JPS623416B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lithographic process using active gas plasma and materials used in the process.

In the lithographic printing method, as typified by offset printing, a hydrophilic area (non-printing area) and an oleophilic area (printing area) are provided on the printing plate, and then printing ink is applied by supplying an appropriate amount of moisture (dampening water). selectively adhering the ink to the image area, and then transferring the ink to the blanket;
Furthermore, this is a method of re-transferring and printing onto a printing material.

The lithographic process has shifted from the old stone lithography to metal plate lithography, and currently PS (Pre-Sensitized) plate making is the mainstream.

A PS plate is a photosensitive resin coated on the surface of a hydrophilic substrate (usually an Al plate).The original photographic plate is exposed to light, and the photosensitive resin in the exposed or non-exposed areas is removed by development (positive type and negative type). The remaining photosensitive resin part becomes the lipophilic part, and the bare substrate surface becomes the hydrophilic part, and a printing plate can be manufactured.

The PS plate making method is very popular because it is simple as mentioned above, but in order to improve the printing plate quality, such as resolution, printing durability, and operability, a large number of photosensitive resins for lithography are used. is proposed. However, the current situation does not necessarily fully satisfy the demands of the printing side. If printing durability is to be satisfied, it is necessary to use a photosensitive resin with high film strength and to increase the film thickness to some extent in consideration of image abrasion during printing. Although there are many materials that have high film strength and wear resistance, the materials that are suitable for imparting photosensitivity are extremely limited. Furthermore, when photosensitive groups are chemically introduced into the substance, it is not always possible to maintain the previous properties, it is necessary to fully satisfy the photographic properties, and the film thickness must be increased to cope with abrasion. There are many problems such as deterioration of photographic properties (such as developability and resolution). Therefore, it is extremely difficult to find a high quality photosensitive resin for PS plates within a limited search range.

In contrast to the above, the present invention uses an inexpensive general resin with good substrate adhesion and abrasion resistance that provides high printing durability.
The object of the present invention is to provide a lithographic plate-making method that provides a high-quality printing plate without changing the resin properties of at least the image area, and a lithographic material used in the plate-making process.

The gist of the present invention is to selectively remove a lipophilic material layer on a hydrophilic substrate using active gas plasma to form image areas and non-image areas.

As is well known, active gas plasma is generated during discharge under a suitable degree of vacuum. A trace amount of gas that exists in a vacuum becomes active radicals or ionized and exists in plasma. Such active gas plasma has a high impact or reactivity on substances; for example, oxygen plasma can convert most organic substances into carbon dioxide gas and water, and metals can easily be converted into oxides. Depending on the type of gas contained, effective and rapid reaction with the reactant substance and vaporization removal of the reaction product can be facilitated.

On the other hand, since gas plasma exhibits particle-like behavior with strong energy under strong electric fields, it also has the effect of destroying and vaporizing other substances through collisions (so-called reverse sputtering). Therefore, the action of gas plasma is carried out both chemically and physically, and it does not matter whether the object to be affected is inorganic or organic.

One field currently utilizing this property is the semiconductor industry, where it is known as plasma etching or sputter etching. One example of usage in the semiconductor industry is to form a photosensitive resist layer on an object to be etched (generally an inorganic material such as silicon), expose and develop it to form a pattern, and then perform plasma treatment to selectively use the resist pattern as a mask. It is used for etching.

In other fields, it may be used in a pre-treatment process to clean the surface of an object by treating the entire surface without masking. In addition, in the case of organic materials, especially when surface processing (for example, printing, coating, vapor deposition, etc.) is performed on films, etc., plasma treatment is sometimes performed when corona discharge treatment is insufficient. In this case, since only the surface layer is treated so as not to change the essence of the film, it is common practice to apply weak plasma to the entire surface.

The present invention newly utilizes the above-mentioned principle in lithographic platemaking, but its basic purpose is to selectively remove the resin layer on the substrate, which has a stronger effect than the surface treatment of organic substances, so to speak. Lithographic plate making is carried out by selectively etching the layer to completely evaporate the layer and expose the surface of the hydrophilic substrate.

Next, the present invention will be explained in detail.

The basic structure of the lithographic material used in the method of the present invention is simple as shown in the first diagram. The planographic substrate 1 is generally an Al plate, and the material used in this method may be the same as the conventional substrate. The surface of the Al plate is usually subjected to graining (roughening), chemical oxidation, or electrochemical anodic oxidation to impart hydrophilicity and water retention properties.

A lipophilic material layer 2 with good adhesion is coated on the surface of this water-retaining substrate 1 with a suitable synthetic or natural resin and dried to obtain a lithographic material. When selecting lipophilic resins, it is more advantageous to use synthetic resins, which are available in a wide variety of types. The coating film thickness is preferably 1 to 5 microns, but is not limited to this. If a grained surface is used, the film must be thick enough to sufficiently cover the tips of the grained protrusions. From the viewpoint of film thickness, a substrate with a smooth surface improved in water retention by anodizing or the like is more advantageous than a grained board. That is, the substrate may have a rough surface, but a smooth surface is preferable. This is because there is no local variation in the thickness of the lipophilic substance layer, so the layer is uniformly removed by the plasma treatment, and no resin remains deep in the area to be removed.

The resin used may be one with elasticity and a two-dimensional molecular structure, but if the goal is particularly high printing durability, a three-dimensional molecular structure can be formed by heat treatment or reaction with a crosslinking agent after application. Resins that exhibit extremely high values of surface strength and abrasion resistance are suitable.

Methods for forming the mask 3 in an arbitrary pattern on this resin layer include drawing, printing, transfer, photography, and other methods.

If the pattern is rough and does not require precision, the masking material may be hand-drawn, or if there are enough copies, it may be masked by silk screen printing.
In order to obtain a more precise pattern, it is preferable to apply a photosensitive resin on another base material (such as a film) in advance, and then transfer it to the lipophilic resin surface after exposure and development. If the photosensitive resin pattern is heat-adhesive, it may be transferred by heat, if it is pressure-sensitive, it may be transferred by pressure, or it may be transferred using another adhesive. Fortunately, even if adhesive remains in the non-masked areas, it is removed during plasma processing.

Similarly, transfer methods using electrography or magnetography can also be used.

Once the mask 3 is formed as shown in the second figure, it is placed in a vacuum persier and processed by generating plasma by vacuum discharge at a vacuum degree of 0.05 to several torr. As a result, as shown in the third figure, the lipophilic substance in the non-shielded portion is removed and the hydrophilic substrate surface is exposed. The current and voltage vary depending on the structure of the apparatus, desired processing speed, material to be processed, gas used, etc., and it is necessary to determine the optimum value in a timely manner. If the lipophilic substance is an organic substance as in the above example, oxygen plasma is generally effective, and the lipophilic resin layer 2 is evaporated and removed as carbon dioxide and water. Even if there are other elements, for example, N is NO ₂
Then, S becomes SO ₂ and is similarly vaporized.

In reality, it is not simple and there are many intermediate products, but they will be removed as soon as they can be vaporized, so there is no need to consider them too much. In addition, some of the inorganic substances mixed in as catalysts during resin synthesis and other causes evaporate, but most remain as ash. However, since it is generally oxidized, hydrophilic, and in a small amount, it does not pose much of a problem. If necessary, it can be easily washed away after the treatment is completed.

Since the mask 3 is generally an organic material, it is attacked in the same way as the resin layer 2 during plasma processing and is gradually evaporated and removed from the surface, and normally decreases at an evaporation rate close to that of the resin layer 2. However, if the film thickness is appropriate, the removal of the resin layer 2 will be completed while the mask 3 remains. In this case, after the treatment, the residual mask material 3 may be removed by an appropriate method as shown in Figure 4, but in general, the adhesion to the resin layer 2 is greater after the plasma treatment, and the mask material itself is less resistant. Since it is oil-based, there is often no need to remove it.

In addition, even if the film thickness of the mask 3 is insufficient to completely remove the resin layer 2, the original level difference is maintained, so the film thickness of the image resin only decreases and it can be used as a printing plate. can do. However, in this case, it is not a good idea because it becomes somewhat unstable in terms of control of printing durability, resolution, etc. In order to improve this mask performance, the following measures should be taken.

It is effective to mix into the mask material an inorganic fine powder that is not easily attacked by the gas plasma used or remains as a solid (ash) even if attacked. For example, metal powder, its oxide powder, etc.

Organic matter on the surface of mask 3 is removed by plasma,
Even if the inorganic powder is attacked, it will not evaporate and will remain, so the mask effect will not diminish. Fortunately, unlike chemical etching, the aggressiveness of plasma is highly directional and enters almost perpendicularly from the edge of the mask, so so-called side etching is extremely rare. Therefore, simply placing an object on it has a masking effect.

In this way, if non-volatile fine particles exist in the mask material, the amount of loss of the mask due to plasma attack is small, so even if the thickness of the mask 3 is small to some extent, it will be able to withstand until the resin layer 2 is completely removed. Become. However, since inorganic substances are exposed on the surface of the mask material after treatment, it tends to become hydrophilic, so it is better to remove the mask material with an appropriate solvent. In some cases, the binder around the inorganic particles has evaporated, so they are not bound to the mask material and can be easily removed by rubbing lightly or washing with water or solvent, and the lipophilic part (of the mask material) is removed. (including unattacked components) may also appear. When this type of mask 3 is used, the original thickness and properties of the resin layer 2 are preserved, making it easy to maintain the printing plate characteristics.

On the other hand, with the mask transfer method, the lithographic material of the present invention itself cannot have PS plate-like characteristics, and plate making is somewhat troublesome and it is difficult to obtain a high-quality printing plate. Therefore, as shown in FIG. 5, if a suitable photosensitive material layer 4 for a mask is further provided on the lithographic material shown in FIG. becomes. Since the photosensitive material layer 4 is also removed by plasma attack, it is preferable to mix a nonvolatile material in the same manner as described above. In this case, even if the photosensitive material layer 4 is relatively thin, the plasma treatment is effective in removing the thick resin layer 2.

When using a general photosensitive resin as the above-mentioned photosensitive material, it is preferable to mix an appropriate amount of inorganic fine powder such as aluminum oxide or titanium white and apply it. Particularly preferred is silicon oxide fine powder called Erosil, which has a refractive index close to that of photosensitive resin and can minimize deterioration in resolution.

The materials used in the present invention are generally the following substances, but are not necessarily limited thereto.

As mentioned above, Al plate is most preferable as the support substrate, but other metal plates such as Fe, Cu, Zn, Mg,
Alternatively, metal plates electroplated with Cr, Ni, etc. can be used for these.

The lipophilic resin layer on the support substrate includes polyester, polypropylene, polyethylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyethylene terephthalate, ABS resin, nylon, polyacetal, acetate resin, acrylic resin, polycarbonate, phenol resin, urea resin, Melamine resins, epoxy resins, xylene resins, alkyd resins, rubbers (natural and synthetic), other natural or synthetic resins, or selective mixtures thereof can be used.

Mask materials include various film-forming natural or synthetic resins and photosensitive resins. Photosensitive resins include cinnamic acid-based, azide-based, diazide-based, acrylic acid-based, nylon-based, cyclized rubber-based, etc. Oil-soluble photosensitive resins, water-soluble photosensitive resins that are photocrosslinked with dichromate, diqueso compounds, etc. based on gelatin, glue, egg white, polyvinyl alcohol, etc. can be used.

Inorganic substances for mask reinforcement preferably include silicon dioxide, titanium oxide, aluminum oxide, zinc oxide, lead oxide, aluminum hydroxide, Fe, and particles with particle sizes of 0.5μ or less for precise images and 30μ or less for rough images.
Zn, Sn, Ni, Cu, Ge, Al, other metal powders, metal sulfides, double salts, complex salts, and other substances that can be powdered (inorganic pigments are preferred) can be used.
These can be used alone or in combination in mask materials.
It is desirable to mix it in an amount of about 10 to 70% by weight.

Gases for active plasma include air, water vapor,
Argon, nitrogen, oxygen, halogen, hydrogen halide, etc. can be used alone or as a mixed gas.

Hereinafter, the present invention will be explained in more detail by showing examples.

Example 1 Polyester resin was applied to a thickness of about 5 μm on a 0.3 mm thick Al plate with a grained surface and dried. Separately, a silk screen with a suitable image prepared by a conventional method was prepared, placed on the polyester surface, and printed using a conventional silk screen ink. The ink film thickness after drying is 8 μm, and the ink is colored with an organic blue pigment (cyanine blue).

After printing, a plasma etching device (manufactured by Tokyo Ohka Co., Ltd.) was used to perform plasma treatment at 300 W in an oxygen atmosphere at a vacuum level of 2 to 3 Torr, but the polyester resin in the non-masking areas was removed to expose the Al plate surface. It took about 40 minutes. The residual ink film thickness after treatment was 1 to 2 microns.

A printing plate was prepared by removing residual ink with a solvent and at the same time cleaning some ash on the surface of the Al plate. This plate had a printing life of 50,000 to 100,000 sheets on an offset printing press using dampening water.

Example 2 In the above example, 20% of fine metal powder (300 mesh iron powder) was mixed into the screen printing ink and treated in the same manner. The ink film thickness at this time was 5 μm, but the residual ink film thickness after treatment was 1 μm, indicating that the masking ink film thickness could be reduced by mixing metal powder.

Example 3 One side of a 0.3 mm thick Al plate was anodized to give water retention properties, and then a phenol resin was applied to a thickness of 3 μm and cured to form a substrate. Separately, AZ・111 (positive type photoresist manufactured by Shippray Co., Ltd.) was applied to a thickness of 4μ on a 0.2mm thick polyester resin film and dried.
The line/inch halftone plate and the letter/photo original plate were vacuum-contact-printed. After developing and drying with a designated developer, the image was transferred onto the phenol resin surface of the Al plate to form a mask. For transfer, a commercially available pressure-sensitive adhesive was applied thinly to the phenol resin surface, AZ-111 image film was layered and pressed with a roller, and then only the polyester film was peeled off.

The adhesion between the polyester film and the AZ-resist was not very strong, so the transfer was relatively easy.

Next, plasma treatment was performed using the plasma apparatus under the same conditions, and an Al surface appeared in about 30 minutes, and the adhesive and phenol resin were removed from areas other than the AZ-111 mask area. Further, the residual resist film thickness was 1 μm and it was firmly adhered, and since it was lipophilic, it was used as a printing plate without being removed.

When this was installed in an offset printing machine and a printing test was carried out, the printing durability was approximately 200,000 sheets, and good printed matter was obtained.

Example 4 Commercially available zinc oxide master paper for light printing (manufactured by Ricoh Co., Ltd.) was corona charged in a dark room, and a halftone photographic film consisting of several line numbers was exposed by the contact method to form an electrostatic latent image. Ta. Then, development was carried out by a magnetic brush method using the same developing toner for master paper (black). On the other hand, after giving a negative corona charge to the polyester surface of the Al-polyester substrate of Example 1 (charge approximately
400W), the above-mentioned developed zinc oxide master paper was placed on top of the paper and the paper was peeled off, and the toner image was transferred to the polyester surface. Next, heating was performed at 120°C to fuse and fix the toner, resulting in a toner mask approximately 10μ thick. This was subjected to plasma treatment under the same conditions as in Example 1, and a printing plate was obtained in about 40 minutes. The printing durability was the same as in Example 1, but the resolution was about 80 lines/inch.

Example 5 AZ-
111 was directly applied to a thickness of about 4μ to make a type of PS plate. After vacuum contact printing of the 150 lines/inch halftone plate and letter photographic original plate, a resist mask plate was obtained by developing and drying according to the specified processing method.

The plate was then treated in the same manner using the plasma apparatus described above, and a printing plate was obtained in about 20 minutes. As compared with Example 3, a better image was obtained and at the same time, the processing time was shortened due to the absence of adhesive.

Example 6 In Example 5, 25% of fine powder of silicon dioxide Sio ₂ (trade name Erosil) was added to the AZ-111 photosensitive solution and applied to give a film thickness of 3 μm. When the above-mentioned photographic original plate was subjected to plasma treatment after contact printing and development, it was found that approximately 20
A print plate with better image quality than the previous example was obtained in minutes. The reason for this is that the masking effect of the SiO ₂ powder made it possible to reduce the resist film thickness and improve resolution.

[Brief explanation of the drawing]

1 to 4 are schematic sectional views illustrating each step of the lithographic plate-making method of the present invention, and FIG. 5 is a schematic sectional view illustrating materials used in the lithographic plate-making method of the present invention. 1...Hydrophilic substrate, 2...Lipophilic substance layer, 3...
...Mask pattern, 4...Photosensitive material layer.

Claims (1)

[Claims] 1. A lipophilic material layer is provided on the surface of a hydrophilic substrate, and an active plasma shielding mask pattern is formed on the layer,
Next, the exposed surface of the lipophilic substance, which is the non-shielded part of the mask pattern, is exposed to active plasma, and the lipophilic substance in the non-shielded part is selectively removed to expose the hydrophilic substrate surface. A planographic process using plasma that is characterized by removing mask patterns. 2. The lithographic platemaking method of item 1 above, wherein the mask pattern is mixed with inorganic fine powder in advance. 3. The lithographic platemaking method according to item 1 or 2 above, wherein the mask pattern is formed by providing a masking photosensitive resin pattern on the base material and then transferring the pattern onto the lipophilic substance layer. 4. The lithographic platemaking method according to item 1 or 2, wherein the mask pattern is formed by providing a photosensitive material layer for masking on the lipophilic substance layer, and then printing and developing a pattern on the material layer. 5. A lithographic printing plate material for use in lithographic platemaking using plasma, characterized by having a lipophilic resin layer on a hydrophilic substrate and further having a photosensitive resin layer thereon. 6. The material according to item 5 above, wherein an inorganic fine powder is mixed in the photosensitive resin layer.