US3850626A

US3850626A - Imaging member and method

Info

Publication number: US3850626A
Application number: US00335982A
Authority: US
Inventors: R Luebbe
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-02-26
Filing date: 1973-02-26
Publication date: 1974-11-26
Anticipated expiration: 1991-11-26
Also published as: FR2219449A1; GB1464653A; FR2219449B1; CA1024391A

Abstract

An imaging member comprising a donor sheet and an imaging layer coated thereon wherein the donor sheet comprises an electret. The imaging member is employed in the manifold imaging process wherein the imaging layer is subjected to an electric field which field is supplied by the electret. While subjected to the electric field the imaging layer is exposed to electromagnetic radiation to which it is sensitive and fractured in imagewise configuration in the manifold imaging mode.

Description

[111 3,850,626 [451 5 Nov. 26, 1974 IMAGING MEMBER AND METHOD [75] Inventor: Ray II. Luebbe, Jr., Rochester, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: Feb. 26, 1973 21 Appl. No.: 335,982

[52] US. Cl. 96/1 M, 96/l.5

OTHER PUBLICATIONS Fridkin, Photoelectrets and the Electrophotographic Process pp. 1-3 174, 175.

Primary Examiner.-David Klein 7 Assistant Examiner.lohn L. Goodrow [5 7] ABSTRACT An imaging member comprising a donor sheet and an imaging layer coated thereon wherein the donor sheet comprises an electret. The imaging member isemployed in the manifold imaging process wherein the imaging layer is subjected to an electric field which field is supplied by the electret. While subjected to the electric field the imaging layer is exposed to electromagnetic radiation to which it is sensitive and fractured in imagewise configuration in the manifold imaging mode.

18 Claims, 6 Drawing Figures PATENTEL W 3,850,626

ACTIVATE FIG. 4/1

I SANDWICH APPLY FIELD AND EXPOSE 7 SEPARATE FIG. 4 A r16. 46

IMAGING MEMBER AND METHOD BACKGROUND OF THE INVENTION This invention relates in general to imaging and more particularly to layer transfer imaging and improvements therein.

The manifold imaging system has been known as an imaging technique based upon the transfer of an imaging layer comprising a cohesively weak or structurally fracturable electrically photosensitive material sandwiched between a pair of'sheets. In the most common embodiment of this imaging technique a layer of electrically photosensitive imaging material is provided residing on a substrate. This substrate is commonly called a donor sheet. In most cases the imaging layer comprises an electrically photosensitive material dispersed in a binder. An electric field is applied across this imaging layer and the imaging layer is exposed to a pattern of light and shadow representative of the image to be reproduced. With a receiver sheet in place over the im-.

aging layer and the electrical field extending across the sandwich, the donor and receiver sheets are separated whereupon the imaging layer fractures along the lines defined by the pattern of light and shadow to whichthe imaging layer is exposed. Part of the imaging layer is transferred to one of the sheets while the remainder is retained on the other sheet so that a positive image, that is a duplicate of the original is produced on one sheet while a negative image is produced on the other. A more complete explanation of such an imaging process is contained in U.S. Pat. No. 3,707,368 hereby'incorporated by reference.

Since the discovery of the manifold imaging process, the electric field across the imaging layer during the exposure step and during the separation of the sandwich has been, for the most part, described as being supplied by a pair of electrodes. The electric field can also be supplied by static electric charges on the surface of at least one or both of electrically insulating donor and receiver sheets. Such a methodis further described in U.S. Pat. No. 3,6l5,393 to Krohn et al. in such a process the manifold sandwich or at least one member such as the donor sheet is electricallycharged such as by passing a member through a pair of roller electrodes oremploying a corona discharge device such as those ployed in order to transmit to the insulator sufficient static charges for usein the process, Further, the loss of the charges could be occasioned by accidental grounding, humid atmospshere and materials which prove to be too conductiveto support such charges. There is therefore, a need for a more convenient method of placing an electric field across an imaging layer in the manifold imaging process. Such a method should eliminate the need for the presence of electrodes and provide a field which can be more conveniently created, handled and utilized in the manifold process.

SUMMARY or THE INVENTION It is, therefore, an object of this invention to provide a layer transfer imaging method having a convenient electrical system.

Another object of this invention is to provide an imaging member for use in a layer transfer imaging method which member provides its'own electrical system.

Another object of this invention is to provide a layer transfer imaging method employing much lower voltages than previously possible.

of the donor sheet ln use, the novel imaging member of this invention provides an electric field across the imaging layer by employing'a conductive layer over each side of the manifold sandwich. The conductive layers are placed in electrical commumication with each other in'such manner the electrical charge stored in the electret is-extended across the imaging member rendering it useful in .the manifold imaging process wherein the electrically photosensitive imaging layer is exposed to electromagnetic radiation and subsequently fractured by the separation of thereceiver and donor sheets.

Thus there is provided in accordance with this invention a manifold imaging process wherein the electrical field across the imaging layer during the exposure step and separation step is provided by the electrical charges stored in a donor sheet which comprises an electret.

As in. the prior art of manifold imaging, the-term donor" is employed herein to describe the structure of an imaging layer coated on a donor sheet. There is also provided in accordance with this invention a novel imaging member for use in the manifold imaging method comprising an electrically photosensitive layer which is or can be rendered structurally fracturable in response to the combined effects of exposure'to electromagnetic radiation to which it is sensitive and an applied electrical field residing upon a donor sheet which donor sheet comprises a electret. Such member can be employed in the manifold imaging process such as by providing thin, transparent electrically conductive coatings on the donor and receiver sheets as described above. Whilev scribed provides an imaging member having a thermosolvent in contact with the imaging layer. Upon heating the thermo-solvent layer above its melting point the melted layer permeates the imaging layer thus activating it or, in other words, renders such layer structurally fracturable in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which the layer is sensitive. Typical thermo-solvents are octadecane, nonadecane, eicosane, docosane and others as described in said patent. The thermo-solvent layer is commonly melted by contacting it with hot air, a heated roller or other suitable heat transfer means.

DETAILED DESCRIPTION OF THE INVENTION The manifold imaging member and process are more clearly described with reference to the attached drawings wherein;

FIG. I is a side sectional view of the novel donor imaging member of this invention.

FIG. 2 is a side sectional view of the electrical configuration of the imaging member donor of this invention prior to its use in the manifold imaging layer.

FIG. 3 is a side sectional view of the electrical configuration of the donor of this invention while supplying the electrical field in the manifold imaging method.

FIG. 4 is a process flow diagram of the method steps of the manifold imaging process of this invention.

FIGS. 4A and 4B are side sectional views diagrammatically illustrating the process steps of this invention.

Referring now to FIG. 1 there is seen donor 10 comprising a supporting donor sheet 11 which is an electret as indicated by the positive and negative charges in said sheet and an imaging layer generally designated as 12. Imaging layer 12 comprises, in this illustrative embodiment, photosensitive material 13 dispersed in an insulating binder 14. Also shown in FIG. I are conductive layers 15 and 15A which are open at switch 16. With respect to the conductive layers 15 and 15A FIG. I is expanded but in practice the conductive layers are placed in contact with the surfaces of the donor. In the open condition the donor (that is, the combination of imaging layer 12 and donor sheet II) may be stored for long periods of time. When ready for use

conductive layers

15 and 15a are connected through switch 16 thereby placing an electrical field across the imaging layer 12 whereupon the imaging layer can be exposed to electromagnetic radiation to which it is sensitive.

Referring now to FIG. 2 there is shown an illustrative electrical circuit provided by the electret of donor sheet II wherein:

' effective charge on imaging layer a, original surface charge on electret K dielectricconstant of electret d thickness of electret K dielectric constant of imaging layer d thickness of imaging layer The potential available in the electret is utilized to provide the electrical field across imaging layer 12 via conductive plate I and a when it is desired. Until such time switch 16 remains open.

FIG. 3 diagrammatically illustrates the electrical field across the imaging layer when switch 16 is closed. Of course, in the manifold imaging process the electrical field in most cases is applied prior to the exposure of the imaging layer to actinic electromagnetic radiation.

However, electrically photosensitive materials having fatigue characteristics can be employed such that the imaging layer is exposed to actinic electromagnetic radiation prior to the application of the electric field. The convenience of the imaging member of the present invention is equally applicable to either situation. Below is a mathematical explanation and description of the electrical field which can be effected by means of an electret-donor in accordance with this invention.

Symbols employed below which are common with those described above retain the same definition.

A V electret A V Imaging Layer e/K o /K (r d /K od /K (rd/K wherein:

AV voltage change across a layer 6,, permittivity of free space The electric field in any given imaging layer (E) is determined by the formula:

E o U0 l'/ P)/( 0/ e K50 assuming for an imaging layer:

d/K d,./K,. then E E (T /K6,,

As stated above, one of the advantages of the present invention is the use of voltages provided by an electret. Electrets can take the form ofa thin layer which can be readily made with surface charges in excess of l0 C/cm Electrets having surface charge densities of from 10 to 10' C/cm are typically useful in this invention and are preferred because they can provide sufficient potential difference across the imaging layer at the time of exposure. Such electrets have decay times of greater than one year for polyester materials and I0 10 years for fluorcarbon materials. Thus imaging members in accordance withthis invention can be stored'for long periods of time without ill effect. Further description of such electrets is found in.the publication entitled Electrets and Related Electrostatic Charge Storage Phenomena" by Lawrence Baxt and Martin Perlman, Copyright 1968 by The Electrochemical Society, lncl, 30 E. 42 St., New York, N.Y., which is hereby incorporated by reference. In the prior art manifold imaging process, the thickness of an insulating donor sheet must be considered when employing electrical field across the imaging layer. That is, higher potentials must be employed with thicker insulating materials in the manifold imaging member. Normally voltages in the range are from about l,000 volts per mil of insulating material up to the electrical breakdown potential of the member is typically found in prior art manifold imaging processes. Such material, of course, refers to the insulating material in the manifold imaging member or sandwich. For convenience in handling and use in manifold imaging process, the thickness of a donor sheet in accordance with this invention is preferably in the range of from about 0.25 to about 10 mils in thickness. Other thicknesses can be used depending upon the charge density of the electret. The electret may comprise wax such as Carnuba wax or beeswax. A preferred electret material is Carnuba wax doped with inorganic salts such as an alkali metal halide. Also, Carnuba wax may be doped with ferric or ferrous chloride Teflon FEP film available from the E. I. DuPont de Nemours and Co. Inc., Wilmington Del. In addition, thermoplastic electrets having sufficient surface charge can be employed and are desirable because of their trans-v parency and durability. A typical example is Mylar, a polythylene terephthalate available commercially from the E. l. DuPont de Nemours Co., Inc., Wilmington,

Del. However, when employed as electret donor sheets 1 of this invention suitable protective layers may be required in order that the soft material of the electret is not damaged during shipping, storage and handling of the donor prior to and during its use in the manifold imaging method. Accordingly, the electret donor sheet may have adhering to its surface opposite the imaging layer a protective layer of more durable material such as aluminum foil, etc. A particularly preferred protective layer is a transparent sheet of aluminized Mylar wherein the transparent aluminum coating is placed adjacent the electret surface. In use, the field across the imaging layer is established by placing the aluminum coating in electrical communicationwith a conductive layer residing on the imaging layer or receiver.

In accordance with this invention, the electret is coated with an imaging layer by any suitable means.

such as by a coating knife or wire wound draw down rod. Such coating techniques are fully described in the above-mentioned prior art manifold patent application and patents.

Referring now to FIGS. 2 and 3, electret 17 may comprise any suitableelectret material and may be employed in the manifold imaging process as the donor sheet. Electrets commonly known in the prior art can provide a suitable electrical field in the imaging layer. Such fields across the imaging layer are conveniently in the range of about 350 volts per mil and above.

Referring now to FIG. 4 there is shown a process flow diagram of a typical prior art manifold imaging process. Coordinated with FIG. 4 are FIGS. 4a and 4b diagrammatically illustrating a typical manifold imaging member of this invention being employed in the manifold Such means desirably includes switching means26 to permit convenient handling of the imaging member during the process. After establishing an electrical field across the imaging layer the layer is' 'expo'sed to light image 29. In the event the electret material is not sufficiently transparent to permit exposure of the imaging layer through it, the imaging layer is then exposed through a transparent receiver. With the field still applied across the manifold sandwich, receiver sheet 22 is separated from donor sheet 21 whereby imaging layer fractures in imagewise configuration providing a negative image on the receiver sheet in'this particular illustrative example and a positive image on the donor sheet.

Thus there is provided a manifold imaging method I 1 which obviates the need for subjecting the manifold imaging member or a part thereof to the high voltages at or near the location it is being used. Even in those instances of the prior art wherein the static electrical charges on the surfaces of one of the donor or receiver sheets were employed to provide theelectrical field across the imaging layer such donor or receiver sheet was subjected to high electrical fields at or near the time and place of the operation of the imaging process. This is required as in most instances static electrical charges on an insulating member are transatory and are subject to loss particularly during handling. In the present invention the electret isproduced at a time and place remote from the operation of the'manifold imaging process. Although a rather high'electrical field is employed to form the electrets such operationis entirely independent from the manifold imaging method. Electrets have the ability to remain stable for long periods of time, thereby enabling a manifold electret imag-.

ing member readily available at any, time or place needed.

Further in accordance with this invention, an image I transfer process is desirably included whereby the imaging process. The usual procedure in the manifold imaging method is to activate the imaging layer so as to render it structurally fracturable in response to the combined effects of an electrical field and exposure to electromagnetic radiation to which it is sensitive. Thus, in FIG. 4a there is shown an activator 18 being sprayed from container 19 onto imaging layer 20. Imaging layer 20 is residing on electret 21 which together form an electret donor. After suitably activating imaging layer 20 receiver sheet 22, having a conductive surface 23, is placed on the surface of the imaging layer. In order to remove excess activator and to insure proper contact with the imaging layer roller 24 traverses receiver 22.

Once the sandwich is formed and the imaging layer is in the suitably structurally fracturable condition, the electrical field is applied. As shown in FIG. 4b, the field supplied by the electret donor sheet 21 is applied across the sandwich by connecting conductive layer 25 under donor sheet 21 with the conductive layer 23 of receiver sheet 22 by means of a conductive wire 24 image produced as shown in FIG. 4b is transferred from either the donor sheet 21 or receiver sheet 22. The manifold imaging method is uniquely suited for image transfer capability; and several excellent methods of method for transferring images produced by the manifold imaging process from non-conductive substrates, wherein the electrostatic charges remaining from the imaging process and residing in the substrate and image are rearranged. The aforementioned patent and patent applications are hereby incorporated by reference.

Other modifications and ramifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. Theseare intended to be included within the scope of this invention.

What is claimed is:

1. An imaging method which comprises the steps of:

a. providing an imaging member comprising an electret having coated thereon an electrically photosensitive imaging layer said layer being structurally fracturable in response to the combined effects of an applied electric field and exposure to electromagnetic radiation to which it is sensitive and residing on said imaging layer a receiver sheet;

b. providing a first conductive surface in contact with said electret and a second conductive surface in contact with said receiver sheet and electrically interconnecting said surfaces whereby an electric field is established across said member;

c. exposing said imaging layer to electromagnetic radiation to which it is sensitive;

d. separating said member. while under said field whereby said imaging layer fractures in imagewise configuration providing a positive image on one of said electret and receiver and a negative image on the other.

2. The process of claim 1 wherein the electret is a thermoplastic resin.

3. The process ofclaim 2 wherein said resin is a polyethylene terephthalate.

4. The method of claim I wherein said electret has a thickness in the range of from about .25 mils to about mils.

5. The process of claim 2 wherein the electrically photosensitive material is an organic material.

6. The method of claim 5 wherein the organic electrically photosensitive material is dispersed in an insulating binder.

7. The method of claim 1 wherein the imaging layer comprises an electrically photosensitive material dispersed in an insulating binder.

8. The process of claim 1 wherein the electret comprises an alkali metal doped Carnuba wax layer.

9. An imaging member comprising an electrically photosensitive imaging layer structurally fracturable in response to the combined effects of electromagnetic radiation to which it is sensitive and an applied electrical field residing upon an electret.

10. The member of claim 9 wherein the electret comprises a thermoplastic resin.

11. The member of claim 10 wherein said resin is a polyethylene terephthalate.

12. The member of claim 9 wherein the electret has a thickness in the range of from about 0.25 mils to about 10 mils.

13. An imaging member comprising a donor sheet comprising an electret having coated thereon an electrically photosensitive imaging layer structurally fracturable in response to the combined effects of the exposure to electromagnetic radiation to which it is sensitive and applied electrical field and residing on said imaging layer a receiver sheet.

14. The member of claim 13 wherein the electret comprises a polymer selected from the group consisting of Carnuba wax, polycarbonates and flouropolymers.

15. The member of claim 13 wherein the imaging layer comprises an organic electrically photosensitive material dispersed in a binder.

16. The method of claim 1 further including the step of transferring at least one of said images to another substrate.

17. The method of claim 16 wherein said transfer is accomplished by the application of pressure to said sheet and substrate.

18. The method of claim 16 wherein said transfer is accomplished by rearrangement of electrostatic charges remaining in said sheet and image from said imaging process.

Claims

1. AN IMAGING METHOD WHICH COMPRISES THE STEPS OF: A. PROVIDING AN IMAGING MEMBER COMPRISING AN ELECTRET HAVING COATED THEREON AN ELECTRICALLY PHOTOSENSITIVE IMAGING LAYER SAID LAYER BEING STRUCTURALLY FRACTURABLE IN RESPONSE TO THE COMBINED EFFECTS OF AN APPLIED ELECTRIC FIELD AND EXPOSURE TO ELECTROMAGNETIC RADIATION TO WHICH IT IS SENSITIVE AND RESIDING ON SAID IMAGING LAYER A RECEIVER SHEET; B. PROVIDING A FIRST CONDUCTIVE SURFACE IN CONTACT WITH SAID ELECTRET AND A SECOND CONDUCTIVE SURFACE IN CONTACT WITH SAID RECEIVER SHEET AND ELECTRICALLY INTERCONNECTING SAID SURFACES WHEREBY AN ELECTRIC FIELD IS ESTABLISHED ACROSS SAID MEMBER; C. EXPOSING SAID IMAGING LAYER TO ELECTROMAGNETIC RADIATION TO WHICH IT IS SENSITIVE; D. SEPARATING SAID MEMBER WHILE UNDER SAID FIELD WHEREBY SAID IMAGING LAYER FRACTURES IN IMAGEWISE CONFIGURATION PROVIDING A POSITIVE IMAGE ON ONE OF SAID ELECTRET AND RECEIVER AND A NEGATIVE IMAGE ON THE OTHER.

2. The process of claim 1 wherein the electret is a thermoplastic resin.

3. The process of claim 2 wherein said resin is a polyethylene terephthalate.

4. The method of claim 1 wherein said electret has a thickness in the range of from about .25 mils to about 10 mils.

10. The member of claim 9 wherein the electret comprises a thermoplastic resin.

11. The member of claim 10 wherein said resin is a polyethylene terephthalate.