Adhesive sheet

Abstract

The invention relates to an adhesive sheet. The present invention provides an adhesive sheet which comprises an adhesive layer and a substrate having a colored layer and which can exhibit excellent holding power. Provided is a pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer formed from a water-dispersed pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer, and a support substrate having a sheet shape having a first surface and a second surface, and supporting the adhesive layer at least on the first surface. The base material includes a colored layer constituting the first surface, and the colored layer includes an ether-based polyurethane.

Description

Technical Field

[0001] This application claims priority based on Japanese Patent Application No. 2023-196371 filed on November 20, 2023, the entire content of which is incorporated herein by reference.

[0002] The present invention relates to an adhesive sheet including an adhesive layer and a substrate having a colored layer. Background Art

[0003] Generally, an adhesive (also referred to as a pressure-sensitive adhesive) is in a state of a soft solid (viscoelastic body) in a temperature region near room temperature and has a property of simply adhering to an adherend by pressure. Utilizing such a property, adhesives are widely used in various applications in the form of an adhesive sheet with a substrate having an adhesive layer provided on one or both surfaces of the substrate. For example, in various applications such as electronic devices such as mobile phones, tablet personal computers, and laptop computers, a colored adhesive sheet is used to impart electrical insulation, masking properties, light-shielding properties, visual recognition properties, design properties, etc. As technical documents related to such adhesive sheets, Japanese Patent Application Laid-Open No. 2013-72074 and Japanese Patent Application Laid-Open No. 2013-203965 can be cited. Summary of the Invention

[0004] In Japanese Patent Application Laid-Open No. 2013-72074 and Japanese Patent Application Laid-Open No. 2013-203965, an adhesive sheet is described which is produced by providing a colored layer on the surface of a resin film as a substrate by printing and providing an adhesive layer on the colored layer by a transfer method. Here, the transfer method refers to the following method: an adhesive composition is coated on a release liner as an engineering paper and dried, whereby an adhesive layer is formed on the release liner, and then, the adhesive layer is bonded to the substrate, whereby the adhesive layer is transferred onto the substrate. In contrast, a method of directly coating an adhesive composition on a substrate 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 using the direct coating method has manufacturing advantages such as not requiring engineering paper compared to the formation of an adhesive layer using the transfer method.

[0005] However, when an adhesive layer is to be formed on a substrate having a colored layer on its surface by the direct method, components from the colored layer are transferred from the colored layer of the substrate to the adhesive composition, sometimes having an adverse effect on the characteristics of the adhesive layer. For example, in the case where it is desired to control the crosslinked structure of the base polymer contained in the adhesive layer by a crosslinking agent or the like to control the characteristics, the components from the colored layer transferred to the adhesive composition hinder its crosslinking reaction, and as a result, the holding power of the adhesive layer sometimes decreases.

[0006] The present invention has been accomplished in view of the above aspects, and an object thereof is to provide an adhesive sheet including an adhesive layer and a base material having a colored layer, and capable of exhibiting excellent holding power.

[0007] The present inventors conducted intensive studies and as a result, obtained the following findings: when the colored layer of the base material contains at least an ether-based polyurethane, there is a tendency to cause crosslinking hindrance in the adhesive layer. Further, it was found that by forming the adhesive layer using a water-dispersible adhesive composition in a form containing a dispersed adhesive component in an aqueous medium, even when the adhesive layer is formed on the base material by a direct method, it is easy to suppress crosslinking hindrance caused by components from the colored layer, and thus the present invention was completed.

[0008] According to the present specification, there is provided an adhesive sheet including an adhesive layer and a support base material, wherein the adhesive layer is formed from a water-dispersible adhesive composition containing an acrylic polymer as a base polymer; the support base material has a sheet shape having a first surface and a second surface, and supports the adhesive layer at least on the first surface. Here, the above base material includes a colored layer constituting the above first surface, and the colored layer contains an ether-based polyurethane. According to the above configuration, since the adhesive layer disposed in contact with the colored layer of the base material is formed from a water-dispersible adhesive composition, transfer of crosslinking hindrance components from the colored layer is less likely to occur, and crosslinking hindrance in the adhesive layer is easily suppressed. Therefore, the above adhesive sheet has a tendency to suppress a decrease in holding power.

[0009] In some embodiments, the above acrylic polymer is: (i) a polymer of a monomer component containing a silanol group-forming monomer and crosslinked using a silanol group derived from the silanol group-forming monomer; or (ii) crosslinked using 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 above-mentioned silanol group-forming monomer in (i) above is a polymerizable compound having at least 1 (preferably 2 or more, for example, 2 or 3) functional groups (silanol group-forming functional groups) capable of forming a silanol group (Si-OH) in one molecule. Preferred examples of the above-mentioned silanol group-forming functional groups include functional groups that form a silanol group by hydrolysis (such as alkoxysilyl groups). By using such a silanol group-forming monomer as a monomer component, a crosslinked structure based on the condensation reaction of silanol groups is introduced into the acrylic polymer. According to the technology disclosed herein, for the crosslinking reaction from the above-mentioned silanol group-forming monomer (i.e., the condensation reaction of silanol groups), crosslinking hindrance is appropriately suppressed. Therefore, when using an acrylic polymer crosslinked with a silanol group-forming monomer as the acrylic polymer contained in the adhesive layer, a decrease in holding power caused by crosslinking hindrance is less likely to occur.

[0011] In addition, according to the technology disclosed herein, for the crosslinking reaction using the crosslinking agent listed in (ii) above, that is, the crosslinking reaction using one or more crosslinking agents selected from oxazoline crosslinking agents, carbodiimide crosslinking agents, epoxy crosslinking agents, and isocyanate crosslinking agents, crosslinking hindrance is also appropriately suppressed. Therefore, when using an acrylic polymer crosslinked with the above-mentioned crosslinking agent as the acrylic polymer contained in the adhesive layer, a decrease in holding power caused by crosslinking hindrance is less likely to occur.

[0012] In some embodiments, the thickness of the above-mentioned adhesive layer is 10 μm or more and 50 μm or less. According to the technology disclosed herein, even for an adhesive sheet having a relatively thin adhesive layer, the influence of crosslinking hindrance components from the colored layer can be suppressed, and a decrease in holding power can be easily suppressed.

[0013] In some embodiments, the above-mentioned substrate includes a first colored layer constituting the above-mentioned first surface and a second colored layer constituting the above-mentioned second surface. A first adhesive layer is disposed on the above-mentioned first surface of the above-mentioned substrate, and a second adhesive layer is disposed on the above-mentioned second surface of the above-mentioned substrate. According to this embodiment, it is easy to realize a double-sided adhesive sheet including a substrate having a colored layer and exhibiting excellent holding power. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic cross-sectional view showing the configuration of an adhesive sheet according to one embodiment.

[0015] Figure 2 It is a schematic cross-sectional view showing the configuration of an adhesive sheet according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] The preferred embodiments of the present invention are described below. It should be noted that matters required for implementing the present invention other than matters specifically mentioned in this specification can be understood by those skilled in the art based on the teachings on the implementation of the invention recorded in this specification and the technical common sense at the time of application. The present invention can be implemented based on the contents disclosed in this specification and the technical common sense in this field. In addition, in the following drawings, components and parts that play the same role are sometimes marked with the same reference numerals for description, and sometimes repeated descriptions are omitted or simplified. In addition, the embodiments described in the drawings are schematically illustrated in order to clearly illustrate the present invention, and may not accurately represent the size and scale of the products actually provided.

[0017] In this specification, "adhesive" refers to a material that is in a soft solid (viscoelastic) state in a temperature range near room temperature and has the property of adhering to an adherend by pressure. The adhesive referred to here is defined in "CADahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) P.143", which can usually be a material having a tensile modulus of elasticity E * (1Hz)<10 7 dyne / cm 2 The material has the above properties (typically, the material has the above properties at 25°C). The adhesive in the technology disclosed herein can also be understood as the solid component (non-volatile component) of the adhesive composition or the constituent component of the adhesive layer.

[0018] In this specification, "(meth)acryloyl" collectively refers to acryloyl and methacryloyl. Similarly, "(meth)acrylate" collectively refers to acrylate and methacrylate, and "(meth)acrylic acid" collectively refers to acrylic acid and methacrylic acid.

[0019] In this specification, "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 monomers refer to monomers derived from monomers having at least one (meth)acryloyl group in one molecule.

[0020] In this specification, "water-dispersible" refers to a form in which at least a part of the components are dispersed in water. For example, "water-dispersible adhesive composition" refers to a composition containing an adhesive composition and water, and at least a part of the adhesive composition is dispersed in water. Water-dispersible includes suspended state and emulsified state.

[0021] <Adhesive Sheet>

[0022] (Structural example of adhesive sheet)

[0023] The adhesive sheet disclosed herein is a substrate - supported adhesive sheet having an adhesive layer on one or both surfaces of a substrate (support). In the concept of the adhesive sheet described herein, objects such as adhesive tapes, adhesive labels, and adhesive films can be included. It should be noted that the above - mentioned adhesive layer is typically formed continuously, but is not limited to this form. For example, it can be an adhesive layer formed in a regular or irregular pattern such as dots or stripes. In addition, the adhesive sheet can be in the form of a roll or a single sheet. Or, it can also be an adhesive sheet in a form further processed into various shapes.

[0024] The adhesive sheet disclosed herein can, for example, have Figure 1 the cross - sectional structure schematically shown in Figure 1 The adhesive sheet 1 shown is configured as a substrate - supported single - sided adhesive adhesive sheet having a sheet - like substrate (support) 10 and an adhesive layer 20 provided on one surface 10A (non - peelable) of the substrate 10. In this adhesive sheet 1, the surface of the adhesive layer 20 is the adhesive surface (bonding surface) 1A that constitutes one surface of the adhesive sheet 1. In addition, in this adhesive sheet 1, the other surface 10B of the substrate 10 becomes the other surface (back surface) 1B of the adhesive sheet 1. That is, the other surface 10B of the substrate 10 also serves as the back surface 1B of the adhesive sheet 1. The substrate 10 includes a substrate film 12 and a coloring layer 14 disposed on the front side of the substrate film 12 (i.e., the side of the substrate film 12 where the adhesive layer 20 is located. Also referred to as the first surface 12A). The coloring layer 14 constitutes the surface 10A of the substrate 10 on the adhesive layer 20 side. In other words, the adhesive sheet 1 has a laminated structure in which the coloring layer 14 and the adhesive layer 20 are sequentially laminated on the first surface 12A of the substrate film 12.

[0025] Before use (i.e., before attaching to the adherend), the adhesive sheet 1 can be in the form of an adhesive sheet 50 with a release liner as shown in Figure 1 where the adhesive surface 1A is protected by a release liner 30 whose at least the side of the adhesive layer 20 is the release surface. Or, it can also be an adhesive sheet in a form where the release liner 30 is omitted, the other surface (back surface) 10B of the substrate layer 10 becomes the release surface, and the surface (adhesive surface 1A) is protected by winding the adhesive sheet 1 into a roll so that the adhesive layer 20 contacts the back surface 10B.

[0026] In another embodiment, the adhesive sheet disclosed herein can have Figure 2 the cross - sectional structure schematically shown in Figure 2The adhesive sheet 3 shown is formed in the form of an adhesive sheet with a sheet-shaped base material (support) 18, and a first adhesive layer 22 and a second adhesive layer 24 respectively supported on both sides of the base material 18, having double-sided adhesiveness with a base material. More specifically, a first adhesive layer 22 and a second adhesive layer 24 are respectively provided on the first surface 18A and the second surface 18B (both non-peelable surfaces) of the base material 18. In this adhesive sheet 3, the surface of the first adhesive layer 22 is the adhesive surface (bonding surface) 3A that constitutes one surface of the adhesive sheet 3, and the surface of the second adhesive layer 24 is the adhesive surface (bonding surface) 3B that constitutes the other surface of the adhesive sheet 3. The base material 18 includes a base material film 13, a first coloring layer 15 disposed on the first adhesive layer 22 side of the base material film 13, and a second coloring layer 16 disposed on the second adhesive layer 24 side of the base material film 13. The first coloring layer 15 constitutes the surface 18A of the base material 18 on the first adhesive layer 22 side, and the second coloring layer 16 constitutes the surface 18B of the base material 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 sequentially laminated on the first surface 13A of the base material film 13, and the second coloring layer 16 and the second adhesive layer 24 are sequentially laminated on the second surface 13B of the base material film 13.

[0027] Before use (before being pasted onto an adherend), the adhesive sheet 3 can be as Figure 2 shown in the form of an adhesive sheet 60 with a release liner, where the adhesive surface 3A is protected by a release liner 32 whose at least the first adhesive layer 22 side becomes a release surface, and the adhesive surface 3B is protected by a release liner 34 whose at least the second adhesive layer 24 side becomes a release surface. Alternatively, the release liner 34 can be omitted, and the surface (back surface) 32B of the release liner 32 on the side opposite to the first adhesive layer 22 becomes a release surface, and the adhesive sheet 3 is wound into a roll shape so that the second adhesive layer 24 contacts the back surface 32B to protect its surface (adhesive surface 3B).

[0028] (Base material)

[0029] The adhesive sheet disclosed herein includes a sheet-shaped base material (support) that supports an adhesive layer. In some embodiments, the above-mentioned base material includes a base material film (basic film) and a coloring layer provided on the base material film.

[0030] (Base material film)

[0031] As the base material film (base film), there is no particular limitation. For example, a resin film mainly composed of a resin material (for example, a component with a content greater than 50% by weight) can be preferably used. In this specification, a "resin film" typically refers to a substantially non-foamed resin film. That is, the resin film in this specification can be a resin film in which there are substantially no air bubbles (void-free) inside the resin film. Therefore, the above resin film is a concept distinct from the so-called foamed body film. In addition, the above resin film is typically a substantially non-porous film, which is a concept distinct from the so-called non-woven fabric and woven fabric. A base material that does not include a porous layer such as a foamed body, non-woven fabric, or woven fabric, that is, a base material including a non-porous layer, can be preferably used. Compared with a foamed body, non-woven fabric, and woven fabric, a resin film generally has a tendency of excellent mechanical strength such as tensile strength. In addition, the processability (for example, blanking processability) is excellent. Therefore, an adhesive sheet using a base material including a resin film is advantageous in terms of processability, dimensional accuracy, and operability. In addition, from the viewpoints of dimensional stability, thickness accuracy, economy (cost), etc., a base material including such a resin film can also be preferably used as the base material in the technology disclosed herein.

[0032] Preferred examples of the resin material constituting the resin film disclosed herein include: polyolefin resins, polyester resins, etc. Here, a polyolefin resin refers to a resin containing polyolefin in a proportion greater than 50% by weight. Similarly, a polyester resin refers to a resin containing polyester in a proportion greater than 50% by weight. Examples of polyolefin resin films include polyethylene (PE) resins, polypropylene (PP) resins, ethylene-propylene copolymers, ethylene-butene copolymers, etc. Examples of polyester resins include: polyethylene terephthalate (PET) resins, polybutylene terephthalate (PBT) resins, polyethylene naphthalate resins, polybutylene naphthalate resins, etc. Among them, from the viewpoint of anchoring property (especially the anchoring property of the acrylic adhesive layer), polyester resins are preferred, and from the viewpoints of strength and processability, PET resins are particularly preferred.

[0033] In the above base material 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 can be blended as needed. The blending ratio of various additives is usually less than about 30% by weight (for example, less than about 20% by weight, typically less than about 10% by weight).

[0034] As the base material film (e.g., resin film), a transparent film (e.g., transparent resin film) can be preferably used. From the viewpoints of strength and the like, such a base material film can substantially contain no colorant. Here, the base material film substantially containing no colorant means that the content of the colorant is less than 1% by weight, preferably less than 0.1% by weight. Alternatively, in order to exhibit desired design properties and optical properties (e.g., light-shielding property, etc.) in the adhesive sheet, the base material film in the technology disclosed herein can be colored in colors such as black, white (e.g., milky white). The above coloring can be carried out, for example, by incorporating a known organic or inorganic colorant (pigment, dye, etc.) into the material constituting the base material film.

[0035] The base material film disclosed herein can have a single-layer structure or a multi-layer structure having 2 layers, 3 layers, or 3 or more layers. From the viewpoint of shape stability, the base material film is preferably a single-layer structure. The manufacturing method of the base material film (typically a resin film) can be appropriately adopted from the conventionally known methods without particular limitation. For example, conventionally known general film forming methods such as extrusion molding, blow molding, T-die casting molding, and calender roll molding can be appropriately adopted.

[0036] Surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of a primer (formation of a primer layer) can be performed on the surface of the above base material film (e.g., resin film). Such surface treatments can be treatments for improving the adhesion between the base material film and the colored layer laminated on its surface and the adhesion between the base material film and the adhesive layer. It should be noted that the technology disclosed herein can be preferably implemented in such a manner that no primer layer is formed between the base material film and the layer laminated on its surface and / or between the base material film and the adhesive layer, and the base material 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 have a thinner thickness.

[0037] The thickness of the base material film is not particularly limited. In some embodiments, the thickness of the base material film is, for example, about 200 μm or less, can be about 100 μm or less, can be 70 μm or less, and can be 50 μm or less. By thinning the thickness of the base material film, the adhesive sheet also becomes thinner, and further, it can be advantageous in terms of thinning, miniaturization, lightening, and resource saving of the product to which the adhesive sheet is applied. In addition, from the viewpoints of operability, processability, etc., the lower limit of the thickness of the base material film is preferably about 0.5 μm or more (e.g., 1 μm or more). In other embodiments, from the viewpoints of processability, etc., the thickness of the base material film can be 5 μm or more, can be 10 μm or more, can be 15 μm or more, and can also be 20 μm or more. In some preferred embodiments, the thickness of the base material 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.

[0038] (Coloring layer)

[0039] The substrate disclosed herein includes a coloring layer. Specifically, the coloring layer is laminated on the adhesive layer side of the substrate film and disposed between the substrate film and the adhesive layer. In the form of an adhesive sheet having single-sided adhesiveness with an adhesive layer formed on one side of the substrate, the coloring layer is disposed so as to at least form the surface on the adhesive layer side of the substrate. Further, in the form of an adhesive sheet having double-sided adhesiveness with adhesive layers formed on both sides of the substrate, the coloring layer is disposed so as to form the surface on at least one adhesive layer side of the substrate, and preferably, two or more coloring layers are respectively disposed so as to form the surfaces on one adhesive layer side and the other adhesive layer side of the substrate. According to the manner in which the coloring layers are respectively disposed on both sides of the substrate, compared with the manner in which the coloring layer is disposed on one side of the substrate, the surface roughness of the coloring layer is likely to be reduced, and further, the surface roughness of the adhesive layer is reduced, thereby improving the adhesiveness to the adherend and easily improving the adhesive performance. In addition, when an adhesive layer is provided on the coloring layer, compared with the case where the adhesive layer is provided on the surface of the substrate without a coloring layer, there is a tendency to improve the anchoring property between the substrate and the adhesive layer. According to the technology disclosed herein, the degree of freedom in manufacturing for providing an adhesive layer on the coloring layer side of the substrate is high, and thus, it is easy to obtain an adhesive sheet having a high anchoring property between the substrate and the adhesive layer.

[0040] By including a coloring layer in the substrate, the hue (color tone) and transmittance of the adhesive sheet can be adjusted, and desired design properties, light-shielding properties, and masking properties can be obtained. The color of the coloring layer is not particularly limited, and various colors can be adopted according to the purpose. In some preferred embodiments, the coloring layer can be, for example, a black layer (e.g., a black printing layer) formed by black printing. An adhesive sheet having a black layer as the coloring layer can be preferably used, for example, for applications where attachment to a module requiring electrical insulation is required.

[0041] The coloring layer can be formed, for example, by coating a coloring layer-forming composition containing a colorant and a binder on the substrate film. As the binder, materials well-known in the coating or printing fields can be used without particular limitation. For example, polyurethane, phenolic resin, epoxy resin, urea melamine resin, polymethyl methacrylate, etc. can be exemplified.

[0042] According to the research of the present inventors, when the coloring layer contains an ether-based polyurethane as the binder, there is a tendency for crosslinking hindrance of the adhesive to easily occur when forming the adhesive layer. Therefore, it is particularly meaningful to apply the technology disclosed herein to a configuration in which the coloring layer contains an ether-based polyurethane as the binder. Herein, the ether-based polyurethane in this specification refers to a polyurethane having an ether bond in the main chain. Typically, it refers to a polyurethane produced by the reaction of an ether-based polyol (e.g., a polyether polyol) and a polyisocyanate.

[0043] In some embodiments, in the total amount of the binder contained in the coloring layer disclosed herein, the proportion of the ether-based polyurethane is greater than 50% by weight, may be 70% by weight or more, may be 80% by weight or more, may be 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 appropriately suppressed and a decrease in the holding force can be suppressed.

[0044] The composition for forming the coloring layer can be, for example, a solvent type, an ultraviolet curable type, a thermosetting type, or the like. The formation of the coloring layer can be carried out by means conventionally used in the formation of the coloring layer without particular limitation. For example, a method of forming the coloring layer (printing layer) by printing such as gravure printing, flexographic printing, or offset printing can be preferably employed.

[0045] The coloring layer can be a single-layer structure composed of 1 layer as a whole, or a multilayer structure including 2 layers, 3 layers, or 3 or more sub-coloring layers. The coloring layer having a multilayer structure including 2 or more sub-coloring layers can be formed, for example, by repeatedly coating (for example, printing) the composition for forming the coloring layer. The color and blending amount of the colorant contained in each sub-coloring layer can be the same or different. In the coloring layer for imparting light-shielding properties, it is particularly meaningful to form a multilayer structure from the viewpoint of preventing the generation of pinholes and improving the reliability of preventing light leakage.

[0046] As the colorant used in the coloring of the coloring layer, known pigments and dyes corresponding to the target color can be appropriately selected. Although there is no particular limitation, examples of white pigments include titanium dioxide, zinc white, and lead white. Examples of black pigments include carbon black, acetylene black, pine soot, and graphite. They can be used alone or in combination of two or more.

[0047] The content of the colorant is set according to the required hue, texture, etc., and thus is not limited to a specific range. It is appropriate to be about 1% by weight or more in the coloring layer, preferably 2% by weight or more (for example, 5% by weight or more), and may be 15% by weight or more. In addition, the content of the above colorant is appropriately about 65% by weight or less, preferably 30% by weight or less (for example, 15% by weight or less), and may also be 8% by weight or less.

[0048] In the manner in which the colored layer forms at least one surface of the substrate, it is generally appropriate that the overall thickness of the colored layer (single-sided) is 0.1 μm or more, preferably 0.5 μm or more, and more preferably 0.7 μm or more. The overall thickness of the colored layer (single-sided) can be about 0.8 μm or more, or can be about 1 μm or more. In other manners, from the viewpoint of obtaining sufficient light-shielding properties and masking properties, the overall thickness of the colored layer (single-sided) can be set to 2 μm or more (for example, 3 μm or more), or can be set to 4 μm or more. Additionally, it is generally appropriate that the overall thickness of the above-mentioned colored layer (single-sided) is 10 μm or less, preferably 7 μm or less, and more preferably 5 μm or less. In some manners, the overall thickness of the colored layer (single-sided) can be set to about 3 μm or less, and further can be set to about 2 μm or less.

[0049] (Additional layer)

[0050] In addition to the above-mentioned substrate film and colored layer (such as a black layer), the substrate can also have an additional layer. For example, in order to obtain interlayer adhesion, an adhesive layer, a primer layer, etc. can be provided between the layers. Alternatively, the technology disclosed herein can preferably be implemented in a manner of using a substrate that does not have layers other than the above-mentioned substrate film and colored layer.

[0051] Although not particularly limited, in the adhesive sheet disclosed herein, the total thickness of the layers other than the adhesive layer (the total thickness of the non-adhesive layer; typically the total thickness of the substrate, such as the total thickness of the substrate film and the colored layer) is, for example, about 200 μm or less, can be about 100 μm or less, can be 70 μm or less, can be 50 μm or less. By thinning the thickness of the above-mentioned non-adhesive layer, the adhesive sheet also becomes thinner, and thus it can also be advantageous in aspects such as thinning, miniaturization, weight reduction, and resource saving of the product to which the adhesive sheet is applied. Additionally, in a configuration where the total thickness of the adhesive sheet is limited to a specified value or less by restricting the thickness of the non-adhesive layer as described above, the ratio of the thickness of the adhesive layer can be increased, and higher adhesive performance can be obtained. The lower limit of the total thickness of the above-mentioned non-adhesive layer is not particularly limited, and from the viewpoints of processability, workability, etc., it is generally appropriate that it is 2 μm or more, preferably 3 μm or more (for example, 3.5 μm or more). From the viewpoints of light-shielding properties and operability, the total thickness of the non-adhesive layer in some other manners can be 5 μm or more, can be 12 μm or more, can be 16 μm or more, can be 20 μm or more, or can be 25 μm or more. In some preferred manners, the thickness of the above-mentioned non-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.

[0052] <Adhesive layer>

[0053] (Water-dispersible adhesive composition)

[0054] The adhesive layer disclosed herein is formed from an aqueous dispersion-type adhesive composition. The above aqueous dispersion-type adhesive composition is an aqueous dispersion-type (typically an aqueous emulsion-type) adhesive composition in which the adhesive component is dispersed in an aqueous medium. Herein, the aqueous medium refers to a solvent that constitutes the medium and is water or a mixed solvent (aqueous solvent) mainly composed of water.

[0055] (Acrylic polymer)

[0056] The adhesive composition disclosed herein is an acrylic adhesive composition containing an acrylic polymer as a base polymer. Herein, the "base polymer" refers to the main component among the polymer components contained in the adhesive composition (which may also be an adhesive). In addition, in this specification, unless otherwise specified, the "main component" refers to a component with a content greater than 50% by weight. In a preferred embodiment, the above acrylic adhesive composition is an acrylic emulsion-type adhesive composition containing an aqueous dispersion-type acrylic polymer. The above aqueous dispersion-type acrylic polymer has an emulsion form in which the acrylic polymer is dispersed in water. As the acrylic polymer, an acrylic polymer mainly composed of (meth)acrylic acid alkyl ester as a monomer component (monomer main component, that is, a component accounting for more than 50% by weight in the total amount of monomers constituting the acrylic polymer) can be preferably used.

[0057] As the acrylic polymer, for example, a polymer of a monomer raw material (monomer component) preferably containing (meth)acrylic acid alkyl ester as a main monomer and may also contain a comonomer copolymerizable with the main monomer is preferred. Herein, the main monomer refers to a component accounting for more than 50% by weight of the monomer composition in the above monomer raw material.

[0058] As the (meth)acrylic acid alkyl ester, for example, a compound represented by the following formula (1) can be preferably used.

[0059] CH 2 =C(R 1 )COOR 2 (1)

[0060] Herein, R 1 in the above formula (1) is a hydrogen atom or a methyl group. In addition, R 2 is a linear alkyl group having 1 to 20 carbon atoms (hereinafter, such a carbon atom number range may be expressed as "C 1-20 "). From the viewpoints of the storage modulus of the adhesive, etc., a (meth)acrylic acid alkyl ester having a linear alkyl group of C 2 is preferred, and a (meth)acrylic acid alkyl ester having a linear alkyl group of C 1-14 is more preferred, and R 2 is C 1-10Alkyl (meth)acrylates having a chain-like alkyl group, particularly preferably R 2 is an alkyl (meth)acrylate having a butyl or 2-ethylhexyl group.

[0061] As R 2 is C 1-20 Alkyl (meth)acrylates having a chain-like alkyl group, examples of which include: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate, etc. These alkyl (meth)acrylates can be used alone or in combination of two or more. As preferred alkyl (meth)acrylates, n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA) can be mentioned.

[0062] The technology disclosed herein can be preferably implemented in the following manner: The above monomer components contain R of the above formula (1) 2 is an alkyl (meth)acrylate having a chain-like alkyl group of C 4-10 (typically at least one of BA and 2EHA). Among the alkyl (meth)acrylates contained in the monomer components, the total amount of the alkyl (meth)acrylates in which R of the above formula (1) 2 is an alkyl (meth)acrylate having a chain-like alkyl group of C 4-10 (typically the total amount of BA and 2EHA) accounts for 70% by weight or more (typically 80% by weight or more).

[0063] When the above alkyl (meth)acrylate contains an alkyl (meth)acrylate having a chain-like alkyl group of C 2 (typically at least one of BA and 2EHA) in the above formula (1), other alkyl (meth)acrylates (R in the above formula (1) 4-10 is C 2 is C 小于4 or C 大于10The total amount of the alkyl (meth)acrylate of the chain-like alkyl group 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. Further, from the viewpoint of obtaining the effects of other alkyl (meth)acrylates, the above 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 above monomer components. As the above other alkyl (meth)acrylates, the R in the above formula (1) can be preferably used. 2 is C 1-3 alkyl (meth)acrylate of the chain-like alkyl group. As specific examples thereof, methyl acrylate (MA), methyl methacrylate (MMA), ethyl acrylate (EA), etc. can be cited. Among them, MA is more preferable.

[0064] The comonomer having copolymerizability with the alkyl (meth)acrylate as the main monomer can contribute to introducing crosslinking points into the acrylic polymer or improving the cohesion 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.

[0065] Carboxyl group-containing monomers: For example, unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), crotonic acid; unsaturated dicarboxylic acids such as maleic acid, itaconic acid, citraconic acid and their acid anhydrides (maleic anhydride, itaconic anhydride, etc.).

[0066] 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.

[0067] Amide group-containing monomers: For example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-hydroxymethyl(meth)acrylamide, N-hydroxymethylpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, N-butoxymethyl(meth)acrylamide.

[0068] Amino group-containing monomers: For example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, tert-butylaminoethyl (meth)acrylate.

[0069] Monomers having an epoxy group: For example, glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, allyl glycidyl ether.

[0070] Cyano group-containing monomers: For example, acrylonitrile, methacrylonitrile.

[0071] Functional group-containing monomers: for example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

[0072] Monomers having a ring containing a nitrogen atom: for example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyl azole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine.

[0073] The above functional group-containing monomers can be used alone or in combination of two or more. Among the above functional group-containing monomers, from the viewpoint of being able to appropriately achieve the introduction of crosslinking points and the improvement of cohesion as described above, carboxyl group-containing monomers, hydroxyl group-containing monomers, and cyano group-containing monomers are preferred, and carboxyl group-containing monomers are more preferred. Among the carboxyl group-containing monomers, AA and MAA are preferred.

[0074] In a preferred embodiment, AA and MAA are used together as the above functional group-containing monomers. The adhesive composition of the acrylic polymer containing the monomer composition (i.e., copolymer composition) can provide a higher-performance (e.g., more excellent resilience resistance) adhesive sheet. The weight ratio of AA to MAA (AA / MAA) can be, for example, in the range of about 0.1 to about 10, more preferably about 0.3 or more (typically about 0.5 or more), and further preferably about 5 or less (typically about 4 or less). When AA / MAA is within the above range, there is a tendency to easily and sufficiently obtain the effect of improving resilience resistance, and there is also a tendency for excellent temporal stability of the adhesive properties after the production of the adhesive sheet.

[0075] When a functional group-containing monomer is copolymerized in the acrylic polymer, the proportion of the functional group-containing monomer in all monomer components constituting the acrylic polymer is not particularly limited. Generally, from the viewpoint of balancing cohesion and adhesiveness, it is preferred that the proportion of the functional group-containing monomer is about 0.1% by weight or more (e.g., about 0.5% by weight or more, typically about 1% by weight or more). In addition, considering the adhesive effect brought by the (meth)acrylic acid alkyl ester, it is preferably about 40% by weight or less (e.g., about 30% by weight or less, typically about 20% by weight or less).

[0076] In the case where a carboxyl group-containing monomer is copolymerized in the acrylic polymer, from the viewpoint of improving water resistance, it is appropriate that the proportion of the carboxyl group-containing monomer in all the monomer components is 15% by weight or less. For example, it can 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 above proportion can 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 be achieved in the embodiments where the proportion of the carboxyl group-containing monomer in all the monomer components is 1% by weight or more, or 1.5% by weight or more.

[0077] In some embodiments, it is preferred that a silanol group-forming monomer is copolymerized in 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 based on a condensation reaction of silanol groups (silanol condensation) into the adhesive (adhesive layer) formed from the above adhesive composition. The silanol group-forming monomer can be understood as a crosslinking agent (silane coupling agent). As a preferred example of the above silanol group-forming monomer, a silanol group-forming monomer having at least 1 (preferably 2 or more, such as 2 or 3) alkoxysilyl groups in one molecule (alkoxysilyl group-containing monomer) can be cited. From the viewpoint of copolymerizability with (meth)acrylic acid alkyl esters, a silanol group-forming monomer having 1 or 2 or more acryloyl groups, methacryloyl groups (hereinafter, acryloyl groups and methacryloyl groups may be collectively referred to as “(meth)acryloyl groups”), vinyl and other ethylenically unsaturated groups in one molecule is preferred. 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 preferred.

[0078] Specific examples of the silanol group-forming monomer include 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-acryloxypropylmethyldiethoxysilane, and the like. In addition, examples of the silanol group-forming monomer other than the above include vinyltrimethoxysilane, vinyltriethoxysilane, 4-vinylbutyltrimethoxysilane, 4-vinylbutyltriethoxysilane, 8-vinyloctyltrimethoxysilane, 8-vinyloctyltriethoxysilane, 10-methacryloxydecyltrimethoxysilane, 10-acryloxydecyltrimethoxysilane, 10-methacryloxydecyltriethoxysilane, 10-acryloxydecyltriethoxysilane, and the like. As a particularly preferred silanol group-forming monomer, 3-methacryloxypropyltrimethoxysilane can be exemplified.

[0079] In some embodiments, the acrylic monomers disclosed herein are crosslinked by condensation through 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 adhesive composition. The aqueous dispersion adhesive composition is in a state where the adhesive component in the form of fine particles is dispersed in an aqueous medium. Therefore, compared with a solvent-based composition, the crosslinking inhibitor component from the colored layer of the substrate is less likely to move. It can be seen that by using the aqueous dispersion adhesive composition, the transfer of the crosslinking inhibitor component from the substrate to the adhesive composition is suppressed. Therefore, even for the condensation reaction of the silanol group as described above, the crosslinking inhibition is appropriately suppressed. Therefore, in the aqueous dispersion adhesive composition, when an acrylic polymer crosslinked by a silanol group-forming monomer is used as the base polymer, it is easy to obtain an adhesive sheet in which the holding force reduction caused by crosslinking inhibition is less likely to occur.

[0080] When a silanol group-forming monomer (e.g., an alkoxysilyl group-containing monomer) is copolymerized in the acrylic polymer, the proportion of the silanol group-forming monomer (e.g., an alkoxysilyl group-containing monomer) in all the monomer components is preferably 0.005% by weight or more (e.g., 0.01% by weight or more) of all the monomer components, and is preferably about 0.1% by weight or less (e.g., about 0.03% by weight or less).

[0081] For the purpose of improving the cohesion of acrylic polymers, etc., other copolymerizable components other than the above-mentioned comonomers can be used. Examples of such copolymerizable components include vinyl ester monomers such as vinyl acetate and vinyl propionate; aromatic vinyl compounds such as styrene, substituted styrenes (such as α-methylstyrene), and vinyltoluene; cyclohexyl (meth)acrylate; cycloalkyl (meth)acrylates such as cyclopentyl (meth)acrylate and isobornyl (meth)acrylate; (meth)acrylate esters containing an aromatic ring such as (meth)acrylate phenyl ester, (meth)acrylate aryloxyalkyl ester (such as phenoxyethyl (meth)acrylate), and (meth)acrylate arylalkyl ester (such as benzyl (meth)acrylate); olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutene; 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, etc.

[0082] As other examples of copolymerizable components other than the above-mentioned comonomers, monomers having multiple functional groups in one molecule can be cited. Examples of such polyfunctional monomers include 1,2-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, glycerol di(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, divinylbenzene, butylene di(meth)acrylate, hexylene di(meth)acrylate, etc.

[0083] The amount of the copolymerizable component other than the above-mentioned comonomers can be appropriately selected according to the purpose and use, and there is no particular limitation. For example, it is preferably 10% by weight or less of the monomer composition of the acrylic polymer.

[0084] In the technology disclosed herein, it is appropriate to design the acrylic polymer such that the glass transition temperature (Tg) of the polymer is below -25°C (typically above -75°C and below -25°C). The Tg of the acrylic polymer can preferably be below -40°C (for example, above -70°C and below -40°C), more preferably below -50°C (typically above -70°C and below -50°C). From the viewpoint of improving adhesion, it is preferred that the Tg of the acrylic polymer is below the above upper limit value. The Tg of the acrylic polymer can be adjusted by the types and usage ratios of the monomers used in the synthesis of the polymer.

[0085] Here, the Tg of the acrylic polymer refers to the Tg calculated by the Fox formula based on the composition of the monomer components used in the synthesis of the polymer. As shown below, the Fox formula is a relational expression between the Tg of a copolymer and the glass transition temperatures Tgi of the homopolymers obtained by homopolymerizing the monomers constituting the copolymer respectively.

[0086] 1 / Tg = Σ(Wi / Tgi)

[0087] It should be noted that in the above Fox formula, Tg represents the glass transition temperature of the copolymer (unit: K), Wi represents the weight fraction of monomer i in the copolymer (copolymerization ratio based on weight), and Tgi represents the glass transition temperature of the homopolymer of monomer i (unit: K).

[0088] As the glass transition temperature of the homopolymer used in the calculation of Tg, the values recorded in known materials are used. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.

[0089] 2-Ethylhexyl acrylate -70°C

[0090] n-Butyl acrylate -55°C

[0091] Methyl methacrylate 105°C

[0092] Methyl acrylate 8°C

[0093] Vinyl acetate 32°C

[0094] Acrylic acid 106°C

[0095] Methacrylic acid 228°C

[0096] Regarding the glass transition temperatures of the homopolymers of monomers other than the above examples, the values recorded in "Polymer Handbook" (Third Edition, John Wiley & Sons, Inc., 1989) are used. In the case where multiple values are recorded in this literature, the highest value is adopted.

[0097] For monomers whose homopolymer glass transition temperatures are not described in the above polymer handbook, the values obtained by the following measurement method are used (refer to Japanese Patent Application Laid-Open No. 2007-51271). Specifically, 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 added to a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube, and a reflux condenser tube, and stirred for 1 hour while flowing nitrogen. Thereby, the oxygen in the polymerization system is removed, and then 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. The test sample is punched into a disc shape with a diameter of 7.9 mm, sandwiched between parallel plates, and using a viscoelasticity tester (ARES, manufactured by Rheometrics), the viscoelasticity is measured in the shear mode at a temperature range of -70°C to 150°C at a heating rate of 5°C / minute while applying a shear strain with a frequency of 1 Hz, and the peak temperature of tanδ is taken as the Tg of the homopolymer.

[0098] 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 the polymerization method that can be preferably adopted, the emulsion polymerization method can be exemplified. The mode of emulsion polymerization is not particularly limited, and various monomer supply methods, polymerization conditions, materials used, etc., similar to the commonly known conventional emulsion polymerization in the past can be appropriately adopted. For example, as the monomer supply method, the one-shot feeding method of supplying all monomer raw materials at once, the continuous supply (dropwise addition) method, the batch supply (dropwise addition) method, etc., can be appropriately adopted. The monomer raw materials can also be added dropwise in the form of an aqueous emulsion. The polymerization temperature can be, for example, about 20°C or higher (usually about 40°C or higher), and it is appropriate to be about 100°C or lower (usually about 80°C or lower).

[0099] Through the above emulsion polymerization, a polymerization liquid in the form of an emulsion in which the acrylic polymer is dispersed in water (acrylic polymer emulsion) can be prepared. The water-dispersible adhesive composition disclosed herein can preferably be manufactured using the above polymerization liquid or a polymerization liquid obtained by appropriately post-treating the polymerization liquid. Alternatively, an acrylic polymer can also be synthesized by a polymerization method other than the emulsion polymerization method (for example, solution polymerization, photopolymerization, bulk polymerization, etc.), and the polymer can be dispersed in water to prepare an acrylic polymer emulsion.

[0100] The initiator used in the polymerization can be appropriately selected from conventionally well-known polymerization initiators according to the type of polymerization method. For example, azo 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'-dimethylisobutylamidine), 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride; persulfate initiators such as potassium persulfate and ammonium persulfate; peroxide initiators such as benzoyl peroxide, tert-butyl hydroperoxide, and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; carbonyl initiators such as aromatic carbonyl compounds; redox initiators such as the combination of persulfate and sodium bisulfite, and the combination of peroxide and sodium ascorbate, etc., but are not limited to these substances. Such polymerization initiators can be used alone or in combination of two or more.

[0101] The amount of the polymerization initiator used may be the usual amount used and is not particularly limited. For example, relative to 100 parts by weight of all monomer components, it can be selected from the range of about 0.005 parts by weight or more (preferably about 0.01 parts by weight or more), and additionally about 1 part by weight or less (preferably about 0.8 parts by weight or less).

[0102] During the polymerization, a chain transfer agent (which can also be understood as a molecular weight regulator or a polymerization degree regulator) can be used as needed. As the chain transfer agent, for example, thiols such as dodecyl mercaptan (dodecane thiol), lauryl mercaptan, glycidyl mercaptan, 2-mercaptoethanol, mercaptoacetic acid, 2-ethylhexyl mercaptoacetate, 2,3-dimercapto-1-propanol, and α-methylstyrene dimer, etc. Such chain transfer agents can be used alone or in combination of two or more.

[0103] Relative to 100 parts by weight of the monomer component, the amount of the chain transfer agent used can be about 0.001 parts by weight or more (typically about 0.005 parts by weight or more, for example about 0.001 parts by weight or more), and additionally, it can be about 5 parts by weight or less (typically about 2 parts by weight or less, for example about 1 part by weight or less). By using the amount of the chain transfer agent within an appropriate range, the desired polymerization rate can be obtained.

[0104] Emulsion polymerization of monomer raw materials is usually carried out in the presence of a surfactant (emulsifier). The amount of surfactant used is not particularly limited. Considering the polymerization stability and the dispersion stability of the polymerization reactants, the amount of surfactant used is usually suitably 0.1 part by weight or more, preferably 0.5 part by weight or more, and from the viewpoint of obtaining higher stability, it can be 1.0 part by weight or more, or 1.5 part by weight or more, relative to 100 parts by weight of the monomer raw materials. On the other hand, from the viewpoint of improving water resistance, it is preferable to suppress the amount of surfactant (especially non-reactive surfactant) used. From this viewpoint, the amount of surfactant used is usually preferably 5 parts by weight or less, and can be 4 parts by weight or less, 3 parts by weight or less, or 2.5 parts by weight or less.

[0105] As the surfactant, known anionic surfactants, nonionic surfactants, cationic surfactants, etc. can be used. Usually, anionic or nonionic surfactants are preferred. Surfactants having reactive functional groups (typically free-radical polymerizable functional groups) can be used. Hereinafter, the surfactant having a reactive functional group may sometimes be referred to as a reactive surfactant, and in contrast, a normal surfactant having no reactive functional group may be referred to as a non-reactive surfactant. The surfactant can be used alone or in combination of two or more.

[0106] 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, etc. In the case where the anionic surfactant forms a salt, the salt can be, for example, a metal salt such as sodium salt, potassium salt, calcium salt, magnesium salt (preferably a salt of a monovalent metal), ammonium salt, amine salt, etc.

[0107] Examples of non-reactive nonionic surfactants include: polyoxyethylene alkyl ethers such as polyoxyethylene lauryl ether and polyoxyethylene stearyl ether; polyoxyethylene alkylphenyl ethers such as polyoxyethylene octylphenyl ether and polyoxyethylene nonylphenyl ether; sorbitan fatty acid esters such as sorbitan monolaurate, sorbitan monostearate, and polyoxyethylene sorbitan monolaurate; polyoxyethylene glycerol ether fatty acid esters; polyoxyethylene-polyoxypropylene block copolymers; etc.

[0108] As the reactive surfactant, a substance having a polymerizable (typically, free-radical polymerizable) functional group is preferably used. For example, a reactive surfactant having a structure in which a free-radical polymerizable functional group is introduced into the anionic surfactant or nonionic surfactant described above can be used. The type of the free-radical polymerizable functional group is not particularly limited, and examples thereof include alkenyl, acryloyl, methacryloyl, vinyl, vinyl ether group (vinyloxy), allyl ether group (allyloxy), etc. As a specific example of the alkenyl, propenyl and isopropenyl (CH 2 =C(CH 3 ))-) can be mentioned. The concept of the propenyl mentioned here includes 1-propenyl (CH 3 -CH=CH-) and 2-propenyl (CH 2 =CH-CH 2 -; sometimes also called allyl).

[0109] Examples of the anionic reactive surfactant include: polyoxyethylene (allyloxymethyl) alkyl ether sulfate (e.g., ammonium salt), polyoxyethylene nonylpropenylphenyl ether sulfate (e.g., ammonium salt), alkyl allyl sulfosuccinate (e.g., sodium salt), methacryloyloxy polyoxypropylene sulfate salt (e.g., sodium salt), polyoxyalkylene alkenyl ether sulfate (e.g., ammonium salt in which the terminal of the above alkenyl is isopropenyl), etc. When the anionic reactive surfactant forms a salt, the salt can be, for example, a metal salt such as sodium salt, or a non-metal salt such as ammonium salt or amine salt.

[0110] Examples of the nonionic reactive surfactant include: polyoxyethylene nonylpropenylphenyl ether, etc.

[0111] Examples of commercially available reactive surfactants include products named "AQUALON HS-05", "AQUALON HS-10", "AQUALON HS-1025", "AQUALON HS-20", "AQUALON KH-10", "AQUALON KH-1025", "AQUALON KH-05", "AQUALON BC-0515", "AQUALON BC-10", "AQUALON BC-1025", "AQUALON BC-20", "AQUALON BC-2020", "AQUALON RN-20", "AQUALON RN-30", "AQUALON RN-50", "AQUALON AR-10", "AQUALON AR-20", "AQUALON AR-1025", "AQUALON AR-2020" manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.; products named "ADEKA REASOAP SE-10N", "ADEKA REASOAP SR-1025" manufactured by ADEKA Corporation; products named "LATEMUL PD-104", "LATEMUL PD-420", "LATEMUL PD-430", "LATEMUL PD-450" manufactured by Kao Corporation; products named "ELEMINOL JS-20", "ELEMINOL RS-3000" manufactured by Sanyo Chemical Industries, Ltd.; products named "Antox MS-60" manufactured by Nippon Emulsion Co., Ltd., etc.

[0112] From the viewpoint of emulsification performance and the like, in one embodiment, an anionic reactive surfactant can be preferably used.

[0113] When using a nonionic reactive surfactant, more suitable results can be achieved by using it in combination with other surfactants, such as an anionic reactive surfactant, an anionic non-reactive surfactant, a nonionic non-reactive surfactant, etc.

[0114] From the viewpoint of improving water resistance, the surfactant used in the technology disclosed herein preferably contains a reactive surfactant. In other words, it is preferred that at least a part of the surfactant used is a reactive surfactant. By subjecting the monomer raw material to emulsion polymerization in the presence of the reactive surfactant, the above reactive surfactant reacts and can enter the acrylic polymer. By allowing the reactive surfactant to enter the acrylic polymer, the amount of free surfactant becomes less. Thereby, water resistance can be improved. Therefore, polymerization using a reactive surfactant is advantageous for achieving both polymerization stability and the water resistance of the adhesive layer obtained from the adhesive composition containing the polymerized acrylic polymer. From the viewpoint of achieving more excellent water resistance, the proportion of the reactive surfactant in the total weight of the surfactant used in emulsion polymerization can be 50% by weight or more, more preferably 70% by weight or more. For example, a mode of using only the reactive surfactant as the surfactant can be preferably adopted. In addition, the movement of the reactive surfactant that has entered the acrylic polymer within the adhesive layer is restricted, so it is not easily exuded to the surface of the adhesive layer. This can also preferably contribute to the improvement of water resistance. It should be noted that in this specification, containing a reactive surfactant means a concept including the reactive surfactant in a state after reacting with the reactive functional group (such as a free-radical polymerizable functional group) of the reactive surfactant. The reactive surfactant in the technology disclosed herein is typically included in the water-dispersible adhesive composition or the adhesive layer in a form in which at least a part of it enters the acrylic polymer as described above.

[0115] The weight-average molecular weight (Mw) of the acrylic polymer is not particularly limited and can be, for example, in the range of 10×10 4 ~500×10 4 . Here, the Mw of the acrylic polymer refers to the Mw of the toluene-soluble component (sol component) of the acrylic polymer. The Mw of the above acrylic polymer refers to a value converted to standard polystyrene based on GPC (gel permeation chromatography). From the viewpoint of improving adhesion characteristics, the Mw of the acrylic polymer is preferably 150×10 4 or less, more preferably 100×10 4 or less. In addition, from the viewpoints of cohesion and the like, the Mw of the acrylic polymer can be preferably 20×10 4 or more, more preferably 30×10 4 or more (for example, 40×10 4 or more).

[0116] (Crosslinking agent)

[0117] The aqueous dispersion adhesive composition for forming the adhesive layer preferably contains a crosslinking agent as an optional component. The adhesive layer in the technology disclosed herein may contain the above crosslinking agent in the form after the crosslinking reaction, the form before the crosslinking reaction, the form in which the crosslinking reaction has been partially carried out, their intermediate or composite forms, etc. Typically, the above crosslinking agent is mainly contained in the adhesive layer in the form after the crosslinking reaction.

[0118] 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. They can be used alone or in combination of two or more.

[0119] Among them, 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. They can be used alone or in combination of two or more. According to the technology disclosed herein, since the adhesive layer is formed from an aqueous dispersion adhesive composition, crosslinking hindrance components are not easily transferred from the substrate to the adhesive composition. As a result, the crosslinking hindrance of the above crosslinking agent to the crosslinking reaction can be appropriately suppressed. Therefore, when an acrylic polymer crosslinked with the above crosslinking agent is used as the acrylic polymer contained in the aqueous dispersion adhesive composition, it is easy to obtain an adhesive sheet in which the holding force reduction caused by crosslinking hindrance does not easily occur.

[0120] As the oxazoline-based crosslinking agent, a crosslinking agent having one or more oxazoline groups in one molecule can be used without particular limitation. The oxazoline-based crosslinking agents can be used alone or in combination of two or more. From the viewpoint of being used in the aqueous dispersion adhesive composition, oxazoline-based crosslinking agents that can be dissolved or dispersed in water are preferred. oxazoline-based crosslinking agents.

[0121] The oxazoline group can be a 2- oxazoline group, a 3- oxazoline group, or a 4- oxazoline group. Usually, an oxazoline-based crosslinking agent having a 2- oxazoline group is preferably used. For example, 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- Oxazolines such as addition polymerizable A water-soluble copolymer or a water-dispersible copolymer obtained by copolymerizing oxazoline with other monomers is used as An oxazoline-based crosslinking agent.

[0122] As Commercially available products of oxazoline-based crosslinking agents, for example, products with trade names "EPOCROS WS-500", "EPOCROS WS-700", "EPOCROS K-2010E", "EPOCROS K-2020E", "EPOCROS K-2030E", etc. manufactured by Nippon Shokubai Co., Ltd.

[0123] As the carbodiimide-based crosslinking agent, a low-molecular compound or a high-molecular compound having two or more carbodiimide groups can be used. In the water-dispersible adhesive composition, a carbodiimide-based crosslinking agent that can be dissolved or dispersed in water is preferably used. Commercially available products of carbodiimide-based crosslinking agents, for example, "CARBODILITE V-02", "CARBODILITE V-02-L2", "CARBODILITE V-04", etc. of the CARBODILITE V series (aqueous solution type) manufactured by Nisshinbo Co., Ltd.; "CARBODILITE E-01", "CARBODILITE E-02", "CARBODILITE E-04", etc. of the CARBODILITE E series (water-dispersible type) of the CARBODILITE series.

[0124] As the epoxy-based crosslinking agent, a crosslinking agent 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 preferred. 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 preferred.

[0125] 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.

[0126] Examples of commercially available epoxy crosslinking agents include products with the trade names "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, "EPICLON CR-5L" manufactured by DIC Corporation, "Denacol EX-512" manufactured by Nagase ChemteX Corporation, "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd., and the like.

[0127] As the isocyanate crosslinking agent, a crosslinking agent having two or more isocyanate groups per molecule can be used without particular limitation. The isocyanate groups in the above isocyanate crosslinking agent can form isocyanate groups having a protecting group, for example, an isocyanate regenerable functional group (blocked isocyanate) in a form in which the isocyanate group is temporarily protected by treatment with a blocking agent or the like. The isocyanate crosslinking agents can be used alone or in combination of two or more.

[0128] Examples of the isocyanate crosslinking agent include aromatic polyisocyanates such as toluene diisocyanate and xylene diisocyanate; aliphatic isocyanates such as isophorone diisocyanate; alicyclic polyisocyanates such as hexamethylene diisocyanate; and the like.

[0129] More specifically, for example, it can include: lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, and isophorone diisocyanate; aromatic diisocyanates such as 2,4-toluene diisocyanate, 4,4'-diphenylmethane diisocyanate, xylylene diisocyanate, and polymethylene polyphenyl diisocyanate; trimethylolpropane / toluene diisocyanate trimer adducts (products with the trade name "CORONATE L" manufactured by Tosoh Corporation, etc.); trimethylolpropane / hexamethylene diisocyanate trimer adducts (manufactured by Tosoh Corporation, trade name "CORONATE HL", etc.), isocyanurate forms of hexamethylene diisocyanate (products with the trade name "CORONATE HX" manufactured by Tosoh Corporation, etc.) and other isocyanate adducts; polyether polyisocyanates, polyester polyisocyanates and other polyisocyanates; adducts of these polyisocyanates with polyols; and polyisocyanates that have been polyfunctionalized by forming isocyanurate bonds, biuret bonds, urethane bonds, etc. with these polyisocyanates; and the like.

[0130] From the viewpoint of a water-dispersible adhesive composition, an isocyanate crosslinking agent capable of being dissolved or dispersed in water is preferred. For example, a water-soluble, water-dispersible or self-emulsifying type of isocyanate crosslinking agent can be preferably used. As commercially available products of such isocyanate crosslinking agents (aqueous isocyanate crosslinking agents), examples include: products with the trade names "BURNOCK DNW-5000", "BURNOCK DNW-5010", "BURNOCK DNW-5100", "BURNOCK DNW-5200", "BURNOCK DNW-5500", "BURNOCK DNW-6000" manufactured by DIC Corporation; products with the trade names "AQUANATE100", "AQUANATE 105", "AQUANATE 110", "AQUANATE 120", "AQUANATE 130", "AQUANATE200", "AQUANATE 210" manufactured by Tosoh Corporation; products with the trade names "TAKENATE WD-220", "TAKENATEWD-240", "TAKENATE WD-720", "TAKENATE WD-725", "TAKENATE WD-726", "TAKENATE WD-730", "TAKENATE WB-700", "TAKENATE WB-720" manufactured by Mitsui Chemicals Polyurethanes, Inc.; products with the trade names "ELASTRON BN-04", "ELASTRON BN-11", "ELASTRON BN-27", "ELASTRON BN-69", "ELASTRONBN-77" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.

[0131] The content (total amount of the crosslinking agent) of the crosslinking agent in the adhesive composition disclosed herein is not particularly limited and can be appropriately set in such a manner as to obtain appropriate properties after crosslinking, taking into account the composition and molecular weight of the base polymer. Although there is no particular limitation, the amount of the crosslinking agent used is preferably about 0.01 parts by weight or more, more preferably about 0.1 parts by weight or more, relative to 100 parts by weight of the base polymer (typically an acrylic polymer), and preferably about 1 part by weight or more (for example, about 2 parts by weight or more). In addition, from the viewpoints of adhesiveness and the like, the amount of the above crosslinking agent used is preferably about 15 parts by weight or less (more preferably about 10 parts by weight or less, for example, about 5 parts by weight or less) relative to 100 parts by weight of the base polymer, and from the viewpoint of improving the adhesiveness to the adherend, it is preferably about 4 parts by weight or less, more preferably less than 3.5 parts by weight, and further preferably less than 3 parts by weight.

[0132] (Tackifying resin)

[0133] The water-dispersible adhesive composition disclosed herein may contain a tackifying resin. By using a tackifying resin, an adhesive sheet exhibiting excellent adhesive properties (such as adhesive force and resilence resistance) can be easily obtained. The above-mentioned tackifying resin may be a water-dispersible tackifying resin (also referred to as a tackifying resin emulsion). For example, by mixing an aqueous emulsion of an acrylic polymer with an emulsion of the above-mentioned tackifying resin, an adhesive composition containing these components in a desired ratio can be easily prepared. As the tackifying resin emulsion, a tackifying resin emulsion that contains at least substantially no aromatic hydrocarbon solvents (more preferably substantially no aromatic hydrocarbon solvents and other organic solvents) is preferably used.

[0134] Examples of the tackifying resin include rosin-based tackifying resins (including rosin derivative tackifying resins), petroleum-based tackifying resins, terpene-based tackifying resins, phenolic tackifying resins, ketone-based tackifying resins, etc. One kind of them can be used alone or two or more kinds can be used in combination.

[0135] Examples of the above-mentioned rosin-based tackifying resins include, in addition to rosins such as gum rosin, wood rosin, and tall oil rosin, stabilized rosins (for example, stabilized rosins obtained by disproportionating or hydrogenating the aforementioned rosins), polymerized rosins (for example, polymers of the aforementioned rosins, typically dimers), modified rosins (for example, unsaturated acid-modified rosins obtained by modifying with unsaturated acids such as maleic acid, fumaric acid, and (meth)acrylic acid), etc.

[0136] Examples of the above-mentioned rosin derivative tackifying resins include esterified products of the above-mentioned rosin-based resins (for example, rosin esters such as stabilized rosin esters and polymerized rosin esters), phenol-modified products of the above-mentioned rosin-based resins (phenol-modified rosins), and their esterified products (phenol-modified rosin esters), etc.

[0137] Examples of the above-mentioned petroleum-based tackifying resins include aliphatic petroleum resins, aromatic petroleum resins, copolymerized petroleum resins, alicyclic petroleum resins, and their hydrogenated products, etc.

[0138] Examples of the above-mentioned terpene-based tackifying resins include α-pinene resins, β-pinene resins, aromatic-modified terpene resins, terpene phenol resins, etc.

[0139] Examples of the above-mentioned ketone-based tackifying resins include ketone resins obtained by the condensation of ketones (for example, aliphatic ketones such as methyl ethyl ketone, methyl isobutyl ketone, and acetophenone; alicyclic ketones such as cyclohexanone and methylcyclohexanone, etc.) with formaldehyde.

[0140] Examples of tackifying resins that can be preferably used in the technology disclosed herein include rosin-based tackifying resins and terpene-based tackifying resins. Preferred examples of rosin-based tackifying resins include stabilized rosin esters and polymerized rosin esters. In addition, preferred examples of terpene-based tackifying resins include terpene phenol resins.

[0141] An emulsion of such a tackifying resin can be prepared using a surfactant (emulsifier) as needed. As the surfactant that can be used in the preparation of the above-mentioned tackifying resin emulsion, one or more can be appropriately selected from the same surfactants that can be used in the preparation of acrylic polymer emulsions. Usually, an anionic surfactant or a nonionic surfactant is preferably used. It should be noted that the surfactant used in the preparation of the acrylic polymer emulsion and the surfactant used in the preparation of the tackifying resin emulsion can be the same or different. For example, a method of using an anionic surfactant in the preparation of any emulsion; a method of using a nonionic surfactant; a method of using an anionic surfactant on one side and a nonionic surfactant on the other side, etc. can be preferably adopted. The amount of the surfactant used is not particularly limited as long as it can prepare the tackifying resin into an emulsion form. For example, relative to 100 parts by weight of the tackifying resin (based on solid content), it can be about 0.2 parts by weight or more (preferably about 0.5 parts by weight or more), and can be about 10 parts by weight or less (preferably about 5 parts by weight or less).

[0142] The softening point of the tackifying resin used is not particularly limited. From the viewpoints of improving cohesion and the like, the softening point of the tackifying resin can be, for example, 80 °C or higher, preferably 90 °C or higher, can be 100 °C or higher, can be 120 °C or higher, and can also be 130 °C or higher.

[0143] Although not particularly limited, in some embodiments, the tackifying resin in the technology disclosed herein can include a high softening point tackifying resin having a softening point of 140 °C or higher. The softening point of the above-mentioned high softening point tackifying resin is preferably 145 °C or higher, and can be, for example, 150 °C or higher. By using the above-mentioned high softening point tackifying resin, adhesiveness and cohesion can be appropriately balanced. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoints of compatibility, low-temperature characteristics, etc., it is usually appropriate to be 200 °C or lower, preferably 180 °C or lower, and can be 175 °C or lower.

[0144] It should be noted that the softening point of the tackifying resin described herein is defined as the value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is rapidly melted at as low a temperature as possible, filled into a ring placed on a flat metal plate, taking care not to generate bubbles. After cooling, the raised portion is cut off from the plane including the upper end of the ring with a slightly heated 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 glycerin in a non-contact manner, and the temperature of the glycerin is maintained at 20°C ± 5°C for 15 minutes. Next, the steel ball is placed at the center of the surface of the sample in the ring and placed at a fixed position on the support. Then, the distance from the upper end of the ring to the glycerin surface is maintained at 50 mm, a thermometer is placed so that the center of the mercury bulb of the thermometer is at the same height as the center of the ring, and the container is heated. The flame of the Bunsen burner used for heating is located between the center and the edge of the bottom of the container to ensure uniform heating. It should be noted that the rate of increase in the bath temperature after reaching 40°C from the start of heating must be 5.0°C ± 0.5°C per minute. The sample gradually softens and flows out of the ring, and finally the temperature when it contacts the bottom plate is read and taken as the softening point. The softening point is measured at least twice, and the average value is used.

[0145] From the viewpoint of suitably exerting its use effect, with respect to 100 parts by weight of the base polymer (typically an acrylic polymer), the amount of the tackifying resin used (on a solid content basis) is usually suitably 1 part by weight or more, preferably 3 parts by weight or more (e.g., 5 parts by weight or more), more preferably 12 parts by weight or more, and further preferably 16 parts by weight or more. According to the technology disclosed herein, good water resistance can be achieved even in a manner where 22 parts by weight or more (e.g., 25 parts by weight or more) of the tackifying resin is contained with respect to 100 parts by weight of the base polymer. In addition, from the viewpoints of cohesion and the like, with respect to 100 parts by weight of the base polymer, the amount of the tackifying 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 further preferably 50 parts by weight or less (e.g., 45 parts by weight or less, typically 40 parts by weight or less).

[0146] When the water-dispersible adhesive composition disclosed herein contains a high softening point tackifying resin, from the viewpoints of cohesion and the like, only the high softening point tackifying resin can be used as the tackifying resin. Further, from the viewpoint of obtaining a balance with various adhesion characteristics, in some embodiments, the high softening point tackifying resin can be used in combination with a tackifying resin having a lower softening point (for example, a tackifying resin having a softening point of 120°C or lower or 110°C or lower). In such embodiments, the proportion of the high softening point tackifying resin in the total amount of the tackifying resin used can be, for example, 20% by weight or more, can be 40% by weight or more, or can be 60% by weight or more. The proportion of the high softening point tackifying resin can be, for example, 90% by weight or less, can be 80% by weight or less, or can be 70% by weight or less.

[0147] (Polyacrylic acid)

[0148] In some embodiments, the water-dispersible adhesive composition may contain polyacrylic acid. Polyacrylic acid can function as a thickener. Further, by including polyacrylic acid in the water-dispersible adhesive composition, the polarity of the adhesive layer formed from the water-dispersible adhesive composition can be increased, and adhesive properties such as metal adhesiveness can be effectively improved. Further, by using polyacrylic acid, there is a tendency for the water resistance to be improved.

[0149] In some embodiments, the weight average molecular weight (Mw) of the polyacrylic acid is 5×10 4 or more, preferably 10×10 4 or more, more preferably 15×10 4 or more. Further, in some embodiments, the Mw of the 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 converted based on standard polyethylene glycol / polyethylene oxide by GPC.

[0150] 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, or can be 3.5 parts by weight or more, based on 100 parts by weight of the base polymer (typically an acrylic polymer). When the amount of polyacrylic acid used is increased, it is easy to improve metal adhesiveness or increase water resistance. In some embodiments, the amount of polyacrylic acid used can be 10 parts by weight or less, can be 8.0 parts by weight or less, can be 6.0 parts by weight or less, can be 5.0 parts by weight or less, or can be 4.0 parts by weight or less, based on 100 parts by weight of the base polymer.

[0151] (Leveling agent)

[0152] In some embodiments, the water-dispersible adhesive composition may contain a leveling agent. According to the water-dispersible adhesive composition containing the leveling agent, the wettability of the water-dispersible adhesive composition to the support substrate can be improved. By improving the wettability, when the water-dispersible adhesive composition is coated to form an adhesive layer, the coating film of the composition is not likely to produce depressions, and the occurrence of appearance defects in the adhesive layer and even the adhesive sheet can be suppressed. In addition, it is easy to make the thickness of the adhesive layer thinner (for example, 30 μm or less).

[0153] The type of the leveling agent is not particularly limited. As the leveling agent, for example, “SURFYNOL 420” (acetylene glycol ethylene oxide surfactant, manufactured by Nissin Chemical Industry Co., Ltd.), “PELEX OT-P” (sodium dialkyl sulfosuccinate, manufactured by Kao Corporation), “Neocol P” (sodium dialkyl sulfosuccinate, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), “Neocol SW-C” (sodium dialkyl sulfosuccinate, manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.), “NOPCOWET50” (sulfonic acid anionic surfactant, manufactured by SANNOPCO Ltd.), “SN WET126” (modified silicone / special polyether surfactant, manufactured by SANNOPCO Ltd.), “SN WETFST2” (nonionic wetting agent of polyoxyalkyleneamine, manufactured by SANNOPCO Ltd.), “SNWETS” (nonionic wetting agent of polyoxyalkyleneamine ether, manufactured by SANNOPCO Ltd.), and “SN WET125” (modified silicone surfactant, manufactured by SANNOPCO Ltd.) can be cited. The leveling agent can be used alone or in combination of two or more.

[0154] In some preferred embodiments, sodium dialkyl sulfosuccinate can be used as the leveling agent. According to the leveling agent, the wettability of the water-dispersible adhesive composition can be further improved.

[0155] The number of carbon atoms of sodium dialkyl sulfosuccinate is not particularly limited. In some embodiments, it is 4 or more, preferably 6 or more, and more preferably 8 or more. In addition, the number of carbon atoms of sodium dialkyl sulfosuccinate is not particularly limited. In some embodiments, it is 20 or less, preferably 12 or less, and more preferably 10 or less.

[0156] In some embodiments, based on 100 parts by weight of the base polymer (typically an acrylic polymer), 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 can also be 0.7 parts by weight or more. When the amount of the leveling agent used is increased, the wettability of the water-dispersible adhesive composition is appropriately improved, and thus there is a tendency to suppress an increase in cratering property (hajiki property) caused by the addition of the thickener. In addition, from the viewpoint of suppressing contamination of the adherend, in some embodiments, based on 100 parts by weight of the base polymer, the amount of the leveling agent used can be 3 parts by weight or less, can be 2.5 parts by weight or less, can be 2 parts by weight or less, can be 1.5 parts by weight or less, can be 1.2 parts by weight or less, and can be 0.8 parts by weight or less.

[0157] (Other Additive Components)

[0158] In addition, from the viewpoint of easy peelability of the self-peeling liner, the water-dispersible adhesive composition disclosed herein preferably contains a silicon compound (typically a silane coupling agent). 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 thioether, etc. can be used. Among them, an alkylalkoxysilane compound is preferred. It is appropriate that the molecular weight of the silicon compound is about 100 or more (for example, about 200 or more), and can also be about 500 or less (for example, about 350 or less).

[0159] As the alkylalkoxysilane compound, alkyltrialkoxysilane, dialkyldialkoxysilane, trialkylmonoalkoxysilane, tetraalkoxysilane, phenylalkoxysilane can all be used. It should be noted that the above alkyl includes linear and cyclic. As specific examples of the above compounds, methyltrimethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, n-butyltrimethoxysilane, isobutyltrimethoxysilane, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, n-decyltrimethoxysilane, hexadecyltrimethoxysilane, methyltriethoxysilane, dimethoxydimethylsilane, diethoxydimethylsilane, cyclohexylmethyldimethoxysilane, methoxymethyltrimethylsilane, octadecyldimethylmethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, diphenylethoxymethylsilane, dimethoxymethylphenylsilane, etc. can be cited. Among them, alkyltrialkoxysilane is preferred.

[0160] From the viewpoint of fully demonstrating its 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) relative to 100 parts by weight of the base polymer (typically an acrylic polymer). Further, 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) relative to 100 parts by weight of the base polymer.

[0161] The adhesive composition disclosed herein may contain, as needed, an acid or a base (such as ammonia water) used for the purpose of pH adjustment or the like. As other optional components that can be incorporated into the adhesive composition disclosed herein, examples include: viscosity modifiers, crosslinking aids, peeling modifiers, plasticizers, softeners, fillers, colorants (pigments, dyes, etc.), antistatic agents, anti-aging agents, ultraviolet absorbers, antioxidants, light stabilizers, and the like. Regarding such various additives, conventionally known additives can be used by conventional methods, and since they are not particular features of the present invention, detailed descriptions thereof are omitted.

[0162] <Adhesive layer>

[0163] The adhesive layer in the technology disclosed herein can be appropriately formed by applying the above-described water-dispersible adhesive composition onto a specified surface and drying or curing it. When applying (typically coating) the adhesive composition, conventional coating machines (such as gravure roll coaters, reverse roll coaters, roll kiss coaters, dip roll coaters, bar coaters, knife coaters, spray coaters, etc.) can be used. The thickness of the adhesive layer is not particularly limited, and generally, it is suitably about 2 μm or more, preferably about 10 μm or more, more preferably 20 μm or more, and can be 30 μm or more. Further, the thickness of the adhesive layer is generally suitably about 150 μm or less, preferably about 100 μm or less (for example, 80 μm or less), more preferably 50 μm or less, further preferably 40 μm or less, and can 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 hindrance component from the colored layer is suppressed, and a decrease in the holding force can be easily suppressed.

[0164] <Release liner>

[0165] As a release liner for protecting or supporting the adhesive layer (which can have both protective and supporting functions), there are no particular restrictions on its material and composition, and an appropriate release liner can be selected from known release liners for use. For example, a release liner having a structure in which at least one surface of a substrate is subjected to a release treatment (typically, a release treatment layer treated with a release treatment agent is provided) can be preferably used. As the substrate (the object of the release treatment) constituting such a release liner, the same substrates as those constituting the adhesive sheet described above (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 above-mentioned release treatment layer, known or conventional release treatment agents (such as silicone-based, fluorine-containing, long-chain alkyl-based release treatment agents, etc.) can be used. In addition, a substrate having low tackiness containing a fluorine-containing polymer (such as polytetrafluoroethylene, poly(chlorotrifluoroethylene), poly(vinyl fluoride), poly(vinylidene fluoride), tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc.) or a low-polarity polymer (such as olefin resins such as polyethylene and polypropylene) can be used as a release liner without subjecting the surface of the substrate to a release treatment. Alternatively, a substrate obtained by subjecting the surface of the low-tackiness substrate to a release treatment can also be used as a release liner.

[0166] There are no particular restrictions on the thickness of the substrate and the release treatment layer constituting the release liner, and they 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 structure with a release treatment layer on the surface of the substrate, the overall thickness including the substrate 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.

[0167] <Method for manufacturing an adhesive sheet with a substrate>

[0168] The adhesive sheet disclosed in this specification includes: a substrate prepared with a colored layer provided on at least one surface; and an adhesive layer provided on the surface of the substrate on the side of the colored layer. Here, in the production of the adhesive sheet disclosed herein, the method of providing the adhesive layer on one surface and / or the other surface of the substrate is not particularly limited. Generally, it is preferable to select from (1) a method of directly applying (typically coating) a water-dispersed adhesive composition onto the substrate 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-dispersed adhesive composition onto a release liner, drying it to form an adhesive layer on the release liner, laminating the adhesive layer onto the substrate and transferring (laminating) it (hereinafter also referred to as the "transfer method"), and applying each of these methods to the above-mentioned one surface and / or the other surface, respectively. According to the technology disclosed herein, even when the adhesive layer is formed by the direct method, crosslinking inhibition in the adhesive layer can be suppressed, and a decrease in holding power can be easily suppressed. Therefore, it is particularly meaningful to form the adhesive layer by the direct method using the water-dispersed adhesive composition disclosed herein. According to the direct method, there are manufacturing advantages such as not requiring a release liner as engineering paper. In addition, in the transfer method, it is necessary to place the release liner to which the adhesive composition has been applied, for example, in a dryer for heating and drying, so heat resistance is sometimes required for the release liner (for example, it will not curl due to heating, etc.). On the other hand, there is no such restriction in the direct method, so there is an advantage of being able to select a low-cost and environmentally friendly release liner.

[0169] In the case of producing a double-sided adhesive sheet with a substrate by providing adhesive layers on one surface and the other surface of the substrate, the direct method can be applied to both surfaces of the substrate to produce a double-sided adhesive sheet (direct-direct method), or the transfer method can be applied to one surface of the substrate (typically the surface where the adhesive layer is initially provided), and the direct coating method can be applied to the other surface to produce a double-sided adhesive sheet (transfer-direct method). In conventional double-sided adhesive sheets with a substrate containing a colored layer, it has been difficult to provide an adhesive layer on the surface of the substrate on the side of the colored layer by the direct method, so there has been a tendency to use a method of providing a colored layer only on one side of the substrate and providing an adhesive layer on the side of the colored layer by the transfer method. On the other hand, according to the present invention, an adhesive layer can be appropriately provided on the surface of the substrate on the side of the colored layer by the direct method, so colored layers can be provided on both surfaces of the substrate, the surface roughness of the colored layer can be reduced, and further the surface roughness of the adhesive layer can be reduced, and the adhesion characteristics can be easily improved.

[0170] <Use>

[0171] The uses of the adhesive sheet disclosed herein are not particularly limited. It can be used for various applications where an adhesive sheet including a substrate having a colored layer can be applied, such as various applications requiring electrical insulation, masking properties, light-shielding properties, visual recognition properties, design properties, etc. The adhesive sheet disclosed herein can be suitably used, for example, as an adhesive sheet attached to vehicles, residential building materials, electronic devices, etc. As non-limiting examples, there can be mentioned the use as an adhesive sheet attached to a module (such as a battery module) requiring electrical insulation inside an electronic device. In addition, the adhesive sheet disclosed herein can also be preferably used for portable electronic devices.

[0172] In non-limiting examples of the above portable electronic devices, there are included: mobile phones, smart phones, tablet personal computers, notebook personal computers, various wearable devices (such as wrist-wearable types like watches, modular types worn on a part of the body with clips, bands, etc., eyewear types including glasses types (monocular types, binocular types. Also including head-mounted types), clothing types worn on shirts, socks, hats, etc. in the form of ornaments, ear-wearable types like earphones worn on the ears, etc.), digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (desk calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, e-books, in-vehicle information devices, portable radios, portable TVs, portable printers, portable scanners, portable modems, etc. It should be noted that in this specification, "portable" is not interpreted as merely being able to be carried, but means having a level of portability that can be relatively easily moved by an individual (standard adult).

[0173] The matters disclosed in this specification include the following matters.

[0174] [1] An adhesive sheet comprising an adhesive layer and a support substrate, the adhesive layer being formed of a water-dispersed adhesive composition containing an acrylic polymer as a base polymer, the support substrate being in a sheet shape having a first surface and a second surface, and supporting the adhesive layer at least on the first surface, wherein the substrate includes a colored layer constituting the first surface, and the colored layer contains an ether-based polyurethane.

[0175] [2] The adhesive sheet according to the above [1], wherein the acrylic polymer is at least one of the following: 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 (i.e., crosslinked with a silane coupling agent); and / or 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.

[0176] [3]The adhesive sheet according to [1] or [2] above, wherein the thickness of the adhesive layer is 10 μm or more and 50 μm or less.

[0177] [4]The adhesive sheet according to any one of [1] to [3] above, wherein the base material includes a first colored layer constituting the first surface and a second colored layer constituting the second surface, a first adhesive layer is disposed on the first surface of the base material, and a second adhesive layer is disposed on the second surface of the base material.

[0178] [5]The adhesive sheet according to any one of [1] to [4] above, wherein the colored layer is a black layer formed by black printing.

[0179] [6]The adhesive sheet according to any one of [1] to [5] above, wherein the base material includes a resin film made of a polyester resin.

[0180] [7]A method for manufacturing an adhesive sheet, wherein the method for manufacturing the adhesive sheet includes: preparing a base material having a colored layer containing an ether-based polyurethane provided on at least one surface; and directly applying a water-dispersion type 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 an adhesive layer.

[0181] Examples

[0182] Hereinafter, several examples related to the present invention will be described, but the present invention is not intended to be limited to the content shown in these examples. It should be noted that in the following description, "parts" and "%" are based on weight unless otherwise specified.

[0183] (Preparation of Emulsion Polymer α)

[0184] In 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: "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 73 parts of distilled water were added. While stirring, nitrogen replacement was carried out at room temperature (25 °C) for 1 hour. 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 adjusted to 60 °C. Polymerization was carried out at 60 °C while dropwise adding the following emulsion over 4 hours. The emulsion was obtained by emulsifying 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 tert-dodecyl mercaptan (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: "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) with 30 parts of distilled water. After cooling to room temperature, the pH was adjusted to pH = 6 using 10% aqueous ammonia as a pH regulator, thereby preparing an emulsion-type polymer α.

[0185] (Preparation of Adhesive Composition A)

[0186] To 100 parts of the solid content of the emulsion-type 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 having a weight average molecular weight (Mw) of 20×10 4 (trade name: "ARON A-10H", manufactured by Toagosei Co., Ltd.), 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 dilution and neutralization were carried out using distilled water and 10% aqueous ammonia, thereby preparing an emulsion-type adhesive composition A having a solid content of 25%.

[0187] (Preparation of Emulsion-Type Polymer β)

[0188] In 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 "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) and 69 parts of distilled water were added. While stirring, nitrogen replacement was carried out at room temperature (25 °C) for 1 hour. 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 adjusted to 60 °C. Polymerization was carried out while dropping the following emulsion thereto at 60 °C for 4 hours. The emulsion was prepared by using 32 parts of distilled water to mix 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 tert-dodecyl mercaptan (chain transfer agent), and 1.9 parts of a surfactant (trade name "Aqualon KH-1025", manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.). After cooling to room temperature, 10% ammonia water as a pH adjuster was used to adjust the pH to 6, thereby preparing an emulsion polymer β.

[0189] (Preparation of Adhesive Composition B)

[0190] Relative to 100 parts of the solid content of the emulsion polymer β, 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 with a weight-average molecular weight (Mw) of 20×10 4 (trade name "ARON A-10H", manufactured by Toagosei Co., Ltd.), 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. Dilution and neutralization were carried out using distilled water and 10% ammonia water, thereby preparing an adhesive composition. Dilution and neutralization of the above adhesive composition were carried out using water, thereby preparing Composition β. 0.1 part of a carbodiimide crosslinking agent (trade name "CARBODILITE V-04", manufactured by Nisshinbo Chemical Inc.) was added to the obtained Composition β, and stirring and mixing were carried out, thereby preparing an emulsion adhesive composition B.

[0191] (Preparation of Adhesive Composition C)

[0192] 0.1 part of a carbodiimide crosslinking agent was added with 0.1 part of an oxazoline crosslinking agent (trade name "EPOCROS WS-500", manufactured by Nippon Shokubai Co., Ltd.) added thereto in the above Composition β. Except for this, the operation was carried out in the same manner as the preparation method of the emulsion adhesive composition B, thereby preparing an emulsion adhesive composition C. ​

[0193] (Preparation of Adhesive Composition D)

[0194] In the above composition β, 1 part of an isocyanate crosslinking agent (trade name “BURNOCK5010”, manufactured by DIC Corporation) was added instead of 0.1 part of a carbodiimide crosslinking agent. Otherwise, the operation was the same as the preparation method of the emulsion-type adhesive composition B, and thus the emulsion-type adhesive composition D was prepared.

[0195] (Preparation of Adhesive Composition E)

[0196] In the above composition β, 1 part of an epoxy crosslinking agent (trade name “Denacol EX313”, manufactured by Nagase ChemteX Corporation) was added instead of 0.1 part of a carbodiimide crosslinking agent. Otherwise, the operation was the same as the preparation method of the emulsion-type adhesive composition B, and thus the emulsion-type adhesive composition E was prepared.

[0197] (Preparation of Solvent-Type Polymer γ)

[0198] 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), 0.08 part of 2,2’-azobisisobutyronitrile (AIBN) as a polymerization initiator, and toluene as a polymerization solvent were added to a reaction vessel equipped with a stirrer, a thermometer, a nitrogen inlet tube, a reflux condenser, and a dropping funnel, and the reaction was carried out at 60 °C for 6 hours, whereby the solvent-type polymer γ was obtained.

[0199] (Preparation of Adhesive Composition F)

[0200] 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 crosslinking agent (trade name “CORONATE L”, manufactured by Tosoh Corporation) were added to 100 parts of the obtained solvent-type polymer γ, and stirring and mixing were carried out, whereby the solvent-type adhesive composition F was prepared.

[0201] (Preparation of Adhesive Composition G)

[0202] 30 parts of a polymerized rosin ester resin (trade name “PENSEL D-125”, manufactured by Arakawa Chemical Industries, Ltd.) and 0.03 part of an epoxy crosslinking agent (trade name “TETRAD-C”, manufactured by Mitsubishi Gas Chemical Company, Inc.) were added to 100 parts of the above solvent-type polymer γ, and stirring and mixing were carried out, whereby the solvent-type adhesive composition G was prepared.

[0203] <Example 1>

[0204] (Production of an adhesive sheet with a black-printed substrate by transfer method)

[0205] The above-mentioned adhesive composition A was coated on a release liner (trade name “PET-75-SCA1”, manufactured by Fujiko Co., Ltd.) to a dry thickness of 10 μm and dried. In addition, a substrate film (total thickness of about 52 μm) was prepared, which had a black layer with a thickness of about 1 μm to about 2 μm containing ether-based polyurethane as the main component provided by printing on one surface of a PET resin film with a thickness of 50 μm (trade name “Lumirror S105”, manufactured by Toray Industries, Inc.). The release liner coated with the above-mentioned adhesive composition A was adhered to the surface of the black-printed side of the above-mentioned substrate film, thereby transferring the adhesive layer, and thus an adhesive sheet with a black-printed substrate obtained by the transfer method in this example was obtained.

[0206] (Production of an adhesive sheet with a black-printed substrate by direct method)

[0207] Similarly to the above, a substrate film (total thickness of about 52 μm) was prepared, which had a black layer with a thickness of about 1 μm to about 2 μm containing ether-based polyurethane as the main component provided by printing on one surface of a PET resin film with a thickness of 50 μm (trade name “Lumirror S105”, manufactured by Toray Industries, Inc.). The above-mentioned adhesive composition A was coated on the surface of the black-printed side of the above-mentioned substrate film to a dry thickness of 10 μm and dried, and it was adhered to a release liner (trade name “PET-75-SCA1”, manufactured by Fujiko Co., Ltd.), and thus an adhesive sheet with a black-printed substrate obtained by the direct method in this example was obtained.

[0208] (Production of an adhesive sheet with an unprocessed substrate by direct method)

[0209] A PET resin film (trade name “Lumirror S105”, manufactured by Toray Industries, Inc.) without black printing was prepared as a substrate film (hereinafter, also referred to as “unprocessed substrate” or “unprocessed substrate film”). The above-mentioned adhesive composition A was coated on one surface of the above-mentioned unprocessed substrate film to a dry thickness of 10 μm and dried, and it was adhered to a release liner (trade name “PET-75-SCA1”, manufactured by Fujiko Co., Ltd.), and thus an adhesive sheet with an unprocessed substrate obtained by the direct method in this example was obtained.

[0210] <Examples 2 to 5 and Comparative Examples 1 and 2>

[0211] Except for using various adhesive compositions shown in Table 1 instead of adhesive composition A, the same operations as in Example 1 were carried out to produce the adhesive sheets with black printed substrates obtained by the transfer method, the adhesive sheets with black printed substrates obtained by the direct method, and the adhesive sheets with unprocessed substrates obtained by the direct method for Examples 2 to 5 and Comparative Examples 1 and 2.

[0212] The outlines of the adhesive sheets of each example are shown in Table 1.

[0213] [Retention force test]

[0214] (Retention force test of the initial adhesive sheet)

[0215] The adhesive sheets of each example (the adhesive sheets with black printed substrates obtained by the transfer method, the adhesive sheets with black printed substrates obtained by the direct method, and the adhesive sheets with unprocessed substrates obtained by the direct method) were cut into dimensions of 10 mm in width and 100 mm in length to prepare test samples. In an environment of 23°C and 50% RH, the adhesive surface of the above test samples was pressed against a bakelite board (phenolic resin board) as the adherend with a paste area of 10 mm in width and 20 mm in length using a 2 kg roller for one round trip. The adherend with the test sample pasted thereon by such operation was allowed to stand 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 according to JIS Z0237, it was placed in an environment of 40°C for 1 hour in the state where the load was applied, and it was observed whether the test sample peeled off and fell from the adherend within 1 hour. The case where it did not fall was recorded as "OK", and the case where it fell was recorded as "NG".

[0216] (Retention force test of the aged adhesive sheet)

[0217] The adhesive sheets of each example (the adhesive sheets with black printed substrates obtained by the transfer method, the adhesive sheets with black printed substrates obtained by the direct method, and the adhesive sheets with unprocessed substrates obtained by the direct method) were allowed to stand in an environment of 50°C and 50% RH for 3 days for aging, and then they were cut into dimensions of 10 mm in width and 100 mm in length to prepare test samples. In an environment of 23°C and 50% RH, the adhesive surface of the above test samples was pressed against a bakelite board (phenolic resin board) as the adherend with a paste area of 10 mm in width and 20 mm in length using a 2 kg roller for one round trip. The adherend with the test sample pasted thereon by such operation was allowed to stand 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 according to JIS Z0237, it was placed in an environment of 40°C for 1 hour in the state where the load was applied, and it was observed whether the test sample peeled off and fell from the adherend within 1 hour. The case where it did not fall was recorded as "OK", and the case where it fell was recorded as "NG".

[0218] (Evaluation of Adhesion Retention)

[0219] Based on the results of the adhesion retention test of the initial adhesive sheet and the results of the adhesion retention test of the cured adhesive sheet, the adhesion retention of each example of the adhesive sheet was evaluated in three grades. Specifically, the case where the results of the adhesion retention tests of both the initial adhesive sheet and the cured adhesive sheet were "OK" was evaluated as "A (excellent)", the case where the result of the adhesion retention test of the cured adhesive sheet was "OK" but the result of the adhesion retention test of the initial adhesive sheet was "NG" was evaluated as "B (good)", and the case where the results of the adhesion retention tests of both the initial adhesive sheet and the cured adhesive sheet were "NG" was evaluated as "C (poor)". The results are shown in Table 1.

[0220]

[0221] As shown in Table 1, it was confirmed that the adhesive sheets of Examples 1 to 5 in which the adhesive layer was formed from the water-dispersible adhesive composition had good adhesion retention even in the method of providing the adhesive on the surface of the substrate on which black printing was performed by the direct method, as compared with the adhesive sheets of Comparative Examples 1 and 2 in which the adhesive layer was formed from the solvent-based adhesive composition. Among them, it was confirmed that the adhesive sheet of Example 1 having an adhesive layer crosslinked with a silanol-based crosslinking agent (silanol group-forming monomer) stably exhibited excellent adhesion retention.

[0222] As described above, specific examples of the present invention have been described in detail, but they are merely illustrative and do not limit the claims. The technology described in the claims includes the content obtained by various modifications and changes to the specific examples illustrated above.

Claims

1. An adhesive sheet comprising an adhesive layer and a supporting substrate, The adhesive layer is formed of a water-dispersible adhesive composition containing an acrylic polymer as a base polymer, The supporting substrate is in the shape of a sheet having a first surface and a second surface, and supports the adhesive layer at least on the first surface, wherein The substrate includes a colored layer constituting the first surface, and the colored layer includes ether polyurethane.

2. The adhesive sheet according to claim 1, wherein The acrylic polymer is at least one of the following: A polymer containing a monomer component of a silanol group-forming monomer, and crosslinked by a silanol group derived from the silanol group-forming monomer; and / or Use selected One or more of the oxazoline crosslinking agent, carbodiimide crosslinking agent, epoxy crosslinking agent and isocyanate crosslinking agent is crosslinked.

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

4. The adhesive sheet according to claim 1, wherein The substrate includes a first colored layer constituting the first surface and a second colored layer constituting the second surface. 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.

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