JP4082446B2 - Electrostatic latent image liquid developing device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an electrostatic latent image liquid developing apparatus that visualizes an electrostatic latent image formed by a method such as electrophotography, electrostatic recording, or ionography using a liquid developer.
[0002]
[Prior art]
Conventionally, in an electrostatic latent image liquid developing apparatus, as a method of supplying a liquid developer to a latent image surface on an image support, unevenness is provided on the surface of a developing roller as a developer support, and liquid development is performed in a recess. A method of holding the developer and supplying it to the image support, using a sponge roller as the developer support, and supplying the liquid developer absorbed by the sponge roller to the image support by pressing the sponge roller against the image support The method etc. are used.
[0003]
[Problems to be solved by the invention]
However, in the monochrome liquid developing apparatus using the above method, the image support and the developer support are always in contact with each other. Further, the color-compatible liquid developing device using the above method includes a plurality of developer supports corresponding to the respective colors, and a plurality of developer supports are switched except when the developer support to be brought into contact with the image support is switched. One of the developer supports and the image support are always in contact with each other. Therefore, there is a problem that the image support and the developer support are easily worn. There is also a problem that dust accumulates at the contact start position between the two, and the surface of the image support is scratched to deteriorate the image quality. Further, in the color-compatible liquid developing device, there is a problem that color mixing occurs due to a liquid reservoir of a small amount of liquid developer generated between the image support and the developer support.
[0004]
【the purpose】
The present invention has been made based on the above circumstances, and can suppress the wear of the image support and the developer support, and can also prevent the image quality from being deteriorated due to scratches on the surface of the image support. An electrostatic latent image liquid developing device capable of preventing color mixing due to a liquid pool generated between an image support and a developer support when the color support is possible. It is intended to provide.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, an electrostatic latent image liquid developing apparatus according to the present invention develops an electrostatic latent image formed on an image support with toner, which is a developed visualization particle. A liquid developing device ofA developer support that forms a thin layer by transporting a liquid developer having a viscosity of 100 to 10000 mPa · s, in which toner is dispersed in a high concentration in an insulating liquid, with a plurality of transport rollers that are separated from and in contact with the developer support. When,The conveyance roller is separated from and contacted with the developer support.Separation meansAnd the developer support are separated from and contacted with the image supportSeparation and connection meansAnd the developer support has flexibility held by at least two rollers.Have a conductive surfaceIt is a belt-like one, and the separation / contact means rotates the single roller so that the developer support is separated from and contacted with the image support without changing the distance between the rollers. It is characterized by being.
[0008]
  Claim 2The electrostatic latent image liquid developing device of the present invention described in 1Claim 1In the described invention, the viscosity of the insulating liquid of the liquid developer is 0.5 to 1000 mPa · s, and the electric resistance is 10¹²Ωcm or more, surface tension of 21 dyne / cm or less, boiling point of 100 ° C. or more.
[0009]
  Claim 3The electrostatic latent image liquid developing device of the present invention described in 1Claim 2In the invention described above, the liquid developer uses silicon oil as an insulating liquid.
[0010]
  Claim 4The electrostatic latent image liquid developing device of the present invention described in 1Claim 1, 2 or 3In the described invention, the liquid developer contains toner having an average particle diameter of 0.1 to 5 μm at a concentration of 5 to 40%.
  According to a fifth aspect of the present invention, there is provided the electrostatic latent image liquid developing apparatus according to the first, second, third or fourth aspect, wherein the thickness of the liquid developer layer formed on the developer support is set. It is characterized by being 5 to 40 μm.
[0011]
[Action]
2. The electrostatic latent image liquid developing apparatus according to claim 1, wherein the liquid developer is supplied to the latent image surface on the image support by providing contact / separation means for separating the developer support from the image support. Only when this is done, the developer support can be brought into contact with the image support. Accordingly, it is possible to suppress the wear of both the image support and the developer support as compared with the apparatus in which the image support and the developer support are always in contact with each other. In addition, since the surfaces of both the image support and the developer support can be cleaned with a blade or the like, it is possible to prevent the developer and dust from accumulating at the contact start position of both. Therefore, in the case of a color-compatible liquid developing device, it is possible to prevent color mixing due to the developer pool generated between the image support and the developer support, and the image support. In the apparatus for applying the pre-wet liquid to the surface, it is possible to prevent the pre-wet liquid from accumulating at the contact start position between the image support and the developer support.
[0012]
  Also,By rotating one roller around the shaft, the developer support is brought into and out of contact with the image support without changing the distance between the axes of the rollers, so that the developer support can always be held at a constant tension. Therefore, it is possible to prevent the occurrence of running troubles such as a change in tension when the image support and the developer support are brought into contact with each other and the developer support meandering.
[0013]
  Furthermore,By using a liquid developer in which toner is dispersed at a high concentration, the amount of liquid can be made much smaller than that of a conventional low concentration liquid developer. When the viscosity of the liquid developer is 10,000 mPa · s or more, it becomes difficult to stir the insulating liquid and the toner, and how to make the liquid developer becomes a problem. Therefore, a liquid developer of 10,000 mPa · s or more is not cost-effective and is not realistic. On the other hand, at 100 mPa · s or less, the toner density is lowered and the dispersibility of the toner is deteriorated, so that it is impossible to develop the developer in a thin layer.
[0014]
  Claim 2The electrostatic latent image liquid developing apparatus described above can obtain a high-viscosity liquid developer by using an insulating liquid having the above characteristics. Since the liquid developer formed on the developer support is formed in a thin layer, the amount of the insulating liquid contained in the liquid developer layer is very small, and is supplied to the latent image surface of the image support. The insulating liquid contained in the liquid developer is very small. Accordingly, the amount of insulating liquid absorbed by the paper or the like at the time of transfer is extremely small, so that the problem of adhesion of the insulating liquid to the paper or the like does not particularly 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 because it is handled as a dangerous substance. If the boiling point of the insulating liquid is 100 ° C. or less, the amount of evaporation increases, so there is a problem in the storage method of the developer, the entire apparatus must be sealed, and it is difficult to improve the working environment. . Electrical resistance is 10¹²If it is less than Ωcm, the insulating properties are deteriorated, and the toner has a problem of electrical conductivity and cannot be used as a developer. Therefore, it is desirable that the electric resistance is as high as possible. When the surface tension is 21 dyne / cm or more, the wettability is deteriorated. Therefore, the surface tension is desirably as low as possible.
[0015]
  Claim 3The electrostatic latent image liquid developing apparatus described is that the insulating liquid is mainly composed of silicon oil,Claim 2An insulating liquid having the described characteristics can be obtained.
[0016]
  Claim 4In the electrostatic latent image liquid developing apparatus, the liquid developer contains toner having an average particle diameter of 0.1 to 5 μm at a concentration of 5 to 40%, so that the toner is dispersed at a high concentration in the insulating liquid. Liquid developer can be obtained. Further, the resolution is improved substantially in inverse proportion to the particle size of the toner. Usually, the toner is present in a mass of about 5 to 10 on the printed paper, and therefore, when the average particle size of the toner is 5 μm or more, the resolution is deteriorated. On the other hand, when the average particle size of the toner is 0.1 μm or less, the physical adhesive force increases, and it becomes difficult to remove the toner during transfer.
[0017]
【Example】
An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a schematic configuration diagram of an electrostatic latent image liquid developing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic front view of a developing apparatus used in the electrostatic latent image liquid developing apparatus shown in FIG. 3 is a left side view of the developing device shown in FIG. 2, FIG. 4 is a schematic sectional view in the direction of arrow AA of the developing device shown in FIG. 3, and FIG. 5 is a schematic diagram in the direction of arrow X of the developing device shown in FIG. FIG. 6 is a diagram for explaining the operation of the separation apparatus used in the developing device shown in FIG. 2, and FIG. 7 is a diagram for explaining the operation of the electrostatic latent image liquid developing device shown in FIG.
[0018]
As shown in FIG. 1, an electrostatic latent image liquid developing apparatus 1 according to an embodiment of the present invention includes a photoconductor 10 as an image support and a prewet apparatus for applying a prewetting liquid onto the photoconductor 10. 20, a charging device 30 for charging the photoconductor 10, an exposure device 40 for exposing an image on the photoconductor 10, and electrostatically supplying toner to a portion of the photoconductor 10 where an electrostatic latent image is formed. A developing device 50 that visualizes a latent image, a separation device 55 that separates and contacts the developing device 50 and the photosensitive member 10, and a transfer device 60 that transfers and fixes toner on the photosensitive member 10 to a predetermined paper P. And a cleaning device 70 that removes the toner remaining on the photoconductor 10, and a static eliminator (not shown) that neutralizes the charged photoconductor 10.
[0019]
For the charging device 30, the exposure device 40, the cleaning device 70, and the charge removal device, the conventional techniques used in conventional electrophotographic printers can be used in most cases. Therefore, in this embodiment, the description of each of the above-described devices is omitted, and the pre-wet device 20, the developing device 50, the separation / contact device 55, and the transfer device 60, which are main parts of the present invention, will be described.
[0020]
A function required for the pre-wet apparatus 20 of the present embodiment is to uniformly apply a predetermined amount of the pre-wet liquid onto the photoreceptor 10. For that purpose, a prewetting liquid is applied by a sponge-like material, a prewetting liquid is discharged from a plurality of nozzles arranged in the width direction of the photoconductor 10, and a prewetting liquid is applied by a sponge roller or the like. It is possible to use a coating method for other purposes, such as a method for making a film. The inventors of the present invention have tried various methods and confirmed that the above method is possible. The most convenient and high-performance method is a pre-wet liquid using Belita (registered trademark: Kanebo Co., Ltd.). It was the method of apply | coating. The bell eta is a continuous porous body having a three-dimensional network structure in which pores are continuous, can hold a prewetting liquid by the volume of pores, and when a prewetting liquid exceeding the pore volume is supplied, Wet liquid can be discharged uniformly from the surface. Note that the bell eater of this embodiment has a substantially semi-cylindrical contact surface with the photoreceptor 10.
[0021]
As shown in FIGS. 2 and 3, the developing device 50 includes a developing unit 51 and a coating unit 52. The developing unit 51 includes a developing belt 510 that is a developer support, driving rollers 512a and 512b that rotationally drive the developing belt 510, scraping blades 514 and 514 that remove liquid developer remaining on the developing belt 510, and Development belt side plates 518 and 518 for the development belt are provided. The application unit 52 includes application units 52a, 52b, 52c, and 52d that apply a liquid developer to the surface of the developing belt 510.
[0022]
The application units 52a to 52d each store and discharge a liquid developer, a bellows pump 520, and transport rollers 522a, 522b, 522c, and 522d that transport the liquid developer discharged by the bellows pump 520 to the developing belt 510, Arms 524 and 524 and application unit side plates 528 and 528 are provided. The bellows pump 520a of the coating unit 52a is a liquid developer containing yellow toner, the bellows pump 520b of the coating unit 52b is a liquid developer containing magenta toner, and the bellows pump 520c of the coating unit 52c is a cyan toner. And a liquid developer containing black toner is stored in the bellows pump 520d of the application unit 52d.
[0023]
The conveying roller 522d is provided so as to contact the conveying roller 522c, the conveying roller 522c is provided to contact the conveying roller 522b, and the conveying roller 522b is provided to contact the conveying roller 522a. The conveyance roller 522d is in the direction opposite to the rotation direction of the developing belt 510, the conveyance roller 522c is in the direction opposite to the rotation direction of the conveyance roller 522d, the conveyance roller 522b is in the direction opposite to the rotation direction of the conveyance roller 522c, and the conveyance roller 522a. Respectively rotate in the direction opposite to the rotation direction of the conveying roller 522b.
[0024]
On the arms 524 and 524, the shafts of the transport rollers 522c and 522d are rotatably attached. The arms 524 and 524 are rotated about the axis of the conveying roller 522c by a driving device (not shown). As a result, the conveying roller 522d is brought into contact with the developing belt 510.
[0025]
A bellows pump 520 is attached to the application unit side plates 528 and 528, and the shafts of the transport rollers 522a to 522c are rotatably attached.
[0026]
The developing belt 510 is rotated in the direction opposite to the rotation direction of the photosensitive member 10 by the driving rollers 512a and 512b. As the developing belt 510, a flexible belt member such as a resin belt such as a seamless nickel belt or a polyimide belt is used. The developing belt 510 must be capable of applying a developing bias. Therefore, when a resin belt is used, it is necessary to reduce the electric resistance value by conducting conductive processing on the belt surface or adding conductive fine particles to the belt material. A rib 510a is formed at one end of the developing belt 510 as shown in FIG. The rib 510a is engaged with one side surface of the drive rollers 512a and 512b. The driving rollers 512a and 512b are formed in a tapered shape so that the outer diameter of the side surface with which the rib 510a is engaged is slightly larger than the outer diameter of the other side surface. This is because the tension T applied to the portion of the developing belt 510 where the rib 510a is not formed.₁The tension T applied to the portion where the rib 510a is formed₂This is because the developing belt 510 is always driven to be pushed in the right direction (arrow A direction) in FIG. 4 by making it slightly weaker. Thereby, it is possible to prevent the developing belt 510 from sagging and wrinkles, and to prevent a running failure such as the developing belt 510 meandering.
[0027]
The shaft of the driving roller 512a is rotatably attached to the developing belt side plates 518 and 518, and is also rotatably attached to an apparatus main body (not shown). The shaft of the drive roller 512b passes through a long hole 518b formed in the developing belt side plate 518 and is rotatably attached to the adjusting plates 518a and 518a. The adjusting plates 518a and 518a are slidably attached to the developing belt side plates 518 and 518. The tension applied to the developing belt 510 can be adjusted by sliding the adjusting plates 518a and 518a to change the distance between the axes of the driving roller 512a and the driving roller 512b.
[0028]
The separation / contact device 55 rotates the developing device 50 about the axis of the drive roller 512a, thereby separating the contact of the developing belt 510 with the photosensitive member 10 without changing the distance between the axes of the drive roller 512a and the drive roller 512b. Let As shown in FIGS. 2 and 5, the separating / connecting device 55 includes a reel 552 that is rotationally driven by a driving device (not shown), and a rope that has one end wound around the reel 552 and the other end wound around a bar 518c. 554, a pulley 556 that supports the rope 554, and a stopper 558 that contacts the adjustment plate 518a. The bar 518c is attached to the developing belt side plates 518 and 518. As described above, since the shaft of the drive roller 512a is also rotatably attached to the apparatus main body (not shown), the side of the developing device 50 on which the drive roller 512b is attached is moved up and down by the rope 554. The developing device 50 can be rotated about the axis of the drive roller 512a, thereby bringing the developing belt 510 into and out of contact with the photoreceptor 10 without changing the distance between the axes of the drive roller 512a and the drive roller 512b. be able to. That is, when the photosensitive member 10 and the developing belt 510 are brought into contact with each other, as shown in FIG. 6A, the adjusting plate 518a is moved by rotating the reel 552 in a direction to release the rope 554 wound around the reel 552. It is brought into contact with the stopper 558. Since the shafts of the drive rollers 512a and 512b are attached to the development belt side plates 518 and 518, the distance between the shafts of the drive roller 512a and the drive roller 512b does not change. Therefore, the developing belt 510 can be brought into contact with the photoreceptor 10 with a constant pressing force. When the photosensitive member 10 and the developing belt 510 are separated from each other, the developing belt 510 is pulled away from the photosensitive member 10 by rotating the reel 552 in the winding direction of the rope 554 as shown in FIG. Since the shafts of the drive rollers 512a and 512b are attached to the development belt side plates 518 and 518, the distance between the shafts of the drive roller 512a and the drive roller 512b does not change. Therefore, the developing belt 510 can be separated from the photoreceptor 10 while maintaining a certain tension.
[0029]
The transfer device 60 includes an intermediate transfer belt 610 that is an intermediate transfer member, and driving rollers 612a and 612b that rotate and drive the intermediate transfer belt 610 and a part of the intermediate transfer belt 610 in contact with the photoconductor 10. , 612 c, a secondary transfer roller 614 that is a secondary transfer member installed so as to contact the intermediate transfer belt 610, and a scraping blade 616 that removes toner remaining on the intermediate transfer belt 610.
[0030]
The intermediate transfer belt 610 is rotationally driven in a direction to follow the photoreceptor 10 by driving rollers 612a, 612b, and 612c. The secondary transfer roller 614 is pressed against the intermediate transfer belt 610 through the paper P. A fixing heater 618 for heating the paper P is provided inside the driving roller 612c.
[0031]
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 is a binder such as an epoxy, a charge control agent that gives a predetermined charge to the toner, a color pigment, a toner that uniformly disperses the toner, a carrier liquid, Consists of. The construction of the toner is basically the same as that used in conventional liquid developers, but their formulation has been changed to be compatible with silicone oil to adjust charging characteristics and dispersibility. The smaller the average particle diameter of the toner, the better the resolution. However, when the particle diameter is small, the physical adhesive force increases and it becomes difficult to peel off when transferring. For this reason, in this embodiment, the average particle diameter of the toner is adjusted so as to be centered around 2 to 4 μm for the purpose of improving transferability.
[0032]
The viscosity of the liquid developer is determined by the carrier liquid used, the resin, the color pigment, the charge control agent, etc., and their concentrations. In this embodiment, the experiment was performed by changing the viscosity in the range of 50 to 6000 mPa · s and the toner concentration in the range of 5 to 40%.
[0033]
As the carrier liquid, a low viscosity liquid such as dimethylpolysiloxane oil or cyclic polydimethylsiloxane oil exhibiting high electrical resistance is used. Since the liquid developer layer formed on the developing belt 510 is formed in a thin layer, the amount of carrier liquid contained in the liquid developer layer is very small. Accordingly, since the amount of carrier liquid contained in the liquid developer supplied to the latent image surface of the photoconductor 10 is extremely small, the amount of carrier liquid absorbed by paper or the like during transfer is extremely small. For this reason, if the viscosity is 1000 mPa · s or less, almost no carrier liquid remains after fixing.
[0034]
According to the experiments by the present inventors, when an image-drawing experiment was performed using DC344 of Dow Corning, Inc., which has a viscosity of 2.5 mPa · s, the carrier liquid remaining on the paper after fixing was observed. I couldn't. However, since the volatility is high, the developing device has to be sealed. In addition, when the image formation experiment was performed using DC345 of US Dow Corning Co., Ltd. having a viscosity of 6.5 mPa · s in the carrier liquid, as in the case of the image formation experiment using DC344, after fixing, on the paper The carrier liquid remaining in was not observed. However, since the volatility is high, the developing device has to be sealed. Furthermore, when an image forming experiment was performed using KF-96-20 manufactured by Shin-Etsu Silicon Co., Ltd., whose viscosity was 20 mPa · s, 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 in a sealed structure. DC344, DC345 and KF-96-20 are generally used in cosmetics and have high safety such as toxicity. There are many types of carrier liquids such as KF9937 manufactured by Shin-Etsu Silicon Co., Ltd., and any of them may be selected as long as electrical resistance, evaporation characteristics, surface tension, safety and the like are satisfied.
[0035]
Further, in experiments conducted by the present inventors, fog and toner lumps may adhere to the photoconductor 10 when the surface tension is large, and experimentally, image quality problems are likely to occur at 21 dyne / cm or higher. I understood that.
[0036]
The electrical resistance value has a problem of toner charging stability.¹⁴Ωcm or more is desirable. 10 at a minimum¹²Ωcm or more is necessary. In the description of this embodiment, in view of these experimental results, an example is shown in which a DC 345 that is inexpensive and easily available is used.
[0037]
The pre-wet liquid is required to evaporate easily at the time of fixing without disturbing the electrostatic latent image formed on the photoconductor 10 so that fog or a lump of toner does not adhere to the photoconductor 10. Examples include DC344, DC200-0.65, -1.0, -2.0 of Dow Corning, USA, KF96L-1, KF9937, etc. of Shin-Etsu Silicon. In general, it is necessary to select a highly evaporable silicone oil.
[0038]
In the experiment conducted by the present inventors, the liquid was dried by development, transfer, and fixing without any problem in the range of the liquid viscosity of 0.5 to 3 mPa · s, but somewhat in the range of 5 mPa · s to 6 mPa · s. There was a tendency for time and temperature to be required for drying the liquid during fixing. At 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 handled as a dangerous substance and is not appropriate. Also, due to the effect of heating the paper, the boiling point needs to be 250 ° C. or less.
[0039]
The surface tension should be as low as possible in order to eliminate the adhesion between the liquid developer and the photosensitive member 10 and improve the releasability to prevent image smearing and fogging, and to improve the image resolution and fogging. According to the experiments by the present inventors, it is necessary to select a value of about 20 to 21 dyne / cm which is lower than the limit.
[0040]
If the electrical resistance is low, the insulating property is deteriorated and the electric charge is leaked. Therefore, it is necessary to use as high as possible. 10 experimentally¹⁴About Ωcm or more is desirable. 10 at a minimum¹²Ωcm is required.
[0041]
Next, the operation of the electrostatic latent image developing apparatus according to the first embodiment of the present invention will be described. First, the separation / contact device 55 is operated, and the photosensitive member 10 and the developing belt 510 are separated from each other as shown in FIG. 6A from the state where the photosensitive member 10 and the developing belt 510 are separated as shown in FIG. Make contact.
[0042]
Next, as illustrated in FIG. 7A, the photosensitive member 10 is charged by the charging device 30. Generally, a corona discharger is used for the charging device 30. Next, an image is exposed on the charged photoreceptor 10. For example, the image is exposed by a laser scanner to form an electrostatic latent image on the surface of the photoreceptor 10. As shown in FIG. 7B, the portion exposed to the light of the laser scanner becomes conductive, so that the charge disappears, and the portion not exposed to the light remains as an electrostatic latent image that is an image of the charge.
[0043]
Next, as shown in FIG. 7C, the pre-wet liquid described above is applied onto the photoreceptor 10 by the pre-wet apparatus 20.
[0044]
Next, the electrostatic latent image is visualized by the developing device 50. As shown in FIG. 2, the liquid developer discharged from the bellows pump 520 is thinly and uniformly applied to the surface of the developing belt 510 via the plurality of conveying rollers 522a to 522d. Thereby, a thin layer of the liquid developer can be formed on the developing belt 510. The developing device 50 abuts any of the coating units 52a to 52d on the developing belt 510 by rotating the arms 524 and 524 provided in the coating units 52a to 52d. As a result, a liquid developer containing toner of any one of yellow, magenta, cyan and black can be applied thinly and uniformly on the developing belt 510.
[0045]
Next, as shown in FIG. 7D, the liquid developer layer formed on the developing belt 510 is brought close to the electrostatic latent image formed on the surface of the photoreceptor 10 and charged by electrostatic force. The toner thus moved is moved onto the photoreceptor 10. As a result, a toner image is formed on the photoreceptor 10. After the toner image is formed, the separation / contact device 55 is operated, and the photosensitive member 10 and the developing device 510 are developed as shown in FIG. 6B from the state where the photosensitive member 10 and the developing belt 510 are in contact with each other as shown in FIG. Pull the belt 510 apart. The liquid developer remaining on the developing belt 510 is removed by the scraping blade 514.
[0046]
On the other hand, the toner image formed on the photoreceptor 10 is primarily transferred onto the intermediate transfer belt 610 by the transfer device 60 as shown in FIG. Thereafter, the liquid developer remaining on the photoconductor 10 is removed by the cleaning device 70, and the photoconductor 10 is discharged by a charge removal device (not shown).
[0047]
Next, by rotating the arms 524 and 524 provided in each of the coating units 52a to 52d, the coating units 52a to 52d contacting the developing belt 510 are switched. Then, the separation / contact device 55 is actuated again to bring the photoconductor 10 and the developing belt 510 into contact with each other, and then the cycle from charging to discharging is repeated, whereby yellow, magenta, cyan on the intermediate transfer belt 610 is repeated. The black toner images are transferred one after another. As a result, a toner image corresponding to colorization is formed on the intermediate transfer belt 610.
[0048]
Next, as shown in FIG. 7 (F), the toner image corresponding to the coloration formed on the intermediate transfer belt 610 is secondarily transferred and fixed on the paper P as a recording medium by the transfer device 60. The toner image corresponding to colorization 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 heat from the fixing heater 618. At the same time, it melts and fixes thermally. As a result, a color image can be formed on the paper P.
[0049]
8 to 12 are diagrams for explaining in detail the development process of one embodiment of the present invention, FIG. 8 is a diagram for explaining the whole development process, and FIG. 9 is a diagram showing an approach process. FIG. 10 is a view showing the state of the toner moving process, FIG. 11 is a view showing the state of the non-image part separation process, and FIG. 12 is a view showing the state of the image part separation process. Unlike the conventional developing process, the developing process of this embodiment includes an approaching process in which the developing belt 510 approaches the photoreceptor 10 and the liquid developer approaches the surface of the photoreceptor 10 as shown in FIG. The toner moving process in which the developer layer and the pre-wet liquid layer are in soft contact with each other to move the toner, and the toner that the developing belt 510 is separated from the photosensitive member 10 and adheres to the developing belt 510 and the toner that adheres to the photosensitive member 10 It is thought that it consists of three processes, the separation process to be separated.
[0050]
In the approaching process, the developing belt 510 is formed of a flexible belt member, so that the liquid developer layer on the developing belt 510 and the pre-wet layer on the photoconductor 10 are in contact with each other as shown in FIG. The contact pressure at the time is dispersed, and the high-viscosity liquid developer composed of the carrier liquid and toner and the pre-wet liquid are in soft contact. As a result, the pre-wet liquid having a low viscosity is slightly pushed back and forth, and a pool of the pre-wet liquid is generated.
[0051]
In the toner movement process, as shown in FIG. 10, in the image portion, the toner on the developing belt 510 is pre-wet liquid mainly by the Coulomb force due to the electric field formed between the charge on the photosensitive member 10 and the developing belt 510. Move through the layers to the latent image plane. On the other hand, in the non-image portion, the toner on the developing belt 510 does not move to the surface of the photoconductor 10 because the surface of the photoconductor 10 and the liquid developer layer are separated by the pre-wet liquid layer.
[0052]
In the separation process, the liquid developer remains on the developing belt 510 in the non-image area as shown in FIG. When the two layers are separated at the interface between the pre-wet liquid layer and the liquid developer layer, 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 portion, as shown in FIG. 12, since the toner moved to the surface of the photoconductor 10 pushes off the pre-wet liquid layer, the pre-wet liquid layer is located on the toner layer, and both of them are the pre-wet liquid layer. Separate inside. A part of the carrier liquid remaining after the toner moves and a part of the pre-wet liquid form a layer on the developing belt 510.
[0053]
FIG. 13 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 a group of toners that are about to move from the developing belt 510 to the surface of the photosensitive member 10 by electrostatic force are surrounded by the liquid developer layer. A cluster is formed without breaking the viscosity of the toner positioned, and the toner moves to the surface of the photoconductor 10. For this reason, the toner moves excessively, the toner image formed on the photoreceptor 10 is disturbed, and image noise is generated. In order to suppress the occurrence of this cluster, it is necessary to suppress the layer thickness of the liquid developer layer to a minimum value at which development can be sufficiently performed.
[0054]
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 reduced when the viscosity of the liquid developer is 50 to 100 mPa · s or more, particularly when the viscosity is 500 mPa · s or more. Ideally, it is slightly thicker than the layer thickness that satisfies the toner development amount required at the time of development (that is, the density when solid black is produced). This is because when a liquid developer having a high viscosity is used, the electrostatically selected toner is moved onto the photoconductor 10 due to the viscosity of the liquid and moves to the photoconductor 10 at the time of development. This is because the toner image formed in this way is disturbed. In the experiments by the present inventors, a good image was obtained with a layer thickness of about 5 μm for the liquid developer having a high toner concentration and with a layer thickness of about 40 μm for the low developer. In particular, when a liquid developer having a toner concentration of 20 to 30% was used, a good image quality was obtained when the layer thickness of the liquid developer was 8 to 20 μm.
[0055]
The thickness of the pre-wet liquid layer on the photoreceptor 10 has an optimum value depending on the viscosity and surface tension of the selected pre-wet liquid. If it is too thin, the toner on the developing belt 510 irregularly moves on the photoconductor 10 and the toner image formed on the photoconductor 10 is disturbed. As the amount of the pre-wet liquid is increased, the disturbance of the toner image is improved and the optimum value is confirmed. As 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 30 μm or less, particularly 20 μm or less. For those having a lower viscosity than this, a thinner or thicker result can be obtained. However, for high viscosity ones, the optimum value tends to narrow.
[0056]
As a result of conducting an image output experiment under the above-described conditions, the optimum range of the viscosity of the liquid developer and the pre-wet liquid for the electrostatic latent image developing apparatus of this embodiment is from 100 mPa · s to 6000 mPa. It was found that the pre-wet liquid was between 0.5 mPa · s and 5 mPa · s. In addition, DC200 series made by Dow Corning was used for the silicon oil of the prewetting liquid, and DC345 made by the same company was used for the carrier liquid of the developer.
[0057]
According to the present exemplary embodiment, by providing the separation / contact device 55 for separating the development belt 510 from and in contact with the photosensitive member 10, the development belt 510 is disposed only when the liquid developer is supplied to the latent image surface on the photosensitive member 10. It can be brought into contact with the photoreceptor 10. As a result, it is possible to suppress the wear of both the photosensitive member and the developing belt as compared with an apparatus in which the photosensitive member and the developing belt are always in contact. Further, since the surface of the photoconductor 10 can be cleaned by the cleaning device 70 in the state where the photoconductor 10 and the developing belt 510 are separated from each other, the surface of the developing belt 510 can be cleaned by the scraping blade 514. It is possible to prevent liquid developer, pre-wet liquid, or dust from accumulating at the contact start position of both. As a result, it is possible to prevent the surface of the photoconductor 10 from being scratched and to deteriorate the image quality, and it is also possible to prevent several liquid developers corresponding to the respective colors from being mixed and mixed. .
[0058]
In addition, by rotating the developing device 50 about the axis of the drive roller 512a, the contact / separation device that moves the developing belt 510 to and from the photoconductor 10 without changing the distance between the axes of the drive roller 512a and the drive roller 512b. 55 is provided so that the developing belt 510 can always be held at a constant tension. Therefore, when the developing belt 510 and the photosensitive member 10 come in contact with each other, the tension changes, and the developing belt 510 meanders. Problems can be prevented.
[0059]
Furthermore, according to this embodiment, the use of silicon oil as the carrier liquid for the liquid developer has the following advantages over the conventional one.
[0060]
Conventional liquid developers generally use IsoparG (registered trademark: manufactured by Exxon) as a carrier liquid. Since Isopar has a resistance value that is not as high as that of silicone oil, when the toner concentration is increased, that is, when the interparticle distance is decreased, the chargeability of the toner is deteriorated. Therefore, in the case of Isopar, there is a limit to the toner density. On the other hand, since the silicone oil used in this embodiment has a sufficiently large resistance value, the toner density can be increased. In general, in the case of Isopar, the dispersion state of the toner is good. Therefore, even when the toner concentration is 1 to 2%, the toners repel each other, so that the toner is uniformly dispersed. On the other hand, when the toner concentration is 1 to 2%, silicone oil does not have good dispersibility and soon precipitates. However, when the toner concentration is 5 to 40%, the toner is densely packed and stably dispersed. For this reason, in this embodiment, a high-viscosity liquid developer in which toner is dispersed at high density is used. Thereby, compared with the conventional low concentration liquid developer, the amount of the developer can be greatly reduced, and the apparatus can be downsized. Furthermore, since the liquid developer of the present embodiment is a high-viscosity liquid, it is easier in terms of storage and handling than conventional low-viscosity liquid developers and powder developers.
[0061]
As described above, Isopar used in a conventional liquid developer has high volatility and emits a foul odor, which causes a problem that it not only deteriorates the working environment but also causes pollution. On the other hand, the silicone oil used in this example is a safe liquid and odorless, as is clear from the fact that it is used for cosmetics. The environment can be improved and pollution problems do not occur.
[0062]
The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist. For example, in the above embodiment, as a separation / contact device for separating the photoreceptor 10 and the developing belt 510 from each other, the rope 554 having one end attached to the bar 518c is wound around the reel 552, or the wound rope 554 is Although what was performed by solving is demonstrated, this invention is not limited to this. For example, as in the separation / contact device 55a shown in FIG. 14, a cam 551 is provided on the upper side of the developing belt side plates 518 and 518, and the upper surfaces of the developing belt side plates 518 and 518 are always in contact with the cam 551 by the spring 553. You may have done. According to the separation apparatus shown in FIG. 14, by rotating the cam 551, the developing apparatus 50 can be lifted and lowered to be in contact with the photoreceptor 10.
[0063]
Moreover, like the separating / connecting device 55b shown in FIG. 15, a disc wheel 555 having a convex portion 555a at the peripheral edge, one end attached to the convex portion 555a of the disc wheel 555, and the other end to the bar 518c. An attached rope 557 may be used. 15, the developing device 50 can be moved up and down to be brought into contact with and separated from the photoreceptor 10 by rotating the disc wheel 555.
[0064]
Furthermore, a solenoid 559 attached to the bar 518c may be used as in the separation / connection device 55c shown in FIG. According to the separation / connection device shown in FIG. 16, the developing device 50 can be moved up and down to be brought into and out of contact with the photosensitive member 10 by flowing a current through the solenoid 559 or by blocking the current flowing through the solenoid 559. In the separation / contact device shown in FIGS. 14 to 16, as in the case of the above-described embodiment, the developing device can be rotated about the axis of the driving roller 512a. Therefore, the driving roller 512a and the driving roller 512b can be rotated. The developing belt 510 can be brought into and out of contact with the photoreceptor 10 without changing the distance between the axes.
[0065]
In the above-described embodiment, the application unit has been described in which the liquid developer is applied onto the developing belt 510 via the plurality of conveying rollers 522a to 522d. However, the present invention is not limited to this. Any method may be used as long as a thin liquid developer layer can be formed on the developing belt 510. For example, a thin liquid developer layer may be formed on the developing belt 510 by regulating the layer thickness of the liquid developer applied on the developing belt 510 with a rubber or rigid blade.
[0066]
Further, in the above-described embodiment, the application unit 52a for applying the liquid developer containing yellow toner to the developing belt 510, the application unit 52b for applying the liquid developer containing magenta toner to the developing belt 510, and cyan The application unit 52c for applying the liquid developer containing toner to the developing belt 510 and the application unit 52d for applying the liquid developer containing black toner to the developing belt 510 have been described. It is not limited. What is necessary is just to provide at least one application part for applying a liquid developer containing toner of a desired color on the developing belt 510 as required.
[0067]
Further, in the above embodiment, the case where the organic photoreceptor 10 is used as the image support has been described, but the present invention is not limited to this. The image support may be a variety of photosensitive members used in the Carlson method, an ion layer or other conductor on which an electrostatic latent image is directly formed, an electrostatic recording paper such as an electrostatic plotter, or the like.
[0068]
In the above-described embodiment, as a transfer device, the toner image formed on the photoreceptor 10 is primarily transferred onto the intermediate transfer belt 610 that is an intermediate transfer member, and then is primarily transferred onto the intermediate transfer belt 610. Although the description has been given of forming an image on the paper P by secondary transfer of the image onto the paper P, the present invention is not limited to this, and the transfer device is formed on the image support. Any toner image can be used as long as it can be transferred to a recording medium. For example, in a monochrome liquid developing apparatus, a toner image formed on an image support may be directly transferred onto a recording medium without being primarily transferred onto an intermediate transfer member.
[0069]
Furthermore, in the above-described embodiment, the description has been given of the case where the image is exposed on the image support charged by the exposure device 40 and then the pre-wet liquid is applied on the image support by the pre-wet device 20. However, the pre-wetting liquid may be applied before the development step. The pre-wet liquid has a viscosity of 0.5 to 5 mPa · s and an electric resistance of 10¹²If it is Ωcm or more, the boiling point is 100 to 250 ° C., and the surface tension is 21 dyne / cm or less, it does not have to be mainly composed of silicon oil. Further, when a material having a releasability coated on the surface of the image support is used, a prewetting process is not particularly required.
[0070]
Further, the present invention is not limited to the above-described embodiment, and the viscosity of the high-viscosity developer may be 10,000 mPa · s as long as the layer thickness of the liquid developer is about 5 to 40 μm. At present, it is considered that a developer having a high viscosity of 6000 mPa · s or higher is difficult to stir between the carrier liquid and the toner, so that it is not cost effective. Good. Those having a viscosity exceeding 10,000 mPa · s are not realistic. Further, the carrier liquid of the liquid developer is not limited to silicon oil.
[0071]
【The invention's effect】
As described above, according to the first aspect of the present invention, the developer support is used as the image support only when the liquid developer is supplied to the latent image surface on the image support. As a result, the wear of the image support and the developer support can be suppressed as compared with a device in which the image support and the developer support are always in contact, and the image support and the developer support are separated. In this state, both surfaces can be cleaned with a blade or the like, so that developer and dust can be prevented from accumulating at the contact start position between the two, and therefore the surface of the image support is scratched. Image quality can be prevented from deteriorating, and in a color-compatible liquid developing apparatus, several types of liquid developers corresponding to each color can be prevented from being mixed and mixed. A liquid developing apparatus is provided. Door can be.
[0072]
  Also,With the above-described configuration, even when the developer support is separated from the image support, the developer support can always be held at a constant tension. It is possible to provide a liquid developing device for an electrostatic latent image that can prevent running problems such as meandering.
[0073]
  Furthermore,By developing a liquid developer with a high viscosity in which toner is dispersed in a thin layer as a thin layer and developing it, a liquid developing device for electrostatic latent images that can be easily reduced in size with high resolution and can be reduced in pollution is provided. Can be provided.
[0074]
  Claim 2According to the described invention, by having the above configuration,Claim 1In addition to the effects of the described invention, an electrostatic latent image liquid developing apparatus having good wettability of the liquid developer can be provided.
[0075]
  Claim 3According to the described invention, by having the above configuration,Claim 2In addition to the effects of the described invention, it is possible to provide a liquid developing device for an electrostatic latent image that has less pollution and can improve the working environment.
[0076]
  Claim 4According to the described invention, by having the above configuration,Claim 1In addition to the effects of the described invention, it is possible to provide a liquid developing device for an electrostatic latent image that facilitates peeling of toner during transfer.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an electrostatic latent image liquid developing apparatus 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. 1;
FIG. 3 is a left side view of the developing device shown in FIG.
4 is a schematic cross-sectional view in the direction of arrow AA of the developing device shown in FIG.
FIG. 5 is a schematic diagram of the developing device shown in FIG.
6 is a view for explaining the operation of a separation / contact device used in the developing device shown in FIG. 2; FIG.
7 is a diagram for explaining the operation of the electrostatic latent image liquid developing device shown in FIG. 1; FIG.
FIG. 8 is a diagram for explaining the entire development process;
FIG. 9 is a diagram for explaining a state of an approach process.
FIG. 10 is a diagram for explaining a toner moving process.
FIG. 11 is a diagram for explaining a non-image part separation process;
FIG. 12 is a diagram for explaining an image part separation process;
FIG. 13 is a diagram for explaining the significance of thinning the liquid developer.
FIG. 14 is a diagram for explaining the operation of the separating / connecting device used in the modified example of the embodiment.
FIG. 15 is a diagram for explaining the operation of a separation / connection device used in a modification of the present embodiment.
FIG. 16 is a diagram for explaining the operation of the separating / connecting device used in the modified example of the embodiment.
[Explanation of symbols]
10 photoconductor
20 Pre-wet device
30 Charging device
40 Exposure equipment
50 Developer
51 Developer
52 Application part
52a, 52b, 52c, 52d Application part
55, 55a, 55b, 55c Separation device
60 Transfer device
70 Cleaning device
510 Development Belt
510a rib
512a, 512b, 612a, 612b, 612c Driving roller
514,616 scraping blade
518 Side plate for developing belt
518a Adjustment plate
518b oblong hole
518c bar
520a, 520b, 520c, 520d Bellows pump
522a, 522b, 522c, 522d Conveying roller
524 arm
528 Application side plate
551 cam
552 reel
553 Spring
554,557 rope
555 disc car
555a Convex part
559 Solenoid
610 Intermediate transfer belt
614 Secondary transfer roller
618 Fixing heater

Claims (5)

An electrostatic latent image liquid developing apparatus for developing an electrostatic latent image formed on an image support with toner, which is a charged visualization particle,
A developer support that forms a thin layer by transporting a liquid developer having a viscosity of 100 to 10000 mPa · s, in which toner is dispersed in a high concentration in an insulating liquid, with a plurality of transport rollers that are separated from and in contact with the developer support. When,
A separation means for separating and contacting the developer support to the image support,
The developer support is a belt-like one that is held by at least two rollers and has a conductive surface , and the contact / separation means rotates about one of the rollers. By doing so, the developer support is brought into and out of contact with the image support without changing the distance between the axes of the rollers. The liquid developer has an insulating liquid viscosity of 0.5 to 1000 mPa · s, electrical resistance of 10 ¹² Ωcm or more, surface tension of 21 dyne / cm or less, and boiling point of 100 ° C or more. The liquid developing device for electrostatic latent images according to 1.   3. The electrostatic latent image liquid developing apparatus according to claim 2, wherein the liquid developer uses silicon oil as an insulating liquid.   4. The electrostatic latent image liquid developing apparatus according to claim 1, wherein the liquid developer contains toner having an average particle diameter of 0.1 to 5 [mu] m in a concentration of 5 to 40%.   5. The electrostatic latent image liquid developing apparatus according to claim 1, wherein a thickness of a liquid developer layer formed on the developer support is 5 to 40 [mu] m.

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