FR2698973A1 - Image creation of photosensitive material on printing plates by a jet printing device or other scanning printing device. - Google Patents

Abstract

The present invention relates to a printing plate manufacturing method which simplifies and reduces the time required to prepare and manufacture the plates for use in a lithographic printer (2). The method produces an image of photosensitive imaging material directly on the printing plate (1) using a jet printing device (4) or other scanning printing device such that a when cured by exposure to radiant energy (40), the image material sprayed onto the surface of the plate allows the plate to receive and transfer ink to a blanket or substrate through a treatment of lithographic printing.

Description

The present invention relates to a device and a method for setting

  work of the latter to create a graphic and / or text on plates intended to be used in a printing press by lithography, and relates more particularly to such a device and such an implementation method in which the plates The prints are transformed into an image using a jet printer which deposits a photo-hardening material on the receiving surface of the printing plate at the locations prescribed by digitized data representing the graphic and / or the text to be printed. In off-set printing presses, printing plates are used to print an image and / or text on a substrate, such as paper, first causing the plate to be inked and then to be pressed against a rubber blanket to transfer the ink which is distributed on the substrate, to transfer the ink located on selected zones of the plate until on the substrate The manufacture of the plates

  printing can be done in many ways.

  One of the most common ways to manufacture such plates is the use of a standard photo-lithographic treatment. The plates used in this treatment are commonly formed from a self-supporting material, usually a metal. ie aluminum, on which a layer has been covered which is soluble by a solvent, such as water, but which becomes insoluble after being exposed to light A transparent mask forming a negative image is placed in contact on the covered plate, usually in a vacuum frame, and the underlying soluble material is then selectively exposed to light Light passes through the transparent areas of the mask and polymerizes or otherwise changes the coating making it insoluble Then, the masked parts of the plate can be and are cleaned using a subsequent application of suitable solvent leaving the material affected by light as distinct image areas on the plate Dissolving the coating is often a source of problems This treatment undesirably requires complete removal of the soluble layer from the area of the plate not forming image Complete removal of the soluble layer from the area of the non-imaging plate is not often achieved, thereby causing contamination of these areas through residual material from the solubilized material. cleaning often are

  harmful to human respiration and / or ingestion.

  Also, in the case where a printing pressure is used to publish a newspaper and where the urgency of the article to be printed is of first priority, this washing step undesirably adds time for this treatment already consuming time Therefore, it is very important that the material arranged has a fast processing capacity with minimal use of solvent. Until now, tests have been carried out to simplify the preparation of printing plates. Such a test has been carried out in the manufacture of lithographic plates without water as described in the US patent.

  4,003,312 issued January 18, 1977 to Gunther.

  In a first method of this patent, a printing plate manufacturing process is described in which light-sensitive hardenable silicone is applied as a layer on a template and the layer is selectively covered using of an opaque substance such that the uncovered parts are then cured by exposure to radiant energy. After this, the removal of the uncured silicone is accomplished by usual means such as washing with a suitable solvent L the step of removing the silicone layer by washing it with a suitable solvent often involves the use of pollutants inherent in the solvents which are used to wash the plate Also, while such washing steps, for the most, adequately remove most of the deposited layer, there are often traces or residual material on the plate, especially when the plate has been roughened by granulation, consequently leading to skimming and a reduction in the lines defining the impression. In another embodiment, it is indicated to coat a template with silicone, to cure the silicone and then to

  transform the silicone into an image using a photo-

  polymer which combines with cured silicone to create ink-receiving areas thereon Again, the coating and subsequent curing treatment of the silicone are steps which add both time and cost to the manufacturing treatment Also, certain characteristics of the cured silicone coating, such as surface tension, can vary from one plate to another plate, thus introducing a

  uncertainty about print processing.

  In an attempt to create plates with areas indicated by digitized data, which must be made oleophilic (accepting oil) therefore leaving the remaining hydrophilic (accepting water), inkjet printers have been used to deposit, for example, an oleophilic ink on a plate in accordance with the data representing point by point a location on which the oleophilic ink must and must not be deposited An example of such a device is described in US Patent 4,833 486 issued May 23, 1989 in the name of Zerillo The oleophilic ink transformed into an image on the plate does not lend itself by itself to extensive repeated use, in comparison to an image material which consists of a polymer or a

hardened resin.

  Although the production of an image on the plates does not necessarily need to be carried out when the plate is mounted on the printing press, there are several favorable aspects for producing the image in this way. An advantage is constituted by the fact that '' there is no movement of the plate for correct alignment to be achieved after the plate has been mounted on the machine Also, since the plate is provided with an image on the roller or cylinder in position on the press, the alignment between the plate and the roller is always maintained This is particularly beneficial in the case of a multi-color printing press in which several rollers forming plates are provided, each intended to apply a colored ink

  indicated on a substrate, in a specified area.

  The digitally formatted data representing the image to be printed is quite suitable for driving an automatic spray jet printer. At the start, an original which is scanned and entered into a computer in digital format can be set up. the scale for desired dimensions using an appropriate computer program to obtain the change of dimension The digitized data are furthermore stored in a memory thus avoiding the need to keep films forming originals which are often large and occupy space file In addition, the stored data is not subject to modifications due to shrinkage or other variables which could otherwise act on them, such as the time spent in the box where the negative film is stored. in the form of digitized data, the image is capable of being distributed to several printing stations, including multiple image processing stations in a multi-color printing press as described above Ultimately, the advantages inherent in digitally formatted graphics allow enhanced separation of colors to be executed by appropriate software to determine the paths between colors Consequently, when colored images are introduced via scanners which separate the colors for yellow, magenta, cyan and black inks used in printing, transparency for each sensitive plate intended to apply a different color is required to ordinary way, which is not the case for digitally stored data for lithographic plates for image creation of

direct way.

  Accordingly, it is an object of the present invention to provide a predictable, low cost device for creating image plates for use in an off-set printing device in which means are provided in the device for quickly positioning the image-forming material without requiring the use of chemicals or other pollutants known hitherto for use in the

  processing to produce a plate.

  It is another object of the present invention to provide a device of the type mentioned above which eliminates the step of removing the coating areas originally deposited on the plates using a jet printing device sprayed to deposit ink receiving material on an uncoated plate. It is yet another object of the present invention to eliminate the use of transparencies which would otherwise be used to display a plate and consequently eliminate the relevant costs of handling and developing the film used to create

the transparency.

  Yet another object of the present invention is to provide a device and an implementation method of the type mentioned above for off-set image printing plates in which the drawing, the graphic and / or the text to be represented is digitally formatted as code which can be used by the machine to drive an image creation device or which is mathematically modified in accordance with dimensional considerations for

  plate which must be transformed into image.

  Another object of the present invention is to reduce inaccuracies resulting from changes in the size of the photographic film during development, misalignment of the film during exposure, and other manipulations of the film during processing.

plate manufacturing.

  The invention relates to a device and an implementation method simplifying and reducing the time necessary for preparing and manufacturing plates for use in an off-set printer. The method for manufacturing a printing plate of the type in which a material is transformed into an image on a surface of the plate in order to receive ink and subsequently allow the transfer of ink onto a substrate comprises the steps of: providing a plate having an upper surface forming a base and providing a device jet printing having a jet head capable of covering selected parts of the upper surface of the plate with an imaging material while leaving other parts of the upper surface bare

  of plate Provide a source of photo- liquid material

  reacting in the jet printing device and

  using it as an imaging material.

  Provide data defining a graphic and / or text to be printed on a substrate and process the data in a computer to generate machine operating data defining selected parts of the upper surface forming the base of the plate to be covered using the imaging material and other parts not to be covered by this material Use machine operating data to control the jet printing device to deposit some of the liquid imaging material on the surface upper base so as to cover the selected portions of the upper base surface of the plate with liquid imaging material, and exposing the imaging material to radiant energy to

form a hardened image.

  We will now describe the present invention, by way of example only, with reference to the accompanying drawings in which: FIG. 1 is a partially cutaway perspective view showing a device constituting an embodiment of the present invention, FIG. 2 is a vertical sectional view taken through the device of FIG. 1, FIG. 3 is a perspective view of the print head and the associated plate cylinder, the plate cylinder being shown separated from its support structure , Figure 4 is an alternative embodiment of the device according to the present invention in which the printing press is capable of printing in several colors, Figure 5 is a perspective view of an embodiment of a plotter image on a drum-type plate, FIG. 6 is a perspective view showing another embodiment of a plotter used for image printing plates, FIG. e 7 is a side view of a third embodiment of the printing plate plotter, Figures Sa to Sc show different

  embodiments of digital formatting of a drawing.

  Figure 1 shows a printing device 2 constituting an embodiment of the present invention, comprising a jet printing device 4 and an associated control device 6 In the embodiment shown in Figure 1, the device d jet printing 4 is mounted in an offset type printing press 8 in order to create an image directly on the printing face 3 facing outwards from a

  cylinder 1 which was previously mounted in the machine.

  The off-set press 8 has a cylinder

  plate or roller 10 which supports the printing plate 1 using conventional mounting means 5 which include means for pulling the plate strongly on the roller 10, a printing roller 9 and a blanket roller 12 interposed between the plate roller and the printing roller 9 and cooperating with the roller 10 forming a cylinder to engage a substrate therebetween Ink rollers 14 are also

  designed to cover selected areas of the carrier roll

  plate 10 using ink while fountain rollers 16 are provided to moisten the other areas of the plate roller with a non-ink liquid during a printing operation The plate roller 10 , the blanket roller 12 and the printing roller 9 are each connected in a driving manner to a printing drive motor 7 so as to cause the blanket roller to rotate in opposite direction synchronously with respect to the two rollers plate and printing carrier when the drive motor 7 is actuated In this way, the plate roller distributes the ink on the blanket roller and after this, the blanket roller prints on the substrate 18 when the substrate is brought to pass between the blanket and printing rollers The fountain rollers 16 and the ink rollers 14 are mounted freely rotating on the press and are associated to rev selectively stretching the respective areas of the plate 1 using an ink-rejecting material and an ink-receiving material In the case of the ink rollers 14, an ink adheres only to the areas of the plate 1 which are rendered ink receiving previously by spraying a photosensitive liquid using the jet printing device 4, which is followed by exposure to actinic radiation as will be described below The rollers 16 forming a fountain are active for applying a liquid solution to the plate 1 to reinforce the definitions of a line and to reduce skimming, that is to say ink reception by areas which do not form an image of the plate A scrub roller 17 is also provided when it is desired to coat the plate 1 with gum arabic, after the plate 1 has been sprayed by the printing device 4 and exposed The scrub roller 17 is mounted in a movable manner on the press 8 between retracted and extended positions, extended position in which the scrub roller is in contact with the plate roller 10 for applying the eraser to the

plate receiving areas.

  A supply of sheets of substrate material 18 to be printed, usually paper, is provided at the reference 20 on the press and advances

  through it during a print operation.

  As shown in Figure 2, a single sheet of substrate material 18 is drawn through the press during a printing operation such that it is caused to pass between the printing roller 9 and the blanket roller 12 and is then pressed directly against the inked surface of the blanket roller to effect the transfer of ink from the inked areas located on the blanket roller to the substrate. In an alternative form, the press 8 may not include the roller 12 blanket interposed between rollers 10 and 9 forming plate and printing, but instead only includes the rollers forming plate and printing so that the substrate material is caused to pass directly between the rollers 10 and 9 forming plate and printing

to print.

  According to the present invention, as can best be seen in FIG. 3, a jet print head 22 is arranged with each printing device 4 and is mounted to move transversely to the direction of flow of the paper T , on slides 24, 24, which overhang the associated plate forming roller The jet head 22 is a commercially available standard jet printing head, which can be a device of the continuous pulse type or of the pulse type by pressure One such commercially available printing device capable of such use is Model 500 Deskjet manufactured by Hewlett-Packard Co. As a variant, the jet head 22 can be a jet of the piezoelectric type, as described in the US patent. no 4 599 626 entitled INJECT DROP EJECTION HEAD, issued on July 8, 1986 in the name of Léonard G Rich The jet head is fixed on a carriage 26 and is driven along the slides 24, 24 by a mo trolley drive 28 Control means 30 are arranged to coordinate the transverse movement of the trolley 26 with the rotation of the plate-carrying roller 10 and further in coordination with the controlled spraying of fluid from the jet head 22 to perform the image of the plate 1 For this purpose, these means comprise the control device or computer 6, a motor 13 for positioning the plate-carrying roller, motor controls 33 and 34 connected to the computer 6 and associated respectively with the motor 28 for positioning the carriage and with the motor 13 for positioning the plate to coordinate the creation line by line of an image on the plate 1 The means 30 furthermore comprise a device 27 for controlling the spray jet connected to the computer 6 to modulate the design of the spraying of liquid sprayed from the jet head in accordance with the digitized data of

  machine operation generated by the computer 6.

  As will be described below with reference to FIGS. 8 a to 8 c, the computer 6 generates the digitized operating data by first processing data representing the image or the text to be printed, which can be entered into the computer in different ways This data is then converted into machine operating data to define the selected parts of the surface 3 of the plate 1 to be covered with the imaging material and the other parts which do not must not be covered with such a material. In this way, the print head 22 creates the image on the plate 1 by selectively spraying the photosensitive material 21 on the surface 3 of the plate, either in the form of an image.

  positive either as a negative image.

  During the image creation processing, the computer 6 causes the positioning drive motor 13 to rotate the plate roller 10 counterclockwise CC after each pass of the head 22 through the substrate The jet head sprays a path having a width PW of dimension equal to the quantity P by which the roller 10 is incremented after each pass of the head 22 The head begins its image creation operation at level 'a known datum D, and from this datum, a drawing is started and continues in coordination with the rotation of the drum until part of the surface 3 or the complete surface 3 of the plate is covered When the creation of an image comprising the exposure to light of the plate 1 is carried out, the printing of the substrate 18 begins with the advancement of the substrate through the printing rollers 9 and 12 rotating in the opposite direction it should be noted that the positioning drive motor 13 is connected in a rotary and driving manner to the plate-carrying roller 10 by means of a unidirectional clutch which allows a controlled rotation of the plate-carrying roller 10 by the positioning motor 13 in one direction, but which allows the plate roller 10 to be rotated by the drive motor 7 in the opposite direction independently of the positioning motor 13 for

the printing operation.

  In the embodiment of Figure 1, only a single color printing operation is shown, and therefore only a plate roller and a set of printing and inking rollers are provided. However, in the case o a press 19 is used to print images and / or texts of several colors on a substrate, any number of associated plate and ink rollers can be arranged to be used to print a single set of substrate material For example , as shown in FIG. 4, the press 19 comprises several printing stations 11, 11 each located along the movement path TT followed by the substrate 18 Each station in addition to having a blanket roller 12 ', a roller plate holder 10 ', a printing roller 9' and rollers 14 ', 16', 17 'of gumming, inking and forming a fountain comprises a jet printing device 4' having a printing head 22 'who reproduces uit an image on the plate mounted on an associated plate-carrying roller to create ink receiving zones corresponding to the zones located on the substrate where the particular colored ink must be applied Each of the printing devices by jet 4 ', 4 ', in the multi-color press 19, is connected to a computer or control device 6' so that one of the individual printing devices prints on an associated plate under the control of a common computer This arrangement is particularly well suited for multi-color printing presses in the sense that when mounted in the press, the plates have a known register which can be easily referenced by the common computer to direct each print head to deposit on the plate involved the

photosensitive material.

  As previously established, the phrases "photosensitive material", "image material" and "photosensitive liquid" indicate liquid compositions which are converted into solid material by exposure to radiant energy. In such a conversion, the material forms an image cured Typically, such compositions react by polymerization, crosslinking or other chemical reaction to form a material cured by exposure to light. The light which causes the chemical reaction which cures the material can be in any range of the spectrum, but from the most typically is in the visible (wavelength between about 400 and 700 nm) and ultraviolet ranges

  (wavelength shorter than about 400 nm).

  Many photosensitive materials known to those skilled in the art can be used to practice the present invention. Such materials are known by many names, including positively working photopolymers, photoresist resins, base resins of diazonium, gelatins and polyvinyl alcohols, but are not limited to these. Photoresists and positively working polymers are chemically very similar in that they are water soluble until they are polymerized or crosslinked by exposure to light Typically, such materials have based for example on esters of substituted acrylic acid, and contain photo-initiators Upon exposure to light, photo-initiators form free radicals which act on the unsaturated parts of the ester molecule to cause polymerization Photoresists are also based on phenolic resins containing photoinitiators such as iodoform Photoresists are often used to resist acids, for example, in the manufacture of computer chips They are suitable for use herein invention if the hardened material is sufficiently abrasion resistant The photopolymers work positively e are soluble in a solvent, typically water, but polymerize or react differently to form a cured material which is practically insoluble in water (and oleophilic)

during polymerization.

  Other suitable photosensitive materials include diazonium resins, which constitute a base resin made soluble in water by combination with the half diazonium. Ultraviolet light causes the half diazonium to be replaced by half hydroxyl, thereby making the base resin insoluble in water Such materials are well known to those skilled in the art Examples of such products available commercially include the powder Diazo-4 available from

  Fairmont Chemical Company of New Jersey.

  In addition to these, other suitable photosensitive materials which are typically less resistant and less self-supporting than, for example, diazonium resins, are also suitable for use in the claimed invention. Examples of such materials include gelatin and systems based on polyvinyl alcohol. Such materials typically use photosensitive initiators of the dichrome or diazo type. The photosensitive materials suitable for application using a jet spraying device according to the present invention are photosensitive liquids, typically solutions, suitable for being applied by such a device Numerous known photosensitive materials described here are very viscous, often having a viscosity exceeding 500 c St. Therefore, those skilled in the art will recognize that it may be necessary to adjust the characteristics of the photosensitive materials to allow application by spray jet As established above, various types of spray jets , comprising pressure pulses and piezo type jet devices can be used for the practice of the present invention Therefore, it may be necessary to adjust, among other things, the concentration of solids, the viscosity, the tension of surface, or p H, for example, of the liquid to ensure correct operation of the device to spray jet and satisfactory concomitant application of the photosensitive material Alternatively, or in combination with the present invention, it may be appropriate to adjust the operating characteristics of the spray jet device With the information provided here, a person skilled in the art will be able to make the appropriate adjustment, either to the characteristics of the photosensitive liquid, or to the spray device itself, in order to use the

  photosensitive liquid in the spray device.

  As those skilled in the art recognize, commercially available photosensitive materials may contain additives, such as dyes and biocides. Such additives may be present in the photosensitive material suitable for use in the

present invention.

  Typically, the cured image formed by light exposure of the photosensitive material described herein is oleophilic. Therefore, it forms ink receiving surfaces for oily type inks. Although such photosensitive materials are preferred for use of the present invention, a photosensitive liquid which forms a hydrophilic solid, thereby forming an ink receiving surface for water-based ink, is also suitable for use in the claimed invention when a device for printing using a

  plate reacting to an oleophilic ink is desired.

  The plate 1 used by the method according to the present invention is a self-supporting sheet formed from a material having an adequate mechanical stability, such as resistance to the stress creep test, to allow use under various conditions. The material chosen is preferably a material which is inexpensive and readily available commercially The material suitable for these effects is most commonly aluminum, but stainless steel can also be used In addition, the plate 1 can be formed non-metallic material, such as paper

  fatty coated or laminated with aluminum foil.

  In the case where the plate is made of paper, the material chosen may have a high grade with a weight of the order of 80 pounds and preferably having a high clay content, with a coating, such as polyvinyl alcohol / polyvinyl acetate filled to provide water absorption In a preferred embodiment, using a photosensitive liquid which forms an oleophilic ink receiving surface, the plate is cleaned with gum arabic by the roller 17 after having been transformed into an image and exposed to actinic radiation to reinforce the hydrophilic zones desired on the plate Plate 1, when it is formed from a metallic material has its printing side or exposed external surface 3 preferably rendered rough, such as by granulation treatment, to better hold the image material sprayed from the print head 22. The image material 21 deposited on the plate 1 by the head jet jet 22 is supplied in liquid form to a reservoir 32 supported by the head 22 The liquid is a photosensitive material which is sprayed in a microscopic flow on the printing side 3 of the plate involved according to a predetermined pattern and is then brought

  to harden by exposure to a radiant energy source.

  For this purpose, the press 8 comprises an elongated ultraviolet lamp 40, fixed on the press so as to overlap the length of the plate roller. The lamp is also juxtaposed with the print head so that after a line has been sprayed onto the plate 1, the roller is incremented by a quantity P to advance the image-forming material deposited beyond the lamp 40 causing the material 21 to harden to form an insoluble covered area of the plate. lamp 40 can be mounted on head 22 in a tail cavity

  to expose the deposited material 21 when sprayed.

  This characteristic is important since it performs the rapid processing of the material 21 for image

otherwise liquid.

  The example which follows is representative of the

  present invention and preferred embodiment.

EXAMPLE 1

  A printing plate is formed and a material

  riau forming the substrate is printed as follows An IBM microcomputer of the PC type using a set of software based on windows was used to produce text made up of different font dimensions of the Helvetica type The data representing this text were written on a disk for files in a format of

  Postscript page description A jet printer

  SCREENJET ink, manufactured by Gerber Scientific Products, Inc, having a Hewlett-Packard Deskjet 500 thermal inkjet head, was used to create the image on the plate The head is powered by a cartridge and written to the using ink dots coming out of the inkjet cartridge at a level of 300 dots per inch. The image material, a resin solution to

  diazonium, was prepared by dissolving in water

  ionized an amount of Diazo-4 powder (Fairmont Chemical Company of New Jersey) sufficient to form a saturated solution at room temperature The saturated solution was then filtered twice and the solution filtered

  resulting was then diluted in a ratio of 3/1.

  This produced an approximately 5% aqueous solution of diazonium resin (by weight). A 0.8 micron filter is attached to the outlet connection of the jet head The ink jet head has been emptied, rinsed using deionized water

  and then filled with the image solution.

  An off-set aluminum printing plate of the type having a granulated surface was supplied and washed at least once with isopropyl alcohol to remove any foaming material existing on the granulated surface This surface was provided with an image by the SCREENJET and left to dry The drying time was 3 minutes Then the areas of the plate provided with an image were exposed to ultraviolet light for approximately 3 minutes using a halogen-metal lamp A slight change color of the image material was observed The plate was erased as standard, and then was used in an off-set printer to print the image

on the sheets forming the substrate.

  As stated above, a commercially available photoresist may be used in place of the solution indicated in Example 1 Such material is commercially available from London Chemical Company Inc, of Bensenville, Illinois 60106 under the trade name KTI RESIST 930 This product has a viscosity, as supplied, of 510 to 625 c St, and is crosslinked using 2.5 milliwatts / cm 2 for 60 seconds of light having a wavelength of 400 at 420 nm In cases where it is desirable to visually identify the graphic transformed into an image, the drawing or the text on the plate, such as in the case where the plate has not been transformed into an image in a press to print having the imaging capabilities, but instead was transformed into an image in a machine separate from the press, such as by one of those shown in Figures 8a to 8c, the

  photoresist must be dried for this purpose.

  When the image material 21 has been hardened to form the graphic 44 arranged on the surface 3 directed towards the outside of the plate 1, it is able either to transfer the ink to the roller 3 forming a blanket or directly to the substrate , as in the case where only printing rollers and plate holders are used In any case, it will be understood that the plate 1 after image formation and after having passed beyond the source of radiant energy 40 , is ready for immediate use Also, to reinforce the distinction between the hydrophilic and oleophilic parts of the plate 1, the plate can be humidified at the station 16 forming a fountain in the usual way during the printing operation using of an eraser, in the case where the oleophilic parts expel the ink, or using a

  oleophilic material in the case where the ink is hydrophilic.

  Alternatively, distilled water or another solution

aqueous can be used.

  In FIGS. 5, 6 and 7, variants of plate imaging devices are shown which are separate free assemblies which are located away from an off-set printing device. In the figure, a printing device drum printing 49 can be used comprising interior components comprising a rotary drum 51 on which is mounted a plate 45 and a complementary printing head 53 These components act in a manner analogous to the analogous components described with reference to FIG. 3 for forming an image on the plate involved In FIG. 6, the image-forming device is a tracer 46 with a flat bed having a support surface 48 on which is mounted an element 50 forming a conveyor The conveyor 50 provides the means for loading and unload a plate 58 in a row

  another such plate ready to be provided with an image.

  Above the conveyor 50 is an X 52 carriage which is capable of moving in a controlled manner in the direction of the indicated X coordinate. The X 52 carriage also carries a Y carriage 54 capable of moving in the direction of the Y coordinate. indicated, and the carriage Y also supports a jet print head 56 which sprays the photosensitive material 21 on the plate 58 The plate 58 has several openings 60, 60 which receive framing fingers 62, 62 projecting upwards at from the conveyor 50 A radiant energy source 64 is received inside the carriage 52 and moves with the carriage to subsequently expose the photosensitive image-forming material 21 sprayed on the

plate 58.

  In FIG. 7, a third embodiment of an image-forming device is described. Plates, 70 are held in a cassette 72 and are pushed upward by a spring element 71 so that only one plate is available at a given time to be manipulated The system further comprises a support surface 74 and a first beam 77 fixed above the support surface 74, along which are arranged manipulation means 80 of the robot type which can be of the type described in another US patent application with serial number 07 660 280 entitled MEDIA HANDLING SYSTEM FOR PHOTOPLOTTER AND METHOD 0 F USE of Gerber Scientific Instruments Company A second fixed beam 76 is also provided above the surface of support 74, along which a jet print head 78 moves in a direction transverse to the direction A of advancement of the plate and

  on which the radiant energy source 64 is mounted.

  Means 82 for advancing the plate are provided for moving a plate intended to be provided with an image relative to the source of radiant energy 64 and to the head 78 The advancing means 82 for this purpose comprise a drive of the rack and pinion type which moves the plate involved in a coordinated movement with respect to the head 78 during an imaging operation In operation, a plate is removed by the means 80 and moved from the cassette 72 and on the surface of support 74 The plate is then advanced relative to the source of radiant energy 64 and to the head 78 to achieve concomitantly

  image and expose the photosensitive material 21.

  Referring now to FIGS. 8 a to 8 c, and to the various types of input devices used to convert a graphic and / or text into digital format, it can be seen that in the embodiment of FIG. 8 a, a lens 86 is used to focus an image of the drawing or text 84 on a scanning network 88 The graphic focused on the scanning network is transferred to a computer 90 and then transformed into code which can be

  used by the machine, ie in digital form.

  The digital form of the data is then used to drive a jet plotter 92 of the type described above. In the second embodiment of FIG. 8 b, a scanner 94 is used to scan and code a drawing or a text 84 supported on a table In the third embodiment of Figure 8c, a composer 96 is provided and includes a screen, a mouse and a keyboard 98, 99, usual used for typing text and / or drawing a drawing which is then entered into a

  computer 100 for driving a plotter 92.

  From the above detailed description,

  it will appear to a person skilled in the art that the invention is described by way of example rather than limitation and is susceptible to numerous modifications and / or substitutions. For example, the substrate material which is printed may alternatively be a continuous strip. of

  material rather than individual sheets of paper.

  Similarly, although the plates 1 have been described as separate assemblies, it is possible to provide a strip of plate material and advance it through a lug drive as shown in Figure 7 for depositing an oleophilic image on the tape Consequently, the invention has

  has been described by way of example rather than limitation.

Claims (18)

  1 Method of manufacturing an image plate   pressure having a hydrophilic base surface, comprising the steps of providing data defining a graph (44) and / or text to be printed on a substrate, processing said data in a computer (6) to generate data operating the machine defining selected parts (44) of said upper base surface to be covered with said imaging material and other parts not to be covered by said imaging material, providing plate (1) having a top surface (3) forming a base, providing a jet printing device (4) having a jet head (22) capable of covering the selected parts of said upper surface forming base of said plate using an imaging material while leaving bare the other parts of said upper surface of said plate, said method being characterized in that: a source (42) is provided e material (21) of   photosensitive liquid image formation in said arrangement   jet printing product, which is curable for   sea of oleophilic regions in the basic structure, we use said machine actuation data to   controlling said jet printing device for deposition   serifying a certain amount of said imaging material on said upper base surface so as to cover said selected portions of said upper base surface with said liquid imaging material, and then exposing the image formation thus deposited at an energy   radiant to form a hardened image.   2 Method according to claim 1, characterized   in that the hardened image is oleophilic.   3 Method according to claim 2, characterized in that the radiant energy is supplied in the form of ultraviolet radiation.   4 Method according to claim 3, characterized in that said photosensitive liquid imaging material is mixed with a dye to be colored. Method according to claim 4, characterized in that said hardened image consists of a coloring material. 6 Method according to claim 1, characterized in that said plate (1) is a non-metallic plate which supports a hydrophilic coating on which is deposited the image-forming material which can be hardened by light. 7 Method according to claim 6, characterized in that said plate (1) is formed of heavy paper provided with a hydrophilic coating.   8 Method according to claim 1, characterized in that said plate (1) is metallic and said upper surface can be made hydrophilic by means of a coating after said material imaging has been cured.   9 Method according to claim 7, characterized in that said plate (1) is covered using   polyvinyl alcohol / polyvinyl acetate filled.   Method according to claim 8, characterized in that said step of coating said plate (1)   is made using gum arabic.   11 Method according to claim 1, characterized in that the photosensitive liquid image-forming material is chosen from the group consisting of photo-polymers, photoresists, diazonium resins,   gelatin and polyvinyl alcohols.   12 Method according to claim 11,   characterized in that the photo-polymers are photo-   polymers acting positively.   13 The method of claim 11, characterized in that the image forming material   photosensitive liquid consists of a photo-polymer.   14 Method according to claim 11, characterized in that the image forming material   photosensitive liquid consists of a diazo resin.   Method according to claim 8, characterized   in that the photosensitive liquid is a solution.   16 Method according to claim 5, characterized in that said solution consists of a diazonium resin and the solution is formed by dissolution   initial said diazonium resin in water.   17 Method according to claim 1, characterized in that said device (4) is provided by   jet as part of an off- printing machine (2)   set and said jet print head is used to form the image on said plate (1) when mounted in the printing machine.   18 Method according to claim 21, characterized in that a radiant energy source (40, 64) is fixed in said printing machine and it is juxtaposed with the plate (1) mounted in the printing machine of such so that the plate involved is provided line by line with an image and the plate is advanced incrementally beyond the power source radiant with each image line.   19 Method according to claim 18, characterized in that said data defining the image on said plate are created by focusing the image on a scanning network and then entering the information   into said computer from the scanning network.   Method according to Claim 18, characterized in that the said data defining the image on the said plate are created by mechanically scanning a graphic or a text and then entering   the information in said computer.   21 Method according to claim l B, characterized in that said data defining said image on said plate (1) are created by a photo-composer made up of connected data input means directly to said computer.   22 Method according to claim 17, characterized in that several stations are provided   separate printing in said off-machine   set, each of the stations (11 ', 11') comprising at least one plate-carrying roller (10 ', 10') and said plate which is mounted therein, each of said printing stations is provided with a different colored ink intended to be printed on a substrate, each of said separate printing stations is provided with a jet printing device (4 ′, 4 ′) and the said data are processed so that each jet printing device associated with each inking station is made to cover the plate associated with this station with the aid of said image-forming material in order to create ink receiving zones and ink rejection zones corresponding respectively to the location where the color involved should be printed and at the location where the color involved should not be printed on the substrate.   23 The method of claim 22, characterized in that said jet printing device associated with each printing station to a common computer (61) and the computer is caused to provide instructions to each device jet printing for   create an image on different areas of the plate.   24 A method of creating a printing plate comprising the steps of providing a metal plate (1) having a hydrophilic upper surface made of the material of the metal plate, providing data defining a graphic and / or text to be printed on a substrate, providing a jet printing device (4) having a jet head (22) capable of covering selected portions of said upper surface of said plate with an image forming material while leaving other parts of the upper surface of said plate bare, processing said data to generate machine actuation data defining the selected parts of the upper surface to be covered with said photosensitive material and the other parts not to be cover with said photosensitive material, said method being characterized in that:   a reservoir (42) of photo material is provided   sensitive, which is curable to form oleophilic regions on the upper surface of the metal plate, said machine actuation data is used to control said jet printing device to deposit a certain amount of said photosensitive material on said upper surface of said printing plate so as to cover said selected parts of said upper surface of said plate with said photosensitive material, and said photosensitive material located on said printing plate is subjected to radiant energy (40, 64) for the '' harden and   to form an oleophilic image which can be hardened.