JP3486115B2 - Electrophotographic equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus using a liquid developer.

[0002]

2. Description of the Related Art An electrophotographic apparatus using a liquid developer has an advantage that cannot be realized by a dry type electrophotographic apparatus, and its value is being reviewed in recent years. That is, since it is possible to use extremely fine toner of submicron size,
It is possible to realize high image quality, it is economical because a sufficient amount of image density can be obtained with a small amount of toner, and it is possible to achieve a texture similar to printing (for example, offset printing), and it is possible to fix toner on paper at a relatively low temperature to save energy. That is, the main advantage of wet electrophotography over dry electrophotography.

On the other hand, the conventional wet electrophotographic technique using liquid toner includes the following essential problems, and therefore, the dry technique has been allowed for a long time. First, in order to develop an electrostatic latent image, a liquid developer using a high resistance or insulating petroleum solvent as a carrier solvent must be used, and the odor or allergic effect on the human body due to the volatilization of this solvent. Was a problem. The second problem is that a large amount of solvent adheres to the latent image at the same time as the toner in the development process, so the process of squeezing the excess solvent after development, the process of removing excess toner floating in the solvent, and the transfer / transfer It is necessary to surely collect and remove the solvent vapor evaporated in the air in all the processes including the fixing process.

The third problem is that since development and post-treatment of development are mainly carried out by electrophoretic development of toner particles in a solvent, the development gap and the gap between the squeezing roller and the latent image holding member are extremely small. It is necessary to set a small value and with high accuracy to realize a high electric field.

To solve such problems, the liquid developer layer carried on the developer carrying member is held in a non-contact state with the latent image holding member, and the developer is attached only to the image area. A so-called liquid non-contact developing method has been proposed.

The concept of such a liquid non-contact developing method is described in, for example, US Pat. Nos. 4,202,913 and 4,202,
No. 620, No. 4,982,692, No. 5,622,8
No. 05, JP-A-5-35116, and JP-A-5-142950.
No. 5,346,692. In these methods, since the developer does not adhere to the non-image area or the background area of the latent image, it is possible to significantly reduce the amount of the solvent adhering to the latent image carrier, which causes the above problems. On the other hand, it can be said that it gives one solution.

However, according to the follow-up experiments conducted by the present inventors,
It was revealed that the following problems still remain in these methods. First, in these liquid non-contact developments, the latent image electric field causes the developer to extend toward the latent image from the surface of the relatively smooth developer carrier,
Development is carried out by making the tip of the extended developer reach the latent image surface, but it has been revealed that such a phenomenon does not occur easily under normal developing conditions. In order for the developer to overcome the surface tension and expand, it is necessary to concentrate an extremely strong electric field, and under the above developing conditions, a practically sufficient electric field strength cannot be obtained.

In Japanese Unexamined Patent Publication No. 5-346692, unevenness is formed on the surface of a developer carrier, and a liquid developer is carried in the recesses, and at the same time, the liquid developer is extended toward a latent image for development. Although a method has been disclosed, the electric field concentration is still insufficient with such unevenness, the elongation of the developer tends to be unstable, and it is difficult to obtain stable developing characteristics.

Even when this extension phenomenon occurs, a channel due to this extension phenomenon is formed between the developer layer on the surface of the developer bearing member and the latent image holding member, so that the solid content (toner particles) is increased. In addition, a relatively large amount of solvent also adheres to the latent image, and when outputting a pattern with a large image area, the conventional environmental problem due to solvent volatilization remains a problem.

On the other hand, a needle-shaped electrode is provided on the surface of the developer carrying member (Japanese Patent Laid-Open No. 2302304) or a known magnetic brush is provided (Japanese Patent Laid-Open No. 5-241451).
Then, an attempt is made to solve the above problems by increasing the concentration of the electric field and thereby causing the droplet to fly to the latent image surface.

However, according to the test by the present inventors, even if the electric field is concentrated, the developer is not transported to the electrode tip position by this, and depending on the positional relationship between the developer and the electrode tip, the liquid droplet may be dropped. However, it was found that the developing characteristics were extremely unstable.

[0012]

As described above, in the electrophotographic apparatus using the conventional liquid developing technique, a large amount of the harmful solvent contained in the developer adheres to the latent image holding member and is out of the machine. However, no effective means for preventing this has yet been found. The present invention has been made under such circumstances, and an object of the present invention is to provide an electrophotographic apparatus capable of suppressing the adhesion and release of the developer solvent to the minimum.

[0013]

SUMMARY OF THE INVENTION A first invention is a latent image forming means for forming an electrostatic latent image on a latent image holding member, and a visible image by supplying a liquid developer to the electrostatic latent image. An electrophotographic apparatus having a developing means for converting the developing means into a developer carrying body having a large number of conductive protrusions on its surface and carrying and moving the liquid developer. Means for supplying the liquid developer to the body, means for arranging the conductive protrusions at a predetermined interval so as not to contact the latent image holding member,
And a means for forming a concentrated electric field between the latent image holding member and the protrusion, and a region or a foam having an affinity for the solvent contained in the liquid developer at the tip of the conductive protrusion. A body is formed, and the developing means develops the electrostatic latent image by causing droplets of the liquid developer to fly from the conductive protrusion to the latent image carrier by the concentrated electric field. An electrophotographic device is provided.

A second invention comprises a latent image forming means for forming an electrostatic latent image on a latent image holding member and a developing means for supplying a liquid developer to the electrostatic latent image to form a visible image. In the electrophotographic apparatus, the developing means has a large number of flexible protrusions on its surface, and carries a developer carrying the liquid developer, and the developer carrying body carries the liquid developer. Means for supplying an agent, means for arranging the tip of the flexible projection so as to make light contact with the latent image carrier, contact with the latent image carrier
Remove the solvent of the developer at the tip of the flexible protrusion before
Means comprises means for forming a focused electric field between the flexible protrusions and said latent image carrier, wherein the electric field concentrates, before
The liquid developer is moved along the flexible protrusion,
Provided is an electrophotographic apparatus, which transfers the electrostatic latent image from a tip portion and develops the electrostatic latent image.

The first and second sources configured as described above
According to the statement, an electrophotographic apparatus can be obtained in which the adhesion and release of the developer solvent can be suppressed to the minimum.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows an electrophotographic apparatus according to an embodiment of the present invention. In FIG.
The latent image carrier 1 is composed of a photosensitive drum in which an organic or amorphous silicon photosensitive layer is provided on a conductive substrate. The latent image carrier 1 is uniformly charged by a well-known corona charger or scorotron charger 2a, and then exposed to an image-modulated laser beam 3a to form an electrostatic latent image on its surface.

Thereafter, the developing device 4 for containing the liquid developer
The electrostatic latent image is visualized by a. The liquid developer or toner attached to the electrostatic latent image may be directly transferred to the transfer process and transferred to the paper by the transfer device 5, but here, the second charger 2b and the second laser exposure 3b continue. A first electrostatic latent image is formed on the first developing device 4
This is developed by the second developing device 4b that stores the second developer of a color different from the liquid developer stored in a. Therefore, after the second development, two color toner images are formed on the latent image carrier 1.

Similarly, the third and fourth developments are carried out,
A full-color toner image is formed on the latent image carrier 1.
This toner image is transferred to the paper by the transfer device 5, but at that time, it may be directly transferred to the paper or may be transferred to the paper 9 via the intermediate transfer medium 6 as illustrated in FIG. May be. Transfer from the latent image carrier 1 to the intermediate transfer medium 6,
Also, in the transfer from the intermediate transfer medium 6 to 9, either transfer by electric field or transfer by pressure (and heat) can be used.

In general, many liquid developers can be fixed on a sheet at room temperature, but the pressure roller 7 may be heated to fix the liquid developer by heat. Such an image forming process is described in, for example, US Pat. No. 5,570,173 and US Pat.
It is disclosed in Japanese Patent No. 0,675 and the like and is a conventionally known process.

FIG. 2 shows an embodiment according to the first invention.
An enlarged view of the developing devices 4a to 4d is shown. The developing device 21 shown in FIG. 2 includes a developer container 23 that stores a liquid developer 22.
And a developer carrier 25 that carries a developer and supplies the developer to the latent image carrier 24.

The developer carrying member 25 comprises a conductive roller base 26 and a large number of needle-like or fibrous protrusions 27 formed on the outer periphery thereof. The protrusion 27 is preferably formed of a conductive material, but is formed of a material having a resistance in the range of 10 ⁶ to 10 ¹⁵ Ω · cm in order to prevent dielectric breakdown due to electric field concentration and air discharge. Is also good.

The developer carrying member 25 is supported so that the tips of the projections 27 face the latent image holding member 24 with a slight gap, and the same direction or the opposite direction to the latent image holding member 24. It rotates at a predetermined speed. The developer carrier 25 is
Since a part thereof is submerged in the liquid developer in the developer container 23, the developer is held in the space between the plurality of protrusions 27 by surface tension, and the latent image holder is rotated by the rotation of the developer carrier. It is conveyed to a position facing 24.

FIG. 3 shows how the liquid developer transported to the developing position is transferred to the latent image carrier. Here, a developer carrier 34 in which a large number of conductive needle-like or fibrous electrodes (hereinafter, abbreviated as needle-like electrodes) 33 are arranged on the surface of the roller base 31 by the adhesive layer 32 is exemplified.

The tips of the plurality of needle electrodes 33 are made of a material having a high affinity with the solvent of the liquid developer 34 (a lyophilic material), that is, a lyophilic surface 38 is formed.
Thereby, the developer is held on the lyophilic surface 38 at the tip of the needle electrode 33.

As a developer, a well-known petroleum-based insulating solvent (for example, Isopar L, Norper 12 (both trade names: manufactured by Exxon Co.)) and charged particles (toner particles) dispersed therein are used. In the case of using a structured material, a hydrophilic material, for example, a metal material such as stainless steel, iron, aluminum, or brass, or a polymer material such as NBR rubber or urethane rubber, is used as a material for the tip of the needle electrode. When the medium surface 38 is formed, the developer can be reliably retained.

Further, the region other than the tip of the needle electrode is made of a material having a low affinity for the solvent (non-philic material), for example, a fluorine-based material or a silicone-based material, and the non-philic surface 39. Then, the effect of holding the developing solution at the tip of the needle electrode can be significantly enhanced. At this time, it is desirable that the surface region from 0.5 mm to 3 mm from the tip of the needle-shaped electrode is the lyophilic surface 38 and the other surface region is the lyophilic surface 39.

Further, instead of using the lyophilic surface 38 at the tip of the needle-shaped electrode 33, it is also effective to use a foam and store and retain the developer in the cells of the foam.
As the foam, sponge having a cell size of 10 to 500 μm, foam metal, foam ceramic, or the like is suitable.
In order to effectively concentrate the electric field, it is preferable to provide a foam around the metal electrode.

As still another method for holding the developing solution on the tip portion of the needle electrode 33, the developer carrying member is formed into a roller shape,
There is a method of utilizing the centrifugal force generated by rotating the developer carrying roller. When the moving speed of the tip portion of the needle electrode 33 is 50 mm / sec or more, a developer holding effect is exhibited, and when it is 75 mm / sec or more, the developer reaches the developing area while being more surely held at the electrode tip. . However, if the moving speed exceeds 400 mm / sec, the developer may be scattered from the tip of the electrode, so caution is required.

When the electrode approaches the area facing the latent image,
Inside the developer held at the tip, the charged particles move in the direction of the electric field along with the surrounding solvent due to the electrophoretic phenomenon. Since a strong electric field is concentrated at the tip of the needle electrode 33, the developer is concentrated, that is, the solid content in the solvent is aggregated. When a certain amount of solid content is aggregated at the tip portion due to aggregation, this aggregate is torn and separated into droplets 37 that fly, adhere to the latent image, and are developed.

Therefore, on the surface of the latent image holding member 36, a high-concentration developer having a small solvent content adheres only to the image portion. The ratio of the solid content in the developer may reach 90 wt%, and the conventional problem of the solvent adhering to the latent image surface has been completely solved by this technique.

That is, the removal of the adhering solvent on the latent image holding member, the recovery of the volatile solvent, the maintenance of the extremely small developing gap and the squeezing gap, etc. are completely unnecessary in the present invention. The size of the droplets was several tens of microns or less, and an extremely high-definition visible image could be obtained.

Here, the case of using a developer containing charged particles has been exemplified, but the charged particles are not always necessary, and the developer has some conductivity (preferably, the resistivity of the developer excluding the solid content is low). 10 ⁶ Ωcm to 10 ¹⁴ cm
It was also confirmed that the charge injection causes the developer to move and fly in the electric field direction.

Further, as shown in FIG. 1, a process of overdevelopment / collective transfer, that is, a system in which a color image is formed on a latent image carrier and then collectively transferred (hereinafter, this process is referred to as "I
In the OI (= Image on Image) process ”), this developing method exhibits a particularly remarkable effect. For example, in the prior art disclosed in US Pat. No. 5,570,173, a conventional liquid developing method is used in which a developer layer on the surface of a developer carrying member is brought into contact with a latent image holding member in the IOI process to perform development. Therefore, in the development of the second and subsequent colors, the problem that the toner image previously adhered to the latent image carrier is stripped off, and the same problem occurs in the step of squeezing the solvent adhered to the latent image carrier after development. There was a problem of stripping. This problem also occurs in the above-described method of developing by stretching the developer,
It was a recognized problem with varying degrees.

On the other hand, in the method of the present invention, the toner of the first color, which has previously adhered to the latent image carrier, is not soaked in the solvent of the developers of the other colors in the development of the second and subsequent colors. You can completely avoid problems such as stripping and color mixing.

As a material for the needle-shaped electrode on the surface of the developer carrying member 34, metals such as stainless steel, iron, aluminum and brass, those subjected to surface treatment such as plating, rayon, acrylic and nylon are used. , Synthetic fibers such as Teflon, natural fibers, animal fur, etc. are applicable.

The length of the needle-shaped electrode can be selected variously, but 10
Range of 0 μm to 5 mm, more preferably 0.5 mm to 3
It is desirable to be in the range of mm. If the needle electrode is too short, the amount of the developer that can be carried becomes too small, and if it is too long, the time required for the developer to reach the tip of the needle electrode becomes long and the development response time becomes too long.

The thickness of the needle-shaped electrode can be variously selected depending on its material, but from the viewpoint of electric field concentration, it is 30 μm to 2 m.
The range of m is more preferable, and the range of 0.1 mm to 1 mm is more preferable. If the needle-shaped electrode is extremely fine, problems occur in mechanical strength, and if it is too thick, electric field concentration weakens. Of course, if the needle electrode has a sharp tip, a thicker electrode can be used.

The arrangement density of the needle-shaped electrodes affects the density of the obtained image. The number per unit area is 4 / c
The range of m ² to 100,000 lines / cm ² is more preferable, and the range of 25 lines / cm ² to 20,000 lines / cm ² is more preferable. If the density of the needle electrodes is low, the apparent resolution can be increased by increasing the rotation speed of the developer carrier, and the number of droplets flying from one needle per unit time can be increased. It is possible to realize a high-definition image by increasing the number of dots, but if the density is extremely low, it is difficult to obtain a practically sufficient resolution even with these methods, and a sufficient amount of space between the needles. It becomes difficult to carry the developer. Further, if the arrangement density is too high, the electric field concentration is weakened by the interaction with the adjacent needles, which is not preferable.

The needle electrode is preferably formed of a conductive material, but a material having a resistance in the range of 10 ⁶ to 10 ¹⁵ Ω · cm in order to prevent dielectric breakdown due to electric field concentration and air discharge. You may comprise by.

The distance between the tip of the needle electrode and the surface of the latent image carrier is in the range of 20 μm to 2 mm, more preferably 50 μm.
It is desirable to set the range to 1 mm. If this distance is too small, the developer will be connected between the developer carrier and the latent image carrier. It is difficult to obtain the effects of the present invention. On the other hand, if it is too large, the electric field is weakened and the flight of droplets becomes insufficient.

The rotation direction of the developer carrying member 34 may be the same as or opposite to the rotation direction of the latent image holding member 36, but in terms of image quality, both rotate in the same direction at the developing position. Often the case is better. If the speed difference between the two is large, the landing point of the developer droplet may deviate from the position at which it should be landed. For the same reason, the speed ratio between the latent image holding member 36 and the developer carrying member 34 is 0.5 when the speed of the latent image holding member is 1.
It is desirable to set to 10, and more preferably 1 to 3. If the speed of the developer carrier is extremely slow, the amount of developer supplied to the latent image becomes too small, and sufficient image density cannot be obtained.

As a method of manufacturing the above-mentioned needle-shaped electrode, as in the above-mentioned embodiment, for example, an epoxy-based adhesive layer is provided on the surface of the development carrier, and the above-mentioned needle-shaped or fibrous substance is added thereto. A method of mechanically implanting, a method of arranging the hair body by a well-known electrostatic flocking method, or a method of implanting the above needles or fibers in a base fabric and forming it into a form called so-called velveteen or velvet What is wound around the surface of the developer carrier is used.

It is desirable that the adhesive or base cloth used in the production of the needle-shaped electrode is electrically conductive, but even if a material having high resistance or insulation is used, the needle or fiber has electrical conductivity. If so, electric field concentration can be realized. In practice, it is necessary to prevent the needles or fibers from falling off or falling, so care must be taken in selecting the adhesive and its thickness.

Although a needle-shaped or fibrous electrode is used as an example of the projection here, various other configurations can be adopted. For example, a conical or pyramidal protrusion may be provided on the surface of the developer carrying member, or a knife-edge-shaped protrusion having a sharp tip with a constant length can achieve the same effect. Those separately prepared may be attached to the developer carrying member, or the surface of the developer carrying member may be processed by etching, machining, sand blasting or the like to form the protrusions. In any case, it is an essential requirement to have an electrical structure capable of supporting the developer and flying the developer by concentrating the electric field.

The potential conditions for the developer carrying member 34 and the latent image holding member 36 are preferably set as follows. First,
As the latent image potential, it is possible to apply the potential conditions for a normal electrophotographic photosensitive member. That is, the potential after charging by the charger is 300V to 1000V, preferably 50V.
0V to 800V can be used. Here, a case of a so-called reversal development process in which the photoconductor and the toner are both positively charged and the toner is attached to the exposed portion of the photoconductor is illustrated, but the principle is the same for the normal development and the negative charge polarity.

In order to obtain sufficient flight of the developer, at least 500 V is applied between the needle electrode 33 and the latent image carrier 36.
/ Mm electric field, more preferably 1000 V / mm to 80
It is necessary to form an electric field of 00 V / mm. Therefore, for example, when the distance between the tip of the protrusion and the latent image carrier is 0.3 mm, the potential difference between the protrusion and the latent image is 150 V or more, preferably 300 V to 2400 V.
Therefore, in this case, the potential of the exposed portion of the photoconductor is 100
If it is V, it is desirable to set the potential of the protrusion to 250 V or more, preferably 400 V to 2500 V.

By superimposing an AC voltage on the DC voltage applied to the protrusions, the flying characteristics of the developer and the image quality are improved. For example, when the gap between the protrusion and the latent image carrier is 0.3 mm, when a DC bias voltage is superimposed with an AC voltage having a frequency of 1 kHz and a peak value difference of 1.0 KV, the DC voltage becomes 300.
Even at about V, a sufficient amount of developer flies. At the same time, the developer adhered to the latent image or the toner particles in the developer realigns along the latent image electric field while undergoing oscillating motion, so that the image quality is significantly improved. Two kinds of phenomena were observed in this vibration, that is, the case where the solid particles covered with the solvent vibrate, and the case where the solid content oscillates inside the solvent layer attached to the latent image carrier. The improvement in image quality was more noticeable in the latter phenomenon.

The AC voltage has a peak value difference of 200 V to 20 V.
00V is preferable, and more preferably 500V to 1500
V or less, the frequency is 400 Hz to 10 kHz,
More preferably, it is 1 kHz to 5 kHz.

Further, in order to suppress air discharge due to electric field concentration on the protrusion, it is desirable to supply a voltage to the protrusion through a protective resistance of 1 MΩ to 10 MΩ. Next, FIG. 4 shows a main part of an electrophotographic apparatus as an embodiment according to the second invention. The whole image of the electrophotographic apparatus is the same as that shown in FIG.

In FIG. 4, a large number of flexible fibrous hairs 42 are arranged on the outer periphery of the developer carrying body 41, and these hairs lightly contact the latent image holding body 43 at the developing position. is doing. The hair body 42 is made of, for example, synthetic fibers such as rayon, acrylic, nylon, or Teflon, natural fibers, or animal fur. Developer carrier 41
Rotates in the direction of the arrow in the figure or in the opposite direction, the liquid developer 44 is conveyed by the hair 42 and reaches the developing position.

At the developing position, an electric field formed between the developer carrying member 41 and the latent image holding member 43 causes the developer to move along the hair body and adhere to the latent image. Immediately before reaching the developing position as shown in FIG. 5, it is desirable that the developer be carried at a position closer to the root than the tip of the hair.

In such a situation, even if the hair body comes into contact with the latent image carrier, the solvent adhered to the non-image area is extremely small, and the problem of solvent adhesion in conventional liquid development is greatly improved. Because it is done. In order to realize such a situation, it is desirable to add a removing member 45 that removes the developer adhering to the tip of the hair body before reaching the developing position.

The removing member 45 may be, for example, a foaming roller having a high ability to absorb a solvent, or a plate-like or rod-like member that simply contacts the tip of the hair and limits the amount of the developer conveyed. good. Of course, such a removing member 4
Even if the development is carried out in a state where the developer is also attached to the vicinity of the tip of the hair body without installing 5, the amount of the solvent attached to the latent image carrier is smaller than that in the conventional liquid developing method. In the latter stage of development,
This is because the solvent once attached to the latent image carrier is reabsorbed by the developer carrier due to the capillary phenomenon or surface tension in the space between the hair bodies. Also in this case, the combined use of the AC bias voltage gives good results.

FIG. 6 shows an embodiment according to the third invention.
The periphery of the developing device 61 is illustrated. A liquid developer is stored in the developer container 62, and the developer carrier 63 is rotatably supported so as to be immersed in the developer. The developer carrying member 63 is a magnet roller 64 having a magnetic pole on its surface.
And a non-magnetic sleeve 65 concentrically arranged outside the magnet roller 64 and rotatably supported.

The magnet roller 64 may be fixed or rotatably driven, but it is more preferable that one of the magnetic poles is fixed at the developing position. Magnetic particles 66 are held by the magnetic force on the surface of the sleeve 65, and a known magnetic brush made of a group of magnetic particles is formed near the magnetic poles of the magnet roller 64.

When the sleeve 65 is rotated with such a structure, the developer 67 is carried between the magnetic particles and is conveyed to the developing position. At the developing position, either a non-contact developing method in which the magnetic brush confronts the latent image holding body 68 with a certain gap or a contact developing method in which the magnetic brush is brought into contact may be adopted. Is more preferable.

The magnetic particles 66 have a particle size of 10 to 100 μm.
A carrier having a thickness of about m is suitable, and a well-known carrier used for dry type two-component magnetic brush development can be used. If the particle size is too small, there is a problem that the magnetic particles adhere to the latent image surface, and if it is too large, the density of the image is lost.
The shape of the magnetic particles 66 may be spherical, rod-shaped, plate-shaped, or amorphous, but in order to enhance the concentration of electrolysis,
A rod shape or a spherical shape is more preferable.

In the case of non-contact development, the distance between the tip of the magnetic particle group and the latent image carrier 68 is preferably in the range of 20 μm to 2 mm, more preferably 50 μm to 1 mm. In addition, the electrical resistance value of the magnetic particles, the rotation speed of the sleeve, the developing potential condition, etc. are in accordance with the configuration described in the embodiment according to the first invention. In addition, the solvent adhesion to the latent image carrier can be effectively suppressed, and stable development characteristics can be obtained by the electric field concentration.
It is realized by the same principle as the invention of.

The magnetic particles are superior to the needles and hairs of the first and second inventions in that they have a high degree of freedom. That is, since the needle and the hair are fixed to the developer carrier,
The solid content in the liquid developer precipitates and agglomerates at these root parts. It may adversely affect the development characteristics,
The magnetic particles are only held by magnetic force, and if a scraper is arranged, the particles can be once peeled off from the developer carrying member. Therefore, it has the advantage that precipitation and agglomeration of the solid content is unlikely to occur and is unlikely to be affected by it.

Also in this case, by forming the surface of the magnetic particles with a lyophilic material, the developer can be reliably held at the tip of the magnetic particle group. In addition, the magnetic particles (amphiphilic magnetic particles) whose surface is made of an amphiphilic material and the non-amphiphilic magnetic particles are mixed in a ratio of 1: 4 to 3: 1 (amphiphilic magnetic particles: non-philic particles). By using a mixture having a ratio of about amphiphilic magnetic particles), the developer can be more reliably held at the tip of the magnetic particle group.

[0061]

As described above, according to the present invention,
Since it is possible to minimize the adhesion of the solvent to the latent image carrier and the paper, it is possible to prevent the solvent from being discharged to the outside of the machine, and a safe and high-performance wet electrophotographic apparatus that can be used even in the office. It is possible to provide. Further, since a device for squeezing a large amount of the solvent adhering to the latent image carrier and a device for removing the toner particles floating in the non-image area are unnecessary,
A simple electrophotographic device can be realized. Further, since the electric field concentration effect is obtained, it is not necessary to maintain the minute gap with high precision, and a device having excellent practicability can be realized. Furthermore, when non-contact development is adopted, ideal characteristics without peeling of toner and color mixture can be obtained even in a so-called IOI (= Image on Image) process of over-development / collective transfer. Also,
In the first and third inventions, the liquid developer is securely held at the tip of the electrode or the tip of the magnetic substance particle group.
A great effect such as stable flight characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing an electrophotographic apparatus according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a main part of the electrophotographic apparatus according to the first invention.

FIG. 3 is an enlarged sectional view showing a developing portion of the electrophotographic apparatus according to the first invention.

FIG. 4 is a sectional view showing a main part of an electrophotographic apparatus according to a second invention.

FIG. 5 is an enlarged view showing a developing portion of the electrophotographic apparatus according to the second invention.

FIG. 6 is a sectional view showing a main part of an electrophotographic apparatus according to a third invention.

[Explanation of symbols]

1, 24, 36, 43, 56, 68 ... Latent image carrier 2a, 2b, 2c, 2d ... Charger 3a, 3b, 3c, 3d ... Laser exposure 4a, 4b, 4c, 4d ... Developing device 5 ... Transfer device 6 ... Intermediate transfer medium 7 ... Pressure roller 8 ... Cleaner 9 ... Paper 21, 46, 61 ... Developing device 22, 35, 44, 67 ... Liquid developer 23, 46, 62 ... Developer container 25, 34, 41, 54, 63 ... Developer carrier 26, 31, 47, 51 ... Roller base 27 ... Projection 32, 52 ... Adhesive layer 33, 53 ... Needle-shaped electrodes 38 ... Amphiphilic surface 39 ... Non-philic surface 42 ... Hair body 64 ... Magnet roller 65 ... Sleeve 66 ... Magnetic particles.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Sasaki 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Toshiba Research & Development Center Co., Ltd. (72) Hirohisa Miyamoto Komu-Toshiba-cho, Kawasaki-shi, Kanagawa No. 1 in Toshiba Research & Development Center (72) Inventor Koichi Tsunemi Komukai Toshiba-cho, Komukai-ku, Kawasaki-shi, Kanagawa No. 1 in Toshiba Research & Development Center (56) Reference JP-A-58-173771 (JP, A) ) JP-A-57-38470 (JP, A) JP-A-54-155055 (JP, A) JP-A-9-269665 (JP, A) JP-A-9-230704 (JP, A) JP-A-1- 277874 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G03G 15/10

Claims (2)

(57) [Claims] 1. An electrophotographic apparatus comprising: a latent image forming means for forming an electrostatic latent image on a latent image holding member; and a developing means for supplying a liquid developer to the electrostatic latent image to form a visible image. The developing means has a large number of conductive protrusions on the surface thereof, and carries a liquid developer carrying the liquid developer, and means for supplying the liquid developer to the developer carrying body. And a means for arranging the conductive protrusions at a predetermined distance so as not to contact the latent image carrier, and a means for forming a concentrated electric field between the latent image carrier and the protrusions, A region or a foam having an affinity for the solvent contained in the liquid developer is formed at the tip of the conductive protrusion, and the developing unit causes the latent image from the conductive protrusion by the concentrated electric field. The liquid droplets of the liquid developer are made to fly to a holding body to form the electrostatic latent image. An electrophotographic apparatus, which develops an image. 2. An electrophotographic apparatus having a latent image forming means for forming an electrostatic latent image on a latent image holding member, and a developing means for supplying a liquid developer to the electrostatic latent image to form a visible image. The developing means has a large number of flexible projections on its surface, and carries a liquid developer carrying the liquid developer, and supplies the liquid developer to the developer carrying body. Means, means for arranging the tip of the flexible protrusion so as to lightly contact the latent image holder, solvent of the developer at the tip of the flexible protrusion before contact with the latent image holder And a means for forming a concentrated electric field between the latent image holding member and the flexible protrusion, and the concentrated electric field causes the liquid developer to move along the flexible protrusion. An electron characterized by being moved, transferred from the tip portion to the electrostatic latent image, and developing the electrostatic latent image. True apparatus.