US 3620621 A
Description (OCR text may contain errors)
United States Patent  inventors Ervin J. Rachwal Framlngham.
Robert W. Marculewicz. Manchester; Douglas B. Campbell, Natlck, all of Mass.
Appl. No. 798,596
Filed Feb. 12, 1969 Patented Nov. I6, 1971 Assignee MatrographicsJnc New York, NY.
EMULSION CONTROL 5 Claims, 1 Drawing Fig.
US. Cl .l v 355/30, 355/67. 355/70 Int. Cl. v G03b 27/76 Field Search. 355/30. 67.
I 5 6 References Cited UNITED STATES PATENTS 233L335 l0/l943 Mayer Primary Examiner-Samuel S. Matthews Assistant Examiner-Richard A. Wintercorn 4uorney Kenneth S. Goldfarb SSS/70X ABSTRACT: An emulsion control for use in making plates for priming An emulsion is used for receiving a photographic image which has a given sensitivity. which can be increased by controlling the humidity and temperature of the environment surrounding the plate, the voltage on the plate, and the light surrounding the plate to the extent that a certain threshold is not exceeded This permits low intensity photographic images to trigger a necessary chemical action to produce an image on the plates PATENTEnuuv 1s l97l 3', 620 621 -II POWER SUPPLY INVENTORS R. W. MARCULEWICZ ERVIN RACHWAL D. B. CAMPBELL ATTORNEY EMULSION CONTROL BACKGROUND OF THE INVENTlON This invention relates to printing and more particularly the fabrication of plates which will be used in the printing process. In manufacturing plates a slide is projected onto a plate of aluminum which has an emulsion thereon. The projected image burns itself into the plate affixing an image thereto. Hy various steps of treatment the surface of the plate is made absorbent to ink in various degrees in accordance with the image that has been produced photographically on the plate. There are a great many techniques for producing images on the plate but all in common employ a lighbsensitive emulsion of a given sensitivity.
One of the difficulties in producing plates in accordance with the prior art methods was that the sensitivity of the plate was kept sufficiently low that they could be exposed to unfavorable conditions of light and in the platemaker inadvertent exposure to perhaps high room and machine temperatures and exposure to charged surfaces all of which would affect the sensitivity of the plate such that some of the chemicals of the emulsion may have been driven into activation which would obviously blur and destroy the image which would be subsequently placed thereon. Such a procedure is understandable and very desirable. However, if the sensitivity is too low, considerable amounts of light and its corollary time must be utilized in order to produce an image on such low sensitivity emulsions. Presently when an image is being projected onto a photosensitive plate, a considerable amount of light must be passed through the film over a correspondingly large period of time in order to produce an image on the photosensitive surface.
It would be immediately apparent that if too much light were forced through ordinary lens systems, the lens would rupture. Accordingly, a great deal of time must be sacrificed in order to keep below the limitation of a ruptured lens. However if a long period of time passes in a production of an image on the plate, sharp images will become difficult to attain for transient vibrations and movement of the various parts of the machine will cause the light to shift. about slightly causing an image to be somewhat fuzzy. An increase in the sensitivity would eliminate this problem in that the limitation of a requirement for high amounts of light energy to produce an image would not be required and furthermore a substantial time interval for burning in the image would be drastically reduced to a point where the images could be produced on the fly. In order to achieve these goals the entire environment in which the plate is placed for production of an image must be carefully controlled.
In the present invention the environment is controlled by surrounding the plate in an atmosphere in which the air is heated and the humidity is controlled. Furthermore, the charge is placed on the plate at a preselected polarity such that this is not permitted to effect the sensitivity of the chemicals within the emulsion. And immediately prior to exposure of the plate the light environment surrounding the plate is gradually raised to below what is considered to be the threshold of the chemicals that constitute the particular emulsion. Thereafter when the plate is exposed to the light which constitutes the image desired, a much more feeble light that would be otherwise satisfactory produces a very sharp clear cut image.
Therefore, an object of the present invention is to presensitize photographic emulsions prior to exposure. Another object of the present invention is to reduce the amount of light required to produce an image through a given lens system.
Another object of the present invention is to reduce the time interval required for production of an image of a given exposure.
Another object of the present invention is to increase the speed for producing plates by photographic techniques.
Other objects, features and advantages of the present invention will become apparent from the following specification when read in conjunction with the attached drawing which is an embodiment of the present invention.
Referring to the drawing showing the embodiment of the present invention. A power source 11 supplies a high intensity light source 13 which can be pulsed or be continuous with a shutter. The light is then reflected from the condensing reflector 15 which is then passed through a condensing lens 16 on through a negative in the film plane 17 thence through an enlarging lens system 18. The light then passes through window 27 of a platemaking device 21. (there s an opening in reflector system 22) and thence onto the plate 34.
Up to this point the system appears very much like that which is presently available commercially. However, the emulsion has a certain sensitivity and in order to produce the desired image the light 13 would have to be of a very high intensity but not so high as to rupture the lenses l6 and 18. Moreover, this light would have to remain on for considerable period of time in order to give the emulsion on plates 34 sufficient time to be activated in order to record the impression that the light beam produces thereon.
Therefore in the present invention in order to produce the amount of light needed in the time that this light would be required to be activated a low intensity secondary light source consisting of a reflector system 22 and the light 33. are turned on just prior to exposure to a preselected level which is below the threshold of the chemicals constituting the given emulsion such that they would not be activated by this light alone. However when a small or substantially smaller quantity of light emerges from lens system 18 it would be sufficient to trigger the chemicals into a satisfactory level of reaction to produce a sharp image on plate 34.
When one enters into a scheme where the threshold level of the emulsion is approached very closely just prior to exposure, other sources of energy which might increase the sensitivity of the emulsion must be carefully controlled. Accordingly a voltage 35 is applied to plate 34 and the vacuum table 38 in order to assure that a specific charge of known polarity would be developed across the plate such that the chemicals would not be activated by any stray currents or charges that might appear within the platemaker. ln addition a stream of controlled air temperature and humidity is passed in through inlet 41 and out through outlet 42 in order to control the thermal energy and conductivity of the lens to the emulsion prior to exposure such that the lights 33 are the only source of controlled energy which will raise the sensitivity to just below the threshold such that we will be assured that the chemicals will not be activated by any energy other than that which is produced by the light emerging from the lens 18.
Emulsions used in photography and in platemaking may differ in their chemical constituents, however they all in common are photosensitive. Of course in the case of photographic techniques the films are much faster and much more light sensitive and do not present the same problems that platemaking presents. In platemaking much higher light levels are required and furthermore great periods of time must elapse before an image is burned into the plate satisfactorily for use in printing. However the principles in both cases would remain somewhat the same. Each molecule of the chemical constituents require a certain quantum of energy before the chemical action will take place. And the suppliers of emulsions are very careful to provide an emulsion which has a uniform coating of molecules which require pretty much the same quantum of energy in order to result in a chemical reaction.
in order to prevent inadvertent activation of the sensitized emulsion its sensitivity is kept well below that which is required in the production of images. The reason for this is that the light level in the platemaking machines and in transferring the plates in their original condition when the emulsion was first applied to the plate cannot be controlled such that absolute darkness would be present. Furthermore increasing the temperature of the plate or its exposure to various electri cal charges may induce activation of the chemical in an unwanted manner. So accordingly the sensitivity of all emulsions has been and will always be considerably below that which is required to trigger the chemical reaction resulting in the production of an image on the plate.
in the present schemes of things the sensitivity of the given emulsion is readily determined imperically by controlling the temperature and charge on the plate and the secondary light produced by the low intensity light source. Once the threshold is determined which results in satisfactory plates the environment can be controlled in the approximate vicinity with assurance. Therefore the amount of light produced by light source 13 can be drastically reduced well below the level which would endanger the lens system 16 and 18. Moreover the time period or interval over which the required exposure is needed can be drastically reduced and in most instances by combining it with a proper light level can be reduced such that images on the plate will be produced on the fly. That is an image will be snapped as rapidly as a photograph.
This latter ability becomes extremely important to platemaking for in a platemaking device several exposures will have to be placed on a given plate to provide for a number of pages perhaps contemplated for use in fabricating a book or newspaper. And with the use of step and imposition type platemaker many slides will be able to be inserted and the pulse light source and negatives can be removed to the various quadrants of the plate thereby producing an image on each given section of the plate almost immediately upon exposure resulting in a substantial advantage in the economy of time but also in the clarity of image which has been free of vibration.
The present invention has been described with reference to particular apparatus. it is well understood that many substitutions and variations can be made by those skilled in the art without departing from the true scope and spirit of the present invention. Therefore, the present inventor only wishes to be limited in his invention by the appended claims.
1. Emulsion control comprising, image projection means, means for receiving projected images, a photosensitive emulsion distributed uniformly over said receiving means, means for illuminating said receiving means uniformly with predetermined quantity of light prior to exposure of said receiving means, and means for placing a preselected charge on said receiving means.
2. Emulsion control according to claim 1 which further includes means for surrounding said receiving means with air of a preselected temperature and humidity.
3. Emulsion control according to claim 2 wherein said receiving means is a plate for use in printing.
4. Emulsion control according to claim 3 wherein said illuminating means includes a reflector having an opening in its center for permitting the passage of projected images, and a multiplicity of low-level light sources distributed about said reflector to provide uniform light distribution.
5. Emulsion control according to claim 4 wherein said image projection means includes photographic slides containing images of printed matter, means for projecting preselected slide images to preselected quadrants ofsaid receiving means.