JPS6255669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to imaging methods, and more particularly to electrophoretic imaging methods.

Special Publication No. 21781 in 1968, Special Publication No. 9708 in 1968
According to Xerox Corporation's electrophoretic imaging method described in this publication and elsewhere, an electrophotosensitive powder dispersed in an insulating liquid is brought into contact with an injection electrode, and in the exposed area, another charge is injected from the injection electrode. As a result, the photosensitive powder undergoes a net change in charge polarity, becoming a photosensitive powder of opposite polarity and moving toward the opposite blocking electrode. On the other hand, the unexposed photosensitive powder, which is charged with the opposite polarity, remains on the injection electrode in the unexposed or dark areas and forms a positive or negative image on the respective electrode. In such conventional methods, it is the exposed photosensitive powder that undergoes a net change in charge polarity, while the unexposed powder maintains its original charge polarity.

However, in the conventional method, the exposed photosensitive powder adheres to the blocking layer of the roller electrode, and the unexposed photosensitive powder remains on the transparent injection electrode, resulting in a positive image on the transparent injection electrode and the roller electrode. A negative image is formed on the blocking layer. Therefore, in order to obtain a positive image, it is necessary to transfer the powder remaining on the transparent injection electrode again by some method. If plain paper is used for the blocking electrode layer, an image can be obtained directly on the plain paper, but unfortunately this method produces a negative image, making it unsuitable for general copying purposes.

The present invention has been made to overcome the above-mentioned drawbacks of conventional electrophoretic imaging methods.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for directly forming a positive image on plain paper, film, etc. by electrophoretic imaging.

Although the principle of the present invention has not yet been fully clarified, it can be explained as follows. FIG. 1 is a schematic diagram for explaining the principle. In the same figure, 1
is an electrode, 2 is an insulating (blocking) layer, 3 is a suspension of photosensitive powder in an electron donating substance (ED),
4 is a transparent injection electrode, 5 is a switch, and 6 is a power source. In the state shown in Figure A, negatively charged photosensitive powder is suspended in an insulating liquid in coexistence (or contact) with an electron donating substance (ED). In Figure B, the switch 5 is closed and an electric field is applied such that the transparent electrode 4 side has positive polarity. There, the negatively charged photosensitive powder is attracted to the transparent electrode 4 side. In Figure C, when light irradiation begins in the direction of the arrow at the same time as or immediately after the application of the electric field (preferably at the moment the photosensitive powder reaches the transparent electrode), the unexposed photosensitive powder X is interposed between the particles and the electrode. With the help of an electron-donating substance (it is thought that the electron-donating substance extracts positive charges and injects them into the powder), the positive charges from the electrode side are injected into the unexposed photosensitive powder and the polarity is reversed. It becomes a positively charged powder. On the other hand, the exposed photosensitive powder Y is also injected with positive charges in the same way as the unexposed photosensitive powder X, but unlike the case of the unexposed photosensitive powder The positive charges in the pores tend to flow into the liquid through the surrounding electron-donating substances that are in contact with them, but the electrons remain inside because the electron-donating substances act as an obstacle to the flow, and the negative charges, that is, electrons, remain inside the pores. is considered to be retained as is. C' and C'' are partially enlarged views of C to help understand the above explanation. Therefore, as seen in D of the same figure, the exposed photosensitive powder Y has almost no negative charge at the beginning. On the other hand, the unexposed photosensitive powder X is converted to a positive charge and moves toward the upper electrode with negative polarity. If plain paper or the like is used as the insulating layer, a positive image can be easily and quickly obtained directly thereon.

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 Xerox Corporation patent specifications, so they will not be described in detail here.

A feature of the invention is a suspension in which an electrophotosensitive powder is contacted with or attached to an electron-donating substance.
Methods for bringing the electron donating substance into contact with or adhering to the electrophotosensitive powder include: dissolving or mixing the electron donating substance in an insulating liquid and thoroughly dispersing it together with the electrophotosensitive powder; There are two methods: attaching the electron-donating substance to the surface of an electrophotosensitive powder and then dispersing it in an insulating liquid that does not dissolve the electron-donating substance; and coating the transparent electrode with the electron-donating substance in advance. Both methods are somewhat inferior to methods.

The method of the present invention is used.

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, diyulene , 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 electrophotosensitive powder may be any suitable electrophotosensitive powder known in conventional photoelectrophoretic imaging technology. A typical example is U.S. Patent No.
Although it is described in the specification of No. 3384488, it goes without saying that photoconductive polymers can also be used if they are mechanically or chemically pulverized into fine particles. Typical powders include organic pigments such as quinacridone, carboxamide, carboxyanalide, triazine, benzopyrocholine, anthraquinone, azos, pyrene, phthalocyanine, cadmium sulfide, cadmium, sulfoselenide, zinc oxide, zinc sulfide, etc. , sulfur, selenium, mercury sulfide, lead oxide, lead sulfide, cadmium selenide, titanium dioxide, indium trioxide or mixtures thereof. The powder can also be composed of multiple components and sensitized with dyes to alter its spectral response. A preferred material from the viewpoint of spectral response is the X-type metal-free phthalocyanine described in US Pat. No. 3,357,989.

Next, the blending ratio of the electrophotosensitive powder and the electron donating substance cannot be generalized as it varies depending on the respective compounding conditions, etc., but based on past experiments, (electrophotosensitive powder): (electron donating substance) )=1:
A ratio of 0.001 (weight ratio) to 1:1 (weight ratio) is possible, and a ratio of 1:0.005 to 1:0.5 is preferable.

The mixing ratio of the suspension is as follows. That is, electrophotosensitive powder (pigment) 1 (parts by weight) Electron-donating substance 0.001-1 (〃) Binder 2-1000 (〃) Insulating liquid 10-1000 (〃) Approximately 10 ⁹ as an insulating liquid Materials having a resistance greater than Ω-cm, preferably greater than about 10 ¹² Ω-cm can be used. Various useful materials include, for example, alkyl-aryl materials such as alkylated benzenes, such as xylenes, and U.S. Pat.
There are other alkylated aromatic hydrocarbons as described in US Pat. No. 2,899,335. Other useful materials include cyclohexane, cyclopentane, alpha-pentane, n-hexane, carbon tetrachloride,
Examples include trichloromonofluoromethane and chromium trifluoroethane.

As a binder, it also acts as a polar stabilizer, so typical polymeric materials are the same as those used in general electrophotographic toner dispersions and are completely or partially incorporated into the suspension liquid medium. It is a natural or synthetic polymer substance, wax, etc. that has electric insulating properties (approximately 10 ⁹ Ω-cm or more) and dissolves in water. For example, Pickkotex 5 and 100 (vinyl-toluene copolymers) are commercially available from Pennsylvania Industrial Chemical Co., Ltd.; Stabelite Ester 5 and 10 are commercially available from Hercules Powder Company; Materials such as Amberol ST-137-X, eicosane, ceresin or similar organic waxes are good.

The selection of a specific charge control agent is generally determined by using a polymeric substance such as an amino group-containing acrylic ester for negative charge, or by modifying it with a surface coating such as a metal-containing dye, sulfonate, or vinyl chloride, or using a phenolic hydroxyl group. and acrylic resins having sulfon groups are often used, but it is difficult to generalize because a considerable part depends on the specific electrophotosensitive powder and liquid medium used. However, economically, Plexigum N80 in combination with toluene
It has been found that the use of acrylate and methacrylate resins, such as those manufactured by Ro¨HM, helps maintain a negative charge polarity in the suspended powder.

Example 1 To prepare a suspension, a liquid having the following formulation is sufficiently dispersed using an ultrasonic disperser.

ε-type copper phthalocyanine pigment (manufactured by BASF) 1g N,N,N',N'-tetramethyl-p-phenylenediamine 0.1g Plexigum N80 (manufactured by Ro¨hm) 2g Toluene 20ml This suspension is shown in Figure 2. Viewed device 8cm x 16
The experiment was carried out by coating it on a commercially available Nesa glass plate 4 of cm. In the figure, 1 is a steel roller electrode whose surface is covered with plain paper 2, 3 is a suspension, 4 is a transparent injection electrode, 5 is a switch, 6 is a high-voltage power source, and 7 is an original. After closing the switch 5 and applying a voltage of 2000V so that the Nesa glass plate side has positive polarity, a light beam is irradiated from below the document 7 in the direction of the arrow 8, and then the steel roller electrode 1 is moved at a speed of about 1 cm/sec. When the paper was rolled in the direction 9, a clear positive image similar to that of the original 7 was formed on the plain paper 2 on the steel roller electrode 1. Of course, a negative image was also formed on the NESA electrode at the same time.

At this time, as a comparative example, after closing the switch 5 and applying a voltage of 2000V so that the negative polarity is on the Nesa glass plate side, a light beam is irradiated from below the document 7 in the direction of the arrow 8, and then the steel roller electrode 1 is
When the paper was rolled in the direction of the arrow 9 at a speed of cm/sec, a negative image opposite to the original 7 was formed on the plain paper 2 on the steel roller electrode 1 with no clarity.

Also, make a suspension by ultrasonically dispersing the liquid with the following formulation excluding N,N,N',N'-tetramethyl-p-phenylenediamine, and add ε-type copper phthalocyanine pigment (manufactured by BASF) 1g Plexigum N80 (manufactured by Ro¨hm) 2g Toluene 20ml When an image was formed as described above, a negative image opposite to the original 7 was formed on the plain paper 2 on the steel roller electrode 1, regardless of the polarity on the Nesa glass plate side. A positive image was formed on the Nesa glass plate side.

Example 2 A suspension was prepared by sufficiently ultrasonically dispersing a liquid having the following formulation.

ε type copper phthalocyanine pigment 1g Phenothiazine 0.1g Plexigum N80 2g Toluene 20ml Image formation was performed in the same manner as in Example 1 using this suspension and the apparatus shown in Figure 2, and a positive 2000V was applied to the Nesa glass plate side. At this time, a positive image similar to that of the original 7 was formed on the plain paper 2 on the steel roller electrode 1, and a negative image was formed when a negative 2000 V was applied to the Nesa glass plate side.

Example 3 The following formulation was thoroughly dispersed in a ball mill for about 1 day, and 40 ml of tetrahydrofuran was added to prepare A.
I made a liquid.

β-type copper phthalocyanine pigment 1g 1,6-diaminopyrene 0.1g Polyvinylcarbazole 2g Tetrahydrofuran 20ml This A solution is stirred with a magnetic stirrer, and a few drops are added to approximately 200ml of Isopar G liquid which is dispersed by ultrasonic waves. I tried to make it finer by dropping it little by little. The liquid containing the copper phthalocyanine fine powder is further filtered and the fine powder adhering to the filter paper is removed at approximately 50°C.
The powder was dried for about 10 hours to produce a photoconductive powder (toner) coated with an electron-donating substance. Next, the dried toner was heated using ultrasonic waves with the following formulation for about 50 minutes.
Dispersion for 1 minute produced a suspension that can be used in the present invention.

The above dry toner: 1 g Toluene: 20 ml Plexigum N80: 2 g When an image was formed using this suspension in the same manner as in Example 1, a clear blue positive image was formed on the plain paper 2 on the steel roller electrode 1. It was done.

[Brief explanation of the drawing]

Figures 1A, B, C, and D are schematic diagrams for explaining the principle of the present invention, C' and C'' are partially enlarged views thereof, and Figure 2 is a schematic diagram of an apparatus for carrying out the present invention. In the figure, 1...electrode, 2...blocking layer, 3...
Suspension, 4... Transparent electrode, 5... Switch, 6...
...High voltage power supply, 7...Manuscript, 8...Light beam.

Claims (1)

[Claims] 1 Applying an electric field to a suspension layer containing an electrophotosensitive powder between a pair of electrodes, at least one of which is at least partially transparent, and imaging said suspension with active electromagnetic radiation through said transparent electrode. In an electrophoretic imaging method in which the suspension is at least partially charged with a negative electrostatic charge and the surface thereof is Electrophoresis characterized in that the suspension layer contains an electrophotosensitive powder attached to or in contact with an electron-donating substance, and an electric field is applied to the suspension layer to make the transparent electrode side positive. Imaging method.