JP2007148073A - Wet type image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which is small in starting torque and with which a high-quality image can be obtained for a long period without performing preliminary rotation to prolong the time of first printing. <P>SOLUTION: At least two or more function members which come into contact with or proximity to each other via a developing solution at the time of image formation operation are parted from each other during the stoppage of the image formation operation and the state that the liquid column of the insulating liquid is maintained in the spaced part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to a wet type image forming apparatus that forms an image using a developer in which toner is dispersed in an insulating carrier liquid.

  Conventionally, a printing machine has been mainly used as a means for producing a large amount of printed matter at high speed. By the way, in the printing field, there is a demand for small-scale printing that makes it impossible to make profits by creating a printed material by raising a plate, and so-called on-demand printing that can respond to such a small number of print requests Technology was sought.

  With the progress of digital technology in recent years, high-quality images that are comparable to printed materials can be obtained by electrophotographic image forming apparatuses. Therefore, an electrophotographic image forming apparatus is attracting attention as a means that can provide a small number of printed materials at a high speed and at a low price. Incidentally, electrophotographic image forming methods include a dry image forming method and a wet image forming method. Among them, a wet image forming method using a developer composed of a toner and an insulating carrier liquid is suitable for high-definition image formation because a toner having a small particle diameter is used. Further, since the developer is interposed between the members constituting the apparatus, in principle, the torque required to operate these members can be kept small, and the life of the apparatus constituent members can be kept long. There are also benefits.

  However, since the liquid component in the developer is volatilized while the operation of the apparatus is stopped, when the operation is resumed, there may be a case where the developer is not left to smoothly operate the member, and the starting torque is increased and the member is increased. Had the problem of loading. Further, due to the evaporation of the liquid component, the residual toner is fixed between the members, which has problems such as affecting the operation and causing image defects.

To solve such a problem, an image forming method has been proposed in which the development unit can be preliminarily driven prior to the development operation timing (see, for example, Patent Document 1). Furthermore, a technique of an image forming apparatus has been proposed in which the rotation speed of the developing roller during preliminary driving is higher than the speed during image formation (see, for example, Patent Document 2).
JP 2001-75365 A JP 2002-278292 A

  However, the image forming apparatuses that require preliminary driving disclosed in Patent Documents 1 and 2 have a problem that it takes time until the first print is started.

  The present invention provides a wet-type image forming apparatus capable of quickly starting a first print without performing preliminary driving and capable of performing smooth print creation without applying a load to apparatus constituent members at the time of startup. For the purpose. That is, according to the present invention, even when the operation stop period is long, the operation can be started with a small torque when the operation is resumed, and it is possible to maintain the life of the apparatus constituent members for a long time and to stably maintain a high-quality toner image for a long time. An object of the present invention is to provide a wet image forming apparatus.

  As a result of extensive research, the present inventor has found that the above problems can be solved by any of the configurations described below.

  According to a first aspect of the present invention, there is provided a wet image forming apparatus comprising: a developer containing a toner and an insulating carrier liquid; and an image carrier that carries a latent image developed by the developer. At least two or more functional members that are in contact with or close to each other via the developer during the forming operation are separated when the image forming operation is stopped, and a liquid column of an insulating liquid is formed in the separated portion. The state is maintained.

  A wet image forming apparatus according to a second aspect is the wet image forming apparatus according to the first aspect, wherein the insulating liquid is a non-volatile liquid.

  A wet image forming apparatus according to a third aspect is the wet image forming apparatus according to the first or second aspect, wherein the insulating liquid is the developer.

  A wet image forming apparatus according to a fourth aspect is the wet image forming apparatus according to the first or second aspect, wherein the insulating liquid is the carrier liquid.

  A wet image forming apparatus according to a fifth aspect of the present invention is the wet image forming apparatus according to any one of the first to fourth aspects, further comprising detecting means for detecting that the liquid column is formed. To do.

  A wet image forming apparatus according to a sixth aspect is the wet image forming apparatus according to any one of the first to fifth aspects, further comprising means for forming the liquid column.

  The wet image forming apparatus according to claim 7 is the wet image forming apparatus according to claim 6, wherein the liquid column forming unit forms the liquid column based on a detection result of the detection unit. To do.

  The wet image forming apparatus according to claim 8 is the wet image forming apparatus according to any one of claims 1 to 7, wherein the two or more functional members include the image carrier and the image carrier. And a peripheral member disposed around.

  A wet image forming apparatus according to a ninth aspect is the wet image forming apparatus according to the eighth aspect, wherein the developing device includes a developing roller facing the image bearing member, and the image bearing member for cleaning the image bearing member. And a cleaning member, and the peripheral member disposed around the image carrier includes at least one of the developing roller and the image carrier cleaning member.

  A wet image forming apparatus according to claim 10 is the wet image forming apparatus according to claim 8 or 9, further comprising an image carrier squeeze member for squeezing a carrier liquid from a developed image carrier. The peripheral member disposed around the image carrier includes the image carrier squeeze member.

  The wet image forming apparatus according to claim 11 is the wet image forming apparatus according to any one of claims 1 to 7, wherein the toner image formed on the image carrier is temporarily transferred. And the two or more functional members include the intermediate transfer member and a peripheral member disposed around the intermediate transfer member.

  A wet image forming apparatus according to a twelfth aspect is the wet image forming apparatus according to the eleventh aspect, wherein a secondary transfer roller for secondarily transferring a toner image transferred onto the intermediate transfer member to a recording medium; An intermediate transfer member cleaning member for cleaning the intermediate transfer member, and peripheral members disposed around the intermediate transfer member include the image carrier, the secondary transfer roller, and the intermediate transfer member cleaning member. At least one of the members is included.

  A wet image forming apparatus according to a thirteenth aspect is the wet image forming apparatus according to the eighth or ninth aspect, further comprising an intermediate transfer member squeeze member for squeezing the carrier liquid from the intermediate transfer member after the toner image is transferred. The peripheral member disposed around the image carrier includes the squeeze member for the intermediate transfer member.

  In an image forming apparatus having a developer containing a toner and an insulating carrier liquid and an image carrier that carries a latent image developed by the developer, they are in contact with or in close proximity to each other via the developer during an image forming operation. At least two or more functional members are separated when the image forming operation is stopped, and a state in which the liquid column of the insulating liquid is formed in the separated portion is small when the operation is resumed. It is possible to provide an image forming apparatus that can be activated by torque, can maintain the life of the apparatus constituent members for a long time, and can stably obtain a high-quality toner image over a long period of time.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing an example of a wet image forming apparatus of the present invention. Around the drum-shaped image carrier 201, the charging device 205, the exposure device 206, the developing device 10, the image carrier squeeze roller 202, the intermediate transfer member 301, and the image carrier cleaning roller 203 are sequentially arranged in the rotation direction indicated by the arrows. The image transfer member cleaning blade 204 is disposed, and the intermediate transfer member squeeze roller 302, the secondary transfer roller 303, the intermediate transfer member cleaning roller 304, and the intermediate transfer member cleaning blade 305 are arranged around the intermediate transfer member 301. It is installed.

  The surface of the image carrier 201 is uniformly charged to a predetermined surface potential by the charging device 205, and then the image information is exposed by the exposure device 206 to form an electrostatic latent image on the surface of the image carrier 201. . Next, the electrostatic latent image on the image carrier 201 is developed with a developer containing toner and a carrier liquid by the developing device 10 to form a toner image on the surface of the image carrier 201. At this time, not only the toner but also the carrier liquid adheres to the surface of the image carrier 201.

  Next, the image carrier 201 removes part of the carrier liquid adhering to the image carrier 201 by the image carrier squeeze roller 202 to which a predetermined voltage is applied. Thereafter, the toner image on the image carrier 201 is transferred to the intermediate transfer member 301 to which a predetermined voltage is applied. Excess carrier liquid adhering to the intermediate transfer body 301 after the transfer is removed by the intermediate transfer body squeeze roller 302 to which a predetermined voltage is applied, and the toner image is transferred onto the transfer paper 306 by the secondary transfer roller 303. The secondary transfer roller 303 may be a simultaneous transfer fixing roller having a built-in heater. Further, the transferred transfer paper 306 may be fixed by a fixing roller (not shown).

  The developing device 10 will be described in more detail. A constant amount of the developer is pumped up from the developing tank 102 storing the developer including toner and carrier liquid by the supply roller 103 and the regulating blade 101, and the constant amount of developer is supplied to the developing roller 106 by the transport roller 104. Charge is given to the toner by the pre-development charger 105 to the developer on the developing roller 104 supplied. Thereafter, the charged toner conveyed to the image carrier 201 by the developing roller 106 develops the image portion on the image carrier 201.

  In the wet image forming apparatus as described above, the two or more functional members that are in contact with or close to each other via a developer during the image forming operation include the following. For example, if one functional member is the image carrier 201, the developing roller 106, the image carrier squeeze roller 202, the intermediate transfer member 301, and the image carrier 201 are functional members that are close to or in contact with the image carrier 201 via the developer. There are a carrier cleaning roller 203 and an image carrier cleaning blade 204. Further, when the intermediate transfer member 301 is used as one functional member, the image bearing member 201, the intermediate transfer member squeeze roller 302, and the secondary transfer roller are functional members that are close to or in contact with the intermediate transfer member 301 via the developer. 303, an intermediate transfer member cleaning roller 304, and an intermediate transfer member cleaning blade 305. Further, when the transport roller 104 of the developing device 10 is a single functional member, there are a developing roller 106 and a supply roller 103 as functional members that are close to or in contact with the transport roller 104 via the developer.

  During an image forming operation, each functional member is in a state of being driven to rotate or relatively slide through the developer in a state of being in proximity or in contact with each other. At this time, the torque of the functional member that is rotationally driven is relatively small and stable. However, in the conventional image forming apparatus, when the image forming operation is finished and the stopped state is continued, the developer between the two functional members that are in contact with each other is pushed out between the two functional members. It will be in the state which the surface of contacts. When the image forming operation is started again from this state, the frictional resistance between the two functional members is large, the driving torque of the rotating member at the initial start-up becomes very large, the movement is unstable, and a large motor is required. In addition, there is a problem in that the contact portion of each functional member is severely worn and the component life is shortened. Further, when the two functional members are slightly separated from each other, if the image forming operation is stopped, the carrier liquid between the two functional members volatilizes, and the toner adheres to the functional member surface. There was a problem of image noise.

  On the other hand, in the present embodiment, even when the image forming operation is stopped, the liquid always exists as a liquid column between the two functional members, and the two functional members are separated from each other. ing. By doing so, the starting torque during the next image forming operation can be reduced, the wear of the members can be reduced, the toner can be used for a long period of time, and the toner can be prevented from sticking. A wet image forming apparatus capable of forming

  The liquid column used here refers to a state where the liquid is filled in a state where two members are bridged by a meniscus. 2a and 2b show the state of the liquid column. In FIG. 2a, the two functional members A and B are cylindrical and form a liquid column in a separated state. FIG. 2b shows one functional member A having a cylindrical shape and the other functional member B having a blade shape. The liquid column between the two functional members is formed in this state in the axial direction of the cylindrical body. The formation range of the liquid column is preferably formed over the entire region in the axial direction, but may be formed over a length of 50% or more of the length of the functional member.

  The two functional members are in a slightly separated state during the image forming operation, and need not be further separated as long as the liquid column can be formed. After stopping the forming operation, a mechanism for separating the two functional members is required. There is no restriction | limiting in particular as a means to space apart, What is necessary is just to space apart to the extent that a liquid column can form the two functioning members which are in contact. For example, when two functional members are pressed and contacted by a spring or the like, a spacer can be inserted between the functional members and separated at a predetermined interval.

  The liquid forming the liquid column may be an insulating liquid, but among them, a non-volatile liquid is preferable. By using the non-volatile liquid, the toner does not aggregate or is not dried and fixed to the functional member even when the image forming operation is stopped for a long time.

  In addition, if the insulating liquid forming the liquid column is a developer, it is economical because it is not necessary to prepare a liquid for forming the liquid column separately.

  Further, if the insulating liquid forming the liquid column is a carrier liquid, there is no fear of toner aggregation, and a higher quality image can be formed.

  The developer mainly comprises an insulating liquid as a carrier liquid, a toner for developing an electrostatic latent image, and a dispersant for dispersing the toner.

  The carrier liquid can be used without particular limitation as long as it is generally used for an electrophotographic developer, but a non-volatile liquid is particularly preferable. Examples of the non-volatile liquid include silicon oil, mineral oil, paraffin oil, mineral oil, and the like.

  Any toner can be used without particular limitation as long as it is generally used for an electrophotographic developer. As the binder resin for toner, for example, thermoplastic resins such as polystyrene resin, styrene-acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, and polyurethane resin can be used. A plurality of these resins may be mixed and used. Also, commercially available pigments and dyes used for coloring the toner can be used. For example, as the pigment, carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, and the like can be used. Solvent red 27, acid blue 9, or the like can be used as the dye.

  The developer can be prepared based on a commonly used technique. For example, the binder resin and the pigment are melt-kneaded using a pressure kneader, a roll mill or the like at a predetermined blending ratio and uniformly dispersed, and the obtained dispersion is finely pulverized by, for example, a jet mill. By classifying the obtained fine powder with, for example, an air classifier, a colored toner having a desired particle diameter can be obtained.

  Subsequently, the obtained toner is mixed with an insulating liquid as a carrier liquid at a predetermined blending ratio. This mixture can be uniformly dispersed by a dispersing means such as a ball mill to obtain a developer.

  The toner concentration of the developer is preferably 10 to 50% by mass.

  The viscosity of the developer at this time is preferably 0.05 Pa · s to 100 Pa · s at 25 ° C., more preferably 0.1 Pa · s to 20 Pa · s. When the viscosity is lower than 0.05 Pa · s, the toner concentration is lowered and the dispersibility of the toner is deteriorated, so that it is impossible to develop the developer in a thin layer.

  On the other hand, when the viscosity is higher than 100 Pa · s, it becomes difficult to agitate the carrier liquid and the toner, and there is a problem that the cost for the apparatus becomes large because an apparatus for producing a uniform developer becomes large. The viscosity of the developer is a value (25 ° C.) measured with a viscosity measuring device Ares (product number: FR-100) manufactured by TA Instruments.

  Next, detection means for detecting whether or not a liquid column is formed between two functional members and supply means for supplying an insulating liquid based on the detection means will be described.

  FIG. 3 shows a liquid column detection device 40. The detection device 40 includes a light emitting element 41 and a light receiving element 42 and can detect whether a liquid column exists between the functional members A and B. The light from the light emitting element 41 is received by the light receiving element 42 and compared with the amount of light measured in advance when there is no liquid column, and it is determined whether or not the liquid column is formed, and there is no liquid column. Sometimes, a liquid column is formed by supplying an insulating liquid with a liquid supply device. A plurality of light emitting elements 41 and light receiving elements 42 may be arranged in the longitudinal direction of the functional member. Moreover, you may make it move to the longitudinal direction of a functional member.

  FIG. 4 shows an embodiment of the liquid supply device 50. The liquid supply device 50 includes an insulating liquid transfer pipe 52, a liquid column forming nozzle 51, and a liquid supply pump 53. Although it is not necessary when the nozzle has a plurality of discharge ports arranged in the longitudinal direction or has a slit-like laterally long discharge port along the longitudinal direction, the liquid column forming nozzle 51 is arranged in the longitudinal direction of the functional member. You may further have a mechanism to move to.

  The image forming operation is stopped and the two functional members are separated from each other, and at the same time, the liquid column detecting means 40 detects the presence of the liquid column. When it is determined that the liquid column is not formed, a predetermined amount of insulating liquid is injected between the two functional members from the liquid column forming nozzle to form the liquid column.

  A specific example will be described below.

  The image carrier squeeze roller 202 in FIG. 1 is a member for removing the carrier liquid on the surface of the image carrier 201 developed by the developing device 10. The image carrier squeeze roller 202 is in contact with the image carrier 201 in a state where a bias voltage having the same polarity as the toner is applied during image formation, and rotates in the direction of the arrow in FIG. 1 at the same speed as the image carrier 201. . As a result, only the excess carrier liquid on the image carrier 201 is transferred to the image carrier squeeze roller 202, and the toner image on the image carrier 201 can be transferred to the intermediate transfer member 301 with a small amount of carrier liquid. . In the present embodiment, after the image forming operation is finished, the image carrier squeeze roller 202 is separated from the surface of the image carrier 201. The separation distance is 0.1 to 0.8 mm. Thereafter, the detection device 40 detects whether or not there is a liquid column in the separation portion between the image carrier 201 and the image carrier squeeze roller 202, and if the liquid column is not formed by 50% or more in the longitudinal direction of the separation portion, The column forming means injects the developer to form a liquid column. When the liquid column is formed by 50% or more, it is left as it is. By doing so, the starting torque at the start of the next image forming operation is reduced, the wear of the surface of the image carrier 201 and the surface of the image carrier squeeze roller 202 is prevented, and the carrier liquid is removed over a long period of time. Can extend the life of parts.

  The carrier liquid and toner that have not been transferred to the intermediate transfer member 301 are collected by the image carrier cleaning roller 203 and the image carrier cleaning blade 204. The image carrier cleaning roller 203 and the image carrier 201 and the image carrier cleaning blade 204 and the image carrier 201 are separated after the image forming operation is completed. The separation distance is 0.1 to 0.8 mm. After the separation, whether the liquid column exists between the functional members is detected in the same manner as the image carrier 201 and the image carrier squeeze roller 202, and the liquid column is formed to reduce the torque at the time of activation. The wear of the member can be prevented and the life of the part can be extended.

  Similarly to the image carrier squeeze roller 202, the intermediate transfer member squeeze roller 302 is a member that removes excess carrier liquid on the intermediate transfer member 301. By performing the same operation as the relationship between the image carrier 201 and the image carrier squeeze roller 202, it is possible to reduce the starting torque and extend the component life.

  As described above, at least two or more functional members that are in contact with or close to each other via the developer during the image forming operation are separated when the image forming operation is stopped, and the liquid column of the insulating liquid is provided in the separation portion. By maintaining the formed state, the pre-rotation that has been conventionally performed is not performed, so that the first printing time is shortened, the starting torque is small, and a high-quality image can be obtained over a long period of time. Can provide. Moreover, the lifetime of each functional member can be lengthened.

Next, examples and comparative examples of the present invention will be described.
Example 1
A wet image forming apparatus having the configuration shown in FIG. 1 was used. The image carrier 201 is obtained by forming an organic photoreceptor film (film thickness: 35 μm) on an aluminum drum having a diameter of 210 mm, and the rotational peripheral speed was set to 350 mm / sec. As the charging device 205, a scorotron charger was used so that the surface potential of the image carrier 1 was -450V. The exposure device 3 was set so that the surface potential of the image carrier 1 was −100 V when the image portion was exposed with a semiconductor laser.

  As a developer, a carrier liquid (silicon oil (manufactured by Shin-Etsu Silicone Co., Ltd.)) was pulverized with black toner for Konica Minolta Business Technologies Co., Ltd. color copier C350, and an average particle diameter of 3 μm was added. . A dispersant (Solsperse 13940, manufactured by Avicia) was added at 10% by mass based on the toner amount. The charge amount of the toner of the obtained liquid developer was −100 μC / g.

  The conditions of the developing roller 106 of the liquid developing device 10 are as follows.

Diameter: 40mm
Material: NBR + carbon black Surface conductivity: 1.0 × 10 ⁷ Ω · cm
Rubber hardness: 50 °
Rotational peripheral speed: 350mm / sec
Bias voltage: -300V
During image formation, the developing roller 104 contacts the image carrier 201 and development is performed.

  As the image carrier cleaning blade, a 3 mm silicon rubber blade is used, and is in contact with the rotation direction of the image carrier at the angle inclined by 20 degrees from the tangent line of the image carrier 201 in the cleaning operation. Yes. The pressure contact force is 0.341 N / cm.

  The intermediate transfer member 301 has a diameter of 100 mm, and is obtained by applying a urethane coat of 1 mm to a substrate surface of 3 mm of silicon rubber. In this embodiment, silicon rubber is used as the intermediate transfer member, but NBR, urethane rubber, fluorine rubber, or the like may be used. Further, these surfaces may be coated with PFA or urethane.

  During image formation, the intermediate transfer member 301 and the image carrier 201 are in contact with each other.

  The conditions of the intermediate transfer member squeeze roller 302 are as follows.

Diameter: 26mm
Material: NBR + carbon black Surface conductivity: 1.0 × 10 ⁷ Ω · cm
Rubber hardness: 50 °
Rotational peripheral speed: 350mm / sec
Bias voltage: -350V
During image formation, the intermediate transfer member 301 and the intermediate transfer member squeeze roller 302 are in contact with each other.

  The conditions of the intermediate transfer member clean roller 304 are as follows.

Diameter: 26mm
Material: NBR + carbon black Surface conductivity: 1.0 × 10 ⁷ Ω · cm
Rubber hardness: 50 °
Rotational peripheral speed: 350mm / sec
Bias voltage: -550V
During image formation, the intermediate transfer member 301 and the intermediate transfer member cleaning roller 304 are in contact with each other. The image forming operation was stopped, and the separation distance between the intermediate transfer member 301 and the intermediate transfer member cleaning roller 304 was set to 0.08 mm. Since the liquid column was not formed at this time, the liquid column of the carrier liquid was formed by supplying the carrier liquid from the liquid supply device. Next, an image forming operation was started, and after the intermediate transfer member 301 and the intermediate transfer member cleaning roller 304 were rotated, both rollers were brought into contact with each other. The starting torque of the intermediate transfer member cleaning roller 304 at the start of the image forming operation was 19.6 N · cm. Further, after the contact, the torque of the intermediate transfer member cleaning roller 304 was 49 N · cm. Under these conditions, an endurance test was performed with a pattern in which a chart of A4 plate having a black and white ratio (B / W) of 5% was stopped after continuous printing. When the cleaning performance of the intermediate transfer member cleaning roller 304 at this time was evaluated, 100,000 sheets still had a cleaning performance of 80%. The cleaning performance includes the amount of toner and carrier liquid A on the surface of the intermediate transfer body 301 after transfer to the transfer paper 306 and the toner and carrier remaining on the surface of the intermediate transfer body 301 after cleaning by the intermediate transfer body cleaning roller. From the amount B of the liquid, it was determined from the formula of (A−B) / A × 100 (%). Further, the life of the intermediate transfer member cleaning roller 304 is set to a time when the cleaning performance becomes 70% or less.
(Comparative Example 1)
In Example 1, image formation was performed in the same manner as in Example 1 except that the liquid column was not formed after the image forming operation was stopped, and each evaluation item was measured. The torque at the start of the intermediate transfer member cleaning roller 304 at the start of the image forming operation was 196 N · cm. Further, after the contact, the torque until the developer reaches the position of the intermediate transfer member cleaning roller 304 was 490 N · cm. The life of the intermediate transfer member cleaning roller 304 according to the durability test was 20,000 sheets.
(Comparative Example 2)
In Example 1, after the image forming operation is stopped, image formation is performed in the same manner as in Example 1 except that the intermediate transfer member 301 and the intermediate transfer member cleaning roller 304 are not separated from each other, and thus no liquid column is formed. Each of the evaluation items was measured. The starting torque of the intermediate transfer member cleaning roller 304 at the start of the image forming operation was 490 N · cm. The life of the intermediate transfer member cleaning roller 304 was 25,000 sheets.
(Example 2)
In the wet image forming apparatus used in Example 1, after completion of the image forming operation, the image carrier 201 and the intermediate transfer member 301 were separated by a separation distance of 0.05 mm, and a carrier liquid was injected by a liquid supply device to form a liquid column. . When the operation for the next image formation was started, the starting torque of the image carrier 201 was 39 N · cm. Thereafter, the image carrier 201 and the intermediate transfer member 301 were brought into contact with each other, and a durability test was performed under the same conditions as in Example 1. The film thickness of the photosensitive layer of the image bearing member 201 after 50,000 sheets was 30 μm, and 5 μm shaving was observed. However, when the created image was visually confirmed, no change was observed.
(Comparative Example 3)
In Example 2, a durability test was performed in the same manner as in Example 2 except that the liquid column was not formed after the image forming operation was stopped. The film thickness of the image carrier 201 after 50,000 endurance tests was 20 μm, and 15 μm shaving was observed. When the created image was visually evaluated, deterioration in image quality was confirmed.
(Comparative Example 4)
In Example 2, after the image forming operation was stopped, an endurance test was performed in the same manner as in Example 2 except that the image carrier 201 and the intermediate transfer member 301 were not separated from each other, and thus no liquid column was formed. When the operation for the next image formation was started, the starting torque of the image carrier 201 was 196 N · cm. The film thickness of the photosensitive layer of the image carrier 201 after 50,000 sheets was 23 μm, and 12 μm shaving was observed. When the created image was visually evaluated, deterioration in image quality was confirmed.
(Example 3)
In the wet image forming apparatus used in Example 1, after completion of the image forming operation, the image carrier 201 and the image carrier cleaning blade 204 are separated by a separation distance of 0.05 mm, and a carrier liquid is injected by a liquid column forming unit. A liquid column was formed. The image forming operation was started with the liquid column formed, and the starting torque when the image carrier 201 was rotated was 9.8 N · cm. Further, after starting, the torque after the image carrier 201 and the image carrier cleaning blade 204 were brought into contact with each other was 29 N · cm. The cleaning performance after 50,000 durability tests was 85%. For the cleaning performance, the same calculation method as in Example 1 was used.
(Comparative Example 5)
In Example 3, image formation was performed in the same manner as in Example 3 except that the liquid column was not formed after the image forming operation was stopped, and each evaluation item was measured. The torque of the image carrier 201 at the time of startup was 9.8 N · cm. After startup, the image carrier cleaning blade 204 comes into contact with the image carrier 201, and the developer from the developing device 10 is transferred to the image carrier. Until the position of the cleaning blade 204 was reached, it was 588 N · cm. Thereafter, after the developer reached the position of the image carrier cleaning blade 204, the torque was 29 N · cm. In the durability test of 25,000 sheets, streaky wiping residue of the developer was generated on the image carrier 201.
(Comparative Example 6)
In Example 3, after the image forming operation was stopped, image formation was performed in the same manner as in Example 3 except that the image carrier 201 and the image carrier cleaning blade 204 were not separated and thus no liquid column was formed. Each of the evaluation items was measured. When the operation for the next image formation was started, the starting torque of the image carrier 201 was 588 N · cm. In the durability test of 28,000 sheets, streaky wiping residue of the developer was generated on the image carrier 201.
Example 4
In the wet image forming apparatus used in Example 1, after the image forming operation is finished, the intermediate transfer member 301 and the intermediate transfer member squeeze roller 302 are separated by a separation distance of 0.05 mm, and a carrier liquid is injected by a liquid supply device. A pillar was formed. The starting torque of the intermediate transfer member squeeze roller 302 when the image forming operation was started with the liquid column formed was 9.8 N · cm. Further, after starting, the torque after bringing the intermediate transfer body 301 and the intermediate transfer body squeeze roller 302 into contact with each other was 29 N · cm. The squeeze performance after 50,000 durability tests was good at 85%. The squeeze performance is determined by the amount A of toner and carrier liquid on the surface of the intermediate transfer member 301 after being transferred from the image carrier 201 to the intermediate transfer member 301 and the surface of the intermediate transfer member 301 after being squeezed by the intermediate transfer member squeeze roller 302. From the amount B of the remaining toner and carrier liquid, the amount was determined from the formula (A−B) / A × 100 (%).
(Comparative Example 7)
In Example 4, the durability test was performed in the same manner as in Example 4 except that the liquid column was not formed after the image forming operation was stopped. The starting torque of the intermediate transfer member squeeze roller 302 when the image forming operation was started was 9.8 N · cm. However, after contact with the intermediate transfer member 301, the developer is placed at the position of the intermediate transfer member squeeze roller 302. The torque until it reached 637 N · cm. In addition, when the durability test was performed, abrasion scratches were observed on the surface of the intermediate transfer member squeeze roller 302 with 18,000 sheets, and obvious squeeze defects that could be visually recognized occurred.
(Comparative Example 8)
In Example 4, after the image forming operation was stopped, the endurance test was performed in the same manner as in Example 4 except that the intermediate transfer member 301 and the image intermediate transfer member squeeze roller 302 were not separated and thus the liquid column was not formed. went. The starting torque of the intermediate transfer member squeeze roller 302 when the image forming operation was started was 390 N · cm. In addition, when the durability test was performed, abrasion scratches were observed on the surface of the intermediate transfer member squeeze roller 302 with 25,000 sheets, and obvious squeeze defects that were apparent to the naked eye occurred.

  As described above, in the wet image forming apparatus according to the present invention, at least two or more functional members that are in contact or close to each other via the developer during the image forming operation are arranged so as to be in a separated state when the image forming operation is stopped. In addition, a liquid image column of an insulating liquid is formed in the separation portion, thereby providing a wet image forming apparatus capable of obtaining a high-quality image over a long period of time with a small starting torque without performing preliminary rotation. And the lifetime of a functional member can be lengthened.

1 is a schematic view of an embodiment of a wet image forming apparatus according to the present invention. It is the schematic which shows the formation state of a liquid column. It is the schematic which shows one Example of the detection means of the liquid column which concerns on this invention. It is the schematic which shows one Example of the formation means of the liquid column which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Developing device 101 Control blade 102 Developing roller 103 Anilox roller 104 Conveying roller 105 Charger before development 106 Developing roller 201 Image carrier 202 Image carrier squeeze roller 203 Image carrier cleaning roller 204 Image carrier cleaning blade 205 Charging device 206 Exposure device 301 Intermediate transfer member 302 Intermediate transfer member squeeze roller 303 Secondary transfer roller 304 Intermediate transfer member cleaning roller 305 Intermediate transfer member cleaning blade 306 Transfer paper

Claims (13)

A developer containing toner and an insulating carrier liquid;
An image carrier carrying a latent image developed by the developer;
In a wet image forming apparatus having
At least two or more functional members that are in contact with or close to each other via the developer during the image forming operation are separated when the image forming operation is stopped, and a liquid column of insulating liquid is formed in the separated portion. A wet image forming apparatus characterized in that the state is maintained. The wet image forming apparatus according to claim 1, wherein the insulating liquid is a non-volatile liquid. The wet image forming apparatus according to claim 1, wherein the insulating liquid is the developer. The wet image forming apparatus according to claim 1, wherein the insulating liquid is the carrier liquid. The wet image forming apparatus according to claim 1, further comprising a detecting unit configured to detect that the liquid column is formed. The wet image forming apparatus according to claim 1, further comprising means for forming the liquid column. The wet image forming apparatus according to claim 6, wherein the liquid column forming unit forms the liquid column based on a detection result of the detection unit. The wet method according to claim 1, wherein the two or more functional members include the image carrier and a peripheral member disposed around the image carrier. Image forming apparatus. A developing device including a developing roller facing the image carrier; and an image carrier cleaning member for cleaning the image carrier; and a peripheral member disposed around the image carrier, 9. The wet image forming apparatus according to claim 8, further comprising at least one of a developing roller and the image carrier cleaning member. An image carrier squeeze member for squeezing the carrier liquid from the developed image carrier, and a peripheral member disposed around the image carrier includes the image carrier squeeze member; The wet image forming apparatus according to claim 8 or 9. The image forming apparatus further includes an intermediate transfer member to which a toner image formed on the image carrier is temporarily transferred, and the two or more functional members are disposed around the intermediate transfer member and the intermediate transfer member. The wet image forming apparatus according to claim 1, further comprising a peripheral member. A secondary transfer roller for secondary transfer of the toner image transferred onto the intermediate transfer member to a recording medium; and an intermediate transfer member cleaning member for cleaning the intermediate transfer member; 12. The wet image forming according to claim 11, wherein the peripheral member disposed around the at least one member includes at least one of the image carrier, the secondary transfer roller, and the intermediate transfer member cleaning member. apparatus. The image forming apparatus further includes an intermediate transfer member squeeze member for squeezing the carrier liquid from the intermediate transfer member after the toner image is transferred, and the peripheral member disposed around the image carrier includes the intermediate transfer member squeeze member. The wet image forming apparatus according to claim 8, wherein the wet image forming apparatus is an image forming apparatus.

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