FR2517438A1 - PROCESS FOR PREPARING PRINTING PLATES - Google Patents

Abstract

PROCESS FOR PREPARING PRINTING PLATES, IN WHICH A PHOTOGRAPHIC PRINTING OF A PHOTOSENSITIVE PLATE BY MEANS OF A COLORED PHOTOGRAPHIC FILM WHICH, AFTER BEING USED FOR COLOR PRINTING BY OVERLAYING TRANSPARENCIES, IS TRANSFORMED INTO A FILM OPAQUE 3D PRINTING BY COLORING OR PIGMENTING THE 2D IMAGES OF THIS FILM BY A COLORING AGENT 9 WHICH MAKES THESE IMAGES OPAQUE AT LEAST WITH A LIGHT WHOSE COLOR GOES FROM BLUE TO ULTRA-PURPLE.

Description

Process for preparing printing plates.

  The present invention relates to a process for preparing printing plates, in which the images on a colored film which has already been used for other purposes, are rendered

  opaque by coloring them so that a plate can be prepared

  than printing from a single film by reusing it.

  Colored films are widely used in industry.

  textile printing, cartography, ceramics

  and electronic, and to prepare photographic plates

  ques in the fields of printing A colored film is normally constituted by a transparent base film, typically polyester, coated with a tosensitive tuna layer, such as a diazo resin which serves as a binder,

  which layer can be colored or tinted with a pig-

  or a coloring matter to reveal the ima-

  ges produced by a photographic exhibition The images are normally semi-transparent and these colored films are commonly used for color printing by

overlay of transparencies.

  However, as these colored films, in particular those used for color printing by superposition of transparencies, are i uffisnîont opaque for directly printing a p Inc Pl

  printing we must reproduce the images of the colo-

  res on a monochromatic silver halide film for

  each base color before preparing the printing plate

  pressure Specifically, it is first necessary

  to print the images of a colored film on a mono- film

  chromatic with silver halide and then prepare a printing plate from the images on the film

  monochromatic silver halide.

  As is known, silver halide photographic films are relatively expensive, in particular because of the

  recent increase in the price of silver, and their treatment

  many long operations.

  Due to the drawbacks of the conventional process for preparing printing plates involving a color print by superposition of transparencies based on the color print by superposition of transparencies, a

  main purpose of this invention is to eliminate these inconveniences

  come and offer a new process for preparing

  printing plates that are simple, economical and reliable.

  In a process for preparing the printing plates according to the present invention, the photographic printing on a photosensitive printing plate is carried out by means of a colored photographic film which is transformed into an opaque printing film by coloring or pigmenting them

  images of this film with a coloring agent which makes the ima-

  opaque to light whose color is found

  in the range from blue to ultra-violet.

  According to a conventional method for preparing color selection printing plates comprising a color printing process by superposition of transparencies, two photographic films, a fundamentally transparent photographic colored film for color printing by transparency superimposition and a photographic film

  monochromatic opaque with silver halide for printing

  directly sea the images on a printing plate,

  were generally required for each background color

  mental. However, according to the present invention, colored films which would otherwise have been discarded after their use for color printing by superimposing transparencies,

  are reused as printing films for printing di-

  images on printing plates, images

  ges carried on these films being colored or pigmented again by means of coloring agents which make these images îO opaque at least vis-à-vis lights whose color will

  from blue to ultra violet, which colors are normal

  Also used to photographically print a printing plate. As a result, the process for preparing the plates is

  considerably simplified by the elimination of training

  tion of images from colored films on pho- to films

  monochromatic toography with silver halide and

  these relatively expensive silver halide films

teux.

  The invention will be better understood on reading the description.

  detailed description, given below by way of example only of a preferred embodiment, in conjunction with the attached drawing, in which: FIG. 1 is a sectional view of a colored film which is exposed photographically under a negative film , according to the present invention; FIG. 2 is a sectional view of an exposed film during development in an aqueous solution; FIG. 3 is a sectional view of a film developed during coloring or pigmentation in a tank; Figure 4 is a sectional view of a printing film in

  color by overlapping transparencies.

  FIG. 5 is a sectional view of a color printing film by superimposition of transparencies which has been colored or pigmented again in a tank; and the figure

  6 is a sectional view of a printing film which is

  tographically printed on a final printing plate.

  In Figure 1, we see a negative film 1 carrying the ima-

  ges 2 a to print The photosensitive film 3 a which must be

  used in the present invention, is prepared in application

  as for a photosensitive layer 5 of a diazo photosensitive agent or, as a variant, of a light-resistant agent (photoresist) on a transparent base 4 As shown

  this drawing, the negative film 1 is exposed to the photosensitive film

ble 3 a in close contact.

  As seen in Figure 2, as soon as these images of the exposed film are developed, we obtain a developed film

  3 b carrying only the fixed images 2 b with all the part

  unexposed tie of the photosensitive layer 5 removed.

  In FIG. 3, when this film developed for 3 h is processed by

  a coloring agent 7 containing, for example, a coloring agent

  in cyan (such as Sumifix Turquoise Blue H-GH @ from Sumitomo Chemical Co, Ltd) in a suitable tank 6, the

  fixed images 2 b become transparent images colo-

  rees in cyan 2 c, which are then washed with water and dried to obtain a color printing film by superimposing transparencies 3 c for the color cyan, as seen

in figure 4.

  After preparing the color printing films by superimposing transparencies of other colors (magenta,

  yellow and black) with dyes (using Aminyl Bril-

  binder Red F-4 B from Sumitomo Chemical Co, Ltd for magenta, Kayanol Milling Yellow 3 GW from Nippon Kayaku Co, Ltd for yellow, and Sumilian Black WA from Sumitomo

  Chemical Co, Ltd for black) and after their superimposition

  on top of each other for color printing by super

  transparency position, and, as soon as these films are treated in a suitable tank 8 with a black coloring agent 9 (such as Neutlan Black A from Yamada Chemical Co, Ltd) as seen in FIG. 5, the transparent colored images become black 2-opage images and, after washing the film with water and drying, we can then

  use this film as an opaque printing film 3 d.

  When this printing film 3 d is used to print images on a printing plate 12 constituted by an aluminum plate 10 coated with a photosensitive layer 11 which is then dried, a printing plate is obtained

color selection.

  As described above, according to this invention, the fact that after having used a photosensitive film 3 a for color printing by superposition of transparencies

  as color print film by overlay of trans-

  parences 3 c according to the known method, it can be reused as a printing film 3 d; in this case, a single film is enough to prepare a printing plate, thereby reducing the necessary expenses and eliminating the stage of manufacturing opaque printing film, as opposed to

  processes for preparing conventional plates.

  In the embodiment described above, the printing film is produced by a black coloring agent, but it is not necessary for this coloring agent to be black. For example, in the case of a cyan plate, a red coloring agent

  produces a black color In the case of a magen-

  ta, a red coloring agent produces a red color

  that blue or ultra-violet light cannot transmit.

  In summary, it is enough for the film to become opaque vis-à-vis a light whose color goes from blue to ultra-violet

  and which should be used to print the license plates

  final pressure In the case of a black plate, none

251 X 438

operation is not to be performed.

  In addition, in the above-described embodiment, the ffi Rm of color printing by superimposition of trasrce is pigmented after the images have been formed with cyan, magenta and yellow coloring agents, but it is likewise possible to expose a photosensitive film q / iuaâ é fully pigmented in advance and remove t Dxtes The parts not taken into account on the film

  (non-image part) other than images.

  The preceding description relates to films of t Lnrage in

  color by overlaying transparencies but it is.

  also possible to produce a 3 d printing film by pigmenting a drawing or color models for cards, piping and electrical circuits and for printing on textiles, ceramics and printed circuit boards so at the U / L / U Lzer for

  print a printing plate 12.

Claims (3)

Claims.   1 Process for preparing printing plates,   risky that a photographic printing is carried out on a photosensitive printing plate by means of a film   colorful photographic film that is made into a print film   opaque by coloring or pigmenting the images carried   on this film by a coloring agent which makes these images opaque   at least vis-à-vis a light whose color ranges from blue to ultra violet.   2 A method for preparing printing plates according to claim 1, characterized in that the colored images are formed on a photographic film for printing   color by overlapping transparencies.   3 Process for preparing printing plates according to the   claim 2, characterized in that the photographic film   that bearing the colored images has originally a layer of a-   gent photosensitive diazo or light-resistant agent (photoresist).