US3445654A - Reflex copying process and apparatus employing infrared exposure and electrolytic development - Google Patents

Description

May 20, 1969 F. J. LOPREST 3.445.654

REFLEX COPYING PROCESS AND APPARATUS EMPLOYING INFRARED EXPOSURE AND ELECTROLYTIC DEVELOPMENT FiledDec. 30. 1966 INVENTOR. Frank J. Loprest ATTORNEY United States Patent 3,445,654 REFLEX COPYING PROCESS AND APPARATUS EMPLOYIN G INFRARED EXPOSURE AND ELEC- TROLYTIC DEVELOPMENT Frank J. Loprest, Vestal, N.Y., assignor to GAF Corporation, a corporation of Delaware Filed Dec. 30, 1966, Ser. No. 606,082 Int. Cl. G01n 21/34; H01j 37/22 US. Cl. 250-65 20 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a process and apparatus for the reflex copying of original documents through the sequential use of infrared heat and an electrical current. Superimposed original documents and sensitized copying sheets are subjected to infrared radiation. The sensitized copying sheet contains a substance adapted to form an electrically conductive base upon application of infrared heat, which upon being subjected to the electrical current will provide a basic medium. The basic medium will then form the desired environment for a developing reaction which will produce a visible dye in the pattern of the original document.

This invention relates to a process and apparatus for the reflex copying of prints and, more particularly, to a reflex copying system utilizing diazo-type copying materials.

Processes and apparatuses for the commercial production of positive prints or photocopies of an original are widely known and used. Among these processes is the so-called ammonia process for imaging an original. This process, in essence, involves the use of a copy paper which supports a light sensitive layer containing a diazo compound and a coupler, in addition to acids and other stabilizing substances adapted to inhibit thermal decomposition of the diazo as well as premature coupling between the diazo and coupler. Development is attained, after exposure of the sensitized copy paper layer to light under the original, by subjecting the sensitized copy paper to hot moist ammonia fumes. The principal objection to this process, aside from other disadvantages, is the use of the highly malodorous ammonia fumes in commercial establishments.

Another extensively used diazo process involves a paper coated with a diazo and a stabilizing substance, but without a coupler. Development is brought about, following exposure to light, by moistening the latent diazo image with a solution of a coupling compound in aqueous alkali. Although this process eliminates the need for ammonia fumes, it requires the manipulation and handling of highly corrosive solutions, thus rendering the process highly difficult and hazardous. Other disadvantages of the aforementioned processes include the necessity of having to dry the wet prints, closely circumscribed restrictions on the choice of suitable diazos and couplers, a pronounced tendency of the color to bleed under the Wet conditions, and excessive loss of production time available due to the need for frequent cleaning of the developing apparatus.

Somewhat more recently, a number of developing processes have been placed into commercial use which involve the action of heat or both heat and moisture on the sensitive layer and in which the necessity for using ammonia or wet development is completely avoided. These more recent developing processes involve the use of improved types of diazo materials which are frequently designated as thermodiazo materials which upon application of heat, liberate either ammonia or other alka- Patented May 20, 1969 line agents which will effect the development of the previously exposed sensitized paper.

Among the developing processes or copying systems using heat are those employing infrared radiation which is converted to heat upon absorption by the characters on the original being copied. Thus, an original sheet is superimposed with a sensitized copying sheet, the latter of which is relatively transparent to infrared radiation. When the infrared radiation is substantially transmitted through the sensitized layer and the base of the copying sheet onto the original sheet therebelow, the infrared radiation is generally absorbed by the black or darkened characters on the original and reflected from the lighter or white background. The absorption of the infrared radiation by the black characters will cause the latter and the superimposed areas of the sensitized copying sheet to rise in temperature, possibly from 70 to C. This temperature rise is utilized to accomplish various chemical reactions in the sensitized copying layer accompanied by the desired color or dye changes.

Generally, the above described dry thermographic developing processes frequently are limited to the use of diazo compounds and couplers dependent upon light or heat to propagate the coupling or developing sequence. Further, in order to avoid the premature coupling of the diazo compounds and the couplers during long periods of storage under climactic conditions not always suitably under control, it has been necessary to use separate papers, one of which provides the diazo layer, and the other of which is impregnated with the coupler. This, of course, results in a rather cumbersome and expensive developing system, requiring the constant and frequent replacement of the coupler impregnated papers.

The present invention overcomes the foregoing and other disadvantages of the prior art copying processes by providing a unique and improved copying system for the imaging of an original document through the sequential use of infrared radiation and an electrical current. An important feature of the present invention resides in the fact that the process may be used in connection with various widely known light or heat-sensitive materials and, in particular, is useful in regard to sensitized copying materials of the so-called diazo-type.

A further feature of this invention may be found in the copying system which uses a copying sheet containing a substance or an agent rendering the copying sheet electrically conductive due to the rise in temperature caused by the absorption of the infrared radiation by the black image characters on an original document positioned below the copying sheet. A particularly suitable substance of that type may consist of a water release agent or precursor, such as a hydrate, which liberates its water imagewise in response to the rise in temperature, with the copying sheet being constituted so that the addition of water renders it electrically conductive. This invention is particularly useful in regard to diazo copying systems since these have had the disadvantage of only being capable of use with translucent original documents having images on one side. The present invention obviates the foregoing disadvantage by being applicable to the reflex imaging of opaque original documents having images on both sides thereof.

It is, accordingly, an object of the present invention to provide a process for making prints through the reflex copying of an original document.

A further object of the present invention is to provide a process for the imaging of original documents on light or heat sensitive copying materials through the sequential use of infrared radiation and an electrical current.

A more particular object of the present invention is to provide a process for making diazo-type prints through the sequential use of infrared radiation and an electrical current by means of a water release agent in the diazo materials adapted to provide the required developing medium in the presence of the electrical current.

Yet another object of the present invention is to pro vide a novel apparatus for carrying out the process of reflex copying of opaque original documents through the sequential use of infrared radiation and an electrical current.

These and other objects and features attained by the process and apparatus of the present invention will become readily apparent from the following description, taken in conjunction with the accompanying drawings, wherein:

The single figure illustrates an elevational schematic view of an apparatus for carrying out the process of the invention.

'In essence, the process of reflex copying according to this invention is comprised of two sequential portions. The first portion of the process utilizes the well known principle of thermography in the superposition of a sensitized material or copy sheet containing a color former directly over an original document to be copied. Infrared radiation, which is essentially heat radiation, is projected onto the original document by passing it through the sensitized copy sheet. The infrared radiation is reflected by the light or white background of the document, and absorbed by the black or dark images and characters thereon. Absorption of the infrared radiation by the dark characters will heat the later, and also the areas of the sensitized copy sheet superimposed thereon, to range of about 70 to 150.

The sensitized copy sheet, which is comprised of a material having a relatively high electrical resistivity under normal conditions is impregnated with or contains a substance adapted to lower the electrical resistance, i.e. raise the conductivity of the material when the temperature thereof is increased through the infrared radiation. In this instance, the substance adapted to increase .the conductivity of the sensitized material in the region of the heated image-reflecting characters, is a water release agent or hydrate which will decompose in the presence of heat to thereby release moisture. The release of the moisture or water creates a latent image on the sensitized material. This, in effect, is an invisible wet pattern corresponding to the heated characters on the original document.

At this stage of the copying process, the original document being imaged may be removed from contact with the sensitized copy sheet which contains the moist latent image. The sensitized copy sheet is now passed between a cathode and an anode and subjected to an electrical current of a polarity such that the cathode of the electrodes is in electrical contact with the latent image containing sensitized layer of the copy sheet. The electric current, flowing through the path of the least electrical resistance, will pass between the anode and cathode of the electrodes and through the moist or latent image portions of the sensitized copy sheet.

In order to propagate the developing reaction between the sensitized layer and color former, a basic medium of a relatively high pH is required. This basic medium is provided by an electrolytic oxidation reduction of the water derived from the decomposition of the hydrate. The cathode of the electrodes is positioned adjacent to the layer of the sensitized material which contains the moist decomposed hydrate, and the electrical current, in a manner well known, will discharge hydrogen ions from the water by attracting the hydrogen ions to the cathode. In essence, this reduction process will increase the pH of the sensitized layer on the copying sheet and thus permit the desired developing reaction between the sensitized material and color former to take place.

Although many suitable water release agents and salt hydrates are known, some particularly useful media would be lithium metaborate octahydrate, sodium sulfate decathydrate, sodium dihydrogen phosphate dodecathydrate, borax, sodium alginate, and sugar. These are only, however, given by way of example inasmuch as numerous other water release agents or substances which will increase the electrical conductivity of the sensitized copying material under the aforedescribed conditions may readily lend themselves to this invention.

Of particular use, although not limited thereto, is the present inventive process when applied to the well-known diazo type developing system. In the application to a diazo-based copying sheet, the developing reaction essentially consists of the coupling reaction between a diazonium salt and a color former or coupler under basic conditions, to produce a visible diazo dye. The basic condition or medium which will propagate or initiate the coupling reaction between the diazonium salt and coupler is of course provided, in this instance, by the water release agent or salt hydrate subjected to the sequential physical environments of heat and electrical current.

Generally, practically all of the innumerable diazonium salts and couplers which will react under basic conditions are suitable for this process. For example, some of the diazonium salts which may be used in carrying out this process are as follows:

4-benzoylamid0-2,S-diethoxybenzene diazonium chloride 4-benzoylarnido-2-chloro5methoxybenzene diazonium chloride 4-benzoylamide-2,S-dimethoxybenzene diazonium chloride 3-chloro-4-diethylaminobenzene diazonium chloride 4-benzoylamido-Z-methoxy-S-methylbenzene diazonium chloride 4- (N -ethyl-N-benzyl)aminobenzene diazonium chloride 4-phenylaminobenzene diazonium sulfate 2-methoxy-4-phenylaminobenzene diazonium chloride (2'-methoXy-4-diazodiphenylamine chloride) 4- (4'-methoxyphenyl)aminobenzene diazonium chloride (4-diazo-4'-methoxydiphenylamine chloride) All of the above listed diazonium salts are derivatives of p-phenylenediamines which are monoor di-substituted on one of the two amino groups while the primary amino group is converted into a diazo group. The diazo compounds are used in the form of their stabilized salts and may be coated in the usual manner upon a suitable carrier, i.e. a copying sheet.

The coupler which is suitably admixed with the diazonium salt on the copying sheet is generally selected from the group consisting of such phenols, naphthols, and compounds containing a reactive methylene group which are free of primary amino groups. As an illustration, a satisfactory coupler would be resorcinol, although numerous other equally effective couplers could be used. For further illustrative examples of diazo-type compounds and couplers, reference may be had to C. H. Benbrook et al. US. Patent No. 2,789,904.

After the developing reaction between the diazonium salt and coupler has been eflected in the imaged region of the sensitized copying sheet made electrically conductive by the salt hydrate and subjected to the current, the areas of the sheet where no coupling has taken place are indicated as an unattractive yellow background formed by the uncoupled diazonium salt. Accordingly, the copying sheet may be then subjected to ultraviolet light rays which will effectively destroy the undeveloped diazonium in the yellow background without affecting the developed diazo dye, and bleach the background to a white color.

Referring now in particular to the drawing, illustrating a schematic embodiment of an apparatus for carrying out the present inventive process, a suitable housing 10 has positioned therein a rotatable cylinder or drum 11. Cylinder 11 may be journaled at each end in the side walls of housing 10. The cylinder should be constituted of a material permitting infrared radiation to pass therethrough with a minimum or negligible amount of absorption to thereby maintain it in a relatively cool temperature during operation of the apparatus. An endless conveyor belt 12 positioned to encompass a substantial portion of the surface of cylinder 11 and move therewith is entrained about suitable drive and idler rollers 13, 1-4, 15, 16 journaled in the walls of housing 10. A source of infrared radiation 17 is positioned within cylinder 11, and may include a reflector 18 adapted to direct the infrared rays through cylinder 11 toward conveyor belt 12.

In operation, a sensitized copying sheet C, hereinafter described as a diazo type although not necessarily limited thereto, having a layer of diazonium salt, a color former or coupler, and a water release agent such as a salt hydrate, is superimposed with an original document D to be copied. The superimposed sheets C and D are fed through an inlet opening 19 in housing into the space between cylinder 11 and conveyor belt 12 so that the copying sheet C is interposed between cylinder 11 and the original document D.

The infrared radiation generated by source 17 will penetrate cylinder 11 and copying sheet C, impinge on document D and will be reflected by the white background of the document D and absorbed by the black characters or images thereon. The absorption of the infrared radiation will heat the images and the superimposed contiguous portions of the copying sheet C to a temperature range of about 70 to 150 C. This increase in temperature will decompose the hydrate in those portions of the copying sheet and generate electrically conductive moisture in the form of a latent image which has been previously described herein.

As the superimposed original document D and superimposed copying sheet C are rotated out of the region of contact between cylinder 11 and conveyor belt 12, the original document D may be separated from the copying sheet through suitable separating means 20, well known in the art, and conveyed out of the housing 10 into a receptacle or tray provided therefor. The sensitized diazo sheet C containing the latent image is conducted toward an endless conveyor belt 21, which is entrained about drive and idler rollers 22, 23, 24, Conveyor belt 21 conducts the copying sheet C between two rollers 25 and 26, forming, respectively, the anode and cathode of a pair of electrodes connected to a suitable source of electrical current. The diazo or copying sheet C is conveyed between the rollers 25, 26 so that the sensitized layer is adjacent to the cathode 26. As electrical current is passed between rollers 25 and 26 through the copying sheet C, the hydrogen ions in the moist or decomposed hydrate forming the latent image are removed or bubbled off through the commonly known reduction process, thus leaving a basic, high pH residue or medium. The basic medium provides the required environment for the coupling of the diazonium salt and the coupler, thereby effecting the developing reaction for the diazo dye in the pattern of the latent image. In general, an electrical current of relatively small magnitude, measured in milliamperes, will be sufficient to achieve the necessary developing reaction.

When a diazo-type copying sheet is subjected to the foregoing process the background of the copying sheet may be bleached to a desired whiteness through exposure of the copying sheet C to a source of ultraviolet light 27. The developed copying sheet C is then conveyed out of housing 10 into a suitable receiving tray.

Although the imaging process and apparatus according to this invention have been described with respect to sensitized copying papers and materials particularly of the diazo-type, it will be readily apparent to one skilled in the art that similar developing reactions may be obtained with silver halide-based emulsions containing developing agents which are operative only under moist, high pH conditions. As an example, it would be feasible to employ a silver halide emulsion containing a uniform distribution of silver latent image specks.

While particular embodiments of this invention are shown above, it will be understood that the invention is obviously subject to variations and modifications without departing from its broader aspects.

What is claimed is:

1. A process of preparing prints from a sensitized material containing a color former and an agent adapted to increase the electrical conductivity of said material when exposed to heat, comprising the steps of exposing said sensitized material to infrared radiation while superimposed on a pattern to thereby increase the electrical conductivity of said sensitized material in the region of said pattern, and passing an electrical current through said sensitized material, said agent providing a basic medium in the presence of said electrical current and facilitating a developing reaction between said color former and the sensitized material.

2. A process as defined in claim 1 wherein said agent comprises a water release agent.

3. A process as defined in claim 2 wherein said sensitized material includes a layer of a diazonium salt, and said color former is constituted of a coupler adapted to react with said diazonium salt in the presence of said basic medium.

4. A process as defined in claim 2 wherein said water release agent is constituted essentially of a salt hydrate.

5. A process as defined in claim 4 wherein said salt hydrate comprises lithium met-aborate octahydrate.

6. A process as defined in claim 4 wherein said salt hydrate comprises sodium sulfate decahydrate.

7. A process as defined in claim 4 wherein said salt hydrate comprises sodium dihydrogen phosphate dodecahydrate.

8. A process as defined in claim 2 wherein said water release agent is constituted essentially of borax.

9. A process as defined in claim 2 wherein said water release agent is constituted essentially of sodium alginate.

10. A process as defined in claim 2 wherein said water release agent is constituted essentially of sugar.

11. A process as defined in claim 3 wherein said coupler is selected from the group consisting of phenols, napthols, and compounds containing a reactive methylene group.

12. A process as defined in claim 3 wherein said coupler is constituted essentially of resorcinol.

13. A process as defined in claim 3 wherein said infrared radiation increases the temperature of the pattern and the surface of the sensitized material superimposed thereon to a range of about 70 to C., and agent being adapted to release moisture in said sensitized material within the region of said temperature rise, the area of said moistened sensitized material forming a region of increased electrical conductivity for said electrical current, said current affecting said agent in said area of moisture to provide said basic medium propagating a coupling reaction between said diazonium salt and said coupler.

14. A process as defined in claim 2 wherein said basic medium is provided through the removal of hydrogen ions from said water release agent by said electrical current.

15. A process as defined in claim 3 including the step of exposing said developed sensitized material to a source of ultraviolet light.

16. A process as defined in claim 1 wherein said electrical current is of the magnitude of milli-amperes.

17. In an apparatus for preparing and developing prints from a sensitized material containing a color former and a water release agent which provides a basic medium in the presence of an electrical current, the combination of means for subjecting said sensitized material to a source of infrared radiation while superimposed on a pattern, the heat of said infrared radiation causing said agent to increase the electrical conductivity of said material in the region of said pattern, and means passing an electrical current through said exposed sensitized material to initiate a pattern image developing reaction between said color former and the sensitized material.

18. An apparatus as defined in claim 17 wherein said radiation means comprises a rotatable cylinder, conveyor means cooperating with said cylinder to convey said superimposed sensitized material and pattern about at least a portion of the peripheral surface of said cylinder, said sensitized material being in contact with said cylinder surface and said pattern positioned radially outwardly thereof, said source of infrared radiation being internally of said cylinder and adapted to convey infrared rays to said pattern through said sensitized mateial.

19. An apparatus as defined in claim 17 wherein said electrical current means comprises a pair of rotatable rollers connected to a source of electrical current, said exposed sensitized material passing between said rollers, a first of said rollers forming a cathode, and a second of said rollers forming an anode, said rollers being in elec- References Cited UNITED STATES PATENTS 2/1951 Vanselow et a1. 9649 3,116,148 12/1963 Miller 96-48 RALPH G. NILSON, Primary Examiner.

15 A. L. BIRCH, Assistant Examiner.

US. Cl. X.R.

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