JP2656366B2 - Replenisher replenishment method for wet electrophotographic developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention supplies a liquid toner to a photosensitive surface of a photosensitive material on which an electrostatic latent image has been formed by image exposure to visualize the electrostatic latent image. The present invention relates to a replenisher replenishing method for a wet electrophotographic developing device.

[Prior art] Conventionally, a photosensitive material on which an electrostatic latent image is formed by image exposure after being charged, for example, an ELP master (a photoconductive layer made of ZnO and a binder is laminated on a waterproof and conductive treated support) Liquid developer (a developer formed of toner particles, a charge control agent, a dispersion medium, etc.) to the photosensitive member, and develops the photosensitive material by visualizing the electrostatic latent image formed on the master. A wet electrophotographic developing device has been proposed.

A developing unit is provided in the wet electrophotographic developing device,
An electrode composed of two metal plates close to each other (a metal plate corresponding to the photosensitive surface of the photosensitive material is referred to as a "development electrode", and a metal plate facing the back surface of the photosensitive material is referred to as a "back electrode"). A voltage was applied between these electrodes, or these electrodes were short-circuited, and the liquid toner was passed between these electrodes while passing through the master for development.

When the liquid toner is supplied to the master passing between the electrodes, toner particles contained in the liquid toner adhere to latent image charges forming the electrostatic latent image on the master, and the electrostatic latent image is visualized. .

However, since the developing unit is in an open state, that is, in communication with the outside air, a large amount of liquid toner evaporates. For this reason, even when the same amount of photosensitive material is developed, the toner density changes between continuous processing and intermittent processing, and stable development processing may not be performed.

For this reason, there has been proposed a structure in which the developing unit is sealed to reduce the amount of evaporation of the liquid toner (Japanese Patent Application No. 1-2297 as an example).
No. 58). According to this, evaporation of the liquid toner can be prevented, and drying of the squeezing roller in the conveyance path of the photosensitive material can be suppressed. Therefore, a change in the liquid toner concentration can be suppressed to some extent.

[Problems to be Solved by the Invention] However, the developing section requires a transporting path for the photosensitive material due to its structure, and it is difficult to completely seal the developing section, and a certain amount of evaporation cannot be denied. Further, since there is a toner that is electrodeposited on the photosensitive material and a liquid toner that is attached to and carried on the photosensitive material, even if it is completely sealed, the concentration of the liquid toner changes according to the processing amount.

In view of the above facts, the present invention can provide a replenisher replenishing method for a wet electrophotographic developing apparatus capable of performing a stable development process by sealing the developing unit and replenishing a replenisher of an appropriate concentration. Is the purpose.

[Means for Solving the Problems] According to the invention described in claim (1), a liquid toner inserted between a developing electrode and a back electrode and electrodeposited on a charged and exposed photosensitive material to be subjected to a developing process is provided. Used in a wet electrophotographic apparatus having a storage tank for storing, and a sealing means for sealing the storage tank including a photosensitive material conveying path, and a wet electrophotographic apparatus for replenishing a replenisher into the storage tank. A replenisher replenishing method, wherein the average area of the photosensitive material to be developed is W × 1, the amount of toner to be electrodeposited per unit area is A, the amount of liquid toner carried by the photosensitive material is B, The image area ratio to the area is X, the carrier liquid evaporation amount in the liquid toner during the processing is C, the processing speed is V, and the transport path length during the development processing is L, The replenisher having a concentration represented by the following formula (1) is replenished by a reduced amount of the liquid toner amount of the liquid in the storage tank.

The invention according to claim (2) is characterized in that, in the invention according to claim (1), the back electrode is in contact with a surface of the photosensitive material opposite to the photosensitive surface.

[Operation] According to the invention described in claim (1), the photosensitive material passes through the passage formed between the developing electrode and the back electrode in a state where the liquid toner is supplied, whereby the image is exposed. The formed electrostatic latent image is visualized.

The storage tank in which the liquid toner is stored is sealed by sealing means, and a conveying path for the photosensitive material is provided in the sealed inside, so that the liquid toner can be circulated in the sealed space, and the liquid toner can be circulated. Evaporation of the toner can be suppressed. By the way, it is difficult to completely seal the sealed space because the entrance and the exit of the photosensitive material are inevitably present. For this reason, the liquid toner will slightly evaporate. Further, as the developing process is continued, the toner particles are reduced due to electrodeposition on the photosensitive material, and the liquid toner is carried along with the photosensitive material. Therefore, it is not always possible to maintain a constant liquid toner concentration. Therefore, in the present invention, a replenisher having a concentration calculated by the following equation is prepared in advance, and the replenisher is replenished by a reduced amount of the liquid toner in the storage tank.

Where, W × l: average area of photosensitive material to be processed, A: amount of toner deposited per unit image surface, B: amount of liquid toner adhering to photosensitive material, X: image relative to area of photosensitive material Area ratio, C: evaporation amount of carrier liquid of liquid toner during processing, V: processing speed, L: transport path length during development processing.

Thus, even if the storage tank cannot be completely closed, the replenisher of the liquid toner can be replenished and the replenisher having an appropriate concentration in the apparatus can be replenished, so that stable development processing can be performed.

In the invention described in claim (2), when the photosensitive material passes between the developing electrode and the back electrode, the back surface opposite to the photosensitive surface of the photosensitive material is in contact with the back electrode. Is sliding. As a result, the development efficiency can be improved and the back electrode can be prevented from being stained.

FIG. 1 shows an embodiment of a wet electrophotographic apparatus 10 to which a wet electrophotographic developing apparatus according to the present invention is applied. FIG. 3 is a side view schematically showing the wet electrophotographic apparatus 10.

As shown in FIG. 3, the wet electrophotographic apparatus 10 has a rectangular cross section, and the outer periphery is covered with a cover 11. The wet type electrophotographic apparatus 10 has legs 13 attached to the four bottom corners, and is installed on the floor by the legs 13. A caster 15 is attached near the leg 13 and is used when the wet electrophotographic apparatus 10 is moved.

As shown in FIG. 3, inside a wet electrophotographic apparatus 10 covered with a cover 11, a long photosensitive member (hereinafter, referred to as a "master") which is a photosensitive material wound up in a roll shape on the upper part. ) 12 is provided.

As shown in FIG. 4, the master 12 used in the present embodiment has a conductive waterproof layer 36 and an intermediate layer 38 on a paper support 34.
A photosensitive layer (ZnO) 40 is laminated on both sides. Also, a conductive waterproof layer 42 is provided on the back side of the support 34. Support
The thickness of the layer 34 is set to about 150 μm, and the thickness of the photosensitive layer 40 is set to about 10 μm. The surface resistance of the waterproof conductive layer is 10 ⁸ to 10
^{A 10} Ω one is used. FIG. 3 shows two roll-shaped masters 12A and 12B, which have different sizes (widths).

A charging unit 16 that charges the surface of the master 12 pulled out from the paper feeding unit 14 is disposed on a side portion of the paper feeding unit 14. Further, an exposure unit 18 is arranged on a side portion and a lower portion of the charging unit 16. A cutter 30 is provided between the charging unit 16 and the paper feeding unit 14 in the middle of the transport path of the master 12, and the master 12 pulled out to a predetermined length from the paper feeding unit 14 is cut. hand,
It is set to a predetermined length.

An exposure table 46 is erected on the exposure unit 18. This exposure table
A plurality of suction holes are formed on the surface of 46, and a negative pressure is supplied from negative pressure supply means (not shown). The master 12, whose surface is charged by the charging unit 16 and cut to a predetermined length, is transported onto the exposure table 46 and is sucked. Exposure section
An exposure lamp 48 for irradiating the original placed on the original table 26 with light and a mirror 50 for reflecting the light emitted from the exposure lamp 48 to the original to the exposure table 46 are arranged on the original 18. A lens 52 is disposed between the base 26 and the mirror 50.

As a result, light is irradiated from an exposure lamp 48 onto an image of a document placed on the document table 26, and the reflected light is transmitted through a lens 52,
The light is applied to the master 12 on the exposure table 46 via the mirror 50, and the master 12 is exposed to an image.

A developing unit 20 is arranged below the exposure unit 18. The developing unit 20 has a developing box 53 as shown in FIGS. The developing box 53 includes a storage tank 152 for storing the liquid toner, and a lid 154 as a sealing means for closing an upper opening of the storage tank 152.
It has a box shape having an inner space. For this reason, the inner space of the developing box 53 is kept substantially sealed. A liquid level sensor 156 is attached to the storage tank 152. The storage tank 152 has a slit-like insertion port 16 for guiding the master 12 into the inner space on the upstream wall 158 thereof.
0 is provided. The downstream wall 162 has a master 12
Is provided from the inner space.

The discharge port 164 is provided with a block 170 which forms a part of a sealing means provided with a slit-like through hole 168 along the transfer path of the master 12. The top plate 172 of the block 170 is driven to rotate about a pin 176 by the driving force of a driving means (not shown) so that the discharge port 164 can be opened and closed.

Here, it is shown that the development box 53 is almost in a sealed state, but the insertion port 160 and the discharge port 164 of the master 12 cannot be always closed, and although a little, the storage tank 15 is not closed.
The second liquid toner will evaporate.

The electrode support frame 54 is provided in the storage tank 152 and is mounted on a rib 182 provided on the inner side surface of the storage tank 152. A transport roller 60 is disposed between the opposed side walls 56 and 58 of the electrode support frame 54 so as to correspond to the insertion port 160, and both ends of the rotating shaft are rotatably supported by the side walls 56 and 58, respectively. . A gear 62 and a sprocket wheel 64 are fixed to the side wall 56 of the rotating shaft.

The end of the rotating shaft supported by the side wall 56 projects through the side wall of the storage tank 152, and a sprocket wheel 66 is fixed to the end. The sprocket 66 has a chain 68 wound around a sprocket wheel fixed to a drive shaft of a motor 184 (see FIG. 1). I do.

A transport roller 70 is disposed in contact with the upper portion of the transport roller 60. Both ends of the rotation shaft of the transport roller 70 are supported by the side walls 56 and 58 via bearings (not shown). A gear 74 is fixed to the side wall 56 of the rotation shaft of the transport roller 70, and meshes with the gear 62 to which the transport roller 60 is fixed. Thus, the rotational driving force transmitted to the transport roller 60 is transmitted to the transport roller 70.

On the opposite side of the transport roller 60, that is, on the exit side of the master 12, a transport roller pair 76 is stretched between the side walls 56 and 58. The conveying roller pair 76 includes the conveying roller 60 and the conveying roller 70.
It is located at a lower position. A sprocket wheel 78 is provided at the end of the lower roller of the conveying roller pair 76 on the side wall 56 side.
Is fixed. A chain 80 is wound around the sprocket wheel 78 and the sprocket wheel 64. Thus, the rotational driving force transmitted to the transport roller 60 is transmitted to the transport roller pair 76. The master 12 transported from the exposure unit 18 is inserted between the transport roller 60 and the skew roller 70, and is sent obliquely downward toward the transport roller pair 76.

A developing electrode 82 and a back electrode 84 are arranged between the conveying roller 60 and the conveying roller 70 and between the conveying roller pair 76. The developing electrode 82 and the back electrode 84 are inclined so that the end on the side of the conveying roller pair 76 is located downward. A gap 86 is formed between the developing electrode 82 and the back electrode 84,
The master 12 sent out from between the transport roller 60 and the transport roller 70 passes through the gap 86 obliquely downward and is inserted between the transport roller pair 76.

The developing electrode 82 is formed of a metal plate, and is located above the transport path of the master 12 corresponding to the photosensitive surface of the master 12. The back electrode 84 is located below the transport path of the master 12 corresponding to the conductive waterproof layer 42 side of the master 12.

The back electrode 84 is housed in a rectangular hole 90A formed in the center of the back plate 90 housed in the electrode support 54. At the four corners at the periphery of the rectangular hole 90A, a male screw 110 protrudes downward from the device. The back electrode 84 is attached to the support plate 112. The support plate 112 has circular holes 114 at positions corresponding to the male screws 110 at four corners. Here, the male screw 110 penetrates the circular hole 114,
The support plate 112 is fixed to the back plate 90 by being screwed with the nut 116.

The back plate 90 has a developing electrode at the entrance of the master 12
It is slightly bent in the direction away from 82, and the master is
Guide plate for receiving 12 between developing electrode 82 and back electrode 84
118 is affixed. The guide plate 118 and the back electrode 84 are flush with each other.

The back electrode 84 is formed of a foamed metal plate. As shown in FIG. 5, the foamed metal plate (back electrode 84) is a metal plate having a plurality of open cells, and the front and back surfaces are uneven.

As shown in FIG. 1, the foam metal plate (back electrode 84) is short-circuited with the developing electrode. When the charged master 12 passes through the gap 86 between the developing electrode 82 and the back electrode 84, an electric field is generated between the developing electrode 82 and the back electrode 84 by electrostatic induction, and the opposite polarity is applied to each electrode. Is induced. If necessary, a bias voltage may be applied between the developing electrode 82 and the back electrode 84.

As shown in FIG. 2, a liquid toner supply box 92 is disposed between the side walls 54 and 56 between the developing electrode 82 and the transport roller 70. The liquid toner supply box 92 is connected to a pipe 91
And is communicated with a storage tank 152 (see FIG. 1).
A supply pump 95 is arranged in the middle of the process. By the operation of the supply pump 95, the liquid toner stored in the storage tank 152 is supplied to the liquid toner supply box 92.

The liquid toner supply box 92 is formed with a liquid toner discharge port that opens toward the space between the developing electrode 82 and the back electrode 84 along the width direction of the master 12. From this liquid toner discharge port, liquid toner is discharged between the developing electrode 82 and the photosensitive surface of the master 12, and supplied to the surface of the master 12 which is conveyed diagonally. Further, the supplied liquid toner flows down to the storage tank 152 again by its own weight, and as a result, the liquid toner is circulated and used.

In addition, the replenisher tank is connected to the storage tank 152 through a line 186.
Communicated with 188. Pump 190 is located in the middle of line 186.
When the pump 190 is driven, the replenisher in the replenisher tank 188 is supplied to the storage tank 152.

The concentration of the replenisher in the replenisher tank 188 is calculated using the following parameters (V, W, 1, A, B, C, X, L) (shown in the section of the operation of the invention). (Refer to equation (1)), and a replenisher adjusted based on the calculation result is stored in advance.

These parameters apply to the wet electrophotographic device 10
, Which will be described in advance.

V: transport speed (m / hour) The transport speed of the master 12 of the wet electrophotographic apparatus 10 to be applied.

W (m), l (m) ... size of master 12 Normally, master for making the same wet electrophotographic apparatus 10
Although the size of 12 is often constant, the size slightly changes depending on the printing machine to which the master 12 is applied.

A: Amount of electrodeposited toner per unit image area (g /
m ² ) The amount of toner particles adhering per unit area of the image section holding a constant charge, and is an amount determined by the properties of the toner. Therefore, if the toner is determined, the value is constant if the toner concentration is constant.

B: amount of toner taken out (g / m ² ) This is the amount of wet toner adhering to the front and back surfaces of master 12 after master 12 has been developed and tied.
When the master 12, the toner and the squeezing device (not shown) are determined, the values become constant.

C: Evaporation amount during processing (g / hour) This is the amount of evaporating component (carrier liquid) in the toner that evaporates per unit time when the master 12 passes, and keeps the ambient atmospheric temperature constant. Then, it becomes a constant value. The evaporation when the master 12 does not pass is not 0, but it is very small and can be ignored if it is closed by the lid 154 or the like as in this embodiment.

X: image area ratio An image to be made by the wet electrophotographic apparatus 10 has many characters, and is usually about 4 to 8%. Therefore, in the case of normal plate making, a constant value of about 6% may be used. However, it is necessary to change it when continuously making a plate whose image area largely changes.

L: from the insertion port 160 to the discharge port 164 of the developing box 53
Is the length of the path along which the master 12 is transported.

In this embodiment, the storage tank 1 is detected by the liquid level sensor 156.
When the liquid level of the liquid toner in 52 falls below a predetermined level, the pump 190 is operated, and a predetermined amount of replenisher having a concentration preset by the above calculation is replenished.

As shown in FIG. 3, a fixing unit 22 is provided beside the developing unit 20.
Is arranged. A transport roller pair 94 is arranged in the fixing unit 22 on the developing unit 20 side. The master 12 sent from the developing unit 20 is inserted between the pair of transport rollers 94.

The fixing unit 22 has a pair of conveying rollers at the exit side of the master 12.
The conveying roller pair 96 is arranged at a position higher than 94. A guide 98 is provided between the conveying roller pair 96 and the conveying roller pair 94,
The conveying roller pair 96 is arranged obliquely upward so as to be higher than the conveying roller pair 94 end. Two lamps 100 are arranged above the guide 98.

As a result, the guide 98
The master 12 that is guided obliquely and conveyed diagonally upward is a ramp
Heated by 100 and fixed.

The accumulation unit 24 is disposed outside the apparatus on the side of the conveyance roller pair 96. The master 12 to which the pair of transport rollers 96 has been fed is accumulated in the accumulation section 24.

 Next, the operation of the present embodiment will be described.

The master 12 loaded in the paper supply unit 14 is drawn out to the charging unit 16 and the surface of the master 12 is uniformly charged.
Sent to 46. When the master 12 has a predetermined length, that is, a length that can be accommodated on the exposure table 46, the master 12 has a predetermined length cut by the cutter 30.

Master cut to a predetermined length and sent to the exposure table 46
12 is attracted to the exposure table 46. From this state, an image of a document (not shown) placed on the document table 26 is irradiated with light from the exposure lamp 48, and the reflected light is irradiated onto the master 12 via the lens 52 and the mirror 50. Thereby, the master 12 on the exposure table 46 is image-exposed, and an electrostatic latent image is formed on the surface.

Here, the pump 95 is operated, and the liquid toner stored in the storage tank 152 is transported to the toner supply box 92. Further, the master 12 on which the electrostatic latent image is formed is
Between the transfer roller 60 and the transfer roller 70, and the developing electrode
It is inserted into a gap 86 between 82 and the back electrode 84. The master 12 is inserted between the developing electrode 82 and the back electrode 84, and the liquid toner is supplied from the liquid toner supply box 82 to the surface of the master 12.

Master inserted between developing electrode 82 and back electrode 84
The rear surface side of 12 is conveyed diagonally downward between the conveying roller pair 76 while the foamed metal plate (rear electrode 84) abuts and slides.

When the master 12 passes between the developing electrode 82 and the back electrode 84, an electric field is generated on the surface of the developing electrode 82 and the master 12 by electrostatic induction. In this electric field, the positively charged toner particles in the liquid toner adhere to the electrostatic latent image formed by the negative charges formed on the surface of the master 12, and the electrostatic latent image is visualized by the toner particles.

Since the entire foamed metal (back electrode 84) is a conductor and the convex portion is in contact with the back side of the master 12, the positive charge on the back side of the master 12 is reduced by the negative charge injected from the back electrode. Neutralize with As described above, the charge is directly injected from the foamed metal plate to the back side of the master 12 by contact, so that the amount of toner particles attached to the back electrode 84 is reduced. Also, the back electrode 84 and the master 12 are always kept electrically conductive, so that the amount of toner adhered to the photosensitive surface of the master 12 can be made uniform, and the density of the master 12 can be made substantially uniform. I can do it.

When the developing process is completed, the top plate 172 is rotated to open the slit 168. Thereby, the master 12 in which the electrostatic latent image has been visualized is sent to the fixing unit 22. Here, top plate 17
2 is again rotated in the opposite direction, and the slit 168 is closed.

The toner that forms an image by adhering to the surface of the master 12 is heated and fixed. Master 12 after fixing by fixing unit 22
Are accumulated in the accumulation unit 24.

When the liquid toner in the storage tank 152 falls below a predetermined level, it is determined that it is necessary to replenish the replenisher, and the pump 190 is operated. Here, when the liquid level of the liquid toner in the storage tank 152 reaches a predetermined level, the pump 190 is stopped.

Here, the replenisher is set to a certain concentration. That is, the above-mentioned parameters are determined by the wet electrophotographic apparatus 10 applied in advance, the density is calculated by the equation (1) based on the parameters, and the replenisher having the calculated concentration is stored in the replenishment tank 188. Is done. Therefore, a replenisher having an appropriate concentration can always be replenished, and stable development can be performed.

As described above, in the present embodiment, the storage tank 152 is substantially closed by the lid 154, and the evaporation of the liquid toner is prevented as much as possible, so that the finished image can be stabilized.
In addition, the insertion opening 160 and the discharge opening 164 which are the minimum necessary openings
The replenisher, which is set to the optimal concentration, is replenished with respect to the evaporation amount from the liquid and the amount of liquid toner carried by the master 12, so that the image quality can be maintained whether the master 12 is processed intermittently or continuously. Stable image recording can be performed without any change.

In the present embodiment, the back electrode 84 is brought into contact with the back surface of the master 12 to supply power directly.However, the back electrode is separated from the master 12 and developed, so that the reservoir 152 is sealed and the concentration of the replenisher is increased. Stable image recording can be performed only by adjustment.

In this embodiment, the foamed metal is used for the back electrode 84. However, a plurality of protrusions may be provided on conductive rubber, and the master 12 may be supported at the tips of the protrusions. It may be.

Further, in the present embodiment, the replenisher having a predetermined concentration is replenished by a reduced amount. However, the replenisher having a high concentration and the carrier liquid are stored in separate tanks, and these are replenished as required if necessary. May be mixed and transported to the storage tank 152. Alternatively, a mother liquor and a concentrated replenisher may be prepared, and these may be mixed at a predetermined ratio to form a replenisher. The setting of the ratio may be controlled so as to be changed based on the processing state or the surrounding environment.

[Effects of the Invention] As described above, the replenisher replenishing method for a wet electrophotographic developing apparatus according to the present invention performs stable developing processing by sealing the developing unit and replenishing a replenisher of an appropriate concentration. The excellent effect that can be obtained is obtained.

[Brief description of the drawings]

FIG. 1 is a side view showing a developing section of a wet electrophotographic developing apparatus according to the present invention, FIG. 2 is an exploded perspective view of an electrode support and its periphery, and FIG. 3 is a wet electrophotographic apparatus to which the present invention is applied. FIG. 4 is a sectional view showing a master, and FIG. 5 is a sectional view of a back electrode (foam metal). 10 ... wet electrophotographic apparatus, 12 ... photoconductor (master), 20 ... developing unit, 32 ... liquid toner, 82 ... developing electrode, 84 ... back electrode (foam metal plate), 152 ... reservoir Tank, 154 ... lid, 188 ... refill tank.

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Claims (2)

(57) [Claims] 1. A storage tank, which is inserted between a developing electrode and a back electrode and stores a liquid toner for electrodepositing and developing a charged and exposed photosensitive material, and a conveying path of the photosensitive material. A sealing means for sealing the storage tank, and is used in a wet electrophotographic apparatus having a replenisher replenishing method of a wet electrophotographic apparatus for replenishing a replenisher into the storage tank,
The average area of the photosensitive material to be developed is W × l,
A is the amount of toner to be electrodeposited per unit area, B is the amount of liquid toner carried by the photosensitive material, X is the image area ratio to the area of the photosensitive material, C is the amount of carrier liquid evaporated in the liquid toner being processed, and C is the processing speed. V, the transport path length during the development process is L, Wherein the replenisher having a concentration represented by the formula (1) is replenished in an amount corresponding to a reduced amount of the liquid toner in the storage tank. 2. A method according to claim 1, wherein said back electrode is in contact with a surface of said photosensitive material opposite to the photosensitive surface.