JPH0314629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ink supply method in waterless planographic printing, and in particular, it is possible to ease the necessary characteristic conditions of the ink used and to obtain printed matter of stable quality. This invention relates to an ink supply method.

In recent years, in planographic printing, dry planographic printing that does not require dampening water has been attempted, and various waterless planographic printing plates and ink compositions for these printing plates have been proposed.

In this way, waterless planographic printing machines do not use dampening water on the plate surface, so the non-image areas of the plate surface are filled with materials that have poor affinity for ink, such as silicone resins, fluorine resins, and saturated hydrocarbons. The repercussions are made using resins and inks with a high internal cohesive force in order to obtain the necessary repercussion.

The specific problem in this case is that the ink has poor on-press stability, and solving this problem has been considered the most important point in the practical application of waterless lithographic printing.

In other words, the temperature of the printing plate surface varies by at least 10°C from the start of printing to the end of printing, and in some cases it changes by around 20°C. This causes problems such as paper peeling, poor drying, blocking, roll contamination, and set-off during winding. In addition, as printing progresses, the temperature of the plate surface rises, and under these high temperature conditions, the viscosity and tack value decrease, and reperency worsens, causing the non-image areas of the plate surface to be contaminated with ink, making printing difficult. There is. It was necessary to solve these problems.

Therefore, in the past, it was considered to partially change the ink composition, but this was not enough to make a sufficient improvement, and at best, the ink type could be changed to high-temperature, medium-temperature, etc.
In reality, the only countermeasures available were to separate one for low-temperature use and use the other at appropriate times according to changes in plate surface temperature.

The present invention was made to solve these problems and inconveniences, and as a result of thorough study of the above problems, the fundamental cause was found in the method of supplying ink to the printing plate. In order to improve this problem, after ink is supplied to the entire plate surface, the ink adhering to the non-image areas of the plate surface with low ink affinity is removed using a jet jet of air, and only the image areas with high ink affinity are removed. A new method has been developed to supply ink to the ink.

According to the ink supply method of the present invention, the viscosity and tack value of the ink can be sufficiently reduced so that printability is not affected even by temperature changes on the plate surface. Since a significant increase in viscosity and tack value can be avoided, high quality, high stability and high speed printing is possible.

The present invention will be explained below with reference to embodiments shown in the drawings.

In the figure, the waterless lithographic printing press includes a plate cylinder 1 and an impression cylinder 3 that presses a printing medium 2 onto the top of the plate cylinder 1 to perform transfer.

Further, an ink roller 4 that uniformly supplies ink to the entire plate surface of the plate cylinder 1 is pressed into contact with the lower part of the plate cylinder 1, and the ink roller 4 is immersed in ink 6 in an ink pan 5.

Also, on the side of the plate cylinder 1, there is a jet nozzle 7 that injects air to remove unnecessary ink from the ink uniformly applied to the plate surface, and a scattering prevention device that guides the removed ink into the oil pan 5. A plate 8 is provided.

The plate surface of the plate cylinder 1 has an ink-friendly printing area 9.
and a non-image area 10 that exhibits sufficient repulsion to ink.The patterning of the image area is usually done in combination with a photosensitive material, and is not related to the development method; A plate prepared by development, solvent development, lift-off development, etc. can be used. In addition to metals such as copper and aluminum, any ink-compatible material mainly composed of a resin component can be used as the material for the image area.

To explain the method of supplying ink to the waterless printing press, the ink roller supplies ink 6 to the entire plate surface of the plate cylinder 1 while rotating as shown by the arrow. The supplied ink is selected to a high position as the plate cylinder 1 rotates, and when it reaches the position of the jet nozzle 7, it is sprayed with air. The ink adhering to the non-image area 10, which has low affinity with ink, is blown away and returns to the ink pan 5, and only the ink adhering to the image area 9 is conveyed to the impression cylinder 3 side. , is transferred onto the printing medium 2.

As described above, in the ink supply method of the present invention, the ink in the non-image areas of the printing plate is forcibly removed by air jetting, so that the viscosity and tack value of the ink are sufficiently reduced to the extent that changes in the temperature of the printing plate do not become a problem. This allows stable, high-quality printing to be performed at high speed.

Although the printing method of the printing press in the above embodiment was waterless direct printing, a blanket (not shown) may be provided between the plate cylinder 1 and the impression cylinder 3 to perform waterless offset printing.

In addition, as the ink that can be used, the above plate cylinder 1
It is necessary to select a solvent that has a low affinity for the material of the non-image area 10, and it is important to select an appropriate solvent. Specific examples of the solvent include polyethylene glycol, polypropylene glycol, and mixed polyalkylene glycols of ethylene and propylene with a monomer addition mole number of 2 to 20. Among those polymers, a part of the main chain has 4 carbon atoms.
Polyalkylene glycols containing the above diols as additional units. One or two of the two terminal hydroxyl groups of the above polyalkylene glycol
is substituted with any one of alkoxyl, alkyl phenoxyl, or carboxyl via an ether bond or an ester bond. In the case of two substitutions among these, it is not necessary that the substituents are of the same type. Other solvents include glycerin, 2,5-hexanediol, 2,4-heptanediol, 1,3-butylene glycol, and γ-valerolactone. The above solvents may be used alone, in combination of two or more, or in combination with solvents other than those listed above. It is preferable that the solubility in water is 30% by weight or more and the boiling point is 200° C. or more, and materials other than those mentioned above can also be used.

Furthermore, as the resin dissolved in the ink vehicle, any resin may be used as long as it exhibits appropriate viscosity and cohesive force, such as rosin-modified resin with an acid value of 100 or more, styrene-maleic acid resin, etc. etc. can be used. Furthermore, there are no particular restrictions on the pigment, and any pigment can be used as long as it can be used in a dispersed state that causes no practical problems.

On the other hand, as an ink supply method during printing, an example of supply using an ink roller has been described;
The present invention is not limited to this, and any method such as dipping or nozzle supply may be used as long as it can sufficiently supply excess ink to the entire plate surface.

In addition, in order to effectively blow off ink with a jet of air, it is recommended that the nozzle shape, blowing direction, gap between the nozzle tip and the printing plate, etc. be fully considered.

As explained above, according to the ink supply method of the present invention, without adjusting the viscosity of the ink,
It can enable high-quality, highly stable, and high-speed waterless planographic printing.

[Brief explanation of the drawing]

The figure is a schematic sectional view showing an embodiment of the ink supply method of the present invention. 1... Plate cylinder, 2... Printing material, 3... Impression cylinder, 4
... Ink roller, 5 ... Ink pan, 6 ... Ink, 7 ... Jet nozzle, 8 ... Scattering prevention plate, 9 ... Printing area, 10... Non-printing area.

Claims (1)

[Claims] 1. In an ink supply method in waterless planographic printing that uses a plate cylinder that forms an image on the plate surface based on differences in ink affinity, after ink is uniformly supplied to the plate surface of the plate cylinder, transfer from the plate cylinder is performed. 1. An ink supply method for waterless planographic printing, characterized in that, before printing is carried out, ink is removed from a portion of a plate surface of a plate cylinder with low ink affinity by a jet of gas.