Pressure-sensitive adhesive sheet, display device, laminate and pressure-sensitive adhesive composition

Abstract

To provide an adhesive sheet capable of concealing an adherend and achieving excellent infrared ray shielding.SOLUTION: There is provided an adhesive sheet having an adhesive layer. The adhesive layer comprises an infrared absorbent and a coloring agent other than the infrared absorbent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet, a display device, a laminate, and a pressure-sensitive adhesive composition. [Background technology]

[0002] Generally, adhesives (also referred to as pressure-sensitive adhesives; the same applies hereinafter) are in a soft solid (viscoelastic) state at temperatures around room temperature and have the property of easily adhering to an adherend when pressure is applied. Utilizing these properties, adhesives are widely used in a variety of applications, for example, for the purpose of joining, fixing, and protecting components within portable electronic devices such as mobile phones. For example, adhesive sheets having a light-blocking adhesive layer are used to prevent light leakage from light sources such as backlight modules of liquid crystal display devices in portable electronic devices such as mobile phones, and from self-luminous elements such as organic electroluminescence (EL). Furthermore, adhesive sheets with a predetermined light-blocking property are used to conceal an adherend, etc. Patent Document 1 is an example of a document relating to this type of technology.

[0003] Also, adhesives containing composite tungsten oxide fine particles represented by the general formula MxWyOz and highly transparent adhesive films using such adhesives are known for the purpose of absorbing and blocking near-infrared rays (wavelengths of 800 to 1100 nm) emitted from plasma displays. Patent documents 2 to 4 are cited as documents relating to this type of technology. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-235053 [Patent Document 2] Japanese Patent Application Publication No. 2018-9053 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-65146 [Patent Document 4] International Publication No. 2009 / 020207 Summary of the Invention [Problem to be solved by the invention]

[0005] Light-shielding pressure-sensitive adhesive sheets achieve the purpose of concealing an adherend by covering the entire visible surface of the adherend. For example, pressure-sensitive adhesive sheets used on the back side of organic EL panels and the like are visible when the display is turned off, so they are required to conceal the adherend with good appearance quality. For such applications, highly light-shielding pressure-sensitive adhesive sheets using a black colorant such as carbon black are preferably used.

[0006] Meanwhile, various devices, such as the portable electronic devices mentioned above, use optical sensors that utilize light rays such as infrared, visible light, and ultraviolet light for purposes such as personal authentication, device operation, detection of nearby objects, detection of ambient brightness (ambient light), and data communication. For example, infrared sensors may be used in biometric authentication technology that authenticates individuals using biometric information such as fingerprints and veins. In such devices, external infrared light can become noise and may reduce the operational accuracy of the sensor. Furthermore, in devices such as remote controls (teleoperators) that use infrared sensors to operate the main unit, it is undesirable for infrared light to leak from sources other than the light-emitting portion that is directed toward the target.

[0007] As described above, in devices equipped with infrared sensors, light-shielding adhesive sheets that are attached to infrared-shielding materials (adherends) such as metals are generally not required to have infrared-shielding properties, since the adherends can block infrared rays. Furthermore, since the light-shielding adhesive sheets can also block infrared rays by blocking visible light using black colorants, there is no need to provide additional infrared-shielding measures. However, for example, in portable electronic devices, components to be concealed by adhesive sheets may be processed to impart new functions, and adhesive sheets attached to such components are expected to be used in a manner that covers the adherend surface, including areas where the adherend component is not present, such as processed portions, to conceal the adherend. In such a manner of use, even if an adhesive sheet can sufficiently block visible light, if its infrared-shielding properties are insufficient, infrared rays may pass through the adhesive sheet and areas where no adherend is present, which may cause malfunction of the optical sensor due to the infrared rays. For example, conventional light-shielding pressure-sensitive adhesive sheets using black colorants such as carbon black can block infrared rays in the near-infrared region (800 to 1100 nm), but tend to have reduced infrared blocking properties in the wavelength region longer than 1100 nm, and do not necessarily have sufficient infrared blocking properties. Furthermore, in the new usage forms described above, higher infrared blocking properties than conventional light-shielding pressure-sensitive adhesive sheets may be required. If a pressure-sensitive adhesive sheet with excellent infrared blocking properties in addition to adherend concealment properties were provided, it would be possible to block infrared rays regardless of the material or shape of the adherend, which would be practically useful.

[0008] The present invention was created in view of the above circumstances, and aims to provide a pressure-sensitive adhesive sheet that can conceal an adherend and provide excellent infrared shielding. Another related object is to provide a display device and a laminate that include the pressure-sensitive adhesive sheet. Yet another related object is to provide a pressure-sensitive adhesive composition that can be used to form the pressure-sensitive adhesive of the pressure-sensitive adhesive sheet. [Means for solving the problem]

[0009] According to this specification, a pressure-sensitive adhesive sheet is provided having a pressure-sensitive adhesive layer containing an infrared absorbent and a colorant different from the infrared absorbent. According to the above configuration, by selecting appropriate types of infrared absorbent and colorant and incorporating appropriate amounts into the pressure-sensitive adhesive, it is possible to conceal the adherend and block infrared rays. Furthermore, by using a combination of an infrared absorbent and a colorant, it is possible to achieve better infrared blocking than when an infrared absorbent is used alone. The pressure-sensitive adhesive sheet can prevent problems caused by the passage of infrared rays, such as reduced operational accuracy or malfunction of an infrared sensor, regardless of the material or shape of the adherend.

[0010] In some embodiments, the infrared absorber is a metal compound. By using a metal compound as an infrared absorber, the effects of the technology disclosed herein are preferably realized.

[0011] In some preferred embodiments, the infrared absorber is selected from tungsten composite oxide and tin composite oxide. By using at least one selected from tungsten composite oxide and tin composite oxide as the infrared absorber, it is possible to achieve adherend concealment and excellent infrared shielding. Specifically, by using tungsten composite oxide and / or tin composite oxide, it is possible to sufficiently shield not only near-infrared rays (800 to 1100 nm) but also infrared rays with wavelengths longer than 1100 nm.

[0012] In some preferred embodiments, the colorant includes a black colorant. By using a black colorant as the colorant, adherend hiding power can be achieved with a small amount of colorant used. Furthermore, the use of a black colorant can efficiently reduce infrared transmittance. This is significant in terms of preventing or suppressing deterioration of adhesive properties due to the inclusion of a colorant, etc.

[0013] In some embodiments, the colorant further comprises a metal oxide. By using a metal oxide as a colorant in addition to a black colorant, light that is about to enter the PSA is reflected, reducing the visible light transmittance, and this effect can be used to conceal the adherend.

[0014] In some preferred embodiments, the total amount of the infrared absorbent and the colorant contained in the pressure-sensitive adhesive layer is within the range of 5 to 30 parts by weight per 100 parts by weight of the base polymer contained in the pressure-sensitive adhesive layer. By setting the total amount of the infrared absorbent and the colorant to 5 to 30 parts by weight per 100 parts by weight of the base polymer, it is possible to preferably achieve the intended concealment of the adherend and infrared shielding while maintaining good adhesive properties.

[0015] In some preferred embodiments, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. In a configuration including an acrylic pressure-sensitive adhesive layer, the technology disclosed herein is preferably implemented.

[0016] In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is within the range of 10 to 50 μm. By making the thickness of the pressure-sensitive adhesive layer 10 μm or more, it is possible to preferably achieve adherend concealment and infrared shielding. In addition, it tends to be easier to achieve the desired adhesive properties. By making the thickness of the pressure-sensitive adhesive layer 50 μm or less, it is possible to effectively meet the demand for thinner and lighter products.

[0017] Some preferred embodiments of the PSA sheet are substrate-less double-sided PSA sheets comprising the PSA layer. Substrate-less double-sided PSA sheets can be made thinner because they do not have a substrate, which can contribute to the miniaturization and space-saving of products to which the double-sided PSA sheet is applied. Furthermore, the technology disclosed herein can achieve concealment of the adherend and infrared shielding based on the PSA structure without relying on a substrate. Furthermore, substrate-less PSA sheets can maximize the effects of the PSA layer, such as adhesive strength and impact resistance.

[0018] Furthermore, the pressure-sensitive adhesive sheet disclosed herein preferably has a 180-degree peel strength against a stainless steel plate of 10 N / 25 mm or more, measured in accordance with JIS Z 0237. The technology disclosed herein makes it possible to realize a pressure-sensitive adhesive sheet that has adherend-concealing properties and infrared shielding properties, and also has adhesive strength equal to or greater than a predetermined value. A pressure-sensitive adhesive sheet with the above adhesive strength can fix an adherend with even greater adhesive strength.

[0019] The pressure-sensitive adhesive sheet disclosed herein can conceal an adherend, and by taking advantage of this feature, it is preferably used in various applications requiring concealment of an adherend. For example, it can be preferably used for fixing components of portable electronic devices. The above-mentioned portable electronic devices may require concealment of components, and it is meaningful to apply the pressure-sensitive adhesive sheet disclosed herein. Furthermore, since portable electronic devices may have built-in optical sensors such as infrared sensors, it is particularly meaningful to ensure the operational accuracy of the optical sensors by blocking infrared rays using the pressure-sensitive adhesive sheet disclosed herein. For example, it is suitable for fixing components of portable electronic devices having built-in infrared sensors.

[0020] This specification also provides a display device including a display unit including a cover member and an organic EL unit, and a support unit. In this display device, an adhesive sheet is attached to the support unit. The adhesive sheet has an adhesive layer, and the adhesive layer contains an infrared absorber and a colorant different from the infrared absorber. The adhesive sheet disclosed herein is preferably used as a component (e.g., a member joining means) of the above-mentioned display device.

[0021] This specification also provides a laminate comprising a metal member and a pressure-sensitive adhesive sheet attached to the surface of the metal member. In this laminate, the pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer also contains an infrared absorbing agent and a colorant different from the infrared absorbing agent. According to the above configuration, the pressure-sensitive adhesive sheet can conceal the metal member by covering it. Furthermore, while the metal member may have infrared-blocking properties, if the metal member is processed, such as by having openings, the pressure-sensitive adhesive sheet may cover the adherend, including areas where the adherend is not present, thereby concealing the adherend. In such cases, infrared rays may pass through the pressure-sensitive adhesive sheet and the areas where the adherend is not present, raising concerns about the occurrence of problems caused by the infrared rays. According to the laminate, the infrared-blocking properties of the pressure-sensitive adhesive sheet can be utilized to block infrared rays across the entire sheet surface, including areas where the metal member is not present.

[0022] This specification also provides a laminate comprising a light-transmitting member and a pressure-sensitive adhesive sheet. In this laminate, one side of the pressure-sensitive adhesive sheet is attached to the light-transmitting member. The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, and the pressure-sensitive adhesive layer contains an infrared absorbing agent and a colorant different from the infrared absorbing agent. According to the above configuration, infrared rays can pass through the light-transmitting member, but the presence of the pressure-sensitive adhesive sheet attached to the light-transmitting member allows the laminate as a whole to achieve infrared shielding. For example, in an embodiment in which the pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, when the pressure-sensitive adhesive side of the pressure-sensitive adhesive sheet opposite to the side to which the light-transmitting member is attached is attached to an adherend, the laminate conceals the adherend and can block infrared rays that have passed through the light-transmitting member with the pressure-sensitive adhesive sheet.

[0023] Furthermore, this specification provides a pressure-sensitive adhesive composition containing an infrared absorbent and a colorant different from the infrared absorbent. By using the pressure-sensitive adhesive composition having the above composition, more specifically by selecting and using appropriate types and amounts of infrared absorbents and colorants to prepare the pressure-sensitive adhesive composition, the pressure-sensitive adhesive sheet disclosed herein can be produced. In other words, by using the pressure-sensitive adhesive composition disclosed herein, a pressure-sensitive adhesive sheet that can conceal an adherend and provide infrared shielding can be produced. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a cross-sectional view schematically showing one example of the configuration of a pressure-sensitive adhesive sheet. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating an example of a configuration of a laminate. [Figure 3] FIG. 1 is an exploded perspective view schematically illustrating a configuration example of a display device. [Figure 4] 1 is a graph showing the light transmittance in the wavelength range of 380 to 1500 nm of pressure-sensitive adhesive sheets according to various examples. DETAILED DESCRIPTION OF THE INVENTION

[0025] Preferred embodiments of the present invention are described below. Matters necessary for carrying out the present invention other than those specifically mentioned in this specification can be understood by those skilled in the art based on the teachings for carrying out the invention described in this specification and the common general technical knowledge at the time of filing. The present invention can be carried out based on the contents disclosed in this specification and the common general technical knowledge in the relevant field. Furthermore, in the following drawings, components and parts that perform the same function may be denoted by the same reference numerals, and redundant explanations may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic to clearly explain the present invention and do not necessarily accurately represent the size or scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product.

[0026] As used herein, the term "adhesive" refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has the property of easily adhering to an adherend by pressure, as described above. 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).

[0027] <Adhesive sheet configuration example> The PSA sheet disclosed herein may be a substrate-attached PSA sheet having the PSA layer on one or both sides of a non-releasable substrate (support substrate), or may be a substrate-less PSA sheet (i.e., a PSA sheet without a non-releasable substrate) in which the PSA layer is held by a release liner. The concept of PSA sheet here may include those referred to as PSA tapes, PSA labels, PSA films, etc. The PSA sheet disclosed herein may be in the form of a roll or sheets. Alternatively, it may be a PSA sheet processed into various shapes.

[0028] FIG. 1 shows an example of the structure of a double-sided adhesive substrateless PSA sheet (substrateless double-sided PSA sheet). The PSA sheet 1 shown in FIG. 1 has a configuration in which both sides 21A and 21B of a substrateless PSA layer 21 (which also correspond to adhesive surfaces 1A and 1B of the PSA sheet 1, respectively) are protected by release liners 31 and 32, each with the PSA layer side serving as a release surface. Alternatively, the PSA sheet may have a configuration in which one surface (adhesive surface, first adhesive surface) of the substrateless PSA layer is protected by a release liner with both surfaces serving as release surfaces, and when rolled up, the other surface (adhesive surface, second adhesive surface) of the PSA layer abuts against the back surface of the release liner, thereby enabling the second adhesive surface of the PSA layer to also be protected by the release liner. The technology disclosed herein can be preferably implemented in such a substrateless form from the viewpoint of reducing the thickness of the PSA sheet. Substrateless PSA sheets are advantageous in that they are easily thinned and can maximize the PSA properties, such as adhesive strength and impact resistance.

[0029] <Adhesive layer> (base polymer) In the technology disclosed herein, the type of adhesive constituting the adhesive layer is not particularly limited. The adhesive may contain, as an adhesive polymer (hereinafter also referred to as a "base polymer," meaning a structural polymer that forms the adhesive), one or more of various rubber-like polymers that can be used in the field of adhesives, such as acrylic polymers, rubber polymers (natural rubber, synthetic rubber, mixtures thereof, etc.), polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine-based polymers. From the viewpoints of adhesive performance, cost, etc., adhesives containing an acrylic polymer or a rubber polymer as a base polymer are preferably used. Among these, adhesives using an acrylic polymer as the base polymer (acrylic adhesives) are preferred. The technology disclosed herein is preferably implemented in an embodiment using an acrylic adhesive.

[0030] The following description will mainly focus on adhesive layers made of acrylic adhesives, i.e., adhesive sheets having acrylic adhesive layers, but it is not intended to limit the adhesive layers of the adhesive sheets disclosed herein to those made of acrylic adhesives.

[0031] The "base polymer" of a pressure-sensitive adhesive refers to the main component of the rubbery polymer contained in the pressure-sensitive adhesive, and is not to be construed in any other limiting sense. The rubbery polymer refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" refers to a component that accounts for more than 50% by weight, unless otherwise specified. Furthermore, the term "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 weight. 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.

[0032] (acrylic polymer) The acrylic polymer in the technology disclosed herein 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 weight of the monomer composition in the monomer raw material.

[0033] 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 1-10 , 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.

[0034] R 2 C 1-20Specific examples of alkyl(meth)acrylate, which is a chain alkyl group, include, but are not limited to, methyl(meth)acrylate, ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl(meth)acrylate, t-butyl(meth)acrylate, pentyl(meth)acrylate, isopentyl(meth)acrylate, hexyl(meth)acrylate, heptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, octyl( Examples of alkyl (meth)acrylates include alkyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate. These alkyl (meth)acrylates can be used alone or in combination of two or more. Suitable examples of alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

[0035] The proportion of alkyl(meth)acrylate in the monomer components constituting the acrylic polymer is typically greater than 50% by weight, and can be, for example, 70% by weight or more, 85% by weight or more, or even 90% by weight or more. The upper limit of the proportion of alkyl(meth)acrylate is not particularly limited, but is preferably 99.5% by weight or less (e.g., 99% by weight or less). Alternatively, from the viewpoint of favorably exhibiting the properties (e.g., cohesive strength) based on the secondary monomer such as a carboxyl group-containing monomer, it may be 98% by weight or less (e.g., less than 97% by weight). Alternatively, the acrylic polymer may be substantially a polymer of alkyl(meth)acrylate alone.

[0036] In addition, C is used as a monomer component. 4-8 When alkyl acrylate is used, C among the alkyl (meth)acrylates contained in the monomer component 4-8 The proportion of alkyl acrylate is preferably 70% by weight or more, and more preferably 90% by weight or more. 4-8 The alkyl acrylates can be used alone or in combination of two or more.

[0037] The technology disclosed herein is a method for producing the acrylic polymer, wherein the monomer component constituting the acrylic polymer is C 1-6 It is preferable to use an embodiment in which the alkyl (meth)acrylate is contained in an amount of 50% by weight or more. 1-6 The polymerization ratio of alkyl (meth)acrylate is preferably 50% by weight or more. 1-6 The proportion of alkyl (meth)acrylate (in other words, the polymerization proportion) is more preferably greater than 50% by weight, even more preferably 60% by weight or more, and particularly preferably 70% by weight or more (for example, 80% by weight or more, or even 85% by weight or more). 1-6 By using a predetermined amount or more of alkyl (meth)acrylate (e.g., BA), it is possible to disperse a colorant such as a black colorant (e.g., carbon black) well in the adhesive layer while maintaining good adhesive properties such as adhesive strength. 1-6 The upper limit of the proportion of alkyl (meth)acrylate is not particularly limited, and may be, for example, 99% by weight or less, or may be 97% by weight or less in relation to the proportion of other copolymerizable monomers used. 1-6 The alkyl (meth)acrylates may be used alone or in combination of two or more. 1-6 As alkyl (meth)acrylate, C 1-6 Alkyl acrylates are preferred, C 2-6 Alkyl acrylates are more preferred, C 4-6 Alkyl acrylates are more preferred. 1-6 The alkyl (meth)acrylate is preferably C1-4 alkyl acrylate, more preferably C 2-4 It is an alkyl acrylate. 1-6 A suitable example of the alkyl(meth)acrylate is BA.

[0038] In embodiments in which BA is used as the main monomer, the copolymerization ratio of BA in the acrylic polymer is preferably greater than 50% by weight, more preferably 70% by weight or more, and even more preferably 90% by weight or more (e.g., greater than 90% by weight). Copolymerization of BA as the main monomer makes it easier for the PSA to achieve good adhesion to the adherend. By using a predetermined amount or more of BA, it is possible to maintain good adhesive properties such as adhesive strength while favorably dispersing a colorant such as a black colorant (e.g., carbon black) in the PSA layer. The copolymerization ratio of BA in the acrylic polymer is not particularly limited, and may be, for example, 99% by weight or less, or, in relation to the copolymerization ratios of other copolymerizable monomers, 97% by weight or less.

[0039] The acrylic polymer in the technology disclosed herein may be copolymerized with a secondary monomer. Examples of secondary monomers that can introduce functional groups that can serve as crosslinking base points into the acrylic polymer or that can contribute to improving adhesive strength include carboxyl group-containing monomers, hydroxyl group (OH group)-containing monomers, acid anhydride group-containing monomers, amide group-containing monomers, amino group-containing monomers, epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers with nitrogen atom-containing rings, alkoxysilyl group-containing monomers, and imide group-containing monomers. The above secondary monomers can be used alone or in combination of two or more.

[0040] When the monomer component constituting the acrylic polymer contains the functional group-containing monomer, the content of the functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exerting the 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 wt% or more, suitably 0.5 wt% or more, or may be 1 wt% or more. Furthermore, from the viewpoint of easily balancing the adhesive performance in relation to the main monomer, the content of the functional group-containing monomer in the monomer component is suitably 40 wt% or less, preferably 20 wt% or less, or may be 10 wt% or less (for example, 5 wt% or less).

[0041] In some preferred embodiments, the acrylic polymer may be one in which the monomer component constituting the acrylic polymer contains a carboxyl group-containing monomer. The inclusion of a carboxyl group-containing monomer in the monomer component facilitates the production of a pressure-sensitive adhesive sheet exhibiting favorable adhesive properties (such as cohesive strength). This can also be advantageous in improving the adhesion between the pressure-sensitive adhesive layer and the adherend. Furthermore, copolymerization of an appropriate amount of a carboxyl group-containing monomer facilitates favorable dispersion of a colorant, such as a black colorant (e.g., carbon black), within the pressure-sensitive adhesive layer, thereby maintaining favorable adhesive properties.

[0042] Examples of carboxyl group-containing monomers include acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, and isocrotonic acid. Of these, AA and MAA are preferred. The carboxyl group-containing monomers can be used alone or in combination of two or more.

[0043] In an embodiment in which a carboxyl group-containing monomer is copolymerized with an acrylic polymer, the content of the carboxyl group-containing monomer in the monomer components constituting the acrylic polymer is not particularly limited, and can be, for example, 0.2 wt% or more (typically 0.5 wt% or more) of the monomer components, suitably 1 wt% or more, or even 2 wt% or more, or even 3 wt% or more. A carboxyl group-containing monomer content of more than 3 wt% exhibits better effects. In some embodiments, the carboxyl group-containing monomer content can be 3.2 wt% or more, 3.5 wt% or more, 4 wt% or more, or even 4.5 wt% or more of the monomer components. The upper limit of the carboxyl group-containing monomer content is not particularly limited, and can be, for example, 15 wt% or less, 12 wt% or less, or 10 wt% or less. The technology disclosed herein can also be preferably implemented in an embodiment in which the carboxyl group-containing monomer content is 7 wt% or less (typically less than 7 wt%, e.g., 6.8 wt% or less, or 6.0 wt% or less) of the monomer components.

[0044] When a carboxyl group-containing monomer is used as a copolymerization component (specifically, a functional group-containing monomer) of an acrylic polymer, 10% by weight or more of the functional group-containing monomers used may be a carboxyl group-containing monomer. This allows the cohesive force of the carboxyl group, its function as a crosslinking point, and the dispersibility of colorants to be suitably exhibited. From the viewpoint of better exhibiting the effect of copolymerizing the carboxyl group-containing monomer, the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers is suitably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more, for example, 97% by weight or more, 98% by weight or more, or even 99% by weight or more (e.g., 99.9% by weight or more). The upper limit of the proportion of the carboxyl group-containing monomer in the total functional group-containing monomers is 100% by weight, and may be, for example, 95% by weight or less.

[0045] In some other embodiments, an acrylic polymer in which a hydroxyl group-containing monomer is copolymerized as the secondary monomer may be used. Examples of the hydroxyl group-containing monomer include hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate; and N-hydroxyethyl (meth)acrylamide. Among these, preferred hydroxyl group-containing monomers include hydroxyalkyl (meth)acrylates in which the alkyl group is linear and has 2 to 4 carbon atoms. The hydroxyl group-containing monomers may be used alone or in combination of two or more.

[0046] Furthermore, when a hydroxyl group-containing monomer is used as the secondary monomer, its content is usually suitably about 0.001 wt% or more of the total monomer components, and may be about 0.01 wt% or more (typically about 0.02 wt% or more). Furthermore, the content of the hydroxyl group-containing monomer is suitably less than 15 wt% of the total monomer components, preferably about 8 wt% or less, more preferably about 3 wt% or less (e.g., less than 1 wt%). Furthermore, the technology disclosed herein can be implemented using a pressure-sensitive adhesive containing an acrylic polymer in which a hydroxyl group-containing monomer is not copolymerized.

[0047] In some other embodiments, an acrylic polymer in which a nitrogen atom-containing monomer is copolymerized as the secondary monomer can be used. Suitable examples of the nitrogen atom-containing monomer include a nitrogen atom-containing ring-containing monomer (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.). The nitrogen atom-containing monomer can be used alone or in combination of two or more.

[0048] When a nitrogen-containing monomer (preferably a monomer having a nitrogen-containing ring) is used as the secondary monomer, its content is not particularly limited and may be, for example, 1% by weight or more, 3% by weight or more, or even 5% by weight or more, or 7% by weight or more of the total monomer components. The amount of the nitrogen-containing monomer used is suitably, for example, less than 20% by weight of the total monomer components, and may be less than 10% by weight, less than 3% by weight, or less than 1% by weight. The technology disclosed herein can be implemented using a pressure-sensitive adhesive containing an acrylic polymer in which a nitrogen-containing monomer is not copolymerized.

[0049] 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.

[0050] The amount of such other copolymerization components can be appropriately selected depending on the purpose and application, and is not particularly limited. However, from the viewpoint of properly exerting the effects of use, it is appropriate to set it to 0.05 wt% or more, and it may be 0.5 wt% or more. Furthermore, from the viewpoint of easily balancing adhesive performance, the content of other copolymerization components in the monomer component is appropriate to set it to 20 wt% or less, and it may be 10 wt% or less (e.g., 5 wt% or less, or even less than 1 wt%). The technology disclosed herein can also be preferably implemented in an embodiment in which the monomer component is substantially free of other copolymerization components. 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 included at, for example, about 0.01 wt% or less.

[0051] The copolymer composition of the acrylic polymer is suitably designed so that the glass transition temperature (Tg) of the polymer is approximately -15°C or lower (for example, approximately -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 weight fraction of monomer i in the copolymer (copolymerization ratio by weight), and Tgi represents the glass transition temperature (unit: K) of the homopolymer of monomer i.

[0052] The glass transition temperature of a homopolymer used to calculate Tg is determined from publicly known sources, specifically, from the Polymer Handbook (3rd Edition, John Wiley & Sons, Inc., 1989). For monomers for which multiple values ​​are listed in this publication, the highest value is used. If the value is not listed in the Polymer Handbook, the value obtained by the measurement method described in JP 2007-51271 A is used.

[0053] Although not particularly limited, from the viewpoint of impact resistance and adhesion to an adherend, the Tg of the acrylic polymer is advantageously about -25°C or less, preferably about -35°C or less, and more preferably about -40°C or less. In some embodiments, from the viewpoint of cohesive strength, the Tg of the acrylic polymer is, for example, about -70°C or more, or may be about -65°C or more, about -60°C or more, or about -55°C or more. The technology disclosed herein can be preferably implemented in an embodiment in which the Tg of the acrylic polymer is about -65°C or more and -35°C or less (e.g., about -55°C or more and -40°C or less). The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (i.e., the types and amount ratios of monomers used in synthesizing the polymer).

[0054] 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, about 20°C to 170°C (typically about 40°C to 140°C).

[0055] The solvent (polymerization solvent) used in solution polymerization can be appropriately selected from conventionally known organic solvents (toluene, ethyl acetate, etc.). The initiator used in polymerization can be appropriately selected from conventionally known polymerization initiators (for example, azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN), peroxide-based initiators, etc.) depending on the type of polymerization method. The amount of polymerization initiator used may be a normal amount, and can be selected, for example, from the range of about 0.005 to 1 part by weight (typically about 0.01 to 1 part by weight) per 100 parts by weight of the monomer components.

[0056] The weight average molecular weight (Mw) of the base polymer (preferably an acrylic polymer) in the technology disclosed herein is not particularly limited, and is, for example, about 10 × 10 4 ~500×10 4 From the viewpoint of adhesive performance, the Mw of the base polymer can be in the range of approximately 30×10 4 ~200×10 4 (More preferably, approximately 45×10 4 ~150×10 4 , typically around 65×10 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.

[0057] (coloring agent) The pressure-sensitive adhesive layer disclosed herein is characterized by containing a colorant. By containing a colorant in the pressure-sensitive adhesive layer, a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer can conceal an adherend. Furthermore, using a combination of an infrared absorber and a colorant can achieve better infrared shielding than using an infrared absorber alone. A colorant is defined as a coloring component that does not fall under the category of an infrared absorber, as described below. Various materials that can absorb and attenuate light traveling through the pressure-sensitive adhesive layer, or various materials that can reduce the amount of light entering the pressure-sensitive adhesive layer, can be used. Examples of colorants include black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, and pearlescent color. The colorant is typically contained in the pressure-sensitive adhesive layer in a dispersed state (or may be dissolved) in the constituent materials of the pressure-sensitive adhesive layer. Conventional pigments and dyes can be used as colorants. Examples of pigments include inorganic pigments and organic pigments. Colorants can be used alone or in combination. By using two or more colorants, the hiding power of the adherend can be improved.

[0058] The colorant contained in the pressure-sensitive adhesive layer is not particularly limited, but may be, for example, a component capable of absorbing and attenuating light traveling through the pressure-sensitive adhesive layer. The inclusion of such a colorant in the pressure-sensitive adhesive layer can reduce the light transmittance of the pressure-sensitive adhesive layer. A black colorant is preferably used as such a colorant (hereinafter also referred to as the "first colorant") because it can efficiently adjust the hiding power with a small amount of use. Furthermore, the combined use of a black colorant and an infrared absorber can efficiently reduce the infrared transmittance. Specific examples of black colorants include carbon black, graphite, aniline black, perylene black, cyanine black, titanium black, inorganic pigment hematite, activated carbon, molybdenum disulfide, chromium complexes, anthraquinone-based colorants, and the like. The black colorants can be used alone or in combination of two or more.

[0059] In some preferred embodiments, the pressure-sensitive adhesive layer contains carbon black particles as a colorant (first colorant). The carbon black particles used may be any of those commonly referred to as carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.) without any particular limitation. Surface-modified carbon black particles having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, and silicon-containing groups (e.g., alkoxysilyl groups, alkylsilyl groups) may also be used. Such surface-modified carbon black particles are also called self-dispersing carbon black, and do not require the addition of a dispersant or can reduce the amount of dispersant added. The above carbon black particles may be used alone or in combination of two or more types.

[0060] Particulate colorants (pigments) are preferably used because they can efficiently adjust the hiding power with a small amount of use. In some preferred embodiments, colorants (e.g., particulate black colorants such as carbon black) having an average particle size of about 10 nm or more (e.g., about 30 nm or more) can be used. The average particle size is, for example, about 50 nm or more, or may be about 100 nm or more, or may be about 150 nm or more. The upper limit of the average particle size of the colorant is not particularly limited, and may be, for example, about 3000 nm or less, or may be about 1000 nm or less. From the viewpoint of improving light-blocking properties, the average particle size of the colorant is suitably about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, and even more preferably 200 nm or less (e.g., about 120 nm or less, or even about 100 nm or less).

[0061] The average particle size of the colorant in this specification refers to the volume average particle size, and specifically refers to 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 50As a measuring device, for example, the product name "Microtrac MT3000II" manufactured by Microtrac Bell or an equivalent product can be used.

[0062] In embodiments in which the pressure-sensitive adhesive layer contains a first colorant, the content of the first colorant (preferably a black colorant such as carbon black particles) is appropriately set taking into consideration the desired adherend hiding power, desired adhesive properties, etc., and is not limited to a specific range. The content of the first colorant may also vary depending on the type of pressure-sensitive adhesive, the shape and particle size of the first colorant, and its compatibility with the pressure-sensitive adhesive. The content of the first colorant in the pressure-sensitive adhesive layer is suitably approximately 0.01 wt % or more (e.g., 0.05 wt % or more). From the viewpoint of adherend hiding power, the content is preferably approximately 0.1 wt % or more, more preferably approximately 0.2 wt % or more, and may be approximately 0.3 wt % or more, for example, approximately 0.5 wt % or more, or even 0.7 wt % or more. In some embodiments, the content of the first colorant is suitably approximately 1 wt % or more (e.g., more than 1 wt %), preferably approximately 2 wt % or more, or approximately 2.5 wt % or more, or even 3 wt % or more. Increasing the amount of the first colorant used can also effectively reduce infrared transmittance. Furthermore, in embodiments in which the pressure-sensitive adhesive layer contains or does not contain a first colorant, the content of the first colorant (preferably a black colorant such as carbon black particles) can be approximately 10% by weight or less, suitably approximately 7% by weight or less, preferably approximately 6% by weight or less, more preferably approximately 5% by weight or less, even more preferably approximately 4% by weight or less, and may even be approximately 3% by weight or less. In some embodiments, the content of the first colorant may be approximately 2% by weight or less (typically less than 2% by weight), may be approximately 1% by weight or less, more preferably approximately 0.6% by weight or less, and may even be approximately 0.5% by weight or less (e.g., 0.3% by weight or less). Limiting the content of the first colorant tends to make it easier to maintain adhesive properties such as adhesive strength. According to the technology disclosed herein, desired adherend concealment can be achieved even in configurations in which the amount of the first colorant used is limited as described above.

[0063] The content of the first colorant (preferably a black colorant such as carbon black particles) can also be determined by its relative relationship to the amount of base polymer. In some embodiments, the content of the first colorant is, for example, 0.01 parts by weight or more, and appropriately 0.05 parts by weight or more, per 100 parts by weight of base polymer (preferably an acrylic polymer). From the viewpoint of concealing properties of the adherend, the content is preferably about 0.1 parts by weight or more, more preferably about 0.2 parts by weight or more, and even more preferably about 0.3 parts by weight or more, for example, about 0.5 parts by weight or more, or even 0.8 parts by weight or more. In other embodiments, the content of the first colorant is suitably about 1 part by weight or more (e.g., more than 1 part by weight), and preferably about 2 parts by weight or more, and more preferably about 2.5 parts by weight or more, per 100 parts by weight of base polymer. Increasing the amount of the first colorant used can also effectively reduce infrared transmittance. In addition, in embodiments in which the pressure-sensitive adhesive layer contains or does not contain a first colorant, the content of the first colorant (preferably a black colorant such as carbon black particles) can be approximately 10 parts by weight or less, preferably approximately 7 parts by weight or less, preferably less than 6 parts by weight, more preferably approximately 5 parts by weight or less, even more preferably approximately 4 parts by weight or less, and may be approximately 3.5 parts by weight or less, relative to 100 parts by weight of the base polymer (preferably an acrylic polymer). In some embodiments, the content of the first colorant is approximately 3 parts by weight or less (typically less than 3 parts by weight), may be approximately 2 parts by weight or less, may be approximately 1.5 parts by weight or less, or may be approximately 1 part by weight or less (e.g., 0.6 parts by weight or less), relative to 100 parts by weight of the base polymer. Limiting the content of the first colorant tends to make it easier to maintain adhesive properties such as adhesive strength.

[0064] In some other embodiments, the pressure-sensitive adhesive layer may contain a second colorant (e.g., a metal oxide) as described below as a colorant. For example, in embodiments in which the pressure-sensitive adhesive layer contains at least two types of colorants, at least one of the multiple colorants used may be the first colorant described above or the second colorant described below. In embodiments in which the pressure-sensitive adhesive layer contains at least two types of colorants, the first colorant and the second colorant described above may be used in combination.

[0065] The second colorant that can be used in the technology disclosed herein is not particularly limited, but may be, for example, a component that can reduce the amount of light entering the pressure-sensitive adhesive layer, and by incorporating the second colorant into the pressure-sensitive adhesive layer, may be a component that increases the light reflectance of the pressure-sensitive adhesive layer. Such second colorants may be one or more selected from inorganic materials (e.g., metals and metal compounds), organic materials, and organic-inorganic composites. Specific examples of the second colorant include metal oxides such as titanium oxide (titanium dioxide such as rutile titanium dioxide and anatase titanium dioxide), zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, and yttrium oxide; carbonate compounds such as magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, and zinc carbonate; and hydroxides such as aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and zinc hydroxide. Examples of suitable second colorants include inorganic materials such as silicate compounds (e.g., aluminum silicate, magnesium silicate, calcium silicate, etc.), barium sulfate, calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, and hydrated halloysite, as well as organic materials such as acrylic resins, polystyrene resins, polyurethane resins, amide resins, polycarbonate resins, silicone resins, urea-formalin resins, and melamine resins. These may be referred to as white colorants. The second colorant may be used alone or in combination of two or more. The second colorant does not contain carbon black particles and may be defined as a colorant different from carbon black particles. Typically, the second colorant does not include a light-absorbing black colorant.

[0066] In some preferred embodiments, the pressure-sensitive adhesive layer contains a metal oxide as a second colorant. The combined use of a first colorant (preferably a black colorant) and a metal oxide reduces the amount of light entering the pressure-sensitive adhesive layer and absorbs the light that has entered the pressure-sensitive adhesive layer, thereby reducing the visible light transmittance and improving the ability to conceal the adherend. The metal oxide can be selected from the materials described above to achieve the desired ability to conceal the adherend. Suitable examples include titanium oxide, zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, and calcium oxide. Of these, titanium oxide, silicon oxide, and zirconium oxide are preferred, with titanium oxide being particularly preferred. The metal oxide can be used alone or in combination of two or more.

[0067] In an embodiment in which the second colorant has a particulate shape, the average particle size of the second colorant (preferably metal oxide particles) is not particularly limited. Particles of an appropriate size that can achieve the desired adherend hiding power can be used depending on the thickness of the pressure-sensitive adhesive layer, the type of pressure-sensitive adhesive, and the like. The average particle size of the second colorant can be, for example, approximately 1 nm or more, and is suitably approximately 5 nm or more. From the viewpoints of the effects of containing the second colorant (e.g., reduced visible light transmittance due to improved light reflectance), compatibility, ease of handling, and the like, the average particle size of the second colorant is preferably approximately 10 nm or more, or may be approximately 20 nm or more, or may be approximately 30 nm or more. From the viewpoints of maintaining adhesive properties, etc., the upper limit of the average particle size is suitably, for example, approximately 300 nm or less. From the viewpoints of the effects of containing the second colorant (e.g., improved light reflectance), etc., the upper limit is preferably less than 100 nm (e.g., 90 nm or less), more preferably approximately 70 nm or less, and may be approximately 50 nm or less, or may be approximately 35 nm or less (e.g., approximately 25 nm or less).

[0068] In an embodiment in which the pressure-sensitive adhesive layer contains a second colorant, the content of the second colorant (preferably a metal oxide) in the pressure-sensitive adhesive layer is appropriately set in consideration of the effect of the second colorant (e.g., a reduction in visible light transmittance due to an improvement in light reflectance) and the required adhesive properties, and is not limited to a specific range. The content of the second colorant may also vary depending on the type of pressure-sensitive adhesive, the shape and particle size of the second colorant, and its compatibility with the pressure-sensitive adhesive. To effectively obtain the effect of the second colorant, the content of the second colorant in the pressure-sensitive adhesive layer is preferably approximately 1% by weight or more, preferably approximately 3% by weight or more, more preferably approximately 5% by weight or more, and even more preferably approximately 7% by weight or more. In addition, in embodiments in which the adhesive layer contains or does not contain a second colorant, the content of the second colorant in the adhesive layer can be about 25 wt % or less, suitably about 20 wt % or less, and preferably about 15 wt % or less, or may be about 12 wt % or less, or may be about 10 wt % or less, or may be about 8 wt % or less, from the viewpoints of compatibility with the adhesive components and maintenance of adhesive properties such as adhesive strength and impact resistance. According to the technology disclosed herein, the desired concealment ability of the adherend can be achieved in a configuration in which the amount of second colorant used is limited as described above.

[0069] The content of the second colorant (preferably a metal oxide) can also be determined by its relative relationship to the amount of the base polymer. The content of the second colorant is suitably approximately 1 part by weight or more, preferably approximately 3 parts by weight or more, more preferably approximately 5 parts by weight or more, even more preferably approximately 8 parts by weight or more, and may be approximately 10 parts by weight or more, per 100 parts by weight of the base polymer (preferably an acrylic polymer). Furthermore, in an embodiment in which the pressure-sensitive adhesive layer contains or does not contain a second colorant, the content of the second colorant can be approximately 30 parts by weight or less, suitably approximately 25 parts by weight or less, preferably approximately 20 parts by weight or less, more preferably approximately 15 parts by weight or less, and may be approximately 12 parts by weight or less, or may be approximately 10 parts by weight or less, per 100 parts by weight of the base polymer, from the viewpoints of compatibility with the pressure-sensitive adhesive components and maintaining adhesive properties such as adhesive strength and impact resistance.

[0070] In embodiments in which the pressure-sensitive adhesive layer contains a first colorant and a second colorant, the ratio of the amount C1 of the first colorant to the amount C2 of the second colorant is appropriately set to achieve the desired concealment of the adherend and is not limited to a specific range. In some embodiments, the weight ratio (C1 / C2) of the amount C1 of the first colorant (preferably a black colorant) to the amount C2 of the second colorant (preferably a metal oxide) is 0.001 or more, and may be 0.005 or more, 0.01 or more, 0.03 or more, 0.05 or more, or 0.10 or more. The greater the weight ratio (C1 / C2), the more favorably the effect of adding the first colorant is exerted. In embodiments in which the first colorant is a black colorant, the light-absorbing properties of the first colorant tend to improve the light-blocking properties of the pressure-sensitive adhesive layer, and the infrared transmittance also tends to decrease. In some embodiments, the weight ratio (C1 / C2) is less than 1, and may be, for example, 0.50 or less, 0.40 or less (e.g., 0.35 or less), preferably 0.30 or less, 0.20 or less, 0.15 or less, 0.12 or less, 0.09 or less, or 0.06 or less (e.g., 0.05 or less). The smaller the weight ratio (C1 / C2), the more favorably the effect of adding the second colorant is exerted. In embodiments in which the second colorant is a metal oxide, the light reflectance of the pressure-sensitive adhesive layer is improved, and adherend hiding ability tends to be more easily achieved.

[0071] In an embodiment in which the pressure-sensitive adhesive layer contains a black colorant as the first colorant and / or a metal oxide as the second colorant, the content of colorants other than the black colorant and the metal oxide is not particularly limited and can be, for example, less than 30 wt %, preferably less than 10 wt %, and can be, for example, less than 5.0 wt %, or even less than 3.0 wt % (e.g., less than 2.0 wt %, or even less than 1 wt %). The technology disclosed herein can be implemented in an embodiment in which the pressure-sensitive adhesive layer is substantially free of colorants other than the black colorant and the metal oxide. In this specification, "substantially free" means that the colorants are not intentionally added, and the content in the pressure-sensitive adhesive layer can be, for example, 0.3 wt % or less (e.g., 0.1 wt % or less, typically 0.01 wt % or less).

[0072] In addition, from the viewpoint of compatibility with the adhesive component, the colorant may be a material (particulate colorant) exemplified as the colorant above that has been surface-treated with a surface treatment agent. The surface treatment is not limited to a specific treatment, and an appropriate treatment can be selected depending on the type of core particle, the type of dispersion medium, etc.

[0073] The adhesive composition disclosed herein may contain a component that contributes to improving the dispersibility of the colorant. Such a dispersibility-improving component may be, for example, a polymer, an oligomer, a liquid resin, a surfactant (anionic, cationic, nonionic, amphoteric surfactant), or the like. The dispersibility-improving component may be used singly or in combination of two or more. The dispersibility-improving component is preferably dissolved in the adhesive composition. The oligomer may be, for example, a low-molecular-weight polymer (e.g., having a Mw of approximately 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, e.g., hydrogenated rosin methyl ester) having a softening point of about 50°C or less, more preferably about 40°C or less. Such a dispersibility-improving component can suppress uneven dispersion of the colorant (e.g., a particulate black colorant such as carbon black), thereby suppressing color unevenness in the pressure-sensitive adhesive layer. Therefore, a pressure-sensitive adhesive layer with better appearance quality can be formed.

[0074] The form of addition of the dispersibility-improving component is not particularly limited, and the dispersibility-improving component may be added to a liquid containing a colorant (e.g., a black colorant such as carbon black particles) before being blended into the pressure-sensitive adhesive composition, or may be supplied to the pressure-sensitive adhesive composition at the same time as the colorant is added, or before or after the colorant is added.

[0075] 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 appropriate to set it to approximately 20% by weight or less (preferably approximately 10% by weight or less, more preferably approximately 7% by weight or less, for example, approximately 5% by weight or less) of the entire adhesive layer. In some embodiments, the content of the dispersibility-improving component can be approximately 10 times or less (preferably approximately 5 times or less, for example, approximately 3 times or less) the weight of the colorant. On the other hand, from the viewpoint of optimally exerting the effects of the dispersibility-improving component, it is appropriate to set its content to approximately 0.2% by weight or more (typically approximately 0.5% by weight or more, preferably approximately 1% by weight or more) of the entire adhesive layer. In some embodiments, the content of the dispersibility-improving component can be approximately 0.2 times or more (preferably approximately 0.5 times or more, for example, 1 time or more) the weight of the colorant.

[0076] The content of the colorant in the pressure-sensitive adhesive layer (when two or more types of colorants are contained, the total amount of the two or more types) is appropriately set in consideration of the desired adherend hiding power, the required adhesive properties, etc., and is not limited to a specific range. The content of the colorant in the pressure-sensitive adhesive layer is, for example, about 0.3 wt % or more, suitably about 0.5 wt % or more, preferably about 1 wt % or more, more preferably about 1.5 wt % or more, and even more preferably about 2 wt % or more. In some embodiments, the content of the colorant in the pressure-sensitive adhesive layer is suitably about 3 wt % or more, preferably about 5 wt % or more, more preferably about 7 wt % or more, and may be about 8 wt % or more. From the viewpoints of compatibility with the pressure-sensitive adhesive components and maintaining adhesive properties such as adhesive strength and impact resistance, the content of the colorant in the pressure-sensitive adhesive layer can be about 30 wt % or less, suitably about 20 wt % or less, preferably about 15 wt % or less, more preferably about 10 wt % or less, and may be about 8 wt % or less.

[0077] The content of the colorant in the pressure-sensitive adhesive layer (when two or more colorants are contained, the total amount of the two or more colorants) can also be determined by its relative relationship with the amount of the base polymer. From the viewpoint of concealing the adherend, the content of the colorant is, for example, approximately 0.3 parts by weight or more, suitably approximately 0.5 parts by weight or more, preferably approximately 1 part by weight or more, more preferably approximately 1.5 parts by weight or more, even more preferably approximately 2 parts by weight or more, and may even be approximately 2.5 parts by weight or more, per 100 parts by weight of the base polymer (suitably an acrylic polymer). In some embodiments, the content of the colorant is suitably approximately 3 parts by weight or more, preferably approximately 5 parts by weight or more, more preferably approximately 8 parts by weight or more, and may even be approximately 10 parts by weight or more, per 100 parts by weight of the base polymer. From the viewpoints of light transmittance, compatibility with adhesive components, and maintaining adhesive properties such as adhesive strength and impact resistance, the content of the colorant can be approximately 30 parts by weight or less per 100 parts by weight of the base polymer, and is suitably approximately 25 parts by weight or less, preferably approximately 20 parts by weight or less, more preferably approximately 15 parts by weight or less, and may be approximately 12 parts by weight or less, approximately 8 parts by weight or less, approximately 6 parts by weight or less, or approximately 4 parts by weight or less.

[0078] (Infrared absorber) The pressure-sensitive adhesive layer disclosed herein is characterized by containing an infrared absorbing agent. When the pressure-sensitive adhesive layer contains an infrared absorbing agent, a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer can block infrared rays. As used herein, "infrared absorbing agent" refers to a material that has greater light absorption in the wavelength range of 800 to 1500 nm than light absorption in the wavelength range of 380 to 550 nm. The infrared absorbing agent may be one or more types selected from inorganic materials, organic materials, and organic-inorganic composites. From the viewpoint of durability, inorganic materials and organic-inorganic composites are preferred, and inorganic materials are more preferred.

[0079] The infrared absorber disclosed herein is a compound that, when incorporated in an appropriate amount (for example, 5 to 18 parts by weight per 100 parts by weight of base polymer) into a 30 μm thick adhesive layer, can reduce the light transmittance (infrared transmittance) in the wavelength range of 800 to 1500 nm compared to an adhesive layer of the same composition and thickness but not containing the infrared absorber, and the reduction rate of the infrared transmittance can be greater than the reduction rate of the light transmittance (visible light transmittance) in the wavelength range of 380 to 550 nm. The reduction rate of the infrared transmittance is the infrared transmittance T of an adhesive layer not containing an infrared absorber. IR0 Infrared transmittance T of the pressure-sensitive adhesive layer containing infrared absorber IR1 Ratio of: (T IR0 -T IR1 ) / T IR0 Similarly, the reduction rate of the visible light transmittance is calculated by the reduction rate of the visible light transmittance T VL0 Visible light transmittance T of the pressure-sensitive adhesive layer containing an infrared absorber VL1 Ratio of: (T VL0 -T VL1 ) / T VL0 The pressure-sensitive adhesive layer used to evaluate the infrared absorbent may be prepared in the same manner as in Example 1 of the Examples described below, except that it does not contain an infrared absorbent. IR0 ,T IR1 The maximum value of the light transmittance in the wavelength range of 800 to 1500 nm is used as the visible light transmittance T VL0 ,T VL1 The maximum light transmittance in the wavelength range of 380 to 550 nm is used as the transmittance.

[0080] In some preferred embodiments, an inorganic material (inorganic compound) is used as the infrared absorber. For example, a metal compound is preferably used as the infrared absorber. Suitable examples of such metal compounds include metal oxides such as tungsten composite oxide and tin composite oxide, and lanthanum borides. For example, by using at least one metal oxide selected from tungsten composite oxide and tin composite oxide as the infrared absorber, excellent infrared shielding can be achieved without impairing the ability to conceal the adherend. Specifically, by using the infrared absorber, it is possible to sufficiently shield not only infrared rays in the near-infrared region (800 to 1100 nm) but also infrared rays in the wavelength region longer than 1100 nm.

[0081] The tungsten composite oxide is not particularly limited, but may be, for example, one represented by the general formula MxWOy (wherein M is one or more elements selected from Cs, Rb, K, Tl, In, Ba, Li, Ca, Sr, Fe, Sn, Al, Cu, and Na, and 0.1≦x≦0.5, 2.2≦y≦3.0). From the viewpoint of forming a crystal structure with excellent infrared absorption, M in the formula preferably includes one or more elements selected from Cs, Rb, K, and Tl, more preferably Cs or Rb. From the viewpoint of durability, Cs is particularly preferred. From the viewpoint of infrared absorption, x in the formula is preferably in the range of 0.20≦x≦0.50, more preferably in the range of 0.25≦x≦0.40, and particularly preferably around 0.33. Furthermore, from the viewpoint of chemical stability, y in the formula is more preferably in the range of 2.45≦y≦3.0. It should be noted that other components may inevitably be mixed into the tungsten composite oxide particles during the manufacturing process or the like.

[0082] The crystal structure of the tungsten composite oxide is not particularly limited, and a composite tungsten oxide having any crystal structure can be contained. From the viewpoint of infrared absorption, the tungsten composite oxide preferably has a hexagonal crystal structure.

[0083] A specific example of a tungsten composite oxide is cesium-containing tungsten composite oxide. A specific example of a tin composite oxide is antimony-doped tin oxide. A specific example of a lanthanum boride is lanthanum hexaboride. Commercially available products include "YMF-02," "FMF-3A1," and "KHF-7AH" manufactured by Sumitomo Metal Mining Co., Ltd.

[0084] In some other embodiments, an organic material (organic compound) or an organic-inorganic composite may be used as the infrared absorber. Examples of such infrared absorbers include cyanine dyes, phthalocyanine dyes, polymethine dyes, squarylium dyes, porphyrin dyes, metal dithiol complex dyes, and diimonium dyes. These may be used alone or in combination of two or more.

[0085] The infrared absorber (e.g., a metal oxide such as a tungsten composite oxide) is preferably used in particulate form. In this embodiment, the average dispersed particle size of the infrared absorber is, for example, 800 nm or less, preferably 200 nm or less, more preferably 100 nm or less, even more preferably 80 nm or less, and particularly preferably 60 nm or less, from the viewpoint of achieving both infrared absorption and visible light transmittance. From the viewpoint of improving infrared absorption, the average dispersed particle size of the infrared absorber is, for example, 1 nm or more, suitably 10 nm or more, and may be 20 nm or more, or even 30 nm or more. The average dispersed particle size of the infrared absorber (e.g., a metal oxide such as a tungsten composite oxide) can be measured using a particle size distribution analyzer (e.g., a Nanotrac particle size distribution analyzer manufactured by Nikkiso Co., Ltd.).

[0086] The content of the infrared absorber in the pressure-sensitive adhesive layer is not limited to a specific range and is appropriately set taking into consideration the desired infrared shielding, not impairing the ability to conceal the adherend, the required adhesive properties, etc. The content of the infrared absorber in the pressure-sensitive adhesive layer is, for example, about 0.1% by weight or more, and appropriately about 0.5% by weight or more, and from the viewpoint of improving the infrared shielding effect, it is preferably about 1% by weight or more, more preferably about 3% by weight or more, and may be about 5% by weight or more, about 8% by weight or more, or about 10% by weight or more (for example, more than 10% by weight). The content of the infrared absorber in the adhesive layer can be approximately 30% by weight or less, suitably approximately 25% by weight or less, preferably approximately 20% by weight or less, more preferably approximately 15% by weight or less, and may be approximately 12% by weight or less, approximately 9% by weight or less, approximately 7% by weight or less, or approximately 5% by weight or less, from the viewpoints of compatibility with the adhesive components and maintaining adhesive properties such as adhesive strength and impact resistance.

[0087] The content of the infrared absorber in the pressure-sensitive adhesive layer can also be specified by its relative relationship with the amount of the base polymer. From the viewpoint of infrared shielding, the content of the infrared absorber is, for example, about 0.1 parts by weight or more, suitably about 0.5 parts by weight or more, preferably about 1 part by weight or more, more preferably about 3 parts by weight or more, even more preferably about 5 parts by weight or more, and may be about 8 parts by weight or more, about 10 parts by weight or more, about 12 parts by weight or more, or about 15 parts by weight or more, per 100 parts by weight of the base polymer (preferably an acrylic polymer). From the viewpoint of compatibility with the adhesive components and maintaining adhesive properties such as adhesive strength and impact resistance, the content of the infrared absorber can be 40 parts by weight or less per 100 parts by weight of the base polymer, and is suitably approximately 30 parts by weight or less, preferably approximately 25 parts by weight or less, more preferably approximately 20 parts by weight or less, and may also be approximately 15 parts by weight or less, approximately 12 parts by weight or less, or approximately 8 parts by weight or less.

[0088] The total amount of infrared absorber and colorant contained in the adhesive layer is not particularly limited, and is, for example, about 1 part by weight or more, or appropriately about 3 parts by weight or more, relative to 100 parts by weight of base polymer (preferably acrylic polymer); from the viewpoint of favorably realizing concealment of the adherend and infrared shielding, it is preferably about 5 parts by weight or more, or may be about 10 parts by weight or more, or may be about 15 parts by weight or more, or may be about 20 parts by weight or more. Furthermore, the total amount of infrared absorber and colorant can be, for example, 40 parts by weight or less, relative to 100 parts by weight of base polymer; from the viewpoint of maintaining good adhesive properties, it is preferably about 30 parts by weight or less, more preferably about 25 parts by weight or less, or may be about 22 parts by weight or less, or may be about 18 parts by weight or less, or may be about 14 parts by weight or less, or may be about 10 parts by weight or less.

[0089] The ratio of the infrared absorbing agent to the coloring agent is appropriately set to achieve the desired concealment of the adherend and infrared shielding, and is not limited to a specific range. IRA and the amount of colorant C COL Weight ratio (C IRA / C COL The weight ratio (C) is 0.1 or more, suitably 0.5 or more, preferably 0.8 or more, may be 1.0 or more, may be 1.2 or more, or may be 1.5 or more. IRA / C COL The larger the weight ratio (C IRA / C COL The weight ratio (C) is 10 or less, suitably 5 or less, preferably 3 or less, more preferably 2 or less, and may be 1.5 or less, 1.2 or less, or even less than 1. IRA / C COL The smaller the value of (a), the more favorably the effect of adding the colorant is exhibited.

[0090] In the technology disclosed herein, the form in which a colorant (e.g., a black colorant such as carbon black particles, or a metal oxide) or an infrared absorber (e.g., a tungsten composite oxide) is added to a pressure-sensitive adhesive composition is not particularly limited. For example, the colorant or infrared absorber may be added to the pressure-sensitive adhesive composition in the form of a dispersion in which the particles are dispersed in a dispersion medium. The dispersion medium constituting the dispersion is not particularly limited, and examples thereof include water (e.g., ion-exchanged water, reverse osmosis water, distilled water, etc.), various organic solvents (e.g., alcohols such as ethanol and butanol; ketones such as acetone and methyl isobutyl ketone; ethers such as butyl cellosolve and propylene glycol monomethyl ether acetate; esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene; and mixtures thereof), and aqueous mixtures of water and the organic solvents. The dispersion may contain the above-mentioned dispersant. By mixing the dispersion with a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition contains not only a colorant and an infrared absorber, but also a dispersant.

[0091] (tackifying resin) The pressure-sensitive adhesive layer in the technology disclosed herein can contain a tackifying resin. This can increase the peel strength of the pressure-sensitive adhesive sheet. The tackifying resin can be one or more selected from various known tackifying resins, such as phenolic tackifying resins, terpene tackifying resins, modified terpene tackifying resins, rosin tackifying resins, hydrocarbon tackifying resins, epoxy tackifying resins, polyamide tackifying resins, elastomer tackifying resins, and ketone tackifying resins. Among these, phenolic tackifying resins, terpene tackifying resins, and modified terpene tackifying resins are preferred, with phenolic tackifying resins (preferably terpene phenolic resins) being more preferred.

[0092] Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkyl phenolic resins, and rosin phenolic resins. 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. Alkylphenol resins are resins (oil-based phenolic resins) obtained from alkylphenols and formaldehyde. Examples of alkylphenol resins include novolac and resol types. 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.

[0093] 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.

[0094] The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving cohesive strength, in some embodiments, a tackifier resin having a softening point (softening temperature) of approximately 80°C or higher (preferably approximately 100°C or higher, for example, above 105°C) 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 weight, more than 50% by weight (more preferably more than 70% by weight, for example, more than 90% by weight) 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, include a terpene phenol resin having a softening point of approximately 135°C or higher (or even approximately 140°C or higher). There is no particular upper limit to the softening point of the tackifier resin. From the viewpoint of improving adhesion to the adherend, in some embodiments, a tackifier resin having a softening point of about 200°C or less (more preferably about 150°C or less, for example, less than 130°C) can be preferably used. By using a tackifier resin with a relatively low softening point, the dispersibility of the infrared absorber and colorant 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.

[0095] Some preferred embodiments include those in which 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 weight, approximately 25% by weight or more (more preferably approximately 30% by weight or more) of the tackifier resins is terpene phenol resin. Approximately 50% by weight or more of the total amount of tackifier resins may be terpene phenol resin, or approximately 80% by weight or more (e.g., approximately 90% by weight or more) may be terpene phenol resin. Substantially all of the tackifier resin (e.g., approximately 95 to 100% by weight, or even approximately 99 to 100% by weight) may be terpene phenol resin.

[0096] Although not particularly limited, in some embodiments, the tackifier resin may contain a tackifier resin having a hydroxyl value of more than 20 mgKOH / g. Of 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 tackifier resin containing such a high hydroxyl value resin can provide a PSA layer that has excellent adhesion to an adherend and high cohesive strength. In some embodiments, 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 may be a value measured by potentiometric titration as specified in JIS K0070:1992.

[0097] 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 greater can be preferably used as the high hydroxyl value resin. In some preferred embodiments, a terpene phenol resin having a hydroxyl value of at least 30 mgKOH / g or greater 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.

[0098] The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the base polymer, the hydroxyl value of the high hydroxyl value resin is suitably approximately 200 mgKOH / g or less, preferably approximately 180 mgKOH / g or less, more preferably approximately 160 mgKOH / g or less, and even more preferably approximately 140 mgKOH / g or less. The technology disclosed herein 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 some embodiments, 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 other embodiments, a high hydroxyl value resin having a hydroxyl value of 70 to 140 mgKOH / g can be preferably used.

[0099] 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 adhesive layer can be, for example, about 25% by weight or more, preferably about 30% by weight or more, and more preferably about 50% by weight or more (e.g., about 80% by weight or more, typically about 90% by weight or more). Substantially all of the tackifier resin (e.g., about 95 to 100% by weight, or even about 99 to 100% by weight) may be the high hydroxyl value resin.

[0100] When 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 a range of about 1 to 100 parts by weight per 100 parts by weight 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 weight of the base polymer (e.g., an acrylic polymer) is suitably 5 parts by weight or more, preferably 10 parts by weight or more, and may be 15 parts by weight or more. Furthermore, from the viewpoint of impact resistance and cohesive strength, the amount of the tackifier resin used per 100 parts by weight of the base polymer (e.g., an acrylic polymer) is suitably 50 parts by weight or less, may be 40 parts by weight or less, or may be 30 parts by weight or less.

[0101] (Crosslinking agent) In the technology disclosed herein, the pressure-sensitive adhesive composition used to form the pressure-sensitive adhesive layer may contain a crosslinking agent, if necessary. The type of crosslinking agent is not particularly limited, and can be appropriately selected from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate-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. Among these, isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, and melamine-based crosslinking agents are preferred, with isocyanate-based crosslinking agents and epoxy-based crosslinking agents being more preferred, and isocyanate-based crosslinking agents being particularly preferred. The use of an isocyanate-based crosslinking agent tends to provide cohesive strength for the pressure-sensitive adhesive layer while also providing better impact resistance than other crosslinking systems. The use of an isocyanate-based crosslinking agent is also advantageous in terms of improving adhesive strength to adherends made of polyester resins such as PET, etc. The crosslinking agents can be used alone or in combination of two or more.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] 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."

[0107] The amount of the isocyanate crosslinking agent used is not particularly limited. For example, it can be approximately 0.5 parts by weight or more per 100 parts by weight of the base polymer. From the viewpoints of achieving both cohesive strength and adhesiveness and impact resistance, the amount of the isocyanate crosslinking agent used per 100 parts by weight of the base polymer can be, for example, 1.0 part by weight or more, or may be 1.5 parts by weight or more (typically 2.0 parts by weight or more, for example 2.5 parts by weight or more). On the other hand, from the viewpoint of improving adhesion to the adherend, the amount of the isocyanate crosslinking agent used is suitably 10 parts by weight or less per 100 parts by weight of the base polymer, and may be 8 parts by weight or less, or may be 5 parts by weight or less (for example 3 parts by weight or less).

[0108] In some preferred embodiments, 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 an isocyanate-based crosslinking agent; hereinafter also referred to as a "non-isocyanate-based crosslinking agent") in combination with an isocyanate-based crosslinking agent, excellent cohesive strength can be exhibited. The pressure-sensitive adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after crosslinking reaction, a form before crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, or the like. The crosslinking agent is typically contained in the pressure-sensitive adhesive layer exclusively in a form after crosslinking reaction.

[0109] The type of non-isocyanate crosslinking agent that can be 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 agent can be used alone or in combination of two or more.

[0110] In some preferred embodiments, an epoxy-based crosslinking agent can be used as the non-isocyanate-based crosslinking agent. For example, by using an isocyanate-based crosslinking agent in combination with an epoxy-based crosslinking agent, it is easy to achieve both cohesiveness and impact resistance. 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.

[0111] Non-limiting examples of epoxy crosslinking agents include 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 Mitsubishi Gas Chemical Company, Inc.'s trade names "TETRAD-C" and "TETRAD-X," DIC Corporation's trade name "Epiclon CR-5L," Nagase ChemteX Corporation's trade name "Denacol EX-512," and Nissan Chemical Industries, Ltd.'s trade name "TEPIC-G."

[0112] 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 weight and approximately 1 part by weight or less (typically, approximately 0.001 to 0.5 parts by weight) per 100 parts by weight 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 suitably approximately 0.002 parts by weight or more per 100 parts by weight of the base polymer, preferably approximately 0.005 parts by weight or more, and more preferably approximately 0.008 parts by weight or more. Furthermore, from the viewpoint of improving adhesion to the adherend, the amount of epoxy-based crosslinking agent used is suitably approximately 0.2 parts by weight or less per 100 parts by weight of the base polymer, preferably approximately 0.1 parts by weight or less, more preferably approximately less than 0.05 parts by weight, and even more preferably approximately less than 0.03 parts by weight (for example, approximately 0.025 parts by weight or less). Impact resistance also tends to improve by reducing the amount of epoxy-based crosslinking agent used.

[0113] In the technology disclosed herein, the relationship between the content of the isocyanate crosslinking agent and the content of the non-isocyanate crosslinking agent (e.g., epoxy crosslinking agent) is not particularly limited. The content of the non-isocyanate crosslinking agent can be, for example, approximately 1 / 50 or less of the content of the isocyanate crosslinking agent. From the viewpoint of more favorably achieving both adhesion to the adherend and cohesive strength, the content of the non-isocyanate crosslinking agent is suitably approximately 1 / 75 or less of the content of the isocyanate crosslinking agent on a weight basis, and preferably approximately 1 / 100 or less (e.g., 1 / 150 or less). Furthermore, from the viewpoint of favorably exhibiting the effects of using an isocyanate crosslinking agent and a non-isocyanate crosslinking agent (e.g., epoxy crosslinking agent) in combination, the content of the non-isocyanate crosslinking agent is suitably approximately 1 / 1000 or more of the content of the isocyanate crosslinking agent, for example, approximately 1 / 500 or more, and may be 1 / 250 or more.

[0114] The total amount of crosslinking agent used (total quantity) is not particularly limited, and can be, for example, about 10 parts by weight or less, preferably about 0.005 to 10 parts by weight, more preferably about 0.01 to 5 parts by weight, per 100 parts by weight of the base polymer (preferably an acrylic polymer).

[0115] (rust inhibitor) The pressure-sensitive adhesive layer according to some preferred embodiments may contain a rust inhibitor. Examples of the rust inhibitor include, but are not limited to, azole-based rust inhibitors, amine compounds, nitrites, ammonium benzoate, ammonium phthalate, ammonium stearate, ammonium palmitate, ammonium oleate, ammonium carbonate, dicyclohexylamine benzoate, urea, urotropine, thiourea, phenyl carbamate, and cyclohexylammonium-N-cyclohexylcarbamate (CHC). The rust inhibitors may be used alone or in combination of two or more.

[0116] As the rust inhibitor, an azole-based rust inhibitor can be preferably used. As the azole-based rust inhibitor, one having as its active ingredient an azole-based compound that is a five-membered ring aromatic compound containing two or more heteroatoms, at least one of which is a nitrogen atom, can be preferably used. A suitable example of a compound that can be used as the azole-based rust inhibitor is a benzotriazole-based rust inhibitor that has as its active ingredient a benzotriazole-based compound. Suitable examples of the benzotriazole-based compound include 1,2,3-benzotriazole, 5-methylbenzotriazole, 4-methylbenzotriazole, carboxybenzotriazole, etc.

[0117] The content of the rust inhibitor is not particularly limited, and can be, for example, 0.01 parts by weight or more (typically 0.05 parts by weight or more) per 100 parts by weight of the base polymer. From the viewpoint of obtaining a better metal corrosion prevention effect, the content may be 0.1 parts by weight or more, 0.3 parts by weight or more, or even 0.5 parts by weight or more. On the other hand, from the viewpoint of increasing the cohesive strength of the adhesive, the content of the rust inhibitor is suitably less than 8 parts by weight per 100 parts by weight of the base polymer, and may be 5 parts by weight or less, or may be 2 parts by weight or less.

[0118] (Other additives) The pressure-sensitive adhesive composition 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.

[0119] (Adhesive composition) The pressure-sensitive adhesive layer (layer comprising a pressure-sensitive adhesive) disclosed herein 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 that cures upon exposure to active energy rays such as ultraviolet light or electron beams. 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) primarily composed of water, and typically includes what are called water-dispersed pressure-sensitive adhesive compositions (compositions in which at least a portion of the pressure-sensitive adhesive is dispersed in water). Furthermore, the solvent-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive in an organic solvent. The organic solvent contained in the solvent-based pressure-sensitive adhesive composition may be one or more of the organic solvents exemplified above as those usable in solution polymerization (e.g., toluene, ethyl acetate, etc.), without particular limitation. From the viewpoint of adhesive properties, etc., the technology disclosed herein is preferably implemented in an embodiment having a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition. In an embodiment having a solvent-based pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition, the refractive index-enhancing effect of the technology disclosed herein is preferably realized.

[0120] As described above, this specification provides a pressure-sensitive adhesive composition containing one or more of the components that can be contained in the pressure-sensitive adhesive layer disclosed herein. The pressure-sensitive adhesive composition can be used to produce the pressure-sensitive adhesive sheet disclosed herein. The pressure-sensitive adhesive composition contains an infrared absorber and a colorant different from the infrared absorber. It may also contain other components (typically a base polymer) that can be contained in the pressure-sensitive adhesive layer described above. The content (wt % or parts by weight) of each component that can be contained in the pressure-sensitive adhesive layer can be rephrased as the content (wt % or parts by weight) based on the solids content (also referred to as the non-volatile content content) of the pressure-sensitive adhesive composition. Details of the other components of the pressure-sensitive adhesive composition are as explained for the pressure-sensitive adhesive layer, so repeated explanation will be omitted.

[0121] (Formation of adhesive layer) The PSA layer disclosed herein can be formed by a conventionally known method. For example, a method can be employed in which a PSA composition is applied to a releasable surface (release surface) and then dried to form a PSA layer. For PSA sheets having a support substrate, a method (direct method) can be employed in which a PSA composition is directly applied (typically coated) to the support substrate and then dried to form a PSA layer. Alternatively, a method (transfer method) can be employed in which a PSA composition is applied to a releasable surface (release surface) and then dried to form a PSA layer on the surface, and then the PSA layer is transferred to a support substrate. The release surface can preferably be, for example, the surface of a release liner, as described below. While the PSA layer disclosed herein is typically formed continuously, it is not limited to this form and may be formed in a regular or random pattern, such as dots or stripes.

[0122] The pressure-sensitive adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, a die coater, a bar coater, etc. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating. From the viewpoints of promoting the crosslinking reaction, improving production efficiency, etc., the pressure-sensitive adhesive composition is preferably dried under heating. The drying temperature can be, for example, about 40 to 150° C., and is preferably about 60 to 130° C. After drying the pressure-sensitive adhesive composition, aging may be further carried out for the purposes of adjusting component migration within the pressure-sensitive adhesive layer, promoting the crosslinking reaction, and alleviating distortion that may exist within the pressure-sensitive adhesive layer.

[0123] The pressure-sensitive adhesive layer disclosed herein may have a single-layer structure or a multi-layer structure of two or more layers. From the viewpoint of productivity, etc., the pressure-sensitive adhesive layer preferably has a single-layer structure.

[0124] The thickness of the adhesive layer is not particularly limited. To prevent the adhesive sheet from becoming excessively thick, the thickness of the adhesive layer is suitably approximately 100 μm or less, preferably approximately 70 μm or less, and more preferably approximately 50 μm or less. The thickness of the adhesive layer can be approximately 35 μm or less, for example, approximately 25 μm or less, or even approximately 15 μm or less. An adhesive layer with a limited thickness can effectively meet the demands for thinness and weight reduction. The lower limit of the thickness of the adhesive layer is not particularly limited, and from the viewpoint of adhesion to the adherend, it is advantageous to set it to approximately 1 μm or more, and it is appropriate to set it to approximately 3 μm or more, preferably approximately 10 μm or more, more preferably approximately 15 μm or more, even more preferably approximately 20 μm or more, and may be approximately 30 μm or more, approximately 35 μm or more, or approximately 40 μm or more. By setting the thickness to a predetermined value or more, it is easy to achieve concealment of the adherend and infrared shielding. In addition, the desired adhesive properties (adhesion strength, impact resistance, etc.) can be easily obtained. In a double-sided pressure-sensitive adhesive sheet with a substrate having a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer on each side of the substrate, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have the same thickness or different thicknesses.

[0125] (Visible light transmittance) The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet disclosed herein preferably has a light transmittance (visible light transmittance) in the wavelength range of 380 to 550 nm limited to a predetermined value or less. By utilizing this limited visible light transmittance of the pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet can conceal the adherend. The visible light transmittance of the pressure-sensitive adhesive layer (in other words, the maximum light transmittance in the wavelength range of 380 to 550 nm) is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less, and may be 8% or less, or even 6% or less. The lower the visible light transmittance, the better the concealing properties that can be exhibited. The lower limit of the visible light transmittance (in other words, the minimum light transmittance in the wavelength range of 380 to 550 nm) is not particularly limited and may be substantially 0%, i.e., below the detection limit, or may be 0.01% or more, for example, 0.1% or more, or 1.0% or more. In some embodiments, the visible light transmittance (in other words, the minimum light transmittance in the wavelength range of 380 to 550 nm) may be 2.0% or more, 3.0% or more, or 4.0% or more. By increasing the visible light transmittance, it becomes possible to visually check the adherend through the pressure-sensitive adhesive sheet and perform inspections, etc. The visible light transmittance of the pressure-sensitive adhesive layer can be measured by the method described in the Examples below.

[0126] (Infrared transmittance) The pressure-sensitive adhesive layer constituting the pressure-sensitive adhesive sheet disclosed herein preferably has a light transmittance (infrared transmittance) in the wavelength range of 800 to 1500 nm limited to a predetermined value or less. This allows a pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer to block infrared rays. For example, the pressure-sensitive adhesive layer can prevent problems caused by the passage of infrared rays, such as reduced operational accuracy or malfunction of an infrared sensor, based on the infrared-blocking properties of the pressure-sensitive adhesive layer, regardless of the material or shape of the adherend. The infrared transmittance of the pressure-sensitive adhesive layer (in other words, the maximum light transmittance in the wavelength range of 800 to 1500 nm) is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, and particularly preferably 2.0% or less, and may be 1.8% or less, or even 1.5% or less. The lower limit of the infrared transmittance (in other words, the minimum value of light transmittance in the wavelength range of 800 to 1500 nm) is not particularly limited, and may be substantially 0%, i.e., below the detection limit, or may be 0.01% or more, 0.05% or more, 0.1% or more, 0.2% or more, or 0.3% or more. The infrared transmittance of the pressure-sensitive adhesive layer can be measured by the method described in the Examples below.

[0127] The relative relationship between the visible light transmittance and the infrared transmittance of the pressure-sensitive adhesive layer is not particularly limited, and can be appropriately set so as to achieve a relationship that satisfies both the adherend concealment property and the infrared shielding property. For example, the infrared transmittance T IR [%] and visible light transmittance T VL [%] difference (T VL -T IR ) is, for example, 15 or less, may be 10 or less, may be 5 or less, or may be 3 or less. VL -T IR The smaller the difference (T VL -T IR ) may be, for example, 0.1 or more, 0.5 or more, 1 or more, 1.5 or more, 1.8 or more, or 2 or more. VL -T IR The larger the difference (T VL -T IR) is calculated using the above infrared transmittance T IR The maximum value [%] of the light transmittance at wavelengths of 800 to 1500 nm is used as the visible light transmittance T VL The minimum value [%] of light transmittance in the wavelength range of 380 to 550 nm is used as the transmittance.

[0128] <Supporting base material> In embodiments in which the PSA sheet disclosed herein is in the form of a single-sided or double-sided PSA sheet with a substrate, the substrate supporting (backing) the PSA layer can be a resin film, paper, cloth, rubber sheet, or a composite thereof. Examples of resin films include polyolefin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer; polyester films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); vinyl chloride resin films; vinyl acetate resin films; polyimide resin films; polyamide resin films; fluororesin films; cellophane, etc. Examples of paper include Japanese paper, kraft paper, glassine paper, wood-free paper, synthetic paper, and top-coated paper. Examples of cloth include woven fabrics and nonwoven fabrics made from various fibrous materials, either alone or in combination. Examples of the fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of the rubber sheet include a natural rubber sheet and a butyl rubber sheet.

[0129] The term "nonwoven fabric" as used herein refers to a nonwoven fabric for adhesive sheets that is primarily used in the field of adhesive tapes and other adhesive sheets, and typically refers to a nonwoven fabric (sometimes referred to as "paper") that is produced using a general papermaking machine. The term "resin film" as used herein typically refers to a non-porous resin sheet, and is a concept that is distinct from, for example, nonwoven fabrics and woven fabrics (in other words, a concept that excludes nonwoven fabrics and woven fabrics). The resin film may be any of a non-stretched film, a uniaxially stretched film, and a biaxially stretched film.

[0130] As the support substrate constituting the substrate-attached PSA sheet, a base film containing a resin film can be preferably used. The base film is typically a member that can independently maintain its shape (independent). The support substrate in the technology disclosed herein may be substantially composed of such a base film. Alternatively, the support substrate 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.

[0131] The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount of more than 50% by weight). From the viewpoints of handling and processability, polyester films are preferred, and PET films are particularly preferred.

[0132] The support substrate may be transparent or may have opacity. In some embodiments, the support substrate (e.g., a resin film) may contain a colorant. This allows the light transmittance of the support substrate to be adjusted. Adjusting the light transmittance (e.g., visible light transmittance) of the support substrate can also be useful for adjusting the light transmittance of the support substrate and, further, the light transmittance of a pressure-sensitive adhesive sheet including the substrate.

[0133] As the colorant, conventionally known pigments and dyes can be used, similar to the colorants that can be contained in the pressure-sensitive adhesive layer. The colorant is not particularly limited, and can be, for example, a colorant of black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, etc. The amount of colorant used in the supporting substrate (e.g., resin film) is not particularly limited, and can be appropriately adjusted to impart desired optical properties.

[0134] The supporting substrate (e.g., a resin 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 about less than 30% by weight (e.g., less than 20% by weight, typically less than 10% by weight).

[0135] The support substrate (e.g., a resin film) may have a single-layer structure, or a multi-layer structure of two, three, or more layers. From the viewpoint of shape stability, the support substrate preferably has a single-layer structure. In the case of a multi-layer structure, it is preferable that at least one layer (preferably all layers) is a layer having a continuous structure of the resin (e.g., a polyester-based resin). The method for producing the support substrate (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, and calendar roll molding may be used as appropriate.

[0136] The supporting substrate may be colored by a colored layer disposed on the surface of a base film (preferably a resin film). In such a substrate 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 the colored layers may be the same or different.

[0137] 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. As with colorants that can be contained in pressure-sensitive adhesive layers and resin films, conventionally known pigments and dyes can be used as colorants. As binders, materials known in the fields of paint and printing can be used 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.

[0138] The colored layer may have a single layer structure consisting of a single layer, or may have a multilayer structure including two, three, or more sub-colored layers. A multilayer colored layer including two or more sub-colored layers can be formed, for example, by repeatedly applying (e.g., printing) a colored layer-forming composition. The color and amount of colorant contained in each sub-colored layer may be the same or different. For colored layers intended to provide hiding properties, a multilayer structure is particularly useful from the viewpoint of preventing the occurrence of pinholes.

[0139] The overall thickness of the colored layer is suitably about 1 μm to 10 μm, preferably about 1 μm to 7 μm, and can be, for example, about 1 μm to 5 μm. In a colored layer including two or more sub-colored layers, the thickness of each sub-colored layer is preferably about 1 μm to 2 μm.

[0140] The thickness of the support substrate is not particularly limited. From the viewpoint of preventing the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the support substrate can be, for example, approximately 200 μm or less (e.g., approximately 100 μm or less). Depending on the purpose and manner of use of the pressure-sensitive adhesive sheet, the thickness of the support substrate may be approximately 70 μm or less, approximately 30 μm or less, or approximately 15 μm or less (e.g., approximately 8 μm or less). There is no particular lower limit to the thickness of the support substrate. From the viewpoint of the handleability and processability of the pressure-sensitive adhesive sheet, the thickness of the support substrate is suitably approximately 2 μm or more, preferably approximately 5 μm or more, for example, approximately 10 μm or more.

[0141] The surface of the support substrate may be subjected to a conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer, etc. Such a surface treatment may be a treatment for improving the adhesion between the support substrate and the pressure-sensitive adhesive layer, in other words, the anchoring ability of the pressure-sensitive adhesive layer to the support substrate.

[0142] Furthermore, when the technology disclosed herein is implemented in the form of a substrate-attached single-sided PSA sheet, the back surface of the support substrate may be subjected to a release treatment, if necessary. The release treatment may be, for example, a treatment in which a typical silicone-based, long-chain alkyl-based, or fluorine-based release agent is applied in the form of a thin film, typically about 0.01 μm to 1 μm (e.g., 0.01 μm to 0.1 μm). By applying such a release treatment, it is possible to obtain effects such as facilitating the unwinding of a roll of the PSA sheet.

[0143] <Release liner> In the technology disclosed herein, a release liner can be used during the formation of the adhesive layer, the production of the adhesive sheet, and the storage, distribution, and shaping of the 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.

[0144] <Characteristics of adhesive sheets> (Visible light transmittance) The pressure-sensitive adhesive sheet disclosed herein preferably has a light transmittance (visible light transmittance) in the wavelength range of 380 to 550 nm limited to a predetermined value or less. By utilizing this limited visible light transmittance, the pressure-sensitive adhesive sheet can conceal an adherend. The visible light transmittance of the pressure-sensitive adhesive sheet (in other words, the maximum light transmittance in the wavelength range of 380 to 550 nm) is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less, and may be 8% or less, or even 6% or less. The lower the visible light transmittance, the better the concealing properties that can be exhibited. The lower limit of the visible light transmittance (in other words, the minimum light transmittance in the wavelength range of 380 to 550 nm) is not particularly limited, and may be substantially 0%, i.e., below the detection limit, or may be 0.01% or more, for example, 0.1% or more, or 1.0% or more. In some embodiments, the visible light transmittance (in other words, the minimum light transmittance in the wavelength range of 380 to 550 nm) may be 2.0% or more, 3.0% or more, or 4.0% or more. Having such a visible light transmittance allows for visual confirmation of the adherend through the pressure-sensitive adhesive sheet, enabling inspection, etc. The visible light transmittance of the pressure-sensitive adhesive sheet can be measured by the method described in the Examples below.

[0145] (Infrared transmittance) The pressure-sensitive adhesive sheet disclosed herein preferably has a light transmittance (infrared transmittance) in the wavelength range of 800 to 1500 nm limited to a predetermined value or less. This allows the pressure-sensitive adhesive sheet to block infrared rays. For example, the pressure-sensitive adhesive sheet, regardless of the material or shape of the adherend, can prevent problems caused by the passage of infrared rays, such as reduced operational accuracy or malfunction of infrared sensors, based on the infrared-blocking properties of the pressure-sensitive adhesive sheet itself. The infrared transmittance of the pressure-sensitive adhesive sheet (in other words, the maximum light transmittance in the wavelength range of 800 to 1500 nm) is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, particularly preferably 2.0% or less, and may be 1.8% or less, or even 1.5% or less. The lower limit of the infrared transmittance (in other words, the minimum value of light transmittance in the wavelength range of 800 to 1500 nm) is not particularly limited, and may be substantially 0%, i.e., below the detection limit, or may be 0.01% or more, 0.05% or more, 0.1% or more, 0.2% or more, or 0.3% or more. The infrared transmittance of the pressure-sensitive adhesive sheet can be measured by the method described in the Examples below.

[0146] The relative relationship between the visible light transmittance and the infrared transmittance of the pressure-sensitive adhesive sheet is not particularly limited, and can be appropriately set so as to achieve a relationship that satisfies both the adherend concealment property and the infrared shielding property. For example, the infrared transmittance T IR [%] and visible light transmittance T VL [%] difference (T VL -T IR ) is, for example, 15 or less, may be 10 or less, may be 5 or less, or may be 3 or less. VL -T IR The smaller the difference (T VL -T IR ) may be, for example, 0.1 or more, 0.5 or more, 1 or more, 1.5 or more, 1.8 or more, or 2 or more. VL -T IR The larger the difference (T VL -T IR) is calculated using the above infrared transmittance T IR The maximum value [%] of the light transmittance at wavelengths of 800 to 1500 nm is used as the visible light transmittance T VL The minimum value [%] of light transmittance in the wavelength range of 380 to 550 nm is used as the transmittance.

[0147] (Adhesive strength) The 180-degree peel strength (adhesive strength) of the PSA sheet disclosed herein may vary depending on the intended use and application location, and is therefore not limited to a specific range. From the viewpoint of achieving good adhesion to the adherend, the adhesive strength of the PSA sheet is, for example, approximately 1.0 N / 25 mm or more, preferably approximately 5.0 N / 25 mm or more, more preferably approximately 10 N / 25 mm or more, even more preferably approximately 12 N / 25 mm or more, and may even be approximately 15 N / 25 mm or more. The technology disclosed herein makes it possible to achieve the above adhesive strength while achieving adherend concealment and infrared shielding. The upper limit of the adhesive strength is not particularly limited, and may be approximately 50 N / 25 mm or less (e.g., 30 N / 25 mm or less). Specifically, the adhesive strength is the 180-degree peel strength against a stainless steel plate measured according to JIS Z 0237, and more specifically, can be measured by the method described in the Examples below. In the case of a double-sided PSA sheet having adhesive surfaces on both sides, the adhesive strength on each side may be the same or different.

[0148] (shear adhesive strength) Although not particularly limited, the pressure-sensitive adhesive sheet disclosed herein preferably exhibits a shear adhesive strength of, for example, 1.0 MPa or more. A pressure-sensitive adhesive sheet exhibiting such a shear adhesive strength exhibits strong resistance to forces that tend to shift the adhesive interface (i.e., shear forces), and therefore has excellent adherend retention performance. From the viewpoint of exhibiting higher retention performance, the shear adhesive strength of the pressure-sensitive adhesive sheet is preferably 1.5 MPa or more, more preferably 1.8 MPa or more, and even more preferably 2.0 MPa or more. There is no particular upper limit for the shear adhesive strength, and generally, the higher the shear adhesive strength, the better. On the other hand, from the viewpoint of easily achieving adherend concealment and infrared shielding, in some embodiments, the shear adhesive strength may be, for example, 20 MPa or less, 10 MPa or less, 5 MPa or less, or 3 MPa or less. The shear adhesive strength can be measured by the method described in the Examples below.

[0149] (total thickness) The total thickness of the pressure-sensitive adhesive sheet disclosed herein (which includes a pressure-sensitive adhesive layer and, in configurations having a supporting substrate, further includes a supporting substrate, but does not include a release liner) is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet can be, for example, approximately 300 μm or less. From the viewpoint of thinning, approximately 200 μm or less is appropriate, and it may be approximately 100 μm or less (e.g., approximately 70 μm or less). In some preferred embodiments, the thickness of the pressure-sensitive adhesive sheet can be approximately 50 μm or less, for example, approximately 35 μm or less. The lower limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, but can be approximately 1 μm or more, for example, approximately 3 μm or more is appropriate, preferably approximately 6 μm or more, more preferably approximately 10 μm or more (e.g., approximately 15 μm or more), and even more preferably approximately 20 μm or more. By achieving a thickness of a predetermined value or more, adherend concealment and infrared shielding can be preferably achieved. Pressure-sensitive adhesive sheets having a thickness of a predetermined value or more tend to be easy to handle and also have excellent adhesion and impact resistance. In the case of a substrate-less pressure-sensitive adhesive sheet, the thickness of the pressure-sensitive adhesive layer is the total thickness of the pressure-sensitive adhesive sheet.

[0150] <Application> The pressure-sensitive adhesive sheet disclosed herein can conceal an adherend, and by taking advantage of this feature, is suitable for various applications requiring concealment of an adherend. For example, some portable electronic devices require the use of a pressure-sensitive adhesive sheet to conceal components. The pressure-sensitive adhesive sheet disclosed herein is preferably used to fix components of such portable electronic devices.

[0151] Non-limiting examples of the portable electronic device include mobile phones, smartphones, tablet PCs, notebook PCs, various wearable devices (e.g., 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 being portable, but also means having a level of portability that allows an individual (average adult) to carry it relatively easily. Examples of the electronic device include personal computers (desktop, notebook, tablet, etc.), televisions, etc. These may be ones that incorporate a display device such as a liquid crystal display or an organic EL display.

[0152] The adhesive sheet disclosed herein can be used, for example, in such portable electronic devices that include a pressure-sensitive sensor, for the purpose of fixing the pressure-sensitive sensor to other members. In some embodiments, the adhesive sheet can be used to fix the pressure-sensitive sensor to other members in an electronic device (typically a portable electronic device) that has 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.

[0153] The adhesive sheet disclosed herein is also suitable for use on the back surface of a display screen (display unit) such as a touch panel display in a portable electronic device. By disposing the adhesive sheet disclosed herein 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.

[0154] The pressure-sensitive adhesive sheet disclosed herein is also suitable for portable electronic devices with built-in optical sensors. Various devices, such as the portable electronic devices described above, may be equipped with optical sensors that utilize infrared, visible, ultraviolet, or other light rays for purposes such as device operation, detection of nearby objects, detection of ambient brightness (ambient light), and data communication. Examples of the optical sensors include, but are not limited to, acceleration sensors, proximity sensors, and brightness sensors (ambient light sensors). Such optical sensors may have light-receiving elements for ultraviolet, visible, infrared, and other light rays, and may also have light-emitting elements for specific light rays, such as infrared. In other words, the optical sensor may include a light-emitting element and / or a light-receiving element for light in a specific wavelength range within a wavelength range that includes ultraviolet, visible, and infrared rays. The pressure-sensitive adhesive sheet disclosed herein may not adversely affect the operational accuracy of the sensor, and therefore may be preferably used as a concealing means or adhesive means in such devices.

[0155] Preferred applications of the pressure-sensitive adhesive sheet disclosed herein include electronic devices with built-in infrared sensors. The pressure-sensitive adhesive sheet disclosed herein can have excellent infrared blocking properties, so when used to secure, protect, cover, or seal components of the electronic devices, it can effectively block infrared rays and reduce the impact of external light on the operational accuracy of the infrared sensor. Such electronic devices can have a biometric authentication function that employs biometric authentication technology to authenticate individuals based on biometric information such as fingerprints or veins. Infrared sensors can be used in such personal authentication. Examples of such electronic devices include portable electronic devices with a biometric authentication function that can authenticate individuals based on fingerprints or other information, and various biometric authentication devices.

[0156] Further, other suitable examples of electronic devices (typically portable electronic devices) incorporating the infrared sensor include devices such as remote controls (teleoperated devices) that use an infrared sensor to operate the main body. In such devices, it is undesirable for infrared rays to leak from any source other than the light-emitting portion directed toward the target. Therefore, it is particularly useful to use the adhesive sheet disclosed herein to block infrared rays and prevent infrared rays emitted from within the device from leaking to the outside from any source other than the light-emitting portion. By utilizing the technology disclosed herein for such applications, it is possible to prevent a decrease in the operational accuracy of the infrared sensor and malfunction.

[0157] Materials (adherend materials) to which the pressure-sensitive adhesive sheets disclosed herein can be attached include, but are not limited to, metal materials such as copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc., or alloys containing two or more of these metals; various resin materials (typically plastic materials) such as polyimide resins, acrylic resins, polyethernitrile resins, polyethersulfone resins, polyester resins (PET resins, polyethylene naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyetheretherketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, polycarbonate resins, and liquid crystal polymers; and inorganic materials such as alumina, zirconia, soda glass, quartz glass, and carbon. Among these, metal materials such as copper, aluminum, and stainless steel; polyester resins such as PET; and resin materials (typically plastic materials) such as polyimide resins, aramid resins, and polyphenylene sulfide resins are widely used. The above materials may be materials for components constituting products such as electronic devices. The adhesive sheet disclosed herein may be attached to a component made of the above materials when used. The above materials may also be materials constituting a fixing target (e.g., a back surface member such as an electromagnetic wave shield or a reinforcing plate) for the pressure-sensitive sensor, display unit, or other such device. The fixing target refers to an object to which the adhesive sheet is attached, i.e., an adherend. The back surface member refers to a member disposed on the opposite side of the front surface (viewing side) of the pressure-sensitive sensor or display unit in, for example, a portable electronic device, and may be, for example, a member constituting the support unit 240 disposed on the back surface of the display device 200 shown in FIG. 3 described below. The fixing target may have either a single-layer structure or a multi-layer structure, and the surface to which the 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 back surface member having a thickness of 1 μm or more (typically 5 μm or more, for example 60 μm or more, or even 120 μm or more) and 1500 μm or less (for example 800 μm or less).

[0158] The adhesive sheet disclosed herein is also suitable for use in concealing at least a portion of the surface of a member or article having a surface (adhesive sheet-attached surface) formed from a metal material such as aluminum or stainless steel. Suitable examples of such adherends include metal members such as stainless steel members and aluminum members. By attaching an adhesive sheet to an area of ​​the surface of a metal member that needs to be concealed, the area of ​​the metal member can be concealed. The adhesive sheet may cover the entire surface of the metal member, or may cover only a portion of the surface (a portion that needs to be concealed). The metal member may be, for example, a member that constitutes the support section 240 of the display device 200 shown in FIG. 3 (described later). In an embodiment in which the adhesive sheet is a double-sided adhesive sheet and different adherends (members or articles) are attached to each side of the sheet, it is preferable that one of the adherends is a metal member.

[0159] The pressure-sensitive adhesive sheet disclosed herein is also suitable for applications involving concealing the surface of a metal member that has been processed, such as an opening. Pressure-sensitive adhesive sheets used for such applications can conceal an adherend by covering the adherend, including areas where the metal member is not present. Therefore, the surface (adhesive surface) of the pressure-sensitive adhesive sheet can have areas where the adherend is present (adherend-adhered areas) and areas where the adherend is not present (adherend-non-adhered areas). In this case, infrared rays can pass through the pressure-sensitive adhesive sheet and the areas where the adherend is not present. By using the infrared-shielding pressure-sensitive adhesive sheet disclosed herein, infrared rays can be blocked even in areas where the metal member is not present, preventing malfunction of optical sensors, etc.

[0160] Furthermore, the component or material to which the PSA sheet is attached (in the case of a double-sided PSA sheet, at least one of the adherends) may be optically transparent. According to the technology disclosed herein, the PSA sheet can conceal the surface of the other adherend through the above-described optically transparent adherend (specifically, in the case of a double-sided PSA sheet, concealment of the surface of the other adherend is possible). Furthermore, the optically transparent adherend allows, for example, light from a sensor to pass through the adherend and reach the PSA sheet, making it easier to obtain the benefits of the technology disclosed herein (infrared shielding). The visible light transmittance of the optically transparent adherend (component, etc.) is, for example, 5% or more, and may be 30% or more. In some embodiments, the visible light transmittance of the optically transparent component, etc., is, for example, greater than 50%, preferably 70% or more, more preferably 80% or more, even more preferably 90% or more, and may even be 95% or more. Such a material may be a resin film (e.g., a polyester-based resin film such as a PET film) that is disposed on the back surface of an image display unit of various devices, such as a portable electronic device. The pressure-sensitive adhesive sheet disclosed herein can be preferably used in an embodiment in which it is attached to an adherend (e.g., a member) having a visible light transmittance of at least a predetermined value as described above. The visible light transmittance can be measured in the same manner as the visible light transmittance of a pressure-sensitive adhesive sheet.

[0161] As described above, the technology disclosed herein provides a laminate comprising a pressure-sensitive adhesive sheet and a member to which the pressure-sensitive adhesive sheet is attached. In some embodiments, the laminate comprising the pressure-sensitive adhesive sheet is a laminate comprising the pressure-sensitive adhesive sheet and a metal member (first member). Such a laminate may comprise a metal member and a pressure-sensitive adhesive sheet covering at least a portion of the surface of the metal member. The pressure-sensitive adhesive sheet may cover the entire surface of the metal member, or may cover a portion of the surface (a partial area that needs to be concealed). Typically, one side (the adhesive surface) of the pressure-sensitive adhesive sheet is attached to the metal member. Also, in some embodiments, the member to which the pressure-sensitive adhesive sheet is attached may have the light transmittance of the adherend material described above. In this embodiment, the laminate comprising the pressure-sensitive adhesive sheet is a laminate comprising the pressure-sensitive adhesive sheet and a light-transmitting member (second member). In some preferred embodiments, the laminate is a laminate comprising a metal member (first member), a pressure-sensitive adhesive sheet, and a light-transmitting member (second member) in this order. The pressure-sensitive adhesive sheet is also referred to as the pressure-sensitive adhesive layer in the laminate.

[0162] An example of the configuration of the laminate is shown in FIG. 2. The laminate 50 shown in FIG. 2 includes a first member 41, a substrate-less adhesive sheet 1, and a second member 42, in this order. Specifically, in the laminate 50, one adhesive surface (first adhesive surface) 1A of the substrate-less adhesive sheet 1 is adhered to the first member 41, and the other adhesive surface (second adhesive surface) 1B of the adhesive sheet 1 is adhered to the second member 42. In this embodiment, the first member 41 and the second member 42 both have a sheet-like or plate-like shape, and the laminate 50 has a multilayer structure. Details of the members constituting the laminate are the same as those described above for the members, materials, and adherends, and therefore will not be described again.

[0163] In some preferred embodiments, the first member 41 is a metal member, and the metal material exemplified above as the adherend material is used. The metal member serving as the first member 41 is preferably an aluminum member or a stainless steel member, and more preferably a stainless steel member. By attaching the pressure-sensitive adhesive sheet 1 disclosed herein to the metal member serving as the first member 41, the metal member can be effectively concealed. Such a metal member may be, for example, a member constituting the support section 240 of the display device 200 shown in FIG. 3 described below. In some preferred embodiments, the second member 42 is a light-transmitting member and has the light transmittance of the light-transmitting adherend described above. The second member 42 is preferably a member made of a resin film, and more preferably a polyester-based resin film (more specifically, a PET-based resin film). The second member 42 may be, for example, a member disposed on the back side of the display section of a display device. The laminate 50 described above may typically be a component of an organic electroluminescence display device, a liquid crystal display device, or the like. The laminate 50 is suitable for use in applications where it is disposed on the back surface of an image display unit (which may be a display unit such as a touch panel display) of various devices such as portable electronic devices.

[0164] The pressure-sensitive adhesive sheet disclosed herein is preferably used in electronic devices including various light sources such as LEDs (light emitting diodes) and light-emitting elements such as self-luminous organic EL devices. For example, it is preferably used in electronic devices (typically portable electronic devices) equipped with organic EL display devices or liquid crystal display devices that require specific optical properties.

[0165] FIG. 3 is an exploded perspective view schematically illustrating an exemplary configuration of a display device. As shown in FIG. 3, the display device 200 included in the portable electronic device 100 includes a display unit 220 including a cover member, an organic EL unit, etc., and a support unit 240. The display device 200 is configured to further include an adhesive sheet 230. In this exemplary configuration, the adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided adhesive sheet) that fixes the members that make up the display unit 220 and the support unit 240. The support unit 240 is configured to include a substrate (a metal plate such as a stainless steel plate or an aluminum plate) and the like. The adhesive sheet disclosed herein is preferably used as a component of the display device described above.

[0166] The matters disclosed by this specification include the following: [1] A display device including a display unit including a cover member and an organic EL unit, and a support unit, an adhesive sheet is attached to the support portion; The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, The pressure-sensitive adhesive layer comprises an infrared absorbing agent and a coloring agent different from the infrared absorbing agent. [2] The display device according to [1] above, which has a built-in optical sensor including a light emitting element and / or a light receiving element for light in a specific wavelength range among wavelength ranges including ultraviolet light, visible light, and infrared light. [3] The display device according to [1] or [2] above, wherein the infrared absorbing agent is a metal compound, and is preferably selected from tungsten composite oxides and tin composite oxides. [4] The display device according to any one of the above [1] to [3], wherein the colorant includes a black colorant. [5] The display device according to [4], wherein the colorant further contains a metal oxide. [6] The display device according to any one of [1] to [5] above, wherein the total amount of the infrared absorber and the colorant contained in the pressure-sensitive adhesive layer is within a range of 5 to 30 parts by weight per 100 parts by weight of the base polymer contained in the pressure-sensitive adhesive layer. [7] The display device according to any one of the above [1] to [6], wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. [8] The display device according to any one of the above [1] to [7], wherein the thickness of the adhesive layer is in the range of 10 to 50 μm. [9] The display device according to any one of the above [1] to [8], wherein the pressure-sensitive adhesive sheet is a substrate-less double-sided pressure-sensitive adhesive sheet made of the pressure-sensitive adhesive layer.

[10] The display device according to any one of [1] to [9] above, wherein the pressure-sensitive adhesive sheet has a 180-degree peel strength against a stainless steel plate measured in accordance with JIS Z 0237 of 10 N / 25 mm or more.

[0167]

[11] A pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing an infrared absorbent and a colorant different from the infrared absorbent.

[12] The pressure-sensitive adhesive sheet according to

[11] above, wherein the infrared absorber is a metal compound, preferably selected from tungsten composite oxides and tin composite oxides.

[13] The pressure-sensitive adhesive sheet according to

[11] or

[12] above, wherein the colorant includes a black colorant.

[14] The pressure-sensitive adhesive sheet according to

[13] above, wherein the colorant further contains a metal oxide.

[15] The pressure-sensitive adhesive sheet according to any one of

[11] to

[14] above, wherein the total amount of the infrared absorber and the colorant contained in the pressure-sensitive adhesive layer is within the range of 5 to 30 parts by weight per 100 parts by weight of the base polymer contained in the pressure-sensitive adhesive layer.

[16] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[15] , wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

[17] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[16] , wherein the pressure-sensitive adhesive layer has a thickness in the range of 10 to 50 μm.

[18] The pressure-sensitive adhesive sheet according to any one of the above

[11] to

[17] , which is a substrateless double-sided pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.

[19] The pressure-sensitive adhesive sheet according to any one of

[11] to

[18] above, which has a 180-degree peel strength against a stainless steel plate measured in accordance with JIS Z 0237 of 10 N / 25 mm or more.

[20] The pressure-sensitive adhesive sheet according to any one of

[11] to

[19] above, which is used for fixing components of a portable electronic device.

[0168]

[21] A laminate comprising a metal member and an adhesive sheet attached to the surface of the metal member, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, The pressure-sensitive adhesive layer comprises an infrared absorbing agent and a coloring agent different from the infrared absorbing agent.

[22] A laminate comprising a light-transmitting member and a pressure-sensitive adhesive sheet, one surface of the pressure-sensitive adhesive sheet is attached to the optically transparent member, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, The pressure-sensitive adhesive layer comprises an infrared absorbing agent and a coloring agent different from the infrared absorbing agent.

[23] A laminate including a metal member (first member), an adhesive sheet, and a light-transmitting member (second member) in this order, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer, The pressure-sensitive adhesive layer comprises an infrared absorbing agent and a coloring agent different from the infrared absorbing agent.

[24] The laminate according to

[21] or

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

[25] The laminate according to the above

[22] or

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

[26] The laminate according to the above

[22] ,

[23] or

[25] , wherein the optically transparent member is made of a resin film.

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

[21] to

[26] , wherein the infrared absorbing agent is a metal compound, and is preferably selected from tungsten composite oxides and tin composite oxides.

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

[21] to

[27] , wherein the colorant includes a black colorant.

[29] The laminate according to

[28] above, wherein the colorant further contains a metal oxide.

[30] The laminate according to any one of

[21] to

[29] above, wherein the total amount of the infrared absorber and the colorant contained in the pressure-sensitive adhesive layer is within the range of 5 to 30 parts by weight per 100 parts by weight of the base polymer contained in the pressure-sensitive adhesive layer.

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

[21] to

[30] , wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

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

[21] to

[31] , wherein the thickness of the pressure-sensitive adhesive layer is in the range of 10 to 50 μm.

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

[21] to

[32] , wherein the pressure-sensitive adhesive sheet is a substrate-less double-sided pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.

[34] The laminate according to any one of

[21] to

[33] above, wherein the pressure-sensitive adhesive sheet has a 180-degree peel strength against a stainless steel plate measured in accordance with JIS Z 0237 of 10 N / 25 mm or more.

[35] The laminate according to any one of

[21] to

[34] above, which is used in a portable electronic device.

[0169]

[36] A pressure-sensitive adhesive composition comprising an infrared absorbent and a colorant different from the infrared absorbent.

[37] The pressure-sensitive adhesive composition according to the above

[36] , wherein the infrared absorber is a metal compound.

[38] The pressure-sensitive adhesive composition according to the above

[36] or

[37] , wherein the infrared absorber is selected from tungsten composite oxides and tin composite oxides.

[39] The pressure-sensitive adhesive composition according to any one of the above

[36] to

[38] , wherein the colorant includes a black colorant.

[40] The pressure-sensitive adhesive composition according to

[39] above, wherein the colorant further contains a metal oxide.

[41] The pressure-sensitive adhesive composition according to any one of the above

[36] to

[40] , wherein the total amount of the infrared absorber and the colorant is within the range of 5 to 30 parts by weight per 100 parts by weight of the base polymer.

[42] The pressure-sensitive adhesive composition according to any one of the above

[36] to

[41] , which contains an acrylic polymer as a base polymer. [Example]

[0170] Hereinafter, several examples of the present invention will be described, but it is not intended that the present invention be limited to those shown in these examples. In the following description, "parts" are by weight unless otherwise specified.

[0171] <Evaluation method> [Visible light transmittance and infrared transmittance] The visible light transmittance [%] and infrared transmittance [%] of the adhesive layer and adhesive sheet are determined by measuring the visible light transmittance (wavelength range 380-550 nm) and infrared transmittance (wavelength range 800-1500 nm) in the thickness direction of the adhesive layer and adhesive sheet peeled from the release liner using a commercially available spectrophotometer. The spectrophotometer used is a Hitachi spectrophotometer (device name "UH4150 spectrophotometer") or an equivalent.

[0172] [180 degree peel strength (adhesive strength)] A 50 μm thick PET film is attached to one adhesive side of a double-sided PSA sheet under a measurement environment of 23°C and 50% RH, and the sheet is then cut to a size of 25 mm wide and 100 mm long to prepare a measurement sample. The adhesive surface of the prepared measurement sample is then pressed against the surface of a stainless steel plate (SUS304BA plate) using a 2 kg roller, moving back and forth once, under conditions of 23°C and 50% RH. After leaving the sheet under the same conditions for 30 minutes, the peel strength (adhesive strength) [N / 25 mm] is measured using a universal tension and compression tester in accordance with JIS Z 0237:2000, at a tension speed of 300 mm / min and a peel angle of 180°. Examples of universal tension and compression testers that can be used include the Minebea "Tension and Compression Tester, TG-1kN" or an equivalent. Note that the PET film backing is not necessary for single-sided PSA sheets.

[0173] [Shear adhesive strength] A measurement sample is prepared by cutting a pressure-sensitive adhesive sheet (double-sided pressure-sensitive adhesive sheet) into a size of 10 mm x 10 mm. In an environment of 23°C and 50% RH, each adhesive side of the measurement sample is placed on the surface of two stainless steel plates (SUS304BA plates) and pressed together with a 2 kg roller by rolling it back and forth once. After leaving this in the same environment for two days, the shear adhesive strength [MPa] is measured using a tensile tester at a tensile speed of 10 mm / min and a peel angle of 0°. For single-sided pressure-sensitive adhesive sheets (single-sided pressure-sensitive adhesive sheets), the non-adhesive side of the sheet is fixed to the stainless steel plate with an adhesive or the like, and the rest of the measurement is performed in the same manner as above. A universal tension and compression tester (product name "TG-1kN", manufactured by Minebea Co., Ltd.) can be used as the tensile tester.

[0174] [Substrate hiding power] A stainless steel plate is prepared as the adherend, and a 10 mm long mark (black mark) is made on its surface using a commercially available black oil-based marker (marking pen). An adhesive sheet is attached to the surface of the adherend to create an evaluation sample. In a normal indoor environment, it is evaluated whether the black mark on the adherend surface can be seen through the adhesive sheet. Evaluation is based on the following two criteria. ○: The black mark cannot be seen. ×: Black marks are visible. In the above evaluation, if the black mark is not visible, it is judged that the adherend can be concealed.

[0175] [Infrared shielding] An adhesive sheet is attached to the circuit pattern surface of a substrate on which a circuit pattern is formed. The circuit pattern is an aluminum wiring pattern with a line width of 1 mm. Next, an infrared microscope is used to check the circuit pattern on the substrate surface through the adhesive sheet and evaluate it based on the following two criteria. Note that the infrared microscope can be a combination device of a stereo microscope (product name "SMZ745T", manufactured by Nikon Corporation) and an infrared camera (product name "MC781P0030", manufactured by Texas Instruments), or an equivalent device. O: Circuit pattern cannot be recognized by infrared. ×: The circuit pattern can be recognized by infrared light.

[0176] <Example 1> (Preparation of Acrylic Polymer) 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 233 parts of ethyl acetate as a polymerization solvent, 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.

[0177] (Preparation of Pressure-Sensitive Adhesive Composition) To the acrylic polymer solution, 20 parts of a terpene phenolic resin (tackifier), 3 parts of an isocyanate crosslinker and 0.02 parts of an epoxy crosslinker (crosslinkers), 3 parts of carbon black particles (Toyocolor Co., Ltd., product name "Multilac A903," average particle size 400 nm) (colorant, black), and 5 parts of cesium-containing tungsten composite oxide particles (Sumitomo Metal Mining Co., Ltd., product name "YMF-02," average dispersed particle size 50 nm) (IR absorber A) were added and stirred to prepare a pressure-sensitive adhesive composition. The terpene phenolic resin (tackifier) ​​used was "YS Polystar T-115" (Yasuhara Chemical Co., Ltd., softening point approximately 115°C, hydroxyl value 30-60 mgKOH / g). The isocyanate crosslinking agent used was "Coronate L" (manufactured by Tosoh Corporation, a 75% ethyl acetate solution of trimethylolpropane / tolylene diisocyanate trimer adduct), and the epoxy crosslinking agent used was "TETRAD-C" (manufactured by Mitsubishi Gas Chemical Co., Inc., 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane).

[0178] (Preparation of adhesive sheet) The above-mentioned pressure-sensitive adhesive composition was applied to the release surface of a 38 μm thick polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Polyester Corporation) and dried at 100°C for 2 minutes to form a 30 μm thick pressure-sensitive adhesive layer. The release surface of a 25 μm thick polyester release liner (trade name "Diafoil MRF", manufactured by Mitsubishi Polyester Corporation) was then bonded to this pressure-sensitive adhesive layer. In this way, a 30 μm thick substrateless double-sided pressure-sensitive adhesive sheet was obtained, both sides of which were protected by the two polyester release liners.

[0179] <Example 2> To the acrylic polymer solution prepared in Example 1, 20 parts of the tackifier resin, 3 parts of the isocyanate-based crosslinking agent and 0.02 parts of the epoxy-based crosslinking agent as crosslinkers, 0.5 parts of the carbon black particles as the first colorant (black colorant), 10 parts of titanium oxide (TiO2) particles (product name "WHITE PASTE R-2228", Dainichiseika Color & Chemicals Mfg. Co., Ltd., average particle size 50 nm) as the second colorant (white colorant), and 10 parts of the cesium-containing tungsten composite oxide microparticles were added per 100 parts of the acrylic polymer contained in the solution, on a solids basis, and the mixture was stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example. A substrateless double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1, except that the resulting pressure-sensitive adhesive composition was used.

[0180] <Example 3> To the acrylic polymer solution prepared in Example 1, 20 parts of the tackifier resin, 3 parts of the isocyanate-based crosslinking agent and 0.02 parts of the epoxy-based crosslinking agent as crosslinking agents, 1.0 part of the carbon black particles as the first colorant (black colorant), 10 parts of the titanium oxide particles as the second colorant (white colorant), and 18 parts of antimony-doped tin oxide particles (manufactured by Sumitomo Metal Mining Co., Ltd., product name "FMF-3A1") as infrared absorber B were added, based on the solids content, per 100 parts of the acrylic polymer contained in the solution, and the mixture was stirred and mixed to prepare a pressure-sensitive adhesive composition according to this example. A substrateless double-sided pressure-sensitive adhesive sheet according to this example was produced in the same manner as in Example 1, except that the resulting pressure-sensitive adhesive composition was used.

[0181] <Example 4> An adhesive composition according to this example was prepared in the same manner as in Example 1, except that no infrared absorber was used and the content of the carbon black particles was changed to 5 parts per 100 parts of the acrylic polymer, and a substrateless double-sided adhesive sheet according to this example was produced using the adhesive composition.

[0182] <Example 5> A substrate-less double-sided PSA sheet according to this example was produced in the same manner as in Example 2, except that no infrared absorbing agent was used.

[0183] <Examples 6-7> To the acrylic polymer solution prepared in Example 1, 20 parts of the tackifier resin, 3 parts of the isocyanate crosslinking agent and 0.02 parts of the epoxy crosslinking agent as crosslinkers, and 5 parts (Example 6) or 40 parts (Example 7) of the cesium-containing tungsten composite oxide microparticles were added, based on solids content, per 100 parts of the acrylic polymer contained in the solution, and the mixture was stirred and mixed to prepare a pressure-sensitive adhesive composition according to each example. Substrate-less double-sided pressure-sensitive adhesive sheets according to each example were produced in the same manner as in Example 1, except that the pressure-sensitive adhesive composition was used.

[0184] An overview of the adhesive of each example, as well as the minimum (Min) and maximum (Max) transmittance (visible light transmittance) [%] in the wavelength range of 380 to 550 nm, the minimum (Min) and maximum (Max) transmittance (infrared transmittance) [%] in the wavelength range of 800 to 1500 nm, adhesive strength [N / 25 mm], shear adhesive strength [MPa], and evaluation results of adherend hiding ability and infrared shielding ability are shown in Table 1. The light transmittance [%] in the wavelength range of 380 to 1500 nm of the adhesive sheet of each example is also shown in Figure 4.

[0185] [Table 1]

[0186] As shown in Table 1, the adhesive sheets of Examples 1 to 3, which had adhesive layers containing an infrared absorber and a colorant, passed the evaluation results for both adherend concealment and infrared shielding. On the other hand, Examples 4 and 5, which did not use an infrared absorber, failed the evaluation results for infrared shielding. Even in Example 4, in which the amount of black colorant was increased and the visible light transmittance was reduced to 0.3 to 0.6%, the maximum infrared transmittance exceeded 5%. Furthermore, Examples 6 and 7, which did not use a colorant, did not achieve adherend concealment. Example 6, in which a small amount of infrared absorber was used, failed the evaluation result for infrared shielding, and Example 7, in which the amount of infrared absorber was increased, showed improved infrared blocking properties but a tendency for adhesive strength to decrease. The above results show that by using a pressure-sensitive adhesive containing an infrared absorber and a colorant, it is possible to realize a pressure-sensitive adhesive sheet that can conceal the adherend and provide excellent infrared shielding.

[0187] Although specific examples of the present invention have been described above in detail, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. [Explanation of symbols]

[0188] 1,230 adhesive sheets 1A Adhesive surface, 1st adhesive surface 1B Adhesive side, 2nd adhesive side 21 adhesive layer 21A Adhesive surface, 1st adhesive surface 21B Adhesive surface, 2nd adhesive surface 31,32 Release liner 41 First member 42 Second member 50 laminate 100 Portable electronic devices 200 Display device 220 Display section 240 Support part

Claims

1. An adhesive sheet used to fix components of a portable electronic device, The adhesive layer has a thickness of 1 μm or more and 100 μm or less, the pressure-sensitive adhesive layer contains at least one inorganic compound selected from the group consisting of metal oxides and lanthanum borides as an infrared absorbent, and a black colorant as a colorant different from the infrared absorbent, the content of the infrared absorber in the pressure-sensitive adhesive layer is 0.1 wt % or more; A pressure-sensitive adhesive sheet, wherein the content of the black colorant in the pressure-sensitive adhesive layer is 0.01% by weight or more.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the infrared absorbing agent is a metal compound.

3. The pressure-sensitive adhesive sheet according to claim 1 , wherein the infrared absorber is selected from the group consisting of tungsten composite oxides and tin composite oxides.

4. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the total amount of the infrared absorber and the colorant contained in the pressure-sensitive adhesive layer is in the range of 5 to 30 parts by weight per 100 parts by weight of the base polymer contained in the pressure-sensitive adhesive layer.

5. The pressure-sensitive adhesive sheet according to any one of claims 1 to 4, wherein the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer.

6. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the pressure-sensitive adhesive layer has a thickness in the range of 10 to 50 µm.

7. The pressure-sensitive adhesive sheet according to any one of claims 1 to 6, which is a substrate-less double-sided pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.

8. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, which has a 180 degree peel strength against a stainless steel plate measured in accordance with JIS Z 0237 of 10 N / 25 mm or more.

9. A display device including a display unit including a cover member and an organic EL unit, and a support unit, an adhesive sheet is attached to the support portion; The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer having a thickness of 1 μm or more and 100 μm or less, the pressure-sensitive adhesive layer contains at least one inorganic compound selected from the group consisting of metal oxides and lanthanum borides as an infrared absorbent, and a black colorant as a colorant different from the infrared absorbent, the content of the infrared absorber in the pressure-sensitive adhesive layer is 0.1 wt % or more; The display device, wherein the content of the black colorant in the pressure-sensitive adhesive layer is 0.01% by weight or more.

10. A laminate constituting a portable electronic device, A metal member and an adhesive sheet attached to a surface of the metal member, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer having a thickness of 1 μm or more and 100 μm or less, the pressure-sensitive adhesive layer contains at least one inorganic compound selected from the group consisting of metal oxides and lanthanum borides as an infrared absorbent, and a black colorant as a colorant different from the infrared absorbent, the content of the infrared absorber in the pressure-sensitive adhesive layer is 0.1 wt % or more; A laminate, wherein the content of the black colorant in the pressure-sensitive adhesive layer is 0.01% by weight or more.

11. A laminate constituting a portable electronic device, A light-transmitting member and an adhesive sheet are provided, one surface of the pressure-sensitive adhesive sheet is attached to the optically transparent member, The pressure-sensitive adhesive sheet has a pressure-sensitive adhesive layer having a thickness of 1 μm or more and 100 μm or less, the pressure-sensitive adhesive layer contains at least one inorganic compound selected from the group consisting of metal oxides and lanthanum borides as an infrared absorbent, and a black colorant as a colorant different from the infrared absorbent, the content of the infrared absorber in the pressure-sensitive adhesive layer is 0.1 wt % or more; A laminate, wherein the content of the black colorant in the pressure-sensitive adhesive layer is 0.01% by weight or more.

12. An acrylic pressure-sensitive adhesive composition used for fixing components of a portable electronic device, comprising: The ink jet recording medium comprises an acrylic polymer as a base polymer, at least one inorganic compound selected from the group consisting of metal oxides and lanthanum borides as an infrared absorber, and a black colorant as a colorant different from the infrared absorber, The content of the infrared absorber based on the solid content is 0.1 wt% or more, The acrylic pressure-sensitive adhesive composition, wherein the content of the black colorant is 0.01 wt % or more based on the solid content.

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