JPS6158032B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for plate-making a highly sensitive photosensitive lithographic material using active gas plasma. 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 to the image area, and then transferring the ink to a 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. PS version is made of hydrophilic substrate (usually Al
A photographic original plate is coated with a photosensitive resin on its surface, and the photosensitive resin in the exposed or non-exposed areas is removed by development (positive and negative types are available), and the remaining photosensitive resin is removed. A printing plate can be manufactured in which the exposed substrate surface becomes a lipophilic region and the exposed substrate surface becomes a hydrophilic region. The plate-making method for PS plates is simple and very popular as described above, but in order to improve 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. On the other hand, in terms of sensitivity, photosensitive resins for PS plates inherently have low sensitivity, and although various sensitization methods have been attempted, no particularly sensitive material has been developed to date. Therefore, printing plates are usually made by exposure using a vacuum contact printing method using a high-output light source such as a mercury lamp, xenon lamp, or halogen lamp, which is rich in ultraviolet rays. Contact printing always requires an intermediate photographic plate, but in recent years there has been a demand for a direct plate-making method in which a plate is made by direct camera exposure from a reflective original in order to save materials and time. Existing materials and methods that meet this demand include, for example, a method that uses a silver salt emulsion called a silver master as a photosensitive agent and a plate material, and a method that uses an electrophotographic master using toner development using an electrophotographic method. These are merely used as high-sensitivity lithographic materials that have photographic sensitivity. However, silver emulsion PS like Silver Master
The binder of the plate is gelatin or other water-absorbing material, and its abrasion resistance when wetted with dampening water is extremely poor. Furthermore, the zinc oxide layer of the electrophotographic master is hydrophilic, and the coated layer containing a relatively large amount of zinc oxide is similarly not very strong. Furthermore, there is also the problem of weak adhesion between the toner (ink-attached portion) and the substrate. For these reasons, printing durability is generally poor, and generally 1000
~2,000 sheets, and even if you are careful, 10,000 sheets at most. This is significantly lower than the printing durability of current photosensitive resin PS plates, which is 30,000 to 100,000 sheets, and is not very suitable for commercial printing. In light of the above-mentioned current situation, the present inventor provides a method for making a PS plate that has photographic sensitivity similar to that of Silver Master and has printing durability equivalent to or greater than that of a normal PS plate. The plate-making principle of the present invention is the selective removal of lipophilic resin by activated plasma, and a silver salt photosensitive material is used as a masking means for this selective removal, and due to the high sensitivity of silver salt, it is possible to photograph as a PS plate. It provides high sensitivity and high resolution, making it possible to obtain high quality printing plates. 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 high aggressiveness or reactivity towards 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. The present invention newly utilizes the above-mentioned principle in lithographic platemaking, and its basic purpose is to selectively remove the resin layer on the substrate using a high-sensitivity silver salt photosensitive material as a masking material, so to speak. The layer is completely evaporated by selective etching to expose the surface of the hydrophilic substrate, thereby performing lithography. Next, the present invention will be explained in detail. The basic structure of the photosensitive flat plate material used in the present invention is as shown in the first diagram, which has a lipophilic resin layer 2 on a hydrophilic substrate 1, and a silver salt photosensitive material layer 3 on top of the lipophilic resin layer 2.
has. 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 resin layer 2 with good adhesiveness is formed on the surface of this water-retaining substrate 1.
is prepared by coating and drying a suitable synthetic or natural resin. When selecting lipophilic substances, it is advantageous to use synthetic resins, which are available in a wide variety of types. Coating film thickness is 1μ to 5μ
is preferred, but is not limited to this. If a grained surface is used, the film thickness must be sufficient to 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 preferred.
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 high printing durability is the goal, it is necessary to form a three-dimensional molecular structure by heat treatment or reaction with a cross-linking agent after coating. , resins exhibiting extremely high values of surface strength and abrasion resistance are suitable. Next, this lipophilic substance layer 2
A silver salt photosensitive layer 3 is provided on the emulsion by coating and drying an emulsion containing silver halide and gelatin as main components, preferably after treatment with a subbing agent. The thickness of the layer is preferably about 2 to 15 microns. The silver salt photosensitive material for masks is most preferably a lithium emulsion, which has high contrast and good halftone reproducibility, since it is used for lithographic printing, but other emulsions may be used depending on the purpose. The materials used in the above-mentioned photosensitive lithographic materials are generally the following substances, but are not necessarily limited thereto. As the supporting substrate, Al plate is most preferable as mentioned above, but other metal plates such as Fe, Cu, Zn, etc.
A single metal plate made of Mg or Mg electroplated with Cr, Ni, etc., or a composite plate with paper, plastic, etc. can be used. 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. Next, a method for plate making using the above photosensitive lithographic material will be described in detail. The first method is to expose the silver salt photosensitive material layer 3 to light through a pattern 4 as shown in FIG. 2A.
After forming the unexposed area 32 and the unexposed area 32, development, fixing, washing, and drying are performed in the usual manner, resulting in the image shown in FIG. 2B.
As shown in the figure, the reduced blackened silver 31 in the exposed area remains,
The silver salt in the non-exposed areas is removed, leaving only the gelatin film 33. If plasma treatment is performed in this state, the blackened silver 31 will remain as ash until the end and will act as a mask, and the gelatin film 33 will be removed by evaporation since it is an organic substance, and then the lipophilic resin layer 2 in the non-mask area will be removed. The substrate surface appears (FIG. 2C). Then blackened silver 3 as a mask if necessary.
Remove 1. In this way, a negative lithographic printing plate for the pattern 4 as shown in FIG. 2D is obtained. The second method is to carry out pattern exposure and then reverse development as shown in FIG. 2A, and two methods are used to form a mask using this method. More specifically, as shown in Figure 2A, after pattern exposure (first exposure), development (first development), bleaching with copper sulfate/hydrogen peroxide solution, washing with water, drying, and blackening. The silver is removed along with the gelatin, leaving an unexposed emulsion area 32 (FIG. 2E). The unexposed emulsion portion 32 is in a positive relationship with the pattern 4. One of the above-mentioned second methods is to perform plasma processing using the unexposed emulsion portion 32 as a mask, thereby removing the lipophilic resin layer 2 in the unmasked portion and exposing the substrate surface (FIG. 2F). Furthermore, the unexposed emulsion portion 32 serving as a mask is removed if necessary. In this way, a positive lithographic printing plate for the pattern 4 as shown in FIG. 2G is obtained. Another method in the second method is to perform reversal exposure (second exposure) on the unexposed emulsion area 32 shown in FIG. 2E, then perform second development, and then fix. By washing with water and drying, a pattern of blackened silver 34 having a positive relationship with the pattern 4 is formed (FIG. 2H). Thereafter, by plasma processing using the blackened silver 34 as a mask, the lipophilic resin layer 2 in the non-mask area is removed and the substrate surface is exposed (FIG. 2I). Further, if necessary, the blackened silver 34 as a mask is removed (FIG. 2G). In this method, the reversal exposure can be carried out after the bleaching, washing with water, and drying, but it can also be carried out directly after being placed in a bleaching solution. According to the second method, the time for removing the gelatin film 33 can be saved compared to the first method. Next, regarding the above plasma processing, once the mask has been formed as described above, it is placed in a vacuum bell jar and processed by generating plasma by vacuum discharge at a vacuum degree of 0.05 to several torr. This removes the lipophilic resin in the non-mask areas and exposes the hydrophilic substrate surface. 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. As mentioned in the above example, since the lipophilic resin is an organic substance, oxygen plasma is generally effective, and the lipophilic resin layer 2 is evaporated and removed into carbon dioxide gas and water. If other elements are present, for example, N becomes NO ₂ and S becomes SO ₂ and are similarly vaporized. In reality, it is not simple and there are many intermediate products, but they are removed immediately if they can be vaporized, so there is no need to consider them too much. In addition, some of the inorganic substances mixed in as a result of catalysts and other causes during resin synthesis 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. Further, as the active plasma gases, air, water vapor, argon nitrogen, oxygen, halogen, hydrogen halide, low boiling point halogen-containing hydrocarbons, etc. can be used alone or as a mixed gas. It is extremely important that the lithographic material and plate-making method of the present invention allow use of a silver salt emulsion with photographic sensitivity as a masking material. For example, it is possible to directly obtain printing plates with high printing durability just by operating the camera,
The process of first making a photographic plate using scanner plate making or laser plate making, which is an application of electrical signal conversion technology, and then contact exposure plate making can now be made directly onto the plate material. This shows that plate making using laser is possible. Hereinafter, the present invention will be explained in more detail by showing examples. Example 1 One side of a 0.3 mm thick Al plate was anodized using a conventional method to impart water retention properties, and then 3 μm thick phenol resin was applied.
It was applied thickly and cured. Next, a thin gelatin solution was applied as a subbing agent to a thickness of about 1 μm when dry, and a silver emulsion having the following formulation was further prepared and applied.

[Table] When adding a concentrated ammonia solution to a silver nitrate solution, the appropriate amount of ammonia water should be the amount that precipitates and redissolves. While stirring Solution A, quickly add Solution B.
After 5 minutes, add 1/2 of Part C, and after another 5 minutes, add the remaining 1/2, and after 10 minutes, ripen, cool, solidify, and wash with water.
After washing with water, the redissolved emulsion is post-ripened at 50°C for 50 to 60 minutes, resulting in a gamma of 3 or higher. The emulsion coating layer was about 20 μm. A photosensitive lithographic material was thus prepared. This photosensitive lithographic material was vacuum-adhered to a 100-line/inch halftone negative master plate, and contact printing was performed using a tungsten lamp. Next, after developing with high-contrast developer D-11 (prescribed by Kodatsu), fixing using the usual method, washing with water,
Dry. A blackened silver halftone positive was formed on the silver emulsion layer. This photosensitive halftone positive was placed in a vacuum bell jar and subjected to active plasma treatment in an air atmosphere with a degree of vacuum of 0.05 to 0.1 Torr. The plasma generator is 600W
RF type (OPM-EM600-2S type manufactured by Tokyo Ohka Co., Ltd.)
Although the processing time required approximately 60 minutes, the blackened silver area turned gray but had a plasma shielding effect, and the gelatin and phenol resin layers were removed from the desilvered area, leaving the Al substrate surface exposed. Next, the silver salt and gelatin were removed with a 5% sodium hypochlorite solution, and a printing plate was obtained after washing with water and drying to form an Al plate-phenol resin pattern. This printed version
It had good halftone reproducibility at 100 lines/inch, was capable of offset printing using ordinary dampening water, and had a printing life of about 100,000 sheets. Example 2 After exposure and development of the photosensitive planographic material of the previous example, the material was washed with water in a dark room, and then 30% of the photosensitive planographic material was added to 1000 c.c. of a 10% copper sulfate aqueous solution.
By immersing it in an aqueous solution containing 20 to 40 c.c. of hydrogen peroxide solution and shaking it or rubbing the surface lightly with absorbent cotton, the blackened silver part is dissolved and removed along with the gelatin, and the unexposed silver part is not attacked. This was subjected to reverse exposure using a conventional method and then subjected to second development to produce a blackened silver relief on the phenol resin surface.
When active plasma treatment was applied using this blackened silver relief as a mask, it was completed in about 20 minutes, faster than in the previous example.
The surface of the Al substrate was exposed. Then, blackened silver and gelatin were removed with a sodium hypochlorite solution to prepare a printing plate. In this example, even if the silver halide is left without the second development, the masking effect is in principle the same, and in fact, the second development can be omitted for the plasma processing mask. Example 3 5μ of polyester resin was applied to the surface of the water-retaining Al plate.
After applying a thin gelatin subbing, a commercially available squirrel-type emulsion was obtained and applied. The emulsion film thickness was approximately 10 μm. A photosensitive lithographic material was thus prepared. This photosensitive lithographic material was placed in a plate-making camera, and imagewise exposed while in close contact with a contact screen (175 lines/inch). By this conventional halftone photography method, a 175 line/inch halftone photograph was obtained on the photosensitive plate. This was subjected to plasma treatment according to the method of Examples 1 and 2 to obtain a printing plate. The printing durability was 50,000 to 100,000 sheets. The print quality of Example 2 was better. It has become clear that this method enables plate making by directly photographing the printing plate surface. Example 4 Using a direct halftone printing scanner that directly forms halftone dots on a film, the photosensitive lithographic material of Example 3 was placed in place of the photographic film, and the operation was carried out. After exposure, the plasma treatment was performed to obtain a printing plate. Example 5 1μ on the substrate and phenolic resin layer of Example 1
The same emulsion was subbed with gelatin to a thickness of 3 m.
It was applied to a thickness of ~5 μm and dried. This photosensitive lithographic material and a 100 line/inch halftone photographic original plate were closely printed with a tungsten lamp, developed with a developer (D-11), fixed, and washed with water. Since this plate surface had a thin photosensitive agent layer, the amount of blackening was small, and the masking effect during plasma treatment was somewhat poor. In order to eliminate this drawback, perform the following reinforcement processing,
The amount of silver was replenished afterward. The masking effect increased due to reinforcement, and good plasma processing was achieved. In this case, compared to Example 1, the gelatin layer in the desilvered area was much thinner, so the plasma treatment time was halved to about 30 minutes even under the same conditions. The following Wellington silver intensification method was used for intensification treatment.

[Table] Liquid preparation: Gradually add 100 c.c. of liquid B to 100 c.c. of liquid A and stir vigorously to make it transparent. Add 250 c.c. of liquid C to this, and then add 50 c.c. of liquid D. The developed substrate is hardened with 10% formalin solution, washed with water, immersed in the pre-bath solution for 1 minute, and then immersed in the prepared solution. Silver precipitation begins in 1 to 2 minutes, so once the pressure is applied appropriately, it is fixed, washed with water, dried, and subjected to plasma treatment.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view illustrating the photosensitive lithographic material used in the present invention, and FIGS. 2A to 2 G are schematic sectional views illustrating each step of the lithographic platemaking method of the present invention. 1...Hydrophilic substrate, 2...Lipophilic resin layer, 3...
...Silver salt photosensitive material layer, 31...Blackened silver part, 32...Unexposed emulsion part, 33...Gelatin film, 34...Blackened silver part, 4...Pattern.

Claims (1)

[Scope of Claims] 1. The silver salt photosensitive material layer of a photosensitive lithographic material having a lipophilic resin layer on a hydrophilic substrate and a silver salt photosensitive material layer thereon is pattern-exposed, and then the silver salt photosensitive material layer is pattern-exposed. After developing and fixing the photosensitive material layer to form a negative pattern of blackened silver areas for the desilvering area, binder layer area, and the above-mentioned exposure pattern, active plasma treatment is performed using the blackened silver areas as a mask. Selectively remove the binder layer of the desilvered part of the silver salt photosensitive material layer and the lipophilic resin layer of the non-mask part to expose the hydrophilic substrate surface, and further remove the blackened silver part as necessary. A planographic process characterized by: 2 The silver salt photosensitive material layer of a photosensitive lithographic material having a lipophilic resin layer on a hydrophilic substrate and a silver salt photosensitive material layer thereon is exposed in a pattern, and then the silver salt photosensitive material layer is developed and bleached. After forming an unexposed emulsion part of a positive pattern with respect to the above exposure pattern, active plasma treatment is performed using the unexposed emulsion part as a mask to selectively remove the lipophilic resin layer of the unmasked part and make it hydrophilic. 1. A lithographic plate-making method, which comprises exposing the surface of the transparent substrate and, if necessary, removing the unexposed emulsion area. 3 The silver salt photosensitive material layer of a photosensitive lithographic material having a lipophilic resin layer on a hydrophilic substrate and a silver salt photosensitive material layer thereon is exposed in a pattern, and then the silver salt photosensitive material layer is exposed to the first layer. After developing, bleaching, reversal exposure, second development and fixing to form a positive pattern blackened silver area with respect to the above exposure pattern, active plasma treatment is performed using the blackened silver area as a mask to remove the non-masked area. A lithographic platemaking method characterized by selectively removing an oleophilic resin layer to expose a hydrophilic substrate surface, and further removing the blackened silver portion as necessary.