JPH01261643A - Planographic printing material for back exposure - Google Patents

Abstract

PURPOSE:To improve definition and sharpness and to enhance printing resistance by incorporating a specific matting agent at 5-100wt.% ratio to a binder and a matting agent of the average grain size larger than the average grain size of said matting agent at 2-20wt.% ratio to the binder into an under coating layer. CONSTITUTION:This printing material has the under coating layer, a silver halide emulsion layer and a physical development nucleus layer successively on a base. The matting agent having 0.5-4mum average grain size is incorporated at 5-100wt.% ratio to the binder and the matting agent having 2-10mum average grain size larger than the average grain size of the matting agent is incorporated at 2-20wt.% ratio to the binder into this under coating layer. Org. polymer particles or inorg. compds. such as silica are usable as the matting agent. The printing material having the excellent definition and sharpness and the high printing resistance is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a lithographic printing material using a silver complex diffusion transfer method (DTR method).

(B) Prior art and its problems A lithographic printing material using the DTR method, specifically, a method in which at least one photosensitive layer is provided on a support, and an image photosensitively recorded on the photosensitive layer is recorded by reversal Φ transfer on the support. A lithographic printing material obtained by imagewise exposing a material consisting of physical development nuclei to light and then subjecting it to a silver diffusion transfer development process to form a metallic silver image on the external surface of the material can be produced using the direct plate making method. Compared to the conventional lithographic printing material (Pa plate), which is characterized by the use of lithographic film as an intermediate process, it has the advantage of simplicity and speed.

Lithographic printing materials using the TR method are manufactured using a special plate-making camera equipped with a built-in image reversal mechanism such as a prism or reflective mirror to prevent the original image from becoming a left-right reversed image.
Everything from photography to plate-making processing is done automatically.

Such a plate-making camera is not only expensive, but also has the disadvantage that the image reversal mechanism reduces image resolution and sharpness.

In order to obtain a lithographic printing plate with a normal image using a plate-making camera that does not have an image reversal mechanism, as described in Japanese Patent Application Laid-Open No. 48-89007, it is necessary to
A method of performing imagewise exposure of a document from the ji side is known. In this specification, this exposure method is referred to as back printing.

On the other hand, lithographic printing materials using the DTR method have insufficient resistance to mechanical abrasion, resulting in the loss of hydrophobic areas that carry ink images or gradual loss of their ink receptivity. Therefore, it has the disadvantage of reducing printing durability. Hydrophilic areas gradually become hydrophobic due to mechanical abrasion, and non-printing areas become smeared with ink, and hydrophobic areas become uniformly receptive to oily inks. defects, which cause variations in ink receptivity in the image area;
Therefore, the area to be printed will not receive a uniform amount of ink. As with other planographic printing plates, it is necessary to increase the printing durability of planographic printing materials using the DTR method by changing the composition of the plate material, the composition of the processing liquid, printing conditions, etc. Various improvements have been made.

The same applies to the lithographic printing materials basically described in the Japanese Patent Publication No. 48-30562.
51-16803, JP-A-51-111103, 5
2-150105, 53-9603. 54-135
002, 55-7704, 55-100554, 56-27151, 57-86835, 58-19
6548 etc., the printability has been significantly improved. In particular, the addition of 2 to 10 μm of a matting agent such as silica, clay, talc, gicrite, or rice starch to the undercoat layer as taught in JP-A-55-100554 and JP-A-58-196548,
It improves the water retention of the plate surface and significantly improves printing durability, and is therefore important in lithographic printing materials using the DTR method.

However, during back printing, the undercoat layer containing a matting agent exists in the optical path on the plate-making camera from the original to the photosensitive layer, and there are differences in the refractive index between the binder and the matting agent, etc. , due to its optical non-uniformity, it strongly diffuses light and reduces resolution and sharpness in reverse printing.

(C) Object of the Invention The object of the present invention is to provide a lithographic printing material for back printing that has excellent resolution and sharpness, good printing durability in halftone areas such as fine lines and halftone dots, and excellent water retention. That's a thing.

(D) Structure of the Invention The object of the present invention is to provide a back-printable lithographic printing material having at least an undercoat, a silver halide emulsion layer and a physical development nucleus layer on a support. In the layer, a matting agent having an average particle diameter of 0.5 to 4 μm and a ratio of 5 to 100% by weight to the binder, and an average particle diameter 2 having an average particle diameter larger than that of the matting agent.
~10μm matting agent to binder ratio 2~20ii
This was achieved by means of a back-printing lithographic printing material characterized by containing i%.

As the matting agent used in the present invention, many known matting agents can be used, such as organic polymer particles or inorganic compounds such as silica, but silica is particularly preferred. Further, it is preferable that the refractive index of the matting agent is 2 or less, and it is preferable that the matting agent has excellent monodispersity.

The matting agent of the present invention has a matting agent having a large average particle size (2 to 10 μm (preferably 4 to 10 μm)) at a binder ratio of 2 to 20 i! %, a matting agent with a small average particle diameter (0.5 to 4 μm (preferably 1 to 4 μm)) is used at a ratio of 5 to 100 wt % to the binder, but the average particle size of the matting agent with a large average particle diameter is The effect is remarkable when a matting agent with a small diameter is used in an amount of 1 to 10 times.

The matting agent of the present invention is effective when sufficiently dispersed, and can be dispersed using, for example, a homomixer, a ball mill, or ultrasonic vibration. Further, a dispersant such as an activator or an organic polymer can also be used.

In the present invention, gelatin is preferably used as the binder for the undercoat layer. Also, Japanese Patent Publication No. 55-100554
Hydrophilic colloids and sodium alginate as described in
Hydrophilic colloids such as cellulose derivatives, polyvinyl alcohol, and polyvinylpyrrolidone can also be used in combination with gelatin.

As a hardening agent for the gelatin layer, formalin, mucochloric acid, geltaraldehyde, glyoxal% JP-A-5
4-130930, a slimy initial condensate, an active halogen disk, an ethylene type, a vinyl sulfone type, an epoxy type,
Alternatively, known salts such as chromium salts can be used.

The undercoat layer used in the present invention preferably contains an anti-scratch agent. Although it is possible to maintain resolution by using an anti-irradiation agent in the emulsion layer, the most preferred method is to use an anti-irradiation agent in the undercoat layer. Pigments that are usually used as anti-fouling agents include pigments,
Although both dyes and dyes can be used, carbon black is particularly preferred. It is preferable to use carbon black together with a suitable dispersant so that the optical density of the undercoat layer is 0.1 to 0.9. Particularly preferred is 0.1 to
The subbing layer has an optical density of 0.5.

The support used in the lithographic printing material of the present invention is a light-transmissive support, such as a film (Cellulose acetate film, poly and nylacetal film, polyethylene film, polypropylene film, polyethylene terephthalate film)
, a composite film in which polyester, polypropylene, polystyrene, or the like is coated with a polyethylene film. Although the thickness is arbitrary, a range of 50 to 200 μm is preferable.

Photosensitive silver halide emulsions known in the field include:
All can be used, but preferably JP-A-49-5
54021.

The physical development nucleus layer is also JP-B No. 48-30562, JP-A No. 49-Sho.
55402, 53-21602, etc. can be used.

The weight ratio of hydrophilic colloid to silver halide, expressed as silver nitrate, is generally between 3 and 0.2, preferably 1.5.
~0.3. The amount of silver halide present on the support ranges from about 0.2 to about 5 f/rr? , preferably 0.5
-3 is coated with the same amount of silver nitrate.

As physical development nuclei, known ones such as metals such as antimony, bismuth, cadmium, cobalt, palladium, nickel, silver, lead, and zinc, and their sulfides can be used. The physical development core layer does not need to contain hydrophilic colloids, and may contain gelatin, carboxymethyl cellulose, gum arabic, sodium alginate, hydroxyethyl starch, dextrin, hydroxyethyl cellulose, polystyrene sulfonic acid, vinyl imidazole, and acrylamide. Hydrophilic colloids such as polymers and polyvinyl alcohol can also be included.

Hygroscopic substances such as wetting agents such as sorbital, glycerol, etc. may be present in the core layer.

Furthermore, the core layer may contain pigments for preventing scumming such as barium sulfate, titanium dioxide, china clay, and silver, hardeners such as formaldehyde, and further complexing agents.

The DTR treatment solution used in the present invention is an alkaline substance such as sodium hydroxide, potassium hydroxide, m=sodium sulfate, etc., sulfite as a preservative, 1M agent such as hydroxyethyl cellulose, carboxymethyl cellulose, anti-fogging agent, etc. agents such as potassium bromide% 1-7enyl-5-mercaptotetrazole, complexing agents such as thiosulfates, thiocyanates, cyclic imides, thiosalicylic acid, etc., such as hydroquinone, 1-7enyl-3-pyrazolidone , p-methylphenol, etc., development modifiers, such as polyoxyalkylene compounds, onium compounds, etc., can be included.

The lithographic printing plate of the present invention is disclosed in Japanese Patent Publication No. 48-29723, for example.
Ink receptivity may be altered or enhanced with compounds such as those described in U.S. Pat. No. 3,721,559. The printing method, the desensitizing liquid, the dampening liquid, etc. used can be based on commonly known methods.

(E) Examples The present invention will be explained below with reference to examples, but the present invention is of course not limited to these examples.

After providing a backing layer on a 175 μm subbed polyester film, carbon black (carbon black) was applied, and the optical density of the gelatin film after drying was 0.5 so that the optical density of the gelatin film after drying was 0.5. An undercoat layer (on the back of gelatin 3.5) containing a matting agent (silica with an average particle size of 7μ and 2.5μ) as shown in Table 1, and an ortho-sensitized A high contrast silver chloride emulsion (gelatin 1.0f'/n?) was mixed with silver nitrate at 1.5t/W? It was coated with. After hardening by heating, the same core coating liquid as Sample J of Example 1 of JP-A-57-86835 was applied to prepare a lithographic printing material.

The density interval is 0 on the document rack of a plate-making camera that does not have an image reversal mechanism.
．． Prepare a draft manuscript including 15 optical wedges, fine lines of different line widths, a halftone image, and a resolution chart,
Documents of these samples were photographed from the long side using reflected light, and developed with the following transfer developer at 30° C. for 20 seconds. The exposure is
The appropriate exposure was set and controlled using an optical wedge.

After the development process, 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, and the excess liquid is removed using a squeezing roller. Dry at room temperature.

Transfer developer neutralizing solution The lithographic printing plate prepared by the above procedure was mounted on an offset printing machine, the following desensitizing liquid was applied all over the plate surface, and printing was carried out using the following dampening liquid.

Desensitizing liquid dampening liquid The results are shown in Table 2.

Table 2 Sample ■■■ is for comparison, and sample ■■ is the present invention.

[Resolution]

We evaluated the thin line on the reproduced resolution chart using appropriate exposure.

[Printing durability]

6 (number of printable pages) evaluated using a 50μ thin line.

1...s, o o o sheets or less 2...s, o o o sheets ~ 10,000 sheets 3...1
0,000 sheets or more [Water retention] Evaluation was performed based on the number of sheets printed at which scumming occurred.

1...s, o o o or less 2...s, ooo to 10,000 sheets 3...io, ooo or more (F) Effects of the Invention The present invention is a plate-making camera that does not have an image reversal mechanism. This is a back-printing planographic printing material that allows left and right images to be obtained using the DTR method, and according to the present invention, a planographic printing material with excellent resolution and sharpness, high printing durability, and high water retention can be obtained.

Claims (1)

[Claims] 1. In a back-baking lithographic printing plate having at least an undercoat layer, a silver halide emulsion layer, and a physical development nucleus layer in this order on a support, the undercoat layer has a matte grain size of 0.5 to 4 μm. A lithographic plate for back printing, characterized in that it contains a matting agent with a ratio of 5 to 100% by weight to the binder, and a matting agent having an average particle size of 2 to 10 μm, which is larger in average particle size than the matting agent, in a ratio of 2 to 20% by weight to the binder. printing materials.