JPH11295898A - Production of lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a producing method of a lithographic printing plate in which printing durability and sharpness of an image on the plate are improved and a silver complex salt diffusion transfer method is used. SOLUTION: In the production of the lithographic printing plate, at least a silver halide emulsion layer is applied and dried on a support, and then a physical developing nuclei layer is applied on the silver halide emulsion layer, and a silver complex salt diffusion transfer method is used. In this method, the surface temp. of the silver halide emulsion layer is controlled to <=15 deg.C when the physical developing nuclei layer is applied. More preferably, the surface temp. of the silver halide emulsion layer is controlled to <=10 deg.C in the production of the lithographic printing plate above described.

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 water and ink are supplied to the lithographic printing plate, 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-receptive 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.

As described above, in the lithographic printing plate, a silver image deposited on a physical development nucleus layer above a gelatin-silver halide emulsion layer is used as an ink-receiving image area.
As compared with a general lithographic printing plate (for example, a PS plate), the image portion has insufficient resistance to mechanical abrasion, and the image portion is missing or the ink receptivity of the image portion gradually decreases. It has the disadvantage of being easily lost.

In addition, since a part of the physical development nuclei sinks into the surface of the gelatin-silver halide emulsion layer, there is a problem that the efficiency of forming the ink-accepting physical development silver on the surface of the lithographic printing plate is reduced. .

To overcome this drawback, the hardness of gelatin is increased, the undercoat layer or the silver halide emulsion layer contains a matting agent to improve abrasion resistance, and the amount of physical development nuclei is increased. Although some studies were conducted, such as
The effect has not been sufficiently obtained.

[0008] The method for producing the lithographic printing plate is as follows.
On a support represented by a polyester film or the like, an undercoat layer that also serves as an antihalation layer, and a silver halide emulsion layer are coated and dried, and after the emulsion layer is heated and cured,
A method of applying a physical development nucleus layer in a normal temperature atmosphere of 20 ° C to 40 ° C has been generally employed.

Japanese Patent Application Laid-Open No. 8-194315 discloses an example in which the temperature at the time of coating the physical development nucleus layer is specified. This is intended to improve the contrast of the printing plate by lowering the coating liquid temperature of the physical development nucleus layer, but it was not possible to sufficiently improve the printing durability. In addition, since the coating solution for the physical development nucleus layer contains various substances such as a metal compound and activator serving as physical development nuclei, lowering the solution temperature weakens the effect of the additive or reduces the solute. However, there is a problem that precipitation is easily caused. In particular, in the case of a type in which a developing agent is contained in a constituent layer such as a physical development nucleus layer and development is performed with an alkali activating solution (activator) substantially containing no developing agent, the coating liquid temperature of the physical development nucleus layer is reduced. When it is lowered, there is a problem that a developing agent is precipitated.

Further, in a lithographic printing plate to which the silver complex 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.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a lithographic printing plate using a silver complex salt diffusion transfer method, which has improved printing durability and image clarity of the plate.

[0012]

The object of the present invention is to provide at least a silver complex emulsion layer on a support, which is coated and dried, and then a physical development nucleus layer is coated on the silver halide emulsion layer. A method for producing a lithographic printing plate applying a transfer method, wherein the surface temperature of the silver halide emulsion layer when the physical development nucleus layer is coated is controlled to 15 ° C. or lower. .

More preferably, in the method for producing a lithographic printing plate, the surface temperature of the silver halide emulsion layer is 10 ° C.
It should be:

The present inventor has studied various conditions when the physical development nucleus layer is coated on the silver halide emulsion layer, and as a result, by reducing the surface temperature of the silver halide emulsion layer, the diffusion of the physical development nucleus is reduced. It was found that sinking was small and physical development nuclei were present in a stable state near the surface of the silver halide emulsion layer.

In the present invention, it is important that the surface temperature of the silver halide emulsion layer at the moment when the physical development nucleus layer is coated on the silver halide emulsion layer be 15 ° C. or less. The method for adjusting the surface temperature is not particularly limited, but a method in which cold air is blown to the emulsion layer surface before coating the physical development nucleus layer, and after coating the silver halide emulsion layer and before coating the physical development nucleus layer. For example, a method of cooling for several days, or a method of cooling the space between the original roll coated with the silver halide emulsion layer and the coating device for the physical development nucleus layer at the time of coating the physical development nucleus layer may be used.

The coating liquid temperature of the physical development nucleus layer is from 15 ° C. to 40 ° C.
A range of ° C is appropriate. When the temperature is lower than 15 ° C., additives and the like may precipitate and precipitate in the coating solution, and when the temperature is higher than 40 ° C., the temporal stability of the coating solution is reduced.

As a method for applying the physical development nucleus layer, hitherto known methods, for example, a slide coating method, a dip coating method, an air knife coating method, a gravure method, a doctor blade method, a reverse roll method, a metaling bar method, and the like can be used. Can be used. Other methods are also possible, and the specific description thereof is described in detail in “Coating Engineering” published by Asakura Shoten, pages 253 to 277 (published by Showa 46.3.20).

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 subjected to chemical sensitization, 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, an undercoat 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 a hydrophilic binder in an amount 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.
Polymers such as a copolymer of vinylimidazole and acrylamide described in JP-A No. 2-21, a copolymer of acrylamide and methyl sulfone substituted with guanylthioureas described in JP-A-8-216614, and polyvinyl alcohol are exemplified. 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, as a typical support, 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 preferred supports are paper coated on both sides or one side with a polyolefin polymer, a polyester film having a hydrophilic surface, an aluminum plate having been subjected to a surface treatment, and the like. 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.

[0029]

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 diameter of 7 μm contains 0.3 g / m ² of 1-phenyl-3-pyrazolidone and 0.1 g of 1-phenyl-3-pyrazolidone on top. Ortho-sensitized high-sensitivity silver chloride emulsion having 1 g / m ² (0.8 g of gelatin)
/ M ² ) as silver nitrate to be 1.0 g / m ² .
Two layers were simultaneously coated.

As hardening agents, 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. The solution A and the solution B were mixed with stirring, and after 30 minutes, passed through a column filled with an ion exchange resin (IR-120E, IRA-400) to obtain a palladium sulfide sol.

<Preparation of Physical Development Nucleus Solution> A copolymer of the aforementioned palladium sulfide sol 100 ml hydroquinone 100 g 1-phenyl-3-pyrazolidone 10 g acrylamide (97) and imidazole (3) 5 g (average molecular weight 100,000) 10% saponin ( (Surfactant) 2 ml water was added to make the total amount 2000 ml.

Next, a method of coating the physical development nucleus layer on the silver halide emulsion layer will be described. A temperature control zone in which the temperature can be set arbitrarily is provided between the main roll coated with the silver halide emulsion and the coating device for the physical development nucleus layer, and a web in which the silver halide emulsion layer is coated in this temperature control zone. To form a physical development nucleus layer on the silver halide emulsion layer having the surface temperature shown in Table 1. The surface temperature was measured using a non-contact thermo recorder IT2-85 manufactured by Keyence Corporation. Under these conditions, the physical development nucleus layer having the liquid temperature shown in Table 1
The slide was applied so as to be 0 ml / m ^2, and dried to prepare a lithographic printing plate.

These lithographic printing plates were subjected to image exposure using a plate-making camera having an image reversing mechanism, and then subjected to a development treatment at 30 ° C. for 1 minute using the following silver complex salt diffusion transfer developer.

<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 Water is added 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 liquid> 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 sharpness 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 greater 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.

[0041]

[Table 1]

From the above results, it can be seen that the method for producing a lithographic printing plate of the present invention, in which the surface temperature of the silver halide emulsion layer is kept at 15 ° C. or less at the time of coating the physical development nucleus layer, is excellent in printing durability and image definition. I found it to give.

[0043]

According to the present invention, the lithographic printing plate to which the silver complex salt diffusion transfer method is applied has improved printing durability and sharpness.

Claims (2)

[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, characterized in that the surface temperature of the silver halide emulsion layer when coated is 15 ° C. or lower. 2. The method according to claim 1, wherein said surface temperature is 10 ° C. or lower.