JPH0570744A - Heat-sensitive composite adhesive sheet and production thereof - Google Patents

Abstract

PURPOSE:To provide the title sheet without difficulties to produce and its production method. CONSTITUTION:The title sheet having transparency is produced by forming, directly or indirectly, a heat-sensitive adhesive layer 1 on both sides of a resin layer 2 which is curable with electron beam. The adhesive layer 1 softens at 110 deg.C or lower, can be thermally laminated into a post card sheet, and exhibits a T-peel strength (at 20 deg.C, a relative humidity of 65%, and a peeling speed of 300mm/min) at the interface of the adhesive layer 1 and the resin layer 2 of 10-200g/50mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite sheet having a multilayer structure having a heat-sensitive adhesive property, and more particularly to a heat-sensitive adhesive composite sheet which can be easily peeled from a central laminated portion and a method for producing the same.

[0002]

2. Description of the Related Art With the recent increase in the amount of information, the amount of information is 2 to 3 in comparison with a normal postcard from the viewpoint of saving shipping cost.
Various postcards have been proposed, such as a postcard that can be doubled and a postcard that can conceal recorded contents from the viewpoint of protecting the privacy of individuals.

Among them, the one in which the heat-sensitive adhesive films are temporarily adhered to each other in a peelable manner is particularly preferable because it is excellent in privacy protection because it is easy to use, easy to manufacture and does not re-adhere.

A postcard using such a heat-sensitive adhesive film is
For example, a heat-sensitive adhesive film may be thermocompression-bonded to a recording surface at a sufficiently high temperature to be adhered, and then folded to bring the heat-sensitive adhesive films into close contact with each other, and then pressure-bonded at a temperature lower than the above temperature to thereby bond the heat-sensitive adhesive films to each other. It is produced by a method such as temporarily peeling off, or by providing a pressure-sensitive adhesive layer on one surface of the heat-sensitive adhesive film, press-bonding the recording surface to the layer, then folding and heat-sealing.

However, in the case of the former method, peeling may occur on the recording surface against the intention and the recorded contents may become unclear or destroyed. Further, in the latter case, the above-mentioned inconvenience is avoided, but it is complicated because it is necessary to strictly control the heat-sealing condition and the heat-sealing condition must be changed according to the type of recording paper.

[0006]

A drawback of the invention is that recording sheets on which information having already been recorded are provided with layers having stronger adhesiveness on both sides of a temporary adhesive sheet in which heat-sensitive adhesive films are preliminarily adhered to each other in a peelable manner. It is solved by a method of sandwiching and thermocompression bonding, but since such an adhesive sheet requires a treatment such as extrusion coating of a thermal adhesive layer or coating liquid coating on both surfaces of a composite sheet that is removably temporarily adhered, The process is not simple and there is a disadvantage in terms of cost.

The inventors of the present invention have made extensive studies to solve the above-mentioned drawbacks, and as a result, they can be thermocompression-bonded to paper or film.
A composite sheet having an electron beam-curable resin layer directly or indirectly provided between at least two thermoplastic resin layers is irradiated with an electron beam to cure the electron beam-curable resin. The inventors have found that a heat-sensitive adhesive composite sheet functioning as a heat-sensitive adhesive film can be easily obtained, and have reached the present invention.

Therefore, a first object of the present invention is to provide a heat-sensitive adhesive film having excellent manufacturability. The second object of the present invention is to provide a novel method for producing a heat-sensitive adhesive film.

[0009]

The above-mentioned various objects of the present invention are transparent heat-sensitive adhesive composite sheets in which heat-sensitive adhesive layers are directly or indirectly provided on both sides of an electron beam curable resin layer. The heat-sensitive adhesive layer has a softening point of 110 ° C. or less, has thermal adhesiveness capable of thermal lamination with a postcard sheet, and has an interfacial peel strength of 20 ° C. relative to the electron beam curable resin layer. The heat-sensitive adhesive composite sheet and the method for producing the same have a T-type peel strength of 10 to 200 g / 50 mm measured at a peeling speed of 300 mm / min in an environment of a humidity of 65%.

The heat-sensitive adhesive layer in the present invention is non-peeling (that is, it does not peel without destroying recorded information) when it is superposed on a recorded sheet and heated. It means a layer having transparency to adhere. Such a layer is a known heat-sensitive adhesive thermoplastic film, the above-mentioned thermoplastic film integrated with a transparent support in a non-peeling manner, or a known heat-sensitive adhesive layer on one surface of the transparent support. Any of the provided films may be used, and in the present invention, the same kind of film may be used as a pair, or different kinds of films may be used as a pair. The transparent support may be a laminate of two or more layers. Examples of the transparent support include polyethylene terephthalate, polyethylene, polypropylene and the like.

The thickness of the heat-sensitive adhesive layer is 20 to 5 on one side.
It is preferably 0 μm. The above-mentioned thermoplastic resin film has a T-type peel strength of 20 ° C. and 65% RH when it is thermocompression-bonded to a paper sheet or film at 110 ° C. or lower.
(RH represents relative humidity) is not particularly limited as long as it is a resin having a peeling speed of 300 mm / min or more and 300 g / 50 mm or more under an environment of (RH), particularly an acrylic resin, an ethylene / vinyl acetate copolymer, Vinyl chloride / vinyl acetate copolymer resin, ethylene / ethyl acrylate copolymer resin,
It is preferable to use an ionomer resin, a polyvinyl formal resin, and a polyvinyl butyral resin, which are appropriately selected and used alone or in combination.

When a heat-sensitive adhesive layer having a heat-sensitive adhesive layer provided on one surface of a transparent support is used as the heat-sensitive adhesive layer,
As the heat-sensitive adhesive layer, any resin selected from an ethylene-based copolymer polyolefin having a Vicat softening point of 50 ° C. or higher, a low-density polyolefin, a vinyl acetate-based copolymer polyolefin, and an ionomer resin dispersion and a glass transition temperature are Aqueous ethylene / vinyl chloride copolymer resin emulsion at 0 ° C or higher, resin mixing ratio 90/1
It is preferable to use a mixture in the range of 0-40 / 60 as the coating liquid.

The electron beam curable resin is not particularly limited as long as it is a radiation curable resin having an unsaturated double bond in the molecule, but in particular, it is a polyfunctional vinyl ether, a polyfunctional (meth) acrylate or a polyfunctional (meth) acrylate. Suitable selection from functional oligo (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, polyurethane (meth) acrylate, polyol (meth) acrylate, polyamide (meth) acrylate and polysiloxane (meth) acrylate. It is preferable to use them alone or as a mixture of two or more kinds.

Further, if necessary, at least one selected from the group consisting of monofunctional (meth) acrylate, vinyl ether, allyl ether, acrylamide derivative and N-vinylpyrrolidone can be used as a diluent.

In the present invention, even when the electron beam curable resin is directly provided between the two thermoplastic resin films functioning as the heat-sensitive adhesive layer, the transparent resin film having the thermoplastic resin film or the heat-sensitive adhesive layer is provided. Even when it is provided indirectly through a support, it can be performed by applying an electron beam curable resin liquid or a liquid containing the same onto the thermoplastic resin film or the support according to a known method. it can. The thickness of the electron beam curable resin layer is preferably 5 to 30 μm.

The heat-sensitive adhesive composite sheet of the present invention is obtained by irradiating the composite sheet having an electron beam-curable resin layer between the heat-sensitive adhesive layers obtained as described above with an electron beam. Obtainable. In this case, the adhesive strength at the electron beam curable resin interface can be appropriately adjusted by adjusting the electron beam irradiation amount and the processing speed.

The electron beam irradiation dose varies depending on the electron beam curable resin used, the thermoplastic resin film sandwiching it, etc., but is usually 1.5 Mrad to 20 Mrad, preferably 3 Mrad to 10 Mrad. As a result, the T-type peel strength at the interface of the electron beam curable resin is 2
In an environment of 0 ° C. and 65% RH, a peeling speed of 300 mm / min, a range of 10 to 200 g / 50 mm, particularly 20 to 150
The range of g / 50 mm is preferable. When the T-type peel strength is 10 g / 50 mm or less, when the heat-sensitive adhesive composite sheet of the present invention is used as a temporary adhesive sheet for postcards as described below, there is a risk of peeling during mailing,
When it is 200 g / 50 mm or more, not only curling occurs when the laminated recording sheets are peeled off, but also the recording sheets may be damaged.

The heat-sensitive adhesive composite sheet of the present invention has a conventional structure of 4
Since the manufacturing process can be simplified compared to a multi-layer structure of more than two layers, it is advantageous in terms of manufacturing cost, and when used as a temporary adhesive sheet for postcards, two heat-sensitive adhesive layers with transparency are laminated. Since the layers are reliably separated, the recorded information is not damaged. Further, it is difficult to re-adhere even after thermocompression bonding after peeling, and it is useful from the viewpoint of personal privacy protection. In particular, when the electron beam curable resin is directly sandwiched between the thermoplastic films, it can be easily torn, so that it can be easily discarded, and it is suitable as a means for inexpensively mailing a document belonging to a secret.

[0019]

In the method for producing a heat-sensitive adhesive composite sheet of the present invention, the number of lamination steps conventionally required has been remarkably reduced, so that the homogeneity and reliability of the heat-sensitive adhesive composite sheet obtained are dramatically improved. . Further, originally, a technique such that a thermoplastic resin film is laminated in a peelable manner and the peeling strength thereof is adjusted is extremely difficult, but in the present invention, a processing method that does not use heat at all (electronic It is easy to manufacture because it adopts the wire hardening method).

[0020]

EXAMPLES The present invention will be described in more detail by way of examples, which should not be construed as limiting the invention.

Example 1. It is made of ethylene-ethyl acrylate copolymer obtained by melt extrusion and has a thickness of 30.
An electron beam curable resin (ENTP2000: manufactured by Kansai Paint Co., Ltd.) containing polypropylene glycol as a main component is applied to a thermoplastic resin film having a transparency of μm so as to have a thickness of 15 μm. ,
A transparent thermoplastic resin film having a thickness of 30 μm is overlaid, and a line speed of 20 m /
The heat-sensitive adhesive composite sheet was obtained by curing at a dose of 5 Mrad for 5 minutes (FIG. 1).

The resulting heat-sensitive adhesive composite sheet was cut into a postcard-sized size, and sandwiched between two pieces of the same postcard-sized size and having a basis weight of 64 g / m ² and then heated with a roll heated to 100 ° C. It was thermocompression bonded and sufficiently cooled (Fig. 3). The postcard thus obtained could be easily peeled from the interface between the two transparent heat-sensitive adhesive composite sheets and the electron beam curable resin layer.

At this time, the interfacial peel strength with the electron beam curable resin layer is 120 g / 50 mm as a T-type peel strength at a peeling speed of 300 mm / min in an environment of 20 ° C. and 65% RH.
Met. Further, the paper surface and the thermoplastic resin surface were sufficiently adhered so that they could not be peeled off. Further, the surface once peeled did not re-adhere even when heat was applied, and could be easily torn by hand.

Example 2 Ethylene-vinyl acetate / polyethylene / polyethylene terephthalate = 1 having a thermoadhesive resin layer as the outermost layer = 1
Using a composite film (manufactured by Sanyo Kokusaku Pulp Co., Ltd.) having a structure of 5 μm / 10 μm / 9 μm, the polyethylene terephthalate surface was coated with an electron beam curable resin, and a heat-sensitive adhesive composite sheet was obtained in the same manner as in Example 1 ( (Fig. 2).

The obtained heat-sensitive adhesive composite sheet was sandwiched between postcard-sized high-quality papers as in Example 1, thermocompression-bonded with a roll heated to 100 ° C., and sufficiently cooled. The postcard thus obtained could be easily peeled from the interface between the electron beam curable resin layer and the polyethylene terephthalate surface.

At this time, the interfacial peel strength between the electron beam curable resin layer and the polyethylene terephthalate surface was 20 ° C., 65.
T at a peeling speed of 300 mm / min under the environment of% RH
The mold peel strength was 100 g / 50 mm. Further, the paper surface and the heat-adhesive resin surface were sufficiently bonded so that they could not be peeled off. Further, the surface once peeled did not adhere even if heat was applied again.

Comparative Example 1 A thermoplastic resin film made of an ethylene-ethyl acrylate copolymer obtained in the same manner as in Example 1 and having a thickness of 30 μm and having transparency was prepared by using an electron beam containing polypropylene glycol as a main component. A curable resin (ENTP2000: manufactured by Kansai Paint Co., Ltd.) is applied so as to have a thickness of 15 μm, and then the same thermoplastic resin film having a thickness of 30 μm as that described above is superposed, and an electron beam is applied. The heat-sensitive adhesive composite sheet was obtained by curing with an irradiation device under the conditions of a line speed of 20 m / min and a dose of 1 Mrad.

Thermocompression bonding and cooling were carried out in the same manner as in Example 1. The postcard thus obtained could not be easily peeled off and the paper was damaged. At this time, it was impossible to measure the interfacial peel strength between the electron beam curable resin layer and the thermoplastic resin film.

Comparative Example 2. A polyethylene film was used as the transparent thermoplastic resin film, and the others were laminated in the same manner as in Example 1 to obtain a heat-sensitive adhesive composite sheet. It thermocompression-bonded like Example 1 and cooled. The postcard thus obtained was easily peeled off at the interface between the paper surface and the thermoplastic resin surface with almost no adhesion.

[Brief description of drawings]

FIG. 1 is a cross-sectional configuration diagram of a transparent heat-sensitive adhesive composite sheet of the present invention.

FIG. 2 is a cross-sectional configuration diagram of a heat-sensitive adhesive composite sheet using a composite film having a heat-adhesive resin as the outermost layer of the present invention.

FIG. 3 is a perspective view showing a state in which the transparent heat-sensitive adhesive composite sheet of the present invention is sandwiched between paper sheets and thermocompression bonded.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transparent thermoplastic resin film 2 ... Electron beam hardening type resin layer 3 ... Postcard paper 10 ... Ethylene-vinyl acetate layer 11 ... Polyethylene layer 12 ... Polyethylene terephthalate layer

Claims (5)

[Claims] 1. A heat-sensitive adhesive composite sheet having transparency, in which heat-sensitive adhesive layers are directly or indirectly provided on both sides of an electron beam curable resin layer, wherein the heat-sensitive adhesive layer is softened at 110 ° C. or lower. The sheet has a point, has a thermal adhesive property capable of being thermally laminated with a postcard sheet, and has an interfacial peel strength of the electron beam-curable resin layer of 300 mm / min in an environment of 20 ° C. and a relative humidity of 65%. T measured at speed
A heat-sensitive adhesive composite sheet having a mold peel strength of 10 to 200 g / 50 mm. 2. When the heat-sensitive adhesive composite sheet is heat-laminated to a postcard sheet, its adhesive strength is 20 ° C.,
T-type peel strength measured at a peeling speed of 300 mm / min in an environment of 65% relative humidity, 300 g / 50 mm
The heat-sensitive adhesive composite sheet according to claim 1, which is as described above. 3. The electron beam curable resin is polyfunctional vinyl ether, polyfunctional (meth) acrylate, polyfunctional oligo (meth) acrylate, polyester (meth) acrylate, epoxy (meth) acrylate, polyurethane (meth) acrylate, polyol. (Meth) acrylate,
The heat-sensitive adhesive composite sheet according to claim 1 or 2, which is at least one selected from the group consisting of polyamide (meth) acrylate and polysiloxane (meth) acrylate. 4. The electron beam curable resin contains at least one selected from the group consisting of monofunctional (meth) acrylates, vinyl ethers, allyl ethers, acrylamide derivatives and N-vinylpyrrolidone as a diluent. The heat-sensitive adhesive composite sheet according to claim 3. 5. A method for producing a transparent heat-sensitive adhesive composite sheet in which an electron beam-curable resin is directly or indirectly interposed between a pair of heat-sensitive adhesive layers, the electron beam-curable resin layer. The method for producing a heat-sensitive adhesive composite sheet, characterized in that the interfacial adhesive strength is controlled so that it can be peeled by the electron beam irradiation conditions.