DE2050068A1 - - Google Patents

Description

Patent attorneys

Dipl.! Ng. F. Welckmenn,

Dipl. Ing. H. Weioirnann, Dipl. Phys. Dr. K. Fincke

Dipl. Ing. FA Weickm? Nn, Dipl. Chem. B. Huber

8 Munich 27, Möhlstr. 22nd

Sch / Gl Z. 476 (XD / 2767)

Ji IMlIl I I I I Il ■ I 1 T [I.

Xerox Corporation, Rochester, Few York, N.Y. / UNITED STATES

Electrically photosensitive particles for photoelectrophoretic Image generation

The invention relates generally to photoelectrophoretic technology Image generation and particularly relates to enhanced photosensitive glow used in photoelectrophoretic Imaging systems can be used.

A photoelectrophoretic imaging system capable of producing color images is known. In this system electrically light-sensitive lights are used. This Process is described in U.S. Patents 3,383,993; 3,384,565 and 3,384,566. In such an imaging system become different colored light absorbing particles

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suspended in a non-conductive liquid carrier. the Suspension is placed between electrodes, exposed to a voltage difference and produced with an image irradiated with electromagnetic radiation. After these stages have been completed, a selective particle ' migration in image configuration, producing a visible image on one or both of the electrodes. An essential one Components of the system are the suspended particles, dxe need to be electrically sensitive to light and obviously a change in charge upon irradiation with the experience electromagnetic activating radiation, namely by a Y / echje! effect with one of the electrodes. In one monoChromatis dien system can consist of a single particle Color can be used. One can also fall back on a combination of colors, which on the wavelengths of the used Address radiation, producing a single colored image, that of a standard black and white photograph is equivalent. In a polychromatic system, images be produced in one or more colors, including the natural colors, by use a mixture of particles of two or more colors, each particle responding to light with a specific wavelength or a specific wavelength range.

After the irradiation and the migration of the particles, the electrodes are separated, whereupon the carrier liquid evaporates left v / ird. Images remain on one or both of the electrodes, namely from selectively applied pigment particles. The carrier liquid may contain small amounts of a wax or other binder that can be used serves to connect the particles in the pictures with each other. However, if more than a small amount of the binder is used, then there are undesirable interactions with the imaging process. The pictures are from this point in time

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fragile and can be easily destroyed. It has been proposed to coat a transparent film on the images or to spray a transparent binder resin on the images to form a protective coating. Even if these methods are able to protect the images when used carefully, the images are often destroyed during the application of the protective material. These protection methods are also unsuitable for use in an external mechanized system. Even if it is desired to transfer the DiId from the electrode material to a receiving sheet, there is a risk that the unfixed image will be smeared ¹ or otherwise destroyed. There is therefore a need for a better system for fixing the particulate image that has been formed on the electrode surface.

So that electrically photosensitive particles for a photo,; electrophoretically, they must meet various requirements. The particles must be very They must be sensitive to light, they must have an intense and pure color and must be able to do so while creating of a permanent image to be able to be fixed. Furthermore, it is particularly useful for a monochrome image generation Pigirant particles available that have a high Density and high contrast result with minimal light exposure and with the particles must be remotely fixable.

It is an object of the invention to provide an improved photoelectrophoretic imaging system. Through the invention new electrically photosensitive particles are provided. These particles can come in a variety of Colors occur that have a relatively high response. These particles constrict relatively high density and with

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High contrast images, with only a minor one .Light exposure is required. Also own the particles have excellent fixation qualities. You can used to produce slides of relatively high quality.

The invention provides a photoelectrophoretic imaging system provided in which an imaging suspension also electrically photosensitive Particles dispersed in a carrier liquid between Electrodes are placed, exposed to the action of an electric pad3 and imagewise with an electromagnetic one Radiation is irradiated to generate a particle migration in image configuration. The electrically photosensitive Particles consist of relatively non-photosensitive resinous colored materials to which a relatively small Adhere a lot of electrically photosensitive materials.

It was found that a surprisingly small amount of one electrically photosensitive material is required to give the system high photoresponsiveness. For example, 0.005 parts of the electrically photosensitive material supply, while 1 part de3 does not adhere to photosensitive material, excellent results with a photoresponsiveness that comes close to that of the photosensitive material alone. Since the material to which the photosensitive material is adhered is not required to be photosensitive For example, the material can be any thermoplastic colored resin that can be found in a simple manner by conventional heat or solvent fixation methods can be fixed. The images can therefore be transferred from the electrodes on which they are formed onto a recording sheet.

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wear and on this through. Heat or a solvent . be fixed. The transfer stage can be achieved by, a electrostatic attraction can be promoted with or without irradiation or by a simple pressure method.

• Electric light-sensitive components consisting of many components borrowed particles are known. For example, 'according to the U.S. Patent 2,940,847 "multi-component" Electrically photosensitive particles are used. These particles however, have light filter layers to improve the response To change particles in an additive color system.

Opposite de: n particles consisting of many components the particles according to the invention are photoelectrophoretic Responsiveness practically identical to that of the photosensitive component alone.

The inventive electrically photosensitive part ' Chen can be made by a variety of methods. The. preferred method of making these particles consists of a suspension of the resin material and the electrically photosensitive material in a carrier liquid to build. A small amount of a solvent is then added to the suspension. The solvent is a Solvent for the resinous component and is miscible with the liquid component. The system then becomes vigorous touched. A stream of dry air is used to remove the solvent from the liquid suspension. The solvent is preferably highly volatile. Other methods of combining the photosensitive pigment with the resinous material can be applied. For example, the liquid suspension to soften the resinous Materials are heated. Stirring has the consequence

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that the photosensitive material adheres to the softened resinous material. Becomes the resinous material by emulsion polymerization then the light-sensitive particles of the emulsion can be formed towards the end of the polymerization process be added so that they even stick to the surface of the resinous Adhesive material. Further, the active pigments can be mixed among the resinous particles by dry blending will. The bonding can also take place in such a way that these particles are suspended in a stream of air, whereupon they are subjected to the action of solvent vapor or heat. The bonding can also be promoted thereby that very fine particles of the photosensitive material are used.

When performing the usual photoelectrophoretic image generation process, as described in U.S. Patents 3,384,565 and 3,384,566, the images are made in the manner formed in that the particles are removed by a conductive electrode at the points struck by the light. Wise at the Production of the electrically photosensitive particles does not have any resinous photosensitive particles adhered to them Pigments, then these particles would remain on the conductive electrode, namely on the image areas where they should be removed, leaving a strong subsurface The result is. However, this problem can be solved in the manner described in US Pat. No. 3,446,722 Procedure is applied. This process creates the ability to obtain the desired photosensitive particles from to separate the non-photosensitive particle. If the desired egg is formed on the insulating surface, i.e., on the electrode to which the particles are facing, then it is not necessary that photosensitive parts be attached to all resin parts Pigments adhere. It is only required that sufficient

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Number of total particles that are sensitive to light to form a viewable image.

The resinous material can be made of any suitable polymeric material, for example a thermoplastic or thermosetting plastic. Thermoplastic materials are preferred because they can be easily attached to a substrate can be fixed by the action of heat. Typical resinous materials are as follows: thermoplastic resins, v / ie for example polyolefins, polyfluorocarbons, vinyl polymers, Polystyrenes, acrylic compounds, polyamides, polyformaldehyde, Polycarbonate ", polychloride, silicone, cellulose & ter, Cellulose ethers and mixtures and copolymers thereof.

Typical hardening resins are: phenolic resins, urea and melamine resins, alkyd resins and polyester resins, and epoxy resins and compounds and copolymers thereof. A styrene / n-butyl methacrylate copolymer pigmented with carbon black, is preferred as the resinous material because it gives a very dense black image.

Any suitable electrically photosensitive may be used Use particles. Typical electrically photosensitive Particles are described in U.S. Patents 3,384,488 and 3,157,989. Typical carrier liquids are ebei. Tails in the foregoing patents. Phthalo- ' cyanine is preferred because of its high sensitivity to light.

You can use any suitable solvent. Typical Solvents are the following: Halogenated hydrocarbons, e.g. methylene chloride, hydrocarbons containing acid, for example methyl ethyl octone, ethyl alcohol,

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Ethyl acetate, ethyl ether or the like, hydrocarbons, such as "for example benzene and hexane, as well as hydrocarbons containing nitrogen, for example pyridine, or mixtures of that.

It has been found that it is necessary to match the photosensitive pigment with the non-photosensitive or relative non-photosensitive resinous material to join. It turns out that a simple addition of the resinous material and the photosensitive pigment to a suspension does not provide an image if this suspension exposed to the action of a field and imagewise exposure. After an addition and an evaporation With no solvent, however, the suspension gives images of excellent quality among the same Image creation conditions.

The advantages of the photoelectrophoretic according to the invention Image forming methods are based on the description below in connection with the accompanying drawings;

Figure 1 shows an elevation of a simple photoelectrophoretic Image generation system.

FIG. 2 shows a cross section through a simplified electrically photosensitive particle according to the present invention, the size of the particle being exaggerated to show the essential characteristics of that particle to show more clearly.

FIG. 1 shows a transparent conductive electrode, which is identified by the reference number 1. In this case

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does she stand out? a layer made of an optically transparent glass 2, which is covered with a thin, optically transparent layer 3 made of ZinnOX3'd. Such a material is commercially available under the name NESA glass. This electrode is hereinafter referred to as the "injecting electrode". On the surface of the dispensing electrode is a thin layer 4 of finely divided electrically photosensitive particles dispersed in an insulating carrier liquid the properties of a particle are understood which, once attracted by an electrode, migrates away from the electrode under the influence of an applied electric field when irradiated with an activating electromagnetic radiation. The delivery electrode 1 preferably consists of a transparent one Conductive electrode, however, materials that are not very conductive and even insulators can be used as these materials can be machined to allow charge exchange on their surface, but it is preferable to use a conductive material to which allows a better separation of the particles. The liquid suspension 4 can furthermore contain a sensitizer and / or a binder for the pigment particles, the binder being at least partially soluble in the suspending liquid or carrier liquid. In the neighboring position to the suspension 4 is a second electrode 5, L ie hereinafter referred to as "blocking electrode"("blockingelectrode") and has a conductive central core. which is connected to one side of a voltage source 6 through a switch 7. The opposite side of the voltage source 6 is connected to the delivery electrode 1, so that if the switch 7 is closed, an electric field across the liquid suspension 4 between the electrodes

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-ΙΟΙ and · 5 is applied. The roller 5 has an insulating outer surface 12. An insulating material is preferred because it helps to reduce the high fields, which are applied according to the invention to keep, with aussprdem a charge exchange on the surface is prevented, which would have to the rim, that the particles migrate to the surface and exchange a charge and again into the system g-3? ei) .3eii »The suspension 4 is created with the image 10 to be generated irradiated while a voltage is applied across the blocking and delivery electrodes by closing the switch 7 will. The roller Jp is over the surface of the delivery electrode

"left to roll, the switch 7 being closed during the irradiation period. This light irradiation has the consequence dasa particles struck by the radiation that are opposite to the Are sensitive to light, migrate through the liquid and adhere to the surface of the blocking electrode 5, wherein leaving a pigment image on the delivery electrode surface 1 which is a duplicate of the original image is. A negative image is formed on the surface of the blocking electrode 5 in a conventional manner. After the irradiation the relatively volatile carrier liquid evaporates, leaving the pigment image behind. This pigment image can then be fixed in place, for example by heating,

ψ if the particles are thermoplastic. The pigment image formed on the surface of the electrode 1 and / or the electrode 5 is preferably transferred to a recording sheet and fixed thereon, for example by the action of heat or a solvent.

Fig. 2 shows an electrically photosensitive particle 20 made of a resin material 22 to which fine particles are attached made of an electrically photosensitive material. That

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"Resin-like particles 22 may, for example, be colored or be pigmented resin. Preferably, the particle 22 is made of a material that is softened by heat or a solvent can be to facilitate the introduction of the particles 21 and to promote the final fixation. That on Pigment adhering to the surface of the blue-green colored particles 3 should be sensitive to red light, while the pigment attached to a purple particle is mainly if you are sensitive to the green light. The pigment that sits on the surface of a yellow particle should be primarily sensitive to blue light in order to have an overall subtractive color imaging system. For example, exposure to red light causes the blue-green colored particles to migrate, while the purple ones and yellow particles remain which, in combination, give the color red in the final image. Be in the same way produced the blue and green colors by removing yellow and purple, respectively. If white light hits the pictures, the suspension of the product is visible then all the particles migrate, leaving the color white or the transparent substrate behind. He follows no irradiation, then all the particles remain, which in combination result in the color black.

The following examples illustrate the invention. Unless otherwise stated, the parts and percentages relate to on weight. The following examples explain various preferred embodiments of the photoelectrophoretic according to the invention Image generation system as well as the new image generating units.

All examples are carried out in an apparatus which corresponds to the apparatus shown by FIG. The WESA glass surface is in series with a switch, a voltage

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source and a conductive inner part of a roller with a Tedlar film on ilirer surface connected (Tedlar is a polyvinyl fluoride, which is available from JDupont). The roller is approximately 63 mm (2 1/2 inches) in diameter and is driven over the NESA plate surface at a rate of vol. moved about 1.5 cm per second. The plate used is about 19 »3 cm (3 square inches) in size and is irradiated with a light intensity of about 8000 meter candles, measured on the uncoated NESA glass surface. The amount of voltage applied is approximately 3000 volts, unless otherwise stated. The irradiation takes place with a 32OO ° K lamp through a positive slide.

Example 1 •

About 1 part of a carbon black pigmented styrene / n-butyl methacrylate copolymer having an average size of about 15 y. is suspended in approximately 6.5 parts of mineral oil. The pigmented styrene / n-butyl methacrylate material is commercially available as a black xerographic toner. About 0.026 part of Monolite Fast Blue GS, a ball milled metal-free phthalocyanine, which is milled to reduce the particle size to about 0.04 microns, is added to the suspension. Then approximately 0.26 part of methylene chloride is added. The suspension is then stirred vigorously for a period of approximately 5 minutes. A stream of dry air is then bubbled through the suspension until the solvent has essentially been removed. The imaging suspension obtained in this way is applied to the NESA glass surface. A voltage is applied across the suspension between the blocking electrode and applied to the delivery electrode, the blocking electrode being positive with respect to the delivery electrode.

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shine. After the roller has finished its way, one sets found that a positive black image adhered to the surface of the NESA glass.

Example 2 ·.

The experiment of Example 1 is repeated with the exception that there is no addition of methylene chloride as a solvent, itoaoh termination of the rolling in the process described in Example 1 One finds out that there is no image attached to any electrode.

Example 3

The experiment of Example 1 is repeated except that 6.9 ropes of mineral oil and approximately 0.046 part of Monolite Past Blue are used per 1 rope of resin. After finishing the rolling, a positive image of good quality adheres to the surface of the NESA glass. This image is transferred to paper by printing. The paper is then heated until the image is attached to it. This gives a well-fixed, friction-resistant image. \

Example 4

The experiment of Example 1 is repeated with the exception of j .that, based on 1 part of the resin, approximately 3.1 parts of mineral oil, about 0.01 part of Monolite Fast Blue and about 0.22 part of methylene chloride can be used. The applied voltage is approximately 9000 volts. A black image of good quality is obtained on the surface of the NESA glass electrode. The image is transferred to paper and fixed there, namely by exposure to methylene chloride vapors the paper until the image is connected to the paper. The finished picture on the paper is well fixed.

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Example 5

Df ₄ S experiment of Example 4 is repeated, parts Monolite and 0.12 parts Methylenchiorid resin are used per 1 part except DAEs about 1.85 parts mineral oil about 0.005 Fast Blue about. After finishing the rolling, a very good black image is obtained on the surface of the NiüCA-Crlases. The image is transferred to paper in such a way that a paper-covered roller, held at a negative voltage of 300 volts with respect to ground, is brought into contact with the image on the surface of the NESA glass. The image is then fixed to the paper by applying heat, whereby a black image of good quality is obtained.

Example 6

Particles of a yellow-pigmented styrene / n-butyl methacrylate copolymer are used which contain an electrically photosensitive yellow pigment, namely N-2 "-pyridyl-8,13-dioxodinaphtho- (2,1-b; 2 ', 3' -d -) - furan-6-carboxamide having such bonded in example 1. the light-sensitive pigment is prepared according to the method described in U.S. Patent 3,447,922 method hergefc ^m eilchen of a blue-green pigmented styrene / n-butylmethacrylate copolymers have.. Monolite Past Blue particles, while particles of a purple colored styrene / n-butyl methacrylate are bonded to particles of Watchung Red B, an electrically photosensitive purple pigment. Approximately equal parts of these three suspensions are thoroughly mixed together to give a black-looking suspension The suspension is provided with an image in the manner described in Example 1, with the exception that this irradiation is carried out by means of a Kodachrome Parb slide.

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follows. two image formations being performed. Included ] you can see that there is a color image on the NESA glass surface is obtained with a low quality. This picture will electrostatically transferred to paper according to the procedure described in Example 1 and heated. A friction-resistant one is obtained Color picture with a good quality.

lW3n: n also certain components in the preceding examples and ratios have been given, ueijjiouh can also use other materials, such as sjLe] above may be used, with similar results being obtained. Furthermore, other materials of the Imaging aspiration can be added to improve or modify its effect. For example, the Resinous Particles Thermal Solvent To FioVder The! Heat fixation included. Further, the resinous particles can be oleophilic to form a lithographic stencil the transfer to a suitable substrate.

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Claims (1)

- 16 claims My Electrically Photosensitive Particle for Photoelectrophoretic Image generation, characterized in that it consists of exnern. Resin consists, with electrical light on the particles sensitive pigment particles adhere. : ,, 1. Particles according to claim 1, characterized in that the resin is a thermoplastic resin. 3. Particles according to claim 1, 'characterized in that "the resin is a thermosetting resin. 4. Particles according to one of claims 1-3, characterized in that the resin is colored, 5. Particles according to one of claims 1-3, characterized in that the resin is pigmented. 6. Imaging suspension for photoelectrophoretic imaging, characterized in that it comprises electrically photosensitive particles in a liquid carrier, wherein these particles from the particles according to one of claims 1 - | f exist. 7. Suspension according to claim 6, characterized in that the electrically light-sensitive particles of yellow, There are blue-green and purple resin particles on which electrically photosensitive yellow, blue-green and purple ones, respectively Pigment particles sit. ' 8. Method of photoelectrophoretic imaging, thereby 109818/1871 BATH ORIGINAL marked that a) the image generation suspension according to claims 6 or 7 is used, b) the suspension is subjected to the action of an electric field and c) the suspension with an image of an activating electromagnetic Radiation is irradiated until * an image has been formed. 9. The method according to claim 8, characterized in that also d) the image is transferred to a recording sheet and e) the image is heated until it is with the recording sheet connected is. 10. The method according to claim 8, characterized in that also d) the image is transferred to a recording sheet and e) the image has been subjected to the action of a solvent for as long until it is connected to the recording sheet, h * Method of making an imaging suspension for photoelectrophoretic imaging, characterized in that that . a) Particles of a resin and particles of an electrically photosensitive material in an insulating liquid be suspended, b) a solvent to the suspension is eugesetat, the Solvent is a solvent for resin parts and is miscible with the insulating liquid, and e) the solvent is removed from the suspension as long as until the photosensitive particles adhere to the hair particles. ^109818/1871 B _- , one »» »- ι * ■ Blank page