JPH0468380A - Liquid developing device - Google Patents

Abstract

PURPOSE:To prevent the staining of a recording medium caused by the rushing out of a developing liquid from a developing liquid supplying groove by providing a negative pressure generating means generating negative pressure inside the developing liquid supplying groove, and stopping the driving of the negative generating means before the separating of a developing heat and the recording medium is started. CONSTITUTION:After developing is finished, the driving of the negative pressure generating means 13 is stopped before the separating of the developing head 3c and the recording medium is started. A state where sucking force into the developing liquid supplying groove 31 by the negative pressure generating means 13 does not work, is obtained at the moment when the separating of the developing head 3c and the recording medium is started, and a shock caused by a change in pressure inside the developing liquid supplying groove 31 when the surface of the developing head and the recording medium are separated, is made small. Thus, the staining of the recording medium caused by the rushing out of the developing liquid from the developing liquid supplying groove 31 at the time when the developing head 3c and the recording medium are separated, is reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a liquid developing device employed in image forming apparatuses such as electrophotographic or electrostatic recording type copying machines, facsimile machines, printers, etc. relates to a liquid developing device that performs development using a developing head disposed facing a conveyance path of a recording medium on which an electrostatic latent image or the like is formed.

[Conventional technology]

A liquid developing device that develops an image to be developed on a recording medium by filling a developer supply groove extending in the width direction of the recording medium provided on the developing head surface facing the recording medium conveyance path with a developer is known, for example, from Jikosho. Publication No. 52-25155, JP-A-61-179
It is known from Publication No. 476 and the like.

In this type of liquid developing device, negative pressure is generated in the developer supply groove by driving a negative pressure generating means such as a pump motor with the developer supply groove blocked by a recording medium such as electrostatic recording paper. By using this negative pressure, the recording medium is attracted to the developing head surface, thereby almost sealing the developer supply groove.
The developer in the developer tank is supplied to the developer supply groove through a developer supply path forming means such as a supply pipe, and the developer in the developer supply groove is conveyed through a developer recovery path forming means such as a recovery vibrator. By circulating the developer between the developer tank and the developer supply groove while collecting the developer into the developer tank, the developer is dripped in the developer supply groove to form an image to be developed such as an electrostatic latent image on the recording medium. After the development operation is completed, the pump motor continues to be driven to drain the developer in the developer supply groove to collect it into the developer tank.

Further, a plurality of developing heads are disposed facing the recording medium conveyance path, and a lifting means moves each developing head to a developing position close to the recording medium conveyance path and a standby position spaced apart from the recording medium conveyance path. There is also known a liquid developing device that is provided with an operating state in which the opening of the developer supply groove is blocked by a recording medium and a standby state in which the developing head and the recording medium are separated (for example, in a special Kaisho 61-179477
Publication No.).

[Problem to be solved by the invention]

However, if the pump motor is driven when starting to separate the developing head from the recording medium, at the moment the developing head is separated from the recording medium, the developer existing near the developing head in the developer supply path forming means will be removed. The solution may blow out from the opening of the developer supply groove and stain the recording medium, or the developer that was previously present in the flow path switching valve may be guided from the flow path switching valve to the pump motor. Even if a liquid recovery path is formed to drain the liquid, the developer adhering to the inner wall of the developer supply groove may scatter from the opening of the developer supply groove and stain the recording medium as dotted droplets. I have confirmed that there is a problem. This is because if the pump motor is driven when starting to separate the developing head and recording medium, the pressure in the developer supply groove will change from negative pressure to atmospheric pressure at the moment the two are forcibly separated. It is thought that the change is as rapid as possible, and the shock causes the developer to jump out from the opening of the developer supply groove.

The present invention has been made in view of the problems of the prior art, and its purpose is to prevent the opening of the developer supply groove from separating the developing head from the recording medium after the completion of development. It is an object of the present invention to provide a liquid developing device that can reduce or prevent staining of a recording medium due to developer splashing out.

[Means to solve the problem]

In order to achieve the above object, the liquid developing device of the present invention includes:
A developing head having an opening on the developing head surface facing the recording medium transport path and having a developer supply groove extending in the width direction of the recording medium, a developer tank containing the developer, and a developer tank containing the developer. A means for forming a developer supply path to the developer supply groove; a means for forming a developer recovery path from the developer supply groove to the developer tank; and a means for forming a developer recovery path from the developer supply groove to the developer tank; The developer supply groove has a negative pressure generating means for generating negative pressure in the developer supply groove when the opening of the developer supply groove is blocked by the recording medium. The developer supply groove is filled with developer by generating negative pressure inside the developer supply groove and circulating the developer between the developer tank and the developer supply groove while sucking the recording medium into the opening of the developer supply groove. In a liquid developing device that performs a developing operation of an image to be developed on a recording medium and separates the developing head from the recording medium after the development operation is completed, before starting to separate the developing head from the recording medium, the above-mentioned This is characterized by stopping the driving of the negative pressure generating means.

[Effect]

The present invention configured as described above stops the driving of the negative pressure generating means after the development is completed and before the separation between the development head and the recording medium is started, thereby causing the separation between the development head and the recording medium. At the moment when the separation starts, the suction force generated by the negative pressure generating means in the developer supply groove is not working, and the pressure change in the developer supply groove when the developing head surface and the recording medium are separated. This acts to reduce the shock compared to when the separation between the developing head and the recording medium is started with the negative pressure generating means being driven.

〔Example〕

A first embodiment of this invention will be described based on FIGS. 1 to 4.

FIG. 2 is a schematic configuration diagram of an electrostatic recording type color image forming apparatus employing a liquid developing device which is a developer processing device according to the present invention.

First, to explain the outline of the operation of this image forming apparatus, in FIG. The portion extending above the electrostatic recording head 2 and the four developing heads 3C93M, 3Y, 3,
With its leading end held between the drive roller 4 and the pinch roller 5, it waits for the start of the recording operation and then enters a standby state. In this standby state, all the developing heads 3C.

3M, 3Y, and 3 are located at standby positions spaced downward from the recording paper conveyance path. When the recording operation is started after data processing of recording information received from an information processing device (not shown) is completed, the cyan developing head 3C is raised to a developing position where the developing head surface is close to the recording paper conveyance path. move it,
A developer tank 6G (first
The developer is supplied from the electrostatic recording head 2, and the developer starts circulating between the two, and the drive roller 4 and feed shaft 1 start rotating, and the recording paper is coated with electrostatic potential on the electrostatic recording head 2. An image is recorded, and the recording paper continues to be conveyed while developing this electrostatic latent image on the developing head 3C. When the development of the electrostatic latent image by the cyan developing head 3C is completed, the cyan developing head 3C is moved to the lower standby position, and the feeding shaft 1 and drive roller 4 are reversely rotated to remove the image area of the recording paper. Return it to the recording head 2 again. Next, magenta,
Color development is performed by performing the formation of an electrostatic latent image for yellow, raising and lowering the developing head, and transporting the recording paper in the same procedure as for cyan. However, the recording paper that has completed the final yellow development and has passed through the development head 3Y continues to move forward, and just before the leading edge of the color developed image passes through the rotary cutter 7, the cutter 7 is driven to rotate. Then, immediately after the trailing edge of the color developed image passes through the cutter 7, the cutter 7 is driven to rotate to cut the recording paper, and then the rotation of the feeding shaft 1 and the drive roller 4 is stopped. On the other hand, the developing head 3Y is retracted to a lower standby position, and then, while only the paper ejection roller pair 8 is rotated, the sheet-shaped recording paper is ejected onto a paper ejection tray (not shown).

Next, the liquid developing device will be described in detail.

The liquid developing device has three developing heads 3C, 3M, and 3 that use cyan, magenta, and yellow developers, respectively.
A developing head 3 using a black developer for developing Y and black and white images, and each developing head 3G, 3M,
A developer tank (which stores the developer supplied to 3Y and 3K)
In FIG. 2, only the black developer tank 6 is shown), and one of these developing heads 3G, 3M, 3Y, 3 is selectively approached and separated from the recording paper by a developing head lifting motor. It is equipped with an elevating means (not shown) driven by. Each developing head 3C93M, 3Y, 3K and developer circulation system have basically the same structure.

Hereinafter, based on FIG. 1, the cyan developing head 3C will be explained as an example.

The developing head 3C has a rectangular bar shape that is elongated in the width direction of the recording paper, and on the surface of the developing head facing the recording paper conveyance path, there are two bars formed in the width direction of the recording paper with a length shorter than the width of the recording paper. Developer supply grooves 31 and 32 and these developer supply grooves 3
An atmospheric groove 33 is provided between 1.32 and 32 mm, which is also formed in the width direction of the recording paper and has a length shorter than the width of the recording paper. The ends of these two developer supply grooves 31 and 32 on the upper front side in the drawing are as shown in the longitudinal sectional view of FIG. 3 taken along the plane A-Ag in FIG. 1 and viewed from the direction of the arrow. A liquid path provided in the supply vibrator 9, which is a means for forming a developer supply path, from the developer tank 6C containing the developer to the developer supply groove 31, 32 through a hole penetrating the back side of the developing head surface. It is connected to the electromagnetic three-way valve 10, which is a switching means, and the right end is used to collect the developer from the developer supply groove 31, 32 to the developer tank 6C through a hole penetrating the back side of the same developing head surface. It is connected to a first recovery vibe 11 which is a path forming means. The atmospheric groove 33 has a third groove approximately at the center in the longitudinal direction.
As shown by the broken line in the longitudinal sectional view of the figure, it is connected to the atmosphere introduction pipe 12 through a hole penetrating the back side of the developing head surface. The diameter of this atmosphere introduction pipe 12 is the same as that of the pump motor 13.
When the inside of the developer supply groove 31.32 is under negative pressure due to the drive of This is an important factor in determining the amount of air (see Figure 3) that is sucked into the developer supply grooves 31 and 32 during development. This is determined in consideration of the fact that the airflow may scrape off some of the toner constituting the toner image on the recording medium, resulting in a low image density and deterioration of the image quality. The electromagnetic three-way valve 10 is connected to one end of a second recovery pipe 14 whose other end is connected to the first recovery vibe 11 through a branch pipe, and this electromagnetic three-way valve 1o is in the ON state. The developer supply grooves 31 and 32 are communicated with the supply vibrator 9 and are cut off from the second recovery vibe 14, and in the OFF state, the developer supply grooves 31 and 32 are communicated with the second recovery pipe 14 and the supply This is to cut off the vibe 9. The developer tank 6C is lower than the part of the first collection vibrator 11 where the second collection pipe 14 is connected.
A pump motor 13 is provided on the side. Further, an electromagnetic two-way valve 16 to which an atmospheric air introduction/negative pressure adjustment valve 15 is connected is connected via a branch pipe to the side of the developing head of the first collection vibrator 11 from where the second collection pipe 14 is connected. Further, a pressure sensor 17 is connected to the developing head 3C side. This atmospheric air introduction/negative pressure adjustment valve L5 is used when the negative pressure in the developer supply groove 31.32 is too large.
The air sucked into the developer supply grooves 31, 32 may become trapped in the developer in the form of bubbles, causing fine white streak-like patterns on the image. If the negative pressure is too small, the developer supply groove 31, 32
Insufficient flow rate of the developer in the developer supply grooves may cause uneven density of the image, and the negative pressure in the developer supply grooves 31 and 32 depends on the planar smoothness of the recording paper used. 3
This is to adjust the negative pressure inside 1 and 32 to an optimal level. In this example, the amount of air introduced is adjusted manually by rotating the knob, but instead of this, a negative pressure system with an automatic adjustment function that automatically introduces and shuts off air to maintain a constant negative pressure can be used. A regulating valve may also be used. The above electromagnetic two-way valve 1
Reference numeral 6 communicates the atmosphere introduction/negative pressure adjustment valve 15 with the first recovery vibrator 11 in the ON state, and blocks the atmosphere introduction/negative pressure adjustment valve 15 from the first recovery vibe 11 in the OFF state.

In the above configuration, in the standby state, the pump motor 13
is stopped, the solenoid 3-way valve], IC and the solenoid 2-way valve 16
is off, and the developing head 3C is located at a standby position spaced downward from the recording paper. After this standby state, when the recording operation is started, the developing head 3C is moved by the elevating means.
The electromagnetic 3
The direction valve 11C is turned on to bring the developing head 3G into communication with the supply pipe 9, and at the same time, driving of the pump motor 13 is started. Although the openings of the developer supply grooves 31 and 32 on the developing head surface are covered by the recording paper, there is a small gap between the developing head surface and the recording paper surface due to minute irregularities on the recording paper surface. exists, and the developer supply groove 31. ．．
32 communicates with the atmosphere, and the atmospheric groove 33 also communicates with the atmosphere via the atmosphere introduction pipe 12. Also, electromagnetic two-way valve 1
6 is the atmosphere introduction/negative pressure adjustment valve 1 while it is in the OFF state.
5 is isolated from the first collection vibrator 11, most of the suction action of the pump motor 13 is applied to the developer supply grooves 31 and 32 through the gap between the developing head surface and the recording paper surface.
Directed to the suction of air from the opening of. This results in
The recording paper is reliably attracted to the opening and comes into close contact with the surface of the developing head, so that the opening is substantially sealed, and the negative pressure within the developer supply grooves 31 and 32 increases rapidly. The negative pressure in the developer supply grooves 31 and 32 causes the developer in the developer tank 6C to flow into the developer supply groove 31.
．． 32, the developer in the developer tank 6C is pumped up into the developer supply groove 31.32 via the supply pipe 9, and further into the developer supply groove 31.32. The developer is flowed in a full state into the developer supply grooves 31 and 32 so as to come into contact with the recording paper that blocks the opening, and is returned to the developer tank 6C via the first collection vibrator 11. The developer is circulated between the supply grooves 31 and 32 and the developer tank 6C. When the circulation of the developer starts, the two-way electromagnetic valve 16 is turned on to connect the atmosphere introduction/negative pressure adjustment valve 15 to the first recovery pipe 11.

At a predetermined time point when the developer circulation is stabilized, the feeding shaft 1 and the drive roller 4 start rotating, and the recording head 2 starts recording an electrostatic latent image, thereby,
The electrostatic latent image recorded on the recording paper by the recording head 2 is conveyed onto the developing head 3C, and developed by being supplied with developer from the openings of the developer supply grooves 31 and 32. At this time, the developer supply groove 32 not only performs a developing function but also performs an excess developer removing function of removing excess developer attached to the recording paper. Even during development, the developer supply groove 32 is leaked from the gap between the developing head surface on the downstream side of the recording paper transport direction and the surface of the recording paper due to minute irregularities on the surface of the recording paper. Air is flowing into the
This is thought to be due to the fact that the excess developer adhering to the recording paper is blown away by this air flow. Note that the development head surface between the developer supply groove 32 and the atmospheric groove 33, the development head surface between the developer supply groove 31 and the atmospheric groove 33, and the development side upstream of the developer supply groove 31 in the recording paper transport direction. Even if there is a gap between the head surface and the recording paper surface, the developer supply groove 32.3
Air is flowing into 1 (see Figure 3). When the trailing edge of the electrostatic latent image on the recording paper passes the developing head surface and the development is completed, the electromagnetic three-way valve 10 is turned off while the pump motor 13 remains driven. By turning off the electromagnetic three-way valve 10, the developing head 3C is cut off from the supply pipe 9 and pumping of the developer from the developer tank 6C is interrupted, and conversely, the developing head 3C is communicated with the second recovery pipe 14. By doing so, the developer in the developer supply grooves 31, 32, etc. is collected into the developer tank not only through the first collection vibrator 11 but also through this second collection pipe 14, and thereby, Not only can the developer in the developer supply groove 31.32 be quickly recovered, but also the electromagnetic three-way valve and the developer supply groove 31.3
It is also possible to reliably collect the developer remaining in the pipe connecting the two parts. Immediately after turning off the electromagnetic three-way valve 10, the electromagnetic two-way valve 16 is turned off to shut off the atmosphere introduction/negative pressure adjustment valve 15 from the first recovery vibe 11, thereby opening the developer supply grooves 31 and 32. Maximize the negative pressure inside.

In this example, when commercially available CAD recording paper is used, the negative pressure during development to obtain a good image is approximately 50 MHz, but with the electromagnetic two-way valve 16 shut off. The maximum negative pressure is approximately 180MHg.

This maximum negative pressure depends on the surface smoothness of the recording paper and is 100
It can take a value of 600mmHg to 600mmHg, but has a high degree of smoothness.
Maximum negative pressure is 400mm Hg using glossy recording paper
If the size becomes larger and conveying the recording paper becomes difficult, the two-way electromagnetic valve 16 may be omitted and the atmosphere introduction/negative pressure adjustment valve 15 may be constantly communicated with the first collection vibrator 11. . After this developer recovery, the entire suction action of the pump motor 13 is directed to sucking air from the opening of the developer supply groove 31,32. Thereby, the developer and the like adhering to the inner surfaces of the developer supply grooves 31 and 32 can also be collected by suction. During the period when the liquid is drained as described above, the recording paper continues to be conveyed and the developer remaining on the developing head surface is applied thinly to the surface of the recording paper. Remove liquid. The developer is applied onto the recording paper several times to several tens of times in the recording paper conveyance direction. When the developer no longer adheres to the recording paper, the drive of the pump motor 13 is stopped, thereby stopping the suction action of the recording paper to the developing head surface and removing the recording paper from the developing head surface. Let it separate naturally. After a certain period of time has passed since the pump motor 13 stopped driving,
The developing head 3C is moved to the standby position by the lifting means. This certain period of time t is caused by the negative pressure in the developer supply groove 31.32 due to the pressure change in the developer supply groove 31.32 at the moment when the development head 3C starts moving to the standby position. This is the time it takes for the developer to decrease to a level that does not cause scattering from the opening of . A timer that generates an output after the elapse of time is used, and the output of this timer starts the movement of the elevating means to the standby position. In this way, instead of determining the timing at which the development head 3C starts moving to the standby position based on the elapse of a set time after the pump motor 13 stops, the developer is The negative pressure in the developer supply grooves 3r and 32 is determined in advance through experiments to the extent that the developer does not scatter from the openings of the developer supply grooves 31 and 32 due to pressure changes in the supply grooves 31 and 32. The development head 3C may start moving to the standby position when the pressure detected by the pressure sensor 17 provided in the first collection vibrator 11 detects such a negative pressure. FIG. 4 is a timing chart of the operation from the time immediately before the end of development to the time when the liquid is drained and the developing head 3C is moved to the standby position.

Next, a second embodiment of a liquid developing device with a modified developer circulation system will be described with reference to FIG.

This embodiment differs from the first embodiment in that instead of using the electromagnetic three-way valve in the first embodiment, the developer supply vibrator 9 and developer supply grooves 31 and 32 are switched between a communicating state and a blocking state. The use of the electromagnetic two-way valve 18 and the electromagnetic valve 3 in the first embodiment
This is because the second collection vibrator 14 that connects the direction valve 10 and the first collection vibrator 11 is omitted. In this example,
Since the developer is collected from the developer supply grooves 31 and 32 after development is completed only through the first collection vibrator 11, the time for draining the developer is longer than in the first embodiment. Approximately 0.
(5 seconds longer), but it has the advantage of simplifying the piping of the vibrator.

According to each of the embodiments described above, after the completion of development, the recording paper is transported while driving the pump motor 13 with the developer supply path from the developer tank to the developer supply grooves 31 and 32 being cut off. After the developer on the developing head surface has adhered to the recording paper, the pump motor 13 is stopped, and as a result,
Allow the recording paper to separate naturally from the developing head surface,
In addition, after the pump motor 13 stops, the negative pressure in the developer supply grooves 31 and 32 causes the developer to be supplied due to the pressure change in the developer supply grooves 31 and 32 at the moment when the development head starts moving to the standby position. After the amount of developer from the openings of the grooves 31, 32 has decreased to a level that does not occur, the developing head starts moving to the standby position, and then the developer is supplied from the openings of the developer supply grooves 31, 32. can be prevented from scattering and staining the surface of the recording paper.

In addition, after the development is completed, the recording paper is conveyed and the developer on the developing head surface is applied to the recording paper to remove the developer adhering to the developing head surface, and the developer is supplied from the developer tank. By driving the pump motor 13 with the developer supply path to the grooves 31 and 32 blocked, the negative pressure in the developer supply grooves 31 and 32 is made larger than that in the developer, and the developer is supplied. Quickly drain the developer in the supply grooves 31 and 32.
By reliably collecting the developer, it is possible to shorten the time required to transport the recording paper to remove the developer attached to the developing head surface, especially in color development where the recording paper is transported back and forth across the developing head. In this case, the development time can be significantly shortened.

Furthermore, an air introduction/negative pressure adjustment means is provided to adjust the negative pressure in the developer solution supply grooves 31 and 32 during development.
．． By adjusting the negative pressure inside the 32 to a negative pressure that allows optimal development, regardless of the smoothness of the recording paper used (determined by the type of recording paper used), it is possible to use various types and uses of recording paper. It can be used.

In each of the embodiments described above, the movement of the developing head to the standby position is started after the pump motor 13 is stopped, but instead of this, the movement may be started at the same time as the pump motor 13 is stopped. Even in this case, at the moment when the development head starts moving to the standby position, the suction force by the pump motor 13 into the developer supply grooves 31 and 32 is not working, so the development head surface and the recording paper are not in contact with each other. Developer supply groove 3 when separating
The shock caused by the pressure change in the developer supply groove 3 can be reduced compared to when the development head starts moving to the standby position with the pump motor 13 being driven.
It is possible to reduce or prevent the developer from spilling out from the opening of 1.32 and staining the surface of the recording paper.

In addition, when switching between a state in which the openings of the developer supply grooves 31 and 32 are covered with recording paper and a state in which the developing head is separated from the recording paper,
Although the developing head is moved up and down, the recording paper conveying means may be moved up and down instead.

Further, each developing head is supplied with developer from one developer tank, and each developing head is configured to contain different colored developers through appropriate liquid path switching means such as valves. It can be selectively connected to any one of a plurality of developer tanks and a tank containing a cleaning solution for cleaning developer supply grooves 31, 32, etc. at the time of color switching,
A developing head may be shared by multiple developer tanks.

Further, although the above embodiment is a developing device for color development equipped with a plurality of developing heads, the present invention has one developing head.
It can also be applied to a monochrome developing device using the present invention.

〔Effect of the invention〕

As described above, according to the present invention, the shock caused by the pressure change in the developer supply groove when the developing head surface and the recording medium are separated after the completion of development is suppressed during development while the negative pressure generating means is driven. Since the separation between the head and the recording medium can be made smaller than when the developing head and the recording medium are started, the moment the developing head and the recording medium are separated, the developer will fly out from the opening of the developer supply groove and cover the recording medium. It has the unique effect of minimizing contamination.

Further, a valve is provided to switch the developer supply path between a communication state and a cutoff state, and the valve is set to a state where the developer supply path is cut off while the recording medium continues to be conveyed after the development operation is completed. If the switching is made such that the developer in the developer supply groove is recovered into the developer tank by driving the negative pressure generating means, and then the development head and the recording medium begin to be separated, the recording medium Since the developer can be naturally separated from the surface of the developing head, it is possible to better prevent the developer from spilling out from the opening of the developer supply groove and staining the recording medium at the moment the developing head and the recording medium are separated. I can do it.

In addition, after the development is completed, the developer is supplied from the developer tank to remove the developer adhering to the development head surface by transporting the recording medium and applying the developer on the development head surface to the recording medium. By driving the negative pressure generating means with the developer supply path to the groove blocked, the negative pressure in the developer supply groove is made larger than that in the developer, and the development in the developer supply groove is performed. By quickly and reliably collecting the liquid, it is possible to shorten the time required to transport the recording paper to remove the developer attached to the developing head surface. In color development using conveyance, the development time can be significantly shortened.

Furthermore, if a means for adjusting the negative pressure in the developer supply groove is provided, the negative pressure in the developer supply groove can be adjusted to the optimal negative pressure for development, making it possible to handle recording paper of various types and uses. It can be used.

[Brief explanation of the drawing]

1 to 4 are drawings for explaining a liquid developing device according to a first embodiment of the present invention, FIG. 1 is a perspective view of the liquid developing device, and FIG. 2 is a perspective view of the liquid developing device. 3 is a longitudinal sectional view taken along the plane along the line A-A in FIG. 1 and viewed from the direction of the arrow, and FIG. 4 is a schematic diagram of the liquid developing device. It is a timing chart explaining operation. FIG. 5 is a schematic configuration diagram of a liquid developing device according to a second embodiment.

Claims (3)

[Claims] (1) A developing head having an opening on the developing head surface facing the recording medium transport path and having a developer supply groove extending in the width direction of the recording medium, a developer tank containing the developer, and a developer tank. A developer supply path forming means from the liquid tank to the developer supply groove, a developer recovery path forming means from the developer supply groove to the developer tank, and an opening of the developer supply groove provided in the developer recovery path. and a negative pressure generating means for generating negative pressure in the developer supply groove when the opening of the developer supply groove is blocked by the recording medium, and the developing device is developed with the opening of the developer supply groove being blocked by the recording medium. By generating negative pressure in the developer supply groove and circulating the developer between the developer tank and the developer supply groove while sucking the recording medium into the opening of the developer supply groove, the developer supply groove can be filled with developer. In a liquid developing device that performs a developing operation of an image to be developed on a recording medium by filling the liquid with liquid, and separates the developing head from the recording medium after the development operation is completed, before starting to separate the developing head from the recording medium. A liquid developing device characterized in that driving of the negative pressure generating means is stopped. (2) A valve is provided to switch the developer supply path between a communication state and a cutoff state, and the valve shuts off the developer supply path while the recording medium continues to be conveyed after the development operation is completed. the developer in the developer supply groove is recovered into the developer tank by driving the negative pressure generating means, and then the developing head and the recording medium begin to be separated from each other. The liquid developing device according to claim (1). (3) The liquid developing device according to claim 1 or 2, further comprising means for adjusting the negative pressure within the developer supply groove.