JPH0313315B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a chromium-plated steel plate for planographic printing,
In particular, the present invention relates to a chromium-plated steel plate that has excellent hydrophilicity, water retention, and rust resistance, and has printing durability equivalent to that of aluminum lithographic plates. In general, the lithographic plate-making process consists of the following steps: pre-treatment of the plate, application of photosensitive liquid, baking, development, and post-treatment of the plate.So-called PS plates are those in which the plate is pre-treated and coated with photosensitive liquid at a photosensitive material manufacturer. Among these steps, the purpose of plate pretreatment is to improve the adhesion of the photoresist film, strengthen the printing durability of the image area of the plate, and improve water retention in the non-image area. As described above, lithographic printing utilizes the difference in hydrophilicity between printed areas and non-printed areas to print, but conventionally the materials used are galvanized steel plates or aluminum plates. Compared to galvanized steel sheets, aluminum sheets have poor lipophilicity and high hydrophilicity, so sharp lines can be obtained and the effect can be further improved by anodizing. Therefore, currently
Aluminum is mainly used as a lithographic material including PS plates. However, recently, due to the rapid rise in the price of non-ferrous metals and from the viewpoint of resource and energy conservation, there is an increasing demand for lower material prices by guaranteeing surface properties equivalent to those of aluminum. An object of the present invention is to provide a chromium-plated steel sheet which is cheaper than aluminum and which guarantees the same surface quality as aluminum as a lithographic material in response to the above-mentioned demands of customers. The gist of the present invention is as follows.
That is, a metallic chromium layer of 70 to 200 mg/ ^m2 is plated on the surface of a steel plate that has been roughened in advance, and a metallic chromium layer of 8 mg/m2 coated on the metallic chromium layer is
~60mg/ ^m2 of chromium hydrated oxide layer, and the surface roughness of the coated steel sheet is the centerline average roughness Ra.
0.3 to 2.0 μm at maximum height Rmax, 1.5 to 10 μm at maximum height Rmax
, and furthermore, the above Ra in the rolling direction and the direction perpendicular to the rolling direction is
This is a chromium-plated steel plate for lithographic printing, characterized in that the difference in chromium-plated steel plate is 0.15 μm or less. First, the structure of the chromium-plated steel plate for planographic printing according to the present invention and the reasons for its limitations will be explained. The chromium-plated steel sheet according to the present invention has a metallic chromium plating layer on the surface of the steel sheet, which is made of a steel sheet whose surface has been roughened in advance by mechanical polishing, chemical polishing, electrolytic polishing, or other suitable methods. It has a coating layer made of hydrated chromium oxide on top. The first metal chromium layer preferably has an amount of 70 to 200 mg/m ² . This is because if the amount of metallic chromium is less than 70 mg/m ² , rust resistance during printing and storage will be poor, and if it exceeds 200 mg/m ² , the cost will increase and it is economically disadvantageous. In addition, the coating of the chromium hydrated oxide layer applied on the first metal chromium layer is 8 to 60% in terms of chromium content.
mg/m ² is preferred. This is because if the amount of chromium in the second chromium hydrated oxide layer is less than 8 mg/m ² , the hydrophilicity and rust resistance will be poor, and if it exceeds 60 mg/m ² , the color tone of the surface will deteriorate and This is because correction becomes difficult. Furthermore, one of the essential requirements is that the surface roughness of the steel plate that covers the first and second layers is in the range of center line average roughness Ra of 0.3 to 2.0 μm and maximum roughness Rmax of 1.5 to 10 μm. Another essential requirement is that the difference in Ra between the rolling direction (hereinafter referred to as L direction) and the direction perpendicular to rolling (hereinafter referred to as C direction) of the raw steel sheet is 0.15 μm or less. The reason for these limits on surface roughness is that it has been confirmed from numerous experimental results that if the surface roughness is outside these limited ranges, when the material is used as a printing plate, the tone reproducibility of the printed matter with respect to the manuscript will be poor and the printing durability will be poor. This is due to a number of reasons. Examples of chromium-plated steel plates for lithographic printing according to the present invention will be described below in comparison with non-limiting comparative examples. Examples Test materials No. 1 to 4 according to the present invention as shown in Table 1
Comparative tests were conducted on Comparative Example Sample Materials Nos. 5 to 7, which are outside the scope of the present invention. All test materials were cold-rolled steel plates with a thickness of 0.22 mm at 80°C.
Alkaline electrolytic degreasing was carried out for 30 seconds at a current density of 5 A/dm ² in a 50 g/concentration NaOH solution. After that, 6% for sample materials No. 1, No. 5, and No. 6.
Pickling was performed by immersing in HNO ₃ solution at room temperature for 20 seconds, and sample No. 2 was immersed in the same solution for 50 seconds.
In addition, sample materials No. 3 and No. 4 were electrolytically pickled in a 3% NHO ₃ solution at room temperature for 15 A/dm ² × 10 seconds and 15 A/dm ² × 20 seconds, respectively.
Regarding No. 7, ordinary pickling was performed by immersing it in a 10% H ₂ SO ₄ solution at 40° C. for 5 seconds.

【table】

[Table] After pickling, all test materials were thoroughly washed with water, and then, for test materials No. 1 to 4 of the invention examples, CrO ₃ 180
A chromium plating solution containing 0.6 g/g/, H ₂ SO ₄ 0.6 g/, and ₆ g/Na ₂ SiF 6 at a temperature of 50°C was electrolyzed for 2 seconds at a current density of 30 A/dm ² as shown in Table 1. Chrome-plated steel sheets having metallic chromium contents of 105, 102, 104, and 108 mg/m ² were obtained. On the other hand, comparative sample material No. 5 was electrolyzed for 1.0 seconds under the same conditions as above, and test materials No. 6 and 7 were chromium plated under the same conditions as test materials No. 1 to 4 of the invention example. , 58, 102, 108mg/respectively as shown in Table 1
A chromium-plated steel plate with a metallic chromium content of m ² was obtained. Next, regarding the formation treatment of the second layer of chromium hydrated oxide layer, for all of the test materials No. 1 to 4 of the present invention examples, the above-mentioned chromium-plated steel plate was treated with CrO ₃ 50g/,
Adjust the temperature of the solution with an electrolytic chromic acid treatment solution containing 0.5 g of H ₂ SO ₄
Electrolytic treatment was carried out at 40° C. and a current density of 5 A/dm ² for 3 seconds to form a chromium hydrated oxide layer. As shown in Table 1, the amount of Cr in the second layer of each sample material is 16,
They were 15, 18, and 20 mg/ ^m2 . Next, regarding sample materials No. 5 to 7 of comparative examples, each of the above-mentioned chromium-plated steel sheets was applied to No. 5, No. 7 was subjected to the same conditions as the present invention example, and No. 6 was applied using the same electrolytic chromium plated steel sheet. Adjust the temperature of the acid treatment solution to 40℃ and apply 5A/
As a result of electrolytic treatment at a current density of dm ² for 1.5 seconds, which is 1/2 of the time of the present example, as shown in Table 1, the amount of chromium hydrated oxide was 17, 5, and 17 mg/m ² in terms of chromium, respectively. A coated steel plate with two layers was obtained. These No. 1 to 4 test materials according to the present invention and
All of the comparative sample materials Nos. 5 to 7 had hydrophilic properties after being subjected to planographic material forming treatment under the same conditions on chromium-plated steel sheets having a first layer of chromium plating and a second layer of hydrated chromium oxide. Comparative tests were conducted on rust resistance, printing durability, and surface roughness. That is, a photosensitive layer consisting of a diazo resin and a binder was formed to a thickness of 3 μm on each test material of the chromium-plated steel plate having the first layer and the second layer, imagewise exposed, and the exposed portion was exposed with an aqueous alkaline solution. It was removed, developed and rubberized with an aqueous solution of gum arabic. The following various tests were conducted using the planographic plate thus obtained. (a) Hydrophilicity Evaluation was performed by conducting a water wetness test on the test piece before plate making. The evaluation method and the markings in Table 1 are as follows. ○: Water repellent area ratio 0% △: Same as above, less than 10% ×: Same as above, 10% or more (b) Rust resistance Rust resistance was evaluated by a dampening water immersion test. In the dampening water immersion test, half of the test piece was immersed in dampening water, and the rusting state after 2 days of immersion was evaluated. The markings in Table 1 are based on the following criteria. ○: Rust rate 0% △: Same as above, less than 5% ×: Same as above, 5% or more (c) Printing durability Offset printing using the obtained lithographic material,
The printing durability up to 50,000 sheets was evaluated. The evaluation method and the markings in Table 1 are as follows. ○: Beautiful printing △: Slight stains and uneven printing on the printed surface. × mark: There is dirt on the printed surface and peeling of the printed area. (d) Surface roughness The surface roughness of the planar material obtained from each of the test materials Nos. 1 to 7 above was determined by the centerline average roughness Ra and maximum height in the rolling direction and the direction perpendicular to the rolling direction of the raw steel plate.
Rmax was measured. The measurement results are shown in Table 1. Note that the surface roughness was measured using a stylus type roughness meter. FIGS. 1 and 2 show examples of the surface roughness profiles in the L direction and the C direction, respectively, of a planographic material obtained from a chromium-plated steel plate according to the present invention. As is clear from the surface roughness measurement results in Table 1 and Figures 1 and 2, the steel plate specimen according to the present invention has an extremely small difference ΔRa between the L direction and the C direction, which is 0.03 to 0.08 μm, and the Ra is 0.35 to 0.63μm,
Rmax was 3.9-5.5 μm. On the other hand, the surface roughness of comparative sample materials No. 5 and No. 6 is almost the same as that of the present invention material, but for No. 7, Ra in the C direction is 0.26 μm, and in the L direction
It was found that the difference ΔRa was extremely large at 0.16 μm, and Rmax was also extremely small at 1.7 μm and 1.2 μm, respectively. FIGS. 3 and 4 show the surface roughness profiles of sample No. 7 in the L direction and C direction, respectively. In addition to the test materials shown in Table 1, the inventors conducted many experiments and found that the surface roughness was 0.3 to 2.0 μm for Ra, 1.5 to 10 μm for Rmax, and △Ra was
It was confirmed that when the thickness was 0.15 μm or less, the printing durability was comparable to that of aluminum printing plates, and when it was outside this limit, the reproducibility of the tone of the printed matter was poor and the printing durability was inferior. Furthermore, the results of measuring the hydrophilicity, rust resistance, and printing durability of each of the above-mentioned test materials No. 1 to No. 7 by the above-mentioned method are shown in Table 1. As is clear from Table 1, test materials No. 1 to 4 according to the present invention are all excellent, but test material No. 5 of the comparative example has a chromium content of 58 mg/m ² in the first layer. Rust resistant for less outside limited,
Although the amount of metallic chromium in sample No. 6 is within the limited range, the second layer of hydrated chromium oxide is 5 mg/ ^m2 , which is outside the limited range, so it is not hydrophilic or rust resistant. The print quality was poor, and printing stains also occurred. Regarding sample material No. 7, both the first and second coating layers satisfy the requirements of the present invention, so although the hydrophilicity and rust resistance are excellent, Ra is less than 0.3 μm, and the C direction and the difference △Ra in the L direction is 0.16μ
m, which resulted in poor adhesion in printed areas and poor water retention in non-printed areas, resulting in poor printing durability. As is clear from the above examples, the chromium-plated steel plate for planographic printing according to the present invention has a metallic chromium layer of 70 to 200 mg/m 2 as the first layer on the surface of the steel plate which has been roughened in advance, and a metallic chromium layer of 70 to 200 mg/m ² as the second layer. 8 in terms of chromium content
with a coating layer of ~60mg/ ^m2 of chromium hydrated oxide,
Moreover, since the surface roughness of the coated steel sheet was limited, the following effects could be achieved. (a) It has excellent hydrophilicity, water retention, and rust resistance, and has printing durability equivalent to that of aluminum lithographic plates. (b) The material price is cheaper than aluminum.

[Brief explanation of the drawing]

1 and 2 are enlarged diagrams showing examples of surface roughness profiles in the L direction and C direction, respectively, of the chromium-plated steel plate for planographic printing according to the present invention, and FIG.
4 are enlarged diagrams showing the surface roughness profiles in the L direction and the C direction, respectively, of sample material No. 7 used in the comparative test conducted by the present inventors.

Claims (1)

[Claims] 1 A metal chromium layer of 70 to 200 mg/m ² plated on the surface of a steel plate that has been roughened in advance, and a metal chromium layer coated on the metal chromium layer with a chromium content of 8 to 60 mg/m2.
mg/ ^m2 of chromium hydrated oxide layer, and the surface roughness of the coated steel sheet is at center line average roughness Ra.
A chromium-plated steel plate for lithographic printing, characterized in that the maximum height Rmax is 0.3 to 2.0 μm, and the maximum height Rmax is 1.5 to 10 μm, and the difference in Ra between the rolling direction and the direction perpendicular to the rolling is 0.15 μm or less.