JP2000231267A - Wet type image forming device, printing machine, and wet type image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wet type image forming device and a wet type image forming method by which an image irregularity caused by the effect of the secular deterioration of a pump and the like and an image irregularity caused by the unevenness of discharge amount of liquid developer at the discharge port thereof is prevented from occurring. SOLUTION: This wet type image forming device is provided with a means for retaining liquid forming the free boundary of the liquid developer 9 in a prescribed area on the surface of an electrostatic latent image carrier 1. The means for retaining liquid is constituted of a developing electrode 4 installed so as to be opposed to the surface of the carrier 1 by keeping a developing gap G being the prescribed gap, a squeeze roller 5a arranged near to the electrode 4 and on the downstream side in the rotating direction of the carrier 1 so as to have a gap spatially connected to the gap G between the surface thereof and the surface of the carrier 1 and a liquid storage means communicating with the gap G so that the gap G and the above mentioned gap is filled with the developer 9 including toner grains with gravity as driving force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet image forming apparatus and a printing machine for forming a toner image on an electrostatic latent image carrier serving as a photosensitive drum and transferring the toner image to a transfer material such as paper. The present invention also relates to a wet image forming method relating to these.

[0002]

2. Description of the Related Art As a conventional wet image forming apparatus, for example, an apparatus as shown in FIG. 5 is used. This is because an electrostatic latent image carrier (photosensitive drum) 1 that rotates in a certain direction
, A charging device 2, an exposure device 3, a fixed developing electrode (dish-shaped or plate-shaped electrode) 4, a squeezing device 5, a transfer device, and the like. 6, a cleaning blade 7, and a static eliminator 8 are sequentially arranged. Of these, the charging device 2 and the transfer device 6 are connected to a power supply (not shown).

The development on the surface of the image carrier 1 is performed by forming an electrostatic latent image on the surface of the image carrier 1 with the exposure device 3, and then the liquid developer 9 is applied to the image carrier 1 by a dish-shaped or plate-shaped development electrode 4. The toner image 11 is formed (developed) by being supplied to the surface and applying an electric attraction force to a portion corresponding to the electrostatic latent image. At this time, the liquid developer 9 is obtained by dispersing positively (+) or negatively (-) charged toner particles in an insulating liquid. The toner image 11 is formed by the toner particles. Here, it is assumed that the toner particles are positively (+) charged.

After the development of the toner image, the squeezing device 5
As a result, surplus insulating liquid in the liquid developer 9 existing on the surface of the image carrier 1 is removed. Thereafter, a charge having a polarity opposite to that of the toner particles of the toner image 11, here a negative (−) charge, is applied from the back surface of the transfer material 12 by the transport roller, and accordingly, the toner image 11 of the image carrier 1 is formed. The toner particles to be formed are transferred to the transfer material 12 by suction. afterwards,
The cleaning blade 7 removes toner particles remaining on the surface of the image carrier 1, and the static eliminator 8 removes charges remaining on the surface of the image carrier 1.

[0005] The method of supplying (applying) the liquid developer 9 to the image carrier 1 has been specifically shown in Figs. 5 and 6 in the prior art. That is, the liquid developer 9 in the tank 13 is sent to the duct 15 (see FIG. 6) by the pump 10 via the supply pipe 14, and is discharged from the discharge port 16 into the developing gap 17 formed by the developing electrode 4 and the image carrier 1. Was to be supplied.

[0006]

In the above-mentioned conventional wet image forming apparatus, the apparatus configuration in which the dish-shaped or plate-shaped developing electrode 4 is provided, or the method of supplying the liquid developer 9 to the surface of the image carrier 1 is employed. In such a case, it is possible to secure a sufficiently long effective development area and to increase the speed of wet development, but it has the following problems.

That is, there is a problem that the discharge amount of the liquid developer 9 from the discharge port 16 shown in FIG. 6 is not preferable due to uneven driving (variation caused by operation and driving of the apparatus). This will be described with reference to FIG. 6 and FIG. Now, consider the case where the liquid developer 9 supplies the liquid developer 9 in the direction of arrow 18 from the side C in FIG. 6, and as shown in FIG. Is increased (increased), and a non-uniform liquid flow resulting from this occurs in the developing gap 17, that is, in the discharge port 16, and the
For No. 1, streak-like image unevenness was to occur. This indicates that the same situation occurs when the liquid developer 9 is supplied from the side D or when the liquid developer 9 is supplied at an intermediate point between C and D.

In addition, in addition to the above problem, in the conventional wet image forming apparatus, the discharge amount (development gap) 16 is changed by the deterioration of the pump 10 with the passage of time.
There has been a problem that a problem such as a change in the flow rate of the liquid inside and a change in the density of the toner image 11 easily occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to achieve image unevenness due to the deterioration of the pump with the passage of time and image unevenness due to the uneven discharge amount at the discharge port of the liquid developer. An object of the present invention is to provide a wet image forming apparatus that does not cause unevenness or the like.

[0010]

The present invention employs the following means in order to solve the above-mentioned problems. That is, the liquid image forming apparatus according to the first aspect is provided with a liquid stagnation means for generating a free interface of the liquid developer in a predetermined area on the surface of the electrostatic latent image carrier. It is a feature.

According to a second aspect of the present invention, in the wet image forming apparatus, the liquid retaining means has its surface opposed to the surface of the rotating electrostatic latent image carrier and has a developing gap at a predetermined interval. A plate-like or plate-like developing electrode, and a surface thereof and the electrostatic latent image immediately adjacent to the developing electrode and downstream of the direction of rotation of the electrostatic latent image carrier with respect to the developing electrode. A liquid retaining roller disposed so as to have a space that is spatially continuous with the developing gap between the surface of the carrier and the developing gap, wherein the liquid developer containing toner particles is driven by gravity as a driving force; And a liquid storage means communicating with the developing gap so as to be filled with a spatially continuous gap.

In these wet image forming apparatuses, the liquid developer stays and exists as a free interface on a predetermined area on the surface of the electrostatic latent image carrier by the liquid staying means. That is, it means that the liquid developer spreads evenly over the predetermined area. This can be described more specifically, as described in the wet-type image forming apparatus according to claim 2, wherein the liquid developer is filled with a developing gap (gap between the surface of the electrostatic latent image carrier and the surface of the developing electrode) and the space between the developing gap and the space. And a driving force for supplying a liquid developer to the developing gap and the gap is provided so as to fill a continuous gap (a gap between the surface of the electrostatic latent image carrier and the surface of the liquid retaining roller). Since the gravity is defined, it is possible to make the liquid developer that forms the free interface appear. Therefore, according to the wet image forming apparatus of the present invention, it is possible to obtain the effect of suppressing the occurrence of image unevenness related to the toner image on the surface of the electrostatic latent image carrier by such a mechanism.

In consideration of such circumstances, the liquid storing means is devised so as to store the liquid developer in such a manner that its own free liquid surface is formed, and the liquid developer is dropped into the developing gap or the like by free fall. Naturally, a liquid developer is supplied. Further, when the liquid developer is separately supplied to the liquid storage means, it can be said that it is most suitable for the purpose if the liquid developer is configured to overflow a part thereof to the outside. The liquid retaining roller may be a squeeze roller that removes an excess of the insulating liquid in the liquid developer from the surface of the electrostatic latent image carrier.

According to a fourth aspect of the present invention, when the size of the inlet gap of the liquid developer in the developing gap is g1, and the size of the outlet gap is g2, g1> g2. The apparatus according to claim 5, wherein one end of the developing electrode, which is located on an outlet side of the liquid developer in the developing gap, is provided. A minimum position in the gap formed by the liquid retaining roller or the vertical vertex position of the squeeze roller and the surface of the electrostatic latent image carrier and the surface of the liquid retaining roller or the surface of the squeeze roller; So that it is located between
It is characterized by being installed.

It can be seen that these wet image forming apparatuses affect the development gap and the behavior of the liquid developer in the gap. First, according to the wet image forming apparatus of the present invention, by making the outlet gap g2 smaller than the inlet gap g1 (g1> g2), the liquid developer flows out at the outlet of the developing gap. Is increased. According to the fifth aspect of the present invention, the liquid developer can easily reach the minimum position in the gap formed by the electrostatic latent image carrier and the liquid retaining roller or the squeeze roller. You can see that. These effects are
This is an important factor related to the above-described free interface generation, and details thereof will be described in the embodiments of the present invention.

In the printing machine according to the sixth aspect, by using the above-mentioned wet image forming apparatus as a constituent element, it is possible to similarly realize the effect of suppressing the occurrence of image unevenness. Things. Further, it can be said that the wet image forming method according to claim 7 is the most suitable image forming method when operating the wet image forming apparatus and the printing machine described above.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the wet image forming apparatus according to the present embodiment has, as main components, an electrostatic latent image carrier (hereinafter, referred to as a photosensitive drum) that is configured to rotate in a direction indicated by an arrow in the figure. (Abbreviated as image carrier) 1. In this wet image forming apparatus, the periphery of the image carrier 1 is arranged along the rotation direction thereof.
A charging device 2, an exposure device 3, a fixed developing electrode 4, a squeezing device 5, a transfer device 6, a cleaning blade 7, and a charge removing device 8 are sequentially arranged. Among these, the charging device 2, the transfer device 6, and the like are connected to a power supply (not shown). Hereinafter, each of these elements will be described.

The charging device 2 charges the image carrier 1 having a photosensitive surface on its entire width surface having a certain size (forms a charged area). The configuration is such that the surface of the image carrier 1 and a kind of electrode capable of generating corona discharge are provided as main parts. The charge on the image carrier 1 is positive (+) in the present embodiment.

The exposure device 3 is for exposing the charged area on the surface of the image carrier 1 to light.
For example, a semiconductor laser or the like is used. In this case, the laser beam oscillated by the device 3 is scanned on the surface of the image carrier 1 based on image information to be printed. As a result, the potential of the charged area in the exposed portion on the surface of the image carrier 1 decreases, and a potential difference is generated between the exposed portion and the non-exposed portion. Hereinafter, these exposed portions and non-exposed portions may be referred to as image portions and non-image portions, respectively.

Next, the developing electrode 4 will be described in detail later, since the structure of the developing electrode 4 and its surroundings is a feature of the present invention. However, here, the shape of the developing electrode 4 is dish-shaped or plate-shaped, and therefore, a sufficient contact time between the surface of the image carrier 1 and the liquid developer 9 (or
Development time).
It should be noted that the development speed can be increased.

The squeezing device 5 is for removing excess insulating liquid in the liquid developer 9 existing on the surface of the image carrier 1. As shown in FIG. 1, this is on the downstream side in the rotation direction of the image carrier 1 as viewed from the developing electrode 4,
Two squeeze rollers 5a and 5b are arranged and arranged in order. These two sets of squeeze rollers 5a, 5a
b rotates in the opposite direction to the image carrier 1. The diameter of the squeeze roller (liquid retention roller) 5a located directly below the developing electrode 4 is 30 mm, and the gap formed between the roller surface and the image carrier 1 surface is about 100 μm. It is arranged to become. Further, the squeeze roller 5b located downstream thereof
Are arranged such that their diameter is 30 mm and the gap defined as above is 50 μm.

Such a configuration is intended to gradually reduce the surplus of the insulating liquid in the liquid developer 9 applied on the surface of the image carrier 1 in the developing electrode 4. The effect of this is apparent, for example, assuming that only the squeeze roller 5a is provided. That is, in such a case, if the surplus of the insulating liquid in the liquid developer 9 is to be sufficiently reduced, the gap between the vibrating image carrier 1 and the squeeze roller 5a must be narrowed. However, in the present apparatus, which attempts to perform high-speed development using the developing electrode 4 having a dish-like or plate-like form, if such measures are taken, streak-like unevenness (fluidity unevenness of liquid) occurs in the toner image. And the likelihood of reducing its quality increases. On the other hand, to avoid this, if the gap between the image carrier 1 and the squeeze roller 5a is increased, the original purpose of removing the excess of the liquid developer 9 becomes insufficient.

The squeeze device 5 shown in FIG. 1 is a powerful means for solving the above-mentioned problems. That is,
In the first stage squeeze roller 5a, the gap between the surface of the image carrier 1 and the surface of the image carrier 1 is slightly widened (approximately 100 μm) so that the appropriate amount of the insulating liquid Is removed, and the second squeeze roller 5b narrows the gap (5
0 μm), the surplus of the insulating liquid is surely removed. From the above, it can be said that the apparatus according to the present embodiment can perform high-quality printing.

Next, the transfer device 6 applies a charge (here, a negative (−) charge) having a polarity opposite to that of the toner particles forming the toner image 11 from the back surface of the transfer material 12, and accordingly, The toner particles of the image carrier 1 are transferred to the transfer material 12 by suction. That is, here, the transfer material 1
The "printing" is performed on the top 2. Further, the cleaning blade 7 is for completely removing the toner particles remaining on the surface of the image carrier 1 after printing, and the charge removing device 8 is also for completely removing the electric charge remaining on the surface of the image carrier 1 after printing. To get rid of it. Here, the former is to physically scrape off the toner particles by making physical contact with the surface of the image carrier 1, and the latter is configured by an LED luminous body or the like, and removes the electric charge by lighting the luminous body.

The apparatus having the above-described configuration according to the embodiment of the present invention has the following features. The characteristic part of the present invention relates to the configuration of the developing electrode 4 and the peripheral device as described above.

As shown in FIG. 1 or FIG. 2 which is an enlarged view of the portion, the developing electrode 4 has a dish-like or plate-like shape, and the dish-like or plate-like surface has an image. It is provided so as to face the surface of the carrier 1.
In the figure, it can be seen that the developing electrode 4 having a wedge-shaped cross section is arranged so that its oblique surface faces the surface of the image carrier 1. The developing gap G is
It can be defined as the area between these two planes. The liquid developer 9 in the development gap G is, as will be clear from the following description of the flow path thereof, in FIG.
It flows from the upper right to the lower left. Also,
The developing gap G is spatially continuous with the gap between the image carrier 1 and the squeeze roller 5a via the lower left portion. That is, the liquid developer 9 flows from the development gap G into the gap. Now, the size of the developing gap G at the upper right is defined as the inlet gap g1, and the value at the lower left is defined as the outlet gap g2.
Then, in the present invention, g1> g2
Imposes certain conditions.

The developing electrode 4 is set such that the position of the top of the head in the wedge-shaped section satisfies the following condition. That is, as shown in FIG. 2, the top P is a straight line AB ′ that extends vertically upward through a center point B ′ of the squeeze roller 5 a directly below the developing electrode 4, the center point B ′ and the center of the image carrier 1. The developing electrode 4 is arranged so as to be located within a region sandwiching the apex angle B 'by a line segment BB' connecting the point B. In other words,
The top P is located at the vertex Q (straight line AB ') of the squeeze roller 5a.
2) (see FIG. 2), the position R where the gap between the surface of the image carrier 1 and the surface of the squeeze roller 5a is minimized is closer. Incidentally, the position R mentioned here is the intersection of the line segment BB 'and the circumferential line of the squeeze roller 5a, and the minimum gap is 100 μm in the present embodiment from the above-mentioned matter. There will be.

On the other hand, a liquid supply duct 15 serving as a supply port for the liquid developer 9 is provided on the lower surface of the developing electrode 4 in the back side direction, and a liquid supply pipe 14 is connected to the liquid supply duct 15. The liquid supply pipe 14 communicates via the pump 10 to the tank 13 storing the liquid developer 9. On the back surface of the developing electrode 4, a flow path wall 30 (partly not shown) surrounding the three sides of the developing electrode 4 separately from the back surface as one flow path wall.
Thus, the flow path 20 partitioned from the outside is formed.
The flow path 20 and the liquid supply duct 15 communicate with each other through openings 19 formed in the width direction on the back side surface of the liquid supply duct 15. However, as shown in FIG. 2, a wall W is separately provided in the flow path 20 so that the liquid developer 9 that has passed through the opening 19 does not flow directly into the flow path 20. Due to this wall W, the liquid developer 9
As shown by the arrow in FIG. 2, the light passes through the flow path 20 while meandering, and reaches the upper surface of the developing electrode 4. The upper portion of the flow channel wall 30 is extended from the upper surface of the developing electrode 4 by a height h2, and is bent inward at a right angle at that point and extended therefrom by an appropriate length. (Or formed like a flange) so as to be the end of the flow path wall 30. As a result, a weir 22 is formed in the flow path 20.

From the above, the flow of the liquid developer 9 or its route is as follows. That is, the liquid developer 9
While being sucked up from the tank 13 by the pump 10, the liquid is supplied to the liquid supply duct 15 through the liquid supply pipe 14, enters the flow path 20 through the opening 19, and is
After a proper amount is accumulated on the upper surface of the developing electrode 4 beyond the developing gap G, it is supplied to the developing gap G and a gap spatially continuous with the developing gap G (hereinafter, may be simply abbreviated as developing gap G), that is, to the surface of the image carrier 1. Will be done. The liquid developer 9 that has passed through the developing gap G and the liquid developer 9 that has overflowed beyond the weir 22 are allowed to freely fall below the liquid developer 9. A container 23 is provided at the drop point (see FIG. 1), and the liquid developer 9 that has reached the container 23 is returned to the tank 13 via the flow path 23a. Reuse is achieved.

The liquid developer 9 is obtained by dispersing positively (+) or negatively (-) charged toner particles in an insulating liquid. The toner particles transferred to the surface of the image carrier 1 are And a toner image 11 (see FIG. 1). The use of positively (+) and negatively (+) charged toner particles is a form generally found when the present wet image forming apparatus is used as a printing machine and a copying machine. .

In the following, the operation and effect of the wet image forming apparatus of the present embodiment having the above configuration will be described focusing on the flow of the liquid developer 9 around the developing electrode 4. As described above, the liquid developer 9 that has passed through the liquid supply pipe 14 passes through the liquid supply duct 15 and the flow path 20, passes over the weir 22, and reaches the upper surface of the developing electrode 4 in a wedge-shaped cross section. In the present embodiment,
It is particularly important that the liquid developer 9 is stored to some extent on the upper surface of the developing electrode 4 at this point, that is, a free liquid surface 21 is formed. At this time,
Needless to say, the “a certain amount” is defined by the equilibrium relationship between the density and volume of the developer 9 and gravity. FIG. 2 shows such an equilibrium state. On the left side of the figure, the liquid developer 9 fills the development gap G and accumulates up to the level line S on the surface of the image carrier 1. You can see that it is. From this figure, the distance h1 measured from the upper surface of the developing electrode 4 to the free liquid surface 21 is obtained. Height h of weir 22 introduced earlier
2 is defined so as to satisfy the condition of h2 ≦ h1. That is, the height h2 is such that the free liquid surface 21 is
May be paraphrased as having a point T that is located at a point that is equal to or always higher than By the way, as is apparent from such circumstances, it is somewhat difficult to clearly define “liquid storage means” in terms of terms used in the present invention as one device configuration in the present embodiment. In other words, it may be considered that it refers to “a part surrounded by the flow path wall 30 with the upper surface of the developing electrode 4 as a floor surface”.

As a result, the toner image 11 formed on the surface of the image carrier 1 does not cause image unevenness as observed in the conventional apparatus. This is because the source of the force for supplying the liquid developer 9 to the developing gap G is apparently gravity from the above description, and the mode of the movement is free fall. Therefore, in the developing gap G and the gap between the surface of the image carrier 1 and the surface of the squeeze roller 5a, a free interface of the liquid developer 9 is generated on an area of a corresponding size on the surface of the image carrier 1. Become.
That is, unlike in the conventional example described with reference to FIG. 7, there is no operation unevenness (variation) such that the discharge liquid amount is large at a certain point and small at other points, and is always constant and stable. Thus, the supply of the liquid developer 9 is realized.

Further, according to the present embodiment, even if the supply amount changes due to the deterioration of the pump 10 over time,
If the change is within a range that does not eliminate the overflow, the free liquid level 21 can be kept almost constant at the height h2 of the weir 22, so that the amount of liquid supplied to the developing gap G becomes constant. Variations in image quality can be prevented. That is, the overflow amount ΔV1
However, stabilization of the flow rate can be achieved by setting ΔV1 ≧ ΔV2 with respect to the fluctuation amount ΔV2 expected due to the deterioration over time of the pump.

Incidentally, the amount of the liquid developer 9 supplied to the developing gap G is determined by the peripheral speed of the image carrier 1, the inlet side gap g1, and the liquid level height h1. By setting to, any supply can be realized.

In this embodiment, the inlet gap g1 and the outlet gap g2 of the developing gap G are set.
As the developing electrode 4 is arranged such that the condition of g1> g2 is satisfied, higher quality image formation of the toner image 11 can be realized. This is because, when the above condition g1> g2 is not satisfied, as shown in FIG.
This is because the inventors of the present application have confirmed that there has been a case in which the occurrence of the problem has occurred.

In the image unevenness 101, the meniscus 50 as shown in FIG. 4A is not formed in the gap between the squeeze roller 5a and the image carrier 1, and the air layer 51 as shown in FIG. Is formed, and the surface of the toner image 11 on the side of the image carrier 1 is conveyed by the squeeze roller 5a.
It is probable that it was caused by being disturbed by 2.
The air layer 51 as shown in FIG. 4B is formed because the drop position U of the liquid flow from the outlet 53 of the developing gap G is formed by the squeeze roller 5a and the image carrier 1. If it is away from the minimum gap position R (described above),
It is considered that the liquid developer 9 is discharged in the direction of the arrow 54 in FIG. 4B due to the rotation of the squeeze roller 5a (in the direction opposite to the rotation of the image carrier 1), and does not reach the minimum gap position R.

If g1> g2, that is, if the inlet gap g1 is larger than the outlet gap g2, the flow velocity of the liquid developer 9 at the outlet 53 of the developing gap G increases, and the landing position is shifted to the minimum gap position R. By approaching, the generation of the air layer 51 described above is suppressed. Therefore, a normal meniscus 50 shown in FIG. 4A is formed in the gap between the squeeze roller 5a and the image carrier 1, and as a result, a wavy image unevenness 101 (see FIG. 3) may occur. It is gone.

Further, in this embodiment, in the present embodiment, the position of the top P of the developing electrode 4 is represented by a straight line AB.
′ And the line segment BB ′ are defined so as to be located in a region sandwiched between the line ′ and the line segment BB ′. That is, according to FIG. 4, the outlet 53 of the liquid flow in the developing gap G is connected to the squeeze roller 5.
Since the liquid developer 9 is set to be closer to the minimum gap position R in the squeeze roller 5a than the apex position Q of a, the liquid developer 9 easily reaches the minimum gap region, and as a result, the meniscus 50 is reliably formed, This is because generation of the wavy unevenness due to the air layer 51 can be suppressed.

In this embodiment, the following operation and effect can be pointed out. This is an effect achieved by the opening 19, the flow path 20, and the wall W formed on the back side surface of the liquid supply duct 15. In the present embodiment, the liquid flow from the liquid supply duct 15 to the upper surface of the developing electrode 4 is not direct due to the presence of the opening 19, the flow path 20, and the wall W. That is, these configurations prevent the liquid developer 9 from directly reaching the developing gap G by the driving force given by the pump 10, and the liquid supply to the developing gap G is caused by free fall. It is possible to do.

The setting of the size and shape of the opening 19, the number of the openings formed and the like, and the setting of the length of the flow path 20 and the like are based on the above circumstances, and the liquid developer 9 to be supplied onto the surface of the image carrier 1 And the driving force applied to the developer 9 by the pump 10 may be determined.

[0041]

As described above, according to the first aspect of the present invention, there is provided a liquid image forming apparatus in which a free surface of a liquid developer is generated in a predetermined area on the surface of an electrostatic latent image carrier. With the provision of the application means, the liquid developer spreads evenly over the predetermined area, and it is possible to suppress the occurrence of image unevenness in forming a toner image on the surface of the electrostatic latent image carrier.

In order to realize the above-mentioned items more effectively, as in the wet-type image forming apparatus according to the second aspect, the stagnation means may include a developing electrode, a liquid stagnation roller, and an accumulator, as described in detail above. This is achieved by supplying the liquid developer to the developing gap and the gap between the liquid holding roller and the electrostatic latent image carrier spatially communicating with the developing gap by using gravity as a driving force.

If the size of the inlet-side gap of the liquid developer in the developing gap is g1, and the size of the outlet-side gap is g2, if the condition of g1> g2 is satisfied (claim 4), The outflow speed of the developer can be increased. In addition, the developing electrode may be configured such that one end of the developing electrode positioned on the outlet side of the liquid developer in the developing gap is located at a vertical apex position of the liquid retaining roller or the squeeze roller and the electrostatic latent image. If it is set so as to be located between the minimum position in the gap formed by the surface of the carrier and the surface of the liquid retaining roller or the surface of the squeeze roller (claim 5), This will make it easier for the developer to reach the minimum position in the gap.

Therefore, if these conditions are satisfied separately or simultaneously, a meniscus can be reliably formed in the gap, that is, a free interface can be surely generated, and the wavy unevenness in the toner image can be reduced. Generation can be suppressed.

In the printing press according to the sixth aspect, by using the above-mentioned wet image forming apparatus as a constituent element, the effect of suppressing the occurrence of image unevenness can be similarly realized. Therefore, the effect that high quality printing can be performed can be easily derived. Further, it can be said that the wet image forming method according to claim 7 is the most suitable image forming method when operating the wet image forming apparatus and the printing machine described above.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a wet image forming apparatus according to the present invention.

FIG. 2 is an explanatory diagram showing an enlarged portion related to development in the configuration shown in FIG. 1;

FIG. 3 is an explanatory diagram showing image unevenness occurring on a wave in a flat screen image.

FIG. 4 is an enlarged explanatory view showing a gap portion formed by an image carrier surface and a squeeze roller surface;
(A) shows a meniscus formed in the gap, (b)
Indicates air layers formed in the gaps, respectively.

FIG. 5 is an explanatory diagram illustrating a configuration of a conventional wet image forming apparatus.

FIG. 6 is an enlarged perspective view showing a portion related to a developing electrode in the configuration shown in FIG. 5;

FIG. 7 is an explanatory diagram showing a state in which a liquid developer is supplied to an image carrier in the developing electrodes shown in FIGS. 5 and 6.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 electrostatic latent image carrier 2 charging device 3 exposure device 4 developing electrode P at top of developing electrode 5 squeezing device 5 a squeeze roller (liquid retaining roller) 5 b squeeze roller 6 transfer device 7 cleaning blade 8 static elimination device 9 liquid Developer 10 Pump 11 Toner image 12 Transfer material 13 Tank 14 Liquid supply pipe 15 Liquid supply duct 19 Opening 20 Flow path 22 Weir 23 Container 23a Flow path 30 Flow path wall 50 Meniscus 51 Air layer 52 Air flow 53 Air flow 53 Outlet h1 Free liquid level height h2 Weir height U Drop position R Minimum position in gap between image carrier and squeeze roller Q Apex position in squeeze roller G Development gap g1 Inlet gap g2 Outlet gap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Etsuro Hirai 4-22, Kannonshinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Prefecture Inside the Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor: Hitoshi Hirose 5007, Itozakicho, Mihara-shi, Hiroshima Mitsubishi F-term in Mihara Works (reference) 2H074 AA03 AA11 AA41 AA44 BB02 BB32 BB43 BB50 BB54 BB72

Claims (7)

[Claims] 1. A wet image forming apparatus comprising: a liquid stagnation means for generating a free interface of a liquid developer in a predetermined area on a surface of an electrostatic latent image carrier. 2. The liquid stagnation means has its surface opposed to the surface of a rotating electrostatic latent image carrier,
And a dish-shaped or plate-shaped developing electrode provided with a developing gap at a predetermined interval, and a downstream side in the direction of rotation of the electrostatic latent image carrier with respect to the developing electrode, which is in the immediate vicinity of the developing electrode. A liquid retaining roller disposed so as to have a space that is spatially continuous with the developing gap between the surface of the electrostatic latent image carrier and the surface of the electrostatic latent image carrier; 2. The wet method according to claim 1, further comprising a liquid storage means communicating with the developing gap so as to be filled with the developing gap as a driving force and a gap spatially continuous with the developing gap. Image forming device. 3. A wet-type wet roller according to claim 2, wherein said liquid retaining roller is a squeeze roller for removing an excess amount of an insulating liquid in said liquid developer from a surface of said electrostatic latent image carrier. Image forming device. 4. The condition of g1> g2 is established, where g1 is the size of the inlet side gap of the liquid developer in the developing gap and g2 is the size of the outlet side gap of the liquid developer. Or a wet image forming apparatus according to 3. 5. A method according to claim 1, wherein one end of the developing electrode positioned on the outlet side of the liquid developer in the developing gap is located at a vertex position of the liquid retaining roller or the squeeze roller in a vertical direction. The gap is formed between the surface of the electrostatic latent image carrier and the surface of the liquid retaining roller or the surface of the squeeze roller. The wet image forming apparatus according to claim 2. 6. A liquid image forming apparatus according to claim 2, wherein said developing electrode, said liquid retaining roller and / or said squeeze roller, said liquid storage means, and said electrostatic latent image carrier. A charging device for forming a charged region on the surface of the body, an exposure device for forming an image portion except for the charging in the charged region and setting the remaining charged region as a non-image portion, and the electrostatic latent image carrier An apparatus for transferring the toner particles to a transfer material from the surface of the body, a cleaning blade for removing the toner particles from the surface of the electrostatic latent image carrier, and an electric charge from the surface of the electrostatic latent image carrier. And a static eliminator for removing the entirety of the printing press. 7. A wet image forming method, wherein an image is formed while generating a free interface of a liquid developer in a predetermined area on a surface of an electrostatic latent image carrier.