JPS58160196A - Planographic chromium plated steel plate - Google Patents

Abstract

PURPOSE:To provide the titled economical chromium plated steel plate excellent in hydrophilicity, water holdability and anti-rust property and having printing durability equal to that of an Al plate, constituted by forming a metal chromium layer and a chromia hydrate layer on the surface of a surface roughened steel plate. CONSTITUTION:After surface roughening treatment is preliminarily applied to the surface of a steel plate by mechanical polishing, a metal chromium layer with a thickness of 100-500mg/m<2> is formed on the surface roughened steel plate and a chromia hydrate layer with chromium content of 50-200mg/m<2> is further formed on said metal chromium layer to obtain an objective steel plate with surface roughness of 0.3-1.0mum Ra and difference of Ra in the rolling (L) direction and the width (C) direction of 0.15mum or less.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a chromium-plated steel plate that is excellent in hydrophilicity, water retention, and rust resistance, and has printing durability equivalent to that of an aluminum printing plate.

The large plate and plate making process consists of - plate processing - photosensitive resin coating - printing - one development and one post-print processing, and the 28 plate (pre-printed and photosensitized plate) is prepared by the photosensitive material manufacturer in advance. Processing - The plate is coated with photosensitive resin, and among these steps, plate surface pretreatment improves the adhesion of the photosensitive film, strengthens the printing durability of the image on the plate, and improves water retention in non-image areas. The purpose is to. Lithographic printing is a printing method that takes advantage of the difference in hydrophilicity between image areas and non-image areas, and zinc or aluminum was used as the material, but aluminum is less oily and more hydrophilic than zinc. is large, so
Sharp lines can be obtained, and the effect can be further improved by anodizing (Currently, aluminum is the main material used for lithographic CF2). In order to save resources and energy, and to rapidly increase the price of non-ferrous metals, there is an increasing demand for lower prices by guaranteeing II surface properties that are more equivalent to those of aluminum. .

4 The present invention attempts to meet such demands.
The plate material is a ROM-plated steel plate, which is cheaper than aluminum. In order to obtain sharp lines without printing stains, the plate material has excellent hydrophilic properties in the non-printing areas. In addition, in order to maintain wood affinity, the dampening water supplied to the non-image areas must have excellent water retention properties. In addition, a material with excellent rust resistance is required, which does not cause rust due to dampening water during printing, and does not rust during storage before and after plate making, and before and after printing.
If the adhesion between the photosensitive agent in the image area and the holding steel plate material is poor, the printing durability will decrease.
The chromium hydrated oxide layer itself is highly hydrophilic, but it is very active and therefore easily contaminated in the air, and becomes water repellent over time after production, making it difficult to maintain hydrophilicity. Before plate making, a hydrophilic treatment is required to remove surface contamination, and water repellency remains after normal degreasing treatment, so a treatment such as 7-e-miston polishing must be performed.However, if such treatment is performed! ! The chromate layer on the surface is removed, reducing rust resistance. In addition, because conventional chrome-plated steel plates have smooth surfaces, they have poor adhesion to photosensitive materials and dampening water retention, resulting in poor printing durability.On the other hand, aluminum plate plates have poor water resistance and water retention. It has excellent hardness, rust resistance, and printing durability, but apart from the high material cost, it requires pre-plate-making treatment of anodizing treatment after surface roughening.

The present invention is lower in cost than aluminum printing plates, and does not require complicated pretreatment such as surface roughening, and can be easily treated with hot water, weakly alkaline water, etc. to remove surface contamination as required. The present invention provides a chromium-plated steel sheet that can be made hydrophilic, has excellent hydrophilicity, water retention, and rust resistance, and has printing durability equivalent to that of an aluminum plate. , provides a chromium-plated steel sheet for lithographic printing in which a metal chromium layer is formed on the surface of the steel sheet after roughening treatment by chemical polishing or electrolytic polishing, and a chromium water-conserving oxide layer is further formed on the surface of the steel sheet. The chromium-plated steel sheet for lithographic printing of the present invention, which can eliminate the various drawbacks of the technology mentioned above, will be explained in detail. After the surface has been roughened by draft polishing, electrolytic polishing, etc., a metallic chromium layer and a chromium hydrated oxide layer are formed on the surface of the steel sheet.
q/- is preferable @ If the amount of metallic chromium is less than xoOwild, rust resistance during printing and storage will be poor;
If it exceeds 00q/11/, it is disadvantageous in terms of economy.

Moreover, the amount of chromium in the film of the chromium water-conserving oxide layer applied on the metal chromium layer is preferably 50 to 200 K/II/. If the amount of chromium in the film is less than 50 v/d, hydrophilicity and rust resistance will be poor, and if it exceeds 2001/d, the surface color tone will deteriorate and correction during plate making will be difficult. After degree plating and electrolytic chromic acid treatment, it is preferable that the Ra is 0.3 to 1.0μ and the difference in Ra between the L (rolling) direction and the C (width) direction is 0.15 pm or less. o If RJL is out of the 0.3 to 1.0μ ratio or the difference in Ra between L direction and C direction is 0.15
If it is larger than p, the tone reproducibility of the printed matter with respect to the original when used as a printing plate is poor, and printing durability is poor.

The chromium-plated steel sheet for planographic printing of the present invention will be described below with reference to Examples and Comparative Examples.0 [Examples 1 to 4] A cold-rolled steel sheet with a thickness of 0.22a+w was subjected to alkaline electrolytic degreasing (caustic soda 501/l, 80e, 5A/ν, 30 seconds, immersion pickling in nitric acid (nitric acid 6X, room temperature, 20~5
0 second immersion) or electrolytic pickling (nitrogen Msxsm temperature, 1
5A/d#/XIO~20 seconds). After pickling, wash thoroughly with water, Cr0.1801/ls H, 8040,
6f/l.

Na, SiF, 6 t/l (7) RIOA Me) was electrolyzed for 4 seconds at a current density of 30A/6/1 at a temperature of 50c, and then trNtecrO, 50
f/1%H, 8040, 5f/t electrolytic chromic acid treatment solution at a temperature of 40°C, 5A/〆 electric @flfj degree.
A chromium-plated steel sheet was obtained by subjecting it to a 0-second dewax treatment.A photosensitive layer consisting of a diazo resin and a binder was applied to this steel sheet.
The film was formed to a thickness of 100 mm, exposed to light, exposed areas were removed and developed with an alkaline aqueous solution, and rubber-reduced with an aqueous solution of Ativi 1 rubber. The following various tests were conducted using the planographic plate thus obtained. The test results are shown in Table 1 along with the test results of the comparative example shown below. In addition, the surface roughness profile of the planographic material obtained as described above is shown in Figure 1 (L direction) and Table 1. In figure 2 (direction C),
Scanning electron micrographs are shown in Fig. 5.As can be seen from these figures, the surface irregularities of the steel sheet according to the present invention are equally distributed in the C direction and the L direction, and the surface roughness is 0. ,5
〜Q,・lka R11k. Therefore, it was found that this copper plate has excellent rust resistance, as well as excellent hydrophilicity, water retention, and adhesion, and has the same printing durability as aluminum plate. (Hydrophilicity) Plate making The previous test piece was evaluated by performing a water wetness test.

The evaluation method is as follows.

○・−・Water repellent area ratio 0 to Δ・−Water repellent area ratio less than 5××−Water repellent area ratio 59 or more (rust resistance) For rust resistance, dampening water immersion test and wet test
In the dampening water immersion test, which evaluated rust resistance during printing and storage, half of the specimen was immersed in dampening water.
The state of rusting after being immersed for one day was evaluated. Humidity test at room temperature,
The zero evaluation method for evaluating the state of rust after storage for one month under conditions of humidity of 95% or higher is as follows.

〇 - Rust rate Ox Δ - Rust rate less than 5X × - Rust rate 5X or more (printing durability) The obtained planographic material was used for offset printing, and the printing durability was evaluated for up to 150,000 sheets0 The evaluation method is as follows.

〇 - Beautiful printing ∆ - Slight stains on the printed surface ×... Dirt on the printed surface, peeling in some parts of the image (measurement of surface roughness) Surface roughness was measured with a stylus-type roughness meter .

[Comparative Example 1] After immersion pickling in nitric acid in the same manner as in the example, plating was performed at 50C in the same chromium plating solution as in the example at 30 A/k.
The steel sheet was decomposed for IJ seconds at a current density of 1, and then subjected to the same electrolytic chromic acid treatment as in the example to produce a chromium-plated steel sheet.

The same tests as in the examples were conducted for this steel plate. As is clear from Table 1 showing this result, this steel sheet had poor rust resistance because the amount of metallic chromium was less than 100iv/w/0 [Comparative Example 2] Similar to the example, it was tested in nitric acid. After immersion pickling, chromium plating treatment was performed under the same conditions as in the example, and then electrolytic treatment was performed in the same electrolytic chromic acid section S* at 40c for 3 seconds at a current density of 5 μm/4d to remove chromium. A plated steel plate was produced. This steel plate was subjected to the same test as in the example, and the results are shown in Table J[1]. Since the amount of chromium in the chromium hydrated oxide film was less than 50 q/d, this steel sheet had poor rust resistance as in Comparative Example 1.It also had poor hydrophilicity, causing printing stains. [Comparative Example 3] A cold-rolled steel sheet with a thickness of 0.22 m was degreased by alkaline electrolytic degreasing.
A chromium-plated copper plate was produced by pickling in an aqueous X-sulfuric acid solution at 40° C. for 5 seconds, chromium plating in the same manner as in the example, and then electrolytic chromic acid treatment. The same tests as in the examples were conducted on this steel plate, and the results are shown in Table 1. In addition, the surface roughness profile of the steel plate according to this example is l
Figures 1311 (L direction and Figure 1!4 (C direction)) and scanning electron micrographs are shown in Figure 6.◎From these results, although this steel plate has excellent rust resistance and hydrophilicity, the surface Because there were few irregularities and the difference in direction in the L direction and the C direction was significant, the adhesion in the image area and the water retention in the 11 non-image areas were poor, and as a result, the printing durability was poor.

[Comparative Example 4] A printing test was carried out using a commercially available aluminum 28 plate that had been pretreated with surface roughening and anodic oxidation, and beautiful printing was obtained after printing 150,000 sheets.

[Brief explanation of drawings]

Figures 1 and 4 are diagrams showing the p-surface roughness profile in the L (rolling) direction and C (width) direction, respectively, of the steel plate of the present invention, and Figure 4 and diagram 4 are diagrams showing the profile of the p-surface roughness in the L (rolling) direction and C (width) direction, respectively, of the steel plate of the present invention, and Figure 4 shows the steel plate obtained in Comparative Example 3. Figures 5 and 6 are electron micrographs showing the surface structure of the metal, and Figure S shows the surface condition of the steel sheet of the present invention. The scanning electron micrograph shown in Fig. 6 is Comparative Example 3.
This is a scanning electron micrograph showing the surface condition of a steel plate. Patent applicant: Kawasaki Steel Corporation

Claims (1)

[Claims] Pre-roughened steel plate surface thickness 10° to 500q
/gIl, and a chromium hydrated oxide layer on top of which the amount of chromium is 50 to 200 vq/d,
The surface roughness is 0.3 to 1.0μ1llR&, and the difference in - between the rolling υ direction and the width 0 direction is 0.157W.
A chrome-plated steel plate for planographic printing, characterized by the following: