JPH11115237A - Direct electrostatic printing apparatus having edge electrode for applying ac electric field to surface of toner transfer device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a printing apparatus that can execute printing at high speed by means of direct electrostatic printing method and to reduce clogging at a control electrode by a method wherein the structure is so constructed that a device for creating DC voltage difference between a face discharging charged toner particles and an image receiving substratum and for making the flow of charged toner particles is provided. SOLUTION: A DEP(direction electrostatic printing method) printing apparatus has a container 101 for developing agent 102 and is equipped with a magnetic brush 103 having a magnet-provided core 103a and a sleeve 103b rotatively attached to the outer circumference of the core. The apparatus also includes a back electrode 105 connected to a DC voltage power source, and an image receiving substratum 108 is made by a transfer device 107 to pass through a space between the sleeve 103b and the back electrode 105 in the direction A. At this time, the difference between power sources V4 and V1 becomes driving electric field for DC, and flow 104 of toner particles running from the sleeve 103b of the magnetic brush 103 to the image receiving substratum 108 can be produced, and images can be formed by the operation of a printing head structure having a control electrode 106a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

FIELD OF THE INVENTION The present invention relates to an apparatus used in electrostatic printing, in particular, direct electrostatic printing (DEP). In DEP, electronically addressable (addressabsab)
le) Electrostatic printing is performed on the image receiving substrate directly from the toner transfer device by the print head structure.

[0002]

BACKGROUND OF THE INVENTION In DEP (Direct Electrostatic Printing), a toner or developing material is deposited directly on an image receiving substrate according to an image, and the image receiving substrate has a latent electrostatic image according to the image. Absent. The substrate can be an intermediate endless flexible belt (eg, aluminum, polyimide, etc.). In this case, the toner deposited according to the image must be transferred to another final substrate. It is preferred that the toner be deposited directly on the final image receiving substrate, eg, flat paper, transparency, or the like, so that an image can be directly formed thereon. This deposition step is followed by a final fusing step.

[0003] This is different from the classical electrophotography. In the latter case, the electrostatic image on the charge retentive surface is developed with a suitable material to make the latent image visible. The powder image is then fused directly to the charge retentive surface for direct electrographic printing, or the powder image is transferred to a final substrate and then fused to this substrate. Later methods provide indirect electrographic printing.
The final substrate is a transparent medium, an opaque polymer film,
It can be paper or the like.

[0004] DEP also differs significantly from electrophotography, which requires additional steps and additional components to create a latent electrostatic image. To put it more simply,
Using a photoconductor, a charging / exposure cycle is required.

The device of DEP is disclosed, for example, in US Pat.
No. 935. This document describes an electrostatic line printer having a multilayer particle modulator or printhead structure having the following configuration: a layer of insulating material called a separation layer.

A shielding electrode consisting of a continuous layer of conductive material on one side of the separating layer.

A number of control electrodes made of delimited layers of conductive material on the other side of the separation layer.

[0008] at least one row of holes;

Each control electrode is formed around one hole,
Insulated from other control electrodes.

A selected voltage (only DC voltage) is applied to each control electrode, and a constant voltage is simultaneously applied to the shield electrode. An overall propulsion electric field imposed between the toner transfer device and the toner receiving substrate causes charged toner particles to fly through a row of holes in the printhead structure. The intensity of this particle flow is modulated by the voltage pattern applied to the control electrode. The modulated stream of charged particles impinges on an image receiving substrate inserted into the modulated particle stream. The image receiving substrate is carried in a direction orthogonal to the print head structure, and printing is performed by scanning each line. The shield electrode may face the toner transfer device and the control electrode may face the image receiving substrate. A DC electric field is applied between the printhead structure and a single back electrode on the receiving substrate. This propulsion electric field
It serves to attract toner to the image receiving substrate located between the printhead structure and the back electrode.

A print head structure in which the print head structure is not an insulating base having holes for printing but a network structure is described in US Pat. No. 5,036,341. According to the patent, in order to increase the printing speed, the frequency is 2 to 5 k.
An AC electric field having a frequency between 500 Hz and 500-2000 V is applied to the toner transfer device.

One of the problems with both of these printhead structures is that toner particles can easily become clogged when the printhead structure is used for an extended period of time.

[0013] This problem of clogging of the printhead structure has been previously solved in several ways. For example, in U.S. Pat. No. 4,491,855, various methods are described to solve some of the above problems. A method is described for stably and uniformly supplying toner particles to a printhead structure to prevent the toner particles from clogging holes in the printhead structure. Accordingly, a transport member for depositing a layer of toner particles is mounted and an alternating voltage is applied between the toner transport member and the continuous layer of conductive material of the printhead structure.
Due to this alternating voltage, the toner particles "jump" between the toner carrying member and the surface of the printhead structure facing the toner carrying member, creating a "toner cloud". AC voltage (in this patent, the peak-to-peak voltage is 300 V, the frequency is 4.5 k
Hz) so that the toner particles reach the printhead structure and the overall DC voltage between the printhead structure and the image receiving substrate member can pull the toner particles out of the cloud of toner powder. To The overall DC voltage drives the toner particles toward an image receiving substrate inserted between the printhead and the back electrode.

The toner particles are "touched"
g) "is believed to help retard printhead structure contamination and pore clogging. At the same time, the patent describes the special design of the holes in the printhead structure and the selection of special materials for making the printhead structure in order to delay clogging. The last method proposed is to "clean" the printhead structure by periodically causing an electrical explosion (spark discharge).

In US Pat. No. 4,478,510, such a spark discharge is used to remove toner particles sticking to the printhead and to clean the printhead again. For this purpose, the printing time is divided into a writing time (time for writing the image on the image receiving material) and a cleaning time.
The voltage applied to the rear electrode is increased during the cleaning time, causing a spark discharge from the printhead to the rear electrode. The toner particles sticking to the print head are removed and collected on the rear electrode. Other possibilities reported so far include spark discharge between the shield electrode and the control electrode, the same effect,
That is, this is a method of obtaining an effect of cleaning the clogging of the holes of the print head.

In US Pat. No. 4,755,837, an alternating voltage is used for the rear electrode during the cleaning cycle. In a preferred embodiment, the alternating voltage applied to the back electrode is the alternating current used for the conveyor of charged toner particles needed to create a dense toner fume and obtain high optical density and short print times. It is 180 ° out of phase with respect to the voltage (peak-to-peak voltage 400 V, frequency not shown). Further, a DC bias voltage is applied to the AC voltage.

In US Pat. No. 4,876,561, the holes are made sufficiently large and / or the thickness of the separating layer is made sufficiently thin to prevent clogging of the printhead.

In US Pat. No. 4,903,050, an alternating voltage is applied to the back electrode as in US Pat. No. 4,755,837, but with a shutter and vacuum system to prevent the removed toner from falling onto the image receiving substrate. Has been added.

In US Pat. No. 5,095,322, a pulse voltage in the middle is applied to the shielding electrode 180 ° out of phase with respect to the AC voltage applied to the charged toner conveyor to prevent clogging of the holes. In another embodiment, an AC voltage having the same frequency as the AC voltage applied to the charged toner conveyor but having a 180 ° phase shift is used and a DC bias is applied to prevent clogging of the printhead holes. In.

In US Pat. No. 5,153,611, good behavior in preventing clogging of holes is obtained by applying ultrasonic vibration to the print head. The same idea is also described in U.S. Pat. No. 5,202,704, in which the printhead is mechanically created with a toner cloud, such that toner particles stuck inside the holes are removed from the holes in the printhead. Vibrates.

In US Pat. No. 5,233,392, better behavior is obtained using ultrasonic vibrations applied to the print head. The improvement is to slightly change the resonance frequency of the vibration used during the writing time for each individual pixel, which can much better prevent hole clogging.

In US Pat. No. 5,256,246, the printhead structure is made from a thin ceramic insulating material, and the ceramic member is thin-filmed, such as sputtering, vacuum deposition, ion plating, chemical vapor deposition and screen printing. The control electrode is attached by.
The patent states that the printhead structure is less sensitive to clogging without the presence of a sticky coating layer below the conductive layer. However, a major disadvantage of this method is that the adhesion of the conductor to the substrate is reduced.

In US Pat. No. 5,283,594, the magnitude of the vibration applied to the print head is varied between the writing time and the cleaning time. Vibration should be high enough during the writing time to prevent large clogging of the holes, and the amplitude of the oscillating motion should be large enough during the cleaning time to allow toner particles to partially clog the holes during the writing cycle. Is removed. As a result, the long-term behavior of the DEP device is considerably improved.

In US Pat. No. 5,293,181, the print head is vibrated in such a way that a mechanically propagating wave is created. A device is mounted on the printhead to prevent reflection of mechanically propagating waves. By performing such mounting, good long-term stability can be obtained without causing clogging of holes, and good writing characteristics can be obtained.

In US Pat. No. 5,307,092, the electrodes of the printhead are coated with an antistatic coating to ground the triboelectric charge accumulated during the writing time. As a result, the net triboelectric charge on the printhead (which is undesirable and causes unexpected results and clogging) is removed and good long-term behavior is obtained.

In WO-A-90 14959, the printhead is treated with pressurized air or vacuum so that too much toner particles do not stick to the printhead compared to a printhead without air treatment. The same document describes applying a much stronger magnetic field in a write cycle than in a cleaning cycle to remove magnetic toner particles from the printhead.

In US Pat. No. 5,526,029, ionized air is used to blow a print head,
World Patent Publication A which reduces the interaction between toner particles and the print head and does not provide any pretreatment of the air used
It is described that toner particles can be removed more easily than in the case of 90 14959.

In EP-A-780 740, the insulating material, a slit as a printing hole made from two sides (SA and SB) of the insulating material, and a control electrode, comprising A print head structure for DEP (Direct Electrostatic Printing) is described, wherein only one of the sides has a control electrode. In such printhead structures, fine (up to about 400 μm diameter) circular, elliptical,
There is less opportunity for the printing holes to become clogged as compared to printhead structures that use rectangular or square printing holes.

In US Pat. No. 5,625,392, instead of individual holes or large slits as described in EP A 780 740, there is a rather large free area between the toner applicator and the toner receiver. However, an edge electrode is described which provides better properties with respect to clogging of the printhead structure.

However, the edge electrode proposed in US Pat. No. 5,625,392 uses a toner applicator to improve the image contrast between the low density image portion and the high density image portion. The disadvantage is that only moderate printing speeds can be obtained, since the overall propulsion field between the toner receiver above the rear electrode must be set to a relatively low value.

The system described in US Pat. No. 5,625,392 works best when the distance between the edge electrode and the back electrode, ie, the distance over which the receiving substrate can pass, is 500 μm. This small distance limits the usefulness of the device. Because European Patent 811 89
This is because printing on a thick image receiving substrate as described in No. 4 is impossible.

Therefore, there is a need for a more time-stable and improved DEP device with increased printing speed and less clogging.

[0033]

SUMMARY OF THE INVENTION It is an object of the present invention to provide high speed with high clogging of the control electrodes, high maximum density and high density resolution (i.e., producing images with large discriminable density levels) and spatial resolution. DEP that can be printed with
It is to provide an apparatus, namely a direct electrostatic printing apparatus.

Another object of this invention is to use with a wide range of toner particles, to provide high clogging of the control electrodes, and to print at high speeds with constant high maximum density and print quality over a long period of time. To provide a DEP device that can be obtained.

Still another object of the present invention is to provide an edge print head structure capable of performing DEP printing at high density without clogging.

It is yet another object of the present invention to provide an edge printhead structure that can produce a DEP printing device that can print without clogging with high spatial resolution over a large density range.

[0037] Other objects and advantages of the present invention will become apparent from the following description.

It is an object of the present invention to provide a flow of charged toner particles from a device for transferring charged toner particles having a toner releasing surface to an image receiving substrate, and a device for transferring the charged toner particles and the image receiving device. A device for applying a DC voltage difference between the substrate and a printhead structure having a control electrode inserted into the stream of toner particles for image-wise controlling the stream of toner particles; The printhead structure controls the flow of the toner particles from one side only, and further provides a direct electrostatic printing device equipped with a device for applying an alternating electric field having a frequency of 1.5 to 3 kHz to the toner discharge surface. Is achieved by

It is a further object of the present invention to create charged toner particles on the surface of a device for transferring toner particles, applying a DC voltage between the surface of the device for transferring charged toner particles and an image receiving substrate, Creating a stream of charged toner particles from the device for transporting the toner particles to the image receiving device; inserting an edge print head structure having a control electrode into the stream of toner particles; Frequency 1.5-3 on the surface of the device to be transferred
applying an alternating voltage of kHz to the image-controlled substrate, depositing the stream of toner particles on the image receiving substrate, and fixing the toner particles to the substrate. Achieved by providing.

[0040]

Definition: An "edge printhead structure" is defined as consisting of an insulating material having control electrodes at the edges of the insulating material for modulating the toner flow according to the image, and in a DEP device only one side of the toner flow. A printhead structure inserted into the stream. On the side of the toner stream opposite to the side where the edge printhead structure is inserted, there are no members that affect the toner stream. European Patent A-780
This differs from printhead structures with slits in which the toner flow is modulated imagewise, as described in US Pat. No. 740.

"Toner release surface (toner beari)
"ng surface" is the surface of the toner particle transfer device where the flow of toner particles toward the image receiving substrate is created.

[0042]

DETAILED DESCRIPTION OF THE INVENTION As described in the "Background of the Invention" section, a stream of charged toner particles is created between an apparatus for transporting charged toner particles in a DC electric field and an image receiving substrate. A DEP such that a printhead structure having a control electrode around a printing aperture is inserted into the stream of toner particles to control the flow of the toner according to an image.
In an apparatus, applying an alternating electric field to the surface of the toner particle transfer device creates a dense cloud of toner particles near the printing aperture, which can increase the printing speed. It is known in the field of printing. From this point of view, it seems that a wide range of values can be used for the frequency of the AC electric field and the peak-to-peak voltage in this regard. For example, the frequency is 2-5 kHz,
As the voltage, a value of 500 to 2000 V is described.

Surprisingly, in the present invention, in a DEP device in which the flow of toner particles is controlled from only one side by the printhead structure (ie, a DEP device using an edge printhead structure), the frequency is extremely high. It has been found that it must be limited to a narrow range. The frequency of the AC electric field applied to the toner discharge surface is 1.5
Good maximum density is obtained only at ~ 3 kHz. The frequency of the AC electric field is preferably 1.75 to 2.75 kHz. Further, a lower peak-to-peak voltage gives better results than those described in the prior art. When the peak-to-peak voltage is 400 to 1000 V, a sufficient _Dmax can be obtained. The peak-to-peak voltage (VAC) of the _AC electric field used is the distance (d) from the toner discharge surface and the control electrode of the edge print head structure.
Was found to be a function of Further, in a DEP device using an edge printhead structure reaches the D _max When V _AC / d is 10 or more, better D _max When V _AC / d of 15 or more is obtained.

An AC electric field is applied to the surface of the device that transports toner particles in a DEP device in which the flow of toner particles is controlled from only one side by the printhead structure (ie, a DEP device with an edge printhead structure). With the introduction of the device, it has been found that printing speeds faster than 100 cm / min, and in some cases even higher than 200 cm / min, can produce DEP devices with sufficiently large _Dmax . Such a fast DEP printing device could be used for a long time without causing print quality problems.

Further, even when the distance between the control electrode of the edge print head structure and the surface of the toner transfer device is not such that the edge of the print head structure and the toner transfer device are in sliding contact with each other. The device was found to be operable. In this case, only the spacer device attached to the edge electrode and the toner transfer device are in sliding contact in the area near the edge of the edge electrode. In another embodiment of the present invention, the edge electrode can be attached to a rigid frame so that the edge electrode and the toner transfer device do not slip and contact with each other. Also, the distance between the edge printhead structure and the back electrode can be increased by 1000 μm or more without compromising the quality of the print, so that printing is performed on a thick receiving substrate or a receiving substrate having a widely varying thickness. can do.

FIG. 1 illustrates a DE according to a specific embodiment of the present invention.
1 shows a P device.

The illustrated DEP device includes a toner particle transfer device having a container (101) for a developer (102), a core (103a) on which a magnet is present, and a sleeve mounted for rotation about the core. There is a magnetic brush (103) with (103b). Developer (102) can be a single component developer containing magnetic toner particles, in which case the toner particles are present on the surface of the sleeve on the surface of the magnetic brush. That is, the surface of the sleeve (103b) of the magnetic brush is a toner emission surface. The developer (102) may be a multi-component developer containing magnetic carrier particles and non-magnetic toner particles, in which case the carrier particles and toner particles are present on the sleeve of the magnetic brush. . However, even in this case, the sleeve is a toner discharging surface. The magnetic brush (103) has a fixed core (103
a) and a sleeve (103b) mounted for rotation about the core and provided with a device for rotating the core. In another embodiment, the magnetic brush core (103a) is also provided with a device for rotating the core, so that the magnetic brush can also rotate, and the sleeve (103b) rotates around the core or It can be kept stationary. (The device for rotating the core and / or the sleeve is not shown in the figure). The portion of the rotating magnetic brush rotates in the direction of arrow B. A device for applying a DC voltage is connected to the sleeve of the magnetic brush,
A device for applying a DC voltage of V1 to the sleeve and applying an AC electric field is connected to the sleeve of the magnetic brush, and applies an AC1 electric field to the sleeve (toner discharge surface). The amount of toner on the toner release surface is determined by the doctor knife blade (11).
Adjusted by 3).

The illustrated device further includes a rear electrode (105) connected to a DC voltage power supply, which supplies a voltage of V4 to the electrode. Image receiving substrate (108)
The sleeve (1) is moved by the device (107) for moving the substrate.
03b) and the rear electrode in the direction of arrow A.
The difference between the voltages V4 and V1 results in a DC propulsion electric field, creating a flow (104) of toner particles from the sleeve (toner emitting surface) of the magnetic brush to the image receiving substrate on the rear electrode.
Due to the alternating electric field AC1 on the sleeve of the magnetic brush, the flow (104) of the toner particles is tighter than without an alternating electric field.

On one side of the toner particle stream, a printhead structure having a control electrode (106a) with an insulating material (106c) is inserted into the toner particle stream (104). A DC power supply (V3) is coupled to the control electrode, and the voltage applied by the DC power supply is imagewise modulated and modulates the toner flow imagewise in the vicinity of the control electrode. The voltage applied by the DC power supply V3 can vary between a value that completely blocks the toner particles and a value that allows all of the toner particles to pass without blocking. The control electrode in this printhead structure is at a distance d from the toner discharge surface and the spacer (1) during operation of the apparatus.
10) keeps this distance d constant.

The illustrated device further includes a device for fixing the toner particles to the image receiving substrate.

In FIG. 1, the toner discharge surface is the surface of the sleeve of the magnetic brush. In FIG. 2, another embodiment is shown, wherein the toner release surface is the surface of an applicator carrying toner particles derived from a non-magnetic single component developer.

The apparatus shown in FIG. 2 is similar to the apparatus shown in FIG.
1 only the numerical differences from those used in FIG. 1 will be described. Within the non-magnetic single component developer container (101) is a roller (112) having one surface. Toner particles are supplied to this surface by a supply roller (114) made from a porous foamed polymer. The non-magnetic single-component developer is mixed by the mixing blade (114) of the developing device, and is conveyed toward the supply roller. The doctor knife blade (113) controls the thickness of the charged toner particles on the surface of the roller (112), the toner discharge surface.

FIG. 3 shows an enlarged view of FIG. 2 (within the circle X in FIG. 2) for an edge printhead structure of a particular design. In this figure, the insulating material (10
6c) is shown, including an edge printhead structure having an edge control electrode (106a). The control electrodes are separated from one another and are each connected via integrated circuits to a DC voltage supply V3. The voltage applied by the DC power supply is modulated according to the image and modulates the flow of toner in the vicinity of the control electrode according to the image. The voltage applied by the DC power supply V3 can be varied between a value that completely blocks the passage of the toner particles and a value that allows all of the toner particles to pass without blocking. The surface of the insulating material (106c) with the control electrode (106a) is covered by the insulating material (110) acting as a spacer, keeping the control electrode at a distance d from the toner discharge surface (112). This surface is connected to a DC power supply (V1) and an AC power supply (AC1). The insulating material (10
On the side of 6c) there is a reinforcing layer (115) made of plastics (preferably polyester). The printhead structure is mounted on the frame (116) so that it has a free length (FL). Rear electrode (1
05), to which a DC voltage V4 is applied. An image receiving substrate (108) is passed between the back electrode and the printhead structure.

FIG. 4 shows an enlarged view of FIG. 2 (within the circle X in FIG. 2) for an edge printhead structure of a particular design. This figure shows an edge printhead structure comprising an insulating material (106c) and having an edge control electrode (106a) on one surface at the edge of the surface, the control electrode being an integrated circuit. DC voltage power supply V
3 is connected. The surface of the insulating material (106c) opposite the surface on which the control electrode (106a) is located is covered with a single shielding electrode (106b) (to which a single DC voltage (V2) is applied). The shield electrode does not extend to the edge of the edge printhead structure, and a spacer (112) is present above the shield electrode to keep the control electrode at a distance d from the toner discharge surface (112). This surface is connected to a DC power supply (V1) and an AC power supply (AC1).) There is a rear electrode (105) to which a DC voltage V4 is applied. An image receiving substrate (108) is passed between the back electrode and the printhead structure.

In FIGS. 1, 2, 3 and 4, the toner release surface is the surface of the magnetic brush sleeve (FIG. 1),
2 is a side view of a dispenser for a non-magnetic single-component developer. The DEP device of the present invention may also be equipped with a charged toner carrier (CTC) on a surface for applying charged toner particles by a magnetic brush or a non-magnetic single-component developer applicator. it can. In this case, the toner discharge surface is the surface of the CTC, and a device for applying an alternating electric field AC1 is connected to this surface.

The printhead structure used in the DEP device of the present invention can have the form described in US Pat. No. 5,625,392. The printhead structure (106) used in the DEP device of the present invention preferably has the shape shown in FIGS.

In this figure, 106c is the insulating material, 106a is the complex addressable electrode structure, hereinafter referred to as the "control electrode", and 106d is the printhead structure inserted into the stream of toner particles. The edge and arrow TF indicate the direction of toner flow from the toner release surface (not shown) to the image receiving substrate (not shown). FIG. 5a shows the simplest form of the first embodiment of the printhead structure according to the invention. On one side of the insulating material (106) is a control electrode (106a). FIG. 5a shows a printhead structure in which the control electrodes are oriented in the direction of toner flow (ie, toward the image receiving substrate), but are oriented in other directions within the DEP device of the present invention. It is also possible to use a printhead structure that has a control electrode that has been oriented toward the toner discharge surface. FIG. 5b shows another variation of the printhead structure that can be used in the DEP device of the present invention. The control electrodes (106) on both sides of the insulating material (106b)
In a), the arrangement is such that the control electrodes (106a) are paired (one on each side) and overlap exactly in the pair. The control electrodes (106a) present on both sides of the insulating material (106c) are connected to each other via a metal plating on the edge (106d) in pairs, as shown in FIG. 5c, to form a single control electrode. creating. Methods and apparatus for connecting electrodes through printing holes are well known in the art. An example of such a device is described in EP-A-753.
No. 413.

In FIGS. 6a and 6b, the D
Another variation of a printhead structure used in an EP device is shown. 6a and 6b, the control electrodes (106a) on both sides of the insulating material are staggered. In FIG. 6a, the width of the control electrode parallel to the length of the edge (106d) is chosen so that there is some overlap between the control electrode on one side of the insulating material (106c) and the control electrode on the other side. Have been. In FIG. 6b, the control electrodes parallel to the length of the edge (106d) are chosen such that there is no overlap between the control electrodes on one side of the insulating material (106c) and the control electrodes on the other side. .

FIG. 7 shows an edge electrode according to another embodiment of the present invention. In FIG. 7,
106c is an insulating material, 106a is a complex addressable electrode structure, hereinafter referred to as a "control electrode", 106b is a common shielding electrode on the other side of the insulating material, and 106d is in the flow of toner particles. And the arrow TF indicates the direction of toner flow from the toner discharge surface device (not shown) to the image receiving substrate (not shown). FIG. 7a shows the simplest form of the printhead structure of this embodiment of the invention. That is, a control electrode (106a) exists on one surface of the insulating material (106c), and a common shielding electrode (106b) exists on the other side. In one plane, both control electrodes, separators and shielding electrodes have been cut off at edge 106d. In FIG. 7a, the printhead structure is shown with control electrodes oriented in the direction of toner flow (i.e., toward the image receiving substrate), but the control electrodes oriented in the other direction, i.e., toward the toner discharge surface. A printhead structure having the same can be introduced into the DEP device of the present invention. FIG. 7b shows another embodiment of the present invention. On one side of the separating member there is a control electrode and on the other side there is a common shielding electrode. Both control electrodes and separating elements are cut off at the edges, but the shielding electrodes do not extend to the edges. That is, the end of the shielding electrode is at a certain distance from this edge, for example, 500 μm. The use of the shield electrode on the edge print head structure has the advantage that printing can be performed in a large density range and a wide range of densities compared to the use of the edge print head structure without a shield electrode. The distance of the shielding electrode from the edge has been found to be an important parameter for obtaining optimal results, with a compromise between the range of printable shading and the degree of printing fog.

FIG. 8 shows an edge electrode according to another embodiment of the present invention. In FIG. 8, 10
6c is the insulating material, 106a is the complex addressable electrode structure, hereinafter referred to as the "control electrode", 106d is the edge of the printhead structure inserted into the stream of toner particles,
Arrow TF indicates the direction of toner flow from a toner discharge surface device (not shown) to an image receiving substrate (not shown). As shown in FIG. 8, this edge is not straight but has a shape with two heights. In FIGS. 8a and 8b, this edge looks like a crenellated chest wall with alternating crenellated and convex walls. The crenellated shape is such that the control electrode can be located at its edge, the convex wall is parallel to the edge of the printhead structure, so that adjacent control electrodes overlap to some extent. FIG. 8c shows another method of making a printhead structure with adjacent control electrodes overlapping to some extent. In this figure, the edges are serrated, with a control electrode at each tooth. As in FIG. 5b, adjacent control electrodes overlap one another in the printing direction, but in the embodiment of FIG. 8 both adjacent control electrodes are on the same plane of insulating material (106c), and therefore in the same plane. It is in. Edge cuts (either serrated or crenellated) can be made, for example, with an excimer laser.

The insulating material used to make the printhead structure used in the DEP device of the present invention can be glass, ceramics, plastics, and the like.
Preferably, the insulating material is plastics,
Polyimide, polyester (for example, polyethylene terephthalate, polyethylene naphthalate, etc.), polyolefin, epoxy resin, organosilicon resin, rubber and the like can be used.

The choice of insulating material used to make the printhead structure used in the DEP device of the present invention is governed by the elastic modulus of the insulating material. The insulating material useful in the present invention has an elastic modulus of 0.1 to 10 G.
Pa, preferably 2-8 GPa, most preferably 4-6 GPa
GPa. The thickness of the insulating material is 25-1000 μm,
Preferably it is 50 to 200 μm.

The rear electrode (105) used in the DEP device of the present invention can be made to work with a printhead structure, for example, US Pat. No. 4,568,955.
No. 4,733,256, and various needles and wires electrically insulated and connected to a single power source. The back electrode that works with the printhead structure is one or more flexible PCBs
(A printed circuit board).

The present invention comprises the steps of: forming charged toner particles on the surface of a device for transferring toner particles; applying a DC voltage between the surface of the device for transferring charged toner particles and an image receiving substrate; A stream of charged toner particles from the device for transporting the toner to the image receiving device;-inserting an edge printhead structure having control electrodes into the stream of toner particles;-a device for transporting the toner. Frequency 1.5-3 on the surface of
applying an alternating voltage of kHz to the image-controlled stream of toner particles on the image receiving substrate, and fixing the toner particles to the substrate. The invention relates to a method of operating a device.

A DEP device according to the invention also provides a method for performing DEP printing on an insulated receiving substrate having first and second surfaces, the method comprising: coating the insulated first surface with a conductive layer; -Connecting the conductive layer to a voltage source by means of a device for charging the conductive charge;-applying a DC electric field between the conductive layer and the device for transferring toner particles, the surface of the toner particle transfer device; Creating a stream of charged toner particles from the surface to the conductive layer, wherein the surface of the toner transfer device has a frequency of 1.5-3k
Applying an alternating voltage of Hz to the edge of the printhead structure having the control electrode into the flow of toner; applying a voltage to the control electrode to control the flow of toner particles according to the image; Imagewise depositing the toner particles through the holes in the head structure and into the conductive layer on the substrate, and fixing the toner particles to the substrate can be operated without a rear electrode. .

Such a method is described in EP-A-82.
No. 3676.

Further, the DEP of the present invention is a method for direct printing with reduced banding, comprising: an image receiving substrate, and a rotatably mounted core and a rotatably mounted core. Creating a direct current potential difference between the magnetic brush assembly having the sleeve and the core; rotating the wick at a rotational speed of 500 revolutions per minute or more;
Rotating the sleeve at a speed of 10 revolutions per minute or less; coating the magnetic brush assembly with a developer consisting of toner particles and magnetically attractable carrier particles; Creating a flow of toner particles to the image receiving substrate; applying a voltage to the control electrode to control the flow of toner particles according to the image; and applying a frequency of 1.5 to the surface of the sleeve of the magnetic brush.
Applying an alternating voltage of ３3 kHz, peak-to-peak voltage of 500-1000 V, inserting the edge of a printhead structure with control electrodes into the stream of toner particles, and through the printing holes onto the substrate Imagewise depositing the toner particles, and fixing the toner particles on the substrate. Such a method is described in EP-A-827 046.

Operated by the above method, the DEP device of the present invention in which the sleeve of the magnetic brush acts as a toner release surface (ie, the flow of toner originates directly from the sleeve of the magnetic brush) can be any type of known carrier particles and Good results can be obtained using toner particles. However, it is preferred to use "soft" magnetic carrier particles. The "soft" magnetic carrier particles used in the DEP device in a preferred embodiment of the present invention are soft ferrite carrier particles. Such soft ferrite particles have low residual magnetic behavior and have a coercive force value of about 4 to about 20 kA / m (50 to 250 Oe). Another useful soft magnetic carrier particle used in a preferred embodiment of the present invention is EP-B-289.
No. 663, and composite carrier particles comprising a mixture of two magnetites having different particle sizes. The particle size of both magnetites varies between 0.05 and 3 μm. The carrier particles have an average volume diameter (dv ₅₀ ) of 1
It is 0 to 300 μm, preferably 20 to 100 μm.
A more detailed description of the above carriers is given in EP 675 417, which is incorporated by reference.

In the DEP device of the present invention, it is possible to use particles whose absolute average charge (| q |) corresponds to 1fc <| q | <20fc, preferably 1fc <| q | <10fc. preferable. The absolute average charge of the toner is the D of Neufahrn D-8056, Germany.
r. R. Epping PES-Laboratoli
It is measured by a device commercially available from um under the name "q-meter". The charge distribution (q, fc units) of the toner particles with respect to the diameter (d, 10 μm units) of the toner particles measured by a q-meter is measured. Absolute average charge per 10 μm (| q | / 1
0 μm) to calculate the absolute average charge. Also, the charge distribution measured by the above device is narrow, that is, the coefficient of variation (ν),
That is, the standard deviation of the average value is preferably 0.33 or less. The toner particles used in the apparatus of the present invention preferably have an average volume diameter (dv ₅₀ ) of 1 to 20 μm, more preferably 3 to 15 μm. A more detailed description of the above toner particles can be found in EP A 675 471.
No.

A DEP device using the toner particles made as described above can be addressed in a manner that performs black and white printing. A "binary method" useful for creating classic two-level halftones that create black and white text and images, and images with continuous shading
Can be operated.

The DEP device of the present invention is particularly suitable for producing images having multiple gray levels. Gray level printing can be controlled by modulating the amplitude of the voltage V2 applied to the control electrode 106a, or by modulating V2 over time. By varying the usage of time modulation at a particular frequency, fine gray level differences can be accurately printed. Further, gray level printing can be controlled by combining amplitude modulation and time modulation of the voltage V3 applied to the control electrode.

Combining the high spatial resolution typical of DEP with the ability to print multiple gray levels, see, for example, EP-A-634 862, "Screening for devices with limited density resolution." Opening the way to implement multiple halftone application methods such as those described under "Methods". Thereby, high quality images can be obtained using the apparatus of the present invention.

[0073]

【Example】

Example 1 Printhead Structure A 50 μm thick polyimide film (106c) was coated on one side with a 5 μm thick copper film to create a printhead structure. Along the front edge of the printhead structure,
Inserting into the flow of toner particles facing the toner transfer device and from the toner transfer device to the rear electrode, the size 22
A rectangular control electrode (106a) of 0 μm (measured in a direction parallel to the edge) is arranged at a linear pitch of 300 μm. Each control electrode is connected via a 2MΩ resistor to the US Supertex
HV507 (R) high voltage switching integrated circuit, which is powered by a high voltage power supply. At the top of the control electrode on the entire surface of the polyimide insulation member is a 110 μm thick polyurethane (110), which is in physical contact with the charged toner particles on the sleeve of the toner transfer device. I have. On the back side of the printhead structure, facing the rear electrode, a thickness of 23
There is a 0 μm adhesive coating (not shown) and a 175 μm thick polyester sheet (11).
5). The printhead structure is attached to a PVC frame, leaving an 8 mm (FL) portion of the edge electrode to bend and bend.

Toner Transfer Device The toner transfer device is COLOR LASER WRITE
COLOR LESAR TONERCART, a non-magnetic single component developer for R (registered trademark of Apple Inc., USA)
A commercially available toner cartridge consisting of RIDGE MAGENTA (M3760GIA). The toner discharge surface is an aluminum roller surface (112), on which toner particles are coated by a supply roller (111). The toner particles are negatively charged.

The edges of the printhead structure attached to the print engine PVC frame (116) are bent and brought into frictional contact with the surfaces of the rollers of the toner transfer device. A 110 μm thick polyurethane coating was used as the self-regulating spacer device (110).

The rear electrode is placed after the printing paper, the distance between the rear electrode (105) and the back of the printhead structure (ie, control electrode (106a)) is 1000 μm, and the paper is run at a speed of 200 cm / min. You.

For each control electrode (according to the image)
A voltage of 0 V to 280 V is applied. The rear electrode is connected to a high voltage power supply, and a voltage of +1000 V is applied to the rear electrode. An AC voltage having a peak-to-peak voltage of 1000 V and a frequency of 1 kHz and a DC bias voltage (V1) of -50 V are applied to the toner discharge surface of the toner transfer device. The DC propulsion electric field, ie, the voltage difference between V4 and V1, is 1050V. Perform gray level printing and use MacBeth TR
Density at all image densities (D _max ) was measured using a 1204 densitometer in reflection mode.

Control Example The same experiment as in Example 1 was performed, except that only a DC voltage of -700 V was applied to the toner discharge surface. DC propulsion electric field, ie V4
Despite raising the voltage difference between V1 and V1 to 1700 V, no image density was obtained under these conditions.

Examples 2 to 6 The same experiment as in Example 1 was conducted, except that the AC frequency applied to the toner discharge surface was changed as shown in Table 1. Table 1 also includes the print density measurement results.

Examples 7 to 9 The same experiment as in Example 1 was performed, except that the print head structure was changed as follows.

A 50 μm thick polyimide film (1
06c) was coated on one side with a 5 μm thick copper film,
Created a printhead structure. 220 μm (measured in a direction parallel to the edge) along the front edge of the printhead structure, facing the toner transport and into the flow of toner particles from the toner transport to the rear electrode do it)
Rectangular control electrode (106a) with a linear pitch of 300 μm
Place with Each control electrode is connected to the U.S.
It is coupled to an HV507 (R) high voltage switching integrated circuit manufactured by uppertex and is powered by a high voltage power supply. At the top of the control electrode on the back of the polyimide insulation member is a 110 μm thick polyurethane member, a 230 μm thick adhesive layer and a 175 μm thick polyester sheet. The edge electrode is attached to a PVC frame 10 mm from the edge. The edge electrode is bent toward the toner transfer device as described in Example 1, but on the sleeve of the toner transfer device via the 50 μm thick polyimide which functions as a self-adjusting spacer device. In contact with charged toner particles. 1000V peak-to-peak voltage, frequency 3
When an alternating voltage (AC1) of kHz was applied to the toner discharge surface, the image density reached 1.04 (compared to 0.54 in Example 3). Only 800 peak-to-peak voltage
Repeating the experiment at V and 500 V resulted in image densities of 0.87 and 0.55, respectively.

Examples 10 to 16 The same experimental conditions as in Example 1 were used, except that the print head structure was changed as follows.

A 50 μm thick polyimide film was coated on one side with a 5 μm thick copper film to create a printhead structure. Along the front edge of the printhead structure,
Inserting into the flow of toner particles facing the toner transfer device and from the toner transfer device to the rear electrode, the size 22
A rectangular control electrode (106a) of 0 μm (measured in a direction parallel to the edge) is arranged at a linear pitch of 300 μm. Each control electrode is connected via a 2MΩ resistor to the US Supertex
HV507 (R) high voltage switching integrated circuit, which is powered by a high voltage power supply. On the other side of the polyimide foil, a continuous copper shielding electrode (106b) having a thickness of 120 μm is attached in a laminate by an adhesive having a thickness of 230 μm. An 800 μm-thick polyimide spacer (1
10), and thus the distance between the toner discharge surface and the control electrode is 800 μm. The edges are sharply cut off at all these layers. The shield electrode is grounded. The other experimental conditions were the same as those in Example 1, except that the AC voltage (AC1) applied to the toner discharge surface had a peak-to-peak voltage of 17
00V and the frequency was 3 kHz.

In Example 10, the shield electrode reached the edge of the printhead structure and the paper ran at a speed of 200 cm / min. That is, the printing speed was 200 cm / min.

In Example 11, the same printing device was used, but a continuous copper shield electrode with a polyimide spacer device was placed 1000 μm away from the edge of the control electrode. The printing speed was 100 cm / min.

In Example 12, the same printing device was used, but a continuous copper shield electrode with a polyimide spacer device was placed 1000 μm away from the edge of the control electrode. The printing speed was 40 cm / min.

In Example 13, Example 12 was repeated, but the printing speed was set to 100 cm / min.

In Example 14, Example 12 was repeated, but the printing speed was set to 200 cm / min.

In Example 15, Example 13 was repeated, but the thickness of the spacer device was changed to 200 μm instead of 800 μm.

In Example 16, Example 14 was repeated, but the thickness of the spacer device was changed to 200 μm instead of 800 μm.

Examples 12 to 16 show that not only the background density (D _min ) is low but also the density range is wide. Comparing the density range of Examples 12-16 with the density range of Example 3, it was found that the density range printed in Examples 12-16 was wider.

The printing conditions, maximum density and minimum density of Examples 1 to 16 are summarized in the following table.

[0093]

[Table 1]

Note) Speed: printing speed, in cm / min.

V _AC : _AC voltage applied to the toner discharge surface in volts (peak-to-peak voltage).

FREQ _AC : The frequency of an AC electric field applied to the toner discharge surface in kHz.

SHIELD: presence or absence of a shielding electrode. no: There is no shielding electrode. e: There is a shielding electrode extending to the edge.
e-500: The shielding electrode exists at a distance of 500 μm from the edge.
e-1000: the control electrode is 1000 μm away from the edge.

SPACING: distance between the control electrode and the toner discharge surface in μm.

D _max : maximum density.

D _min : minimum density.

As will be apparent to those skilled in the art, many modifications to the inventive concept can be made without departing from the scope of the invention. For example, the edge electrode can be fixed to the toner transfer device without using a spacer device on a fixed frame, and by creating an edge electrode having another set of control electrodes different from that of FIG. 6b. The resolution of the device can be increased, or by displacing and overlapping sets of control electrodes, either on a different surface than in FIG. 6a or on the same surface as depicted in FIG. 7, over a large area. The effect of the control electrode can also be increased.

The main features and embodiments of the present invention are as follows.

1. A device for creating a flow of charged toner particles from the surface from which the charged toner particles are released to the image receiving substrate and for applying a DC voltage difference between the surface from which the charged toner particles are released and the image receiving substrate; And an insulating material having a second major surface;
One of the surfaces is a print for controlling the flow of the toner particles from one side only, with one edge supporting a control electrode inserted into the flow of the toner particles for imagewise controlling the flow of the toner particles. A direct electrostatic printing device comprising a head structure and a device for applying an alternating electric field having a frequency of 1.5 to 3 kHz to the toner discharge surface.

2. The alternating electric field has a frequency of 1.75-2.
2. The device according to claim 1, wherein the frequency is 75 kHz.

3. The apparatus of claim 1 wherein said toner discharge surface is within said printhead structure at a distance greater than 100 μm from said control electrode.

4. The apparatus of claim 1 wherein said control electrode is on both said major surface of said insulating material of said printhead structure.

5. 5. The apparatus of claim 4, wherein said control electrodes on said both major surfaces are offset.

6. 6. The apparatus of claim 5, wherein adjacent ones of said staggered control electrodes overlap one another.

7. The first aspect, wherein the control electrode is on only one of the major surfaces, and wherein the printhead structure has an edge having a shape selected from the group consisting of a serrated shape and a crenellated shape. The described device.

8. The control electrode is on the first major surface of the insulating material, and a shielding electrode is on the second major surface, the control electrode extending to the edge of the insulating material. 2. The apparatus of claim 1 wherein said shielding electrode is at least 200 [mu] m from said edge.

9. -Forming charged toner particles on the surface of the device for transferring the toner particles;-applying a DC voltage between the surface of the device for transferring the charged toner particles and the image receiving substrate to transfer the toner particles from the device for transferring the toner particles. Creating a stream of charged toner particles towards the image receiving device;-inserting the edge of the printhead structure supporting the control electrode from only one side into said stream of toner particles;-directing the stream of toner particles according to the image. Applying a DC voltage according to the image data to the control electrode for controlling; a frequency of 1.5 to 3 on the surface of the device for transferring the toner;
a direct electrostatic printing process comprising applying an alternating voltage of kHz to the image-controlled flow of the toner particles on the image receiving substrate, and fixing the toner particles to the substrate.

[Brief description of the drawings]

FIG. 1 shows a DEP device that uses an edge printhead structure and a magnetic brush as a toner source.

FIG. 2 shows a DEP device using an edge printhead structure and a non-magnetic single component developer dispenser as a toner source.

FIG. 3 is an enlarged view of a portion surrounded by a circle X in FIG. 2 and shows a specific embodiment of the edge print head structure of the present invention.

FIG. 4 is an enlarged view of a portion surrounded by a circle X in FIG. 2 and shows another specific embodiment of the edge print head structure of the present invention.

FIG. 5 illustrates various embodiments of the edge printhead structure of the present invention.

FIG. 6 illustrates various embodiments of the edge printhead structure of the present invention.

FIG. 7 illustrates another possible embodiment of the edge printhead structure of the present invention.

FIG. 8 illustrates yet another possible embodiment of the edge printhead structure of the present invention.

[Explanation of symbols]

 101 Container 102 Developer 103 Magnetic Brush 104 Flow 108 Image Receiving Substrate 110 Spacer

Claims (2)

[Claims] An apparatus for creating a flow of charged toner particles from a surface that discharges charged toner particles to an image receiving substrate, and applying a DC voltage difference between the surface that discharges the charged toner particles and the image receiving substrate. -Having an insulating material having first and second major surfaces;
One of the surfaces is a print for controlling the flow of the toner particles from one side only, with one edge supporting a control electrode inserted into the flow of the toner particles for imagewise controlling the flow of the toner particles. A direct electrostatic printing device, comprising: a head structure; and a device for applying an alternating electric field having a frequency of 1.5 to 3 kHz to the toner discharge surface. 2. forming charged toner particles on the surface of the device for transferring the toner particles, and applying a DC voltage between the surface of the device for transferring the charged toner particles and the image receiving substrate to transfer the toner particles. Creating a stream of charged toner particles from the device to the image receiving device; inserting into the stream of toner particles the edge of the printhead structure supporting the control electrode from only one side; Applying a DC voltage according to the image data to the control electrodes in order to control the flow according to the image; a frequency of 1.5 to 3 on the surface of the device for transferring the toner;
applying an alternating voltage of kHz to the image-controlled deposition of the stream of toner particles on the image receiving substrate, and fixing the toner particles to the substrate.