JPH01154796A - Thermal stencil paper and production thereof - Google Patents

Abstract

PURPOSE:To obtain a thermal stencil paper less liable to be deteriorated by a solvent contained in an ink and having favorable sensitivity to thermal perforation and favorable durability to repeated printing, by using a UV- or electron ray-curable polymer or oligomer which does not swell or shrink a heat- shrinkable plastic film, as an adhesive. CONSTITUTION:A UV- or electron ray-curable polymer or oligomer which does not swell or shrink a heat-shrinkable plastic film is used as an adhesive for lamination, in a thermal stencil paper obtained by laminating the heat-shrinkable plastic film with an ink-permeable base. The stencil paper is obtained by crosslinking the polymer or oligomer after adhesion of the film and the base. Alternatively, the stencil is obtained by laminating the film and the base by use of an alcoholic solution of the polymer or oligomer, then drying off the solvent, and crosslinking the polymer or oligomer by irradiation with UV rays or electron rays. The adhesive provides resistance to an organic solvent mixed in an ink, and when the adhesive is applied as an alcoholic solution thereof, the solution as a whole hardly shrink the plastic film, so that a preventive effect is obtained on lowering in perforation sensitivity and on generation of curling.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a base paper for thermal stencil printing and a method for producing the same.

[Prior Art] Heat-sensitive stencil printing base paper, which is made by adhesively laminating a plastic film that is easily perforated by heating and a base material such as ink-permeable porous thin paper or gauze, is widely used in the field of light printing. This type of base paper is perforated and printed by heating with a heat ray such as a xenon lamp or a thermal head.
Adhesives that are easily deformed at relatively low temperatures have been used so as not to inhibit drilling. On the other hand, printing machines using this type of base paper have also become more sophisticated and faster, and demands on the durability of the base paper have become stricter. In particular, because frictional strength and quick drying properties are required for the printed image, strong organic solvents are often mixed into the ink used, which tends to weaken the adhesive strength of the adhesive, and the number of copies printed. When there are many images, the image often becomes distorted or blurred.

In order to improve this problem of solvent resistance, JP-A-61-1
No. 16595 proposes a base paper using a specific urethane adhesive. According to the method of JP-A-61-116595, a base paper with good solvent resistance can be obtained, but on the other hand, if the degree of crosslinking of the adhesive is increased in order to sufficiently increase the solvent resistance of the urethane adhesive, However, there was a problem in that the sensitivity of perforation of the base paper was considerably impaired. It has been extremely difficult to simultaneously obtain such good sensitivity and solvent resistance. In addition, urethane adhesives react with polar thinning materials such as alcohol, so if a solvent is used,
It is necessary to dilute with a solvent such as a ketone, ester, or aromatic hydrocarbon that does not contain these polar solvents, but these solvents often attack plastic films. In particular, films with high thermal perforation sensitivity tend to have relatively low solvent resistance, and have significant drawbacks such as a decrease in sensitivity and curling of laminates due to contact with these solvents. In addition, urethane adhesives have the problem of reacting with moisture in the solvent and causing variations in their reactivity, especially the crosslinking density after curing. It has been extremely difficult to control both the solvent resistance of the base paper to the solvent in the ink within a desirable range.

[Problems to be Solved by the Invention] The present invention provides a thermal stencil printing base paper that is less susceptible to deterioration due to the solvent in the ink, has good thermal perforation sensitivity, and has good printing resistance, and a control system that does not vary due to atmospheric moisture, etc. The purpose of this invention is to provide an easy-to-use manufacturing method.

[Means for Solving the Problems] That is, the present invention provides a heat-sensitive stencil printing base paper in which an ink-permeable base material is laminated on a heat-shrinkable plastic film, using an ultraviolet or electron beam crosslinkable adhesive as a lamination adhesive,
It is a base paper for heat-sensitive stencil printing that is cross-linked after adhesion using a polymer or oligomer that does not cause the heat-shrinkable plastic film to swell or contract, and is laminated and bonded using an alcoholic solution of a polymer or oligomer that is cross-linkable with ultraviolet or electron beams. This is a method for producing a base paper for heat-sensitive stencil printing, which is characterized in that the solvent is dried and then crosslinked with ultraviolet rays or electron beams.

The heat-shrinkable plastic film used in the present invention is a thin plastic film that is easily perforated by heating. As such a film, a thin thermoplastic heat-shrinkable film as exemplified in the above-mentioned JP-A-61-116595 and JP-A-59-16795 can be used. In particular, a film that has a relatively low melting temperature, high heat shrinkability, and whose melt viscosity easily decreases with temperature rise is preferably used.

Examples of suitable films include vinylidene chloride copolymers, polyesters, copolyesters, polyamides,
It is a thin stretched film of 10 to 1 micron, such as copolyamide.

The ink-permeable substrate used in the present invention is preferably one that is porous enough to allow the ink supplied from the ink-permeable substrate side of the laminate to pass through, and has mechanical strength as a stencil paper. , e.g. porous tissue paper,
Nonwoven fabrics, gauze, etc. are used.

As the adhesive between the base material and the film, a polymer or oligomer that is crosslinkable with ultraviolet rays or electron beams and does not cause the heat-shrinkable plastic film to swell or shrink is used. Adhesive lamination must be performed using this adhesive, and further crosslinking must be performed using ultraviolet rays or electron beams. Examples of such polymers include polyvinyl acetate, copolymers of vinyl acetate and other vinyl monomers, polybutadiene and butadiene-based copolymers, all of which can be applied in the form of solutions or emulsions. Also suitable as oligomers are oligomers such as polyester acrylates, epoxy acrylates, polyurethane acrylates, polyether acrylates, polyacrylates, etc., which are made especially for crosslinking and curing by ultraviolet rays or electron beams. However, when using oligomers, special attention should be paid to the fact that when low molecular weight acrylate oligomers come into contact with heat-shrinkable plastic films, they often cause the films to swell or shrink.

Swelling and shrinkage of the film should be avoided as much as possible since it reduces the thermal perforation sensitivity of the resulting base paper and causes the base paper to curl. For this purpose, it is effective to selectively use oligomers with a relatively high molecular weight and to use an alcoholic diluent to increase the polarity of the entire liquid to reduce the swelling property.

Swelling and shrinkage of the film due to contact with the oligomer can be relatively easily examined by placing the film flat, leaving one side of the film in contact with the oligomer, and observing shrinkage and curl formation on the contact surface. When using oligomers, it is necessary to conduct a contact test in advance and avoid using oligomers that cause significant shrinkage, or to keep the blending ratio to an extremely small amount. must be prevented from swelling or shrinking. As mentioned above, when an alcoholic diluent is used, lamination adhesion and crosslinking can be completed while substantially no swelling or shrinkage occurs even if a small amount of a component that causes some shrinkage is added.

It is better not to substantially include acrylate monomers, which are usually always included in UV-curable adhesives.

Since the adhesive of the present invention needs to be crosslinked by ultraviolet rays or electron beams, it is desirable to add an increaser/decrease agent to the adhesive. Various types of additives can be used, such as p-dimethylaminoacetophenone, benzophenone, benzoin alkyl ether, 1-hydroxycyclohexylphenyl ketone, and di-t-butyl peroxide.

As a method for laminating the film and the base material using an adhesive, a dry lamination method, a wet lamination method, etc. can be used, but a particularly suitable method is the
- As described in No. 47997, a film and an ink-permeable base material are overlapped, and then an adhesive liquid is impregnated from the side of the ink-permeable base material to allow the adhesive to permeate the film surface and bond. It's a method.

Crosslinking of the adhesive is performed by irradiation with ultraviolet rays or electron beams. At this time, the heat-shrinkable plastic film will shrink if heated excessively, so care must be taken to avoid temperature rise as much as possible.

[Function] By cross-linking the adhesive with ultraviolet rays or electron beams, the adhesive becomes resistant to organic solvents contained in ink, and can withstand printing on a large number of sheets for a long period of time.

Further, a decrease in perforation sensitivity and curling can be prevented. In particular, when the adhesive is applied as an alcoholic liquid, the liquid as a whole becomes difficult to shrink the heat-shrinkable plastic film.
This is effective in reducing perforation sensitivity and preventing curl formation.

[Implementation example] The present invention will be specifically explained below with reference to Examples.

Example 1 A heat-shrinkable biaxially stretched polyester film with a thickness of 2 microns and Manila hemp tissue paper with high ink permeability of 8.5 g/I were superimposed, and a photopolymerized sensitizer was applied from the thin paper side. as, 1-hydroxycyclohexylphenyl ketone (manufactured by Ciba Geigy, Irgacure ■184)
5%, UV crosslinkable multi-tubular polyurethane acrylate (Aronix MI100 manufactured by Toagosei Co., Ltd.) 45%,
A 50% mixed adhesive of acrylic vinyl acetate copolymer resin (manufactured by Nippon Gosei Co., Ltd., Cohonyl 4711) was applied as a methanol solution at a non-volatile content of 1.5 g/rrI', dried, and then exposed to ultraviolet rays from the side of the polyester film. The adhesive was crosslinked. In addition, separately for the mixed liquid and each component, heat-shrinkable biaxially stretched polyester film l,
When tested by contacting it with water, virtually no swelling or contraction occurred.

The base paper for thermal stencil printing thus obtained was made into plates using a thermal mimeograph machine RISOGRAPH FX7200 manufactured by Riso Kagaku Kogyo.
Good images were obtained when printed on a printing press Lithograph AP 7200.

After leaving the ink on the base paper as it was for 24 hours, further printing was performed, and more than 5,000 sheets were successfully printed.

Example 2 In Example 1, the adhesive was a methanol solution containing 5% di-t-butyl peroxide and 95% ethylene-vinyl acetate copolymer resin (Solex E 830 manufactured by Nippon Gosei) as a non-volatile content, and the non-volatile content was 1. 0.5 g/d was similarly applied and dried, and then irradiated with an electron beam to crosslink the adhesive. Using the base paper for thermal stencil printing thus obtained, plate making and printing tests were conducted in the same manner as in Example 1, and more than 5,000 copies with good images could be printed.

Comparative Example 1 Using a methanol solution of polyvinyl acetate as an adhesive, a dry amount of 1.5 g/ba was applied and dried in the same manner as in Example 1 to obtain a base paper for thermal stencil printing. When a printing test was conducted using this base paper, image shift occurred as early as 1,500 sheets after being left unused.

[Effects of the Invention] According to the present invention, a good base paper for thermal stencil printing that can withstand printing on a large number of sheets can be obtained even after being attached to a printing machine, ink is applied to the base paper, and left for a long time.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. In a heat-sensitive stencil printing base paper in which a heat-shrinkable plastic film and an ink-permeable base material are bonded and laminated with an adhesive, the heat-shrinkable plastic film is swollen with ultraviolet or electron beam crosslinking properties. Or base paper for heat-sensitive stencil printing using an adhesive made of non-shrinkable polymers or oligomers cross-linked with ultraviolet light or electron beams. 2. Adhesively laminate a heat-shrinkable plastic film and an ink-permeable substrate with an alcoholic liquid that does not swell or shrink the heat-shrinkable plastic film, which is made of ultraviolet or electron beam crosslinkable polymer or oligomer, and after drying the solvent, A method for producing base paper for heat-sensitive stencil printing, characterized by crosslinking with ultraviolet rays or electron beams.