JP6245381B2 - Adhesive sheet and electronic device - Google Patents

Description

  The present invention relates to a pressure-sensitive adhesive sheet that can be used in the production of various articles such as electronic devices.

  The pressure-sensitive adhesive sheet having a foam as a base material is widely used, for example, in a scene where two or more casings, rechargeable batteries, circuit boards and the like constituting an electronic device are fixed.

  The pressure-sensitive adhesive sheet is, for example, a resin foam obtained by foaming a resin composition containing a polyolefin resin and an incompatible resin with respect to the polyolefin resin in a ratio of 90:10 to 60:40, and the polyolefin resin and There is known a pressure-sensitive adhesive sheet based on a foamed sheet characterized in that an average major axis of an island part of a sea-island structure formed by an incompatible resin is 1 μm or more (see, for example, Patent Document 1).

  By the way, as the information display part of the portable electronic terminal is enlarged and the portable electronic terminal is being made thinner, a thin and narrow adhesive sheet is required as an adhesive sheet used for manufacturing them. Yes.

  However, a thin and narrow pressure-sensitive adhesive sheet is generally not sufficient in terms of followability with respect to a stepped portion of an adherend, and in the event of an impact when the portable electronic terminal is dropped or the like, In some cases, it is not sufficient in terms of impact resistance, such as being liable to cause peeling due to cracks and the like.

  Until now, the pressure-sensitive adhesive sheet has often been required to have a level of impact resistance that can prevent peeling due to cracking of the foam when subjected to an impact in the surface direction (thickness direction).

  However, in recent years, the application of adhesive sheets has expanded, and even when the impact is applied in the shear direction of the adhesive sheet, it has a level of impact resistance that can prevent peeling due to foam cracks, etc. There is a demand for a pressure-sensitive adhesive sheet having (shock resistance against impact in the shearing direction).

  In addition, since the followability to the step portion of the adherend and the impact resistance against the impact in the shear direction are generally in a trade-off relationship, both the followability and the impact resistance against the impact in the shear direction are compatible. No such adhesive sheet has been found so far.

JP 2008-274073 A

  The problem to be solved by the present invention is to have a level of impact resistance that can prevent peeling of the adherend due to cracking of the foam even when shear direction force (impact) is applied. And it is providing the adhesive sheet which has favorable followable | trackability with respect to the level | step-difference part of a to-be-adhered body.

  In order to achieve both the impact resistance against the impact in the shearing direction and the followability, the present inventors have selected a specific apparent density range, and the thickness × width direction distance (1.5 mm). ) Range and thickness × flow direction distance (1.5 mm) range was selected, and it was found that the above problems could be solved by combining them.

That is, the present invention is, on one side or both sides of the foam apparent density is in the range of ^{0.40g / cm 3 ~0.59g / cm 3} , a pressure-sensitive adhesive sheet having an adhesive layer, said foam Among the surfaces obtained by cutting the foam in the flow direction, the number of bubbles present in the range of thickness × width direction distance (1.5 mm) is 20 or more among the surfaces cut in the width direction Further, the present invention relates to a pressure-sensitive adhesive sheet characterized in that the number of bubbles present in the range of thickness × flow direction distance (1.5 mm) is 20 or more.

  The pressure-sensitive adhesive sheet of the present invention does not cause peeling of the adherend due to foam cracking or the like even when a shearing force (impact) is applied to the stepped portion of the adherend. Good follow-up performance. The pressure-sensitive adhesive sheet can be used in various scenes including the manufacture of electronic devices such as portable electronic terminals, the fixing of automobile parts, the fixing of interior and exterior of buildings, and the like.

It is a conceptual diagram of the test piece used for evaluation of the impact resistance of a shear direction. It is a conceptual diagram which shows the evaluation method of the impact resistance of a shear direction.

Pressure-sensitive adhesive sheet of the present invention, on one side or both sides of the apparent density is in the range of 0.40g ^/ cm ³ ~0.59g ^/ cm 3 foam, a pressure-sensitive adhesive sheet having an adhesive layer, said foam Of the surfaces of the body cut in the width direction, the number of bubbles present in the range of thickness x width direction distance (1.5 mm) is 20 or more, and the surface of the surface of the foam cut in the flow direction Among them, the number of bubbles present in the range of thickness × flow direction distance (1.5 mm) is 20 or more.

The pressure-sensitive adhesive sheet of the present invention, as constituting the substrate (middle core), an apparent density using the foam in the range of ^{0.40g / cm 3 ~0.59g / cm 3} . By using a foam having a density in the above range, even if a force (impact) in the shear direction is applied, the adherend is not peeled off due to cracking of the foam, etc. It is preferable for obtaining a pressure-sensitive adhesive sheet having good followability to the step portion of the body.

As the ^foam, it is preferable to use a foam having an apparent density in the range of ^{0.42g / cm 3 ~0.58g / cm 3} , a range of 0.45g / cm ³ ~0.56g / cm 3 It is possible to use the one having the apparent density of the adherend without causing peeling of the adherend due to cracking of the foam even when a shearing force (impact) is applied. It is more preferable for obtaining a pressure-sensitive adhesive sheet having good followability to the stepped portion. The apparent density refers to an apparent density measured according to JISK6767. A foam cut into a 4 cm × 5 cm rectangle is prepared for 15 cm ³ minutes, and its mass is measured. Based on the mass and the volume, Refers to the calculated value.

  Moreover, as said foam, the number of the bubbles which exist in the range of arbitrary thickness x width direction distance (1.5 mm) is 20 or more among the surfaces (cutting surface) cut in the width direction. Use something. As the foam, those having 25 or more bubbles are preferably used, more preferably those having 30 to 150, and those having 30 to 120 are used. More preferably, 30 to 50 foams are used, and 30 to 45 foams are used even when a shearing force (impact) is applied. In particular, it is preferable to obtain a pressure-sensitive adhesive sheet having good followability with respect to the stepped portion without causing cracks or peeling from the adherend. The thickness refers to the thickness of the foam. Therefore, the number of the bubbles is the thickness of the foam 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 It may be the number of bubbles existing in the range of the width direction distance (1.5 mm).

  Further, as the foam, the number of bubbles existing in an arbitrary range of thickness × flow direction distance (1.5 mm) in the surface (cut section) cut in the flow direction is 20 or more. Use something. More preferably, the foam has 30 to 150 bubbles, more preferably 30 to 120, more preferably 30 to 50. It is more preferable to use 30 to 45, and even if a shearing direction force (impact) is applied, the adherend peels off due to foam cracks or the like. In particular, it is preferable to obtain a pressure-sensitive adhesive sheet having good followability with respect to the stepped portion of the adherend without causing it.

  It should be noted that the number of bubbles in the range of the thickness × flow direction distance (1.5 mm) is 20 or more, and the number of the foams is necessarily 20 in the range of the thickness × width direction distance (1.5 mm). It does not necessarily have the above bubbles.

  In the present invention, instead of simply using the foam having the number of bubbles in the range of the thickness of the foam × the distance in the flow direction (1.5 mm) of 20 or more, the thickness × width direction is further used. The use of the one having 20 or more bubbles in the distance (1.5 mm) range was caused by foam cracking even when shear direction force (impact) was applied. This is suitable for obtaining a pressure-sensitive adhesive sheet that does not cause peeling of the adherend and has good followability to the stepped portion of the adherend.

  The number of bubbles present in the range of thickness x width direction distance (1.5 mm) and thickness x flow direction distance (1.5 mm) of the foam refers to a value measured in the following manner.

  First, the foam whose thickness was measured is cut into a width direction of 2 cm and a flow direction of 2 cm. Next, the cut surface of the foam is magnified 200 times with a digital microscope (trade name “KH-7700”, manufactured by HiROX), and a surface (cut surface) cut in the width direction and the flow direction is photographed. .

  Next, the number of bubbles existing in an arbitrary range of thickness × width direction distance (1.5 mm) in the cut surface in the width direction of the foam is counted. Further, the number of bubbles existing in an arbitrary range of the foam thickness × flow direction distance (1.5 mm) in the cut surface in the flow direction of the foam is counted.

  As the foam, it is preferable to use a foam in which the ratio (B) of the average cell diameter in the width direction to the average cell diameter in the thickness direction is in the range of 0.3 to 4, preferably in the range of 1 to 4. It is more preferable to use a thing, it is more preferable to use what is in the range of 1 to 3, and when using a thing in the range of 2 to 3, when a force (impact) in the shearing direction is applied Even in this case, it is particularly preferable for obtaining a pressure-sensitive adhesive sheet having good followability with respect to the stepped portion without causing cracking of the foam or peeling from the adherend.

  As the foam, it is preferable to use a foam in which 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, preferably in the range of 1 to 4. It is more preferable to use a thing, it is more preferable to use what is in the range of 1 to 3, and when using a thing in the range of 2 to 3, when a force (impact) in the shearing direction is applied Even in such a case, it is particularly preferable to obtain a pressure-sensitive adhesive sheet having good followability with respect to the stepped portion without causing peeling of the adherend due to cracking of the foam.

  As the foam, a lower limit of the average cell diameter in the flow direction is preferably 20 μm or more, more preferably 30 μm or more, more preferably 80 μm or more, and further preferably 90 μm or more. It is preferably 160 μm or less, more preferably 140 μm or less, and still more preferably 120 or less.

  Further, as the foam, a lower limit of the average cell diameter in the width direction is preferably 20 μm or more, more preferably 30 μm or more, more preferably 80 μm or more, and further preferably 90 μm or more. The upper limit is preferably 160 μm or less, more preferably 140 μm or less, and still more preferably 120 or less.

  By using a foam having an average cell diameter in the above range, even when a shearing force (impact) is applied, it does not cause peeling of the adherend due to cracking of the foam, etc. It is particularly preferable for obtaining a pressure-sensitive adhesive sheet having good followability to the stepped portion.

  As the foam, it is preferable to use a foam having a closed cell structure because it is possible to effectively prevent water from entering from the cut surface of the foam.

  In addition, the average bubble diameter of the width direction of the said foam, a flow direction, and thickness direction points out the value measured in the following way. First, the foam was cut into 2 cm in the width direction and 2 cm in the flow direction to produce 10 test pieces having a width direction of 2 cm and a flow direction of 2 cm. Next, the cut surface of the test piece was magnified 200 times with a digital microscope (trade name “KH-7700”, manufactured by HiROX), and the cut surfaces in the width direction and the flow direction were photographed.

  Next, all the diameters of bubbles existing in the range of thickness × flow direction distance (1.5 mm) in the cut surface of the test piece in the flow direction were measured. Of the cut surfaces of the test piece, the value obtained by averaging the measured diameters at any 10 locations was defined as the average cell diameter in the flow direction of the foam. The average cell diameter in the width direction of the foam was determined by measuring all the diameters of the bubbles existing in the range of thickness × width direction distance (1.5 mm) in the cut surface in the width direction of the test piece. The average diameter of the foam in the width direction was determined by averaging the measured diameters at any 10 locations in the cut surface of the test piece.

  The foam preferably has a thickness in the range of 50 μm to 400 μm, more preferably in the range of 100 μm to 300 μm, and more preferably in the range of 110 μm to 250 μm. For example, even if it is thin enough to contribute to thinning of a portable electronic terminal, the adherend peels off due to foam cracking when a shearing force (impact) is applied. This is preferable because a pressure-sensitive adhesive sheet having even better followability to the step portion can be obtained.

  As the foam, it is preferable to use one having an interlayer strength of 20 N / cm or more, more preferably from 30 N / cm to 150 N / cm, and from 35 N / cm to 100 N / cm. It is more preferable to use a certain one, and it is particularly preferable to use a certain one of 35 N / cm to 60 N / cm.

  By using a foam having an interlaminar strength in the above range, the adherend can be prevented from peeling off due to cracking of the foam when a shearing force (impact) is applied. It is possible to obtain a pressure-sensitive adhesive sheet having good followability with respect to the step portion. Moreover, when manufacturing an electronic device etc. using the said adhesive sheet, in order to improve the yield, the components fixed by the adhesive sheet from an electronic device etc. may be isolate | separated. At that time, the pressure-sensitive adhesive sheet obtained using the foam having the interlayer strength is less likely to cause an interlayer crack of the foam, and even when the interlayer crack is caused, from the surface of the component, The remainder of the adhesive sheet (such as part of the foam) is easily removed.

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

  Affixed to the both sides of the foam with a pressure-sensitive adhesive layer having a thickness of 50 μm (one that does not peel off from the adherend and the foam during the following high-speed peel test) one by one, and then aged at 40 ° C. for 48 hours Then, a double-sided pressure-sensitive adhesive sheet for measuring interlayer strength is prepared.

  Next, a single-sided pressure-sensitive adhesive sheet having a width of 1 cm and a length of 15 cm lined with a 25 μm-thick polyester film on one side of the pressure-sensitive adhesive surface is 50 μm thick, 3 cm wide and 20 cm long at 23 ° C. and 50% RH. After being pasted on the surface of the polyester film and reciprocating a 2 kg roller by one reciprocation, they are left to stand in a 60 ° C. environment for 48 hours, and then left in a 23 ° C. environment for 24 hours.

  Thereafter, the surface of the polyester film having a thickness of 50 μmm is fixed to an attachment jig of a high-speed peeling tester at 23 ° C. and 50% RH, and the polyester film having a thickness of 25 μm is 90 ° at a tensile speed of 15 m / min. The maximum strength measured when pulling in the direction and tearing the foam is defined as the interlayer strength.

  As the foam, it is preferable to use a foam whose 25% compressive strength is 380 kPa or more, preferably 380 kPa to 1300 kPa, preferably 450 kPa to 1100 kPa, Using the one having 500 kPa to 1000 kPa has excellent followability with respect to an adherend having an uneven shape and a rough surface, and when it is used as a base material for an adhesive sheet, It is more preferable because a pressure-sensitive adhesive sheet having excellent followability to the adherend can be obtained.

  In addition, 25% compressive strength points out the value measured according to JISK6767. Specifically, the foam cut into 25 mm squares is overlapped to a thickness of about 10 mm, sandwiched between stainless plates, and about 2.5 mm (original thickness at a rate of 10 mm / min at 23 ° C. Is a value obtained by measuring the strength when compressed by 25%).

As the foam, it is preferable that the flow direction and the width direction of the tensile modulus to use not more respectively 200 N / cm ² or ^more, the use of what is 300N / cm ² ~1800N / cm 2 More preferred.

Of among the tensile modulus of the flow direction and the width direction, the tensile modulus is ^low, it is preferably ^{500N / cm 2 ~1400N / cm 2} , is 600N / cm ² ~1300N / cm 2 Is more preferable. Further, among of which the tensile modulus of the flow direction and the width direction, the tensile modulus is high value is ^{preferably 700N / cm 2 ~1800N / cm 2} , at 800N / cm ² ~1600N / cm 2 More preferably.

  In addition, the tensile elasticity modulus of the flow direction of the said foam and the width direction points out the value measured according to JISK6767. Specifically, a foam with a marked line length of 2 cm and a width of 1 cm was measured with a maximum strength measured using a Tensilon tensile tester under an environment of 23 ° C. and 50% RH under a measurement condition of a tensile speed of 300 mm / min. is there.

  Further, the tensile elongation at the time of cutting in the tensile test of the foam is preferably 200% to 1500%, more preferably 400% to 1000%, more preferably 450%. More preferably, it is ˜800%. The foam having the tensile modulus or tensile elongation in the above range is less likely to cause interlaminar breakage, tearing, etc., so that the workability and pasting workability that can occur in a pressure-sensitive adhesive sheet obtained using a general foam Can be suppressed. The pressure-sensitive adhesive sheet obtained using the foam is easy to remove from the surface of the adherend.

  As the foam, one obtained by using at least one selected from the group consisting of polyolefin, polyurethane and acrylic polymer can be used. Specifically, polyethylene, polypropylene, ethylene-propylene copolymer can be used. Further, a polyolefin foam obtained by using an ethylene-vinyl acetate copolymer or the like, a polyurethane foam, a rubber foam obtained by using acrylic rubber, other elastomers, or the like can be used. Among them, as the foam, a polyolefin foam is used because it has excellent conformability to surface irregularities of the adherend and impact resistance to the surface direction and shear direction even if it is thin. Is preferred.

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

  Examples of the polyethylene resin include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, ethylene-α-olefin copolymer, ethylene-vinyl acetate copolymer, and the like. More than one species can be used in combination.

  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. .

  The polyethylene resin is preferably contained in an amount of 40% by mass or more, more preferably 50% by mass or more, and more preferably 60% by mass or more based on the total amount of the polyolefin resin used for the production of the foam. It is more preferable that it is contained in an amount of 80% by mass or more.

  As the polyethylene-based resin, it is possible to use a resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. It is relatively easy to stretch uniformly, and the thickness of the polyolefin-based foam is uniform overall. Since a body can be obtained, it is preferable.

  The polyethylene-based resin does not cause peeling of the adherend due to cracking of the foam when a force (impact) in the shear direction is applied, and has an excellent followability to the stepped portion. In order to obtain a sheet, an elastomer such as a styrene-based thermoplastic elastomer, an olefin-based thermoplastic elastomer, or an ethylene / α-olefin-based thermoplastic elastomer can be used.

  The method for producing the foam is not particularly limited, 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 if necessary, pyrolysis A foamable polyolefin resin sheet is prepared by supplying a foamable polyolefin resin composition containing a mold foaming agent, a foaming aid, and a colorant to an extruder, melt-kneading, and extruding the sheet from the extruder. Examples of the method include a step of producing, a step of crosslinking the expandable polyolefin resin sheet as necessary, and a step of foaming the expandable polyolefin resin sheet.

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

  As a method for producing the expandable polyolefin resin sheet, a polyolefin resin, a pyrolytic foaming agent, a foaming aid, a colorant, and other optional components constituting the expandable polyolefin resin composition are uniaxial. It can be manufactured by supplying to an extruder such as an extruder or a twin screw extruder, melting and kneading at a temperature lower than the decomposition temperature of the pyrolytic foaming agent, and extruding by extrusion molding or the like.

  The step of crosslinking the expandable polyolefin resin sheet obtained by the above method includes, for example, a method of irradiating the expandable polyolefin resin sheet with ionizing radiation, and an expandable polyolefin resin composition containing an organic peroxide. And it can carry out by the method etc. which heat the foamable polyolefin resin sheet obtained by using it.

  Examples of the ionizing radiation include electron beams, α rays, β rays, and γ rays. The dose of ionizing radiation is appropriately adjusted so that the gel fraction of the polyolefin resin foam is within the above-mentioned preferable range, but a range of 5 to 200 kGy is preferable. Moreover, since it is easy to obtain a uniform foamed state, it is preferable to irradiate ionizing radiation on both surfaces of the expandable polyolefin resin sheet, and it is more preferable that the doses irradiated on both surfaces are the same.

  Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, 2,2-bis ( t-butylperoxy) octane, n-butyl-4,4-bis (t-butylperoxy) valerate, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α, α ′ -Bis (t-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-di (t-butyl) Peroxy) hexyne-3, benzoyl peroxide, cumyl peroxyneodecanate, t-butyl peroxybenzoate, 2,5-dimethyl-2,5-di (ben (Zoylperoxy) hexane, t-butylperoxyisopropyl carbonate, t-butylperoxyallyl carbonate and the like may be mentioned, and these may be used alone or in combination of two or more.

  0.01 mass part-5 mass parts are preferable with respect to 100 mass parts of polyolefin resin, and, as for the addition amount of an organic peroxide, 0.1 mass part-3 mass parts are more preferable.

  The step of foaming the expandable polyolefin resin sheet can be performed by, for example, a method of heating with hot air, a method of heating with infrared rays, a method using a salt bath, a method using an oil bath, or the like. Of these, a method of heating with hot air or a method of heating with infrared rays is preferable.

  When foaming the foamable polyolefin resin sheet, a foamable polyolefin resin sheet containing a pyrolytic foaming agent can be used.

  The pyrolytic foaming agent may be appropriately determined according to the expansion ratio of the polyolefin resin foam, but is used in the range of 0.5 to 40 parts by mass with respect to 100 parts by mass of the polyolefin resin. Preferably, it is used in the range of 1 part by mass to 30 parts by mass, more preferably in the range of 1 part by mass to 20 parts by mass, and in the range of 1 part by mass to 10 parts by mass. Is more preferable, and it is more preferable to use in the range of 1 to 5 parts by mass.

  As the thermally decomposable foaming agent, those having a decomposition temperature higher than the melting temperature of the polyolefin resin are preferable, the decomposition temperature is more preferably 160 ° C to 270 ° C, and further preferably 160 ° C to 220 ° C. .

  Examples of the pyrolytic foaming agent include organic compounds such as azo compounds such as azodicarbonamide, nitroso compounds such as N, N′-dinitrosopentamethylenetetramine, and hydrazine compounds such as 4,4′-oxybis (benzenesulfonylhydrazide). Examples include foaming agents, carbonates such as sodium bicarbonate and ammonium carbonate, inorganic foams such as ammonium nitrite, sodium borohydride, and anhydrous sodium citrate, but azo compounds and nitroso compounds are preferred, azodicarbonamide and N, N′-dinitrosopentamethylenetetramine is more preferred.

  As the thermal decomposable foaming agent, it is preferable to use a powdery one, preferably a 50% average particle diameter (median diameter) of 50 μm or less, preferably 40 μm or less. It is more preferable to use one having a thickness of 30 μm or less, and the number of bubbles present in the range of thickness × width direction distance (1.5 mm) is 20, and the foam is cut in the flow direction. Of these surfaces, it is preferable to produce a foam having 20 bubbles in the range of thickness × flow direction distance (1.5 mm).

  The 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 expandable polyolefin resin sheet.

  The stretching step may be continued in a state where the molten state in the foaming step is maintained, or may be performed after the foaming step by cooling and heating the foam again.

  As the foam, a foam having the specific average cell diameter ratios (A) and (B) can be obtained by using the foam that has undergone the stretching step, and the foam is used. Accordingly, it is possible to obtain a pressure-sensitive adhesive sheet that is less likely to cause cracking due to impact and has good followability to the stepped portion.

  Here, the molten state of the foam means a state where the foam is heated to a temperature equal to or higher than the melting point of a resin such as a polyolefin resin constituting the foam. The softening of the foam means a state where the foam is heated to a temperature not lower than the melting point and lower than the melting point of a resin such as polyolefin resin constituting the foam.

  As said polyolefin-type foam obtained by the said method, what has a crosslinked structure can be used.

  The polyolefin-based foam having the crosslinked structure is preferably a foam having a crosslinking 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. However, it is possible to obtain a pressure-sensitive adhesive sheet having good followability to a step portion without causing peeling of the adherend due to cracking of the foam when a force (impact) in the shear direction is applied. Is preferable.

  The degree of cross-linking is calculated from the proportion of insoluble matter when the polyolefin foam is immersed in xylene at 105 ° C. for 24 hours.

As the foam of the present invention, a colored product can be used for the purpose of imparting design properties, light shielding properties, concealing properties, light reflectivity, and light resistance. As the colorant that can be used for the coloring, for example, a black colorant 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, anthraquinone organic black pigment and the like can be used. Among these, as a colorant, it is preferable to use carbon black in order to maintain cost, availability, insulation, and heat resistance.

  As the colorant, a white colorant can be used. Specifically, titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, oxidation Cesium, yttrium oxide, magnesium carbonate, 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, diatomaceous earth, bentonite, lithopone, zeolite, sericite, and other inorganic white colorants and silicone resin particles, acrylic Resin particles Tan resin particles, such as organic white colorants such as melamine resin particles can be used. Among these, as the colorant, it is preferable to use aluminum oxide or zinc oxide in order to maintain cost, availability, color tone, and heat resistance.

  In addition, as the foam of the present invention, foaming aids such as plasticizers, antioxidants, and zinc oxides, cell core modifiers, thermal stabilizers, metal inertness, as long as the physical properties are not impaired. Addition of additives, flame retardants such as aluminum hydroxide and magnesium hydroxide, antistatic agents, glass and plastic hollow balloon beads, metal powder, fillers such as metal compounds, conductive fillers, thermal conductive fillers, etc. What contains an agent can be used.

  As said foam, 0.1 mass%-10 mass% are preferable with respect to resin, such as polyolefin resin, in order to maintain moderate followable | trackability and cushioning property, and 1 mass%-7 Mass% is preferred.

  When producing a foam containing additives such as the colorant, the thermally decomposable foaming agent and the foaming aid, the foamable polyolefin resin is used to prevent color unevenness, partial excessive foaming, foam shortage and the like. The number of bubbles present in the range of thickness × width direction distance (1.5 mm) is that a thermoplastic resin that is highly compatible with the composition and the additive previously kneaded into a master batch are used. Is a foam in which the number of bubbles present in the range of thickness × flow direction distance (1.5 mm) is 20 or more among the surfaces of the foam cut in the flow direction. It is preferable in manufacturing.

  As the foam, it is preferable to use a foam having a surface with a wetting index of 36 mN / m or more by a wetting reagent for the purpose of improving the adhesiveness with the pressure-sensitive adhesive layer or other layers. It is more preferable to use a material having a surface of m or more, and it is even more preferable to use a material having a surface of 48 mN / m or more. Examples of the method for adjusting the wetness index of the surface of the foam to the above range include surface treatment methods such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone treatment, ultraviolet treatment, and application of an easy adhesion treatment agent. .

  The pressure-sensitive adhesive sheet of the present invention has a structure in which a pressure-sensitive adhesive layer is directly laminated on one side or both sides of the foam, or a pressure-sensitive adhesive on one side or both sides of the foam via another layer. What has the structure by which the agent layer was laminated | stacked is mentioned.

  Examples of the adhesive that can be used for forming the adhesive layer include acrylic adhesives, urethane adhesives, synthetic rubber adhesives, natural rubber adhesives, and silicone adhesives. , Containing an acrylic polymer that is a polymer of monomer components including a (meth) acrylic monomer, and using an acrylic pressure-sensitive adhesive containing a tackifier resin, a crosslinking agent, or the like, if necessary. preferable.

  Examples of the (meth) acrylic monomer that can be used for the production of the acrylic polymer include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t- Carbon such as butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate A (meth) acrylate having an alkyl group having 1 to 12 atoms can be used.

  Among these, as the (meth) acrylic monomer, it is preferable to use a (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and having an alkyl group having 4 to 8 carbon atoms. It is more preferable to use (meth) acrylate, and it is particularly preferable to use either one or both of n-butyl acrylate and 2-ethylhexyl acrylate in order to achieve 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, based on the total amount of monomers used for the production of the acrylic polymer. It is more preferable to use in the range of 98.5% by mass, and it is further preferable to use in the range of 90% by mass to 98.5% by mass in order to achieve both excellent adhesive force and excellent followability.

  Moreover, when manufacturing the said acrylic polymer, a highly polar vinyl monomer can be used as a monomer. As the highly polar vinyl monomer, a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, a vinyl monomer having an amide group, or the like can be used alone or in combination.

  Examples of the monomer having a hydroxyl group include a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl (meth) acrylate. (Meth) acrylates 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 oxalic acid acrylate, etc. can be used. Of these, acrylic acid is preferably 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 high-polarity vinyl monomer, vinyl acetate, ethylene oxide-modified succinic acid acrylate, 2-acrylamido-2-methylpropane sulfonic acid and the like can be used in addition to those described above.

  The high-polarity vinyl monomer is preferably used in a range of 1.5% by mass to 20% by mass with respect to the total amount of monomers used for the production of the acrylic polymer. It is more preferable to use in the range of 10 to 10% by mass, and it is more preferable to use in the range of 2 to 8% by mass in order to achieve both excellent adhesive force and excellent followability.

  When using the thing containing the crosslinking agent mentioned later as the said adhesive, it is preferable to use the acrylic polymer which has a functional group which reacts with the functional group which the said crosslinking agent has as said acrylic polymer. Examples of the functional group that the acrylic polymer may have include a hydroxyl group.

  The hydroxyl group can be introduced into the acrylic polymer, for example, by using a vinyl 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 with respect to the total amount of monomers used for the production of the acrylic polymer. It is more preferable to use in the range of mass% to 0.3 mass%.

  The acrylic polymer can be produced by polymerizing the monomer by a method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method, etc., and adopting a solution polymerization method Is preferable for improving the production efficiency of the acrylic polymer.

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

  Examples of the polymerization initiator include peroxides such as benzoyl peroxide and lauryl peroxide, azo thermal polymerization initiators such as azobisisobutylnitrile, acetophenone photopolymerization initiators, benzoin ether photopolymerization initiators, benzyl A ketal photopolymerization initiator, an acyl phosphine oxide photopolymerization initiator, a benzoin photopolymerization initiator, a benzophenone photopolymerization initiator, or the like can be used.

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

  As said acrylic polymer, it is preferable to use what has a weight average molecular weight of 400,000-3 million, and it is more preferable to use what has a weight average molecular weight of 700,000-2,500,000.

  The weight average molecular weight is a value measured by gel permeation chromatography (GPC method) and calculated in terms of standard polystyrene. Specifically, the weight average molecular weight can be measured under the following conditions using a GPC apparatus (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 Measuring temperature: 40 ° C
This column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: Differential refractometer Weight average molecular weight of standard polystyrene: 10,000 to 20 million (manufactured by Tosoh Corporation)

  As the pressure-sensitive adhesive that can be used for forming the pressure-sensitive adhesive layer, it is possible to use a material containing a tackifying resin in order to achieve both excellent adhesion to an adherend and foam and excellent followability. preferable.

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

  Examples of the tackifying resin include disproportionated rosin ester tackifying resin, polymerized rosin ester tackifying resin, rosin phenol tackifying resin, hydrogenated rosin ester tackifying resin, (meth) acrylate, among others. It is preferable to use one or a combination of two or more of resins, terpene phenol resins, and petroleum resins.

  As the tackifier resin, those having a softening point in the range of 30 ° C. to 180 ° C. are preferable, and those having a softening point in the range of 70 ° C. to 140 ° C. are used. ) Is more preferable for achieving both excellent adhesive strength and excellent followability. When the (meth) acrylate tackifying resin is used, it is preferable to use a (meth) acrylate tackifying resin having a glass transition temperature of 30 ° C. to 200 ° C., and a resin having a temperature of 50 ° C. to 160 ° C. It is more preferable.

  The tackifying resin is preferably used in the range of 5 to 65 parts by mass, and in the range of 8 to 55 parts by mass, based on 100 parts by mass of the acrylic polymer. It is more preferable for achieving both excellent adhesion to the body and foam and excellent followability.

  As a pressure-sensitive adhesive used for forming the pressure-sensitive adhesive layer, a cross-linking agent is used in forming a pressure-sensitive adhesive layer that has both excellent adhesion to an adherend and foam and excellent followability. Is preferred.

  As said crosslinking agent, an isocyanate type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent, an aziridine type crosslinking agent etc. can be used, for example. Especially, as said crosslinking agent, it is preferable to use any one or both of the isocyanate type crosslinking agent and epoxy-type crosslinking agent which are rich in the reactivity with an acrylic polymer, and using an isocyanate type crosslinking agent is preferable. More preferred.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, trimethylolpropane-modified tolylene diisocyanate, and the like. It is preferable to use trimethylolpropane-modified tolylene diisocyanate.

  The crosslinking agent is preferably selected and used in such an amount that the gel fraction of the pressure-sensitive adhesive layer relative to toluene is 70% by mass or less, and is selected and used in such an amount that the gel fraction is 20% by mass to 60% by mass. It is more preferable to select and use an amount with a gel fraction of 25% by mass to 55% by mass, which achieves both excellent adhesion to the adherend and foam substrate and excellent followability. It is further preferable when obtaining an adhesive sheet.

  In addition, the said gel fraction points out the value measured by the method shown below.

  The pressure-sensitive adhesive coated on the release treatment surface of the release liner so that the thickness after drying is 50 μm is dried for 3 minutes in an environment of 100 ° C., and then 2 in an environment of 40 ° C. The pressure-sensitive adhesive layer was formed by aging for a day.

  A test piece was prepared by cutting the pressure-sensitive adhesive layer into a square of 50 mm length and 50 mm width.

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

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

    Gel fraction (mass%) = (G2 / G1) × 100

  Examples of the pressure-sensitive adhesive include plasticizers, softeners, antioxidants, flame retardants, glass and plastic fibers and balloons, beads, metals, metal oxides, metal nitride fillers, pigments, dyes, and the like. What contains additives, such as a coloring agent, a leveling agent, a thickener, a water repellent, an antifoamer, can be used.

  The pressure-sensitive adhesive layer that can be formed using the pressure-sensitive adhesive preferably has a temperature showing a peak value of loss tangent (tan δ) at a frequency of 1 Hz, preferably -40 ° C to 15 ° C. By making the peak value of the loss tangent of the pressure-sensitive adhesive layer within the above range, it becomes easy to impart good adhesion to the adherend at room temperature. In particular, in improving the drop impact resistance in a low temperature environment, the temperature is more preferably −35 ° C. to 10 ° C., and further preferably −30 ° C. to 6 ° C.

  The loss tangent (tan δ) at a frequency of 1 Hz is obtained from the equation of tan δ = G ″ / G ′ from the storage elastic modulus (G ′) and loss elastic modulus (G ″) obtained by dynamic viscoelasticity measurement by temperature dispersion. It is done. In the measurement of dynamic viscoelasticity, the pressure-sensitive adhesive layer formed to a thickness of about 2 mm was used with a viscoelasticity testing machine (trade name: ARES G2 manufactured by T.A. Instruments Japan). A test piece is sandwiched between parallel disks having a diameter of 8 mm, which is a measuring part, and a storage elastic modulus (G ′) and a loss elastic modulus (G ″) from −50 ° C. to 150 ° C. are measured at a frequency of 1 Hz.

  The thickness of the pressure-sensitive adhesive layer used in the present invention is preferably 5 μm to 100 μm, preferably 10 μm to 80 μm in order to achieve both excellent adhesion to the adherend and foam and excellent followability. More preferably, it is particularly preferably 15 μm to 80 μm.

  The pressure-sensitive adhesive sheet of the present invention is formed by, for example, a direct method in which the pressure-sensitive adhesive is directly applied to the foam and dried, or after a pressure-sensitive adhesive layer is formed by applying a pressure-sensitive adhesive to the release sheet and then drying. It can be manufactured by a transfer method that is bonded to the body. When an adhesive containing an acrylic polymer and a crosslinking agent is used as the adhesive that forms the adhesive layer, the adhesive layer is laminated on one or both sides of the foam by the direct method or the transfer method. Aging, preferably 2 to 7 days in an environment of 20 ° C. to 50 ° C., more preferably 23 ° C. to 45 ° C., and excellent adhesion to the adherend and foam substrate, and excellent This is preferable for achieving both the following ability.

  As the pressure-sensitive adhesive sheet of the present invention, it is preferable to use a sheet having a total thickness of 500 μm or less because it is easy to contribute to thinning of a small electronic device, and it is more preferable to use a sheet having a thickness of 80 μm to 400 μm. It is more preferable to use what is 100 micrometers-350 micrometers, and it is especially preferable to use what is 150 micrometers-300 micrometers. Since the pressure-sensitive adhesive sheet uses a 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, a force (impact) in the shearing direction is generated. When it is added, the adherend is not peeled off due to cracking of the foam or the like, and good followability can be achieved with respect to the stepped portion.

  As said adhesive sheet, what has another layer other than the said foam and an adhesive layer as needed can be used.

  Examples of the other layers include a laminated layer such as a polyester film, a light shielding layer, a light reflecting layer, a heat conductive layer such as a metal layer, etc. Is mentioned.

  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.

  As the release sheet, for example, a film obtained by using a synthetic resin such as polyethylene, polypropylene, polyester, paper, non-woven fabric, cloth, foamed sheet, metal substrate, and at least one side of a laminate thereof is treated with silicone. In addition, those subjected to a peeling treatment such as a long-chain alkyl treatment or a fluorine treatment can be used.

  The pressure-sensitive adhesive sheet of the present invention can be used, for example, for fixing a member in which the width of the narrowest portion of the pressure-sensitive adhesive sheet is limited to 5 mm or less due to restrictions such as an application site and a shape.

  The narrow member is often used as a member in industrial applications such as electronic terminals such as mobile phones, automobiles, building materials, OA, and home appliance industries.

  Specific examples of the member include two or more casings 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 to which two or more cases and lens members are fixed using the pressure-sensitive adhesive sheet of the present invention is not easily disassembled by an impact such as dropping, and has an excellent waterproof property.

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

[Preparation Example 1] Production method of acrylic polymer (A-1) In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen introduction tube and a thermometer, 95.9 parts by mass of n-butyl acrylate and 4 parts by mass of acrylic acid Then, 0.1 part by mass of 2-hydroxyethyl acrylate and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72 ° C. while blowing nitrogen under stirring.

  Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.

  Next, the mixture was filtered through a 200-mesh wire mesh to obtain an acrylic polymer (A-1) solution (non-volatile content: 33.3% by mass) having a weight average molecular weight of 1,860,000.

[Preparation Example 2] Method for Producing Acrylic Polymer (A-2) In a reaction vessel equipped with a stirrer, reflux condenser, nitrogen inlet tube and thermometer, 63.9 parts by mass of n-butyl acrylate, 2-ethylhexyl acrylate 32 Part by mass, 4 parts by mass of acrylic acid, 0.1 part by mass of 4-hydroxybutyl acrylate, and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72 ° C. while blowing nitrogen under stirring.

  Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.

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

[Example 1]
In a container, 10 parts by mass of a polymerized rosin ester-based tackifier resin D-125 (manufactured by Arakawa Chemical Co., Ltd.) and a disproportionated rosin ester-based tackifier resin with respect to 100 parts by mass of the acrylic polymer (A-1). After mixing and stirring 15 parts by mass of A-100 (Arakawa Chemical Industries, Ltd.), ethyl acetate was added to obtain a pressure-sensitive adhesive composition (A) having a solid content of 31% by mass.

  Next, with respect to 100 parts by mass of the pressure-sensitive adhesive composition (A), Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile as a crosslinking agent After adding 1.4 parts by mass of (min. 40% by mass) and stirring and mixing so as to be uniform, an adhesive (A) was obtained by filtering through a 100 mesh wire net.

  Next, the pressure-sensitive adhesive (A) is applied to the surface of the release liner using a bar coater so that the thickness of the pressure-sensitive adhesive layer after drying is 50 μm, and dried at 80 ° C. for 3 minutes. Thus, an adhesive layer was prepared.

  Next, the pressure-sensitive adhesive layer was affixed to both surfaces of the polyolefin resin-based foam 1 listed in Table 1 having a wettability index adjusted to 54 mN / m by corona treatment, and a 48 ° C. environment at 40 ° C. A pressure sensitive adhesive sheet was prepared by curing for a period of time.

[Example 2]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1, except that the polyolefin resin foam 2 shown in Table 1 was used.

[Example 3]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 3 shown in Table 1 was used.

[Example 4]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 4 shown in Table 1 was used.

[Example 5]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1, except that the polyolefin resin foam 5 shown in Table 1 was used.

[Example 6]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 6 shown in Table 1 was used.

[Example 7]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 7 shown in Table 1 was used.

[Example 8]
In a container, with respect to 100 parts by mass of the acrylic polymer (A-2), 10 parts by mass of polymerized rosin ester-based tackifier resin D-125 (Arakawa Chemical Industries, Ltd.) and disproportionated rosin ester-based tackifier resin After 15 parts by mass of A-100 (Arakawa Chemical Industries, Ltd.) were mixed and stirred, an ethyl acetate was added to obtain a pressure-sensitive adhesive composition (B) having a solid content of 31% by mass.

  Next, Vernock D-40 (manufactured by DIC Corporation, trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile as a crosslinking agent with respect to 100 parts by mass of the pressure-sensitive adhesive composition (B) After adding 1.4 parts by mass of (min. 40% by mass) and stirring and mixing so as to be uniform, an adhesive (B) was obtained by filtering through a 100 mesh wire net.

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

[Example 9]
Instead of using the polyolefin resin foam 1, the polyolefin resin foam 8 shown in Table 2 was used, and the thickness of the pressure-sensitive adhesive layer after drying the pressure-sensitive adhesive (A) was 40 μm. A pressure-sensitive adhesive sheet was obtained in the same manner as in Example 1.

[Example 10]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 13 shown in Table 2 was used.

[Example 11]
Instead of the polyolefin resin foam 4, an adhesive sheet was obtained in the same manner as in Example 8 except that the polyolefin resin foam 14 shown in Table 2 was used.

[Example 12]
Instead of the polyolefin resin foam 8, an adhesive sheet was obtained in the same manner as in Example 9 except that the polyolefin resin foam 15 shown in Table 2 was used.

[Comparative Example 1]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 9 shown in Table 2 was used.

[Comparative Example 2]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 10 shown in Table 2 was used.

[Comparative Example 3]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 11 shown in Table 2 was used.

[Comparative Example 4]
Instead of the polyolefin resin foam 1, an adhesive sheet was obtained in the same manner as in Example 1 except that the polyolefin resin foam 12 shown in Table 2 was used.

  The apparent density, average bubble diameter, average bubble diameter ratio, and number of bubbles in Tables 1 and 2 were measured by the same method as described in this specification. MD in Tables 1 and 2 represents the flow direction, CD represents the width direction, and VD represents 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 represent values measured using a dial series gauge G type manufactured by Ozaki Seisakusho.

[Method of evaluating impact resistance in shear direction]
A test tape was obtained by cutting the pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples into a size of 1 mm in width and 1.5 cm in length.

  Next, the four 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 is smooth) having a thickness of 2 mm, a width of 5 cm, and a length of 5 cm is placed on the surface of the test tape, and the upper surface thereof is placed on page 8 of JISZ0237 (2009) ( After pressing the roller by reciprocating once in a roller having a diameter of 85 ± 2.5 mm, a width of 45 ± 1.5 mm and a mass of 2000 ± 100 g described in “10. The specimen left for a period of time was used as a test piece (see FIG. 1).

  A metal weight having a weight of 100 g was continuously dropped twice from a height of 5 cm onto the side surface of the glass plate constituting the test piece (FIG. 2). The presence or absence of cracks in the foam constituting the test piece after dropping was visually confirmed. The test piece which could not confirm the crack of the said foam was dropped 5 times continuously from the position (10 cm in height) which was 5 cm higher, and the presence or absence of the crack of the foam which comprises the test piece was confirmed visually. The above test was repeated, and the height at which the crack of the foam was confirmed is shown in Tables 2 and 3.

  As a result of the test, the drop height was 25 cm or more as “◎◎”, 20 cm as “◎”, 15 cm as “◯”, 10 cm as “Δ”. What was 5 cm was evaluated as "x".

[Evaluation method of step following ability]
The pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples are cut into a frame shape having a width of 2 mm and a width of 64 mm × 43 mm, and this is attached to an acrylic plate having a thickness of 2 mm and a width of 65 mm × 45 mm. An attached acrylic board was obtained.

  Next, a single-sided pressure-sensitive adhesive tape (thickness 30 μm, width 5 mm and length 45 mm) having an adhesive layer on one side of a polyethylene terephthalate base material at the center of an acrylic plate having a thickness of 2 mm and an outer shape 65 mm × 45 mm different from the above ) Acrylic plates having a stepped portion were prepared by sticking two pieces in parallel in the vertical direction at intervals of 1 cm.

  By placing the surface having the pressure-sensitive adhesive layer of the acrylic plate with the frame pressure-sensitive adhesive sheet on the surface having the stepped portion of the acrylic plate having the stepped portion at 23 ° C., and pressurizing the upper part one time with a 2 kg roller. A laminate was obtained.

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

  (Double-circle): The space | gap, such as a bubble, was not confirmed at all in the interface of a level | step-difference part and an adhesive sheet.

  ○: Although voids such as fine bubbles were confirmed at the interface between the stepped portion and the pressure-sensitive adhesive sheet, it was at a level that does not cause any problems in practice.

  (Triangle | delta): The space | gap, such as a bubble, was confirmed in the interface of a level | step-difference part and an adhesive sheet.

  X: A clear void such as a large bubble was observed at the interface between the step portion and the pressure-sensitive adhesive sheet.

1 Glass plate 2 Test tape 3 Weight 4 Polycarbonate plate

Claims (7)

Apparent density on one side or both sides of the foam is in the range of ^{0.40g / cm 3 ~0.59g / cm 3} , a pressure-sensitive adhesive sheet having an adhesive layer, was cut the foam in the width direction Among the surfaces, the number of bubbles existing in the range of thickness × width direction distance (1.5 mm) is 20 to 150 , and among the surfaces obtained by cutting the foam in the flow direction, thickness × flow the number of bubbles present in the range of directions distance (1.5 mm) is Ri 20-150 amino der, an average cell diameter of the flow direction 20Myuemu～160myuemu, and the average cell diameter in the width direction at 20Myuemu～160myuemu There, the foam is a polyolefin foam, adhesive sheet thickness of the foam and wherein 50~400μm der Rukoto. 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 ratio of the average bubble diameter in the width direction to the average bubble diameter in the thickness direction (B ) Is a pressure-sensitive adhesive sheet according to claim 1, which has bubbles of 0.3 to 4. The pressure-sensitive adhesive sheet according to claim 1 or 2 , wherein the foam has a thickness in the range of 50 µm to 400 µm. The pressure-sensitive adhesive sheet according to any one of claims 1 to 3 , wherein the foam has a 25% compressive strength of 500 kPa to 1000 kPa. The pressure-sensitive adhesive sheet according to any one of claims 1-4 thickness of the adhesive layer is 10Myuemu～80myuemu. The pressure-sensitive adhesive sheet according to any one of claims 1 to 5 , wherein the pressure-sensitive adhesive layer contains an acrylic polymer having a weight average molecular weight of 700,000 to 2.5 million. An electronic apparatus having a configuration in which two or more adherends are bonded by the pressure-sensitive adhesive sheet according to any one of claims 1 to 6 .

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