Double-sided adhesive sheet with a release liner

Abstract

The present invention provides a double-sided adhesive sheet with a release liner that can highly suppress deformation of the adhesive surface caused by peeling of the release liner. The present invention provides a double-sided adhesive sheet with a release liner, the double-sided adhesive sheet with a release liner having: a double-sided adhesive sheet; a first release liner that protects a first adhesive surface of the double-sided adhesive sheet; and a second release liner that protects a second adhesive surface of the double-sided adhesive sheet. The double-sided adhesive sheet has a colored adhesive layer. Further, the adhesive layer contains an acrylic polymer. In addition, the difference in peel force between the peel force R1 of the first release liner on the first adhesive surface and the peel force R2 of the second release liner on the second adhesive surface is 0.07 N / 50 mm or more. The storage modulus of the adhesive layer at 0°C is 0.95 MPa or less.

Description

Technical Field

[0001] The present invention relates to a double-sided adhesive sheet with a release liner.

[0002] This application claims priority based on Japanese Patent Application No. 2022-145687 filed on September 13, 2022, the entire content of which is incorporated herein by reference. Background Art

[0003] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter.) exhibits a state of a soft solid (viscoelastic body) within a temperature range near room temperature and has the property of being easily adhered to an adherend by pressure. Utilizing such a property, in various industrial fields from portable electronic devices such as smartphones, home appliances to automobiles, office automation equipment, etc., adhesives are typically used in the form of adhesive sheets containing an adhesive layer for purposes such as joining components and surface protection. Preferred examples of the uses of such adhesive sheets include joining, fixing, and protecting components within electronic devices. In addition, for example, for the purpose of preventing light leakage from light sources such as backlight modules of liquid crystal display devices in electronic devices, self-luminous elements such as organic EL (electroluminescence), masking the adherend, adjusting the appearance and designability of the adherend through the adhesive sheet, etc., an adhesive sheet having a specified light-shielding property and light-reducing property is used. As a document regarding such technology, Patent Document 1 can be cited. Patent Documents 2 and 3 are prior art documents that disclose adhesives containing an acrylic polymer obtained by polymerizing heptyl acrylate as a monomer component.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-37657

[0007] Patent Document 2: International Publication No. 2021 / 125247

[0008] Patent Document 3: International Publication No. 2021 / 125278 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] An adhesive sheet used for the purpose of masking an adherend, adjusting the appearance, imparting design, etc. achieves the purpose of masking, etc. by covering the entire surface on the visual recognition side of the adherend. Since this adhesive sheet can be visually recognized from the outside, it is required to have good appearance quality. For example, in the display unit of an electronic device, an adhesive sheet used for masking a metal member disposed on the back side of an organic electroluminescent panel, etc. can be seen by the user when the illumination of the display unit is turned off, so it is required to mask the adherend with good appearance quality.

[0011] Incidentally, a double-sided pressure-sensitive adhesive sheet (also referred to as a double-sided adhesive sheet.) used for joining various components such as the above-mentioned portable electronic devices, etc. can be circulated, stored, and processed in a form in which each adhesive surface is protected by two release liners from the viewpoint of operability, etc. before use (i.e., before being pasted onto the adherend). By protecting the adhesive surface with the release liner, the adhesive surface remains smooth and can adhere well to the surface of the adherend to exhibit the desired adhesive characteristics. In addition, an adhesive sheet having an adhesive surface protected by a release liner and kept smooth can be evenly pasted onto the adherend, thereby providing a good appearance when the surface of the above-mentioned adherend is visually recognized.

[0012] A double-sided adhesive sheet with release liners in a form in which each adhesive surface is protected by the above two release liners is usually used in the following manner: the first release liner is peeled off to expose one adhesive surface, this adhesive surface is pasted onto the adherend, and then the second release liner is peeled off to expose the other adhesive surface and this adhesive surface is pasted onto a different adherend, thereby joining the two adherends. For example, a double-sided adhesive sheet used for masking a metal member disposed on the back side of the above-mentioned organic electroluminescent panel, etc. is pasted onto the metal member and the transparent member, thereby joining the two while masking the metal member from the visual recognition side.

[0013] However, in the above-described double-sided adhesive sheet with release liners, when the difference in the release force between the two release liners is small, when the first release liner is peeled off, a bulge is generated on the release liner on the opposite side. Due to the above bulge, the smoothness of the adhesive surface on the opposite side may be impaired at a visually recognizable level. In addition, on the adhesive surface on the side where the release liner is peeled off, sometimes the adhesive surface is pulled by the release liner, and the adhesive surface undulates or becomes striated (roughened), etc. The adhesive surface mainly deforms in the thickness direction, and this deformation remains and is visually recognizable even after being pasted onto the adherend. Such a visually recognizable deformation of the adhesive surface in terms of size cannot be eliminated when it is stabilized after being pasted onto the adherend. In particular, a colored adhesive sheet in which the adhesive layer contains a colorant, etc., has a greater tendency to exhibit deformation of the adhesive surface compared to a transparent adhesive sheet, and the change in appearance caused by the deformation of the adhesive surface is more likely to be obvious. In addition, in recent years, there has been a tendency to require higher appearance quality for the display part of electronic devices, and it can be envisaged that an adhesive surface with fine deformation suppressed at a level that has not been a problem in the past is required. The deformation of the adhesive surface generated when the release liner is peeled off as described above may depend on the peeling operator, peeling conditions, etc., and therefore it is usually difficult to highly control only by studying the release liner and designing the release force. If a colored double-sided adhesive sheet that highly suppresses the deformation of the adhesive surface caused by the peeling of the release liner is realized, it is useful for improving the appearance quality of the surface of the double-sided adhesive sheet applied to the joining and fixing of components, etc.

[0014] The present invention was created in view of the above circumstances, and its object is to provide a double-sided adhesive sheet with a release liner that can highly suppress the deformation of the adhesive surface caused by the peeling of the release liner.

[0015] Means for Solving the Problem

[0016] According to the present specification, there is provided a double-sided adhesive sheet with a release liner, the double-sided adhesive sheet with a release liner having a double-sided adhesive sheet; a first release liner that protects the first adhesive surface of the double-sided adhesive sheet; and a second release liner that protects the second adhesive surface of the double-sided adhesive sheet. In the above double-sided adhesive sheet with a release liner, the double-sided adhesive sheet has a colored adhesive layer. In addition, the adhesive layer contains an acrylic polymer. Further, the difference in the release force between the release force R1 [N / 50 mm] of the first release liner on the first adhesive surface and the release force R2 [N / 50 mm] of the second release liner on the second adhesive surface is 0.07 or more. Moreover, the storage modulus of the adhesive layer at 0°C is 0.95 MPa or less.

[0017] The double-sided adhesive sheet with a release liner configured as described above has a difference in release force R1 of the first release liner and release force R2 of the second release liner of 0.07 N / 50 mm or more. Therefore, when the release liner is peeled off, bulging is not likely to occur, and deformation (such as undulation, streaky roughening, etc.) is not likely to occur on the adhesive surface. In addition, since the storage modulus of the adhesive layer at 0°C is 0.95 MPa or less, even if deformation occurs on the adhesive surface when the release liner is peeled off, this deformation can be highly suppressed by the surface shape relaxation effect of the adhesive. Since the double-sided adhesive sheet has a colored adhesive layer, deformation of the adhesive surface is likely to be conspicuous. However, according to the configuration having the adhesive layer with the storage modulus at 0°C as described above, the above deformation is highly suppressed, and thus the adhesive surface has excellent appearance quality.

[0018] In some embodiments, the monomer components constituting the above acrylic polymer include an alkyl acrylate having a linear alkyl group with 4 to 8 carbon atoms. According to the acrylic polymer containing an alkyl acrylate having a linear alkyl group with 4 to 8 carbon atoms (acrylic C 4-8 alkyl ester) as a monomer component, the storage modulus of the adhesive layer at 0°C can be moderately reduced. The technology disclosed herein is preferably implemented in a manner using an acrylic polymer containing acrylic C 4-8 alkyl ester as a monomer component.

[0019] In some preferred embodiments, the monomer components constituting the above acrylic polymer include heptyl acrylate. By using an acrylic polymer containing heptyl acrylate as a monomer component, it is easy to form a soft adhesive having a storage modulus at 0°C below a specified value, and it is easy to obtain the surface shape relaxation effect of the adhesive.

[0020] In some embodiments, the monomer components constituting the above acrylic polymer include n-butyl acrylate. According to the technology disclosed herein, by using a composition of an acrylic polymer containing n-butyl acrylate as a monomer component, an adhesive with good surface shape relaxation and a storage modulus at 0°C below a specified value can be obtained.

[0021] In some preferred embodiments, the above adhesive layer contains a black colorant. The black colorant can effectively adjust the light transmittance with a small amount, and it is easy to obtain high masking properties for adherends. The effects produced by the technology disclosed herein (highly suppressing the deformation of the adhesive surface caused by the peeling of the release liner) can be effectively exerted in the double-sided adhesive sheet having an adhesive layer containing a black colorant.

[0022] In some preferred embodiments, the above-mentioned adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant. By using the above two colorants, it is possible to satisfactorily achieve the target design and hue (color tone) while adjusting the optical properties (such as light transmittance). The effects produced by the technology disclosed herein are effectively exerted in the double-sided adhesive sheet having an adhesive layer containing the above two colorants.

[0023] In some preferred embodiments, the peeling force R1 [N / 50 mm] of the above-mentioned first release liner from the above-mentioned first adhesive surface is lower than the peeling force R2 [N / 50 mm] of the above-mentioned second release liner from the above-mentioned second adhesive surface. In addition, the peeling force R1 of the above-mentioned first release liner from the above-mentioned first adhesive surface is 0.3 N / 50 mm or less. In the method of first peeling the first release liner and then using it, by setting the peeling force of the first release liner on the light-peeling side to 0.3 N / 50 mm or less, when the first release liner is peeled, there is a tendency that the adhesive surface is not easily deformed such as undulating or striated roughening.

[0024] In some embodiments, the above-mentioned double-sided adhesive sheet is a substrate-free adhesive sheet composed of the above-mentioned adhesive layer. The substrate-free double-sided adhesive sheet can be thinned to the extent of not having a substrate, which can contribute to the miniaturization and space-saving of products using the double-sided adhesive sheet. In addition, according to the substrate-free double-sided adhesive sheet, the functions of the adhesive layer such as adhesive strength can be maximized. In addition, the effects produced by the technology disclosed herein can be effectively exerted on the substrate-free double-sided adhesive sheet.

[0025] In some other embodiments, the above-mentioned double-sided adhesive sheet is a substrate-bearing double-sided adhesive sheet containing the above-mentioned adhesive layer and a support substrate layer. The double-sided adhesive sheet with a substrate is advantageous from the viewpoints of processability and operability.

[0026] The double-sided adhesive sheet disclosed herein can be preferably used for joining components of electronic devices such as household appliances, office automation equipment, and portable electronic devices such as smartphones. For example, an electronic device has a part visible to the user and may require excellent appearance quality. Since the double-sided adhesive sheet disclosed herein highly suppresses the deformation of the adhesive surface caused by the peeling of the release liner and can have an adhesive surface with excellent appearance quality, by applying it to the visually recognizable part of the electronic device, a surface with good appearance quality can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A cross-sectional view schematically showing a double-sided adhesive sheet with a release liner according to an embodiment.

[0028] Figure 2 A cross-sectional view schematically showing the structure of a double-sided adhesive sheet with a release liner according to another embodiment.

[0029] Figure 3 A cross-sectional view schematically showing a configuration example of a laminate.

[0030] Figure 4 A perspective exploded view schematically showing a configuration example of a display device. Detailed embodiments

[0031] Hereinafter, preferred embodiments of the present invention will be described. It should be noted that matters required for implementing the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for the implementation of the invention described in this specification and the common general knowledge in the art at the time of filing. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the art. In addition, in the following drawings, components / parts that perform the same function may sometimes be denoted by the same reference numerals, and repeated descriptions may sometimes be omitted or simplified. In addition, in order to clearly illustrate the present invention, the embodiments described in the drawings are schematized and do not necessarily accurately represent the dimensions and scales of the double-sided adhesive sheet with a release liner of the present invention actually provided as a product.

[0032] In this specification, an "adhesive" refers to a material that is in a soft solid (viscoelastic body) state in a temperature range near room temperature as described above and has the property of being easily adhered to an adherend by pressure. The adhesive here, as defined in "C.A. Dahlquist, 'Adhesion: Fundamentals and Practice', McLaren & Sons, (1966) P.143", can generally be a material having a complex tensile elastic modulus E ＊ (1 Hz) < 10 7 dyne / cm 2 (typically, a material having the above properties at 25°C).

[0033] In this specification, carbon derived from biomass refers to carbon from biomass materials, that is, materials from renewable organic resources (renewable carbon). The above biomass materials typically refer to materials from biological resources (typically photosynthetic plants) that can be continuously reproduced if there is a source of sunlight, water, and carbon dioxide. Therefore, materials from fossil resources (fossil resource-based materials) that are exhausted after extraction and use are excluded from the concept of biomass materials as described herein. The biomass carbon ratio of the adhesive layer and the adhesive sheet, that is, the proportion of carbon derived from biomass in the total carbon contained in the adhesive layer and the adhesive sheet, can be estimated based on the carbon isotope content of mass number 14 measured by ASTM D6866.

[0034] <Constitutional Example of Double-Sided Adhesive Sheet with Release Liner>

[0035] The double-sided adhesive sheet with a release liner disclosed herein is a double-sided adhesive sheet in which each adhesive surface is protected by two release liners, and has a laminated structure including a first release liner, a double-sided adhesive sheet, and a second release liner. Specifically, the double-sided adhesive sheet with a release liner includes: a double-sided adhesive sheet, a first release liner that protects the first adhesive surface of the double-sided adhesive sheet, and a second release liner that protects the second adhesive surface of the double-sided adhesive sheet. The first release liner and the second release liner are respectively laminated on the first adhesive surface and the second adhesive surface of the double-sided adhesive sheet in a peelable manner. In addition, the double-sided adhesive sheet can be, for example, in the form of a substrate-free double-sided adhesive sheet having a first adhesive surface formed by one surface of the adhesive layer and a second adhesive surface formed by the other surface of the adhesive layer. Or, the double-sided adhesive sheet can be in the form of a double-sided adhesive sheet with a substrate in which the above-mentioned adhesive layer is laminated on each surface of the support substrate. Hereinafter, the support substrate may sometimes be simply referred to as "substrate". It should be noted that the concept of the adhesive sheet described herein may include articles such as adhesive tapes, adhesive labels, and adhesive films. It should be noted that the double-sided adhesive sheet with a release liner disclosed herein can be in the form of being wound into a roll shape, or can be in a single sheet form. Or, it can also have a form further processed into various shapes.

[0036] In Figure 1 FIG. schematically shows the constitution of a double-sided adhesive sheet with a release liner according to an embodiment. The double-sided adhesive sheet 100 with a release liner includes: a double-sided adhesive sheet 1 having a first adhesive surface 1A and a second adhesive surface 1B, a first release liner 31 laminated on the first adhesive surface 1A, and a second release liner 32 laminated on the second adhesive surface 1B. The double-sided adhesive sheet 1 is a substrate-free double-sided adhesive sheet formed by an adhesive layer 21, and each surface 21A, 21B of the substrate-free adhesive layer 21 is also the first adhesive surface 1A and the second adhesive surface 1B of the double-sided adhesive sheet 1, respectively. The adhesive layer 21 is colored. The surface 31A on the first adhesive surface 1A side of the first release liner 31 is formed as a release surface, that is, a surface that can be peeled from the first adhesive surface 1A. In the first release liner 31, the opposite surface (back surface) 31B of the surface 31A can be a release surface or a non-release surface. The surface 32A of the second release liner 32, which is the surface on the second adhesive surface 1B side, is formed as a release surface, that is, a surface that can be peeled from the second adhesive surface 1B. In the second release liner 32, the opposite surface (back surface) 32B of the surface 32A can be a release surface or a non-release surface.

[0037] In Figure 2Another embodiment of a double-sided adhesive sheet with a release liner is schematically shown. In the double-sided adhesive sheet 200 with a release liner, the double-sided adhesive sheet 2 is formed in the form of a double-sided adhesive sheet with a substrate, and the double-sided adhesive sheet with a substrate has: a sheet-like support substrate (e.g., a resin film) 10 having a first surface 10A and a second surface 10B, a first adhesive layer 21 fixedly provided on the first surface 10A side, and a second adhesive layer 22 fixedly provided on the second surface 10B side. In the present embodiment, both the first adhesive layer 21 and the second adhesive layer 22 are colored. As Figure 2 shown, a first release liner 31 and a second release liner 32 are respectively laminated on the surface 21A (first adhesive surface 1A) of the first adhesive layer 21 and the surface 22A (second adhesive surface 1B) of the second adhesive layer 22. Such a double-sided adhesive sheet with a substrate is preferred because of its excellent processability, operability, etc.

[0038] It should be noted that the first adhesive layer and the second adhesive layer may not both be colored, as long as they are formed in the form of an adhesive layer in which at least one of the first adhesive layer and the second adhesive layer is colored.

[0039] The technology disclosed herein can preferably be implemented in the form of a substrate-free double-sided adhesive sheet. Since the substrate-free double-sided adhesive sheet does not have a support substrate, it is easy to be thinned, and it is also advantageous in terms of maximizing adhesive properties such as adhesive strength and impact resistance. On the other hand, in the substrate-free double-sided adhesive sheet, since there is no support substrate, bumps and roughening are likely to occur on the adhesive surface when the release liner is peeled off. However, according to the technology disclosed herein, for the substrate-free double-sided adhesive sheet, deformation of the adhesive surface caused by the peeling of the release liner can be highly suppressed.

[0040] <Release force characteristics of the release liner>

[0041] The double-sided adhesive sheet with a release liner disclosed herein is configured such that the release force difference (|R2 - R1|) between the release force R1 [N / 50 mm] of the first release liner on the first adhesive surface and the release force R2 [N / 50 mm] of the second release liner on the second adhesive surface is 0.07 or more. By designing in such a way that the release force difference between the first release liner and the second release liner is above a specified value, when the release liner on the light peeling side of the first sheet (e.g., the first release liner) is peeled off, bumps are not likely to occur on the release liner on the heavy peeling side on the opposite side (e.g., the second release liner). In addition, the adhesive surface is not easily pulled by the release liner on the light peeling side, and deformation of the adhesive surface in the thickness direction such as undulation of the adhesive surface or stripe-like roughening caused by the pulling of the release liner is not likely to occur. According to the configuration having the above release force difference, the occurrence of phenomena such as deformation of the adhesive surface caused by the peeling of the release liner can be suppressed.

[0042] From the viewpoints of preventing the swelling of the release liner on the side for preventing re-peeling and suppressing the pulling force on the adhesive surface caused by the release liner on the side for easy peeling, the above-mentioned peeling force difference (|R2 - R1|) can be 0.09 or more, can be 0.11 or more, can be 0.13 or more, and can also be 0.15 or more. The upper limit of the above-mentioned peeling force difference (|R2 - R1|) is appropriately set according to the purpose of use and the usage mode, and is not limited to a specific range. From the viewpoints of the peeling workability of the release liner on the side for heavy peeling and the protectiveness of the release liner for the adhesive surface, etc., in some modes, it is appropriate that the above-mentioned peeling force difference (|R2 - R1|) is 2.0 or less, preferably 1.0 or less, more preferably 0.5 or less, further preferably less than 0.3, and can also be less than 0.25 (for example, less than 0.20).

[0043] The double-sided adhesive sheet with a release liner disclosed herein can be used in the following manner: First, peel off the release liner with a relatively low peeling force (the release liner on the side for easy peeling) from the double-sided adhesive sheet, paste the exposed adhesive surface onto the adherend, and then peel off the release liner with a relatively high peeling force (the release liner on the side for heavy peeling) from the double-sided adhesive sheet. Either the first release liner or the second release liner can be used as the side for easy peeling (in this case, the other is the side for heavy peeling). Therefore, in the double-sided adhesive sheet with a release liner disclosed herein, the relationship between the peeling force R1 [N / 50 mm] of the first release liner for the first adhesive surface and the peeling force R2 [N / 50 mm] of the second release liner for the second adhesive surface can be R1 > R2, or can be R1 < R2.

[0044] The peeling force R1 of the first peeling liner (the peeling force on the first adhesive surface of the double-sided adhesive sheet) is appropriately set within the range that satisfies the above-mentioned peeling force difference (|R2 - R1|), and is not limited to a specific range. In some embodiments, the peeling force R1 is lower than the peeling force R2. In this embodiment, the first peeling liner serves as the peeling liner on the light-peeling side and peels off from the double-sided adhesive sheet before the second peeling liner. In some preferred embodiments, for example, the peeling force R1 is less than 0.50 N / 50 mm, and it is appropriate that it is 0.30 N / 50 mm or less, more preferably 0.20 N / 50 mm or less, it can be 0.15 N / 50 mm or less, it can be 0.12 N / 50 mm or less, and it can also be 0.10 N / 50 mm or less. By setting the peeling force R1 low, there is a tendency for the peeling workability to be improved. In addition, by setting the peeling force of the first peeling liner on the light-peeling side low, when the first peeling liner is peeled off, there is a tendency that it is not easy to generate deformations such as undulations and striped roughening on the adhesive surface. The first peeling liner showing the above-mentioned peeling force R1 is preferably the peeling liner on the light-peeling side. In some embodiments, for example, the peeling force R1 can be 0.01 N / 50 mm or more, it can be 0.03 N / 50 mm or more, it can be 0.05 N / 50 mm or more, and it can also be 0.07 N / 50 mm or more (for example, 0.09 N / 50 mm or more). When the peeling force R1 is a specified value or more, for example, in the case of processing a double-sided adhesive sheet with a peeling liner, the phenomenon of the first peeling liner bulging or peeling is not likely to occur, and the first adhesive surface can be well protected by the first peeling liner.

[0045] The peeling force R2 of the second release liner (the peeling force on the second adhesive surface of the double-sided adhesive sheet) is appropriately set within the range that satisfies the above peeling force difference (|R2 - R1|), and is not limited to a specific range. In some embodiments, the peeling force R2 is higher than the peeling force R1. In this embodiment, the second release liner serves as the release liner on the heavy peeling side. First, the first release liner is peeled from the double-sided adhesive sheet, and then the second release liner is peeled from the double-sided adhesive sheet. In some preferred embodiments, the peeling force R2 is, for example, less than 1.0 N / 50 mm, preferably 0.50 N / 50 mm or less, more preferably 0.30 N / 50 mm or less, and may be 0.25 N / 50 mm or less, or may be 0.20 N / 50 mm or less. By setting the peeling force R2 low, there is a tendency to improve the peeling workability. For example, when the first release liner is peeled from the first adhesive surface, the exposed adhesive surface is pasted onto the adherend, and then the second release liner is peeled from the second adhesive surface, there is a tendency to easily obtain good peelability. In addition, from the viewpoint of preventing deformation of the adhesive surface, it is preferable that the peeling force of the release liner on the heavy peeling side is not too high. In some embodiments, the peeling force R2 may be, for example, 0.10 N / 50 mm or more, may be 0.15 N / 50 mm or more, may be 0.20 N / 50 mm or more, or may be 0.25 N / 50 mm or more. By setting the peeling force R2 to a value equal to or higher than the specified value, it is easy to obtain the difference in peeling force (peeling force difference) from the first release liner, and in addition, the second adhesive surface can be well protected by the second release liner. The second release liner showing the above peeling force R2 is suitable for the release liner on the heavy peeling side.

[0046] It should be noted that the peeling force of the release liner (the peeling force R1 of the first release liner and the peeling force R2 of the second release liner) can be adjusted by selecting the type of release liner according to the type of adhesive used, or by selecting the material and thickness of the release liner substrate, the type of release treatment agent used to form the release treatment layer, the thickness of the release treatment layer, and the formation conditions.

[0047] The peeling force R1 of the first release liner and the peeling force R2 of the second release liner are measured by preparing a double-sided adhesive sheet with a release liner cut to a length of 150 mm and a width of 50 mm, and under the conditions of an atmosphere of 23°C and 50% RH, a pulling speed of 300 mm / minute, and a peeling angle of 180°. Specifically, the measurement is performed by the method described in the following examples.

[0048] <Release Liner>

[0049] The release liner (including the first release liner and the second release liner. The same applies hereinafter unless otherwise specified) is not particularly limited, and an appropriate release liner can be used within the range that satisfies the above-mentioned release force difference (|R2 - R1|). Non-limiting examples of the release liner that can be used include: a release liner having a release treatment layer on the surface of the release liner substrate; and a release liner containing a low tack resin such as a fluoropolymer (polytetrafluoroethylene, etc.) and a polyolefin resin (polyethylene, polypropylene, etc.).

[0050] As the release liner disclosed herein, a release liner having a release treatment layer on the release liner substrate can be preferably employed. The above-mentioned release treatment layer can be formed by surface-treating the release liner substrate with a release treatment agent. The release treatment agent can be a known release treatment agent such as a polysiloxane-based release treatment agent, a long-chain alkyl-based release treatment agent, a fluorine-containing type release treatment agent, molybdenum(IV) sulfide, etc. In some embodiments, a release liner having a release treatment layer formed by a polysiloxane-based release treatment agent can be preferably employed. The thickness and formation method of the release treatment layer are not particularly limited, and can be set in such a manner as to exhibit appropriate releasability on the surface of the adhesive side of the release liner.

[0051] As the release liner substrate, various plastic films can be used. In this specification, the plastic film is typically a non-porous sheet, which is a concept distinct from, for example, non-woven fabric (i.e., non-woven fabric is not included). As the above-mentioned release liner substrate, a resin film having a non-porous structure and typically substantially free of air bubbles (void-free) can be preferably used. The above-mentioned resin film can be a single-layer structure or a multi-layer structure of two or more layers (e.g., a three-layer structure).

[0052] Examples of the material of the above-mentioned plastic film include: polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN); polyolefin resins such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, ethylene-butene copolymer; cellulose resins such as triacetyl cellulose; acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, cyclic olefin resins such as norbornene resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymer resins, polyarylate resins, polyphenylene sulfide resins, etc. A release liner substrate formed of any one of these resins or a mixture of two or more of them can be used. Among them, as a preferred release liner substrate, a polyester resin film (e.g., a PET film) formed of a polyester resin can be cited.

[0053] The plastic film used as the above-mentioned release liner substrate can be any one of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, the above-mentioned plastic film can have a single-layer structure or a multi-layer structure including two or more sub-layers. Known additives that can be used for the release liner substrate, such as antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, slip agents, anti-blocking agents, and nucleating agents, can be incorporated into the above-mentioned plastic film. In the plastic film with a multi-layer structure, each additive can be incorporated into all sub-layers or only into a part of the sub-layers.

[0054] The thickness of the release liner is not particularly limited and can be, for example, about 10 μm to about 500 μm. From the viewpoints of the strength and dimensional stability of the release liner, it is appropriate for the thickness of the release liner to be 20 μm or more, preferably 30 μm or more, and can be 40 μm or more, 50 μm or more, 60 μm or more, or 70 μm or more. By protecting the adhesive surface with a release liner having a sufficient thickness, it is easy to maintain the smoothness of the adhesive surface. In addition, from the viewpoints of the operability of the release liner (for example, ease of winding), etc., it is appropriate for the thickness of the release liner to be 300 μm or less, preferably 200 μm or less, and can be 150 μm or less or 100 μm or less. When the thickness of the release liner is below a specified value, the removal from the double-sided adhesive sheet tends to become smooth.

[0055] The thicknesses of the first release liner and the second release liner can be the same or different. The ratio of the thickness t1 of the first release liner to the thickness t2 of the second release liner, that is, the thickness ratio (t1 / t2), can be, for example, about 0.3 to about 10. In some embodiments, the above thickness ratio (t1 / t2) can be about 0.5 to about 5, or can be about 0.8 to about 1.2. In some other embodiments, the ratio (t1 / t2) can be greater than or equal to 0.3 and less than 1, can be greater than or equal to 0.5 and less than 1, or can be 0.5 to 0.9. By using the first release liner and the second release liner having the above thickness ratio (t1 / t2), it is easy to obtain good peeling workability and operability.

[0056] <Adhesive layer>

[0057] In the double-sided adhesive sheet disclosed herein, the adhesive layer (in the embodiment having the first adhesive layer and the second adhesive layer, at least one of the first adhesive layer and the second adhesive layer. The same applies hereinafter unless otherwise specified.) is colored. According to the double-sided adhesive sheet having a colored adhesive layer, the adherend can be masked while bonding the adherend. In addition, by adjusting the degree of coloring of the adhesive layer, optical properties such as light transmittance can be adjusted, and design and hue can be imparted to the surface of the adherend.

[0058] (Viscoelastic properties)

[0059] In the double-sided adhesive sheet disclosed herein, the adhesive layer is characterized in that the storage modulus at 0 °C (0 °C storage modulus) is 0.95 MPa or less. By adjusting the 0 °C storage modulus of the above-mentioned adhesive layer to 0.95 MPa or less, it is possible to highly suppress the deformation of the adhesive surface caused by the peeling of the release liner. More specifically, by designing the peeling force difference between the peeling force R1 of the first release liner and the peeling force R2 of the second release liner to be 0.07 N / 50 mm or more as described above, in addition to suppressing the occurrence of phenomena such as the release liner being pulled by the adhesive surface and deforming in the thickness direction of the adhesive surface (undulations, striped roughening, etc.) during the peeling of the release liner, even if a visually recognizable size of deformation occurs on the adhesive surface during the peeling of the release liner, the above deformation is relaxed in a short time through the surface shape relaxation effect of the adhesive based on the above 0 °C storage modulus, and there is no such deformation or the above deformation is highly suppressed after being pasted onto the adherend. In addition, in a double-sided adhesive sheet having a colored adhesive layer, the deformation of the adhesive surface is likely to be conspicuous, but on the adhesive surface of the adhesive layer having the above 0 °C storage modulus, the above deformation is highly suppressed, so it has excellent appearance quality.

[0060] In some embodiments, from the perspective of suppressing the deformation of the adhesive surface, the above 0 °C storage modulus is 0.85 MPa or less, can be 0.75 MPa or less, or can be 0.65 MPa or less. In some preferred embodiments, the above 0 °C storage modulus is 0.60 MPa or less, more preferably 0.50 MPa or less, further preferably 0.40 MPa or less, particularly preferably 0.30 MPa or less, can be 0.25 MPa or less, can be 0.22 MPa or less, can be 0.20 MPa or less, or can be 0.18 MPa or less. In addition, from the perspective of improving the processability of the double-sided adhesive sheet, etc., in some embodiments, the above 0 °C storage modulus is about 0.01 MPa or more, can be about 0.05 MPa or more. In addition, when the release liner is peeled from the surface of the adhesive layer (adhesive surface) at a specified speed, from the perspective of suppressing the deformation of the surface of the adhesive layer being pulled by the release liner, in some preferred embodiments, the above 0 °C storage modulus is about 0.10 MPa or more, more preferably 0.15 MPa or more, can be 0.20 MPa or more, or can be 0.24 MPa or more. In some other embodiments, the above 0 °C storage modulus can be 0.35 MPa or more, can be 0.45 MPa or more, or can be 0.55 MPa or more. The above 0 °C storage modulus is specifically measured by the method described in the examples below.

[0061] Although there is no particular limitation, from the viewpoints such as adhesiveness to adherends, in some embodiments, the storage modulus of the adhesive layer at 23°C (23°C storage modulus) is about 0.15 MPa or less, preferably 0.13 MPa or less, more preferably 0.12 MPa or less, further preferably 0.11 MPa or less, and may also be less than 0.10 MPa. By adjusting the above 23°C storage modulus to a specified value or less, the adhesive layer closely contacts the smooth release surface of the release liner, and thus it is likely to become a smooth adhesive surface even after the release liner is peeled off. In addition, after being pasted onto an adherend, the adhesive layer adheres to the adherend, and it is easy to form a homogeneous adhesive interface without bulges and air bubbles mixed in. In some preferred embodiments, the above 23°C storage modulus is 0.08 MPa or less, may be 0.07 MPa or less, may be 0.06 MPa or less, and may also be 0.05 MPa or less. In addition, in some embodiments, the above 23°C storage modulus is about 0.005 MPa or more, and may be about 0.01 MPa or more. In some preferred embodiments, the above 23°C storage modulus is about 0.02 MPa or more, may be 0.03 MPa or more, may be 0.05 MPa or more, may be 0.06 MPa or more, may be 0.07 MPa or more, and may also be 0.08 MPa or more. The higher the 23°C storage modulus, the more likely the cohesion of the adhesive layer is to increase. For example, the processability is improved, and in addition, by having appropriate cohesion, there is a tendency to easily obtain adhesive reliability. The above 23°C storage modulus is specifically measured by the method described in the examples below.

[0062] (Light transmittance)

[0063] The light transmittance of the colored adhesive layer varies depending on the purpose of use, the purpose of coloring, etc., and is not limited to a specific range, but generally the colored adhesive layer has a lower light transmittance than the transparent adhesive layer. For example, in some embodiments, the light transmittance of the adhesive layer at a wavelength of 550 nm (550 nm light transmittance. Also referred to as visible light transmittance.) is less than 80%, can be less than 70%, can be less than 60%, can be less than 50%, and can also be less than 40%. The double-sided adhesive sheet with a reduced visible light transmittance due to the coloring of the adhesive layer is suitable for masking the adherend and can also be used to impart design. In addition, it can also be used as a light-shielding adhesive sheet for the purpose of preventing light leakage, etc. In some preferred embodiments, the 550 nm light transmittance of the adhesive layer is 30% or less, can be 20% or less, can be 15% or less, can be 10% or less, can be 8% or less, and can also be 6% or less. The lower the visible light transmittance, the better the masking property can be exerted. In the case where higher masking property is required, the above 550 nm light transmittance can be less than 5%, can be less than 4%, can be less than 3%, can be less than 2%, can be less than 1%, and can also be less than 0.5%. The lower limit of the above 550 nm light transmittance is not particularly limited, can be substantially 0%, i.e., below the detection limit, can be 0.1% or more, can be 1% or more, can be 3% or more, and can also be 5% or more. In some embodiments, the above 550 nm light transmittance can be 10% or more, can be greater than 20%, and can also be greater than 30%. By having a certain degree of visible light transmittance, the adherend can be moderately masked, or the appearance of the adherend (such as a metal material) can be adjusted, or a design and hue with the texture of the adherend remaining can be imparted. In addition, from the viewpoints of maintaining adhesive properties, productivity, etc., an adhesive layer with moderate light transmittance is also preferred. The 550 nm light transmittance of the adhesive layer can be measured by the method described in the following examples.

[0064] Although not particularly limited, the light transmittance of the adhesive layer at a wavelength of 1380 nm (1380 nm light transmittance, also referred to as infrared transmittance) is less than 90%, can be less than 80%, can be less than 70%, can be less than 60%, can be less than 50%, or can also be less than 40%. In some preferred embodiments, the 1380 nm light transmittance of the adhesive layer is 30% or less, can be 20% or less, can be 15% or less, can be 10% or less, can be 5% or less, or can also be 3% or less. According to the adhesive layer that limits the above infrared transmittance, it is possible to block light in a wide wavelength region including infrared rays, and it is easy to obtain excellent light-shielding properties. In addition, for example, when used around an infrared sensor, by blocking infrared rays, it is possible to prevent the reduction of the operation accuracy of the sensor. The lower limit of the above 1380 nm light transmittance is not particularly limited, and can be substantially 0%, that is, below the detection limit, can be 0.1% or more, can be 1% or more, can be 3% or more, or can also be 5% or more. In some embodiments, the above 1380 nm light transmittance can be 10% or more, can be 30% or more, or can also be 50% or more. The 1380 nm light transmittance of the adhesive layer can be measured by the method described in the following examples.

[0065] There is no particular limitation on the relative relationship between the visible light transmittance and the infrared transmittance of the adhesive layer. In some embodiments, the infrared transmittance T IR [%] and the visible light transmittance T VL [%] ratio (T IR / T VL ) is, for example, in the range of 0.1 to 10, can be 5 or less, can be 3 or less, and can also be 0.5 or more, can be 1 or more (e.g., greater than 1), or can also be 2 or more. By appropriately setting the ratio (T IR / T VL ) according to the use purpose, application site, etc. of the double-sided adhesive sheet, it is possible to achieve the target adherend masking property and infrared shielding property.

[0066] (Acrylic polymer)

[0067] The adhesive layer constituting the double-sided adhesive sheet disclosed herein contains an acrylic polymer. The above-mentioned adhesive layer is typically an adhesive layer having an acrylic polymer as the base polymer. Such an adhesive layer is also referred to as an acrylic adhesive layer. It should be noted that the base polymer refers to the main component of the rubber-like polymer (a polymer showing rubber elasticity in the temperature range near room temperature) contained in the adhesive layer. In addition, in this specification, the "main component" refers to a component having a content greater than 50% by weight in the absence of special description. In addition, the following description of the components that can be contained in the adhesive and the adhesive layer can be applied to the adhesive composition used for forming the adhesive (layer) as long as there is no special description.

[0068] In addition, in this specification, an "acrylic polymer" refers to a polymer containing monomer units derived from monomers having at least one (meth)acryloyl group in one molecule as the monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer". Therefore, the acrylic polymer in this specification is defined as a polymer containing monomer units derived from acrylic monomers. It should be noted that in this specification, "(meth)acryloyl group" generically represents the meanings of acryloyl group and methacryloyl group. Similarly, "(meth)acrylate" generically represents the meanings of acrylate and methacrylate, and "(meth)acrylic acid" generically represents the meanings of acrylic acid and methacrylic acid.

[0069] As the acrylic polymer in the technology disclosed herein, a polymer of a monomer raw material preferably containing, for example, an alkyl (meth)acrylate as the main monomer and optionally further containing a comonomer copolymerizable with the main monomer is preferred. Here, the main monomer refers to a component having a content greater than 50% by weight in the monomer composition of the above monomer raw material.

[0070] As the alkyl (meth)acrylate, a compound represented by the following formula (1) can be preferably used, for example.

[0071] CH2=C(R 1 )COOR 2 (1)

[0072] Wherein, R 1 in the above formula (1) is a hydrogen atom or a methyl group. In addition, R 2 is a linear alkyl group having 1 to 20 carbon atoms. Hereinafter, such a carbon atom number range is sometimes expressed as "C 1-20 ". From the viewpoints such as the storage modulus of the adhesive, with R 2 being C 1-14 (for example, being C 1-10 , typically being C 4-8An alkyl (meth)acrylate having a chain-like alkyl group of ( ) is suitable as the main monomer.

[0073] As R 2 is C 1-20 Specific examples of the alkyl (meth)acrylate having a chain-like alkyl group of are not particularly limited, and examples thereof include: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. These alkyl (meth)acrylates can be used alone or in combination of two or more.

[0074] The proportion of the alkyl (meth)acrylate in the monomer components constituting the acrylic polymer is typically greater than 50% by weight, for example, it can be 70% by weight or more, it can be 85% by weight or more, and it can also be 90% by weight or more (for example, greater than 90% by weight), and 92% by weight or more is suitable, it can be 94% by weight or more, and it can also be greater than 95% by weight. The upper limit of the proportion of the alkyl (meth)acrylate is not particularly limited, and it is preferably 99.5% by weight or less (for example, 99% by weight or less), or, from the viewpoint of preferably exhibiting the characteristics (such as cohesion) based on comonomers such as carboxyl group-containing monomers, it can be 98% by weight or less (for example, less than 97% by weight). Or, the acrylic polymer can be a polymer obtained by substantially polymerizing only the alkyl (meth)acrylate.

[0075] In some embodiments, it is preferred that R in the above formula (1) 1 is a hydrogen atom and R 2 is C 4-8 alkyl acrylate having a chain-like alkyl group of (hereinafter, also simply referred to as acrylic C 4-8 alkyl ester.) as the main monomer. According to the acrylic polymer containing acrylic C 4-8 alkyl ester as a monomer component, the storage modulus at 0 °C of the adhesive layer can be moderately reduced. When using acrylic C 4-8When the alkyl ester is used as a monomer component, the proportion of the C 4-8 alkyl acrylate in the monomer component is, for example, more than 50% by weight, preferably 70% by weight or more, more preferably 90% by weight or more (e.g., more than 90% by weight), still more preferably 92% by weight or more, and may be 94% by weight or more (e.g., more than 95% by weight). The C 4-8 alkyl acrylate has no particular limitation on the upper limit of its proportion. For example, it is preferably 99% by weight or less, and from the viewpoint of satisfactorily exhibiting the properties (e.g., cohesion) based on comonomers such as carboxyl group-containing monomers, it may be 98% by weight or less (e.g., less than 97% by weight). The C 4-8 alkyl acrylate may be used alone or in combination of two or more. As preferred examples of the C 4-8 alkyl acrylate, n-butyl acrylate (BA), n-heptyl acrylate (n-HpA), and 2-ethylhexyl acrylate (2EHA) can be mentioned.

[0076] In some embodiments, the monomer component constituting the above acrylic polymer contains BA. The proportion of BA in the monomer component of the acrylic polymer is, for example, more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, still more preferably 85% by weight or more, particularly preferably 90% by weight or more (e.g., more than 90% by weight), may be 92% by weight or more, may be 94% by weight or more, may be 95% by weight or more, and may also be 96% by weight or more. According to the acrylic polymer containing BA as the main monomer component, an adhesive having good adhesion reliability to the adherend can be easily obtained. In addition, by using BA in a specified amount or more as the monomer component, for example, while enabling a colorant such as a black colorant (e.g., carbon black) to be well dispersed in the adhesive layer, the adhesive properties such as adhesive strength can be well maintained. From the viewpoint of copolymerizing other copolymerizable monomers, the proportion of BA in the monomer component may be 99% by weight or less, or may be 97% by weight or less.

[0077] In some preferred embodiments, the monomer component constituting the acrylic polymer contains heptyl acrylate. Compared with polymers of other acrylic alkyl esters such as n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA), the acrylic polymer obtained by polymerizing using a monomer component containing heptyl acrylate has more excellent flexibility. The reason is not particularly limited, but it is considered that the glass transition temperature of the polymer containing heptyl acrylate as a monomer unit is low, and the space between the main chains in the adhesive is relatively large. By using an acrylic polymer containing heptyl acrylate as a monomer component, it is easy to form an adhesive with a low storage modulus at 0 °C, and it is easy to obtain an adhesive with good surface shape relaxation. Among heptyl acrylates, n-heptyl acrylate is preferred from the viewpoint of flexibility. It is considered that the acrylic polymer synthesized by using n-heptyl acrylate as a monomer component has a relatively long straight-chain side chain, so the space between the main chains is more likely to become larger.

[0078] In some embodiments, the proportion of heptyl acrylate in the monomer component of the acrylic polymer is, for example, 50% by weight or more (e.g., greater than 50% by weight), 70% by weight or more is appropriate, preferably 80% by weight or more, more preferably 85% by weight or more, further preferably 90% by weight or more (e.g., greater than 90% by weight), particularly preferably 92% by weight or more, may be 94% by weight or more, may be 95% by weight or more, and may also be 96% by weight or more. By increasing the amount of heptyl acrylate used, its use effect can be effectively exhibited (e.g., reduction of the storage modulus of the adhesive at 0 °C, and further improvement of the surface shape relaxation effect of the adhesive). On the other hand, the upper limit of the proportion of heptyl acrylate in the monomer component is 100% by weight, may be 99% by weight or less, and may also be 98% by weight or less. From the viewpoint of copolymerizing a carboxyl group-containing monomer and other monomers, in some embodiments, the proportion of heptyl acrylate in the monomer component is less than 97% by weight. In some preferred embodiments, the proportion of heptyl acrylate in the monomer component is 96% by weight or less, may be 95% by weight or less, and may also be 94% by weight or less.

[0079] In the embodiment of using heptyl acrylate as a monomer component, an (alkyl) acrylate other than heptyl acrylate may be copolymerized in the acrylic polymer. As the (alkyl) acrylate other than heptyl acrylate, for example, an (alkyl) acrylate other than heptyl acrylate represented by the above formula (1) can be cited. The (alkyl) acrylate other than heptyl acrylate may be used alone or in combination of two or more.

[0080] In some embodiments, the proportion of heptyl acrylate in the total amount of the (meth)acrylic acid alkyl esters contained in the above monomer components is, for example, 50% by weight or more (specifically, 50% by weight to 100% by weight, for example, greater than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, still more preferably 90% by weight or more, particularly preferably 95% by weight or more, may be 99% by weight or more, or may be 100% by weight. By adopting such a monomer composition, the use effect of heptyl acrylate can be effectively exerted.

[0081] In some embodiments, the above monomer components may contain a (meth)acrylic acid alkyl ester having an alkyl group derived from biomass at the ester terminal (hereinafter also referred to as “(meth)acrylic acid biomass alkyl ester”). In recent years, environmental problems such as global warming have been taken seriously, and it is desired to reduce the usage amount of fossil resource-based materials such as petroleum. In such a situation, reducing the usage amount of fossil resource-based materials is also required in the field of adhesives. By using the (meth)acrylic acid biomass alkyl ester, an acrylic adhesive that takes into account the suppression of dependence on fossil resource-based materials can be appropriately achieved.

[0082] (Meth)acrylic acid biomass alkyl ester is not particularly limited. For example, it is an ester of an alkanol derived from biomass and (meth)acrylic acid derived from biomass or non-biomass. Examples of the alkanol derived from biomass include alkanols derived from plant raw materials such as bioethanol, palm oil, palm kernel oil, coconut oil, and castor oil. When the number of carbon atoms of the alkanol derived from biomass is 3 or more, the alkanol may be linear or may have a branched chain. In some embodiments, as the (meth)acrylic acid biomass alkyl ester used in the synthesis of an acrylic polymer, an ester of an alkanol derived from biomass and (meth)acrylic acid derived from non-biomass can be used. In this (meth)acrylic acid biomass alkyl ester, the larger the number of carbon atoms of the alkanol, the higher the number ratio of the carbon derived from biomass in the total number of carbon atoms contained in this (meth)acrylic acid biomass alkyl ester, that is, the biomass carbon ratio of the (meth)acrylic acid alkyl ester. Therefore, in the above (meth)acrylic acid biomass alkyl ester, from the viewpoint of reducing the dependence on fossil resource-based materials, it is preferred that the number of carbon atoms of the alkyl group derived from biomass is large. On the other hand, when the number of carbon atoms of the alkyl group constituting the (meth)acrylic acid alkyl ester is too large, there is a tendency that adhesive properties such as adhesiveness are difficult to obtain, and it also becomes disadvantageous from the viewpoints of productivity such as synthesis, operability, and cost. In the embodiment where an ester of an alkanol derived from biomass and (meth)acrylic acid derived from non-biomass is used as the (meth)acrylic acid biomass alkyl ester, it is preferred to use a material that balances adhesive properties and reduction of dependence on fossil resource-based materials (more specifically, the biomass carbon ratio of the above (meth)acrylic acid alkyl ester).

[0083] In some preferred embodiments, heptyl acrylate derived from biomass (biomass-derived heptyl acrylate) is used as heptyl acrylate. By using biomass-derived heptyl acrylate, it is possible to achieve the effects produced by the technology disclosed herein while reducing the dependence on fossil resource-based materials. The above-mentioned biomass-derived heptyl acrylate is an ester of an alkanol derived from biomass and acrylic acid derived from biomass or non-biomass. For example, an ester of an alkanol derived from biomass and acrylic acid derived from non-biomass can be used. In this compound, only the heptyl group is derived from biomass. As the heptyl acrylate derived from biomass, n-heptyl acrylate derived from biomass (biomass-derived n-heptyl acrylate) is preferably used.

[0084] (The proportion of) biomass-derived alkyl (meth)acrylate (preferably biomass-derived heptyl acrylate) in the monomer components of the above acrylic polymer is, for example, 50% by weight or more (e.g., greater than 50% by weight) in some embodiments, preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, particularly preferably 90% by weight or more, can be 92% by weight or more, can be 94% by weight or more, or can also be 96% by weight or more. In addition, the proportion of biomass-derived alkyl (meth)acrylate (preferably biomass-derived heptyl acrylate) in the monomer components is less than 97% by weight. In some embodiments, it can be 95% by weight or less, can be 93% by weight or less, or can also be 91% by weight or less.

[0085] In addition, the monomer components of the acrylic polymer preferably contain a carboxyl group-containing monomer. The carboxyl group-containing monomer can enhance the cohesion based on its polarity. In addition, when a crosslinking agent such as an isocyanate or an epoxy crosslinking agent is used, this carboxyl group can become a crosslinking point of the acrylic polymer. By using a carboxyl group-containing monomer, it is easy to obtain an adhesive having appropriate cohesion. In addition, by using a carboxyl group-containing monomer, for example, it is possible to exhibit more excellent adhesiveness to adherends such as high-polarity materials. Furthermore, by copolymerizing an appropriate amount of a carboxyl group-containing monomer, for example, even when a black colorant such as carbon black is incorporated into the adhesive, it is easy to disperse the colorant well in the layer, and the adhesive properties can be satisfactorily maintained.

[0086] As the carboxyl group-containing monomer, for example, the following can be mentioned: ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, isocrotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, citraconic acid. In addition, the carboxyl group-containing monomer can be a monomer having a metal salt (e.g., an alkali metal salt) of a carboxyl group. The carboxyl group-containing monomer can be used alone or in combination of two or more. Among them, as the preferred carboxyl group-containing monomers, AA and MAA can be mentioned. AA is particularly preferred. When using one or two or more carboxyl group-containing monomers, the proportion of AA in the above carboxyl group-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, further preferably 90% by weight or more. In a particularly preferred embodiment, the carboxyl group-containing monomer substantially consists only of AA. Considering the combined effects such as the polarity based on its carboxyl group, the role as a crosslinking point, and Tg (106 °C), AA is considered to be one of the best monomer materials for achieving adhesive properties in a balanced manner among the carboxyl group-containing monomers disclosed herein.

[0087] The proportion of the carboxyl group-containing monomer in the monomer component of the acrylic polymer is not particularly limited, and can be 0.1% by weight or more, can be 0.5% by weight or more, can be 1% by weight or more, or can be 2% by weight or more. In some preferred embodiments, the proportion of the carboxyl group-containing monomer in the above monomer component is greater than 3% by weight (specifically greater than 3.0% by weight), preferably 4.0% by weight or more, more preferably 4.5% by weight or more, further preferably 5.0% by weight or more (e.g., greater than 5.0% by weight), particularly preferably 5.5% by weight or more, can be 6.0% by weight or more, can be 6.5% by weight or more, or can be 7.0% by weight or more. By increasing the amount of the carboxyl group-containing monomer used, the cohesion of the adhesive layer can be improved based on the action of the carboxyl group-containing monomer. In addition, the amount of the carboxyl group-containing monomer is suitably, for example, 20% by weight or less of the monomer component, preferably 15% by weight or less, more preferably 12% by weight or less. In some preferred embodiments, the amount of the above carboxyl group-containing monomer can be 10% by weight or less, can be 8% by weight or less, can be 6% by weight or less, or can be 5% by weight or less. By reducing the amount of the carboxyl group-containing monomer (e.g., AA) used, there is a tendency for the storage modulus at 0 °C to decrease.

[0088] In the acrylic polymer, a functional group-containing monomer (including any functional group monomer) other than the carboxyl group-containing monomer can be copolymerized. As the functional group-containing monomer that can form a crosslinking base point or contribute to improving the adhesive strength in the acrylic polymer, examples include: monomers containing a hydroxyl group (OH group) (2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc., hydroxyalkyl (meth)acrylates; polypropylene glycol mono(meth)acrylate, etc.), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.), amino group-containing monomers ((meth)acrylic acid aminoethyl ester, N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers having a nitrogen atom-containing ring (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl group-containing monomers, imide group-containing monomer classes, etc. The above-mentioned any functional group-containing monomers can be used alone or in combination of two or more.

[0089] When the monomer component constituting the acrylic polymer contains the above-mentioned any functional group-containing monomer, the content of the any functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the effects brought about by using the any functional group-containing monomer, the content of the any functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, preferably 0.5% by weight or more, and can also be 1% by weight or more. In addition, for example, in a mode where the monomer component of the acrylic polymer contains heptyl acrylate and a carboxyl group-containing monomer, from the viewpoint of easily obtaining a balance of adhesive properties through the relationship with these monomer components, the content of the any functional group-containing monomer in the monomer component is preferably 40% by weight or less, more preferably 20% by weight or less, and can also be 10% by weight or less (for example, 5% by weight or less). In some modes, the content of the any functional group-containing monomer in the monomer component is, for example, less than 3% by weight, can be less than 1% by weight, can be less than 0.5% by weight, can be less than 0.3% by weight, and can also be less than 0.1% by weight. The technology disclosed herein can preferably be implemented in such a way that the monomer component of the acrylic polymer substantially does not contain any functional group-containing monomer.

[0090] It should be noted that in this specification, the monomer component substantially does not contain monomer A (such as the above-mentioned any functional group-containing monomer) means that at least the monomer A is not intentionally used, and it is allowed to unintentionally contain the monomer A at, for example, about 0.01% by weight or less.

[0091] In addition, a hydroxyl group-containing monomer can be used as the above-mentioned monomer having any functional group. In this case, the content of the hydroxyl group-containing monomer in the monomer component is preferably about 10% by weight or less (for example, 0.001% by weight to 10% by weight), more preferably about 5% by weight or less, and still more preferably about 2% by weight or less. In some embodiments, the content of the hydroxyl group-containing monomer in the monomer component can be, for example, less than 1% by weight, less than 0.5% by weight, less than 0.3% by weight, less than 0.1% by weight, or less than 0.01% by weight. The monomer component of the acrylic polymer can substantially not contain a hydroxyl group-containing monomer. In the technology disclosed herein, the desired properties and effects can be satisfactorily achieved by restricting the amount of the hydroxyl group-containing monomer used or by using a monomer composition that does not contain a hydroxyl group-containing monomer.

[0092] From the viewpoint of effectively exerting the effect of copolymerizing the carboxyl group-containing monomer, the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers (the total functional group-containing monomers including the carboxyl group-containing monomer) used as the copolymerization component of the acrylic polymer is preferably 30% by weight or more, more preferably 50% by weight or more, still more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more. For example, it can be 95% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more (for example, 99.9% by weight or more). The upper limit of the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers is 100% by weight, and for example, it can be 95% by weight or less.

[0093] For the purpose of improving cohesion and the like, the monomer component constituting the acrylic polymer may also contain other copolymerization components in addition to the above-mentioned functional group-containing monomers. Examples of other copolymerization 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; (meth)acrylates containing an aromatic ring such as (meth)acrylic acid aryl esters (for example, phenyl (meth)acrylate), (meth)acrylic acid aryloxyalkyl esters (for example, phenoxyethyl (meth)acrylate), and (meth)acrylic acid aralkyl esters (for example, 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 above-mentioned other copolymerization components can be used alone or in combination of two or more.

[0094] The amount of the other copolymerizable component can be appropriately selected according to the purpose and use, and there is no particular limitation. However, from the viewpoint of appropriately exerting the effects brought about by using the other copolymerizable component, it is appropriate that the amount of the other copolymerizable component is 0.05% by weight or more, and it can also be 0.5% by weight or more. In addition, from the viewpoint of easily obtaining a balance in adhesive properties, it is appropriate that the content of the other copolymerizable component in the monomer component is 20% by weight or less. From the viewpoint of appropriately exerting the adhesive characteristics based on the essential monomer component, the amount of the other copolymerizable component is preferably 10% by weight or less, more preferably 8% by weight or less, and further preferably less than 5% by weight. For example, it can be less than 3% by weight or less than 1% by weight. The technology disclosed herein can preferably be implemented in such a manner that the monomer component substantially does not contain other copolymerizable components.

[0095] The acrylic polymer may contain a polyfunctional monomer having at least two polymerizable functional groups having an unsaturated double bond such as (meth)acryloyl group and vinyl group (typically a free-radical polymerizable functional group) as the other monomer component. By using a polyfunctional monomer as the monomer component, the cohesion of the adhesive layer can be improved. The polyfunctional monomer can be used as a crosslinking agent. There is no particular limitation on the polyfunctional monomer. For example, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, neopentyl glycol di(meth)acrylate, etc. can be cited. The polyfunctional monomer can be used alone or in combination of two or more.

[0096] The amount of the polyfunctional monomer used is not particularly limited and can be appropriately set in a manner that achieves the purpose of using the polyfunctional monomer. The amount of the polyfunctional monomer used can be about 3% by weight or less of the above monomer component, preferably about 2% by weight or less, and more preferably about 1% by weight or less (for example, about 0.5% by weight or less). The lower limit of the amount used in the case of using the polyfunctional monomer can be greater than 0% by weight and there is no particular limitation. Generally, by setting the amount of the polyfunctional monomer used to be about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component, the use effect of the polyfunctional monomer can be appropriately exerted.

[0097] In a particularly preferred embodiment, as the acrylic polymer, an acrylic polymer synthesized using a monomer component substantially containing heptyl acrylate (preferably n-heptyl acrylate) and a carboxyl group-containing monomer (preferably acrylic acid) can be used. According to the above monomer composition, the effects of heptyl acrylate and the carboxyl group-containing monomer can be effectively exerted, good adhesion characteristics can be obtained, and at the same time, a storage modulus at 0 °C below a specified value can be satisfactorily achieved. From such a viewpoint, it is appropriate that the total proportion of heptyl acrylate and the carboxyl group-containing monomer in the above monomer component is 90% by weight or more (90% by weight to 100% by weight), preferably 95% by weight or more, more preferably 99% by weight or more, further preferably greater than 99.5% by weight, particularly preferably greater than 99.9% by weight (for example, greater than 99.99% by weight), and the total proportion of heptyl acrylate and the carboxyl group-containing monomer in the above monomer component can be 100% by weight.

[0098] The biomass carbon ratio of the monomer component constituting the above acrylic polymer (biomass carbon ratio of the acrylic polymer) can be, for example, 1% or more, appropriately 10% or more, preferably 30% or more, more preferably 50% or more (for example, greater than 50%), can be 70% or more, can be 80% or more, or can also be 90% to 100%. By designing in this way, an acrylic adhesive that takes into account the suppression of dependence on fossil resource-based materials can be obtained.

[0099] Although not particularly limited, it is appropriate to design the copolymerization composition of the acrylic polymer so that the glass transition temperature (Tg) of the polymer is about -15 °C or lower (for example, about -70 °C or higher and about -15 °C or lower). Here, the Tg of the acrylic polymer refers to the Tg obtained by the Fox formula based on the composition of the monomer component used in the synthesis of the polymer. The Fox formula is as follows. The Fox formula is a relational expression between the Tg of the copolymer and the glass transition temperatures Tgi of the homopolymers obtained by homopolymerizing the monomers constituting the copolymer.

[0100] 1 / Tg = Σ(Wi / Tgi)

[0101] It should be noted that in the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0102] As the glass transition temperature of the homopolymer used in the calculation of Tg, the values described in publicly known materials, specifically "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) can be used. For monomers for which multiple values are described in this literature, the highest value is adopted. In the case where it is not described in the above Polymer Handbook, the value obtained by the measurement method described in Japanese Patent Application Laid-Open No. 2007-51271 is used.

[0103] Although not particularly limited, from the viewpoints of impact resistance and adhesiveness to the adherend, it is advantageous for the Tg of the acrylic polymer to be about -25°C or lower, preferably about -35°C or lower, and more preferably about -40°C or lower. In some embodiments, from the viewpoint of cohesion, the Tg of the acrylic polymer is, for example, about -70°C or higher, and can be, for example, about -65°C or higher, can be about -60°C or higher, and can also be about -55°C or higher. The technology disclosed herein can be preferably implemented in such a manner that the Tg of the acrylic polymer is about -65°C or higher and about -35°C or lower (for example, about -55°C or higher and about -40°C or lower). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the types and usage ratios of the monomers used to synthesize the polymer).

[0104] The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthesis methods for acrylic polymers, such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization, can be appropriately employed. For example, solution polymerization can be preferably employed. As the monomer supply method during solution polymerization, a one-time input method of supplying all monomer raw materials at once, a continuous supply (dropwise addition) method, a batch supply (dropwise addition) method, etc. can be appropriately adopted. The polymerization temperature can be appropriately selected according to the types of monomers and solvents used, the type of polymerization initiator, etc., and can be, for example, about 20°C to about 170°C (typically about 40°C to about 140°C).

[0105] The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixed solvent of two or more solvents selected from aromatic compounds such as toluene (typically aromatic hydrocarbons); acetate esters such as ethyl acetate; aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane; halogenated alkanes such as 1,2-dichloroethane; lower alcohols such as isopropyl alcohol (for example, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; ketones such as methyl ethyl ketone; etc. can be used.

[0106] The initiator for polymerization can be appropriately selected from conventionally well-known polymerization initiators according to the type of polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of the polymerization initiator include: persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide (BPO) and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; etc. Another other example of the polymerization initiator includes redox initiators composed of a peroxide and a reducing agent. Such polymerization initiators can be used alone or in combination of two or more. The usage amount of the polymerization initiator can be a usual usage amount. For example, it can be selected from the range of about 0.005 parts by weight to about 1 part by weight (typically about 0.01 parts by weight to about 1 part by weight) relative to 100 parts by weight of the total monomer components.

[0107] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and an acrylic polymer having an appropriate Mw capable of achieving the above-mentioned storage modulus characteristics at 0 °C can be used. For example, the Mw of the acrylic polymer can be in the range of about 10×10 4 to about 500×10 4 . From the viewpoint of adhesion performance, the Mw of the base polymer can be about 20×10 4 or more, can be about 30×10 4 or more, can be about 40×10 4 or more, and can also be 50×10 4As described above. In some embodiments, the Mw of the acrylic polymer is greater than 600,000, may be greater than 650,000, suitably 700,000 or more, and may be 750,000 or more. The larger the Mw of the acrylic polymer, the more likely it is to obtain an adhesive with good cohesion. In some preferred embodiments, the Mw of the acrylic polymer is 800,000 or more, may be 850,000 or more, may be 900,000 or more, may be 1,000,000 or more (e.g., greater than 1,000,000), may be 1,200,000 or more, may be 1,400,000 or more, may be 1,500,000 or more, and may also be 1,600,000 or more. For example, according to the monomer composition containing heptyl acrylate, it is easy to maintain a low viscosity, so the synthesis of high molecular weight polymers is good, and it is easy to obtain an acrylic polymer with the above Mw. In addition, by using an acrylic polymer containing heptyl acrylate as a monomer unit and having an Mw of a specified value or more, based on the viscoelastic properties (specifically, the storage modulus at 0 °C) based on the chemical structure of the polymer and the cohesion based on the molecular weight, it is possible to satisfactorily balance the surface shape relaxation effect of the adhesive surface and the adhesive properties. On the other hand, from the viewpoints of adhesive properties such as adhesive strength and ease of synthesis, the Mw of the acrylic polymer is generally suitably about 3,000,000 or less, preferably 2,500,000 or less, more preferably 2,000,000 or less, further preferably 1,800,000 or less, may be 1,500,000 or less, and may also be 1,300,000 or less. In some preferred embodiments, the Mw of the acrylic polymer may be 1,100,000 or less, may be 1,000,000 or less, may be 950,000 or less, and may also be 900,000 or less.

[0108] The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and obtained in terms of the value converted to standard polystyrene. Specifically, the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation) can be used as the GPC measuring device, and the measurement can be carried out under the following conditions to obtain the result. The same applies to the following examples.

[0109] [GPC measurement conditions]

[0110] Sample concentration: 0.2 wt% (tetrahydrofuran solution)

[0111] Sample injection volume: 10 μL

[0112] Eluent: Tetrahydrofuran (THF)

[0113] Flow rate: 0.6 mL / min

[0114] Column temperature (measurement temperature): 40 °C

[0115] Column:

[0116] Sample column: 1 piece of "TSKguardcolumn Super HZ-H" (trade name) + 2 pieces of "TSKgel Super HZM-H" (trade name) (manufactured by Tosoh Corporation)

[0117] Reference column: 1 piece of "TSKgel SuperH-RC" (trade name) (manufactured by Tosoh Corporation)

[0118] Detector: Differential refractive index detector (RI)

[0119] Standard sample: Polystyrene

[0120] (Colorant)

[0121] In the technology disclosed herein, the colored adhesive layer typically contains a colorant. By using the colorant, the adhesive layer is colored and can become an object having target optical properties (such as light transmittance), masking property, design property, and hue. The colorant can be, for example, a colorant such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, etc. The above colorant can typically be contained in the adhesive layer in a state of being dispersed in the constituent material of the adhesive layer (which can be a dissolved state). As the colorant, conventionally known pigments and dyes can be used. As pigments, inorganic pigments and organic pigments can be cited. The colorant can be used alone or in combination of two or more. It should be noted that in the case where the double-sided adhesive sheet disclosed herein contains an uncolored adhesive layer, the adhesive layer substantially does not contain a colorant.

[0122] The colorant is not particularly limited. For example, it can be a component that can absorb light traveling in the adhesive layer and attenuate it, and is a component that reduces the light transmittance of the adhesive layer by containing the colorant in the adhesive layer (therefore also referred to as a "light transmittance reducing component"). As such a colorant (hereinafter also referred to as a "first colorant"), a black colorant can be preferably used because the masking property and light shielding property can be efficiently adjusted by using a small amount. Specific examples of the black colorant include: carbon black, graphite, aniline black, perylene black, cyanine black, titanium black, inorganic pigment hematite, activated carbon, molybdenum disulfide, chromium complex, anthraquinone-based colorants, etc. The black colorant can be used alone or in appropriate combination of two or more.

[0123] In some preferred embodiments, the adhesive layer contains carbon black particles as a colorant (first colorant). As the carbon black particles used, carbon black particles generally referred to as carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.) can be used without particular limitation. In addition, as the carbon black particles, 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) can also be used. Such surface-modified carbon black particles are also referred to as self-dispersing carbon black, and do not require the addition of a dispersant, or can reduce the amount thereof added. The above carbon black particles can be used alone or in combination of two or more.

[0124] Particulate colorants (pigments) can be preferably used because the light transmittance of the adhesive layer can be efficiently adjusted by using a small amount. In some preferred embodiments, colorants (e.g., particulate black colorants such as carbon black) having an average particle diameter of about 10 nm or more (e.g., about 30 nm or more) can be used. The above average particle diameter can be, for example, about 50 nm or more, can be about 100 nm or more, can be about 150 nm or more, can be about 200 nm or more, can be about 300 nm or more, and can also be about 350 nm or more. The upper limit of the average particle diameter of the above colorant is not particularly limited, and is, for example, about 3000 nm or less, and can also be about 1000 nm or less. From the viewpoint of reducing the light transmittance, it is appropriate that the average particle diameter of the above colorant is about 500 nm or less, can be about 300 nm or less, and can also be 200 nm or less.

[0125] It should be noted that the average particle diameter of the colorant in this specification refers to the volume average particle diameter. Specifically, it refers to the particle diameter (50% volume average particle diameter; hereinafter sometimes simply referred to as D 50 .) at which the cumulative value in the particle size distribution measured by a particle size distribution measuring device based on the laser scattering / diffraction method is 50%. As the measuring device, for example, a product named "Microtrac MT3000II" manufactured by MicrotracBell Corporation or its equivalent can be used.

[0126] In the technology disclosed herein, there is no particular limitation on the form of addition of a colorant (preferably a black colorant such as carbon black particles) to the adhesive composition. The colorant such as carbon black particles can be added to the adhesive composition in the form of a dispersion liquid in a state where the particles are dispersed in a dispersion medium. There is no particular limitation on the dispersion medium constituting the dispersion liquid, and examples thereof include water (ion-exchanged water, reverse osmosis water, distilled water, etc.), various organic solvents (alcohols such as ethanol; ketones such as acetone; ethers such as butyl cellosolve and propylene glycol monomethyl ether acetate; esters such as ethyl acetate; aromatic hydrocarbons such as toluene; and their mixed solvents), and an aqueous mixed solvent of water and the above organic solvents. The above dispersion liquid may contain the above dispersant. By mixing the above dispersion liquid into the adhesive composition, the adhesive composition contains a colorant (preferably a black colorant such as carbon black particles) and may also contain a dispersant.

[0127] In a manner where the adhesive layer contains a first colorant, the content of the first colorant (preferably a black colorant such as carbon black particles) is appropriately set in consideration of the masking property of the adherend, adjustment of optical properties (such as light transmittance), required adhesive properties, etc., and is not limited to a specific range. In addition, the content of the first colorant may vary depending on the type of adhesive, the shape and particle size of the first colorant, and the compatibility with the adhesive. The content of the first colorant in the adhesive layer is preferably about 0.01% by weight or more, may be 0.05% by weight or more, may be 0.1% by weight or more, and from the viewpoint of the masking property of the adherend, is preferably about 0.3% by weight or more, more preferably about 0.5% by weight or more. In some manners, the content of the above first colorant is preferably about 1% by weight or more (for example, greater than 1% by weight), and preferably about 2% by weight or more. In addition, in a manner where the adhesive layer contains a first colorant or a manner where the adhesive layer does not contain a first colorant, the content of the above first colorant (preferably a black colorant such as carbon black particles) may be about 30% by weight or less, is preferably about 20% by weight or less, more preferably about 10% by weight or less, further preferably about 7% by weight or less, and may be about 3% by weight or less. In some manners, the content of the above first colorant (preferably a black colorant such as carbon black particles) may be about 2% by weight or less, may be about 1% by weight or less, and may also be about 0.5% by weight or less (for example, 0.3% by weight or less). By restricting the content of the first colorant, there is a tendency to easily maintain adhesive properties such as adhesiveness.

[0128] In some other ways, the adhesive layer can be implemented in such a manner that it contains a second colorant (such as a metal oxide described below) as the colorant. The second colorant is defined as a colorant different from the first colorant. For example, in the case where the adhesive layer contains at least two colorants, at least one of the multiple colorants used is the above-mentioned first colorant, and another one of the above-mentioned colorants is the second colorant described below, and the first colorant and the second colorant are used. In some other ways, the adhesive layer may contain the second colorant and substantially not contain the above-mentioned first colorant.

[0129] The second colorant is not particularly limited. For example, it can be a component that reduces the light transmittance of the adhesive layer in the same way as the first adhesive, and it can also be a component that can reduce the amount of incident light into the adhesive layer. In addition, the second colorant can also be a component that imparts a color and color combination different from those of the first colorant. Such a second colorant can be selected from, for example, white colorants and gray colorants. The second colorant can be one or more selected from inorganic materials (such as metals, metal compounds), organic materials, and organic-inorganic composites. Specific examples of the second colorant can include: metal oxides such as titanium oxide (rutile titanium dioxide, anatase titanium dioxide, etc.), zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide; carbonate compounds such as magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate; hydroxides such as aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide; silicate compounds such as aluminum silicate, magnesium silicate, calcium silicate; barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, clay, kaolin, titanium phosphate, mica, gypsum, silica, diatomaceous earth, bentonite, lithopone, zeolite, sericite, halloysite hydrate, etc.; inorganic materials such as acrylic resins, polystyrene resins, polyurethane resins, amide resins, polycarbonate resins, silicone resins, urea-formaldehyde resins, melamine resins, etc. It should be noted that the second colorant does not contain carbon black particles and can be defined as a colorant different from carbon black particles. Typically, the second colorant does not contain a light-absorbing black colorant.

[0130] In some preferred embodiments, the adhesive layer contains a metal oxide as a second colorant. By using the first colorant (preferably a black colorant) and the metal oxide in combination, a color combination that cannot be obtained with a single colorant can be achieved, and at the same time, optical properties such as light transmittance can be adjusted. In addition, the masking property of the adherend can also be improved. As the metal oxide, it can be selected from the above materials. As a preferred example, titanium oxide, zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, and calcium oxide can be cited. Among them, titanium oxide, silicon oxide, and zirconium oxide are preferred, and titanium oxide is particularly preferred. The metal oxides can be used alone or in combination of two or more.

[0131] In an embodiment where the second colorant has a particle shape, the average particle size of the second colorant (for example, a white colorant, preferably metal oxide particles) is not particularly limited. Particles of an appropriate size that can achieve the desired optical properties (such as light transmittance) can be used according to the thickness of the adhesive layer, the type of adhesive, etc. The average particle size of the second colorant can be, for example, about 1 nm or more, and about 5 nm or more is appropriate. From the viewpoints of compatibility, operability, etc., the average particle size of the second colorant is preferably about 10 nm or more, can be about 20 nm or more, and can also be about 30 nm or more. From the viewpoint of maintaining adhesive properties, etc., the upper limit of the above average particle size is, for example, appropriately about 300 nm or less, preferably less than 100 nm (for example, 90 nm or less), more preferably about 70 nm or less, further preferably about 50 nm or less, and can also be about 35 nm or less (for example, about 25 nm or less).

[0132] In an embodiment where the adhesive layer contains a second colorant, the content of the second colorant (for example, a white colorant, preferably a metal oxide) in the adhesive layer is appropriately set in consideration of the effects of containing the second colorant and the required adhesive properties, etc., and is not limited to a specific range. In addition, the content of the second colorant can vary depending on the type of adhesive, the shape and particle size of the second colorant, the compatibility with the adhesive, etc. From the viewpoint of effectively obtaining the effects of containing the second colorant, the content of the second colorant in the adhesive layer is appropriately about 1% by weight or more, preferably about 2% by weight or more, more preferably about 3% by weight or more, can be about 4% by weight or more, and can also be about 5% by weight or more. In addition, in an embodiment where the adhesive layer contains a second colorant or does not contain a second colorant, from the viewpoints of compatibility with the adhesive component, adhesive strength, impact resistance, etc., for maintaining adhesive properties, etc., the content of the second colorant in the adhesive layer can be about 30% by weight or less, about 25% by weight or less is appropriate, can be about 20% by weight or less, can be about 15% by weight or less, can be about 12% by weight or less, can be about 10% by weight or less, and can also be about 8% by weight or less.

[0133] In a manner where the adhesive layer contains a first colorant and a second colorant, the use ratio of the amount C1 of the first colorant to the amount C2 of the second colorant is appropriately set in a manner to achieve the target adherend masking property, adjustment of optical properties (such as light transmittance), design, and hue, and is not limited to a specific range. In some manners, the weight ratio (C2 / C1) of the amount C1 of the first colorant (preferably a black colorant) to the amount C2 of the second colorant (such as a white colorant, preferably a metal oxide) is about 0.01 or more, 0.1 or more is appropriate, preferably 1 or more (such as greater than 1), can be 10 or more, can be 30 or more, and can also be 50 or more (such as 70 or more). The larger the above weight ratio (C2 / C1), the more satisfactorily the addition effect of the second colorant is exerted. Additionally, in some manners, the above weight ratio (C2 / C1) is about 1000 or less, 500 or less is appropriate, preferably 300 or less, can be 100 or less, can be 80 or less, and can also be 60 or less. The smaller the above weight ratio (C2 / C1), the more satisfactorily the addition effect of the first colorant is exerted. In a manner where the first colorant is a black colorant, there is a tendency for the adherend masking property to be improved.

[0134] In a manner where the adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant, there is no particular limitation on the content of colorants other than the black colorant and the metal oxide. For example, it can be less than 30% by weight of the entire adhesive layer, preferably less than 10% by weight. For example, it can be less than 5.0% by weight, can be less than 3.0% by weight (such as less than 2.0% by weight, further less than 1% by weight). The technology disclosed herein can be implemented in a manner having an adhesive layer that substantially does not contain colorants other than the black colorant and the metal oxide. It should be noted that in this specification, "substantially does not contain" means not intentionally adding. For example, the content in the adhesive layer can be 0.3% by weight or less (such as 0.1% by weight or less, typically 0.01% by weight or less).

[0135] It should be noted that as the colorant, from the viewpoint of compatibility with the adhesive component, a colorant obtained by surface-treating the materials (particle-like colorants) exemplified as the above colorant with a surface treatment agent can be used. As the surface treatment, an appropriate treatment can be selected according to the type of core particles, the type of dispersion medium, etc., and thus is not limited to a specific treatment.

[0136] The adhesive composition disclosed herein may contain components that contribute to improving the dispersibility of the above-described colorant. Such dispersibility-improving components may be, for example, polymers, oligomers, liquid resins, surfactants (anionic surfactants, cationic surfactants, nonionic surfactants, amphoteric surfactants), etc. The dispersibility-improving components may be used alone or in combination of two or more. The above dispersibility-improving components are preferably dissolved in the adhesive composition. The above oligomers may be, for example, low molecular weight polymers containing one or more of the above-exemplified acrylic monomers (e.g., acrylic oligomers with Mw less than about 10×10 4 , preferably less than 5×10 4 ). The above liquid resins may be, for example, tackifying resins with a softening point of about 50°C or lower, more preferably about 40°C or lower (typically tackifying resins such as rosin-based, terpene-based, hydrocarbon-based resins, e.g., hydrogenated methyl rosinate, etc.). By using such dispersibility-improving components, uneven dispersion of the colorant (e.g., particulate black colorants such as carbon black) can be suppressed, and further, color unevenness of the adhesive layer can be suppressed. Therefore, an adhesive layer with better appearance quality can be formed.

[0137] There is no particular limitation on the addition method of the dispersibility-improving component. It may be contained in a liquid containing a colorant (e.g., a black colorant such as carbon black particles) before being incorporated into the adhesive composition, or may be supplied to the adhesive composition at the same timing as the colorant or before or after adding the colorant.

[0138] There is no particular limitation on the content of the dispersibility-improving component. From the viewpoint of suppressing the influence on the adhesive properties (e.g., reduction in cohesiveness), it is appropriate to be about 20% by weight or less (preferably about 10% by weight or less, more preferably 7% by weight or less, e.g., about 5% by weight or less) of the entire adhesive layer. In some embodiments, the content of the dispersibility-improving component may be about 10 times or less (preferably about 5 times or less, e.g., about 3 times or less) the weight of the colorant. On the other hand, from the viewpoint of appropriately exerting the effect of the dispersibility-improving component, its content is appropriately about 0.2% by weight or more (typically about 0.5% by weight or more, preferably about 1% by weight or more) of the entire adhesive layer. In some embodiments, the content of the dispersibility-improving component may be about 0.2 times or more (preferably about 0.5 times or more, e.g., 1 time or more) the weight of the colorant.

[0139] The content of the colorant in the adhesive layer (in the case of containing two or more colorants, it is the total amount of two or more, the total content) can be appropriately set in consideration of the masking property of the target adherend, optical properties (light transmittance, etc.), design, hue, etc., and the required adhesive properties, etc., and is not limited to a specific range. The content of the colorant in the adhesive layer is about 0.1% by weight or more, and about 0.5% by weight or more is appropriate. From the viewpoint of the masking property of the adherend, etc., it is preferably about 1% by weight or more, more preferably about 1.5% by weight or more, and further preferably about 2% by weight or more. In some embodiments, the content of the colorant in the adhesive layer is appropriately about 3% by weight or more, can be about 5% by weight or more, and can also be about 7% by weight or more. From the viewpoints of maintaining compatibility with the adhesive component, adhesive strength, impact resistance, and other adhesive properties, etc., the content of the colorant in the adhesive layer can be about 30% by weight or less, and usually about 20% by weight or less is appropriate, can be about 15% by weight or less, can be about 10% by weight or less, can be about 8% by weight or less, can be about 6% by weight or less, and can also be about 4% by weight or less.

[0140] (Tackifying resin)

[0141] In some preferred embodiments, the adhesive layer contains a tackifying resin. By using a tackifying resin, the adhesive strength can be improved. According to the technology disclosed herein, an adhesive layer having specified viscoelastic properties (specifically, the storage modulus at 0°C) is achieved by a composition containing a tackifying resin. There is no particular limitation on the tackifying resin. For example, various tackifying resins such as rosin-based tackifying resins, terpene-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, polyamide-based tackifying resins, elastomer-based tackifying resins, phenol-based tackifying resins, and ketone-based tackifying resins can be used. Such tackifying resins can be used alone or in combination of two or more.

[0142] As specific examples of rosin-based tackifying resins, the following can be cited: unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc. The same applies hereinafter); various other rosin derivatives; etc. As examples of the above rosin derivatives, the following can be cited: substances obtained by esterifying unmodified rosin with alcohols (i.e., esters of rosin), substances obtained by esterifying modified rosin with alcohols (i.e., esters of modified rosin), etc., such as rosin esters; unsaturated fatty acid-modified rosins obtained by modifying unmodified rosin or modified rosin with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxyl groups in unmodified rosin, modified rosin, unsaturated fatty acid-modified rosins, or unsaturated fatty acid-modified rosin esters; metal salts of rosins such as unmodified rosin, modified rosin, and various rosin derivatives (especially rosin esters); rosin phenol resins obtained by adding phenol to rosins (unmodified rosin, modified rosin, various rosin derivatives, etc.) using an acid catalyst and performing thermal polymerization; etc. Among them, rosin esters are preferred.

[0143] Although not particularly limited, as specific examples of rosin esters, the following can be cited: esters of unmodified rosin or modified rosin (such as hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), for example, methyl esters, triethylene glycol esters, glycerol esters, pentaerythritol esters, etc.

[0144] As examples of terpene-based tackifying resins, the following can be cited: terpene resins such as α-pinene polymers, β-pinene polymers, and terpinene polymers; modified terpene resins obtained by modifying these terpene resins (phenol modification, aromatic modification, hydrogenation modification, hydrocarbon modification, etc.); etc. As an example of the above modified terpene resins, terpene phenol resin can be cited.

[0145] Terpene phenol resin refers to a polymer containing terpene residues and phenol residues, and is a concept that includes both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and resins obtained by phenol-modifying homopolymers or copolymers of terpenes (phenol-modified terpene resins). As specific examples of the terpenes constituting such terpene phenol resins, the following can be cited: monoterpenes such as α-pinene, β-pinene, and limonene (including the d-form, l-form, and d / l-form (terpinene)). Hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes also referred to as hydrogenated terpene phenol resin.

[0146] Examples of hydrocarbon tackifying resins include: aliphatic (C5 type) petroleum resins, aromatic (C9 type) petroleum resins, aliphatic / aromatic copolymer (C5 / C9 type) petroleum resins, their hydrogenated products (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), their various modified products (e.g., maleic anhydride modified products), coumarone resins, coumarone-indene resins, and other resins of various hydrocarbons.

[0147] In some embodiments, as the tackifying resin, at least one selected from rosin-based tackifying resins and terpene-based tackifying resins is preferably used. By incorporating a rosin-based tackifying resin and / or a terpene-based tackifying resin into the acrylic adhesive, it is easy to obtain excellent adhesive properties such as adhesive strength. In some preferred embodiments, the total proportion of the rosin-based tackifying resin and the terpene-based tackifying resin in the total tackifying resin contained in the adhesive layer can be, for example, greater than about 50% by weight (greater than about 50% by weight and less than or equal to about 100% by weight), can be about 70% by weight or more, can be about 80% by weight or more, can be about 90% by weight or more, can be 95% by weight or more, or can be 99% by weight or more.

[0148] As some preferred embodiments, there can be mentioned embodiments in which the above-mentioned tackifying resin contains one or more terpene phenol resins. The technology disclosed herein can be preferably implemented in a manner such that, for example, the terpene phenol resin is about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of the tackifying resin. The proportion of the terpene phenol resin in the total amount of the tackifying resin can be about 50% by weight or more, can be about 70% by weight or more, can be about 80% by weight or more, or can be about 90% by weight or more. It can be that substantially all of the tackifying resin (e.g., 95% by weight or more and 100% by weight or less, further 99% by weight or more and 100% by weight or less) is the terpene phenol resin.

[0149] The content of the terpene phenol resin in the adhesive layer is not particularly limited as long as the target viscoelastic properties are satisfied. In some embodiments, from the viewpoint of improving adhesive strength, the content of the terpene phenol resin is usually about 1 part by weight or more, and about 5 parts by weight or more is appropriate, preferably about 8 parts by weight or more, more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (e.g., 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. Additionally, in some embodiments, the content of the terpene phenol resin in the adhesive layer can be, for example, 70 parts by weight or less, can be 60 parts by weight or less, can be 50 parts by weight or less, can be 40 parts by weight or less, or can be 30 parts by weight or less relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, the content of the above-mentioned terpene phenol resin is less than 30 parts by weight, more preferably 25 parts by weight or less, further preferably 22 parts by weight or less, and can be 20 parts by weight or less.

[0150] The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesion, a tackifying resin having a softening point (softening temperature) of about 80°C or higher can be preferably used. The softening point of the tackifying resin can be about 100°C or higher, or can be about 110°C or higher. In addition, from the viewpoint of the adhesiveness to the adherend, a tackifying resin having a softening point of about 200°C or lower (more preferably about 180°C or lower) can be preferably used. In some embodiments, the softening point of the tackifying resin can be less than 160°C, or can be less than 150°C.

[0151] It should be noted that the softening point of the tackifying resin in this specification is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is rapidly melted at the lowest possible temperature, and it is carefully filled into a ring placed on a flat metal plate without forming bubbles. After cooling, the raised portion is cut off from the plane including the upper end of the ring using a slightly heated knife. Then, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerol is poured to a depth of 90 mm or more. Then, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerol without contacting each other, and the temperature of the glycerol is maintained at 20°C ± 5°C for 15 minutes. Then, the steel ball is placed at the center of the surface of the sample in the ring and placed at a fixed position on the support. Then, the distance from the upper end of the ring to the glycerol surface is maintained at 50 mm, and a thermometer is placed so that the center of the mercury bulb of the thermometer is at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating is brought into contact with the middle of the bottom center and the edge of the container to heat evenly. It should be noted that the rate of increase in the bath temperature after reaching 40°C from the start of heating must be 5.0°C ± 0.5°C per minute. The temperature at which the sample gradually softens and flows off the ring and finally contacts the bottom plate is read and used as the softening point. The determination of the softening point is carried out for 2 or more samples, and the average value is used.

[0152] In some embodiments, as the tackifying resin, a tackifying resin T having a softening point less than 150°C can be used. L . By using the tackifying resin T L , a higher adhesive strength can be obtained. In some preferred embodiments, the softening point of the above-mentioned tackifying resin T L is less than 140°C, more preferably less than 130°C, further preferably less than 120°C, can be 110°C or lower, can be 100°C or lower, or can be 90°C or lower. By using a tackifying resin having a softening point below the above-specified value, the storage modulus at 0°C can be moderately reduced. The tackifying resin T LThere is no particular limitation on the lower limit of the softening point. In some embodiments, from the viewpoint of exhibiting appropriate cohesion, the tackifying resin T L may have a softening point of, for example, about 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, or 110°C or higher.

[0153] As the tackifying resin T L , one or more appropriately selected from the tackifying resins having a softening point of less than 150°C among the above-exemplified tackifying resins may be used alone, or two or more may be used in combination. In some embodiments, the tackifying resin T L preferably contains at least one selected from rosin-based tackifying resins and terpene-based tackifying resins. The tackifying resin T L may contain one rosin-based tackifying resin alone, or may contain two or more rosin-based tackifying resins in combination. Further, the tackifying resin T L may contain one terpene-based tackifying resin (e.g., terpene phenol resin) alone, or may contain two or more terpene-based tackifying resins in combination.

[0154] In some embodiments, the proportion of the terpene-based tackifying resin (e.g., terpene phenol resin) in the total amount of the tackifying resin T L may be, for example, greater than about 50% by weight, about 65% by weight or more, about 75% by weight or more, 85% by weight or more, or 95% by weight or more. The technology disclosed herein can be preferably implemented in such a manner that substantially all of the tackifying resin T L (e.g., about 97% by weight or more, about 99% by weight or more, or 100% by weight) is a terpene-based tackifying resin.

[0155] Although there is no particular limitation, examples of the rosin-based tackifying resin that can be preferably used as the tackifying resin T L include rosin esters such as unmodified rosin esters and modified rosin esters. Preferred examples of the modified rosin ester include hydrogenated rosin esters. For example, esters of unmodified rosin or modified rosin (e.g., hydrogenated rosin), such as methyl esters and glycerol esters, can be used as the tackifying resin T L .

[0156] In some embodiments, the tackifying resin T L may contain a hydrogenated rosin ester. Further, for example, the tackifying resin T L may contain a non-hydrogenated rosin ester. Herein, the non-hydrogenated rosin ester is a concept that collectively represents rosin esters other than hydrogenated rosin esters among the above-mentioned rosin esters. Examples of the non-hydrogenated rosin ester include unmodified rosin esters, disproportionated rosin esters, and polymerized rosin esters. The tackifying resin T LHydrogenated rosin esters and non-hydrogenated rosin esters can be combined as rosin esters. It can contain only one or two or more hydrogenated rosin esters, or only one or two or more non-hydrogenated rosin esters. In some preferred embodiments, the adhesive layer contains only one or two or more hydrogenated rosin esters as tackifying resin T L The rosin esters contained therein.

[0157] In some embodiments, the rosin-based tackifying resin in tackifying resin T L The proportion in the whole can be, for example, about 1% by weight or more, about 10% by weight or more, about 20% by weight or more, 30% by weight or more, or 40% by weight or more. In addition, the proportion of the rosin-based tackifying resin in tackifying resin T L The proportion in the whole can be 100% by weight, 90% by weight or less, 80% by weight or less, 70% by weight or less, or 60% by weight or less. In some preferred embodiments, the proportion of the rosin-based tackifying resin in tackifying resin T L The proportion in the whole is less than 50% by weight, can be 30% by weight or less, 10% by weight or less, or 1% by weight or less.

[0158] In addition, as tackifying resin T L , for example, it can contain a tackifying resin with a softening point of less than 50 °C, more preferably about 40 °C or less (typically a tackifying resin such as rosin-based, terpene-based, hydrocarbon-based, etc., such as methyl hydrogenated rosin), or it may not contain it. Such a low softening point tackifying resin can be a liquid tackifying resin that is liquid at 30 °C. The liquid tackifying resin can be used alone or in combination of two or more. From the viewpoints of cohesion and the like, the content of the liquid tackifying resin can be about 30% by weight or less of the whole tackifying resin T L The whole, about 10% by weight or less (for example, 0% by weight to 10% by weight) is appropriate, can be about 2% by weight or less (0.5% by weight to 2% by weight), or less than 1% by weight.

[0159] The content of tackifying resin T L is not particularly limited. In some embodiments, it is appropriate to be about 70 parts by weight or less, can be 60 parts by weight or less, 50 parts by weight or less, 40 parts by weight or less, or 30 parts by weight or less relative to 100 parts by weight of the acrylic polymer. By limiting the amount of tackifying resin T L used to a specified amount or less, the storage modulus at 0 °C can be moderately reduced. In some preferred embodiments, relative to 100 parts by weight of the acrylic polymer, tackifying resin T LThe content of [substance] is less than 30 parts by weight, more preferably 25 parts by weight or less, further preferably 22 parts by weight or less, and may also be 20 parts by weight or less. Additionally, in some embodiments, from the perspective of improving the adhesive strength, relative to 100 parts by weight of the acrylic polymer, the tackifying resin T L The content of [substance] is, for example, 1 part by weight or more, and 5 parts by weight or more is appropriate, preferably 8 parts by weight or more, more preferably 10 parts by weight or more, further preferably 12 parts by weight or more, and may also be 15 parts by weight or more.

[0160] In some embodiments, the above adhesive layer may contain the tackifying resin T in combination within the range that does not impair the effects of the invention L and a tackifying resin T having a softening point of 150°C or higher (for example, 150°C to 200°C) H . As the tackifying resin T H , one or more of the tackifying resins having a softening point of 150°C or higher among the above-exemplified tackifying resins may be used alone or two or more may be used in combination.

[0161] In some embodiments, the tackifying resin T L preferably accounts for more than 50% by weight of the total amount of the tackifying resins contained in the adhesive layer. Thereby, it is easy to effectively exhibit the effects of containing the tackifying resin T L . From the perspective of more effectively exerting the use effects of the tackifying resin TL, the proportion of the tackifying resin T L in the total amount of the tackifying resins contained in the adhesive layer is preferably 60% by weight or more, more preferably 70% by weight or more, further preferably 80% by weight or more, particularly preferably 90% by weight or more, may be 95% by weight or more, and may also be 98% by weight or more. In some preferred embodiments, the tackifying resins contained in the adhesive layer substantially only include the tackifying resin T L . In this embodiment, the proportion of the tackifying resin T L in the total amount of the tackifying resins contained in the adhesive layer is in the range of 99% by weight to 100% by weight.

[0162] Although not particularly limited, in some embodiments, the above tackifying resin may contain a tackifying resin having a hydroxyl value higher than 20 mgKOH / g. Among them, a tackifying resin having a hydroxyl value of 30 mgKOH / g or more is preferred. Hereinafter, a tackifying resin having a hydroxyl value of 30 mgKOH / g or more is sometimes referred to as a "high hydroxyl value resin". According to the tackifying resin containing such a high hydroxyl value resin, an adhesive layer excellent in adhesion to an adherend and having high cohesion can be achieved. In some embodiments, the above tackifying resin may contain a high hydroxyl value resin having a hydroxyl value of 50 mgKOH / g or more (for example, 70 mgKOH / g or more). Although not particularly limited, it is preferred to use the above-mentioned high hydroxyl value resin (for example, terpene phenol resin) in combination with an acrylic polymer containing, for example, heptyl acrylate as a monomer component, so as to balance the adhesive strength and cohesion.

[0163] The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoints of compatibility with acrylic polymers, etc., the hydroxyl value of the high hydroxyl value resin is generally about 300 mgKOH / g or less, suitably about 200 mgKOH / g or less, preferably about 180 mgKOH / g or less, more preferably about 160 mgKOH / g or less, further preferably about 140 mgKOH / g or less, may be 120 mgKOH / g or less, may be 100 mgKOH / g or less, and may also be 80 mgKOH / g or less (for example, 65 mgKOH / g or less). The technology disclosed herein can be preferably implemented in such a manner that the tackifying resin contains a high hydroxyl value resin having a hydroxyl value of 30 mgKOH / g to 160 mgKOH / g (for example, terpene-based tackifying resin, preferably terpene phenol resin). In some embodiments, a high hydroxyl value resin having a hydroxyl value of 30 mgKOH / g to 80 mgKOH / g (for example, 30 mgKOH / g to 65 mgKOH / g) can be preferably used.

[0164] Here, as the value of the above hydroxyl value, the value measured by the potentiometric titration method specified in JIS K0070:1992 can be adopted. The specific measurement method is as follows.

[0165] [Measurement Method of Hydroxyl Value]

[0166] 1. Reagents

[0167] (1) As the acetylation reagent, use the reagent obtained as follows: Take about 12.5 g (about 11.8 mL) of acetic anhydride, add pyridine thereto so that the total amount is 50 mL, and stir well. Or use the reagent obtained as follows: Take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine thereto so that the total amount is 100 mL, and stir well.

[0168] (2) As the measurement reagent, use a 0.5 mol / L potassium hydroxide ethanol solution.

[0169] (3) In addition, prepare toluene, pyridine, ethanol, and distilled water.

[0170] 2. Operation

[0171] (1) Weigh accurately about 2 g of the test sample in a flat-bottom flask, add 5 mL of the acetylation reagent and 10 mL of pyridine, and install an air condenser.

[0172] (2) Heat the above flask in a bath at 100 °C for 70 minutes, then cool it naturally. Add 35 mL of toluene as a solvent from the upper part of the condenser and stir, then add 1 mL of distilled water and stir to decompose the acetic anhydride. To ensure complete decomposition, heat it in the bath again for 10 minutes and then cool it naturally.

[0173] (3) Wash the condenser with 5 mL of ethanol and remove it. Then, add 50 mL of pyridine as a solvent and stir.

[0174] (4) Add 25 mL of 0.5 mol / L potassium hydroxide ethanol solution using a total pipette.

[0175] (5) Perform potentiometric titration with 0.5 mol / L potassium hydroxide ethanol solution. Take the inflection point of the obtained titration curve as the end point.

[0176] (6) For the blank test, perform the above steps (1) - (5) without adding the test sample.

[0177] 3. Calculation

[0178] Calculate the hydroxyl value according to the following formula.

[0179] Hydroxyl value (mgKOH / g) = [(B - C) × f × 28.05] / S + D

[0180] Here,

[0181] B: The volume (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the blank test,

[0182] C: The volume (mL) of 0.5 mol / L potassium hydroxide ethanol solution used in the test sample,

[0183] f: The factor of 0.5 mol / L potassium hydroxide ethanol solution,

[0184] S: The weight (g) of the test sample,

[0185] D: Acid value,

[0186] 28.05: 1 / 2 of the molecular weight 56.11 of potassium hydroxide.

[0187] As the high hydroxyl value resin, resins having a hydroxyl value of more than a specified value among the above various tackifying resins can be used. The high hydroxyl value resin can be used alone or in combination of two or more. For example, as the high hydroxyl value resin, a terpene phenol resin having a hydroxyl value of 30 mgKOH / g or more can be preferably used. The terpene phenol resin can arbitrarily control the hydroxyl value by the copolymerization ratio of phenol, and thus is suitable.

[0188] Although not particularly limited, when using the high hydroxyl value resin, the proportion of the high hydroxyl value resin (such as terpene phenol resin) in the total tackifying resin contained in the adhesive layer can be about 5% by weight or more, can be 10% by weight or more, can be 15% by weight or more, or can be 20% by weight or more. In some embodiments, the proportion of the high hydroxyl value resin in the total tackifying resin is preferably about 30% by weight or more, for example. Thereby, the effect of using the high hydroxyl value resin can be satisfactorily exerted. In some preferred embodiments, the proportion of the high hydroxyl value resin in the total tackifying resin is about 40% by weight or more, can be about 50% by weight or more (such as more than 50% by weight), can be about 60% by weight or more, can be about 70% by weight or more, can be about 80% by weight or more, or can be about 90% by weight or more. It can be substantially all of the tackifying resin (such as about 95% to about 100% by weight, further about 99% to about 100% by weight) being the high hydroxyl value resin.

[0189] The softening point of the above high hydroxyl value resin is not particularly limited. The softening point of the high hydroxyl value resin can be, for example, about 50°C or more. From the viewpoint of improving cohesion, a high hydroxyl value resin having a softening point (softening temperature) of about 80°C or more can be preferably used. For example, a terpene phenol resin having such a softening point can be preferably used. The softening point of the high hydroxyl value resin can be about 100°C or more, or can be about 110°C or more. The upper limit of the softening point of the high hydroxyl value resin is not particularly limited. From the viewpoint of the adhesiveness to the adherend, a high hydroxyl value resin having a softening point of about 200°C or less (more preferably about 180°C or less) can be preferably used. In some embodiments, the softening point of the high hydroxyl value resin can be less than 160°C, can be less than 150°C, can be less than 145°C, can be less than 140°C, can be less than 130°C, or can be less than 120°C.

[0190] The content of the high hydroxyl value resin in the adhesive layer is not particularly limited as long as the target viscoelastic properties are satisfied. In some embodiments, from the perspective of improving the adhesive strength, the content of the high hydroxyl value resin is usually about 1 part by weight or more, preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, still more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (for example, 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. Additionally, in some embodiments, the content of the high hydroxyl value resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, may be 50 parts by weight or less, may be 40 parts by weight or less, or may be 30 parts by weight or less relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, the content of the above-mentioned high hydroxyl value resin is less than 30 parts by weight, more preferably 25 parts by weight or less, still more preferably 22 parts by weight or less, and may be 20 parts by weight or less.

[0191] In the case where the adhesive layer disclosed herein contains a tackifying resin, as the tackifying resin, from the perspective of increasing the biomass carbon ratio of the adhesive layer, a tackifying resin derived from plants (vegetable tackifying resin) can be preferably used. Examples of the vegetable tackifying resin include, for example, the above-mentioned rosin-based tackifying resins and terpene-based tackifying resins. The vegetable tackifying resin can be used alone or in combination of two or more. In the case where the adhesive layer disclosed herein contains a tackifying resin, the proportion of the vegetable tackifying resin in the total amount of the tackifying resin is preferably 30% by weight or more (for example, 50% by weight or more, typically 80% by weight or more). In some embodiments, the proportion of the vegetable tackifying resin in the total amount of the tackifying resin is 90% by weight or more (for example, 95% by weight or more, typically 99% - 100% by weight). The technology disclosed herein can be preferably implemented in a manner that substantially does not contain a tackifying resin other than the vegetable tackifying resin.

[0192] The content of the tackifying resin in the adhesive layer is not particularly limited as long as the target viscoelastic properties are satisfied. In some embodiments, from the perspective of improving the adhesive strength, the content of the tackifying resin is usually about 1 part by weight or more, preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, still more preferably 10 parts by weight or more, and further preferably about 12 parts by weight or more (for example, 15 parts by weight or more) relative to 100 parts by weight of the acrylic polymer. Additionally, in some embodiments, the content of the tackifying resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, may be 50 parts by weight or less, may be 40 parts by weight or less, or may be 30 parts by weight or less relative to 100 parts by weight of the acrylic polymer. In some preferred embodiments, from the perspective of reducing the storage modulus at 0°C, the content of the above-mentioned tackifying resin is less than 30 parts by weight, more preferably 25 parts by weight or less, still more preferably 22 parts by weight or less, and may be 20 parts by weight or less.

[0193] In the technology disclosed herein, the total amount (total) of the acrylic polymer and the tackifying resin in the adhesive layer is appropriately set in a manner that enables the effects produced by the technology disclosed herein to be exhibited, and is not limited to a specific range. In some preferred embodiments, from the perspective of satisfactorily exhibiting the effects produced by the technology disclosed herein, it is appropriate for the total amount (total) of the acrylic polymer and the tackifying resin in the entire adhesive layer to be greater than 50% by weight, preferably about 70% by weight or more, more preferably about 90% by weight or more, and further preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less or less than 100% by weight), and it can be 98% by weight or more.

[0194] (Acrylic oligomer)

[0195] In some embodiments, the adhesive layer may contain an acrylic oligomer. By containing an acrylic oligomer, the adhesive strength of the adhesive can be improved. The acrylic oligomer may be used alone or in combination of two or more. The Tg of the above acrylic oligomer is about 0°C or more and about 300°C or less, preferably about 20°C or more and about 300°C or less, and further preferably about 40°C or more and about 300°C or less. By having the Tg within the above range, the adhesive strength can be appropriately improved. In some preferred embodiments, from the perspective of the cohesiveness of the adhesive, the Tg of the acrylic oligomer is about 30°C or more, more preferably about 50°C or more (for example, about 60°C or more), and from the perspective of tackiness, it is preferably about 200°C or less, more preferably about 150°C or less, and further preferably about 100°C or less (for example, about 80°C or less). It should be noted that in this specification, the Tg of the acrylic oligomer refers to the Tg calculated by the Fox formula based on the composition of the above monomer components in the same manner as the Tg of the above acrylic polymer.

[0196] The weight-average molecular weight (Mw) of the acrylic oligomer can typically be greater than or equal to about 1000 and less than about 30000, preferably greater than or equal to about 1500 and less than about 20000, and more preferably greater than or equal to about 2000 and less than about 10000. With the Mw within the above range, good adhesiveness can be easily obtained. In some preferred embodiments, the Mw of the acrylic oligomer is about 2500 or more (e.g., about 3000 or more). Additionally, from the perspective of adhesiveness, it is preferably about 7000 or less, and more preferably about 5000 or less (e.g., about 4500 or less, typically about 4000 or less). The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and obtained in the form of values converted according to standard polystyrene. Specifically, in HPLC8020 manufactured by Tosoh Corporation, TSKgel GMH-H(20)×2 columns are used, and the measurement is carried out with tetrahydrofuran solvent under the condition of a flow rate of about 0.5 mL / minute.

[0197] Examples of the monomers constituting the acrylic oligomer include: (meth)acrylic acid alkyl esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (meth)acrylate containing an alicyclic hydrocarbon group such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, tetrahydrodicyclopentadienyl (meth)acrylate; aryl (meth)acrylates such as phenyl (meth)acrylate, benzyl (meth)acrylate; (meth)acrylates obtained from terpene compound derivative alcohols; etc. Such (meth)acrylates can be used alone or in combination of two or more.

[0198] As an acrylic oligomer, from the viewpoint of being able to further improve the adhesiveness of the adhesive layer, it is preferably contains (meth)acrylic acid alkyl esters having a branched-chain structure in the alkyl group such as isobutyl (meth)acrylate and tert-butyl (meth)acrylate; esters of (meth)acrylic acid and alicyclic alcohols (meth)acrylate containing an alicyclic hydrocarbon group such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentadienyl tetrahydro (meth)acrylate; (meth)acrylic acid aryl esters such as phenyl (meth)acrylate and benzyl (meth)acrylate, etc. Acrylic monomers having a relatively large volume structure represented by (meth)acrylate are used as monomer units. In addition, from the viewpoint of being less likely to cause polymerization inhibition when ultraviolet rays are used during the synthesis of acrylic oligomers and the production of the adhesive layer, monomers having a saturated bond are preferred, and (meth)acrylic acid alkyl esters having a branched-chain structure in the alkyl group or esters with alicyclic alcohols (meth)acrylate containing an alicyclic hydrocarbon group can be appropriately used as monomers constituting the acrylic oligomer. It should be noted that the above-mentioned branched-chain (meth)acrylic acid alkyl esters, alicyclic hydrocarbon group (meth)acrylates, and (meth)acrylic acid aryl esters all correspond to (meth)acrylate monomers in the technology disclosed herein. The alicyclic hydrocarbon group can be a saturated or unsaturated alicyclic hydrocarbon group.

[0199] (Meth)acrylate monomers (for example, (meth)acrylate containing an alicyclic hydrocarbon group) typically account for more than 50% by weight, preferably 60% by weight or more, more preferably 70% by weight or more (for example, 80% by weight or more, further 90% by weight or more) in the monomer components constituting the acrylic oligomer. In some preferred embodiments, the acrylic oligomer has a monomer composition consisting essentially of only (meth)acrylate monomers.

[0200] As monomer components constituting the acrylic oligomer, functional group-containing monomers can be used in addition to the above-mentioned (meth)acrylate monomers. Preferred examples of the above-mentioned functional group-containing monomers include: monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocyclic ring) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxyl group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers can be used alone or in combination of two or more. Among them, carboxyl group-containing monomers are preferred, and AA is particularly preferred. For example, by using a carboxyl group-containing monomer as the functional group-containing monomer, it is easy to improve the adhesiveness to a highly polar adherend.

[0201] When the monomer component constituting the acrylic oligomer contains a functional group-containing monomer, it is appropriate that the proportion of the functional group-containing monomer (for example, a carboxyl group-containing monomer such as AA) in the above monomer component is about 1% by weight or more, preferably 2% by weight or more, more preferably 3% by weight or more, and further preferably about 15% by weight or less, preferably 10% by weight or less, and more preferably 7% by weight or less.

[0202] The acrylic oligomer can be formed by polymerizing its constituent monomer components. There are no particular limitations on the polymerization method and polymerization mode, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be adopted in an appropriate manner. The types of polymerization initiators (for example, azo polymerization initiators such as AIBN) that can be used as needed are roughly as exemplified in the synthesis of acrylic polymers. The amount of the polymerization initiator and the amount of a chain transfer agent such as n-dodecyl mercaptan optionally used are appropriately set based on common technical knowledge so as to achieve the desired molecular weight, and thus detailed description is omitted here.

[0203] From the above viewpoints, preferred acrylic oligomers include, for example, homopolymers of dicyclopentadienyl tetrahydro methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentadienyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), 1-adamantyl acrylate (ADA), and copolymers of CHMA and isobutyl methacrylate (IBMA), CHMA and IBXMA, CHMA and N-acryloylmorpholine (ACMO), CHMA and diethylacrylamide (DEAA), CHMA and AA, ADA and methyl methacrylate (MMA), DCPMA and IBXMA, DCPMA and MMA, etc.

[0204] When an acrylic oligomer is contained in the adhesive layer disclosed herein, its content is preferably 0.1 part by weight or more (e.g., 1 part by weight or more) relative to 100 parts by weight of the acrylic polymer. From the viewpoint of better exerting the effects of the acrylic oligomer, the content of the acrylic oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, still more preferably about 10 parts by weight or more, and particularly preferably about 12 parts by weight or more. In addition, in some embodiments, from the viewpoints of compatibility with the acrylic polymer, etc., the content of the acrylic oligomer is preferably less than 50 parts by weight (e.g., less than 40 parts by weight) relative to 100 parts by weight of the acrylic polymer, more preferably less than 30 parts by weight, still more preferably about 25 parts by weight or less, and further preferably about 20 parts by weight or less. In other embodiments, the content of the acrylic oligomer can be 10 parts by weight or less, can be 5 parts by weight or less, or can be 1 part by weight or less (e.g., less than 1 part by weight) relative to 100 parts by weight of the acrylic polymer. The technology disclosed herein can be implemented in such a manner that the adhesive layer substantially does not contain an acrylic oligomer.

[0205] (Crosslinking agent)

[0206] In the technology disclosed herein, the adhesive composition used in the formation of the adhesive layer may contain a crosslinking agent as needed. The type of the crosslinking agent is not particularly limited, and examples thereof 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, silane coupling agents, etc. The crosslinking agent can be used alone or in combination of two or more. Among them, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and melamine crosslinking agents are preferred, and isocyanate crosslinking agents and epoxy crosslinking agents are more preferred. By appropriately selecting and using the crosslinking agent, the adhesive layer can have appropriate cohesion. It should be noted that the adhesive layer in the technology disclosed herein can contain the above crosslinking agent in the form after the crosslinking reaction, the form before the crosslinking reaction, the form of partial crosslinking reaction, their intermediate or composite forms, etc. The above crosslinking agent is typically contained in the adhesive layer only in the form after the crosslinking reaction.

[0207] As the isocyanate crosslinking agent, a polyfunctional isocyanate (a compound in which each molecule has an average of two or more isocyanate groups, including substances having an isocyanurate structure) can be preferably used. The isocyanate crosslinking agent can be used alone or in combination of two or more.

[0208] Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, etc.

[0209] Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; 1,2-butylene diisocyanate, 1,3-butylene diisocyanate, 1,4-butylene diisocyanate and other butylene diisocyanates; 1,2-hexylene diisocyanate, 1,3-hexylene diisocyanate, 1,4-hexylene diisocyanate, 1,5-hexylene diisocyanate, 1,6-hexylene diisocyanate, 2,5-hexylene diisocyanate and other hexylene diisocyanates; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, lysine diisocyanate, etc.

[0210] Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, 1,4-cyclohexyl diisocyanate and other cyclohexyl diisocyanates; 1,2-cyclopentyl diisocyanate, 1,3-cyclopentyl diisocyanate and other cyclopentyl diisocyanates; hydrogenated xylylene diisocyanate, hydrogenated toluene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, etc.

[0211] Specific examples of aromatic polyisocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyl diphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene 1,4-diisocyanate, naphthylene 1,5-diisocyanate, 3,3'-dimethoxy diphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, etc.

[0212] As a preferred polyfunctional isocyanate, polyfunctional isocyanates having on average more than three isocyanate groups per molecule can be exemplified. The isocyanates having three or more functional groups can be polymers (typically dimers or trimers), derivatives (for example, addition reaction products of polyols and two or more molecules of polyfunctional isocyanates), polymers, etc. of difunctional or trifunctional or higher functional isocyanates. For example, a dimer of diphenylmethane diisocyanate or a trimer of diphenylmethane diisocyanate, an isocyanurate of hexamethylene diisocyanate (a trimer adduct having an isocyanurate structure), a reaction product of trimethylolpropane and toluene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, poly(methylene polyphenyl isocyanate), polyether polyisocyanate, polyester polyisocyanate and other polyfunctional isocyanates can be cited. As commercially available products of such polyfunctional isocyanates, products named "DURANATETPA-100" manufactured by Asahi Kasei Chemicals Corporation, products named "CORONATE L", "CORONATE HL", "CORONATE HK", "CORONATE HX", "CORONATE 2096" manufactured by Tosoh Corporation, etc. can be cited.

[0213] The technology disclosed herein can preferably be implemented in such a manner that at least an isocyanate crosslinking agent is used as a crosslinking agent. The amount of the isocyanate crosslinking agent used is not particularly limited. With respect to 100 parts by weight of the acrylic polymer, the amount of the isocyanate crosslinking agent used can be, for example, about 0.1 part by weight or more. From the viewpoints of balancing cohesion and adhesiveness, etc., with respect to 100 parts by weight of the acrylic polymer, the amount of the isocyanate crosslinking agent used is generally preferably about 0.3 part by weight or more (for example, 0.5 part by weight or more). In some preferred embodiments, the amount of the isocyanate crosslinking agent used with respect to 100 parts by weight of the acrylic polymer is about 1.0 part by weight or more, more preferably about 1.5 part by weight or more, further preferably about 2.0 part by weight or more, particularly preferably about 2.5 part by weight or more, and can be about 2.8 part by weight or more. In addition, from the viewpoint of improving the adhesiveness to the adherend, it is appropriate that the amount of the above isocyanate crosslinking agent used with respect to 100 parts by weight of the acrylic polymer is 10 parts by weight or less, preferably 8 parts by weight or less, more preferably 6 parts by weight or less, further preferably 5 parts by weight or less, particularly preferably 4 parts by weight or less, and can be 3.5 parts by weight or less, or can also be 3.2 parts by weight or less.

[0214] As the epoxy crosslinking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy crosslinking agent having three to five epoxy groups in one molecule is preferred. The epoxy crosslinking agent can be used alone or in combination of two or more.

[0215] Although there is no particular limitation, specific examples of the epoxy crosslinking agent include, for example: N,N,N’,N’-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc. Commercially available products of the epoxy crosslinking agent include: the product name “TETRAD-C” and the product name “TETRAD-X” manufactured by Mitsubishi Gas Chemical Company, the product name “EPICLON CR-5L” manufactured by DIC Corporation, the product name “Denacol EX-512” manufactured by Nagase ChemteX Corporation, the product name “TEPIC-G” manufactured by Nissan Chemical Industries, Ltd., etc.

[0216] The amount of the epoxy crosslinking agent used is not particularly limited. For example, relative to 100 parts by weight of the acrylic polymer, the amount of the epoxy crosslinking agent used can be greater than 0 part by weight and less than or equal to about 1 part by weight (typically about 0.001 part by weight to about 1 part by weight). From the viewpoint of appropriately exerting the effect of improving cohesion, generally, relative to 100 parts by weight of the acrylic polymer, it is appropriate that the amount of the epoxy crosslinking agent used is about 0.002 part by weight or more, preferably about 0.005 part by weight or more, for example, it can be about 0.01 part by weight or more, and can also be about 0.02 part by weight or more. In addition, from the viewpoint of improving the adhesion to the adherend, relative to 100 parts by weight of the acrylic polymer, it is appropriate that the amount of the epoxy crosslinking agent used is about 0.5 part by weight or less, preferably about 0.2 part by weight or less, more preferably about 0.1 part by weight or less (for example, less than 0.1 part by weight), can be 0.07 part by weight or less, can be 0.04 part by weight or less, and can also be 0.03 part by weight or less. By limiting the amount of the epoxy crosslinking agent used within a specified range, it is easy to maintain sufficient adhesive strength.

[0217] In some preferred embodiments, as the crosslinking agent, an isocyanate crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from the isocyanate crosslinking agent can be used in combination. In the technology disclosed herein, it can be preferably implemented in such a manner that a crosslinking agent other than the isocyanate crosslinking agent (that is, a crosslinking agent having a different type of crosslinking reactive group from the isocyanate crosslinking agent. Hereinafter, it is also referred to as a “non-isocyanate crosslinking agent.”) and an isocyanate crosslinking agent are used in combination.

[0218] 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 above-mentioned crosslinking agents. The non-isocyanate crosslinking agents can be used alone or in combination of two or more. In some preferred embodiments, epoxy crosslinking agents can be used as the non-isocyanate crosslinking agents. For example, by using an isocyanate crosslinking agent and an epoxy crosslinking agent in combination, more excellent adhesion characteristics can be achieved.

[0219] There is no particular limitation on the relationship between the content of the isocyanate crosslinking agent and the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent). For example, relative to the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent), the content of the isocyanate crosslinking agent is more than 1 time, preferably about 10 times or more, more preferably about 50 times or more, further preferably about 80 times or more, and still further preferably about 100 times or more (e.g., greater than 100 times), and can be about 120 times or more (e.g., about 140 times or more). In addition, from the viewpoint of appropriately exerting the effects produced by using an isocyanate crosslinking agent and a non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) in combination, generally, relative to the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent), the content of the isocyanate crosslinking agent is, for example, about 1000 times or less, preferably about 500 times or less, more preferably about 300 times or less, further preferably about 200 times or less, and still further preferably about 180 times or less, and can be about 150 times or less.

[0220] There is no particular limitation on the content of the crosslinking agent (total amount of the crosslinking agent) in the adhesive composition disclosed herein. From the viewpoint of cohesion, generally, relative to 100 parts by weight of the acrylic polymer, the content of the above crosslinking agent is about 0.001 part by weight or more, preferably about 0.01 part by weight or more, more preferably about 0.1 part by weight or more, further preferably about 1 part by weight or more, and particularly preferably about 2.5 parts by weight or more. In addition, generally, relative to 100 parts by weight of the acrylic polymer, the content of the crosslinking agent in the adhesive composition is about 20 parts by weight or less, preferably about 15 parts by weight or less. In some preferred embodiments, relative to 100 parts by weight of the acrylic polymer, the content of the crosslinking agent is 5.0 parts by weight or less, can be 4.0 parts by weight or less, or can be 3.5 parts by weight or less.

[0221] (Other additives)

[0222] In the adhesive composition, in addition to containing the above-mentioned components, leveling agents, crosslinking aids, plasticizers, softeners, fillers, antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, rust inhibitors, light stabilizers, and other various additives commonly used in the field of adhesives may be contained as needed. For such various additives, substances known in the past can be used by conventional methods, which is not a feature of the present invention, and thus detailed description is omitted.

[0223] (Method for forming the adhesive layer)

[0224] The adhesive layer (layer containing an adhesive) disclosed herein can be an adhesive layer formed from an aqueous adhesive composition, a solvent-based adhesive composition, a hot-melt adhesive composition, or an active energy ray-curable adhesive composition. An aqueous adhesive composition refers to an adhesive composition in a form in which an adhesive (adhesive layer-forming component) is contained in a solvent (aqueous solvent) having water as a main component, and typically includes what is called a water-dispersed adhesive composition (a composition in a form in which at least a part of the adhesive is dispersed in water). In addition, a solvent-based adhesive composition refers to an adhesive composition in a form in which an adhesive is contained in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more of those exemplified as the organic solvents usable in the above solution polymerization (toluene, ethyl acetate, etc.) can be used without particular limitation. The technology disclosed herein can be preferably implemented in a manner having an adhesive layer formed from a solvent-based adhesive composition from the viewpoint of adhesion characteristics and the like.

[0225] The adhesive layer disclosed herein can be formed by a method known in the past. For example, a method of forming an adhesive layer by applying an adhesive composition on a surface having releasability (release surface) or a non-releasable surface and drying it can be adopted. For an adhesive sheet having a substrate structure, for example, a method (direct method) of directly applying (typically coating) an adhesive composition on the substrate and drying it to form an adhesive layer can be adopted. In addition, a method (transfer method) of forming an adhesive layer on a surface having releasability (release surface) by applying an adhesive composition and drying it, and transferring the adhesive layer to a substrate can be adopted. From the viewpoint of productivity, the transfer method is preferred. As the above release surface, the surface of a release liner, the back surface of a substrate subjected to a release treatment, etc. can be used.

[0226] The coating of the adhesive composition can be carried out using conventionally well-known coaters such as gravure roll coaters, die coaters, bar coaters, etc. Alternatively, the adhesive composition can also be coated by dipping, curtain coating method, etc. From the viewpoints of promoting crosslinking reaction, improving manufacturing efficiency, etc., the drying of the adhesive composition is preferably carried out under heating. The drying temperature can be, for example, about 40°C to about 150°C, and is usually preferably about 60°C to about 130°C. After drying the adhesive composition, further curing can be carried out for the purposes of adjusting the transfer of components in the adhesive layer, promoting the crosslinking reaction, relaxing the strain that may exist in the adhesive layer, etc.

[0227] The adhesive layer can be a single-layer structure or a multi-layer structure having two or more layers. From the viewpoints of productivity, etc., the adhesive layer is preferably a single-layer structure.

[0228] (Thickness)

[0229] The thickness of the adhesive layer is not particularly limited, and depending on the use, purpose of use, etc., for example, a configuration having an adhesive layer with an appropriate thickness in the range of 0.1 μm to 500 μm can be adopted. In some embodiments, from the viewpoint of avoiding excessive thickness of the double-sided adhesive sheet, the thickness of the adhesive layer is usually appropriately about 100 μm or less, preferably about 70 μm or less, more preferably about 60 μm or less, further preferably about 50 μm or less, and can be about 40 μm or less. The thickness of the adhesive layer can be about 35 μm or less, and can be about 30 μm or less, for example. The adhesive layer with a limited thickness can well meet the requirements of thickness reduction and weight reduction. From the viewpoint of adhesion to the adherend, in some embodiments, the lower limit of the thickness of the adhesive layer is appropriately about 0.5 μm or more, can be about 1 μm or more, is advantageously about 3 μm or more, preferably about 10 μm or more, more preferably about 12 μm or more (for example, greater than 12 μm), further preferably about 15 μm or more, and can be about 18 μm or more, for example. In some preferred embodiments, the thickness of the adhesive layer is greater than 20 μm, can be 24 μm or more, can be 27 μm or more, can be about 30 μm or more, can be about 35 μm or more, and can also be about 40 μm or more. By increasing the thickness of the adhesive layer, it is easy to adjust optical properties such as the reduction of light transmittance. In addition, the greater the thickness of the adhesive layer, the more the adhesive strength tends to increase. It should be noted that in the double-sided adhesive sheet with a substrate having a first adhesive layer and a second adhesive layer on each surface of the substrate, the first adhesive layer and the second adhesive layer can have the same thickness or different thicknesses from each other.

[0230] (Biomass carbon ratio)

[0231] In some embodiments, the adhesive layer contains materials derived from biomass, and the biomass carbon ratio thereof can be above a specified value. For example, the biomass carbon ratio of the adhesive layer can be 1% or more, can be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the adhesive means less use of fossil resource-based materials represented by petroleum and the like. From this perspective, the higher the biomass carbon ratio of the adhesive, the more preferable. For example, the biomass carbon ratio of the adhesive layer can be 55% or more, can be 60% or more, can be 70% or more, can be 75% or more, can be 80% or more, or can be greater than 80%. The upper limit of the biomass carbon ratio is 100% by definition, can be 99% or less, and from the perspective of easy availability of materials, can be 95% or less, or can be 90% or less. From the perspective of easily exhibiting good adhesive performance, in some embodiments, the biomass carbon ratio of the adhesive layer can be 90% or less, can be 85% or less, or can be 80% or less.

[0232] <Substrate>

[0233] In the embodiment where the double-sided adhesive sheet disclosed herein is in the form of a double-sided adhesive sheet with a substrate, as the substrate supporting the adhesive layer, a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, a composite thereof, etc. can be used. Examples of paper can include: Japanese paper, kraft paper, cellophane, fine paper, synthetic paper, surface-coated paper, etc. Examples of cloth can include woven fabrics, non-woven fabrics, etc. obtained by individually or blend-spinning various fibrous substances. Examples of the above fibrous substances can include: cotton, rayon staple fiber, manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, polyolefin fiber, etc. Examples of rubber sheets can include: natural rubber sheets, butyl rubber sheets, etc. Examples of foam sheets can include: foamed polyolefin sheets, foamed polyurethane sheets, foamed chloroprene rubber sheets, etc. Examples of metal foils can include aluminum foil, copper foil, etc. It should be noted that the substrate is also referred to as the substrate layer in the double-sided adhesive sheet.

[0234] The substrate can be formed from materials derived from biomass or from materials derived from non-biomass. From the perspective of manufacturing the adhesive sheet considering the suppression of dependence on fossil resource-based materials, it is preferable to use a substrate material derived from biomass (typically a resin film).

[0235] In addition, the base material can be a base material formed using recyclable materials or recycled materials (also referred to as recycled materials). As such recycled materials, resin films can preferably be used. Resin films (such as polyester films like PET films, etc.) can be recycled. Therefore, regardless of whether plant-derived materials are used, by reusing the used resin films, continuous reproduction can be carried out, and the impact on the environment can be reduced. Such recyclable resin films and recycled resin films are also referred to as recycled films. The above-mentioned recycled materials (such as recycled films) can be formed from materials derived from biomass or from materials derived from non-biomass.

[0236] As the base material constituting the double-sided adhesive sheet with a base material, a base material containing a resin film as a base film can preferably be used. The above-mentioned base film is typically a member that can independently maintain its shape (non-dependent). The base material in the technology disclosed herein can be substantially composed of such a base film. Alternatively, the above-mentioned base material can further include an auxiliary layer in addition to the above-mentioned base film. As examples of the above-mentioned auxiliary layer, a coloring layer, a reflective layer, a primer layer, an antistatic layer, etc. provided on the surface of the above-mentioned base film can be cited.

[0237] The above-mentioned resin film is a film having a resin material as a main component (for example, a component having a content of more than 50% by weight in the resin film). As examples of the resin film, polyolefin resin films such as polyethylene (PE), polypropylene (PP), ethylene-propylene copolymer, etc.; polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc.; vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane; etc. The resin film can be a rubber film such as a natural rubber film or a butyl rubber film. Among them, from the viewpoints of operability and processability, polyester films are preferred, and PET films are particularly preferred.

[0238] It should be noted that in this specification, the "resin film" is typically a non-porous sheet, which is a concept different from so-called non-woven fabrics and woven fabrics (in other words, it does not include the concepts of non-woven fabrics and woven fabrics). The above-mentioned resin film can be any one of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. In addition, such a resin film can be a non-foamed resin film. Here, a non-foamed resin film refers to a resin film that does not undergo intentional treatment for forming a foam. Specifically, the non-foamed resin film can be a resin film having a foaming ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

[0239] The base material can be transparent, or can have light-shielding or light-reducing properties. In some embodiments, a colorant can be contained in the base material (such as a resin film). Thereby, the light transmittance (light-shielding property) of the base material can be adjusted. Adjusting the light transmittance of the base material (such as the perpendicular light transmittance) helps to adjust the light transmittance of the base material, and further adjust the light transmittance of the double-sided adhesive sheet containing the base material.

[0240] As the colorant, the same colorants as those that can be contained in the adhesive layer can be used, and conventionally known pigments and dyes can be used. The colorant is not particularly limited. For example, colorants such as black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, and pearl color can be used.

[0241] In some embodiments, as the colorant for the base material, a black colorant can be preferably used because the light-shielding property (such as the perpendicular light transmittance) can be efficiently adjusted with a small amount of the colorant. As specific black colorants, the black colorants exemplified as the colorants that can be contained in the adhesive layer can be listed. In some preferred embodiments, pigments with an average particle size of 10 nm to 500 nm, more preferably 10 nm to 120 nm (for example, particulate black colorants such as carbon black) can be used.

[0242] The usage amount of the colorant in the base material (such as a resin film) is not particularly limited, and can be set to an amount appropriately adjusted in a manner that can impart desired optical properties. It is appropriate to set the usage amount of the colorant to about 0.1 wt% to about 30 wt% of the weight of the base material. For example, it can be 0.1 wt% to 25 wt% (typically 0.1 wt% to 20 wt%).

[0243] In the above-mentioned base material (such as a resin film), various additives such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, and plasticizers can be blended as needed. The blending ratio of various additives can be about less than 30 wt% (for example, about less than 20 wt%, typically about less than 10 wt%).

[0244] The above-mentioned base material (such as a resin film) can be a single-layer structure, or can have a multi-layer structure of two layers, three layers, or more than three layers. From the viewpoint of shape stability, the base material is preferably a single-layer structure. In the case of a multi-layer structure, it is preferred that at least one layer (preferably all layers) is a layer having a continuous structure of the above-mentioned resin (such as a polyester resin). The manufacturing method of the base material (typically a resin film) can be appropriately adopted from conventionally known methods and is not particularly limited. For example, conventionally known general film forming methods such as extrusion molding, blow molding, T-die casting molding, and calender roll molding can be appropriately adopted.

[0245] The base material can be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In a base material having such a configuration including a base film and a colored layer, the above-mentioned base film may or may not contain a colorant. The colored layer can be disposed on either surface of the base film, or can be respectively disposed on both surfaces. In a configuration where colored layers are respectively disposed on both surfaces of the base film, the configurations of these colored layers can be the same or different.

[0246] Typically, such a colored layer can be formed by coating a colored layer-forming composition containing a colorant and a binder on the base film. As the colorant, the same colorants as those that can be contained in the adhesive layer and the resin film can be used, and conventionally known pigments and dyes can be used. As the binder, materials known in the fields of coatings or printing can be used without particular limitation. For example, polyurethane, phenolic resin, epoxy resin, urea melamine resin, polymethyl methacrylate, etc. can be exemplified. The colored layer-forming composition can be, for example, solvent-based, ultraviolet curable, heat curable, etc. The formation of the colored layer can be carried out by means conventionally used in the formation of colored layers without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, or offset printing can be preferably adopted.

[0247] The colored layer can be a single-layer structure composed entirely of one layer, or can be a multi-layer structure including two, three, or more sub-colored layers. The colored layer having a multi-layer structure including two or more sub-colored layers can be formed, for example, by repeating the coating (e.g., printing) of the colored layer-forming composition. The colors and blending amounts of the colorants contained in each sub-colored layer can be the same or different. In a colored layer for imparting light-shielding properties, it is particularly meaningful to form a multi-layer structure from the viewpoint of preventing the generation of pinholes and improving the reliability of light leakage prevention.

[0248] The overall thickness of the colored layer is suitably about 1 μm to about 10 μm, preferably about 1 μm to about 7 μm, and can be, for example, about 1 μm to about 5 μm. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 1 μm to about 2 μm.

[0249] Conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and coating of a primer can be performed on the surface of the base material. Such surface treatment can be a treatment for improving the adhesion between the base material and the adhesive layer, in other words, the anchoring of the base material to the adhesive layer.

[0250] In the double-sided adhesive sheet of the embodiment including a base material, the thickness of the base material is not particularly limited. From the viewpoint of preventing the double-sided adhesive sheet from becoming too thick, the thickness of the base material can be, for example, about 200 μm or less, preferably about 150 μm or less, more preferably about 100 μm or less. Depending on the purpose of use and the usage mode of the double-sided adhesive sheet, the thickness of the base material can be about 70 μm or less, can be about 50 μm or less, and can also be about 30 μm or less (for example, about 25 μm or less). In some embodiments, the thickness of the base material can be about 20 μm or less, can be about 15 μm or less, and can also be about 10 μm or less (for example, about 5 μm or less). By reducing the thickness of the base material, even if the total thickness of the double-sided adhesive sheet is the same, the thickness of the adhesive layer can be further increased, which is advantageous from the viewpoint of improving the adhesiveness to the adherend and the base material. In addition, the base material with a limited thickness can well meet the requirements of thickness reduction and weight reduction. From the viewpoints of the operability (processability), workability, etc. of the double-sided adhesive sheet, the thickness of the base material is generally about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example, about 6 μm or more. In some embodiments, the thickness of the base material can be about 8 μm or more, can be about 10 μm or more.

[0251] <Total thickness of double-sided adhesive sheet>

[0252] The total thickness of the double-sided adhesive sheet (including the adhesive layer, may further include a base material layer, but does not include a release liner.) disclosed herein is not particularly limited. The total thickness of the double-sided adhesive sheet is, for example, about 1 mm or less, can be about 500 μm or less, can be about 300 μm or less. From the viewpoint of thinning, about 200 μm or less is appropriate, and can also be about 150 μm or less (for example, about 100 μm or less). In some preferred embodiments, the thickness of the double-sided adhesive sheet can be about 50 μm or less, for example, can be about 35 μm or less. The lower limit of the thickness of the double-sided adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), about 3 μm or more is appropriate, preferably about 10 μm or more, more preferably about 15 μm or more, further preferably about 20 μm or more, can be about 30 μm or more, and can also be about 50 μm or more. The double-sided adhesive sheet having a thickness of more than a specified value is likely to obtain adhesiveness to the adherend, and also has a tendency of excellent operability. It should be noted that in the double-sided adhesive sheet without a base material, the thickness of the adhesive layer is the total thickness of the double-sided adhesive sheet.

[0253] <Properties of double-sided adhesive sheet>

[0254] (Light transmittance)

[0255] The light transmittance of the double-sided adhesive sheet varies depending on the purpose of use, the purpose of coloring, etc., and is not limited to a specific range. In some embodiments, the light transmittance of the double-sided adhesive sheet at a wavelength of 550 nm (550 nm light transmittance, also referred to as visible light transmittance) is less than 80%, can be less than 70%, can be less than 60%, can be less than 50%, or can also be less than 40%. The double-sided adhesive sheet that limits the visible light transmittance below a specified value by coloring the adhesive layer is suitable for masking the adherend and can also be used to impart design. In addition, it can also be used as a light-shielding adhesive sheet for the purpose of preventing light leakage, etc. In some preferred embodiments, the 550 nm light transmittance of the double-sided adhesive sheet is 30% or less, can be 20% or less, can be 15% or less, can be 10% or less, can be 8% or less, or can also be 6% or less. The lower the visible light transmittance, the better the masking property can be exhibited. In the case where higher masking property is required, the above 550 nm light transmittance can be less than 5%, can be less than 4%, can be less than 3%, can be less than 2%, can be less than 1%, or can also be less than 0.5%. The lower limit of the above 550 nm light transmittance is not particularly limited and can be substantially 0%, i.e., below the detection limit, can be 0.1% or more, can be 1% or more, can be 3% or more, or can also be 5% or more. In some embodiments, the above 550 nm light transmittance can be 10% or more, can be greater than 20%, or can also be greater than 30%. By having a certain degree of visible light transmittance, the adherend can be moderately masked, or the appearance of the adherend (such as a metal material) can be adjusted, or a design and color tone with the texture of the adherend remaining can be imparted. In addition, from the viewpoints of maintaining adhesive properties, productivity, etc., a double-sided adhesive sheet with moderately good light transmittance is preferred. The 550 nm light transmittance of the double-sided adhesive sheet can be measured by the method described in the examples below.

[0256] Although not particularly limited, the light transmittance of the double-sided adhesive sheet at a wavelength of 1380 nm (1380 nm light transmittance, also referred to as infrared transmittance) is less than 90%, may be less than 80%, may be less than 70%, may be less than 60%, may be less than 50%, or may be less than 40%. In some preferred embodiments, the 1380 nm light transmittance of the double-sided adhesive sheet is 30% or less, may be 20% or less, may be 15% or less, may be 10% or less, may be 5% or less, or may be 3% or less. According to the double-sided adhesive sheet with the above-mentioned infrared transmittance limited, it is possible to block light in a wide wavelength region including infrared rays, and excellent light-shielding properties can be easily obtained. In addition, for example, when used around an infrared sensor, by blocking infrared rays, it is possible to prevent the operation accuracy of the sensor from decreasing. The lower limit of the above-mentioned 1380 nm light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit, may be 0.1% or more, may be 1% or more, may be 3% or more, or may be 5% or more. In some embodiments, the above-mentioned 1380 nm light transmittance may be 10% or more, may be 30% or more, or may be 50% or more. The 1380 nm light transmittance of the double-sided adhesive sheet can be measured by the method described in the following examples.

[0257] There is no particular limitation on the relative relationship between the visible light transmittance and the infrared transmittance of the double-sided adhesive sheet. In some embodiments, the infrared transmittance T IR [%] and the visible light transmittance T VL [%] ratio (T IR / T VL ) is, for example, in the range of 0.1 to 10, may be 5 or less, may be 3 or less, and may also be 0.5 or more, may be 1 or more (e.g., greater than 1), or may be 2 or more. By appropriately setting the ratio (T IR / T VL ) according to the use purpose, application part, etc. of the double-sided adhesive sheet, it is possible to achieve the target adherend masking property and infrared shielding property.

[0258] (Adhesion to SUS)

[0259] Although there is no particular limitation, in some embodiments, the 180-degree peel strength of the double-sided adhesive sheet on the stainless steel plate (adhesive force to SUS) is about 1 N / 25 mm or more, and preferably about 5 N / 25 mm or more. In some preferred embodiments, the adhesive force to SUS is about 10 N / 25 mm or more, can be about 12 N / 25 mm or more, or can be about 15 N / 25 mm or more. The double-sided adhesive sheet showing the above-mentioned adhesive force to SUS exhibits good adhesive force to the adherend and can preferably be used for joining and fixing of components, etc. The upper limit of the adhesive force to SUS is not particularly limited, but from the viewpoint of balancing with other adhesive properties, it is usually, for example, about 50 N / 25 mm or less, and in some embodiments, can be about 30 N / 25 mm or less.

[0260] For the above-mentioned adhesive force to SUS, the measurement is carried out under the measurement environment of 23 °C and 50% RH, at a pulling speed of 300 mm / minute and a peel angle of 180 degrees, using a SUS plate as the adherend. More specifically, the measurement is carried out by the following method.

[0261] [Adhesive force to SUS]

[0262] Under the measurement environment of 23 °C and 50% RH, a PET film with a thickness of 50 μm is pasted on one adhesive surface of the double-sided adhesive sheet and backlined, and cut into a size of 25 mm in width and 100 mm in length to prepare a measurement sample. Under the environment of 23 °C and 50% RH, a 2 kg roller is reciprocated once to press the other adhesive surface of the above-mentioned measurement sample onto the surface of a stainless steel plate (SUS304BA plate) cleaned with ethyl acetate. It is left in this environment for 72 hours, and then the peel strength (adhesive force to SUS) [N / 25 mm] is measured using a universal tensile-compression testing machine in accordance with JIS Z 0237:2000, at a pulling speed of 300 mm / minute and a peel angle of 180 degrees. In the measurement of the above peel strength, as the universal tensile-compression testing machine, "Tensile-Compression Testing Machine, TG-1kN" manufactured by Minebea Company or its equivalent is used.

[0263] (Biomass carbon ratio)

[0264] In some embodiments, the double-sided adhesive sheet contains a material from biomass, and its biomass carbon ratio can be above a specified value. The biomass carbon ratio of the double-sided adhesive sheet is, for example, 1% or more, 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio of the double-sided adhesive sheet indicates that the amount of fossil resource materials represented by petroleum is small. In this view, the higher the biomass carbon ratio of the double-sided adhesive sheet, the more preferred. For example, the biomass carbon ratio of the double-sided adhesive sheet can be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or greater than 80%. The upper limit of the biomass carbon ratio is defined as 100%, and can be 99% or less. From the perspective of the availability of materials, it can be 95% or less, or 90% or less. From the perspective of easy to exert good adhesive performance, in some embodiments, the biomass carbon ratio of the double-sided adhesive sheet can be, for example, 90% or less, 85% or less, or 80% or less.

[0265] <Application>

[0266] The double-sided adhesive sheet disclosed herein has a colored adhesive layer, highly suppresses the deformation of the adhesive surface caused by the peeling of the release liner, and has an adhesive surface with excellent appearance quality. Therefore, it is suitable for the use of the double-sided adhesive sheet attached to the surface of the adherend to be visually recognized, such as the use of requiring the masking brought by the double-sided adhesive sheet; the use of the colored adhesive layer to give design and color tone; and the use of requiring specified optical properties (light transmittance, etc.) and other uses. For example, in electronic devices such as portable electronic devices, there are devices that require the use of double-sided adhesive sheets for masking components, adjusting appearance, etc. For such electronic devices, the double-sided adhesive sheet disclosed herein is suitable.

[0267] Non-limiting examples of the above portable electronic devices include: mobile phones, smart phones, tablet personal computers, notebook personal computers, various wearable devices (such as wrist-worn devices like watches, modular devices worn on a part of the body with clips, straps, etc., eyewear (monocular, binocular. Also includes helmet type.) worn on the eyes, clothing type worn on shirts, socks, hats, etc. in the form of accessories, ear-worn devices like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, voice recorders, etc.), calculators (desktop calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, e-books, in-vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. It should be noted that in this specification, "portable" being merely able to be carried is not sufficient. Its essence has a level of portability that an individual (standard adult) can relatively easily move. Additionally, as examples of the above electronic devices, personal computers (desktop, notebook, tablet, etc.), TVs, etc. can be cited. These electronic devices can be electronic devices with display devices (display equipment) such as liquid crystal, organic electroluminescence, etc. built in.

[0268] In some ways, the double-sided adhesive sheet is used, for example, for the purpose of fixing a pressure-sensitive sensor to other components in a portable electronic device having a pressure-sensitive sensor in the above portable electronic device. In some ways, the double-sided adhesive sheet can be used to fix a pressure-sensitive sensor and other components in an electronic device (typically a portable electronic device) having a function of specifying an absolute position on a board (typically a touch panel) corresponding to a screen by means of a device for indicating a position on the screen (typically a pen-type, mouse-type device) and a device for detecting the position.

[0269] Furthermore, in some preferred ways, the double-sided adhesive sheet is suitable for use in configuring on the back of a display screen (display unit) such as a touch panel display in a portable electronic device. By configuring the double-sided adhesive sheet of some preferred ways on the back of the above display screen (display unit), regardless of the usage mode of the portable electronic device, a reduction in the visual recognition of the display screen can be prevented.

[0270] In addition, in some embodiments, the double-sided adhesive sheet is suitable for a portable electronic device incorporating an optical sensor. For various devices such as the above-mentioned portable electronic devices, for purposes such as device operation, proximity sensing, detection of ambient brightness (ambient light), and data communication, the devices may have an optical sensor that utilizes light such as infrared rays, visible light, and ultraviolet rays. Although not particularly limited, examples of the above-mentioned optical sensor include an acceleration sensor, a proximity sensor, a brightness sensor (ambient light sensor), etc. Such an optical sensor has a light receiving element for light such as ultraviolet rays, visible light, and infrared rays, and may also have a light emitting element for specific light such as infrared rays. In other words, the optical sensor may include a light emitting element and / or a light receiving element for light in a specific wavelength region within the wavelength region including ultraviolet rays, visible light, and infrared rays. For such a device, by applying the double-sided adhesive sheet of some embodiments and restricting the incidence of light that can be refracted and scattered within the adhesive layer, the light within the device can be controlled, thereby preventing a reduction in the operation accuracy of the sensor.

[0271] As the material (adherend material) to which the double-sided adhesive sheet disclosed herein is adhered, although not particularly limited, examples include: metal materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc., or alloys containing two or more of them; various resin materials (typically plastic materials) such as polyimide resins, acrylic resins, polyether nitrile resins, polyether sulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyether ether ketone resins, polyamide resins (so-called aromatic polyamide resins, etc.), polyarylate resins, polycarbonate resins, liquid crystal polymers; inorganic materials such as alumina, zirconia, soda-lime glass, quartz glass, carbon, etc. Among them, metal materials such as copper, aluminum, and stainless steel, and resin materials (typically plastic materials) such as polyester resins such as PET, polyimide resins, aromatic polyamide resins, and polyphenylene sulfide resins are widely used. The above materials may be materials for components constituting products such as electronic devices. The double-sided adhesive sheet disclosed herein can be adhered to components made of the above materials for use. In addition, the above materials may be materials for constituting fixed objects (such as electromagnetic wave shields, reinforcement plates, etc., which are back components) such as the above-mentioned pressure-sensitive sensor and display unit. It should be noted that the fixed object refers to the object to which the double-sided adhesive sheet is adhered, that is, the adherend. In addition, the back component refers to, for example, a component disposed on the opposite side of the surface (visually recognizable side) of the above-mentioned pressure-sensitive sensor and display unit in a portable electronic device. For example, it may be a component constituting the following Figure 4Components such as the support portion 540 on the back surface of the display device 500 shown. In addition, the above-mentioned object to be fixed can be in any form of a single-layer structure or a multi-layer structure, and various surface treatments can also be performed on the surface (adhesive surface) to which the double-sided adhesive sheet is adhered. Although not particularly limited, as an example of the object to be fixed, a back member having a thickness of about 1 μm or more (typically about 5 μm or more, for example about 60 μm or more, and further about 120 μm or more) and about 1500 μm or less (for example about 800 μm or less) can be cited.

[0272] In some embodiments, the member or material to which the double-sided adhesive sheet is adhered can be a member or material having light transmissivity (light-transmissive adherend). Since the adhesive surface of the double-sided adhesive sheet adhered to the light-transmissive adherend can be visually recognized through the light-transmissive adherend, an adhesive surface with good appearance quality is desired. The light transmittance of the above-mentioned light-transmissive adherend is, for example, greater than 50%, and can be 70% or more. In some preferred embodiments, the light transmittance of the adherend is 80% or more, more preferably 90% or more, and can be 95% or more (for example, 95% to 100%). Such a material can be a resin film (for example, a polyester resin film such as a PET film) disposed on the back surface of the image display portion of various devices such as portable electronic devices. The double-sided adhesive sheet disclosed herein can preferably be used in a manner of adhering to an adherend (such as a member) having a light transmittance of a specified value or more as described above. The above-mentioned light transmittance is the light transmittance at a wavelength of 550 nm, and can be measured by the same method as the light transmittance at a wavelength of 550 nm of the double-sided adhesive sheet.

[0273] In addition, in some embodiments, the double-sided adhesive sheet is used in a manner of adhering to a metal member. As the material of the metal member, the metal materials exemplified as the above-mentioned adherend materials can be cited. The metal member is, for example, a member or article having a surface (adhesive sheet adhesion surface) formed of a metal material such as aluminum or stainless steel. As a preferred example, metal members such as stainless steel members and aluminum members can be cited. By adhering the double-sided adhesive sheet disclosed herein to the area of the metal member surface that needs to be masked, the above-mentioned area of the metal member can be masked. The double-sided adhesive sheet can cover the entire surface of the metal member or a part of the above surface (for example, a part of the area required to be masked). The above-mentioned metal member can be, for example, a member constituting the support portion 540 of the display device 500 shown in Figure 4 etc. The above-mentioned metal member is preferably an adherend on one side of the double-sided adhesive sheet.

[0274] As described above, according to the technology disclosed herein, a laminate is provided which has a double-sided adhesive sheet and a member to which the double-sided adhesive sheet is adhered. In some embodiments, the laminate including the double-sided adhesive sheet is a laminate having the double-sided adhesive sheet and a metal member (first member). The laminate may have a metal member and a double-sided adhesive sheet covering at least a part of the surface of the metal member. The double-sided adhesive sheet may cover the entire surface of the metal member or may cover a part of the above surface (for example, a part of the area to be masked). Typically, one surface (adhesive surface) of the above double-sided adhesive sheet is adhered to the above metal member. In addition, in some embodiments, the member to which the double-sided adhesive sheet is adhered may have the light transmittance of the above adherend material. In this embodiment, the laminate including the double-sided adhesive sheet is a laminate having the double-sided adhesive sheet and a member having light transmittance (second member). In addition, in some preferred embodiments, the laminate is a laminate having a metal member (first member), a double-sided adhesive sheet, and a member having light transmittance (second member) in this order. It should be noted that the double-sided adhesive sheet without a substrate is also referred to as an adhesive layer in the laminate.

[0275] An example of the configuration of the above laminate is illustrated in Figure 3 as follows. Figure 3 The laminate 50 shown has a first member 41, a double-sided adhesive sheet 1 without a substrate, and a second member 42 in this order. Specifically, in the laminate 50, one adhesive surface (first adhesive surface) 1A of the double-sided adhesive sheet 1 without a substrate is adhered to the first member 41, and the other adhesive surface (second adhesive surface) 1B of the double-sided adhesive sheet 1 is adhered to the second member 42. In this embodiment, both the first member 41 and the second member 42 have a sheet-like or plate-like shape, and the laminate 50 has a multi-layer structure. In addition, in this embodiment, the first member 41 is a metal member and the second member 42 is a light-transmissive member. Details of the members constituting the laminate are as described as the above members, materials, and adherends, and thus will not be described repeatedly.

[0276] In addition, in some embodiments, the double-sided adhesive sheet is preferably used for electronic devices including various light sources such as LEDs (light-emitting diodes) and self-luminous light-emitting elements such as organic electroluminescence. For example, it can be preferably used for electronic devices (typically portable electronic devices) of an organic electroluminescence display device and a liquid crystal display device having required specified optical characteristics.

[0277] Figure 4 is a three-dimensional exploded view schematically showing an example of the configuration of a display device. As Figure 4As shown, the display device 500 of the portable electronic device 400 includes a display unit 520 composed of a cover member, an organic EL unit, etc., and a support unit 540. The display device 500 is constituted by further including a double-sided adhesive sheet 530. In this configuration example, the double-sided adhesive sheet 530 fixes the members constituting the display unit 520 and the support unit 540. It should be noted that the support unit 240 is constituted by including a substrate (such as a metal plate like a stainless steel plate or an aluminum plate). The adhesive sheet disclosed herein is preferably used as a constituent element of the display device as described above.

[0278] In addition, in some embodiments, the double-sided adhesive sheet disclosed herein may have an adhesive layer containing an acrylic polymer with a high biomass carbon ratio, so it can be used as a substitute for the acrylic adhesive in various applications where a conventional ordinary acrylic adhesive (i.e., an acrylic adhesive with a low biomass carbon ratio) is used, which can help reduce the dependence on fossil resource-based materials. The double-sided adhesive sheet disclosed herein can preferably be used as a double-sided adhesive sheet with a reduced dependence on fossil resource-based materials.

[0279] The matters disclosed in accordance with this specification include the following.

[0280] [1] A display device, the display device includes a display unit and a support unit, the display unit includes a cover member and an organic EL unit, wherein,

[0281] A double-sided adhesive sheet is joined to the support unit,

[0282] The double-sided adhesive sheet has a colored adhesive layer,

[0283] The adhesive layer contains an acrylic polymer,

[0284] The storage modulus of the adhesive layer at 0 °C is 0.95 MPa or less.

[0285] [2] The display device according to [1] above, wherein the monomer component constituting the acrylic polymer includes an acrylic alkyl ester having a linear alkyl group with 4 to 8 carbon atoms.

[0286] [3] The display device according to [1] or [2] above, wherein the monomer component constituting the acrylic polymer includes heptyl acrylate.

[0287] [4] The display device according to any one of [1] to [3] above, wherein the monomer component constituting the acrylic polymer includes n-butyl acrylate.

[0288] [5] The display device according to any one of [1] to [4] above, wherein the adhesive layer contains a black colorant.

[0289] [6] The display device according to any one of [1] to [5] above, wherein the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant.

[0290] [7] The display device according to any one of [1] to [6] above, wherein the double-sided adhesive sheet is a substrate-free adhesive sheet composed of the adhesive layer.

[0291] [8] The display device according to any one of [1] to [6] above, wherein the double-sided adhesive sheet is a substrate-bearing adhesive sheet including the adhesive layer and a support substrate.

[0292]

[11] A double-sided adhesive sheet with a release liner, the double-sided adhesive sheet with a release liner having: a double-sided adhesive sheet; a first release liner that protects a first adhesive surface of the double-sided adhesive sheet; and a second release liner that protects a second adhesive surface of the double-sided adhesive sheet, wherein

[0293] the double-sided adhesive sheet has a colored adhesive layer,

[0294] the adhesive layer contains an acrylic polymer,

[0295] the difference in peel force between the peel force R1 [N / 50 mm] of the first release liner on the first adhesive surface and the peel force R2 [N / 50 mm] of the second release liner on the second adhesive surface is 0.07 or more,

[0296] the storage modulus of the adhesive layer at 0 °C is 0.95 MPa or less.

[0297]

[12] The double-sided adhesive sheet with a release liner according to

[11] above, wherein the monomer component constituting the acrylic polymer contains an acrylic alkyl ester having a linear alkyl group with 4 to 8 carbon atoms.

[0298]

[13] The double-sided adhesive sheet with a release liner according to

[11] or

[12] above, wherein the monomer component constituting the acrylic polymer contains heptyl acrylate.

[0299]

[14] The double-sided adhesive sheet with a release liner according to any one of

[11] to

[13] above, wherein the monomer component constituting the acrylic polymer contains n-butyl acrylate.

[0300]

[15] The double-sided adhesive sheet with a release liner according to any one of

[11] to

[14] above, wherein the adhesive layer contains a black colorant.

[0301]

[16] The double-sided adhesive bonding sheet with a release liner as described in any one of

[11] to

[15] above, wherein the adhesive layer contains a black colorant as the first colorant and a metal oxide as the second colorant.

[0302]

[17] The double-sided adhesive bonding sheet with a release liner as described in any one of

[11] to

[16] above, wherein the peel force R1 [N / 50 mm] for peeling the first release liner from the first adhesive surface is lower than the peel force R2 [N / 50 mm] for peeling the second release liner from the second adhesive surface.

[0303] The peel force R1 for peeling the first release liner from the first adhesive surface is 0.3 N / 50 mm or less.

[0304]

[18] The double-sided adhesive bonding sheet with a release liner as described in any one of

[11] to

[17] above, wherein the double-sided adhesive bonding sheet is a substrate-free adhesive sheet composed of the adhesive layer.

[0305]

[19] The double-sided adhesive bonding sheet with a release liner as described in any one of

[11] to

[17] above, wherein the double-sided adhesive bonding sheet is a substrate-containing adhesive sheet including the adhesive layer and a support substrate.

[0306]

[20] The double-sided adhesive bonding sheet with a release liner as described in any one of

[11] to

[19] above, wherein the double-sided adhesive bonding sheet is used for fixing components in an electronic device.

[0307]

[21] A laminate having a metal component (first component) and a double-sided adhesive bonding sheet, wherein

[0308] The double-sided adhesive bonding sheet has a colored adhesive layer.

[0309] The adhesive layer contains an acrylic polymer.

[0310] The storage modulus of the adhesive layer at 0 °C is 0.95 MPa or less.

[0311]

[22] A laminate having: a component with light transmissivity (second component) and a double-sided adhesive bonding sheet, wherein

[0312] The double-sided adhesive bonding sheet has a colored adhesive layer.

[0313] The adhesive layer contains an acrylic polymer.

[0314] The storage modulus of the adhesive layer at 0 °C is 0.95 MPa or less.

[0315]

[23] A laminate having, in this order, a metal member (first member), a double-sided adhesive sheet, and a light-transmissive member (second member), wherein,

[0316] The double-sided adhesive sheet has a colored adhesive layer,

[0317] The adhesive layer contains an acrylic polymer,

[0318] The storage modulus of the adhesive layer at 0 °C is 0.95 MPa or less.

[0319]

[24] The laminate according to the above

[21] or

[23] , wherein the metal member is an aluminum member or a stainless steel member.

[0320]

[25] The laminate according to the above

[22] or

[23] , wherein the light transmittance of the light-transmissive member is greater than 50%.

[0321]

[26] The laminate according to the above

[22] ,

[23] , or

[25] , wherein the light-transmissive member includes a resin film.

[0322]

[27] The laminate according to any one of the above

[21] to

[26] , wherein the monomer component constituting the acrylic polymer includes an alkyl acrylate having a linear alkyl group with 4 to 8 carbon atoms.

[0323]

[28] The laminate according to any one of the above

[21] to

[27] , wherein the monomer component constituting the acrylic polymer includes heptyl acrylate.

[0324]

[29] The laminate according to any one of the above

[21] to

[28] , wherein the monomer component constituting the acrylic polymer includes n-butyl acrylate.

[0325]

[30] The laminate according to any one of the above

[21] to

[29] , wherein the adhesive layer contains a black colorant.

[0326]

[31] The laminate according to any one of the above

[21] to

[30] , wherein the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant.

[0327]

[32] The laminate according to any one of the above

[21] to

[31] , wherein the double-sided adhesive sheet is a substrate-free adhesive sheet composed of the adhesive layer.

[0328]

[33] The laminate according to any one of

[21] to

[31] above, wherein the double-sided adhesive sheet is a substrate-bearing adhesive sheet including the adhesive layer and the support substrate.

[0329]

[34] The laminate according to any one of

[21] to

[33] above, wherein the laminate is for an electronic device.

[0330] Examples

[0331] Hereinafter, several examples related to the present invention will be described, but the present invention is not limited to the content shown in these examples. It should be noted that in the following description, unless otherwise specified, "parts" and "%" used as units of content and addition amount are both based on weight.

[0332] <Evaluation method>

[0333] (Storage modulus)

[0334] The storage modulus of the adhesive layer can be obtained by dynamic viscoelasticity measurement. Specifically, by overlapping multiple adhesive layers to be measured (in the case of a double-sided adhesive sheet without a substrate, it is a double-sided adhesive sheet), an adhesive layer with a thickness of about 2 mm was fabricated. The adhesive layer was punched into a disk shape with a diameter of 7.9 mm, and the obtained specimen was sandwiched and fixed between parallel plates, and dynamic viscoelasticity measurement was performed under the following conditions using a viscoelasticity tester (for example, manufactured by TA Instruments, ARES or its equivalent) to obtain the storage modulus (storage modulus at 0 °C and 23 °C).

[0335] · Measurement mode: Shear mode

[0336] · Temperature range: -70 °C to 150 °C

[0337] · Heating rate: 5 °C / minute

[0338] · Measurement frequency: 1 Hz

[0339] It should be noted that as the adhesive layer to be measured, an adhesive layer formed by coating the corresponding adhesive composition in a layer and drying or curing it can be used.

[0340] (Transmittance)

[0341] The light transmittance [%] of the adhesive layer and the adhesive sheet was determined by measuring the light transmittance in the thickness direction of the adhesive layer and the adhesive sheet peeled from the release liner (light transmittance at wavelengths of 550 nm and 1380 nm) using a commercially available spectrophotometer. As the spectrophotometer, a spectrophotometer manufactured by Hitachi, Ltd. (equipment name "U4150 type spectrophotometer") or its equivalent can be used. It should be noted that the light transmittance at wavelengths of 550 nm and 1380 nm corresponds to the visible light transmittance and the infrared light transmittance, respectively. In addition, the above-mentioned light transmittance of the substrate-free double-sided adhesive sheet composed of the adhesive layer is also the light transmittance of the adhesive layer.

[0342] (Peeling force of the release liner)

[0343] The peeling force R1 of the first release liner from the first adhesive surface was measured by the following method. That is, the double-sided adhesive sheet with the release liner in each example was cut into a strip with a width of 50 mm and a length of 150 mm to obtain a test piece. In an environment of 23°C and 50% RH, the above test piece was set on a universal tensile-compression testing machine, and according to JIS Z0237, at a peeling angle of 180 degrees and a pulling speed of 300 mm / minute, the first release liner was peeled from the first adhesive surface, and the 180° peeling adhesion force (resistance to the above pulling) at this time was measured. The measurement was carried out 3 times (N = 3), and their average value was taken as the peeling force R1 [N / 50 mm] of the first release liner from the first adhesive surface.

[0344] The peeling force R2 of the second release liner from the second adhesive surface was measured by the following method. That is, the first release liner was peeled from the double-sided adhesive sheet with the release liner in each example, a PET film with a thickness of 25 μm was pasted on the exposed first adhesive surface and back-lined, and then it was cut into a strip with a width of 50 mm and a length of 150 mm to obtain a test piece. In an environment of 23°C and 50% RH, the above test piece was set on a universal tensile-compression testing machine, and according to JIS Z0237, at a peeling angle of 180 degrees and a pulling speed of 300 mm / minute, the second release liner was peeled from the second adhesive surface, and the 180° peeling adhesion force (resistance to the above pulling) at this time was measured. The measurement was carried out 3 times (N = 3), and their average value was taken as the peeling force R2 [N / 50 mm] of the second release liner from the second adhesive surface.

[0345] As the universal tensile-compression testing machine, a device named "Tensile-Compression Testing Machine, TCM-1kNB" manufactured by Minebea Co., Ltd. or its equivalent can be used.

[0346] (Evaluation of the adhesive surface after liner peeling)

[0347] Cut the double-sided adhesive sheet with a release liner (a laminate of a first release liner / double-sided adhesive sheet / second release liner) for each example into a size of 50 mm × 100 mm, and use it as a sample for evaluation. In a clean room environment, under the conditions of a peeling angle of 180 degrees and a peeling speed of 6 m / minute, peel the first release liner from the evaluation sample. After 1 hour, at the midpoint between a point light source arranged at a distance of about 100 cm and a projection screen (a position at a distance of about 50 cm from the point light source), hold the evaluation sample in a planar shape, and arrange it such that the exposed adhesive layer surface of the evaluation sample is at an angle of about 90 degrees with respect to the light from the point light source. For the evaluation sample, arrange the adhesive layer surface from which the first release liner has been peeled on the side of the point light source. In a dark room under an environment of 23°C and 50% RH, turn on the above-mentioned point light source, and visually observe the image projected onto the screen through the above-mentioned evaluation sample, thereby evaluating whether there is deformation on the adhesive layer surface (specifically, deformation extending in one direction on the adhesive surface such as undulation, striped roughening, etc.). As the point light source, for example, "Xenon lamp C2577" manufactured by Hamamatsu Photonics K.K. can be used. Prepare 10 evaluation samples for each example and conduct 10 evaluation tests (N = 10), and use the number X ( / 10) of evaluation tests (qualified) in which no visually recognizable deformation is observed as the evaluation result of the adhesive surface after the liner is peeled. If the number of qualified samples is 6 or more (i.e., 6 / 10 or more), it is determined that the deformation of the adhesive surface caused by the peeling of the release liner is sufficiently suppressed.

[0348] <Example 1>

[0349] (Preparation of acrylic polymer)

[0350] Into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel, put 95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components and ethyl acetate as a polymerization solvent, and stir for 2 hours while introducing nitrogen. Thereby, the oxygen in the polymerization system was removed, and then 0.2 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator was added, and solution polymerization was carried out at 60°C for 8 hours to obtain a solution of an acrylic polymer. The Mw of this acrylic polymer is about 70×10 4 .

[0351] (Preparation of adhesive composition)

[0352] In the above acrylic polymer solution, 20 parts of terpene phenol resin as a tackifying resin, 3 parts of isocyanate crosslinking agent as a crosslinking agent, and 0.01 part of epoxy crosslinking agent were added relative to 100 parts of the acrylic polymer contained in the solution. Further, carbon black particles as a colorant (black colorant) were added so as to reach 2.3% (based on solid content) in the adhesive layer, and the mixture was stirred and mixed to prepare an adhesive composition. As the terpene phenol resin (tackifying resin), the product name "YS Polystar T-115" (manufactured by Yasuhara Chemical Co., Ltd., softening point of about 115 °C, hydroxyl value of 30 mgKOH / g to 60 mgKOH / g) was used. As the isocyanate crosslinking agent, the product name "CORONATE L" (manufactured by Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane / toluene diisocyanate trimer adduct) was used. As the epoxy crosslinking agent, the product name "TETRAD-C" (manufactured by Mitsubishi Gas Chemical Company, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) was used. As the carbon black particles, the product name "Multilac A903" (manufactured by Toyocolor Co., Ltd., carbon black particle dispersion, average particle size of 400 nm) was used.

[0353] (Fabrication of Double-Sided Adhesive Sheet with Release Liner)

[0354] A first release liner (product name "Diafoil MRFF4", manufactured by Mitsubishi Chemical Corporation, thickness 75 μm, polyester release liner) and a second release liner (product name "SCA0", manufactured by Fuji Kogyo Co., Ltd., thickness 75 μm, PET release liner) were prepared. The above adhesive composition was coated on the release surface of the second release liner and dried at 100 °C for 2 minutes to form an adhesive layer with a thickness of 35 μm. The release surface of the first release liner was adhered to this adhesive layer. By such an operation, a double-sided adhesive sheet with a release liner was obtained in a form in which the first and second adhesive surfaces of a substrate-free double-sided adhesive sheet with a thickness of 35 μm composed of the above adhesive layer were protected by the first and second release liners, respectively.

[0355] <Examples 2 to 6>

[0356] Except for changing the type and amount of the colorant, the amount of the crosslinking agent, and the thickness of the adhesive layer in the adhesive layer as shown in Table 1, the same operations as in Example 1 were carried out to prepare the adhesive compositions for each example, and double-sided adhesive sheets with release liners for each example were fabricated using the adhesive compositions. In the table, the white colorant represents titanium oxide (TiO2) particles (product name "WHITE PASTE R-2228", manufactured by Dainichi Seika Kogyo Co., Ltd., average particle size 50 nm).

[0357] <Examples 7 to 10>

[0358] (Synthesis of acrylic polymer)

[0359] 93 parts of n-heptyl acrylate (n-HpA) and 7 parts of AA as monomer components and ethyl acetate as a polymerization solvent were charged into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel, and stirred for 2 hours while introducing nitrogen. Thereby, the oxygen in the polymerization system was removed, and then 0.2 part of AIBN as a polymerization initiator was added, and solution polymerization was carried out at 60°C to 70°C for 8 hours to obtain a solution of an acrylic polymer. The weight average molecular weight (Mw) of this acrylic polymer was 1.2 million. It should be noted that the above n-HpA is a compound synthesized using heptanol derived from biomass and having a heptyl group derived from biomass at the ester terminal.

[0360] (Production of double-sided adhesive sheet with release liner)

[0361] Except for using the above acrylic polymer solution and changing the types and amounts of the components contained in the adhesive layer and the adhesive layer thickness as shown in Table 1, the adhesive compositions of each example were prepared in the same manner as in Example 1, and double-sided adhesive sheets with release liners of each example were produced using the adhesive compositions. In the table, the rosin resin as a tackifying resin is a product named "HARITAC SE10" (hydrogenated rosin glyceride, softening point 75°C to 85°C, hydroxyl value 25 mgKOH / g to 40 mgKOH / g) manufactured by Harima Kasei Co., Ltd.

[0362] <Example 11>

[0363] Except for changing the monomer composition of the acrylic polymer to 97 parts of n-HpA and 3 parts of AA, a solution of the acrylic polymer of this example was obtained by substantially the same method as the preparation of the acrylic polymer in Example 7. Using the obtained acrylic polymer solution, the types and amounts of the crosslinking agent were changed as shown in Table 1, and except for this, the adhesive composition of this example was prepared in the same manner as in Example 7, and a double-sided adhesive sheet with a release liner of this example was produced using the adhesive composition.

[0364] <Example 12>

[0365] A double-sided adhesive sheet with a release liner of this example was produced by using a PET release liner (product name "MFAS", thickness 38 μm) manufactured by Toray Industries, Inc. instead of "Diafoil MRFF4" as the first release liner and operating in the same manner as in Example 7.

[0366] <Example 13>

[0367] A pressure-sensitive adhesive composition prepared by the method described in Example 2 was taken, and the above pressure-sensitive adhesive composition was coated on one surface (the first surface) of a PET film (trade name "Lumirror", manufactured by Toray Industries, Inc.) with a thickness of 2 μm as a base material layer, and dried at 100 °C for 2 minutes to form a first pressure-sensitive adhesive layer with a thickness of 20 μm. The release surface of a first release liner (trade name "Diafoil MRFF4", manufactured by Mitsubishi Chemical Corporation, thickness 75 μm, polyester release liner) was adhered to the above first pressure-sensitive adhesive layer. As the second release liner, a PET release liner (trade name "SCA0", thickness 75 μm) manufactured by Fuji Kogyo Co., Ltd. was prepared, and the above pressure-sensitive adhesive composition was coated on the release surface of the second release liner and dried at 100 °C for 2 minutes to form a second pressure-sensitive adhesive layer with a thickness of 20 μm. The second pressure-sensitive adhesive layer was transferred to the surface of the base material layer having the first pressure-sensitive adhesive layer where the pressure-sensitive adhesive layer was not formed. By such an operation, a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with a base material) of this example was produced.

[0368] <Examples 14 to 16>

[0369] Except for using the pressure-sensitive adhesive composition prepared by the method described in Example 7 as the pressure-sensitive adhesive composition, the same operations as in Example 13 were carried out to produce a double-sided pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet with a base material) of Example 14. In addition, in Example 15, the thickness of the pressure-sensitive adhesive layer was changed to 35 μm. In Example 16, a PET film (trade name "Lumirror", manufactured by Toray Industries, Inc.) with a thickness of 12 μm was used as the base material layer. In addition, the same operations as in Example 14 were carried out to produce double-sided pressure-sensitive adhesive sheets (double-sided pressure-sensitive adhesive sheets with a base material) of Examples 15 and 16.

[0370] <Comparative Example 1>

[0371] Except for changing the monomer composition of the acrylic polymer to 75 parts of 2-ethylhexyl acrylate (2EHA), 25 parts of N-acryloylmorpholine (ACMO), 0.1 part of 2-hydroxyethyl acrylate (HEA), and 3 parts of AA, an acrylic polymer solution of this example was obtained by substantially the same method as the preparation of the acrylic polymer in Example 1. Using the obtained acrylic polymer solution, the types and amounts of the components contained in the pressure-sensitive adhesive layer were changed as shown in Table 2. Except for this, the same operations as in Example 1 were carried out to prepare the pressure-sensitive adhesive composition of this example, and the pressure-sensitive adhesive composition was used to produce a double-sided pressure-sensitive adhesive sheet with a release liner of this example.

[0372] <Comparative Examples 2 to 4>

[0373] Using the acrylic polymer prepared by the method described in Example 1, the types and amounts of the components contained in the adhesive layer, the adhesive layer thickness, and the adhesive sheet configuration (presence or absence of a substrate) were changed as shown in Table 2. Except for this, the operations were the same as those in Example 1, and the adhesive compositions of each example were prepared respectively. Using the adhesive compositions, double-sided adhesive sheets with release liners were produced for each example.

[0374] <Comparative Example 5>

[0375] In Example 7, a PET release liner manufactured by Fuji Kogyo Co., Ltd. (trade name "SCA0", thickness 75 μm) was used as the first release liner, and a PET release liner manufactured by Toray Industries, Inc. (trade name "Cerapeel BX8A", thickness 75 μm) was used as the second release liner. Otherwise, the operations were the same as those in Example 7 to prepare the adhesive composition of this example. Using the adhesive composition, a double-sided adhesive sheet with a release liner was produced for this example.

[0376] The outlines and evaluation results of each example are shown in Tables 1 and 2.

[0377]

[0378]

[0379] As shown in Tables 1 and 2, the difference in peel force between the first release liner and the second release liner of the double-sided adhesive sheets with release liners of Examples 1 to 16 was 0.07 [N / 50 mm] or more, and they had a colored adhesive layer. The storage modulus of this adhesive layer at 0°C was 0.95 MPa or less, and the number of qualified evaluations of the adhesive surface after liner peeling was 6 / 10 or more. On the other hand, although the difference in peel force between the first release liner and the second release liner of Comparative Examples 1 to 4 where the storage modulus of the adhesive layer at 0°C was greater than 0.95 MPa was 0.07 or more, the evaluation results of the adhesive surface after liner peeling were worse than those of Examples 1 to 16. It is considered that due to the high storage modulus of the adhesive layer at 0°C, the deformation of the adhesive surface was not sufficiently relaxed. In addition, Comparative Example 5 was a variation of the release liner of the double-sided adhesive sheet used in Example 7, but the difference in peel force between the first release liner and the second release liner was insufficient, being 0.06, and the evaluation result of the adhesive surface after liner peeling was worse than that of Example 7.

[0380] From the above results, it can be seen that in a double-sided adhesive sheet with a release liner having a first release liner and a second release liner and having a colored adhesive layer containing an acrylic polymer, by adjusting the difference in peel force between the first release liner and the second release liner to 0.07 or more and adjusting the storage modulus of the adhesive layer at 0°C to 0.95 MPa or less, it is possible to highly suppress the deformation of the adhesive surface caused by the peeling of the release liner.

[0381] As described above, specific examples of the present invention have been described in detail, but they are merely illustrative and do not limit the claims. The technology described in the claims includes the content obtained by various modifications and changes to the above-described specific examples.

[0382] Reference Numeral Explanation

[0383] 1, 2, 530 Double-sided Adhesive Sheet

[0384] 1A First Adhesive Surface

[0385] 1B Second Adhesive Surface

[0386] 10 Support Substrate

[0387] 10A First Surface

[0388] 10B Second Surface

[0389] 21 First Adhesive Layer (Adhesive Layer)

[0390] 22 Second Adhesive Layer

[0391] 31 First Release Liner

[0392] 31A Release Surface

[0393] 31B Back Surface

[0394] 32 Second Release Liner

[0395] 32A Release Surface

[0396] 32B Back Surface

[0397] 41 First Component

[0398] 42 Second Component

[0399] 50 Laminate

[0400] 100, 200 Double-sided Adhesive Sheet with Release Liner

[0401] 400 Portable Electronic Device

[0402] 500 Display Device

[0403] 520 Display Unit

[0404] 540 Support Unit

Claims

1. A double-sided adhesive bonding sheet with a release liner, the double-sided adhesive bonding sheet with a release liner having: a double-sided adhesive bonding sheet; a first release liner that protects a first adhesive surface of the double-sided adhesive bonding sheet; and a second release liner that protects a second adhesive surface of the double-sided adhesive bonding sheet, wherein, the double-sided adhesive bonding sheet has a colored adhesive layer, the adhesive layer contains an acrylic polymer, the monomer components constituting the acrylic polymer contain 85% by weight or more of heptyl acrylate and contain 1% to 15% by weight of a carboxyl group-containing monomer, the difference in peel force between the peel force R1 [N / 50 mm] of the first release liner from the first adhesive surface and the peel force R2 [N / 50 mm] of the second release liner from the second adhesive surface is 0.07 or more and 1.0 or less, the storage modulus of the adhesive layer at 0°C is 0.95 MPa or less.

2. The double-sided adhesive bonding sheet with a release liner according to claim 1, wherein, the adhesive layer contains a black colorant.

3. The double-sided adhesive bonding sheet with a release liner as claimed in claim 1, wherein, the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant.

4. The double-sided adhesive bonding sheet with a release liner according to any one of claims 1 to 3, wherein, the peel force R1 [N / 50 mm] of the first release liner peeled from the first adhesive surface is lower than the peel force R2 [N / 50 mm] of the second release liner peeled from the second adhesive surface, the peel force R1 of the first release liner peeled from the first adhesive surface is 0.3 N / 50 mm or less.

5. The double-sided adhesive bonding sheet with a release liner according to any one of claims 1 to 3, wherein, the double-sided adhesive bonding sheet is a substrate-free bonding sheet composed of the adhesive layer.

6. The double-sided adhesive bonding sheet with a release liner according to any one of claims 1 to 3, wherein, the double-sided adhesive bonding sheet is a substrate-containing bonding sheet including the adhesive layer and a support substrate.

7. The double-sided adhesive bonding sheet with a release liner according to any one of claims 1 to 3, wherein, the double-sided adhesive bonding sheet is used for fixing components in an electronic device.

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