JPS6261137B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a screen printing plate used for screen printing or etching. More specifically, the present invention relates to a method for producing thick film screen printing plates having a long printing life and excellent printing resolution.

Conventionally, screen printing plates are made by inserting a screen cloth made of fibers such as silk, nylon, Tetoron, or stainless steel wire into a plate frame, and applying a light-sensitive emulsion onto the screen cloth manually or mechanically. After drying, it was manufactured using photolithography, a method in which a pattern was drawn on the dried film using a photochemical method using a positive as an original image, and the film was used as a screen for printing or etching. however,
In this method, the non-volatile content of the emulsion used is low and the film thickness produced by one coating is thin, so in order to obtain the desired film thickness, the emulsion must be coated and dried multiple times. The process has to be repeated and the resulting film thickness is inevitably non-uniform.
Moreover, this method has the disadvantage that the exposure time is extremely long because the photosensitive emulsion uses dichromate or diazonium salt as a sensitizer and basically utilizes a photocrosslinking reaction. . Furthermore, the photosensitive emulsion is mainly composed of a combination of polyvinyl alcohol and vinyl acetate emulsion, and its water solubility and water resistance are controlled. This tendency is exacerbated as the film thickness increases, and there is a drawback that sharp edges of the image cannot be obtained after development, resulting in poor print quality and film peeling during printing. Many of them ran out quickly and had a short printing life.

Therefore, in recent years, as a way to compensate for these shortcomings,
Many attempts have been made to apply UV-polymerized photosensitive resins to screen printing plates. This ultraviolet-polymerized photosensitive resin has an extremely high quantum efficiency of light compared to conventional photocrosslinkable resins, so it does not cause any problems even when the film thickness becomes thicker. It is now possible to make the film 10 times thicker, and since many UV-polymerized photosensitive resins are developed using solvents or weakly alkaline aqueous solutions, they have extremely good solubility, resulting in sharp edges. And of course, the water resistance was also extremely good.

However, in such UV-polymerized photosensitive resins, polymerization is significantly inhibited by the large amount of oxygen contained in the air, so the problem is that the surface layer of the photosensitive resin, where oxygen diffuses, is difficult to cure. There is. Particularly in the case of screen printing plates, the positive is in close contact with the other side and, apart from the side where the light enters during exposure, the opposite side with the gauze is exposed to the air, so oxygen curing damage is a serious problem. It becomes a problem. Therefore, if the resin on the gauze side is exposed to a large amount of ultraviolet rays in order to sufficiently harden it, the photosensitive resin in the gaps in the gauze will harden and fill in due to the diagonal rays and the halation of the ultraviolet rays from the gauze threads. When it gets easier, problems arise. Therefore, when attempting to cut through narrow gaps with a sharp edge in a sufficiently thick film, the gauze side of the photosensitive resin becomes underexposed, causing accidents such as peeling during plate making.

As a result of intensive research to solve the problems associated with such conventional methods, the inventors of the present invention discovered that after applying a specific coating to the surface of the ultraviolet polymerization type photosensitive resin layer in advance, irradiation with ultraviolet rays was performed. The inventors have discovered that the object can be achieved, and have completed the present invention based on this knowledge.

That is, the present invention provides a screen printing plate by providing an ultraviolet ray polymerized photosensitive resin layer on a screen cloth that is inserted into a plate frame, exposing a positive film to the film to form an image, and then developing it. In the method for manufacturing, screen printing is characterized in that the surface of the photosensitive resin layer is coated with a mixture of a water-soluble or water-dispersible polyvinyl alcohol composition and a polyvinyl acetate emulsion, and then irradiated with ultraviolet rays. The present invention provides a method for manufacturing a plate.

The present invention is based on the fact that polyvinyl alcohol has excellent impermeability to oxygen gas. The polyvinyl alcohol used may be completely saponified, partially saponified, or a copolymer as long as it is soluble in high-temperature water. However, if the degree of saponification is too low, the impermeability to oxygen gas will decrease, which is undesirable, so a saponification degree of 80% or higher is usually used. The degree of polymerization of polyvinyl alcohol is preferably in the range of 500 to 2000.

When a copolymer is used, it is necessary that the vinyl alcohol unit in the copolymer is 60 mol% or more. If it is less than 60 mol%, the opacity of oxygen gas may decrease. Copolymer components include vinyl acetate (meth)acrylic acid, acrylamide, N-methylolacrylamide, styrene,
Ethylene, propylene, maleic anhydride, acrylonitrile, (meth)acrylic acid ester, etc. are used.

In the present invention, the coating applied to the surface of the photosensitive resin layer must be formed using a mixture of the above-mentioned polyvinyl alcohol or its copolymer and polyvinyl acetate emulsion. Polyvinyl alcohol or its copolymer alone cannot be used because it is difficult to form a good coating film and lacks affinity for photosensitive resins such as acrylic, urethane, and epoxy resins. At this time, the amount of polyvinyl acetate emulsion to be used is selected within the range of 10 times or less, preferably 5 times or less, based on the weight of polyvinyl alcohol. If the amount used exceeds the above range, the amount of polyvinyl alcohol will be reduced and the oxygen gas shielding effect will be weakened, and at the same time, the film will not be able to be washed away during development.

Furthermore, if the heat shrinkage rates of the film obtained from the water-dispersed polyvinyl alcohol composition and the ultraviolet-polymerized photosensitive resin layer are too different, cracks are likely to occur, so a known plasticizer is usually added to the former composition. It is desirable to mix it. In addition, additives such as a solvent, a filler, and a fungicide may be added as necessary.

Regarding the ultraviolet polymerization type photosensitive resin used in the present invention, there are particular restrictions as long as it is a type of resin that generates radicals when exposed to ultraviolet light and hardens through a radical polymerization reaction, and that can form a film on the gauze. It does not matter whether the original state is liquid or solid. Examples of such materials include polyamide-polyfunctional vinyl monomer systems used in solid photosensitive resin letterpress materials, cellulose derivatives-polyfunctional vinyl monomer systems, polyvinyl alcohol-polyfunctional vinyl monomer systems, and unsaturated double Photosensitive resins such as acrylic, urethane, and epoxy resins with a large number of bonds, or their solvent or water solutions;
Examples include emulsion and dispersion.

According to the method of the present invention, a screen printing plate with a thick film that has a long printing life and little variation in thickness, and has sharp edges with excellent reproducibility of fine lines etc. can be easily obtained. The resolution is improved, and even in thick film substrates and resistors, high printing resolution and stable film thickness printing can reduce variations in resistance values, making it possible to provide stable thick film substrates with excellent quality. Furthermore, in printing, it is possible to print thin lines with a three-dimensional effect, and in textile printing, a large amount of dye is transferred to the fabric, allowing for deep, delicate and beautiful dyeing.

Next, the present invention will be explained in more detail with reference to Examples.

Note that parts and % in each example are parts by weight and % by weight, respectively.

Example 1 Polyethylene glycol (number average molecular weight =
1000) 1000 parts and xylylene diisocyanate 384
After 2 hours of reaction at 100°C, 268 parts of 2-hydroxyethyl methacrylate was added and the reaction was carried out at 80°C for 4 hours in an air stream. Phenol 1.5
Add 1 part and dissolve well.

To 60 parts of the photosensitive varnish thus obtained,
Add 40 parts of hydroxypropyl methylcellulose phthalate, which has been ground into fine particles of 300 mesh or more, and mix well with a Henschel mixer to form wet granules. This was kneaded at 120°C using an extruder, extruded from a T-die into a 350μ thick sheet, and laminated onto a 25μ thick polyester film.

On the other hand, a photosensitive solution was prepared by dissolving 20 parts of the blend of the above photosensitive varnish and hydroxypropyl methyl cellulose phthalate in 80 parts of ethyl acetate, and this was applied with a brush to the resin surface laminated to a polyester film, while the ethyl acetate did not dry. A 100-mesh polyester gauze attached to the frame was pressed onto the frame, and the same photosensitive solution was applied with a brush over the gauze and dried at 40°C for 30 minutes. At this stage, the gauze fibers were wrapped in a dry film of photosensitive liquid, and the unevenness of the gauze was still sufficiently intact. A 25μ polyester film was removed from this resin plate.

Meanwhile, 50 parts of 20% polyvinyl alcohol solution (Denka Poval K-05, Denki Kagaku Kogyo product), 50 parts of 50% vinyl acetate emulsion containing 15 PHR of dibutyl phthalate (Vinizol 595, Daido Kasei product), and 100 parts of water were mixed well. The solution obtained by mixing (hereinafter abbreviated as polyvinyl alcohol solution) was applied to both sides of the resin with a brush and dried.
The obtained film thickness was 10μ. Next, a positive film (using lithium film, floral pattern) was placed in close contact with the film, and a 2KW ultra-high pressure mercury lamp was used from a distance of 1 meter from the positive film.
After removing the positive, a 0.2% caustic soda aqueous solution was sprayed at a pressure of 5 kg/cm ² for 80 seconds to remove the polyvinyl alcohol layer and the unexposed portions of the photosensitive resin layer and photosensitive liquid layer. After washing and drying this plate, it was re-irradiated under the above-mentioned exposure conditions to make it even more durable. When the plate thus obtained was used to print on an acrylic plate with screen ink for plastics, a display with an ink layer thickness of 300 μm, which had never been achieved before, was obtained with a relief effect.

Comparative Example 1 When a plate was made under the same conditions as in Example 1 except that the application of the polyvinyl alcohol solution in Example 1 was omitted, the photoresist film on the gauze side was not sufficiently cured due to oxygen damage, and during the development process. A part of the photosensitive film (exposed area) peeled off from the gauze.

Example 2 Methacrylic acid was added to 200 parts of a 50% butyl acetate solution of an acrylic copolymer obtained from 30 parts of methyl methacrylate, 30 parts of styrene, 15 parts of butyl acrylate, and 25 parts of acrylic acid using 0.4 part of tetraethylammonium bromide as a catalyst. A varnish with an acid value of 34 was obtained by reacting 30 parts of glycidyl at 130°C. 2 parts of benzoin ethyl ether was dissolved in this, and the solution was further diluted with 30 parts of toluene to obtain a photosensitive solution.

This photosensitive solution was applied using a ball squeegee to a 200-mesh polyester screen attached to a metal frame, and then heated and dried at 80°C for 15 minutes. Then,
The polyvinyl alcohol solution used in Example 1 was brushed onto both sides and dried at 60°C for 10 minutes.

Next, attach the positive for the electric circuit,
After irradiating with a 3KW high-pressure mercury lamp from a distance of 50cm for 15 seconds to remove the positive, spray a 0.2% caustic soda aqueous solution at 35℃ at 3.5Kg/cm ² pressure to dissolve and remove the polyvinyl alcohol layer and unirradiated areas, wash with water, and dry. , re-irradiated with the same lamp for 1 minute. When electrical circuits were printed using the plate thus obtained, the resulting print was extremely sharp and clear compared to conventional screen plates.

Comparative Example 2 When a plate was made under the same conditions as in Example 2 except that the application of the polyvinyl alcohol solution in Example 2 was omitted, the entire photoresist film was insufficiently cured and fell apart during the development process, resulting in no image being formed. Nakatsuta.

Comparative Example 3 Plate making was carried out in the same manner as in Example 2 except that a 5% by weight aqueous solution of polyvinyl alcohol with a degree of polymerization of 1700 and a degree of saponification of 90% was used instead of the polyvinyl alcohol solution in Example 2. The photoresist film was not coated uniformly, causing some unevenness, and the surface of the photoresist film that was not coated with polyvinyl alcohol was insufficiently cured, resulting in incomplete image formation.

Claims (1)

[Claims] 1. A method of manufacturing a screen printing plate by providing an ultraviolet polymerizable photosensitive resin layer on a screen cloth inserted and stretched in a plate frame, exposing a positive film to form an image by closely contacting the layer, and then developing the layer. After applying a double coating of a mixture of a water-soluble or water-dispersible polyvinyl alcohol composition and a polyvinyl acetate emulsion to the surface of the photosensitive resin layer,
A method for producing a screen printing plate, characterized by irradiating it with ultraviolet rays.