JP2024041041A - Double-sided adhesive sheet with release liner - Google Patents

Abstract

[Problem] To provide a double-sided adhesive pressure-sensitive adhesive sheet with a release liner that can highly suppress deformation of the adhesive surface caused by peeling off of the release liner. [Solution] A double-sided adhesive pressure-sensitive adhesive sheet with a release liner is provided, which comprises a double-sided adhesive sheet, a first release liner that protects the first adhesive surface of the double-sided adhesive sheet, and a second release liner that protects the second adhesive surface of the double-sided adhesive sheet. The double-sided adhesive pressure-sensitive adhesive sheet has a colored adhesive layer. The adhesive layer also contains an acrylic polymer. Furthermore, the peel force difference between the peel force R1 from the first adhesive surface of the first release liner and the peel force R2 from the second adhesive surface of the second release liner is 0.07 N/50 mm or more. The adhesive layer has a storage modulus of 0.95 MPa or less at 0°C. [Selected Figure] Figure 1

Description

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

In general, adhesives (also referred to as pressure-sensitive adhesives; hereinafter the same) exhibit a soft solid state (viscoelastic body) in a temperature range around room temperature, and have the property of easily adhering to adherends under pressure. Taking advantage of these properties, adhesives are used in various industrial fields, from mobile electronic devices such as smartphones and home appliances to automobiles and office automation equipment, to attach parts to parts, typically in the form of adhesive sheets containing an adhesive layer. It is widely used for purposes such as bonding and surface protection. Preferred examples of uses of such adhesive sheets include joining, fixing, and protecting members within electronic devices. In addition, for example, it can be used to prevent light leakage from light sources such as backlight modules of liquid crystal display devices in electronic devices and self-luminous elements such as organic EL (electroluminescence), to hide adherends, and to protect the appearance of adherends through adhesive sheets. Adhesive sheets having predetermined light-shielding and light-attenuating properties are used for the purpose of adjusting lighting, design, and the like. Patent Document 1 can be cited as a document related to this type of technology. Patent Documents 2 and 3 are prior art documents that disclose adhesives containing acrylic polymers polymerized using heptyl acrylate as a monomer component.

JP2020-37657A International Publication No. 2021/125247 International Publication No. 2021/125278

Adhesive sheets, which are used for the purpose of concealing, adjusting the appearance, and adding design to an adherend, achieve the purpose of concealment by covering the entire visible surface of the adherend. Since such pressure-sensitive adhesive sheets can be visually recognized from the outside, they are required to have good appearance quality. For example, in the display section of electronic devices, adhesive sheets used to hide metal components placed on the back side of organic EL panels, etc., can come into contact with the user's eyes when the display section is turned off, so the appearance It is required to cover the adherend with good quality.

By the way, double-sided adhesive sheets (also referred to as double-sided adhesive sheets) used for bonding various components of portable electronic devices, etc., are difficult to handle before being used (that is, before being affixed to an adherend). From these viewpoints, the product can be distributed, stored, and processed with each adhesive surface protected by two release liners. By protecting the adhesive surface with a release liner, the adhesive surface is kept smooth and adheres well to the surface of the adherend, allowing it to exhibit desired adhesive properties. Moreover, the adhesive sheet having the adhesive surface protected by a release liner and held smooth can be uniformly applied to an adherend and provide a good appearance when the adherend surface is visually recognized. .

A double-sided pressure-sensitive adhesive sheet with a release liner in which each adhesive surface is protected by two release liners is usually produced by peeling off the first release liner to expose one adhesive surface and then covering the adhesive surface. After being attached to an adherend, the second release liner is peeled off to expose the other adhesive surface, and the adhesive surface is attached to a different adherend to join the two adherends. do. For example, a double-sided adhesive sheet used to hide a metal member placed on the back side of an organic EL panel, etc., is attached to a metal member and a transparent member to bond the two while hiding the metal member from the visible side. do.

However, in the above-mentioned double-sided pressure-sensitive adhesive sheet with a release liner, if the difference in peeling force between the two release liners is small, when the first release liner is peeled off, the release liner on the opposite side will lift. , the smoothness of the opposite adhesive surface may be visibly impaired. In addition, on the side of the adhesive surface from which the release liner is peeled off, the adhesive surface is pulled by the release liner, causing deformation mainly in the thickness direction, such as waving or streak-like roughness on the adhesive surface. The deformation may remain and be visible even after being attached to the adherend. Such visible deformation of the adhesive surface does not disappear once it is affixed to an adherend and stabilized. In particular, adhesive sheets whose adhesive layers are colored, such as containing a coloring agent, tend to exhibit more contrast in deformation of the adhesive surface than transparent adhesive sheets, and changes in appearance due to deformation of the adhesive surface tend to be more noticeable. Furthermore, in recent years, there has been a trend toward higher appearance quality for the display parts of electronic devices, and it is expected that adhesive surfaces that suppress minute deformation at a level that was not considered a problem in the past will be required. Ru. The deformation of the adhesive surface that occurs when the release liner is peeled off as described above can depend on the peeling operator, peeling conditions, etc., and therefore is usually difficult to control to a high degree only by devising the release liner or designing the peeling force. If a colored double-sided pressure-sensitive adhesive sheet that highly suppresses deformation of the adhesive surface due to peeling of the release liner is realized, it will be possible to improve the appearance quality of the surface to which the double-sided pressure-sensitive adhesive sheet is applied, which is used for joining and fixing parts. is possible and useful.

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

According to this specification, a double-sided adhesive adhesive sheet, a first release liner that protects a first adhesive surface of the double-sided adhesive sheet, and a second release liner that protects a second adhesive surface of the double-sided adhesive sheet. A double-sided adhesive pressure-sensitive adhesive sheet with a release liner is provided. In the double-sided adhesive adhesive sheet with a release liner, the double-sided adhesive sheet has a colored adhesive layer. Further, the adhesive layer includes an acrylic polymer. Furthermore, a peeling force between a peeling force R ₁ [N/50mm] of the first release liner on the first adhesive surface and a peeling force R ₂ [N/50mm] of the second release liner on the second adhesive surface. The difference is 0.07 or more. The adhesive layer has a storage modulus of 0.95 MPa or less at 0°C.

The double-sided pressure-sensitive adhesive sheet with a release liner having the above structure is designed to have a difference in release force of 0.07 N/50 mm or more between the release force R ₁ of the first release liner and the release force R ₂ of the second release liner. Lifting is less likely to occur when the liner is peeled off, and the adhesive surface is less likely to be deformed (deformations such as waving or streaky roughness). Furthermore, since the storage modulus of the adhesive layer at 0°C is 0.95 MPa or less, even if the adhesive surface is deformed when the release liner is peeled off, such deformation is highly suppressed by the surface shape relaxing effect of the adhesive. obtain. Since the above-mentioned double-sided pressure-sensitive adhesive sheet has a colored pressure-sensitive adhesive layer, the deformation of the pressure-sensitive adhesive surface is likely to be noticeable. However, according to the structure including the pressure-sensitive adhesive layer having the above-mentioned 0°C storage modulus, the above-mentioned deformation is highly suppressed. Therefore, the adhesive surface has excellent appearance quality.

In some embodiments, the monomer component constituting the acrylic polymer includes an alkyl acrylate having a chain alkyl group having 4 to 8 carbon atoms. According to an acrylic polymer containing as a monomer component an alkyl acrylate having a chain alkyl group having 4 to 8 carbon atoms (C _4-8 alkyl acrylate), the 0°C storage modulus of the adhesive layer is moderately reduced. be able to. The technology disclosed herein is preferably implemented in an embodiment using an acrylic polymer containing C _4-8 alkyl acrylate as a monomer component.

In some preferred embodiments, the monomer component constituting the acrylic polymer includes heptyl acrylate. By using an acrylic polymer containing heptyl acrylate as a monomer component, it is easy to form a flexible adhesive whose 0° C. storage modulus is below a predetermined value, and it is easy to obtain a surface shape relaxing effect of the adhesive.

In some embodiments, the monomer component constituting the acrylic polymer includes n-butyl acrylate. According to the technology disclosed herein, it is possible to obtain a pressure-sensitive adhesive having a composition that uses an acrylic polymer containing n-butyl acrylate as a monomer component and has a 0°C storage modulus of not more than a predetermined value and has good surface shape relaxation properties. .

In some preferred embodiments, the adhesive layer includes a black colorant. When using a small amount of black colorant, light transmittance can be efficiently adjusted, and high covering properties can easily be obtained. The effect of the technology disclosed herein (high degree of suppression of deformation of the adhesive surface due to peeling of the release liner) can be effectively exhibited in a double-sided adhesive sheet having an adhesive layer containing a black colorant.

In some preferred embodiments, the adhesive layer includes a black colorant as a first colorant and a metal oxide as a second colorant. By using the above two types of colorants, it is possible to preferably achieve the desired design and color while adjusting the optical properties (light transmittance, etc.). The effects of the technology disclosed herein can be effectively exhibited in a double-sided pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer containing the above two types of colorants.

In some preferred embodiments, a release force R 1 [N/50mm] of the first release liner against the first adhesive surface is equal to a release force _{R 2 [} N/50mm] of the second release liner against the second adhesive surface. ] lower than. Further, a peeling force _R1 of the first release liner with respect to the first adhesive surface is 0.3 N/50 mm or less. In an embodiment in which the first release liner is peeled off first and used, by setting the peel force of the first release liner on the light release side to 0.3 N/50 mm or less, the adhesive surface will not be undulated when the first release liner is peeled off. Deformations such as streak-like roughness tend not to occur.

In some embodiments, the double-sided pressure-sensitive adhesive sheet is a base material-less pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer described above. Since the base material-less double-sided pressure-sensitive adhesive sheet does not have a base material, it can be made thinner, and can contribute to miniaturization and space saving of products to which the double-sided pressure-sensitive adhesive sheet is applied. Moreover, according to the base material-less double-sided pressure-sensitive adhesive sheet, the effects of the pressure-sensitive adhesive layer, such as adhesive strength, can be maximized. Further, the effects of the technology disclosed herein can be effectively exhibited on a base material-less double-sided pressure-sensitive adhesive sheet.

In some other embodiments, the double-sided pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet with a substrate, which includes the pressure-sensitive adhesive layer and a supporting substrate layer. Double-sided pressure-sensitive adhesive sheets with a substrate are advantageous in terms of processability and handling.

The double-sided pressure-sensitive adhesive sheet disclosed herein can be preferably used, for example, to bond members of electronic devices including home appliances, office automation equipment, and portable electronic devices such as smartphones. For example, electronic devices have parts that are visible to users and may be required to have excellent appearance quality. The double-sided adhesive sheet disclosed herein has highly suppressed deformation of the adhesive surface due to peeling of the release liner, and can have an adhesive surface with excellent appearance quality, so it is suitable for use in visible areas of electronic devices. can be applied to achieve surfaces of good appearance quality.

FIG. 1 is a cross-sectional view schematically showing a double-sided pressure-sensitive adhesive sheet with a release liner according to an embodiment. FIG. 3 is a cross-sectional view schematically showing the structure of a double-sided pressure-sensitive adhesive sheet with a release liner according to another embodiment. FIG. 2 is a cross-sectional view schematically showing an example of the structure of a laminate. FIG. 1 is an exploded perspective view schematically showing a configuration example of a display device.

Hereinafter, preferred embodiments of the present invention will be described. Matters other than those specifically mentioned in this specification that are necessary for carrying out the present invention are based on the teachings regarding carrying out the invention described in this specification and the common general knowledge at the time of filing. can be understood by those skilled in the art. The present invention can be implemented based on the content disclosed in this specification and the common general knowledge in the field. Furthermore, in the following drawings, members and portions that have the same function may be described with the same reference numerals, and overlapping descriptions may be omitted or simplified. Furthermore, the embodiments shown in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the double-sided pressure-sensitive adhesive sheet with a release liner of the present invention that is actually provided as a product. It's not something I did.

As mentioned above, the term "adhesive" as used herein refers to a material that exhibits a soft solid (viscoelastic) state in the temperature range around room temperature and has the property of easily adhering to an adherend under pressure. . The adhesive referred to here generally has a complex tensile modulus E ^* (1Hz) as defined in "CA Dahlquist, "Adhesion: Fundamentals and Practice", McLaren & Sons, (1966) P. 143". <10 ⁷ dyne/cm ² (typically, a material having the above properties at 25° C.).

In this specification, biomass-derived carbon means carbon derived from biomass materials, that is, materials derived from renewable organic resources (renewable carbon). The above-mentioned biomass materials are typically materials derived from biological resources (typically plants that perform photosynthesis) that can be reproduced sustainably in the presence of sunlight, water, and carbon dioxide. means. Therefore, materials derived from fossil resources that are depleted through use after mining (fossil resource-based materials) are excluded from the concept of biomass materials here. The biomass carbon ratio of the adhesive layer and the adhesive sheet, that is, the proportion of biomass-derived carbon in the total carbon contained in the adhesive layer and the adhesive sheet, is the carbon isotope content with a mass number of 14 measured in accordance with ASTM D6866. It can be estimated from the amount.

<Example of configuration of double-sided adhesive sheet with release liner>
The double-sided adhesive sheet with a release liner disclosed herein has a double-sided adhesive sheet with each adhesive surface protected by two release liners, and the first release liner, the double-sided adhesive sheet, and the second release liner are connected to each other. It has a laminated structure. Specifically, the double-sided adhesive sheet with a release liner includes a double-sided adhesive sheet, a first release liner that protects the first adhesive surface of the double-sided adhesive sheet, and a second release liner that protects the second adhesive surface of the double-sided adhesive sheet. and, including. The first release liner and the second release liner are releasably laminated on the first adhesive surface and the second adhesive surface of the double-sided adhesive sheet, respectively. Further, the double-sided adhesive sheet includes, for example, a first adhesive surface formed by one surface of an adhesive layer and a second adhesive surface formed by the other surface of the adhesive layer. It may be in the form of an adhesive sheet. Alternatively, the double-sided pressure-sensitive adhesive sheet may be in the form of a double-sided pressure-sensitive adhesive sheet with a base material, in which the pressure-sensitive adhesive layer is laminated on each side of a support base material. Hereinafter, the supporting base material may be simply referred to as "base material". Note that the concept of adhesive sheet here may include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. Note that the double-sided pressure-sensitive adhesive sheet with a release liner disclosed herein may be wound into a roll or may be sheet-like. Alternatively, it may be further processed into various shapes.

FIG. 1 schematically shows the structure of a double-sided pressure-sensitive adhesive sheet with a release liner according to one embodiment. This double-sided adhesive sheet 100 with a release liner includes a double-sided adhesive sheet 1 having a first adhesive surface 1A and a second adhesive surface 1B, a first release liner 31 laminated on the first adhesive surface 1A, and a second adhesive surface. 1B. The double-sided adhesive sheet 1 is a base material-less double-sided adhesive sheet consisting of an adhesive layer 21, and each surface 21A, 21B of the base material-less adhesive layer 21 is the first adhesive surface 1A, 21B of the double-sided adhesive sheet 1, respectively. It is also the second adhesive surface 1B. The adhesive layer 21 is colored. The first release liner 31 has a surface 31A on the first adhesive surface 1A side formed as a release surface, that is, a surface that can be peeled off from the first adhesive surface 1A. In the first release liner 31, the opposite surface (back surface) 31B to the surface 31A may be a release surface or a non-release surface. The second release liner 32 has a surface 32A on the second adhesive surface 1B side formed as a release surface, that is, a surface that can be peeled off from the second adhesive surface 1B. In the second release liner 32, the opposite surface (back surface) 32B to the surface 32A may be a release surface or a non-release surface.

FIG. 2 schematically shows the structure of a double-sided pressure-sensitive adhesive sheet with a release liner according to another embodiment. In this double-sided adhesive sheet 200 with a release liner, the double-sided adhesive sheet 2 includes a sheet-shaped support base material (for example, a resin film) 10 having a first surface 10A and a second surface 10B, and a fixed support material on the first surface 10A side. The double-sided pressure-sensitive adhesive sheet with a base material includes a first pressure-sensitive adhesive layer 21 provided on the second surface 10B and a second pressure-sensitive adhesive layer 22 fixedly provided on the second surface 10B. In this embodiment, both the first adhesive layer 21 and the second adhesive layer 22 are colored. As shown in FIG. 2, the surface 21A (first adhesive surface 1A) of the first adhesive layer 21 and the surface 22A (second adhesive surface 1B) of the second adhesive layer 22 have a first release liner 31 and a A second release liner 32 is laminated. Such a double-sided pressure-sensitive adhesive sheet with a base material is preferable because it has excellent processability, handling properties, and the like.

Note that both the first adhesive layer and the second adhesive layer may not be colored, and at least one of the first adhesive layer and the second adhesive layer may be configured as a colored adhesive layer. All you have to do is stay there.

The technology disclosed herein can be preferably implemented in a form provided with a base material-less double-sided pressure-sensitive adhesive sheet. Since the base material-less double-sided pressure-sensitive adhesive sheet does not have a supporting base material, it is easy to form a thin layer, and is also advantageous in that it can maximize adhesive properties such as adhesive strength and impact resistance. On the other hand, since double-sided pressure-sensitive adhesive sheets without a base material do not have a supporting base material, the adhesive surface tends to be lifted or rough when the release liner is removed. Therefore, deformation of the adhesive surface due to peeling of the release liner can be highly suppressed.

<Release force characteristics of release liner>
The double-sided adhesive sheet with a release liner disclosed herein has a peel force R ₁ [N/50 mm] of the first release liner on the first adhesive surface, and a peel force R ₂ [N/50 mm] of the second release liner on the second adhesive surface. /50mm] and the peeling force difference (|R ₂ −R ₁ |) is 0.07 or more. In this way, by designing the release liner so that the difference in release force between the first release liner and the second release liner is greater than or equal to a predetermined value, the release liner on the first light release side (for example, the first release liner) can be removed. Furthermore, the release liner on the opposite heavy release side (for example, the second release liner) is less likely to lift. In addition, the adhesive surface is less likely to be pulled by the release liner on the light release side, and the tension of the release liner may cause deformation of the adhesive surface in the thickness direction, such as waving or streak-like roughness. It becomes less likely to occur. According to the structure having the above-mentioned difference in release force, occurrence of phenomena such as deformation of the adhesive surface due to peeling of the above-mentioned release liner is suppressed.

The above-mentioned release force difference (|R ₂ −R ₁ |) is 0.09 or more from the viewpoint of preventing the release liner on the heavy release side from lifting and suppressing tension on the adhesive surface by the release liner on the light release side. It may be 0.11 or more, 0.13 or more, or 0.15 or more. The upper limit of the peeling force difference (|R ₂ −R ₁ |) is appropriately set depending on the purpose and mode of use, and is not limited to a specific range. From the viewpoint of the peeling workability of the release liner on the heavy release side, the adhesive surface protection property of the release liner, etc., in some embodiments, the above peeling force difference (|R ₂ - _{R 1} |) is 2.0 or less. It is appropriate to do so, preferably 1.0 or less, more preferably 0.5 or less, even more preferably less than 0.3, and may be less than 0.25 (for example, less than 0.20).

The double-sided pressure-sensitive adhesive sheet with a release liner disclosed herein is obtained by first peeling off a release liner with a relatively low release force (light-release side release liner) from the double-sided pressure-sensitive adhesive sheet, and pasting the exposed adhesive surface onto an adherend. After that, a release liner with a relatively high release force (heavy release liner) is peeled off from the double-sided pressure-sensitive adhesive sheet. Either of the first release liner and the second release liner may be on the light release side (in that case, the other will be on the heavy release side). Therefore, in the double-sided adhesive sheet with a release liner disclosed herein, the peeling force R ₁ [N/50 mm] of the first release liner with respect to the first adhesive surface and the peeling force R ₂ of the second release liner with respect to the second adhesive surface. The relationship with [N/50mm] may be R ₁ >R ₂ or R ₁ <R ₂ .

The peeling force R ₁ of the first release liner (the peeling force against the first adhesive side of the double-sided adhesive sheet) is appropriately set within a range that satisfies the above peeling force difference (|R ₂ - R ₁ |), and is within a specific range. but not limited to. In some embodiments, the peel force R ₁ is lower than the peel force R ₂ . In this embodiment, the first release liner is a light release liner and is peeled off from the double-sided pressure-sensitive adhesive sheet before the second release liner. In some preferred embodiments, the peeling force R ₁ is, for example, less than 0.50 N/50 mm, suitably 0.30 N/50 mm or less, more preferably 0.20 N/50 mm or less, It may be 0.15 N/50 mm or less, 0.12 N/50 mm or less, or 0.10 N/50 mm or less. By setting the peeling force _R1 low, the peeling workability tends to improve. Furthermore, by setting the release force of the first release liner on the light release side to be low, deformation such as waving or streak-like roughness tends to occur on the adhesive surface when the first release liner is peeled off. The first release liner exhibiting the above-mentioned release force _R1 is suitable as a release liner on the light release side. In some embodiments, the peeling force R ₁ may be, for example, 0.01 N/50 mm or more, 0.03 N/50 mm or more, 0.05 N/50 mm or more, or 0.07 N/50 mm or more ( For example, it may be 0.09 N/50 mm or more). By setting the above-mentioned release force _R1 to a predetermined value or more, for example, when processing a double-sided pressure-sensitive adhesive sheet with a release liner, the first release liner is unlikely to lift or peel off, and the first pressure-sensitive adhesive surface is It can be well protected by a release liner.

The peeling force R ₂ of the second release liner (the peeling force against the second adhesive surface of the double-sided adhesive sheet) is appropriately set within a range that satisfies the above peeling force difference (|R ₂ - R ₁ |), and is within a specific range. but not limited to. In some embodiments, the peel force _R2 is higher than the peel force _R1 . In this embodiment, the second release liner is a heavy release liner and is peeled off from the double-sided adhesive sheet after the first release liner is first peeled off from the double-sided adhesive sheet. In some preferred embodiments, the peeling force _R2 is, for example, less than 1.0 N/50 mm, suitably 0.50 N/50 mm or less, more preferably 0.30 N/50 mm or less, It may be 0.25 N/50 mm or less, or may be 0.20 N/50 mm or less. By setting the peeling force _R2 low, the peeling workability tends to improve. For example, after the first release liner is peeled off from the first adhesive surface and the exposed adhesive surface is affixed to the adherend, when the second release liner is peeled off from the second adhesive surface, good peelability is obtained. It tends to be easier to obtain. Further, it is preferable that the release force of the release liner on the heavy release side is not too high from the viewpoint of preventing deformation of the adhesive surface. In some embodiments, the peeling force R ₂ may be, for example, 0.10 N/50 mm or more, 0.15 N/50 mm or more, 0.20 N/50 mm or more, or 0.25 N/50 mm or more. good. By setting the above-mentioned release force _R2 to a predetermined value or more, it is easy to obtain a difference from the release force of the first release liner (peel force difference), and the second adhesive surface is well protected by the second release liner. obtain. The second release liner exhibiting the above-mentioned release force _R2 is suitable as a release liner on the heavy release side.

The release force of the release liner (the release force R ₁ of the first release liner and the release force R ₂ of the second release liner) depends on the type of release liner selected or the release liner type depending on the type of adhesive used. It can be adjusted by selecting the material and thickness of the base material, the type of release agent used for forming the release layer, the thickness and formation conditions of the release layer, and the like.

The peel force _R1 of the first release liner and the peel force _R2 of the second release liner were determined by preparing a double-sided adhesive sheet with a release liner cut into a length of 150 mm and a width of 50 mm, and under an atmosphere of 23°C and 50% RH. , a tensile speed of 300 mm/min, and a peeling angle of 180°. Specifically, it is measured by the method described in Examples below.

<Release liner>
The release liner (including the first release liner and the second release liner; the same applies hereinafter unless otherwise specified) is not particularly limited, and may be used within a range that satisfies the above release force difference (|R ₂ - R ₁ |). You can use any suitable one. Non-limiting examples of release liners that can be used include release liners having a release treatment layer on the surface of the release liner substrate; and fluorine-based polymers (such as polytetrafluoroethylene) and polyolefin-based resins (such as polyethylene and polypropylene). ); a release liner made of a low-adhesion resin;

As the release liner disclosed herein, one having a release treatment layer on a release liner base material can be preferably employed. The release treatment layer may be formed by surface treating a release liner base material with a release treatment agent. The release agent may be a known release agent such as a silicone release agent, a long chain alkyl release agent, a fluorine release agent, or molybdenum (IV) sulfide. In some embodiments, a release liner having a release layer formed of a silicone release agent may be preferably employed. The thickness and formation method of the release treatment layer are not particularly limited, and can be set so that appropriate release properties are exhibited on the adhesive side surface of the release liner.

Various plastic films can be used as the release liner base material. In this specification, a plastic film is typically a non-porous sheet, and is a concept that is distinguished from, for example, nonwoven fabric (that is, it does not include nonwoven fabric). As the release liner substrate, a resin film having a non-porous structure and typically substantially free of air bubbles (voidless) may preferably be used. The resin film may have a single layer structure or a multilayer structure of two or more layers (for example, a three layer structure).

Examples of materials for the plastic film include polyester resins such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymer. Polyolefin resins such as ethylene-butene copolymers, cellulose resins such as triacetylcellulose, acetate resins, polysulfone resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, norbornene resins Cyclic polyolefin resins such as resins, (meth)acrylic resins, polyvinyl chloride resins, polyvinylidene chloride resins, polystyrene resins, polyvinyl alcohol resins, ethylene-vinyl acetate copolymer resins, ethylene-vinyl alcohol copolymers Examples include coalescent resin, polyarylate resin, polyphenylene sulfide resin, and the like. A release liner base material formed from any one type or a mixture of two or more of these resins can be used. Among them, a preferred release liner base material is a polyester resin film (for example, a PET film) formed from a polyester resin.

The plastic film used as the above-mentioned release liner base material may be any of an unstretched film, a uniaxially stretched film, and a biaxially stretched film. Further, the plastic film may have a single layer structure or a multilayer structure including two or more sublayers. The above plastic film contains antioxidants, anti-aging agents, heat stabilizers, light stabilizers, ultraviolet absorbers, colorants such as pigments and dyes, lubricants, fillers, antistatic agents, slip agents, anti-blocking agents, Known additives that can be used in release liner base materials, such as nucleating agents, may be blended. In a plastic film with a multilayer structure, each additive may be blended in all sublayers, or may be blended only in some sublayers.

The thickness of the release liner is not particularly limited, and may be, for example, about 10 μm to 500 μm. From the viewpoint of strength and dimensional stability of the release liner, the thickness of the release liner is suitably 20 μm or more, preferably 30 μm or more, 40 μm or more, 50 μm or more, and even 60 μm or more. Generally, the thickness may be 70 μm or more. By protecting the adhesive surface with a release liner having sufficient thickness, the smoothness of the adhesive surface is easily maintained. In addition, from the viewpoint of handleability of the release liner (for example, ease of winding), the thickness of the release liner is suitably 300 μm or less, preferably 200 μm or less, and may be 150 μm or less. It may be 100 μm or less. By setting the thickness of the release liner to a predetermined value or less, removal from the double-sided pressure-sensitive adhesive sheet tends to be smooth.

The thickness of the first release liner and the second release liner may be the same or different. The ratio of the thickness t _{1 of the first release liner to the thickness t 2 of} the second release liner, ie, the thickness ratio (t ₁ /t ₂ ), can be, for example, about 0.3 to 10. In some embodiments, the thickness ratio (t ₁ /t ₂ ) may be about 0.5 to 5, or about 0.8 to 1.2. In some other embodiments, the ratio (t ₁ /t ₂ ) may be 0.3 or more and less than 1, 0.5 or more and less than 1, and 0.5 to 0.9. By using the first release liner and the second release liner having the above thickness ratio (t ₁ /t ₂ ), good release workability and handleability can be easily obtained.

<Adhesive layer>
In the double-sided pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer (in an embodiment including a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, at least one pressure-sensitive adhesive layer of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer). The same applies hereinafter unless otherwise specified) are colored. According to a double-sided adhesive sheet having a colored adhesive layer, it is possible to hide the adherend while bonding the adherend. Furthermore, by adjusting the degree of coloring of the adhesive layer, it is possible to adjust optical properties such as light transmittance, and to impart design and color to the surface of the adherend.

(Viscoelastic properties)
In the double-sided pressure-sensitive adhesive sheet disclosed herein, the pressure-sensitive adhesive layer is characterized by a storage modulus at 0°C (0°C storage modulus) of 0.95 MPa or less. By setting the 0° C. storage modulus of the adhesive layer to 0.95 MPa or less, deformation of the adhesive surface due to peeling of the release liner can be highly suppressed. More specifically, as described above, the difference in release force between the release force R ₁ of the first release liner and the release force R ₂ of the second release liner is designed to be 0.07 N/50 mm or more, so that the release In addition to suppressing the occurrence of phenomena in which the release liner is pulled by the adhesive surface and deformed in the thickness direction of the adhesive surface (waving, streak-like roughness, etc.) when the release liner is peeled off, the adhesive surface Even if a visible size deformation occurs, the deformation will be alleviated in a short time due to the surface shape relaxation effect of the adhesive based on the above 0°C storage modulus, and after being attached to the adherend. The above deformation does not exist or the above deformation is highly suppressed. In addition, in a double-sided adhesive sheet having a colored adhesive layer, the deformation of the adhesive surface is easily noticeable, but the deformation is highly suppressed on the adhesive surface of the adhesive layer having the above-mentioned 0°C storage modulus, so it is excellent. It has a good appearance quality.

In some embodiments, from the viewpoint of suppressing deformation of the adhesive surface, the 0° C. storage modulus is 0.85 MPa or less, may be 0.75 MPa or less, or may be 0.65 MPa or less. In some preferred embodiments, the 0°C storage modulus is 0.60 MPa or less, more preferably 0.50 MPa or less, even more preferably 0.40 MPa or less, particularly preferably 0.30 MPa or less, and 0. It may be 25 MPa or less, 0.22 MPa or less, 0.20 MPa or less, or 0.18 MPa or less. Further, from the viewpoint of improving the workability of the double-sided pressure-sensitive adhesive sheet, the 0° C. storage modulus may be approximately 0.01 MPa or more, and may be approximately 0.05 MPa or more in some embodiments. Further, in some preferred embodiments, the above-mentioned The 0°C storage modulus is approximately 0.10 MPa or more, more preferably 0.15 MPa or more, may be 0.20 MPa or more, or may be 0.24 MPa or more. In some other embodiments, the 0°C storage modulus may be 0.35 MPa or more, 0.45 MPa or more, or 0.55 MPa or more. The above 0°C storage modulus is specifically measured by the method described in Examples below.

Although not particularly limited, the storage modulus of the adhesive layer at 23°C (23°C storage modulus) is approximately 0.15 MPa in some embodiments from the viewpoint of adhesion to adherends, etc. or less, preferably 0.13 MPa or less, more preferably 0.12 MPa or less, even more preferably 0.11 MPa or less, and may be less than 0.10 MPa. By setting the storage modulus at 23° C. to a predetermined value or less, the adhesive layer comes into close contact with the smooth release surface of the release liner, so that even after the release liner is removed, the adhesive layer tends to remain smooth. Further, after being attached to an adherend, the adhesive layer adheres closely to the adherend, and tends to form a homogeneous adhesive interface without floating or bubbles. In some preferred embodiments, the 23°C storage modulus is 0.08 MPa or less, may be 0.07 MPa or less, may be 0.06 MPa or less, or may be 0.05 MPa or less. In some embodiments, the 23°C storage modulus is approximately 0.005 MPa or more, and may be approximately 0.01 MPa or more. In some preferred embodiments, the 23°C storage modulus is approximately 0.02 MPa or more, may be 0.03 MPa or more, may be 0.05 MPa or more, may be 0.06 MPa or more, and may be 0.07 MPa or more. It may be more than 0.08 MPa. As the 23° C. storage modulus increases, the cohesive force of the pressure-sensitive adhesive layer tends to improve, for example, processability improves, and having an appropriate cohesive force tends to improve adhesive reliability. The above 23°C storage modulus is specifically measured by the method described in Examples below.

(light transmittance)
The light transmittance of a colored adhesive layer varies depending on the purpose of use and the purpose of coloring, and is not limited to a specific range, but usually, a colored adhesive layer has a higher light transmittance than a transparent adhesive layer. It also has low light transmittance. For example, in some embodiments, the light transmittance at a wavelength of 550 nm (550 nm light transmittance, also referred to as visible light transmittance) of the adhesive layer is less than 80%, may be less than 70%, and may be less than 60%. It may be less than 50%, or less than 40%. A double-sided pressure-sensitive adhesive sheet whose visible light transmittance is reduced by coloring the pressure-sensitive adhesive layer is suitable for hiding an adherend, and can also be used to add design properties. It can also be used as a light-shielding adhesive sheet for purposes such as preventing light leakage. In some preferred embodiments, the 550 nm light transmittance of the adhesive layer is 30% or less, may be 20% or less, may be 15% or less, may be 10% or less, may be 8% or less, It may be 6% or less. The lower the visible light transmittance, the more excellent hiding power can be exhibited. When higher hiding power is required, the 550 nm light transmittance may be less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, or 0. It may be less than .5%. The lower limit of the 550 nm light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit, 0.1% or more, 1% or more, or 3% or more. Often, it may be 5% or more. In some embodiments, the 550 nm light transmittance may be 10% or more, more than 20%, or more than 30%. By having a certain degree of visible light transmittance, it is possible to appropriately hide the adherend, adjust the appearance of the adherend (for example, metal materials), and create a design or color that retains the texture of the adherend. can be granted. Further, an adhesive layer having appropriate light transmittance is preferable from the viewpoint of maintaining adhesive properties and productivity. The 550 nm light transmittance of the adhesive layer can be measured by the method described in Examples below.

Although not particularly limited, the light transmittance of the adhesive layer at a wavelength of 1380 nm (1380 nm light transmittance, also referred to as infrared transmittance) is less than 90%, may be less than 80%, and may be less than 70%. It may be less than 60%, less than 50%, or less than 40%. In some preferred embodiments, the 1380 nm light transmittance of the adhesive layer is 30% or less, may be 20% or less, may be 15% or less, may be 10% or less, may be 5% or less, It may be 3% or less. According to the pressure-sensitive adhesive layer with limited infrared transmittance, it is possible to block light in a wide wavelength range including infrared rays, and it is easy to obtain excellent light blocking properties. Further, for example, when used near an infrared sensor, by blocking infrared rays, it is possible to prevent a decrease in the operational accuracy of the sensor. The lower limit of the 1380 nm light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit, 0.1% or more, 1% or more, or 3% or more. Often, it may be 5% or more. In some embodiments, the 1380 nm light transmittance may be 10% or more, 30% or more, or 50% or more. The 1380 nm light transmittance of the adhesive layer can be measured by the method described in Examples below.

The relative relationship between the visible light transmittance and the infrared transmittance of the adhesive layer is not particularly limited. In some embodiments, the ratio (T _IR /T _VL ) of the infrared transmittance T _IR [%] and the visible light transmittance T _VL [%] of the adhesive layer is, for example, within a range of 0.1 to 10. It may be 5 or less, 3 or less, 0.5 or more, 1 or more (for example, more than 1), or 2 or more. By appropriately setting the ratio (T _IR /T _VL ) depending on the purpose of use of the double-sided pressure-sensitive adhesive sheet, the application location, etc., it is possible to achieve the intended adherend hiding properties and infrared shielding properties.

(acrylic polymer)
The adhesive layer constituting the double-sided adhesive sheet disclosed herein contains an acrylic polymer. The pressure-sensitive adhesive layer is typically a pressure-sensitive adhesive layer containing an acrylic polymer as a base polymer. Such an adhesive layer is also referred to as an acrylic adhesive layer. Note that the base polymer refers to the main component of a rubbery polymer (a polymer that exhibits rubber elasticity in a temperature range around room temperature) contained in the adhesive layer. Furthermore, in this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight, unless otherwise specified. Further, the following description regarding the adhesive and the components that can be included in the adhesive layer is also applicable to the adhesive composition used to form the adhesive (layer) unless otherwise specified.

In addition, as used herein, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule, as monomer units constituting the polymer. . Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule will also be referred to as an "acrylic monomer." Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomer units derived from acrylic monomers. In addition, in this specification, "(meth)acryloyl" refers comprehensively to acryloyl and methacryloyl. Similarly, "(meth)acrylate" comprehensively refers to acrylate and methacrylate, and "(meth)acrylic" comprehensively refers to acrylic and methacrylic.

As the acrylic polymer in the technology disclosed herein, for example, a polymer of a monomer raw material that contains an alkyl (meth)acrylate as a main monomer and may further contain a submonomer copolymerizable with the main monomer is preferable. Here, the main monomer refers to a component that accounts for more than 50% by weight of the monomer composition in the monomer raw material.

As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be suitably used.
CH ₂ =C(R ¹ )COOR ² (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. Further, R ² is a chain alkyl group having 1 to 20 carbon atoms. Hereinafter, such a range of the number of carbon atoms may be expressed as "C _1-20 ". From the viewpoint of the storage modulus of the adhesive, an alkyl (meth)acrylate in which R ² is a C _1-14 (for example, C _1-10 , typically C _4-8 ) chain alkyl group is used as the main monomer. It is appropriate to do so.

Specific examples of alkyl (meth)acrylates in which R ² is a C _1-20 chain alkyl group include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and isopropyl. (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, ) 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 ) 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, and the like. These alkyl (meth)acrylates can be used alone or in combination of two or more.

The proportion of alkyl (meth)acrylate in the monomer components constituting the acrylic polymer is typically more than 50% by weight, for example, it can be 70% by weight or more, it may be 85% by weight or more, and it can be 90% by weight or more. It may be more than 90% by weight (for example, more than 90% by weight), suitably more than 92% by weight, more than 94% by weight, and more than 95% by weight. The upper limit of the proportion of alkyl (meth)acrylate is not particularly limited, but it is preferably 99.5% by weight or less (for example, 99% by weight or less), or characteristics based on submonomers such as carboxy group-containing monomers (for example, aggregation). From the viewpoint of preferably exerting the force), the content may be 98% by weight or less (for example, less than 97% by weight). Alternatively, the acrylic polymer may be obtained by polymerizing substantially only alkyl (meth)acrylate.

In some embodiments, an alkyl acrylate in which R ¹ in the above formula (1) is a hydrogen atom and R ² is a C _4-8 chain alkyl group (hereinafter also simply referred to as a C _4-8 alkyl acrylate). ) is preferably used as the main monomer. By using an acrylic polymer containing C _4-8 alkyl acrylate as a monomer component, the 0°C storage modulus of the adhesive layer can be appropriately reduced. When C _4-8 alkyl acrylate is used as a monomer component, the proportion of C _4-8 alkyl acrylate contained in the monomer component is, for example, more than 50% by weight, preferably 70% by weight or more, and 90% by weight or more. It is more preferably 92% by weight or more, more preferably 92% by weight or more, and may be 94% by weight or more (for example, more than 95% by weight). The upper limit of the proportion of C _4-8 alkyl acrylate is not particularly limited, but it is preferably 99% by weight or less, for example, from the viewpoint of preferably exhibiting the characteristics (for example, cohesive force) based on the submonomer such as the carboxy group-containing monomer. It may be 98% by weight or less (for example, less than 97% by weight). One type of C _4-8 alkyl acrylate can be used alone or two or more types can be used in combination. Suitable examples of C _4-8 alkyl acrylates include n-butyl acrylate (BA), n-heptyl acrylate (n-HpA) and 2-ethylhexyl acrylate (2EHA).

In some embodiments, the monomer component constituting the acrylic polymer includes BA. The proportion of BA in the monomer components of the acrylic polymer is, for example, more than 50% by weight, preferably 70% by weight or more, more preferably 80% by weight or more, still more preferably 85% by weight or more, particularly preferably 90% by weight. or more (for example, more than 90% by weight), may be 92% by weight or more, may be 94% by weight or more, may be 95% by weight or more, or may be 96% by weight or more. When using an acrylic polymer containing BA as a main monomer component, it is easy to obtain a pressure-sensitive adhesive with good adhesion reliability to an adherend. Furthermore, by using a predetermined amount or more of BA as a monomer component, a colorant such as a black colorant (e.g. carbon black) can be well dispersed within the adhesive layer, while maintaining good adhesive properties such as adhesive strength. be able to. From the viewpoint of copolymerizing other copolymerizable monomers, the proportion of BA in the monomer component may be 99% by weight or less, or may be 97% by weight or less.

In some preferred embodiments, the monomer component that makes up the acrylic polymer includes heptyl acrylate. Acrylic polymers polymerized using monomer components containing heptyl acrylate have better flexibility than polymers of other alkyl acrylates such as n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA). The reason for this is not to be construed as particularly limiting, but polymers containing heptyl acrylate as a monomer unit have a low glass transition temperature and a relatively large space between the main chains within the adhesive. it is conceivable that. By using an acrylic polymer containing heptyl acrylate as a monomer component, it is easy to form an adhesive having a low storage modulus at 0° C., and it is easy to obtain an adhesive with good surface shape relaxation properties. Among heptyl acrylates, n-heptyl acrylate is preferred from the viewpoint of flexibility. Acrylic polymers synthesized containing n-heptyl acrylate as a monomer component are considered to have relatively long linear side chains, and therefore tend to have larger spaces between main chains.

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

In the embodiment in which heptyl acrylate is used as a monomer component, the acrylic polymer may be copolymerized with an alkyl (meth)acrylate other than heptyl acrylate. Examples of the alkyl (meth)acrylates other than heptyl acrylate include compounds represented by the above formula (1), and alkyl (meth)acrylates other than heptyl acrylate. Alkyl (meth)acrylates other than the above heptyl acrylate can be used alone or in combination of two or more.

In some embodiments, the proportion of heptyl acrylate in the total amount of alkyl (meth)acrylates contained in the monomer component is, for example, 50% by weight or more (specifically 50 to 100% by weight, for example, more than 50% by weight). It is preferably 70% by weight or more, more preferably 80% by weight or more, still more preferably 90% by weight or more, particularly preferably 95% by weight or more, may be 99% by weight or more, and may be 100% by weight. . By employing such a monomer composition, the effects of using heptyl acrylate can be effectively exhibited.

In some embodiments, the monomer component may include an alkyl (meth)acrylate having a biomass-derived alkyl group at an ester end (hereinafter also referred to as "biomass alkyl (meth)acrylate"). In recent years, environmental issues such as global warming have become more important, and it is desired to reduce the amount of fossil resource-based materials such as petroleum used. Under these circumstances, there is a need to reduce the amount of fossil resource-based materials used in the adhesive field as well. By using biomass alkyl (meth)acrylate, it is possible to suitably realize an acrylic pressure-sensitive adhesive that is designed to reduce dependence on fossil resource-based materials.

The biomass alkyl (meth)acrylate is not particularly limited, and is, for example, an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived (meth)acrylic acid. Examples of alkanols derived from biomass include biomass ethanol, alkanols derived from plant materials such as palm oil, palm kernel oil, coconut oil, and castor oil. When the biomass-derived alkanol has three or more carbon atoms, the alkanol may be linear or branched. In some embodiments, an ester of a biomass-derived alkanol and a non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate used in the synthesis of the acrylic polymer. In such a biomass alkyl (meth)acrylate, the greater the number of carbon atoms in the alkanol, the greater the number ratio of biomass-derived carbon to the total number of carbons contained in the biomass alkyl (meth)acrylate, that is, the biomass carbon ratio of the alkyl (meth)acrylate. becomes higher. Therefore, in the above-mentioned biomass alkyl (meth)acrylate, it is desirable that the alkyl group derived from biomass has a large number of carbon atoms in order to reduce dependence on fossil resource materials. On the other hand, if the number of carbon atoms in the alkyl group constituting the alkyl (meth)acrylate is too large, it tends to be difficult to obtain adhesive properties such as adhesive strength, and it also has a negative impact on productivity such as synthesis, ease of handling, and cost. It can be disadvantageous. In an embodiment in which an ester of biomass-derived alkanol and non-biomass-derived (meth)acrylic acid is used as the biomass alkyl (meth)acrylate, adhesive properties and reduced dependence on fossil resource materials (more specifically, It is desirable to use a material that is compatible with the above-mentioned alkyl (meth)acrylate biomass carbon ratio) in a well-balanced manner.

In some preferred embodiments, biomass-derived heptyl acrylate (biomass heptyl acrylate) is used as the heptyl acrylate. By using biomass heptyl acrylate, the effects of the technology disclosed herein can be achieved while reducing dependence on fossil resource materials. The biomass heptyl acrylate is an ester of a biomass-derived alkanol and a biomass-derived or non-biomass-derived acrylic acid. For example, an ester of a biomass-derived alkanol and a non-biomass-derived acrylic acid can be used. In such compounds, only the heptyl groups are derived from biomass. As the biomass-derived heptyl acrylate, it is preferable to use biomass-derived n-heptyl acrylate (biomass n-heptyl acrylate).

In some embodiments, the proportion of biomass alkyl (meth)acrylate (preferably biomass heptyl acrylate) in the monomer components of the acrylic polymer is, for example, 50% by weight or more (for example, more than 50% by weight), preferably 70% by weight or more, more preferably 80% by weight or more, further preferably 85% by weight or more, particularly preferably 90% by weight or more, may be 92% by weight or more, may be 94% by weight or more, and may be 96% by weight or more. good. Further, the proportion of biomass alkyl (meth)acrylate (preferably biomass heptyl acrylate) among the monomer components is less than 97% by weight, and in some embodiments may be 95% by weight or less, and may be 93% by weight or less. It may be 91% by weight or less.

Moreover, it is preferable that the monomer component of the acrylic polymer includes a carboxy group-containing monomer. Carboxy group-containing monomers can improve cohesive force based on their polarity. Further, when using a crosslinking agent such as an isocyanate type crosslinking agent or an epoxy type crosslinking agent, the carboxy group can serve as a crosslinking point of the acrylic polymer. By using a carboxyl group-containing monomer, it is easy to obtain an adhesive having an appropriate cohesive force. Further, by using a carboxyl group-containing monomer, better adhesion can be exhibited, for example, to adherends such as highly polar materials. Furthermore, by copolymerizing an appropriate amount of a carboxyl group-containing monomer, even when a black colorant such as carbon black is blended into the adhesive, the colorant can be easily dispersed in the layer and the adhesive properties can be improved. It can be maintained preferably.

Carboxy group-containing monomers include, for example, acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, crotonic acid, isocrotonic acid, and other ethylenically unsaturated monocarboxylic acids; maleic acid; acid, ethylenically unsaturated dicarboxylic acids such as itaconic acid and citraconic acid. Further, the carboxyl group-containing monomer may be a monomer having a metal salt (for example, an alkali metal salt) of a carboxyl group. Carboxy group-containing monomers can be used alone or in combination of two or more. Among these, preferred carboxy group-containing monomers include AA and MAA. AA is particularly preferred. When one or more carboxy group-containing monomers are used, the proportion of AA in the carboxy group-containing monomers is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. It is. In a particularly preferred embodiment, the carboxy group-containing monomer consists essentially of AA. AA has a combination of functions such as polarity based on its carboxyl group, role as a crosslinking point, and Tg (106°C), so in achieving well-balanced adhesive properties in the carboxyl group-containing monomer disclosed herein, AA is It is considered to be one of the most suitable monomer materials.

The proportion of the carboxyl group-containing monomer in the monomer component of the acrylic polymer is not particularly limited, and may be 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 2% by weight or more. It may be more than % by weight. In some preferred embodiments, the proportion of the carboxy group-containing monomer in the monomer component is more than 3% by weight (specifically more than 3.0% by weight), preferably 4.0% by weight or more, More preferably 4.5% by weight or more, still more preferably 5.0% by weight or more (for example, more than 5.0% by weight), particularly preferably 5.5% by weight or more, and 6.0% by weight or more. The content may be 6.5% by weight or more, or 7.0% by weight or more. By increasing the amount of the carboxyl group-containing monomer used, the cohesive force of the adhesive layer can be improved based on the action of the carboxyl group-containing monomer. Further, the amount of the carboxyl group-containing monomer is, for example, suitably 20% by weight or less of the monomer components, preferably 15% by weight or less, and more preferably 12% by weight or less. In some preferred embodiments, the amount of the carboxy group-containing monomer may be 10% by weight or less, 8% by weight or less, 6% by weight or less, or 5% by weight or less. By reducing the amount of the carboxy group-containing monomer (eg, AA) used, the 0°C storage modulus tends to decrease.

The acrylic polymer may be copolymerized with a functional group-containing monomer (any functional group-containing monomer) other than the carboxy group-containing monomer. Examples of optional functional group-containing monomers that can introduce functional groups that can serve as crosslinking base points into acrylic polymers or contribute to improving adhesive strength include hydroxyl group (OH group)-containing monomers (2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2- Hydroxyalkyl (meth)acrylates such as hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; polypropylene glycol mono(meth)acrylate, etc. ), acid anhydride group-containing monomers, amide group-containing monomers ((meth)acrylamide, N,N-dimethyl(meth)acrylamide, etc.), amino group-containing monomers (aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, etc.), epoxy group-containing monomers, cyano group-containing monomers, keto group-containing monomers, monomers with nitrogen atom-containing rings (N-vinyl-2-pyrrolidone, N-(meth)acryloylmorpholine, etc.), alkoxysilyl Examples include group-containing monomers, imide group-containing monomers, and the like. The above arbitrary functional group-containing monomers can be used alone or in combination of two or more.

When the monomer component constituting the acrylic polymer contains the above-mentioned optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component is not particularly limited. From the viewpoint of appropriately exhibiting the effect of using the optional functional group-containing monomer, the content of the optional functional group-containing monomer in the monomer component can be, for example, 0.1% by weight or more, and 0.5% by weight or more. It is appropriate that the amount is 1% by weight or more. For example, in an embodiment in which the monomer component of the acrylic polymer includes heptyl acrylate and a monomer containing a carboxyl group, from the viewpoint of making it easier to balance the adhesive performance in relation to these monomer components, optional functional group-containing monomers in the monomer component may be used. The content of is suitably 40% by weight or less, preferably 20% by weight or less, and may be 10% by weight or less (for example, 5% by weight or less). In some embodiments, the content of optional functional group-containing monomers in the monomer component is, for example, less than 3% by weight, may be less than 1% by weight, may be less than 0.5% by weight, and may be less than 0.3% by weight. % or less than 0.1% by weight. The technique disclosed herein can be preferably carried out in an embodiment in which the monomer component of the acrylic polymer does not substantially contain any functional group-containing monomer.

In addition, in this specification, when the monomer component does not substantially contain monomer A (for example, the above-mentioned optional functional group-containing monomer), it means that the monomer A is not used at least intentionally, and the monomer component is, for example, Unintentional inclusion of about 0.01% by weight or less is acceptable.

Furthermore, a hydroxyl group-containing monomer may be used as the optional functional group-containing monomer. In that case, the content of the hydroxyl group-containing monomer in the monomer components is suitably about 10% by weight or less (for example, 0.001 to 10% by weight), preferably about 5% by weight or less, more preferably about 5% by weight or less. It is 2% by weight or less. In some embodiments, the content of hydroxyl group-containing monomer in the monomer component may be less than 1% by weight, may be less than 0.5% by weight, may be less than 0.3% by weight, and may be less than 0.1% by weight. % or less than 0.01% by weight. The monomer component of the acrylic polymer may be substantially free of hydroxyl group-containing monomers. In the technology disclosed herein, desired characteristics and effects can be preferably achieved by limiting the amount of the hydroxyl group-containing monomer used or by using a monomer composition that does not use the hydroxyl group-containing monomer.

The ratio of the carboxy group-containing monomer to the total functional group-containing monomers (total functional group-containing monomers including the carboxy group-containing monomer) used as a copolymerization component of the acrylic polymer is determined by the effect of copolymerizing the carboxy group-containing monomer. From the viewpoint of achieving the desired performance, the content is suitably 30% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, particularly preferably 90% by weight or more, such as It may be 95% by weight or more, 97% by weight or more, 98% by weight or more, or 99% by weight or more (for example, 99.9% by weight or more). The upper limit of the proportion of the carboxy group-containing monomer to the total of the functional group-containing monomers is 100% by weight, and may be, for example, 95% by weight or less.

The monomer components constituting the acrylic polymer may contain copolymerization components other than the above-mentioned functional group-containing monomers for the purpose of improving cohesive force and the like. Examples of other copolymerization components include vinyl ester monomers such as vinyl acetate; aromatic vinyl compounds such as styrene; cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl ) acrylates; aryl (meth)acrylates (e.g. phenyl (meth)acrylate), aryloxyalkyl (meth)acrylates (e.g. phenoxyethyl (meth)acrylate), arylalkyl (meth)acrylates (e.g. benzyl (meth)acrylate), etc. Aromatic ring-containing (meth)acrylate; Olefinic monomer; Chlorine-containing monomer; Isocyanate group-containing monomer such as 2-(meth)acryloyloxyethyl isocyanate; Alkoxy such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate Group-containing monomers; vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether; and the like. The other copolymerization components mentioned above can be used alone or in combination of two or more.

The amount of such other copolymerized components is not particularly limited as long as it can be selected as appropriate depending on the purpose and use, but from the viewpoint of appropriately exhibiting the effects of use, it is appropriate to set it to 0.05% by weight or more. , 0.5% by weight or more. In addition, from the viewpoint of making it easier to balance the adhesive performance, it is appropriate that the content of other copolymer components in the monomer component is 20% by weight or less, so that the adhesive properties based on the essential monomer components can be suitably exhibited. From this point of view, it is preferably 10% by weight or less, more preferably 8% by weight or less, still more preferably less than 5% by weight, for example, it may be less than 3% by weight, and may be less than 1% by weight. The technology disclosed herein can also be preferably practiced in an embodiment in which the monomer component does not substantially contain other copolymer components.

Acrylic polymers are polyfunctional polymers that have at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth)acryloyl groups and vinyl groups as other monomer components. It may also contain monomers. By using a polyfunctional monomer as a monomer component, the cohesive force of the adhesive layer can be increased. Polyfunctional monomers can be used as crosslinking agents. The polyfunctional monomer is not particularly limited, and includes, for example, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and neopentyl glycol di(meth)acrylate. etc. One type of polyfunctional monomer can be used alone or two or more types can be used in combination.

The amount of the polyfunctional monomer to be used is not particularly limited, and can be appropriately set so that the intended use of the polyfunctional monomer is achieved. The amount of the polyfunctional monomer used can be about 3% by weight or less of the monomer components, preferably about 2% by weight or less, and more preferably about 1% by weight or less (for example, about 0.5% by weight or less). The lower limit of the amount used when using a polyfunctional monomer is not particularly limited, as long as it is greater than 0% by weight. Usually, the effect of using the polyfunctional monomer can be appropriately exhibited by setting the amount of the polyfunctional monomer to be approximately 0.001% by weight or more (for example, approximately 0.01% by weight or more) of the monomer components.

In a particularly preferred embodiment, the acrylic polymer is an acrylic polymer synthesized using a monomer component consisting essentially of heptyl acrylate (preferably n-heptyl acrylate) and a carboxy group-containing monomer (preferably acrylic acid). It will be done. According to the above monomer composition, the effects of heptyl acrylate and the carboxy group-containing monomer are effectively exhibited, and while obtaining good adhesive properties, it is possible to preferably achieve a 0°C storage modulus of not more than a predetermined value. From such a point of view, the total proportion of heptyl acrylate and the carboxyl group-containing monomer in the monomer components is suitably 90% by weight or more (90 to 100% by weight), preferably 95% by weight or more, more preferably 99% by weight or more. % by weight or more, more preferably more than 99.5% by weight, particularly preferably more than 99.9% by weight (for example, more than 99.99% by weight), and the total proportion of heptyl acrylate and the carboxy group-containing monomer in the monomer components may be 100% by weight.

The biomass carbon ratio of the monomer component constituting the acrylic polymer (biomass carbon ratio of the acrylic polymer) may be, for example, 1% or more, suitably 10% or more, preferably 30% or more, and more preferably is 50% or more (for example, more than 50%), may be 70% or more, may be 80% or more, or may be 90% to 100%. By designing in this way, an acrylic pressure-sensitive adhesive can be obtained that takes into account the suppression of dependence on fossil resource materials.

Although not particularly limited, the copolymer composition of the acrylic polymer is designed such that the glass transition temperature (Tg) of the polymer is approximately -15°C or lower (for example, approximately -70°C or more and -15°C or less). It is appropriate that Here, the Tg of the acrylic polymer refers to the Tg determined by the Fox equation based on the composition of monomer components used in the synthesis of the polymer. The Fox equation, as shown below, is a relational equation between Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer.
1/Tg=Σ(Wi/Tgi)
In the above Fox equation, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the weight fraction of monomer i in the copolymer. Represents the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer used to calculate Tg, the numerical value described in publicly known materials, specifically "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. . For monomers for which multiple types of values are described in this document, the highest value is adopted. If it is not described in the above Polymer Handbook, the value obtained by the measurement method described in JP-A No. 2007-51271 shall be used.

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

The method for obtaining the acrylic polymer is not particularly limited, and various polymerization methods known as methods for synthesizing acrylic polymers such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, and photopolymerization may be used. may be adopted as appropriate. For example, a solution polymerization method can be preferably employed. As a monomer supply method when performing solution polymerization, a batch charging method in which all monomer raw materials are supplied at once, a continuous supply (dropping) method, a divided supply (dropping) method, etc. can be appropriately adopted. The polymerization temperature can be selected as appropriate depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and is, for example, about 20°C to 170°C (typically about 40°C to 140°C). I can do it.

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

The initiator used for polymerization can be appropriately selected from conventionally known polymerization initiators depending on the type of polymerization method. For example, one or more azo polymerization initiators such as 2,2'-azobisisobutyronitrile (AIBN) can be preferably used. Other examples of polymerization initiators include persulfates such as potassium persulfate; peroxide initiators such as benzoyl peroxide (BPO) and hydrogen peroxide; substituted ethane initiators such as phenyl-substituted ethane; aromatic carbonyl compounds; and the like. Still another example of the polymerization initiator is a redox initiator using a combination of a peroxide and a reducing agent. Such polymerization initiators can be used alone or in combination of two or more. The amount of the polymerization initiator used may be any normal amount, for example, approximately 0.005 to 1 part by weight (typically approximately 0.01 to 1 part by weight) per 100 parts by weight of all monomer components. degree).

The weight average molecular weight (Mw) of the acrylic polymer is not particularly limited, and an acrylic polymer having an appropriate Mw that can realize the above-mentioned 0° C. storage modulus characteristics is used. For example, the Mw of the acrylic polymer can range from approximately 10×10 ⁴ to 500×10 ⁴ . From the viewpoint of adhesive performance, the Mw of the base polymer may be about 20×10 ⁴ or more, about 30×10 ⁴ or more, about 40×10 ⁴ or more, or about 50×10 ⁴ or more. In some embodiments, the Mw of the acrylic polymer may be greater than 600,000, greater than 650,000, suitably greater than 700,000, and may be greater than 750,000. There is a tendency that the larger the Mw of the acrylic polymer, the easier it is to obtain a pressure-sensitive adhesive exhibiting good cohesive force. In some preferred embodiments, the Mw of the acrylic polymer is 800,000 or more, may be 850,000 or more, may be 900,000 or more, may be 1 million or more (for example, more than 1 million), or may be 1.2 million or more. Often, it may be 1.4 million or more, 1.5 million or more, or 1.6 million or more. For example, according to a monomer composition containing heptyl acrylate, the viscosity can be easily maintained at a low level, so that synthesis of a high molecular weight product is good, and an acrylic polymer having the above Mw can be easily obtained. In addition, by using an acrylic polymer that contains heptyl acrylate as a monomer unit and has an Mw greater than a predetermined value, it is possible to improve the viscoelastic properties based on the chemical structure of the polymer (specifically, the storage modulus at 0°C) and the molecular weight. Based on the cohesive force based on this, it is possible to preferably achieve both the surface shape relaxation effect of the adhesive surface and the adhesive properties. On the other hand, from the viewpoint of adhesive properties such as adhesive strength, ease of synthesis, etc., the Mw of the acrylic polymer is usually approximately 3 million or less, preferably 2.5 million or less, and more preferably 2 million or less. , more preferably 1.8 million or less, may be 1.5 million or less, or may be 1.3 million or less. In some preferred embodiments, the Mw of the acrylic polymer may be 1.1 million or less, 1 million or less, 950,000 or less, or 900,000 or less.

The Mw of the acrylic polymer can be measured by gel permeation chromatography (GPC) and determined as a value in terms of standard polystyrene. Specifically, it can be determined by measuring under the following conditions using a GPC measurement device with the trade name "HLC-8220GPC" (manufactured by Tosoh Corporation). The same applies to the embodiments described later.
[GPC measurement conditions]
Sample concentration: 0.2% by weight (tetrahydrofuran solution)
Sample injection volume: 10μL
Eluent: Tetrahydrofuran (THF)
Flow rate (flow rate): 0.6 mL/min Column temperature (measurement temperature): 40°C
column:
Sample column: 1 product name “TSKguardcolumn SuperHZ-H” + 2 product name “TSKgel SuperHZM-H” (manufactured by Tosoh Corporation)
Reference column: 1 piece of product name “TSKgel SuperH-RC” (manufactured by Tosoh Corporation)
Detector: Differential refractometer (RI)
Standard sample: polystyrene

(colorant)
In the technology disclosed herein, the colored adhesive layer typically contains a colorant. By using a colorant, the adhesive layer is colored and can have desired optical properties (light transmittance, etc.), hiding properties, design properties, and color. The colorant may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent, or the like. The above-mentioned coloring agent may be contained in the adhesive layer, typically in a dispersed state (or may be in a dissolved state) in the constituent material of the adhesive layer. As the colorant, conventionally known pigments and dyes can be used. Examples of pigments include inorganic pigments and organic pigments. One type of colorant can be used alone or two or more types can be used in combination. Note that when the double-sided pressure-sensitive adhesive sheet disclosed herein includes a non-colored pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer does not substantially contain a colorant.

The colorant is not particularly limited, and is, for example, a component that can absorb and attenuate light traveling through the adhesive layer.By incorporating the colorant in the adhesive layer, the light transmittance of the adhesive layer can be increased. (therefore also referred to as a "light transmittance reducing component"). As such a coloring agent (hereinafter also referred to as "first coloring agent"), a black coloring agent can be preferably used because it is possible to efficiently adjust hiding properties and light blocking properties by using a small amount. Specific examples of the black colorant include carbon black, graphite, aniline black, perylene black, cyanine black, titanium black, inorganic pigment hematite, activated carbon, molybdenum disulfide, chromium complex, anthraquinone colorant, and the like. The black coloring agent can be used alone or in an appropriate combination of two or more.

In some preferred embodiments, the adhesive layer contains carbon black particles as a colorant (first colorant). As the carbon black particles used, those generally referred to as carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.) can be used without particular limitation. It is also possible to use surface-modified carbon black particles having functional groups such as carboxyl groups, amino groups, sulfonic acid groups, and silicon-containing groups (eg, alkoxysilyl groups, alkylsilyl groups) as carbon black particles. Such surface-modified carbon black particles are also referred to as self-dispersing carbon black, and it is not necessary to add a dispersant or the amount added can be reduced. The above carbon black particles can be used alone or in combination of two or more.

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

In addition, the average particle size of the colorant in this specification refers to the volume average particle size, and specifically, the integrated value of 50% in the particle size distribution measured based on a particle size distribution measuring device based on a laser scattering/diffraction method. refers to the particle size (50% volume average particle size; hereinafter sometimes abbreviated as _D50 ). As the measuring device, for example, the product name "Microtrac MT3000II" manufactured by Microtrac Bell Co., Ltd. or its equivalent product can be used.

In the technology disclosed herein, the form in which the colorant (preferably a black colorant such as carbon black particles) is added to the adhesive composition is not particularly limited. A colorant such as carbon black particles may be added to the adhesive composition in the form of a dispersion in which the particles are dispersed in a dispersion medium. The dispersion medium constituting the dispersion liquid is not particularly limited, and may include water (ion exchange water, reverse osmosis water, distilled water, etc.), various organic solvents (alcohols such as ethanol; ketones such as acetone; butyl cellosolve, propylene glycol monomethyl). Examples include ethers such as ether acetate; esters such as ethyl acetate; aromatic hydrocarbons such as toluene; mixed solvents thereof), and aqueous mixed solvents of water and the above organic solvents. The above-mentioned dispersion liquid may contain the above-mentioned dispersant. By mixing the dispersion into a pressure-sensitive adhesive composition, the pressure-sensitive adhesive composition contains a colorant (preferably a black colorant such as carbon black particles) and may also contain a dispersant.

In an embodiment in which the adhesive layer contains the first colorant, the content of the first colorant (preferably a black colorant such as carbon black particles) is determined based on the adherend hiding ability and optical properties (light transmittance, etc.). It is appropriately set in consideration of adjustment, required adhesive properties, etc., and is not limited to a specific range. Further, the content of the first colorant may vary depending on the type of adhesive, the shape and particle size of the first colorant, compatibility with the adhesive, and the like. The content of the first colorant in the adhesive layer is suitably approximately 0.01% by weight or more, may be 0.05% by weight or more, may be 0.1% by weight or more, and From the viewpoint of concealing properties, the content is preferably about 0.3% by weight or more, more preferably about 0.5% by weight or more. In some embodiments, the content of the first colorant is suitably about 1% by weight or more (eg, more than 1% by weight), preferably about 2% by weight or more. Further, in an embodiment in which the adhesive layer contains the first colorant or in an embodiment in which the adhesive layer does not contain the first colorant, the content of the first colorant (preferably a black colorant such as carbon black particles) is approximately 30% by weight. % or less, suitably about 20% by weight or less, preferably about 10% by weight or less, more preferably about 7% by weight or less, still more preferably about 5% by weight or less, and about 3% by weight. The following may be sufficient. In some embodiments, the content of the first colorant (preferably a black colorant such as carbon black particles) may be about 2% by weight or less, about 1% by weight or less, or about 0% by weight. The content may be .5% by weight or less (for example, 0.3% by weight or less). By limiting the content of the first colorant, adhesive properties such as adhesive strength tend to be easily maintained.

In some other embodiments, the adhesive layer may be implemented in embodiments that include a second colorant as described below (eg, a metal oxide as described below) as a colorant. A second colorant is defined as a different colorant than the first colorant. For example, when the adhesive layer includes at least two types of colorants, at least one of the plurality of colorants used is the above-mentioned first colorant, and the other one of the colorants is described below. It is a second coloring agent, and the first coloring agent and the second coloring agent are used together. In some other embodiments, the adhesive layer may include a second colorant and be substantially free of the first colorant described above.

The second colorant is not particularly limited, but for example, like the first adhesive, it may be a component that reduces the light transmittance of the adhesive layer, and may also be a component that reduces the amount of light incident into the adhesive layer. It may also be a component that can reduce the Further, the second colorant may be a component that imparts a different color or hue from the first colorant. Such a second colorant may be selected from, for example, a white colorant or a gray colorant. The second colorant may be one or more selected from inorganic materials (eg, metals, metal compounds), organic materials, and organic-inorganic composites. Specific examples of the second colorant include titanium oxide (rutile titanium dioxide, anatase titanium dioxide, etc.), zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, Metal oxides such as tin, barium oxide, cesium oxide, yttrium oxide; carbonate compounds such as magnesium carbonate, calcium carbonate (light calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate; aluminum hydroxide, calcium hydroxide , hydroxides such as magnesium hydroxide, zinc hydroxide; silicate compounds such as aluminum silicate, magnesium silicate, calcium silicate; barium sulfate, calcium sulfate, barium stearate, zinc white, zinc sulfide, talc, clay, kaolin, phosphoric acid Inorganic materials such as titanium, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, hydrated halloysite, etc., acrylic resin, polystyrene resin, polyurethane resin, amide resin, polycarbonate resin, Examples include organic materials such as silicone resins, urea-formalin resins, and melamine resins. Note that the second colorant does not include carbon black particles and may be defined as a colorant different from carbon black particles. Typically, the second colorant does not include a light absorbing black colorant.

In some preferred embodiments, the adhesive layer includes a metal oxide as a second colorant. By using the first colorant (preferably a black colorant) and a metal oxide together, it is possible to obtain a hue that cannot be obtained by using only one type of colorant, while adjusting optical properties such as light transmittance. can. Furthermore, it is also possible to improve the ability to hide the adherend. The metal oxide can be selected from the materials mentioned above. Suitable examples include titanium oxide, zinc oxide, cerium oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, and calcium oxide. Among them, titanium oxide, silicon oxide, and zirconium oxide are preferred, and titanium oxide is particularly preferred. preferable. One kind of metal oxide can be used alone or two or more kinds can be used in combination.

In an embodiment in which the second colorant has a particle shape, the average particle size of the second colorant (for example, a white colorant, preferably metal oxide particles) is not particularly limited. Depending on the thickness of the adhesive layer, the type of adhesive, etc., particles of an appropriate size that can achieve desired optical properties (light transmittance, etc.) can be used. The average particle size of the second colorant can be, for example, about 1 nm or more, and suitably about 5 nm or more. From the viewpoints of compatibility, handleability, etc., the average particle size of the second colorant is preferably about 10 nm or more, about 20 nm or more, or about 30 nm or more. From the viewpoint of maintaining adhesive properties, the upper limit of the average particle diameter is, for example, approximately 300 nm or less, preferably less than 100 nm (for example, 90 nm or less), more preferably approximately 70 nm or less, and still more preferably approximately 50 nm or less. , approximately 35 nm or less (for example, approximately 25 nm or less).

In an embodiment in which the adhesive layer contains a second colorant, the content of the second colorant (for example, a white colorant, preferably a metal oxide) in the adhesive layer is determined by the effect of containing the second colorant; It is appropriately set in consideration of the required adhesive properties, etc., and is not limited to a specific range. Further, the content of the second colorant may vary depending on the type of adhesive, the shape and particle size of the second colorant, compatibility with the adhesive, and the like. The content of the second colorant in the adhesive layer is suitably about 1% by weight or more, preferably about 2% by weight or more, more preferably about 2% by weight or more, from the viewpoint of effectively obtaining the effect of containing the second colorant. It is 3% by weight or more, may be about 4% by weight or more, and may be about 5% by weight or more. In addition, in embodiments in which the adhesive layer contains the second colorant or in embodiments in which it does not contain the second colorant, the content of the second colorant in the adhesive layer depends on its compatibility with the adhesive component, adhesive strength, and durability. From the viewpoint of maintaining adhesive properties such as impact resistance, it can be about 30% by weight or less, suitably about 25% by weight or less, may be about 20% by weight or less, and even about 15% by weight or less. Generally, it may be about 12% by weight or less, about 10% by weight or less, or about 8% by weight or less.

In an embodiment in which the adhesive layer includes a first colorant and a second colorant, the ratio of the amount C1 of the first colorant to the amount C2 of the second colorant depends on the intended adherend hiding property and the optical It is appropriately set to achieve adjustment of characteristics (light transmittance, etc.), design, and color, and is not limited to a specific range. In some embodiments, the weight ratio (C2/ C1) is approximately 0.01 or more, suitably 0.1 or more, preferably 1 or more (for example, more than 1), may be 10 or more, may be 30 or more, and is 50 or more (for example, 70 or more). But that's fine. The larger the weight ratio (C2/C1) is, the more preferably the effect of adding the second colorant is exhibited. In some embodiments, the weight ratio (C2/C1) is approximately 1000 or less, suitably 500 or less, preferably 300 or less, may be 100 or less, may be 80 or less, It may be 60 or less. The smaller the weight ratio (C2/C1) is, the better the effect of adding the first colorant is exhibited. In an embodiment in which the first colorant is a black colorant, there is a tendency for the covering property to be improved.

In an embodiment in which the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant, the content of colorants other than the black colorant and the metal oxide is not particularly limited. , for example, less than 30% by weight of the entire adhesive layer, preferably less than 10% by weight, for example, may be less than 5.0% by weight, and less than 3.0% by weight (for example, 2.0% by weight) or even less than 1% by weight). The technology disclosed herein can be implemented in an embodiment that includes an adhesive layer that does not substantially contain a black colorant and a colorant other than a metal oxide. In this specification, "substantially not contained" means not intentionally added, and for example, the content in the adhesive layer is 0.3% by weight or less (for example, 0.1% by weight or less, (typically 0.01% by weight or less).

Note that, from the viewpoint of compatibility with the adhesive component, the colorant may be one obtained by surface-treating the material (particulate colorant) exemplified as the above-mentioned colorant with a surface treatment agent. As the surface treatment, an appropriate treatment can be selected depending on the type of core particles, the type of dispersion medium, etc., so it is not limited to a specific treatment.

The adhesive composition disclosed herein may contain a component that contributes to improving the dispersibility of the colorant. Such dispersibility-enhancing components can be, for example, polymers, oligomers, liquid resins, surfactants (anionic, cationic, nonionic, amphoteric surfactants), and the like. The dispersibility improving components can be used alone or in combination of two or more. It is preferable that the dispersibility improving component is dissolved in the adhesive composition. The oligomer is, for example, a low molecular weight polymer of a monomer component containing one or more of the acrylic monomers exemplified above (for example, Mw is less than about 10 x 10 ⁴ , preferably less than 5 x 10 ⁴ acrylic oligomers). The liquid resin may be, for example, a tackifying resin (typically a rosin-based, terpene-based, or hydrocarbon-based tackifying resin, such as a hydrogenated rosin) having a softening point of approximately 50°C or lower, more preferably approximately 40°C or lower. methyl ester, etc.). Such a dispersibility improving component can suppress uneven dispersion of a colorant (for example, a particulate black colorant such as carbon black) and, in turn, suppress uneven coloring of the adhesive layer. Therefore, it is possible to form an adhesive layer with better appearance quality.

The form of addition of the dispersibility improving component is not particularly limited, and it may be included in a liquid containing a colorant (for example, a black colorant such as carbon black particles) before being added to the adhesive composition, or it may be added to the adhesive composition. It may be supplied into the product at the same time as the colorant, or before or after the addition of the colorant.

The content of the dispersibility-improving component is not particularly limited, and from the viewpoint of suppressing the influence on adhesive properties (for example, a decrease in cohesiveness), the content of the dispersibility-improving component is about 20% by weight or less (preferably about 10% by weight or less, more preferably about 10% by weight or less) of the entire adhesive layer. The content is preferably 7% by weight or less, for example approximately 5% by weight or less). In some embodiments, the content of the dispersibility-enhancing component can be about 10 times or less (preferably about 5 times or less, for example about 3 times or less) the weight of the colorant. On the other hand, from the viewpoint of suitably exhibiting the effect of the dispersibility improving component, its content should be approximately 0.2% by weight or more (typically approximately 0.5% by weight or more, preferably approximately 1% by weight) based on the entire adhesive layer. % by weight or more). In some embodiments, the content of the dispersibility improving component can be about 0.2 times or more (preferably about 0.5 times or more, for example, 1 time or more) the weight of the colorant.

The content of the colorant in the adhesive layer (if two or more types of colorants are included, the total amount of the two or more types, the total content) depends on the intended adherend hiding ability, optical properties (light transmittance, etc.), It is appropriately set in consideration of design, color, etc., required adhesive properties, etc., and is not limited to a specific range. The content of the colorant in the pressure-sensitive adhesive layer is approximately 0.1% by weight or more, suitably approximately 0.5% by weight or more, and preferably approximately 1% by weight or more from the viewpoint of hiding the adherend. , more preferably about 1.5% by weight or more, still more preferably about 2% by weight or more. In some embodiments, the content of the colorant in the adhesive layer is suitably about 3% by weight or more, may be about 5% by weight or more, or may be about 7% by weight or more. The content of the colorant in the adhesive layer can be approximately 30% by weight or less from the viewpoint of compatibility with the adhesive component and maintenance of adhesive properties such as adhesive strength and impact resistance, and is usually approximately 30% by weight or less. Appropriately it is 20% by weight or less, it may be about 15% by weight or less, it may be about 10% by weight or less, it may be about 8% by weight or less, it may be about 6% by weight or less, it may be about 4% by weight or less. good.

(tackifying resin)
In some preferred embodiments, the adhesive layer includes a tackifying resin. Adhesive strength can be improved by using a tackifying resin. According to the technology disclosed herein, an adhesive layer having a predetermined viscoelastic property (specifically, 0° C. storage modulus) can be realized with a composition containing a tackifying resin. The tackifier resin is not particularly limited and includes, for example, rosin-based tackifier resin, terpene-based tackifier resin, hydrocarbon-based tackifier resin, epoxy-based tackifier resin, polyamide-based tackifier resin, elastomer-based tackifier resin, Various tackifying resins such as phenolic tackifying resins and ketone tackifying resins can be used. Such tackifying resins can be used alone or in combination of two or more.

Specific examples of rosin-based tackifying resins include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; Hydrogenated rosin, disproportionated rosin, polymerized rosin, other chemically modified rosin, etc. (the same applies hereinafter); and other various rosin derivatives. Examples of the above-mentioned rosin derivatives include rosins such as those obtained by esterifying unmodified rosin with alcohols (i.e., esterified products of rosin), and those obtained by esterifying modified rosin with alcohols (i.e., esterified products of modified rosin). Esters: Unsaturated fatty acid-modified rosins, which are unmodified rosin or modified rosin modified with unsaturated fatty acids; Unsaturated fatty acid-modified rosin esters, which are rosin esters modified with unsaturated fatty acids; Unmodified rosin, modified rosin, unsaturated Rosin alcohols obtained by reducing the carboxyl group in fatty acid-modified rosins or unsaturated fatty acid-modified rosin esters; metal salts of rosins (especially rosin esters) such as unmodified rosin, modified rosin, and various rosin derivatives; rosins; Examples include rosin phenol resins obtained by adding phenol to (unmodified rosin, modified rosin, various rosin derivatives, etc.) with an acid catalyst and thermally polymerizing them. Among these, rosin ester is preferred.

Although not particularly limited, specific examples of rosin esters include esters of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.), such as methyl ester, triethylene glycol ester, glycerin ester. , pentaerythritol ester and the like.

Examples of terpene-based tackifying resins include terpene resins such as α-pinene polymer, β-pinene polymer, and dipentene polymer; modified terpene resins; and the like. An example of the above-mentioned modified terpene resin is terpene phenol resin.

Terpene phenol resin refers to a polymer containing terpene residues and phenol residues, and includes copolymers of terpenes and phenol compounds (terpene-phenol copolymer resins), and homopolymers or copolymers of terpenes. This concept includes both phenol-modified products (phenol-modified terpene resins). Specific examples of terpenes constituting such terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-form, l-form, and d/l-form (dipentene)); can be mentioned. The hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. Sometimes called hydrogenated terpene phenolic resin.

Examples of hydrocarbon-based tackifying resins include aliphatic (C5-based) petroleum resins, aromatic (C9-based) petroleum resins, aliphatic/aromatic copolymerized (C5/C9-based) petroleum resins, and Hydrogenated substances (e.g., alicyclic petroleum resins obtained by hydrogenating aromatic petroleum resins), various modified products thereof (e.g., maleic anhydride modified products), coumaron-based resins, coumaron-indene-based resins Examples include various hydrocarbon resins such as.

In some embodiments, it is preferable to use at least one selected from rosin-based tackifying resins and terpene-based tackifying resins as the tackifying resin. By incorporating a rosin-based tackifying resin and/or a terpene-based tackifying resin into an acrylic adhesive, excellent adhesive properties such as adhesive strength can be easily obtained. In some preferred embodiments, the total proportion of the rosin-based tackifying resin and the terpene-based tackifying resin in the entire tackifying resin contained in the adhesive layer is, for example, approximately more than 50% by weight (more than 50% by weight and not more than 100% by weight). ), and may be about 70% by weight or more, about 80% by weight or more, about 90% by weight or more, about 95% by weight or more, or about 99% by weight or more.

Some preferred embodiments include embodiments in which the tackifying resin contains one or more terpene phenol resins. The technology disclosed herein can be preferably implemented, for example, in an embodiment in which about 25% by weight or more (more preferably about 30% by weight or more) of the total amount of tackifying resin is a terpene phenol resin. The proportion of the terpene phenol resin in the total amount of tackifying resin may be approximately 50% by weight or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more. Substantially all of the tackifying resin (for example, about 95% to 100% by weight, and even about 99% to 100% by weight) may be a terpene phenol resin.

The content of the terpene phenol resin in the adhesive layer is not particularly limited as long as it satisfies the desired viscoelastic properties. In some embodiments, the content of the terpene phenol resin is usually about 1 part by weight or more, and suitably about 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength. The amount is preferably about 8 parts by weight or more, more preferably about 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). In some embodiments, the content of the terpene phenol resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, and may be 50 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be less than 40 parts by weight, or less than 30 parts by weight. In some preferred embodiments, the content of the terpene phenol resin is less than 30 parts by weight, more preferably 25 parts by weight or less, even more preferably 22 parts by weight or less, and may be 20 parts by weight or less. .

The softening point of the tackifier resin is not particularly limited. From the viewpoint of improving cohesive force, a tackifier resin having a softening point (softening temperature) of about 80° C. or higher can be preferably employed. The softening point of the tackifying resin may be approximately 100°C or higher, or approximately 110°C or higher. Further, from the viewpoint of adhesion to the adherend, a tackifying resin having a softening point of approximately 200° C. or lower (more preferably approximately 180° C. or lower) may be preferably used. In some embodiments, the softening point of the tackifying resin may be less than 160°C, and may be less than 150°C.

Note that the softening point of the tackifying resin in this specification is defined as a value measured based on the softening point test method (ring and ball method) specified in JIS K5902 and JIS K2207. Specifically, the sample is melted as quickly as possible at the lowest possible temperature, and the sample is carefully filled into a ring placed on a flat metal plate, taking care not to form bubbles. After it has cooled down, use a slightly heated knife to cut off the raised part from the plane including the top of the ring. Next, a supporter (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 into the container to a depth of 90 mm or more. Next, the steel ball (diameter 9.5 mm, weight 3.5 g) and the ring filled with the sample were immersed in glycerin without coming into contact with each other, and the temperature of the glycerin was maintained at 20°C plus or minus 5°C for 15 minutes. . A steel ball is then placed in the center of the surface of the sample in the ring and placed in position on the support. Next, keeping the distance from the top of the ring to the glycerin surface at 50 mm, place a thermometer, set the center of the mercury bulb of the thermometer at the same height as the center of the ring, and heat the container. The flame of the Bunsen burner used for heating should be halfway between the center of the bottom of the container and the edge to ensure even heating. Note that the rate at which the bath temperature increases after heating starts and reaches 40°C must be 5.0 plus or minus 0.5°C per minute. The sample gradually softens and flows down from the ring, and the temperature at which it finally touches the bottom plate is read, and this is taken as the softening point. The softening point is measured at two or more points at the same time, and the average value is used.

In some embodiments, the tackifying resin is a tackifying resin T _L having a softening point of less than 150°C. By using the tackifier resin T _L , higher adhesive strength can be obtained. In some preferred embodiments, the softening point of the tackifier resin T _L is less than 140°C, more preferably less than 130°C, even more preferably less than 120°C, and may be 110°C or less, and has a softening point of 100°C or less. The temperature may be lower than or equal to 90°C. By using a tackifier resin having a softening point equal to or lower than the above-mentioned predetermined value, the 0°C storage modulus can be appropriately reduced. The lower limit of the softening point of the tackifier resin T _L is not particularly limited. In some embodiments, the softening point of the tackifier resin T _L may be approximately 50°C or higher, 60°C or higher, 70°C or higher, or 80°C from the viewpoint of exhibiting appropriate cohesive force. or higher, 90°C or higher, 100°C or higher, or 110°C or higher.

As the tackifier resin T _L , one type suitably selected from among the tackifier resins exemplified above having a softening point of less than 150°C can be used alone or in combination of two or more types. In some embodiments, the tackifying resin T _L preferably includes at least one selected from rosin-based tackifying resins and terpene-based tackifying resins. The tackifying resin T _L may contain one type of rosin-based tackifying resin alone, or may contain a combination of two or more types of rosin-based tackifying resin. Further, the tackifying resin T _L may contain one type of terpene-based tackifying resin (eg, terpene phenol resin) alone, or may contain a combination of two or more types of terpene-based tackifying resin.

In some embodiments, the proportion of the terpene-based tackifying resin (e.g., terpene phenol resin) in the entire tackifying resin T _L can be, for example, more than about 50% by weight, and may be about 65% by weight or more, The content may be approximately 75% by weight or more, 85% by weight or more, or 95% by weight or more. The technology disclosed herein is an embodiment in which substantially all of the tackifier resin T _L (for example, approximately 97% by weight or more, or 99% by weight or more, and may be 100% by weight) is a terpene-based tackifier resin. It can be preferably carried out.

Although not particularly limited, examples of rosin-based tackifier resins that can be preferably employed as the tackifier resin T _L include rosin esters such as unmodified rosin esters and modified rosin esters. A suitable example of the modified rosin ester is a hydrogenated rosin ester. For example, esters of unmodified rosin or modified rosin (eg hydrogenated rosin), such as rosin esters such as methyl ester, glycerin ester, etc., can be used as the tackifying resin T _L.

In some embodiments, the tackifying resin T _L may include a hydrogenated rosin ester. Also, for example, the tackifying resin T _L may include a non-hydrogenated rosin ester. Here, the term "non-hydrogenated rosin ester" is a concept that comprehensively refers to rosin esters other than hydrogenated rosin esters mentioned above. Examples of non-hydrogenated rosin esters include unmodified rosin esters, disproportionated rosin esters and polymerized rosin esters. The tackifier resin T _L may contain a combination of a hydrogenated rosin ester and a non-hydrogenated rosin ester as rosin esters, or may contain only one or more hydrogenated rosin esters. It may contain only one species or two or more non-hydrogenated rosin esters. The adhesive layer according to some preferred embodiments contains only one or more hydrogenated rosin esters as the rosin esters contained in the tackifier resin T _L.

In some embodiments, the proportion of the rosin-based tackifier resin in the entire tackifier resin T _L can be, for example, about 1% by weight or more, may be about 10% by weight or more, and may be about 20% by weight or more. The content may be 30% by weight or more, or may be 40% by weight or more. Further, the proportion of the rosin-based tackifying resin in the entire tackifying resin T _L may be 100% by weight, 90% by weight or less, 80% by weight or less, or 70% by weight or less. It may be 60% by weight or less. In some preferred embodiments, the proportion of the rosin-based tackifier resin in the entire tackifier resin T _L is less than 50% by weight, may be 30% by weight or less, may be 10% by weight or less, and is 1% by weight or less. It may be less than %.

In addition, as the tackifying resin T _L , for example, a tackifying resin having a softening point of less than 50°C, more preferably approximately 40°C or less (typically a rosin-based, terpene-based, hydrocarbon-based, etc. tackifying resin, e.g. Hydrogenated rosin methyl ester, etc.) may or may not be included. Such a low softening point tackifier resin may be a liquid tackifier resin that exhibits a liquid state at 30°C. The liquid tackifying resin can be used alone or in combination of two or more. The content of the liquid tackifying resin can be approximately 30% by weight or less of the entire tackifier resin T _L from the viewpoint of cohesive force etc., and should be approximately 10% by weight or less (for example, 0 to 10% by weight). is suitable, and may be approximately 2% by weight or less (0.5 to 2% by weight), and may be less than 1% by weight.

The content of the tackifier resin T _L is not particularly limited, but in some embodiments, it is appropriate to set it to about 70 parts by weight or less based on 100 parts by weight of the acrylic polymer, and even if it is 60 parts by weight or less. Generally, the amount may be 50 parts by weight or less, 40 parts by weight or less, or 30 parts by weight or less. By limiting the amount of tackifying resin T _L used to a predetermined amount or less, the 0° C. storage modulus can be appropriately reduced. In some preferred embodiments, the content of the tackifying resin T _L is less than 30 parts by weight, more preferably 25 parts by weight or less, and even more preferably 22 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be 20 parts by weight or less. In some embodiments, from the viewpoint of improving adhesive strength, the content of the tackifier resin T _L is, for example, 1 part by weight or more, preferably 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer. The amount is preferably 8 parts by weight or more, more preferably 10 parts by weight or more, still more preferably 12 parts by weight or more, and may be 15 parts by weight or more.

In some embodiments, the adhesive layer combines a tackifying resin T _L and a tackifying resin T _H having a softening point of 150° C. or higher (for example, 150° C. to 200° C.) within a range that does not impair the effects of the invention. may also be included. As the tackifier resin T _H , one kind or a combination of two or more kinds of tackifier resins having a softening point of 150° C. or more among the tackifier resins exemplified above can be used.

In some embodiments, it is preferred that the tackifier resin T _L accounts for more than 50% by weight of the total amount of tackifier resins included in the adhesive layer. Thereby, the effect of containing the tackifying resin _TL tends to be effectively expressed. The proportion of the tackifying resin _{T L} in the total amount of the tackifying resin contained in the adhesive layer is preferably 60% by weight or more, more preferably The content is 70% by weight or more, more preferably 80% by weight or more, particularly preferably 90% by weight or more, may be 95% by weight or more, or may be 98% by weight or more. In some preferred embodiments, the tackifying resin contained in the adhesive layer consists essentially only of tackifying resin _TL . In this embodiment, the proportion of the tackifying resin T _L in the total amount of tackifying resin contained in the adhesive layer is in the range of 99 to 100% by weight.

Although not particularly limited, in some embodiments, the tackifying resin may include a tackifying resin having a hydroxyl value higher than 20 mgKOH/g. Among these, tackifying resins having a hydroxyl value of 30 mgKOH/g or more are preferred. Hereinafter, a tackifier resin having a hydroxyl value of 30 mgKOH/g or more may be referred to as a "high hydroxyl value resin". According to the tackifying resin containing such a high hydroxyl value resin, an adhesive layer having excellent adhesion to an adherend and high cohesive force can be realized. In some embodiments, the tackifying resin may include a high hydroxyl value resin having a hydroxyl value of 50 mgKOH/g or more (for example, 70 mgKOH/g or more). Although not particularly limited, the above-mentioned high hydroxyl value resins (e.g. terpene phenol resins) are preferably used in combination with, for example, acrylic polymers containing heptyl acrylate as a monomer component to improve adhesive strength and cohesive strength. It is possible to achieve both.

The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with the acrylic polymer, the hydroxyl value of the high hydroxyl value resin is usually about 300 mgKOH/g or less, suitably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, or more. It is preferably about 160 mgKOH/g or less, more preferably about 140 mgKOH/g or less, and may be 120 mgKOH/g or less, 100 mgKOH/g or less, or 80 mgKOH/g or less (for example, 65 mgKOH/g or less). The technology disclosed herein can be preferably practiced in an embodiment in which the tackifier resin includes a high hydroxyl value resin (for example, a terpene-based tackifier resin, preferably a terpene phenol resin) with a hydroxyl value of 30 to 160 mgKOH/g. In some embodiments, a high hydroxyl value resin having a hydroxyl value of 30 to 80 mgKOH/g (for example, 30 to 65 mgKOH/g) can be preferably employed.

Here, as the value of the hydroxyl value, a value measured by the potentiometric titration method specified in JIS K0070:1992 can be adopted. The specific measurement method is as shown below.
[Method for measuring hydroxyl value]
1. Reagent (1) As the acetylation reagent, take about 12.5 g (about 11.8 mL) of acetic anhydride, add pyridine to make a total volume of 50 mL, and stir thoroughly. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to make a total volume of 100 mL, stir thoroughly, and use.
(2) A 0.5 mol/L potassium hydroxide ethanol solution is used as the measurement reagent.
(3) Additionally, prepare toluene, pyridine, ethanol, and distilled water.
2. Procedure (1) Accurately weigh about 2 g of sample into a flat bottom flask, add 5 mL of acetylation reagent and 10 mL of pyridine, and attach an air cooling tube.
(2) After heating the above flask in a bath at 100°C for 70 minutes, let it cool, add 35 mL of toluene as a solvent from the upper part of the cooling tube and stir, and then add 1 mL of distilled water and stir to remove acetic anhydride. Disassemble. To complete decomposition, heat again in the bath for 10 minutes and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove it. Next, 50 mL of pyridine is added as a solvent and stirred.
(4) Add 25 mL of 0.5 mol/L potassium hydroxide ethanol solution using a whole pipette.
(5) Perform potentiometric titration with a 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is defined as the end point.
(6) For a blank test, perform (1) to (5) above without adding a sample.
3. Calculation Calculate the hydroxyl value using the following formula.
Hydroxyl value (mgKOH/g)=[(B-C)×f×28.05]/S+D
here,
B: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the blank test,
C: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the sample,
f: factor of 0.5 mol/L potassium hydroxide ethanol solution,
S: weight of sample (g),
D: acid value,
28.05: 1/2 of the molecular weight of potassium hydroxide, 56.11,
It is.

As the high hydroxyl value resin, one having a hydroxyl value of a predetermined value or more among the various tackifier resins mentioned above can be used. The high hydroxyl value resins can be used alone or in combination of two or more. For example, as the high hydroxyl value resin, a terpene phenol resin having a hydroxyl value of 30 mgKOH/g or more can be preferably employed. Terpene phenol resins are advantageous because the hydroxyl value can be arbitrarily controlled by adjusting the copolymerization ratio of phenol.

Although not particularly limited, when using a high hydroxyl value resin, the proportion of the high hydroxyl value resin (for example, terpene phenol resin) to the entire tackifying resin contained in the adhesive layer should be approximately 5% by weight or more. The content may be 10% by weight or more, 15% by weight or more, or 20% by weight or more. In some embodiments, the proportion of the high hydroxyl value resin in the entire tackifier resin is preferably about 30% by weight or more, for example. Thereby, the effect of using the high hydroxyl value resin is preferably exhibited. In some preferred embodiments, the proportion of the high hydroxyl value resin in the entire tackifying resin is about 40% by weight or more, and may be about 50% by weight or more (for example, more than 50% by weight), and about 60% by weight. % or more, approximately 70% by weight or more, approximately 80% by weight or more, or approximately 90% by weight or more. Substantially all of the tackifier resin (for example, approximately 95 to 100% by weight, or even approximately 99 to 100% by weight) may be a high hydroxyl value resin.

The softening point of the high hydroxyl value resin is not particularly limited. The softening point of the high hydroxyl value resin may be, for example, approximately 50°C or higher, and from the viewpoint of improving cohesive force, a high hydroxyl value resin having a softening point (softening temperature) of approximately 80°C or higher may be preferably employed. For example, a terpene phenol resin having such a softening point can be preferably used. The softening point of the high hydroxyl value resin may be approximately 100°C or higher, or approximately 110°C or higher. The upper limit of the softening point of the high hydroxyl value resin is not particularly limited. From the viewpoint of adhesion to the adherend, a high hydroxyl value resin having a softening point of approximately 200° C. or lower (more preferably approximately 180° C. or lower) may be preferably used. In some embodiments, the softening point of the high hydroxyl value resin may be less than 160°C, may be less than 150°C, may be less than 145°C, may be less than 140°C, may be less than 130°C, may be less than 120°C. But that's fine.

The content of the high hydroxyl value resin in the adhesive layer is not particularly limited as long as it satisfies the desired viscoelastic properties. In some embodiments, the content of the high hydroxyl value resin is usually about 1 part by weight or more, and can be about 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength. It is suitable, preferably about 8 parts by weight or more, more preferably about 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). In some embodiments, the content of the high hydroxyl value resin in the adhesive layer is, for example, 70 parts by weight or less, and may be 60 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be 50 parts by weight or less, 40 parts by weight or less, or 30 parts by weight or less. In some preferred embodiments, the content of the high hydroxyl value resin is less than 30 parts by weight, more preferably 25 parts by weight or less, still more preferably 22 parts by weight or less, even if it is 20 parts by weight or less. good.

When the adhesive layer disclosed herein includes a tackifier resin, from the viewpoint of improving the biomass carbon ratio of the adhesive layer, a tackifier resin derived from plants (vegetable tackifier resin) is preferably used as the tackifier resin. It can work. Examples of the vegetable tackifier resin include the above-mentioned rosin-based tackifier resin and terpene-based tackifier resin. The vegetable tackifying resins can be used alone or in combination of two or more. When the adhesive layer disclosed herein includes a tackifying resin, the proportion of the vegetable tackifying resin in the total amount of the tackifying resin is 30% by weight or more (for example, 50% by weight or more, typically 80% by weight). above) is preferable. In some embodiments, the proportion of vegetable tackifying resin in the total amount of tackifying resin is 90% by weight or more (eg, 95% by weight or more, typically 99-100% by weight). The technology disclosed herein can be preferably implemented in an embodiment that does not substantially contain tackifying resins other than vegetable tackifying resins.

The content of the tackifying resin in the adhesive layer is not particularly limited as long as it satisfies the desired viscoelastic properties. In some embodiments, the content of the tackifier resin is usually about 1 part by weight or more, and suitably about 5 parts by weight or more, based on 100 parts by weight of the acrylic polymer, from the viewpoint of improving adhesive strength. The amount is preferably about 8 parts by weight or more, more preferably about 10 parts by weight or more, and even more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). In some embodiments, the content of the tackifier resin in the adhesive layer is, for example, 70 parts by weight or less, may be 60 parts by weight or less, and may be 50 parts by weight or less, based on 100 parts by weight of the acrylic polymer. The amount may be less than 40 parts by weight, or less than 30 parts by weight. In some preferred embodiments, the content of the tackifying resin is less than 30 parts by weight, more preferably 25 parts by weight or less, still more preferably 22 parts by weight or less, from the viewpoint of lowering the 0°C storage modulus. , 20 parts by weight or less.

In the technology disclosed herein, the total amount (total amount) of the acrylic polymer and tackifier resin in the adhesive layer is appropriately set and within a specific range so that the effect of the technology disclosed herein is exhibited. It is not limited. In some preferred embodiments, the total amount (total amount) of the acrylic polymer and tackifying resin in the entire adhesive layer is more than 50% by weight from the viewpoint of preferably exhibiting the effects of the technology disclosed herein. is suitable, preferably about 70% by weight or more, more preferably about 90% by weight or more, even more preferably 95% by weight or more (for example, 95% by weight or more and 100% by weight or less, or less than 100% by weight), and 98% by weight. % or more.

(acrylic oligomer)
In some embodiments, the adhesive layer may contain an acrylic oligomer. By containing an acrylic oligomer, the adhesive strength of the pressure-sensitive adhesive can be improved. Acrylic oligomers can be used alone or in combination of two or more. It is desirable that the acrylic oligomer has a Tg of about 0°C or more and about 300°C or less, preferably about 20°C or more and about 300°C or less, and more preferably about 40°C or more and about 300°C or less. When Tg is within the above range, adhesive strength can be suitably improved. In some preferred embodiments, the Tg of the acrylic oligomer is about 30°C or higher, more preferably about 50°C or higher (for example, about 60°C or higher), from the viewpoint of adhesive cohesiveness, and From this point of view, the temperature is preferably about 200°C or less, more preferably about 150°C or less, and even more preferably about 100°C or less (for example, about 80°C or less). Note that, in this specification, the Tg of the acrylic oligomer refers to the Tg determined by the Fox equation based on the composition of the monomer components, similar to the Tg of the acrylic polymer described above.

The weight average molecular weight (Mw) of the acrylic oligomer is typically about 1,000 or more and less than about 30,000, preferably about 1,500 or more and less than about 20,000, and more preferably about 2,000 or more and less than about 10,000. When Mw is within the above range, good adhesive strength is likely to be obtained. In some preferred embodiments, the Mw of the acrylic oligomer is about 2,500 or more (for example, about 3,000 or more), and from the viewpoint of adhesiveness, it is preferably about 7,000 or less, more preferably about 5,000 or less (for example, about 4,500 or less). , typically about 4000 or less). The Mw of the acrylic oligomer can be measured by gel permeation chromatography (GPC) and determined as a value in terms of standard polystyrene. Specifically, the measurement is performed using HPLC8020 manufactured by Tosoh Corporation with two columns of TSKgelGMH-H (20) using tetrahydrofuran solvent at a flow rate of about 0.5 mL/min.

Examples of monomers constituting the acrylic oligomer include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, and s-butyl. (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate , isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate. ; Esters of (meth)acrylic acid and alicyclic alcohol such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate (alicyclic hydrocarbon group-containing (meth)acrylate) ; Aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylates obtained from terpene compound derivative alcohols; and the like. Such (meth)acrylates can be used alone or in combination of two or more.

Examples of acrylic oligomers include alkyl (meth)acrylates in which the alkyl group has a branched structure, such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentaacrylate; Esters of (meth)acrylic acid and alicyclic alcohol such as phenyl (meth)acrylate ((meth)acrylate containing an alicyclic hydrocarbon group); aryl such as phenyl (meth)acrylate and benzyl (meth)acrylate Containing as a monomer unit an acrylic monomer having a relatively bulky structure, such as (meth)acrylate having a cyclic structure, further improves the adhesiveness of the adhesive layer. It is preferable from the viewpoint that In addition, when using ultraviolet rays when synthesizing acrylic oligomers or preparing adhesive layers, it is preferable to use ultraviolet rays that have saturated bonds because they are less likely to inhibit polymerization, and those that have alkyl groups with a branched structure are preferable. Alkyl (meth)acrylates or esters with alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates) can be suitably used as monomers constituting the acrylic oligomer. Note that all of the branched alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates described above correspond to (meth)acrylate monomers in the technology disclosed herein. The cycloaliphatic hydrocarbon group can be a saturated or unsaturated cycloaliphatic hydrocarbon group.

The proportion of (meth)acrylate monomer (for example, alicyclic hydrocarbon group-containing (meth)acrylate) in the monomer components constituting the acrylic oligomer is typically more than 50% by weight, preferably 60% by weight. The content is more than 70% by weight, more preferably 70% by weight or more (for example, 80% by weight or more, even 90% by weight or more). In some preferred embodiments, the acrylic oligomer has a monomer composition consisting essentially of (meth)acrylate monomers.

In addition to the above-mentioned (meth)acrylate monomers, functional group-containing monomers can be used as constituent monomer components of the acrylic oligomer. Suitable examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; N,N-dimethylamino Amino group-containing monomers such as ethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxy group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate Monomers; These functional group-containing monomers can be used alone or in combination of two or more. Among these, carboxy group-containing monomers are preferred, and AA is particularly preferred. For example, by using a carboxy group-containing monomer as the functional group-containing monomer, the adhesive strength to a highly polar adherend can be easily improved.

When the monomer component constituting the acrylic oligomer includes a functional group-containing monomer, the proportion of the functional group-containing monomer (for example, a carboxy group-containing monomer such as AA) in the monomer component can be approximately 1% by weight or more. It is appropriate, preferably 2% by weight or more, more preferably 3% by weight or more, and approximately 15% by weight or less, preferably 10% by weight or less, more preferably 7% by weight or less. be.

Acrylic oligomers can be formed by polymerizing their constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and various conventionally known polymerization methods (e.g., solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in an appropriate mode. The types of polymerization initiators (for example, azo polymerization initiators such as AIBN) that can be used as necessary are generally the same as those exemplified in the synthesis of acrylic polymers, and the amount of polymerization initiators and the amount of polymerization initiators optionally used may vary. The amount of the chain transfer agent such as n-dodecyl mercaptan is appropriately determined based on common technical knowledge so as to obtain a desired molecular weight, and therefore detailed explanation will be omitted here.

From the above viewpoint, suitable acrylic oligomers include dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclopentanyl In addition to each homopolymer of acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), a copolymer of CHMA and isobutyl methacrylate (IBMA), a copolymer of CHMA and IBXMA, Copolymer of CHMA and acryloylmorpholine (ACMO), copolymer of CHMA and diethylacrylamide (DEAA), copolymer of CHMA and AA, copolymer of ADA and methyl methacrylate (MMA), DCPMA and IBXMA copolymers of DCPMA and MMA, and copolymers of DCPMA and MMA.

When the adhesive layer disclosed herein contains an acrylic oligomer, the content is preferably, for example, 0.1 part by weight or more (for example, 1 part by weight or more) based on 100 parts by weight of the acrylic polymer. It is. From the viewpoint of better exhibiting the effects of the acrylic oligomer, the content of the acrylic oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more, still more preferably about 10 parts by weight or more, especially Preferably it is about 12 parts by weight or more. In some embodiments, from the viewpoint of compatibility with the acrylic polymer, the content of the acrylic oligomer is less than 50 parts by weight (for example, less than 40 parts by weight) based on 100 parts by weight of the acrylic polymer. The amount is preferably less than 30 parts by weight, more preferably about 25 parts by weight or less, even more preferably about 20 parts by weight or less. In some other embodiments, the content of the acrylic oligomer may be 10 parts by weight or less, 5 parts by weight or less, 1 part by weight or less (for example, 1 part by weight or less) based on 100 parts by weight of the acrylic polymer. (less than parts by weight). The technique disclosed herein can be implemented in an embodiment in which the adhesive layer does not substantially contain an acrylic oligomer.

(Crosslinking agent)
In the technology disclosed herein, the adhesive composition used to form the adhesive layer may contain a crosslinking agent as necessary. The type of crosslinking agent is not particularly limited, and examples include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, peroxide crosslinking agents, urea crosslinking agents, and metals. Examples include alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, and silane coupling agents. One type of crosslinking agent can be used alone or two or more types can be used in combination. Among these, isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, and melamine crosslinking agents are preferred, and isocyanate crosslinking agents and epoxy crosslinking agents are more preferred. By appropriately selecting and using a crosslinking agent, the adhesive layer can have appropriate cohesive strength. The adhesive layer in the technology disclosed herein may contain the crosslinking agent in a form after a crosslinking reaction, a form before a crosslinking reaction, a partially crosslinked form, an intermediate or composite form thereof, etc. May contain. The crosslinking agent is typically contained in the adhesive layer exclusively in the form after crosslinking reaction.

As the isocyanate-based crosslinking agent, polyfunctional isocyanates (referring to compounds having an average of two or more isocyanate groups per molecule, including those having an isocyanurate structure) can be preferably used. The isocyanate crosslinking agents can be used alone or in combination of two or more.

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

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

Specific examples of aromatic polyisocyanates include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, and 2,2'-diphenylmethane diisocyanate. , 4,4'-diphenyl ether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate , 4,4'-diphenylpropane diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5-diisocyanate, 3,3'-dimethoxydiphenyl-4,4'-diisocyanate , xylylene-1,4-diisocyanate, xylylene-1,3-diisocyanate, and the like.

Preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of three or more isocyanate groups per molecule. Such trifunctional or higher functional isocyanates are polymers (typically dimers or trimers) of bifunctional or trifunctional or higher functional isocyanates, derivatives (for example, combinations of polyhydric alcohols and two or more molecules of polyfunctional isocyanates). addition reaction products), polymers, etc. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurates of hexamethylene diisocyanate (trimeric adducts of isocyanurate structures), reaction products of trimethylolpropane and tolylene diisocyanate, and products of the reaction between trimethylolpropane and hexamethylene diisocyanate. Examples include polyfunctional isocyanates such as reaction products with methylene diisocyanate, polymethylene polyphenylisocyanate, polyether polyisocyanate, and polyester polyisocyanate. Commercially available products of such polyfunctional isocyanates include "Duranate TPA-100" manufactured by Asahi Kasei Chemicals, "Coronate L", "Coronate HL", "Coronate HK", and "Coronate HL" manufactured by Tosoh Corporation. Examples include "Coronate 2096" and "Coronate 2096".

The technology disclosed herein can be preferably implemented in an embodiment using at least an isocyanate-based crosslinking agent as the crosslinking agent. The amount of the isocyanate crosslinking agent used is not particularly limited. The amount of the isocyanate crosslinking agent used can be, for example, about 0.1 part by weight or more based on 100 parts by weight of the acrylic polymer. From the perspective of achieving both cohesive force and adhesion, the amount of isocyanate crosslinking agent used per 100 parts by weight of the acrylic polymer should usually be approximately 0.3 parts by weight or more (for example, 0.5 parts by weight or more). is preferred. In some preferred embodiments, the amount of the isocyanate crosslinking agent used per 100 parts by weight of the acrylic polymer is about 1.0 parts by weight or more, more preferably about 1.5 parts by weight or more, and still more preferably about 2.0 parts by weight. The amount is at least 2.5 parts by weight, particularly preferably at least 2.5 parts by weight, and may be at least 2.8 parts by weight. In addition, from the viewpoint of improving adhesion to the adherend, the amount of the isocyanate crosslinking agent used is suitably 10 parts by weight or less, preferably 8 parts by weight or less, per 100 parts by weight of the acrylic polymer. , more preferably 6 parts by weight or less, still more preferably 5 parts by weight or less, particularly preferably 4 parts by weight or less, may be 3.5 parts by weight or less, and may be 3.2 parts by weight or less.

As the epoxy crosslinking agent, any compound having two or more epoxy groups in one molecule can be used without particular limitation. Epoxy crosslinking agents having 3 to 5 epoxy groups in one molecule are preferred. The epoxy crosslinking agents can be used alone or in combination of two or more.

Although not particularly limited, specific examples of epoxy crosslinking agents include N,N,N',N'-tetraglycidyl-m-xylene diamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available epoxy crosslinking agents include Mitsubishi Gas Chemical's product names "TETRAD-C" and "TETRAD-X", DIC's product name "Epicron CR-5L", and Nagase ChemteX's product name Examples include the product name "Denacol EX-512" manufactured by Nissan Chemical Industries, Ltd. and the product name "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd.

The amount of the epoxy crosslinking agent used is not particularly limited. The amount of the epoxy crosslinking agent used may be, for example, more than 0 parts by weight and no more than about 1 part by weight (typically about 0.001 to 1 part by weight) per 100 parts by weight of the acrylic polymer. can. From the viewpoint of suitably exhibiting the effect of improving cohesive force, it is usually appropriate to use the epoxy crosslinking agent in an amount of about 0.002 parts by weight or more per 100 parts by weight of the acrylic polymer, preferably The amount may be approximately 0.005 part by weight or more, for example, approximately 0.01 part by weight or more, or approximately 0.02 part by weight or more. In addition, from the viewpoint of improving adhesion to the adherend, the amount of the epoxy crosslinking agent used is approximately 0.5 parts by weight or less per 100 parts by weight of the acrylic polymer, and approximately 0.2 parts by weight. It is preferably at most 0.1 parts by weight, more preferably at most 0.1 parts by weight (for example, less than 0.1 parts by weight), it may be at most 0.07 parts by weight, it may be at most 0.04 parts by weight, It may be 0.03 parts by weight or less. By limiting the amount of epoxy crosslinking agent used within a predetermined range, sufficient adhesive strength can be easily maintained.

In some preferred embodiments, as the crosslinking agent, an isocyanate crosslinking agent and at least one crosslinking agent having a different type of crosslinkable functional group from the isocyanate crosslinking agent are used in combination. The technology disclosed herein uses a crosslinking agent other than an isocyanate crosslinking agent (i.e., a crosslinking agent with a different type of crosslinkable reactive group from an isocyanate crosslinking agent; hereinafter also referred to as a "non-isocyanate crosslinking agent") and an isocyanate. It can be preferably carried out in an embodiment in which the method is used in combination with a crosslinking agent.

The type of non-isocyanate crosslinking agent that can be used in combination with the isocyanate crosslinking agent is not particularly limited, and can be appropriately selected from the above-mentioned crosslinking agents. The non-isocyanate crosslinking agents can be used alone or in combination of two or more. In some preferred embodiments, an epoxy crosslinker can be employed as the non-isocyanate crosslinker. For example, better adhesive properties can be achieved by using an isocyanate crosslinking agent and an epoxy crosslinking agent in combination.

The relationship between the content of the isocyanate crosslinking agent and the content of the non-isocyanate crosslinking agent (preferably the epoxy crosslinking agent) is not particularly limited. The content of the isocyanate crosslinking agent is, for example, more than 1 time, preferably about 10 times or more, relative to the content of the non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent). is about 50 times or more, more preferably about 80 times or more, still more preferably about 100 times or more (for example, more than 100 times), and may be about 120 times or more (for example, about 140 times or more). In addition, from the viewpoint of suitably exhibiting the effect of using an isocyanate crosslinking agent and a non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) in combination, a non-isocyanate crosslinking agent (preferably an epoxy crosslinking agent) is usually used. The content of the isocyanate crosslinking agent relative to the content of the crosslinking agent (crosslinking agent) is, for example, approximately 1000 times or less, suitably approximately 500 times or less, preferably approximately 300 times or less, and more preferably approximately 200 times or less. , more preferably about 180 times or less, and may be about 150 times or less.

The content of crosslinking agent (total amount of crosslinking agent) in the adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesion, the content of the crosslinking agent is usually about 0.001 parts by weight or more, and preferably about 0.01 parts by weight or more, based on 100 parts by weight of the acrylic polymer. Preferably it is about 0.1 part by weight or more, more preferably about 1 part by weight or more, still more preferably about 2 parts by weight or more, particularly preferably about 2.5 parts by weight or more. The content of the crosslinking agent in the adhesive composition is usually about 20 parts by weight or less, preferably about 15 parts by weight or less, and about 10 parts by weight based on 100 parts by weight of the acrylic polymer. The following is preferable. In some preferred embodiments, the content of the crosslinking agent per 100 parts by weight of the acrylic polymer is 5.0 parts by weight or less, may be 4.0 parts by weight or less, or may be 3.5 parts by weight or less.

(Other additives)
In addition to the above-mentioned components, the adhesive composition may optionally contain a leveling agent, a crosslinking aid, a plasticizer, a softener, a filler, an antistatic agent, an antiaging agent, an ultraviolet absorber, an antioxidant, Various additives common in the adhesive field, such as rust preventives and light stabilizers, may be included. Regarding such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed explanations will be omitted.

(Method for forming adhesive layer)
The adhesive layer (layer consisting of an adhesive) disclosed herein is formed from a water-based adhesive composition, a solvent-based adhesive composition, a hot-melt adhesive composition, or an active energy ray-curable adhesive composition. It may be an adhesive layer. The aqueous adhesive composition refers to an adhesive composition containing an adhesive (adhesive layer forming component) in a water-based solvent (aqueous solvent), and is typically a water-based adhesive composition. This includes what is called a type adhesive composition (a composition in which at least a portion of an adhesive is dispersed in water). Moreover, a solvent-based adhesive composition refers to an adhesive composition containing an adhesive in an organic solvent. As the organic solvent contained in the solvent-based adhesive composition, one or more of the organic solvents (toluene, ethyl acetate, etc.) that can be used in the above-mentioned solution polymerization can be used without particular limitation. The technology disclosed herein can be preferably implemented in an embodiment including an adhesive layer formed from a solvent-based adhesive composition from the viewpoint of adhesive properties and the like.

The adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method can be adopted in which a pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive composition to a surface having peelability (peelability surface) or a non-peelability surface and drying it. For an adhesive sheet having a base material, for example, a method (direct method) of forming an adhesive layer by directly applying (typically coating) an adhesive composition to the base material and drying is adopted. be able to. In addition, a method (transfer method) in which an adhesive composition is applied to a surface that has releasability (release surface) and dried to form an adhesive layer on the surface, and the adhesive layer is transferred to a base material. may be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of a release liner, the back surface of a release-treated base material, etc. can be used.

The adhesive composition can be applied using a conventionally known coater such as a gravure roll coater, die coater, or bar coater. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.
From the viewpoint of promoting crosslinking reaction, improving production efficiency, etc., it is preferable to dry the adhesive composition under heating. The drying temperature can be, for example, about 40 to 150°C, and usually preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, aging may be performed for the purpose of adjusting component migration within the pressure-sensitive adhesive layer, progressing the crosslinking reaction, alleviating distortion that may exist within the pressure-sensitive adhesive layer, and the like.

The adhesive layer may have a single layer structure or a multilayer structure of two or more layers. From the viewpoint of productivity etc., it is preferable that the adhesive layer has a single layer structure.

(thickness)
The thickness of the adhesive layer is not particularly limited, and a configuration having an adhesive layer having an appropriate thickness in the range of, for example, 0.1 to 500 μm may be adopted depending on the use and purpose of use. In some embodiments, from the viewpoint of preventing the double-sided adhesive sheet from becoming excessively thick, the thickness of the adhesive layer is usually approximately 100 μm or less, preferably approximately 70 μm or less, and more preferably approximately 60 μm or less. , more preferably about 50 μm or less, and may be about 40 μm or less. The thickness of the adhesive layer can be approximately 35 μm or less, and may be approximately 30 μm or less, for example. An adhesive layer with a limited thickness can meet the demands for thinning and weight reduction. In some embodiments, the lower limit of the thickness of the adhesive layer is suitably about 0.5 μm or more, from the viewpoint of adhesion to the adherend, it may be about 1 μm or more, and it may be about 3 μm or more. Advantageously, it is approximately 10 μm or more, more preferably approximately 12 μm or more (eg greater than 12 μm), still more preferably approximately 15 μm or more, and may for example be approximately 18 μm or more. In some preferred embodiments, the thickness of the adhesive layer is greater than 20 μm, may be 24 μm or greater, may be 27 μm or greater, may be approximately 30 μm or greater, may be approximately 35 μm or greater, may be approximately 40 μm or greater. By increasing the thickness of the adhesive layer, it is easy to adjust optical properties such as reducing light transmittance. Furthermore, as the thickness of the adhesive layer increases, the adhesive strength tends to improve as well. In addition, in a double-sided adhesive sheet with a base material that has a first adhesive layer and a second adhesive layer on each side of the base material, the first adhesive layer and the second adhesive layer have the same thickness. They may have different thicknesses.

(Biomass carbon ratio)
In some embodiments, the adhesive layer may include a biomass-derived material, and the biomass carbon ratio may be greater than or equal to a predetermined value. The biomass carbon ratio of the adhesive layer is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio in the adhesive means that less fossil resource-based materials, such as petroleum, are used. From this point of view, the higher the biomass carbon ratio of the adhesive, the more preferable. For example, the biomass carbon ratio of the adhesive layer may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. good. The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and from the viewpoint of material availability, it may be 95% or less, or 90% or less. In some embodiments, from the viewpoint of facilitating good adhesive performance, the biomass carbon ratio of the adhesive layer may be, for example, 90% or less, 85% or less, or 80% or less.

<Base material>
In an embodiment in which the double-sided pressure-sensitive adhesive sheet disclosed herein is in the form of a double-sided pressure-sensitive adhesive sheet with a base material, the base material supporting the pressure-sensitive adhesive layer may include a resin film, paper, cloth, rubber sheet, foam sheet, metal foil, Complexes of these, etc. can be used. Examples of paper include Japanese paper, kraft paper, glassine paper, high quality paper, synthetic paper, top coated paper, and the like. Examples of the fabric include woven fabrics and nonwoven fabrics made of various fibrous substances alone or in combination. Examples of the above-mentioned fibrous materials include cotton, staple fiber, Manila hemp, pulp, rayon, acetate fiber, polyester fiber, polyvinyl alcohol fiber, polyamide fiber, and polyolefin fiber. Examples of rubber sheets include natural rubber sheets, butyl rubber sheets, and the like. Examples of foam sheets include foamed polyolefin sheets, foamed polyurethane sheets, foamed polychloroprene rubber sheets, and the like. Examples of metal foil include aluminum foil, copper foil, and the like. In addition, a base material is also called a base material layer in a double-sided adhesive sheet.

The base material may be formed from a biomass-derived material or a non-biomass-derived material. From the viewpoint of producing a pressure-sensitive adhesive sheet in consideration of reducing dependence on fossil resource-based materials, biomass-derived base materials (typically resin films) are preferably used.

Further, the base material may be formed using a recyclable material or a recycled material (also referred to as recycled material). As such a recycled material, a resin film is preferably used. Resin films (for example, polyester films such as PET films) can be recycled, so whether or not they are made from plant-based materials, reusing the used resin film allows for sustainable reproduction. It is possible to reduce the environmental burden. Such a recyclable resin film or a recycled resin film is also referred to as a recycled film. The recycled material (for example, recycled film) may be formed from a biomass-derived material or a non-biomass-derived material.

As the base material constituting the double-sided pressure-sensitive adhesive sheet with a base material, one containing a resin film as a base film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The base material in the technology disclosed herein may be substantially composed of such a base film. Alternatively, the base material may include an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc. provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene-propylene copolymers; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. Examples include polyester resin film; vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; fluororesin film; cellophane; and the like. The resin film may be a rubber film such as a natural rubber film or a butyl rubber film. Among these, polyester films are preferred from the viewpoint of handling and processability, and among these, PET films are particularly preferred.

In addition, in this specification, "resin film" is typically a non-porous sheet, and is a concept that is distinguished from so-called non-woven fabrics and woven fabrics (in other words, a concept excluding non-woven fabrics and woven fabrics). be. The resin film may be an unstretched film, a uniaxially stretched film, or a biaxially stretched film. Also, such resin films may be non-foamed. Here, the term "non-foamed resin film" refers to a resin film that has not been intentionally processed to form a foam. Specifically, the non-foamed resin film may be a resin film with an expansion ratio of less than 1.1 times (for example, less than 1.05 times, typically less than 1.01 times).

The base material may be transparent, or may have light-blocking or light-attenuating properties. In some embodiments, the substrate (eg, resin film) can contain a colorant. Thereby, the light transmittance (light-shielding property) of the base material can be adjusted. Adjusting the light transmittance (for example, vertical light transmittance) of the base material can be useful for adjusting the light transmittance of the base material and further the light transmittance of the double-sided pressure-sensitive adhesive sheet containing the base material.

As the colorant, conventionally known pigments and dyes can be used as well as colorants that can be included in the adhesive layer. The colorant is not particularly limited, and may be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearl color, or the like.

In some embodiments, a black coloring agent can be preferably used as the coloring agent for the substrate because light blocking properties (for example, vertical light transmittance) can be efficiently adjusted with a small amount of the coloring agent. Specific black colorants include those exemplified as colorants that can be included in the adhesive layer. In some preferred embodiments, pigments (eg, particulate black colorants such as carbon black) with an average particle size of 10 nm to 500 nm, more preferably 10 nm to 120 nm, can be used.

The amount of colorant used in the base material (eg, resin film) is not particularly limited, and can be adjusted as appropriate so as to impart desired optical properties. The amount of coloring agent used is suitably about 0.1 to 30% by weight of the base material, for example 0.1 to 25% by weight (typically 0.1 to 20% by weight). can do.

The base material (for example, resin film) may contain fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, Various additives such as antistatic agents, lubricants, and plasticizers may be blended. The blending ratio of various additives is about less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

The base material (for example, a resin film) may have a single layer structure, or may have a multilayer structure of two layers, three layers, or more. From the viewpoint of shape stability, the base material preferably has a single-layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) is preferably a layer having a continuous structure of the above resin (for example, polyester resin). The method for manufacturing the base material (typically a resin film) is not particularly limited, and any conventionally known method may be appropriately adopted. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die casting molding, and calender roll molding can be appropriately employed.

The base material may be colored with a colored layer disposed on the surface of the base film (preferably a resin film). In the base material having such a structure including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be arranged on either surface of the base film, or may be arranged on both surfaces. In a configuration in which colored layers are arranged on both surfaces of the base film, the configurations of the colored layers may be the same or different.

Such a colored layer can typically be formed by applying a colored layer forming composition containing a colorant and a binder to a base film. As the colorant, conventionally known pigments and dyes can be used, as well as colorants that can be included in the adhesive layer or resin film. As the binder, materials known in the paint or printing fields can be used without particular limitation. Examples include polyurethane, phenol resin, epoxy resin, urea melamine resin, polymethyl methacrylate, and the like. The composition for forming a colored layer may be, for example, a solvent type, an ultraviolet curable type, a thermosetting type, or the like. The colored layer can be formed by any means conventionally used for forming colored layers without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexographic printing, or offset printing can be preferably employed.

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

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

The surface of the base material may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat. Such surface treatment may be a treatment for improving the adhesion between the base material and the adhesive layer, in other words, the ability of the adhesive layer to anchor to the base material.

In the double-sided pressure-sensitive adhesive sheet of the embodiment including a base material, the thickness of the base material is not particularly limited. From the viewpoint of preventing the double-sided pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the base material can be, for example, approximately 200 μm or less, preferably approximately 150 μm or less, and more preferably approximately 100 μm or less. The thickness of the base material may be approximately 70 μm or less, approximately 50 μm or less, or approximately 30 μm or less (eg, approximately 25 μm or less) depending on the purpose and manner of use of the double-sided adhesive sheet. In some embodiments, the thickness of the substrate can be about 20 μm or less, about 15 μm or less, about 10 μm or less (eg, about 5 μm or less). By reducing the thickness of the base material, the thickness of the adhesive layer can be increased even if the total thickness of the double-sided adhesive sheet is the same, which improves the adhesion to the adherend and base material. It can be advantageous from this point of view. In addition, a base material with a limited thickness can meet the demands for thinning and weight reduction. The thickness of the base material is usually about 0.5 μm or more (for example, 1 μm or more), preferably about 2 μm or more, for example about 6 μm or more, from the viewpoint of handleability and processability of the double-sided adhesive sheet. . In some embodiments, the thickness of the substrate can be about 8 μm or more, and can be about 10 μm or more.

<Total thickness of double-sided adhesive sheet>
The total thickness of the double-sided pressure-sensitive adhesive sheet disclosed herein (which includes a pressure-sensitive adhesive layer and may further include a base layer, but does not include a release liner) is not particularly limited. The total thickness of the double-sided adhesive sheet is, for example, approximately 1 mm or less, may be approximately 500 μm or less, and may be approximately 300 μm or less, and from the viewpoint of thinning, approximately 200 μm or less is appropriate, and approximately 150 μm. The thickness may be less than 100 μm (for example, approximately 100 μm or less). In some preferred embodiments, the thickness of the double-sided pressure-sensitive adhesive sheet can be approximately 50 μm or less, for example, approximately 35 μm or less. The lower limit of the thickness of the double-sided adhesive sheet is, for example, 0.1 μm or more (for example, 0.5 μm or more), suitably about 3 μm or more, preferably about 10 μm or more, more preferably about 15 μm or more. , more preferably about 20 μm or more, may be about 30 μm or more, and may be about 50 μm or more. A double-sided pressure-sensitive adhesive sheet having a thickness of a predetermined value or more tends to have good adhesion to an adherend and also tends to have excellent handling properties. In addition, in a double-sided adhesive sheet without a base material, the thickness of the adhesive layer is the total thickness of the double-sided adhesive sheet.

<Characteristics of double-sided adhesive sheet>
(light transmittance)
The light transmittance of a double-sided adhesive sheet varies depending on the purpose of use, the purpose of coloring, etc., and is not limited to a specific range. In some embodiments, the light transmittance at a wavelength of 550 nm (550 nm light transmittance, also referred to as visible light transmittance) of the double-sided adhesive sheet is less than 80%, may be less than 70%, and may be less than 60%. It may be less than 50%, or even less than 40%. A double-sided pressure-sensitive adhesive sheet whose visible light transmittance is limited to a predetermined value or less by coloring the pressure-sensitive adhesive layer is suitable for hiding an adherend, and can also be used to impart design properties. It can also be used as a light-shielding adhesive sheet for purposes such as preventing light leakage. In some preferred embodiments, the 550 nm light transmittance of the double-sided adhesive sheet is 30% or less, may be 20% or less, may be 15% or less, may be 10% or less, may be 8% or less, It may be 6% or less. The lower the visible light transmittance, the more excellent hiding power can be exhibited. When higher hiding power is required, the 550 nm light transmittance may be less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, or 0. It may be less than .5%. The lower limit of the 550 nm light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit, 0.1% or more, 1% or more, or 3% or more. Often, it may be 5% or more. In some embodiments, the 550 nm light transmittance may be 10% or more, more than 20%, or more than 30%. By having a certain degree of visible light transmittance, it is possible to appropriately hide the adherend, adjust the appearance of the adherend (for example, metal materials), and create a design or color that retains the texture of the adherend. can be granted. Further, a double-sided pressure-sensitive adhesive sheet having appropriate light transmittance is preferable from the viewpoint of maintaining adhesive properties and productivity. The 550 nm light transmittance of the double-sided adhesive sheet can be measured by the method described in Examples below.

Although not particularly limited, the light transmittance at a wavelength of 1380 nm (1380 nm light transmittance, also referred to as infrared transmittance) of the double-sided adhesive sheet is less than 90%, may be less than 80%, and may be less than 70%. It may be less than 60%, less than 50%, or less than 40%. In some preferred embodiments, the 1380 nm light transmittance of the double-sided adhesive sheet is 30% or less, may be 20% or less, may be 15% or less, may be 10% or less, may be 5% or less, It may be 3% or less. According to the above-mentioned double-sided adhesive sheet with limited infrared transmittance, it is possible to block light in a wide wavelength range including infrared rays, and it is easy to obtain excellent light blocking properties. Further, for example, when used near an infrared sensor, by blocking infrared rays, it is possible to prevent a decrease in the operational accuracy of the sensor. The lower limit of the 1380 nm light transmittance is not particularly limited, and may be substantially 0%, that is, below the detection limit, 0.1% or more, 1% or more, or 3% or more. Often, it may be 5% or more. In some embodiments, the 1380 nm light transmittance may be 10% or more, 30% or more, or 50% or more. The 1380 nm light transmittance of the double-sided adhesive sheet can be measured by the method described in Examples below.

The relative relationship between visible light transmittance and infrared transmittance of the double-sided adhesive sheet is not particularly limited. In some embodiments, the ratio (T _IR /T _VL ) of the infrared transmittance T _IR [%] and the visible light transmittance T _VL [%] of the double-sided adhesive sheet is, for example, within the range of 0.1 to 10. It may be 5 or less, 3 or less, 0.5 or more, 1 or more (for example, more than 1), or 2 or more. By appropriately setting the ratio (T _IR /T _VL ) depending on the purpose of use of the double-sided pressure-sensitive adhesive sheet, the application location, etc., it is possible to achieve the intended adherend hiding properties and infrared shielding properties.

(Adhesive strength to SUS)
Although not particularly limited, in some embodiments, the double-sided adhesive sheet has a 180 degree peel strength against a stainless steel plate (adhesion strength against SUS) of about 1 N/25 mm or more, and about 5 N/25 mm or more. Appropriate. In some preferred embodiments, the adhesive force to SUS is approximately 10 N/25 mm or more, may be approximately 12 N/25 mm or more, or may be approximately 15 N/25 mm or more. The double-sided adhesive sheet exhibiting the above adhesive strength to SUS exhibits good adhesive strength to adherends and is preferably used for joining and fixing members. The upper limit of the adhesive force to SUS is not particularly limited, but from the viewpoint of coexistence with other adhesive properties, it is usually about 50 N/25 mm or less, and in some embodiments, it may be about 30 N/25 mm or less. good.

The adhesive strength to SUS is measured using an SUS plate as an adherend under the conditions of a tensile speed of 300 mm/min and a peel angle of 180 degrees in a measurement environment of 23° C. and 50% RH. More specifically, it is measured by the following method.
[Adhesive strength to SUS]
Under a measurement environment of 23°C and 50% RH, a 50 μm thick PET film was pasted on one adhesive side of a double-sided adhesive sheet to back it, and the measurement sample was cut to a size of 25 mm in width and 100 mm in length. do. In an environment of 23° C. and 50% RH, the other adhesive surface of the measurement sample is pressed onto the surface of a stainless steel plate (SUS304BA plate) that has been cleaned with ethyl acetate by making one reciprocation with a 2 kg roller. After leaving it in the same environment for 72 hours, using a universal tensile compression tester, the peel strength (relative to SUS Adhesive force) [N/25mm] is measured. In the above peel strength measurement, the universal tensile compression tester used is Minebea's "Tensile Compression Tester, TG-1kN" or its equivalent.

(Biomass carbon ratio)
In some embodiments, the double-sided adhesive sheet may contain a biomass-derived material, and the biomass carbon ratio may be greater than or equal to a predetermined value. The biomass carbon ratio of the double-sided adhesive sheet is, for example, 1% or more, and may be 10% or more, preferably 30% or more, and more preferably 50% or more. A high biomass carbon ratio in the double-sided adhesive sheet means that the amount of fossil resource-based materials typified by petroleum etc. used is small. From this point of view, the higher the biomass carbon ratio of the double-sided pressure-sensitive adhesive sheet, the more preferable it is. For example, the biomass carbon ratio of the double-sided adhesive sheet may be 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or more than 80%. good. The upper limit of the biomass carbon ratio is 100% by definition, and may be 99% or less, and from the viewpoint of material availability, it may be 95% or less, or 90% or less. In some embodiments, the biomass carbon ratio of the double-sided adhesive sheet may be, for example, 90% or less, 85% or less, or 80% or less, from the viewpoint of facilitating good adhesive performance.

<Application>
The double-sided adhesive sheet disclosed herein has a colored adhesive layer, highly suppresses deformation of the adhesive surface due to peeling of the release liner, and has an adhesive surface with excellent appearance quality. Therefore, the double-sided adhesive sheet attached to the surface of the adherend is used in applications where it is visually recognized, for example, applications where the double-sided adhesive sheet is required to have concealing properties, and the colored adhesive layer is used to improve design and color. It is suitable for various applications such as applications that impart flavor and applications that require predetermined optical properties (light transmittance, etc.). For example, some electronic devices such as portable electronic devices require the use of double-sided adhesive sheets to conceal components and adjust the appearance. The double-sided adhesive sheet disclosed herein is suitable for such electronic devices.

Non-limiting examples of the above-mentioned portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, and various wearable devices (e.g., wrist-wear type that is worn on the wrist like a wristwatch, and Modular type that is attached to a part of the body, eyewear type that includes glasses type (monocular type and binocular type, including head-mounted type), clothing type that is attached to shirts, socks, hats, etc. in the form of accessories, and earphones. digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, and in-vehicle devices. This includes information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. Note that in this specification, "portable" does not mean that it is sufficient to simply be able to carry it; it also means that it has a level of portability that allows an individual (standard adult) to carry it relatively easily. shall mean. Furthermore, examples of the electronic devices include personal computers (desktop type, notebook type, tablet type, etc.), televisions, and the like. These may include a built-in display device such as a liquid crystal or organic EL.

In some embodiments, the double-sided adhesive sheet can be used, for example, for the purpose of fixing a pressure-sensitive sensor and other members in a portable electronic device including a pressure-sensitive sensor among the above-mentioned portable electronic devices. In some embodiments, the double-sided adhesive sheet includes a device for indicating a position on the screen (typically a pen-shaped or mouse-shaped device) and a device for detecting the position, and a plate corresponding to the screen. For fixing a pressure-sensitive sensor and other components in an electronic device (typically a portable electronic device) that has a function that allows specifying an absolute position on a touch panel (typically a touch panel). can be used.

In some preferred embodiments, the double-sided adhesive sheet is suitable for use in applications where it is placed on the back side of a display screen (display section) such as a touch panel display in a portable electronic device. By arranging the double-sided adhesive sheet according to some preferred embodiments on the back surface of the display screen (display section), it is possible to prevent the visibility of the display screen from decreasing regardless of how the portable electronic device is used.

In some embodiments, the double-sided pressure-sensitive adhesive sheet is suitable for a portable electronic device having a built-in optical sensor. Various devices such as the portable electronic device described above may be equipped with an optical sensor that uses infrared light, visible light, ultraviolet light, or other light rays for the purpose of operating the device, detecting nearby objects, detecting the brightness of the surroundings (ambient light), data communication, or the like. Examples of the optical sensor include, but are not limited to, an acceleration sensor, a proximity sensor, a brightness sensor (ambient light sensor), and the like. Such an optical sensor may have a light receiving element for ultraviolet light, visible light, infrared light, or other light, and may also have an emitting element for a specific light ray such as infrared light. In other words, the optical sensor may include an emitting element and/or a receiving element for a light ray in a specific wavelength range among wavelength ranges including ultraviolet light, visible light, and infrared light. By applying the double-sided pressure-sensitive adhesive sheet according to some embodiments to such a device and limiting the entry of light that may be refracted or scattered within the adhesive layer, the light in the device can be controlled and a decrease in the operating accuracy of the sensor can be prevented.

The material (adherend material) to which the double-sided adhesive sheet disclosed herein is attached is not particularly limited, but includes, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, titanium, Metal materials such as chromium, zinc, etc., or alloys containing two or more of these, such as polyimide resin, acrylic resin, polyether nitrile resin, polyether sulfone resin, polyester resin (PET resin, polyethylene various resins such as naphthalate resins, etc.), polyvinyl chloride resins, polyphenylene sulfide resins, polyetheretherketone resins, polyamide resins (so-called aramid resins, etc.), polyarylate resins, polycarbonate resins, liquid crystal polymers, etc. Examples include materials (typically plastic materials), inorganic materials such as alumina, zirconia, soda glass, quartz glass, and carbon. Among these, metal materials such as copper, aluminum, and stainless steel, and resin materials (typically plastic materials) such as polyester resins such as PET, polyimide resins, aramid resins, and polyphenylene sulfide resins are widely used. ing. The above-mentioned material may be a material of a member constituting a product such as an electronic device. The double-sided pressure-sensitive adhesive sheet disclosed herein can be used by being attached to a member made of the above material. Moreover, the above-mentioned material may be a material constituting the fixed object (for example, a back member such as an electromagnetic wave shield or a reinforcing plate) such as the pressure-sensitive sensor and the display section. Note that the object to be fixed refers to an object to which the double-sided pressure-sensitive adhesive sheet is attached, that is, an adherend. In addition, the back surface member refers to a member disposed on the opposite side of the pressure-sensitive sensor and the front surface (viewing side) of the display section in, for example, a portable electronic device, and for example, the display device shown in FIG. 4 described below. It may be a member constituting the support portion 540 disposed on the back surface of the device 500 . Further, the object to be fixed may have either a single-layer structure or a multi-layer structure, and the surface to which the double-sided pressure-sensitive adhesive sheet is attached (attached surface) may be subjected to various surface treatments. Although not particularly limited, an example of the object to be fixed is a back member with a thickness of 1 μm or more (typically 5 μm or more, e.g. 60 μm or more, even 120 μm or more) and 1500 μm or less (e.g. 800 μm or less). Can be mentioned.

In some embodiments, the member or material to which the double-sided pressure-sensitive adhesive sheet is attached may be light-transparent (light-transparent adherend). Since the adhesive surface of a double-sided adhesive sheet attached to a light-transparent adherend can be visually recognized through the light-transparent adherend, it is desirable to have an adhesive surface with good appearance quality. The light transmittance of the light-transmitting adherend may be, for example, greater than 50%, and may be 70% or more. In some preferred embodiments, the light transmittance of the adherend is 80% or more, more preferably 90% or more, and may be 95% or more (for example, 95 to 100%). Such a material may be a resin film (for example, a polyester resin film such as a PET film) placed on the back surface of an image display section of various devices such as portable electronic devices. The double-sided pressure-sensitive adhesive sheet disclosed herein can be preferably used in a mode where it is attached to an adherend (for example, a member) having a light transmittance of a predetermined value or more as described above. The above-mentioned light transmittance is a light transmittance at a wavelength of 550 nm, and can be measured in the same manner as the light transmittance at a wavelength of 550 nm of a double-sided pressure-sensitive adhesive sheet.

Moreover, in some embodiments, the double-sided pressure-sensitive adhesive sheet is used in a mode in which it is attached to a metal member. Examples of the material of the metal member include the metal materials exemplified as the adherend material. Such a metal member is, for example, a member or article having a surface (adhesive sheet pasting surface) made of a metal material such as aluminum or stainless steel, and a preferable example is a metal member such as a stainless steel member or an aluminum member. Examples include members. By attaching the double-sided pressure-sensitive adhesive sheet disclosed herein to the area on the surface of the metal member where concealment is required, the area of the metal member can be hidden. The double-sided adhesive sheet may cover the entire surface of the metal member, or may cover a portion of the surface (for example, a partial area where concealment is required). The metal member may be, for example, a member that constitutes a support portion 540 of a display device 500 shown in FIG. 4, which will be described later. The metal member is preferably one adherend of the double-sided pressure-sensitive adhesive sheet.

As described above, according to the technology disclosed herein, a laminate including a double-sided adhesive sheet and a member to which the double-sided adhesive sheet is attached is provided. In some embodiments, a laminate including a double-sided adhesive sheet is a laminate including the double-sided adhesive sheet and a metal member (first member). Such a laminate may include a metal member and a double-sided adhesive sheet covering at least a portion of the surface of the metal member. The double-sided adhesive sheet may cover the entire surface of the metal member, or may cover a portion of the surface (for example, a partial area where concealment is required). Typically, one surface (adhesive surface) of the double-sided adhesive sheet is attached to the metal member. In some embodiments, the member to which the double-sided pressure-sensitive adhesive sheet is attached may have the light transmittance of the adherend material described above. In this embodiment, the laminate including the double-sided adhesive sheet is a laminate including the double-sided adhesive sheet and a light-transmitting member (second member). In some preferred embodiments, the laminate includes a metal member (first member), a double-sided adhesive sheet, and a light-transmitting member (second member) in this order. Note that the base material-less double-sided adhesive sheet is also referred to as an adhesive layer in the laminate.

An example of the structure of the above-mentioned laminate is shown in FIG. The laminate 50 shown in FIG. 3 includes a first member 41, a double-sided adhesive sheet 1 without a base material, and a second member 42 in this order. Specifically, in the laminate 50, one adhesive surface (first adhesive surface) 1A of the base material-less double-sided adhesive sheet 1 is adhered to the first member 41, and the other adhesive surface of the double-sided adhesive sheet 1 is adhered to the first member 41. The surface (second adhesive surface) 1B is adhered to the second member 42. In this embodiment, both the first member 41 and the second member 42 have a sheet-like or plate-like shape, and the laminate 50 has a multilayer structure. Further, in this embodiment, the first member 41 is a metal member, and the second member 42 is a light-transmitting member. The details of the members constituting the laminate are the same as those described above for the members, materials, and adherends, so duplicate explanations will not be repeated.

Further, in some embodiments, the double-sided pressure-sensitive adhesive sheet is preferably used in electronic devices that include various light sources such as LEDs (light emitting diodes) and light emitting elements such as self-luminous organic EL. For example, it can be preferably used in electronic equipment (typically portable electronic equipment) that includes an organic EL display device or a liquid crystal display device that requires predetermined optical characteristics.

FIG. 4 is an exploded perspective view schematically showing a configuration example of a display device. As shown in FIG. 4, the display device 500 included in the portable electronic device 400 includes a display section 520 including a cover member, an organic EL unit, etc., and a support section 540. The display device 500 is configured to further include a double-sided adhesive sheet 530. In this configuration example, the double-sided adhesive sheet 530 fixes the members that constitute the display section 520 and the support section 540. Note that the support portion 540 includes a substrate (a metal plate such as a stainless steel plate or an aluminum plate), and the like. The double-sided pressure-sensitive adhesive sheet disclosed herein is preferably used as a component of the display device as described above.

In addition, since the double-sided adhesive sheet disclosed herein may have an adhesive layer containing an acrylic polymer with a high biomass carbon ratio in some embodiments, a conventional general acrylic adhesive ( That is, by being used as a substitute for acrylic adhesives in various applications where acrylic adhesives with a low biomass carbon ratio are used, it is possible to contribute to reducing dependence on fossil resource-based materials. The double-sided adhesive sheet disclosed herein can be preferably used as a double-sided adhesive sheet with reduced dependence on fossil resource materials.

The matters disclosed by this specification include the following.
[1] A display device including a display section including a cover member and an organic EL unit, and a support section,
A double-sided adhesive adhesive sheet is bonded to the support portion,
The double-sided adhesive sheet has a colored adhesive layer,
The adhesive layer includes an acrylic polymer,
In the display device, the adhesive layer has a storage modulus of 0.95 MPa or less at 0°C.
[2] The display device according to [1] above, wherein the monomer component constituting the acrylic polymer contains an alkyl acrylate having a chain alkyl group having 4 to 8 carbon atoms.
[3] The display device according to [1] or [2] above, wherein the monomer component constituting the acrylic polymer contains heptyl acrylate.
[4] The display device according to any one of [1] to [3] above, wherein the monomer component constituting the acrylic polymer contains n-butyl acrylate.
[5] The display device according to any one of [1] to [4] above, wherein the adhesive layer contains a black colorant.
[6] The display device according to any one of [1] to [5] above, wherein the adhesive layer includes a black colorant as a first colorant and a metal oxide as a second colorant. .
[7] The display device according to any one of [1] to [6] above, wherein the double-sided adhesive pressure-sensitive adhesive sheet is a base material-less pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.
[8] The display device according to any one of [1] to [6] above, wherein the double-sided adhesive pressure-sensitive adhesive sheet is a base-attached pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer and a supporting base material.

[11] A double-sided adhesive adhesive sheet, a first release liner that protects the first adhesive surface of the double-sided adhesive sheet, and a second release liner that protects the second adhesive surface of the double-sided adhesive sheet. A double-sided adhesive adhesive sheet with a release liner, comprising:
The double-sided adhesive sheet has a colored adhesive layer,
The adhesive layer includes an acrylic polymer,
The difference in release force between the release force R ₁ [N/50 mm] of the first release liner on the first adhesive surface and the release force R ₂ [N/50 mm] of the second release liner on the second adhesive surface is is 0.07 or more,
The adhesive layer is a double-sided adhesive adhesive sheet with a release liner and has a storage modulus of 0.95 MPa or less at 0°C.
[12] The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to [11] above, wherein the monomer component constituting the acrylic polymer contains an alkyl acrylate having a chain alkyl group having 4 to 8 carbon atoms.
[13] The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to [11] or [12] above, wherein the monomer component constituting the acrylic polymer contains heptyl acrylate.
[14] The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to any one of [11] to [13] above, wherein the monomer component constituting the acrylic polymer contains n-butyl acrylate.
[15] The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to any one of [11] to [14] above, wherein the pressure-sensitive adhesive layer contains a black colorant.
[16] The release liner according to any one of [11] to [15] above, wherein the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant. Comes with double-sided adhesive adhesive sheet.
[17] The peeling force R ₁ [N/50mm] of the first release liner from the first adhesive surface is greater than the peeling force R ₂ [N/50mm] of the second release liner from the second adhesive surface. is also low,
The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to any one of [11] to [16] above, wherein the release force R ₁ of the first release liner from the first adhesive surface is 0.3 N/50 mm or less.
[18] The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to any one of [11] to [17] above, wherein the double-sided adhesive pressure-sensitive adhesive sheet is a base material-less pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.
[19] The double-sided adhesive sheet with a release liner according to any one of [11] to [17] above, wherein the double-sided adhesive sheet is a base-attached adhesive sheet containing the adhesive layer and a supporting base material. adhesive sheet.
[20] The double-sided adhesive adhesive sheet with a release liner according to any one of [11] to [19] above, wherein the double-sided adhesive adhesive sheet is used for fixing members in electronic devices.

[21] A laminate comprising a metal member (first member) and a double-sided adhesive sheet,
The double-sided adhesive sheet has a colored adhesive layer,
The adhesive layer includes an acrylic polymer,
The adhesive layer is a laminate having a storage modulus of 0.95 MPa or less at 0°C.
[22] A laminate comprising a light-transmitting member (second member) and a double-sided adhesive adhesive sheet,
The double-sided adhesive sheet has a colored adhesive layer,
The adhesive layer includes an acrylic polymer,
The adhesive layer is a laminate having a storage modulus of 0.95 MPa or less at 0°C.
[23] A laminate comprising, in this order, a metal member (first member), a double-sided adhesive adhesive sheet, and a light-transmitting member (second member),
The double-sided adhesive sheet has a colored adhesive layer,
The adhesive layer includes an acrylic polymer,
The adhesive layer is a laminate having a storage modulus of 0.95 MPa or less at 0°C.
[24] The laminate according to [21] or [23] above, wherein the metal member is an aluminum member or a stainless steel member.
[25] The laminate according to [22] or [23] above, wherein the light transmittance of the light transmitting member is greater than 50%.
[26] The laminate according to [22], [23] or [25] above, wherein the light-transmitting member is made of a resin film.
[27] The laminate according to any one of [21] to [26] above, wherein the monomer component constituting the acrylic polymer contains an alkyl acrylate having a chain alkyl group having 4 to 8 carbon atoms. .
[28] The laminate according to any one of [21] to [27] above, wherein the monomer component constituting the acrylic polymer contains heptyl acrylate.
[29] The laminate according to any one of [21] to [28] above, wherein the monomer component constituting the acrylic polymer contains n-butyl acrylate.
[30] The laminate according to any one of [21] to [29] above, wherein the adhesive layer contains a black colorant.
[31] The laminate according to any one of [21] to [30] above, wherein the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant. .
[32] The laminate according to any one of [21] to [31] above, wherein the double-sided adhesive pressure-sensitive adhesive sheet is a base material-less pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer.
[33] The laminate according to any one of [21] to [31] above, wherein the double-sided adhesive pressure-sensitive adhesive sheet is a base-attached pressure-sensitive adhesive sheet containing the pressure-sensitive adhesive layer and a supporting base material.
[34] The laminate according to any one of [21] to [33] above, which is used for electronic equipment.

Hereinafter, some examples relating to the present invention will be described, but the present invention is not intended to be limited to what is shown in these examples. In the following description, "part" and "%" used as units of content and addition amount are based on weight unless otherwise specified.

<Evaluation method>
(storage modulus)
The storage modulus of the adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, a pressure-sensitive adhesive layer with a thickness of about 2 mm is produced by stacking a plurality of pressure-sensitive adhesive layers to be measured (in the case of a double-sided pressure-sensitive adhesive sheet without a base material, double-sided pressure-sensitive adhesive sheets). A sample of this adhesive layer was punched into a disk shape with a diameter of 7.9 mm, which was sandwiched and fixed between parallel plates. Dynamic viscoelasticity measurement is performed under the following conditions to determine the storage modulus (storage modulus at 0°C and 23°C).
・Measurement mode: Shear mode ・Temperature range: -70℃~150℃
・Heating rate: 5℃/min
・Measurement frequency: 1Hz
Note that the adhesive layer to be measured may be formed by applying a corresponding adhesive composition in a layered manner and drying or curing it.

(light transmittance)
The light transmittance [%] of the pressure-sensitive adhesive layer and pressure-sensitive adhesive sheet is measured using a commercially available spectrophotometer. It is determined by measuring the transmittance (transmittance). As the spectrophotometer, a spectrophotometer manufactured by Hitachi (device name: "U4150 type spectrophotometer") or its equivalent is used. Note that the light transmittances at wavelengths of 550 nm and 1380 nm correspond to visible light transmittance and infrared transmittance, respectively. Further, the above-mentioned light transmittance of the base material-less double-sided pressure-sensitive adhesive sheet consisting of the pressure-sensitive adhesive layer is also the light transmittance of the pressure-sensitive adhesive layer.

(Release force of release liner)
The release force R ₁ of the first release liner against the first adhesive surface is measured by the following method. That is, a test piece is obtained by cutting the double-sided pressure-sensitive adhesive sheet with a release liner according to each example into a strip having a width of 50 mm and a length of 150 mm. In an environment of 23° C. and 50% RH, the above test piece was set in a universal tensile compression testing machine, and the first release liner was applied at a peel angle of 180 degrees and a tensile speed of 300 mm/min in accordance with JIS Z0237. It is peeled off from the first adhesive surface, and the 180° peeling adhesive force (resistance to the above-mentioned tension) at this time is measured. The measurement is performed three times (N=3), and the average value thereof is defined as the peeling force R ₁ [N/50 mm] from the first adhesive surface of the first release liner.
The release force _R2 of the second release liner against the second adhesive surface is measured by the following method. That is, after peeling off the first release liner from the double-sided adhesive sheet with a release liner according to each example, and lining the exposed first adhesive surface with a PET film having a thickness of 25 μm, a strip having a width of 50 mm and a length of 150 mm was formed. Cut it into pieces to obtain test pieces. In an environment of 23°C and 50% RH, the above test piece was set in a universal tensile compression testing machine, and a second release liner was applied at a peel angle of 180 degrees and a tensile speed of 300 mm/min in accordance with JIS Z0237. It is peeled off from the second adhesive surface, and the 180° peeling adhesive force (resistance to the above-mentioned pulling force) at this time is measured. The measurement was performed three times (N=3), and the average value thereof was taken as the peeling force R ₂ [N/50 mm] from the second adhesive surface of the second release liner.
As the universal tensile compression tester, a device named "Tensile Compression Tester, TCM-1kNB" manufactured by Minebea Corporation or its equivalent is used.

(Evaluation of adhesive surface after removing liner)
The double-sided adhesive sheet with a release liner (laminate of first release liner/double-sided adhesive sheet/second release liner) according to each example was cut into a size of 50 mm x 100 mm and used as a sample for evaluation. In a clean room environment, the first release liner was peeled off from this evaluation sample at a peeling angle of 180 degrees and a peeling speed of 6 m/min, and after 1 hour, a point light source placed at a distance of about 100 cm and a projection liner were peeled off. The evaluation sample is held flat at the midpoint between the screen and the screen (at a distance of approximately 50 cm from the point light source), and the angle of the exposed adhesive layer surface of the evaluation sample with respect to the light beam from the point light source is determined. Arrange so that the angle is approximately 90 degrees. In the evaluation sample, the surface of the adhesive layer from which the first release liner was removed was placed on the point light source side. Deformation of the surface of the adhesive layer ( Specifically, the presence or absence of deformation extending in one direction on the adhesive surface, such as waving or streak-like roughness, is evaluated. As a point light source, for example, "xenon lamp C2577" manufactured by Hamamatsu Photonics Co., Ltd. can be used. For each example, 10 evaluation samples were prepared and the evaluation test was performed 10 times (N=10), and the number of evaluation tests (passed) in which no visible deformation was observed was determined by X (/10) after the liner was removed. This is the evaluation result of the adhesive surface. If the number of passes is 6 or more (that is, 6/10 or more), it is determined that deformation of the adhesive surface due to peeling of the release liner has been sufficiently suppressed.

<Example 1>
(Preparation of acrylic polymer)
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel, 95 parts of n-butyl acrylate (BA) and 5 parts of acrylic acid (AA) as monomer components and as a polymerization solvent were added. Ethyl acetate was charged and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.2 parts of 2,2'-azobisisobutyronitrile (AIBN) was added as a polymerization initiator, and solution polymerization was carried out at 60°C for 8 hours to obtain acrylic resin. A solution of the polymer was obtained. The Mw of this acrylic polymer was approximately 70×10 ⁴ .

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

(Preparation of double-sided adhesive sheet with release liner)
First release liner (product name "Diafoil MRF F4", manufactured by Mitsubishi Chemical Corporation, thickness 75 μm, polyester release liner) and second release liner (product name "SCA0", manufactured by Fujiko Co., Ltd., thickness 75 μm, made of PET) A release liner was prepared. The pressure-sensitive adhesive composition was applied to the release surface of the second release liner and dried at 100° C. for 2 minutes to form a pressure-sensitive adhesive layer with a thickness of 35 μm. The release surface of the first release liner was attached to this adhesive layer. In this way, the first and second adhesive surfaces of the 35 μm thick base material-less double-sided adhesive sheet made of the adhesive layer are protected by the first release liner and the second release liner, respectively. A double-sided adhesive sheet was obtained.

<Examples 2 to 6>
The adhesive compositions according to each example were prepared in the same manner as in Example 1, except that the type and amount of colorant in the adhesive layer, the amount of crosslinking agent, and the adhesive layer thickness were changed as shown in Table 1. A double-sided pressure-sensitive adhesive sheet with a release liner according to each example was prepared using the pressure-sensitive adhesive composition. In the table, the white colorant represents titanium oxide (TiO ₂ ) particles (product name "WHITE PASTE R-2228", manufactured by Dainichiseika Kagyo Co., Ltd., average particle size 50 nm).

<Examples 7 to 10>
(Synthesis of acrylic polymer)
In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser, and a dropping funnel, 93 parts of n-heptyl acrylate (n-HpA) and 7 parts of AA as monomer components, and ethyl acetate as a polymerization solvent were added. was charged and stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this manner, 0.2 part of AIBN was added as a polymerization initiator, and solution polymerization was carried out at 60° C. to 70° C. for 8 hours to obtain a solution of an acrylic polymer. The weight average molecular weight (Mw) of this acrylic polymer was 1.2 million. Note that the above n-HpA is a compound having a biomass-derived heptyl group at the ester end, which was synthesized using biomass-derived heptyl alcohol.

(Preparation of double-sided adhesive sheet with release liner)
The adhesive composition according to each example was prepared in the same manner as in Example 1 except that the above acrylic polymer solution was used and the types and amounts of the components contained in the adhesive layer and the adhesive layer thickness were changed as shown in Table 1. A double-sided pressure-sensitive adhesive sheet with a release liner according to each example was prepared using the pressure-sensitive adhesive composition. In the table, the rosin-based resin used as the tackifying resin is manufactured by Harima Kasei Co., Ltd. under the trade name "Haritac SE10" (hydrogenated rosin glycerin ester, softening point 75-85°C, hydroxyl value 25-40 mgKOH/g).

<Example 11>
An acrylic polymer solution according to this example was obtained basically in the same manner as in the preparation of the acrylic polymer in Example 7, except that the monomer composition of the acrylic polymer was changed to 97 parts of n-HpA and 3 parts of AA. A pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 7, except that the obtained acrylic polymer solution was used and the type and amount of the crosslinking agent were changed as shown in Table 1. A double-sided pressure-sensitive adhesive sheet with a release liner according to this example was prepared using the agent composition.

<Example 12>
This example was carried out in the same manner as in Example 7, except that a PET release liner manufactured by Toray Industries, Inc. (trade name "MFAS", thickness 38 μm) was used as the first release liner instead of "Diafoil MRF F4". A double-sided pressure-sensitive adhesive sheet with a release liner was produced.

<Example 13>
An adhesive composition prepared by the method described in Example 2 was prepared, and the adhesive composition was applied to one side of a 2 μm thick PET film (trade name "Lumirror", manufactured by Toray Industries, Inc.) as a base layer. It was applied to the surface (first side) and dried at 100° C. for 2 minutes to form a first adhesive layer with a thickness of 20 μm. The release surface of a first release liner (trade name "Diafoil MRF F4", manufactured by Mitsubishi Chemical Corporation, thickness 75 μm, polyester release liner) was bonded to the first adhesive layer. As the second release liner, a PET release liner manufactured by Fujiko Co., Ltd. (trade name "SCA0", thickness 75 μm) was prepared, the above-mentioned adhesive composition was applied to the release surface of the above-mentioned second release liner, and the pressure-sensitive adhesive composition was heated at 100°C. It was dried for 2 minutes to form a second adhesive layer with a thickness of 20 μm. This second adhesive layer was transferred to the adhesive layer-free surface of the base layer on which the first adhesive layer was formed. In this way, a double-sided adhesive sheet with a release liner (a double-sided adhesive sheet with a base material) according to this example was produced.

<Examples 14 to 16>
A double-sided adhesive sheet with a release liner (a double-sided adhesive sheet with a base material) according to Example 14 was prepared in the same manner as in Example 13, except that the adhesive composition prepared by the method described in Example 7 was used as the adhesive composition. sheet) was produced. Further, in Example 15, the thickness of the adhesive layer was changed to 35 μm. In Example 16, a 12 μm thick PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) was used as the base material layer. In other respects, double-sided pressure-sensitive adhesive sheets with a release liner (double-sided pressure-sensitive adhesive sheets with a base material) according to Examples 15 and 16 were produced in the same manner as in Example 14.

<Comparative example 1>
Example 1 was basically the same except that the monomer composition of the acrylic polymer was changed to 75 parts of 2-ethylhexyl acrylate (2EHA), 25 parts of acryloylmorpholine (ACMO), 0.1 part of hydroxyethyl acrylate (HEA), and 3 parts of AA. An acrylic polymer solution according to this example was obtained in the same manner as in the preparation of the acrylic polymer. Using the obtained acrylic polymer solution, a pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 1, except that the types and amounts of the components contained in the pressure-sensitive adhesive layer were changed as shown in Table 2. A double-sided pressure-sensitive adhesive sheet with a release liner according to this example was prepared using the pressure-sensitive adhesive composition.

<Comparative Examples 2 to 4>
Using the acrylic polymer prepared by the method described in Example 1, the types and amounts of components contained in the adhesive layer, adhesive layer thickness, and adhesive sheet configuration (presence or absence of base material) were changed as shown in Table 2. Other than that, adhesive compositions according to each example were prepared in the same manner as in Example 1, and double-sided adhesive sheets with release liners according to each example were produced using the adhesive compositions.

<Comparative example 5>
In Example 7, a PET release liner manufactured by Fujiko Co., Ltd. (product name "SCA0", thickness 75 μm) was used as the first release liner, and a PET release liner manufactured by Toray Industries, Inc. (product name "SCA0", thickness 75 μm) was used as the second release liner. ``Therapel BX8A'' (thickness: 75 μm) was used. Otherwise, a pressure-sensitive adhesive composition according to this example was prepared in the same manner as in Example 7, and a double-sided pressure-sensitive adhesive sheet with a release liner according to this example was produced using the pressure-sensitive adhesive composition.

The outline and evaluation results of each example are shown in Tables 1 and 2.

As shown in Tables 1 and 2, the double-sided pressure-sensitive adhesive sheets with release liners according to Examples 1 to 16 have a peel force difference of 0.07 [N/50 mm] or more between the first release liner and the second release liner. and has a colored adhesive layer, the storage modulus of the adhesive layer at 0°C is 0.95 MPa or less, and the number of passes in the adhesive surface evaluation after liner peeling is 6/10 or more Met. On the other hand, in Comparative Examples 1 to 4 in which the storage modulus of the adhesive layer at 0°C was over 0.95 MPa, the difference in peel force between the first release liner and the second release liner was 0.07 or more. However, the adhesive surface evaluation results after peeling off the liner were inferior to Examples 1 to 16. This is considered to be because the deformation of the adhesive surface was not sufficiently alleviated because the 0° C. storage modulus of the adhesive layer was high. In addition, Comparative Example 5 is an example of changing the release liner using the same double-sided adhesive sheet as in Example 7, but the difference in release force between the first release liner and the second release liner was 0.06, which was not sufficient. Compared to Example 7, the adhesive surface evaluation results after peeling off the liner were inferior.
From the above results, in a double-sided adhesive sheet with a release liner that has a first release liner and a second release liner and has a colored adhesive layer containing an acrylic polymer, the first release liner and the second release liner It can be seen that deformation of the adhesive surface due to peeling of the release liner can be highly suppressed by setting the peel force difference to 0.07 or more and the 0°C storage modulus of the adhesive layer to 0.95 MPa or less. .

Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above.

1, 2, 530 Double-sided adhesive sheet 1A First adhesive surface 1B Second adhesive surface 10 Support base material 10A First surface 10B Second surface 21 First adhesive layer (adhesive layer)
22 Second adhesive layer 31 First release liner 31A Release surface 31B Back surface 32 Second release liner 32A Release surface 32B Back surface 41 First member 42 Second member 50 Laminated body 100, 200 Double-sided adhesive sheet with release liner 400 Mobile electronic device 500 Display device 520 Display section 540 Support section

Claims (10)

A release comprising a double-sided adhesive adhesive sheet, a first release liner that protects a first adhesive surface of the double-sided adhesive sheet, and a second release liner that protects a second adhesive surface of the double-sided adhesive sheet. A double-sided adhesive adhesive sheet with a liner,
The double-sided adhesive sheet has a colored adhesive layer,
The adhesive layer includes an acrylic polymer,
The difference in release force between the release force R ₁ [N/50 mm] of the first release liner on the first adhesive surface and the release force R ₂ [N/50 mm] of the second release liner on the second adhesive surface is is 0.07 or more,
The adhesive layer is a double-sided adhesive adhesive sheet with a release liner and has a storage modulus of 0.95 MPa or less at 0°C. The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to claim 1, wherein the monomer component constituting the acrylic polymer contains an alkyl acrylate having a chain alkyl group having 4 to 8 carbon atoms. The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to claim 1, wherein the monomer component constituting the acrylic polymer contains heptyl acrylate. The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to claim 1, wherein the monomer component constituting the acrylic polymer contains n-butyl acrylate. The double-sided adhesive sheet with a release liner according to any one of claims 1 to 4, wherein the adhesive layer contains a black colorant. The double-sided adhesive with a release liner according to any one of claims 1 to 4, wherein the adhesive layer contains a black colorant as a first colorant and a metal oxide as a second colorant. adhesive sheet. A peel force R ₁ [N/50 mm] of the first release liner from the first adhesive surface is lower than a peel force R ₂ [N/50 mm] of the second release liner from the second adhesive surface,
The double-sided adhesive pressure-sensitive adhesive sheet with a release liner according to any one of claims 1 to 4, wherein a peel force R ₁ of the first release liner from the first adhesive surface is 0.3 N/50 mm or less. The double-sided adhesive adhesive sheet with a release liner according to any one of claims 1 to 4, wherein the double-sided adhesive adhesive sheet is a base material-less adhesive sheet comprising the adhesive layer. The double-sided adhesive sheet with a release liner according to any one of claims 1 to 4, wherein the double-sided adhesive sheet is a base-attached adhesive sheet containing the adhesive layer and a support base material. The double-sided adhesive sheet with a release liner according to any one of claims 1 to 4, wherein the double-sided adhesive sheet is used for fixing members in electronic devices.

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