US3630729A

US3630729A - Electrophotographic multicolor copy process employing solubilizable dyes

Info

Publication number: US3630729A
Application number: US836415A
Authority: US
Inventors: Frederick O Bach; Leo N Chapin; Robert Freed; Thomas J Cernoch
Original assignee: AB Dick Co
Current assignee: AB Dick Co
Priority date: 1969-06-25
Filing date: 1969-06-25
Publication date: 1971-12-28
Anticipated expiration: 1988-12-28
Also published as: DE2031534B2; JPS4926587B1; CA920859A; DE2031534A1; FR2051193A5; BE752540A; NL7009333A; CH532804A; GB1311114A; DE2031534C3

Abstract

An electrophotographic process and materials for the production of multicolor copies of a multicolor original in which an electrostatic charge is applied to a receptor sheet having a face portion subdivided into photoconductive segments containing sensitizing components in interspersed segments which cover different portions of the visible light spectrum and in which each such segment contains a solubilizable dye color corresponding to the color of the spectrum other than that to which the segment is sensitized and in which the exposed receptor is developed with a toner in which the dye component is soluble in response to toner activation for transfer of dye color from the developed receptor to copy sheets brought into surface contact therewith.

Description

United States Patent Inventors App]. No.

Filed Patented Assignee Frederick O. Bach Villa Park;

Leo N. Chapin, Des Plaines; Robert Freed, Lincolnwood; Thomas J. Cernoch, Chicago, all of 111.

June 25, 1969 Dec. 28, 1971 A. B. Dick Company Niles, 111.

ELECTROPHOTOGRAPHIC MULTICOLOR COPY PROCESS EMPLOYING SOLUBILIZABLE DYES 10 Claims, 6 Drawing Figs.

US. Cl 96/l.2, 117/175, 252/62.1, 96/1 7 Int. Cl ..G03g 13/00 V G03g 9/00 Field of Search 96/1 .2, 1.5,

[56] References Cited UNITED STATES PATENTS 3,549,359 12/1970 Honjo et a1. 96/1.2 2,962,374 11/1960 Dessauer 96/1 3,212,887 10/1965 Miller et al. 96/1 3,329,590 7/1967 Renfrew 204/18 3,458,310 7/1969 Arneth et a1 96/1.2

Primary ExaminerGeorge F. Lesmes Assistant Examiner-M. B. Wittenberg AttorneyMcDougall, Hersh, Scott & Ladd than that to which the segment is sensitized and in which the exposed receptor is developed with a toner in which the dye component is soluble in response to toner activation for transfer of dye color from the developed receptor to copy sheets brought into surface contact therewith.

ELECTROPHOTOGRAPHIC MULTICOLOR COPY PROCESS EMPLOYING SOLUBILIZABLE DYES This invention relates to an electrophoto'graphic process, materials and elements for the production of true color copies from multicolor originals with but a single exposure to light.

It is an object of this invention to provide a process for producing true color copies of multicolor originals by use of an electrophotographic technique which requires but a single exposure to light; which makes use of a single-receptor sheet from which one or a number of multicolor copies can be produced; in which multicolor copy is produced by transfer from the receptor sheet to copy sheets for true color reproductions, and it is a related object to provide a composition and elements for use in the practice of the same.

These and other objects and advantages of this invention will hereinafter appear for purposes of illustration, but not of limitation, an embodiment of the invention is illustrated in the accompanying drawings in which FIG. 1 is a top plan view of a portion of a receptor embodying the coatings applied in accordance with a preferred practice of this invention;

FIG. 2 is an enlarged sectional view through a portion of the receptor sheet shown in FIG. 1;

FIG. 3 is a schematic sectional view similar to that of FIG. 2, illustrating the conditions existing in response to exposure to a multicolor original;

FIG. 4 is a schematic sectional view of the exposed receptor of FIG. 3 after treatment with a developer composition; FIG. 5 is a schematic diagram showing the transfer of the multicolor image from the receptor to a copy sheet; and

FIG. 6 is a top plan view of the multicolor copy produced from the exposed receptor of FIG. 5.

Briefly described, the concepts of this invention are practiced with a receptor provided with a number of photoconductive coatings each of which is formulated to contain I) an organic insulating binder, such as an organosilicon resin, a butadiene-styrene copolymer resin, a modified alkyd resin and the like; (2) a photoconductor such as photoconductive zinc oxide or other photoconductive material such as described in the Middleton et al. US. Pat. No. 3,l2l,006; (3) a sensitizing component, such as a sensitizing wavelength within the photo conductor to light of a selected wavelength within the visible light spectrum while reflecting wavelengths outside said range, with each coating containing a sensitizing ingredient which sensitizes the photoconductive coating to a different portion of the visible light range, whereby the total of the coating provides sensitivity which covers the entire visible light range, and (4) a soluble dye component in each coating having a color transfer value corresponding to the subtractive color for which the particular coating is sensitized, as represented by a color produced by the combination of ranges of light reflected by the sensitized photoconductor of the particular coating composition and in which the concepts of this invention include the use of a developer which is formulated with a component, normally identified as a toner, which comprises a solid material in finely divided form which, in response to activation as by heat, solvent, vapors or the like, functions as a solvent for the soluble dye component (4) of the photoconductive coating to effect transfer of the dye color from the portions of the coating immediately underlying the activated solvent for transfer to copy sheets pressed into surface contact with the receptor to produce true color copies of multicolor originals in response to a single exposure.

By way of illustration, the visible spectrum may be subdivided into contiguous segments, preferably three or more segments, such as subdivision of the visible light spectrum, assumed to be included within the range of 400-700 nm. into segments of about 400-500, 500-600 and 600-700 nm. The sensitizng component for one coating would then be selected to sensitize the photoconductor to light of within the range of 400-500 nm. (blue sensitivity) and to reflect light within the range of 500-700 nm. This particular effect can be achieved by the use of a dyestuff corresponding to the yellow layer in the well known photographic color processes based upon the subtractive tripack, such as Auramine 0 (Cl. 4!,000 The soluble dye component formulated into the described coating composition is selected of a dyestuff having a yellow color or a color which represents the combination of the reflected light range of 500-700 nm.

Another or second coating is formulated with a sensitizing component effective to sensitize the photoconductor in the light range of 500-600 nm. (green sensitivity), while reflecting light within the range of 400-500 nm. and 600-700 nm. This can be achieved by the use of a magenta coating, when reference is made to the subtractive tripack system, such as by formulating the coating composition to contain acridine red (C.I. 45,000 The soluble dye component formulated into the described coating would be selected of a dyestuff having preferably a blue-red color corresponding to the combination of the reflected light within the range of 400-500 and 600-700 nm.

The third coating would be formulated to contain a sensitizing component which sensitizes the photoconductor to absorbed light within the range of 600-700 nm. (red sensitivity), while reflecting light within the range of 400-600 nm. This can be achieved by a cyan coat, such as with Patent Blue (CI. 42045). The soluble dye component in the third coating would be selected of a dyestuff giving a blue-green color corresponding to the range of reflected light or the combination of colors within the range of 400-600 nm.

When based upon the amount of photoconductive zinc oxide, the described coating compositions can be formulated to contain the resinous binder in an amount within the range of 10-40 parts by weight of resinous binder per parts by weight of zinc oxide, and preferably in an amount within the range of 15-30 parts by weight of resinous binder per I00 parts by weight of zinc oxide. The sensitizing component or dyestuff is formulated in the coating composition in an amount within the range of 0.001 to 5.0 part by weight per 100 parts by weight zinc oxide and preferably within the range of 0.01 to 2.5 part by weight per 100 parts by weight of zinc oxide, the amount depending somewhat upon the sensitizing dye, such as 0.13 percent by weight of magenta color, as in the form of acridine red having a spectral response in the range of 495-620 A., 0.06 percent of the cyan color, as represented by Patent Blue having a spectral response in the range of 600-700 A., and 1.2 percent by weight of the yellow color as represented by Auramine 0 having a spectral response within the range of 405-500 A. It will be understood that, except for cost, more than 5.0 parts by weight of sensitizer per 100 parts by weight zinc oxide can be used. The soluble dye component can be formulated into each coating in an amount within the range of 05-200 parts by weight per 100 parts by weight of zinc oxide and preferably in an amount within the range of l-5 parts by weight per I00 parts by weight of zinc oxide. The foregoing amounts of sensitizer and soluble dye components to the percent by weight of the photoconductive coatings formulated of photoconductive zinc oxide or a photoconductor other than zinc oxide, but in which the percentage is adjusted by the weight ratio of zinc oxide to said other photo conductive material in the coating.

The soluble dye component is preferably formulated in the respective coating compositions as a dispersed dye but it will be understood that the soluble dye component can be incorporated in other states.

The coatings are produced from compositions containing the described components in combination with a diluent which is a solvent for the resinous binder and application may be made to the substrate in coating weights, when formulated of a zinc oxide photoconductor, within the range of 8-40 pounds per 3,000 square feet of surface area, and preferably within the range of 15-30 pounds per 3,000 square feet of surface area.

The separate coating compositions are applied or other wise imprinted on the surface of the substrate in various patterns. The essential requirement is that the face of the coated substrate define a final pattern of separate, small light responsive areas of each coating interspersed one with another substantially uniformly over the surface of the substrate in closely spaced relation.

This can be accomplished by application of the separate coating compositions in a pattern of dots, circles, beads, spheres, squares, lines or the like configurations. Since it is not essential that the separate light responsive areas be arranged coplanar, it is preferred to apply the coating compositions either in the form of lines which crisscross one another over the surface of the substrate or more preferably to apply one coating composition as a continuous coating over the surface of the substrate and to apply the remaining coatings as lines which crisscross over the underlying base coat as islands or dots of various configuration which overlie the base coat. Thus the receptor sheet will be formed of a substrate having portions coated with only one layer of the first coating, other portions with two layers formed of the first and second coats and first and third coats; and still other portions formed of three layers of the first, second and third coating, etc.

Having described the basic concepts of the invention from the standpoint of compositions and construction of the elements employed, illustration will now be made by way of examples which represent the practice of the invention and in the utilization thereof in carrying out the new and novel process for multicolor reproduction of multicolor originals by the electrophotographic technique. The description will hereinafter be made with respect to a system of compositions based upon the subtractive tripack but it will be understood that the visible light spectrum can be otherwise divided for the selection of component identified as the sensitizing component and corresponding soluble dye component embodied in each of the separate coating formulations.

EXAMPLE 1 Magenta coating composition: (green sensitive):

100 grams photoconductive zinc oxide (Photox 80New Jersey Zinc Company) 25 grams modified alkyd resin (DeSoto E-l04l3A DeSoto Chemical Coatings, Inc.

0.13 gram sensitizing dyeAcridine Red-Cl. 45,000 (Allied Chemical Corp.)

1.5 grams dispersed dye-spirit soluble Fast Red 33 60 ml. toluene EXAMPLE 2 Yellow coating composition (blue sensitive):

100 grams photoconductive zinc oxide (Photox 80) 25 grams modified alkyd resin (DeSoto E- 104l3A) 0.05 gram sensitizing dye-Auramine O--C.l. 41,000 (Allied Chemical Corp.)

[.5 grams dispersed dyeCalcofast Spirit Yellow TG (American Cyanmid Company) 60 ml. solvent-toluene EXAMPLE 3 Cyan coating composition (red sensitive): 100 grams photoconductive zinc oxide (Photox 80) 25 grams modified alkyd resin (DeSoto E- 104-13A) 0.05 gram sensitizing dye-Patent Blue-Cl. 42,045 (Allied Chemical Corp.) 1.5 grams dispersed dyespirit soluble Fast Blue 6G (Allied Chemical Corp.) 60 ml. solvent-toluene ln each of the examples, the resinous binder, zinc oxide and solvent are first blended together by mixing for about minutes. The sensitizing dye, in solution in methanol, is added and blended by mixing for about 1 minute. The dispersed dye is finally added and blended with mixing for about 1 to 2 minutes.

The first coating 20, which may be the magenta coat of example is applied either by a roller coater, by a metering rod,

or by hand draw-down with a wire wound rod, onto Weyerhauser Base A paper it) in a coating weight of about 20 pounds per 3,000 square feet, and then dried. The yellow coating composition of example 2 is applied, as by silk screen in a coating weight of about 15 pounds per 3,000 square feet of surface area in a pattern of closely spaced parallel lines 22 which extend crosswise over the surface of the first coating 20. lt will be understood that the described coatings can be applied in various other sequences such as a first coating of the yellow coat of example 2 followed by second and third coatings of example I and 3, or a first coat of example 3 and second and third coatings of examples 3 and 2 or 2 and 3, etc.

The cyan coating composition of example 3 is also applied, as by silk screen in a coating weight of about 15 pounds per 3,000 square feet of surface area in a pattern of closely parallel lines 24 which extend lengthwise over the first and second coatings to provide crossover points 26 having three thicknesses of coating with the third coating 24 uppermost on the face of the substrate or paper base sheet.

The final coated sheet constitutes a receptor suitable for use in the practice of this invention with separate sections 28 having a single-coating thickness of the magenta coating, separate sections 30 having a double-coating thickness formed of a lowermost magenta coating 20 and an uppermost yellow coating 22 and a lowermost magenta coating 20 and an uppermost cyan coating 24 and still other sections 32 having a triple coating thickness formed of a lowermost magenta coating 20, an intermediate yellow coating 22 and an uppermost cyan coating 24. Thus the exposed face of the receptor presents separate sections of each of the coatings in substantially uniformly dispersed relation over the face of the receptor sheet.

The receptor sheet is charged in the usual manner, now well known to the electrostatic copy art, as by subjecting the face of the receptor to a corona spray as it is exposed to corona discharge from wires operating at a potential of about 6,000 to 8,000 volts. The charged wires, which extend across the face of the receptor, are either transported over the face of the receptor or the receptor is displaced beneath the wires. The electrostatic charge is deposited over the entire receptor covered by one or more of the photoconductive coatings.

The charged receptor is next exposed to the multicolor original. Such portions of the original which are blue in color, for example, will cause discharge of the corresponding areas on the face of the receptor formed of the yellow coating which is sensitized to blue, leaving the charges in the corresponding areas on the exposed face sections of the magenta and cyan coatings for subsequent development.

The portions of the original which are green in color cause discharge of the corresponding areas 28 on the face of the receptor of the magenta coating, which are sensitized to green, leaving the charge 34 on the corresponding areas on the face sections 32 of cyan and sections 30 of the yellow coating for subsequent development, as depicted in H6. 3.

Similarly, the portions of the original which have the color red will cause discharge in the corresponding areas of the receptor of the cyan sections'32 on the exposed face of the receptor sheet which are sensitized to red, leaving the charges on the corresponding areas in the exposed faces sections of magenta and yellow for subsequent development.

The exposed receptor sheet is developed in the conventional manner either with a dry powder developer or with a liquid developer, but in which the conventional particles of toner in the dry powder developer suspended in the liquid developer are substituted by finely divided particles of a compound which, when activated as by heat or solvent, vapor and the like, becomes a solvent for the dispersed dye in the coating.

The following examples are given by way of illustration, but not by way of limitation, of liquid developing compositions embodying the features of this invention:

EXAMPLE 4 5.0 grams toner (Antipyrine) 400 ml. liquid carrier (lsopar G-Humble Oil Co.) 5 grams charge director (Fuel Oil Additive No. 2--DuPont EXAMPLE 5 5.0 grams toner (l-allyl-Z-thiourea) 400 ml. liquid carrier 5 grams charge director The Isopar G used as the liquid carrier in the above example is parafi'mic hydrocarbon liquid having 1l.8 percent C hydrocarbons, 56.2 percent C hydrocarbons, 31.7 percent C hydrocarbons, less than 0.3 aromatics and less than 0.1 olefins, a boiling point within the range of 3l8-350 F., a flash point of 104 F. and a specific gravity of 0.748. Other liquid carriers used in liquid developers may be used as long as the toner compound is not dissolved therein. The Fuel Oil Additive No. 2 is a solution of a methacrylate copolymer having an average molecular weight of 50,000. Again, other conventional charge directors can be employed.

The antipyrine of example 4 and the l-allyl-Z-thiourea of example 5 are merely representative of suitable toner particles which may be used for development of the latent electrostatic image of the charged sections that remain after exposure. Other toner particles may be used which meet the requirements:

1. a solvent for the soluble dye component in the coatings when the toner is in a molten or activated state;

2. capable of being reduced to a finely divided form in which it is retained in the liquid or powdered developer composition;

3. capable of taking on a charge, such as a positive charge when used with a charged photoconductive coating of zinc oxide;

. suitably located within the triboelectric series to produce the desirable charge development. Representative of other suitable compounds which meet these requirements and can be used as toners are vanillin, 1,6-hexanediol, 1,10decanediol, ethyl urea, acetamide, benzohydrol, 2,2- dimethyl-l,3-propanediol, ammonium acetate, ammonium formate and pyrazine. The toner particles can be employed in various concentrations in the developer composition, such as within the range of 2-20 percent by weight, and preferably 3-10 percent by weight, in a dry powder developer and within the range of 02-20 percent by weight and preferably 2-10 percent by weight in a liquid developer. When use is made of a dry powdered developer which is applied by brushing or the like, the toner concentration can range up to 100 percent by weight toner in the developer.

Continuing with the development process, in response to the application of the developer composition, toner particles 36 will be retained the portions of the face of the receptor which remain charged to define the latent electrostatic image after exposure while the discharge sections on the face of the receptor will remain substantially free of the toner particles, as depicted in FIG. 41.

Thereafter the developer receptor sheet is pressed into surface contact with a copy sheet 40, as by passage of the composite assembly between compression rollers heated to a temperature above the melting point temperature for the toner, such as at a temperature above lll-l 13 C. which is the melting point for antipyrine, or above a temperature of 77-78 C. which is the melting point for l-allyl-2-thiourea, and preferably by heating the toner particles to a temperature which exceeds their melting point by a slight amount preferably about 5-l0 lF. As a result, the toner particles are reduced to a fluidized state to enable solution of the dispersed dye in the underlying portions of the photoconductive coating in the face of the receptor for transfer of the corresponding dye color, as by diffusion, from the receptor to the copy sheet 40.

1n the example illustrated in FIGS. 4 and 5, the cyan and

yellow coatings

32 and 30, respectively, which remain charged and retain the toner particles 34 on development, solubilize the Calcofast Spirit Yellow TG and the Spirit Soluble Fast Blue 6G to cause transfer to the copy sheet with the resultant reproductions 50 of the green color of the original. In such areas of the original which are black, such as the printed areas, none of the sections in the face of the coated receptor would become discharged upon exposure. As a result, each of the areas accept toner for transfer of dyestuffs from all of the three basic color sections which together appear black in the copy sheet.

It will be apparent that the copy produced by the combination of colors transferred from the developed receptor sheet will correspond to the colored original and that the developed receptor can function in a manner of a spirit master to produce multiple copies of the multicolor original, as by the successive passage of copy sheets into pressure contact with the developed receptor until the soluble dyestuff in the toned face segments are exhausted.

It will be apparent from the foregoing that I have provided a new and novel electrophotographic process for the production of true color copies of multicolor originals by the use of but a single exposure for the development of a master from which one or more multicolor copies can be produced.

It will be understood that changes may be made in the details of formulation, application and process steps without departing from the spirit of the invention, especially as defined in the following claims.

We claim:

1. An electrophotographic process for the production of multicolor copies of a multicolor original comprising the steps of applying an electrostatic charge onto the face of a receptor formed of a substrate having on its face interspersed sections of two or more photoconductive coatings each of which contains a photoconductive component, a sensitizer for the photoconductive component and a solubilizable dye, in which the sensitizer in one coating sensitizes the photoconductor to a particular segment of the visible light range for absorption of light within said range and reflection of light outside said range, and in which the solubilizable dye corresponds with the color of the reflected light, and in which separate coatings are provided with sensitizing components designed to cover substantially the entire visible light range, whereby and electrostatic charge is retained by each of said photoconductive coatings, exposing the charge receptor to the original whereby the sections on the face of the receptor are discharged in response to exposure to color in corresponding areas of the original to which the particular sections have been sensitized, leaving the charge on the sections from which the light has been reflected, developing the exposed receptor with a developer containing a toner in the form of finely divided particles of a material which is a solvent for the dyestuff in response to activation whereby toner is retained on the sections retaining the electrostatic charge, ans bringing a copy sheet in surface contact with the face of the developed receptor with the toner in an activated stage to cause transfer of solubilized dye colors from the corresponding areas of the receptor to the copy sheet.

2. The process as claimed in claim 1 in which the interspersed sections of photoconductive coatings comprise interspersed sections of three separate coating systems sensitized to the additive primary colors of red, green, blue, respectively.

3. The process as claimed in claim 1 in which the photoconductor component of the photoconductive coating comprises photoconductive zinc oxide.

4. The process as claimed in claim 1 in which the sensitizing component is a sensitizing dye.

5. The process as claimed in claim 4 in which the sensitizing dye id present in the coating in an amount within the range of 0.001 to 5.0 percent by weight when the photoconductive component is a photoconductive zinc oxide with the said percentage varying in proportion to the weight of zinc oxide and other photoconductor when said other photoconductor forms the photoconductive component.

9. The process as claimed in claim 1 in which the toner is an organic compound selected from the group consisting of antipyrene and 1-allyl-2-thiourea 10. The process as claimed in claim 1 in which the toner has a melting point at a temperature above ambient temperature and in which activation of the toner comprises the step of heating the coated receptor to a temperature above the melting point temperature of the toner while the copy sheet is in pressure contact with the face of the receptor.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 3,630,729 Dated December 28, 1971 Frederick O. Bach et al.

Patent No.

Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

column 1, line 43, after "sensitizing" cancal "wavelength within" and substitute dye which sensitizes column 2, after line 55, insert the following line:

"specified in parts by weight may be taken as corresponding";

column 6, line 44, change "and" to "an" (SEAL) Attest:

EDWARD TLFLETGI-IFH JR ROBERT GOT TSCHALK Attesting Officer I Commissioner of Patents USCOMM-DC 60376-P69 us. GOVERNMENT PRINTING ornc: I969 0-365-334 FORM PO-105O (10-69)

Claims

2. The process as claimed in claim 1 in which the interspersed sections of photoconductive coatings comprise interspersed sections of three separate coating systems sensitized to the additive primary colors of red, green, blue, respectively.
3. The process as claimed in claim 1 in which the photoconductor component of the photoconductive coating comprises photoconductive zinc oxide.
4. The process as claimed in claim 1 in which the sensitizing component is a sensitizing dye.
5. The process as claimed in claim 4 in which the sensitizing dye id present in the coating in an amount within the range of 0.001 to 5.0 percent by weight when the photoconductive component is a photoconductive zinc oxide with the said percentage varying in proportion to the weight of zinc oxide and other photoconductor when said other photoconductor forms the photoconductive component.
6. The process as claimed in claim 1 in which the colored dye component corresponding to reflected light is a dispersed dye.
7. The process as claimed in claim 6 in which the dispersed dye is a spirit soluble dye.
8. The process as claimed in claim 6 in which the dye component is present in an amount within the range of 0.5 to 20 parts by weight per 100 parts by weight of the photoconductive component when that photoconductive component is zinc oxide.
9. The process as claimed in claim 1 in which the toner is an organic compound selected from the group consisting of antipyrene and 1-allyl-2-thiourea
10. The process as claimed in claim 1 in which the toner has a melting point at a temperature above ambient temperature and in which activation of the toner comprises the step of heating the coated receptor to a temperature above the melting point temperature of the toner while the copy sheet is in pressure contact with the face of the receptor.