KR20170093791A - Adhesive sheet and electronic device - Google Patents

Abstract

A problem to be solved by the present invention is to provide a resin composition which has impact resistance at a level that does not cause cracking of the foam or peeling off from the adherend even when a force (impact) in the shear direction is applied, Sensitive adhesive sheet.
The present invention, an apparent density through on one side or both sides of the range of ^{0.40g / cm 3 ~ 0.59g / cm} 3 foam, directly or in a different layer, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, cutting the foam in the transverse direction Wherein the number of bubbles present in the range of thickness x width direction distance (1.5 cm) in one surface (cutting surface) is 20 or more.

Description

[0001] ADHESIVE SHEET AND ELECTRONIC DEVICE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure-sensitive adhesive sheet usable in the production of various articles such as electronic apparatuses.

BACKGROUND ART [0002] A pressure-sensitive adhesive sheet based on a foam is widely used, for example, in a case of fixing two or more housings, rechargeable batteries, circuit boards, etc. constituting electronic equipment.

The pressure-sensitive adhesive sheet is, for example, a resin foam obtained by foaming a resin composition containing a polyolefin resin and a non-compatible resin for a polyolefin resin in a ratio of 90:10 to 60:40, and the polyolefin resin And an average long diameter of an island portion of a sea-island structure formed by a non-resisting resin is 1 占 퐉 or more (see, for example, Patent Document 1).

[0003] Meanwhile, as the large-sized information display portion of the portable electronic terminal described above and the portable electronic terminal thinned, there is a demand for a thin and narrow width pressure-sensitive adhesive sheet used for such manufacturing.

However, the thin and widened pressure sensitive adhesive sheet is generally insufficient in terms of the followability with respect to the stepped portion of the adherend. Further, when the portable electronic terminal is dropped, It is not easy to cause peeling due to the impact resistance.

Up to now, in many cases, the pressure-sensitive adhesive sheet is required to have a level of impact resistance at a level that can prevent peeling due to cracks or the like in the foamed body in the case of impact in the plane direction (thickness direction).

However, recently, even when the application of the adhesive sheet is enlarged, even when the impact is applied in the direction of the front end of the adhesive sheet, the impact resistance (impact resistance against impact in shear direction) Sensitive adhesive sheet is required.

In addition, since the followability to the stepped portion of the adherend and the impact resistance against the impact in the shearing direction are generally in a trade-off relationship, the pressure-sensitive adhesive sheet having both of the following property and impact resistance against impact in the shearing direction , Had not been found so far.

Japanese Patent Application Laid-Open No. 2008-274073

A problem to be solved by the present invention is to provide a resin composition which has impact resistance at a level that can prevent peeling of an adherend due to cracks of the foam or the like even when force (impact) in the shear direction is applied, And to provide a pressure-sensitive adhesive sheet having following properties.

In order to achieve both the impact resistance and the followability with respect to the shock in the shear direction, the present inventors have selected a specific apparent density range and also selected a range of thickness x width direction distance (1.5 mm) and thickness x flow direction distance (1.5 mm) are selected, and when these are combined, it is found that the above problems can be solved.

That is, the present invention, the apparent density on one side or both sides of the foam in the range of from ^{0.40g / cm 3 ~ 0.59g / cm} 3, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, one side of the foundation for the foam in the transverse direction , The number of bubbles existing in the range of thickness x width direction distance (1.5 mm) is 20 or more, and the foam is present in the range of thickness x flow direction distance (1.5 mm) Wherein the number of bubbles is 20 or more.

INDUSTRIAL APPLICABILITY The pressure-sensitive adhesive sheet of the present invention has good followability to a stepped portion of an adherend without causing exfoliation of the adherend due to cracks of the foam or the like even when force (impact) in the shear direction is applied. Such a pressure-sensitive adhesive sheet can be used in various scenes including, for example, the manufacture of electronic devices such as portable electronic terminals, the fixing of automobile parts, and the fixing of inside and outside of a building.

1 is a conceptual diagram of a test piece used for evaluating the impact resistance in the shear direction.
2 is a conceptual diagram showing a method for evaluating the impact resistance in the shear direction.

Pressure-sensitive adhesive sheet of the present invention, the apparent density of the one side or both sides of the foam range from ^{0.40g / cm 3 ~ 0.59g / cm} 3, a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer, a surface cut the foam in the transverse direction , The number of bubbles present in the range of the thickness x width direction distance (1.5 mm) is 20 or more, and the foam is present in the range of the thickness x the flow direction distance (1.5 mm) The number of bubbles is 20 or more.

As the pressure-sensitive adhesive sheet of the present invention, as constituting the base material (core), an apparent density uses a range of foams of ^{0.40g / cm 3 ~ 0.59g / cm} 3. By using the foam having the density in the above-mentioned range, it is possible to provide a pressure-sensitive adhesive sheet with excellent followability to the stepped portion of the adherend without causing peeling of the adherend due to cracks of the foam or the like, .

Using the in the range of the apparent density of the Examples of the ^{foam, 0.42g / cm 3 ~ 0.58g /} cm 3 range is preferred to use a foam having an apparent ^{density, 0.45g / cm 3 ~ 0.56g /} cm 3 of Is more preferable for obtaining a pressure-sensitive adhesive sheet having good followability to the stepped portion of the adherend without causing peeling of the adherend due to cracks or the like of the foam, even when force (impact) in the shear direction is applied. The apparent density refers to the apparent density measured in accordance with JIS K6767. A foam obtained by cutting a rectangular body having a size of 4 cm x 5 cm is prepared for 15 cm ³ minutes, and its mass is measured, and the value calculated based on the mass and the volume Point.

As the foam, there is used any one of 20 or more bubbles existing in a range of a thickness x widthwise distance (1.5 mm) among the faces (cut faces) cut in the width direction thereof. The number of bubbles is preferably 25 or more, more preferably 30 to 150, more preferably 30 to 120, and most preferably 30 to 50, More preferably 30 to 45. It is preferable to use a material having a good followability with respect to the step portion without causing cracking of the foam or peeling off from the adherend even if a force (impact) in the shearing direction is applied, And is particularly preferable for obtaining a pressure-sensitive adhesive sheet. Further, the thickness refers to the thickness of the foam. Therefore, the number of the bubbles is preferably in the range of a suitable range described below (preferably 50 μm to 400 μm, more preferably 100 μm to 300 μm, and more preferably 110 μm to 250 μm), a flow direction distance (1.5 mm) And the number of bubbles present in the range of the direction distance (1.5 mm).

As the above-mentioned foam, an arbitrary number of bubbles existing in a range of a thickness x a flow direction distance (1.5 mm) in a plane (cut face) cut in the flow direction thereof is 20 or more. As the foam, the number of the bubbles is more preferably from 30 to 150, more preferably from 30 to 120, further preferably from 30 to 50, more preferably from 30 to 150, To 45% is used in order to obtain a pressure-sensitive adhesive sheet having good followability to the stepped portion of the adherend without causing peeling of the adherend due to cracks or the like of the foam, even when a force in the shear direction (impact) Particularly preferred.

In addition, a foam having a number of bubbles in the range of the thickness x the flow direction distance (1.5 mm) of 20 or more can not necessarily have 20 or more bubbles in the range of the thickness x the widthwise distance (1.5 mm) .

In the present invention, the number of bubbles existing in the range of the thickness of the foamed material x the flow direction distance (1.5 mm) is not more than 20, and the thickness of the foamed material existing in the range of thickness x widthwise distance The use of a foam sheet having a number of bubbles of 20 or more makes it possible to provide a pressure-sensitive adhesive sheet with excellent followability to the stepped portion of the adherend without causing peeling of the adherend due to cracks or the like of the foam, . ≪ / RTI >

The number of bubbles present in the range of the thickness of the foam material x the width direction distance (1.5 mm) and the thickness x the flow direction distance (1.5 mm) indicates the value measured by the following method.

First cut the foams with the thickness measured to 2 cm in the width direction and 2 cm in the flow direction. Next, the cut surface of the foam is expanded 200 times with a digital microscope (trade name " KH-7700 ", manufactured by Hirox), and the cut surface (cut surface) cut in the width direction and the flow direction is photographed.

Next, the number of bubbles existing in the range of the thickness x width direction distance (1.5 mm) is arbitrarily selected among the cut surfaces in the width direction of the foam. The number of bubbles present in the range of the thickness of the foamed product x the flow directional distance (1.5 mm) is arbitrarily selected among the cut faces in the flow direction of the foamed product.

As the foam, it is preferable to use a foam having a ratio (B) of the average cell diameter in the width direction to the average cell diameter in the thickness direction of 0.3 to 4, more preferably 1 to 4 , More preferably from 1 to 3, and more preferably from 2 to 3, even if a force in the shear direction (impact) is applied, without causing cracks in the foam or peeling off from the adherend, And is particularly preferable for obtaining a pressure-sensitive adhesive sheet having good followability with respect to the stepped portion.

As the foam, it is preferable to use a foam having a ratio (A) of the average cell diameter in the flow direction to the average cell diameter in the thickness direction of 0.3 to 4, more preferably 1 to 4 , More preferably from 1 to 3, and more preferably from 2 to 3 is used, even if force in the shear direction (impact) is applied, peeling of the adherend due to cracks or the like of the foam is not caused , And is particularly preferable for obtaining a pressure-sensitive adhesive sheet having good followability to the stepped portion.

As the foam, a lower limit of the average cell diameter in the flow direction is preferably 20 占 퐉 or more, more preferably 30 占 퐉 or more, more preferably 80 占 퐉 or more, and further preferably 90 占 퐉 or more. The upper limit is preferably May be 160 탆 or less, more preferably 140 탆 or less, and even more preferably 120 or less.

As the foam, the lower limit of the average cell diameter in the width direction is preferably 20 占 퐉 or more, more preferably 30 占 퐉 or more, more preferably 80 占 퐉 or more, and further preferably 90 占 퐉 or more. Preferably not more than 160 mu m, more preferably not more than 140 mu m, further preferably not more than 120 mu m.

By using the foam having the average cell diameter in the above range, it is possible to provide a pressure-sensitive adhesive sheet having good followability to the step portion without causing peeling of the adherend caused by cracks or the like of the foam even if force (impact) Is particularly preferable.

As the above-mentioned foam, it is preferable to use a foam having a closed-cell structure because it can effectively prevent flooding from the cut surface of the foam.

The average cell diameter in the width direction, the flow direction, and the thickness direction of the foam refers to a value measured in the following manner. First, 10 pieces of specimens having a width of 2 cm and a flow direction of 2 cm were prepared by cutting the foam at a width of 2 cm and a flow direction of 2 cm. Next, the cut surface of the test piece was enlarged 200 times with a digital microscope (trade name " KH-7700 ", manufactured by Hirox), and the cut surface in the width direction and the flow direction was photographed.

Next, the diameters of the bubbles existing in the range of the thickness x the flow direction distance (1.5 mm) among the cut surfaces in the flow direction of the test piece were all measured. A value obtained by averaging the diameters measured by performing the measurement at any 10 of the cut surfaces of the test piece was regarded as an average cell diameter in the flow direction of the foam. The average cell diameter in the width direction of the foam was measured as the diameter of the cells existing in the range of the thickness x width direction distance (1.5 mm) among the cut surfaces in the width direction of the test piece. A value obtained by averaging the diameters measured by performing the measurement at any 10 of the cut surfaces of the test piece was regarded as an average cell diameter in the width direction of the foam.

The foam preferably has a thickness in the range of 50 탆 to 400 탆, more preferably in the range of 100 탆 to 300 탆, and more preferably in the range of 110 탆 to 250 탆, for example, Even if the level contributing to the thinning of the terminal is small, the pressure-sensitive adhesive sheet having a better followability with respect to the step portion can be obtained without causing peeling of the adherend due to cracks or the like of the foam when the force (impact) It is preferable.

The foam preferably has an interlaminar 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 particularly preferably from 35 N / cm to 60 N / cm.

By using the foam having the interlaminar strength in the above-mentioned range, it is possible to obtain a pressure-sensitive adhesive sheet having good followability to the stepped portion of the adherend without causing peeling of the adherend due to cracks of the foam or the like, A sheet can be obtained. In order to improve the yield when producing electronic equipment or the like using the adhesive sheet, there is a case where a component fixed by an adhesive sheet is separated from an electronic apparatus or the like. At this time, the pressure-sensitive adhesive sheet obtained by using the foam having the above interlaminar strength is hard to cause interlayer cracking of the foam, and even when the interlayer crack is caused, the remaining part of the pressure-sensitive adhesive sheet Etc.) easily.

The interlaminar strength refers to a value measured by the following method.

The pressure-sensitive adhesive layer having a thickness of 50 占 퐉 (one not to be peeled off from the adherend and the foam at the time of the following high-speed peeling test) was adhered on both surfaces of the foamed article and then aged at 40 占 폚 for 48 hours, Thereby forming an adhesive sheet.

Next, a single-sided pressure-sensitive adhesive sheet having a width of 1 cm and a length of 15 cm, which was adhered to a pressure-sensitive adhesive side of one side with a polyester film having a thickness of 25 m, was laminated on a polyester film having a thickness of 50 m, a width of 3 cm and a length of 20 cm And they are pressed and attached by reciprocating 2 kg rollers one by one. Thereafter, they are pressed under the environment of 60 deg. C for 48 hours and then left under the environment of 23 deg. C for 24 hours.

Thereafter, the side of the polyester film with the thickness of 50 m was fixed to the attachment jig of the high-speed peeling tester under conditions of 23 deg. C and 50% RH, and the polyester film having the thickness of 25 m was stretched at 90 deg. , The maximum strength measured when the foam is torn is defined as the interlaminar strength.

The foam preferably has a compression strength of 25% at 380 kPa or more, preferably at 380 kPa to 1300 kPa, preferably at 450 kPa to 1100 kPa, and preferably at 500 kPa to 1000 kPa, A pressure-sensitive adhesive sheet having excellent followability with respect to an adherend having an irregular shape or a roughened surface and having excellent followability to the adherend can be obtained when the adherend is used as a substrate of the pressure-sensitive adhesive sheet More preferable.

The 25% compression strength refers to a value measured in accordance with JIS K6767. Concretely, the foamed body cut to 25 mm ² was laminated until the thickness became about 10 mm, sandwiched between the stainless steel plates, and then pressed at a rate of 10 mm / min at 23 캜 for about 2.5 mm (25% of the original thickness) And is a value obtained by measuring the strength at the time of compression.

As the foam, preferable to use the flow direction and less than the tensile modulus in the transverse direction, respectively 200N / cm ^2, and more preferably used in that the ^{300N / cm 2 ~ 1800N / cm} 2.

The flow direction and the width of the tensile modulus, low tensile modulus values of the direction, it is more preferable that the ^{500N / cm 2 ~ 1400N / cm} 2 is preferred, and ^{600N / cm 2 ~ 1300N / cm} 2. Further, in the flow direction and the width tension, the high value of the tensile modulus of elasticity of the direction, it is more preferable that the ^{700N / cm 2 ~ 1800N / cm} 2 is preferred, and ^{800N / cm 2 ~ 1600N / cm} 2.

The tensile modulus in the flow direction and the width direction of the foam refers to a value measured in accordance with JIS K6767. Specifically, it is the maximum strength measured under a measurement condition of a tensile rate of 300 mm / min under an environment of 23 DEG C and 50% RH using a tensile tensile tester with a foam having a tabular line length of 2 cm and a width of 1 cm.

The tensile elongation at break of the foam in the tensile test is preferably 200% to 1500%, more preferably 400% to 1000%, and even more preferably 450% to 800% Is more preferable. The foam having the above-mentioned tensile modulus or tensile elongation in the above range is hard to cause interlayer fracture or breakage, so that it is possible to suppress deterioration in workability and adhesion workability that can be caused in a pressure-sensitive adhesive sheet obtained using a general foam. In addition, the pressure-sensitive adhesive sheet obtained by using the above-mentioned foam is easy to remove from the surface of the adherend.

As the above-mentioned foam, those obtained using at least one kind selected from the group consisting of polyolefin, polyurethane and acrylic polymer can be used. Specific examples thereof include polyethylene, polypropylene, ethylene-propylene copolymer polymer, ethylene-vinyl acetate copolymer polymer Polyolefin-based foams, rubber-based foams obtained by using an acrylic rubber or other elastomer, or the like can be used. Among them, it is preferable to use a polyolefin-based foam as the above-mentioned foam, since it is excellent in the followability to the surface unevenness of the adherend and the impact resistance in the plane direction and the shearing direction.

As the polyolefin-based foam, those obtained using a polyolefin-based resin can be used. Among them, as the polyolefin-based foam, it is preferable to use a foam obtained by using a polyethylene-based resin because it is easy to manufacture with a uniform thickness and can impart appropriate flexibility.

Examples of the polyethylene-based resin include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene -? - olefin copolymer, ethylene-vinyl acetate copolymer and the like, .

Examples of olefins constituting the ethylene-? -Olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, have.

The polyethylene-based resin is preferably contained in an amount of 40 mass% or more, more preferably 50 mass% or more, and more preferably 60 mass% or more, relative to the total amount of the polyolefin- , And particularly preferably 80 mass% or more.

As the polyethylene-based resin, it is preferable to use a product obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst because it is easy to stretch relatively uniformly and a polyolefin-based foam having a uniform thickness as a whole can be obtained Do.

In order to obtain a pressure-sensitive adhesive sheet having good followability to the step portion without causing peeling of the adherend due to cracks or the like of the foam when the force in the shearing direction (impact) is applied, the polyethylene- , An olefinic thermoplastic elastomer, and an ethylene /? - olefinic thermoplastic elastomer.

The method for producing the above foam is not particularly limited and, for example, a polyolefin resin containing a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and a pyrolytic foaming agent , A foaming auxiliary, and a colorant to an extruder, melt-kneading the mixture, and extruding the foamed polyolefin-based resin composition into a sheet form from an extruder to produce a foamable polyolefin-based resin sheet, A step of crosslinking the sheet, and a step of foaming the expandable polyolefin-based resin sheet.

The foam obtained by the above method may be melted or softened as necessary and stretched in either one or both of the flow direction and the width direction. The stretching may be performed a plurality of times as necessary.

Examples of the method for producing the foamable polyolefin-based resin sheet include a method in which a polyolefin resin, a pyrolytic foaming agent, a foaming assistant, a colorant, and other optional components constituting the foamable polyolefin-based resin composition are extruded into an extrusion molding machine such as a single screw extruder, And melting and kneading the mixture at a temperature lower than the decomposition temperature of the thermally decomposable foaming agent and extruding the mixture by extrusion molding or the like.

The step of crosslinking the foamable polyolefin-based resin sheet obtained by the above-mentioned method can be carried out by, for example, a method of irradiating a foamable polyolefin-based resin sheet with electrolytic radiation or a foamable polyolefin-based resin composition containing an organic peroxide, And a method of heating the obtained foamable polyolefin-based resin sheet.

Examples of the ionizing radiation include electron beams,? Rays,? Rays,? Rays, and the like. The dose of ionizing radiation is appropriately adjusted so that the gel fraction of the polyolefin-based resin foam is in the above preferable range, but is preferably in the range of 5 to 200 kGy. It is preferable to irradiate both surfaces of the foamable polyolefin-based resin sheet, and it is more preferable to irradiate the both surfaces with the same dose because irradiation with ionizing radiation is easy to obtain uniform foaming state.

Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2- (t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate, di- Di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl- Butylperoxy) hexyne-3, benzoyl peroxide, cumyl peroxyneodecanate, t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di (benzoylperoxy) hexane, Butyl peroxy allyl carbonate, etc. These may be used singly or in combination of two or more kinds.

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

The step of foaming the expandable polyolefin-based resin sheet can be carried out by, for example, a method of heating by hot air, a method of heating by infrared rays, a method by a salt bath, a method using an oil bath, and the like. Among them, a method of heating by hot air or a method of heating by infrared rays is preferable.

When foaming the foamable polyolefin-based resin sheet, a foamable polyolefin-based resin sheet containing a thermally decomposable foaming agent can be used.

The thermally decomposable foaming agent may be appropriately determined according to the foaming ratio of the polyolefin-based resin foam, but it is preferably used in a range of 0.5 to 40 parts by mass with respect to 100 parts by mass of the polyolefin-based resin, more preferably 1 to 30 parts by mass More preferably from 1 part by mass to 20 parts by mass, more preferably from 1 part by mass to 10 parts by mass, and more preferably from 1 part by mass to 5 parts by mass It is more preferable to use it.

The pyrolytic foaming agent preferably has a decomposition temperature higher than the melting temperature of the polyolefin-based resin, more preferably a decomposition temperature of 160 ° C to 270 ° C, and more preferably 160 ° C to 220 ° C.

Examples of the pyrolytic foaming agent include azo compounds such as azodicarbonamide, nitroso compounds such as N, N'-dinitrosopentamethylenetetramine, and hydrazine compounds such as 4,4'-oxybis (benzenesulfonylhydrazide) Based foaming agents such as sodium hydrogencarbonate and ammonium carbonate, inorganic foams such as ammonium nitrite, sodium borohydride, sodium citrate anhydrous and the like, but azo compounds and nitroso compounds are preferable, and azodicarbonamide N, N'-dinitrosopentamethylenetetramine is more preferable.

As the pyrolytic foaming agent, it is preferable to use a powdery one, preferably 50% average particle diameter (median diameter) of 50 탆 or less, more preferably 40 탆 or less, and 30 탆 or less , The number of bubbles existing in the range of thickness x width direction distance (1.5 mm) is 20, and the number of bubbles existing in the range of thickness x flow direction distance (1.5 mm) Of the total amount of the foam.

The stretching process may be performed on the foam obtained by the above method, or may be performed in parallel with the foaming process of the foamable polyolefin-based resin sheet.

The stretching step may be performed in a state in which the molten state in the foaming step is maintained. Alternatively, the foaming step may be followed by cooling and again heating the foam.

By using the foam obtained through the stretching process as the foam, a foam having the specific average cell diameter ratios (A) and (B) can be obtained. By using such a foam, cracks It is possible to obtain a pressure-sensitive adhesive sheet having good followability with respect to the stepped portion.

Here, the molten state of the foam refers to a state in which the resin is heated to a temperature equal to or higher than the melting point of the polyolefin-based resin constituting the foam. The softening of the foam refers to a state in which the resin is heated to a temperature lower than the softening point or melting point of the resin such as polyolefin resin constituting the foam.

As the polyolefin-based foam obtained by the above method, those having a crosslinked structure can be used.

The polyolefin foam having the crosslinked structure is preferably a foam having a degree of crosslinking of 10% by mass to 80% by mass, more preferably 15% by mass to 75% by mass, further preferably 20% It is preferable that a pressure-sensitive adhesive sheet having satisfactory followability with respect to the step portion can be obtained without causing peeling of the adherend due to cracks or the like of the foam when the force (impact) in the direction is applied.

The degree of crosslinking is calculated from the ratio of insoluble fractions when the polyolefin-based foam is dipped in xylene at 105 ° C for 24 hours.

As the foam of the present invention, colored ones may be used for the purpose of imparting designability, light shielding property, hiding property, light reflecting property and light resistance. As the coloring agent usable for the coloring, for example, a black coloring agent 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 black pigment, Organic black pigments and the like can be used. Among them, carbon black is preferably used as the colorant in terms of cost, availability, insulation, and heat resistance.

As the colorant, a white colorant can be used. Specific examples thereof include titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, Calcium carbonate, barium carbonate, barium stearate, zirconium, talc, silica, alumina, clay, kaolin, phosphoric acid, calcium carbonate, calcium carbonate, calcium carbonate, barium carbonate, zinc carbonate, magnesium hydroxide, magnesium hydroxide, Based white coloring agents such as titanium, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithophone, zeolite and sericite and organic white coloring agents such as silicone resin particles, acrylic resin particles, urethane resin particles and melamine resin particles . Among them, aluminum oxide or zinc oxide is preferably used as the colorant in order to maintain cost, availability, color tone, and heat resistance.

As foams of the present invention, foaming agents such as plasticizers, antioxidants, zinc oxide and the like, foam stabilizers, heat stabilizers, metal deactivators, aluminum hydroxide, magnesium hydroxide and the like may be added, if necessary, A filler such as a flame retardant, an antistatic agent, a hollow balloon or beads made of glass or plastic, a metal powder, a metal compound, an electrically conductive filler, or a thermally conductive filler.

As the foam, the additive is preferably contained in an amount of 0.1% by mass to 10% by mass, more preferably 1% by mass to 7% by mass based on the resin such as a polyolefin resin in order to maintain proper followability and cushioning property.

When a foam containing a coloring agent, a pyrolytic foaming agent or an additive such as a foaming auxiliary agent is produced, a thermoplastic resin having high compatibility with the foamable polyolefin-based resin composition in order to prevent color irregularity, partial excessive foaming, And the masterbatch which has been preliminarily kneaded with the above additive is used, it is preferable that the number of bubbles existing in the range of thickness x widthwise distance (1.5 mm) is 20 or more, , And the number of bubbles existing in the range of thickness x flow direction distance (1.5 mm) is 20 or more.

As the foam, it is preferable to use one having a surface with a wettability index of 36 mN / m or more by a wetting reagent for the purpose of improving adhesion with the pressure-sensitive adhesive layer or another layer, and it is preferable to use a foam having a surface of 40 mN / m or more More preferably 48 mN / m or more. Examples of the method of adjusting the wetting index of the surface of the foam to the above range include a surface treatment method such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone treatment, ultraviolet ray treatment, and application of an easy adhesion treatment agent.

As the pressure-sensitive adhesive sheet of the present invention, it is possible to use a pressure-sensitive adhesive sheet having a structure in which a pressure-sensitive adhesive layer is directly laminated on one side or both sides of the above-mentioned foam, or a pressure-sensitive adhesive layer laminated on another side of the above- .

Examples of the pressure-sensitive adhesive that can be used for forming the pressure-sensitive adhesive layer include acrylic pressure-sensitive adhesives, urethane pressure-sensitive adhesives, synthetic rubber pressure-sensitive adhesives, natural rubber pressure-sensitive adhesives, silicone pressure- It is preferable to use an acrylic pressure-sensitive adhesive containing a polymer and, if necessary, containing a pressure-sensitive adhesive resin or a crosslinking agent.

Examples of the (meth) acrylic monomer usable in the preparation of the acrylic polymer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl Acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (Meth) acrylate having an alkyl group having 1 to 12 carbon atoms such as 2-ethylhexyl (meth) acrylate can be used.

Among them, as the (meth) acrylic monomer, it is preferable to use (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and (meth) acrylate having an alkyl group having 4 to 8 carbon atoms And it is particularly preferable to use either or both of n-butyl acrylate and 2-ethylhexyl acrylate in order to achieve excellent adhesion and good 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, more preferably 80% by mass to 98.5% by mass relative to the total amount of the monomers used in the production of the acrylic polymer More preferably in the range of 90% by mass to 98.5% by mass, more preferably in the range of excellent adhesion and excellent followability.

When the acrylic polymer is produced, a high polar vinyl monomer may be used as the monomer. As the high polar vinyl monomer, a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, a vinyl monomer having an amide group, etc. may be used alone or in combination of two or more.

Examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate having a hydroxyl group can be used.

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 and the like can be used. .

As the monomer having an amide group, for example, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide and the like can be used.

As the above-mentioned high polar vinyl monomer, vinyl acetate, ethylene oxide modified succinic acid acrylate, 2-acrylamide-2-methylpropane sulfonic acid and the like may be used in addition to the above.

The high polar vinyl monomer is preferably used in a range of 1.5% by mass to 20% by mass, more preferably 1.5% by mass to 10% by mass, based on the total amount of the monomers used for producing the acrylic polymer , And more preferably 2% by mass to 8% by mass in view of achieving excellent adhesion and excellent followability.

When a pressure-sensitive adhesive containing a crosslinking agent described later is used, it is preferable to use an acrylic polymer having a functional group reactive with the functional group of the crosslinking agent as the acrylic polymer. The functional group that the acrylic polymer may have includes, for example, a hydroxyl group.

The hydroxyl group can be introduced into an acrylic polymer by using, for example, a vinyl monomer having a hydroxyl group as the monomer.

The vinyl monomer having a hydroxyl group is preferably used in a range of 0.01 mass% to 1.0 mass%, preferably 0.03 mass% to 0.3 mass%, based on the total amount of the monomers used in the production of the acrylic polymer .

The acrylic polymer can be produced by polymerizing the monomer by a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method or the like, and employing a solution polymerization method improves the production efficiency of the acrylic polymer .

Examples of the solution polymerization method include a method of mixing and stirring the monomer, the polymerization initiator, and the organic solvent, preferably at a temperature of 40 ° C to 90 ° C, and performing radical polymerization.

Examples of the polymerization initiator include peroxides such as benzoyl peroxide and lauryl peroxide, azo type thermal polymerization initiators such as azobisisobutyl nitrile, acetophenone type photopolymerization initiators, benzoin ether type photopolymerization initiators, benzylketal type photopolymerization initiators, An acylphosphine oxide photopolymerization initiator, a benzoin photopolymerization initiator, and a benzophenone photopolymerization initiator.

The acrylic polymer obtained by the above method may be dissolved or dispersed in an organic solvent as long as it is produced by, for example, solution polymerization.

As the acrylic polymer, those having a weight average molecular weight of 400,000 to 3,000,000 are preferably used, and those having a weight average molecular weight of 700,000 to 2,500,000 are more preferably used.

The weight average molecular weight refers to a value measured by gel permeation chromatography (GPC) and calculated in terms of standard polystyrene. Specifically, the weight average molecular weight can be measured by using a GPC apparatus (HLC-8320 GPC) manufactured by Tosoh Co., Ltd. under the following conditions.

Sample concentration: 0.2 mass% (tetrahydrofuran solution)

Sample injection volume: 100 μl

Eluent: tetrahydrofuran

Flow rate: 1.0 ml / min

Measuring temperature: 40 ° C

This column: 2 TSKgel GMHHR-H (20)

Guide column: TSKgel HXL-H

Detector: differential refractometer

Weight average molecular weight of standard polystyrene: 10,000 to 20,000,000 (manufactured by Tosoh Corporation)

As a pressure-sensitive adhesive which can be used for forming the pressure-sensitive adhesive layer, it is preferable to use a pressure-sensitive adhesive containing a pressure-sensitive adhesive resin in order to achieve both excellent adhesion to the adherend and foam and excellent follow-up.

Examples of the tackifier resin include rosin-based tackifying resin, polymerized rosin-based tackifying resin, polymerized rosin ester-based tackifying resin, rosin phenol-based tackifying resin, stabilized rosin ester tackifying resin, disproportionated rosin ester- A hydrogenated rosin ester-based tackifying resin, a terpene-based tackifying resin, a terpene phenol-based tackifying resin, a petroleum resin-based tackifying resin, a (meth) acrylate resin-based tackifying resin and the like. When an emulsion-type pressure-sensitive adhesive is used as the pressure-sensitive adhesive, it is preferable to use an emulsion-type pressure-sensitive adhesive resin as the pressure-sensitive adhesive resin.

As the tackifier resin, among them, a tackifier resin such as a disproportionated rosin ester tackifier resin, a polymerized rosin ester tackifier resin, a rosin phenol tackifier resin, a hydrogenated rosin ester tackifier resin, a (meth) acrylate resin , A terpene phenolic resin, and a petroleum resin, or a combination of two or more thereof.

As the tackifier resin, it is preferable to use a resin having a softening point in the range of 30 ° C to 180 ° C and a resin having a softening point in the range of 70 ° C to 140 ° C to provide excellent adhesion to the adherend or the foam substrate (B) It is more preferable to make followability compatible. When the (meth) acrylate tackifier resin is used, the (meth) acrylate tackifier resin preferably has a glass transition temperature of 30 ° C to 200 ° C, preferably 50 ° C to 160 ° C More preferable.

The tackifier resin is preferably used in a range of 5 parts by mass to 65 parts by mass with respect to 100 parts by mass of the acrylic polymer and more preferably in a range of 8 parts by mass to 55 parts by mass, It is more preferable in terms of achieving both an adhesive force and excellent followability.

As a pressure-sensitive adhesive to be used for forming the pressure-sensitive adhesive layer, it is preferable to use a crosslinking agent in forming a pressure-sensitive adhesive layer that combines excellent adhesion to an adherend or foam and excellent followability.

As the crosslinking agent, for example, an isocyanate crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, and an aziridine crosslinking agent can be used. Among them, as the crosslinking agent, it is preferable to use one or both of an isocyanate crosslinking agent and an epoxy crosslinking agent rich in reactivity with an acrylic polymer, more preferably an isocyanate crosslinking agent.

Examples of the isocyanate crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, , Tolylene diisocyanate, and trimethylol propane-modified tolylene diisocyanate are preferably used.

The cross-linking agent is preferably used in such an amount that the gel fraction of the pressure-sensitive adhesive layer with respect to toluene is 70 mass% or less, more preferably 20 mass% to 60 mass% By weight and a gel fraction of 25% by mass to 55% by mass is selected and used for obtaining a pressure-sensitive adhesive sheet in which an excellent adhesion to an adherend or a foam substrate and excellent followability are obtained.

The gel fraction refers to a value measured by the following method.

The pressure-sensitive adhesive layer was formed on the releasing treatment surface of the release liner by drying for 3 minutes under an environment of 100 deg. C and then aging for 2 days in an environment of 40 deg. C so that the thickness after drying was 50 mu m.

The pressure-sensitive adhesive layer was cut into a square having a length of 50 mm and a width of 50 mm as a test piece.

After the mass (G1) of the test piece was measured, the test piece was immersed in toluene for 24 hours under an environment of 23 占 폚.

After the immersion, the mixture of the test piece and toluene was filtered using a 300-mesh wire mesh to extract an insoluble component to toluene. The mass (G2) of the insoluble component dried at 110 DEG C for 1 hour was measured.

The gel fraction was calculated on the basis of the mass (G1), the mass (G2) and the following formula.

Gel fraction (mass%) = (G2 / G1) x100

Examples of the pressure-sensitive adhesive include fillers such as plasticizers, softeners, antioxidants, flame retardants, fibers and balloons made of glass or plastic, beads, metals, metal oxides and metal nitrides, coloring agents such as pigments and dyes, leveling agents, , Defoaming agent, and the like may be used.

The pressure-sensitive adhesive layer that can be formed using the pressure-sensitive adhesive preferably has a temperature at which the peak of the loss tangent (tan?) At a frequency of 1 Hz is preferably from -40 ° C to 15 ° C. By setting the peak value of the loss tangent of the pressure-sensitive adhesive layer within the above-mentioned range, good adhesion with the adherend at room temperature can be easily imparted. More preferably -35 占 폚 to 10 占 폚, and more preferably -30 占 폚 to 6 占 폚 in improving the drop impact resistance particularly in a low-temperature environment.

The loss tangent (tan?) At a frequency of 1 Hz is determined from the storage elastic modulus (G ') and the loss elastic modulus (G ") obtained by dynamic viscoelasticity measurement by temperature dispersion, by the expression tan? = G" / G'. In the measurement of the dynamic viscoelasticity, a pressure-sensitive adhesive layer formed with a thickness of about 2 mm was measured with a viscoelasticity tester (product name: ARESG2, manufactured by Japan Aerospace Co., Japan) using a test piece And the storage elastic modulus (G ') and the loss elastic modulus (G ") at a frequency of 1 Hz from -50 ° C to 150 ° C are measured.

The thickness of the pressure-sensitive adhesive layer used in the present invention is preferably 5 탆 to 100 탆, more preferably 10 탆 to 80 탆, and more preferably 15 탆 to 80 탆 in order to achieve both excellent adhesion to the adherend and the foam and good follow- Particularly preferred.

The pressure-sensitive adhesive sheet of the present invention can be produced, for example, by a direct method in which the pressure-sensitive adhesive is applied directly to the foam, followed by drying, or by forming a pressure-sensitive adhesive layer by applying a pressure- can do. When a pressure-sensitive adhesive containing the acrylic polymer and the crosslinking agent is used as the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer laminated on one side or both sides of the foam by the direct method or the transfer method is preferably 20 ° C to 50 ° C, More preferably 2 to 7 days under the environment of 23 to 45 DEG C in order to achieve both good adhesion to the adherend or the foam substrate and excellent followability.

As the pressure-sensitive adhesive sheet of the present invention, it is preferable to use a pressure-sensitive adhesive sheet having a total thickness of 500 탆 or less, since it contributes to the thinness of small-sized electronic equipment, more preferably 80 탆 to 400 탆, and more preferably 100 탆 to 350 탆 And more preferably 150 mu m to 300 mu m. Since the pressure-sensitive adhesive sheet uses the foam having the specific apparent density and the number of bubbles, even if the total thickness of the pressure-sensitive adhesive sheet is thin as described above, the pressure- Peeling of one adherend is not caused, and favorable followability can be compatible with the stepped portion.

As the pressure-sensitive adhesive sheet, those having other layers in addition to the above-mentioned foam and pressure-sensitive adhesive layer may be used.

Examples of the other layers include thermally conductive layers such as a laminate layer such as a polyester film, a light-shielding layer, a light reflection layer, and a metal layer for imparting dimensional stability, good tensile strength and rework suitability of the pressure- have.

As the pressure sensitive adhesive sheet of the present invention, a release sheet may be laminated on the surface of the pressure sensitive adhesive layer.

Examples of the release sheet include a film obtained by using a synthetic resin such as polyethylene, polypropylene or polyester, a paper, a nonwoven fabric, a cloth, a foamed sheet, a metal substrate, Long-chain alkyl-based treatment, and fluorine-based treatment may be used.

The pressure-sensitive adhesive sheet of the present invention can be used for fixing a member whose width at the narrowest part of the pressure-sensitive adhesive sheet is limited to 5 mm or less, depending on restrictions such as the attachment site and shape.

The narrow-width member is often used as a member in industrial use such as an electronic terminal such as a cellular phone, an automobile, a building material, an office automation (OA), a household electric appliance industry, and the like.

Specifically, examples of the member include two or more housings constituting an electronic terminal, a lens member, an information display module constituting an information display device, various sensors, a battery, a decorative part, a mirror and the like.

An article such as an electronic terminal in which two or more housings or lens members are fixed using the adhesive sheet of the present invention is not easily disassembled by an impact such as dropping and has excellent waterproofness.

[Example]

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Preparation Example 1] Production method of acrylic polymer (A-1)

95.9 parts by mass of n-butyl acrylate, 4 parts by mass of acrylic acid, 0.1 part by mass of 2-hydroxyethyl acrylate and 200 parts by mass of ethyl acetate were charged in a reaction vessel equipped with a stirrer, a reflux condenser, And the temperature was raised to 72 캜 while nitrogen was blown in with stirring.

Subsequently, 2 parts by mass (solid content: 0.1% by mass) of a 2,2'-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the above mixture, And then held at 75 DEG C for 5 hours.

Next, the mixture was filtered through a 200 mesh wire netting to obtain an acrylic polymer (A-1) solution (non-volatile content 33.3 mass%) having a weight average molecular weight of 1,660,000.

[Preparation Example 2] Production method of acrylic polymer (A-2)

63.9 parts by mass of n-butyl acrylate, 32 parts by mass of 2-ethylhexyl acrylate, 4 parts by mass of acrylic acid, 0.1 part by mass of 4-hydroxybutyl acrylate 0.1 parts by mass were added to a reaction vessel equipped with a stirrer, And 200 parts by mass of ethyl acetate were put in the flask, and the mixture was heated to 72 캜 while nitrogen was blown under stirring.

Subsequently, 2 parts by mass (solid content: 0.1% by mass) of a 2,2'-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the above mixture, And then held at 75 DEG C for 5 hours.

Next, the mixture was filtered through a 200 mesh wire netting to obtain an acrylic polymer (A-2) solution (nonvolatile matter content 33.3 mass%) having a weight average molecular weight of 750,000.

[Example 1]

10 parts by mass of a polymerized rosin ester-based tackifier resin D-125 (Arakawa Chemical Industries, Ltd.) and 10 parts by mass of a disproportionated rosin ester-based tackifier resin A-100 (trade name, Manufactured by Arakawa Chemical Industries, Ltd.) were mixed and stirred, and then ethyl acetate was added to obtain a pressure-sensitive adhesive composition (A) having a solid content of 31 mass%.

Next, 100 parts by mass of the pressure-sensitive adhesive composition (A) was melt-kneaded with 100 parts by mass of a crosslinking agent such as Bernock D-40 (trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content: 7% by mass, %) Was added thereto, stirred and mixed so as to be uniform, and then filtered through a 100 mesh wire netting to obtain a pressure-sensitive adhesive (A).

Next, the pressure-sensitive adhesive (A) was coated on the surface of the release liner using a bar coater so that the thickness of the pressure-sensitive adhesive layer after drying was 50 占 퐉, followed by drying at 80 占 폚 for 3 minutes.

Next, the pressure-sensitive adhesive layer was applied to both surfaces of the polyolefin resin-based foam 1 shown in Table 1 whose surface was subjected to corona treatment by adjusting the wettability index to 54 mN / m, and cured for 48 hours under an environment of 40 ° C to produce a pressure-sensitive adhesive sheet .

[Example 2]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 2 shown in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 3]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 3 shown in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 4]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the polyolefin resin-based foam 4 shown in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 5]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the polyolefin resin-based foam 5 shown in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 6]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the polyolefin resin-based foam 6 shown in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 7]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 7 shown in Table 1 was used in place of the polyolefin resin-based foam 1.

[Example 8]

10 parts by mass of a polymerized rosin ester-based tackifier resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) and 10 parts by mass of a disproportionated rosin ester-based tackifier resin A-100 Manufactured by Arakawa Chemical Industry Co., Ltd.) were mixed and stirred, and then ethyl acetate was added to obtain a pressure-sensitive adhesive composition (B) having a solid content of 31 mass%.

Next, 100 parts by mass of the pressure-sensitive adhesive composition (B) was melt-kneaded with 100 parts by mass of a crosslinking agent such as Bernod D-40 (trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content of 7% by mass, %) Was added thereto, stirred and mixed so as to be uniform, and then filtered through a 100 mesh wire netting to obtain a pressure-sensitive adhesive (B).

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 4 shown in Table 1 was used in place of the polyolefin resin-based foam 1 and the pressure-sensitive adhesive (B) was used in place of the pressure-sensitive adhesive (A).

[Example 9]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1, except that the polyolefin resin-based foam 8 shown in Table 2 was used in place of the polyolefin resin-based foam 1 and the pressure-sensitive adhesive layer after drying of the pressure-sensitive adhesive (A) .

[Example 10]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 13 shown in Table 2 was used in place of the polyolefin resin-based foam 1.

[Example 11]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 8 except that the polyolefin resin-based foamed material 14 shown in Table 2 was used in place of the polyolefin resin-based foamed material 4.

[Example 12]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 9, except that the polyolefin resin-based foam 15 shown in Table 2 was used in place of the polyolefin resin-based foam 8.

[Comparative Example 1]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 9 shown in Table 2 was used in place of the polyolefin resin-based foam 1.

[Comparative Example 2]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 10 shown in Table 2 was used in place of the polyolefin resin-based foam 1.

[Comparative Example 3]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 11 shown in Table 2 was used in place of the polyolefin resin-based foam 1.

[Comparative Example 4]

A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin-based foam 12 shown in Table 2 was used in place of the polyolefin resin-based foam 1.

The apparent density, the average cell diameter, the ratio of the average cell diameter, and the number of cells in the foams in Tables 1 and 2 were measured in the same manner as described in the description of this specification. MD in Tables 1 and 2 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 flow direction to the average bubble diameter in the thickness direction. The thicknesses of the foams in Tables 1 and 2 indicate the values measured using a dialysis gauge type G made by Ozaki Seisakusho.

[Evaluation method of impact resistance in shear direction]

The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut to a size of 1 mm in width and 1.5 cm in length to obtain test tapes.

Next, two sheets of the above-mentioned test tapes were stuck horizontally on one side of a glass plate having a thickness of 2 mm, a width of 2 cm and a length of 2 cm.

Next, a polycarbonate plate (surface smooth) having a thickness of 2 mm, a width of 5 cm and a length of 5 cm was placed on the surface of the test tape, and the upper surface thereof was covered with a 2 kg roller (page 10.2 of JIS Z0237 (2009)). (A roller having a diameter of 85 ± 2.5 mm, a width of 45 ± 1.5 mm and a weight of 2000 ± 100 g as described in "4-squeezing device") and left at 23 ° C. for 24 hours as a test piece ).

A metal weight of 100 g in weight was dropped twice from the height of 5 cm on the side of the glass plate constituting the test piece (Fig. 2). The presence or absence of cracks in the foam constituting the test piece after the drop was visually confirmed. The test piece, which could not confirm the crack of the foam, was dropped 5 times from the position 5 cm high (10 cm in height) for five consecutive times, and the presence or absence of cracks in the foam constituting the test piece was visually confirmed. The above tests were repeated, and the height at which cracks in the foam were confirmed are shown in Tables 2 and 3.

As a result of the test, it was found that the drop height was 25 cm or more, "? &Quot;, 20 cm or less was?, 15 cm or less was?, 10 cm or less was? I appreciated.

[Evaluation method of stepwise followability]

The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were cut into a frame shape having an outer shape of 64 mm x 43 mm and a width of 2 mm and adhered to an acrylic plate having a thickness of 2 mm and an outer shape of 65 mm x 45 mm to obtain an acrylic plate ≪ / RTI >

Next, two single-sided pressure-sensitive adhesive tapes (30 μm in thickness, 5 mm in width and 45 mm in length) each having a pressure-sensitive adhesive layer on one side of a polyethylene terephthalate base were placed at the center of an acrylic plate having a thickness of 2 mm and an external shape of 65 mm × 45 mm, Direction, and an acrylic plate having a stepped portion was prepared.

A surface having an adhesive layer of an acrylic plate having the frame adhesive sheet attached thereto was raised on a surface of the stepped portion of the acrylic plate having the stepped portion at 23 DEG C and the upper portion thereof was subjected to one reciprocating pressing with a 2 kg roller to obtain a laminated body .

The followability of the pressure-sensitive adhesive sheet to the stepped portion was visually evaluated from the acrylic plate side having the step portion constituting the laminate.

?: No voids such as air bubbles were found at the interface between the stepped portion and the pressure-sensitive adhesive sheet.

?: Although voids such as fine bubbles were found at the interface between the stepped portion and the pressure-sensitive adhesive sheet, there was no problem in practice.

?: Voids such as air bubbles were found at the interface between the stepped portion and the pressure-sensitive adhesive sheet.

X: Clear voids such as large bubbles were found at the interface between the stepped portion and the pressure-sensitive adhesive sheet.

1 Glass plate 2 Test tape
3 Addition 4 Polycarbonate plate

Claims (6)

The apparent density is a pressure-sensitive adhesive sheet having a pressure-sensitive adhesive layer on one side or both sides of the range of ^{0.40g / cm 3 ~ 0.59g / cm} 3 foam,
Wherein the number of bubbles existing in the range of the thickness x width direction distance (1.5 mm) among the faces cut in the width direction of the foam is 20 or more, and the thickness of the foam in the flow direction Wherein the number of bubbles existing in the range of the distance (1.5 mm) is 20 or more. The method according to claim 1,
The ratio A of the average cell diameter in the flow direction to the average cell diameter in the thickness direction is in the range of 0.3 to 4 and the ratio B of the average cell diameter in the width direction to the average cell diameter in the thickness direction is 0.3 Adhesive sheet having air bubbles of ~ 4. The method according to claim 1 or 2,
Wherein an average cell diameter in the flow direction is 20 占 퐉 to 160 占 퐉 and an average cell diameter in the width direction is 20 占 퐉 to 160 占 퐉. The method according to any one of claims 1 to 3,
Wherein the foam has a thickness in the range of 50 mu m to 400 mu m. The method according to any one of claims 1 to 4,
Wherein the foam is obtained by using at least one member selected from the group consisting of a polyolefin, a polyurethane and an acrylic polymer. An electronic device characterized in that two or more adherends are adhered by the adhesive sheet according to any one of claims 1 to 5.

Images