JP2795570B2 - Wet electrophotographic developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention develops an electrophotographic photosensitive material on which an electrostatic latent image is formed with a developing solution (toner solution) and prevents image deterioration due to toner adhesion to a developing electrode. The present invention relates to a wet electrophotographic developing device.

[0002]

2. Description of the Related Art FIG. 10 shows the structure of a conventional general wet-type electrophotographic developing apparatus. A back guide 100 made of an insulating material is provided at a predetermined angle and is opposed to the back guide 100. The developing electrode 101 is provided with a predetermined developing gap as described above. The developing electrode 101 is biased to 150 [V] to 200 [V] by a bias power supply 102, and the electrophotographic photosensitive material 120 on which an electrostatic latent image is formed in an exposure unit (not shown) is brought together with the developing solution 110 into a back guide The developer is conveyed through the developing gap on the upper surface 100 and is developed. The electrophotographic photosensitive material 120 includes a support layer 121 made of a conductive material such as aluminum and an OPC.
(Organic Photoconductor), and a photosensitive layer 122 is formed in a plate shape, and the support layer 121 is grounded and developed.

The reversal developing method is a method in which an image is formed by charging and exposing the photosensitive layer 122 and developing it with toner having the same polarity as the photosensitive layer. In the reversal development, a developing electrode is usually provided opposite to the photosensitive layer, and an intermediate bias potential between the surface potential and the residual potential of the photosensitive layer is applied. The application of the bias voltage is performed for the purpose of preventing image fogging or edge effects. In the developing section, when the area of the non-image area of the photosensitive material 120 is very large, the developing electrode 10 on the opposite surface is used.
As shown in FIG. 11, the toner 111 adheres and accumulates on the surface 1. After the deposited toner 111 passes through the photosensitive layer 101, the electric repulsion between the developing electrode 101 and the toner 111,
While it gradually lost by electrical leakage or the liquid flow of the developer 110, the electrophotographic photosensitive material 120 before the toner charge erasure
Is transported to the developing unit, the bias voltage apparently becomes higher than the bias voltage of the bias power supply 102 due to the charge of the toner 111, the fog becomes large, and this causes blurring such as a shadow portion of a halftone dot. Was.

[0004] Such a phenomenon is caused by a two-page newspaper version (about 11 pages).
In the case of developing a long photoconductor such as (00 mm), it occurs within the same photoconductor, and the image reproducibility at the front end and the rear end of the photoconductor is different. Further, as the repetition cycle of development becomes shorter, this effect becomes larger, and it is very important to keep the bias potential stable.

[0005] A similar phenomenon also occurs in normal development. In normal development, development is performed with toner having a polarity opposite to the charge polarity of the photosensitive layer. Therefore, usually, a bias voltage higher than the residual potential is applied to prevent fog. For this reason, toner adheres to the developing electrode, causing fogging as in the case of reversal development.

In order to prevent such inconvenience, it is only necessary to prevent (reduce) toner from adhering to the developing electrode or to quickly remove the adhering toner. For this purpose, conventionally, a winding type developing device as shown in FIG. 12 (JP-A-60-57875) or a movable developing device as shown in FIG. 13 (JP-A-61-20967).
No.) is used. That is, in the take-up type developing device shown in FIG. 12, the electrophotographic photosensitive material 201 is conveyed along the back guide 200 and the take-up roller 206 from the roller 205 via the rollers 202 and 203.
The belt-like developing electrode 204 is wound up. Since the winding of the band-shaped developing electrode 204 is performed in synchronization with the conveyance of the electrophotographic photosensitive material 201, the development is always performed with the new band-shaped developing electrode 204. Further, in the movable developing device of FIG. 13, the electrode member 212 has an endless belt shape and is wound around the drive roller 210 and the free roller 211, and is moved in synchronization with the conveyance of the electrophotographic photosensitive material 201. It has become. Further, the toner adhered to the surface of the electrode member 212 in the developing gap is
The developer is scraped off by a doctor blade 213 provided in contact with the ten electrode members 212, and is always developed with a clean electrode member 212 that has been cleaned.

[0007]

The above-described conventional winding type and moving type developing devices both focus on the removal of adhered toner and have a movable developing electrode. However, there is a disadvantage that the maintenance performance is deteriorated. In addition, since it is movable, it is very difficult to maintain the flatness of the developing electrode, and it is difficult to realize a narrow developing gap.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent image deterioration by efficiently reducing toner adhesion to a developing electrode without having a movable portion. It is another object of the present invention to provide a wet electrophotographic developing device.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a wet electrophotographic developing apparatus, and an object of the present invention is to provide a back guide for guiding the conveyance of an electrophotographic photosensitive material having an electrostatic latent image formed thereon, and a back guide for the electrophotographic photosensitive material. When less the disposed a specific surface area in opposition to the photosensitive layer of an electrophotographic light-sensitive material is transported back guide on
Having a non-uniform rough surface of 2500 m ² / m ³ or more
And a supporting member for supporting the porous metal body.
Developing electrode and a photosensitive layer of the electrophotographic photosensitive material.
A developing device provided on the support member for supplying a developing solution;
When voltage is applied to the supply means and the porous metal body,
A developing via for grounding the support layer of the electrophotographic photosensitive material.
This is achieved by providing the assembling means .

[0010]

[0011]

SUMMARY OF] The onset Ming, large heterogeneity a specific surface area of the developer electrode
By a such rough surface, developed by it is possible to reduce the distance between the toner and the electrode to adhere, to prevent unnecessary increase in the bias voltage, inconvenience such as collapsed image Ru is divided <br/> .

[0012] Multi porosifying metal product of a developing electrode (e.g., Serume
The material of the pit (porous metal body such as a trade name) is Al,
A conductor such as Cu, Ni, or Ag is desirable, and a metal having a higher conductivity has a better effect. FIG. 5 shows the difference in roughness between the developing electrodes and the state of toner adhesion.
Indicates that the toner 2 is aligned and adheres to the surface of the developing electrode 1 having a flat specific surface area of 1 m ² / m ³ , and the distance between the toner and the electrode is the largest as compared with the roughened electrode. Has the smallest surface area of the electrode that attracts the electric charge.
The synergistic effect of these causes an apparent increase in bias voltage. This is the relationship between the conventional general developing electrode and toner adhesion. FIG. 5 (B) shows an uneven rough surface having a grooved specific surface area of about 70 to 100 m ³ / m ^3.
One toner 2 to the surface of the developing electrode 3 shows a state in which adhesion, integrity toner adhesion becomes worse than the case of FIG. (A), the distance of the toner 2 and the developing electrode 3 becomes close, the electrode surface area A synergistic effect due to the increase is obtained. FIG. 5C shows a specific surface area of 2500 to 3000 m ² / m.
^This is a case where the porous metal body 4 having a non-uniform rough surface of about ³ is used as the developing electrode. The integrity of the toner 2 is completely lost, and the distance between the toner 2 and the developing electrode 4 becomes extremely short. And the rise of the bias voltage can be suppressed to a very small value. By improving the relative positional relationship between the toner and the developing electrode when the toner adheres, the developing bias does not rise abnormally due to the toner adhesion.

When reversal development is performed by the wet electrophotographic developing apparatus of the present invention, a potential intermediate between the surface potential of the non-image area and the residual voltage of the image area is applied as a bias. When the bias potential is lower than the surface potential, fogging can be prevented, and the reproducibility of the shadow portion can be improved. In particular, when the beam itself has an energy distribution such as laser exposure, it is difficult to reproduce the shadow portion, but good reproducibility can be obtained by setting a low bias. Therefore, it is difficult to reproduce the shadow portion well after a large white background portion. Further, when such a low bias is used, the toner adhesion amount becomes low, and a sufficient density cannot be reproduced. Inconvenience occurs. Conversely, when the bias voltage is set to a value close to the surface potential, the toner accumulation on the developing electrode is reduced, and the deterioration of image reproducibility when the same image is developed within the same image or in a repeated short cycle can be prevented. Problems such as fogging occur due to fluctuations in potential. However, the use of the wet electrophotographic developing device of the present invention enables development with a wider range of bias potentials than in the case where a smooth electrode is used, and significantly improves development stability and image reproducibility. I was able to do it. That is, the bias potential is 5 as the surface potential.
To about 95% of the surface potential, and more preferably about 15 to 85% of the surface potential, whereby a better image and stable development can be realized. Similarly, in the case of normal development, if the bias potential is high, fogging is suppressed, but toner accumulation on the developing electrode increases. Conversely, if the bias potential is set low, fogging tends to occur, and the same problem as described above occurs. Suruga, it was possible to extend the range of use of by Ri bias potential to be used liquid electrophotographic developing device of the present invention greatly. That is, as the bias potential, about 5 to 95% of the surface potential can be used, and more preferably, 15 to 85% of the surface potential.
By using the degree, a better image and stable development can be realized.

FIG. 6 shows the specific surface area of the developing electrode [ m ² / m ³ ].
(1, 70, 2500) and the reproducibility when the bias voltage during reversal development was changed. The image reproducibility at the initial stage of development is almost the same regardless of the bias voltage, but 500 m
It can be seen that the reproducibility after the specific image portion having a long m is significantly improved by increasing the specific surface area.

[0015]

FIG. 1 shows an embodiment of the present invention, in which a back guide 10 inclined at a predetermined angle (for example, 7 °) is placed on a back guide 10.
The electrophotographic photosensitive material 20 on which the electrostatic latent image is formed is conveyed at a predetermined speed.
Are grounded via ground terminals 21 and 22. The back guide 10 has minute projections for the purpose of reducing the contact resistance with the back surface of the photosensitive material to improve the transportability and pressing down the volume of the developing chamber so as not to unnecessarily increase the liquid sending amount. It is composed of a glass plate. A predetermined developing gap is provided above the rear guide 10,
A developing electrode 30 whose structure is shown in FIG. 2 is provided.
And 12 are provided. After the developed electrophotographic photosensitive material 20 is squeezed between the squeezing rollers 11 and 12, it is conveyed to a fixing unit (not shown) at the next stage. A cleaning pad 13 for cleaning is attached to the squeezing roller 11.
1 and 12 are automatically cleaned.

The developing electrode 30 has two separated electrode support plates 31 and 32, and the electrode support plates 31 and 32
Are connected by connecting plates 33 and 34 at the ends. Further, the specific surface area on the lower surface side of the electrode support plates 31 and 32 should be small.
Also , Celmet (trade name: manufactured by Sumitomo Electric Industries, Ltd.) layers 35 and 36 are provided as a porous metal body having a non-uniform rough surface of 2500 m ² / m ³ or more . Celmet layer 3
5 and 36 are electrically connected via a lead wire 37, and a bias voltage is applied to the cermet layers 35 and 36 by a bias power supply 38.

On the other hand, the support plate 3 on which the developing electrode 30 is separated
1, a developer supply section 40 is provided, and a supply pipe 4 is provided.
The developer supplied and stored from the nozzles 1 and 42 supplies the developer 44 to the developing gap from a cylindrical discharge portion 43 having a porous or slit discharge port. The developing solution is pulled up from a developing solution tank (not shown) by a pump, is stored in a developing solution supply unit 40 from supply pipes 41 and 42, is supplied to a developing gap from a discharge unit 43 of the developing solution supply unit 40, and is supplied to a developing electrode. The developer overflowing from 30 is collected by the bath and returns to the developer tank. Such developer circulation is performed continuously or intermittently at the time of development and before and after development. Also, the downward inclination of the back guide 10 and the developing electrode 30 is such that the developing solution supply amount is small and the developing gap is not filled with the developing solution 44 so that the developing solution 44 does not flow to the upstream side along the electrophotographic photosensitive material 20. The inclination is set to 7 ° (7 ° in this example) such that bubbles are not mixed in and excessive developer overflows out of the developing gap to promote the evaporation of the toner and the toner performance does not change. You.

FIG. 3 shows a cross-sectional structure of the developing unit. The front end of the cermet layer 36 is closed by a projection 32A projecting downward at the front end of the support plate 32. Since the celmet layer 36 is a porous material, the celmet layer 36 absorbs the developer 44 in a full state. When the protrusion 32A is not provided, the cermet layer 36 is several times larger than in the case where the protrusion 32A is provided to fill the gap with the developer. Is required. When the protrusion 32A is provided at the tip of the cermet layer 36, the developer absorbed by the cermet layer 36 is blocked without flowing in the inclined direction, so that the gap can be filled with a small amount of liquid supply. . That is, if the protrusion 32A is provided as shown in FIG. 3, the inside of the gap length L1 can be filled with a small amount of liquid supply, but if the protrusion is not provided as shown in FIG. In addition, since the liquid also flows out from L2) and fills the inside thereof, a liquid supply amount several times corresponding to the gap length L3 (= L1 + L2) is required. When the amount of liquid supply increases, it is necessary to increase the capacity of the liquid supply pump, and there is a disadvantage that the liquid supply device becomes large in response to the large circulation amount. It is better that the number of cells of Celmet is large as long as air is replaced with toner.
(26 to 35 pieces / inch). When the thickness of the celmet layer 36 is small, the effect is reduced and the strength is weak. Further, if the thickness of the celmet layer 36 is too large, air is not formed and a good image is not obtained.
mm is desirable, and good conditions should be selected according to the toner prescription. In this embodiment, the thickness is set to L2 = 2 mm.

Since the surface of the developing electrode 30 of the present invention is a porous body of the cermet layers 35 and 36, the specific surface of the rough surface is considerably higher than that of the flat electrode 1 as shown in FIG. The toner adheres in a state as shown in FIG. By the way, when a portion (unexposed portion) of the photosensitive material having a high surface potential is below the developing electrode, the toner adheres to the developing electrode by an electric field of a difference between the developing bias voltage and the surface potential. This appeared increased charge amount with the adherent toner as the fluctuation of the developing bias voltage, the development of a high bias voltage value than the normal state is carried out in an unexposed portion rearward dot shadow portion, such as white text collapse Causes the reproducibility to decrease. However, as in the present invention, the developing electrode has a large non-uniform specific surface area.
By using a porous metal body having a rough surface, the surface area of the electrode can be increased, the distance between the toner adhering to the electrode and the electrode can be shortened, and an apparent increase in bias voltage can be prevented. For this reason, the phenomenon that the developing bias voltage fluctuates depending on the image pattern is reduced, and a remarkable effect is obtained particularly in the processing of a long plate such as a two-page vertical newspaper and the speeding up of a multiple plate cycle. . FIG. 7 shows the specific surface area [ m
² / m ³ ] (1, 70, 2500) and the halftone dot area ratio (%) of the halftone dot reproduction region.
electrodes of m ² / ^{m 3} is a cermet part # 4.

FIGS. 8 and 9 show another embodiment of the present invention, in which a developing electrode 50 having an integrated structure is shown. A developer supply unit 51 is provided at the center of the electrode, and the developer is supplied to the development gap from a discharge port 51A at the bottom. The upper surface of the developing electrode 50 is constituted by a support plate 52, the lower surface of which is provided with a cermet layer 54, and the support plate 52 at the tip thereof forms a projection 52A having a bent structure. Thus, a predetermined developing gap length L4 is maintained. Since the developer is supplied to the development gap through the Celmet layer 54,
An air hole 55 is provided on the upstream side. With such a developing electrode 50, the electrophotographic photosensitive material 61 conveyed on the rear guide 60 is developed.

According to the development electrode 50, the maintenance structure is improved due to the integrated structure, and the development gap length is easily maintained at the predetermined length L4 since the cermet layer 54 is not separated.

[0022]

According to the developing device of the present invention, the developing electrode is
A porous metal body with a large specific surface area and a non-uniform rough surface
By doing so , the distance between the toner adhering to the electrode and the electrode can be reduced, and the apparent increase in the bias voltage due to the charge of the toner adhering due to the synergistic effect of the increase in the electrode surface area can be reduced. Therefore, the phenomenon that the developing bias voltage fluctuates depending on the image pattern is reduced,
In addition to eliminating inconveniences such as image collapse ,
Development can be performed with a narrow development gap. Further, in the present invention, since there is no movable portion, the mechanism is simple and there is an advantage that the maintenance performance is improved.

[Brief description of the drawings]

FIG. 1 is a structural diagram showing one embodiment of the present invention.

FIG. 2 is a perspective view showing a perspective structure of a developing electrode of FIG. 1;

FIG. 3 is a cross-sectional view illustrating a cross-sectional structure of a developing electrode of FIG. 1;

FIG. 4 is a diagram for explaining the operation of a developing electrode.

FIG. 5 is a diagram illustrating a roughness of a developing electrode surface and a state of toner adhesion.

FIG. 6 is a diagram for explaining the operation of the present invention.

FIG. 7 is a diagram for explaining the effect of the present invention.

FIG. 8 is a sectional view showing another embodiment of the present invention.

FIG. 9 is a perspective view showing a schematic structure of a developing electrode of FIG. 8;

FIG. 10 is a view for explaining the structure of a general wet electrophotographic developing device.

FIG. 11 is a view for explaining a state of development in FIG. 7;

FIG. 12 is a diagram showing an example of a conventional device.

FIG. 13 is a diagram showing another example of the conventional device.

[Explanation of symbols]

 1, 3, 4 Developing electrode 2 Toner 10 Back guide 11, 12 Squeeze roller 20 Electrophotographic photosensitive material 21, 22 Ground terminal 30 Developing electrode 31, 32 Support plate 35, 36 Celmet layer 40 Developer supply section

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Akihiro Kanazawa 1005 Kozono, Ayase-shi, Kanagawa Prefecture Inside Fuji Micro Graphics Co., Ltd. (56) References JP-A-58-4165 (JP, A) 16027 (JP, B2) (58) Field surveyed (Int. Cl. ⁶ , DB name) G03G 15/10

Claims (1)

(57) [Claims] A rear guide 1. A guiding the conveyance of the electrophotographic light-sensitive material on which an electrostatic latent image is formed, is disposed opposite to the photosensitive layer of the electrophotographic light-sensitive material is transported the rear guide on The specific surface area is at least 2500 m ² / m ³ or more.
A porous metal body having a uniform rough surface and the porous metal body
A developing electrode comprising a supporting member for supporting the electrophotographic device;
In order to supply the developing solution to the photosensitive layer of the optical material, the support is provided.
Developing supply means disposed on a holding member, and the porous metal body
And a support for the electrophotographic photosensitive material.
And a developing bias applying unit for grounding the layer .