US3891990A

US3891990A - Imaging process using donor material

Info

Publication number: US3891990A
Application number: US374215A
Authority: US
Inventors: John B Wells
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1973-06-27
Filing date: 1973-06-27
Publication date: 1975-06-24
Anticipated expiration: 1992-06-24
Also published as: DE2412064A1; JPS5038542A; NL7408735A; FR2235405A1; FR2235405B1; CA1036652A; GB1459468A

Abstract

A duplicating process wherein a charge pattern is formed on the surface of an insulating member. The insulating member is backed by a conductive member and is placed in an electroded system. The opposing electrode is a conductive member having on its surface in imagewise configuration a layer of a material which upon application of electrical field alone will generate charge carriers. An insulating layer is provided between the imagewise generating material and the insulating member. Application of electrical field causes the formation of a charge pattern on the surface of the insulating member corresponding to the imagewise charge carrier generating material. The charge pattern may then be rendered visible using conventional techniques. The process is particularly applicable to the repetitive formation of images.

Description

United States Patent 1191 Wells IMAGING PROCESS USING DONOR MATERIAL 111 3,891,990 June 24, 1975 Primary E.\'aminerVincent P. Canney Assistant Examiner.lay P. Lucas Attorney, Agent, or FirmJames J. Ralabate; David C. Petre; Richard A. Tomlin l 5 7] ABSTRACT A duplicating process wherein a charge pattern is formed on the surface of an insulating member. The insulating member is backed by a conductive member and is placed in an electroded system. The opposing electrode is a conductive member having on its surface in imagewise configuration a layer of a material which upon application of electrical field alone will generate charge carriers. An insulating layer is provided between the imagewise generating material and the insulating member. Application of electrical field causes the formation of a charge pattern on the sur face of the insulating member corresponding to the imagewise charge carrier generating material. The charge pattern may then be rendered visible using conventional techniques. The process is particularly applicable to the repetitive formation of images.

ll Claims, 3 Drawing Figures PATENTEnJuu24 ms 3,891; 990

sum 1 FIG. 1

IMAGING PROCESS USING DONOR MATERIAL BACKGROUND OF THE INVENTION This invention relates to duplicating systems. More specifically, this invention concerns a duplicating system in which electrical charge patterns are formed.

The use of electrical fields or charge patterns to form images is well-known. For example, in xerography such as described in US. Pat. No. 2,297,691 to C. F. Carlson, photoconductors are used on which an electrostatic charge pattern is formed. This charge pattern may be developed by contacting the charge pattern with a developer liquid containing particles of colorant which are drawn to the charge pattern by electrostatic attraction. Many variations of the above process exist. In one variation the surface of a photoconductor is exposed to a light image while an electrical field is applied across the photoconductor. The photoconductor does not accept a charge in illuminated conductive areas but does in dark insulating areas thus forming an electrostatic charge pattern. Particles of colorant in, e.g., a liquid developer are drawn to or precipitated on the surface of the photoconductor in the charged areas forming a visible image.

The main disadvantage of these prior art systems using photoconductors is that, conventionally, only one image is obtained from each exposure. Further, process speed is controlled by a number of factors such as time of charging and discharging with visible light and photosensitivity.

There are prior art processes for producing multiple images such as printing processes, e.g., lithography. These processes, however, usually require complex and expensive preparation and are seldom considered for short run processing.

SUMMARY OF THE INVENTION It is an object of this invention to provide a method of image duplicating which overcomes the above-noted disadvantages.

[t is another object of this invention to provide a novel image duplicating system.

It is another object of this invention to provide an image duplicating system which can provide a relatively large number of copies from one imagewise exposure, or no imagewise exposures.

It is another object of this invention to provide an image duplicating system utilizing a relatively inexpensive and rapidly formed master.

The above objects and others are accomplished in accordance with this invention by providing an image duplicating system wherein a charge carrier generating and injecting material is placed in imagewise configuration on the surface of a conducting substrate material. This member will hereafter be referred to as an injecting master. An insulating liquid is coated on the injecting master. An insulating charge pattern accepting member is placed in contact with the liquid. An electrical field is then imposed between the conductive sub strate of the injecting master and a second electrode placed behind the insulating charge accepting member. Application of field causes the charge carrier generating and injecting material to inject charge into and through the liquid to the insulating surface, forming a charge pattern thereon corresponding to the image formed on the injecting master.

The critical component of the present invention is the charge carrier generating and injecting material. The preferred charge injecting material is a material capable of high generation and injection of charge car- 5 riers in response to electrical field. To facilitate handling of the dark injecting materials, they may be dispersed in a binder. Preferred binders are those materials capable of accepting and transporting charge carriers generated by the injection material and themselves being capable of allowing injection into other materials.

No imagewise exposure is used in or required by the present process except where desired to form the original injecting master. The phrase injection is intended to describe the present process mechanism in which application ofd.c. electrical field across a material causes that material to inject charge carriers into a medium which is within interaction range of the material. Many of the materials which are capable of generating and injecting charge carriers are photoconductive when used in xerographic processes. It should be noted, however, that the present process does not rely on the use of light or other radiation to which the photoconductive materials respond.

Any suitable injecting material may be used in the present invention and these include organic as well as inorganic materials. Typical organic materials include pigments such as quinacridones, carboxamides, carboxanalides, triazines, benzopyrrocolines, anthraquinones, azos, salts and lakes of compounds derived from 9-phenylxanthene, dioxazines, lakes of fluorescein dyes, substituted pyrene, bisazos, phthalocyanines and mixtures thereof. Specific organic pigment materials are listed at columns 8 and 9 of U.S. Pat. No. 3,384,488 issued May 21, 1968, the disclosure of which is incorporated herein by reference.

Further, organic and inorganic materials include diethyl thiourea, allyl thiourea and those materials listed at column 9, line 67 through column 1 1, line 1 of U.S. Pat. No. 3,384,488, the disclosure of which is incorporated herein by reference.

Other inorganic materials include cadmium sulfide, cadmium sulfoselenide, zinc oxide, zinc sulfide, sulphur, selenium, mercuric sulfide, lead oxide, lead sulfide, cadmium selenide, titanium dioxide, indium trioxide and mixtures thereof. Mixtures of inorganic and organic materials may also be used.

The above materials may be used alone or combined with a binder. Any suitable film-forming material may be used as a binder and includes materials such as thermoplastic or thermosetting resins. Preferred binder materials are those capable of accepting and transporting charge carriers over a relatively long distance.

Typical materials include polymeric materials such as polyvinylcarbazole, poly-l-vinylpyrene, polymethylene pyrene and N-substituted polymeric acrylic acid amides of pyrene and mixtures thereof. Typical non- 6O polymeric materials include carbazole; N-

ethylcarbazole; N-phenylcarbazole; pyrene; tetraphene; l-acetylpyrene; 2,3-benzochrysene; 6,7-

benzopyrene; lbromopyrene; l-ethylpyrene; 1- methylpyrene; perylene; Z-phenylindole; tetracene; picene; l,3,6,8tetraphenylpyrene; chrysene; fluorene; fluorenone; phenanthrene; triphenylene; 1,25,6- dibenzanthracene; l,2,3,4-dibenzanthracene; 2,3 benzopyrene; 2,3-benzochrysene; anthraquinone;

dibenzothiophene', naphthalene; mixtures thereof and mixtures of non-polymeric and polymeric materials.

The insulating liquid may be of any suitable insulating material. Typical insulating materials include decane, dodecane, tetradecane, kerosene, molten paraffin, molten beeswax or other molten thermoplastic material, mineral oil, silicone oils such as dimethyl polysiloxane, fluorinated hydrocarbons and mixtures thereof.

The insulating liquid must allow passage of charge carriers but be sufficiently insulating to prevent dissipation of the charge pattern formed on the insulating surface while the insulating surface is in contact with the liquid.

The substrate for the injecting master and the second electrode may comprise any suitable conductive material. Typical transparent conductive materials include cellophane, conductively coated glass such as aluminum or tin oxide coated glass, or metallized transparent plastic materials such as polyester film. Other typical conductive materials include metals and conductive rubber.

The insulating material on which the charge pattern is formed may be of any suitable material. Typical insulating materials include paper, plastic coated paper, cellulose acetate, nitro cellulose, polystyrene, polytetrafluoroethylene, and related fluorinated polyolefins, polyvinyl fluoride, polyurethane and polyethylene terephthalate. Again, it is necessary that the material be sufficiently insulating to retain a charge pattern formed on its surface.

Once a charge pattern is formed on the insulating surface, it may be developed or rendered visible in any conventional manner known to those skilled in, for example, xerography. For example, standard liquid development wherein finely divided particles of a toner material such as carbon black dispersed in an insulating liquid is placed in contact with the insulating member bearing the charge pattern the particles will be drawn to the areas of charge forming a visible image which can be fixed in place.

Conventional cascade development can be used in which carrier beads instead of liquid is used to bring the toner into contact with the charge bearing surface.

Also, a number of other techniques can be used. For example, where the insulating liquid is formed into a layer on the insulating charge bearing member of thickness in the range of from about 80 to about 125 millimicrons, the charge pattern or electrostatic image creates interference colors or light scattering patterns in the liquid which are visible. In this connection, the liquid may be a combination of a wax and solvent or a solid material which can be converted to a liquid material. The use of these films to develop electrostatic images is set out in U.S. Pat. No. 3,196,0l0, the complete disclosure of which is incorporated herein by reference.

Further, the charge pattern may be made visible by using a soft solid material which can be deformed by the pattern.

A further technique is to use a developer liquid which contains or is made up of a liquid crystal material. The use of liquid crystal materials to develop or make visible electrostatic charge patterns is well-known and dc pends, for example, on phase changes caused by the charge pattern or a change in optical polarization caused by the charge pattern which result in color or opacity differences in the liquid crystal material. The use of both cholesteric and nematic liquid crystals is contemplated. Patents showing the use of liquid crystals to develop or make visible electrical fields are, for example, U.S. Pat. No. 3,642,348 and U.S. Pat. No. 3,707,322, the disclosures of which are incorporated herein by reference.

In accordance with this invention, images may be made of virtually any material. For the production of colored images, the particles used to develop the charge pattern may be dyed thermoplastic materials which are especially suitable for full color transparency or opaque image formation. One advantage of using dyed thermoplastic materials is that brightly colored materials may be used which are readily fused to form a fixed final image. To produce a polychrome image, two or more images may be made and transferred to a common receiver in register and fused thereon. For other applications the particles may be chosen to be reflective glass beads, luminescent phosphors, resin coated ferromagnetic materials, pigments, reflective resin coated metal particles, microcapsules containing liquids or other materials, catalytic particles or particles otherwise specially formulated for specific end uses when in the form of shaped patterns.

The injecting master may be formed by any convenient method such as by painting the injecting material in image configuration onto a conductive substrate. The material can be sprayed through a stencil, brushed through a stencil or applied by any other suitable mechanical means. For these processes it may be desirable to dissolve or suspend the injecting material in a volatile material with or without a binder.

Further, since many of the injecting materials respond to electrcial field and light, processes such as photoelectrophoresis as shown in U.S. Pat. No. 3,384,566 to H. E. Clark or manifold imaging as shown in U.S. Pat. No. 3,707,368 to W. G. Van Dorn may be used to form injecting masters. Conventional xerography may also be used to form an injection master by developing the electrostatic charge pattern using injecting material and transferring the injecting material to a conductive substrate. It is necessary only to provide an image of the injecting material on a conductive substrate and to provide a reasonable bond between the material and substrate so that the material does not become dislodged in use. To aid in bonding or for other reasons such as surface protection, it may be desirable to apply a thin layer of a non-conductive material to the conductive substrate before formation of the injecting master image thereon. Where such layer is used, it must be relatively thin or be of a material which will not interfere with field application sufficiently to render the injecting material inoperative.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 2 are schematic representations of the charge pattern forming steps of the present invention. The spacings, sizes and shapes have been distorted for purposes of clarity.

FIG. 3 is a schematic representation of another embodiment of an imaging member suitable for practicing the present invention.

Referring now to FIG. 1, conductive electrode 1 has acnded to its surface in image configuration injecting material 2 forming an injecting master. Injection material 2 may be particles dispersed in a binder, a single phase material or other material as explained above. Coated over the surface of the injecting master is a layer of insulating liquid 3. in contact with the free surface of liquid 3 is insulating member 4 on which the charge pattern is formed. Conductive electrode 5 is provided behind insulating member 4. The FIGS. 1 and 2 should be taken as representing a small section of flat plates, drums, rollers, webs entrained over rollers or any suitable combination. For example, conductive electrode 1 may be a flat plate and electrode 5 may be a roller, or they could both be metallic webs. Potential source 6 is connected to electrode 1 and to ground. The other side of potential source 6 is connected through switch 7 to electrode 5.

Referring now to FIG. 2, in operation, switch 7 is closed applying a potential difference between

electrodes

1 and 5. In embodiments such as represented herein, voltages of from 300 volts to 7000 volts d.c. or higher may be used. The allowable voltage depends on the thickness and nature of the liquid layer 3 used, the thickness and nature of the insulating member 4 and whether or not conductive layer 1 has a relatively insulating material over its surface.

The application of the potential difference causes injecting material 2 to generate charge carriers and inject charge carriers into liquid 3. A charge pattern is formed on the surface of layer 4 represented here by negative charges 8 corresponding to the original image 2. The spacing between the surface of injecting material 2 and the surface of member 4 should be preferably less than about one mil. In practice the member 4 is pressed into virtual contact with injecting master 1.

The charge pattern 8 may then be rendered visible by any of the techniques outlined above. Where desired electrode 5 may be replaced by a source of corona. Also, although electrode 1 is shown as biased negative in relation to electrode 5, electrode 5 may be biased negative with respect to electrode 1.

FIG. 3 illustrates another embodiment of an imaging member suitable for practicing the present invention. The member shown in FIG. 3 is similar to that illustrated in FIGS. 1 and 2 with the exception that the former includes a thin layer of an insulating material 10 residing on conductive substrate 1. The steps of forming a charge pattern are the same as those described above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples further specifically illustrate the improved imaging process of this invention. The examples are intended to illustrate various preferred embodiments of this invention.

Parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 Approximately one part of metal-free phthalocyanine is suspended in a solution of about five parts of polyvinylcarbazole in 50 parts by weight toluene. The suspension is ball milled until the phthalocyanine particles are uniformly suspended and have an average particle size of about l-2 microns. This suspension is coated onto the conductive surface of a conductive metal plate in image configuration so that when dry, the image is approximately 10 microns thick. This image is used as the injection master in Examples I and ll. Because this particular injecting material is light sensitive, the charge pattern forming steps are performed in the dark only to show that the light sensitivity of the injecting material is not being utilized.

The injection master is coated with about a 2 micron layer of Sohio Odorless Solvent 3454, a mixture of kerosene fractions. A source of high potential is connected to a roller electrode which has a l inch diameter steel core and on its surface a three quarter inch layer of polyurethane having a resistivity of about 1 X 10 ohmcm forming a total diameter or about 2.5 inches. A paper sheet is placed over the polyurethane surface to receive the charge pattern. The other lead of the source of high potential is connected to the conductive image bearing plate and to ground.

With a potential of 5000 volts applied, the roller being negative with respect to the grounded injection master, the roller is caused to traverse the mineral oil at a rate of about 2 inches/second. On completion of roller traverse, a charge pattern is formed on the paper surface. The charge pattern is then made visible by utilizing conventional liquid development techniques.

EXAMPLE [I The experiment of Example I is repeated utilizing mineral oil in place of the Sohio 3454 with comparable results.

EXAMPLE [ii A mixture of one part of metal-free phthalocyanine and ten parts of melamine formaldehyde resin are milled in about 50 parts by weight Sohio 3454 until particle size is reduced to about 12 microns. The mixture is coated imagewise onto a conductive metal flat substrate to a thickness dry of about 10 microns. The layer is heated to remove solvent and adhere the phthalocyanine and resin to the substrate. This image is used as in Example I with comparable results.

EXAMPLE [V The experiment of Example Ill is repeated using mineral oil as the insulating liquid between the injection master and paper sheet providing comparable results.

EXAMPLE V An injection master is prepared by coating a conductive plate imagewise with a mixture of one part of polyvinylcarbazole and 10 parts by weight toluene to provide a dry thickness of about 10 microns. The solvent is removed providing a polyvinylcarbazole image on the substrate. The injection master thus formed is used as in Example I with comparable results.

EXAMPLES Vl-X in each of the above experiments, the injecting master is recycled by recoating with insulating liquid and providing a new paper surface for each cycle. Twenty charge patterns are formed using the embodiments of Examples l\/ with no decrease in final developed image quality being observable. These experiments show that the injecting master may be reused providing a number of images.

EXAMPLES XI-XX The experiments of Examples l-X are repeated in the presence of ambient illumination of normal room light levels with similar results.

Although the above examples show the injecting material being placed directly on a conductive substrate,

the material may be placed on an insulating web. For example, the process has been shown to be operable with a web of 3 mil Mylar, a polyester available from duPont, placed between the conductive substrate and the injecting material. For rapid recycling, this embodiment requires the removal of accumulated charge from the insulating web which may be accomplished, for example, by the use of a corona discharge.

Although specific components and proportions have been described in the above examples, other materials as listed above, where suitable, may be used with similar results. In addition, other materials may be added to the various layers to synergize, enhance or otherwise modify their properties. For example, materials such as triphenylamine and trinitrofluorenone may be added to the injecting material to enhance charge carrier transport.

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

What is claimed is:

l. A method for forming charge patterns which comprises the steps of:

a. providing in imagewise configuration a layer of an injecting material on a conductive substrate to form an injecting master, said injecting material being capable of generating and injecting charge carriers in response to electrical field alone;

b. providing a layer of an insulating liquid on said injecting master;

c. contacting the free surface of said layer of insulating liquid with an insulating member; and,

d. applying an electrical potential difference across said injecting material and said insulating liquid layer of sufficient magnitude to cause said injecting material to form a charge pattern on said insulating member as a result of charge carrier injection from said injection material.

2. The method of claim I wherein said potential difference is applied between an electrode positioned in contact with the free surface of said insulating member and said conductive substrate for said injecting master.

3. The method of claim 1 wherein said injecting material comprises a charge carrier generating and injecting material dispersed in a binder.

4. The method of claim 1 wherein said injecting material comprises a charge carrier generating and injecting material in solid solution in a binder.

5. The method of claim 1 wherein said injecting material is homogeneous.

6. The method of claim 1 wherein said injecting material is inorganic.

7. The method of claim I wherein said injecting material is organic.

8. The method of claim I and further including the step of; (e) contacting said insulating member bearing said charge pattern with a liquid developer until an image is formed.

9. The method of claim 1 and further including the step of; (e) contacting said insulating member bearing said charge pattern with a thin film of an insulating liquid until an interference pattern is formed.

10. The method of claim 1 and further including the step of; (e) contacting said insulating member bearing said charge pattern with a liquid crystalline material until an image is formed.

11. The method of claim 1 wherein said injecting material is provided on the surface of an insulating web. i 1

Claims

1. A method for forming charge patterns which comprises the steps of: a. providing in imagewise configuration a layer of an injecting material on a conductive substrate to form an injecting master, said injecting material being capable of generating and injecting charge carriers in response to electrical field alone; b. providing a layer of an insulating liquid on said injecting master; c. contacting the free surface of said layer of insulating liquid with an insulating member; and, d. applying an electrical potential difference across said injecting material and said insulating liquid layer of sufficient magnitude to cause said injecting material to form a charge pattern on said insulating member as a result of charge carrier injection from said injection material.

2. The method of claim 1 wherein said potential difference is applied between an electrode positioned in contact with the free surface of said insulating member and said conductive substrate for said injecting master.

5. The method of claim 1 wherein said injecting material is homogeneous.

6. The method of claim 1 wherein said injecting material is inorganic.

7. The method of claim 1 wherein said injecting material is organic.

8. The method of claim 1 and further including the step of; (e) contacting said insulating member bearing said charge pattern with a liquid developer until an image is formed.

11. The method of claim 1 wherein said injecting material is provided on the surface of an insulating web.