GB2112959A

GB2112959A - Originals for making printing plates

Info

Publication number: GB2112959A
Application number: GB08232748A
Authority: GB
Inventors: Shuji Kondo
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1981-11-30
Filing date: 1982-11-17
Publication date: 1983-07-27
Also published as: FR2517438B1; IT8224493A0; JPS6246851B2; DE3243724C2; FR2517438A1; IT1191104B; JPS5895348A; DE3243724A1; IT8224493A1

Abstract

Disclosed is a method of making printing plates in which photographic printing of a photosensitive plate is made by way of a dye photographic film which, after being used for overlay color proofing, is made into an opaque printing film by coloring or dyeing the images thereon with a coloring agent which makes the images opaque at least with respect to light having a color within the range of from blue to ultraviolet.

Description

SPECIFICATION Printing plates This invention relates to a method of making printing plates in which the images on a dye film which has been already used for other purposes are made opaque by coloring them so that a printing plate may be made from a single film by reutilizing it.

Dye films are widely used in the industries of textile printing, making maps, pottery and electronics, and photographic plate-making in the fields of the printing industry. A dye film is normally comprised of a transparent film base, typically made of polyester, coated with a photosensitive layer, such as diazo resin which serves as a binder, which may be colored or dyed with pigment or due to form the images produced by photographic exposure. The images are normally semitransparent and such dye films are commonly used for overlay color proofing.

However, as these dye films, in particular those for overlay color proofing, are not sufficiently opaque for directly printing a printing plate, the images on the dye films had to be reproduced on a silver halide monochromatic film for each basic color before making the printing plate.

Specifically, it was necessary first to print the images on a dye film on a silver halide monochromatic film and then to make a printing plate from the images on the silver halide monochromatic film.

As is well known, silver halide photographic films are relatively expensive, in particular due to the recent rise in the price of silver, and require laborious and time consuming steps for their processing.

In view of such shortcomings of the conventional method of making printing plates involving color proofing based on the overlay color proofing, a primary object of this invention is to eliminate or reduce these shortcomings and offer a new method of making printing plates which is simple, economical and reliable.

According to the present invention, a method of making printing plates is provided in which the photographic printing on a photosensitive printing plate is made by way of a dye photographic film which is made into an opaque printing film by coloring or dyeing the images thereon with a coloring agent which makes the images opaque with respect to light having a color within the range of from blue to ultraviolet.

According to a conventional method of making color separation printing plates including a process of overlay color proofing, two photographic films, a basically transparent photographic dye film for color proofing and an opaque silver halide monochromatic photographic film for directly printing images on a printing plate, were generally necessary for each basic color.

However, according to the present invention, dye films which are otherwise discarded after they have been used for overlay color proofing are reutilized as printing films for directly printing images on printing plates with the images thereon colored or dyed again by means of coloring agents which make these images opaque at least to light having a color within the range of from blue to ultraviolet which is normally used in photographically printing a printing plate: As a result, the plate-making process is drastically simplified through the elimination of the step of forming images from dye films on silver halide monochromatic photographic films and the use of silver halide films which are relatively expensive.

Other features and advantages of the present invention will become apparent from the following description and the appended drawings, in which: Fig. 1 is a sectional view of a dye film which is being photographically exposed under a negative film according to the present invention; Fig. 2 is a sectional view of an exposed film which is being developed in an aqueous solution; Fig. 3 is a sectional view of a developed film which is being colored or dyed in a tank; Fig. 4 is a sectional view of a color proofing film; Fig. 5 is a sectional view of a color proofing film which is being colored or dyed again in a tank; and Fig. 6 is a sectional view of a printing film which is being photographically printed on a final printing plate.

In Fig. 1, numeral 1 denotes a negative film carrying the images to be printed and numeral 2a denotes these images. Numeral 3a denotes a photosensitive film that is to be used in the present invention and it is made by coating a photosensitive layer 5 made of a diazo photosensitive agent or, alternatively, photoresist over a transparent base 4. As shown in this drawing, the negative film 1 is exposed to the photosensitive film 3a in close contact.

As shown in Fig. 2, once these exposed film images are developed, a developed film 3b carrying only fixed images 2b is obtained with all the unexposed part of the photosensitive layer 5 removed out.

As shown in Fig. 3, when this developed film 3b is processed by a coloring agent 7 containing, for instance, a cyan coloring agent (such as Sumifix Turquoise Blue H-GF() of Sumitomo Chemical Co., Ltd.) in an appropriate tank 6, the fixed images 2b turn into transparent cyan colored images 2c which are then washed by water and dried up to produce a color proofing film 3c for the cyan color as shown in Fig. 4.

After the color proofing films of the other colors (magenta, yellow and black) are prepared by coloring (using Aminyl Brilliant Red F-4B~ of Sumitomo Chemical Co., Ltd. for magenta, Kayanol Milling Yellow 3GW~ of Nippon Kayaku Co., Ltd. for yellow and Sumilian Black WA~ of Sumitomo Chemical Co., Ltd. for black) and overlaid one over the other for color proofing, and, once these films are processed in an appropriate tank 8 by black coloring agent 9 (such as Neutlan Black A~ of Yamada Chemical Co., Ltd.) as shown in Fig. 5, the transparent dye images turn into opaque black images 2d and, after the film is washed by water and dried up, the film can then be used as an opaque printing film 3d.

When this printing film 3d is used for printing images on a printing plate 12 made of an aluminum plate 10 coated with a photosensitive layer 11 which is then dried up, a color separation printing plate is obtained.

As described above, according to this invention, since after a photosensitive film 3a is used for color proofing as a color proofing film 3c according to the known method, it can be reutilized as a printing film 3d for printing, and only one film is required for making a printing plate, thus reducing the necessary cost and eliminating the step of manufacturing opaque printing films as opposed to conventional platemaking methods.

In the above-described embodiment, the printing film was produced by a black coloring agent but the coloring agent need not be black.

For instance, in the case of a cyan plate, a red coloring agent will produce a black color as a result. In the case of a magenta plate, a red coloring agent will produce a red color which blue or ultraviolet light can not transmit through. In short, it suffices as long as the film becomes opaque with respect to light having a color within the range of from blue to ultraviolet which is to be used for printing the final printing plates. In the case of a black plate, nothing need be done.

Moreover, in the above-described embodiment, the color proofing film was dyed after the images are formed by cyan, magenta and yellow coloring agents but it is likewise possible to expose a photosensitive film which has been wholly dyed in advance and remove all the extraneous part on the film (non-image part) other than images later.

The preceding description was made with reference to overlay color proofing films, but it is also possible to produce a printing film 3d by dyeing a color drawing and patterns for maps, piping and electric circuitry and textile printing, pottery and printed circuit boards so as to use it for printing a printing plate 12.

Claims

1. A method of making printing plates, wherein: a photographic printing on a photosensitive printing plate is made by way of a dye photographic film which is made into an opaque printing film by coloring or dyeing the images thereon with a coloring agent which makes the images opaque at least with respect to light having a color within the range of from blue to ultraviolet.

2. A method of making printing plates according to claim 1, wherein the dye imates are formed on a photographic film for overlay color proofing.

3. A method of making printing plates according to claim 2, wherein the photographic film carrying the dye images originally has a layer of a diazo photosensitive agent of photoresist.

4. A method of making printing plates substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.