DE1085177B - Method and device for the electrostatic production of images - Google Patents

Description

GERMAN

The invention relates to a method and a device for electrostatic production a visible representation of a visible object.

Various electrophotographic apparatuses are known which, by projecting a visible image of an object on a photoconductive plate a latent electrostatic image can be produced. The electrostatic image is then formed by the deposition of a powder corresponding to the electrostatic charge of the latent image is developed into a visible image.

The known devices have means to first produce this latent electrostatic image and in a subsequent process into a visible reproduction.

In one of the known methods, a visible reproduction of a visible object is achieved in this way produced that a light image of the object to be reproduced onto a transparent layer of electrically conductive material and from there via a layer of photoconductive material on top Material thrown onto an adjacent but removable layer of electrically insulating material which is arranged on a metal base layer. One pressed onto the metal base layer Potential then generates an electrostatic reproduction of the light image on the insulating layer. Thereupon becomes the surface of the insulating material that supports the electrostatic reproduction of the light image separated from the previously applied photoconductive material, and the production of the visible Image is then done by applying a dispersion of powdered material to the charged Surface.

It has also been proposed by changing the electrical characteristics of the charging means the photoconductive surface instead of through the photoconductive layer through stray flux to load with the help of the loading equipment. The aforementioned devices consist of separate elements for charging the photoconductive material and developing a visible image thereon.

The invention is based on the object of creating a method and a device with which Help by electrophotographic means images are captured and printed at high speed can be.

This object is achieved according to the invention in that a light image of the object on a first, an organ or an organ consisting of a conductor layer and a high-resistance photoconductive layer Part of the same is thrown that a second, a metallic core and a semiconductor layer on it exhibiting organ in intimate contact with aufein-procedure and device

for electrostatic manufacturing

of pictures

Applicant:

General Dynamics Corporation,
San Diego, Calif. (V. St. A.)

Representative: Dr.-Ing. W. Höger, Dr.-Ing. E. Maier

and Dipl.-Ing. M. Sc. W. Stellrecht, patent attorneys,

Stuttgart O, Uhlandstr. 16

Claimed priority:
V. St. v. America March 7, 1955

Edward Francis Mayer, Cleveland, Ohio (V. St. A.),
has been named as the inventor

other parts of the photoconductive layer of the first organ is brought that at the same time a voltage across the photoconductive layer or the exposed part thereof and the semiconductor layer is applied and that on the photoconductive layer or the exposed part of the same with the help an opaque powder is applied to the semiconductor layer. This is a method of inclusion and for printing images by electrophotographic means in which an electrostatic latent image is created and developed at about the same time, thereby completing the whole process is simplified significantly. The device according to the invention for carrying out the method has a minimum of moving parts, as in contrast to the known device in the invention only a single element is still present, which both carries the charge on the photoconductive Layer as well as developing the final image.

Exemplary embodiments of the invention are shown in the drawing. It shows

1 shows a schematic section through a preferred embodiment,

009 550 / 6J

3 4

. Fig. 2 shows a similar section through a second but it can be smaller if necessary. As a

Embodiment in which ^ the photoconductive EIe- have conductive rubber and semi-

ment is designed as a flat plate. proven conductive organic materials.

The electrophotographic device according to The two drums 10 and 20 are so arranged. Figure 1 shows a photoconductive element in shape 5 arranged to be in rotational contact along an upper one rotating drum 10, which stand together from a trans-surface element and are in parent base layer 12, a transparent electri- cally opposite directions. As a result of trically conductive intermediate layer 14 and a trans-elasticity of the material of the layer 24 can Parent photoconductive outer layer 16 consists. Contact area can be enlarged somewhat, and at

The base layer 12 can be a cylinder made of glass io of the present invention at one up to

or plastic, preferably from a 1.27 cm wide contact area, has achieved good results.

Material that has a certain transparency and a center of the drum 10 is the

has low resistance. For example, have light source 46, the light properties of which on the

materials whose transparency in white light sensitivity properties of the photoconductive

50% and their resistance per surface unit 15 of material 16 are matched. Between the light

100 to 1000 ohms has been found to be suitable. source 46 and the photoconductive layer 16 is

However, these values depend on the intensity of a negative 18 to be reproduced so that it

respective light source 46 together and can rest on the inner wall of the drum 10. as

may be increased or decreased. Negatives are suitable stencils or silver

Preferably, the transparent electrically ² ° halide films are made. The negative does not need a conductive intermediate layer 14 made of vapor-deposited gold to be inserted directly; instead, a bismuth, tin oxide or other optical image of the same can be placed on the contact surface of the suitable conductive materials, which are projected in the form of drums 10 and 20 . This thin transparent film on the base layer 12 optical image can be a surface or just a line deposited. ² 5 be negative.

An optimum would result if the photo- When rotating the two drums 10 and 20 in the conductive layer 16 in the dark, the isolated contact line migrates in completely different directions. In practice, materials with along the surface of the drum 10. A current of resistivity of at least source 30, passing through a line 34 of electrical 10 ¹² [ohm · cm], have been found to be suitable. Furthermore, a 3 ° conductive layer 14 would be particularly advantageous if the conductive layer 16 used for the photoconductive layer 16 is connected to the metal core at 22 and the photoconductive layer 16 is applied through a line 32 to it. Exposure would be a good leader. In practice, this allows a charge from the power source 30 to be used with materials whose specific resistance, with the exception of the surface of the photoconductor, is up to 10 ¹⁰ [ohm · cm] when exposed to light. 35 seep. When the drums are rotated, a third, important factor is the speed of the drum 20 and the photoconductive speed of the drop in resistance when the Beiich layer 14 enters, a constantly small capacitor. One thing. A suitable dark resistance, a suitable light resistance that seeps through the low-ohmic layer 24 and a suitable charge charges this capacitor up to a value, the speed of the drop in resistance when the exposure occurs due to the electrical properties of the known semi-conductive drums 10 and 20, which Rotation speed of the materials, ie semiconductors, on the photoconductive drums and the size of the aforementioned condensate and in the form of thin films are transparent, as is determined sators. The charge absorbed by the photoconductive layer 16, for example selenium, arsenic selenide, zinc cadmium, is determined by the exposure that hits this layer 16 on sulfide compounds and many other materials. The photoconductive layers and formed on the photoconductive layer advantageously continuously and advantageously be a charge image applied inversely proportional to the by precipitation in \ ^r acuum. Exposure of the corresponding partial area of the

A second drum 20 consists of a metal negative.

core 22, and a cover layer 24 serves the 5 ° Das formed on the photoconductive layer

Photoconductive layer 16 a charge on- electrostatic image is now made with the help of the drum

and on this layer for development 20, which is suitable, not shown, the drum

of a final visible image isolating an opaque from the rest of the installation

to apply visible powder. For the top layer bearings stored is developed into a visible image.

24 materials are used favorably, the 55 The drum 20 is immersed in a one for this purpose

Resistance lower than the resistance of the container containing the photo developer liquid 28,

Conductive layer is, so that when touched is grounded by a line 38.

the two layers take a charge from the metal in known electrophotographic devices

core 22 on the surface of the photoconductor with various suspensions of impenetrable

can seep through at the desired speed. 60 fine powders used to create the photo

The cover layer 24 must have some electrical and conductive latent electrostatic image

have physical properties. To turn one into a visible image. But has

unnecessary wear of the photoconductive layer dispersed in a liquid, carbon black being particularly

To avoid, it is advisable, for example, to choose the proven beneficial.

a relatively soft, resilient material 65. The developer 28 therefore preferably consists of for the cover layer 24. Experiments have shown that in petroleum or another suitable, dielectric resistance from one point on the surface of the tric liquid, for example hydrocarbon core 22, to a point on the surface of the or chlorinated hydrocarbon, dispersed layer 24 depending on the speed of the working carbon black. By means of the drum 20, the developer process should be between 10 ³ to 10 ⁵ ohms. 70 suspension applied to the photoconductive layer

and as a result of the electrical properties of the various parts of the device, it strikes the soot is proportional to the electrostatic charge on the surface of the photoconductor on it down, which results in a positive of the reverse imprinted light image on the surface.

To remove the soot image from the surface of the drum 10, means are also provided, which from a transfer roller 40 covered with an endless paper web 42, such as this Fig. 1 shows. Furthermore, the surface of the drum 10 is still with a cleaning agent 44, for example a roll made of felt or other absorbent material To make the drum usable again.

In the embodiment according to FIG. 2, the photoconductive layer is not applied to a drum, but forms part of a flat plate 10 '. The plate is preferably made of a transparent one Base layer 12 'made of glass or plastic, an electrically conductive intermediate layer 14' made of the same materials as the layer 14 can consist, and one of the layer 16 corresponding, high-resistance photoconductive layer 16 '. A negative 18 'of the image to be reproduced becomes immediately placed on this plate element. A light source 46 'is arranged above it that it is the photoconductive Layer exposed through the negative. Of course, other, suitable Means can be provided in order to project the object to be reproduced onto the photoconductive layer.

Below the plate element is a vessel 26 'into which a drum 20' is immersed, which is used for Charge the photoconductor and develop the electrostatic latent image into a visible one Image serves. When the flat plate 10 'is moved over the drum 20', a charge image is created in developed in the same way as for drum 10. To make firm contact with the surface of the plate 10 'to ensure the surface of the drum 20', electrically insulated rollers 48 can also be used be provided.

The inventive charge of the Photokonduktors and developing the S ⁴ according to the invention the latent electrostatic image, various advantages are achieved. On the one hand, the construction of the device is much simpler than with the previously known devices. On the other hand, the development of this image, which takes place approximately at the same time as the production of the electrostatic image, counteracts any tendency of the photoconductor to distribute its charge and thus to the decay of the electrostatic image during the period between the generation of the latent electrostatic image and its development Improving the sharpness of the image contributes.

The device shown in the drawing, for example, was at a potential within the Range from 300 to 900 volts between the negatively charged developer drum and the electrically charged one conductive, positively charged, layer 14 is used. The speed of the endless paper web was 245 cm per minute with satisfactory images.

Ill

Claims (5)

Patent claims: 1. Process for the electrostatic production of images using photoconductive material, in which a light image through a transparent layer of electrically conductive material and through an adjacent transparent photoconductive layer of high resistance to a in contact with this but separable layer of another material that is deposited by a supporting metal layer, is thrown to the supporting metal layer a potential opposite to that of the transparent, electrically conductive layer is placed, whereupon a dispersion of Opaque powder applied and the imagewise powder deposit optionally on another area is permanently transferred, characterized in that the separable layer consists of a semiconductor material and the opaque powder on the surface of the photoconductive layer is transferred over the layer of the semiconductor material. 2. The method according to claim 1, characterized in that the visible on the surface of the The image formed by the photoconductive layer is transferred to a separate layer of sheet material will. 3. Device for performing the method according to claim 1 and 2 with a transparent, electrically conductive layer, a transparent photoconductive layer adjacent to it High resistance layer, one in contact with the latter but separating layer of electrically insulating material, which is supported by a metal layer is deposited, a voltage source that is applied to the electrically conductive layers, and a light source that sends a light image through the transparent, electrically conductive layer onto the photoconductive layer throws, characterized in that the separable layer consists of a There is semiconductor material and the lower part of the layer consisting of semiconductor material in one electrically insulating liquid is immersed, in which an opaque, electrostatically attractable Powder is dispersed. 4. Apparatus according to claim 3, characterized in that the lower part of the semiconductor material existing layer is arranged so that it is in an electrically insulating liquid immersed, in which the electrostatically attractable material, opaque Powder is dispersed. 5. Apparatus according to claim 4, characterized in that that the electrically insulating liquid is electrically connected to ground Metal container is arranged and that the consisting of electrically conductive material, the layer carrying the photoconductive material is also electrically connected to ground. Legacy Patents Considered:
German Patent No. 1 042 613. 1 sheet of drawings