JPS6215358B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a support for a lithographic printing plate having excellent strength. Conventionally, in planographic printing original plates, aluminum plates have been mainly used as supports for supporting image-receiving layers such as photoconductive layers, photosensitive layers, and heat-sensitive layers. Generally, aluminum plates with a thickness of 0.3 mm or more are used for strength reasons, but since the aluminum plates themselves are soft, deformation and uneven damage occur during plate making and printing, making it difficult to use repeatedly. The problem was that the ratio was extremely low and printing costs were high. For this reason, the present inventors conducted various studies on supports with excellent strength, and as a result, they devised the use of a hot-dip aluminum plated steel plate as the support, and succeeded in solving the above problem. The plating layer 1 of the molten aluminum plated steel sheet is
As shown in the cross section shown in FIG. 1, it is composed of an alloy layer 3 bonded to the steel plate 2 and an aluminum layer 4 located on the alloy layer, but the surface aluminum layer 4 has the same properties as aluminum, Its thickness is such that it can be subjected to treatments such as graining, and can be sufficiently used as a support. Moreover, since the plating layer 1 is supported by a steel plate, it exhibits excellent strength. However, the surface of the hot-dip aluminum plated steel sheet as it is plated has depressions and pinholes at the spangle grain boundaries, and it cannot normally be used as a support body in which minute defects are a problem. Therefore, in order to use a molten aluminum plated steel plate as a support, after plating it is cold rolled with a bright roll at a total reduction rate of 30 to 85%, and after rolling, the alloy layer in the plated layer is reduced by 0.2% on one side.
~5μ, and it was necessary to maintain the aluminum layer on one side to 7μ or more. However, although the pinholes were crimped even after rolling at the above-mentioned rolling reduction ratio, some spangle irregularities and grain boundary depressions remained, and the surface of the support still had some problems. The present invention aims to provide a method for manufacturing a support using a hot-dip aluminum plated steel plate, which completely eliminates such spangle irregularities and grain boundary depressions. The inventors of the present invention have repeatedly studied various ways to completely eliminate irregularities in spangles and depressions in grain boundaries, and have found that after plating, before cold rolling with bright rolls, cold rolling is performed with dull rolls. It has been found that by applying this method, it is possible to completely eliminate the concavities at the spangled grain boundaries. Conventionally, in the production of molten aluminum-plated steel sheets used as supports, cold rolling was performed using a bright roll after plating to eliminate concavities and pinholes at spangle grain boundaries. Since the frictional force with the surface is weak, pinholes in the plated layer can be crimped, but even if the reduction rate is increased, the friction coefficient is small, so dents that occur in the surface layer, such as spangled grain boundaries, can be crimped in the rolling direction. Therefore, the present inventors used dull rolls with a large friction coefficient as a method of increasing the frictional force between the surface of the plating layer and the roll surface. By strengthening the plastic flow on the surface, they succeeded in eliminating the depressions in the spangled grain boundaries. The present invention will be described in detail below. As is well known, there are two methods of manufacturing hot-dip aluminum-plated steel sheets: one is to manufacture a weather-resistant steel sheet by plating the steel sheet in a bath containing molten industrially pure aluminum, and the other is to manufacture a weather-resistant steel sheet by plating the steel sheet in a bath containing molten industrially pure aluminum. There are two methods for manufacturing heat-resistant and processable products by plating in a bath. Usually, when manufacturing with the former method, the alloy layer develops significantly and the workability of the plated layer is extremely poor. bad. For this reason, in the case of a support that requires bending when attached to a plate cylinder, the former method is inappropriate and the latter method is required. Therefore, the case of manufacturing according to the latter method will be explained below with reference to FIG. FIG. 2 is a schematic diagram of a Sendzimer type continuous molten aluminum plating apparatus, in which a cold rolled steel plate 2a, which is a plating original plate, is set on a payoff reel 5. An unannealed material is normally used as the cold-rolled steel sheet 2a, but an annealed material is used when an in-line annealing furnace is not provided, such as in a flux-type continuous hot-melting apparatus. The cold-rolled steel sheet 2a from the payoff reel 5 is annealed and pretreated (reduced) in a reduction furnace 6, then immersed in a molten aluminum bath 7 and vertically pulled up through a sink roll 8 to form molten aluminum. The thickness of the plating layer is adjusted by wiping with a pair of gas throttle nozzles 9 placed directly above the bath 7. In this case, the thickness of the plating layer on one side is as follows:
20-60μ, preferably 30-50μ. By the way, as the molten aluminum bath 7, in the case of the present invention, a bath containing 1 to 10% of Si is used. This is because when the Si content is less than 1%, the effect of suppressing the alloy layer due to Si is small, and the thickness of the alloy layer reaches 60 to 70% of the entire plating layer. This is because it becomes impossible to ensure the thickness (7 μm) of the aluminum layer required as a support after processing. In addition, when the alloy layer becomes thick like this, protrusions protruding from the surface side of the alloy layer appear on the surface due to the cold rolling process performed after plating, and when a photosensitive layer etc. is applied on top of the protrusions, defects such as pinholes may occur. It can also cause On the other hand, the greater the amount of Si added, the greater the effect of suppressing the alloy layer;
If it exceeds 10%, it approaches the eutectic point, causing various damage in terms of quality and work. For this reason, such high Si-containing baths have generally not been used in the past. After plating with the bath composition as described above, it is cooled and wound onto a tension reel 10 to form a molten aluminum plated steel sheet 11. As shown in Figure 3, the molten aluminum plated steel sheet obtained here has spangle grain boundary depressions 12 and pinholes 13 on the surface, and is suitable for planographic printing original plates that require a smooth, defect-free surface. It cannot be used immediately as a support. Therefore, in the present invention, in order to eliminate these drawbacks, cold rolling is performed. When performing this cold rolling, a dull roll is used in the initial stage, and then a bright roll is used thereafter. As mentioned above, the cold rolling process is divided into two stages, and although pinholes can be crimped using only bright rolls, it is not possible to eliminate the dents in the spangled grain boundaries, and both defects can be eliminated using only dull rolls. However, this is because you cannot get smooth skin with a mirror finish. The reason why such a smooth surface is required is that if the concavities of the spangled grain boundaries remain on the surface, uneven printing will occur, making it impossible to use it for high-grade lithographic printing. The purpose of this cold rolling process using dull rolls is to eliminate the dents in the grain boundaries of the spangles that exist on the surface, so it is sufficient to strengthen the plastic flow near the surface layer of the plated layer. Light rolling (about 2 to 10% reduction) of skin pass
It takes about + minutes to apply 2 passes. On the other hand, cold rolling using bright rolls compresses pinholes and smoothes the surface, so it is necessary to apply plastic deformation to the entire plated layer, and a minimum total rolling reduction of 30% or more is required. . However, if the total rolling reduction exceeds 85%, work hardening will be excessive, making bending work difficult when attaching it to the plate cylinder, so the upper limit should be 85% or less. Generally, the preferable total reduction rate in the cold rolling process in the present invention is 50 to 70%, including cases using dull rolls and bright rolls. The steel plate and the plating layer are usually rolled in proportion to each other by the above-mentioned cold rolling processes, but in the case of the present invention, after these cold rolling processes, the aluminum layer in the plating layer has a thickness of 7μ or more ( one side). The present invention will be explained below with reference to Examples. Example A cold-rolled steel plate with a thickness of 0.5 mm and a width of 914 mm was plated in a molten aluminum bath containing 8% Si, and the plating thickness on one side was adjusted to 43 μm. After plating, this steel plate is divided into two parts, one of which is cold-rolled with only a bright roll at a reduction rate of 60%, and the other is subjected to a skin pass with a dull roll at a reduction rate of 5% as an initial stage, and then brightened. Two types of supports each having a thickness of 0.2 mm were produced by cold rolling using rolls at a reduction rate of 55%. Here, the sample numbers of the supports obtained in the former and latter steps were designated as No. 1 and No. 1a, respectively. On the other hand, a cold-rolled steel plate with a thickness of 0.3 mm and a width of 914 mm was plated in a molten aluminum bath containing 9% Si, and the plating thickness on one side was adjusted to 31 μm. After plating, this steel plate is divided into two parts in the same manner as described above, and one part is cold-rolled with only a bright roll at a rolling reduction of 60%, and the other is subjected to a skin pass with a dull roll at a rolling reduction of 5% and a bright roll. Reduction rate of 45%
Two types of supports each having a thickness of 0.15 mm were manufactured by sequentially performing cold rolling. The sample numbers of these supports were designated as No. 2 (by the former process) and No. 2a (by the latter process), respectively. Among the obtained supports, in No. 1a and No. 2a, the depressions at the spangle grain boundaries were completely eliminated. In addition, regarding each of these supports, JIS, B,
When the surface roughness Hmax was measured using 0651, the results shown in Table 1 were obtained.

[Table] Table 2 also shows the thickness of the single-sided plated layer of each of the supports and its changes.

[Table] Next, check the presence or absence of pinholes in the aluminum layer.
Table 3 shows the results of investigation using the feroxyl test method specified in JIS-H-8672-1969. Five test pieces of 100 x 100 mm were prepared for each support, and the number of pinholes generated in each test piece was investigated.

[Table] In addition, each of the above-mentioned supports is grained and coated with a photocuring resin in accordance with conventional methods to produce master plates for lithographic printing. I did a printing test. As a result, each original plate was good, but images of No. 1a and No. 2a were slightly clearer than the others. As described above, according to the present invention, it is possible to obtain a plating layer of a support with a desired thickness structure, and also to completely eliminate concavities of spangle grain boundaries on the surface.
A lithographic printing original plate support with excellent strength that can be used for high-grade printing can be obtained.

[Brief explanation of the drawing]

Figure 1 is a sectional view of a molten aluminum coated steel sheet, Figure 2 is a schematic diagram of a continuous molten aluminum plating apparatus, and Figure 3 is a sectional view of a molten aluminum coated steel plate with pinholes and spangle grain boundary depressions. be. 1... Plated layer, 2... Steel plate, 2a... Cold rolled steel plate, 3... Alloy layer, 4... Aluminum layer,
5... Payoff reel, 6... Annealing, reduction furnace, 7
...molten aluminum bath, 8... sink roll,
9... Gas squeezing mezzle, 10... Tension reel, 11... Molten aluminum plated steel plate, 12
...Dents in spangled grain boundaries, 13...Pinholes.

Claims (1)

[Claims] 1 After pre-treating the cold rolled steel plate, Si is added to 1~
A molten aluminum plated steel plate is produced by plating in a molten aluminum bath containing 10%,
After that, the steel plate is cold-rolled using dull rolls, and then the processed steel plate is further cold-rolled using bright rolls at a total reduction rate of 30 to 85%, so that the aluminum layer in the plating layer is rolled on one side. A method for producing a support for a lithographic printing original plate, characterized in that the support is maintained at a thickness of 7μ or more.