JPH0761458A - Adhesive sheet - Google Patents

Abstract

PURPOSE:To obtain an adhesive sheet which is excellent both in adhesion strength to an object to be adhered and in an effect for reducing the adhesion strength due to heat foaming. CONSTITUTION:An adhesive sheet comprises a pressure-sensitive adhesive layer 2 with parts with strong adhesion and weak adhesion with a base material 1 distributed on a single face or both faces of the base material l wherein the pressure-sensitive adhesive layer 2 contains foaming agent which foams and/or expands by heating. Thus adhesion characteristics for rigidly adhering to an object with roughened surface to be adhered are maintained, and the pressure-sensitive adhesive layer 2 three-dimensionally deforms due to heating to have an adhered area effectively reduced, so that the sheet can be easily peeled off from the object with drop in adhesion excellent, thereby ensuring easy and secure separation.

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 has been provided on a substrate with a uniform adhesive strength, and is easily peeled from an adherend by a heat foaming treatment in which the foaming agent is foamed or expanded by heating. Adhesive sheets made possible were known. (Japanese Patent Publication No. 50-13878, No. 51-24534, Japanese Patent Laid-Open No. 56-61468, No. 56-6146).
9 and 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]

DISCLOSURE OF THE INVENTION The present invention has a pressure-sensitive adhesive layer on one or both sides of a base material in which a portion having a strong adhesive force with the base material and a portion having a weak adhesive force are distributed. The pressure-sensitive adhesive layer contains a foaming agent that expands and / or expands by heating, and provides an adhesive sheet.

[0008]

[Function] The adhesive force between the base material and the pressure-sensitive adhesive layer has a distribution of strength and weakness, so that the pressure-sensitive adhesive layer in the weak adhesive force portion with weak binding force is peeled off from the base material when heat-foaming is performed. It can be deformed three-dimensionally such as waviness or corrugation by lifting up, and as a result, the reduction of the adhesive area is efficiently achieved and the reduction of the adhesive strength that facilitates peeling is surely realized. To be done.

Therefore, even when a pressure-sensitive adhesive having a large adhesive force to an adherend is used, or when 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 used, heating is performed. By the foaming treatment, the adhesion area can be sufficiently reduced, and the easy peeling from the adherend due to the decrease in the adhesion 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 the substrate, and has a weak adhesion to the substrate. It is provided with the distribution of. An example of this is shown in FIG.
It is shown in FIG. 1 is a base material and 2 and 3 are pressure-sensitive adhesive layers.

The base material serves as a support base for the adhesive sheet, and a plastic film or sheet is generally used. For example, paper, cloth, non-woven fabric, metal foil, or a plastic laminate thereof or a laminate of plastics. An appropriate thin leaf body such as a body may be used. Further, a substrate having an embossed surface or the like may be used. The thickness of the substrate is
5 to 250 μm is general.

Further, as the substrate, a film made of a polymer showing rubber-like elasticity or a foamed film can be used. Further, it may be a substrate having an organic elastic layer made of a polymer showing rubber-like elasticity on the surface. Such an organic elastic base material contributes to the improvement of the adhesive area due to the easy deformability and the promotion of the three-dimensional deformation of the pressure-sensitive adhesive layer during the heat foaming treatment to reduce the adhesive area.

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. The organic elastic layer may be formed of a pressure-sensitive adhesive substance whose main component is a polymer showing rubber-like elasticity.

Polymers exhibiting rubber-like elasticity that can be preferably used are 50 or less, and especially 40 or less, based on the Shore D type hardness by the D type Shore of ASTM D-2240. When provided as an organic elastic layer on the surface of a base material, the thickness is generally 0.1 to 150 μm. When the surface layer is provided on the substrate like the organic elastic layer,
It is also possible to obtain a release type adhesive sheet in which the pressure-sensitive adhesive layer together with the surface layer of the substrate is peeled off and applied to an adherend.

The strength distribution of the adhesive force between the base material and the pressure-sensitive adhesive layer is formed by, for example, a method of partially performing a release treatment or an easy-adhesion treatment on one surface or both surfaces of the base material using a mask or the like. It can be carried out. For the release treatment, a known method of reducing the adhesive force such as a method of coating a release agent typified by a silicone resin or a fluororesin may be applied. In addition, for easy adhesion treatment, for example, chromic acid treatment,
Apply known methods to increase adhesion such as ozone or flame exposure, high piezoelectric bombardment, chemical or physical treatment that oxidizes the surface by ionizing radiation treatment, or coating a primer layer. Good.

Therefore, when the base material has a strong adhesive property made of a polymer having a high polarity such as polyester, it is possible to improve the adhesive force with the pressure-sensitive adhesive layer by partially performing the releasing treatment. It can have a strong and weak distribution. On the other hand, when the base material has a weak adhesive property made of a non-polar polymer such as polyethylene or polypropylene, a partial distribution of the above-mentioned easy-adhesion treatment gives a strong and weak distribution to the adhesive force with the pressure-sensitive adhesive layer. Can be held.

When the surface of the base material has irregularities due to embossing or fiber components, the pressure-sensitive adhesive layer is provided so as to adhere to the convex portions but not to the concave portions. It is also possible to give a distribution of strength to the adhesive force between the pressure sensitive adhesive layer and the adhesive layer.

The above-described partial application such as the releasing treatment or the easy-adhesion treatment is also carried out by a method of partially applying an arbitrary pattern such as dots or lines by a gravure printing method, a screen printing method or the like. be able to. In the case of the above-mentioned surface oxidation method, a treatment method through a mask having a predetermined hole pattern or the like is advantageous from the viewpoint of treatment efficiency and the like, but the mask material is the one exemplified in the above base material. And the like can be appropriately selected and used according to the treatment method.

In the present invention, the distribution state of the strong adhesive portion and the weak adhesive portion between the base material and the pressure-sensitive adhesive layer is such that the strong portion and the weak portion are alternately arranged in the same area as possible. It is preferable. Further, the size of the area of the strong and weak sections is appropriately determined depending on the adhesive strength, the heat-foaming treatment condition, etc. 1 ~ 900m
m ² is preferably 1 to 100 mm ² , especially 1 to 25 mm ² .

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. An appropriate pressure-sensitive adhesive or the like can be used, and an ultraviolet-curable adhesive or the like can also be used (JP-A-56-61468, JP-A-61-17).
4857, 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 the adherend, and when the pressure-sensitive adhesive is mixed with a foaming agent, it is foamed and / or heated. A pressure sensitive adhesive layer that expands can be formed. That is, an appropriate method in accordance with the method of forming an adhesive tape such as a method of coating a pressure-sensitive adhesive containing a foaming agent on a substrate or a method of transferring an adhesive layer formed on a separator to a substrate. A pressure sensitive adhesive layer can be formed.

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 for 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 appropriately determined according to the intended degree of reduction in adhesive strength, etc., but is generally 10% by weight or more, preferably 15 to 95.
%, Especially 20-80% by weight. The thickness of the pressure-sensitive adhesive layer and the expansion ratio are appropriately determined depending on the surface shape and material of the adherend, and are generally 3 to 70 μm. The expansion ratio is preferably designed 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 superposed form may be formed according to the above-mentioned foaming agent-containing pressure-sensitive adhesive layer, or as a mixed layer of the foaming agent and the binder. May be. 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 above-mentioned mixed layer of the foaming agent and the binder, when the adhesive sheet adhered to the adherend is peeled off from the adherend at any time, the strength of the adhesion to the base material is increased by the heat-foaming treatment. A volume change is given to the pressure-sensitive adhesive layer based on the distribution 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 described above.

The layer containing no foaming agent in the pressure-sensitive adhesive layer in the form of superposition may be formed by using a pressure-sensitive adhesive containing no foaming agent according to the above-mentioned pressure-sensitive adhesive layer containing a foaming agent. it can. The thickness of the layer containing no blowing agent is
It is preferable that the distance between the adherend and the foaming agent-containing layer is as short as possible so as to improve the peelability, but it is preferable that the thickness is about 0 in consideration of workability of forming and adhesion to the adherend. 1-50μ
m, especially 0.5 to 30 μm is preferable.

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, the adhesive strength between the base material and the pressure-sensitive adhesive layer has a strong and weak distribution, so that the adhesive property of firmly adhering even to a rough surface type adherend or the like In addition, the pressure-sensitive adhesive layer is three-dimensionally deformed by heat treatment to effectively reduce the adhesive area, and the adhesive strength is excellently reduced, allowing easy peeling from the adherend, and easy separation. In addition, it can be performed reliably.

[0037]

【Example】

Example 1 A substrate having a 25 μm-thick polyester film coated with a thermosetting silicone resin in a dot pattern having a diameter of 1 mm and an interval of 1 mm by a gravure coater and heat-cured to disperse the release-treated portions. A pressure-sensitive adhesive layer containing a foaming agent having a thickness of 40 μm was provided on the surface to obtain an adhesive sheet of the present invention. The foaming agent-containing pressure-sensitive adhesive layer was prepared by adding 5 parts of a terpene-based tackifying resin and heat-expandable microspheres to a solution of a copolymer consisting of 90 parts of butyl acrylate (parts by weight; the same applies hereinafter) and 10 parts of acrylic acid. (Average particle size 15 μm, specific gravity 1.01, same below)
30 parts and 2 parts of a polyisocyanate-based crosslinking agent were blended, and a coating and drying treatment was performed to form them.

Example 2 As a base material, in a laminate of a polyester film having a thickness of 38 μm and a polypropylene film having a thickness of 30 μm, a polypropylene film having a thickness of 12 μm and having a dot-shaped hole pattern having a diameter of 1 mm and an interval of 1 mm was formed on the polypropylene film surface. An adhesive sheet of the present invention was obtained in the same manner as in Example 1 except that masks were superposed on each other, subjected to corona treatment, and used in which the easily adhesively treated portions were distributed.

Example 3 One side of 100 μm thick polyester non-woven fabric has a diameter of 1 m.
An embossed film was adhered to a dot pattern having m and a space of 1 mm, and a foaming agent-containing pressure-sensitive adhesive layer having a thickness of 30 μm was provided thereon to obtain an adhesive sheet of the present invention. In the embossed portion, the foaming agent-containing pressure-sensitive adhesive layer was in a state of not adhering to the base material. The foaming agent-containing pressure-sensitive adhesive layer was added to a solution containing 100 parts of a base polymer composed of an acrylic graft rubber grafted with 20 parts of methyl methacrylate,
10 parts of terpene-based tackifying resin, glass transition point is 180
It was formed by mixing 60 parts of a high softening point resin at 30 ° C., 30 parts of heat-expandable microspheres and 2 parts of a vulcanizing agent, and coating and drying it.

Comparative Example An adhesive sheet was obtained in the same manner as in Example 1 except that the base material that was not subjected to the release treatment was used.

Evaluation test Adhesive sheets with a width of 20 mm obtained in the examples and comparative examples were used in a thickness of 2
Adhesion to a 5 μm polyester film and its 180 degree peel adhesion (peel film peeling, peeling speed 300 mm / min, 23 ° C.) is measured. Adhesion before heating (initial) and heat treatment at 170 ° C. for 45 seconds After that, the adhesive strength was examined.

The above results are shown in Table 1.

[Table 1]

From the enlarged photographs of the states of the adhesive sheets of Examples and Comparative Examples after the heat treatment, it is found that the pressure-sensitive adhesive layer is three-dimensionally deformed to form a waviness structure in each Example. Was confirmed. 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. No state structure formation was 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 2, 3: Pressure-sensitive adhesive layer 31: Layer containing foaming agent 32: Layer containing no foaming agent

Claims (3)

[Claims] 1. A pressure-sensitive adhesive layer in which a portion having strong adhesion to the substrate and a portion having weak adhesion are distributed on one or both sides of the substrate, and the pressure-sensitive adhesive layer is foamed by heating. as well as/
Alternatively, an adhesive sheet containing a foaming agent that expands. 2. The adhesive sheet according to claim 1, wherein one surface or both surfaces of the base material is partially subjected to a release treatment or an easy adhesion treatment. 3. The pressure-sensitive adhesive layer is foamed and / or heated by heating.
Alternatively, the adhesive sheet according to claim 1 or 2, which is composed of a superposed layer of a layer which contains a expanding foaming agent and is capable of thermal expansion and a layer which does not contain the expanding agent.