JPS59142192A - Chromium-plated steel plate for planographic printing - Google Patents

Abstract

PURPOSE:To obtain a chromium-plated steel plate excellent in hydrophilic property, water retention and anti-rusting property and having durability in printing comparable to that of an aluminum planographic printing plate, by providing a metallic chromium layer and a hydrated chromium oxide layer on a surface of a steel plate roughened by an electrolytic treatment with the steel plate as an anode in an aqueous solution of sulfuric acid. CONSTITUTION:In an aqueous solution containing 30-300g/l of H2SO4 and not more than 300g/l of FeSO4 at a temperature of 20-100 deg.C, a steel plate is roughened by electrolytic washing by using the plate as an anode with a quantity of electricity of 200-2,000C/dm<2> so that the surface roughness after providing the metallic chromium layer and the hydrated chromium oxide layer thereon becomes an Ra value of 0.3-1.0mum and a PPI value at 0.5mum of 100-800. The quantity of metallic chromium is preferably 70-200mg/m<2>, and the quantity of chromium in the hydrated chromium oxide layer is preferably 8-60mg/m<2>.

Description

Detailed Description of the Invention The present invention has a lower layer of metallic chromium and an upper layer of chromium water-conserving oxide on the surface of a steel plate, and has excellent hydrophilicity, water retention, and rust resistance, and has a resistance equivalent to that of aluminum lithographic plates. This relates to a chrome-plated steel sheet that has printability.

The lithographic plate-making process consists of plate surface pretreatment → application of photosensitive liquid → baking → development → plate surface pretreatment, and for PS plates (plates that have been previously given photosensitivity), the plate surface is pretreated at the photosensitive material manufacturer, followed by photosensitive liquid application. Among these processes, plate surface pretreatment improves the adhesion of the photosensitive film, strengthens the printing durability of the image area of the plate, and improves water retention in the non-image area. It is a purpose. Lithographic printing is a printing method that takes advantage of the difference in hydrophilicity between printed areas and non-printed areas, and the materials used are galvanized steel plates or aluminum plates, but aluminum is more lipophilic than zinc. Since it has poor hydrophilicity and high hydrophilicity, sharp lines can be obtained, and the effect can be further improved by anodic oxidation treatment.

At present, aluminum is mainly used as a lithographic (PS plate) material. However, this is also due to recent resource saving,
Due to energy conservation and the rapid rise in prices of non-ferrous metals, there is an increasing demand for lower prices by guaranteeing surface quality equivalent to that of aluminum.

The present invention is intended to meet such demands, and uses a ROM-plated silver plate, which is cheaper than aluminum, as a printing plate material. As a printing plate material, there are no printing stains,
In order to obtain sharp lines, the non-print areas must have excellent hydrophilicity, and in order to maintain hydrophilicity, the dampening water supplied to the non-print areas must have excellent water retention. In addition, a material with excellent rust resistance is required, which does not rust due to dampening water during printing, and does not rust during storage before and after plate making, and before and after printing. On the other hand, if the chemotaxis between the photosensitive agent in the image area and the holding plate material is poor, printing durability will be reduced. In conventional chromium-plated steel sheets, the chromium hydrated oxide layer itself on the surface of the steel sheet is highly hydrophilic, but because it is extremely active, it is easily contaminated in the air. It becomes difficult to maintain IAIm.

Therefore, a hydrophilic treatment is required to remove surface contamination before plate making, and since water repellency remains after normal degreasing treatment, a treatment such as permiston polishing must be performed. However, such treatment scrapes off the chromate layer on the surface, reducing rust resistance.

Furthermore, since the surface of conventional chromium-plated steel sheets is smooth, they have poor adhesion to photosensitizers and water retention of dampening water, resulting in poor printing durability. On the other hand, aluminum printing plates have excellent hydrophilicity, water retention, and printing durability, but the material cost is high, and
Requires pre-plate-making treatment of anodizing treatment after surface roughening.

The present inventors have previously disclosed a chromium-plated steel plate for lithographic printing, which has a metallic chromium layer and a chromium water-conserving oxide layer on the surface of the steel plate, which has been roughened in advance.

The surface roughening treatment is carried out by nitric acid pickling or brush polishing, and it is possible to obtain a surface rough enough to be used as a chromium-plated steel plate for planographic printing. However, with nitric acid pickling, the pickling solution ages quickly, and with brush polishing, the brush wear is severe, making it difficult to control the roughness.

The present inventors conducted a detailed study on the surface roughening method,
A desired rough surface can be easily obtained by electrolytic pickling using a steel plate as an anode in an aqueous sulfuric acid solution, and a chromium metal layer and a chromium water-conserving oxide layer are formed on the steel plate thus obtained. It was discovered that plated steel plates have excellent quality as materials for planographic printing, and the present invention was completed.

Hereinafter, the chromium-plated steel plate for lithographic printing of the present invention will be explained in detail.

The chromium-plated steel sheet for lithographic printing of the present invention is obtained by forming a metallic chromium layer and a chromium water-conserving oxide layer on a steel sheet that has been subjected to surface roughening treatment, which will be described later.

The amount of metallic chromium is preferably 70 to 200 η/nl.

The amount of metallic chromium is 70■/W? If it is less than 200■/W, the rust resistance will be poor. Exceeding this is economically disadvantageous. Also, the amount of chromium in the coating of the chromium water conserving oxide layer applied on the metal chromium layer is 8 to 60/rl? is suitable. When the amount of chromium in the film is less than 8/I, it is hydrophilic;
Rust resistance is poor, and if it exceeds 60η/i, the surface color tone will be poor (
Therefore, correction during plate making becomes difficult.Ff6 becomes difficult.

Next, a method for roughening a steel plate will be described.

30-300' I/l H, 80, and 300 f
/ in an aqueous solution containing the following peso at a temperature of 20 to 100 °C, using the n plate as an anode at 200 to 2000 °C /
After the formation of a metallic chromium layer and a chromium hydrated oxide layer, the surface roughness was determined to be Ra O, 3-1.0 pm and PPI at 0.5 μm by a surface roughening method using electric WF pickling of dtl. It can be 100-800.

If Ra is less than 0.3 or PPI is less than 100, the hydrophilicity, water retention, and adhesion between the photosensitive agent and the support saw plate are insufficient, and the image area will flow during development, making plate making impossible. Or, even if plate making is possible, stains occur during printing, image areas tend to peel off, and printing durability is poor. Ra is 1.0
If the μm or PPI exceeds 800, the tone reproducibility of the printed matter relative to the original when used as a printing plate deteriorates, and printing unevenness tends to occur, making it impossible to print beautifully.

Next, a surface roughening method for obtaining the above-mentioned roughness will be described in detail.

The temperature of the pickling liquid may be lower than 20°C, but it is difficult to control the liquid temperature, and if the liquid temperature exceeds 100°C, the deterioration of the pickling tank will be significant. Temperature is 20-10
0°C range C (preferably.

The concentration of H,80 in the pickling solution is also important.

When the HzSOa concentration is lower than 30 t/l, the desired P
It is difficult to obtain PI, and if it exceeds 3001/l, smut will increase, rust resistance and printing durability will deteriorate, and moreover, rtI! The deterioration of the washing becomes significant.

Therefore, the concentration of σtan i, so in the pickling solution is 30-300
It is best to punch in the f/l range.

Since the steel plate is pickled in a Hf1SO* aqueous solution, iron naturally dissolves in the pickling solution as ions and F
e50. The concentration will increase. Fe So in the pickling solution,
If the amount of Fe increases too much, the ability to roughen the surface deteriorates, especially
50. It is not preferable for the concentration to exceed 300 f/l.

Therefore, it is necessary to suppress the FeSO4 (e% degree) in the pickling solution to 300 t/ or less.

In addition, the electrolytic pickling process must be carried out using the cast plate as the anode, and the desired roughness cannot be obtained even if the plate is electrolytically pickled using the plate as the cathode. This is because the iron base is forcibly melted by electrolysis using the cast plate as an anode. If the amount of electricity in electrolytic pickling is less than 200 C/dn/, the degree of roughening will be insufficient and the desired roughness cannot be obtained, and conversely, if the amount of electricity is more than 2000 C/dnl, the surface will be roughened. The degree of oxidation becomes excessive, and the amount of smut generated also increases. Therefore, the amount of electricity for S pickling is 200~
2000 C/dn? It is preferable that

In addition, for the purpose of suppressing the generation of smut or stabilizing pickling, the electrolytic pickling process can be operated more stably by adding an inhibitor containing mainly cationic or nonionic organic compounds to the pickling solution. become able to.

The present invention will be specifically described below with reference to Examples and Comparative Examples.

Alkaline electrolytic degreasing treatment of cold-rolled armor plate with plate thickness of 0.22-(
NaOH50t/l, 80℃, 5A/dm",
30 seconds), and then treated under the roughening treatment conditions shown in Table 1. After treatment, wash thoroughly with water, cro, 160f
/11Na*5IFs 5 f/l, HJO40,5
f/l.

In a chromium plating solution at 50°C, electrolysis is carried out for several seconds using a steel plate as a cathode at a current density of 30A/dm', and then chromium plating is carried out through a water washing tank.
rys 50 f/L, Na1SiF6 o, 5
f/t.

Electrolytic treatment was performed for several seconds at a current density of 15 A/di in an electrolytic chromic acid treatment solution containing H, 5 O, 40, 10 f/l at 40° C. to obtain a chromium-plated steel sheet. A photosensitive layer consisting of a diazo resin and a binder was formed on this flyplate to a thickness of 3 μm, and after imagewise exposure, the exposed portion was removed and developed with an aqueous alkaline solution, and rubberized with an aqueous gum arabic solution. The following various tests were conducted using the planographic plate thus obtained.

<Hydrophilicity> Evaluation was performed by conducting a water wetness test on the test piece before plate making. The evaluation method is as follows.

O...Water repellent area ratio 0% △... I Less than 10% evaluated. In the dampening water immersion test, half of the test piece was immersed in dampening water, and evaluation was made on the state of rust after being immersed for 2 days.

O...Rust rate 0% △...t Less than 10%×...l 10% or more <Printing life> Offset printing is performed using the obtained planographic material, and printing durability is up to 50,000 sheets. was evaluated. The evaluation method is as follows.

○... Beautiful printing △... There is some dirt on the printing surface, uneven printing ×...
Staining of the printed surface and peeling of the printed area (Measurement of surface roughness) The surface roughness was measured using a stylus type roughness meter in terms of RaO and PPI at 5 μm.

In all of Examples 1 to 5, the roughening treatment conditions were liquid m30~
100℃, 30-300 f/1(7)) I, So4 aqueous solution, using steel plate as anode, processing electricity amount 200-200
The surface is roughened by electrolytic pickling at 0 C/d-, followed by chromium plating conditions and electrolytic chromic acid treatment, resulting in a metallic chromium content of 70 to 200 η/nl and a chromium water-containing oxide! 8
~60119/rr? It is a chromium-plated steel plate adjusted to have a surface roughness of RaO, 3-1.0 pm, 0.
It satisfies the PPl of 100 to 800 at 5 pm. It was found that the thus obtained chromium-plated steel sheet has excellent rust resistance, as well as excellent hydrophilicity, water retention, and adhesion, and therefore has excellent printability.

In Comparative Example 1, sufficient PPI could not be obtained due to low H, SO, and 6 degrees in the pickling solution, resulting in poor printing durability.

Comparative Example 2 shows that H! in the pickling solution. 804 &%, a large amount of smut occurred, and the iiifg properties and printing durability were poor.

In Comparative Example 3, the surface roughness was too large due to the large amount of electricity used in the electric fffiWl washing, and the printing durability was poor.

In Comparative Example 4, the surface roughness was too small because the amount of electricity used in the electric pickling process was too small, and the printing durability was poor.

Comparative Examples 5 and 6 had poor rust resistance and poor printing durability due to insufficient amount of metallic chromium or hydrated chromium oxide.

Comparative Example 7 is a case where electrolytic pickling was performed using a steel plate as a cathode, and the surface roughness was too small, resulting in poor printing durability.

In Comparative Example 8, the temperature of the pickling solution was low, and the surface roughness, especially PP
Since I was small, printing durability was poor.

In Comparative Example 9, Fe50. The printing durability was poor due to the high concentration and sufficient surface roughness, especially low PPI.

Claims (1)

[Claims] 30-300 f/L of H, SO, and 300 f/L of Fe 80. in an aqueous solution of 20-100°C containing 200-2000'C/
A metallic chromium layer of 70 to 200197 m' is formed on the surface of the steel plate, which has been roughened by electrolytic treatment using an amount of electricity of dff/.
Furthermore, a chromium hydrated oxide layer with a chromium content of 8 to 60 μ/nl is formed thereon, and its surface roughness is Ra 0.3.
A chromium-plated steel sheet for lithographic printing, characterized in that the PPI at ~1.0 pm and 0.5 pvyh is 100 to 800.