JPS614062A - Direct plate making method - Google Patents

Abstract

PURPOSE:To perform direct plate making with high resolution in daylight by superposing a contact screen and a printing plate one over another in a light shield state, exposing a continuous tone part of an original where continuous tones and lines are present together in a contact state, and taking only the screen out of a light shield part in the light shield state and exposing a line part. CONSTITUTION:The original has a continuous tone image and a line image together and the contact screen 6 and printing plate 1 are mounted on the mount table 5 of a photosensitive planographic plate 1 one over another in daylight; and the plate is exposed to the continuous tone image in a vacuum contact state and only the contact screen 6 is drawn out of a light shield cover sheet 7 in the light shield state. Then, the plate is exposed to the line image. In another way, the printing plate 1 is exposed to the line image and the screen 6 is inserted into the light shield cover sheet 7 in the light shield state and stacked, the plate is exposed to the continuous tone image in the vacuum contact state, and then the plate making process of the printing plate 1 is carried out. Thus, direct plate making, specially, multicolor direct plate making is easy carried out in daylight through said operation and numbers of printed bodies which are faithful to the original and have high resolution are obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industry> 2 Field of Application The present invention relates to a Gyleft plate-making method, particularly a multicolor Gyleft 1 plate-making method.

<Prior art and its problems> Today, a wide variety of lithographic printing plates are known and put into practical use. Examples include presensicized plates (so-called PS plates) using diazonium compounds, electrophotographic printing plates using zinc oxide or organic photoconductors, and silver salt photolithographic printing plates using silver halide emulsions. It is listed as a typical example. In particular, lithographic printing plates with high photosensitivity, such as the latter three, can be easily and quickly made using an automatic plate making machine, from photographing the document to be printed to processing. It has become rapidly popular as a lithographic printing plate suitable for

In particular, lithographic printing plates for direct plate making using silver salt as a photosensitive component are useful because they have extremely high photosensitivity, contrast, and resolution.

Lithographic printing plates for direct plate making have such excellent properties and have improved in quality. Until now, multicolor color printing plates have been produced using direct plate making methods from continuous tone color originals such as multicolor color photographs. Obtaining printed material had not been realized. There are various possible reasons, but one important one is
The image reproduction ability and printing durability were significantly inferior to those of the 18th edition. In other words, the 18th plate prints from an expensive lithographic film as an intermediate manuscript; high image reproducibility can be obtained by one print, whereas the direct plate printing method produces inferior images because it is photographed with a camera through a lens. It is well known that only reproducibility can be achieved.

Furthermore, as described in JP-A-48-89 (107), plate-making cameras have a built-in prism or reflective mirror in order to obtain correct prints on the left and right sides of the image. After all, (□1.□□(fs%-y 7.yu, 7,
□6i, 5.6o, and 6i, all commonly used plate-making cameras use a method of photographing using reflected light. Therefore, the originals to be used include characters and lines (characters and lines) created with high-contrast image-forming materials using light-impermeable supports such as phototypesetting paper and carbon paper using the silver complex diffusion transfer method.
These are only so-called reflected images, such as line images) or images obtained by converting continuous tone images such as photographs into halftone dot images (this is called halftone images), and these irregular images can be used to create a desired composition. The reality was that the manuscript was made after reviewing it.

When such a halftone dot reflection image plate is used as a manuscript and is directly plate-made using a silver halide lithographic printing plate or an electrophotographic lithographic printing plate, the number of halftone dots per inch is 80, or at most 100 lines per inch. Point images could only be reproduced to an acceptable degree for practical use.

Therefore, in conventional multicolor direct plate making,
As a draft manuscript for color printing, it was not only necessary to create multiple black and white dot reflection images using panchromatically spectrally sensitized continuous tone film for color separation or lithography, but also Even if color printing is performed using a lithographic printing plate obtained by a direct plate making method using a defective original containing a mixture of halftone dot images and line images, only color printed images with unsatisfactory image reproducibility can be obtained.
The printing durability was also not sufficient.

In addition, in the direct plate making method, it is preferable to make plates under bright room light like in conventional plate making machines. It was not possible to make a lithographic printing plate.

<Object of the invention> The object of the present invention was made in view of the above circumstances, and it is an object of the present invention to improve direct plate making, especially multicolor direct plate making,
To provide a method capable of obtaining a larger number of printed matter with high resolution and faithfulness to the original at low cost by simple operation and preparation of a draft manuscript under bright room light.

<Structure of the Invention> As a result of intensive research, the present inventors have found that the object 1- can be achieved by the method shown below.

In other words, the present invention provides a die-left plate-making method in which imagewise exposure of a photosensitive lithographic printing plate and plate-making processing are carried out under bright room light, in which an original containing a mixture of continuous tone images and line images is printed in at least one of the printing plates. The printing plate is exposed to light, and at that time, the contact screen and the printing plate are placed in a superimposed manner on a mounting table of the printing plate that is shielded from light by at least a light-shielding cover sheet of the printing plate, and the contact screen and the printing plate are placed in a vacuum-adhesive state. After exposing the continuous tone image and pulling only the contact screen out of the light-shielding color sheet while keeping it in a light-shielded state, exposing the line image, or (I) after exposing the line image on the printing plate. , the contact screen is inserted into the light-shielding cover sheet to overlap the light-shielding book, and a continuous tone image is exposed in a vacuum-adhered state, and then the printing plate, which has completed the exposure of the original, is transferred to a plate-making processing section. This is a direct plate-making method characterized by transporting the plate to a plate-making process.

The present invention will be explained in more detail below.

The present inventors have been diligently researching ways to improve the image reproducibility of direct plate-made lithographic printing plates, but it is certain that the reason for the poor image reproducibility is due to optical systems such as lenses and reflective mirrors. However, even if optical systems such as lenses or reflective mirrors are used, and even if the original is a reflective original, i.e., a continuous-tone reflective color image, a photosensitive layer that is spectrally sensitized in a panchromatic manner can be used. They discovered that if color separation exposure is performed with the lithographic printing plate and contact screen in close contact with each other, high-quality color printed matter comparable to the reproducibility of the 18th plate can be obtained.

Furthermore, the lithographic printing plate obtained in this manner had a higher printing durability than a lithographic printing plate produced by a conventional plate-making method, and was capable of printing a large number of sheets in color. In other words, the use of a contact screen enables direct plate making of multicolor originals, and also allows the contact screen to be used under bright room light (i.e., when the photosensitive lithographic printing plate is shielded from light by a light-shielding cover sheet without having to be rewound into a cassette or the like). If you pull it out of the light-shielding cover sheet while it is still fixed on the mounting table, or insert it inside the light-shielding cover sheet,
Thanks to this innovation, it is possible to photograph originals containing both continuous tone images and line images with simple operations.In particular, in multicolor color direct plate making, there are many printed materials with excellent positional accuracy of each color plate and good color image reproducibility. It is designed so that you can get one.

The lithographic printing plate used in the present invention may be a silver halide photolithographic printing plate, an electrophotographic lithographic printing plate, etc. as long as it has a so-called panchromatic spectral photosensitive layer that is sensitive to blue, green, and red light respectively. The type of the photosensitive layer does not matter.

For example, in the case of a lithographic printing plate using a silver complex diffusion transfer method, from among the spectral sensitizing dyes represented by the general formula described in JP-A-53-21601, the green sensitive region, the red sensitive region, and the necessary The one that spectrally sensitizes the blue-sensitive region can be selected and used.

However, although the present invention is suitable for multi-color direct plate making, it is clear that it is also useful for conventional monochrome direct plate making.

Next, the direct plate making method of the present invention will be explained with reference to the drawings.

<Example> Production of a photosensitive lithographic printing plate A silver chlorobromide gelatin emulsion containing 3 mol % of silver bromide was produced by a conventional method. This silver halide has an average grain size of 0.4 μm.
Met. After chemical sensitization, the following dyes (1) to (3) were added to perform panromantic optical sensitization. A stabilizer, hardener, and coating agent were added to form a coating solution.

An antihalation layer of carbon black containing silica particles with an average particle size of 7 μm, hydroquinone and phenidone was provided on a subbed-treated polyester film of 100 μm, and the emulsion layer (AgN0315 g/l112
) was established.

Dye (1): 90 mg/silver halide 1 mol I
SO3, hsoρ Dye (2): 700mg/1 mole of silver halide color! (3): 500 mg/1 mole of silver halide A physical development nucleus layer containing palladium sulfide was coated on this emulsion layer to prepare a lithographic printing plate.

Exposure and Plate Making Process FIG. 4 is a side view showing an example of a bright room plate making machine suitable for carrying out the method of the present invention. 1 to 3 show partially enlarged views of the plate-making machine shown in FIG. 4. In FIG. 4, 21 is a base frame, and this base frame 21
” n = i 22 e fixedly installed on the second side, lens 23 and dark box 22
A lens rack 25, an optical device 26, and a document rack 27 are slidably mounted on this frame 21''. It is desirable to provide a light source device (not shown) for transmission exposure on the back side of the document rack 27 in addition to the light source device 26 for reflective exposure. A color separation filter rack (not shown) is provided between the lens 23 and the bellows 24,
Each color separation filter can be removed as a rotating set. The color separation filter rack may be located in front of the lens 23. An image reversing mirror 28 is fixed in the dark box 22, and a photographing section 3 is provided on the +1 side of the dark box 22.

The photosensitive planographic printing plate 1 is transported from the cassette 2 containing it to the photographing section 3 and exposed. At the end of exposure 1,
Engineering 6. I1IrJi, 1 + 1. . 17,71 Yu,
, 1□ 11th B. The plate is transported to a plate-making processing section 40 which has a built-in diagonal such as a desensitizing tank and is processed to complete the plate-making.

1 to 3, a mounting table 5 made of a transparent glass plate is provided on the base 4 of the photographing section 3, and an original image is formed on the upper surface of the mounting table 5. The mounting table 5 may be not only horizontal but also inclined. On one side of the base 4, the printing plate 1 is fed onto the mounting table 5 with the end of the printing plate being clamped, and the printing plate 1 with the dew point completed is sent to the plate-making processing section 40. A pair of supply/discharge rollers 11/11 are provided for conveyance.This supply/discharge roller 11/1
1 is connected by a guide 29 to a cassette 2 that stores the printing plate 1 in the form of a roll, and when the printing plate 1 of a required length is sent out from the cassette 2 by a feed roller 32, the cassette 2 is The printing plate 1 is cut by manually operating a handle 33 of a movable rotary cutter 31 provided near the printing plate outlet 30. The feed roller 32 and the supply/discharge roller 11 are configured to be interlocked by a drive device (not shown), and the cutter 31 can also be interlocked as required.

In FIG. 2, the cassette 2 may be provided on the opposite side of the pair of feed/discharge rollers 11 and 11 to the plate making processing section 40 to feed the plate. It may have a pair.

In addition, in FIG. 1, the light-shielding base frame 9 is arranged so that it can be opened and closed with a hinge 34 relative to the base 4, and its cross section is formed in a substantially U-shape that opens downward (towards the base 4). has been done. As shown in FIG. 2, a frame member 8 having an I-shaped cross section and having a light-shielding cover sheet 7 stretched thereon is attached to this opening 10. It is fixed within the opening 10 of the base frame 9, and the opposite side is attached within the opening 10 so as to be movable in the vertical direction as appropriate via adjustment means such as a cam 36, and as described later, If necessary, the space formed by the mounting table 5 and the light-shielding cover sheet 7 can be adjusted by adjusting means such as the cam 36, etc.
For example, by rotating the grip 36', the light-shielding cover sheet 7 on the side to which the printing plate 1- is supplied can be appropriately restored.

Further, a light-shielding base frame 9 in which the printing plate supply/discharge roller 11 is provided
A roller 12 made of an elastic material is provided on the adjacent side of the base 4, that is, on the front side of the base 4, as a light shielding means when the contact screen 6 is taken out. Rotatably arranged inside.

One side of the contact screen 6 is attached to a screen frame 37 having a handle 38. When installing the contact screen 6, first hold the handle 39 of the light-shielding base frame 9 and press it as shown by arrow A. The screen frame 37 is placed on the mounting table 5 with the screen frame 37 being fixed to the reference side 42 provided on the base 4. At this time, the light-shielding base frame 9 is maintained in the open state by a spring member (not shown) provided at the hinge 734.

First, the light shielding base frame 9 is opened and the contact screen 6 is placed on the mounting table 5 from the direction of arrow B. This sharpening contact screen 6 is connected to the lower roller 1 disposed on the base 4.
2 and guide it, place it on the mounting table 5] 2, and set it so that the screen frame 37 is fixed in contact with the reference side 42 as described above.

Next, when the light-shielding base frame 9 is closed, the contact screen 6 is held between the pair of rollers 12, which are the light-shielding means, and the space covered by the mounting table 5 and the light-shielding cover sheet 7 becomes light-tight. Please note that this light density is
For example, as shown in FIG. 3, a light-shielding cover sheet 7 is stretched and a bank-like light-tight member 41 made of sponge or the like is pasted around the lower surface of the L-shaped frame member 8. You can also do this. Next, before placing the photosensitive lithographic printing plate 1 on the mounting table 5, the frame member 8 on the side that supplies the printing plate 1 is lifted up by the adjusting means. Next, the feed roller 32 of the cassette 2 is driven (at this time, the feed/discharge roller 11 also operates) to feed the printing plate 1 to a required degree of quality.After the feed roller 32 and the feed/discharge roller 11 are stopped, the cutter 31 drives the printing plate 1. The printing plate 1 is cut.

(When the cutting of the photosensitive planographic printing plate 1 is completed, only the feeding roller 11 is further driven to feed the printing plate 1 onto the contact screen 6 placed on the mounting table 5 with the photosensitive surface facing down. The feeding is in a superimposed state. When the feeding is completed, as shown in FIG. This is to prevent the contact screen 6 from being misaligned when the contact screen 6 is taken out.

Next, the grip 36' of the adjustment means is operated to adjust the frame member 8.
Lower the light-shielding cover sheath 7 stretched over the mounting table 5, and drive a vacuum suction device such as a vacuum pump (not shown) to evacuate the space surrounded by the mounting table 5 and the light-shielding cover sheath 17. The placed contact screen 6 and the printing plate 1 are brought into close contact.

The manuscript shelf 27 contains continuous tone multicolor photographs and text (
The manuscript is prepared with a mixture of black).

In order to print the heading letters A in red, the heading letters B in green, and the text C in black, the yellow plate, magenta plate, cyan plate, and black plate were each exposed under the following conditions. When exposing using the contact screen described in item 1 above, text originals were masked, and when exposing text originals, photographs and unnecessary text originals were masked.

■ indicates with a contact screen, ■ indicates without a contact screen.

The photographic original was given 7 lash exposures (f) in addition to the main exposure time (Et). All exposures were performed with an aperture of r-16. The contact screens used were GCDN 150ρ/inch manufactured by Dainippon Screen Mfg. Co., Ltd. with different screen angles (15° for cyan, 45° for magenta, 0° for yellow, and 75° for black). .

In the exposure of each color plate, the photographic original is first exposed through the contact screen, and then, before exposing the line drawing characters to the same plate, the close contact with the vacuum suction device is released, and the handle 38 is released. to pull out the contact screen 6 outside the photographing section 3. In addition, since the contact screen 6 is held between the pair of rollers 12, the light density inside the photographing section 3 is not impaired.
Further, since the pair of supply/discharge rollers 11 and 11 are in a state where the terminal end of the printing plate 1 is held between them, no positional deviation occurs.

Furthermore, in order to release the vacuum adhesion state, it is preferable not only to stop the vacuum suction device, but also to use a device equipped with an air supply function as the device to quickly release the vacuum adhesion state. Quick and complete release of the vacuum adhesion state is achieved by water retention (prevention of scumming) as in the above-mentioned photosensitive lithographic printing plate.
It is also effective in preventing scumming and damage to the contact screen due to friction when pulling out the contact screen 6, when the powder contains the powder for the purpose of improving contact screen 6.

Thereafter, the vacuum suction device is driven again to bring the printing plate 1 into close contact with the mounting table 5, and a line drawing is taken.

The color plates for which the exposure of the original document was completed in this manner were conveyed in sequence to the plate-making processing section 40 containing the following plate-making processing liquids by the progressive drive of the feeding roller 11, and subjected to plate-making processing.

[Transfer developer 1 Water 700d Potassium hydroxide 20g Anhydrous sodium sulfite 50g 2-mercaptobenzoic acid 1.5゜2-methylaminoethanol
Add 15g of water to make 1Q.

([Neutralizing solution 1] Water 600d, phosphoric acid 10g Sodium citrate 35g Froidal silicate (20% liquid) 5v7! Ethylene glycol 5d Add water to bring the total volume to 11.

[Degreasing liquid 1 water 60011
7! Isopropyl alcohol 400xl Ethylene glycol 5()g3-Mercapto-4-acetamido-5-〇-hebutyl-1,2,4
, - Triazole 1g When each of these lithographic printing plates was overprinted using offset printing ink of the corresponding color, the dot area ranged from 5% to 95% not only for text manuscripts but also for multicolor manuscripts. It is a print with good color reproducibility, and more than 30,000 copies.
It had the second highest printing durability.

The direct plate making method of the present invention is based on the first method described above.
The present invention is not limited to the embodiment using the plate making machine shown in FIGS. 4 to 4 and partially modified thereof, but includes various applications and modified implementation methods.

In FIG. 1, the pair of rollers 12, 12 for pulling out the contact screen 6 may be provided on the side of the printing plate 1 facing the pair of supply/discharge rollers 11, 11. Further, similar roller pairs may be provided on the opposite sides of the roller pairs 12, 12 in FIG.
Connecting more than one type of contact screen with a transparent sheet (2
In the case of "Insert" 2, a transparent sheet is provided between each contact screen) By using a long object, the line image is first exposed on the printing plate 1, and the transparent sheet is placed under the printing plate 1. ), then the elongated object is moved and a predetermined contact screen is inserted under the printing plate 1 to perform screen exposure of the continuous tone original image. Furthermore, this method does not necessarily require the pair of rollers 12 and 12 that form a light-shielding (light-tight) state together with the light-shielding cover sheet 7; for example, a light-shielding flexible material (such as sponge) to which the light-shielding cover sheet 7 is attached is used. Is it possible to replace it with a shading cover sheet? It is also possible to form a light-shielding state by using only the light-shielding state.

In the above-mentioned embodiments, the frame member on which the light-shielding cover sheet is stretched is pulled up 97 times when the printing plate is fed and placed on the mounting table, but in the present invention, for example, Directly on the shading base frame itself! A light-shielding cover sheet may be stretched and the frame member may be omitted.

Reference Example For reference, 150ρ/
A magenta plate was prepared in the same manner using the lithographic printing plate described above, except that a contact screen and 7-lash exposure were not used, and a magenta plate was prepared using an original with an inch halftone image (5% to 95%) and printed. When I tried to reproduce 50% of the halftone dots, the highlights (5 to 20% of the halftone dots) were not obtained, and some of the shadows (80 to 95% of the halftone dots) were crushed, resulting in a total of 20,000 sheets. The halftone image would be blown out by the time it was printed. <Effects of the Invention> The direct plate making method of the present invention has the following excellent effects.

(b) By using a contact screen in a photosensitive lithographic printing plate for direct plate making, halftone images of 133 lines/inch or more, which was previously impossible to reproduce, can be reproduced well, and printing durability can be improved. My strength has also improved.

(b) It has become possible to use a direct plate-making method that can produce high-quality multicolor printed matter.

(c) There is no need to create a draft manuscript by converting a continuous tone image into a halftone image, thereby reducing labor and improving economic profits.

(d) Since it becomes possible to pull out or insert the contact screen under bright room light, that is, in a light-shielded state,
Continuous-tone images and line images can be exposed while the photosensitive lithographic printing plate is fixed on the mounting table, and the positional accuracy of these images is also improved. This is effective for plate making methods.

(e) Work efficiency is high because plate making can be performed in a bright room with extremely simple operations.

[Brief explanation of drawings]

FIG. 4 is a side view showing an example of a bright room plate-making machine that can be used when carrying out the direct plate-making method of the present invention, and FIG. 1 is a partially cutaway perspective view of the photographing section in FIG. 4. FIG. 2 is a side sectional view of the photographing section, and FIG. 3 is an enlarged view of the main part of FIG. 1... Photosensitive planographic printing plate, 2... Cassette, 3...
... Photographing department, 5... Mounting table, 6... Contact screen, 7... Light-shielding cover sheet, 1
DESCRIPTION OF SYMBOLS 1... Printing plate feeding roller, 12... Contact screen clamping roller pair, 40... Plate-making processing section.

Claims (1)

[Claims] (1) In a direct plate-making method in which imagewise exposure to a photosensitive lithographic printing plate and plate-making processing are performed under bright room light, an original containing a mixture of continuous tone images and line images is exposed to at least one of the printing plates, At that time, (a) the contact screen and the printing plate are placed in a superimposed manner on a mounting table of the printing plate that is shielded from light by at least a light-shielding cover sheet of the printing plate, and a continuous tone image is exposed in a vacuum-adhered state. (b) After exposing the line image to the printing plate, after only the contact screen is pulled out of the light-shielding cover sheet while it is still in the light-shielded state, or (b) after the line image is exposed on the printing plate, the contact screen is left in the light-shielded state. A contact screen is inserted into the light-shielding cover sheet and placed in an overlapping manner, a continuous tone image is exposed in a vacuum state, and the printing plate, which has completed exposure of the original, is conveyed to a plate-making processing section for plate-making processing. Characteristic direct plate making method