Laminate

Abstract

To provide a laminate capable of simultaneously realizing a followability to a complicated shape and a distortion resistance.SOLUTION: A laminate includes: a core body; a first adhesive sheet including an adhesive layer, arranged on one surface of the core body; and a second adhesive sheet including an adhesive layer, arranged on the other surface of the core body. A product (EA×TA) of a Young's modulus EA [MPa] and thickness TA [μm] of the core body is 500000 or more. In one or both of the first adhesive sheet and the second adhesive sheet, thickness TB is larger than 10 μm and a storage elastic modulus at 25°C G'(25°C) is less than 0.20 MPa.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a laminate comprising a core and adhesive sheets arranged on each surface of the core. [Background technology]

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies hereinafter) exhibit a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to a substrate under pressure. Taking advantage of this property, adhesives are widely used in various industrial fields, from home appliances to automobiles and office automation equipment, as a joining method that is easy to work with and highly reliable in adhesion. For example, adhesives are widely used for purposes such as joining, fixing, and protecting components in smartphones and other portable electronic devices. Patent documents 1 and 2 are examples of technical documents relating to adhesive tapes used for fixing components in portable electronic devices. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-70102 [Patent Document 2] Japanese Patent Publication No. 2018-28051 [Overview of the project] [Problems that the invention aims to solve]

[0004] In recent years, in addition to miniaturization and thinning, the development of portable electronic devices with curved shapes such as three-dimensional shapes has progressed, and the shapes of their constituent components are becoming more complex. Adhesives that are attached to such complex shapes require the ability to conform well to the shape and adhere tightly. For example, in the aforementioned portable electronic device, an adhesive that fixes a component with a complex surface shape (which may be a curved shape) needs to maintain a state where it conforms to the complex shape without gaps while exhibiting good fixing function. If the adhesive does not conform to the curved shape of the object to be attached and gaps are created between the object and the adhesive, water may enter through the gaps, potentially causing problems such as impaired waterproofing.

[0005] Furthermore, adhesives are required to have the ability to protect the adherend. In particular, portable electronic devices tend to be subjected to external impacts and loads due to their portability, so adhesives used in portable electronic devices are required to have the ability to suppress deformation (strain) of other components (such as the adherend or components placed on the back side of the adherend) due to impacts, etc. If an adhesive has poor adherend protection, for example, if the adherend is a flexible printed circuit board to which electronic components are fixed, there is a risk that the electronic components may be deformed and damaged due to external impacts, etc. Therefore, adhesives are required to have the ability to suppress deformation (strain) of other components due to impacts, etc. (hereinafter, this ability is referred to as "strain resistance").

[0006] With conventional adhesive compositions, it is not easy to achieve both conformability to complex shapes and protection of the adherend. This invention was created in view of the above circumstances, and aims to provide a structure (laminated body) that can achieve both conformability to complex shapes and resistance to distortion. [Means for solving the problem]

[0007] With structures composed of a single element, such as adhesive sheets made up of only one adhesive layer, it tends to be difficult to achieve a high level of compatibility between two or more different performance characteristics. The inventors have found that by employing a laminate composed of two or more components, each containing at least an adhesive layer, it is possible to improve both conformability to complex shapes and the aforementioned distortion resistance.

[0008] According to this specification, a laminate is provided comprising a core body, a first adhesive sheet disposed on one surface of the core body, and a second adhesive sheet disposed on the other surface of the core body. Here, the first adhesive sheet and the second adhesive sheet each include an adhesive layer. In this laminate, the Young's modulus E of the core body A [MPa] and thickness T A [μm] product (E A ×T A ) is 500,000 or more. By using such a core, even if the thickness T A Even if the laminate is relatively thin, excellent deformation resistance can be easily achieved. In addition, one or both of the first adhesive sheet and the second adhesive sheet have a thickness T B The thickness is greater than 10 μm, and the storage modulus G'(25°C) at 25°C is less than 0.20 MPa. Such adhesive sheets are particularly suitable for the above-mentioned thickness T B Furthermore, when the adhesive sheet side having a storage modulus of elasticity G' (25°C) is attached to a substrate having a complex shape (e.g., steps), the conformability of the laminate to the complex shape (e.g., steps) tends to improve. Therefore, with the laminate of the above configuration, both conformability to complex shapes and strain resistance can be achieved simultaneously.

[0009] In some preferred embodiments, one or both of the first and second adhesive sheets have a storage modulus G'(85°C) at 25°C of less than 0.05 MPa. Using such adhesive sheets tends to improve the conformability of the laminate to complex shapes.

[0010] 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' (120°C) at 120°C of less than 0.03 MPa. The use of such a pressure-sensitive adhesive sheet tends to improve the conformability to the complex shape of the laminate.

[0011] In some preferred embodiments, the thickness T of the core body A is not less than 10 µm and not more than 300 µm. According to this configuration, thinning of the laminate and excellent distortion resistance can be easily achieved.

[0012] In some preferred embodiments, the Young's modulus E of the core body A is not less than 3000 MPa. According to this configuration, thinning of the laminate and excellent distortion resistance can be easily achieved.

[0013] In some preferred embodiments, the light transmittance C of the laminate total is not more than 10%. Such a laminate, when used in a product including a light source such as a backlight module, tends to be excellent in suppressing light leakage from the light source (light-shielding property) and imparting designability.

[0014] In some preferred embodiments, the total thickness T of the laminate total is not less than 50 µm and not more than 400 µm. Such a laminate tends to be excellent in conformability to complex shapes.

[0015] The laminate disclosed herein can be preferably used in electronic devices. In particular, by utilizing the feature of being excellent in conformability to complex shapes and distortion resistance, the laminate disclosed herein is preferably used in portable electronic devices which include members having complex shapes and are prone to external impact and load. Since the thickness of the laminate disclosed herein is limited, from this point of view as well, it is preferably used in portable electronic devices that are undergoing thinning and weight reduction.

[0016] Furthermore, combinations of the elements described herein may also be included within the scope of the invention for which patent protection is sought in this patent application. [Brief explanation of the drawing]

[0017] [Figure 1] This is a schematic cross-sectional view showing the structure of a laminate according to one embodiment. [Figure 2] This is a schematic cross-sectional view showing the configuration of a laminate according to another embodiment. [Figure 3] This is a schematic cross-sectional view showing the configuration of a laminate according to another embodiment. [Figure 4] This is a schematic diagram illustrating the method of strain resistance testing. [Modes for carrying out the invention]

[0018] Preferred embodiments of the present invention are described below. Matters other than those specifically mentioned herein but necessary for carrying out the present invention can be understood by those skilled in the art based on the teachings on carrying out the invention described herein and the common technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed herein and the common technical knowledge in the art. Furthermore, in the following drawings, members and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Also, the embodiments shown in the drawings are schematic for the purpose of clearly illustrating the present invention and do not necessarily accurately represent the size or scale of the laminates or adhesive sheets of the present invention that are actually offered as products.

[0019] In this specification, "adhesive" refers to a material that, as described above, exhibits a soft solid (viscoelastic) state at temperatures around room temperature and has the property of easily adhering to a substrate under pressure. The adhesive referred to here is generally defined as having a complex tensile modulus E, as defined in "CA Dahlquist, “Adhesion: Fundamentals and Practice”, McLaren & Sons, (1966) p. 143". *(1Hz) < 10 7 dyne / cm 2 It may be a material having properties that satisfy the above conditions (typically, a material having the above properties at 25°C).

[0020] <Example of laminated structure> The laminate disclosed herein includes a non-peelable 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. Here, the first adhesive sheet is an adhesive sheet including an adhesive layer, and the second adhesive sheet is also an adhesive sheet including an adhesive layer. The first adhesive sheet may be an adhesive sheet with a substrate having adhesive layers on both sides of a non-peelable substrate (support substrate), or it may be a substrate-less adhesive sheet without a non-peelable substrate. The second adhesive sheet may also be an adhesive sheet with a substrate having adhesive layers on both sides of a non-peelable substrate (support substrate), or it may be a substrate-less adhesive sheet without a non-peelable substrate.

[0021] The concept of a laminate as used herein may include what is called an adhesive sheet with a substrate. Furthermore, the concept of a laminate as used herein may include what is called an adhesive sheet, adhesive tape, adhesive label, adhesive film, etc. The laminate disclosed herein is typically in the form of a sheet, but may also be in the form of a roll or a single sheet. Alternatively, it may be a laminate processed into various shapes.

[0022] Figure 1 shows an example of the configuration of a laminate when both the first adhesive sheet and the second adhesive sheet are double-sided adhesive type substrate-less adhesive sheets (substrate-less double-sided adhesive sheets). The laminate 1 shown in Figure 1 includes a core body 15, and the first adhesive sheet 11 and the second adhesive sheet 12 are provided on the first surface 15A and the second surface 15B (both non-peelable) of the core body 15, 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. Before use (before being attached to an object), the laminate 1 may be in a spiral shape, as shown in Figure 1, with the front surface 21A and the back surface 21B both being peelable surfaces of a release liner 21. In this 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. Alternatively, the adhesive surface 11A and the adhesive surface 12A may be protected by two separate release liners.

[0023] Figure 2 shows an example of the configuration of a laminate when the first adhesive sheet is a double-sided adhesive type substrate-less adhesive sheet (substrate-less double-sided adhesive sheet) and the second adhesive sheet is a double-sided adhesive type substrate-attached adhesive sheet (substrate-attached double-sided adhesive sheet). The laminate 1 shown in Figure 2 includes a core body 15, and the first adhesive sheet 11 and the second adhesive sheet 12 are provided on the first surface 15A and the second surface 15B (both non-peelable) of the core body 15, 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 non-peelable) of the substrate 35, respectively. Before use (before being attached to an object), the laminate 1 may be in a spiral shape, as shown in Figure 2, with the front surface 21A and the back surface 21B both being peelable surfaces, overlapped with a peelable liner 21. In this 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 adhesive surface 11A of the first adhesive sheet 11 is protected by the back surface 21B of the release liner 21. Alternatively, the adhesive surface 11A and the adhesive surface 34A may be protected by two independent release liners.

[0024] Figure 3 shows an example of the configuration of a laminate when both the first adhesive sheet and the second adhesive sheet are double-sided adhesive sheets with a substrate (double-sided adhesive sheet with a substrate). The laminate 1 shown in Figure 3 includes a core body 15, and the first adhesive sheet 11 and the second adhesive sheet 12 are provided on the first surface 15A and the second surface 15B (both non-peelable) of the core body 15, 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 non-peelable) of the substrate 25, respectively. The second adhesive sheet 12 also includes a substrate 35, and adhesive layers 32 and 34 are provided on the first surface and the second surface (both non-peelable) of the substrate 35, respectively. Before use (before being attached to an object), the laminate 1 may be in a spiral shape, as shown in Figure 3, with the front surface 21A and the back surface 21B both being peelable surfaces, overlapped with a peelable liner 21. In this 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. Alternatively, the adhesive surfaces 34A and 36A may be protected by two independent release liners.

[0025] <Core body> The core disclosed herein is a support member that supports a first adhesive sheet and a second adhesive sheet. In the technology disclosed herein, the core is characterized in that the product of Young's modulus and thickness is greater than or equal to a predetermined value. Specifically, the value of Young's modulus of the core when the unit is MPa E A And, the value T of the core thickness when the unit is μm. A The value E is calculated by multiplying by and A ×T A The value is 500,000 or more. Using such a core material tends to improve the deformation resistance of the laminate.

[0026] In some preferred embodiments, E A ×T A 70×10 4 That is all, more preferably 90 × 10 4 (Using 100 x 10)4 The above is 110 x 10 4 or more, or 120 x 10 4 (The above) and more preferably 130 × 10 4 That's all. A ×T A The upper limit is not particularly limited. From the viewpoint of thinning and lightening the laminate, 1500 × 10 4 Preferably, the following, and more preferably, 1000 × 10 4 Below (for example, 800 x 10 4 The above, 600 x 10 4 or more, or 500 x 10 4 The following are more preferably 400 × 10 4 The following applies:

[0027] Young's modulus E of the core A The thickness of the core is T A It is not particularly limited as long as the product of is greater than or equal to a predetermined value. From the viewpoint of improving the strain resistance of the laminate, the Young's modulus E of the core A The Young's modulus E of the core is preferably 3000 MPa or higher, more preferably 5000 MPa or higher (e.g., 7000 MPa or higher, 8000 MPa or higher, or 9000 MPa or higher), and even more preferably 10000 MPa or higher. From the viewpoint of achieving a higher level of strain resistance, the Young's modulus E of the core is A The Young's modulus E of the core is preferably 60,000 MPa or higher, more preferably 70,000 MPa or higher (for example, 90,000 MPa or higher, 100,000 MPa or higher, or 130,000 MPa or higher), and even more preferably 150,000 MPa or higher. A The upper limit is not particularly limited. From the viewpoint of processability and handling, the Young's modulus E of the core A It is preferably 650,000 MPa or less, more preferably 400,000 MPa or less (for example, it may be 300,000 MPa or less, 280,000 MPa or less, or 250,000 MPa or less).

[0028] Core thickness T A The Young's modulus of the core is E AIt is not particularly limited as long as the product of is greater than or equal to a predetermined value. From the viewpoint of strain resistance, the thickness T of the core body A The thickness of the core is preferably 10 μm or more, more preferably 12 μm or more (for example, 15 μm or more), and even more preferably 20 μm or more. A The upper limit is not particularly limited. From the viewpoint of thinning and lightening the laminate, the thickness T of the core body is considered. A The particle size is preferably 500 μm or less (for example, 300 μm or less), more preferably 270 μm or less, 250 μm or less, or 150 μm or less.

[0029] The core material included in the laminate disclosed herein is not particularly limited. For example, metal foil, resin film, foam film, paper, cloth, composites thereof, etc., can be used as the core.

[0030] From the viewpoint of improving the distortion resistance of the laminate, a metal foil can preferably be used as the core. As the metal foil, common metal foils such as stainless steel foil, aluminum foil, copper foil, titanium foil, and zinc foil can be used. Among these, stainless steel foil, aluminum foil, and copper foil can be preferably used from the viewpoint of cost and processability. The metal foil may have a single layer form, or it may have a multilayer structure of two, three or more layers. For example, it may be a plated foil in which different types of metals are plated on the surface of the metal foil. Alternatively, it may have a multilayer structure that includes a metal layer and a layer composed of other materials (e.g., paper).

[0031] Alternatively, a core body may preferably be made of a resin film as the base film. The base film is typically an independently shape-retaining (independent) component. The core body in the art disclosed herein may be substantially composed of such a base film. Alternatively, the core body may include auxiliary layers in addition to the base film. Examples of such auxiliary layers include an undercoat layer, an antistatic layer, a coloring layer, etc., provided on the surface of the base film. From the viewpoint of reducing the light transmittance of the laminate, a core body in which a coloring layer is disposed on the surface of the base polymer can preferably be used. The coloring agent included in the coloring layer may preferably be the same as the coloring agent used in the adhesive sheet described later.

[0032] The above-mentioned resin film is a film whose main component is a resin material (a component that makes up more than 50% by weight in the resin film). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; and the like. The resin film may also be a rubber film such as natural rubber film or butyl rubber film. Among these, polyester films are preferred from the viewpoint of handling and processability, and PET films are particularly preferred.

[0033] The above-mentioned resin film may have a single-layer structure, or it may have a multilayer structure of two, three, or more layers. From the viewpoint of shape stability, a single-layer structure is preferred for the resin film. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the above-mentioned resin (e.g., polyester resin). The method for manufacturing the resin film is not particularly limited and may be any conventionally known method as appropriate. For example, conventionally known general film molding methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be used as appropriate.

[0034] The core, which includes a resin film (such as PET film), may contain various additives as needed, such as fillers (inorganic fillers, organic fillers, etc.), colorants, dispersants (surfactants, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, and plasticizers. The proportion of each additive is usually less than approximately 30% by weight (for example, less than approximately 20% by weight, preferably less than approximately 10% by weight).

[0035] In some embodiments, a foamed film may be used as the core material. The foamed film used as the core is a film having portions with bubbles (bubble structure), and is typically a film containing at least one layer of layered foam (foam layer). Although not particularly limited, one preferred example of a foamed film in the technology disclosed herein is a foamed film consisting of a single layer of foam.

[0036] In some other embodiments, paper or cloth is used as the core material. Examples of paper that can be used as the core include Japanese paper, kraft paper, glassine paper, fine paper, synthetic paper, and topcoat paper. Examples of cloth include woven or nonwoven fabrics made from various fibrous materials individually or in blends. Examples of the above-mentioned fibrous materials include cotton, rayon, Manila hemp, pulp, rayon, acetate fibers, polyester fibers, polyvinyl alcohol fibers, polyamide fibers, and polyolefin fibers.

[0037] The term "nonwoven fabric" as used herein primarily refers to nonwoven fabrics for adhesive sheets used in the field of adhesive tapes and other adhesive sheets, and typically refers to nonwoven fabrics (sometimes called "paper") produced using a general-purpose paper machine. The term "resin film" as used herein typically refers to a non-porous resin sheet and is a concept distinct from, for example, nonwoven fabric (i.e., does not include nonwoven fabric). The resin film may be an unoriented film, a uniaxially oriented film, or a biaxially oriented film. Furthermore, the surface of the substrate to which the adhesive layer is provided may be subjected to surface treatments such as the application of a primer, corona discharge treatment, or plasma treatment.

[0038] 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, or application of a primer. Such surface treatments may be intended to improve the adhesion between the core and the adhesive sheet (adhesive layer), in other words, the anchoring ability of the adhesive sheet (adhesive layer) to the core.

[0039] <Adhesive sheet> (Storage modulus at 25°C) The adhesive sheets included in the laminate disclosed herein (one or both of the first and second adhesive sheets; the same applies hereinafter) are characterized by having a storage modulus G'(25°C) of less than 0.20 MPa. Using an adhesive sheet with a G'(25°C) below a predetermined value tends to improve the step-following ability of the laminate. The G'(25°C) is preferably less than 0.19 MPa, more preferably less than 0.18 MPa, even more preferably less than approximately 0.17 MPa (e.g. less than 0.15 MPa), particularly preferably less than 0.14 MPa, and may also 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 higher, more preferably 0.035 MPa or higher, may also be 0.05 MPa or higher, may also be 0.1 MPa or higher, and may also be 0.12 MPa or higher.

[0040] (Storage modulus at 85°C) In some embodiments, the storage modulus G'(85°C) of the adhesive sheet at 85°C may be less than 0.08 MPa. Using an adhesive sheet with a G'(85°C) below a predetermined value tends to improve the step-following ability of the laminate. The G'(85°C) is preferably less than 0.07 MPa, more preferably less than 0.06 MPa, and even more preferably less than approximately 0.05 MPa (e.g., less than 0.045 MPa). The lower limit of the G'(85°C) is not particularly limited, but from the viewpoint of adhesion, it is usually appropriate for the G'(85°C) to be 0.01 MPa or higher, preferably 0.02 MPa or higher, and may also be 0.03 MPa or higher, or 0.04 MPa or higher.

[0041] (Storage modulus at 120°C) In some embodiments, the storage modulus G'(120°C) of the adhesive sheet at 120°C may be less than 0.04 MPa. When an adhesive sheet with G'(120°C) below a predetermined value is used, the step-following ability of the laminate tends to improve. G'(120°C) is preferably less than 0.035 MPa, more preferably less than 0.033 MPa, and even more preferably less than 0.03 MPa (e.g., less than 0.028 MPa). The lower limit of G'(120°C) is not particularly limited, but from the viewpoint of adhesion, it is usually appropriate for G'(120°C) to be 0.01 MPa or higher, preferably 0.015 MPa or higher, more preferably 0.02 MPa or higher, and even more preferably 0.023 MPa or higher.

[0042] The viscoelastic properties of the adhesive sheet described above can be adjusted based on the information provided herein by adjusting the monomer composition of the base polymer contained in the adhesive layer, appropriately selecting the type and amount of tackifying resin as needed, appropriately setting the adhesive composition including other components (such as crosslinking agents) as needed, and by adjusting the polymerization conditions of the polymer and the manufacturing conditions of the adhesive layer.

[0043] In the technology disclosed herein, the 25°C, 85°C, and 120°C storage moduli of an adhesive sheet can be determined by dynamic viscoelasticity measurement. Specifically, a test specimen with a thickness of approximately 2 mm is prepared by stacking multiple adhesive sheets to be measured. A sample punched out of this test specimen into a disc shape with a diameter of 7.9 mm is sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement is performed using a viscoelasticity tester (e.g., ARES or equivalent manufactured by T.A. Instruments Inc.) under the following conditions to determine the 25°C, 85°C, and 120°C storage moduli. • Measurement mode: Shear mode Temperature range: -70℃ to 150℃ • Heating rate: 5°C / min ·Measurement frequency: 1Hz The measurement will also be performed using the method described above in the examples described later.

[0044] The thickness T of the adhesive sheet (excluding the release liner) disclosed herein. B The thickness of the adhesive sheet is preferably 3 μm or more, more preferably 5 μm or more, more preferably more than 10 μm, and even more preferably 15 μm or more. B By increasing the thickness of the adhesive sheet, it becomes easier to improve both the ability to follow uneven surfaces and the adhesive properties. B From the viewpoint of thinning, the thickness can be, for example, 500 μm or less, and is usually suitable at 350 μm or less, with 270 μm or less (for example, 250 μm or less) being preferable.

[0045] If the above adhesive sheet is a substrate-free adhesive sheet with a base material organic, then the thickness T of the substrate-free adhesive sheet is... B1 The thickness is usually 3 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 15 μm or more. B1 By increasing the thickness T of the substrate-less adhesive sheet, it becomes easier to achieve both step-following ability and adhesive properties simultaneously. B1The thickness is usually suitable to be 200 μm or less, and from the viewpoint of thin film formation, it is preferably 100 μm or less, more preferably 70 μm or less (for example, 60 μm or less), and even more preferably 50 μm or less.

[0046] If the above adhesive sheet is an adhesive sheet with a base material, the thickness T of the adhesive sheet with the base material B2 The thickness of the adhesive sheet with the substrate is preferably greater than 10 μm, more preferably 20 μm or more, even more preferably 25 μm or more, and particularly preferably 30 μm or more. B2 By increasing the thickness T of the adhesive sheet with base material, it is easier to improve both the ability to follow uneven surfaces and the adhesive properties. B2 The thickness is usually suitable to be 500 μm or less, preferably 300 μm or less, more preferably 270 μm or less (for example, 260 μm or less), and may also be 150 μm or less.

[0047] Light transmittance C of adhesive sheet B This is not particularly limited. In the technologies disclosed herein, from the viewpoint of providing aesthetic appeal or improving the light-shielding properties of the laminate, the light transmittance C B An adhesive sheet with a light transmittance of 20% or less (preferably 10% or less, more preferably 5% or less, and especially preferably 1.5% or less) may be used. B The lower limit is not particularly limited and may be substantially 0%, i.e., below the detection limit, or it may be 1% or more, 5% or more, or 15% or more. In some other embodiments, the light transmittance C of the adhesive sheet B It may be more than 30%, more than 50%, or 70% or more (for example, 75% or more).

[0048] In the technology disclosed herein, the light transmittance C of the adhesive sheet B It can be measured by the following method. In the examples described later, it will also be measured by the following method.

[0049] [Light transmittance C B ] Light transmittance C of adhesive sheet B[%] represents the light transmittance in the thickness direction of the adhesive sheet peeled from the release liner (light transmittance at a wavelength of 550 nm), and is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a spectrophotometer manufactured by Hitachi, Ltd. (device name "U4150 type spectrophotometer") or an equivalent product is used.

[0050] (Adhesive) In the technology disclosed herein, the type of adhesive constituting the adhesive layer contained in the adhesive sheet is not particularly limited. The adhesive may contain one or more types of rubber-like polymers that can be used in the field of adhesives, such as acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers, as the adhesive polymer (meaning the structural polymer that forms the adhesive, hereinafter also referred to as the "base polymer"). From the viewpoint of adhesive performance and cost, an adhesive containing an acrylic polymer or a rubber polymer as the base polymer can be preferably used. Among these, an adhesive using an acrylic polymer as the base polymer (acrylic adhesive) is preferred. The technology disclosed herein is preferably implemented in a manner that uses an acrylic adhesive.

[0051] The following description will primarily focus on adhesive sheets having an acrylic adhesive layer, i.e., an adhesive sheet having an acrylic adhesive layer. However, the intention is not to limit the adhesive layer of the adhesive sheet disclosed herein to those composed of an acrylic adhesive.

[0052] Here, the "base polymer" of the adhesive refers to the main component of the rubbery polymer contained in the adhesive, and is not to be interpreted in any other way. The rubbery polymer refers to a polymer that exhibits rubber elasticity in the temperature range around room temperature. Furthermore, in this specification, unless otherwise specified, the "main component" refers to a component contained in more than 50% by weight.

[0053] Furthermore, "acrylic polymer" refers to a polymer that contains monomer units derived from monomers having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, monomers having at least one (meth)acryloyl group in one molecule will also be referred to as "acrylic monomers." Therefore, in this specification, acrylic polymers are defined as polymers that contain monomer units derived from acrylic monomers. A typical example of an acrylic polymer is an acrylic polymer in which the proportion of acrylic monomers among all monomer components used in the synthesis of the acrylic polymer is greater than 50% by weight. Furthermore, "(meth)acryloyl" comprehensively refers to both acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to both acrylate and methacrylate, and "(meth)acrylic" comprehensively refers to both acrylic and methacrylic.

[0054] (Acrylic polymer) In the technologies disclosed herein, the acrylic polymer used as the polymer is preferably a polymer of a monomer raw material that contains, for example, an alkyl (meth)acrylate as the main monomer and may further contain a secondary monomer copolymerizable with the main monomer. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the above monomer raw material.

[0055] As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used. CH2=C(R 1 )COOR 2 (1) Here, in equation (1) above, R 1 R is a hydrogen atom or a methyl group. 2 C is a chain-like alkyl group having 1 to 20 carbon atoms. Hereafter, this range of carbon atoms will be referred to as "C 1-20 It is sometimes expressed as ". From the viewpoint of the storage modulus of the adhesive, R 2 C 1-14 (For example C 1-10 Typically C4-8 It is appropriate to use alkyl (meth)acrylate, which is a chain-like alkyl group, as the main monomer. 2 Alkyl (meth)acrylates in which the group is a butyl group or a 2-ethylhexyl group are preferred. Also, from the viewpoint of adhesive properties, R 1 is a hydrogen atom and R 2 C 4-8 Alkyl acrylates (hereinafter simply referred to as C) are chain-like alkyl groups. 4-8 It is preferable to use alkyl acrylate (also known as alkyl acrylate) as the main monomer.

[0056] R 2 C 1-20Specific examples of alkyl(meth)acrylates, which are chain-like alkyl groups, are not particularly limited, but include, for example, 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( Examples include meth)acrylate, isooctyl(meth)acrylate, nonyl(meth)acrylate, isononyl(meth)acrylate, decyl(meth)acrylate, isodecyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl(meth)acrylate, heptadecyl(meth)acrylate, octadecyl(meth)acrylate, nonadecyl(meth)acrylate, eicosyl(meth)acrylate, etc. These alkyl(meth)acrylates can be used individually or in combination of two or more. Preferred 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).

[0057] The proportion of alkyl (meth)acrylate in the monomer components constituting the acrylic polymer is typically more than 50% by weight, and can be, for example, 70% by weight or more, 85% by weight or more, or 90% by weight or more. There is no particular upper limit to the proportion of alkyl (meth)acrylate, but it is preferably 99.5% by weight or less (for example, 99% by weight or less), or from the viewpoint of favorably exhibiting properties (for example, cohesive force) based on sub-monomers such as carboxyl group-containing monomers, it may be 98% by weight or less (for example, less than 97% by weight). Alternatively, the acrylic polymer may be substantially polymerized from alkyl (meth)acrylate alone.

[0058] In addition, C is used as a monomer component. 4-8 When using alkyl acrylates, of the alkyl (meth)acrylates contained in the monomer component, C 4-8 The proportion of alkyl acrylate is preferably 70% by weight or more, and more preferably 90% by weight or more.

[0059] The technology disclosed herein can preferably be implemented in a manner in which the monomer component constituting the acrylic polymer includes 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% by weight or more (usually 85% by weight or more, for example 90% by weight or more, and even more than 95% by weight or more). The technology disclosed herein can be implemented, for example, in a manner in which the alkyl (meth)acrylate contained in the monomer component is BA alone, 2EHA alone, or a combination of BA and 2EHA.

[0060] In some preferred embodiments, the monomer component constituting the acrylic polymer is C 1-6 Contains 50% by weight or more of alkyl (meth)acrylate. In other words, C in the above acrylic polymer. 1-6 The polymerization ratio of alkyl (meth)acrylate is preferably 50% by weight or more. 1-6By using alkyl (meth)acrylate as the main monomer, the storage elastic modulus can be appropriately improved. In this embodiment, the C content in the monomer component 1-6 The proportion (in other words, the polymerization proportion) of alkyl (meth)acrylate is preferably 80% by weight or more, more preferably 90% by weight or more, still more preferably 92% by weight or more (for example, more than 95% by weight). The C content in the monomer component 1-6 The upper limit of the proportion of alkyl (meth)acrylate is not particularly limited, it is usually 99% by weight or less, and from the relationship with the usage amount of other copolymerizable monomers, it is suitably 98% by weight or less, preferably 97% by weight or less, and may be less than 95% by weight. C 1-6 One kind of alkyl (meth)acrylate may be used alone, or two or more kinds may be used in combination. C 1-6 As the alkyl (meth)acrylate, C 1-6 alkyl acrylates are preferred, C 2-6 alkyl acrylates are more preferred, C 4-6 alkyl acrylates are even more preferred. In some other embodiments, C 1-6 alkyl (meth)acrylate is preferably C 1-4 alkyl acrylate, more preferably C 2-4 alkyl acrylate. C 1-6 A preferred example of alkyl (meth)acrylate is BA.

[0061] In some other preferred embodiments, the monomer component constituting the acrylic polymer comprises C 7-10 containing 50% by weight or more of alkyl (meth)acrylate. In other words, in the acrylic polymer, the C 7-10 The copolymerization proportion of alkyl (meth)acrylate is preferably 50% by weight or more. By using C 7-10 alkyl (meth)acrylate as the main monomer, the storage elastic modulus at 25°C can be favorably reduced, thereby improving flexibility and enhancing conformability to an adherend. The C content in the monomer component 7-10The proportion of alkyl (meth)acrylate (in other words, the copolymerization ratio) may be greater than 60% by weight, greater than 70% by weight, more preferably greater than 80% by weight, even more preferably 90% by weight or more, and particularly preferably 92% by weight or more (for example, 95% by weight or more). 7-10 The upper limit of the alkyl (meth)acrylate percentage is not particularly limited, but is usually 99% by weight or less, and in relation to the percentage of other copolymerizable monomers (e.g., acid group-containing monomers) used, it is appropriate to be 97% by weight or less, and preferably 96% by weight or less. 7-10 Alkyl (meth)acrylates can be used individually or in combination of two or more types. 7-10 Preferred examples of alkyl (meth)acrylates include C2EHA, isooctyl acrylate, isononyl acrylate, etc. 7-10 Alkyl acrylates are examples, with 2EHA being particularly preferred.

[0062] The acrylic polymers in the technologies disclosed herein may be copolymerized with sub-monomers. Examples of sub-monomers that can introduce functional groups that can act as crosslinking sites into acrylic polymers or that can contribute to improved adhesion include carboxyl group-containing monomers, hydroxyl group (OH group)-containing monomers (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 nitrogen atom-containing rings (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, imide group-containing monomers, and the like. The above sub-monomers can be used individually or in combination of two or more.

[0063] 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 effects 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, is appropriate to be 0.5% by weight or more, and may be 1% by weight or more. Furthermore, from the viewpoint of easily balancing the adhesive performance in relation to the main monomer, the content of the functional group-containing monomer in the monomer component is appropriate to be 40% by weight or less, is preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less).

[0064] In some preferred embodiments, an acidic group-containing monomer is used as a monomer copolymerizable with the alkyl (meth)acrylate, which is the main monomer. The acidic group-containing monomer can exhibit improved cohesiveness due to its polarity and good bonding strength to polar adherends. Furthermore, when a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent is used, the acidic group (typically a carboxyl group) becomes the crosslinking site of the acrylic polymer.

[0065] As the acidic group-containing monomer, carboxyl group-containing monomers are preferably used. Examples of carboxyl group-containing monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, crotonic acid, and isocrotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (maleic anhydride, itaconic anhydride, etc.). In addition, the acidic group-containing monomer may be a monomer having a metal salt (e.g., an alkali metal salt) of the carboxyl group. Among these, AA and MAA are preferred, and AA is more preferred.

[0066] In the technologies disclosed herein, the content of acidic group-containing monomers (typically carboxyl group-containing monomers) in the monomer component (in other words, the copolymerization ratio of acidic group-containing monomers in acrylic polymers) is appropriately set to 1.0% by weight or more. By using an amount or more of acidic group-containing monomers, the cohesive strength of the adhesive layer can be improved. The copolymerization ratio of acidic group-containing monomers in acrylic polymers is preferably 1.5% by weight or more, more preferably 2.0% by weight or more, even 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 acidic group-containing monomers in acrylic polymers is 4.0% by weight or more, may be greater than 5.0% by weight, may be 6.0% by weight or more, and may be 6.5% by weight or more. The copolymerization ratio of acidic group-containing monomers in acrylic polymers is usually appropriate to be 20% by weight or less. From the viewpoint of improving adhesion to the substrate and, consequently, conformability, it is preferably less than 10% by weight, more preferably less than 8.0% by weight, even more preferably less than 7.0% by weight, and particularly preferably less than 6.0% by weight, and may even be less than 5.0% by weight (for example less than 4.0% by weight).

[0067] The acrylic polymers preferably used in the technologies disclosed herein may be copolymers obtained by copolymerizing an alkyl (meth)acrylate as a main monomer and an acidic group-containing monomer as a secondary monomer. In such acrylic polymers, 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, less than 1% by weight, less than 0.1% by weight, or less than 0.03% by weight (for example, less than 0.01% by weight). The monomer components constituting the acrylic polymer may substantially not contain functional group-containing monomers other than the acidic group-containing monomer. An acrylic polymer substantially composed of alkyl (meth)acrylate and an acidic group-containing monomer can maximize the effects of the alkyl (meth)acrylate and the acidic group-containing monomer.

[0068] Alternatively, in some embodiments, the monomer component forming the acrylic polymer may include, for example, a hydroxyl group-containing monomer as a functional group-containing monomer other than the acidic group-containing monomer. The proportion of the hydroxyl group-containing monomer in the monomer component can be, for example, 0.01% by weight or more and less than 1% by weight, and may be less than 0.5% by weight or less than 0.1% by weight.

[0069] The monomer components constituting the acrylic polymer may include other copolymer components other than the aforementioned sub-monomers for purposes such as improving cohesiveness. Examples of other copolymer components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as aryl (meth)acrylate (e.g., phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (e.g., phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylate (e.g., benzyl (meth)acrylate); olefin monomers; chlorine-containing monomers; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; and the like. The other copolymerization components mentioned above can be used individually or in combination of two or more.

[0070] The amount of such other copolymer components is not particularly limited and can be appropriately selected according to the purpose and application, but from the viewpoint of properly exhibiting the effects of use, it is appropriate to set it to 0.05% by weight or more, and may be set to 0.5% by weight or more. Furthermore, from the viewpoint of easily balancing the adhesive performance, it is appropriate to set the content of other copolymer components in the monomer component to 20% by weight or less, and may be set to 10% by weight or less (for example, 5% by weight or less). The technology disclosed herein can also be preferably implemented in a form in which the monomer component substantially does not contain other copolymer components. Here, "substantially free of other copolymer components" means that other copolymer components are not used at least intentionally, and it is permissible for other copolymer components to be unintentionally included in amounts of, for example, 0.01% by weight or less.

[0071] Acrylic polymers may also contain polyfunctional monomers as other monomer components, having at least two polymerizable functional groups (typically radical polymerizable functional groups) that have unsaturated double bonds, such as (meth)acryloyl groups or vinyl groups. By using polyfunctional monomers as monomer components, the cohesive force of the adhesive layer can be increased. Polyfunctional monomers can be used as crosslinking agents. Polyfunctional monomers are not particularly limited and include, for example, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, etc. Polyfunctional monomers can be used individually or in combination of two or more.

[0072] The amount of polyfunctional monomer used is not particularly limited and can be appropriately set so as to achieve the purpose of using the polyfunctional monomer. The amount of polyfunctional monomer used can be approximately 3% by weight or less of the monomer component, 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). The lower limit of the amount used when using polyfunctional monomer is not particularly limited as long as it is greater than 0% by weight. Usually, by using an amount of polyfunctional monomer of approximately 0.001% by weight or more of the monomer component (for example, approximately 0.01% by weight or more), the effect of using the polyfunctional monomer can be appropriately achieved.

[0073] The composition of the monomer components constituting the acrylic polymer is appropriately designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately -15°C or lower (for example, approximately -70°C to -15°C). Here, the Tg of the acrylic polymer refers to the Tg determined by Fox's formula based on the above-mentioned monomer component composition. Fox's formula is a relationship 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 Fox's equation above, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (weight-based copolymerization ratio), and Tgi represents the glass transition temperature of the monomer i homopolymer (unit: K).

[0074] The glass transition temperature of the homopolymer used in calculating Tg shall be the value specified in publicly available documents. For example, for the monomers listed below, the following values ​​shall be used as the glass transition temperature of the homopolymer of the monomer. 2-Ethylhexyl acrylate -70℃ n-butyl acrylate -55℃ 2-Hydroxyethyl acrylate -15℃ 4-Hydroxybutyl acrylate -40℃ Vinyl acetate 32℃ Acrylic acid 106℃ Methacrylic acid 228℃

[0075] For the glass transition temperatures of monomer homopolymers other than those exemplified above, the values ​​listed in the "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 shall be adopted. If the value is not listed in the Polymer Handbook, the value obtained by the measurement method described in Japanese Patent Publication No. 2007-51271 shall be used.

[0076] While not particularly limited, from the viewpoint of adhesion and flexibility, the Tg of the acrylic polymer is advantageous to be approximately -25°C or lower, preferably approximately -35°C or lower, more preferably approximately -40°C or lower, and even more preferably -45°C or lower. For example, it may be -50°C or lower, or -55°C or lower. Also, from the viewpoint of the cohesive force of the adhesive layer, the Tg of the acrylic polymer is usually approximately -75°C or higher, preferably approximately -70°C or higher. In some embodiments, the Tg of the acrylic polymer may be -60°C or lower, or -62°C or lower (for example, -64°C or lower). Also, from the viewpoint of the cohesive force of the adhesive layer, the Tg of the acrylic polymer may be approximately -65°C or higher, or approximately -60°C or higher (for example, approximately -55°C or higher). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the type and ratio of monomers used in the synthesis of the polymer).

[0077] The weight-average molecular weight Mw of the base polymer disclosed herein is preferably approximately 30 × 10 from the viewpoint of improving adhesion. 4 More preferably 40 × 10 4 (For example, 45 x 10) 4 (The above), more preferably about 50 × 10 4 In particular, approximately 55 × 10 4 (For example, approximately 58 x 10) 4(The above) Also, the above Mw is usually approximately 300 x 10 4 The following is approximately 200 × 10 4 The following is appropriate. From the viewpoint of improving flexibility, the above Mw is preferably approximately 100 × 10 4 The following is approximately 70 x 10 4 The following (for example, approximately 65 x 10 4 The following may also be used. As the base polymer, one or more of the various polymers exemplified above as rubbery polymers can be used. For example, in the case of acrylic polymers obtained by solution polymerization, it is preferable to have Mw within the above range.

[0078] The degree of dispersion (Mw / Mn) of the base polymer (preferably an acrylic polymer) disclosed herein is not particularly limited. Here, degree of dispersion (Mw / Mn) refers to the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn). In some preferred embodiments, the degree of dispersion (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 limiting the molecular weight distribution to an appropriate range, stable properties are more likely to be 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. Having a certain degree of molecular weight distribution tends to allow for a balanced expression of the effects of low-molecular-weight and high-molecular-weight components. Such polymers also tend to have excellent productivity.

[0079] Furthermore, Mw, Mn, and Mw / Mn can be adjusted by polymerization conditions (time, temperature, etc.), the concentration of non-volatile components (monomer components) during polymerization, the amount of polymerization initiator used, the use of chain transfer agents, and the selection of polymerization solvents based on the chain transfer constant. In addition, Mw and Mn can be determined from values ​​obtained by GPC (gel permeation chromatography) on a standard polystyrene basis. For example, the GPC instrument "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used.

[0080] The method for obtaining the base polymer (e.g., acrylic polymer) is not particularly limited, and various polymerization methods known as polymer synthesis techniques, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, solution polymerization can be preferably employed. The polymerization temperature when performing solution polymerization can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, around 20°C to 170°C (typically around 40°C to 140°C).

[0081] The solvent used for solution polymerization (polymerization solvent) can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators (e.g., azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN), peroxide-based initiators, etc.) depending on the type of polymerization method. The amount of polymerization initiator used can be the usual amount, for example, it can be selected from a range of approximately 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of monomer component.

[0082] (Adhesive-forming resin) The adhesive layer in the technology disclosed herein may contain a tackifying resin. This can increase the peel strength of the adhesive sheet. As the tackifying resin, one or more can be selected from phenolic tackifying resins, terpene tackifying resins, modified terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, ketone tackifying resins, etc. Among these, phenolic tackifying resins, terpene tackifying resins, and modified terpene tackifying resins are preferred, and phenolic tackifying resins (preferably terpene phenolic resins) are more preferred.

[0083] Examples of phenolic tackifying resins include terpene phenol resins, hydrogenated terpene phenol resins, alkyl phenol resins, and rosin phenol resins. Terpene phenol resins refer to polymers containing terpene and phenol residues, and the concept encompasses both copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins) and homopolymers or copolymers of terpenes modified with phenol (phenol-modified terpene resins). Suitable examples of terpenes constituting such terpene phenol resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-isomers, l-isomers, and d / l-isomers (dipentene)). Hydrogenated terpene phenol resins refer to hydrogenated terpene phenol resins having a structure obtained by hydrogenating such terpene phenol resins. They are sometimes also called hydrogenated terpene phenol resins. Alkylphenol resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac and resol types. Rosinphenol resins are typically phenol-modified products of rosins or the various rosin derivatives mentioned above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosinphenol resins include those obtained by methods such as adding phenol to rosins or the various rosin derivatives mentioned above using an acid catalyst and then thermal polymerization.

[0084] Examples of terpene-based tackifying resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. These may be homopolymers of a single terpene or copolymers of two or more terpenes. Examples of homopolymers of a single terpene include α-pinene polymers, β-pinene polymers, and dipentene polymers. Examples of modified terpene resins include those obtained by modifying the above-mentioned terpene resins. Specifically, examples include styrene-modified terpene resins and hydrogenated terpene resins.

[0085] The concept of rosin-based tackifying resins as used here encompasses both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins (hydrogenated rosin, disproportionated rosin, polymerized rosin, and other chemically modified rosins) obtained by hydrogenation, disproportionation, polymerization, etc.

[0086] Rosin derivative resins are typically derivatives of the rosins described above. The concept of rosin-based resins as used here includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). Examples include rosin esters such as unmodified rosin esters, which are esters of unmodified rosin with alcohols, and modified rosin esters, which are esters of modified rosin with alcohols; unsaturated fatty acid modified rosins, which are rosins modified with unsaturated fatty acids; unsaturated fatty acid modified rosin esters, which are rosin esters modified with unsaturated fatty acids; rosin alcohols, which are rosins or the above-mentioned rosin derivatives (including rosin esters, unsaturated fatty acid modified rosins, and unsaturated fatty acid modified rosin esters) obtained by reducing their carboxyl groups; and metal salts of rosins or the above-mentioned rosin derivatives. Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerol esters, and pentaerythritol esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

[0087] Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic-aromatic petroleum resins (such as styrene-olefin copolymers), aliphatic-alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins, among other hydrocarbon resins.

[0088] The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesive force, a tackifying resin with a softening point (softening temperature) of approximately 80°C or higher (preferably approximately 100°C or higher) can be preferably used. For example, a phenolic tackifying resin (such as a terpene phenol resin) having such a softening point can be preferably used. In some embodiments, a terpene phenol resin with a softening point of approximately 135°C or higher (more preferably approximately 140°C or higher) can be used. There is no particular upper limit to the softening point of the tackifying resin. From the viewpoint of adhesion to the adherend or substrate, a tackifying resin with a softening point of approximately 200°C or lower (more preferably approximately 180°C or lower) can be preferably used. The softening point of the tackifying resin can be measured based on the softening point test method (ring-ball method) specified in JIS K2207.

[0089] Some preferred embodiments include the tackifying resin comprising one or more phenolic tackifying resins (typically terpene phenol resins). The techniques disclosed herein can preferably be implemented, for example, in an embodiment where the total amount of tackifying resin is 100% by weight, of which approximately 25% or more (more preferably approximately 30% or more by weight) is terpene phenol resin. Approximately 50% or more by weight of the total amount of tackifying resin may be terpene phenol resin, and approximately 70% or more by weight (for example, approximately 80% or more by weight) may be terpene phenol resin. Substantially all of the tackifying resin (for example, approximately 95-100% by weight, and even more precisely, approximately 99-100% by weight) may be terpene phenol resin.

[0090] While not particularly limited, in some embodiments, the tackifying resin may include a tackifying resin with a hydroxyl value higher than 20 mgKOH / g. Among these, a tackifying resin with a hydroxyl value of 30 mgKOH / g or higher is preferred. Hereinafter, a tackifying resin with a hydroxyl value of 30 mgKOH / g or higher may be referred to as a "high hydroxyl value resin." Using a tackifying resin containing such a high hydroxyl value resin (e.g., a phenolic tackifying resin, preferably a terpene phenolic resin), an adhesive layer with excellent adhesion to the adherend and high cohesive force can be realized. There is no particular upper limit to the hydroxyl value of the high hydroxyl value resin. From the viewpoint of compatibility with the base polymer, the hydroxyl value of the high hydroxyl value resin is appropriate to be approximately 200 mgKOH / g or less, preferably approximately 100 mgKOH / g or less, and may also be approximately 70 mgKOH / g or less, or approximately 65 mgKOH / g or less. The high hydroxyl value resin can be used alone or in combination of two or more types.

[0091] Here, the hydroxyl value can be the value measured by potentiometric titration as specified in JIS K0070:1992. The specific measurement method is as follows. [Method for measuring hydroxyl value] 1. Reagents (1) As the acetylation reagent, take approximately 12.5 g (approximately 11.8 mL) of acetic anhydride, add pyridine to make a total volume of 50 mL, and stir thoroughly before use. Alternatively, take approximately 25 g (approximately 23.5 mL) of acetic anhydride, add pyridine to make a total volume of 100 mL, and stir thoroughly before use. (2) A 0.5 mol / L potassium hydroxide ethanol solution is used as the measurement reagent. (3) Prepare toluene, pyridine, ethanol, and distilled water. 2.Operation (1) Accurately weigh out approximately 2 g of the sample into a flat-bottom flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air condenser. (2) After heating the flask in a 100°C bath for 70 minutes, allow it to cool, add 35 mL of toluene as a solvent from the top of the condenser and stir, then add 1 mL of distilled water and stir to decompose the acetic anhydride. To complete the decomposition, heat it again in the bath for 10 minutes and allow it to cool. (3) Wash the condenser with 5 mL of ethanol and remove it. Then add 50 mL of pyridine as a solvent and stir. (4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a volumetric pipette. (5) Perform potentiometric titration with a 0.5 mol / L potassium hydroxide ethanol solution. The inflection point of the resulting titration curve is taken as the endpoint. (6) For a blank test, perform steps (1) to (5) above without adding a sample. 3.Calculation The hydroxyl value is calculated using the following formula. Hydroxyl value (mgKOH / g) = [(BC) × f × 28.05] / S + D Here, B: Volume (mL) of 0.5 mol / L potassium hydroxide ethanol solution used for the blank test. C: Volume (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the sample. f: Factor of 0.5 mol / L potassium hydroxide ethanol solution, S: Weight of the sample (g), D: Acid value, 28.05: Half the molecular weight of potassium hydroxide, 56.11. That is the case.

[0092] When the adhesive layer contains a tackifying resin, the amount (total amount) of the tackifying resin used is not particularly limited and can be appropriately set in the range of 1 to 100 parts by weight per 100 parts by weight of the base polymer. From the viewpoint of suitably exhibiting the effect of improving peel strength, it is appropriate to use 5 parts by weight or more of the tackifying resin per 100 parts by weight of the base polymer (e.g., an acrylic polymer), preferably 10 parts by weight or more, and it may also be 15 parts by weight or more. Furthermore, from the viewpoint of impact resistance and cohesive force, it is appropriate to use 50 parts by weight or less of the tackifying resin per 100 parts by weight of the base polymer (e.g., an acrylic polymer), may also be 40 parts by weight or less, or 30 parts by weight or less.

[0093] (Crosslinking agent) In the technology disclosed herein, the adhesive composition used to form the adhesive layer may optionally contain a crosslinking agent. The type of crosslinking agent is not particularly limited and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, and silane coupling agents. Among these, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and melamine crosslinking agents are preferred, isocyanate crosslinking agents and epoxy crosslinking agents are more preferred, and isocyanate crosslinking agents are particularly preferred. By appropriately selecting and using a crosslinking agent, the cohesive force of the adhesive layer can be obtained, improving the conformability to the adherend and adhesive strength. The adhesive layer in the technology disclosed herein may contain the crosslinking agent in the form after the crosslinking reaction, in the form before the crosslinking reaction, in a partially crosslinked form, or in intermediate or combined forms therein. Typically, the crosslinking agent is contained in the adhesive layer exclusively in the form after the crosslinking reaction.

[0094] As isocyanate-based crosslinking agents, polyfunctional isocyanates (compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. Isocyanate-based crosslinking agents can be used individually or in combination of two or more.

[0095] 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 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; and 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0096] 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; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0097] Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, and 2,2'-diphenylpropane-4,4'-diisocyanate. Examples include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropanediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0098] Examples of preferred polyfunctional isocyanates include those having an average of three or more isocyanate groups per molecule. Such trifunctional or trifunctional isocyanates may be macromers (typically dimers or trimers) of bifunctional or trifunctional or trifunctional isocyanates, derivatives (e.g., addition reaction products of a polyhydric alcohol and two or more polyfunctional isocyanates), polymers, etc. Examples include dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, reaction products of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and other polyfunctional isocyanates. Examples of commercially available polyfunctional isocyanates include "Duranate TPA-100" from Asahi Kasei Chemicals, and "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096" from Tosoh Corporation.

[0099] The amount of isocyanate-based crosslinking agent used is not particularly limited. For example, it can be approximately 0.1 parts by weight or more per 100 parts by weight of the base polymer. From the viewpoint of achieving both cohesive force and adhesion, as well as impact resistance, the amount of isocyanate-based crosslinking agent used per 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 or more, more preferably 0.75 parts by weight or more, and even more preferably 1.0 part by weight or more (for example 1.2 parts by weight or more). On the other hand, from the viewpoint of improving adhesion to the adherend and conformability, it is appropriate to use 10 parts by weight or less per 100 parts by weight of the base polymer, preferably less than 7 parts by weight, more preferably less than 5 parts by weight, even more preferably less than 4.5 parts by weight, and particularly preferably less than 4 parts by weight.

[0100] In some preferred embodiments, an isocyanate-based crosslinking agent is used in combination with at least one crosslinking agent having a different type of crosslinkable functional group than the isocyanate-based crosslinking agent. In the techniques disclosed herein, a crosslinking agent other than an isocyanate-based crosslinking agent (i.e., a crosslinking agent having a different type of crosslinkable reactive group than the isocyanate-based crosslinking agent; hereinafter also referred to as a "non-isocyanate-based crosslinking agent") can be used in combination with an isocyanate-based crosslinking agent.

[0101] The types of non-isocyanate crosslinking agents that can be used in combination with isocyanate crosslinking agents are not particularly limited, and can be appropriately selected from the crosslinking agents described above. Non-isocyanate crosslinking agents can be used individually or in combination of two or more.

[0102] In some preferred embodiments, epoxy crosslinking agents can be used as non-isocyanate crosslinking agents. For example, combining an isocyanate crosslinking agent with an epoxy crosslinking agent makes it easier to achieve both cohesiveness and impact resistance. As the epoxy crosslinking agent, any compound having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. Epoxy crosslinking agents can be used individually or in combination of two or more.

[0103] While not particularly limited, specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, and polyglycerol polyglycidyl ether. Commercially available epoxy crosslinking agents include "TETRAD-C" and "TETRAD-X" from Mitsubishi Gas Chemical Co., Ltd., "Epiclon CR-5L" from DIC Corporation, "Denacol EX-512" from Nagase ChemteX Corporation, and "TEPIC-G" from Nissan Chemical Industries, Ltd.

[0104] The amount of epoxy crosslinking agent used is not particularly limited. For example, the amount of epoxy crosslinking agent used can be greater than 0 parts by weight and approximately 1 part by weight or less (typically about 0.001 to 0.5 parts by weight) per 100 parts by weight of the base polymer. From the viewpoint of suitably exhibiting the effect of improving cohesive force, it is preferable that the amount of epoxy crosslinking agent used is approximately 0.005 parts by weight or more per 100 parts by weight of the base polymer. Furthermore, from the viewpoint of improving adhesion to the adherend and conformability, it is appropriate to use approximately 0.2 parts by weight or less per 100 parts by weight of the base polymer, preferably approximately 0.1 parts by weight or less, and more preferably less than approximately 0.05 parts by weight.

[0105] The total amount of crosslinking agent used is not particularly limited. For example, it can be approximately 10 parts by weight or less per 100 parts by weight of the base polymer (preferably an acrylic polymer), preferably in the range of approximately 0.005 to 10 parts by weight, and more preferably in the range of approximately 0.01 to 5 parts by weight.

[0106] (Coloring agent) The adhesive layer disclosed herein may contain a colorant that can help reduce light transmittance, or it may not contain such a colorant. Conventionally known pigments and dyes can be used as the colorant. The colorant is preferably colored. The color of the colorant may be, for example, black, gray, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl, etc. Colored colorants can impart light-shielding properties and design properties. The colorant may contain a colorless colorant in combination with the colored colorant, or it may not. An adhesive layer according to a typical embodiment disclosed herein may substantially not contain a colorless colorant. In this specification, "colored" includes black and metallic colors, and "colorless" includes white. The adhesive layer may have a multilayer structure including a colored layer containing a colorant. Alternatively, the adhesive layer may contain the colorant in a substantially dispersed state (which may be dissolved).

[0107] Various pigments and dyes can be used as colorants. Examples of pigments include inorganic pigments such as zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium dioxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide-based, iron hydroxide-based, chromium oxide-based, spinel-type calcined-based, chromic acid-based, chromium vermilion-based, Prussian blue-based, aluminum powder-based, bronze powder-based, silver powder-based, and calcium phosphate, as well as organic pigments such as phthalocyanine-based, azo-based, condensed azo-based, 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 pigments. Examples of dyes include azo dyes, anthraquinone, quinophthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine. The colorants can be used individually or in appropriate combinations of two or more.

[0108] Since light-shielding properties can be efficiently adjusted with a small amount of colorant, black colorants can be preferably used. In one preferred embodiment of the technology disclosed herein, the adhesive layer contains a black colorant. As the black colorant contained in the adhesive layer, organic or inorganic colorants (pigments, dyes, etc.) can be used. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone-based colorants, etc. Among these, carbon black is preferred. It is also possible to use surface-modified carbon black particles having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, and silicon-containing groups (e.g., alkoxysilyl groups, alkylsilyl groups) as carbon black particles. Such surface-modified carbon black particles are also called self-dispersing carbon black, and they eliminate the need for dispersants or reduce the amount of dispersant added. The above carbon black particles can be used individually or in combination of two or more types.

[0109] The black coloring agent is not particularly limited, and particulate coloring agents (pigments) can be preferably used. In a preferred embodiment, a black coloring agent (for example, a black pigment such as carbon black) with an average particle size of about 10 nm or more (for example, about 50 nm or more) can be used. The upper limit of the average particle size of the above black coloring agent 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 this specification, "average particle size" refers to the particle size at 50% of the cumulative value in the particle size distribution measured based on a particle size distribution analyzer based on the laser scattering-diffraction method (50% volume average particle diameter; hereafter, D 50 It is sometimes abbreviated as ).

[0110] The amount of colorant (solid content) used in the adhesive layer is not particularly limited and can be adjusted as appropriate to provide the desired light-shielding properties. The amount of black colorant used is usually appropriate to be 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 20% by weight).

[0111] (Rust inhibitor) The adhesive layer according to some embodiments may contain a rust inhibitor. The rust inhibitor is not particularly limited and includes azole rust inhibitors, amine compounds, nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropin, thiourea, phenyl carbamate, cyclohexylammonium-N-cyclohexylcarbamate (CHC), and the like. The rust inhibitor can be used alone or in combination of two or more.

[0112] As a rust inhibitor, azole-based rust inhibitors can be preferably used. Preferably, azole-based rust inhibitors contain a five-membered ring aromatic compound with two or more heteroatoms, where at least one of the heteroatoms is a nitrogen atom, as the active ingredient. A good example of a compound that can be used as an azole-based rust inhibitor is a benzotriazole-based rust inhibitor containing a benzotriazole compound as the active ingredient. Good examples of benzotriazole compounds include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, and carboxybenzotriazole.

[0113] The amount of 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) per 100 parts by weight of the base polymer. From the viewpoint of obtaining a better metal corrosion prevention effect, the above amount 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 force of the adhesive, it is appropriate to have an amount of rust inhibitor less than 8 parts by weight per 100 parts by weight of the base polymer, and may be 5 parts by weight or less, or 2 parts by weight or less.

[0114] (Other additives) The adhesive composition may optionally contain various additives common in the field of adhesives, such as leveling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, UV absorbers, antioxidants, and light stabilizers. These additives can be conventionally used by any known method and do not particularly characterize the present invention; therefore, a detailed explanation is omitted.

[0115] The adhesive layer (layer consisting of adhesive) disclosed herein may be formed from an aqueous adhesive composition, a solvent-type adhesive composition, a hot-melt adhesive composition, or an active energy ray-curable adhesive composition that hardens upon irradiation with active energy rays such as ultraviolet rays or electron beams. An aqueous adhesive composition refers to an adhesive composition in which an adhesive (adhesive layer-forming component) is contained in a solvent (aqueous solvent) mainly composed of water, and typically includes what is called a water-dispersible adhesive composition (a composition in which at least a part of the adhesive is dispersed in water). A solvent-type adhesive composition refers to an adhesive composition in which an adhesive is contained in an organic solvent. As the organic solvent contained in the solvent-type adhesive composition, one or more of the organic solvents exemplified above as organic solvents that can be used in solution polymerization (such as toluene and ethyl acetate) can be used without particular limitation. The technology disclosed herein can preferably be implemented in a form comprising an adhesive layer formed from a solvent-type adhesive composition, from the viewpoint of adhesive properties, etc. In embodiments comprising a solvent-type adhesive layer formed from a solvent-type adhesive composition, the effects of the techniques disclosed herein are preferably realized.

[0116] The adhesive layer disclosed herein can be formed by conventionally known methods. For example, a method can be employed in which an adhesive layer is formed by applying an adhesive composition to a release surface and drying it. In the case of an adhesive sheet having a substrate, for example, a method can be employed in which an adhesive layer is formed by directly applying (typically coating) the adhesive composition to the substrate and drying it (direct method). Alternatively, a method can be employed in which an adhesive layer is formed on a release surface by applying an adhesive composition to a release surface and drying it, and then the adhesive layer is transferred to the substrate (transfer method). As the release surface, for example, the surface of a release liner described later can be preferably used. Although the adhesive layer disclosed herein is typically formed continuously, it is not limited to this form, and may be formed in a regular or random pattern such as dots or stripes.

[0117] The adhesive composition can be applied using conventionally known coaters, such as gravure roll coaters, die coaters, or bar coaters. Alternatively, the adhesive composition may be applied by impregnation or curtain coating methods. From the viewpoint of promoting the crosslinking reaction and improving manufacturing efficiency, it is preferable to dry the adhesive composition under heating. The drying temperature can be, for example, around 40 to 150°C, and is preferably around 60 to 130°C. After drying the adhesive composition, aging may be performed for the purpose of adjusting the migration of components within the adhesive layer, promoting the crosslinking reaction, and alleviating any strain that may exist within the adhesive layer.

[0118] 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, etc., a single-layer structure of the adhesive layer is preferred.

[0119] The thickness of the adhesive layer is not particularly limited. The thickness of the adhesive layer is usually about 300 μm or less, about 150 μm or less is appropriate, preferably about 100 μm or less, more preferably about 70 μm or less, and may also be about 60 μm or less (for example, 55 μm or less). An adhesive layer with a limited thickness can well meet the demands for thinning and weight reduction. The lower limit of the thickness of the adhesive layer is not particularly limited, but from the viewpoint of adhesion and adherendability, for example, about 3 μm or more, and about 10 μm or more is appropriate. In some preferred embodiments, the thickness of the adhesive layer may be about 20 μm or more, more preferably about 30 μm or more, and about 40 μm or more. In an adhesive sheet having an adhesive layer on each side of the substrate (double-sided adhesive sheet with substrate), the thickness of each adhesive layer may be the same or different.

[0120] (Gel fraction) While not particularly limited, the gel fraction of the adhesive layer disclosed herein can be, for example, 20% or more by weight, and is usually appropriate to be 30% or more, and preferably greater than 35%. By increasing the gel fraction of the 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 more, even more preferably 50% or more, particularly preferably 55% or more, and may be 60% or more. On the other hand, from the viewpoint of conformability to the adherend, the gel fraction of the adhesive layer is appropriate to be 90% or less, preferably 70% or less (for example, 65% or less), and may be less than 60%.

[0121] Here, "gel fraction of the adhesive layer" refers to the value measured by the following method. This gel fraction can be determined as the weight percentage of ethyl acetate-insoluble material in the adhesive layer. [Method for measuring gel fraction] Approximately 0.1 g of adhesive sample (weight Wg1) is wrapped in a drawstring-like shape with a porous polytetrafluoroethylene membrane (weight Wg2) having an average pore size of 0.2 μm, and the opening is tied with string (weight Wg3). As the porous polytetrafluoroethylene (PTFE) membrane, the product name "Nitoflon (registered trademark) NTF1122" (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or an equivalent product available from Nitto Denko Corporation is used. The package is immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23°C) for 7 days to elute only the sol component from the adhesive layer. After that, the package is removed, the ethyl acetate adhering to the outer surface is wiped off, and the package is dried at 130°C for 2 hours. The weight of the package (Wg4) is then measured. Gel fraction F of the adhesive layer. G This can be obtained by substituting each value into the following formula. The same method is used in the examples described later. Gel fraction F G (%) = [(Wg4 - Wg2 - Wg3) / Wg1] × 100

[0122] <Base material> The adhesive sheet disclosed herein may include a substrate (support substrate). The structure and material of the substrate disclosed herein are not particularly limited. The substrate is typically a film-like substrate (also referred to as the "substrate film"). Preferably, the substrate film includes a resin film as the base film. The base film is typically an independently shape-retaining (independent) component. The substrate film in the disclosed technology may be substantially composed of such a base film. Alternatively, the substrate film may include auxiliary layers in addition to the base film. Examples of such auxiliary layers include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc., provided on the surface of the base film.

[0123] The above-mentioned resin film is a film whose main component is a resin material (for example, a component that is present in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyurethane resin films; vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; and the like. The resin film may also be a rubber film such as natural rubber film or butyl rubber film. Among these, polyester films are preferred from the viewpoint of handling and processability, and PET films are particularly preferred.

[0124] The base film may be colored by a colored layer disposed on the surface of the base film (preferably a resin film). A base film having a colored layer in this configuration can be given light-shielding properties and design appeal. In a base film having a base film and a colored layer, the base film may or may not contain a coloring agent. The colored layer may be disposed on either one surface of the base film, or on both surfaces. In a configuration where colored layers are disposed on both surfaces of the base film, the configurations of these colored layers may be the same or different.

[0125] Such a colored layer can typically be formed by applying a colored layer-forming composition containing a colorant and a binder to a base film. Conventionally known pigments and dyes can be used as the colorant. Colored colorants are preferred. The color of the colorant may be, for example, black, gray, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl, etc. Colored colorants can impart light-shielding properties and design properties. The colorant may or may not contain a colorless colorant in combination with the colored colorant. A base film according to a typical embodiment disclosed herein may substantially not contain a colorless colorant. In this specification, "colored" includes black and metallic colors, and "colorless" includes white.

[0126] As the binder, any material known in the field of paints or printing can be used without particular limitations. Examples include polyurethane, phenolic resin, epoxy resin, urea-melamine resin, and polymethyl methacrylate. The composition for forming the colored layer may be solvent-based, UV-curing, or thermosetting. The colored layer can be formed by employing any conventional method used for forming colored layers without particular limitations. For example, a method of forming the colored layer (printed layer) by printing such as gravure printing, flexographic printing, or offset printing can be preferably employed.

[0127] The colored layer may be a single-layer structure consisting of one layer, or it may be a multilayer structure including two, three or more sub-colored layers. A multilayer colored layer including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For colored layers intended to provide light-shielding properties, a multilayer structure is particularly beneficial from the viewpoint of preventing the occurrence of pinholes and improving light-shielding.

[0128] The overall thickness of the colored layer is usually appropriate to be 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 a colored layer that includes two or more sub-colored layers, the thickness of each sub-colored layer is usually preferably about 1 μm to 2 μm.

[0129] The base film (typically a resin film) may contain a colorant. A base film containing a colorant in this way can be given 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 one preferred embodiment of the technology disclosed herein, the base film is a base film containing a black colorant, and more specifically, a resin film into which a black colorant has been kneaded. Here, a base film into which a black colorant has been kneaded means a base film in which a black colorant has been mixed into the main constituent material of the base film (the material that is most abundant in the base film; typically a resin material). The black colorant is contained substantially in a dispersed state in the base film.

[0130] As the black coloring agent included in the base film, organic or inorganic coloring agents (pigments, dyes, etc.) can be used. Specific examples of black coloring agents include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone-based coloring agents, etc. Among these, carbon black is preferred.

[0131] The black coloring agent is not particularly limited, and particulate coloring agents (pigments) can be preferably used. In one preferred embodiment, a black coloring agent (for example, a black pigment such as carbon black) with an average particle size of about 10 nm or more (for example, about 50 nm or more) can be used. The upper limit of the average particle size of the above black coloring agent 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).

[0132] The amount of colorant used in the base film is not particularly limited and can be adjusted as appropriate to provide the desired light-shielding properties. The amount of black colorant used is usually appropriate to be 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 20% by weight).

[0133] The substrate film disclosed herein may contain colorants other than black colorants (pigments and dyes). Examples of such non-black colorants include white colorants. Examples of white colorants include titanium dioxide (such as rutile titanium dioxide and anatase 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 (such as light calcium carbonate and heavy calcium carbonate), barium carbonate, zinc carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, aluminum silicate, magnesium silicate, and calcium silicate. Examples include inorganic white colorants such as um, 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, and hydrated halloysite, as well as organic white colorants such as acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, silicone resin particles, urea-formaldehyde resin particles, and melamine resin particles.

[0134] The amount of non-black colorant used in the base film is not particularly limited and can be adjusted as appropriate to provide the desired light-shielding properties. The amount of non-black colorant used is usually appropriate to be 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).

[0135] The above-mentioned base film may contain various additives as needed, such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, UV absorbers, antistatic agents, lubricants, and plasticizers. The proportion of each additive is usually less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

[0136] The above-mentioned base film may have a single-layer structure, or it may have a multilayer structure of two, three, or more layers. From the viewpoint of shape stability, a single-layer structure of the base film is preferable. In the case of a multilayer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the above-mentioned resin (e.g., polyester resin). The method for manufacturing the base film (typically a resin film) is not particularly limited and may be any conventionally known method as appropriate. For example, conventionally known general film molding methods such as extrusion molding, inflation molding, T-die casting, and calender roll molding can be appropriately employed.

[0137] The thickness of the substrate disclosed herein is not particularly limited. The thickness of the substrate is usually 3 μm or more, preferably 5 μm or more (e.g., 10 μm or more). In some embodiments, the thickness of the substrate may be 20 μm or more, 30 μm or more, 40 μm or more, 100 μm or more, or 200 μm or more. The thickness of the substrate is usually 500 μm or less, preferably 400 μm or less from the viewpoint of weight reduction, and more preferably 300 μm or less. In some embodiments, 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 is composed of 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.

[0138] 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, or application of a primer. Such surface treatments may be treatments to improve the adhesion between the base film and the adhesive layer, in other words, the anchoring ability of the adhesive layer to the base film. When the technology disclosed herein is implemented in the form of a single-sided adhesive sheet with a base, the back surface of the base film may be subjected to a release treatment as needed. The release treatment may be a treatment in which a release agent such as a general silicone-based, long-chain alkyl-based, or fluorine-based agent is applied in a thin film typically of about 0.01 μm to 1 μm (e.g., 0.01 μm to 0.1 μm). By applying such a release treatment, effects such as facilitating the unwinding of a roll of adhesive sheets can be obtained.

[0139] <Removable Liner> In the technologies disclosed herein, release liners can be used in the formation of adhesive layers, the production of adhesive sheets, the production of laminates, the storage of laminates before use, distribution, and shaping. The release liners are not particularly limited, and for example, release liners having a release treatment layer on the surface of a liner substrate such as a resin film or paper, or release liners made of low-adhesion materials such as fluoropolymers (polytetrafluoroethylene, etc.) or polyolefin resins (PE, PP, etc.) can be used. The release treatment layer may be formed by surface treating the liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

[0140] <Characteristics of laminated materials> The laminates disclosed herein preferably have a level of step-following ability that passes the step-proofing test measured by the method described in the embodiments below. Laminates that satisfy the above characteristics are more likely to maintain a state in which they follow complex shapes without gaps.

[0141] The laminates disclosed herein preferably have a passing level of strain resistance (i.e., do not cause strain) in strain deformation tests measured by the methods described in the embodiments below. Laminates satisfying the above characteristics have excellent deformation resistance to loads applied substantially in the thickness direction (Z-axis direction) of the laminate, and easily suppress strain on the adherend.

[0142] The total thickness T of the laminate (excluding the release liner) disclosed herein total This is not particularly limited. Total thickness T of the laminate total For example, the thickness can be 1000 μm or less, and from the viewpoint of thin film formation, the total thickness T of the laminate. total The thickness is preferably 500 μm or less (for example, 400 μm or less), more preferably 350 μm or less, and even more preferably 300 μm or less. According to the technology disclosed herein, even if the total thickness T of the laminate is small, total Even if it is sufficiently small, it tends to exhibit good strain resistance. Total thickness T of the laminate totalThe lower limit is not particularly limited, but is usually suitable at 20 μm or more, preferably 30 μm or more, more preferably 40 μm or more, even more preferably 50 μm or more, and may also be 60 μm or more, 70 μm or more, or 80 μm or more.

[0143] Light transmittance C of the laminate total This is not particularly limited. In the technologies disclosed herein, from the viewpoint of providing aesthetic appeal or improving the light-shielding properties of the laminate, the light transmittance C of the laminate is total The light transmittance C is preferably 20% or less, more preferably 10% or less, even more preferably 5% or less, and particularly preferably 1.5% or less. total The lower limit is not particularly restricted and may be effectively 0%, i.e., below the detection limit, or it may be 1% or more, 5% or more, or 15% or more.

[0144] In the technology disclosed herein, the light transmittance C of the laminate total It can be measured by the following method. In the examples described later, it will also be measured by the following method.

[0145] [Light transmittance C total ] Light transmittance C of the laminate total [%] represents the light transmittance in the thickness direction of the laminate peeled from the release liner (light transmittance at a wavelength of 550 nm), and is measured using a commercially available transmittance meter in accordance with JIS K 7136:2000. As the transmittance meter, a spectrophotometer manufactured by Hitachi, Ltd. (device name "U4150 type spectrophotometer") or an equivalent product is used.

[0146] <Application> The laminate disclosed herein offers excellent conformability to complex shapes and superior strain resistance. Taking advantage of these characteristics, the laminate can be used in various applications requiring deformation and strain resistance. For example, it is suitable for fixing components in various portable electronic devices that have bent shapes. Furthermore, since portable electronic devices are subject to external impacts and loads, the adhesive sheet disclosed herein offers significant advantages in suppressing the occurrence of strain on the adherend. Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (e.g., wristwear-type devices worn on the wrist like watches, modular devices attached to a part of the body with clips or straps, eyewear-type devices including glasses (monocular and binocular, including head-mounted types), clothing-type devices attached to shirts, socks, hats, etc. as accessories, earwear-type devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game consoles, electronic dictionaries, electronic organizers, e-books, in-car information systems, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" means not merely being able to carry, but having a level of portability that allows an individual (a typical adult) to carry it relatively easily.

[0147] Furthermore, the adhesive sheet disclosed herein is preferably used in portable electronic devices to fix components such as cover glass having a three-dimensional shape (typically a curved shape) that constitute the portable electronic device. It is also suitable for fixing surfaces of adherends that have steps. Because the adhesive sheet disclosed herein has excellent conformability to the adherend, it can conform well and adhere tightly to complex shapes, including the three-dimensional shapes and steps mentioned above. While providing excellent fixing functionality by adhering tightly to such three-dimensional shapes and surfaces of adherends without gaps, it can also provide excellent waterproofing to products that require waterproofing (for example, electronic devices such as portable electronic devices).

[0148] Furthermore, the laminate disclosed herein is preferably used in portable electronic devices to fix components such as flexible printed circuit boards that constitute the portable electronic device. Because the laminate disclosed herein has excellent conformability to complex shapes, it can reliably adhere to adherends having a bent shape, such as flexible printed circuit boards. In addition, it can suppress distortion in electronic components fixed to flexible printed circuit boards, etc.

[0149] The laminates disclosed herein, in the form of bonding materials processed into various external shapes, can be used to fix components constituting portable electronic devices as described above. They are particularly suitable for use in electronic devices equipped with organic EL displays or liquid crystal displays (typically portable electronic devices). For example, the adhesive sheets disclosed herein are preferably used to fix components of electronic devices having a display unit such as a touch panel display (typically portable electronic devices such as smartphones) that have a large screen display unit. The laminates disclosed herein may also be used to fix components such as cover members or organic EL units. The laminates disclosed herein are preferably used as components of the above-mentioned display devices.

[0150] The matters disclosed in this specification include the following: [1] Core body and, A first adhesive sheet containing an adhesive layer is disposed on one surface of the core body, A laminate comprising a second adhesive sheet containing an adhesive layer, disposed on the other surface of the core body, Young's modulus E of the above core A [MPa] and thickness T A [μm] product (E A ×T A ) is over 500,000, The thickness T of one or both of the first adhesive sheet and the second adhesive sheet. B A laminate having a thickness greater than 10 μm and a storage modulus G'(25°C) of less than 0.20 MPa at 25°C. [2] One or both of the first adhesive sheet and the second adhesive sheet are The laminate described in [1] above, wherein the storage modulus G'(85°C) at 85°C is less than 0.05 MPa. [3] One or both of the first adhesive sheet and the second adhesive sheet are The laminate according to [1] or [2] above, wherein the storage modulus G'(120°C) at 120°C is less than 0.03 MPa. [4] The adhesive sheet according to any one of [1] to [3] above, wherein the adhesive layer contained in one or both of the first adhesive sheet and the second adhesive sheet is an acrylic adhesive layer containing an acrylic polymer as a base polymer. [5] Thickness T of the above core A The laminate is one of the above [1] to [4], having a thickness of 20 μm or more and 270 μm or less. [6] Young's modulus E of the above core A The laminate described in any of [1] to [5] above, having a pressure of 3000 MPa or higher. [7] Light transmittance C total A laminate according to any of the above [1] to [6], wherein the content is 10% or less. [8] Total thickness T of the above laminate total The laminate according to any of [1] to [7] above, wherein the thickness is 50 μm or more and 400 μm or less. [9] A laminate according to any of [1] to [8] above, used for fixing components in portable electronic devices. [Examples]

[0151] The following describes several embodiments of the present invention, but the present invention is not intended to be limited to those shown in these embodiments. In the following description, "parts" and "%" refer to weight unless otherwise specified.

[0152] (Preparation of adhesive composition E) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 95 parts BA and 5 parts AA as monomer components and 233 parts ethyl acetate as polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts 2,2'-azobisisobutyronitrile (AIBN) 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 E. The Mw of this acrylic polymer E is approximately 60 × 10⁻⁶ 4 That was the case.

[0153] To the above acrylic polymer solution, 100 parts of the acrylic polymer E contained in the solution were mixed with 20 parts of terpene phenol resin B as a tackifying resin, 3 parts of an isocyanate-based crosslinking agent and 0.01 parts of an epoxy-based crosslinking agent as crosslinking agents, and the mixture was stirred to prepare adhesive composition E. As terpene phenol resin B (tackifying resin B), the trade name "YS Polystar T-115" (manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mgKOH / g) was used.

[0154] (Adhesive composition E) black (Preparation) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 95 parts BA and 5 parts AA as monomer components and 233 parts ethyl acetate as polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts 2,2'-azobisisobutyronitrile (AIBN) 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 E. The Mw of this acrylic polymer E is approximately 60 × 10⁻⁶ 4 That was the case.

[0155] To the above acrylic polymer solution, 20 parts of terpene phenol resin B as a tackifying resin, 3 parts of isocyanate crosslinking agent and 0.01 parts of epoxy crosslinking agent are added to 100 parts of the acrylic polymer E contained in the solution, and a dispersion of carbon black particles (manufactured by Toyo Color Co., Ltd., product name "Multi-Rack A903") is added as a coloring agent (black coloring agent) so that the carbon black particle content is 2 parts per 100 parts of acrylic polymer E, and the mixture is stirred to form adhesive composition E black The following was prepared. As the terpene phenol resin B (tackifying resin B), the trade name "YS Polystar T-115" (manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mg KOH / g) was used.

[0156] (Preparation of adhesive composition F) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 70 parts BA, 30 parts 2EHA, and 3 parts AA as monomer components, and 233 parts ethyl acetate as polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.08 parts 2,2'-azobisisobutyronitrile (AIBN) 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 F. The Mw of this acrylic polymer F is approximately 40 × 10⁻⁶ 4 That was the case.

[0157] To the above-mentioned acrylic polymer solution, 2 parts of an isocyanate-based crosslinking agent and 0.01 parts of an epoxy-based crosslinking agent were added to 100 parts of the acrylic polymer F contained in the solution, and the mixture was stirred to prepare an adhesive composition F.

[0158] (Preparation of adhesive composition G) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 100 parts of 2EHA and 2 parts of AA as monomer components and 233 parts of ethyl acetate as polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.02 parts of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd., 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 G. The Mw of this acrylic polymer G is approximately 40 × 10⁻⁶ 4 That was the case.

[0159] To the above-mentioned acrylic polymer solution, 2 parts of an isocyanate-based crosslinking agent and 0.01 parts of an epoxy-based crosslinking agent were added to 100 parts of the acrylic polymer G contained in the solution, and the mixture was stirred to prepare an adhesive composition G.

[0160] (Preparation of adhesive composition H) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 95 parts of 2EHA and 5 parts of AA as monomer components and 233 parts of ethyl acetate as polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.03 parts of benzoyl peroxide (manufactured by Nippon Oil & Fats Co., Ltd., 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. The Mw of this acrylic polymer H is approximately 120 × 10⁻⁶ 4 That was the case.

[0161] To the above acrylic polymer solution, 3 parts of an isocyanate-based crosslinking agent and 0.03 parts of an epoxy-based crosslinking agent were added to 100 parts of the acrylic polymer H contained in the solution, and the mixture was stirred to prepare adhesive composition H.

[0162] (Preparation of adhesive composition A) In a reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel, 95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components, and 233 parts of ethyl acetate as polymerization solvent were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) 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 A. The Mw of this acrylic polymer A is approximately 60 × 10⁻⁶ 4 That was the case.

[0163] To the above acrylic polymer solution, 30 parts of terpene phenol resin A as tackifying resin A, 2 parts of isocyanate crosslinking agent and 0.01 parts of epoxy crosslinking agent were added to 100 parts of acrylic polymer A contained in the solution, and the mixture was stirred to prepare adhesive composition A. As terpene phenol resin A (tackifying resin A), the trade name "YS Polystar S-145" (manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 145°C, hydroxyl value 70-110 mg KOH / g) was used. As the isocyanate crosslinking agent, the trade name "Coronate L" (manufactured by Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct) was used. As the epoxy crosslinking agent, the trade name "TETRAD-C" (manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was used. The same isocyanate-based and epoxy-based crosslinking agents were used when preparing the following other adhesive compositions.

[0164] Adhesive composition E,E black Table 1 shows an overview of the composition of F, G, H, and A, as well as the weight-average molecular weight of the base polymer.

[0165] [Table 1]

[0166] <Example 1> (Making adhesive sheets) Adhesive composition E was applied to the release surface of a 38 μm thick polyester release liner (product name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.), and dried at 100°C for 2 minutes to form a 15 μm thick adhesive layer. In this way, a 15 μm thick substrate-less double-sided adhesive sheet was obtained, with one side protected by the polyester release liner. Two of these substrate-less double-sided adhesive sheets were prepared and designated as the first and second adhesive sheets of this example.

[0167] (Fabrication of laminates) The adhesive surface of the first adhesive sheet was attached to one side of a 20 μm thick stainless steel sheet (SUS 304BA) which served as the core. The adhesive surface of the second adhesive sheet was attached to the other side of the same stainless steel sheet (SUS 304BA). In this way, the first and second adhesive sheets were arranged on both sides of the core, and a laminate was created in which the adhesive surfaces of the first and second adhesive sheets were protected by two release liners. This laminate was used as the laminate in this example.

[0168] <Examples 2-4> The laminate of this example was obtained in the same manner as in Example 1, except that the thickness of the first adhesive sheet (adhesive layer), the second adhesive sheet (adhesive layer), and / or the core body were as shown in Table 1.

[0169] <Example 5> Two polyester release liners with a thickness of 38 μm (product name "Diafoil MRF", manufactured by Mitsubishi Polyester Co., Ltd.) were prepared. 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 with a thickness of 10 μm. As a support substrate, a multilayer support substrate with a total thickness of approximately 10 μm was prepared, consisting of a transparent PET film with a thickness of 5 μm (product name "Lumirror", manufactured by Toray Industries, Inc.) and a black printed layer provided on one side of the PET film. The black printed layer was formed by printing using a gravure printing method with an ink composition containing a black coloring agent. By laminating the adhesive layers formed on each release liner to the first and second surfaces of the support substrate, a 30 μm thick double-sided adhesive sheet with a substrate was prepared, having adhesive layers on the first and second surfaces of the black printed PET film. Two of these double-sided adhesive sheets with a substrate were prepared and designated as the first and second adhesive sheets of this example. The laminate of this example was fabricated using the same method as in Example 1, except that the first and second adhesive sheets of this example were used.

[0170] <Example 6> Except for setting the thickness of the adhesive layer formed on each release liner to 45 μm and using a 50 μm thick PET film (product name "Lumirror", manufactured by Toray Industries, Inc.) with black pigment kneaded into it as the support substrate, a 140 μm thick double-sided adhesive sheet with a substrate was prepared in the same manner as in Example 5, and these were used as the first and second adhesive sheets of this example. The laminate of this example was prepared using the same method as in Example 1, except for the use of the first and second adhesive sheets of this example.

[0171] <Example 7> Except for setting the thickness of the adhesive layer to 20 μm, a substrate-less double-sided adhesive sheet with a thickness of 20 μm was prepared using the same method as in Example 1, and this was used as the first adhesive sheet in this example.

[0172] Except for setting the thickness of the adhesive layer formed on each release liner to 50 μm and using a 160 μm thick transparent PET film (product name "Lumirror", manufactured by Toray Industries, Inc.) as the support substrate, a 260 μm thick double-sided adhesive sheet with a substrate was prepared in the same manner as in Example 5, and this was designated as the second adhesive sheet of this example.

[0173] The laminate of this example was fabricated using the same method as in Example 1, except that the first and second adhesive sheets of this example were used.

[0174] <Example 8> Except for setting the thickness of the adhesive layer to 20 μm, a substrate-less double-sided adhesive sheet with a thickness of 20 μm was prepared using the same method as for the first and second adhesive sheets in Example 1, and this was designated as the first adhesive sheet in this example.

[0175] Except for setting the thickness of the adhesive layer formed on each release liner to 12.5 μm and using a 235 μm thick transparent PET film (product name "Lumirror", manufactured by Toray Industries, Inc.) as the support substrate, a 260 μm thick double-sided adhesive sheet with a substrate was prepared in the same manner as in Example 5, and this was the second adhesive sheet of Example 8.

[0176] The laminate of this example was fabricated using the same method as in Example 1, except that the first and second adhesive sheets of this example were used.

[0177] <Example 9> The laminate in this example was fabricated using the same method as in Example 1, except that a 20 μm thick aluminum sheet (product name "A1N30H-O", manufactured by Takeuchi Metal Foil & Powder Co., Ltd.) was used as the core.

[0178] <Example 10> The laminate in this example was fabricated using the same method as in Example 1, except that a 20 μm thick copper sheet (product name "C1020R-H", manufactured by Takeuchi Metal Foil & Powder Co., Ltd.) was used as the core.

[0179] <Example 11> The laminate in this example was fabricated using the same method as in Example 1, except that a 125 μm thick transparent PET film (product name "Lumirror," manufactured by Toray Industries, Inc.) was used as the core.

[0180] <Example 12> Instead of adhesive composition E, use adhesive composition E blackAside from using the same method as in Example 1, a 15 μm thick substrate-less double-sided adhesive sheet was prepared and used as the first and second adhesive sheets of this example. Aside from using the first and second adhesive sheets of this example, the laminate of this example was prepared using the same method as in Example 11.

[0181] <Example 13> Except for using adhesive composition F instead of adhesive composition E, a substrate-less double-sided adhesive sheet with a thickness of 30 μm was prepared using the same method as in Example 2, and this was used as the first and second adhesive sheets of this example. Except for using the first and second adhesive sheets of this example, the laminate of this example was prepared using the same method as in Example 1.

[0182] <Example 14> Except for using adhesive composition G instead of adhesive composition E, a substrate-less double-sided adhesive sheet with a thickness of 30 μm was prepared using the same method as in Example 2, and these were used as the first and second adhesive sheets of this example. Except for using the first and second adhesive sheets of this example, the laminate of this example was prepared using the same method as in Example 1.

[0183] <Example 15> Except for using adhesive composition H instead of adhesive composition E, a substrate-less double-sided adhesive sheet with a thickness of 30 μm was prepared using the same method as in Example 2, and this was used as the first and second adhesive sheets of this example. Except for using the first and second adhesive sheets of this example, the laminate of this example was prepared using the same method as in Example 1.

[0184] <Example 16> Except for making the adhesive layer thickness 10 μm, a substrate-less double-sided adhesive sheet with a thickness of 10 μm was prepared using the same method as in Example 1, and this was used as the first and second adhesive sheets of this example. Except for using the first and second adhesive sheets of this example, the laminate of this example was prepared using the same method as in Example 1.

[0185] <Example 17> The laminate in this example was fabricated using the same method as in Example 1, except that a 100 μm thick transparent PET film (product name "Lumirror," manufactured by Toray Industries, Inc.) was used as the core.

[0186] <Example 18> Except for using adhesive composition A instead of adhesive composition E and making the adhesive layer thickness 35 μm, a substrate-less double-sided adhesive sheet with a thickness of 35 μm was prepared using the same method as in Example 1, and this was designated as the first adhesive sheet of this example. Furthermore, a substrate-less double-sided adhesive sheet with a thickness of 25 μm was prepared using the same method as in Example 1, except for using adhesive composition F instead of adhesive composition A and making the adhesive layer thickness 25 μm, and this was designated as the second adhesive sheet of this example. The laminate in this example was fabricated using the same method as in Example 1, except that the first and second adhesive sheets of this example were used, and a 40 μm thick stainless steel sheet (SUS 304BA) was used as the core.

[0187] Tables 2 and 3 show an overview of the laminates for each example; and the light transmittance C of the adhesive sheet for each example. B Light transmittance C of the laminate total Young's modulus of the core body E A [MPa], Thickness T A [μ]m and E A ×T A Total thickness T of the laminate total Add a semicolon.

[0188] <Evaluation Method> [Step Waterproofing Test] In each example, the laminate, with both adhesive surfaces protected by a release liner, was cut into a window frame shape (picture frame shape) with a 24.5 mm x 24.5 mm square outer edge and a width of 2 mm to obtain a window frame-shaped laminate. The release liner on the second adhesive sheet side of this window frame-shaped laminate was peeled off, and the exposed adhesive surface was attached to a 50 mm x 50 mm square acrylic plate with a thickness of 2 mm to produce an acrylic plate with a window frame-shaped laminate. The release liner on the first adhesive sheet side was peeled off the acrylic plate with the window frame-shaped laminate. A polycarbonate sheet larger than the acrylic sheet mentioned above was prepared, and a stepped tape (5 mm wide, 20 μm high) was attached to its surface. This stepped tape is used to create a protrusion (step) on the surface of the polycarbonate sheet. Here, an adhesive sheet with an adhesive layer on one side of a PET substrate was used as the stepped tape. The acrylic sheet with the window frame-shaped laminate prepared above was then placed on this polycarbonate sheet in a position where the first adhesive sheet side of the laminate faced the polycarbonate side, and the centers of the two parallel sides of the window frame-shaped laminate crossed the stepped tape (so that the two parallel sides of the window frame-shaped laminate intersected (orthogonal to) the stepped tape), and pressed together under conditions of 0.2 MPa for 1 minute. An evaluation sample was obtained in this way. In the obtained evaluation sample, when the window frame-shaped laminate is in close contact with the adherends (acrylic sheet, polycarbonate sheet, and stepped tape), the inside becomes a sealed space from the outside. The step-over waterproofing performance was evaluated by submerging the evaluation sample in water in an autoclave, applying pressure at 25°C and 0.5 MPa for 30 minutes, and visually observing whether or not water entered the inside of the evaluation sample (inside the window frame-shaped laminate). The presence or absence of water entering the inside of the evaluation sample was evaluated as step-over conformability. If water entry into the inside of the evaluation sample was observed, it was judged as "×: Fail," and if it was not observed, it was judged as "○: Pass." The evaluation results are shown in the step-over conformability section of Tables 2 and 3. The above step waterproofing test was performed after aging the evaluation sample under standard conditions (23°C, 50%RH) for 30 minutes.

[0189] [Strain resistance test] As shown in Figure 4(a), a PET film 80 measuring 50 mm in length, 50 mm in width, and 125 μm in thickness, and a stepped tape 82 measuring 2 mm in width, 50 mm in length, and 8 mm in height were prepared. The stepped tape 82 was attached to the center of the surface of the PET film 80 so that the length of the stepped tape 82 coincided with the direction of one side of the PET film 80. The stepped tape 82 is used to create a protrusion (step) on the surface of the PET film 80. Here, an adhesive sheet having an adhesive layer on one side of the PET substrate was used as the stepped tape 82. Next, the laminates for each example, with both adhesive surfaces protected by release liners, were cut to a size of 10 mm in length and 10 mm in width. Two release liners were peeled off the laminate, and a PET film with a thickness of 5 μm was attached to each exposed adhesive surface as a backing to form a laminate sample piece 84. In addition, a commercially available silicone rubber sheet 86 measuring 50 mm in length, 50 mm in width, and 3 mm in thickness was prepared. The laminated sample piece 84 was placed in the center of the upper surface of the silicone rubber sheet 86, such that the direction of one side of the laminated sample piece 84 coincided with the direction of one side of the silicone rubber sheet 86.

[0190] The PET film 80 was placed above the silicone rubber sheet 86 with the stepped tape 82 facing downwards. At this time, the PET film 80 was positioned so that it overlapped with the silicone rubber sheet 86 when viewed from above. Next, as shown in Figure 4(b), a load of 40N was applied to the PET film 80 from above toward the silicone rubber sheet 86 for 10 seconds in an environment of 25°C and 50%RH. After that, as shown in Figure 4(c), the PET film 80 was pulled upwards, and the silicone rubber sheet 86, from which the laminate sample piece 84 had been removed, was left for 24 hours in an environment of 25°C and 50%RH. The strain height of the silicone rubber sheet 86 after the period of time was measured using a surface shape measuring device (model number "Wyko NT9100", manufactured by Veeco), and this strain height was evaluated as the strain resistance of the laminate. Here, as shown in Figure 4(d), for the silicone rubber sheet 86 after being left for 24 hours, the strain height c was defined as the value obtained by subtracting the height b of the loaded portion from the height a of the unloaded portion of the silicone rubber sheet 86 (a-b). A strain height c of 3 μm or less was judged as "○: Pass," and a strain height c greater than 3 μm was judged as "×: Fail." The evaluation results are shown in the strain resistance section of Tables 2 and 3.

[0191] [Table 2]

[0192] [Table 3]

[0193] As is clear from the results shown in Tables 2 and 3, the Young's modulus of the core E A [MPa] and thickness T A [μm] product (E A ×T A The laminates of Examples 1-16 and 18, where ) is 500,000 or more, are (E A ×T A Compared to the laminate of Example 17, where the ratio is 400,000, it showed significantly superior strain resistance. Also, the thickness T of the first and second adhesive sheets BThe laminates of Examples 1 to 15, 17 and 18, in which all are larger than 10 µm, have thicknesses T of the first and second pressure-sensitive adhesive sheets B all of which are 10 µm, exhibited remarkably superior step followability compared with the laminate of Example 16. 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 pressure-sensitive adhesive sheets is less than 0.20 MPa, exhibited superior step followability compared with the laminate of Example 18, in which the storage elastic modulus G′(25°C) of the first and second pressure-sensitive adhesive sheets is 0.260 MPa.

[0194] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technology set forth in the claims includes various modifications and alterations of the specific examples illustrated above. [Description of Reference Numerals]

[0195] 1 Laminate 11 First pressure-sensitive adhesive sheet 12 Second pressure-sensitive adhesive sheet 15 Core body 21 Release liner 25, 35 Base material 32, 34, 36, 38 Pressure-sensitive adhesive layer 50 PC plate 60 PET film 70 Laminate sample piece 80 PET film 82 Step tape 84 Laminate sample piece 86 Silicone rubber sheet

Claims

1. The core body, A first adhesive sheet containing an adhesive layer is disposed on one surface of the core body, A laminate comprising a second adhesive sheet containing an adhesive layer, disposed on the other surface of the core body, The core is made of stainless steel foil or resin film. Young's modulus E of the core Ａ [MPa] and thickness T Ａ Product of [μm] (E Ａ ×T Ａ ) is 500,000 or more, One or both of the first adhesive sheet and the second adhesive sheet are substrate-less adhesive sheets that do not contain a substrate. The aforementioned substrate-less adhesive sheet has a thickness T Ｂ A laminate in which the thickness is 15 μm or more, and the storage modulus G' (25°C) at 25°C is less than 0.20 MPa.

2. The core body, A first adhesive sheet containing an adhesive layer is disposed on one surface of the core body, A laminate comprising a second adhesive sheet containing an adhesive layer, disposed on the other surface of the core body, The core is made of stainless steel foil or resin film. The Young's modulus E of the core body Ａ [MPa] and the thickness T Ａ [μm] product (E Ａ × T Ａ ) is 500000 or more, One or both of the first adhesive sheet and the second adhesive sheet are adhesive sheets with a substrate, The aforementioned adhesive sheet with a base material is Thickness T Ｂ It is 25 μm or larger, The storage modulus G'(25°C) at 25°C is less than 0.20 MPa, and A laminate in which each adhesive layer contained in the adhesive sheet with a substrate has a thickness of 10 μm or more.

3. One or both of the first adhesive sheet and the second adhesive sheet are The laminate according to claim 1 or 2, wherein the storage modulus G'(85°C) at 85°C is less than 0.05 MPa.

4. One or both of the first adhesive sheet and the second adhesive sheet are The laminate according to any one of claims 1 to 3, wherein the storage modulus G'(120°C) at 120°C is less than 0.03 MPa.

5. The thickness T of the aforementioned core Ａ The laminate according to any one of claims 1 to 4, wherein the thickness is 10 μm or more and 300 μm or less.

6. Young's modulus E of the core Ａ The laminate according to any one of claims 1 to 5, wherein the pressure is 3000 MPa or more.

7. Light transmittance C ｔｏｔａｌ The laminate according to any one of claims 1 to 6, wherein the percentage is 10% or less.

8. The total thickness T of the laminated body ｔｏｔａｌ The laminate according to any one of claims 1 to 7, wherein the thickness is 50 μm or more and 400 μm or less.

9. A laminate according to any one of claims 1 to 8, used for fixing components in a portable electronic device.

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