JPS581771B2 - Gravure plate making method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gravure plate-making method, and more particularly to a method for obtaining a gravure plate that produces high-quality printed matter by using two different types of gravure screens.

Conventional gravure printing methods include the so-called conventional gravure method, in which the cell size of the gravure plate remains constant and only the depth changes; A plain gravure method in which both the cell depth and the cell area of the gravure plate are varied are well known.

In the conventional gravure method, a continuous tone positive is used, so a net-resolved positive (half-tone positive) is used.
The gradation is richer than that of the halftone gravure method.

However, since the tone reproduction depends only on the depth of the cells in the gravure plate, errors in depth during corrosion immediately affect the tone reproduction.

The influence of such a depth error is noticeable in the light portion having shallow cells.

For example, in the conventional gravure method, in light areas where the cell depth is approximately 1 to 2 μm, the error in depth during corrosion must be extremely small, and corrosion must always be maintained at a constant depth. It is very difficult to do so.

The net gravure method was devised to eliminate the corrosion instability of the conventional gravure method.

In the net gravure method, since the area of the cell in the light part is small, the depth of the cell can be increased by that much.

Therefore, even if a depth error occurs during corrosion in the net gravure method, the influence of this error is smaller than in the conventional method.

However, in the halftone gravure method, it is not possible to use continuous tone positives as they are, but it is inconvenient that continuous tone negatives (or continuous tone positives) must be converted to halftone positives (or halftone negatives) before use. There is.

The present invention provides a gravure plate-making method that has both the stability of the corrosion work of the light part as in the net gravure method and the richness of gradation as in the conventional gravure method.

Conventionally, in conventional gravure methods, one type of gravure screen has been used to form a dowel for supporting a doctor blade.

Because of this, there were major inconveniences. It is easily understood from the above explanation that in order to obtain stability of corrosion in the light part, the gravure screen 10 should have a smaller area of the opaque part 1 corresponding to the area of the cells of the gravure plate. It can be understood.

That is, the ratio of the opaque portion 1 to the transparent portion 2 may be reduced.

However, if this is done, the area of the cells in the shadow portion will naturally become smaller, and it will also be difficult to corrode the cells to a sufficient depth, resulting in insufficient printing density in the shadow portion.

Conversely, in order to obtain sufficient printing density in the shadow area, it is better to increase the area of the opaque area 1 of the gravure screen 10.

In other words, it is better to increase the ratio of the opaque portion 1 to the transparent portion 2.

However, in this case, the cells in the light part must be made shallow, and as described above, variations in the corrosion process are likely to occur.

The present inventor has completed the present invention by discovering that the above-mentioned drawbacks can be overcome by printing two types of gravure screens onto photoresist using a special method.

The present invention will be explained in more detail below with reference to the drawings.

The present invention includes at least three exposure steps.

One of them, as shown in FIG. 4, is a step in which a gravure screen 10' and a continuous tone positive layer 30 are laminated on the photosensitive layer 3 side of a photoresist 20, and then the continuous tone positive layer is exposed to light.

In this exposure process, the photoresist is exposed by simultaneously using the gravure screen and the continuous tone positive, so in the light section A, a large amount of light passes through the continuous tone positive 30, and then the gravure screen 10'. The light passes through the transparent part 2 to sufficiently harden the photosensitive layer 3 under the transparent part 2, while in the shadow part C, since the concentration of the continuous tone positive 30 is high, almost no light passes through this positive. Therefore, the gravure screen is not printed onto the photoresist in this area.

Further, in the halftone portion B, the photosensitive layer 3 of the photoresist is hardened to a moderate degree depending on the density of the continuous tone positive 30.

The other one of the three exposure steps (hereinafter referred to as the second exposure step for convenience, although it is not necessarily the second one to be performed) is the process of forming the photoresist 20 as shown in FIG. On the photosensitive layer 3 side, a continuous tone negative 40 and a gravure screen in which the opaque portion 1' accounts for a larger proportion than the gravure screen 10' used in the exposure process shown in FIG. 4 are laminated to form a continuous tone negative 40 side. This is the process of exposing to light.

This exposure step is opposite to the exposure step shown in FIG. 4 (hereinafter referred to as the first exposure step, although it is not necessarily the first step) in terms of the printing state.

That is, since the light portion R has a high density in the continuous tone negative 40, the gravure screen 10'' is not printed on the photoresist 20.

On the other hand, since the shadow part C has a low density in the continuous tone negative 40, a large amount of light passes through the continuous tone negative 40, and then passes through the transparent part γ of the gravure screen 10' to reach the lower part of the transparent part 2'. The photosensitive layer 3 is sufficiently cured.

Further, in the halftone portion B', the photosensitive layer 3 is hardened to a moderate degree depending on the density of the continuous tone negative 40.

In the remaining of the three exposure steps (hereinafter referred to as the third exposure step for convenience), as shown in FIG. 6, a continuous tone positive 30' is laminated on the photoresist 20. This is a process of exposing from the continuous tone positive side.

In the third exposure step, the photosensitive layer 3 of the photoresist 20 is hardened according to the density of the continuous tone positive 30'.

The continuous tone positives 30 and 30' of the present invention can be the same.

Furthermore, continuous tone negative 40 of the present invention is a negative corresponding to continuous tone positive 30 or 30'.

In the present invention, the above three exposure steps are performed in any order, but in the first exposure step and second exposure step of printing the gravure screen onto the photoresist, the emulsion surface of the gravure screen and the photoresist are exposed. It is preferable that the layers 3 and 3 are in close contact with each other, and in the upper stage of the third exposure, it is preferable that the emulsion surface of the continuous tone positive 30' and the photosensitive layer 3 of the photoresist be in close contact with each other. It is not limited to this.

In the present invention, the light section is the gravure screen 10
' is burned into the photoresist 20, and the gravure screen 10' is not burned.

In addition, in the shadow area, the gravure screen 10"
is printed onto the photoresist 20, and the gravure screen 10' is not printed.

Furthermore, in the halftone part, gravure screens 10, 10
' are printed onto the photoresist 20.

As can be seen from FIG. 6, the hardening of the photosensitive layer 3 due to screen baking in the intermediate tone area is less than the hardening of the photosensitive layer 3 due to screen baking in the light area or shadow area, but It is necessary to obtain sufficient hardening to form the grooves 6 of the gravure plate 5 when the plate corrodes through the plate (FIG. 7).

To do this, the gravure screen 10 or 10'
When printing onto the photoresist 20, the exposure amount for both may be applied sufficiently to form the dots in the halftone area, or the exposure amount at the time of either printing may be set to be enough to form the dots in the halftone area. It may be applied as much as necessary to form.

In the present invention, from the first exposure step to the third exposure step, continuous tone positive 30. 30' and continuous tone negative 40 must each be laminated to the gravure screen or photoresist in register with each other.

Any means may be used to achieve registration in these exposure steps.Adoption of a system using register bins will facilitate registration.

Registration is well known to those skilled in the art and does not require further explanation.

Furthermore, in the halftone area, since both the gravure screen 10 and the crapier screen 10'' are printed on the photoresist 20, moiré may occur between the halftone dot structures of these gravure screens.

Therefore, when printing these gravure screens on photoresist, it is preferable to print at an angle that minimizes moiré.

As the gravure screen used in the first exposure step and the second exposure step of the present invention, a normal gravure screen having a rectangular opaque portion 1 surrounded by orthogonal transparent portions 2 as shown in FIG. 1 can be used. Furthermore, it is possible to use a gravure screen, as shown in FIG. 2, in which a round opaque part 1 is surrounded by a transparent part 2.

In addition, a gravure screen in which an opaque part 1 and a transparent part 2 are arranged in an arrangement like a stack of bricks as shown in FIG. 3, a gravure screen as described in British Patent Publication No. 974884, etc. Any gravure screen can be used as long as it is suitable for the purpose of the present invention.

In addition, in the present invention, in the first exposure step, the gravure screen 10, which is printed in the areas corresponding to the light area to the intermediate tone area, has an opaque area 1' that accounts for 10 to 40% in order to stabilize corrosion and provide sharpness. It is preferable to use a gravure screen of about 30% to 35%, and it is more preferable to use a gravure screen of about 30 to 35%.

Furthermore, the gravure screen 10' that is printed on the areas corresponding to the light area to the intermediate tone area can be printed using a gravure screen in which the opaque area 1 has a round shape, which is very similar to that shown in FIG. This is preferable because the ink transfer in the light area is performed well.

Furthermore, in the present invention, the gravure screen 10' that is printed in the areas corresponding to the halftone area to the shadow area in the second exposure process is a gravure screen that has a larger proportion of opaque areas than the crapier screen 10' used in the upper part of the first exposure. Use.

The reason for this is to ensure sufficient printing density in the printed matter in the shadow area.

In the second exposure process, using a gravure screen with square opaque dots as shown in Figure 1 or Figure 3 has excellent reproducibility of characters, etc., and it is easy to obtain sufficient print density. preferable.

The gravure screen 10' used in the second exposure step is preferably a gravure screen in which the proportion of the opaque portion 1' is approximately 40 to 80%, and is preferably 55 to 60%.
It is more preferable to use a gravure screen of about 5%.

The photoresist used in the present invention is not particularly limited, and for example, photosensitized carbon tissue, Kodak gravure resist film, rotofil, rotargo film, etc. are used.

Alternatively, a photoresist material may be applied to the gravure cylinder in advance, such as in the Portiel method.

The photoresist exposed according to the method of the present invention is used to etch gravure cylinders (including plate-shaped cylinders, hereinafter the same) according to a conventional method.

The etching process is usually carried out in the order of transferring the photoresist to the gravure cylinder, developing, drying, and etching, but it may be carried out in an appropriate manner depending on the type of photoresist used, and such order and operations may be carried out. The steps etc. are not limited to the above.

If necessary, chrome plating may be further performed after corrosion.

In the present invention configured as described above, gravure screens suitable for each of the light section and the shadow section are used.

Therefore, in the light part, a small cell area suitable for the light part can be formed, and the cells in the light part can be deepened accordingly.

Therefore, in the light part, there is no need to control the depth of several microns between 1 and 2 microns like the depth of the cell in the conventional method, and it can be as deep as 3 to 5 microns.
Corrosion becomes stable and sharp like net gravure method.

In addition, for the shadow area, you can choose a gravure screen with an area that matches the shadow area, giving you a deep tone typical of gravure.

Further, in the present invention, since continuous tone positive is used, the gradation is richer than in the dot gravure method which uses dot-divided positive, and there is no need for a halftone photographing process.

As described above, the present invention can provide a gravure plate-making method that combines the advantages of the conventional gravure method and the net gravure method, and the printed matter produced by the gravure cylinder obtained by the present invention can be of high quality, and the quality is stable. You get what you get.

[Brief explanation of the drawing]

Figures 1 to 3 are explanatory diagrams of the gravure screen, and Figure 4 is an illustration of the gravure screen.
6 to 6 are explanatory diagrams of the exposure process of the present invention, and FIG. 7 is an explanatory diagram of the corrosion process. 1, 1', 1''... Opaque part, 2, 2', 2'... Transparent figure, 3... Photosensitive layer, 3'... Resist layer, 5... Gravure plate, 6... Dote, 10, 10', 10"...Gravure screen, 20...Photoresist, 30,30'...
...Continuous tone positive, 40...Continuous tone negative, A
, A'...Light part, B, B...Middle tone part, C, C'...
...Shadow Department.

Claims (1)

[Claims] 1. A step in which a gravure screen and a continuous tone positive are laminated on the photosensitive layer side of the photoresist and exposed from the continuous tone positive side, and a part is more opaque than the gravure screen used in the step on the photosensitive layer side of the photoresist. A process of laminating a gravure screen with a large proportion of gravure screen and a continuous tone negative and exposing from the continuous tone negative side, and laminating a continuous tone positive on the photosensitive layer side of the photoresist, and exposing the continuous tone negative to the continuous tone positive side. 1. A gravure plate-making method, which comprises performing three steps in an arbitrary order, including a step of exposing to light, and then obtaining a gravure plate by a conventional method using the exposed photoresist.