DE1105277B - Photoconductive paper sheet for the electrophotographic reproduction of images - Google Patents

Description

Coated paper, which can be made photosensitive, is for electrophotographic purposes Playback of images known. It is used to make a positive or negative copy by means of a four-step process. The paper is first made photosensitive by that the coated side of the paper receives a negative electrostatic charge in the dark, for example by ion transfer from a corona discharge. The sheet is then after any to conventional photographic processes exposed, reducing the electrostatic charge in the exposed Areas are diminished or disappeared, whereas they remain in the unexposed areas to form an electrostatic latent image on the surface of the paper. Same will then developed by applying a resin powder to the exposed surface which dyes is or contains colored pigment (hereinafter referred to as "toner") and one is electrostatic Owns charge. The powder image is then fixed by melting the resin; by referring to the When the paper surface melts, an indelible image is obtained, the richness of which differs from the Pigmentation of the toner is determined.

The driver intended for the direct production of copies must be colored. The color can by the natural color of the resin used or by a pigment carried by it to be delivered. The sounder is held in place by the image surfaces to create an image with the same brightness values like the original, or from the unexposed areas to a reversed one To deliver image, depending on its polarity with regard to the surface areas to be developed. If the Töner is positively charged with respect to the image area to be developed, a direct image is obtained If the driver is negatively charged with respect to the image surface, a reverse image is obtained.

Papers of this type, which carry a developed image, are suitable for use as planographic printing foils. Such foils are prepared by means of a toner which, after melting, provides a surface the fat printing ink accepts ... Resins such as copal, sandarac, rosin, »Vinsol« (a natural resin made from Coniferous wood), as well as hard waxes can be used as toners for these purposes. In planographic printing, the sheet is treated with water to make the non-layered areas water-absorbent and the bold color will only adhere to the water-repellent letters or image areas of the sheet, but not on the damp paper surface. This color image is then transferred to another sheet of paper transferred to what you get a planographic photoconductive Sheet of paper

for electrophotographic

Reproduction of pictures

Applicant:

The Plastic Coating Corporation,
Holyoke, Mass. (V. St. A.)

Representative: Dipl.-Ing. AH Fischer, patent attorney,
Ludwigshafen / Rhine, Schumannstr. 21

Claimed priority:
V. St. v. America April 10, 1958

Jay J. Over, South Hadley, Mass.,

and Victor Broto, Belchertown, Mass. (V. St. A.),

have been named as inventors

press operated. For this reason, the last step in creating a printable film is this Kind of making their non-printing areas water-absorbent so that they don't have a greasy color accept more.

As used herein, the term "electrophotographic matrix" is used to denote to designate a sheet which is capable of taking an image by electrophotographic processes, which, however, does not yet bear such a picture, and which, furthermore, can be shaped by its shape and dimensions on the cylinder can be attached to a planographic press or office duplicating machine.

The term "sheet of flat printing paper" is used in the most common sense to denote a To denote a paper sheet which has water-repellent image areas which take on bold color, and further areas which, when moistened with water, no longer take on a greasy color. With this expression are called paper foils that are either for offset printing or direct flat printing carry usable pictures.

The present invention is the result of studies which have shown that a film or a layer of electrically conductive material on a sheet of paper sandwiched between the surface of the sheet and a photoconductive coating located for electrophotographic Image reproduction required distribution of a static

109 577/343

see cargo with concern, even when the paper carrier is completely dry and not itself is an electrical conductor. Furthermore, the studies have shown that a film or a Layer, expediently made of an organic film-forming material, which is a finely divided, electrically contains conductive, solid substance, the distribution of static required for image formation Generates electricity even though the film-forming material is an electrical insulator.

The photosensitizable coated or uncoated paper sheet according to the invention for the Electrophotographic reproduction of images has a layer of finely divided photoconductive material inorganic pigment, e.g. B. zinc oxide, embedded in a layer of a film-forming, electrically insulating Materials.

The new thing is that an electrically conductive layer with finely divided, electrically conductive Substance is provided between the paper sheet and the photoconductive layer, the finely divided electrically conductive substance in a layer of organic film-forming material is dispersed. Etched and pressed plates have already been used in the electronics industry There are plastic plates that carry a copper plate with a photoconductive layer of zinc oxide pigment covered in silicone resin; the use of paper is not the case here Speech, and the only purpose of the copper plate is to act as an electrical conductor for the whole disc too to serve. Otherwise no advantage will be obtained.

It is also known in lithography that paper and metal can be exchanged as a conductive base are, which simply means that paper naturally has sufficient electrical conductivity when moist to serve as a base for electrophotographic plates.

The fundamental difference between the present invention and the known lies in the first place Line in the fact that the teaching is nowhere to be found, the electrophotographic plate of three Layers in a certain order, namely a base of paper, an intermediate layer of finely divided electrical substance and an overlying layer of photoconductive pigment in electrical insulating material. It is only with this novel arrangement that the aforementioned become significant Benefits achieved.

The photoconductive sheet can be used to form images by electrophotographic processes the moisture content of the paper can be disregarded. This is a Significant, the present invention accruing advantage, since this eliminates the need for Control of the moisture content of the paper base when using known photoconductive Paper transparencies are required. According to the present invention, the additional Advantage achieved that the sheets have improved folding resistance and the use of a allow thinner photoconductive layer, thereby increasing the folding resistance of the sheet even further is increased.

The paper sheet can be a coated paper, as is known in the manufacture of photosensitive paper Papers of this type are used, d. H. be a paper made with a clay-casein layer or is coated with a similar layer. Such papers are well known in the paper industry and among various brand names available in stores.

However, the paper sheet can also be an uncoated cellulose film. Using a Such a film offers both an economic advantage over the use of a coated sheet Aspects, since it is cheaper, as well as an advantage from a technical point of view, since when using it of an uncoated sheet with a cellulose base, a photoconductive film is obtained which is more transparent than one made of coated paper.

Further features of the invention emerge from the following description of exemplary embodiments

¹ S len, in conjunction with the drawing and the claims. It shows, in a schematic representation,

1 shows a partial cross section through a photoconductive paper film according to the invention,

2 shows a partial cross-section of a modified embodiment of the film,

3 shows a partial cross-section through a copy obtained by means of a sheet as shown in FIG was, and an embodiment of a planographic printing film according to the invention and

4 is a plan view of an electrophotographically produced planographic printing sheet according to the invention.

In Figs. 1 and 3, a cellulose sheet 1 is shown, which has a thin film 2 on its surface, which has a finely divided, electrically conductive, Contains solid substance dispersed in an organic film-forming solid substance. The movie 2 carries on its outer surface a film or a layer 3 made of a finely divided, photoconductive, inorganic pigment embedded in a film-forming, insulating material.

In Fig. 2, a film 4 is assumed, which consists of a coated paper. The combination of one Cellulose film 1 with a coated paper film 2 is nothing more than one of the many different ones commercially available coated papers.

In Fig. 3, the fused toner 5 is shown, which is on the surface of the film 3 in the course of development has been knocked down. The areas 5 of the melted-on tweeter like either one result in a positive or a negative image. Since these are water-repellent areas, which Able to accept a rich printing ink is usually the case in the case of a planographic printing plate acts, creates a positive image. The areas 6 are merely exposed areas of the film surface 3, in the case of sheets that are not to be used as planographic printing foils. Should, however are printed, these areas must be specially treated to make them water-absorbent close. For example, this can be done by treating the areas with an acidified Treated ferrocyanide solution.

In Fig. 4 there is an electrophotographically produced one Die-sketched with perforated fastening edges, with the help of which it is on the cylinder one Flat printing press can be attached. Both the length between the attachment ends and the Width are set up to allow use in one of the conventional planographic printing presses. The cross section of this die is shown in FIGS.

The electrically conductive, finely divided, solid material used in the intermediate layer can e.g. B.

το aluminum pigment, powdered copper, powdery

Contains soaked solution. Which organic solvent or solvent mixture is used depends on the particular film-forming material used.

Lacquer compositions which are suitable for forming an electrically conductive intermediate film are listed in the following examples, which are summarized in Table I:

Table I.

Example I 2 i

Parts by weight

ized bronze, powdered zinc pigment, black lead, tin oxide, copper sulfite, silver sulfite, graphite or be electrically conductive soot.

Some types of soot, such as B. acetylene black, furnace black

and channel soot, also have the electrical conductivity required for the above purpose on. An aluminum pigment gives good results; it is therefore preferred for this purpose related.

As an embedding material for the electrically conductive 10

Pigment can be any of the many known film-forming plastics. Is preferred the use of a film-forming material that

does not require the addition of a plasticizer

a possible migration into the elektrophotographi- 15 Celluloseacetobutvrat see avoid coating .berner is for this p _o lv 'n lbutvr 1 coating a film-forming material is preferably
used that of the solvent used to apply the electrophotographic coating
is not significantly attacked. The following film- 20
Formative materials are suitable for this purpose:
Cellulose acetate butyral, ethyl cellulose, polyvinyl butyral, copolymers of vinylidene chloride with
Acrylonitrile as well as those of vinylidene chloride with

Vinyl chloride and vinyl chloride with vinyl acetate 25 then with an electrophotographic sensitizer The mixed polyesters are covered by ethylene terephthalable film, which is made from a photoconductive material and ethylene sebacate and like polyesters. tive, finely divided, inorganic pigment and

The minimum amount of a finely divided, electrically film-forming insulating material consists of the Conductive substance that is required to bind the necessary layer of paint to the underlying layer of paint. These agile dissipation of static electricity at 30 composition is in solution form The exposure to bring about on the sheet depends on how an organic solvent is applied

Ethyl cellulose
Aluminum powder
toluene

Butyl acetate

10 60 15 14

10

10 25 50

14th

The lacquer layer deposited on the paper sheet by the above coating process is

on the type of film-forming material in which it is dispersed, the particle size of the related finely divided, solid substance and its degree of dispersion in the film-forming material. It was found, that when aluminum powder is used as the pigment, there is a ratio when the film is used from 1 part of the film-forming material to about 0.25 to about 1.5 parts aluminum powder causes sufficient static discharge.

Silicone resins, polyvinyl chloride resins, polyethylene, phenolic resins, polyester resins, methacrylic resins, polystyrene resins, Styrenated alkyd resins and copolymers of vinyl acetate-vinyl chloride are suitable as substances that hold the inorganic pigment on the surface of the intermediate layer.

As a photoconductive inorganic pigment, for. B. zinc or lead oxide can be used. One according to the invention Usable zinc oxide shows the following analysis

Insoluble in H Cl 0.03Vo maximum

Loss at 110 ° C 0.25% maximum

Total sulfur as SO «0.04% maximum

Lead Oxide (Pb O) 0.01% ■ Maximum

Total zinc oxide as ZnO 99.50% minimum

The electrophotographic layer can contain 1 part by weight of the insulating film-forming material and about 2.6 to 4.5 parts by weight, preferably about 2.8 to about 4 parts by weight, of zinc oxide.

In preparing the sheet for electrophotographic image reproduction, the paper sheet is used first according to one of the known processes with a lacquer in which a finely divided, electrically conductive, solid substance is suspended, coated.

The preparation used for layer formation consists of a solution of the film-forming material in a suitable organic solvent that contains the finely divided, electrically conductive, solid substance can be seen from the following examples: Example 4

Silicone resin solution 26 parts by weight

Zinc oxide 39 parts by weight

Toluene 35 parts by weight

100 parts by weight

The silicone resin solution used in this mixture contains 60 percent by weight of solids and 40 percent by weight Xylene. The solution has a viscosity of about 5 to about 30 cP at 25 ° C and is straw-colored.

Example 5

Mixed polymer

from n-butyl meth-

acrylate and isobutyl

methacrylate 12.25 parts by weight

Zinc oxide 43.00 parts by weight

Toluene 56.25 parts by weight

111.50 parts by weight

The copolymer of n-butyl methacrylate and isobutyl methacrylate used in this mixture is obtained by mixing equal parts by weight of the two monomers, it has a density of 1.05 and a refractive index of 1.4778 at 25 ° C.

Example 6

Polymerized isobutyl methacrylate. 12.25 parts by weight

Zinc oxide 43.00 parts by weight

Toluene 56.25 parts by weight

111.50 parts by weight

The polymerized isobutyl methacrylate, which is uniformly suspended in and thoroughly contained in this 70 of this mixture, has a density of

1.05, a refractive index of 1.477 and a dielectric constant from 2.5.

Example 7

Mixed polymer

Styrene-butadiene 10.00 parts by weight

Zinc oxide 34.00 parts by weight

Toluene 71.50 parts by weight

111.50 parts by weight

The copolymer used in this composition has a high styrene content, a softening point of 50 ± 3 ° C, a solution viscosity of about 160 to about 195 seconds (when measured using a Ford cup No. 4 in a xylene solution, the 33% by weight of the Resin), a specific gravity of 1.05, a refractive index of 1.585, a specific surface ^{resistance of 10 · 10 16} and a dielectric constant of 2.56 at 1000 Hz.

Example 8

Styrenated alkyd

resin solution 24.00 percent by weight

Zinc oxide 42.50% by weight

Xylene 33.50 weight percent

100.00 percent by weight

30th

The styrenated alkyd resin solution used in this mixture contains 50 ± 1 percent by weight more solid Components that are dissolved in petroleum distillates. The solution is color 5 to 8 (Gardner 1933J, a viscosity at 25 ° C from Zl to Z4. The solid resin has an acid number of 3 to 8.

According to the invention, images can be used both on electro / rophotographic Scrolling and planographic printing stencils are generally the same such as images on electrophotographic sheets, which are a well-known paper base own. Furthermore, the device hitherto used in electrophotographic Sheets on paper was used to reproduce images using the new invention Products suitable. Accordingly, using these products is not a new technique and no new equipment required. These are major advantages of the new products get.

The products of the invention offer over the prior art electrophotographic sheets two other advantages on paper in terms of their use to produce images. Deviating from With the known paper foils, the new Er certificates do not require any control of the moisture content of the support as the electrostatic image is formed. The moisture content of the paper is negligible; the leaves do not need to be treated to maintain a certain level of moisture.

This eliminates an undesirable factor associated with using the known electrophotographic Leaves must be expected.

The second added benefit of the new products is that their underside not in close and uniform contact with an electrical conductor during imaging must stand, as is the case with the known paper-based electrophotographic sheets is. A film that, according to the invention, has an electrically conductive, solid substance between the paper and the contains photoconductive layer, creates a uniform base for the photoconductive coating, while these the uniform, negative, electrostatic charge layer during their development is maintained, resting on a grounded conductor or being grounded by being at one point from a grounded electrical conductor is pierced.

Claims (6)

Patent claims: 1. Photoconductive, coated or uncoated paper sheet for the electrophotographic reproduction of images with a layer of photoconductive finely divided inorganic pigment, e.g. B. zinc oxide, in a layer of a film-forming, electrically insulating material, characterized by an electrically conductive layer between the paper sheet and the first-mentioned layer, the z. B. may consist of organic film-forming material that carries a finely divided, electrically conductive solid substance. 2. Sheet according to claim 1, characterized in that the layer consists of a film of an organic film-forming material exists as a finely divided, electrically conductive solid substance Aluminum carries. 3. Sheet according to claim 2, characterized in that the film-forming organic material is a from a cellulose derivative, ζ. B. cellulose acetobutyrate or ethyl cellulose, existing paint is. 4. Sheet according to claim 2, characterized in that the film-forming organic material Is polyvinyl butyral. 5. Photoconductive template, consisting of a sheet according to any one of claims 1 to 3, characterized characterized in that its dimensions and opposite edges are chosen and set up are that the sheet is attached to the cylinder of one of the usual planographic printing presses can be. 6. Die according to claim 5, characterized in that the image areas are made of water-repellent Consist of material that accepts bold printing ink, and in the remaining areas of its surface is water-absorbent. Considered publications:
British Patent No. 775,812. 1 sheet of drawings © 109 577/343 4.