CA2064848C - Imaging method and apparatus - Google Patents
Imaging method and apparatus Download PDFInfo
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- CA2064848C CA2064848C CA002064848A CA2064848A CA2064848C CA 2064848 C CA2064848 C CA 2064848C CA 002064848 A CA002064848 A CA 002064848A CA 2064848 A CA2064848 A CA 2064848A CA 2064848 C CA2064848 C CA 2064848C
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- liquid
- image
- solids
- toner image
- transfer member
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Classifications
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/06—Apparatus for electrographic processes using a charge pattern for developing
- G03G15/10—Apparatus for electrographic processes using a charge pattern for developing using a liquid developer
- G03G15/11—Removing excess liquid developer, e.g. by heat
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G15/00—Apparatus for electrographic processes using a charge pattern
- G03G15/14—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base
- G03G15/16—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer
- G03G15/1605—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using at least one intermediate support
- G03G15/161—Apparatus for electrographic processes using a charge pattern for transferring a pattern to a second base of a toner pattern, e.g. a powder pattern, e.g. magnetic transfer using at least one intermediate support with means for handling the intermediate support, e.g. heating, cleaning, coating with a transfer agent
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- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/02—Charge-receiving layers
- G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
- G03G5/14—Inert intermediate or cover layers for charge-receiving layers
- G03G5/142—Inert intermediate layers
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G7/00—Selection of materials for use in image-receiving members, i.e. for reversal by physical contact; Manufacture thereof
Abstract
A method and apparatus for transferring liquid toner images from an image forming surface (10) to an intermediate transfer member (40) for subsequent transfer to a final substrate (42). The liquid toner images include carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and which form a single phase at elevated temperatures. The method includes the steps of: concentrating the liquid toner image by compacting the solids portion of the liquid toner image and removing earner liquid therefrom;
transferring the liquid toner image to the intermediate transfer member (40), heating the liquid toner image on the intermediate transfer member (40) to a temperature at which the toner particles and the carrier liquid form a single phase; and transferring the heated liquid toner image to a final substrate (42).
transferring the liquid toner image to the intermediate transfer member (40), heating the liquid toner image on the intermediate transfer member (40) to a temperature at which the toner particles and the carrier liquid form a single phase; and transferring the heated liquid toner image to a final substrate (42).
Description
IMAGING MBTHOD AND APPARTUS
Field of the Invention The present invention relates to image transfer techniques and apparatus for use in electrophotography.
Background of the Invention Liquid toner images are developed by varying the density of pigmented solids in a developer material on a latent image bearing surface in accordance with an imaged pattern. The variations in density are produced by the corresponding pattern of electric fields extending outward from the latent image bearing surface. The fields are produced by the different latent image and background voltages on the latent image bearing surface and a voltage on a developer plate or roller.
In general, developed liquid toner images comprise carrier liquid and toner particles and are not homogeneous.
Typically, a liquid toner developer contains about 1.5~ to 2% solids and a developed image contains about 15% solids.
The developed image has a higher density region closer to the latent image bearing surface and "fluffy", i.e. loosely bound, region further away from the latent image bearing surface .
In order to improve transfer of a developed image from the latent image bearing surface to a substrate, it is most desirable to ensure that, before transfer, the pigmented solids adjacent background regions are substantially removed and that the density of pigmented solids in the developed image is increased, thereby compacting or rigidizing the developed image. Compacting or rigidizing of the developed image increases the image viscosity and enhances the ability PCT/' L90/00099 ~"' ~ ,,~ 5._; Pt A ._.
1 of the image to maintain its integrity under the stresses 2 encountered during image transfer, It is also desirable that 3 excess liquid be removed from the latent image bearing 4 surface before transfer. ' It is known in the prior art, as described in U.S.
6 Patent 3,955,533, to employ a reverse roller spaced about 7 50 microns from the latent image bearing surface to shear 8 off the carrier liquid and pigmented solids in the region 9 beyond the outer edge of the image and thus leave relatively l0 clean areas above the background.
11 The technique of removing carrier liquid is known 12 generally as metering. An alternative metering technique, 13 described in U.S. patents 3,767,300 and 3,741,643, employs 14 an air knife, but has not been particularly successful due to sullying of the background as a result of turbulence, 16 Corona discharge has also been used to compress and remove 17 liquid from a developed liguid image.
18 In U.S. patent 3,957,016, the use of a positive biased 19 metering roller is proposed wherein the metering roller is maintained at a voltage intermediate the image and 21 background voltages to clean the background while somewhat 22 compacting the image.
23 Tn the prior art it is known to effect image transfer 24 from a photoreceptor onto a substrate backed by a charged roller. Unless the image is rigidi~ed before it reaches the 26 nip of the photoreceptor and the roller, image squash and 27 flow may occur. This is particularly true if the substrate 28 is a non-porous material, such as plastic.
29 In the prior art, liquid toner images are generally transferred to substrates by electrophoresis, whereby the 31 charged image moves groin the latent image bearing surface to ~2 the substrate through the carrier liquid under the influence 33 of an electric field produced by a high voltage, associated 34 with the substrate, which is of opposite polarity to the charge on the image particles.
36 The voltage and thus the field strength available for 37 electrophoretic transfer are limited by the danger of 38 electrical breakdown which can occur at both the input and '~'t~ 91/03007 F'CT/'~JL90/00099 1 output edges of the nip, due to the minimum of the Paschen 2 curve being at about 8 micxons. Thus, according to the 3 Paschen curve, the voltage difference at the nip preferably ,4 should not exceed abaut 360 volts, in order, to avoid electrical breakdown and possible damage to the image and 6 latent image bearing surface.
7 ~lectrophoretic compaction of images prior to transfer 8 thereof is described in U.S. Patent 4,286,039 which shows a 9 metering roller followed by a negatively biased squeegee roller. The squeegee roller is operative both for compacting 11 the image and for removing excess liquid.
12 U. S. Patents 4,690,539 and 4,708,460 describe 13 apparatus for removing substantially all of the carrier 14 liquid from a liquid image ~n an image transfer member, prior to transfer to the final substrate.
16 U. S. Patent 4,684,238 describes the use of an 17 electrified roller spaced away~from a liquid image on an 18 intermediate transfer member. The stated object of this 19 mechanism is the compacting of the image and the removal of liquid therefrom.
21 U. S. Patent 4,796,048 describes a system for 22 transferring a liquid tones image from a photoconductor to 23 an image transfer member. The image transfer member is urged 24 against the photoconductor during transfer to squeegee Carrier liquid away from the non-image areas. The image 26 areas are kept in a spaced relationship from the 27 intermediate transfer member by spacer particles in the 28 tuner material as described in U: S. Patent Number 29 4,582,774. This toner material is the only toner described in U. S. Patent 4,796,048 as being a suitable toner.
i~'C) 9 i /0360 - 4 - . .. ;, PCT/; L9il/00099 1 SUMM~ItY OF T'IiiM 1NVEP1TI~~1 2 The present invention seeks to provide improved 3 apparatus far enhancement of image transfer.
4 In a preferred embodiment of the invention a liquid - 5 toner image is transferred from an image forming surface to an intermediate transfer member for subsequent transfer to a 7 final substrate. The liquid toner image includes a liquid 8 portion including carrier liquid and a solids portion including pigmentcad polymeric toner particles which are essentially non-.soluble in the carrier liquid at room 11 temperature, and the polymer portion of which forms 12 substantially a single phase with carrier liquid at elevated 13 temperatures. An imaging method is provided which includes 14 the steps of concentrating the liquid toner image to a given non-volatile solids percentage by compacting the solids 16 portion thereof and removing carrier liquid therefrom;
17 transferring the liquid toner image to an intermediate 18 transfer member; heating the liquid toner image on the 19 intermediate transfer member to a temperature at least as high as that at which the polymer portion of the toner 21 particles and the carrier liquid form substantially a single 22 phase at the given solids percentage; and transferring the 23 heated liquid toner image to a final substrate.
24 In a preferred embodiment of the invention a liquid toner image is transferred from an image farming surface to 2~ an intermediate transfer member for subsequent transfer to a 27 final substrate. The liquid toner image includes a liquid 28 portion including carrier liquid and a solids portion 29 including toner particles. An imaging method is provided which includes the steps of concentrating the liquid toner 31 image by compacting the solids portion thereof and removing 32 carrier liquid therefrom such that the image has a non-33 volatile solids percentage of between, 20~ and 35%;
34 transferring the liquid toner image to an intermediate transfer member; and transferring the liquid toner image to 3s a final substrate.
37 In a preferred embodiment of the invention, the step of 38 concentrating includes the simultaneous application of an 'Wl~ 91 /03007 ~CT/',~L9U/OOJ99 _ ~ ~'a ~iC ,~t !~::'~
1 electric field to compact the solids portion of the image 2 and of pressure to remove liquid from the image.
3 Zn preferred embodiments of the invention the non-4 volatile solids percentage can be about 20, 25%,,:30% or 350 5 or greater after the step of concentration.
Field of the Invention The present invention relates to image transfer techniques and apparatus for use in electrophotography.
Background of the Invention Liquid toner images are developed by varying the density of pigmented solids in a developer material on a latent image bearing surface in accordance with an imaged pattern. The variations in density are produced by the corresponding pattern of electric fields extending outward from the latent image bearing surface. The fields are produced by the different latent image and background voltages on the latent image bearing surface and a voltage on a developer plate or roller.
In general, developed liquid toner images comprise carrier liquid and toner particles and are not homogeneous.
Typically, a liquid toner developer contains about 1.5~ to 2% solids and a developed image contains about 15% solids.
The developed image has a higher density region closer to the latent image bearing surface and "fluffy", i.e. loosely bound, region further away from the latent image bearing surface .
In order to improve transfer of a developed image from the latent image bearing surface to a substrate, it is most desirable to ensure that, before transfer, the pigmented solids adjacent background regions are substantially removed and that the density of pigmented solids in the developed image is increased, thereby compacting or rigidizing the developed image. Compacting or rigidizing of the developed image increases the image viscosity and enhances the ability PCT/' L90/00099 ~"' ~ ,,~ 5._; Pt A ._.
1 of the image to maintain its integrity under the stresses 2 encountered during image transfer, It is also desirable that 3 excess liquid be removed from the latent image bearing 4 surface before transfer. ' It is known in the prior art, as described in U.S.
6 Patent 3,955,533, to employ a reverse roller spaced about 7 50 microns from the latent image bearing surface to shear 8 off the carrier liquid and pigmented solids in the region 9 beyond the outer edge of the image and thus leave relatively l0 clean areas above the background.
11 The technique of removing carrier liquid is known 12 generally as metering. An alternative metering technique, 13 described in U.S. patents 3,767,300 and 3,741,643, employs 14 an air knife, but has not been particularly successful due to sullying of the background as a result of turbulence, 16 Corona discharge has also been used to compress and remove 17 liquid from a developed liguid image.
18 In U.S. patent 3,957,016, the use of a positive biased 19 metering roller is proposed wherein the metering roller is maintained at a voltage intermediate the image and 21 background voltages to clean the background while somewhat 22 compacting the image.
23 Tn the prior art it is known to effect image transfer 24 from a photoreceptor onto a substrate backed by a charged roller. Unless the image is rigidi~ed before it reaches the 26 nip of the photoreceptor and the roller, image squash and 27 flow may occur. This is particularly true if the substrate 28 is a non-porous material, such as plastic.
29 In the prior art, liquid toner images are generally transferred to substrates by electrophoresis, whereby the 31 charged image moves groin the latent image bearing surface to ~2 the substrate through the carrier liquid under the influence 33 of an electric field produced by a high voltage, associated 34 with the substrate, which is of opposite polarity to the charge on the image particles.
36 The voltage and thus the field strength available for 37 electrophoretic transfer are limited by the danger of 38 electrical breakdown which can occur at both the input and '~'t~ 91/03007 F'CT/'~JL90/00099 1 output edges of the nip, due to the minimum of the Paschen 2 curve being at about 8 micxons. Thus, according to the 3 Paschen curve, the voltage difference at the nip preferably ,4 should not exceed abaut 360 volts, in order, to avoid electrical breakdown and possible damage to the image and 6 latent image bearing surface.
7 ~lectrophoretic compaction of images prior to transfer 8 thereof is described in U.S. Patent 4,286,039 which shows a 9 metering roller followed by a negatively biased squeegee roller. The squeegee roller is operative both for compacting 11 the image and for removing excess liquid.
12 U. S. Patents 4,690,539 and 4,708,460 describe 13 apparatus for removing substantially all of the carrier 14 liquid from a liquid image ~n an image transfer member, prior to transfer to the final substrate.
16 U. S. Patent 4,684,238 describes the use of an 17 electrified roller spaced away~from a liquid image on an 18 intermediate transfer member. The stated object of this 19 mechanism is the compacting of the image and the removal of liquid therefrom.
21 U. S. Patent 4,796,048 describes a system for 22 transferring a liquid tones image from a photoconductor to 23 an image transfer member. The image transfer member is urged 24 against the photoconductor during transfer to squeegee Carrier liquid away from the non-image areas. The image 26 areas are kept in a spaced relationship from the 27 intermediate transfer member by spacer particles in the 28 tuner material as described in U: S. Patent Number 29 4,582,774. This toner material is the only toner described in U. S. Patent 4,796,048 as being a suitable toner.
i~'C) 9 i /0360 - 4 - . .. ;, PCT/; L9il/00099 1 SUMM~ItY OF T'IiiM 1NVEP1TI~~1 2 The present invention seeks to provide improved 3 apparatus far enhancement of image transfer.
4 In a preferred embodiment of the invention a liquid - 5 toner image is transferred from an image forming surface to an intermediate transfer member for subsequent transfer to a 7 final substrate. The liquid toner image includes a liquid 8 portion including carrier liquid and a solids portion including pigmentcad polymeric toner particles which are essentially non-.soluble in the carrier liquid at room 11 temperature, and the polymer portion of which forms 12 substantially a single phase with carrier liquid at elevated 13 temperatures. An imaging method is provided which includes 14 the steps of concentrating the liquid toner image to a given non-volatile solids percentage by compacting the solids 16 portion thereof and removing carrier liquid therefrom;
17 transferring the liquid toner image to an intermediate 18 transfer member; heating the liquid toner image on the 19 intermediate transfer member to a temperature at least as high as that at which the polymer portion of the toner 21 particles and the carrier liquid form substantially a single 22 phase at the given solids percentage; and transferring the 23 heated liquid toner image to a final substrate.
24 In a preferred embodiment of the invention a liquid toner image is transferred from an image farming surface to 2~ an intermediate transfer member for subsequent transfer to a 27 final substrate. The liquid toner image includes a liquid 28 portion including carrier liquid and a solids portion 29 including toner particles. An imaging method is provided which includes the steps of concentrating the liquid toner 31 image by compacting the solids portion thereof and removing 32 carrier liquid therefrom such that the image has a non-33 volatile solids percentage of between, 20~ and 35%;
34 transferring the liquid toner image to an intermediate transfer member; and transferring the liquid toner image to 3s a final substrate.
37 In a preferred embodiment of the invention, the step of 38 concentrating includes the simultaneous application of an 'Wl~ 91 /03007 ~CT/',~L9U/OOJ99 _ ~ ~'a ~iC ,~t !~::'~
1 electric field to compact the solids portion of the image 2 and of pressure to remove liquid from the image.
3 Zn preferred embodiments of the invention the non-4 volatile solids percentage can be about 20, 25%,,:30% or 350 5 or greater after the step of concentration.
6 In a preferred embodiment of the invention the single 7 phase is a liquid phase. Alternatively or additionally, in a 8 preferred embodiment of the invention the step of 9 concentrating is operative to increase the solids percentage to a value at which phase separation cannot occur.
11 There is also provided, in a preferred embodiment of i2 the invention, imaging apparatus utilizing a liquid 13 developer comprising carrier liquid and pigmented polymeric 14 toner particles which are essentially non-soluble in the carrier liquid at room temperature, and the polymer portion 16 of which form substantially a single phase with carrier 17 liquid at elevated temperatures, the apparatus including: an 18 image forming surface, apparatus, utilizing the liquid 19 developer, for forming a liquid toner image having a liquid portion including carrier liquid and a solids portion 21 including toner particles, on the image forming surface, 22 apparatus for concentrating the liquid toner image to a 23 given non-volatile solids percentage by compacting the 24 solids portion of the liquid toner image and removing carrier liquid therefrom; apparatus for transferring the 26 liquid toner image to an intermediate transfer member after 27 concentration thereof, apparatus for heating the liquid 28 toner image on the intermediate transfer member to a 29 temperature at least as high as that at which the polymer portion of the toner particles and the carrier liquid form 31 substantially a single phase at the given concentration and 32 apparatus for transferring the liquid toner image, after 33 heating thereof, to a final substrate.
34 There is further provided in a preferred embodiment of the invention, imaging apparatus utilizing a liquid 36 developer, the apparatus including: an image forming 37 surface, apparatus utilizing the liquid developer, for 38 forming a liquid toner image having a liquid portion ~'O 91!03007 Y~'fl.'~1L90/00099 -~.~,,~ .9 .~;.~
1 including carrier liquid and a solids portion including 2 toner particles, on the image forming surface, apparatus for 3 concentrating the liquid toner image by compacting the 4 solids portion thereof and removing carrier liquid ' therefrom, including apparatus far increasing the nor.-6 volatile solids percentage of the liquid toner image to 7 between 20% and 35%, apparatus for transferring the liquid 8 toner image to an intermediate transfer member and apparatus 9 for transferring the liquid toner image from the intermediate transfer member to a final substrate.
11 In a preferred embodiment of the invention the 12 apparatus for concentrating includes apparatus for the 13 simultaneous application of an electric field to compact the 14 solids portion of the image and of mechanical pressure to remove liquid from the image. In a preferred embodiment of 16 the invention the apparatus far concentrating includes an Z7 electrified squeegee roller urged against the image forming 1$ surface.
1~ In a preferred embodiment of the application the single phase is a liquid phase. Alternatively ar additionally, the 21 apparatus far concentrating is operative to increase the 22 solids percentage to a value at which phase separation 23 cannot occur.
24 In a preferred embodiment o~ the invention the imaging apparatus also includes optical radiation apparatus far 26 discharging both image and background areas prior to image 27 transfer to the image transfer member. In a preferred 28 embodiment of the invention the optical radiation apparatus 2~ includes at least one light emitting diode. In a preferred embodiment, the optical radiation apparatus includes at 31 least two radiation sources radiating different color light.
WtJ 91 /0300? PC'('/;~L90/00099 ~'~.':i a ~~ °.~:'~
.- ~ ... J
1 BRIEF OE8CRIPTION OF THE DRATaTIN~S
The present invention will be understood and 3 appreciated more fully from the follawing detailed description, taken in conjunction with the drawings in " 5 which:
Fig. 1 is a simplified sectional illustration of 7 electrophotographic apparatus constructed and operative in 8 accordance with a preferred embodiment of the present 9 invention; and Fig. 2 is part of a partial simplified typical phase 11 diagram for a preferred liquid toner for the present 12 invention.
_8_ Detailed Description of Preferred Embodiments Reference is now made to Fig. 1 which illustrates electrophotographic imaging apparatus constructed and operative in accordance with a preferred embodiment of the present invention.
The invention is described for liquid developer systems with negatively charged toner particles, and negatively charged photoconductors, i.e., systems operating in the reversal mode.
For other combinations of toner particle and photoconductor polarity, the values and polarities of the voltages are changed, in accordance with the principles of the invention.
The invention can be practiced using a variety of liquid developer types but is especially useful for liquid developers comprising carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and which solvate carrier liquid at elevated temperatures. This is a characteristic of the liquid developer of Example 1 of U.S. Patent 4,794,651. Part of a simplified phase diagram of a typical toner of this type is shown in Fig. 2. This diagram represents the states of the polymer portion of the toner particles and the carrier liquid. The pigment in the particles generally takes little part in the process, and references herein to ~~single phase~~ and to ~~solvation~~ refer to the state of the polymer part of the toner particles together with the carrier liquid.
In a preferred embodiment of the invention a liquid developer is prepared by mixing 10 parts of Elvax II 5950*
(E. I. du Pont) and 5 parts by weight of Isopar L* (Exxon) at low speed in a jacketed double planetary mixer connected to an oil heating unit for one hour, the heating unit being set at 130°C.
A mixture of 2.5 parts by weight of Mogul L* carbon black (Cabot) and 5 parts by weight of Isopar L* is then added to the mix in the double planetary mixer and the resultant mixture is further mixed for one hour at high speed. 20 parts by weight of Isopar L* pre-heated to 110°C
* Trade marks are added to the mixer and mixing is continued at high speed for one hour. The heating unit is disconnected and mixing is continued until the temperature of the mixture drops to 40°C
100 g of the resulting material is mixed with 120 g of Isopar L' and the mixture is milled for 19 hours in an attritor to obtain a dispersion of particles. The material is dispersed in Isopar L' to a solids content of 1.5% by weight.
The preferred liquid developer prepared comprises toner particles which are formed with a plurality of fibrous extensions or tendrils as described in U.S. Patent 4,794,651. The preferred liquid developer is characterized in that when the concentration of toner particles is increased above 20%, the viscosity of the material increases greatly, apparently in approximately and exponential manner.
A charge director, prepared in accordance with Example 1 of US Patent No. 5,047,306 issued September 10, 1991 is added to the dispersion in an amount equal to about 3% of the weight of the solids in the developer.
As in conventional electrophotographic systems, the apparatus of Fig. 1 typically comprises a drum 10 arranged for rotation about an axle 12 in a direction generally indicated by arrow 14.
Drum 10 is formed with a cylindrical photoconductor surface 16.
A corona discharge device 18 is operative to generally uniformly charge photoconductor surface 16 with a negative charge.
Continued rotation of drum 10 brings charged photoconductor surface 16 into image receiving relationship with an exposure unit including a lens 20, which focuses an image onto charged photoconductor surface 16, selectively discharging the photoconductor surface, thus producing an electrostatic latent image thereon. The latent image comprises image areas at a given range of potentials and * Trade marks WO 91/03007 P~1'%~iL90/00099 _ lfl _ ,~f ."~ r~<.~
1 background areas at a different potential. The image may be 2 laser generated as in printing from ~a computer or it may be 3 the image of an original as in a copier.
4 Continued, rotation of drum 10 brings charged .5 photoconductor surface 16, bearing the electrostatic latent 6 iaage, into a development unit 22, which is operative to 7 apply liquid developer, comprising a solids portion 8 including pigmented toner particles and a liquid portion 9 including carrier liquid, to develop the electrostatic latent image. The developed image includes image areas 11 having pigmented toner particles thereon and background 12 areas. Development unit 22 may be a single color developer 13 of any conventional type, or may be a plurality of single 14 color developers for the production of full color images as is known in the art. Alternatively, full color images may be 16 produced by changing the liquid toner in the development 17 unit when the color to be printed is changed. Alternatively, 18 highlight color development may be employed, as is known in 19 the art.
In accordance with a preferred embodiment of the 21 invention, fol2owing application of toner thereto, 22 photoconductor surface 16 passes a typically charged 23 rotating roller 26, preferably rotating in a direction 24 indicated by an arrow 28. Typically the spatial separation of the roller 26 from the photoconductor surface 16 is about 26 50 microns. Roller 26 thus acts as a metering roller as is 27 known in the art, reducing the amount of carrier liquid on 28 the background areas and reducing the amount of liquid 29 overlaying the image.
Preferably the potential on roller 26 is intermediate 31 that of the latent image areas and of the background areas 32 on the photoconductor surface. Typical approximate voltages ' 33 are: roller 26: -500 V, background area: -1000 ~7 and latent 34 image areas: -150 V.
The liquid toner image which passes roller 26 should be 36 relatively free of pigmented particles except in the region 3'~ of the latent image.
38 Downstream of roller 26 there is preferably provided a rigidizing roller 30. Rigidizing roller 30 is preferably formed of resilient polymeric material, such as polyurethane which may have only its natural conductivity or which may be filled with carbon black to increase its conductivity.
According to one embodiment of the invention, roller 30 is urged against photoconductor surface 16 as by a spring mounting (not shown). The surface of roller 30 typically moves in the same direction and with the same velocity as the photoconductor surface to remove liquid from the image.
Preferably, the biased squeegee described in U.S.
Patent 4,286,039 is used as the roller 30. Roller 30 is biased to a potential of at least several hundred and up to several thousand Volts with respect to the potential of the developed image on photoconductor surface 16, so that it repels the charged pigmented particles and causes them to more closely approach the image areas of the photoconductor surface 16, thus compacting and rigidizing the image.
In a preferred embodiment of the invention, rigidizing roller 30 comprises an aluminum core having a 20 mm diameter, coated with a 4 mm thick carbon-filled polyurethane coating having a Shore A hardness of about 30-35, and a volume resistivity of about 108 ohm-cm. Preferably roller 30 is urged against photoconductor surface 16 with a pressure of about 40-70 grams per linear cm of contact, which extends along the length of the drum. The core of rigidizing roller 30 is energized to between about -1800 and -2800 volts, to provide a voltage difference of preferably between about 1600 and 2700 volts between the core and the photoconductor surface in the image areas. Voltage differences of as low as 600 volts are also useful.
After rigidization under these conditions and for the preferred toner, the solids percentage in the image portion is believed to be as high as 35% or more, when carrier liquid absorbed as plasticizer is considered as part of the solids portion. It is preferable to have an image with at least 20-30% solids, after rigidizing. When the solids percentage is calculated on a non-volatile solids basis, the solids percentage is preferably above 20% and is usually less than 30%. Values of 25% have been found to especially useful. At these concentrations the material has a paste s like consistency.
Alternatively, the carbon filled polyurethane can be replaced by unfilled polyurethane with a volume resistivity of about 3 x 101°, and the voltage is adjusted to give proper rigidizing.
Downstream of rigidizing roller 30 there is preferably provided a plurality of light emitting diodes (LEDs) 29 to discharge the photoconductor surface, and equalize the potential between image and background areas. For process color systems, where yellow, magenta and cyan toners are used, both red and green LEDs are provided to discharge the areas of the photoconductor behind the developed image as well as the background areas.
Downstream of LEDs 29 there is provided an intermediate transfer member 40, which rotates in a direction opposite to that of photoconductor surface 16, as shown by arrow 41. The intermediate transfer member is operative for receiving the toner image from the photoconductor surface and for subsequently transferring the toner image to a receiving substrate 42, such as paper.
Various types of intermediate transfer members are known and are described, for example, in U.S. Patent 4,684,238 and in U.S. Patent No. 5,636,349 issued June 3, 1997and U.S. Patent No. 5,028,964 issued July 2, 1991.
In general, intermediate transfer member 40 is urged against photoconductor surface 16. One of the effects of the rigidization described above is to prevent substantial squash or other distortion of the image caused by the pressure resulting from the urging. The rigidization effect is especially pronounced due to the sharp increase of 1'dCJ 91/03007 PC'i'/'~L90/0009G
~.f 'S''~s ~"vi~
.. .~ s J
1 viscosity with concentration for the preferred toner.
2 Transfer of the image to interanediate transfer mer"ber 3 40 is preferably sided by providing electrical bias to the .4 intermediate transfer member 40 to attract the charged toner thereto, although other methods known im the art may be 6 employed. Subsequent transfer of the image to substrate 42 7 is preferably aided by heat and pressure, with pressure 8 applied by a backing roller 43, although other methods known 9 in the art may be employed.
l0 It has been noted that when the negatively biased 11 squeegee roller of U.S. Patent 4,286,039, with high negative 12 voltage, is utilized as the roller 30, the voltage 13 difference between the intermediate transfer member and the 14 photoconductor surface, required to transfer the image to i5 the intermediate transfer member is sharply reduced. It is 16 believed that this reduction is possibly due to current flow 17 tending to equalize and discharge the potential of image and 18 background areas on the image bearing surface. LEDs 29 19 discharge both image and non-image areas and are operative 20 to further reduce this voltage difference.
21 For the particular illustrative example described 22 herein, the intermediate transfer member voltage is between 23 --300 V and 0 V where no pre~transfer LEDs are used and 24 between X200 V and +500 V where they are used.
25 Following transfer of the toner image to the 26 intermediate transfer member, photoconductor surface 16 is 27 engaged by a cleaning roller 50, which typically rotates in 28 a direction indicated by an arrow 52, such that its surface 29 moves in a.directian opposite to the movement of adjacent 30 photoconductor surface 16 which it operatively engages.
31 Cleaning roller 50 is operative to scrub and clean surface 32 16. A cleaning material, such as toner, may be supplied to 33 the cleaning roller 50, via a conduit 54. A wiper blade 56 34 completes the cleaning of the photoconductor surface. Any 35 residual charge left on photocanductor surface 16 is removed 36 by flooding the photoconductor surface with light from a 37 lamp 58.
38 In a.multi-color system, subsequent to completion of the cycle for one color , the cycle is sequentially repeated for the other colors which are sequentially transferred from photoconductor surface 16 to intermediate transfer member 40. The single color images may be sequentially transferred to the paper, in alignment, or may alternatively be overlaid on the intermediate transfer member and transferred as a group to the substrate 42.
Details of the construction of the surface layers of preferred intermediate transfer members are shown in assignee's U.S. Patent No. 5,089,856 issued February 18, 1992.
Generally, the image is heated on intermediate transfer member 40 in order to facilitate its transfer to substrate 42. This heating is preferably to a temperature above a threshold temperature of substantial solvation of the carrier liquid in the toner particles.
As seen in Fig. 2, when the image is heated, the state of the image, i.e. of the polymer portion of the toner particles and the carrier liquid, depends on several factors, mainly on the temperature of the intermediate transfer member and on the concentration of toner particles.
Thus, if the percentage of toner particles is "A" and the intermediate transfer member temperature is "Y" the liquid image separates into two phases, one phase being substantially a liquid polymer/ carrier-liquid phase and the other phase consisting mainly of carrier liquid. On the other hand, if the percentage of toner particles is "B" at the same temperature, then substantially only one phase, a liquid polymer/carrier-liquid phase will be present. It is believed to be preferable that separate liquid polymer/carrier-liquid and liquid phases do not form to any substantial degree, as will be the case for example if the concentration is "C".
This type of phase separation is believed to be undesirable on the intermediate transfer member. It is believed that an absence of substantial phase separation of this type in the image on the intermediate transfer member results in improved image quality, including an improvement in line uniformity.
It is understood that heating the image on the intermediate transfer member is not meant to completely dry the image, although some evaporation of carrier liquid may result. Rather, the image on the intermediate transfer member remains a viscous liquid until its transfer to the final substrate.
The invention has been described by a specific embodiment utilizing an electrified squeegee roller for concentrating the liquid toner image on the photoconductor surface. Alternatively other methods of concentrating the image, i.e., compacting the solids portion thereof and removing liquid therefrom, can be utilized provided they concentrate the image to the extent required. These methods include the use of separate solids portion compactors and liquid removal means, such as those described in U.S. Patent No. 5,028,964 issued July 2, 1991. Alternatively the apparatus may utilize a solids portion compactor followed by an intermediate transfer member urged against the photoconductor to remove liquid from the image. As a further alternative, the commutated intermediate transfer member described in U.S. Patent No. 5,028,964 may be used to provide both solids portion compacting and liquid removal, just prior to transfer to the intermediate transfer member.
Furthermore the concentrating step may take place on the intermediate transfer member after transfer of the liquid toner image thereto and before heating the image.
It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the present invention is defined only by the claims which follow:
11 There is also provided, in a preferred embodiment of i2 the invention, imaging apparatus utilizing a liquid 13 developer comprising carrier liquid and pigmented polymeric 14 toner particles which are essentially non-soluble in the carrier liquid at room temperature, and the polymer portion 16 of which form substantially a single phase with carrier 17 liquid at elevated temperatures, the apparatus including: an 18 image forming surface, apparatus, utilizing the liquid 19 developer, for forming a liquid toner image having a liquid portion including carrier liquid and a solids portion 21 including toner particles, on the image forming surface, 22 apparatus for concentrating the liquid toner image to a 23 given non-volatile solids percentage by compacting the 24 solids portion of the liquid toner image and removing carrier liquid therefrom; apparatus for transferring the 26 liquid toner image to an intermediate transfer member after 27 concentration thereof, apparatus for heating the liquid 28 toner image on the intermediate transfer member to a 29 temperature at least as high as that at which the polymer portion of the toner particles and the carrier liquid form 31 substantially a single phase at the given concentration and 32 apparatus for transferring the liquid toner image, after 33 heating thereof, to a final substrate.
34 There is further provided in a preferred embodiment of the invention, imaging apparatus utilizing a liquid 36 developer, the apparatus including: an image forming 37 surface, apparatus utilizing the liquid developer, for 38 forming a liquid toner image having a liquid portion ~'O 91!03007 Y~'fl.'~1L90/00099 -~.~,,~ .9 .~;.~
1 including carrier liquid and a solids portion including 2 toner particles, on the image forming surface, apparatus for 3 concentrating the liquid toner image by compacting the 4 solids portion thereof and removing carrier liquid ' therefrom, including apparatus far increasing the nor.-6 volatile solids percentage of the liquid toner image to 7 between 20% and 35%, apparatus for transferring the liquid 8 toner image to an intermediate transfer member and apparatus 9 for transferring the liquid toner image from the intermediate transfer member to a final substrate.
11 In a preferred embodiment of the invention the 12 apparatus for concentrating includes apparatus for the 13 simultaneous application of an electric field to compact the 14 solids portion of the image and of mechanical pressure to remove liquid from the image. In a preferred embodiment of 16 the invention the apparatus far concentrating includes an Z7 electrified squeegee roller urged against the image forming 1$ surface.
1~ In a preferred embodiment of the application the single phase is a liquid phase. Alternatively ar additionally, the 21 apparatus far concentrating is operative to increase the 22 solids percentage to a value at which phase separation 23 cannot occur.
24 In a preferred embodiment o~ the invention the imaging apparatus also includes optical radiation apparatus far 26 discharging both image and background areas prior to image 27 transfer to the image transfer member. In a preferred 28 embodiment of the invention the optical radiation apparatus 2~ includes at least one light emitting diode. In a preferred embodiment, the optical radiation apparatus includes at 31 least two radiation sources radiating different color light.
WtJ 91 /0300? PC'('/;~L90/00099 ~'~.':i a ~~ °.~:'~
.- ~ ... J
1 BRIEF OE8CRIPTION OF THE DRATaTIN~S
The present invention will be understood and 3 appreciated more fully from the follawing detailed description, taken in conjunction with the drawings in " 5 which:
Fig. 1 is a simplified sectional illustration of 7 electrophotographic apparatus constructed and operative in 8 accordance with a preferred embodiment of the present 9 invention; and Fig. 2 is part of a partial simplified typical phase 11 diagram for a preferred liquid toner for the present 12 invention.
_8_ Detailed Description of Preferred Embodiments Reference is now made to Fig. 1 which illustrates electrophotographic imaging apparatus constructed and operative in accordance with a preferred embodiment of the present invention.
The invention is described for liquid developer systems with negatively charged toner particles, and negatively charged photoconductors, i.e., systems operating in the reversal mode.
For other combinations of toner particle and photoconductor polarity, the values and polarities of the voltages are changed, in accordance with the principles of the invention.
The invention can be practiced using a variety of liquid developer types but is especially useful for liquid developers comprising carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature, and which solvate carrier liquid at elevated temperatures. This is a characteristic of the liquid developer of Example 1 of U.S. Patent 4,794,651. Part of a simplified phase diagram of a typical toner of this type is shown in Fig. 2. This diagram represents the states of the polymer portion of the toner particles and the carrier liquid. The pigment in the particles generally takes little part in the process, and references herein to ~~single phase~~ and to ~~solvation~~ refer to the state of the polymer part of the toner particles together with the carrier liquid.
In a preferred embodiment of the invention a liquid developer is prepared by mixing 10 parts of Elvax II 5950*
(E. I. du Pont) and 5 parts by weight of Isopar L* (Exxon) at low speed in a jacketed double planetary mixer connected to an oil heating unit for one hour, the heating unit being set at 130°C.
A mixture of 2.5 parts by weight of Mogul L* carbon black (Cabot) and 5 parts by weight of Isopar L* is then added to the mix in the double planetary mixer and the resultant mixture is further mixed for one hour at high speed. 20 parts by weight of Isopar L* pre-heated to 110°C
* Trade marks are added to the mixer and mixing is continued at high speed for one hour. The heating unit is disconnected and mixing is continued until the temperature of the mixture drops to 40°C
100 g of the resulting material is mixed with 120 g of Isopar L' and the mixture is milled for 19 hours in an attritor to obtain a dispersion of particles. The material is dispersed in Isopar L' to a solids content of 1.5% by weight.
The preferred liquid developer prepared comprises toner particles which are formed with a plurality of fibrous extensions or tendrils as described in U.S. Patent 4,794,651. The preferred liquid developer is characterized in that when the concentration of toner particles is increased above 20%, the viscosity of the material increases greatly, apparently in approximately and exponential manner.
A charge director, prepared in accordance with Example 1 of US Patent No. 5,047,306 issued September 10, 1991 is added to the dispersion in an amount equal to about 3% of the weight of the solids in the developer.
As in conventional electrophotographic systems, the apparatus of Fig. 1 typically comprises a drum 10 arranged for rotation about an axle 12 in a direction generally indicated by arrow 14.
Drum 10 is formed with a cylindrical photoconductor surface 16.
A corona discharge device 18 is operative to generally uniformly charge photoconductor surface 16 with a negative charge.
Continued rotation of drum 10 brings charged photoconductor surface 16 into image receiving relationship with an exposure unit including a lens 20, which focuses an image onto charged photoconductor surface 16, selectively discharging the photoconductor surface, thus producing an electrostatic latent image thereon. The latent image comprises image areas at a given range of potentials and * Trade marks WO 91/03007 P~1'%~iL90/00099 _ lfl _ ,~f ."~ r~<.~
1 background areas at a different potential. The image may be 2 laser generated as in printing from ~a computer or it may be 3 the image of an original as in a copier.
4 Continued, rotation of drum 10 brings charged .5 photoconductor surface 16, bearing the electrostatic latent 6 iaage, into a development unit 22, which is operative to 7 apply liquid developer, comprising a solids portion 8 including pigmented toner particles and a liquid portion 9 including carrier liquid, to develop the electrostatic latent image. The developed image includes image areas 11 having pigmented toner particles thereon and background 12 areas. Development unit 22 may be a single color developer 13 of any conventional type, or may be a plurality of single 14 color developers for the production of full color images as is known in the art. Alternatively, full color images may be 16 produced by changing the liquid toner in the development 17 unit when the color to be printed is changed. Alternatively, 18 highlight color development may be employed, as is known in 19 the art.
In accordance with a preferred embodiment of the 21 invention, fol2owing application of toner thereto, 22 photoconductor surface 16 passes a typically charged 23 rotating roller 26, preferably rotating in a direction 24 indicated by an arrow 28. Typically the spatial separation of the roller 26 from the photoconductor surface 16 is about 26 50 microns. Roller 26 thus acts as a metering roller as is 27 known in the art, reducing the amount of carrier liquid on 28 the background areas and reducing the amount of liquid 29 overlaying the image.
Preferably the potential on roller 26 is intermediate 31 that of the latent image areas and of the background areas 32 on the photoconductor surface. Typical approximate voltages ' 33 are: roller 26: -500 V, background area: -1000 ~7 and latent 34 image areas: -150 V.
The liquid toner image which passes roller 26 should be 36 relatively free of pigmented particles except in the region 3'~ of the latent image.
38 Downstream of roller 26 there is preferably provided a rigidizing roller 30. Rigidizing roller 30 is preferably formed of resilient polymeric material, such as polyurethane which may have only its natural conductivity or which may be filled with carbon black to increase its conductivity.
According to one embodiment of the invention, roller 30 is urged against photoconductor surface 16 as by a spring mounting (not shown). The surface of roller 30 typically moves in the same direction and with the same velocity as the photoconductor surface to remove liquid from the image.
Preferably, the biased squeegee described in U.S.
Patent 4,286,039 is used as the roller 30. Roller 30 is biased to a potential of at least several hundred and up to several thousand Volts with respect to the potential of the developed image on photoconductor surface 16, so that it repels the charged pigmented particles and causes them to more closely approach the image areas of the photoconductor surface 16, thus compacting and rigidizing the image.
In a preferred embodiment of the invention, rigidizing roller 30 comprises an aluminum core having a 20 mm diameter, coated with a 4 mm thick carbon-filled polyurethane coating having a Shore A hardness of about 30-35, and a volume resistivity of about 108 ohm-cm. Preferably roller 30 is urged against photoconductor surface 16 with a pressure of about 40-70 grams per linear cm of contact, which extends along the length of the drum. The core of rigidizing roller 30 is energized to between about -1800 and -2800 volts, to provide a voltage difference of preferably between about 1600 and 2700 volts between the core and the photoconductor surface in the image areas. Voltage differences of as low as 600 volts are also useful.
After rigidization under these conditions and for the preferred toner, the solids percentage in the image portion is believed to be as high as 35% or more, when carrier liquid absorbed as plasticizer is considered as part of the solids portion. It is preferable to have an image with at least 20-30% solids, after rigidizing. When the solids percentage is calculated on a non-volatile solids basis, the solids percentage is preferably above 20% and is usually less than 30%. Values of 25% have been found to especially useful. At these concentrations the material has a paste s like consistency.
Alternatively, the carbon filled polyurethane can be replaced by unfilled polyurethane with a volume resistivity of about 3 x 101°, and the voltage is adjusted to give proper rigidizing.
Downstream of rigidizing roller 30 there is preferably provided a plurality of light emitting diodes (LEDs) 29 to discharge the photoconductor surface, and equalize the potential between image and background areas. For process color systems, where yellow, magenta and cyan toners are used, both red and green LEDs are provided to discharge the areas of the photoconductor behind the developed image as well as the background areas.
Downstream of LEDs 29 there is provided an intermediate transfer member 40, which rotates in a direction opposite to that of photoconductor surface 16, as shown by arrow 41. The intermediate transfer member is operative for receiving the toner image from the photoconductor surface and for subsequently transferring the toner image to a receiving substrate 42, such as paper.
Various types of intermediate transfer members are known and are described, for example, in U.S. Patent 4,684,238 and in U.S. Patent No. 5,636,349 issued June 3, 1997and U.S. Patent No. 5,028,964 issued July 2, 1991.
In general, intermediate transfer member 40 is urged against photoconductor surface 16. One of the effects of the rigidization described above is to prevent substantial squash or other distortion of the image caused by the pressure resulting from the urging. The rigidization effect is especially pronounced due to the sharp increase of 1'dCJ 91/03007 PC'i'/'~L90/0009G
~.f 'S''~s ~"vi~
.. .~ s J
1 viscosity with concentration for the preferred toner.
2 Transfer of the image to interanediate transfer mer"ber 3 40 is preferably sided by providing electrical bias to the .4 intermediate transfer member 40 to attract the charged toner thereto, although other methods known im the art may be 6 employed. Subsequent transfer of the image to substrate 42 7 is preferably aided by heat and pressure, with pressure 8 applied by a backing roller 43, although other methods known 9 in the art may be employed.
l0 It has been noted that when the negatively biased 11 squeegee roller of U.S. Patent 4,286,039, with high negative 12 voltage, is utilized as the roller 30, the voltage 13 difference between the intermediate transfer member and the 14 photoconductor surface, required to transfer the image to i5 the intermediate transfer member is sharply reduced. It is 16 believed that this reduction is possibly due to current flow 17 tending to equalize and discharge the potential of image and 18 background areas on the image bearing surface. LEDs 29 19 discharge both image and non-image areas and are operative 20 to further reduce this voltage difference.
21 For the particular illustrative example described 22 herein, the intermediate transfer member voltage is between 23 --300 V and 0 V where no pre~transfer LEDs are used and 24 between X200 V and +500 V where they are used.
25 Following transfer of the toner image to the 26 intermediate transfer member, photoconductor surface 16 is 27 engaged by a cleaning roller 50, which typically rotates in 28 a direction indicated by an arrow 52, such that its surface 29 moves in a.directian opposite to the movement of adjacent 30 photoconductor surface 16 which it operatively engages.
31 Cleaning roller 50 is operative to scrub and clean surface 32 16. A cleaning material, such as toner, may be supplied to 33 the cleaning roller 50, via a conduit 54. A wiper blade 56 34 completes the cleaning of the photoconductor surface. Any 35 residual charge left on photocanductor surface 16 is removed 36 by flooding the photoconductor surface with light from a 37 lamp 58.
38 In a.multi-color system, subsequent to completion of the cycle for one color , the cycle is sequentially repeated for the other colors which are sequentially transferred from photoconductor surface 16 to intermediate transfer member 40. The single color images may be sequentially transferred to the paper, in alignment, or may alternatively be overlaid on the intermediate transfer member and transferred as a group to the substrate 42.
Details of the construction of the surface layers of preferred intermediate transfer members are shown in assignee's U.S. Patent No. 5,089,856 issued February 18, 1992.
Generally, the image is heated on intermediate transfer member 40 in order to facilitate its transfer to substrate 42. This heating is preferably to a temperature above a threshold temperature of substantial solvation of the carrier liquid in the toner particles.
As seen in Fig. 2, when the image is heated, the state of the image, i.e. of the polymer portion of the toner particles and the carrier liquid, depends on several factors, mainly on the temperature of the intermediate transfer member and on the concentration of toner particles.
Thus, if the percentage of toner particles is "A" and the intermediate transfer member temperature is "Y" the liquid image separates into two phases, one phase being substantially a liquid polymer/ carrier-liquid phase and the other phase consisting mainly of carrier liquid. On the other hand, if the percentage of toner particles is "B" at the same temperature, then substantially only one phase, a liquid polymer/carrier-liquid phase will be present. It is believed to be preferable that separate liquid polymer/carrier-liquid and liquid phases do not form to any substantial degree, as will be the case for example if the concentration is "C".
This type of phase separation is believed to be undesirable on the intermediate transfer member. It is believed that an absence of substantial phase separation of this type in the image on the intermediate transfer member results in improved image quality, including an improvement in line uniformity.
It is understood that heating the image on the intermediate transfer member is not meant to completely dry the image, although some evaporation of carrier liquid may result. Rather, the image on the intermediate transfer member remains a viscous liquid until its transfer to the final substrate.
The invention has been described by a specific embodiment utilizing an electrified squeegee roller for concentrating the liquid toner image on the photoconductor surface. Alternatively other methods of concentrating the image, i.e., compacting the solids portion thereof and removing liquid therefrom, can be utilized provided they concentrate the image to the extent required. These methods include the use of separate solids portion compactors and liquid removal means, such as those described in U.S. Patent No. 5,028,964 issued July 2, 1991. Alternatively the apparatus may utilize a solids portion compactor followed by an intermediate transfer member urged against the photoconductor to remove liquid from the image. As a further alternative, the commutated intermediate transfer member described in U.S. Patent No. 5,028,964 may be used to provide both solids portion compacting and liquid removal, just prior to transfer to the intermediate transfer member.
Furthermore the concentrating step may take place on the intermediate transfer member after transfer of the liquid toner image thereto and before heating the image.
It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described herein above. Rather the scope of the present invention is defined only by the claims which follow:
Claims (23)
1. A method for transferring a liquid toner image including a liquid portion comprising carrier liquid and a solids portion which includes pigmented polymeric toner particles being essentially non-soluble in the carrier liquid at room temperature, said method for transferring being operative to transfer a liquid toner image from an image forming surface to a final substrate, and comprising the steps of:
concentrating the liquid toner image to a given non-volatile solids percentage by compacting the solids portion thereof and removing carrier liquid therefrom; and transferring the liquid toner image to an intermediate transfer member; and heating the liquid toner image on the intermediate transfer member to a given temperature at least as high as an elevated temperature at which the toner particles and carrier liquid at the given solids percentage form substantially a single phase; and transferring the liquid toner image to the final substrate from the intermediate transfer member.
concentrating the liquid toner image to a given non-volatile solids percentage by compacting the solids portion thereof and removing carrier liquid therefrom; and transferring the liquid toner image to an intermediate transfer member; and heating the liquid toner image on the intermediate transfer member to a given temperature at least as high as an elevated temperature at which the toner particles and carrier liquid at the given solids percentage form substantially a single phase; and transferring the liquid toner image to the final substrate from the intermediate transfer member.
2. A method according to claim 1, wherein said single phase is a liquid phase.
3. A method according to claim 1 or claim 2, wherein said step of concentrating is operative to increase said solids percentage to a value at which phase separation cannot occur.
4. A method according to claim 1 wherein said solids percentage is above about 20%.
5. A method according to any of the preceding claims wherein concentrating the liquid image precedes said step of transferring the liquid image to the intermediate transfer member.
6. A method for transferring a liquid toner image comprising a solids portion and a liquid portion from an image forming surface to a final substrate comprising:
concentrating the liquid toner image by compacting the solids portion thereof and removing carrier liquid therefrom such that the image has a non-volatile solids percentage of between 20 and 35%;
transferring the liquid toner image to an intermediate transfer member after the step of concentrating; and transferring the liquid toner image to the final substrate from the intermediate transfer member.
concentrating the liquid toner image by compacting the solids portion thereof and removing carrier liquid therefrom such that the image has a non-volatile solids percentage of between 20 and 35%;
transferring the liquid toner image to an intermediate transfer member after the step of concentrating; and transferring the liquid toner image to the final substrate from the intermediate transfer member.
7. A method according to any of the preceding claims wherein said step of concentrating comprises the simultaneous application of an electric field to compact the solids portion of the image and of mechanical pressure to remove liquid from the image.
8. A method according to any of the preceding claims wherein said solids percentage is below about 30 %.
9. A method according to any of the preceding claims wherein said solids percentage is about 25 %.
10. A method according to any of the preceding claims and also including the step of irradiating the image with optical radiation.
11. A method according to claim 10 wherein said optical radiation includes radiation from at least two radiation sources radiating different color light.
12. Imaging apparatus utilizing a liquid developer comprising carrier liquid and pigmented polymeric toner particles which are essentially non-soluble in the carrier liquid at room temperature the apparatus comprising:
an image forming surface (16) having a liquid toner image formed form said liquid developer and comprising a liquid portion comprising carrier liquid and a solids portion comprising toner particles, on said image forming surface;
a concentrator (28,30) which concentrates the liquid toner image by compacting the solids portion of the liquid toner image and removing carrier liquid therefrom to form a liquid image having a given non-volatile solids percentage; and an image transfer member (40) to which the image is transfered after concentration thereof and from which it is transferred to a final substrate (42); and a heater which heats the liquid toner image on the intermediate transfer member to a temperature at least as high as that at which the toner particles and the carrier liquid form substantially a single phase at the given solids percentage.
an image forming surface (16) having a liquid toner image formed form said liquid developer and comprising a liquid portion comprising carrier liquid and a solids portion comprising toner particles, on said image forming surface;
a concentrator (28,30) which concentrates the liquid toner image by compacting the solids portion of the liquid toner image and removing carrier liquid therefrom to form a liquid image having a given non-volatile solids percentage; and an image transfer member (40) to which the image is transfered after concentration thereof and from which it is transferred to a final substrate (42); and a heater which heats the liquid toner image on the intermediate transfer member to a temperature at least as high as that at which the toner particles and the carrier liquid form substantially a single phase at the given solids percentage.
13. Apparatus according to claim 12, wherein said single phase is a liquid phase.
14. Apparatus according to claim 12 or 13, wherein said concentrator is operative to increase said solids percentage to a value at which phase separation cannot occur.
15. Apparatus according to any of claims 12-14 wherein said solids percentage is above about 20 %.
16. Imaging apparatus utilizing a liquid developer, said apparatus comprising:
an image forming surface (16) having a liquid toner image formed form said liquid developer and comprising a liquid portion comprising carrier liquid and a solids portion comprising toner particles, on said image forming surface;
a concentrator (28,30) which concentrates the liquid toner image by compacting the solids portion of the liquid toner image and removing carrier liquid therefrom to increase the non-volatile solids percentage of said liquid toner image to between about 20 % and 35 %;
an intermediate transfer member (40) to which the image is transferred prior to transfer to the final substrate.
an image forming surface (16) having a liquid toner image formed form said liquid developer and comprising a liquid portion comprising carrier liquid and a solids portion comprising toner particles, on said image forming surface;
a concentrator (28,30) which concentrates the liquid toner image by compacting the solids portion of the liquid toner image and removing carrier liquid therefrom to increase the non-volatile solids percentage of said liquid toner image to between about 20 % and 35 %;
an intermediate transfer member (40) to which the image is transferred prior to transfer to the final substrate.
17. Apparatus according to any of claims 12-16 wherein the concentrator is operative to simultaneously apply, to the image an electric field to compact the solids portion of the image and of mechanical pressure to remove liquid from the image.
18. Apparatus according to any one of claims 12-17 where said concentrator comprises an electrified squeegee roller (30) urged against said image forming surface.
19. Apparatus according to any one of claims 12-18, wherein said solids percentage is below about 30 %.
20. Apparatus according to any one of claims 12-19, wherein said solids percentage is about 25 %.
21. Apparatus according to any one of claims 12-20 and also including a source of optical radiation (29) which discharges both image and background areas prior to image transfer to said image transfer member.
22. Apparatus according to claim 21 wherein said source of optical radiation includes at least one light emitting diode.
23. Apparatus according to claim 21 or claim 22 wherein said source of optical radiation includes at least two radiation sources radiating different color light.
Applications Claiming Priority (12)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/393,649 US5047808A (en) | 1989-02-06 | 1989-08-14 | Image transfer apparatus including a compliant transfer member |
| US393,649 | 1989-08-14 | ||
| US400,717 | 1989-08-30 | ||
| US07/400,717 US5555185A (en) | 1988-09-08 | 1989-08-30 | Method and apparatus for imaging using an intermediate transfer member |
| US44687789A | 1989-12-06 | 1989-12-06 | |
| US446,877 | 1989-12-06 | ||
| US50828790A | 1990-04-13 | 1990-04-13 | |
| US508,287 | 1990-04-13 | ||
| PCT/NL1990/000049 WO1991003006A1 (en) | 1989-08-14 | 1990-04-17 | Image transfer apparatus and method |
| NLPCT/NL90/00048 | 1990-04-17 | ||
| PCT/NL1990/000099 WO1991003007A1 (en) | 1989-08-14 | 1990-07-23 | Imaging method and apparatus |
| CA002075948A CA2075948C (en) | 1989-01-04 | 1990-12-13 | Imaging system with intermediate transfer member |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2064848A1 CA2064848A1 (en) | 1991-02-15 |
| CA2064848C true CA2064848C (en) | 2001-05-29 |
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|---|---|---|---|
| CA002064848A Expired - Fee Related CA2064848C (en) | 1989-08-14 | 1990-07-23 | Imaging method and apparatus |
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| EP (1) | EP0486534B1 (en) |
| JP (1) | JP3263069B2 (en) |
| CA (1) | CA2064848C (en) |
| DE (1) | DE69013000T2 (en) |
| HK (1) | HK137595A (en) |
| WO (1) | WO1991003007A1 (en) |
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| US5592269A (en) * | 1993-03-26 | 1997-01-07 | Indigo N.V. | Imaging system having an intermediate transfer member |
| WO1993011472A1 (en) * | 1991-11-29 | 1993-06-10 | Spectrum Sciences B.V. | Serial electrographic imaging apparatus |
| US5570173A (en) * | 1994-10-31 | 1996-10-29 | Xerox Corporation | Color printer using liquid developer |
| IL112731A0 (en) * | 1995-02-21 | 1995-05-26 | Indigo Nv | Imaging apparatus with temperature control |
| IL114992A0 (en) | 1995-08-17 | 1995-12-08 | Indigo Nv | Intermediate transfer blanket and method of producing the same |
| AU7098896A (en) * | 1995-09-08 | 1997-03-27 | Indigo N.V. | Imaging apparatus and improved exit device therefor |
| US5655192A (en) * | 1996-04-01 | 1997-08-05 | Xerox Corporation | Method and apparatus for compaction of a liquid ink developed image in a liquid ink type electrostatographic system |
| CA2292592A1 (en) | 1997-06-03 | 1998-12-10 | Indigo N.V. | Intermediate transfer blanket and method of producing the same |
| WO2003017008A1 (en) * | 2001-08-21 | 2003-02-27 | Pfu Limited | Liquid development electrophotographic device |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4286039A (en) * | 1979-05-15 | 1981-08-25 | Savin Corporation | Method and apparatus for removing excess developing liquid from photoconductive surfaces |
| US4794651A (en) * | 1984-12-10 | 1988-12-27 | Savin Corporation | Toner for use in compositions for developing latent electrostatic images, method of making the same, and liquid composition using the improved toner |
| US4684238A (en) * | 1986-06-09 | 1987-08-04 | Xerox Corporation | Intermediate transfer apparatus |
| US4708460A (en) * | 1986-07-25 | 1987-11-24 | Xerox Corporation | Simultaneous transfer and fusing in electrophotography |
| US4796048A (en) * | 1987-11-23 | 1989-01-03 | Xerox Corporation | Resilient intermediate transfer member and apparatus for liquid ink development |
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1990
- 1990-07-23 WO PCT/NL1990/000099 patent/WO1991003007A1/en active IP Right Grant
- 1990-07-23 EP EP90911661A patent/EP0486534B1/en not_active Expired - Lifetime
- 1990-07-23 DE DE69013000T patent/DE69013000T2/en not_active Expired - Lifetime
- 1990-07-23 CA CA002064848A patent/CA2064848C/en not_active Expired - Fee Related
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| EP0486534A1 (en) | 1992-05-27 |
| DE69013000D1 (en) | 1994-11-03 |
| EP0486534B1 (en) | 1994-09-28 |
| JPH04507303A (en) | 1992-12-17 |
| CA2064848A1 (en) | 1991-02-15 |
| HK137595A (en) | 1995-09-08 |
| JP3263069B2 (en) | 2002-03-04 |
| DE69013000T2 (en) | 1995-05-04 |
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