JP7339009B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet.

In general, pressure-sensitive adhesives (also referred to as pressure-sensitive adhesives; hereinafter the same) exhibit a soft solid (viscoelastic) state in a temperature range around room temperature, and have the property of being easily adhered to an adherend by pressure. Taking advantage of such properties, pressure-sensitive adhesives are widely used for the purpose of joining, fixing, protecting members in mobile electronic devices such as mobile phones. In addition, in the portable electronic devices described above, for the purpose of preventing leakage of light from a light source such as a backlight module, for example, a light-shielding adhesive sheet is used. Documents related to this type of technology include Patent Documents 1 to 6. Patent Documents 1 to 5 disclose pressure-sensitive adhesive sheets having a black printed layer on one side of a resin film substrate. Patent Document 6 is a prior art document that discloses a single-sided adhesive sheet laminated to a graphite sheet.

JP 2013-87246 A JP 2013-166891 A JP 2015-83660 A JP 2017-57375 A Japanese Patent Application Laid-Open No. 2018-2898 JP 2017-52835 A

For example, adhesive sheets used for portable electronic devices are subjected to processing such as punching to match the shape and size of the device and to remove the portion corresponding to the display screen of the electronic device. However, in the light-shielding pressure-sensitive adhesive sheets having a black printed layer as described in Patent Documents 1 to 5, when the black printed layer is peeled off due to poor cutting or the like during processing such as punching, the black coloring agent contained in the black printed layer (Typically, black pigments such as carbon black) are scattered and become a cause of dust generation. Dust generation is a cause of contamination of the clean environment, and can affect the maintenance of precision equipment and eventually the quality of the pressure-sensitive adhesive sheet as a product.

Further, among the above light-shielding pressure-sensitive adhesive sheets, there are those in which the pressure-sensitive adhesive layer contains a coloring agent to enhance light-shielding properties (for example, Patent Document 4). However, the coloring agent in the adhesive layer may adhere to the blade during processing such as punching. Adhesion of the coloring agent to the processing blade causes secondary contamination, which is a limiting factor for continuous use of the processing machine.

The present invention was created in view of the above circumstances, and an object of the present invention is to provide a clean pressure-sensitive adhesive sheet having good light-shielding properties.

According to the present specification, a pressure-sensitive adhesive sheet is provided that includes a base film layer containing a black colorant and a light-transmitting pressure-sensitive adhesive layer disposed on at least one surface of the base film layer. This adhesive sheet has a light transmittance of less than 5% in the thickness direction. By using a black colorant-containing base film as a base material, the pressure-sensitive adhesive sheet having the above configuration can exhibit good light-shielding properties in spite of having a light-transmitting pressure-sensitive adhesive layer. In this pressure-sensitive adhesive sheet, the black colorant that contributes to the light-shielding property is contained in a base film having a predetermined rigidity, so it is difficult to peel off and lose, and it is difficult to adhere to processing blades, etc. and does not cause contamination. The amount of coloring agent used is limited to such an extent that the pressure-sensitive adhesive layer also has light transmittance, or it contains no coloring agent. Therefore, contamination of the colorant from the adhesive is also limited. In short, the pressure-sensitive adhesive sheet having the above-described structure can be a clean product that prevents dust generation and contamination while exhibiting good light-shielding properties.

In some preferred embodiments, the pressure-sensitive adhesive layer has a light transmittance of 5% or more in its thickness direction. According to the technology disclosed herein, it is possible to achieve both good light shielding properties and cleanness in a configuration in which the pressure-sensitive adhesive layer has a light transmittance of 5% or more. More preferably, the pressure-sensitive adhesive layer has a light transmittance of more than 50% in the thickness direction. Such a pressure-sensitive adhesive layer has high transparency and can be highly prevented from being contaminated with a coloring agent.

In some preferred embodiments, the pressure-sensitive adhesive sheet has a light transmittance of 0.01% or less in the thickness direction. A pressure-sensitive adhesive sheet that satisfies this characteristic can achieve excellent light-shielding properties in the thickness direction. In another preferred embodiment, the pressure-sensitive adhesive sheet has a light transmittance in the thickness direction of more than 0.01% and less than 5%. A pressure-sensitive adhesive sheet that satisfies this characteristic has a predetermined light transmittance in the thickness direction, so that the appearance of the adherend can be inspected through the pressure-sensitive adhesive sheet.

In some preferred embodiments, the through-thickness light transmittance of the base film layer is less than 5%. By setting the light transmittance in the thickness direction of the base material layer to a predetermined value or less in this manner, good light shielding properties are preferably realized.

In some preferred embodiments, the base film layer is a resin film layer containing the black colorant. By using a resin film containing a black colorant as a base material, it is possible to preferably obtain a pressure-sensitive adhesive sheet having a desired light-shielding property. The black colorant-containing resin film is also excellent in processability, and is also a material from which a clean pressure-sensitive adhesive sheet can be easily obtained.

In some preferred embodiments, the adhesive layer has a thickness of 1.5 μm to 60 μm. By setting the thickness of the adhesive layer to 1.5 μm or more, adhesive properties such as adhesive strength and impact resistance tend to be improved. Also, by setting the thickness to 60 μm or less, the pressure-sensitive adhesive sheet can be made thinner.

The pressure-sensitive adhesive sheet disclosed herein utilizes its light-shielding property and is suitable for electronic devices including light-emitting elements, such as liquid crystal display (LCD) devices including a backlight unit, as a sheet that combines adhesive means and light-shielding property. Used.

Moreover, the pressure-sensitive adhesive sheet disclosed herein is preferably used for portable electronic devices. In applications for portable electronic devices, the pressure-sensitive adhesive sheet can be processed into various shapes such as a frame shape and a narrow width according to the shape of the electronic device and the shape of the member. The pressure-sensitive adhesive sheet disclosed herein can be clean without generating dust or contamination during processing, and is easy to handle without impairing a clean environment during processing such as punching. In addition, portable electronic devices that have a light source are required to prevent light leakage, and devices that have a display screen are required to prevent light reflection and the like to ensure the visibility of the display screen. By using the adhesive sheet disclosed herein, it is possible to prevent light leakage and ensure the visibility of the display screen, which is significant.

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

Preferred embodiments of the present invention are described below. Matters other than the matters specifically mentioned in the present specification, which are necessary for the implementation of the present invention, are based on the teaching of the implementation of the invention described in the present specification and the common general knowledge at the time of filing. can be understood by those skilled in the art. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field. Further, in the following drawings, members and portions having the same function may be denoted by the same reference numerals, and redundant description may be omitted or simplified. In addition, the embodiments described in the drawings are schematic for clearly explaining the present invention, and do not necessarily accurately represent the size and scale of the pressure-sensitive adhesive sheet of the present invention that is actually provided as a product. .

As used herein, the term “adhesive” refers to a material that exhibits a soft solid (viscoelastic) state in a temperature range around room temperature and has the property of easily adhering to an adherend under pressure, as described above. . The adhesive used herein generally has a complex tensile elastic modulus E ^* (1 Hz) It may be a material having properties satisfying <10 ⁷ dyne/cm ² (typically, a material having the above properties 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 a substrate film layer (also referred to as a supporting substrate). The concept of the adhesive sheet as used herein can include what is called an adhesive tape, an adhesive label, an adhesive film, and the like. The pressure-sensitive adhesive sheet disclosed herein may be roll-shaped or sheet-shaped. Alternatively, it may be a pressure-sensitive adhesive sheet processed into various shapes.

<Structure of Adhesive Sheet>
The adhesive sheet disclosed herein can have, for example, the cross-sectional structure schematically shown in FIG. The pressure-sensitive adhesive sheet 1 shown in FIG. and Specifically, a resin film containing a black colorant is used as the base film layer 10 . Both the first adhesive layer 21 and the second adhesive layer 22 have optical transparency. Both the first surface 10A and the second surface 10B are non-peeling surfaces (non-peeling surfaces). The adhesive sheet 1 is used by attaching 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. That is, the pressure-sensitive adhesive sheet 1 is configured as a double-sided pressure-sensitive adhesive sheet (double-sided adhesive pressure-sensitive adhesive sheet). In the pressure-sensitive adhesive sheet 1 before use, the first pressure-sensitive adhesive surface 21A and the second pressure-sensitive adhesive surface 22A are protected by release liners 31 and 32, respectively, in which at least the pressure-sensitive adhesive surface side is a surface having releasability (release surface). have a configuration. Alternatively, the release liner 32 may be omitted and a release liner 31 having release surfaces on both sides may be used. Therefore, the second adhesive surface 22A may also be protected by the release liner 31 .

The technology disclosed herein is preferably implemented in the form of the double-sided pressure-sensitive adhesive sheet with the above-described base material for fixing or joining members. Alternatively, the PSA sheet disclosed herein may be in the form of a single-sided PSA sheet with a substrate having a PSA layer only on one side of a non-releasable substrate film layer, although not shown. As an example of the form of the single-sided pressure-sensitive adhesive sheet, there is a form that does not have either the first pressure-sensitive adhesive layer 21 or the second pressure-sensitive adhesive layer 22 in the structure shown in FIG.

<Thickness direction light transmittance of adhesive sheet>
The adhesive sheet disclosed herein is characterized by having a light transmittance in the thickness direction of less than 5%. Thereby, the pressure-sensitive adhesive sheet can exhibit good light-shielding properties in spite of having a light-transmitting pressure-sensitive adhesive layer. In some embodiments, the through-thickness light transmittance of the adhesive sheet is preferably about 4% or less, more preferably about 3% or less (eg, about 2% or less). In this embodiment, the lower limit of the thickness direction light transmittance of the adhesive sheet is not particularly limited, and the adhesive sheet may have light attenuation that allows inspection of the adherend through the adhesive sheet. From such a viewpoint, the thickness direction light transmittance of the pressure-sensitive adhesive sheet is preferably 0.01% or more (for example, more than 0.01%), more preferably more than 0.04%, and still more preferably about 0.1%. or more (for example, more than 0.1%), particularly preferably about 0.5% or more (for example, about 1% or more). In some other embodiments, the light transmittance in the thickness direction is preferably about 1% or less, more preferably about 0.1% or less, still more preferably 0.04, from the viewpoint of obtaining higher light shielding properties. % or less, particularly preferably 0.02% or less (typically about 0.01% or less). The light transmittance in the thickness 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 in the thickness direction of the adhesive sheet is measured by the method described in Examples below.

<Base film layer>
The adhesive sheet disclosed herein includes a base film layer. The base film layer disclosed herein is a base film layer containing a black colorant. More specifically, it can be said to be a base film layer (typically a resin film layer) into which a black colorant is kneaded. Here, the base film layer in which the black colorant is kneaded means that the main constituent material of the base film (the material most contained in the base film, typically a resin material) contains a black colorant. Refers to a mixed base film layer. The black colorant is substantially dispersed in the base film layer. The dispersion state of the black colorant in the base film layer is not particularly limited. It is preferably dispersed throughout the layer.

According to the pressure-sensitive adhesive sheet provided with the black colorant-containing base film layer, it is possible to achieve good light-shielding properties in the thickness direction. In addition, since the black colorant, which contributes to light-shielding properties, is contained in a base film that has a predetermined rigidity, it is difficult to peel off or disperse, and it is difficult to adhere to processing blades, etc., so dust generation and contamination are prevented. does not occur. In addition, migration of the colorant from the black colorant-containing base film layer to the pressure-sensitive adhesive layer does not occur or is negligible. Furthermore, the black colorant-containing base film layer is relatively thicker than a laminate of a conventional colored layer (printed layer) having the same thickness as the base film layer and a resin film. It has good elasticity and is also advantageous in terms of workability. In particular, since the black colorant-containing resin film layer is excellent in workability, it is difficult to generate fragments and dust due to cutting defects, and it is easy to obtain a clean pressure-sensitive adhesive sheet. Furthermore, since the black colorant-containing base film does not require an additional colored layer, it is easy to maintain good adhesive properties by allocating the thickness of the additional colored layer to the pressure-sensitive adhesive layer. A pressure-sensitive adhesive sheet comprising a black colorant-containing base film does not cause defects such as pinholes even when it is folded, and thus has excellent durability as a light-shielding pressure-sensitive adhesive sheet. In other words, the black colorant-containing base film layer itself is colored black, and can be called a black base film layer (for example, a black resin film layer).

The structure and material of the base film layer disclosed herein are not particularly limited as long as they satisfy the light transmittance in the thickness direction of the pressure-sensitive adhesive sheet. The base film layer is specifically made of a film base (also referred to as a "base film"). As the base film, a base film containing a resin film can be preferably used. The base film is typically an independently shape-maintainable (independent) member. The base film in the technique disclosed here can be substantially composed of such a base film. Alternatively, the base film layer may contain an auxiliary layer in addition to the base film. Examples of the auxiliary layer include a colored layer, a reflective layer, an undercoat layer, an antistatic layer, etc. provided on the surface of the base film.

The resin film is a film containing a resin material as a main component (for example, a component contained in the resin film in an amount exceeding 50% by weight). Examples of resin films include polyolefin resin films such as polyethylene (PE), polypropylene (PP), and ethylene/propylene copolymer; polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), and the like. polyurethane resin film; vinyl chloride resin film; vinyl acetate resin film; polyimide resin film; polyamide resin film; The resin film may be a rubber-based film such as a natural rubber film or a butyl rubber film. The resin film may be a blend film in which two or more of the resins exemplified above are mixed. Among them, from the viewpoint of handleability and workability, polyester films are preferable, and among them, PET films are particularly preferable. In this specification, the term "resin film" is typically a non-porous sheet, and is a concept distinguished from so-called nonwoven fabrics and woven fabrics (in other words, a concept excluding nonwoven fabrics and woven fabrics). be.

As the black colorant contained in the base film layer, an organic or inorganic colorant (pigment, dye, etc.) can be used. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, and cyanine. Black, activated carbon, ferrite (nonmagnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone colorants, and the like. A black colorant can be used individually by 1 type or in combination of 2 or more types. Among them, carbon black is preferred.

The black colorant is not particularly limited, and a particulate colorant (pigment) can be preferably used because the light-shielding property can be efficiently adjusted by using a small amount of the black colorant. In some preferred embodiments, black colorants (eg, black pigments such as carbon black) having an average particle size of about 10 nm or greater (eg, approximately 50 nm or greater) can be used. The upper limit of the average particle size of the black colorant is not particularly limited, and can be about 500 nm or less, preferably about 300 nm or less, more preferably about 250 nm or less, for example 200 nm or less (e.g., about 120 nm or less). . In addition, unless otherwise specified, the "average particle size" in this specification means the particle size at 50% of the integrated value in the particle size distribution measured based on the particle size distribution measuring device based on the laser scattering/diffraction method (50% volume mean particle diameter; hereinafter sometimes abbreviated as _D50 ).

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

The base film layer disclosed herein may contain one or more coloring agents (pigments and dyes) other than the black coloring agent. The color of such non-black colorants can be, for example, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent, and the like. In some embodiments, non-black colorants include, for example, white colorants. White colorants include, 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 (light 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 white, zinc sulfide, talc, silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite , Inorganic white colorants such as hydrated halloysite, acrylic resin particles, polystyrene resin particles, polyurethane resin particles, amide resin particles, polycarbonate resin particles, silicone resin particles, urea-formalin resin particles, melamine and organic white colorants such as organic resin particles. These can be used individually by 1 type or in combination of 2 or more types.

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

If necessary, the base film layer may contain fillers (inorganic fillers, organic fillers, etc.), dispersants (surfactants, etc.), anti-aging agents, antioxidants, ultraviolet absorbers, antistatic agents. , lubricants, plasticizers, and other additives may be added. The blending ratio of various additives may be approximately less than 30% by weight (for example, less than 20% by weight, typically less than 10% by weight).

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

The base film layer may typically be free of colored layers such as those disposed on the surface of the base film, since the base film (preferably resin film) contains a black colorant. The colored layer here is typically a layer called an ink layer or a printed layer, which is formed by coating a base film with a colored layer-forming composition containing a coloring agent and a binder. The thickness of such a colored layer can be on the order of 1 μm to 10 μm. According to the technology disclosed herein, the use of the black colorant-containing base film provides good light-shielding properties, eliminating the need to use a colored layer that may cause dust generation. This is advantageous in terms of preventing pinholes and local light leakage caused by pinholes that can be a problem in types that obtain light shielding properties with colored layers, as well as scratch resistance and chemical resistance (for example, solvent resistance). be.

The surface of the base film layer may be subjected to conventionally known surface treatments such as corona discharge treatment, plasma treatment, ultraviolet irradiation treatment, acid treatment, alkali treatment, application of an undercoat agent, and the like. Such a surface treatment can be a treatment for improving the adhesion between the base film layer and the pressure-sensitive adhesive layer, in other words, the anchoring property of the pressure-sensitive adhesive layer to the base film layer. In addition, when the technology disclosed herein is implemented in the form of a substrate-attached single-sided pressure-sensitive adhesive sheet, the back surface of the substrate film layer may be subjected to release treatment as necessary. For the release treatment, for example, general silicone-based, long-chain alkyl-based, and fluorine-based release agents are typically applied to a thin film of about 0.01 μm to 1 μm (eg, 0.01 μm to 0.1 μm). It can be a treatment to give. By performing such a peeling treatment, it is possible to obtain effects such as facilitating the unwinding of the adhesive sheet wound into a roll.

The thickness direction light transmittance of the base film layer disclosed herein can be appropriately set so that the thickness direction light transmittance 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 light-shielding properties in the thickness direction of the adhesive sheet, the thickness direction light transmittance of the base film layer is suitably less than 5%, preferably about 4% or less, more preferably about 3%. or less (for example, about 2% or less). In this embodiment, the lower limit of the thickness direction light transmittance of the base film layer is not particularly limited, and the base film layer may have light attenuation that allows inspection of the adherend through the adhesive sheet. From such a viewpoint, the thickness direction light transmittance of the base film layer is preferably 0.01% or more (for example, more than 0.01%), more preferably more than 0.04%, and still more preferably about 0.04%. It is 1% or more (eg, more than 0.1%), particularly preferably about 0.5% or more (eg, about 1% or more), and may be about 1.5% or more. Making the light transmittance in the thickness direction of the base film layer equal to or higher than a predetermined value is significant from an industrial point of view, including maintenance of the properties (processability, mechanical properties) of the base film and productivity and efficiency. is. In some other embodiments, the light transmittance in the thickness direction is preferably about 1% or less, more preferably about 0.1% or less, still more preferably 0.04, from the viewpoint of obtaining higher light shielding properties. % or less, particularly preferably 0.02% or less (typically about 0.01% or less). The light transmittance in the thickness direction of the base film layer is measured by the method described in Examples below.

The thickness of the base film 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 film layer (for example, the resin film layer) is, for example, about 200 μm or less, preferably about 150 μm or less, and about 100 μm or less. can. A base film layer with a limited thickness is preferably used for applications that require thinness and weight reduction. In addition, for example, by limiting the thickness of the base film layer and relatively increasing the thickness of the adhesive layer, it is possible to improve adhesive properties such as peel strength and impact resistance, resulting in uneven adhesion. There is also a tendency to improve the conformability to the body surface (conformability to steps). From such a viewpoint, the thickness of the base film layer is preferably less than 75 μm (for example, approximately 60 μm or less), more preferably approximately 50 μm or less (for example, less than 50 μm), still more preferably approximately 40 μm or less, and particularly preferably approximately 30 μm. (eg less than 30 μm, typically about 25 μm or less). In some embodiments, the thickness of the base film layer may be about 20 μm or less, about 12 μm or less, or about 7 μm or less (eg, about 3 μm or less).

The lower limit of the thickness of the base film layer is not particularly limited. The thickness of the base film layer is suitably about 0.5 μm or more (for example, about 1 μm or more) from the standpoint of handleability and workability of the pressure-sensitive adhesive sheet. By increasing the thickness of the base film layer, high light-shielding properties tend to be obtained. In some embodiments, the thickness of the base film layer may be approximately 3 μm or greater. In some other embodiments, the thickness of the base film layer can be about 8 μm or greater, can be about 13 μm or greater, or can be about 16 μm or greater.

<Adhesive layer>
(base polymer)
In the technology disclosed herein, the type of adhesive that constitutes the adhesive layer is not particularly limited as long as the adhesive layer has optical transparency. The above-mentioned pressure-sensitive adhesives include various rubber-like polymers such as acrylic polymers, rubber-based polymers, polyester-based polymers, urethane-based polymers, polyether-based polymers, silicone-based polymers, polyamide-based polymers, fluorine-based polymers, etc., which are known in the field of pressure-sensitive adhesives. 1 or 2 or more as a base polymer. From the viewpoint of adhesive performance, cost, etc., a pressure-sensitive adhesive containing an acrylic polymer or a rubber-based polymer as a base polymer can be preferably employed. Among them, a pressure-sensitive adhesive having an acrylic polymer as a base polymer (acrylic pressure-sensitive adhesive) is preferable. 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 below. It is not intended to be limited to

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 term "rubber-like polymer" refers to a polymer that exhibits rubber elasticity in a temperature range around room temperature. In this specification, the term "main component" refers to a component contained in an amount exceeding 50% by weight unless otherwise specified.
Further, the term "acrylic polymer" refers to a polymer containing monomer units derived from a monomer having at least one (meth)acryloyl group in one molecule as monomer units constituting the polymer. Hereinafter, a monomer having at least one (meth)acryloyl group in one molecule is also referred to as "acrylic monomer". Accordingly, an acrylic polymer in this specification is defined as a polymer containing monomeric units derived from an acrylic monomer. A typical example of an acrylic polymer is an acrylic polymer containing more than 50% by weight of the acrylic monomer in the total monomer components used to synthesize the acrylic polymer.
In addition, "(meth)acryloyl" is a generic term for acryloyl and methacryloyl. Similarly, "(meth)acrylate" is a generic term for acrylate and methacrylate, and "(meth)acrylic" is generic for acrylic and methacrylic.

(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 monomer raw materials containing an alkyl (meth)acrylate as a main monomer and may further contain a sub-monomer copolymerizable with the main monomer. The term "main monomer" as used herein refers to a component that is contained in an amount exceeding 50% by weight in the raw material for the monomer.

As the alkyl (meth)acrylate, for example, a compound represented by the following formula (1) can be preferably used.
_CH2 =C( ^R1 ) ^COOR2 (1)
Here, R ¹ in the above formula (1) is a hydrogen atom or a methyl group. R ² is a chain alkyl group having 1 to 20 carbon atoms (hereinafter, such a range of carbon atoms may be referred to as "C _1-20 "). From the viewpoint of the storage modulus of the pressure-sensitive adhesive, alkyl (meth)acrylates in which R ² is a C _1-14 chain alkyl group are preferred, and alkyl (meth)acrylates in which R ² is a C _1-10 chain alkyl group. ) acrylates are more preferred, and alkyl (meth)acrylates in which R ² is a butyl group or a 2-ethylhexyl group are particularly preferred.

Examples of alkyl (meth)acrylates in which 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, 2-ethylhexyl (meth)acrylate , octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, eicosyl (meth)acrylate and the like. . These alkyl (meth)acrylates may be used singly or in combination of two or more. Particularly preferred alkyl (meth)acrylates include n-butyl acrylate (BA) and 2-ethylhexyl acrylate (2EHA).

In the technique 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 wt. % or more (typically 85% by weight or more, for example 90% by weight or more, further 95% by weight or more). The technology disclosed herein can be practiced, for example, in a mode in which the alkyl (meth)acrylate contained in the monomer component is BA alone, 2EHA alone, BA and 2EHA, and the like.

The technique disclosed herein can be preferably carried out in a mode 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. By using a C _1-6 alkyl (meth)acrylate as a main monomer in this way, an acrylic polymer having excellent deformation resistance (for example, deformation resistance under constant load) can be preferably designed. The proportion of C _1-6 alkyl (meth)acrylate in the monomer component (in other words, polymerization proportion) is more preferably greater than 50% by weight, still more preferably 60% by weight or more, and particularly preferably 70% by weight or more (for example, 80% by weight or more, further 85% by weight or more). The upper limit of the ratio of C _1-6 alkyl (meth)acrylate in the monomer component is not particularly limited, and is, for example, 99% by weight or less, and 97% by weight or less in relation to the ratio of other copolymerizable monomers used. is appropriate, and it is preferably 95% by weight or less. The C _1-6 alkyl (meth)acrylates may be used singly or in combination of two or more. The C _1-6 alkyl (meth)acrylate is preferably a C _1-6 alkyl acrylate, more preferably a C _2-6 alkyl acrylate, and still more preferably a C _4-6 alkyl acrylate. In some other embodiments, the C _1-6 alkyl (meth)acrylate is preferably a C _1-4 alkyl acrylate, more preferably a C _2-4 alkyl acrylate. A preferred example of the C _1-6 alkyl (meth)acrylate is BA.

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 50% by weight or more, still more preferably 60% by weight or more, and particularly preferably 70% by weight or more (for example, 80% by weight or more, further 85% by weight or more), more preferably 90% by weight or more (for example, more than 90% by weight). By copolymerizing BA as the main monomer, the pressure-sensitive adhesive tends to have good adhesion to adherends. Further, the copolymerization ratio of BA in the acrylic polymer is not particularly limited. It is suitable that the content is 95% by weight or less, preferably 95% by weight or less.

In some preferred embodiments, an acidic group-containing monomer is used as the monomer copolymerizable with the main monomer alkyl (meth)acrylate. The acidic group-containing monomer can improve cohesiveness based on its polarity and exhibit good bonding strength to polar adherends. When using a cross-linking agent such as an isocyanate-based or epoxy-based cross-linking agent, the acidic group (typically a carboxyl group) becomes a cross-linking point of the acrylic polymer. Due to these actions, deformation resistance can be suitably realized. By using an acidic group-containing monomer in a predetermined ratio or more, for example, an acrylic polymer capable of realizing initial adhesiveness (for example, initial adhesiveness for light pressure bonding) and deformation resistance can be preferably designed.

A carboxy group-containing monomer is preferably used as the acidic group-containing monomer. Examples of carboxy group-containing monomers include ethylenically unsaturated monocarboxylic acids such as acrylic acid (AA), methacrylic acid (MAA), carboxyethyl (meth)acrylate, crotonic acid and isocrotonic acid; maleic acid, itaconic acid and citraconic acid; ethylenically unsaturated dicarboxylic acids such as and anhydrides thereof (maleic anhydride, itaconic anhydride, etc.). The acidic group-containing monomer may also be a monomer having a metal salt (for example, an alkali metal salt) of a carboxy group. The acidic group-containing monomers may be used singly or in combination of two or more. Among them, AA and MAA are preferred, and AA is more preferred. When one or two or more acidic group-containing monomers are used, 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 still more preferably 90% by weight or more. is. In a particularly preferred embodiment, the acidic group-containing monomer consists essentially of AA. AA has multiple effects such as polarity based on its carboxyl group, role as a cross-linking point, and Tg (106° C.). It is considered to be the most suitable monomer material for realizing

In the technique disclosed herein, the content of an 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 particularly limited. It can be about 0.1% by weight or more, and it is suitable to be about 1% by 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 the acidic group-containing monomer, it is possible to preferably realize an acrylic polymer capable of achieving both initial adhesiveness and deformation resistance based on the action of improving the cohesiveness and the like. The copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is suitably 20% by weight or less, and preferably 18% by weight or less from the viewpoint of maintaining the properties of the main monomer. The copolymerization ratio may be 15% by weight or less, for example, 13% by weight or less. In a more preferred embodiment, the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is approximately 12% by weight or less, more preferably approximately 10% by weight or less, and particularly preferably approximately 8% by weight or less. In an acrylic polymer having a monomer composition containing a large amount of C _1-6 alkyl (meth)acrylate (typically BA), the content of the acidic group-containing monomer (for example, AA) in the monomer component should be within the above range. Effective.

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, suitably about 3% or more, and about It is preferably 5% or more, and may be, for example, about 7% or more. By using a predetermined amount or more of an acidic group-containing monomer with respect to the main monomer (typically alkyl (meth)acrylate), the adhesive performance of the main monomer and the cohesiveness improvement effect of the acidic group-containing monomer are preferably obtained. Compatible acrylic polymers can be obtained. The above ratio (C _A /C _M ) is suitably about 25% or less, 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, for example 13% or less. In a more preferred embodiment, the ratio (C _A /C _M ) is about 11% or less, more preferably about 9% or less. In an acrylic polymer having a monomer composition containing a large amount of C _1-6 alkyl (meth)acrylate (typically BA), the content of the acidic group-containing monomer (for example, AA) in the monomer component should be within the above range. Effective.

In the technique disclosed herein, a copolymerizable monomer other than an acidic group-containing monomer (typically a carboxy group-containing monomer) is used as a sub-monomer copolymerizable with the alkyl (meth)acrylate that is the main monomer. be able to. As such a sub-monomer, for example, the following functional group-containing monomers can be used.
hydroxyl group-containing monomers: hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate; Unsaturated alcohols such as vinyl alcohol and allyl alcohol; polypropylene glycol mono(meth)acrylate;
Amido group-containing monomers: for example (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl(meth)acrylamide;
Amino group-containing monomers: for example aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, t-butylaminoethyl (meth)acrylate.
Monomers with epoxy groups: eg glycidyl (meth)acrylate, methylglycidyl (meth)acrylate, allyl glycidyl ether.
Cyano group-containing monomers: for example acrylonitrile, methacrylonitrile.
Keto group-containing monomers: for example diacetone (meth)acrylamide, diacetone (meth)acrylate, vinylmethylketone, vinylethylketone, allylacetoacetate, vinylacetoacetate.
Monomers having a nitrogen atom-containing ring: such as N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinyl pyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, N-(meth)acryloylmorpholine;
Alkoxysilyl group-containing monomers: such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxy Propylmethyldiethoxysilane.

The functional group-containing monomers 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 proportion of the functional group-containing monomer in the monomer component is appropriately determined according to the required performance. The ratio (copolymerization ratio) of the functional group-containing monomer (e.g., hydroxyl group-containing monomer) is 0.01% by weight or more (e.g., 0.02% by weight or more, typically 0.03% by weight or more) in the monomer component. It is suitable to be about 0.1% by weight or more (for example, 0.5% by weight or more, typically 1% by weight or more). Moreover, the upper limit 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 proportion of functional group-containing monomers other than the acidic group-containing monomer is, for example, 10% by weight or less, preferably 5% by weight or less, and can be 1% by weight or less. In a more preferred embodiment, the proportion of functional group-containing monomers (for example, hydroxyl group-containing monomers) other than the acidic group-containing monomer is about 0.5% by weight or less (for example, about 0.2% by weight or less).

As the monomer component constituting the acrylic polymer, a copolymer component other than the aforementioned acidic group-containing monomer and other sub-monomers can be used for the purpose of increasing 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 vinyltoluene; ) acrylate, cyclopentyl (meth)acrylate, cycloalkyl (meth)acrylate such as isobornyl (meth)acrylate; aryl (meth)acrylate (e.g. phenyl (meth)acrylate), aryloxyalkyl (meth)acrylate (e.g. phenoxyethyl (meth)acrylate ) acrylate), aromatic ring-containing (meth)acrylates such as arylalkyl (meth)acrylates (e.g., benzyl (meth)acrylate); olefinic monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; vinyl chloride, vinylidene chloride chlorine-containing monomers such as; isocyanate group-containing monomers such as 2-(meth)acryloyloxyethyl isocyanate; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; vinyl ethers such as methyl vinyl ether and ethyl vinyl ether system monomer; and the like.
The amount of such other copolymerization component may be appropriately selected depending on the purpose and application, and is not particularly limited, but is preferably 10% by weight or less of the monomer component. For example, when a vinyl ester monomer (for example, vinyl acetate) is used as the other copolymerization component, the content thereof is, for example, about 0.1% by weight or more (typically about 0.5% by weight or more) of the monomer component. ), and it is suitable to be about 20% by weight or less (typically about 10% by weight or less).

Acrylic polymers are polyfunctional having at least two polymerizable functional groups (typically radically polymerizable functional groups) having unsaturated double bonds such as (meth)acryloyl groups and vinyl groups as other monomer components. It may contain a monomer. By using a polyfunctional monomer as the monomer component, the cohesive force of the pressure-sensitive adhesive layer can be increased. Polyfunctional monomers can be used as cross-linking agents.

Examples of multifunctional monomers 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, penta Erythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,2-ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1, Polyhydric alcohols such as 6-hexanediol di(meth)acrylate, 1,12-dodecanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, and (meth)acryl Esters with acids; 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-hexanediol di(meth)acrylate and dipentaerythritol hexa(meth)acrylate. A particularly preferred example is 1,6-hexanediol di(meth)acrylate. A polyfunctional monomer can be used individually by 1 type or in combination of 2 or more types. Polyfunctional monomers having two or more acryloyl groups are preferred from the viewpoint of reactivity and the like.

The amount of the polyfunctional monomer to be used is not particularly limited, and can be appropriately set so as to achieve the intended use of the polyfunctional monomer. From the viewpoint of achieving a good balance between the preferred storage elastic modulus disclosed herein and other adhesive properties or other properties, the amount of the polyfunctional monomer used can be about 3% by weight or less of the monomer component, About 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 when using a polyfunctional monomer is not particularly limited as long as it is greater than 0% by weight. By setting the amount of the polyfunctional monomer used to 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 properly exhibited.

The composition of the monomer components constituting the acrylic polymer is designed so that the glass transition temperature (Tg) of the acrylic polymer is approximately −15° C. or lower (for example, approximately −70° C. or higher and −15° C. or lower). is appropriate. Here, the Tg of the acrylic polymer refers to the Tg determined by the Fox formula based on the composition of the monomer components. The Fox equation is a relational expression between the Tg of a copolymer and the glass transition temperature Tgi of a homopolymer obtained by homopolymerizing each of the monomers constituting the copolymer, as shown below.
1/Tg=Σ(Wi/Tgi)
In the above Fox formula, Tg is the glass transition temperature of the copolymer (unit: K), Wi is the weight fraction of the monomer i in the copolymer (copolymerization ratio on a weight basis), and Tgi is the content of the monomer i. It represents the glass transition temperature (unit: K) of a homopolymer.

As the glass transition temperature of the homopolymer used for calculating the Tg, the value described in the known materials shall be used. For example, for the monomers listed below, the following values are used as the glass transition temperatures of the homopolymers of the monomers.
2-ethylhexyl acrylate -70°C
n-butyl acrylate -55°C
Ethyl acrylate -22°C
Methyl acrylate 8°C
Methyl methacrylate 105°C
2-hydroxyethyl acrylate -15°C
4-hydroxybutyl acrylate -40°C
Vinyl acetate 32°C
Styrene 100°C
Acrylic acid 106°C
Methacrylic acid 228°C

For the glass transition temperatures of homopolymers of monomers other than those exemplified above, the values described in "Polymer Handbook" (3rd edition, John Wiley & Sons, Inc., 1989) shall be used. For monomers for which multiple values are listed in this document, the highest value is adopted.

For monomers for which the glass transition temperatures of homopolymers are not described in the above literature, the values obtained by the following measurement methods are used.
Specifically, a reactor equipped with a thermometer, a stirrer, a nitrogen inlet tube and a reflux condenser was charged with 100 parts by weight of a monomer, 0.2 parts by weight of 2,2′-azobisisobutyronitrile and acetic acid as a polymerization solvent. 200 parts by weight of ethyl is added, and the mixture is stirred for 1 hour while circulating nitrogen gas. After oxygen is removed from the polymerization system in this manner, the temperature is raised to 63° C. and the reaction is allowed to proceed for 10 hours. Then, it is cooled to room temperature to obtain a homopolymer solution having a solid concentration of 33% by weight. Next, this homopolymer solution is cast-coated on a release liner and dried to prepare a test sample (sheet-like homopolymer) having a thickness of about 2 mm. This test sample was punched into a disk shape with a diameter of 7.9 mm, sandwiched between parallel plates, and shear strain at a frequency of 1 Hz using a viscoelasticity tester (manufactured by TA Instruments Japan, model name "ARES"). The viscoelasticity is measured in the shear mode at a temperature range of -70°C to 150°C at a heating rate of 5°C/min while giving , and the temperature corresponding to the peak top temperature of tan δ is taken as the homopolymer Tg.

Although not particularly limited, from the viewpoint of adhesiveness, the Tg of the acrylic polymer is advantageously about −25° C. or less, preferably about −35° C. or less, more preferably about −40° C. or less. , more preferably -45°C or lower, for example, it may be -50°C or lower, or -55°C or lower. From the viewpoint of the cohesive strength 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 technology disclosed herein can be preferably practiced in a mode in which the Tg of the acrylic polymer is approximately −65° C. or higher and approximately −40° C. or lower (for example, approximately −65° C. or higher and approximately −45° C. or lower). In some preferred embodiments, the Tg of the acrylic polymer can be about -55°C or higher and about -45°C or lower. In some other embodiments, the Tg of the acrylic polymer can be about -65°C or higher and about -55°C or lower. The Tg of the acrylic polymer can be adjusted by appropriately changing the monomer composition (that is, the types and usage ratio of the monomers used in synthesizing the polymer).

Mw of the acrylic polymer is not particularly limited, and may be, for example, about 10×10 ⁴ or more and 500×10 ⁴ or less. From the viewpoint of cohesiveness, the above Mw is, for example, about 30×10 ⁴ or more, and is suitably about 45×10 ⁴ or more (for example, about 65×10 ⁴ or more). In some preferred embodiments, the Mw of the acrylic polymer is 70×10 ⁴ or greater. It is suitable that the Mw of the acrylic polymer is greater than 70×10 ⁴ . By using an acrylic polymer with Mw greater than 70×10 ⁴ , due to its cohesiveness, excellent deformation resistance against sustained deformation loads can be obtained. 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, Mw is about 100×10 ⁴ or more (eg about 110×10 ⁴ or more), typically 120×10 ⁴ or more (eg 130×10 ⁴ or more). Also, the above Mw is suitably about 300×10 ⁴ or less (more preferably about 200×10 ⁴ or less, for example about 150×10 ⁴ or less). Mw of the acrylic polymer may be approximately 145×10 ⁴ or less. For example, acrylic polymers obtained by a solution polymerization method or an emulsion polymerization method preferably have Mw within the above range.

The degree of dispersion (Mw/Mn) of the acrylic polymer disclosed herein is not particularly limited. The dispersity (Mw/Mn) here means the dispersity (Mw/Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn). In some preferred embodiments, the polydispersity (Mw/Mn) of the acrylic polymer is less than 15. For example, in the case of a relatively high-molecular-weight acrylic polymer (typically having an Mw of more than 700,000) obtained by a solution polymerization method or an emulsion polymerization method, it is preferable to set Mw/Mn within the above range. The fact that the Mw/Mn of the acrylic polymer is less than 15 means that when the polymer has a relatively high molecular weight, it contains a considerable amount of a relatively uniform high molecular weight body. It expresses with high accuracy and exhibits excellent deformation resistance. The Mw/Mn is preferably less than 12, more preferably less than 10, still more preferably less than 8 (for example, 7.5 or less). The Mw/Mn is theoretically 1 or more, and may be, for example, 2 or more, 3 or more, or 4 or more (typically 5 or more).

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 the chain transfer constant, and the like. Moreover, Mw and Mn are obtained from values converted to standard polystyrene obtained by GPC (gel permeation chromatography). As the GPC apparatus, for example, model name "HLC-8320GPC" (column: TSKgelGMH-H(S), manufactured by Tosoh Corporation) can be used.

The polymerization method of the base polymer (typically an acrylic polymer) is not particularly limited, and conventionally known various polymerization methods can be appropriately adopted. For example, thermal polymerization such as solution polymerization, emulsion polymerization, bulk polymerization (typically performed in the presence of a thermal polymerization initiator); photopolymerization performed by irradiating light such as ultraviolet rays (typically, conducted in the presence of a photopolymerization initiator); radiation polymerization conducted by irradiating radiation such as β-rays and γ-rays; Among them, solution polymerization and photopolymerization are preferred. In these polymerization methods, the mode of polymerization is not particularly limited. , surfactants, etc.) can be selected as appropriate.

For example, in some preferred embodiments, solution polymerization techniques may be employed to synthesize acrylic polymers. According to the above solution polymerization, a polymerization reaction liquid in which the 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 an acrylic polymer solution obtained by subjecting the polymerization reaction solution or the reaction solution to appropriate post-treatment. As the above-mentioned acrylic polymer solution, the above-mentioned polymerization reaction solution may be prepared to have an appropriate viscosity (concentration) as necessary. Alternatively, an acrylic polymer solution prepared by synthesizing an acrylic polymer by a polymerization method other than solution polymerization (e.g., emulsion polymerization, photopolymerization, bulk polymerization, etc.) and dissolving the acrylic polymer in an organic solvent may be used. good.

As a method for supplying the monomers when carrying out solution polymerization, a batch charging method for supplying all monomer raw materials at once, a continuous supply (dropping) method, a divided supply (dropping) method, or the like can be appropriately adopted. The polymerization temperature can be appropriately selected depending on the type of monomer and solvent used, the type of polymerization initiator, etc., and can be, for example, about 20° C. to 170° C. (usually about 40° C. to 140° C.). . In some preferred embodiments, the polymerization temperature can be about 75° C. or lower (more preferably about 65° C. or lower, eg about 45° C. to 65° C.).

The solvent (polymerization solvent) used for solution polymerization can be appropriately selected from conventionally known organic solvents. For example, aromatic compounds (e.g., aromatic hydrocarbons) such as toluene and xylene; acetic esters such as ethyl acetate and butyl acetate; aliphatic or alicyclic hydrocarbons such as hexane, cyclohexane, and methylcyclohexane; Halogenated alkanes such as ,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 and the like, or a mixed solvent of two or more.

Although the polymerization initiator is not particularly limited, for example, an azo polymerization initiator, a peroxide initiator, a redox initiator obtained by combining a peroxide and a reducing agent, a substituted ethane initiator, etc. can be used. More specifically, for example, 2,2′-azobisisobutyronitrile (AIBN), 2,2′-azobis(2-methylpropionamidine) disulfate, 2,2′-azobis(2-amidinopropane ) dihydrochloride, 2,2′-azobis[2-(5-methyl-2-imidazolin-2-yl)propane]dihydrochloride, 2,2′-azobis(N,N′-dimethyleneisobutyramidine), 2 , 2′-azobis[N-(2-carboxyethyl)-2-methylpropionamidine] hydrate; persulfates such as potassium persulfate, ammonium persulfate; benzoyl peroxide (BPO), Peroxide initiators such as t-butyl hydroperoxide, hydrogen peroxide; substituted ethane initiators such as phenyl substituted ethane; combinations such as persulfate and sodium bisulfite, peroxide and sodium ascorbate. Redox initiators such as combinations with; and the like, but are not limited to these. A polymerization initiator can be used individually by 1 type or in combination of 2 or more types as appropriate. 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 such a polymerization initiator to be used is not particularly limited, and can be set appropriately according to the polymerization method, polymerization mode, and the like. For example, about 0.001 to 5 parts by weight (typically about 0.01 to 2 parts by weight, for example about 0.01 to 1 part by weight) of a polymerization initiator is used with respect to 100 parts by weight of the monomer to be polymerized. can be done.

(crosslinking agent)
The pressure-sensitive adhesive composition (preferably solvent-based pressure-sensitive adhesive composition) used for forming the pressure-sensitive adhesive layer preferably contains a cross-linking agent as an optional component. The inclusion of a cross-linking agent can advantageously achieve the viscoelastic properties disclosed herein. The pressure-sensitive adhesive layer in the technology disclosed herein contains the cross-linking agent in the form after the cross-linking reaction, the form before the cross-linking reaction, the form in which the cross-linking reaction is partially performed, the intermediate or composite form thereof, or the like. obtain. The cross-linking agent is contained in the pressure-sensitive adhesive layer exclusively in the form after the cross-linking reaction.

The type of cross-linking agent is not particularly limited, and can be appropriately selected from conventionally known cross-linking agents. Examples of such cross-linking agents include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, oxazoline-based cross-linking agents, aziridine-based cross-linking agents, melamine-based cross-linking agents, carbodiimide-based cross-linking agents, hydrazine-based cross-linking agents, amine-based cross-linking agents, Examples include peroxide-based cross-linking agents, metal chelate-based cross-linking agents, metal alkoxide-based cross-linking agents, metal salt-based cross-linking agents, and the like. A crosslinking agent can be used individually by 1 type or in combination of 2 or more types. Examples of cross-linking agents that can be preferably used in the technology disclosed herein include isocyanate-based cross-linking agents, epoxy-based cross-linking agents, and oxazoline-based cross-linking agents.

As the epoxy-based cross-linking agent, a compound having two or more epoxy groups in one molecule can be used without particular limitation. An epoxy-based cross-linking agent having 3 to 5 epoxy groups in one molecule is preferred. Epoxy-based cross-linking agents may be used singly or in combination of two or more.

Specific examples of epoxy-based cross-linking agents include, but are not limited to, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl ) cyclohexane, 1,6-hexanediol diglycidyl ether, polyethylene glycol diglycidyl ether, polyglycerol polyglycidyl ether and the like. Commercial products of epoxy-based cross-linking agents include Mitsubishi Gas Chemical Company's trade name "TETRAD-C" and trade name "TETRAD-X", DIC's trade name "Epiclon CR-5L", and Nagase ChemteX Corporation. and "TEPIC-G" manufactured by Nissan Chemical Industries, Ltd. under the trade name of "Denacol EX-512".

In embodiments using an epoxy-based cross-linking agent, the amount used is not particularly limited. The amount of the epoxy-based cross-linking agent used is, for example, more than 0 parts by weight and about 1 part by weight or less (preferably about 0.001 to 0.5 parts by weight) with respect to 100 parts by weight of the acrylic polymer. can. From the viewpoint of suitably exhibiting the effect of improving the cohesive strength, the amount of the epoxy-based cross-linking agent to be used is appropriately about 0.002 parts by weight or more, preferably about 0, per 100 parts by weight of the acrylic polymer. 005 parts by weight or more, for example, may be about 0.01 parts by weight or more, may be about 0.02 parts by weight or more, or may be about 0.03 parts by weight or more. From the viewpoint of avoiding insufficient adhesion due to excessive cross-linking, the amount of the epoxy-based cross-linking agent to be used is appropriately about 0.2 parts by weight or less per 100 parts by weight of the acrylic polymer, and about 0.2 part by weight. It is preferably 1 part by weight or less (for example, 0.05 part by weight or less).

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

Examples of preferred polyfunctional isocyanates include polyfunctional isocyanates having an average of 3 or more isocyanate groups per molecule. Such tri- or more functional isocyanates are polymers (e.g., dimers or trimers) of di- or tri- or more functional isocyanates, derivatives (e.g., addition reactions of polyhydric alcohols and two or more molecules of polyfunctional isocyanates products), polymers, and the like. For example, dimers and trimers of diphenylmethane diisocyanate, isocyanurate of hexamethylene diisocyanate (trimeric adduct of isocyanurate structure), reaction products of trimethylolpropane and tolylene diisocyanate, trimethylolpropane and hexa Polyfunctional isocyanates such as reaction products with methylene diisocyanate, polymethylene polyphenyl isocyanate, polyether polyisocyanate, and polyester polyisocyanate can be mentioned. Commercially available polyfunctional isocyanates include "Duranate TPA-100" (trade name) manufactured by Asahi Kasei Chemicals, "Coronate L" (trade name), "Coronate HL", "Coronate HK" (trade name) and "Coronate HK" (trade names) manufactured by Tosoh Corporation. HX", "Coronate 2096", and the like.

In embodiments using an isocyanate-based cross-linking agent, the amount used is not particularly limited. The amount of the isocyanate-based cross-linking agent used can be, for example, about 0.5 parts by weight or more and about 10 parts by weight or less with respect to 100 parts by weight of the acrylic polymer. From the viewpoint of cohesiveness, the amount of the isocyanate cross-linking agent to be used with respect to 100 parts by weight of the acrylic polymer is suitably about 0.1 parts by weight or more, and about 0.3 parts by weight or more (for example, 0.5 parts by weight part or more). In a more preferred embodiment, the amount of the isocyanate-based cross-linking agent to be used is about 1 part by weight or more, and may be about 1.5 parts by weight or more with respect to 100 parts by weight of the acrylic polymer. The amount of the isocyanate cross-linking agent to be used for 100 parts by weight of the acrylic polymer is suitably about 8 parts by weight or less, preferably about 5 parts by weight or less (for example, less than about 4 parts by weight). In a more preferred embodiment, the amount of the isocyanate-based cross-linking agent used is about 3 parts by weight or less, for example, 2 parts by weight or less, relative to 100 parts by weight of the acrylic polymer.

The technology disclosed herein can be preferably implemented in a mode using at least an epoxy-based cross-linking agent as the cross-linking agent. The epoxy group of the epoxy-based cross-linking agent can react with an acidic group that can be introduced into the acrylic polymer to build a cross-linked structure. This cross-linking reaction increases the cohesiveness of the pressure-sensitive adhesive, and exhibits more favorable resistance to deformation under constant load. Examples of such aspects include an aspect in which an epoxy-based cross-linking agent is used alone and an aspect in which an epoxy-based cross-linking agent and another cross-linking agent are used in combination. In some aspects, the pressure-sensitive adhesive composition contains an epoxy-based cross-linking agent as a cross-linking agent, but does not substantially include an isocyanate-based cross-linking agent.

In some other aspects, the pressure-sensitive adhesive composition contains an isocyanate-based cross-linking agent as a cross-linking agent. The isocyanate group of the isocyanate-based cross-linking agent reacts with an acidic group that can be introduced into the acrylic polymer in a reaction mode different from that of the epoxy-based cross-linking agent, and can construct a cross-linked structure. From the viewpoint of improving the anchoring property to the base film, it is significant to use an isocyanate-based cross-linking agent.

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

The content of the cross-linking agent (total amount of cross-linking agent) in the adhesive composition disclosed herein is not particularly limited. From the viewpoint of cohesiveness, the content of the cross-linking agent can be about 0.001 parts by weight or more, and about 0.002 parts by weight or more with respect to 100 parts by weight of the base polymer (preferably acrylic polymer). Preferably about 0.005 parts by weight or more, more preferably about 0.01 parts by weight or more, more preferably about 0.02 parts by weight or more, particularly preferably about 0.03 parts by weight or more is. In addition, from the viewpoint of avoiding insufficient initial adhesiveness, the content of the cross-linking agent in the pressure-sensitive adhesive composition can be about 20 parts by weight or less with respect to 100 parts by weight of the base polymer, and should be about 15 parts by weight or less. is suitable, and it is preferably about 10 parts by weight or less (for example, about 5 parts by weight or less).

(tackifying resin)
In some preferred embodiments, the adhesive layer comprises a tackifying resin. Examples of the tackifying resin include phenol-based tackifying resins, terpene-based tackifying resins, modified terpene-based tackifying resins, rosin-based tackifying resins, hydrocarbon-based tackifying resins, epoxy-based tackifying resins, and polyamide-based tackifying resins. , elastomer-based tackifying resins, ketone-based tackifying resins, and other known tackifying resins. The use of tackifying resins improves adhesion.

Examples of phenolic tackifying resins include terpene phenolic resins, hydrogenated terpene phenolic resins, alkylphenolic resins and rosin phenolic resins.
Terpene phenol resin refers to a polymer containing a terpene residue and a phenol residue, a copolymer of terpenes and a phenol compound (terpene-phenol copolymer resin), terpenes or homopolymers or copolymers thereof. It is a concept that includes both phenol-modified coalescence (phenol-modified terpene resin). Preferred examples of terpenes constituting such a terpene phenol resin include monoterpenes such as α-pinene, β-pinene, and limonene (including d-, l- and d/l-forms (dipentene)). is mentioned. A hydrogenated terpene phenol resin refers to a hydrogenated terpene phenol resin having a structure obtained by hydrogenating such a terpene phenol resin. It is sometimes called a hydrogenated terpene phenolic resin.
Alkylphenol resins are resins obtained from alkylphenols and formaldehyde (oily phenolic resins). Examples of alkylphenol resins include novolac and resole types.
Rosin phenolic resins are typically rosins or phenol-modified products of the various rosin derivatives described above (including rosin esters, unsaturated fatty acid-modified rosins, and unsaturated fatty acid-modified rosin esters). Examples of rosin phenol resins include rosin phenol resins obtained by a method of adding phenol to rosins or various rosin derivatives described above with an acid catalyst and thermally polymerizing the mixture.
Among these phenolic tackifying resins, terpene phenol resins, hydrogenated terpene phenol resins and alkylphenol resins are preferred, terpene phenol resins and hydrogenated terpene phenol resins are more preferred, and terpene phenol resins are particularly preferred.

Examples of terpene-based tackifying resins 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 kind of terpenes, or a copolymer of two or more kinds of terpenes. One type of terpene homopolymer includes α-pinene polymer, β-pinene polymer, dipentene polymer and the like.
Examples of modified terpene resins include those obtained by modifying the above terpene resins. Specific examples include styrene-modified terpene resins and hydrogenated terpene resins.

The concept of rosin-based tackifying resins as used herein includes both rosins and rosin derivative resins. Examples of rosins include unmodified rosins (fresh rosins) such as gum rosin, wood rosin and tall oil rosin; homogenized rosin, polymerized rosin, other chemically modified rosins, etc.);

Rosin derivative resins are typically derivatives of rosins as described above. The concept of rosin-based resin as used 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 undenatured rosin esters, which are esters of undenatured rosin and alcohols, and denatured rosin esters, which are esters of denatured rosin and alcohols; Saturated fatty acid-modified rosins; for example, unsaturated fatty acid-modified rosin esters obtained by modifying rosin esters with unsaturated fatty acids; rosin alcohols obtained by reducing the carboxy group of rosin esters modified with fatty acids; for example, rosins or metal salts of the various rosin derivatives described above; Specific examples of rosin esters include methyl esters, triethylene glycol esters, glycerin esters and pentaerythritol esters of unmodified rosins or modified rosins (hydrogenated rosins, disproportionated rosins, polymerized rosins, etc.).

Examples of hydrocarbon-based tackifying resins include aliphatic hydrocarbon resins, aromatic hydrocarbon resins, aliphatic cyclic hydrocarbon resins, aliphatic/aromatic petroleum resins (styrene-olefin copolymers, etc. ), aliphatic/alicyclic petroleum resins, hydrogenated hydrocarbon resins, coumarone-based resins, and coumarone-indene-based resins.

The softening point of the tackifying resin is not particularly limited. From the viewpoint of improving cohesive strength, a tackifier resin having a softening point (softening temperature) of about 80° C. or higher (preferably about 100° C. or higher) can be preferably used. For example, a phenol-based tackifying resin (terpene phenol resin, etc.) having such a softening point can be preferably used. In some preferred embodiments, terpene phenolic resins with softening points of approximately 135° C. or higher (and even approximately 140° C. or higher) can be used. There is no particular upper limit for the softening point of the tackifying resin. A tackifying resin having a softening point of about 200° C. or lower (more preferably about 180° C. or lower) can be preferably used from the viewpoint of adhesion to an adherend or base film. The softening point of the tackifying resin can be measured based on the softening point test method (ring and ball method) defined in JIS K2207.

In some preferred embodiments, the tackifying resin comprises one or more phenolic tackifying resins (eg, terpene phenolic resins). The technology disclosed herein can be preferably practiced, 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 tackifying resin is a terpene phenolic resin. Approximately 50% by weight or more of the total amount of tackifying resin may be the terpene phenolic resin, and approximately 80% by weight or more (eg, approximately 90% by weight or more) may be the terpene phenolic resin. Substantially all of the tackifying resin (eg, approximately 95% to 100% by weight, or even approximately 99% to 100% by weight) may be a terpene phenolic resin.

The content of the phenol-based tackifier resin (eg, terpene phenol resin) is not particularly limited. The content of the phenolic tackifying resin (for example, terpene phenolic resin) can be about 1 part by weight or more with respect to 100 parts by weight of the acrylic polymer, from the viewpoint of adhesive strength (for example, initial adhesiveness for light pressure bonding). About 5 parts by weight or more is suitable, 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). From the viewpoint of resistance to deformation, the content of the phenol-based tackifying resin is preferably about 45 parts by weight or less, preferably about 35 parts by weight, with respect to 100 parts by weight of the acrylic polymer. Below, more preferably about 30 parts by weight or less, still more preferably less than 30 parts by weight (for example, 25 parts by weight or less, typically 20 parts by weight or less).

Although not particularly limited, in some embodiments of the technology disclosed herein, the tackifying resin may comprise 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 may be referred to as a "high hydroxyl value resin". A tackifying resin containing such a high hydroxyl value resin can realize a pressure-sensitive adhesive layer with high cohesive strength by interacting with a cross-linking agent such as an isocyanate-based cross-linking agent in addition to the pressure-sensitive adhesive strength. 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-mentioned high hydroxyl value resin (for example, terpene phenol resin) is preferably used in combination with, for example, an acrylic polymer containing C _1-6 alkyl (meth)acrylate as a main monomer, good adhesive strength.

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, suitably about 200 mgKOH/g or less, preferably about 180 mgKOH/g or less, more preferably about 180 mgKOH/g or less. is about 160 mg KOH/g or less, more preferably about 140 mg KOH/g or less. The technology disclosed herein can be preferably practiced in a mode in which the tackifying resin comprises a high hydroxyl value resin (eg, a phenolic tackifying resin, preferably a terpene phenolic resin) having a hydroxyl value of 30-160 mgKOH/g. In some embodiments, a high hydroxyl value resin with a hydroxyl value of 30-80 mgKOH/g (eg, 30-65 mgKOH/g) can be preferably employed. In some other embodiments, a high hydroxyl value resin with a hydroxyl value of 70-140 mgKOH/g can be preferably employed.

Here, as the value of the hydroxyl value, a value measured by a potentiometric titration method specified in JIS K0070:1992 can be adopted. A specific measuring method is as follows.
[Method for measuring hydroxyl value]
1. Reagent (1) As the acetylation reagent, approximately 12.5 g (approximately 11.8 mL) of acetic anhydride is taken, pyridine is added to bring the total amount to 50 mL, and the mixture is thoroughly stirred and used. Alternatively, take about 25 g (about 23.5 mL) of acetic anhydride, add pyridine to bring the total amount to 100 mL, and use the mixture after thorough stirring.
(2) A 0.5 mol/L potassium hydroxide ethanol solution is used as a measurement reagent.
(3) In addition, prepare toluene, pyridine, ethanol and distilled water.
2. Operation (1) About 2 g of a sample is accurately weighed and collected in a flat-bottomed 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 bath at 100°C for 70 minutes, allowing it to cool, adding 35 mL of toluene as a solvent from the top of the cooling tube and stirring, then adding 1 mL of distilled water and stirring to obtain acetic anhydride. decompose. Heat again in the bath for 10 minutes for complete decomposition and allow to cool.
(3) Wash the cooling tube with 5 mL of ethanol and remove. 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 whole pipette.
(5) Perform potentiometric titration 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) are performed without any sample.
3. Calculation Calculate the hydroxyl value by the following formula.
Hydroxyl value (mgKOH/g) = [(BC) x f x 28.05]/S + D
here,
B: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used in the blank test,
C: Amount (mL) of 0.5 mol/L potassium hydroxide ethanol solution used for the sample,
f: factor of 0.5 mol/L potassium hydroxide ethanol solution,
S: weight of sample (g),
D: acid value,
28.05: ½ of the molecular weight of potassium hydroxide, 56.11;
is.

As the high hydroxyl value resin, among the various tackifying resins described above, those having a hydroxyl value equal to or higher than a predetermined value 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 the high hydroxyl value resin, a phenolic tackifying resin having a hydroxyl value of 30 mgKOH/g or more can be preferably employed. The terpene phenol resin is convenient because the hydroxyl value can be arbitrarily controlled by the copolymerization ratio of phenol.

Although not particularly limited, when using a high hydroxyl value resin, the ratio of the high hydroxyl value resin (for example, terpene phenol resin) to the total tackifying resin contained in the adhesive layer is, for example, about 25% by weight or more. about 30% by weight or more is preferable, and about 50% by weight or more (eg, about 80% by weight or more, typically about 90% by weight or more) is more preferable. Substantially all of the tackifying resin (eg, about 95-100 weight percent, or even about 99-100 weight percent) may be a high hydroxyl value resin.

In embodiments using a tackifying resin, the content of the tackifying resin is not particularly limited. The content of the tackifying resin can be about 1 part by weight or more, can be about 5 parts by weight or more, and can be about 8 parts by weight or more with respect to 100 parts by weight of the base polymer (for example, an acrylic polymer). (for example, approximately 10 parts by weight or more). The technology disclosed herein can be preferably carried out in a mode in which the content of the tackifying resin is about 12 parts by weight or more (for example, about 15 parts by weight or more) relative to 100 parts by weight of the base polymer. The upper limit of the content of the tackifying resin is not particularly limited. From the viewpoint of compatibility with the base polymer and deformation resistance, the content of the tackifying resin with respect to 100 parts by weight of the base polymer is suitably about 70 parts by weight or less, preferably about 55 parts by weight or less, and more. Preferably, it is 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 tackifying resin is less than 30 parts by weight per 100 parts by weight of base polymer, more preferably no more than about 25 parts by weight, and even more preferably no more than about 20 parts by weight.

((meth)acrylic oligomer)
The pressure-sensitive adhesive composition (and thus the pressure-sensitive adhesive layer) disclosed herein can contain a (meth)acrylic oligomer from the viewpoint of improving adhesive strength and the like. As the (meth)acrylic oligomer, the Tg of the copolymer corresponding to the composition of the monomer component (typically, the Tg of the (meth)acrylic polymer contained in the adhesive formed from the adhesive composition It is preferable to use a polymer having a Tg higher than the Tg. 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 to about 300°C, preferably about 20°C to about 300°C, more preferably about 40°C to about 300°C. When Tg is within the above range, the adhesive strength can be favorably improved. In some preferred embodiments, the (meth)acrylic oligomer has a Tg of about 30° C. or higher, more preferably about 50° C. or higher (e.g., about 60° C. or higher), and From the viewpoint of initial adhesiveness, the temperature is preferably about 200° C. or less, more preferably about 150° C. or less, even more preferably about 100° C. or less (for example, about 80° C. or less). The Tg of the (meth)acrylic oligomer is a value calculated based on the Fox formula, like the Tg of the copolymer corresponding to the composition of the monomer components.

The weight average molecular weight (Mw) of the (meth)acrylic oligomer can typically be about 1,000 or more and less than about 30,000, preferably about 1,500 or more and about 20,000 or less, more preferably about 2,000 or more and about 10,000 or less. It is preferable that Mw is within the above range because good adhesive strength and retention properties can be obtained. In some preferred embodiments, the Mw of the (meth)acrylic oligomer is about 2500 or more (for example, about 3000 or more) from the viewpoint of deformation resistance, and preferably about 7000 or less from the viewpoint of initial adhesion. It is more preferably about 5000 or less (eg about 4500 or less, typically about 4000 or less). The Mw of the (meth)acrylic oligomer can be measured by GPC and calculated as a value in terms of standard polystyrene. Specifically, measurement is performed using HPLC8020 manufactured by Tosoh Corporation, using TSKgelGMH-H(20)×2 columns, and using tetrahydrofuran as a solvent at a flow rate of about 0.5 mL/min.

Monomers constituting the (meth)acrylic oligomer include, 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 ( Alkyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate meth)acrylates; esters of (meth)acrylic acid and alicyclic alcohols (alicyclic hydrocarbon group-containing (meth)acrylates such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate) ) acrylate); aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; (meth)acrylates obtained from terpene compound derivative alcohols; Such (meth)acrylates can be used singly or in combination of two or more.

(Meth)acrylic oligomers include alkyl (meth)acrylates having branched alkyl groups such as isobutyl (meth)acrylate and t-butyl (meth)acrylate; cyclohexyl (meth)acrylate and isobornyl (meth)acrylate; Esters of (meth) acrylic acid and alicyclic alcohol such as dicyclopentanyl (meth) acrylate (alicyclic hydrocarbon group-containing (meth) acrylate); Phenyl (meth) acrylate and benzyl (meth) acrylate From the viewpoint of improving adhesive strength, it is preferable to contain, as a monomer unit, an acrylic monomer having a relatively bulky structure, typified by (meth)acrylate having a cyclic structure such as aryl (meth)acrylate. In addition, when ultraviolet rays are used when synthesizing a (meth)acrylic oligomer or when producing a pressure-sensitive adhesive layer, those having saturated bonds are preferable because they are less likely to cause polymerization inhibition, and alkyl groups are branched. An alkyl (meth)acrylate having a structure or an ester with an alicyclic alcohol (alicyclic hydrocarbon group-containing (meth)acrylate) can be suitably used as a monomer constituting the (meth)acrylic oligomer. All of the above branched-chain alkyl (meth)acrylates, alicyclic hydrocarbon group (meth)acrylates, and aryl (meth)acrylates correspond to (meth)acrylate monomers in the technology disclosed herein. Alicyclic hydrocarbon groups can be saturated or unsaturated alicyclic hydrocarbon groups.

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

As the constituent monomer component of the (meth)acrylic oligomer, functional group-containing monomers can be used in addition to the above (meth)acrylate monomers. Preferable examples of the functional group-containing monomer include monomers having a nitrogen atom-containing ring (typically a nitrogen atom-containing heterocyclic ring) such as N-vinyl-2-pyrrolidone and N-acryloylmorpholine; N,N-dimethylamino Amino group-containing monomers such as ethyl (meth)acrylate; amide group-containing monomers such as N,N-diethyl (meth)acrylamide; carboxyl group-containing monomers such as AA and MAA; hydroxyl group-containing monomers such as 2-hydroxyethyl (meth)acrylate monomer; These functional group-containing monomers can be used singly or in combination of two or more. Among them, carboxyl group-containing monomers are preferred, and AA is particularly preferred.

When all monomer components constituting the (meth)acrylic oligomer contain functional group-containing monomers, the ratio of functional group-containing monomers (for example, carboxyl group-containing monomers such as AA) to all the monomer components is about 1% by weight. or more, preferably 2% by weight or more, more preferably 3% by weight or more, and about 15% by weight or less, preferably 10% by weight or less, more preferably 10% by weight or less, more preferably 7% by weight or less.

A (meth)acrylic oligomer can be formed by polymerizing its constituent monomer components. The polymerization method and polymerization mode are not particularly limited, and conventionally known various polymerization methods (for example, solution polymerization, emulsion polymerization, bulk polymerization, photopolymerization, radiation polymerization, etc.) can be employed in an appropriate mode. The type of polymerization initiator that can be used as necessary (e.g., an azo polymerization initiator such as AIBN) is generally as exemplified in the synthesis of the acrylic polymer, and the amount of the polymerization initiator and the arbitrarily used The amount of the chain transfer agent such as n-dodecyl mercaptan, etc., is appropriately set based on common general technical knowledge so as to obtain the desired molecular weight, and therefore detailed description is omitted here.

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

When the pressure-sensitive adhesive composition disclosed herein contains a (meth)acrylic oligomer, the content thereof is, for example, 0.1 parts by weight or more (preferably an acrylic polymer) with respect to 100 parts by weight of the base polymer ( for example, 1 part by weight or more). From the viewpoint of better exhibiting 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, relative to 100 parts by weight of the base polymer. Part by weight or more, more preferably about 10 parts by weight or more, particularly preferably about 12 parts by weight or more. From the viewpoint of compatibility with the base polymer, the content of the (meth)acrylic oligomer is preferably less than 50 parts by weight (for example, less than 40 parts by weight) with respect to 100 parts by weight of the base polymer. Yes, preferably less than 30 parts by weight, more preferably about 25 parts by weight or less, and even more preferably about 20 parts by weight or less.

In some preferred embodiments, the pressure-sensitive adhesive layer contains one or more of the tackifying resins described above and one or more of (meth)acrylic oligomers. In a composition containing a high-molecular-weight acrylic polymer, by using a tackifying resin and a (meth)acrylic oligomer in combination, it is possible to obtain excellent initial adhesiveness while being exposed to harsher conditions such as strong repulsion. Also in this aspect, highly excellent deformation resistance can be exhibited. The ratio of the content C _T of _the tackifier resin and the content C _O of the (meth)acrylic oligomer _is not particularly limited. , 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 (meth)acrylic oligomer contained in the pressure-sensitive adhesive layer is the base polymer (preferably (acrylic polymer) is about 1 part by weight or more, preferably about 10 parts by weight or more, more preferably about 16 parts by weight or more, and still more preferably 20 parts by weight or more; Particularly preferably, it is 25 parts by weight or more. Also, the total amount of the tackifier resin and (meth)acrylic oligomer is preferably less than 120 parts by weight (for example, about 80 parts by weight or less) with respect to 100 parts by weight of the base polymer (preferably acrylic polymer). Yes, preferably less than 60 parts by weight, more preferably about 50 parts by weight or less, and even more preferably about 40 parts by weight or less.

(coloring agent)
The pressure-sensitive adhesive layer disclosed herein may contain a colorant within a range that does not impair the light transmittance. By including a coloring agent in the adhesive, it is possible to adjust the light transmittance of the adhesive sheet including the adhesive layer. As the coloring agent, various materials that can attenuate light traveling through the pressure-sensitive adhesive layer by reflecting and/or absorbing it can be used. The color of the coloring agent is not particularly limited, and may be colored or colorless. The color of the coloring agent can be, for example, black, gray, white, red, blue, yellow, green, yellow-green, orange, purple, gold, silver, pearlescent, and the like. The above colorant can typically be contained in the pressure-sensitive adhesive layer in a state of being dispersed (or in a dissolved state) in the constituent materials of the pressure-sensitive adhesive layer.

Various pigments and dyes can be used as the colorant. Examples of pigments include zinc carbonate, zinc oxide, zinc sulfide, talc, kaolin, calcium carbonate, titanium oxide, silica, lithium fluoride, calcium fluoride, barium sulfate, alumina, zirconia, iron oxide, and iron hydroxide. , Chromium oxide type, Spinel type firing type, Chromic acid type, Chromium vermillion type, Prussian blue type, Aluminum powder type, Bronze powder type, Silver powder type, Inorganic pigment such as calcium phosphate, Phthalocyanine type, Azo type, Condensed azo type , azo lake-based, anthraquinone-based, perylene/perinone-based, indigo-based, thioindigo-based, isoindolinone-based, azomethine-based, dioxazine-based, quinacridone-based, aniline black-based, triphenylmethane-based, carbon black-based organic pigments. be done. Examples of dyes include azo dyes, anthraquinone, quinophthalone, styryl, diphenylmethane, triphenylmethane, oxazine, triazine, xanthan, methane, azomethine, acridine, and diazine. Colorants may be used singly or in appropriate combination of two or more.

In the embodiment in which the pressure-sensitive adhesive layer contains a coloring agent, a black coloring agent can be preferably used because the light-shielding property can be efficiently adjusted with a small amount of the coloring agent. Specific examples of black colorants include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine smoke, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, and cyanine. Black, activated carbon, ferrite (nonmagnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone colorants, and the like. These can be used individually by 1 type or in combination of 2 or more types as appropriate. Among them, carbon black is preferred.

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

In the embodiment in which the pressure-sensitive adhesive layer contains a colorant, the content of the colorant can be appropriately set so as to form a pressure-sensitive adhesive sheet that satisfies the desired thickness direction light transmittance, and is limited to a specific range. not. The content of the colorant in the pressure-sensitive adhesive layer can be approximately 0.1% by weight or more, and is suitably approximately 0.5% by weight or more. % by weight or more, more preferably about 2% by weight or more, and even more preferably about 3% by weight or more (for example, about 4% by weight or more). Moreover, the upper limit of the content of the colorant in the pressure-sensitive adhesive layer can be, for example, less than 15% by weight. From the viewpoint of preventing or suppressing contamination due to adhesion of the coloring agent to the processing blade, the content of the coloring agent in the pressure-sensitive adhesive layer is suitably less than 10% by weight, preferably less than 8% by weight. Preferably, it is less than 7% by weight. Limiting the amount of the colorant used in the pressure-sensitive adhesive layer is also preferable from the viewpoint of suppressing deterioration in pressure-sensitive adhesive properties and maintaining the intended performance. In some preferred embodiments, the colorant content in the adhesive layer is less than 3 wt%, more preferably less than 1 wt% (eg, less than 0.1 wt%). The technology disclosed herein can be preferably implemented in a mode in which the pressure-sensitive adhesive layer does not substantially contain a colorant.

In the embodiment in which the pressure-sensitive adhesive layer contains a colorant, the pressure-sensitive adhesive layer may contain a component that contributes to improving the dispersibility of the colorant. Such dispersibility-enhancing ingredients can be, for example, polymers, oligomers, liquid resins, surfactants, and the like. The dispersibility-improving component is preferably dissolved in the pressure-sensitive adhesive layer. The oligomer is, for example, a low-molecular weight polymer of a monomer component containing one or more acrylic monomers as exemplified above (for example, Mw is less than about 10×10 ⁴ , preferably less than 5×10 ⁴ acrylic 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 a rosin-based, terpene-based, or hydrocarbon-based tackifying resin, such as a hydrogenated rosin methyl ester, etc.). Such a dispersibility-improving component can suppress dispersion unevenness of a coloring agent (for example, a particulate black coloring agent such as carbon black), and thus suppress color unevenness of the pressure-sensitive adhesive layer. Therefore, it is possible to form a pressure-sensitive adhesive sheet with 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, a decrease in cohesion), the total amount of the adhesive layer is about 20% by weight or less (preferably about 10% by weight or less, more (preferably 7% by weight or less, for example approximately 5% by weight or less). In some embodiments, the content of the dispersibility-enhancing component can be about 10 times or less (preferably about 5 times or less, such as about 3 times or less) by weight of the colorant. On the other hand, from the viewpoint of suitably exhibiting the effect of the dispersibility improving component, the content thereof is about 0.2% by weight or more (typically about 0.5% by weight or more, preferably about 1% by weight) of the entire pressure-sensitive adhesive layer. % or more). In some embodiments, the content of the dispersibility-enhancing component can be about 0.2 times or more (preferably about 0.5 times or more, such as 1 time or more) of the weight of the colorant.

(Other additives)
In addition to the components described above, the pressure-sensitive adhesive composition may optionally contain a leveling agent, a cross-linking aid, a plasticizer, a softening agent, an antistatic agent, an anti-aging agent, an ultraviolet absorber, an antioxidant, and a light stabilizer. , various additives commonly used in the field of pressure sensitive adhesives such as rust inhibitors (for example, azole rust inhibitors, specifically benzotriazole rust inhibitors). As for such various additives, conventionally known ones can be used in a conventional manner, and since they do not particularly characterize the present invention, detailed description thereof will be omitted.

(Formation of adhesive layer)
The pressure-sensitive adhesive layer disclosed herein can be a pressure-sensitive adhesive layer formed from a water-based pressure-sensitive adhesive composition, a solvent-based pressure-sensitive adhesive composition, a hot-melt pressure-sensitive adhesive composition, or an active energy ray-curable pressure-sensitive adhesive composition. . The water-based pressure-sensitive adhesive composition refers to a pressure-sensitive adhesive composition in the form of containing a pressure-sensitive adhesive (adhesive layer-forming component) in a water-based solvent (aqueous solvent), typically water-dispersed. Also included are so-called type adhesive compositions (compositions in which at least part of the adhesive is dispersed in water) and the like. Moreover, the solvent-type adhesive composition refers to an adhesive composition in the form of containing an adhesive in an organic solvent. The technology disclosed herein can be preferably implemented in a mode comprising a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition, from the viewpoint of adhesive properties and the like.

The adhesive layer disclosed here can be formed by a conventionally known method. For example, a method (direct method) of forming an adhesive layer by directly applying (typically applying) an adhesive composition to a substrate film as described above and drying it can be employed. In addition, a method of applying an adhesive composition to a surface having releasability (release surface) and drying it to form an adhesive layer on the surface and transferring the adhesive layer to a base film (transfer method ) may be adopted. From the viewpoint of productivity, the transfer method is preferred. As the release surface, the surface of a release liner, the back surface of a base film subjected to a release treatment, or the like can be used. The pressure-sensitive adhesive layer disclosed herein is typically formed continuously, but is not limited to such a form. It may be a formed pressure-sensitive adhesive layer.

Application of the pressure-sensitive adhesive composition can be performed using a conventionally known coater such as a gravure roll coater, die coater, bar coater, and the like. Alternatively, the adhesive composition may be applied by impregnation, curtain coating, or the like.
From the viewpoint of promoting the cross-linking reaction, improving production efficiency, etc., it is preferable to dry the pressure-sensitive adhesive composition under heating. The drying temperature can be, for example, about 40 to 150.degree. C., preferably about 60 to 130.degree. After drying the pressure-sensitive adhesive composition, it is further aged for the purpose of adjusting the migration of components in the pressure-sensitive adhesive layer, progressing the cross-linking reaction, relaxing distortion that may exist in the base film and the pressure-sensitive adhesive layer, and the like. good too.

(Light transmittance of adhesive layer)
Since the pressure-sensitive adhesive layer disclosed herein has light transmittance, it exhibits a predetermined or more light transmittance in the thickness direction. The light transmittance in the thickness direction of the pressure-sensitive adhesive layer is 0.1% or more (for example, about 1% or more, or even more than 3.1%), can be about 5% or more, and can be about 30% or more. It is appropriate to The pressure-sensitive adhesive layer disclosed herein can be, for example, a clean one that does not use a coloring agent. From the viewpoint of such cleanness, in some embodiments, the light transmittance in the thickness direction of the pressure-sensitive adhesive layer preferably exceeds 50%, and is about 70% or more (for example, about 80% or more). more preferred. A pressure-sensitive adhesive layer that exhibits a light transmittance of a predetermined value or more is advantageous from an industrial point of view, including easy maintenance of pressure-sensitive adhesive properties and productivity and efficiency. The upper limit of the light transmittance in the thickness direction of the pressure-sensitive adhesive layer is theoretically 100%, and practically it can be about 95% or less (for example, 90% or less). The light transmittance in the thickness direction of the pressure-sensitive adhesive layer is measured by the method described in Examples below.

(Viscoelastic properties)
The storage elastic 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 application, required performance, and the like. For example, the storage modulus G' (25°C) of the pressure-sensitive adhesive layer at 25°C may be about 0.15 MPa or more. A pressure-sensitive adhesive having the above G' (25°C) can preferably exhibit good resistance to deformation from an early stage after being attached to an adherend. In addition, since it tends to exhibit good workability in punching and the like, contamination is less likely to occur during processing, and cleanness can be excellent. The G′ (25° C.) is preferably 0.17 MPa or higher, more preferably 0.2 MPa or higher, and still more preferably 0.23 MPa or higher. The G′ (25° C.) is particularly preferably 0.25 MPa or more, and may be 0.3 MPa or more, for example. In addition, the above G' (25°C) is suitably about 1.0 MPa or less, preferably 0.6 MPa or less, more preferably 0.6 MPa or less, more preferably 0.6 MPa or less from the viewpoint of achieving both initial adhesiveness and deformation resistance. It is 4 MPa or less, more preferably 0.35 MPa or less. A pressure-sensitive adhesive layer having a storage elastic modulus limited to a predetermined value or less tends to have excellent impact resistance, and is suitable, for example, as a pressure-sensitive adhesive for portable electronic devices that require a predetermined drop impact resistance.

Also, the loss elastic 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 application, required performance, and the like. For example, the pressure-sensitive adhesive layer suitably has a loss elastic 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, and even more preferably 0.5 MPa or less. In addition, the above G″ (25° C.) is suitably 0.01 MPa or more, and from the viewpoint of wettability to the adherend surface and initial adhesiveness, etc., is preferably 0.05 MPa or more, and more It is preferably 0.1 MPa or more, more preferably 0.2 MPa or more, and may be, for example, 0.25 MPa or more.

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, the 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, for example, about 0.3 or more, preferably about 0.5 or more, more preferably about 0.7 or more, and still more preferably about 0 from the viewpoint of deformation resistance. 0.8 or more, particularly preferably about 0.9 or more (eg about 1 or more). When tan δ (25° C.) is at least a predetermined value, the pressure-sensitive adhesive layer tends to have excellent impact resistance, and is suitable, for example, as a pressure-sensitive adhesive for portable electronic devices that require predetermined drop impact resistance. . In addition, tan δ (25° C.) is, for example, about 3 or less, preferably about 2 or less, more preferably about 1.5 or less, still more preferably about 1.2 or less from the viewpoint of initial adhesiveness. . Since the tan δ (25° C.) is limited to a predetermined value or less, it tends to exhibit good workability in punching and the like, is less likely to be contaminated during processing, and can be excellent in cleanness.

The storage elastic modulus G′ (25° C.), loss elastic modulus G″ (25° C.) and tan δ (25° C.) of the pressure-sensitive adhesive layer described above are determined by the base polymer species of the pressure-sensitive adhesive layer, its molecular structure and molecular weight, tackifying It can be adjusted by selecting an additive component such as a resin and its usage amount, a cross-linking agent type and its usage amount, and the like.

In the technology disclosed herein, the storage elastic modulus G′ (25° C.), loss elastic modulus G″ (25° C.) and tan δ (25° C.) of the pressure-sensitive adhesive layer can be determined by dynamic viscoelasticity measurement. . Specifically, a pressure-sensitive adhesive layer having a thickness of about 2 mm is produced by stacking a plurality of pressure-sensitive adhesive layers to be measured. A sample obtained by punching this adhesive layer into a disk shape with a diameter of 7.9 mm is sandwiched between parallel plates and fixed, and a viscoelasticity tester (for example, manufactured by TA Instruments, ARES or its equivalent) is used as follows. A dynamic viscoelasticity measurement is performed under the conditions of , and a storage modulus G' (25°C), a loss modulus G'' (25°C) and tan δ (25°C) are determined.
・Measurement mode: Shear mode ・Temperature range: -70°C to 150°C
・Temperature increase rate: 5°C/min
・Measurement frequency: 1Hz
It is also measured by the above method in the examples described later. The pressure-sensitive adhesive layer to be measured can be formed by applying the corresponding pressure-sensitive adhesive composition in layers and drying or curing.

(Gel fraction)
Although not particularly limited, the gel fraction of the pressure-sensitive adhesive layer disclosed herein can be, for example, 20% or more, suitably 30% or more, and 35% or more on a weight basis. is preferred. By increasing the gel fraction of the pressure-sensitive adhesive layer within an appropriate range, deformation resistance tends to be easily obtained. In the technology 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 higher, particularly preferably 50% or higher. The gel fraction may be, for example, 55% or more. On the other hand, if the gel fraction is too high, the initial adhesiveness may deteriorate. From such a viewpoint, the gel fraction of the 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 species, its molecular structure, molecular weight, additive components such as tackifier resins and their usage amounts, cross-linking agent species and its usage amounts, and the like. .

Here, the "gel fraction of the pressure-sensitive adhesive layer" refers to a value measured by the following method. The gel fraction can be grasped as the weight ratio of ethyl acetate-insoluble matter in the pressure-sensitive adhesive layer.
[Gel fraction measurement method]
An adhesive sample of about 0.1 g (weight Wg ₁ ) is wrapped in a porous polytetrafluoroethylene membrane (weight Wg ₂ ) having an average pore size of 0.2 μm, and the opening is tied with a string (weight Wg ₃ ). As the porous polytetrafluoroethylene (PTFE) membrane, trade name "Nitoflon (registered trademark) NTF1122" available from Nitto Denko Corporation (average pore size 0.2 μm, porosity 75%, thickness 85 μm) or equivalent use the product.
This package was immersed in 50 mL of ethyl acetate and kept at room temperature (typically 23° C.) for 7 days to elute only the sol component in the adhesive layer outside the film. The adhering ethyl acetate is wiped off, the packet is dried at 130° C. for 2 hours, and the weight (Wg ₄ ) of the packet is measured. The gel fraction _FG of the pressure-sensitive adhesive layer is obtained by substituting each value into the following formula. A similar method is adopted in the examples described later.
Gel fraction F _G (%)=[(Wg ₄ -Wg ₂ -Wg ₃ )/Wg ₁ ]×100

The thickness of the adhesive layer is not particularly limited. From the viewpoint of avoiding excessive thickness of the adhesive sheet, the thickness of the adhesive layer is appropriately about 100 μm or less, and from the viewpoint of thinning, preferably about 70 μm or less, more preferably about 60 μm or less (for example, about 55 μm below), more preferably about 50 μm or less, particularly preferably about 40 μm or less (for example, about 30 μm or less). The thickness of the adhesive layer can be about 20 μm or less, for example about 15 μm or less, or about 10 μm or less or about 5 μm or less (eg about 3 μm or less). For example, the thinner the pressure-sensitive adhesive layer, the lower the light-shielding property in the thickness direction, but the light transmittance in the sheet surface direction becomes less problematic. Considering such things, 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 can be about 1 μm or more, about 1.5 μm or more is suitable, and preferably about 1 μm or more. It is 5 μm or more, more preferably about 7 μm or more, and may be about 12 μm or more (for example, about 15 μm or more). By setting the thickness of the pressure-sensitive adhesive layer to a predetermined value or more, the pressure-sensitive adhesive properties such as adhesive strength and impact resistance can be improved, and there is a tendency to improve conformability to unevenness. When the pressure-sensitive adhesive sheet disclosed herein is implemented in a mode comprising a first pressure-sensitive adhesive layer and a second pressure-sensitive adhesive layer, the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may have the same thickness. , can be different.

The ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet is not particularly limited. Here, the total thickness of the pressure-sensitive adhesive layer in the total thickness of the pressure-sensitive adhesive sheet refers to the thickness of the pressure-sensitive adhesive layer provided on one surface of the base film layer and the pressure-sensitive adhesive layer provided on the other surface. Refers to the total thickness. In the case of a single-sided pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer is provided only on one surface of a base film layer, the thickness of the pressure-sensitive adhesive layer provided on the other surface is zero, and the thickness of the pressure-sensitive adhesive layer on the other surface is zero. The thickness of the pressure-sensitive adhesive layer provided in the above is the same as the total thickness of the pressure-sensitive adhesive layer. The technology disclosed herein, for example, the ratio of the total thickness of the adhesive layer to the total thickness of the adhesive sheet is 40% or more (preferably 50% or more, typically more than 50%, more preferably 60%). % or more, more preferably 70% or more). Such a structure tends to exhibit a higher level of impact resistance even in a narrow width compared to the total thickness of the pressure-sensitive adhesive sheet. In some aspects, 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, or even 80% or more. A high thickness ratio of the pressure-sensitive adhesive layer is also advantageous in terms of improving conformability to unevenness. Although 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, it is suitably 95% or less, preferably 90% or less.

<Release liner>
In the technology disclosed herein, a release liner can be used in the formation of the adhesive layer, production of the adhesive sheet, storage of the adhesive sheet before use, distribution, shape processing, and the like. The release liner is not particularly limited. A release liner or the like made of a low-adhesion material such as polypropylene can be used. The release treatment layer may be formed by surface-treating the liner base material with a release treatment agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide release agent.

<Thickness of adhesive sheet>
The total thickness of the pressure-sensitive adhesive sheet disclosed herein (including the pressure-sensitive adhesive layer and the base film layer, but not including the release liner) is not particularly limited. The total thickness of the 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 adhesive sheet is not particularly limited, and may be approximately 1 μm or more, for example, approximately 3 μm or more, preferably approximately 6 μm or more, more preferably approximately 10 μm or more (for example, approximately 15 μm). above).

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

<Adhesive strength>
The pressure-sensitive adhesive sheet disclosed herein may have a predetermined or higher adhesive strength suitable for bonding, fixing, and the like. The pressure-sensitive adhesive sheet has, for example, a 180° C. peel strength (adhesive strength to SUS) measured according to JIS Z 0237:2000 to a stainless steel plate (SUS plate) of about 3 N/20 mm or more (for example, about 5 N/20 mm or more). It is preferable that the adhesive strength to SUS is approximately 8 N/20 mm or more. The pressure-sensitive adhesive sheet having the above adhesion to SUS exhibits good adhesion to adherends. The pressure-sensitive adhesive sheet having the above adhesive strength tends to exhibit good adhesiveness to resin materials used in electronic devices, such as polycarbonate (PC) and polyimide (PI). The adhesive strength to SUS is more preferably 10 N/20 mm or more, still more preferably 12 N/20 mm or more, and particularly preferably 14 N/20 mm or more (for example, 18 N/20 mm or more). Although the upper limit of the adhesive strength to SUS is not particularly limited, approximately 50 N/20 mm or less (for example, approximately 45 N/20 mm or less) is appropriate.

The adhesive strength to SUS is measured by the following method. Specifically, the adhesive sheet is cut into a size of 20 mm in width and 100 mm in length to prepare a sample piece. In the case of a double-sided pressure-sensitive adhesive sheet, one side of the pressure-sensitive adhesive sheet is lined with a PET film having a thickness of 50 μm. Under the environment of 23° C. and 50% RH, the adhesive surface of the sample piece is press-bonded to a stainless steel plate (SUS304BA plate) to prepare a measurement sample. The pressure bonding is performed by reciprocating a 2 kg roller once. After leaving the measurement sample in an environment of 23 ° C. and 50% RH for 30 minutes, using a tensile tester, according to JIS Z 0237: 2000, a tensile speed of 300 mm / min and a peel angle of 180 degrees. to measure the peel strength [N/20 mm]. Let this value be the adhesive strength to SUS. As the tensile tester, "Precision Universal Testing Machine Autograph AG-IS 50N" manufactured by Shimadzu Corporation or its equivalent can be used.

<Application>
The use of the pressure-sensitive adhesive sheet disclosed herein is not particularly limited, and it can be used for various uses that require light-shielding properties. The pressure-sensitive adhesive sheet disclosed herein, for example, in the form of a double-sided pressure-sensitive adhesive sheet, can be preferably used for fixing or joining members while exhibiting predetermined light-shielding properties. In some aspects, the pressure-sensitive adhesive sheet can be attached to parts constituting an electronic device, and can be used for fixing, bonding, reinforcing, etc., the parts while imparting light-shielding properties in the electronic device. In addition, since the pressure-sensitive adhesive sheet disclosed herein can be clean without dust or contamination during processing, it can be processed into a specific shape or narrowed for use in applications such as portable electronic devices. It is suitable for fixing members in Since some electronic devices such as portable electronic devices include light-emitting elements for the purpose of image display and the like, the pressure-sensitive adhesive sheet may be required to have a light-shielding property. In addition, since the pressure-sensitive adhesive sheet disclosed herein can be made thin while having a predetermined light-shielding property, it can meet the needs for thinning and lightening portable electronic devices.

Non-limiting examples of the above portable electronic devices include mobile phones, smartphones, tablet computers, notebook computers, various wearable devices (for example, wrist wear type worn on the wrist like a wristwatch, Eyewear type including glasses type (monocular type and binocular type, including head-mounted type), clothes type attached to shirts, socks, hats, etc. in the form of accessories, earphones ear-wear type, etc.), digital cameras, digital video cameras, audio equipment (portable music players, IC recorders, etc.), calculators (calculators, etc.), portable game devices, electronic dictionaries, electronic notebooks, electronic books, vehicle-mounted information equipment, portable radios, portable televisions, portable printers, portable scanners, portable modems, etc. In this specification, the term “portable” means not only being able to be simply carried, but also having a level of portability that allows an individual (a typical adult) to carry it relatively easily. shall mean.

The pressure-sensitive adhesive sheet disclosed herein can be preferably used, for example, for the purpose of fixing a pressure-sensitive sensor and other members in a portable electronic device having a pressure-sensitive sensor among such portable electronic devices. In some preferred embodiments, the adhesive sheet includes a device for indicating a position on the screen (typically a pen-type or mouse-type device) and a device for detecting the position. In order to fix a pressure sensor and other members in an electronic device (typically a portable electronic device) with a function that allows specifying an absolute position on a (typically touch panel) can be used.

The pressure-sensitive adhesive sheet disclosed herein is also suitable for use in preventing reflection of light through the display screen when placed on the back surface of a display screen (display unit) such as a touch panel display in portable electronic devices. By arranging the pressure-sensitive adhesive sheet disclosed herein on the back surface of the display screen (display section), it is possible to prevent deterioration of the visibility of the display screen regardless of how the portable electronic device is used. In addition, the above-mentioned reflection can be caused by a metal member arranged on the back side of the display screen. can be realized at the same time as bonding and imparting light shielding properties.

The material constituting the fixed object (for example, the back surface member such as the electromagnetic shield and the reinforcing plate) such as the pressure sensor and the display unit is not particularly limited, but examples include copper, silver, gold, iron, Metal materials such as tin, palladium, aluminum, nickel, titanium, chromium, zinc, etc., or alloys containing two or more of these, such as polyimide-based resins, acrylic-based resins, polyethernitrile-based resins, and polyethersulfone-based resins , polyester resin (polyethylene terephthalate resin, polyethylene naphthalate resin, etc.), polyvinyl chloride resin, polyphenylene sulfide resin, polyether ether ketone resin, polyamide resin (so-called aramid resin, etc.), polyarylate resin , various resin materials (typically plastic materials) such as polycarbonate resins and liquid crystal polymers, and inorganic materials such as alumina, zirconia, soda glass, quartz glass and carbon. 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. The object to be fixed may have either a single-layer structure or a multi-layer structure, and the surface to which the pressure-sensitive adhesive sheet is attached (attachment surface) may be subjected to various surface treatments. Although not particularly limited, an example of a fixed object is a back member having a thickness of 1 μm or more (typically 5 μm or more, for example 60 μm or more, further 120 μm or more) and about 1500 μm or less (for example, 800 μm or less). mentioned.

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

FIG. 2 is a schematic exploded perspective view schematically showing a configuration example of the liquid crystal display device. As shown in FIG. 2 , the liquid crystal display device 200 included in the mobile electronic device 100 includes an LCD unit (component) 210 and a BL unit (component) 220 . The liquid crystal display device 200 further includes an adhesive sheet 230 . In this configuration example, the adhesive sheet 230 is in the form of a double-sided adhesive sheet (double-sided adhesive sheet) processed into a frame shape (picture frame shape), and is arranged between the BL unit 220 and the LCD unit 210 to bond them together. are joined. Note that the BL unit 220 typically includes, in addition to the light source, a reflective sheet, a light guide plate, a diffusion sheet, a prism sheet, and the like.

The pressure-sensitive adhesive sheet disclosed herein can be used in the form of bonding members processed into various external shapes, for example, for bonding the LCD unit and the BL unit, as described above, and for other bonding purposes. A preferable form of such a joint member includes a form having a narrow portion with a width of less than 2.0 mm (for example, less than 1.0 mm). The pressure-sensitive adhesive sheet disclosed herein can exhibit good light-shielding properties even when used as a bonding member having a shape (for example, a frame shape) including the narrow width portion as described above. Moreover, in some embodiments, the pressure-sensitive adhesive sheet can exhibit excellent pressure-sensitive adhesive properties such as impact resistance even in the form of a narrow pressure-sensitive adhesive sheet. In some aspects, 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 from the standpoint of handleability of the adhesive sheet, 0.1 mm or more (typically 0.2 mm or more) is appropriate.

The narrow portion is typically linear. Here, the linear shape is a concept that includes linear shapes, curved shapes, polygonal shapes (for example, L-shaped), etc., as well as annular shapes such as frame shapes and circular shapes, and complex or intermediate shapes thereof. . The above-mentioned annular is not limited to those composed of curved lines, and is partly or wholly formed linearly, such as a shape (frame shape) along the outer circumference of a quadrangle or a shape along the outer circumference of a sector. It is a concept that includes a ring. The length of the narrow portion is not particularly limited. For example, in a form in which the narrow portion has a length of 10 mm or more (typically 20 mm or more, for example 30 mm or more), the effect of applying the technique disclosed herein can be suitably exhibited.

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 for joining the liquid crystal display module unit and the backlight module unit,
The pressure-sensitive adhesive sheet comprises a base film layer containing a black colorant and light-transmitting pressure-sensitive adhesive layers disposed on both sides of the base film layer,
The liquid crystal display device, wherein the pressure-sensitive adhesive sheet has a light transmittance of less than 5% in the thickness direction.
(2) The liquid crystal display device according to (1) above, wherein the pressure-sensitive adhesive layer has a light transmittance in the thickness direction of 5% or more.
(3) The liquid crystal display device according to (1) or (2) above, wherein the pressure-sensitive adhesive layer has a light transmittance of more than 50% in the thickness direction.
(4) The liquid crystal display device according to any one of (1) to (3) above, wherein the pressure-sensitive adhesive sheet has a light transmittance in the thickness direction of 0.01% or less.
(5) The liquid crystal display device according to any one of (1) to (3) above, wherein the pressure-sensitive adhesive sheet has a light transmittance in the thickness direction of more than 0.01% and less than 5%.
(6) The liquid crystal display device according to any one of (1) to (5) above, wherein the light transmittance in the thickness direction of the base film layer is less than 5%.
(7) The liquid crystal display device according to any one of (1) to (6) above, wherein the base film layer is a resin film layer containing the black colorant.
(8) The liquid crystal display device according to any one of (1) to (7) above, wherein the pressure-sensitive adhesive layer has a thickness of 1.5 μm to 60 μm.
(9) The liquid crystal display device according to any one of (1) to (8) above, wherein the base film layer is made of a polyester resin film.
(10) The liquid crystal display device according to any one of (1) to (9) above, wherein the adhesive sheet has a total thickness of 300 μm or less.

(11) Equipped with a base film layer containing a black colorant and a light-transmitting pressure-sensitive adhesive layer disposed on at least one surface of the base film layer, and having a light transmittance in the thickness direction of less than 5%. Adhesive sheet.
(12) The pressure-sensitive adhesive sheet according to (11) above, wherein the pressure-sensitive adhesive layer has a light transmittance in the thickness direction of 5% or more.
(13) The pressure-sensitive adhesive sheet according to (11) or (12) above, wherein the pressure-sensitive adhesive layer has a light transmittance of more than 50% in the thickness direction.
(14) The pressure-sensitive adhesive sheet according to any one of (11) to (13) above, wherein the light transmittance in the thickness direction is 0.01% or less.
(15) The adhesive sheet according to any one of (11) to (13) above, wherein the light transmittance in the thickness direction is more than 0.01% and less than 5%.
(16) The pressure-sensitive adhesive sheet according to any one of (11) to (15) above, wherein the light transmittance in the thickness direction of the base film layer is less than 5%.
(17) The adhesive sheet according to any one of (11) to (16) above, wherein the base film layer is a resin film layer containing the black colorant.
(18) The pressure-sensitive adhesive sheet according to any one of (11) to (17) above, wherein the pressure-sensitive adhesive layer has a thickness of 1.5 μm to 60 μm.
(19) The pressure-sensitive adhesive sheet according to any one of (11) to (18) above, wherein the base film layer is made of a polyester resin film.
(20) The pressure-sensitive adhesive sheet according to any one of (11) to (19) above, wherein the total thickness of the pressure-sensitive adhesive sheet is 300 μm or less.

(21) The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive layer containing 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 pressure-sensitive adhesive sheet according to any one of (11) to (20) above, wherein the acrylic polymer has a dispersity (Mw/Mn) of less than 15.
(22) The adhesive according to (21) above, wherein the acrylic polymer is polymerized at a rate of 50% by weight or more of an alkyl (meth)acrylate having an alkyl group having 1 to 6 carbon atoms at the ester end. sheet.
(23) The adhesive sheet according to (21) or (22) above, wherein the acrylic polymer is copolymerized with an acidic group-containing monomer.
(24) The pressure-sensitive adhesive sheet according to (23) above, wherein the copolymerization ratio of the acidic group-containing monomer in the acrylic polymer is less than 10% by weight.
(25) Any one of (21) to (24) above, wherein in the acrylic pressure-sensitive adhesive layer, the tackifying resin is contained at a rate of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. The adhesive sheet described in .
(26) The above (21) to (25), wherein in the acrylic pressure-sensitive adhesive layer, the (meth)acrylic oligomer is contained in a proportion of less than 30 parts by weight with respect to 100 parts by weight of the acrylic polymer. The pressure-sensitive adhesive sheet according to any one of 1.
(27) The pressure-sensitive adhesive sheet according to any one of (21) to (26) above, wherein the acrylic pressure-sensitive adhesive layer contains both the tackifying resin and the (meth)acrylic oligomer.
(28) The pressure-sensitive adhesive sheet according to any one of (11) to (27) above, wherein the pressure-sensitive adhesive layer has a storage modulus G' (25°C) at 25°C of 0.15 MPa or more.
(29) The pressure-sensitive adhesive sheet according to any one of (11) to (28) above, wherein the pressure-sensitive adhesive layer has a gel fraction of 40% by weight or more.
(30) The pressure-sensitive adhesive sheet according to any one of (11) to (29) above, wherein the acrylic polymer is crosslinked.
(31) The pressure-sensitive adhesive sheet according to any one of (11) to (30) above, wherein the acrylic polymer is copolymerized with n-butyl acrylate at a rate of 50% by weight or more.
(32) Any one of (11) to (31) above, wherein the pressure-sensitive adhesive layer contains the tackifying resin, and about 50% by weight or more of the tackifying resin is a phenolic tackifying resin (eg, terpene phenolic resin). The adhesive sheet described in Crab.
(33) The pressure-sensitive adhesive sheet according to (32) above, wherein the phenol-based tackifier resin contains a terpene phenol resin having a hydroxyl value of less than approximately 30 mgKOH/g.
(34) The pressure-sensitive adhesive sheet according to any one of (11) to (33) above, wherein the pressure-sensitive adhesive layer has a loss elastic modulus G'' (25°C) at 25°C of 2.0 MPa or less.
(35) The pressure-sensitive adhesive according to any one of (11) to (34) above, wherein the pressure-sensitive adhesive layer is a pressure-sensitive adhesive layer formed from a solvent-based pressure-sensitive adhesive composition or an active energy ray-curable pressure-sensitive adhesive composition. sheet.
(36) The pressure-sensitive adhesive sheet according to any one of (11) to (35) above, which is configured as a double-sided adhesive pressure-sensitive adhesive sheet with a thickness of less than 50 μm.
(37) The adhesive sheet according to (23) or (24) above, wherein the acidic group-containing monomer is acrylic acid.

(38) The pressure-sensitive adhesive sheet according to any one of (11) to (37) above, which is used in an electronic device containing a light-emitting element.
(39) The pressure-sensitive adhesive sheet according to any one of (11) to (38) above, which is used for fixing a member in a portable electronic device.

Several examples relating to the present invention are described below, but are not intended to limit the present invention to those shown in the examples. In the following description, "parts" and "%" are by weight unless otherwise specified.

<Evaluation method>
[Thickness direction light transmittance]
It can be grasped by preparing an adhesive sheet and measuring the light transmittance in the thickness direction. The light transmittance in the thickness direction is measured by irradiating light with a wavelength of 380 to 780 nm perpendicularly to the sheet surface of the measurement sample using a commercially available spectrophotometer, and measuring the intensity of the light transmitted through the other surface. is obtained by measuring As the spectrophotometer, a spectrophotometer manufactured by Hitachi (apparatus name “U4100 spectrophotometer”) or an equivalent thereof is used. The thickness direction light transmittance of the supporting substrate (substrate film) is also measured by the same method. The thickness direction light transmittance of the pressure-sensitive adhesive layer is measured in the thickness direction of the pressure-sensitive adhesive layer alone obtained by peeling off the pressure-sensitive adhesive layer with a release liner from the release liner before being transferred to the supporting substrate when producing the pressure-sensitive adhesive sheet. can be obtained by measuring the light transmittance.
If the light transmittance in the thickness direction is less than 5%, it can be evaluated as having good light shielding properties.

[Dust generation]
The coloring agent scraped off during the production of the adhesive sheet is sampled, and the presence or absence of dust generation is visually observed. A case where the colorant was not scraped off was evaluated as "good", and a case where the colorant was observed to be scraped off was evaluated as "poor".

<Example 1>
(Preparation of acrylic polymer)
A reaction vessel equipped with a stirrer, thermometer, nitrogen gas inlet tube, reflux condenser and dropping funnel was charged with 93 parts of BA, 7 parts of AA and 0.05 part of 4-hydroxybutyl acrylate (4HBA) as a polymerization solvent. of ethyl acetate were charged, and the mixture was stirred for 2 hours while introducing nitrogen gas. After removing oxygen from the polymerization system in this manner, 0.1 part of AIBN was added as a polymerization initiator, and solution polymerization was carried out at 60° C. for 6 hours to obtain an acrylic polymer solution according to this example. Mw of this acrylic polymer was 140×10 ⁴ and Mw/Mn was 5.5.

(Preparation of adhesive composition)
To the acrylic polymer solution obtained above, 1.5 parts of an isocyanate cross-linking agent (trade name "Coronate L", trimethylolpropane/tolylene diisocyanate 3 parts per 100 parts of the acrylic polymer contained in the solution) 75% ethyl acetate solution of the polyadduct, manufactured by Tosoh Corporation) and 0.01 part of an epoxy-based cross-linking agent (trade name “TETRAD-C”, 1,3-bis (N, N-diglycidylaminomethyl) cyclo Hexane, manufactured by Mitsubishi Gas Chemical Co., Ltd.), 15 parts of a terpene phenol resin (trade name "YS Polyster S-145" manufactured by Yasuhara Chemical Co., Ltd., softening point of about 145 ° C., hydroxyl value of 70 to 110 mgKOH / g), and 15 parts and a (meth)acrylic oligomer were added and mixed with stirring to prepare a pressure-sensitive adhesive composition according to this example.
As the (meth)acrylic oligomer, one 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 added to a reaction vessel equipped with a stirrer, a thermometer, a nitrogen gas inlet tube, a reflux condenser and a dropping funnel. and stirred in a nitrogen stream for 1 hour to remove oxygen in the polymerization system, then heated to 85° C. and reacted for 5 hours to obtain a (meth)acrylic oligomer having a solid concentration of 50%. Mw of the obtained (meth)acrylic oligomer was 3,600.

(Preparation of adhesive sheet)
As the release liner, two sheets of a polyester release film (trade name: "Diafoil MRF", thickness: 38 µm, manufactured by Mitsubishi Polyester Co., Ltd.) were prepared, one side of which is a release surface. The pressure-sensitive adhesive composition was applied to the release surfaces of these release liners so that the thickness after drying was 7.5 μm, and dried at 100° C. for 2 minutes. Thus, a pressure-sensitive adhesive layer was formed on each of the release surfaces of the two release liners. The obtained adhesive layer had a gel fraction of 60%, a storage elastic modulus G' (25°C) of the adhesive layer at 25°C of 0.32 MPa, and a loss elastic modulus G'' (25°C) of 0.32 MPa. It was 36 MPa.
As a base film, a PET film having a thickness of 5 μm was prepared by kneading carbon black particles so that the light transmittance in the thickness direction was 2.4%. The pressure-sensitive adhesive layers formed on the two release liners were attached to the first and second surfaces of the base film, respectively, to prepare a double-sided pressure-sensitive adhesive sheet having a total thickness of 20 μm (transfer method). . The release liner was left on the pressure-sensitive adhesive layer and used to protect the surface (adhesive surface) of the pressure-sensitive adhesive layer.

<Example 2>
To the pressure-sensitive adhesive composition according to Example 1, 6.5 parts of a black pigment (manufactured by Dainichiseika Kogyo Co., Ltd., trade name "ATDN101 Black") is added to 100 parts of the acrylic polymer contained in the composition, and stirred. A mixture was prepared as a pressure-sensitive adhesive composition according to this example. Using this pressure-sensitive adhesive composition, 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 a pressure-sensitive adhesive layer having a thickness of 12.5 μm was formed.

<Example 3>
As the base film, a 12 μm thick PET film prepared by kneading carbon black particles so that the light transmittance in the thickness direction was less than 0.01% was used. Also, the thickness of each adhesive layer was changed to 9 μm. A double-sided pressure-sensitive adhesive sheet having a total thickness of 30 μm was produced in the same manner as in Example 1.

<Example 4>
As the base film, a 19 μm thick PET film prepared by kneading carbon black particles so that the light transmittance in the thickness direction was less than 0.01% was used. Also, the thickness of each adhesive layer was changed to 15.5 μm. A double-sided pressure-sensitive adhesive sheet having a total thickness of 50 μm was produced in the same manner as in Example 3.

<Example 5>
As the base film, a 25 μm thick PET film prepared by kneading carbon black particles so that the light transmittance in the thickness direction was less than 0.01% was used. Also, the thickness of each adhesive layer was changed to 27.5 μm. A double-sided pressure-sensitive adhesive sheet having a total thickness of 80 μm was produced in the same manner as in Example 3.

<Example 6>
A double-sided pressure-sensitive adhesive sheet having a total thickness of about 100 μm was produced in the same manner as in Example 5, except that the thickness of each pressure-sensitive adhesive layer was changed to 38 μm.

<Example 7>
As the base film, a PET film having a thickness of 50 μm and produced by kneading carbon black particles so that the light transmittance in the thickness direction was 1.1% was used. Also, the thickness of each adhesive layer was changed to 35 μm. A double-faced pressure-sensitive adhesive sheet having a total thickness of 120 μm was produced in the same manner as in Example 1.

<Example 8>
A PET film having a thickness of 75 μm and produced by kneading carbon black particles so that the light transmittance in the thickness direction was 0.53% was used as the base film. Also, the thickness of each adhesive layer was changed to 38 μm. A double-sided pressure-sensitive adhesive sheet having a total thickness of about 150 μm was produced in the same manner as in Example 7.

<Example 9>
A double-sided pressure-sensitive adhesive sheet having a total thickness of about 125 μm was produced in the same manner as in Example 5, except that the thickness of each pressure-sensitive adhesive layer was changed to 50 μm.

<Example 10>
A double-sided pressure-sensitive adhesive sheet having a total thickness of about 150 μm was produced in the same manner as in Example 7, except that the thickness of each pressure-sensitive adhesive layer was changed to 50 μm.

<Example 11>
As the base film, a 100 μm thick PET film prepared by kneading carbon black particles so that the light transmittance in the thickness direction was less than 0.01% was used. Also, the thickness of each adhesive layer was changed to 50 μm. A double-sided pressure-sensitive adhesive sheet having a total thickness of about 200 μm was produced in the same manner as in Example 1.

<Example 12>
In this example, as the substrate, a multilayer structure having a total thickness of about 10 μm consisting of a transparent PET film (trade name “Lumirror”, manufactured by Toray Industries, Inc.) and a black printed layer provided on the second surface of the PET film. A supporting substrate was used. The black printed layer was formed by printing using an ink composition containing a black colorant and using a gravure printing method. The amount of the pressure-sensitive adhesive composition applied to the release film was adjusted so that the thickness after drying was 10 μm. Otherwise, in the same manner as in Example 1, a pressure-sensitive adhesive sheet according to this example was produced.

For the adhesive sheet according to each example, the light transmittance [%] in the thickness direction, the light transmittance [%] in the thickness direction of the adhesive layer, the light transmittance [%] in the thickness direction of the base film, and the light transmittance [%] Dustiness was measured or evaluated. Table 1 shows the results.

As shown in Table 1, the pressure-sensitive adhesive sheets according to Examples 1 to 11 achieved a light transmittance of less than 5% in the thickness direction by using a base film containing a black colorant, and had good light shielding properties. Indicated. In addition, all of these pressure-sensitive adhesive sheets were clean without generating dust. On the other hand, in Example 12, in which the base film containing the black colorant was not used, although the light-shielding property was good due to the use of the black printed layer, dust generation was observed.
From the above results, a base film layer containing a black colorant and a light-transmitting pressure-sensitive adhesive layer disposed on at least one surface of the base film layer are provided, and the light transmittance in the thickness direction is 5. %, the pressure-sensitive adhesive sheet can be clean and have good light-shielding properties.

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

Reference Signs List 1 Adhesive sheet 10 Base film layer 10A First surface 10B Second surface 21 First adhesive layer 21A First adhesive surface 22 Second adhesive layer 22A Second adhesive surface 31, 32 Release liner

Claims (10)

It comprises a base film layer containing a black colorant and a light-transmitting pressure-sensitive adhesive layer disposed on at least one surface of the base film layer, and has a light transmittance in the thickness direction of less than 5%. ,
The pressure-sensitive adhesive layer has a storage modulus at 25°C of 0.17 MPa or more and 0.6 MPa or less, and a tan δ at 25°C of 0.5 or more and 2 or less,
The pressure-sensitive adhesive layer contains, as a base polymer, an acrylic polymer having an acidic group, a tackifying resin, an isocyanate-based cross-linking agent, and an epoxy-based cross-linking agent,
The pressure-sensitive adhesive sheet, wherein the tackifier resin contains a terpene phenol resin having a hydroxyl value of 30 mgKOH/g or more . The pressure-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer has a light transmittance in the thickness direction of 5% or more. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a light transmittance of more than 50% in the thickness direction. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the light transmittance in the thickness direction is 0.01% or less. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3, wherein the light transmittance in the thickness direction is more than 0.01% and less than 5%. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5, wherein the light transmittance in the thickness direction of the base film layer is less than 5%. The adhesive sheet according to any one of claims 1 to 6, wherein the base film layer is a resin film layer containing the black colorant. The pressure-sensitive adhesive sheet according to any one of claims 1 to 7, wherein the pressure-sensitive adhesive layer has a thickness of 1.5 µm to 60 µm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 8, which is used in electronic devices containing light-emitting elements. The pressure-sensitive adhesive sheet according to any one of claims 1 to 9, which is used for fixing members in portable electronic devices.

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