JP7096306B2 - Adhesive sheet - Google Patents

Description

The present invention relates to an adhesive sheet having a protective layer on the surface of the adhesive layer.

Adhesive sheets are used to fix parts and members in various fields such as electrical and electronic fields, automobile-related fields, and civil engineering and construction fields. The adhesive sheet is provided with an adhesive layer such as an epoxy-based or acrylic-based adhesive having high adhesiveness in order to realize strong adhesion to the adherend.

The adhesive sheet before use needs to protect the surface (adhesive surface) of the adhesive layer from foreign matter, dust, scratches, deterioration, etc. in order to prevent a decrease in adhesive strength. In addition, it can be said that protection of the adhesive surface is indispensable in order to prevent unintentional adhesion to unintended places (so-called blocking) and contamination of workers' hands.

Patent Document 1 discloses a thermosetting adhesive tape or sheet provided with a release liner in order to prevent foreign substances such as dust from adhering to the surface of the thermosetting adhesive layer. Further, Patent Document 2 discloses an invention in which a liner made of a resin film is provided on an adhesive surface of an adhesive sheet for fixing an electric component to facilitate handling.

However, for adhesive tapes or sheets with release liners, it is necessary to introduce equipment equipped with a liner winding mechanism in the automatic process of continuously assembling members. In addition, the peeling liner that is no longer needed becomes dust, which is not preferable from the viewpoint of protecting the global environment.

On the other hand, Patent Document 3 discloses a technique of incorporating an inorganic filler in the adhesive layer in order to improve the blocking resistance of the adhesive layer. Further, Patent Document 4 discloses a technique that eliminates the need for a release sheet by providing a second pressure-sensitive adhesive layer containing a plurality of fine particles on the first pressure-sensitive adhesive layer.

However, although these inventions can prevent blocking and improve work efficiency without using a release liner, there is a concern that the adhesive may affect the skin. In particular, epoxy-based adhesives and acrylic-based adhesives are said to cause skin damage (Non-Patent Document 1), and even if the adhesive layer contains fine particles such as an inorganic filler, such skin damage can be avoided. It's not something you can do.

Japanese Unexamined Patent Publication No. 2012-51994 Japanese Unexamined Patent Publication No. 2008-280436 Japanese Unexamined Patent Publication No. 08-60108 Japanese Unexamined Patent Publication No. 2017-19993

Edited by ThreeBond Co., Ltd. "ThreeBond Technical News No.40" published on December 25, 1992

The present invention has been made to solve the above-mentioned problems of the prior art. That is, an object of the present invention is to provide an adhesive sheet that can protect the adhesive surface without using a release liner and does not cause blocking or skin damage.

As a result of diligent studies to solve the above object, the present inventors have found that it is very effective to provide a protective layer on at least a part of the surface of the adhesive layer, and have completed the present invention. rice field.

That is, the present invention is an adhesive sheet having an adhesive layer on at least a part of one side or both sides of a base material, and the present invention is characterized by having a protective layer on at least a part of the surface of the adhesive layer. be.

The adhesive sheet of the present invention can protect the adhesive surface without using a release liner, and does not cause blocking or skin damage. Further, by impregnating the protective layer with a substance having various functions such as an antioxidant, a colorant, a hard coat agent, a lubricant, a heat radiating material, a metal deactivating agent, an antioxidant, and a flame retardant. The adhesive sheet can have various functions without impairing the characteristics of the adhesive layer.

It is a schematic sectional drawing which shows the embodiment of the adhesive sheet of this invention. It is a schematic diagram for demonstrating the test method of the shear adhesive force of an Example. It is a graph which shows the result of the reflection IR measurement about the surface composition of the protective layer (before foaming) of the adhesive sheet of Example 6 and the adhesive layer (before foaming) of the adhesive sheet of Comparative Example 1.

FIG. 1 is a schematic cross-sectional view showing an embodiment of the adhesive sheet of the present invention. In the embodiment shown in FIG. 1 (a), the adhesive layer 2 is provided on the entire surface of the base material 1, and the protective layer 3 is provided on the entire surface of the adhesive layer 2. However, the present invention is not limited to this embodiment, and for example, the adhesive layer 2 may be provided on both sides of the base material 1.

The adhesive layer 2 may be provided on one side or a part of both sides of the base material 1. In this case, as shown in FIG. 1B, the protective layer 3a may be provided so as to cover the entire surface of the adhesive layer 2 and the entire surface of the base material on which the adhesive layer is not provided. As shown in 1 (c), it may be provided so as to cover only the entire surface of the adhesive layer 2. Further, as shown in FIG. 1 (d), the protective layer 3 may be provided on a part of the surface of the adhesive layer 2.

The protective layer 3 is an antistatic agent, a colorant, a hard coat agent, a lubricant, a heat radiating material, a metal deactivating agent, an antioxidant, a flame retardant, a water / oil repellent agent, and a solvent resistant resin, which will be described in detail later. It may contain a functional component such as. Thereby, a desired function other than protection can be imparted to the protective layer 3. Further, the adhesive layer 2 may also contain the same or different functional components as the protective layer 3.

Two types of protective layers 3 can also be provided. For example, as shown in FIG. 1 (e), a protective layer having a two-layer structure may be provided in which another protective layer 3b is provided on the surface of the protective layer 3a provided on the adhesive layer 2. The protective layer 3 having such a two-layer structure may be formed by superimposing the protective layer 3b on the protective layer 3a, or by separating the protective layer 3 in the coating process. Further, the protective layer may be configured to have three or more layers. Further, as shown in FIG. 1 (f), the protective layer 3a and the protective layer 3b may be provided at different positions on the surface of the adhesive layer 2. The protective layer 3a and the protective layer 3b are, for example, layers containing functional components different from each other. As a result, two different functions can be imparted to the entire surface (FIG. 1 (e)), or two different functions can be imparted to different positions (FIG. 1 (f)).

Hereinafter, each configuration of the adhesive sheet of the present invention will be described.

[Base material 1]
As shown in FIG. 1, the base material 1 used in the present invention is a member for supporting the adhesive layer 2.

The base material 1 is not particularly limited, but is preferably a heat-resistant insulating base material. The level of heat resistance varies depending on the intended use, but for example, the melting temperature of the base material 1 is preferably 200 ° C. or higher, more preferably 250 ° C. or higher. Further, for example, the continuous use temperature of the base material 1 measured according to UL-746B is preferably 100 ° C. or higher, more preferably 150 ° C. or higher.

As shown in FIG. 1, the base material 1 may be a single-layer base material composed of one member, or a laminated body having a laminated structure in which one member and another member are bonded by a bonding adhesive. It may be a base material made of. The base material 1 may have flexibility or resilience, and its properties are appropriately selected depending on the intended use. In applications where the strength (stiffness) and shape retention of the adhesive sheet are required, the base material 1 is preferably a base material made of a laminated body.

The member constituting the base material 1 is preferably a resin film, a non-woven fabric or paper, and more preferably a resin film. When the base material is a base material made of a laminate, the member is preferably one or more members selected from the group consisting of a resin film, a non-woven fabric and paper, and at least one is more preferably a resin film. preferable.

Specific examples of the resin film include polyester-based resins such as polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), and aromatic polyester; polycarbonate; polyallylate; polyurethane; polyamide, polyamide-based such as polyetheramide. Resin; Polyester-based resin such as polyimide, polyetherimide, polyamideimide; Polysulfone-based resin such as polysulfone and polyethersulfone; Polyetherketone-based resin such as polyetherketone and polyetheretherketone;Polyphenylene sulfide (PPS); Modification Polyphenylene oxide; Two or more kinds of resin films may be used together. Of these, polyphenylene sulfide (PPS), polyethylene naphthalate (PEN), polyimide, and polyetheretherketone are preferable.

The base material 1 may be subjected to a corona treatment or a primer treatment in order to improve the adhesion to the adhesive layer 2.

The thickness of the base material 1 may be appropriately selected depending on the intended use. Generally, it is 2 to 200 μm, preferably 9 to 100 μm, and more preferably 12 to 50 μm.

[Adhesive layer 2]
As shown in FIG. 1, the adhesive layer 2 used in the present invention is provided on at least a part of one side or both sides of the base material.

The type of the adhesive layer 2 is not particularly limited, but is preferably a thermosetting adhesive layer containing a thermosetting resin, a curing agent, and a curing catalyst, and more preferably an expansion containing a temperature-sensitive foaming agent. It is a sex adhesive layer, and particularly preferably a foamable epoxy adhesive layer in which the thermosetting resin is an epoxy resin.

The epoxy resin preferably contains a polyfunctional epoxy resin. The type of the polyfunctional epoxy resin is not limited, but a novolak type epoxy resin such as a phenol novolac type and a cresol novolak type and a mixture thereof are preferable. When a novolak type epoxy resin is used, the glass transition point of the cured product becomes high, so that the adhesive strength tends to be stable even at high temperatures.

As the epoxy resin, an epoxy resin other than the polyfunctional epoxy resin may be used in combination. By mixing and using a polyfunctional epoxy resin and other epoxy resins, physical properties such as softening point, melt viscosity, glass transition point, and storage elastic modulus of the epoxy resin can be easily and finely adjusted. In general, mixing an epoxy resin having a low softening point or a liquid can enhance the fluidity of the adhesive layer during heating and the flexibility before and after curing. On the other hand, when a semi-solid or solid epoxy resin having a high softening point is mixed, the adhesiveness of the surface of the adhesive layer can be lowered. Further, the liquid epoxy resin can be used for the purpose of pre-dispersing components such as powdery or granular heat-expandable microcapsules contained in the temperature-sensitive foaming agent and for the purpose of uniformly mixing the epoxy resin components.

Specific examples of such a mixable epoxy resin include bisphenol type epoxy resins such as bisphenol A type, dimer acid-modified bisphenol A type, and bisphenol F type; epoxy resins having an aliphatic skeleton such as hexanediol diglycidyl ether; Phenoxy resins (polyhydroxypolyethers synthesized from bisphenols and epichlorohydrin); crystalline epoxy resins. The crystalline epoxy resin is a non-adhesive solid at room temperature, whereas the melt viscosity is significantly reduced above the melting point, so that it acts as a reactive diluent above the melting point. Therefore, when the crystalline epoxy resin is included in the adhesive layer 2, the fluidity of the adhesive layer 2 at the time of heating can be further enhanced, which is advantageous for the thermal expansion of the adhesive layer 2. Further, since it is a non-adhesive solid at room temperature, it is useful for reducing the adhesiveness of the surface of the adhesive layer or making the surface of the adhesive layer non-adhesive. When the adhesive layer 2 is formed by the melt coating method, the melt viscosity of the epoxy resin can be lowered and the melt coating speed can be increased by heating the adhesive layer 2 above the melting point of the crystalline epoxy resin.

The number average molecular weight of the epoxy resin is generally 100 to 60,000 in terms of standard polystyrene by GPC. The epoxy equivalent of the epoxy resin is generally 50 to 30,000 g / eq.

The curing agent used for the adhesive layer 2 is not particularly limited, but when an epoxy resin is used, a phenol resin is preferable. When a phenol resin is used as a curing agent and used in combination with an imidazole-based compound as a curing catalyst described later, the curing time can be shortened and the heat resistance can be improved. Further, by using a phenol resin as a curing agent, it becomes easy to design heat resistance, electrical characteristics and the like. The amount of the phenol resin added is theoretically determined so that the number of hydroxyl groups of the phenol resin is close to 1: 1 with respect to the number of epoxy equivalents of the epoxy resin. The ratio of the hydroxyl group equivalent number of the phenol resin to the epoxy equivalent number of the epoxy resin is usually 0.5 to 2.0, preferably 0.8 to 1.2.

The curing catalyst used for the adhesive layer 2 is not particularly limited, but when a phenol resin is used as the curing agent, an imidazole-based compound is preferable. When an imidazole-based compound is used as a curing catalyst and used in combination with a phenol resin as a curing agent, the curing time is shortened and the heat resistance is improved. Further, the imidazole-based compound has an advantage that it can be used as a single catalyst and is easy to use because it has a grade with a very fine particle size as compared with other curing catalysts.

Specific examples of the imidazole-based compound include 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methylimidazole, 2-ethyl-4-methylimidazole, 2,4-diethylimidazole, and 2-phenyl-. Examples thereof include imidazole derivatives such as 4-methyl-5-hydroxyimidazole. Two or more kinds of imidazole compounds may be used in combination. Of these, 2-phenyl-4,5-dihydroxymethylimidazole is preferable. The content of the imidazole-based compound is preferably 0.1 to 1.0 parts by mass, and more preferably 0.3 to 0.8 parts by mass with respect to 100 parts by mass of the resin component in the adhesive layer.

Examples of the temperature-sensitive foaming agent used for the adhesive layer 2 include inorganic foaming agents such as ammonium carbonate, ammonium hydrogencarbonate, ammonium nitrite, ammonium boron hydride, and azidos; alkane fluorides such as trichloromonofluoromethane, and the like. Azo compounds such as azobisisobutyronitrile, hydrazine compounds such as paratoluenesulfonyl hydrazide, semicarbazide compounds such as p-toluenesulfonyl semicarbadide, and triazoles such as 5-morpholyl-1,2,3,4-thiatriazole. Examples thereof include organic foaming agents such as N-nitroso compounds such as N, N-dinitrosoterephthalamide; and heat-expandable microcapsules obtained by microencapsulating a heat-expanding agent composed of a hydrocarbon-based compound and the like. Two or more kinds of temperature-sensitive foaming agents may be used in combination. When an epoxy resin is used, heat-expandable microcapsules are preferable because they do not inhibit the curing of the epoxy resin and reduce the adverse effect on the physical properties of the epoxy resin.

The heat-expandable microcapsules are microcapsules in which a thermoplastic resin having a gas barrier property is used as a shell and a heat-expanding agent is encapsulated inside the shell. When the heat-expandable microcapsules are heated, the thermoplastic resin in the shell softens and the volume of the heat-expanding agent increases, so that the capsule expands. For example, the vaporization of low boiling hydrocarbon compounds can be used to expand the capsule.

The expansion (foaming) temperature of the heat-expandable microcapsules is preferably equal to or higher than the softening point of the epoxy resin and lower than the activation temperature of the curing reaction of the epoxy resin. When the foaming temperature is equal to or higher than the softening point of the epoxy resin, the thermal expansion agent can be sufficiently expanded in the softened epoxy resin, and the thickness of the adhesive layer 2 after foaming can be made uniform. Further, if the foaming temperature is equal to or lower than the activation temperature of the curing reaction of the epoxy resin, it is possible to prevent the epoxy resin from curing before foaming. Further, by setting the softening point of the epoxy resin to be equal to or lower than the activation temperature of the curing reaction, when the manufacturing process of the adhesive sheet includes melting or solution coating, the epoxy resin is generated during these coating steps and the accompanying drying step. It is possible to prevent gelation.

The softening point of the epoxy resin can be measured by using the annular softening point test method specified in JIS K 2207. The foaming temperature of the heat-expandable microcapsules is a temperature at which the volume of the heat-expandable microcapsules changes, and can be selected from, for example, 70 ° C. or higher and 200 ° C. or lower, preferably 100 ° C. or higher and 180 ° C. or lower.

The content and volume expansion rate of the temperature-sensitive foaming agent can be appropriately determined according to the strength and adhesive strength required for the cured adhesive layer 2, the expansion rate required for the adhesive sheet, and the like. The content of the temperature-sensitive foaming agent is preferably 0.5 to 20 parts by mass, and more preferably 2 to 15 parts by mass with respect to 100 parts by mass of the resin component in the adhesive layer 2. The increase multiple of the thickness of the adhesive sheet after foaming can be, for example, 1.1 times or more and 10 times or less.

The adhesive layer 2 has adhesion to the base material 1, flexibility when the adhesive sheet is bent, leveling property when the adhesive is applied, prevention of liquid dripping during heat foam curing, and the like. , It is preferable to add another resin (heat resistant resin, etc.). Specific examples of other resins include polyester resin, butyral resin, urethane resin, carboxyl group-terminated butadiene nitrile rubber (CTBN), and epoxy-modified butadiene. Of these, urethane resin is most preferable from the viewpoint of flexibility and adhesiveness.

The urethane resin is generally a resin containing a soft segment composed of a polyol monomer unit and a hard segment composed of a polyfunctional isocyanate compound or a low molecular weight glycol monomer unit. The polyol used for the urethane resin is a compound having two or more hydroxyl groups. The number of hydroxyl groups of the polyol is preferably 2 to 3, and more preferably 2 from the viewpoint of enhancing characteristics such as the rubber elastic elongation recovery rate. As the polyol, for example, a polyester polyol, a polyether polyol, a polycaprolactone polyol, a polycarbonate polyol, and a castor oil-based polyol can be used. Two or more kinds of polyols may be used in combination.

As the polyfunctional isocyanate compound used as a cross-linking agent for cross-linking the polyol, for example, a polyfunctional aliphatic isocyanate compound, a polyfunctional alicyclic isocyanate compound, and a polyfunctional aromatic isocyanate compound can be used. Further, a trimethylolpropane adduct form of these compounds, a biuret form reacted with water, and a trimer having an isocyanurate ring can also be used. Two or more kinds of polyfunctional isocyanate compounds may be used in combination.

Specific examples of the polyfunctional aliphatic isocyanate compound include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,3-butylenediocyanate, and dodecamethylene diisocyanate, 2,4. , 4-trimethylhexamethylene diisocyanate.

Specific examples of the polyfunctional alicyclic isocyanate compound include 1,3-cyclopentene diisocyanate, 1,3-cyclohexanediisocyanate, 1,4-cyclohexanediisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate, and hydrogenated xylylene diisocyanate. Examples thereof include hydrogenated tolylene diisocyanate and hydrogenated tetramethylxylylene diisocyanate.

Specific examples of the polyfunctional aromatic diisocyanate compound include phenylenediocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, and 4,4'-diphenylmethane diisocyanate. Examples thereof include 4,4'-toluene diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalenediocyanate and xylylene diisocyanate.

The urethane resin is obtained by curing a composition containing the polyol and the polyfunctional isocyanate compound described above. In particular, low crystalline linear polyester polyurethane resin is preferable, and hexanediol copolyester polyurethane resin and polytetramethylene glycol polyurethane resin are more preferable from the viewpoint of characteristics such as rubber elastic elongation recovery rate.

The content of the urethane resin is preferably 60 parts by mass or less in 100 parts by mass of the resin component in the adhesive layer 2.

The adhesive layer 2 preferably contains a heat-resistant filler from the viewpoint of heat resistance and thermal conductivity. The type of the heat-resistant filler is not particularly limited, and examples thereof include inorganic fillers such as aluminum oxide, magnesium oxide, calcium oxide, aluminum hydroxide, magnesium hydroxide, boron nitride, silicon nitride, silicon oxide, and talc (magnesium silicate). Be done. Two or more types of heat resistant fillers may be used in combination. The content of the heat-resistant filler is preferably 20 to 300 parts by mass, and more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the resin component in the adhesive.

The adhesive layer 2 is, if necessary, a phenolic antioxidant, an antioxidant such as sulfur-based antioxidant, a silane coupling agent such as epoxy-modified alkoxysilane, and a thixotropy agent such as fumed silica, for identification purposes. It may contain additives such as pigments and dyes of.

The adhesive layer 2 may be a continuous layer or a discontinuous layer composed of a pattern such as a plurality of stripes and dots. Further, unevenness such as embossing may be formed on the surface of the adhesive layer 2. By making the adhesive layer 2 discontinuous, or by forming irregularities such as embossing on the surface of the adhesive layer 2, the adhesiveness of the surface of the adhesive layer 2 is reduced, or the adhesive strength of the adhesive layer 2 is formed. The adhesive layer 2 can be formed only in a necessary portion. Further, since the non-uniformity of the surface of the adhesive layer 2 is reduced or canceled at the time of foaming, the adverse effect on the adhesive force due to the non-uniformity is unlikely to occur.

The thickness of the adhesive layer 2 may be appropriately determined depending on the intended use. It is usually 2 to 300 μm, preferably 2 to 150 μm.

[Protective layer 3]
As shown in FIG. 1, the protective layer 3 used in the present invention is provided on at least a part of the surface of the adhesive layer. The protective layer 3 is preferably a layer that flows, decomposes, or sublimates by heating when the adhesive sheet is adhered, and as a result does not prevent the adhesive layer 2 from adhering to the adherend. In particular, at room temperature (the temperature at which the adhesive sheet is stored before use), the surface of the adhesive layer 2 is protected to suppress the generation of foreign matter, scratches, blocking, etc., and the high temperature (curing temperature of the adhesive sheet during use). ), It is more preferable that the components constituting the protective layer 3 are dispersed and absorbed in the adhesive layer 2. For example, when the protective layer 3 is a heat-meltable protective layer and the adhesive layer 2 is an expandable adhesive layer (adhesive layer containing a temperature-sensitive foaming agent), the adhesive sheet is heated by heating. Microbubbles are generated in the expandable adhesive layer, and at the same time, the heat-meltable protective layer flows, and the components constituting the protective layer diffuse into the adhesive layer due to the influence of foaming. As a result, the hot-meltable protective layer almost disappears from the surface of the adhesive layer and is adhered to the adherend without impairing the original adhesiveness of the adhesive.

The protective layer 3 is a part of a member constituting the adhesive sheet at the time of use. For example, the release liner to be peeled off at the time of use is not the protective layer 3.

When the protective layer 3 is a heat-meltable protective layer, the type of the heat-meltable substance contained in the protective layer 3 is not limited, and it is a solid state at room temperature, and at least an adhesive is obtained by heating when adhering the adhesive sheet. Any component that flows to the extent that it diffuses into the layer (for example, a thermoplastic resin component) may be used. The glass transition point (Tg) of the hot meltable substance is preferably 100 ° C. or lower, the melting point is preferably 200 ° C. or lower, and the softening point is preferably 180 ° C. or lower.

By incorporating a functional component in the protective layer 3, a desired function other than protection can be imparted to the protective layer 3. The hot-meltable substance itself may be a functional component, or the hot-meltable substance may be mixed with a functional component. Specific examples of functional components include antistatic agents, colorants, hard coat agents, lubricants, heat dissipation materials, metal deactivating agents, antioxidants, flame retardants, water / oil repellents, and solvent resistant resins. Can be mentioned. When the functional component is a hot-meltable substance, it is preferable that the functional component flows by heating when the adhesive sheet is adhered and diffuses into the adhesive layer. On the other hand, when the functional component is not a hot-meltable substance, it is preferable to include a hot-meltable binder together with the functional component.

When the protective layer 3 contains an antistatic agent, the adhesive sheet can be imparted with antistatic properties. For example, it is possible to suppress sparks due to static electricity in the adhesive sheet manufacturing process (during feeding and transporting) and prevent poor peeling during feeding of the adhesive sheet. The type of antistatic agent is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a colorant, the adhesive sheet can be given distinctiveness by coloring. Specifically, for example, it is possible to prevent mistakes in installing the adhesives and adhesive sheets having different configurations on both sides. The type of the colorant is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a hard coat agent, the adhesive sheet can be imparted with scratch resistance. Specifically, for example, in a recent portable electronic device or the like, when a small part is fixed at a predetermined place, it is possible to prevent the adhesive sheet from hitting another part and deteriorating the insulating property. The type of hard coat agent is not particularly limited, and a commercially available product may be used. Further, printing may be performed on the protective layer 3 containing a hard coat agent by a method such as gravure printing containing a colorant. Such a method can be used, for example, when it is desired to display information on the adhesive sheet (Lot, caution display, etc.) on the adhesive sheet.

When the protective layer 3 contains a lubricant, the adhesive sheet can be provided with slipperiness. Specifically, for example, the frictional resistance when arranging the adhesive sheet inside the portable electronic device can be reduced, and the adhesive sheet can be easily arranged even in a complicated and complicated place. The type of lubricant is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a heat radiating material, thermal conductivity can be imparted to the adhesive sheet. The heat radiating material is preferably used together with the binder resin. Since the heat radiating material stays in the vicinity of the surface layer of the adhesive layer after the binder resin is melted and disappears, the thermal conductivity of the surface layer of the adhesive sheet can be particularly improved. As a result, for example, the adhesive layer can be uniformly foamed and cured even if the surface of the adherend has uneven temperature. The type of the heat radiating material is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a metal inactivating agent, deterioration of the adhesive layer due to an adherend (metal) on the adhesive sheet can be prevented. The type of the metal inactivating agent is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains an antioxidant, it is possible to prevent oxidative deterioration of the adhesive sheet. The type of the antioxidant is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a flame retardant, the adhesive sheet can be imparted with flame retardancy. The type of flame retardant is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a water-repellent / oil-repellent agent, the adhesive sheet can be provided with waterproof / oil-proof properties. Specifically, for example, it is possible to prevent the adhesion of foreign substances containing water or oil during the manufacturing process of the adhesive sheet, and prevent the generation of defective products. The type of water-repellent / oil-repellent agent is not particularly limited, and a commercially available product may be used.

When the protective layer 3 contains a solvent-resistant resin, the adhesive sheet can be imparted with solvent resistance. The type of the solvent-resistant resin is not particularly limited, and a commercially available product may be used.

The thickness of the protective layer 3 is usually 0.01 to 30 μm, preferably 0.03 to 20 μm, and more preferably 0.05 to 15 μm.

[Adhesive sheet]
The adhesive sheet of the present invention is an adhesive sheet having the protective layer 3 described above, and more specifically, the adhesive layer 2 has an adhesive layer 2 on at least a part of one side or both sides of the base material 1. It is an adhesive sheet having a protective layer 3 on at least a part of the surface of the above. The adhesive sheet of the present invention does not require a release liner. However, for example, in the case of a double-sided adhesive sheet, a protective layer 3 may be provided on one adhesive layer, and a release liner may be provided on the other adhesive layer 2.

When the adhesive layer 2 contains a temperature-sensitive foaming agent, the adhesive sheet of the present invention has a thickness of preferably 10 to 1000 μm, more preferably 10 to 250 μm, and particularly preferably 20 to 200 μm before foaming and curing.

The method for producing the adhesive sheet of the present invention is not particularly limited. In the case of a single-sided adhesive sheet, it can be manufactured by forming an adhesive layer 2 on one surface of the base material 1 and then forming a protective layer 3 on the surface of the adhesive layer 2. The adhesive layer 2 can be formed by a conventionally known method such as a solution coating method, a melt coating method, a melt extrusion method, or a rolling method. The melt coating method can be performed without a solvent and does not require a solvent removing step, processing equipment, etc., and is therefore preferable in terms of productivity and economy. When the melt coating method is used, it is preferable that the epoxy resin contains a crystalline epoxy resin. In this case, by heating above the melting point of the crystalline epoxy resin, the melt viscosity of the epoxy resin can be lowered and the speed of the melt coating can be increased. As the protective layer 3, a known coating method may be appropriately used depending on the type of the material.

Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

<Expandable adhesive>
Each of the following components was mixed in an amount (part by mass) shown in Table 1 to obtain an expandable adhesive.

[Epoxy resin]
"EP1": Epoxy resin (semi-solid, dissolution viscosity of butyl carbitol 60% solution 220-300 mPa · s (25 ° C), epoxy equivalent 180 g / eq, novolak type, general type)
"EP2": Epoxy resin (liquid, viscosity 13,000 mPa · s, epoxy equivalent 188 g / eq, general-purpose epoxy resin)

[Elastomer]
"E": Linear polyester polyurethane (softening point 87 ° C., molecular weight 222300, hydroxyl group content 0.1%, adhesiveness, flexibility type)

[Curing agent / catalyst]
"T1": Phenol resin (softening point 110 ° C., hydroxyl group equivalent 97 g / eq, high heat resistance type)
"T2": 2-Phenyl-4,5-dihydroxymethylimidazole (manufactured by Shikoku Chemicals Corporation, trade name 2PHZ-PW, melting point 220 ° C., active region 141-153 ° C., starting region 153-168 ° C.)

[Temperature-sensitive foaming agent]
"H": Temperature-sensitive foaming agent (average particle size 15 μm, expansion start temperature 125 to 135 ° C, maximum expansion temperature 150 to 160 ° C)

[Heat resistant filler]
"J1": Magnesium oxide (average particle size 3 μm, thermal conductivity, heat resistance, electrical insulation type)
"J2": Magnesium silicate (average particle size 5 μm, thermal conductivity, heat resistance, electrical insulation type)

<Material for protective layer>
The following materials that make up each protective layer were prepared.

"Formulation 2": Antistatic agent (manufactured by Chukyo Oil and Fat, trade name S-495, Tg 55 ° C) 100 parts by mass

"Formulation 3": Hard coat agent (Made by Goo Chemical Co., Ltd., trade name Plus Coat Z-565, Tg 64 ° C, softening point 170-175 ° C) 100 parts by mass, dye (manufactured by Shachihata Inc., trade name Stamp Ink S-1) 1 part by mass

"Formulation 4": Hard coat agent (Made by Goo Chemical Co., Ltd., trade name Plus Coat Z-565, Tg 64 ° C, softening point 170-175 ° C) 100 parts by mass, dye (manufactured by Shachihata Inc., trade name Stamp Ink S-1) 1 part by mass

"Formulation 5": 100 parts by mass of hard coat agent (manufactured by Goo Chemical Co., Ltd., trade name Plus Coat Z-565, Tg 64 ° C, softening point 170-175 ° C)

"Formulation 6": Fluorine-based coating agent (manufactured by AGC Seimi Chemical, SF Coat (registered trademark) SWK-601) 100 parts by mass

"Formulation 7": Solvent resistant acrylic emulsion (Mitsui Chemicals, Bonlon (registered trademark) XHS-50, Tg 60 ° C.) 100 parts by mass

"Formulation 8": Heat dissipation material (3M, trade name Platelets 006) 100 parts by mass, linear polyester polyurethane (softening point 87 ° C., molecular weight 222300, hydroxyl group content 0.1%, adhesiveness, flexibility type) 50 parts by mass

"Mixing 9": Lubricant (manufactured by Chukyo Oil and Fat, trade name Resem P677, melting point 80 ° C) 100 parts by mass

"Formulation 10": Flame retardant (manufactured by Otsuka Chemical Co., Ltd., trade name SPB-100, melting point 110 ° C.) 100 parts by mass, linear polyester polyurethane (softening point 87 ° C., molecular weight 222300, hydroxyl group content 0.1%, adhesiveness, Flexible type) 50 parts by mass

<Examples 1 to 10>
The expandable adhesive of Formulation 1 was applied to both sides of the substrate (PPS resin, manufactured by Toray Industries, Inc., Toraya (registered trademark) # 100-3030, 75 μm) so that the thickness after drying would be 50 μm each, and then 90 ° C. The solvent was removed by drying in 5 minutes to form an expansive adhesive layer. On the surface of this expandable adhesive layer, each protective layer having the composition and thickness shown in Tables 2 and 3 was formed, and the adhesive sheets of Examples 1 to 10 were obtained.

<Comparative Example 1>
An adhesive sheet was obtained in the same manner as in Example 1 except that the protective layer was not formed.

The adhesive sheets of Examples 1 to 10 and Comparative Example 1 were evaluated according to the following methods. The results are shown in Tables 2-5.

[Thickness of protective layer]
The thickness of the protective layer of the adhesive sheet before foaming was obtained by subtracting the thickness of the adhesive sheet without the protective layer from the thickness of the adhesive sheet with the protective layer. Each thickness was measured by a test method using a thickness gauge according to JIS Z 0237 "Adhesive Tape / Adhesive Sheet Test Method".

[tack]
Tuck sensually tested the presence or absence of stickiness when the thumb was pressed against the surface of the sheet with a slight force and peeled off in a very short time, and the presence or absence of stickiness was determined.

[Foreign matter adhesion]
After sprinkling 0.1 g of sea sand of 20 to 30 mesh manufactured by Wako Pure Chemical Industries, Ltd. on the surface of the sheet in an atmosphere of 40 ° C, the sheet was inverted 180 ° so that the side sprinkled with sea sand faced downward. .. Then, the surface of the sheet was visually observed and evaluated according to the following criteria.
"○": No sea sand adhered.
"Δ": 4 or less grains of sea sand adhered.
"X": 5 or more grains of sea sand adhered.

[Adhesiveness]
The shearing adhesive force of the foamed adhesive sheet as shown in FIG. 2 was measured according to the tensile shear adhesive force test method described in JIS Z 1541 "Ultra-strong double-sided adhesive tape". As the adherend, an SPCC plate (manufactured by Nissin Steel Co., Ltd., trade name SPCC-SB NCB, 1.0 mm thickness, 12 × 100 mm) was used. The sample attachment area was 10 × 10 mm, the foaming and curing conditions were 180 ° C. for 10 minutes, and the tensile speed was 200 mm / min. First, as shown in FIG. 2A, the adhesive sheet 4 before foaming was placed on the SPCC plate 5, and another SPCC plate 5 was further placed via two metal feeler gauges (0.300 mm) 6. Next, as shown in FIG. 2B, the adhesive sheet 4 was foamed and cured, and a tensile shear adhesive force test (23 ° C.) was performed on the foamed adhesive sheet 4.

[Surface resistance]
The surface resistance (Ω) of the adhesive sheet before foaming was measured according to JIS K6911 “General test method for thermosetting plastics”.

[Visual identification]
The front and back of the adhesive sheet before foaming were visually observed and evaluated according to the following criteria.
"○": The front and back could be distinguished.
"X": The front and back could not be distinguished.

[Pencil hardness]
The pencil hardness of the adhesive sheet before foaming was measured according to JIS K5600 "General paint test method".

[Contact angle]
The contact angle of the adhesive sheet before foaming was measured according to JIS R3257 “Test method for wetting property of substrate glass surface”. As the contact angle of water, industrial purified water A300 manufactured by AS ONE Corporation was used, and as the contact angle of oil, Toyota genuine auto fluid WS (ATF) was used.

[Stainless adhesion]
The shearing adhesive strength of the ATF-contaminated pre-foamed adhesive sheet was measured by the same procedure as the method for evaluating the adhesiveness, and the ratio was calculated when the non-contaminated adhesive sheet was taken as 100%. The contaminated adhesive sheet was obtained by immersing the adhesive sheet in ATF for 1 second and then sandwiching the sheet with a dry paper cloth to absorb excess ATF on the sheet surface.

[Solvent resistance]
The sheet surface was rubbed three times with a cotton wool impregnated with toluene at a pressure of 0.1 MPa for three round trips, and evaluated according to the following criteria.
"○": No surface roughness was visually recognized.
"Δ": Whitened but did not elute.
"X": The adhesive layer was eluted on the cotton wool.

[Thermal conductivity]
The thermal conductivity of the adhesive sheet after foaming was measured in the thin film measurement mode using a rapid thermal conductivity meter manufactured by Kyoto Denshi Kogyo. Specifically, three types of reference blocks with known thermal conductivity are placed on an aluminum plate (thickness 10 mm, 250 x 350 mm), and a measurement test piece (45 x 100 mm) is placed on the block. A sensor probe for measuring thermal conductivity (trade name PD-11, 40 × 97 mm, 820 g) equipped with a heater wire and a thermocouple was placed on the sensor probe (trade name: PD-11, 40 × 97 mm, 820 g), and the measurement was started. As the reference block, foamed polyethylene (thermal conductivity 0.0347 W / mK), silicone rubber (thermal conductivity 0.236 W / mK), and quartz glass (thermal conductivity 1.416) were used.

[Stiction coefficient]
The static friction coefficient of the adhesive sheet before foaming was measured according to JIS K7125 “Plastic-Film and Sheet-Friction Coefficient Test Method”.

[Flame retardance]
The sample size adhesive sheet used in the UL94V test was foamed and cured in a constant temperature bath, and the test was performed and evaluated according to the following criteria.
"○": Passed the UL94V test under the test conditions of V0.
"Δ": A part of the sample did not burn and remained after two flame contact with the flame contact time of the UL94V test set to 2 seconds.
"X": All burned.

[IR measurement]
Reflection IR measurements were performed on the surface compositions of the protective layer (before foaming) of the adhesive sheet of Example 6 and the adhesive layer (before foaming) of the adhesive sheet of Comparative Example 1. FIG. 3 is a graph showing the result. As is clear from this result, the absorption peak derived from epoxy is present on the surface of the adhesive layer of the adhesive sheet of Comparative Example 1, but the peak is not present on the surface of the protective layer of the adhesive sheet of Example 6. Therefore, the adhesive sheet of Example 6 does not cause skin damage due to the epoxy resin component.

The adhesive sheet of the present invention can protect the adhesive surface without using a release liner, and does not cause blocking or skin damage. Further, the adhesive sheet can be provided with various functions without impairing the characteristics of the adhesive layer. Therefore, it is useful for various applications in a wide range of fields such as electrical and electronic fields, automobile-related fields, and civil engineering and construction fields.

1 Base material 2 Adhesive layer 3 Protective layer 3a Protective layer 3b Protective layer 4 Adhesive sheet 5 SPCC plate 6 Metal feeler gauge

Claims (4)

An adhesive sheet having an adhesive layer on at least a part of one side or both sides of a base material.
The adhesive layer is a thermosetting foamable epoxy adhesive layer containing a polyfunctional epoxy resin and an epoxy resin other than the polyfunctional epoxy resin.
An adhesive sheet comprising a heat-meltable protective layer on at least a part of the surface of the adhesive layer, wherein the protective layer contains an antistatic agent, a lubricant, or a metal deactivating agent. The adhesive sheet according to claim 1, wherein the thickness of the adhesive layer is 2 to 300 μm. The adhesive sheet according to claim 1, wherein the adhesive layer further contains a curing agent and a curing catalyst. The adhesive sheet according to claim 1, wherein the heat-meltable protective layer flows, decomposes or sublimates by heating when the adhesive sheet is adhered.

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