JPS5936263A - Lithographic printing plate for electrophotographic plate making - Google Patents

Abstract

PURPOSE:To improve an image characteristic and to obtain a lithographic printing plate which is superior overall, by laminating successively a layer contg. an ionomer resin, a layer of an ionomer resin and a water soluble polymer material, and a zinc oxide-resin dispersion photoconductive layer on a substrate. CONSTITUTION:A layer consisting essentially of an ionomer resin is provided in two layers of an undercoating layer 2 and a precoating layer 3 between the substrate raw paper 1 on a conduction treated layer and a photosensitive layer 4. The undercoating layer has the functions to provide film forming property, high print resisting power and reduced printing elongation and the precoating layer has the functions to improve image quality and to provide film forming property. The ionomer resin alone may be used for the binder of the undercoating layer and the ionomer resin and a water soluble polymer resin are used in combination for the purpose of improving the image quality. It is further possible to add inorg. pigments such as calcium carbonate, talc, or the like in the undercoating layer and if necessary, in the precoating layer, by which the quality of the photoengraving image is much bettered.

Description

[Detailed description of the invention] The present invention relates to a lithographic printing plate for electrophotolithography.

In general, lithographic printing plates (printing plates) for electrophotographic engraving are provided with a precoat layer on the surface of a base paper support, and a photosensitive layer of a zinc oxide/resin dispersion system is provided on top of this, either directly or via a water-resistant layer. In addition, if necessary, a conductive treatment layer is provided on the back side of the base paper support.

This printing plate needs to have an electrophotographic image forming function and strength to withstand physical external pressure during printing, and has many properties such as printing durability, water resistance, film forming properties, solvent resistance, and electrophotographic properties. functionality is required.

For this reason, various studies have been made regarding the layers constituting the printing plate and the materials thereof. However, none of the conventional printing plates satisfies all of the characteristics required for printing plates as described above.

For example, water-soluble polymer resins (polyvinyl alcohol, starch, cartaxymethyl cellulose, methyl cellulose, alginic acid, casein, etc.) are used as the pre-coat layer, and they also have the drawbacks of poor water resistance and wet adhesion. A layer that uses a water-soluble polymer resin and an emulsion resin (acrylic acid ester, vinyl acetate, styrene-citadiene copolymer, etc.) in combination to provide water-resistant adhesion has also been proposed; If the emulsion resin is too large, the solvent resistance and group 1 interstitial property will be extremely poor, leading to deterioration of electrophotographic properties.On the other hand, if the emulsion resin is too small, the water resistance and printing durability will be poor.
It has the disadvantage that the appropriate range of its blending ratio is narrow.

Furthermore, there are also known products that aim at water resistance by using a water-soluble polymer resin in combination with a crosslinking agent (glyoxal, melamine, polyamide, etc.), but the crosslinking process requires high heat treatment, and It has drawbacks such as generation of gas such as formaldehyde or migration during heating.

On the other hand, a water-resistant layer (formed from a thermosetting type, a thermally crosslinking type emulsion, or a solvent type resin) may be provided between the precoat layer and the photosensitive layer. in this case,
Since the material for the water-resistant layer has high resistance, increasing the amount of the material deposited deteriorates the electrophotographic properties. If the amount of adhesion is small, the printing durability, which is improved by water resistance, will be reduced. Furthermore, if the pre-coat layer does not have sufficient film-forming properties, there is a problem that the water-resistant layer will seep into the coating when applied.

Therefore, it can be said that a printing plate that does not require a water-resistant layer is desirable.

Therefore, the present inventors investigated the material for forming the precoat layer and found that an ionomer resin is suitable.

Ionomer resin is a copolymer of ethylene, unsaturated carboxylic acid, and carboxylic acid ester crosslinked with metal ions (-valent metal cations Na", K", L+", and Sn"), and has excellent water resistance and It is characterized by both solvent resistance and film-forming properties not found in general emulsion resins. This is said to be due to the unique property of ionomer resins, where heating weakens ionic crosslinking and gives it fluidity, and conversely, when it is cooled, it returns to a strongly ionic crosslinked structure. Therefore, the film after coating and drying has the property of being formed neatly without pinholes.

If this ionomer resin is used alone as a precoat layer, it tends to have low photosensitivity and also has the drawback that it penetrates into low-grade supports to a large extent, resulting in image unevenness.

SUMMARY OF THE INVENTION An object of the present invention is to take advantage of the unique advantages of ionomer resins, to improve the above-mentioned image characteristics using this resin as a main ingredient, and to provide an overall excellent printing plate.

That is, the printing plate of the present invention uses at least a mixture of an ionomer resin and a water-soluble polymer resin as the binder component of the precoat layer, and a subbing layer mainly composed of an ionomer resin is provided between the paper support and the photosensitive layer. It is characterized by intervening.

The figure is a schematic cross-sectional view of the printing plate of the present invention, in which 1 is a support base paper, 2 is a subbing layer, 3 is a precoat layer, 4 is a photosensitive layer,
5 indicates a conductive treatment layer.

As is clear from this figure, in the present invention, two layers mainly composed of a transparent ionomer resin are provided between the support base paper 1 and the photosensitive material 11j4, as Divide/#2 and Solekote I13.

Here, lower price! - and the functions of the precoat layer are: tearing layer...film formability, high printing durability, reduction of printing elongation, precoat layer...
...Improvement in image quality and film formability.

The binding agent for the F pulling layer may be an ionomer resin alone, but the precoat layer in contact with the photosensitive layer uses a combination of an ionomer resin and a water-soluble polymer resin for the purpose of improving image quality.

Furthermore, inorganic pigments such as calcium carbonate, clay, talc, titanium oxide, etc. can be added to the F coating 1- and the precoat layer as needed, thereby further improving the quality of the plate-making image. can.

Also, a toner image is formed on the printing plate by electrophotography,
When fixing this by heat ray radiation, it is preferable to disperse and contain carbon cracks with high heat ray absorption ability in the undercoat layer, thereby reducing the difference in thermal shrinkage between the image area and the non-image area. It is possible to prevent wrinkles from occurring during printing.

Incidentally, conventionally, it is known that carbon cracks are added internally to the support base paper, and those that are included in the conductive treatment layer, but the former has a higher printing elongation than the one that does not have carbon cracks internally added to the base paper. The latter has the disadvantage that carbon cracks adhere to the photosensitive layer and cause stains, which tends to deteriorate the photosensitive properties, so Kerr 27 Black was mostly used as a low-resistance processing agent. .

The materials used for the drawn layer and precoat layer of the present invention are the above-mentioned materials, but in order to fully exhibit their respective functions, it is preferable to use the following composition ratio.

Ionomer resin as binder: 100-50 parts, preferably 100-80 parts Water-soluble polymer resin: 0-50 parts, preferably 0-20 parts Inorganic pigment per 100 parts binder: 0-50 parts 100 parts When using a solid-free offset master and carbon crack, the ratio of Car 27 Black + other pigments is 1 to 100 parts for 100 parts of the binder, and the ratio of carbon crack and other pigments is 1 to 100 parts. 27 Black 1 to 0 to 1°.

The amount of adhesion without F pulling is 3 to 10 f/d, preferably 5 to 7 f/d, and the amount of adhesion as carbon crack is 0.05 to 5 y/nl, preferably O, 1 to 2 f/n.
? Select so that

Ionomer resin: 95 to 60 parts, preferably 90 to 70 parts Water-soluble polymer resin: 5 to 40 parts, preferably 10 to 30 parts Inorganic pigment: based on the above binder 1 0 to 1.5, preferably 0 to 0.5 coating! : 3~10? /r? Preferably 5~
7 f/rr? In addition, as a commercially available ionomer resin, for example, Surlyn ≠ 1555 (N
a type) and Surlyn φ1652 (Zn type) or Asahi Yutsusha! l! ! There is L-4000 (Na type).

Conductive treatment on the back side of the paper support (1-())
11) can be provided, and the conductive treatment layer is formed of a pigment-dispersed resin layer containing a cationic organic conductive substance or a pigment-free resin layer.

A resin (binder) that is one of the components of the back coat layer
For this purpose, water-soluble polymer resins or emulsion resins as described above, which have been conventionally used, can be used.

Furthermore, an ionomer resin can be used in the non-woven coating layer when both water resistance and solvent resistance are required, or even when only water resistance or solvent resistance is required. Further, an appropriate amount of inorganic pigment may be added.

The photosensitive layer on the surface is the same as the photosensitive layer in general electrophotographic photosensitive materials, and is made of lipophilic materials such as polydityl methacrylate, acrylic ester, polyvinyl chloride, polyvinyl acetate, polystyrene, silicone resin, and polyvinyl butyral. It has a form in which zinc oxide is dispersed in resin.

Actually, in order to produce the printing plate of the present invention, a desired electrically conductive treatment layer is provided on the back side of the base paper support, and an undercoat layer and
A precoat layer is provided, and a photosensitive layer is placed on top of the wire nozzle.
They may be formed sequentially.

To obtain an offset printing plate (master) using this printing plate, use an ordinary dry or wet electrophotographic method, that is,
After uniformly charging the photosensitive layer in a dark place, imagewise exposure (light image irradiation) is performed to form an electrostatic latent image, which is developed with a lipophilic toner developer [2, and this toner image is fixed. Next, this may be treated with a desensitizing solution. Such plate making can be easily carried out using a dry or wet electrophotographic plate making machine.

Hereinafter, the effects of the present invention will be clarified through Examples. All parts are parts by weight.

Example 1 Ionomer ceramic resin: L-400 Asahi Dow Co., Ltd. Water-soluble polymer resin: PVA-105 Kuraray Co., Ltd. Inorganic pigment: UW
-90 (Ultra White 90) Using the above material,
Coating solutions for the dipping layer and precoat layer were prepared in the combinations shown in Table 1.

The samples within the double line frame in the table are the samples of the present invention.

(The following is a blank space.) Next, a coating solution for a photosensitive layer and a treatment layer having the following formulation was prepared.

Photosensitive J- Rose Bengal 0.07 parts Senkan treatment layer calcium carbonate 50 parts Polyethylene wax 10 parts Cation type conductive agent
Then, on the back side of the commercially available high-quality paper with 12 (IIP/l), a conductive treatment layer of 10 f/nrl was applied and dried. ~5 f/m”
A printing press sample was prepared by providing a precoat layer of 5 to 5 f/m2 of a cloth needle and a photosensitive layer of zsy/m'' coating layer thereon.

In addition, printing plate samples provided with a precoat layer and a water-resistant layer shown in Table 2 were prepared.

Table 2 Both stations were formed on the obtained printing plate using a conventional electrophotographic method, fixed, and plate-made. Next, the printing machine (Rino AP-26
00) F trowel printing was performed and performance evaluation was performed.

The results were as shown in Table-3.

(Left below) Evaluation method * Pre-exposure labor: 1000 with a 20W white fluorescent lamp stand
Irradiation for 20 seconds at Lux illuminance (20,000 tux-s
ec) Immediately after the plate making.

** Sub-printing Crab The number of sheets printed using a printing machine was determined until the photosensitive layer peeled off.

***Print elongation: Same print as the printing durability test
The first printed page of the object is taken as the reference dimension, and the dimensional change rate of the printed matter is measured every 1,000 years.Dimensions of the first printed page t1 1,000th page II tloo.

1 As is clear from the results shown in Table 3I, the printing durability of the product of the present invention is significantly improved, and the printing elongation is also very small (
In comparison with 425.26, which had a water-resistant layer), the image quality was also satisfactory.

Samples f, 427, and 28 could not be coated because the PVA in the precoat layer swelled and dissolved when the water-resistant layer was coated.

Example 2 Ionomer resin: L-4000 Water-soluble polymer resin manufactured by Asahi Dow Co., Ltd.: PVA-105 Carbon black manufactured by Kuraray Co., Ltd.: TB-711) Inorganic pigment: Clay tJW-90 Using the above materials, carbon Coating solutions for the pull layer and precoat layer were prepared according to the rough combinations shown in Table 4. The samples in the double box in the table are the samples of the present invention.

Table 4 Next, Example 1 except that the samples shown in Table 4 were used.
A printing plate sample was prepared in exactly the same manner as above.

In addition, as a comparative example, printing plate samples shown in Table 51 with a water resistance of 7 m, a precoat layer, and a carbon undercoat layer were prepared.

Table 5 Next, printing was carried out in the same manner as in Example 1, and the results of performance evaluation are shown in Table 6.

As is clear from the results shown in Table 6, the product of the present invention, which has a carbon undercoat layer, can be used even around the image area (especially the solid area) after being fixed (radiant fixing) with the infrared lamp of the dry plate making machine. There was no waving at all, and therefore no printing wrinkles occurred even when printing originals containing solid images. (No solid wrinkles)

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view of the lithographic printing plate of the present invention. ! ... Support base paper 2 ... Undercoat layer 3 ... Precoat layer 4 ... Photosensitive layer 5 ... Conductive treatment layer Patent applicant Rico Co., Ltd. 1471-

Claims (1)

[Claims] 1. On a support, a) a subbing layer containing at least an ionomer resin, b) a precoat layer containing an ionomer resin and a water-soluble polymeric substance as main components, and C) a zinc oxide-resin dispersion. A lithographic printing plate for electrophotographic engraving, characterized in that it is formed by sequentially laminating photoconductive layers. 2. The lithographic printing plate for electrophotographic engraving according to claim 1, wherein an inorganic pigment is dispersed in the F-printing layer and/or the precoat layer. 3. The lithographic printing plate for electrophotolithography according to claim 1, wherein the 'F drawing layer contains a water-soluble resin. 4. The lithographic printing plate according to claim 1 or 2, wherein Kazen black is dispersed in the undercoat layer.