JPH0796964A - Adhesive sheet - Google Patents

Abstract

PURPOSE:To obtain an adhesive sheet which is excellent in both adhesive strength of an applied body an decreasing effect of the adhesive strength due to the heat-foaming treatment. CONSTITUTION:A base material 1 is provided with a pressure-sensitive adhesive layer 2 having substantially a flat but uneven thickness-distribution surface at one or both sides thereof. The pressure-sensitive adhesive layer 2 includes a foaming agent foaming and/or swelling with heat. Thereby, a firm adhesive characteristics can be obtained even against a coarse-surface material and the pressure-sensitive adhesive layer deforms three-dimensionaly with heat and the adhesion area decreases effectively and the adhesive force also decreases effectively. And hence, the sheet can be easily, simply, and securely separated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive sheet which has excellent adhesive strength and can be easily peeled from an adherend by heat treatment at any time.

[0002]

2. Description of the Related Art Conventionally, a pressure-sensitive adhesive layer containing a foaming agent is provided on a substrate in a uniform thickness, and the foaming agent is easily foamed or expanded by heating so that it can be easily peeled from an adherend. The adhesive sheet that was made was known. (Japanese Patent Sho 50
No. 13878, No. 51-24534, Japanese Unexamined Patent Publication No. 56-61468, No. 56-61469, No. 60-252681).

However, due to the decrease in the adhesive strength due to the inclusion of the foaming agent, it is difficult to develop sufficient adhesive strength to an adherend, and in order to supplement the decrease in the adhesive strength, heat-foaming is performed when a pressure-sensitive adhesive having a large adhesive strength is used. There was a problem that the adhesive strength was not sufficiently reduced even when treated, and the peelability from the adherend was poor.

On the other hand, in order to overcome the above-mentioned problem of lowering the adhesive strength due to the inclusion of a foaming agent, an adhesive sheet has been proposed in which a pressure-sensitive adhesive layer containing no foaming agent is provided on a pressure-sensitive adhesive layer containing a foaming agent. (Japanese Patent Laid-Open No. 63-186791).

However, although the controllability such as the increase of the adhesive strength with respect to the adherend can be overcome by providing the pressure-sensitive adhesive layer containing no foaming agent, the adhesive strength is decreased due to the decrease of the adhesive area in the case of the heat foaming treatment. The decrease was not sufficient, and even in this case, there was a problem that it was difficult to obtain a satisfactory peeling effect.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to develop an adhesive sheet which is excellent in both the adhesive strength with respect to an adherend and the effect of reducing the adhesive strength by the heat foaming treatment.

[0007]

SUMMARY OF THE INVENTION The present invention has a pressure-sensitive adhesive layer on one or both sides of a substrate, the pressure-sensitive adhesive layer having a thin and thin distribution of thickness and having a substantially planar surface. Provided is an adhesive sheet, wherein the adhesive layer contains a foaming agent that expands and / or expands by heating.

[0008]

[Function] By providing the pressure-sensitive adhesive layer with a thickness distribution, it is possible to impart a three-dimensional deformation such as a waviness or a wavy shape based on a change in the foam thickness when heat-foaming. As a result, the reduction of the adhesive area is efficiently achieved, and the reduction of the adhesive strength that facilitates the peeling from the adherend is surely realized. Further, by using the pressure-sensitive adhesive layer whose surface is in a substantially flat state, securing an adhesive force by a large adhesive area and sealing and adhering to an adherend can be achieved.

Therefore, a method using a pressure-sensitive adhesive having a large adhesive force to an adherend or a method using a pressure-sensitive adhesive layer having a layered structure containing a layer containing a foaming agent and a layer not containing a foaming agent is sufficient for an adherend. Even if a sufficient adhesive force is given, the bonding area can be sufficiently reduced by the heat foaming treatment, and the easy peeling from the adherend due to the decrease in the bonding strength can be surely achieved.

[0010]

Examples of constituent elements of the invention: The adhesive sheet of the present invention has a pressure-sensitive adhesive layer containing a foaming agent that expands and / or expands upon heating, on one or both sides of a substrate, and has a thickness distribution. Moreover, it is provided so that the surface thereof is substantially flat. Examples thereof are shown in FIGS. 1 and 2. 1 is the base material,
2 and 3 are pressure sensitive adhesive layers. Reference numeral 11 is a hole provided in the base material 1.

In the present invention, the pressure-sensitive adhesive layer having a thin and thick distribution in which thin and thick portions are distributed is formed based on a change in the thickness of the base material, and the pressure-sensitive adhesive layer is attached. Can be carried out by an appropriate method such as a method based on, or a method using them together. The method based on the change in the thickness of the base material is preferable from the viewpoint of easily and efficiently forming the pressure-sensitive adhesive layer having a substantially flat surface by a small amount of work.

As a method for providing a pressure-sensitive adhesive layer with a thickness distribution based on a change in the thickness of the base material, for example, a base material having a thickness distribution such as a fiber processed product, a mesh body or an embossed product. , Or / and a method in which pores are distributed can be used. In this case, by applying a pressure-sensitive adhesive layer to the substrate by a method according to a conventional adhesive tape forming method such as a coating method or a transfer method for those formed on a separator, the surface is in a substantially planar state. In addition, a pressure-sensitive adhesive layer having a thickness distribution based on the unevenness of the substrate can be obtained.

The material of the substrate used is not particularly limited, and may be, for example, a processed fiber such as paper, cloth, or non-woven fabric, a plastic or rubber-like polymer film or foamed film or mesh, a metal foil or a wire mesh, or Appropriate thin sheets that can serve as a support base of the adhesive sheet, such as those plastic laminates, laminates of plastics, and those having an organic elastic layer made of a polymer showing rubber-like elasticity on the surface, can be used.

A film or foamed film of the above-mentioned polymer exhibiting rubber-like elasticity, or such a polymer layer is added to
The organic elastic base material having a thickness of about 1 to 150 μm on the surface facilitates the improvement of the adhesive area due to the easy deformation and facilitates the three-dimensional deformation of the pressure-sensitive adhesive layer during the heat-foaming treatment to improve the adhesive area. Contribute to reduction.

Examples of the rubber-like polymer exhibiting rubber-like elasticity include natural rubber, synthetic rubber such as nitrile series, diene series, acrylic series, thermoplastic elastomers such as polyolefin series and polyester series, ethylene-vinyl acetate copolymer. , Polyurethane, polybutadiene, soft polyvinyl chloride, and other synthetic resins having rubber elasticity. Polymers showing rubber-like elasticity that can be preferably used are
It is 50 or less, especially 40 or less, based on the Shore D type hardness by D type Shore of ASTM D-2240.

The thickness of the substrate may be appropriately determined, but is generally about 5 to 250 μm. In the case of a base material having a thickness distribution, its thickness change is appropriately determined by the thickness of the pressure-sensitive adhesive layer to be provided, etc., but is generally 1 to 250 μm.
It is about m. The unevenness of the base material can also be achieved by embossing, dispersal and mixing of particles, perforation, or the like.

The pressure-sensitive adhesive layer having a thickness distribution based on the attachment form of the pressure-sensitive adhesive layer can be obtained by pattern coating with a solid-coated pressure-sensitive adhesive layer by a gravure printing method, a screen printing method, or the like. It can be carried out by a method of overlapping a pressure-sensitive adhesive layer such as a dotted or linear shape. In this case, the surface in a planar state is achieved on one side of the solid-coated pressure-sensitive adhesive layer, and can be used as an adhesive sheet in a form sandwiched by separators or the like for the purpose of adhering the temporarily fixed product to the main body.

The thickness distribution of the pressure-sensitive adhesive layer is appropriately determined depending on the adhesive strength and the conditions of the heat-foaming treatment, but the thick portion and the thin portion are alternately arranged in the same area as possible. The area size of the thick and thin compartments is preferably 0.1 to 900 mm ² , particularly 1 to 1 from the viewpoint of the decrease in the adhesive area due to three-dimensional deformation during heat foaming.
300 mm ^2, in particular 1 to 25 mm ² is generally preferred, in the present invention can sufficiently achieve the object even when the thickness thin distribution based on a mesh or net-like base material.

The thickness of the pressure-sensitive adhesive layer, especially the thickness of the foaming agent-containing layer is appropriately determined depending on the surface shape and material of the adherend, but generally 0 based on the thickness of the thin portion. ~ 100μ
m, especially 5 to 70 μm. Further, the difference between the thin portion and the thick portion is appropriately determined by the three-dimensional deformation amount during the heat-foaming treatment depending on the surface shape and material of the adherend, the foaming ratio, and the like. Since the amount of deformation may be small and the peelability may be impaired, it is preferable to make unevenness of 10 μm or more, especially 50 μm or more, by the heat foaming treatment.
m to 1 mm, especially 2 to 500 μm, especially 5 to 300 μm. Therefore, such a thickness difference can be easily provided even based on the unevenness of the base material.

The pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer includes a rubber-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a styrene / conjugated diene block copolymer-based pressure-sensitive adhesive, and a silicone-based pressure-sensitive adhesive. Appropriate adhesives and the like can be used, and ultraviolet curable adhesives and the like can also be used (JP-A-56-61468, JP-A-61-174).
857, JP-A-63-17981).

[0021] Further, those which contain a hot-melting resin having a melting point of about 200 ° C or less to improve the creep property, and those which have a low adhesive strength at room temperature and exhibit sufficient adhesive strength by heating. A pressure sensitive adhesive may also be used (Japanese Patent Publication No.
-13040, Japanese Patent Publication No. 2-50146, and Japanese Patent Laid-Open No. 56-13040). The pressure sensitive adhesive is
If necessary, a crosslinking agent, a tackifier, a plasticizer, a filler,
It may be a mixture of appropriate additives such as an anti-aging agent.

More specifically, for example, a rubber-based pressure-sensitive adhesive containing natural rubber or various synthetic rubbers as a base polymer,
Methyl group, ethyl group, propyl group, butyl group, 2-ethylhexyl group, isooctyl group, isononyl group, isodecyl group, dodecyl group, lauryl group, tridecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, Acrylic acid-based alkyl esters such as acrylic acid and methacrylic acid having an alkyl group having 20 or less carbon atoms such as eicosyl group, and acrylic acid having functional group-containing groups such as hydroxyethyl group, hydroxypropyl group and glycidyl group And acrylic acid containing methacrylic acid and other esters, acrylic acid, methacrylic acid, itaconic acid, N-methylolacrylamide, acrylonitrile, methacrylonitrile, vinyl acetate, styrene, isoprene, butadiene, isobutylene, vinyl ether, etc. Such as acrylic pressure-sensitive adhesive and the like to the system a polymer as a base polymer

The pressure-sensitive adhesive is appropriately selected and used according to the purpose of use of the adhesive sheet such as the adhesive strength to an adherend, and the pressure-sensitive adhesive layer that foams and / or expands by heating is
It can be formed by blending the pressure-sensitive adhesive with a foaming agent.

As the foaming agent, various kinds can be used which can achieve the above-mentioned object. Therefore, for example, when a heat-sensitive pressure sensitive adhesive is used, a foaming agent that foams and / or expands at a temperature higher than the bonding treatment temperature of the adhesive is used. Examples of foaming agents that can be used include decomposition-type inorganic foaming agents such as ammonium carbonate, ammonium hydrogen carbonate, sodium hydrogen carbonate, ammonium nitrite, sodium borohydride, and azides.

An organic foaming agent such as an azo compound may also be used. Examples thereof include fluorinated alkanes such as trichloromonofluoromethane and dichloromonofluoromethane, azo compounds such as azobisisobutyronitrile and azodicarbonamide, barium azodicarboxylate, paratoluenesulfonyl hydrazide and diphenyl sulfone-. 3,3'-disulfonyl hydrazide, 4,4'-
Hydrazine compounds such as oxybis (benzenesulfonylhydrazide) and allylbis (sulfonylhydrazide), ρ-toluylenesulfonyl semicarbazide and 4,
Semicarbazide compounds such as 4'-oxybis (benzenesulfonyl semicarbazide), 5-morpholyl-
Triazole compounds such as 1,2,3,4-thiatriazole, N-nitroso compounds such as N, N'-dinitrosopentamethylenetetramine and N, N'-dimethyl-N, N'-dinitrosoterephthalamide , Other low boiling point compounds, and the like.

Further, in the present invention, as a foaming agent, for example, a suitable substance such as isobutane, propane and pentane which is easily gasified and exhibits thermal expansion property is included in the shell forming substance by the coacervation method or the interfacial polymerization method. Heat-expandable microspheres can also be used. The average particle size of the heat-expandable microspheres used is generally 1 to 50 μm.

As the shell-forming substance forming the heat-expandable microspheres, for example, vinylidene chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl butyral, polymethyl methacrylate, polyacrylonitrile, polyvinylidene chloride, polysulfone, etc. are generally used. However, in the present invention, it may be made of a heat-meltable substance or a substance that is destroyed by thermal expansion.

The content ratio of the foaming agent in the pressure-sensitive adhesive layer is
Although it is appropriately determined depending on the degree of reduction in the adhesive strength, etc., it is generally 10% by weight or more, preferably 15 to 95% by weight, particularly 20 to 80% by weight. The expansion ratio of the pressure-sensitive adhesive layer is appropriately determined depending on the surface shape, material, etc. of the adherend, but it is generally preferable to design the expansion ratio to be about 1.5 to 100 times.

In the present invention, as illustrated in FIG. 2, the pressure-sensitive adhesive layer may be formed as a superposed layer of a layer 31 containing a foaming agent and capable of thermal expansion and a layer 32 containing no foaming agent. The pressure-sensitive adhesive layer 3 in the overlapping form has an advantage that the adhesive strength of the layer containing no foaming agent to be adhered to the adherend can be easily controlled.

The foaming agent-containing layer in the pressure-sensitive adhesive layer in the overlapping form may be formed according to the above-mentioned foaming agent-containing pressure-sensitive adhesive layer, or may be formed as a mixed layer of the foaming agent and the binder. Good. As the binder, a generally known polymer such as a rubber-based or resin-based polymer that allows foaming and / or expansion of the foaming agent, preferably one that does not restrain foaming and / or expansion of the foaming agent as much as possible. To be

The mixed layer of the foaming agent and the binder is pressure-sensitive on the basis of the thickness distribution by the heat-foaming process when the adhesive sheet adhered to the adherend is peeled from the adherend at any time. A volume change is given to the adhesive layer to reduce the adhesive area with the adherend, and the adhesive sheet can be easily peeled from the adherend. Such a mixed layer can be formed by using a binder instead of the pressure sensitive adhesive, and the thickness, the content ratio of the foaming agent and the like can be the same as those of the pressure sensitive adhesive layer containing the foaming agent.

The layer containing no foaming agent in the pressure-sensitive adhesive layer in the superposed form can be formed by using a pressure-sensitive adhesive containing no foaming agent, in the same manner as the above-mentioned pressure-sensitive adhesive layer containing a foaming agent. The thickness of the layer containing no foaming agent is preferably as thin as possible from the point of improving the releasability by making the distance between the adherend and the foaming agent-containing layer as close as possible. Considering the adhesiveness to etc., it is preferably about 0.1 to 50 μm, especially 0.5 to 5 μm. In the present invention, the surface of the pressure-sensitive adhesive layer may be flattened by pressing, heating laminating or the like, if necessary.

The adhesive sheet of the present invention can be firmly adhered to an adherend at the time of adhering, and can be easily peeled or separated from the adherend by a heat foaming treatment when it is desired to release the adhered state. Therefore, it can be used for permanent adhesion of adherends composed of appropriate articles, etc., but a preferable application is to bond the adherends for a predetermined period of time and then to release the adhesion state after achieving the adhesion purpose, or desired. It is the intended use.

There are various applications for the above. Incidentally, examples thereof include formation of an adhesive composite for recycling two or more articles, for example, an article made of a polymer and an article made of metal, fiber, paper, or the like, various electric devices or electronic devices, and display devices. Such as carrier tape for transporting and temporarily fixing parts in the assembly process such as etc., temporary fixing material or fixing material, surface protection material and masking material for the purpose of preventing contamination damage of metal plate, plastic plate, glass plate etc. It can be used for many purposes.

The heat treatment conditions for allowing the adhesive sheet to be easily peeled off from the adherend are such that the surface area of the adherend and the type of foaming agent can reduce the adhesive area, the substrate and the adherend. Although it is determined by the heat resistance and other conditions, general conditions are 100 to 250 ° C. and 1 to 90 seconds. The heat treatment can be performed at an appropriate stage depending on the purpose of use.

[0036]

EFFECTS OF THE INVENTION According to the adhesive sheet of the present invention, since the pressure-sensitive adhesive layer has a thickness distribution, the adhesive sheet can be adhered to a rough surface type adherend firmly, The pressure-sensitive adhesive layer is three-dimensionally deformed by the treatment and the adhesive area is efficiently reduced, and the adhesive strength is excellent and it can be easily peeled from the adherend, and the separation is performed easily and reliably. be able to.

[0037]

【Example】

Example 1 On one surface of a polyester non-woven fabric having a thickness of 100 μm, a depth of 5
A film with embossed dot-like pattern of 0 μm, diameter 1 mm, and interval 1 mm is adhered, and a pressure-sensitive adhesive containing a foaming agent is applied on top of it, which is heated and laminated at a linear pressure of 5 kg / cm and a temperature of 50 ° C. By processing, an adhesive sheet of the present invention having a pressure sensitive adhesive layer containing a foaming agent having a thin layer portion with a thickness of 30 μm and a flat surface was obtained. The embossed portion was in a state of being filled with the foaming agent-containing pressure-sensitive adhesive layer.

The pressure-sensitive adhesive containing a foaming agent used above is a terpene-based tackifier added to a solution containing 100 parts of a base polymer composed of an acrylic graft rubber grafted with 20 parts (parts by weight, the same hereinafter) of methyl methacrylate. Resin 1
0 part, 60 parts of high softening point resin having a glass transition point of 180 ° C.,
30 parts of heat-expandable microspheres (average particle size: 15 μm, specific gravity: 1.01, the same applies hereinafter) and 2 parts of a vulcanizing agent were blended.

Example 2 A polyester film having a thickness of 50 μm treated with a release agent was coated with a pressure-sensitive adhesive containing a foaming agent to give a thickness of 40 μm.
Foaming agent containing pressure sensitive adhesive layer of 50μm thick
Polyamide mesh (100 mesh) is pressure-bonded on both sides and linearly heated at a pressure of 5 kg / cm at a temperature of 50 ° C for laminating to form a thin layer with a thickness of 20 μm. An adhesive sheet of the invention having layers was obtained. The foaming agent-containing pressure-sensitive adhesive layer was buried in the pores of the mesh.

The pressure-sensitive adhesive containing a foaming agent used in the above is a solution of a copolymer consisting of 90 parts of butyl acrylate and 10 parts of acrylic acid, 5 parts of a terpene-based tackifying resin and 30 heat-expandable microspheres. Parts and polyisocyanate crosslinking agent 2
It is a mixture of parts.

Example 3 Example ² except that a polyester non-woven fabric having a thickness of 50 μm (basis weight: 80 g / m ² ) was used in place of the polyamide mesh.
An adhesive sheet of the present invention was obtained according to the above.

Comparative Example An adhesive sheet was obtained in the same manner as in Example 1 except that a flat polyester film having a thickness of 50 μm was used as a substrate.

Evaluation test Adhesive sheets with a width of 20 mm obtained in the examples and comparative examples were made to have a thickness of 1
Adhesion to 50μm polyester film, 180
Degree peel adhesive strength (peel rate 300 mm / min, 23 ° C)
The adhesive strength after heat treatment for 5 seconds was examined.

The above results are shown in Table 1.

[Table 1]

An enlarged photograph (120 times) of the state of the adhesive sheets of Examples and Comparative Examples after heat treatment was taken.
From each of the examples, it was confirmed that the pressure-sensitive adhesive layer was three-dimensionally deformed to form a waviness structure. On the other hand, in the case of the comparative example, the pressure-sensitive adhesive layer had almost the same thickness, and small irregularities based on the size of the foamed and / or expanded state were formed as in the case of the example, but the whole was wavy. Was not observed.

[Brief description of drawings]

FIG. 1 is a sectional view of an example.

FIG. 2 is a sectional view of another embodiment.

[Explanation of symbols]

 1: Base material 11: Pore 2, 3: Pressure-sensitive adhesive layer 31: Layer containing a foaming agent 32: Layer containing no foaming agent

Front page continuation (72) Inventor Kaoru Aizawa 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation

Claims (4)

[Claims] 1. A pressure-sensitive adhesive layer having a thin and thin distribution of thickness and having a substantially planar surface, which is foamed and / or foamed by heating. Alternatively, an adhesive sheet containing a foaming agent that expands. 2. The adhesive sheet according to claim 1, wherein the substrate has a thickness distribution and / or a pore distribution. 3. The adhesive sheet according to claim 2, wherein the base material is a fiber product, a mesh body or an embossed body. 4. The adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer comprises a superposed layer of a layer which contains a foaming agent which expands and / or expands by heating and which can be thermally expanded, and a layer which does not contain the foaming agent. .