TWI694130B - Adhesive sheet and electronic equipment - Google Patents

Abstract

The problem to be solved by the present invention is to provide an adhesive sheet having a level of impact resistance that does not cause the foam to break and peel off from the adherend even if a force (impact) in the shear direction is applied. And it has good followability to the height difference part of the adherend. The present invention relates to an adhesive sheet having an adhesive layer on one or both sides of a foam body having an apparent density in the range of 0.40 g/cm ³ to 0.59 g/cm ³ directly or intervening with other layers; : The foam is cut in the width direction (cut surface), and the number of bubbles in the range of thickness x distance in the width direction (1.5 mm) is 20 or more.

Description

Adhesive sheet and electronic equipment

The present invention relates to an adhesive sheet that can be used for manufacturing applications including various items such as electronic equipment.

Adhesive sheets using a foam as a base material can be widely used, for example, to fix two or more frames, rechargeable batteries, and circuit boards that constitute an electronic device.

The above-mentioned adhesive sheet is known, for example, using the following foam sheet as a base material (for example, refer to Patent Document 1.). This foam sheet contains a polyolefin resin in a ratio of 90:10 to 60:40. A resin foam formed by foaming a resin composition of a non-compatible resin with respect to a polyolefin-based resin, characterized by an island of sea-island structure formed by the polyolefin-based resin and the non-compatible resin The average long diameter of the portion is 1 μm or more.

As the information display portion of the portable electronic terminal is becoming larger and the thickness of the portable electronic terminal is being developed, the adhesive sheet used in the manufacture of such a thin and narrow-width adhesive sheet is required. However, in general, the thin and narrow adhesive sheet is not satisfactory in terms of the followability of the height difference part of the adherend, and when the portable electronic terminal is dropped, etc., an impact occurs, sometimes It is easy to cause peeling and the like due to cracking of the foam, etc., and is not satisfactory in terms of impact resistance. Conventionally, the pressure-sensitive adhesive sheet has been required to have a level of impact resistance that can prevent peeling due to cracking of the foam or the like when subjected to an impact in its surface direction (thickness direction). However, in recent years, the application of adhesive sheets is expanding, and it is required to have a level of impact resistance (shear resistance to shear) that can prevent peeling due to cracking of the foam even when the above impact is applied in the shear direction of the adhesive sheet. (Shock resistance to impact in the tangential direction). In addition, there is generally a trade-off relationship between the followability of the height difference part of the adherend and the impact resistance to the impact against the shearing direction. So far, there has not been found a balance between the followability and the shearing resistance. Shock resistant adhesive sheet with impact in the tangential direction. 【Patent Literature】

[Patent Document 1] Japanese Patent Laid-Open No. 2008-274073

[Problems to be solved by the invention]

The problem to be solved by the present invention is to provide an adhesive sheet having a level of impact resistance that can prevent peeling of an adherend due to breakage of the foam or the like even when a force (impact) in the shear direction is applied It has good followability to the height difference of the adherend. [Means to solve the problem]

The inventors of the present invention, in order to balance the impact resistance against the impact in the shear direction and the followability, found that a range of specific apparent density was selected, and the range was selected from the range of thickness x width direction distance (1.5 mm) and thickness x flow direction The number of bubbles in the distance (1.5mm) range can be solved by combining these conditions.

That is, the present invention relates to an adhesive sheet having an adhesive layer on one side or both sides of a foam body having an apparent density in the range of 0.40 g/cm ³ to 0.59 g/cm ³ , characterized by: In the surface cut in the width direction of the foam, the number of bubbles existing in the range of thickness x distance in the width direction (1.5 mm) is 20 or more, and the surface of the foam cut in the flow direction, The number of bubbles in the range of thickness × distance in flow direction (1.5 mm) is more than 20. [Effect of invention]

The adhesive sheet of the present invention does not cause peeling of the adherend due to cracking of the foam even when a force (impact) in the shear direction is applied, and has good followability to the level difference of the adherend . The adhesive sheet can be used in various applications including the manufacture of electronic devices such as portable electronic terminals, the fixing of automobile parts, and the fixing of interior and exterior of buildings.

The adhesive sheet of the present invention has an adhesive layer on one side or both sides of the foam with an apparent density ranging from 0.40 g/cm ³ to 0.59 g/cm ³ , and is characterized in that the foam has a width In the surface cut in the direction, the number of bubbles in the range of thickness × distance in the width direction (1.5mm) is more than 20, and the surface of the foam cut in the flow direction, thickness × distance in the flow direction The number of bubbles in the range of (1.5mm) is more than 20.

The adhesive sheet of the present invention uses a foam having an apparent density in the range of 0.40 g/cm ³ to 0.59 g/cm ³ for the material constituting its base material (core). By using a foam having a density in this range, even if a force (impact) in the shear direction is applied, it does not cause peeling of the adherend due to breakage of the foam, etc. The height difference part has an adhesive sheet with good followability. For this foam, it is preferable to use a foam having an apparent density in the range of 0.42 g/cm ³ to 0.58 g/cm ³ , and a range having 0.45 g/cm ³ to 0.56 g/cm ³ is used. Those with apparent density will not peel off the adherend due to cracking of the foam even when the force (impact) in the shear direction is applied, and it has a good effect on the level difference of the adherend The aspect of the follow-up adhesive sheet is better. In addition, the apparent density refers to the apparent density measured in accordance with JISK6767, which refers to preparing a 15cm ³ portion of a foam that has been cut into a rectangular shape of 4cm x 5cm, measuring its mass, and calculating it based on the mass and the volume Value.

In addition, as for the above-mentioned foam, the number of bubbles existing in the range of arbitrary thickness x width direction distance (1.5 mm) in the surface cut in the width direction (cut surface) is 20 or more. . For the foam, the number of the bubbles is preferably 25 or more, more preferably 30 to 150, more preferably 30 to 120, especially 30 to 50 Good, when using 30 to 45, it will not cause the foam to break and peel off from the adherend even when the shearing force (impact) is applied, and it has good follow-up to the height difference The aspect of the sexual adhesive sheet is particularly good. In addition, the thickness refers to the thickness of the foam. Therefore, the number of the bubbles may be a thickness in a suitable range described later (preferably 50 μm to 400 μm, more preferably 100 μm to 300 μm, more preferably 110 μm to 250 μm) × flow direction distance (1.5 mm) or width direction distance The number of bubbles in the range of (1.5mm). In addition, as for the above foam, the number of bubbles existing in the range of arbitrary thickness x flow direction distance (1.5 mm) in the surface cut in the flow direction (cut surface) is 20 or more . For the foam, the number of the bubbles is preferably 30 to 150, more preferably 30 to 120, more preferably 30 to 50, and 30 to 45 If the force (shock) in the shearing direction is applied, it will not cause the peeling of the adherend due to the breakage of the foam, etc., and it has good followability for the height difference of the adherend The adhesive sheet is particularly good. In addition, the number of bubbles in the range of thickness x flow direction distance (1.5 mm) is more than 20 foams, and the thickness x width direction distance (1.5 mm) does not necessarily have more than 20 bubbles . In the present invention, not only the number of bubbles existing in the range of the thickness of the foam × the distance in the flow direction (1.5 mm) is more than 20, but also the number of bubbles existing in the range of the thickness × the distance in the width direction (1.5 mm). If the number is more than 20, even if the force (impact) in the shear direction is applied, it will not cause the peeling of the adherend due to the breakage of the foam, etc., and it has the height difference part of the adherend The adhesive sheet with good followability is suitable. The number of bubbles existing in the range of the thickness × width direction distance (1.5 mm) and thickness × flow direction distance (1.5 mm) of the foam refers to the value measured according to the following procedure. First, the foam whose thickness has been measured is cut into 2 cm in the width direction and 2 cm in the flow direction. Then, the cut surface of the foam was magnified by a digital microscope (trade name "KH-7700", manufactured by HiROX Corporation) to 200 times, and the surface (cut surface) cut in the width direction and the flow direction was photographed. Then, the number of bubbles in the range of arbitrary thickness x width direction distance (1.5 mm) in the cut surface of the foam in the width direction was calculated. In addition, the number of bubbles in the range of the thickness of the foam × the distance in the flow direction (1.5 mm) in the cut surface of the foam in the cutting direction was calculated.

For the foam, the ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction (B) is preferably in the range of 0.3 to 4, more preferably in the range of 1 to 4, more preferably 1 The range of ～3 is more preferable. If the range of 2-3 is used, the foam will not break or peel off from the adherend even if the force (impact) in the shear direction is applied. The adhesive sheet having a good followability at the difference is particularly preferable.

For the foam, the ratio of the average bubble diameter in the flow direction to the average bubble diameter in the thickness direction (A) is preferably in the range of 0.3 to 4, preferably in the range of 1 to 4, more preferably 1 The range of ～3 is more preferable. If the range of 2-3 is used, even if a force (impact) in the shearing direction is applied, it will not cause peeling of the adherend due to breakage of the foam, etc. In addition, it is particularly preferable in terms of an adhesive sheet that has good followability for the level difference portion.

For the above-mentioned foam, the lower limit of the average bubble diameter in the flow direction is preferably 20 μm or more, more preferably 30 μm or more, more preferably 80 μm or more, more preferably 90 μm or more, and the upper limit is preferably 160 μm The following is preferably 140 μm or less, and more preferably 120 μm or less. As for the foam, the lower limit of the average bubble diameter in the width direction is preferably 20 μm or more, more preferably 30 μm or more, more preferably 80 μm or more, particularly preferably 90 μm or more, and the upper limit is preferably used It is 160 μm or less, more preferably 140 μm or less, and particularly preferably 120 μm or less. By using a foam having an average bubble diameter in the above range, even if a force (impact) in the shearing direction is applied, it does not cause peeling of the adherend due to cracking of the foam, etc. The adhesive sheet having a good followability at the difference is particularly preferable.

If the foam has an independent bubble structure, it is preferable to effectively prevent water seepage from the cut surface of the foam.

In addition, the average bubble diameter in the width direction, flow direction, and thickness direction of the foam refers to a value measured according to the following procedure. First, the foam was cut into 2 cm in the width direction and 2 cm in the flow direction, thereby preparing 10 test pieces with a width of 2 cm and a flow direction of 2 cm. Then, the cut surface of the test piece was enlarged to 200 times using a digital microscope (trade name "KH-7700", manufactured by HiROX Corporation), and the cut surface in the width direction and the flow direction was photographed. Then, the diameter of all bubbles existing in the range of thickness x distance in the flow direction (1.5 mm) in the cut surface of the test piece in the flow direction was measured. The measurement is performed at any 10 places in the cut surface of the test piece, and the value obtained by averaging the measured diameter is taken as the average bubble diameter in the flow direction of the foam. The average bubble diameter in the width direction of the foam is the diameter of all the bubbles existing in the range of thickness x width direction distance (1.5 mm) in the cut surface of the test piece in the width direction. The measurement is performed at any 10 places in the cut surface of the test piece, and the value obtained by averaging the measured diameter is taken as the average bubble diameter in the width direction of the foam.

For the above-mentioned foam, a thickness in the range of 50 μm to 400 μm is preferred, a range in the range of 100 μm to 300 μm is more preferred, and a range in the range of 110 μm to 250 μm can be obtained even if it can contribute to, for example The thinness of the portable electronic terminal does not cause the peeling of the adherend due to the breakage of the foam when the force (impact) in the shear direction is applied, and it has more Adhesive sheets with excellent followability are preferred.

As for the above-mentioned foam, it is more preferable to use an interlayer strength of 20 N/cm or more, more preferably 30 N/cm to 150 N/cm, more preferably 35 N/cm to 100 N/cm, and 35 N /cm～60N/cm is especially good.

By using a foam having an interlayer strength in the above range, peeling of the adherend due to breakage of the foam or the like when the force (impact) in the shear direction is applied can be obtained, and The height difference part of the body has an adhesive sheet with good followability. In addition, when manufacturing an electronic device or the like using the adhesive sheet, in order to increase the productivity, parts fixed by the adhesive sheet may be separated from the electronic device or the like. At this time, the adhesive sheet obtained by using the foam having the above-mentioned interlayer strength does not easily cause the interlayer cracking of the foam, and even if the interlayer cracking is caused, the remaining portion of the adhesive sheet (foam Part of the body, etc.) is removed from the surface of the part.

The interlayer strength refers to the value measured by the following method. After bonding an adhesive layer with a thickness of 50 μm on both sides of the foam body (not peeled from the adherend and the foam body during the following high-speed peel test), it was cured at 40°C for 48 hours. Two-sided adhesive sheet for measuring the strength between layers. Then, a single-sided adhesive sheet with a width of 1 cm and a length of 15 cm with a 25 μm thick polyester film as the backing on one side of the adhesive surface was attached to a thickness of 50 μm, a width of 3 cm, and a length at 23° C. and 50% RH. The surface of the 20 cm polyester film was attached by pressing back and forth once with a 2 kg roller, and then allowed to stand for 48 hours in an environment of 60°C, and then for 24 hours in an environment of 23°C. Then, at 23° C. and 50% RH, the surface of the polyester film with a thickness of 50 μm was fixed to a jig of a high-speed peel tester, and the thickness of 25 μm was collected at a tensile speed of 15 m/min. The ester film was stretched in the direction of 90 degrees, and the maximum strength measured when the foam was torn was taken as the interlayer strength.

For the above-mentioned foams, those having a 25% compressive strength of 380 kPa or more are preferred, those using 380 kPa to 1300 kPa are preferred, those using 450 kPa to 1100 kPa are preferred, and those using 500 kPa to 1000 kPa provide An adherend having an uneven shape and a rough surface has excellent followability, and when it is used as a base material of an adhesive sheet, an adhesive sheet having excellent followability for the adherend is better.

In addition, 25% compression strength means the value measured based on JISK6767. Specifically, the foam cut into a square of 25 mm was superimposed to a thickness of about 10 mm, sandwiched between stainless steel plates, and compressed at a rate of 10 mm/min by measuring about 2.5 mm (original thickness) at 23° C. 25% of the weight).

For the foam, the tensile elastic modulus in the flow direction and the width direction is preferably 200 N/cm ² or more, and more preferably 300 N/cm ² to 1800 N/cm ² . The tensile modulus of the flow direction and the width direction, the lines of low tensile modulus of ^{500N / cm 2 ~ 1400N / cm} 2 ^{Preferably, 600N / cm 2 ~ 1300N /} cm 2 more preferably. Moreover, the tensile modulus of the flow direction and the width direction, the tensile modulus of elasticity based high value of ^{700N / cm 2 ~ 1800N / cm} 2 ^{Preferably, 800N / cm 2 ~ 1600N /} cm 2 more preferably.

In addition, the tensile modulus of elasticity in the flow direction and the width direction of the foam refers to a value measured in accordance with JISK6767. Specifically, it is the maximum strength measured using a TENSILON tensile tester at 23°C and 50% RH in a foam with a length of 2 cm and a width of 1 cm, under a measurement condition of a tensile speed of 300 mm/min. In addition, regarding the tensile elongation of the foam when it is cut in a tensile test, the tensile elongation in the flow direction is preferably 200% to 1500%, more preferably 400% to 1000%, and 450% to 800 % Is better. The foam having a tensile modulus of elasticity and a tensile elongation in the above range is less likely to cause interlayer breakage, tearing, etc., and can be suppressed from workability and sticking that may occur with the adhesive sheet obtained by using a general foam Attach a reduction in workability. In addition, the adhesive sheet obtained by using the foam is easily removed from the surface of the adherend.

The foam can be obtained by using at least one selected from the group consisting of polyolefins, polyurethanes, and acrylic polymers. Specifically, polyethylene, polypropylene, and ethylene-propylene can be used. Polyolefin-based foams obtained from copolymers, ethylene-vinyl acetate copolymers, etc.; polyurethane-based foams; rubber-based foams obtained from acrylic rubbers, other elastomers, etc. Among them, the polyolefin-based foam is used in consideration of the excellent followability of the surface unevenness of the adherend, the impact resistance in the direction of the surface or the shear direction, even when the foam is thin. The bubble is better.

The polyolefin-based foam can be obtained by using a polyolefin-based resin. Among them, when the polyolefin-based foam is obtained by using a polyethylene-based resin, it is easy to manufacture with a uniform thickness, and it is preferable to impart moderate flexibility.

For the above-mentioned polyethylene-based resin, for example, linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, etc., or More than two uses. Examples of the olefin constituting the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, and 1-octene. Ene etc. The polyethylene-based resin is preferably contained in an amount of 40% by mass or more, more preferably in an amount of 50% by mass or more, and particularly preferably in an amount of 60% by mass, relative to the total amount of polyolefin-based resin used in the production of the foam. Contains more than 80% by mass.

The above-mentioned polyethylene-based resin is preferably obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst to obtain a polyolefin-based foam that is relatively uniformly stretchable and whose thickness is generally uniform.

The above-mentioned polyethylene-based resin can be adhered to the stepped portion without causing peeling of the adherend due to breakage of the foam or the like when a force (impact) in the shear direction is applied. For the sheet, elastomers such as styrene-based thermoplastic elastomer, olefin-based thermoplastic elastomer, ethylene·α-olefin-based thermoplastic elastomer can be used.

The manufacturing method of the above foam is not particularly limited, for example, a method including the following steps: polyolefin containing "polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst" Resin, thermally decomposable foaming agent, foaming aid, and coloring agent” as needed. The foamable polyolefin-based resin composition is supplied to the extruder, melt-kneaded, and Extruded in a sheet shape to produce a foamable polyolefin-based resin sheet; if necessary, crosslink the foamable polyolefin-based resin sheet; and foam the foamable polyolefin-based resin sheet. The foam obtained by this method can also be melted or softened if necessary, and extend in either or both of its flow direction and width direction. This extension can be carried out as many times as necessary.

As for the method for producing the above-mentioned foamable polyolefin-based resin sheet, the polyolefin-based resin constituting the foamable polyolefin-based resin composition, a thermally decomposable foaming agent, a foaming aid, a colorant, and Other arbitrary components are provided to single-shaft extruders, double-shaft extruders and other extruders, and are melted and kneaded at a temperature that does not reach the decomposition temperature of the thermally decomposable foaming agent. Manufactured by extrusion.

The step of crosslinking the foamable polyolefin-based resin sheet obtained by the above method, for example, a method of irradiating the foamable polyolefin-based resin sheet with ionizing radiation; preparing a foamability containing an organic peroxide The polyolefin-based resin composition is heated by a method of heating the foamable polyolefin-based resin sheet obtained by using the foamable polyolefin-based resin composition.

Examples of the ionizing radiation include electron beams, α rays, β rays, and γ rays. The amount of ionizing radiation can be appropriately adjusted so that the gel fraction of the polyolefin-based resin foam is in the above-mentioned preferred range, preferably in the range of 5 to 200 kGy. In addition, it is preferable to irradiate ionizing radiation from both sides of the foamed polyolefin-based resin sheet in consideration of easily obtaining a uniform foamed state, and it is more preferable to irradiate the same amount of radiation on both sides.

Organic peroxides include, for example, 1,1-bis(tertiary butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis(tertiary butylperoxy) Cyclohexane, 2,2-bis(tertiary butylperoxy)octane, 4,4-bis(tertiary butylperoxy) valerate n-butyl, di-tertiary butyl peroxide , Tertiary butyl cumyl peroxide, dicumyl peroxide, α,α'-bis(tertiary butylperoxy-m-isopropyl)benzene, 2,5-dimethyl Yl-2,5-di(tertiary butylperoxy)hexane, 2,5-dimethyl-2,5-di(tertiary butylperoxy)hex-3-yne, benzene peroxide Formamide, cumyl peroxyneodecanoate, tertiary butyl peroxide benzoate, 2,5-dimethyl-2,5-bis(benzylperoxy) hexane, isoperoxide Tertiary butyl carbonate, tertiary butyl carbonate, etc., these can be used alone or in combination of two or more.

The amount of the organic peroxide added is preferably 0.01 to 5 parts by mass relative to 100 parts by mass of the polyolefin resin, and more preferably 0.1 to 3 parts by mass.

In addition, the step of foaming the expandable polyolefin-based resin sheet can be performed by, for example, a method of heating by hot air, a method of heating by infrared rays, a method of salt bath, a method of oil bath, etc. . Among them, the method of heating by hot air and the method of heating by infrared rays are preferred.

When foaming the foamable polyolefin-based resin sheet, a foamable polyolefin-based resin sheet containing a thermally decomposable foaming agent can be used. The thermal decomposition type foaming agent can be appropriately determined according to the expansion ratio of the polyolefin-based resin foam, and it is preferably used in the range of 0.5 to 40 parts by mass relative to 100 parts by mass of the polyolefin-based resin. , More preferably used in the range of 1 part by mass to 30 parts by mass, preferably used in the range of 1 part by mass to 20 parts by mass, more preferably used in the range of 1 part by mass to 10 parts by mass, and used by 1 part by mass to 5 parts by mass The range of serving is better.

As the thermal decomposition type foaming agent, the decomposition temperature is preferably higher than the melting temperature of the polyolefin resin. The decomposition temperature is more preferably 160°C to 270°C, and particularly preferably 160°C to 220°C.

Examples of thermally decomposable foaming agents include azo compounds such as azodimethylamide, nitroso compounds such as N,N'-dinitrosopentamethylenetetramine, and 4,4'-oxobis(benzene Sulfonamide) and other organic foaming agents such as hydrazine compounds; carbonates such as sodium bicarbonate and ammonium carbonate; inorganic foams such as ammonium nitrite, sodium borohydride and anhydrous sodium citrate; azo compounds and nitroso The base compound is preferred, and azodimethanamide and N,N'-dinitrosopentamethylenetetramine are more preferred.

For the thermal decomposition type foaming agent, it is preferable to use a powdery substance, it is more preferable to use a 50% average particle diameter (median diameter) of 50 μm or less, it is more preferable to use 40 μm or less, and it is 30 μm or less , The number of bubbles existing in the range of manufacturing thickness x width direction distance (1.5mm) is 20, and the surface of the foam cut in the flow direction, thickness x flow direction distance (1.5mm) It is preferable that the number of bubbles existing in the foam is 20 foams.

The above stretching step may be performed on the foam obtained by the above method, or may be performed in parallel with the step of foaming the foamable polyolefin-based resin sheet. This stretching step can be continued while maintaining the molten state in the foaming step. After the foaming step, the cooling step can be performed first, and the foam can be heated again. As for the above-mentioned foam, by using the foam that has undergone the stretching step, a foam having the above-mentioned specific average cell diameter ratios (A) and (B) can be obtained, and by using the foam It is possible to obtain an adhesive sheet that is less likely to cause cracking due to impact, and has good followability for the stepped portion.

Here, the molten state of the foam refers to a state heated to a melting point or higher of resins such as polyolefin resins constituting the foam. In addition, the softening of the foam refers to a state of heating to a temperature above the softening point of the resin such as a polyolefin resin constituting the foam and not reaching the melting point.

The polyolefin-based foam obtained by the above-mentioned method may be one having a cross-linked structure.

The polyolefin-based foam having a cross-linked structure is preferably a foam having a cross-linking degree of 10% by mass to 80% by mass, more preferably 15% by mass to 75% by mass, and 20% by mass to 70% by mass If it is mass %, it is possible to obtain an adhesive sheet that is not likely to cause peeling of the adherend due to cracking of the foam when the force (impact) in the shear direction is applied, and has an adhesive sheet that has good followability for the height difference portion. good.

In addition, the degree of crosslinking is calculated based on the ratio of insolubles when the polyolefin-based foam is immersed in xylene at 105° C. for 24 hours.

As the foam of the present invention, for the purpose of imparting designability, light-shielding property, concealing property, light reflectivity, and light resistance, a colored one can be used. Coloring agents that can be used for the coloring, for example, black coloring agents can be used, specifically, carbon black, graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon , Ferrite, magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complex, complex oxide-based black pigment, anthraquinone-based organic black pigment, etc. Among them, it is preferable to use carbon black as a colorant in terms of maintenance cost, availability, insulation, and heat resistance.

As the coloring agent, a white coloring agent can be used, specifically, titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, yttrium oxide, carbonic acid Magnesium, calcium carbonate, barium carbonate, zinc carbonate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, aluminum silicate, calcium silicate, barium sulfate, calcium sulfate, barium stearate, zinc white, talc , Silica, alumina, clay, kaolin, titanium phosphate, mica, gypsum, white carbon black, diatomaceous earth, bentonite, zinc barium white, zeolite, sericite and other inorganic white colorants; silicone resin particles, acrylic acid Organic white colorants such as resin particles, urethane resin particles, melamine resin particles, etc. Among them, it is preferable to use aluminum oxide and zinc oxide as the colorant in consideration of maintenance cost, availability, color tone, and heat resistance.

In addition, the foam of the present invention may contain foaming aids such as plasticizers, antioxidants, and zinc oxide, bubble core regulators, heat stabilizers, and metal deactivators if necessary, as long as their physical properties are not impaired. , Flame retardants such as aluminum hydroxide or magnesium hydroxide, antistatic agents, fillers such as air balloons, beads, metal powders, metal compounds made of glass or plastic; additives such as conductive fillers and thermally conductive fillers . As the foam, in consideration of maintaining appropriate followability and cushioning properties, it is preferable to contain the additive in an amount of 0.1% by mass to 10% by mass, preferably 1% by mass to 7% by mass, relative to resins such as polyolefin resins. .

When manufacturing foams containing additives such as the above-mentioned colorants, thermally decomposable foaming agents, foaming aids, etc., in consideration of preventing color unevenness, local excessive foaming, insufficient foaming, etc. If the thermoplastic resin with high compatibility of the polyolefin-based resin composition and the additive are mixed and master batched, the number of bubbles existing in the range of manufacturing thickness x distance in the width direction (1.5 mm) is 20 or more And, in the surface of the foam cut in the flow direction, it is preferable that the number of bubbles existing in the range of thickness×flow direction distance (1.5 mm) is 20 or more.

As the above-mentioned foam, for the purpose of improving the adhesiveness with the adhesive layer or other layers, it is preferable to use a surface having a wetting index of 36 mN/m or more as measured by a wetting reagent. A surface of m or more is more preferable, and a surface having a surface of 48 mN/m or more is particularly preferable. Examples of methods for adjusting the wettability index of the foam surface to the above range include surface treatment methods such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone treatment, ultraviolet treatment, and coating of an easy-to-adhere treatment agent.

The adhesive sheet of the present invention may include a structure in which the adhesive layer is directly laminated on one or both sides of the foam, or an adhesive layer may be interposed between other layers on one or both sides of the foam. Layered structure.

Adhesives that can be used in the formation of the above adhesive layer, for example, acrylic adhesives, urethane adhesives, synthetic rubber adhesives, natural rubber adhesives, silicone adhesives, etc. can be used An acrylic polymer containing a polymer containing a monomer component of a (meth)acrylic monomer, and an acrylic adhesive such as a tackifying resin and a crosslinking agent as necessary are preferred.

The (meth)acrylic monomer that can be used in the production of the acrylic polymer described above, for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, (method Group) Isobutyl acrylate, tertiary butyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, isonon (meth)acrylate (Meth)acrylates such as esters, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and the like having an alkyl group having 1 to 12 carbon atoms. Among them, for the (meth)acrylic monomer, it is preferred to use a (meth)acrylate having an alkyl group having 4 to 12 carbon atoms, and to use a (meth)acrylic acid having an alkyl group having 4 to 8 carbon atoms. The base) acrylate is more preferable, and when either or both of n-butyl acrylate and 2-ethylhexyl acrylate are used, it is particularly preferable in terms of having both excellent adhesion and excellent followability.

The (meth)acrylate having an alkyl group having 1 to 12 carbon atoms is preferably used in an amount of 60% by mass or more relative to the total amount of monomers used in the production of the acrylic polymer, and is 80% by mass to The range of 98.5 mass% is more preferably used, and when it is used in the range of 90 mass% to 98.5 mass%, it is particularly preferable in terms of excellent adhesion and excellent followability.

In addition, when manufacturing the acrylic polymer, a highly polar ethylenic monomer can be used as a monomer. As the highly polar ethylenic monomer, one kind or two or more kinds of ethylenic monomer having a hydroxyl group, an ethylenic monomer having a carboxyl group, and an ethylenic monomer having an amide group can be used.

As the monomer having a hydroxyl group, for example, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxy (meth)acrylate (Meth) acrylate having a hydroxyl group such as hexyl ester.

As the vinyl monomer having a carboxyl group, for example, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth)acrylic acid dimer, crotonic acid, ethylene oxide modified succinic acid acrylate, etc. can be used It is better to use acrylic.

啉、丙烯醯胺、N,N－二甲基丙烯醯胺等。As the monomer having an amide group, for example, N-vinylpyrrolidone, N-vinylcaprolactam, acrylamide can be used

Chloroline, acrylamide, N,N-dimethyl acrylamide, etc.

As the above-mentioned highly polar ethylenic monomer, in addition to the above-mentioned substances, vinyl acetate, ethylene oxide-modified succinic acrylate, 2-acrylamide-2-methylpropanesulfonic acid, and the like can be used.

The above-mentioned highly polar ethylenic monomer is preferably used in the range of 1.5% by mass to 20% by mass, and in the range of 1.5% by mass to 10% by mass relative to the total amount of monomers used in the production of the acrylic polymer. More preferably, when used in the range of 2% by mass to 8% by mass, it is particularly preferable in terms of taking into consideration both excellent adhesion and excellent followability.

When using a crosslinking agent described later as the adhesive, it is preferable to use an acrylic polymer containing a functional group that reacts with a functional group possessed by the crosslinking agent for the acrylic polymer. The functional group which this acrylic polymer may have is, for example, a hydroxyl group. This hydroxyl group can be introduced into an acrylic polymer by using an ethylene monomer having a hydroxyl group as the monomer. The vinyl monomer having a hydroxyl group is preferably used in the range of 0.01% by mass to 1.0% by mass, and in the range of 0.03% by mass to 0.3% by mass relative to the total amount of monomers used in the production of the acrylic polymer. Better to use.

The acrylic polymer can be produced by polymerizing the above monomers by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, etc. If the solution polymerization method is used, the production of acrylic polymer can be improved The efficiency aspect is better.

The above-mentioned solution polymerization method includes, for example, a method of mixing the above monomers, a polymerization initiator, and an organic solvent at a temperature of preferably 40° C. to 90° C., stirring, and performing radical polymerization.

As the polymerization initiator, for example, peroxides such as benzoyl peroxide or lauryl peroxide, azo-based thermal polymerization initiators such as azobisisobutyronitrile, acetophenone-based photopolymerization initiators, and benzoin ether-based A photopolymerization initiator, a benzyl ketal-based photopolymerization initiator, an acetylphosphine oxide-based photopolymerization initiator, a benzoin-based photopolymerization initiator, a benzophenone-based photopolymerization initiator, and the like.

The acrylic polymer obtained by the above method may be in a state of being dissolved or dispersed in an organic solvent when produced by a solution polymerization method, for example.

The acrylic polymer preferably has a weight average molecular weight of 400,000 to 3 million, and preferably has a weight average molecular weight of 700,000 to 2.5 million. In addition, the weight average molecular weight refers to a value calculated by gel permeation chromatography (GPC) and converted with standard polystyrene. Specifically, the weight average molecular weight can be measured under the following conditions using a GPC device (HLC-8320GPC) manufactured by Tosoh Corporation. Sample concentration: 0.2% by mass (tetrahydrofuran solution) Sample injection volume: 100 μL Eluent: Tetrahydrofuran Flow rate: 1.0 mL/min Measurement temperature: 40°C Main column: TSKgel　GMHHR-H(20) 2 protection columns: TSKgel　HXL －H detector: weight average molecular weight of standard polystyrene of differential refractometer: 10,000～20 million (manufactured by TOSOH Corporation)

As the adhesive that can be used in the formation of the adhesive layer described above, it is preferable to use a tackifying resin in consideration of taking into consideration both the excellent adhesion to the adherend and the foam and the excellent followability. As the tackifying resin, for example, rosin-based tackifying resin, polymeric rosin-based tackifying resin, polymeric rosin ester-based tackifying resin, rosin phenol-based tackifying resin, stabilized rosin ester-based tackifying resin, disproportionated rosin ester-based tackifying resin Adhesive resin, hydrogenated rosin ester based tackifying resin, terpene based tackifying resin, terpene phenol based tackifying resin, petroleum resin based tackifying resin, (meth)acrylate resin based tackifying resin, etc. When an emulsion-type adhesive is used as the adhesive, an emulsion-type tackifying resin is also preferably used as the tackifying resin.

As for the above-mentioned tackifying resin, disproportionated rosin ester-based tackifying resin, polymeric rosin ester-based tackifying resin, rosin phenol-based tackifying resin, hydrogenated rosin ester-based tackifying resin, (meth)acrylate-based One or more of resin, terpene phenol resin and petroleum resin are preferably used.

The above-mentioned tackifying resin is preferably in the range of softening point 30°C to 180°C. When the range of 70°C to 140°C is used, it has both excellent adhesion and excellent adhesion to the adherend and foam substrate The aspect of followability is better. When using the (meth)acrylate tackifying resin, it is preferable to use a (meth)acrylate tackifying resin with a glass transition temperature of 30°C to 200°C, and more preferably 50°C to 160°C .

The tackifying resin is preferably used in the range of 5 parts by mass to 65 parts by mass with respect to 100 parts by mass of the acrylic polymer. When used in the range of 8 parts by mass to 55 parts by mass, the tackifying resin, The foam has better adhesion and excellent followability.

As the adhesive used in the formation of the above-mentioned adhesive layer, considering the formation of the adhesive layer that takes into account the excellent adhesion to the adherend and the foam and the excellent followability, the use of a crosslinking agent is preferable . As the cross-linking agent, for example, an isocyanate-based cross-linking agent, an epoxy-based cross-linking agent, a metal chelate-based cross-linking agent, an aziridine-based cross-linking agent and the like can be used. Among these, it is preferable to use either or both of an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent with high reactivity with acrylic polymers, and it is more preferable to use an isocyanate-based crosslinking agent. good.

As the isocyanate-based crosslinking agent, for example, toluene diisocyanate, 1,5-naphthalene diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane modification can be used Toluene diisocyanate and the like are preferably toluene diisocyanate and trimethylolpropane modified toluene diisocyanate.

The above-mentioned crosslinking agent is selected so that the gel fraction of the adhesive layer with respect to toluene becomes 70% by mass or less and used preferably, and the amount selected so that the gel fraction is 20% by mass to 60% by mass and used more If the gel fraction is selected to be 25% by mass to 55% by mass and used, in terms of obtaining an adhesive sheet that combines excellent adhesion to adherends and foam substrates and excellent followability Is particularly good.

In addition, the said gel fraction refers to the value measured by the method shown below. After the above-mentioned adhesive was applied to the release-treated surface of the release liner so that the thickness after drying was 50 μm, it was dried in an environment of 100° C. for 3 minutes, and then matured in an environment of 40° C. for 2 days to form Adhesive layer. The adhesive layer was cut into a square with a length of 50 mm and a width of 50 mm as a test piece. After measuring the mass (G1) of the test piece, the test piece was immersed in toluene for 24 hours in an environment of 23°C. After this immersion, the mixture of the test piece and toluene was filtered through a 300-mesh metal mesh to extract insoluble components in toluene. The insoluble component was dried in an environment of 110°C for 1 hour, and its mass (G2) was measured. The gel fraction is calculated from the above mass (G1) and mass (G2) according to the following formula. Gel fraction (mass %) = (G2/G1) × 100

For the above-mentioned adhesives, for example, fillers containing plasticizers, softeners, antioxidants, flame retardants, fiber/balloons made of glass or plastics, beads, metals, metal oxides, metal nitrides, etc.; pigments, dyes Such as coloring agent; leveling agent, viscosity increasing agent, waterproofing agent, defoaming agent and other additives.

The adhesive layer that can be formed using the adhesive described above preferably has a temperature at a peak value of the loss tangent (tanδ) at a frequency of 1 Hz of -40°C to 15°C. By making the peak value of the loss tangent of the adhesive layer into this range, it is easy to give good adhesion to the adherend at ordinary temperature. Especially when the drop impact resistance in a low-temperature environment is improved, it is preferably -35°C to 10°C, and particularly preferably -30°C to 6°C.

The loss tangent (tan δ) at a frequency of 1 Hz is determined by the storage elastic modulus (G′) and the loss elastic modulus (G”) obtained by the dynamic viscoelasticity measurement by temperature dispersion according to the formula tan δ=G”/G 'And obtained. In the measurement of dynamic viscoelasticity, a viscoelasticity testing machine (manufactured by TA Instruments. Japan, trade name: ARES G2) was used to sandwich the test piece forming an adhesive layer with a thickness of about 2 mm into the diameter of the measuring portion of the same testing machine Between 8mm parallel discs, the storage elastic modulus (G') and the loss elastic modulus (G") from -50°C to 150°C were measured at a frequency of 1 Hz.

The thickness of the adhesive layer used in the present invention is 5 μm to 100 μm, preferably 10 μm to 80 μm, and 15 μm to 80 μm in consideration of the excellent adhesion and adherence to the adherend and the foam. Very good.

The adhesive sheet of the present invention can be applied directly to the hair after forming the adhesive layer by directly applying the adhesive to the foam and drying it, or by applying and drying the adhesive on the release sheet to form an adhesive layer. The foam is produced by the transfer method. When an adhesive containing an acrylic polymer and a crosslinking agent is used as the adhesive for forming the adhesive layer, the adhesive layer is laminated on one side or both sides of the foam by the direct method or the transfer method. It is preferably 20°C to 50°C, and more preferably 23°C to 45°C for about 2 days to 7 days, taking into account both excellent adhesion to adherends and foam substrates and excellent followability Is better.

When the total thickness of the adhesive sheet of the present invention is 500 μm or less, it is easy to contribute to the thinning of small electronic devices, so it is better to use 80 μm to 400 μm, more preferably 100 μm to 350 μm, and 150 μm to 300μm is particularly good. This adhesive sheet uses a foam having the above-mentioned specific apparent density and number of bubbles, so even if the total thickness of the adhesive sheet is thin as described above, it will not cause foaming when a force (impact) in the shear direction is applied. The body is peeled off due to cracking of the body, etc., and good followability for the height difference can be taken into account. As the adhesive sheet, other layers other than the foam and the adhesive layer may be used if necessary. Examples of the other layers include thermally conductive layers such as laminate layers such as polyester films, light-shielding layers, light-reflecting layers, and metal layers in consideration of dimensional stability, good tensile strength, and applicability of heavy industry to the adhesive sheet.

The adhesive sheet of the present invention may also be laminated with a release sheet on the surface of its adhesive layer. For the release sheet, for example, a film obtained by using synthetic resins such as polyethylene, polypropylene, polyester, etc.; paper, non-woven fabric, cloth, foamed sheet, metal substrate; and applying silicone to at least one side of these laminates System treatment, long-chain alkyl treatment, fluorine treatment and other peeling treatment.

The adhesive sheet of the present invention can limit the width of the narrowest part of the adhesive sheet to 5 mm or less by, for example, the limitation of the attachment position and shape.

The aforementioned narrow-width members are mostly used as members in industrial applications such as mobile phones and other electronic terminals, automobiles, building materials, OA, and home appliance industries.

Specific examples of the above-mentioned components include two or more housings and lens components that constitute an electronic terminal; information display modules that constitute an information display device, various sensors, batteries, decorative parts, and mirrors.

Using the adhesive sheet of the present invention to fix two or more frames, an electronic terminal such as a lens member, etc., it is not easily disintegrated due to impacts such as dropping, and has excellent waterproofness. 【Example】

Hereinafter, the present invention will be described more specifically with examples and comparative examples.

[Preparation Example 1] A method for producing an acrylic polymer (A-1) was added to a reaction vessel equipped with a stirrer, a reflux cooling tube, a nitrogen introduction tube, and a thermometer, and 95.9 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid, and acrylic acid were added 0.1 parts by mass of 2-hydroxyethyl ester and 200 parts by mass of ethyl acetate were heated to 72°C while blowing nitrogen while stirring.

Then, 2 parts by mass (solid content 0.1% by mass) of 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the above mixture, and the mixture was kept at 72°C under stirring for 4 After hours, hold at 75°C for 5 hours.

Then, the above mixture was filtered with a 200-mesh metal mesh to obtain a solution of acrylic polymer (A-1) having a weight average molecular weight of 1.86 million (a nonvolatile component of 33.3% by mass).

[Preparation Example 2] Method for producing acrylic polymer (A-2) In a reaction vessel equipped with a stirrer, a reflux cooling tube, a nitrogen introduction tube, and a thermometer, 63.9 parts by mass of n-butyl acrylate and 2-ethylhexyl acrylate were added 32 parts by mass of ester, 4 parts by mass of acrylic acid, 0.1 parts by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were heated to 72°C while blowing nitrogen while stirring.

Then, 2 parts by mass (solid content 0.1% by mass) of 2,2'-azobis(2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the above mixture, and the mixture was kept at 72°C under stirring for 4 After hours, hold at 75°C for 5 hours.

Then, the above mixture was filtered with a 200-mesh metal mesh to obtain an acrylic polymer (A-2) solution (non-volatile component 33.3% by mass) with a weight average molecular weight of 750,000.

[Example 1] In a container, polymerized rosin ester-based tackifying resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) was disproportionated to 100 parts by mass of the acrylic polymer (A-1) and disproportionated After mixing and stirring 15 parts by mass of rosin ester-based tackifying resin A-100 (manufactured by Arakawa Chemical Industries Co., Ltd.), ethyl acetate was added to obtain an adhesive composition (A) with a solid content of 31% by mass.

Then, to 100 parts by mass of the above-mentioned adhesive composition (A), Burnock D-40 (made by DIC (shares), trimethylolpropane adduct of toluene diisocyanate, isocyanate group content 7 mass %, non (1.4% by mass of volatile components) 1.4 parts by mass was used as a crosslinking agent, and after stirring and mixing to make it uniform, it was filtered with a 100-mesh metal mesh to obtain an adhesive (A).

Then, the adhesive agent (A) was coated on the surface of the release liner with a coating bar so that the thickness of the adhesive layer after drying was 50 μm, and dried at 80° C. for 3 minutes, thereby preparing an adhesive layer.

Then, the surface of the polyolefin resin-based foam 1 described in Table 1 was corona-treated to adjust the wetting index to 54 mN/m, and then the above adhesive layer was attached to both sides of the adhesive layer at 40°C. It is cured for 48 hours in an environment where the adhesive sheet is produced.

[Example 2] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 2 described in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 3] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 3 described in Table 1 was used instead of the polyolefin resin-based foam 1.

[Example 4] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 4 described in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 5] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 5 described in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 6] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 6 described in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 7] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 7 described in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 8] In a container, 10 parts by mass of polymerized rosin ester tackifying resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) was disproportionated to 100 parts by mass of the acrylic polymer (A-2). After mixing and stirring 15 parts by mass of rosin ester-based tackifying resin A-100 (Arakawa Chemical Industries Co., Ltd.), ethyl acetate was added to obtain an adhesive composition (B) with a solid content of 31% by mass.

Then, to 100 parts by mass of the above adhesive composition (B), Burnock D-40 (made by DIC (stock), trimethylolpropane adduct of toluene diisocyanate, isocyanate group content 7 mass%, non (1.4% by mass of volatile components) 1.4 parts by mass was used as a crosslinking agent, and after stirring and mixing to make it uniform, it was filtered with a 100-mesh metal mesh to obtain an adhesive (B). The polyolefin resin-based foam 4 described in Table 1 was used in place of the polyolefin resin-based foam 1 and the adhesive (B) was used in place of the adhesive (A), except that the same method as in Example 1 was used. Obtain the adhesive sheet.

[Example 9] The polyolefin resin-based foam 1 described in Table 2 was used in place of the polyolefin resin-based foam 1, and the thickness of the adhesive layer after drying of the adhesive (A) was 40 μm, except this Other than this, the adhesive sheet was obtained by the method similar to Example 1.

[Example 10] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 13 described in Table 2 was used in place of the polyolefin resin foam 1.

[Example 11] An adhesive sheet was obtained in the same manner as in Example 8 except that the polyolefin resin foam 14 described in Table 2 was used in place of the polyolefin resin foam 4.

[Example 12] An adhesive sheet was obtained in the same manner as in Example 9 except that the polyolefin resin foam 15 described in Table 2 was used instead of the polyolefin resin foam 8.

[Comparative Example 1] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 9 described in Table 2 was used instead of the polyolefin resin foam 1.

[Comparative Example 2] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 10 described in Table 2 was used in place of the polyolefin resin foam 1.

[Comparative Example 3] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 11 described in Table 2 was used instead of the polyolefin resin foam 1.

[Comparative Example 4] An adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 12 described in Table 2 was used in place of the polyolefin resin foam 1.

【Table 1】

【Table 2】

The apparent density, average bubble diameter, average bubble diameter ratio and number of bubbles of the foams in Tables 1 and 2 were measured by the same method as described in this specification. In Tables 1 and 2, MD indicates the flow direction, CD indicates the width direction, and VD indicates the thickness direction. "MD/VD" represents the ratio of the average bubble diameter in the flow direction to the average bubble diameter in the thickness direction, and "CD/VD" represents the ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction. The thickness of the foam in Tables 1 and 2 represents the value measured by the Dial Thickness Gauge G model manufactured by Ozaki.

[Evaluation method of impact resistance in shear direction] The adhesive sheet obtained in Examples and Comparative Examples was cut into a size of 1 mm in width and 1.5 cm in length, thereby obtaining a test tape. Then, on one side of a glass plate having a thickness of 2 mm, a width of 2 cm, and a length of 2 cm, four pieces of the test tape were attached so that each of the two pieces became horizontal. Then, on the surface of the test tape, a polycarbonate plate (smooth surface) with a thickness of 2 mm, a width of 5 cm, and a length of 5 cm was placed on the top surface, using a 2 kg roller (JISZ0237 (2009), page 8 ("10 . 2. 4 Crimping device”) The rollers with a diameter of 85±2.5mm, a width of 45±1.5mm and a mass of 2000±100g as described in the above) are pressed back and forth once, and then left at 23°C for 24 hours as a test piece (See Figure 1). On the side of the glass plate constituting the test piece, a metal weight weighing 100 g was continuously dropped twice from a height of 5 cm (FIG. 2 ). Visually confirm whether the foam constituting the dropped test piece is broken. It was confirmed that the test piece of the foam did not break, and it was further dropped 5 times from a position higher than 5 cm (height 10 cm), and visually confirmed whether the foam constituting the test piece was broken. This test was repeated, and the height at which the crack of the foam was confirmed was described in Tables 2 and 3. As a result of this test, those with a drop height of 25 cm or more were evaluated as "◎◎", those with 20 cm as "◎", those with 15 cm as "○", those with 10 cm as "△", and those with 5 cm The evaluation is "╳".

[Evaluation method of height difference followability] The adhesive sheets obtained in the examples and comparative examples were cut into a frame shape with an outer shape of 64 mm×43 mm and a width of 2 mm, and were attached to a pressure of 2 mm thickness and an outer shape of 65 mm×45 mm. Acrylic board, thereby obtaining the acrylic board with frame adhesive sheet. Then, two pieces of single-sided adhesive tape (thickness 30 μm, width 5 mm and length 45 mm) with an adhesive layer on one side of the polyethylene terephthalate substrate were attached in parallel with a longitudinal interval of 1 cm At the central portion of another acrylic plate with a thickness of 2 mm and an external shape of 65 mm×45 mm, an acrylic plate with a height difference portion is made. At 23°C, on the surface of the height difference portion of the acrylic plate provided with the height difference portion, place the surface of the adhesive layer of the acrylic plate with the frame-attached adhesive sheet on top of these , Press back and forth once with a 2kg roller to obtain a laminate. From the side of the acrylic plate having the height difference portion constituting the laminate, the followability of the adhesive sheet to the height difference portion was visually evaluated. ◎: No gaps such as air bubbles were observed at the interface between the level difference portion and the adhesive sheet. ○: It has been confirmed that there are slight air bubbles and other voids at the interface between the level difference part and the adhesive sheet, but it is a level that is practically free from problems. △: It has been confirmed that there are voids such as bubbles at the interface between the level difference portion and the adhesive sheet. ╳: It has been confirmed that there are obvious air bubbles such as large bubbles at the interface between the level difference part and the adhesive sheet.

【table 3】

【Table 4】

1‧‧‧glass plate 2‧‧‧Test tape 3‧‧‧Heavy 4‧‧‧Polycarbonate board

[Fig. 1] A conceptual diagram of a test piece used in the evaluation of impact resistance in the shear direction. [Fig. 2] A conceptual diagram showing an evaluation method of impact resistance in the shear direction.

no.

1‧‧‧glass plate

2‧‧‧Test tape

4‧‧‧Polycarbonate board

Claims (6)

An adhesive sheet having an adhesive layer on one side or both sides of a foam body having an apparent density in the range of 0.40 g/cm ³ ~0.59 g/cm ³ ; characterized in that the foam body is cut in the width direction In the cut surface, the number of bubbles in the range of thickness×distance in the width direction (1.5mm) is more than 31, and the surface of the foam cut in the flow direction, thickness×flow direction distance (1.5 The number of bubbles in the range of mm) is more than 32. As for the adhesive sheet of claim 1, the ratio (A) of the average bubble diameter in the flow direction to the average bubble diameter in the thickness direction is in the range of 0.3 to 4, and the average bubble diameter in the width direction relative to the thickness The ratio of the average bubble diameter in the direction (B) is 0.3 to 4 bubbles. For example, in the adhesive sheet of claim 1 or 2, the average bubble diameter in the flow direction is 20 μm to 160 μm, and the average bubble diameter in the width direction is 20 μm to 160 μm. For example, the adhesive sheet of claim 1 or 2, wherein the foaming system has a thickness ranging from 50 μm to 400 μm. An adhesive sheet as claimed in item 1 or 2 of the patent application, wherein the foaming system is obtained by using at least one selected from the group consisting of polyolefin, polyurethane and acrylic polymer. An electronic device, characterized by: It has a structure in which more than 2 adherends are adhered by the adhesive sheet as described in any one of claims 1 to 5.

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