JPS647654B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gravure plate making method, and particularly to a net gravure plate making method.

In order to obtain a halftone gravure printing plate, it is well known to use not only a halftone positive for gravure, but also a halftone positive for lithography or letterpress printing, as shown in Japanese Patent Laid-Open No. 50-26603. As shown in FIG. 1, in a halftone positive 1 for planography or letterpress printing, opaque halftone dots 2 are in contact with or overlap each other from shadow areas to halftone areas. The opaque halftone dots 2 become independent halftone dots toward the light portion. Such a net positive for planography or letterpress 1
When performing net gravure plate making using
It is necessary to use a gravure screen 4 which has transparent lines 3 as shown in the figure and whose other parts are opaque. The reason for this is that in halftone dots 1 for planography or letterpress printing, the opaque halftone dots 2 touch or overlap from the shadow areas to the halftone areas, and this prevents ink from flowing in these areas during printing. be.

However, net positive 1 for planography or letterpress
When used in combination with the gravure screen 4, not only does it have the disadvantage that moire is likely to occur from the light part to the intermediate tone part, but also the halftone dots in the light part are missing or disappear due to the transparent lines of the gravure screen. This has the disadvantage that the tone reproducibility of the light section is impaired.

Considering the above points, as a method to prevent the light section from being affected by the gravure screen, it is especially important to overlap the negative on the gravure screen when printing the gravure screen with transparent lines on the carbon tissue. Kaisho 50-161303
It is shown in the publication No.

Alternatively, a gravure screen with transparent lines and a negative are overlapped and printed on a photosensitive film.
Furthermore, by printing the net positive, a negative net with black lines from the original shadow area to the halftone area is created, and this is inverted to create a negative net with transparent lines from the shadow area to the halftone area. Japanese Patent Application Laid-Open No. 131703/1983 discloses that this net positive is used for net gravure plate making.

According to these methods, the problems of preventing moiré and reproducibility of tone in light areas can be solved. However, in the former case, when printing the gravure screen on the carbon tissue, the light part is not burned, so the gravure screen is printed on the necessary parts and the gravure screen is not used on the unnecessary parts. It is difficult to confirm that it has not been printed until after the net positive is printed, the carbon tissue is transferred to a gravure cylinder and developed. Therefore, if the gravure screen is not printed on the necessary areas, or if the gravure screen is printed on unnecessary areas, it will be necessary to start over from the beginning, which will save on material costs and work time. waste becomes large.

Furthermore, in the latter case, the transparent lines of the gravure screen are inserted into the halftone positive itself, so that the opaque halftone dots in the shadow to halftone areas of the halftone positive are also divided into minute independent points by the transparent lines. On the other hand, when printing a net positive onto a photosensitive material, a method was developed by Japanese Patent Laid-Open No. 2003-120030 that could produce the same effect as a continuous positive by blurring the dots of the net positive.
It is disclosed in many documents including Japanese Patent No. 50-26603. If the above-mentioned halftone positive (i.e., the halftone positive with transparent lines of a gravure screen) is used in such a method, when blurring the halftone dots of the halftone positive, extra light will be emitted from the transparent lines from the shadow area to the halftone area. This results in the disadvantage that tone reproducibility from shadow areas to halftone areas is impaired.

The present invention was completed as a result of various researches aimed at solving the above-mentioned drawbacks. That is, the present invention has discovered that the various drawbacks mentioned above can be overcome by using a special gravure screen, and has also discovered a method for performing net gravure plate making using this special gravure screen.

The gravure screen used in the present invention is suitable for net gravure plate making, and is particularly suitable for net gravure plate making, and is particularly suitable for net positives in which opaque halftone dots touch or overlap from shadow areas to halftone areas, such as net positives for planography or letterpress printing. Suitable for obtaining net gravure plates using this method.

As illustrated in FIG. 3, the gravure screen 5 used in the present invention has a transparent line 6 from a portion A corresponding to the shadow portion of the net positive to be used to a portion B corresponding to the halftone portion. Portion C corresponding to the positive light portion does not have a transparent line. The part other than the transparent line 6 is an opaque part 7
It is becoming.

The halftone area of halftone positive has a halftone percentage of approximately 50%.
It has a certain width around the center. Therefore, the percentage of halftone dots to include the transparent line 6 within the range of part B corresponding to the halftone part should be determined by considering the pattern to be printed and the quality required for the printed material. and select appropriately. In addition, in the above-mentioned part, the expression that the opaque halftone dots in the halftone part of halftone positive for planography or letterpress are touching or overlapping means that the halftone dots in the halftone part having a certain width are It should be noted that the point percentage is for a portion greater than approximately 50%.

It is important for the gravure screen used in the present invention to have transparent lines 6 in the area corresponding to the halftone dot percentage range of 100% to 50% of the halftone positive for the purpose of preventing ink flow during printing. However, if the print is of a quality that can be tolerated even if a slight ink flow occurs, it may not be necessary to have transparent lines up to the 50% area, for example, approximately 60%. Sometimes it's good to have something to do. In addition, the transparent line 6 has a portion corresponding to a halftone dot percentage of 50% of the halftone positive, and has no transparent line in a portion corresponding to a halftone dot percentage of less than 50% of the halftone positive. It may be hot.

Further, the gravure screen used in the present invention may have transparent lines 6 up to a portion corresponding to a halftone dot percentage lower than 50% of the halftone positive. In this case, the desired percentage of the transparent line 6 to be included may be appropriately selected depending on the pattern to be printed, quality, and other conditions.

The reason why transparent lines 6 are provided in areas corresponding to halftone dots less than 50% is that depending on the pattern to be printed, transparent lines 6 may be provided in areas corresponding to halftone dots of 50% or more. If the transparent line suddenly disappears in the area corresponding to fewer halftone dots than the 50% boundary, the gradation of the printed material may suddenly change at that boundary, causing an undesirable effect. It is from. Therefore, as long as there is no such problem, it is preferable that it be close to 50%.

Further, the opaque portion of the gravure screen used in the present invention preferably has a density of 2.5 or more, and more preferably has a density of 3.0 or more.

In order to obtain the gravure screen used in the present invention, as illustrated in FIG. A positive such as a continuous tone positive or a net positive is required. These black line screens and positives are each printed separately on the same photosensitive film.
In this case, either the black line screen printing or the positive printing may be performed first.

For positive printing, either continuous tone positive or net positive may be used.

FIG. 5 is an explanatory cross-sectional view showing the state of printing on a photosensitive film when a continuous tone positive film is used as the positive film. As shown in FIG. 5, a continuous tone positive film 13 is brought into close contact with the photosensitive layer 12 side of the photosensitive film 11, and light is irradiated from the continuous tone positive film side as shown by the arrow in the figure. A shaded area 14 in the photosensitive layer 12 schematically represents the amount of light that has passed through the continuous tone positive plate 13 and reached the photosensitive layer 12. That is, the amount of light is the smallest in the shadow area a, the largest in the light area c, and the amount of light is between the shadow area and the light area in the halftone area b.

When a net positive is used as a positive,
When printing this halftone positive onto a photosensitive film, the halftone dots are diffused and printed. The purpose of diffusing the halftone dots of a halftone positive is to create an effect similar to that of printing a continuous tone positive.

The method of diffusing halftone dots of a halftone positive and printing them onto a photosensitive material has already been disclosed in various documents, so that method may be employed. For example, as shown in FIG.
Diffusion sheet 15 on the photosensitive layer 12 side of 1
The net positive 16 may be brought into close contact with the net through the net, and light may be irradiated from the net positive side as shown by the arrow in the figure. In FIG. 6, a hatched portion 14 in the photosensitive layer 12 schematically represents the amount of light that has passed through the net positive and reached the photosensitive layer 12, as in FIG. 5.

As another method for diffusing halftone dots, a method is known in which a transparent sheet is used instead of a diffusion sheet and irradiated with diffused light, and such a method may also be used.

Incidentally, the diffusion sheet means a sheet having the property of diffusing light, and is usually a milky-white sheet, and may be appropriately selected from matte film, opal glass, ground glass, etc.

When the positive is brought into close contact with the photosensitive film 12, the choice of which of the base layer 17 and the emulsion layer 18 of the positive should be directed toward the photosensitive film 11 is determined by the choice of which of the base layer 17 and the emulsion layer 18 of the positive should be directed toward the photosensitive film 11. It is only necessary that the pattern and the pattern of the special gravure screen used in the present invention are visible in the same direction when viewed from the emulsion surface (or base surface).

To print the black line screen, as shown in FIG. 7, the black line screen 19 is brought into close contact with the photosensitive layer 12 side of the photosensitive film 11, and light is irradiated from the black line screen side as shown by the arrow in the figure. .

The part 20 indicated by diagonal lines on the lower left in Fig. 7
1 schematically represents the amount of light that has passed through the transparent portion 21 of the black line screen 19 and reached the photosensitive layer 12 of the photosensitive film 11.

Since the opaque portion 22 of the black line screen 19 does not transmit light, the portion of the photosensitive layer 23 corresponding to the opaque portion 22 is not irradiated with light during this printing process.

When the black line screen 19 is brought into close contact with the photosensitive film 11, it is preferable to place the emulsion layer 24 of the black line screen 19 on the photosensitive layer 12 side of the photosensitive film because the image of the black line screen will not be blurred.

Note that the black line screen 19 is replaced by a photosensitive film 11.
The amount of exposure when printing differs depending on the type of photosensitive film used, so apply the amount appropriate for each photosensitive film used.

As the photosensitive film used in the present invention, it is desirable to use a film that is used for making ordinary gravure screens, that is, a film that has a large gamma value and a strong contrast.

Such a film is usually called a lithium type film.

Among photosensitive films having a large gamma value, in addition to silver salt type films, for example, vesicular films can also be used.

The photosensitive film used in the present invention has a gamma value of
A film of 3.0 or more is preferred, and a film having properties similar to those of a squirrel-type film for contact reversal of net positives or for net photography is more preferred.

The photosensitive film 11, which has undergone positive printing and black line screen printing as described above, is developed. As shown in FIG. 8, a screen used in the present invention is obtained by this development process. This screen has a transparent line 25 from a portion corresponding to a positive shadow portion to a portion corresponding to an intermediate tone portion, and has no transparent line in a portion corresponding to a positive light portion. The portion other than the transparent line 25 is an opaque portion 26.

The screen thus obtained is used to obtain a net gravure plate using a net positive, particularly a net positive for planography or letterpress printing. Therefore, it is preferable to use this net positive as the positive used when printing the photosensitive film.

In the present invention, the screen obtained as described above and the net positive for planography or letterpress printing are printed in close contact with a photosensitive material for resist formation such as carbon tissue, roto film, or the like. It is necessary that the pattern of the mesh positive printed on the carbon film or other photosensitive material for resist formation and the pattern of the screen for mesh gravure plate making used in the present invention are aligned with each other when printing.

Note that the shape of the transparent lines of the special screen used in the present invention is not limited to perpendicular transparent lines as shown in FIG. It may be something like a so-called backstein screen.

As with the usual gravure screen, various screen numbers can be used for the screen used in the present invention.

The printing of the net gravure plate-making screen used in the present invention onto the photosensitive material for resist formation may be carried out in the same manner as the printing of a normal gravure screen.

The printing of a screen positive for planography or letterpress onto a photosensitive material for forming a resist may be carried out by a conventional method.

By printing the net positive onto the photosensitive material for resist formation, elements of large and small cell area are formed.

In the present invention, baking can also be performed to form deep and shallow elements of the cell. Various methods are known for forming the bathymetric elements of cells. Some examples include a method of printing a continuous tone positive on a photosensitive material for forming a resist, and a method of diffusing halftone dots of a halftone positive and printing it on a photosensitive material for forming a resist. The method of diffusing and printing the halftone dots of the halftone positive is to interpose a diffusion sheet between the halftone positive and the photosensitive material for resist formation and irradiate it with light, or to irradiate the halftone dots of the halftone positive and the photosensitive material for resist formation. There is a method of interposing a transparent sheet between the two and irradiating with diffused light. In the present invention, baking for forming deep and shallow elements of the cell may be performed by any of the various methods described above.

In the present invention, printing of the net gravure plate making screen of the present invention onto a photosensitive material for resist formation, printing of a net positive to form elements of large and small areas of cells, and forming deep and shallow elements of cells are performed. The positive burns can be performed in any order.

In the present invention, the same net positive can be used as the net positive printed on the photosensitive film and the net positive printed on the photosensitive material for resist formation to form elements of the size of the cell area.
In this way, it is possible to carry out the present invention without using a continuous tone positive, which is convenient. Furthermore, the same net positive as above can be used as the net positive to be printed on the photosensitive material for resist formation in order to form the deep and shallow elements of the cell.
It is possible and advantageous to practice the present invention without using all continuous tone positives.

According to the plate making method of the present invention, there are dots caused by the gravure screen from the shadow areas to the halftone areas, but there are no dots caused by the gravure screen in the light areas, so not only does a moire pattern not occur, but also the dots in the light areas. Printed matter with excellent gradation reproducibility can be obtained.

The conventional method of preventing moiré by overlapping a gravure screen and a negative and printing them on the photoresist not only has poor workability in the process of printing onto the photoresist, but also has a problem in that the gravure screen only covers a certain percentage of the net positive. Although it was difficult to confirm that it had been burned in,
Even in this respect, the problems can be solved by adopting the plate making method of the present invention.

Furthermore, according to the present invention, it is possible to use a net positive for lithography or letterpress printing without incorporating the transparent lines of a gravure screen as it is. Therefore, even if it becomes necessary to diffuse the halftone dots of a net positive to form deep and shallow elements of a cell, it is sufficient to use such a net positive, which prevents light from unnecessarily passing through the shadow portion of the net positive. This makes it possible to ensure sufficient density in shadow areas and to obtain printed matter with wide gradations.

Next, examples of the present invention will be shown.

<Example 1> A 200 μm thick matted film was inserted between a 150 line/inch lithographic screen positive and a lithographic film, and a vacuum pump was used in a printer to bring them into close contact with each other. Next, light was irradiated for 5 seconds from a distance of 80 cm using a 12 V, 50 W halogen lamp. Next, after removing the net positive and the matte film, a 250 line/inch black line screen having an angle of 45° is placed on the same lith type film so that the emulsion layer of the black line screen and the photosensitive layer of the lith type film are in close contact with each other. They were overlapped in this manner, brought into close contact with each other using a vacuum pump in the printer, and irradiated with the same amount of light as that used to print the net positive.

Next, the lithium type film on which the net positive and black line screen had been printed was developed and fixed according to the instructions, washed with water, and dried. An automatic developing machine was used for these developing treatments.

In this way, the screen used in the present invention was obtained. This screen has positive halftone dots.
There were transparent lines in the area corresponding to the area where the halftone dots exceeded 50%, and there were no transparent lines in the area corresponding to the area where the halftone dots of the halftone positive were about 0% to 50%.

Next, the screen thus obtained was vacuum-adhered to a photosensitized carbon film using register pins in a baking frame, and irradiated with light from a high-pressure mercury lamp. The exposure amount at this time was 7 million lux/second.

Next, after removing the screen, the lithographic net positive used in making the screen was superimposed on the same carbon tissue using register pins so as to be in register with the printed image on the screen. In this case, a matted film with a thickness of 200 μm was inserted between the carbon tissue and the net positive. Next, these were vacuum-adhered and irradiated with light from a high-pressure mercury lamp. The exposure amount at this time was 1.7 million lux/second. Next, only the matted film was removed, and the net positive was brought into close contact with the carbon tissue.

At this time, the position of the net positive was made not to shift. Next, light was irradiated using a high-pressure mercury lamp. The exposure amount at this time was 5.7 million lux/second.
After the baked carbon tissue was exposed to light three times in this way, the gelatin layer of the carbon tissue was transferred to the copper cylinder whose surface had been degreased and rusted while applying pressure with a roller while pouring water on the cylinder.

Next, add 50 gelatin layers transferred to the copper cylinder.
A resist was formed by developing at a temperature of 0.degree. C. to dissolve and remove unhardened gelatin.

Apply corrosion-resistant resist to areas that do not require corrosion.
A mesh gravure printing plate was obtained by etching with a ferric chloride solution of 39°Be′ for 6 minutes.

The plate depth of the solid part of this net gravure printing plate is 27μ
The print depth of the 10% halftone area was 10μ.

When printing was carried out using this printing plate, printed matter with no noticeable moiré was obtained.

<Example 2> Instead of printing the net positive and matte film used in Example 1 on the lithium film, the net positive used in Example 1 was used to print on the carbon film, and the net positive had the same size and the same pattern. A halftone gravure printing plate was obtained in the same manner as in Example 1 except that a continuous tone positive was used to irradiate light at 25 lux for 5 seconds. The net gravure printing plate thus obtained was almost the same as the net gravure printing plate obtained in Example 1.

[Brief explanation of drawings]

Fig. 1 is a schematic plan view of a net positive for planography or letterpress printing, Fig. 2 is a plan view of a normal gravure screen, Fig. 3 is a plan view of a screen for net gravure plate making used in the present invention, and Fig. 4 is a plan view of a net gravure screen used in the present invention. A plan view of the black line screen, FIGS. 5 and 6 are illustrations of the state of printing on the positive photosensitive film, FIG. 7 is an illustration of the state of printing of the photosensitive film of the black line screen, and FIG. 8 is an illustration of the state of printing of the photosensitive film of the black line screen. 1A and 1B show cross-sectional explanatory views of the screen for net gravure plate making used in the present invention. 1... Halftone positive, 2... Halftone dot, 3... Transparent line, 4... Gravure screen, 5... Gravure screen used in the present invention, 6... Transparent line, 7...
...opaque area, 8...opaque line, 9...transparent part, 10...black line screen, 11...photosensitive film, 12...photosensitive layer, 13...continuous tone positive, 15...diffusion Seat, 16...
Net positive, 17... Base layer, 18... Emulsion layer, 19... Black line screen, 21... Transparent part, 22... Opaque part, 24... Emulsion layer, 25
...transparent line, 26...opaque area.

Claims (1)

[Scope of Claims] 1. A step of contact-printing a continuous tone positive film on a photosensitive film or diffusing halftone dots of a half-tone positive film, and a step of contact-printing a black line screen for gravure onto the photosensitive film. are applied in an arbitrary order, and then the photosensitive film is developed so that transparent lines are formed in the areas corresponding to the halftone areas from the shadow areas of the halftone positive, and transparent lines are formed in the areas corresponding to the light areas. A net gravure plate-making screen without the above net gravure plate-making screen and a net positive plate for planography or letterpress printing are bond-baked in any order in register with the photosensitive material for resist formation, and then the contact baking is performed. A net gravure plate making method comprising etching a gravure plate material using a photosensitive material for resist formation which has been completed. 2. The plate-making method according to claim 1, further comprising the step of contact-printing a continuous tone positive onto the photosensitive material for resist formation. 3. The plate-making method according to claim 1, further comprising the step of diffusing and printing dots of halftone positive for planography or letterpress on the photosensitive material for resist formation. 4. The plate making method according to claim 1, wherein the net positive printed on the photosensitive film and the net positive printed on the resist forming photosensitive material are the same.