KR20200115258A - Pressure sensitive adhesive sheet - Google Patents

Abstract

An object of the present invention is to provide an adhesive sheet which can exhibit satisfactory light-shielding properties in the direction of the sheet surface and can realize product inspection across the adhesive sheet. The present invention provides an adhesive sheet equipped with a base layer and an adhesive layer disposed on at least one surface of the base layer. In the adhesive sheet, a light transmittance T_z in the Z direction of the adhesive sheet exceeds 0.04% and is 50% or below, and the light transmittance T_XY per 1 mm width of the XY face of the adhesive sheet is smaller than the light transmittance T_Z in the Z direction. In this case, the XY face of the adhesive sheet is the sheet surface of the adhesive sheet, and the Z direction is the thickness direction of the adhesive sheet.

Description

Adhesive sheet {PRESSURE SENSITIVE ADHESIVE SHEET}

The present invention relates to an adhesive sheet.

In general, a pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive, hereinafter the same) exhibits a soft solid (viscoelastic material) state in a temperature range around room temperature, and has a property of simply adhering to an adherend under pressure. By utilizing such properties, pressure-sensitive adhesives are widely used for purposes of bonding, fixing, and protecting members in portable electronic devices such as mobile phones. Further, in the portable electronic device, for the purpose of preventing light leakage from a light source such as a backlight module, for example, a light-shielding adhesive sheet is used. Patent documents 1-6 are mentioned as a document concerning this kind of technology. Patent Documents 1 to 5 disclose a pressure-sensitive adhesive sheet provided with a black printing layer on one side of a resin film substrate. Patent document 6 is a prior art document which discloses a single-sided adhesive sheet laminated on a graphite sheet.

Japanese Laid-Open Patent Publication No. 2013-87246 Japanese Published Patent Publication No. 2013-166891 Japanese Published Patent Publication No. 2015-83660 Japanese Published Patent Publication No. 2017-57375 Japanese Published Patent Publication No. 2018-2898 Japanese Laid-Open Patent Publication No. 2017-52835

Portable electronic devices are required to be thinner and lighter for their portability and handling. In addition, from the viewpoint of visibility and operability, the display screen has a wider area (large screen), and accordingly, the periphery of the display screen There is a tendency for explosion. Therefore, in this application, a thin, thin light-shielding adhesive sheet is used. However, thinning or narrowing of the light-shielding pressure-sensitive adhesive sheet is accompanied by a decrease in light-shielding property because of a decrease in the light transmission distance. In particular, the narrow pressure-sensitive adhesive sheet is required to prevent light leakage from the narrow portion than in the thickness direction in which other members are laminated, and the light-shielding property in the pressure-sensitive adhesive sheet surface direction is more important. In addition, with respect to the object to be pasted (adhered body) of the light-shielding pressure-sensitive adhesive sheet, from the viewpoint of quality control or the like, it may be preferable to perform inspection after pasting the pressure-sensitive adhesive sheet.

The present invention has been created in view of the above circumstances, and an object of the present invention is to provide a pressure-sensitive adhesive sheet capable of exhibiting good light-shielding property in the direction of the sheet surface and capable of inspecting beyond the pressure-sensitive adhesive sheet.

According to the present specification, there is provided an adhesive sheet including a substrate layer and an adhesive layer disposed on at least one surface of the substrate layer. The pressure-sensitive adhesive sheet has a light transmittance T _Z of more than 0.04% and 50% or less in the Z direction, and a light transmittance T _XY per 1 mm of a width of the XY plane thereof is smaller than the light transmittance T _Z in the Z direction. Here, the XY plane of the PSA sheet is the sheet surface of the PSA sheet, and the Z direction is the thickness direction of the PSA sheet. Since the light transmittance T _XY in the XY plane direction is smaller than the light transmittance T _Z in the Z direction, the pressure-sensitive adhesive sheet having the above configuration can exhibit good light-shielding property in the sheet plane direction. The pressure-sensitive adhesive sheet having good light-shielding property in the direction of the sheet surface is excellent in preventing light leakage from the narrow portion, for example, in the aspect of using after being narrowed. Further, since the pressure-sensitive adhesive sheet has photosensitivity in the thickness direction, it is possible to inspect the adherend over the pressure-sensitive adhesive sheet.

In some preferred embodiments, the pressure-sensitive adhesive sheet has a light transmittance T _Z of 0.1% or more and 15% or less in the Z direction. When the light transmittance in the thickness direction is 15% or less, the pressure-sensitive adhesive sheet can preferably exhibit better light blocking properties. Further, according to the pressure-sensitive adhesive sheet having a light transmittance of 0.1% or more in the Z-direction, the inspection accuracy of the adherend beyond the pressure-sensitive adhesive sheet can be improved.

In some preferred embodiments, the pressure-sensitive adhesive sheet has a light transmittance T _XY of 0.04% or less per 1 mm of the width of the XY plane. A pressure-sensitive adhesive sheet that satisfies the above characteristics can exhibit more excellent light-shielding properties in the sheet surface direction.

In some preferred embodiments, the pressure-sensitive adhesive sheet has a difference (T _Z -T _XY ) between the light transmittance T _XY [%] and the light transmittance T _Z [%] of 1.00 or more. By constituting in this way, it is possible to suitably achieve both light shielding properties in the sheet surface direction and photosensitivity in the thickness direction.

In some preferred embodiments, the substrate layer contains a resin film containing a black colorant. By using a resin film containing a black colorant as a base material, a pressure-sensitive adhesive sheet having a predetermined XY plane direction light transmittance and a Z direction light transmittance can be preferably obtained. On the other hand, if the light transmittance in the thickness direction is increased in the configuration including the black printing layer, the black printing layer is thinned (typically, the number of layers of the multilayered black printing layer is reduced). The thinning of the black print layer has a problem that the risk of pinholes increases. In contrast, according to the black colorant-containing resin film, such pinholes do not occur, and local light leakage does not occur. Further, since the pressure-sensitive adhesive sheet provided with the black colorant-containing resin film is excellent in workability, it can be narrowed down with high precision. This can be an advantageous feature in a pressure-sensitive adhesive sheet that can preferably prevent light leakage from a narrow portion.

In some preferred embodiments, the thickness of the base layer is 0.5 µm to 10 µm. In the configuration using the substrate layer having the above thickness, light-shielding property in the sheet surface direction and photosensitivity in the thickness direction can be preferably realized.

In some preferred embodiments, the pressure-sensitive adhesive layer contains a black colorant. By using the pressure-sensitive adhesive containing a black colorant, the light transmittance in the XY plane direction of a predetermined value or less can be preferably realized.

In some preferred embodiments, the thickness of the pressure-sensitive adhesive layer is 1.5 µm to 60 µm. When the thickness of the pressure-sensitive adhesive layer is 1.5 µm or more, adhesion performance such as adhesion and impact resistance tends to be improved. Further, by making the thickness of the pressure-sensitive adhesive layer 60 μm or less, the pressure-sensitive adhesive sheet can be thinned. Further, in the configuration including the thin pressure-sensitive adhesive layer, there is a tendency that the light-shielding property in the direction of the sheet surface of the pressure-sensitive adhesive sheet is easily obtained.

The pressure-sensitive adhesive sheet disclosed herein has both an adhesive means and a light-shielding property by utilizing the light-shielding property in the direction of the sheet surface thereof. For example, it is used in an electronic device including a light emitting element such as a liquid crystal display (LCD) device including a backlight unit. It is preferably used.

In addition, the pressure-sensitive adhesive sheet disclosed herein is preferably used for portable electronic devices. In the use of portable electronic devices, the pressure-sensitive adhesive sheet may be processed and used in various shapes that become rims or narrow in accordance with the shape of the electronic device or the shape of the member. Since the light transmittance in the sheet surface direction of the pressure-sensitive adhesive sheet disclosed here is set to a relatively low value, good light-shielding property can be exhibited even if it is narrowed. The pressure-sensitive adhesive sheet disclosed herein is suitable for use in portable electronic devices having a light source, particularly in many cases, and is particularly preferred for use in portable electronic devices having a display screen. Such a portable electronic device may have a relatively large display screen (large screen) with respect to the device size.

1 is a cross-sectional view schematically showing a configuration example of an adhesive sheet.
2 is a schematic exploded perspective view schematically showing a configuration example of a liquid crystal display device.

Hereinafter, preferred embodiments of the present invention will be described. In addition, matters necessary for carrying out the present invention as matters other than those specifically mentioned in the present specification may be understood by those skilled in the art based on the teachings concerning the practice of the invention described in the present specification and common technical knowledge at the time of filing. The present invention can be implemented based on the content disclosed in this specification and the common technical knowledge in the field. In addition, in the following drawings, members and portions exhibiting the same action are denoted by the same reference numerals, and overlapping descriptions are omitted or simplified. In addition, the embodiment described in the drawings is schematically illustrated to clearly explain the present invention, and does not necessarily accurately display the size or scale of the pressure-sensitive adhesive sheet of the present invention actually provided as a product.

In the present specification, the "adhesive agent" refers to a material that exhibits a state of a soft solid (viscous elastic body) in a temperature range near room temperature and has a property of simply adhering to an adherend under pressure, as described above. As defined in "CA Dahlquist."Adhesion: Fundamental and Practice", McLaren & Sons, (1966) P.143", the pressure-sensitive adhesive referred to herein is generally a complex tensile modulus E ^* (1Hz) <10 ⁷ dyne/cm ^It may be a material having a property satisfying ² (typically, a material having the property at 25°C).

The pressure-sensitive adhesive sheet disclosed herein is a pressure-sensitive adhesive sheet with a substrate having a pressure-sensitive adhesive layer on at least one surface of the substrate layer (also referred to as a supporting substrate). The concept of the pressure-sensitive adhesive sheet referred to herein may include what is called an adhesive tape, an adhesive label, or an adhesive film. In addition, the pressure-sensitive adhesive sheet disclosed herein may be in the form of a roll or sheet form. Alternatively, it may be a pressure-sensitive adhesive sheet processed into more various shapes.

<Composition of adhesive sheet>

The pressure-sensitive adhesive sheet disclosed herein may, for example, have a cross-sectional structure schematically shown in FIG. 1. The pressure-sensitive adhesive sheet 1 shown in FIG. 1 includes a substrate layer 10, a first pressure-sensitive adhesive layer 21 and a first adhesive layer 21 supported on the first side 10A and the second side 10B of the base layer 10, respectively. It has 2 pressure-sensitive adhesive layer 22. Both the first surface 10A and the second surface 10B are non-removable surfaces (non-removable surfaces). The adhesive sheet 1 adheres the surface (first adhesive surface) 21A of the first adhesive layer 21 and the surface (second adhesive surface) 22A of the second adhesive layer 22 to an adherend, respectively. Used. That is, the adhesive sheet 1 is constituted as a double-sided adhesive sheet (double-sided adhesive adhesive sheet). The pressure-sensitive adhesive sheet 1 before use is applied to the release liners 31 and 32 in which the first adhesive surface 21A and the second adhesive surface 22A are at least the pressure-sensitive adhesive surface side to be a surface (release surface) having a peelability. Each has a protected configuration. Alternatively, the release liner 32 is omitted, and the release liner 31 is used as the release liner 31 on both sides, and the adhesive sheet 1 is wound to attach the second adhesive surface 22A to the release liner 31. By abutting on the back surface, the second adhesive surface 22A may also be configured to be protected by the release liner 31.

The technique disclosed herein is preferably implemented in the form of the above-described double-sided pressure-sensitive adhesive sheet with a base material for fixing or bonding a member. Alternatively, the pressure-sensitive adhesive sheet disclosed herein is not particularly illustrated, but may be in the form of a single-sided pressure-sensitive adhesive sheet with a substrate having an adhesive layer only on one side of the non-peelable substrate layer. As an example of the form of a single-sided pressure-sensitive adhesive sheet, in the configuration shown in FIG. 1, a form that does not have either the first pressure-sensitive adhesive layer 21 and the second pressure-sensitive adhesive layer 22 can be mentioned.

<Light transmittance of adhesive sheet>

The pressure-sensitive adhesive sheet disclosed herein is characterized by having a light transmittance T _Z of more than 0.04% in the Z direction. Here, the Z-direction of the pressure-sensitive adhesive sheet is a thickness direction (a direction extending according to the thickness) of the pressure-sensitive adhesive sheet, and it can be said that it is a direction extending perpendicularly to the sheet surface of the pressure-sensitive adhesive sheet. In this way, according to the pressure-sensitive adhesive sheet having a predetermined or more light transmittance (photosensitive property) with respect to the thickness direction, it is possible to inspect the adherend over the pressure-sensitive adhesive sheet. In addition, in the present specification, the term "photosensitive" refers to a light-shielding property that allows a certain degree of light transmittance without aiming for complete light-shielding. Photosensitivity can be understood as a different concept than transparency. The light transmittance T _Z in the Z direction of the pressure-sensitive adhesive sheet is preferably about 0.05% or more, more preferably about 0.1% or more (such as 0.1% or more), more preferably about 0.5% or more, particularly preferably about 1%. It is more than or equal to 1%. The upper limit of the Z-direction light transmittance T _Z is not particularly limited as long as the desired photosensitivity is obtained, and may be, for example, 50% or less. T _Z is appropriately about 30% or less (e.g., about 15% or less), and from the viewpoint of light-shielding property, preferably about 5% or less, more preferably about 4% or less, even more preferably about 3% or less ( For example, about 2% or less). The light transmittance T _Z of the pressure-sensitive adhesive sheet in the Z direction can be adjusted based on the light-shielding properties of the pressure-sensitive adhesive layer and the base material layer. The light transmittance T _Z of the pressure-sensitive adhesive sheet in the Z direction is measured by the method described in Examples to be described later.

One of the characteristics of the pressure-sensitive adhesive sheet disclosed herein is that the light transmittance T _XY per 1 mm of the width of the XY plane thereof is smaller than the light transmittance T _Z in the Z direction. Thereby, the adhesive sheet has good light-shielding property with respect to the sheet surface direction. Here, the XY surface of the adhesive sheet is the sheet surface of the adhesive sheet, and the light transmittance T _XY refers to the light transmittance per 1 mm of width (length) in one direction (also referred to as the sheet surface direction) along the sheet surface. In addition, it can be said that the X direction of the pressure-sensitive adhesive sheet is one direction along the sheet surface of the pressure-sensitive adhesive sheet and one direction on the sheet surface of the pressure-sensitive adhesive sheet. It can be said that the Y direction of the pressure-sensitive adhesive sheet is a direction along the sheet surface of the pressure-sensitive adhesive sheet or orthogonal to the X direction, is one direction on the sheet surface of the pressure-sensitive adhesive sheet, and is a direction orthogonal to the X direction. From the viewpoint of improving the light-shielding property in the direction of the sheet surface, the light transmittance T _XY is, for example, approximately 15% or less (for example, less than 15%), and may be approximately 5% or less (for example, less than 5%), and less than 4%, Further, it is suitable to be less than 3% (for example, approximately 1% or less). From the viewpoint of obtaining sufficient light-shielding property, the light transmittance T _XY is preferably 0.04% or less, more preferably 0.03% or less, still more preferably 0.02% or less, and particularly preferably 0.01% or less. The light transmittance T _XY in the XY plane direction of the pressure-sensitive adhesive sheet can be adjusted based on the light-shielding _properties of the pressure-sensitive adhesive layer and the substrate layer. The light transmittance T _XY is measured by the method described in Examples to be described later.

Since the pressure-sensitive adhesive sheet disclosed herein can have good light-shielding property in the direction of the sheet surface and photosensitivity in the thickness direction, the light transmittance T _XY [%] in the XY plane direction and the light transmittance in the Z direction It is different from T _Z [%]. In some embodiments, the difference (T _Z -T _XY ) between the light transmittance T _XY [%] and the light transmittance T _Z [%] is preferably 0.10 or more and 0.50 or more. From the viewpoint of compatibility between the light-shielding property in the sheet surface direction and the photosensitive property in the thickness direction, the difference (T _Z -T _XY ) is preferably 1.00 or more, more preferably 1.20 or more (for example, 1.40 or more). The upper limit of the difference (T _Z -T _XY ) is not particularly limited, but in some embodiments, it is approximately 10 or less (for example, approximately 5 or less), and 3.00 or less (for example, 2.00 or less) is suitable.

<Base layer>

The light transmittance of the substrate layer disclosed herein in the XY plane direction is appropriately set so that the light transmittance in the XY plane direction of the pressure-sensitive adhesive sheet is equal to or less than a predetermined value, and is not limited to a specific range. From the viewpoint of improving the light-shielding property in the direction of the sheet surface of the pressure-sensitive adhesive sheet, the light transmittance in the XY plane direction of the substrate layer is, for example, about 15% or less (eg, less than 15%), and may be about 5% or less (eg, less than 5%), , Less than 4%, further less than 3% (eg, less than about 1%) is suitable. The light transmittance of the substrate layer in the XY plane direction is preferably 0.04% or less, more preferably 0.03% or less, still more preferably 0.02% or less, and particularly preferably 0.01% or less. Such XY plane direction light transmittance can be preferably realized by use of a base film containing a black colorant (preferably a resin film in which a black colorant is kneaded).

The light transmittance in the Z direction of the base material layer can be appropriately set within a range in which the light transmittance in the Z direction of the pressure-sensitive adhesive sheet becomes a predetermined value, and is not limited to a specific range. It is appropriate that the light transmittance of the substrate layer in the Z direction exceeds 0.04%. The light transmittance in the Z direction of the substrate layer is preferably about 0.05% or more, more preferably about 0.1% or more (such as 0.1%), more preferably about 0.5% or more, particularly preferably about 1% or more (such as 1%). Setting the Z-direction light transmittance of the base layer to a predetermined value or more is significant not only from photosensitive properties, but also from an industrial point of view including maintenance of properties (processability, mechanical properties) of the base layer, and productivity and efficiency. The upper limit of the light transmittance in the Z direction of the base layer may be approximately 50% or less. The light transmittance is preferably approximately 30% or less (eg, approximately 15% or less). From the viewpoint of light-shielding property, the light transmittance is preferably about 5% or less, more preferably about 4% or less, and even more preferably about 3% or less (eg, about 2% or less). The light transmittance in the Z direction of the base layer can be adjusted by use of a base film containing a black colorant or arrangement of a black layer.

The light transmittance in the XY plane direction of the base layer is the light transmittance per 1 mm of the width of the XY plane of the base layer, and specifically, it can be measured by the same method as the method of measuring the light transmittance in the XY plane direction of the adhesive sheet in the examples described later. Alternatively, it can be estimated from the light transmittance in the Z direction of the substrate layer. The light transmittance in the Z direction of the base layer is measured by the method described in Examples to be described later.

The structure and material of the substrate layer disclosed herein is not particularly limited as long as it satisfies the light transmittance characteristic of the pressure-sensitive adhesive sheet. The substrate layer specifically includes a film-like substrate (also referred to as a "substrate film"). As a base film, what contains a resin film as a base film can be used preferably. The base film is typically an independently shape-maintainable (independent) member. The base film in the technology disclosed herein may be substantially composed of such a base film. Alternatively, the base layer 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, and an antistatic layer provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (eg, a component contained in an amount exceeding 50% by weight in the resin film). Examples of the resin film include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymer; Polyester resin films such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN); Polyurethane 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. The resin film may be a blend film obtained by mixing two or more of the resin types exemplified above. Among them, from the viewpoint of handling property and workability, a polyester film is preferred, and among them, a PET film is particularly preferred. In addition, in this specification, the "resin film" is typically a non-porous sheet, and is a concept distinguished from a so-called nonwoven fabric or woven fabric (a concept excluding nonwoven fabric or woven fabric when reduced).

The base layer (typically a resin film) can contain a colorant. Thereby, the light transmittance (light-shielding property) of the base layer can be adjusted. Specifically, it is possible to adjust the light transmittance characteristics of the base layer and further the light transmittance characteristics of the pressure-sensitive adhesive sheet. Various pigments and dyes can be used as the colorant. As the color of the colorant, colored is preferable. The color of the colorant may be, for example, black, gray, red, blue, yellow, green, yellowish green, orange, purple, gold, silver, pearl, and the like. Colored colorants tend to be excellent in light-shielding properties, and tend to be excellent in visibility and design properties in the sense including discriminant by machine. From the viewpoint of light-shielding properties, the use of a black colorant is preferred. The colorant may or may not contain a colorless colorant in combination with a colorless colorant. The substrate layer according to a typical embodiment disclosed herein may be one that does not substantially contain a colorless colorant. In addition, in the present specification, "colored" means including black or metallic color. In addition, "colorless" means including white.

In a typical embodiment, the substrate layer is a substrate layer comprising a black colorant. More specifically, it can be said that it is a base film layer (typically a resin film layer) in which a black colorant was kneaded. Here, the base film (typically a resin film) in which a black colorant is kneaded refers to a base film in which a black colorant is mixed in the main constituent material of the base film (the material most often contained in the base film, typically a resin material). Say. The black colorant is substantially contained in the base film in a dispersed state. The dispersion state of the black colorant in the base film is not particularly limited, and the black colorant is preferably dispersed in the base layer to the extent that the light transmittance in the XY plane direction of the pressure-sensitive adhesive sheet becomes a predetermined value or less. In addition, the above-described black colorant-containing base layer can be said to be a black base layer (for example, a black resin film layer) because it itself is colored black.

According to the pressure-sensitive adhesive sheet provided with the black colorant-containing base layer, good light-shielding property can be realized in the direction of the sheet surface. In addition, since the PSA sheet provided with the black colorant-containing base film does not cause defects such as pinholes even when it is bent, it is also excellent in durability as a light-shielding PSA sheet. In particular, when trying to obtain photosensitivity in a colored layer (e.g., a black printing layer) disposed on the surface of the base film, the colored layer is thinned (typically, reducing the number of layers of the multilayered black printing layer), but coloring When the layer is made thinner, pinholes are liable to occur. According to the base film containing the black colorant, such pinholes do not occur, and local light leakage can be prevented. Moreover, since the adhesive sheet provided with the base film containing a black coloring agent is excellent in processability, it can finely narrow down with precision.

As the black colorant contained in the base layer, an organic or inorganic colorant (pigment, dye, etc.) can be used. Specific examples of the black colorant include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, smoke smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black. , Activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, anthraquinone-based colorants, and the like. Black colorants may be used alone or in combination of two or more. Among them, carbon black is preferable.

The black colorant is not particularly limited, and a particulate colorant (pigment) can be preferably used because the light-shielding property can be efficiently controlled by using a small amount. In some preferred embodiments, black colorants (eg, black pigments such as carbon black) with an average particle diameter of about 10 nm or more (eg, about 50 nm or more) may be used. The upper limit of the average particle diameter of the black colorant is not particularly limited, and may be about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, such as 200 nm or less (for example, about 120 nm or less). . In addition, the term ``average particle diameter'' in this specification refers to a particle diameter at 50% of the cumulative value in the particle size distribution measured based on a particle size distribution measuring device based on laser scattering and diffraction, unless otherwise specified. Particle diameter; hereinafter, it may be abbreviated as D ₅₀ ).

The content of the black colorant in the base layer is not particularly limited, and may be an amount adjusted appropriately so as to impart the desired light-shielding property. The content of the black colorant is suitably about 0.1 to 30% by weight of the total weight of the base layer, and may be, for example, 0.1 to 25% by weight (typically 0.1 to 20% by weight).

The base material layer disclosed here may contain one type or two or more types of colorants (pigments or dyes) other than black colorants. As such a non-black colorant, a white colorant can be mentioned, for example. As a white colorant, for example, titanium oxide (titanium dioxide such as rutile type titanium dioxide and anatase type titanium dioxide), zinc oxide, aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, calcium oxide, tin oxide, barium oxide, Cesium oxide, yttrium oxide, magnesium carbonate, calcium carbonate (hard calcium carbonate, heavy calcium carbonate, etc.), barium carbonate, zinc carbonate, aluminum hydroxide, calcium hydroxide, magnesium hydroxide, zinc hydroxide, aluminum silicate, magnesium silicate, calcium silicate, barium sulfate , Calcium sulfate, barium stearate, zinc oxide, zinc sulfide, talc, silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, serie Inorganic white colorants such as sites and hydrohalosite, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, silicone resin particles, urea-formalin resin particles, melamine resin And organic white colorants such as particles. These can be used alone or in combination of two or more.

The content of the non-black colorant in the base layer is not particularly limited, and can be adjusted as appropriate so as to impart desired optical properties. The content of the non-black colorant is suitably about 0.1 to 30% by weight of the weight of the base layer, and may be, for example, 0.1 to 25% by weight (typically 0.1 to 20% by weight).

Various additives such as fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents, lubricants, plasticizers, etc. may be blended in the base layer as necessary. The blending ratio of the various additives is on the order of less than about 30% by weight (eg, less than 20% by weight, typically less than 10% by weight).

The base layer may have a single-layer structure, or may have a two-layer, three-layer, or more multilayer structure. From the viewpoint of shape stability, it is preferable that the base layer has a single layer structure. In the case of a multilayer structure, at least one layer (preferably all layers) may be a layer having a continuous structure of a resin containing a black colorant (eg, a polyester-based resin containing a black colorant). The manufacturing method of the base material layer (for example, a resin film layer) should just adopt a conventionally well-known method suitably, and is not specifically limited. For example, conventionally known general film forming methods such as extrusion molding, inflation molding, T-die cast molding, and calender roll molding can be appropriately employed.

The base film may be colored by a colored layer disposed on the surface of the base film (preferably a resin film). As described above, in the substrate layer having a configuration including a base film and a colored layer, the base film may or may not contain a colorant. The colored layer may be disposed on either surface of the base film or may be disposed on both surfaces. In a configuration in which colored layers are disposed on both surfaces of the base film, respectively, the configuration of the colored layers may be the same or different.

Such a colored layer can be formed by applying a composition for forming a colored layer, typically containing a colorant and a binder, to a base film. As the colorant, similarly to the colorant that can be contained in the pressure-sensitive adhesive layer or the base film, a conventionally known pigment or dye can be used. As the binder, materials known in the field of paints or printing can be used without particular limitation. For example, a polyurethane, a phenol resin, an epoxy resin, a urea melamine resin, a polymethyl methacrylate, etc. are illustrated. The composition for forming a colored layer may be, for example, a solvent type, an ultraviolet curing type, or a heat curing type. The formation of the colored layer can be performed by employing a means employed for forming the colored layer than in the prior art without particular limitation. For example, a method of forming a colored layer (printed layer) by printing such as gravure printing, flexo printing, or offset printing can be preferably employed.

The colored layer may have a single-layer structure including one layer as a whole, or a multilayer structure including two, three or more sub-colored layers. The colored layer having a multilayer structure including two or more sub-colored layers can be formed, for example, by repeatedly applying (for example, printing) a colored layer forming composition. The color and compounding amount of the colorants contained in each sub-colored layer may be the same or different.

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

In the aspect in which the base film (preferably a resin film) contains a black colorant, the base layer may be one that does not contain a colored layer such as that disposed on the surface of the base film. According to the technique disclosed herein, since good light-shielding property is obtained by use of the base film containing a black colorant, the use of the colored layer is not required. This is advantageous also in terms of preventing a pinhole, which may be a problem in the type of obtaining light-shielding property in the colored layer, local light leakage due to it, scratch resistance, and chemical resistance (eg, solvent resistance).

The surface of the substrate layer (typically the substrate film) may be subjected to conventionally known surface treatment such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, and application of an undercoat agent. Such surface treatment may be a treatment for improving the adhesion between the base layer and the pressure-sensitive adhesive layer, in other words, the seepage property of the pressure-sensitive adhesive layer to the base layer. In addition, when the technique disclosed herein is implemented in the form of a single-sided pressure-sensitive adhesive sheet with a substrate, a peeling treatment may be applied to the back surface of the substrate layer as necessary. The peeling treatment may be, for example, a treatment in which a general silicon-based, long-chain alkyl-based, fluorine-based peeling treatment agent is applied in a thin film shape of typically 0.01 μm to 1 μm (eg, 0.01 μm to 0.1 μm). By performing such peeling treatment, an effect such as facilitating rewinding of the wound body in which the pressure-sensitive adhesive sheet is wound in a roll shape can be obtained.

The thickness of the substrate layer disclosed herein is not particularly limited. From the viewpoint of avoiding the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the base layer (eg, resin film layer) is, for example, approximately 200 µm or less, approximately 150 µm or less is appropriate, and may be approximately 100 µm or less. The substrate layer having a limited thickness is preferably used for applications requiring thinner or lighter weight. In addition, by increasing the thickness of the pressure-sensitive adhesive layer by limiting the thickness of the base layer, for example, it is possible to improve adhesion properties such as peel strength and impact resistance, and followability to the adherend surface having a step (step followability). There is a tendency to improve. From such a point of view, the thickness of the substrate layer is preferably less than 75 μm (eg, less than about 60 μm), more preferably less than about 50 μm (eg less than 50 μm), more preferably less than about 40 μm, particularly It is preferably approximately 30 μm or less (eg, less than 30 μm, typically approximately 25 μm or less). In some embodiments, the thickness of the substrate layer may be approximately 20 μm or less, approximately 12 μm or less, and may be approximately 7 μm or less (eg, approximately 3 μm or less).

The lower limit of the thickness of the base layer is not particularly limited. From the viewpoint of handling property (handling property) and workability of the pressure-sensitive adhesive sheet, it is appropriate that the thickness of the substrate layer is approximately 0.5 μm or more (eg, approximately 1 μm or more). By increasing the thickness of the base layer, there is a tendency that high light-shielding properties are easily obtained. In some embodiments, the thickness of the substrate layer may be approximately 3 μm or more. In some other embodiments, the thickness of the base layer may be approximately 8 μm or more, may be approximately 13 μm or more, and may be approximately 16 μm or more.

<Adhesive layer>

The pressure-sensitive adhesive layer disclosed herein is not particularly limited as long as the pressure-sensitive adhesive sheet satisfies a predetermined light transmittance characteristic, and may be used by selecting an appropriate one from among various pressure-sensitive adhesives according to target adhesive properties. The light transmittance of the pressure-sensitive adhesive layer is also not limited to a specific range because the pressure-sensitive adhesive sheet can be appropriately set within a range that satisfies the predetermined light transmittance characteristic. From the viewpoint of improving the light-shielding property of the pressure-sensitive adhesive sheet, the light transmittance in the Z direction of the pressure-sensitive adhesive layer is suitably about 70% or less, preferably about 60% or less, for example, about 50% or less. According to the pressure-sensitive adhesive layer having the Z-direction light transmittance, good light-shielding property tends to be preferably obtained in the direction of the sheet surface of the pressure-sensitive adhesive sheet. In addition, since the pressure-sensitive adhesive sheet disclosed herein has photosensitivity in the thickness direction, the light transmittance in the Z direction of the pressure-sensitive adhesive layer is 0.1% or more (for example, approximately 1% or more), and can be approximately 5% or more. It is suitable to be 10% or more, and preferably about 20% (for example, about 30% or more). The pressure-sensitive adhesive layer exhibiting a light transmittance of a predetermined value or more is easy to maintain adhesive properties, and is advantageous from an industrial standpoint including productivity and efficiency. The light transmittance of the pressure-sensitive adhesive layer in the Z direction is measured by the method described in Examples to be described later.

(Base polymer)

In the technique disclosed herein, the kind of the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is not particularly limited. The pressure-sensitive adhesive is one or two types of various rubber-like polymers such as acrylic polymers, rubber polymers, polyester polymers, urethane polymers, polyether polymers, silicone polymers, polyamide polymers, and fluorine polymers known in the adhesive field. It may include the above as a base polymer. From the viewpoint of adhesion performance and cost, etc., a pressure-sensitive adhesive containing an acrylic polymer or a rubber polymer as a base polymer can be preferably employed. Among them, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) using an acrylic polymer as a base polymer is preferable. Hereinafter, a pressure-sensitive adhesive layer composed of an acrylic pressure-sensitive adhesive, that is, a pressure-sensitive adhesive sheet having an acrylic pressure-sensitive adhesive layer will be mainly described, but it is not intended to limit the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet disclosed herein to that of an acrylic pressure-sensitive adhesive.

In addition, the'base polymer' of the pressure-sensitive adhesive refers to the main component of the rubber-like polymer contained in the pressure-sensitive adhesive. The rubbery polymer refers to a polymer exhibiting rubber elasticity in a temperature range near room temperature. In addition, in this specification, the "main component" refers to a component contained in excess of 50% by weight, unless otherwise specified.

In addition, "acrylic polymer" refers to a polymer comprising a monomer unit derived from a monomer having at least one (meth)acryloyl group in one molecule as a monomer unit constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as an “acrylic monomer”. Accordingly, the acrylic polymer in this specification is defined as a polymer containing a monomer unit derived from an acrylic monomer. As a typical example of the acrylic polymer, an acrylic polymer in which the proportion of acrylic monomers among all monomer components used for synthesis of the acrylic polymer is greater than 50% by weight can be mentioned.

In addition,'(meth)acryloyl' is a meaning that comprehensively indicates acryloyl and methacryloyl. Similarly,'(meth)acrylate' refers to acrylate and methacrylate, and'(meth)acryl' refers to acryl and methacrylic, respectively.

(Acrylic polymer)

Although not particularly limited, in a preferred embodiment of the technology disclosed herein, the pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is preferably a polymer of a raw material of a monomer that contains an alkyl (meth) acrylate as a main monomer and may further contain a minor monomer copolymerizable with the main monomer. Here, the main monomer refers to a component contained in the monomer raw material in excess of 50% by weight.

As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.

[Formula 1]

CH ₂ =C(R ¹ )COOR ²

Here, R ¹ in Formula 1 is a hydrogen atom or a methyl group. In addition, R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, the range of the number of carbon atoms is sometimes expressed as “C _1-20 ”). From the viewpoint of the storage modulus of the pressure-sensitive adhesive, etc., an alkyl (meth)acrylate in which R ² is a C _1-14 chain alkyl group is preferable, and an alkyl (meth) acrylate in which R ² is a C _1-10 chain alkyl group is more preferable. And, an alkyl (meth)acrylate in which R ² is a butyl group or a 2-ethylhexyl group is particularly preferable.

Examples of the alkyl (meth)acrylate wherein R ² is a C _1-20 chain alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n -Butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate )Acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate , Isodecyl(meth)acrylate, undecyl(meth)acrylate, dodecyl(meth)acrylate, tridecyl(meth)acrylate, tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexa Decyl (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. Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

In the technology disclosed herein, the monomer component constituting the acrylic polymer contains at least one of BA and 2EHA, and the total amount of BA and 2EHA in the alkyl (meth)acrylate contained in the monomer component is 75% by weight or more ( Typically, 85% by weight or more, such as 90% by weight or more, and further 95% by weight or more). The technique disclosed herein can be implemented, for example, in an embodiment in which the alkyl (meth)acrylate contained in the monomer component is BA alone, 2EHA alone, and BA and 2EHA.

The technology disclosed herein can be preferably carried out in an embodiment in which the monomer component constituting the acrylic polymer contains 50% by weight or more of C _1-6 alkyl (meth)acrylate. In other words, the polymerization ratio of C _1-6 alkyl (meth) acrylate in the acrylic polymer is preferably 50% by weight or more. As described above, by using C _1-6 alkyl (meth) acrylate as the main monomer, an acrylic polymer having excellent deformation resistance (eg, deformation resistance to a continuous load) can be preferably designed. The proportion of C _1-6 alkyl (meth)acrylate in the monomer component (in other words, the polymerization ratio) is more preferably greater than 50% by weight, still more preferably 60% by weight or more, particularly preferably 70% by weight Or more (for example, 80% by weight or more, further 85% by weight or more). By using C _1-6 alkyl (meth)acrylate (e.g. BA) in a predetermined amount or more, even when a black colorant such as carbon black is mixed with the pressure-sensitive adhesive, the colorant is well dispersed in the layer, while adhesion such as adhesion. It can maintain good properties. The upper limit of the ratio of C _1-6 alkyl (meth) acrylate in the monomer component is not particularly limited, for example, 99% by weight or less, in relation to the ratio of use of other copolymerizable monomers, it is suitable that it is 97% by weight or less, It is preferable to set it as 95 weight% or less. C _1-6 alkyl (meth)acrylate may be used alone or in combination of two or more. As C _1-6 alkyl (meth)acrylate, C _1-6 alkyl acrylate is preferable, C _2-6 alkyl acrylate is more preferable, and C _4-6 alkyl acrylate is still more preferable. In some other embodiments, the C _1-6 alkyl(meth)acrylate is preferably a C _1-4 alkylacrylate, more preferably a C _2-4 alkylacrylate. BA is mentioned as a preferable example of C _1-6 alkyl (meth)acrylate.

In the embodiment using BA as the main monomer, the copolymerization ratio of BA in the acrylic polymer is preferably 50% by weight or more, more preferably more than 50% by weight, still more preferably 60% by weight or more, particularly preferably 70% by weight or more (eg 80% by weight or more, further 85% by weight or more), more particularly preferably 90% by weight or more (eg more than 90% by weight). By copolymerizing BA as the main monomer, the pressure-sensitive adhesive is easy to obtain good adhesion to the adherend. When BA is used in a predetermined amount or more, even when a black colorant such as carbon black is mixed with the pressure-sensitive adhesive, the colorant can be satisfactorily dispersed in the layer while maintaining good adhesion properties such as adhesion. In addition, the copolymerization ratio of BA in the acrylic polymer is not particularly limited, for example, 99% by weight or less, in relation to the copolymerization ratio of other copolymerizable monomers (such as an acidic group-containing monomer), it is suitable that it is 97% by weight or less, It is preferable to set it as 95 weight% or less.

In some preferred embodiments, an acidic group-containing monomer is used as a monomer copolymerizable with the main monomer, alkyl (meth)acrylate. The acidic group-containing monomer can exhibit improved cohesiveness based on its polarity and good bonding strength to a polar adherend. In addition, when a crosslinking agent such as an isocyanate-based or epoxy-based crosslinking agent is used, the acidic group (typically a carboxyl group) becomes a crosslinking point of the acrylic polymer. Deformation resistance can be preferably realized by these actions. By using the acidic group-containing monomer in a predetermined or higher ratio, it is possible to suitably design an acrylic polymer capable of realizing, for example, initial adhesiveness (for example, light compression initial adhesiveness) and resistance to deformation.

As the acid group-containing monomer, a carboxy group-containing monomer is preferably used. Examples of the carboxy group-containing monomer include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, crotonic acid, and isocrotonic acid; And ethylenically unsaturated dicarboxylic acids such as maleic acid, itaconic acid, and citraconic acid, and anhydrides thereof (maleic anhydride, itaconic anhydride, etc.). Further, the acidic group-containing monomer may be a monomer having a carboxy group metal salt (eg, an alkali metal salt). The acidic group-containing monomer can be used singly or in combination of two or more. Among them, AA and MAA are preferable, and AA is more preferable. When using one or more acidic group-containing monomers, the proportion of AA in the acidic group-containing monomer is preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight. % Or more. In a particularly preferred embodiment, the acidic group-containing monomer contains substantially only AA. AA is optimal for achieving a balance between initial adhesion and deformation resistance in the acidic group-containing monomer disclosed herein because of its complex action such as polarity based on its carboxy group, a role as a crosslinking point, and Tg (106°C). It is considered a monomer material.

In the technique disclosed herein, the content of the acidic group-containing monomer (typically a carboxy group-containing monomer) in the monomer component (in other words, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer) is not particularly limited, and is approximately 0.1 It can be made into weight% or more, and it is suitable to be approximately 1 weight% or more. In some preferred embodiments, the content of the acidic group-containing monomer in the monomer component is approximately 3% by weight or more, more preferably approximately 5% by weight or more. By using a predetermined amount or more of an acidic group-containing monomer, it is possible to preferably realize an acrylic polymer capable of achieving both initial adhesiveness and deformation resistance based on its cohesiveness improving action and the like. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is suitably 20% by weight or less, and from the viewpoint of maintaining the properties of the main monomer, preferably 18% by weight or less. The copolymerization ratio may be 15% by weight or less, such as 13% by weight or less. In a more preferred embodiment, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is about 12% by weight or less, more preferably about 10% by weight or less, and particularly preferably about 8% by weight or less. In an acrylic polymer with a monomer composition containing a large amount of C _1-6 alkyl (meth) acrylate (typically BA), it is particularly effective to set the content of the acidic group-containing monomer (such as AA) in the monomer component within the above range. . In addition, by copolymerizing a predetermined amount of an acidic group-containing monomer (typically a carboxy group-containing monomer) in the above range, even when a black colorant such as carbon black is mixed with the pressure-sensitive adhesive, the colorant is well dispersed in the layer, Adhesive properties can be preferably realized.

In some preferred embodiments, in the monomer component constituting the acrylic polymer, the ratio of the content ratio C _A of the acidic group-containing monomer to the content ratio C _M of the above-described main monomer (typically alkyl (meth) acrylate) ( C _A /C _M (%); calculated from C _A /C _M ×100) can be about 1% or more by weight, it is appropriate to be about 3% or more, and about 5% or more Preferably, it may be about 7% or more, for example. By using a monomer containing a predetermined amount or more of an acidic group with respect to the main monomer (typically alkyl (meth)acrylate), the adhesion performance by the main monomer and the cohesiveness improvement effect by the acidic group-containing monomer can be preferably compatible. An acrylic polymer can be obtained. It is appropriate that the ratio (C _A /C _M ) be approximately 25% or less, and preferably 20% or less from the viewpoint of maintaining the properties of the main monomer. The ratio (C _A /C _M ) may be 15% or less, such as 13% or less. In a more preferred embodiment, the ratio (C _A /C _M ) is approximately 11% or less, and more preferably approximately 9% or less. In an acrylic polymer with a monomer composition containing a large amount of C _1-6 alkyl (meth) acrylate (typically BA), it is particularly effective to set the content of the acidic group-containing monomer (such as AA) in the monomer component within the above range. .

In the technique disclosed herein, a copolymerizable monomer other than an acid group-containing monomer (typically a carboxy group-containing monomer) can be used as a secondary monomer copolymerizable with the main monomer, alkyl (meth)acrylate. As such a sub-monomer, for example, the following functional group-containing monomers can be used.

Hydroxyl-containing monomer: For example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc. Hydroxyalkyl (meth)acrylates; Unsaturated alcohols such as vinyl alcohol and allyl alcohol; Polypropylene glycol mono(meth)acrylate.

Amide group-containing monomer: For example, (meth)acrylamide, N,N-dimethyl (meth)acrylamide, N-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methylolpropane (meth) )Acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide.

Amino group-containing monomers: For example, aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.

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

Cyano group-containing monomers: for example, acrylonitrile and methacrylonitrile.

Keto group-containing monomers: For example, diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, vinyl acetoacetate.

Monomers having a nitrogen atom-containing ring: For example, N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine , N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinyl caprolactam, N-(meth)acryloylmorpholine.

Alkoxysilyl group-containing monomer: For example, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-( Meth)acryloxypropylmethyldiethoxysilane.

The functional group-containing monomer may be used singly or in combination of two or more. When the monomer component constituting the acrylic polymer contains a functional group-containing monomer, the ratio of the functional group-containing monomer occupying the monomer component is appropriately determined according to the required performance. The ratio (copolymerization ratio) of the functional group-containing monomer (e.g., a hydroxyl group-containing monomer) is suitably about 0.01% by weight or more (eg 0.02% by weight or more, typically 0.03% by weight or more), further 0.1% by weight. It may be about 0.5% by weight or more, typically 1% by weight or more. In addition, the upper limit thereof is preferably about 40% by weight or less (for example, 30% by weight or less, typically 20% by weight or less). In a more preferred embodiment, the ratio of the functional group-containing monomer other than the acidic group-containing monomer is suitably set to, for example, 10% by weight or less, and further 5% by weight or less, and may be 1% by weight or less. In a more preferred embodiment, the proportion of a functional group-containing monomer other than the acidic group-containing monomer (eg, a hydroxyl group-containing monomer) is approximately 0.5% by weight or less (for example, approximately 0.2% by weight or less). The acrylic polymer having the monomer composition may be one that is easy to disperse a black colorant such as carbon black.

As the monomer component constituting the acrylic polymer, other copolymerization components other than the acidic group-containing monomer and other sub-monomers can be used for the purpose of enhancing the cohesive strength of the acrylic polymer. Examples of such copolymerization components include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; Aromatic vinyl compounds such as styrene, substituted styrene (α-methylstyrene, etc.), and vinyl toluene; Cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate, cyclopentyl (meth)acrylate, and isobornyl (meth)acrylate; Aryl (meth) acrylate (e.g., phenyl (meth) acrylate), aryloxyalkyl (meth) acrylate (e.g., phenoxyethyl (meth) acrylate), arylalkyl (meth) acrylate (e.g., benzyl ( Aromatic ring-containing (meth)acrylates such as meth)acrylate); Olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; Chlorine-containing monomers such as vinyl chloride and vinylidene chloride; Isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; Alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; Vinyl ether-based monomers such as methyl vinyl ether and ethyl vinyl ether; And the like.

The amount of these other copolymerization components may be appropriately selected depending on the purpose and use, and is not particularly limited, but is preferably 10% by weight or less of the monomer component. For example, when a vinyl ester-based monomer (such as vinyl acetate) is used as the other copolymerization component, the content thereof may be, for example, about 0.1% by weight or more (typically about 0.5% by weight or more) of the monomer component, and about 20 It is appropriate to set it as weight% or less (typically about 10 weight% or less).

As another monomer component, the acrylic polymer may contain a polyfunctional monomer having at least two polymerizable functional groups (typically radically polymerizable functional groups) having an unsaturated double bond such as a (meth)acryloyl group or a vinyl group. . By using a polyfunctional monomer as the monomer component, the cohesive strength of the pressure-sensitive adhesive layer can be increased. The polyfunctional monomer can be used as a crosslinking agent.

Examples of the polyfunctional monomer include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, neopentyl glycol di (meth) Acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,4 -Butanedioldi(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, 1,12-dodecanedioldi(meth)acrylate, trimethylolpropanetri(meth)acrylate, tetramethylolmethanetri Esters of polyhydric alcohols such as (meth)acrylate and (meth)acrylic acid; Allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, and the like. Preferred examples of these include trimethylolpropane tri(meth)acrylate, 1,6-hexanedioldi(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. Among these, 1,6-hexanedioldi(meth)acrylate is mentioned as a preferable example. The polyfunctional monomer may be used alone or in combination of two or more. From the viewpoint of reactivity, etc., a polyfunctional monomer having two or more acryloyl groups is preferable.

The amount of the polyfunctional monomer used is not particularly limited, and may be appropriately set so that the purpose of use of the polyfunctional monomer is achieved. From the viewpoint of good balance between the preferred storage modulus disclosed herein and other adhesive performance or other properties, the amount of the polyfunctional monomer used may be approximately 3% by weight or less of the monomer component, and approximately 2% by weight or less is preferable. And, about 1% by weight or less (for example, about 0.5% by weight or less) is more preferable. The lower limit of the amount used in the case of using the polyfunctional monomer may be greater than 0% by weight, and is not particularly limited. By setting the amount of the polyfunctional monomer to be about 0.001% by weight or more (for example, about 0.01% by weight or more) of the monomer component, the effect of using the polyfunctional monomer can be appropriately exhibited.

The composition of the monomer component constituting the acrylic polymer is suitably designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately -15°C or lower (eg, approximately -70°C or higher and -15°C or lower). Here, Tg of the acrylic polymer refers to Tg obtained by Fox's formula based on the composition of the monomer component. The formula of Fox is a relational expression between the Tg of the copolymer and the glass transition temperature Tgi of the homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.

1/Tg=Σ(Wi/Tgi)

In addition, in the formula of Fox, Tg is the glass transition temperature (unit: K) of the copolymer, Wi is the weight fraction (copolymerization ratio based on weight) of the monomer (i) in the copolymer, and Tgi is the monomer (i). It shows the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer to be used for calculating Tg, the value described in publicly known data is assumed to be used. For example, for the monomers listed below, the following values are used as the glass transition temperature of the homopolymer of the monomer.

2-ethylhexylacrylate -70℃

n-butyl acrylate -55℃

Ethyl acrylate -22℃

Methyl acrylate 8℃

Methyl methacrylate 105℃

2-hydroxyethyl acrylate -15℃

4-hydroxybutylacrylate -40℃

Vinyl acetate 32℃

Styrene 100℃

Acrylic acid 106℃

Methacrylic acid 228℃

For the glass transition temperature of a homopolymer of a monomer other than those exemplified above, the numerical values described in the "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) are used. For the monomers for which plural types of values are described in this document, the highest value is adopted.

For a monomer for which the glass transition temperature of the homopolymer is not described in the document as well, a value obtained by the following measurement method is used.

Specifically, 100 parts by weight of a monomer, 0.2 parts by weight of 2,2'-azobisisobutyronitrile, and 200 parts by weight of ethyl acetate as a polymerization solvent were added to a reactor equipped with a thermometer, a stirrer, a nitrogen introduction tube and a reflux cooling tube, Stir for 1 hour while flowing nitrogen gas. After removing oxygen in the polymerization system in this way, the temperature is raised to 63°C and reacted for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid content concentration of 33% by weight. Subsequently, this homopolymer solution is cast onto a release liner and dried to prepare a test sample (sheet-shaped homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, inserted into a parallel plate, and a viscoelasticity tester (manufactured by T-A Instrument Japan, model name'ARES') was used to apply shear deformation at a frequency of 1 Hz, while temperature The viscoelasticity is measured by shear mode at a temperature rising rate of -70°C to 150°C in the range of 5°C/min, and the temperature corresponding to the peak top temperature of tan δ is taken as Tg of the homopolymer.

Although not particularly limited, from the viewpoint of adhesion, it is advantageous that the acrylic polymer has a Tg of about -25°C or less, preferably about -35°C or less, more preferably about -40°C or less, even more preferably -45 It is less than or equal to C. For example, it may be less than or equal to -50 C, or less than or equal to -55 C. Further, from the viewpoint of the cohesive force of the pressure-sensitive adhesive layer, the Tg of the acrylic polymer is approximately -75°C or higher, preferably approximately -70°C or higher. The technique disclosed herein can be preferably implemented in an aspect in which the acrylic polymer has a Tg of approximately -65°C or higher and approximately -40°C or lower (eg, approximately -65°C or higher and approximately -45°C or lower). In some preferred embodiments, the Tg of the acrylic polymer may be approximately -55°C or higher and approximately -45°C or lower. In some other embodiments, the Tg of the acrylic polymer may be greater than or equal to about -65°C and less than or equal to about -55°C. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the type or amount of the monomer used for synthesis of the polymer).

Mw of the acrylic polymer is not particularly limited, and may be, for example, approximately 10×10 ⁴ or more and 500×10 ⁴ or less. From the viewpoint of cohesiveness, the Mw is, for example, about 30×10 ⁴ or more, and it is suitable to be about 45×10 ⁴ or more (eg, about 65×10 ⁴ or more). In some preferred embodiments, Mw of the acrylic polymer is 70×10 ⁴ or more. Mw of the acrylic polymer is suitably larger than 70×10 ⁴ . By using an acrylic polymer having a Mw of more than 70×10 ⁴ , excellent deformation resistance is obtained against a continuous deformation load based on its cohesiveness. Mw of the acrylic polymer is more preferably about 75×10 ⁴ or more, still more preferably about 90×10 ⁴ or more, and particularly preferably about 95×10 ⁴ or more. In a particularly preferred embodiment, the Mw is about 100×10 ⁴ or more (eg, about 110×10 ⁴ or more), and typically 120×10 ⁴ or more (eg 130×10 ⁴ or more). Further, it is appropriate that the Mw is approximately 300 × 10 ⁴ or less (more preferably approximately 200 × 10 ⁴ or less, for example, approximately 150 × 10 ⁴ or less). Mw of the acrylic polymer may be approximately 145×10 ⁴ or less. For example, in an acrylic polymer obtained by a solution polymerization method or an emulsion polymerization method, it is preferable to use Mw in the above range.

The dispersion degree (Mw/Mn) of the acrylic polymer disclosed here is not particularly limited. The dispersity (Mw/Mn) here refers to the dispersity (Mw/Mn) expressed by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In some preferred embodiments, the dispersion degree (Mw/Mn) of the acrylic polymer is less than 15. For example, in an acrylic polymer having a relatively high molecular weight (typically more than 700,000 Mw) obtained by a solution polymerization method or an emulsion polymerization method, Mw/Mn in the above range is preferable. The Mw/Mn of an acrylic polymer of less than 15 means that when the polymer has a relatively high molecular weight, it contains a significant amount of a relatively uniform high molecular weight, and the cohesiveness based on the high molecular weight is accurately expressed and excellent deformation resistance is exhibited. The Mw/Mn is preferably less than 12, more preferably less than 10, even more preferably less than 8 (eg 7.5 or less). Further, the Mw/Mn is theoretically 1 or more, for example 2 or more, 3 or more, and 4 or more (typically 5 or more).

In addition, Mw, Mn, and Mw/Mn can be adjusted by polymerization conditions (time, temperature, etc.), use of a chain transfer agent, selection of a polymerization solvent based on a chain transfer constant, and the like. In addition, Mw and Mn are obtained from values in terms of standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC device, for example, the model name "HLC-8320GPC" (column: TSKgelGMH(S), manufactured by Tosoh Corporation) can be used.

The polymerization method of the base polymer (typically acrylic polymer) is not particularly limited, and various conventionally known polymerization methods can be appropriately employed. Thermal polymerization such as solution polymerization, emulsion polymerization, and bulk polymerization (typically, it is carried out in the presence of a thermal polymerization initiator); Photopolymerization performed by irradiating light such as ultraviolet rays (typically, it is performed in the presence of a photopolymerization initiator); radiation polymerization performed by irradiating radiation such as β-rays and γ-rays; Etc. can be appropriately adopted. Among them, solution polymerization and photopolymerization are preferable. In these polymerization methods, the mode of polymerization is not particularly limited, and a conventionally known method of supplying monomers, polymerization conditions (temperature, time, pressure, light irradiation, radiation dose, etc.), materials other than monomers (polymerization initiator, surfactant, etc. ) And the like can be selected appropriately.

For example, in some preferred embodiments, a solution polymerization method can be employed for synthesis of an acrylic polymer. According to the solution polymerization, a polymerization reaction solution in which an acrylic polymer is dissolved in an organic solvent is obtained. The pressure-sensitive adhesive layer in the technology disclosed herein may be formed from a pressure-sensitive adhesive composition containing the polymerization reaction solution or an acrylic polymer solution obtained by performing a suitable post-treatment on the reaction solution. As the acrylic polymer solution, one prepared by preparing the polymerization reaction solution to an appropriate viscosity (concentration) as necessary can be used. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (eg, emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used.

As a method of supplying the monomers when performing solution polymerization, a batch injection method, a continuous supply (dropping) method, a divided supply (dropping) method, or the like in which all monomer raw materials are supplied at once can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent to be used, the type of polymerization initiator, and the like, and may be, for example, about 20°C to 170°C (usually about 40°C to 140°C). In some preferred embodiments, the polymerization temperature may be about 75°C or less (more preferably about 65°C or less, such as about 45°C to 65°C).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from known organic solvents. Aromatic compounds such as toluene and xylene (eg, aromatic hydrocarbons); Acetic acid esters such as ethyl acetate and butyl acetate; Aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane; Halogenated alkanes such as 1,2-dichloroethane; Lower alcohols such as isopropyl alcohol (eg, monohydric alcohols having 1 to 4 carbon atoms); ethers such as tert-butyl methyl ether; Ketones such as methyl ethyl ketone and acetone; Any one type of solvent or two or more types of mixed solvents selected from, for example, can be used.

Although it does not specifically limit as a polymerization initiator, For example, an azo-based polymerization initiator, a peroxide-based initiator, a redox-based initiator obtained by a combination of a peroxide and a reducing agent, and a substituted ethane-based initiator can be used. More specifically, for example, 2,2'-azobisisobutyronitrile (AIBN), 2,2'-azobis(2-methylpropionamidine) disulfate, 2,2'-azobis(2-amidin) Dinopropane)dihydrochloride, 2,2'-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2'-azobis(N,N' -Azo initiators such as dimethylene isobutylamidine) and 2,2'-azobis[N-(2-carboxyethyl)-2-methylpropionamidine]hydrate; Persulfates such as potassium persulfate and ammonium persulfate; Peroxide initiators such as benzoyl peroxide (BPO), t-butyl hydroperoxide, and hydrogen peroxide; Substituted ethane initiators such as phenyl substituted ethane; Redox initiators such as a combination of persulfate and sodium hydrogen sulfite, and a combination of peroxide and sodium ascorbate; Etc. are illustrated, but are not limited to these. The polymerization initiator can be used singly or in appropriate combinations of two or more. Further, the polymerization can be preferably carried out at a temperature of, for example, about 20 to 100°C (typically 40 to 80°C).

The amount of the polymerization initiator used may be an appropriate amount depending on the polymerization method or polymerization type, and is not particularly limited. For example, about 0.001 to 5 parts by weight of the polymerization initiator (typically about 0.01 to 2 parts by weight, for example, about 0.01 to 1 part by weight) can be used per 100 parts by weight of the monomer to be polymerized.

(Crosslinking agent)

It is preferable that the adhesive composition (preferably a solvent-type adhesive composition) used for formation of an adhesive layer contains a crosslinking agent as an optional component. By including a crosslinking agent, the viscoelastic properties disclosed herein can be preferably realized. The pressure-sensitive 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 form partially crosslinked, or an intermediate or complex form thereof. The crosslinking agent is included in the pressure-sensitive adhesive layer only after the crosslinking reaction.

The kind of crosslinking agent is not particularly limited, and can be appropriately selected and used from conventionally known crosslinking agents. Examples of such crosslinking agents include isocyanate crosslinking agents, epoxy crosslinking agents, oxazoline crosslinking agents, aziridine crosslinking agents, melamine crosslinking agents, carbodiimide crosslinking agents, hydrazine crosslinking agents, amine crosslinking agents, peroxide crosslinking agents, and metal chelate crosslinking agents. , A metal alkoxide-based crosslinking agent, and a metal salt-based crosslinking agent. Crosslinking agents may be used alone or in combination of two or more. As a crosslinking agent which can be preferably used in the technology disclosed herein, an isocyanate crosslinking agent, an epoxy crosslinking agent, and an oxazoline crosslinking agent are exemplified.

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

Although not particularly limited, examples of the epoxy-based crosslinking agent include, for example, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylamino Methyl) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether, and the like. Commercially available epoxy-based crosslinking agents include Mitsubishi Gas Chemical's brand name'TETRAD-C' and brand name'TETRAD-X', DIC's brand name'Epiclon CR-5L', and Nagase Chemtex's brand name'Denacol EX-'. 512' and the brand name'TEPIC-G' manufactured by Nissan Chemical Industries, Inc. are mentioned.

In the aspect of using the epoxy-based crosslinking agent, the amount of use thereof is not particularly limited. The amount of the epoxy-based crosslinking agent may be, for example, more than 0 parts by weight and approximately 1 part by weight or less (preferably approximately 0.001 to 0.5 parts by weight) based on 100 parts by weight of the acrylic polymer. From the viewpoint of desirably exhibiting the effect of improving cohesion, the amount of the epoxy-based crosslinking agent is appropriately set at about 0.002 parts by weight or more, preferably about 0.005 parts by weight or more, for example, about 0.01 parts by weight based on 100 parts by weight of the acrylic polymer. It may be at least part, about 0.02 part by weight or more, and about 0.03 part by weight or more. In addition, from the viewpoint of avoiding insufficient adhesion due to excessive crosslinking, the amount of the epoxy-based crosslinking agent is appropriately set to be approximately 0.2 parts by weight or less, and approximately 0.1 parts by weight or less (for example, 0.05 parts by weight or less) based on 100 parts by weight of the acrylic polymer. It is desirable to do.

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

As a preferred polyfunctional isocyanate, a polyfunctional isocyanate having three or more isocyanate groups on average per molecule is exemplified. The trifunctional or higher isocyanate may be a multimer (e.g., a dimer or a trimer), a derivative (e.g., an addition reaction product of a polyhydric alcohol and a polyfunctional isocyanate having two or more molecules), a polymer, or the like of a bifunctional or trifunctional or higher isocyanate. . For example, a dimer or a trimer of diphenylmethane diisocyanate, an isocyanurate product of hexamethylene diisocyanate (a trimer adduct of an isocyanurate structure), a reaction product of trimethylolpropane and tolylene diisocyanate, trimethyl Polyfunctional isocyanates such as reaction products of allpropane and hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate. As a commercial product of such a polyfunctional isocyanate, Asahi Kasei Chemicals' brand name'Duranate TPA-100', Toso's brand name'Colonate L','Colonate HL','Colonate HK','Colonate HX' And'Colonate 2096'.

In the aspect in which an isocyanate-based crosslinking agent is used, the amount of use thereof is not particularly limited. The amount of the isocyanate crosslinking agent may be, for example, about 0.5 parts by weight or more and about 10 parts by weight or less based on 100 parts by weight of the acrylic polymer. From the viewpoint of cohesiveness, the amount of the isocyanate-based crosslinking agent to 100 parts by weight of the acrylic polymer is appropriately set to be approximately 0.1 parts by weight or more, and preferably approximately 0.3 parts by weight or more (for example, 0.5 parts by weight or more). In a more preferred embodiment, the amount of the isocyanate crosslinking agent to 100 parts by weight of the acrylic polymer is approximately 1 part by weight or more, and may be approximately 1.5 parts by weight or more. In addition, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is appropriately set to approximately 8 parts by weight or less, and approximately 5 parts by weight or less (for example, less than approximately 4 parts by weight). In a more preferred embodiment, the amount of the isocyanate-based crosslinking agent used per 100 parts by weight of the acrylic polymer is approximately 3 parts by weight or less, for example, 2 parts by weight or less.

The technique disclosed herein can be preferably implemented in an aspect using at least an epoxy-based crosslinking agent as a crosslinking agent. The epoxy group of the epoxy-based crosslinking agent can react with an acidic group that can be introduced into the acrylic polymer to form a crosslinked structure. The cohesiveness of the pressure-sensitive adhesive is increased by the crosslinking reaction thereof, and deformation resistance to a continuous load is more preferably exhibited. Examples of such an aspect include an aspect in which an epoxy-based crosslinking agent is used alone, and an aspect in which an epoxy-based crosslinking agent and another crosslinking agent are used in combination. In some embodiments, the pressure-sensitive adhesive composition substantially does not contain an isocyanate-based crosslinking agent including an epoxy-based crosslinking agent as a crosslinking agent.

In some other embodiments, the pressure-sensitive adhesive composition includes an isocyanate-based crosslinking agent as a crosslinking agent. The isocyanate group of the isocyanate-based crosslinking agent may react with an acidic group that may be introduced into the acrylic polymer in a reaction form different from that of the epoxy-based crosslinking agent to form a crosslinked structure. It is significant to use an isocyanate-based crosslinking agent from the viewpoint of improving the water permeability to the base layer.

In a particularly preferred embodiment, the pressure-sensitive adhesive composition contains both an epoxy crosslinking agent and an isocyanate crosslinking agent as a crosslinking agent. For example, by using an epoxy-based crosslinking agent and an isocyanate-based crosslinking agent in combination with an acrylic polymer having an acidic group, deformation resistance can be further improved without impairing initial adhesion. The ratio of the content C _I of the isocyanate crosslinking agent to the content C _E of the epoxy crosslinking agent (C _I /C _E ) is not particularly limited, and is appropriately set according to the required characteristics. The ratio (C _I /C _E ) is, for example, greater than 1, suitably greater than or equal to about 5, preferably greater than or equal to about 15, more preferably greater than or equal to about 30, more preferably greater than or equal to about 60, particularly preferably greater than or equal to about 80 or more (eg about 100 or more). Further, the ratio (C _I /C _E ) is, for example, about 1000 or less, and it is appropriate to be about 500 or less, and preferably about 200 or less.

The content of the crosslinking agent (total amount of the crosslinking agent) in the pressure-sensitive adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesiveness, the content of the crosslinking agent may be approximately 0.001 parts by weight or more, and it is appropriate to be approximately 0.002 parts by weight or more, preferably approximately 0.005 parts by weight based on 100 parts by weight of the base polymer (preferably acrylic polymer). It is at least about 0.01 parts by weight, more preferably at least about 0.02 parts by weight, and particularly preferably at least about 0.03 parts by weight. In addition, from the viewpoint of avoiding lack of initial adhesiveness, the content of the crosslinking agent in the pressure-sensitive adhesive composition may be approximately 20 parts by weight or less, and preferably approximately 15 parts by weight or less, and approximately 10 parts by weight per 100 parts by weight of the base polymer. It is preferable to use it in parts or less (for example, approximately 5 parts by weight or less).

(coloring agent)

A colorant may be contained in the pressure-sensitive adhesive layer. Thereby, the light transmittance (light-shielding property) of the pressure-sensitive adhesive layer can be adjusted. Adjusting the light transmittance of the pressure-sensitive adhesive layer can also be helpful in adjusting the light transmittance of the pressure-sensitive adhesive sheet including the pressure-sensitive adhesive layer. As the colorant, various materials capable of attenuating by reflecting and/or absorbing light traveling inside the pressure-sensitive adhesive layer can be used. The color of the colorant is not particularly limited, and may be colored or colorless. The color of the colorant may be, for example, black, gray, white, red, blue, yellow, green, yellow green, orange, purple, gold, silver, pearl, and the like. The colorant may be included in the pressure-sensitive adhesive layer, typically in a dispersed state (may be dissolved) in the constituent material of the pressure-sensitive adhesive layer.

As the colorant, various pigments and dyes can be used. As a pigment, for example, zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide, iron hydroxide, chromium oxide, spinel Inorganic pigments such as calcination type, chromic acid type, chromium vermillion type, photosensitive type, aluminum powder type, bronze powder type, silver powder type, calcium phosphate type, phthalocyanine type, azo type, condensed azo type, azo lake type, anthra Organic pigments such as quinone-based, perylene-perinone-based, indigo-based, thioindigo-based, isoindolinone-based, azomethine-based, dioxazine-based, quinacridone-based, aniline black-based, triphenylmethane-based, and carbon black-based. I can. Examples of the dye include azo dyes, anthraquinone, quinonephthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine. . The coloring agent may be used alone or in combination of two or more as appropriate.

Since the light-shielding property can be efficiently controlled with a small amount of colorant, a black colorant can be preferably used. Specific examples of the black colorant include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, smoke smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, Ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, anthraquinone-based colorants, and the like. These may be used alone or in combination of two or more as appropriate. Among them, carbon black is preferable.

Since the light-shielding property of the pressure-sensitive adhesive layer can be efficiently controlled with a small amount of colorant, a particulate colorant (pigment) can be preferably used. In some preferred embodiments, a pigment having an average particle diameter of about 10 nm or more (eg, a particulate black colorant such as carbon black) may be used. The average particle diameter may be, for example, approximately 50 nm or more, approximately 100 nm or more, or approximately 150 nm or more. The upper limit of the average particle diameter of the colorant is not particularly limited, and may be, for example, about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, and even more preferably 200 nm or less (eg, 120 nm or less). .

The content of the colorant can be appropriately set so that a pressure-sensitive adhesive sheet that satisfies the predetermined light transmittance characteristic is formed, and is not limited to a specific range. The content of the colorant may be about 0.1% by weight or more in the pressure-sensitive adhesive layer, and it is appropriate to be about 0.5% by weight or more, and from the viewpoint of light-shielding property, preferably about 1% by weight or more, more preferably about 2% by weight. % Or more, more preferably about 3% by weight or more (eg about 4% by weight or more). In addition, the upper limit of the content of the colorant can be, for example, less than 15% by weight in the pressure-sensitive adhesive layer. From the viewpoint of photosensitivity, the content of the colorant is suitably less than 10% by weight in the pressure-sensitive adhesive layer, preferably less than 8% by weight, and more preferably less than 7% by weight. Limiting the amount of the colorant contained in the pressure-sensitive adhesive layer is also preferable from the viewpoint of suppressing deterioration of the adhesive properties and maintaining the desired performance.

The pressure-sensitive adhesive layer may contain a component that contributes to improving the dispersibility of the colorant. Such dispersibility enhancing components may be, for example, polymers, oligomers, liquid resins, surfactants, and the like. It is preferable that the said dispersibility improving component is dissolved in an adhesive layer. The oligomer is, for example, a low molecular weight polymer of a monomer component comprising one or two or more acrylic monomers as exemplified above (e.g., an acrylic polymer having an Mw of less than about 10×10 ⁴ , preferably less than 5×10 ⁴ Oligomer). The liquid resin is, for example, a tackifying resin having a softening point of about 50°C or less, more preferably about 40°C or less (typically, a tackifying resin such as rosin-based, terpene-based, or hydrocarbon-based, for example, hydrogenated rosin. Methyl ester, etc.). With such a dispersibility improving component, it is possible to suppress the dispersion unevenness of the colorant (for example, a particulate black colorant such as carbon black) and further suppress the color unevenness of the pressure-sensitive adhesive layer. Therefore, it is possible to form a pressure-sensitive adhesive sheet having better appearance quality.

The content of the dispersibility improving component is not particularly limited, and from the viewpoint of suppressing the influence on the adhesive properties (for example, lowering of cohesiveness), about 20% by weight or less of the entire pressure-sensitive adhesive layer (preferably about 10% by weight or less, more Preferably it is 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, such as about 3 times or less) the weight of the colorant. On the other hand, from the viewpoint of preferably exerting the effect of the dispersibility improving component, its content should be about 0.2% by weight or more (typically about 0.5% by weight or more, preferably about 1% by weight or more) of the entire pressure-sensitive adhesive layer. It is suitable. In some embodiments, the content of the dispersibility enhancing component may be approximately 0.2 times or more (preferably approximately 0.5 times or more, such as 1 or more times) the weight of the colorant.

(Adhesive imparting resin)

In some preferred embodiments, the pressure-sensitive adhesive layer contains a tackifier resin. Examples of the tackifying resin include phenol-based tackifying resin, terpene-based tackifying resin, modified terpene-based tackifying resin, rosin-based tackifying resin, hydrocarbon-based tackifying resin, epoxy-based tackifying resin, polyamide-based tackifying resin, and elastomer. One type or two or more types selected from various known tackifying resins such as a system tackifying resin and a ketone type tackifying resin can be used. Adhesive strength is improved by the use of tackifying resin.

Examples of the phenolic tackifying resin include terpenephenol resins, hydrogenated terpenephenol resins, alkylphenol resins, and rosin phenol resins.

The term terpenephenol resin refers to a polymer containing a terpene residue and a phenol residue, and a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin) and terpenes or a homopolymer or copolymer thereof is phenol modified ( It is a concept including both phenol-modified terpene resin). Preferred examples of terpenes constituting such a terpenephenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d, l and d/l forms (dipentene)). have. The hydrogenated terpenephenol resin refers to a hydrogenated terpenephenol resin having a structure obtained by hydrogenating such a terpenephenol resin. It is sometimes referred to as a hydrogenated terpenephenol resin.

The alkylphenol resin is a resin (oil-based phenol resin) obtained from alkylphenol and formaldehyde. Examples of the alkylphenol resin include novolac-type and resor-type ones.

The rosin phenol resin is typically a phenol modified product of rosin or various rosin derivatives described above (including rosin esters, unsaturated fatty acid modified rosin and unsaturated fatty acid modified rosin ester). Examples of rosin phenol resins include rosin phenol resins obtained by thermal polymerization by adding phenol as an acid catalyst to rosin or various rosin derivatives described above.

Among these phenolic tackifying resins, terpenephenol resins, hydrogenated terpenephenol resins, and alkylphenol resins are preferred, terpenephenol resins and hydrogenated terpenephenol resins are more preferred, and terpenephenol resins are particularly preferred.

Examples of the terpene-based tackifying resin include polymers of terpenes (eg, monoterpenes) such as α-pinene, β-pinene, d-limonene, l-limonene, and dipentene. It may be a homopolymer of one type of terpene, or a copolymer of two or more types of terpenes. As a homopolymer of one type of terpene, an α-pinene polymer, a β-pinene polymer, and a dipentene polymer may be mentioned.

Examples of the modified terpene resin include those obtained by modifying the terpene resin. Specifically, a styrene-modified terpene resin, a hydrogenated terpene resin, etc. are illustrated.

The concept of the rosin-based tackifying resin referred to herein includes both rosin and rosin derivative resins. Examples of rosin include unmodified rosin (raw rosin) such as gum rosin, wood rosin, and tall oil rosin; These unmodified rosin are modified by hydrogenation, disproportionation, polymerization, or the like, and modified rosin (hydrogenated rosin, disproportionation rosin, polymerized rosin, other chemically modified rosin, etc.).

The rosin derivative resin is typically a derivative of the above rosin. The concept of the rosin-based resin herein includes derivatives of unmodified rosin and derivatives of modified rosin (including hydrogenated rosin, disproportionated rosin, and polymerized rosin). For example, rosin esters such as unmodified rosin esters, which are esters of unmodified rosin and alcohols, and modified rosin esters, which are esters of modified rosin and alcohols; For example, unsaturated fatty acid modified rosin in which rosin is modified with unsaturated fatty acid; For example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; For example, rosin alcohols obtained by reducing the carboxy group of rosin or various rosin derivatives (including rosin esters, unsaturated fatty acid-modified rosin and unsaturated fatty acid-modified rosin esters); For example, rosin or metal salts of the above various rosin derivatives may be mentioned. Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerin esters, pentaerythritol esters, and the like of unmodified rosin or modified rosin (hydrogenated rosin, disproportionated rosin, polymerized rosin, etc.).

Examples of hydrocarbon-based tackifier resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc.), aliphatic/alicyclic petroleum resins, and hydrogenated hydrocarbons. Various hydrocarbon-based resins such as resin, coumarone resin, and coumarone indene resin may be mentioned.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesion, a tackifying resin having a softening point (softening temperature) of approximately 80°C or higher (preferably approximately 100°C or higher) can be preferably employed. For example, a phenolic tackifying resin (terpenephenol resin, etc.) having such a softening point can be preferably used. In some preferred embodiments, a terpenephenol resin with a softening point of approximately 135° C. or higher (or approximately 140° C. or higher) can be used. The upper limit of the softening point of the tackifying resin is not particularly limited. From the viewpoint of adhesion to the adherend or the substrate layer, a tackifying resin having a softening point of about 200°C or less (more preferably about 180°C or less) can be preferably used. In some preferred embodiments, the softening point of the tackifying resin (typically a terpene phenol resin) is less than 160°C, such as about 150°C or less. By using the tackifying resin having a relatively low softening point as described above, the dispersibility of a colorant such as a black colorant (typically carbon black) can be improved. In addition, the softening point of the tackifying resin can be measured based on the softening point test method (ring ball method) prescribed in JIS K2207.

In some preferred embodiments, the tackifying resin includes one or two or more phenolic tackifying resins (such as terpenephenol resins). The technique disclosed herein can be preferably implemented, for example, in an aspect in which approximately 25% by weight or more (more preferably approximately 30% by weight or more) of the total amount of the tackifying resin is a terpenephenol resin. About 50% by weight or more of the total amount of the tackifying resin may be a terpenephenol resin, and about 80% by weight or more (for example, about 90% by weight or more) may be a terpenephenol resin. Substantially all of the tackifying resin (eg, about 95% by weight or more and 100% by weight or less, and further, about 99% by weight or more and 100% by weight or less) may be a terpenephenol resin.

The content of the phenolic tackifying resin (eg, terpenephenol resin) is not particularly limited. The content of the phenolic tackifying resin (e.g., terpenephenol resin) may be approximately 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, from the viewpoint of adhesive strength (e.g., initial adhesion to light pressure bonding), and approximately 5 parts by weight or more. It is appropriate to do this, preferably about 8 parts by weight or more (typically 10 parts by weight or more), more preferably about 12 parts by weight or more (for example, 15 parts by weight or more). In addition, from the viewpoint of resistance to deformation, etc., the content of the phenolic tackifier resin is appropriately set to be approximately 45 parts by weight or less, preferably approximately 35 parts by weight or less, more preferably approximately, based on 100 parts by weight of the acrylic polymer. 30 parts by weight or less, more preferably less than 30 parts by weight (eg 25 parts by weight or less, typically 20 parts by weight or less).

Although not particularly limited, in some embodiments of the techniques disclosed herein, the tackifying resin may contain a tackifying resin having a hydroxyl value higher than 20 mgKOH/g. Among them, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more is preferable. Hereinafter, a tackifying resin having a hydroxyl value of 30 mgKOH/g or more is sometimes referred to as a "high hydroxyl value resin". According to such a tackifying resin containing a resin having a high hydroxyl value, a pressure-sensitive adhesive layer having high cohesive strength can be realized by interacting with a crosslinking agent such as an isocyanate-based crosslinking agent in addition to the adhesive force. In some embodiments, the tackifying resin may contain a high hydroxyl value resin having a hydroxyl value of 50 mgKOH/g or more (more preferably 70 mgKOH/g or more). In addition, the above-described high hydroxyl value resin (e.g., terpenephenol resin) is preferably used in combination with an acrylic polymer containing, for example, C _1-6 alkyl (meth) acrylate as its main monomer, and exhibits good adhesion to the adherend. I can.

The upper limit of the hydroxyl value of the high hydroxyl value resin is not particularly limited. From the viewpoint of compatibility with acrylic polymers, etc., the hydroxyl value of the high hydroxyl value resin is, for example, about 300 mgKOH/g or less, about 200 mgKOH/g or less is suitable, preferably about 180 mgKOH/g or less, more preferably about It is 160 mgKOH/g or less, more preferably about 140 mgKOH/g or less. The technology disclosed herein can be preferably implemented in an embodiment in which the tackifying resin includes a high hydroxyl value resin (e.g., a phenolic tackifying resin, preferably a terpenephenol resin) having a hydroxyl value of 30 to 160 mgKOH/g. have. In some embodiments, a high hydroxyl value resin having a hydroxyl value of 30 to 80 mgKOH/g (eg, 30 to 65 mgKOH/g) can be preferably employed. In some other embodiments, a high hydroxyl value resin having a hydroxyl value of 70 to 140 mgKOH/g may be preferably employed.

Here, as the value of the hydroxyl value, a value measured by the potential difference titration method specified in JIS K0070:1992 can be adopted. A specific measurement method is as shown below.

[Measurement method of hydroxyl value]

1. Reagent

(1) As an acetylation reagent, about 12.5 g (about 11.8 mL) of acetic anhydride is taken, pyridine is added to this, and the total amount is 50 mL, and sufficiently stirred. Alternatively, about 25 g (about 23.5 mL) of acetic anhydride is taken, pyridine is added thereto, the total amount is made 100 mL, and sufficiently stirred is used.

(2) As a measurement reagent, a 0.5 mol/L potassium hydroxide ethanol solution is used.

(3) In addition, toluene, pyridine, ethanol and distilled water are prepared.

2. Operation

(1) Approximately 2 g of a sample is accurately collected in a flat bottom flask, 5 mL of an acetylation reagent and 10 mL of pyridine are added, and an air cooling tube is attached.

(2) After heating the flask in a 100°C bath for 70 minutes, it is allowed to cool, and after stirring by adding 35 mL of toluene as a solvent from the top of the cooling tube, 1 mL of distilled water is added and stirred to decompose acetic anhydride. In order to complete decomposition, it is heated again in a bath for 10 minutes and allowed to cool.

(3) Wash the cooling tube with 5 mL of ethanol and remove it. Then, 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 hole pipette.

(5) Potentiometric titration is performed with 0.5 mol/L potassium hydroxide ethanol solution. The inflection point of the obtained titration curve is taken as the end point.

(6) In the blank test, the above (1) to (5) is carried out without adding a sample.

3. Calculation

The hydroxyl value is calculated by the following formula.

Hydroxyl value (mgKOH/g)=[(B-C)×f×28.05]/S+D

From here,

B: the amount of 0.5 mol/L potassium hydroxide ethanol solution (mL) used in the blank test,

C: amount of 0.5 mol/L potassium hydroxide ethanol solution used in the sample (mL),

f: a factor of 0.5 mol/L potassium hydroxide ethanol solution,

S: weight of the sample (g),

D: acid value,

28.05: 1/2 of the molecular weight of potassium hydroxide 56.11

to be.

As the high hydroxyl value resin, among the various tackifying resins described above, those having a hydroxyl value of a predetermined value or more can be used. High hydroxyl-value resin can be used individually by 1 type or in combination of 2 or more types. For example, as a resin with a high hydroxyl value, a phenol-based tackifying resin having a hydroxyl value of 30 mgKOH/g or more can be preferably employed. Terpene phenol resin is preferable because the hydroxyl value can be arbitrarily controlled according to the copolymerization ratio of phenol.

Although not particularly limited, when a resin with a high hydroxyl value is used, the proportion of the resin with a high hydroxyl value (e.g., terpenephenol resin) in the entire tackifying resin included in the pressure-sensitive adhesive layer should be, for example, approximately 25% by weight or more. Can be, with at least about 30% by weight preferred, and at least about 50% by weight (eg, at least about 80% by weight, typically at least about 90% by weight) more preferred. Substantially all of the tackifying resin (eg, about 95 to 100% by weight, further about 99 to 100% by weight) may be a high hydroxyl value resin.

In the aspect of using the tackifying resin, the content of the tackifying resin is not particularly limited. The content of the tackifying resin may be approximately 1 part by weight or more, and may be approximately 5 parts by weight or more, and approximately 8 parts by weight or more (for example, approximately 10 parts by weight) based on 100 parts by weight of the base polymer (eg, acrylic polymer). Above) is appropriate. The technique disclosed herein can be preferably implemented in an aspect in which the content of the tackifying resin relative to 100 parts by weight of the base polymer is approximately 12 parts by weight or more (eg, approximately 15 parts by weight or more). The upper limit of the content of the tackifying resin is not particularly limited. From the viewpoint of compatibility with the base polymer and resistance to deformation, the content of the tackifying resin with respect to 100 parts by weight of the base polymer is appropriately set to about 70 parts by weight or less, preferably about 55 parts by weight or less, more preferably About 45 parts by weight or less (eg about 40 parts by weight or less, typically about 30 parts by weight or less). In some preferred embodiments, the content of the tackifying resin relative to 100 parts by weight of the base polymer is less than 30 parts by weight, more preferably approximately 25 parts by weight or less, and still more preferably approximately 20 parts by weight or less.

((Meth)acrylic oligomer)

The pressure-sensitive adhesive composition disclosed here (and further, the pressure-sensitive adhesive layer) can contain a (meth)acrylic oligomer from the viewpoint of improving adhesion. As the (meth)acrylic oligomer, Tg is higher than the Tg of the copolymer corresponding to the composition of the monomer component (typically, it generally corresponds to the Tg of the (meth)acrylic polymer contained in the pressure-sensitive adhesive formed from the pressure-sensitive adhesive composition). It is preferred to use a polymer. By containing a (meth)acrylic oligomer, the adhesive strength of the pressure-sensitive adhesive can be improved.

The (meth)acrylic oligomer preferably 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 preferably improved. In some preferred embodiments, from the viewpoint of cohesiveness of the pressure-sensitive adhesive, the Tg of the (meth)acrylic oligomer is about 30°C or more, more preferably about 50°C or more (for example, about 60°C or more), and from the viewpoint of initial adhesiveness At, preferably, it is about 200°C or less, more preferably about 150°C or less, more preferably about 100°C or less (eg, about 80°C or less). In addition, the Tg of the (meth)acrylic oligomer is a value calculated based on the Fox equation in the same manner as the Tg of the copolymer corresponding to the composition of the monomer component.

The weight average molecular weight (Mw) of the (meth)acrylic oligomer may be typically about 1000 or more and less than about 30000, preferably about 1500 or more and less than 20000, and more preferably about 2000 or more and less than about 10000. When Mw is in the above range, good adhesion and retention properties are obtained, which is preferable. In some preferred embodiments, from the viewpoint of deformation resistance, the Mw of the (meth)acrylic oligomer is about 2500 or more (for example, about 3000 or more), and from the viewpoint of initial adhesion, preferably about 7000 or less, more preferably Is about 5000 or less (eg about 4500 or less, typically about 4000 or less). Mw of the (meth)acrylic oligomer can be measured by GPC and calculated as a value in terms of standard polystyrene. Specifically, it is measured under the conditions of a flow rate of about 0.5 mL/min in a tetrahydrofuran solvent using an HPLC8020 manufactured by Tosoh Corporation, using TSKgelGMH-H (20) x 2 as a column.

As a monomer constituting the (meth)acrylic oligomer, for example, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (Meth)acrylate, 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, Alkyl (meth)acrylates such as isodecyl (meth)acrylate, undecyl (meth)acrylate, and dodecyl (meth)acrylate; Esters of (meth)acrylic acid and alicyclic alcohols 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)acrylate obtained from terpene compound derivative alcohol; And the like. Such (meth)acrylates can be used alone or in combination of two or more.

Examples of (meth)acrylic oligomers include alkyl (meth)acrylates having a branched structure in an alkyl group such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; Esters of (meth)acrylic acid and alicyclic alcohols such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, and dicyclopentanyl (meth)acrylate (alicyclic hydrocarbon group-containing (meth)acrylate); An acrylic monomer having a relatively bulky structure represented by a (meth)acrylate having a cyclic structure such as phenyl (meth)acrylate or aryl (meth)acrylate such as benzyl (meth)acrylate is included as a monomer unit, It is preferable from the viewpoint of improving adhesion. In addition, when ultraviolet rays are used in the synthesis of (meth)acrylic oligomers or in the production of the pressure-sensitive adhesive layer, it is preferable to have a saturated bond, and the alkyl group has a branched structure in that it is difficult to induce polymerization. A rate or an ester with an alicyclic alcohol (alicyclic hydrocarbon group-containing (meth)acrylate) can be preferably used as a monomer constituting the (meth)acrylic oligomer. In addition, the branched chain alkyl (meth) acrylate, alicyclic hydrocarbon group (meth) acrylate, and aryl (meth) acrylate all correspond to the (meth) acrylate monomer in the technology disclosed herein. The alicyclic hydrocarbon group may be a saturated or unsaturated alicyclic hydrocarbon group.

The proportion of the (meth)acrylate monomer (e.g., alicyclic hydrocarbon group-containing (meth)acrylate) in all monomer components constituting the (meth)acrylic oligomer is typically more than 50% by weight, preferably 60% by weight. % Or more, more preferably 70% by weight or more (eg, 80% by weight or more, and further 90% by weight or more). In some preferred embodiments, the (meth)acrylic oligomer has a monomer composition substantially containing only (meth)acrylate monomers.

As the constituent monomer component of the (meth)acrylic oligomer, a functional group-containing monomer can be used in addition to the (meth)acrylate monomer. Preferred examples of the functional group-containing monomer include a monomer having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocycle) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; Amino group-containing monomers such as N,N-dimethylaminoethyl (meth)acrylate; Amide group-containing monomers such as N,N-diethyl (meth)acrylamide; Carboxyl group-containing monomers such as AA and MAA; And hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate. These functional group-containing monomers may be used alone or in combination of two or more. Among them, a carboxyl group-containing monomer is preferred, and AA is particularly preferred.

When all the monomer components constituting the (meth)acrylic oligomer contain a functional group-containing monomer, the ratio of the functional group-containing monomer (e.g., a carboxyl group-containing monomer such as AA) occupied by the all monomer components is approximately 1% by weight or more. Is suitable, 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 to be.

The (meth)acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method or polymerization mode is not particularly limited, and various conventionally known polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed as appropriate modes. The types of polymerization initiators that can be used as needed (e.g., azo polymerization initiators such as AIBN) are generally as exemplified in the synthesis of acrylic polymers, and the amount of polymerization initiators or chains such as n-dodecylmercaptan used arbitrarily Since the amount of the transfer agent is appropriately set based on common technical knowledge so as to achieve a desired molecular weight, a detailed description is omitted here.

Preferred (meth)acrylic oligomers from the above viewpoint include, for example, dicyclopentanyl methacrylate (DCPMA), cyclohexyl methacrylate (CHMA), isobornyl methacrylate (IBXMA), isobornyl acrylate (IBXA), dicyclo In addition to each homopolymer of fentanyl acrylate (DCPA), 1-adamantyl methacrylate (ADMA), and 1-adamantyl acrylate (ADA), a copolymer of CHMA and isobutyl methacrylate (IBMA), CHMA And IBXMA, CHMA and acryloylmorpholine (ACMO), CHMA and diethylacrylamide (DEAA), CHMA and AA, ADA and methyl methacrylate (MMA) Copolymers, copolymers of DCPMA and IBXMA, copolymers of DCPMA and MMA, and the like.

When a (meth)acrylic oligomer is contained in the pressure-sensitive adhesive composition disclosed herein, it is appropriate that the content thereof is, for example, 0.1 parts by weight or more (for example, 1 part by weight or more) based on 100 parts by weight of the base polymer (preferably acrylic polymer). Do. From the viewpoint of better exerting the effect of the (meth)acrylic oligomer, the content of the (meth)acrylic oligomer is preferably about 5 parts by weight or more, more preferably about 8 parts by weight or more based on 100 parts by weight of the base polymer. , More preferably about 10 parts by weight or more, particularly preferably about 12 parts by weight or more. In addition, from the viewpoint of compatibility with the base polymer, the content of the (meth)acrylic oligomer is suitably less than 50 parts by weight (for example, less than 40 parts by weight) based on 100 parts by weight of the base polymer, preferably 30 It is less than parts by weight, more preferably less than about 25 parts by weight, and still more preferably less than about 20 parts by weight.

In some preferred embodiments, the pressure-sensitive adhesive layer contains one type or two or more types of the tackifying resin described above and one type or two or more types of (meth)acrylic oligomers. In a composition containing a high molecular weight acrylic polymer, excellent initial adhesion is obtained by using a tackifier resin and a (meth)acrylic oligomer in combination, while exhibiting highly excellent deformation resistance even in a usage mode exposed to more severe conditions such as strong repulsion. I can. The ratio of the content C _T of the tackifying resin and the content C _O of the (meth)acrylic oligomer is not particularly limited, and for example, C _T :C _O is suitably 1:9 to 9:1, preferably 2: 8 to 8:2, more preferably 3:7 to 7:3, still more preferably 4:6 to 6:4.

In some preferred embodiments, the total amount (total amount) of the tackifying resin and the (meth)acrylic oligomer contained in the pressure-sensitive adhesive layer is from the viewpoint of preferably exerting the effect of the technology disclosed herein, the base polymer (preferably Acrylic polymer) It is appropriate to be about 1 part by weight or more based on 100 parts by weight, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, even more preferably 20 parts by weight or more, particularly preferably Is 25 parts by weight or more. In addition, the total amount of the tackifying resin and the (meth)acrylic oligomer is suitably less than 120 parts by weight (e.g., approximately 80 parts by weight or less) based on 100 parts by weight of the base polymer (preferably acrylic polymer), and preferably It is less than 60 parts by weight, more preferably about 50 parts by weight or less, even more preferably about 40 parts by weight or less.

(Other additives)

In addition to the aforementioned components, the pressure-sensitive adhesive composition includes a leveling agent, a crosslinking aid, a plasticizer, a softener, an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, a light stabilizer, a rust inhibitor (e.g., an azole-based rust inhibitor, specifically, a benzotriazole-based Various additives common in the field of adhesives such as rust inhibitors) may be contained. For such various additives, conventionally known additives can be used according to a conventional method, and since they do not particularly characterize the present invention, detailed descriptions are omitted.

(Formation of adhesive layer)

The pressure-sensitive adhesive layer disclosed herein may be a pressure-sensitive adhesive layer formed from a water-based pressure-sensitive adhesive composition, a solvent-type pressure-sensitive adhesive composition, a hot-melt-type pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. An aqueous pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive (a component for forming an adhesive layer) in a solvent (aqueous solvent) containing water as a main component, and typically, a water-dispersible pressure-sensitive adhesive composition (at least part of the adhesive is dispersed in water). And the like). In addition, the solvent-type pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition containing a pressure-sensitive adhesive in an organic solvent. The technique disclosed herein can be preferably implemented in an aspect provided with a pressure-sensitive adhesive layer formed of a solvent-type pressure-sensitive adhesive composition from the viewpoint of adhesive properties and the like.

The pressure-sensitive adhesive layer disclosed herein can be formed by a conventionally known method. For example, a method of forming a pressure-sensitive adhesive layer by directly applying (typically applying) the pressure-sensitive adhesive composition to the base film as described above and drying it (direct method) may be employed. In addition, a method (transfer method) of forming a pressure-sensitive adhesive layer on the surface by applying and drying the pressure-sensitive adhesive composition to a surface having releasability (releasing surface) and transferring the pressure-sensitive adhesive layer to a base film may be employed. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of the release liner or the back surface of the base film subjected to the release treatment can be used. In addition, although the pressure-sensitive adhesive layer disclosed herein is typically formed continuously, it is not limited to this form, and may be, for example, a pressure-sensitive adhesive layer formed in a regular or random pattern such as dots or stripes.

The application of the pressure-sensitive adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, a die coater, and a bar coater. Alternatively, the pressure-sensitive adhesive composition may be applied by impregnation or curtain coating.

From the viewpoint of accelerating the crosslinking reaction and improving production efficiency, it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 to 150°C, and preferably about 60 to 130°C. After drying the pressure-sensitive adhesive composition, aging may be further performed for the purpose of adjusting component migration in the pressure-sensitive adhesive layer, advancing the crosslinking reaction, and alleviating the deformation that may exist in the base film or the pressure-sensitive adhesive layer.

(Viscoelastic properties)

The storage modulus of the pressure-sensitive adhesive layer disclosed herein is not limited to a specific range because it can be appropriately set depending on the use, required performance, and the like. For example, the storage modulus G'(25°C) at 25°C of the pressure-sensitive adhesive layer may be approximately 0.15 MPa or more. According to the pressure-sensitive adhesive having G'(25° C.), good deformation resistance can be preferably exhibited from an early stage after affixing to an adherend. Further, since it tends to exhibit good workability in punching or the like, it can be suitable for fine processing. The G'(25°C) is preferably 0.17 MPa or more, more preferably 0.2 MPa or more, and still more preferably 0.23 MPa or more. The G'(25° C.) is particularly preferably 0.25 MPa or more, and may be, for example, 0.3 MPa or more. In addition, the G'(25°C) is appropriately set to be approximately 1.0 MPa or less, preferably 0.6 MPa or less, more preferably 0.4 MPa or less, further preferably from the viewpoint of compatibility between initial adhesiveness and deformation resistance. It is 0.35 MPa or less. The pressure-sensitive adhesive layer whose storage modulus is limited to a predetermined value or less tends to have excellent impact resistance, and is, for example, preferable as a pressure-sensitive adhesive for portable electronic devices that requires a predetermined drop impact resistance.

In addition, the loss modulus of the pressure-sensitive adhesive layer disclosed herein is not limited to a specific range because it can be appropriately set according to the use, required performance, and the like. For example, it is appropriate that the pressure-sensitive adhesive layer has a loss modulus G" (25°C) of 2.0 MPa or less at 25°C. The G" (25°C) is preferably 1.5 MPa or less, more preferably 1.0 MPa or less, even more preferably It is 0.5 MPa or less. In addition, the G" (25°C) is suitably 0.01 MPa or more, and preferably 0.05 MPa or more, more preferably 0.1 MPa or more, even more preferably from the viewpoint of wettability to the surface of the adherend, further initial adhesion, etc. Is 0.2 MPa or more, and may be 0.25 MPa or more, for example.

In addition, tan δ (25°C) at 25°C of the pressure-sensitive adhesive layer disclosed herein can be appropriately set in consideration of initial adhesiveness and deformation resistance at room temperature. Here, tan δ (loss tangent) of the pressure-sensitive adhesive layer refers to the ratio of the loss elastic modulus G" to the storage elastic modulus G'of the pressure-sensitive adhesive layer, that is, tan δ = G"/G'. tan δ (25° C.) is suitably, for example, approximately 0.3 or higher, and preferably approximately 0.5 or higher, more preferably approximately 0.7 or higher, more preferably approximately 0.8 or higher, particularly preferably approximately from the viewpoint of deformation resistance. 0.9 or more (eg, approximately 1 or more). When tan δ (25° C.) is equal to or greater than a predetermined value, the pressure-sensitive adhesive layer tends to have excellent impact resistance, and is preferable, for example, as a pressure-sensitive adhesive for portable electronic devices requiring a predetermined drop impact resistance. In addition, tan δ (25° C.) is suitably, for example, approximately 3 or less, and preferably approximately 2 or less, more preferably approximately 1.5 or less, and still more preferably approximately 1.2 or less from the viewpoint of initial adhesiveness. When tan δ (25° C.) is limited to a predetermined value or less, it tends to exhibit good workability in punching or the like, and can be suitable for fine processing.

The storage modulus G'(25°C), loss elastic modulus G" (25°C) and tanδ (25°C) of the pressure-sensitive adhesive layer described above are the base polymer species of the pressure-sensitive adhesive layer, its molecular structure and molecular weight, and additive components such as tackifier resin, and It can be adjusted by selecting the amount used, the type of crosslinking agent, and the amount thereof used.

In the technique disclosed herein, the storage modulus G'(25°C), loss elastic modulus G" (25°C), and tanδ (25°C) of the pressure-sensitive adhesive layer can be determined by dynamic viscoelasticity measurement. Specifically, the pressure-sensitive adhesive to be measured. A pressure-sensitive adhesive layer having a thickness of about 2 mm is produced by stacking a plurality of layers on top of each other, and a sample punched out of the pressure-sensitive adhesive layer into a disk shape with a diameter of 7.9 mm is sandwiched and fixed to a parallel plate, and a viscoelasticity tester (for example, T-A- The dynamic viscoelasticity measurement is performed under the following conditions by the instrument company make, ARES or its equivalent), and the storage modulus G'(25 degreeC), the loss modulus G" (25 degreeC), and tan delta (25 degreeC) are calculated|required.

Measurement mode: shear mode

·Temperature range: -70℃∼150℃

·Temperature rise rate: 5℃/min

Measurement frequency: 1Hz

It is also measured by the above method in Examples described later. Further, the pressure-sensitive adhesive layer to be measured can be formed by applying a corresponding pressure-sensitive adhesive composition in a layered form and drying or curing.

(Gel fraction)

Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein may be, for example, 20% or more by weight, it is appropriate to be 30% or more, and 35% or more is preferable. By increasing the gel fraction of the pressure-sensitive adhesive layer in an appropriate range, there is a tendency that the deformation resistance is easily obtained. In the technique disclosed herein, it is more preferable to use an adhesive layer having a gel fraction of 40% or more. The gel fraction is more preferably 45% or more, particularly preferably 50% or more. The gel fraction may be, for example, 55% or more. On the other hand, when the gel fraction is too high, there may be a case where the initial adhesion is deteriorated. From such a viewpoint, the gel fraction of the pressure-sensitive adhesive layer is preferably 90% or less, more preferably 80% or less, and even more preferably 70% or less. The gel fraction of the pressure-sensitive adhesive layer can be adjusted by selecting the base polymer type, its molecular structure, molecular weight, additive components such as tackifier resin, and the amount thereof, the crosslinking agent species, and the amount thereof.

Here, the "gel fraction of the adhesive layer" refers to a value measured by the following method. The gel fraction can be determined as a weight ratio of ethyl acetate insoluble in the pressure-sensitive adhesive layer.

[Method of measuring gel fraction]

About 0.1 g of a pressure-sensitive adhesive sample (weight Wg ₁ ) is wrapped in a pouch shape with a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore diameter of 0.2 μm, and the inlet is tied with a soft thread (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, a brand name'Nitopron (registered trademark) NTF1122' available from Nitto Denko Corporation (average pore diameter 0.2 μm, porosity 75%, thickness 85 μm) or equivalent thereof is used. .

This bundle was immersed in 50 mL of ethyl acetate, maintained at room temperature (typically 23°C) for 7 days to elute only the sol component in the pressure-sensitive adhesive layer to the outside of the film, and then removed the package to wash the ethyl acetate adhering to the outer surface. Out and dry the package at 130° C. for 2 hours, and measure the weight (Wg ₄ ) of the package. The gel fraction F _G of the pressure-sensitive adhesive layer is determined by substituting each value into the following equation. The same method is employed in the examples described later.

Gel fraction F _G (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

The thickness of the pressure-sensitive adhesive layer is not particularly limited. From the viewpoint of avoiding the pressure-sensitive adhesive sheet from becoming excessively thick, the thickness of the pressure-sensitive adhesive layer is suitably approximately 100 μm or less, and from the viewpoint of thinning, preferably approximately 70 μm or less, more preferably approximately 60 μm or less (for example, approximately 55 μm Or less), more preferably about 50 μm or less, particularly preferably about 40 μm or less (eg about 30 μm or less). The thickness of the pressure-sensitive adhesive layer may be approximately 20 μm or less, for example, approximately 15 μm or less, and further approximately 10 μm or less or approximately 5 μm or less (eg, approximately 3 μm or less). For example, as the thickness of the pressure-sensitive adhesive layer decreases, the light-shielding property in the thickness direction decreases, whereas the light transmittance in the sheet surface direction becomes less problematic. In consideration of such a thing, the thickness of the pressure-sensitive adhesive layer can be appropriately set. The lower limit of the thickness of the pressure-sensitive adhesive layer is not particularly limited, and from the viewpoint of adhesion to the adherend, it may be approximately 1 μm or more, and it is appropriate to be approximately 1.5 μm or more, preferably approximately 5 μm or more, more preferably Is approximately 7 µm or more, and may be approximately 12 µm or more (eg, approximately 15 µm or more). By setting the thickness of the pressure-sensitive adhesive layer to a predetermined value or more, it is possible to improve adhesion properties such as adhesive strength and impact resistance, and there is a tendency to improve step followability. When the pressure-sensitive adhesive sheet disclosed herein is implemented in an aspect including a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, the thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be the same or different.

The ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet is not particularly limited. Here, the total thickness of the pressure-sensitive adhesive layer occupied by the total thickness of the pressure-sensitive adhesive sheet refers to the total thickness of the pressure-sensitive adhesive layer provided on one surface of the substrate layer and the pressure-sensitive adhesive layer provided on the other surface. In the case of a single-sided adhesive sheet in which an adhesive layer is provided on only one surface of the substrate layer, the thickness of the adhesive layer provided on the other surface is zero, and the thickness of the adhesive layer provided on the one surface and the adhesive layer The total thickness coincides. The technology disclosed herein, for example, has a ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet is 40% or more (preferably 50% or more, typically more than 50%, more preferably 60% or more, furthermore Preferably, it can be carried out in an aspect of 70% or more). By constituting in this way, there is a tendency that a higher level of impact resistance is exhibited even in a narrow width compared to the total thickness of the pressure-sensitive adhesive sheet. In some embodiments, the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet may be 75% or more, and further 80% or more. The high thickness ratio of the pressure-sensitive adhesive layer is also advantageous in terms of improving the step-following property. The upper limit of the ratio of the total thickness of the pressure-sensitive adhesive layer to the total thickness of the pressure-sensitive adhesive sheet is not particularly limited, but it is appropriate to be 95% or less, and preferably 90% or less.

<Peeling liner>

In the technique disclosed herein, a release liner can be used for formation of an adhesive layer, production of an adhesive sheet, storage of an adhesive sheet before use, distribution, and shape processing. The release liner is not particularly limited, for example, a release liner having a release treatment layer on the surface of a liner substrate such as a resin film or paper, a fluorine-based polymer (polytetrafluoroethylene, etc.), or a polyolefin-based resin (polyethylene, polypropylene, etc.). A release liner or the like containing a low adhesive material can be used. The release treatment layer may be formed by surface treatment of the liner substrate with a release treatment agent such as silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide.

<Thickness of adhesive sheet>

The total thickness of the pressure-sensitive adhesive sheet disclosed here (including the adhesive layer and the substrate layer, but not including the release liner) is not particularly limited. The total thickness of the pressure-sensitive adhesive sheet can be, for example, approximately 300 μm or less, and approximately 200 μm or less is suitable from the viewpoint of thinning. The lower limit of the thickness of the pressure-sensitive adhesive sheet is not particularly limited, and may be about 1 μm or more, for example, it is appropriate to be about 3 μm or more, preferably about 6 μm or more, more preferably about 10 μm or more (for example , About 15㎛ or more).

In some preferred embodiments, the total thickness of the pressure-sensitive adhesive sheet is less than 150 μm, more preferably less than about 120 μm, more preferably less than about 70 μm, particularly preferably less than 50 μm (e.g., less than about 40 μm. ), for example, 35 µm or less, about 25 µm or less, and further, about 15 µm or less or about 10 µm or less (eg, about 7 µm or less). Even in a configuration using such a thin pressure-sensitive adhesive sheet, the light-shielding effect by the technique disclosed herein can be preferably exhibited.

<Adhesion>

The pressure-sensitive adhesive sheet disclosed herein may have a predetermined or higher adhesive force suitable for bonding or fixing. The pressure-sensitive adhesive sheet is suitable for exhibiting a peel strength of 180°C (vs. SUS adhesion) to a stainless steel plate (SUS plate) measured according to JIS Z0237:2000, for example, approximately 3N/20mm or more (for example, approximately 5N/20mm or more). , It is preferable that the adhesion to SUS is approximately 8N/20mm or more. The pressure-sensitive adhesive sheet having the above-described adhesion to SUS shows good adhesion to an adherend. The pressure-sensitive adhesive sheet having the above adhesive strength tends to exhibit good adhesion to resin materials used in electronic devices such as polycarbonate (PC) and polyimide (PI). The adhesion to SUS is more preferably 10N/20mm or more, still more preferably 12N/20mm or more, and particularly preferably 14N/20mm or more (eg 18N/20mm or more). The upper limit of the adhesion to SUS is not particularly limited, but about 50N/20mm or less (for example, about 45N/20mm or less) is suitable.

The adhesion to SUS is measured by the following method. Specifically, a test piece obtained by cutting an adhesive sheet into a size of 20 mm in width and 100 mm in length is prepared. In the case of a double-sided pressure-sensitive adhesive sheet, a PET film having a thickness of 50 µm is affixed to one side of the pressure-sensitive adhesive sheet and placed thereon. A measurement sample was prepared by pressing the adhesive surface of the test piece to a stainless steel plate (SUS304BA plate) in an environment of 23°C and 50%RH. The pressing is performed by making one reciprocation of a 2 kg roller. After allowing the measurement sample to stand for 30 minutes in an environment of 23° C. and 50%RH, using a tensile tester, according to JIS Z0237:2000, a tensile speed of 300 mm/min, a peel angle of 180 degrees, peel strength [N/20 mm] ]. This value is taken as the adhesion to SUS. In addition, as a tensile testing machine, "Precision Universal Testing Machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation or its equivalent can be used.

<use>

The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and can be used for various applications requiring light-shielding properties. The pressure-sensitive adhesive sheet disclosed herein can be suitably used, for example, in the form of a double-sided pressure-sensitive adhesive sheet, in the form of a double-sided pressure-sensitive adhesive sheet, for fixing or bonding a member while exhibiting a predetermined light blocking property. In some embodiments, the pressure-sensitive adhesive sheet is affixed to components constituting an electronic device, and can be used for fixing, bonding, reinforcing, etc. of the component while imparting light-shielding property in the electronic device. In addition, since the pressure-sensitive adhesive sheet disclosed herein has photosensitivity in the thickness direction, the adherend can be inspected over the pressure-sensitive adhesive sheet while being fixed to an adherend such as a component. The pressure-sensitive adhesive sheet disclosed herein is also suitable for applications that can be used after being processed into a specific shape or small, such as for fixing members in portable electronic devices. Since some electronic devices such as such portable electronic devices contain light-emitting elements for purposes of image display or the like, light-shielding properties may be required for the adhesive sheet. Further, since the pressure-sensitive adhesive sheet disclosed herein can be thinned while having a predetermined light-shielding property, it may be in accordance with the needs of thinning and weight reduction of portable electronic devices.

Non-limiting examples of the portable electronic device include a mobile phone, a smartphone, a tablet PC, a notebook, and various wearable devices (e.g., a wrist wear type such as a wrist watch, mounted on a part of the body with a clip or strap, etc.) Modular type, eyewear type including eyewear type (including monocular, binocular type, and head-mounted type), clothing type installed in the form of accessories such as shirts, socks, hats, etc., ear wear mounted on the ear such as earphones Type, etc.) Digital cameras, digital video cameras, audio devices (portable music players, IC recorders, etc.), calculators (portable calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle information devices, portable radios, portables These include TVs, portable printers, portable scanners, and portable modems. In addition, in this specification, the term'portable' is not enough to simply be portable, but means that an individual (a standard adult) has a level of portability that can be carried relatively easily.

The pressure-sensitive adhesive sheet disclosed herein can be preferably used for the purpose of fixing the pressure-sensitive sensor and other members, for example, in a portable electronic device including a pressure-sensitive sensor among such portable electronic devices. In some preferred embodiments, the pressure-sensitive adhesive sheet is a device for indicating a position on the screen (typically a pen-type device, a mouse-type device) and a device for detecting the position, and a plate corresponding to the screen (typically a touch device). Panel), in an electronic device (typically a portable electronic device) that has a function that makes it possible to specify an absolute position on top of the panel), it may be used to fix the pressure-sensitive sensor and other members.

Further, the pressure-sensitive adhesive sheet disclosed herein is disposed on the back surface of a display screen (display portion) such as a touch panel display in a portable electronic device, and is also suitable for use in preventing reflection of light beyond the display screen. By disposing the pressure-sensitive adhesive sheet disclosed herein on the back surface of the display screen (display unit), it is possible to prevent a decrease in visibility of the display screen regardless of the usage mode of the portable electronic device. In addition, the above-described reflection can be caused by a metal member disposed on the back side of the display screen, but by using the adhesive sheet disclosed herein, for example, for bonding the metal member and the display unit, bonding of the members and imparting light-shielding properties are achieved. It can be realized at the same time.

The material constituting the fixed object such as the pressure-sensitive sensor or the display unit (e.g., a rear member such as an electromagnetic shield or a reinforcing plate) is not particularly limited, but, for example, copper, silver, gold, iron, tin, palladium, aluminum, nickel, Metal materials such as titanium, chromium, zinc, etc., or an alloy containing two or more of these, or, for example, polyimide resins, acrylic resins, polyethernitrile resins, polyethersulfone resins, polyester resins (polyethylene tere Phthalate resin, polyethylene naphthalate resin, etc.), polyvinyl chloride resin, polyphenylene sulfide resin, polyetheretherketone resin, polyamide resin (so-called aramid resin, etc.), polyarylate resin, poly Various resin materials such as carbonate-based resins and liquid crystal polymers (typically plastic materials), inorganic materials such as alumina, zirconia, soda glass, quartz glass, carbon, etc. are mentioned. Among them, metal materials such as copper, aluminum, and stainless steel, and resin materials (typically plastic materials) such as polyimide resins, aramid resins, and polyphenylene sulfide resins are widely used. In addition, the fixed object may have a single-layer structure or a multi-layer structure, and various types of surface treatments may be applied to the surface to which the pressure-sensitive adhesive sheet is affixed (attached surface). Although not particularly limited, as an example of a fixed object, a back member having a thickness of about 1 μm or more (typically 5 μm or more, such as 60 μm or more, further 120 μm or more), 1500 μm or less (eg 800 μm or less) Can be mentioned.

Since the pressure-sensitive adhesive sheet disclosed herein has good light-shielding properties, it is preferably used in electronic devices including various light sources such as LEDs (light emitting diodes) or light emitting elements such as self-luminous organic EL (electro-luminescence). . For example, it can be suitably used for an electronic device (typically a portable electronic device) equipped with a liquid crystal display device requiring predetermined optical properties. More specifically, in a liquid crystal display device including a liquid crystal display module unit (LCD unit) and a backlight module unit (BL unit), it may be preferably used for bonding the LCD unit and the BL unit.

2 is a schematic exploded perspective view schematically showing a configuration example of a liquid crystal display device. As shown in FIG. 2, the liquid crystal display 200 in which the portable electronic device 100 is provided includes an LCD unit (part) 210 and a BL unit (part) 220. The liquid crystal display device 200 is configured to further include an adhesive sheet 230. In this configuration example, the pressure-sensitive adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided pressure-sensitive adhesive sheet) processed into a frame shape (frame shape), and is disposed between the BL unit 220 and the LCD unit 210 to provide both We are joining. Further, the BL unit 220 is typically constituted by including a reflective sheet, a light guide plate, a diffusion sheet, a prism sheet, etc. in addition to a light source.

The pressure-sensitive adhesive sheet disclosed herein, in the form of a bonding member processed into various external shapes, can be used for, for example, bonding of an LCD unit and the BL unit, and other bonding applications as described above. As a preferred form of such a bonding member, a form having a narrow portion having a width of less than 2.0 mm (eg, less than 1.0 mm) is exemplified. Even if the pressure-sensitive adhesive sheet disclosed herein is used as a bonding member having a shape (eg, a frame shape) including the above-described narrow portion, it can exhibit good light blocking properties. In addition, in some embodiments, the pressure-sensitive adhesive sheet can exhibit adhesive properties such as excellent impact resistance even in the form of a narrow pressure-sensitive adhesive sheet. In some embodiments, the width of the narrow portion may be 0.7 mm or less, 0.5 mm or less, or about 0.3 mm or less. The lower limit of the width of the narrow portion is not particularly limited, but usually 0.1 mm or more (typically 0.2 mm or more) is suitable from the viewpoint of handling properties of the pressure-sensitive adhesive sheet.

The narrow portion is typically linear. Here, the term “linear” is a concept including a linear shape, a curved shape, a broken line shape (eg, L-shape) and the like, as well as an annular shape such as an edge shape or a circular shape, and a complex or intermediate shape thereof. The annular is not limited to being constituted by a curve, and includes an annular part or all of which is formed in a straight line, for example, a shape along the outer circumference of a square (border shape) or a shape along the outer circumference of a fan shape. to be. The length of the narrow portion is not particularly limited. For example, in a form in which the length of the narrow portion is 10 mm or more (typically 20 mm or more, for example, 30 mm or more), the effect of applying the technology disclosed herein can be preferably exhibited.

The matters disclosed by this specification include the following.

(1) a liquid crystal display module unit, a backlight module unit, and a double-sided adhesive adhesive sheet bonding the liquid crystal display module unit and the backlight module unit,

The adhesive sheet has a light transmittance T _Z of more than 0.04% and less than 50% in the Z direction, and a light transmittance T _XY per 1 mm of the width of the XY plane thereof is smaller than the light transmittance T _Z in the Z direction. The XY surface of the sheet is the sheet surface of the pressure-sensitive adhesive sheet, and the Z direction is the thickness direction of the pressure-sensitive adhesive sheet.

(2) 　 The liquid crystal display device according to (1), wherein the pressure-sensitive adhesive sheet includes a substrate layer and an adhesive layer disposed on at least one surface of the substrate layer.

(3) The liquid crystal display device according to (1) or (2), wherein the pressure-sensitive adhesive sheet has a light transmittance T _Z of 0.1% or more and 15% or less in the Z direction.

(4) The liquid crystal display device according to any one of (1) to (3), wherein the pressure-sensitive adhesive sheet has a light transmittance T _XY of 0.04% or less per 1 mm of the width of the XY surface.

(5) The liquid crystal display according to any one of (1) to (4), wherein the difference (T _Z -T _XY ) between the light transmittance T _XY [%] and the light transmittance T _Z [%] is 1.00 or more. .

(6) 　 The liquid crystal display device according to any one of (1) to (5), wherein the base layer contains a resin film containing a black colorant.

(7) 　 The liquid crystal display device according to any one of (1) to (6), wherein the thickness of the base layer is 0.5 µm to 10 µm.

(8) 　 The liquid crystal display device according to any one of (1) to (7), wherein the pressure-sensitive adhesive layer contains a black colorant.

(9) The liquid crystal display device according to any one of (1) to (8), wherein the thickness of the pressure-sensitive adhesive layer is 1.5 µm to 60 µm.

(10) The liquid crystal display device according to any one of (1) to (9), wherein the total thickness of the pressure-sensitive adhesive sheet is 300 μm or less.

(11) The light transmittance T _Z in the Z direction exceeds 0.04% and is 50% or less, and the light transmittance T _XY per 1 mm of the width of the XY plane thereof is smaller than the light transmittance T _Z in the Z direction. The XY surface is the sheet surface of the adhesive sheet, and the Z direction is the thickness direction of the adhesive sheet.

(12) The pressure-sensitive adhesive sheet according to (11), comprising a substrate layer and an adhesive layer disposed on at least one surface of the substrate layer.

(13) The adhesive sheet according to (11) or (12), wherein the light transmittance T _Z in the Z direction is 0.1% or more and 15% or less.

(14) The adhesive sheet according to any one of (11) to (13), wherein the light transmittance T _XY per 1 mm of the width of the XY surface is 0.04% or less.

(15) The pressure-sensitive adhesive sheet according to any one of (11) to (14), wherein the difference (T _Z -T _XY ) between the light transmittance T _XY [%] and the light transmittance T _Z [%] is 1.00 or more.

(16) The adhesive sheet according to any one of (11) to (15), wherein the base material layer contains a resin film containing a black colorant.

(17) The pressure-sensitive adhesive sheet according to any one of (11) to (16), wherein the base layer has a thickness of 0.5 µm to 10 µm.

(18) The adhesive sheet according to any one of (11) to (17), wherein the adhesive layer contains a black colorant.

(19) The pressure-sensitive adhesive sheet according to any one of (11) to (18), wherein the thickness of the pressure-sensitive adhesive layer is 1.5 to 60 μm.

(20) The adhesive sheet according to any one of (11) to (19), wherein the total thickness of the adhesive sheet is 300 μm or less.

(21) The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer comprising an acrylic polymer as a base polymer and at least one selected from tackifying resins and (meth)acrylic oligomers,

The weight average molecular weight of the acrylic polymer is greater than 70×10 ⁴ ,

The adhesive sheet according to any one of (11) to (20), wherein the degree of dispersion (Mw/Mn) of the acrylic polymer is less than 15.

(22) The pressure-sensitive adhesive sheet according to (21), wherein the acrylic polymer has an alkyl (meth)acrylate having an alkyl group having 1 or more and 6 or less carbon atoms at the ester terminal thereof in a ratio of 50% by weight or more.

(23) The adhesive sheet according to (21) or (22), in which the acrylic polymer is copolymerized with an acidic group-containing monomer.

(24) The adhesive sheet according to (23), wherein a copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is less than 10% by weight.

(25) The pressure-sensitive adhesive sheet according to any one of (21) to (24), wherein in the acrylic pressure-sensitive adhesive layer, the tackifying resin is contained in a ratio of less than 30 parts by weight based on 100 parts by weight of the acrylic polymer.

(26) In the acrylic pressure-sensitive adhesive layer, the (meth)acrylic oligomer is contained in a ratio of less than 30 parts by weight based on 100 parts by weight of the acrylic polymer, the pressure-sensitive adhesive sheet according to any one of (21) to (25) above. .

(27) The adhesive sheet according to any one of (21) to (26), wherein the acrylic pressure-sensitive adhesive layer contains both the tackifying resin and the (meth)acrylic oligomer.

(28) The adhesive sheet according to any one of (11) to (27), wherein the pressure-sensitive adhesive layer has a storage modulus G'(25°C) of 0.15 MPa or more at 25°C.

(29) The adhesive sheet according to any one of (11) to (28), wherein the gel fraction of the adhesive layer is 40% by weight or more.

(30) The adhesive sheet according to any one of (11) to (29), wherein the acrylic polymer is crosslinked.

(31) The adhesive sheet according to any one of (11) to (30), wherein the acrylic polymer is copolymerized with N-butyl acrylate in a proportion of 50% by weight or more.

(32) The pressure-sensitive adhesive layer includes the tackifying resin, and about 50% by weight or more of the tackifying resin is a phenol-based tackifying resin (for example, terpenephenol resin), any one of the above (11) to (31). The adhesive sheet described in.

(33) The pressure-sensitive adhesive sheet according to (32), wherein the phenolic tackifying resin contains a terpenephenol resin having a hydroxyl value of less than about 30 mgKOH/g.

(34) The pressure-sensitive adhesive sheet according to any one of (11) to (33), wherein the pressure-sensitive adhesive layer has a loss modulus G" (25°C) of 2.0 MPa or less at 25°C.

(35) The adhesive sheet according to any one of (11) to (34), wherein the adhesive layer is an adhesive layer formed from a solvent-type adhesive composition or an active energy ray-curable adhesive composition.

(36) The pressure-sensitive adhesive sheet according to any one of (11) to (35), configured as a double-sided adhesive pressure-sensitive adhesive sheet having a thickness of less than 50 µm.

(37) The adhesive sheet according to (23) or (24), wherein the acidic group-containing monomer is acrylic acid.

(38) The adhesive sheet according to any one of (11) to (37), which is used in an electronic device containing a light emitting element.

(39) The adhesive sheet according to any one of (11) to (38), which is used for fixing a member in a portable electronic device.

[Example]

Hereinafter, some examples of the present invention will be described, but it is not intended to limit the present invention to those shown by examples. In addition, in the following description,'parts' and'%' are based on weight unless otherwise noted.

<Evaluation method>

[Light-shielding property in the direction of the sheet surface]

Using a hand roller, the pressure-sensitive adhesive sheet is laminated while taking care not to curl air bubbles, and a pressure-sensitive adhesive sheet laminate having a total thickness of 25 mm or more and 30 mm or less is obtained. This laminate is cut into a strip shape so as to have a width of 1 mm, and this laminate is used as a measurement sample. The measurement of the light transmittance T _XY per 1 mm width in the XY plane direction is performed by vertically irradiating light with a wavelength of 380 to 780 nm to the side (cross-section) of the 1 mm wide adhesive sheet laminate as a measurement sample using a commercially available spectrophotometer. , Can be obtained by measuring the intensity of light transmitted to the other side. As the spectrophotometer, a spectrophotometer manufactured by Hitachi Corporation (device name "U4100 type spectrophotometer") or its equivalent is used.

If the light transmittance T _XY per 1 mm of the width in the XY plane direction is lower than the following Z direction light transmittance T _Z , the light-shielding property in the sheet plane direction is evaluated as'○', and those that are not evaluated as'×'.

[Z direction light transmittance]

It can be grasped by preparing an adhesive sheet and measuring the light transmittance T _Z in the Z direction. To measure the light transmittance T _{Z in} the Z direction, use a commercially available spectrophotometer to vertically irradiate light with a wavelength of 380 to 780 nm to the sheet surface of the measurement sample, and measure the intensity of the light transmitted to the other surface. It can be obtained by doing. As the spectrophotometer, a spectrophotometer manufactured by Hitachi Corporation (device name "U4100 type spectrophotometer") or its equivalent is used. The Z-direction light transmittance of the supporting substrate (substrate layer) is also measured by the same method. The Z-direction light transmittance of the pressure-sensitive adhesive layer can be determined by peeling off the pressure-sensitive adhesive layer with a release liner before being transferred to the supporting substrate during the production of the pressure-sensitive adhesive sheet from the release liner, and measuring the light transmittance in the thickness direction of the obtained pressure-sensitive adhesive layer alone.

[Inspectability]

A commercially available graphite sheet (trade name'Graffinity 25 μm', manufactured by Kaneka Corporation, 25 μm in thickness) is prepared, and a plurality of defects of different sizes (stem defects of about 3 to 5 cm in length) are formed on the surface. A pressure-sensitive adhesive sheet is affixed to this graphite sheet, and the pressure-sensitive adhesive sheet side is placed on a light box (trade name'HF-SL-A48LCG', manufactured by Dentsu Industries) so that the side of the pressure-sensitive adhesive sheet is on the upper side. Then, the graphite sheet was visually detected over the pressure-sensitive adhesive sheet, and the ease of detection of the defect was evaluated based on the following 2 criteria.

(evaluation)

(Circle): Defect detection operation can be performed efficiently.

X: It is difficult to detect a defect.

<Example 1>

(Preparation of acrylic polymer)

In a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a reflux condenser and a dropping funnel, 93 parts of BA, 7 parts of AA, and 0.05 parts of 4-hydroxybutyl acrylate (4HBA) as monomer components and ethyl acetate as a polymerization solvent were put into a reaction vessel, The mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen in the polymerization system in this way, 0.1 part of AIBN was added as a polymerization initiator, and solution polymerization was performed at 60°C for 6 hours to obtain a solution of the acrylic polymer according to the present example. Mw of this acrylic polymer was 140×10 ⁴ and Mw/Mn was 5.5.

(Preparation of adhesive composition)

To the solution of the acrylic polymer obtained above, 1.5 parts of an isocyanate crosslinking agent (trade name'Colonate L', a 75% ethyl acetate solution of the trimethylolpropane/tolylenediisocyanate trimer adduct, per 100 parts of the acrylic polymer contained in the solution, Tosoh Corporation), 0.01 parts of an epoxy-based crosslinking agent (trade name'TETRAD-C', 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, manufactured by Mitsubishi Gas Chemical Corporation), and 15 parts terpenephenol Resin (the brand name'YS Polystar S-145' manufactured by Yasuhara Chemical, softening point of about 145°C, hydroxyl value of 70-110 mgKOH/g), and 15 parts of (meth)acrylic oligomer were added, stirred and mixed. The following adhesive composition was prepared.

As (meth)acrylic oligomer, what was prepared by the following method was used. Specifically, 95 parts of CHMA and 5 parts of AA, 10 parts of AIBN as a polymerization initiator, and toluene as a polymerization solvent were placed in a reaction vessel equipped with a stirrer, thermometer, nitrogen gas introduction tube, reflux condenser, and dropping funnel, and stirred in a nitrogen stream for 1 hour. Then, after removing oxygen in the polymerization system, the temperature was raised to 85°C and reacted for 5 hours to obtain a (meth)acrylic oligomer having a solid content concentration of 50%. Mw of the obtained (meth)acrylic oligomer was 3600.

(Production of adhesive sheet)

As a release liner, two release films made of polyester (trade name'Dia foil MRF', 38 µm in thickness, manufactured by Mitsubishi Polyester Co., Ltd.) having one side as a release side subjected to release treatment were prepared. The pressure-sensitive adhesive composition was applied to the release surface of these release liners so that the thickness after drying became 1.5 µm, and dried at 100°C for 2 minutes. In this way, an adhesive layer was formed on the release surfaces of the two release liners, respectively. The gel fraction of the obtained pressure-sensitive adhesive layer was 60%, the storage modulus G'(25°C) of the pressure-sensitive adhesive layer at 25°C was 0.32 MPa, and the loss elastic modulus G" (25°C) was 0.36 MPa.

As a base film, a PET film having a thickness of 5 μm prepared by mixing carbon black particles so that the light transmittance in the thickness direction was 2.4% was prepared. Each of the pressure-sensitive adhesive layers formed on the two release liners was adhered to the first and second sides of the base film, and a double-sided pressure-sensitive adhesive sheet having a total thickness of 20 μm was prepared (transfer method). The release liner was left on the pressure-sensitive adhesive layer as it is and used to protect the surface (adhesive surface) of the adhesive layer.

<Example 2>

To the pressure-sensitive adhesive composition according to Example 1, 6.5 parts of a black pigment (manufactured by Dainichi Seika, brand name'ATDN101 Black') was added to 100 parts of the acrylic polymer contained in the composition, and the mixture was stirred and used as the pressure-sensitive adhesive composition according to this example. I did. A double-sided pressure-sensitive adhesive sheet having a total thickness of 30 μm was produced in the same manner as in Example 1 except that the pressure-sensitive adhesive layer having a thickness of 12.5 μm was formed using this pressure-sensitive adhesive composition. With respect to this adhesive sheet, the light transmittance per 1 mm of the width in the XY plane direction was measured and found to be less than 0.01%.

<Example 3>

As the base film, a PET film having a thickness of 12 µm prepared by mixing carbon black particles so that the light transmittance in the thickness direction is less than 0.01% was used. In addition, the thickness of each pressure-sensitive adhesive layer was changed to 9 μm. Otherwise, in the same manner as in Example 1, a double-sided pressure-sensitive adhesive sheet having a total thickness of 30 μm was produced.

<Example 4>

As the base film, a PET film having a thickness of 50 µm prepared by mixing carbon black particles so that the light transmittance in the thickness direction was 1.1% was used. In addition, the thickness of each pressure-sensitive adhesive layer was changed to 35 μm. Otherwise, in the same manner as in Example 1, a double-sided adhesive sheet having a total thickness of 120 µm was produced.

<Example 5>

As the base film, a PET film having a thickness of 75 μm prepared by mixing carbon black particles so that the light transmittance in the thickness direction was 0.53% was used. In addition, the thickness of each pressure-sensitive adhesive layer was changed to 38 μm. Otherwise, in the same manner as in Example 4, a double-sided pressure-sensitive adhesive sheet having a total thickness of about 150 μm was produced.

<Example 6>

In this example, a support substrate having a total thickness of about 10 μm and a multilayer structure including a transparent PET film (trade name “Lumira” manufactured by Toray Corporation) and a black print layer provided on the second side of the PET film was used as the substrate. The black printing layer was formed by using an ink composition containing a black colorant and performing printing using a gravure printing method. The applied amount of the pressure-sensitive adhesive composition to the release film was adjusted so that the thickness after drying was 10 µm. Other than that, the pressure-sensitive adhesive sheet according to this example was manufactured in the same manner as in Example 1.

For the pressure-sensitive adhesive sheet according to each example, the light transmittance in the Z direction T _Z [%], the light transmittance in the Z direction [%] of the pressure-sensitive adhesive layer, the light transmittance in the Z direction [%] of the substrate layer, light-shielding property in the sheet surface direction, and inspection Sex was measured or evaluated. Table 1 shows the results.

[Table 1]

As shown in Table 1, the PSA sheet according to Example 2 has good light-shielding properties in the sheet surface direction, and the light transmittance T _Z in the Z direction exceeds 0.04%. This pressure-sensitive adhesive sheet had good light-shielding property in the sheet surface direction, and had photosensitivity to the extent that inspection beyond the pressure-sensitive adhesive sheet was possible in the thickness direction. On the other hand, in the pressure-sensitive adhesive sheets according to Examples 1 and 3 to 6, either or both of the light-shielding properties and inspection properties in the sheet surface direction were not at pass levels.

In the above, specific examples of the present invention have been described in detail, but these are only examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

1 adhesive sheet
10 base layer
10A first side
10B side 2
21 First adhesive layer
21A first adhesive surface
22 Second adhesive layer
22A second adhesive surface
31, 32 release liners

Claims (10)

A pressure-sensitive adhesive sheet comprising a substrate layer and an adhesive layer disposed on at least one surface of the substrate layer,
The adhesive sheet has a light transmittance T _Z of more than 0.04% and less than 50% in the Z direction, and a light transmittance T _XY per 1 mm of the width of the XY plane thereof is smaller than the light transmittance T _Z in the Z direction. The XY surface of the sheet is the sheet surface of the adhesive sheet, and the Z direction is the thickness direction of the adhesive sheet. The method of claim 1,
The pressure-sensitive adhesive sheet, wherein the light transmittance T _Z in the Z direction is 0.1% or more and 15% or less. The method according to claim 1 or 2,
The adhesive sheet having a light transmittance T _XY of 0.04% or less per 1 mm of the width of the XY surface. The method according to any one of claims 1 to 3,
The difference between the light transmittance T _XY [%] and the light transmittance T _Z [%] (T _Z -T _XY ) is 1.00 or more. The method according to any one of claims 1 to 4,
The substrate layer is a pressure-sensitive adhesive sheet comprising a resin film containing a black colorant. The method according to any one of claims 1 to 5,
The thickness of the base layer is 0.5㎛ to 10㎛, the pressure-sensitive adhesive sheet. The method according to any one of claims 1 to 6,
The pressure-sensitive adhesive layer includes a black colorant, the pressure-sensitive adhesive sheet. The method according to any one of claims 1 to 7,
The thickness of the pressure-sensitive adhesive layer is 1.5 μm to 60 μm, the pressure-sensitive adhesive sheet. The method according to any one of claims 1 to 8,
A pressure-sensitive adhesive sheet used in an electronic device containing a light-emitting element. The method according to any one of claims 1 to 9,
An adhesive sheet used for fixing a member in a portable electronic device.

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