JPS6059351A - Developing method of lithographic printing plate requiring no damping water - Google Patents

Abstract

PURPOSE:To improve easily and surely dot shape by developing a lithographic printing plate requiring no damping water by means of brush rolls which revolve oppositely from each other. CONSTITUTION:A developing soln. is sprayed from a pump 6 and a nozzle 7 to swell the silicone rubber layer of an original printing plate 1 or weakens the adhesion thereof. At least one of a brush roll which rubs the plate 1 in the same direction as the direction where said plate is conveyed and a brush roll which rubs the plate in the direction opposite thereto are required for brush rolls 8, 9. The 1st roll rubs preferably the plate in the same direction as the conveying direction. The functions of the rolls 8, 9 are divided to the function for removing roughly the silicone rubber layer in the dot part and the function for removing finally the rubber layer remaining slightly at the edges of the succeeding dots. Thus the 1st brush roll 8 removes roughly the rubber layer in the same direction and the next roll 9 is rotated slowly and oppositely to remove finally the rubber layer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for developing a lithographic printing plate that does not require dampening water, and more particularly to a lithographic printing plate that does not require dampening water and has a silicone rubber layer backed by a substrate as the uppermost layer. It relates to a method for developing printing plates.

Prior art As a lithographic printing plate that does not require dampening water and has a silicone rubber layer as the top layer backed by a substrate, for example, 9
Examples include those proposed in JP-A No. 044, JP-A-50-50102, and JP-A-55-59466. These lithographic printing original plates that do not require dampening water are developed after being subjected to image exposure processing by a known method.
When developing using an automatic developing machine, while the printing original plate is being conveyed on rolls, one to six brush rolls placed in contact with the surface of the printing original plate are used to perform printing at the contact area between the printing original plate and the brush rolls. Generally, a developing method is adopted in which the original printing plate is rotated so as to be rubbed in the same direction as the printing original plate, and the silicone rubber layer in the image area of the printing original plate is removed.

As described above, the reason why brush rolls are used for automatic development of lithographic printing plates that do not require dampening water is that the silicone rubber on the surface layer is generally insoluble, so in order to remove it, it is necessary to scrape it off with mechanical force. This is due to necessity, but also because it is a practical and efficient means to meet this objective. The reason why the brush roll is rotated in the same direction as the printing original plate so as to rub it is to prevent the tip of the printing original plate from flying up with the brush roll.

When such a developing method is adopted, the shape of the halftone dots to be developed depends on the direction of the brush roll.

This often results in the disadvantage that halftone dots of uniform shape cannot be obtained. In other words, while the silicone rubber layer is almost completely removed on the downstream side of the brush roll in the direction of the edges within the halftone dots, the silicone rubber layer tends to remain on the upstream side, especially at the edges of the halftone dots. As a result, serious defects occurred during printing, such as a decrease in tone reproducibility and deviations in nine tones.

For problems like this, use a 2-strong brush roll. Alternatively, an improvement method can be considered, such as increasing the number of brush rolls, but the former method has a strong risk of damaging the printing plate, and the latter method makes the automatic developing machine difficult to use.

Purpose of the Invention The purpose of the present invention is to overcome the drawbacks of the prior art as described above,
It is an object of the present invention to provide a new method for easily and reliably improving the halftone dot shape of a lithographic printing plate that does not require dampening water.

Structure and operation of the invention The present invention has the following structure to achieve the above object.

That is, when developing a lithographic printing plate that does not require dampening water and has a silicone rubber layer as the uppermost layer backed by a substrate by rubbing it with a brush roll, at least two brush rolls are used, and at least one of the This is a method for developing a lithographic printing plate that does not require dampening water, and is characterized in that development is performed by rotating a book brush roll in the opposite direction to other brush rolls.

Furthermore, the operation of configuration 9 of the present invention will be explained in detail.

The substrate of the printing plate in the present invention has a thickness of 10μ to
2nun, preferably 50μ to 500μ paper.

Plastic films or sheets, elastic sheets such as combs, metal plates such as aluminum, laminated composite materials such as paper and plastic film, metal plates and comb sheets, and plating on these.

Surface treatments such as coatings are used.

The thickness of the silicone comb layer in the present invention is 0.
．． 1-50μ, preferably 0.5-10μ.

A known room temperature curing type or low temperature curing type silicone rubber is suitable. These silicone rubbers are mainly composed of linear organic polysiloxanes, and generally have crosslinking agents, catalysts, and the like added thereto. Further, the silicone rubber layer in the present invention may be photosensitive.

These can be obtained by chemically reacting or mixing an organic polysiloxane compound and a known photosensitive compound.

The brush roll of the present invention is generally one in which a brush material such as a plastic material or animal hair with a diameter of 20 to 500 μm is embedded radially into a core made of plastic or metal.

The above-mentioned brush material may be embedded in a base material such as a plastic sheet or cloth and wrapped around a core, or furthermore, the above-mentioned brush material may be embedded in a plastic or metal channel member in rows and attached to the core. It can also be something.

The developing method of the present invention comprising the above-mentioned components will be explained in detail based on the drawings.

FIG. 1 is a schematic diagram showing an example of an automatic developing machine using the developing method according to the present invention. In FIG. 1, a printing original plate 1 which has been subjected to an image exposure process is inserted into a developing machine main body O from a 9-plate loading table 2, and is discharged onto a printing plate 4 after undergoing a development process. Inside the developing machine, the printing original plate is conveyed at a constant speed by rolls 5.

During this process, the developer sent by the pump 6 is sprayed through the spray nozzle 7. The developer swells the silicone rubber layer. Alternatively, the silicone rubber layer in the image area can be easily removed by weakening the adhesion between the silicone rubber layer in the image area and the underlying layer, and at the same time, the removed silicone rubber pieces are washed off onto the original printing plate. Generally, it has a function. Next, the printing original plate is rubbed by brush rolls 8 and 9 placed in contact with it to remove the silicone rubber layer in the image area, but the printing original plate is placed opposite the brush roll so that the printing original plate does not escape even from the brush rolls. It is desirable to provide a support mechanism 10 of.

As an automatic developing machine, it not only has the above basic mechanism.

There may be a pre-processing section, a post-processing section, a drying section, etc., and the brush rolls may also be distributed in the developing section and the post-processing section.

As shown in the rotating direction of the brush rolls 8 and 9 in FIG. 1, the brush roll in the present invention has at least one roller that rubs the printing original plate 1 in the same direction as the conveying direction, and one that rubs the printing original plate 1 in the opposite direction. At least one brush roll is required, but it is preferable that the first brush roll be rotated so as to rub it in the same direction as the conveyance direction of the printing original plate, and the second or subsequent brush rolls be rotated so as to rub it in the opposite direction. . This is because the function of the brush roll is divided into the function of roughly removing the silicone rubber layer at the halftone dot area and the function of finishing and removing the silicone rubber layer slightly remaining at the edge of the 9th halftone dot. It is better to use a brush roll made of strong brush material and rotate it quickly.

If this is rotated so as to rub in the direction opposite to the direction in which the printing original plate travels, there is a risk that the leading edge of the printing original plate will fly up. On the other hand, the latter function can be achieved by gently rotating a brush roll made of a soft brush material.
The above-mentioned danger can be reduced to the extent that there is no problem in practical use. The first brush roll is made of, for example, a single yarn of nylon 6O10 with a diameter of 200 to 400μ and a pile length of 10 to 400μ.
A brush roll with an outer diameter of 100 to 150 m is implanted in the nozzle of No. 15, and the silicone rubber layer is roughly removed by rotating it at 200 to 500 revolutions per minute in the same direction as the direction in which the original printing plate moves. Brush to remove the silicone rubber layer left on the point edges.

For example, a single thread of nylon 6/10 with a diameter of 50 to 200 μm is implanted into a pile length of 15 to 60 plates with an outer diameter of 50 to 100 mm.
It is conceivable to use a brush roll and rotate it at 50 to 200 revolutions per minute so as to rub it in the direction opposite to the direction in which the printing original plate travels. The specifications of the brush roll are determined based on the ease with which the silicone rubber layer is removed, the ease with which the silicone rubber layer is scratched, the stiffness of the original printing plate, etc., and are not limited to the above specifications.

Effects of the Invention Since the present invention has the above-mentioned configuration 9, it is possible to obtain uniform halftone dots without directionality in the development of a lithographic plate that does not require dampening water, and as a result, it is possible to maintain a stable ink density during printing. This makes it possible to obtain high-quality printed matter with excellent tone reproducibility.

Example 1 An aluminum plate with a thickness of 0.24 mm was used as the base, and a photosensitive layer with a thickness of 5 μm containing a urethane-based polymer and a photopolymerizable monomer as a main component and a sensitizer, a dye, etc., and a crosslinked film with a polydimethylsiloxane as a main component. A silicone rubber layer with a thickness of 3 μm containing additives and catalysts was coated, and a polyester film with a thickness of 10 μm was further laminated to form a positive waterless lithographic printing plate, and a halftone exposure process was performed using a known method to form a polyester film. After peeling off, development was carried out using an automatic developing machine having two brush rolls. The developer used was one whose main component was an aliphatic saturated hydrocarbon petroleum solvent, to which dyes, surfactants, etc. were added.

Brush roll is made of nylon 6/10, single thread diameter 200μ9
A first brush roll having a bristly length of 15 mm and an outer diameter of 130+ nm was rotated at 300 revolutions per minute so as to rub in the same direction as the traveling direction of the printing original plate. The second brush roll was made of nylon 6-10, single yarn diameter 160 μ, bristles length 26 m [I+, outer diameter 80 I, and rotated at 180 revolutions per minute in the direction opposite to the direction in which the printing original plate travels. .

As a result, as shown in FIG. 2, it was possible to obtain homogeneous halftone dots 11 in which the silicone rubber layer at the edges was also removed, and it was also possible to obtain high-quality printed matter during printing.

Comparative Example The same lithographic printing original plate that does not require dampening water as in Example 1 was exposed to light in the same manner as in Example 1, and developed using the same developer and the same automatic developing machine. Brush rolls of the same shape were used at the same rotation speed.

Both plates were rotated in the same direction as the direction in which the original printing plate was traveling so as to rub it.

As a result, as shown in FIG. 6, only halftone dots 12 were obtained in which the silicone comb layer remained on the upstream edge in the scouring direction by the brush roll. Even in printing, it was not possible to obtain high-quality printed matter, and in addition, when the dust that had adhered to the printing plate during printing was rubbed off with a cloth, the silicone rubber layer that remained on the edges of the halftone dots in that area was also removed. They were removed at the same time, and subsequent printing resulted in only prints with different tones in that area.

Example 2 The same lithographic printing original plate that does not require dampening water as in Example 1 was exposed to light in the same manner as in Example 1.

Development was carried out using an automatic developing machine that consisted of three parts, a developing section and a post-processing section, and had one brush roll each for the developing section and the post-processing section. That is, propylene glycol was sprayed on the printing original plate, and then water was sprayed on the printing original plate in the pretreatment section 2, and the same brush roll as the first brush roll in Example 1 was used to spray the printing original plate every time in the same direction as the traveling direction of the printing original plate. The developing section rubs this at 300 revolutions per minute, and finally, while spraying an aqueous solution of dye and surfactant on the printing original plate, use the same brush roll as the first brush roll in Example-1 to perform EI]ti
An automatic developing machine was used, which consisted of a post-processing process in which the original plate was rubbed at 180 revolutions per minute in the opposite direction to the direction in which the original plate was traveling.

As a result, it was possible to obtain homogeneous halftone dots in which the silicone rubber layer at the edges was also removed, and it was also possible to obtain high-quality printed matter during printing.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an automatic developing machine according to the present invention. FIG. 2 shows an example of the shape of halftone dots obtained by the developing method of the present invention, and FIG. 6 shows an example of the shape of halftone dots obtained by the conventional method. 1: Original printing plate 2: Printer stand 6: Developing machine body 4: Plate loading 5: Roll 6: Pump 7: Spray nozzle 819: Brush roll 10: Support mechanism 11, 12: Halftone patent applicant Toshi Co., Ltd.

Claims (1)

[Claims] At least two brush rolls are used, and at least one of the brush rolls is A method for developing a lithographic printing plate that does not require dampening water, characterized in that development is performed by rotating a roll in the opposite direction to other brush rolls.