Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/09—Sensitisors or activators, e.g. dyestuffs
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G13/00—Electrographic processes using a charge pattern
  • G03G13/22—Processes involving a combination of more than one step according to groups G03G13/02 - G03G13/20
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/12—Recording members for multicolour processes
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G9/00—Developers
  • G03G9/08—Developers with toner particles

Definitions

• the invention relates to a process for sensitising electrophotographic layers, mainly layers of zinc oxide and a binding agent, by means of which mosaic sensitization or image sensitization is possible.
• an alcoholic solution of the sensitizing dyestufi' is stirred or ground with photoconductive ZnO, the solvent is then removed by drying, and the slightly colored zinc oxide is mixed with the insulating binding agent in the usual manner and the dispersion cast onto the support.
• the sensitizing dyestuli is not previously dissolved in alcohol but added to the solvent for the binding agent, e.g., toluene, and ground in this form with zinc oxide.
• the unsensitized electrophotographic paper is bathed in a solution of sensitizing dyestuff.
• Another process for preparing sensitized layers comprises applying two superimposed ZnO.layers onto the carrier, the outer of the two layers containing the sensitizing dyestuff. This method is used for obtaining maximum sensitization with low coloration.
• the development is accomplished with a solution or dispersion of the sensitizing dyestulf which is not colored or is only very weakly colored. A practically invisible image of the sensitizing dyestulf is thereby formed on the electrophotographic layer.
• the application of the sensitizing dyestufi on the exposed material may be carried out by known developing processes.
• the dry powder of a sensitizing dyestulf may be used in the usual powder process, employing the development of cascades or dust clouds, and the powder, which is deposited in a pattern corresponding to the image, may be fixed by after-treatment with a solvent. Suitable processes are described, for example, in US Patents 2,297,691; 2,618,552; 2,725,304 and British Patents 793,331 and 835,044.
• electrophotographic developing processes 7 may also be used, for example, the wetting processes described in Belgian Patent 616,644 in which the different wetting capacity of electrophotographic layers which have been charged in patterns corresponding to the image or which have been rendered conductive by exposure in patterns corresponding to the image is utilized for development.
• an uncolored or only slightly colored solution of sensitizing dyestuff is used instead of the deeply colored dyestuff solution.
• the developing processes in which a colored aerosol is used preferably one that has been produced by electrostatic means.
• the electrostatic charging of the aerosol thereby effected provides a particularly advantageous deposition of the sensitizing dyestutf on the exposed electrophotographic layer.
• Developing processes of the last mentioned type are described, for example, in Belgian Patent 616,914.
• the highly concentrated dyestulf solutions which may be used for'development of the picture are more easily atomized with positive atomizing electrodes than with negative electrodes, and much simpler electrode arrangements may be used for positive atomization.
• the droplets of liquid formed are positively charged.
• a positive developing process by means of aerosol sensitization may be employed.
• electrostatic charged images may be developed by means of colored aerosols with the aid of an electro-- static atomizer electrode combined with a grid shaped developer electrode. Due to the low concentrations of a sensitizing dyestuff instead of the highly concentrated dyestuif solutions, the resulting image is invisible. However, the quantity of sensitizing dyestuff applied is sufficient to increase the photoconductivity of the zinc oxide layer or to render the photoconductive layer, sensitive to other regions of the spectrum at the developed and sensitized areas.
• the process described above provides an electrophotographic material whose photoconductive substance has been sensitized by the differential application of sensitizing dyestuff distributed in accordance with the image.
• the final picture is now produced by charging the layer again and then exposing it uniformly, i.e. not imagewise. This produces a charged image which is negative to that of the sensitizing dyestuif, and this charged image is rendered visible by means of a blackening or deep coloring developer recording to common practice. Any of the usual processes may be used for this purpose, but development with a colored aerosol is again preferred.
• the electrophotographic material, sensitized in a pattern corresponding to the image by the process accord-ing to the invention would be charged negatively, exposed uniformly and developed in the usual manner, for example by the colored aerosol processes described in the above mentioned Belgian patent. A positive picture of the negative original is thereby obtained.
• the invisible intermediate sensitization image which is characterised by the feature that the sensitivity of the zinc oxide layer is altered in accordance with the image, is stable a very long time and may, for example, be left for several months before it is finely developed even if the layer has in the meantime not been kept away from the light, provided that the light is not so intense that it decomposes the sensitizing dyestutf.
• the only condition that must be observed to ensure that the image may be rendered visible is that, for the reasons already known, the layer must be stored in darkness for some time before the picture is developed.
• Screenlike sensitized electrophotographic layer or papers have great advantages compared with non-screened layers. For example, the range of exposure is considerably increased, and a screened charged image may be produced by a simple exposure of the previously charged layer. Owing to the inhomogeneity of the electric field distributed over such a layer, uniform blackening is obtained over large surfaces even with toner dust development. Furthermore, a multiple screen may be produced with sensitizers for different wavelengths of light. In this case, the differently sensitized surface elements of the layer will not or will only partly coincide with one another. This type of screen formation is of greater importance for the development of multicolor images because the colors will not be deposited over one another but on minute surface areas side by side.
• the screenlike sensitization which can be obtained by the inventive process may correspond to a screen having of between 100-200 lines/cm.
• sensitization may 'be controlled as desired by varying the concentration of the deposition of sensitizer or by mixing different sensitizers. These measures may be effected particularly simply by spraying the sensitizer with the aid of one of the known colored aerosol processes, preferably electrostatic aerosol processes.
• Example 1 320 g. of a silicone resin (e.g., type Bayer P150) as a 60% solution in toluene, 5100 g. of toluene and 450 g. of chemically pure photoconductive zinc oxide are ground for about 3 hours in a ball mill and then cast on to a paper and dried.
• the electrophotographic paper so produced is given a negative electric charge in known manner by means of a charging apparatus and then exposed through a film by means of an incandescent lamp so that a charged image is produced on the layer.
• the layer is sensitized in a pattern corresponding to the charged image with a solution of br-omophenol blue in benzyl alcohol in the proportion 1:1200. After storing the paper for 3 hours in the dark, the layer is charged again and exposed diffusely with yellow light of wavelegnth 0.60 to 0.65,. Subsequently development with a solution of Ceresblack in benzyl alcohol in the proportion 4:7 using the apparatus described in the last mentioned Belgian patent produces a reversed black image of the original.
• Example 2- Screen sensitizati0n.An electrophotographic paper according to Example 1 is given a negative electric charge by means of a charging apparatus and exposed to light through a film which has a cross line screen (5 lines per cm.), which is placed on the layer.
• the electric screen image thereby formed is sensitized by the aerosol of a solution of fluorescein in benzyl alcohol in the proportion 1:2000, using the same apparatus as in Example 1,
• the electrophotographic layer is sensitized in a screen pattern. Similar results are obtained if line or cross line screens are used for the exposure which have -200 lines/cm.
• the paper After storing the paper for 3 to 5 hours in the dark, it may 'be processed in the usual manner. That is to say, it is charged and then exposed through the original.
• the light used for the exposure is one to which both the sensitized and the non-sensitized region of the electrophotographic layer are sensitive although to different extents.
• the picture may be developed either by aerosol process or by the toner process.
• the process according to the invention can be varied in many respect.
• electrophotographic layers other than those given in the examples may be used.
• the silicone resins may be replaced by other bin-ding agents such as alkyd resins, formaldehyde or phenol resins or other binding agents.
• bin-ding agents such as alkyd resins, formaldehyde or phenol resins or other binding agents.
• zinc oxide other organic or inorganic photoconductive substances may be used.
• the process according to the invention is independent of the type of sensitizing dyestuff used. Any of the known sensitizers may be used, for example:

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Photoreceptors In Electrophotography (AREA)
• Color Electrophotography (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=6931986

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (1)

Citations (6)

• 0
  • BE BE635517D patent/BE635517A/xx unknown
• 1962
  • 1962-06-16 DE DEA40459A patent/DE1267090B/de active Pending
• 1963
  • 1963-05-09 CH CH581163A patent/CH436990A/de unknown
  • 1963-05-14 US US280433A patent/US3298830A/en not_active Expired - Lifetime
  • 1963-05-22 GB GB20476/63A patent/GB1020831A/en not_active Expired

Patent Citations (6)

Also Published As

Similar Documents