JPH1165294A - Wet type electrophotographic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the function of recycling liquid toner by recovering a liquid mixture of a liquid developer and a prewet liquid, remaining on the surface of a developing roller and separating liquids subject to recycling for the liquid developer and the prewet liquid. SOLUTION: A prewet device 13 coats the surface of a photoreceptor 10 with silicone oil having a specific viscosity. The developer is supplied to a developing device 14, in such a manner that the developer is carried from a toner puddle, while spreading thin, by an applicator roller. Thus, a toner layer is formed on the developing roller. Then, the positively charged toner is supplied to the photoreceptor 10, in accordance with the electric field between the developing roller and the photoreceptor 10, so that the toner is stuck to the exposed part of the charged photoreceptor 10. The liquid mixture of the liquid developer and the prewet liquid remaining on the surface of the developing roller is recovered by a recovering means and the liquids subject to recycling for the liquid developer and the prewet liquid are separated from the liquid mixture recovered by the recovering means by a separating means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet electrophotographic apparatus using a non-volatile, high-viscosity, high-concentration liquid toner, and more particularly to a wet electrophotographic apparatus having a liquid toner recycling function.

[0002]

2. Description of the Related Art In an electrophotographic apparatus in which an electrostatic latent image is formed on a photosensitive member (photosensitive drum), toner is adhered to the image, and the image is transferred to paper and fixed, a dry type using powder toner is widely used. Used.

However, the powder toner has a problem that the toner is scattered, and the toner particles have a particle size of 7 to 10 μm.
There is a problem that the resolution is poor due to the large value of m.
Therefore, when high resolution is required, a wet type using a liquid toner is used. This is because the liquid toner has toner particles as small as about 1 μm and the charge amount is large, so that disturbance of the toner image hardly occurs and high resolution can be realized.

In a conventional wet-type electrophotographic apparatus, a low-viscosity liquid toner in which a toner is mixed with an organic solvent at a ratio of 1 to 2% is used as a developing solution. However, such a developer uses an organic solvent that is harmful to the human body and uses a large amount of the organic solvent because of its low toner concentration, which has a serious problem of causing environmental problems.

[0005] Against this background, a wet type using a high-viscosity, high-concentration developer constituted by dispersing a high-concentration toner in silicon oil or the like is described in International Publication No. WO95 / 08792. An invention of an electrophotographic apparatus has been disclosed.

The use of this liquid toner has the advantages that the problem of harm to the human body does not occur, and the high toner concentration eliminates the need to use a large amount of developer.

In the case of using such a non-volatile liquid toner having a high viscosity and a high concentration, it is very convenient to provide a function of recycling the liquid toner. Generally, in a dry electrophotographic apparatus using a powder toner, there is no idea of recycling the powder toner.
This is because the powder toner is not diluted. That is, in a dry-type electrophotographic apparatus, the toner is supplied to the photoconductor by supplying powder toner to the developing roller while frictionally charging using a blade, and the development transferred to the photoconductor is performed. Only the process of supplying powder toner to the roller portion is performed.

On the other hand, in a liquid electrophotographic apparatus using a liquid toner, since the liquid toner is diluted,
The idea of recycling liquid toner comes up.
However, in a wet electrophotographic apparatus using a low-viscosity liquid toner in which a toner is mixed in an organic solvent at a ratio of 1 to 2%,
Although there is an idea to recycle the organic solvent, there is no idea to recycle the liquid toner itself. Due to the low toner concentration, this liquid toner is configured to be supplied in such a manner that it is ejected in large quantities to the photoreceptor, and from this, the organic solvent is recycled,
On the other hand, the liquid toner itself cannot be collected, even though there is a configuration that replenishes the liquid toner.

Accordingly, the international publication number “WO95 / 087”
92 "does not adopt a configuration in which the liquid toner is recycled in accordance with an extension of the conventional technology.

[0010]

However, a high-viscosity, high-concentration liquid toner constituted by dispersing a high-concentration toner in silicone oil or the like is a liquid toner used in a conventional wet electrophotographic apparatus. Since the toner has properties completely different from those of the toner, it is possible to introduce a concept of recycling the liquid toner differently from before.

In this case, it is necessary to realize a recycling method utilizing the characteristics of high viscosity and high concentration. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a new wet electrophotographic apparatus having a liquid toner recycling function when employing a configuration using a non-volatile, high-viscosity, high-concentration liquid toner. The purpose is to provide.

The present invention is also directed to a configuration using a non-volatile, high-viscosity, high-concentration liquid toner.
To provide a new wet-type electrophotographic apparatus having a pre-wet liquid application function, a development function, a development liquid application function to a development roller, an intermediate transfer and a heating function therefor suitable for combining such a liquid toner recycling function. Aim.

[0013] That is, the porous sponge used in the prior art is excellent in the retention of the pre-wet liquid, but cannot be said to have a sufficiently high insulating property. If you follow
When a pre-wet solution is applied after exposing the photoreceptor, the electrostatic sponge formed on the photoreceptor is formed by the contact of the porous sponge with insufficient insulation with the photoreceptor. There is a problem that the image is disturbed. When the present invention employs a configuration using a non-volatile, high-viscosity, high-concentration liquid toner, the pre-wet liquid is applied to the entire surface of the photoreceptor when a pre-wet liquid film is applied to the photoreceptor. The purpose is to enable stable application.

Developing Function and Developing Solution Coating Function: When a non-volatile high-viscosity, high-concentration liquid toner is used, the electrostatic latent on the photoreceptor to which the toner does not adhere even when pre-wet processing is performed. There is a problem that image noise is generated due to toner being attached to a non-exposed portion of an image.

To explain this problem in detail, as shown in FIG. 2, the liquid toner is conveyed while being spread thinly from the toner pool using an applicator roller 140, so that the toner layer is applied to the developing roller 141. And a developing device that adheres the charged toner to an exposed portion of the photoconductor in accordance with an electric field between the photoconductor and the photoconductor.

At this time, in the nip portion between the developing roller and the applicator roller, the toner layer receives the compression pressure from both rollers. When the toner layer reaches the nip outlet, the compression pressure is released, and the high viscosity characteristic As shown in FIG. 12, the toner is separated so that the toner is separated from both sides by being subjected to a tensile force due to the viscosity of the toner itself and the adhesive force to the roller surface. Streak-like unevenness (unevenness) will remain on the developing roller. As a result, as shown in FIG. 13, the pre-wet layer is pierced by the stripe-shaped protrusions, and reaches the surface of the photoconductor, thereby generating noise in the non-exposed portion. In addition, in the exposed portion, the non-uniform layer appears in the exposed portion, so that a good image cannot be obtained. As described above, according to the related art, there is a problem that image noise is generated due to the toner being attached to the non-exposed portion of the electrostatic latent image of the photosensitive member to which the toner is not attached. was there.

The present invention, when employing a configuration using a high-viscosity, high-concentration liquid toner exhibiting non-volatility, does not damage the pre-wet layer applied to the photoreceptor, It is an object to stably supply a liquid toner and to apply a uniform developing solution to a developing roller.

Intermediate transfer and heating functions: When a color image is handled, the toner adhered to the photoreceptor is transferred to the intermediate transfer member, and the intermediate transfer member is heated to melt the toner and fix it on the print medium. It will take the method of going. When adopting a configuration in which toner is fixed on a print medium according to this method, as shown in the conventional configuration of FIG. 34, an intermediate transfer roller composed of a hollow metal drum is prepared as an intermediate transfer body, and the hollow portion is provided in the hollow portion. A configuration in which a halogen heater is disposed to heat the entire intermediate transfer body has been adopted. However, according to this configuration, there is a problem that the heat of the intermediate transfer body whose surface is constantly high is transferred to the photoconductor, which adversely affects the photoconductor. However, when using a high-viscosity, high-concentration developer composed by dispersing a high-concentration toner in silicon oil or the like, the heat capacity of the toner decreases due to the small toner particles. Different methods of heating the intermediate transfer member are feasible, which may be able to prevent the photoconductor from being affected by heat. When the present invention employs a configuration using a non-volatile, high-viscosity, high-concentration liquid toner, and when using an intermediate transfer member, the image is transferred to the intermediate transfer member without affecting the photoconductor. It is an object of the present invention to make it possible to heat and melt the toner efficiently.

[0019]

FIG. 1 shows the overall structure of a wet electrophotographic apparatus according to the present invention. The photoconductor 10 is
After being charged to about 700 V by the charging device 11, it is exposed by the exposure device 12, and the potential of the exposed portion becomes about 1
An electrostatic latent image of 00V is formed.

The pre-wetting device 13 applies silicone oil having a viscosity of about 2.5 cSt to the surface of the photoreceptor 10 with a thickness of 4 to 5 μm. The developing device 14 has a yellow /
Provided in association with magenta / cyan / black and biased against the photoreceptor, the toner viscosity is 400 to 4
A non-volatile, high-viscosity, high-concentration liquid toner having a carrier viscosity of 20 cSt at 000 mPa · S is used as the liquid developer. The supply of the developing solution is performed by using an applicator roller while thinly extending the toner from the reservoir to convey the developing solution, whereby a toner layer having a thickness of 2 to 3 μm is formed on the developing roller.
By supplying the positively charged toner to the photoconductor 10 according to the electric field between the photoconductor 10 and the toner, the toner adheres to the exposed portion of the photoconductor 10 charged to about 100V.

The collecting means collects a liquid mixture of the liquid developer and the pre-wet liquid remaining on the surface of the developing roller, and the separating means collects the mixed liquid collected by the collecting means.
The liquid to be regenerated from the liquid developer and the liquid to be regenerated from the pre-wet liquid are separated.

The intermediate transfer member 15 is biased to about -800 V, and the photosensitive member 1 is moved according to an electric field between the intermediate transfer member 15 and the photosensitive member 10.
The toner attached to 0 is transferred in the order of yellow, magenta, cyan, and black. The pressure roller 19 fixes the toner of the intermediate transfer body 15 melted by the heating device 18 on the print medium. The heating device 18 includes a pressure roller 19
At a position before contact with the surface of the intermediate transfer member 15, the surface of the intermediate transfer member 15 is partially heated.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail according to embodiments. In the present invention, a non-volatile, high-viscosity, high-concentration liquid toner is used as a liquid developer. The liquid toner is obtained by dispersing toner particles such as a pigment in a liquid carrier (oil). It is.

FIG. 1 shows the overall configuration of a wet electrophotographic apparatus provided with the present invention. As shown in FIG. 1, a wet electrophotographic apparatus according to the present invention includes a photosensitive member 10 and a charging device 11.
, An exposure device 12, a pre-wet device 13, a developing device 14, an intermediate transfer member 15, a blade 16, a charge removing device 17, a heating device 18, and a pressure roller 19.

The charging device 11 applies about 700 V
To be charged. The exposure device 12 forms an electrostatic latent image on the photoconductor 10 by exposing the photoconductor 10 using a laser beam having a wavelength of 780 nm so that the potential of the exposed portion becomes about 100 V.

The pre-wetting device 13 applies silicone oil having a viscosity of about 2.5 cSt to the surface of the photoreceptor 10 in a thickness of 4 to 5 μm. Here, the pre-wet device 1
In No. 3, the pre-wet process may be performed before the exposure process performed by the exposure device 12, or the pre-wet process may be performed after the exposure process.

The developing device 14 is provided in association with yellow / magenta / cyan / black, is biased to about 400 V, and has a toner viscosity of 400 V as shown in FIG.
Forming a 2-3 μm thick toner layer on the developing roller 141 by transporting liquid toner having a carrier viscosity of 20 cSt at 4000 mPa · S while thinly extending it from the toner pool using the applicator roller 140. By supplying the positively charged toner to the photoconductor 10 in accordance with the electric field between the photoconductor 10 and the
The toner adheres to the exposed portion of the photoconductor 10 charged to 0V.

According to the pre-wet layer applied by the pre-wet device 13, as shown in FIG. 3, it is possible to prevent the toner from adhering to the non-exposed portion of the photoreceptor 10.

The intermediate transfer member 15 is biased to about -800 V, and the photosensitive member 1 is moved in accordance with the electric field between the intermediate member 15 and the photosensitive member 10.
The toner attached to 0 is transferred. This intermediate transfer member 15
First, yellow toner adhered to the photoconductor 10 is transferred, then magenta toner adhered to the photoconductor 10 is transferred, and then cyan toner adhered to the photoconductor 10 is transferred. Then, the black toner attached to the photoconductor 10 is transferred.

The blade 16 removes toner and pre-wet liquid remaining on the photoreceptor 10. The neutralization device 17 neutralizes the photoconductor 10. The heating device 18 is used for the intermediate transfer member 15.
By heating the surface, the toner attached to the intermediate transfer member 15 is melted. The pressure roller 19 fixes the toner of the intermediate transfer body 15 melted by the heating device 18 on the print medium. Thus, the heating device 18 and the pressure roller 19
, The toner adhered to the intermediate transfer body 15 is melted and fixed to the print medium without heating the print medium, so that print media other than paper can be handled.

Hereinafter, each function will be described in more detail. As for the “pre-wet function”, as in the present invention, 4
When a developer of a liquid toner having a high viscosity such as 00 to 4000 mPa · S is used, as described above, in order to improve image quality such as preventing toner fog during development, In order to prevent the toner from adhering to the non-exposed portion and to give a releasing property in advance, a configuration in which a pre-wet layer is applied to the surface of the photoreceptor 10 is adopted. A configuration is adopted in which the photosensitive member 10 is brought into contact with the photosensitive member 10 at a contact pressure that does not cause breakage.

As described above, the pre-wet liquid is applied to the photosensitive member 1
The insulating oil is applied uniformly in a thin layer on 0, but is usually the same liquid as the carrier agent used for the liquid toner. For example, as the pre-wet liquid, the same silicone oil as the liquid toner, but having a low viscosity of about 2.5 cSt is used. The pre-wet liquid is applied to the surface of the photoreceptor 10 with a thickness of 4 to 5 μm. You.

FIG. 4 shows an example of a pre-wet liquid coating configuration. The plurality of liquid spray nozzles 31 are arranged in a line in the axial direction facing the surface of the photosensitive drum 10 so as to be in non-contact with the photosensitive drum 10. The pre-wet liquid is pumped up from the storage tank 33 by the pump 32 and sprayed on the surface of the photosensitive drum 10 in a line in the axial direction.
Is done. Thus, the prewetting liquid can be applied in a uniform and thin layer.

As described above, the photoreceptor 10 is charged by the charging device 11, the photoreceptor 10 is exposed by the exposure device 12, and an electrostatic latent image is formed on the photoreceptor 10.
Thereby, a pre-wet liquid is applied. The advantage of this non-contact method is that it does not disturb the charged electrostatic latent image because it is non-contact.

FIG. 5 illustrates another configuration for applying a pre-wet liquid in contact with the photosensitive drum 10. The pre-wet liquid supply configuration includes a roller 1 that is driven to rotate in contact with the photosensitive drum 10 and a roller 2 that is further driven to rotate. An appropriate amount of the pre-wet liquid is dropped continuously using a separate pump or the like so that a pre-wet liquid pool is formed between the rollers 1 and 2. The dropped pre-wet liquid is applied onto the surface of the photosensitive drum 10 through the rotation of the rollers 1 and 2.

At this time, since an appropriate amount of pre-wet liquid (PW) is accumulated between the rollers 1 and 2 as shown in the figure, the amount of pre-wet liquid passing between the rollers is constant. Assuming that a certain amount of layer thickness of the prewetting liquid is t, the layer thickness t is distributed to the roller 1 at a constant rate and to the roller 2 at a constant rate of (1-a) t. As described above, since the pre-wet liquid conveyed to the photosensitive drum 10 by the roller 1 is a fixed amount (at), it must be entirely passed between the photosensitive member 10 and the roller 1, in other words, the photosensitive drum It is not necessary to form a liquid pool at the contact inlet portion between the roller 10 and the roller 10.

The amount of the pre-wet liquid passing between the rollers 1 and 2 depends on the contact state between the rollers 1 and 2 such as the applied pressure or the applied amount, that is, the position at which the rollers 1 and 2 are mounted. It can be adjusted by adjustment or by adjusting the roller hardness. In order to allow all of the pre-wet liquid on the roller 1 after passing through the contact portion between the roller 1 and the roller 2 to pass through the contact portion between the photosensitive drum 10 and the roller 1, a roller 1 having a relatively low hardness is used. In order to allow an appropriate amount of pre-wet liquid to pass between the rollers 1 and 2, a roller 2 having a relatively high hardness is used as the roller 2 which contacts the roller 1 having a low hardness. For example, the roller 1 is made of EPDM (JIS-JIS) which is an insulating rubber.
A hardness 30 degrees) is applied to the roller 2 with ebonite (JIS-A
Hardness of 90 degrees or more).

As another example of the roller 1, the roller 1
Is made of urethane sponge, and the surface thereof has a thickness of 20
One coated with a polyimide film of about μm can be used. The surface roughness of the polyimide film is Rz
About 0.2 is preferable.

FIG. 6 is a diagram for explaining another configuration of the roller 2. 6 shows the case where the surface roughness of the roller 2 is reduced, and the diagram on the right side shows the case where the surface roughness is increased. As shown in the figure, the surface roughness of the roller 2 is adjusted, the amount of the pre-wet liquid held in the concaves and convexes of the surface is adjusted, and the pre-wet liquid passing through the contact portion between the roller 1 and the roller 2 is adjusted. The amount can be controlled. Then, for example, the surface roughness of the roller 2 is set to Rz1
When it is roughened to about 0 and the amount passing through the contact portion is increased, the amount finally conveyed to the photoconductor 10 by the roller 1 increases, and for example, the surface roughness of the roller 2 is reduced to Rz.
When the passing amount is reduced to about 1, the photosensitive member 1
The amount carried to zero is reduced. In contrast, roller 1
In order to reduce unevenness in the layer thickness, a material having a small surface roughness of about Rz1 or less is used.

The following Table 1 shows the charging and exposure potentials on the photosensitive drum measured using a roller 1 having a high insulating property. The case where a roller is used is shown. The photosensitive drum is pre-wet after being charged and exposed. At the time of this pre-wet, it is desirable to maintain the charge and exposure potential before the pre-wet. As shown in Table 1 below, when a highly insulating roller was used, no decrease in potential as observed in the measurement results was observed.

[0041]

[Table 1] Measurement results of charge and exposure potential on photosensitive drum Measurement conditions Potential measured by surface voltmeter Photosensitive drum: φ150, A-Si, drum peripheral speed (250 mm / s) Roller 2: EPDM rubber roller Roller 1: High As an insulating roller, a urethane firing roller, a volume resistance value of 10 ¹¹ Ωcm A low insulating roller, a urethane firing roller, a volume resistance value of 10 ⁴ Ωcm The application amount of the pre-wet needs to be optimally adjusted according to the liquid toner to be used, in particular, its chargeability or mobility. The pre-wet liquid applying means is a photosensitive drum 10
In the case of a type in which a roller is brought into contact with the photosensitive drum 10, the amount of pre-wet applied can be adjusted by changing the pressure applied to the photosensitive drum 10 by the roller. This change in the applied pressure can be performed by changing the feed amount of the pulse motor that moves the roller with respect to the photosensitive drum 10. In addition, such a configuration can also serve as a roller retracting mechanism, and can retract the roller from the photosensitive drum 10 when pre-wet coating is not required.

FIG. 7 is a block diagram showing the concept of pre-wet control. The pre-wet control means 60 detects the paper size and controls the pre-wet roller contact / retreat means 63 in order to perform pre-wet coating accordingly. In order to adjust the prewet layer thickness for each color, the prewet control means 60 detects a toner color that is currently in progress, and based on the prewet applied amount set for each color, Attached amount changing means 61
Control. Further, the pre-wet control means 60 detects the toner color currently in progress in order to change the peripheral speed of the pre-wet for each color and adjust the pre-wet layer thickness,
The pre-wet roller rotating unit 62 is controlled based on the pre-wet roller rotation number set for each color.

FIG. 8 shows a flowchart of the operation for controlling such a retracting mechanism. If it is assumed that the entire surface of the photosensitive drum corresponds to A3 paper, for example, A
In the case of printing on paper No. 4, it is sufficient to apply the prewetting liquid to the photosensitive drum not on the entire surface but only on the area corresponding to the A4 paper. FIG. 8 shows an operation of changing the retraction timing of the pre-wet roller according to the paper size from such a viewpoint and eliminating the pre-wet application to an extra area.

In step 1, the printing sequence starts. In step 2, check the paper size,
A target corresponding to the paper size is set, and a beam detector (BD) counter is reset. In step 3, the pre-wet roller is brought into contact with the photosensitive drum. In step 4, the content of the BD counter updated with the rotation of the pre-wet roller is compared with the set target. If they do not match, the process loops. If they match, in step 5, the target position set by the pre-wet roller is set. When it is determined that the pre-wet roller is reached, the pre-wet roller is retracted.

FIG. 9 is a flowchart of an operation of changing the film thickness by changing the amount of application of the pre-wet roller to the photosensitive drum 10. The viscosity, mobility, and conductivity of the toner change according to the difference in the color of the toner. Accordingly, it is necessary to control the thickness of the pre-wet layer. For example, when the toner viscosity decreases in the order of yellow / magenta / cyan / black, the film thickness of the pre-wet layer must also be reduced in that order. This control of the film thickness can be performed by moving the pre-wet roller with respect to the photosensitive drum 10 and changing the number of feed pulses of a pulse motor for changing the applied amount to the photosensitive drum 10.

In step 6 of FIG. 9, each color (i = 1
４4) The pre-wet applied amount is set for each, and the corresponding pulse motor feed pulse number Li is set. In step 7, a printing sequence is started. In step 8, exposure for printing the first color is first started. In step 9, the pulse motor for bringing the pre-wet roller into contact with the photosensitive drum 10 is rotated by the set Li pulse. Step 10
In, the exposure of the i-th (first at first) color is completed. In step 11, the pre-wet roller is retracted. In step 12, i is incremented to determine whether or not all colors have been completed, and it is determined whether or not this has exceeded four of the four colors. If not, go back to step 8,
The exposure for printing the next color is started. If all the colors have been completed, the process proceeds to step S13, and the printing sequence ends.

FIG. 10 is a flowchart of an operation for changing the peripheral speed difference of the pre-wet roller with respect to the photosensitive drum 10 in order to control the film thickness. By changing the peripheral speed of the pre-wet, a peripheral speed difference is generated between the pre-wet and the photosensitive drum 10, whereby the coating amount can be changed.

In step 14 of FIG. 10, the number of rotations of the pre-wet roller is set for each color. Step 15
, A printing sequence is started. Step 1
At 6, the exposure for printing the i-th (first at first) color is started. In step 17, the pre-wet roller rotation speed is changed to Ri. In step 18, the pre-wet roller is brought into contact with the photosensitive drum 10. In step 19, the exposure for the i-th color is completed. In step 20, the pre-wet roller is retracted. In step 21, i is incremented and compared with 4 of the four colors to determine whether or not all colors have been completed, and it is determined whether or not the number has been exceeded. If all four colors have not been completed, the process returns to step 16 to start exposure for printing the next color. If all the colors have been completed, the process proceeds to step 22, and the printing sequence ends.

FIG. 11 is a flowchart of an operation for changing the rotation speed of the pre-wet pump in order to control the film thickness. By changing the supply amount of the pre-wet liquid to the pre-wet roller, the supply amount of the pre-wet liquid to the pre-wet roller can be changed, thereby changing the application amount. In this example, instead of controlling the flow rate of the pre-wet liquid passing through using the contact state of the two rollers, a pre-wet liquid supply amount control unit such as a pump is used.

In step 23 of FIG. 11, the rotation speed Pi of the pre-wet pump is set for each color. In step 24, a printing sequence is started. In step 25, exposure for printing the i-th color is started. In step 26, the pre-wet pump rotation speed is changed to Pi. In step 27, the pre-wet roller is brought into contact. In step 28,
The exposure of the i-th color is completed. In step 29,
Retract the pre-wet roller. In step 30, i is incremented and compared to four of the four colors to determine if it has been completed for all colors to determine if it has been exceeded. If all of the four colors have not been completed, the process returns to step 25, and exposure for printing the next color is started. If all the colors have been completed, the process proceeds to step 31, where the printing sequence ends.

Regarding "Developing Function" As in the present invention, when a liquid toner developer having a high viscosity of 400 to 4000 mPa · S is used,
As described above, the surface of the photoconductor 10 has a viscosity lower than that of the silicone oil of the liquid toner in order to prevent the toner from adhering to the non-exposed portion of the photoconductor 10 in advance. By adopting a configuration in which silicone oil is applied as a pre-wet layer, the developing roller 141 is pressed against the photosensitive member 1 with a contact pressure that does not destroy the pre-wet layer.
In this case, a configuration of contacting with zero is adopted.

From now on, the developing device 14 is mounted on the photosensitive drum 1
It is necessary to allow the amount of the liquid toner or the pre-wet liquid carried by the rotation of the developing roller 141 to 0 to pass through the contact portion between the photosensitive drum 10 and the developing roller 141. Also, the hardness of the developing roller 141 should not be too large. If it is shown by a specific numerical value, it is preferable that it is 60 degrees or less in JIS-A hardness measurement. As the hardness of the developing roller 141 decreases, the amount of liquid toner and pre-wet liquid that can pass therethrough increases. In this regard, it is preferable to use a sponge or the like.

On the other hand, the higher the external dimension accuracy and the higher the runout accuracy during rotation of the developing roller 141, the more preferable the pressure applied to the liquid layer is kept. However, if the hardness is low, it is difficult to improve the processing accuracy. . It is necessary to balance the hardness of the developing roller 141 with the external accuracy of the developing roller 141.

Note that as the rotation speed of the developing roller 141 increases, the amount of liquid passing increases and the pressure condition is relaxed, but the application time of the electric field acting on the liquid toner decreases, and the time required for the movement of the toner is reduced. Will run out of
There are naturally restrictions. Further, as the diameter of the developing roller 141 is larger, the amount of liquid passing therethrough increases, and the pressure condition is eased. However, it is difficult to maintain the outer shape accuracy.

Further, because of the high viscosity, the surface of the toner layer applied to the developing roller 141 may not be a uniform flat surface and may have irregularities. When such a case occurs, as shown in FIG. Then, the pre-wet layer is pierced by the convex portion, and reaches the surface of the photosensitive drum 10, thereby causing noise in a non-exposed portion. Also, in the exposed portion, the non-uniform layer appears in the image portion, and a good image cannot be obtained. From this, it is necessary to construct a stable amount of toner applied to the entire surface of the developing roller 141.

According to the present invention, as a developing roller, a soft roller having elasticity, preferably a hardness of 60 ° or less (JIS
A) is used. Therefore, when the drum is stationary, the drum and the roller are in contact with each other (gap 0). However, as the drum rotates, the viscosity of the liquid causes the drum and the roller to receive buoyancy according to the rotation speed of the drum, and the elastic roller becomes , Resulting in a gap between the drum and the roller. Thus, a toner layer having a constant thickness can be formed.

FIG. 14 shows an example of such an elastic roller. As shown in the figure, a sponge roll is used as a base around a cored bar, and the surface is covered with a film tube. In addition, an electric field is applied to the developing roller, for which the sponge roll and the film tube are each made conductive, preferably 10 ⁴ to 10 ⁹ Ω · cm, respectively. For example, Bridgestone EPT-51 (Asker-F hardness 68 °) can be used as the conductive sponge, and a conductive PFA tube (thickness 30 μm) can be used as the surface film tube. As an example of the size of such a developing roller, as shown, the diameter is 32 mm and the surface length is 220 mm.

The following table shows the measurement of the liquid passage amount using such a developing roller. Note that DC34
4 is a silicone oil manufactured by Dow Corning.

[0059]

[Table 2] As shown by the measurement results, it can be seen that the amount of liquid passing per unit area increases as the roller peripheral speed increases.

Further, by making the surface of the surface film tube rough, for example, Rz1 to 10, the toner can be held and conveyed in the concave portion of the roughened roller surface unevenness, and the toner adsorbing property can be increased.

Further, silicone rubber can be used as the elastic roller. This silicone rubber has a volume resistivity of about 10 ⁴ to 10 ⁹ Ωcm, a hardness of 60 degrees (JISA) or less, and excellent mechanical repulsion. Although the elastic roller can be constituted by this alone, it is preferable to use it together with the surface film tube.

FIG. 15 shows another example of such a developing roller. As shown, the developing roller has spacer rollers on both sides thereof coaxially with the developing roller. The spacer roller is provided to maintain a constant distance between the developing roller and the photosensitive drum (OPC drum), and must be basically insulative. This can be made of, for example, an insulating resin, or can be made by providing an insulating resin layer on a metal surface to improve accuracy. And, for example,
For a developing roller having a diameter of 32 mm, the spacer roller can have a diameter of 31.8 mm, so that the developing roller has a bite amount of 0.1 mm and is applied to the photosensitive drum to optimize the nip pressure of the roller. Can be maintained. In the above description, an elastic roller is used as the developing roller, but the one shown in FIG. 16 or 17 uses a rigid roller or a roller of any hardness as the developing roller. The developing roller shown in FIG. 16 applies a pressure by its own weight. As shown in the drawing, a developing roller is attached to the other end of a rotating arm supported at one end by a support in a substantially horizontal direction, and applies a pressure to the photosensitive drum by its own weight. .

FIG. 17 shows an example in which a pressing force is applied by a spring instead of its own weight. As shown in the drawing, a developing roller is attached to the other end of the rotating arm supported by the support at one end, and a pressure is applied between the rotating arm and the support so that the developing roller is pressed against the photosensitive drum to be biased. A spring is attached.

As described above, when the developing drum is pressed against the photosensitive drum by its own weight or by a spring, the developing roller and the photosensitive drum are in contact with each other at rest, as in the case of the elastic developing roller described above. With the rotation of the developing roller and the photosensitive drum due to the viscosity of the liquid,
Due to the buoyancy corresponding to the rotation speed of the drum, the developing roller
This causes a gap proportional to the weight of the developing roller or the spring force. As a result, a desired constant thickness toner layer can be formed.

FIG. 18 shows a developing roller in contact with the photosensitive drum 10 and a series of applicator rollers for supplying the developing solution to the developing roller. The applicator roller includes an applicator final roller that contacts the developing roller, and a plurality of other rollers. Although the number of applicator rollers is exemplified by rollers, rollers, and rollers,
Generally, the developing roller is provided with an appropriate number of developing liquids necessary for thin and uniform spreading of the developing solution.

In FIG. 18, the roller contacts the photosensitive drum 10 so as to maintain a two-layer structure with the pre-wet liquid film on the photosensitive drum 10 and supplies the liquid developing solution.
The developing roller is configured to adhere positively charged toner particles of the liquid developer to the photosensitive drum 10 in accordance with an electric field between the photosensitive drum 10 and the developing roller. The roller is the last stage roller of the developer conveying applicator roller, and most of the developing solution is generated by a bias electric field between the developing roller and the last stage roller of the applicator, for example, a potential difference of 600-500 = 100 V as shown in the figure. Can be moved to the developing roller side. As described above, when the developer is applied to the developing roller by the roller to form a thin layer, minute unevenness (streak) of the developer occurs due to the balance of the viscosity of the developer, the supply amount, the rotation speed, and the like. As described above, by forming an electric field between the developing roller and the final stage roller and applying most of the developing solution to the developing roller, minute unevenness (streak) can be reduced.

FIG. 19 is a diagram for explaining the operation of the application of the bias voltage. By applying a bias voltage between the developing roller and the final roller of the applicator, an electric field force is applied to the nip portion of both rollers to increase the holding force and the attracting force of toner particles (solid particles) to the developing roller side. As a result, it is possible to reduce the occurrence of streak-like unevenness occurring at the nip portion exit portion. In other words, the solid particles (particles) dispersed in the carrier oil are dispersed in a state in which each of them retains a charge, and the state of destruction and separation at the nip exit can be reduced by effectively utilizing the electric force. It is possible to change. However, if the particles are, for example, a positively charged developer, a negative potential is applied to the developing roller side, and a positive potential is applied to the applicator roller side, so that the positive particles are moved to the developing roller side, and are applied to the developing roller side. The toner particles can be strongly attracted, and as a result, the toner particles generated near the exit of the nip can be adhered and applied to the developing roller without being disturbed.

The results of verification by applying an electric field are shown below. Table 3 shows the result of examining the uniformity of the toner layer on the developing roller. When the average toner amount is set to about 1 μm for three developers having different apparent viscosities, the variation (irregularity) of the thickness of the toner layer on the developing roller is reduced by the voltage (Va−Vd) between the applicator roller and the developing roller. ) Was measured. Although the variation in the layer thickness depends on the apparent viscosity (the type of the carrier agent), it can be seen that the developer having any viscosity decreases as the voltage (Va-Vd) increases. The apparent viscosity is determined by the content concentration of toner particles, particle size, pigment characteristics, carrier viscosity, and the like.

[0069]

[Table 3] Developer 1: 400 mPa · s Developer 2: 500 mPa · s Developer 3: 2000 mPa · s ：: Peak value on the developing roller is less than 3 μm, Δ: less than 5 μm, ×: 5 μm or more. , The result of verification by applying an electric field, and the quality of developed image quality (fog: unnecessary toner adhesion)
It is the result of having investigated. For the same three developers as in Experiment 1, the state of image quality (fog) was measured by changing the voltage (Va-Vd) between the applicator roller and the developing roller. Although the image quality depends on the apparent viscosity, the voltage (Va-V
It can be seen that it increases as d) increases.

[0070]

[Table 4] Developing agent: same as in Experiment 1 ○: Good image quality, Δ: Slight fogging observed, ×: Severe fogging Table 5 below also shows the results of verification by applying an electric field. It is the result of similarly examining the uniformity of the toner layer. For one developer, (1 μm)
m, 2 μm, 3 μm), and variations (irregularities) in the thickness of the toner layer on the developing roller were measured by changing the voltage (Va−Vd) between the applicator roller and the developing roller. Although the variation in the layer thickness depends on the amount of the developer (average layer thickness), it can be seen that for any average layer thickness, it decreases as the voltage (Va-Vd) increases.

[0071]

[Table 5] ：: The peak value on the developing roller is less than 3 μm, Δ: less than 5 μm, ×: 5 μm or more As described above, it can be seen that as the voltage increases, the uniformity of the toner layer or the image quality improves. However, this voltage upper limit is set so as to apply unnecessary stress to the toner as a whole and to prevent the dispersed toner from aggregating. That is, the electric field between the developing roller and the final roller, and the electric field applied between the developer transport rollers described below are both set to be smaller than the electric field formed between the photosensitive drum 10 and the developing roller. Or the time for passing between the electric fields is set short, for example, by changing the length of the nip portion. With this configuration, the dispersed toner does not aggregate.

The roller is the last roller for transporting the developing solution, and spreads the developing solution sent from the roller widely to form a thin layer and applies it to the surface of the developing roller. The roller takes out a required amount of the developing solution from the developing solution reservoir 43 at the nip between the rollers. By adjusting the value of the voltage applied to the roller and its polarity, the magnitude and direction of the electric field between the rollers can be changed, thereby controlling the amount of developer supplied to the roller. Can be.

FIG. 18 also shows an example of a configuration in which the developer is collected and reused. The details will be described later in the description of the recycling function. FIG. 21 shows a nip portion of a roller that is going to separate after two rollers come into contact with each other. When the nip portion of the roller is separated by the rotation of the roller, the liquid toner layer is broken and separated at the center of the liquid toner layer to form a layer due to the balance between the viscosity of the liquid toner itself and the adhesion to both rollers. At this time, the carrier oil, which tends to concentrate on the torn portion, collects the liquid toner around the carrier oil. As a result, local concentration of the liquid toner occurs, and the liquid toner exists on the developing roller as a streak in the rotational direction. . Further, the liquid toner hardly adheres between the streaks.

The generation of such streaks can be achieved by increasing the adhesive force between the liquid toner and the roller, so that the liquid toner is not attracted, does not have any streaks, and can be uniformly applied. This is because, as a roller, a roller of JISA 90 degrees or more and a roller of 60 degrees or less are combined,
This can be achieved by using a roller having silicone rubber or a silicone resin applied to the surface thereof as a roller material and uniformly applying the liquid toner to the entire roller. In addition to such adjustment of the roller hardness, the amount of toner can be adjusted by a developer transport amount adjusting means such as adjustment of pressure between rollers or adjustment of a distance between roller shafts. Occurrence can be suppressed.

In order to increase the wettability between the liquid toner and each roller, the surface of the roller, particularly the final roller of the applicator, can be subjected to a blast treatment with a surface roughness Rz ≧ 10 μm or more. In addition, when the roller diameter is large, the time during which the pulling force is applied becomes long, and the interval between the streaks becomes large. Therefore, the diameter of the final roller of the applicator should be small, preferably 2
By setting the thickness to 0 mm or less and 10 mm or more, the liquid toner layer can be separated at an early stage and the streak can be reduced.

FIG. 20 shows a method of making the layers uniform by using a reverse roller which is brought into contact with the developing roller and rotated in the direction opposite to the developing roller. After the toner layer is formed on the developing roller by the final roller of the applicator, the layer can be made uniform by the reverse roller as shown. The apparent viscosity of the toner decreases due to the shear speed (# 4- # 5) generated between the developing roller and the reverse roller. The streak of the toner layer greatly affects the apparent viscosity of the toner, and the lower the viscosity, the more uniform the layer.

The shear rate between the rollers can be used to more effectively apply the shearing force.
It is difficult to reduce the apparent viscosity of the toner by the final roller of the applicator itself. Since the last roller of the applicator has a function of transporting and supplying the toner, it is difficult to use the reverse roller as a reverse roller. FIG. 20 shows an apparent viscosity obtained by providing a reverse roller on the developing roller separately from the final roller of the applicator for supplying toner, and rotating the reverse roller at a peripheral speed of three times or more the peripheral speed of the developing roller. Is reduced, the generation of streaks is suppressed, and a uniform layer is obtained.

FIG. 22 shows the relationship between the shear rate and the apparent viscosity of the toner. Toray as carrier liquid
Dow Corning silicone oil SH-200-
Using 20 cSt, an average particle diameter of 0.6 consisting of resin and pigment
The results are measured by a B-type viscometer using cyan toner (PFU-C-001) and magenta toner (PFU-M-002) in which particles having a particle size of 0.7 μm to 20% by weight are dispersed at a weight ratio. As shown in the figure, the viscosity is sharply reduced by applying a shear rate (shear force).

The data in Table 6 below shows that the streak height decreases as the roller peripheral speed increases.
This data was obtained by forming a toner layer with an applicator roller pair combining two rollers having a diameter of 40 mm. The height of the streaks when the roller rotation speed at this time was changed to 25 mm / s, 125 mm / s, and 250 mm / s at peripheral speed was measured with an Erichsen film thickness meter. The toner has a viscosity of 400 mPa · s and 2000 m
Pa · s. The results show that the streak height decreases as the roller peripheral speed increases. This is because toner is torn off at an early stage due to an increase in the speed at which the roller surfaces pass through the nip and move away from each other.

[0080]

[Table 6] The same can be obtained by reducing the roller diameter. The data in Table 7 below is the result of measuring the height of the streaks when the toner layer was formed by a pair of applicator rollers combining two rollers having a small diameter of 20 mm with an Erichsen film thickness meter. . As can be seen from comparison with the data in Table 6 above, by reducing the roller diameter, the speed at which the roller surface separates is substantially increased, and the streak height is reduced.

[0081]

[Table 7] In FIG. 20, the last roller of the applicator, the roller, the roller, and the roller are rollers for transmitting the liquid toner and spreading the liquid toner over the entire developing roller. A liquid toner reservoir can be formed just before the nip portion between the rollers. Further, by providing a peripheral speed difference between the rollers, a toner amount sufficient to obtain a sufficient image density on the developing roller, preferably 5 to 10
Adjust to μm. As apparent from the above description, by changing the peripheral speed ratio of each roller of the applicator, the apparent viscosity of the liquid toner can be controlled, so that the type of the liquid toner (yellow / magenta / cyan / black) can be changed. Accordingly, the toner supply amount can be adjusted by changing the peripheral speed ratio between the rollers.

The rollers and rollers make their hardness softer than that of the rollers in order to supply sufficient liquid toner as needed. The final roller and the developing roller are blast-treated with a surface roughness of 10 μm or more to increase wettability and suppress streaking. As a result, the toner can be held and transported in the concave portions of the roughened roller surface, so that the amount of toner can be adjusted without applying unnecessary stress (pressure) to the liquid toner.

When silicone oil is used as a carrier material for the liquid toner in order to improve the affinity with the liquid toner, the roller material may be silicone rubber or a silicone resin coated on the surface. .

On the developing roller, for example, a conductive blade is provided separately from the applicator, an electric field is formed by applying a voltage, and a uniform toner layer can be formed by giving the toner an adhesive force on the developing roller side. .

Further, in order to remove all residual toner on the developing roller and pre-wet adhering to the developing roller, and to newly supply toner on the developing roller, the developing roller is always supplied in a clean state. A blade can be provided on the developing roller so as to impinge on the developing roller rotation direction and the counter direction after passing the developing point. Alternatively, a reverse roller may be provided in place of the blade as described above, a voltage may be applied, and the residual toner on the developing roller may be removed in combination with the electric field force.

The liquid toner is supplied to the first stage of the applicator roller. However, since the viscosity of the liquid toner is high, it is difficult to form a toner layer on the developing roller in a region width required for printing on the developing roller. Therefore, when the liquid toner is supplied onto the applicator roller by the pump, the liquid toner can be supplied to multiple points along the applicator axial direction. Thereby, the toner layer is easily formed on the developing roller along the width of the developing area.

In order to realize this multi-point supply using one pump, a pipe having a plurality of holes in the axial direction was provided on the applicator, and one end of the pipe was closed and the other end was connected to the pump. Make structure. Alternatively, the structure may be such that both ends of the pipe are closed and liquid toner is supplied from the center of the pipe by a pump. With such a configuration, the liquid toner can be supplied to the applicator at multiple points from the holes in the pipe. At this time, since the amount of toner flowing out of the holes on the pump side and the terminal side differs due to the difference in pressure distribution inside the pipe, the hole diameter increases from the pump side toward the terminal side. With such a configuration, the toner tank is provided at a position separated from the developing unit, and the size of the developing unit can be reduced.

A means for controlling the amount of toner to be supplied to the applicator by checking the amount of toner to be supplied to the applicator in order to supply the amount of toner to the applicator in accordance with the amount of liquid toner consumed, for example, turning on / off the pump or rotating the pump Control means can be provided. Alternatively, the amount of toner consumption can be checked by detecting the rotation speed or rotation time of the developing roller, and the rotation time and rotation speed of the pump can be controlled.

The presence or absence of the toner layer of the applicator roller to which the liquid toner is supplied can be detected by the outputs of sensors provided at both ends of the applicator roller, and the supply of the liquid toner can be controlled by turning on and off the pump. At this time, the sensor checks the toner accumulated in the nip portion between the first-stage applicator roller to which the liquid toner is supplied and the next-stage applicator roller, and constantly collects the toner between the first-stage applicator roller and the next-stage applicator roller. Control the pump so that there is.

Regarding the “recycling function”, FIG. 18 is referred to again. FIG. 18 illustrates a configuration in which the developer is collected and reused. The liquid toner of the present invention
Solid particles (pigments, etc.) in an insulating liquid (carrier agent)
Are dispersed, and its viscosity is 10
It has a high viscosity of 0 to 10000 mPa · S. In order to use this liquid toner as a liquid developer,
A thin layer of μm is applied on the developing roller and fed to the developing gap. The liquid developer remaining on the developing roller after passing through the developing gap is diluted by moving solid particles onto the photosensitive drum, and further diluted by mixing of pre-wet oil. It is necessary to return to the concentration of

In FIG. 18, the roller is a developing roller, and the final roller of the applicator, the conveying roller,
As described above, the developer is supplied from the developer reservoir 43 by the rollers.

The roller is rotated in the counter direction with respect to the developing roller to scrape off the residual developer on the developing roller and send it to the developer conveying belt 48 on the roller. The rollers and rollers are rollers for driving the developer transport belt 48. The developer transport belt 48 has conductivity, and a roller pair capable of transporting the developer can be used instead of the belt.

The developer conveyed by the developer conveying belt 48 has a high solid content between the rollers due to an electric field based on a bias voltage applied with the plus side as a roller as shown in the figure. On the roller side, those having a low solids concentration are separated on a roller, that is, a developer transport belt 48. The low-concentration liquid separated on the developer transport belt 48 is stored in the developer storage section 44 and sent to the pre-wet section via the filter 47. The high-concentration developer separated on the roller is accumulated in the accumulation section 43, and as described above, a necessary amount is taken out by the roller and the roller, and is reused.

FIG. 23 shows another example for recovering the developer. The developer collected from the developing roller by the roller is collected in a collecting part 45, is then pumped up by a pump 49, is put into a sedimentation tank 51, is separated by sedimentation, and has a relatively high concentration of a lower developer. Is pumped up by the pump 50 into the developer reservoir 46 and is reused.

Regarding "Intermediate Transfer and Heating Function" Next, the structure of the intermediate transfer member and the heating device thereof, which are features of the present invention, will be described in detail.

FIG. 24 shows an example of heating such an intermediate transfer member (illustrated as a roller, but a belt described later can also be used). The four color toners are respectively transferred from the photosensitive drum 10 to the intermediate transfer member 15.
After a total of four transfers, the toner transferred to the intermediate transfer member 15 is heated and then melt-transferred to a print medium such as paper once. According to the present invention, only the surface of the intermediate transfer member 15 and the toner transferred thereon are heated when the intermediate roller is heated.

In FIG. 24, as a heat source outside the intermediate transfer member, a heat roller having a heat source therein is provided outside the intermediate transfer member so as to be driven and rotated by the intermediate transfer member. Due to the contact heat transfer between the heat roller and the intermediate transfer member, the surface of the intermediate transfer member and the toner transferred thereon are heated. A toner release coat layer such as a fluorine coating can be formed so that the toner does not adhere to the surface of the heat roller. In addition, the surface layers of the heat roller and the intermediate transfer member can be made of a metal material such as aluminum or copper having good thermal conductivity. This makes it possible to improve the contact heat transfer from the heat roller to the intermediate transfer member, and to sufficiently raise the surface temperature of the intermediate transfer member.

FIG. 25 shows another example of such an external heat source. In this example, the surface of the intermediate transfer member can be heated by a non-contact heating source by radiant heat transfer, for example, a halogen lamp. Further, a reflector (reflector) for reflecting radiant heat from the halogen lamp toward the intermediate transfer member is provided. With such a radiation heat transfer source, not only the surface of the intermediate transfer body but also the toner is directly heated. At this time, a radiation heat transfer source that does not make a difference between the four colors of the toner is selected. It is desirable to do. As such a radiation heat transfer source, a far-infrared halogen heater can be used.

By forming the surface of the intermediate transfer member as a mirror surface or a metallic glossy surface that reflects infrared rays, the infrared rays emitted from the radiation heat transfer source can be reflected and far infrared rays can be collected in the toner image area. The input energy of the far-infrared heater can be controlled so as to be changed according to the amount of toner transferred to the intermediate transfer member based on, for example, an output signal from an exposure laser source or image data. As a result, it is possible to prevent excessive temperature rise of the toner in the small image area, and to make the toner melting state appropriate.

Further, it is possible to heat the toner on the surface of the intermediate transfer body, thereby heating the toner on the surface, rather than heating the toner directly. As a radiant heat source therefor, a near-infrared heater is suitable, and the heating efficiency of the surface of the intermediate transfer member can be increased by making the surface of the intermediate transfer member black with high near-infrared absorptivity.

The near-infrared type radiance peak is at a wavelength of about 1 μm which is close to the visible light range (380 nm to 780 nm). The color of a color toner is generated by absorption (or transmission) in a certain wavelength region in visible light. For example, yellow absorbs short wavelength blue light and reflects green and red light. Black toner has a high absorptivity regardless of wavelength. Therefore,
If a near-infrared type is used, it is more appropriate to uniformly heat the surface of the black intermediate transfer member and then indirectly heat the toner by heat conduction, rather than directly heating the color toner.

On the other hand, the wavelength of the output peak of the far infrared ray type is at 3 to 4 μm. The infrared absorption characteristic of the polymer resin, which is a main component of the toner, has a peak at about 3 μm. For infrared heating, it is more efficient to match the output peak on the heating side with the absorption peak wavelength on the heated side. Therefore, the far-infrared type can uniformly heat the toner regardless of the color (absorption characteristics).

FIG. 26 shows an example of the structure of the intermediate transfer member. Here, the intermediate transfer roller exemplified as the roller configuration has a rigid impression cylinder formed of metal such as aluminum at the center. This impression cylinder has conductivity so that a voltage can be applied from a shaft or the like to transfer the toner image on the photosensitive drum onto the intermediate transfer body by electrostatic force. Has the hardness to apply the pressure necessary for melt transfer onto the medium. A sponge foam or rubber having good thermal insulation is provided on the impression cylinder, and a thin solid film layer which receives heat is provided on the surface thereof. As the solid film material, a metal foil film of copper, aluminum, or the like having excellent heat conductivity to the toner can be used.
As a result, the heat capacity is reduced as a whole, and the amount of heat supplied can be reduced, while the surface temperature can be easily increased. In addition, since the heat capacity is small, the cooling property after transferring the molten toner to a medium such as paper is good,
The photosensitive drum 10 is not unnecessarily heated. By setting the thickness of the solid film layer as thin as possible in terms of strength, and preferably in the range of 30 to 100 μm, instantaneous heating and power saving are further improved.
Further, on the surface of the solid film layer, a coat layer for releasing the molten toner, for example, a fluorine coating can be formed.

FIG. 27 shows an example of the residual heat cooling means for the intermediate transfer member. The above-described intermediate transfer body can be configured to have a small heat capacity, and therefore, the intermediate transfer body after the toner is melt-transferred to a medium such as paper has a good cooling property, but it is necessary to further improve the cooling property. Means can be provided at a position after the melt transfer. As this means, as shown, a metal roller or a pipe can be driven to rotate on the surface of the intermediate transfer member, thereby removing heat on the surface of the intermediate transfer member. This can prevent secondary heating of the photosensitive drum 10 by the intermediate transfer member. Further, by providing fins with folds inside the cooling metal pipe and flowing a fluid such as air or water inside the pipe, the cooling effect of the intermediate transfer member can be further enhanced.

As another example of the cooling means, a liquid having good volatility such as a pre-wet liquid used for liquid development can be applied to the surface of the intermediate transfer member after the toner is melted. Alternatively, such volatile liquids can be sprayed from the metal roller when used with a cooling metal roller as described above. Thereby, the intermediate transfer member can be cooled by the heat of vaporization when the liquid evaporates.

FIG. 28 shows an example of an intermediate transfer member for preheating. Normally, as described above, each toner of the four colors is transferred from the photosensitive drum 10 to the intermediate transfer member.
After all of the transfer, the toner on the intermediate transfer body is heated. In this example, before the last toner of the fourth color is transferred, for example, at the time of transferring the second or third color toner, A preliminary voltage that does not melt the toner is applied to the halogen lamp.

By setting the preliminary voltage to a fraction of the rated value, it is possible to volatilize a pre-wet liquid and a carrier agent unnecessary for toner fusion transfer, and to reduce the rise time when the main voltage is applied to the halogen heater. It can also be shortened. Furthermore, by preheating the surface of the intermediate transfer member and the toner, power consumption during main heating can be reduced.

FIGS. 29 and 30 illustrate a configuration in which the heat roller is brought into contact with the intermediate transfer belt only during fusion transfer. 29 shows that the intermediate transfer belt is driven around three small rollers (one also serves as a transfer backup roller), while FIG. 30 is driven around four small rollers. An example is shown.

In each of the above examples, the toner of the photoreceptor is transferred to the intermediate transfer belt in four colors and then melt-transferred to a print medium such as paper at one time. It is configured to be in contact with.
29 and 30 each show a retracted state in which the heat roller is inside the belt and not in contact with the belt. In the retracted state, the toner of each color is transferred from the photoconductor to the belt.

After the completion of the transfer, the heat roller is brought into contact with the belt as shown in the right-side views of FIGS. 29 and 30. The heater inside the heat roller is turned on in advance so that the temperature of the heat roller becomes an appropriate temperature during the fusion transfer, and is heated.

The belt used as the intermediate transfer member has a high thermal conductivity, such as a metal belt.
Alternatively, a thin film such as a polyimide thin film is preferable. Further, as shown in FIG. 30, this heat roller can be provided in the medium transfer section, and can be configured to also serve as a backup roller for transferring to the medium.

With this configuration, the belt is heated only when necessary, so that unnecessary heat is not applied to the photosensitive drum, and the toner does not melt before the fusion transfer. Further, a stable temperature can be obtained from the leading end of the medium without worrying about the rise time of the temperature rise of the belt.

FIGS. 31 and 32 show a heating method using a heat belt. FIG. 31 shows when the heat belt is retracted, and FIG. 32 shows when the heat belt is in contact. In this example, the heat belt is driven by two rollers, and at least one of the rollers is formed by a heat roller using a halogen lamp or the like as a heat source. Preferably, both rollers are configured as heat rollers to increase the contact time between the belt and the heat roller to promote the recovery of the belt temperature in order to recover the temperature of the heat belt, which drops while the toner and the intermediate transfer member are being heated. It is.
Since the heating is performed by the belt having a constant length, the contact can be soft and the heating can be performed for a long time. In the illustrated example, a retreat configuration of the heat belt unit is provided. The heat belt is configured to be heated in advance, to be brought into contact with the intermediate transfer member only when performing the melt transfer, and to be in the retracted state at other times.

The heat belt can be made of a metal having good thermal conductivity as a whole or a base material.
It is possible to promptly supply heat from the heat belt to the intermediate transfer member and recover the temperature of the heat belt. further,
The surface layer of the belt may be a fluorine coat for toner release.

Since the heat belt and the toner image on the intermediate transfer member are in contact with each other, the state of mutual contact affects the image quality. Therefore, desirably, when the heat belt is brought into contact, only the so-called antinode portion located between the rollers, excluding the roller contact portion of the heat belt, makes soft contact. Such a configuration can be achieved by increasing the distance between the rollers. Further, in order to reduce the collapse and spread of the toner image caused by the contact pressure of the heat belt, an elastic layer such as silicone rubber having high heat resistance can be provided on the surface of the heat belt. Further, in order to eliminate the difference in peripheral speed between the belt and the intermediate transfer member, it is desirable that the belt be driven from the same drive source as the intermediate transfer member. Since the heat belt is heated while being in contact with the toner on the intermediate transfer member, the heat belt must have a characteristic (release property) such that the molten toner does not adhere to the heat belt. In other words, the wettability to the molten toner is greater on the surface of the intermediate transfer member than on the surface of the heat belt, and
The print media surface must be large. This can be achieved, for example, by coating the surface of the heat belt with fluorine and coating the surface of the intermediate transfer member with fluorine rubber. As a result, all the toner heated by the heat belt remains on the intermediate transfer member without adhering to the heat belt, and then is entirely melted on the print medium.

When heating the toner on the intermediate transfer member,
As a result, the intermediate transfer body itself is heated. Further, the heated toner needs to be kept in a molten state from the time the toner is separated from the heat belt to the time the paper contacts the printing medium under pressure. By forming the intermediate transfer member into a layer structure, the heat retention can be improved. For this reason, the intermediate transfer member is on a sponge foam or rubber with high heat insulation,
By providing a thin release resin layer, for example, a fluorine coat, which is excellent in the releasability of the molten toner, it is possible to improve the heat retaining property of the intermediate transfer body and the surface heat retaining property. At this time, the toner temperature is set to the set temperature of the heat belt (100 to 200 °).
In order to approach C), the heat capacity of the heat belt is made larger than the heat capacity of the surface resin layer of the intermediate transfer member.

The amount of toner on the intermediate transfer member varies depending on a place or a printed image, particularly during full-color printing. The heat capacity of the surface resin layer of the intermediate transfer member is made sufficiently larger than that of the toner layer so that the change in toner layer thickness does not affect the toner heating temperature. This can be achieved, for example, by setting the thickness of the surface resin layer of the intermediate transfer member to about 50 μm for a toner layer of 5 to 6 μm in total for four colors.

FIG. 33 shows a heating method using three rollers. After the toner on the intermediate transfer body is heated, the surface temperature of the toner and the intermediate transfer body decreases due to convection and heat transfer loss to the sponge layer inside the intermediate transfer body until the toner is transferred to the medium. It is necessary to shorten the time until transfer. For this purpose, it is desired to reduce the diameter of the belt drive roller on the fusion transfer side and arrange it closer to the pressure roller. However, the minimum values of the belt thickness and the roller diameter are determined from the repetitive compressive stress.

This problem is caused by the fact that, as shown in FIG.
By applying tension with the present roller, even if a small-diameter roller is used, the bending of the belt (internal compression and tensile stress) can be reduced. With this configuration, the time for which the heat belt faces the print medium is increased, so that the pre-heating of the print medium can be expected. Also,
As shown in the figure on the right side of FIG. 33, by using this small-diameter roller as a heat-resistant sponge roller (silicone rubber or the like), the sponge roller is elastically deformed by the tension of the belt, and the belt is bent in spite of the small-diameter roller. Can be relatively reduced.

[0120]

According to the present invention, a high-viscosity toner constituted by dispersing a high-concentration toner in silicon oil or the like having completely different properties from the liquid toner used in a conventional wet electrophotographic apparatus is provided. Efficiently utilizing the characteristics of the high-concentration liquid toner, a collecting means for collecting a liquid mixture of the liquid developer and the pre-wet liquid remaining on the surface of the developing roller is provided, and from the mixed liquid collected by the collecting means, To provide a separation means for separating the liquid to be regenerated from the liquid developer and the liquid to be regenerated from the pre-wet liquid, and to introduce a different way to recycle the liquid toner. Can be.

Further, the present invention relates to a configuration using a non-volatile, high-viscosity, high-concentration liquid toner.
The pre-wet liquid can be stably applied to the entire surface of the photoconductor, and the liquid toner can be stably supplied to the photoconductor without breaking the pre-wet layer applied to the photoconductor. it can.

Further, since the toner adheres to the non-exposed portion of the electrostatic latent image on the photoreceptor, image noise does not occur and a uniform developing solution can be applied to the developing roller. And the effect that the toner transferred to the intermediate transfer member can be efficiently heated and melted without affecting the photoconductor.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a wet electrophotographic apparatus according to the present invention.

FIG. 2 is an explanatory diagram of functions of an applicator roller and a developing roller.

FIG. 3 is an explanatory diagram of a function of a pre-wet layer applied by a pre-wet process.

FIG. 4 shows an example of a pre-wet liquid application configuration using a plurality of liquid spray nozzles.

FIG. 5 illustrates a roller configuration for applying a pre-wet liquid in contact with a photosensitive drum.

6 is a diagram for explaining another configuration of the roller 2 in FIG. 5, wherein the left side diagram shows a case where the surface roughness of the roller 2 is reduced, and the right side diagram shows a case where the surface roughness is rough. It shows the case where it is done.

FIG. 7 is a block diagram illustrating the concept of pre-wet control.

FIG. 8 shows a flowchart of an operation for controlling the retraction mechanism of the pre-wet roller.

FIG. 9 is a flowchart of an operation of changing a film thickness by changing an applied amount of a pre-wet roller to a photosensitive drum 10.

FIG. 10 is a flowchart of an operation of changing a peripheral speed difference between a pre-wet roller and a photosensitive drum 10 in order to control a film thickness.

FIG. 11 is a flowchart of an operation for changing the rotation speed of a pre-wet pump to control the film thickness.

FIG. 12 is a diagram illustrating a state of a toner layer in a nip portion between a developing roller and an applicator roller.

FIG. 13 is a diagram illustrating the operation of a pre-wet layer on the surface of a photoconductor.

FIG. 14 is an example of an elastic roller used as a developing roller.

FIG. 15 shows another example of the elastic roller.

FIG. 16 is an example of a developing roller that applies pressure by its own weight.

FIG. 17 is an example of another developing roller for applying a pressure by a spring.

FIG. 18 shows a developing roller and a series of applicator rollers in contact with the photosensitive drum.

FIG. 19 is a diagram illustrating the action of a bias voltage between an applicator final roller and a developing roller.

FIG. 20 shows a method of uniforming layers by using a reverse roller which is brought into contact with a developing roller and rotated in a reverse direction.

FIG. 21 is a diagram illustrating a state of a nip portion of a roller that is going to separate after two rollers come into contact with each other.

FIG. 22 is a diagram illustrating a relationship between a shear rate and apparent viscosity of toner.

FIG. 23 shows another example for collecting the developer.

FIG. 24 illustrates an example of heating of the intermediate transfer member using a heat roller.

FIG. 25 illustrates an example of heating of the intermediate transfer member using a halogen heater.

FIG. 26 illustrates an example of an intermediate transfer member configuration.

FIG. 27 illustrates an example of a residual heat cooling unit of the intermediate transfer member.

FIG. 28 illustrates an example of an intermediate transfer member that performs preheating.

FIG. 29 illustrates a configuration in which a heat roller is brought into contact with an intermediate transfer belt only during fusion transfer.

FIG. 30 illustrates another configuration in which a heat roller is brought into contact with an intermediate transfer belt only during fusion transfer.

FIG. 31 shows a heating method using a heat belt, and shows a state in which the heat belt is retracted.

FIG. 32 shows a heating method using a heat belt, and shows the state at the time of contact with the heat belt.

FIG. 33 shows a heating method using three rollers.

FIG. 34 shows a conventional intermediate transfer body in which a halogen heater is disposed in a hollow portion of a hollow metal drum to heat the entire intermediate transfer body.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 photoconductor (drum) 11 charging device 12 exposing device 13 prewetting device 14 developing device 15 intermediate transfer member (roller) 16 blade 17 static eliminator 18 heating device 19 pressure roller 31 spray nozzle 32 pump 33 PW tank 43 developer reservoir Unit 44 developer pool 45 developer pool 46 developer pool 47 filter 48 transport belt 49 pump 50 pump 51 sedimentation tank

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hongo 98 Unoki-nu 98, Unoki-cho, Kawakita-gun, Ishikawa Pref. 2 Inside PFU Co., Ltd. (72) Masataka Takahata 98 Uno-nu 98, Unoki-cho, Kawakita-gun, Ishikawa No. 2 Inside PFU Co., Ltd. (72) Inventor Genji Ichida Unoki-cho, Unoki-cho, Kawakita-gun, Ishikawa 98-2 Inventor P72 Co., Ltd. (72) Inventor Shigeharu Okano Unoki-nu, Unokicho, Kawakita-gun, Ishikawa 98-2 Inside PFU Co., Ltd. (72) Inventor Yasukazu Takeda 98-2 Unoki-nu, Unoki-cho, Kawakita-gun, Ishikawa Pref.

Claims (12)

[Claims] 1. A wet electrophotographic apparatus using a non-volatile, high-viscosity, high-concentration liquid toner as a liquid developer, comprising: an image support on which an electrostatic latent image is formed; and a surface of the image support. A pre-wet liquid coating means for applying a pre-wet liquid film composed of the same type as the liquid developer, and a two-layer structure of a pre-wet liquid film on the image support. A developing roller for supplying a liquid developer in contact with the image support and for attaching toner particles of the liquid developer to the image support according to an electric field generated between the image support and the image developer; And a plurality of rotating rollers connected to each other. The liquid developing solution supplied is conveyed while being applied to the surface while being stretched by the rotating rollers, and is applied to the surface of the final-stage rotating roller that contacts the developing roller. Liquid present A developing solution applying unit that applies a liquid film to the contact surface of the developing roller; a collecting unit that collects a liquid mixture of a liquid developer and a pre-wet liquid remaining on the surface of the developing roller; A wet electrophotographic apparatus, comprising: a separation unit configured to separate a liquid to be regenerated from a liquid developer and a liquid to be regenerated from a pre-wet liquid from a mixed liquid to be recovered. 2. The wet electrophotographic apparatus according to claim 1, wherein said pre-wet liquid applying means is arranged to face said photoreceptor, and supports said pre-wet liquid on said image support. By spraying in rows in the longitudinal direction of the body,
A wet electrophotographic apparatus, characterized by comprising a spraying means for applying a film of the pre-wet liquid to the surface of the image support. 3. The wet electrophotographic apparatus according to claim 1, wherein said pre-wet liquid applying means has a high insulation property, and a first roller which rotates while being in contact with said image support; A second roller that rotates while being in contact with the roller, adjusts a contact state between the first roller and the second roller, and constantly contacts a contact portion between the first roller and the second roller. By supplying the pre-wet liquid sufficiently to form a liquid pool, a film of the pre-wet liquid passing through the contact portion between the two rollers is applied to the surface of the image support at a constant thickness. A wet electrophotographic apparatus, characterized in that: 4. The wet electrophotographic apparatus according to claim 1, wherein said prewetting liquid applying means is supplied to a roller having high insulation properties and rotating while being in contact with said image support, and said rotating roller. Control means for controlling the thickness of the pre-wet liquid applied to the image support by controlling the supply amount of the pre-wet liquid. 5. The wet electrophotographic apparatus according to claim 1, wherein said developing roller has conductivity and elasticity for applying an electric field, and has a length substantially equal to a length of said image support. It has a length and, when stationary, comes into contact with the image support, and when rotated, the elasticity, the viscosity of the liquid developer applied to the surface, and the viscosity of the pre-wet liquid on the image support, A liquid developer is supplied onto the image support while rotating in contact with the image support in a non-contact manner, and toner particles of the liquid developer are supplied according to an electric field generated between the image support and the image developer. Is attached to the image support. 6. The wet electrophotographic apparatus according to claim 1, wherein the developing roller has conductivity and rigidity for applying an electric field, and has a length substantially equal to a length of the image support. Having a length, rotating while contacting the image support, supplying a liquid developer onto the image support, and developing the liquid developer according to an electric field generated between the liquid support and the image support. Liquid electrophoresis, comprising: a pressing unit that causes liquid toner particles to adhere to the image support, and presses the developing roller against the image support in accordance with a repulsive force received by the developing roller. apparatus. 7. The wet electrophotographic apparatus according to claim 1, wherein said developing solution applying means comprises a plurality of rotating rollers connected to each other, and supplies the supplied liquid developing solution to said rotating rollers. Along with applying the ink to the surface while transporting, the bias voltage is supplied to the final stage rotating roller that contacts the developing roller, and the bias voltage is applied in accordance with the electric field generated between the developing roller and the rotating roller. Applying a liquid developer film applied to the surface of the final-stage rotating roller to the contact surface of the developing roller. 8. The wet electrophotographic apparatus according to claim 1, wherein said developing solution applying means includes a plurality of rotating rollers connected to each other, and supplies the supplied liquid developing solution to said rotating rollers. It has a means for adjusting the transport amount of the liquid developer while applying it to the surface while stretching it, and has a means for adjusting the transport amount of the liquid developer. A wet electrophotographic apparatus characterized in that it is applied uniformly on a surface. 9. The wet electrophotographic apparatus according to claim 1, wherein the toner particles adhering to the image support are transferred in accordance with an electric field generated between the image support and the image support. An intermediate transfer member, a pressure roller that rotates while abutting on the intermediate transfer member and conveys a print medium while pressing the intermediate transfer member, and a position before contact with the pressure roller, the intermediate transfer member. A heating means for partially heating the surface of the body; 10. The wet electrophotographic apparatus according to claim 1, wherein said collection means includes a scraping roller which comes into contact with said developing roller and rotates in a direction opposite to said developing roller. Wet electrophotographic equipment. 11. The wet-type electrophotographic apparatus according to claim 1, wherein the separation unit performs a separation process by applying an electric field to the liquid mixture recovered by the recovery unit. Electrophotographic equipment. 12. The wet electrophotographic apparatus according to claim 1, wherein the separation unit performs a separation process by causing a mixed solution collected by the collection unit to settle. apparatus.