DE2217319A1 - PROCESS FOR PRODUCING REVERSE COPIES OF ELECTRIC CHARGE IMAGES - Google Patents

Description

Nideggener Str. 38) P.O. Box: 516 Düren 445 Uns.Z .: EA 1291 - sf / pn

Process for making reverse copies of electrical charge images

The invention relates to a method for making reverse copies by covering the surface of a carrier with a layer of toner, bringing this layer of toner into contact with a the material carrying the charge image and subsequent separation of the carrier from this material.

From the American patent specification 2 839 400 it is already known, dry toner by means of an electric field between deposit two electrodes on the surface of an electrically insulating sheet.

Furthermore, it is already known, for example, from US Pat. No. 2,895,847, an electrostatic charge image to develop in that a support is covered with a layer of toner and this toner layer then with the charge image is brought into contact. After separating the developer substrate A negative and reversed image can then be produced from the surface carrying the latent image on the developer substrate lag behind.

The invention solves the problem of an electrophotographic reversal process To develop this way, the resulting reversed negative copy is correct in tone to the latent positive Image is created. For an application of the method for the production of color reversal copies, however, the production is more correct in tonal value Negative copies required,

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This object is achieved in that a with Liquid toner coated carrier used as developer substrate is, wherein the deposition of the liquid toner on the substrate in a known manner by means of an electrical Field is caused between two electrodes.

With the method according to the invention, both three-dimensional as well as two-dimensional charge images.

According to a further subject matter of the invention, a device for carrying out the aforementioned method is characterized by a two-roller green pressure synchronous arrangement as contacting contraption. With such a device it is possible to make reverse copies and enlargements on uncoated paper with the help of electrophotographic recording paper and liquid toner.

The invention is described below on the basis of a preferred exemplary embodiment explained in more detail.

The following toner transfer process is used to produce a positive copy of a negative original on normal paper :

First, in a manner known per se, there is a latent electrostatic Image of the original made on electrophotographic paper. Then liquid toner is set to the desired normal Paper deposited electrophoretically oriented homogeneously.

The electrophotographic paper with the latent image and the Paper coated with liquid toner is fed with the layer side to each other through a nip roller arrangement in such a way that that the contact of the sides of the layer takes place only in the nip. In doing so, the electrostatic image of the electrophotographic Paper toner from

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removed from the paper coated homogeneously with liquid toner, with a negative, inverted copy of the Original or latent image remains on normal paper.

A negative template therefore becomes a positive one that is reversed Copy received. In the case of transparent originals, e.g. film negatives, a correct-sided positive Copy can be obtained by exposing the transparent original reversed.

The latent electrophotographic image on the electrophotographic During this process, paper is developed with the correct tonal value. It turns out, surprisingly, that the otherwise Electrostatic copies occurring edge effect largely eliminated is, that is, an image-wise high-quality copy is produced.

Positive copies of negative originals on electrostatic Paths can, however, also be generated by the development of the latent electrostatic Image can be achieved with reverse toner. In contrast however, the toner transfer method of the present invention has the following advantages:

1. The copy is made on normal paper.

2. The copy can also be made on transparent paper and on suitable foils (eg cellulose foils), and thus serve as a template for cheap reproductions, ζ _β Β _β by means of blueprints,

3. The pictorial quality of the copies is much better than can be achieved using the known method. Leave it halftones can also be achieved, but at least a full area filling.

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4. The particular electrophotographic paper used can can be adjusted entirely to the requirements that are made for the generation of the latent image, without on Appearance, feel, or other properties of the electrophotographic Paper is to be taken into consideration. In particular, sensitizers can be used which reduce the electrophotographic Color the layer.

5. The visible image is formed at high speed.

The method according to the invention can be used for the most varied of purposes, in particular for creating high-quality back enlargements of transparent negative originals, e.g. microfilm, and also, if necessary, of amateur negatives.

The method described is also suitable for the production of a true-color positive copy of an original over a color negative applicable. To use the procedure for making a color reverse copy, do the following:

The colors of the color negative are complementary to the original.

1. There is now a latent electrostatic image on EP Paper made of the red, blue and green color separation from the color negative. This can be done by one through pull-out filter on panchromatic electrophotographice Paper exposed, or by setting the exposure on the filters for the respective color separations - uses selectively sensitized electrophotographic layers, i.e. works without a filter.

The individual electrophotographic layers must then be sensitized as follows: red extract red, blue extract blue and green extract green.

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2. Blectrophoretic deposition of one transparent each Blue-green, magenta and yellow liquid toner on transparent paper or film.

3. The latent electrophotographic is applied over the roller assembly Image of the red separation of cyan toner transferred from the paper coated with it, onto the latent electrophotographic Image of green abstract more magenta Toner of the paper coated therewith, and yellow toner on the latent electrophotographic image of the blue separation of the paper coated with this.

To achieve page accuracy, proceed as above, or simply reverse the transparent positive obtained.

The three transparent positives then result in perfect register on top of each other placed or glued a true-color, transparent copy of the original (slide) on an opaque white surface placed or glued represents a colored top view. However, there should be no toner of the required colors, transparency and quality are available, the color separations can also be produced by transferring with e.g. black toner and then in the blueprint process on diazo foils (commercially available available) can be copied. These foils then also result in a true-to-color, transparent one when placed one on top of the other in register Copy of the original. This method is useful when a large number of copies of an original have to be made.

The following is a tabular overview of the individual stages of the color process:

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CJ O CjD QO

black
White
Color separation red
(Development cyan): White
black blue
yellow green
magenta Red
cyan yellow
blue magenta
green cyan
Red original
Color negative Development based on elec-
trophotographic
Layer: -
Reverse image on
plain paper: cyan
Color separation green
(Development magenta): cyan cyan cyan cyan cyan cyan cyan Development based on elec-
trophotographic
Layer: -
Reverse image on
plain paper: magenta
Color separation blue
(Development yellow): magenta magenta magenta magenta magenta magenta magenta Development based on elec-
trophotographic
Layer:
Reverse image on
plain paper: yellow
black yellow
White yellow
blue yellow
green yellow
Red yellow
yellow yellow
magenta yellow
cyan NO
Positive elec- ^
tr ο pho t ο graph ^
see copy au5:
plain paper, be
standing from the 3
Single copies ver
sticks

The invention is explained in the following for example:

An electrophotographic, panchromatically sensitized Zinc oxide paper DIN A4 is electrostatically negatively charged in a commercially available electrostatic charger.

The charged paper is by means of a photographic Magnifier with a lamp power of 100 watts and a 50 mm lens at aperture 4.0 15 see. with the wrong one Image of a black and white amateur 35mm negative of normal scale, exposed at 8x magnification.

A 80 g / m2 transparent paper DIN A4 with an electrical specific surface resistance of approx. 10 ohm cm is in an electrophoresis cell coated with liquid toner of positive polarity.

The electrophoresis cell consists of a glass trough 2o χ 22 χ 9 cm, which is filled with 3 liters of black liquid toner of positive polarity is filled, and into which two copper plates are immersed at a distance of 8 cm from each other.

The paper is inserted in the middle between the electrodes. During 3 see. a DC voltage of 4 _f 1 kV is applied to the electrodes. Toner is deposited on the side of the paper opposite the anode and on the cathode. The coated paper is then removed from the cell, the deposited toner-carrier liquid layer remaining adhered.

The element; photographic paper with the latent image, .and the wet paper coated with liquid toner will be with the Layer side to each other in this way by a 2-roller counter-pressure synchronous device out that the contact of the layer sides nar takes place in the nip.

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The rollers are made of metal and each have a diameter of 20 mm and a distance of 0.05 mm from one another. Your drive takes place synchronously via gears by a motor with 3 ο U / oiin.

One pass that is free of the edge effect is created when the rollers pass Image on the electrophotographic paper and one negative correct tonal reversed copy of the latent image on the tracing paper.

Accordingly, an 8-fold enlargement of the small picture negative is obtained on the tracing paper, which is correct on the side and in the correct tonal value, which in the review shows a slide and on a white base a reflective picture.

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Claims (5)

Claims £ U / Method of making reverse copies on electrophotographic Ways by covering the surface of a carrier with a layer of toner, bringing this layer of toner into contact with a material carrying the charge image and subsequent separation of the carrier from this material, characterized in that a liquid coated with KLüssigtbner Material is used as a developer substrate, with the deposition of the plus toner on the substrate in in a known manner by means of an electric field between two electrodes "is effected» 2. The method according to claim 1 _f, characterized in that a true-to-color copy is made from an original on a Golornegativ. 3 »Method according to claim 1 or 2, characterized in that that a transparent material coated with plush toner is used as the developer substrate, » 4. Apparatus for performing the method according to claims 1 or 3, characterized in that a two-roller counter pressure-G-leichlatifanordnung is provided as a contacting device. 5. Apparatus according to claim 4 _9, characterized in that the roll material is metal _o 309842/1054