JPH0467520B2 - - Google Patents

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to an improvement of an exit nip roll (hereinafter simply referred to as an exit roll) in a device for hydrophilizing an offset master. <Prior Art> An offset master used as a plate in offset printing is a paper-like material with a photosensitive surface formed on a support, such as zinc oxide paper. An image is usually formed on this offset master using a plate making machine. That is, after the offset master is charged, the image of the original is projected on it.
A latent image is formed. The image is then developed with a developer containing a lipophilic substance such as vinyl acetate, followed by fixing and drying. Next, this offset master is brought into contact with a hydrophilic treatment liquid whose main components are yellow blood salt and phosphate to make the non-image areas of the photosensitive surface hydrophilic. Thereafter, it is pulled out between a pair of outlet rolls, and at this time, excess hydrophilic treatment liquid is squeezed out, and an appropriate amount of hydrophilic treatment liquid is applied. <Problems to be Solved by the Invention> It is important that the hydrophilic treatment liquid applied to the photosensitive surface of the offset master be applied in an appropriate amount and uniformly.
That is, if it is applied in excess, the number of prints that can be printed will decrease during printing (hereinafter referred to as "poor printing durability"), and processing liquid will be wasted, resulting in increased costs. Furthermore, if too little is applied, the hydrophilic treatment will be insufficient and printing stains will occur in non-image areas. Conventional exit rolls are generally made of rubber, such as silicone or NBR, and the hardness and nip pressure are adjusted by changing the material. A certain amount of the hydrophilic treatment solution is applied not only to the photosensitive surface but also to the surface of the support and is wasted. As shown in Figure 2-b, a large amount of processing liquid was applied to both ends of the master, resulting in uneven coating. SUMMARY OF THE INVENTION In view of the above-mentioned prior art, it is an object of the present invention to provide an economical exit roll capable of uniformly applying a hydrophilic treatment liquid to the necessary minimum amount. <Means for Solving the Problems> The structure of the present invention that achieves the above object is to bring the developed offset master into contact with a hydrophilic treatment solution to make the non-image area on the photosensitive surface of the offset master hydrophilic. In a hydrophilic treatment device designed for use in dry cleaning, the surface of the exit roll that comes into contact with the photosensitive surface of the offset master is made of rubber, among a pair of exit rolls that squeeze out excess processing liquid by sandwiching the treated offset master between them. In addition, the surface of the exit roll that comes into contact with the support of the offset master is made of a water-absorbing material having appropriate elasticity. <Function> When the offset master is held between a pair of exit rolls and squeezes out excess processing liquid, the photosensitive surface of the offset master comes into contact with the exit roll whose surface is made of rubber, allowing an appropriate amount of hydrophilic processing liquid to be squeezed out. In contrast, since the support surface of the offset master comes into contact with the exit roll whose surface is made of a water-absorbing material, it is wiped off and hardly any hydrophilic treatment liquid is applied. Its consumption is reduced. In addition, the uneven coating that occurs when a large amount is applied to both ends of the master is almost eliminated, and the coating is applied evenly. Conventionally, the hydrophilic treatment liquid flows around through the triangular gap formed between the end face of the master in the nip part and the surface of the pair of rolls, creating uneven coating on both ends, but in the present invention, it comes into contact with the support surface. It is thought that this is because the appropriate elasticity of the rolls prevents the formation of this triangular gap. <Example> Hereinafter, an example of the present invention will be described in detail with reference to the drawings. An embodiment of the present invention is shown in FIGS. 1 to 3. As shown in FIG. 3, in this embodiment, a hydrophilic treatment device 1 is incorporated into a plate making machine. That is,
In the plate making machine, the offset master 2 wound into a roll is stored in the paper feed chamber 3, and is unrolled to an appropriate length and cut by the cutter 4, and the cut offset master 2 is transferred to the charger 5. After being directly charged by corona discharge, it is temporarily held on the exposure table 6. Then, by illuminating the original set on the original platen 7 with the lamp 8, the original image is reflected by the projection mirror 9, and projected onto the offset master 2 on the exposure plate 5 via a lens (not shown). Form a latent image. Furthermore, this offset master 2 is sent to a developing chamber 11 through a conveyance guide 10, developed there, and then fixed in a fixing device 12. Thereafter, as shown in FIG. 2, it is sandwiched between a pair of inlet rolls 13 and 14 and guided to the hydrophilic treatment apparatus 1, where it is immersed in a hydrophilic treatment liquid 15. As the hydrophilic treatment liquid 15, for example, a mixture of yellow blood salt and phosphate is used. The offset master 2 immersed in the hydrophilic treatment liquid 15 becomes hydrophilic in its non-image area, and is subsequently held between a pair of exit rolls 16 and 17 and pulled up. In the figure, the upper surface of the offset master 2 is a photosensitive surface and the lower surface is a support surface, so the upper exit roll 16 of the pair of exit rolls is made of rubber. On the other hand, the lower exit roll 7 is made by winding a band-shaped Ecsaine (trade name, manufactured by Toray Industries, Inc.) 19 spirally around the outer peripheral surface of a roll 18 made of metal or plastic, as shown in FIG. It is made up of adhesive. Like natural leather, Ecsaine 19 is a single layer of intertwined bundles of extremely fine fibers (0.01 to 0.09 duules), so it has appropriate elasticity and water absorption. Therefore, the offset master 2 is connected to the pair of exit rolls 1.
When the photosensitive surface is held between the rollers 6 and 17 and pulled up, the surface of the photosensitive surface comes into contact with the exit roll 16 made of rubber, so that an appropriate amount of hydrophilic processing liquid is applied. Since it comes into contact with the formed exit roll 17, it is wiped off by the Ecsaine 19 and hardly any hydrophilic processing liquid is applied. The optimal amount of the hydrophilic processing liquid applied to the photosensitive surface is 2 to 3 g/ ^m2 , but it depends on the rubber material of the exit roll 16, the rubber hardness,
1.0~5.0g/ ^m2 by changing the surface roughness
can be freely controlled within the range. Furthermore, since Ecsaine 19 has appropriate elasticity, uneven coating does not occur on the photosensitive surface. Also Ecsaine 19
The thickness of the roll was 0.8 to 1.5 mm, and the elongation direction of the Ecsaine was made to coincide with the longitudinal direction of the roll. Note that the lower part of the lower outlet roll 17 is immersed in the hydrophilic treatment liquid 15 because once the Ecsaine 19 dries, it becomes stiff due to the hydrophilic treatment liquid, which deteriorates its elasticity and water absorption. This is because it is not desirable. The offset master 2 thus pulled out by the exit rolls 16 and 17 is dried in a drying chamber 20 and then discharged onto a discharge tray 21, as shown in FIG. In the outlet roll of the hydrophilic treatment apparatus of this embodiment having the above configuration, the surface of the lower outlet roll 17 is formed of Ecsaine 19, so that the hydrophilic treatment liquid does not remain on the support surface of the offset master 2. Instead, it gets wiped off. Although Ecsaine 19 was used in this embodiment, the material is not limited to this, and any water-absorbing material having appropriate elasticity may be used. The reason why appropriate elasticity is required is to prevent uneven coating on both ends of the photosensitive surface of the offset master. Next, the results of testing the amount of coating on the photosensitive surface, the amount of coating on the support surface, and coating unevenness of the offset master will be explained with reference to Table 1. As shown in the same table, in Comparative Examples 1, 2, and 3, the roll material is rubber-based, so the coating amount on the support surface is 1.2 to 1.
It is relatively large at 2.5 g/m ² and the hydrophilic treatment liquid is wasted. In contrast, Examples 1, 2,
In Examples 3, 4, and 5, the material of the exit roll on the support surface side (B) is water-absorbing Ecsaine, so the amount of coating on the support surface is significantly small at 0.4 to 0.5 g/m ² . Furthermore,
In Comparative Example 3, the roll material had a high rubber hardness.
Because it is NBR, there was uneven application.

[Table] However, in Example 5, the roll material on the photosensitive surface side (B) was
Even though it is NBR, the support side (B) is Excelline with appropriate elasticity, so uneven coating does not occur. Here, ○, △,
× was determined based on the extent of thick coating on both sides of the offset master. Also, the offset master used was ELP-
Mark (manufactured by Fuji Photo Film Co., Ltd.), and the hydrophilic treatment liquid was ELP-E (manufactured by Fuji Photo Film Co., Ltd.). <Effects of the Invention> As described above in detail with respect to the embodiments, the exit roll of the hydrophilic treatment device of the present invention has a water-absorbing material having appropriate elasticity in contact with the support surface of the offset master. It is economical as it reduces the amount of chemical treatment liquid consumed.

[Brief explanation of the drawing]

Figures 1 to 3 relate to one embodiment of the present invention; Figure 1 is an explanatory diagram showing how an exit roll is manufactured by winding Exaine around a roll made of metal or plastic, and Figure 2-a is FIG. 2-b is an explanatory diagram showing coating unevenness at both ends, and FIG. 3 is a schematic structural diagram of a plate-making machine equipped with a hydrophilic treatment device. In the drawings, 1 is a hydrophilic treatment device, 2 is an offset master, 15 is a hydrophilic treatment liquid, 16 and 17 are outlet rolls, and 19 is an exaine.

Claims (1)

[Claims] 1. In a hydrophilic treatment device that makes the non-image area on the photosensitive surface of the offset master hydrophilic by bringing the developed offset master into contact with a hydrophilic treatment solution, the treated offset master is sandwiched between the two. Of a pair of exit nip rolls for squeezing out excess processing liquid, the surface of the exit nip roll that comes into contact with the photosensitive surface of the offset master is made of rubber, and the surface of the exit nip roll that comes into contact with the support of the offset master is made of a moderately flexible material. An outlet nip roll for a hydrophilic treatment device, characterized in that it is made of a water-absorbing material having: