JPH0313394A - Thermal screen printing base paper - Google Patents

Abstract

PURPOSE:To well perform re-printing and to prevent the release of a film and a porous support at the time of plate making due to heat perforation using a thermal head by laminating a polyester film to the porous support and using an adhesive wherein a specific amount of an epoxy resin is compound with a saturated polyester resin. CONSTITUTION:As an adhesive for laminating a polyester film to a porous support, an adhesive wherein 5-50wt.% of an epoxy resin is mixed with a thermoplastic resin based on a saturated polyester resin is used. As the main component of the thermoplastic resin in the adhesive, a saturated polyester with an MW of 5000-40000 pref. having glass transition temp. of 40-70 deg.C is proper. A small amount of other thermoplastic resin, for example, a vinyl chloride resin or a petroleum resin may be appropriately added thereto. As the epoxy resin being the other component of the adhesive, a bisphenol A type epoxy resin obtained by the condensation reaction of bisphenol A and epichlorohidrin is pref.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-sensitive stencil paper having a structure in which a polyester film is laminated to a porous support such as porous thin paper or a mesh-like sheet.

[Prior Art] Conventionally used heat-sensitive stencil paper has a structure in which a heat-melting shrinkable resin film is bonded to a porous support that is permeable to stencil printing ink, which does not melt and shrink at the temperature at which the film melts and shrinks. A coating is provided on the surface of the film to prevent fusion with the original or the heating element.

That is, the basic components of the heat-sensitive stencil paper are the two members, the heat-melt shrinkable film and the porous support, and it is essential that these members are closely laminated and adhered to each other.

The reason is that the heat melt shrinkable film used is 10, in
Because it is an ultra-thin product, it is not only weak and inconvenient to handle when used alone, but also deforms and distorts when heated during plate making.
Alternatively, the perforated portion may fall off, which is of no use.

Therefore, it is necessary to adopt a laminated structure of a film and a porous support, and since it is a laminated structure, an adhesive is essential. It is an important factor that affects the quality of base paper.

Therefore, many techniques have been proposed in this regard.

For example, bonding methods include stacking a film and porous paper, impregnating the porous paper with a synthetic resin solution, drying and bonding (Japanese Patent Publication No. 55-47997), and applying adhesive to the porous paper using a gravure roll. A method of coating and bonding with a film (Japanese Unexamined Patent Publication No. 147396/1983)
, a method in which adhesive is gravure coated on either the film or porous paper and then adhered with a pressure roll (
(Japanese Unexamined Patent Publication No. 58-188896), a method in which a hot melt adhesive is applied to a film in advance, porous paper is stacked on top of the other, and the adhesive is bonded by pressing with a heated roll (Japanese Unexamined Patent Publication No. 59-1679).
0), a method of applying an adhesive solution with a viscosity of 100 epS or less to the film surface, overlapping porous paper in an undried state, drying and adhering (Japanese Patent Application Laid-Open No. 59-2279Ii), adhesion to the film. There is a method in which porous paper is impregnated with a solvent, the two are overlapped in an undried state, and then dried and bonded (Japanese Patent Application Laid-Open No. 61-2597).

Regarding the selection of adhesive, use 1.5 to 1 liters of acrylic resin.
How to apply og/go (Special Publication No. 1187/1987)
, 2 to 10 g of adhesive whose main component is vinyl acetate resin
/d coating method (Japanese Patent Publication No. 47-1188), method of dissolving vinyl acetate resin in a mixed solvent of methanol and other alcohol solvent (Japanese Patent Publication No. 47-1733)
8), a method using an adhesive made by adding polyvinyl alcohol to polyvinylidene chloride latex (Japanese Patent Publication No. 48-29730), and a method using an adhesive whose main component is an acrylic resin at 0.5 to 2 c/rr? Coating method (Japanese Patent Publication No. 51-33004), method using vinyl acetate resin added with rosin resin (Japanese Patent Publication No. 59-1878)
0 Publication), a method in which a vinyl acetate-based or acrylic adhesive is applied to a film and dried, a porous paper impregnated with a water-dispersed vinyl acetate resin is layered on this surface in an undried state, and the film is dried and bonded. (Japanese Unexamined Patent Publication No. 18795-1879), a method using methoxymethylated polyamide (Japanese Unexamined Patent Publication No. 59-18795),
115899), a method of applying 0.1 to 5 g/g of an adhesive mainly composed of vinyl chloride copolymer (Japanese Patent Laid-Open No. 115899),
9-215H4), a method of applying 0.3 to 2.5 g/rrr of incyanate prepolymer to the film surface and pressing at 2 kg/nf or more (Japanese Patent Application Laid-Open No. 1986-11
6595), diisocyanate and average molecular weight 40
NGOloH with polyether diol from 0 to 2000
A method using an adhesive whose main component is a reacted prepolymer with an equivalent ratio of 1.5 to 2.0 and whose flow initiation temperature after curing is 150 to 260°C (Japanese Patent Application Laid-Open No. 181374/1983), etc. be.

[Problems to be Solved by the Invention] With the heat-sensitive stencil paper having the above structure, it is necessary to achieve stronger and more uniform adhesion using as little adhesive as possible.

That is, if the amount of adhesive is large, the thermal perforation sensitivity of the film will be reduced and the perforations will be blocked, preventing ink from passing through, making it impossible to produce clear printed matter. This defect is more pronounced as the adhesive has higher heat resistance and melt viscosity, and the harder and stronger the adhesive film is, the more this tendency is exhibited.

On the other hand, if the amount of adhesive is small, the adhesive force will be weak and serious defects such as film lifting and wrinkles will easily occur during the bonding process, and the printing ink will penetrate into the porous support during printing. Since a tensile force is applied between the film and the film, the two easily separate, causing the film to break and making it impossible to print. The weaker and poorer the heat resistance of the adhesive, the more this tendency occurs.

However, since the above requirements are mutually contradictory with many other requirements required for thermal stencil paper, they have not been satisfactorily resolved by conventional techniques.

For example, an attempt was made to improve resolution by impregnating porous paper with a synthetic resin and overlapping it with a film, without intervening an adhesive layer between the film and the porous paper. In the first place, adhesion between a film and porous paper is nothing but adhesion at the interface between the two, so if the amount of resin impregnated is small, most of the resin will be adsorbed to the porous paper, and the amount that contributes to adhesion at the interface will be reduced. If the adhesive strength is too low, the required adhesive force cannot be obtained. If the amount of resin is increased to increase adhesive strength, it will fill the pores in the porous paper and prevent ink from passing through, making it impossible to produce clear prints.

Therefore, a method was proposed in which an adhesive is applied to a film, the film is overlapped with a porous paper in an undried state, and the film is dried and bonded so that the adhesive is effectively present at the interface between the film and the porous paper.

Although this method allows the amount of adhesive to be reduced compared to the above method, the adhesive solution permeates into the porous paper from the time the adhesive is stacked until the adhesive dries. When the viscosity is low, penetration is significant, the amount of adhesive at the interface is reduced, and the adhesive strength is reduced. On the other hand, if the viscosity of the adhesive solution is high, penetration will be reduced, but it will be difficult to uniformly apply a small amount of adhesive to the film, resulting in variations in quality.

Furthermore, in an attempt to make a small amount of adhesive exist only at the interface between the film and porous paper, a solvent-free adhesive that had been heated to a low viscosity was applied to the film, and then porous paper was layered on top of it. A method of applying heat and pressure has been proposed. However, with this method, it is difficult to adjust the tack when heating to lower the viscosity, and the adhesive does not wet and dig into the porous paper simply by stacking, so heating and pressure after stacking is required, which requires a considerable amount of work. Due to the high temperature, it cannot be used in porous paper made of synthetic resin fibers such as polyester and polypropylene.

Regarding the adhesive itself, if vinyl acetate resin, acrylic resin, vinyl chloride resin, polyester resin, etc. are used, the solid resin content at the time of bonding is 1 g/r.
r? If the porous paper is not present, the film will lift and wrinkle, and these resins will soften, swell, and dissolve due to the printing ink, so if the porous paper is made of synthetic resin fibers, there will be no particular problem. If the product is made of natural fibers such as Manila hemp, the printing ink will penetrate into the fibers and if the amount of adhesive is too small, the product will peel off, so the amount of adhesive should be at least 1.5g/ It is necessary to increase the number to d or more, and then the print clarity will decrease. Furthermore, vinyl chloride resin has the disadvantage that it releases harmful chlorine into the thermal head during plate making.

Furthermore, when using a moisture-curing urethane adhesive that is a reaction prepolymer of diisocyanate and polyether diol, this resin has good ink resistance, so even a small amount can be replaced with one that has high printing durability. It is difficult to manage pot life and adjust humidity.
It tends to cause uneven curing.

In addition, when conventional heat-sensitive stencil paper is left on a printing press for a long period of time, the adhesive is affected by the oil and solvent in the printing ink, resulting in a significant decrease in adhesive strength, and the bond between the porous support and the film. There were also problems such as peeling and being unable to print again.

Furthermore, when performing heated perforation plate making with a thermal head,
There was a problem in that not only the film but also the adhesive softened and melted, causing peeling between the film and the porous support.

In view of the above-mentioned points, the present invention is a heat-sensitive stencil paper that solves the problems of the prior art, in particular, can be reprinted well and the film and porous support do not separate during plate-making with a thermal head. The purpose is to provide

[Means for Solving the Problems] The present invention provides a heat-sensitive stencil paper made by laminating a polyester film and a porous support with an adhesive, in which the adhesive is a thermoplastic resin mainly composed of a saturated polyester resin. To provide a heat-sensitive stencil paper, characterized in that it is a mixture of 5 to 50ffi 111% of epoxy resin.

Here, the ratio of epoxy resin to thermoplastic resin is
This is a value calculated using the total amount of epoxy resin and its curing agent as the amount of epoxy resin (the same applies hereinafter).

[Function and Examples] Although the epoxy resin used in the present invention has been widely used as a thermosetting adhesive, it has poor plate-making properties and lamination processability as an adhesive for heat-sensitive stencil paper, and has conventionally been used as a thermosetting adhesive. It wasn't used.

In the present invention, as an adhesive for laminating a polyester film and a porous support, 5 to 5% of the epoxy resin is added to a thermoplastic resin mainly composed of a saturated polyester resin.
When using a mixture of 0 weight percent, the solid content is 0.
．． By laminating with an extremely small coating amount of 5-2.0 g/rd, a heat-sensitive stencil paper having the following characteristics can be obtained.

■Even if the adhesive is left on the printing press for a long period of time, the printing ink on the press will not soften or weaken the adhesive, which means that the printing durability during reprinting is extremely high.

■During the heating perforation using the thermal head during plate making,
Since the adhesive maintains sufficient adhesive strength, peeling between the porous support and the film due to fusion of the film to the thermal head was extremely reduced.

There is a method of solving the problem of film adhesion to the thermal head by applying an anti-fusing agent (for example, silicone resin) to the surface of the film, but according to the present invention, there is no anti-fusing layer. Even if an anti-fusing layer is provided, there is little peeling, and even if an anti-fusing layer is provided, its effect can be achieved with a very small amount.

The polyester film used in the present invention is a stretched film having a thickness of 5 mm or less, preferably 1.0 to 23.0 mm. If the thickness exceeds the above range, the perforation performance due to the thermal energy of the thermal head will be poor and it will not be possible to create a stencil that is faithful to the original.

If the thickness is less than the above range, the strength will be too low, which is not preferable. A biaxially stretched film is usually used as the polyester film, and preferably has a stretching ratio of 150 to 250% in both the longitudinal and transverse directions.

The porous support may be made of natural fibers such as cypress, mitsumata, Manila hemp, and jute, semi-synthetic fibers such as rayon, and synthetic fibers such as polyester, vinylon, nylon, and polypropylene, singly or in combination of two or more, with a basis weight of 5. ~
15g/rtf porous tissue paper, semi-synthetic! 50 consisting of one type or a mixture of 28 or more a-fibers or synthetic fibers
Screen gauze with a mesh size of ˜200 is preferably used.

The main component of the thermoplastic resin in the adhesive has a molecular weight of 5.000 to 40,000, preferably 10.000.
~30,000 saturated polyester resin, preferably having a glass transition temperature of 40 to 70°C. A small amount of other thermoplastic resin, such as vinyl chloride resin or petroleum resin, may be added as appropriate. However, the amount is usually 1 Off for the saturated polyester resin.
If it exceeds ln%, the adhesive force and lamination processability will deteriorate, which is not preferable.

The saturated polyester resin is mainly composed of an amorphous linear saturated polyester resin produced by polycondensation of a dicarboxylic acid component and a diol component. For example, dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and diol components include ethylene glycol, 1,4-butanediol, diethylene glycol, Examples include neopentyl glycol. By adjusting the combination of types and blending amounts of these two components, internal plasticization can be achieved, resulting in crystallinity and
The desired melting point and solubility in solvent can be selected. 3 low molecular weight polyethylene terephthalate components
Particularly preferred is one containing 0 to 50% by weight.

The other component of adhesive, epoxy resin, is
A bisphenol A type epoxy resin represented by the following formula, which is obtained by a condensation reaction of bisphenol A and epichlorohydrin, is preferred.

Molecular weight is 200-5,000, preferably 300-1.
500 and an epoxy equivalent of 100 to 5,000, preferably 180 to 3,000.

If the amount of epoxy resin added to the thermoplastic resin, which is mainly composed of saturated polyester resin, is less than 20% by weight, it can be used even if it is liquid at room temperature.
In terms of weight percent, epoxy resins that are semi-solid or solid at room temperature are preferred. This is to improve initial adhesion during lamination. Generally, the curing reaction speed of epoxy resins is slow, ranging from 5 to 10 minutes at the earliest to 1 to 24 hours at the slowest. The curing speed varies greatly depending on the curing agent used to cure the epoxy resin and the processing conditions, but in any case, during the lamination process, it is preferable that the adhesive hardens in a short time after lamination, and is semi-solid or solid at room temperature. With epoxy resin, you don't have to wait until it hardens.
This is because the solid resin has adhesive strength sufficient to maintain the bond between the film and the porous support during lamination, drying, and winding.

As the curing agent for the epoxy resin, aliphatic polyamine,
Examples include amine-based or amide-based compounds such as aromatic polyamines, polyamide resins, and amino resins, acid anhydrides, and phenolic resins. Particularly preferred are modified amine curing agents based on aliphatic polyamines and heterocyclic amines represented by the following structural formula.

The amount of curing agent added is based on the epoxy resin ff1 (
It may be determined as appropriate by taking into consideration the molecular weight of the epoxy resin/number of epoxy groups) and the equivalent of the curing agent (active hydrogen force ff1 such as amine equivalent (molecule ffi of curing agent/number of active hydrogen)). The curing agent is usually added in a stoichiometric amount [(active hydrogen equivalent/epoxy equivalent) X too (%)] of 0.9 to 1.
A saturated polyester resin, an epoxy resin, and a curing agent to be used approximately once are dissolved in an appropriate solvent such as toluene, ethyl acetate, butyl acetate, methyl ethyl ketone, acetone, alcohol, etc. to prepare an adhesive solution.

The proportion of the epoxy resin added to the thermoplastic resin mainly composed of saturated polyester resin needs to be in the range of 5 to 50% by weight, preferably 15 to 30% by weight. If the proportion of the epoxy resin exceeds the above range, the adhesive strength (adhesive strength) of the adhesive immediately after drying and immediately after processing will decrease significantly when laminating the porous support and the polyester film, resulting in slight extrusion. Due to mechanical effects (for example, mechanical tension), peeling and lifting occur frequently, increasing the number of defective products, and the heating plate-making properties using the thermal head deteriorate, making it impossible to produce clear printed matter.

On the other hand, if the proportion of the epoxy resin is less than the above range, ink resistance and adhesive strength at high temperatures will decrease, making it impossible to reprint, for example, after being left on a printing press.
In addition, peeling between the film and the porous support occurs due to the film being fused to the thermal head during heat plate making.
I can't change the clear print.

Next, a method for preparing the adhesive used in the present invention and a bonding method using the same will be described.

A thermoplastic resin mainly composed of a saturated polyester resin is dissolved in the above-mentioned solvent so that the solid content concentration is 3 to 10% by weight, and then an epoxy resin is added to this so that the proportion to the thermoplastic resin is 5 to 50% by weight. Add and mix until combined. Furthermore, just before lamination processing, mix an appropriate amount of an epoxy resin curing agent, and apply the adhesive solution thus obtained to the polyester film in a dry coating amount of 0.5 to 2.0 g/d, preferably 0.8 to 1 g/d. .5 g/nf, and before the solvent evaporates, a porous support is laminated on the coated surface and dried by heating at about 60 to 90°C.

Note that, if necessary, an anti-fusing agent may be applied to the surface of the film. As the anti-fusing agent, silicone rubber, silicone oil, silicone resin, or fluorine compound is usually used. It is desirable that the amount of the anti-fusing agent applied does not exceed 0.2 g/rf in terms of solid content.

Next, the present invention will be explained with reference to Examples and Comparative Examples.

Example 1 An adhesive solution having the following formulation was prepared. Note that the epoxy curing agent was added immediately before lamination.

Ingredients Weight% Byron-2008.1 (saturated polyester resin manufactured by Toyobo ■) Epicoat 828 1.2 (bisphenol A epoxy resin manufactured by Yuka Shell Epoxy ■, epoxy equivalent 190) Evomate BOO20.7 (Yuka Shell Epoxy ■ polyamine-based epoxy curing agent, amine equivalent 110) butyl acetate 50,0 toluene
An adhesive solution having the above composition was applied to a polyester film with a thickness of 40oO and 2ρ so that the coating amount after drying was 1.0g/g, and then a Manila hemp with a thickness of 45" and a thickness of 1g/g was immediately applied to the coated surface. After the porous thin paper made by wet papermaking as the main component was layered on top of each other, it was dried at about 70°C. Next, apply 0.05% silicone rubber to the film surface opposite to the porous tissue paper.
It was coated at a ratio of g/nf to form a product.

The resulting heat-sensitive stencil paper was transferred to CD-5 manufactured by Gestelatner.
When installed on an 80-inch thermal head thermal plate printing machine and printed on a plate, extremely clear printed matter was obtained. When I printed again after leaving it for about two months, I was able to get 10,000 prints with the same clarity as the original.

Example 2 A heat-sensitive stencil paper was obtained in the same manner as in Example 1, except that the adhesive solution was changed to one having the following formulation.

Ingredients Weight% Byron
2009,20 Epicote 828 0.50 Ebomate BOO20,30 Butyl acetate 50. O toluene
40. Using the obtained heat-sensitive stencil paper, plate printing was carried out in the same manner as in Example 1, and as a result, extremely clear printed matter was obtained. When I printed again after leaving it for about 2 months, I was able to get s,000 prints with the same sharpness as the original.

Example 3 A heat-sensitive stencil paper was obtained in the same manner as in Example 1, except that the adhesive solution was changed to one having the following formulation.

Ingredients Weight% Vylon-200 [i, 84 Epicote 828 2.00 Ebome)
BOO21,1B Butyl acetate 50.0 Toluene
Using heat-sensitive stencil paper obtained at 40.0,
As a result of plate-making printing in the same manner as in Example 1, clear printed matter was obtained (slightly inferior to Example 1). When I printed again after leaving it for about two months, I was able to get 10,000 prints with the same clarity as the original.

Comparative Example 1 A heat-sensitive stencil paper was obtained using an adhesive solution consisting only of a polyester resin obtained by removing the epoxy resin and curing agent from the adhesive composition used in Example 1.

The obtained thermal stencil paper was used for stencil printing in the same manner as in Example 1. Initially, the prints were as clear as in Example 1, but when reprinted after being left for 2 months, about 500 prints were obtained. The film was peeled off from the lines and ruled areas.

Comparative Example 2 When lamination was carried out under the same conditions as in Example 1 except that the adhesive solution was changed to one with the following formulation, lifting and wrinkles occurred in some parts, and the defective rate was high. Furthermore, when a portion free from defects such as lifting and wrinkles was cut out and plate-made under the same conditions as in Example 1, clear prints were obtained.

Ta.

Ingredients Vylon-200 Epicoat 828 Evomate 8-02 Butyl acetate Toluene [Effect of the invention] By using an adhesive containing a saturated polyester resin and a specific amount of epoxy resin to bond the polyester film and the porous support. , there is no decrease in adhesive strength due to printing ink, and many clear prints can be obtained even when reprinted after being left on a printing press for a long period of time. In addition, due to its excellent heat resistance, peeling of the film from the porous support due to fusion of the film to the thermal head during heating platemaking does not occur, resulting in a stencil plate without defects. 45 50.0 40.0 Asia Paper Co., Ltd.

Claims (1)

[Claims] 1. In a heat-sensitive stencil paper formed by laminating a polyester film and a porous support with an adhesive, the adhesive is a thermoplastic resin mainly composed of a saturated polyester resin,
A heat-sensitive stencil paper characterized in that it is a mixture of 5 to 50% by weight of an epoxy resin.