Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Electrostatic image transfer
Patent
1982-01-26
1983-06-14
Welsh, John D.
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Electrostatic image transfer
430 53, 430 55, 430 97, 355 3TE, G03G 1318
Patent
active
043883907
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to the field of producing of visible images by means of an electrophotographic method using electrostatic charged images. More particularly, the invention relates to methods of obtaining a picture on a dielectric film.
BACKGROUND OF THE INVENTION
The known electrophotographic methods for obtaining a picture on films are based on transfer of a latent image from a charged and exposed selenium layer onto a dielectric film by producing a gas discharge in the air gap between the selenium layer and the dielectric film (U.S. Pat. No. 2,937,943, published on May 24, 1960).
This method has insufficient resolution. The picture thus obtained is blurred due to scattering of ions in the gas-discharge gap.
Furthermore, when developing the wide fields on the transferred latent image a marginal effect is observed, as well as on the exposed selenium layer. The value of the charge of the transferred image is different for the image elements of different width. Therefore, during the development the optical density of the image elements is different.
Known in the art is a charge-free method for obtaining an image on a dielectric film, in which the dielectric film is brought in contact with surface of a charged and exposed electrophotographic layer, then the field of the latent image is developed and fixed (cf. R. Shaffert "Electrophotography", "Mir" publishers, Moscow, 1968, p.p. 323-333).
In this discharge-free method the image is sharper than in the above-mentioned method, however, it is still inadequate for practical purposes. This is associated with a decrease in the gradient of the field intensity at the boundaries of the fine lines on the film surface to the refraction of the field line in the film.
Like in the methods based on a gas discharge, the discharge-free method does not suitable for producing an image with wide fields without fringe effect. Furthermore, the optical density of the image elements of different width is also not constant.
All this hinders utilization of the images obtained for making copies on the light-sensitive layer of an offset plate. Furthermore, the above described method does not allow one to obtain several images using a once-exposed electrophotographic layer.
DISCLOSURE OF THE INVENTION
The main object of the invention is to develop an electrophotographic method for producing an image on a dielectric film, in which production of a latent image on the film, which is a bipolar system of charges located in the same plane, would make it possible to improve the sharpness of the edge of the fine lines of the image and to eliminate the fringe effect.
This object is attained by providing an electrophotographic method for producing an image on a dielectric film, in which the dielectric film is contacted with the surface of a charged and exposed electrophotographic layer, the image produced on the film being developed and fixed; according to the invention, after the dielectric film has been brought in contact with the electrophotographic layer, the dielectric film is acted on by positive and negative ions of the same concentration from an ion source; the ions settle on the film and produce a latent image thereon; prior to developing this image the electrophotographic layer is illuminated by an actinic light source.
During and after the illumination of the electrophotographic layer by the actinic light source, it is expedient to separate the dielectric film from the electrophotographic layer for eliminating the fringe effect during subsequent development of the once reproduced latent image.
The object of the invention is also attained due to the fact that in the electrophotographic method for producing an image on a dielectric film, in which the dielectric film is contacted with the surface of a charged and exposed electrophotographic layer; the latent image is developed and fixed; according to the invention, after the dielectric film has been brought in contact with the electrophotographic layer, the dielectric film is acted on by positive and neg
REFERENCES:
patent: 2937943 (1960-05-01), Walkup
patent: 3545969 (1970-12-01), Herrick et al.
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