CH640069A5 - Contact duplicator for reproducing developed images - Google Patents

Abstract

The images are applied from a film (10) coming from a roll (14) on an electrophotographic film (12) coming from a roll (18). A thin layer of insulating hydrocarbon (41) is applied onto the electrophotographic film (12) before it enters into contact with the film (10) in order to prevent static discharge when the two films are separated. The films (10 and 12) of the two rolls (14 and 18) are placed in contact and conveyed to a projection station (22) where a light beam is projected onto and through them. The electrophotographic film (12) is charged just before it is placed in contact with the photographic film. A station for applying toner (26) and a fixing station (54) are arranged in order to act on the electrophotographic film after its exposure. The subsequent transfer of the image provided with toner onto a strip of base film is provided in order to allow subsequent reuse of the electrophotographic film (12). <IMAGE>

Description

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1. A film contact duplicator for reproducing images of an elongated ribbon of photographic film on another support in a continuous electrophotographic process which comprises devices for charging, exposing and providing a tacker, characterized in that it comprises a transport train for gradually bringing a limited area of an elongated ribbon (10) of photographic film provided with images in face-to-face contact with an identical region of an elongated ribbon (12) of electrophotographic film in the dark in one continuous progression of such limited areas along the lengths of the respective films, a charging device (42) for applying a potential charge to each of said limited areas on the electrophotographic film in the dark before it is brought into contact with the corresponding zone of the photographic film (10), a projection station (22) arranged so as to project light through the films in contact, on the side of the photographed film as (10), to produce a latent image reproduced of the limited area of the photographic film (10) on the electrophotographic film

(12), a separator (24, 25) arranged so as to separate the films from one another immediately after they have been brought into contact and the latent image has been formed, an application device tack (46) for applying tack to the latent image in the dark after the films have separated, and a gripping device (20) for receiving the electrophotographic film after the operation of the tack application device .

2. Film contact duplicator according to claim I, characterized in that it comprises a fixing device (54) arranged so as to receive the electrophotographic film (12) after the application of the tacker.

3. Film contact duplicator according to claim 2, characterized in that it comprises an elongated film ribbon (13), a conveyor train (82, 86, 25) capable of bringing a transparent film

(13) in progressive contact with the electrophotographic film (12) after the operation of the tacking application station (46) for transferring the images provided with tacking onto said transparent film (13), and a fixing device (54) arranged to fix the transferred images on the transparent film (13) and a gripping device (90) arranged to receive the transparent film carrying the transferred images.

4. Film contact duplicator according to claim 2, comprising a measuring device for measuring and deriving a signal related to the density of the limited areas of the photographic film before these are brought into contact with the film. electrophotographic film, characterized in that it comprises a controller (45) coupled to said charging device (42) and which responds to said signal to produce the image reproduced on the electrophotographic film by adjusting the amount of charge applied to said electrophotographic film.

5. Film contact duplicator according to one of claims 2, 3 or 4, characterized in that it comprises a lubricator (40) for lubricating the surface of the electrophotographic film which comes into contact with the photographic film, this lubricator being arranged to operate before the photographic film and the electrophotographic film are brought into contact.

The photographic films currently used require several chemical operations and critical development processes, so that they must be processed under boundary conditions and stored in the dark; finally they are perishable.

It is therefore desirable to find contact printing methods which can be used electrophotographically to transpose images from a photographic film onto a support consisting of an electrophotographic film or the like. Both economic and quality improvements could be obtained as long as the contact can be made without erasing the latent image. However, it may be thought that the charge defining a resulting latent image would tend to be dissipated by direct contact with a traditional negative film.

These aims are achieved by the means defined in claim 1.

The drawing represents, by way of example, an embodiment of the object of the invention and a variant.

Fig. 1 is a block diagram of an apparatus for reproducing images, and FIG. 2 is a variant.

The film 10 which carries the images which have to be reproduced is a conventional silver halide photographic film supplied by a reserve 14. The film 10 is normally perforated and is transported by toothed rollers as shown at 24 in order to avoid any contact with soft photographic emulsion. When transporting the film 10 in the apparatus, its emulsified face is preferably arranged so as to face the face provided with a coating layer of the electrophotographic film. The receiving reel and the receiving mechanism of the film are shown at 16. The film 10 can be a cinematographic film, a microfilm, a microfiche or a series of negatives, etc.

The electrophotographic film 12 is supplied from a reel 18 and can be transported by toothed wheels. However, the film 12 has an abrasion resistant surface, so that it is not delicate. Transport references are shown at 25.

The film 12 is mounted on a support constituted by a ribbon of transparent polyester resin about 125/1000 mm thick and has an ohmic layer deposited on one of its faces, which adheres closely thereto. This ohmic layer is produced by means of indium tin oxide and has a thickness of approximately 300 Å, and is transparent. The ohmic layer is provided with a coating of photoconductive material on its surface, so that this ohmic layer can be described as being sandwiched between the photoconductive layer and the substrate. The photoconductive layer is deposited by vaporization; it is entirely inorganic, made of a highly oriented crystal material in which the crystals are arranged parallel to each other and perpendicular to the plane of the substrate. The coating is transparent to a degree that it absorbs between 15 and 30% of the white light. It has a quantitative yield which is at least a hundred times greater than that of known photoconductive materials. It is very fast and has a resolution which is higher than that of known photographic films and is panchromatic. It has an almost infinite surface resistance due to the formation of a barrier layer on the surface during the vaporization of the material. When deposited, it is electrically anisotropic in the sense that its resistivity along the axes of the crystals, that is to say perpendicular to its surface, is much lower than its surface resistivity. It can be charged by a surface potential which allows a field appreciably greater than that of known photoconductive materials and discharges at zero under the effect of white light, with an almost infinite intermediate gray scale.

The preferred coating material is extremely pure cadmium sulfide. Arsenic trisulfide and mixtures of cadmium sulfide with zinc sulfide have produced excellent coatings. Different spectral characteristics result from different materials.

The film 12 passes through the device its side provided with coating facing the side provided with emulsion of the photographic film 10.

The electrophotographic film 12 is first of all loaded at the station 42, then brought into contact with the film 10 at a projection station 22 where the light coming from a lamp 36 is projected by means of a simple collimator or the like, designated by optics 38, through the films in contact with each other. The film-loaded coating 12 is then provided with an image so that a latent image is produced, and then moves to the application station of

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tacker 46 where it is provided with tacker, which is fixed to a fixing station 54 by means such as a heating lamp. Spray coating can be used. When the tacker used is self-fixing, the fixing station 54 can be omitted. The film 12 ′, provided with the exact reproduction of the images of the photographic film 10, is seized by the receiving reel 20. The reproduced film 10 ′ is seized by the receiving reel 16, then is taken up for recovery of the money he's wearing.

The loaded film 12 has its charge which adheres to it so tightly, due to the nature of its coating, that there is no pressure drop when the coating is in contact with the film 10. In addition, there is no there is little or no loss of latent image when the films separate after leaving the projection station 22. The surface coated with the film 12 is preferably lubricated before being loaded and before passing into the station projection 22, which is done at the lubrication station 40. The material which is applied to the film is a liquid hydrocarbon which is insulating and used for several purposes. It wets the film 12 and produces an intimate adhesion of the film 10 to it during the passage of the two films in contact in the projection station 22. It prevents any possibility that one or the other of the films will scratch and it is antistatic in the sense that it prevents the formation of static charges which could occur, due to the fact that the films come into contact and separate. Thus, there is no erasure of the latent image on the electrophotographic film after it has been formed by static charges. In addition, this lubricant layer is optically preferable to an air layer, since its refractive index is lower than that of air.

Regarding the last function of the liquid hydrocarbon, it should be noted that even the most intimate mechanical contact between the two film surfaces has a thin layer of air. The presence of hydrocarbon excludes air and replaces a microscopic film of material which has better optical transmission qualities than air because the diffusion, dispersion and distortion decrease.

A preferred lubrication material is commercially available as Isopar G by Exxon Company of Houston (Texas, USA). There is complete compatibility between the lubricant and the tacker at the tacking application station 46. The lubricant is applied to the lubrication station 40 by means of any suitable device such as a fountain 41 with transfer rollers, the latter of which is in contact with the surface coated with the film 12. The lubricant can be applied by spraying at point 40 'after the film has been loaded.

An adjustment of the film ribbons so that they move perfectly in synchronism can be obtained by well known means such as adjustable loops 24 'and 25', or the like.

The average density of the images on the film 10 can be detected by means of a lamp 28 and a photoelectric cell 26 to produce a signal on a line 56 which can be compared with a signal from a reference source 64 appearing on a line 62 in a differential amplifier 60 to control the charge of the film 12. The output of the amplifier 60 appears at 66 and varies the output of the charge voltage control circuit 68 which is applied, by a delay circuit 74, to the charging device which may be a Corona device or the like. The energy source for the charge voltage control circuit is shown at 70. The purpose of the delay circuit 74 is to give the image of the film 10, the density of which must be measured, sufficient time to reach the station. projection 22, if necessary.

The film 12 has a sensitivity which varies according to its surface potential. In place of the reference signal, a signal derived from a measurement of the surface potential of the loaded film can be used. Thus, the density of the image on the photographic film 10 is measured and is compared with the surface potential of the film 12. When the potential on the film reaches a value which produces a signal leaving circuit 49 on line 51 which has been predetermined

as representing the ideal sensitivity of the film 12 for the particular lighting conditions of the lamp 36 to produce the measured density of the particular image, the charge ceases. This variant is a circuit different from that which uses a reference signal, but the circuit block has been shown by moving the arm of the switch Sw 1 so as to come into contact with the line 51.

The charging station 42, the projection station 22 and the tacking application station 46 of FIG. 1 are all housed in a casing indicated by the dotted line 80 so that these elements are kept in the dark.

The film ribbons 10 and 12 can be moved step by step or continuously. The exposed photographic film provides much more information than can be obtained from print views and ordinary projection. Computers or other sophisticated devices can synthesize this information using techniques that will not be discussed here. The present invention, however, improves the quality of information from a film and automatically produces a better quality copy of it than the original. This is achieved by measuring the density and relating the image information by charge control, as explained above. This is obtained due to the variable sensitivity of the electrophotographic film 12. The electrophotographic film 12 preferably used is of the type which is provided with a coating of inorganic material, mostly mineral, having characteristic colors in crystalline form. For example, the color of cadmium sulfide is a light yellow. If the dubbing film 12 ′ is produced directly on the coating of the film by fixing the image provided with a tacker, obtaining copies of this film 12 ′ poses no problem. If, on the other hand, it is intended to be projected, the background will be yellow, unless filters, or a treatment of the film, are used. Furthermore, as economical as this film 12 is, it is not as economical as a transparent polyester film.

As shown in fig. 2, the image provided with a tacker can be transferred to a transparent film tape and the electrophotographic film can be cleaned and reused indefinitely. An apparatus such as that of FIG. 2 is quite similar to that of FIG. 1 up to the tacking application station 46 where, instead of passing through a fixing station, the film 12 ′ carrying the image provided with tacking passes to a transfer station 84 where the image is transferred to a ribbon 13 of transparent base film which comes from a supply of transparent base film 82. The transfer station 84 is housed in a dark enclosure 80 and comprises a pair of rollers pressure 86 and 88 between which the strips 13 and 12 'are pinched. The tacker is seized with the film 12 'and passes to the fixing station 54 and then is accumulated on a take-up reel 90. Obviously, the tacker may not be of the self-fixing type or, if it is, the process of drying may not take place until transfer.

As in the case of the film 12 ′, after the image provided with a marker has been transferred, the film is cleaned in any suitable manner at the cleaning station 92. It could, for example, be sprayed or rinsed with using the same hydrocarbon used to lubricate the film 40. This would dissolve all the tacker that could remain there. Means could be provided for sweeping or brushing to brush the dry tacker, etc. A bright lamp could be used to discharge the coating of any remaining electrical charge. In any case, after cleaning, the film 12 is no different from the film which has been removed from the reserve reel 18 in FIG. 1 and, therefore, can be used again. Because the electrophotographic film described above does not tire electrostatically, it can be reused as long as its coating is mechanically resistant to wear.

Besides the economy, one of the advantages of the transfer of the transparent film is that the tacker, which is made of carbon and resin particles, is not expensive and is certainly much cheaper than the brine emulsions. money from photographic films.

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2 drawings sheets