CA1120337A - Developing latent electrostatic images using a liquid toner and a development electrode - Google Patents
Developing latent electrostatic images using a liquid toner and a development electrodeInfo
- Publication number
- CA1120337A CA1120337A CA000326155A CA326155A CA1120337A CA 1120337 A CA1120337 A CA 1120337A CA 000326155 A CA000326155 A CA 000326155A CA 326155 A CA326155 A CA 326155A CA 1120337 A CA1120337 A CA 1120337A
- Authority
- CA
- Canada
- Prior art keywords
- development electrode
- insulating liquid
- toner
- bias voltage
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
- G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
- G03G13/00—Electrographic processes using a charge pattern
- G03G13/06—Developing
- G03G13/10—Developing using a liquid developer, e.g. liquid suspension
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Wet Developing In Electrophotography (AREA)
- Developing For Electrophotography (AREA)
- Electrochromic Elements, Electrophoresis, Or Variable Reflection Or Absorption Elements (AREA)
Abstract
ABSTRACT
A method and apparatus for developing a latent electrostatic image on the surface of an electrophotographic member using an A.C. bias voltage applied between the electrophotographic member and a development electrode.
A method and apparatus for developing a latent electrostatic image on the surface of an electrophotographic member using an A.C. bias voltage applied between the electrophotographic member and a development electrode.
Description
This inventi~n relates to a method and apparatus for developing latent electrostatic images using a liquid toner and a development electrode.
It is known to form a latent electrostatic image on the surface of an electrophotographic membe. by first applying a uniform electrostatic charge to the surface and then exposing the surface to a pattern of light; thereafter, the latent electrostatic image thus formed is developed with a toner before it has deteriorated.
The two types of toners most frequently used in developing latent electrostatic images are liquid toners and dry powder toners, Liquid toners, which appear to be necessary for high spatial resolution, are made up essentially of small pigmented particles, called toner particles, dispersed in an insulating liquid. When a liquid toner is brought into contact with a surface containing a latent electrostatic image, such as by immersing the surface in a chamber containing liquid toner, the toner particles in the liquid migrate to the surface and deposit on the image bearing portions through a phenomenon known a.s electrophoresis.
When it is desired to reproduce a continuous tone image or an image containing a solid area, a device known as a development electrode is usually employed to assist in the developing operation. The development electrode consists basically of a flat electrically conductive plate positioned proximate and parallel to the image bearing surface, The development electrode changes the field configuration of the electrostati.c image and increases the field in the space above areas of uniform charge. The development electrode further intensifi.es the electrical field near the image bearing surface.
Normally, the development electrode is electrically shorted to the electrophoto~raphic member Jt has been found that special effects can be obtained such as reversal toning or fog reduction, by establishing a D.C. potential difference bet~een the development electrode and the electrophotographic member during the development electrode and the electrophoto~raphic member during the development process.
Liquid toners have been found to have a tendency to generate spatially stable convection cells during the developing opeeation when used with a development electrode.
These convection cells, which are generally spheri.cally ~haped, are formed over a range of field strengths and h~ve the effect of shielding portions of the surface of the electrophotographic member rom coming into contact with the toner particles, As a result of the convection cells, a cellular shaped optical density pattern is superimposed over the image pattern and is visible in the developed image. The siæe of the convecti.on cells which are formed is dependent on the fi.eld strength, the volume concentration of toner particles, and the spacing between the electrophotographic surface and the development el.ectrode. The range of field strengths over whi.ch the convection cells ~re formed can vary depending on the composit;on of the particul.al^ ~.i.quid toner. It i.s believed tha~ such convection cells a~e formed as a result. of 11;~0337 hydrodynamic instability in liquid toners.
The generation of these convection cells may be avoided by performing the developing operation at field steengths o~ltside the range at which the cells have a tendency to form This could be achieved by changing the spacing between the electrophotographic member and the development electrode since the field strength varies directly with voltage on the photoconductive surface of the electrophotographic member and inversely with the distance between the development eJectrode and the electrophotographic member. Such expedient is not satisfactory since most el~ctrophotographic members requi~e a range of field strengths to produce good continuous tone images or good images containing solid areas which is within the range, or includes at least some part of the range, of field strengths over which the convection cells are generated Thus, a need arises to provide a more feasible technique for preventing the formation of such convection cells for the purpose of promoting uniform deposition of toner particles in areas of uniform charge density during the development of said electrostatic images.
According to the teachings of this invention, the generation of convection cells in a liquid toner when used ~ith a development electrode to develop an electrostatic image on an electrophotographic member is prevented without adve~sely effecting sensitometry, image detail or developing time, by applying an A C. bias voltage between the electrophotographic member and the development electrode during the developing operation. Apparatus is provided for effecting such development by applying said A.C. bias voltage.
03~7 The preferred embodiment~ of this invention now will be described, by way of example, with reference to the drawings accompanying this specification in which:
Figure 1 is a diagrammatic sectional view of an apparatus for cleveloping a latent electrostatic image on the surface of an electrophotographic member according to the teachings of this invention, some of the parts being drawn out of p~oportion for ease in viewing;
Figure 2 is a photomicrograph enlarged ten times,lshowing the cellular densi~y pattern formed on an image developed with a liquid toner and a development electrode as a result of convection cells being generated in the liquid toner during the developing process; and Figure 3 is a photomicrograph enlarged ten times showing lS how the cellular pattern referred to above is greatly reduced by applying the teachings of this invention.
Referring to Figure 1, there is shown an electrophoto-_5 _ 0;137 Referring to Figure 1, there is shown an electrophoto_graphic member identified generally by reference numeral 1l.
Electrophotographic member 11 includes a photoconductive layer 13 and a conductive substrate 15. The conductive substrate 15 includes a conductive layer 17 and a base or carrier 19.
S PhotoconducLive layer 13 is formed of R.F. sputtered cadmium sulfide and conductive substrate 1~ is a layer of indium-tin-oxide on a polyester plastic base.
A development electrode 21 is provided for use in assisting in developing a l,atent electrostatic image on the surface of photoconductive layer 13. Electeode 21 is positioned above the electrophotographic member 11 and a quantity o~ a liquid toner type developer 23 is disposed in the space between the electrophotographic member 11 and the , development electrode 21, The liquid toner 23, which is confined in a chamber (not shown), includes toner particles 25 suspended i,n a non-csnductive (electrically i,nsulating) liquid 27. The particular liquid toner employed is dependent upon the characteristics of the particular electrophotographic member. One preferable liquid toner comprises a comminuted powder of carbon and resin dispersed in an isoparaffinic hydrocarbon fraction available from the Exxon Company of Houston, Texas, under the name of "Isopar".~
Jt is believed that the A.C. bias voltage eliminates the hydrodynamic instahility of the liquid toner which produces the convection cells by interrupting or disturbing the otherwise unidirectional movement of the charged toner particles to the photoconductive surface. These interruptions or disturbances il'~O337 result in chan~es in direction of the forces exerted by the particles on the liquid in which the pflrticles are suspended, The A.C. bias waveform is preferably symmetrically shaped. The range of frequencies and amplitudes of the A.C.
S bias over which formation o~ the convection cells is either prevented or reduced to some noticeable extent is dependent on the particular liquid toner employed, the distance between the electrophotographic member and the development electrode and the maximum charge voltage on the electrophotograppic member.
If the frequency of the A.C. bias is either too high or too low the resulting changes in the direction of movement of the toner particles will have insufficient effect on the direction of movement of the in.sulating liquid and consequently, will not prevent the generation of the convection cells. If the amplitude of the A,C. bias is too low it will not effect the movement of the toner particles which control the movem~nt of the insulating liquid. If the amplitude of the A C. bias is too high it will prevent generation of the convection cells but will also prevent the toner particles from depositing on the surface of the electrophotographic membe~.
Preferably, the half-wave amplitude of the A C. bias should be equal to at least the maximum charge voltage on the photoconductive surface. If the amplitude is not up to this level, the bias voltage will not inte~rupt the movement of the toner partic~es sufficiently to prevent the generation 11'~0337 of the convection cells in the higher ~oltage image areas.
lhe effectiveness of the A.C. bias also depends on its waveform. For a given frequency and amplitude a square waveform is more effective in inhibiting formation of convection cells than a sinusoidal waveform, and a sinusoidal waveform is more efective th~n a triangular waveform It has been found, however, that any waveform may be used to prevent formation of convection cells by suitable adjustment of the A.C. frequency and/or amplitude For every combination of electrophotographic member, charge voltage, liquid toner, and physical arrangement, there exists an optimum combination of A C. bias amplitude, frequency, and waveform which can prevent formation of the convection cells believed responsible for the objectionable cellular optical density pattern in uniformly-charged image areas. The optimum combination can be ascertained in each instance of application.
Herein, an A.C source 29 is connected between the development electrode 21 and the conductive layer 17 to provide an A C. voltage bias between the two members. The A.C
voltage bias is applied between these two members to prevent the formation of convection cells in the liquid toner. The A G. bias voltage is applied at least dùring the time period the liquid toner is disposed between the two me~bers and during the process of developing the electrostatic image.
The invention will be more fully appreciated with reference to the following examples;
EXAMPI.E I
An electrophotographic member containing an R.F. sputtered cadmium sulfide photoconductive layer was uniformly corona charged to a negative surface potenti,al of 25 volts, contacted with a grainless ~tep tablet, exposed to a Xenon discharge light pulse and then developed for a period of about 15 seconds using a liquid toner comprising a comminuted powder of carbon and resin dispersed in Isopar and a development electrode that was parallel to, and spaced 0.010 inches from, the photoconductive surface of the electrophotographic member.
Throughout the developing operation the development electrode and the. electrophotographic member were both held at ground potential. The developed image contained a severe cellular density pattern superimposed on the image pattern. A
photomicrograph of the developed ima~e is shown in Figure 2, EXAMPLE II
Rxample I was repeated, except that during the developing operation a symmetrical sinusoidal A.C. bias havi,ng a peak-to-peak amplitude of 50 volts and a frequency of 44 Hz and a D,~.
level of 0 volts was applied between the development electrode ' and the electrophotographic member, The substantial reduction in the cellular density pattern is shown in Figure 3.
EXAMPLE III
Example I was again repeated except that the electrophoto-graphic membe~ was charged to a negative surface potential of10 volts~ the A.C. bias voltage had a peak-to-peak amplitude 11'~0337 of 68 volt.s alld a frequency of 7.S H7., and the liquid toner wa~ dilu~ d by a factor of 2, The cellular densi.ty pattern was compl~tel.y eliminated.
EXA7.~lPLS IV THROUGH VIII
.. . .
An ~1ectrophotographic Ine!nl~eL~ of the same type as used in Exampl.e 1 was uniformly corona charged to a negative su.face potentia~ of 15 volts and exposed to an image light pattern, The member was then developed for a period of about 15 seconds using a liqui~ toner and a development electrode th~t was parallel to, and spaced 0,0l5 inches from the photocon~uctive su~ace o the electrophotographic membe~. The liquid toner was comprised of a comminuted powder of carbon and resin dispersed in Isopar, but having no fixi.ng resi.n as in Æxample ~, The following ta1~1e shows the -.-esults when no bias voltage was applied and then when square wave biaæ voltage of different frequencies and a~plitudes were applied.
PEAK-TO-PEAKCELLULAR DENSITY
EXAMPLE A.C. FREQUENCY A.C. A~LITUDEPATTERN
IV NO BIAS VOLTAGE PRESENT
V 5 H~ 50 VOLTS ELI~IINATED
. .
VII l0 H~ 25 VOLTS ELIMINATED
.
Example VII shor~7s that the A.C. bias ellecti.vely removed the cellula~ density pattern even though the peak-to-peak voltage was less than the sutface potential on the photo-11;~0337 conductive surface of the electrophotographic member.
It can be appreciated that the concept of applying an A.~, bias voltage to prevent the formation of convection cells in a liquid toner which is di~persed between two parallel conductive member~s can find use also in electrophoretic display devices wherein a quantity of liquid toner is disposed between two paral.lel electrodes which are connected to voltage sources of different polarity.
The ~,C. bias voltage applied accordi.ng to the te~chings of this invention, can be superimposed over a D,C, bias voltage applied for some othe~^ purpose, such as reversal toning, for example.
It is known to form a latent electrostatic image on the surface of an electrophotographic membe. by first applying a uniform electrostatic charge to the surface and then exposing the surface to a pattern of light; thereafter, the latent electrostatic image thus formed is developed with a toner before it has deteriorated.
The two types of toners most frequently used in developing latent electrostatic images are liquid toners and dry powder toners, Liquid toners, which appear to be necessary for high spatial resolution, are made up essentially of small pigmented particles, called toner particles, dispersed in an insulating liquid. When a liquid toner is brought into contact with a surface containing a latent electrostatic image, such as by immersing the surface in a chamber containing liquid toner, the toner particles in the liquid migrate to the surface and deposit on the image bearing portions through a phenomenon known a.s electrophoresis.
When it is desired to reproduce a continuous tone image or an image containing a solid area, a device known as a development electrode is usually employed to assist in the developing operation. The development electrode consists basically of a flat electrically conductive plate positioned proximate and parallel to the image bearing surface, The development electrode changes the field configuration of the electrostati.c image and increases the field in the space above areas of uniform charge. The development electrode further intensifi.es the electrical field near the image bearing surface.
Normally, the development electrode is electrically shorted to the electrophoto~raphic member Jt has been found that special effects can be obtained such as reversal toning or fog reduction, by establishing a D.C. potential difference bet~een the development electrode and the electrophotographic member during the development electrode and the electrophoto~raphic member during the development process.
Liquid toners have been found to have a tendency to generate spatially stable convection cells during the developing opeeation when used with a development electrode.
These convection cells, which are generally spheri.cally ~haped, are formed over a range of field strengths and h~ve the effect of shielding portions of the surface of the electrophotographic member rom coming into contact with the toner particles, As a result of the convection cells, a cellular shaped optical density pattern is superimposed over the image pattern and is visible in the developed image. The siæe of the convecti.on cells which are formed is dependent on the fi.eld strength, the volume concentration of toner particles, and the spacing between the electrophotographic surface and the development el.ectrode. The range of field strengths over whi.ch the convection cells ~re formed can vary depending on the composit;on of the particul.al^ ~.i.quid toner. It i.s believed tha~ such convection cells a~e formed as a result. of 11;~0337 hydrodynamic instability in liquid toners.
The generation of these convection cells may be avoided by performing the developing operation at field steengths o~ltside the range at which the cells have a tendency to form This could be achieved by changing the spacing between the electrophotographic member and the development electrode since the field strength varies directly with voltage on the photoconductive surface of the electrophotographic member and inversely with the distance between the development eJectrode and the electrophotographic member. Such expedient is not satisfactory since most el~ctrophotographic members requi~e a range of field strengths to produce good continuous tone images or good images containing solid areas which is within the range, or includes at least some part of the range, of field strengths over which the convection cells are generated Thus, a need arises to provide a more feasible technique for preventing the formation of such convection cells for the purpose of promoting uniform deposition of toner particles in areas of uniform charge density during the development of said electrostatic images.
According to the teachings of this invention, the generation of convection cells in a liquid toner when used ~ith a development electrode to develop an electrostatic image on an electrophotographic member is prevented without adve~sely effecting sensitometry, image detail or developing time, by applying an A C. bias voltage between the electrophotographic member and the development electrode during the developing operation. Apparatus is provided for effecting such development by applying said A.C. bias voltage.
03~7 The preferred embodiment~ of this invention now will be described, by way of example, with reference to the drawings accompanying this specification in which:
Figure 1 is a diagrammatic sectional view of an apparatus for cleveloping a latent electrostatic image on the surface of an electrophotographic member according to the teachings of this invention, some of the parts being drawn out of p~oportion for ease in viewing;
Figure 2 is a photomicrograph enlarged ten times,lshowing the cellular densi~y pattern formed on an image developed with a liquid toner and a development electrode as a result of convection cells being generated in the liquid toner during the developing process; and Figure 3 is a photomicrograph enlarged ten times showing lS how the cellular pattern referred to above is greatly reduced by applying the teachings of this invention.
Referring to Figure 1, there is shown an electrophoto-_5 _ 0;137 Referring to Figure 1, there is shown an electrophoto_graphic member identified generally by reference numeral 1l.
Electrophotographic member 11 includes a photoconductive layer 13 and a conductive substrate 15. The conductive substrate 15 includes a conductive layer 17 and a base or carrier 19.
S PhotoconducLive layer 13 is formed of R.F. sputtered cadmium sulfide and conductive substrate 1~ is a layer of indium-tin-oxide on a polyester plastic base.
A development electrode 21 is provided for use in assisting in developing a l,atent electrostatic image on the surface of photoconductive layer 13. Electeode 21 is positioned above the electrophotographic member 11 and a quantity o~ a liquid toner type developer 23 is disposed in the space between the electrophotographic member 11 and the , development electrode 21, The liquid toner 23, which is confined in a chamber (not shown), includes toner particles 25 suspended i,n a non-csnductive (electrically i,nsulating) liquid 27. The particular liquid toner employed is dependent upon the characteristics of the particular electrophotographic member. One preferable liquid toner comprises a comminuted powder of carbon and resin dispersed in an isoparaffinic hydrocarbon fraction available from the Exxon Company of Houston, Texas, under the name of "Isopar".~
Jt is believed that the A.C. bias voltage eliminates the hydrodynamic instahility of the liquid toner which produces the convection cells by interrupting or disturbing the otherwise unidirectional movement of the charged toner particles to the photoconductive surface. These interruptions or disturbances il'~O337 result in chan~es in direction of the forces exerted by the particles on the liquid in which the pflrticles are suspended, The A.C. bias waveform is preferably symmetrically shaped. The range of frequencies and amplitudes of the A.C.
S bias over which formation o~ the convection cells is either prevented or reduced to some noticeable extent is dependent on the particular liquid toner employed, the distance between the electrophotographic member and the development electrode and the maximum charge voltage on the electrophotograppic member.
If the frequency of the A.C. bias is either too high or too low the resulting changes in the direction of movement of the toner particles will have insufficient effect on the direction of movement of the in.sulating liquid and consequently, will not prevent the generation of the convection cells. If the amplitude of the A,C. bias is too low it will not effect the movement of the toner particles which control the movem~nt of the insulating liquid. If the amplitude of the A C. bias is too high it will prevent generation of the convection cells but will also prevent the toner particles from depositing on the surface of the electrophotographic membe~.
Preferably, the half-wave amplitude of the A C. bias should be equal to at least the maximum charge voltage on the photoconductive surface. If the amplitude is not up to this level, the bias voltage will not inte~rupt the movement of the toner partic~es sufficiently to prevent the generation 11'~0337 of the convection cells in the higher ~oltage image areas.
lhe effectiveness of the A.C. bias also depends on its waveform. For a given frequency and amplitude a square waveform is more effective in inhibiting formation of convection cells than a sinusoidal waveform, and a sinusoidal waveform is more efective th~n a triangular waveform It has been found, however, that any waveform may be used to prevent formation of convection cells by suitable adjustment of the A.C. frequency and/or amplitude For every combination of electrophotographic member, charge voltage, liquid toner, and physical arrangement, there exists an optimum combination of A C. bias amplitude, frequency, and waveform which can prevent formation of the convection cells believed responsible for the objectionable cellular optical density pattern in uniformly-charged image areas. The optimum combination can be ascertained in each instance of application.
Herein, an A.C source 29 is connected between the development electrode 21 and the conductive layer 17 to provide an A C. voltage bias between the two members. The A.C
voltage bias is applied between these two members to prevent the formation of convection cells in the liquid toner. The A G. bias voltage is applied at least dùring the time period the liquid toner is disposed between the two me~bers and during the process of developing the electrostatic image.
The invention will be more fully appreciated with reference to the following examples;
EXAMPI.E I
An electrophotographic member containing an R.F. sputtered cadmium sulfide photoconductive layer was uniformly corona charged to a negative surface potenti,al of 25 volts, contacted with a grainless ~tep tablet, exposed to a Xenon discharge light pulse and then developed for a period of about 15 seconds using a liquid toner comprising a comminuted powder of carbon and resin dispersed in Isopar and a development electrode that was parallel to, and spaced 0.010 inches from, the photoconductive surface of the electrophotographic member.
Throughout the developing operation the development electrode and the. electrophotographic member were both held at ground potential. The developed image contained a severe cellular density pattern superimposed on the image pattern. A
photomicrograph of the developed ima~e is shown in Figure 2, EXAMPLE II
Rxample I was repeated, except that during the developing operation a symmetrical sinusoidal A.C. bias havi,ng a peak-to-peak amplitude of 50 volts and a frequency of 44 Hz and a D,~.
level of 0 volts was applied between the development electrode ' and the electrophotographic member, The substantial reduction in the cellular density pattern is shown in Figure 3.
EXAMPLE III
Example I was again repeated except that the electrophoto-graphic membe~ was charged to a negative surface potential of10 volts~ the A.C. bias voltage had a peak-to-peak amplitude 11'~0337 of 68 volt.s alld a frequency of 7.S H7., and the liquid toner wa~ dilu~ d by a factor of 2, The cellular densi.ty pattern was compl~tel.y eliminated.
EXA7.~lPLS IV THROUGH VIII
.. . .
An ~1ectrophotographic Ine!nl~eL~ of the same type as used in Exampl.e 1 was uniformly corona charged to a negative su.face potentia~ of 15 volts and exposed to an image light pattern, The member was then developed for a period of about 15 seconds using a liqui~ toner and a development electrode th~t was parallel to, and spaced 0,0l5 inches from the photocon~uctive su~ace o the electrophotographic membe~. The liquid toner was comprised of a comminuted powder of carbon and resin dispersed in Isopar, but having no fixi.ng resi.n as in Æxample ~, The following ta1~1e shows the -.-esults when no bias voltage was applied and then when square wave biaæ voltage of different frequencies and a~plitudes were applied.
PEAK-TO-PEAKCELLULAR DENSITY
EXAMPLE A.C. FREQUENCY A.C. A~LITUDEPATTERN
IV NO BIAS VOLTAGE PRESENT
V 5 H~ 50 VOLTS ELI~IINATED
. .
VII l0 H~ 25 VOLTS ELIMINATED
.
Example VII shor~7s that the A.C. bias ellecti.vely removed the cellula~ density pattern even though the peak-to-peak voltage was less than the sutface potential on the photo-11;~0337 conductive surface of the electrophotographic member.
It can be appreciated that the concept of applying an A.~, bias voltage to prevent the formation of convection cells in a liquid toner which is di~persed between two parallel conductive member~s can find use also in electrophoretic display devices wherein a quantity of liquid toner is disposed between two paral.lel electrodes which are connected to voltage sources of different polarity.
The ~,C. bias voltage applied accordi.ng to the te~chings of this invention, can be superimposed over a D,C, bias voltage applied for some othe~^ purpose, such as reversal toning, for example.
Claims (11)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method for developing a latent electrostatic image formed on the surface of an electrophotographic member using a liquid toner formed of toner particles suspended in an insulating liquid and a development electrode, the insulating liquid being hydrodynamically unstable during toning, the hydrodynamic instability being effected by movement of the toner particles through said insulating liquid under the influence of the electric field forces between said electrophographic member and the development electrode, propulsion of said toner particles effecting a concurrent movement of the insulating liquid whereby a body thereof is carried with each particle as a trailing body of insulating liquid to define spatially stable convection cells therewithin; the improvement comprising applying an AC bias voltage between the development electrode and the electrophotographic member across the liquid toner during the developing operation changing the direction of the electric field forces exerted on the particles by said electric field impelling those particles through the insulating liquid materially inhibiting the formation of said spatially stable convection cells within the said toner suspension.
2. The method as defined in claim 1, wherein the waveform of the AC bias voltage is sinusoidal.
3. The method as defined in claim 1, wherein the waveform of the AC bias voltage is rectangular.
4. The method as defined in any one of claims 1, 2 or 3, wherein the waveform of the AC bias voltage is of uniform configuration.
5. The method as defined in any one of claims 1 to 3 wherein the peak-to-peak amplitude of the AC bias voltage is at least about twice as great as the maximum charge voltage on the electrophotographic member.
6. The method as defined in any one of claims 1 to 3 wherein the AC bias voltage is applied continuously during the developing operation.
7. The method as defined in any one of claims 1 to 3 wherein the peak-to-peak amplitude of the AC bias voltage is about 50 volts.
8. The method as defined in any one of claims 1 to 3 wherein the liquid toner comprises a comminuted powder of carbon and resin dispersed in an isoparaffinic hydrocarbon fraction.
9. The method as defined in any one of claims 1 to 3 wherein the distance between the development electrode and the electrophotographic member is about 0.010 inches and the AC bias voltage has a peak-to-peak amplitude of about 50 volts and a frequency of about 44 Hz.
10. The method as defined in any one of claims 1 to 3, wherein the peak-to-peak amplitude of the AC bias is about 18 volts and the frequency is about 7.5 Hz.
11. In an apparatus including a liquid toner comprising toner particles suspended in an insulating liquid and a development electrode for use in developing a latent electrostatic image formed on the surface of an electrophotographic member, means defining a toning chamber between the development electrode and the electrophotographic member and means for introducing toner suspension into said chamber, the development electrode being spaced from said member, the insulating liquid being hydrodynamically unstable during toning occasioned by the movement of the toner particles through said insulating liquid under the influence of the electric field across said member and development electrode, such movement establishing spatially stable convection cells in the insulating liquid due to the propulsion of the toner particles though the insulating liquid developing a trailing body of insulating liquid as a result of the concurrent movement of the insulating liquid and the particles, the improvement comprising an AC voltage source connected between the development electrode and the electrophotographic member whereby to apply repetitive changes to the direction of forces exerted on the particles by the electrical field so as materially to inhibit the formation of said spatially stable convection cells.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US89872978A | 1978-04-24 | 1978-04-24 | |
| US898,729 | 1978-04-24 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1120337A true CA1120337A (en) | 1982-03-23 |
Family
ID=25409963
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000326155A Expired CA1120337A (en) | 1978-04-24 | 1979-04-23 | Developing latent electrostatic images using a liquid toner and a development electrode |
Country Status (15)
| Country | Link |
|---|---|
| JP (1) | JPS554082A (en) |
| AT (1) | AT370890B (en) |
| AU (1) | AU526461B2 (en) |
| BE (1) | BE875806A (en) |
| CA (1) | CA1120337A (en) |
| CH (1) | CH629316A5 (en) |
| DE (1) | DE2916320A1 (en) |
| DK (1) | DK166779A (en) |
| FR (1) | FR2424571A1 (en) |
| GB (1) | GB2019747B (en) |
| IL (1) | IL57210A (en) |
| IT (1) | IT1162297B (en) |
| LU (1) | LU81179A1 (en) |
| NL (1) | NL7903168A (en) |
| SE (1) | SE7903287L (en) |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3346475A (en) * | 1963-02-25 | 1967-10-10 | Australia Res Lab | Electrophotographic method using an unsymmetrical ac current during development |
| US3547076A (en) * | 1967-03-23 | 1970-12-15 | Sherwin Williams Co | Apparatus for increasing the contrast in liquid immersion developing of electrostatic image |
| US3811764A (en) * | 1968-10-03 | 1974-05-21 | Xerox Corp | Apparatus for photoelectrophoretic imaging using a periodic electric field |
-
1979
- 1979-04-12 SE SE7903287A patent/SE7903287L/en unknown
- 1979-04-17 AU AU46137/79A patent/AU526461B2/en not_active Ceased
- 1979-04-19 AT AT0292679A patent/AT370890B/en not_active IP Right Cessation
- 1979-04-20 GB GB7913774A patent/GB2019747B/en not_active Expired
- 1979-04-23 JP JP4915879A patent/JPS554082A/en active Pending
- 1979-04-23 DE DE19792916320 patent/DE2916320A1/en not_active Withdrawn
- 1979-04-23 LU LU81179A patent/LU81179A1/en unknown
- 1979-04-23 NL NL7903168A patent/NL7903168A/en not_active Application Discontinuation
- 1979-04-23 DK DK166779A patent/DK166779A/en not_active IP Right Cessation
- 1979-04-23 CA CA000326155A patent/CA1120337A/en not_active Expired
- 1979-04-23 IT IT48818/79A patent/IT1162297B/en active
- 1979-04-23 FR FR7910198A patent/FR2424571A1/en not_active Withdrawn
- 1979-04-24 BE BE2/57746A patent/BE875806A/en not_active IP Right Cessation
- 1979-04-24 CH CH383179A patent/CH629316A5/en not_active IP Right Cessation
- 1979-05-04 IL IL57210A patent/IL57210A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| GB2019747A (en) | 1979-11-07 |
| AU526461B2 (en) | 1983-01-13 |
| JPS554082A (en) | 1980-01-12 |
| LU81179A1 (en) | 1980-12-16 |
| AT370890B (en) | 1983-05-10 |
| ATA292679A (en) | 1982-09-15 |
| FR2424571A1 (en) | 1979-11-23 |
| IT7948818A0 (en) | 1979-04-23 |
| DE2916320A1 (en) | 1979-10-31 |
| BE875806A (en) | 1979-10-24 |
| AU4613779A (en) | 1979-11-01 |
| NL7903168A (en) | 1979-10-26 |
| IL57210A (en) | 1983-12-30 |
| CH629316A5 (en) | 1982-04-15 |
| GB2019747B (en) | 1982-08-11 |
| IT1162297B (en) | 1987-03-25 |
| SE7903287L (en) | 1979-10-25 |
| DK166779A (en) | 1979-10-25 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |