JPS6255670B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to imaging methods, and more particularly to electrophoretic imaging methods. An imaging method that combines an electrode with a photoconductive layer and an inert powder is disclosed in, for example, Japanese Patent Publication No. 40580 published in 1972.
No., 1975, Special Publication No. 89043, etc., and is publicly known. The key to this imaging method is that the carrier generated in the photoconductive layer irradiated through the transparent electrode transfers to the inert powder that is in contact with or adheres to the photoconductive layer, reversing the charge polarity of the powder. It is in. The inert powder whose charge polarity has been reversed in this way moves onto another electrode and forms an image on it, but with current technology, the carrier generated by light irradiation is There is a drawback that a satisfactory image cannot be obtained because it is not sufficiently injected into the powder and the charge polarity is not sufficiently reversed. The present invention has been made to overcome the above-mentioned drawbacks of conventional imaging methods. It is an object of the present invention to provide an electrophoretic imaging method that can produce high quality images using a wide variety of photoconductive layers and powders. Although the principle of the present invention has not yet been fully clarified, it can be tentatively explained as follows. FIG. 1 is a schematic diagram for explaining the principle. In the figure, 1 is an electrode, 2 is an insulating (blocking) layer, 3 is a suspension of fine powder 4 coated with an electron-donating substance (ED) suspended in an insulating liquid, and 6 is a light source. conductive layer,
7 is a transparent electrode, 9 is a switch, and 10 is a power source. In the state shown in Figure A, fine powder 4 coated with electron-donating substance 5 is suspended in an insulating liquid. Next, as shown in Figure B, switch 9
When the transparent electrode 7 is closed and a high voltage is applied so that the transparent electrode 7 side has positive polarity, the negatively charged fine powder is attracted onto the photoconductive layer 6. Then, as shown in Figure C, the voltage is applied simultaneously or immediately after (preferably at the moment when the fine powder reaches the photoconductive layer).
When a light beam is irradiated in the direction of the arrow through the transparent electrode 7, hole-electron pairs are generated in the exposed portion of the photoconductive layer, and the holes are injected into the powder.
Powders coated with electron-donating substances are injected more than uncoated powders. Therefore, as shown in Figure D, the powder into which holes are injected has its charge polarity reversed and moves toward the upper electrode, while the powder whose polarity is not reversed remains on the photoconductive layer. As mentioned above, the electron-donating substance, which has not been a problem with conventional technology, is coated with a fine powder that can be suspended in a suspension, and a high voltage is applied so that the transparent electrode side has positive polarity. Therefore, the hole injection effect is significantly increased compared to the conventional technique, and the images produced are naturally of better quality. Next, each component of the present invention will be explained. The upper electrode 1, the insulating (blocking) layer 2, the transparent electrode 4, etc. may be any of the known ones described in the above-mentioned patent specifications, and will not be described in detail here. The feature of the present invention is the suspension, and it is important that the surface of the fine powder suspended therein is coated with an electron-donating substance. The following two methods can be used to coat the surface of fine powder with an electron donating substance. The electron donating substance is dissolved in advance, the fine powder is sufficiently dispersed therein, and the surface of the fine powder is coated with the electron donating substance and then dried. Next, the dried fine powder is sufficiently dispersed in an electron-donating substance and an insulating liquid that does not dissolve the fine powder to form a suspension. Dissolve the electron donating substance and binder in advance,
A fine powder is added thereto, sufficiently dispersed, and dried using a spray dryer or the like to obtain a fine powder coated with an electron-donating substance and a binder. The fine powder is further sufficiently dispersed in an insulating liquid that does not dissolve the electron donating substance and the binder to form a suspension. Examples of electron-donating substances include polycyclic aromatic compounds such as anthracene, pyrene, phenanthrene, and coronene in the main chain or side chain, or indole, carbazole, oxazole, isoxazole, thiazole, imidazole, pyrazole, oxadiazole, thiadiazole, triazole, etc. Examples include high-molecular compounds or low-molecular compounds having a nitrogen-containing cyclic compound as a skeleton. Examples of polymers include poly N-vinylcarbazole and its derivatives (for example, those having a halogen such as chlorine or bromine, or a substituent such as a methyl group or an amino group in the carbazole skeleton), polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde condensed Polymers and their derivatives (for example, those having a pyrene skeleton with a halogen such as bromine or a substituent such as a nitro group), and low molecular weight ones such as hexamethylene diamine, phenylene diamine, N-(4-aminobutyl ) Cadaverine, As-didodecylhydrazine, p-toluidine, 4-amino-o-xylene, N,N'-diphenyl-1,2-diaminoethane, o-, m- or p-ditolylamine, triphenylamine, diylene , 2-bromo-3,7
-dimethylnaphthalene, 2,3,5-trimethylnaphthalene, N'-(3-bromphenyl)-N-
(β-naphthyl)urea, N'-methyl-N-(α-
naphthyl) urea, N,N'-diethyl-N-(α-
naphthyl) urea, 2,6-dimethylanthracene, anthracene, 2-phenylanthracene,
9,10-diphenylanthracene, 9,9'-bianthranil, 2-dimethylaminoanthracene,
phenanthrene, 9-aminophenanthrene,
3,6-dimethylphenanthrene, 5,7-dibromo-2-phenylindole, 2,3-dimethylindoline, 3-indolylmethylamine, carbazole, 2-methylcarbazole, N-ethylcarbazole, 9-phenyl enylcarbazole,
1,1'-dicarbazole, 3-(p-methoxyphenyl)oxazolidine, 3,4,5-trimethylisoxazole, 2-anilino-4,5-diphenylthiazole, 2,4,5-trinitrophenyl imidazole , 4-amino-3,5-dimethyl-1-phenylvirazole, 2,5-diphenyl-1,3,4-oxadiazole, 1,3,
5-triphenyl-1,2,4-triazole,
1-Amino-5-phenyltetrazole, bis-
Examples include diethylaminophenyl-1,3,6-oxadiazole and phenothiazine. Examples of inorganic substances include iodine and bromine. The fine powder may be any suitable powder known in conventional photoelectrophoretic imaging technology. Moreover, it may be insulating, semiconductive, or conductive, and may be a combination thereof. Typical powders include quinacridone, carboxamide, carboxyanalide, triazine, benzopyrrocholine, anthraquinone,
Organic pigments such as azos, pyrene, phthalocyanine, etc.
Metal-containing or non-metallic materials consisting of cadmium sulfide, cadmium, sulfoselenide, zinc oxide, zinc sulfide, sulfur, selenium, mercury sulfide, lead oxide, lead sulfide, cadmium selenide, titanium dioxide, indium trioxide, or mixtures thereof. Contains inorganic substances. Furthermore, it is important that this powder has the property of receiving and retaining the charge emitted from the photoconductive electrode, so the surface of the powder should have a volume resistivity of at least about 10 ⁵ Ω-cm. It must be made of material. The powder for forming colored images is preferably a dyed thermoplastic material which is particularly suitable for producing colored transparent or opaque images. An advantage of using dyed thermoplastics in place of opaque color pigments is that a brightly colored material can be obtained that can be easily melted to create a fixed final image. In order to create a multicolor image, at least two types of monochrome images are formed, which are transferred in registration onto a single substrate and then fused thereon. Further, as another application example, the powder can be used as reflective glass beads, luminescent pigments, fluorescent pigments, ferromagnetic pigments or reflective resin-coated metal powders, capsule bodies containing liquids, catalytic powders, or specific The powder may be selected depending on the shape of the image pattern to be obtained from other powders processed according to the final use of the powder. For example, the image can be used as a mask for graphic art or as a resist for etching. The liquid carrier may be any suitable insulating material. Typical examples of this insulating liquid carrier include Decane,
These include dodecane, tetradecane, kerosene, molten paraffin, molten wax or other molten thermoplastic, mineral oil or silicone oil such as dimethylporosiloxane, chlorinated hydrocarbons, or mixtures thereof. However, among these, mineral oil and kerosene are particularly good. The reason for this is that it is inexpensive and has excellent insulation properties. Alternatively, for convenience in handling and storage, a colored powder is mixed into a solid binder such as polystyrene resin, eicosane, or wax, which is commercially available from Pencil Vanier Industrial Chemical Co., Ltd. under the trade name Pickkotex, and then applied onto the photoconductive electrode. It may be coated in advance. This binder is melted or dissolved by a dielectric solvent as described above before image formation, and
After this binder melts, the powder can freely move from one electrode to the other. Other representative examples of solvent-soluble dielectric binder materials include hydrogenated rosin esters, loams, commercially available from Hercules Powder Company under the tradenames Stabelite Ester 5 or 10.
Amberol ST-137-X from & Haas
Phenolaldehyde resins are commercially available under the trade names ``Piccotex 75 or 100'' and ``Piccopeil 70'' from Pencil Vanier Industrial Chemical Company. Furthermore, the smaller the particle size of the powder, the more stable the resulting suspension will be, and the higher the resolution of the image, so it is desirable that the powder used be as small as possible. Therefore, although particles up to about 5 microns are readily available and available, it is desirable to use powders with an average particle size of 2 microns or less. The concentration of powder dispersed in the liquid carrier is determined by the desired final image density, the intended use of the image, the particle size, the solubility of the added dispersant, and a variety of other well-known factors. Next, the blending ratio of the fine powder and the electron-donating substance cannot be generalized as it varies depending on the respective compounding conditions, etc., but based on past experiments, (fine powder): (electron-donating substance) = 1 :0.001~
A ratio of 1:1 (weight ratio) is considered, and a ratio of 1:0.005 to 1:0.5 is desirable. Considering the binder for coating, the following mixing ratio is appropriate. Fine powder 1 (parts by weight) Electron-donating substance 0.001-0.1 (〃) Binder 0.1-10 (〃) This binder is different from the above-mentioned binders and is insoluble in the insulating liquid carrier. Examples of such resins include polystyrene, acrylic, silicone, and polyester resins. Also, when adding a specific charge control agent to the suspension and applying a high voltage so that the transparent electrode side has positive polarity, it is better to make the powder negatively charged to obtain more efficient images. It will be done. Generally, for negative charges, polymer substances such as amino group-containing acrylic esters are used, and furthermore, they are modified with surface coatings such as metal-containing dyes, sulfonates, vinyl chloride, etc., or acrylics with phenolic hydroxyl groups or sulfonate groups are used. Resins and the like are often used, but it cannot be generalized because a considerable part is determined by the fine powder and liquid medium specifically used. As a method for charging the powder, there is also a method in which the powder is charged in advance by corona discharge or the like. FIG. 2 is a schematic diagram showing the device. In the figure, a suspension layer 3 placed on a photoconductive layer 6 on a transparent electrode 7 made of Nesa glass is uniformly negatively charged by the discharge of a corona electrode 11. The transparent conductive substrate for the photoconductive layer may be any suitable material, typically glass coated with a conductive material such as aluminum or tin oxide coated glass or similar materials. Alternatively, there are transparent plastic materials such as polyester film coated with cellophane. Alternatively, a layer such as a resin film or sheet may be interposed between the photoconductive layer and its backing electrode. This method is particularly effective when the photoconductive layer is exposed only once. The photoconductive layer can also be self-supporting. The photoconductive layer may be made of any suitable photoconductive layer material, but typical examples include cadmium sulfide, cadmium, sulfoselenide, selenium,
There are inorganic substances such as mercury sulfide, lead oxide, lead sulfide, cadmium selenide, and mixtures thereof, which are dispersed in the binder to form a homogeneous layer. Examples of photoconductive organic substances include pigments such as quinacridone, 8,13-dioxydinaphtho-(2,1-b:
2',3'-d)-Furan-6-carboxy-p-methoxyanilide, 8,13-dioxydinaphtho-
Carboxanilides such as (2,1-b:2',3'-d)-furan-6-carboxy-m-chloroanilide or n-2'-pyridyl-8,13-dioxydinaphtho-(2,1-b :2′,3′-d)-Furan-6-carboxyamide, α-2″-(1″-3″-diazyl)-8,13-dioxydinaphtho-(2,1-b:
Carboxamides such as 2',3'-d)-furan-6-carboxamide, triazinone, benzopyrocholine, anthraquinone, azo compounds having an aromatic substituent containing a hydroxyl group at the ortho position to the azo bond, dioxazine, There are substituted pyrenes, phthalocyanines, etc., and these organic photoconductive materials are used by being dispersed in a binder. Still other organic photoconductive materials include homogeneous photoconductive layers whose photosensitivity can be increased by combining with appropriate Lewis acids, as described by H. Hegel in Journal of Physical Chemistry 69755 (1965). Poly(N-vinyl carbazole), poly(9-vinyl anthracene), poly(3-vinyl pyrene) or poly(triphenylamine) as described in U.S. Pat. No. 3,265,496, U.S. Pat. 3341472, as well as mixtures thereof. The photoconductor can be made from several components, or it can be made from a photoconductive pigment dispersed in a photoconductive or inert binder. Alternatively, the photoconductor may be coated, for example, with a protective layer comprising an active transport layer capable of transporting the type of charge carrier desired to be imparted to the particles. An active transport layer for holes, such as polyvinyl carbazole, may be deposited on a vapor deposited amorphous selenium layer or on a binder consisting of X-type phthalocyanine or trigonal selenium or mixtures thereof in an inert dielectric binder. May be coated. It may also be incorporated into a binder made of polyvinyl carbazole, as long as the backing electrode is kept positive with respect to the opposite electrode. Imaging speed is determined by the speed of the carrier transport through the substrate. Therefore, it is desirable to use a material that can provide a high velocity carrier vehicle. A preferred photoconductive layer may be one in which selenium is coated with a layer of poly(N-vinyl carbazole). This poly(N-vinyl carbazole) can provide a path for the holes generated and released upon photoirradiation, and protects the selenium from wear and corrosion by solvents. In addition to the above-mentioned materials, poly(methylene pyrene), poly-1-vinyl pyrene, and compounds thereof can be used as coating materials that protect the photoconductor while allowing holes, electrons, and both to pass through.
triphenylamine or 2, containing at least % by weight
There is a dispersion binder of 4,7-trinitro-9-fluorenone. Example 1 First, a liquid with the following formulation was dispersed for 5 minutes using an ultrasonic disperser to prepare liquid A.

[Table] 200ml of Isopar G in a separate 300ml beaker
was thoroughly stirred using a magnetic stirrer, and while the mixture was being dispersed using ultrasonic waves, the above-mentioned liquid A was added little by little to make the liquid A fine.
This mixed solution was filtered, and the powder attached to the filter paper was placed in a constant temperature bath at about 50° C. and dried for about 10 hours to obtain carbon powder coated with an electron-donating substance. Further, this carbon powder was sufficiently dispersed in liquid B having the following formulation to prepare a suspension.

[Table] On the other hand, in order to prepare an electrode having a photoconductive layer, a photosensitive liquid having the following formulation was dispersed for 5 minutes using an ultrasonic disperser. ε-type copper phthalocyanine pigment (manufactured by BASF) 1g Plexigum N-80 2g Toluene 20ml After further diluting with toluene, apply the above liquid to a thickness of about 10μ on the conductive surface of a commercially available Nesa glass plate measuring 8cm x 16cm. A photoconductive electrode was obtained. A suspension was applied on this electrode as shown in Figure 3, and the voltage was set at 200V so that a positive voltage was applied to the transparent electrode 7 side.
Immediately after connecting the power source 10, light is irradiated onto the document 8 placed on the Nesa glass plate from the direction of the arrow, and then the steel roller 1 is rolled in the direction of the arrow at a speed of approximately 2 cm/sec. A clear negative image was formed on the plain paper 2 on the steel roller 1. Furthermore, using new plain paper on another steel roller, a negative voltage was applied to the transparent electrode side.
When a 2000 V power source 10 was connected and the roller was rolled over the photoconductive electrode in the direction of the arrow at a speed of about 2 cm/sec, a clear positive image identical to the original was formed on the plain paper on the steel roller. At this time, as a comparative example, when a 2000V power supply was connected so that the applied voltage was negative on the Nesa glass side, an unclear negative image was formed on the plain paper on the steel roller. Second, PDA in suspension (N, N,
(N',N'-Tetramethyl-p-phenylenediamine) coating was omitted, and the solution with the following formulation was thoroughly dispersed by ultrasonic waves, and an image was formed in the same manner as in However, regardless of the polarity of the voltage applied to the Nesa glass side, a blurred negative image opposite to the original was formed on the plain paper on the steel roller. Similarly, when a positive image on the photoconductive layer was transferred, an unclear positive image was formed. Example 2 A photoconductive transparent electrode was fabricated by vacuum depositing selenium as a photoconductive layer onto the conductive surface of a Nesa glass plate to a thickness of about 1.5 μm. Immediately after applying the suspension prepared in Example 1 onto this electrode and connecting a 2000V power source so that the transparent electrode side has positive polarity, exposure was started. When rolled in the same direction, a clear negative image opposite the original was formed on the plain paper on the steel roller. When the image on the photoconductive layer was transferred in the same manner as in Example 1 using fresh plain paper on another steel roller, a clear positive image identical to the original was formed on the plain paper on the steel roller. At this time, as a comparative example, when a 2000V power supply was connected so that the Nesa glass side had negative polarity, an unclear negative image was formed on plain paper on a steel roller. In addition, when using a liquid that omitted the PDA coating in the suspension from the previous example, an unclear negative image opposite to the original was formed on the plain paper on the steel roller, regardless of the polarity of the voltage applied to the Nesa glass plate side. When the positive image on the photoconductive layer was transferred, an unclear positive image was formed.

[Brief explanation of the drawing]

FIGS. 1A, B, C, and D are schematic diagrams for explaining the principle of the present invention, and FIGS. 2 and 3 are schematic diagrams showing an apparatus for carrying out the present invention, respectively. In the figure, 1... electrode, 2... blocking layer (plain paper), 3... suspension, 4... powder, 5... electron donating substance, 6... photoconductive layer, 7... transparent electrode, 8
...Manuscript, 9...Switch, 10...Power supply.

Claims (1)

[Claims] 1. Applying an electric field to a suspension containing a fine powder, which is present between an at least partially transparent electrode provided with a photoconductive layer and another electrode, and imagewise exposing it to active electromagnetic radiation through said transparent electrode. In an electrophoretic imaging method in which a powder image is formed on at least one of the electrodes, the powder is formed from a fine powder whose surface is coated with an electron-donating substance and which is negatively charged. . An electrophoretic imaging method, characterized in that a high voltage is applied to the suspension so that the transparent electrode side has positive polarity.