US 3658533 A
A photosensitive non-silver free radical film is placed in physical contact with copy material to be duplicated and on exposing the film to radiation from a powerful red light, either positive copy or negative copy is obtained.
Claims available in
Description (OCR text may contain errors)
United States Patent Fotland et al.
[ 51 Apr. 25, 1972  COPYING PROCESS  Inventors: Richard A. Fotland, Lyndhurst; Virgil E.
Straughan, Euclid; John Cameron, Cleveland, all of Ohio Horizons Incorporated, a Division of Horizons Research Incorporated 22 Filed: June11,1969
21 Appl.No.: 832,143
 U.S. Cl ..96/48, 96/47, 96/90  Int. Cl v.G03c 5/24, G030 11/00, G030 1/92  Field of Search ..96/90, 48, 47
 References Cited UNITED STATES PATENTS 3,042,519 7/1962 Wainer ..96/48 Fotland et al ..96/27 3,510,300 5/1970 3,194,659 7/1965 Baus et al. ...96/47 3,445,232 5/1969 Shirey et al. ..96/47 Primary Examiner-Norman G. Torchin Assistant Examiner-Richard E. Fichter AnorneyLawrence 1. Field  ABSTRACT A photosensitive non-silver free radical film is placed in physi' cal contact with copy material to be duplicated and on exposing the film to radiation from a powerful red light, either positive copy or negative copy is obtained.
7 Claims, 2 Drawing Figures Patented A ril 25, 1972 I FIG.
N NWA E H V NT FTO S A E D mm 6N W W ,mv
ATTORNEY COPYING PROCESS This invention relates to a completely dry, non-silver photographic process for obtaining either a positive or a negative full size copy of an original document, and a process capable of providing continuous-tone copies with control over the contrast of the copy.
More particularly, the invention relates to the use of free radical photosensitive formulations which are capable of being optically developed, the compositions being coated upon a transparent base or imbibed in a paper base in an ap paratus of the type hereinafter described.
The invention will be more readily understood from the description which follows, taken with the drawings in which:
FIG. 1 is a schematic showing of a copying apparatus; and
FIG. 2 is a similar view of a modified apparatus.
The copying apparatus shown in FIG. 1 comprises a lamp 30, mounted within a reflector 32, positioned and shaped so as to reflect radiation from lamp 30 towards two glass filters. Filter 34 is a red glass filter, such as Corning No. 2,408, and filter 36 is a heat absorbing glass filter, such as Corning Glass No. 2,600, or similar filter. Suitable means (not shown) are provided for supporting a copy sheet 16 and an original 14 in physical contact with each other, the copy sheet being positioned between the lamp and the original to be copied. If copy sheet 16 bears a photosensitive coating, this is positioned next to the original 14.
FIG. 2 is a similar view of a copying apparatus in which means are provided for moving material through the apparatus, intermittently or continuously.
The copying apparatus shown in FIG. 2 may include a housing in which the several moving parts of the apparatus are supported, including a main drive roller 12 by means of which an original 14 and a photosensitive copy sheet 16 are drawn through the apparatus, entering through an entrance 18 and exiting through an exit 20. Drive roller 12 is supported in suitable bearings which may be supported in a frame or in bearing blocks (not shown) suitably mounted on the housing 10.
Means are provided in the apparatus for holding the original and the copy sheet in intimate contact, this being an endless transparent belt 22, trained around a plurality of idler rollers 24. Rollers 24 may be independently rotatable or they may be connected to one another by suitable gearing, and may be supported either in housing 10 or in a separate frame. Any other suitable means may be used to hold the copy sheet and the original in intimate contact as they pass through the apparatus.
The apparatus includes means for providing the radiation required for the copying process, such means include a lamp 30, for example a lr Kw General Electric Quartzline (RTM) Lamp Type O l500T3/CL, having a lighted length of at least the width of the copy sheet. Lamp 30 is supported in a reflector 32 having a generally elliptical configuration whereby the radiation output of the lamp is directed toward the open end of reflector 32 and passes out of the reflector and through one or more filters 34, 36.
The quality or spectral distribution of the radiation reaching the copy sheet and original is determined by the spectral filters 34 and 36. Preferably filter 34 is a Corning red glass filter (Corning No. 2408) while filter 36 is a heat-absorbing glass filter (Corning Glass No. 2600) having a long wavelength cutoff near 750 nanometers. The heat-absorbing glass filter 36 is mounted on a mechanical linkage so that it may be moved out of the radiation path in such a manner that radiation falling on the original and copy sheet may be either filtered by the red glass filter alone or by both the red glass and heat-absorbing filters. An additional radiation source in the apparatus is provided by a white fluorescent lamp 38 mounted in its own cylindrical reflector housing 40.
The function of the fluorescent lamp 38 is to provide the photosensitive copy sheet with a blanket exposure of radiation to which the photosensitive film or paper is sensitive prior to the copying step; generally this radiation lies in the near UV and violet portions of the spectrum. The use of the fluorescent lamp 38 is optional since the blanket exposure may be provided by merely subjecting the copy sheet to normal room illumination for a period of several seconds before it is drawn into the apparatus housing through entrance 18.
Among the non-silver photosensitive compositions which may be employed in this copying process are the free-radical photosensitive compositions patented by Eugene Wainer and his co-workers, including those described in the following:
U.S. Patents The following specific examples are intended to demonstrate the application and utility of the copying process of this invention and are not intended to be construed as limiting the invention.
EXAMPLE I A photosensitive copy sheet was prepared under a red safelight by dissolving 400 mg of 4,4-vinylidene-bis-(N,N- dimethylaniline), 100 mg of 2,6-di-tert-butyl-p-creso], 25 mg of Z-p-dimethylaminostyryl pyridine, and 400 mg of iodoform in a 10 percent solution of polycarbonate in methylene chloride. The solution was coated on a 5 mil polyester film base using a Bird applicator bar having a wet coating thickness of 1.5 mils. The film was dried in an oven for two minutes at C. The coating procedure is fully described in Photographic Science and Engineering, Vol. 8, No. 2., pp. -l03 andVol. 5,p. 98 (1961).
This photosensitive material, as well as those described in the aforementioned patents, is capable of being optically developed. In this technique for increasing the sensitivity of the film, a faint initial exposure generates trace quantities of image dye which then selfor auto-sensitize the photosensitive material to the red portions of the spectrum. If the film, subsequent to the initial exposure, is subjected to a blanket exposure to red illumination, image intensification occurs in exposed areas. It has been found that the rate of optical development, i.e., the rate at which the density increases with time during optical development, is a sensitive function of film temperature. The rate of density increase for most films is such that an increase in this rate of 2% times occurs for every 10 C rise in film temperature. It is this thermal sensitivity of optical development which is employed in the copying process to obtain a positive image. A significant improvement over prior art thermographic processes resides in the degree of control over the contrast of the positive copy which is provided by virtue of the provision for blanket post-exposure of the film which, in turn, determines the temperature sensitivity and degree of optical development required.
This control may best be understood from the following discussion. If the image being copied is of low contrast, i.e., there exists a low density difference between image and background areas, a high contrast copy may be obtained by adjusting the intensity of the blanket exposure lamp 38 so that the level of exposure of the photosensitive layer is in the region of 500 ft.-candle seconds as measured by a conventional photographic light meter. This low exposure level imposes a requirement for a longer optical development time which involves a higher sensitivity to thermal effects to thus provide a high contrast copy. In the apparatus shown in FIG. 2, a high contrast copy is obtained at a paper speed through the apparatus of 6 ft./min. High quality, high contrast, continuoustone images may be copied in this manner.
A low contrast copy may be obtained by providing a high level blanket exposure together with a low degree of optical development. To realize these conditions, the intensity of the fluorescent blanket exposure lamp 38 is raised so that the photosensitive layer exposure is in the region of 5,000 ft.-candle-seconds, and the speed of the apparatus is increased so that the copying operation is carried out at a speed of 20 ft./min. Under these conditions, the copy has a lower contrast than the original.
In this process of obtaining a positive copy, the heat-absorbing glass filter 36 must be removed from the radiation path so that the thermal radiation from the lamp selectively heats dark image areas on the original. The thermal energy in image areas of the original is transferred to localized areas of the photosen-' sitive layer, thus increasing the rate of optical development in image areas to provide a positive image.
A negative copy may be obtained employing the same photosensitive materials and apparatus by slightly changing the copying conditions. Negative copies are obtained by a reflex copy technique during the red light exposure. In this mode of operation, the heat-absorbing glass filter 36 must be interposed in the radiation path to prevent the selective image heating which leads to a positive copy. The photosensitive copy sheet is subjected to the same blanket exposure and run through the apparatus with the image to be copied and the photosensitive layer in intimate contact. The rate of density buildup with red light exposure is exponential. Because of the high dependence of density upon red light exposure, reflex copies may be obtained since, in areas where the image being copied is white, the red light is reflected, thus almost doubling the red light exposure compared to image areas or areas where the area being copied is black.
Contrast control may be effected in negative copying in much the same manner as that realized for a positive copy. In order to realize a low contrast negative copy, a high level of initial blanket exposure from lamp 38 is provided together with a low degree of optical development, i.e., a high machine speed. The converse conditions will result in obtaining a high contrast copy of the original.
In all of the above procedures, a final step is required to fix or render the copy sheet light insensitive. This fixing operation is carried out by subjecting the copy sheet to elevated temperatures which serve to drive the volatile activator (iodoform in the above example) out of the film. For the photosensitive formulation described above, fixing is carried out at a temperature of 145 C for a period of 1 minute.
Reflex copying is possible because of the extremely high contrast obtained in optical development, i.e., the image density varies quite rapidly with exposure. In black areas of the original, possibly only 5 percent of the incident red light exposure is reflected. In white areas of the original, 80 percent of the red light is reflected. The ratio of copy sheet red light exposure between white areas and black areas is thus 1.8/1.05 or about 1.7: 1. This ratio is sufficient to provide a dark image on the copy sheet corresponding to the highly reflecting regions on the original and no copy sheet darkening in low reflectivity areas.
The simplicity of switching from a negative to a positive is apparent. One constraint is present in forming a positive image that is not present in forming a negative image. This is the requirement for a minimum power level (about 1 watt/cm minimum total power at the copy sheet) required to generate a differential temperature between the dark (heat absorbing) areas and white areas on the original. At lower power levels, the differential heating is reduced due to lateral heat conduction in the original. The positive mode works because of the very high temperature coefficient of optical development rate. The rate of optical development goes up a factor of 2.5 for every C increase in temperature. Thus, development occurs much faster in hot areas (areas of the copy sheet in contact with a dark area on the original) than in cooler areas.
Summarizing, the present invention is directed to reflex copying processes utilizing free radical non silver photosensitive films, in wind! exposing radiation strikes a copy sheet while the copy sheet is in physical contact with an original (to be copied), the exposing radiation striking the copy sheet before it strikes the original. Either a negative or a positive image may be produced, as described above.
What is claimed is:
l. A method of producing positive copies of a document which comprises:
1. exposing a copy sheet containing a free radical, non
silver, photosensitive composition capable of being optically developed to uniform blanket radiation in near U.V., violet or blue wavelengths (3,500 A to 4,500 A) sufficient to sensitize the composition to subsequent exposure to visible radiation in the red;
2. bringing the sensitized copy sheet into physical contact with the document to be reproduced;
. projecting red and infrared radiation onto said copy sheet in a manner such that the radiation passes through at least one optical filter which transmits only in the red and infrared portions of the spectrum before said radiation strikes the copy sheet and wherein said radiation strikes the copy sheet before it passes to the document to be reproduced, the amount of radiation projected being sufficient to produce an image on said copy sheet; and
4. thereafter fixing the resulting image in the copy sheet by heating the sheet to a temperature of about C for a short interval.
2. The process of claim 1 wherein a high contrast positive copy is obtained by adjusting the blanket exposure of step l to a relatively low level and providing a relatively high level of red and infrared radiation for optical development.
3. The process of claim 1 wherein a low contrast positive copy is obtained by adjusting the blanket exposure of step l) to a relatively high level and providing a relatively low level of red and infrared radiation for optical development.
4. A method of producing negative copies of an original document which comprises:
1. exposing a copy sheet containing a free radical non-silver, photosensitive composition capable of being optically developed to uniform blanket radiation in near U.V., violet or blue wavelengths (3,500 A to 4,500 A) sufficient to sensitize the composition to subsequent exposure to visible radiation in the red;
2. bringing the sensitized copy sheet into physical contact with the original document to be reproduced;
. projecting red radiation onto said copy sheet in a manner such that the radiation passes through a heat-absorbing filter and at least one optical filter transmitting only in the red portion of the spectrum before it strikes the copy sheet and wherein said radiation strikes the copy sheet before it passes to the document to be reproduced, the amount of radiation projected being sufficient to produce an image on said copy sheet; and
4. thereafter fixing the resulting image in the copy sheet by heating the sheet to a temperature of about 145 C for a short interval.
5. The process of claim 4 wherein a high contrast negative copy is obtained by adjusting the blanket exposure of step (I) to a relatively high level and providing a relatively low level of radiation for optical development.
6, The process of claim 4 wherein a low contrast negative copy is obtained by adjusting the blanket exposure of step (I) to a relatively low level and providing a relatively high level of radiation for optical development.
7. The process of claim 4 wherein the free radical film is a coating on one surface of the copy sheet, and that surface is the one in physical contact with the material to be reproduced.