WO1997028966A1

WO1997028966A1 - Electronic printing apparatus and method

Info

Publication number: WO1997028966A1
Application number: PCT/AU1997/000065
Authority: WO
Inventors: Phillip Eric Staples; Luis Lima-Marques; Trevor Donald Nation
Original assignee: Research Laboratories of Australia Pty Ltd
Current assignee: Research Laboratories of Australia Pty Ltd
Priority date: 1996-02-08
Filing date: 1997-02-07
Publication date: 1997-08-14
Anticipated expiration: 1998-08-08
Also published as: AUPN799896A0

Abstract

An electronic printer and a method of printing comprising a source of toner (2), a solid state toner conveyor array (1) to transfer toner from the source of toner to a transfer location (3). The conveyor array has a plurality of conveyor columns (10) with each column comprising a plurality of selectively chargeable electrodes (11). A transfer array (5) is spaced apart from the transfer location with at least one electrode (12) in the transfer array for each column of the conveyor array. Toner is conveyed along a selected column of the conveyor array to the transfer location and then attracted to the respective electrode or electrodes of the transfer array to be intercepted by a receiving member (4) placed between the transfer location and the transfer array and to be deposited thereon.

Description

TITLE : ELECTRONIC PRINTING APPARATUS AND METHOD

FIELD OF THE INVENTION

This invention relates to improvements in electrographic printing for use in a wide range of printing applications including photocopying, fax machines, monotone and colour printers and industrial marking.

In particular the invention relates to the use of solid state technology as a means of forming an image onto a substrate.

BACKGROUND OF THE INVENTION

Printing processes are well known using electro-photography techniques where light is used to define charge patterns on a recorder surface with toner being selectively laid down on to the charge pattern. Such machines necessarily require optical components which increases their complexity and cost.

Electrographic or electronic printing on the other hand does not use a light step to define charge areas but uses electrical means such as electronics and electric fields to define points on a recording member to which is applied an ink or a toner. Typical of such devices is an ink jet printer which uses means to release a drop of ink which is caused to deposit in a selected spot on a recording member. Such ink jet machines are restricted in resolution because of the minimum size drop that can be formed and ejected. Such processes are also not completely electronic because of the requirement to mechanically produce the ink drops.

Digital packet printing has been proposed as a more entirely electronic process of defining the amount and location of ink or toner to be deposited at a location on a recording member.

The concept of digital packet printing is described in United States Patent No. 5,153,617 in the name of Salmon. Salmon uses a miniature electrode array to pump toner along columns of the array from a toner source to a recording member as required by electronically defining the required column and pumping for a selected period to give a selected density of toner on the recording member. The toner described and exemplified by Salmon is a dry powder toner. It is a relatively simple matter electronically to define the column and time for a particular point of the desired final image from a stream of printing instructions from for instance a computer. Theoretically, therefore, there is described a relatively simple printer engine.

There are, however, a number of practical problems particularly when fine resolution is required.

Firstly, due to the spatial construction of the enabling elements, as so described, the speed of movement of such dry powder toner as so described therein, is very slow, which severely restricts the effective printing speed of any system employing this embodiment. Indeed, the mobility of the dry powder particles in such a device as therein described would not allow adequate deposition of such toner particles on to paper or any other substrate, with sufficient optical density. Secondly control of the toner particles as they leave the so called conveyer mechanism is impeded by a number of mechanisms including the stepwise movement of the paper, as so described and the air movement associated with such paper movement thereby causing resolution loss due to lateral displacement of the dry toner particles before impingement on to the paper. As a third consideration, dry powder toner, due to its very nature with respect to particle size and charge per particle would be difficult to control with respect to this conveyer mechanism in that such toner particles do not respond to the applied electric field thereby also giving rise to toner blockages within the conveyer as well as particle placement considerations with respect to their movement from the conveyer to the paper. In addition as is known to those skilled in the art, the movement of dry powder toner gives rise to the so called dusting problem. In the embodiment as disclosed therein, containment of the dry powder toner with respect to adjoining electrical circuitry has not been addressed. Such dusting problem could be perceived as causing component failure thereby rendering such a device unreliable.

Salmon also requires that the dry powder toner particles are substantially spherical to achieve good transport down the conveyor array.

Implementation of liquid toner technology with respect to the apparatus disclosed in US patent 5,153,617 may reduce some of the impediments described above. Dry powder toner as is known has a particle size in the order of 5 - 10 microns; liquid toners however exhibit particle size in the order of 0.1 to 1 micron.

In the present invention the use of such liquid toners in the device disclosed has been observed to alleviate the above problems. Indeed, the nature of the liquid toner and in particular the carrier liquid serves to aid the movement of the toner particles with respect to the conveyer mechanism. As is known, the charging mechanism of liquid toner particles is defined by their chemistry; which allows greater control of the charge on the particles which in the disclosed embodiment creates a more uniform movement of toner particles. There is no requirement for external intrinsic charging of such particles. This is in contrast to dry powder toners where particle charging with a donor roller is required. Changes in response of such particles as they move along the conveyer due to charge relaxation on the surface of such particles is evident.

Further problems exist with placement of packets of toner onto the recording member once they have been transported to the end of the array. Salmon proposes the use of a charged platen behind the recording member to attract the toner particles. This has problems with accuracy and the diffusion of charge if the receiving member is conductive or slightly conductive such as if it is a paper recording member which is slightly damp.

In US patent 4,344,002 filed on June 8, 1982, Roger D Bouette of Repco Research discloses a recording member which is instantly addressable. Although such a recording member allows deposition of liquid toner, resolution and optical density are believed inadequate for many printing applications.

Problems therefore exist with printing resolution and it is the object of this invention to provide an electronic printing system which has an improved resolution.

It is therefore an object of the invention to provide novel apparatus and method for developing electrostatic latent images emanating from the solid state recording member. It is a further object to this invention to provide a novel method of printing using digital electronic solid state technology to effect a cost effective and reliable output device for current computer technology.

It is a further object to this invention that the electrostatic latent images emanating from the solid state recording member be developed by way of a solid state liquid toner conveyance system.

It is yet a further object to this invention that the liquid toner used for such electronic printing contain a carrier whose physical and chemical property may differ substantially from conventional materials.

It is a further object to this invention to provide a novel method of printing using digital electronic solid state technology to deliver liquid toner in a controlled manner, dependant on the image to be printed, to an electrostatic recording member where upon the so formed toner image is transferred to paper or various substrates.

BRIEF SUMMARY OF THE INVENTION

In one form therefore the invention is said to reside in an electronic printer comprising; a source of toner, a toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, and a transfer array spaced apart from the transfer location, there being at least one electrode in the transfer array for each column of the conveyor array, whereby toner conveyed along a selected column of the conveyor array to the transfer location can be attracted to the respective electrode or electrodes of the transfer array across a gap between them to be intercepted by a receiving member placed in the gap between the transfer location and the transfer array and to be deposited thereon.

Preferably the toner comprises a liquid toner having a substantially non- conductive carrier which is liquid at the operating temperature of the printer and marking particles. The use of a liquid toner has the advantage that the carrier can act as a lubricant to facilitate the movement of toner particles supported in the carrier. Dusting is also not a problem. With a dry powder toner the individual particles tend to hop from one electrode to the next and it has been found that there is in effect a limiting speed of forward movement above which particles may tend to stay stationary rather than move forward. With a liquid toner while at slow speeds the toner may tend to hop from electrode to electrode at higher speeds movement does not stop but appears to be more linear providing more even flow.

The gap between the transfer location and the receiving member may be an air gap in the case of either a dry powder toner or a liquid toner. In the case of a liquid toner the gap may be comprised of or filled with a meniscus of the carrier liquid.

Each electrode in each column of the toner conveyor array may be selectively charged positively, negatively or be neutrally charged.

When the toner is a liquid toner the chargeable marking particles may have a particle size of between 0.25 to 5 μ and may be selected from pigment particles, polymeric particles, magnetic particles and the like.

The carrier for the liquid toner may be selected from paraffinic, aromatic and aliphatic hydrocarbons, vegetable oils, silicone oils and chlorinated hydrocarbons, aromatic and aliphatic esters including those curable by ultraviolet or electron beam radiation.

The carrier may have an electrical resistivity of greater than 10⁶ ohm-cm.

There may be further included means to fix the toner onto the receiving member to form an image thereon.

The electronic printer may have a single source of toner to be a monochrome printer or it may comprise a plurality of toner sources, toner conveyor arrays and transfer arrays whereby toners of different colours may be used for colour printing.

The toner conveyor array and the transfer array may be formed as integrated circuits on respective monolithic substrates.

In a preferred embodiment the toner conveyor array may be fixed in location and the receiving member may move longitudinally with respect to the toner conveyor array, each of the conveyor columns corresponding to a respective pixel site across the width of the receiving member and the receiving member may be adapted to be moved between deposits of pixels longitudinally.

The toner conveyor array may be adapted to extend across the width of the receiving member.

Each electrode of the toner conveyor array and the transfer array may be coated with a dielectric.

The receiving member may be a sheet of paper which may not need to be treated in any way, hence providing plain paper printing. Alternatively the receiving member may be an offset printing plate, an intermediate roller from which the developed image is transferred to a final medium or a item of manufacture upon which information is printed.

In an alternative form the invention may be said to reside in an electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, means to extract toner from the transfer location and to impinge the toner onto a receiving member, characterised by the toner comprising a liquid toner having a non- conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles.

The means to extract toner from the transfer location and to impinge the toner onto a receiving member may comprise a transfer array spaced apart from the transfer location, there being at least one electrode in the transfer array for each column of the conveyor array, whereby toner conveyed along a selected column of the conveyor array to the transfer location can be attracted to the respective electrode or electrodes of the transfer array to be intercepted by the receiving member placed between the transfer location and the transfer array. Each electrode in each column of the toner conveyor array may be selectively charged positively, negatively or be neutrally charged. By this means packets of toner may be conveyed forward to deposit toner on the recording member, packets may be held stationary or they may be conveyed in reverse.

Alternatively the direction of travel of toner on a column of the array may be by suitable pulsing of the electrodes of a column of the conveyor array. Toner may be caused to flow forward by forward stepping of the charge to a column and flow back by reverse stepping of the charge to the electrodes of a column. In the case of a liquid toner for instance there may be a slight positive pressure provided by gravity or a pump such as a peristaltic pump which would normally cause toner to flow towards the transfer location to enable printing but by suitable activation of the electrodes of the array to cause reverse stepping then printing at that column could be stopped.

The toner conveyor array may be bounded within walls to thereby define a conveyor space through which toner is conveyed to the transfer location.

In one embodiment opposite walls of the conveyor space each comprise toner conveyor arrays, each conveyor array including a plurality of conveyor columns, each pair of opposed columns comprising a plurality of jointly and selectively chargeable electrodes.

The width of the conveyor space may be in the order of 50μ or less.

In an alternative form the invention may be said to reside in an electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, means to extract toner from the transfer location and to impinge the toner onto a receiving member, characterised by the toner comprising a liquid toner having a non- conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles and the toner conveyor array being bounded within walls to thereby define a conveyor space through which toner is conveyed to the transfer location. It will be seen that in this embodiment of the invention there is provided an arrangement wherein the walls defining the conveyor space act to prevent the toner from drying out when the printer is not in operation.

Opposite walls of the conveyor space may each comprise toner conveyor arrays, each conveyor array including a plurality of conveyor columns, each pair of opposed columns comprising a plurality of separate or jointly and selectively chargeable electrodes.

The width of the conveyor space may be in the order of 50μ.

The width of the conveyor space and the material of construction of the dielectric material covering the electrodes of the conveyor array may be selected so that liquid toner may flow from the toner source up the space by capillary action. Further the surface energy of the dielectric coating may be such as to encourage predominantly toner particles to move up the conveyor space but not to encourage movement of carrier liquid in the toner in that direction. Further the dielectric coating may be selected from suitable materials whose surface energy is such that toner particles do not readily deposit thereon, thereby allowing the dielectric surface to be substantially free of deposited particles which reduces possible maintenance of the conveyor array.

Such a dielectric coating may be polytetrafluoroethylene.

There may further provided at least a pair of control electrodes which are positioned at opposed sides of the toner conveyor array to provide an electric field which is at right angles to the direction of travel of toner down the columns of the toner conveyor array and also at right angles to the electric field produced by the electrodes of the array. The control electrode may be charged with a static voltage or AC, of any waveform which would assist with the control of toner particles passing through the conveyor space. The number and spacing of such electrodes would be compliant on the nature of the toner and architecture of the embodiment. There may also be further means to extract excess toner from the region of the transfer position.

There may also be further means to extract excess toner from the region of the transfer position. This may be suction provided near the transfer location or it may be that the tip of the transfer location is provided with a porous frit or similar through which excess carrier may be removed.

To assist with transfer of the toner from the transfer location to the receiving member there may be a separately controllable gap electrode at the transfer location so that the required moment of transfer the separately controllable electrode may be charged to the opposite polarity to that of the respective electrode of the transfer array. Alternatively the gap electrode may be the final electrode of each column of the toner conveyor array.

In an alternative form the invention may be said to reside a method of electrographic printing using an electronic printer, the electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, and a transfer array spaced apart from the transfer location, there being at least one electrode in the transfer array for each column of the conveyor array, the method characterised by the steps of; loading toner from the source of toner to respective columns of the toner conveyor array, selectively conveying toner along the columns to the respective transfer locations by charging successive electrodes in each column, selectively charging the electrodes of the transfer array such that toner at the transfer location is attracted to the respective electrode or electrodes of the transfer array to be intercepted by a receiving member placed between the transfer location and the transfer array.

The toner may comprise a liquid toner having a non-conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles and the method may further include the step of extracting excess carrier.

The step of attracting the toner from the transfer location to the receiving member may include the step of selectively attracting the chargeable marking particles and not the non-conductive carrier whereby the toner when impinged on the receiving member has less carrier than the bulk of the toner at the toner source.

The method may further including the step of fixing the toner on the receiving member.

In one embodiment of the method of the invention the carrier may be a reactive carrier and the method may further include the step of reacting the carrier after it is deposited on the receiving member to fix the toner thereon.

In a preferred embodiment of the invention there may be a control electrode arrangement positioned at opposed sides of the toner conveyor array to provide an electric field which is at right angles to the direction of travel of toner down the columns of the toner conveyor array and also at right angles to the electric field produced by the electrodes of the array whereby to assist with control of the movement of toner particles in the conveyor space.

According to this invention, therefore, there is provided an electronic printer in which the print engine may be essentially solid state with no moving parts except the actual toner and the movement of the receiving member.

This then generally describes the invention but to assist with understanding of the invention reference will now be made to the accompanying drawings which show preferred embodiments of the invention.

In the drawings:

FIG 1 shows a schematic view of one embodiment of a printing engine of the present invention;

FIG 2 shows a cross sectional view of a conveyor and transfer arrays of the present invention using liquid toner as the developer;

FIG 3 shows a cross sectional view of alternative conveyor and transfer arrays of the present invention using liquid toner as the developer;

FIG 4 shows a cross sectional view of further embodiments of conveyor and transfer arrays of the present invention using liquid toner as the developer; FIG 5 shows a cross sectional view of further embodiments of conveyor and transfer arrays of the present invention using liquid toner as the developer;

FIG 6 shows a schematic view of an alternative embodiment of a printing engine of the present invention adapted for colour printing;

FIG 7 shows a schematic view of a printer engine according to one embodiment of the invention;

FIG 8 shows a schematic view of a printer engine according to another embodiment of the invention; and

FIG 9A and B show isometric views of conveyor arrays of the present invention using liquid toner as the developer and control electrodes.

DETAILED DESCRIPTION

Now looking at the drawings in more detail and in particular Figure 1 it will be seen that there is depicted a schematic view of an electronic printer engine. The conveyor array 1 extends from a toner source 2 to a transfer location 3. There is an air gap at the transfer region 3 before there is positioned a receiving member 4. Behind the receiving member 4 is a transfer array 5.

The conveyor array 1 is comprised of a number of columns 10 of electrodes 11 which extend from the toner source to the transfer location. By successive activation of electrodes of a column of toner represented by the circular droplets in this schematic drawing is caused to move along the column until it reaches the transfer location. At that point a corresponding electrode 12, for instance, of the transfer array is charged and a portion of toner 13 is cause to move across the air gap to impinge upon the receiving member.

In a preferred embodiment the voltage applied to each electrode of the conveyor array may be in the region of 50 to 80 volts and the voltage applied to the transfer array may be up to 200 volts. In practice the charging of the conveyor array may actually be to only each second or third electrode in a column so that flow of toner down the column may occur in the required direction. The conveyor electrodes can be parallel connected to form a sequence of phase groups along the entire length of the conveyor. The number of electrodes in a phase group must be any odd number greater than one. Each phase group is driven by a clocked voltage source. The phase angle relationship of any one phase group with respect to its neighbouring pair of groups is 360 degrees divided by the number of phase group elements. Direction of toner movement if dependent on the sign of the phase angle relationship between one phase group and its neighbouring pair of groups.

For example, in the simplest case every third electrode along the entire length of the conveyor forms one of three phase groups. Each phase group is driven by a clocked voltage source whose phase relationship is 120 degrees with respect to the other two phase groups.

The frequency of the clock may be in the range from 1 Hz to 1 Mhz. Preferred frequency of operation is in the range of from 100 Hz to 10OKhz. The frequency at which the device operates is determined by the number of particles required to develop the image. The frequency is also conditional on the nature of the toner, the spatial dimensions of the electrodes and the conveyor array and the electric field emanating from the electrodes of the array.

The toner of this embodiment is depicted a discontinuous phase in a continuous fluid phase but it may be a powdered toner with the toner source including means to charge the toner particles before they are transported down the columns of the array.

For a resolution of 600 dots per inch in a printer each column may have a width of about 40 microns which is achievable using solid state printing techniques onto monolithic substrates. For a resolution of 1000 dpi each column may have a width of about 25 microns.

Figure 2 shows a schematic view of an embodiment of a printer engine according to this invention using a liquid toner. The schematic view is a side cross sectional view. Each electrode 20 is formed onto monolithic substrate 21 and is covered by a dielectric material 22 which is provided to prevent erosion of the electrodes and provide a smooth surface for flow of liquid toner. The liquid toner comes from a toner source 23 which is held at a slight positive pressure so that a layer of liquid toner 24 extends onto the electrodes. By sequentially charging the electrodes 20 in the direction given by the arrow 25 a flow of liquid toner including particles will tend to move towards the transfer region 26 at which time the transfer array 27 may be charged to cause a droplet of toner preferably enriched with particles to step across the air gap 28 and to impinge upon the receiving member 29. Excess toner 30 may tend to move over the end of the transfer array and may be extracted by a side suction in a depleted toner extractor 31. After sufficient toner has been caused to impinge upon the receiving member this may be moved slightly so the next pixel may be marked or not as necessary.

Suitable solid state electronics may be provided to sequentially charge the electrodes 20 to cause forward movement of the liquid toner. Reverse sequential activation of the electrodes may cause toner to be held back from the transfer location to prevent printing when a particular pixel does not require printing.

FIG 3 shows an arrangement of printer engine similar to that of FIG 2 using a liquid toner but with a porous portion 32 at the transfer end of the conveyor array which is adapted to withdraw liquid from the liquid toner so that by the time it is ready to be transferred at the transfer location 33 across the gap 28 to the receiving member 29 there is a higher particle concentration in the toner. Gap electrode 34 is provided at the transfer location to assist with the transfer of the droplet of concentrated toner. The gap electrode may be provided with a voltage which is opposite to that provided on the respective electrode of the transfer array. Alternatively the gap electrode may be the final electrode of each column of the toner conveyor array.

FIG 4 shows an embodiment of printer engine that uses a pair of conveyer arrays 35 and 36 face to face to provide a conveyor channel 37 between them. the liquid toner travels up the channel by capillary action and under the action of the electrodes and is drawn across to the receiving member 39 by the charge on the transfer array 38 to form a meniscus 44 across the gap.

FIG 5 shows a similar view to that of FIG 4 but includes a control electrode 55, one of which is at each side of the pair of arrays 56 and 57 to assist in providing control of the flow of toner in the channel 58. Such an electrode may be continuous (as shown with 55) or segmented and juxtaposed at the sides with respect to the monolithic substrate 21. FIG 6 shows an alternative embodiment of printer engine according to this invention which is particularly adapted for colour printing.

In this case there are 4 pairs of conveyor arrays with each array of each pair facing each other and spaced slightly apart to provide a channel through which toner can flow under the influence of the electrodes towards the transfer location and the receiving member.

To look at one of the channels, a toner source 40 provides toner under slight positive pressure so that it tends to flow up the channel 41 towards the transfer location 42. By sequentially activating the electrodes 43 in a reverse direction toner flow can be stopped until a droplet is required at which time the electrodes might may be sequentially operated forward to cause toner to reach the transfer location at which time the transfer array electrode 45 is activated to draw a portion of toner across to the receiving member 46. Excess carrier for the liquid toner 47 may be withdrawn by suction down channels 48 between the pairs of arrays.

By this means there may be a slight concentration of the toner particles in the droplet of toner that transfers across to the receiving member 46 thereby providing a more accurate resolution onto the receiving member. The receiving member is removed in the direction shown by the arrow 50 so that each pixel site on the receiving member is subjected to the potential for having a droplet of toner from each colour.

Figure 7 shows a schematic view of a printer engine according to this invention in which a toner conveyor array of the type shown in Figure 3 provides toner onto a receiving member 61 which is driven by driver rolls 62. The transfer array 63 ensures that the toner of each colour reaches the correct spot on the receiving member.

The driver rolls 62 transfer the receiving member 61 through fuser rolls 64 in which the toner is fused to the receiving member.

Figure 8 shows an arrangement which the toner conveyor array 60 transfers a self-fixing toner onto the receiving member 61 by means of the transfer array 63 and then the driver rolls 62 cause the receiving member to pass under a UV source 65 which sets the toner to fix the image onto the receiving member. FIG 9A shows a schematic perspective view of a pair of conveyor arrays 70 and 71 with a number of control electrodes 72 positioned at the sides and between the conveyor arrays. These control electrodes may hold a static voltage to control the flow or movement of toner particles in the direction shown by the arrows 73 in a liquid toner between the conveyor arrays or they may be sequentially actuated as required.

FIG 9B shows a schematic perspective view of a pair of conveyor arrays 75 and 76 with a single control electrode 77 positioned at one side and another control electrode 78 positioned at the other side of the conveyor arrays and between the conveyor arrays. These control electrodes may hold a static voltage to control the flow or movement of toner particles in a liquid toner as required in the direction shown by the arrows 79.

Throughout this specification and the claims that follow unless the context requires otherwise, the words 'comprise' and 'include' and variations such as 'comprising' and 'including' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims

1. An electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, and a transfer array spaced apart from the transfer location, there being at least one electrode in the transfer array for each column of the conveyor array, whereby toner conveyed along a selected column of the conveyor array to the transfer location can be attracted to the respective electrode or electrodes of the transfer array to be intercepted by a receiving member placed between the transfer location and the transfer array and to be deposited thereon.

2. An electronic printer as in Claim 1 wherein the toner comprises a liquid toner having a non-conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles.

3. An electronic printer as in Claim 1 wherein each electrode in each column of the toner conveyor array may be selectively charged positively or negatively or be neutral in charge.

4. An electronic printer as in Claim 2 wherein the chargeable marking particle has a size of between 0.25 to 5 μ and is selected from pigment particles, polymeric particles and magnetic particles.

5. An electronic printer as in Claim 2 wherein the carrier is selected from paraffinic, aromatic and aliphatic hydrocarbons, vegetable oils, silicone oils and chlorinated hydrocarbons, aromatic and aliphatic esters including those curable by ultraviolet or electron beam radiation..

6. An electronic printer as in Claim 2 wherein the carrier has an electrical resistivity of greater than 10^ ohm-cm.

7. An electronic printer as in Claim 1 further including means to fix the toner onto the receiving member to form an image thereon.

8. An electronic printer as in Claim 1 comprising a plurality of toner sources, toner conveyor arrays and transfer arrays whereby toners of different colours may be used for colour printing.

9. An electronic printer as in Claim 1 wherein the toner conveyor array and the transfer array are formed as integrated circuits on respective monolithic substrates.

10. An electronic printer as in Claim 1 wherein the receiving member is selected from a sheet of paper which may not need to be treated in any way, hence providing plain paper printing, an offset printing plate, an intermediate roller from which the developed image is transferred to a final medium or a item of manufacture upon which information is printed.

11. An electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, means to extract toner from the transfer location and to impinge the toner onto a receiving member, characterised by the toner comprising a liquid toner having a non- conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles.

12. An electronic printer as in Claim 11 wherein the means to extract toner from the transfer location and to impinge the toner onto a receiving member comprises a transfer array spaced apart from the transfer location, there being at least one electrode in the transfer array for each column of the conveyor array, whereby toner conveyed along a selected column of the conveyor array to the transfer location can be attracted to the respective electrode or electrodes of the transfer array to be intercepted by the receiving member placed between the transfer location and the transfer array.

13. An electronic printer as in Claim 11 wherein each electrode in each column of the toner conveyor array may be selectively charged positively, negatively or be neutrally charged.

14. An electronic printer as in Claim 11 wherein the toner conveyor array is bounded within walls to thereby define a conveyor space through which toner is conveyed to the transfer location.

15. An electronic printer as in Claim 14 wherein opposite walls of the conveyor space each comprise toner conveyor arrays, each conveyor array including a plurality of conveyor columns, each pair of opposed columns comprising a plurality of jointly and selectively chargeable electrodes.

16. An electronic printer as in Claim 14 or 15 wherein the width of the conveyor space is in the order of 50μ.

17. An electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, means to extract toner from the transfer location and to impinge the toner onto a receiving member, characterised by the toner comprising a liquid toner having a non- conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles and the toner conveyor array being bounded within walls to thereby define a conveyor space through which toner is conveyed to the transfer location.

18. An electronic printer as in Claim 17 wherein opposite walls of the conveyor space each comprise toner conveyor arrays, each conveyor array including a plurality of conveyor columns, each pair of opposed columns comprising a plurality of jointly and selectively chargeable electrodes.

19. An electronic printer as in Claim 17 or 18 wherein the width of the conveyor space is in the order of 50μ.

20. An electronic printer as in Claim 17 wherein the walls defining the conveyor space acting to prevent the toner from drying out when the printer is not in operation.

21. An electronic printer as in Claim 17 further including at least a pair of control electrodes which are positioned at opposed sides of the toner conveyor array to provide an electric field which is at right angles to the direction of travel of toner down the columns of the toner conveyor array and also at right angles to the electric field produced by the electrodes of the array

22. An electronic printer as in Claim 17 further including extraction means to extract excess toner from the region of the transfer position.

23. An electronic printer as in Claim 17 further including a separately controllable gap electrode at the transfer location so that the required moment of transfer the separately controllable electrode may be charged to the opposite polarity to that of the respective electrode of the transfer array.

24. A method of electrographic printing using an electronic printer, the electronic printer comprising; a source of toner, toner conveyor array to transfer toner from the source of toner to a transfer location, the conveyor array including a plurality of conveyor columns, each column comprising a plurality of selectively chargeable electrodes, and a transfer array spaced apart from the transfer location, there being at least one electrode in the transfer array for each column of the conveyor array, the method characterised by the steps of; loading toner from the source of toner to respective columns of the toner conveyor array, selectively conveying toner along the columns to the respective transfer locations by charging successive electrodes in each column, selectively charging the electrodes of the transfer array such that toner at the transfer location is attracted to the respective electrode or electrodes of the transfer array to be intercepted by a receiving member placed between the transfer location and the transfer array.

25. A method of electrographic printing as in Claim 24 wherein the toner comprises a liquid toner having a non-conductive carrier which is liquid at the operating temperature of the printer and chargeable marking particles and the method further including the step of extracting excess carrier.

26. A method of electrographic printing as in Claim 25 wherein the step of attracting the toner from the transfer location to the receiving member includes the step of selectively attracting the chargeable marking particles and not the non-conductive carrier whereby the toner when impinged on the receiving member has less carrier than the bulk of the toner at the toner source.

27. A method of electrographic printing as in Claim 24 further including the step of fixing the toner on the receiving member.

28. A method of electrographic printing as in Claim 25 wherein the carrier is a reactive carrier and further including the step of reacting the carrier after it is deposited on the receiving member to fix the toner thereon.

29. A method of electrographic printing as in Claim 24 further including the step of providing a separately controllable gap electrode at the transfer location so that the required moment of transfer the separately controllable electrode may be charged to the opposite polarity to that of the respective electrode of the transfer array.

30. A method of electrographic printing as in Claim 24 further including the step of providing a control electrode arrangement positioned at opposed sides of the toner conveyor array to provide an electric field which is at right angles to the direction of travel of toner down the columns of the toner conveyor array and also at right angles to the electric field produced by the electrodes of the array whereby to assist with control of the movement of toner particles in the conveyor array.