JP6058016B2 - Double-sided adhesive tape - Google Patents

Description

  The present invention relates to a double-sided pressure-sensitive adhesive tape that can be used for fixing various members including electronic devices.

  The double-sided pressure-sensitive adhesive tape is used for fixing members of various electronic devices, for example. Specifically, the double-sided adhesive tape is a rigid part such as fixing the protective panel of the image display unit and the casing constituting a small electronic device such as a mobile phone, a camera, a personal computer, an exterior part, a battery, and various member modules. Often used to fix each other.

  As a double-sided pressure-sensitive adhesive tape that can be suitably used for fixing components such as small electronic devices, a thin and good followable tape can be suitably used. For example, a flexible foam is used as a base material. A double-sided pressure-sensitive adhesive tape is known (for example, see Patent Document 1 or 2).

  On the other hand, the small electronic device has many opportunities to be carried and used, and the double-sided pressure-sensitive adhesive tape may be peeled off due to an impact when the small electronic device is dropped. Therefore, the double-sided pressure-sensitive adhesive tape is required to have a level of impact resistance that can withstand the impact of the drop.

  In addition, expensive electronic parts such as a protective panel for an image display unit, an image display module, and a thin plate-like rigid body such as a thin battery are often used in portable electronic devices that have advanced functions. For this reason, the adhesive tape is required to have a level of disassembly that allows the components to be separated from the electronic device relatively easily and efficiently when a failure of the electronic device occurs.

JP 2010-155969 A JP 2010-260880 A

  The problem to be solved by the present invention is to provide a double-sided pressure-sensitive adhesive tape that has suitable impact resistance and can be easily disassembled when a certain force is applied.

The present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a foam base material, the foam base material having a density of 0.45 g / cm ³ or less and an interlayer strength of 10 N / cm or more. The pressure-sensitive adhesive layer is a 25 μm-thick polyethylene terephthalate base material provided with a 25 μm-thick pressure-sensitive adhesive layer on an aluminum plate in an environment of a temperature of 23 ° C. and a relative humidity of 65% RH. The adhesive force is 12N when peeled by 180 ° at a peeling speed of 300 mm / min measured after being pressed for one hour using a 2 kg roller and allowed to stand in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH for 1 hour. The above-mentioned problem is solved by a double-sided pressure-sensitive adhesive tape characterized by being a pressure-sensitive adhesive layer of / 20 mm or more.

  With the above configuration, the double-sided pressure-sensitive adhesive tape of the present invention has a suitable impact resistance, and when a certain force is applied, the foam base material can be easily disassembled by causing an interlaminar crack. For this reason, when an impact such as dropping is applied to an electronic device using the double-sided pressure-sensitive adhesive tape of the present invention, the component is not easily detached, and can be disassembled with a constant force. Can suppress cracking and distortion. In addition, when a specific part is dismantled from a defective product such as the electronic device or a recycled product, it can be disassembled efficiently. The double-sided pressure-sensitive adhesive tape of the present invention as described above is used, for example, for fixing parts of small electronic devices, particularly for fixing thin plate-like rigid parts such as protective panels and image display modules for thin electronic devices and image display modules. It can be suitably applied to.

It is the conceptual diagram which looked at the test piece used for the test for impact tests from the upper surface. It is the conceptual diagram which looked at the test piece used for the test for impact tests from the upper surface. It is a conceptual diagram of the test method of an impact resistance test.

The double-sided pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of a foam substrate, and the foam substrate has a density of 0.45 g / cm ³ or less and an interlayer strength of 10 N / cm or more. A pressure-sensitive adhesive tape, which is a foam base material and is formed by providing a 25 μm thick adhesive layer on a 25 μm thick polyethylene terephthalate base material, in an environment at a temperature of 23 ° C. and a relative humidity of 65% RH With a 2 kg roller, the aluminum plate is crimped by reciprocating once, and then 180 ° peeling at a peeling speed of 300 mm / min measured after standing for 1 hour in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH. It is an adhesive layer having an adhesive strength of 12 N / 20 mm or more.

[Foam substrate]
The foam substrate for use in the present invention, density of 0.45 g / cm ³ or less, preferably ^{0.1g / cm 3 ~0.45g / cm 3} , more preferably 0.15g ^/ cm 3 ~0. What is 42 g / cm ³ can be used. By using a foam substrate having a density in the above range, it is possible to obtain a double-sided pressure-sensitive adhesive tape having suitable dismantling properties when a certain force is applied.

  In addition, as the foam base material used in the present invention, one having an interlayer strength of 10 N / cm or more, preferably 10 N / cm to 50 N / cm, more preferably 10 N / cm to 25 N / cm is used. Can do. By using a foam base material having an interlayer strength in the above range, it is possible to achieve both suitable dismantling properties and suitable impact resistance, and the paste remaining on the surface of the adherend such as parts after dismantling It becomes possible to easily peel off the remaining materials such as.

  The interlayer strength can be measured by the following method.

  One sheet of strong adhesive layer with a thickness of 50 μm (adhesive layer with a level of adhesive that does not peel from the adherend and foam substrate by the following high-speed peel test) on both surfaces of the foam substrate After laminating each one, aging at 40 ° C. for 48 hours creates a double-sided pressure-sensitive adhesive tape for measuring interlayer strength.

  Next, the pressure-sensitive adhesive layer surface on one side of the double-sided pressure-sensitive adhesive tape for measuring the interlayer strength was lined with a polyester film having a thickness of 25 μm, and cut into a size of 1 cm in the width direction of the foam substrate and 15 cm in the flow direction. After sticking them to a polyester film having a thickness of 50 μm, a width of 3 cm, and a length of 20 cm under a temperature of 23 ° C. and a relative humidity of 50% RH, the surface was crimped by reciprocating a 2 kg roller, A test piece is obtained by leaving still at 60 degreeC environment for 24 hours, and then leaving still at 23 degreeC for 1 hour.

  Next, at a temperature of 23 ° C. and a relative humidity of 50% RH, the 50 μm thick polyester film side constituting the test piece is fixed to a mounting jig of a high-speed peel tester, and the test piece is constituted by a 25 μm thick By pulling the polyester film in the direction of 90 degrees at a tensile speed of 15 m / min, the maximum strength when the foam substrate constituting the test piece is torn is measured.

  As the foam base material, it is preferable to use one having a 25% compressive strength of 500 kPa or less, more preferably one having 10 kPa to 300 kPa, and one having 10 kPa to 200 kPa. More preferably, those having 30 kPa to 180 kPa are more preferably used, and those having 50 kPa to 150 kPa are particularly preferable. By using a foam base material having a compressive strength of 25% within the above range, a double-sided pressure-sensitive adhesive tape having both suitable impact resistance and dismantling properties and suitable followability to an adherend is obtained. be able to.

  The 25% compressive strength can be measured according to JISK6767. Specifically, the double-sided pressure-sensitive adhesive tape sample cut into 25 corners is overlaid until the thickness is about 10 mm. The laminate of the double-sided adhesive tape sample is sandwiched between stainless steel plates having a larger area than the double-sided adhesive tape sample, and the laminate of the sample is about 2.5 mm (of the original thickness) at a speed of 10 mm / min at 23 ° C. 25%) Measure the strength when compressed.

As the foam substrate is not particularly limited tensile strength of the flow direction and the width direction, it is preferable to use those having a tensile strength is 500N ^/ cm ² ~1300N / cm 2 it is more preferable to use those having a tensile strength is ^{600N / cm 2 ~1200N / cm 2} .

  In addition, the tensile strength of the flow direction of the above-mentioned foam base material and the width direction can be measured according to JISK6767. Specifically, the double-sided pressure-sensitive adhesive tape sample cut to a size of a marked line length of 2 cm and a width of 1 cm was used at a tensile speed of 300 mm / min in a 23 ° C. and 50% RH environment using a Tensilon tensile tester. It is the maximum intensity measured under the measurement conditions.

  Further, the foam base material is not particularly limited in tensile elongation at the time of cutting the foam base material measured by the tensile test, but the tensile elongation in the flow direction is 100% to 1200%. It is preferable to use those that are 100% to 1000%, more preferably 200% to 600%.

  By using a foam base material having a tensile strength and a tensile elongation in the above ranges, a double-sided pressure-sensitive adhesive tape having good workability and sticking workability, and having even better dismantling properties is obtained. Can do.

  The average cell diameter in the flow direction and the width direction of the foam substrate is not particularly limited, but is preferably in the range of 10 μm to 500 μm, more preferably in the range of 30 μm to 400 μm, and in the range of 50 μm to 300 μm. More preferably. By using a foam substrate having an average cell diameter in the flow direction and width direction within the above range, it is possible to obtain a double-sided pressure-sensitive adhesive tape that is more excellent in adhesion to an adherend and more excellent in impact resistance. it can.

  The ratio of the average bubble diameter in the flow direction and the width direction of the foam base material (average bubble diameter in the flow direction / average bubble diameter in the width direction) is not particularly limited, but may be in the range of 0.2 to 4. Preferably, it is in the range of 0.3 to 3, more preferably in the range of 0.4 to 1. By using a foam base material having a ratio in the above range, it is possible to obtain a double-sided pressure-sensitive adhesive tape in which variations in flexibility and tensile strength in the flow direction and width direction are suppressed.

  The average cell diameter in the thickness direction of the foam substrate is preferably 3 μm to 100 μm, more preferably 5 μm to 80 μm, and even more preferably 5 μm to 50 μm. The average cell diameter in the thickness direction is preferably 1/2 or less, and preferably 1/3 or less of the thickness of the foam base material. By using a foam base material having an average cell diameter in the thickness direction within the above range, the density and tensile strength of the foam base material can be adjusted to a suitable range, and as a result, even better. Even when the disassembly and impact resistance and a rigid body is used as the adherend, a double-sided pressure-sensitive adhesive tape with even better adhesion can be obtained.

  As the foam substrate, the ratio of the average bubble diameter in the flow direction to the average bubble diameter in the thickness direction (average bubble diameter in the flow direction / average bubble diameter in the thickness direction), and the thickness direction It is preferable to use those in which the ratio of the average bubble diameter in the width direction to the average bubble diameter (average bubble diameter in the width direction / average bubble diameter in the thickness direction) is 1 or more. It is more preferable to use a certain thing, and it is still more preferable to use what is 4-25.

  By using a foam base material having the ratio of the average cell diameter, it has excellent flexibility in the thickness direction, and even better adhesion even when a rigid body is used as the adherend. Can be obtained.

  The average bubble diameter in the width direction, the average bubble diameter in the flow direction, and the average bubble diameter in the thickness direction of the foam substrate can be measured in the following manner.

  First, a foam base material is cut | disconnected to the magnitude | size of the width method 1cm and the flow direction 1cm.

  Next, a digital microscope (trade name “KH-7700”, manufactured by HiROX) is set to a magnification of 200 times, and a cut surface in the width direction or the flow direction of the foam substrate is observed. In that case, the full length of the thickness direction of the cut surface of the said foam base material is observed. In the observation, all the bubble diameters of the bubbles existing in the range of 2 mm in the flow direction or the width direction of the cut surface are measured. Next, the range of 2 mm is changed, and all the bubble diameters of bubbles existing in arbitrary 10 ranges are measured.

  The value obtained by calculating the average value of the bubble diameters measured above was defined as the average bubble diameter.

  As the foam base material, it is preferable to use one having a closed cell structure because it is possible to effectively prevent water immersion or dust from the cut surface of the foam base material. As the shape of the bubbles forming the closed cell structure, the average bubble diameter in the flow direction or width direction or in both directions is larger than the average bubble diameter in the thickness direction. It is preferable for obtaining a double-sided pressure-sensitive adhesive tape having excellent followability and cushioning properties.

  As the foam base material, it is preferable to use one having a thickness of 250 μm or less, more preferably from 50 μm to 250 μm, and even more preferably from 80 μm to 200 μm. It is particularly preferable to use one having a thickness of 100 μm to 150 μm in order to obtain a double-sided pressure-sensitive adhesive tape having even better impact resistance and dismantling properties even if it is thin.

  The density, interlayer strength, compressive strength, tensile strength, and the like of the foam base material can be appropriately adjusted depending on the material and foam structure of the foam base material to be used.

  Examples of the foam base material include polyolefin-based foams, polyurethane-based foams, and acrylic-based foams obtained by using polyolefins such as polyethylene, polypropylene, ethylene-propylene copolymers, ethylene-vinyl acetate copolymers, and the like. Other rubber-based foams can be used.

  As the foam base material, among those described above, polyolefin foam is used because it is easy to produce a foam base material having a closed cell structure that can suitably follow the surface irregularities of the adherend and has excellent impact resistance. It is preferable to do.

  As the polyolefin-based foam base material, it is preferable to use a foam base material obtained by using a polyethylene-based resin because it has a relatively uniform thickness and more suitable flexibility.

  The content of the polyethylene resin contained in the polyolefin resin is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, and 100% by mass. % Is particularly preferred.

  Examples of the polyethylene resin that can be used in the production of the polyolefin foam include linear low density polyethylene, low density polyethylene, medium density polyethylene, high density polyethylene, and ethylene-α containing 50% by mass or more of ethylene. An olefin copolymer, an ethylene-vinyl acetate copolymer containing 50% by mass or more of ethylene can be used alone or in combination of two or more.

  Examples of the α-olefin constituting the ethylene-α-olefin copolymer include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene and the like. Is mentioned.

  The polypropylene resin is not particularly limited, and examples thereof include polypropylene, a propylene-α-olefin copolymer containing 50% by mass or more of propylene, and these may be used alone or in combination of two or more. You may use together. Examples of the α-olefin constituting the propylene-α-olefin copolymer include ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene and 1-octene. Can be mentioned.

  As the polyethylene resin, it is preferable to use a polyethylene resin having a narrow molecular weight distribution obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst. In addition, the polyethylene resin obtained by the above method can adjust the copolymerization ratio of the copolymerization component to be almost equal even if it is a polyethylene resin having any molecular weight. A polyolefin foam can be obtained. The substantially uniformly crosslinked polyolefin-based foam can be easily stretched, and the thickness thereof can be easily uniformed as a whole.

  As said polyethylene resin, you may use the polyolefin resin obtained by other manufacturing methods other than what was obtained using the metallocene compound containing a tetravalent transition metal.

  The polyolefin-based foam base material may have a crosslinked structure. When producing a polyolefin-based foam by foaming a polyolefin-based resin sheet with a pyrolytic foaming agent or the like, it is preferable to design to form the crosslinked structure. The degree of crosslinking is preferably in the range of 5% by mass to 60% by mass, and more preferably in the range of 10% by mass to 55% by mass to achieve better adhesion to the pressure-sensitive adhesive layer and impact resistance. It is more preferable in improving.

  The degree of crosslinking can be measured by the following method. A set of five 40 mm × 50 mm square foam base materials is used as a sample, and the total mass (G1) is measured. Next, after immersing the sample in xylene at 120 ° C. for 24 hours, the xylene-insoluble matter was separated by filtration through a 300 mesh wire net, and the residue mass (G2) after drying at 110 ° C. for 1 hour was measured. To do. The xylene-insoluble content determined according to the following formula is defined as the degree of crosslinking.

    Crosslinking degree (mass%) = (G2 / G1) × 100

  The method for producing the polyolefin foam is not particularly limited. For example, a polyolefin resin containing 40% by weight or more of a polyethylene resin obtained by using a metallocene compound containing a tetravalent transition metal as a polymerization catalyst, and A polyolefin-based resin composition containing a pyrolytic foaming agent, a foaming aid, and a colorant for coloring the foam in black or white is supplied to an extruder and melt-kneaded. From the extruder into a sheet form A step of producing a polyolefin-based resin sheet by extruding, a step of crosslinking the polyolefin-based resin sheet, a step of foaming the polyolefin-based resin sheet, and melting or softening the obtained foamed sheet, A method comprising a step of stretching a foam sheet by stretching in either or both of the width directions And the like. In addition, the process of extending | stretching a foam sheet should just be performed as needed, and may be performed in multiple times.

  The pyrolytic foaming agent is not particularly limited as long as it is conventionally used in the production of foams. For example, azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, p-toluenesulfonyl Semicarbazide and the like can be mentioned, and among them, azodicarbonamide is preferable. In addition, a thermal decomposition type foaming agent may be individual, or 2 or more types may be used together.

  The amount of the pyrolytic foaming agent added may be appropriately determined according to the expansion ratio of the polyolefin foam, but is preferably 1 part by mass to 40 parts by mass with respect to 100 parts by mass of the polyolefin resin. It is more preferable that the amount is 1 part by mass to 30 parts by mass because the expansion ratio, tensile strength, compression recovery rate, and the like can be easily adjusted to a desired range.

  As a method of crosslinking the polyolefin foam substrate, for example, a method of irradiating the polyolefin foam substrate with ionizing radiation, an organic peroxide was previously blended in the polyolefin resin composition, and obtained. The method of heating a polyolefin-type foam base material and decomposing | disassembling an organic peroxide etc. is mentioned, These methods may be used together.

  Examples of ionizing radiation include electron beams, α rays, β rays, and γ rays. The dose of ionizing radiation can be appropriately adjusted so that the cross-linking degree of the polyolefin-based foam substrate is within the above-mentioned preferable range, but is preferably in the range of 5 kGy to 200 kGy. Moreover, since it is easy to obtain a uniform foamed state, it is preferable to irradiate both surfaces of the polyolefin-based foam base material, and it is more preferable that the radiation dose to both surfaces be 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.

  The organic peroxide is preferably in the range of 0.01 to 5 parts by mass, and in the range of 0.1 to 3 parts by mass with respect to 100 parts by mass of the polyolefin resin. It is more preferable for suppressing the residue of the decomposition residue of the organic peroxide.

  The method of foaming the polyolefin resin sheet is not particularly limited, and examples thereof include 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, and the like. May be. Among them, the method of heating with hot air or the method of heating with infrared rays is preferable because the difference in appearance between the front and back surfaces of the polyolefin-based foam substrate is reduced.

  The foam substrate may be stretched. The stretching may be performed after foaming the polyolefin resin sheet to obtain a foam substrate, or may be performed when foaming the polyolefin resin sheet.

  After foaming a polyolefin resin sheet to obtain a foam base material, when the foam base material is stretched, the foam base material is continuously maintained while maintaining the molten state at the time of foaming without cooling the foam base material. Even after stretching, the foam base material may be stretched after cooling the foam base material and heating the foam sheet again to a molten or softened state.

  The molten state of the foam base material means a state in which the foam base material is heated to a temperature equal to or higher than the melting point of the polyolefin resin constituting the foam base material. Further, the softening of the foam base material refers to a state where the foam base material is heated to a temperature not lower than the melting point and lower than the melting point of the polyolefin resin constituting the foam base material. By stretching the foam base material, the foam of the foam base material can be produced by stretching the foam base material in a predetermined direction and deforming the foam base material so that the aspect ratio of the foam is within a predetermined range.

  The extending direction of the foam base material is preferably in the flow direction or the width direction of the elongated polyolefin resin sheet, or in the flow direction and the width direction. When the foam base material is stretched in the flow direction and the width direction, the foam base material may be stretched simultaneously in the flow direction and the width direction, or may be stretched separately one by one. .

  As a method of stretching the foam base material in the flow direction, for example, a long polyolefin resin sheet after foaming is used rather than a speed (supply speed) at which the long polyolefin resin sheet is supplied to the foaming process. A method of stretching the foam base material in the flow direction by increasing the winding speed (winding speed) while cooling, foaming rather than the speed (supply speed) of supplying the obtained foam base material to the stretching process Examples include a method of stretching the foam base material in the flow direction by increasing the speed of winding the body base material (winding speed).

  Since the polyolefin resin sheet easily expands in the flow direction due to its own foaming, when the foam base material obtained using the polyolefin resin sheet is stretched in the flow direction, the polyolefin resin sheet Considering the amount of expansion in the flow direction due to foaming, it is preferable to adjust the supply speed and winding speed of the foam substrate so that the polyolefin resin sheet is stretched in the flow direction more than the expansion amount. .

  As a method of stretching the foam base material in the width direction, both ends in the width direction of the foam base material are gripped by a pair of gripping members, and the pair of gripping members are gradually moved in directions away from each other. A method of stretching the foam base material in the width direction is preferred. Since the polyolefin resin sheet expands in the width direction by its own foaming, when the foam base material is stretched in the width direction, the expansion in the width direction due to the foaming of the polyolefin resin sheet is taken into account. Above, it is preferable to adjust so that a foam base material may be extended | stretched in the width direction more than the expansion | swelling part.

  The draw ratio in the flow direction of the foam substrate is preferably 1.1 to 5 times, and more preferably 1.3 to 3.5 times. Further, the draw ratio in the width direction is preferably 1.2 to 4.5 times, and more preferably 1.5 to 3.5 times. By using a foam base material having a draw ratio in the above range, good flexibility and tensile strength can be maintained.

  As the foam base material, a colored foam base material may be used in order to obtain an adhesive tape having design properties, light shielding properties, concealing properties, light reflectivity, light resistance, and the like. In the case of the said coloring, a conventionally known coloring agent can be used individually or in combination of 2 or more types.

  When the light-shielding property, the concealing property and the light resistance are imparted to the adhesive tape, it is preferable to use a material colored black as the foam base material.

  Examples of the black colorant include 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, and chromium complex. , Complex oxide black dyes, anthraquinone organic black dyes, and the like can be used. Among these, as the colorant, it is preferable to use carbon black from the viewpoint of cost, availability, insulation, and heat resistance at a level that can withstand the temperature of the process of extruding the polyolefin resin composition and the heating and foaming process. .

  Moreover, when providing the said adhesive tape with designability, light reflectivity, etc., it is preferable to use what was colored white as said foam base material.

  Examples of the white colorant include titanium oxide, zinc oxide, aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium oxide, tin oxide, barium oxide, cesium oxide, 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, Inorganic white colorants such as titanium phosphate, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, silicone resin particles, acrylic resin particles, urethane resin particles, melamine resin particles Which organic white colorants or the like can be used. Among these, as the colorant, titanium oxide, aluminum oxide, or zinc oxide should be used from the viewpoint of cost, availability, color tone, heat resistance that can withstand the temperature of the process of extruding the polyolefin resin composition and the heating and foaming process. Is preferred.

  If necessary, the foam base material may be a plasticizer, an antioxidant, a foaming aid such as zinc oxide, a cell core modifier, a heat stabilizer, a flame retardant such as aluminum hydroxide or magnesium hydroxide, and an antistatic agent. It may contain known agents such as agents, fillers such as glass or plastic hollow balloons / beads, metal powders, metal compounds, conductive fillers, and heat conductive fillers.

  In addition, the colorant, the thermally decomposable foaming agent, the foaming auxiliary agent, etc., in order to prevent poor appearance such as uneven color shading, and poor foaming such as excessive foaming and non-foaming, a polyolefin resin, or It is preferable that the masterbatch is made of another thermoplastic resin that is easily compatible with the polyolefin resin.

  As the foam base material, surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone treatment, ultraviolet treatment, and easy adhesion treatment is performed in order to improve the adhesion with the pressure-sensitive adhesive layer and other layers. The applied one can be used.

  The surface of the surface-treated foam base material preferably has a wetting index by a wetting reagent of 36 mN / m or more, preferably 40 mN / m or more, and 48 mN / m or more. It is further preferable for maintaining good adhesion with a layer or the like.

  The foam base material with improved adhesion may be bonded to the pressure-sensitive adhesive layer in a continuous process. Further, the foam base material with improved adhesion may be temporarily wound up and stored, and then bonded to the adhesive layer at a later date.

  In addition, when winding up the foam base material having improved adhesion, it is preferable to wind it through a film made of paper, polyethylene, polypropylene, polyester, or the like in order to prevent blocking of the foam base material. . The film is preferably a polypropylene film or a polyester film having a thickness of 25 μm or less.

[Adhesive layer]
The adhesive layer which the double-sided adhesive tape of this invention has is provided in the front and back (both surfaces) of a foam base material. At least one of the pressure-sensitive adhesive layers provided on each surface, preferably both pressure-sensitive adhesive layers are formed by forming a pressure-sensitive adhesive tape formed by providing a 25 μm-thick pressure-sensitive adhesive layer on a 25 μm-thick polyethylene terephthalate substrate. Measured after pressure-bonding to an aluminum plate by reciprocating once using an aluminum plate in an environment of ℃ and relative humidity of 65% RH, and standing for 1 hour in an environment of temperature of 23 ℃ and relative humidity of 50% RH. It is a pressure-sensitive adhesive layer having a 180 ° peeling adhesive strength of 12 N / 20 mm or more at a peeling speed of 300 mm / min. By using the specific pressure-sensitive adhesive layer, it is possible to obtain a double-sided pressure-sensitive adhesive tape that can realize interlaminar cracking of the foam base material by applying a certain force at the time of disassembly and that has excellent impact resistance.

  As the pressure-sensitive adhesive layer, it is preferable to use a layer having a 180 ° peeling adhesive strength of 10 N / 20 mm or more, and a layer having a 180 ° peeling adhesive strength of 12 N / 20 mm or more can be used at the time of disassembly. It is preferable to obtain a double-sided pressure-sensitive adhesive tape that can realize interlaminar cracking of the foam base material by applying a certain force and has excellent impact resistance.

  The upper limit of the 180 ° peeling adhesion is not particularly limited, but is preferably 25 N / 20 mm or less, and more preferably 20 N / 20 mm or less.

  As the pressure-sensitive adhesive composition capable of forming the pressure-sensitive adhesive layer, for example, a (meth) acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a synthetic rubber-based pressure-sensitive adhesive, a natural rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, or the like is used. Can do. Among these, as the pressure-sensitive adhesive composition, it is desirable to use an acrylic pressure-sensitive adhesive composition containing an acrylic polymer as a base polymer and containing additives such as a tackifier resin and a crosslinking agent as necessary. It is preferable for forming a pressure-sensitive adhesive layer having a 180 ° peeling adhesive strength.

  Examples of the (meth) acrylate 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, and t-butyl (meth) ) Acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, isononyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, etc. (Meth) acrylate etc. which have an alkyl group of -12 are mentioned, These 1 type (s) or 2 or more types can be used. Among these, it is preferable to use (meth) acrylate having an alkyl group having 4 to 12 carbon atoms, and to use (meth) acrylate having a linear or branched alkyl group having 4 to 8 carbon atoms. More preferably, it is preferable to use at least one selected from the group consisting of n-butyl acrylate and 2-ethylhexyl acrylate in order to form a pressure-sensitive adhesive layer having a desired 180 ° peel-off adhesive force and the like.

  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 monomer components used in the production of the acrylic polymer, and is 80% by mass. % To 98.5 mass% is more preferable, and 90 mass% to 98.5 mass% is more preferable.

  In producing the acrylic polymer, a highly polar vinyl monomer can be used as a monomer component. Examples of the highly polar vinyl monomer include a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, a vinyl monomer having an amide group, etc., and one or more of these are used. can do.

  Examples of the vinyl monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and the like. (Meth) acrylates having the following 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 vinyl monomer having an amide group, for example, N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide and the like can be used.

  As other highly polar vinyl monomers, vinyl monomers having a sulfonic acid group such as vinyl acetate, ethylene oxide-modified succinic acid acrylate, and 2-acrylamido-2-methylpropanesulfonic acid can be used.

  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 monomer components used in the production of the acrylic polymer. It is more preferable to use in the range of 10% by mass to 10% by mass, and it is preferable to use in the range of 2% by mass to 8% by mass for forming a pressure-sensitive adhesive layer having a desired 180 ° peel-off adhesive force and the like. preferable.

  Moreover, when using an isocyanate type crosslinking agent with the said acrylic polymer as said adhesive composition, it is preferable to use the acrylic polymer which has a functional group which reacts with the isocyanate group.

  As a monomer component that can be used in this case, for example, a vinyl monomer having a hydroxyl group is preferably used, and 2-hydroxyethyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and 6-hydroxyhexyl. It is more preferable to use (meth) acrylate or the like.

  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 of monomer components used for the production of the acrylic polymer. It is more preferable to use in the range of 0.03 mass% to 0.3 mass%.

  The acrylic polymer can be produced by polymerizing the monomer component. Examples of the polymerization method include known polymerization methods such as a solution polymerization method, a cage polymerization method, a suspension polymerization method, and an emulsion polymerization method, and a solution for obtaining a pressure-sensitive adhesive composition having good water resistance. It is preferable to employ a polymerization method or a bulk polymerization method.

  For the polymerization, a method using a peroxide thermal polymerization initiator such as benzoyl peroxide or lauroyl peroxide, an azo thermal polymerization initiator such as azobisisobutylnitrile, an acetophenone photopolymerization initiator, a benzoin ether photopolymer Polymerization initiator, benzyl ketal photopolymerization initiator, acyl phosphine oxide photopolymerization initiator, benzoin photopolymerization initiator, a method using a benzophenone photopolymerization initiator, a method of irradiating an electron beam, Can be advanced.

  As the acrylic polymer, it is preferable to use a polymer having a weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatograph (GPC) in the range of 400,000 to 3 million. It is more preferable to use one having a range of 2.5 million.

  Here, the measurement of the molecular weight by the GPC method is a standard polystyrene conversion value measured using a GPC device (HLC-8329GPC) manufactured by Tosoh Corporation, and the measurement conditions are as follows.

Sample concentration: 0.5% by mass (tetrahydrofuran solution)
Sample injection volume: 100 μl
Eluent: THF
Flow rate: 1.0 ml / min Measurement temperature: 40 ° C
This column: TSKgel GMHHR-H (20) 2 Guard column: TSKgel HXL-H
Detector: differential refractometer Standard polystyrene molecular weight: 10,000 to 20 million (manufactured by Tosoh Corporation)

  As the pressure-sensitive adhesive composition used in the present invention, a pressure-sensitive adhesive composition containing a tackifying resin is preferably used for the purpose of further improving the adhesion to the adherend and the surface adhesion strength. Examples of tackifier resins include rosin-based tackifier resins, polymerized rosin-based tackifier resins, polymerized rosin ester-based tackifier resins, rosin phenol-based tackifier resins, stabilized rosin ester-based tackifier resins, and disproportionated rosin ester-based tackifiers. An imparting resin, a hydrogenated rosin ester tackifier resin, a terpene tackifier resin, a terpene phenol tackifier resin, a petroleum resin tackifier resin, a (meth) acrylate resin tackifier resin, or the like can be used.

  Among them, as the tackifying resin, disproportionated rosin ester tackifying resin, polymerized rosin ester tackifying resin, rosin phenol tackifying resin, hydrogenated rosin ester tackifying resin, (meth) acrylate resin It is preferable to use a tackifier resin and a terpene phenol tackifier resin alone or in combination of two or more.

  When an emulsion-type pressure-sensitive adhesive composition is used as the pressure-sensitive adhesive composition, it is preferable to use an emulsion-type pressure-sensitive adhesive resin as the tackifier resin.

  As the tackifying resin, a resin having a softening point of 30 ° C. to 180 ° C. is preferably used, and a resin having a softening point of 70 ° C. to 140 ° C. is used to peel off the desired 180 ° adhesive strength. It is preferable when forming a pressure-sensitive adhesive layer having the above. When using the said (meth) acrylate type tackifying resin, it is preferable to use what has a glass transition temperature of 30 to 200 degreeC as said (meth) acrylate type tackifying resin, 50 to 160 degreeC. It is more preferable to use those.

  The tackifying resin is preferably used in the range of 5 to 65 parts by mass, and preferably in the range of 8 to 55 parts by mass with respect to 100 parts by mass of the acrylic polymer. It is preferable for forming a pressure-sensitive adhesive layer having a 180 ° peeling adhesive strength.

  As the pressure-sensitive adhesive composition, in addition to the acrylic polymer and tackifying resin, it is preferable to use a material containing a crosslinking agent as necessary in order to form a pressure-sensitive adhesive layer having a high cohesive force. .

  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.

  Among these, as the cross-linking agent, it is preferable to use an isocyanate cross-linking agent and an epoxy cross-linking agent rich in reactivity with an acrylic polymer alone or in combination, and the use of an isocyanate cross-linking agent is a pressure-sensitive adhesive. This is preferable because the adhesion between the layer and the foam substrate can be further improved.

  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. Especially, as said isocyanate type crosslinking agent, it is preferable to use what has three or more isocyanate groups, Specifically, the trimethylol propane adduct of tolylene diisocyanate, a triphenylmethane triisocyanate, etc. are mentioned. .

  As the pressure-sensitive adhesive composition, in addition to the above-described components, plasticizers, softeners, antioxidants, flame retardants, glass and plastic fibers, balloons, beads, metal powders, metal oxides, metals as necessary Those containing additives such as fillers such as nitrides, colorants such as pigments and dyes, leveling agents, thickeners, water repellents, and antifoaming agents can be used.

  As the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive composition, it is desirable to use a layer having a temperature at which the peak value of loss tangent (tan δ) at a frequency of 1 Hz is in the range of −40 ° C. to 15 ° C. It is preferable for providing a good adhesion with an adherend at room temperature at a normal temperature. On the other hand, as the pressure-sensitive adhesive layer, it is preferable to use a layer having a temperature of −35 ° C. to 10 ° C., which has a desired 180 ° peel-off adhesive force and has good adhesion to an adherend at room temperature. It is preferable to further improve the impact resistance in a low temperature environment, and it is more preferable to use a material having a temperature of -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 pressure-sensitive adhesive layer has a desired 180 ° peeling adhesive strength, and as a result, it is preferably in the range of 5 μm to 100 μm in order to further improve the adhesion with the adherend. The range of 80 μm is more preferable, and the range of 15 μm to 80 μm is more preferable.

[Double-sided adhesive tape]
The double-sided pressure-sensitive adhesive tape of the present invention is, for example, a direct copy method in which an adhesive is applied and dried directly on a foam base material or on the surface of another layer laminated on the foam base material, and sticks to a release sheet. After the agent is applied and dried, it can be produced by a transfer method in which it is bonded to the surface of the foam substrate or other layer.

  When using what contains a crosslinking agent as said adhesive composition, when advancing the said crosslinking reaction, Preferably a double-sided adhesive tape is 20 degreeC-50 degreeC, More preferably, it is an environment of 23 degreeC-45 degreeC. Aging for 2 to 7 days can provide the desired 180 ° peel-off adhesive force and can further improve the adhesion between the foam substrate and the pressure-sensitive adhesive layer.

  The release sheet is not particularly limited, but is adhered to at least one surface of a base material such as a synthetic resin film such as polyethylene, polypropylene, or polyester film, paper, nonwoven fabric, cloth, foam sheet or metal foil, and a laminate thereof. A material that has been subjected to a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment for improving the releasability from the agent can be used.

  Among them, as the release sheet, it is possible to use a high-quality paper obtained by laminating polyethylene having a thickness of 10 to 40 μm on both sides, a polyester film base material which has been subjected to silicone release treatment on one side or both sides, and the like. preferable.

  As an embodiment of the pressure-sensitive adhesive tape of the present invention, a basic structure is a structure in which a foam base material is used as a core and an adhesive layer is provided on at least one surface, preferably both surfaces of the foam base material. The foam substrate and the pressure-sensitive adhesive layer may be directly laminated or may be laminated via another layer.

  The said adhesive tape may have another layer as needed other than the said foam base material and an adhesive layer. As said other layer, when obtaining the adhesive tape provided with dimensional stability, tensile strength, and rework suitability, laminate layers, such as a polyester film, are mentioned. In addition, as the other layer, when obtaining a pressure-sensitive adhesive tape having a light-shielding property or a light-reflecting property, a printed layer, and when obtaining a pressure-sensitive adhesive tape having electromagnetic wave shielding characteristics or thermal conductivity in the surface direction, a metal You may have the layer which consists of a nonwoven fabric plated with foil or a metal mesh electroconductive metal.

  As the laminate layer, a film such as a polyester film such as polyethylene terephthalate, a polyethylene film, or a polypropylene film can be used.

  The thickness of the laminate layer is not particularly specified, but is preferably in the range of 1 μm to 25 μm and more preferably in the range of 2 μm to 12 μm in order to ensure good followability to the foam substrate. . When bonding a foam base material and a laminate layer, a conventionally known pressure-sensitive adhesive or an adhesive for dry lamination can be used.

  Examples of the light shielding layer include a layer printed with an ink containing a colorant such as a pigment, and a layer printed with black ink can be preferably used.

  Examples of the reflective layer include a layer printed with an ink containing a colorant such as a pigment, and a layer printed with a white ink can be preferably used.

  The thickness of the light-shielding layer and the reflective layer is preferably 2 μm to 20 μm, and preferably 4 μm to 6 μm because curling of the adhesive tape due to curing shrinkage of the ink can be suppressed.

  The total thickness of the double-sided pressure-sensitive adhesive tape of the present invention obtained by the above method may be appropriately adjusted depending on the mode of use, but is preferably 300 μm or less, more preferably 80 μm to 300 μm, and more preferably 100 μm to 300 μm. It is more preferable because it is thin and can have both excellent impact resistance and dismantling properties and contribute to the thinning of a small electronic terminal.

  The pressure-sensitive adhesive tape of the present invention has suitable impact resistance and dismantling properties according to the above-described configuration, so that it is a component of a small electronic device, for example, a protection panel or an image display module for an information display unit of a small electronic device, Fixing speakers, receivers, piezoelectric elements, printed circuit boards, flexible printed circuit boards (FPCs), digital camera modules, sensors, other modules, cushioning rubber members such as polyurethane and polyolefin, decorative parts and various members It can be suitably applied to. In particular, the present invention can be suitably applied to fixing a thin plate-like rigid part such as a protection panel, an image display module, or a thin battery for an information display unit of a small electronic device.

(Preparation of pressure-sensitive adhesive composition (A))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 97.97 parts by mass of n-butyl acrylate, 2.0 parts by mass of acrylic acid, 0.03 mass of 4-hydroxybutyl acrylate Part by weight, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator was dissolved in 100 parts by mass of ethyl acetate and polymerized at 70 ° C. for 12 hours, whereby the weight average molecular weight was 2 million ( An ethyl acetate solution of an acrylic polymer (in terms of polystyrene) was obtained.

  Next, 25 parts by mass of “Superester A100” (produced by Arakawa Chemical Industries, Ltd., glycerin ester of disproportionated rosin) and “Pencel D135” (Arakawa Chemical Industries, Ltd.) with respect to 100 parts by mass of the acrylic polymer. By adding 5 parts by mass of pentaerythritol ester of polymerized rosin and 20 parts by mass of “FTR6100” (made by Mitsui Chemicals, styrene petroleum resin), and further adding ethyl acetate and mixing uniformly, A pressure-sensitive adhesive composition (a) having a nonvolatile content of 40% by mass was obtained.

  Next, 100 parts by mass of the pressure-sensitive adhesive composition (a) and 1.3 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based crosslinking agent, non-volatile content 45% by mass) are mixed. The mixture was stirred for 15 minutes to obtain a pressure-sensitive adhesive composition (A). The adhesive composition (A) had a 180 ° peel adhesion of 12 N / 20 mm. The 180 ° peel adhesion is a value measured by the method described later.

[Adhesive strength of adhesive layer by 180 ° peeling]
The pressure-sensitive adhesive composition (A) was applied to a polyethylene terephthalate substrate having a thickness of 25 μm so that the thickness of the pressure-sensitive adhesive layer after drying was 25 μm, dried at 80 ° C. for 3 minutes, and then heated to 40 ° C. An adhesive tape was obtained by aging in an environment for 48 hours.

  The adhesive tape is affixed to an aluminum plate in an environment of a temperature of 23 ° C. and a relative humidity of 65% RH, and the upper surface of the adhesive tape (the surface on the polyethylene terephthalate substrate side) is reciprocated once using a 2 kg roller. Crimped them with.

  The material pressure-bonded by the above method was allowed to stand for 1 hour in an environment of a temperature of 23 ° C. and a relative humidity of 50% RH, and then the strength when peeled by 180 ° at a peeling speed of 300 mm / min was measured. The 180 ° peel adhesive strength of the pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive compositions (B) to (D) described later was also measured by the same method as described above.

(Preparation of pressure-sensitive adhesive composition (B))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 93.4 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate, 2-hydroxy By dissolving 0.1 part by weight of ethyl acrylate and 0.1 part by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator in 100 parts by weight of ethyl acetate and polymerizing at 70 ° C. for 12 hours, An ethyl acetate solution of an acrylic polymer having an average molecular weight of 1,600,000 (polystyrene conversion) was obtained.

  Next, with respect to 100 parts by mass of the acrylic polymer, 30 parts by mass of “Superester A100” (produced by Arakawa Chemical Industries, Ltd., glycerin ester of disproportionated rosin) and “Pencel D135” (Arakawa Chemical Industries, Ltd.) 5 parts by mass of polymerized rosin pentaerythritol ester) and 25 parts by mass of “FTR6100” (manufactured by Mitsui Chemicals, styrene-based petroleum resin), and further mixed with ethyl acetate to make it non-volatile A pressure-sensitive adhesive composition (b) having a content of 38% by mass was obtained.

  Next, 100 parts by mass of the pressure-sensitive adhesive composition (b) and 1.3 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based crosslinking agent, nonvolatile content 45% by mass) are mixed. The mixture was stirred for 15 minutes to obtain a pressure-sensitive adhesive composition (B). The adhesive composition (B) had a 180 ° peel adhesion of 13.7 N / 20 mm.

(Preparation of pressure-sensitive adhesive composition (C))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 93.4 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate, 2-hydroxy By dissolving 0.1 part by weight of ethyl acrylate and 0.1 part by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator in 100 parts by weight of ethyl acetate and polymerizing at 70 ° C. for 12 hours, An ethyl acetate solution of an acrylic polymer having an average molecular weight of 1,600,000 (polystyrene conversion) was obtained.

  Next, with respect to 100 parts by mass of the acrylic polymer, 20 parts by mass of “Superester A100” (produced by Arakawa Chemical Industries, Ltd., glycerin ester of disproportionated rosin) and “FTR6100” (produced by Mitsui Chemicals, Inc., By adding 20 parts by mass of styrene-based petroleum resin) and 10 parts by mass of “Halitak PCJ” (produced by Harima Chemical Group Co., Ltd., polymerized rosin pentaerythritol ester), ethyl acetate is added and mixed uniformly. A pressure-sensitive adhesive composition (c) having a content of 38% by mass was obtained.

  100 parts by mass of the pressure-sensitive adhesive composition (c) and 1.3 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based cross-linking agent, nonvolatile content 45% by mass) are mixed for 15 minutes. The pressure-sensitive adhesive composition (C) was obtained by stirring. The adhesive composition (C) had a 180 ° peel-off adhesive strength of 12.8 N / 20 mm.

(Preparation of pressure-sensitive adhesive composition (D))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 44.94 parts by mass of n-butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of vinyl acetate, acrylic acid 2 1 part by mass, 0.06 part by mass of 4-hydroxybutyl acrylate, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator are dissolved in 100 parts by mass of ethyl acetate, and are heated at 70 ° C. for 12 hours. By polymerization, an ethyl acetate solution of an acrylic polymer having a weight average molecular weight of 1,200,000 (polystyrene conversion) was obtained.

  Next, with respect to 100 parts by mass of the acrylic polymer, 30 parts by mass of “Superester A100” (Arakawa Chemical Industries, Ltd., glycerin ester of disproportionated rosin) and “FTR6100” (Mitsui Chemicals, By adding 25 parts by mass of styrene-based petroleum resin) and 5 parts by mass of “Pencel D135” (produced by Arakawa Chemical Industries, Ltd., pentaerythritol ester of polymerized rosin), ethyl acetate is added and mixed uniformly. A pressure-sensitive adhesive composition (d) having a content of 45% by mass was obtained.

  100 parts by mass of the pressure-sensitive adhesive composition (d) and 1.3 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based crosslinking agent, 45% by mass of non-volatile content) were mixed for 15 minutes. The pressure-sensitive adhesive composition (D) was obtained by stirring. The adhesive composition (D) had a 180 ° peel adhesion of 13.2 N / 20 mm.

(Preparation of pressure-sensitive adhesive composition (E))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 63.4 parts by mass of n-butyl acrylate, 30 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of acrylic acid, 3 vinyl acetate 0.5 part by mass, 0.1 part by mass of 2-hydroxyethyl acrylate, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator were dissolved in 100 parts by mass of ethyl acetate, and 70 ° C. By polymerizing for 12 hours, an ethyl acetate solution of an acrylic polymer having a weight average molecular weight of 1.4 million (in terms of polystyrene) was obtained.

  Next, with respect to 100 parts by mass of the acrylic polymer, 30 parts by mass of “Superester A100” (Arakawa Chemical Industries, Ltd., glycerin ester of disproportionated rosin) and “FTR6100” (Mitsui Chemicals, By adding 25 parts by mass of styrene-based petroleum resin) and 5 parts by mass of “Pencel D135” (produced by Arakawa Chemical Industries, Ltd., pentaerythritol ester of polymerized rosin), ethyl acetate is added and mixed uniformly. A pressure-sensitive adhesive composition (e) having a content of 38% by mass was obtained.

  100 parts by mass of the pressure-sensitive adhesive composition (e) and 1.3 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based crosslinking agent, non-volatile content: 45% by mass) are mixed for 15 minutes. The pressure-sensitive adhesive composition (E) was obtained by stirring. The adhesive composition (E) had a 180 ° peel-off adhesive strength of 12.3 N / 20 mm.

(Preparation of pressure-sensitive adhesive composition (F))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 44.94 parts by mass of n-butyl acrylate, 50 parts by mass of 2-ethylhexyl acrylate, 3 parts by mass of vinyl acetate, acrylic acid 2 1 part by mass, 0.06 part by mass of 4-hydroxybutyl acrylate, 0.1 part by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator are dissolved in 100 parts by mass of ethyl acetate, and are heated at 70 ° C. for 12 hours. By polymerization, an ethyl acetate solution of an acrylic polymer having a weight average molecular weight of 1,200,000 (polystyrene conversion) was obtained.

  Next, 10 parts by weight of “Pencel D135” (Arakawa Chemical Industries, Ltd., pentaerythritol ester of polymerized rosin) is added to 100 parts by weight of the acrylic polymer, and ethyl acetate is further added and mixed uniformly. A pressure-sensitive adhesive composition (f) having a nonvolatile content of 45% by mass was obtained.

  100 parts by mass of the pressure-sensitive adhesive composition (f) and 0.9 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based cross-linking agent, non-volatile content: 45% by mass) are mixed for 15 minutes. The pressure-sensitive adhesive composition (F) was obtained by stirring. The adhesive composition (F) had a 180 ° peel adhesion of 8.5 N / 20 mm.

(Preparation of pressure-sensitive adhesive composition (G))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 93.4 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 3 parts by mass of vinyl acetate, 2-hydroxy By dissolving 0.1 part by weight of ethyl acrylate and 0.1 part by weight of 2,2′-azobisisobutyronitrile as a polymerization initiator in 100 parts by weight of ethyl acetate and polymerizing at 70 ° C. for 12 hours, An ethyl acetate solution of an acrylic polymer having an average molecular weight of 1,600,000 (polystyrene conversion) was obtained.

  Next, with respect to 100 parts by mass of the acrylic polymer, 9.4 parts by mass of “Superester A100” (produced by Arakawa Chemical Industries, Ltd., glycerin ester of disproportionated rosin) and “Halitak PCJ” (Harima Chemical Group) 9.4 parts by mass of pentaerythritol ester of polymerized rosin (manufactured by Co., Ltd.) was added, and ethyl acetate was further added and mixed uniformly to obtain an adhesive composition (g) having a nonvolatile content of 38% by mass.

  100 parts by mass of the pressure-sensitive adhesive composition (g) and 1.1 parts by mass of “Coronate L-45” (manufactured by Nippon Polyurethane Industry Co., Ltd., isocyanate-based crosslinking agent, non-volatile content: 45% by mass) were mixed for 15 minutes. The pressure-sensitive adhesive composition (G) was obtained by stirring. The adhesive composition (G) had a 180 ° peel adhesion of 8.9 N / 20 mm.

Example 1
By applying the pressure-sensitive adhesive composition (A) to a release-treated surface of a 75 μm-thick polyethylene terephthalate film (PET film) so that the thickness after drying is 25 μm, and drying at 80 ° C. for 3 minutes. An adhesive layer was formed. The gel fraction of the pressure-sensitive adhesive layer was 42.5% by mass.

Next, black polyolefin-based foam (1) (thickness 100 μm, density 0.40 g / cm ³ , interlayer strength 12.6 N / cm, 25% compression strength: 103 kPa, tensile strength in the flow direction: 1084 N / cm ² The pressure-sensitive adhesive is applied to both sides of a base material made of Sekisui Chemical Co., Ltd. foam surface having a wetting index of 54 mN / m by tensile strength in the width direction: 790 N / cm ² . After laminating the layers one by one, laminating them by pressing with a roll with a linear pressure of 5 kg / cm at 23 ° C., and aging at 40 ° C. for 48 hours, a double-sided adhesive tape with a thickness of 150 μm was obtained. It was.

(Example 2)
A double-sided pressure-sensitive adhesive tape having a thickness of 130 μm was obtained in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 25 μm to 15 μm.

(Example 3)
A double-sided pressure-sensitive adhesive tape having a thickness of 200 μm was obtained in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 25 μm to 50 μm.

Example 4
Instead of the black polyolefin foam (1), the black polyolefin foam (2) (thickness: 80 μm, density 0.40 g / cm ³ , interlayer strength 10.2 N / cm, 25% compression strength: 92 kPa, flow The tensile strength in the direction: 1062 N / cm ² , the tensile strength in the width direction: 962 N / cm ² , and the surface of the foam made by Sekisui Chemical Co., Ltd. was subjected to corona treatment to a wetting index of 54 mN / m) A double-sided pressure-sensitive adhesive tape having a thickness of 110 μm was obtained in the same manner as in Example 1 except that the thickness after drying of the pressure-sensitive adhesive layer was changed from 25 μm to 15 μm.

(Example 5)
Black polyolefin foam (3) instead of black polyolefin foam (1) (thickness: 100 μm, density 0.45 g / cm ³ , interlayer strength 16.2 N / cm, 25% compressive strength: 190 kPa, flow direction The surface of the foam made by Sekisui Chemical Co., Ltd. having a tensile strength of 964 N / cm ² and a width direction tensile strength of 861 N / cm ² is obtained by corona treatment with a wetting index of 54 mN / m) A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that it was not.

(Example 6)
A double-sided pressure-sensitive adhesive tape having a thickness of 200 μm was obtained in the same manner as in Example 5 except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 15 μm to 50 μm.

(Example 7)
Black polyolefin foam (4) instead of black polyolefin foam (1) (thickness: 140 μm, density 0.40 g / cm ³ , interlayer strength 19.1 N / cm, 25% compressive strength: 130 kPa, flow direction The surface of the foam made by Sekisui Chemical Co., Ltd. with a tensile strength of 994 N / cm ² and a width direction tensile strength of 713 N / cm ² was used to obtain a wet index of 54 mN / m by corona treatment. A double-sided pressure-sensitive adhesive tape having a thickness of 200 μm was obtained in the same manner as in Example 1 except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 15 μm to 30 μm.

(Example 8)
A double-sided pressure-sensitive adhesive tape having a thickness of 250 μm was obtained in the same manner as in Example 7, except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 30 μm to 55 μm.

Example 9
A double-sided pressure-sensitive adhesive tape having a thickness of 300 μm was obtained in the same manner as in Example 7, except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 30 μm to 80 μm.

(Example 10)
A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (B) was used instead of the pressure-sensitive adhesive composition (A) (the pressure-sensitive adhesive layer). Gel fraction 40% by mass).

(Example 11)
A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (C) was used instead of the pressure-sensitive adhesive composition (A) (the pressure-sensitive adhesive layer). Gel fraction 43% by mass).

(Example 12)
A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (D) was used instead of the pressure-sensitive adhesive composition (A) (the pressure-sensitive adhesive layer). Gel fraction 25% by mass).

(Example 13)
A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (E) was used instead of the pressure-sensitive adhesive composition (A) (the pressure-sensitive adhesive layer). Gel fraction 39% by mass).

(Comparative Example 1)
Black polyolefin foam (5) instead of black polyolefin foam (1) (thickness: 100 μm, density 0.33 g / cm ³ , interlayer strength 8.9 N / cm, 25% compressive strength: 70 kPa, flow direction The surface of the foam made by Sekisui Chemical Co., Ltd. having a tensile strength of 799 N / cm ² and a width direction tensile strength of 627 N / cm ² is obtained by corona treatment with a wetting index of 54 mN / m. A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1, except that it was not.

(Comparative Example 2)
Black polyolefin foam (6) instead of black polyolefin foam (1) (thickness: 100 μm, density 0.50 g / cm ³ , interlayer strength 13.6 N / cm, 25% compressive strength: 270 kPa, flow direction The surface of the foam made by Sekisui Chemical Co., Ltd. having a tensile strength of 1456 N / cm ² and a tensile strength in the width direction of 956 N / cm ² is obtained by corona treatment with a wetting index of 54 mN / m) A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that it was not.

(Comparative Example 3)
A double-sided pressure-sensitive adhesive tape having a thickness of 200 μm was obtained in the same manner as in Comparative Example 2 except that the thickness of the pressure-sensitive adhesive layer after drying was changed from 15 μm to 50 μm.

(Comparative Example 4)
A double-sided pressure-sensitive adhesive tape having a thickness of 150 μm was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive composition (F) was used instead of the pressure-sensitive adhesive composition (A) (the pressure-sensitive adhesive layer). Gel fraction 38% by mass).

(Comparative Example 5)
A double-sided pressure-sensitive adhesive tape having a thickness of 200 μm was obtained in the same manner as in Example 7 except that the pressure-sensitive adhesive composition (G) was used instead of the pressure-sensitive adhesive composition (A) (the pressure-sensitive adhesive layer). Gel fraction 48% by mass).

  The following evaluation was performed about the foam base material used by the said Example and comparative example, and the double-sided adhesive tape obtained by the said Example and comparative example. The results obtained are shown in the table.

[Foam substrate and adhesive tape thickness]
The thickness of the foam base material was measured using a dial series gauge G type manufactured by Ozaki Seisakusho. The thickness of the pressure-sensitive adhesive tape was measured by using a dial thickness gauge G type after peeling the release film.

[Density of foam substrate]
The density of the foam substrate was measured according to JISK6767. Specifically, a foam base material cut into a 4 cm × 5 cm rectangle was prepared for 15 cm ³ minutes, and the mass was measured to determine the density.

[Interlayer strength of foam substrate]
40 ° C. obtained by laminating adhesive layers each having a strong adhesiveness of 50 μm in thickness (one that does not peel from the adherend and the foam base during the following high-speed peel test) on both sides of the foam base Was aged for 48 hours to prepare a double-sided pressure-sensitive adhesive tape for measuring interlayer strength.

  Next, the adhesive surface on one side of the double-sided adhesive tape was lined with a polyester film having a thickness of 25 μm, and then cut into a size of 1 cm in the width direction of the foam base material and 15 cm in the flow direction. Affixed to a polyester film having a relative humidity of 50% RH, a thickness of 50 μm, a width of 3 cm, and a length of 20 cm. The test piece was obtained by leaving still at time and then leaving still at 23 degreeC for 1 hour.

  Next, under 23 ° C. and relative humidity 50% RH, the polyester film side of 50 μm thickness constituting the test piece is fixed to a mounting jig of a high-speed peel tester, and the 25 μm thick polyester constituting the test piece is fixed. By pulling the film in the direction of 90 degrees at a tensile speed of 15 m / min, the maximum strength when the foam base material constituting the test piece was torn was measured.

[Tensile strength of foam substrate]
The tensile strength in the flow direction and width direction of the foam substrate was measured according to JISK6767. A sample with a marked line length of 2 cm and a width of 1 cm was measured using a Tensilon tensile tester in an environment of 23 ° C. and a relative humidity of 50% RH under the measurement conditions of a tensile speed of 300 mm / min. The maximum strength of the measured value obtained is the tensile strength of the sample.

[25% compressive strength of foam substrate]
The 25% compressive strength of the foam substrate was measured according to JISK6767. Samples cut into 25 squares were stacked to a thickness of about 10 mm. The sample was sandwiched between stainless plates having a larger area than the sample, and the strength was measured when the sample was compressed at about 25 mm (25% of the original thickness) at a rate of 10 mm / min at 23 ° C.

[Measurement of average cell diameter of foam substrate]
First, the foam base material was cut into 1 cm in both the width method and the flow direction. Next, the foam cell part is enlarged 200 times with a digital microscope (trade name “KH-7700”, manufactured by HiROX) at the center of the cut surface of the cut foam base material. The cross section in the width direction or the flow direction is observed on the entire length of the cut surface of the foam base material in the thickness direction of the base material. In the obtained enlarged image, all the bubble diameters of the bubbles existing on the cut surface having an actual length of 2 mm before expansion in the flow direction or the width direction were measured, and the average bubble diameter was calculated from the average value. The average bubble diameter was determined from the results of measurement at any 10 locations.

[Easy disassembly]
1) Polycarbonate plate of 2.5 cm in length, 4.0 cm in width, and 2 mm thickness on a double-sided adhesive tape with a foam base material core processed into a test piece having a length of 2 cm (the flow direction of the foam base material) and a width of 1 cm Two sheets were affixed to the center of the sheet at an interval of 2 cm in the width direction.

  2) An end of a PET film having a length of 20 cm, a width of 1.5 cm, and a thickness of 50 μm was fixed to the back surface of the tape application surface of the polycarbonate plate, and the PET film was wound so as to pass through two double-sided adhesive tapes. At that time, the center of the width of the PET film was made to coincide with the center of the two double-sided pressure-sensitive adhesive tapes.

  3) The polycarbonate plate on which the PET film is wound and fixed is adhered and fixed to the surface of an aluminum plate having a length of 20 cm and a width of 20 cm so that the double-sided adhesive tape comes into contact with the polycarbonate plate, and pressure-bonded using a 2 kg weight. . The test piece was left standing at 23 ° C. and 50% RH for 72 hours.

  4) The end portion of the PET film of the test piece was pulled up in the direction of 90 ° with respect to the aluminum plate, and the polycarbonate plate was peeled off. The peeling state of the double-sided adhesive tape at that time was observed.

  A: The entire surface of the double-sided pressure-sensitive adhesive tape was broken and peeled between the layers of the foam base material.

  ○: 90% or more of the double-sided pressure-sensitive adhesive tape was broken and peeled between the layers of the foam base material.

  X: The part which destroyed between the layers of the foam base material of a double-sided adhesive tape was less than 90%.

[Impact resistance test]
1) Weak adhesive surface of two double-sided adhesive tapes 40mm long and 5mm wide on an acrylic plate (Mitsubishi Rayon Co., Ltd. Acrylite L "trade name", hue: transparent) with a thickness of 2mm and an external dimension of 50mm x 50mm Are attached in parallel with an interval of 40 mm (Fig. 1), and then an ABS plate having a thickness of 2 mm and an outer shape of 150 mm x 100 mm (manufactured by Sumitomo Bakelite Co., Ltd., Tuface R "trade name" hue: natural, no grain, the same applies hereinafter) It stuck on the center part of (FIG. 2). After reciprocating pressure with a 2 kg roller, the test piece was left at 23 ° C. for 1 hour.

  2) A U-shaped measuring table (made of aluminum with a thickness of 5 mm) having a length of 150 mm, a width of 100 mm and a height of 45 mm is installed on the base of the DuPont impact tester (manufactured by Tester Sangyo Co., Ltd.). The test piece was placed on top with the acrylic plate facing down (FIG. 3). A stainless steel striker with a diameter of 25 mm and a mass of 300 g from the ABS plate side is changed in height by 10 cm and dropped 5 times at 10-second intervals from the height to the center of the ABS plate, and the tape is peeled off from the test piece. The height at which breakage was observed was measured.

○: No peeling or breaking of the tape after the test even at a height of 60 cm ×: peeling or breaking of the tape occurred at a height of 60 cm or less

  As the said Examples 1-13, the double-sided adhesive tape of this invention had the outstanding drop impact resistance with a to-be-adhered body, and easy disassembly property (interlaminar crack property). On the other hand, the double-sided pressure-sensitive adhesive tapes of Comparative Examples 1 to 6 did not have sufficient resistance to drop impact, or were inferior in easy disassembly (interlaminar crackability).

DESCRIPTION OF SYMBOLS 1 Adhesive tape 2 Acrylic board 3 ABS board 4 U-shaped measuring stand 5 Strike core

Claims (7)

A double-sided adhesive tape having an adhesive layer on both sides of a foam substrate,
The pressure-sensitive adhesive layer is formed from a pressure-sensitive adhesive composition containing an acrylic polymer, a crosslinking agent, and 50 to 65 parts by mass of a tackifier resin with respect to 100 parts by mass of the acrylic polymer. Is,
The foam base material has a density of 0.15 to 0.45 g / cm ³ , an interlayer strength of 10 to 50 N / cm, a thickness of 50 to 250 μm, a 25% compressive strength of 10 to 500 kPa, and a tensile strength in the flow direction and the width direction. It is a polyolefin-based foam base material having 500 to 1300 N / cm ² , tensile elongation of 100 to 1200% in the flow direction, average cell diameter in the flow direction and width direction of 10 to 500 μm, and average cell diameter in the thickness direction of 3 to 100 μm. ,
After the pressure-sensitive adhesive layer is applied to a polyethylene terephthalate substrate having a thickness of 25 μm, the pressure-sensitive adhesive composition is applied so that the thickness of the pressure-sensitive adhesive layer after drying is 25 μm, and dried at 80 ° C. for 3 minutes. An adhesive tape formed by aging for 48 hours in an environment of 40 ° C. and having an adhesive layer having a thickness of 25 μm was applied to an aluminum plate in an environment of a temperature of 23 ° C. and a relative humidity of 65% RH using a 2 kg roller. Adhesiveness of 12 to 25 N / 20 mm with 180 ° peel adhesion at a peel rate of 300 mm / min measured after being reciprocated once and left in an environment of temperature 23 ° C. and relative humidity 50% RH for 1 hour. A double-sided pressure-sensitive adhesive tape characterized by being an agent layer. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the tackifying resin contains a disproportionated rosin ester-based tackifying resin, a polymerized rosin ester-based tackifying resin, and a petroleum resin-based tackifying resin. The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the acrylic polymer has a weight average molecular weight of 800,000 to 3,000,000. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 3, wherein the foam base material is a polyolefin foam base material having an interlayer strength of 10 N / cm to 25 N / cm. The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the total thickness is 300 µm or less. The tensile strength of the foam substrate is ^double-sided adhesive tape according to claim 1 which is ^{500N / cm 2 ~1300N / cm 2} . The double-sided pressure-sensitive adhesive tape according to any one of claims 1 to 6, which is used for fixing components constituting an electronic device.

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