JPH0844216A - Wet process electrophotographic developing method and device - Google Patents

Abstract

PURPOSE:To provide a wet process electrophotographic device capable of rapidly forming a toner layer of a uniform thickness. CONSTITUTION:Developing electrodes 20 are divided along the rotating direction of a photoreceptor 11 and a low voltages is impressed to the downstream side divided electrode 20b part facing the downstream side by impressing a high voltage to the upstream side divided electrode 20a facing the upstream side of the rotating direction, by which toners 26 to be adhered onto the photoreceptor 11 are put into a satd. state and the layer thereof is formed at the time of forming the layer by interposing a developer contg. the electrostatically charged toners between the developing electrodes 20 and the photoreceptor 11 and generating a potential gradient between the developing electrodes 20 and the photoreceptor 11 to adhere the toners onto the photoreceptor. Since electrodeposition is executed under the high voltage by the upstream side electrode 20a in the beginning of the electrodeposition, the electrodeposition quantity with respect to the electrodeposition time is large and the large quantity of electrodeposition is obtd. in a short time. The electrodeposition is executed under the voltage under which the desired electrodeposition quantity by the downstream side electrode 20b is satd, near the completion of the electrodeposition and, therefore, the uniform and exact electrodeposition quantity is obtd. even if unequalness arises in the discharge speed of a developer supplying pump and the rotating speed of the photoreceptor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a wet type developer in which charged toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid, and a wet type developer for adhering the toner particles to the entire surface of a photoreceptor is used. The present invention relates to an electrophotographic developing method and apparatus.

[0002]

2. Description of the Related Art As a conventional technique, charged toner particles mainly containing a thermoplastic resin are supplied between a developing electrode placed facing an electrophotographic photosensitive member and a potential gradient applied by an external power source. There is an electrophotographic transfer method in which a peelable transfer layer is formed by electrophoresing and electrostatically adhering or electrodepositing on an electrophotographic photosensitive member to form a film.

The film thickness of the transfer layer is determined by the amount of toner particles attached to the photoreceptor. Among these methods, in the method of film formation by electrodeposition, the amount of toner adhered is changed by changing the time for which the photoconductor being conveyed passes over the opposing developing electrode or the voltage applied from the external power source to the developing electrode. Control. But,
If there is an error in the setting setting of the developing electrode, a momentary fluctuation of the supplied toner particles, or uneven transport speed of the photoconductor, the film thickness will change, and it will not be possible to obtain a transfer layer with a uniform film thickness. A layer is formed. The non-uniform transfer layer has a problem that peelability and image formation are adversely affected.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to set the film thickness of the transfer layer even if there is an error in the setting of the mounting of the developing electrode, a momentary fluctuation of the toner particles to be supplied, an uneven transport speed of the photosensitive member, or the like. It is an object of the present invention to provide a wet electrophotographic developing method and apparatus capable of forming a transfer layer having a uniform thickness at a high speed without changing the temperature.

[0005]

The above object of the present invention is achieved by the following constitution. (1) At least an electrophotographic photosensitive member, developing means for providing a toner image of one or more colors on a transfer layer on the surface of the photosensitive body by an electrophotographic process, and transfer means for thermally transferring the toner image together with the transfer layer onto a transfer material. In the electrophotographic transfer method using, a wet developer in which charged toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid is interposed between a developing electrode and a photoconductor to form the toner particles. Wet electron characterized by performing electrostatic adhesion or electrodeposition to a saturated adhesion state when forming a peelable transfer layer by electrostatically adhering or electrodepositing on the surface of a photoreceptor Photo development method.

(2) At least an electrophotographic photosensitive member, developing means for providing a toner image of one or more colors on a transfer layer on the surface of the photosensitive member by an electrophotographic process, and the toner image together with the transfer layer are thermally transferred onto a transfer material. In an electrophotographic transfer device having a transfer means, a wet type developer in which charged toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid is interposed between a developing electrode and a photoconductor to form the toner. When a peelable transfer layer is formed by electrostatically attaching or electrodepositing particles onto the surface of the photoconductor to form a peelable transfer layer, the distance between the developing electrode and the photoconductor is constant and the direction of rotation of the photoconductor is fixed. Wet electrons characterized by being divided into two or more parts along a line, and applying a voltage having a higher potential difference to the surface of the photoconductor to the part facing the upstream side in the rotational direction of the photoconductor than to the part facing the downstream side. Photo development equipment .

(3) At least an electrophotographic photosensitive member, developing means for providing a toner image of one or more colors on a transfer layer on the surface of the photosensitive member by an electrophotographic process, and the toner image together with the transfer layer are thermally transferred to a transfer material. In an electrophotographic transfer device having a transfer means, a wet type developer in which charged toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid is interposed between a developing electrode and a photoconductor to form the toner. When a peelable transfer layer is formed by electrostatically attaching or electrodepositing particles onto the surface of the photoconductor to form a peelable transfer layer, the distance between the developing electrode and the photoconductor is constant and the direction of rotation of the photoconductor is fixed. Along the rotation direction, the portion facing the downstream side in the rotational direction is applied with a voltage having a lower potential difference from the surface of the photoreceptor than the upstream portion, and the portion facing the upstream side is a portion facing the downstream side from the higher potential difference. Potential difference In the wet electrophotographic developing device, a voltage is continuously applied in a linear or exponential manner so that the potential difference gradually decreases.

[0008]

According to the above configuration (1), when the toner particles are electrostatically adhered or electrodeposited on the photoconductor, the toner particles can be electrostatically adhered on the photoconductor by sufficient time. In addition, the transfer layer film thickness is determined by the surface potential on the photoconductor when the photoconductor is charged, the electrostatic capacitance of the photoconductor, and the saturated adhesion amount of toner particles determined by the physical property value of the wet developer. When the toner particles are deposited on the photoconductor by electrodeposition, the transfer layer is determined by the saturated adhesion amount of the toner particles, which is determined by the voltage applied to the developing electrode, the electrostatic capacity of the photoconductor, and the physical properties of the wet developer. The film thickness is determined. Therefore, it is possible to form a transfer layer having a uniform film thickness, even if there is an error in setting the developing electrode, a momentary fluctuation of the toner particles to be supplied, or a non-uniform conveyance speed of the photoconductor.

According to the above configuration (2), by appropriately setting the division ratio of the divided electrodes and the voltage applied to the divided electrodes, the potential difference between the surface of the photoconductor and the electrode on the downstream side in the rotation direction, the photoconductor. The film thickness of the transfer layer is determined by the film thickness of the saturated adhesion amount of the toner particles, which is determined by the electrostatic capacity and the physical property value of the wet developer. The electrode on the upstream side applies a voltage having a higher potential difference than the electrode on the downstream side to adhere toner particles on the photoconductor in an amount slightly smaller than the saturated adhesion amount in a short time. Toner particles are deposited to a saturated deposit amount. As a result, the transfer layer can be formed by the saturated adhesion amount of the toner particles in a short time, and even if there is a setting error of the developing electrode, a momentary fluctuation of the supplied toner particles, or an uneven conveyance speed of the photoconductor, It is possible to form a transfer layer having a uniform film thickness, which is hardly affected.

According to the above configuration (3), by appropriately setting the division ratio for dividing the electrode pole into two and the method of reducing the potential difference applied to the divided upstream side in the rotation direction, the rotation of the surface of the photoconductor is prevented. The transfer layer film thickness is determined by the film thickness of the saturated adhesion amount of the toner particles, which is determined by the potential difference of the electrode on the downstream side in the direction, the electrostatic capacity of the photoconductor, and the physical property value of the wet developer. The electrode on the upstream side gradually and linearly or exponentially gradually reduces and applies from a high potential difference to a low potential difference on the downstream side, so that toner particles slightly less than the saturated adhesion amount on the photoconductor in a short time. To the saturated amount by the downstream electrode. As a result, the transfer layer can be formed by the saturated adhesion amount of the toner particles in a short time, the setting error of the developing electrode and the
Even if there are momentary fluctuations in the supplied toner particles, uneven transport speed of the photoconductor, and the like, it is possible to form a transfer layer having a uniform film thickness, which is hardly affected by the influence.

The division ratio of the developing electrode is appropriately set according to the target toner adhesion amount, toner physical properties, developer supply flow rate, distance from the photosensitive member, applied voltage, and the like. The voltage ratio applied to each of the upstream side electrode and the downstream side electrode is appropriately determined according to the target toner adhesion amount, toner physical properties, developer supply flow rate, distance from the photoconductor, number of divisions of the developing electrode, etc. Is set. For example, when the developing electrode is divided into two, the length of the upstream electrode is preferably 1/10 to 1/2 of the total length of the developing electrode, and particularly preferably 1/5. Also, for example, if the developing electrode is 2
When divided, the voltage applied to the upstream electrode is preferably 1.2 times to 10 times the voltage applied to the downstream voltage, and particularly preferably 1.5 times to 5 times. The flow rate for supplying the developing solution is preferably 1 mm / sec to 200 mm / sec, particularly 10 mm / sec.
mm / sec to 100 mm / sec is preferable. The peripheral speed of the photosensitive member is preferably 1 mm / sec to 200 mm / sec, and particularly preferably 10 mm / sec to 100 mm / sec.

The toner in the present invention is required to have either a positive charge or a negative charge, and the polarity of the charge is arbitrarily determined by the polarity of the electrophotographic photosensitive member with which it is charged. The material to be transferred used in the present invention is not particularly limited, and includes fine paper, coated paper,
Art paper, natural paper, synthetic paper support, aluminum, iron, SU
Any of reflective materials such as metal supports such as S, transmissive materials such as resin films (plastic films) such as polyester, polyolefin, polyvinyl chloride and polyacetate, direct writing plates (straight master etc.), etc. Good.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a schematic configuration diagram of a wet electrophotographic apparatus. This wet electrophotographic apparatus forms a transfer layer 12 on a photoreceptor 11 for each recording, forms an image on the transfer layer 12, and transfers the formed image together with the transfer layer to a transfer material such as plain paper. Then, a hard copy is obtained. Photoconductor 11
Around the periphery of the transfer layer 12, a corona charging device 18 for uniformly charging the photoconductor 11, an exposure unit 19 for forming a latent image on the charged photoconductor 11, and a transfer layer 12 made of a dispersion liquid of thermoplastic resin particles (transparent toner). Wet developing unit set 14 for forming a latent image and developing a latent image, and a drying device 15 for drying the surface of the photoreceptor 11 wetted by the dispersion liquid.
A heating device 17a for melting the thermoplastic resin particles to form a film, and a heating transfer device 17 for bringing the transfer material 16 into pressure contact with the transfer layer 12.

As the exposure unit 19, a slit scanning exposure unit using a halogen lamp or the like as a light source, Ar,
A laser beam scanning exposure unit having a He-Ne semiconductor laser or the like as a light source is used. Wet development unit set 14
Is a wet developer containing an electrodeposition unit 14T for electrodepositing thermoplastic resin particles on the photoreceptor 11 and a wet toner of each color of C (cyan), M (magenta), Y (yellow), and BK (black). And developing units 14C, 14M, 14Y, and 14BK for developing the latent image by means of the respective units 14T, 14C, 14M, 14Y, and 14Y.
The BK is movable so that it can be brought into and out of contact with the photoconductor 11. Each developing unit 14C, 14M, 14Y, 1
The 4BK is provided with pre-bath, rinse and squeeze means also for preventing stains on the non-image area. As the pre-bath and rinse liquid, a carrier liquid of a wet developer is usually used.

As the drying device 15, for example, the photoconductor 11 is used.
A warm air blower fan 15a that blows warm air toward the fan, an exhaust fan 15b that sucks the blown warm air, a device that combines a lamp heater and a blower fan, and the like are used. The heat transfer device 17 for thermally transferring the transfer layer 12 to the transfer material 16 includes a heating roller 17b, a cooling roller 17c, and
A driving means for bringing the rollers into and out of contact with the photoconductor 11 is provided. The transferred material 16 is pressed against the photoconductor 11 while being stretched between the heating roller 17b and the cooling roller 17c.

The heating roller 17b is formed by coating a metal roller with rubber containing a heating element. Cooling roller 17
c is made of, for example, a heat conductive metal such as aluminum or copper and coated with silicone rubber, and it is desirable that heat is radiated to the inside of the roller or the outer peripheral portion not in contact with the transfer paper by using a cooling means. A cooling fan, a cooling circuit, an electronic cooling element, or the like is used as the cooling means, and it is preferable to maintain it in a predetermined temperature range in combination with a temperature controller.
Nip pressure of the heating roller 17b and the cooling roller 17c is 0.2~20kgf / cm ^2, more preferably 0.5~15kgf / cm ^2, at both ends of the not shown roller axis as roller pressing means An air cylinder using springs or compressed air can be provided.

The liquid dispersion 12a of thermoplastic resin particles for forming the transfer layer 12 is filled in the electrodeposition unit 14T in the wet developing unit 14. To form the transfer layer 12, first, the electrodeposition unit 14T is mounted on the surface 11 of the photoconductor.
And is fixed so that the distance between the electrodeposition unit 14T and the developing electrode is a constant value. This distance is preferably 0.3 mm to 5 mm, more preferably 0.5 mm
~ 3 mm. FIG. 2 shows an enlarged main part of the electrodeposition unit 14T. The particle dispersion liquid 12a is supplied between the developing electrode 20 and the photoconductor 11 and rotated while applying a voltage to both of them from an external power source (not shown), and the particles are charged on the entire image forming area on the surface of the photoconductor 11. Try to wear it.

After a predetermined amount of particles are electrodeposited on the surface of the photoconductor 11, they are attached to the surface of the photoconductor 11 by a squeeze device such as a squeeze roller, an air knife, a vacuum means, etc. built in the electrodeposition unit 14T. Excessive particle dispersion 12a is removed, and the thermoplastic resin particles electrodeposited on the surface of the photoconductor 11 are dried by passing under the drying means 15. Then, the transfer layer 1 made of the thermoplastic resin is formed by melting the thermoplastic resin particles by the heating means 17a to form a film.
Get 2. After that, if necessary, from the outside of the photoconductor with a cooling device composed of a cold air fan or an exhaust fan (not shown),
Alternatively, the inside of the photoconductor is cooled to a predetermined temperature. When a film of a thermoplastic resin as the transfer layer 12 is formed on the surface of the photoconductor 11, the electrodeposition unit 14T becomes
Away from.

Next, the electrophotographic process is started. The photoreceptor 11 on which the transfer layer 12 made of a thermoplastic resin is formed is uniformly charged positively or negatively by the corona charging device 19. After that, when the photoconductor 11 is image-exposed by the semiconductor laser 20 based on the yellow image information, the potential of the exposed portion is reduced, and a potential contrast is obtained between the exposed portion and the unexposed portion. After that, development is performed with a wet toner. The development method includes a reversal development method in which development is performed using a toner having the same polarity as that when charging, and a development using a toner having a polarity different from that in charging There is a positive development method. Either method can be used in the electrophotographic process of the present invention. In the following, reversal development will be described as an example.

The yellow developing unit 14Y is the photosensitive member 11.
And an appropriate gap is formed between the developing electrode 20 and the photoconductor 11. The yellow developing unit 14Y is filled with a wet type developer in which a yellow pigment having a charge having the same polarity as that at the time of charging is dispersed in an electrically insulating dispersion medium. First, the photoconductor 11 is pre-bused by the pre-bus means included in the yellow developing unit 14Y. Then, while a developing bias voltage is applied between the photoconductor 11 and the developing electrode by a bias power supply and electrical connection (not shown), the yellow wet developer is supplied to the surface of the photoconductor 11. At this time, the bias voltage is connected such that the photoconductor side is grounded and the development electrode side is the same polarity as the toner, and the applied voltage is slightly lower than the surface potential of the unexposed portion. This is because if the applied voltage is too low, a sufficient toner density cannot be obtained in the image, and if the applied voltage is equal or higher, the fog in the non-image area becomes large.

After that, the developing solution is washed off by the rinsing means built in the yellow developing unit 14Y, and then the rinsing adhering to the surface of the photosensitive body is removed by the squeeze means, and the surface of the photosensitive body is passed under the drying device 15. To dry. After the development of yellow is completed, latent images are formed and developed for magenta, cyan and black in the same process. During this time, the heating device 17 is kept away from the surface of the photoconductor.

After a four-color image is formed on the transfer layer 12 of the photoreceptor, the transfer layer 1 is heated by the heating device 17a for thermal transfer.
2 is given a predetermined preheat. As the heating device 17a, for example, an infrared lamp heater or a flash lamp heater that is non-contact is used, and preheating is performed within a range not exceeding the surface temperature of the photosensitive layer obtained by the heating roller 17b. Next, a heating roller 17b containing a heating element having a temperature control means and a cooling roller 17c are pressed against the transfer layer 12 via the material 16 to be transferred, and the transfer layer 12 is heated by the heating roller 17b to heat the photoconductor. After the surface toner, together with the transfer layer, is thermally transferred onto the transfer paper, it is cooled by the cooling roller 17c and the series of steps is completed. The heating surface temperature of the photosensitive layer by the heating roller 17b is preferably 50 to 150 ° C, more preferably 80 to 120 ° C.

The rotation speed of the photoconductor 11 is 1 to 20 at the peripheral speed.
It is 0 mm / sec, more preferably in the range of 30 to 100 mm / sec, and may be different in the electrophotographic process and the thermal transfer process. In addition, by stopping the device with the transfer layer formed, the electrophotographic process can be started immediately when the next device is in operation, and the transfer layer protects the surface of the photoconductor 11 to deteriorate the characteristics due to the influence from the external environment. Can also be prevented. Naturally, the above condition settings should be optimized depending on the photoconductor used, that is, the transfer layer, the photoconductor and the support, and the physical properties of the material to be transferred. In particular, the preheating, heating by the roller, and cooling conditions in the thermal transfer step must be determined in consideration of factors such as the glass transition point of the transfer layer, the softening temperature, the fluidity, the tackiness, the film property, and the film thickness.

For example, when the transfer layer that has been softened to some extent by preheating passes under the heating roller, the transfer layer becomes more sticky and adheres to the material to be transferred, but after passing under the cooling roller, the temperature decreases and the fluidization occurs. Since the adhesiveness and the adhesiveness are reduced and the adhesion to the material to be transferred is lowered, the conditions should be set so that the transfer layer 12 together with the toner is separated from the surface of the photoconductor 11.

Next, referring to FIGS. 2 to 4, the transfer layer 12
The developing electrode 20 in the electrodeposition unit 14T for forming the will be described. As shown in FIG. 2, the electrodeposition unit 14T supplies the thermoplastic resin particle dispersion liquid 12a filled in the tank 22 to the surface of the photoconductor 11 by the pump 24, and between the developing electrode 20 and the photoconductor 11. A voltage is applied to generate a potential gradient, and the thermoplastic resin particles are electrodeposited on the photoconductor 11. The dispersion liquid 12a is shown in FIG.
It moves cyclically as shown by the arrow and is repeatedly used.

As shown in the perspective view of FIG. 3, the developing electrode 20 is divided into two along the rotation direction of the photoconductor 11. FIG. 4 is a principle diagram of electrodeposition, in which each split electrode 20
Different voltages V1 and V2 are applied to a and 20b, respectively. Here, the applied voltage has a relationship of V1> V2,
A high voltage is applied to a split electrode (hereinafter, referred to as an upstream split electrode) 20a located on the upstream side in the rotation direction of the photoreceptor 11, and a high voltage is applied to a split electrode (hereinafter, referred to as the downstream split electrode) 20b located at the downstream side in the rotation direction. A low voltage is applied.

Dispersion liquid is supplied between the photoconductor 11 and the developing electrode 20, and while the photoconductor 11 is rotated, each divided electrode 2 is rotated.
When the respective voltages V1 and V2 are applied to 0a and 20b, the thermoplastic resin particles 26 having a charge of the same polarity as the applied voltage in the dispersion liquid adheres to the photoconductor 11. Upstream split electrode 20
By applying a high voltage to a, the deposition rate of particles is increased at the beginning of electrodeposition, and the deposition amount is rapidly increased. Therefore, the particle layer can be brought closer to the target thickness by electrodeposition for a short time while the photoconductor 11 moves the length L1 facing the upstream split electrode 20a.

Although the particle layer 26a has not yet reached the target thickness when the photoconductor 11 has passed through the upstream split electrode 20a, when the photoconductor 11 starts to face the downstream split electrode 20b, particles are further attached. Keep doing Then, the voltage applied to the downstream side divided electrode 20b is set to a voltage that sets the target thickness of the particle layer 26a as the saturated electrodeposition amount so that the particles continue to adhere until the amount of adhesion of the particles becomes saturated.

FIG. 5 is a graph showing the increase of electrodeposition with respect to the electrodeposition time. As shown in FIG. 5A, when the electrodeposition time is the same, the saturated electrodeposition amount is w1 when the applied voltage is V2.
When the applied electrode is V1, the saturated electrodeposition amount is as small as w2. Therefore, it can be seen that the higher the applied voltage, the greater the rate of increase in the electrodeposition amount. Therefore, as described above, the high voltage V1 is applied to the upstream divided electrode 20a, and the downstream divided electrode 2 is
When a low voltage V2 is applied to 0b, as shown in FIG. 5 (b), while electrodeposition is performed by the upstream split electrode 20a to which a high voltage V1 is applied, the increase rate of electrodeposition is large and the purpose is short time T1. It approaches the amount of electrodeposition. Further, while electrodeposition is performed by the downstream divided electrode 20b to which the low voltage V2 is applied, the electrodeposition increase rate is low, but gradually approaches the saturated electrodeposition amount, and a stable electrodeposition amount is obtained. Therefore, according to the present invention, the saturation electrodeposition time can be shortened and a stable electrodeposition amount can be obtained, as compared with the conventional case where the voltage V2 for always obtaining the target electrodeposition amount is applied. .

The developing electrode 20 is divided into two along the rotation direction of the photoconductor 11, but the number of divisions is not limited to this and may be divided into three or more. At that time, the applied voltage is set to be higher for the divided electrodes on the upstream side in the rotation direction of the photoconductor 11. Further, the developing electrode is divided into two, a low voltage is applied to the downstream divided electrode, and the voltage from the high voltage to the low voltage of the downstream divided electrode is gradually reduced linearly or exponentially to the upstream divided electrode. The voltage may be applied so that Further, the developing electrode does not have to have a divided structure, and the resistance is smaller in a portion facing the photoconductor 11 on the upstream side in the rotation direction of the photoconductor 11, and the resistance is smaller on the downstream side in the rotation direction. You may comprise so that resistance may become large so that it may oppose. With this configuration, even if a voltage is uniformly applied to the developing electrode, the potential difference with the photoconductor becomes linearly larger in the portion facing the photoconductor 11 on the upstream side in the rotation direction, and the potential difference on the downstream side in the rotation direction is increased. The potential difference from the photosensitive member linearly decreases toward the portion facing the photosensitive member 11, which is the same as when the applied voltage is changed between the upstream side and the downstream side.

Example 1 In order to uniformly deposit a transfer layer at 2 g / m ² on a photoconductor having a photoconductive layer containing phthalocyanine on the surface of a conductive drum having a diameter of 200 mm and a length of 400 mm, the following method was used. went. The developing electrode has a length of 30 mm along the rotation direction of the photoconductor, and is divided into two along the rotation direction of the photoconductor, and as shown in FIG. 4, L1 = 6 mm and L2 = 24 mm.
And Then, V1 = is applied to each of the divided developing electrodes.
DC voltage of 500V and V2 = 200V was applied to carry out electrodeposition. The distance between the photoconductor and the developing electrode is 1 mm, and the rotation speed of the photoconductor is 30 mm / sec in linear velocity. The following toner was used as the toner. This experiment was conducted in a dark room.

Production Example of Thermoplastic Resin Particles: TL-1 10 g of dispersion stabilizing resin [Q-1] having the following structure, 2 g of vinyl stearyl methacrylate and 3 parts of Isopar H.
While stirring 84 g of the mixed solution under a nitrogen stream, a temperature of 70
Warmed to ° C. 0.8 g of 2,2'-azobis (isovaleronitrile) (abbreviation AIVN) was added as a polymerization initiator, and the reaction was carried out for 3 hours. 20 by adding initiator
White turbidity occurred after a minute and the reaction temperature rose to 88 ° C. Further, 0.5 g of an initiator was added and after reacting for 2 hours, the temperature was raised to 100 ° C. and stirred for 2 hours to distill off unreacted vinyl acetate. After cooling, it was passed through a nylon cloth of 200 mesh, and the obtained white dispersion had a polymerization rate of 90% and an average particle size of 0.23 μm.
It was a mono-dispersed layer fax machine. Particle size is CAPA-50
0 (manufactured by HORIBA, Ltd.).

[0033]

Embedded image

The result according to the first embodiment is indicated by reference character A in FIG. The average electrodeposition amount is 2.02 g / m ² , and the fluctuation range of the electrodeposition amount along the traveling direction is 1.995 to 2.045 g / m ^2.
2 , a uniform release layer was obtained.

Comparative Example Electrodeposition was performed by a conventional method in which the electrodes were not divided. 3 electrodes
The conditions are the same as in Example 1 except that the direct current voltage of 00V was applied. The result of the comparative example is indicated by reference character B in FIG.
The average electrodeposition amount was 2.07 g / m ² , but the fluctuation range of the electrodeposition amount along the traveling direction was 1.970 to 2.170 g / m 2.
² , it was not possible to obtain a uniform release layer. When the rotation speed unevenness of the photoconductor was measured, the speed fluctuation width during one rotation of the photoconductor was 1 mm / sec at the maximum. This is considered to be the cause of the variation in the amount of electrodeposition.

As shown in the graph of FIG. 6, the result A according to the method of the present invention and the result B according to the conventional method have different changes in the electrodeposition amount with respect to the electrodeposition time. Therefore, in the present invention, a stable and uniform release layer can be obtained even if the rotation speed becomes uneven.

[0037]

According to the present invention, since electrodeposition is performed at a high voltage by the upstream electrode at the beginning of electrodeposition, the amount of electrodeposition with respect to the electrodeposition time is large and a large amount of electrodeposition is achieved in a short time. Further, near the completion of electrodeposition, since the target electrodeposition amount by the downstream electrode is the electrodeposition at the voltage which is the saturated electrodeposition amount, a uniform and accurate electrodeposition amount can be obtained. Further, even when the discharge speed of the developing solution supply pump or the rotation speed of the photoconductor is uneven, the electrodeposition amount varies according to the conventional method, but according to the method of the present invention, the electrodeposition is completed at the end of electrodeposition. Since the corresponding saturated electrodeposition amount is obtained, a constant electrodeposition amount can always be obtained even if the developing solution discharge speed or the photosensitive member rotation speed changes.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a wet electrophotographic apparatus.

FIG. 2 is an enlarged view of a main part of an electrodeposition unit.

FIG. 3 is a perspective view of a developing electrode.

FIG. 4 is a principle diagram of electrodeposition.

FIG. 5 (a) is a graph showing a state of electrodeposition by a conventional method,
(B) is a graph showing an electrodeposition state according to the present invention.

FIG. 6 is a graph showing an electrodeposition state of a comparative example and an electrodeposition state of an example of the present invention by a conventional method.

[Explanation of symbols]

 11 Photoreceptor 12 Transfer Layer 12a Thermoplastic Resin Particle Dispersion Liquid 14 Development Unit Set 14T Electrodeposition Unit Set 14C Cyan Development Unit 14M Magenta Development Unit 14Y Yellow Development Unit 14BK Black Development Unit 15 Drying Device 15a Hot Air Blower Fan 15b Exhaust Fan 16 Transferred material 17 Heat transfer device 17a Heating device 17b Heating roller 17c Cooling roller 18 Corona charging device 19 Exposure unit 20 Developing electrode 20a Upstream side split electrode 20b Downstream side split electrode 22 Tank 24 Pump 26 Thermoplastic resin particles (transparent toner) 26a Particle layer

Claims (3)

[Claims] 1. At least an electrophotographic photosensitive member, a developing means for providing a toner image of one or more colors on a transfer layer on the surface of the photosensitive member by an electrophotographic process, and a transfer for thermally transferring the toner image together with the transfer layer onto a transfer target material. In the electrophotographic transfer method using the means, a wet developer in which charged toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid is interposed between a developing electrode and a photoreceptor, The present invention is characterized in that when a peelable transfer layer is formed by electrostatically attaching or electrodepositing particles on the surface of a photoconductor to form a film, electrostatic attachment or electrodeposition is performed up to a saturated attachment state. Wet electrophotographic development method. 2. An electrophotographic photosensitive member, a developing means for providing a toner image of one or more colors on a transfer layer on the surface of the photosensitive member by an electrophotographic process, and a transfer for thermally transferring the toner image together with the transfer layer onto a transfer target material. In the electrophotographic transfer apparatus having the means, the toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid, and a wet type developer is interposed between the developing electrode and the photosensitive member. When the peelable transfer layer is formed by electrostatically adhering or electrodepositing the film on the surface of the photoconductor, the distance between the developing electrode and the photoconductor is constant and Split into 2 or more,
A wet electrophotographic developing apparatus characterized in that a voltage having a higher potential difference with respect to the surface of the photoconductor is applied to a part facing the upstream side in the rotation direction of the photoconductor than to a part facing the downstream side. 3. An electrophotographic photosensitive member, a developing means for providing a toner image of one or more colors on a transfer layer on the surface of the photosensitive member by an electrophotographic process, and a transfer for thermally transferring the toner image together with the transfer layer onto a transfer target material. In the electrophotographic transfer apparatus having the means, the toner particles mainly containing a thermoplastic resin are dispersed in an electrically insulating liquid, and a wet type developer is interposed between the developing electrode and the photosensitive member. When the peelable transfer layer is formed by electrostatically adhering or electrodepositing the film on the surface of the photoconductor, the distance between the developing electrode and the photoconductor is constant and The voltage is applied to the portion facing the downstream side in the rotational direction with a lower potential difference from the surface of the photoconductor than the upstream portion, and the portion facing the upstream side has a potential difference from the high potential difference to the portion facing the downstream side. Up to To liquid electrophotographic developing device and applying a voltage as a linear or exponentially progressively potential difference is reduced.