JP2003280206A - Method for producing planographic printing plate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a planographic printing plate using a silver complex salt diffusion transfer process and ensuring improved printing resistance and image definition of a plate. <P>SOLUTION: In the method for producing a planographic printing plate in which the top of a support is coated with at least a silver halide emulsion layer and further coated with a physical developing nucleus layer, the face coated with the silver halide emulsion layer is washed and then coated with the physical developing nucleus layer. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a lithographic printing plate using a silver complex salt diffusion transfer method.

[0002]

2. Description of the Related Art A lithographic printing plate is composed of an oleophilic image portion that accepts oily ink and an oil-repellent non-image portion that does not accept ink. Generally, the non-image portion consists of a hydrophilic portion that accepts water. It is configured. In ordinary lithographic printing, both water and ink are supplied to the plate surface, the image part selectively receives colored ink, and the non-image part selectively receives water, and the ink on the image, for example, paper, film, etc. Printing is performed by transferring the image onto the printing medium.

Therefore, in order to obtain a good printed matter, the difference in lipophilicity and hydrophilicity between the image part and the non-image part is sufficiently large, and when water and ink are supplied to the lithographic printing plate surface, the image part has a sufficient amount. It is important and necessary to accept the ink of the above and not accept the ink of the non-image area at all.

A lithographic printing plate using a silver complex salt diffusion transfer method, in particular, a lithographic printing plate having a physical development nucleus layer on a silver halide emulsion layer is described in, for example, US Pat.
No. 114, No. 4,134,769, No. 4,16
0,670, 4,336,321, 4,5
01, 811, No. 4,510, 228, No. 4,
No. 621,041 specification, unexposed silver halide crystals are converted into silver salt complexes by the silver salt complexing agent in the developer and diffused to the physical development nucleus layer on the surface, and the presence of nuclei exists. Physical development is carried out to form an image area mainly composed of ink-receptive physically developed silver on the surface of the lithographic printing plate. On the other hand, the exposed silver halide crystal undergoes chemical development by silver salt diffusion transfer development to become black silver and forms a hydrophilic non-image area.

In such a lithographic printing plate, since the silver image deposited on the physical development nucleus layer is used as an ink-receptive image portion, it is deposited on the physical development nucleus layer which can withstand a large amount of printing. The strength (printing durability) of the silver image area must be maintained. Also, in a lithographic printing plate that uses the repulsion of water and ink to form an image of a printed matter, the non-image area needs to be sufficiently water-repellent to repel the ink, and to have sufficient water retention to prevent ink stains. And Further, in the plate making process of the planographic printing plate, it is possible to perform comparison confirmation and correction with the original document such as whether the exposure is appropriate, whether minute halftone dots or fine lines appear, so that the image is There is a need for a lithographic printing plate that has a clearer contrast, that is, a stronger contrast between the non-image area, which is black silver, and the image area, which is physically developed silver.

Further, when the halftone image is exposed, it is necessary to judge whether the obtained halftone dot is proper or not. As a method of managing the halftone dot area ratio, a method of obtaining the halftone dot area ratio from the optical density is often used. In this case, in order to obtain the area ratio of the halftone dot image more accurately, it is necessary to increase the difference in optical density between the image portion and the non-image portion. It is possible to calculate the concentration. In other words, by lowering the optical reflection density of the silver image area deposited on the physical development nucleus layer to increase the difference between the density of the non-image area and the optical reflection density of the image area, Making identification easy is important in the plate making process of a lithographic printing plate using the silver complex salt diffusion transfer method.

Regarding these problems, Japanese Patent Laid-Open No. 8-194
JP-A No. 315/1993 describes that the temperature at the time of coating the physical development nucleus layer is regulated and improved, and JP-A No. 11-295898 discloses that the surface temperature of the silver halide emulsion layer is regulated and improved. However, although the effect is recognized, the result has not been fully satisfactory.

In order to lower the optical reflection density of the image area, for example, the kind or amount of the hardener used for crosslinking hydrophilic colloid in the silver halide emulsion layer, such as gelatin, is changed. However, in these techniques, even if the optical reflection density of the silver image area deposited on the physical development nucleus layer can be reduced, the printing durability of the image area and the water retention of the non-image area can be reduced. It is not preferable because it lowers the basic performance of the planographic printing plate.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a lithographic printing plate to which a silver complex salt diffusion transfer method is applied, which has sufficient printing performance as a lithographic printing plate and has a physical development nucleus layer. Provided is a method for producing a lithographic printing plate using the silver complex salt diffusion transfer method, in which the optical reflection density of the silver image area deposited on the surface of the image is reduced and the image area and non-image area can be easily distinguished, that is, the image definition is improved. It is to be.

[0010]

The above object of the present invention is to provide a method for producing a lithographic printing plate in which at least a silver halide emulsion layer is coated on a support, and a physical development nucleus layer is further coated thereon. This is achieved by a method for producing a lithographic printing plate characterized in that the surface coated with the silver halide emulsion layer is washed with water and then the physical development nucleus layer is coated.

More preferably, in the method for producing a lithographic printing plate, the temperature of the water washing treatment is preferably 5 to 30 ° C. Further, if the one-pass treatment (tandem method) is continuously performed without winding up the washing treatment and the coating of the physical development nucleus layer, it becomes a more preferable figure without increasing the number of steps.

[0012]

DETAILED DESCRIPTION OF THE INVENTION As a result of various studies on the conditions for coating a physical development nucleus layer on a silver halide emulsion layer, the present inventors have conducted a washing treatment on the surface coated with a silver halide emulsion layer. By applying the physical development nucleus layer afterwards, the optical reflection density of the silver image portion deposited on the physical development nucleus layer is reduced without impairing the printing performance as a lithographic printing plate, and the image area and the non-image area are reduced. It has been found that a lithographic printing plate with improved image sharpness can be obtained by increasing the difference in optical reflection density.

Conventionally, since some of the physical development nuclei sink into the silver halide emulsion layer, there is a problem that the ink receptivity is lowered, and the sharpness is also deteriorated. When a hydrophilic polymer is present around the physical development nuclei, the precipitated silver is covered with the polymer and becomes small-sized physical development silver particles, which increases the optical reflection density and increases the optical reflection of the chemical development area. It was presumed that the difference from the concentration would be small, and various investigations were conducted by the method of eliminating the presence of the water-soluble substance around the physical development nuclei.

For example, as described in JP-A-8-194315, lowering the temperature of the coating solution for coating the physical development nucleus layer lowers the solubility of the water-soluble substance, so that the amount eluted is reduced. Then, the improvement of the sharpness was seen. Also,
As described in JP-A No. 11-295898, even when the surface temperature of the silver halide emulsion layer is lowered, the elution of the water-soluble substance is reduced by the same effect, and the sharpness is improved. However, the effects obtained by those methods have been insufficient.

The lithographic printing plate targeted by the present invention is usually provided with an undercoat layer also serving as an antihalation layer between the support and the silver halide emulsion layer. The surface of the silver halide emulsion layer coated in the present invention is preferably washed with water after the undercoat layer and the silver halide emulsion layer have been coated and dried on the support and heat-treated. In the heat treatment, after the halogenated emulsion layer is coated and dried, it may be wound once and heated in a warming chamber, or after the silver halide emulsion layer is coated and dried, it is continuously wound without being wound. You may heat-process with a heating roll etc. In the case of heat treatment in the heating chamber,
It is preferable to heat at a temperature of about 40 to 60 ° C. for several days. At this time, in order to eliminate the influence of the humidity of the warming box, if moisture-proof packaging that does not allow water to pass through is performed, even if a large roll is wound, the heating will be substantially even. When the heat treatment is performed with the latter heating roll or the like, it is preferable that the surface temperature of the surface coated with the halogenated emulsion layer is 70 ° C. or higher.

The washing treatment of the present invention is to wash off with water, and the time and method required therefor are not particularly limited. If the washing treatment and the coating of the physical development nuclei layer are continuously carried out without winding, it is necessary to sprinkle with water, and it is preferable to scrape with an air knife. Specifically, "Coating Engineering" published by Asakura Shoten
The silver halide is prepared by applying water with a dip coat, which is a coating method described in detail on pages 253 to 277 (published by Showa 46.320), and then scraping off the water with an air knife. It is possible to wash away unnecessary water-soluble substances that have not been adsorbed on. Further, if the washing water is supplied by the fountain system, the amount of water can be regulated and the line speed can be increased.

The physical development nucleus layer is applied after washing with water. As the application method, there are known methods such as slide application method, dip application method, air knife application method, gravure method, doctor blade method, and the like. A reverse roll method, a metering bar method, etc. can be used. Other methods are also possible, and specific explanations thereof are described in detail in the above-mentioned “Coating Engineering” pages 253 to 277 (published 46.320 of Showa).

The silver halide emulsion layer is, for example, silver chloride,
It is composed of silver chlorobromide and those containing silver iodide.
The silver halide crystals may contain heavy metal salts such as rhodium salt, iridium salt, palladium salt, ruthenium salt, nickel salt and platinum salt. The crystal form of silver halide is not particularly limited, and may be cubic or tetradecahedral grains, or core-shell type or tabular grains. The silver halide crystals may be monodisperse or polydisperse crystals, and the average particle size thereof is in the range of 0.2 to 0.8 μm.

The silver halide photographic emulsion of the present invention may be a so-called primitive emulsion (primitive emulsion) which is not chemically sensitized, but it is usually chemically sensitized. For chemical sensitization, a sulfur sensitization method, a reduction sensitization method, a noble metal sensitization method or the like can be performed alone or in combination.

The silver halide emulsion can also be spectrally sensitized or desensitized with cyanine dyes, merocyanine dyes and the like. There is no particular limitation on the wavelength range that can be sensitized or desensitized.

In the lithographic printing plate of the present invention, an undercoat layer which also serves as an antihalation layer is usually provided between the support and the silver halide emulsion layer. The silver halide photographic emulsion layer and the undercoat layer may contain various compounds for the purpose of stabilizing the photographic performance during the production process thereof, and during storage as a product and development processing. For example, antifoggants, antistatic agents, antihalation dyes, plasticizers,
A surfactant, a matting agent, carbon black, a polymer latex, a developing agent, a development accelerator and the like can be contained.

The lithographic printing plate which is the subject of the present invention contains gelatin, and the layers containing it are a silver halide photographic emulsion layer, a subbing layer, a backing layer and a physical development nucleus. It can also be a layer. The gelatin in the gelatin-containing layer of the present invention can be partially replaced with another hydrophilic colloid.

The gelatin-containing layer of the present invention can be hardened with an inorganic or organic gelatin hardener. The hardener can be added to all layers or to some or only one layer. Of course, the diffusible hardener can be added to only one layer in the case of simultaneous coating of two layers. As an addition method, it can be added at the time of emulsion production or in-line at the time of coating.

The physical development nucleus layer is usually provided adjacent to the upper portion of the silver halide emulsion layer. As the physical development nuclei of this physical development nuclei layer, silver, antimony, bismuth, cadmium, cobalt, lead, nickel, palladium, rhodium,
Fine particles of metal colloid such as gold and platinum, sulfides of these metals, polysulfides, selenides, or a mixture or mixed crystal thereof may be used. The physical development nucleus layer preferably contains a hydrophilic binder of about 0.1 to 1.0 g / m ² . Examples of the hydrophilic binder include gelatin, starch, dialdehyde starch, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl cellulose, polystyrene sulfonic acid, and JP-A-53-2160.
Examples thereof include copolymers of vinyl imidazole and acrylamide described in No. 2 report, copolymers of acrylamide and methyl sulfone substituted with guanylthioureas described in No. 8-212614 report, and polymers such as polyvinyl alcohol. Further, the physical development nucleus layer may contain a developing agent such as hydroquinone, methylhydroquinone and catechol, and a known hardener such as formalin and dichloro-s-triazine.

As a support for the lithographic printing plate of the present invention, a typical support is paper, RC paper or a synthetic or semi-synthetic polymer film, a metal plate such as aluminum or iron, and the like.
Any material that can withstand lithographic printing can be used.
The surface of the support may be coated on one side or both sides with one or more polymer films or metal thin films. The surface of these supports can be surface-treated in order to improve the adhesion with the coating layer.

Particularly preferably used supports are papers whose both surfaces or one surface is coated with a polyolefin polymer, polyester films whose surfaces are hydrophilized, and surface-treated aluminum plates. These supports may contain pigments for preventing halation and solid fine particles for improving the physical properties of the surface. The support may also be light transmissive so that backside exposure is possible.

The developing solution used in the present invention may contain an alkaline substance, a preservative, a silver halide solvent, a viscous agent, an antifoggant, a developer, a development modifier and the like. An activator type developing solution which does not contain it may be used. Further, a compound or the like which improves ink transfer of the surface silver layer can be used in the developing solution.

The surface silver layer after development of the lithographic printing plate of the present invention can be converted into ink receptivity or the receptivity can be enhanced by any known surface treatment agent. The printing method, or the desensitizing liquid, the dampening liquid, or the like to be used may be a commonly known method. The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0029]

EXAMPLE A matting layer (backing layer) containing silica particles having an average particle size of 5 μ was provided on one surface of a 135 g / m ² double-sided polyethylene-coated paper, and the opposite surface was subjected to corona discharge machining, followed by carbon black, and An undercoat layer (gelatin 3.5 g / m ² ) containing silica powder having an average particle size of 7 μ contains 1-phenyl-3-pyrazolidone 0.3 g / m ² and 1-phenyl-3-pyrazolidone 0. Ortho-sensitized high-sensitivity silver chloride emulsion with 1 g / m ² (gelatin 0.8 g
(Including / m ² ) to obtain 1.0 g / m ² as silver nitrate,
Two layers were simultaneously coated.

As a hardener, 2,4-dichloro-6-
Hydroxy-S-triazine sodium in the undercoat layer 1
70 mg / m ² and 80 mg / m ² of N-methylol ethylene urea were contained in the emulsion layer. After coating and drying the sample, it was moisture-proof packaged and heated at 50 ° C. for 3 days.

Next, a method for washing the sample discharged from the heating with water will be described. After coating a large amount of water on the surface of the silver halide emulsion layer by a dip method, most of the water is blown off by an air knife to dry. In this step, unnecessary water-soluble substances which are not adsorbed on silver halide are mostly washed off. Here, the sample which was not washed with water was used as a comparative sample A, and the temperature of the washing water was 5 ° C, 10 ° C, 20 ° C, 30 ° C, 40 ° C,
The temperature was changed to 50 ° C., and each was designated as B, C, D, E, F, G.

Next, a coating solution for the physical development nucleus layer having the following formulation was prepared. Liquid A and liquid B were mixed with stirring, and after 30 minutes, they were passed through a column packed with an ion exchange resin (IR-120E, IRA-400) to obtain a palladium sulfide sol.

[0033] <Preparation of physical development core solution>   100 ml of the above-mentioned palladium sulfide sol   Hydroquinone 100g   1-phenyl-3-pyrazolidone 10 g   Acrylamide (97) and imidazole (3) 5g       Copolymer (average molecular weight 100,000)   2% of 10% saponin (surfactant)   Water was added to bring the total volume to 2000 ml.

The physical development nuclei prepared as described above were coated on the above-washed silver halide emulsion layer by a slide bead coating method continuously at 25 ml / m ^{2 following} the above washing treatment. A lithographic printing plate was prepared by drying at 50 ° C.

These lithographic printing plates were image-exposed with a plate-making camera having an image reversing mechanism, and developed with the following silver complex salt diffusion transfer developer at 30 ° C. for 1 minute.

<Transfer developer> 700 ml of water 20 g of potassium hydroxide 50 g of anhydrous sodium sulfite 50 g 2-mercaptobenzoic acid 1.5 g 2-methylaminoethanol 15 g Water is added to make 1 liter. After the development treatment, the original plate is passed between two squeezing rollers to remove excess developer, and immediately treated with a neutralizing solution having the following composition at 25 ° C. for 20 seconds. Dried in.

<Neutralizing liquid> 600 ml of water Citric acid 10 g Sodium citrate 35 g Colloidal silica (20% liquid) 5 ml Ethylene glycol 5 ml Add water to make 1 liter.

The optical densities of the deposited silver image lines and the blackened silver non-image lines of the lithographic printing plate prepared by the above operation were measured with a DM-800 reflection densitometer manufactured by Dainippon Screen. The larger the difference in optical reflection density between the image portion and the non-image portion, the easier the discrimination between the image portion and the non-image portion. 0.75 or more is preferable as a standard of the density difference, and 0.
80 or more is more preferable. Further, in order to examine the printing quality of each planographic printing plate, the obtained planographic printing plate was used as a Ryobi 3200CD (trademark of Ryobi offset printing machine).
After mounting on a printing machine, the following desensitizing liquid was applied all over the plate surface, and printing was carried out for confirmation of printing durability using F gloss black 85N made by Dainippon Ink and the following dampening liquid as ink.

[0039]   <Desensitizing liquid>     600 ml of water     Isopropyl alcohol 400 ml     Ethylene glycol 50 g     3-mercapto-4-acetamide-     5-n-heptyl-1,2,4-triazole 1 g     Add water to make 1 liter.

<Moisturizing liquid> o-phosphoric acid 10 g Nickel nitrate 5 g Sodium nitrite 5 g Ethylene glycol 100 g Colloidal silica (20% liquid) 28 g Add water to make 2 liters.

From the result of printing, the number of printed sheets when the image was skipped due to the missing of the silver image portion and the image could not be used for printing was judged according to the following evaluation criteria. ○ No problem even with 5,000 sheets or more △ 1,000-5,000 sheets lack silver image area × Less than 1,000 sheets lack silver image area

Further, as a confirmation of the water retention (background stain) in the non-image area, the ink is F Gloss Purple 68 manufactured by Dainippon Ink.
S was used, and Eu-3,1% liquid (PS plate dampening water / etching liquid made by Fuji Film) was used as a dampening liquid, and printing was performed with Ryobi 3200CD. From the printing results, the number of printed sheets when the background stain occurred and the printing was stopped, and the judgment was made according to the following evaluation criteria. Table 1 shows the evaluation results of 1,000 sheets or more and Δ500 to 1,000 sheets × 500 sheets or less.

[0043]

[Table 1] ────────────────────────────────────                 Image density non-image area density difference Printing durability Water retention Note                 Reflection density reflection density ────────────────────────────────────   Planographic printing plate A 0.64 1.33 0.69 ○ ○ Comparison   Planographic printing plate B 0.55 1.33 0.78 ○ ○ The present invention   Planographic printing plate C 0.53 1.33 0.80 ○ ○ The present invention   Planographic printing plate D 0.52 1.33 0.81 ○ ○ The present invention   Planographic printing plate E 0.55 1.33 0.78 ○ ○ The present invention   Planographic printing plate F 0.56 1.33 0.77 ○ ○ The present invention   Planographic printing plate G 0.57 1.33 0.76 ○ ○ The present invention ────────────────────────────────────

From the above results, the production method in which the silver halide emulsion layer of the present invention is applied, heated, washed with water, and then applied with the physical development nuclei layer, the image sharpness is improved without impairing the printing performance. It has been found to give excellent lithographic printing plates.

[0045]

According to the present invention, the optical reflection of the silver image portion deposited on the physical development nucleus layer of the lithographic printing plate to which the silver complex salt diffusion transfer method is applied without impairing the printing performance as the lithographic printing plate. It is possible to reduce the density and facilitate the distinction between the image area and the non-image area, that is, improve the sharpness.

Claims (3)

[Claims] 1. A method for producing a lithographic printing plate comprising coating a support with at least a silver halide emulsion layer, and further coating a physical development nucleus layer on the support, wherein the surface coated with the silver halide emulsion layer is A method for producing a lithographic printing plate, comprising applying the physical development nucleus layer after washing with water. 2. The method for producing a lithographic printing plate according to claim 1, wherein the temperature of the water washing treatment is 5 to 30 ° C. 3. The method for producing a lithographic printing plate as claimed in claim 1, wherein the washing treatment and the coating of the physical development nucleus layer are continuously carried out.