JP3510252B2 - Apparatus for developing latent images - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates generally to developing devices, and more particularly to latent image developing devices in electrophotographic printing devices.

BACKGROUND OF THE INVENTION Methods for developing a latent image formed on a photoconductive surface by electrophoretic transfer of liquid toner are well known in the art. In this method, charged particles suspended in a non-polar insulating carrier liquid move by the action of an electrostatic field and are concentrated in imaged form on the relative charged or discharged areas of the photoconductive surface. The developed image is then transferred to a substrate such as paper, either directly or by one or more intermediate transfer members.

In U.S. Pat. No. 4,504,138 another method of developing a latent image is described. The patent states that a thin, viscous, dense layer of toner particles is applied to the peripheral surface of the roller, and the layer thus formed is brought to the photoconductive surface. A selected portion of the toner layer is then transferred onto the photoconductive surface by the electric field induced by the latent image.

In Canadian Patent 990 589, an electrostatic image is developed which involves developing a film of liquid toner in a first applicator and contacting the applicator with a final substrate having a latent image. How to do is described. A second applicator with a layer of carrier liquid is then brought into contact with the substrate to remove bag deposits and squeeze out excess liquid. Canadian patent 990 589
The film of the liquid toner described in JP-A No. 2000-242242 has 2 to 4% of the toner concentrate dispersed in the carrier liquid.

The latent image developing device described in U.S. Pat. No. 4,327,664 includes a porous elastic sponge developing roller that is circumferentially surrounded by a fine mesh size net. The developing roller is pressed against the surface of the drum having the latent image, and the liquid toner carried by the roller is squeezed out from the compressed sponge through a fine net. Toner particles contained in the liquid toner are selectively deposited on the surface of the drum by an electrophoretic method to form an image.

U.S. Pat. No. 4,400,079 describes a liquid toner developing device for developing a latent image on an optical receptor using a non-contact developing roller. The surface of the developing roller can move in the same or opposite direction as the surface of the photoreceptor.

Most of the above-mentioned devices, as well as many other techniques known in the art, create a layer of toner on the surface of the developing roller, the entire thickness of which is the latent image in the layer bearing the image. Regarding to transfer to. For such devices, layer thickness uniformity is important because this thickness determines the image density. Generally, controlling the uniformity of the layer being developed is expensive and even using multiple means, especially if the layer thickness is generally dictated by the previous imaging history of the device. Extremely difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a simple method for developing a latent image in an electrophotographic printing apparatus by transferring a concentrated liquid toner in which the optical density of the toner in the tone areas of the final image is generally uniform. It is to provide a device that is realized.

In a preferred embodiment of the present invention, the developer roller, which is preferably made of an elastic material, has a first voltage image area and a second voltage image area.
Voltage is applied against an image forming surface, such as an optical receptor, having a background area formed above the image area. The developing roller is coated with a relatively thin film of concentrated liquid toner material having a predetermined layer thickness. At least a portion of this layer thickness is selectively transferred to the imaging surface according to the latent image formed thereon.

According to one aspect of the invention, the developer is charged to a voltage intermediate the first and second voltages. In the preferred embodiment of the invention, the development voltage is selected so that only a portion of the layer thickness is transferred to the image area of the latent image. The inventor of the present invention has found that when the developing voltage is properly selected, the density of toner particles per unit area (DMA) is more than the layer thickness of the toner concentrate on the developing roller, or the solid concentration of the layer. I found that it was not strongly influenced. Thus, even if the layer thickness on the developing roller varies by an unacceptable amount, the non-uniformity of the layer transferred to the imaging surface is improved by a factor of at least 2.

In a second aspect of the invention, the layer thickness uniformity of the toner concentrate on the developing roller is such that the toner concentrate is pressed against the developing roller, preferably at a speed different from the speed of the developing roller. From the rotating sponge roller,
It is improved by feeding at the contact points between the individual rollers. Uniformity is improved even if the toner concentrate remaining on the developer roller is not removed from the roller before applying a new layer of toner concentrate. When the applicator roller and the developing roller are moving at the same speed at the contact point, there is a noticeable "memory" (trace) of the preceding image, and the non-uniformity is a per unit area of the layer on the developing roller. Affects the developed toner particle mass (DMA).

In the preferred embodiment of the invention, the concentration of toner particles in the layer is increased by applying a squeegee roller charged to the layer prior to transfer to the imaging surface.

In the preferred embodiment of the invention, the applicator roller moves in the opposite direction of the developer roller at the point of contact therebetween.

In one preferred embodiment of the invention, the developing roller is coated with a toner layer by developing a layer of toner particles thereon by electrophoresis from liquid toner using a fixed plate type developing roller. .

Subsequent to the coating step, the layer on the developing roller is squeezed at high voltage and pressure using a squeegee roller so that most of the liquid in that layer is applied to the imaging surface in all or part of the layer thickness. Is preferably removed before transferring.

Further, it is preferable to remove material remaining on the developing roller after developing the latent image in a cleaning step before reapplying the developing roller.

In a preferred embodiment of the present invention, it may be cleaned by a tandem roller system such as a developing roller, where a first pressed squeegee roller removes toner particles from the developing roller by electrostatic transfer. The second sponge cleaning roller preferably removes toner particles from the frictionally pressed squeegee roller assisted by an electrostatic field. The toner digs into the surface of the sponge and is removed from the sponge roller by a blade that scrapes off the extruded material. Preferably, one or both of the squeegee development surface and the squeegee sponge surface are moistened with a cleaning liquid or diluted toner to facilitate transfer and removal of toner particles. The removed toner is preferably circulated and used to recoat the developer roller.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of an image forming apparatus constructed and operative in accordance with a preferred embodiment of the invention, and FIG. 2 is a further development apparatus constructed and operative in accordance with a preferred embodiment of the invention. Detailed Schematic, FIG. 3 is a schematic of a developer assembly showing an alternative cleaning device in accordance with a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Reference is now made to FIGS. 1 and 2 which illustrate an image forming apparatus constructed and operative in accordance with a preferred embodiment of the present invention.

The apparatus includes a drum 10 that preferably has a cylindrical photoreceptor surface 16 made of selenium, a selenium compound, an organic photoconductor or any other suitable photoconductor known in the art. .

During operation, the drum 10 rotates in the direction indicated by the arrow 13,
Photoreceptor surface 16 is charged by charger 18 to a generally uniform predetermined voltage of the order of 1000 volts. The charger 18 may be any type of charger known in the art, such as a crotron, scorotron or roller.

The optical receptor surface 16 charged by the continuous rotation of the drum 10 is used as a laser scanner (in the case of a printer) and an exposure device such as a light source 19 which is a projection of an original plate (in the case of a photocopier). Bring to the image reception relationship. light source
19 selectively discharges a portion of the photoreceptor surface 16 to form the desired latent image on the charged photoreceptor surface 16. The image portion is at the first voltage and the background portion is at the second voltage. The discharged parts preferably have a voltage below about 100 volts.

Subsequent rotation of drum 10 causes selectively charged photoreceptor surface 16 to be in operative contact with surface 21 of developer roller 22. The developing roller 22 is a drum as indicated by an arrow 13.
It is preferable to rotate in the opposite direction to 10, so that the relative movement between the respective faces at the contact points is approximately zero. Most preferably, the developing roller 22 is pressed against the drum 10.

In one embodiment of the present invention, the developing roller 22 is formed from a metal core preferably coated with 1-2 millimeters of a soft elastic material having a Shore A hardness of 20-40. In one embodiment of the invention, the coating is preferably made conductive to a resistance between 10 ⁵ and 10 ⁷ ohm sensors. In this embodiment, the conductive layer is formed by casting or another method so as to have a smooth surface, preferably N ₃ or more.

In a second embodiment of the invention, a soft elastic material, which may be non-conductive, is coated with a very thin conductive layer, such as a metal or conductive lacquer layer electrically attached to a metal core. This conductive layer is preferably 10 ⁷ to 1
It is preferably coated with a thin (preferably 15-60 micrometer) layer of a conductive polymer having a resistance of ⁰⁹ ohm-cm.

Alternatively, the drum 10 is formed of a relatively elastic material,
Surface 21 may be constructed of a rigid or compliant material.

As mentioned above, surface 21 is coated with a thin layer of liquid toner, which is preferably a highly concentrated liquid toner. The developing roller itself 22 is charged to an intermediate voltage between the charging surface and the discharging surface of the optical receptor surface 16.

When surface 21 having the layer of liquid toner concentrate engages photoreceptor surface 16 of drum 10, the potential difference between developer roller 22 and surface 16 causes the layer of toner particles to selectively transfer to surface 16. Develop the latent image. Depending on the choice of toner charge polarity and the use of "write-white" or "write-black" devices well known in the art, either the charged or discharged areas of surface 16 are selectively charged with toner particles. The layer is attracted and the rest of the toner layer continues to adhere to surface 21.

When a liquid toner containing a very high concentration of solids is used during development, as in the preferred embodiment of the present invention, there is less electrophoresis and the entire layer thickness or controllable portion of the layer is on the surface of the developing roller. Is transferred to the image area of the latent image with the toner density approximately the same as

In an alternative and particularly preferred embodiment of the present invention, the voltage difference between the image portion of the latent image and the developing roller is such that only a small fraction of the toner concentrate layer thickness is transferred from the developing roller to the latent image. Decrease the value so that it is transferred to the part.

The thickness of the transferred layer is determined primarily by the amount of charge per unit volume of the layer and is slightly dependent on the local thickness of the layer and / or the concentration of solids. in this way,
Even if the layers on the developer roller are not uniform, the layers transferred to the image areas will have uniform DMA and thus uniform optical density.

This development is probably due to the following effects. When a voltage is applied across the layer of toner concentrate between the developer roller and the image area of the imaging surface, an electric field is created between the two surfaces. This electric field is most intense at the imaging surface and is reduced by charging the layer at points within the layer itself. When a high voltage is applied to a layer of toner concentrate, the electric field in the layer becomes unidirectional, acting to push the entire toner layer toward the imaging surface in the image area. If the applied voltage is low, the electric field can reverse at some point in the layer. For those parts of the layer between this location and the developer roller, the electric field actually acts to press the toner particles towards the developer roller.

If the cohesion of the layer is not too high, the layer is split at or near this point while transferring a portion of the toner layer to the imaging surface and leaving a portion on the developing roller.

The amount of solids transferred is dependent only on the amount of charge per unit mass in the layer and is not strongly related to the layer thickness or the exact concentration of toner particles in the layer. Thus, it can be seen that the developing device of the present invention is not significantly sensitive to changes in the applied parameters that are difficult to control.

Moreover, since DMA is basically directly proportional to the difference in applied voltage, DMA can be easily controlled by changing this voltage. In particular, in the preferred embodiment of the present invention,
As is well known in the art, a sensor 100 is located on the imaging surface downstream of the development area and measures the optical density (and thus DMA) of the image.

The measured value of optical density then controls the controller 102, which operates to control the power supply 104 that supplies voltage to the developer roller 22.

The preferred liquid toner of the present invention is (about 0.17 to 0.25 mgm / cm ²
With a variation of 0.2 mgm / cm ² of DMA from 25 to 30 on the developing layer.
If used at a toner particle concentration of%, the transferred layer is preferably about 0.15 mgm / cm ^2, with a worst case variation of less than ± 10%.

In this state, 500 between the image area and the developing roller
Complete transfer of layers with a voltage difference of ~ 600 volts, while 3
A voltage difference of 00-500 volts results in the more uniform grain transfer described above at a processing speed of 50 millisecond per second.

The use of partial development as described above surprisingly reduces the possible effects of non-uniformity of the toner layer on surface 21. More specifically, the inventor of the present invention has found that the developing surface 21 has about ± 20%
Layer non-uniformity (ie ± 20 of toner layer between various areas
By using the partial development method, it is possible to reduce the nonuniformity of the image portion of the latent image on the photoreceptor surface 16 to less than about ± 10%. If the initial non-uniformity is low, eg ± 5%, the non-uniformity is reduced to the range of 1-2%.

This method provides a more uniform image of density and is particularly useful for halftone imaging where the image density is controlled by the area ratio to be printed.

Other concentrations of liquid toner as high as 40 to 50% relative to the preferred toner material or other toner materials can be used for the layers on the developer roller in the practice of the invention. The exact voltage required for these other toners, other densities or various processing speeds can be determined by experiment.

For multi-color devices, multiple developing rollers, one for each color, can be provided around the photoreceptor, spaced apart, and sequentially engaged with the photoreceptor surface 16 to create latent images in sequence. To develop.

In the preferred embodiment of the invention, the roller 22 is applied by an applicator assembly generally designated by the reference numeral 23.

Applicator assembly 23 includes a toner distributor 62, which can be viewed as having a flute shape, which is a cylindrical tubular shape having a plurality of holes at various locations along its longitudinal dimension. Through which the liquid toner is distributed to the surface 64 of the applicator roller 65. Applicator 65 is preferably formed from a metal core 66 coated with a relatively thick layer 68 of an elastic continuous foam (sponge) such as foamed polyurethane which preferably contains a conductive additive. It is preferred that the polyurethane (non-porous) has a body resistance of between 10 ^{7 and} 10 ⁹ ohm cm. In the preferred embodiment, the surface 64 of the applicator roller 65 is pressed against the surface 21 of the developing roller 22 by, for example, a spring 72 acting on the end of the core 66.

As can be seen in FIG. 2, the distributor 62 is pushed into the applicator roller 65, thereby
It is preferred that the outer surface of 65 be recessed so that a deformed surface 64 is formed. Continued deformation of the surface 64 and compression of the layer 68 act to open the cells of the layer 68 that can occasionally become clogged during operation of the developer assembly 23,
By gradually releasing the deformation, it acts to fill the continuous bubble. Most of the toner dispensed from the dispenser 62 is rapidly absorbed by the layer 68 of the applicator roller 65, the layer being a sponge-like continuous bubble structure and evenly distributed within the layer 68 due to roller deformation. It The pressure required to dispense the toner is preferably supplied by a small pump (not shown) that pumps the toner from a toner container (not shown) at a preset pressure. To this end, any suitable pump known in the art, any suitable container, and others that provide the desired toner pressure (eg, a pressure tank containing the desired liquid toner). Any suitable means can be used. Excess toner not absorbed by layer 68 is returned to the container for reuse.

In the preferred embodiment of the present invention, the developing roller 22 and the applicator roller 65 are shown in FIG.
Because they rotate in the same direction of rotation (as indicated by 13 and 70), their faces move in opposite directions. In this embodiment, the applicator roller 65 rubs against the surface 21,
It acts to remove the residual toner on 21 (usually left after the selective transfer of toner to surface 16), while electrophoresing to provide a new uniform layer of toner to the surface. Specifically, in the preferred embodiment, the absolute velocity of face 64 is preferably about 2-3 times faster than the velocity of face 21.

Assuming that this rubbing action is absent and that the toner remaining on the developing roller after development is not removed, the DMA on the developing roller is non-uniform within a fluctuation range of 30%. Further, the toner remaining on the developing roller after developing the image is extremely concentrated and is not easy to remove, especially if a sponge roller is used for cleaning so as not to damage the surface 21.

As opposed to the preferred method of rubbing type, as the surfaces 21 and 64 meet and meet at the surface mating line 74, the significant relative motion between the surfaces and the pressure exerted by the spring 72 causes residual toner to continue to surface 64. Being scraped off surface 21 by a blunder. During the relatively long face engagement time, the scraped off toner mixes with the fresh toner carried by face 64 without decomposition, and a homogeneous layer of toner forms on face 21 as the face deviates at divergence line 76. Remain.

Roller 65 is preferably charged by a DC power source to a voltage different from that of surface 21 to electrophoretically transfer toner particles from roller 65 to surface 21. The physical contact between the surfaces does not impart an electrophoretically applied layer of toner as previously described, but rather acts to squeeze and homogenize the applied layer of toner. Generally, the solid concentration of the toner rises significantly while electrostatically applying the toner to the surface 21.

In a preferred embodiment of the invention, the solids concentration is between 5% and 10%.
% Of the liquid toner is supplied from the distributor 62 to the roller 65.
The layer has a solids concentration of between 15 and 20% after being applied to the developing roller.

When more concentrated toner is supplied by the distributor 62, the applicator 65 may additionally or alternatively be connected to an AC voltage source, which slightly reduces the viscosity of the toner, and generally of the developer roller 22. The surface 21 acts to weld a smoother layer.

Generally, it is desirable that the layer of the liquid toner for developing the latent image has as high a solid concentration as possible, preferably 30 to 50%.

In the preferred embodiment of the present invention, developer assembly 23 further includes a squeegee roller 78 downstream of distribution roller 65 and in operative contact with roller 22 before roller 22 contacts drum 10. The squeegee roller 78 is charged with a voltage comparable to that of the applicator 65 and the outer surface of the squeegee roller is surface 21.
Emit charged particles in the upper toner layer. Squeegee roller 78
Is also preferably pressed against the roller 22,
As a result, liquid carrier is removed from the layer as it passes through the squeegee roller. The mechanical pressure and the electrical output of the roller 78 act to squeeze the layer of toner so it becomes more concentrated and uniform as it reaches the image bearing surface 16. By adjusting the mechanical pressure and biasing the roller to the appropriate voltage, the density of the toner layer can be adjusted to the desired level.

Thus, in the preferred embodiment, the liquid toner has a density below that required to optimally develop the latent image.
Supplied to 78. When the roller 78 is pressed against the surface 21 of the developing roller 22, it mechanically removes excess toner fluid from the layer applied to the surface 21 and when charged to a suitable potential difference,
The charged toner particles are expelled and the particles are brought into more intimate contact with the surface 21. The excess fluid removed is collected for reuse. The solids content of the layer is mainly a function of the mechanical properties of the roller and the applied voltage and pressure,
Very little is affected by the initial density over a significant range of initial toner densities.

In the preferred embodiment of the invention, the squeegee roller 78 is anodized and coated with a thin (about 50 micrometer) layer of polyurethane.

In principle, the apparatus described above does not require that portions of the toner layer not transferred to the drum 10 during development of the latent image be removed from the development roller 22 during the cycle. However, the inventors of the present invention have discovered that if the residual toner on the developing roller is removed during the coating cycle, the toner uniformity can be further improved. To this end, a cleaning station 82, which may be a sponge or brush or similar device, may be provided to remove excess toner concentrate from the surface 21 of the developer roller 22. The toner thus removed may be mixed with fresh toner and then pumped back through the distributor 62 into the sponge of the applicator 65 for reuse.

The cleaning station 82 preferably comprises a sponge roller 84, which is preferably formed of an elastic continuous cell structure material similar to that of the layer 68 of the roller 65.
Roller 84 is attached to the transfer area (ie, surface 21 engaging surface 16).
Of the residual toner from surface 21 before it is replenished with new toner by resiliently engaging a portion of surface 21 between the application area (ie, the area of surface 21 that engages surface 64). Is located to remove. In the preferred embodiment of the present invention, sponge 84 may be provided with a toner carrier liquid which may facilitate cleaning of surface 21 by loosening and carrying away residual toner particles scraped from the surface.

A third alternative preferred embodiment of the cleaning system 110 is particularly suitable for removing residual toner from the developer roller.
As shown in the figure. The cleaning system 110 includes a tandem roller arrangement in which a first repressed squeegee roller 112 removes residual toner particles from the developer roller 22 by electrostatic transfer. For this purpose, the roller 112 is biased to a voltage that causes charged toner particles to be attracted to the roller 112 in relation to the voltage on the developing roller. The overall structure of roller 112 is preferably similar to that described above for roller 78.

The cleaning roller 114 made of the second sponge is
Friction, preferably with the assistance of an electrostatic field, removes toner particles from the biased squeegee roller 112.
The toner is removed from the sponge roller by a blade 116 that digs into the surface of the sponge and scrapes off the extruded material. Under some circumstances, depending on the toner material used, either or both the squeegee roller / developing roller surface, the squeegee roller / sponge roller surface, or a cleaning liquid or diluted toner that facilitates transfer and removal of toner particles. Be moistened with.

The toner removed by either method is preferably circulated and used to recoat the developer roller.

It has been found that such cleaning tends to reduce or even eliminate the effect of "memory" on the developer roller, if not perfect. The cleaning station 82 is particularly useful when the toner is a type of toner that becomes discharged by the electric field at the interface between the development roller 22 and drum 10 surfaces.

The latent image developed by the methods described above can be transferred directly from the imaging surface to the desired substrate in a manner well known in the art. Alternatively, as shown in FIG. 1, an intermediate transfer member
40 may be provided, which may be a drum or belt and is operatively engaged with the photoreceptor surface 16 of the drum 10 having the developed image. The intermediate transfer member 40 is rotated in the opposite direction of that of the photoreceptor surface 16, as indicated by arrow 43, to provide approximately zero relative movement between the respective surfaces at the image transfer location.

The intermediate transfer member 40 receives the toner image from the photoreceptor surface 16 and operates to transfer the toner image to a final substrate 42 such as paper. A heater 45 may be provided inside the intermediate member 40 to heat the intermediate transfer member 40, as is well known in the art. The transfer of the image to the intermediate transfer member 40 preferably assists in charging the intermediate transfer member 40 to provide an electric field between the intermediate transfer member 40 and the image area of the photoreceptor surface 16. The intermediate transfer member 40 has an underlying elastic layer 46, which is preferably a slightly conductive elastic polymer layer.

Various types of intermediate transfer members are described in, for example, US Pat.
4,684,238, International Patent Publication No. WO 90/04216 and US Pat. No. 4,974,027, the disclosures of all of which are incorporated herein by reference.

Following the transfer of the toner image to substrate 42 or intermediate transfer member 40, photoreceptor surface 16 engages cleaning station 49, which may be any conventional cleaning station. The scraper 56 completes the removal of any residual toner not removed by the cleaning station 49. The lamp 58 then completes the cycle by removing the residual charge of the preceding image from the photoreceptor surface 16.

In the preferred embodiment of the present invention, cleaning station 49 is replaced by the cleaning device shown in FIG. In that case, a slightly softer, more compatible roller is used to ensure good contact between the squeegee roller 112 and the imaging surface.

In an alternative embodiment of the invention reverse transcription is used. In this embodiment, the desired image is formed by the areas of toner concentrate remaining on the surface 21 of the developing roller 22 after the photoreceptor surface 16 has been developed, and then the developing roller rather than the drum 10 is the intermediate transfer member or the final member. To obtain the desired image imprint in operative association with the substrate. The preferred embodiment of the developer assembly described above can also be used with this embodiment.

In yet another preferred embodiment of the present invention, applicator assembly 65 replaces a curved charging plate developer located parallel to the surface of the developer roller at about 6 o'clock on the developer roller. Good. Liquid toner having a solids concentration of about 1-10%, preferably 5-10%, is fed into the region between the plate and the developing roller, and the developing roller has about 5-20% toner solids, preferably 15-20%. The layer having The cleaning roller is then activated to further concentrate the layer to the desired density for developing the latent image. In this embodiment, when the cleaning station 49 is provided, a toner layer having a uniformity of ± 5% is provided on the image forming surface.

A preferred, but not necessarily limiting, liquid toner material for use in the present invention is prepared as follows.

Mixed (DuPont) Surlyn 1605 Ionoma (Io
nomer) 865.4g, (Cabot) Mogul-L carbon black 288.5g, (Cookson) Endurophtal
Blue 28.8 grams and (Merck's) aluminum stearate 17.3 grams, until they are homogeneous, 150
Mix for 20 minutes on a 2-roll mill heated to ℃. The mixed material is removed from the mill and sheared in preparation for the next step.

Plasticized 2 kg of the above materials mixed with Marcol 8 (from EXXON)
22 kg are heated for 1 hour in a double planetary mixer without mixing. The materials are then mixed for 45 minutes at low speed and 30 minutes at high speed. The material is discharged from the mixer while warm, sheared and ground in a cooled meat grinder in preparation for grinding.

Milling-particle size reduction 690 grams of plasticized material weighs 1610 grams in an attritor loaded with 4.76 millimeters (3/16 inch) carbon steel balls.
Crushed with Marcol 82. This material is 30 at 55 ℃ ± 3 ℃
Crushed at 250 RPM for hours. The resulting material is diluted to a non-evaporable solids (NVS) content of 10% and screened through a 300 micrometer screen to remove unmilled particles. The metallic contaminants contained in the toner are removed by magnetic treatment and the resulting material is charged by a charging waveguide to form a 10% NVS liquid developer suitable for the present invention.

It will be appreciated by those skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. The invention is rather defined only by the claims which follow.

Front Page Continuation (72) Inventor Labon, Amiran Israel 59576 Bat Yam, Balfar Street 143/5 (72) Inventor Chatou, Ehud Israel 49100 Petak Tikva, Haaviv Street 15 (56) References JP 57 -185464 (JP, A) JP 54-56844 (JP, A) JP 53-125851 (JP, A) JP 52-139425 (JP, A) JP 4-156485 (JP, A) ) Japanese Patent Laid-Open No. 4-104177 (JP, A) SAI 61-99173 (JP, U) JP-B 51-17049 (JP, B1) JP-A 7-500679 (JP, A) JP-A 6- 508932 (JP, A) Special table 6-506067 (JP, A) Special table 6-506065 (JP, A) Special table 6-500406 (JP, A) Special table 4-505222 (JP, A) US Patent 4974027 (US, A) US Patent 4400079 (US, A) International Publication 92/013299 (WO, A1) International Publication 92/013297 (WO, A1) (5 8) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/10

Claims (22)

(57) [Claims] 1. An image forming surface on which an electrostatic latent image is formed, the electrostatic latent image including an image region of a first voltage and a background region of a second voltage. A surface charged to a third voltage intermediate the first and second voltages, biased against the imaging surface in the development area and operatively engaged therewith. A developing surface, an applicator assembly operable to apply a concentrated liquid toner layer of charged toner particles and a carrier liquid to the developing surface, and a developing device for developing the latent image. , In the developing device, the third voltage transfers a thickness less than the total thickness of the layer of liquid toner concentrated from the developing surface from the developing surface to an image area of the image forming surface, whereby the image A developing device for forming a developed image on the formation surface; A transfer means for transferring the formed image from the image forming surface to the final substrate, the applicator assembly having an applicator having a surface adapted to resiliently engage the developing roller in the application area; Between the developing surface and the applicator, means for elastically pressing the applicator in contact with the developing roller in the area, a toner dispenser operative to supply the applicator with a liquid toner containing charged toner particles and carrier liquid. The electric field created by the voltage difference in the applied area of the voltage biases the applicator to energize the charged toner particles toward the development surface, thereby forming a layer of charged liquid toner concentrate on the development surface. An imaging device comprising a power supply operating to be charged, wherein the applicator and the developing surface make a substantial relative movement in an application area. Location. 2. A developing roller charged to a predetermined potential by the developing device so that an electric field generated by the voltage of the developing roller, the voltage of the image area, and the charging of the toner layer reverses the direction in the layer. The apparatus of claim 1, comprising: 3. The voltage difference between the developing roller and the image forming area is 50.
Device according to claim 1 or 2, characterized in that it is below 0 volts. 4. The voltage difference between the developing roller and the image area is 300.
The bolt is higher than the bolt.
The apparatus according to any one of 1. 5. An image forming surface on which an electrostatic latent image is formed, the electrostatic latent image including an image area of a first voltage and a background area of a second voltage. A developing surface having a surface that is charged to a third voltage intermediate the first and second voltages, is biased against the imaging surface in the developing area, and is operatively engaged therewith; An applicator assembly operative to apply a layer of concentrated liquid toner containing charged toner particles and a carrier liquid to the development surface, the applicator assembly elastically engaging the development roller and the application roller in the application area. An applicator having a mating surface, a means for elastically pressing the applicator into contact with the development surface, and a toner operative to supply liquid toner containing charged toner particles and carrier liquid to the application area. The dispensing device and the application area So that the electric field created by the voltage difference between the developing surface and the applicator urges the charged toner particles toward the developing roller, thereby forming a layer of charged liquid toner concentrate on the developing surface. A power source that operates to charge the applicator with a voltage, wherein the applicator and the developing surface undergo substantial relative movement in the application area, the developing surface being the total thickness of the layer of concentrated liquid toner. At least a part of the thickness of the developed surface is transferred from the developing surface to the image area of the image forming surface to develop the latent image to form the developed image on the image forming surface. An image forming apparatus further comprising means for transferring from an image forming surface to a final substrate. 6. The device according to claim 1, wherein the applicator is a sponge roller including continuous bubble holes. 7. The apparatus according to claim 1, wherein the applicator and the developing surface move in opposite directions in the application area. 8. The apparatus according to claim 7, wherein the relative movement between the applicator and the developing surface is 3 to 4 times the absolute velocity of the developing surface. 9. The relative speed between the developing surface and the applicator is 15
9. Device according to any one of claims 1 to 8, characterized in that it is faster than 0 mm / sec. 10. The toner dispensing device of claim 5, wherein the toner dispensing device includes a porous dispensing tube biased against the applicator in an area remote from the application area. apparatus. 11. The liquid toner supplied to the applicator assembly has a solids concentration of less than 10% and a solids concentration in the toned portion of the developed image is at least 25%. Item 10. The apparatus according to Item 10. 12. A squeegee area downstream of the application area and in front of the development area for operatively engaging the development surface and squeezing the concentrated liquid toner to increase the concentration of the liquid toner. 6. A method according to claim 1, further comprising a charged squeegee roller that operates in the manner described above.
11. The device according to any one of 11 above. 13. A cleaning station operative to remove residual toner from the development surface after development of the latent image and before application of new toner by the applicator assembly. 13. An apparatus according to any one of claims 12 to 13. 14. The apparatus of claim 13 wherein the cleaning station includes a sponge roller adapted for operative engagement with the development surface in the cleaning area downstream of the development area. 15. The cleaning station includes a squeegee roller biased to the surface and biased to a voltage that attracts the particles to the squeegee roller, and biased to the squeegee roller and the squeegee roller. 15. The apparatus of claim 14 comprising a rotating compressible toner absorbing element moving at different speeds with respect to adjacent faces of the roller, and means for removing toner particles from the compressible toner absorbing element. . 16. The apparatus of claim 15, wherein the compressible toner absorbing element is biased to a voltage that attracts toner particles to the roller. 17. An apparatus according to claim 15 or claim 16 including means for supplying liquid to the interface between said squeegee roller and the surface to be cleaned. 18. The apparatus according to claim 15, further comprising means for supplying a liquid to a boundary between the squeegee roller and the compressible toner absorbing element. . 19. A device according to claim 1, wherein the solids concentration in the image portion of the developed image is at least 30%. 20. Apparatus according to claim 1, wherein the solids concentration in the image portion of the developed image is at least 40%. 21. The compressive toner absorbing element is a sponge roller, as claimed in claim 15.
The device according to any one of 20. 22. The means for removing toner particles comprising an element for compressing the compressible toner absorbing element and for removing toner extruded therefrom. The apparatus according to any one of 1.