JP5175565B2 - Liquid developing apparatus and wet image forming apparatus - Google Patents

Description

  The present invention relates to a liquid developing apparatus and a wet image forming apparatus, and more particularly, to a liquid developing apparatus and a wet image forming apparatus that are excellent in recovery efficiency of toner having a predetermined polarity.

In the wet image forming apparatus, a liquid developing device is mounted as a developing device, and the electrostatic latent image formed on the photosensitive drum is developed with a liquid developer supplied from the liquid developing device.
In the liquid developing device, the liquid developer stored in the liquid developer tank is pumped up by a pumping roller, thinned by a supply roller, and then applied as a thin layer to the developing roller. Supplied to the drum.
Conventionally, an anilox roller has been used as a supply roller for the purpose of forming a uniform thin layer of liquid developer. The anilox roller is a roller having a precise cell engraved on the surface, and the liquid developer supplied by the scooping roller is stored in the cell and conveyed to the developing roller.
At this time, by restricting the surface of the anilox roller with a doctor blade, a precisely defined amount of liquid remains in each cell and is applied to the developing roller to form a thin layer of liquid developer. ing.

The thin layer of liquid developer thus formed on the developing roller is a charging device provided on the upstream side in the rotation direction of the developing roller with respect to the photosensitive drum in order to improve the developing performance to the photosensitive drum. Thus, a bias potential is applied.
That is, the toner component in the thin layer of the liquid developer is collected and compressed (toner compaction processing) by the electric field action on the developing roller side, and a liquid developer layer having a high concentration toner component is formed on the developing roller side. . Thereafter, the thin layer of liquid developer is supplied to the photosensitive drum, and the electrostatic latent image on the photosensitive drum is developed to form a fine toner image.

However, after developing the toner image on the photosensitive drum, the liquid developer that has not been transferred from the developing roller to the photosensitive drum remains in the developing roller.
If such residual liquid developer accumulates on the developing roller and aggregates, toner contamination or the like may be induced, and the formed image may be adversely affected.
Therefore, in order to perform stable and stable image formation, it is necessary to remove and clean the liquid developer remaining on the developing roller each time to maintain the surface state of the developing roller appropriately.

Examples of the means for removing the liquid developer remaining on the developing roller or the like generally include an electric field action and a mechanical action.
As for the electric field action, the toner component is adsorbed by applying a bias potential by using a cleaning roller or the like that rotates in synchronization with the developing roller by being brought into contact with the developing roller and applied with a bias potential. In general, the structure is removed from the developing roller.
In general, the mechanical action is such that the cleaning blade is brought into contact with the developing roller and the liquid developer is removed from the developing roller by a mechanical action such as a frictional force.
In addition, a liquid developing apparatus that simultaneously applies an electric field action and a mechanical action has also been proposed, and a removing means configured to remove the liquid developer by providing the cleaning roller with a function such as a friction action is proposed. (For example, see Patent Documents 1 and 2).

Further, when a liquid developer that is not used for developing a toner image is supplied to the developing roller, toner compaction processing is not performed, and liquid developer that is not used for developing the toner image is not collected by the cleaning roller. Thus, a liquid developing method for recovering the liquid developer in a highly reusable state has been proposed (see, for example, Patent Document 3).
That is, as shown in FIGS. 6 to 7, the toner component 331a recovered by the electric field removing unit 332 and the mechanical removing unit 333 is separated from the other liquid developer component (having a large carrier component) 331b. Separately, the liquid developing method efficiently recovers and discards the liquid developer by collecting it in separate tanks.
More specifically, as shown in FIG. 8, an electric field removing unit 332 and a mechanical removing unit 333 are sequentially provided around the developing roller 312, and the electric field is synchronized with charging by the charging device 317. Control means for applying a predetermined bias potential to the automatic removal means 332 is provided.

On the other hand, although the cleaning of the developing roller is not performed, the residual toner on the electrostatic image carrier after transfer is electrostatically applied to a plurality of cleaning members in a non-contact state with the electrostatic image carrier regardless of the charging polarity. There has been proposed a means for transferring to the surface of the electrostatic image carrier and removing it from the electrostatic image carrier (see, for example, Patent Document 4).
More specifically, as shown in FIG. 9, bias voltages having different polarities are applied to a plurality of cleaning members 420A and 420B arranged side by side from the surface of the electrostatic image carrier 410 by bias applying devices 425A and 425B. The removing means is configured to suck and transfer the residual toner on the electrostatic image carrier 410 to the cleaning members 420A and 420B.
Japanese Patent Application Laid-Open No. 9-211993 JP 2001-92259 A JP 2007-225893 A JP-A-7-306617

However, in the wet image forming apparatuses described in Patent Documents 1 to 3, no consideration is given to the presence of a liquid developer having a reverse polarity contained in the liquid developer having a predetermined charge.
That is, as shown in FIG. 10, even a small amount of liquid developer having a reverse polarity may be collected together with a liquid developer having a desired charge, and the performance of the collected liquid developer is unused. There was a problem that it was extremely poor as compared with the liquid developer.

For example, the polarity of the liquid developer is basically determined by the type of the charge imparting agent, but even if it is a positively charged liquid developer using a charge imparting agent such as a metal salt (fatty acid, resin acid, naphthenic acid). It has been found that negatively charged liquid developer is mixed.
On the other hand, it has been found that even a negatively charged liquid developer using a charge imparting agent such as alkylbenzene sulfonic acid is mixed with a positively charged liquid developer.
However, there is a problem that the transfer efficiency is lowered during image formation when a small amount of liquid developer having a reverse polarity is mixed with a liquid developer having a desired polarity. In addition, even when a predetermined bias potential is applied in the liquid developing device, there is a problem that cleaning failure is likely to occur because electrophoresis does not effectively occur from the developing roll to the cleaning member.

  Note that the electrophoresis experiment shown in FIG. 10 is a microscopic observation photograph after 10 seconds have passed with the collected liquid developer applied with an electric field of 500 V between both electrodes. As understood from this photograph, it is confirmed that the negatively charged liquid developer is mixed in the positively charged liquid developer.

On the other hand, the image forming apparatus of Patent Document 4 discloses that a plurality of non-contact cleaning devices for a photoconductor are provided and a bias potential having a reverse polarity is applied.
However, when applied to a liquid development system that removes the liquid developer attached to the developing roller using electrophoresis, there has been a problem that the liquid developer cannot be completely removed.

Therefore, as a result of intensive studies, the present inventors have found that both a positively charged liquid developer and a negatively charged liquid developer are effective by providing a predetermined cleaning means for electrically cleaning the developer carrier. And found that it can be cleaned.
That is, according to the present invention, a liquid developing device that eliminates the influence of a liquid developer having a reverse polarity and is excellent in the recovery efficiency of a liquid developer having a desired polarity, and a wet image forming apparatus including such a liquid developing device. The purpose is to provide.

According to the present invention,
A developer carrier for supplying a liquid developer in which toner is dispersed in an insulating liquid to the image carrier;
A charging device provided facing the developer carrying member;
Mechanical removal means provided on the downstream side of the charging device with respect to the rotation direction of the developer carrying member to remove the liquid developer remaining on the developer carrying member;
A liquid developing apparatus comprising:
A cleaning means for electrically removing the liquid developer remaining on the developer carrier, the cleaning means is a metal roller, and
In the cleaning unit, a first cleaning unit that applies a first bias potential for electrophoresis of toner of a predetermined polarity from the developer carrying member, and a second bias potential for electrophoresis of toner of a reverse polarity from the developer carrying member. And a second cleaning means for applying the liquid , and the first cleaning means is disposed upstream of the second cleaning means, and a liquid developing device is provided, The problems described above can be solved.

Accordingly, a cleaning unit that applies a plurality of bias potentials respectively corresponding to the toner of the predetermined polarity and the toner of the reverse polarity is provided, and, for example, the first bias potential and the second bias potential are alternately applied. Thus, it is possible to electrically clean the toner of a predetermined polarity and a toner of reverse polarity by an electric field.
As a result, it is possible to provide a liquid developing apparatus that is extremely excellent in the electric field cleaning effect on the developer carrying member, and thus a wet image forming apparatus that is excellent in transfer efficiency.
In addition, since toner of a predetermined polarity can be mainly separated and collected, the influence of reverse polarity toner is eliminated, and the development characteristics such as transfer efficiency are not changed compared with an unused liquid developer. It can also be reused as a liquid developer containing toner.
By providing a plurality of cleaning means in this way, it is possible to accurately apply the first bias potential and the second bias potential. As a result, even if the toner has a predetermined polarity, the opposite polarity is obtained. Even these toners can be collected efficiently.
Further, with this configuration, toner having a predetermined polarity can be collected first and efficiently.
That is, when the toner of a predetermined polarity is a positively charged toner and the toner of the reverse polarity is a negatively charged toner, the positively charged toner is first recovered, so that a relatively large amount of positively charged toner is present. The toner can be efficiently removed.
Further, after a relatively large amount of positively charged toner is removed first, it is not obstructed by it, and even a small amount of negatively charged toner can be efficiently removed.

In configuring the liquid developing device of the present invention, it is preferable that the toner having a predetermined polarity is a positively charged toner and the toner having a reverse polarity is a negatively charged toner.
By comprising in this way, the liquid developing apparatus suitable for the amorphous silicon photoconductor excellent in solvent resistance etc. can be provided. That is, because of the characteristics of the amorphous silicon photoreceptor, only a liquid developer containing a positively charged toner can be used.

Further, in configuring the liquid developing device of the present invention, it is preferable to send the toner of a predetermined polarity collected by the first cleaning means to the recycling device.
With this configuration, the collected toner having a predetermined polarity, for example, a positively charged toner can be efficiently reused.

Another aspect of the present invention is as follows:
A developer carrier for supplying a liquid developer in which toner is dispersed in an insulating liquid to the image carrier;
A charging device provided facing the developer carrying member;
Mechanical removal means provided on the downstream side of the charging device with respect to the rotation direction of the developer carrying member to remove the liquid developer remaining on the developer carrying member;
A wet image forming apparatus having a liquid developing device comprising:
A cleaning means for electrically removing the liquid developer remaining on the developer carrier, the cleaning means is a metal roller, and

In the cleaning unit, a first cleaning unit that applies a first bias potential for electrophoresis of toner of a predetermined polarity from the developer carrying member, and a second bias potential for electrophoresis of toner of a reverse polarity from the developer carrying member. serially example Bei and second cleaning means for applying, to a first cleaning means, than the second cleaning means is a wet image forming apparatus characterized by is arranged on the upstream side .

Accordingly, a cleaning unit that applies a plurality of bias potentials respectively corresponding to the toner of the predetermined polarity and the toner of the reverse polarity is provided, and, for example, the first bias potential and the second bias potential are alternately applied. Thus, it is possible to effectively clean the toner having a predetermined polarity and a toner having a reverse polarity.
As a result, it is possible to provide a wet image forming apparatus having a liquid developing device having an extremely excellent electrical cleaning effect on the developer carrying member and having excellent transfer efficiency.
Further, since only toner having a predetermined polarity can be separated and collected, the influence of reverse polarity toner is eliminated, and development characteristics such as transfer efficiency are not changed as compared with an unused liquid developer (toner). A liquid developer having a predetermined polarity can be reused.

[First embodiment]
As shown in FIG. 1 and FIG.
A developer carrier 12 for supplying a liquid developer 11 in which toner is dispersed in an insulating liquid to the image carrier 51;
A charging device 17 provided to face the developer carrier 12,
Mechanical removal means 33 provided on the downstream side of the charging device 17 with respect to the rotation direction of the developer carrier 12, and for removing the liquid developer remaining on the developer carrier 12.
A liquid developing apparatus 10 comprising:
A plurality of cleaning means 32a, 32b for electrically removing the liquid developer 11 remaining on the developer carrier 12, the cleaning means being a metal roller; and
In the plurality of cleaning units 32a and 32b, a first cleaning unit that applies a first bias potential for electrophoresing toner having a predetermined polarity from the developer carrier 12 and a toner having a reverse polarity from the developer carrier 12 are electrically second and second cleaning means, the serially example Bei applying a bias potential to be electrophoresed, a first cleaning means, than the second cleaning means, and characterized in that is disposed on the upstream side It is the liquid developing device 10 which performs.

The liquid developing apparatus according to the present invention will be specifically described below with reference to FIGS.
The liquid developing apparatus according to the present invention will be described on the assumption that the toner of a predetermined polarity is a positively charged toner and the toner of the reverse polarity is a negatively charged toner.
1 and FIG. 2 are diagrams for explaining the basic configuration of the liquid developing apparatus 10, and FIG. 2 is a partially enlarged view of the liquid developing apparatus 10 of FIG.

1. Basic Configuration As shown in FIGS. 1 and 2, the liquid developing device 10 includes a liquid developer tank 18 that stores a liquid developer 11 containing toner.
Further, inside the liquid developing apparatus 10, a developing roller 12, an anilox roller 13, a pumping roller 14, a doctor blade 15, a cleaning blade 33, a charging device 17, a cleaning unit 32, and the like are provided. The developing roller 12, the anilox roller 13, and the scooping roller 14 are each driven to rotate by a driving means including a gear train.
A predetermined liquid developer is supplied onto the anilox roller 13 in the vicinity of the contact portion between the anilox roller 13 and the pumping roller 14 by the supply device 18c.

  An anilox roller 13 is provided above the pumping roller 14. A developing roller 12 is further provided above the anilox roller 13.

  The doctor blade 15 is in contact with the upper part of the anilox roller 13 and on the upstream side in the rotational direction of the anilox roller 13 with respect to the developing roller 12 in the axial direction of the anilox roller 13. The liquid developer 11 supplied to the 13 roller surfaces is thinned. The photosensitive drum 51 is outside the liquid developing device 10 and is in contact with the developing roller 12.

2. Developer carrier 12 Further, the developing roller 12 receives the supply of the liquid developer 11 from the anilox roller 13, forms a thin layer of the liquid developer on the surface thereof, and supplies the liquid developer to the photosensitive drum 51. Then, the electrostatic latent image formed on the photosensitive drum 51 is developed.
The surface of the developing roller 12 is a resin-coated conductive rubber layer, which enhances toner releasability. And it is desirable to use a rubber roller having a hardness of 35 to 50 degrees (JIS A). Further, the toner in the thin layer of the liquid developer 11 formed on the surface of the developing roller 12 is configured to be applied with an electric field by a charging device 17 described later. That is, the toner that has been subjected to the predetermined charging process is pushed to the surface side of the developing roller 12 by an electrical repulsive action generated in the charging device 17.

3. The charging device 17 is, as an example, a corotron charging device, and is upstream of the photosensitive drum 51 in the rotation direction of the developing roller 12 and faces the developing roller 12. The output potential and the operation timing are controlled by a control means (not shown).
The charging device 17 is provided to face the developing roller 12, and a voltage having the same polarity as the charging polarity of the toner component of the liquid developer 11 is applied to the corona wire of the charging device 17.
Therefore, when the charging device 17 is turned on, in the thin layer of the liquid developer 11 on the surface of the developing roller 12 facing the charging device 17, the toner component in the liquid developer 11 is caused to be charged by the electric field action. 17 is configured to be assembled on the developing roller 12 side in the thin layer of the liquid developer 11 (toner compaction process).

4). Mechanical removal means Further, on the downstream side in the rotation direction of the cleaning roller 32 with respect to the developing roller 12 (on the right side of the cleaning roller 32 in FIGS. 1 and 2), a cleaning blade 33 as a mechanical removal means is developed. It is provided so as to contact the roller 12.
Although this cleaning blade 33 is an example, it is a plate member made of urethane rubber having a thickness of 1.8 mm and a rubber hardness of 77 degrees, and one end of the blade in the longitudinal direction with respect to the developing roller 12 in the axial direction thereof, The counter abuts accurately with a deflection of 1 mm and a pressure contact angle of 10 degrees.

  The cleaning blade 33 mechanically removes the liquid developer 11 on the developing roller 12 that has not been collected by the plurality of cleaning rollers 32 (32a, 32b), and the liquid developer mainly including the carrier is collected. After being collected in the waste liquid reservoir 18b which is a part, it is configured to be discarded outside.

5. Cleaning Unit A plurality of cleaning rollers 32 (32 a and 32 b) as electrical cleaning units are provided on the downstream side in the rotation direction of the developing roller 12 with respect to the photosensitive drum 51.
As shown in FIGS. 1 and 2, the lower surfaces of the plurality of cleaning rollers 32 (32 a and 32 b) are provided in pressure contact with the upper surface of the developing roller 12.
The plurality of cleaning rollers 32 (32a, 32b) are rotationally driven by a rotational driving means using a motor, gears, or the like, and rotate with a constant speed or a linear speed difference in the same direction with respect to the developing roller 12. Is configured to do.

The first cleaning unit 32a as one of the plurality of cleaning rollers 32 is configured to apply a first bias potential so that positively charged toner is electrophoresed from the developer roller 12.
The second cleaning means 32b as another one of the plurality of cleaning rollers 32 is configured to apply a second bias potential from which the negatively charged toner is electrophoresed from the developer roller 12.

Therefore, as shown in FIGS. 1 and 2, the cleaning rollers 32 (32a and 32b) for applying a plurality of bias potentials corresponding to the positively charged liquid developer and the negatively charged liquid developer are provided in series. Thus, both the positively charged liquid developer and the negatively charged liquid developer can be effectively cleaned. As a result, it is possible to provide the liquid developing device 10 having an excellent cleaning effect on the developing roller 12.
Further, as shown in FIG. 1, since only a positively charged liquid developer can be separated and recovered as a liquid developer of a predetermined polarity, the influence of the negatively charged liquid developer is eliminated, and an unused liquid Compared with a developer, a positively charged liquid developer whose characteristics do not change can be reused.
Note that about half of the carrier liquid during liquid development adheres to the cleaning roller 32a and moves. Further, about half of the remaining carrier liquid adheres to the downstream cleaning roller 32b and moves.

In addition, the first bias potential at which positively charged toner is electrophoresed and the second bias potential at which negatively charged toner is electrophoresed are alternately applied to the plurality of cleaning rollers 32 (32a and 32b). Is preferred.
The reason for this is that by applying a voltage in this way, even a positively charged toner or a negatively charged toner can be collected more efficiently than when not applied alternately. Because.
That is, in response to alternately applying the first bias potential at which the positively charged toner is electrophoresed and the second bias potential at which the negatively charged toner is electrophoresed, the positively charged toner and the negatively charged toner It is preferable to collect or discard each toner as appropriate so as not to mix with the other toner.

Further, since the residual amount of the positively charged liquid developer is generally overwhelmingly larger than the residual amount of the negatively charged liquid developer, the application of the first bias potential at which the positively charged toner is electrophoresed is applied. It is preferable that the time is at least longer than the application time of the second bias potential for electrophoresing the negatively charged toner.
As an example, when the application time of the first bias potential is T seconds, the application time of the second bias potential is preferably 0.01 to 0.5 T seconds.

Further, in the plurality of cleaning rollers 32 (32a, 32b), the first cleaning means 32a is disposed upstream of the second cleaning means 32b in the rotational direction, that is, on the left side in FIGS. It is characterized by being.
The reason for this is that although the residual amount of the positively charged liquid developer is selectively removed by the first cleaning means 32a, the residual amount of the negatively charged liquid developer is first removed by the second cleaning means 32b. Even if it is to be removed, the removal efficiency is lowered because it exists in the positively charged liquid developer as if it was buried.
Accordingly, the first cleaning unit 32a is disposed upstream of the second cleaning unit 32b in the rotation direction, and the positively charged liquid developer is selectively removed first, so that the positively charged liquid developer is developed. Not only the removal efficiency of the agent but also the removal efficiency of the negatively charged liquid developer can be increased.

Further, as shown in FIG. 1, it is preferable to send the liquid developer 11 collected by the first cleaning means 32a to the reuse device 45 through the waste liquid reservoir 18a and the valve 44.
The reason for this is that, if the collected positively charged liquid developer is configured in this way, it is not affected by the negatively charged liquid developer, and therefore is equivalent to an unused positively charged liquid developer. This is because it can be efficiently reused.

Further, as shown in FIG. 1, it is preferable that the liquid developer recovered by the second cleaning unit 32b is sent to a disposal device (a disposal tank) 47 through a waste liquid reservoir 18b and a valve 46.
The reason for this is that the negatively charged liquid developer, which is not preferable as a liquid developer, can be effectively eliminated, and the effect can be effectively reduced when the positively charged liquid developer is reused. This is because it can be eliminated.

The cleaning roller 32 is formed of a cylindrical roller member made of a metal material such as stainless steel. The surface roughness of the roller member is, for example, a ten-point average roughness Rz (JIS B 0601: The surface is preferably polished so that (measured according to 2001) is 1.6 to 3.2.
As shown in FIG. 1, bias potential applying means 42 and 43 are electrically connected to the cleaning roller 32 (32a and 32b), and control means (not shown) for these bias potential applying means 42 and 43 is provided. ), The output potential and the operation timing are precisely controlled.
In the present embodiment, as an example, the bias potential applying means 41 is also electrically connected to the developing roller 12, and the bias potential is set to +300 V, but the first cleaning means 32a is used. The bias potential for the second cleaning means 32b is + 500V.

Further, in order to cause the toner component on the developing roller 12 to be attracted to the cleaning roller by an electric field action and removed, the potential difference between the developing roller 12 and the first cleaning unit 32a by the bias potential applying means 41 and 42 is as follows. The difference is preferably 50 to 200 V, and more preferably 80 to 120 V.
Similarly, the potential difference between the developing roller 12 and the second cleaning unit 32b by the bias potential applying units 41 and 43 is preferably 50 to 200V, more preferably 80 to 120V. preferable.
Therefore, for example, a voltage of 200 to 400 V is applied to the developing roller 12 by the bias potential applying means 41, 42, and 43, and the first bias potential is less than 10 to 200 V to the first cleaning means 32a. It is preferable to apply a voltage of more than 400 to 800 V as the second bias potential to the second cleaning means 32b.

6). Operation Next, the operation of the liquid developing apparatus 10 will be described with reference to FIG.
Here, in the liquid developer 11, toner particles (particle size: about 1 μm) made of fine resin having a positive charge are dispersed and turbid in a nonpolar insulating liquid usually made of silicon oil or the like as a carrier. Is.

Then, as shown in FIG. 2, a predetermined liquid developer is supplied by the supply device 18c onto the anilox roller 13 in the vicinity of the contact portion between the anilox roller 13 and the scooping roller 14.
Next, the coating is sequentially applied to the roller surface of the anilox roller 13 that rotates synchronously through the nip portion between the anilox roller 13 and the pumping roller 14.

Next, the liquid developer 11 applied to the anilox roller 13 is made into a uniform thin layer by the doctor blade 15 and comes into contact with the anilox roller 13 to be uniform with respect to the roller surface of the developing roller 12 that rotates synchronously. Transfer coated as a thin layer.
Next, the thin layer of the liquid developer 11 formed on the developing roller 12 is subjected to toner compaction processing that collects toner components on the developing roller 12 side by the charging device 17, and then an electrostatic latent image is formed. The toner image is supplied to the photosensitive drum 51 and developed on the photosensitive drum 51.

After the development, the liquid developer 11 remaining on the developing roller 12 is removed from the developing roller 12 by the cleaning unit 32, and then collected by the reuse device 45 through the waste liquid reservoir 18a and the valve 44. .
Further, a predetermined density is confirmed by the densitometer 45 b for the liquid developer 11 collected in the reuse device 45. Then, the required amount of carrier liquid or the developing device 10 is added to a liquid developer having a toner concentration higher than that normally used to adjust to a predetermined concentration. Thereafter, the pipe is returned to the nip portion between the anilox roller 13 and the pumping roller 14 via the pipe 45c, the valve 48, and the supply device 18c.
On the other hand, the liquid developer 11 collected in the waste liquid reservoir 18b is sent to the waste liquid tank 47 through the valve 46 and then discarded to the outside.
Therefore, since only a liquid developer containing positively charged toner can be separated and collected as a liquid developer containing toner of a predetermined polarity, a liquid containing negatively charged toner is used as a liquid developer containing reverse polarity toner. By eliminating the influence of the developer, it can be reused as a positively charged liquid developer whose characteristics do not change compared to an unused liquid developer.

[Second embodiment ]
The second embodiment is a modification of the first embodiment, and as shown in FIG. 3, a cleaning means for electrically removing the liquid developer 11 remaining on the developer carrier 12. This is a liquid developing device 10 ′ including one 32.
That is, a developer carrier 12 that supplies a liquid developer 11 in which toner is dispersed in an insulating liquid to the image carrier 51;
A charging device 17 provided to face the developer carrier 12,
Mechanical removal means 33 provided on the downstream side of the charging device 17 with respect to the rotation direction of the developer carrier 12, and for removing the liquid developer remaining on the developer carrier 12.
A liquid developing apparatus 10 ′ comprising:
One cleaning means 32 for electrically removing the liquid developer 11 remaining on the developer carrier 12, and
In one cleaning unit 32, a first bias potential at which toner of a predetermined polarity is electrophoresed from the developer carrier 12 and a second bias potential at which toner of a reverse polarity is electrophoresed from the developer carrier are respectively provided. This is a liquid developing apparatus 10 'that is applied.

Therefore, as shown in FIG. 3, by providing one cleaning means 32 for applying a plurality of bias potentials corresponding to positively charged toner and negatively charged toner, either positively charged toner or negatively charged toner can be provided. Can also be cleaned effectively.
As a result, also in the second embodiment, as in the first embodiment, it is possible to provide the liquid developing device 10 ′ that is extremely excellent in the electrical cleaning effect for the developer carrier 12.
Further, even with the single cleaning means 32, it is possible to separate and collect only a toner having a predetermined polarity, for example, a positively charged toner. Compared to the above, the liquid developer (positively charged toner) 11 whose characteristics do not change can be effectively reused.
Furthermore, since the cleaning unit 32 is one, the liquid developing device can be made smaller and lighter than the case of providing a plurality of cleaning units as in the first embodiment.
In addition, since the toner of a predetermined polarity and the toner of opposite polarity are likely to be mixed because it is one cleaning means 32, the problem of mixing can be effectively solved by providing a switching valve after the valve 46. Can do.
In addition, except for the number of cleaning means being one, the basic configuration and operation of the liquid developing device in the second embodiment, how to reuse, etc. are substantially the same as those of the liquid developing device in the first embodiment. Therefore, detailed description thereof is omitted here.

[Third embodiment]
The third embodiment is a wet image forming apparatus 150 having the liquid developing apparatus 10 of the first embodiment as shown in FIG. 4, or the liquid developing apparatus of the second reference embodiment as shown in FIG. 10 is a wet image forming apparatus 200 having 10 ′.
That is, as shown in FIGS. 4 and 5, a developer carrier that supplies a liquid developer in which toner is dispersed in an insulating liquid to the image carrier 51, and
A charging device provided on the upstream side of the rotation direction of the developer carrier and facing the developer carrier;
A mechanical removal means provided on the downstream side of the charging device and for removing the liquid developer remaining on the developer carrier;
A wet image forming apparatus 150, 200 having a liquid developing device 10, 10 ′ comprising:
A cleaning means for electrically removing the liquid developer remaining on the developer carrying member; and
The cleaning means applies a first bias potential at which toner of a predetermined polarity is electrophoresed from the developer carrier and a second bias potential at which toner of a reverse polarity is electrophoresed from the developer carrier. The wet image forming apparatuses 150 and 200 are characterized.

Hereinafter, a wet image forming apparatus will be described by taking a wet image forming apparatus (color printer) for color image formation as an example.
FIG. 4 is a diagram for explaining a basic configuration of a tandem type wet image forming apparatus (color printer) 150 having the liquid developing apparatus 10 of the first embodiment.
FIG. 5 is a diagram for explaining a basic configuration of a tandem type wet image forming apparatus (color printer) 200 having the liquid developing apparatus 10 ′ of the second embodiment.

1. Basic Configuration The color printer 150 shown in FIG. 4 (and the color printer 200 shown in FIG. 5) is arranged in an upper main body 150A in which various units and parts for image formation are stored, and a lower portion of the upper main body 150A. And a lower main body 150B in which liquid developer circulating devices LY, LM, LC, and LB (mixed liquid supply systems) for the respective colors are housed.
In the upper main body 150A, a tandem-type image forming unit 2 that forms a toner image based on image data, a paper storage unit 3 that stores paper, and a toner image formed by the image forming unit 2 are printed on paper. From the secondary transfer unit 4 to be transferred upward, the fixing unit 5 for fixing the transferred toner image on the paper, the discharge unit 6 for discharging the fixed paper, and from the paper storage unit 3 to the discharge unit 6 And a paper transport unit 7 for transporting paper.

Here, the image forming unit 2 corresponds to the intermediate transfer belt 21, the cleaning unit 22 of the intermediate transfer belt 21, and each color of yellow (Y), magenta (M), cyan (C), and black (Bk). Image forming units FY, FM, FC, and FB.
The intermediate transfer belt 21 is a belt-like member having an endless shape, that is, a loop shape, which is wider than the maximum length paper in the direction perpendicular to the usable paper transport direction. , Circulated in a clockwise direction. In the circulation driving of the intermediate transfer belt 21, the surface facing outward is hereinafter referred to as a front surface, and the other surface is referred to as a back surface.

Further, four image forming units FY, FM, FC, and FB are arranged in the vicinity of the intermediate transfer belt 21 and arranged between the cleaning unit 22 of the intermediate transfer belt 21 and the secondary transfer unit 4.
Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image.

The image forming units FY, FM, FC, and FB include a photosensitive drum 51, a charging device 53, an LED exposure device 54, a developing device 56, a primary transfer roller 20, a cleaning device 58, and a static eliminating device. 52.
In correspondence with the image forming units FY, FM, FC, and FB, liquid developer circulating devices LY, LM, LC, and LB are provided, respectively, so that the liquid developer of each color is supplied and recovered. It has become.

2. Liquid developing apparatus Since it can be made the same as the content demonstrated in 1st Embodiment and 2nd Embodiment, description here is abbreviate | omitted.
A liquid developer tank 18 serving as a liquid developer storage tank in the liquid developing device 10 stores a liquid developer 11 as a liquid developer including toner particles and a carrier which is an insulating liquid.
The liquid developer 11 is adjusted so that toner particles are dispersed at a high concentration in a carrier liquid that is a nonpolar, ie, electrically neutral, solvent such as silicone oil.
The toner particles contain a colorant, a resin (binder) and, if necessary, a charge control agent. The resin (binder) is adsorbed on the colorant, is well dispersed in the carrier liquid, and applies a positive or negative charge to the adsorbed colorant.

The toner particles are charged to a positive potential (+) by a resin (binder). On the other hand, as the carrier liquid, an isoparaffin-based solvent (for example, Isopar G (manufactured by Exxon)), a higher fatty acid ester, silicon oil, or the like can be used.
Then, the liquid developer 11 is supplied from a developing roller 12 as a developer carrying member to an electrostatic latent image of a portion irradiated with light from the photosensitive drum 51, whereby a toner image is applied to the photosensitive drum 51. Develop.

According to the liquid developing apparatus of the present invention, by providing a cleaning unit that applies a plurality of bias potentials corresponding to a liquid developer having a predetermined polarity and a liquid developer having the opposite polarity, a liquid developer having a predetermined polarity (for example, In addition to a positively charged liquid developer), even a small amount of a reverse polarity liquid developer (for example, a negatively charged liquid developer) contained in the predetermined polarity liquid developer is effectively cleaned. I was able to do that.
As a result, it has become possible to provide a liquid developing apparatus having an extremely excellent electrical cleaning effect on the developer carrying member and a wet image forming apparatus including such a liquid developing apparatus.

Also, since only a liquid developer containing toner of a predetermined polarity, for example, a liquid developer containing positively charged toner, can be separated and recovered, a liquid developer containing a toner of reverse polarity, such as negatively charged toner, can be collected. Eliminating the effects of the liquid developer contained, and effectively using a liquid developer with a predetermined polarity (for example, a liquid developer containing positively charged toner) whose transfer characteristics do not change compared to an unused liquid developer. It can be reused.
Therefore, the liquid developing device of the present invention can be suitably and economically applied to a wet image forming apparatus as various printers, facsimiles, copiers, etc. excellent in reusability of the liquid developer.

FIG. 2 is a diagram for explaining a liquid developing device according to the present invention (part 1); It is a figure with which it uses for demonstrating the liquid developing device which concerns on this invention (the 2). FIG. 5 is a diagram provided for explaining another reference liquid developing device according to the present invention. 1 is a diagram provided for explaining a tandem type wet color image forming apparatus equipped with a liquid developing apparatus according to the present invention. FIG. 5 is a diagram for explaining a tandem type wet color image forming apparatus equipped with another reference liquid developing device according to the present invention. It is a figure provided in order to demonstrate the image forming apparatus carrying the conventional liquid developing device. It is a figure provided in order to demonstrate operation | movement of the conventional liquid developing device. It is a figure provided in order to demonstrate the structure of the conventional liquid developing device. It is a figure provided in order to demonstrate another conventional developing device. It is a figure provided in order to demonstrate an example of the electrophoresis experimental image of the collect | recovered liquid developer.

Explanation of symbols

2: Image forming unit 3: Paper storage unit 4: Secondary transfer unit 5: Fixing unit 6: Ejecting unit 7: Paper transport unit 10: Liquid developing device 10 ': Another liquid developing device 11: Liquid developer 12: Development Roller (developer carrier)
13: Anilox roller 14: Pumping roller 15: Doctor blade 17: Charging device 18: Liquid developer tank 18a: Collected liquid reservoir 18b: Waste liquid reservoir 18c: Supply device 20: Primary transfer roller 21: Intermediate transfer belt 22: Cleaning unit 32: Cleaning roller (electric field removing means)
32a: first cleaning means 32b: second cleaning means 33: cleaning blade (mechanical removal means)
45: Reuse device 46: Waste liquid tank (disposal tank)
51: Photosensitive drum (image carrier)
52: Charge eliminating device 53: Charging device 54: LED exposure device 56: Developing device 58: Cleaning device 150: Color printer (image forming device)
200: Color printer (image forming apparatus)

Claims (5)

A developer carrier for supplying a liquid developer in which toner is dispersed in an insulating liquid to the image carrier;
A charging device provided facing the developer carrying member;
Mechanical removal means provided on the downstream side of the charging device with respect to the rotation direction of the developer carrying member to remove the liquid developer remaining on the developer carrying member;
A liquid developing apparatus comprising:
A cleaning means for electrically removing the liquid developer remaining on the developer carrying member;
The cleaning means is a metal roller, and
In the cleaning means, a first cleaning means for applying a first bias potential for electrophoresing toner of a predetermined polarity from the developer carrier, and a second for electrophoretic toner having a reverse polarity from the developer carrier. comprising a second cleaning means for applying a bias potential, a serially,
The liquid developing apparatus according to claim 1, wherein the first cleaning unit is disposed upstream of the second cleaning unit .   The liquid developing device according to claim 1, wherein the toner of the predetermined polarity is a positively charged toner, and the toner of the reverse polarity is a negatively charged toner. Liquid developing device according to claim 1 or 2, characterized in that the liquid developer collected by the first cleaning unit, and sends the re-use device. Wherein the liquid developer collected by the second cleaning means, the liquid developing device according to any one of claims 1 to 3, characterized in that delivering the disposal device. A developer carrier for supplying a liquid developer in which toner is dispersed in an insulating liquid to the image carrier;
A charging device provided facing the developer carrying member;
Mechanical removal means provided on the downstream side of the charging device with respect to the rotation direction of the developer carrying member to remove the liquid developer remaining on the developer carrying member;
A wet image forming apparatus having a liquid developing device comprising:
A cleaning means for electrically removing the liquid developer remaining on the developer carrying member;
The cleaning means is a metal roller, and
In the cleaning means, a first cleaning means for applying a first bias potential for electrophoresing toner of a predetermined polarity from the developer carrier, and a second for electrophoretic toner having a reverse polarity from the developer carrier. comprising a second cleaning means for applying a bias potential, a serially,
The wet image forming apparatus, wherein the first cleaning unit is disposed upstream of the second cleaning unit .