WO2018116844A1

WO2018116844A1 - Pressure-sensitive adhesive tape

Info

Publication number: WO2018116844A1
Application number: PCT/JP2017/043959
Authority: WO
Inventors: 智古川; 秀晃武井; 啓之中島
Original assignee: Dic株式会社
Priority date: 2016-12-22
Filing date: 2017-12-07
Publication date: 2018-06-28
Also published as: JPWO2018116844A1

Abstract

The problem to be solved by the present invention is to provide a pressure-sensitive adhesive tape including a foamed base, the pressure-sensitive adhesive tape being excellent in terms of applicability and conformability when applied to a member, capable of retaining the shape even when exposed to high temperatures, and capable of retaining the original physical properties after returned to room temperature. The present invention relates to a pressure-sensitive adhesive tape which comprises a foamed base and a pressure-sensitive adhesive layer disposed on at least one surface of the foamed base, characterized in that the foamed base has a 25% compression strength of 20-170 kPa and that when the machine-direction tensile modulus at 23°C and 100% elongation is expressed by E1 and the machine-direction tensile modulus at 120°C and 100% elongation is expressed by E2, then the E2/E1 ratio is 0.1 or higher or when the width-direction tensile modulus at 23°C and 100% elongation is expressed by E1' and the width-direction tensile modulus at 120°C and 100% elongation is expressed by E2', then the E2'/E1' ratio is 0.1 or higher.

Description

Adhesive tape

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

The adhesive tape is used for fixing components constituting various electronic devices including the mobile field and the automobile field. For example, if the adhesive tape is a manufacturing scene of the electronic device, the adhesive tape is used for applications such as fixing two or more casings constituting the electronic device.
When an adhesive tape is used in the scene as described above, air tends to remain at the bonded interface between the pressed member and the tape. For this reason, a foam-based adhesive tape is used that has an appropriate cushioning property in the thickness direction of the tape, appropriately follows in the joining of rigid bodies, and has a feature that the joining component and the adhesive layer are easily adhered to each other. The

For such applications, for example, a foam-based adhesive tape having excellent flexibility using, for example, polyethylene resin or urethane resin has been used (Patent Document 1).

However, in recent years, in the mobile field and the automobile field, adhesion reliability in a harsher environment is required. Specifically, there has been a demand for an adhesive tape that hardly changes in physical properties even after being left in a high temperature environment of 100 ° C. or higher, and the heat resistance of conventional adhesive tapes for foam substrates has been insufficient.

As described above, the pressure-sensitive adhesive tape used in the above-mentioned application is a foam-based pressure-sensitive adhesive tape that is flexible and can follow, and can maintain its form even when exposed to a high temperature environment, and even when it is returned to room temperature. Although a foam-based adhesive tape that can maintain the physical properties of the foam is required, it has not been found yet.

JP 2011-168658 A

The problem to be solved by the present invention 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 its original physical properties even when it is returned to room temperature. It is to provide such a foam-based adhesive tape.

When the present inventors examined in order to solve the said subject, the said subject by the adhesive tape which has a specific 25% compressive strength and the foam base material which has a specific ratio of the tensile elasticity modulus in 23 degreeC and 120 degreeC. It was found that can be solved.
That is, the present invention is a pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on at least one surface side of a foam base material, wherein the foam base material has a 25% compressive strength of 20 to 170 kPa and an elongation of 100 at 23 ° C. The ratio E2 / E1 is 0.1 or more when the tensile modulus of elasticity in the flow direction is% E1 and the tensile modulus of elasticity in the flow direction of 100% elongation at 120 ° C. is E2, or the elongation at 23 ° C. The ratio E2 ′ / E1 ′ is 0.1 or more when the tensile modulus in the width direction at a degree of 100% is E1 ′ and the tensile modulus in the width direction at an elongation of 100% at 120 ° C. is E2 ′. It is related with the adhesive tape characterized by these.

The pressure-sensitive adhesive tape of the present invention has adhesion and followability when bonded to an adherend, can maintain its form even when exposed to a high temperature environment, and can maintain its original physical properties even when it is returned to room temperature. Therefore, it can be suitably used for fixing two or more housings constituting an electronic device such as a mobile terminal or an automobile.

The pressure-sensitive adhesive tape of the present invention is a pressure-sensitive adhesive tape used for fixing components constituting an electronic device, and has a pressure-sensitive adhesive layer on at least one surface side of a foam substrate, and the foam base When the 25% compressive strength of the material is 20 to 170 kPa, the tensile modulus in the flow direction at 100% elongation at 23 ° C. is E1, and the tensile modulus in the flow direction at 100% elongation at 120 ° C. is E2. The ratio E2 / E1 is 0.1 or more, or the tensile modulus in the width direction at an elongation of 100% at 23 ° C. is E1 ′, and the tensile modulus in the width direction at an elongation of 100% at 120 ° C. is E2. The ratio E2 ′ / E1 ′ when “is” is 0.1 or more.

[Foam substrate]
A foam base material is used as the base material constituting the pressure-sensitive adhesive tape of the present invention.
As the foam substrate, those having a 25% compressive strength of 20 to 170 kPa are used, but those having 30 to 140 kPa are more preferable, and those having 40 to 120 kPa are used. It is further preferable in terms of expressing suitable followability for an adherend having an uneven shape or a rough surface.

In addition, 25% compressive strength was measured according to JISK6767. The samples cut into 25 corners are overlapped to a thickness of about 10 mm. The sample is sandwiched with a stainless plate having a larger area than the sample, and the strength is measured when the sample is compressed by approximately 2.5 mm (25% of the original thickness) at a rate of 10 mm / min at 23 ° C.

The tensile elastic modulus in the flow direction and the width direction of the foam base material is not particularly limited, but the tensile elastic modulus in the flow direction at an elongation of 100% at 23 ° C. is E1, and the flow direction at an elongation of 100% at 120 ° C. It is necessary that the ratio E2 / E1 is 0.1 or more when the tensile elastic modulus of E2 is E2, or the tensile elastic modulus in the width direction at an elongation of 100% at 23 ° C. is E1 ′, and 120 ° C. When the tensile modulus in the width direction at 100% elongation 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 0.2 or more can maintain the form of the foam substrate even when exposed to a high temperature environment. It is preferable in that the physical properties after being exposed 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 , 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. The ratio Eh / El between the tensile modulus El in the low tensile modulus and the tensile modulus Eh in the high direction among the tensile modulus in the flow direction and the width direction at the same temperature is 1.0 to 3.0. In view of providing workability and dimensional stability, 1.0 to 2.0 is preferable.

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

The maximum tensile elastic modulus of the foam base material in the flow direction and the width direction is not particularly limited, but the maximum tensile elastic modulus at 23 ° C. is preferably 50 to 450 N / cm ² , more preferably When it is 70 to 400 N / cm ² , deterioration of the workability of the pressure-sensitive adhesive tape and deterioration of the workability of applying can be suppressed even with a foamed flexible base material. Moreover, when peeling an adhesive tape, it is hard to generate | occur | produce the interlayer destruction of a foam, and a tear, and even when an interlayer crack generate | occur | produces, the ease of peeling of an adhesive tape can be provided. Further, the ratio Eh / El between the tensile modulus El in the low tensile modulus and the tensile modulus Eh in the high direction among the maximum tensile modulus in the flow direction and the width direction at 23 ° C. is 1.0 to 3.0. In view of imparting workability and dimensional stability, 1.0 to 2.0 is preferable.

The maximum tensile elastic modulus in the flow direction and the width direction of the foam substrate is not particularly limited, but the maximum tensile elastic modulus in the flow direction or the width direction at 120 ° C. is 15 to 450 N / cm ² or more, respectively. More preferably, it is 15 to 400 N / cm ² or more, so that the form of the foam substrate can be maintained even when exposed to a high temperature environment, and the physical properties after being exposed to the high temperature environment can be maintained. In addition, it is preferable. Further, the ratio Eh / El between the tensile modulus El in the low tensile modulus and the tensile modulus Eh in the high direction among the maximum tensile modulus in the flow direction and the width direction at 120 ° C. is 1.0 to 3.0. In view of imparting workability and dimensional stability, 1.0 to 2.0 is preferable.

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, and more preferably 10 N / cm to 60 N / cm. Use of the body substrate can realize good pastability and followability to the adherend and excellent adhesion.

The interlayer strength is measured by the following method. A pressure-sensitive adhesive layer having a thickness of 50 μm (which does not peel off from the adherend and the foam substrate during the following high-speed peel test) was bonded to both surfaces of the foam base material for evaluating the interlayer strength one by one. Thereafter, aging is carried out at 40 ° C. for 48 hours to prepare an adhesive tape for measuring interlayer strength. Next, a pressure-sensitive adhesive tape having a width of 1 cm and a length of 15 cm (in the flow direction and width direction of the foam base material) lined with a polyester film having a thickness of 25 μm on one side is thickened at 23 ° C. and 50% RH. A polyester film having a thickness of 50 μm, a width of 3 cm, and a length of 20 cm is pressure-applied with one reciprocation of a 2 kg roller and allowed to stand at 60 ° C. for 48 hours. After standing at 23 ° C. for 24 hours, the side bonded to the 50 μm-thick polyester film at 23 ° C. and 50% RH is fixed to a mounting jig of a high-speed peel tester, and the 25 μm-thick polyester film is pulled at a speed of 15 m. The maximum strength is measured when the foam is torn in the direction of 90 degrees per minute.

The cell structure of the foam substrate may be either a closed cell structure or an open cell structure. However, the closed cell structure has an adhesive property and followability when bonded to an adherend, and excellent adhesive strength. preferable.
The average cell diameter in the flow direction and the width direction of the foam substrate is 1.2 to 700 μm, preferably 10 to 500 μm, more preferably 30 to 400 μm, and still more preferably 50 to 300 μm. By setting the average cell diameter in the flow direction and the width direction within the above range, it is preferable in order to have stickability and followability when bonded to an adherend using the pressure-sensitive adhesive tape of the present invention, and excellent adhesive strength.

The average cell diameter in the thickness direction of the foam base material is preferably 1 to 150 μm, more preferably 10 to 100 μm, although it depends on the thickness of the foam base material. In view of having good performance and followability, and excellent adhesive strength.
In addition, as a measuring method of an average bubble diameter, first, a foam base material is cut | disconnected to the square of 1 cm of width directions, and 1 cm of flow directions. Next, the cut surface of the cut foam base material is enlarged 200 times using a digital microscope (trade name “KH-7700”, manufactured by HiROX), and then the width direction and the flow direction of the foam base material The cut surface of was photographed.

Next, among the cut surfaces in the width direction of the foam base material, the bubble diameters of all the bubbles existing in an arbitrary range of thickness × width direction distance (2 mm) were measured, and the average value was calculated. . Moreover, what averaged ten average values calculated by performing the said measurement with respect to arbitrary 10 places of the said cut surface was made into the average bubble diameter of the width direction.

Moreover, the bubble diameters of all the bubbles existing in an arbitrary range of thickness × flow direction distance (2 mm) among the cut surfaces in the flow direction of the foam base material were measured, and the average value was calculated. Moreover, what averaged ten average values calculated by performing the said measurement with respect to arbitrary 10 places of the said cut surface was made into the average bubble diameter of a flow direction.

The apparent density of the foam base material is not particularly limited, but the interlaminar strength, compressive strength, average cell diameter, etc. are adjusted to the above ranges, and the adhesiveness and followability when adhering to the adherend, and the adherend Since it is easy to realize both 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. is there.
The apparent density was measured according to JISK6767. A foam base material cut into a 4 cm × 5 cm rectangle is prepared, and its mass is measured to determine the apparent density.

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

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

Among the polyolefin resins that form the polyolefin foam, it is possible to use a polypropylene resin to follow the unevenness of the adherend surface and maintain the shape at high temperatures, even after taking out from high temperatures. This is preferable because the original physical properties are easily maintained.

In addition, when the polyolefin resin is 100 mol% of all the monomer components constituting the resin, the polyolefin resin in which the olefin hydrocarbon component in the resin is 10 mol% or more and 100 mol% or less may be used. Is preferred. For example, a polypropylene resin (A) containing a propylene component such as a propylene homopolymer or an ethylene-propylene copolymer (random polypropylene, block polypropylene), an ethylene homopolymer, ethylene and a carbon number of 3 to 10 Examples thereof include 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.

The polyolefin resin can be used alone or in combination of two or more, and preferably contains the polypropylene resin (A) and / or the polyethylene resin (B), and the polypropylene resin (A) and the polyethylene resin. It is preferable that (B) is contained in order to maintain the original physical properties even when taken out from a high temperature, and the sticking property and followability when sticking to the adherend, the form maintaining property at a high temperature.
In forming the polyolefin-based foam, a thermoplastic elastomer-based resin (C) can be used as necessary. By adding the thermoplastic elastomer resin (C), it is possible to maintain the original physical properties even when taken out from a high temperature, the sticking property and followability when pasting to the adherend, the form maintaining property at a high temperature. Further 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, and if necessary, a propylene monomer and another copolymerizable monomer. Copolymers can also be used. The polypropylene resin (A) in the polyolefin resin may be used by blending not only one type but also two or more types. Random polypropylene and / or polypropylene resin 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) (B) A 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 preferable.

The proportion of the polypropylene resin (A) contained in the total resin constituting the foam is preferably 10 to 80% by weight, more preferably 20 to 70% by weight, and more preferably 25 to 65% by weight. When using a resin containing 70% by weight or more of the polypropylene resin (A), sufficient flexibility of the polyolefin resin foam cannot be obtained, and when using a resin containing less than 20% by weight of the polypropylene resin (A). 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) etc. are mentioned, The copolymer of an ethylene monomer and another copolymerizable monomer can also be used as needed. These polyethylene resins (B) may be blended not only in one type but also in two or more types. As the polyethylene resin (B), those having a density of 890 to 950 kg / m ³ and an MFR (190 ° C.) in the range of 1 to 15 g / 20 minutes are preferably used. Among them, the density is 920 to 940 kg / m ³ and the MFR is used. An ethylene-α-olefin copolymer having a (190 ° C.) of 2 to 10 g / 10 min and a melting point of 100 to 130 ° C. is more preferable.

The proportion of the polyethylene resin (B) is preferably 5 to 35% by weight, more preferably 10 to 30% by weight, and even more preferably 15 to 25% by weight. When using a resin containing 35% by weight or more of polyethylene resin (B), sufficient flexibility and heat resistance cannot be obtained, and when using a resin containing less than 5% by weight of polyethylene resin (B), it is obtained. There is a risk of impairing the cold resistance of the polyolefin foam.

The thermoplastic elastomer resin (C) that can be used in the present invention is a polystyrene thermoplastic elastomer (SBC, TPS), a polyolefin thermoplastic elastomer (TPO), a vinyl chloride thermoplastic elastomer (TPVC), or a polyurethane heat. 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 type but also in two or more types. As the thermoplastic elastomer resin (C), those having a density of 850 to 920 kg / m 3 and an MFR (230 ° C.) in the range of 1 to 15 are preferably used. Among them, the density is 860 to 910 kg / m 3 and the MFR (230 Those having a temperature of 5 to 10 are particularly preferably used.

The content of the thermoplastic elastomer resin (C) is preferably 5 to 70% by mass, more preferably 10 to 60% by mass, and more preferably 20 to 50% by mass. When using a thermoplastic elastomer resin (C) containing less than 5 wt%, sufficient flexibility cannot be obtained, and when using a thermoplastic elastomer resin (C) containing 70 wt% or more, There is a risk of impairing the heat resistance of the resulting polyolefin foam.

In the foam base material in the present invention, the content of the polypropylene resin (A) in the total resin constituting the foam is 30 to 60% by mass, and the polyethylene resin (B) is 1 to 20% by mass. The thermoplastic elastomer-based resin (C) is preferably contained in an amount of 30 to 60 ** mass%, and the polypropylene resin (A) is contained in an amount of 30 ** to 55 ** mass%, and the polyethylene resin When (B) is 10 ** to 20 **% by mass and the thermoplastic elastomer resin (C) is contained in 30 ** to 50 **% by mass, It is more preferable in terms of followability, form maintainability at high temperatures, and the original physical properties can be maintained even when taken out from high temperatures.

In the present invention, within the range not impairing the effects of the present invention, antioxidants such as phenols, phosphoruss, amines and sulfurs, metal damage inhibitors, divinylbenzene, trimethylolpropane trimethacrylate, 1,6 -Hexanediol dimethacrylate, 1,9-nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, triallyl isocyanurate, ethyl vinylbenzene, ethylene vinyl dimethacrylate, 1,2-benzenedicarboxylic acid diallyl ester, 1, Cross-linking assistants such as 3-benzenedicarboxylic acid diallyl ester, 1,4-benzenedicarboxylic acid diallyl ester and 1,2,4-benzenetricarboxylic acid diallyl ester, fillers such as mica and talc, bromine-based and phosphorus-based Flame retardant, ammonium trioxide Flame retardant aid such as Mon, antistatic agents, may be added a lubricant, a pigment, and a polyolefin additives such as polytetrafluoroethylene.

The foam base material of the present invention is produced by mixing a foaming agent capable of generating gas into a mixture of polyolefin resins, and as a production method thereof, a mixture of polyolefin resins, as a foaming agent, and thermally decomposed. Normal pressure foaming method that melts and kneads by adding a mold chemical foaming agent and foams under normal pressure heating, Extrusion foaming method that heats and decomposes the thermal decomposition type chemical foaming agent in an extruder and foams while extruding under high pressure, press Such as a press foaming method in which a thermal decomposable chemical foaming agent is thermally decomposed in a mold and foamed while reducing pressure, and an extrusion foaming method in which a gas or a vaporizing solvent is melt-mixed in an extruder and foamed while being extruded under high pressure. A method is mentioned.

The thermal decomposition type chemical foaming agent used here is a chemical foaming agent that decomposes by applying heat and releases a gas. For example, azodicarbonamide, N, N′-dinitrosopentamethylenetetramine, P, P Examples thereof include organic foaming agents such as' -oxybenzenesulfonylhydrazide, and inorganic foaming agents such as sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, and calcium azide.
Examples of the gas or the solvent to be vaporized include gases such as carbon dioxide, nitrogen and helium, and vaporized solvents such as propane, normal butane and isobutane.
A foaming agent can be used individually or in combination of 2 types or more, respectively. In order to obtain a high-magnification foam that is flexible and has high moldability and a smooth surface, a normal pressure foaming method using azodicarbonamide as a foaming agent is preferably used.

Next, a method for producing a polyolefin resin foam will be described. The method for producing a polyolefin resin foam is not particularly limited, and the polyolefin resin, the thermal decomposition-type foaming agent and the foaming aid, and the foaming property containing a colorant for coloring the foam black or white. Supplying a polyolefin-based resin composition to an extruder, melt-kneading, producing a foamable polyolefin-based resin sheet by extruding into a sheet from the extruder, and crosslinking the foamable polyolefin-based resin sheet; The foaming polyolefin resin sheet is foamed; the thinned film is sliced; and the foamed sheet is melted or softened, and either or both of the flow direction and the width direction are used. A method comprising a step of heating and stretching in the direction to stretch the foamed tape and providing a pseudo skin layer on the surface of the foamed sheet. It is below.

The step of crosslinking the expandable polyolefin resin sheet is, for example, a method of irradiating the expandable polyolefin resin sheet with ionizing radiation, an organic peroxide previously blended in the expandable polyolefin resin composition, Examples include a method of heating the obtained expandable polyolefin resin sheet to decompose the organic peroxide, and these methods may be used in combination.

Examples of ionizing radiation include electron beams, α rays, β rays, and γ rays. The dose of ionizing radiation is such that the gel fraction of the polyolefin resin foam substrate is preferably 5% by mass to 70% by mass, more preferably 20% by mass to 60% by mass, and even more preferably 25% by mass to 55% by mass.
However, the range of 5 to 200 kGy is preferable. Further, the irradiation with ionizing radiation forms a uniform cross-linked structure, and as a result, in order to form a relatively uniform foamed structure, it is preferable to irradiate from both sides of the foamable polyolefin resin sheet. 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, 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 Nzoylperoxy) hexane, t-butylperoxyisopropyl carbonate, t-butylperoxyallyl carbonate, and the like. These may be used alone or in combination of two or more.

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

Further, 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 using a salt bath, and a method using an oil bath. May be used in combination. Among them, the method of heating with hot air or the method of heating with infrared rays is preferable because there is little difference between the front and back surfaces of the polyolefin resin foam substrate surface.

The method for slicing the foam base material is not particularly limited, and it may or may not be sliced. When slicing is performed, it may be appropriately adjusted depending on the thickness used by the foam base material, and both surfaces may be sliced or only one surface may be sliced.
The method for heating and stretching the foam substrate is not particularly limited, and it may or may not be heated and stretched. When performing heat stretching, it may be performed after slicing the foam base material, and may be performed on both surfaces or only on one surface.

Furthermore, in the extending direction of the foam base material, the long foamable polyolefin resin sheet is stretched in the flow direction or width direction, or in the flow direction and 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. .

The foam base material may be colored in order to develop design properties, light shielding properties, concealing properties, light reflectivity, and light resistance in the adhesive tape. The colorants can be used alone or in combination of two or more.
When the light shielding property, the concealing property, and the light resistance are imparted 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, complex oxidation Physical black pigments and anthraquinone organic black pigments can be used. Of these, carbon black is preferred from the viewpoint of cost, availability, insulation, and heat resistance that can withstand the temperatures of the process of extruding the foamable polyolefin resin composition and the heating foaming process.

When the design properties and light reflectivity are imparted to the adhesive tape, the foam base is colored white. 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, 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 Organic white colorants such as titanium, mica, gypsum, white carbon, diatomaceous earth, bentonite, lithopone, zeolite, sericite, etc., and organics such as silicone resin particles, acrylic resin particles, urethane resin particles, melamine resin particles And the like can be used white colorant. Of these, aluminum oxide and zinc oxide are preferable from the viewpoint of cost, availability, color tone, and heat resistance that can withstand the temperature of the step of extruding the foamable polyolefin resin composition and the heating and foaming step.

In addition, the foamable polyolefin-based resin composition includes a foaming aid such as a plasticizer, an antioxidant, and zinc oxide, and a cell core modifier 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, metal powder, fillers such as metal compounds, conductive fillers, thermal conductive fillers A known material such as may be optionally contained in the resin. The polyolefin resin foam base material used for the adhesive tape of the present invention is 0.1% by mass to 10% by mass with respect to the polyolefin resin in order to maintain the sticking property and followability when being bonded to the adherend. % Is preferable, and 1% by mass to 7% by mass is preferable.

In addition, when blending the colorant, the thermally decomposable foaming agent, the foaming aid, and the like into the foamable polyolefin resin composition, it is supplied to the extruder from the viewpoint of preventing color unevenness, partial excessive foaming, and insufficient foaming. It is preferable to prepare a masterbatch with a thermoplastic resin having high compatibility with the expandable polyolefin resin composition or the expandable polyolefin resin composition in advance.

In order to improve the adhesion of the foam substrate to the pressure-sensitive adhesive layer and other layers, surface treatment such as corona treatment, flame treatment, plasma treatment, hot air treatment, ozone / ultraviolet treatment, easy-adhesive treatment agent application, etc. May have been made. In the surface treatment, when the wetting index by the wetting reagent is 36 mN / m or more, preferably 40 mN / m, more preferably 48 mN / m, good adhesion to the 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 with improved adhesion may be temporarily wound up and stored, and then bonded to the pressure-sensitive adhesive layer in a separate process 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]
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 (meth) acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, synthetic rubber-based pressure-sensitive adhesives, natural rubber-based pressure-sensitive adhesives, and silicone-based pressure-sensitive adhesives. A (meth) acrylic copolymer containing a copolymer of (meth) acrylate and other monomers as a base polymer, and additives such as tackifiers and crosslinking agents blended as necessary. An adhesive composition can be preferably used.

Examples of the acrylic pressure-sensitive adhesive composition include (meth) acrylates having 1 to 12 carbon atoms such as 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 the like, and one or more of these are used. Among these, (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 ensure adhesion with the 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 in the monomer component constituting the acrylic copolymer, and is preferably 90 to 98. More preferably, it is 5 mass%.
In addition, the acrylic copolymer used in the present invention may be copolymerized with a highly polar vinyl monomer. Examples of the highly polar vinyl monomer include a vinyl monomer having a hydroxyl group, a vinyl monomer having a carboxyl group, and a vinyl having an amide group. A monomer etc. are mentioned, These 1 type (s) or 2 or more types are used.

Examples of the monomer having a hydroxyl group include hydroxyl groups such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate and the like ( A (meth) acrylate can be used.

As the vinyl monomer having a carboxyl group, acrylic acid, methacrylic acid, itaconic acid, maleic acid, (meth) acrylic acid dimer, crotonic acid, ethylene oxide-modified succinic acid acrylate, etc. can be used. It is preferable to use it as a polymerization component.

Examples of the monomer having an amide group include N-vinylpyrrolidone, N-vinylcaprolactam, acryloylmorpholine, acrylamide, N, N-dimethylacrylamide and the like.

Examples of other highly polar vinyl monomers include sulfonic acid group-containing monomers such as vinyl acetate, ethylene oxide-modified succinic acid acrylate, and 2-acrylamido-2-methylpropanesulfonic acid.
The content of the highly polar vinyl monomer is preferably 1.5 to 20% by mass, more preferably 1.5 to 10% by mass in the monomer component constituting the acrylic copolymer, and 2 to More preferably, it is 8 mass%. By containing in the said range, it is easy to adjust the cohesive force, holding force, and adhesiveness of an adhesive to a suitable range.

When an isocyanate crosslinking agent is used as the crosslinking agent, the vinyl monomer having a functional group that reacts with it is preferably a hydroxyl group-containing vinyl monomer, such as 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate. 6-hydroxyhexyl (meth) acrylate is particularly preferred. The content of the hydroxyl group-containing vinyl monomer that reacts with the isocyanate-based crosslinking agent is preferably 0.01 to 1.0% by mass of the monomer component constituting the acrylic copolymer, and is 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 cage polymerization method, a suspension polymerization method, or an emulsion polymerization method. A combination method or a bulk polymerization method is preferred. Polymerization can be initiated by peroxides such as benzoyl peroxide and lauroyl peroxide, thermal initiation using azo-based thermal polymerization initiators such as azobisisobutylnitrile, acetophenone-based, benzoin ether-based, benzyl A starting method by ultraviolet irradiation using a ketal-based, acylphosphine oxide-based, benzoin-based or benzophenone-based photopolymerization initiator, or a method by electron beam irradiation can be arbitrarily selected.

As for the molecular weight of the acrylic copolymer, the weight average molecular weight in terms of standard polystyrene measured by gel permeation chromatography (GPC) is from 4 to 3 million, and preferably from 80 to 2.5 million.
Here, the molecular weight measurement by the GPC method is a standard polystyrene conversion value measured using a GPC apparatus (HLC-8329GPC) manufactured by Tosoh Corporation, and the measurement conditions are as follows.

Sample concentration: 0.5% by mass (THF 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)

In the acrylic pressure-sensitive adhesive composition used in the present invention, it is preferable to use a tackifying resin in order to improve adhesion and adhesion strength with the adherend. 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 Examples thereof include (meth) acrylate resins and the like. When used in an emulsion-type pressure-sensitive adhesive composition, it is preferable to use an emulsion-type tackifying resin.
Of these, disproportionated rosin ester tackifying resins, polymerized rosin ester tackifying resins, rosin phenol tackifying resins, hydrogenated rosin ester tackifying resins, and (meth) acrylate resins are preferred. One or more tackifying resins may be used.

The softening point of the tackifying resin is not particularly limited, but is 30 to 180 ° C, preferably 70 to 140 ° C. By blending a tackifying resin with a high softening point, high adhesive performance can be expected. In the case of a (meth) acrylate-based tackifying resin, the glass transition temperature is 30 to 200 ° C., preferably 50 to 160 ° C.

The blending ratio when using the acrylic copolymer and the tackifying resin is such that the content of the tackifying resin with respect to 100 parts by mass of the acrylic copolymer is preferably 5 to 60 parts by mass, It is preferable that it is a mass part. By setting the ratio between the two in this range, it becomes easy to ensure adhesion with 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 crosslinking agent, an epoxy crosslinking agent, a metal chelate crosslinking agent, and an aziridine crosslinking agent. Among these, a crosslinking agent of a type that is added after the completion of polymerization and causes the crosslinking reaction to proceed is preferable, and an isocyanate-based crosslinking agent and an epoxy-based crosslinking agent that are highly reactive with a (meth) acrylic copolymer are preferable. An isocyanate-based cross-linking agent is more preferable because 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, trimethylolpropane-modified tolylene diisocyanate, and the like. Particularly preferred are trifunctional polyisocyanate compounds. Examples of the trifunctional isocyanate compound include tolylene diisocyanate, trimethylolpropane adducts thereof, and triphenylmethane isocyanate.

As an index of the degree of cross-linking, the value of the gel fraction for measuring the insoluble content after the pressure-sensitive adhesive layer is immersed in toluene for 24 hours is used. The gel fraction is preferably 25 to 70% by mass. When the content is more preferably in the range of 30 to 60% by mass, still more preferably in the range of 30 to 55% by mass, both the cohesiveness and the adhesiveness are good.
The gel fraction is measured as follows. On the release sheet, the pressure-sensitive adhesive composition was applied so that the thickness after drying was 50 μm, dried at 100 ° C. for 3 minutes, and aged at 40 ° C. for 2 days. To do. Next, the weight (G1) of the sample before being immersed in toluene is measured in advance, and the toluene-insoluble matter of the sample after being immersed in a toluene solution at 23 ° C. for 24 hours is filtered by a 300-mesh wire mesh. 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 formula.
Gel fraction (mass%) = (G2 / G1) × 100

Additives for adhesives such as plasticizers, softeners, antioxidants, flame retardants, fillers such as glass and plastic fibers / balloons / beads, metal powders, metal oxides, metal nitrides Colorants such as pigments and dyes, leveling agents, thickeners, water repellents, antifoaming agents and the like can be optionally added to the pressure-sensitive adhesive composition.

The pressure-sensitive adhesive layer used for the pressure-sensitive adhesive tape of the present invention preferably has a temperature showing a peak value of loss tangent (tan δ) at a frequency of 1 Hz, preferably -40 ° C. to 15 ° C. By making the peak value of the loss tangent of the pressure-sensitive adhesive layer within the above range, it becomes easy to impart good adhesion to the adherend at room temperature. In particular, in order to improve the drop impact resistance in a low temperature environment, it is more preferably −35 ° C. to 10 ° C., and −30 ° C. to 6 ° C. is good adhesion to the adherend at room temperature. Since it becomes easy to provide property, it is preferable.
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.

Dynamic viscoelastic properties are the types and ratios of monomers used in the acrylic copolymer constituting the pressure-sensitive adhesive, types and amounts of polymerization initiators, crosslinking agents, and polymerized rosin ester-based tackifying resins. It can be adjusted by appropriately selecting the type, amount used, polymerization method and the like.
The dynamic viscoelastic properties of the pressure-sensitive adhesive layer are defined by the loss tangent of the dynamic viscoelastic spectrum or the loss tangent and the storage elastic modulus at a specific frequency and a specific temperature. It is defined by the temperature indicating the maximum value of the loss tangent of the viscoelastic spectrum or the maximum value of the loss tangent. In the measurement of dynamic viscoelasticity, using a viscoelasticity testing machine (TA Instruments Japan Co., Ltd., trade name: ARES G2), a test piece is sandwiched between parallel disks which are measuring parts of the testing machine, The storage elastic modulus (G ′) and loss elastic modulus (G ″) are measured at a frequency of 1 Hz from −50 ° C. to 150 ° C. The test piece is formed in parallel by forming an adhesive layer or an adhesive tape to a thickness of about 2 mm. Measure between the disks.

The thickness of the pressure-sensitive adhesive layer used in the present invention is 10 to 100 μm in terms of the thickness of one side because it is easy to ensure adhesion to the adherend, rework suitability and removability even when a thin tape is used. Preferably, the thickness is 30 to 80 μm.

Although it does not specifically limit as a release sheet used for this invention, At least one surface of base materials, such as synthetic resin films, such as polyethylene, a polypropylene, and a polyester film, paper, a nonwoven fabric, cloth, a foam sheet, metal foil, and these laminated bodies In addition, examples in which a release treatment such as a silicone treatment, a long-chain alkyl treatment, a fluorine treatment or the like for improving the peelability from the adhesive are given.
Among these, a polyethylene-laminated paper and a release sheet in which a silicone release treatment is performed on one side of a polyester film are preferable.

[Production method of adhesive tape]
As a manufacturing method of the adhesive tape of this invention, it can manufacture by a well-known and usual method. For example, it can be produced by applying the pressure-sensitive adhesive on one side or both sides of the substrate using a roll coater or a die coater and drying it. In addition, the pressure-sensitive adhesive tape previously forms the pressure-sensitive adhesive layer by applying the pressure-sensitive adhesive on the surface of the release liner using a roll coater and the like, and then drying the pressure-sensitive adhesive layer. It can be manufactured by a transfer method in which both surfaces are bonded.

By using the foam base material and the pressure-sensitive adhesive layer, the pressure-sensitive adhesive tape of the present invention has excellent followability at the time of sticking, can maintain its form even when exposed to high temperatures, and is taken out from high temperatures However, since the original physical properties can be maintained, it can be used for fixing parts constituting various electronic devices including the mobile field and the automobile field.

An embodiment of the pressure-sensitive adhesive tape of the present invention has a basic structure in which a foam base material is used as a core and a pressure-sensitive adhesive layer is provided on one side or both sides of the base material. The substrate and the pressure-sensitive adhesive layer may be directly laminated or may have other layers. These modes may be appropriately selected depending on the intended use. When further imparting dimensional stability and tensile strength to the tape, a laminate layer such as a polyester film is used. When providing the tape with light-shielding properties, a light-shielding layer is provided. When ensuring light reflectivity, a light reflection 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 it is preferably 70 to 1700 μm. In the case of fixing electronic device parts, particularly small and thin electronic devices, since a thin tape thickness is required, the thickness is more preferably 100 to 600 μm, and particularly preferably 120 μm to 500 μm.

The pressure-sensitive adhesive tape of the present invention is excellent in pastability and followability 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 taken out from high temperatures, It can be used to fix parts that make up various electronic devices, including mobile and automobile fields.

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, reflux condenser, nitrogen inlet tube and 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, 4 -0.06 part by mass of hydroxybutyl acrylate and 200 parts by mass of ethyl acetate were charged, and the temperature was raised to 72 ° C. while blowing nitrogen under stirring.

Next, 2 parts by mass of a 2,2′-azobis (2-methylbutyronitrile) solution previously dissolved in ethyl acetate (solid content: 0.1% by mass) was added to the mixture, and the mixture was stirred at 72 ° C. After holding for 4 hours, it was held at 75 ° C. for 5 hours.
Next, the mixture was diluted with 98 parts by mass of ethyl acetate and filtered through a 200 mesh wire mesh to obtain an acrylic polymer (a) solution (non-volatile content: 40% by mass) having a weight average molecular weight of 1,600,000.

In addition, the said weight average molecular weight is a weight average molecular weight in standard polystyrene conversion measured by a gel permeation chromatograph (GPC), and was measured with the following method.
The molecular weight measurement by the GPC method is a standard polystyrene conversion value measured using a GPC apparatus (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: 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)

(Production of acrylic polymer (b))
In a reaction vessel equipped with a stirrer, reflux condenser, thermometer, dropping funnel and nitrogen gas inlet, 96.4 parts by mass of n-butyl acrylate, 3.5 parts by mass of acrylic acid, 0.1 parts by mass of 2-hydroxyethyl acrylate And 0.12 parts by mass of 2,2′-azobisisobutyronitrile as a polymerization initiator was dissolved in a solvent consisting of 100 parts by mass of ethyl acetate and polymerized at 70 ° C. for 12 hours to obtain a weight average molecular weight. An acrylic copolymer (b) of 800,000 (polystyrene conversion) was obtained.

(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 polymerized rosin ester-based tackifier resin D-125 (Arakawa Chemical Industries, Ltd.) and disproportionated rosin ester-based tackifier resin A- After mixing and stirring 10 parts by mass of 125 (manufactured by Arakawa Chemical Co., Ltd.), an adhesive solution having a solid content of 31% by mass was obtained by adding ethyl acetate.

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

(Adjustment of adhesive solvent (b))
In a container, with respect to 100 parts by mass of the acrylic polymer (b), 10 parts by mass of a polymerized rosin ester-based tackifier resin D-135 (Arakawa Chemical Industries, Ltd.) and a disproportionated rosin ester-based tackifier resin A After mixing and stirring 10 parts by mass of −100 (Arakawa Chemical Co., Ltd.), ethyl acetate was added to obtain an adhesive solution having a solid content of 31% by mass.

Next, 1.1 parts by mass of Coronate L-45 (manufactured by Nippon Polyurethane Co., Ltd., isocyanate-based crosslinking agent, solid content 45%) is added to 100 parts by mass of the pressure-sensitive adhesive solution, and the mixture is stirred uniformly. After mixing, the pressure-sensitive adhesive solvent (b) was obtained by filtering through a 100 mesh wire net.

[Example 1]
On the surface of the release liner, the adhesive is applied using a bar coater 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 base material A (polypropylene foam, adjusted to a thickness of 300 μm, and an apparent density of 0.129 g / cm ³ ). An adhesive tape was prepared by curing for 48 hours.

[Example 2]
Instead of the polyolefin foam A, a polyolefin foam B (polypropylene + polyethylene elastomer foam, adjusted to a thickness of 300 μm and an apparent density of 0.158 g / cm ³ ) was used, and an adhesive tape was produced in the same manner as in Example 1. Was made.

[Example 3]
In place of the polyolefin foam A, a polyolefin foam C (polypropylene + polyethylene elastomer foam, adjusted to a thickness of 300 μm and an apparent density of 0.158 g / cm ³ ) was used, and an adhesive tape was produced in the same manner as in Example 1. Was made.

[Example 4]
Instead of the polyolefin foam A, a polyolefin foam D (polypropylene + polyethylene elastomer foam, adjusted to a thickness of 300 μm and an apparent density of 0.060 g / cm ³ ) was used, and an adhesive tape was produced in the same manner as in Example 1. Was made.

[Example 5]
Instead of the polyolefin foam A, a polyolefin foam E (polypropylene + polyethylene elastomer foam, adjusted to a thickness of 300 μm and an apparent density of 0.066 g / cm ³ ) was used, and an adhesive tape was produced in the same manner as in Example 1. Was made.

[Examples 6 to 10]
Using the adhesive solvent (b) instead of the adhesive solvent (a), an adhesive tape was prepared for each of the polyolefin foams A to E in the same manner as in Example 1.

[Comparative Example 1]
On the surface of the release liner, the adhesive is applied using a bar coater 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 is pasted on both surfaces of a polyolefin-based foam base material F (polyethylene foam, thickness adjusted to 300 μm, apparent density adjusted to 0.179 g / cm ³ ), and in an environment of 40 ° C. An adhesive tape was prepared by curing for 48 hours.

[Comparative Example 2]
Instead of the polyolefin foam F, a polyolefin foam G (polyethylene foam, thickness adjusted to 300 μm, apparent density adjusted to 0.126 g / cm ³ ) was used to produce an adhesive tape in the same manner as in Example 1. .

[Comparative Examples 3 to 4]
Using the adhesive solvent (b) instead of the adhesive solvent (a), an adhesive tape was prepared for each of the polyolefin foams F and G in the same manner as in Example 1.

[Apparent density of foam substrate]
The apparent density of the foam base material was measured according to JISK6767. A foam base material cut into a 4 cm × 5 cm rectangle is prepared, and its mass is measured to determine the apparent density.

[25% compression load of foam substrate]
The 25% compressive strength of the foam substrate was measured according to JISK6767. The samples cut into 25 corners are overlapped to a thickness of about 10 mm. The sample is sandwiched with a stainless plate having a larger area than the sample, and the strength is measured when the sample is compressed by approximately 2.5 mm (25% of the original thickness) at a rate of 10 mm / min at 23 ° C.

[Tensile modulus of 100% elongation of foam substrate]
The tensile elastic modulus of the foam base material was measured according to JISK6767. A foam substrate having 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 50% RH or 120 ° C. under measurement conditions of a tensile speed of 300 mm / min. From the obtained measurement value, the tensile modulus of elasticity of 100% was determined.

[Maximum tensile modulus of foam substrate]
The tensile elastic modulus of the foam base material was measured according to JISK6767. A foam substrate having a marked line length of 2 cm and a width of 1 cm was measured using a Tensilon tensile tester under conditions of 23 ° C., 50% RH and 120 ° C. under measurement conditions of a tensile speed of 300 mm / min. It is the maximum intensity of the measured value obtained.

[Average cell diameter in the flow direction and width direction of the foam substrate]
The foam base material was cut to about 1 cm in both the flow direction and the width direction, and the center part of the cut surface of the foam base material was enlarged 200 times with a microscope (trade name “KH-7700”, manufactured by HIROX). Then, the cross section of the width direction of a foam base material or the flow direction was photographed so that the cut surface of a foam base material might fit in a photograph over the full length of the base material thickness direction. In the obtained photograph, all the bubble diameters 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. This was measured at 10 arbitrary points, and the average value was defined as the average cell diameter in the flow direction (MD), the width direction (CD) and the thickness direction (VD).

[Dimensional change rate of foam base material]
For the dimensional change rate of the foam base material, the polyolefin resin foam is accurately cut into 10 cm square and left in an oven set at 120 ° C. for 24 hours. After 24 hours, remove from the oven and cool at room temperature for about 60 minutes. The sample dimensions were measured, the dimensional change rate was calculated based on the following formula, and evaluated as follows.
Dimensional change rate (%) = {(sample length before being put into the oven−sample length after being taken out of the oven) / sample length before being put into the oven} × 100
A: Dimensional change rate is less than 10% B: Dimensional change rate is 10% to 20%
X: The dimensional change rate is greater than 20% or the original shape is not retained.

[Retention force]
The holding force of the pressure-sensitive adhesive tape is obtained by cutting the measurement sample into 20 mm width × required length with respect to the flow direction of the pressure-sensitive adhesive tape prepared in the examples and comparative examples. A backing material such as aluminum foil is attached to the non-measurement side adhesive surface, and is attached so that an area of 20 mm × 20 mm is in contact with a SUS test plate at room temperature. The test piece affixed to the test plate is reciprocated once 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. After the standing, the test plate is set on a holding force meter, a load of 500 g is applied to the test piece, and the test piece is left in a 120 ° C. environment for 24 hours. . The deviation distance of the test piece after 24 hours was evaluated as follows.
A: Deviation distance is less than 2 mm B: Deviation distance is 2 mm to 10 mm
×: The displacement distance is 10 mm or more

[Repulsive stress]
For the repulsive stress, a test piece was prepared by sticking an adhesive tape cut to a 25 mm square to a stainless plate having a larger area than the sample. The strength of a sample that has been allowed to stand at 23 ° C. for 24 hours and a sample that has been allowed to stand at 120 ° C. for 24 hours and then returned to 23 ° C. in a 23 ° C. environment at a speed of 10 mm / min is measured. The intensity ratio σ2 / σ1 of the strength σ1 after storage at 23 ° C. and the strength σ2 after storage at 120 ° C. was evaluated as follows.
A: Less than σ2 / σ1 = 5 ○: σ2 / σ1 = 5 to 20
×: greater than σ2 / σ1 = 20

As described above, in the pressure-sensitive adhesive tapes of the examples, the foam base material having excellent stickability and followability is used, and the dimensional change of the foam base material at a high temperature is suppressed, and at a high temperature of the pressure-sensitive adhesive tape. It can be seen that it has excellent holding power and has little change in repulsive stress during high temperature storage. On the other hand, in the comparative example, the dimensional change at a high temperature of the foam base material is large, the holding force of the adhesive tape at a high temperature is inferior, and the rebound stress changes at a high temperature and at room temperature are also large. . That is, it can be seen that the form can be maintained even when exposed to a high temperature environment, and the original physical properties can be maintained even when the temperature is returned to room temperature.

Claims

An adhesive tape having an adhesive layer on at least one surface side of a foam base material, wherein the foam base material has a 25% compressive strength of 20 to 170 kPa and an elongation of 100% at 23 ° C. The ratio E2 / E1 is 0.1 or more when the tensile elastic modulus is E1 and the tensile elastic modulus in the flow direction at an elongation of 100% at 120 ° C. is E2, or the width at an elongation of 100% at 23 ° C. The ratio E2 ′ / E1 ′ is 0.1 or more when the tensile modulus in the direction is E1 ′ and the tensile modulus in the width direction at an elongation of 100% at 120 ° C. is E2 ′. tape.
The pressure-sensitive adhesive tape according to claim 1, wherein the apparent density of the foam substrate is 0.05 to 0.35 g / cm 3 .
The pressure-sensitive adhesive tape according to claim 1 or 2, wherein the foam substrate 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 substrate is a polyolefin-based foam substrate.
The pressure-sensitive adhesive tape according to any one of claims 1 to 5, wherein the polyolefin-based foam substrate contains 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.