JPH10297129A - Support for lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a support for a lithographic printing plate, which develops no flake-like picture quality unevenness even when an alkali treatment is executed, is excellent in an external appearance and, at the same time, a printability. SOLUTION: This support is made of an aluminum alloy having aluminum purity of 99.5% or more containing Fe: 0.20-0.50%, Si: 0.05-0.15%, Cu: 0.005-0.04%, Ti: 0.005-0.03% and the rest of unavoidable impurities and has the average area of an aluminum crystalline particle after its final cold rolling or the straightening following with the cold rolling of 1.0×10<-3> -7.0×10<-3> mm<2> . The support is executed by a roughening treatment containing a chemical treatment with an alkali aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithographic printing plate support, and more particularly to a lithographic printing plate support excellent in appearance and printing performance after a surface roughening treatment.

[0002]

2. Description of the Related Art An aluminum plate (including an aluminum alloy plate) is used as an aluminum support for a printing plate, particularly as a support for an offset printing plate. In order to use this aluminum plate as a support for offset printing plates, it is necessary that the aluminum plate has appropriate adhesiveness and water retention to the photosensitive material. Generally, any one of chemical surface roughening and chemical surface roughening, or a combination thereof is appropriately subjected to a surface roughening treatment, and a grain is formed on the surface.

It has also been proposed to specify an aluminum plate from its microstructure so as to be suitable for the surface roughening treatment and to obtain a uniform and fine grain. For example, Japanese Patent Application Laid-Open No. 8-179496 discloses that the size of the macrostructure grains in the outermost surface layer in the direction perpendicular to the rolling direction is 50 to 200 μm.
And a lithographic printing plate support electrochemically roughened with an aqueous nitric acid solution. In addition, Japanese Unexamined Patent Publication
Japanese Patent No. 218495 discloses that the grain size of an aluminum plate after continuous casting is 2 to 2 in a cross section perpendicular to the casting progress direction.
A lithographic printing plate support having a thickness of 500 μm and a crystal grain size of an aluminum plate after final cold rolling or annealing of 2 to 100 μm in a cross section perpendicular to the direction of progress of casting and rolling is described. Further, Japanese Unexamined Patent Application Publication No.
No. 39 discloses a lithographic printing plate support in which the aluminum crystal grains having a microstructure in a direction perpendicular to the rolling direction of the continuous casting material are specified to be 150 μm or less, and the non-uniformity is improved by electrolytic surface roughening treatment. Have been described.

[0004]

In the above-described lithographic printing plate support, the size of aluminum crystal grains in the direction perpendicular to the rolling direction, that is, the width direction of the support (hereinafter, referred to as the crystal grain width). ), Which is particularly effective in eliminating streak-like unevenness called a streak extending in the rolling direction. However, an aluminum plate is usually etched with an aqueous alkali solution to remove sharp projections on the surface during a series of surface roughening treatments. Quality unevenness occurs and the appearance is greatly impaired. Conventionally, there is no effective solution for the occurrence of this surface quality unevenness,
Even if the width of the aluminum crystal grains is specified as described above, it cannot be solved, and this is a major problem in obtaining a lithographic printing plate support.

[0005] The present invention has been made in view of such a situation, in particular, it does not cause scaly surface unevenness even when subjected to an alkali treatment, and has excellent appearance.
An object of the present invention is to provide a lithographic printing plate support excellent in printing performance.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide an image forming apparatus comprising:
e: 0.20 to 0.50%, Si: 0.05 to 0.15
%, Cu: 0.005% to 0.04%, Ti: 0.00
Al purity 9 including 5 to 0.03% and the balance unavoidable impurities
9.5% or more of aluminum alloy, and the average area of aluminum crystal grains after final cold rolling or after straightening following the cold rolling is 1.0 × 10 ^{−3 to} 7.0 ×.
This is achieved by a lithographic printing plate support characterized in that the support has a surface roughness of 10 ⁻³ mm ² and a chemical treatment using an alkaline aqueous solution. In the lithographic printing plate support, the average length in the direction parallel to the rolling direction of the aluminum crystal grains after the final cold rolling or straightening is preferably 300 to 500 µm.

The present invention is based on the finding that there is a correlation between the occurrence of scaly surface quality unevenness and the area of aluminum crystal grains and the average length in a direction parallel to the rolling direction (hereinafter referred to as crystal grain length). It is based on this finding. That is, the average area of the aluminum crystal grains is 1.0 × 10 ⁻³ or more.
7.0 × 10 ⁻³ mm ² , and the crystal grain length is 300 to 5
The specific aluminum plate in the range of 00 μm is excellent in appearance without causing scale-like surface unevenness even when subjected to alkali treatment, and is an excellent support with no printing stains when used as a printing plate. In the present invention, the area of the aluminum crystal grains means that the surface of the aluminum plate is observed with a metal microscope (a microscope for observing using a polarizing filter),
The length of the line segment (y) parallel to the rolling direction and the length of the line segment (x) perpendicular to the rolling direction are measured, and the product of the two is divided by 2 to define a value (ie, x × y ÷ 2). . This is because most of the aluminum crystal grains have a long elliptical shape as their planar shape, and are approximated by a rhombus for simplicity.

The range of the average area of the aluminum crystal grains shown above is considerably smaller than that of a general aluminum crystal grain. Therefore, it is extremely difficult to achieve an average area of less than 1.0 × 10 ⁻³ , which is not practical. In addition, the crystal grains are too small and have poor mechanical strength to be used as a lithographic printing plate support. On the other hand, 7.
If it exceeds 0 × 10 ⁻³ mm ² , the crystal grains are too coarse, and scaly surface unevenness occurs. In addition, extremely elongated crystal grains are allowed, and streak-like unevenness is likely to occur. For the same reason, it is difficult to achieve a crystal grain length of less than 300 μm, and there is a problem in mechanical strength as a support. On the other hand, if there are many long crystal grains exceeding 500 μm, streak-like unevenness is likely to occur. The support for a lithographic printing plate of the present invention is obtained by subjecting an aluminum ingot to a soaking treatment and a hot rolling treatment, followed by an intermediate CAL annealing method, a HOT-CAL annealing method or a HOT-CAL annealing method described later.
It is obtained by homogenizing (recrystallizing) aluminum crystal grains by a non-annealing method.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the lithographic printing plate support of the present invention will be described in detail according to the manufacturing steps. The method for casting an aluminum plate as a support for a lithographic printing plate of the present invention is not particularly limited. For example, in addition to a method of injecting molten aluminum into a mold and cooling it to obtain an ingot,
A method of continuously casting and rolling from a molten aluminum using twin rolls or twin belts, that is, a so-called continuous casting method can be used. In particular, the continuous casting method is preferable in terms of production efficiency. The continuous casting method using twin rolls includes a hunter method and a 3C method. The continuous casting method using twin belts includes a continuous casting technique such as a Hazelley method using a metal belt and an Al Swiss Caster II using a caterpillar block. Has been put to practical use. The composition of the molten aluminum is F
e: 0.20 to 0.50%, Si: 0.05 to 0.15
%, Cu: 0.005% to 0.04%, Ti: 0.00
It contains 5 to 0.03% and the balance of inevitable impurities, and has an Al purity of 99.5% or more. Most aluminum ingots commercially available for lithographic printing plate supports fall within the range of this alloy composition. For example, JIS A1050 material can be used as the molten aluminum having the above composition. Further, in many cases, impurity structures are unevenly distributed on the surface layer of the obtained ingot, and it is preferable to cut the surface over a predetermined thickness using a facing machine.

In the aluminum plate thus obtained, the aluminum crystal grains do not fall within the scope of the present invention. Then, after removing the internal stress and homogenizing the structure by holding at 480 to 610 ° C., preferably 500 to 580 ° C. for about 6 to 12 hours in the soaking furnace, the following processing is performed to obtain aluminum. The crystal grains are recrystallized.

(1) Intermediate CAL annealing method This treatment method is a method in which an aluminum plate is subjected to the above soaking treatment and hot rolling, then to cold rolling, then to CAL annealing, and finally to cold rolling. Hot rolling is performed at a starting temperature of 400.
It is preferable to carry out at 540 ° C. At temperatures other than this,
The grain area and the grain length of the present invention cannot be obtained. That is, if the starting temperature is lower than 400 ° C., sufficient recrystallization is not performed in the final plate, resulting in non-uniform microstructure and 540
If the temperature is higher than ℃, crystal grains grow too much in the final plate. At temperatures other than the above-mentioned temperatures, it is difficult to obtain sufficient flatness in the final plate. By this hot rolling, the sheet is rolled to a thickness of, for example, about 5 to 40 mm. Thereafter, cold rolling is performed at room temperature. CAL
Annealing is performed at 400 to 500 ° C. at a rate of 10 ° C./sec or higher. Outside this temperature range, the crystal grain area and crystal grain length of the present invention cannot be obtained. And it rolls to predetermined thickness by final cold rolling. The temperature at this time is room temperature.

(2) HOT-CAL annealing method This processing method is a method of subjecting an aluminum plate to the above-mentioned soaking treatment, hot rolling, intermediate annealing, and final cold rolling. The starting conditions in each treatment are the same as in the above-mentioned intermediate CAL annealing method.

(3) HOT-non-annealing method This treatment method is a method in which an aluminum plate is hot-rolled after the above soaking treatment, and recrystallization is completed at this time.
Therefore, in the hot rolling, the end temperature needs to be higher than the recrystallization temperature of aluminum (300 ° C. or higher). Then, after hot rolling, final cold rolling is performed in the same manner as in other methods. According to this method, since the intermediate annealing can be omitted, the process is simplified, and the manufacturing cost can be reduced.

According to the above-mentioned processes, a lithographic printing plate support is rolled to a predetermined thickness and has an average area of 1.0 ×
It is possible to obtain an aluminum plate in which aluminum crystal grains having an average length in the rolling direction of 10 ^{-3 to} 7.0 × 10 ^-3 mm ² and a rolling direction of 300 to 500 μm are uniformly distributed. Further, it is preferable to improve the flatness of the aluminum plate by using a straightening roller.

The aluminum plate obtained as described above is thereafter subjected to a surface roughening treatment according to a conventional method to form a lithographic printing plate support. The surface roughening treatment is configured by appropriately combining mechanical surface roughening treatment, electrochemical surface roughening treatment, chemical surface roughening treatment and the like. In this roughening treatment, sharp and sharp projections may be formed on the roughened surface, which causes stains on the printing plate. Therefore, the projections are usually eliminated by using an alkaline aqueous solution, or the spire portion is made smooth, but in this case, scale-like surface quality unevenness often occurs. However, according to the present invention, the area and length of the aluminum crystal grains are specified, so that the scale-like unevenness of the surface quality does not occur unlike the related art. Hereinafter, one embodiment of the surface roughening process will be described.

Examples of the mechanical graining method include a ball grain, a wire grain, a brush grain, and a liquid honing method. As the electrochemical graining method, an AC electrolytic etching method is generally adopted, and a normal sine wave AC current or a special alternating current such as a rectangular wave is used as a current. As a pretreatment of the electrochemical surface roughening treatment, an etching treatment with caustic soda or the like may be performed. When electrochemical surface roughening is performed, the surface is preferably roughened by an alternating current with an aqueous solution mainly composed of hydrochloric acid or nitric acid. The details will be described below. First, the aluminum support is first alkali etched. Preferred alkaline agents are sodium hydroxide, potassium hydroxide, sodium metasilicate, sodium carbonate, sodium aluminate, sodium gluconate and the like. Concentration 0.01-20%, temperature 20-9
The temperature and time are preferably selected from the range of 5 sec to 5 min.
1 to 5 g / m ² . Particularly, in the case of a support having a large amount of impurities, the amount is preferably 0.01 to 1 g / m ² (Japanese Patent Laid-Open No. 1-2).
No. 37197). Subsequently, since a substance (smut) insoluble in alkali remains on the surface of the alkali-etched aluminum plate, desmutting may be performed as necessary.

The pre-processing is as described above.
AC electrolytic etching is performed in an electrolytic solution mainly containing hydrochloric acid or nitric acid. The frequency of the alternating current is 0.1 to
100 Hz, more preferably 0.1 to 1.0 or 10 to 10
60 Hz. The liquid concentration is 3 to 150 g / l,
More preferably, it is 5 to 50 g / l, and the amount of aluminum dissolved in the bath is suitably 50 g / l or less, more preferably 2 to 20 g / l. Additives may be added if necessary, but in the case of mass production, it becomes difficult to control the liquid concentration. The current density is 5 to 100 A / dm.
² is suitable, but 10 to 80 A / dm ² is more preferable. In addition, the power supply waveform is appropriately selected depending on the quality required and the components of the aluminum support used,
It is more preferable to use the special alternating waveforms described in JP-B-56-19280 and JP-B-55-19191. Such waveform and liquid conditions are appropriately selected depending on the quality required together with the quantity of electricity and the components of the aluminum support used. The electrolytically roughened aluminum is then immersed in an alkaline solution as part of the smut treatment to dissolve the smut. As the alkaline agent, there are various kinds such as caustic soda, and the pH is 10 or more, and the temperature is 25 to 60 ° C.
It is preferable to carry out in a very short time of 10 to 10 sec. Next, it is immersed in a liquid mainly composed of sulfuric acid. As the sulfuric acid solution conditions, the concentration was 50 to 400 g / l, and the temperature was 25 to
65 ° C. is preferred. When the concentration of sulfuric acid is 400 g / l or more, or the temperature is 65 ° C. or more, corrosion of the treated layer and the like increases, and in the case of an aluminum alloy containing manganese of 0.3% or more, sand which is electrochemically roughened is used. My eyes collapse. The dissolution amount of the aluminum base is 0.2 g / m
^{If two} or more etchings are performed, the printing durability will decrease. Therefore, it is preferable that the etching resistance be 0.2 g / m ² or less. The anodic oxide coating has a thickness of 0.1 to 10 g / m ² , more preferably 0.1 to 10 g / m ² .
It is preferable to form ³ to 5 g / m ² on the surface. The anodizing treatment conditions vary depending on the electrolytic solution used, and thus are not generally determined. However, in general, the concentration of the electrolytic solution is 1 to 80% by weight, the liquid temperature is 5 to 70 ° C, and the current density is 0.5 ~
60A / cm ² , voltage 1-100V, electrolysis time 1 second-5
A range of minutes is appropriate.

The grained aluminum plate having an anodic oxide film obtained in this manner is stable and excellent in hydrophilicity. Therefore, a photosensitive coating film can be immediately provided on the aluminum plate. Can further apply a surface treatment. For example, a silicate layer of an alkali metal silicate or an undercoat layer of a hydrophilic polymer compound can be provided. The coating amount of the undercoat layer is preferably from 5 to 150 mg / m ² . A lithographic printing plate can be obtained by using the aluminum plate obtained by the above treatment as a support and providing a photosensitive coating film on the surface thereof.

[0019]

【Example】

(Examples 1 to 4, Comparative Examples 1 to 5) A molten aluminum melt of a JIS A1050 material ingot is cast by a semi-continuous casting method. Obtained ingot (400-600m thick)
m, width 1000-2000mm, length 2000-600
0 mm) with a facing machine to cut 3 to 10 mm.
Then, the aluminum plate was subjected to soaking and hot rolling at different processing temperatures and times, respectively, and recrystallization of aluminum crystal grains was performed together with the rolling. Then
Final cold rolling and straightening were performed. The surface of the aluminum plate thus obtained was observed using a metallographic microscope, and the size (width) of the crystal grains in the direction perpendicular to the rolling direction and the size (length) in the direction parallel to the rolling direction were measured. The average area and average crystal grain length were measured. The area is a value approximated as (width × length / 2). After the surface of the aluminum plate is mechanically and electrochemically roughened, the aluminum plate is etched with an aqueous solution of caustic soda (solution temperature 60 ° C.) so that the amount of aluminum dissolved is 5.0 g / m ^2, and then an aqueous solution of sulfuric acid Was used to form an anodic oxide film at a coating amount of 2.0 g / m ² . For comparison, in Comparative Examples 4 and 5, no etching was performed. The surface of the aluminum plate on which the anodic oxide film was formed was visually observed to evaluate its appearance. The evaluation criterion was “○” when no unevenness was observed, “△” when partially unevenness was observed, and “×” when unevenness was observed over the entire surface.
And those below “△” are not suitable as printing plates. Table 1 shows the evaluation results of the average area, average length, and appearance of the aluminum crystal grains.

[0020]

[Table 1]

Furthermore, a photosensitive lithographic printing plate was prepared by applying a photosensitive solution using the aluminum plate on which the anodic oxide film was formed as a support for a lithographic printing plate, and a printing test was performed. In the printing test, the stain property of the non-image area was evaluated. The evaluation criterion is as follows: “○” indicates that the non-image portion has a small amount of dirt, “△” indicates that the non-image portion is poor, and “×” indicates that the inferior portion is inferior. Table 1 also shows the evaluation results.

As is clear from Table 1, the aluminum plate of the embodiment in which the average area and the average length of the aluminum crystal grains are within the range of the present invention has a streak-like unevenness and a scale-like shape even after being treated with an alkaline aqueous solution. It can be seen that the surface quality unevenness does not occur, and that the lithographic printing plate using this as a support has excellent printing performance. It was also confirmed that even if the average area and average length of the aluminum crystal grains were within the range of the present invention, the printing performance was poor when the treatment with the aqueous alkali solution was not performed.

As described above, the support for a lithographic printing plate of the present invention does not have scaly surface unevenness on its surface even when subjected to an alkali treatment, has excellent appearance, and has excellent printing performance, especially resistance. Excellent stain resistance.

Claims (2)

[Claims] 1. Fe: 0.20 to 0.50%, Si:
0.05 to 0.15%, Cu: 0.005% to 0.04
%, Ti: an aluminum alloy having an Al purity of 99.5% or more containing 0.005 to 0.03% and the balance of inevitable impurities, and after final cold rolling or after straightening following the cold rolling. The average area of the grains is 1.0
× 10 ^-3 to 7.0 a × 10 ^-3 mm ^2, and a lithographic printing plate support, characterized in that the roughening treatment include chemical treatment using an alkaline aqueous solution is performed. 2. The lithographic plate according to claim 1, wherein an average length in a direction parallel to a rolling direction of the aluminum crystal grains after the final cold rolling or straightening is 300 to 500 μm. Support for printing plate.