JPS6051703B2 - 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 determined by the density of the halftone dot. 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 Darziyan method, which uses a continuous tone positive and a halftone positive.
According to this method, a halftone positive is printed on a sensitized carbon film, a continuous tone positive is printed on the unexposed areas, the carbon film is transferred to a cylinder, and then developed and etched. Make a plate. Although this method improves the stability of platemaking, the dimensions of the continuous-tone positive and the halftone positive must be exactly the same, which complicates the work process and is technically difficult. There are also 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 a means for contact-printing a special contact screen having a continuous density change of 0.1 to 3.0 on a sensitized carpon tissue, and a means for contact-printing a mesh positive for offset or letterpress printing. and,
A diffusion sheet and a means for contact-printing the above-mentioned halftone positive are sequentially stacked on the above-mentioned carpon stock in any order, and then the carpon stock is transferred to a plate material, further developed, and then etched. This is a net gravure plate making method characterized by:

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

In the present invention, the carpon chisel is not particularly limited, and those used in conventional conventional gravure or net gravure can be widely used. The carpon tissue is sensitized by soaking it in a several percent solution of potassium dichromate and drying in a dark room, and then subjected to the following three baking procedures in any order. One means of applying a sensitized carpon tissue is to contact bake 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 the lowest density of 0.1, and the screen has a shape like a square or a square with rounded apex corners, and the rim is blurred. The number of lines of 100 to 3 marks/Jnch is used. This special contact screen can be obtained, for example, by double exposing a film using two types of apertures from a grid-like glass screen having a number of lines corresponding to the desired number of lines. The two types of diaphragms mentioned above are a round diaphragm and a square diaphragm, and the exposure amount using the round diaphragm is operated at 1.5 to 3 times the exposure amount using the horn diaphragm. The above-mentioned special contact screen is closely baked onto a sensitized carpon chip 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 banks necessary for gravure printing, and at the same time, the halftone dots are not cut sharply like when using a white line screen, and the halftone dots are relatively round overall, making it easier for ink to adhere. It is something. The special contact screen mentioned above has a maximum density of 3.0, so compared to the case where a contact screen with a maximum density of 3.0 or higher is used, the carpon chip hardens slightly even in the highest density area. Acts as a resist during corrosion, prevents excessive corrosion in the shadow areas, and prevents variations in corrosion depth in the shadow areas. Also 0.1 to 3.0
Since it has a continuous density change, the halftone dots are not sharply cut, and this has the advantage that moiré is less likely to occur in the printed matter, and the printed matter is finished smoothly overall.Furthermore, the special contact used in the present invention Since the screen has a continuous density change, the ring of each halftone dot is blurred, but the shape is square, so the area ratio of the halftone dot is high and the printing effect is excellent. If the halftone dots have a flat apex angle, the halftone dots will not be sharply cut by the intersection of the banks, so moiré and roughness of the printed matter will be less likely to occur.Furthermore, in the process of contact-printing the halftone positive, The size of the halftone dots formed is changed again in the process of printing the halftone positive and the diffusion sheet in close contact with each other to obtain a tone reproduction close to that of the original.Therefore, the saw layer is more stable and more stable than the general halftone gravure plate making method. It is possible to reproduce good tone, and it also eliminates the drawback that the prints have a rough feel and the overall smoothness is lost. One method is to closely bake a net positive.

Here, as the halftone positive, it is possible to use a halftone positive for offset or letterpress printing. 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 again,
Yet another means for applying the sensitized carpon chittle is to stack a diffusion sheet and the above-mentioned net positive on the carpon chittle in order and bake them in close contact with each other.

The printing can be carried out in the same manner as in the case of the above-mentioned special contact screen, and the light transmitted through the net positive is diffused by the diffusion sheet. The amount of light that passes through the positive halftone screen is small in the shadow areas, and large in the highlight areas. This amount of transmission, accompanied by the above-mentioned diffusion effect, produces a continuous gradation change. Here, the light transmittance of the diffusion sheet is 60 to 90.
%, thickness of about 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 include, for example, matte film , diffusion glass, etc. When applying the above three methods to the sensitized carpon stock, the special contact screen should be baked at the same exposure level as the conventional conventional method; The exposure amount is less than the exposure amount for printing, and is about 60 to 90% of that amount.Furthermore, the exposure amount for overlapping the diffusion sheet and net positive is about half of the exposure amount for contact screen printing, that is, about 40 to 60%. This can be done by adjusting the exposure amount. Next, transfer the carpon chiticle on which the above three methods have been applied in any order to a plate material,
A gravure plate can be obtained by further development and subsequent etching.

This operation can be carried out almost in the same way as the usual conventional method. The baked carpon chip is immediately 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 to seven kinds of ferric chloride solutions having different specific gravities, or by a one-component 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. 7 to the above solution as an additive with one or more of a mixture of an alkaline solution of amino acids such as alanine and glycine and inorganic copper salts such as copper sulfate, cupric chloride, and cupric nitrate. ~
It is desirable to use a corrosive solution containing 8% or less.

In the net gravure plate making method of the present invention, the halftone dots in the light area are smaller than those in the conventional method, so using an etchant without the above additives will prevent corrosion of the thin shadow areas of the resist. Corrosion progresses slowly in the light areas where the resist is thick compared to the progress of the resist, and no halftone dots are formed in the light areas, and corrosion becomes excessive in the shadow areas, causing bank breakage. When a liquid is used, the permeability of the corrosive liquid is improved, and as a result, there is no breakage of the bank in the shadow area, corrosion of the light area can be carried out smoothly, and the reproducibility of the light area is improved. Furthermore, although conventional manual methods can be used to etch the plate surface using the above-mentioned etchant, it is extremely effective to physically penetrate the etchant into the plate surface using a roller or the like. For this method, for example, a commercially available automatic etching machine is used. An example of this is Gravure Pilot (West Germany, K. Walt
er), Kurabo Master (Switzerland, MaxDaf?)
Yler & CO. ), etc. In particular, if a ferric chloride solution containing the above additives is used as a corrosive solution and the corrosion is carried out in an automatic corrosive machine, the corrosive time can be shortened.
Also, due to the effect of side etching, the depth of the plate is shallow, ensuring a sufficient amount of ink. Therefore, halftone dots having a halftone dot percentage of 5 to 8% can be easily and stably reproduced without causing 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 will not appear on the printed matter,
Furthermore, 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, in addition to the advantages of gravure, such as the sense of mass, you can incorporate the advantages of offset, improving the tone reproducibility of originals, and making it possible to proof print using offset. becomes. Furthermore, in the method of the present invention, since an additive is added to the corrosive solution to improve its permeability, it is possible to form halftone dots in the light area without bank breakage in the shadow area. Thus, it is possible to reliably express the color tone and shading of the light area.

Furthermore, in the present invention, it is possible to prevent the bank from breaking in the shadow area, so the width of the bank can be narrowed, and in this way, the area where the halftone dots are to be formed in the light area overlaps with the bank, so that the halftone dots are not formed. It also becomes possible to lower the probability that it will not be formed.

Claims (1)

[Claims] 1. A special contact screen in the form of a blurred square or a square with rounded apex angles is baked in close contact with the sensitized carbon tissue, with each halftone dot having a continuous density change of 0.1 to 3.0. A means for contact-baking a mesh positive for offset or letterpress printing, and a means for stacking and contact-baking the diffusion sheet and the mesh positive on the carbon tissue in any order, and then, Transferring the carbon film to a plate material,
After further development, one or more of ferrous sulfate, ferric sulfate, ferric nitrate, or a mixture of an alkaline solution of an amino acid and an inorganic copper salt is added as an additive to ferric chloride. A net gravure plate-making method characterized by etching using an etching solution added to a solution.