JP6294541B1 - Double-sided adhesive tape - Google Patents

Abstract

A double-sided pressure-sensitive adhesive tape having excellent resilience is provided.
A double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both surfaces of a substrate, wherein the stress when the elongation is 0.5 mm, measured by the following tensile test, is 55 N or less.
(Tensile test)
Using a double-sided adhesive tape cut to 25 mm × 25 mm, a polycarbonate plate having a thickness of 2 mm and a jig made of stainless steel having a thickness of 2 mm are bonded together. After fixing the polycarbonate plate, the jig made of stainless steel is pulled in the surface direction under the condition of 0.1 mm / min, and the stress of the double-sided adhesive tape is measured.
[Selection figure] None

Description

The present invention relates to a double-sided pressure-sensitive adhesive tape having excellent resilience.

In portable electronic devices such as mobile phones and personal digital assistants (PDAs), double-sided adhesive tapes are used for assembly (for example, Patent Documents 1 and 2). In addition, double-sided adhesive tape is also used for fixing an in-vehicle electronic device component such as an in-vehicle panel to a vehicle body.

High adhesive strength is required for double-sided adhesive tapes used for fixing portable electronic device parts, in-vehicle electronic device parts, and the like. Furthermore, in recent years, portable electronic devices, in-vehicle electronic devices, and the like tend to become more complicated in shape with higher functionality, and therefore, a double-sided adhesive tape is affixed to steps, corners, non-planar parts, etc. There is. In such a case, since the double-sided adhesive tape is fixed in a deformed state, a force to return to the original shape, that is, a restoring force or a repulsive force works, and the double-sided adhesive tape may peel off over time. It was. In particular, when fixing a part in a deformed state, the part itself tries to return to its original shape, so that the double-sided adhesive tape is subjected to restoring force and repulsion, and the fixing is insufficient, Sometimes it peeled off.

Examples of a method for fixing a portion to which a restoring force or a repulsive force is applied include a method of fixing with a conventional liquid or paste adhesive. However, fixing with an adhesive increases the tact time, and it is difficult to cure the adhesive in a state where the parts are deformed.

JP 2009-242541 A JP 2009-258274 A

An object of this invention is to provide the double-sided adhesive tape excellent in the resilience-proof power.

The present invention is a double-sided pressure-sensitive adhesive tape having a pressure-sensitive adhesive layer on both surfaces of a substrate, and having a stress of 55 N or less at an elongation of 0.5 mm as measured by the following tensile test.
(Tensile test)
Using a double-sided adhesive tape cut to 25 mm × 25 mm, a polycarbonate plate having a thickness of 2 mm and a jig made of stainless steel having a thickness of 2 mm are bonded together. After fixing the polycarbonate plate, the jig made of stainless steel is pulled in the surface direction under the condition of 0.1 mm / min, and the stress of the double-sided adhesive tape is measured.
The present invention is described in detail below.

In the double-sided pressure-sensitive adhesive tape having pressure-sensitive adhesive layers on both sides of the base material, the restoring force and repulsive force are applied by adjusting the stress of the double-sided pressure-sensitive adhesive tape measured by a specific tensile test within a specific range. As a result, it was found that the adhesive reliability of the double-sided pressure-sensitive adhesive tape can be improved in a state where it has been removed, and the present invention has been completed.

The double-sided pressure-sensitive adhesive tape of the present invention has pressure-sensitive adhesive layers on both surfaces of the substrate.
The base material is preferably a foam, and when the base is a foam, it may have an open cell structure or a closed cell structure, but preferably has an open cell structure. By using a base material having an open-cell structure, the stress of the double-sided pressure-sensitive adhesive tape can be relaxed, and the adhesive reliability of the double-sided pressure-sensitive adhesive tape in a state where a restoring force or repulsive force is applied can be improved.

In FIG. 1, the cross section of the base material which has an open cell structure, and the schematic diagram of the cross section of the base material which has a closed cell structure are shown.
As shown in FIG. 1, the open cell structure (left in the figure) is a cell structure in which adjacent foam cells 8 are joined to form a continuous cell, and the closed cell structure (right in the figure) is Adjacent foamed cells 8 are not bonded to each other and have a bubble structure that exists independently. As long as the open cell structure is not impaired, independent foam cells may exist in the open cell structure.

Examples of a method for determining whether or not the substrate has an open cell structure include the following methods.
The substrate is cut into 50 mm squares, immersed in liquid nitrogen for 1 minute, and then cut along a plane parallel to the thickness direction with a razor blade. Using a digital microscope (for example, “VHX-500” manufactured by Keyence Corporation), an enlarged photograph of the obtained cut surface is taken at a magnification of 100 to 500 times, and adjacent foam cells are joined together If multiple are confirmed, it can be judged that the said base material has an open-cell structure.

The substrate may have a single layer structure or a multilayer structure.
The said base material is not specifically limited, For example, foams, such as a polyurethane foam, polyolefin foam, an acrylic foam, and rubber-type resin are mentioned. Among them, since the open cell structure is easy to form and the stress of the double-sided pressure-sensitive adhesive tape measured by a specific tensile test described later tends to be within a specific range, the base material may be a polyurethane foam or a rubber-based resin. A polyurethane foam is more preferable.

Examples of the polyurethane foam include a polyurethane foam produced by heat-curing a urethane resin composition containing polyisocyanate and polyol.
The said polyisocyanate is not specifically limited, The aromatic polyisocyanate or aliphatic polyisocyanate used for a general polyurethane foam is mentioned. Specifically, for example, 4,4′-diphenylmethane diisocyanate (MDI), tolylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,5-naphthalene diisocyanate, paraphenylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate 2,4,4-trimethylhexamethylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, m-xylene diisocyanate, hexamethylene diisocyanate, hydrogenated MDI, isophorone diisocyanate and the like. Moreover, as said polyisocyanate, the urethane prepolymer which has an isocyanate group is mentioned, for example. These polyisocyanates may be used alone or in combination of two or more.

The said polyol is not specifically limited, The polyol used for a general polyurethane foam is mentioned. Specific examples include polyether polyol, polyester polyol, polyether ester polyol, and the like. Moreover, as said polyol, short chain diols, such as trifunctional polyether polyol ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1, 4- butanediol, glycerol, a trimethylol propane, are mentioned, for example. These polyols may be used alone or in combination of two or more.

The weight average molecular weight of the polyol is not particularly limited, but a preferable lower limit is 2000 and a preferable upper limit is 12000. If the weight average molecular weight of the polyol is 2000 or more, it is possible to suppress the flexibility of the base material from being excessively lowered, and the stress of the double-sided pressure-sensitive adhesive tape measured by a specific tensile test described later falls within a specific range. It becomes easy. When the weight average molecular weight of the polyol is 12000 or less, the substrate can be prevented from being too soft, and the stress of the double-sided pressure-sensitive adhesive tape measured by a specific tensile test described later easily falls within a specific range.

The isocyanate index of the polyisocyanate in the urethane resin composition is not particularly limited, but a preferred lower limit is 70 and a preferred upper limit is 120.
The isocyanate index is an index related to an isocyanate equivalent in the reaction between an isocyanate and an active hydrogen-containing compound. When the isocyanate index is less than 100, the reactive group such as a hydroxyl group is excessive from the isocyanate group, and when the isocyanate index exceeds 100, the isocyanate group is excessive from the reactive group such as a hydroxyl group.
If the said isocyanate index is 70 or more, the bridge | crosslinking by the said polyisocyanate will become enough, and the said base material can have a moderate softness | flexibility. If the said isocyanate index is 120 or less, it can suppress that the bridge | crosslinking by the said polyisocyanate advances too much and the said base material hardens | cures. In any case, the stress relaxation property of the base material is increased, the stress of the double-sided pressure-sensitive adhesive tape measured by a specific tensile test described later tends to be within an appropriate range, and peeling of the double-sided pressure-sensitive adhesive tape is further suppressed. The

The urethane resin composition may contain a catalyst as necessary.
Examples of the catalyst include organic tin compounds such as stannous octoate, dibutyltin diacetate and dibutyltin dilaurate, organic zinc compounds such as zinc octylate, organic nickel compounds such as nickel acetylacetoate and nickel diacetylacetoate, iron acetyl Organic iron compounds such as acetoate, alkali metal or alkaline earth metal alkoxides such as sodium acetate, metal catalysts such as phenoxide, triethylamine, triethylenediamine, N-methylmorpholine dimethylaminomethylphenol, imidazole, 1,8-diazabicyclo [ 5.4.0] tertiary amine catalysts such as undecene, organic acid salts and the like. Of these, organotin compounds are preferred. These catalysts may be used independently and may use 2 or more types together.
The addition amount of the catalyst is not particularly limited, but a preferable lower limit with respect to 100 parts by weight of the polyol is 0.05 parts by weight, a preferable upper limit is 5.0 parts by weight, and a more preferable upper limit is 4.0 parts by weight.

The urethane resin composition may contain a foaming agent as necessary.
Examples of the foaming agent include foaming agents used for general polyurethane foams. Specific examples include water, pentane, cyclopentane, hexane, cyclohexane, dichloromethane, carbon dioxide gas and the like.
The addition amount of the foaming agent is not particularly limited and is an appropriate amount. When the foaming agent is water, the amount is usually about 0.1 to 3 parts by weight with respect to 100 parts by weight of the polyol. is there.

The urethane resin composition may contain a foam stabilizer as necessary.
Examples of the foam stabilizer include silicone foam stabilizers such as dimethylsiloxane, polyether dimethylsiloxane, and phenylmethylsiloxane. Of these, polyether dimethylsiloxane is preferable, and among the polyether dimethylsiloxanes, a block copolymer of dimethylpolysiloxane and polyether is more preferable. These foam stabilizers may be used alone or in combination of two or more.
Although the addition amount of the foam stabilizer is not particularly limited, the preferable lower limit with respect to 100 parts by weight of the polyol is 0.2 parts by weight, the preferable upper limit is 7 parts by weight, and the more preferable lower limit is 0.4 parts by weight. Is 5 parts by weight.

The urethane resin composition may contain additives generally used in the production of polyurethane foams such as an ultraviolet absorber, an antioxidant, an organic filler, an inorganic filler, and a colorant, if necessary. Good.

As a method for producing the polyurethane foam, for example, a urethane resin composition (liquid) that is foamed by mechanically mixing air, nitrogen, or the like is applied to the surface of a release liner or resin film, and the applied urethane resin composition is applied. The method (mechanical floss method) etc. which manufacture a foam by heat-hardening is mentioned. Moreover, the method (chemical foaming method) etc. which make the said polyisocyanate react with the raw material for forming the said polyurethane foam and generate | occur | produce gas are mentioned. Of these, the mechanical floss method is preferable. The polyurethane foam obtained by the mechanical froth method tends to have a higher density and the cell structure tends to be fine and uniform than the polyurethane foam obtained by the chemical foaming method.

Examples of the rubber resin include natural rubber, isoprene rubber, styrene butadiene rubber, butyl rubber, butadiene rubber, EPDM, nitrile rubber, chloroprene rubber, silicone rubber, block copolymers such as SEBS and SEPS, and the like.

The density of the base material is not particularly limited, preferable lower limit is 0.05 g / cm ^3, a preferred upper limit is 0.8 g / cm ^3. If the density of the base material is 0.05 g / cm ³ or more, the strength of the base material and the double-sided pressure-sensitive adhesive tape is sufficiently high, and the dust resistance and waterproofness of the base material and the double-sided pressure-sensitive adhesive tape are ensured. Cheap. If the density of the base material is 0.8 g / cm ³ or less, the stress of the double-sided pressure-sensitive adhesive tape measured by a specific tensile test described later tends to be within a specific range, and a restoring force or a repulsive force is applied. Adhesion reliability of double-sided adhesive tape is improved. A more preferred lower limit of the substrate is 0.1 g / cm ^3, and more preferred upper limit is 0.7 g / cm ^3, still more preferred lower limit 0.15 g / cm ^3, still more preferred upper limit is 0.5 g / cm ³ is there.
Further, from the viewpoint of adjusting the peeling energy of the double-sided pressure-sensitive adhesive tape described later, the density of the base material is preferably 490 kg / m ³ or less. If the density is 490 kg / m ³ or less, the base material can have appropriate flexibility, so that the stress relaxation property of the base material is increased, and the peeling energy of the double-sided pressure-sensitive adhesive tape described later is in an appropriate range. Easy to adjust. A more preferable upper limit of the density is 450 kg / m ³ .
The density can be measured using an electronic hydrometer (for example, “ED120T” manufactured by Mirage) in accordance with JIS K 6401 (when using polyurethane) and JIS K 6767 (when using polyethylene).

The 25% compressive strength of the substrate is not particularly limited, but a preferred lower limit is 1 kPa and a preferred upper limit is 50 kPa. If the 25% compressive strength of the base material is 1 kPa or more, the strength of the base material and the double-sided pressure-sensitive adhesive tape is sufficiently high, and the double-sided pressure-sensitive adhesive tape is difficult to peel off even if a restoring force or a repulsive force is applied. If the 25% compressive strength of the substrate is 50 kPa or less, the pressure bonding when the substrate is taped becomes sufficient, and the double-sided adhesive tape is difficult to peel off. The more preferable lower limit of the 25% compressive strength of the substrate is 3 kPa, the more preferable upper limit is 45 kPa, the still more preferable lower limit is 5 kPa, and the still more preferable upper limit is 40 kPa.
Moreover, from the viewpoint of adjusting the peeling energy of the double-sided pressure-sensitive adhesive tape described below, the 25% compressive strength of the substrate is preferably 38 kPa or less. If the 25% compressive strength is 38 kPa or less, the base material can have appropriate flexibility, so that the stress relaxation property of the base material is increased, and the peeling energy of the double-sided pressure-sensitive adhesive tape described later is in an appropriate range. Easy to adjust. Moreover, if the 25% compressive strength is 38 kPa or less, the double-sided pressure-sensitive adhesive tape can be favorably bonded.
In addition, 25% compressive strength can be calculated | required by measuring based on JISK6254.

The glass transition point of the substrate is not particularly limited, but is preferably greater than 0 ° C. If the glass transition point is higher than 0 ° C., the base material can have appropriate flexibility, so that the stress relaxation property of the base material becomes high, and the peeling energy of the double-sided pressure-sensitive adhesive tape described later is within an appropriate range. Easy to adjust. In addition, as a base material with a glass transition point larger than 0 degreeC, the polyurethane foam mentioned above etc. are mentioned, for example. A more preferable lower limit of the glass transition point is 10 ° C.
The upper limit of the glass transition point of the substrate is not particularly limited, but if it is too high, the flexibility is impaired, so the preferable upper limit is 25 ° C., and the more preferable upper limit is 20 ° C.
In addition, a glass transition point can be measured based on JISK7121 at a temperature increase rate of 10 degree-C / min, for example using a differential scanning calorimeter (the Seiko Electronics Industry make, DSC-6200R).

The shear storage elastic modulus of the substrate is not particularly limited, but the frequency is 1.0 × 10 ^{−4 to} 1.0 × 10 ⁻⁵ Hz in a master curve measured by a dynamic viscoelastic device and synthesized at a reference temperature of 23 ° C. The maximum value of the shear storage modulus in the region is preferably 1.0 × 10 ⁵ Pa or less.
The frequency range is a frequency corresponding to a peeling stress at a low speed generated when a restoring force or a repulsive force is applied to the double-sided pressure-sensitive adhesive tape. If the maximum value of the shear storage elastic modulus in the frequency region is 1.0 × 10 ⁵ Pa or less, the stress when a restoring force or repulsive force is applied to the double-sided pressure-sensitive adhesive tape is relaxed by the base material, Since it is difficult to convey to the layers, the adhesion reliability of the double-sided pressure-sensitive adhesive tape can be improved.
Although the minimum value of the shear storage elastic modulus in the frequency region is not particularly limited, it is preferably 1.0 × 10 ³ Pa or more. If the minimum value of the shear storage elastic modulus in the frequency range is 1.0 × 10 ³ Pa or more, the strength of the base material is sufficiently high, and the double-sided pressure-sensitive adhesive tape is prevented from being excessively stretched and sufficiently bonded. And fixing can be realized.
The shear storage modulus is in the range of −60 ° C. to 250 ° C. using a dynamic viscoelasticity measuring device (for example, DVA-200 manufactured by IT Measurement Co., Ltd.) at a rate of temperature increase of 5 ° C./min. It can be measured. When measuring the shear storage elastic modulus, measurement is performed by applying an adhesive on both sides of the substrate in order to suppress the deviation of the sample during the measurement. Although such an adhesive is not specifically limited, it measures by adjusting so that the thickness of the adhesive apply | coated to the both sides of the said base material may be 15% or less of the thickness of the said base material. By setting the thickness of the pressure-sensitive adhesive to 15% or less of the thickness of the base material, the shear storage elastic modulus of the base material can be measured while eliminating the influence of the pressure-sensitive adhesive as much as possible.

Although the thickness of the said base material is not specifically limited, A preferable minimum is 0.3 mm and a preferable upper limit is 2.9 mm. If the thickness of the base material is 0.3 mm or more, the double-sided pressure-sensitive adhesive tape is difficult to peel off even if a restoring force or a repulsive force is applied. If the thickness of the base material is 2.9 mm or less, the double-sided pressure-sensitive adhesive tape can realize sufficient adhesion and fixation. The minimum with more preferable thickness of the said base material is 0.4 mm, and a more preferable upper limit is 2.5 mm.
Moreover, it is preferable that the thickness of the said base material is larger than 0.9 mm from a viewpoint of adjusting the peeling energy of the double-sided adhesive tape mentioned later. If the thickness is larger than 0.9 mm, the base material can have appropriate flexibility, so that the stress relaxation property of the base material becomes high, and the peeling energy of the double-sided pressure-sensitive adhesive tape described later is adjusted to an appropriate range. It becomes easy to do. A more preferable lower limit of the thickness is 1 mm.
The thickness of the substrate can be measured using a dial thickness meter (for example, “ABS Digimatic Indicator” manufactured by Mitutoyo).

The double-sided pressure-sensitive adhesive tape of the present invention may further have a resin sheet integrated with the substrate. By using the resin sheet, it is possible to prevent the base material from stretching and breaking at the time of handling, and reworkability can be imparted to the double-sided pressure-sensitive adhesive tape.
The resin constituting the resin sheet is not particularly limited. For example, polyester resin such as polyethylene terephthalate, polyethylene resin, polypropylene resin, polyvinyl chloride, epoxy resin, silicone resin, phenol resin, polyimide, polyester, polycarbonate, etc. Is mentioned. Of these, polyethylene resins, polypropylene resins, and polyester resins are preferred because of their excellent flexibility. Among the polyester resins, polyethylene terephthalate is preferable.

Although the thickness of the said resin sheet is not specifically limited, A preferable minimum is 10 micrometers and a preferable upper limit is 100 micrometers. When the thickness of the resin sheet is 10 μm or more, the resin sheet is hardly broken even when the resin sheet is pulled. If the thickness of the said resin sheet is 100 micrometers or less, the fall of the followable | trackability to a to-be-adhered body may be suppressed.

The resin sheet may be colored. By coloring the resin sheet, light-shielding properties can be imparted to the double-sided pressure-sensitive adhesive tape.
The method for coloring the resin sheet is not particularly limited. For example, a method of kneading particles such as carbon black or titanium oxide or fine bubbles in the resin constituting the resin sheet, or applying ink to the surface of the resin sheet. Methods and the like.

The double-sided pressure-sensitive adhesive tape of the present invention has pressure-sensitive adhesive layers on both surfaces of the substrate. The pressure-sensitive adhesive layers formed on both surfaces of the substrate may have the same composition or different compositions.
The pressure-sensitive adhesive layer is not particularly limited, and examples thereof include an acrylic pressure-sensitive adhesive layer, a rubber-based pressure-sensitive adhesive layer, a urethane pressure-sensitive adhesive layer, and a silicone-based pressure-sensitive adhesive layer. Among these, an acrylic pressure-sensitive adhesive layer is preferable because it is relatively stable to light, heat, moisture, and the like, and adherend selectivity is low.

The acrylic copolymer constituting the acrylic pressure-sensitive adhesive layer is obtained by copolymerizing a monomer mixture. Especially, it is preferable to obtain by copolymerizing the monomer mixture containing butyl acrylate and 2-ethylhexyl acrylate.
The preferable content of butyl acrylate in the total monomer mixture is 40 to 80% by weight. When the content of butyl acrylate is 40% by weight or more, the acrylic pressure-sensitive adhesive layer has an appropriate hardness and sufficient cohesive strength, and the double-sided pressure-sensitive adhesive tape has high adhesive strength. If content of butyl acrylate is 80 weight% or less, it can suppress that the said acrylic adhesive layer becomes hard and tackiness and wettability (adhesive strength of an interface with a to-be-adhered body) fall.
The preferable content of 2-ethylhexyl acrylate in the total monomer mixture is 10 to 40% by weight. If content of 2-ethylhexyl acrylate is 10 weight% or more, the adhesive force of the said acrylic adhesive layer will become enough. If content of 2-ethylhexyl acrylate is 40 weight% or less, it can suppress that the said acrylic adhesive layer becomes too soft and cohesion force falls.

The monomer mixture may contain other polymerizable monomers other than butyl acrylate and 2-ethylhexyl acrylate as necessary.
Examples of other polymerizable monomers that can be copolymerized include, for example, carbon number of alkyl groups such as methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and isopropyl (meth) acrylate. 1 to 3 (meth) acrylic acid alkyl ester, tridecyl methacrylate, and (meth) acrylic acid alkyl ester having 13 to 18 carbon atoms such as stearyl (meth) acrylate, hydroxyalkyl (meth) acrylate , Glycerin dimethacrylate, glycidyl (meth) acrylate, 2-methacryloyloxyethyl isocyanate, (meth) acrylic acid, itaconic acid, maleic anhydride, crotonic acid, maleic acid, fumaric acid and the like.

In order to copolymerize the monomer mixture to obtain the acrylic copolymer, the monomer mixture may be radically reacted in the presence of a polymerization initiator. As a method of radical reaction of the monomer mixture, that is, a polymerization method, a conventionally known method is used, and examples thereof include solution polymerization (boiling point polymerization or constant temperature polymerization), emulsion polymerization, suspension polymerization, bulk polymerization and the like.
The said polymerization initiator is not specifically limited, For example, an organic peroxide, an azo compound, etc. are mentioned. Examples of the organic peroxide include 1,1-bis (t-hexylperoxy) -3,3,5-trimethylcyclohexane, t-hexylperoxypivalate, t-butylperoxypivalate, 2,5 -Dimethyl-2,5-bis (2-ethylhexanoylperoxy) hexane, t-hexylperoxy-2-ethylhexanoate, t-butylperoxy-2-ethylhexanoate, t-butylperoxy Examples include isobutyrate, t-butylperoxy-3,5,5-trimethylhexanoate, and t-butylperoxylaurate. Examples of the azo compound include azobisisobutyronitrile and azobiscyclohexanecarbonitrile. These polymerization initiators may be used alone or in combination of two or more.

As for the weight average molecular weight (Mw) of the said acrylic copolymer, a preferable minimum is 400,000 and a preferable upper limit is 1.5 million. When the weight average molecular weight is 400,000 or more, the acrylic pressure-sensitive adhesive layer has an appropriate hardness and sufficient cohesive force, and the double-sided pressure-sensitive adhesive tape has high adhesive force. When the weight average molecular weight is 1.5 million or less, the adhesive force of the acrylic pressure-sensitive adhesive layer is sufficient. A more preferable lower limit of the weight average molecular weight is 500,000, and a more preferable upper limit is 1,400,000. In order to adjust the weight average molecular weight within the above range, polymerization conditions such as a polymerization initiator and a polymerization temperature may be adjusted.

A preferable upper limit of the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the acrylic copolymer is 10.0. If Mw / Mn is 10.0 or less, the content of low molecular weight components and the like is reduced, so the cohesive force and wettability (adhesive strength of the interface with the adherend) of the acrylic pressure-sensitive adhesive layer is increased, Adhesive strength increases. A more preferable upper limit of Mw / Mn is 3.0. In order to adjust Mw / Mn within the above range, polymerization conditions such as a polymerization initiator and a polymerization temperature may be adjusted.
In addition, a number average molecular weight (Mn) and a weight average molecular weight (Mw) are the weight average molecular weights of standard polystyrene conversion by GPC (Gel Permeation Chromatography: gel permeation chromatography). In GPC, for example, 2690 Separations Model (manufactured by Waters) can be used.

The pressure-sensitive adhesive layer may contain a tackifier resin.
Examples of the tackifier resins include rosin ester resins, hydrogenated rosin resins, terpene resins, terpene phenol resins, coumarone indene resins, alicyclic saturated hydrocarbon resins, C5 petroleum resins, and C9 resins. Examples thereof include petroleum resins and C5-C9 copolymer petroleum resins. These tackifying resins may be used alone or in combination of two or more.

The content of the tackifying resin is not particularly limited, but a preferable lower limit with respect to 100 parts by weight of a resin (for example, an acrylic copolymer) as a main component of the pressure-sensitive adhesive layer is 10 parts by weight, and a preferable upper limit is 60 parts by weight. . If content of the said tackifying resin is 10 weight part or more, the adhesive force of the said adhesive layer will become high. If the content of the tackifying resin is 60 parts by weight or less, the pressure-sensitive adhesive layer is too hard to suppress a decrease in adhesive strength, tackiness or wettability (adhesive strength at the interface with the adherend). can do.

In the pressure-sensitive adhesive layer, a cross-linking structure is formed between main chains of a resin (for example, the acrylic copolymer, the tackifying resin, etc.) constituting the pressure-sensitive adhesive layer by adding a cross-linking agent. Is preferred.
The said crosslinking agent is not specifically limited, For example, an isocyanate type crosslinking agent, an aziridine type crosslinking agent, an epoxy-type crosslinking agent, a metal chelate type crosslinking agent etc. are mentioned. Of these, isocyanate-based crosslinking agents are preferred. By adding an isocyanate-based crosslinking agent to the pressure-sensitive adhesive layer, an alcohol in a resin (for example, the acrylic copolymer, the tackifying resin, etc.) constituting the pressure-sensitive adhesive layer and the isocyanate group of the isocyanate-based crosslinking agent The reactive hydroxyl group reacts to loosen the pressure-sensitive adhesive layer. Therefore, the pressure-sensitive adhesive layer can disperse the intermittently applied peeling stress, and the adhesive strength of the double-sided pressure-sensitive adhesive tape is further improved.
The amount of the crosslinking agent added is preferably 0.01 to 10 parts by weight, preferably 0.1 to 7 parts by weight, based on 100 parts by weight of the resin (for example, the acrylic copolymer) as the main component of the pressure-sensitive adhesive layer. Is more preferable.

The degree of cross-linking of the pressure-sensitive adhesive layer is preferably too high or too low, and may be easily peeled off from the adherend when a large stress is applied. Therefore, 5 to 60% by weight is preferable, and 10 to 55% by weight is preferable. More preferred is 15 to 50% by weight.
The degree of crosslinking of the pressure-sensitive adhesive layer was determined by collecting W ₁ (g) of the pressure-sensitive adhesive layer, immersing this pressure-sensitive adhesive layer in ethyl acetate at 23 ° C. for 24 hours, and filtering the insoluble matter with a 200-mesh wire mesh. Then, the residue on the wire mesh is vacuum-dried, and the weight W ₂ (g) of the dried residue is measured, and calculated by the following formula (1).
Crosslinking degree (% by weight) = 100 × W ₂ / W ₁ (1)

Although the thickness of the said adhesive layer is not specifically limited, The preferable minimum of the thickness of the adhesive layer of one side is 0.01 mm, and a preferable upper limit is 0.1 mm. If the thickness of the said adhesive layer is 0.01 mm or more, it can suppress that the tackiness of the said adhesive layer falls, and can affix a double-sided adhesive tape on a to-be-adhered body favorably. If the thickness of the said adhesive layer is 0.1 mm or less, when processing the said adhesive layer or a double-sided adhesive tape, it can suppress that an adhesive oozes out and can prevent a process defect. The minimum with more preferable thickness of the said adhesive layer is 0.015 mm, and a more preferable upper limit is 0.09 mm.
Moreover, from a viewpoint of adjusting the peeling energy of the double-sided pressure-sensitive adhesive tape described later, the preferable lower limit of the thickness of the pressure-sensitive adhesive layer on one side is 20 μm. The more preferable lower limit of the thickness of the pressure-sensitive adhesive layer is 30 μm, and the more preferable upper limit is 80 μm.
The thickness of the pressure-sensitive adhesive layer can be measured using a dial thickness meter (for example, “ABS Digimatic Indicator” manufactured by Mitutoyo).

The pressure-sensitive adhesive layer may contain a silane coupling agent for the purpose of improving the adhesive strength. The silane coupling agent is not particularly limited, and examples thereof include epoxy silanes, acrylic silanes, methacryl silanes, amino silanes, and isocyanate silanes.

The pressure-sensitive adhesive layer may contain a colorant for the purpose of imparting light shielding properties. The colorant is not particularly limited, and examples thereof include carbon black, aniline black, and titanium oxide. Among these, carbon black is preferable because it is relatively inexpensive and chemically stable.

The double-sided pressure-sensitive adhesive tape of the present invention has a stress of 55 N or less when measured by the following tensile test and an elongation of 0.5 mm.
(Tensile test)
Using a double-sided adhesive tape cut to 25 mm × 25 mm, a polycarbonate plate having a thickness of 2 mm and a jig made of stainless steel having a thickness of 2 mm are bonded together. After fixing the polycarbonate plate, the jig made of stainless steel is pulled in the surface direction under the condition of 0.1 mm / min, and the stress of the double-sided adhesive tape is measured.

The tensile test will be described in detail.
In FIG. 2, the schematic diagram which shows the tension test of the double-sided adhesive tape of this invention is shown.
As shown in FIG. 2, using a double-sided adhesive tape 1 cut to 25 mm × 25 mm, a jig made of 2 mm thick polycarbonate plate (length 50 mm × width 50 mm) 2 and 2 mm thick stainless steel (30 mm × 30 mm) (Not shown, but with a handle) 3 is laminated. This laminate was pressure-bonded using a roller under conditions of 5 kg for 10 seconds, and then allowed to stand for 24 hours to produce a sample for tensile test in which the polycarbonate plate 2 and the jig 3 were bonded together via the double-sided adhesive tape 1. To do. After fixing the polycarbonate plate 2 of this tensile test sample, the jig 3 was pulled in the surface direction (arrow direction in the figure) at 0.1 mm / min under the condition of 23 ° C., and the stress of the double-sided adhesive tape 1 Measure. In addition, the measurement of elongation is started by starting a stroke (elongation 0 mm) where a stress of 1 N is applied to the double-sided pressure-sensitive adhesive tape 1, and the stress when the elongation is 0.5 mm is measured.

In the tensile test, the stress of the double-sided pressure-sensitive adhesive tape is measured not at a tensile speed of 300 mm / min specified in JIS Z 0237 but at a very low tensile speed of 0.1 mm / min. Thereby, the performance of the double-sided pressure-sensitive adhesive tape can be evaluated in a state where the peeling stress at low speed generated when a restoring force or repulsive force is applied to the double-sided pressure-sensitive adhesive tape is reproduced (assumed).

FIG. 3 shows a stress-elongation curve in which the horizontal axis indicates the elongation (mm) of the double-sided pressure-sensitive adhesive tape in the tensile test and the vertical axis indicates the stress (N) of the double-sided pressure-sensitive adhesive tape in the tensile test.
The present inventors evaluated the relationship between the stress-elongation curve shown in FIG. 3 and the adhesive reliability of the double-sided pressure-sensitive adhesive tape in a state where a restoring force and a repulsive force are applied. As a result, the present inventors have found that the slope of the stress-elongation curve needs to be gradual in order to obtain high adhesion reliability even in a state where a restoring force and a repulsive force are applied. It was. Furthermore, the present inventors adjusted the stress when the elongation is 0.5 mm, measured by the above tensile test, to 55 N or less, whereby the adhesive reliability of the double-sided pressure-sensitive adhesive tape in a state where a restoring force or a repulsive force is applied. It was found that can be improved. The stress when the elongation is 0.5 mm, measured by the tensile test, is preferably 50 N or less, more preferably 45 N or less, and still more preferably 40 N or less.
On the other hand, when the slope of the stress-elongation curve is large, the stress is large even with a slight displacement (elongation), so that the force concentrates on the interface with the adherend and the double-sided adhesive tape is easily peeled off.

The lower limit of the stress measured by the tensile test when the elongation is 0.5 mm is not particularly limited, but 1N or more is preferable. If the stress at an elongation of 0.5 mm measured by the above tensile test is 1 N or more, it is possible to suppress the displacement (elongation) from becoming too large with a little stress, not only difficult to peel, but also double-sided adhesive The tape becomes difficult to stretch, and sufficient adhesion and fixation can be realized. As for the stress at the time of elongation 0.5mm measured by the said tension test, 5 N or more is more preferable.

Although the minimum of the stress measured by the said tension test is not specifically limited, 1 N or more is preferable. If the stress measured by the tensile test is 1 N or more, it is possible to prevent the displacement (elongation) from becoming too large with a little stress, and it is difficult not only to peel but also to make the double-sided adhesive tape difficult to stretch. Bonding and fixing can be realized. The stress measured by the tensile test is more preferably 5N or more.

In order to adjust the stress of the double-sided pressure-sensitive adhesive tape measured by the tensile test within the above range, it is preferable to use a base material having an open cell structure, and the composition, manufacturing method, density, 25% of the base material. It is preferable to adjust the compression strength, the maximum and minimum values of the shear storage modulus, the thickness, and the like.

As for the double-sided adhesive tape of this invention, it is preferable that the peeling energy of the double-sided adhesive tape in 60 degreeC measured by the tack test is 350 gf * s or more.
In the present specification, the release energy is an index for evaluating the stress relaxation property of the entire double-sided pressure-sensitive adhesive tape, and can be measured by the following tack test. By adjusting the peeling energy to a specific range, peeling of the double-sided pressure-sensitive adhesive tape can be suppressed even under conditions where high temperature and high humidity and restoring force are applied.

The tack test is performed as follows. First, a double-sided pressure-sensitive adhesive tape is placed on a plate set to 60 ° C. of a tack tester (for example, TAC-1000 manufactured by Reska Co., Ltd.) with the pressure-sensitive adhesive layer facing up. The non-measurement surface of the double-sided pressure-sensitive adhesive tape is backed with a film such as a polyethylene terephthalate (PET) film. Next, a cylindrical stainless steel probe having a diameter of 5 mm is pressed against the double-sided adhesive tape at a probe temperature of 60 ° C., a pressing speed of 2 mm / s, and a pressing load of 100 gf, and held in that state for 0.1 second. Thereafter, the probe is pulled up at a lifting speed of 0.2 mm / s. During this time, the stress of the double-sided adhesive tape is measured.

The peel energy is an integrated value from time T ₁ when the stress is 0 to time T ₂ when the stress is 0 in the stress curve showing the stress of the double-sided adhesive tape at 60 ° C. measured by the tack test. Means.
In FIG. 5, an example of the stress curve which shows the stress of the double-sided adhesive tape in 60 degreeC measured by the tack test was shown typically. The stress curve 17 is a stress curve indicating the stress of the double-sided adhesive tape at 60 ° C. measured by a tack test. In the tack test, when the probe is pressed against the double-sided adhesive tape (A in FIG. 5), the stress curve 17 descends, and then when the probe starts to be pulled up (B in FIG. 5), the stress curve 17 rises. I will do it. (In Figure 5, C) the integral value of the stress from the time T ₁ showing a is 0 to time T ₂ showing the maximum stress (peak top) is calculated and this peeling energy.
By adjusting the peeling energy within the above range, peeling of the double-sided pressure-sensitive adhesive tape can be suppressed even under conditions where high temperature and high humidity and restoring force are applied. A preferable lower limit of the peeling energy is 400 gf · s, and a more preferable lower limit is 550 gf · s.
Moreover, the upper limit of the peeling energy is not particularly limited.

The method for adjusting the peeling energy to the above range is not particularly limited, but in order to increase the peeling energy, the time from the time T ₁ when the stress is 0 to the time T ₂ where the maximum stress (peak top) is shown, That is, the longer the peeling time, the better. Moreover, the larger the maximum stress, the better.
A preferable lower limit of the peeling time is 2.7 seconds, and a more preferable lower limit is 3.5 seconds. A preferable lower limit of the maximum stress is 200 gf, and a more preferable lower limit is 225 gf.

As a method for increasing the peeling energy, for example, a method for increasing the stress relaxation property of the substrate by adjusting the physical properties of the substrate, a cohesive force (bulk strength) and / or wettability (coverage) of the pressure-sensitive adhesive layer. And a method for increasing the adhesive strength at the interface with the adherend.
As a method for improving the stress relaxation property of the substrate by adjusting the physical properties of the substrate, for example, after using a foam as the substrate, the thickness, density, glass transition point, 25% of the foam A method for adjusting the compression strength and the like can be mentioned.

Although the 180 degree adhesive force of the double-sided adhesive tape of this invention is not specifically limited, A preferable minimum is 3 N / 25mm and a preferable upper limit is 35 N / 25mm. If the 180 ° adhesive strength of the double-sided pressure-sensitive adhesive tape of the present invention is 3 N / 25 mm or more, tackiness is sufficient, and workability when the double-sided pressure-sensitive adhesive tape is attached to an adherend is improved. When the 180 ° adhesive strength of the double-sided pressure-sensitive adhesive tape of the present invention is 35 N / 25 mm or less, the rework property becomes high and re-attachment becomes possible.
In addition, 180 degree adhesive force can be calculated | required by measuring based on JISZ0237.

The thickness of the double-sided pressure-sensitive adhesive tape of the present invention is not particularly limited, but a preferred lower limit is 0.4 mm and a preferred upper limit is 3 mm. If the thickness of the double-sided pressure-sensitive adhesive tape of the present invention is 0.4 mm or more, the double-sided pressure-sensitive adhesive tape is difficult to peel off even if restoring force or repulsive force is applied. If the thickness of the double-sided pressure-sensitive adhesive tape of the present invention is 3 mm or less, sufficient adhesion and fixation can be realized. The minimum with more preferable thickness of the double-sided adhesive tape of this invention is 0.5 mm, and a more preferable upper limit is 2.8 mm.

As a manufacturing method of the double-sided adhesive tape of this invention, the following methods are mentioned, for example.
First, a solution of an adhesive A is prepared by adding a solvent to an acrylic copolymer, a tackifier resin, and a cross-linking agent as necessary, and the solution of the adhesive A is applied to the surface of the substrate. The solvent is completely removed by drying to form the pressure-sensitive adhesive layer A. Next, the release film is superimposed on the pressure-sensitive adhesive layer A so that the release treatment surface faces the pressure-sensitive adhesive layer A.
Next, a release film different from the above release film is prepared, the adhesive B solution is applied to the release treatment surface of the release film, and the solvent in the solution is completely removed by drying, thereby releasing the release film. A laminated film in which the pressure-sensitive adhesive layer B is formed on the surface of the mold film is produced. The obtained laminated film is laminated on the back surface of the base material on which the pressure-sensitive adhesive layer A is formed, with the pressure-sensitive adhesive layer B facing the back surface of the base material to produce a laminate. And by pressing the said laminated body with a rubber roller etc., the double-sided adhesive tape which has an adhesive layer on both surfaces of a base material, and the surface of the adhesive layer was covered with the release film can be obtained.

In addition, two sets of laminated films are produced in the same manner, and a laminated body is produced by superposing these laminated films on both sides of the base material with the adhesive layer of the laminated film facing the base material. By pressing the laminate with a rubber roller or the like, a double-sided pressure-sensitive adhesive tape having an adhesive layer on both surfaces of the base material and having the surface of the adhesive layer covered with a release film may be obtained.

The use of the double-sided pressure-sensitive adhesive tape of the present invention is not particularly limited. The shape of the double-sided pressure-sensitive adhesive tape of the present invention in these applications is not particularly limited, and examples thereof include a rectangle, a frame shape, a circle, an ellipse, and a donut shape.

The double-sided pressure-sensitive adhesive tape of the present invention is excellent in adhesion reliability in a state where peeling stress at low speed such as restoring force and repulsive force is applied, so it can be attached to a step, corner, non-planar part, etc. It is preferably used for fixing in a deformed state.
Articles using the double-sided adhesive tape of the present invention include, for example, flat panel displays used in TVs, monitors, portable electronic devices, camera modules for portable electronic devices, internal members of portable electronic devices, vehicle interiors, home appliances ( For example, the interior and exterior of a TV, an air conditioner, a refrigerator, etc.) can be mentioned. Examples of the adherend of the double-sided pressure-sensitive adhesive tape of the present invention include side panels, back panels, various nameplates, decorative films, decorative films and the like of portable electronic devices.

ADVANTAGE OF THE INVENTION According to this invention, the double-sided adhesive tape excellent in the restoring force can be provided.

It is a schematic diagram of the cross section of the base material which has an open cell structure, and the cross section of the base material which has a closed cell structure. It is a schematic diagram which shows the tensile test of the double-sided adhesive tape of this invention. It is a stress-elongation curve with the horizontal axis representing the elongation (mm) of the double-sided pressure-sensitive adhesive tape in the tensile test and the vertical axis representing the stress (N) of the double-sided pressure-sensitive adhesive tape in the tensile test. It is a schematic diagram which shows the resilience test of a double-sided adhesive tape. It is a figure which shows typically an example of the stress curve which shows the stress of the double-sided adhesive tape in 60 degreeC measured by the tack test.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Production of polyurethane (PU) foam Polyol 1 (polyether polyol, weight average molecular weight 6000, hydroxyl number 3, hydroxyl value 48 mg KOH / g) 100 parts by weight of amine catalyst (Dabco LV33, Sankyo Air Products Co., Ltd.) 0.7 parts by weight and 1 part by weight of a foam stabilizer (SZ5740M, manufactured by Toray Dow Corning) were added and stirred. Polyisocyanate (Cosmonate TM-20, manufactured by Mitsui Chemicals Co., Ltd.) was adjusted and added to have an isocyanate index of 80. Then, it mixed and stirred with nitrogen gas so that it might be set to 0.2 g / cm < ³ >, and the solution in which the fine bubble was mixed was obtained. The solution is applied to a predetermined thickness on a 50 μm thick PET separator (Nippon V-2) using an applicator, and the foam raw material is reacted to obtain a 0.9 mm thick polyurethane (PU) foam. It was.
The obtained polyurethane (PU) foam was cut into a 50 mm square, immersed in liquid nitrogen for 1 minute, and then cut along a plane parallel to the thickness direction with a razor blade. As a result of taking an enlarged photograph of the obtained cut surface at a magnification of 100 using a digital microscope (manufactured by Keyence Corporation, “VHX-500”), many portions where adjacent foamed cells are bonded are confirmed. It was confirmed that the polyurethane (PU) foam had an open cell structure. In addition, the density of the obtained polyurethane (PU) foam was measured using an electronic hydrometer (Mirage, “ED120T”) in accordance with JIS K 6401. As a result, it was 0.2 g / cm ^3. It was. Furthermore, it was 8 kPa as a result of calculating | requiring 25% compressive strength of the obtained polyurethane (PU) foam by measuring based on JISK6254. Furthermore, the glass transition point of the obtained polyurethane (PU) foam was measured in accordance with JIS K 7121 at a heating rate of 10 ° C./min using a differential scanning calorimeter (DSC-6200R, manufactured by Seiko Denshi Kogyo Co., Ltd.). As a result, it was 5 ° C.

(2) Preparation of pressure-sensitive adhesive After putting 52 parts by weight of ethyl acetate into a reactor equipped with a thermometer, a stirrer, and a condenser, the reactor was heated to reflux after replacing with nitrogen. 30 minutes after ethyl acetate boiled, 0.08 parts by weight of azobisisobutyronitrile was added as a polymerization initiator. A monomer mixture consisting of 70 parts by weight of butyl acrylate, 27 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid and 0.2 parts by weight of 2-hydroxyethyl acrylate was added dropwise uniformly and gradually over 1 hour 30 minutes. Reacted. 30 minutes after completion of the dropping, 0.1 part by weight of azobisisobutyronitrile was added, and the polymerization reaction was further performed for 5 hours. Ethyl acetate was added to the reactor and cooled while diluting to obtain a solid content of 40% by weight. A solution of the acrylic copolymer (a) was obtained. When the weight average molecular weight of the obtained acrylic copolymer (a) was measured by a GPC method using “2690 Separations Model” manufactured by Water as a column, it was 710,000. The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was 5.5.
15 parts by weight of a polymerized rosin ester having a softening point of 150 ° C., 10 parts by weight of terpenephenol having a softening point of 145 ° C., and a rosin ester having a softening point of 70 ° C. with respect to 100 parts by weight of the solid content of the obtained acrylic copolymer (a) 10 parts by weight were added. Furthermore, 30 parts by weight of ethyl acetate (manufactured by Fuji Chemical Co., Ltd.) and 3.0 parts by weight of an isocyanate-based cross-linking agent (trade name “Coronate L45” manufactured by Nippon Polyurethane Co., Ltd.) were added, stirred, and pressure-sensitive adhesive (A) Got.

(3) Manufacture of double-sided pressure-sensitive adhesive tape A release paper having a thickness of 150 μm is prepared, and a pressure-sensitive adhesive (A) is applied to the release-treated surface of this release paper and dried at 100 ° C. for 5 minutes. An acrylic pressure-sensitive adhesive layer was formed. This acrylic adhesive layer was bonded to the surface of a 0.9 mm thick polyurethane (PU) foam. Next, in the same manner, the same acrylic pressure-sensitive adhesive layer as described above was bonded to the opposite surface of the polyurethane (PU) foam after peeling off the PET separator. Then, curing was performed by heating at 40 ° C. for 48 hours. Thereby, a double-sided pressure-sensitive adhesive tape having a thickness of 1 mm covered with a release paper having a thickness of 150 μm was obtained.

(4) Tensile test The stress of the double-sided adhesive tape was measured by the following tensile test when the elongation was 0.5 mm. The results are shown in Table 1.
In FIG. 2, the schematic diagram which shows the tension test of the double-sided adhesive tape of this invention is shown.
As shown in FIG. 2, using a double-sided adhesive tape 1 cut to 25 mm × 25 mm, a jig made of 2 mm thick polycarbonate plate (length 50 mm × width 50 mm) 2 and 2 mm thick stainless steel (30 mm × 30 mm) (Not shown, but provided with a handle) 3 was laminated. This laminate was pressure-bonded using a roller under conditions of 5 kg for 10 seconds, and then allowed to stand for 24 hours to produce a sample for tensile test in which the polycarbonate plate 2 and the jig 3 were bonded together via the double-sided adhesive tape 1. did. After fixing the polycarbonate plate 2 of this tensile test sample, the jig 3 was pulled in the surface direction (arrow direction in the figure) at 0.1 mm / min under the condition of 23 ° C., and the stress of the double-sided adhesive tape 1 Was measured. In addition, the measurement of the elongation was started by starting the stroke (elongation 0 mm) where a stress of 1 N was applied to the double-sided pressure-sensitive adhesive tape 1, and the stress when the elongation was 0.5 mm was measured.

(5) Measurement of maximum value of shear storage modulus Double-sided pressure-sensitive adhesive tape was cut into a width of 6 mm × 10 mm and set in a shear measurement jig of a dynamic viscoelasticity measuring apparatus (DVA-200 manufactured by IT Measurement Co., Ltd.). . The shear storage elastic modulus was measured in the range of −60 ° C. to 250 ° C. at a rate of temperature increase of 5 ° C./min, and a master curve was synthesized at a reference temperature of 23 ° C., so that the frequency at 23 ° C. was 1.0 × 10 ⁻⁴ to The maximum value of the shear storage modulus in the 1.0 × 10 ⁻⁵ Hz region was determined. In Table 1, the logarithm (log G ′) of the maximum value of the shear storage elastic modulus is shown.

(6) Tack test A double-sided pressure-sensitive adhesive tape was placed on a plate set at 60 ° C of a tack tester (TAC-1000 manufactured by Reska Co., Ltd.) with the pressure-sensitive adhesive layer facing up. The non-measurement surface of the double-sided pressure-sensitive adhesive tape was lined with a polyethylene terephthalate (PET) film. Next, a cylindrical stainless steel probe having a diameter of 5 mm was pressed against the double-sided adhesive tape at a probe temperature of 60 ° C., a pressing speed of 2 mm / s, and a pressing load of 100 gf, and held in that state for 0.1 second. Thereafter, the probe was pulled up at a lifting speed of 0.2 mm / s, and the stress of the double-sided adhesive tape during this period was measured.
In the obtained stress curve, an integrated value from time T ₁ when the stress is 0 to time T ₂ where the maximum stress (peak top) is shown was calculated, and this was taken as the peeling energy. Table 1 also shows the peeling time and the maximum stress.

(Example 2)
In “(1) Production of polyurethane (PU) foam”, the polyurethane (PU) foam was changed as shown in Table 1 by adjusting the amount of nitrogen gas to be mixed, as in Example 1. Thus, a double-sided adhesive tape was obtained. The polyurethane (PU) foam had open cells and a density of 0.41 g / cm ³ . In the same manner as in Example 1, the stress of the double-sided pressure-sensitive adhesive tape when the elongation was 0.5 mm and the maximum value of the shear storage modulus were measured, and a tack test was performed.

(Example 3)
In “(1) Production of polyurethane (PU) foam”, a polyurethane (PU) foam is shown in Table 1 by using polyol 2 shown below instead of polyol 1 and changing the isocyanate index to 100. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the above was changed. The polyurethane (PU) foam had open cells and a density of 0.49 g / cm ³ . In the same manner as in Example 1, the stress of the double-sided pressure-sensitive adhesive tape when the elongation was 0.5 mm and the maximum value of the shear storage modulus were measured, and a tack test was performed.

Polyol 2 (polyether polyol, weight average molecular weight 3000, hydroxyl number 3, hydroxyl value 38 mgKOH / g)

Example 4
In “(1) Production of polyurethane (PU) foam”, the polyurethane (PU) foam was changed as shown in Table 1 by adjusting the amount of nitrogen gas to be mixed, as in Example 1. Thus, a double-sided adhesive tape was obtained. The polyurethane (PU) foam had open cells and a density of 0.45 g / cm ³ . In the same manner as in Example 1, the stress of the double-sided pressure-sensitive adhesive tape when the elongation was 0.5 mm and the maximum value of the shear storage modulus were measured, and a tack test was performed.

(Example 5)
(1) Polyethylene (PE) foam XLH-2001 (thickness 1 mm, manufactured by Sekisui Chemical Co., Ltd.) was used as a polyethylene (PE) foam. The foamed state of the polyethylene (PE) foam was confirmed in the same manner as in Example 1, and the density, 25% compressive strength, and glass transition point were determined. The polyethylene (PE) foam had closed cells and a density of 0.05 g / cm ³ .

(2) Preparation of pressure-sensitive adhesive A pressure-sensitive adhesive (A) was obtained in the same manner as in Example 1.

(3) Production of double-sided pressure-sensitive adhesive tape A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that polyethylene (PE) foam was used.

(4) Tensile test In the same manner as in Example 1, the stress of the double-sided adhesive tape was measured when the elongation was 0.5 mm.

(5) Measurement of maximum value of shear storage modulus The maximum value of shear storage modulus was measured in the same manner as in Example 1.

(6) Tack test A tack test was conducted in the same manner as in Example 1.

(Example 6)
(1) Polyurethane (PU) foam A polyurethane (PU) foam was obtained in the same manner as in Example 1.

(2) Preparation of pressure-sensitive adhesive A reactor equipped with a thermometer, a stirrer, and a cooling pipe is 70 parts by weight of butyl acrylate, 27 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of acrylic acid, and 0.2 parts by weight of 2-hydroxyethyl acrylate. Then, 165 parts by weight of ethyl acetate was added and the atmosphere was replaced with nitrogen, and then the reactor was heated to start refluxing. Subsequently, 0.06 part by weight of azobisisobutyronitrile was added as a polymerization initiator in the reactor. Reaction was carried out at 55 ° C. for 10 hours, and ethyl acetate was added to the reactor and cooled while diluting to obtain a solution of an acrylic copolymer (b) having a solid content of 35% by weight. With respect to the obtained acrylic copolymer (b), the weight average molecular weight was measured by GPC method using “2690 Separations Model” manufactured by Water Co. as a column, which was 730,000. The ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) was 2.9.
15 parts by weight of a polymerized rosin ester having a softening point of 150 ° C., 10 parts by weight of terpene phenol having a softening point of 145 ° C., and a rosin ester having a softening point of 70 ° C. with respect to 100 parts by weight of the solid content of the obtained acrylic copolymer (b) 10 parts by weight were added. Further, 15 parts by weight of ethyl acetate (Fuji Chemical Co., Ltd.) and 3.0 parts by weight of an isocyanate-based crosslinking agent (trade name “Coronate L45” manufactured by Nippon Polyurethane Co., Ltd.) were added, stirred, and pressure-sensitive adhesive (B). Got.

(3) Production of double-sided pressure-sensitive adhesive tape A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the pressure-sensitive adhesive (B) was used.

(4) Tensile test In the same manner as in Example 1, the stress of the double-sided adhesive tape was measured when the elongation was 0.5 mm.

(5) Measurement of maximum value of shear storage modulus The maximum value of shear storage modulus was measured in the same manner as in Example 1.

(6) Tack test A tack test was conducted in the same manner as in Example 1.

(Example 7)
In “(1) Production of polyurethane (PU) foam”, the following polyol 4 is used in place of polyol 1, and the isocyanate index is changed to 110, whereby the polyurethane (PU) foam is shown in Table 1. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the above was changed. The polyurethane (PU) foam had open cells and a density of 482 kg / m ³ (0.482 g / cm ³ ). In the same manner as in Example 1, the stress of the double-sided pressure-sensitive adhesive tape when the elongation was 0.5 mm and the maximum value of the shear storage modulus were measured, and a tack test was performed.

Polyol 4 (polyether polyol A (weight average molecular weight 6000, hydroxyl number 3, hydroxyl value 56 mgKOH / g) 60 parts by weight, polyester polyol A (weight average molecular weight 6000, hydroxyl number 3, hydroxyl value 240 mgKOH / g) 40 parts by weight)

(Comparative Example 1)
(1) Polyethylene (PE) foam IF08008 (thickness 0.8 mm, manufactured by Sekisui Chemical Co., Ltd.) was used as a polyethylene (PE) foam. The foamed state of the polyethylene (PE) foam was confirmed in the same manner as in Example 1, and the density, 25% compressive strength, and glass transition point were determined. The polyethylene (PE) foam had closed cells and a density of 0.1 g / cm ³ .

(2) Preparation of pressure-sensitive adhesive A pressure-sensitive adhesive (A) was obtained in the same manner as in Example 1.

(3) Production of double-sided pressure-sensitive adhesive tape A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that polyethylene (PE) foam was used.

(4) Tensile test In the same manner as in Example 1, the stress of the double-sided adhesive tape was measured when the elongation was 0.5 mm.

(5) Measurement of maximum value of shear storage modulus The maximum value of shear storage modulus was measured in the same manner as in Example 1.

(6) Tack test A tack test was conducted in the same manner as in Example 1.

(Comparative Example 2)
In “(1) Polyethylene (PE) foam”, a double-sided pressure-sensitive adhesive tape was prepared in the same manner as Comparative Example 1 except that XLH-1001 (thickness 1 mm, manufactured by Sekisui Chemical Co., Ltd.) was used as the polyethylene (PE) foam. Obtained. The polyethylene (PE) foam had closed cells and a density of 0.07 g / cm ³ . In the same manner as in Comparative Example 1, the stress of the double-sided pressure-sensitive adhesive tape when the elongation was 0.5 mm and the maximum value of the shear storage modulus were measured, and a tack test was performed.

(Comparative Example 3)
In “(1) Production of polyurethane (PU) foam”, a polyurethane (PU) foam is shown in Table 1 by using the polyol 3 shown below instead of the polyol 1 and changing the isocyanate index to 130. A double-sided pressure-sensitive adhesive tape was obtained in the same manner as in Example 1 except that the above was changed. The polyurethane (PU) foam had open cells and a density of 0.51 g / cm ³ . In the same manner as in Example 1, the stress of the double-sided pressure-sensitive adhesive tape when the elongation was 0.5 mm and the maximum value of the shear storage modulus were measured, and a tack test was performed.

Polyol 3 (polyether polyol, weight average molecular weight 1000, hydroxyl number 4, hydroxyl value 30 mgKOH / g)

<Evaluation>
The following evaluation was performed about the double-sided adhesive tape obtained by the Example and the comparative example. The results are shown in Table 1.

(1) Resilience resistance test FIG. 4 is a schematic diagram showing a resilience resistance test of a double-sided pressure-sensitive adhesive tape.
As shown in FIG. 4, using a double-sided pressure-sensitive adhesive tape 4 cut to a length of 150 mm × width of 3 mm, a first restoring force test polycarbonate plate (length 150 mm × width 30 mm × thickness 1 mm) 5 and a second A polycarbonate plate 6 (length 200 mm × width 30 mm × thickness 1 mm) 6 for a resilience test was laminated. The laminate was pressure-bonded using a roller under the condition of 2 kg, and then allowed to stand for 24 hours, to prepare a sample for a resilience test in which two polycarbonate plates were bonded together with a double-sided adhesive tape 4. Under the conditions of 85 ° C. and 90% humidity, the sample for the resilience test is sandwiched between the jigs 7 with the polycarbonate plate 6 for the second resilience test facing up, and the width of the jig 7 is reduced to 165 mm. The sample for a resilience test was warped in a bow shape. Observation of the occurrence of lifting of the double-sided pressure-sensitive adhesive tape 4 in the resilience test sample, x indicates that lifting occurred within 6 hours after bowing, and lifting occurred within 24 hours beyond 6 hours The case was evaluated as Δ, and the case where no floating occurred even after 24 hours was evaluated as ○.

In the resilience test, the double-sided pressure-sensitive adhesive tape of Example 6 had a longer time until the float occurred than the double-sided pressure-sensitive adhesive tape of Example 1. The double-sided pressure-sensitive adhesive tape of Example 1 peeled after 100 hours, but the double-sided pressure-sensitive adhesive tape of Example 6 did not peel for 120 hours or more. This is because the pressure-sensitive adhesive is difficult to soften even at high temperatures and the bulk strength is maintained in addition to the effect due to the stress in the above-described tensile test being within an appropriate range, and the occurrence of peeling (floating) is suppressed for a longer time. It is thought that it was possible.

ADVANTAGE OF THE INVENTION According to this invention, the double-sided adhesive tape excellent in the restoring force can be provided.

1 Double-sided adhesive tape cut to 25 mm x 25 mm 2 Polycarbonate plate with a thickness of 2 mm (length 50 mm x width 50 mm)
3 Jig made of stainless steel with a thickness of 2 mm (30 mm x 30 mm)
4 Double-sided adhesive tape cut to 150 mm length x 3 mm width 5 Polycarbonate plate for first resilience test (length 150 mm x width 30 mm x thickness 1 mm)
6 Polycarbonate plate for second resilience test (length 200 mm x width 30 mm x thickness 1 mm)
7 Jig 8 Foamed cell 17 Stress curve

Claims (7)

A double-sided adhesive tape having an adhesive layer on both sides of a substrate,
A double-sided pressure-sensitive adhesive tape characterized in that the force applied to the double-sided pressure-sensitive adhesive tape when the elongation is 0.5 mm, measured by the following tensile test, is 55 N or less.
(Tensile test)
Using a double-sided adhesive tape cut to 25 mm × 25 mm, a polycarbonate plate having a thickness of 2 mm and a jig made of stainless steel having a thickness of 2 mm are bonded together. After fixing the polycarbonate plate, the stainless steel jig is pulled in the direction perpendicular to the surface at a rate of 0.1 mm / min, and the force applied to the double-sided adhesive tape is measured. In the force-time curve showing the force applied to the double-sided pressure-sensitive adhesive tape at 60 ° C. measured by the following tack test, the integral value from time T1 at which the force is 0 to time T2 at which the maximum force (peak top) is shown is 350 gf · s or more. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein
(Tack test)
A double-sided pressure-sensitive adhesive tape is placed on the plate set at 60 ° C. of the tack tester so that the pressure-sensitive adhesive layer is on top. The non-measurement surface of the double-sided pressure-sensitive adhesive tape is backed with a polyethylene terephthalate film. Next, a cylindrical stainless steel probe having a diameter of 5 mm is pressed against the double-sided adhesive tape at a probe temperature of 60 ° C., a pressing speed of 2 mm / s, and a pressing load of 100 gf, and held in that state for 0.1 second. Thereafter, the probe is pulled up at a lifting speed of 0.2 mm / s. During this period, the force applied to the double-sided adhesive tape is measured. The double-sided pressure-sensitive adhesive tape according to claim 1 or 2, wherein the substrate is a polyurethane foam. The double-sided pressure-sensitive adhesive tape according to claim 1, 2 or 3, wherein the substrate has a thickness larger than 0.9 mm. 5. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the substrate has a density of 490 kg / m ³ or less. 6. The double-sided pressure-sensitive adhesive tape according to claim 1, wherein the substrate has a 25% compressive strength of 38 kPa or less. The double-sided pressure-sensitive adhesive tape according to claim 1, 2, 3, 4, 5 or 6, wherein the thickness of the double-sided pressure-sensitive adhesive tape is 3 mm or less.

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