JPH0990722A - Image forming device and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device and a method by which a high definition image can be obtained at high speed. SOLUTION: An image forming device and a method are provided with an image carrier belt 1 composed of a semiconductive substance whose volume resistivity changes by depending on an electric field, an electric charge injecting means 9 to inject electric charge into the image carrier belt 1 in a pattern according to an image and a developing electrode roller 4 which is arranged between it and the image carrier belt 1 by interposing a prescribed clearance G and forms an electric field between it and the image carrier belt 1, and are provided with a developing means 40 to form an image by coloring particles on a surface of the image carrier belt 1 by depositing the cloring particles in liquid ink 15 on A pattern according to an electric charge injecting pattern formed on a surface of the image carrier belt 1 by the electric charge injecting means 9 by filling the clearance G with the liquid ink 15 by dispersing the coloring particles in a conductive solvent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and method used in printers, copiers, facsimiles, etc., and more particularly to an image forming apparatus and method for developing using a liquid developer.

[0002]

2. Description of the Related Art Conventionally, many proposals have been made regarding a developing method using a liquid developer. One of them is a developing method of electrically depositing a pigment using a conductive liquid ink. Typical developing methods include a developing method utilizing an electrodeposition method and an electrolytic developing method. (1) Development Method Utilizing Electrodeposition Method Electrodeposition method is a kind of resin coating method, in which a paint resin containing pigment, or colored particles and water-soluble resin are dispersed in a water-soluble solvent. A conductive liquid is used, and a voltage is applied between two electrodes immersed in the conductive liquid, and the resin is deposited by exchanging charge of the ionized resin on the surface of one electrode, and a resin layer is formed on the electrode. Is a method of forming.

The developing method utilizing this electrodeposition method is, in principle, a method in which a water-soluble resin in the form of polar molecules, emulsions, colloids or the like is deposited on the electrode surface by the action of electrophoresis, electrolysis, electroosmosis or the like. The characteristic is that development can be performed at a relatively high speed, and the thickness of the obtained resin film is uniform. There is also an advantage that the film thickness can be easily controlled by the amount of current.

As an example of the developing method utilizing the electrodeposition method,
Japanese Patent Laid-Open No. 50-55335 discloses that a developing solution containing water, an electrolyte and a colloid as a main component is filled between a matrix electrode composed of a plurality of electrodes and a developing roll, and the space between the matrix electrode and the developing roll is filled. A method is disclosed in which a colloid is solidified on a developing roll by applying a voltage.

FIG. 13 is a schematic view of a conventional example of a developing method utilizing the above electrodeposition method. In FIG. 13, a plurality of electrodes 102a, 102b, 10 embedded in a resin electrode substrate 101 and arranged in a matrix at a pitch of 75 μm.
2c, the developing roll 103, and a developer 10 that fills a gap G of about 50 μm between the electrode substrate 101 and the developing roll 103.
4 is shown.

The plurality of electrodes 102a, 102b, 1
02c, when a voltage is applied to the electrodes 102b and 102c, the colloid in the developer 103 coagulates in the regions 103b and 103c on the developing roll 103 facing the electrodes 102b and 102c to which the voltage is applied, and the colloid layer is formed. 104
b, 104c are formed. On the other hand, the area 10 on the developing roll 103 facing the electrode 102a to which no voltage is applied.
No colloid layer is formed on 3a.

Therefore, a desired image can be formed by controlling the voltages applied to the plurality of electrodes according to the image pattern. It is also possible to obtain a color image by repeating such a developing process with a developing solution for a plurality of colors. It is reported that a high solidification rate of up to 10 μsec was obtained by this method. As another conventional example of the developing method utilizing the electrodeposition method, JP-A-63-2370 is disclosed.
In Japanese Patent Publication No. 85, an electric charge is supplied to the conductive film by means of an electrode needle that slides on the conductive film, and the paint in the developer contacting the surface on the opposite side of the conductive film is applied to the conductive film. A method of precipitating is disclosed.

FIG. 14 is a schematic view of another conventional example of the developing method utilizing the above electrodeposition method. In FIG. 14, an anisotropic conductive film, that is, a conductive film 105 whose conductivity in the thickness direction is higher than that in the other direction, and an electrode needle head 106 in contact with one surface 105 a of the conductive film 105.
And the other surface 105b of the conductive film 105, the developer 104 containing a paint, and the counter electrode 10 provided on the inner wall (not shown) of the container containing the developer 104.
2 is shown. 6 dot for the electrode needle head 106
When thin electrode needles with a density of / mm are provided and a current synchronized with the image is applied to each of these electrode needles,
An energization phenomenon occurs between the applied electrode needle and the counter electrode 102, and the developer 1 is formed on the surface 105b of the conductive film 105 in contact with the developer 104 in a region 105c corresponding to the electrode needle.
The paint in 04 is deposited to form a paint layer 107. Since this paint layer 107 is formed to have a thickness according to the amount of electricity, it is possible to express an intermediate gradation. By this electrodeposition method, the same conductive film is sequentially developed with each developer of cyan, magenta, and yellow to form a developed image of each color on the conductive film. .
Then, the developed image is transferred to a recording medium and fixed, whereby a color image is obtained. (2) Electrolytic Development Method As one of the electrolytic development methods, for example, Japanese Patent Publication No. 45-959.
In JP-A-2, a photosensitive sheet coated with a photosensitive material such as zinc oxide is exposed in advance according to an image, and this is immersed in an electrolytic solution containing an acid such as hydrochloric acid to electrolyze,
A developing method is disclosed in which zinc oxide in the exposed portion of the photosensitive sheet is reduced and a metallic image of zinc is obtained on the photosensitive sheet.

In a method similar to this developing method, a photosensitive sheet similar to that described above is used. After exposure, the photosensitive sheet is immersed in an aqueous solution, and a voltage is applied between the photosensitive sheet and an aluminum electrode facing the zinc oxide. A developing method has also been proposed in which zinc ions are eluted from the layer and the eluted zinc ions are deposited again on the photosensitive sheet.

[0010]

However, the above-mentioned conventional method has a problem that it is difficult to obtain a high-definition image at a high speed. That is, the method disclosed in Japanese Patent Application Laid-Open No. 50-55335 uses a matrix electrode for writing an image, and therefore, the 1200 dpi as in normal printing is used.
It is difficult to obtain an image with high definition of about (dot / inch) or more.

With respect to the developing speed, since the deposition speed for each pixel is high, there is no problem in the case of monochromatic image formation. The color is not disclosed in the above publication. Further, in the method disclosed in Japanese Patent Laid-Open No. 63-237085, an electrode needle head having an electrode needle density of 6 dot / mm is used, and with such an electrode needle density, a high definition image cannot be obtained. difficult. It is practically difficult to further refine the electrode needles and increase the density of the electrode needles in terms of the accuracy of machining. Further, in the above method, an anisotropic conductive film whose conductivity in the thickness direction is higher than that in the other direction is used, but it also has some conductivity in the width direction. Therefore, the current spreads in the width direction and the diameter of the deposited paint becomes larger than the diameter of the electrode needle, making it difficult to obtain a high-definition image.

The method disclosed in Japanese Examined Patent Publication No. 45-9592 uses an electrolytic solution containing an acid such as hydrochloric acid.
Although it is necessary to increase the amount of acid added to the electrolytic solution in order to accelerate the development time, increasing the amount of acid addition accelerates corrosion of the photosensitive sheet, and therefore there is a limit to the reduction in development time. Further, it is difficult to speed up the process because it takes time to remove the electrolytic solution adhering to the photosensitive sheet after electrolysis.

In view of the above circumstances, it is an object of the present invention to provide an image forming apparatus and method capable of obtaining a high definition image at high speed.

[0014]

An image forming apparatus of the present invention which achieves the above object comprises an image carrier made of a semi-conductive material whose volume resistivity changes depending on an electric field and an image carrier.
A charge injection unit that injects charges into a pattern according to an image and a predetermined gap are provided between the image carrier and the image carrier.
Having a developing electrode for forming an electric field between the image carrier and the liquid ink in which colored particles are dispersed in a conductive solvent is filled in the gap between the image carrier and the developing electrode, and the surface of the image carrier is A developing means for forming an image by the colored particles on the surface of the image carrier by precipitating the colored particles in the liquid ink in a pattern corresponding to the charge injection pattern formed by the charge injecting means. .

Here, the image forming apparatus includes a moving unit that relatively moves the image carrier and the developing electrode,
It may be provided with a transfer means for transferring the image formed on the surface of the image carrier to a predetermined recording medium. The charge injecting means may inject charge into the image carrier using an ion head, or the charge injecting means may inject charge into the image carrier using an electron gun. May be injected.

Further, the image bearing member has a hydrophobic surface.
It is preferable that Further, the image carrier
Is the volume resistivity in the thickness direction when a given electric field is applied.
Is 10⁶ Made of semi-conductive material that changes to less than Ωcm
Is preferred. Furthermore, the image carrier is
Volume resistivity in the thickness direction when 10 is not given ¹²Ωc
It is also preferable that it is composed of a semi-conductive substance having a size of m or more.
Good.

Further, in the image forming method of the present invention which achieves the above object, charges are injected in a pattern corresponding to an image to an image carrier made of a semiconductive material whose volume resistivity changes depending on an electric field. And the image bearing member is filled with liquid ink in which colored particles are dispersed in a conductive solvent in the gap between the developing electrode and the image bearing member disposed at a predetermined distance between the image bearing member and An electric field is formed between the developing electrode and the surface of the image carrier by precipitating the colored particles in the liquid ink on the surface of the image carrier in a pattern corresponding to the charge injection pattern formed by the charge injecting means. And a step of forming an image with colored particles.

Here, the image forming method includes a step of relatively moving the image carrier and the developing electrode, and a step of transferring the image formed on the surface of the image carrier to a predetermined recording medium. It may be provided.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention. As shown in FIG. 1, the image forming apparatus 100 includes an image carrier belt 1 and a charge injection unit 9.
A developing unit 40, an image carrier moving unit 50, and a transfer unit 60.

The image carrier belt 1 is an endless belt made of a thin film of a semiconductive material whose volume resistivity changes depending on an electric field, and is a drive / heat roll 20, a tension roll 26, and guide rolls 27a and 27b. , 27
c and an image carrier moving means 50 composed of a driving device (not shown). In the present embodiment, the image carrier belt 1 is moved by the image carrier moving unit 50.
Is configured to move with respect to the developing means 40, but it is not always necessary to move the image carrier belt 1 by the image carrier moving means 50, and the developing means may be moved with respect to the image carrier. The moving means may be provided for moving, or the moving means for relatively moving both the image carrier and the developing means may be provided.

By the way, the semiconductive substance used in the image bearing member of the present invention is required to have a volume resistivity which changes depending on an electric field. By using such a semiconductive substance for the image carrier, it is possible to form a charge injection pattern on the image carrier by injecting charges into the image carrier in a pattern corresponding to the image. Next, in the image carrier on which the charge injection pattern is formed, colored particles in the liquid ink are electrodeposited on the image carrier by contact with the liquid ink, and a deposited ink image having a pattern corresponding to the image is formed on the image carrier. Is formed.

The semiconductive substance is not limited to a particular substance as long as it has a volume resistivity that changes depending on an electric field. In the present embodiment, the semiconductive material for the image carrier belt 1 has a thickness of 50 μm to 100 μm.
m of PVC (polyvinyl chloride) film is used. The image carrier preferably has a hydrophobic surface so that the excess developing ink remaining on the surface of the image carrier after development can be easily removed.

FIG. 2 is a diagram showing the electric field dependence of the volume resistivity of the image carrier used in one embodiment of the present invention. As shown in FIG. 2, the volume resistivity in the thickness direction of the non-image portion to which no electric field is applied is about 10 ¹⁶ Ωcm, while the electric field strength is 3 × 10 ⁵ V / m. The volume resistivity in the thickness direction in a given image area decreases to about 10 ³ Ωcm as indicated by the arrow.

Next, the relationship between the volume resistivity in the thickness direction of the image carrier and the image quality will be described. First, an image bearing member was made of various materials having different volume resistivities in the thickness direction when no electric field was applied, and images were formed. When the area ratio of 50% halftone dots in the obtained image was evaluated, the following results were obtained. FIG. 3 is a graph showing the relationship between the volume resistivity in the thickness direction and the image quality when an electric field is not applied to the image carrier material.

Since a material having a lower volume resistivity in the thickness direction when no electric field is applied has a larger amount of current leakage in the width direction of the image carrier, as shown in FIG. % The area ratio of halftone dots deteriorates. In particular, when the volume resistivity in the thickness direction in the absence of an electric field is around 10 ¹² Ωcm, the image quality deteriorates sharply when the volume resistivity becomes lower than that. Therefore, the volume resistivity in the thickness direction of the semiconductive material used for the image carrier is 10 when no electric field is applied.
It is preferably ¹² Ωcm or more.

Next, while the volume resistivity in the thickness direction when the electric field is not applied is kept constant, images of materials having various volume resistivity in the thickness direction when a predetermined electric field is applied are formed. An image was formed using the carrier, and the density of the solid image was evaluated. The following results were obtained. FIG.
7 is a graph showing the relationship between the volume resistivity in the thickness direction and the image quality when a predetermined electric field is applied to the image carrier material.

As shown in FIG. 4, the density of a solid image decreases as the material has a higher volume resistivity in the thickness direction when a predetermined electric field is applied. In particular, the image quality deteriorates rapidly when the volume resistivity in the thickness direction when a predetermined electric field is applied is around 10 ⁶ Ωcm. Therefore, it is preferable that the semiconductive material used for the image carrier has a volume resistivity in the thickness direction of 10 ⁶ Ωcm or less when a predetermined electric field is applied.

The electron beam emitted from the image writing device 9a is applied to the image carrier belt 1 through a shield plate with a slit described below. FIG. 5 is a diagram showing a shield plate for injecting charge, a slit provided in the shield plate, and a scanning locus of an electron beam in one embodiment of the present invention.
FIG. 5 shows the shielding plate 16 in which a slit having a width of 22 μm in the vertical direction is opened. An electron beam is scanned from the image writing device 9a provided on the front side of the drawing onto the shield plate 16 in a scanning locus as shown in FIG.

The scanning locus 14 of the electron beam starts from the left end of FIG. 5 and is scanned in the horizontal direction in the non-image portion, but since the scanning locus 14 of the non-image portion is out of the slit 13, the electron beam is grounded. It is blocked by the shield plate 16 and cannot reach the other side of the shield plate 16. When the scanning locus 14 reaches the halftone dot image portion 17a, the electron beam is scanned in the vertical direction according to the image, and the electron beam entering the slit 13 is provided on the image carrier belt 1 (see FIG. 1)). When the halftone dot image area 17a is finished and enters the non-image area again, the electron beam is again scanned in the horizontal direction, and when reaching the line image area 17b, the electron beam is scanned in the vertical direction according to the image and enters the slit 13. The electron beam is applied to the image carrier belt 1 arranged on the other side of the shield plate. When the line image portion 17b is finished, the electron beam is again scanned in the horizontal direction, and then the solid image portion 17c is scanned.
Then, the electron beam is scanned in the vertical direction according to the image, and the electron beam entering the slit 13 is applied to the image carrier belt 1.

Image carrier belt 1 irradiated with an electron beam
The amount of electric charge injected into the image portion of the image carrier belt 1 is controlled so that a current of 0.4 mA / mm ² flows in the thickness direction of the image carrier belt 1 when the image portion of the image carrier belt 1 passes through the gap G. It In the present embodiment, for the convenience of designing the charge injecting means and the developing means, the shape of the image carrier is configured as an endless belt so that the image can be written from the back side of the surface of the image carrier that contacts the developing ink. In response to this, a roll system is adopted as the developing means so that continuous development can be performed, but the shape of the image carrier is not limited to the endless belt, but an endless drum shape. The developing means is not limited to the endless one, and the developing means is not limited to the roll method. For example,
Either one or both of the image bearing member and the developing unit may be configured as a batch type device.

The charge injection means 9 processes a signal corresponding to an image to generate a write image signal, and a write image processing circuit 9b.
From the image writing device 9a, an electron gun type image writing device 9a that scans the electron beam in the width direction and the traveling direction of the image carrier belt 1 based on the writing image signal from the writing image processing circuit 9b. It comprises a writing image processing circuit 9b for scanning the emitted electron beam in a direction perpendicular to the traveling direction of the image carrier belt 1, and injects charges into the image carrier belt 1 in a pattern according to the image. As a result, a charge injection pattern corresponding to the image is formed on the image carrier belt 1.

In this embodiment, since the ink is deposited on the portion of the image carrier belt 1 facing the developing electrode roll 4 corresponding to the image, a predetermined amount of electric charge is applied to the image corresponding portion of the image carrier belt 1. Need to inject. Therefore, the image writing device 9a using an electron gun scans the image carrier belt 1 with the electron beam, and charges are injected into the image corresponding portion on the image carrier belt 1.

The charge injection means 9 may be an electron gun or an ion head for injecting negative ions or positive ions into the image carrier belt 1. The ion head will be described later. The developing means 40 is provided with a developing electrode roll 4 which rotates in the direction of arrow B and is arranged with a predetermined gap G between it and the image carrier belt 1. A developing bias voltage is applied to the developing electrode roll 4 by the power source 5, and the colored particles in the liquid ink 15 are deposited in a pattern corresponding to the charge injection pattern formed on the image carrier belt 1 by the charge injection means 9. Then, an image is formed by the colored particles.

The developing electrode roll 4 has a diameter of 28 mm,
It rotates in the against direction with respect to the image carrier belt 1 by a driving device (not shown). The gap G from the image carrier belt 1 is 100 μm. The bias voltage applied to the developing electrode roll 4 by the power source 5 is 30V. The liquid ink 15 is a colored resin ink or a conductive ink in which colored particles and a water-soluble resin are dispersed in a conductive solvent. Details of the ink will be described later.

In order to fill the gap G between the image carrier belt 1 and the developing electrode roll 4 with the liquid ink 15, the developing means 40 has the liquid ink tank 4 containing the liquid ink 15.
2, a pump 41 for supplying the liquid ink 15 in the liquid ink tank 42 to the developing electrode roll 4, and the liquid ink 1
A liquid ink circulation means 45 including a pump 44 for collecting 5 in the liquid ink tank 42 is provided.

The transfer means 60 is composed of a drive / heat roll 20 and a pressure roll 21, and an image formed by colored particles deposited on the image carrier belt 1 moved to the transfer position T by the image carrier moving means 50, The image is transferred onto the recording medium 12 moving in the direction of arrow D. In addition, the image forming apparatus 100 includes a cleaning liquid supply device 24 for cleaning excess liquid ink adhering to the surface of the image carrier belt 1 after passing through the developing means 40, and the liquid ink on the surface of the image carrier belt 1. The ink collecting roll 10 rotating in the direction of arrow C for scraping and collecting the ink, and the ink still remaining on the surface of the image carrier belt 1 are pneumatically pressured.
Blower 11 for pushing back toward 0 and cleaning liquid recovery device 25 for recovering cleaning liquid containing liquid ink after cleaning
And are provided.

Further, the image forming apparatus 100 is provided with a cleaning blade 22 and a cleaning brush 23 for cleaning the surface of the image carrier belt 1 after passing through the transfer means 60. Next, the liquid ink used in the image forming apparatus 100 and the developing mechanism thereof will be described.

As the liquid ink, a conductive liquid ink in which colored particles such as pigments are dispersed in a conductive solvent is used. In this embodiment, a resin containing colored particles and dispersed in a conductive solvent is used. When water is used as the solvent, a conductive developing ink in which colored particles are dispersed in a water-soluble resin is used. The form of the resin dispersed in the solvent may be any of water-soluble molecules of 0.01 μm or less, colloidal dispersion of about 0.01 to 0.1 μm, or emulsion of 0.1 μm or more. Can be appropriately selected according to the developing speed and the developing film thickness.

The resin in the form of water-soluble molecule is not particularly limited as long as it is a water-soluble resin. As the resin in the form of colloidal dispersion, inks for various anion type electrodeposition coatings and inks for cation type electrodeposition coatings are used. Ink is suitable. As the cation-type ink, an ink obtained by neutralizing a polyamine-type resin with an acid to make it water-soluble is suitable, and for example, an epoxy resin to which an amine is added and a blocked isocyanate is bonded is used. it can. In addition, a maleic oil, an epoxy ester, a polybutadiene resin, an amino acrylic resin, an epoxy resin or the like may be used as a base to which another polymer or a functional group is added.

As the resin in the form of emulsion, a vinyl group is introduced into polyvinyl acetate, a copolymer containing vinyl acetate, an acrylic emulsion, a styrene-acrylic polymer emulsion, and a C10 synthetic fatty acid having a branch at the α position. A vinyl acetate emulsion containing 30% or more of the ester component can be used. As the conductive solvent,
Water is preferable from the viewpoint of easy handling, but it is not limited to water.

When water is used as a conductive solvent,
By appropriately adding various hydrophilic solvents such as alcohols, glycols and esters to water, the thickness of the developed image, the developing speed and the like can be adjusted. Further, if necessary, a coloring material, a dispersant, a flow control agent, a fungicide, etc. are added. In such an image forming apparatus 100, the charge injecting means 9 injects charges from the back surface of the image carrier belt 1 into a pattern corresponding to an image, and a charge injection pattern corresponding to the image is formed on the image carrier belt 1. It is formed. The gap G between the image carrier belt 1 and the developing electrode roll 4 is filled with the liquid ink 15, where the development by electrodeposition is performed.

Next, the developing mechanism of the developing means 40 will be described in detail with reference to the drawings. FIG.
FIG. 3 is a schematic diagram showing a development process when a cationic developer according to an embodiment of the present invention is used. As shown in FIG. 6, a liquid ink in which ink particles 3 made of a water-soluble resin and a pigment which are colored particles are dispersed in a conductive solvent 2 in a gap G between the image carrier belt 1 and the developing electrode roll 4. 15 is full. A positive developing bias voltage is applied to the developing electrode roll 4 by the power source 5.

When the charge 6 is injected into the image carrier belt 1 by the charge injecting means 9 (see FIG. 1) in a pattern corresponding to the image, the cationic ink particles 3 are cathodes due to the electrophoretic phenomenon. Image forming portion 7 on the image carrier belt 1
Attracted to. The ink particles 3 attracted to the image carrier belt 1 receive charges on the surface of the image carrier belt 1 and deposit the ink 8 by an electrolysis phenomenon. Alternatively, the ink particles 3 that have reached the image carrier belt 1 and are composed of resin components, pigment particles, etc., become insoluble after receiving an electric charge and deposit the ink 8 on the image carrier belt 1 (electrodeposition phenomenon). .

When a voltage is further applied, only water moves from the ink film in contact with the image carrier belt 1 in the direction away from the image carrier belt 1, and the ink film in contact with the image carrier belt 1 gradually. It is dehydrated and changes into a water-insoluble ink film (electroosmosis phenomenon). In this way, an ink image corresponding to an image is formed on the image carrier belt 1 by a combination of several kinds of phenomena.

After the development, the image carrier belt 1 is cleaned and cleaned by the cleaning liquid supplied from the cleaning liquid supply device 24 and the ink collecting roll 10, and then reaches the transfer position T. , Drive and heat roll 2
0 (see FIG. 1) and the pressure roll 21 to heat under pressure, and the ink image on the image carrier belt 1 is transferred onto the recording medium 12.

The result of image formation using the image forming apparatus 100 will be described. As the image carrier belt 1, a PVC endless belt having a width of 220 mm and a thickness of 100 μm was used, and the moving speed thereof was set to 100 mm / sec. As the image, there are 3 images, which are a 50% halftone dot image of 1200 dpi, a solid image, and a line image of 1 dot / line.
Various types were written on the image carrier belt 1 by the charge injecting means 9 composed of the electron gun type image writing device 9a and the writing image processing circuit 9b. The halftone image is a binary halftone dot, as in general printing.

As the liquid ink 15, used is 85% water in which 10% of an acrylic emulsion containing a cyan pigment and 5% of other additives are dispersed. Transfer means 6
The transfer conditions at 0 are a temperature of 40 ° C. and a pressure of 1 kg /
It is 250 mm. Fixing was by natural drying.

As the recording medium 12, OK special art paper was used. As described above, the solid density is 1.1, 50.
It was possible to obtain a high-definition high-quality image without fog on the recording medium 12 with a dot density of 0.65% and a dot width of 28 μm. The film thickness of the ink in the image area on the image carrier belt 1 at the end of development is 0.5 to 3 μm, and the film thickness of the ink in the image area on the image carrier belt 1 after fixing is 0.3. ~
It was 2 μm.

By the way, since the developing means in the image forming apparatus of the present invention is developed by using the electrodeposition method, the ink is changed according to the change of the parameters such as the density of the liquid ink, the process speed and the developing bias voltage. The amount of precipitation is greatly affected. Therefore, the influence of these parameters on the image density was investigated by changing each of these parameters.

The concentration of the liquid ink was changed in three stages of 5, 15 and 20%, and an appropriate amount of an auxiliary agent was added to each of them in order to make the fluidity of the ink constant at each concentration.
Process speed is 5mm / sec to 300mm /
The developing bias voltage was set in the range up to sec, and the developing bias voltage was set in relation to the passing time of the developing area. As a result, in each ink density and the process speed of the above, in the range of bias current from 0.05 mA / mm ² to 1 mA / mm ^2, more than monochrome density 1.0, no image defects high-definition image was gotten.

Next, an example in which a cationic electrodeposition coating is used as an example of a colloidal dispersion type resin instead of the above emulsion type resin will be described. The liquid ink used was 85% water, 8% commercial cationic electrodeposition paint, 5% ethylene glycol, and 2 adjusting agents.
% Is dispersed. For fixing, an oven type fixing device (not shown) set at a temperature of 150 ° C. was used.

As a result of image formation, the solid density is 1.3 and 50%.
With a halftone dot density of 0.75 and a 1-dot line width of 28 μm, a high-definition high-quality image without fog was obtained. In the embodiment described above, P is used as the semiconductive substance for the image carrier.
Although an example in which VC is used has been described, PET (polyethylene terephthalate), PPS is used instead of PVC.
(Polyphenylene sulfide), PVdF (Polyvinylene Fluoride), Polyimide, Teflon, PE (Polyethylene) as a base, and using the image carrier belt 1 in which the resistance value in the thickness direction is controlled as in the above description. When images were formed, it was possible to obtain the same images as in the case of PVC.

Next, an embodiment in which an ion head method is used as the charge injection means 9 instead of the electron gun method will be described. FIG. 7 is a conceptual diagram of an ion head used in an embodiment of the present invention. As shown in FIG.
The ion head 90 is provided on the glass substrate 95 with the ion head main body 91 installed on the glass substrate 95, the shield portion 92, the corotron 93 installed on the ion head main body 91, and the corotron 93 facing the corotron 93. A plurality of shutter electrodes 94, a fan 97, and a filter 98
And a slit-shaped ion emission port 96 that emits ions.

Next, the function of the ion head will be described in detail with reference to the drawings. FIG. 8 is a schematic view showing the function of the ion head used in the embodiment of the present invention. In FIG. 8, an ion emission port 96 formed inside the ion head main body 91 and opened toward the image carrier belt 1 is provided, and the image carrier belt 1 is shielded by the shield portion 92.
Ion chamber 91a shielded against the ion chamber 91a
A corotron 93 installed therein, a plurality of shutter electrodes 94 installed to face the corotron 93, and a high-voltage power supply 99 that supplies a high-voltage DC voltage to the shutter electrodes 94,
The write image processing unit 19 that supplies a high voltage to the plurality of shutter electrodes 94 is shown.

The air blown from a fan 97 (see FIG. 7) (not shown) is cleaned by a filter 98, and then an ion chamber 91 having a corotron 93 and a shutter electrode 94 is provided.
Then, it enters into a and is ejected from the ion emission port 96 toward the image carrier belt 1. Here, of the plurality of shutter electrodes 94, a predetermined shutter electrode 9 corresponding to the writing image signal is used.
When a high voltage is applied between 4 and the corotron 93,
Negative ions are generated in the gap between the shutter electrode 94 and the corotron 93, and the generated negative ions are emitted toward the opposing image carrier belt 1 and charges corresponding to the image are injected onto the image carrier belt 1. It

Using such an ion head 90, an image was formed under the following conditions. There are three types of image formation: a 50% halftone image, a solid image, and a 1 dot / line line image. The moving speed of the image carrier belt 1 is 10 mm
/ S, and the maximum current density on the image carrier belt 1 is 10
μA / mm ² .

The shutter electrode 94 of the ion head 90 is 1
The method is to scan horizontally horizontally for each pole. Ion head 9
The resolution of the shutter electrode 94 of 0 is 800 dpi.
Further, the gap G between the image carrier belt and the ion head is 30.
It was set to 0 μm. The developing bias voltage is -500V.
As a result of forming an image in this way, the solid density is 1.
1, 50% halftone dot density 0.7, 1dot line width 38 μm,
It was possible to obtain a high quality image without fogging.

Further, 100 samples were prepared by this image forming apparatus, but deterioration of the image carrier belt, which is considered to be caused by the image writing apparatus, was not recognized. The advantage of using an ion head for the charge injection means is that image writing can be performed without contacting the image carrier belt, as in the case of using an electron gun, but the disadvantage is that a too large current density cannot be secured, so the process speed is reduced. Is to be constrained.

By the way, in the case of the electron gun type charge injection means, the gradation expression of the image is performed by the area gradation method. However, according to the ion head type charge injection means, the area gradation method and the density gradation method are used. It is possible to express both gradations of the system. In the above-described image formation by the ion head method, an example of area gradation has been described, but an example of performing density gradation expression by the charge injection unit of the ion head method will be described below. In this example, the voltage supplied to each shutter electrode 94 is 4
By setting the number of stages, it is possible to express the density gradation of 64 gradations.

FIG. 9 is a schematic configuration diagram of an ion head type charge injection means used in an embodiment of the present invention.
As shown in FIG. 9, the charge injection unit 18 of the ion head system includes a write image processing unit 19 that generates a write image signal according to an image, and the image carrier belt 1 that moves in the direction of arrow A. An ion head 90 for writing an image thereon is provided. The write image processing unit 19 includes a switch circuit 19
b, the shutter voltage switching circuit 19c, and the switch circuit 1
9b and a control circuit 19a for controlling the shutter voltage switching circuit 19c. The switch circuit 19b is
The shutter voltage switching circuit 19c is a circuit for turning on / off the operation of the plurality of shutter electrodes 94 according to the write image signal, and the shutter voltage switching circuit 19c applies the shutter voltage applied to the plurality of shutter electrodes 94 according to the write image signal. Is a circuit for switching to four levels to perform density gradation expression.

The write image processing unit 19 configured as described above
The operation in the case of performing the density gradation expression using will be described. Now, when the write image signal is input to the control circuit 19a, the control circuit 19a sends 200 lines to the write image signal.
Allocation with 4 gradations is performed. The switch circuit 19b turns on / off the voltage of each shutter electrode 94 based on the write image signal.
Control off. At the same time, the shutter voltage switching circuit 19c controls the shutter electrode 9 depending on which of the four levels of density the write image signal assigned by the control circuit 19a is.
The shutter voltage supplied to No. 4 is selected and the voltage is applied to the shutter electrode 94. In this way, each shutter electrode 94 generates ions having a density corresponding to the write image signal, the ions are supplied to the image carrier belt 1, and the ions on the image carrier belt 1 correspond to the image density. A quantity of charge is injected.

On the other hand, in the case of the area gradation performed for comparison, when the write image signal is input, the allocation of 133 lines and 36 gradations is performed, and the switch circuit 19b causes
Ion generation is turned on / off by simply turning on / off the voltage of each shutter electrode 94 according to the writing image signal, and image writing is performed. As a result of comparing the two images after the image formation, in the case of the area gradation, the image is slightly rough, whereas in the case of the density gradation, the area gradation and the density gradation are combined and expressed. Therefore, no graininess of the image was recognized, and a clear image could be obtained.

Since the ion head can generate both positive and negative ions, an image was formed with anion type liquid ink using an ion head which generates positive ions. As the anionic liquid ink, used was an ink in which 10% of an emulsion containing a pigment and mainly composed of an R—COOH group and 5% of other additives were dispersed in 85% of water.

As a result of image formation, the solid density is 1.2 and 50%.
With a halftone dot density of 0.7 and a dot width of 55 μm, a high-quality image free of fogging was obtained. In the above description, an example in which a single color image is formed using a liquid ink containing one type of colorant has been described. However, in the following, the image forming apparatus 100 shown in FIG. A case of forming a full-color image with four types of liquid inks of magenta, yellow, and black will be described.

First, development is performed using cyan liquid ink, the formed cyan image is transferred to OK special art paper, and then the ink in the liquid ink tank 42 is replaced with magenta to develop magenta. Then, the magenta image thus formed is transferred onto the OK special art paper on which the cyan image is transferred, and then the yellow and black development and transfer are repeated to obtain a high-definition full-color image. Can be obtained.

In the above embodiment, a full-color image cannot be obtained unless the image forming operation by the image forming apparatus 100 shown in FIG. 1 is repeated four times, but the full-color image forming apparatus described below is used. If 1
A full-color image can be obtained with a single image forming operation. FIG. 10 is a schematic diagram of a case where four units of the image forming apparatus of the present invention are combined to form a full-color image forming apparatus.

As shown in FIG. 10, the full-color image forming apparatus 200 includes four units of monochromatic image forming apparatuses 100a, 100b, 100c and 100d, and these image forming apparatuses 100a, 100b, 100c and 100d.
A recording medium conveying belt 111 made of PET having a high heat resistance and a thickness of 75 μm for connecting d, a drive roll 112 and a metal roll 110 for driving the recording medium conveying belt 111.
And a corotron 114 for adsorbing the recording medium 12 to the recording medium conveying belt 111, and the recording medium conveying belt 1
A static eliminator 113 for removing the electric charge of the battery 11, an oven-type fixing device 116, and a conveyor belt 115 thereof are provided.
Each image forming apparatus 100a, 100b, 100c, 100
Reference numeral d denotes an apparatus that is substantially the same as the image forming apparatus 100 shown in FIG. 1, and operates as a cyan unit, a magenta unit, a yellow unit, and a black unit, respectively. Recording medium 12
Is a corotron 1 placed opposite the metal roll 110
14 is attracted to the recording medium transport belt 111 and moves in the direction of arrow A, and
The images of the respective colors are sequentially superimposed and transferred onto the recording medium 12 by 100c and 100d. Next, the recording medium 12 is peeled off from the drive roll 112, transferred to the conveyor belt 115 for the fixing device, and subjected to the fixing process by the oven-type fixing device 116. On the other hand, the recording medium conveyance belt 111 is neutralized by the static eliminator 113 provided on the return side, returns to the position of the metal roll 110 again, and shifts to the next image forming cycle.

Such a full-color image forming apparatus 2
As a result of forming a full-color image at a process speed of 100 mm / sec with No. 00, the same result as that for a single color was obtained for each color, and no problem was observed in the overlapping portion of the colors. Next, an embodiment in which a cathode ray tube and a pin array are used for image writing in the charge injection means will be described.

FIG. 11 is a schematic block diagram of a charge injection means using a cathode ray tube and a pin array used in one embodiment of the present invention, and FIG. 12 is a pin array used in the charge injection means shown in FIG. FIG. FIG.
11A is a top view of the charge injection means 80, and FIG. 11B is a side view thereof.

As shown in FIGS. 11A and 11B, the charge injection means 80 includes a cathode ray tube 81 and a cathode ray tube 81.
And a pin array 82 arranged in contact with the electron beam irradiation surface 81a. Further, the pin array 82 of the charge injection unit 80 is in contact with the image carrier belt 1. Further, a developing electrode roll 4 is provided across the gap G on the other side of the image carrier belt 1, and the gap G is filled with the liquid ink 15.

The pin array 82, as shown in FIG.
A plurality of metal needles 85 are embedded in a resin substrate 86. The metal needles 85 are arranged in two rows in a staggered pattern with a density of 48 needles / mm. The two rows are arranged in a staggered pattern in order to improve insulation and resolution. The electron beam 83 emitted from the cathode ray tube 81 is deflected by the deflection coil 8.
4, scanning is performed by a scanning method substantially similar to the scanning locus 14 shown in FIG. The electron beam 83 scans a portion corresponding to the image portion of the electron beam irradiation surface 81a according to the image,
When the electron beam 83 is applied to the metal needle at that position, charges are injected into the image carrier belt 1 in contact with the metal needle. When the electron beam 83 is scanning the non-image portion, the area outside the area where the metal needle is arranged irradiates, so that no charge is injected into the image carrier belt 1.

When an image was formed using this charge injection means 80, it was possible to obtain a high-definition image with a 1-dot line width of 30 μm and no fog.

[0073]

As described above, in the image forming apparatus and method of the present invention, a semiconductive material whose volume resistivity changes depending on an electric field is used as the image carrier, and the image carrier is The charge is injected according to the image, only the resistance in the thickness direction of the part (image part) where the charge is injected decreases, and a predetermined current flows, and the ink is deposited only in the image part. On the other hand, the resistance of the portion around the image area where no charges are injected (non-image area) remains high, so that no current flows in the non-image area and ink does not deposit. Therefore, a high-definition image can be formed.

Further, in the image forming apparatus and method of the present invention, by injecting charges into the image carrier made of a semiconductive material whose volume resistivity changes depending on the electric field, in a pattern according to the image. Since the pattern is formed electrically, it is possible to form the pattern at high speed. In addition, since the colored particles in the liquid ink are electrically deposited in the narrow gap between the image carrier on which the electric charge is injected and the resistance is lowered and the developing electrode to perform the development, the developing speed is high and therefore the image can be formed at high speed. Forming can take place.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an image forming apparatus of the present invention.

FIG. 2 is a diagram showing the electric field dependence of the volume resistivity of the image carrier used in the embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the volume resistivity in the thickness direction and the image quality when an electric field is not applied to the image carrier material.

FIG. 4 is a graph showing the relationship between the volume resistivity in the thickness direction and the image quality when a predetermined electric field is applied to the image carrier material.

FIG. 5 is a diagram showing a shield plate for injecting charge, a slit provided in the shield plate, and a scanning locus of an electron beam in one embodiment of the present invention.

FIG. 6 is a schematic diagram showing a developing process when a cationic developer according to an embodiment of the present invention is used.

FIG. 7 is a conceptual diagram of an ion head used in an embodiment of the present invention.

FIG. 8 is a schematic view showing the function of the ion head used in the embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of an ion head type charge injection unit used in an embodiment of the present invention.

FIG. 10 is a schematic view of a case where a four-color image forming apparatus of the present invention is combined to form a full-color image forming apparatus.

FIG. 11 is a schematic configuration diagram of a charge injection unit using a cathode ray tube and a pin array used in an embodiment of the present invention.

12 is a schematic diagram of a pin array used in the charge injection unit shown in FIG.

FIG. 13 is a schematic diagram of a conventional example of a developing method using an electrodeposition method.

FIG. 14 is a schematic view of another conventional example of the developing method using the electrodeposition method.

[Explanation of symbols]

1 image carrier belt 2 conductive solvent 3 ink particles 4 developing electrode roll 5 power supply 6 electric charge 7 image forming portion 8 ink 9 charge injection means 9a image writing device (electron gun system) 9b writing image processing circuit 10 ink recovery roll 11 Blower 12 Recording Medium 13 Slit 14 Electron Beam Scanning Trajectory 15 Liquid Ink 16 Shielding Plate 17a Halftone Image Section 17b Line Image Section 17c Solid Image Section 18 Charge Injection Means (Ion Head Method) 19 Write Image Processing Section 19a Control Circuit 19b switch circuit 19c shutter voltage switching circuit 20 drive / heat roll 21 pressure roll 22 cleaning blade 23 cleaning brush 24 cleaning liquid supply device 25 cleaning liquid recovery device 26 tension rolls 27a, 27b, 27c guide roll 40 developing means 41, 4 4 Pump 42 Liquid Ink Tank 45 Liquid Ink Circulation Means 50 Image Carrier Moving Means 60 Transfer Means 80 Charge Injecting Means (Pin Array Method) 81 Cathode Ray Tube 81a Electron Beam Irradiation Surface 82 Pin Array 83 Electron Beam 84 Deflection Coil 85 Metal Needle 86 Substrate 90 Ion head 91 Ion head body 91a Ion chamber 92 Shield part 93 Corotron 94 Shutter electrode 95 Glass substrate 96 Ion emission port 97 Fan 98 Filter 99 High voltage power supply 100, 100a, 100b, 100c, 100d
Image forming apparatus 110 Metal roll 111 Recording medium conveying belt 112 Drive roll 113 Static eliminator 114 Corotron 115 Conveying belt 116 Fixing device 200 Full color image forming apparatus

Claims (9)

[Claims] 1. An image carrier made of a semi-conductive material whose volume resistivity changes depending on an electric field, charge injection means for injecting charges into the image carrier in a pattern according to an image, and the image. Deployed with a predetermined gap between the carrier and
The image bearing member has a developing electrode for forming an electric field between the image bearing member and the gap between the image bearing member and the developing electrode filled with a liquid ink in which colored particles are dispersed in a conductive solvent. And a developing means for forming an image by the colored particles on the surface of the image carrier by precipitating colored particles in the liquid ink in a pattern corresponding to the charge injection pattern formed by the charge injecting means on the body surface. An image forming apparatus characterized by being provided. 2. A moving means for relatively moving the image carrier and the developing electrode, and a transfer means for transferring an image formed on the surface of the image carrier to a predetermined recording medium. Claim 1
The image forming apparatus as described in the above. 3. The image carrier comprises:
3. The image forming apparatus according to claim 1, wherein the charge is injected using an ion head. 4. The image carrier comprises the charge injecting means,
The image forming apparatus according to claim 1, wherein the electric charge is injected by using an electron gun. 5. The image forming apparatus according to claim 1, wherein the image carrier has a hydrophobic surface. 6. The image carrier is made of a semi-conductive material whose volume resistivity in the thickness direction changes to 10 ⁶ Ωcm or less when a predetermined electric field is applied. The image forming apparatus according to item 1 or 2. 7. The image carrier is made of a semiconductive material having a volume resistivity in the thickness direction of 10 ¹² Ωcm or more when an electric field is not applied.
Or the image forming apparatus according to 2. 8. A step of injecting charges in a pattern according to an image into an image carrier made of a semi-conductive material whose volume resistivity changes depending on an electric field, and a predetermined distance between the image carrier and the image carrier. The gap between the developing electrode and the image carrier arranged at a distance is filled with a liquid ink in which colored particles are dispersed in a conductive solvent, and an electric field is formed between the image carrier and the developing electrode. , On the surface of the image carrier,
A step of forming an image by the colored particles on the surface of the image carrier by precipitating the colored particles in the liquid ink in a pattern corresponding to the charge injection pattern formed by the charge injection means. Image forming method. 9. A step of moving the image carrier and the developing electrode relatively, and a step of transferring an image formed on the surface of the image carrier to a predetermined recording medium. The image forming method according to claim 8.