pressure-sensitive adhesive sheet having a substrate, for example, a method (direct method) of forming a pressure-sensitive adhesive layer by directly applying (typically applying) a pressure-sensitive adhesive composition to the substrate and drying it can be employed. can. Alternatively, a method of applying a pressure-sensitive adhesive composition to a surface having releasability (release surface) and drying to form a pressure-sensitive adhesive layer on the surface and transferring the pressure-sensitive adhesive layer to a substrate (transfer method). may be adopted. As the release surface, for example, the surface of a release liner, which will be 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. It may be a formed pressure-sensitive adhesive layer.

Application of the adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, a die coater, and a bar coater. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.
From the viewpoint of promoting the cross-linking reaction, improving production efficiency, etc., it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 to 150.degree. C., preferably about 60 to 130.degree. After drying the pressure-sensitive adhesive composition, it may be further aged for the purpose of adjusting migration of components in the pressure-sensitive adhesive layer, progressing the crosslinking reaction, relaxing strain that may exist in the pressure-sensitive adhesive layer, and the like.

The adhesive layer disclosed herein may have a single layer structure or a multilayer 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, suitably 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). good too. A pressure-sensitive adhesive layer with a limited thickness can well meet demands for thinning and weight reduction. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, but from the viewpoint of adhesiveness and conformability to an adherend, it is, for example, about 3 μm or more, and about 10 μm or more is suitable. In some preferred embodiments, the thickness of the adhesive layer is approximately 20 μm or greater, more preferably approximately 30 μm or greater, and may be approximately 40 μm or greater. In a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on each side of a substrate (double-sided pressure-sensitive adhesive sheet with substrate), 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 suitable. % is preferred. By increasing the gel fraction of the pressure-sensitive adhesive layer within an appropriate range, the conformability to the adherend can be improved. In the technology disclosed herein, the gel fraction is more preferably 45% or higher, still more preferably 50% or higher, particularly preferably 55% or higher, and may be 60% or higher. On the other hand, from the viewpoint of conformability to the adherend, the gel fraction of the pressure-sensitive adhesive layer is suitably 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" refers to a value measured by the following method. The gel fraction can be grasped as the weight ratio of ethyl acetate-insoluble matter in the pressure-sensitive adhesive layer.
[Gel fraction measurement method]
An adhesive sample of about 0.1 g (weight Wg ₁ ) is wrapped in a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore size of 0.2 μm, and the opening is tied with a string (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, trade name "Nitoflon (registered trademark) NTF1122" available from Nitto Denko Corporation (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or equivalent use the product.
This package was immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days to elute only the sol component in the adhesive layer outside the film. The adhering ethyl acetate is wiped off, the packet is dried at 130° C. for 2 hours, and the weight (Wg ₄ ) of the packet is measured. The gel fraction _FG of the pressure-sensitive adhesive layer is obtained by substituting each value into the following formula. A similar method is adopted in the examples described later.
Gel fraction F _G (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

<Base material>
The adhesive sheet disclosed herein may contain a substrate (supporting substrate). The structure and material of the substrate disclosed herein are not particularly limited. The base material is typically a film-like base material (also referred to as "base film"). 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 base film in the technique disclosed here can be substantially composed of such a base film. Alternatively, the base film may contain an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc. provided on the surface of the base film.

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

The base film may be colored with a colored layer arranged on the surface of the base film (preferably resin film). A base film having a structure including a colored layer in this way can impart light-shielding properties and design properties. In a base film having a structure including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be arranged on either one surface of the base film, or may be arranged on both surfaces. In the configuration in which the colored layers are arranged on both surfaces of the base film, the configurations of the colored layers may be the same or different.

Such a colored layer can typically be formed by coating a base film with a colored layer-forming composition containing a coloring agent and a binder. Conventionally known pigments and dyes can be used as the colorant. As the color of the coloring agent, colored is preferred. The color of the coloring agent can be, for example, black, gray, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent, and the like. A colored coloring agent can impart light-shielding properties and design properties. The coloring agent may or may not contain a colorless coloring agent in combination with a colored coloring agent. A base film according to a typical aspect disclosed herein may be substantially free of a colorless colorant. In addition, in this specification, "colored" is a meaning including black and metallic color. In addition, the term “colorless” is meant to include white.

As the binder, materials known in the field of paints or printing can be used without particular limitation. Examples include polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate, and the like. The composition for forming a colored layer may be, for example, a solvent type, an ultraviolet curable type, a heat curable type, or the like. The formation of the colored layer can be carried out by adopting means conventionally used for forming the colored layer without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, and offset printing can be preferably employed.

The colored layer may have a single layer structure consisting entirely of one layer, or may have a multilayer structure including two, three or more sub-colored layers. A colored layer having a multi-layer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (for example, printing) a composition for forming a colored layer. The colors and blending amounts of the colorants contained in each sub-colored layer may be the same or different. In the colored layer for imparting light shielding properties, it is particularly significant to have a multi-layer structure from the viewpoint of preventing pinholes and enhancing light shielding properties.

The thickness of the entire colored layer is usually suitably about 1 μm to 10 μm, preferably about 1 μm to 7 μm, and can be, for example, about 1 μm to 5 μm. In the colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 1 μm to 2 μm.

The base film (typically a resin film) may contain a coloring agent. A base film containing a coloring agent in this way can impart light-shielding properties and design properties. Conventionally known pigments and dyes can be used as the colorant to be contained in the base film. In a preferred embodiment of the technology disclosed herein, the base film is a base film containing a black colorant, more specifically a resin film into which a black colorant is kneaded. Here, the base film in which the black colorant is kneaded means that the black colorant is mixed in the main constituent material of the base film (the material most contained in the base film, typically a resin material). It refers to a base film that has been coated. The black colorant is substantially dispersed in the base film.

An organic or inorganic colorant (pigment, dye, etc.) can be used as the black colorant contained in the base film. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, and cyanine. Black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone colorants, and the like. Among them, carbon black is preferred.

The black colorant is not particularly limited, and a particulate colorant (pigment) can be preferably used. In one preferred embodiment, a black colorant (eg, a black pigment such as carbon black) having an average particle size of about 10 nm or more (eg, about 50 nm or more) can be used. The upper limit of the average particle size of the black colorant is not particularly limited, and is usually about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, for example 200 nm or less (for example, about 120 nm or less).

The amount of the coloring agent used in the base film is not particularly limited, and the amount can be appropriately adjusted so as to impart the desired light-shielding properties. The amount of the black colorant used is usually about 0.1 to 30% by weight of the total weight of the base film, for example 0.1 to 25% by weight (typically 0.1 to 30% by weight). 20% by weight).

The base film disclosed herein may contain coloring agents (pigments and dyes) other than black coloring agents. Such non-black colorants include, for example, white colorants. White colorants include, for example, titanium oxide (titanium dioxide such as rutile-type titanium dioxide and anatase-type titanium dioxide), zinc oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, tin oxide, barium oxide, Cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, aluminum silicate, magnesium silicate , calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite , Inorganic white colorants such as hydrated halloysite, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, silicone resin particles, urea-formalin resin particles, melamine and organic white colorants such as organic resin particles.

The amount of the non-black colorant used in the base film is not particularly limited, and the amount can be appropriately adjusted so as to impart the desired light-shielding properties. The amount of the non-black colorant used is usually about 0.1 to 30% by weight of the resin film, for example 0.1 to 25% by weight (typically 0.1 to 20% by weight). % by weight).

If necessary, the base film may contain fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, Various additives such as lubricants and plasticizers may be added. The blending ratio of various additives is usually about less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

The base 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 substrate film preferably has a single-layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (for example, polyester resin). The method for producing the substrate film (typically the resin film) is not particularly limited, and any conventionally known method may be appropriately adopted. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be employed as appropriate.

The thickness of the base material disclosed here is not particularly limited. The thickness of the substrate is usually 3 μm or more, preferably 5 μm or more (for example, 10 μm or more). In some embodiments, the thickness of the substrate may be 20 μm or greater, 30 μm or greater, 40 μm or greater, 100 μm or greater, 200 μm or greater. The thickness of the substrate is usually 500 μm or less, preferably 400 μm or less, more preferably 300 μm or less from the viewpoint of weight reduction. In some aspects, the thickness of the substrate may be 250 μm or less, 200 μm or less, 150 μm or less, 100 μm or less, or 50 μm or less. When the substrate includes a base film and a colored layer, the thickness of the substrate may be the total thickness of the base film and the colored layer.

The surface of the base film may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, and the like. Such a surface treatment can be a treatment for improving the adhesion between the base film and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the base film. When the technology disclosed herein is implemented in the form of a substrate-attached single-sided pressure-sensitive adhesive sheet, the back surface of the substrate film may be subjected to release treatment as necessary. For the release treatment, for example, a general silicone-based, long-chain alkyl-based, fluorine-based, etc. release agent is typically applied to a thin film of about 0.01 μm to 1 μm (eg, 0.01 μm to 0.1 μm). It can be a treatment to give. By performing such a peeling treatment, it is possible to obtain effects such as facilitating the unwinding of the adhesive sheet wound into a roll.

<Release liner>
In the technology disclosed herein, a release liner can be used in the formation of the adhesive layer, the production of the adhesive sheet, the production of the laminate, the storage of the laminate before use, distribution, shape processing, and the like. The release liner is not particularly limited. For example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluoropolymer (such as polytetrafluoroethylene), or a polyolefin resin (PE, A release liner or the like made of a low-adhesive material such as PP can be used. The release treatment layer may be formed by surface-treating the liner base material with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide release agent.

<Laminate characteristics>
The laminate disclosed herein preferably has step followability at a pass level in a step waterproof test measured by the method described in Examples below. A laminate that satisfies the above characteristics tends to maintain a state in which it follows a complicated shape without gaps.

The laminate disclosed herein preferably has an acceptable level of strain resistance (that is, does not cause strain) in a strain deformation test measured by the method described in Examples below. A laminate that satisfies the above characteristics has excellent deformation resistance against a load applied substantially in the thickness direction (Z-axis direction) of the laminate, and suppresses the occurrence of distortion in the adherend. It's easy to do.

The total thickness T _total of the laminate (not including the release liner) disclosed herein is not particularly limited. The total thickness T _total of the laminate can be, for example, 1000 μm or less, and from the viewpoint of thinning, the total thickness T _total of the laminate is preferably 500 μm or less (eg, 400 μm or less), more preferably 350 μm or less. and more preferably 300 μm or less. According to the technology disclosed herein, even if the total thickness T _total of the laminate is sufficiently small, it tends to exhibit good strain resistance. The lower limit of the total thickness T _total of the laminate is not particularly limited, but is usually 20 μm or more, preferably 30 μm or more, more preferably 40 μm or more, still more preferably 50 μm or more, and even 60 μm or more. Well, it may be 70 μm or more, or it may be 80 μm or more.

The light transmittance C _total of the laminate is not particularly limited. In the technology disclosed herein, the light transmittance C _total of the laminate is preferably 20% or less, more preferably 10% or less, from the viewpoint of imparting design properties and improving the light-shielding property of the laminate. , more preferably 5% or less, particularly preferably 1.5% or less. The lower limit of the light transmittance C _total is not particularly limited, and may be substantially 0%, that is, the detection limit or less, 1% or more, 5% or more, or 15% or more.

In the technique disclosed here, the light transmittance C _total of the laminate can be measured by the following method. Also in the examples described later, it is measured by the following method.

[Light transmittance C _total ]
The light transmittance C _total [%] of the laminate is the light transmittance in the thickness direction of the laminate peeled off from the release liner (light transmittance at a wavelength of 550 nm). is measured using a transmissometer. As the transmittance meter, a spectrophotometer manufactured by Hitachi (apparatus name “U4150 type spectrophotometer”) or an equivalent thereof is used.

<Application>
The laminate disclosed herein has excellent conformability to complicated shapes and resistance to distortion. Taking advantage of such characteristics, the laminate can be used in various applications requiring deformation resistance and strain resistance. For example, it is suitable for fixing members of various portable electronic devices having members having a bent shape. In addition, since portable electronic devices may be subjected to external impacts and loads, the use of the pressure-sensitive adhesive sheet disclosed herein is highly advantageous in suppressing the occurrence of distortion of adherends. Non-limiting examples of the above portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear type worn on the wrist like a wristwatch, Eyewear type including glasses type (monocular type and binocular type, including head-mounted type), clothes type attached to shirts, socks, hats, etc. in the form of accessories, earphones ear-wear type, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, the term “portable” means not only being able to be simply carried, but also having a level of portability that allows an individual (a typical adult) to carry it relatively easily. shall mean.

In addition, the pressure-sensitive adhesive sheet disclosed herein is preferably used 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 steps. Since the pressure-sensitive adhesive sheet disclosed herein is excellent in followability to an adherend, it can adhere well to the above three-dimensional shape and complicated shape having steps. While exhibiting a good fixing function by closely adhering to the surface of the adherend having such a three-dimensional shape and steps, for example, it is suitable for products that require waterproofness (for example, electronic devices such as portable electronic devices). It can provide excellent waterproofness.

In addition, the laminate disclosed herein is preferably used in mobile electronic devices for fixing members such as flexible printed wiring boards constituting the mobile electronic devices. Since the laminate disclosed herein has excellent conformability to a complicated shape, it can be reliably adhered to an adherend having a bent shape such as the flexible printed wiring board. Moreover, it is possible to suppress the occurrence of distortion in the electronic components fixed to the flexible printed wiring board or the like.

The laminate disclosed here can be used in the form of bonding materials processed into various external shapes to fix members constituting the portable electronic device as described above. Among others, it can be preferably used for electronic equipment (typically portable electronic equipment) equipped with an organic EL display device or a liquid crystal display device. For example, an electronic device having a display part such as a touch panel display (typically a mobile electronic device such as a smartphone), and the adhesive sheet disclosed herein is used for fixing members of the device having a large-screen display part. is preferably used. The laminate disclosed herein may be used to fix a member such as a cover member or an organic EL unit. The laminate disclosed herein is preferably used as a component of the display device as described above.

Matters disclosed by this specification include the following.
[1] a core body;
a first pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer disposed on one surface of the core;
and a second pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer disposed on the other surface of the core, wherein
The product (E _A ×T _A ) of Young's modulus E _A [MPa] and thickness T _A [μm] of the core is 500000 or more,
The thickness T _B of one or both of the first adhesive sheet and the second adhesive sheet is greater than 10 μm, and the storage elastic modulus G′ at 25° C. (25° C.) is less than 0.20 MPa. laminate.
[2] one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet,
The laminate according to [1] above, which has a storage modulus G' (85°C) at 85°C of less than 0.05 MPa.
[3] one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet,
The laminate according to [1] or [2] above, which has a storage modulus G' (120°C) at 120°C of less than 0.03 MPa.
[4] The pressure-sensitive adhesive layer contained in one or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer, the above [1] to [ 3] The pressure-sensitive adhesive sheet according to any one of the above items.
[5] The laminate according to any one of [1] to [4] above, wherein the core has a thickness T _A of 20 μm or more and 270 μm or less.
[6] The laminate according to any one of [1] to [5] above, wherein the Young's modulus E _A of the core is 3000 MPa or more.
[7] The laminate according to any one of [1] to [6] above, which has a light transmittance C _total of 10% or less.
[8] The laminate according to any one of [1] to [7], wherein the laminate has a total thickness T _total of 50 μm or more and 400 μm or less.
[9] The laminate according to any one of [1] to [8] above, which is used for fixing a member in a portable electronic device.

Several examples of the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

(Preparation of adhesive composition E)
95 parts of BA and 5 parts of AA as monomer components and 233 parts of ethyl acetate as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel, and nitrogen gas was introduced. The mixture was stirred for 2 hours while stirring. After removing oxygen in the polymerization system in this way, 0.2 parts of 2,2′-azobisisobutyronitrile (AIBN) is added as a polymerization initiator, and the solution is polymerized at 60° C. for 8 hours to obtain acrylic resin. A solution of system polymer E was obtained. Mw of this acrylic polymer E was about 60×10 ⁴ .

In the above acrylic polymer solution, 20 parts of terpene phenol resin B as a tackifying resin, 3 parts of an isocyanate cross-linking agent and 0.01 part of an epoxy cross-linking agent are added to 100 parts of the acrylic polymer E contained in the solution. was added and mixed with stirring to prepare a pressure-sensitive adhesive composition E. As terpene phenol resin B (tackifier resin B), 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.

(Preparation of adhesive composition E _black )
95 parts of BA and 5 parts of AA as monomer components and 233 parts of ethyl acetate as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel, and nitrogen gas was introduced. The mixture was stirred for 2 hours while stirring. After removing oxygen in the polymerization system in this way, 0.2 parts of 2,2′-azobisisobutyronitrile (AIBN) is added as a polymerization initiator, and the solution is polymerized at 60° C. for 8 hours to obtain acrylic resin. A solution of system polymer E was obtained. Mw of this acrylic polymer E was about 60×10 ⁴ .

In the above acrylic polymer solution, 20 parts of terpene phenol resin B as a tackifying resin, 3 parts of an isocyanate cross-linking agent and 0.01 part of an epoxy cross-linking agent are added to 100 parts of the acrylic polymer E contained in the solution. In addition, a dispersion of carbon black particles (manufactured by Toyocolor Co., Ltd., trade name "Multilac A903") is added as a coloring agent (black coloring agent), and the content of carbon black particles is set to 100 parts of acrylic polymer E was added so as to be 2 parts, and mixed with stirring to prepare a pressure-sensitive adhesive composition E _black . As terpene phenol resin B (tackifier resin B), 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.

(Preparation of adhesive composition F)
A reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel was charged with 70 parts of BA, 30 parts of 2EHA and 3 parts of AA as monomer components, and 233 parts of ethyl acetate as a polymerization solvent. Stirred for 2 hours while introducing gas. After removing oxygen in the polymerization system in this way, 0.08 part of 2,2′-azobisisobutyronitrile (AIBN) is added as a polymerization initiator, and the solution is polymerized at 60° C. for 8 hours to obtain acrylic resin. A solution of system polymer F was obtained. Mw of this acrylic polymer F was about 40×10 ⁴ .

To the above acrylic polymer solution, 2 parts of an isocyanate cross-linking agent and 0.01 part of an epoxy cross-linking agent are added as cross-linking agents to 100 parts of the acrylic polymer F contained in the solution, and mixed with stirring to form a pressure-sensitive adhesive composition. Item F was prepared.

(Preparation of adhesive composition G)
A reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel was charged with 100 parts of 2EHA and 2 parts of AA as monomer components, and 233 parts of ethyl acetate as a polymerization solvent, and nitrogen gas was introduced. The mixture was stirred for 2 hours while stirring. After removing oxygen from the polymerization system in this way, 0.02 part of benzoyl peroxide (manufactured by NOF Corporation, trade name "Nyper BW") was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 8 hours. to obtain a solution of acrylic polymer G. Mw of this acrylic polymer G was about 40×10 ⁴ .

To the above acrylic polymer solution, 2 parts of an isocyanate cross-linking agent and 0.01 part of an epoxy cross-linking agent are added as cross-linking agents to 100 parts of the acrylic polymer G contained in the solution, and mixed with stirring to form a pressure-sensitive adhesive composition. Item G was prepared.

(Preparation of adhesive composition H)
A reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel was charged with 95 parts of 2EHA and 5 parts of AA as monomer components and 233 parts of ethyl acetate as a polymerization solvent, and nitrogen gas was introduced. The mixture was stirred for 2 hours while stirring. After removing oxygen from the polymerization system in this way, 0.03 parts of benzoyl peroxide (manufactured by NOF Corporation, trade name "NIPER BW") was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 8 hours. to obtain a solution of acrylic polymer H. Mw of this acrylic polymer H was about 120×10 ⁴ .

To the above acrylic polymer solution, 3 parts of an isocyanate cross-linking agent and 0.03 parts of an epoxy cross-linking agent are added as cross-linking agents to 100 parts of the acrylic polymer H contained in the solution, and mixed with stirring to form an adhesive composition. Item H was prepared.

(Preparation of adhesive composition A)
A reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel was charged with 95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components, and 233 parts of ethyl acetate were charged, and the mixture was stirred for 2 hours while nitrogen gas was introduced. After removing oxygen in the polymerization system in this way, 0.2 parts of 2,2′-azobisisobutyronitrile (AIBN) is added as a polymerization initiator, and the solution is polymerized at 60° C. for 8 hours to obtain acrylic resin. A solution of system polymer A was obtained. Mw of this acrylic polymer A was about 60×10 ⁴ .

In the above acrylic polymer solution, 30 parts of terpene phenol resin A as tackifier resin A, 2 parts of isocyanate cross-linking agent and 0.01 of epoxy cross-linking agent are added to 100 parts of acrylic polymer A contained in the solution. and mixed with stirring to prepare a pressure-sensitive adhesive composition A. As the terpene phenol resin A (tackifier resin A), the 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. As the isocyanate-based cross-linking agent, trade name "Coronate L" (manufactured by Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane/tolylene diisocyanate trimer adduct) was used. As the epoxy-based cross-linking agent, trade name "TETRAD-C" (manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was used. The isocyanate-based cross-linking agent and the epoxy-based cross-linking agent were the same as those described above when preparing other pressure-sensitive adhesive compositions below.

Table 1 summarizes the composition of the adhesive compositions E, E _black , F, G, H and A and the weight average molecular weight of the base polymer.

<Example 1>
(Preparation of adhesive sheet)
Adhesive composition E was applied to the release surface of a 38 μm thick polyester release liner (trade name “Diafoil MRF”, manufactured by Mitsubishi Polyester Co., Ltd.) and dried at 100° C. for 2 minutes to form a 15 μm thick adhesive. formed a layer. Thus, a substrate-less double-sided PSA sheet having a thickness of 15 μm, one side of which was protected by the polyester release liner, was obtained. Two sheets of the substrate-less double-sided pressure-sensitive adhesive sheet were prepared and used as the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet of this example.

(Preparation of laminate)
The adhesive surface of the first adhesive sheet was attached to one surface of a stainless steel sheet (SUS 304BA) having a thickness of 20 μm as a core. Also, the adhesive surface of the second adhesive sheet was attached to the other surface of the stainless steel sheet (SUS 304BA). In this manner, the first and second adhesive sheets are arranged on both sides of the core, and the two release liners protect the adhesive surface of the first adhesive sheet and the adhesive surface of the second adhesive sheet. A laminated body was produced, and this was used as the laminated body of this example.

<Examples 2 to 4>
In the same manner as in Example 1, except that the thickness of the first adhesive sheet (adhesive layer), the thickness of the second adhesive sheet (adhesive layer) and/or the core body are as shown in Table 1. , to obtain the laminate of this example.

<Example 5>
Two sheets of a 38 μm thick polyester release liner (trade name “Diafoil MRF”, manufactured by Mitsubishi Polyester Co., Ltd.) were prepared. The adhesive composition E was applied to the release surface of each release liner and dried at 100° C. for 2 minutes to form an adhesive layer having a thickness of 10 μm. As a supporting substrate, a multi-layer structure support with a total thickness of about 10 μm consisting of a 5 μm thick transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) and a black printed layer provided on one side of the PET film. A substrate was prepared. The black printed layer was formed by printing using an ink composition containing a black colorant and using a gravure printing method. By laminating the adhesive layer formed on each release liner to the first surface and the second surface of the supporting substrate, a thick film having an adhesive layer on the first surface and the second surface of the black printed PET film is obtained. A double-sided pressure-sensitive adhesive sheet with a substrate having a thickness of 30 μm was produced. Two sheets of the double-sided pressure-sensitive adhesive sheet with the base material were prepared and used as the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet of this example. A laminate of this example was produced using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 6>
The pressure-sensitive adhesive layer formed on each release liner has a thickness of 45 μm, and a 50 μm-thick PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) kneaded with a black pigment is used as a support base material. A 140 μm-thick double-sided pressure-sensitive adhesive sheet with a substrate was produced in the same manner as in Example 5 except that the pressure-sensitive adhesive sheets were the first and second pressure-sensitive adhesive sheets of this example. A laminate of this example was produced using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 7>
A substrate-less double-sided PSA sheet with a thickness of 20 μm was produced using the same method as in Example 1, except that the thickness of the PSA layer was 20 μm, and used as the first PSA sheet of this example.

Example 5 except that the pressure-sensitive adhesive layer formed on each release liner had a thickness of 50 μm, and a transparent PET film having a thickness of 160 μm (trade name “Lumirror”, manufactured by Toray Industries, Inc.) was used as the supporting substrate. A double-faced PSA sheet with a substrate having a thickness of 260 μm was prepared in the same manner as in , and used as the second PSA sheet of this example.

A laminate of this example was produced using the same method as in Example 1, except that the first and second adhesive sheets of this example were used.

<Example 8>
A substrate-less double-sided pressure-sensitive adhesive sheet with a thickness of 20 μm was prepared using the same method as the first and second pressure-sensitive adhesive sheets of Example 1, except that the thickness of the pressure-sensitive adhesive layer was 20 μm. 1 adhesive sheet.

Except that the thickness of the pressure-sensitive adhesive layer formed on each release liner was 12.5 μm, and a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) with a thickness of 235 μm was used as the supporting substrate. In the same manner as in Example 5, a double-sided pressure-sensitive adhesive sheet with a substrate having a thickness of 260 μm was produced as the second pressure-sensitive adhesive sheet of Example 8.

<Example 9>
A laminate of this example was produced in the same manner as in Example 1, except that an aluminum sheet with a thickness of 20 μm (trade name “A1N30H-O”, manufactured by Takeuchi Metal Foil & Powder Co., Ltd.) was used as the core. bottom.

<Example 10>
A laminate of this example was produced in the same manner as in Example 1, except that a 20 μm thick copper sheet (trade name “C1020R-H”, manufactured by Takeuchi Metal Foil & Powder Co., Ltd.) was used as the core. bottom.

<Example 11>
A laminate of this example was produced in the same manner as in Example 1, except that a 125 μm thick transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) was used as the core.

<Example 12>
A substrate-less double-sided PSA sheet with a thickness of 15 μm was produced in the same manner as in Example 1, except that PSA composition E _black was used instead of PSA composition E. 1 and 2 pressure-sensitive adhesive sheets. A laminate of this example was produced using the same method as in Example 11, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 13>
A 30 μm-thick substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 2, except that the pressure-sensitive adhesive composition F was used instead of the pressure-sensitive adhesive composition E. and a second adhesive sheet. A laminate of this example was produced using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 14>
A 30 μm-thick substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 2, except that the pressure-sensitive adhesive composition G was used instead of the pressure-sensitive adhesive composition E. and a second adhesive sheet. A laminate of this example was produced using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 15>
A 30 μm-thick substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 2, except that the pressure-sensitive adhesive composition H was used instead of the pressure-sensitive adhesive composition E. and a second adhesive sheet. A laminate of this example was produced using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 16>
A 10 μm-thick substrate-less double-sided pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the thickness of the pressure-sensitive adhesive layer was 10 μm. and A laminate of this example was produced using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used.

<Example 17>
A laminate of this example was produced in the same manner as in Example 1, except that a 100 μm thick transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) was used as the core.

<Example 18>
A substrate with a thickness of 35 μm was prepared in the same manner as in Example 1 except that the adhesive composition A was used instead of the adhesive composition E and the thickness of the adhesive layer was 35 μm. A less double-sided pressure-sensitive adhesive sheet was prepared and used as the first pressure-sensitive adhesive sheet of this example. In addition, the same method as in Example 1 was used except that the adhesive composition F was used instead of the adhesive composition A and the thickness of the adhesive layer was 25 μm. A substrate-less double-sided pressure-sensitive adhesive sheet was produced and used as the second pressure-sensitive adhesive sheet of this example.
Using the same method as in Example 1, except that the first and second pressure-sensitive adhesive sheets of this example were used and a stainless steel sheet (SUS 304BA) having a thickness of 40 μm was used as the core body, this Example laminates were produced.

Tables 2 and 3 show the outline of the laminate of each example; light transmittance _CB of the adhesive sheet of each example; light transmittance C _total of the laminate; Young's modulus _EA [MPa] of the core, thickness _TA [μ]m and E _A ×T _A ; the total thickness T _total of the laminate are described.

<Evaluation method>
[Step waterproof test]
The laminate according to each example in which both adhesive surfaces are protected with a release liner is cut into a window frame shape (picture frame shape) having a square outer edge of 24.5 mm × 24.5 mm and a width of 2 mm. A frame-shaped laminate was obtained. The release liner on the side of the second adhesive sheet of this window-frame laminate is peeled off, and the exposed adhesive surface is attached to an acrylic plate having a square size of 50 mm × 50 mm and a thickness of 2 mm. A plate was made. The release liner on the side of the first pressure-sensitive adhesive sheet was peeled off from the window-frame laminate-attached acrylic plate.
A polycarbonate plate having a size larger than that of the acrylic plate was prepared, and a level difference tape (width 5 mm, height 20 μm) was attached to the surface of this polycarbonate plate. This level difference tape is used for the purpose of providing projections (level differences) on the surface of the polycarbonate plate. Here, an adhesive sheet having an adhesive layer on one side of a PET substrate was used as the stepped tape. Then, on this polycarbonate plate, the acrylic plate with the window-frame-shaped laminate prepared above was placed on two parallel sides of the window-frame-shaped laminate in such a position that the first adhesive sheet side of the laminate faces the polycarbonate side. The central portion of the window frame-like laminate crosses the stepped tape (so that the two parallel sides of the window frame laminate intersect (perpendicularly) with the stepped tape), and crimped under the conditions of 0.2 MPa and 1 minute. A sample for evaluation was thus obtained. In the obtained evaluation sample, when the window-frame-shaped laminate is adhered to the adherend (acrylic plate, polycarbonate plate, and stepped tape), the inside becomes a space sealed from the outside.
Evaluation of step waterproofing is carried out by immersing the evaluation sample in water in the autoclave, pressurizing at 25 ° C. and 0.5 MPa for 30 minutes in the autoclave, and the inside of the evaluation sample (window frame-like laminate The presence or absence of water intrusion into the inside of the body) was visually observed. The presence or absence of water infiltration into the evaluation sample was evaluated as step followability. When water infiltration into the evaluation sample was observed, it was judged as "P: Poor", and when it was not observed, it was judged as "G: Good". The evaluation results are shown in Tables 2 and 3 in the step followability item.
The step waterproof test was performed after aging the evaluation sample for 30 minutes under standard conditions (23° C., 50% RH).

[Distortion resistance test]
As shown in FIG. 4A, a PET film 80 having a length of 50 mm, a width of 50 mm, and a thickness of 125 μm and a stepped tape 82 having a width of 2 mm, a length of 50 mm, and a height of 8 mm are prepared. The stepped tape 82 was attached to the central portion so that the length direction of the PET film 80 was aligned with the direction of one side of the PET film 80 . The stepped tape 82 is used for the purpose of forming projections (steps) on the surface of the PET film 80 . Here, as the level difference tape 82, an adhesive sheet having an adhesive layer on one side of a PET base material was used. Next, the laminate according to each example in which both adhesive surfaces were protected with a release liner was cut into a size of 10 mm in length and 10 mm in width, and two release liners were peeled off from the laminate, and each adhesive surface was exposed to a thickness. A 5 μm PET film was adhered and backed to obtain a laminate sample piece 84 . A commercially available silicone rubber sheet 86 having a length of 50 mm, a width of 50 mm and a thickness of 3 mm was prepared. A laminate sample piece 84 was placed in the center of the upper surface of a silicon rubber sheet 86 so that the direction of one side of the laminate sample piece 84 and the direction of one side of the silicon rubber sheet 86 were aligned.

The PET film 80 was placed above the silicon rubber sheet 86 with the stepped tape 82 facing downward. At this time, the PET film 80 was arranged at a position overlapping the silicon rubber sheet 86 when viewed from above. Then, as shown in FIG. 4B, a load of 40 N was applied from above the PET film 80 toward the silicon rubber sheet 86 for 10 seconds under an environment of 25° C. and 50% RH. After that, as shown in FIG. 4C, the PET film 80 was pulled upward, and the silicon rubber sheet 86 from which the laminate sample piece 84 was removed was left for 24 hours in an environment of 25° C. and 50% RH. The strain height of the silicon rubber sheet 86 was measured using a surface shape measuring device (model number "Wyko NT9100", manufactured by Veeco), and the strain height was evaluated as the strain resistance of the laminate. Here, as shown in FIG. 4D, for the silicon rubber sheet 86 after being left for 24 hours, the height b of the portion to which the load was applied from the height a of the portion to which no load was applied to the silicon rubber sheet 86 The value (ab) obtained by subtracting is taken as the strain height c. When the strain height c was 3 μm or less, it was determined as “G: Good”, and when the strain height c was greater than 3 μm, it was determined as “P: Poor”. The evaluation results are shown in Tables 2 and 3 in the item of strain resistance.

As is clear from the results shown in Tables 2 and 3, Examples 1 to 16 in which the product (E _A ×T _A ) of the Young's modulus E _A [MPa] and the thickness T _A [μm] of the core is 500000 or more. and 18 showed significantly better strain resistance compared to the laminate of Example 17, where (E _A ×T _A ) is 400,000. In addition, the laminates of Examples 1 to 15, 17 and 18, in which the thickness T _B of the first and second pressure-sensitive adhesive sheets are all larger than 10 μm, have the thickness T _B of the first and second pressure-sensitive adhesive sheets Compared to the laminate of Example 16, which has a thickness of 10 μm, it exhibited remarkably excellent step followability. Furthermore, the laminates of Examples 1 to 17, in which the storage elastic modulus G' (25°C) at 25°C of the first and second adhesive sheets is less than 0.20 MPa, are the storage elastic moduli of the first and second adhesive sheets. Compared to the laminate of Example 18, which had a modulus G' (25°C) of 0.260 MPa, it showed excellent step followability.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1 laminate 11 first adhesive sheet 12 second adhesive sheet 15 core 21

release liners

25, 35

substrates

32, 34, 36, 38 adhesive layer 50 PC board 60 PET film 70 laminate sample piece 80 PET film 82 step tape 84 laminate sample piece 86 silicon rubber sheet

Claims

a core body;
a first pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer disposed on one surface of the core;
and a second pressure-sensitive adhesive sheet containing a pressure-sensitive adhesive layer disposed on the other surface of the core, wherein
The product (E A ×T A ) of Young's modulus E A [MPa] and thickness T A [μm] of the core is 500000 or more,
One or both of the first pressure-sensitive adhesive sheet and the second pressure-sensitive adhesive sheet have a thickness TB greater than 10 μm and a storage elastic modulus G′ at 25° C. (25° C.) of less than 0.20 MPa. laminate.
one or both of the first adhesive sheet and the second adhesive sheet,
2. Laminate according to claim 1, wherein the storage modulus G' at 85[deg.]C (85[deg.]C) is less than 0.05 MPa.
one or both of the first adhesive sheet and the second adhesive sheet,
3. The laminate according to claim 1, wherein the storage modulus G' at 120[deg.] C. (120[deg.] C.) is less than 0.03 MPa.
The laminate according to any one of claims 1 to 3, wherein the core has a thickness TA of 10 µm or more and 300 µm or less.
The laminate according to any one of claims 1 to 4, wherein the core has a Young's modulus EA of 3000 MPa or more.
The laminate according to any one of claims 1 to 5, wherein the light transmittance C total is 10% or less.
The laminate according to any one of claims 1 to 6, wherein the laminate has a total thickness T total of 50 µm or more and 400 µm or less.
The laminate according to any one of claims 1 to 7, which is used for fixing members in portable electronic devices.