JPH0430358B2 - - Google Patents

Description

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

Aluminum is currently widely used as a substrate for manufacturing lithographic printing plates. Aluminum lithographic printing plates are made by roughening the surface of an aluminum plate to form grains, applying a photosensitive composition, exposing and developing this, and leaving the image area to be printed as a resist layer. You can get it. The purpose of forming grains on the surface of the aluminum plate is twofold: firstly, to provide the printing plate with adequate water retention during printing operations, and secondly, to increase the adhesion between the photoresist coating and the surface of the aluminum plate and to provide sufficient water retention. The purpose is to provide printing durability.

There are various graining methods, but they are broadly classified into mechanical methods and chemical methods. Mechanical methods include ball graining, wire graining, brush graining, etc., and chemical methods include corrosion in an acid or alkaline solution, electrochemical corrosion, and the like. However, these methods have the following problems. In other words, the problems with mechanical graining are that it requires considerable skill in adjusting the machine and the abrasive material, and that there is no possibility of the abrasive material getting into the roughened surface of the aluminum plate, aluminum shavings, etc. This requires work to remove.

The problems with the chemical graining method are
It is necessary to adjust the electrolytic conditions, etc. within a fairly narrow range, and furthermore, when electrochemical graining is adopted, which provides the highest quality grain, the power consumption makes up a large proportion of the printing plate manufacturing cost. The point is that it will be quite large.

As a method that can eliminate these drawbacks, Japanese Patent Application Laid-Open No. 55-74898 discloses that an aluminum plate is passed through a roll having an inverted graining surface, and a depth
A grain production method is described that produces pores of 3.5μ or less. Furthermore, JP-A No. 57-500329 describes a method of passing an aluminum piece through a roll having a specified surface roughness to form a specified surface roughness (depth), and then anodizing it. ing.

These graining methods are simple to operate, do not require the removal of abrasive materials, aluminum chips, etc. that are required with conventional mechanical graining methods, and are also faster, greatly streamlining the manufacturing process. there is a possibility. However, when creating holes by pressing, controlling only the depth of the holes as described in these publications does not provide a desirable grain for a lithographic printing plate, and this method is still insufficient. It has not been put into practical use. In view of these circumstances, the present inventors have conducted extensive research with the aim of creating a grained plate that not only streamlines the manufacturing process but also satisfies its performance as a support for planographic printing plates. As a result, it was discovered that the desired goal could be achieved by providing oval press depressions at a specific density on the surface of the support, with some of them overlapping to form a wavy pattern. invention has been achieved. In other words, the gist of the present invention is to form 200 oval press recesses/mm ² on the surface.
The present invention relates to a lithographic printing plate support made of an aluminum plate having the above density and formed so that the press depressions partially overlap to form a wavy pattern.

The aluminum plate used in the present invention includes a pure aluminum plate and an aluminum alloy plate. Various aluminum alloys can be used, such as alloys of aluminum and metals such as silicon, copper, manganese, magnesium, chromium, zinc, lead, iron, titanium, and nickel.

The rough surface of the aluminum plate can be formed using, for example, a rolling roll as described below. That is, the surface of the roll (for example, a steel roll) used to roll the aluminum plate is roughened,
By rolling the aluminum plate through this roll, it is possible to transfer the rough shape of the roll surface onto the aluminum plate surface. For example, a roughened steel roll contains fine particles of 100 to 1000μ (e.g. silica, oxides such as alumina, steel, etc.)
can be produced by injecting it onto a rotating steel roll under conditions of an impeller rotation speed of 1500 to 3000 rpm, a grid input rate of 100 to 500 kg/min, and a shot time of 1 to 30 minutes. The rolling reduction ratio when rolling the aluminum plate is preferably in the range of 3 to 50% per pass, and it is also possible to perform the rolling process multiple times as necessary. The rolled aluminum plate has oval recesses arranged densely on its surface, and the fringes of the recesses partially overlap to form a wavy pattern. At this time, the shape and density of the elliptical recesses are related to the suitability of the lithographic printing plate, and these values are controlled within a certain range.

First, the density of the oval press recesses is 200 pieces/mm ²
As mentioned above, it is desirable that the number is preferably in the range of 200 to 15,000 pieces/mm ² , more preferably in the range of 1,000 to 10,000 pieces/mm ² . If the density of the press depressions is lower than 200 pieces/mm ² , the adhesiveness between the resist and the aluminum surface will decrease, and the water retention will also decrease.

In addition, in the present invention, it is important that the oval press recesses partially overlap and their fringes form a wavy pattern, as shown in Example 1 (FIG. 1) described later. be.

A pattern obtained by conventional brush polishing, for example, a pattern as shown in FIG. 3, or Comparative Example 1 described below.
A line-like grained pattern as shown in FIG. 2 tends to cause stains.

Since the shape of the press recess is formed by rolling, the long axis of the ellipse is generally parallel to the stretching direction of the coil, and the short axis is arranged perpendicular to the stretching direction. The average length of the major axis is preferably 10 to 140μ,
To obtain a lithographic printing plate which has good adhesion of the resist to the aluminum surface and has excellent dot reproducibility and water retention when the average length of the short axis is preferably in the range of 7 to 80μ. I can do it. If the size of the elliptical recess is larger than this, both adhesiveness and dot reproducibility will deteriorate.

In addition, regarding the depth of the recess, the center line average roughness
When Ra is in the range of 0.3 to 1.5μ, it is preferable in terms of balance between water retention and small spot reproducibility. If it is 0.3μ or less, water retention is insufficient, and if it is 1.5μ or more, small spot reproducibility decreases.

The grain obtained by the present invention has a simple manufacturing operation, and the processing speed is much higher than that of conventional brush polishing grain and electrochemical grain, and it can be used not only for single-sided lithography but also for double-sided lithography. It also has the advantage of being manufacturable. The grained aluminum plate can be used as it is as a support for a lithographic printing plate, but if necessary, it can be further subjected to treatments such as anodizing treatment and chemical conversion treatment. The anodizing treatment can be performed under conditions conventionally employed in this field. Specifically, in an aqueous solution of sulfuric acid, phosphoric acid, chromic acid, oxalic acid, sulfamic acid, benzenesulfonic acid, etc. or a combination of two or more of these, the electrolysis time is 15 seconds to 15 seconds at a current density of ¹ to 50 A/dm2. It is appropriate to carry out the reaction at a liquid temperature of 25 to 70°C. After the anodization, further sealing or hydrophilic treatment may be performed using hot water, silicate, dichromate, acetate, hydrophilic polymer compound, or the like.

The photosensitive material applied to the aluminum grained plate of the present invention is not particularly limited, and various known materials can be used. For example, a negative-working photosensitive composition comprising a diazo resin and a binder, a positive-working photosensitive composition comprising an o-quinonediazide compound and a binder, a negative-working photosensitive composition comprising an azide compound and a binder,
Examples include negative-working photosensitive compositions made of a photodimerizable photopolymer, negative-working photosensitive compositions made of a photopolymerizable monomer and a binder, and the like. A photosensitive lithographic printing plate can be produced by dissolving these photosensitive compositions in a suitable solvent, applying the solution to the aluminum grained plate of the present invention, and drying it. By repeating exposure and development, it is possible to obtain an excellent printing plate with excellent hydrophilicity and water retention, and strong adhesion between the photosensitive layer and the grain.

The present invention will be described in detail below based on Examples, but the present invention is not limited to the following Examples unless the gist of the invention is exceeded.

In addition, in the examples, the density of the elliptical press recesses and the average length of the major axis and short axis were measured for the elliptical press recesses within a certain area by magnifying the aluminum surface 400 times with a scanning electron microscope. , calculated. In addition, the average line center roughness was determined according to the method of JIS B0601-1976.

Example 1 Steel particles with a hardness (HV) of 860 and an average particle size of 500μ,
Impeller rotation speed 2000 rpm, grid input amount 250
A steel roll was sprayed under conditions of Kg/min and shot time of 23 minutes to produce a rolling roll having a roughened surface. An aluminum plate that has been hot-rolled and cold-rolled to a thickness of 0.27 mm is passed through these rolls, and rolled with a reduction rate of 7.6% in the first rolling and 6% in the second rolling. A roughened grain with a thickness of 0.235 mm was obtained. The average roughness of the center line of the grain is 0.65μ, the average length of the long axis of the oval press recess is 55μ, the average length of the short axis is 30μ, and the density is 600 pieces/mm ²
It was hot. A 400x scanning electron micrograph of the resulting grained surface is shown in Figure 1. It can be seen that a wavy pattern is formed on the surface of the support. Then, sulfuric acid
After alumite treatment in a 20% bath at 6 A/dm ² and electrolysis time of 20 seconds, an o-quinonediazide photosensitive solution with the following composition was applied to a film thickness of 20 mg/dm ² and photosensitive printing was performed. Got the edition.

Condensate of naphthoquinone diazide-5-sulfonyl chloride and m-cresol formaldehyde novolac resin 5.0 g m-cresol formaldehyde novolac resin (manufactured by Sumitomo Dures) 9.0 g Victoria Pure Blue BOH (manufactured by Hodogaya Chemical Co., Ltd.) (Product name) 0.1g Naphthoquinone diazide-4-sulfonyl chloride 0.19g Ethyl cellosolve 100g The halftone chart, step doublet and positive film were adhered to the thus obtained photosensitive printing plate, exposed with a metal halide lamp, and then exposed to light using a metal halide lamp. When development was performed using a 4% aqueous solution of sodium metasilicate, 2% halftone dots were reproduced in 5-stage clear. Next was an offset printing machine (manufactured by Roland).
When we conducted a printing test using PARVA (product name), we were able to successfully print 50,000 sheets without any particular stains.

Example 2 Steel particles with a hardness (HV) of 860 and an average particle size of 250μ,
Impeller rotation speed 2000 rpm, grid input amount 250
The mixture was sprayed onto a steel roll under conditions of Kg/min and shot time of 23 minutes to produce a rolling roll having a roughened surface. With this rolling roll, sand was rolled in the same manner as in Example 1 to produce sand with a center line roughness of 0.6μ, an average major axis length of the oval press recess of 28μ, an average short axis length of 14μ, and a density of 2000 particles/mm ^2. An aluminum plate with holes was obtained. The obtained roughened aluminum plate was anodized in a 20% sulfuric acid bath at 6 A/dm ² for 20 seconds, followed by chemical conversion treatment in a 1% sodium silicate aqueous solution at 80°C for 1 minute. I went. A diazo photosensitive liquid having the following composition was applied to the grain thus obtained at a film thickness of 17 mg/dm ² to obtain a photosensitive printing plate.

p-Diazodiphenylamine/formaldehyde condensate pF ₆ salt (diazonium salt) 0.42g Copolymer of p-hydroxyphenylmethacrylamide/acrylonitrile/ethyl acrylate/methacrylic acid 6.0g Victoria Pure Blue BOH (Hojidani) 0.16g polyacrylic acid (manufactured by Nippon Pure Chemical Industries, Ltd., product name)
-10L (Product Name)) 0.18g Methyl Cellosolve 100g A halftone chart, step tablet, and negative film are adhered to a photosensitive printing plate, exposed with a metal halide lamp, and then processed with a developer with the following composition.
After removing the unexposed area, in the 5-level solid,
2% halftone dots were reproduced.

Benzyl alcohol 30ml Sodium carbonate 5g Sodium sulfite 5g Sodium isopropylnaphthalene sulfonate
10 g water 1 The obtained printing plate was subjected to a printing test using an offset printing machine in the same manner as in Example 1, and 50,000 good prints were obtained without staining in the non-image area.

Example 3 Steel particles with a hardness (HV) of 860 and an average particle size of 500μ,
Impeller rotation speed 2000 rpm, grid input amount 250
The mixture was sprayed onto a steel roll under conditions of Kg/min and shot time of 20 minutes to produce a rolling roll having a roughened surface. With this rolling roll, sand was rolled in the same manner as in Example 1 to produce sand with a center line roughness of 0.5μ, an average length of the long axis of the oval press recess of 60μ, an average length of the short axis of 35μ, and a density of 400 pieces/ ^mm2 . An aluminum plate with holes was obtained. The thus obtained roughened aluminum plate was
% phosphoric acid bath, current density 3 A/dm ² , treatment time 5
After alumite treatment at a bath temperature of 25°C, 14ml of photodimerized photopolymer photosensitive solution with the following composition was
The coating was applied to a film thickness of g/dm ² to obtain a photosensitive printing plate.

Polyester obtained by condensation of p-phenylene diacrylic acid diethyl ester and 1,4-dihydroxyethoxy-cyclohexane 4.0 g 2-benzoylmethylene-1-methyl-β-naphthothiazoline 0.32 g Benzoic acid 0.16 g Hydroquinone 0.08 g Phthalocyanine blue Face wash 0.8g Monochlorobenzene 100ml The halftone dot chart, step tablet, and negative chart were adhered to the photosensitive lithographic printing plate thus obtained, exposed using a metal halide lamp as a light source, and the unexposed areas were removed with a developer having the composition shown below. Removed.

4-Butyrolactone 500ml Triethanolamine 50ml Glycerin 50ml Methyl abietate 5ml Hydrogenated Utudrozine (Stabelite Resin (trade name) manufactured by Hercules Bauder) 0.5g Wetting agent (Zonyl A (trade name) manufactured by Dupont)
4.5 ml The resulting printing plate reproduced 1% halftone dots in a 5-level solid pattern. When printing was carried out using an offset printing machine in the same manner as in Example 1, 100,000 sheets of good printed matter were obtained without any particular trouble.

Comparative Example 1 While rotating a steel roll, the roll surface was polished with a grindstone to obtain a rolling roll having a linear pattern. Using this rolling roll, an aluminum plate was rolled in the same manner as in Example 1. A linear pattern of grain with a center line average roughness of 1.2μ was obtained (Figure 2).

Next, alumite treatment was performed in a 20% sulfuric acid bath at a current density of 5 A/dm ² and a treatment time of 20 seconds, and then 20 m of the same o-quinonediazide photosensitive solution as in Example 1 was applied.
When the film was coated at a film thickness of g/dm ² and exposed and developed, streaks with a grained line pattern were observed in the intermediate tone areas. Furthermore, a printing test was carried out using the printing plate on an offset printing machine, but because of the linear pattern of the grain, staining was likely to occur and good printed matter could not be obtained. This fact indicates that if the press recesses do not have a wavy pattern, they are likely to get dirty.

Comparative Example 2 Steel particles with a hardness (HV) of 860 and an average particle size of 500μ,
Impeller rotation speed 1750 rpm, grid input amount 250
The mixture was sprayed onto a roll under conditions of Kg/min and shot time of 10 minutes to produce a rolling roll. Rolling was carried out using this roll under the same conditions as in Example 2, with a center line average roughness of 0.5μ, a long axis average length of the oval recesses of 120μ,
Grains with an average short axis length of 70μ and a density of 190 pieces/mm ² were obtained. This grain was anodized and chemically treated under the same conditions as in Example 2, and a photosensitive liquid of the same composition was applied to the same film thickness, and exposed and developed under the same conditions. The adhesion to the eyes was insufficient, and the sensitivity was about one step lower than in Example 2. This fact indicates that when the density of press depressions is 200 pieces/mm ² or less, the adhesiveness with the resist is insufficient.

[Brief explanation of drawings]

FIG. 1 is an electron micrograph (400x magnification) of the surface of the aluminum plate roughened with a rolling roll, obtained in Example 1. FIG. 2 is an electron micrograph (400x magnification) of the surface of the aluminum plate obtained in Comparative Example 1 and roughened by grindstone polishing. FIG. 3 is an electron micrograph (400x magnification) of the surface of an aluminum plate roughened by brush polishing.

Claims (1)

[Scope of Claims] 1. A planographic plate made of an aluminum plate having oval press recesses formed on its surface at a density of 200 pieces/mm ² or more, and in which the press recesses partially overlap to form a wavy pattern. Support for printing plates. 2 The average length of the major axis of the oval press recess is 10~
140μ, the short axis average length is in the range of 7 to 80μ, and the center line average roughness of the aluminum plate surface is 0.3 to 80μ.
The support for a lithographic printing plate according to claim 1, characterized in that the support has a thickness in the range of 1.5μ.