DE1522592A1 - Process for making electrophotographic images - Google Patents

Description

Process for making electrophotographic images. the Invention relates to electrophotographic processes, and more particularly to a method of electrophotography using photoelectric insulating powders.

Electrophotography using photoconductive or photoelectric insulating powders is explained in detail in Japanese Patent Publication No. 22,645/63.

First, a photoelectrically conductive insulating powder is spread out uniformly over a suitable device with a certain electrical conductivity, on which an image is to be formed, and the powder layer is charged by means of corona discharge. The powder adheres tightly to the carrier as a result of the electrostatic leakage to such an extent that it is hardly removed. If the layer of photoelectrically conductive insulating powder is exposed to light in any suitable manner, the electrical charge in the exposed Dorcich falls to zero due to the photoelectric conductivity of the powder and the electrostatic force due to the electro-batic charging is extinguished, whereby the powder on the exposed part is easily removed. After this has been removed or removed by means of gravity # by mechanical forces or oil trojutatic forces, only a photoelectrically conductive insulating powder remains on the unleaded areas, which leads to the creation of an image, in electrophotography using photoelectrically conductive insulating powder it is erfahrungof7cmüß generally known that a high Belichtun pausmaß is required to obtain a good image # -E;! ogenüber the rall, wherein a light electrically conductive material as a continuous; lent layer is used for the usual electrophotographic process. This is presumably due to the fact that the powder layer has a large amount of contact under the grains and thereby delays the drop in the electrostatic charge to zero. The invention aims to eliminate the Llinflu., -,: 3os of residual electrostatic charging under insufficient exposure in order to obtain C.ate pictures and to increase the apparent photosensitivity in electrophotography using the photoelectrically suffering insulating powder. ' The invention is explained in more detail below with reference to the drawing, in which FIGS. 19 2 and 3 show a schematic representation of the basic principle of the present invention.

If the Zunuchst # lichtelektriach conductive insulating powder gleichförmig'auf a suitable T:.. Rb * ger'mit e-.Lnt, r bo "#" gezeiCit U 'immten electrical Leltfähigkeit as in PiG, 1, auSgelbreitote The gauge or thickness the powder layer should be selected in a scorching manner in accordance with the electrical #Ugonochaften of the form and deois-specific Ge% TichtgV. A mono- or single layer is - in general not sufficient and preferably - therefore the multi-layer is used. Then the photoelectrically conductive layer is used # insulating powder coating is charged by, for example, the process of corona discharge, which is generally known in the usual electrostatic and electrophotography # The polarity of the charging pen is determined by the electrical properties of the light-electrical leolierpowder Zinc oxide and bilicon resin are used as photoelectrically conductive insulating powder with a nosatige polarity 1 - * 'ulvers can be extended before spreading.

The charged, photoelectrically charged insulating powder is then exposed to light using, for example, a photographic pre-magnifier such as Ln Pig. 2 So showsv exposed. The electrostatic charge on the electrically conductive insulating powder layer of an exposed area decreases with a speed corresponding to the intensity of the light to zero, the rate of decrease being considerably slower than when a powdery electrically conductive material is a usually continuous or continuous electron photograph For further elucidation it is stated that the time function of the decrease or the disappearance of the electrostatic charge obviously has two-fold systems of constants, whereby the disappearance with a short-term constant is equal to that of the usual continuous layer from photoelectrically conductive material, while the disappearance is very slow with a large time constant, which requires a very high light intensity ttr4 in order to obtain a suitable exposure time which is practically feasible lten * Since the difference between the density of the electrostatic charge in the exposed area and the unexposed area is small within a conventional visualized area. hence the weightive distance drying the electrically conductive light in the exposed 2ulvors e-) p to Area jolm in contrast to that in the unbeliolite area <alone> very difficult * Ie # 'it couldn't take good pictures have been held, since the potting of the powder in the exposed area is incomplete or the renewal also extends to the unexposed area.

Now.wüü-after.'the -'exposure, the light-electrically conductive insulating powder with the opposite polarity ** # so above the first given #g as this in 2ig. 3 is shown.

In this case, if the entire upper 15% of the photoelectrically conductive, volatile powder layer can be given a suitable and appropriate, uniform electrostatic charge through the arrangement or regulation of the construction of the discharge electrodes, the discharge distance, the applied voltage and the charging speed, the static, electrostatic charge in the exposed area drops to zero or can be neglected 9 while the difference in the electrostatic charge in the exposed and unexposed area is retained in its shape * as a sufficiently large difference. between the electrostatic forces that act between the photoelectrically conductive, insulating powder layer and the carrier on the bonded surface and the exposed surface under this condition, and the force acting on the exposed area is negligible. . can effortlessly lichtelöktrisch lei-VI end Irjolierpulver in the bolichteten, area alone entfärnt '(Iono was- by the method according to the invention, the amount of Belichtunr be saved and the apparent -. light receiver ini friendliness can be increased so that it may be the practical Anviendung been fed "since a Bolichtungshöhe to such an extent that the electrostatic charge in the exposed region disappears indigo uilst * .- # mcl not = '* is crforderlich

Claims (1)

Patent also applies to a process for the production of electrophotographic images, in which a photoelectrically conductive insulating powder is evenly spread out on a carrier with at least a certain electrical conductivity, and a charged, photoelectrically conductive insulating powder is spread evenly on the carrier. exposed and the difference between the electrostatic .Krattg which between the photoelectrically conductive'Is olier- ' powder and the carrier <works> due to the difference between see the remaining electrostatic charge on the exposure area and the unexposed area <-> for selective tiven] removal of only the photoelectrically conductive insulating powder in the exposed area is used to form an image, characterized in that after the exposure, an electrostatic charge with reversed polarity. ity . to derdenigeng the previous to the light-electric - powder tend isollao-warg the entire surface is given the powder uniformly $ so that only the rest Liehe eleXtrostatische charge in the exposed region substantially or completely drop to zero can and thereby the conductive lichtelektriaoh Iso: Lerpulver on the unexposed part can easily been removed.