JP2009229717A - Developing device, electrophotographic device, and developing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device and an electrophotographic device in which costs are reduced by simplifying a device, and service lives are extended by improving a printing quality. <P>SOLUTION: The developing device 14 applied to the electrophotographic device includes: a tank 21 which stores liquid toner; a supply roller 22 which draws the liquid toner of the tank 21; a developing roller 23 which comes into opposite contact with the supply roller 22 and receives the liquid toner from the supply roller 22; a uniformizing blade 24 which makes the liquid toner supplied to the circumferential surface of the developing roller 23 uniform; a voltage applying device 25 which applies a bias voltage to the developing roller 23; and an electrifying device 51 which electrifies the liquid toner supplied to the circumferential surface of the developing roller 23. Roller moving directions in the opposite contact part A between the supply roller 22 and the developing roller 23 are set to the same. The film thickness of the liquid toner moved from the developing roller 23 to a photoreceptive drum 11 is previously made uniform, and then, a corona discharge is performed to improve quality. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device and a developing method for supplying a charged liquid toner to a photosensitive drum to form a toner image, and an electrophotographic apparatus for transferring and fixing a toner image formed by the developing device onto a sheet. is there.

  Conventionally, in an electrophotographic apparatus, a uniformly charged photoconductor is irradiated with light from a light source such as a laser or an LED (Light Emitting Diode), and the image area where the light hits is neutralized to electrostatic latent in the photoconductor. An image is formed, and a toner charged to the same polarity as the charged polarity of the photosensitive member is attached to the image line portion to form an image.

  As the toner to be used, there are a powder toner and a liquid toner, and a two-component developing system is known as a method for attaching the powder toner to the photoreceptor. In the two-component development method, a magnetic brush of a carrier (for example, a particle size of 40 to 120 μm), which is a magnetic particle, is formed by a magnetic force on a developing roll (magnet roller) composed of a multipolar magnet, and the surface of the photoreceptor is covered with this brush. In this method, powder toner (for example, particle size of 6 to 20 μm) adhering to the carrier surface by rubbing is developed on the photoreceptor.

  In these methods, a developer in which a carrier and powder toner are mixed at a constant ratio is adhered to the entire surface of the developing roll, and the amount of adhesion is made constant by a gap between the regulating blades, and is supplied to a gap formed between the photosensitive member and the developing roller. Rub on the photoreceptor. At this time, an electrostatic latent image corresponding to the image data is formed on the photosensitive member, and the electrostatic force generated by the potential difference from the charged powder toner is used to draw the powder toner from the carrier in the image area. Is peeled off and attached to the photosensitive member side, and the toner is not attached to the photosensitive member by a repulsive force in the non-image area. In this way, a toner image (image) corresponding to the electrostatic latent image is formed on the photoreceptor.

  Further, as a device for adhering liquid toner to a photosensitive member, a conventional electrophotographic device includes a photosensitive drum, a charging device that charges the photosensitive drum, an exposure device that exposes an image on the photosensitive drum, and a static drum. A developing device that supplies charged liquid toner to a portion where the electrostatic latent image is formed to visualize the electrostatic latent image, a transfer drum that transfers the toner image formed on the photosensitive drum to the paper, and a paper And a fixing device for fixing the transferred toner image.

  Liquid toner is transferred to the developing roller by the supply roller, and a thin liquid toner layer is formed on the developing roller. Then, the liquid toner layer on the developing roller is brought close to the electrostatic latent image formed on the surface of the photosensitive drum, and the toner layer charged by applying a voltage of the same polarity as the toner to the developing roller is moved onto the photosensitive drum, thereby A toner image is formed on the drum. The toner image formed on the photosensitive drum is primarily transferred to a transfer device, further transferred onto a sheet, and the toner image transferred onto the sheet by a fixing device is thermally melted and fixed. This liquid toner is a toner (carrier) mixed with a toner made of pigment, resin, etc., and has a high concentration and a high viscosity.

  Then, the surface of the photosensitive drum is charged in advance by a charging device, the image is exposed on the photosensitive drum charged by the exposure device to form an electrostatic latent image, and the liquid toner layer supplied on the developing roller is removed from the liquid toner layer. By bringing the toner image close to the electrostatic latent image on the photosensitive drum, a toner layer charged by applying a voltage having the same polarity as the toner to the developing roller is moved onto the photosensitive drum to form a toner image.

  As described above, according to the developing device of the conventional electrophotographic apparatus, the liquid toner contains toner particles having charging characteristics, and the liquid toner is transferred to the developing roller by the supply roller. A thin liquid toner layer is formed, and the liquid toner layer on the developing roller is moved onto the photosensitive drum by applying a voltage having the same polarity as the toner to the developing roller to form a toner image.

  An example of the configuration of a developing device of a conventional electrophotographic apparatus is shown in FIG. As shown in FIG. 6, in the developing device 100A of the conventional electrophotographic apparatus, the surface of the photosensitive drum 102 is charged with a polarity corresponding to the toner characteristics by a conductive blade 101 as a charging device, and charged by an exposure device (not shown). An image is exposed on the drum 101. On the other hand, the toner is supplied to the two application rollers 104 and 105 from the toner supply port 103, and the liquid toner is spread widely to form a uniform and thin layer and applied to the surface of the developing roller 106. As a result, a thin liquid toner layer is formed on the developing roller 106. The conductive blade 101 provided on the outer periphery of the developing roller 106 has appropriate elasticity, and the end surface of the conductive blade 101 is brought into contact with the developing roller 106 in the forward direction.

  A voltage having the same polarity as the toner polarity and a bias voltage (for example, +1300 V) are applied from the power supply apparatus 108 to the conductive blade 101 with respect to the developing bias voltage (for example, +450 V) from the power supply apparatus 107. As a result, the toner having the same polarity as the bias voltage repels and moves to the surface of the developing roller 106 to become a compacted normal state. A state in which the toner particles contained in the toner are sparse is formed. Thus, the toner layer is prevented from being disturbed, and development is performed while the uniform toner layer is in contact with the image support. An excessive toner layer is recovered by a toner recovery blade 109 (see Patent Document 1).

  FIG. 7 shows another configuration of the developing device of the conventional electrophotographic apparatus. As shown in FIG. 7, in another conventional developing device 100B of an electrophotographic apparatus, liquid toner stored in a tank (not shown) is supplied to a developing roller 106 by a supply roller 111 via a leveling roller 112, and the developing roller A thin liquid toner layer is formed on 106. Further, the surface of the photosensitive drum 102 is charged in advance by the charging device 113, and an image is exposed on the photosensitive drum 102 charged by an exposure device (not shown) to form an electrostatic latent image. Then, the liquid toner layer on the developing roller 106 is brought close to the electrostatic latent image formed on the surface of the photosensitive drum 102, the toner layer charged by electrostatic force is moved onto the photosensitive drum 102, and the toner is placed on the photosensitive drum 102. An image is formed, the toner image formed on the photosensitive drum 102 is transferred to a sheet, and the toner image transferred onto the sheet is thermally fused and fixed by a fixing device (not shown). This liquid toner is a powder toner mixed in a solvent, and has a high concentration and a high viscosity. The supply roller 111 uses an anilox roller having a large number of honeycomb-shaped concave portions on the outer peripheral surface (see Patent Document 2). In FIG. 7, reference numeral 114 denotes a housing, and 115 denotes a tungsten wire (discharge electrode).

  According to the developing device 100B of the electrophotographic apparatus, when the supply roller 111 immersed in the liquid toner is rotated, the liquid toner adheres to a large number of recesses, so that the liquid toner stored in a tank (not shown) is supplied by the supply roller 111. Can be pumped up. Liquid toner stored in a tank (not shown) is pumped up by the supply roller 111 and supplied to the leveling roller 112, and is transferred from the leveling roller 112 to the developing roller 106, whereby a thin layer of liquid toner is formed on the developing roller 106. Forming a layer.

  Further, the liquid toner layer formed on the developing roller 106 is in a state where toner particles having charging characteristics in a solvent are floating, and when the liquid toner layer is moved onto the photosensitive drum 102 by electrostatic force, the toner particles Inadequate adhesive strength is likely to result in a non-uniform film thickness of the toner image, which may reduce the quality. On the other hand, by causing the leveling roller 112 and the developing roller 106 to rotate in the reverse direction, the excess liquid toner layer is scraped off to eliminate the phenomenon of uneven stripe-like film layers such as a ring pattern and a living room. ing.

Japanese Patent No. 3806135 JP 2007-171529 A

  Here, in the developing device 100A of the electrophotographic apparatus described in Patent Document 1, the rotation direction at the contact portion 110 between the application roller 105 and the developing roller 106 is the same direction, and is necessary for the life of the parts, nip adjustment, and driving. Torque reduction is possible.

  However, when developing by applying a voltage to the conductive blade 101, changing the bias to change the development amount or the like changes the carrier film thickness, and changes the solid content and carrier liquid state in the toner layer. Further, since the film thickness of the toner image changes and becomes non-uniform due to the elasticity of the conductive blade 101, there is a problem that it is necessary to perform development separately from voltage application and corona.

  Further, in the developing device 100B of the electrophotographic apparatus described in Patent Document 2, by rotating the rotating direction at the contact portion 116 between the leveling roller 112 and the developing roller 106 in the reverse direction, the service life of the parts is shortened. There is a problem that nip adjustment is required and torque (motor capacity) required for driving is increased.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to provide a developing device and an electrophotographic apparatus that can simplify the apparatus, reduce costs, improve printing quality, and extend the service life. And

  A first aspect of the present invention for solving the above-described problem is a tank in which liquid toner of a predetermined concentration is stored, and a supply roller capable of pumping up the liquid toner by being partially immersed in the liquid toner in the tank. A developing roller that comes into contact with the supply roller and receives liquid toner from the supply roller, a leveling blade that uniformly supplies the liquid toner supplied to the outer peripheral surface of the development roller, and a bias voltage applied to the development roller And a charging device for charging the liquid toner supplied to the outer peripheral surface of the developing roller, and the roller moving direction at the contact portion between the supplying roller and the developing roller is set in the same direction. The developing device is characterized in that:

  A second invention is the developing device according to the first invention, wherein the charging device is provided between the blade and a photosensitive drum.

  According to a third aspect of the invention, there is provided the developing device according to the first or second aspect, wherein the charging device is provided at a position that is not in contact with the liquid toner.

  A fourth invention is the developing apparatus according to any one of the first to third inventions, wherein the supply roller is a metal anilox roller having a number of concave portions on a surface portion.

  A fifth invention is the developing device according to any one of the first to fourth inventions, wherein the carrier agent of the liquid toner is mineral oil.

  According to a sixth aspect of the present invention, there is provided a developing device according to any one of the first to fifth aspects, a photosensitive drum that is in contact with the developing roller and receives liquid toner, and a photosensitive drum that charges the outer peripheral surface of the photosensitive drum. An apparatus, an exposure device that exposes an image on the charged photosensitive drum, a transfer drum on which the toner image is primarily transferred in contact with the photosensitive drum, and the paper sandwiched between the transfer drum and the paper An electrophotographic apparatus comprising: a secondary transfer roller for secondary transfer of the toner image; and a fixing device for fixing the toner image secondarily transferred onto the paper.

  A seventh invention is a photosensitive drum in which the liquid toner is supplied to the surface of the developing roller using the developing device of any one of the first to fifth inventions, and an electrostatic latent image is formed on the developing roller. And developing the electrostatic latent image in contact with a toner.

  According to an eighth aspect of the present invention, there is provided a developing method in which a liquid toner having a predetermined concentration is carried on a developing roller in a thin film form, the liquid toner is supplied to a photosensitive drum on which an electrostatic latent image is formed, and the electrostatic latent image is developed. The leveling blade provided on the outer peripheral surface of the developing roller, which is in contact with the supply roller, delivers the liquid toner pumped up by the supply roller to the developing roller in which the roller moving direction at the contact portion with the supply roller is the same direction Then, the liquid toner supplied to the developing roller is uniformly leveled, and then the uniformly leveled liquid toner on the outer peripheral surface of the developing roller is charged.

  According to the developing device of the first aspect of the present invention, a tank in which liquid toner of a predetermined concentration is stored, a supply roller that is partially immersed in the liquid toner in the tank, and the liquid toner can be pumped up, and the supply roller A developing roller to which liquid toner is delivered from the supply roller, a leveling blade for uniformizing the liquid toner supplied to the outer peripheral surface of the developing roller, and a voltage application for applying a bias voltage to the developing roller And a charging device for charging the liquid toner supplied to the outer peripheral surface of the developing roller, and the roller moving direction at the contact portion between the supplying roller and the developing roller is set in the same direction. For this reason, since the liquid toner can be directly supplied from the supply roller to the developing roller rotating in the same direction as the supply roller, the apparatus can be simplified, the cost can be reduced, the torque can be reduced, and the length can be reduced. Life can be extended.

  Further, after the liquid toner supplied to the outer peripheral surface of the developing roller is uniformly leveled by the leveling blade, toner particles are uniformly charged on the entire liquid toner by corona discharge. Therefore, the film thickness of the liquid toner on the developing roller can be easily made uniform with a simple configuration, and the toner particles of the charged liquid toner layer are arranged on the photosensitive drum while being in close contact with each other. It can be moved and quality can be improved.

  According to a developing device of a second aspect of the present invention, since the charging device is provided between the leveling blade and a photosensitive drum, the liquid toner is moved onto the photosensitive drum before the liquid toner is moved. After the liquid toner is uniformly leveled in advance, the toner particles can be uniformly charged over the entire liquid toner by corona discharge.

  According to the developing device of the invention of claim 3, since the charging device is provided at a position that is not in contact with the liquid toner, the toner particles can be uniformly charged over the entire liquid toner. it can.

  According to the developing device of a fourth aspect of the present invention, the supply roller is a metal anilox roller having a large number of recesses on the surface, so that a liquid toner layer having a predetermined thickness is formed on the surface of the developing roller. It can be formed and the quality can be improved.

  According to the developing device of claim 5, since the carrier agent of the liquid toner is mineral oil, it has a threshold value due to an applied charge, and carrier separation or charge charge due to piezoelectric action does not occur. The charging device can cause carrier separation and charge charging to charge the toner particles in the liquid toner layer.

  According to an electrophotographic apparatus of a sixth aspect of the present invention, any one of the developing devices described above, a photosensitive drum that receives liquid toner in contact with the developing roller, and an outer peripheral surface of the photosensitive drum is charged. A photosensitive drum charging device, an exposure device that exposes an image on the charged photosensitive drum, a transfer drum on which the toner image is primarily transferred in contact with the photosensitive drum, and a sheet between the transfer drum Thus, the electrophotographic apparatus includes a secondary transfer roller that secondarily transfers the toner image onto the paper and a fixing device that fixes the toner image secondarily transferred onto the paper.

  For this reason, the photosensitive drum charging device charges the outer peripheral surface of the photosensitive drum, and the exposure device exposes the image to the charged photosensitive drum, while the supply roller pumps up the liquid toner in the tank and delivers it to the developing roller. A bias voltage is applied to the developing roller, the liquid toner on the developing roller is charged by the toner charging device, the charged liquid toner is transferred from the developing roller to the photosensitive drum, and the toner image on the photosensitive drum is primarily transferred to the transfer drum. The toner image is secondarily transferred onto the paper by sandwiching the paper between the transfer drum and the secondary transfer roller, and the fixing device fixes the toner image secondarily transferred onto the paper. The liquid toner is charged by a voltage applying device and a toner charging device. Therefore, by supplying the liquid toner directly from the supply roller to the developing roller, the apparatus can be simplified, the cost can be reduced, the torque can be reduced, and the life can be extended. Further, the liquid toner supplied to the outer peripheral surface of the developing roller can be uniformly leveled in advance by the leveling blade, and the toner particles are uniformly charged to the entire liquid toner by corona discharge, thereby solidifying the solid content. Thus, a toner layer whose surface is the carrier liquid is formed. Therefore, the film thickness of the liquid toner on the developing roller can be easily made uniform with a simple configuration, and the toner particles of the charged liquid toner layer are moved onto the photosensitive drum while being in close contact with each other. The quality can be improved.

  According to a developing method of a seventh aspect of the invention, the liquid toner is supplied to the surface of the developing roller using the developing device of any one of the above inventions, and an electrostatic latent image is formed on the developing roller. Since the electrostatic latent image is developed in contact with the formed photosensitive drum, the liquid toner can be directly supplied from the supply roller to the development roller, thereby simplifying the apparatus and reducing the cost. Torque can be reduced and the life can be extended.

  In addition, the liquid toner on the outer peripheral surface of the developing roller can be uniformly leveled in advance by the leveling blade, the toner particles are uniformly charged throughout the liquid toner by corona discharge, and the solid content is consolidated. A toner layer in which the carrier liquid is a surface layer is formed. Therefore, the film thickness of the liquid toner on the developing roller can be easily made uniform with a simple configuration, and the toner particles of the charged liquid toner layer are moved onto the photosensitive drum while being in close contact with each other. The quality can be improved.

  According to the developing method of the present invention, the liquid toner having a predetermined concentration is carried on the developing roller in a thin film shape, and the liquid toner is supplied to the photosensitive drum on which the electrostatic latent image is formed. In the developing method for developing the latent image, the liquid toner pumped by the supply roller is delivered to the development roller that is in contact with the supply roller and has the same roller movement direction at the contact portion with the supply roller. The liquid toner supplied to the developing roller is uniformly leveled by a leveling blade provided on the outer peripheral surface, and then the uniformly leveled liquid toner on the outer peripheral surface of the developing roller is charged to solidify the solid content. A toner layer in which the liquid is a surface layer is formed. Therefore, by supplying the liquid toner directly from the supply roller to the developing roller, the apparatus can be simplified, the cost can be reduced, the torque can be reduced, and the life can be extended.

  Further, the liquid toner supplied to the outer peripheral surface of the developing roller can be uniformly leveled in advance by the leveling blade, and the toner particles are uniformly charged to the entire liquid toner by corona discharge, thereby solidifying the solid content. Thus, a toner layer whose surface is the carrier liquid is formed. Therefore, the film thickness of the liquid toner on the developing roller can be easily made uniform with a simple configuration, and the toner particles of the charged liquid toner layer are moved onto the photosensitive drum while being in close contact with each other. The quality can be improved.

  Exemplary embodiments of a developing device and an electrophotographic apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a schematic configuration diagram of an electrophotographic apparatus to which a developing device according to a first embodiment of the present invention is applied. FIG. 2 is a schematic diagram illustrating an operation of the developing device according to the first embodiment. It is a front view of the anilox roller in the developing device.

As shown in FIG. 1, an electrophotographic apparatus 10 to which the developing device of Example 1 is applied includes a photosensitive drum 11, a charging device (photosensitive drum charging device) 12 that charges the photosensitive drum 11, and a photosensitive drum 11. An exposure device 13 that exposes an image, a developing device 14 that visualizes an electrostatic latent image by supplying charged toner to a portion of the photosensitive drum 11 where the electrostatic latent image is formed, and a photosensitive drum 11 that is formed on the photosensitive drum 11. The image forming apparatus includes a transfer device 15 that transfers the toner image transferred onto a predetermined sheet, and a fixing device 16 that fixes the toner image transferred onto the sheet.
In this embodiment, a single photosensitive drum 11 is provided for the transfer device 15, and a charging device 12, an exposure device 13, and a developing device 14 are provided for the photosensitive drum 11. However, in the case of a color photograph, A plurality of, for example, four photosensitive drums are provided for the transfer device 15, and a charging device, an exposure device, and a developing device are provided for the photosensitive drum.

  The photosensitive drum 11 has a configuration in which an organic or amorphous silicon photosensitive layer is provided on a conductive substrate such as aluminum, and is supported on a frame (not shown) so as to be rotatable counterclockwise in FIG. By exposing the photosensitive layer to light, an electrostatic latent image can be formed on the surface. A charging device 12 and an exposure device 13 are arranged around the photosensitive drum 11 along the rotation direction.

  The charging device 12 can uniformly apply an electrostatic potential to the surface of the photosensitive drum 11 by corona discharge or the like. The exposure device 13 can form an electrostatic latent image by irradiating the photosensitive layer of the photosensitive drum 11 with a light image.

  Further, around the photosensitive drum 11, a neutralization device 17 is disposed upstream of the charging device 12 and the exposure device 13 in the rotation direction, and a cleaning device 18 is disposed further upstream. The liquid toner remaining on the surface of the photosensitive drum 11 is disposed. Can be removed and recovered in the tank 21. The cleaning device 18 includes a cleaning roller or a cleaning blade.

  Further, as shown in FIG. 2, the developing device 14 includes a tank 21 in which liquid toner of a predetermined concentration is stored, and a supply roller (partly immersed in the liquid toner in the tank 21 to pump up the liquid toner ( An anilox roller) 22, a developing roller 23 that contacts the supply roller 22 and receives liquid toner from the supply roller 22, and a leveling blade 24 that uniformizes the liquid toner supplied to the outer peripheral surface of the development roller 23. And a power supply device (voltage applying device) 25 for applying a bias voltage to the developing roller 23, and a charging device 51 for charging the liquid toner supplied to the outer peripheral surface of the developing roller 23. The supply roller 22 and the developing roller 23 The roller moving direction at the contact portion A is set in the same direction. The developing roller 23 is in contact with the photosensitive drum 11. The roller moving direction at the contact portion B between the developing roller 23 and the photosensitive drum 11 is set in the same direction.

  The supply roller 22 is composed of a metal anilox roller having a large number of recesses. For example, as shown in FIG. 3, the recess is formed by a helical groove 22 a inclined by a predetermined angle θ with respect to the axial direction of the supply roller 22, and the helical groove 22 a is formed in parallel over the entire circumference of the supply roller 22. Has been. The ink supply performance of the anilox roller is determined by the shape and depth of the surface engraving. The liquid toner supply amount is adjusted by adjusting the shapes and depths of the many recesses, and the supplied liquid toner amount is stabilized. Further, the supply roller 22 is not limited to an anilox roller, and any roller that can supply liquid toner stably can be used.

  The developing roller 23 is also composed of NBR (nitrile / butylene / rubber), and the surface is formed of a conductive member that does not swell in the liquid toner. The developing roller 23 is not limited to NBR, and may be a low-hardness rubber member such as foam, such as polystyrene, polyethylene, polyurethane, and polyvinyl chloride, silicon rubber, and urethane rubber.

  The supply roller 22 and the developing roller 23 are arranged in a substantially linear shape in a contact state, and are rotatably supported by a frame (not shown). In this case, in FIG. 1, the supply roller 22 rotates counterclockwise, the developing roller 23 rotates clockwise, and the photosensitive drum 11 rotates counterclockwise. Therefore, by rotating the supply roller 22, the liquid toner stored in the tank 21 can be pumped up, and this liquid toner can be supplied to the developing roller 23 in which the contact portion A moves in the same direction. As the developing roller 23 rotates, the liquid toner can be transferred to and supplied to the photosensitive drum 11 in which the contact portion B moves in the same direction.

  Further, a power supply device (voltage application device) 25 is connected to the developing roller 23. Therefore, by applying a bias voltage to the developing roller 23 by the power supply device 25, the supply amount of the liquid toner can be adjusted by the electric field generated in the developing roller 23. In addition, a toner stirring device 26 that stirs the liquid toner in the tank 21 is provided. Therefore, by driving the toner stirring device 26, the concentration of the liquid toner stored in the tank can be maintained uniformly.

  Further, as described above, in the developing device 14, the roller moving directions 22a and 23a at the contact portion A between the supply roller 22 and the developing roller 23 are set in the same direction as shown in FIG. As described above, the supply roller 22 is a metal anilox roller, and the helical groove 22a is formed as a recess. Further, since the developing roller 23 is formed of NBR, it has an elastic layer at least on the outer peripheral surface, and a nip through which liquid toner can pass is provided at a contact portion A with the developing roller 23. Further, the solvent of the liquid toner has a lubricating performance.

  Accordingly, the liquid toner stored in the tank 21 can pass through this nip and be supplied from the supply roller 22 to the developing roller 23.

  Further, a leveling blade 24 is provided on the outer peripheral surface of the developing roller 23 to uniformly level the film thickness of the liquid toner layer supplied to the developing roller 23 in advance. Since the roller moving directions 22a and 23a are the same in the contact portion A between the supply roller 22 and the development roller 23, film thickness unevenness may occur in the liquid toner layer supplied from the supply roller 22 to the development roller 23. is there. In this embodiment, since the leveling blade 24 is provided on the outer peripheral surface of the developing roller 23, the liquid toner supplied to the developing roller 23 can be made uniform. Thereby, the film thickness unevenness of the liquid toner layer is eliminated, and the film thickness of the liquid toner on the developing roller 23 is made uniform.

  That is, the liquid toner entering the helical groove 22a of the supply roller 22 moves to the developing roller 23 when it contacts the developing roller 23, but this liquid toner layer has an anilox pattern (helical shape). Further, as the leveling blade 24 provided on the outer peripheral surface of the developing roller 23, a soft material such as a pet film is used. When the liquid toner on the surface of the developing roller 23 comes into contact with the leveling blade 24 and is leveled, the liquid toner layer of this anilox pattern is crushed by the leveling blade 24 onto the surface of the developing roller 23, thereby increasing the film thickness. It is made uniform. In this case, since the anilox pattern has a helical shape, the liquid toner is crushed along the longitudinal direction of the helical shape, and the film thickness becomes uniform on the developing roller 23. Then, the liquid toner solvent enters a nip provided between the developing roller 23 and the photosensitive drum 11 through which the liquid toner can pass, so that the contact portion B between the developing roller 23 and the photosensitive drum 11 is lubricated. The

  For example, mineral oil is used as the carrier agent for the liquid toner. Mineral oil is a mixture of saturated hydrocarbon compounds also called liquid paraffin or mineral oil. Moreover, it is a liquid hydrocarbon mixture obtained by distillation from petrolatum, and is also called liquid paraffin, liquid petrolatum, white oil, etc., and includes low specific gravity light oil.

  Further, the leveling blade 24 may be applied with the same potential as that of the developing roller 23 or with a reverse potential to prevent contamination. Since the mineral oil-based toner is not a charged toner like the conventionally used silicon-based toner, no carrier separation or charge charging occurs even when a bias voltage is applied to the leveling blade 24.

  Further, as shown in FIGS. 1 and 2, the developing device 14 of the present embodiment is connected to a power supply device 25 with respect to the developing roller 23, and supplies liquid toner supplied to the outer peripheral surface of the developing roller 23. A charging device (toner charging device) 51 for charging is provided. The charging device 51 includes a tungsten wire 52 serving as a discharge electrode, a box-shaped housing 53 that surrounds the tungsten wire 52 and has an opening 53 a on one side, and a power supply device 54. The housing opening 53 a is disposed so as to face the outer peripheral surface of the developing roller 23.

  Therefore, the liquid toner is made of a solvent containing toner particles, and the liquid toner supplied from the supply roller 22 to the developing roller 23 passes through the developing roller 23 by the bias voltage of the power supply device 25 as shown in FIG. As shown in FIG. 4, it is applied as a liquid toner layer on the surface of the developing roller 23, and the toner particles are suspended in the solvent.

  Here, when the tungsten wire 52 is energized by the power supply device 54 in the charging device 51, corona discharge occurs, and the liquid toner layer on the developing roller 23 is irradiated through the housing opening 53a, and the toner particles in the liquid toner layer are discharged. The toner is charged and consolidated on the surface side of the developing roller 23 to be in close contact with each other. Then, when the liquid toner layer in which the developing roller 23 rotates and the toner particles are aligned comes close to the electrostatic latent image formed on the surface of the photosensitive drum 11, as shown in FIG. The toner particles in the layer move on the photosensitive drum 11 while keeping in close contact with each other.

  Further, since the charging device 51 is provided between the leveling blade 24 and the photosensitive drum 11, the liquid toner is uniformly leveled in advance before the liquid toner is moved onto the photosensitive drum 11, and then the corona discharge is performed. The toner particles can be uniformly charged throughout the liquid toner.

  Since the charging device 51 is provided at a position that is not in contact with the liquid toner, the toner particles can be uniformly charged over the entire liquid toner.

  Therefore, according to the developing device 14 of the present embodiment, the liquid toner is directly supplied from the supply roller 22 to the developing roller 23, thereby simplifying the device, reducing the cost, reducing the torque, and extending the life. Can be achieved. Further, by providing the leveling blade 24, the liquid toner supplied to the outer peripheral surface of the developing roller 23 can be leveled in advance, and the toner particles are uniformly charged to the entire liquid toner in a non-contact manner by corona discharge. The solid content is consolidated to form a toner layer in which the carrier liquid is a surface layer. For this reason, the film thickness of the liquid toner on the developing roller 23 can be easily made uniform with a simple configuration, and the charged toner particles can be moved onto the photosensitive drum 11 in an aligned state, Quality can be improved.

  Further, as shown in FIG. 1, the developing device 14 measures the concentration of the liquid toner pumped up by the supply roller 22 and the toner concentration adjusting device 27 that adjusts the toner concentration by supplying the toner and the solvent to the tank 21. The toner density measuring device 28 and a control device 29 for controlling the toner density adjusting device 27 based on the measurement result of the toner density measuring device 28 are provided.

  That is, in the toner concentration adjusting device 27, the first and second replenishing tanks 32 and 33 are connected to the tank 21 via the first and second supply lines 30 and 31. The first replenishment tank 32 stores concentrated toner, the second replenishment tank 33 stores solvent, and the first replenishment tank is opened and closed by opening and closing the open / close valves 34 and 35 provided in the supply lines 30 and 31. The concentrated toner stored in 32 can be supplied to the tank 21 through the first supply line 30, and the solvent stored in the second replenishing tank 33 can be supplied to the tank 21 through the second supply line 31. In this case, the liquid toner is obtained by dispersing a resin containing a pigment in a solvent, and the toner particles are resin particles having charging characteristics.

  The toner concentration measuring device 28 is an optical sensor disposed opposite to the outer peripheral surface of the supply roller 22 and includes a light emitting portion 28a and a light receiving portion 28b, and measures the concentration of the liquid toner based on the light transmittance. be able to. In this case, the supply roller 22 is an anilox roller, and is rotated while immersed in the liquid toner stored in the tank 21, so that the liquid toner is pumped up by entering into the numerous helical grooves 22 a. The toner concentration measuring device 28 can appropriately measure the concentration of the liquid toner entering the helical groove 22a by irradiating and receiving a predetermined area on the outer peripheral surface of the supply roller 22.

  The control device 29 is connected to the toner concentration adjusting device 27 and the toner concentration measuring device 28. The toner concentration measured by the toner concentration measuring device 28 is inputted, and the measured toner concentration is set to a predetermined toner set in advance. The toner density adjusting device 27 is controlled so as to obtain the density. That is, when the toner concentration measured by the toner concentration measuring device 28 is lower than the predetermined toner concentration, the control device 29 opens the on-off valve 34 and supplies the concentrated toner stored in the first replenishing tank 32 to the first supply. When the toner concentration supplied from the line 30 to the tank 21 and measured by the toner concentration measuring device 28 is higher than the predetermined toner concentration, the on-off valve 35 is opened, and the solvent stored in the second replenishing tank 33 is stored in the second replenishing tank 33. Supply from the supply line 31 to the tank 21.

  The transfer device 15 includes a transfer drum 41 and a secondary transfer roller 42. The transfer drum 41 is disposed so as to be in contact with the photosensitive drum 11, and the toner image on the photosensitive drum 11 can be primarily transferred onto the transfer drum 41 by electrostatic force. The transfer drum 41 is formed of, for example, NBR (nitrile / butylene / rubber), and rotates in a clockwise direction in FIG. 1 on a frame (not shown). The secondary transfer roller 42 rotates in a counterclockwise direction in FIG. 1 on a frame (not shown), and can sandwich and press a sheet with the transfer drum 41. A cleaning device 43 is disposed around the transfer drum 41 on the downstream side in the rotational direction from the position of contact with the secondary transfer roller 42. The cleaning device 43 is provided by a cleaning roller, a cleaning blade, or the like. The liquid toner remaining on the surface of the transfer drum 41 can be removed and collected in the tank 21.

  The fixing device 16 includes a fixing roller 44 and a pressure roller 45. The fixing roller 44 is formed of a silicon sponge roller and is heated to a high temperature by a built-in heater, and rotates in a clockwise direction in FIG. 1 on a frame (not shown). The pressure roller 45 is made of NBR (nitrile / butylene / rubber) and rotates in a counterclockwise direction in FIG. 1 on a frame (not shown). Accordingly, the sheet S sandwiched between the fixing roller 44 and the pressure roller 45 is heated by the fixing roller 44, and the toner particles in the transferred toner image are melted to be fixed on the sheet S.

  In the electrophotographic apparatus of this embodiment, the photosensitive drum 11, the supply roller 22, the developing roller 23, the transfer drum 41, the secondary transfer roller 42, the fixing roller 44, and the pressure roller 45 have one drive (not shown). Synchronous rotation is possible by transmitting the driving force of the motor via a plurality of gears or chains. The driving method is not limited to this method, and the photosensitive drum 11, the supply roller 22, the developing roller 23, the transfer drum 41, the secondary transfer roller 42, the fixing roller 44, and the pressure roller 45 are rotated by individual driving motors. It may be.

  Here, the operation of the above-described electrophotographic apparatus of this embodiment will be described.

  In the electrophotographic apparatus of this embodiment, first, the charging device 12 performs corona discharge on the photosensitive drum 11 to charge the surface of the photosensitive drum 11 with a polarity corresponding to the toner characteristics. Next, the image is exposed on the photosensitive drum 11 charged by the exposure device 13. In this case, the image is exposed by a scanner to form an electrostatic latent image on the surface of the photosensitive drum 11. That is, the portion exposed to the light from the scanner becomes conductive, so that the charge disappears, and the portion not exposed to the light remains as an electrostatic latent image that is an image of the charge.

  On the other hand, the electrostatic latent image on the photosensitive drum 11 is visualized by the developing device 14. That is, when the supply roller 22 is rotated, the liquid toner stored in the tank 21 is pumped up by the supply roller 22, and the liquid toner of the supply roller 22 is directly supplied to the developing roller 23, and is thinly applied on the developing roller 23. A liquid toner layer is formed. At this time, by adjusting the bias voltage applied to the developing roller 23 by the power supply device 25, the film thickness of the liquid toner layer transferred to the photosensitive drum 11 is adjusted by the electric field generated in the developing roller 23.

  Further, the liquid toner supplied to the developing roller 23 by the leveling blade 24 provided on the outer peripheral surface of the developing roller 23 is leveled in advance, so that the film thickness can be made uniform. Further, the toner particles floating in the solvent are brought into an intimately aligned state by corona discharging the liquid toner on the developing roller 23 with a uniform thickness in advance by the charging device 51.

  Therefore, the liquid toner supplied to the outer peripheral surface of the developing roller 23 by the leveling blade 24 is uniformly leveled in advance and then charged by corona discharge, so that the liquid toner film on the developing roller 23 can be easily formed with a simple configuration. While uniforming the thickness, the charged toner particles are moved onto the photosensitive drum 11 while being in close contact with each other in an aligned state, thereby improving the quality.

  At this time, the toner density measuring device 28 irradiates the surface of the supply roller 22 with light from the light emitting unit 28a, and receives the reflected light with the light receiving unit 28b. The concentration of the liquid toner adhering to the surface is measured. Then, the control device 29 controls the toner concentration adjusting device 27 based on the toner concentration measured by the toner concentration measuring device 28. That is, when the toner concentration measured by the toner concentration measuring device 28 is lower than the predetermined toner concentration, the control device 29 opens the on-off valve 34 and supplies the concentrated toner in the first replenishing tank 32 from the first supply line 30 to the tank. By supplying to 21, the concentration of the liquid toner in the tank 21 is increased. On the other hand, when the toner concentration measured by the toner concentration measuring device 28 is higher than the predetermined toner concentration, the control device 29 opens the on-off valve 35 to remove the solvent in the second replenishing tank 33 from the second supply line 31. By supplying to 21, the concentration of the liquid toner in the tank 21 is reduced.

  Then, by bringing the liquid toner layer on the developing roller 23 close to the electrostatic latent image formed on the surface of the photosensitive drum 11, the liquid toner charged by electrostatic force is moved onto the photosensitive drum 11, A toner image is formed on the surface. At this time, since the liquid toner layer on the developing roller 23 is in an aligned state in which the toner particles are in close contact with each other with a uniform film thickness, the liquid toner layer is close to the electrostatic latent image formed on the surface of the photosensitive drum 11. Then, the charged liquid toner layer moves onto the photosensitive drum 11 while the toner particles are in an aligned state with a uniform film thickness, and a toner image with a uniform film thickness is formed on the photosensitive drum 11.

  Subsequently, the toner image formed on the photosensitive drum 11 is transferred onto the paper S by the transfer device 15. That is, the toner image formed on the photosensitive drum 11 is primarily transferred onto the transfer drum 41 due to a potential difference generated between the photosensitive drum 11 and the toner image primarily transferred onto the transfer drum 41. A sheet fed between the transfer drum 41 and the secondary transfer roller 42 by a pressing force to the transfer drum 41 by the secondary transfer roller 42 and an applied voltage (a toner and a reverse polarity voltage are applied from the opposite side of the sheet S). Secondary transfer to S. On the other hand, the liquid toner remaining on the photosensitive drum 11 and the transfer drum 41 is removed by the cleaning devices 18 and 43 and collected in the tank 21.

  Finally, the toner image secondarily transferred onto the sheet is fixed by the fixing device 16. That is, as the sheet S passes between the high-temperature fixing roller 44 and the pressure roller 45, the sheet S is heated by the high-temperature fixing roller 44, and the toner particles in the transferred toner image are melted. Fix to paper S.

  As described above, in the developing device 14 applied to the electrophotographic apparatus according to the first exemplary embodiment, the tank 21 in which the liquid toner having a predetermined concentration is stored and the liquid toner in the tank 21 is partially immersed in the liquid toner. A supply roller (anilox roller) 22 that can draw up toner, a developing roller 23 that contacts the supply roller 22 and receives liquid toner from the supply roller 22, and a liquid toner that is supplied to the outer peripheral surface of the development roller 23 Leveling blade 24, a power supply device (voltage applying device) 25 for applying a bias voltage to the developing roller 23, and a charging device 51 for charging the liquid toner supplied to the outer peripheral surface of the developing roller 23. The roller moving direction at the contact portion A between the supply roller 22 and the developing roller 23 is set to the same direction.

  Accordingly, the supply roller 22 pumps up the liquid toner in the tank 21, delivers it to the developing roller 23, and the leveling blade 24 provided on the outer peripheral surface of the developing roller 23 causes the liquid toner on the surface of the developing roller 23 to be leveled with the leveling blade 24. The liquid toner layer is crushed on the surface of the developing roller 23 by the leveling blade 24 and the film thickness is made uniform.

  As the charging device 51, a tungsten wire 52, a housing 53 that surrounds the tungsten wire 52 and has an opening 53 a on one side, and a power supply device 54 are provided, and the opening 53 a of the housing 53 is formed on the outer peripheral surface of the developing roller 23. It arrange | positions so that it may oppose. Accordingly, corona discharge generated from the tungsten wire 52 is irradiated toward the surface of the developing roller 23 by the housing 53.

  By performing corona discharge by the charging device 51, the toner particles are uniformly charged over the entire liquid toner supplied to the outer peripheral surface of the developing roller 23, and the liquid toner on the developing roller 23 is compressed in order to compress the solid content of the liquid toner. In this case, the adhesion force between the toner particles becomes higher, and the toner particles charged from the developing roller 23 to the photosensitive drum 11 are moved onto the photosensitive drum 11 in an aligned state.

  Therefore, according to the electrophotographic apparatus of the present embodiment, the thickness of the liquid toner on the developing roller 24 can be easily uniformed with a simple configuration, and the charged toner particles can be photosensitive while being in close contact with each other. It can be moved onto the drum 11. Thereby, the edge of the toner image can be formed sharply, and the resolution of electrophotography can be increased to improve the quality.

  Further, in the developing device 14 of this embodiment, the supply roller 22 is a metal anilox roller having a large number of recesses on the surface, and a liquid toner layer having a predetermined thickness can be easily formed on the surface of the developing roller 23. Can improve quality. Furthermore, the concave portion of the supply roller 22 is formed as a helical groove 22a inclined by a predetermined angle θ with respect to the axial direction, so that a liquid toner layer having a predetermined thickness can be uniformly formed on the surface of the developing roller 23, thereby improving quality. can do.

  Further, in the developing device 14 of this embodiment, the developing roller 23 is formed of NBR to provide an elastic layer on the outer peripheral surface and provide a lubricating performance to the liquid toner solvent. Accordingly, since the roller moving direction is the same at the contact portion A between the supply roller 22 and the developing roller 23, liquid toner having a lubricating performance enters between the elastic layers, and the supply roller 22 and the developing roller 23. It is possible to suppress damage to the surface of the surface. In this case, a nip through which the liquid toner can pass is provided at the contact portion B between the developing roller 23 and the photosensitive drum 11, and the liquid toner having lubricating performance passes through the nip. 11 surface damage can be appropriately suppressed.

  In addition, the electrophotographic apparatus according to the present exemplary embodiment includes the photosensitive drum 11, the charge eliminating device 17, the charging device 12, the exposure device 13, the developing device 14, the transfer device 15, and the fixing device 16. The developing device 14 includes a tank 21, a supply roller 22, a leveling blade 24, a developing roller 23, a power supply device 25, and a charging device 51.

  Accordingly, the film thickness of the liquid toner supplied from the developing device 14 to the photosensitive drum 11 can be made uniform, and the charged toner particles can be moved onto the photosensitive drum 11 in an aligned state, and printing can be performed. Quality can be improved.

  The cleaning devices 18 and 43 may be cleaning rollers or cleaning blades. At this time, a spare tank in which a part of the cleaning roller and the cleaning blade is immersed in the liquid toner may be provided. Further, a part of the cleaning roller and the cleaning blade may be immersed in the liquid toner in the tank 21.

  In this embodiment, the developing device 14 includes the tank 21, the supply roller 22, the leveling blade 24, and the development roller 23, but a plurality of leveling rollers such as a leveling roller are provided between the supply roller 22 and the development roller 23. A roller may be provided.

  In addition to the cleaning devices 18 and 43 on the supply roller 22 and the developing roller 23, for example, toner fixed to the surface of the developing roller 23 such as a loosening roller made of a rubber roller such as a sponge roller is physically applied. You may make it provide the member liberated from the surface. Thereby, the removal function by the cleaning operation can be made more complete.

  In each of the above-described embodiments, the electrophotographic apparatus includes the photosensitive drum 11, the charge eliminating device 17, the charging device 12, the exposure device 13, the developing device 14, the transfer device 15, and the fixing device 16. In this case, the same process can be repeated four times.

  In the developing device and the electrophotographic apparatus according to the present invention, the thickness of the liquid toner layer to be moved from the developing roller to the photosensitive drum is uniformed in advance and the quality is improved by corona discharge. The present invention can also be applied to the electrophotographic apparatus.

1 is a schematic configuration diagram of an electrophotographic apparatus to which a developing device according to Embodiment 1 of the present invention is applied. 6 is a schematic diagram illustrating an operation in the developing device of Embodiment 1. FIG. 3 is a front view of an anilox roller in the developing device of Embodiment 1. FIG. FIG. 3 is a schematic diagram illustrating a movement state of toner particles by the developing device according to the first exemplary embodiment. FIG. 3 is a schematic diagram illustrating a movement state of toner particles by the developing device according to the first exemplary embodiment. It is a figure which shows an example of a structure of the developing device of the conventional electrophotographic apparatus. It is a figure which shows the other structure of the developing device of the conventional electrophotographic apparatus.

Explanation of symbols

10 Electrophotographic device 11 Photosensitive drum 12 Charging device (photosensitive drum charging device)
DESCRIPTION OF SYMBOLS 13 Exposure apparatus 14 Developing apparatus 15 Transfer apparatus 16 Fixing apparatus 17 Static elimination apparatus 18 Cleaning apparatus 21 Tank 22 Supply roller 23 Developing roller 24 Leveling blade 25, 54 Power supply apparatus (voltage application apparatus)
27 toner density adjusting device 28 toner density measuring device 29 control device 41 transfer drum 42 secondary transfer roller 51 charging device (toner charging device)
52 Tungsten wire (discharge electrode)
53 Housing

Claims (8)

A tank for storing liquid toner of a predetermined concentration;
A supply roller that is partially immersed in the liquid toner in the tank and can pump up the liquid toner;
A developing roller that is in contact with the supply roller and receives liquid toner from the supply roller;
A leveling blade for uniformizing the liquid toner supplied to the outer peripheral surface of the developing roller;
A voltage applying device for applying a bias voltage to the developing roller;
A charging device for charging the liquid toner supplied to the outer peripheral surface of the developing roller,
2. A developing device according to claim 1, wherein a roller moving direction at a contact portion between the supply roller and the developing roller is set in the same direction. In claim 1,
The developing device, wherein the charging device is provided between the blade and a photosensitive drum. In claim 1 or 2,
The developing device according to claim 1, wherein the charging device is provided at a position not in contact with the liquid toner. In any one of Claims 1 thru | or 3,
2. A developing device according to claim 1, wherein the supply roller is a metal anilox roller having a number of concave portions on a surface portion. In any one of Claims 1 thru | or 4,
A developing device, wherein the carrier agent of the liquid toner is mineral oil. A developing device according to any one of claims 1 to 5;
A photosensitive drum that receives liquid toner in contact with the developing roller;
A photosensitive drum charging device for charging the outer peripheral surface of the photosensitive drum;
An exposure device that exposes an image to the charged photosensitive drum;
A transfer drum on which a toner image is primarily transferred in contact with the photosensitive drum;
A secondary transfer roller for secondary transfer of a toner image onto the paper by sandwiching the paper with the transfer drum;
An electrophotographic apparatus comprising: a fixing device that fixes a toner image secondarily transferred to the paper.   6. The developing device according to claim 1, wherein the liquid toner is supplied to a surface of the developing roller, and the developing roller is brought into contact with a photosensitive drum on which an electrostatic latent image is formed. A developing method comprising developing a latent image. In a developing method in which a liquid toner having a predetermined concentration is carried on a developing roller in a thin film shape, the liquid toner is supplied to a photosensitive drum on which an electrostatic latent image is formed, and the electrostatic latent image is developed.
In contact with the supply roller, the liquid toner pumped up by the supply roller is delivered to the developing roller in which the roller moving direction at the contact portion with the supply roller is the same direction,
After uniformly leveling the liquid toner supplied to the developing roller by a leveling blade provided on the outer peripheral surface of the developing roller,
A developing method comprising charging uniformly and uniformly liquid toner on an outer peripheral surface of the developing roller.

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