adhesive sheet

Abstract

To provide an adhesive sheet that has wavelength selectivity and blocks visible light but allows passage of infrared light.SOLUTION: The present invention relates to an adhesive sheet which contains a base polymer and a pigment, and has a light transmittance of 25% or less at a wavelength of from 380 to 500 nm, while having a light transmittance of 60% or more at a wavelength of from 800 to 2,500 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet, and particularly to an infrared-transmitting pressure-sensitive adhesive sheet. [Background technology]

[0002] Generally, adhesives (also called pressure-sensitive adhesives; the same applies below) are soft solids (viscoelastic bodies) at temperatures around room temperature, and have the property of easily adhering to adherends when pressure is applied. Utilizing these properties, adhesives are widely used for purposes such as joining, fixing, and protecting components inside mobile electronic devices such as mobile phones.

[0003] For example, in portable electronic devices, light-blocking pressure-sensitive adhesive sheets are used to prevent light leakage from light sources such as backlight modules. Patent documents 1 to 6 are cited as documents relating to this type of technology. Patent documents 1 to 5 disclose pressure-sensitive adhesive sheets having a black printed layer on one side of a resin film substrate. Patent document 6 is a prior art document that discloses a single-sided adhesive sheet to be laminated on a graphite sheet. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-87246 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-166891 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-83660 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-57375 [Patent Document 5] Japanese Patent Application Laid-Open No. 2018-2898 [Patent Document 6] Japanese Patent Application Publication No. 2017-52835 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional light-blocking adhesive sheets block not only visible light but also infrared light. Therefore, when such adhesive sheets are used in sensing devices that emit infrared light, the infrared light is also blocked, preventing the infrared light from reaching the target object and preventing the desired effect from being achieved. In addition, when inspecting the smoothness of such adhesive sheets, infrared light is irradiated onto the sheet surface using AOI (automated optical inspection) or the like, and blocking the infrared light also poses a problem, making such inspection impossible.

[0006] Therefore, the present invention has been made to solve the above problems in the prior art, and has an object to provide a pressure-sensitive adhesive sheet that has wavelength selectivity, blocking visible light and transmitting infrared light. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the inventors discovered that an adhesive sheet with wavelength selectivity can be obtained by adjusting the type and content of pigment contained in the adhesive layer, and thus completed the present invention.

[0008] That is, the present invention is as follows. [1] A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer containing a base polymer and a pigment, A pressure-sensitive adhesive sheet having a light transmittance of 25% or less for wavelengths of 380 to 500 nm and a light transmittance of 60% or more for wavelengths of 800 to 2500 nm. [2] The pressure-sensitive adhesive sheet according to [1], wherein the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. [3] The pressure-sensitive adhesive sheet according to [1] or [2], wherein the pressure-sensitive adhesive layer contains 0.5 to 20 parts by mass of a pigment per 100 parts by mass of a base polymer. [4] The pressure-sensitive adhesive sheet according to any one of [1] to [3], which has a thickness of 10 to 200 μm. [5] The pressure-sensitive adhesive sheet according to any one of [1] to [4], which has a 180° peel adhesive strength (N / 25 mm) of 3 N / 25 mm or more against a SUS304BA plate. [6] The pressure-sensitive adhesive sheet according to any one of [1] to [5], which does not have a substrate. [7] The pressure-sensitive adhesive sheet according to any one of [1] to [5], which has a substrate. [8] The pressure-sensitive adhesive sheet according to any one of [1] to [7], which is used in an electronic device equipped with a pressure-sensitive sensor. [9] The adhesive sheet according to [8], which is used to fix a pressure-sensitive sensor to other components in a portable electronic device equipped with the pressure-sensitive sensor.

[10] A portable electronic device using the adhesive sheet according to any one of [1] to [9]. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a pressure-sensitive adhesive sheet having wavelength selectivity, which blocks visible light and transmits infrared light. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is an example of a schematic cross-sectional view of a pressure-sensitive adhesive sheet (pressure-sensitive adhesive layer) according to an embodiment of the present invention. [Figure 2] FIG. 2 is an example of a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to an embodiment of the present invention. [Figure 3] FIG. 3 is an example of a schematic cross-sectional view of a pressure-sensitive adhesive sheet according to an embodiment of the present invention. [Figure 4] FIG. 4 is a graph showing the change in light transmittance in the pressure-sensitive adhesive sheets of the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments and can be modified as desired without departing from the spirit of the present invention. Furthermore, the symbol "to" indicating a numerical range is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0012] In this specification, the term "adhesive" refers to a material that is in a soft solid (viscoelastic) state at temperatures around room temperature and has the property of easily adhering to an adherend by pressure. The adhesive referred to here is generally a material having a complex tensile modulus E * (1Hz)< 10 7 dyne / cm 2 The material may be a material having the properties satisfying the above (typically, a material having the above properties at 25°C).

[0013] In addition, in this specification, unless otherwise specified, the term "main component" refers to a component that is contained in an amount of more than 50 mass %. In this specification, percentages based on mass are synonymous with percentages based on weight.

[0014] An adhesive sheet (hereinafter sometimes simply referred to as adhesive sheet) according to an embodiment of the present invention comprises an adhesive layer (hereinafter sometimes simply referred to as adhesive layer) containing a base polymer and a pigment, and is characterized by having a light transmittance of 25% or less for wavelengths of 380 to 500 nm and a light transmittance of 60% or more for wavelengths of 800 to 2500 nm.

[0015] <Light transmittance> The pressure-sensitive adhesive sheet of this embodiment has a light transmittance of 25% or less for wavelengths of 380 to 500 nm and 60% or more for wavelengths of 800 to 2500 nm. Here, "a light transmittance of 25% or less for wavelengths of 380 to 500 nm" means that the light transmittance is 25% or less over the entire wavelength range of 380 to 500 nm. Furthermore, "a light transmittance of 60% or more for wavelengths of 800 to 2500 nm" means that the light transmittance is 60% or more over the entire wavelength range of 800 to 2500 nm.

[0016] Wavelengths of 380 to 500 nm correspond to a part of the visible light range. By setting the light transmittance for wavelengths of 380 to 500 nm to 25% or less, the transmission of visible light can be sufficiently suppressed. It is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less. Wavelengths of 800 to 2500 nm correspond to a part of the infrared light range. When the light transmittance for wavelengths of 800 to 2500 nm is 60% or more, infrared light can be sufficiently transmitted. It is preferably 65% ​​or more, more preferably 70% or more, and even more preferably 75% or more.

[0017] The light transmittance at the specific wavelength can be set within the specific range by adjusting the type and content of a pigment, which is a component of the pressure-sensitive adhesive layer described below. Specifically, pigments come in various colors, such as red, yellow, green, blue, and purple, and each pigment exhibits its own unique light transmittance behavior. This can be achieved by selecting a pigment having the specified light transmittance from various pigments exhibiting various light transmittance behaviors, combining two or more pigments, or adjusting the content and content ratio of the various pigments. The above-mentioned light transmittance behavior is similar even when the compound is contained in the pressure-sensitive adhesive layer.

[0018] The light transmittance of the pressure-sensitive adhesive sheet of this embodiment can be determined by measuring the absorption spectrum using a spectrophotometer, for example, a U-4100 spectrophotometer (manufactured by Hitachi High-Technologies Corporation) at a measurement wavelength of 380 to 2500 nm.

[0019] The pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer that constitutes the pressure-sensitive adhesive sheet of this embodiment will be described below.

[0020] <Adhesive layer> The pressure-sensitive adhesive layer of this embodiment contains a base polymer and a pigment. Fig. 1 shows a schematic cross-sectional view of one example of the configuration of the pressure-sensitive adhesive layer of one embodiment of the present invention. While Fig. 1 shows a pressure-sensitive adhesive layer with a single layer structure, the pressure-sensitive adhesive layer may have a multi-layer structure of two or more layers. Each component contained in the pressure-sensitive adhesive layer will be described below.

[0021] (base polymer) In the present embodiment, the term "base polymer" refers to the main component of a rubbery polymer contained in the PSA. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature.

[0022] In this embodiment, the type of base polymer is not particularly limited, and any base polymer known in the field of pressure-sensitive adhesives can be used. For example, the base polymer may contain one or more of various rubber-like polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine-based polymers. From the viewpoints of adhesive performance and cost, it is preferable to contain an acrylic polymer or a rubber polymer as the base polymer. In particular, from the viewpoint of pigment dispersibility, which will be described later, it is more preferable to use an acrylic polymer as the base polymer. Hereinafter, a pressure-sensitive adhesive layer containing an acrylic polymer as the base polymer will be mainly described, but it is not intended to limit the pressure-sensitive adhesive layer in this embodiment to one composed of an acrylic polymer.

[0023] An "acrylic polymer" refers to a polymer containing, as a monomer unit constituting the polymer, a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an "acrylic monomer." Therefore, in this specification, an acrylic polymer is defined as a polymer containing a monomer unit derived from an acrylic monomer. A typical example of an acrylic polymer is an acrylic polymer in which the proportion of acrylic monomers in all monomer components used in the synthesis of the acrylic polymer is more than 50% by mass. Additionally, "(meth)acryloyl" refers collectively to acryloyl and methacryloyl. Similarly, "(meth)acrylate" refers collectively to acrylate and methacrylate, and "(meth)acrylic" refers collectively to acrylic and methacrylic.

[0024] The acrylic polymer is preferably a polymer of a monomer raw material that contains, for example, an alkyl(meth)acrylate as a main monomer and may further contain a secondary monomer copolymerizable with the main monomer, where the main monomer refers to a component that accounts for more than 50% by mass of the monomer composition in the monomer raw material.

[0025] As the alkyl(meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used. CH2=C(R 1 )COOR 2 (1) Here, R in the above formula (1) 1 is a hydrogen atom or a methyl group. 2 is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, this range of carbon atoms will be referred to as "C 1-20 From the viewpoint of the storage modulus of the adhesive, R 2 C 1-14 (For example, C 2-10 , typically C 4-8 From the viewpoint of adhesive properties, it is appropriate to use alkyl (meth)acrylate, which is a chain alkyl group of R 1 is a hydrogen atom and R 2 C 4-8 Alkyl acrylate (hereinafter simply referred to as C 4-8 It is preferable to use alkyl acrylate as the main monomer.

[0026] R 2 C 1-20Examples of alkyl(meth)acrylates, which are chain alkyl groups, include methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, and isooctyl(meth)acrylate. Examples of alkyl (meth)acrylates include butyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These alkyl (meth)acrylates can be used alone or in combination of two or more. Preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

[0027] The proportion of alkyl(meth)acrylate in the monomer components constituting the acrylic polymer is typically more than 50% by mass, and can be, for example, 70% by mass or more, or 85% by mass or more, or even 90% by mass or more. The proportion of alkyl(meth)acrylate in the monomer components is typically less than 100% by mass, and from the viewpoint of cohesive strength, etc., it is usually appropriate to set it to 99.5% by mass or less, and it may be 98% by mass or less (for example, less than 97% by mass).

[0028] In this embodiment, the monomer component is C 1-4 It is preferable to use an embodiment in which alkyl (meth)acrylate is contained in an amount of 50% by mass or more. 1-4The proportion of alkyl (meth)acrylate may be 70% by mass or more, or 85% by mass or more (for example, 90% by mass or more). 1-4 The proportion of alkyl (meth)acrylate is usually suitably 99.5% by mass or less, and may be 98% by mass or less (for example, less than 97% by mass).

[0029] In this embodiment, the monomer component is C 2-4 This can be preferably implemented in an embodiment in which alkyl acrylate is contained in an amount of 50% by mass or more (for example, 70% by mass or more, 85% by mass or more, or 90% by mass or more). 2-4 Specific examples of alkyl acrylates include ethyl acrylate, propyl acrylate, isopropyl acrylate, n-butyl acrylate (BA), isobutyl acrylate, s-butyl acrylate, and t-butyl acrylate. 2-4 The alkyl acrylates can be used alone or in combination of two or more. In this embodiment, a pressure-sensitive adhesive sheet with good adhesion to the adherend is easily realized. In a particularly preferred embodiment, the monomer component contains more than 50% by mass of BA (for example, 70% by mass or more, 85% by mass or more, or 90% by mass or more). C 2-4 By using a predetermined amount or more of alkyl acrylate (e.g., BA), even when a pigment described later is blended in the adhesive layer, the pigment can be well dispersed in the layer while maintaining good adhesive properties such as adhesive strength. On the other hand, from the viewpoint of obtaining good cohesive strength, etc., C 2-4 The proportion of alkyl (meth)acrylate is usually suitably 99.5% by mass or less, and may be 98% by mass or less (for example, less than 97% by mass).

[0030] In another embodiment, the monomer component is C 5-20 It is also possible to use an embodiment in which the alkyl (meth)acrylate is contained in an amount of 50% by mass or more (for example, 70% by mass or more, 85% by mass or more, or 90% by mass or more). 5-20As alkyl (meth)acrylate, C 6-14 Alkyl (meth)acrylates are preferred. 6-10 Alkyl acrylate (e.g., C 8-10 Alkyl acrylate) can be preferably used.

[0031] In this embodiment, the monomer component constituting the base polymer (e.g., an acrylic polymer) may contain a carboxyl group-containing monomer. By including a carboxyl group-containing monomer in the monomer component, it becomes easier to obtain a pressure-sensitive adhesive layer that exhibits good durability against impact in the shear direction. This can also be advantageous in improving the adhesion between the pressure-sensitive adhesive layer and the adherend. Examples of carboxyl group-containing monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, and isocrotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and their anhydrides (e.g., maleic anhydride, itaconic anhydride); and the like. These can be used alone or in combination. Among these, acrylic acid (AA) and methacrylic acid (MAA) are preferred as carboxyl group-containing monomers. AA is particularly preferred.

[0032] In an embodiment in which a carboxy group-containing monomer is copolymerized with the base polymer, the content of the carboxy group-containing monomer in the monomer components constituting the base polymer is not particularly limited and can be, for example, 0.2% by mass or more (typically 0.5% by mass or more) of the monomer components, and is usually 1% by mass or more, or may be 2% by mass or more, or may be 3% by mass or more. By making the content of the carboxy group-containing monomer greater than 3% by mass, a more effective effect is achieved, resulting in a pressure-sensitive adhesive layer with more excellent holding performance. From this perspective, in a preferred embodiment, the content of the carboxy group-containing monomer can be 3.2% by mass or more of the monomer components, more preferably 3.5% by mass or more, even more preferably 4% by mass or more, or may be 4.5% by mass or more. By copolymerizing such an amount of the carboxy group-containing monomer, even when a pigment described below is incorporated into the pressure-sensitive adhesive layer, the pigment can be well dispersed within the layer, while favorable adhesive properties such as shear holding power can be achieved.

[0033] The upper limit of the content of the carboxyl group-containing monomer is not particularly limited, and can be, for example, 15% by mass or less, or alternatively 12% by mass or less, or 10% by mass or less. By limiting the copolymerization ratio of the carboxyl group-containing monomer to a predetermined amount or less, even when a pigment described below is blended into the adhesive layer, the pigment can be well dispersed within the layer while maintaining good adhesive properties such as adhesive strength. This embodiment can also be preferably implemented in an embodiment in which the content of the carboxyl group-containing monomer is 7% by mass or less (typically less than 7% by mass, for example, 6.8% by mass or less, or 6.0% by mass or less) of the monomer components.

[0034] The secondary monomer copolymerizable with the alkyl (meth)acrylate main monomer can be useful for introducing crosslinking points into the acrylic polymer and for increasing the cohesive strength of the acrylic polymer. As the secondary monomer, for example, the following functional group-containing monomers (excluding the above-mentioned carboxy group-containing monomers) can be used alone or in combination of two or more. Hydroxyl group-containing monomers: for example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol and allyl alcohol; and polypropylene glycol mono(meth)acrylate. Amide group-containing monomers: for example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide. Amino group-containing monomers: for example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Monomers having an epoxy group: for example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether. Cyano group-containing monomers: for example, acrylonitrile, methacrylonitrile. Keto group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate. Monomers having a nitrogen atom-containing ring: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, and N-(meth)acryloylmorpholine. Alkoxysilyl group-containing monomers: for example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane.

[0035] When the monomer component constituting the acrylic polymer contains the functional group-containing monomer described above, the content of the functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of properly achieving the effects of using the functional group-containing monomer, the content of the functional group-containing monomer in the monomer component can be, for example, 0.1% by mass or more, typically 0.5% by mass or more is appropriate, and may be 1% by mass or more. Furthermore, from the viewpoint of easily balancing adhesive performance in relation to the main monomer and the carboxyl group-containing monomer, the content of the functional group-containing monomer in the monomer component is typically 40% by mass or less, preferably 20% by mass or less, and may be 10% by mass or less (e.g., 5% by mass or less). The technology disclosed herein can also be preferably implemented in an embodiment in which the monomer component is substantially free of the functional group-containing monomer (e.g., an embodiment in which the monomer component is substantially composed only of an alkyl (meth)acrylate and a carboxyl group-containing monomer). Here, "the monomer components are substantially free of functional group-containing monomers" means that functional group-containing monomers are not used at least intentionally, and it is acceptable for functional group-containing monomers to be unintentionally included in an amount of, for example, 0.05% by mass or less (typically 0.01% by mass or less). An acrylic polymer having such a monomer composition can be one in which pigments, which will be described later, can be easily dispersed.

[0036] The monomer components constituting the acrylic polymer may contain copolymerization components other than the above-mentioned minor monomers for the purpose of improving cohesion, etc. Examples of the copolymerization components include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrenes (such as α-methylstyrene), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; and aromatic ring-containing (meth)acrylates such as aryl (meth)acrylates (e.g., phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g., phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylates (e.g., benzyl (meth)acrylate). olefin-based monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; 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-based monomers such as methyl vinyl ether and ethyl vinyl ether; polyfunctional monomers having two or more (e.g., three or more) polymerizable functional groups (e.g., (meth)acryloyl groups) in one molecule, such as 1,6-hexanediol di(meth)acrylate and trimethylolpropane tri(meth)acrylate; and the like.

[0037] The amount of such other copolymerization components is not particularly limited and may be appropriately selected depending on the purpose and application. From the viewpoint of properly achieving the effects of use, it is usually appropriate to set it to 0.05% by mass or more, and it may be 0.5% by mass or more. Furthermore, from the viewpoint of easily balancing adhesive performance, the content of other copolymerization components in the monomer components is usually appropriate to 20% by mass or less, and may be 10% by mass or less (e.g., 5% by mass or less). In this embodiment, an embodiment in which the monomer components are substantially free of other copolymerization components is also preferred. Here, "substantially free of other copolymerization components" means that other copolymerization components are not used at least intentionally, and it is acceptable for other copolymerization components to be unintentionally present at, for example, 0.01% by mass or less. Acrylic polymers having such a monomer composition may be ones in which pigments, as described below, are easily dispersed.

[0038] The copolymer composition of the acrylic polymer is suitably designed so that the glass transition temperature (Tg) of the polymer is −15° C. or lower (for example, −70° C. or higher and −15° C. or lower). Here, the Tg of the acrylic polymer refers to the Tg calculated by the Fox equation based on the composition of the monomer components used in the synthesis of the polymer. The Fox equation, as shown below, is a relationship between the Tg of the copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer. 1 / Tg=Σ(Wi / Tgi) In the above Fox formula, Tg represents the glass transition temperature (unit: K) of the copolymer, Wi represents the mass fraction of monomer i in the copolymer (copolymerization ratio on a mass basis), and Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i.

[0039] The glass transition temperature of the homopolymer used to calculate Tg is determined based on the value described in the publicly available literature. For example, for the following monomers, the following values ​​are used as the glass transition temperatures of the homopolymers of the monomers: 2-Ethylhexyl acrylate -70℃ Isononyl acrylate -60℃ n-Butyl acrylate -55℃ Ethyl acrylate -22℃ Methyl acrylate 8℃ Methyl methacrylate 105℃ 2-Hydroxyethyl acrylate -15℃ 4-Hydroxybutyl acrylate -40℃ Vinyl acetate 32℃ Acrylic acid 106℃ Methacrylic acid 228℃

[0040] For the glass transition temperatures of homopolymers of monomers other than those listed above, the values ​​described in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) shall be used. For monomers for which multiple values ​​are described in this document, the highest value shall be used. If the value is not described in the Polymer Handbook, the value obtained by the measurement method described in JP 2007-51271 A shall be used.

[0041] Although not particularly limited, from the viewpoint of adhesion to an adherend, the Tg of the acrylic polymer is advantageously -25°C or lower, preferably -35°C or lower, and more preferably -40°C or lower. In one embodiment, from the viewpoint of cohesive strength, the Tg of the acrylic polymer may be, for example, -65°C or higher, -60°C or higher, or -55°C or higher. The technology disclosed herein can be preferably implemented in an embodiment in which the Tg of the acrylic polymer is -65°C or higher and -35°C or lower (e.g., -55°C or higher and -40°C or lower). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the types and ratios of monomers used in synthesizing the polymer).

[0042] The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing 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. The polymerization temperature during solution polymerization can be appropriately selected depending on the types of monomers and solvents used, the type of polymerization initiator, and the like, and can be, for example, 20°C to 170°C (typically 40°C to 140°C).

[0043] The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents. For example, any one solvent or a mixture of two or more solvents selected from aromatic compounds (typically aromatic hydrocarbons) such as toluene, acetate esters such as ethyl acetate, aliphatic or alicyclic hydrocarbons such as hexane and cyclohexane, halogenated alkanes such as 1,2-dichloroethane, lower alcohols (for example, monohydric alcohols having 1 to 4 carbon atoms) such as isopropyl alcohol, ethers such as tert-butyl methyl ether, and ketones such as methyl ethyl ketone can be used.

[0044] The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, one or more azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide-based initiators such as benzoyl peroxide and hydrogen peroxide; substituted ethane-based initiators such as phenyl-substituted ethane; and aromatic carbonyl compounds. Still other examples of polymerization initiators include redox-based initiators formed by combining a peroxide with a reducing agent. Such polymerization initiators can be used alone or in combination of two or more. The amount of polymerization initiator used may be a typical amount, and can be selected, for example, from the range of 0.005 to 1 part by mass (typically 0.01 to 1 part by mass) per 100 parts by mass of the monomer components.

[0045] The solution polymerization produces a polymerization reaction solution in the form of an acrylic polymer dissolved in an organic solvent. The pressure-sensitive adhesive layer in this embodiment may contain the polymerization reaction solution or an acrylic polymer solution obtained by subjecting the reaction solution to an appropriate post-treatment. The acrylic polymer solution may be prepared by adjusting the polymerization reaction solution to an appropriate viscosity (concentration) as necessary. Alternatively, an acrylic polymer solution may be prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (e.g., emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent.

[0046] The mass average molecular weight (Mw) of the base polymer (preferably an acrylic polymer) in the technology disclosed herein is not particularly limited, and may be, for example, 10 × 10 4 ~500×10 4 From the viewpoint of adhesive performance, the Mw of the base polymer can be in the range of 30×10 4 ~200×10 4 (More preferably 45 × 10 4 ~150×10 4 , typically 65 x 10 4 ~130×10 4 ) range. By using a base polymer with a high Mw, better impact resistance tends to be obtained by utilizing the cohesive force of the polymer itself. Here, Mw refers to the value calculated as standard polystyrene by GPC (gel permeation chromatography). As a GPC device, for example, a model "HLC-8320GPC" (column: TSKgel GMH-H(S), manufactured by Tosoh Corporation) can be used.

[0047] (pigment) In this embodiment, it is important to use a pigment in order to impart the functions of visible light absorption and infrared light transmission while maintaining adhesive strength. When a pigment is used, there is no concern that the pigment component will bleed out onto the adhesive surface during accelerated environment storage (storage at high temperature and humidity), and the adhesive strength as an adhesive can be fully exerted.

[0048] The type of pigment used in this embodiment is selected so that the pressure-sensitive adhesive sheet of this embodiment has a light transmittance of 25% or less at wavelengths of 380 to 500 nm and a light transmittance of 60% or more at wavelengths of 800 to 2500 nm. As long as the condition for light transmittance at the above-mentioned specific wavelengths is met, the type of pigment is not particularly limited, and both organic and inorganic pigments can be used.

[0049] Examples of organic pigments include azo pigments such as azo lake pigments, insoluble monoazo pigments, insoluble disazo pigments, condensed azo pigments, and chelate azo pigments; polycyclic pigments such as phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments; chelates such as basic dye chelates and acid dye chelates; nitro pigments; and nitroso pigments. These can be used alone or in combination of two or more.

[0050] Examples of inorganic pigments include titanium oxide, iron oxide, red iron oxide, chromium oxide, iron blue, ultramarine, molybdenum red, iron black, yellow lead, etc. These can be used alone or in combination of two or more. Among these, isoindolinone pigments, quinacridone pigments, condensed azo pigments, phthalocyanine pigments, quinophthalone pigments, and anthraquinone pigments are preferably used in view of light resistance.

[0051] Specific examples of organic pigments include Pigment Yellow 1 (Color Index (CI) 11680), Pigment Yellow 3 (CI 11710), Pigment Yellow 14 (CI 21095), Pigment Yellow 17 (CI 21105), Pigment Yellow 42 (CI 77492), Pigment Yellow 74 (CI 11741), Pigment Yellow 83 (CI 21108), Pigment Yellow 93 (CI 20710), and Pigment Yellow 98 (CI 11727). , Pigment Yellow 109 (CI 56284), Pigment Yellow 110 (CI 56280), Pigment Yellow 128 (CI 20037), Pigment Yellow 129 (CI 48042), Pigment Yellow 138 (CI 56300), Pigment Yellow 139 (CI 56298), Pigment Yellow 147 (CI 60645), Pigment Yellow 150 (CI 12764), Pigment Yellow 154 (CI 11781), Pigment Yellow 155 (CI 20031 0), Pigment Yellow 180 (CI 21290), Pigment Yellow 185 (CI 56280), Pigment Yellow 199 (CI 653200), Pigment Orange 5 (CI 12075), Pigment Orange 13 (CI 21110), Pigment Orange 16 (CI 21160), Pigment Orange 34 (CI 21160), Pigment Orange 43 (CI 71105), Pigment Orange 61 (CI 11265), Pigment Orange 71 (CI 561200), Pigment Pigment Red 5 (CI 12490), Pigment Red 8 (CI 12335), Pigment Red 17 (CI 12390), Pigment Red 22 (CI 12315), Pigment Red 48:2 (CI 15865:2), Pigment Red 112 (CI 12370), Pigment Red 122 (CI 73915), Pigment Red 170 (CI 12475), Pigment Red 176 (CI 12515), Pigment Red 177 (CI 65300), Pigment Red 178 (CI71155), Pigment Red 179 (CI 71130), Pigment Red 185 (CI 12516), Pigment Red 202 (CI 73907), Pigment Red 208 (CI 12514), Pigment Red 254 (CI 56110), Pigment Red 255 (CI 561050), Pigment Red 264, Pigment Red 272 (CI 561150), Pigment Violet 19 ( Examples of suitable pigments include Pigment Blue 15:1 (CI 74160), Pigment Blue 15:3 (CI 74160), Pigment Blue 15:4 (CI 74160), Pigment Blue 60 (CI 69800), Pigment Green 7 (CI 74260), and Pigment Green 36 (CI 74265), and a mixture of two or more of these pigments is preferred.

[0052] Specific examples of inorganic pigments include Pigment Yellow 42 (CI 77492), Pigment White 6 (CI 77891), Pigment Blue 27 (CI 77510), Pigment Blue 29 (CI 77007), and Pigment Black 7 (CI 77266), and one or a mixture of two or more thereof is preferred.

[0053] Considering the hue and tinting strength, the following pigments are listed: Pigment Yellow 74 (CI 11741), Pigment Yellow 109 (CI 56284), Pigment Yellow 110 (CI 56280), Pigment Yellow 128 (CI 20037), Pigment Yellow 138 (CI 56300), Pigment Yellow 150 (CI 12764), Pigment Yellow 155 (CI 200310), Pigment Yellow 180 (CI 21290), Pigment Green 7 (CI 74260), Pigment Green 36 (CI 74265), Pigment Red 122 (CI 7 Pigment Red 177 (CI 65300), Pigment Red 202 (CI 73907), Pigment Red 254 (CI 56110), Pigment Violet 19 (CI 73900), Pigment Violet 23 (CI 51319), Pigment Blue 15:1 (CI 74160), Pigment Blue 15:3 (CI 74160), Pigment Blue 15:4 (CI 74160), Pigment Blue 15:6 (CI 74160), Pigment Blue 60 (CI 69800), and Pigment Black 7 (CI 77266) are preferred. Pigments can be in powder, granular, wet cake, or slurry form.

[0054] Among these, one or more pigments selected from the group consisting of Pigment Red 177 (CI 65300), Pigment Red 254 (CI 56110), and Pigment Yellow 150 (CI 12764) are particularly suitable for use as red pigments. The combination of Pigment Red 177 (CI 65300) and Pigment Yellow 150 (CI 12764) is particularly suitable, as is the combination of Pigment Red 177 (CI 65300), Pigment Red 254 (CI 56110), and Pigment Yellow 150 (CI 12764). Optimizing the blending ratio of these pigments can further improve the contrast ratio, which is one of the color performance features. Since it is important to match the blending ratio of Pigment Yellow 150 to the desired chromaticity, a blending ratio of 5 to 40% by weight of the pigment content is preferred.

[0055] For green ink, one or more pigments selected from the group consisting of Pigment Green 7 (CI 74260), Pigment Green 36 (CI 74265), Pigment Yellow 138 (CI 56300), and Pigment Yellow 150 (CI 12764) can be suitably used. On the other hand, for blue ink, pigments such as Pigment Blue 15:6 (CI 74160) and / or Pigment Violet 23 (CI 51319) can be suitably used.

[0056] In this embodiment, the average particle size of the pigment can be set so that a pressure-sensitive adhesive sheet having the desired light transmittance is formed, and is not particularly limited. From the viewpoint of light scattering and diffraction, the lower limit of the average particle size of the pigment can be, for example, 10 nm or more, and may be 50 nm or more, 100 nm or more, or 150 nm or more. From the viewpoint of light scattering and diffraction, the upper limit of the average particle size of the pigment can be, for example, 500 nm or less, 300 nm or less, 250 nm or less, or 200 nm or less.

[0057] The average particle size of the pigment mentioned above refers to the volume average particle size, specifically the particle size at 50% of the cumulative value in the particle size distribution measured using a particle size distribution measuring device based on the laser scattering and diffraction method (50% volume average particle size; hereinafter, D 50 As a measuring device, for example, a product named "Microtrac MT3000II" manufactured by Microtrac Bell or an equivalent product can be used.

[0058] In this embodiment, the form in which the pigment is added to the PSA composition is not particularly limited. For example, the pigment may be added to the PSA composition in the form of a dispersion in which the pigment particles are dispersed in a dispersion medium. The dispersion medium constituting the dispersion is not particularly limited, 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 mixtures thereof), and aqueous mixtures of water and the above organic solvents. The dispersion may contain a dispersant, as described below. By mixing the dispersion with the PSA composition, the PSA composition contains the pigment and may also contain a dispersant, as described below.

[0059] The amount of pigment to be added is not particularly limited and can be set so as to form a pressure-sensitive adhesive sheet that satisfies the above-mentioned desired light transmittance. Usually, it is appropriate to add 0.5 parts by mass or more per 100 parts by mass of the base polymer, and from the viewpoint of light-blocking properties, it is preferably 1.0 part by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more (for example, 4.0 parts by mass or more). In addition, from the viewpoint of suppressing a deterioration in adhesive properties that may occur due to the incorporation of pigment, the upper limit of the amount of pigment to be incorporated is preferably 20 parts by mass or less per 100 parts by mass of base polymer, more preferably 10 parts by mass or less, even more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less.

[0060] (Other ingredients) [Dispersibility improving component] The adhesive composition forming the adhesive layer of the present embodiment may contain a component that contributes to improving the dispersibility of the pigment. Such a dispersibility-improving component may be, for example, a polymer, an oligomer, a liquid resin, a surfactant, or the like. The dispersibility-improving component is preferably dissolved in the adhesive composition. The oligomer may be, for example, a low-molecular-weight polymer (e.g., a polymer having an Mw of 10×10) of a monomer component containing one or more of the acrylic monomers exemplified above. 4 Less than 5 x 10 4 The liquid resin may be, for example, a tackifying resin (typically a rosin-, terpene-, or hydrocarbon-based tackifying resin, such as hydrogenated rosin methyl ester) having a softening point of 50°C or less, more preferably 40°C or less. Such a dispersibility-improving component can suppress uneven pigment dispersion, and thus suppress color unevenness in the pressure-sensitive adhesive layer. Therefore, a pressure-sensitive adhesive layer and a pressure-sensitive adhesive sheet with better appearance quality can be formed.

[0061] The content of the dispersibility-improving component is not particularly limited, and from the viewpoint of suppressing effects on adhesive properties (e.g., reduced cohesion), it is usually appropriate to set it to 20% by mass or less (preferably 10% by mass or less, more preferably 7% by mass or less, for example 5% by mass or less) of the entire pressure-sensitive adhesive layer. In one embodiment, the content of the dispersibility-improving component can be 10 times or less (preferably 5 times or less, for example 3 times or less) the mass of the pigment. On the other hand, from the viewpoint of optimally exerting the effects of the dispersibility-improving component, it is usually appropriate to set it to 0.2% by mass or more (typically 0.5% by mass or more, preferably 1% by mass or more) of the entire pressure-sensitive adhesive layer. In one embodiment, the content of the dispersibility-improving component can be 0.2 times or more (preferably 0.5 times or more, for example 1 time or more) the mass of the pigment.

[0062] [Tackifying resin] The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer of this embodiment can contain a tackifier resin. This can increase the peel strength of the pressure-sensitive adhesive layer and the pressure-sensitive adhesive sheet. The tackifier resin can be one or more selected from various known tackifier resins, such as phenol-based tackifier resins, terpene-based tackifier resins, modified terpene-based tackifier resins, rosin-based tackifier resins, hydrocarbon-based tackifier resins, epoxy-based tackifier resins, polyamide-based tackifier resins, elastomer-based tackifier resins, and ketone-based tackifier resins.

[0063] Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkyl phenolic resins, and rosin phenolic resins.

[0064] Terpene phenolic resin refers to a polymer containing terpene residues and phenol residues, and is a concept that encompasses both copolymers of terpenes and phenolic compounds (terpene-phenol copolymer resins) and phenol-modified terpene homopolymers or copolymers of terpenes (phenol-modified terpene resins). Suitable examples of terpenes that constitute such terpene phenolic resins include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l-, and d / l- (dipentene) forms). Hydrogenated terpene phenolic resins have a structure obtained by hydrogenating such terpene phenolic resins. They are also sometimes called hydrogenated terpene phenolic resins.

[0065] Alkylphenol resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac and resol types.

[0066] Rosin phenolic resins are typically phenol-modified products of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosin phenolic resins include those obtained by adding phenol to rosins or the various rosin derivatives described above using an acid catalyst and then thermally polymerizing the resulting mixture.

[0067] Examples of terpene-based tackifying resins include polymers of terpenes (typically monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. They may be homopolymers of one type of terpene, or copolymers of two or more types of terpenes. Examples of homopolymers of one type of terpene include α-pinene polymers, β-pinene polymers, and dipentene polymers. Examples of modified terpene resins include those obtained by modifying the above-mentioned terpene resins. Specific examples include styrene-modified terpene resins and hydrogenated terpene resins.

[0068] The concept of rosin-based tackifying resins herein encompasses both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (raw rosins) such as gum rosin, wood rosin, and tall oil rosin; and modified rosins obtained by modifying these unmodified rosins through hydrogenation, disproportionation, polymerization, etc. (hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosins, etc.).

[0069] Rosin derivative resins are typically derivatives of the rosins described above. The term "rosin-based resin" as used herein encompasses derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). Examples include rosin esters, such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; unsaturated fatty acid-modified rosins, which are rosin esters modified with unsaturated fatty acids; unsaturated fatty acid-modified rosin esters, which are rosin esters modified with unsaturated fatty acids; rosin alcohols, which are obtained by reducing the carboxyl groups of rosins or the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters); and metal salts of rosins or the various rosin derivatives described above. Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, and the like of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

[0070] Examples of hydrocarbon-based tackifying resins include various hydrocarbon-based resins such as aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic / aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic / alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone resins, and coumarone-indene resins.

[0071] The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving cohesive strength, in one embodiment, a tackifier resin having a softening point (softening temperature) of 80°C or higher (preferably 100°C or higher) can be preferably used. The technology disclosed herein can be preferably implemented in an embodiment in which, assuming the total amount of tackifier resins contained in the PSA layer as 100% by mass, more than 50% by mass (more preferably more than 70% by mass, for example more than 90% by mass) of the tackifier resins have the above softening point. For example, a phenolic tackifier resin (such as a terpene phenol resin) having such a softening point can be preferably used. The tackifier resin may, for example, contain a terpene phenol resin having a softening point of 135°C or higher (or even 140°C or higher). The upper limit of the softening point of the tackifier resin is not particularly limited. From the viewpoint of improving adhesion to an adherend, in one embodiment, a tackifier resin having a softening point of 200°C or lower (more preferably 180°C or lower) can be preferably used. In a preferred embodiment, the softening point of the tackifier resin (typically a terpene phenol resin) is less than 130° C., for example, 120° C. or less. By using a tackifier resin with a relatively low softening point, for example, the dispersibility of pigments can be improved. The softening point of the tackifier resin can be measured based on the softening point test method (ring and ball method) specified in JIS K2207.

[0072] In one preferred embodiment, the tackifier resin comprises one or more phenolic tackifier resins (typically terpene phenol resins). The technology disclosed herein can be preferably implemented, for example, in an embodiment in which, assuming the total amount of tackifier resins to be 100% by mass, 25% by mass or more (more preferably 30% by mass or more) of the tackifier resins is terpene phenol resin. Terpene phenol resins may account for 50% by mass or more of the total amount of tackifier resins, or 80% by mass or more (e.g., 90% by mass or more). Substantially all of the tackifier resins (e.g., 95 to 100% by mass, or even 99 to 100% by mass) may be terpene phenol resins.

[0073] Although not particularly limited, in the PSA composition forming the PSA layer of the present embodiment, the tackifier resin may contain a tackifier resin having a hydroxyl value of more than 20 mgKOH / g. Among these, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more is preferred. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH / g or more may be referred to as a "high hydroxyl value resin." A PSA layer having excellent adhesion to an adherend and high cohesive strength can be obtained by using a tackifier resin containing such a high hydroxyl value resin. In one embodiment, the tackifier resin may contain a high hydroxyl value resin having a hydroxyl value of 50 mgKOH / g or more (more preferably 70 mgKOH / g or more). The hydroxyl value can be measured by potentiometric titration as specified in JIS K0070:1992.

[0074] As the high hydroxyl value resin, any of the above-mentioned various tackifier resins having a hydroxyl value equal to or greater than a predetermined value can be used. The high hydroxyl value resins can be used singly or in combination of two or more. For example, a phenolic tackifier resin having a hydroxyl value of 30 mgKOH / g or more can be preferably used as the high hydroxyl value resin. In a preferred embodiment, a terpene phenol resin having a hydroxyl value of at least 30 mgKOH / g or more is used as the tackifier resin. Terpene phenol resins are advantageous because the hydroxyl value can be freely controlled by the copolymerization ratio of phenol.

[0075] The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the base polymer, the hydroxyl value of the high hydroxyl value resin is usually 200 mgKOH / g or less, preferably 180 mgKOH / g or less, more preferably 160 mgKOH / g or less, and even more preferably 140 mgKOH / g or less. This embodiment can be preferably implemented in an embodiment in which the tackifier resin contains a high hydroxyl value resin having a hydroxyl value of 30 to 160 mgKOH / g (e.g., a phenolic tackifier resin, preferably a terpene phenol resin). In one embodiment, a high hydroxyl value resin having a hydroxyl value of 30 to 80 mgKOH / g (e.g., 30 to 65 mgKOH / g) can be preferably used. In another embodiment, a high hydroxyl value resin having a hydroxyl value of 70 to 140 mgKOH / g can be preferably used.

[0076] Although not particularly limited, when a high hydroxyl value resin is used, the proportion of the high hydroxyl value resin (e.g., terpene phenol resin) in the total tackifier resin contained in the PSA composition forming the PSA layer can be, for example, 25% by mass or more, preferably 30% by mass or more, and more preferably 50% by mass or more (e.g., 80% by mass or more, typically 90% by mass or more). Substantially all of the tackifier resin (e.g., 95 to 100% by mass, or even 99 to 100% by mass) may be the high hydroxyl value resin.

[0077] When the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer contains a tackifier resin, the amount of the tackifier resin used is not particularly limited and can be appropriately set, for example, within the range of 1 to 100 parts by mass per 100 parts by mass of the base polymer. From the viewpoint of optimally exhibiting the effect of improving peel strength, the amount of the tackifier resin used per 100 parts by mass of the base polymer (e.g., an acrylic polymer) is typically 5 parts by mass or more, preferably 10 parts by mass or more, and may be 15 parts by mass or more. For example, in a pressure-sensitive adhesive layer containing a pigment, the dispersibility of the pigment tends to be improved by including a predetermined amount of a tackifier resin (e.g., a terpene phenol resin having a softening point of 120°C or less). Furthermore, from the viewpoint of heat-resistant cohesive strength, the amount of the tackifier resin used per 100 parts by mass of the base polymer (e.g., an acrylic polymer) is typically 50 parts by mass or less, and may be 40 parts by mass or less, or may be 30 parts by mass or less.

[0078] [Crosslinking agent] The pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer of this embodiment may contain a crosslinking agent, if necessary. The type of crosslinking agent is not particularly limited, and may be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, melamine-based crosslinking agents, peroxide-based crosslinking agents, urea-based crosslinking agents, metal alkoxide-based crosslinking agents, metal chelate-based crosslinking agents, metal salt-based crosslinking agents, carbodiimide-based crosslinking agents, hydrazine-based crosslinking agents, amine-based crosslinking agents, and silane coupling agents. The crosslinking agents may be used alone or in combination of two or more.

[0079] In a preferred embodiment, the crosslinking agent is a combination of an isocyanate-based crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from that of the isocyanate-based crosslinking agent. According to the technology disclosed herein, by using a crosslinking agent other than an isocyanate-based crosslinking agent (i.e., a crosslinking agent having a different type of crosslinkable reactive group from that of the isocyanate-based crosslinking agent; hereinafter also referred to as a "non-isocyanate-based crosslinking agent") in combination with an isocyanate-based crosslinking agent, it is possible to achieve both high heat-resistant cohesive strength and excellent metal corrosion prevention properties in a composition containing, for example, an azole-based rust inhibitor. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after crosslinking, a form before crosslinking, a partially crosslinked form, or an intermediate or composite form thereof. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking.

[0080] As the isocyanate-based crosslinking agent, a polyfunctional isocyanate (which refers to a compound having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate-based crosslinking agent can be used alone or in combination of two or more.

[0081] Examples of polyfunctional isocyanates include aliphatic polyisocyanates, alicyclic polyisocyanates, and aromatic polyisocyanates. Specific examples of aliphatic polyisocyanates include 1,2-ethylene diisocyanate; tetramethylene diisocyanates such as 1,2-tetramethylene diisocyanate, 1,3-tetramethylene diisocyanate, and 1,4-tetramethylene diisocyanate; hexamethylene diisocyanates such as 1,2-hexamethylene diisocyanate, 1,3-hexamethylene diisocyanate, 1,4-hexamethylene diisocyanate, 1,5-hexamethylene diisocyanate, 1,6-hexamethylene diisocyanate, and 2,5-hexamethylene diisocyanate; 2-methyl-1,5-pentane diisocyanate, 3-methyl-1,5-pentane diisocyanate, and lysine diisocyanate.

[0082] Specific examples of alicyclic polyisocyanates include isophorone diisocyanate; cyclohexyl diisocyanates such as 1,2-cyclohexyl diisocyanate, 1,3-cyclohexyl diisocyanate, and 1,4-cyclohexyl diisocyanate; cyclopentyl diisocyanates such as 1,2-cyclopentyl diisocyanate and 1,3-cyclopentyl diisocyanate; hydrogenated xylylene diisocyanate, hydrogenated tolylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated tetramethylxylene diisocyanate, and 4,4'-dicyclohexylmethane diisocyanate.

[0083] Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, Examples of the diisocyanate include 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate, xylylene-1,4-diisocyanate, and xylylene-1,3-diisocyanate.

[0084] A preferred example of a polyfunctional isocyanate is one having an average of three or more isocyanate groups per molecule. Such a trifunctional or higher isocyanate may be a multimer (typically a dimer or trimer) of a bifunctional or trifunctional or higher isocyanate, a derivative (for example, an addition reaction product of a polyhydric alcohol and two or more molecules of a polyfunctional isocyanate), a polymer, or the like. Examples of polyfunctional isocyanates include a dimer or trimer of diphenylmethane diisocyanate, an isocyanurate of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), a reaction product of trimethylolpropane and tolylene diisocyanate, a reaction product of trimethylolpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, polyester polyisocyanate, and the like. Commercially available products of such polyfunctional isocyanates include those manufactured by Asahi Kasei Chemicals Corporation under the trade name "Duranate TPA-100," and those manufactured by Tosoh Corporation under the trade names "Coronate L," "Coronate HL," "Coronate HK," "Coronate HX," and "Coronate 2096."

[0085] The amount of the isocyanate-based crosslinking agent used is not particularly limited. For example, it can be 0.5 parts by mass or more per 100 parts by mass of the base polymer. From the viewpoint of obtaining higher cohesive strength (particularly heat-resistant cohesive strength), the amount of the isocyanate-based crosslinking agent used per 100 parts by mass of the base polymer can be, for example, 1.0 part by mass or more, and may be 1.5 parts by mass or more (typically 2.0 parts by mass or more, for example 2.5 parts by mass or more). On the other hand, from the viewpoint of improving adhesion to the adherend, the amount of the isocyanate-based crosslinking agent used is usually suitably 10 parts by mass or less per 100 parts by mass of the base polymer, and may be 8 parts by mass or less, or may be 5 parts by mass or less.

[0086] The type of non-isocyanate crosslinking agent used in combination with the isocyanate crosslinking agent is not particularly limited, and can be appropriately selected from the crosslinking agents described above. The non-isocyanate crosslinking agents can be used alone or in combination of two or more.

[0087] In a preferred embodiment, an epoxy-based crosslinking agent can be used as the non-isocyanate-based crosslinking agent. As the epoxy-based crosslinking agent, any compound having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy-based crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. The epoxy-based crosslinking agents can be used alone or in combination of two or more.

[0088] Specific examples of epoxy crosslinking agents include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc. Commercially available epoxy crosslinking agents include "TETRAD-C" and "TETRAD-X" manufactured by Mitsubishi Gas Chemical Company, Inc., "Epiclon CR-5L" manufactured by DIC Corporation, "Denacol EX-512" manufactured by Nagase ChemteX Corporation, and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

[0089] The amount of epoxy-based crosslinking agent used is not particularly limited. For example, the amount of epoxy-based crosslinking agent used can be more than 0 part by mass and not more than 1 part by mass (typically 0.001 to 0.5 parts by mass) per 100 parts by mass of the base polymer. From the viewpoint of optimally exhibiting the effect of improving cohesive strength, the amount of epoxy-based crosslinking agent used is typically 0.002 parts by mass or more per 100 parts by mass of the base polymer, preferably 0.005 parts by mass or more, and more preferably 0.008 parts by mass or more. Furthermore, from the viewpoint of improving adhesion to the adherend, the amount of epoxy-based crosslinking agent used is typically 0.2 parts by mass or less per 100 parts by mass of the base polymer, preferably 0.1 parts by mass or less, more preferably less than 0.05 parts by mass, and even more preferably less than 0.03 parts by mass (for example, 0.025 parts by mass or less).

[0090] In this embodiment, the relationship between the content of the isocyanate-based crosslinking agent and the content of the non-isocyanate-based crosslinking agent (e.g., epoxy-based crosslinking agent) is not particularly limited. The content of the non-isocyanate-based crosslinking agent can be, for example, 1 / 50 or less of the content of the isocyanate-based crosslinking agent. From the viewpoint of more favorably achieving both adhesion to the adherend and cohesive strength, the content of the non-isocyanate-based crosslinking agent is suitably 1 / 75 or less of the content of the isocyanate-based crosslinking agent on a mass basis, and preferably 1 / 100 or less (e.g., 1 / 150 or less). Furthermore, from the viewpoint of favorably exhibiting the effects of using an isocyanate-based crosslinking agent and a non-isocyanate-based crosslinking agent (e.g., epoxy-based crosslinking agent) in combination, the content of the non-isocyanate-based crosslinking agent is usually suitably 1 / 1000 or more, for example, 1 / 500 or more of the content of the isocyanate-based crosslinking agent.

[0091] The total amount of crosslinking agent used is not particularly limited and can be, for example, 10 parts by mass or less, preferably 0.005 to 10 parts by mass, more preferably 0.01 to 5 parts by mass, per 100 parts by mass of the base polymer (preferably an acrylic polymer).

[0092] Furthermore, the pressure-sensitive adhesive composition forming the pressure-sensitive adhesive layer may contain, as necessary, various additives commonly used in the field of pressure-sensitive adhesives, such as a leveling agent, a crosslinking aid, a plasticizer, a softener, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, etc. As for such various additives, conventionally known ones can be used in the usual manner, and they do not particularly characterize the present invention, so detailed description thereof will be omitted.

[0093] The pressure-sensitive adhesive layer of this embodiment may be a pressure-sensitive adhesive layer formed from an aqueous pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. The aqueous pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive (a pressure-sensitive adhesive layer-forming component) in a solvent (aqueous solvent) whose main component is water, and typically includes what is called a water-dispersed pressure-sensitive adhesive composition (a composition in which at least a portion of the pressure-sensitive adhesive is dispersed in water). The solvent-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive in an organic solvent. From the viewpoint of adhesive properties, etc., this embodiment can be preferably implemented in an embodiment having a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition.

[0094] When the pressure-sensitive adhesive layer has a multilayer structure of two or more layers, it can be produced by laminating pre-formed pressure-sensitive adhesive layers. Alternatively, a pressure-sensitive adhesive composition may be applied to a pre-formed first pressure-sensitive adhesive layer, and the pressure-sensitive adhesive composition may be cured to form a second pressure-sensitive adhesive layer. When the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet described below, which is used in an attachment mode in which the sheet is attached to an adherend and then photo-cured, has a multilayer structure, the pressure-sensitive adhesive layer to be photo-cured may be a part (e.g., one layer) or all of the layers included in the multilayer structure.

[0095] When a pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive composition, the application can be carried out using a conventional coater such as a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, etc. In a pressure-sensitive adhesive sheet having a substrate, which will be described later, a direct method in which a pressure-sensitive adhesive layer is formed by directly applying a pressure-sensitive adhesive composition to the substrate may be used as a method for providing a pressure-sensitive adhesive layer on the substrate, or a transfer method in which a pressure-sensitive adhesive layer formed on a release surface is transferred to the substrate may be used.

[0096] The thickness of the pressure-sensitive adhesive layer is not particularly limited and may be, for example, 3 μm to 2000 μm. From the viewpoint of adhesion to the adherend, such as conformability to unevenness, in some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 5 μm or more, suitably 10 μm or more, preferably 20 μm or more, and more preferably 30 μm or more. The thickness of the pressure-sensitive adhesive layer may be 50 μm or more, more than 50 μm, 70 μm or more, 100 μm or more, or 120 μm or more. Furthermore, from the viewpoint of preventing adhesive residue due to cohesive failure of the pressure-sensitive adhesive layer, in some embodiments, the thickness of the pressure-sensitive adhesive layer may be, for example, 1000 μm or less, 700 μm or less, 500 μm or less, 300 μm or less, 200 μm or less, or 170 μm or less. The technology according to this embodiment can also be suitably implemented in the form of a pressure-sensitive adhesive sheet, as described below, in which the thickness of the pressure-sensitive adhesive layer is 130 μm or less, 90 μm or less, or 60 μm or less (for example, 40 μm or less). In the pressure-sensitive adhesive sheet, as described below, having a pressure-sensitive adhesive layer with a multilayer structure of two or more layers, the thickness of the pressure-sensitive adhesive layer refers to the thickness from the pressure-sensitive adhesive surface attached to the adherend to the surface opposite to the pressure-sensitive adhesive surface.

[0097] <Adhesive sheet> An adhesive sheet according to one embodiment of the present invention comprises the adhesive layer. The adhesive sheet according to this embodiment may be a substrate-attached adhesive sheet having an adhesive layer on one side (FIG. 2) or both sides (FIG. 3) of a sheet-like substrate (support), or may be a substrateless adhesive sheet having an adhesive layer supported on a release sheet. The concept of adhesive sheet here may include those known as adhesive tapes, adhesive labels, adhesive films, etc.

[0098] The pressure-sensitive adhesive layer is typically formed continuously, but is not limited to such a form, and may be formed in a regular or random pattern such as a dotted or striped pattern. The pressure-sensitive adhesive sheet of the present embodiment may be in the form of a roll or sheets. Alternatively, the pressure-sensitive adhesive sheet may be processed into various shapes.

[0099] From the viewpoint of having step-conforming properties, the pressure-sensitive adhesive sheet of this embodiment is preferably a substrate-less form, i.e., does not have a substrate, as shown in Figure 1. When the object to which the pressure-sensitive adhesive sheet is to be attached has a step (e.g., 10 μm), the pressure-sensitive adhesive sheet's step-conforming properties allow the pressure-sensitive adhesive sheet to be attached along the step. This allows the pressure-sensitive adhesive sheet to be attached to the object without any gaps, thereby improving the waterproofness of the object.

[0100] The pressure-sensitive adhesive sheet of this embodiment may also include a support substrate, as shown in FIG. 2. This allows the pressure-sensitive adhesive sheet to be processed with high precision by punching or the like. Such a pressure-sensitive adhesive sheet is preferred for applications in which it is processed into a specific shape or narrowed for use. The thickness of the support substrate in this embodiment is, for example, less than 75 μm. A support substrate with a limited thickness is preferably used for applications requiring thinness and weight reduction. For example, limiting the thickness of the support substrate to relatively increase the thickness of the pressure-sensitive adhesive layer can improve adhesive properties such as peel strength and impact resistance. From this perspective, the thickness of the support substrate is preferably 60 μm or less, more preferably 50 μm or less (e.g., less than 50 μm), even more preferably 40 μm or less, and particularly preferably 30 μm or less (e.g., less than 30 μm, typically 25 μm or less). In one embodiment, the thickness of the support substrate may be 20 μm or less, 12 μm or less, or 7 μm or less (e.g., 3 μm or less). There is no particular lower limit on the thickness of the support substrate. From the viewpoint of the handleability and processability of the PSA sheet, the thickness of the support substrate is usually 0.5 μm or more (e.g., 1 μm or more). In one embodiment, the thickness of the support substrate may be 3 μm or more. In another embodiment, the thickness of the support substrate may be 8 μm or more, or may be 13 μm or more, or may be 16 μm or more.

[0101] The structure and material of the supporting substrate are not particularly limited, and it is typically a film-like substrate (also referred to as a "substrate film"). As the substrate film, one containing a resin film as a base film can be preferably used. The base film is typically a member that can independently maintain its shape (independent). The substrate film in this embodiment may be substantially composed of such a base film. Alternatively, the substrate film may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc., provided on the surface of the base film.

[0102] The resin film is a film containing a resin material as a main component (e.g., a component contained in the resin film at more than 50% by mass). Examples of resin films include polyolefin-based resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester-based resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); polyurethane-based resin films; vinyl chloride-based resin films; vinyl acetate-based resin films; polyimide-based resin films; polyamide-based resin films; fluororesin films; cellophane; and the like. The resin film may also be a rubber-based film such as a natural rubber film or a butyl rubber film. Among these, polyester films are preferred from the viewpoint of handleability and processability, and PET films are particularly preferred. In this specification, the term "resin film" refers to a typically non-porous sheet, a concept distinguished from so-called nonwoven fabrics and woven fabrics (in other words, a concept excluding nonwoven fabrics and woven fabrics).

[0103] The above-mentioned pigments can also be incorporated into the substrate film (typically a resin film), thereby adjusting the light transmittance and light blocking properties of the substrate film.

[0104] The amount of pigment used in the base film is not particularly limited and can be adjusted as appropriate to impart the desired optical properties. The amount of pigment is usually 0.1 to 30% by mass of the total mass of the base film, and can be, for example, 0.1 to 25% by mass (typically 0.1 to 20% by mass).

[0105] The base film may contain various additives, such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), antioxidants, antioxidants, UV absorbers, antistatic agents, lubricants, plasticizers, etc. The blending ratio of the various additives is usually less than 30% by mass (for example, less than 20% by mass, typically less than 10% by mass).

[0106] The substrate film may have a single layer structure, or a multilayer structure of two, three or more layers. From the viewpoint of shape stability, the substrate film preferably has a single layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the resin (e.g., polyester resin, typically a resin containing a black colorant). The method for producing the substrate film (typically a resin film) is not particularly limited and may be any conventionally known method. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calendar roll molding may be used appropriately.

[0107] The substrate film may be colored by a colored layer disposed on the surface of the base film (preferably a resin film). In such a substrate film having a configuration including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be disposed on either one surface of the base film, or may be disposed on both surfaces. In a configuration in which colored layers are disposed on both surfaces of the base film, the configurations of these colored layers may be the same or different.

[0108] Such a colored layer can typically be formed by applying a colored layer-forming composition containing a colorant and a binder to a base film. Conventionally known pigments and dyes can be used as the colorant. Materials known in the fields of paint and printing can be used as the binder without particular limitation. Examples include polyurethane, phenolic resin, epoxy resin, urea melamine resin, and polymethyl methacrylate. The colored layer-forming composition can be, for example, solvent-based, UV-curable, or heat-curable. The colored layer can be formed using any method conventionally used for forming colored layers, without particular limitation. For example, methods of forming a colored layer (printed layer) by printing, such as gravure printing, flexographic printing, and offset printing, can be preferably used.

[0109] The colored layer may have a single layer structure consisting of a single layer, or a multilayer structure including two, three, or more sub-colored layers. A colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For a colored layer intended to impart light-blocking properties, a multilayer structure is particularly useful from the viewpoint of preventing pinholes from occurring and increasing the reliability of preventing light leakage.

[0110] The overall thickness of the colored layer is usually 1 μm to 10 μm, preferably 1 μm to 7 μm, and can be, for example, 1 μm to 5 μm. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is usually preferably 1 μm to 2 μm.

[0111] The surface of the substrate film may be subjected to a conventional surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, or application of a primer. Such a surface treatment may be a treatment for improving the adhesion between the substrate film and the PSA layer, in other words, the anchoring ability of the PSA layer to the substrate film. Furthermore, when the technology disclosed herein is implemented in the form of a substrate-attached single-sided PSA sheet, the back surface of the substrate film may be subjected to a release treatment, if necessary. The release treatment may be, for example, a treatment in which a general silicone-based, long-chain alkyl-based, or fluorine-based release agent is applied in the form of a thin film, typically 0.01 μm to 1 μm (e.g., 0.01 μm to 0.1 μm). Such a release treatment may have the effect of facilitating unwinding of a roll of the PSA sheet.

[0112] Furthermore, in the pressure-sensitive adhesive sheet of this embodiment, a release liner can be used during the formation of the pressure-sensitive adhesive layer, the production of the pressure-sensitive adhesive sheet, and the storage, distribution, and shaping of the pressure-sensitive adhesive sheet before use. The release liner is not particularly limited, and examples that can be used include release liners having a release treatment layer on the surface of a liner substrate such as a resin film or paper, and release liners made of low-adhesion materials such as fluorine-based polymers (polytetrafluoroethylene, etc.) and polyolefin-based resins (polyethylene, polypropylene, etc.). The release treatment layer can be formed by surface-treating the liner substrate with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

[0113] (Adhesive sheet thickness) The total thickness of the pressure-sensitive adhesive sheet of this embodiment (which includes a pressure-sensitive adhesive layer and, in a configuration having a supporting substrate, further includes a supporting substrate, but does not include a release liner) is not particularly limited. From the viewpoint of achieving a thinner pressure-sensitive adhesive sheet, the total thickness is typically 200 μm or less. There are no particular lower limits for the thickness of the pressure-sensitive adhesive sheet, and it can typically be 1 μm or more, for example, 3 μm or more is suitable, preferably 6 μm or more, and more preferably 10 μm or more (e.g., 15 μm or more).

[0114] In a preferred embodiment, the total thickness of the pressure-sensitive adhesive sheet is 150 μm or less, more preferably 120 μm or less, even more preferably 70 μm or less, and particularly preferably 50 μm or less (e.g., 40 μm or less), and may be, for example, 35 μm or less, 25 μm or less, or even 15 μm or less or 10 μm or less (e.g., 7 μm or less). Even in a configuration using such a thin pressure-sensitive adhesive sheet, the light-blocking effect of this embodiment can be preferably exhibited.

[0115] The ratio of the total thickness of the pressure-sensitive adhesive layers contained in the pressure-sensitive adhesive sheet to the total thickness of the pressure-sensitive adhesive sheet is not particularly limited. Here, the total thickness of the pressure-sensitive adhesive layers contained in the pressure-sensitive adhesive sheet refers to the total thickness of the pressure-sensitive adhesive layer provided on one surface of the substrate film and the pressure-sensitive adhesive layer provided on the other surface. In the case of a single-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided only on one surface of the substrate film, the thickness of the pressure-sensitive adhesive layer provided on the other surface is zero, and the thickness of the pressure-sensitive adhesive layer provided on the one surface and the total thickness of the pressure-sensitive adhesive layers are the same. The technology disclosed herein can be implemented, for example, in an embodiment in which the ratio of the total thickness of the pressure-sensitive adhesive layers to the total thickness of the pressure-sensitive adhesive sheet is 40% or more (preferably 50% or more, typically more than 50%, more preferably 60% or more, and even more preferably 70% or more). This configuration tends to exhibit a higher level of impact resistance, even in narrow widths, compared to the total thickness of the pressure-sensitive adhesive sheet. In one embodiment, the ratio of the total thickness of the pressure-sensitive adhesive layers to the total thickness of the pressure-sensitive adhesive sheet may be 75% or more, or even 80% or more. There is no particular upper limit on the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet, but it is usually appropriate that it be 95% or less, and preferably 90% or less.

[0116] (Characteristics of adhesive sheet) The adhesive sheet of this embodiment preferably has a 180° peel adhesive strength (N / 25mm) against a SUS304BA plate of 3N / 25mm or more, more preferably 5N / 25mm or more, and even more preferably 10N / 25mm or more.

[0117] The adhesive strength can be measured by a peel adhesion test in accordance with JIS Z 0237:2009. Specifically, a 50 μm thick PET film is attached to one adhesive surface of a double-sided pressure-sensitive adhesive sheet under an environment of 23°C and 50% RH, and the sheet is then cut to a width of 25 mm to prepare a measurement sample. The other adhesive surface of the measurement sample is attached to a SUS304BA plate as an adherend, with a 25 mm wide, 100 mm long adhesive area, by rolling a 2 kg roller back and forth once. The measurement sample thus attached to the adherend is left for 5 days under an environment of 65°C and 90% RT. The force (N / 25 mm) is then measured when the measurement sample is peeled from the adherend at a peel angle of 180° and a pulling rate of 300 mm / min.

[0118] <Application> The pressure-sensitive adhesive sheet of the present embodiment has excellent processing accuracy, and is therefore suitable for applications in which it can be processed into a specific shape or narrowed for use, such as fixing components in portable electronic devices. Some electronic devices, such as portable electronic devices, include light-emitting elements for purposes such as image display, so the pressure-sensitive adhesive sheet may be required to have light-blocking properties. Some devices also use infrared light, and may be required to have light-blocking properties against visible light and selectively transmit infrared light. The pressure-sensitive adhesive sheet of this embodiment has wavelength selectivity, blocking visible light and transmitting infrared light, and therefore may meet the needs of the above-mentioned devices.

[0119] Non-limiting examples of the portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wristwear devices worn on the wrist like a wristwatch, modular devices worn on a part of the body with a clip or strap, eyewear devices including eyeglasses (monocular and binocular, including head-mounted devices), clothing devices attached to shirts, socks, hats, etc. as accessories, earwear devices attached to the ears like earphones, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic organizers, e-books, in-car information devices, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, "portable" does not simply mean that the device is portable, but rather means that the device has a level of portability that allows an individual (average adult) to carry it relatively easily.

[0120] The pressure-sensitive adhesive sheet of the present embodiment can be preferably used, for example, for the purpose of fixing a pressure-sensitive sensor to other members in a portable electronic device equipped with a pressure-sensitive sensor among such portable electronic devices. In a preferred embodiment, the pressure-sensitive adhesive sheet can be used to fix a pressure-sensitive sensor to other members in an electronic device (typically a portable electronic device) equipped with a function that enables an absolute position to be specified on a plate (typically a touch panel) corresponding to the screen using a device for indicating a position on the screen (typically a pen-type or mouse-type device) and a device for detecting the position.

[0121] The pressure-sensitive adhesive sheet of the present embodiment is also suitable for use in applications in which it is disposed on the back surface of a display screen (display unit) such as a touch panel display in a portable electronic device to prevent light reflection through the display screen. By disposing the pressure-sensitive adhesive sheet of the present embodiment on the back surface of the display screen (display unit), it is possible to prevent a decrease in visibility of the display screen regardless of how the portable electronic device is used. Furthermore, the above-mentioned reflection can be caused by a metal member disposed on the back side of the display screen. However, by using the pressure-sensitive adhesive sheet disclosed herein, for example, to bond the metal member to the display unit, it is possible to simultaneously achieve bonding of the members and impart light-blocking properties.

[0122] Materials constituting the fixing object (e.g., back surface member such as an electromagnetic wave shield or a reinforcing plate) of the pressure-sensitive sensor, display unit, etc. are not particularly limited, and examples thereof include metal materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc., or alloys containing two or more of these; various resin materials (typically plastic materials) such as polyimide resin, acrylic resin, polyethernitrile resin, polyethersulfone resin, polyester resin (e.g., polyethylene terephthalate resin, polyethylene naphthalate resin), polyvinyl chloride resin, polyphenylene sulfide resin, polyetheretherketone resin, polyamide resin (so-called aramid resin, etc.), polyarylate resin, polycarbonate resin, and liquid crystal polymer; and inorganic materials such as alumina, zirconia, soda glass, quartz glass, and carbon. Among these, metal materials such as copper, aluminum, and stainless steel, and resin materials (typically plastic materials) such as polyimide resin, aramid resin, and polyphenylene sulfide resin are widely used. The object to be fixed may have either a single layer structure or a multilayer structure, and the surface to which the pressure-sensitive adhesive sheet is attached (the attachment surface) may be subjected to various surface treatments. Although not particularly limited, an example of the object to be fixed is a backing member having a thickness of 1 μm or more (typically 5 μm or more, e.g., 60 μm or more, or even 120 μm or more) and 1500 μm or less (e.g., 800 μm or less). [Example]

[0123] The present invention will be described in more detail below with reference to examples and comparative examples, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

[0124] <Evaluation method> [Light transmittance] The light transmittance of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples in the wavelength range of 380 nm to 2500 nm was determined by measuring the absorption spectrum using a spectrophotometer (U-4100 spectrophotometer, manufactured by Hitachi High-Technologies Corporation).

[0125] [180° peel adhesive strength] The adhesive strength of the pressure-sensitive adhesive sheets of the Examples and Comparative Examples was evaluated by a peel adhesion test in accordance with JIS Z 0237:2009. Specifically, a 50 μm thick PET film was attached to one adhesive surface of a double-sided pressure-sensitive adhesive sheet under an environment of 23°C and 50% RH, and the sheet was then cut to a width of 25 mm to prepare a measurement sample. The other adhesive surface of the measurement sample was attached to a SUS304BA plate as an adherend, with a bonding area of ​​25 mm wide and 100 mm long, by rolling a 2 kg roller back and forth once. The measurement sample thus attached to the adherend was left for 5 days under an environment of 65°C and 90% RT. The force (N / 25 mm) when the measurement sample was peeled from the adherend at a peel angle of 180° and a pulling speed of 300 mm / min was then measured.

[0126] [Profile tracking] The pressure-sensitive adhesive sheets of the Examples and Comparative Examples were evaluated for their ability to conform to uneven surfaces by conducting a waterproof evaluation test. First, the pressure-sensitive adhesive sheets of the Examples and Comparative Examples prepared were cut into window frame shapes (picture frame shapes) with a width of 1 mm (width: 60 mm, height: 40 mm) to obtain window frame-shaped double-sided pressure-sensitive adhesive tapes. Next, the window frame-shaped double-sided pressure-sensitive adhesive tapes were attached to four acrylic plates (acrylic lenses, width: 60 mm, height: 40 mm, thickness: 1 mm), and then the four acrylic plates with the window frame-shaped double-sided pressure-sensitive adhesive tapes attached were pressed against a polycarbonate plate (PC plate) with two step tapes (width: 5 mm) attached using a 2 kg roller, moving back and forth once, to obtain evaluation samples for each unevenness height (10 μm). Waterproofing evaluation tests were conducted in accordance with the IPX7 standard (JIS C 0920 / IEC60529) by submerging the above evaluation samples for each unevenness height in a water tank 1m deep for 30 minutes under standard conditions (temperature: 23°C, humidity: 50%) and checking for water seepage.The waterproofing property evaluation test was conducted after aging the evaluation samples for each unevenness height for 30 minutes under standard conditions (temperature: 23°C, humidity: 50%). The presence or absence of water penetration into the sample was visually observed and evaluated as follows. No flooding: Yes Water ingress: ×

[0127] Example 1 (Preparation of Pressure-Sensitive Adhesive Composition) A reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser, and dropping funnel was charged with 95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this way, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 8 hours to obtain an acrylic polymer solution. The Mw of this acrylic polymer was approximately 70 x 10 4 It was. To the acrylic polymer solution, 0.4 parts of 1,2,3-benzotriazole (trade name "BT-120" manufactured by Johoku Chemical Industry Co., Ltd.), 2 parts of a pigment (pigment type "PG (Pigment Green)-7"), 20 parts of a terpene phenolic resin (trade name "YS Polystar T-115" manufactured by Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mgKOH / g) as a tackifier, 3 parts of an isocyanate crosslinking agent (trade name "Coronate L" manufactured by Tosoh Corporation, 75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct) as a crosslinker, and 0.01 parts of an epoxy crosslinking agent (trade name "TETRAD-C" manufactured by Mitsubishi Gas Chemical Co., Ltd., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) as a crosslinker were added and stirred to prepare a pressure-sensitive adhesive composition.

[0128] (Preparation of adhesive sheet) As release liners, one polyester release film (trade name "Diafoil MRF", thickness 38 μm and thickness 75 μm, manufactured by Mitsubishi Polyester Corporation) with one release-treated release surface was prepared. The above-mentioned pressure-sensitive adhesive composition was applied to the release surface of these release liners so that the thickness after drying was 35 μm, and then dried at 100°C for 2 minutes. In this way, a pressure-sensitive adhesive layer was formed on each release surface of the two release liners. In this way, a substrate-less double-sided pressure-sensitive adhesive sheet with a thickness of 35 μm and both sides protected by the two polyester release liners was obtained.

[0129] <Example 2> In this example, the substrateless double-sided adhesive sheet of this example was produced in the same manner as the adhesive sheet of Example 1, except that 2 parts of the pigment type "PR-177" was used as the pigment.

[0130] Example 3 In this example, the substrateless double-sided adhesive sheet of this example was produced in the same manner as the adhesive sheet of Example 1, except that 2 parts of the pigment type "PG-36" was used as the pigment.

[0131] Example 4 In this example, the substrateless double-sided adhesive sheet of this example was produced in the same manner as the adhesive sheet of Example 1, except that 1 part of the pigment type "PV-23" and 1 part of the pigment type "PY-74" were used as pigments.

[0132] <Example 5> In this example, the substrateless double-sided adhesive sheet of this example was produced in the same manner as the adhesive sheet of Example 1, except that 1 part of the pigment type "PV-23" and 1 part of the pigment type "PY-138" were used as pigments.

[0133] Example 6 In this example, the substrateless double-sided adhesive sheet of this example was produced in the same manner as the adhesive sheet of Example 1, except that 1 part of the pigment type "PV-23" and 1 part of the pigment type "PY-150" were used as pigments.

[0134] Example 7 In this example, the substrateless double-sided adhesive sheet of this example was produced in the same manner as the adhesive sheet of Example 1, except that 1.5 parts of the pigment type "PV-23" and 1.5 parts of the pigment type "PY-150" were used as pigments.

[0135] Example 8 In this example, the substrateless double-sided adhesive sheet of this example was prepared in the same manner as the adhesive sheet of Example 1, except that 0.4 parts of the pigment type "PR-177" and 1.6 parts of the pigment type "PB-15:6" were used as pigments.

[0136] Example 9 The adhesive composition was prepared in the same manner as in Example 1, except that 2 parts of the pigment type "PV-23" and 2 parts of the pigment type "PY-150" were used as the pigments. For the PSA sheets, one polyester release film (trade name "Diafoil MRF", thickness 38 μm and thickness 75 μm, manufactured by Mitsubishi Polyester Corporation) with one release-treated release surface was prepared as a release liner. The PSA composition was applied to the release surface of each of these release liners to a dry thickness of 13 μm, and then dried at 100° C. for 2 minutes. In this way, a PSA layer was formed on the release surface of each of the two release liners. A 5 μm thick PET film (trade name "Lumirror S10", manufactured by Toray Industries, Inc.) was used as the support substrate. The pressure-sensitive adhesive layers formed on the two release liners were attached to the first and second surfaces of the support substrate, respectively, to produce a substrate-attached double-sided pressure-sensitive adhesive sheet according to this example (transfer method). The release liner was left on the pressure-sensitive adhesive layer and used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer.

[0137] Example 10 The adhesive composition was prepared in the same manner as in Example 9, except that 1.5 parts of pigment species "PV-23" and 1.5 parts of pigment species "PY-150" were used as the pigments. The adhesive sheet was prepared in the same manner as in Example 9, except that the adhesive composition was applied to the release surface of the release liner so that the thickness after drying was 17 μm, and the thickness of the supporting substrate was 16 μm.

[0138] Example 11 The adhesive composition was prepared in the same manner as in Example 9, except that 1 part of pigment species "PV-23" and 1 part of pigment species "PY-150" were used as the pigments. The adhesive sheet was prepared in the same manner as in Example 9, except that the adhesive composition was applied to the release surface of the release liner so that the thickness after drying was 28 μm, and the thickness of the supporting substrate was 25 μm.

[0139] Example 12 The adhesive composition was prepared in the same manner as in Example 9, except that 0.9 parts of pigment species "PV-23" and 0.9 parts of pigment species "PY-150" were used as the pigments. The adhesive sheet was prepared in the same manner as in Example 9, except that the adhesive composition was applied to the release surface of the release liner so that the thickness after drying was 38 μm, and the thickness of the supporting substrate was 25 μm.

[0140] Example 13 The adhesive composition was prepared in the same manner as in Example 1, except that 1.15 parts of pigment species "PV-23" and 1.15 parts of pigment species "PY-150" were used as the pigments. The pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was applied to the release surface of the release liner so as to have a dry thickness of 50 μm.

[0141] Example 14 The adhesive composition was prepared in the same manner as in Example 1, except that 0.75 parts of pigment species "PV-23" and 0.75 parts of pigment species "PY-150" were used as the pigments. The pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was applied to the release surface of the release liner so that the thickness after drying would be 100 μm.

[0142] <Comparative Example 1> The substrateless double-sided adhesive sheet of this example was prepared in the same manner as the adhesive sheet of Example 1, except that 2 parts of "IR BLACK NX" (manufactured by Seiko Advance Co., Ltd.) was used as the dye instead of the pigment.

[0143] <Comparative Example 2> The substrateless double-sided adhesive sheet of this example was prepared in the same manner as the adhesive sheet of Example 1, except that the adhesive composition used contained 0.7 parts of "ATDN101 Black" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) as the pigment.

[0144] <Comparative Example 3> The substrateless double-sided adhesive sheet of this example was prepared in the same manner as the adhesive sheet of Example 1, except that 2 parts of "ATDN101 Black" (manufactured by Dainichiseika Color & Chemicals Mfg. Co., Ltd.) was used as the pigment for the adhesive composition.

[0145] Of the measurement results for light transmittance in the wavelength range of 380 to 2500 nm, the light transmittance for wavelengths of 380 nm, 500 nm, 800 nm, and 2000 nm is shown in Table 1. For Examples 1, 2, 7, and 8 and Comparative Example 3, the light transmittance spectra in the wavelength range of 380 to 2500 nm are shown in Figure 4. Table 1 also shows the measurement results for 180° peel adhesive strength and step followability. In Table 1, "-" indicates that the material is not included or has not been measured.

[0146] [Table 1]

[0147] As shown in Table 1 and Figure 4, the pressure-sensitive adhesive sheets of Examples 1, 2, 7, and 8 had a light transmittance of 25% or less over the entire wavelength range of 380 to 500 nm, and a light transmittance of 60% or more over the entire wavelength range of 800 to 2000 nm. Although not shown in Figure 4, it was also confirmed that the light transmittance was 60% or more over the wavelength range of 2000 to 2500 nm. Furthermore, although not shown in FIG. 4, it was confirmed that Examples 3 to 6 and 9 to 14 had a light transmittance of 25% or less over the entire wavelength range of 380 to 500 nm, and a light transmittance of 60% or more over the entire wavelength range of 800 to 2500 nm. Furthermore, the pressure-sensitive adhesive sheets of Examples 1 to 14 also exhibited high adhesive strength values.

[0148] On the other hand, Comparative Example 1 used a dye instead of a pigment, and had weak adhesive strength. Comparative Examples 2 and 3 could not achieve a light transmittance of 60% or more in the wavelength range of 800 to 2500 nm.

[0149] In this way, by selecting a pigment having the above-mentioned specified light transmittance from various pigments, or by combining two or more pigments, or by adjusting the content and content ratio of various pigments, it is possible to realize an adhesive sheet with wavelength selectivity that blocks visible light and transmits infrared light. [Explanation of symbols]

[0150] 1, 2, 3 adhesive sheet 11, 21, 31a, 31b Adhesive layer 22, 32 Base material

Claims

1. A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer made of a pressure-sensitive adhesive containing a base polymer and a pigment, and having no substrate, The light transmittance at wavelengths of 380 to 500 nm is 25% or less, and the light transmittance at wavelengths of 800 to 2500 nm is 60% or more, the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer, The monomer component constituting the acrylic polymer is C １－４ Contains 50% by mass or more of alkyl (meth)acrylate, Used to fix a pressure sensor to another member in a portable electronic device equipped with a pressure sensor. Adhesive sheet.

2. 2. The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer contains 0.5 to 20 parts by mass of the pigment per 100 parts by mass of the base polymer.

3. The pressure-sensitive adhesive sheet according to claim 1 or 2, which has a thickness of 10 to 200 μm.

4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which has a 180° peel adhesive strength (N / 25 mm) from a SUS304BA plate of 3 N / 25 mm or more.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, which has a substrate.

6. A portable electronic device using the pressure-sensitive adhesive sheet according to any one of claims 1 to 5.

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