COLOUR-SEPARATED FILM PRODUCTION METHOD BY MEANS OF COLOUR SCANNING, AND APPARATUS THEREFOR

Abstract: A color-separated film is produced by color-separating one or more original pictures, which require trimming, by means of a color scanner. The original pictures are adhered to trimming widows of a light-shielding sheet-like member, which trimming windows define trimming regions for the original pictures respectively. The color-separated images recorded by the photoelectric conversion means on a photosensitive material supported on a recording cylinder. Binary-coded picture signals corresponding to areas where the light is shielded by the sheet-like member are discrimi­ nated. By the binary-coded picture signals, images capable of serving as masks upon exposure are recorded on the photosensitive material. The subsequent contact-printing step requires fewer contact-printing processings. This has brought about such advantageous effects that the reliability and accuracy of the contact printing work have been im­ proved and the superposing work of films has been sim­ plified and the work efficiency has hence been improved.

Description: This invention relates to a method for producing a color-separated film in accordance with a printing plate fabrication technique making use of a color scanner, in which upon formation of a color-separated picture by the color-scanner, a mask region serving as an outlining mask required in subsequent treatment step is exposed to the color-separated picture concurrently with the recordation of the picture. (e.g. as in US-A-4 471 386) In recent production processes of printing plates, preparation steps such as machine plate preparation steps and block copy preparation steps have been progressively rationalized. Layout scanners which can achieve electronic performance of most of such steps have been finding utility in some areas. The conventional process is, however, still in wide use, in which after production of color-separated pictures by means of a color scanner, their pasting-up and assembly are carried out by manual work and contact exposure work respectively. With a view toward making the pasting-up and assembly work still simpler, it is also practised, to a certain extent, to paste up original color pictures per se on a layout sheet in accordance with a desired layout pattern so as to provide a pasted-up original color page picture and then to scan the original color page picture by means of a color scanner so as to color-separate the color page picture as a whole (see, for example, Japanese Patent Laid-Open No. 226,348/1984). For example, as depicted in Figure 5 which illustrates a process for producing a printing plate by making us or the conventional multiple exposure and printing technique, a pasted-up layout sheet C with original picture patterns B₁,B₂,B₃ which have been pasted up on the layout sheet C on the basis of a desired layout pattern and require color separation and halftone photography is mounted on an input cylinder A. The original picture patterns B₁,B₂,B₃ are then subjected to color separation and halftone photography and with the same dimensions, recorded as a halftone negative on a recording film E mounted on a recording cylinder D. In this case, as the original picture patterns B₁,B₂,B₃, it is possible to use an intermediate which has in advance been reproduced, with a magnification designated upon preparation of a layout pattern, on a color duplicate film or color photographic paper from an original such as color film or the like by means of a duplicate camera. At this time, in order to facilitate simultaneous processing by a color scanner, original picture patterns to be pasted up on a common pasting-up layout sheet D (e.g., a transparent film or white paper sheet which may optionally be equipped with registration marks or the like as desired) are subjected to balancing such as graduation. In order to assemble characters, line pictures and/or the like together with picture patterns on a layout sheet, it is necessary to follow such steps that a negative (F) of a line picture block copy of these characters and line pictures are prepared separately, a trimming layout mask G is also prepared separately with trimming regions for picture patterns rendered transparent in the form of windows and the remaining parts rendered opaque, and [1] a registered unit of a picture pattern negative E' and the layout mask G and [2] the line picture negative F are subjected to double contact exposure on a fresh film H so as to obtain a finished positive J. This multiple contact exposure process requires correct positioning and registration. Especially when so-called "precise registration", in other words, a layout making the boundaries of picture patterns hardly noticeable is required, a high degree of accuracy is indispensable in positioning and registering a plurality of masking patterns relative to one another. As an alternative process, intermediates are produced respectively from originals on color duplicate films, the intermediates are cut into dimensions which conform with their corresponding desired trimming frames, the thus-cut intermediates are pasted up on a transparent sheet, the transparent-sheet is wrapped on an original cylinder with the originals in contact with the circumferential outer wall of the original cylinder, and the originals are then scanned. The above process is however accompanied by a practical drawback that considerable difficulties are encountered upon cutting the desired trimming regions of the intermediates precisely in accordance with desired trimming sizes. It is also accompanied by an inconvenience that the process has to be repeated from the preparation of intermediates when the desired trimming frames are changed after color separation. In Japanese Patent Laid-Open No. 226,348/1984, the present applicant has disclosed to prepare a color-separated film by recording and exposing picture patterns bearing not only characters and/or line pictures but also necessary rectangular masks on rectangular trimming regions. However, Japanese Patent Laid-Open No. 226,348/1984 does not disclose anything about the recording of picture patterns with masks of desired shapes. An object of this invention is to record picture patterns only with a high accuracy level by a color scanner even if the shapes of the masks are complex, so that the superposing work of films in the above-described multiple exposure process making use of a contact-printing printer can be effected only with a color-separated negative and a negative of characters, line pictures and/or the like. According to features of the present invention which is set out in the appended claims, a color-separated films of the same type as those obtained conventionally by using red peel masks in subsequent processing steps can be obtained directly by means of a color scanner without need for any post processing or treatment. Reflecting the above advantage, the subsequent contact-printing step requires fewer contact-printing processings in each of which the respective films must be superposed one over another with a high degree of accuracy. This has in turn brought about such advantageous effects that the reliability and accuracy of the contact printing work have been improved and the superposing work of films has been simplified and the work efficiency has hence been improved. In the present invention, picture-recording signals adapted to mask trimming regions are produced from color-separated picture signals which have been output from the photoelectric conversion unit adapted to photoelectrically scan originals. It is therefore possible to record the masking areas of individual trimming regions with the resolution of the scanner without making any errors with respect to the scanned points. As the recording unit, it is possible to employ either a recording device controlled by analog signals or a dot generator controlled by digital signals. This invention may also be applied with ease to a scanner equipped with a recording unit which makes use of a contact screen. The above and other objects, features and advantages of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings, in which: Figure 1 is a block diagram of a color scanner in which the present invention has been incorporated; Figure 2 shows a plan view of an original picture to be mounted on an input unit of a color scanner for its scanning as well as a plan view of an output picture thereof; Figure 3 illustrates a cross-sectional view of the scanned original picture of Figure 2 taken along line III-III and viewed in the direction indicated by the arrows as well as a schematic diagram showing the waveforms of signals converted photoelectrically by the cross-sectioned part in comparison with the cross-sectioned part; Figure 4 shows a plan view a color-separated film obtained in accordance with this invention, a plan view of a line picture film prepared separately, and a plan view of a film suitable for use in the production of a printing plate, the last-mentioned film having been obtained by subjecting both films to multiple exposure on a photosensitive material; and Figure 5 shows a conventional process for the production of a printing plate, which makes use of a multiple exposure and printing step. One embodiment of this invention will hereinafter be described in detail. Prior to proceeding with the description of the embodiment, the basic principle of this invention will first be described in brief. Using a light-shielding white peel-off film (see, for example, Japanese Patent Laid-Open No. 124,351/1982), trimming regions are cut off and original pictures are superposed in registration with the trimming regions respectively. Since the above-mentioned white peel-off film has good light-shielding property, the originals have to be prepared with densities lower than that of the white peel-off film. Recording is then effected in such a way that each light-shielded area is recorded solid and each of the areas not light-shielded permits transmission of light, thereby to obtain a color-separated picture of the same quality as conventional color-separated pictures. In the manner mentioned above, a color-separated picture which has been masked and trimmed is prepared. Figure 1 illustrates the structure of a color-scanner according to this invention. The color scanner is equipped with an input cylinder 2, input head 3, sub-scanning feed screw 4 for the input head 3, and a motor 5 for driving the feed screw 4. A recording unit 6 is on the other hand equipped with a recording cylinder 7, recording head 8 of the dot generator type, a sub-scanning feed screw 9 for the recording head 8, and a motor 10 for driving the feed screw 9. The input cylinder 2 and recording cylinder 7 are both rotated by a motor 12, which drives a rotary shaft 11 common to both of the input cylinder 2 and recording cylinder 7. Owing to the rotation of the input cylinder 2 and recording cylinder 7, the main scanning of each of the input unit 1 and recording unit 6 is performed. A photoelectrical conversion unit 13 of the input head 3 scans photoelectrically original pictures 14a,14b of a scanned original picture 14 mounted on the peripheral wall of the input cylinder 2 and outputs color-separated picture signals g₁ consisting of conventional three color signals R,G,B, which correspond respectively to red, green and blue, and an unsharp signal U for emphasizing contours. The color-separated picture signals g₁ are then input to a picture signal processing circuit 15, in which they are subjected to masking, color correction, graduation correction, etc. in the same manner as conventional methods. Output signals g₂ of the picture signal processing circuit 1 are then fed to the recording head 8 by way of a gate 16. When the other input of the gate 16 is "L", the color-separated picture signals which are similar to conventional color-separated picture signals are recorded on a photosensitive recording material 17 mounted on the recording unit 6. On the other hand, the photoelectric conversion unit 13 of the input head 3 is designed in such a way that the three color signals R,G,B of the output color-separated picture signals g₁ are delivered to a selector 18, which selects the maximum value for example, so as to obtain a light/dark signal e₁ as an output of the selector 18. The light-dark signal e₁ is used to detect areas which shield light 13a from a transmitting light source 13d by means of a patching layout sheet 19 with the original pictures pasted up thereon. This light/dark signal e₁ is converted into a binary-coded signal e₂ in accordance with the threshold of a comparator 20. The resultant binary-coded signal e₂ is fed to the other input terminal of the gate 16. When an area shielding the light from the transmitting light source 13a is detected in the course of the above-described process, the recording head 8 outputs exposing light of the maximum light quantity level when the output e₂ of the comparator 20 is "H". Thus, the photosensitive material 17 is exposed to blacken the corresponding area so that the corresponding area has a light-shielding property after its development. When the binary-coded signal e₂ is "L" on the other hand, the output signal g₂ is output from the gate 16 as an output signal g₃ as is. The output signal g₃ is recorded with a halftone dot area percent which corresponds only to the level of the output signal g₂ of the picture signal processing circuit 15. Figure 2(a) is a plan view of a scanned original picture 14 to be mounted on the input cylinder 2, namely, a patching layout sheet 19 with the original pictures 14a,14b pasted thereon, in which the layout sheet 19 is seen from the side of the input head 3. Figure 2(b) is a front view of the scanned original picture 14 shown in Figure 2(a) after reproduced and recorded on the photosensitive material 17 mounted on the recording cylinder 7 and then subjected to a development treatment, in which the thus-recorded original picture is viewed from the side of the recording head 8. As illustrated in Figure 3 which will be described herein, the patching layout sheet 19 is a sheet-like material formed by laminating a transparent film base 19a having good light transmissibility and a light-shielding peel layer 19b. THe patching layout sheet 19 is provided with at least 2 registration holes 19c which are to be registered with register pins for its precise positioning. The photosensitive material 17 is of substantially the same dimensions as the patching layout sheet 19. This photosensitive material 17 is also provided with registration holes 17a which correspond respectively to the registration holes 19c. The registration pins with which the registration holes 19c and registration holes 17a are brought into registration are provided with a diameter and pitch common to the input cylinder 2 and recording cylinder 7 of the scanner as well as a CAD system and contact-printing printer, which will be described herein, and other work-facilitating devices. These positioning means are employed routinely and their detailed description is thus omitted. The patching layout sheet 19 is provided with trimming windows 21a,21b formed by cutting through a peel 19b at areas where desired trimming regions corresponding to the original pictures 14a,14b are laid out on the basis of a layout pattern specified in a patched and assembled sheet (hereinafter called "layout sheet of completed block copy"). Since the cutting step of the trimming windows 21a,21b is not directly related to the features of this invention, its details are not described here. It is substantially the same as the cutting step for conventional red peel films. Where high degrees of accuracy such as "precise registration" is required, it is however preferred to position and cut the contours of designated trimming regions by a pattern processing technique such as CAD system or the like. As the original pictures 14a,14b to be pasted up on the patching layout sheet 19, it may conveniently used those prepared as intermediates of good duplicate film pictures adjusted in color tone, graduation and the like in accordance with a desired magnification determined beforehand from the first original for its expansion or reduction. Furthermore, the preparation of such a duplicate film is carried out in such a manner that transmitted light is allowed to remain to a certain extent in an area having the maximum density in the above duplicate film at the output level when the incident light is shielded by the peel layer 19b. The pasting-up of the original pictures 14a,14b onto the patching layout sheet 19 may be effected in the following manner. Namely, supposing that the peel layer 19b is on the front side of the layout sheet 19, the original pictures 14a,14b are pasted up by adhesive tapes or the like on the back side of the patching layout sheet 19, namely, on the transparent film base 19a in such a way that their front surfaces are brought into contact with the cylinder 2 and the trimming regions of the original pictures 14a,14b are positioned and registered with their corresponding trimming windows 21a,21b. This pasting-up step of the original pictures 14a,14b onto the patching layout sheet 19 is not different at all from conventional work, except that a conventional patching layout sheet formed of a sheet, which is transparent all over its surface, has been replaced by the patching layout sheet 19 equipped at one surface thereof with the peel layer 19b of this invention. In Figure 3, the color-separated picture signals g₁ output from the photoelectric conversion unit 13 (note: only one of the three channels, R, G and B, is shown) and the light/dark signal e₁ of the selector 18 are shown corresponding to the cross-sectional view of the patching layout sheet 19 and original picture 14a in Figure 2. The photoelectric conversion unit 13 serves to conduct photoelectric conversion of the original picture 14a inside the trimming window 21a cut out in the peel layer 19b by means of transmitting light 13b from the transmitting light source 13a. The light/dark signal e₁ of the selector 18 which selects the minimum value from the R,G,B signals output from the photoelectric conversion unit 13 produces a dark output at a density level higher than each shadow point of the original picture 14a at each area where the peel layer 19b still remains but at a level brighter than that of the shadow point at the area corresponding to each of the trimming windows 21a through which the original picture 14a is visible. Owing to the difference in output level between the signal corresponding to each shadow point of the original picture 14 and the dark output corresponding to each point shielded from the transmitting light 13b by the peel layer 19b among the light/dark signals e₁ produced from the selector 18 are converted respectively into distinct binary-coded signals in accordance with a threshold set between these two levels in the comparator 20. This comparator 20 produces binary-coded signals e₂ as "H"s while detecting the surface of the peel layer 19b. Accordingly, a region 22 corresponding to the remaining part of the black peel 19b in the output picture shown in Figure 2(b) is always subjected to exposure with a halftone dot area percent of 100% or higher so that printing light is successfully shielded upon its exposure, so that the region 22 is blackened to a density high enough to act as a mask. In the trimming windows 21a,21b, the original pictures 14a,14b can be seen through trimming regions 23 respectively. At the trimming regions 23, the signals e₂ are output as "H"s. The gate 16 receives the signals e₂ which are "H"s, and allows the output signals g₂ of the picture signal processing circuit 15 to pass therethrough as they are. Accordingly, picture signals similar to conventional picture signals are input to the recording head 8. In the above-mentioned manner, trimmed and color-separated halftone pictures 14a'14b' are recorded. In a color-separated film 17' which has been recorded and developed in the above manner, color-separated halftone negatives are formed at the regions corresponding to the halftone pictures 14a',14b'. All the remaining area is blackened to a high density. Unlike conventional techniques, the color-separated film 17' can be hence used in the subsequent printer-dependent contact printing step without need for any layout masks. In Figure 3, the mounting on the cylinder 2 has been effected in the order of the original picture 14a, transparent film base 19a and peel layer 19b. So long as the peel layer 19b and original picture 14a can be distinguished in reflectivity from each other, they may be applied in the order of the original picture 14a, peel layer 19b and transparent film base 19a. Furthermore, the front surface of the original picture 14a may be located on the side of the white peel-off film. The above description has been made supposing that the original pictures 14a,14b are light-transmitting original pictures. The present invention may however be applied equally to light-reflective original pictures. By making the surface reflectivity of the patching layout sheet 19 higher than the reflectivity of the maximum surface-reflecting area in a reflective original picture (i.e., the high light point in a positive), the difference in reflectivity between the original picture and patching layout sheet can be discriminated at the comparator 20. Figure 4(a) shows the color-separated picture 17' prepared in the above-described manner, while Figure 4(b) illustrates a negative film 24 of line pictures such as characters, line pictures, flat tints, etc., which has been prepared separately from a completed block copy layout sheet. On the other hand, Figure 4(c) shows a final film original 25 which has been obtained by double-printing the films 17',24 on another photosensitive material by means of a contact-printing printer and then developing the thus-printed photosensitive material and is useful in printing positive printing plates. It is of course possible to double-print the color-separated film picture 17' and line film picture 24 directly on a presensitized plate. In this case, numeral 25 indicates a printing plate. In this printer-dependent printing step, it is unnecessary to use any separate mask upon printing the color-separated film picture 17', the pin registration can be achieved with ease and the efficiency of the work is thus improved. Use of the method of this invention results in improvements to both contact property and work efficiency, because the superposition of two or more films is not effected simultaneously in the operation of a contact-printing printer. When a dot generator is used in the recording head 8, each contour may be photoelectrically detected with a high resolution and its corresponding smooth contour may hence be recorded provided that as disclosed by the present application in Japanese Paten Application No. 100,236/1983 a photodetector for color-separated printing plates and a photodetector for the detection of contours are provided as separate devices in the input head 3 and an array sensor is used as the contour-detecting photodetector. As the gate 16, an analog switch may be used when the picture signals are analog signals while a gate device may also be used when the picture signal g₂ are digital signals. Needless to say, the present invention may equally be practiced with a scanner which makes use of a contact screen. The gate 18 serves to record a halftone dot area percent of 0% when the surface of the peel layer 19b has been detected and to send the color-separated signals g'₂, which have been converted to positive signals, to the recording head 8 when the trimming windows 21a,21b have been detected. Owing to this function of the gate 18, color-separated positive pictures with masks thereon [for example , the positive picture shown in Figure 4(c)] can be exposed and recorded. At each masked area, a separately-given halftone dot area percent (%) may be recorded. The above embodiment has been described using the white peel-off film. Needless to say, the present invention can also be practised by using a light-shielding paper sheet which can function in much the same way as the white peel-off film. Having now fully described the invention, it will be apparent to one of ordinary skill in the art that many changes and modifications can be made thereto without departing from the scope of the invention as comprised by the claims.

Claims: A method of producing a color separation film from an original bearing both a desired image area to be selected and an undesired image area including the steps of designating a desired image area of the original and discriminating the desired image area from the undesired image area, photoelectrically scanning the original, inputting image signals obtained by said scanning, discriminating the signals of the undesired area from those of the desired image area on the criterion of a predetermined threshold potential, and outputting the image signals of the desired image area to the exclusion of the undesired area, characterized in that the steps of designation the desired image area and discriminating said area from the undesired area are realized by covering the desired and the undesired image area of the original with a transparent and with an opaque film (19a, 19b) and removing the opaque film (19b) above the desired image area (23). A method according to claim 1, wherein the original (14) to be scanned for color separation is a secondary original reproduced from a first original, said secondary original being controlled so that the highest density value of a desired image area (g1) is less than the density of the covered undesired area. An apparatus for producing a color separation film from an original (14) bearing both a desired image area to be selected and an undesired area, comprising scanning means (3) for photoelectrically scanning the original to obtain image signals (g1), processing means (15) connected to said scanning means (3) for processing the image signals (g1) obtained by said scanning means (3), recording means (8) connected to said processing means (15) for recording the desired image on a photosensitive material (17), and means (16, 18, 20) being disposed in parallel with respect to the processing means (15) for selectively outputting only the image signals of the desired image area; characterized in that a masking sheet (19) is provided which covers the original (14) to be scanned and which is composed of a transparent base sheet (19a) and an opaque layer (19b) removably disposed on said base sheet, whereby an area (21a, 21b) of the opaque layer corresponding to the desired image area (23) of the original (14) is removed from said base sheet. An apparatus as claimed in claim 1 whereby the density value of the masking sheet (19) is so arranged that the undesired image area covered by the transparent and the opaque sheets (19a, 19b) is represented as having a density value larger than that of the desired image area, while the desired image area (23) covered only by the transparent base sheet (19a) is represented as having a density value corresponding to the image signal obtained by the scanning means.

Inventors: ISHIDA, AKIRA, SAITO, NAOTADA, YUMEN, AKIRA
Applicants: DAINIPPON SCREEN MFG. CO., LTD.
Application year: 1985
Main classification: H04N1
IPC codes: G03F1, H04N1