JP2006178417A - Liquid development apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress elimination of the charges of an electrostatic latent image formed on an image carrier by an additive other than a toner and to obtain an image having a satisfactory image density, in a liquid development unit for developing an electrostatic latent image formed on an image carrier with a liquid developer comprising an insulative liquid containing therein a toner and an additive. <P>SOLUTION: In the liquid development apparatus 10 in which a liquid developer 11 comprising an insulative liquid containing therein a toner and an additive is formed into a thin layer and transported by a developer carrier 13 to a development area opposite to an image carrier 1 to develop an electrostatic latent image on the image carrier, a charger 15 for charging the liquid developer prior to delivery by the developer carrier to the development area opposite to the image carrier is disposed, and the liquid developer contains free additive unattached to the toner in an amount of ≤0.1 wt.% based on the insulative liquid. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In an image forming apparatus such as a copying machine or a printer, the present invention provides an image carrier using a liquid developer in which an insulating liquid contains a toner and an additive such as a dispersion stabilizer or a charge control agent. The present invention relates to a liquid developing apparatus that develops a formed electrostatic latent image, and in particular, is designed to suppress the erasure of charges in an electrostatic latent image formed on an image carrier by additives other than toner. It has characteristics.

  In an image forming apparatus such as a copying machine or a printer, generally, an electrostatic latent image corresponding to image information is formed on an image carrier such as a photosensitive member, and toner is supplied to the electrostatic latent image by a developing device for development. The developed toner image is transferred to a recording medium such as recording paper and fixed to obtain an image.

  As described above, as a developing device for developing by supplying toner to the electrostatic latent image, in addition to a dry developing device using toner or a powdered developer obtained by mixing toner and a carrier, There is known a liquid developing apparatus using a liquid developer in which an insulating liquid contains a toner and an additive such as a dispersion stabilizer or a charge control agent.

  Here, in the case of a dry-type developing device using a powder developer, the size of the toner can be made fine because there is a possibility that the toner or the like may scatter in the surrounding atmosphere and float in the air. In general, those having an average particle diameter of about 5 to 10 μm are used, and it is difficult to obtain a high-definition and high-resolution image.

  On the other hand, in the case of a liquid developing device using a liquid developer in which an additive such as a dispersion stabilizer or a charge control agent is added to an insulating liquid to disperse the toner, there is no possibility that the toner is scattered in the atmosphere. There are advantages that the toner can be made fine and an image having high resolution and excellent gradation can be obtained.

  In such a liquid developing device, the liquid developer as described above is made into a thin layer state and transported to a developing region facing the image carrier by the developer carrier, and the liquid developer is charged. There has been proposed an apparatus in which an electrostatic latent image formed on an image carrier is developed (see, for example, Patent Document 1).

  However, in the case of the liquid developing apparatus as described above, since the liquid developer contains additives such as a dispersion stabilizer and a charge control agent that are free without being adsorbed by the toner, When the developer is charged, the free additive as well as the toner is charged, and the electrostatic charge thus formed on the image carrier is formed by the free and charged additive. The charge of the electrostatic latent image is consumed by being applied to the portion of the image, whereby the adhesion of the toner to the electrostatic latent image is inhibited, and there is a problem that an image having a sufficient image density cannot be obtained.

  In recent years, there has been a demand for downsizing the apparatus and forming an image at a high speed. For this reason, it is required to increase the moving speed of the toner in the liquid developer and shorten the development time. Has been.

  Here, in order to increase the moving speed of the toner in the liquid developer as described above, it is necessary to increase the charge amount of the toner. Therefore, an additive such as a charge control agent to be added to the liquid developer. Increasing the amount of the toner, increasing the amount of the additive such as a charge control agent adsorbed on the toner to increase the charge amount of the toner.

However, when the amount of an additive such as a charge control agent added to the liquid developer is increased in this way, the amount of the additive that is free in the liquid developer also increases, and as described above, The electrostatic latent image consumed by the free additive has increased in charge, causing many problems such as failure to obtain an image having a sufficient image density.
Japanese Patent Laid-Open No. 10-319725

  The present invention relates to a liquid for developing an electrostatic latent image formed on an image carrier using a liquid developer in which an insulating liquid contains a toner and an additive such as a dispersion stabilizer or a charge control agent. An object of the present invention is to solve the above-described problems in the developing device, and suppress the charge in the electrostatic latent image formed on the image bearing member from being erased by additives other than the toner. An object of the present invention is to obtain an image having a sufficient image density even when the image is miniaturized or an image is formed at a high speed.

  In the first liquid developing device of the present invention, in order to solve the above-described problems, a developer carrying member in which a liquid developer containing a toner and an additive in an insulating liquid is made into a thin layer state. In the liquid developing device for developing the electrostatic latent image formed on the image carrier by transporting it to the developing area facing the image carrier, the liquid developer is made into a thin layer and the image is formed by the developer carrier. A charging device for charging the liquid developer is provided in the middle of conveyance to the developing region facing the carrier, and the amount of the free additive that is not adsorbed by the toner is the insulating property. A liquid developer having a concentration of 0.1% by weight or less with respect to the liquid was used.

  In the first liquid developing device, the amount of the free additive not adsorbed on the toner as described above is 0.08% by weight or less with respect to the insulating liquid. It is more preferable to use a developer, and it is more preferable to use a liquid developer that is 0.05% by weight or less.

  Further, in the second liquid developing device according to the present invention, in order to solve the above-mentioned problems, the developer in which the liquid developer containing the toner and the additive in the insulating liquid is made into a thin layer state is used. In a liquid developing apparatus for developing an electrostatic latent image formed on an image carrier by transporting it to a development area facing the image carrier by the carrier, the developer carrier in the above-described liquid developer in a thin layer state A charging device for charging the liquid developer is provided in the middle of conveyance to the developing area facing the image carrier, and the charge of the electrostatic latent image is erased by the toner contained in the liquid developer. The ratio was 90% or more.

  In the second liquid developing device, it is more preferable that the ratio of the charge of the electrostatic latent image erased by the toner contained in the liquid developer is 95% or more as described above.

  Here, as in the liquid developing device according to the present invention, a charging device is provided in the middle of transporting the liquid developer in a thin layer state to the developing area facing the image carrier by the developer carrier, and the charging device provides a liquid. When the developer is charged, the liquid developer used for development can be efficiently and sufficiently charged.

  As in the first liquid developing device of the present invention, as the liquid developer, the amount of the free additive not adsorbed on the toner is 0.1% by weight or less with respect to the insulating liquid. When the liquid developer is used, the amount of the additive that is released from the toner and charged is reduced, and the electrostatic latent image formed on the image carrier is formed by the additive thus released and charged. The charge of the electrostatic latent image is suppressed from being consumed by the additive, and the ratio of the charge of the electrostatic latent image erased by the toner is increased. As in the second liquid developing device, the ratio at which the charge of the electrostatic latent image is erased by the toner contained in the liquid developer can be 90% or more.

  As a result, in the liquid developing device according to the present invention, even when the device is downsized or an image is formed at a high speed, an image having a sufficient image density can be obtained and even at a low potential. Stable development can be performed.

  Hereinafter, an image forming apparatus using a liquid developing device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings. The liquid developing apparatus according to the present invention is not limited to those shown in the following embodiments, and can be implemented with appropriate modifications within a range not changing the gist thereof.

  In the image forming apparatus using the liquid developing apparatus of this embodiment, as shown in FIG. 1, an image carrier 1 composed of a photosensitive drum is rotated, and the surface of the image carrier 1 is charged by a charger 2. After that, the surface of the image carrier 1 thus charged is exposed according to image information by the exposure device 3 to form an electrostatic latent image according to the image information on the surface of the image carrier 1. Like that.

  Then, the toner contained in the liquid developer 11 is supplied to the surface of the image carrier 1 on which the electrostatic latent image is formed in this way by the liquid developing device 10 and developed, and the surface of the image carrier 1 is thus developed. A toner image corresponding to the electrostatic latent image is formed.

  Next, the toner image thus formed on the surface of the image carrier 1 is guided to the position of the transfer device 4, and a recording medium (not shown) such as recording paper is provided between the transfer device 4 and the image carrier 1. ), The toner image formed on the surface of the image carrier 1 is transferred to the recording medium by the transfer device 4, and the toner image thus transferred is fixed to the recording medium by a fixing device (not shown). Thus, an image is formed on the recording medium.

  On the other hand, the toner remaining on the surface of the image carrier 1 after the transfer is removed from the surface of the image carrier 1 by the cleaning member 5, and then the potential remaining on the surface of the image carrier 1 by the charge eliminating device 6. Is removed, and the next image formation is performed.

  Here, in the liquid developing device 10 in this embodiment, the liquid developer 11 containing toner and additives such as a dispersion stabilizer and a charge control agent in an insulating liquid is accommodated in the developing tank 12. At the same time, a part of the developer carrying member 13 composed of a developing roller is immersed in the liquid developer 11, the developer carrying member 13 is rotated, and the liquid developer 11 is placed on the surface of the developer carrying member 13. Is held and transported to a development area facing the image carrier 1.

  Then, the regulating member 14 and the charging device 15 are provided while the liquid developer 11 is held on the surface of the developer carrier 13 and conveyed to the development region as described above, and the developer carrier 13 is provided by the regulation member 14. The amount of the liquid developer 11 held and transported on the surface of the developer is regulated so that the liquid developer 11 held and transported on the surface of the developer carrier 13 is made into a thin layer state. The liquid developer 11 in a layer state is charged by the charging device 15 described above.

  Then, the liquid developer 11 charged in the thin layer state as described above is held on the surface of the developer carrying member 13 and led to a developing region facing the image carrier 1, and in this liquid developer 11 Development is performed by supplying the charged toner to the surface of the image carrier 1 on which the electrostatic latent image is formed as described above.

  Further, after developing in this way, the liquid developer 11 remaining on the surface of the developer carrier 13 is guided into the developing tank 12 and remains on the surface of the developer carrier 13 by the cleaning member 16. The liquid developer 11 is detached from the developer carrier 13 and returned to the developing tank 12.

  Here, in the liquid developing device 10 according to this embodiment, the amount of the free additive that is not adsorbed by the toner as the liquid developer 11 is 0.1% by weight or less with respect to the insulating liquid. I'm trying to use something.

  When the liquid developer 11 in which the amount of the free additive not adsorbed on the toner is 0.1% by weight or less with respect to the insulating liquid is used, the developer carrier is used as described above. The liquid developer 11 in a thin layer state on the surface 13 is charged by the charging device 15, and the liquid developer 11 is guided to the developing area facing the image carrier 1 to be formed on the surface of the image carrier 1. When developing the electrostatic latent image, the electrostatic latent image formed on the surface of the image carrier 1 is charged with an additive charged free from the toner and charged on the electrostatic latent image. Is less likely to be erased, the charged toner is quickly supplied to the portion of the electrostatic latent image, and a sufficient amount of toner is applied to the electrostatic latent image, so that the image density is sufficient. An image having is obtained.

  Here, when preparing the liquid developer 11 in which the amount of the free additive not adsorbed on the toner is 0.1 wt% or less with respect to the insulating liquid as described above, a certain particle size is required. The toner thus pulverized is dispersed in an insulating liquid in which the concentration of an additive such as a dispersant is 0.1% by weight or less, and the toner is further pulverized to a predetermined particle size. The toner can be prepared by adhering the above additives to the toner.

  In addition, the toner pulverized to a certain particle size is dispersed in an insulating liquid having a high concentration of additives such as a dispersant, and the above toner is pulverized to a predetermined particle size. After the above additives are attached to the toner, the toner thus attached is separated from the insulating liquid containing a large amount of additives such as a dispersant, and the thus separated toner is insulated. Can also be dispersed in the sexual liquid to reduce the amount of free additive. When the toner pulverized to a certain particle size as described above is dispersed in an insulating liquid having a high concentration of additives such as a dispersant, the toner is quickly and appropriately dispersed. In addition, the amount of the free additive not adsorbed on the toner can be easily adjusted to 0.1% by weight or less with respect to the insulating liquid. Further, the lower limit of the amount of the free additive that is not adsorbed by the toner is not particularly limited, but making this amount very small not only makes its preparation difficult, Since no further effect can be obtained, the content should be 0.05% by weight or more.

  The insulating liquid used for the liquid developer 11 is a liquid satisfying characteristics such as high electrical insulation, low flammability, and low odor, such as aliphatic hydrocarbons, alicyclic hydrocarbons, aromatics. Group hydrocarbons, halogenated hydrocarbons, polysiloxanes and the like can be used. Among them, liquid paraffin and silicone oil are preferably used.

  Further, as the toner, colored resin particles containing a colorant such as a pigment and a binder resin can be used, and those having a volume average particle size of 0.1 μm to 5 μm are preferably used. The toner concentration in the liquid developer 11 is preferably 10 to 40% by mass.

  The viscosity of the liquid developer 11 is preferably 0.2 Pa · s to 10000 Pa · s (25 ° C.). This is because if the viscosity of the liquid developer 11 becomes too low, it becomes difficult to sufficiently guide the liquid developer 11 to the development area facing the image carrier 1, while the viscosity of the liquid developer 11 becomes too high. This is because the developing speed becomes slow.

  Examples of the dispersant used in the liquid developer 11 include rubber resins, long chain alkyl group-containing acrylic resins, alkyl-modified polyvinyl pyrrolidone, hydrogenated rosin esters, modified alkyd resins, polyester resins, and various types. A surfactant or the like can be used.

(Experimental example)
Next, an experiment was conducted to examine the effect on the electrostatic latent image formed on the image bearing member when the amount of the additive free in the insulating liquid was changed.

  In this experiment, Moresco White P-120 made of aliphatic hydrocarbon (manufactured by Matsumura Oil Research Co., Ltd.) was used as the insulating liquid, and a dispersant made of polyester resin was used as an additive. Five types of tests using Solsperse 13940 (Abyssia) and changing the amount of the additive to be added to the insulating liquid, so that the concentration of the additive was in the range of 1% to 0.01% by weight. Liquids A1 to A6 were used.

  Further, in this experiment, as shown in FIG. 2, as a test apparatus, a developer conveyance in which a conductive rubber layer 22 made of NBR having a thickness of 5 mm is formed on the surface of an aluminum drum 21 having a diameter of 100 mm. An insulating roller 30 having an insulating layer 32 made of PET formed on the surface of an aluminum drum 31 having a diameter of 100 mm is provided so as to face the roller 20, and the developer transport roller 20 and the insulating roller 30 described above are respectively provided. The developer transport roller 20 is grounded, and the developer transport roller 20 and the insulating roller 30 move in the same direction at the portion where the developer transport roller 20 and the insulating roller 30 face each other. And the insulating roller 30 were rotated at a peripheral speed of 200 mm / sec.

  And using each said test liquid A1-A6, it apply | coats so that the thickness of test liquid A1-A6 may be set to about 7 micrometers on the surface of the developer conveyance roller 20, respectively, Test liquid A1- applied in this way Before the A6 is guided to the insulating roller 30, the corotron charger 23 having an opening width of 90 mm is used to charge the test solutions A1 to A6 by applying a current of +10 μA, while the surface of the insulating roller 30 is scorotron. An electrostatic latent image of −300 V was formed by the charger 33.

  Then, after the test solutions A1 to A6 charged as described above are brought into contact with the surface of the insulating roller 30 on which the electrostatic latent image of −300 V is formed, the potential Va on the surface of the insulating roller 30 is changed to the surface potential. The total image was measured by a total of 34 (manufactured by TREK: MODEL304), and the decrease rate of the latent image potential after contacting each of the test solutions A1 to A6 was calculated by the following formula. The results are shown in Table 1 below. Note that Vo in the following equation represents the potential of the electrostatic latent image formed on the surface of the insulating roller 30 by the scorotron charger 33 as described above.

  Reduction rate of latent image potential (%) = [(Vo−Va) / Vo] × 100

  As a result, when the test solutions A3 to A6 in which the concentration of the additive to be added to the insulating liquid is 0.1% by weight or less are used, the rate of decrease in the latent image potential is greatly reduced. In the case of using test solutions A4 to A6 in which the decrease in the potential of the electrostatic latent image due to the free additive is suppressed and the concentration of the additive is 0.08% by weight or less, the rate of decrease in the latent image potential Became even lower. In particular, when the test solutions A5 and A6 having an additive concentration of 0.05% by weight or less were used, the rate of decrease in the latent image potential was very low, and the electrostatic additive image of the electrostatic latent image was reduced by the free additive. The potential is further suppressed from decreasing.

  Next, an experiment for measuring the reduction rate of the latent image potential was performed on the liquid developer used in the examples and the liquid developer used in the comparative example.

Example 1
In Example 1, in preparing a liquid developer, 100 parts by weight of a thermoplastic polyester resin (softening point 121 ° C., glass transition point 67 ° C.), copper phthalocyanine blue cyan pigment (CI Pigment Blue 15: 1) 20 parts by weight, negatively charged control agent zinc salicylate complex (Orient Chemical Co., Ltd .: Bontron E-84) in a ratio of 5 parts by weight, these were sufficiently mixed by a Henschel mixer, and then biaxially extruded. The kneaded product was cooled by kneading with a machine.

  Then, the cooled kneaded product is coarsely pulverized by a cutter mill, and further pulverized using a jet mill [Nippon Pneumatic Industry Co., Ltd.] to give a color toner having a volume average particle size of about 10 μm. Coarse particles were obtained.

  Next, an insulating liquid composed of an aliphatic hydrocarbon [manufactured by Matsumura Oil Research Co., Ltd .: Moresco White P-120], a dispersant composed of a polyester resin as an additive (Avisia: Solsperse 13940) 30 parts by weight of the above colored toner coarse particles are mixed with 70 parts by weight of a dispersant solution to which 0.05% by weight is added, and a sand grinder (manufactured by IGARASHI KIKAI SEIZO CO., Ltd.) is used and the media is used. Using 150 cc of glass beads with a diameter of 1 mm as described above, the above mixed solution was wet-grinded for 15 hours under a condition of a cooling water temperature of 20 ° C. and a disk rotation speed of 2000 rpm using a 1/8 gallon vessel with a water jacket. A liquid developer stock solution in which toner having an average particle diameter of 3.66 μm is dispersed is obtained. . The volume average particle diameter of the toner was measured using a laser diffraction type particle size distribution measuring apparatus (manufactured by Shimadzu Corporation: SALD-2200).

  Then, the above-mentioned insulating liquid [Matsumura Oil Research Co., Ltd .: Moresco White P-120] is added to the liquid developer stock solution, and the solid content of the liquid developer stock solution becomes 20% by weight. A liquid developer was prepared by diluting as described above. Here, as a result of measuring the viscosity of the liquid developer using an ARES viscosity measuring device (ARES FR-100) under an ambient temperature of 25 ° C., the viscosity of the liquid developer is 5.34 Pa.・ It was s.

(Example 2)
In Example 2, in preparing the liquid developer, the above insulating liquid [manufactured by Matsumura Oil Research Co., Ltd.] was added to the liquid developer stock solution prepared in the same manner as in Example 1 above. : Moresco White P-120] is added a dispersant solution containing 0.05% by weight of an additive dispersant (Avisia: Solsperse 13940), and the solid content of the liquid developer stock solution is 20 A liquid developer was prepared so as to have a weight percent. As for the liquid developer, as in the case of Example 1 above, the viscosity at an ambient temperature of 25 ° C. was measured. As a result, the viscosity of the liquid developer was 5.21 Pa · s. It was.

(Example 3)
In Example 3, in preparing a liquid developer, colored toner coarse particles were obtained in the same manner as in Example 1 above, and then an insulating liquid [manufactured by Matsumura Oil Research Co., Ltd. 30 parts by weight of the above-mentioned colored toner coarse particles are mixed with 70 parts by weight of a dispersant solution obtained by adding 2% by weight of the additive dispersant (manufactured by Avicia: Solsperse 13940) to Sco White P-120]. Thereafter, in the same manner as in Example 1 above, the mixed solution was wet-grinded for 15 hours, and the first liquid developer in which the toner having a volume average particle size of 3.59 μm was dispersed was obtained. A stock solution was obtained.

  Then, this first liquid developer stock solution is rotated at 15000 rpm for 10 minutes using a centrifuge (manufactured by Kokusan Co., Ltd .: H-9R) to separate the solid content into a solid content and a liquid content. Take out, add the above insulating liquid [manufactured by Matsumura Oil Research Co., Ltd .: Moresco White P-120] so that the solid content becomes 20% by weight, and add a second liquid developer stock solution. Obtained.

  Next, the second liquid developer stock solution is again separated into a solid content and a liquid content using a centrifuge (manufactured by Kokusan Co., Ltd .: H-9R) as described above, and this solid content is taken out. The above insulating liquid [manufactured by Matsumura Oil Research Co., Ltd .: Moresco White P-120] was added so that the solid content was 20% by weight to obtain a liquid developer. Also for this liquid developer, the viscosity at an ambient temperature of 25 ° C. was measured in the same manner as in Example 1 above. As a result, the viscosity of this liquid developer was 5.01 Pa · s. It was.

(Comparative Example 1)
In Comparative Example 1, when the liquid developer was prepared, the above insulating liquid [Matsumura Oil Research Co., Ltd.] was added to the first liquid developer stock solution prepared in the same manner as in Example 3 above. A liquid developer was prepared such that the solid content of the first liquid developer stock solution was 20% by weight. Also for this liquid developer, the viscosity at an ambient temperature of 25 ° C. was measured in the same manner as in Example 1 above. As a result, the viscosity of this liquid developer was 3.51 Pa · s. It was.

  Next, each liquid developer prepared in Examples 1 to 3 and Comparative Example 1 was rotated at 15000 rpm for 10 minutes using the above centrifuge (manufactured by Kokusan Co., Ltd .: H-9R). The liquid component in each liquid developer is collected, and the amount of the additive that is released with respect to the insulating liquid is measured for each liquid component. The results are shown in Table 2 below.

  Further, using the liquid content in each of the liquid developers of Examples 1 to 3 and Comparative Example 1 collected as described above, the latent image potentials were respectively measured in the same manner as in the test solutions A1 to A5 in the above experimental example. The reduction rate was measured and the results are shown in Table 2 below.

  As a result, those in Examples 1 to 3 in which the concentration of the additive with respect to the insulating liquid was 0.1% by weight or less were comparative examples in which the concentration of the additive with respect to the insulating liquid exceeded 0.1% by weight. The decrease rate of the latent image potential is greatly reduced as compared with the case of No. 1, and the decrease in the potential of the electrostatic latent image due to the free additive is suppressed. In Examples 1 and 2, the decrease rate of the latent image potential was very low, and the decrease in the potential of the electrostatic latent image due to the liberated additive was further suppressed.

1 is a schematic explanatory diagram of an image forming apparatus using a liquid developing device according to an embodiment of the present invention. In the experiment example of this invention, an Example, and a comparative example, it is a schematic explanatory drawing of the test apparatus used in order to measure the decreasing rate of a latent image electric potential.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image carrier 2 Charger 3 Exposure apparatus 4 Transfer apparatus 5 Cleaning member 6 Static elimination apparatus 10 Liquid developing apparatus 11 Liquid developer 12 Developing tank 13 Developer carrier 14 Control member 15 Charging apparatus 16 Cleaning member

Claims (5)

  Using a liquid developer in which toner and additives are contained in an insulating liquid, the liquid developer is made into a thin layer state and conveyed to a development area facing the image carrier by the developer carrier, and an image is obtained. In the liquid developing device for developing the electrostatic latent image formed on the carrier, the liquid developer is made into a thin layer and is transported to the development area facing the image carrier by the developer carrier. In addition to providing a charging device for charging the developer, as the liquid developer, a liquid in which the amount of the free additive not adsorbed on the toner is 0.1% by weight or less with respect to the insulating liquid. A liquid developing apparatus using a developer.   2. The liquid developing device according to claim 1, wherein the amount of the free additive not adsorbed by the toner is 0.08% by weight or less with respect to the insulating liquid. A liquid developing apparatus.   2. The liquid developing apparatus according to claim 1, wherein the amount of the free additive not adsorbed by the toner is 0.05% by weight or less with respect to the insulating liquid. A liquid developing apparatus.   Using a liquid developer in which toner and additives are contained in an insulating liquid, the liquid developer is made into a thin layer state and conveyed to a development area facing the image carrier by the developer carrier, and an image is obtained. In the liquid developing device for developing the electrostatic latent image formed on the carrier, the liquid developer is made into a thin layer and is transported to the development area facing the image carrier by the developer carrier. A liquid developing apparatus comprising: a charging device for charging the developer; and a ratio at which the charge of the electrostatic latent image is erased by the toner contained in the liquid developer is set to 90% or more.   5. The liquid developing device according to claim 4, wherein a ratio of erasing charges of the electrostatic latent image by toner contained in the liquid developer is 95% or more.

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