US 3655379 A
A liquid ink layer is formed on the surface of a transparent substrate. The ink layer is exposed through the substrate to high energy radiation causing exposed ink areas to move to a receiver sheet. It is believed that the ink is transferred by the rapid expansion of vapor.
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Description (OCR text may contain errors)
United States Patent Gundlac'h  3,655,379 [451 Apr. 11, 1972  PRINTING BY VAPOR PROPULSION  Inventor: Robert W. Gundlach, Victor, NY. A
 Assignee: Xerox Corporation, Rochester, N.Y.
 Filed: Oct. 29, 1969 [21 1. Appl. No.: 872,135
3,207,602 9/1965 Shely 3,280,735 10/1966 Clark et a1. 3,360,367 12/1967 Stricklin ..96/27 X 3,408,216 10/1968 Mott et a1. ..117/37 X 3,446,617 5/1969 Stricklin ..96/ 27 3,455,687 7/1969 Holstead et a1. ....250/65.1 X
3,490,371 l/1970 Games ..250/65.1 X
OTHER PUBLICATIONS Rositon et al., IBM Technical Disc. Bull, Vol. 7, N0. 3, Aug. 1964, page 224.
Primary Examiner-John T. Goolkasian Assistant Examiner.loseph C. Gil
Attorney-James .1. Ralabate, Richard A. Tomlin and David C.
Petre [5 7] ABSTRACT A liquid ink layer is formed on the surface of a transparent substrate. The ink layer is exposed through the substrate to high energy radiation causing exposed ink areas to move to a receiver sheet. 1t isbelieved that the ink is' transferred by the rapid expansion of vapor.
8 Claims, 2 Drawing Figures PATENTEDAPR H I972 INVENTOR ROBERT w. GUNDLACH fiww ATTORNEY PRINTING BY VAPOR PROPULSION BACKGROUND OF THE INVENTION This invention relates in general to image formation and more specifically to the formation of images by the transfer of liquid from a donor member to a receiver member in response.
to imagewise high energy electromagnetic radiation.
Many methods are known for producing visible images including printing and photographic methods where the color of a light sensitive chemical is changed by the action of light. Other methods of forming a visible image are known where light is used to alter the hardness, tackiness, solvent resistance, or ink receptivity of a suitable material. Other methods include electrostatic methods where an electrostatic charge pattern is formed on the surface of a material and is developed by electroscopic material. Further methods are known where high energy light is used to cause the evaporation of a material in image configuration from a donor sheet with subsequent condensation in image configuration on a receiver sheet. An additional process is shown in U.S. Pat. No. 2,503,759 to A. Murray in which a material is evaporated from a substrate in image configuration leaving behind a positive image. The above processes all require complex image forming and developing steps or the evaporation of a material to form a final print.
Another method of forming an image is disclosed in copending application Ser. No. 783,059 filed Dec. 11, 1968 by W. E. L. Haas et al. in which a layer of radiation absorbing particles is placed on a donor sheet and exposed to an imagewise pattern of high intensity short duration radiation which propells the particles from the donor sheet in an imagewise pattern to a receiving sheet. The donor layers used in this process are, however, difficult to reconstitute and are disposed.
SUMMARY OF THE INVENTION It is an object of this invention to provide an imaging system which overcomes the above mentioned disadvantages.
It is another object of this invention to provide a relatively simple imaging system.
It is another object of this invention to provide an imaging system which requires no chemical developing step.
It is another object of this invention to provide an imaging system which does not require complex chemicals or charge patterns.
It is another object of this invention to provide a method for printing images without the necessity for preparing printing plates.
The above objects and others are accomplished in accordance with this invention by providing a'layer of liquid ink on the surface of a transparent member. A receiver sheet is placed close to the liquid layer. The liquid layer is then exposed to high energy electromagnetic radiation in image configuration. It has been found that when these steps are completed the liquid in light struck areas jumps across a gap to the receiver sheet in image configuration. The image on the receiver sheet may then be fixed by allowing the ink to dry or the receiver sheet may be somewhat porous allowing the liquid to permeate therein. By exposing the liquid layer to radiation projected through a negative transparency a positive image may be formed on the receiver sheet. In a preferred embodiment the substrate on which the liquid layer is formed is in the form of a gravure or grooved plate. The grooves or cups are filled with the liquid and the raised areas which contact the receiver are substantially free of ink. The receiver sheet may then be placed in contact with the raised areas of the gravure or grooved plate. Sharper images are obtained when the liquid layer is in the ,form of a series of minute, discrete pools rather than in the form of a uniform liquid layer. A further advantage exists in that since the receiver sheet is in contact with the raised areas of the plate it is almost in contact with the liquid thereby requiring less light energy to move the liquid to the receiver sheet than would be required if the receiver sheet were placed at some distance from the liquid layer and also provides sharper images.
Although the exact mechanism which causes the layer to be transferred to the receiver sheet is not known, apparently small pockets of vapor are formed in image areas by the conversion of radiant energy to heat energy upon absorption near the interface between the transparent member and the liquid layer. The rapid expansion of these vapor pockets propels the liquid away from the transparent member. It has been found that images may be formed across as much as a V; inch gap. Since evaporation of more than a very small'fraction of the liquid layer is not required to cause transfer, the energy requirements are much less than for those systems which require the evaporation and condensation of an entire layer.
It is desirable to use a relatively short period of illumination to cause transfer. The energy provided by an extended low level of illumination would tend to be dissipated by conduction to the substrate or surrounding ink layer. A preferred illumination would have an energy of less than about 1.0 joules/cm. for a time not greater than about 10 sec., depending on the thickness of the'layer, the nature of the layer, the gap to be traversed and whether blowing agents are incorporated in the layer. For example, where the illumination time is reduced to about 4 X 10 seconds an energy level of about 0.3 joules/cm. is sufficient.
Images may be formed in any color depending only on the color of the liquid ink used. Further, full color images may be prepared by using color separation transparencies and superimpo sing a succession of colored images on a single receiver sheet.
Fixing of the image produced may be aided by utilizing a liquid ink in which a paraffin or wax-like material has been dissolved. On evaporation of the liquid component the waxlike material will form a binder for the final image. Or the liquid layer may be a material which is a liquid at elevated temperatures and where fixing is accomplished by allowing the image to cool.
The liquid layer may be a dispersion, a suspension, or a solution and may be of one or more phases. The liquid layer may be a printing ink such as a mixture of finely divided pigment such as carbon black suspended in a drying oil such as heatbodied linseed oil. Alkyds, phenol-formaldehyde or other synthetic resins and cobalt, manganese, and lead soaps may be added to achieve rapid drying by oxidation and polymerization. Inks which dry by evaporation of a volatile solvent such as mineral oil may be used. For colored inks pigmented or dyed inks such as inks containing chrome yellows, benzidine yellows or lithol reds may be used.
A preferred liquid layer comprises a suspension of carbon black in isopropyl alcohol. This liquid layer is preferred because it gives dark black images and dries rapidly.
To aid transfer blowing agents whether gaseous, liquid or solid may be incorporated into the inks. Blowing agents or foaming agents are those materials which produce an inert gas such as nitrogen or carbon dioxide when heated. Typical blowing agents include pentane, hexane, isohexane, methylene chloride and trichlorotrifluoroethane.
BRIEF DESCRIPTION OF THE DRAWINGS The advantages of this improved method of imaging will become apparent upon consideration of the detailed disclosure of the invention, especially when taken in conjunction with the accompanying drawings wherein:
FIG. 1 shows a side view of a simple exemplary system for carrying out the process of this invention wherein a transparency is placed on the inside of a transparent drum and exposure is made through the transparency. The thickness of the liquid ink layer has been greatly exaggerated for purposes of clarity.
FIG. 2 shows an enlarged cross sectional side view of an exemplary imaging station in accordance with this invention. Sizes and distances have been distorted for purposes of clarity.
Referring now to FIG. 1 there is seen transparent drum 1 which may be for example glass, plastic, or other suitable transparent material. Liquid ink 2 is applied to the surface of drum 1 by applicator roller 3. The thickness and uniformity of liquid ink 2 is controlled by flexible doctor blade 4. A transparency 5 is placed on the inside of transparent drum 1. This arrangement is exemplary, many other arrangements would provide similar results. Preferably the surface of drum 1 is in the form of a gravure or grooved plate, which provides cleaner separation between image and non-image areas. Light source 7 which may be, for example, a laser or other collimated light source and lens 9 are used to provide a high energy source of radiation which is focused in a fine line on the inner surface of liquid ink layer 2. In dark areas of transparency 5 sufficient energy is absorbed to prevent transfer of ink layer 2. In transparent areas of transparency 5 sufficient energy is imparted to liquid ink 2 to cause it to move across the gap to receiver sheet which may be, for example, paper. Receiver sheet 15 in this exemplary instance is entrained over drum 17. A positive image 19, that is the image which has light and dark areas corresponding to light and dark areas of transparency 5 is formed on drum 1. This image may be transferred and retained where desired. Negative image 21, that is the image which has dark areas corresponding to light areas of transparency 5 is formed on the surface of receiver sheet 15.
Referring now to FIG. 2 there is seen a greatly enlarged cross sectional area of a preferred imaging station for use in this invention. Transparent donor layer 23 is provided with small grooves or dimples 25. Grooves 25 are filled with liquid ink 26 and doctored such that when receiving member 27 is placed in contact with donor 23 no ink transfers without the application of light 29 which is focused to a fine line by cylindrical lens 30. Transparency 33 having image areas 34 provides imagewise illumination of the donor member 23.
DESCRIPTION OF PREFERRED EMBODIMENTS The following examples further specifically illustrate the improved imaging process of this invention. All parts and percentages are based on weight unless otherwise stated. The following examples are intended to illustrate various preferred embodiments of the improved imaging process.
EXAMPLE I Approximately 50 parts by weight of finely divided carbon black is dispersed in about 50 parts isopropanol. A glass slide is prepared by placing 3 mil tape on its ends. The space between the tape is coated with about a 25 microns thick layer of the suspension. The slide is placed face down over a piece of paper. The tape provides a gap between the ink and the paper of about 2 mils. A stencil is placed on the top side of the glass. The liquid ink is illuminated through the stencil and glass slide by a flash from a gas discharge lamp which provides an energy level of about 0.4 joules/cm. over a time of about 3 X 10 sec. On separation of the glass slide and paper receiver an image is found on the paper corresponding to the stencil.
EXAMPLE II The experiment of Example I is repeated except that the glass slide is placed ink side up, the paper is placed over the slide and the stencil is placed under the slide. That is the paper, slide, stencil combination of Example I is turned over. The ink is exposed through the stencil as in Example I. An image corresponding to the stencil is again found on the paper. This demonstrates that the ink may be driven against the force of gravity.
EXAMPLE III The experiment of Example I is repeated except that the carbon black is replaced by a carbon black pigmented copolymer of polystyrene and n-butylmethacrylate available as xerographic toner. The image is fixed by application of heat providing a rub'resistant high quality image.
EXAMPLE IV A glass plate is provided having about I50 grooves to the linear inch both horizontally and vertically. The grooves are approximately 3 mils deep providing a raised area of about l0 percent of the total area. The plate is inked with the ink of Example I using a doctor blade which provides an ink level about /2 mil below the level of the raised areas. A smooth surfaced paper receiver sheet is placed in contact with the plate. The liquid ink is illuminated through a stencil as in Example I providing an image on the receiver paper. This image is compared to the image prepared in Example I and found to be of higher resolution evidencing cleaner separation between illuminated and non-illuminated areas.
EXAMPLE V In this Example an opaque black donor member is used and the radiation is directed through the receiver sheet and ink layer before being converted to heat energy by the black donor member. A donor member is' made by forming about 200 parallel grooves per linear inch in black anodized aluminum and at about a right angle to the parallel grooves another about 200 parallel grooves per linear inch are made providing a donor member similar to that of Example IV. The grooves are about 1 mil deep. The inking is doctored so that a /2 mil deep layer of ink is formed in the grooves. A translucent receiver sheet is placed over the inked aluminum donor plate. Illumination is made through a template using infrared radiation of about 0.4 joules/cm. 2 for about 4 X 10 seconds providing an image on the surface of the translucent paper. A
and the image transferred to paper if desired.
EXAMPLES Vl-IX The experiments of Examples I-IV are repeated using an illumination of 0.2 joules/cm. for l X 10 seconds. The images are found not to be of as high quality as those of Examples I-IV.
Although specific components and proportions have been stated in the above description of preferred embodiments of the invention other typical materials as listed above, where suitable, may be used with similar results. In addition, other materials may be added to the ink to synergize, enhance or otherwise modify the properties of the ink. For example, polymerization initiators activated by light may be added to assist the fixing of the final image.
Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the disclosure. These are intended to be included within the scope of this invention.
What is claimed is:
1. An imaging process comprising:
a. providing a donor member;
b. applying a layer of a liquid ink to said donor member;
c. exposing at least a portion of the interface of said liquid ink layer and said donor member to a pattern of electromagnetic radiation until an image is formed by the vapor propulsion of liquid from said donor member.
2. The process of claim 1 including the additional step of:
(1. providing a receiver member to intercept the ink which is removed from said donor member at least prior to or con currently with step (c).
3. The process of claim 1 wherein said electromagnetic radiation is collimated light.
4. The process of claim 1 wherein said donor member comprises a transparent member having recessed areas.
5. The process of claim 1 wherein said donor member comprises an opaque member having recessed areas.
6. The process of claim 1 wherein said ink comprises finely divided particles of pigment dispersed in a liquid.
7. The process of claim 1 wherein said ink comprises a dye solution.
8. The method of claim 1 wherein said donor member is transparent and said radiation is projected through said transparent donor member.