JP2000284485A - Production of planographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a process for producing a planographic printing plate which enables high-speed coating application and drying without the degradation in printing performance by applying a physical development nucleus layer at a specific coating application speed and a specific moisture content coating weight by a gravure coating application system in the process for producing the plate by applying the physical development nucleus layer on a silver halide emulsion layer. SOLUTION: The physical development nucleus layer is applied by the gravure coating application system in the process for producing the planographic printing plate by applying the silver halide emulsion layer on a base and dying the coating, then applying the physical development nucleus layer on the silver halide emulsion layer. The gravure coating application system enables the high-speed and uniform coating application of the low coating weight and further allows the physical development nuclei to exist in a stable state near the surface of the silver halide emulsion layer. Here the high-speed coating application refers to 100 m/minute and further strictly >=150 m/min. The thin layer coating application refers to a weight coating weight of <=20 ml/m2, more strictly <=15 ml/m2. The coating film liquid temperature of the physical development nucleus liquid is preferably in a range of 15 to 40 deg.C.

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 to which a silver complex salt diffusion transfer method is applied.

[0002]

2. Description of the Related Art A lithographic printing plate is composed of an oleophilic image portion that receives oily ink and an oil-repellent non-image portion that does not receive ink. Generally, the non-image portion includes a hydrophilic portion that receives water. It is configured. In normal lithographic printing, both water and ink are supplied to the printing plate, the image portion selectively receives colored ink, and the non-image portion selectively receives water, and the ink on the image is, for example, paper or film. The printing is performed by transferring the image to a printing medium.

Therefore, in order to obtain a good printed matter, the difference between the lipophilicity and the hydrophilicity between the image area and the non-image area is sufficiently large, and when the water and the ink are supplied to the lithographic printing plate surface, the image area has a sufficient amount. It is important and necessary that the non-image areas accept no ink 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 disclosed in, for example, US Pat. No. 3,728,
No. 114, No. 4,134,769, No. 4,16
Nos. 0,670, 4,336,321 and 4,5
No. 01,811, No. 4,510,228, No. 4,
No. 621,041, the unexposed silver halide crystals are converted into a silver salt complex by a silver salt complexing agent in a developing solution, diffused to the physical development nucleus layer on the surface, and the presence of nuclei. Causes a physical development to form an image portion mainly composed of ink-receiving physical 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 and becomes black silver to form a hydrophilic non-image portion.

[0005] The above-mentioned general method of producing a lithographic printing plate is to coat a primer layer and a halogenated emulsion layer which also prevent halation on a support and then to dry the coated layer to obtain a gelatin film having strength enough to withstand printing. After that, a physical development nucleus layer is coated on the silver halide emulsion layer and dried. The coating of the physical development nucleus layer is described in JP-A-59-22684,
As described in JP-A-8-194315, an air knife system and a slide bead coating system have been used.

The physical development nucleus layer contains various water-soluble polymers to serve as protective colloids for the physical development nuclei and to improve the water retention of the non-image area. On the other hand, since the water-soluble polymer impairs the ink receptivity of the silver image portion, the content of the water-soluble polymer is generally about several mg to several tens mg per 1 m ² . Therefore, the viscosity of the coating solution for the physical development layer is extremely low, up to about 3 CP.

[0007] High-speed coating is indispensable for improving the productivity, and attempts have been made to increase the speed of the physical development nucleus layer. However, when the low-viscosity physical development nucleus layer as described above is applied at a high speed, if the amount or speed of blowing dry air is increased in order to increase the drying efficiency, the applied surface is disturbed and coating unevenness occurs. Occurs. In addition, there is a problem that uniform coating properties cannot be obtained if the coating amount of the physical development nucleus layer coating liquid is reduced. There is a problem that the (printing durability) is reduced, and a problem that the drying device is enlarged.

Further, in a lithographic printing plate to which the silver salt diffusion transfer method is applied, since the original is sometimes checked and corrected using the printing plate, the image is sharper, that is, a non-black silver plate is used. There is a need for a lithographic printing plate having a stronger contrast between the image area and the image area which is physically developed silver.

[0009]

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a method of manufacturing a lithographic printing plate which enables high-speed coating and drying without deteriorating printing performance. Another object of the present invention is to provide a method for producing a lithographic printing plate having a clear image on the plate surface.

[0010]

The object of the present invention is to provide a lithographic printing plate wherein at least a silver halide emulsion layer is coated on a support, dried, and then a physical development nucleus layer is coated on the silver halide emulsion layer. In the manufacturing method, the physical development nucleus layer is applied by a gravure coating method.

It has been found that, in the drying after the application of the physical development nucleus layer, the drying speed affects printability, especially printing durability. That is, if the drying rate is reduced, it is considered that physical development nuclei diffuse into the inside of the halogenated emulsion layer, and as a result, it is difficult to form strong physical development silver on the surface layer.

Therefore, it is important to dry relatively quickly without using a strong drying air with a low coating amount.
However, with the conventional coating method as described above, uniform coating could not be obtained with a low coating amount. Therefore, as a result of intensive studies, the gravure coating method, which is not widely applied in the field of photosensitive materials, enables high-speed uniform coating with a low coating amount, and furthermore, the physical development nuclei are stable near the surface of the silver halide emulsion layer. Found to exist in a state.

In the present invention, high-speed coating means 100 m / min or more, and more specifically, 150 m / min or more.
In addition, the thin layer coating means a moisture coating amount of 20 ml / m ² or less,
More strictly, it means 15 ml / m ² or less. In the present invention, the cell shape of the gravure roll used in the gravure coating method may be any of a lattice, an oblique line, a pyramid and the like. The rotation direction of the gravure roll is inverse to the running of the web. Any of river earths may be used, and there is no particular limitation. The supply of the coating liquid to the gravure roll is preferably a method of suppressing the generation of bubbles by a closed type closed edge die, a fountain die and the like. The coating solution temperature of the physical development nucleus solution is preferably in the range of 15 ° C to 40 ° C.

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

The silver halide photographic emulsion of the present invention can be a so-called primitive emulsion which is not chemically sensitized, but 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 used alone or in combination.

Silver halide emulsions can also be spectrally sensitized or desensitized with cyanine dyes, merocyanine dyes and the like. There is no particular limitation on the wavelength range in which the sensitization or desensitization can be performed.

The lithographic printing plate of the present invention is usually provided with an undercoat layer for preventing halation between the support and the silver halide emulsion layer. The silver halide photographic emulsion layer and the undercoat layer can contain various compounds for the purpose of stabilizing the photographic performance during the production process, during storage as a product, and during development. 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 object of the present invention contains gelatin, and the layer containing the gelatin is a silver halide photographic emulsion layer, a subbing layer, a backing layer, and a physical development nucleus. It can also be a layer. Part of the gelatin in the gelatin-containing layer of the present invention can be replaced by another hydrophilic colloid.

The gelatin-containing layer of the present invention can be hardened with an inorganic or organic gelatin hardener. Hardeners can be added to all layers or to some or only one layer. Of course, in the case of two-layer simultaneous application, the diffusible hardener can be added to only one of the layers. The addition method 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 part of the silver halide emulsion layer. The physical development nuclei of this physical development nucleus layer include silver, antimony, bismuth, cadmium, cobalt, lead, nickel, palladium, rhodium,
Fine particles of metal colloids such as gold and platinum, sulfides, polysulfides, selenides of these metals, or mixtures or mixed crystals thereof may be used.

The physical development nucleus layer preferably contains about 0.5 to 50 mg / m ² of a hydrophilic binder. As the hydrophilic binder, gelatin, starch, dialdehyde starch, carboxymethylcellulose, gum arabic,
Sodium alginate, hydroxyethyl cellulose,
Polystyrene sulfonic acid, a copolymer of vinylimidazole and acrylamide described in JP-A-53-21602, a copolymer of acrylamide and methylsulfone substituted with guanylthioureas described in JP-A-8-21614, polyvinyl alcohol And the like. Further, the physical development nucleus layer may contain a developing agent such as hydroquinone, methylhydroquinone, or catechol, or a known hardener such as formalin or dichloro-s-triazine.

As the support of the lithographic printing plate of the present invention, typical supports include paper, RC paper or a synthetic or semi-synthetic polymer film, a metal plate such as aluminum or iron, etc.
Any material that can withstand lithographic printing can be used.
One or both surfaces of the support may be coated with one or more polymer films or metal thin films. The surface of these supports can be subjected to a surface treatment in order to improve the adhesion to the coating layer.

Particularly preferably used supports include paper coated on both sides or one side with a polyolefin polymer, polyester film having a hydrophilic surface, and aluminum plate having been subjected to a surface treatment. These supports may contain pigments for preventing halation and solid fine particles for improving the surface properties. Further, the support may 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 thickener, an antifoggant, a developer, a development modifier and the like. An activator-type developing solution that does not contain the same may be used. Further, a compound or the like which improves the ink running of the surface silver layer can be used as the developing solution.

The surface silver layer after development of the lithographic printing plate of the present invention can be converted to ink receptivity or enhanced in receptivity with any known surface treating agent. The printing method, the desensitizing solution, the humidifying solution, and the like to be used can be a commonly known method. Hereinafter, the present invention will be described with reference to Examples, but it should be understood that the present invention is not limited thereto.

[0026]

EXAMPLE A matting layer (back coating layer) containing silica particles having an average particle size of 5 μm was provided on one side of 135 g / m ² double-sided polyethylene coated paper, and the opposite side was subjected to corona discharge machining, carbon black, and An undercoat layer (3.5 g / m ² gelatin) containing silica powder having an average particle size of 3.5 μm contains 0.3 g / m ² of 1-phenyl-3-pyrazolidone, and 1-phenyl-3-pyrazolidone is further placed thereon. Ortho-sensitized high-sensitivity silver chloride emulsion with 0.1 g / m ² (gelatin 0.
(Including 8 g / m ² ) to give a silver nitrate of 1.0 g / m ² .

As the hardening agent, 2,4-dichloro-6-
Hydroxy-S-triazine sodium is added to the undercoat layer.
70 mg / m ² and containing, in the emulsion layer N- methylol urea was 80 mg / m ² containing. After coating and drying, 50 ℃
For 2 days.

Next, a coating solution for a physical development nucleus layer having the following formulation was prepared. <Preparation of palladium sulfide sol> Solution A palladium chloride 5 g hydrochloric acid 40 ml distilled water 1000 ml solution B sodium sulfide 8.6 g distilled water 1000 ml The solution A and the solution B were mixed with stirring, and after 30 minutes, the ion exchange resin (IR-120E, The mixture was passed through a column packed with IRA-400) to obtain a palladium sulfide sol.

<Preparation of Physical Development Nucleus Solution> The above-mentioned palladium sulfide sol 100 ml Hydroquinone 100 g 1-phenyl-3-pyrazolidone 10 g Copolymer of acrylamide (97) and imidazole (3) 0.5 g (average molecular weight 100,000) 10% Saponin (surfactant) 2 ml water was added to bring the total amount to 1500 ml.

Next, a method of coating the physical development nucleus layer on the silver halide emulsion layer will be described. A physical development nucleus solution (viscosity: 1.5 CP) having the above composition was applied at a speed of 100 to 500 m / min using a gravure coater equipped with a 150-line / inch oblique gravure roll (reverse rotation), and applied at 15 ml / m ^2. Was applied. As a result, a uniform coated surface was obtained.

As another example using a gravure roll, the total amount of the physical development nucleus solution was adjusted to 800 ml, and
0 line / inch grid gravure roll (inverse rotation)
, 8 ml / m ² was applied at a speed of 100 to 500 m / min. As a result, a similar uniform coated surface was obtained.

Comparative Example 1 A 15 ml / m ² physical development nucleus solution was applied by an air knife application method. The coating was possible at a speed of 100 to 150 m / min, but at a speed higher than that, it could not be completely removed with an air knife, and a phenomenon that a large amount of coating was applied was observed, and a uniform coated surface could not be obtained. Further, 8 ml / m ² of a physical development nucleus solution was applied in the same manner, but even at 100 to 150 m / min, mist was generated and a uniform coated surface could not be obtained. A phenomenon was seen.

Comparative Example 2 Next, an attempt was made to apply a 15 ml / m ² physical development nucleus solution by a slide bead coating method, but the solution was not applied at all and could not be applied. By diluting to 25 ml / m ² , coating could be performed at a speed of 100 to 150 m / min for the first time. At a speed lower than that, the slide surface is not formed and coating is not possible,
At higher speeds, the surface irregularities of the web on which the halogenated emulsion layer was coated brought in air, which resulted in a foam-coated surface with air entrainment.

The lithographic printing material thus obtained was made by the following process. <Transfer developer> Water 700 ml Potassium hydroxide 20 g 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 processing, the original plate was passed between two squeezing rollers to remove excess developer, and immediately processed with a neutralizing solution having the following composition at 25 ° C. for 20 seconds. And dried.

<Neutralizing solution> Water 600 ml Citric acid 10 g Sodium citrate 35 g Colloidal silica (20% solution) 5 ml Ethylene glycol 5 ml Add water to make 1 liter. The lithographic printing plate created by the above operation is mounted on an offset printing machine, and the following desensitizing solution is applied to the plate surface,
Printing was performed using the following humidifying solution.

<Desensitizing solution> Water 600 ml Isopropyl alcohol 400 ml Ethylene glycol 50 g 3-mercapto-4-acetamido-5-n-heptyl-1,2,4-triazole 1 g

<Humidifier> o-phosphoric acid 10 g nickel nitrate 5 g sodium nitrite 5 g ethylene glycol 100 g colloidal silica (20% solution) 28 g Water is added to make 2 liters.

The printing machine is an Abdick 350CD
(A.B.Dick's offset printing press trademark) is used to determine the printing durability according to the following evaluation criteria. evaluated.な し No problem at 20,000 sheets. 銀 Silver image part missing at 15,000 to 20,000 sheets. 銀 Silver image part missing at less than 15,000 sheets. Printing results are shown in Table 1.

The definition of the lithographic printing plate was evaluated by the difference between the reflection density of the blackened silver portion corresponding to the non-image portion and the reflection density of the diffusion transfer physically developed silver portion corresponding to the image portion. The reflection density was measured with a Macbeth densitometer. The larger the difference between the two, the higher the sharpness of the image, and the density difference is preferably 0.7 or more, more preferably 0.75 or more.
Table 1 shows the results.

[0040]

[Table 1]

From the above results, the application of the physical development nucleus layer by the gravure coating method of the present invention enables the thin layer to be coated at a high speed, and furthermore, the sharpness and the printing durability of the image brought by the thinning. It has been found that an ideal lithographic printing plate can be obtained without losing excellent effects.

[0042]

According to the present invention, in a method of manufacturing a lithographic printing plate to which a silver complex salt diffusion transfer method is applied, high-speed coating is possible, and quality with improved printing durability and sharpness is obtained.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akio Yoshida 3-4-2, Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Paper Mills F-term (reference) 2H096 AA06 BA17 CA02 CA05 CA12 CA20 GA08 GA18 HA02

Claims (3)

[Claims] 1. A method for producing a lithographic printing plate comprising coating at least a silver halide emulsion layer on a support, drying and coating a physical development nucleus layer on the silver halide emulsion layer. A method for producing a lithographic printing plate, wherein the method is applied by a gravure coating method. 2. The method according to claim 1, wherein a speed of applying the gravure coating method is 150 m / min or more. 3. The method according to claim 1, wherein the amount of moisture applied by the gravure coating method is 15 ml / m ² or less.