GB1564968A

GB1564968A - Electrophotographic contact duplicating method and apparatus

Info

Publication number: GB1564968A
Application number: GB4993876A
Authority: GB
Original assignee: Coulter Systems Corp
Current assignee: Coulter Systems Corp
Priority date: 1975-12-15
Filing date: 1976-11-30
Publication date: 1980-04-16
Also published as: DE2656661C2; NL7613943A; DE2656661A1; JPS5284738A; FR2335879A1; IT1069831B; CH640069A5; BE849420A; CA1091749A; FR2335879B1; CH628162A5

Abstract

Images are applied, from a film (10) coming from a roll (14), onto an electrophotographic film (12) coming from a roll (18). A thin layer of insulating hydrocarbon (41) is applied to the electrophotographic film (12) before it comes into contact with the film (10), so as to prevent an electrostatic discharge when the two films are separated. The films (10 and 12) of the two rolls (14 and 18) are brought into contact and transferred to a projection unit (22) where a light beam is projected onto and through them. The electrophotographic film (12) is charged just before it comes into contact with the photographic film. A toner-applying unit (46) and a fixing unit (54) are arranged so as to act on the electrophotographic film after its exposure. The subsequent transfer of the image supplied with toner, onto a base film strip, is provided in order to enable the electrophotographic film (12) to be reused later. <IMAGE>

Description

(54) ELECTROPHOTOGRAPHIC CONTACT DUPLICATING METHOD AND APPARATUS (71) We, COULTER SYSTEMS CORPORA TION, formerly Coulter Information Systems Inc., a Corporation organised and existing under the laws of the State of Illinois, United States of America of 35 Wiggins Avenue, Bedford, Massachusetts 01730, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: Apparatus for duplicating long strips of film onto other strips of film is used particularly in the motion picture industry as well as in other fields.

It would be desirable if contact printing methods could be utilized electrophotographically to duplicate images on a photo- graphic film to an electrophotographic film carrier or other medium. Improvements both economic and in quality could be effected but contact would have to be effected without erasing the latent image. However it would be expected that the charge defining a resultant latent image would be thought to be dissipated by direct contact with a conventional film negative.

The invention provides a method of duplicating developed images carried on a first strip of film onto a transparent flexible second strip of electrophotographic film which has a coating of a wholly inorganic oriented crystalline photoconductive material carried on a substrate, said method including the steps of charging the coating of the electrophotographic film in darkness independently of the first strip, projecting a beam of radiant energy to the strips to produce on the coating a latent image and toning and optionally fixing the toned image in darkness independently of the first film strip: the first and second film strips being moved into face to face engagement after charging of the coating, the beam being projected through both strips while same are enraged and the film strips being separated before the latent image on the electrophotographic image is toned. optionally thereafter fixing the toned image in the second strip or transferring the toned image to strips of blank film.

Further the invention provides apparatus for duplicating images on an elongate first film strip onto an elongate second strip formed of electrophotographic film, the apparatus including a supply of first film strip having a succession of developed images thereon and first means for transporting the film to first take-up means, a supply of electrophotographic film strip which has a coating of a wholly inorganic oriented crystalline photoconductive material carried on a substrate, and second means for transporting the electrophotographic film to second take-up means, defining a darkened chamber, means for guiding both film strips into and thereafter out of the chamber before same are directed to their respective take-up means, a charging station in the chamber and having means for charging the coating of the electrophotographic film strip uniformly while same passes said charging station, an exposure station including means for projecting a beam of radiant energy through both film strips while in said chamber, and a toning station in the said chamber including means for toning the latent images produced on the electrophotographic film strip after passing through said exposure station; said first and second transporting means including means for bringing the strips of fi!ms both into intimately engaged contact while in said chamber and moving at the same rate and in the same direction after the electrophotographic film strip has passed the charging station, the film strips being in contact while the beam passes therethrough, and said first and second transporting means also including means for separating the film strips after the exposure station and before the electrophotographic film passes through said toning station and optionally, a fixing station.

Additionally, the invention provides a contact film duplicator for duplicating the images of a strip of image carrying film onto another medium in a continuous process, said duplicator comprising means for progressively bringing a limited area of an elongate strip of imaged image carrying film into face to face engaged contact with identical area of an elongate strip of electrophotographic film in a continuous progression of such limited areas along the lengths of the respective films and including first and second supply means and first and second take up means for said image carrying film strip and said electrophotographic film strip respectively, means for transporting said strips to said take up means from said supply means means for maintaining the films in darkness at their contacting areas, means for charging each said limited area of the electrophotographic film in darkness before it is brought into contact with its counter part area of the image carrying film, means for projecting light through the films from the side of the image carrying film in an exposure zone to produce a latent duplicate image of the limited area of the photographic film on the electrophotographic film, means for moving the films apart immediately after exposure and the latent image has been formed, and means for toning the latent image in darkness after the films have moved apart, said second take up means being arranged to acclmulate the electrophotographic film after the operation of the toning means.

The preferred embodiments of this invention will now be described, by way of example, with reference to the drawings accompanying this specification in which: Figure 1 is a block diagram of apparatus constructed in accordance with the invention, and Figure 2 is a modified form of the invention.

The apparatus of the invention is illustrated in Figures 1 and 2 diagrammatically.

The film 10 which carries the images that are to be reproduced is conventional silver halide photographic film provided at supply 14. The film 10 normally is perforated and transported through the use of sprocket wheels such as shown at 24 in order to prevent any contact with the soft photographic emulsion.

In transporting the film 10 through the apapparatus the emulsion side preferably is ar ranoed to face the coating side of the electrophotographic film. The take-up reel and mechanism for the photographic film is shown at 16. The film 10 can be cinematographic, microfilm, microfiche, a series of stills etc.

The electrophotographic film 12 is supplied from a suitable reel 18 and it can be transported by sprocket wheels as well. However, the film 12 has an abrasion-resistant surface so this is not mandatory. Transport idlers are shown at 25.

The film 12 is based upon a strip of transparent polyester resin substrate about .005 inch thick and has an electrically conductive layer hereinafter called an ohmic layer deposited on its surface and well-bonded thereto. The ohmic layer is made up of indiumtin oxide and is about 300 Angstroms thick and transparent. The ohmic layer has a coating of photoconductive material on its surface and hence the ohmic layer can be described as sandwiched between the photoconductive coating and the substrate. The photoconductive coating is a sputterdeposited, wholly inorganic, highly oriented crystalline material in which the crystals are arranged parallel to one another and perpendicular to the plane of the substrate.The coating is transparent to a degree whereby it absorbs between 15 and 30% of white light It has a quantum efficiency that is at least 100 times greater than those of known photoconductive materials. It has high speed, a resolution that is greater than known photographic film and is panchromatic. It has an almost infinite surface resistivity due to the formation of a barrier layer on the surface during the sputtering of the material. When deposited it is electrically anisotropic in that its resistivity along the axes of the crystals, that is perpendicular to its surface, is very much less than its surface resistivity. It can be charged with a surface potential that gives a substantially greater field than known photoconductive materials and discharges to zero by white light, with an almost infinite intermediate grey scale.

The preferred coating material is cadmium sulfide of extremely high purity. Zinc 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 apparatus with its coating side facing the emulsion side of the photographic film 10.

The electrophotographic film 12 is charged at station 42, then brought into contact with the film 10 at a projection station 22 (more precisely a contact or near contact printing station) where light from the lamp 36 is projected by way of a simple collimator or the like, designated optics 38, through the engaged films. The charged coating of the film 12 is imaged to provide a latent image which moves to the toning station 46 where it is toned and thereafter fixed at a fixing station 54 by some means such as a heat lamp. Spray coating may be used. Where the toner used is self-fixing, the fixing station 54 can be omitted. The film 121, now provided with the exact duplicate of the images on the photographic film 10 is taken up on the take-up reel 20. The reproduced film 101 is taken up on the take-up reel 16 and thereafter may be salvaged to recover the silver therefrom.

The charged film 12 has the charges so strongly bound thereto because of the nature of the coating that there is no loss of charge when the coating contacts the film 10. Furthermore, there will be little or no loss of the latent image when the films separate after leaving the projection station 22, this being done at a lubricating station 40. The material which is applied to the film is a liquid hydrocarbon that is insulating in character and serves several purposes. It wets the film 12 and causes intimate adherence of the film 10 thereto during passage of the contacting films through the projecting station 22. The coated surface of the film 12 preferably is lubricated before being charged and passing through the projection station 22, this being done at a lubricating station 40.The material which is applied to the film is a liquid hydrocarbon that is insulating in character and serves several purposes. It wets the film 12 and causes intimate adherence of the film 10 thereto during passage of the contacting films through the projection station 22.

It prevents any possibility of scratching either film and is anti-static in that it prevents the buildup of static charges by virtue of the coming together and separating of the films.

Thus, there is no wiping off of the latent image of the electrophotographic film after it has been formed by such static charges.

Additionally, it is optically better than an intervening layer of air because its index of refraction is less than that of air.

In connection with the latter function of the liquid hydrocarbon, it should be understood that even the most intimate mechanical contact between two film surfaces is bound to include a thin layer of air. The presence of hydrocarbon excludes air and substitutes a microscopic film of material therefor which has better optical transmission properties than air because diffusion, scattering and bending are decreased.

A preferred lubricating material is sold under the trademark Isopar G by the Exxon Company of Houston, Texas. There is complete compatibility between the lubricant and the toner at the toning station 46. The lubricant is applied at a lubricating station 40 by means of any suitable device, such as a fountain 41 with transfer rolls, the last one of which contacts the coating side of the film 12. Lubricant can be applied by spraying at the point 401 after the film has been charged.

Adjustment of the film strips to move fairly synchronously can be achieved by well-known means such as the adjustable loops 241 and 251 or the like.

The average density of the images on the film 10 can be detected by means of the lamp 28 and photocell 26 to provide a signal on the line 56 that can be compared with a signal from a reference source 64 appearing on the line 62 in the differential amplifier 60 to control the charging 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 through delay circuit 74 to the charging ap paratus, which can be a corona or similar device. The power supply for the charge voltage control circuit is shown at 70. The delay 74 is to give the image of the film 10 whose density is being measured sufficient time to reach the projection station 22, if necessary.

The film 12 has a sensitivity which varies in accordance with its surface potential. The alternative to utilizing a reference signal is the use of a signal derived from a measurement of the surface potential of the charged film. Thus, the density of the image on the photographic film is measured and compared with the surface potential of the film 12.

When the potential on the film rises to a value which produces a signal out of the circuit 49 on the line 51 which has been predetermined to represent the ideal sensitivity of the film 12 for the particular lighting conditions of the lamp 36 to produce the density measured for the particular image, the charging stops. This form of the invention is a circuit different from that which uses a reference signal, but the circuitry block diagram readily is represented by moving the arm of the switch Sw 1 to the contact of the line 51.

The charging station 42, projection station 22 and the toning station 46 of Figure 1 are enclosed all in a suitable housing indicated by the broken line 80 to maintain those elements involved in darkness.

The film strips 10 and 12 can be moved intermittently or continuously.

There is considerably more information on exposed photographic film than can be derived from ordinary viewing, printing or projecting of the same. Computers and other sophisticated apparatus can synthesize this information by techniques which are not involved here. The invention herein does, however, derive quality information from the film and automatically produces a better quality duplicate than the original film. This is done by the measurement of density and relation of this information to image enhancement by controlling the charge as explained above. This is effected because of the variable sensitivity of the electrophotographic film 12.

The electrophotographic film 12 as used preferably is one in which there is a coating of inorganic material and most minerals have characteristic colors in crystalline form. For example, the color of cadmium sulfide is a light yellow. If a duplicate film 121 is made directly on the film coating by fixing the toned image, the making of prints from this film 121 does not pose any problems. If, on the other hand it is to be projected, the background will be yellow unless filters or film treatment are used. Furthermore, economical as this film 12 is, it is not as economical as clear base film of some polyester.

As illustrated in Figure 2, the toned image can be transferred to a strip of clear base film and the electrophotographic film cleaned and reused over and over. Such apparatus of Figure 2 is quite similar to that up to the toning station 46 where, instead of passing to the fixing station, the film 121 carrying the toned image passes to a transfer station 84 where the image is transferred to a strip 13 of clear base film that is stripped off a clear base film supply 82. The transfer station 84 is located in the darkened enclosure 80 and comprises a pair of pressure rollers 86 and 88 which bring the strips 13 and 12' into the nip of the rollers. The toner is picked up from the film 12 and passes to the fixing station 54 and thereafter is accumulated onto a take-up reel 90.Obviously, the toner should not be of the self-fixing type, or if it is, the process of drying should not take place until after transfer.

As for the film 191, after the toned image has been transferred, the film is cleaned in any suitable manner at the cleaning station 92. It could for example, be sprayed and/or rinsed by the same hydrocarbon used to lubricate the film at 40. This would dissolve whatever toner remained. There could be squeegee means, brushes to brush off dried toner, etc. A brilliant lamp could be used to discharge any remaining electrical charge on the coating. In any event, after cleaning, the film 12 is no different from the film which is shown being stripped off the supply reel 18 in Figure 1 and hence can be used again. Since the electrophotographic film described above does not become electrostatically fatigued, it can be reused as many times as its coating mechanically can withstand the wear thereon.

After economy, one of the benefits of transferring to blank film is that the toner, being made of carbon and resin particles, is inexpensive, certainly a lot cheaper than the silver halide emulsions of photographic film.

WHAT WE CLAIM IS: 1. Method of duplicating developed images carried on a first strip of film onto a transparent flexible second strip of electrophotographic film which has a coating of a wholly inorganic oriented crystalline photoconductive material carried on a substrate, said method including the steps of charging the coating of the electrophotographic film in darkness independently of the first strip, projecting a beam of radiant energy to the strips to produce on the coating a extent image and toning and optionally fixing the toned image in darkness independently of the first film strip; the first and second film strips being moved into face to face engagement after charging of the coating, the beam being projected through both strips while same are engaged and the film strips being separated before the latent image on the electrophotographic image is toned, optionally thereafter fixing the toned image on the second strip or transferring the toned image to a strip of blank film.

2. The method according to claim 1 in which the film strip is photographic film carrying developed images and the emulsion side of said film and the coating of the electrophotographic film are brought into contacting engagement.

3. The method according to claims 1 or 2 in which the coating side of the electrophotographic film strip is lubricated with an insulating hydrocarbon solvent before the strips are moved into engagement.

4. The method according to any one of claims 1 to 3 in which the densities of the images of the first film strip are measured in succession before the strips are moved into engagement, signals derived therefrom which are respectively proportional to said densities being used to control the amount of charge applied to the coating at locations which respectively come into contacting engagement with the said first film strip when ihe corresponding images are present, the amount of charge for any given location being adjusted to provide sensitivity of the coating for optimum duplication of the corresponding image.

5. The method according to claim 4 in which each signal derived from an image is compared with a predetermined reference signal to determine the amount of said charge.

6. The method according to claim 4 in which each signal derived from an image is compared with the surface potential of said coating as the charging thereof commences, said charging being discontinued when said comparison reaches a predetermined relationship.

7. Apparatus for duplicating images on an elongate first film strip onto an elongate second strip formed of electrophotographic film, the apparatus including a supply of first film strip having a succession of developed images thereon and first means for transporting the film to first take-up means, a supply of electrophotographic film strip which has a coating of a wholly inorganic oriented crystalline photo conductive material carried on a substrate, and a second means for transporting the electrophotographic film to second take-up means, means defining a darkened chamber, means for guiding both film strips into and thereafter out of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the other hand it is to be projected, the background will be yellow unless filters or film treatment are used. Furthermore, economical as this film 12 is, it is not as economical as clear base film of some polyester. As illustrated in Figure 2, the toned image can be transferred to a strip of clear base film and the electrophotographic film cleaned and reused over and over. Such apparatus of Figure 2 is quite similar to that up to the toning station 46 where, instead of passing to the fixing station, the film 121 carrying the toned image passes to a transfer station 84 where the image is transferred to a strip 13 of clear base film that is stripped off a clear base film supply 82. The transfer station 84 is located in the darkened enclosure 80 and comprises a pair of pressure rollers 86 and 88 which bring the strips 13 and 12' into the nip of the rollers. The toner is picked up from the film 12 and passes to the fixing station 54 and thereafter is accumulated onto a take-up reel 90.Obviously, the toner should not be of the self-fixing type, or if it is, the process of drying should not take place until after transfer. As for the film 191, after the toned image has been transferred, the film is cleaned in any suitable manner at the cleaning station 92. It could for example, be sprayed and/or rinsed by the same hydrocarbon used to lubricate the film at 40. This would dissolve whatever toner remained. There could be squeegee means, brushes to brush off dried toner, etc. A brilliant lamp could be used to discharge any remaining electrical charge on the coating. In any event, after cleaning, the film 12 is no different from the film which is shown being stripped off the supply reel 18 in Figure 1 and hence can be used again. Since the electrophotographic film described above does not become electrostatically fatigued, it can be reused as many times as its coating mechanically can withstand the wear thereon. After economy, one of the benefits of transferring to blank film is that the toner, being made of carbon and resin particles, is inexpensive, certainly a lot cheaper than the silver halide emulsions of photographic film. WHAT WE CLAIM IS:

1. Method of duplicating developed images carried on a first strip of film onto a transparent flexible second strip of electrophotographic film which has a coating of a wholly inorganic oriented crystalline photoconductive material carried on a substrate, said method including the steps of charging the coating of the electrophotographic film in darkness independently of the first strip, projecting a beam of radiant energy to the strips to produce on the coating a extent image and toning and optionally fixing the toned image in darkness independently of the first film strip; the first and second film strips being moved into face to face engagement after charging of the coating, the beam being projected through both strips while same are engaged and the film strips being separated before the latent image on the electrophotographic image is toned, optionally thereafter fixing the toned image on the second strip or transferring the toned image to a strip of blank film.

chamber before same are directed to their respective take-up means, a charging station in the chamber and having means for charging the coating of the electrophotographic film strip uniformly while same passes said charging station, an exposure station including means for projecting a beam of radiant energy through both film strips while in said chamber, and a toning station in the said chamber including means for toning the latent images produced on the electrophotographic film strip after passing through said exposure station; said first and second transporting means including means for bringing the strips of films both into intimately engaged contact while in said chamber and moving at the same rate and in the same direction after the electrophotographic film strip has passed the charging station, the film strips being in contact while the beam passes therethrough, and said first and second transporting means also including means for separating the film strips after the exposure station and before the electrophotographic film passes through said toning station and optionally, a fixing station.

8. The apparatus according to claim 7 in which the second transporting means moves the strip of electrophotographic film through said fixing station after the toning station and before the second takeup means.

9. The contact duplicating apparatus according to claim 7 in which there is a supply of blank film, third take-up means, a toned image transfer station, third transport means for transporting the blank film from the supply to the transfer station and thence to the fixing station and thereafter to the third take-up means, the second transporting means including means moving the electrophotographic film from the toning station to the transfer station and into engagement with the blank film thereat to effect transfer of the toned image to the blank film before the second take-up means.

10. The contact duplicating apparatus according to any one of claims 7, 8 or 9 in which means are provided for lubricating that surface of the electrophotographic film which contacts the first film strip, said lubricating means being located before the electrophotographic film passes to said exposure station.

11. The contact duplicating apparatus according to any one of claims 7 to 10 in which means are provided for measuring the density of the developed image on a given area along the leneth of said strip of first film strip at a location spaced ahead of said projection station and for adjusting the charged surface potential of that portion of the electrophotographic film strip which will meet said given area at said exposure station to provide optimum conditions of duplication of said image onto said electrophotographic film strip.

12. A contact film duplicator for duplicating the images of a strip of image carrying film onto another medium in a continuous process, said duplicator comprising means for progressively bringing a limited area of an elongate strip of imaged image carrying film into face to face engaged contact with identical area of an elongate strip of electrophotographic film in a continuous progression of such limited areas along the lengths of the respective films and including first and second supply means and first and second take up means for said image carrying film strip and said electrophotographic film strip respectively, means for transporting said strips to said take up means from said supply means, means for maintaining the films in darkness at their contacting areas, means for charging each said limited area of the electrophotographic film in darkness before it is brought into contact with its counterpart area of the image carrying film, means for projecting light through the films from the side of the image carrying film in an exposure zone to produce a latent duplicate image of the limited area of the image carrying film on the electrophotographic film, means for moving the films apart immediately after exposure and the latent image has been formed, and means for toning the lalent image in darkness after the films have moved apart, said second take up means being arranged to accumulate the electrophotographic film after the operation of the toning means.

13. The contact duplicator according to claim 12 in which means are provided for fixing the toned image after it has been toned.

14. The contact duplicator according to claim 12 in which an elongate strip of blank film is provided and means are provided to bring the blank film into progressive engagement with the electrophotographic film after the operation of the toning means to transfer the toned images to said blank film, and including means for fixing the transferred images onto the blank fi'm and means to accumulate the blank film thereafter.

15. The contact duplicator according to claim 12 or 13 which includes means to measure and derive a signal related to the density of the limited areas of the image carrying film before same are brought into contact with the electrophotographic film and said charging means have means responsive to the signal to enhance the image duplicated on the electrophotographic film by adjustment of the amount of charge applied to said electrophotographic film.

16. The contact duplicator according to any one of claims 12 to 15 which includes means for lubricating the surface of the elec trophotographic film which contacts the image carrying film, said lubricating means being located before the location at which the image carrying film and electrophotographic film are brought into contact.

17. A method of duplicating images substantially as described with reference to the accompanying drawings.

18. An apparatus for duplicating images substantially as described with reference to the accompanying drawings.