JPH07334006A - Liquid developing device for electrostatic latent image - Google Patents

Abstract

PURPOSE:To provide a liquid developing device for an electrostatic latent image capable of uniformly supplying liquid developer to the latent image surface of an image supporting body by applying a small amount of high concentration and high viscosity liquid developer on a developer supporting body with a uniform thickness. CONSTITUTION:As for the liquid developing device for the electrostatic latent image for developing the electrostatic latent image formed on a photoreceptor by toner, the device is provided with applying devices 52a to 52d for applying the high concentration and high viscosity liquid developer on a developing belt 510 through plural rollers such as a carrying roller 522b and an adjusting roller 522d having hardness >=60 deg. (JISA), a carrying roller 522a and a carrying roller 522c having hardness <=60 deg. (JISA) arranged in contact with each other from the roller 522a to the roller 522d in order, and the device is also provided with a developing part 51 for supplying the liquid developer to the latent image surface of the photoreceptor through the developing belt 510 on which the liquid developer is applied.

Description

Detailed Description of the Invention

[0001]

The present invention relates to electrophotography, electrostatic recording,
The present invention relates to a liquid developing device for an electrostatic latent image that visualizes an electrostatic latent image formed by a method such as ionography using a liquid developer.

[0002]

2. Description of the Related Art Conventionally, in a liquid developing apparatus for an electrostatic latent image, as a method for supplying a liquid developer to a latent image surface on an image support, unevenness is provided on the surface of a developing roller which is a developer support. A method of holding a liquid developer in a concave portion and supplying it to an image support, using a sponge roller as the developer support, and pressing the sponge roller against the image support to image the liquid developer absorbed by the sponge roller. A method of supplying to the support, or a method of directly supplying the liquid developer to the image support without using the developer support by immersing the image support in a developer tank in which the liquid developer is stored, etc. It is used.

[0003]

However, in the conventional large-sized electrostatic recording apparatus and the like, Isop which is an organic solvent is generally used.
arG (registered trademark: manufactured by Exxon) is used as a low-viscosity liquid developer in which a toner is mixed at a ratio of about 1 to 2%. Therefore, a high-concentration and high-viscosity liquid developer (a high-viscosity liquid developer of 100 to 10,000 mPa · s in which the toner is dispersed in the insulating liquid in a high concentration) is supplied in a small amount to the image support. When used, it is not clear which method is suitable for supplying the liquid developer to the latent image surface of the image support.

[0004]

The present invention has been made in view of the above circumstances, and a small amount of a high-concentration and high-viscosity liquid developer is applied to a developer support in a uniform thickness to form a latent image on the image support. An object of the present invention is to provide a liquid developing device for an electrostatic latent image that can uniformly supply a liquid developer.

[0005]

In order to achieve the above-mentioned object, a liquid developing apparatus for an electrostatic latent image according to the present invention described in claim 1 charges an electrostatic latent image formed on an image support. Is a liquid developing device for an electrostatic latent image, which is developed with a toner that is a visualized particle, and a high-viscosity liquid developer of 100 to 10000 mPa · s in which a toner is dispersed in an insulating liquid at a high concentration, Coating on a developer support through at least two rollers arranged by alternately contacting a hard roller having a hardness of 60 ° (JIS A) or more and a soft roller having a hardness of 60 ° (JIS A) or less. It is characterized by comprising: a coating means; and a developing means for supplying the liquid developer to the latent image surface of the image support through the developer support coated with the liquid developer. .

According to a second aspect of the present invention, there is provided a liquid developing device for an electrostatic latent image according to the first aspect, wherein the hard roller has a hardness of 90 ° (JIS A) and the soft roller has a hardness of 90 °. Is 40 ° (JIS A).

According to a third aspect of the present invention, there is provided a liquid developing device for an electrostatic latent image according to the first or second aspect, in which regulating wheels are provided on both sides of the hard roller and the soft roller which are adjacent to each other. By bringing the regulation wheel of the hard roller and the regulation wheel of the soft roller into contact with each other, the axial distance between the adjacent hard rollers and the soft rollers is shorter than the total radius of the adjacent hard rollers and the soft rollers. It is characterized in that

A liquid developing device for an electrostatic latent image according to a fourth aspect of the present invention is the liquid latent image developing device according to the first or second aspect, wherein the outer diameter of the soft roller is slightly smaller than the outer diameter of the soft roller. A regulated vehicle is provided, and the regulated vehicle is brought into contact with the hard roller.

According to a fifth aspect of the present invention, there is provided an electrostatic latent image liquid developing device according to the first, second, third or fourth aspect, wherein the insulating liquid of the liquid developer has a viscosity of 0.5. ~ 1
000 mPa · s, electric resistance is 10 ¹² Ωcm or more, surface tension is 21 dyne / cm or less, and boiling point is 100 ° C. or more.

According to a sixth aspect of the invention, there is provided an electrostatic latent image liquid developing apparatus according to the fifth aspect, wherein the liquid developer uses silicon oil as an insulating liquid. It is what

According to a seventh aspect of the present invention, there is provided an electrostatic latent image liquid developing apparatus according to the first, second, third, fourth, fifth or sixth aspect, wherein the liquid developer has an average particle diameter of 0. 1-5μ
m toner is contained at a concentration of 5 to 40%.

[0012]

A liquid developing apparatus for an electrostatic latent image according to claim 1 has a hard roller having a hardness of 60 ° (JIS A) or more and a hardness of 60 °.
(JIS A) By arranging the following soft rollers alternately in contact with each other, the soft roller is elastically deformed by the pressing force applied to the hard roller, and a nip width is formed at the contact portion with the hard roller. Since the liquid developer on each roller is thinly and uniformly regulated by providing the nip width, the liquid developer can be thinly and uniformly applied on the developer support. As a result, a small amount of high-concentration and high-viscosity liquid developer can be uniformly supplied to the latent image surface of the image support. Further, since the liquid developer in which the toner is dispersed in a high concentration is used, the liquid amount can be much smaller than that of the conventional low concentration liquid developer. Liquid developer has a viscosity of 1
When it is 0000 mPa · s or more, it becomes difficult to stir the insulating liquid and the toner, and there is a problem in how to make the liquid developer. Therefore, 10,000 mPa · s
The liquid developer described above becomes unrealistic in terms of cost and becomes unrealistic. On the other hand, when it is 100 mPa · s or less, the toner concentration becomes low and the dispersibility of the toner becomes poor, so that it becomes impossible to develop the developer in a thin layer.

The liquid latent image developing device according to a second aspect of the invention has the same operation as the invention according to the first aspect because of the above-mentioned configuration. In order to elastically deform the soft roller, the harder the harder the better. The hardness of the hard roller is preferably 90 ° (JIS A) or more. Further, when the pressing force of the soft roller to the hard roller is strong, a high torque is required to rotate each roller. Therefore, it is preferable that the soft roller is elastically deformed by a weak pressing force. The hardness of the soft roller is preferably 40 ° (JIS A) or less. However, when the hardness is 15 ° (JIS A) or less, it becomes impossible to maintain a constant shape, and thus it becomes difficult to form a constant nip width at the contact portion with the hard roller.

According to a third aspect of the present invention, there is provided an electrostatic latent image liquid developing apparatus in which regulating wheels are provided on both sides of an adjacent soft roller and hard roller, and the regulating wheels are brought into contact with each other to thereby adjoin the adjacent soft rollers. Also, since the distance between the axes of the hard rollers is shorter than the total radius of the soft rollers and the hard rollers adjacent to each other, the adjacent soft rollers and the hard rollers can be brought into contact with each other with a constant pressing force with a simple structure. .

According to another aspect of the liquid developing apparatus for an electrostatic latent image of the present invention, regulating wheels having an outer diameter slightly smaller than the outer diameter of the soft roller are provided on both sides of the soft roller, and the regulating wheels abut on adjacent hard rollers. By doing so, the soft roller can be brought into contact with the adjacent hard roller with a constant pressing force with a simple structure.

According to a fifth aspect of the present invention, there is provided an electrostatic latent image liquid developing device, wherein an insulating liquid having the above characteristics is used.
A high-viscosity liquid developer can be obtained. Since the liquid developer formed on the developer support is formed in a thin layer,
Since the amount of insulating liquid contained in the liquid developer layer is extremely small, the amount of insulating liquid contained in the liquid developer supplied to the latent image surface of the image support is also very small. Therefore, the amount of the insulating liquid absorbed on the paper or the like at the time of transfer is extremely small, so that the problem of the insulating liquid adhering to the paper or the like does not occur if the viscosity is 1000 mPa · s or less. However, if the viscosity is 0.5 mPa · s or less, the volatility becomes high and it is not suitable as a hazardous material. When the boiling point of the insulating liquid is 100 ° C. or less, the amount of evaporation is large, so that there is a problem in the method of storing the developer, the entire device must have a closed structure, and it is difficult to improve the working environment. . When the electric resistance is 10 ¹² Ωcm or less, the insulating property is deteriorated, and the toner has a problem of conductivity and cannot be used as a developer. Therefore, it is desirable that the electric resistance be as high as possible. When the surface tension is 21 dyne / cm or more, the wettability becomes poor. Therefore, it is desirable that the surface tension be as low as possible.

In the electrostatic latent image liquid developing device according to the sixth aspect, since the insulating liquid contains silicon oil as a main component, the insulating liquid having the characteristics according to the fifth aspect can be obtained. it can.

According to a seventh aspect of the present invention, there is provided a liquid developing device for an electrostatic latent image, wherein the liquid developer contains 5 toner particles having an average particle diameter of 0.1 to 5 μm.
By containing it at a concentration of -40%, it is possible to obtain a liquid developer in which the toner is dispersed in the insulating liquid at a high concentration. In addition, the resolution is improved in almost inverse proportion to the particle size of the toner. Usually, the toner is present as a mass of about 5 to 10 pieces on the printed paper, so that when the average particle diameter of the toner becomes 5 μm or more,
The resolution is poor. On the other hand, the average particle size of the toner is 0.1μ
When it is less than m, the physical adhesive strength becomes large and it becomes difficult to peel off the toner during transfer.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 is a schematic configuration diagram of an electrostatic latent image liquid developing device according to an embodiment of the present invention. FIG. 2 is a schematic front view of a developing device used in the electrostatic latent image liquid developing device shown in FIG. 3 is a right side view of the developing device shown in FIG. 2, and FIG.
5 is a diagram for explaining the operation of the coating unit of the developing device shown in FIG. 5, FIG. 5 is a diagram showing a method of contacting adjacent rollers of the coating unit shown in FIG. 4, and FIG. 6 is a liquid of the electrostatic latent image shown in FIG. FIG. 6 is a diagram for explaining the operation of the developing device.

As shown in FIG. 1, an electrostatic latent image liquid developing apparatus 1 according to an embodiment of the present invention applies a photoconductor 10 as an image support and a prewetting liquid on the photoconductor 10. A pre-wetting device 20, a charging device 30 that charges the photoconductor 10, and an exposure device 40 that exposes an image on the photoconductor 10.
And a developing device 50 that visualizes the electrostatic latent image by supplying toner to the portion of the photoconductor 10 on which the electrostatic latent image is formed.
A transfer device 60 for transferring and fixing the toner on the photoconductor 10 to a predetermined paper P, a cleaning device 70 for removing the toner remaining on the photoconductor 10, and a charged photoconductor (not shown). A static eliminator for static erasing 10 is provided.

For the charging device 30, the exposure device 40, the cleaning device 70, and the static eliminator, the conventional technique used in the conventional electrophotographic printer can be used in most cases. Therefore, in the present embodiment, the description of each of the above devices will be omitted, and the pre-wetting device 20, the developing device 50, and the transfer device 60, which are the main parts of the present invention, will be described.

The function required of the pre-wetting device 20 of this embodiment is to apply a uniform amount of the pre-wetting liquid onto the photoconductor 10 uniformly. For that purpose, a method of applying the pre-wetting liquid with a sponge-like material,
It is possible to use a coating method for other purposes such as a method of discharging from a plurality of nozzles arranged in the width direction of the photoconductor 10 or a method of applying with a sponge roller or the like. The inventors of the present invention tried various methods and confirmed that the above method was possible. However, as the most simple and high-performance method, Bell-Eta (registered trademark: Kanebo Co., Ltd.) was used as a pre-wet liquid. There is a method of applying. Bellita is
A continuous porous sponge having a three-dimensional network structure with continuous pores, capable of holding the pre-wet liquid only for the volume of the pores, and when the pre-wet liquid exceeding the volume of the pores is supplied, the pre-wet liquid Can be uniformly released from the surface. In this embodiment, the photoconductor 10
The contact surface with and was used in a substantially semicircular shape.

As shown in FIGS. 2 and 3, the developing device 50 comprises a developing section 51 and a coating section 52.
The developing section 51 includes a developing belt 510 that is a developer support.
Drive rollers 512a and 512b for rotating and driving the developing belt 510 and holding a portion of the developing belt 510 in contact with the photoconductor 10, and the developing belt 51.
Scraping blade 5 for removing the liquid developer remaining at 0
14 and a conveyance roller 522a described later
When the developing belt 510 comes into contact with the developing belt 510,
And a supporting roller 516 that supports the same from the back surface of the. The coating unit 52 includes coating devices 52a, 52b, 52c, and 52d that coat the surface of the developing belt 510 with the liquid developer.

The developing belt 510 includes a driving roller 512.
The a and 512b rotate the photosensitive member 10 in a direction opposite to the rotating direction. As the developing belt 510, a flexible belt member such as a seamless nickel belt or a resin belt such as a polyimide belt is used. The developing belt 510 must be capable of applying a developing bias. Therefore, when a resin belt is used, conductive particles are added to reduce the electric resistance value, or
It is necessary to apply conductive processing to the surface of the belt.

The coating devices 52a to 52d store a liquid developer and discharge the liquid developer, and conveying rollers 522a and 522b for conveying the liquid developer discharged by the bellows pump 520 to the developing belt 510.
522c, adjusting roller 522d, and conveying roller 522
and a separating / contacting device 524 that separates and contacts a from the developing belt 510. A liquid developer containing yellow toner is applied to the bellows pump 520a of the coating device 52a, a liquid developer containing magenta toner is loaded to the bellows pump 520b of the coating device 52b, and a bellows pump 520c of the coating device 52c.
Liquid developer containing cyan toner, and a bellows pump 520d of the coating device 52d stores liquid developer containing black toner.

The carrying roller 522a is a carrying roller 522b.
The transport roller 522b is configured to come into contact with the transport roller 5
22c so that it abuts against the transport roller 522c.
Are provided so as to contact the adjusting roller 522d. The transport roller 522a is in the direction opposite to the rotation direction of the developing belt 510, the transport roller 522b is in the direction opposite to the rotation direction of the transport roller 522a, and the transport roller 522c is in the opposite direction.
Rotates in the direction opposite to the rotation direction of the transport roller 522b, and the adjusting roller 522d rotates in the direction opposite to the rotation direction of the transport roller 522c.

Conveying roller 522b and adjusting roller 522
A hard roller having a hardness of 60 ° (JIS A) or more is used for d, and a soft roller having a hardness of 60 ° (JIS A) or less is used for the conveying roller 522a and the conveying roller 522c. Hard rollers with a hardness of 60 ° (JIS A) or more and soft rollers with a hardness of 60 ° (JIS A) or less were alternately contacted and arranged, as shown in FIG. This is to form the nip width t at the contact portion with the adjacent hard roller. The harder the hard roller, the better for elastically deforming the soft roller. Therefore, the hardness of the hard roller is preferably 90 ° (JIS A) or more. As a roller having a hardness of 90 ° (JIS A) or more, ULTRA-S made by urea resin (made by Miyagawa Roller Co., Ltd.), a ceramic roller made by ceramics containing alumina as a main component (made by Nippon Steel Co., Ltd.) ), And a resin roller such as a roller formed of ebonite. Further, when the pressing force of the soft roller to the hard roller is strong, a high torque is required to rotate each roller. Therefore, it is preferable that the soft roller is elastically deformed by a weak pressing force. Therefore, the hardness of the soft roller is preferably 40 ° (JIS A) or less. However, when the hardness is 15 ° (JIS A) or less, it becomes impossible to maintain a constant shape, and thus it becomes difficult to form a constant nip width at the contact portion with the hard roller. As a roller having a hardness of 15 ° to 40 ° (JIS A), BEET (manufactured by Miyagawa Roller Co., Ltd.) made of synthetic resin, NB
There is a roller formed of R (acrylonitrile-butadiene rubber). Incidentally, the transport rollers 522a to 522c
Since it is necessary to apply the liquid developer described later thinly and evenly on the surface, it is desirable that it has good lipophilicity.

As shown in FIG. 5, the carrying roller 522b is provided on both sides of the carrying roller 522b and the adjusting roller 522d.
And the disc wheel 52 having the same outer diameter as the outer diameter of the adjusting roller 522d.
6a is also the transport roller 522a and the transport roller 52.
2c on both sides of the conveyance roller 522a and the conveyance roller 5
Disc wheels 526b each having an outer diameter slightly smaller than the outer diameter of 22c are provided. And the adjacent disc wheel 526a
And the disk wheel 526b are brought into contact with each other, so that the axial distance between the adjacent transport rollers and the axial distance between the transport roller 522c and the adjusting roller 522d are the sum of the radii of the adjacent transport rollers, the transport roller 522c and the adjusting roller 522d. Each radius is shorter than the total radius. As a result, the adjacent conveyance roller and conveyance roller 522c and the adjustment roller 522d are adjacent to each other.
Contact each other with a constant pressing force. In this embodiment, the conveying rollers 522a to 522c and the adjusting roller 522d have an outer diameter of φ20 mm, and the disc wheel 526a has an outer diameter of φ2.
A disc wheel 526b having an outer diameter of 19 mm was used. The disc wheel may be a cylindrical roller.

The separating / connecting device 524 includes arms 524a, 52a.
4a. A transport roller 522a and a transport roller 522b are fixed to the arms 524a and 524a. The arms 524a, 524a rotate about the transport roller 522b as an axis by a driving device (not shown).
As a result, the transport roller 522a is brought into contact with and separated from the developing belt 510.

The transfer device 60 includes an intermediate transfer belt 610, which is an intermediate transfer member, and a driving roller that rotates and drives the intermediate transfer belt 610 and holds a part of the intermediate transfer belt 610 so as to contact the photosensitive member 10. 612a, 61
2b and 612c, and a secondary transfer roller 6 that is a secondary transfer member installed so as to be in contact with the intermediate transfer belt 610.
14 and a scraping blade 616 for removing the toner remaining on the intermediate transfer belt 610.

The intermediate transfer belt 610 includes a driving roller 61.
2a, 612b, and 612c rotate and drive the photoconductor 10 in the opposite direction. Secondary transfer roller 614
Is pressed against the intermediate transfer belt 610 via the paper P.
A fixing heater 618 that heats the paper P is provided inside the drive roller 612c.

Next, the image forming material used in one embodiment of the present invention will be described. The liquid developer used in this example includes a resin that serves as a binder such as epoxy, a charge control agent that gives a predetermined charge to the toner, a color pigment, a toner that includes a dispersant that uniformly disperses the toner, and a carrier liquid. Consists of. The toner composition is basically similar to that used in conventional liquid developers, but their formulation has been modified to be compatible with silicone oils for adjusting charging characteristics and dispersibility. The smaller the average particle size of the toner is, the better the resolution is. However, the smaller the particle size is, the larger the physical adhesive force is, and the more difficult it is to remove when transferring. Therefore, in this embodiment, the average particle diameter of the toner is adjusted so that the center is around 2 to 4 μm for the purpose of improving transferability.

The viscosity of the liquid developer depends on the carrier liquid used,
It depends on the resin, color pigment, charge control agent, etc. and their concentrations. In this example, the viscosity is 50 to 6000 m.
An experiment was conducted by changing the Pa · s and the toner concentration within the range of 5 to 40%.

As the carrier liquid, one having a low viscosity such as dimethylpolysiloxane oil having high electric resistance and cyclic polydimethylsiloxane oil is used. Incidentally, the developing belt 510
Since the liquid developer layer formed thereon is formed in a thin layer, the carrier liquid contained in the liquid developer layer is extremely small. Therefore, the amount of carrier liquid contained in the liquid developer supplied to the latent image surface of the photoconductor 10 is also extremely small, so that the amount of carrier liquid absorbed by the paper or the like during transfer is extremely small. Therefore, the viscosity is 1000 mPas
If it is below, almost no carrier liquid remains after fixing.

According to the experiments conducted by the present inventors, when the image output experiment was conducted using DC344 of Dow Corning Co., USA having a viscosity of 2.5 mPa · s as the carrier liquid, the carrier remaining on the paper after fixing was determined. No liquid was seen. But,
Due to its high volatility, it was necessary to make the developing device a closed structure. In addition, when the image output experiment was conducted using DC345 of Dow Corning Co., USA, which has a viscosity of 6.5 mPa · s as the carrier liquid, it was fixed on paper after fixing similarly to the case where the image output experiment was conducted using DC344. No carrier liquid remained in the. However, since the volatility is high, it is necessary to make the developing device have a closed structure. Furthermore, the carrier liquid has a viscosity of 20 mPas, Shin-Etsu Silicon KF-96
When the image output experiment was carried out using -20, no carrier liquid remained on the paper after fixing. Further, since the volatility is not so high, it is not necessary to make the developing device have a closed structure. DC344, DC345 and KF-
96-20 is generally used for cosmetics and has high safety such as toxicity. There are many kinds of carrier liquids such as KF9937 manufactured by Shin-Etsu Silicon Co., Ltd., and any one may be selected as long as the electric resistance, the evaporation property, the surface tension, the safety and the like are satisfied.

Further, according to an experiment conducted by the present inventors, when the surface tension is large, fogging or a lump of toner is generated on the photoreceptor 10.
21 dyne / cm experimentally
From the above, it was found that the problem of image quality is likely to occur.

The electric resistance value is preferably 10 ¹⁴ Ωcm or more because of the problem of toner charging stability. At least 1
0 ¹² Ωcm or more is necessary. In the description of the present embodiment, in view of these experimental results, the DC3 is low in price and easily available.
An example using 45 is shown.

The pre-wetting liquid easily evaporates during fixing without disturbing the electrostatic latent image formed on the photosensitive member 10,
It is required that the fog and the lump of toner do not adhere to the photoconductor 10. As an example, DC344, DC200-0.65, -1.0,-, manufactured by Dow Corning, USA
2.0, Shin-Etsu Silicon KF96L-1, KF993
7 etc. are mentioned. Generally, it is necessary to select a highly evaporative silicone oil.

In an experiment conducted by the present inventors, the liquid was dried by development, transfer and fixing without any problem when the liquid viscosity was in the range of 0.5 to 3 mPa · s, but from 5 mPa · s to 6 m
At about Pa · s, there was a tendency that a time and a temperature were required for drying the liquid at the time of fixing. If it is 10 mPa · s, the energy required for drying becomes too large, which is not general. Further, if it is 0.5 mPa · s or less, the volatility becomes high, so that it is regarded as a hazardous material and is not suitable. In addition, the boiling point needs to be 250 ° C. or lower because of the effect of heating the paper.

The surface tension eliminates the adhesive force between the liquid developer and the photoconductor 10 and improves the releasability to prevent image stains and fogging, and improves the resolution and fogging of image quality.
It should be as low as possible. According to experiments conducted by the present inventors, the limit is about 20 to 21 dyne / cm, and it is necessary to select one lower than this.

When the electric resistance is low, the insulating property deteriorates and electric charges are leaked. Therefore, it is necessary to use the highest possible one. Experimentally, about 10 ¹⁴ Ωcm or more is desirable. A minimum of 10 ¹² Ωcm is required.

Next, the operation of the electrostatic latent image developing device according to the first embodiment of the present invention will be described. First, FIG. 6 (A)
As shown in, the charging device 30 charges the photoconductor 10. Generally, a corona discharger is used for the charging device 30. Next, the image is exposed on the charged photoreceptor 10. For example, the image is exposed by a laser scanner to expose the photoreceptor 10.
To form an electrostatic latent image on the surface of. As shown in FIG. 6B, the portion of the laser scanner exposed to the light becomes conductive, so that the electric charge disappears, and the portion not exposed to the light remains as an electrostatic latent image which is an image of the electric charge.

Next, as shown in FIG. 6C, the above-mentioned pre-wetting liquid is applied onto the photoconductor 10 by the pre-wetting device 20.

Next, the developing device 50 visualizes the electrostatic latent image. As shown in FIG. 4, the liquid developer discharged by the bellows pump 520 to the contact start position of the adjusting roller 522d and the conveying roller 522c is the nip width t formed at the contact portion of the adjusting roller 522d and the conveying roller 522c. It is applied to the transport roller 522c after being regulated to have a uniform thickness. The liquid developer applied onto the carrying roller 522c is regulated to a more uniform thickness by the nip width t formed at the contact portion between the carrying roller 522c and the carrying roller 522b, and then applied onto the carrying roller 522b. The liquid developer applied on the carrying roller 522b is transferred to the carrying roller 52.
2b and the transport roller 522a are regulated to have a more uniform thickness by the nip width t formed at the contact portion of the transport roller 52a.
2a is applied. The liquid developer thus applied to the carrying roller 522a via the plurality of carrying rollers in a uniform thickness is applied thinly and evenly on the surface of the developing belt 510. Form a thin layer. The thickness of the thin layer formed on the developing belt 510 can be adjusted by changing the nip width t. In the developing device 50, any one of the coating devices 52 a to 52 d is connected to the developing belt 5 by the separating / connecting device 524.
Abut on 10. As a result, the liquid developer containing any one of the toners of yellow, magenta, cyan, and black can be thinly and evenly applied onto the developing belt 510.

Next, the liquid developer layer formed on the developing belt 510 is brought close to the electrostatic latent image formed on the surface of the photoconductor 10 as shown in FIG. Thus, the charged toner is moved onto the photoconductor 10. As a result, a toner image is formed on the photoconductor 10.

Next, as shown in FIG. 6E, the toner image formed on the photoconductor 10 is primarily transferred onto the intermediate transfer belt 610 by the transfer device 60. On the other hand, the photoconductor 10
The liquid developer remaining on the photoconductor 10 is removed by the cleaning device 70, and then the charge is removed by a charge removing device (not shown). Then, the coating devices 52a to 52 that come into contact with the developing belt 510 by the separating / connecting means 524.
After switching d, the above-described cycle from charging to static elimination is repeated again, so that yellow, magenta, cyan, and black toner images are transferred one after another onto the intermediate transfer belt 610. As a result, the intermediate transfer belt 6
A toner image corresponding to colorization is formed on 10.

Next, as shown in FIG. 6 (F), the toner image corresponding to the color formed on the intermediate transfer belt 610 by the transfer device 60 is secondarily transferred onto the paper P which is a recording medium and fixed at the same time. Let The toner image corresponding to the color formed on the intermediate transfer belt 610 moves onto the paper P and is secondarily transferred by the pressing force of the secondary transfer roller 614 to the intermediate transfer belt 610 and the heat from the fixing heater 618. At the same time, it is thermally melted and fixed. As a result, the paper P
A color image can be formed on it.

7 to 11 are views for explaining the developing process of one embodiment of the present invention in detail, FIG. 7 is a diagram for explaining the developing process as a whole, and FIG. 8 is an approaching process. FIG. 9, FIG. 9 is a diagram showing a state of a toner moving process, FIG. 10 is a diagram showing a separation process of a non-image part, and FIG. 11 is a diagram showing a separation process of an image part. Unlike the conventional developing process, in the developing process of the present embodiment, the developing belt 510 approaches the photoconductor 10 and the liquid developer approaches the surface of the photoconductor 10, as shown in FIG. The toner moving process in which the developer layer and the pre-wet liquid layer are in soft contact to move the toner, and the developing belt 510 is separated from the photoconductor 10 and adheres to the developing belt 510.
It is considered to be composed of three processes, that is, a separation process in which the toner adheres to 0 and a separation process.

In the approaching process, since the developing belt 510 is made of a flexible belt member, as shown in FIG. 8, the liquid developer layer on the developing belt 510 and the photoconductor 1 are made.
The contact pressure at the time of contact with the pre-wet layer above 0 is dispersed, and the high-viscosity liquid developer consisting of the carrier liquid and the toner is soft-contacted with the pre-wet liquid. As a result, the pre-wet liquid having a low viscosity is slightly pushed back and forth, and a liquid pool of the pre-wet liquid is generated.

In the toner moving process, as shown in FIG. 9, in the image portion, the toner on the developing belt 510 is mainly caused by the Coulomb force due to the electric field formed between the charges on the photoconductor 10 and the developing belt 510. It passes through the pre-wet liquid layer and moves to the latent image surface. On the other hand, in the non-image portion, the toner on the developing belt 510 has the surface of the photoconductor 10 and the liquid developer layer separated by the pre-wet liquid layer.
It does not move to the surface of the photoconductor 10.

In the separation process, in the non-image part, as shown in FIG.
As shown in 0, the liquid developer remains on the developing belt 510. At the interface between the pre-wet liquid layer and the liquid developer layer, when the two layers are separated, a part of the pre-wet liquid layer having a low viscosity is transferred to the liquid developer layer and separated. Therefore, the separation point of the two layers is considered to be inside the pre-wet liquid layer. On the other hand, in the image area, as shown in FIG. 11, the toner that has moved to the surface of the photoconductor 10 pushes away the pre-wet liquid layer, so that the pre-wet liquid layer is located above the toner layer, and both are in the pre-wet liquid layer. Separate inside. On the developing belt 510, a part of the carrier liquid remaining after the toner is moved and a part of the pre-wetting liquid form a layer.

FIG. 12 is a diagram for explaining the significance of thinning the liquid developer. If the liquid developer layer applied on the developing belt 510 is too thick, the viscosity of the liquid developer is high, so that the electrostatic force can cause the developing belt 510 to move to the photoreceptor 1.
The toner group that is about to move to the surface of 0 forms a cluster without breaking the viscosity of the toner located around it and moves to the surface of the photoconductor 10. For this reason, the toner excessively moves, the toner image formed on the photoconductor 10 is disturbed, and image noise occurs. In order to suppress the generation of these clusters, it is necessary to control the layer thickness of the liquid developer layer to a minimum value that allows sufficient development.

FIG. 13 is a diagram showing a state in which the developing roller, which is the developing support, and the photoconductor 10 are in hard contact, and FIG. 14 is a diagram for explaining the soft contact in this embodiment. As described above, the function of the pre-wet liquid layer for image formation is important in the developing process of this embodiment. Therefore, an important requirement in the developing process is to maintain the two-layer state of the pre-wet liquid layer and the liquid developer layer. As shown in FIG. 13, when the developing roller and the photoconductor are in hard contact, the two-layer state cannot be maintained. Therefore, in this embodiment, as shown in FIG. By using the developing belt 510 including the belt member having the prewetting liquid layer, the prewetting liquid layer on the photoconductor 10 and the liquid developer layer on the developing belt 510 are dispersed by the contact pressure being dispersed. The two layers of the liquid developer layer and the liquid developer layer are maintained.

Next, the layer thickness of the liquid developer layer on the developing belt 510 and the layer thickness of the pre-wet liquid layer on the photoreceptor 10 will be described. The layer thickness of the liquid developer layer on the developing belt 510 needs to be thin when the viscosity of the liquid developer is 50 to 100 mPa · s or more, particularly 500 mPa · s or more. Ideally, the layer thickness is slightly thicker than the layer thickness that satisfies the toner development amount (that is, the density when solid black is produced) required at the time of development. This is because when a high-viscosity liquid developer is used, the electrostatically selected toner moves to the photoconductor 10 along with the extra toner due to the viscosity of the liquid during development.
This is because the toner image formed on the image surface 0 is disturbed.
In an experiment conducted by the inventors, a good image was obtained with a layer thickness of about 5 μm for a liquid developer having a high toner concentration and with a layer thickness of about 40 μm for a liquid developer having a low toner concentration. In particular, when a liquid developer having a toner concentration of 20 to 30% was used, good image quality was obtained when the layer thickness of the liquid developer was about 20 μm.

The layer thickness of the pre-wet liquid layer on the photoconductor 10 has an optimum value depending on the viscosity and surface tension of the selected pre-wet liquid. If it is too thin, the development belt 51
The toner on 0 moves irregularly on the photoconductor 10 and disturbs the toner image formed on the photoconductor 10. As the amount of the pre-wet liquid is increased, the disorder of the toner image is improved, and the optimum value is confirmed. When the amount is further increased, the toner on the photoconductor 10 flows and the toner image on the photoconductor 10 tends to be blurred. In the experiment using DC344, good results were obtained with a thickness of 5 to 30 μm. For those with a lower viscosity, a thinner or thicker result can be obtained. However, for high viscosity ones, the optimum value tends to have a narrow range.

As a result of conducting an image development experiment under the above-mentioned conditions, the optimum range of the liquid developer and the viscosity of the pre-wet liquid for the electrostatic latent image developing apparatus of this embodiment is 100 mPa. s to 6000 mPa · s, and the pre-wet liquid was found to be between 0.5 mPa · s and 5 mPa · s. The silicone oil of the pre-wet liquid is DC200 series manufactured by Dow Corning, and the carrier liquid of the developing liquid is DC345 of the same company.
Was used.

According to this embodiment, the carrying roller 522a, which is a soft roller, the carrying roller 522a, the carrying roller 522b, which is a hard roller, and the adjusting roller 522d are arranged in contact with each other in the order of 522a to 522d. The liquid developer supplied to the contact start position of the conveying roller 522c and the conveying roller 522c is adjusted by the adjusting roller 522d.
And the nip width formed at the contact portion of the transport roller 522c,
A uniform thickness is regulated by the nip width formed at the contact portion between the transport roller 522c and the transport roller 522b, and the nip width formed at the contact portion between the transport roller 522b and the transport roller 522a. To be done.
As a result, the high-concentration and high-viscosity liquid developer is applied to the developing belt 5.
It can be applied thinly and evenly on the surface of the photoconductor 10, and therefore a small amount of high-concentration and high-viscosity liquid developer can be uniformly supplied to the latent image surface of the photoconductor 10.

If the liquid developer is applied on the developer support through two or more rollers, the liquid developer can be applied thinly and evenly on the developer support. . However, when the hard rollers are adjacent to each other, the layer thickness of the liquid developer layer is regulated by a minute gap formed between the adjacent hard rollers, and therefore high accuracy is required when setting each roller. Further, in order to make the layer thickness of the liquid developer layer uniform, the surface accuracy of the roller surface must be improved.

Further, according to the present embodiment, a disk wheel 526a having the same outer diameter as the roller outer diameter is provided on both sides of the carrying roller 522b and the adjusting roller 522d which are hard rollers, and the carrying roller 522a and the carrying roller which are soft rollers. 522c
On both sides of the disc wheel 526 with an outside diameter slightly smaller than the outside diameter of the roller
b are provided respectively, and the disc wheel 526a and the disc wheel 5 which are adjacent to each other are provided.
By contacting 26b, the adjacent soft roller and hard roller can be brought into contact with each other with a constant pressing force with a simple structure.

Further, according to the present embodiment, since silicon oil is used as the carrier liquid for the liquid developer,
It has the following advantages over conventional ones.

Conventional liquid developers generally use IsoparG (registered trademark: manufactured by Exxon) as a carrier liquid.
Since this Isopar has a resistance value not as high as that of silicone oil, when the toner concentration is increased, that is, when the distance between particles is reduced, the chargeability of the toner is deteriorated. Therefore, Isop
In the case of ar, the toner density is limited. On the contrary,
Since the silicone oil used in this embodiment has a sufficiently large resistance value, the toner concentration can be increased. Also,
Generally, in the case of Isopar, the toner is well dispersed, and therefore even if the toner concentration is 1 to 2%, the toners repel each other, so that the toner is uniformly dispersed. On the other hand, silicone oil has a toner concentration of 1 to 2%,
The dispersibility is not good and it will precipitate soon. However, when the toner concentration is set to 5 to 40%, the toner is densely packed and stably dispersed. Therefore, in this embodiment, a high-viscosity liquid developer in which toner is dispersed at high density is used. As a result, the amount of the developer can be significantly reduced as compared with the conventional low-concentration liquid developer, and the device can be downsized. Furthermore, since the liquid developer of this embodiment is a high-viscosity liquid, it is easier to store and handle than the conventional low-viscosity liquid developer or powder developer.

Isopar used in the conventional liquid developer is
As mentioned above, it is highly volatile and emits a foul odor,
There is a problem that it not only deteriorates the work environment but also causes pollution. On the other hand, the silicone oil used in this example is a safe liquid and is odorless, as is clear from the fact that it is used for cosmetics. The environment can be improved and pollution problems do not occur.

The present invention is not limited to this embodiment, and various modifications can be made within the scope of the gist thereof. For example, in this embodiment, as the coating device, the one in which the liquid developer is coated on the developing belt 510 via the three conveying rollers 522a to 522c has been described, but the present invention is not limited to this. The coating device has a hardness of 6
Hard rollers of 0 ° (JIS A) or higher and hardness of 60 ° (JIS
A) The following soft rollers may be arranged so as to be alternately in contact with each other so as to apply the liquid developer onto the developing belt via at least two rollers.

Further, on both sides of the transport roller 522b and the adjusting roller 522d, a disk wheel 526 having the same outer diameter as the roller outer diameter is provided.
a is provided with a disc wheel 526b having an outer diameter slightly smaller than the outer diameter of the roller on each side of the conveying roller 522a and the conveying roller 522c.
However, the present invention is not limited to this, and the axial distance between adjacent hard rollers and soft rollers is determined by the total radius of the adjacent hard rollers and soft rollers. Anything that can be shortened will do. For example, as shown in FIG. 15, a disk wheel 5 having an outer diameter slightly smaller than the outer diameter of the roller is provided on both sides of the soft roller.
26c may be provided, and the disc wheel 526c may be brought into contact with the surface of an adjacent hard roller.

Further, a coating device 52a for coating the developing belt 510 with a liquid developer containing yellow toner, a coating device 52b for coating the developing belt 510 with a liquid developer containing magenta toner, and a cyan toner. Application device 52c for applying the liquid developer to the development belt 510
And a liquid developer containing black toner on the developing belt 5
Although the apparatus including the coating device 52d for coating the 10 has been described, the present invention is not limited to this.
It suffices if at least one coating device for coating the liquid developer containing the toner of a desired color onto the developing belt via at least two rollers is provided as needed.

Further, in the present embodiment, the developing belt 51 composed of a flexible belt member as the developer support.
However, the present invention is not limited to this. The developer support may be a developing roller formed of a conductive member such as metal. However, the liquid developer layer formed on the developing roller and the pre-wet liquid layer formed on the image support are contacted while maintaining a two-layer state, and both are separated inside the pre-wet liquid layer. Therefore, it is necessary to use a flexible belt member as the image support or to install the developing roller so as to form a minute gap between the developing roller and the image support. .

Further, in this embodiment, the case where the organic photoconductor 10 is used as the image support has been described.
The present invention is not limited to this. The image support may be various photoconductors used in the Carlson method, those in which an insulating layer is formed on a conductor that directly forms an electrostatic latent image such as ionography, or electrostatic recording paper such as an electrostatic plotter.

Further, in this embodiment, as a transfer device, the toner image formed on the photoconductor 10 is primarily transferred onto the intermediate transfer belt 610 which is an intermediate transfer member, and then primarily transferred onto the intermediate transfer belt 610. Although a toner image is secondarily transferred onto the paper P to form an image on the paper P, the present invention is not limited to this, and the transfer device is not limited to the image support. Any toner can be used as long as it can transfer the formed toner image to a recording medium. For example, in a monochrome liquid developing device, the toner image formed on the image support may be directly transferred onto a recording medium without primary transfer onto the intermediate transfer member.

Further, in this embodiment, the image was exposed on the image support charged by the exposure device 40, and then the pre-wet liquid was applied on the image support by the pre-wetting device 20. The present invention is not limited to this, and the application of the pre-wet liquid may be performed before the developing step.

Further, the present invention is not limited to this embodiment, and if the pre-wet liquid layer is formed and the layer thickness of the liquid developer is 5 to 40 μm, the viscosity of the high viscosity developer is It may be 10,000 mPa · s. In the present circumstances,
A developer having a high viscosity of 6000 mPa · s or more is difficult to agitate the carrier liquid and the toner, so it is considered to be cost-effective, but if it becomes available at a low price,
It may be 6000 mPa · s or more. Viscosity 10000m
Those exceeding Pa · s become unrealistic. In addition, the pre-wetting liquid has a viscosity of 0.5 to 5 mPa · s, an electric resistance of 10 ¹² Ωcm or more, a boiling point of 100 to 250 ° C., and a surface tension of 21 dyne / cm or less, and contains silicon oil as a main component. It does not have to be a thing. Furthermore, the carrier liquid of the liquid developer is not limited to silicone oil.

In this embodiment, the liquid developing method for the electrostatic latent image has the pre-wetting step, but the present invention is not limited to this. For example, if the surface of the image support is coated with a material having releasability, the pre-wetting step is not particularly required.

[0072]

As described above, according to the first aspect of the present invention, the liquid developer on each roller is regulated thinly and uniformly by providing the nip width. , The liquid developer can be applied thinly and uniformly on the developer support, whereby a small amount of the liquid developer can be uniformly supplied to the latent image surface of the image support, and the toner can be highly charged. To provide a liquid developing device for an electrostatic latent image, which has a high resolution, can be easily miniaturized, and can reduce pollution by developing a thin layer of a high-viscosity liquid developer dispersed in a concentration. You can

According to the second aspect of the present invention, with the above configuration, it is possible to provide a liquid developing device for an electrostatic latent image having the same effect as that of the first aspect of the invention.

According to the invention described in claim 3, by virtue of the above construction, in addition to the effect of the invention described in claim 1, the adjacent soft roller and hard roller are pressed with a constant pressing force by a simple structure. It is possible to provide a liquid developing device for an electrostatic latent image that can be brought into contact with each other.

According to the invention described in claim 4, in addition to the effect of the invention described in claim 1, the soft roller can be applied to the adjacent hard roller with a constant pressing force by a simple structure. A liquid developing device for an electrostatic latent image that can be brought into contact can be provided.

According to the invention described in claim 5, in addition to the effect of the invention described in claim 1, by virtue of the above-mentioned structure, an electrostatic latent image liquid developing device having good wettability with the liquid developer is provided. Can be provided.

According to the invention described in claim 6, in addition to the effect of the invention described in claim 5, by virtue of the above-mentioned constitution, the electrostatic latent image which can reduce the pollution and improve the working environment can be achieved. It is possible to provide the liquid developing device.

According to the invention described in claim 7, in addition to the effect of the invention described in claim 1, by virtue of the above-mentioned constitution, the liquid developing apparatus for electrostatic latent image in which the toner is easily peeled off at the time of transfer Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a liquid developing device for an electrostatic latent image that is an embodiment of the present invention.

FIG. 2 is a schematic front view of a developing device used in the electrostatic latent image liquid developing device shown in FIG.

FIG. 3 is a right side view of the developing device shown in FIG.

FIG. 4 is a diagram for explaining an operation of a coating unit of the developing device shown in FIG.

FIG. 5 is a diagram showing a method of contacting adjacent rollers of the coating unit shown in FIG.

6A and 6B are diagrams for explaining the operation of the liquid developing device for the electrostatic latent image shown in FIG.

FIG. 7 is a diagram for explaining the entire developing process.

FIG. 8 is a diagram showing a state of an approaching process.

FIG. 9 is a diagram showing a state of a toner movement process.

FIG. 10 is a diagram showing a separation process of a non-image part.

FIG. 11 is a diagram showing a process of separating an image portion.

FIG. 12 is a diagram for explaining the significance of thinning the liquid developer.

FIG. 13 is a diagram showing a state in which a developing roller and a photoconductor are in hard contact with each other.

FIG. 14 is a diagram for explaining soft contacts of the electrostatic latent image liquid developing apparatus according to the present embodiment.

FIG. 15 is a diagram showing a modified example of a method of contacting adjacent rollers of the coating unit shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Photoconductor 20 Pre-wetting device 30 Charging device 40 Exposure device 50 Developing device 51 Developing part 52 Coating part 52a, 52b, 52c, 52d Coating device 60 Transfer device 70 Cleaning device 510 Developing belt 512a, 512b, 612a, 612b, 612c
Drive roller 514, 616 Scraping blade 516 Support roller 520 Bellows pump 522a, 522b, 522c Conveying roller 522d Adjusting roller 524 Contacting / separating device 524a Arm 526a, 526b, 526c Disc wheel 614 Secondary transfer roller 618 Heater

Claims (7)

[Claims] 1. A liquid developing device for an electrostatic latent image, which develops an electrostatic latent image formed on an image support with toner, which is a charged developing particle, wherein the toner is high in an insulating liquid. 100 to 1 dispersed in concentration
A high-viscosity liquid developer of 0000 mPa · s has a hardness of 6
Hard rollers of 0 ° (JIS A) or higher and hardness of 60 ° (JIS
A) coating means for coating on a developer support through at least two rollers arranged by alternately abutting the following soft rollers, and via the developer support coated with the liquid developer A developing device for supplying the liquid developer to the latent image surface of the image support, and a liquid developing device for electrostatic latent image. 2. The hardness of the hard roller is 90 ° (JIS
A) or above, and the hardness of the soft roller is 40 ° (JIS
A) The liquid developing device for an electrostatic latent image according to claim 1, wherein: 3. A regulation wheel is provided on both sides of the adjacent hard roller and soft roller, and the regulation wheel of the hard roller and the regulation wheel of the soft roller are brought into contact with each other, whereby 3. The electrostatic latent image liquid developing device according to claim 1, wherein the axial distance of the soft roller is shorter than the sum of the radii of the hard roller and the soft roller which are adjacent to each other. 4. A regulation wheel having an outer diameter slightly smaller than an outer diameter of the soft roller is provided on both sides of the soft roller, and the regulation wheel is brought into contact with the adjacent hard roller. Or a liquid developing device for an electrostatic latent image as described in 2 above. 5. The liquid developer has an insulating liquid having a viscosity of 0.5 to 1000 mPa · s and an electric resistance of 10 ¹² Ωcm.
Above, surface tension is 21 dyne / cm or less and boiling point is 10.
The liquid developing device for an electrostatic latent image according to claim 1, 2, 3 or 4, wherein the temperature is 0 ° C or higher. 6. The electrostatic latent image liquid developing device according to claim 5, wherein the liquid developer uses silicon oil as an insulating liquid. 7. The liquid developer has an average particle diameter of 0.1 to 5
7. The electrostatic latent image liquid developing device according to claim 1, wherein the toner contains .mu.m toner at a concentration of 5 to 40%.