JP2020002232A - Adhesive tape - Google Patents

Abstract

To provide an adhesive tape with a foamed base material excellent in pasting property, and followability, capable of maintaining a form even if exposed to a high temperature, and maintaining original physical properties when returned to room temperature.SOLUTION: The adhesive tape of the present invention has an adhesive layer on at least one surface side of a foamed base material having pseudo-skin layers on both surfaces thereof, where the 25% compression strength of the foamed base material is 20-170kPa, and when a tensile elastic modulus in a flow direction of 100% elongation at 23°C is E1, and a tensile elastic modulus in a flow direction of 100% elongation at 120°C is E2, the ratio E1/E2 is 0.1 or more, or when a tensile elastic modulus in a width direction of 100% elongation at 23°C is E1', and a tensile elastic modulus in a width direction of 100% elongation at 120°C is E2', the ratio E1'/E2' is 0.1 or more.SELECTED DRAWING: None

Description

  The present invention relates to an adhesive tape that can be used for fixing components constituting various electronic devices including the mobile field and the automobile field.

BACKGROUND ART Adhesive tapes are used for fixing components constituting various electronic devices such as a mobile field and an automobile field. The adhesive tape is used for applications such as fixing two or more housings constituting the electronic device, for example, in the case of manufacturing the electronic device.
When an adhesive tape is used in the above-described scene, air tends to remain at the bonding interface between the pressure-bonded member and the tape. For this reason, an adhesive tape of a foam base material is used which has an appropriate cushioning property in the thickness direction of the tape, has an appropriate follow-up property in joining rigid bodies, and has a feature that the joining component and the adhesive layer are easily adhered to each other. You. In such applications, for example, a pressure-sensitive adhesive tape of a foam base material having excellent flexibility using a polyethylene resin, a urethane resin, or the like has been used (Patent Document 1).

  However, in recent years, for display applications, adhesion reliability in more severe environments has been required. Specifically, there is a demand for a pressure-sensitive adhesive tape having almost no change in physical properties even after being left in a high-temperature environment of 100 ° C. or more, and the heat resistance of the conventional foam-based pressure-sensitive adhesive tape was insufficient.

  In the above case, a pressure-sensitive adhesive tape of a foam base material using a heat-resistant polypropylene resin is often used, but a foam base material having a double-sided skin layer has poor flexibility and poor adhesion. . In addition, when the double-sided slice layer is provided, the adhesion between the foam base material and the pressure-sensitive adhesive layer is poor, and the adhesiveness and the retention are reduced (Patent Document 2).

  As described above, in the pressure-sensitive adhesive tape used in the above-mentioned applications, the pressure-sensitive adhesive tape is a flexible and compliant foam base material, and can maintain its form even when exposed to a high-temperature environment, and can maintain the adhesiveness and the holding property. Although such a foam-based pressure-sensitive adhesive tape has been demanded, it has not been found yet.

JP 2011-168658 A JP-A-2006-183292

  The problem to be solved by the present invention is to provide a foam which is excellent in sticking property and followability when sticking to a member, can maintain its form even when exposed to a high-temperature environment, and can maintain adhesion and holding properties. It is to provide a base adhesive tape.

The inventors of the present invention have studied to solve the above-mentioned problem, and have a foam base material having a specific 25% compressive strength and a specific ratio of tensile elasticity at 23 ° C. and 120 ° C. It has been found that the above problem can be solved by an adhesive tape having a pseudo skin layer.
That is, the present invention relates to an adhesive tape having an adhesive layer on at least one surface side of a foam base material having a pseudo skin layer on both surfaces, wherein the foam base material has a 25% compressive strength of 20 to 170 kPa. The ratio E2 / E1 is 0.1 or more, where E1 is the tensile elastic modulus in the flow direction at 100 ° C of elongation at 23 ° C and E2 is the tensile elastic modulus in the flow direction at 100 ° C of elongation at 120 ° C. Or E2 ′ / E1 ′ when the tensile modulus in the width direction at 100 ° C. at 23 ° C. is 100%, and the tensile modulus in the width direction at 120 ° C. in 100% elongation is E2 ′. Is 0.1 or more.

  The pressure-sensitive adhesive tape of the present invention has a sticking property and a followability when bonded to an adherend, can maintain its form even when exposed to a high-temperature environment, and can maintain the adhesive property and the holding property. It can be suitably used for fixing two or more housings constituting an electronic device such as a terminal or an automobile.

  The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on at least one surface side of a foam substrate having a pseudo skin layer on both surfaces, wherein the foam substrate has a 25% compressive strength of 20 to 20%. The ratio E2 / E1 is 170 kPa, where E1 is the tensile modulus of elasticity in the flow direction at 100% elongation at 23 ° C. and E2 is the tensile modulus of elasticity in the flow direction of 100% elongation at 120 ° C. The ratio E2 '/ E2' / when the tensile elastic modulus in the width direction at 100 ° C. of elongation at 23 ° C. is E1 ′ and the tensile elastic modulus in the width direction at 120 ° C. at 100% elongation is E2 ′. E1 ′ is 0.1 or more.

[Foam substrate]
As the base material constituting the pressure-sensitive adhesive tape of the present invention, a foam base material having pseudo skin layers on both surfaces is used. Here, the pseudo skin layer is a layer in which the skin layers on both surfaces of the extruded foam sheet are removed by slicing, and the surface of the sliced foam is melted and solidified by heating. By having the pseudo skin layer, it is possible to provide the sticking property and the follow-up property at the time of bonding to the adherend from the skin layer, and to provide the adhesion between the pressure-sensitive adhesive and the foam base material more than the slice layer.

  As the foam base material, a material having a 25% compressive strength of 20 to 170 kPa is used, and a material having a compressive strength of 30 kPa to 140 kPa is more preferably used, and a material having a compressive strength of 40 to 120 kPa is used. It is further preferable to exhibit suitable followability to an adherend having an uneven shape or a rough surface.

  The 25% compressive strength was measured according to JIS K6767. The samples cut into 25 squares are overlapped to a thickness of about 10 mm. The sample is sandwiched between stainless steel plates having an area larger than that of the sample, and the strength is measured when the sample is compressed at 2.5 ° C. at 25 ° C. at a speed of 10 mm / min (25% of the original thickness).

The tensile elastic modulus in the flow direction and the width direction of the foam base material is not particularly limited. The tensile elastic modulus in the flow direction at 100 ° C of elongation at 23 ° C is E1, and the tensile direction in the flow direction at 100 ° C of elongation at 120 ° C is E1. When the tensile modulus of E2 is E2, the ratio E2 / E1 needs to be 0.1 or more, or the tensile modulus in the width direction of 100% elongation at 23 ° C. is E1 ′, and 120 ° C. Assuming that the tensile elastic modulus in the width direction at an elongation of 100% is E2 ′, the ratio E2 ′ / E1 ′ needs to be 0.1 or more.
The ratio E2 / E1 or E2 ′ / E1 ′ is preferably 0.15 or more, and more preferably 0.2 or more, so that the form of the foam base material can be maintained even when exposed to a high-temperature environment. It is preferable because physical properties after exposure to the environment can be maintained. The ratio E2 / E1 or 2 ′ / E1 ′ is preferably 1.0 or less.

The tensile modulus E1 in the flow direction or the tensile modulus E1 ′ in the width direction at an elongation of 100% at 23 ° C. is preferably 50 to 400 N / cm ² and 50 to 350, and more preferably 50 to 250. The tensile modulus E2 in the flow direction or the tensile modulus E2 ′ in the width direction at an elongation of 100% at 120 ° C. is preferably 5 to 400, more preferably 10 to 250, and preferably 15 to 200. Further, the ratio Eh / El of the tensile elastic modulus El in the low tensile elastic modulus and the tensile elastic modulus Eh in the high direction among the tensile elastic moduli in the flow direction and the width direction at the same temperature is 1.0 to 3.0. It is preferably from 1.0 to 2.0 for imparting processability and dimensional stability.

  In addition, the tensile elastic modulus of the above-mentioned foam base material was measured according to JISK6767. A sample having a mark length of 2 cm and a width of 1 cm was measured at a tensile rate of 300 mm / min in an environment at a temperature of 23 ° C. or 120 ° C. using a Tensilon tensile tester at a tensile elasticity of 100% elongation. is there.

Further, the maximum tensile modulus in the flow direction and the width direction of the foam base material is not particularly limited, but the maximum tensile modulus at 23 ° C. is preferably 50 to 450 N / cm ² , and more preferably. When it is 70 to 400 N / cm ² , even if it is a foamed and flexible base material, it is possible to suppress the deterioration of the workability of the pressure-sensitive adhesive tape and the deterioration of the sticking workability. In addition, when the adhesive tape is peeled off, interlayer destruction and creaking of the foam hardly occur, and even when interlayer cracking occurs, the adhesive tape can be easily peeled off. Further, the ratio Eh / El between the tensile elastic modulus El in the low tensile elastic modulus direction and the tensile elastic modulus Eh in the high tensile direction among the maximum tensile elastic moduli in the flow direction and the width direction at 23 ° C. is 1.0 to 3.0. Is preferable, and it is preferable that it is 1.0 to 2.0 in order to provide workability and dimensional stability.

The maximum tensile modulus in the flow direction and the width direction of the foam base material is not particularly limited, but the maximum tensile modulus in the flow direction or the width direction at 120 ° C. is 15 to 450 N / cm ² or more, respectively. It is preferable that it is not less than 15 to 400 N / cm ² , so that the form of the foam base material can be maintained even when exposed to a high temperature environment, and the physical properties after exposure to a high temperature environment can be maintained. Above. Further, the ratio Eh / El of the tensile elastic modulus El in the direction of low tensile elasticity and the tensile elastic modulus Eh in the high direction of the maximum tensile elastic modulus in the flow direction and the width direction at 120 ° C. is 1.0 to 3.0. Is preferable, and it is preferable that it is 1.0 to 2.0 in order to provide workability and dimensional stability.

  The foam base material has an interlayer strength of 4 N / cm or more, preferably 6 N / cm to 150 N / cm, more preferably 10 N / cm to 100 N / cm, more preferably 10 N / cm to 60 N / cm. The use of a body base material can realize good sticking and following properties to an adherend and excellent adhesiveness.

  The interlayer strength is measured by the following method. A 50-μm-thick pressure-sensitive adhesive layer (one that does not peel off from the adherend and the foam substrate during the high-speed peeling test described below) was attached to both surfaces of the foam base material for evaluating the interlayer strength one by one. Then, it is aged at 40 ° C. for 48 hours to prepare an adhesive tape for measuring interlayer strength. Next, an adhesive tape of 1 cm in width and 15 cm in length (the flow direction and the width direction of the foam base material), which is lined with a 25 μm-thick polyester film on one side of the adhesive surface, is applied at 23 ° C. and 50% RH. A 2 kg roller is pressed and reciprocated on a polyester film having a size of 50 μm, a width of 3 cm and a length of 20 cm by one reciprocation, and is left at 60 ° C. for 48 hours. After standing at 23 ° C. for 24 hours, the side bonded to the polyester film having a thickness of 50 μm at 23 ° C. and 50% RH was fixed to a mounting jig of a high-speed peeling tester, and the polyester film having a thickness of 25 μm was pulled at a speed of 15 m. The maximum strength at the time of pulling the foam at 90 degrees in the direction of 90 / min is measured.

The cell structure of the foam base material may be either a closed cell structure or an open cell structure, but has a sticking property and followability when bonded to an adherend, and a closed cell structure having excellent adhesive strength. preferable.
The average cell diameter in the flow direction and the width direction of the foam base material is 1.2 to 700 µm, preferably 10 to 500 µm, more preferably 30 to 400 µm, and further preferably 50 to 300 µm. It is preferable that the average bubble diameter in the flow direction and the width direction be in the above range, since the adhesive tape of the present invention has excellent sticking properties and followability when bonded to an adherend, and excellent adhesive strength.

The average cell diameter in the thickness direction of the foam base material depends on the thickness of the foam base material, but is preferably 1 to 150 μm, more preferably 10 to 100 μm. It is preferred because it has good properties and followability, and excellent adhesive strength.
As a method for measuring the average cell diameter, first, the foam base material is cut into a square having a width of 1 cm and a flow direction of 1 cm. Next, the cut surface of the cut foam base material was enlarged 200 times using a digital microscope (trade name “KH-7700”, manufactured by HiROX Corporation), and then the width direction and the flow direction of the foam base material were measured. The cross section was photographed.

  Next, among the cut surfaces in the width direction of the foam base material, the cell diameters of all the cells present in an arbitrary range of thickness × width direction distance (2 mm) were measured, and the average value was calculated. . In addition, the average value of the ten average values calculated by performing the above-described measurement at arbitrary ten locations on the cut surface was defined as the average bubble diameter in the width direction.

  In addition, among the cut surfaces in the flow direction of the foam base material, the cell diameters of all the cells present in an arbitrary range of thickness × distance in the flow direction (2 mm) were measured, and the average value was calculated. Further, the average value of the ten average values calculated by performing the above-described measurement at any ten places on the cut surface was further averaged to obtain an average bubble diameter in the flow direction.

The apparent density of the foam base material is not particularly limited, but the interlayer strength and the compressive strength, the average cell diameter and the like are adjusted to the above ranges, and the sticking property and the followability when sticking to the adherend, and the adherence to the adherend. Since it is easy to achieve excellent adhesion, it is 0.05 to 0.35 g / cm ³ , preferably 0.075 to 0.20 g / cm ³ , more preferably 0.1 to 0.15 g / cm ³ . is there.
The apparent density was measured according to JIS K6767. A foam base material cut into a rectangle of 4 cm × 5 cm is prepared, and its mass is measured to determine the apparent density.

  The thickness of the foam substrate may be appropriately adjusted depending on the mode of use, but is preferably 0.05 to 1.5 mm. For fixing components of electronic devices, especially in the case of small and thin mobile devices, a thin tape thickness is required, so the base material thickness is preferably 50 to 500 μm, and more preferably 70 to 400 μm. . Even at such a thin thickness, sufficient heat resistance can be maintained.

  The compression strength and tensile modulus of the foam base material can be appropriately adjusted depending on the base material and foam structure used. The type of the foam base material used in the present invention is not particularly limited as long as it has the above-mentioned 25% compressive strength and tensile modulus, but polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer may be used. Polyolefin foams such as polymerized polymers, polyurethane foams, rubber foams such as acrylic rubbers and other elastomers, etc. can be used. The polyolefin-based foam can be preferably used because the shape retention property and the original physical properties are easily maintained even after being taken out from a high temperature.

  The compression strength and tensile modulus of the foam base material can be appropriately adjusted depending on the base material and foam structure used. The type of the foam base material used in the present invention is not particularly limited as long as it has the above-mentioned 25% compressive strength and tensile modulus, but polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer may be used. Polyolefin foams such as polymerized polymers, polyurethane foams, rubber foams such as acrylic rubbers and other elastomers, etc. can be used. The polyolefin-based foam can be preferably used because the shape retention property and the original physical properties are easily maintained even after being taken out from a high temperature.

  Among the polyolefin-based resins forming the polyolefin-based foam, the use of a polypropylene-based resin makes it possible to follow irregularities on the surface of the adherend and retain the form at high temperatures, even after removal from high temperatures. This is preferable because the original physical properties can be easily maintained.

  In addition, the polyolefin-based resin may be one in which the olefin-based hydrocarbon component in the resin is 10 mol% or more and 100 mol% or less when all the monomer components constituting the resin are 100 mol%. It is suitable. For example, a polypropylene resin (A) containing a propylene component such as a propylene homopolymer or an ethylene-propylene copolymer (random polypropylene or block polypropylene), and an ethylene homopolymer, ethylene and a C3-10 Examples include a polyethylene resin (B) containing an ethylene component such as an ethylene-α-olefin copolymer composed of α-olefin and a copolymer of ethylene and non-olefin.

As the polyolefin-based resin, one kind or a mixture of two or more kinds can be used. The polyolefin-based resin preferably contains the polypropylene resin (A) and / or the polyethylene resin (B), and the polypropylene resin (A) and the polyethylene resin It is preferable to include (B) in terms of sticking property and followability at the time of sticking to an adherend, shape maintaining property at high temperature, and maintaining original physical properties even when taken out from high temperature.
In forming the polyolefin foam, a thermoplastic elastomer resin (C) can be used, if necessary. By adding the thermoplastic elastomer-based resin (C), it is possible to maintain the original physical properties even when taken out from a high temperature, by sticking and following properties when bonding to an adherend, maintaining shape at high temperatures. More preferred.

  Examples of the polypropylene resin (A) used in the present invention include homopolypropylene, ethylene-propylene random copolymer, ethylene-propylene block copolymer, and the like. If necessary, a propylene monomer and another copolymerizable monomer can be used. Can also be used. The polypropylene resin (A) in the polyolefin resin is not limited to one type, and two or more types may be blended and used. Random polypropylene having an ethylene content of 5 to 15% by mass, a melting point of 135 to 155 ° C, and an MFR (230 ° C) of 0.5 to 5.0 in 100% by mass of the polypropylene resin (A), and / or a polypropylene resin (B) Block polypropylene having an ethylene content of 1 to 5% by mass in 100% by mass, a melting point of 150 to 170 ° C, and an MFR (230 ° C) of 1.0 to 7.0 is particularly preferred.

  The content of the polypropylene resin (A) in all the resins constituting the foam is preferably from 10 to 80% by weight, more preferably from 20 to 70% by weight, and even more preferably from 25 to 65% by weight. In the case where the resin containing 70% by weight or more of the polypropylene resin (A) is used, sufficient flexibility of the polyolefin resin foam cannot be obtained, and the case where the resin containing the polypropylene resin (A) is less than 20% by weight is used. The heat resistance of the resulting polyolefin resin foam may be impaired.

The polyethylene resin (B) used in the present invention includes high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl An acrylate copolymer (EBA) and the like can be mentioned. If necessary, a copolymer of an ethylene monomer and another copolymerizable monomer can be used. These polyethylene resins (B) may be blended not only in one kind but also in two or more kinds. As the polyethylene resin (B), those having a density of 890 to 950 kg / m ³ and an MFR (190 ° C.) within a range of 1 to 15 g / 20 minutes are preferably used, and especially, a density of 920 to 940 kg / m ³ and an MFR (190 ° C.) is more preferably an ethylene-α-olefin copolymer having a melting point of 2 to 10 g / 10 min and a melting point of 100 to 130 ° C.

  The content ratio of the polyethylene resin (B) is preferably from 5 to 35% by weight, more preferably from 10 to 30% by weight, and even more preferably from 15 to 25% by weight. When a resin containing 35% by weight or more of polyethylene resin (B) is used, sufficient flexibility and heat resistance cannot be obtained, and when a resin containing less than 5% by weight of polyethylene resin (B) is used, it is obtained. The cold resistance of the polyolefin foam may be impaired.

  The thermoplastic elastomer resin (C) that can be used in the present invention includes polystyrene-based thermoplastic elastomers (SBC, TPS), polyolefin-based thermoplastic elastomers (TPO), vinyl chloride-based thermoplastic elastomers (TPVC), and polyurethane-based thermoplastic elastomers. Any conventionally known materials such as a thermoplastic elastomer (TPU), a polyester-based thermoplastic elastomer (TPEE, TPC), a polyamide-based thermoplastic elastomer (TPAE, TPA), and a polybutadiene-based thermoplastic elastomer may be used. These thermoplastic elastomer resins (C) may be blended not only in one kind but also in two or more kinds. As the thermoplastic elastomer resin (C), those having a density of 850 to 920 kg / m 3 and an MFR (230 ° C.) within a range of 1 to 15 are preferably used, and among them, a density of 860 to 910 kg / m 3 and an MFR (230 C.) of 5 to 10 are particularly preferably used.

  The content of the thermoplastic elastomer resin (C) is preferably from 5 to 70% by mass, more preferably from 10 to 60% by mass, and still more preferably from 20 to 50% by mass. When a resin containing less than 5% by weight of the thermoplastic elastomer resin (C) is used, sufficient flexibility cannot be obtained, and when a resin containing 70% by weight or more of the thermoplastic elastomer resin (C) is used, The heat resistance of the obtained polyolefin foam may be impaired.

  In the foam base material of the present invention, the content of the polypropylene resin (A) in all the resins constituting the foam is 30 to 60% by mass, and the polyethylene resin (B) is 1 to 20% by mass. The thermoplastic elastomer resin (C) preferably contains 30 to 60% by mass, the content of the polypropylene resin (A) is 30 to 55% by mass, and the polyethylene resin (B) contains 10 to 55% by mass. 20% by mass, and 30 to 50% by mass of the thermoplastic elastomer-based resin (C), when used for sticking to an adherend, conformability, shape retention at high temperature, and high temperature. It is more preferable that the original physical properties can be maintained even when it is taken out.

  In the present invention, as long as the effects of the present invention are not impaired, phenol-based, phosphorus-based, amine-based and sulfur-based antioxidants, metal harm inhibitors, divinylbenzene, trimethylolpropane trimethacrylate, 1,6 -Hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, triallyl isocyanurate, ethylvinylbenzene, ethylenevinyldimethacrylate, 1,2-benzenedicarboxylic acid diallyl ester, 1, Cross-linking aids such as diallyl ester of 3-benzenedicarboxylic acid, diallyl ester of 1,4-benzenedicarboxylic acid and diallyl ester of 1,2,4-benzenetricarboxylic acid; fillers such as mica and talc; Flame retardant, anti trioxide Flame retardant aid such as down, antistatic agents, lubricants, pigments, and the polyolefin additives such as polytetrafluoroethylene may be added.

  The foam base material of the present invention is produced by mixing a polyolefin resin mixture with a foaming agent capable of generating a gas. The production method is as follows. Pressure foaming method in which a chemical blowing agent is added and melt-kneaded, and foaming is performed by heating under normal pressure. Extrusion foaming method, in which a pyrolytic chemical foaming agent is thermally decomposed in an extruder and foamed while extruding under high pressure, press Press foaming method in which a thermal decomposition type chemical foaming agent is thermally decomposed in a mold and foaming is performed under reduced pressure, and extrusion foaming method in which a gas or a vaporized solvent is melt-mixed in an extruder and foamed while extruding under high pressure. Method.

The thermal decomposition type chemical foaming agent used here is a chemical foaming agent which decomposes and releases gas by applying heat, for example, azodicarbonamide, N, N'-dinitrosopentamethylenetetramine, P, P Organic blowing agents such as' -oxybenzenesulfonyl hydrazide; and inorganic blowing agents such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate and calcium azide.
Examples of the gas or the solvent that evaporates include gases such as carbon dioxide, nitrogen, and helium, and solvents that evaporate such as propane, normal butane, and isobutane.
The foaming agents can be used alone or in combination of two or more. In order to obtain a flexible foam having high moldability and a high smoothness with a smooth surface, a normal pressure foaming method using azodicarbonamide as a foaming agent is suitably used.

  Next, a method for producing a polyolefin-based resin foam will be described. The method for producing the polyolefin-based resin foam is not particularly limited, and the foaming property containing the polyolefin-based resin and the pyrolytic foaming agent and a foaming aid, and a coloring agent for coloring the foam to black or white, etc. Supplying a polyolefin-based resin composition to an extruder, melt-kneading the same, extruding the extruder into a sheet to produce an expandable polyolefin-based resin sheet, and cross-linking the expandable polyolefin-based resin sheet. , A step of foaming the expandable polyolefin-based resin sheet, a step of slicing the obtained foam sheet and removing the skin layer, and melting or softening the obtained foam sheet, either in the flow direction or the width direction or The foamed tape is stretched by heating and stretching in both directions, and the surface of the foamed sheet is melt-solidified to provide a pseudo skin layer. How containing extent thereof.

  The step of cross-linking the expandable polyolefin-based resin sheet is, for example, a method of irradiating the expandable polyolefin-based resin sheet with ionizing radiation, previously blending an organic peroxide with the expandable polyolefin-based resin composition, and obtaining A method of heating the foamable polyolefin-based resin sheet thus obtained to decompose the organic peroxide, and the like, may be used in combination.

Examples of the ionizing radiation include an electron beam, α-ray, β-ray, and γ-ray. As for the dose of the ionizing radiation, the gel fraction of the polyolefin resin foam base material is preferably 5% by mass to 70% by mass, more preferably 20% by mass to 60% by mass, and still more preferably 25% by mass to 55% by mass.
, But is preferably in the range of 5 to 200 kGy. In addition, irradiation with ionizing radiation is preferably performed from both sides of the expandable polyolefin resin sheet in order to form a uniform crosslinked structure and, as a result, form a relatively uniform foamed structure. Are preferably the same.

  Examples of the organic peroxide include 1,1-bis (t-butylperoxy) 3,3,5-trimethylcyclohexane, 1,1-bis (t-butylperoxy) cyclohexane, and 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, cumylperoxyneodecanate, t-butylperoxybenzoate, 2,5-dimethyl-2,5-di (ben Examples thereof include zoylperoxy) hexane, t-butylperoxyisopropyl carbonate, and t-butylperoxyallyl carbonate. These may be used alone or in combination of two or more.

The addition amount of the organic peroxide is preferably from 0.01 to 5 parts by mass, more preferably from 0.1 to 3 parts by mass, per 100 parts by mass of the polyolefin resin.
The amount of the pyrolytic foaming agent in the foamable polyolefin-based resin composition may be appropriately determined according to the expansion ratio of the polyolefin-based resin foam base material. Part to 40 parts by mass is preferable, and 1 part to 30 parts by mass is more preferable.

  The method for foaming the expandable 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 of using a salt bath, a method of using an oil bath, and the like. May be used in combination. Among them, a method of heating with hot air and a method of heating with infrared rays are preferable because there is little difference between the front and back of the appearance of the surface of the polyolefin resin foam base material.

  The method of slicing the foam substrate is not particularly limited, and the skin layers on both sides of the molded foam sheet may be removed, and the thickness of the foam substrate may be appropriately adjusted according to the thickness mode used. good. The method of heating and stretching the foam base material is performed after slicing the foam base material, and the pseudo skin layer is applied by melting and solidifying the surfaces of both surfaces. The stretching is not particularly limited, and may or may not be stretched.

  Furthermore, in the stretching direction of the foam base material, the elongated foamable polyolefin-based resin sheet is stretched in the flow direction or the width direction, 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 simultaneously stretched in the flow direction and the width direction, or may be separately stretched in each direction. .

The foam base material may be colored in the pressure-sensitive adhesive tape in order to exhibit a design property, a light shielding property, a concealing property, a light reflection property, and a light resistance. The coloring agents can be used alone or in combination of two or more.
When imparting light-shielding properties, hiding properties, and light resistance to the adhesive tape, the foam base material is colored black. Black colorants 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, chromium complex, and complex oxides. Substance black pigment, anthraquinone organic black pigment, and the like. Among them, carbon black is preferred from the viewpoint of cost, availability, insulating properties, and heat resistance to withstand the temperature of the step of extruding the foamable polyolefin-based resin composition and the step of heating and foaming.

  When a design property or light reflectivity is imparted to the pressure-sensitive adhesive tape, the foam base is colored white. Examples of white colorants 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, and 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, phosphoric acid Inorganic white colorants such as titanium, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, and organic such as silicone resin particles, acrylic resin particles, urethane resin particles, and melamine resin particles And the like can be used white colorant. Among these, aluminum oxide and zinc oxide are preferred from the viewpoint of cost, availability, color tone, and heat resistance to withstand the temperature of the step of extruding the foamable polyolefin-based resin composition or the step of heating and foaming.

  The foamable polyolefin-based resin composition may further include a plasticizer, an antioxidant, a foaming aid such as zinc oxide, a foam nucleus adjusting material, if necessary, as long as the physical properties of the polyolefin-based resin foam substrate are not impaired. , Heat stabilizers, flame retardants such as aluminum hydroxide and magnesium hydroxide, antistatic agents, glass and plastic hollow balloon beads, fillers such as metal powders and metal compounds, conductive fillers, and thermal conductive fillers A known material such as a resin may be arbitrarily contained in the resin. As the polyolefin-based resin foam base material used for the pressure-sensitive adhesive tape of the present invention, 0.1% by mass to 10% by mass with respect to the polyolefin-based resin in order to maintain sticking property and followability when pasting to an adherend. %, Preferably 1% to 7% by mass.

  When the coloring agent, the thermally decomposable foaming agent, the foaming aid and the like are blended in the foamable polyolefin-based resin composition, they are supplied to an extruder from the viewpoint of preventing color unevenness and partial excessive foaming or insufficient foaming. It is preferable to form a masterbatch with a foamable polyolefin-based resin composition or a thermoplastic resin having high compatibility with the foamable polyolefin-based resin composition beforehand.

  The foam base material should be subjected to surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone / ultraviolet light treatment, and application of an easy adhesion treatment agent in order to improve the adhesion with the pressure-sensitive adhesive layer and other layers. It may be done. In the surface treatment, when the wetting index by the wetting reagent is 36 mN / m or more, preferably 40 mN / m, and more preferably 48 mN / m, good adhesion to the pressure-sensitive adhesive can be obtained. The foam base material having improved adhesion may be bonded to the pressure-sensitive adhesive layer in a continuous process. Further, the foam base material having improved adhesion may be once wound up and stored, and then may be bonded to the pressure-sensitive adhesive layer in a separate step at a later date.

  Incidentally, when once winding the foam substrate with improved adhesion, in order to prevent blocking of the foam substrate, it is preferable to wind through a film made of paper, polyethylene, polypropylene, polyester, or the like. . The film is preferably a polypropylene film or a polyester film having a thickness of 25 μm or less.

[Adhesive layer]
As the pressure-sensitive adhesive composition constituting the pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention, a pressure-sensitive adhesive composition used for a normal pressure-sensitive adhesive tape can be used. Examples of the pressure-sensitive adhesive composition include 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, and a silicone-based pressure-sensitive adhesive. An acrylic copolymer composed of a copolymer of (meth) acrylate and another monomer as a base polymer, to which additives such as a tackifying resin and a cross-linking agent are blended if necessary. An adhesive composition can be preferably used.

  As the acrylic pressure-sensitive adhesive composition, examples of the (meth) acrylate having 1 to 12 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. , 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 And one or more of these are used. Among them, (meth) acrylates having 4 to 12 carbon atoms in the alkyl group are preferable, and (meth) acrylates having a linear or branched structure having 4 to 8 carbon atoms are more preferable. In particular, n-butyl acrylate is preferable because it is easy to secure adhesion to an adherend.

  The content of the (meth) acrylate having 1 to 12 carbon atoms in the acrylic copolymer is preferably 80 to 98.5% by mass of the monomer component constituting the acrylic copolymer, and is preferably 90 to 98%. More preferably, it is 0.5% by mass. The acrylic copolymer used in the present invention may be obtained by copolymerizing a highly polar vinyl monomer. Examples of the highly polar vinyl monomer include a vinyl monomer having a hydroxyl group, a vinyl monomer having an acid group, and a vinyl monomer having an amide group. Monomers and the like are used, and one or more of these are used.

  Examples of the vinyl monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxybutyl ( (Meth) acrylate, 2-hydroxyhexyl (meth) acrylate, 6-hydroxyhexyl (meth) acryl, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, etc. Hydroxyl-containing (meth) acrylates can be used. Of these, 4-hydroxybutyl (meth) acrylate is preferably used as the vinyl monomer having a hydroxyl group, and 4-hydroxybutyl acrylate is preferably used such as 2-hydroxyethyl (meth) acrylate. It is more preferable to obtain a pressure-sensitive adhesive sheet having a more excellent static load holding force as compared with the case where it is used.

  The hydroxyl group-containing monomer is preferably used in a range of 0.01% by mass to 0.2% by mass based on all monomer components constituting the acrylic copolymer, and is preferably used in an amount of 0.01% by mass to 0.1% by mass. It is more preferable to use it in a range of less than 1% by mass, and it is more preferable to use it in a range of 0.02% by mass to 0.08% by mass by setting the tensile strength of the pressure-sensitive adhesive layer to a specific range. It is more preferable to obtain an adhesive sheet having a static load holding force.

  Examples of the vinyl monomer having an acid group include carboxyls such as acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, (anhydride) itaconic acid, (anhydride) maleic acid, fumaric acid, crotonic acid and the like. (Meth) acrylic monomer having a group, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) acrylate, (meth) acryloyloxynaphthalenesulfonic acid, sodium vinylsulfonic acid, styrenesulfonic acid, allylsulfonic acid, 2- (Meth) acrylamide-2-methylpropanesulfonic acid, vinyl monomer having a sulfonic acid group such as (meth) acrylamidopropanesulfonic acid, and (meth) acrylic monomer having a phosphoric acid group such as 2-hydroxyethylacryloyl phosphate It can be used the body or the like. Among them, it is preferable to use a (meth) acrylic monomer having a carboxyl group, and it is more preferable to use acrylic acid or methacrylic acid in order to obtain a pressure-sensitive adhesive sheet having more excellent static load holding power. .

  The vinyl monomer having an acid group is not particularly limited as long as the acid value of the acrylic copolymer falls within a predetermined preferable range, but is preferably 1 to all monomer components constituting the acrylic copolymer. It is preferably used in the range of from 30% by mass to 30% by mass, more preferably in the range of from 1% by mass to 15% by mass, and more preferably in the range of from 1% by mass to 7% by mass. It is further preferable to obtain a pressure-sensitive adhesive sheet having a static load holding force.

  When producing the acrylic copolymer, a (meth) acrylic monomer having an aliphatic cyclic structure is used to introduce the aliphatic cyclic structure into the acrylic copolymer. Is preferred. As the vinyl monomer having an aliphatic cyclic structure, it is preferable to use cyclohexyl (meth) acrylate or the like, and it is more preferable to use cyclohexyl acrylate.

  The vinyl monomer having the aliphatic cyclic structure is more preferably used in the range of 0.5% by mass to 30% by mass based on all the monomer components constituting the acrylic copolymer. It is preferable to obtain a pressure-sensitive adhesive sheet having a load holding force, and it is more preferable to use the adhesive sheet in the range of 4% by mass to 25% by mass.

  Examples of the monomer having an amide group include acrylamide, methacrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N, N- Diethyl methacrylamide, N, N'-methylenebisacrylamide, N, N-dimethylaminopropyl acrylamide, N, N-dimethylaminopropyl methacrylamide, diacetone acrylamide, acryloyl morpholine and the like can be used.

Further, the acrylic copolymer used in the present invention may be a vinyl monomer having an amino group or a vinyl monomer having an imide group.
As the vinyl monomer having an amino group, for example, aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate and the like can be used.

Examples of the vinyl monomer having an imide group include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide, and itaconimide.
The content of the highly polar vinyl monomer is preferably from 1.5 to 20% by mass, more preferably from 1.5 to 10% by mass, and more preferably from 2 to 10% by mass, based on the monomer components constituting the acrylic copolymer. More preferably, it is 8% by mass. When the content is in the above range, the cohesive force, the holding power, and the adhesiveness of the pressure-sensitive adhesive can be easily adjusted to suitable ranges.

  When an isocyanate-based cross-linking agent is used as the cross-linking agent, the hydroxyl-containing vinyl monomer is preferable as the vinyl monomer having a functional group that reacts with the cross-linking agent, and 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate And 6-hydroxyhexyl (meth) acrylate are particularly preferred. The content of the hydroxyl group-containing vinyl monomer that reacts with the isocyanate-based cross-linking agent is preferably 0.01 to 1.0% by mass of the monomer component constituting the acrylic copolymer, and is preferably 0.03 to 0.3% by mass. % Is particularly preferred.

  The acrylic copolymer can be obtained by copolymerization by a known polymerization method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, and an emulsion polymerization method. Preference is given to a batch process or a bulk polymerization process. The method of initiating polymerization is also a method of initiating by heat using a peroxide-based thermal polymerization initiator such as benzoyl peroxide or lauroyl peroxide, or an azo-based thermal polymerization initiator such as azobisisobutylnitrile, or an acetophenone-based, benzoin ether-based, or benzyl A method of starting by ultraviolet irradiation using a ketal-based, acylphosphine oxide-based, benzoin-based, or benzophenone-based photopolymerization initiator, or a method of electron beam irradiation can be arbitrarily selected.

The pressure-sensitive adhesive layer of the pressure-sensitive adhesive tape of the present invention preferably has a tensile strength of 6 N / cm ² or more based on a stress-strain curve at a strain amount of 100%.
Here, the tensile strength was determined by laminating an adhesive layer having a thickness of 50 μm, a test piece consisting of an adhesive layer having a thickness of about 400 μm, a mark interval of 2 cm, and a width of 1 cm, at a temperature of 23 ° C. and a humidity of 23 ° C. When the amount of strain is 100% in a stress-strain curve (so-called SS curve) measured by performing a tensile test at a tensile speed of 300 mm / min using a tensile tester under a measurement environment of 50%. Refers to the tensile strength of In a pressure-sensitive adhesive sheet provided with a pressure-sensitive adhesive layer having a tensile strength of less than 6 N / cm ² , practically sufficient static load holding force may not be exhibited.

The upper limit of the tensile strength is not particularly limited, is preferably 30 N / cm ² or less, more preferably 25 N / cm ² or less, it is 20 N / cm ² or less, and the peel adhesive strength It is further preferable to express the performance of the pressure-sensitive adhesive sheet such as the push strength and the static load holding force in a well-balanced manner.

The pressure-sensitive adhesive layer preferably has a tensile strength of 12 N / cm ² or more based on a stress-strain curve at a strain amount of 500%, and more preferably has a tensile strength of 13 N / cm ² or more. more preferably, more preferably the use of 15N / cm ² or more of, more preferably the use of 17N / cm ² or more of, it is particularly preferred to use 19N / cm ² or more. The upper limit of the tensile strength is preferably at 70N / cm ² or less, it is more preferable to use those 65N / cm ² or less. By using a pressure-sensitive adhesive layer having a tensile strength based on a stress-strain curve at a strain amount of 500% in the above range, a balanced adhesive performance such as a static load holding force, a peel adhesive force, and a push strength is provided. It is preferable to obtain a pressure-sensitive adhesive sheet.

  Further, as the acrylic copolymer, the tensile strength of the pressure-sensitive adhesive layer is set to a specific range, as a result, to form a pressure-sensitive adhesive layer having a more excellent static load holding force, from 1 to It is preferable to use one having an acid value of 50, more preferably one having an acid value of 10 to 50, and more preferably one having an acid value of 25 to 40. Is more preferable. The acid value is preferably an acid value derived exclusively from a carboxyl group. In addition, the said acid value points out mg of potassium hydroxide required for neutralizing the acid group which exists in the said acrylic copolymer solution.

  In addition, as the acrylic copolymer, it is preferable to use an acrylic copolymer having an aliphatic cyclic structure in order to form a pressure-sensitive adhesive layer having more excellent static load holding power.

  Examples of the aliphatic cyclic structure include a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a propylcyclohexyl group, a tricyclo [5,2,1,0,2,6] decyl group, a bicyclo [ 4,3,0] -nonyl group, tricyclo [5,3,1,1] dodecyl group, propyltricyclo [5,3,1,1] dodecyl group, norbornene group, isobornyl group, dicyclopentanyl group, An adamantyl group and the like can be mentioned, among which cyclohexyl group, norbornene group, isobornyl group, and adamantyl group, in order to obtain a pressure-sensitive adhesive sheet that has more excellent peel adhesion and more excellent push strength. preferable.

  Further, as the acrylic copolymer, it is preferable to use a copolymer having a weight average molecular weight of 800,000 or more, in order to obtain a pressure-sensitive adhesive sheet having a more excellent static load holding force, and from 800,000 to 300,000. It is more preferable to use one having a weight average molecular weight in the range of 10,000, and to use one having a weight average molecular weight in the range of 1,000,000 to 2.2 million to set the tensile strength of the pressure-sensitive adhesive layer to a specific range. As a result, it is more preferable to obtain an adhesive sheet having excellent static load holding power. The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC).

  The measurement of the molecular weight by the GPC method is a value obtained by using a GPC device (HLC-8329GPC) manufactured by Tosoh Corporation and converted to polystyrene.

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: 2 TSKgel GMHHR-H (20) Guard column: TSKgel HXL-H
Detector: Differential refractometer Standard polystyrene molecular weight: 10,000-20,000,000 (manufactured by Tosoh Corporation)

  As the acrylic copolymer, those having a glass transition temperature of −15 ° C. or lower are preferably used, and those having a glass transition temperature of −45 ° C. to −20 ° C. are more excellent. It is more preferable to obtain a pressure-sensitive adhesive sheet that has both good static load holding power. The glass transition temperature indicates a value calculated by the FOX equation.

In the acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a tackifier resin in order to improve the adhesion to the adherend and the adhesive strength. Tackifying resins include rosin, polymerized rosin, polymerized rosin ester, rosin phenol, stabilized rosin ester, disproportionated rosin ester, hydrogenated rosin ester, terpene, terpene phenol, petroleum resin And (meth) acrylate resins. When used in an emulsion-type pressure-sensitive adhesive composition, it is preferable to use an emulsion-type tackifier resin.
Among them, as the tackifying resin, two or more selected from the group consisting of a polymerized rosin ester-based tackifying resin, a disproportionated rosin ester-based tackifying resin, a petroleum-based tackifying resin, and a terpene phenol-based tackifying resin. It is preferable to use them in combination in order to obtain a pressure-sensitive adhesive sheet having excellent compatibility with the acrylic polymer and further excellent static load holding power, and more preferably three or more kinds.

  The softening point of the tackifier resin is not particularly limited, but is 30 to 180C, preferably 70C to 170C, more preferably 100C to 160C, and further preferably 120C to 150C. When the content is in the above range, a pressure-sensitive adhesive sheet having more excellent peel adhesive strength, more excellent push strength, and more excellent static load holding force can be obtained.

  The mixing ratio when the acrylic copolymer and the tackifier resin are used, the content of the tackifier resin with respect to 100 parts by mass of the acrylic copolymer is preferably 5 to 60 parts by mass, and 8 to 50 parts by mass. It is preferably in parts by mass. By setting the ratio of the two to the above range, it is easy to secure the adhesion to the adherend.

  In the acrylic pressure-sensitive adhesive composition, it is preferable to crosslink the pressure-sensitive adhesive in order to increase the cohesive strength of the pressure-sensitive adhesive layer. Examples of such a crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a metal chelate-based crosslinking agent, and an aziridine-based crosslinking agent. Among them, a cross-linking agent which is added after the polymerization is completed and which promotes a cross-linking reaction is preferable, and an isocyanate-based cross-linking agent and an epoxy-based cross-linking agent having high reactivity with the (meth) acrylic copolymer are preferable. Isocyanate-based cross-linking agents are more preferable because the adhesion to the substrate is improved.

  Examples of the isocyanate-based crosslinking agent include tolylene diisocyanate, naphthylene-1,5-diisocyanate, hexamethylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and trimethylolpropane-modified tolylene diisocyanate. Particularly preferred are trifunctional polyisocyanate compounds. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, their adducts of trimethylolpropane, and triphenylmethane isocyanate.

As an index of the degree of crosslinking, a gel fraction value for measuring an insoluble content after immersing the pressure-sensitive adhesive layer in toluene for 24 hours is used. The gel fraction is preferably from 25 to 70% by mass. When the content is more preferably in the range of 30 to 60% by mass, and still more preferably in the range of 30 to 55% by mass, both cohesiveness and adhesiveness are good.
The measurement of the gel fraction is as follows. A pressure-sensitive adhesive composition was applied on a release sheet so that the thickness after drying was 50 μm, dried at 100 ° C. for 3 minutes, and aged at 40 ° C. for 2 days, cut into 50 mm squares, and this was used as a sample. I do. Next, the weight (G1) of the sample before immersion in toluene was measured in advance, and the sample was immersed in a toluene solution at 23 ° C. for 24 hours. Then, the weight (G2) of the residue after drying at 110 ° C. for 1 hour is measured, and the gel fraction is determined according to the following equation.
Gel fraction (% by mass) = (G2 / G1) × 100

  As additives for adhesives, plasticizers, softeners, antioxidants, flame retardants, fillers such as glass and plastic fibers, balloons, beads, metal powders, metal oxides, metal nitrides, as required Any known additives such as coloring agents such as pigments and dyes, leveling agents, thickeners, water repellents and defoamers can be optionally added to the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive layer used in the pressure-sensitive adhesive tape of the present invention preferably has a temperature at which the peak value of the loss tangent (tan δ) at a frequency of 1 Hz is present, and more preferably the temperature is −40 ° C. to 15 ° C. By setting the peak value of the loss tangent of the pressure-sensitive adhesive layer in the above range, it becomes easy to provide good adhesion to an adherend at normal temperature. In particular, when improving the drop impact resistance in a low-temperature environment, the temperature is more preferably from −35 ° C. to 10 ° C., and the temperature is preferably from −30 ° C. to 6 ° C. for good adhesion to the adherend at room temperature. It is preferable because the property can be easily provided.
The loss tangent (tan δ) at a frequency of 1 Hz is obtained from the storage elastic modulus (G ′) and the loss elastic modulus (G ″) obtained by dynamic viscoelasticity measurement based on temperature dispersion according to the equation tan δ = G ″ / G ′. Can be

Dynamic viscoelastic properties are based on the type and ratio of monomers used in the acrylic copolymer constituting the adhesive, the type and amount of polymerization initiator used, the cross-linking agent, and a tackifying resin such as a polymerized rosin ester-based tackifying resin. Can be adjusted by appropriately selecting the type, amount used, polymerization method and the like.
The dynamic viscoelastic properties of the above-mentioned pressure-sensitive adhesive layer are defined by a loss tangent of a dynamic viscoelastic spectrum or a loss tangent and a storage elastic modulus at a specific frequency and a specific temperature. It is defined by the temperature at which the loss tangent has a maximum value in the viscoelastic spectrum or the maximum value of the loss tangent. In the measurement of dynamic viscoelasticity, using a viscoelasticity tester (manufactured by TA Instruments Japan, trade name: ARES G2), a test piece is sandwiched between parallel disks, which are measurement units of the tester, The storage elastic modulus (G ′) and the loss elastic modulus (G ″) are measured at a frequency of 1 Hz from −50 ° C. to 150 ° C. The test piece is formed by forming an adhesive layer or an adhesive tape to a thickness of about 2 mm, and forming a parallel. Measure between discs.

  The thickness of the pressure-sensitive adhesive layer used in the present invention is 10 to 100 μm in one-sided thickness because the adhesiveness to the adherend and the reworkability and removability are easily ensured even when a thin tape is used. More preferably, it is 30 to 80 μm.

The release sheet used in the present invention is not particularly limited, but may be at least one side of a substrate such as a synthetic resin film such as polyethylene, polypropylene, and polyester film, paper, nonwoven fabric, cloth, foamed sheet and metal foil, and a laminate thereof. In addition, those which have been subjected to a release treatment such as a silicone-based treatment, a long-chain alkyl-based treatment, or a fluorine-based treatment for improving the releasability from the adhesive can be exemplified.
Above all, a paper laminated with polyethylene and a release sheet in which one side of a polyester film is subjected to a silicone-based release treatment are preferable.

[Production method of adhesive tape]
The method for producing the pressure-sensitive adhesive tape of the present invention can be produced by a known and commonly used method. For example, it can be manufactured by applying the pressure-sensitive adhesive to one or both surfaces of the base material using a roll coater, a die coater, or the like, and drying. Further, the pressure-sensitive adhesive tape is formed by applying the pressure-sensitive adhesive on the surface of a release liner in advance using a roll coater or the like and drying to form a pressure-sensitive adhesive layer. It can be manufactured by a transfer method of attaching to both sides.

  The pressure-sensitive adhesive tape of the present invention, by using the foam base material and the pressure-sensitive adhesive layer, has excellent followability at the time of application, can maintain its shape even when exposed to high temperature, and is taken out from under high temperature. However, since the original physical properties can be maintained, it can be used for fixing components constituting various electronic devices such as a mobile field and an automobile field.

  As an embodiment of the pressure-sensitive adhesive tape of the present invention, a basic configuration is such that a foam base material is used as a core and a pressure-sensitive adhesive layer is provided on one or both surfaces of the base material. The base and the pressure-sensitive adhesive layer may be directly laminated or may have another layer. These embodiments may be appropriately selected depending on the intended use, and when a tape is further provided with dimensional stability or tensile strength, a laminated layer such as a polyester film is provided, and when a tape is provided with a light blocking property, a light blocking layer is provided. When ensuring light reflectivity, a light reflecting layer may be provided.

  The thickness of the pressure-sensitive adhesive tape of the present invention may be appropriately adjusted depending on the mode of use, but is preferably 70 to 1700 μm. For fixing components of electronic devices, particularly in the case of small and thin electronic devices, a thin tape thickness is required. Therefore, the thickness is more preferably 100 to 600 μm, and particularly preferably 120 to 500 μm.

  The pressure-sensitive adhesive tape of the present invention has excellent sticking properties and conformability when bonded to an adherend, can maintain its form even when exposed to high temperatures, and can maintain its original physical properties even after being removed from high temperatures. It can be used for fixing components constituting various electronic devices such as the mobile field and the automobile field.

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

(Production of acrylic polymer (a))
In a reaction vessel equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, and a thermometer, 80.94 parts by mass of n-butyl acrylate, 5 parts by mass of 2-ethylhexyl acrylate, 10 parts by mass of cyclohexyl acrylate, 4 parts by mass of acrylic acid, 0.06 parts by mass of -hydroxybutyl acrylate and 200 parts by mass of ethyl acetate were charged, and the mixture was heated to 72 ° C. while blowing nitrogen under stirring.

Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the 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 diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh wire net to obtain an acrylic polymer (a) solution having a weight average molecular weight of 1.6 million (nonvolatile content: 40% by mass).

The weight average molecular weight is a weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC), and was measured by the following method.
The measurement of the molecular weight by the GPC method is a standard polystyrene conversion value measured by using a GPC device (HLC-8329GPC) manufactured by Tosoh Corporation.

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

(Production of acrylic polymer (b))
The amount of the 4-hydroxybutyl acrylate is changed from 0.06 parts by mass to 0.1 parts by mass, and the amount of the n-butyl acrylate is changed from 80.94 parts by mass to 80.9 parts by mass. Except for the above, an acrylic polymer (A-3) solution having a weight average molecular weight of 1,620,000 (nonvolatile content: 40% by mass) was obtained in the same manner as in Preparation Example 1.

(Production of acrylic polymer (c))
The use amount of the acrylic acid was changed from 4 parts by mass to 6 parts by mass, and the use amount of n-butyl acrylate was changed from 80.94 parts by mass to 93.94 parts by mass, and 2-ethylhexyl acrylate was used. An acrylic polymer (A-6) solution having a weight average molecular weight of 1,640,000 (nonvolatile content: 40% by mass) was obtained in the same manner as in Preparation Example 1 except that it was not used.

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

  Next, 2 parts by mass (solid content 0.1% by mass) of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate was added to the 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 diluted with 98 parts by mass of ethyl acetate and filtered through a 200-mesh wire net to obtain an acrylic polymer (B-1) solution having a weight average molecular weight of 1.86 million (nonvolatile content: 40% by mass).

(Adjustment of adhesive solvent (a))
In a container, with respect to 100 parts by mass of the acrylic polymer (a), 15 parts by mass of a polymerized rosin ester-based tackifying resin D-125 (manufactured by Arakawa Chemical Industry Co., Ltd.) and disproportionated rosin ester-based tackifying resin A- After mixing with 10 parts by mass of 125 (manufactured by Arakawa Chemical Industry Co., Ltd.), ethyl acetate was added to obtain a 31% by mass solid solution of a pressure-sensitive adhesive.

  Next, with respect to 100 parts by mass of the pressure-sensitive adhesive solution, Vernock D-40 (manufactured by DIC Corporation, a trimethylolpropane adduct of tolylene diisocyanate, isocyanate group content 7% by mass, non-volatile content 40% by mass) was used as a crosslinking agent. ) 1.4 parts by mass were added, and the mixture was stirred and mixed so as to be uniform. Then, the mixture was filtered through a 100-mesh wire net to obtain an adhesive solvent (a).

(Adjustment of adhesive solvent (b))
Instead of using the acrylic polymer (a) solution, the acrylic polymer (b) solution was used, except that the blending amount of Vernock D-40 was changed from 1.4 parts by mass to 1.2 parts by mass. An adhesive (b) was obtained in the same manner as described above.

(Adjustment of adhesive solvent (c))
An adhesive solvent (c) was obtained in the same manner as described above, except that the acrylic polymer (c) solution was used instead of the acrylic polymer (a) solution.

(Adjustment of adhesive solvent (d))
Instead of the acrylic polymer (a) solution, the acrylic polymer (d) solution was used, and except that the amount of Burnock D-40 was changed from 1.4 parts by mass to 1.2 parts by mass, An adhesive solvent (d) was obtained in the same manner.

[Example 1]
The adhesive is applied using a bar coater on the surface of the release liner so that the thickness of the adhesive layer after drying the adhesive solvent (a) is 50 μm, and dried at 80 ° C. for 3 minutes. Thus, an adhesive layer was prepared.
Next, the pressure-sensitive adhesive layer was applied to both surfaces of a polyolefin-based foam A (polypropylene foam, a double-sided pseudo skin layer, having a thickness of 300 µm, and having an apparent density of 0.129 g / cm ³ ). An adhesive tape was prepared by curing under an environment for 48 hours.

[Example 2]
Polyolefin foam B (polypropylene foam, double-sided pseudo skin layer, thickness adjusted to 300 μm, apparent density 0.158 g / cm ³ ) was used in place of polyolefin foam A in the same manner as in Example 1. An adhesive tape was produced.

[Example 3]
A polyolefin foam C (polypropylene foam, a double-sided pseudo skin layer, having a thickness of 300 μm, and having an apparent density of 0.066 g / cm ³ ) was used in place of the polyolefin foam A in the same manner as in Example 1. An adhesive tape was produced.

[Example 4]
Polyolefin-based foam A (polypropylene foam, double-sided pseudo skin layer, thickness 300 μm, apparent density 0.129 g / cm ³ , using pressure-sensitive adhesive solvent (b) instead of pressure-sensitive adhesive solvent (a)) ) And cured under an environment of 40 ° C. for 48 hours to produce an adhesive tape.

[Example 5]
Polyolefin-based foam A (polypropylene foam, double-sided pseudo skin layer, thickness 300 μm, apparent density 0.129 g / cm ³ , using pressure-sensitive adhesive solvent (c) instead of pressure-sensitive adhesive solvent (a)) ) And cured under an environment of 40 ° C. for 48 hours to produce an adhesive tape.

[Example 6]
Polyolefin foam A (polypropylene foam, double-sided pseudo skin layer, thickness of 300 μm, apparent density 0.129 g / cm ³ , using pressure-sensitive adhesive solvent (d) instead of pressure-sensitive adhesive solvent (a)) ) And cured under an environment of 40 ° C. for 48 hours to produce an adhesive tape.

[Comparative Example 1]
The adhesive is applied using a bar coater on the surface of the release liner so that the thickness of the adhesive layer after drying the adhesive solvent (a) is 50 μm, and dried at 80 ° C. for 3 minutes. Thus, an adhesive layer was prepared.
Next, the pressure-sensitive adhesive layer was applied to both surfaces of a polyolefin foam D (polyethylene foam, thickness 300 μm, a double-sided pseudo skin layer, adjusted to an apparent density of 0.179 g / cm ³ ). An adhesive tape was prepared by curing under an environment for 48 hours.

[Comparative Example 2]
Polyolefin foam E (polypropylene foam, double-sided pseudo skin layer, 300 μm in thickness, adjusted to an apparent density of 0.241 g / cm ³ ) was used in place of polyolefin foam D in the same manner as in Comparative Example 1. An adhesive tape was produced.

[Comparative Example 3]
Polyolefin foam F (polypropylene foam, a double-sided pseudo skin layer, having a thickness of 300 μm, adjusted to an apparent density of 0.024 g / cm ³ ) was used in place of the polyolefin foam D in the same manner as in Comparative Example 1. An adhesive tape was produced.

[Comparative Example 4]
Instead of the polyolefin foam D, a polyolefin foam G (polypropylene foam, a double-sided skin layer, a thickness adjusted to 300 μm, an apparent density of 0.263 g / cm ³ ) was used, and the adhesive was applied in the same manner as in Comparative Example 1. A tape was made.

[Comparative Example 5]
Instead of the polyolefin foam D, a polyolefin foam H (polypropylene foam, a double-sided slice layer, a thickness adjusted to 300 μm, an apparent density of 0.131 g / cm ³ ) was used, and the adhesive was applied in the same manner as in Comparative Example 1. A tape was made.

[Apparent density of foam base material]
The apparent density of the foam base material was measured according to JIS K6767. A foam base material cut into a rectangle of 4 cm × 5 cm is prepared, and its mass is measured to determine the apparent density.

[25% compression load of foam base material]
The 25% compressive strength of the foam base material was measured according to JIS K6767. The samples cut into 25 squares are overlapped to a thickness of about 10 mm. The sample is sandwiched between stainless steel plates having an area larger than that of the sample, and the strength is measured when the sample is compressed at 2.5 ° C. at 25 ° C. at a speed of 10 mm / min (25% of the original thickness).

[Tensile modulus of 100% elongation of foam base material]
The tensile modulus of the foam base material was measured according to JIS K6767. A foam base material having a mark length of 2 cm and a width of 1 cm was measured using a Tensilon tensile tester under the measurement conditions of 23 ° C., 50% RH or 120 ° C. at a tensile speed of 300 mm / min. The tensile modulus at an elongation of 100% was determined from the obtained measured values.

[Maximum tensile modulus of foam base material]
The tensile modulus of the foam base material was measured according to JIS K6767. A foam base material having a mark length of 2 cm and a width of 1 cm was measured using a Tensilon tensile tester under the conditions of 23 ° C., 50% RH and 120 ° C. under a measuring condition of a tensile speed of 300 mm / min. It is the maximum intensity of the measured value obtained.

[Dimensional change rate of foam base material]
The dimensional change rate of the foam base material is as follows: a polyolefin resin foam is accurately cut into a 10 cm square, and left in an oven set at 120 ° C. for 24 hours. After 24 hours, remove from the oven and cool for about 60 minutes at room temperature. The dimensions of the sample were measured, the dimensional change was calculated based on the following equation, and evaluated as follows.
Dimensional change rate (%) = {(sample length before placing in oven-sample length after removing from oven) / sample length before placing in oven} x 100
：: dimensional change rate is less than 10% △: dimensional change rate is 10% to 15%
×: dimensional change rate is greater than 15%

[Method of measuring tensile strength based on stress-strain curve at strain amounts of 100% and 500%]
One side of an optional release liner is coated with the adhesive so that the thickness after drying is 50 μm, dried at 80 ° C. for 3 minutes, and aged at 40 ° C. for 48 hours to form an adhesive layer. did. Next, a test piece having a mark line interval of 2 cm and a width of 1 cm was prepared by laminating this pressure-sensitive adhesive layer to a thickness of about 400 μm.

  From the stress-strain curve (so-called SS curve) measured at a tensile speed of 300 mm / min using a tensile tester under a measurement environment of a temperature of 23 ° C. and a humidity of 50%, The tensile strength at 100% and 500% was determined.

[Pasteability]
Under the environment of a temperature of 23 ° C. and a relative humidity of 50% RH, a rectangular acrylic plate having a thickness of 2 mm and an outer diameter of 65 mm × 45 mm (Acrylite MR200 “Mitsubishi Rayon Co., Ltd.”, hue) on both sides of a 40 mm × 20 mm adhesive sheet : Transparent), and the applied area after pressurization at 5 N / cm ² was evaluated as follows.
○: Pasting area is 90% or more △: Pasting area is 70% to 90%
×: Pasting area is less than 70%

[Push strength]
Under an environment of a temperature of 23 ° C. and a relative humidity of 50% RH, a frame-shaped pressure-sensitive adhesive sheet having an outer diameter of 14 mm × 14 mm and a width of 2 mm is adhered to a perforated stainless steel plate and an acrylic plate, and subjected to 50 N / cm ² for 10 seconds. What was pressurized and allowed to stand for 24 hours was used as a test piece.

  Next, the acrylic plate was pressed at a rate of 10 mm / min with a tensile tester equipped with a stainless steel probe having a diameter of 8 mm from the stainless steel hole, and the strength at which the acrylic plate was peeled was measured.

[Evaluation method of static load holding force]
In an atmosphere of a temperature of 23 ° C. and a relative humidity of 50%, one adhesive layer of a frame-shaped adhesive sheet having an outer size of 14 mm × 14 mm and an adhesive sheet width of 2 mm was coated with an acrylic plate (Mitsubishi Rayon) having a thickness of 2 mm and an outer shape of 15 mm × 15 mm. Acrylite MR200 (trademark), hue: transparent).

Next, the acrylic plate with the pressure-sensitive adhesive sheet is attached to a rectangular stainless steel plate having a thickness of 2 mm and an outer shape of 65 mm × 30 mm having a hole of 8 mm in the center portion so as to cover the hole, and then 50 N / cm ^2. For 10 seconds to obtain a test piece.

  In an atmosphere at a temperature of 40 ° C. and a relative humidity of 50%, the test piece was leveled with the acrylic plate side down, and both ends of the short side of the stainless plate were fixed. Next, a 400 g weight was attached to the central portion of the acrylic plate, and the acrylic plate was allowed to stand with a downward load.

  Next, in an atmosphere at a temperature of 40 ° C. and a relative humidity of 50%, the time (minute) until the distance between the acrylic plate on which the weight was attached and the stainless steel plate was 0.2 mm apart from before the start of the test was measured. did. If the increase in the distance between the acrylic plate and the stainless steel plate was less than 0.2 mm even after 24 hours from the start of the measurement, it was described as "1440 minutes or more" in the table described later.

[Shear retention force]
The holding force of the pressure-sensitive adhesive tape is obtained by cutting a test sample into a required length of 20 mm and a required length in the flow direction of the pressure-sensitive adhesive tapes prepared in Examples and Comparative Examples to prepare test pieces. A backing material such as an aluminum foil is adhered to the non-measurement side adhesive surface, and is adhered to a SUS test plate at room temperature so that an area of 20 mm × 20 mm is in contact. The test piece affixed to the test plate is subjected to one reciprocating pressure at a speed of about 300 mm / min using a 2 kg rubber roller. The pressurized test piece is allowed to stand at 23 ° C. for about 1 hour, and after the standing, the test plate is set on the holding force meter, a load of 500 g is applied to the test piece, and the test piece is allowed to stand at 120 ° C. for 24 hours. . The displacement distance of the test piece after 24 hours was evaluated as follows.
◎: Displacement distance is less than 1 mm ：: Displacement distance is 1 mm to 2 mm
Δ: deviation distance is 2 mm to 10 mm
×: The displacement distance is 10 mm or more, or peeling occurs between the base material and the adhesive.

  As described above, in the pressure-sensitive adhesive tape of the example according to the present invention, a foam base material having excellent sticking properties is used, and the dimensional change of the foam base material at a high temperature is suppressed, and the pressure-sensitive adhesive tape is heated at a high temperature. It can be seen that the holding power is excellent. On the other hand, in the comparative example, it can be seen that the dimensional change of the foam base material at a high temperature is large, the holding power of the adhesive tape at a high temperature is inferior, and the sticking property is reduced. In other words, it can be seen that the form can be maintained even when exposed to a high-temperature environment, and the adhesiveness and the retention can be maintained.

Claims (7)

A pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on at least one surface side of a foam base material having a pseudo skin layer on both surfaces, wherein the foam base material has a 25% compressive strength of 20 to 170 kPa, at 23 ° C. The ratio E2 / E1 is 0.1 or more when the tensile elastic modulus in the flow direction at an elongation of 100% is E1 and the tensile elastic modulus in the flow direction at an elongation of 100% at 120 ° C. is E2, or 23. The ratio E2 '/ E1' is 0.1 or more when the tensile modulus in the width direction at 100 ° C. is 100% and the tensile modulus in the width direction at 120 ° C. is 100%. An adhesive tape, characterized in that: Pressure-sensitive adhesive tape according to claim 1 apparent density of the foam substrate is 0.05~0.35g / cm ^3. The pressure-sensitive adhesive tape according to claim 1, wherein the foam base material has a thickness of 0.05 to 1.5 mm. The maximum tensile elastic modulus in the flow direction or width direction at 23 ° C. of the foam substrate is an adhesive tape according to any one of claims 1 to 3 is 50~400N / cm ² or more. The pressure-sensitive adhesive tape according to any one of claims 1 to 4, wherein the foam base material is a polyolefin-based foam base material. The pressure-sensitive adhesive tape according to any one of claims 1 to 5, wherein the polyolefin-based foam base material includes one or both of a polypropylene resin and a polyethylene resin. The pressure-sensitive adhesive tape according to any one of claims 1 to 6, wherein the pressure-sensitive adhesive sheet is used for fixing an electronic component.