Adhesive sheet

Abstract

To provide an adhesive sheet containing a base material having a colored layer and an adhesive layer, which can show excellent holding power.SOLUTION: There is provided an adhesive sheet which contains an adhesive layer formed from a water dispersion type adhesive composition comprising an acrylic polymer as a base polymer and a support base material which is in a sheet-like shape having a first surface and a second surface and supports the adhesive layer on at least the first surface. The base material contains a colored layer constituting the first surface and the colored layer constituting the first surface contains an ether-based polyurethane.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an adhesive sheet including a base material having a colored layer and an adhesive layer.

Background Art

[0002] Generally, an adhesive (also referred to as a pressure-sensitive adhesive. The same applies hereinafter) exhibits a state of a soft solid (viscoelastic body) in a temperature range near room temperature and has a property of easily adhering to an adherend by pressure. Taking advantage of such properties, adhesives are widely used in various applications in the form of an adhesive sheet with a base material having an adhesive layer provided on one or both surfaces of the base material. For example, in various applications such as electronic devices such as mobile phones, tablet computers, and laptop computers, a colored adhesive sheet is used for the purpose of imparting electrical insulation, concealment, light shielding, visibility, design, etc. Patent Documents 1 and 2 can be cited as technical documents related to this type of adhesive sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Patent Documents 1 and 2 describe an adhesive sheet produced by providing a colored layer on the surface of a resin film as a base material by printing and providing an adhesive layer on the colored layer by a transfer method. Here, the transfer method is a method of forming an adhesive layer on a release liner as a process paper by applying an adhesive composition and drying it, and then transferring the adhesive layer onto the base material by bonding the adhesive layer to the base material. On the other hand, a method of directly applying an adhesive composition to a base material and drying it to form an adhesive layer is called a direct coating method (hereinafter also referred to as the "direct method"). The formation of an adhesive layer by the direct coating method has manufacturing advantages such as the needlessness of a process paper compared to the formation of an adhesive layer by the transfer method.

[0005] However, when attempting to form an adhesive layer on a base material provided with a colored layer on its surface by the direct method, components derived from the colored layer may migrate from the colored layer of the base material to the adhesive composition, which may act to adversely affect the properties of the adhesive layer. For example, when attempting to control the crosslinked structure of a base polymer contained in the adhesive layer for property control by a crosslinking agent or the like, components derived from the colored layer that have migrated into the adhesive composition may inhibit the crosslinking reaction, resulting in a decrease in the holding power of the adhesive layer.

[0006] The present invention has been made in view of such points, and an object thereof is to provide an adhesive sheet including a base material having a colored layer and an adhesive layer, which can exhibit excellent holding power.

Means for Solving the Problems

[0007] As a result of intensive studies, the present inventors have obtained the finding that crosslinking inhibition tends to occur in the adhesive layer when the colored layer of the base material contains at least an ether-based polyurethane. Further, by forming the adhesive layer using an aqueous dispersion-type adhesive composition in which a dispersion-type adhesive component is contained in an aqueous medium, even when the adhesive layer is formed on the base material by the direct method, crosslinking inhibition by components derived from the colored layer is likely to be suppressed, and the present invention has been completed.

[0008] According to this specification, there is provided an adhesive sheet including an adhesive layer formed from an aqueous dispersion type adhesive composition containing an acrylic polymer as a base polymer, and a support substrate having a first surface and a second surface and supporting the adhesive layer at least on the first surface. Here, the substrate includes a colored layer constituting the first surface, and the colored layer contains an ether-based polyurethane. According to such a configuration, since the adhesive layer disposed in contact with the colored layer of the substrate is formed from an aqueous dispersion type adhesive composition, the migration of crosslinking inhibitor components from the colored layer hardly occurs, and crosslinking inhibition in the adhesive layer is easily suppressed. Therefore, the adhesive sheet tends to suppress a decrease in holding power.

[0009] In some embodiments, the acrylic polymer is (i) a polymer of a monomer component containing a silanol group-forming monomer and crosslinked with a silanol group derived from the silanol group-forming monomer, or (ii) crosslinked with one or more crosslinking agents selected from oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, and isocyanate-based crosslinking agents.

[0010] The silanol group-forming monomer in the above (i) is a polymerizable compound having at least one (preferably two or more, for example, two or three) functional groups (silanol group-forming functional groups) capable of forming a silanol group (Si-OH) in one molecule. Preferable examples of the silanol group-forming functional group include functional groups (such as alkoxysilyl groups) that form a silanol group by hydrolysis. By using such a silanol group-forming monomer as a monomer component, a crosslinked structure due to the condensation reaction of silanol groups is introduced into the acrylic polymer. According to the technology disclosed herein, crosslinking inhibition is preferably suppressed with respect to the crosslinking reaction (that is, the condensation reaction of silanol groups) derived from the silanol group-forming monomer as described above. Therefore, when an acrylic polymer crosslinked with a silanol group-forming monomer is used as the acrylic polymer contained in the adhesive layer, a decrease in holding power due to crosslinking inhibition hardly occurs.

[0011] Also, according to the technology disclosed herein, crosslinking inhibition is preferably suppressed even for the crosslinking reaction by the crosslinking agent listed in the above (ii), that is, the crosslinking reaction by one or more crosslinking agents selected from oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, and isocyanate-based crosslinking agents. Therefore, when an acrylic polymer crosslinked by the above crosslinking agent is used as the acrylic polymer contained in the pressure-sensitive adhesive layer, a decrease in the holding force due to crosslinking inhibition is less likely to occur.

[0012] In some embodiments, the thickness of the pressure-sensitive adhesive layer is 10 μm or more and 50 μm or less. According to the technology disclosed herein, even in a pressure-sensitive adhesive sheet having a relatively thin pressure-sensitive adhesive layer, the influence of the crosslinking inhibition component from the colored layer is suppressed, and a decrease in the holding force is likely to be suppressed.

[0013] In some embodiments, the base material includes a first colored layer constituting the first surface and a second colored layer constituting the second surface, a first pressure-sensitive adhesive layer is disposed on the first surface of the base material, and a second pressure-sensitive adhesive layer is disposed on the second surface of the base material. According to such an embodiment, it is easy to realize a double-sided pressure-sensitive adhesive sheet including a base material having a colored layer and exhibiting excellent holding force.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Modes for Carrying Out the Invention

[0015] Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification and necessary for the implementation of the present invention can be understood by those skilled in the art based on the teachings regarding the implementation of the invention described in this specification and the common general knowledge in the art at the time of filing. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the relevant field. Also, in the following drawings, members and parts having the same function may be denoted by the same reference numerals for explanation, and duplicate explanations may be omitted or simplified. Further, the embodiments described in the drawings are schematized for clearly explaining the present invention and do not necessarily accurately represent the size and scale of the actually provided product.

[0016] In this specification, the “adhesive” refers to a material that exhibits a state of a soft solid (viscoelastic body) in the temperature range near room temperature and has the property of adhering to an adherend by pressure. As defined in “C. A. Dahlquist, ‘Adhesion : Fundamentals and Practice’, McLaren & Sons, (1966) P. 143”, the adhesive generally has a complex tensile elastic modulus E * (1 Hz) < 10 7 dyne / cm 2 and can be a material having such a property (typically, a material having the above property at 25°C). The adhesive in the technology disclosed herein can also be understood as the solid content (non-volatile content) of the adhesive composition or a constituent of the adhesive layer.

[0017] In this specification, “(meth)acryloyl” comprehensively refers to acryloyl and methacryloyl. Similarly, “(meth)acrylate” comprehensively refers to acrylate and methacrylate, and “(meth)acrylic” comprehensively refers to acrylic and methacrylic, respectively.

[0018] In this specification, the "acrylic polymer" refers to a polymer containing more than 50% by weight of monomer units derived from acrylic monomers as monomer units constituting the polymer. The above acrylic monomer refers to a monomer derived from a monomer having at least one (meth)acryloyl group in one molecule.

[0019] In this specification, "water-dispersible" means a form in which at least some components are dispersed in water. For example, the "water-dispersible pressure-sensitive adhesive composition" means a composition containing a pressure-sensitive adhesive composition and water, and at least a part of the pressure-sensitive adhesive composition is dispersed in water. The water-dispersible form includes a suspended state and an emulsified state.

[0020] <Adhesive sheet> (Structural example of adhesive sheet) The adhesive sheet disclosed herein is an adhesive sheet with a substrate having an adhesive layer on one or both surfaces of the substrate (support). The concept of the adhesive sheet herein may include those referred to as adhesive tapes, adhesive labels, adhesive films, etc. The above adhesive layer is typically formed continuously, but is not limited to such a form, and may be an adhesive layer formed in a regular or random pattern such as dot-like or stripe-like. Further, the adhesive sheet may be in the form of a roll or a single sheet. Alternatively, it may be an adhesive sheet in a form further processed into various shapes.

[0021] The pressure-sensitive adhesive sheet disclosed herein may, for example, have a cross-sectional structure schematically shown in FIG. 1. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 is configured as a single-sided pressure-sensitive adhesive sheet with a substrate, which includes a sheet-like substrate (support) 10 and a pressure-sensitive adhesive layer 20 provided on one surface 10A (non-peeling surface) of the substrate 10. In this pressure-sensitive adhesive sheet 1, the surface of the pressure-sensitive adhesive layer 20 is an adhesive surface (pressure-sensitive adhesive surface) 1A that constitutes one surface of the pressure-sensitive adhesive sheet 1. Also, in this pressure-sensitive adhesive sheet 1, the other surface 10B of the substrate 10 serves as the other surface (back surface) 1B of the pressure-sensitive adhesive sheet 1. That is, the other surface 10B of the substrate 10 also serves as the back surface 1B of the pressure-sensitive adhesive sheet 1. The substrate 10 includes a substrate film 12 and a colored layer 14 disposed on the front side of the substrate film 12 (that is, the pressure-sensitive adhesive layer 20 side of the substrate film 12, also referred to as the first surface 12A). The colored layer 14 constitutes the surface 10A of the substrate 10 on the pressure-sensitive adhesive layer 20 side. In other words, the pressure-sensitive adhesive sheet 1 has a laminated structure in which the colored layer 14 and the pressure-sensitive adhesive layer 20 are laminated in this order on the first surface 12A of the substrate film 12.

[0022] Before use (that is, before attachment to an adherend), the pressure-sensitive adhesive sheet 1 may be in the form of a pressure-sensitive adhesive sheet 50 with a release liner, as shown in FIG. 1, where the adhesive surface 1A is protected by a release liner 30 in which at least the pressure-sensitive adhesive layer 20 side serves as a release surface. Alternatively, the release liner 30 may be omitted, and the other surface (back surface) 10B of the substrate layer 10 serves as a release surface, and the pressure-sensitive adhesive sheet 1 may be in a form in which the pressure-sensitive adhesive layer 20 abuts against the back surface 10B when the pressure-sensitive adhesive sheet 1 is wound in a roll shape to protect its surface (adhesive surface 1A).

[0023] In another aspect, the adhesive sheet disclosed herein may have a cross-sectional structure schematically shown in FIG. 2. The adhesive sheet 3 shown in FIG. 2 is configured as a double-sided adhesive sheet with a substrate, which includes a sheet-like substrate (support) 18, and a first adhesive layer 22 and a second adhesive layer 24 supported on both surfaces of the substrate 18, respectively. More specifically, the first adhesive layer 22 and the second adhesive layer 24 are provided on the first surface 18A and the second surface 18B (both non-peelable surfaces) of the substrate 18, respectively. In this adhesive sheet 3, the surface of the first adhesive layer 22 is an adhesive surface (sticking surface) 3A that constitutes one surface of the adhesive sheet 3, and the surface of the second adhesive layer 24 is an adhesive surface (sticking surface) 3B that constitutes the other surface of the adhesive sheet 3. The substrate 18 includes a substrate film 13, a first coloring layer 15 disposed on the first adhesive layer 22 side of the substrate film 13, and a second coloring layer 16 disposed on the second adhesive layer 24 side of the substrate film 13. The first coloring layer 15 constitutes the surface 18A of the substrate 18 on the first adhesive layer 22 side, and the second coloring layer 16 constitutes the surface 18B of the substrate 18 on the second adhesive layer 24 side. In other words, the adhesive sheet 3 has a laminated structure in which the first coloring layer 15 and the first adhesive layer 22 are laminated in this order on the first surface 13A of the substrate film 13, and the second coloring layer 16 and the second adhesive layer 24 are laminated in this order on the second surface 13B of the substrate film 13.

[0024] Before use (before attachment to an adherend), as shown in FIG. 2, the adhesive sheet 3 may be in the form of an adhesive sheet with a release liner 60, in which the adhesive surface 3A is protected by a release liner 32 with at least the first adhesive layer 22 side being the release surface, and the adhesive surface 3B is protected by a release liner 34 with at least the second adhesive layer 24 side being the release surface. Alternatively, the release liner 34 may be omitted, and the surface (back surface) 32B of the release liner 32 on the side opposite to the first adhesive layer 22 is the release surface, and the adhesive sheet 3 may be in the form of an adhesive sheet in which the second adhesive layer 24 abuts against the back surface 32B when the adhesive sheet 3 is wound in a roll shape to protect its surface (adhesive surface 3B).

[0025] (Substrate) The pressure-sensitive adhesive sheet disclosed herein includes a sheet-shaped base material (support) that supports a pressure-sensitive adhesive layer. In some embodiments, the base material includes a base film and a colored layer provided on the base film.

[0026] (Base film) The base film (base film) is not particularly limited, and for example, a resin film having a resin material as a main component (for example, a component contained in an amount exceeding 50% by weight) can be preferably employed. In this specification, the "resin film" typically refers to a substantially non-foamed resin film. That is, the resin film in this specification can be one in which air bubbles are substantially absent (voidless) in the resin film. Therefore, the resin film is a concept distinct from a so-called foam film. Further, the resin film is typically a substantially non-porous film, which is a concept distinct from a so-called non-woven fabric or woven fabric. A base material that does not include a porous layer such as a foam, non-woven fabric, or woven fabric, that is, a base material composed of a non-porous layer, can be preferably used. Resin films generally tend to be superior in mechanical strength such as tensile strength compared to foams, non-woven fabrics, and woven fabrics. Also, they are excellent in processability (for example, punching processability). Therefore, a pressure-sensitive adhesive sheet using a base material including a resin film is advantageous in terms of processability, dimensional accuracy, and handleability. Such a base material including a resin film can also be preferably used as the base material in the technology disclosed herein from the viewpoints of dimensional stability, thickness accuracy, economy (cost), and the like.

[0027] Preferable examples of the resin material constituting the resin film disclosed herein include polyolefin resins, polyester resins, and the like. Here, the polyolefin resin refers to a resin containing polyolefin at a ratio exceeding 50% by weight. Similarly, the polyester resin refers to a resin containing polyester at a ratio exceeding 50% by weight. Examples of the polyolefin resin film include polyethylene (PE) resins, polypropylene (PP) resins, ethylene-propylene copolymers, ethylene-butene copolymers, and the like. Examples of the polyester resin include polyethylene terephthalate (PET) resins, polybutylene terephthalate (PBT) resins, polyethylene naphthalate resins, polybutylene naphthalate resins, and the like. Among them, from the viewpoint of the anchoring property (especially the anchoring property of the acrylic adhesive layer), polyester resins are preferred, and PET resins are particularly preferred from the viewpoints of strength and processability.

[0028] In the above-mentioned base film (for example, resin film), various additives such as fillers (inorganic fillers, organic fillers, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, and plasticizers may be blended as necessary. The blending ratio of various additives is usually less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

[0029] As the base film (for example, resin film), a transparent film (for example, a transparent resin film) can be preferably adopted. Such a base film may be substantially free of a colorant from the viewpoint of strength and the like. Here, the base film being substantially free of a colorant means that the content of the colorant is less than 1% by weight, preferably less than 0.1% by weight. Alternatively, the base film in the technology disclosed herein may be colored in black, white (for example, milky white), or other colors in order to exhibit desired design properties and optical properties (for example, light-shielding properties, etc.) in the adhesive sheet. The above coloring may be performed, for example, by blending a known organic or inorganic colorant (pigment, dye, etc.) into the material constituting the base film.

[0030] The base film disclosed herein may have a single-layer structure or may have a multi-layer structure of two layers, three layers or more. From the viewpoint of shape stability, the base film preferably has a single-layer structure. The method for manufacturing the base film (typically a resin film) may be appropriately selected from conventionally known methods and is not particularly limited. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, calender roll molding, etc. can be appropriately adopted.

[0031] On the surface of the above base film (e.g., resin film), conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of a primer (formation of a primer layer), etc. may be performed. Such surface treatment can be a treatment for improving the adhesion between the base film and the colored layer laminated on its surface and the adhesion between the base film and the adhesive layer. It should be noted that the technology disclosed herein is preferably implemented in a manner where no primer layer is formed between the base film and the layer laminated on its surface and / or between the base film and the adhesive layer, and the base film is in direct contact with the layer laminated on its surface and / or the adhesive layer. The adhesive sheet having such a configuration can be made thinner.

[0032] The thickness of the base film is not particularly limited. In some embodiments, the thickness of the base film may be, for example, approximately 200 μm or less, and may be approximately 100 μm or less, 70 μm or less, or 50 μm or less. By reducing the thickness of the base film, the adhesive sheet also becomes thinner, which can be advantageous in terms of thinning, miniaturization, weight reduction, and resource conservation of the product to which the adhesive sheet is applied. Further, from the viewpoints of handleability and processability, etc., the lower limit of the thickness of the base film is preferably approximately 0.5 μm or more (for example, 1 μm or more). In some other embodiments, from the viewpoints of handleability, etc., the thickness of the base film may be 5 μm or more, 10 μm or more, 15 μm or more, or 20 μm or more. In some preferred embodiments, the thickness of the base film is, for example, 1 μm or more and 100 μm or less, more preferably 10 μm or more and 80 μm or less, and particularly preferably 25 μm or more and 75 μm or less.

[0033] (Coloring layer) The base material disclosed herein includes a colored layer. Specifically, the colored layer is laminated on the adhesive layer side of the base material film and is disposed between the base material film and the adhesive layer. In an embodiment where the adhesive sheet is configured as a single-sided adhesive sheet having an adhesive layer formed on one side of the base material, the colored layer is disposed so as to constitute at least the surface of the base material on the adhesive layer side. Further, in an embodiment where the adhesive sheet is configured as a double-sided adhesive sheet having adhesive layers formed on both sides of the base material, the colored layer is disposed so as to constitute at least the surface of the base material on one of the adhesive layer sides, and preferably two or more colored layers are disposed so as to respectively constitute the surfaces of the base material on the one and the other adhesive layer sides. According to the embodiment in which the colored layers are respectively disposed on both sides of the base material, compared with the embodiment in which the colored layer is disposed on one side of the base material, the surface roughness of the colored layer is likely to be reduced, and thus the surface roughness of the adhesive layer is reduced, so that the adhesion to the adherend is improved and the adhesion performance is easily improved. Further, when an adhesive layer is provided on the colored layer, the anchoring property between the base material / adhesive layer tends to be improved as compared with the case where the adhesive layer is provided on the base material surface without the colored layer. According to the technology disclosed herein, since there is a high degree of freedom in manufacturing for providing an adhesive layer on the colored layer side of the base material, it is easy to obtain an adhesive sheet having a high anchoring property between the base material / adhesive layer.

[0034] By including a colored layer in the base material, the color tone and transparency of the adhesive sheet can be adjusted, and desired design properties, light-shielding properties, and concealing properties can be obtained. The color of the colored layer is not particularly limited, and various colors can be adopted according to the purpose. In some preferred embodiments, the colored layer can be, for example, a black layer (e.g., a black printing layer) formed by black printing. An adhesive sheet provided with a black layer as the colored layer can be preferably used, for example, for applications where it is attached to a module that requires electrical insulation.

[0035] The colored layer can be formed, for example, by applying a composition for forming a colored layer containing a colorant and a binder to the base material film. As the binder, materials known in the fields of paints or printing can be used without particular limitation. For example, polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate, etc. are exemplified.

[0036] According to the studies by the present inventors, it has been found that when the colored layer contains an ether-based polyurethane as a binder, crosslinking inhibition of the adhesive is likely to occur when the adhesive layer is formed. Therefore, the technology disclosed herein is particularly meaningful when applied to a configuration in which the colored layer contains an ether-based polyurethane as a binder. Here, the ether-based polyurethane in this specification refers to a polyurethane whose main chain is an ether bond. Typically, it refers to a polyurethane produced by the reaction of an ether-based polyol (for example, polyether polyol) and a polyisocyanate.

[0037] In some embodiments, the proportion of the ether-based polyurethane in the total amount of the binder contained in the colored layer disclosed herein is more than 50% by weight, and may be 70% by weight or more, 80% by weight or more, or 90% by weight or more (for example, 100% by weight). According to the technology disclosed herein, even when the content of the ether-based polyurethane increases, crosslinking inhibition can be preferably suppressed, and a decrease in holding power can be suppressed.

[0038] The composition for forming the colored layer can be, for example, a solvent type, an ultraviolet curable type, a thermosetting type, or the like. The formation of the colored layer can be carried out by adopting, without particular limitation, the means conventionally employed for forming the colored layer. For example, a method of forming a colored layer (printing layer) by printing such as gravure printing, flexographic printing, or offset printing can be preferably adopted.

[0039] The colored layer may have a single-layer structure consisting of one layer as a whole, or may have a multilayer structure including two, three, or more sub-colored layers. The colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (for example, printing) the composition for forming the colored layer. The color and blending amount of the colorant contained in each sub-colored layer may be the same or different. In the colored layer for imparting light-shielding properties, from the viewpoint of preventing the occurrence of pinholes and enhancing the reliability of preventing light leakage, it is particularly meaningful to adopt a multilayer structure.

[0040] As the colorant used for coloring the coloring layer, known pigments and dyes according to the target color can be appropriately selected. Although not particularly limited, examples of white pigments include titanium dioxide, zinc white, lead white, etc. Examples of black pigments include carbon black, acetylene black, pine soot, graphite, etc. These can be used alone or in combination of two or more.

[0041] Since the content of the colorant is set according to the required color tone, texture, etc., it is not limited to a specific range. However, in the coloring layer, it is appropriate to be approximately 1% by weight or more, preferably 2% by weight or more (for example, 5% by weight or more), and can be 15% by weight or more. Also, the content of the above colorant is appropriately approximately 65% by weight or less, preferably 30% by weight or less (for example, 15% by weight or less), and may be 8% by weight or less.

[0042] In the aspect where the coloring layer constitutes at least one surface of the base material, the thickness of the entire coloring layer (single-sided) is usually appropriately 0.1 μm or more, preferably 0.5 μm or more, more preferably 0.7 μm or more. The thickness of the entire coloring layer (single-sided) may be approximately 0.8 μm or more, and may be approximately 1 μm or more. In some other aspects, from the viewpoint of obtaining sufficient light-shielding properties and concealing properties, the thickness of the entire coloring layer (single-sided) may be 2 μm or more (for example, 3 μm or more), and may be 4 μm or more. Also, the thickness of the entire above coloring layer (single-sided) is usually appropriately 10 μm or less, preferably 7 μm or less, more preferably 5 μm or less. In some aspects, the thickness of the entire coloring layer (single-sided) can be approximately 3 μm or less, and further can be approximately 2 μm or less.

[0043] (Additional layer) The base material may have an additional layer in addition to the above base material film and coloring layer (for example, black layer). For example, an adhesive layer, an undercoat layer, etc. may be provided between each layer to obtain interlayer adhesion. Alternatively, the technology disclosed herein can be preferably implemented in an aspect using a base material that does not have layers other than the above base material film and coloring layer.

[0044] Although not particularly limited, in the pressure-sensitive adhesive sheet disclosed herein, the total thickness of the layers other than the pressure-sensitive adhesive layer (the total thickness of the non-pressure-sensitive adhesive layers. Typically, it is the total thickness of the base material, for example, the total thickness of the base material film and the coloring layer) is, for example, about 200 μm or less, and may be about 100 μm or less, 70 μm or less, or 50 μm or less. By reducing the thickness of the non-pressure-sensitive adhesive layer, the pressure-sensitive adhesive sheet also becomes thinner, and thus it can be advantageous in terms of thinning, miniaturization, weight reduction, resource saving, etc. of the product to which the pressure-sensitive adhesive sheet is applied. Further, by limiting the thickness of the non-pressure-sensitive adhesive layer as described above, in a configuration where the total thickness of the pressure-sensitive adhesive sheet is limited to a predetermined value or less, the ratio of the thickness of the pressure-sensitive adhesive layer can be increased, and higher adhesive performance can be obtained. The lower limit of the total thickness of the non-pressure-sensitive adhesive layer is not particularly limited, and from the viewpoints of handleability, processability, etc., usually 2 μm or more is appropriate, and 3 μm or more (for example, 3.5 μm or more) is preferable. In some other embodiments, the total thickness of the non-pressure-sensitive adhesive layer may be 5 μm or more, 12 μm or more, 16 μm or more, 20 μm or more, or 25 μm or more from the viewpoints of light-shielding property and handleability. In some preferred embodiments, the thickness of the non-pressure-sensitive adhesive layer is, for example, 1 μm or more and 100 μm or less, more preferably 10 μm or more and 80 μm or less, and particularly preferably 25 μm or more and 75 μm or less.

[0045] <Pressure-sensitive adhesive layer> (Water-dispersible pressure-sensitive adhesive composition) The pressure-sensitive adhesive layer disclosed herein is formed from a water-dispersible pressure-sensitive adhesive composition. The water-dispersible pressure-sensitive adhesive composition is a water-dispersible (typically, water-based emulsion type) pressure-sensitive adhesive composition in which the pressure-sensitive adhesive component is dispersed in an aqueous medium. Here, the aqueous medium refers to a medium in which the solvent constituting the medium is water or a mixed solvent (aqueous solvent) having water as a main component.

[0046] (Acrylic polymer) The pressure-sensitive adhesive composition disclosed herein is an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer. Here, the "base polymer" refers to the main component among the polymer components contained in the pressure-sensitive adhesive composition (which may also be a pressure-sensitive adhesive). Further, in this specification, the "main component" refers to a component contained in an amount exceeding 50% by weight, unless otherwise specified. In a preferred embodiment, the acrylic pressure-sensitive adhesive composition is an acrylic emulsion-type pressure-sensitive adhesive composition containing a water-dispersed acrylic polymer. The water-dispersed acrylic polymer has an emulsion form in which the acrylic polymer is dispersed in water. As such an acrylic polymer, those having an alkyl (meth)acrylate as a main constituent monomer component (monomer main component, that is, a component occupying more than 50% by weight of the total amount of monomers constituting the acrylic polymer) can be preferably employed.

[0047] As the acrylic polymer, for example, a polymer of a monomer raw material (monomer component) containing an alkyl (meth)acrylate as a main monomer and further containing a comonomer copolymerizable with the main monomer is preferred. Here, the main monomer refers to a component occupying more than 50% by weight of the monomer composition in the monomer raw material.

[0048] As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used. CH 2 =C(R 1 )COOR 2 (1) Here, R 1 in the above formula (1) is a hydrogen atom or a methyl group. Further, R 2 is a linear alkyl group having 1 to 20 carbon atoms (hereinafter, such a carbon atom number range may be represented as "C 1-20 "). From the viewpoint of the storage elastic modulus of the pressure-sensitive adhesive, etc., an alkyl (meth)acrylate in which R 2 is a linear alkyl group of C 1-14 is preferred, and an alkyl (meth)acrylate in which R 2 is a linear alkyl group of C 1-10 is more preferred, and R 2An alkyl (meth)acrylate which is a butyl group or 2-ethylhexyl group is particularly preferred.

[0049] R 2 is C 1-20 Examples of the alkyl (meth)acrylate in which the alkyl group is a linear alkyl group of C

[0050] The technology disclosed herein is such that the monomer component is the R of the above formula (1) 2 is C 4-10 The alkyl (meth)acrylate (typically at least one of BA and 2EHA) in which the alkyl group is a linear alkyl group of C 2 is C 4-10The total amount of the alkyl (meth)acrylate which is a chain alkyl group (typically the total amount of BA and 2EHA) can be preferably carried out in an embodiment where it occupies 70% by weight or more (typically 80% by weight or more).

[0051] When the alkyl (meth)acrylate is an alkyl (meth)acrylate in which R in the above formula (1) 2 is C 4-10 is a chain alkyl group, and includes an alkyl (meth)acrylate (typically at least one of BA and 2EHA), the total amount of other alkyl (meth)acrylates (R in the above formula (1) 2 is C 4 less than or C 10 is a chain alkyl group with more than) is preferably about 30% by weight or less (for example, 20% by weight or less, typically 15% by weight or less) in the monomer components constituting the acrylic polymer. Also, from the viewpoint of obtaining the effects of other alkyl (meth)acrylates, the total amount is preferably about 1% by weight or more (for example, 5% by weight or more, typically 10% by weight or more) in the monomer components. As the other alkyl (meth)acrylate, an alkyl (meth)acrylate in which R in the above formula (1) 2 is C 1-3 is a chain alkyl group can be preferably used. Specific examples thereof include methyl acrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA), etc. Among them, MA is more preferable.

[0052] The comonomer having copolymerizability with the alkyl (meth)acrylate as the main monomer can be useful for introducing crosslinking points into the acrylic polymer or increasing the cohesive force of the acrylic polymer. As the comonomer, for example, the following functional group-containing monomer components can be used alone or in combination of two or more. Carboxyl group-containing monomers: For example, ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid; ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, citraconic acid and their anhydrides (maleic anhydride, itaconic anhydride, etc.). Hydroxyl group-containing monomers: For example, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate; unsaturated alcohols such as vinyl alcohol, allyl alcohol. Amide group-containing monomers: For example, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide. Amino group-containing monomers: For example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate. Monomers having an epoxy group: For example, glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether. Cyano group-containing monomers: For example, acrylonitrile, methacrylonitrile. Keto group-containing monomers: For example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate. Monomers having a nitrogen atom-containing ring: For example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl oxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine.

[0053] The above functional group-containing monomers can be used alone or in combination of two or more. Among the above functional group-containing monomers, carboxyl group-containing monomers, hydroxyl group-containing monomers, and cyano group-containing monomers are preferred because they can preferably achieve the introduction of crosslinking points and the improvement of cohesive force as described above, and carboxyl group-containing monomers are more preferred. Among the carboxyl group-containing monomers, AA and MAA are preferred.

[0054] In a preferred embodiment, AA and MAA are used in combination as the above functional group-containing monomers. An adhesive composition containing an acrylic polymer having such a monomer composition (i.e., copolymer composition) can provide a more high-performance (for example, more excellent in anti-rebound property) adhesive sheet. The weight ratio of AA to MAA (AA / MAA) can be, for example, in the range of approximately 0.1 to 10, more preferably at least approximately 0.3 (typically at least 0.5), and more preferably at most approximately 5 (typically at most 4). When AA / MAA is within the above range, the effect of improving the anti-rebound property is likely to be sufficiently obtained, and the adhesive physical properties tend to be excellent in terms of stability over time after the production of the adhesive sheet.

[0055] When a functional group-containing monomer is copolymerized with an acrylic polymer, the ratio of the functional group-containing monomer in all the monomer components constituting the acrylic polymer is not particularly limited. Usually, from the viewpoint of achieving a good balance between cohesive force and adhesiveness, it is preferable to set the ratio of the functional group-containing monomer to about 0.1% by weight or more (for example, 0.5% by weight or more, typically 1% by weight or more). Also, considering the adhesive action of alkyl (meth)acrylate, it is preferable to set it to about 40% by weight or less (for example, 30% by weight or less, typically 20% by weight or less).

[0056] When a carboxyl group-containing monomer is copolymerized with an acrylic polymer, from the viewpoint of improving water resistance, the proportion of the carboxyl group-containing monomer in the total monomer components is suitably 15% by weight or less, for example, it may be 10% by weight or less, 5% by weight or less, or 3% by weight or less. On the other hand, from the viewpoints of cohesiveness and the like, in some embodiments, the proportion may be, for example, 0.1% by weight or more, or 0.5% by weight or more. According to the technology disclosed herein, good water resistance can also be achieved in embodiments where the proportion of the carboxyl group-containing monomer in the total monomer components is 1% by weight or more, or 1.5% by weight or more.

[0057] In some embodiments, it is preferable that a silanol group-forming monomer is copolymerized with the acrylic polymer. That is, in some preferred embodiments, the monomer components constituting the acrylic polymer include a silanol group-forming monomer. The silanol group-forming monomer can be a monomer having at least one functional group capable of introducing a crosslinked structure by a condensation reaction of silanol groups (silanol condensation) into the pressure-sensitive adhesive (pressure-sensitive adhesive layer) formed from the pressure-sensitive adhesive composition. This silanol group-forming monomer can also be regarded as a crosslinking agent (silane coupling agent). Preferred examples of the silanol group-forming monomer include a silanol group-forming monomer having at least 1 (preferably 2 or more, for example, 2 or 3) alkoxysilyl groups in one molecule (alkoxysilyl group-containing monomer). From the viewpoint of copolymerizability with alkyl (meth)acrylate, a silanol group-forming monomer having one or more ethylenically unsaturated groups such as an acryloyl group, a methacryloyl group (hereinafter, the acryloyl group and the methacryloyl group may be collectively referred to as "(meth)acryloyl group"), and a vinyl group in one molecule is preferable. Among them, a silanol group-forming monomer having a (meth)acryloyl group and an alkoxysilyl group (for example, 1 (meth)acryloyl group and 2 or 3 alkoxysilyl groups) in one molecule is preferable.

[0058] Specific examples of such silanol group-forming monomers include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropylmethyldiethoxysilane, and the like. Further, as silanol group-forming monomers other than the above, vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloxydecyltrimethoxysilane, 10-acryloxydecyltrimethoxysilane, 10-methacryloxydecyltriethoxysilane, 10-acryloxydecyltriethoxysilane, and the like can be mentioned. As a particularly preferred silanol group-forming monomer, 3-methacryloxypropyltrimethoxysilane is exemplified.

[0059] In some embodiments, the acrylic monomers disclosed herein are crosslinked by the condensation of silanol groups derived from silanol group-forming monomers. In other words, in some embodiments, the acrylic monomers disclosed herein are crosslinked by a silane coupling agent. According to the technology disclosed herein, the adhesive layer is formed from an aqueous dispersion-type adhesive composition. Since the aqueous dispersion-type adhesive composition is a state in which an adhesive component having a micro-particle form is dispersed in an aqueous medium, the crosslinking inhibitor component derived from the colored layer of the base material is less likely to move compared to a solvent-based composition. Thus, by using an aqueous dispersion-type adhesive composition, the transfer of the crosslinking inhibitor component from the base material to the adhesive composition is suppressed, so that crosslinking inhibition is preferably suppressed also for the condensation reaction of the silanol groups as described above. Therefore, in an aqueous dispersion-type adhesive composition, when an acrylic polymer crosslinked by a silanol group-forming monomer is used as the base polymer, it is easy to realize an adhesive sheet in which a decrease in the holding force due to crosslinking inhibition hardly occurs.

[0060] When a silanol group-forming monomer (for example, an alkoxysilyl group-containing monomer) is copolymerized with an acrylic polymer, the proportion of the silanol group-forming monomer (for example, an alkoxysilyl group-containing monomer) in the above total monomer components is suitably 0.005% by weight or more (for example, 0.01% by weight or more) of the total monomer components, and is suitably about 0.1% by weight or less (for example, 0.03% by weight or less).

[0061] For the purpose of enhancing the cohesive force of the acrylic polymer or the like, other copolymerization components other than the above-mentioned sub-monomers can be used. Examples of such copolymerization components include vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyltoluene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; aromatic ring-containing (meth)acrylates such as aryl (meth)acrylate (for example, phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (for example, phenoxyethyl (meth)acrylate), and arylalkyl (meth)acrylate (for example, benzyl (meth)acrylate); olefin 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 monomers such as methyl vinyl ether and ethyl vinyl ether; and the like.

[0062] Other examples of copolymerizable components other than the above-mentioned secondary monomers include monomers having a plurality of functional groups in one molecule. Examples of such polyfunctional monomers include 1,6-hexanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, glycerin di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, divinylbenzene, butyl di(meth)acrylate, hexyl di(meth)acrylate, and the like.

[0063] The amount of the copolymerization component other than the above-mentioned secondary monomer may be appropriately selected according to the purpose and use and is not particularly limited. For example, it is preferably 10% by weight or less of the monomer composition of the acrylic polymer.

[0064] It is appropriate that the acrylic polymer in the technology disclosed herein is designed such that the glass transition temperature (Tg) of the polymer is -25°C or lower (typically -75°C or higher and -25°C or lower). The Tg of the acrylic polymer can preferably be -40°C or lower (for example, -70°C or higher and -40°C or lower), more preferably -50°C or lower (typically -70°C or higher and -50°C or lower). Setting the Tg of the acrylic polymer to be equal to or lower than the above-mentioned upper limit value is preferable from the viewpoint of improving the adhesive strength. The Tg of the acrylic polymer can be adjusted by the types and usage ratio of the monomers used in the synthesis of the polymer.

[0065] Here, the Tg of the acrylic polymer refers to the Tg determined by Fox's equation based on the composition of the monomer components used in the synthesis of the polymer. Fox's equation is a relational expression between the Tg of the copolymer and the glass transition temperatures Tgi of the homopolymers obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below. 1 / Tg = Σ(Wi / Tgi) In the above Fox's equation, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0066] As the glass transition temperatures of the homopolymers used for calculating Tg, the values described in publicly known materials shall be used. For example, for the monomers listed below, the following values shall be used as the glass transition temperatures of the homopolymers of the monomers. 2-Ethylhexyl acrylate -70 °C n-Butyl acrylate -55 °C Methyl methacrylate 105 °C Methyl acrylate 8 °C Vinyl acetate 32 °C Acrylic acid 106 °C Methacrylic acid 228 °C

[0067] For the glass transition temperatures of the homopolymers of monomers other than those exemplified above, the numerical values described in "Polymer Handbook" (3rd Edition, John Wiley & Sons, Inc., 1989) shall be used. When multiple types of values are described in this document, the highest value shall be adopted.

[0068] For monomers for which the glass transition temperature of the homopolymer is not described in the above Polymer Handbook, the values obtained by the following measurement method shall be used (see Japanese Patent Application Laid-Open No. 2007-51271). Specifically, into a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 100 parts by weight of the monomer, 0.2 parts by weight of azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent are charged, and stirred for 1 hour while flowing nitrogen gas. After removing the oxygen in the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution with a solid content concentration of 33% by weight. Next, this homopolymer solution is cast and coated on a release liner and dried to produce a test sample (sheet-like homopolymer) with a thickness of about 2 mm. This test sample is punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and using a viscoelasticity tester (ARES, manufactured by Rheometrics), while applying a shear strain at a frequency of 1 Hz, the viscoelasticity is measured in the shear mode at a temperature range of -70 to 150°C and a heating rate of 5°C / min, and the peak top temperature of tanδ is taken as the Tg of the homopolymer.

[0069] The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as synthesis methods for acrylic polymers, such as solution polymerization method, emulsion polymerization method, bulk polymerization method, suspension polymerization method, photopolymerization method, etc., can be appropriately adopted. As a preferably adoptable polymerization method, the emulsion polymerization method is exemplified. The mode of emulsion polymerization is not particularly limited, and various monomer supply methods, polymerization conditions, materials used, etc. similar to the conventionally known general emulsion polymerization can be appropriately adopted. For example, as the monomer supply method, a batch charging method of supplying all the monomer raw materials at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The monomer raw materials may be dropped in the form of an aqueous emulsion. The polymerization temperature can be, for example, about 20°C or higher (usually 40°C or higher), and it is appropriate to be about 100°C or lower (usually 80°C or lower).

[0070] According to the above emulsion polymerization, a polymerization liquid in the form of an emulsion (acrylic polymer emulsion) in which an acrylic polymer is dispersed in water can be prepared. The water-dispersible pressure-sensitive adhesive composition disclosed herein can be preferably produced using the above polymerization liquid or a product obtained by subjecting the polymerization liquid to appropriate post-treatment. Alternatively, an acrylic polymer may be synthesized using a polymerization method other than the emulsion polymerization method (for example, solution polymerization, photopolymerization, bulk polymerization, etc.), and the polymer may be dispersed in water to prepare an acrylic polymer emulsion.

[0071] The initiator used for the polymerization can be appropriately selected from conventionally known polymerization initiators according to the type of the polymerization method. For example, azo-based initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-methylpropionamidine) dihydrochloride, 2,2'-azobis(2-amidinopropane) dihydrochloride, 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate, 2,2'-azobis(N,N'-dimethyleneisobutylamidine), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride; for example, persulfate-based initiators such as potassium persulfate and ammonium persulfate; for example, peroxide-based initiators such as benzoyl peroxide, t-butyl hydroperoxide, and hydrogen peroxide; for example, substituted ethane-based initiators such as phenyl-substituted ethane; for example, carbonyl-based initiators such as aromatic carbonyl compounds; for example, redox-based initiators such as a combination of persulfate and sodium bisulfite, and a combination of peroxide and sodium ascorbate; etc. are mentioned, but not limited thereto. Such polymerization initiators can be used alone or in combination of two or more.

[0072] The amount of the polymerization initiator used may be a normal amount used and is not particularly limited. For example, it can be selected from the range of about 0.005 parts by weight or more (preferably 0.01 parts by weight or more) and about 1 part by weight or less (preferably 0.8 parts by weight or less) with respect to 100 parts by weight of all monomer components.

[0073] When polymerizing, a chain transfer agent (which can also be regarded as a molecular weight regulator or a degree of polymerization regulator) can be used as needed. Examples of the chain transfer agent include mercaptans such as dodecyl mercaptan (dodecanethiol), lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol, and α-methylstyrene dimer. Such chain transfer agents can be used alone or in combination of two or more.

[0074] The amount of the chain transfer agent used can be approximately 0.001 part by weight or more (typically approximately 0.005 part by weight or more, for example, approximately 0.001 part by weight or more) based on 100 parts by weight of the monomer component, and can also be, for example, approximately 5 parts by weight or less (typically approximately 2 parts by weight or less, for example, approximately 1 part by weight or less). By setting the amount of the chain transfer agent used within an appropriate range, a desired polymerization rate can be obtained.

[0075] The emulsion polymerization of the monomer raw material is usually carried out in the presence of a surfactant (emulsifier). The amount of the surfactant used is not particularly limited. Considering the polymerization stability and the dispersion stability of the polymerization reaction product, the amount of the surfactant used is usually appropriately 0.1 part by weight or more based on 100 parts by weight of the monomer raw material, preferably 0.5 part by weight or more, and from the perspective of obtaining higher stability, it may be 1.0 part by weight or more, or 1.5 part by weight or more. Also, the amount of the surfactant used can be, for example, 10 parts by weight or less based on 100 parts by weight of the monomer raw material. On the other hand, from the perspective of improving water resistance, it is desirable to suppress the amount of the surfactant (especially non-reactive surfactant) used. From such a perspective, the amount of the surfactant used is usually preferably 5 parts by weight or less, and may also be 4 parts by weight or less, 3 parts by weight or less, or 2.5 parts by weight or less.

[0076] As the surfactant, known anionic surfactants, nonionic surfactants, cationic surfactants, etc. can be used. Usually, an anionic or nonionic surfactant is preferred. A surfactant having a reactive functional group (typically a radically polymerizable functional group) may also be used. Hereinafter, a surfactant having a reactive functional group is sometimes referred to as a reactive surfactant, and in contrast, a general surfactant having no reactive functional group is sometimes referred to as a non-reactive surfactant. The surfactant can be used alone or in combination of two or more kinds.

[0077] Examples of non-reactive anionic surfactants include alkyl sulfates such as lauryl sulfate and octadecyl sulfate; fatty acid salts; alkylbenzene sulfonates such as nonylbenzene sulfonate and dodecylbenzene sulfonate; naphthalene sulfonates such as dodecylnaphthalene sulfonate; alkyl diphenyl ether disulfonates such as dodecyl diphenyl ether disulfonate; polyoxyethylene alkyl ether sulfates such as polyoxyethylene octadecyl ether sulfate and polyoxyethylene lauryl ether sulfate; polyoxyethylene alkyl phenyl ether sulfates such as polyoxyethylene lauryl phenyl ether sulfate; polyoxyethylene styrenated phenyl ether sulfate; sulfosuccinates such as lauryl sulfosuccinate and polyoxyethylene lauryl sulfosuccinate; polyoxyethylene alkyl ether phosphates; polyoxyethylene alkyl ether acetates; and the like. When the anionic surfactant forms a salt, the salt can be, for example, a metal salt such as a sodium salt, potassium salt, calcium salt, magnesium salt (preferably a salt of a monovalent metal), ammonium salt, amine salt, etc.

[0078] Examples of non-reactive nonionic surfactants include polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkyl phenyl ethers such as polyoxyethylene octyl phenyl ether and polyoxyethylene nonyl phenyl ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, and polyoxyethylene sorbitan monolaurate; polyoxyethylene glyceryl ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; and the like.

[0079] As the reactive surfactant, those having a polymerizable (typically radically polymerizable) functional group can be preferably employed. For example, reactive surfactants having a structure in which a radically polymerizable functional group is introduced into the above-described anionic surfactant or nonionic surfactant can be used. The type of the radically polymerizable functional group is not particularly limited, and examples thereof include an alkenyl group, an acryloyl group, a methacryloyl group, a vinyl group, a vinyl ether group (vinyloxy group), an allyl ether group (allyloxy group), and the like. Specific examples of the alkenyl group include a propenyl group and an isopropenyl group (CH 2 =C(CH 3 ))-. The concept of the propenyl group herein includes a 1-propenyl group (CH 3 -CH=CH-) and a 2-propenyl group (CH 2 =CH-CH 2 -; sometimes referred to as an allyl group.).

[0080] Examples of anionic reactive surfactants include polyoxyethylene (allyloxymethyl) alkyl ether sulfates (e.g., ammonium salts), polyoxyethylene nonylpropenyl phenyl ether sulfates (e.g., ammonium salts), alkyl allyl sulfosuccinates (e.g., sodium salts), methacryloxy polyoxypropylene sulfate esters (e.g., sodium salts), polyoxyalkylene alkenyl ether sulfates (e.g., ammonium salts where the terminal of the above alkenyl group is an isopropenyl group), and the like. When the anionic reactive surfactant forms a salt, the salt may be a metal salt such as a sodium salt, or a non-metal salt such as an ammonium salt or an amine salt. Examples of nonionic reactive surfactants include polyoxyethylene nonylpropenyl phenyl ether and the like.

[0081] Commercially available reactive surfactants include products with the trade names "Aquaron HS-05", "Aquaron HS-10", "Aquaron HS-1025", "Aquaron HS-20", "Aquaron KH-10", "Aquaron KH-1025", "Aquaron KH-05", "Aquaron BC-0515", "Aquaron BC-10", "Aquaron BC-1025", "Aquaron BC-20", "Aquaron BC-2020", "Aquaron RN-20", "Aquaron RN-30", "Aquaron RN-50", "Aquaron AR-10", "Aquaron AR-20", "Aquaron AR-1025", "Aquaron AR-2020" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; "Adekaria Soap SE-10N", "Adekaria Soap SR-1025" manufactured by ADEKA Corporation; "Latemul PD-104", "Latemul PD-420", "Latemul PD-430", "Latemul PD-450" manufactured by Kao Corporation; "Ereminol JS-20", "Ereminol RS-3000" manufactured by Sanyo Chemical Industries, Ltd.; "Antox MS-60" manufactured by Nippon Emulsion Co., Ltd., and the like.

[0082] From the viewpoint of emulsifying performance and the like, in one aspect, an anionic reactive surfactant can be preferably employed. When using a nonionic reactive surfactant, more favorable results can be achieved by using it in combination with other surfactants, such as anionic reactive surfactants, anionic non-reactive surfactants, nonionic non-reactive surfactants, and the like.

[0083] From the viewpoint of improving water resistance, the surfactant used in the technology disclosed herein preferably contains a reactive surfactant. In other words, at least a part of the surfactant to be used is preferably a reactive surfactant. By emulsion polymerizing the monomer raw material in the presence of the reactive surfactant, the reactive surfactant can react and be incorporated into the acrylic polymer. When the reactive surfactant is incorporated into the acrylic polymer, the amount of free surfactant decreases. Thereby, water resistance can be improved. Therefore, performing polymerization using a reactive surfactant can be advantageous for achieving both polymerization stability and the water resistance of the pressure-sensitive adhesive layer obtained from the pressure-sensitive adhesive composition containing the acrylic polymer after polymerization. From the viewpoint of achieving more excellent water resistance, the proportion of the reactive surfactant in the total weight of the surfactant used during emulsion polymerization can be 50% by weight or more, more preferably 70% by weight or more. For example, an embodiment in which only a reactive surfactant is used as the surfactant can be preferably adopted. In addition, since the movement of the reactive surfactant incorporated into the acrylic polymer is restricted within the pressure-sensitive adhesive layer, it is difficult to bleed out to the surface of the pressure-sensitive adhesive layer. This can also preferably contribute to the improvement of water resistance. In this specification, including a reactive surfactant is a concept that includes containing the reactive surfactant in a state after its reactive functional group (for example, a radical polymerizable functional group) has reacted. The reactive surfactant in the technology disclosed herein is typically contained in the water-dispersion type pressure-sensitive adhesive composition and the pressure-sensitive adhesive layer in a form in which at least a part of it is incorporated into the acrylic polymer as described above.

[0084] The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited. For example, 10×10 4 ~500×10 4It can be in the range of. Here, Mw of the acrylic polymer refers to Mw of the toluene-soluble component (sol fraction) of the acrylic polymer. Mw of the above acrylic polymer refers to a value in terms of standard polystyrene conversion based on GPC (gel permeation chromatography). From the viewpoint of improving the adhesive properties, Mw of the acrylic polymer is preferably 150×10 4 or less, more preferably 100×10 4 or less. Also, from the viewpoints such as cohesiveness, Mw of the acrylic polymer is preferably 20×10 4 or more, more preferably 30×10 4 or more (for example, 40×10 4 or more) and can be.

[0085] (Crosslinking agent) The water-dispersible adhesive composition used to form the adhesive layer preferably contains a crosslinking agent as an optional component. In the technology disclosed herein, the adhesive layer can contain the above crosslinking agent in the form after the crosslinking reaction, the form before the crosslinking reaction, the form of being partially crosslinked, intermediate or composite forms thereof, etc. The above crosslinking agent is typically contained in the adhesive layer exclusively in the form after the crosslinking reaction.

[0086] Specific examples of the crosslinking agent include oxazoline-based crosslinking agents, aziridine-based crosslinking agents, isocyanate-based crosslinking agents, epoxy-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, silane coupling agents, etc. These can be used alone or in combination of two or more.

[0087] Among others, preferred examples of the crosslinking agent used in the technology disclosed herein include oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, and isocyanate-based crosslinking agents. These can be used alone or in combination of two or more. According to the technology disclosed herein, since the adhesive layer is formed from a water-dispersible adhesive composition, it is difficult for the crosslinking inhibitor component to migrate from the base material to the adhesive composition. As a result, crosslinking inhibition against the crosslinking reaction by the above crosslinking agent is preferably suppressed. Therefore, when an acrylic polymer crosslinked by the above crosslinking agent is used as the acrylic polymer contained in the water-dispersible adhesive composition, it is easy to realize a pressure-sensitive adhesive sheet in which a decrease in the holding power due to crosslinking inhibition hardly occurs.

[0088] As the oxazoline-based crosslinking agent, those having one or more oxazoline groups in one molecule can be used without particular limitation. The oxazoline-based crosslinking agent can be used alone or in combination of two or more. From the viewpoint of use in a water-dispersible adhesive composition, an oxazoline-based crosslinking agent that can be dissolved or dispersed in water is preferred. The oxazoline group may be any of a 2-oxazoline group, a 3-oxazoline group, and a 4-oxazoline group. Usually, an oxazoline-based crosslinking agent having a 2-oxazoline group can be preferably used. For example, a water-soluble copolymer or a water-dispersible copolymer obtained by copolymerizing an addition-polymerizable oxazoline such as 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline with another monomer can be used as the oxazoline-based crosslinking agent. Examples of commercially available products of the oxazoline-based crosslinking agent include those with the trade names "Epocros WS-500", "Epocros WS-700", "Epocros K-2010E", "Epocros K-2020E", "Epocros K-2030E", etc. manufactured by Nippon Shokubai Co., Ltd.

[0089] As the carbodiimide-based crosslinking agent, a low molecular weight compound or a high molecular weight compound having two or more carbodiimide groups can be used. In the water-dispersible pressure-sensitive adhesive composition, it is preferable to use a carbodiimide-based crosslinking agent that can be dissolved or dispersed in water. Examples of commercially available carbodiimide-based crosslinking agents include the Carbodilite V series (aqueous solution type) such as "Carbodilite V-02", "Carbodilite V-02-L2", "Carbodilite V-04", etc. manufactured by Nisshinbo Industries, Inc., and the Carbodilite E series (water dispersion type) such as "Carbodilite E-01", "Carbodilite E-02", "Carbodilite E-04", etc. of the Carbodilite series.

[0090] As the epoxy-based crosslinking agent, those having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based crosslinking agent having 3 to 5 epoxy groups in one molecule is preferable. The epoxy-based crosslinking agent can be used alone or in combination of two or more. An epoxy-based crosslinking agent that can be dissolved or dispersed in water is preferable. Specific examples of the epoxy-based crosslinking agent include N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, etc. Examples of commercially available epoxy-based crosslinking agents include the product names "TETRAD-X", "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc., the product name "Epiclon CR-5L" manufactured by DIC Corporation, the product name "Denacol EX-512" manufactured by Nagase ChemteX Corporation, the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., etc.

[0091] As the isocyanate crosslinking agent, those having two or more isocyanate groups per molecule can be used without particular limitation. The isocyanate groups in the isocyanate crosslinking agent may form an isocyanate regenerable functional group (blocked isocyanate) in which the isocyanate group is temporarily protected, for example, by treatment with a blocking agent or the like. The isocyanate crosslinking agent can be used alone or in combination of two or more.

[0092] Examples of the isocyanate crosslinking agent include aromatic polyisocyanates such as tolylene diisocyanate and xylylene diisocyanate; aliphatic isocyanates such as isophorone diisocyanate; alicyclic polyisocyanates such as hexamethylene diisocyanate; and the like. More specifically, for example, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic polyisocyanates such as dicyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl diisocyanate; isocyanate adducts such as trimethylolpropane / tolylene diisocyanate trimer adduct (trade name "Coronate L" manufactured by Tosoh Corporation, etc.), trimethylolpropane / hexamethylene diisocyanate trimer adduct (manufactured by Tosoh Corporation, trade name "Coronate HL", etc.), and isocyanurate form of hexamethylene diisocyanate (trade name "Coronate HX" manufactured by Tosoh Corporation, etc.); polyisocyanates such as polyether polyisocyanate and polyester polyisocyanate; adducts of these polyisocyanates and polyols; and polyisocyanates obtained by polyfunctionalizing these polyisocyanates with isocyanurate bonds, burette bonds, allophanate bonds, etc.; and the like.

[0093] From the viewpoint of use in a water-dispersible adhesive composition, an isocyanate-based crosslinking agent that is soluble or dispersible in water is preferred. For example, a water-soluble, water-dispersible, or self-emulsifying isocyanate-based crosslinking agent can be preferably employed. Examples of commercially available products of such isocyanate-based crosslinking agents (aqueous isocyanate-based crosslinking agents) include "Barnock DNW-5000", "Barnock DNW-5010", "Barnock DNW-5100", "Barnock DNW-5200", "Barnock DNW-5500", "Barnock DNW-6000" manufactured by DIC Corporation; "Aquaneat 100", "Aquaneat 105", "Aquaneat 110", "Aquaneat 120", "Aquaneat 130", "Aquaneat 200", "Aquaneat 210" manufactured by Tosoh Corporation; "Takenate WD-220", "Takenate WD-240", "Takenate WD-720", "Takenate WD-725", "Takenate WD-726", "Takenate WD-730", "Takenate WB-700", "Takenate WB-720", "Takenate WB-920" manufactured by Mitsui Chemicals Polyurethane Co., Ltd.; "Elastron BN-04", "Elastron BN-11", "Elastron BN-27", "Elastron BN-69", "Elastron BN-77" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; and the like.

[0094] The content of the crosslinking agent (total amount of the crosslinking agent) in the adhesive composition disclosed herein is not particularly limited and can be appropriately set so as to obtain suitable properties after crosslinking in consideration of the composition and molecular weight of the base polymer. Although not particularly limited, the amount of the crosslinking agent used per 100 parts by weight of the base polymer (typically an acrylic polymer) is suitably about 0.01 part by weight or more, preferably about 0.1 part by weight or more, and preferably about 1 part by weight or more (for example, about 2 parts by weight or more). Also, from the viewpoint of adhesiveness and the like, the amount of the crosslinking agent used is suitably about 15 parts by weight or less (preferably about 10 parts by weight or less, for example, about 5 parts by weight or less) per 100 parts by weight of the base polymer, and from the viewpoint of enhancing the adhesion to the adherend, it is preferably about 4 parts by weight or less, more preferably less than 3.5 parts by weight, and even more preferably less than 3 parts by weight.

[0095] (Adhesion-imparting resin) The water-dispersible pressure-sensitive adhesive composition disclosed herein may contain an adhesion-imparting resin. By using an adhesion-imparting resin, it is easy to obtain a pressure-sensitive adhesive sheet exhibiting excellent adhesion properties (e.g., adhesive strength, anti-rebound properties). The above adhesion-imparting resin can be a water-dispersible adhesion-imparting resin (also referred to as an adhesion-imparting resin emulsion). For example, by mixing an aqueous emulsion of an acrylic polymer and an emulsion of the above adhesion-imparting resin, a pressure-sensitive adhesive composition containing these components in a desired ratio can be easily prepared. As the adhesion-imparting resin emulsion, it is preferable to use one that substantially does not contain at least an aromatic hydrocarbon solvent (more preferably, one that substantially does not contain an aromatic hydrocarbon solvent or other organic solvents).

[0096] Examples of the adhesion-imparting resin include rosin-based adhesion-imparting resins (including rosin derivative adhesion-imparting resins), petroleum-based adhesion-imparting resins, terpene-based adhesion-imparting resins, phenol-based adhesion-imparting resins, ketone-based adhesion-imparting resins, and the like. These can be used alone or in combination of two or more.

[0097] Examples of the above rosin-based adhesion-imparting resins include rosins such as gum rosin, wood rosin, and tall oil rosin, as well as stabilized rosins (e.g., stabilized rosins obtained by disproportionating or hydrogenating the above rosins), polymerized rosins (e.g., multimers of the above rosins, typically dimers), and modified rosins (e.g., unsaturated acid-modified rosins modified with unsaturated acids such as maleic acid, fumaric acid, and (meth)acrylic acid). Examples of the above rosin derivative adhesion-imparting resins include esters of the above rosin-based resins (e.g., rosin esters such as stabilized rosin esters and polymerized rosin esters), phenol-modified products of the above rosin-based resins (phenol-modified rosins), and their esters (phenol-modified rosin esters). Examples of the above petroleum-based adhesion-imparting resins include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and their hydrogenated products. Examples of the terpene-based tackifying resin include, for example, α-pinene resin, β-pinene resin, aromatic-modified terpene-based resin, terpene phenol-based resin, and the like. Examples of the ketone-based tackifying resin include, for example, ketone resins obtained by condensation of ketones (e.g., aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone, etc.) and formaldehyde; and the like.

[0098] Examples of the tackifying resin that can be preferably used in the technology disclosed herein include rosin-based tackifying resin and terpene-based tackifying resin. Preferred examples of the rosin-based tackifying resin include stabilized rosin ester and polymerized rosin ester. Also, a preferred example of the terpene-based tackifying resin is terpene phenol-based resin.

[0099] Such an emulsion of the tackifying resin can be prepared using a surfactant (emulsifier) as necessary. As the surfactant that can be used for the preparation of the above-mentioned tackifying resin emulsion, one or more kinds can be appropriately selected and used from the same surfactants as those that can be used for the preparation of acrylic polymer emulsions. Usually, it is preferable to use an anionic surfactant or a nonionic surfactant. Note that the surfactant used for the preparation of the acrylic polymer emulsion and the surfactant used for the preparation of the tackifying resin emulsion may be the same or different. For example, modes such as using an anionic surfactant for the preparation of any emulsion, using a nonionic surfactant for both, using an anionic surfactant for one and a nonionic surfactant for the other, etc. can be preferably adopted. The amount of the surfactant used is not particularly limited as long as it can prepare the tackifying resin in the form of an emulsion. For example, it can be about 0.2 parts by weight or more (preferably 0.5 parts by weight or more) based on 100 parts by weight (solid content basis) of the tackifying resin, and can also be about 10 parts by weight or less (preferably 5 parts by weight or less).

[0100] The softening point of the tackifying resin to be used is not particularly limited. From the viewpoint of improving cohesion and the like, the softening point of the tackifying resin may be, for example, 80°C or higher, preferably 90°C or higher, may be 100°C or higher, may be 120°C or higher, or may be 130°C or higher.

[0101] Although not particularly limited, in some embodiments, the tackifying resin in the technology disclosed herein may include a high softening point tackifying resin having a softening point of 140°C or higher. The softening point of the high softening point tackifying resin is preferably 145°C or higher, and may be, for example, 150°C or higher. By using the high softening point tackifying resin, it is possible to suitably balance adhesiveness and cohesiveness. The upper limit of the softening point of the tackifying resin is not particularly limited, but from the viewpoints of compatibility, low temperature properties, etc., it is usually suitably 200°C or lower, preferably 180°C or lower, and may be 175°C or lower.

[0102] The softening point of the pressure-sensitive resin mentioned here is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at a low temperature, and this is carefully filled into a ring placed on a flat metal plate without forming bubbles. After it has cooled, the raised part including the upper end of the ring is cut off with a slightly heated small knife. Next, a support (ring stand) is placed in a glass container (heating bath) with a diameter of 85 mm or more and a height of 127 mm or more, and glycerin is poured until the depth reaches 90 mm or more. Then, a steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample are immersed in the glycerin so as not to contact each other, and the temperature of the glycerin is maintained at 20 °C plus or minus 5 °C for 15 minutes. Next, the steel ball is placed on the center of the surface of the sample in the ring and placed at a fixed position above the support. Then, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed, the center position of the mercury bulb of the thermometer is set at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating should be at the middle between the center and the edge of the bottom of the container to ensure even heating. Note that the rate of increase in the bath temperature after reaching 40 °C after the start of heating should be 5.0 plus or minus 0.5 °C per minute. The temperature is read when the sample gradually softens and flows out of the ring and finally contacts the bottom plate, and this is taken as the softening point. The softening point is measured for two or more samples simultaneously, and the average value is adopted.

[0103] The amount of the tackifier resin used (on a solid content basis) is usually suitably 1 part by weight or more, preferably 3 parts by weight or more (for example, 5 parts by weight or more), more preferably 12 parts by weight or more, and still more preferably 16 parts by weight or more with respect to 100 parts by weight of the base polymer (typically an acrylic polymer) from the viewpoint of preferably exerting its use effect. According to the technology disclosed herein, good water resistance can also be achieved in an embodiment containing 22 parts by weight or more (for example, 25 parts by weight or more) of the tackifier resin with respect to 100 parts by weight of the base polymer. Further, from the viewpoint of cohesion and the like, the amount of the tackifier resin used is usually suitably 90 parts by weight or less, preferably 70 parts by weight or less, more preferably 55 parts by weight or less, and still more preferably 50 parts by weight or less (for example, 45 parts by weight or less, typically 40 parts by weight or less) with respect to 100 parts by weight of the base polymer.

[0104] When the water-dispersible pressure-sensitive adhesive composition disclosed herein contains a high softening point tackifier resin, from the viewpoint of cohesion and the like, only the high softening point tackifier resin may be used as the tackifier resin. Further, from the viewpoint of achieving a balance with various tack characteristics, in some embodiments, the high softening point tackifier resin and a tackifier resin having a lower softening point (for example, a tackifier resin having a softening point of 120°C or lower, or 110°C or lower) can be used in combination. In such an embodiment, the proportion of the high softening point tackifier resin in the total amount of the tackifier resin used may be, for example, 20% by weight or more, may be 40% by weight or more, or may be 60% by weight or more. The proportion of the high softening point tackifier resin may be, for example, 90% by weight or less, may be 80% by weight or less, or may be 70% by weight or less.

[0105] (Polyacrylic acid) In some embodiments, the water-dispersible pressure-sensitive adhesive composition may contain polyacrylic acid. Polyacrylic acid can function as a thickener. Further, by incorporating polyacrylic acid into the water-dispersible pressure-sensitive adhesive composition, the polarity of the pressure-sensitive adhesive layer formed from the water-dispersible pressure-sensitive adhesive composition can be increased, and the adhesive performance such as metal adhesiveness can be effectively improved. Also, the use of polyacrylic acid tends to improve water resistance.

[0106] In some embodiments, the weight average molecular weight (Mw) of polyacrylic acid is 5×10 4 or more, preferably 10×10 4 or more, more preferably 15×10 4 or more. Also, in some embodiments, the Mw of polyacrylic acid is 30×10 4 or less, preferably 25×10 4 or less. The Mw of the above polyacrylic acid refers to the value in terms of standard polyethylene glycol / polyethylene oxide conversion based on GPC.

[0107] In some embodiments, the amount of polyacrylic acid used can be 1.0 part by weight or more, preferably 1.5 parts by weight or more, more preferably 3.0 parts by weight or more, and may also be 3.5 parts by weight or more, based on 100 parts by weight of the base polymer (typically an acrylic polymer). Increasing the amount of polyacrylic acid used tends to improve metal adhesiveness and water resistance. In some embodiments, the amount of polyacrylic acid used can be 10 parts by weight or less, and may also be 8.0 parts by weight or less, 6.0 parts by weight or less, 5.0 parts by weight or less, or 4.0 parts by weight or less, based on 100 parts by weight of the base polymer.

[0108] (Leveling agent) In some embodiments, the aqueous dispersion type pressure-sensitive adhesive composition may contain a leveling agent. According to the aqueous dispersion type pressure-sensitive adhesive composition containing a leveling agent, the wettability of the aqueous dispersion type pressure-sensitive adhesive composition with respect to the support substrate can be improved. By improving the wettability, when the aqueous dispersion type pressure-sensitive adhesive composition is applied to form an adhesive layer, repelling of the coating film of the composition is less likely to occur, and the occurrence of appearance defects in the adhesive layer and thus in the adhesive sheet is suppressed. Also, it becomes easier to make the thickness of the adhesive layer thinner (for example, 30 μm or less in thickness).

[0109] The type of the leveling agent is not particularly limited. Examples of the leveling agent include "Surfynol 420" (an acetylene glycol ethylene oxide-based surfactant, manufactured by Nissin Chemical Industry Co., Ltd.), "Pelecos OT-P" (sodium dialkyl sulfosuccinate, manufactured by Kao Corporation), "Neocol P" (sodium dialkyl sulfosuccinate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Neocol SW-C" (sodium dialkyl sulfosuccinate, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), "Nopco Wet 50" (a sulfonic acid-based anionic surfactant, manufactured by San Nopco Ltd.), "SN Wet 126" (a modified silicone / special polyether-based surfactant, manufactured by San Nopco Ltd.), "SN Wet FST2" (a polyoxyalkyleneamine nonionic wetting agent, manufactured by San Nopco Ltd.), "SN Wet S" (a polyoxyalkyleneamine ether nonionic wetting agent, manufactured by San Nopco Ltd.), and "SN Wet 125" (a modified silicone-based surfactant, manufactured by San Nopco Ltd.). The leveling agent can be used alone or in combination of two or more kinds.

[0110] In some preferred embodiments, sodium dialkyl sulfosuccinate can be used as the leveling agent. According to such a leveling agent, the wettability of the water-dispersible pressure-sensitive adhesive composition can be further improved.

[0111] The carbon number of sodium dialkyl sulfosuccinate is not particularly limited, but in some embodiments, it is 4 or more, preferably 6 or more, more preferably 8 or more. Also, the carbon number of sodium dialkyl sulfosuccinate is not particularly limited, but in some embodiments, it is 20 or less, preferably 12 or less, more preferably 10 or less.

[0112] In some embodiments, the amount of the leveling agent used can be 0.3 parts by weight or more, preferably 0.4 parts by weight or more, more preferably 0.5 parts by weight or more, and may be 0.7 parts by weight or more, based on 100 parts by weight of the base polymer (typically an acrylic polymer). When the amount of the leveling agent used is increased, the wettability of the water-dispersible pressure-sensitive adhesive composition is preferably improved, so that the increase in repellency caused by the addition of the tackifier can be suppressed. Also, from the viewpoint of suppressing contamination of the adherend, in some embodiments, the amount of the leveling agent used can be 3 parts by weight or less, may be 2.5 parts by weight or less, may be 2 parts by weight or less, may be 1.5 parts by weight or less, may be 1.2 parts by weight or less, and may be 0.8 parts by weight or less, based on 100 parts by weight of the base polymer.

[0113] (Other additive components) Further, the water-dispersible pressure-sensitive adhesive composition disclosed herein preferably contains a silicon compound (typically a silane coupling agent) from the viewpoint of easy peelability from the release liner. As the silicon compound, one or more of an alkylalkoxysilane compound, a vinyl group-containing silane compound, an epoxy group-containing silane compound, a styryl group-containing silane compound, a (meth)acryloyl group-containing silane compound, an amino group-containing silane compound, a ureido group-containing silane compound, a mercapto group-containing silane compound, an isocyanate group-containing silane compound, a silyl group-containing sulfide, etc. can be used. Among them, an alkylalkoxysilane compound is preferred. The molecular weight of the silicon compound is suitably about 100 or more (for example, 200 or more), and may be about 500 or less (for example, 350 or less).

[0114] As the alkylalkoxysilane compound, any of alkyltrialkoxysilane, dialkyldialkoxysilane, trialkylmonoalkoxysilane, tetraalkoxysilane, and phenylalkoxysilane can be used. Here, the above alkyl includes both linear and cyclic ones. Specific examples of the above compounds include methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, hexadecyltrimethoxysilane, methyltriethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, cyclohexylmethyldimethoxysilane, methoxytrimethylsilane, octadecyldimethylmethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, diphenylethoxymethylsilane, dimethoxymethylphenylsilane, etc. Among them, alkyltrialkoxysilane is preferred.

[0115] From the viewpoint of fully expressing the addition effect, the content of the silicon compound is preferably 0.005 parts by weight or more (for example, 0.01 parts by weight or more, typically 0.03 parts by weight or more) based on 100 parts by weight of the base polymer (typically an acrylic polymer). Also, from the viewpoint of storage stability, the content of the silicon compound is preferably less than 1.0 part by weight (for example, 0.5 part by weight or less, typically 0.3 part by weight or less) based on 100 parts by weight of the base polymer.

[0116] The pressure-sensitive adhesive composition disclosed herein may contain an acid or a base (such as aqueous ammonia) used for purposes such as pH adjustment, if necessary. Examples of other optional components that can be incorporated into the pressure-sensitive adhesive composition disclosed herein include viscosity modifiers, crosslinking aids, peel modifiers, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, etc. Since such various additives are conventionally known and can be used by conventional methods and are not particularly characteristic of the present invention, detailed description thereof is omitted.

[0117] <Adhesive layer> In the technology disclosed herein, the adhesive layer can be preferably formed by applying the above-described aqueous dispersion-type adhesive composition onto a predetermined surface and drying or curing it. When applying (typically coating) the adhesive composition, a conventional coater (for example, a gravure roll coater, a reverse roll coater, a kiss roll coater, a dip roll coater, a bar coater, a knife coater, a spray coater, etc.) can be used. The thickness of the adhesive layer is not particularly limited, and usually it is suitably about 2 μm or more, preferably about 10 μm or more, more preferably 20 μm or more, and may be 30 μm or more. Also, the thickness of the adhesive layer is usually suitably about 150 μm or less, preferably about 100 μm or less (for example, 80 μm or less), more preferably 50 μm or less, still more preferably 40 μm or less, and may be 30 μm or less. According to the technology disclosed herein, even in the case of an adhesive sheet having a thin adhesive layer as described above, the influence of the crosslinking inhibitor component from the coloring layer is suppressed, and a decrease in the holding force is likely to be suppressed.

[0118] <Release liner> As the release liner that protects or supports the adhesive layer (which may have both protective and supporting functions), there are no particular restrictions on its material or structure, and an appropriate one can be selected from known release liners and used. For example, a release liner having a structure in which at least one surface of the base material is subjected to a release treatment (typically, a release treatment layer by a release treatment agent is provided) can be preferably used. As the base material (the object to be release-treated) constituting this type of release liner, the same base materials as those described above as the base materials constituting the adhesive sheet (various plastic films, papers, cloths, rubber sheets, foam sheets, metal foils, composites thereof, etc.) can be appropriately selected and used. As the release treatment agent for forming the release treatment layer, known or commonly used release treatment agents (for example, silicone-based, fluorine-based, long-chain alkyl-based release treatment agents, etc.) can be used. Further, a low-adhesion base material made of a fluorine-based polymer (for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.) or a low-polarity polymer (for example, olefin resins such as polyethylene and polypropylene) may be used as a release liner without subjecting the surface of the base material to a release treatment. Alternatively, a release liner obtained by subjecting the surface of such a low-adhesion base material to a release treatment may be used.

[0119] The thickness of the base material and the release treatment layer constituting the release liner is not particularly limited and can be appropriately selected according to the purpose and the like. In some preferred embodiments, the total thickness of the release liner (in the case of a release liner having a release treatment layer on the surface of the base material, the total thickness including the base material and the release treatment layer) is 1 μm or more and 100 μm or less, more preferably 10 μm or more and 80 μm or less, and particularly preferably 25 μm or more and 75 μm or less.

[0120] <Method for manufacturing an adhesive sheet with a substrate> The pressure-sensitive adhesive sheet disclosed herein includes preparing a base material provided with a colored layer on at least one surface, and providing a pressure-sensitive adhesive layer on the surface of the base material on the colored layer side. Here, in the production of the pressure-sensitive adhesive sheet disclosed herein, the method of providing the pressure-sensitive adhesive layer on one surface and / or the other surface of the base material is not particularly limited. Usually, (1) a method of directly applying (typically coating) a water-dispersible pressure-sensitive adhesive composition to the base material and drying it (hereinafter also referred to as the "direct coating method" or "direct method"); and (2) a method of applying (typically coating) a water-dispersible pressure-sensitive adhesive composition to a release liner, drying it to form a pressure-sensitive adhesive layer on the release liner, and laminating (transferring) the pressure-sensitive adhesive layer to the base material (hereinafter also referred to as the "transfer method"); it is preferable to apply any of the selected methods to each of the one surface and / or the other surface. According to the technology disclosed herein, even if the pressure-sensitive adhesive layer is formed by the direct method, crosslinking inhibition in the pressure-sensitive adhesive layer is suppressed, and a decrease in holding power is likely to be suppressed. Therefore, it is particularly meaningful to form the pressure-sensitive adhesive layer by the direct method using the water-dispersible pressure-sensitive adhesive composition disclosed herein. According to the direct method, there is a manufacturing advantage that the release liner as a process sheet becomes unnecessary. Also, in the transfer method, since it is necessary to heat and dry the release liner with the pressure-sensitive adhesive composition applied thereto, for example, by putting it in a dryer, heat resistance (for example, not curling due to heating, etc.) may be required for the release liner. On the other hand, since there are no such restrictions in the direct method, there is an advantage that a low-cost and environmentally friendly release liner can be selected.

[0121] When producing a double-sided adhesive sheet with a substrate by providing adhesive layers on one side and the other side of the substrate, the double-sided adhesive sheet may be manufactured by applying the direct method to both sides of the substrate (direct-direct method), or the transfer method may be applied to one side of the substrate (typically, the side on which the adhesive layer is first provided), and the direct coating method may be applied to the other side to manufacture the double-sided adhesive sheet (transfer-direct method). In conventional double-sided adhesive sheets with a colored layer-containing substrate, it was difficult to provide an adhesive layer directly on the surface of the colored layer side of the substrate. Therefore, a colored layer was provided only on one side of the substrate, and a method in which the adhesive layer was provided on the colored layer side by the transfer method was tended to be adopted. On the other hand, according to the present invention, since an adhesive layer can be suitably provided directly on the surface of the colored layer side of the substrate, a colored layer can be provided on each of the two sides of the substrate, the surface roughness of the colored layer can be reduced, and thus the surface roughness of the adhesive layer can be reduced, and the adhesive characteristics are likely to be improved.

[0122] <Use> The use of the adhesive sheet disclosed herein is not particularly limited. It can be used in various applications that require various properties such as electrical insulation, concealment, light shielding, visibility, and design, for example, in various applications where an adhesive sheet including a substrate having a colored layer is applicable. The adhesive sheet disclosed herein can be suitably used, for example, as an adhesive sheet to be attached to vehicles, housing building materials, electronic devices, etc. As a non-limiting example, there is an application as an adhesive sheet to be attached to a module (for example, a battery module) that requires electrical insulation inside an electronic device. Further, the adhesive sheet disclosed herein can also be preferably used for portable electronic devices.

[0123] Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist-wear type worn on the wrist like a wristwatch, modular type worn on a part of the body with a clip or strap, etc., eyewear type including glasses type (monocular or binocular. Also including head-mounted type.), clothing type attached to a shirt, socks, hat, etc. in the form of an accessory, ear-wear type attached to the ear like earphones, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), computers (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, e-books, in-vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. In this specification, "portable" does not simply mean that it can be carried, but means that it has a level of portability that an individual (standard adult) can relatively easily carry around.

[0124] The matters disclosed by this specification include the following. 〔1〕 An adhesive sheet including an adhesive layer formed from an aqueous dispersion type adhesive composition containing an acrylic polymer as a base polymer, and a support substrate having a sheet shape with a first surface and a second surface, and supporting the adhesive layer on at least the first surface, wherein the substrate includes a colored layer constituting the first surface, and the colored layer contains an ether-based polyurethane, the adhesive sheet. 〔2〕 The acrylic polymer is: a polymer of a monomer component containing a silanol group-forming monomer and crosslinked with silanol groups derived from the silanol group-forming monomer (i.e., crosslinked with a silane coupling agent); and, crosslinked with one or more crosslinking agents selected from oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, and isocyanate-based crosslinking agents; The adhesive sheet according to the above-mentioned 〔1〕, which is at least one of the above. 〔3〕The pressure-sensitive adhesive sheet according to the above 〔1〕 or 〔2〕, wherein the thickness of the pressure-sensitive adhesive layer is 10 μm or more and 50 μm or less. 〔4〕The base material includes a first colored layer constituting the first surface and a second colored layer constituting the second surface, The pressure-sensitive adhesive sheet according to any one of the above 〔1〕 to 〔3〕, wherein a first pressure-sensitive adhesive layer is disposed on the first surface of the base material and a second pressure-sensitive adhesive layer is disposed on the second surface of the base material. 〔5〕The pressure-sensitive adhesive sheet according to any one of the above 〔1〕 to 〔4〕, wherein the colored layer is a black layer formed by black printing. 〔6〕The pressure-sensitive adhesive sheet according to any one of the above 〔1〕 to 〔5〕, wherein the base material includes a resin film made of a polyester-based resin. 〔7〕Preparing a base material provided with a colored layer containing an ether-based polyurethane on at least one surface, A method for manufacturing a pressure-sensitive adhesive sheet, comprising directly applying a water-dispersible pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer to the surface of the base material on the side of the colored layer to form a pressure-sensitive adhesive layer.

Examples

[0125] Hereinafter, several examples of the present invention will be described, but the present invention is not intended to be limited to those shown in such examples. In the following description, "parts" and "%" are based on weight unless otherwise specified.

[0126] (Preparation of emulsion polymer α) Into a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 0.070 part of a surfactant (trade name "Aquaron KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 73 parts of distilled water were added, and nitrogen substitution was carried out at room temperature (25 °C) for 1 hour while stirring. Then, 0.10 part of a polymerization initiator (trade name "VA-057", manufactured by Fujifilm Wako Pure Chemical Corporation) was added thereto, and the temperature was raised to 60 °C. To this, 85 parts of 2-ethylhexyl acrylate (2EHA), 13 parts of methyl acrylate (MA), 1.2 parts of acrylic acid (AA), 0.75 part of methacrylic acid (MAA), 0.035 part of t-dodecanethiol (chain transfer agent), 0.02 part of 3-methacryloxypropyltrimethoxysilane (trade name "KBM-503", manufactured by Shin-Etsu Chemical Co., Ltd.), and 1.9 parts of a surfactant (trade name "Aquaron KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) emulsified with 30 parts of distilled water were polymerized by dropping over 4 hours at 60 °C. After cooling to room temperature, the pH was adjusted to 6 using 10% aqueous ammonia as a pH adjuster to prepare an emulsion polymer α.

[0127] (Preparation of Adhesive Composition A) To 100 parts of the solid content of the emulsion polymer α, 35.4 parts of a tackifying resin (trade name "Tamanol E-200-NT", manufactured by Arakawa Chemical Industries, Ltd.), 3.67 parts of polyacrylic acid (trade name "Aron A-10H", manufactured by Toagosei Co., Ltd.) having a weight average molecular weight (Mw) of 20×10 4 , 0.89 part of a leveling agent (trade name "Neocol SW-C", manufactured by Kao Corporation), and 1.0 part of a carboxylic acid copolymer (trade name "Aron B-500", manufactured by Toagosei Co., Ltd.) were added, and diluted and neutralized with distilled water and 10% aqueous ammonia to prepare an emulsion adhesive composition A having a solid content of 25%.

[0128] (Preparation of Emulsion Polymer β) Into a reaction vessel equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser, 0.070 part of a surfactant (trade name "Aquaron KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 69 parts of distilled water were added, and nitrogen substitution was carried out at room temperature (25 °C) for 1 hour while stirring. Then, 0.10 part of a polymerization initiator (trade name "VA-057", manufactured by Fujifilm Wako Pure Chemical Corporation) was added thereto, and the temperature was raised to 60 °C. To this, 41 parts of 2-ethylhexyl acrylate (2EHA), 34 parts of butyl acrylate (BA), 23 parts of methyl methacrylate (MMA), 0.7 part of acrylic acid (AA), 0.54 part of methacrylic acid (MAA), 0.02 part of t-dodecanethiol (chain transfer agent), and 1.9 parts of a surfactant (trade name "Aquaron KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) emulsified with 32 parts of distilled water were polymerized by dropping over 4 hours at 60 °C. After cooling to room temperature, the pH was adjusted to 6 using 10% aqueous ammonia as a pH adjuster to prepare an emulsion polymer β.

[0129] (Preparation of Adhesive Composition B) To 100 parts of the solid content of the emulsion polymer β, 35.4 parts of a tackifier resin (trade name "Tamanoal E-200-NT", manufactured by Arakawa Chemical Industries, Ltd.), 3.67 parts of polyacrylic acid (trade name "Aron A-10H", manufactured by Toagosei Co., Ltd.) having a weight average molecular weight (Mw) of 20×10 4 and 0.89 part of a leveling agent (trade name "Neocol SW-C", manufactured by Kao Corporation), 1.0 part of a carboxylic acid copolymer (trade name "Aron B-500", manufactured by Toagosei Co., Ltd.) were added, and diluted and neutralized with distilled water and 10% aqueous ammonia to prepare an adhesive composition. The above adhesive composition was diluted and neutralized with water to prepare Composition β. To the obtained Composition β, 0.1 part of a carbodiimide crosslinking agent (trade name "Carbodilite V-04", manufactured by Nisshinbo Chemicals Inc.) was added and stirred and mixed to prepare an emulsion adhesive composition B.

[0130] (Preparation of Adhesive Composition C) An emulsion-based pressure-sensitive adhesive composition C was prepared in the same manner as the preparation method of the emulsion-based pressure-sensitive adhesive composition B, except that 0.1 part of an oxazoline-based crosslinking agent (trade name "Epocros WS-500", manufactured by Nippon Shokubai Co., Ltd.) was added to the above composition β instead of 0.1 part of a carbodiimide-based crosslinking agent.

[0131] (Preparation of Pressure-Sensitive Adhesive Composition D) An emulsion-based pressure-sensitive adhesive composition D was prepared in the same manner as the preparation method of the emulsion-based pressure-sensitive adhesive composition B, except that 1 part of an isocyanate-based crosslinking agent (trade name "Varnoc 5010", manufactured by DIC Corporation) was added to the above composition β instead of 0.1 part of a carbodiimide-based crosslinking agent.

[0132] (Preparation of Pressure-Sensitive Adhesive Composition E) An emulsion-based pressure-sensitive adhesive composition E was prepared in the same manner as the preparation method of the emulsion-based pressure-sensitive adhesive composition B, except that 1 part of an epoxy-based crosslinking agent (trade name "Denacol EX313", manufactured by Nagase ChemteX Corporation) was added to the above composition β instead of 0.1 part of a carbodiimide-based crosslinking agent.

[0133] (Preparation of Solvent-Based Polymer γ) Into a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel, 90 parts of butyl acrylate (BA), 30 parts of 2-ethylhexyl acrylate (2EHA), 3 parts of acrylic acid (AA), 0.05 part of 4-hydroxybutyl acrylate (4-HBA) as monomer components, 0.08 part of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and toluene as a polymerization solvent were charged, and reacted at 60 °C for 6 hours to obtain a solvent-based polymer γ.

[0134] (Preparation of Pressure-Sensitive Adhesive Composition F) To 100 parts of the obtained solvent-based polymer γ, 30 parts of a polymerized rosin ester resin (trade name "Pensel D-125", manufactured by Arakawa Chemical Industries, Ltd.) and 2 parts of an isocyanate-based crosslinking agent (trade name "Coronate L", manufactured by Tosoh Corporation) were added, and stirred and mixed to prepare a solvent-based pressure-sensitive adhesive composition F.

[0135] (Preparation of Adhesive Composition G) Per 100 parts of the above solvent-based polymer γ, 30 parts of a polymerized rosin ester resin (trade name "Pencil D-125", manufactured by Arakawa Chemical Industries, Ltd.) and 0.03 part of an epoxy-based crosslinking agent (trade name "TETRAD-C", manufactured by Mitsubishi Gas Chemical Company, Inc.) were added and stirred and mixed to prepare a solvent-based adhesive composition G.

[0136] <Example 1> (Production of Adhesive Sheet with Black-Printed Substrate by Transfer Method) The above adhesive composition A was applied to a release liner (trade name "PET-75-SCA1", manufactured by Fujicor Co., Ltd.) so that the thickness after drying would be 10 μm and dried. Also, a base film (total thickness of about 52 μm) was prepared in which a black layer having a thickness of approximately 1 to 2 μm containing an ether-based polyurethane as a main component was provided on one surface of a PET resin film having a thickness of 50 μm (trade name "Lumirror S105", manufactured by Toray Industries, Inc.) by printing. By bonding the release liner coated with the adhesive composition A to the surface of the base film on the black-printed side, the adhesive layer was transferred to obtain an adhesive sheet with a black-printed substrate according to the transfer method of this example.

[0137] (Production of Adhesive Sheet with Black-Printed Substrate by Direct Method) In the same manner as above, a base film (total thickness of about 52 μm) was prepared in which a black layer having a thickness of approximately 1 to 2 μm containing an ether-based polyurethane as a main component was provided on one surface of a PET resin film having a thickness of 50 μm (trade name "Lumirror S105", manufactured by Toray Industries, Inc.) by printing. The adhesive composition A was applied to the surface of the base film on the black-printed side so that the thickness after drying would be 10 μm, dried, and then bonded to a release liner (trade name "PET-75-SCA1", manufactured by Fujicor Co., Ltd.) to obtain an adhesive sheet with a black-printed substrate according to the direct method of this example.

[0138] (Production of Adhesive Sheet with Raw Substrate by Direct Method) A PET resin film (trade name: "Lumirror S105", manufactured by Toray Industries, Inc.) without black printing was prepared as a base film (hereinafter also referred to as "raw base material" or "raw base film"). The above pressure-sensitive adhesive composition A was applied to one surface of the above raw base film so that the thickness after drying would be 10 μm, dried, and then laminated to a release liner (trade name: "PET-75-SCA1", manufactured by Fujicor Co., Ltd.) to obtain a pressure-sensitive adhesive sheet with a raw base material by the direct method according to this example.

[0139] <Examples 2 to 5 and Comparative Examples 1 and 2> Except that various pressure-sensitive adhesive compositions shown in Table 1 were used instead of the pressure-sensitive adhesive composition A, in the same manner as in Example 1, pressure-sensitive adhesive sheets with a black-printed base material by the transfer method, pressure-sensitive adhesive sheets with a black-printed base material by the direct method, and pressure-sensitive adhesive sheets with a raw base material by the direct method according to Examples 2 to 5 and Comparative Examples 1 and 2 were produced.

[0140] The outlines of the pressure-sensitive adhesive sheets of each example are shown in Table 1.

[0141] [Retention Force Test] (Retention Force Test of Initial Pressure-Sensitive Adhesive Sheet) The pressure-sensitive adhesive sheets of each example (pressure-sensitive adhesive sheets with a black-printed base material by the transfer method, pressure-sensitive adhesive sheets with a black-printed base material by the direct method, and pressure-sensitive adhesive sheets with a raw base material by the direct method) were cut into a size of 10 mm in width and 100 mm in length to prepare measurement samples. In an environment of 23°C and 50% RH, the adhesive surface of the above measurement sample was pressure-bonded to a bakelite plate (phenolic resin plate) as an adherend with a pasting area of 10 mm in width and 20 mm in length by reciprocating a 2 kg roller once. The adherend with the measurement sample pasted thereon was allowed to stand still in an environment of 23°C and 50% RH for 30 minutes. Then, a load of 1 kg was applied to the above test piece, and in accordance with JIS Z 0237, the test piece was left in an environment of 40°C for 1 hour with the load applied, and it was observed whether or not the measurement sample peeled off from the adherend and fell within 1 hour. If it did not fall, it was judged as "OK", and if it fell, it was judged as "NG".

[0142] (Retention Force Test of Aged Pressure-Sensitive Adhesive Sheet) Each adhesive sheet (adhesive sheet with a black-printed base material by the transfer method, adhesive sheet with a black-printed base material by the direct method, and adhesive sheet with a raw base material by the direct method) was left standing for 3 days in an environment of 50°C and 50% RH for aging, and then cut into a size of 10 mm in width and 100 mm in length to prepare measurement samples. At 23°C and 50% RH, the adhesive surface of the above measurement sample was pressure-bonded to a bakelite plate (phenolic resin plate) as an adherend with an adhesion area of 10 mm in width and 20 mm in length by reciprocating a 2-kg roller once. The adherend with the measurement sample attached in this way was left standing for 30 minutes in an environment of 23°C and 50% RH. Next, a load of 1 kg was applied to the above test piece, and in accordance with JIS Z 0237, it was left in an environment of 40°C for 1 hour in the state where the load was applied, and it was observed whether the measurement sample peeled off from the adherend and fell within 1 hour. If it did not fall, it was judged as "OK", and if it fell, it was judged as "NG".

[0143] (Evaluation of holding power) Based on the results of the holding power test of the initial adhesive sheet and the results of the holding power test of the aged adhesive sheet, the holding power of the adhesive sheet of each example was evaluated in three levels. Specifically, when the results of the holding power tests of both the initial adhesive sheet and the aged adhesive sheet were "OK", it was rated as "A (excellent)"; when the result of the holding power test of the aged adhesive sheet was "OK" but the result of the holding power test of the initial adhesive sheet was "NG", it was rated as "B (good)"; when the results of the holding power tests of both the initial adhesive sheet and the aged adhesive sheet were "NG", it was rated as "C (poor)". The results are shown in Table 1.

[0144]

Table 1

[0145] As shown in Table 1, the pressure-sensitive adhesive sheets of Examples 1 to 5 in which the pressure-sensitive adhesive layer was formed from the water-dispersible pressure-sensitive adhesive composition had good holding power even in a mode where the pressure-sensitive adhesive was provided on the surface of the substrate printed in black by the direct method, as compared with the pressure-sensitive adhesive sheets of Comparative Examples 1 and 2 in which the pressure-sensitive adhesive layer was formed from the solvent-based pressure-sensitive adhesive composition. Among them, it was confirmed that the pressure-sensitive adhesive sheet of Example 1 having a pressure-sensitive adhesive layer crosslinked with a silanol-based crosslinking agent (silanol group-forming monomer) exhibited stable and excellent holding power.

[0146] As described above, specific examples of the present invention have been described in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified above.

Explanation of Signs

[0147] 1 Pressure-sensitive adhesive sheet 3 Pressure-sensitive adhesive sheet 10 Substrate 12 Substrate film 13 Substrate film 14 Coloring layer 15 First coloring layer 16 Second coloring layer 18 Substrate 20 Pressure-sensitive adhesive layer 22 First pressure-sensitive adhesive layer 24 Second pressure-sensitive adhesive layer 30 Release liner 32, 34 Release liner 50 Pressure-sensitive adhesive sheet with release liner 60 Pressure-sensitive adhesive sheet with release liner

Claims

1. An adhesive sheet comprising: an adhesive layer formed from an aqueous dispersion type adhesive composition containing an acrylic polymer as a base polymer; and a support substrate having a first surface and a second surface and supporting the adhesive layer on at least the first surface, wherein the substrate includes a colored layer constituting the first surface, and the colored layer contains an ether-based polyurethane, the adhesive sheet.

2. The acrylic polymer is: a polymer of a monomer component containing a silanol group-forming monomer and crosslinked with silanol groups derived from the silanol group-forming monomer; and crosslinked with one or more crosslinking agents selected from oxazoline-based crosslinking agents, carbodiimide-based crosslinking agents, epoxy-based crosslinking agents, and isocyanate-based crosslinking agents; The adhesive sheet according to claim 1, which is at least one of the above.

3. The adhesive sheet according to claim 1 or 2, wherein the thickness of the adhesive layer is 10 μm or more and 50 μm or less.

4. The substrate includes a first colored layer constituting the first surface and a second colored layer constituting the second surface, and a first adhesive layer is disposed on the first surface of the substrate, and a second adhesive layer is disposed on the second surface of the substrate. The adhesive sheet according to claim 1 or 2.

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