JPH05376Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) This invention is a printing blanket used in an offset printing machine, and is particularly designed to have shock absorbing properties or
Concerning printing blankets with excellent halftone dot reproducibility and ink collapse.

(Prior Art) Generally, the printing surface of a printing blanket is formed to have a certain roughness in order to improve the adhesion of ink. Also, printing blankets with compressible layers are used in high speed offset printing machines.

Conventionally, methods for forming a rough printing surface on a printing blanket include a method of using talc and a method of polishing or grinding. The method of using talc is to apply talc to the surface rubber layer and vulcanize it, then
Excess talc is removed to form a predetermined rough surface. On the other hand, the polishing or grinding method involves polishing the surface rubber layer with a sandpaper grinder to make the surface rough after vulcanization.

Further, one of the reasons for providing the compressible layer is to reduce and absorb the impact when two or more sheets of printing paper are accidentally inserted during a printing operation, and to prevent damage to the blanket.

Furthermore, another reason for providing the compressible layer is to prevent the peripheral length of the blanket from changing due to bulge phenomenon even under pressure during operation.

In other words, in offset printing, the printing plate is transferred to the blanket and then printed on the paper, so the peripheral speeds of the plate cylinder of the printing plate, the blanket cylinder of the blanket, and the impression cylinder that passes the printing paper are the same. must be maintained. If the circumferential speeds do not match, the image will shift, and this shift will become larger as the speed of the printing machine increases. By providing a compressible layer, discrepancies in peripheral speed due to the so-called bulge phenomenon are prevented, and "blurring" of the printed image is prevented.

(Problems to be Solved by the Invention) However, the above-mentioned conventional printing blankets had the following problems.

First, the method for forming the printing surface had the following problems. That is, in the method using talc, it is difficult to completely remove the talc after vulcanization. Therefore, the talc remaining on the printing surface inhibits ink transfer, and a considerable number of sheets must be printed before the printing quality becomes stable. Furthermore, it was difficult to apply talc uniformly, and a uniform printing surface could not be obtained. On the other hand, when polishing is used, the polishing process is increased, which not only increases the cost, but also causes problems such as clogging of the abrasive material.

Furthermore, in a structure with a compressible layer, the compressible layer is provided with a reinforcing layer between it and the surface rubber layer, which is the printing surface, so it takes time for the impact from above to be transmitted. There is a time gap between when the compressible layer is deformed and when the printed surface receives an impact. This causes structural distortions in the printing blanket itself. Therefore, it becomes impossible to reproduce accurate images for a long time.

This invention was made in view of the current situation, and the object thereof is to provide a printing blanket particularly excellent in halftone dot reproducibility and shock absorption.

(Means for Solving the Problems) In order to achieve the above object, the configuration of this invention is to provide a printing blanket consisting of at least one reinforcing layer and a surface rubber layer that will be the printing surface, and to make the surface rubber layer oil-resistant. It has a structure in which a fine porous rubber layer is provided on the top surface of the rubber layer.

(Example) This invention will be explained below based on the drawings.

FIG. 1 is a sectional view of a compressible printing blanket according to this invention, and the compressible printing blanket 10 is made by laminating three layers of woven fabric 11 made of non-stretchable fibers to form a reinforcing layer 12. A compressible layer 13 is provided on this reinforcing layer 12, and two layers of woven fabric 11a are laminated on the upper surface of this compressible layer 13 to form a reinforcing layer 14.Finally, a fine porous layer is formed on the upper surface of the oil-resistant rubber layer 15. A surface rubber layer 17 is provided by laminating rubber layers 16.

Woven fabrics 11 and 1 forming reinforcing layers 12 and 14
1a can be made of cotton cloth, rayon cloth, polyester cloth, etc. as in the past, and may also be a nonwoven cloth. The woven fabrics 11 and 11a may be laminated by applying rubber paste as an adhesive with a spreader, or separately molded rubber sheets may be laminated using an adhesive.

Compressible layer 13 can be manufactured by a known method. That is, a foaming method is used in which a foaming agent is blended into the rubber composition and foamed by heating during rubber vulcanization, or a powder (e.g., salt) that dissolves in the eluent is added to the rubber composition and rubber vulcanization is performed. The so-called salt leaching method, in which the powder is then eluted to form bubbles,
Alternatively, any method such as a hollow microsphere mixing method in which hollow microspheres are mixed into a rubber composition to form independent cells may be used.

The oil-resistant rubber layer constituting the surface rubber layer 17 is formed of oil-resistant rubber, such as chloroprene rubber, nitrile rubber, polyurethane, acrylic rubber, or the like.

Further, the porous rubber layer 16 can be formed by the same method as the compressible layer 13. When using the salt leaching method, a water-soluble crystalline substance (powder) with an average particle size of 1 μm to 50 μm, such as sodium chloride, sodium bicarbonate, sugar, etc., is added to the oil-resistant rubber formulation. For 100 parts by weight of rubber compound,
Mix 20 parts by weight to 200 parts by weight. The mixing amount, particle size, etc. of the crystalline substance (powder) dissolved in water may be determined depending on the thickness of the compressible layer, usage conditions, etc.

The structure of the porous rubber layer 16 may be polished after vulcanization and eluted after polishing, or may be eluted without polishing. A smooth surface can be obtained by pressing paper, film, etc. onto the surface during vulcanization. At this time, mineral powder may be used to prevent paper, film, etc. from adhering.

Furthermore, as shown in Figure 2, the final surface shape is the state in which the crystalline substance (powder) is eluted, so the surface properties depend on the particle shape of the blended crystalline substance (powder). , stable surface properties can be obtained.

Further, the fine porous rubber layer 16 can also be formed by other known methods.

In the above embodiment, a compressible printing blanket has been described, but it goes without saying that a non-compressible printing blanket may also be used.

(Effects of the invention) As explained above, according to the structure of this invention, the reproducibility of halftone dots is excellent because so-called beards do not occur when polishing with a grinder.
It is also excellent for one-color solid printing.

In addition, since small impacts can be absorbed instantly, the printing blanket itself is unlikely to suffer structural distortion, making it possible to reproduce accurate images for a long time.

Furthermore, even if the surface rubber layer is thick, it has appropriate compressibility, so a printing blanket with excellent halftone dot reproducibility can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a compressible printing blanket according to this invention, and FIG. 2 is a partially enlarged sectional view. 10 is a compressible printing blanket, 11, 11
a is a woven fabric, 12 is a reinforcing layer, 13 is a compressible layer, 14
15 is a reinforcing layer, 15 is an oil-resistant rubber layer, 16 is a fine porous rubber layer, and 17 is a surface rubber layer.

Claims (1)

[Scope of utility model registration request] A printing blanket comprising at least one reinforcing layer and a surface rubber layer serving as a printing surface, characterized in that the surface rubber layer is formed by providing a fine porous rubber layer on top of the oil-resistant rubber layer. Printable blanket.