JPS63236692A - Offset printing plate and its preparation - Google Patents

Abstract

PURPOSE:To enhance dimensional stability, printing durability, a bending characteristic and the mountability to a plate cylinder, by laminating a metal foil preliminarily coated with an adhesive to the back surface of an offset printing plate having paper or a plastic film as a support. CONSTITUTION:As a paper or plastic film support, water resistant paper, syn thetic paper and polyethylene double-coated paper are designated. As a metal plate, an aluminum plate is pref. and the thickness thereof is pref. 75-300mu in general. When a hot melt type adhesive containing no water or solvent is used as an adhesive, working efficiency is well since drying after adhesion is unnecessary and the rising of adhesive strength is fast and the formation of a printing plate is completed within a short time. As the resin used in the hot melt adhesive, ethyl cellulose, a vinyl acetate resin and synthetic rubber are designated and generally heated to 95-180 deg.C and melted before use in many cases but one having melting temp. as low as possible is pref. used. The coating thickness thereof is pref. 30-50mum in usual.

Description

Detailed Description of the Invention (A> Industrial Application Fields The present invention is applicable to paper or plastics, such as polyethylene, polycarbonate, polystyrene, polyvinyl chloride,
This invention relates to an offset printing plate in which a metal plate made of aluminum, iron, etc. is adhered to the back side of an offset printing plate using a laminate of paper and plastic as a support.

(B) Prior art and problems Conventionally, offset printing plates have been PS plates using aluminum foil as a support, paper, plastic, or laminates of paper and plastic (for example, polyethylene coated paper).
Offset printing plates using supports such as are often used.

Although the former is superior in terms of quality, it has the problem of high cost, and in order to reduce costs, the latter, which is cheaper, is used as an offset printing plate.

However, offset printing plates using paper, plastic, etc. as a support are inferior in dimensional stability and printing durability compared to PS plates, etc. using aluminum plates as a support, and are difficult to use for offset printing machines. Resistance to tension during installation, tension due to rotation during printing, and friction is weak, and the generally required dimensional stability accuracy of 0.3 rrvn may be exceeded.

In addition, when printing using a large offset rotary press, the printing plate is attached to the plate cylinder by inserting both ends of the printing plate into grooves formed in the width direction of the plate cylinder surface, and by tensioning the tension shaft at the bottom of the groove. By pulling it, it is fixed tightly against the surface of the plate cylinder. In this case, it is necessary to bend both ends of the printing plate in advance to about 30" to 90", but it is difficult to maintain this bending angle with printing plates that use paper, plastic film, etc. as a support. The printing plate may come off during printing.

In addition, the leading edge of the printing plate was often wavy, which sometimes caused problems when it was attached to the printing cylinder.

For this reason, offset printing plates that use paper, plastic, etc. as a support are mainly used in the field of small offset printing called light printing, and the cost is high for large offset printing machines or rotary offset printing machines that are half or full size or larger. Currently, the PS version is mainly used.

(C) Purpose of the Invention The present invention improves the dimensional stability, printing durability, bending characteristics, and ease of installation onto a plate cylinder of low-cost offset printing plates using paper, plastic, polyethylene coated paper, etc. as a support. The purpose of the present invention is to provide a low-cost offset printing plate that can replace the high-cost PS plate.

Another object of the present invention is to produce a printing plate for the above purpose at low cost.
It is an object of the present invention to provide a method for producing an offset printing plate that can be easily obtained.

Other objects of the invention will become apparent from the description below.

(D) Structure of the Invention The object of the present invention has been achieved by providing an offset printing plate in which gold TiM is laminated on the back side of an offset printing plate using paper or a plastic film as a support.

Another object of the invention was achieved by laminating a metal foil pre-applied with an adhesive to the back side of an offset printing plate having a paper or plastic film support.

Examples of the filter paper or plastic film support in the present invention include water-resistant paper, synthetic paper, polystyrene phthalate film, polystyrene film, triacetate film, polycarbonate film, polypropylene film, double-sided polyethylene terephthalate film, double-sided polyethylene coated paper, etc. but is not limited to these.

Typical metal plates used in the present invention include aluminum plates, iron plates, copper plates, etc., and aluminum plates are preferred in terms of cost, handling, etc. The thickness of these metal plates is appropriately selected depending on the thickness of the printing plate to be applied, the type of support, and the type of metal plates to be laminated, but a range of 75 to 300 μm is generally preferred.

In carrying out the present invention, an adhesive is used to bond the offset printing plate and the metal plate. The adhesive is not particularly limited, but a hot melt type adhesive that does not contain these solvents is preferable to a solvent type adhesive that contains water or a solvent. The reason for this is that solvent-based adhesives require drying after adhesion and take time to create a printing plate, resulting in poor work efficiency.In particular, adhesives containing organic solvents may cause deterioration or deformation of the printing plate depending on the type, and There is a problem in that when the printing plate is bent when it is installed in a printing press, cracks occur in the coating layer of the printing plate, and ink adheres to these cracks, causing stains on the printed matter. Moreover, organic solvents are not very preferable from the viewpoint of environmental hygiene.

On the other hand, hot-melt adhesives are 100% solids solvent-free adhesives that are mainly based on thermoplastic resins, and bond by heating and melting, and then by cooling and assimilating.
There is no need for drying after adhesion, and the adhesive strength increases quickly.
Work efficiency is high because printing plate creation can be completed in a short time.

Further, there is an advantage that the various problems mentioned above caused by organic solvents, namely, deterioration and deformation of the printing plate and cracking at the folded portion, do not occur.

Resins used in hot melt adhesives include ethyl cellulose, vinyl acetate resin, polyethylene, ethylene-vinyl acetate copolymer, butyl methacrylic resin, polystyrene, polyisobutylene, polypropylene, polyamide resin, polyester resin, petroleum resin, synthetic rubber, etc. These include, but are not limited to.

In hot melt adhesives, waxes, plasticizers, tackifiers, antioxidants, fillers, etc. are usually added to the resin as appropriate for well-known purposes.

Hot-melt adhesives are generally used after being heated and melted at 95 to 180°C, but if the temperature is too high, it will cause deterioration and deformation of the printing plate to be adhered to, so use one with a melting temperature as low as possible. It is preferable to use Particularly in the case of a printing plate using double-sided polyethylene-coated paper as a support, it is preferable to use a synthetic rubber-based hot-melt adhesive that melts at 95°C or lower, preferably 40 to 70°C.

When carrying out the present invention, an adhesive may be applied to the back side of the printing plate or the surface of the metal plate each time an offset printing plate and a metal plate are laminated together. It is preferable to prepare a large number of plates in order to make printing plates more efficient.

When hot-melt adhesive is applied, it does not have adhesive properties at room temperature, so the adhesive surface may be exposed; however, in the case of melt-in-type adhesive, the adhesive surface is viscous, so it cannot be coated with release paper. Better to protect it.

In practicing the present invention, it is preferred that the adhesive be applied as uniformly as possible. The coating thickness depends on the thickness of the printing plate and metal plate,
Although an appropriate thickness is selected depending on the total thickness of lamination, etc., a range of 30 to 50 μm is usually preferred.

In the present invention, when using a hot melt adhesive,
Direct roll method,
Extrusion method etc. are generally used.

In addition, as a method for laminating a metal plate coated with adhesive and a printing plate, after heating the metal plate or the printing plate, or both,
The adhesive surfaces may be pressed together using a pressure roller, or one or both of the pair of pressure rollers may be heated to perform heating and pressure at the same time.

(E) Examples Next, the present invention will be described in detail, but is not limited thereto.

Example 1 A hot-melt adhesive (manufactured by Sekisui Co., Ltd.) containing synthetic rubber as a main component was prepared in advance in a size of 800 InInX by the method described above.
The coating was applied to a thickness of approximately 30μ on one side of an aluminum plate measuring 1000m long and 150μ thick.

Next, the adhesive-coated side of the aluminum plate and the back side of a direct offset printing plate made by the silver complex diffusion transfer method and having the same size as the aluminum plate and using double-sided polyethylene coated paper as a support are combined to form the printing plate. The mixture was heated at 50'C, pressed with a rubber roller, and cooled to adhere to form a printing plate.

The obtained offset printing plates were bent at a bending angle of 30'' to 135°, which is necessary for mounting on an offset printing machine.

Even after being left for 1 hour, the initial angle remained unchanged.

In addition, while commercially available spray-type adhesives do not adhere completely and peel off from the bonded area, the hot-melt adhesive of the present invention did not peel off. At the same time, cracks occurred in the printing plate using a spray-type adhesive at the crease portion, but the hot-melt adhesive of the present invention did not cause cracks and was in good condition as an offset printing plate.

When this offset printing plate was installed on an offset rotary printing machine, there was no change in the angle of the bent part or waving of the tip, and it could be installed smoothly, and the clamp did not slip, making it easy to apply tension. did it.

In this state 18. ○ After printing 50,000 sheets at a printing speed of 0 sheets to 30,000 sheets/hour, there was little plate misalignment, plate misalignment, ink adhesion at the corners of the folded part, and printing started with little plate stretching. 17 good prints were produced that did not change over time.

The printing life of an offset printing plate using double-sided polyethylene coated paper as a support is usually about 5,000 to 10° OOO sheets, but according to the present invention, it has become possible to print more than 50,000 sheets.

Example 2 A hot melt adhesive mainly composed of ethylene-vinyl acetate copolymer was prepared in advance in a size of 800 m x 1 using the method described above.
00ONn, was coated to a thickness of about 50μ on one side of a 150μ thick aluminum plate.

Next, the adhesive-coated side of the aluminum plate and the back side of a direct offset printing plate made by the silver complex diffusion transfer method and having the same size as the aluminum plate and using a polyethylene terephthalate film as a support are overlapped, and the side of the aluminum plate is The adhesive was melted by heating, then pressed with a rubber roller and cooled to bond. Example 1 using this
When tested in the same manner as above, similar good results were obtained.

(F) Effects of the invention According to the invention, even if an offset printing plate uses paper or plastic film as a support, its rigidity and
The dimensional stability, bending characteristics, and ease of mounting on the plate cylinder were significantly improved, and it was possible to easily obtain an offset printing plate comparable to a PS plate at a low cost.

Claims (3)

[Claims] (1) An offset printing plate characterized by being made by laminating a metal plate to the back side of an offset printing plate using paper or plastic film as a support. (2) A method for making an offset printing plate, which comprises laminating a metal plate coated with an adhesive in advance on the back side of an offset printing plate using paper or plastic film as a support. (3) The method for making an offset printing plate according to claim 2, wherein the adhesive is of a hot melt type.