DE1950028A1 - Electrophotographic printer or copier device - Google Patents

Description

Patent attorneys

Dr. Ing.H. Negendank

Dipl. Ing. H. Hauck

Dipl. Phys. W. Schmitz

8 Munich 15 _r Mozartsir. 23

Tel. 5 38 05 8ο

OWENS-ILLINOIS, Inc.

to5 Madison Avenue

Toledo, Ohio / USA Munich, October 3, 1S69

Lawyer File M-881

Electrophotographic printer or copier

The invention relates to an electrophotographic printing or Copying device that works with persistent internal polarization and in which two conductive elements are attached to a photoconductive body Electrodes are arranged.

For persistent internal polarization (hereinafter PIP), positive and negative charges in a conductive insulating material are separated by exposing it to radiation and an electric field. The charges are then trapped and remain "frozen" so that they form an internal polarization field for a period of time that is sufficient for sounding. PIP and the associated theory are known to those skilled in the electrophotographic technique. For this reference is made to the following \ Publications: Electrophotography, RMSchaffert -

The Focal Press, London and New York (1965), pages 59 to 77 j Persistent Internal Polarization, Kalimann and Rosenberg, The Physical Review, Volume 97, No. 5 (March 15, 1955), pages 1596 to

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-1.61ο.- The general theory of AC PIP is also out U.S. Patent 3,199,086.

In general, a PIP photography device has a layer of photoconductive insulating material sandwiched between two Electrodes is used to generate the field. The effect of the persistent internal polarization can be in any material which has the following properties:

1) The material must have great resistance in the dark (low density of free charge carriers) so that he is a good Isolator in the absence of radiation .istv

2) The material must be photoconductive, i.e. its resistance must fall off when stimulated by appropriate irradiation will.

Typical PIP materials, which are considered in the following, are ■ Dispersions of photoconductors in binders or without binders; thin layers of photoconductors.

Inorganic photoconductors which can be used in the device according to the invention are, for example, activated zinc sulfide, cadmium sulfide, zinc selenide, cadmium selenide, cadmium oxide, zinc-cadmium selenide and zinc-cadmium sulfide. Examples of organic photoconductors are anthracene, chrysene and polyvinylcarbazole, For example, suitable resin binders include cellulose acetate, cellulose ethers, cellulose esters, silicones, vinyl resins, alkyd resins '' and / or epoxy resins. The invention is not limited to that specified

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Substances restricted. When photoconductive sulfides are used, the use of glass binders is preferred because they are low-melting compositions that do not contain lead, that could poison the sulphide-containing phosphors.

The PIP material can be irradiated by any electromagnetic radiation or corpuscular radiation or energy, visible or invisible, which excites the PIP material so that a separation of the charges can take place in an electromagnetic field. Such radiations are, for example, visible Light, infrared, ultraviolet, x-rays, gamma rays, and beta rays. Light is usually used for printing and copying used in the visible area. The invention is not restricted to the specified types of radiation. In the case of electrophotographic Printing and copying usually involves applying an electric field and applying the PIP material at the same time used a pair of conductive electrodes with the lamp, which are separated by a layer of PIP material. Such an arrangement can be difficult to manage because the The substrate layer must be conductive and changes in the thickness and composition of the PIP layer affect the operating properties affect the device.

The invention provides a new electrode device with which the above-mentioned shortcomings of known facilities can be remedied. According to the invention, an electrode device is provided, of the two electrodes of opposite polarity in the same plane or on the same side of the PIP layer

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order when direct current is used.

According to an advantageous embodiment of the invention, each Electrode several elements in a row at intervals are arranged in the same plane and alternate * The elements are attached to or embedded in the surface of the PIP layer.

When an electrostatic latent image is to be created in the PIP material using direct current, a ,. electric field is applied and the PIP material is an active

Exposed to four radiations that create a picture or another Pattern can be. The electrode elements in the irradiated sections take on PIP charge, the sign of which corresponds to that of the applied charge Charge is opposite. This makes one half positively charged and the other half negatively charged.

If the image irradiation is continued long enough, the irradiated area of the PIP layer is polarized. In this way, the image is simulated by an inner latent electrostatic 'image or pattern which can be scanned on the surface of the PIP material.

When using alternating current a latent electrostatic Image is to be generated in the PIP material, the electric field is applied and the PIP material is the activating

Image exposure exposed. If the image irradiation lasts long enough, the irradiated area takes up the PIP layer

s-

Potential whose sign is the same as that of the less mobile

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Is charge carrier in the PIP material used. This will creates an internal latent electrostatic image attached to the. Surface of the PIP material can be scanned. The charge separation is in this case due to the mobility of the one Charge carrier type compared to the immobility of the other charge carrier type causes, the mobilities from the properties the selected PIP material.

The electrostatic latent image is then charged with or dipolar toner particles designed to create a 'visible reproduction of the image that can be viewed, photographed or viewed using the known electrophotographic printing or Copying process can be transferred.

It should be noted that due to the properties of the PIP material the electrostatic latent image is preserved in the PIP material, allowing a limited number of reproductions can be produced. The image can be completely irradiated be extinguished so that the PIP material is returned to the neutral state in which it is used to form a new one electrostatic image can be used.

Either an alternating field or a direct voltage field is applied between the two discontinuous electrodes, and the radiation is projected onto the PIP layer through the discontinuous electrodes. This creates a .j electrostatic latent image that can be tinted and transferred as a \ toner image * i

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Embodiments of the invention will now be based on the enclosed Drawings, described. Show it:

Fig. 1 is a schematic representation of a PIP device according to the invention, which operates with direct current and two having discontinuous electrodes that are attached to the surface a PIP layer are arranged and onto which the image irradiation is projected;

Fig. 2 is an end view of the PIP device shown in Fig. 1, wherein the electrode device is shown schematically;

3 shows a schematic representation of a PIP device according to the invention, which works with alternating current and has two discontinuous electrodes on the top a PIP layer are arranged and onto which the image irradiation is projected;

Figure 4 is an end view of the PIP device shown in Figure 1; wherein the electrode device is shown schematically

In the drawings, the PIP body Io is shown, on which two electrodes 12 and It- are attached or embedded, which are connected to a DC voltage source E. For the purpose of illustration, the electrode 12 (FIG. 2) is connected to the positive terminal of the DC voltage source and the electrode Ik is connected to the negative terminal of the DC voltage source E. _i

The two electrodes 12 and IM- are discontinuous. Every Electrode can be in the form of a comb attached to the surface of the PIP body Io is attached or embedded in it. According to In a preferred embodiment, the comb is any Electrode made up of several elements 16 arranged in a row in the same Level are arranged and alternate with each other. Therefore, several electrode elements 16 lie next to one another in the same Level, the polarity of which alternately has the opposite value. Both electrodes 12 and 14 are on the same Side of the PIP body Io, so that a support electrode or a conductive substrate on the other side of the PIP body Io becomes superfluous.

When the device is subjected to image irradiation (circled area 18) and an electric field, it reacts PIP body Io as shown in Fig.2. Only in the areas which are exposed to image irradiation, i.e. the areas in the circled area 18 of the image irradiation, become movable Charges generated under the action of the field increase lead to an internal polarization. The PIP facility is open creates a latent electrostatic image in this way (shown schematically by the "charges in area 18 of FIG. 2)" that can be transferred and reprinted using charged electroscopic powder. To the electrostatic To erase the image, the PIP body is irradiated as a whole.

A continuous electrode has the disadvantage that it ■ must be removed in order to remove the electrostatic latent image

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to be able to sound and transmit, as it acts as a shield between the electrostatic image and the electroscopic particles, because image charges are present everywhere. In contrast, the inventive discontinuous comb-shaped electrodes 12 and Ik, with their high percentage of openings, do not shield the electroscopic particles from the fields of the electrostatic latent image and therefore these electrodes do not need to be removed while the image is tinted and printed. Therefore, the discontinuous electrode has the advantage that, in that it cannot be removed, a considerable time saving is achieved and the transmission speed easily achieved which is necessary when using a PIP device in a printing or copying machine. '

In conventional copying machines it has been shown that the tinting of large contiguous areas often results in an increased toner density has the consequence. This will disturb the image in the areas farthest from the edges. With others Words appear the middle portions of a large contiguous area that is toned and of such a thing Image was transferred, often less clearly than the edge portions. By using a discontinuous electrode (such as the comb-shaped electrodes 12 and 14) the large areas are electrically divided so that one gives uniform development over the large areas of the latent image.

An advantage of non-removable electrodes such as

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the attached or embedded comb-shaped electrodes 12 and m, consists in that it is possible for the accumulation of dust and to avoid toner between the electrode and the PIP layer. Removable electrodes often trap dust and other particles Foreign material that has the effect of the field lines on the PIP layer interferes if it is between the electrode and the PIP layer got. By the non-removable electrodes embedded in the surface of the PIP layer, such as the comb-shaped electrodes 12 and 14, the possibility of dust particles is eliminated between the electrodes and accumulate in the PIP layer, so that a protection against a disturbance _

secure the field lines / is set.

When the non-removable, comb-shaped electrodes together Used with a layer of PIP material are different Modifications are possible within the scope of the invention. Either a charged toner or a dipolar toner can be used will. It should be noted that a dipolar toner has both polarities tints so that the image resolution is kept the same as the line resolution. Can do the same result by using two oppositely charged toners either in admixture or sequentially.

The comb-shaped electrodes 12 and IM · can consist of thin conductive metal strips which are attached layer on the surface of the PIP or embedded in it, you electrodes may be vapor-deposited on the surface of the PIP-layer metal layers in a conventional manner. You can also

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printed on as a thick layer of a microelectronic paste

In the embodiment according to FIG. 3, an alternating electric field is applied by an alternating current source and the PIP body 2o reacts as shown in FIG. 3. Only the charge carriers which are exposed to the image irradiation, ie those in the encircled image irradiation area 28, lead to an internal polarization under the effect of the field generated by the alternating current source. For the purpose of illustration, the positive charge carriers have the lower mobility and therefore form the latent electrostatic image. The PIP device therefore creates a latent electrostatic field, shown schematically by the charges in circled area 28 in Fig. 3, which is imprinted by tinting, transferring and using charged electroscopic powder . can. ■■■■ '_

The mutually alternating elements 26 of the invention Electrodes 22 and 24 can be made from thin conductive metal strips consist that attached to the surface of the PIP layer or are embedded in them. It can also be vapor-deposited onto the surface of the PIP layer in a conventional manner Metal strips can be used. The conductive elements 26 can also be small wires or strips of glass with a conductive Tin oxide coating so that they are essentially transparent. ι

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The conductive, non-removable, comb-shaped according to the invention Electrodes lie in the same plane on the same side of the PIP layer and each consist of several conductive ones Elements arranged in a row at intervals and each alternating; Such discontinuous electrodes can be used to simultaneously apply an electric field and the impingement of the radiation on the PIP layer to allow the electrodes not to be removed when tinting and transferring the image. Both electrodes will be on the same side of the PIP layer the invention created a compact unit that is a conductive Eliminates the need for a substrate or a support electrode. Since this facility is both in the case of a constant field and in the case of works in an alternating field, the electrostatic latent image consists of a continuously identical charge and can be completely tinted and rendered.

It should be noted that the device according to the invention, although it is only shown in connection with a planar system, can also be used with a rotatable drum device and can be connected in such a way that the drum can be moved is. According to a preferred embodiment, the comb-shaped Electrodes are appropriately segmented so that different sections of the drum perform different functions can run at the same time.

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Claims (8)

Claims (Iy electrophotographic printer or copier which works with persistent internal polarization and in which two conductive electrodes are arranged on a photoconductive body, characterized in that both electrodes (12, 14) (22, 24) are discontinuous and in the same plane the same side of the photoconductive body (lo, 2o) are arranged. 2. Apparatus according to claim 1, characterized in that a constant electric field is applied to the electrodes (12, 14, 22, 24) or alternating field is applied to the photoconductive layer body, and that the body (lo, 2o) through the open spaces the discontinuous electrodes (12, 14, 22, 24) is irradiated. 0 0 9 8 3 8/1877 3. Apparatus according to claim 1, characterized in that each discontinuous electrode (12, 14, 22, 2M-) several Has elements in a row at intervals of the same Level are arranged and alternate with each other. 4. Apparatus according to claim 1, characterized in that the Electrodes (12, IM-, 22, 24) on the same face of the photoconductive Body (Io, 2o) are attached. 5. Apparatus according to claim 1, characterized in that the Electrodes (12, 11, 22, 24) at least partially in the same Surface of the body (lo, 2o) are embedded. 6. The device according to claim 1, characterized in that the Electrodes (12, 14, 22, 24) are completely embedded in the same area of the photoconductive body (lo, 2o). 7. Apparatus according to claim 3, characterized in that the Electrode elements (16, 26) are substantially transparent. 8. Apparatus according to claim 2, characterized in that the. two electrodes (12, 14, 22, 24) formed in a comb shape j are. . . ■ ■■ ■ '.-... 009838/1877