JPS5852582B2 - Net gravure plate making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a net gravure plate making method that is highly reproducible in tone.

While offset and photo-letter printing reproduce the tone of the original by varying the size of the halftone dot area, in gravure the halftone dot area is most commonly square dots.

Each of these halftone dots has a different depth, so the amount of ink that enters each halftone dot is proportional to the depth of the halftone dot. It is done by shading.

This method is widely known as conventional gravure.

On the other hand, in gravure printing, there is a plate-making method that reproduces the tone by changing the size of the halftone dot area and the depth of the halftone dot for the purpose of preventing variations in printing tone or improving printing durability.

This method is called net gravure. A common plate-making method for halftone gravure is the so-called d'Argent civil method, which uses continuous tone positives and halftone positives.

According to this method, a halftone positive is printed on a sensitized carbon tissue, then a continuous tone positive is printed on the unexposed areas, the carbon tissue is transferred to a cylinder, and then developed and etched. Make a plate.

Although this method improves the stability of platemaking, it requires that the dimensions of the continuous tone positive and halftone positive be exactly the same, which complicates the work process and improves the technique. It also has drawbacks that make it difficult.

Furthermore, this method has the disadvantage that the light areas, especially the light areas with a halftone dot percentage of about 5 to 8% in halftone positives, are not expressed, giving the printed matter a rough feel and resulting in a loss of overall smoothness.

For this reason, complicated operations such as making halftone dots larger than usual are required when creating halftone positives.

The method of the present invention eliminates the various drawbacks of the conventional net gravure plate making methods as described above.

That is, the present invention provides means for contact-printing a special contact screen having a continuous density change of 0.1 to 3.0 on sensitized carbon tissue, and contact-printing a mesh positive for offset or letterpress printing. means and
A diffusion sheet, a light mask, and a means for contact-printing the above-mentioned halftone positive are layered in order on the carbon tissue in any order, and then the carbon tissue is transferred to a plate material, further developed, and then This is a net gravure plate making method that is characterized by corrosion.

Hereinafter, the above-mentioned present invention will be explained in detail.

In the present invention, the carbon tissue is not particularly limited, and those used in conventional conventional gravure or mesh gravure can be widely used.

The carbon tissue is sensitized by soaking it in a few percent potassium dichromate solution and drying it in a dark room, and the following three baking steps are applied in any order.

One means of applying a sensitized carbon tissue is by contact baking a special contact screen having a continuous density variation of 0.1 to 3.0.

The special contact screen mentioned above has the highest density in the center 3.
0, and the density becomes lighter continuously toward the periphery, and the periphery has a minimum density of 0.1 and has a blurred outline. Accordingly, one having a number of lines of 100 to 350 lines/1 nch is used.

This special contact screen can be obtained, for example, by double exposing a film through two types of apertures through a grid-like glass screen having a number of lines depending on the desired number of lines.

The two types of apertures mentioned above are round apertures and Tsuna-shape apertures.
The exposure amount with the round diaphragm is 1.5 to 3 times the exposure amount with the round diaphragm.

The special contact screen described above is baked in close contact with the sensitized carbon tissue using a vacuum baking frame.

At this time, a commonly used light source such as a mercury lamp or an arc lamp can be used as a light source for exposure.

This baking forms the so-called bank necessary for gravure printing, and at the same time, the halftone dots are not sharply cut as is the case when using a white line screen, and the halftone dots are relatively round overall, which improves ink adhesion. It is something to do.

Furthermore, the size of the halftone dots formed in the process of contact-printing the screen positive is changed again in the process of contact-printing the screen positive and the diffusion sheet, thereby obtaining tone reproduction close to that of the original.

Therefore, it is possible to reproduce the tone more stably and better than the general net gravure plate making method, and it also solves the drawback that the printed matter has a rough feel and loses its overall smoothness.

Next, another method to apply to the sensitized carbon tissue is to closely bake a net positive.

Here, as the halftone positive, it is possible to use an offset or letterpress halftone positive.

The printing of the halftone dots can be carried out in the same manner as in the case of the above-mentioned special contact screen, thereby forming the size of the halftone dots.

Next, yet another method to apply to the sensitized carbon tissue is to sequentially stack a diffusion sheet, a light mask, and the above-mentioned net positive on the carbon tissue and bake them in close contact with each other.

Baking can be done in the same way as for the special contact screen mentioned above.The light that has passed through the halftone positive passes through a light mask, which prevents the halftone dots from being insufficiently deep or small in the light area. Prevented.

Thereby, halftone dots having a halftone dot percentage of 5 to 8% of the above halftone positive can be reproduced.

As a result, it becomes possible to reproduce the tone of the light portion, which is the biggest drawback when using a net positive for offset or letterpress printing in net gravure plate making.

Here, the light mask is a continuous tone blurring mask having a maximum density of about 0.6, and can be produced from a halftone positive.

For example, this light mask is made by placing a diffusion sheet on top of a continuous tone film or a lithographic film, and then layering the same halftone dot as above on top of that and sticking it tightly. The exposure amount is adjusted so that the maximum density is about 0.6, and the area with a halftone dot percentage of 8% or more has a density of O, and is exposed and printed from the positive halftone side.
Obtained by developing and fixing.

It is preferable to use a squirrel-type film to obtain a light mask with a hard tone.

Additionally, the diffusion sheet used to create this light mask has a transmittance of 30-50% and a thickness of 150-250μ.
It may be selected as appropriate depending on the density range of halftone positive, the condition of the original, etc.

Next, the light transmitted through the net positive and the light mask is diffused by a diffusion sheet.

The light passing through the halftone positive and light mask has a small amount of light transmitted in the shadow areas, and a large amount of light transmitted in the highlighted areas.

The amount of transmission is more or less accompanied by the above-mentioned diffusion effect, creating a continuous gradation change.

Here, the diffusion sheet can be selected as appropriate from those with a light transmittance of 60 to 90% and a thickness of approximately 50 to 100μ, depending on the density range of the halftone positive, the condition of the original, the development method, the etching method, etc. Specific examples thereof include matte films, diffusion glasses, and the like.

In addition, in the invention previously disclosed by the present applicant, the order in which the diffusion sheet and light mask are stacked in the third of the above three means is reversed from that of the present invention, so that the screen positive is not transmitted. The light is first diffused and spread by the diffusion sheet, and then passes through the light mask while maintaining its spread while spreading.As a result, the small halftone dots in the Highlight I area become slightly crushed, becoming smaller and smaller. It is reproduced in a blurred manner (Japanese Unexamined Patent Publication No. 52-9504).

In contrast, in the present invention, the diffusion sheet, which is primarily involved in light diffusion, is in direct contact with the carbon tissue, which prevents excessive light diffusion and reproduces small halftone dots in highlighted areas without blurring. be done.

When applying the above three methods to the sensitized carbon tissue, the special contact screen is baked with the same exposure amount as the conventional screen baking method, and the printing of the net positive is done by baking the contact screen. less than the exposure amount of 6
It is carried out with an exposure amount of about 0 to 90%, and a diffusion sheet,
Baking a light mask and a net positive is about half the exposure amount of contact screen printing, that is, 40 ~
This can be done with an exposure amount of about 60%.

Next, a gravure plate can be obtained by transferring the carbon tissue to which the above three means have been applied in any order onto a plate material, further developing it, and then etching it.

This operation can be performed almost in the same way as the operation of the normal competitive method.

The baked carbon tissue is quickly transferred to a predetermined position on the printing plate.

In addition to regular rotary cylinders, copper plates can also be used as plate materials.

The transfer method can be a wet method or a dry method.

After transfer, the insoluble parts remain on the printing plate, so the unsensitized parts are dissolved and removed with hot water.

After complete removal, wash with water and dry.

Erosion is then carried out with a ferric chloride solution.

This corrosion can be carried out by a method using several types of ferric chloride solutions with different specific gravities or by a one-liquid corrosion method.

After corrosion, plate material can be plated with chrome or nickel to increase printing durability.

In the present invention, in order to stabilize corrosion and improve the reproducibility of light areas, inorganic iron salts such as ferrous sulfate, ferric sulfate, and ferric nitrate, or phenylalanine are added to the ferric chloride solution. , a mixture of an alkaline solution of amino acids such as alanine, glycine, and inorganic salts of copper such as copper sulfate, cupric chloride, cupric nitrate, etc. to the above solution by adding one or more additives to the above solution. It is desirable to use a corrosive solution containing 8% or less.

Furthermore, etching of the plate surface using the above-mentioned etching solution can be carried out by conventional manual methods.

Furthermore, it is also effective to physically penetrate the etching liquid into the plate surface using a roller or the like; for example, a commercially available automatic etching machine is used for this method.

An example of this is Gravure Pilot (West Germany, K., Wal
ter), Gravomaster (Switzerland, Graphi)
(manufactured by Cart Inc.).

In particular, if etching is carried out in an automatic etching machine using a ferric chloride solution with the above additives added as an etching liquid, the etching time can be shortened, and the depth of the plate is shallow due to side etching, resulting in less ink. can be secured.

Therefore, halftone dots having a halftone dot percentage of 5 to 8% can be easily and stably reproduced without occurrence of bank breakage or background fogging in shadow areas.

As is clear from the above description, the present invention is a net gravure plate making method with excellent reproducibility.

In the present invention, by using the above-mentioned special contact screen, the halftone dots are not sharply cut as is the case when a white line screen is used, and the halftone dots are relatively round overall.

Therefore, the deformation of the halftone dots may clearly appear on the printed matter.
-1 Also, since the doctor's contact with the halftone dots on the printing plate is averaged, smoothness can be imparted to the entire printed matter.

Further, in the method of the present invention, it is possible to use a halftone positive for offset printing or letterpress printing.

In particular, if you use an offset net positive, you can incorporate the advantages of offset in addition to the advantages of gravure, such as the sense of mass, and improve the tone reproducibility of the original.
Offset proof printing becomes possible.

In the present invention, the process can be simplified because plate making can be performed using only halftone dots, and since the expression format depends on both the size of halftone dots and their depth, it is not affected by slight variations in corrosion, making it extremely safe to reproduce tone. It is rich in sexuality.

Further, in the present invention, since a light mask is used, the reproducibility of the light portion is excellent, and printed matter with rich gradations can be obtained.

In addition, in the present invention, since the diffusion sheet, light mask, and net positive are sequentially stacked and exposed on the carbon nut, compared to the case where the light mask, the diffusion sheet, and the net positive are sequentially stacked and exposed on the carbon nut, finer details can be obtained. Excellent reproducibility of patterns, lines, and characters.

Claims (1)

[Claims] 1. Add o, i to sensitized carbon tissue.
A means for contact-printing a special contact screen having a shape of a square with a blurred outline or a square with rounded apex angles having a continuous density change of 3.0, and a means for contact-printing a mesh positive for offset or letterpress printing. Then, a diffusion sheet is placed on the carbon tin, a diffusion sheet is placed on the continuous tone film or a squirrel-type film, and the same net positive as above is placed on top of that, and the portion of the net positive with a halftone dot percentage of 5% or less is The light mask obtained by adjusting the exposure amount so that the maximum density is 0.6 and the area with a halftone dot percentage of 8% or more has a density O, and then exposing from the positive halftone side, printing, developing, and fixing, and the above. 1. A net gravure plate-making method characterized by applying means for stacking net positives in order and baking them in close contact in an arbitrary order, then transferring the carbon tissue to a plate material, developing it, and then etching it.