JPH09174914A - Printing head structure and dep apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To materialize high density and high spatial resolving power at a high printing speed by supporting a control electrode only by one of two sides forming a slit. SOLUTION: Control electrodes 102a are provided on one surface of the insulating material 102 forming one side SA of a slit 103 and no electrodes are provided on the insulating material 102 forming the other side SB of the slit. As clear from a toner flow direction TF, the control electrode 102a on one side SA of the slit faces to a toner receiving part. As the insulating material 102a to be used, a plastic material is suitable and has the modulus of elasticity of 0.1-10Gpa, most pref., 4-6Gpa. By this constitution, during the arrangement of a printing head structure, the special condition related to the registration of the insulating material 102 forming the sides SA, SB of the slit is not occurred.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to devices used in electrostatic printing processes and more particularly in direct electrostatic printing (DEP). In DEP, electrostatic printing is done directly by electronically addressable printhead structures from toner delivery means on a receiving component substrate.

[0002]

BACKGROUND OF THE INVENTION In DEP (Direct Electrostatic Printing), toner or developing material is directly deposited in an image-wise manner on a receiving substrate, the latter or receiving substrate having an image-wise electrostatic latent image. I haven't. The substrate can be an intervening flexible endless belt (aluminum, polyimide, etc.). In that case, the image-wise deposited toner must be transferred onto another final substrate. Preferably the toner is deposited on the final receiving substrate, giving the possibility to form the image directly on the final receiving substrate, eg plain paper, clear positive. This deposition step is followed by the final melting step.

This distinguishes the method from classical electrophotography by developing an electrostatic latent image on a charge-bearing surface with a suitable material that makes the latent image visible. In addition, the powder image is either directly fused to the charge-bearing surface, which then results directly in electrophotographic printing, or the powder image is subsequently transferred to the final substrate and then fused with the medium. The latter method results in indirect electrophotographic printing. The final substrate can be a transparent medium, an opaque polymeric film, paper and the like.

DEP is also significantly different from electrophotography in which additional steps and components for forming an electrostatic latent image have been added. In particular, photoconductors are used and charge / exposure cycles are required.

A DEP device is disclosed, for example, in US Pat. No. 3,689,
No. 935. This document refers to: a layer of insulating material called the separating layer, a shield electrode consisting of a continuous layer of conducting material on one side of the separating layer, a division of the conducting material on the other side of the separating layer. Disclosed is an electrostatic line printer having a plurality of control electrodes formed by patterned layers, and-a multilayer particle modulator or printhead structure comprising at least one row of apertures. 1 for each control electrode
They are formed around two apertures and are separated from each other by the control electrodes.

A selected potential is applied to each of the control electrodes while a constant potential is applied to the shield electrodes. Due to the generally applied propulsion field between the toner delivery means and the receiving part, the charged toner particles project through a row of apertures in the printhead structure. The intensity of the particle stream is modulated according to the pattern of potentials applied to the control electrodes. The modulated stream of charged particles impinges on a receptor substrate interposed in the modulated particle stream. The receiver substrate is transported in a direction orthogonal to the printhead structure to provide line-by-line scan printing. The shield electrode may face the toner delivery means and the control electrode may face the receiving component substrate. A DC field is applied between the printhead structure and a single back electrode on the receiver support. This propulsion field is responsible for the attraction of toner to the receiving component substrate located between the printhead structure and the counter electrode.

DEP devices are well suited for printing halftone images. The density variations present in the halftone image are obtained by modulation of the voltage applied to the individual control electrodes. In most DEP systems, different columns of apertures are used to obtain an image with high density resolution (ie to form an image comprising a high amount of identified density levels) and spatial resolution.

Printhead structures having multiple rows of apertures have been described in the literature. For example, U.S. Pat. No. 4,860,036 discloses at least three (preferably four or more) apertures capable of printing an image having a smooth pagewidth density scale without the formation of white bands. ) A printhead structure consisting of rows is described. The main drawback of this type of printhead structure relates to the toner particle application element, which has to be able to provide charged toner particles in the vicinity of all print apertures with almost equal fluidity. U.S. Pat. No. 5,040,004 addresses this problem by introducing a moving belt that slides over a precisely positioned receiver located at a close distance from the printhead structure. However, it has been demonstrated that toner application elements operated by the friction method do not give stable results over time due to belt wear due to friction of the belt on the receiver.

US Pat. No. 5,214,451 addresses the problem of providing charged toner particles near all printing apertures having nearly equal fluidity, each shield electrode corresponding to a different row of apertures. By applying a different set of shield electrodes to the printhead structure. During printing, the apertures located at a relatively large distance from the toner application element are varied by varying the voltage applied to the different shield electrodes corresponding to the different columns of apertures. Bending a relatively large electrostatic propulsion field from the element towards the counter electrode structure results in an increase in the concentration profile.

US Pat. No. 5,136,311 describes a charged toner conveyor that extends over four roller bars such that a flat surface is located adjacent to the receiving part. In this case, no printhead structure is used, but the charged toner on the charged toner conveyor on the side facing away from the receiving part and facing away from the charged toner conveyor. An electrode structure is constructed which allows image pickup to be image-wise jumped to the receiving part. No examples are given in this document,
Extrusion of the toner from behind the charged toner conveyor to the receiving part is regulated by the printhead structure located between the charged toner conveyor and the receiving part. It must provide less accurate adjustments to the toner flow compared to the device.

European application 95201048.6, filed April 25, 1995, is an optimized toner capable of printing images of constant density and quality using a printhead structure having multiple rows of apertures. Applicable elements are listed. A very compact design of a printhead structure consisting of only two rows of square apertures is described in this document.

US Pat. No. 4,491,855 discloses a printhead structure consisting of a plastic sheet material having long slits as printing apertures and individual control electrodes on both ends of the slits and on both sides of the plastic material. Is listed.

A major drawback of this type of printhead structure is the arrangement that must be made between the two sheets of plastic material. Since the two sheets of plastic material carry the control electrodes, a drive circuit for image information must be provided on the two sheets of plastic material.

Hosaka et al. ("A new ion-jet printing hea
d controlled by a low-voltage signal ", SPIE Vol. 2
413 pp. 76-86), a bend structure of one plastic material can be used to equip a printhead structure with on-board drive ICs on either side of the print aperture. Although FIG. 4 of the document shows four rows of printing apertures, they can be replaced by a single printing slit.

However, because the toner delivery means in DEP technology is generally much larger than the ion-generating means in ion-printing technology, the printhead structure for ion-printing as described in the above-referenced publications. Such an arrangement has mounting problems in DEP technology.

The apparatus described above alleviates the problem of supplying charged toner particles to an image receiving member in an image-wise adjusted manner without the drawbacks of complex printhead structures or complex guiding structures. There are big and small, but it solves.

Therefore, a DEP system comprising a printhead structure that forms an image with high density and spatial resolution, and a simple and reliable toner application element that does not involve expensive and complex mechanical parts. There is still a desire for.

[0018]

OBJECTS AND SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved Direct Electrostatic Printing (DEP) device that prints at high density and high spatial resolution at high printing speeds.

Another object of the invention is a DE that combines high spatial and density resolution with good long-term stability and reliability.
It is to provide a P device.

Yet another object of the present invention is to provide a printhead structure for a DEP device in which the printhead structure combines a compact design with good long-term stability and reliability.

Another object of the present invention is to provide an inexpensive charged toner application element that combines a compact design with high printing speed and good long term stability.

Another object of the present invention is to provide a DEP device having a printhead structure in which clogging of the printing apertures is minimized and the printing apertures can be easily cleaned.

Further objects and advantages of the present invention will become clear from the description hereinafter.

The above purpose is to provide a slit (10) as a printing aperture formed by an insulating material (102) and two sides (SA and SB) of the insulating material (102).
3), as well as a control electrode (102a), DE
A printhead structure for a P (direct electrostatic printing) device, characterized in that only one of the two sides forming the slit aperture has a control electrode. It is realized by providing.

These objectives are further addressed by the counter electrode (10
5), a printhead structure comprising an insulating substrate (102), a control electrode (102a) and a slit aperture (103) such that the particle flow therethrough can be electrically modulated by the control electrode, a toner delivery means ( A DEP device comprising 101), characterized in that the control electrode (102a) is present on only one side of the slit aperture.

Another aspect is the two ends (EA) in which the slit is formed by at least one sheet of insulating material.
And EB) two sides SA and SB defined by
And the insulating material has the formula 0.1 GPa < YM < 1
It has a modulus of elasticity (Young's modulus, YM) that satisfies 0 Gpa, and the ends A and B with respect to each other are expressed by the formula 0 ° < α <45.
Provide a DEP device positioned at an angle α that satisfies °.

In another embodiment, the slit is made of insulating material.
It is formed by two sheets.

In another aspect of the invention, the side S of the slit is
Besides the control electrode (102a) present in A, a general shield electrode (102b) is present on the side SB of the slit.

[0029]

DETAILED DESCRIPTION OF THE INVENTION The literature describes many devices which operate according to the principle of DEP (Direct Electrostatic Printing). All these devices are capable of gray scale printing by voltage modulation or by time modulation of the voltage applied to the control electrodes.

FIG. 1 shows diagrammatically the essential features of a DEP device in which a printhead structure according to the invention can be used. Toner delivery means (101) delivers toner particles near the printhead structure (102) in which the print aperture (105) resides. The charged toner particles are generated from the toner delivery means in a DC field generated by having a back electrode (105) behind the toner delivery means of voltage V1 and the toner receiving component of voltage V4. 104). The amount of toner passing through the aperture (103) is the voltage V
3 is applied to the split control electrode (102a) around the printing aperture (103).
For example, using negatively charged toner and V1 is 0
When V and V4 are 500V, toner particles will flow to the toner receiving component when V3 is held at zero. When part 3 is held at -500 parts, toner cannot pass through the print aperture (107). At constant print time, V3 at 0V prints the maximum density and V3 at -500V prints the minimum density. Keeping V3 at various voltages between 0 and -500V,
Intermediate densities can be printed. DEP devices typically include toner receiving components (not shown in FIG. 1) (1
Further comprising means for moving 04) beyond the printing aperture (103) and means for fixing the toner image to the toner receiving means.

The problem with DEP devices is that they need to have a printhead structure with 5, 6 rows of printing apertures that can print at high speeds, and close to all printing apertures that have nearly equal flow of charged toner particles. It has been described above that there is a need to supply to. This problem has been addressed by the use of belts as CTCs, in which case it is possible to equip a flat surface with toner particles underneath a row of apertures and consequently to This is because it is possible to provide a uniform distance from the printing aperture. However, the use of moving belts results in wear of the belt due to friction on the guide parts or geometrical problems of use position to avoid said friction. Other documents describe the use of toner delivery means having a cylindrical shape with a large diameter in order to overcome the disadvantage of non-uniform toner flow towards another row of apertures.

The trend in printing devices and also in DEP printing devices is to provide a device that operates as small as possible but at high speed. From this point of view, the use of cylindrical rotating toner delivery means having a large diameter is not preferred.

As described in European Application 95200556.9, filed March 7, 1995,
It is also possible to reduce the length of the printhead structure to enable toner delivery means having a small diameter. A very compact design with only two rows of square apertures is described in this patent application.

US Pat. No. 4,491,855 describes a printhead structure, or slit aperture, having an extremely small size. This prior art printhead structure is shown in FIG. Control electrodes (102a) are present on either side of the slit formed by the two ends of the insulating material (102) that make up the printhead structure and the printing aperture (slit).
Control electrode (102a ') existing on the opposite side of (103)
There is also. High quality printing with such printhead structures requires that the corresponding control electrodes (102a and 102a ') be very accurately aligned with respect to each other. No easy and inexpensive way to equip such a printhead structure that requires very precise alignment of the flexible substrate on both sides of the slit aperture has hitherto been provided.

All of the above drawbacks are associated with printhead structures having a slit as the print aperture (103) such that there is a control electrode which must be connected to the driver IC only on one side of the slit. It can be solved by using it. Since only one side of the slit has a split control electrode, misalignment between two rows of split control electrodes is not possible.

A variety of printhead structures that are variations on the first aspect of the invention are shown in FIG. In this figure, 102 represents an insulating material, 102a represents a composite addressable electrode structure, hereinafter referred to as "control electrode", 103 represents a printing aperture (in this case a slit), and arrow TF represents the toner delivery means. Represents the direction of toner flow from (not shown) to the toner receiving component (not shown). Figure 3a shows the simplest form of the first aspect of the printhead structure according to the invention, on one side of the insulating material (102) forming the side A (SA) of the slit (103). There is a control electrode (102a). Insulating material forming the side B (SB) of the slit (1
No electrodes are present on 02). As can be seen from the direction of arrow TF, which represents the direction of toner flow from the toner delivery means (not shown) to the toner receiving component (not shown), the control electrode (1
02a) faces the toner receiving part. In FIG. 3b,
A variant is shown for the first aspect of the printhead structure according to the invention. Here again, the control electrode (102a) is present on one surface of the insulating material (102) forming the side A (SA) of the slit (103). Slit side B (S
Above the insulating material (102) forming B) is a continuous electrode (102b), or "shield electrode". As can be seen from the direction of arrow TF, which represents the direction of toner flow from the toner delivery means to the toner receiving component (not shown), the control electrode (10) on the slit side A (SA).
2a) and continuous electrodes (102b) on side B (SB)
Both face the toner receiving component. FIG. 3c shows another variant of the first aspect of the printhead structure according to the invention. This variant has a control electrode (102a) on side A and a shield electrode (102b) on side B like the variant shown in FIG. 3b, but here the control electrode (102a) is the toner receiving component (shown). No.) and the shield electrode (102b) faces the toner delivery means. Each of the printhead structures shown in Figures 3a-3c may be upside down. By doing so, the electrode structure facing the toner delivery means in Figures 3a-c faces the toner receiving component and vice versa.

The shield electrode (102b) is provided on both sides of the insulating material forming the side B (SB) of the slit (103), and the control electrode (102) is provided only on one side of the insulating material (102).
The printhead structure comprising a) is also another variation of the first embodiment of the printhead structure of the present invention and is shown in Figure 3d. In this figure, the control electrode (102
It is clear that a) faces the toner receiving component and that the printhead structure can be installed upside down in such a way that the control electrodes (102a) face the toner delivery means as shown in FIG. 3d. Is.

In another variation of the printhead structure according to the invention such that side A (SA) of the printhead structure has the control electrode (102a) on one side of the insulating material, the continuous shield electrode is a control electrode ( It can be on the side of the insulating material (102) forming side A of the slit of the printhead structure opposite the side having 102a).

FIG. 4 shows a variation on the second aspect of the printhead structure according to the invention. FIG. 4a again shows the simplest form of a printhead structure according to the second aspect of the invention. Side A of the slit (103)
Control electrodes (102a) are present on both sides of the insulating material (102) forming (SA). Slit side B (SB)
There are no electrodes on the insulating material (102) forming the. The control electrodes (102a) on both sides of the insulating material forming side A (SA) have exactly one pair of control electrodes (102a) (one on each side) in the paired registration device. Are arranged as follows.

FIG. 4b shows another variant of the second aspect of the printhead structure according to the invention. FIG.
The side A (SA) of the printhead structure shown in b is the same as that shown in FIG. 4a on the insulating material forming side B (SB), but with the toner delivery means (shown). As can be seen from the direction of arrow TF, which represents the direction of toner flow from the (not shown) to the toner receiving component (not shown),
A continuous shield electrode (102 facing the toner receiving component)
b) is present. FIG. 4c represents another variant of the printhead structure according to the second aspect of the invention, and in this variant the shield electrode (10 facing the toner delivery means).
2b) is the same as the printhead structure shown in FIG. 4b. Figure 4d shows yet another variation on the printhead structure according to the second aspect of the invention. Side A (S of the printhead structure shown in FIG. 4d)
A) is the same as that shown in Figure 4a, but side B
There is a continuous shield electrode (102b) on both sides of the insulating material forming (SB).

The control electrodes (102a) existing on both sides of the insulating material (102) forming the side A (SA) of the slit (103) are paired and metallized with each other.
sation) can be connected through the aperture (107) to form one control electrode. Methods and means for connecting electrodes through printing apertures are known in the art. An example of such a means is 199
European application 95201 filed on July 14, 1993
939.

FIG. 5a shows a variant of the third aspect of the printhead structure according to the invention. 5a and 5
In b, the control electrodes (102a) are staggered on both sides of the insulating material forming side A (SA). FIG.
In, the width of the control electrode parallel to the length of the slit (103) is chosen to have some overlap between the control electrodes on one side and the other side of the insulating material (102). FIG.
Then, the width of the control electrode parallel to the length of the slit (103) is selected so that there is no overlap between the control electrodes on one side and the other side of the insulating material (102). 5a and 5b
Shows a printhead structure having no electrodes on the insulating material forming side B (SB) of the printhead structure. Side A, as shown in Figures 5a and 5b.
A printhead structure having a shield electrode (facing the toner delivery means or the toner receiving means) on one side of the insulating material, or side B having the shield electrodes on both sides of the insulating material. It can also be used in combination with. Use of a printhead structure with control electrodes staggered on both sides of an insulating material forming a slit and side A (SA) as a printing aperture is used in a DEP device to obtain high resolution printing. It is advantageous to add.

The invention is not limited to printhead structures in which the side A of the slit is formed by a film of insulating material such that the control electrodes are present on both sides. It is also possible to manufacture side A of the slit by stacking 5 or 6 sheets of insulating material and to have control electrodes on each interface. In this aspect, multiple control electrodes can be staggered, which significantly enhances the resolution obtained with this printhead structure.

The essence of the printhead structure according to the invention is:
It comprises a slit as the printing aperture and the presence of the control electrode on only one side of the slit. This offers the advantage that during installation of the printhead structure in the DEP device no special requirements are placed on the registration of the insulating material forming the side of the slit.

The insulating material used to manufacture the printhead structure according to the present invention can be glass, ceramic, plastic or the like. Suitably the insulating material is a plastic material and can be polyimide, polyester (eg polyethylene terephthalate, polyethylene naphthalate etc.), polyolefins, epoxy resins, organosilicon resins, rubbers and the like.

The choice of insulating material for the manufacture of printhead structures according to the present invention is governed by the elastic modulus of the insulating material.
Insulating materials useful in the present invention are between 0.1 and 10 Gpa,
Preferably between 2 and 8 Gpa and most preferably between 4 and 6
It has a modulus of elasticity between Gpa.

The insulating material has a thickness between 25 and 1000 μm, preferably between 50 and 200 μm.

The width of the slits in the printhead structure according to the invention can be between 50 and 500 μm. This width can be selected according to the resolution required in the final printing.

The printhead structure according to any of the aspects of the present invention can be installed in a DEP device in several ways. A printhead structure having control electrodes on only one side, according to the invention, is preferably (i) the slit aperture being defined by two ends (A and B) formed by at least one sheet of insulating material. Two sides, namely side A (SA) and side B (SB), and (ii) the insulating material has the formula 0.1 GPa < YM < 1.
It has a modulus of elasticity (Young's modulus, YM) that satisfies 0 Gpa, and (iii) the ends A and B with respect to each other are of the formula 0 ° <
DEP placed at an angle α satisfying α <45 °
Used in equipment.

6 and 7 show a particular embodiment of a DEP device incorporating a printhead structure according to the present invention. FIG. 6 shows a DEP device incorporating a printhead structure according to a variant of the first aspect of the invention.
A toner delivery means (101) is placed in a toner container formed by a sheet of plastic material (102) placed in a rigid frame (106). The slit (103) is a plastic material (102)
Is formed by the edges (EA) and (EB) of one of the above sheets. The side A (SA) is provided with the control electrode (10) on one surface facing the toner feeding means (101).
2a) and side B (SB) has no electrodes. Printhead structure sides A and B on the rigid frame,
They have a free unsupported length (FL) and the angle α is greater than or equal to 0 ° and less than 45 ° and the ends (EA and EB) are opposite electrode (105) and toner receiving. It is installed so as to project in the direction of the component (104). Printing aperture (10
3), through a slit in this case, by a DC field generated by having a toner delivery means of voltage V1 and a counter electrode (105) behind the toner receiving component (104) of voltage V4, Toner particles are attracted to the toner receiving component. The amount of toner that passes through the printing aperture (103) is divided into voltage V3 divided control electrodes (1
02a). The control electrode, in the embodiment shown, faces the toner delivery means. The plastic material forming sides A and B of the slit is in contact with the toner delivery means (101).

FIG. 7 illustrates another method for incorporating a printhead structure according to a variation of the first aspect of the invention. The printhead structure (102) comprises a slit aperture (103). The side A (SA) of the slit defined by the end A (EA) is the control electrode (102
a). Side A (SA) and Side B (SB) are, in this particular aspect of the invention, two separate plastic sheets mounted on a rigid frame (106) having a free unsupported length (FL). Is. These two sheets are installed so that the angle α satisfies the expression 0 ° < α < 45 °. DC generated by having a toner delivery means of voltage V1 and a back electrode (105) behind the toner receiving component (104) of voltage V4 through a printing aperture (103), in this case a slit.
The field causes the toner particles to be attracted to the toner receiving component.
The amount of toner passing through the printing aperture (103) is adjusted by applying a voltage V3 to the split control electrode (102a). The control electrode, in the embodiment shown, faces the toner delivery means in the DEP device. Side B (SB) of the printhead structure (102) has no electrodes. The two sheets of plastic material in the printhead structure are bent towards the toner delivery means (101) and upon contact therewith a regulated pressure is applied to the toner delivery means. The pressure is
It is well controlled by proper adjustment of both angles of the sheet of plastic toner relative to the frame and by choosing a plastic material with a suitable modulus of elasticity (Young's modulus) and thickness.

When a slit is realized in a printhead structure according to the invention by installing two separate sheets of insulating material to form sides A (SA) and side B (SB) of the slit, sheet A It is preferred that and B are manufactured from the same material. As long as both insulating materials satisfy the above-mentioned elastic modulus (Young's modulus) conditions, side A (S
The insulating material used to form A) is side B (S
It may be different from the insulating material used to form B). Both insulating materials can have the same or different thicknesses.

The shape, material and location of the rigid frame (106) is not critical to the invention. Depending on the geometry of the DEP device and the modulus of elasticity of the insulating material that forms the printhead structure (102), the frame (106) may be optional if the angle α satisfies the equation 0 ° < α < 45 °. Can be placed.

In the DEP device according to the invention, the angle α is 0.
Greater than or equal to ° and less than 45 °.
In the preferred embodiment the angle varies from 0 ° to 25 ° and in the most preferred embodiment the angle varies from 0 ° to 10 °.

The printhead structure according to the invention is preferably in a DEP device, as shown in FIGS. 6 and 7, the insulating material forming the printhead structure contacts the surface of the toner delivery means. Is installed. However, it is also possible to place the printhead structure according to the invention in a DEP device such that there is no contact between the insulating material forming the printhead structure and the surface of the toner delivery means.

Although FIGS. 6 and 7 show only one printhead structure according to the first aspect of the invention of the DEP device, all variants for the three aspects of the invention are DE.
It can be incorporated into a P device.

Toner delivery means (10) used in a DEP device using a printhead structure according to the present invention.
1) may be a CTC (charged toner conveyor) that carries toner particles near the slit (printing aperture), and the toner particles are CTC by a magnetic brush
Can be carried to. It is also possible to use the printhead structure according to the invention in a DEP device in which the toner particles are taken directly from a magnetic brush (the magnetic brush being the toner delivery means here). A DEP device in which toner particles are taken directly from a magnetic brush is disclosed in EP-A 675 417, which is hereby incorporated by reference.

The back electrode (105) of this DEP device can also be moved with the printhead structure, such as for example US Pat. No. 4,568,955 and US Pat.
No. 733,256, consisting of another needle or wire galvanically isolated and connected to a power source. The counter electrode that moves with the printhead structure may comprise one or more flexible PCBs (printed circuit boards).

A counter electrode (105) between the printhead structure and the charged toner conveyor (101) and behind the control electrode facing the slit aperture (103) and the toner receiving component (104). And a different electric field is applied between and on the one electrode surface or between the electrode surfaces of the printhead structure. In a particular embodiment of the device useful for the DEP method, the use of a printing device with a geometric shape according to the invention is shown in FIG.
Toner conveyor (CTC) (1) charged with voltage V1
Is applied to the sleeve 01), the voltage V3 ₀ to V3 _n control electrode facing the one slit aperture 103 on the side A (SA) of the slit of the printhead structure (10
Applies to 2a). The value of V3 is the time reference, or gray-level basis, between the values V3 ₀ to V3 _n, is selected in accordance with the modulation of the image forming signals. Voltage V4 is applied to the counter electrode (105) behind the toner receiving component (104). The shield electrode is on the side B of the slit of the printhead structure.
In another aspect of the invention present on (SB), the voltage V2
Is applied to the shield electrode. In another aspect, V3 is V3 ₀
Not only vary between to V3 _n, multiple voltages V2 ₀ ~V
It is also possible to use 2 _n and / or V4 ₀ to V4 _n. When the toner particles are carried by the magnetic brush onto the CTC, a voltage V5 is applied to the surface of the sleeve of the magnetic brush. When there is no shield electrode, there is no voltage V2.

The DEP device according to the present invention can be successfully operated when one magnetic brush is used in contact with the CTC to provide a layer of charged toner on the CTC. The device can also be operated when removing toner particles directly from the magnetic brush.

In the DEP device according to the present invention, an additional AC source can be coupled to the sleeve of the magnetic brush when the toner is used to carry the toner particles onto the CTC and when the toner particles are removed directly from the magnetic brush.

CTC the toner particles using a magnetic brush.
The magnetic brushes preferably used in the DEP device according to the present invention for carrying up and for removing toner particles directly from the magnetic brush are of the type having a stationary core and a rotating sleeve.

In a DEP device using a magnetic brush of the type having a stationary core and a rotating sleeve according to the present invention, any of the known carrier particle and toner particle types can be successfully used. However, it is preferred to use "soft" magnetic carrier particles. The "soft" magnetic carrier particles useful in the DEP device according to the preferred embodiment of the present invention are soft ferrite carrier particles. Such soft ferrite particles exhibit only a small amount of remanent magnetic properties and are characterized by coercivity values in the range of about 50-250 Oe. Another very useful soft magnetic carrier for use in a DEP device according to a preferred embodiment of the present invention is a resin binder as described in EP-B 289 663 and 2 having different particle sizes. A composite carrier particle comprising a mixture of seed magnetites. The particle size of the two magnetites will vary between 0.05 and 3 μm. The carrier particles suitably have a mean volume diameter (d _v50 ) of between 10 and 300 μm, preferably between 20 and 100 _μm . A more detailed description of the above carrier particles can be found in EP 675 417, which is hereby incorporated by reference.

In the DEP device according to the invention, 1fC < |
q | < 20fC, preferably 1fC < | q | < 10fC,
It is preferred to use toner particles having an absolute average charge (| q |) corresponding to The absolute average charge of the toner particles is calculated by Dr. R. Epping PES-Laboratorium D-8056 Neufahr.
n, Germany by a device sold under the name "q-meter". Toner particle diameter (d, 10 μm) measured using a q-meter
The distribution of toner particles d (q, fC) is measured with respect to.
The absolute average charge | q | is calculated from the absolute average charge per 10 μm (| q | / 10 μm). Furthermore, the narrow charge distribution measured by the above device, ie the coefficient of variation (v), ie the ratio of standard deviation to average value, is 0.33.
It is also preferred to exhibit a distribution equal to or lower than. Preferably, the toner particles used in the device according to the invention are between 1 and 20 μm, more preferably 3 to 15 μm.
It has an average volume diameter (d _v50 ) of between m. A more detailed description of the above toner particles can be found in EP 675 417 which is hereby incorporated by reference. A DEP device including a printhead structure according to the present invention can be operated by using a one-component magnetic toner with a two-component developing agent, wherein the toner particles are triboelectric with carrier particles and a non-magnetic one-component developing system. Charged by physical contact. In order to achieve the final development scheme, the insulating material forming the printhead structure is selected to have a specific triboelectric property, or the insulating material is coated to have a specific triboelectric property to it. Can be given. When doing this, the toner particles on the rotating toner supply roller can be brought into rotary contact with the insulating material forming the printhead structure and charged by this contact. The use of the non-magnetic one-component system described immediately above makes it possible to produce very small and inexpensive DEP devices.

DEP devices using the above identified toner particles can be addressed in such a way as to give black and white. Therefore, it can be operated in a "binary method" useful for black and white text and figures and useful for classical two-level halftoning to produce continuous tone images.

The DEP device according to the invention is particularly suitable for providing multiple gray levels to an image. Gray level printing is a voltage V3 applied on the control electrode 102a.
Can be adjusted by the amplitude modulation of V3 or by the time modulation of V3. By varying the duty cycle of the time modulation at a particular frequency, fine differences in gray level can be accurately printed. Gray level printing can also be adjusted by a combination of amplitude modulation and time modulation of the voltage V3 applied to the control electrodes.

The combination of high spatial resolution and multiple gray level capabilities for DEP is described, for example, in the European patent entitled "Screening Device for Displays with Limited Density Resolution", filed June 29, 1994. It opens the way to multi-level halftoning techniques such as those described in application number 942018755.5. Thereby, the DEP according to the present invention
The device is capable of displaying high quality images.

[0068]

EXAMPLES Throughout the printing examples the same developing agent comprising toner and carrier particles was used.

Carrier Particles A macroscopic "soft" ferrite carrier consisting of MgZn-ferrite having an average particle size of 50 μm and a magnetization at saturation of 29 emu / g was provided with a 1 μn thick acrylic coating. This material showed virtually no remanence.

Toner Particles The toner used for the experiments had the following composition: 9
7 parts of a co-polyester of fumaric acid with an acid number of 18 and a volume resistivity of 5.1 × 10 ¹⁶ ohm.cm and bispropoxylated bisphenol A in a laboratory kneader Melt-blended with Cu-phthalocyanine pigment (Color Index PB15: 3) for 30 minutes. As described in WO94 / 027192,
^{_{Formula: (CH 3) 3 N +}} C 16 H 33 Br - was added at 0.5% of the amount with respect to a binder resistivity decreasing substance having a. It was found that by mixing with 5% of the ammonium salt, the volume resistivity of the applied binder resin was reduced to 5 × 10 ¹⁴ Ω.cm. This proves high resistivity decreasing ability (decreasing factor: 100).

After cooling, the solidified material is treated with Alpine Friesbet Gegenstrahl mules (ALPINE Fliess).
bettgegenstrahlmuehle) Type 100 AFG (trade name)
And crush with Alpine Multiplex
Zigzag (ALPINE multiplexzig-zag) classifier type 10
Further classification was performed using 0MZR (trade name). The average particle size was measured by a Coulter Counter model Multisizer (trade name) and found to be 6.3 μm by number and 8.2 μm by volume. To improve the fluidity of the toner material, 0.5% of toner particles are used.
Hydrophobic colloidal silica particles (BET value 130 m ² /
g).

Developing Agent An electrostatographic developing agent was prepared by mixing the 4% ratio (weight / weight) mixture of toner particles and colloidal silica with carrier particles. Triboelectric charging of the toner-carrier mixture was performed by stirring the mixture for 10 minutes at a standard agitation setting. The triboelectric properties were measured by running the developer mixture mixture into a magnetic brush, after which the toner was sampled and the method described in European Application 94201026.5 filed April 14, 1994, supra. did. The average charge q of the toner particles was -7.1 fC.

Toner Feeding Means The toner feeding means is a TEFLON (trade name) coating and a surface roughness of 2.5 μm (ANSI / A).
Ra-measured according to SME B46.1-1985
Value) and a cylindrically charged toner conveyor with an aluminum sleeve having a diameter of 20 mm. 50 charged toner conveyor
It was spinning at a speed of rpm. The charged toner conveyor was connected to an AC power source with a square wave vibration field of 600V at a frequency of 3.0kHz with a 20V DC-offset.

The charged toner consists of two mixing rods and one
The conveyor was propelled to this conveyor from a stationary core / rotating sleeve type magnetic brush comprising two metering rollers. 1
One bar was used to transfer the developing agent into the device and the other bar was used to mix the toner with the developing agent.

The magnetic brush consists of a so-called magnetic roller, which in this case is in an open position (no magnetic poles) so that the developing agent used can fall from the magnetic roller inside the roller assembly. It contained a static magnetic core with three poles (the open position was 1/4 of the circumference and was positioned opposite the CTC). The magnetic brush sleeve is 20m
m diameter and roughened with fine particles to aid transport (ANSI / ASMEB 46.1
Ra = 3 μm, measured according to 1985) made of stainless steel, and in the area between the magnetic brush and the CTC, measured on the outer surface of the sleeve of the magnetic brush,
It showed an external magnetic field strength of 0.045T.

The developer was forcefully removed from the magnetic roller using a scraper blade. On the other side, a doctoring blade was used to meter a small amount of developing agent onto the surface of the magnetic brush. 100 rpm sleeve
The internal parts were rotating at a speed compatible with good internal transfer in the developing device. Magnetic brush is -2
It was connected to a DC power source of 00V.

In Examples 1-12, a printhead structure according to the first aspect of the invention, which is shown schematically in FIG. 6, is used.

Example 1 A first sheet of plastic material (50 μm thick polyimide) (sheet A) was equipped with individual control electrodes 85 μm wide and separated from each other by separation zones 85 μm wide. It was The control electrode was covered with a second layer of 50 μm thick polyimide. A second sheet of plastic material (sheet B) was made from a 50 μm thick polyimide with a continuous copper layer 8 μm thick, the copper layer facing the toner delivery means. Both layers were mounted on a PVC frame with an angle α = 15 ° and an unsupported free length (FL) of 20 mm. The two sheets were separated by a 150 μm slit. The first of the plastic sheets having a control electrode and a double polyimide layer is that the surface of a charged toner conveyor has a double layer of polyimide and a copper electrode having a double layer of plastic from the first sheet of the printing aperture slit. On top, 50μ with continuous copper layer
It was placed in a position to rotate towards the m-thick polyimide sheet. Each of the control electrodes was individually addressable from a high voltage power supply.

Regarding the method of making the printhead structure,
Common copper etching methods known to those skilled in the art were used.

A printhead structure consisting of two separate plastic sheets is in contact with the charged toner conveyor sleeve. The distance between the counter electrode and the backside of the printhead structure is set to 150 μm and the paper is 1 cm
/ Sec. 0V to -300V for each control electrode
A (image-wise) voltage V3 of between was applied. Reverse electrode 10
No. 5 was connected to a + 600V high voltage power supply. CTC
An AC voltage of 600V at 3.0kHz was applied to the sleeve of the, along with a 20V DC offset.

Example 2 Example 1 was repeated except that a 50 μm thick polyimide film without a continuous copper layer was used as the second sheet of plastic material (sheet B). All other parameters were the same as listed in Example 1.

Example 3 8 μ as a second sheet of plastic material (sheet B)
Example 1 was repeated except that a 50 μm thick polyimide film with a continuous copper layer of m thickness was used. The copper side of the second sheet of plastic material faced the counter electrode. All other parameters were the same as listed in Example 1.

Example 4 Example 1 was repeated except that a 50 μm thick polyimide film with a continuous copper layer of 8 μm thickness on each side was used as the second sheet of plastic material (sheet B). All other parameters were the same as listed in Example 1.

Example 5 8 μm facing the counter electrode as structure of the first sheet of plastic material (sheet A) comprising control electrodes
Example 1 was repeated except that the sheet of 125 μm thick plastic material with a copper control electrode thickness was used. The angle of the two sheets of plastic material with respect to the plastic frame is set to 10 ° and FL
Was 50 mm.

Example 6 8 μm facing the counter electrode as structure of the first sheet of plastic material (sheet A) comprising control electrodes
Example 2 was repeated, except that the sheet of 125 μm thick plastic material with a copper control electrode thickness of 4 μm was used. The angle of the two sheets of plastic material with respect to the plastic frame is set to 10 ° and F
L was 50 mm.

Example 7 8 μm facing the counter electrode as structure of the first sheet of plastic material (sheet A) comprising control electrodes
Example 3 was repeated except that the sheet of 125 μm thick plastic material with a copper control electrode thickness was used. The angle of the two sheets of plastic material with respect to the plastic frame is set to 10 ° and FL
Was 50 mm.

Example 8 8 μm facing the counter electrode as structure of the first sheet of plastic material (sheet A) comprising control electrodes
Example 4 was repeated, except that the sheet of 125 μm thick plastic material with a copper control electrode thickness was used. The angle of the two sheets of plastic material with respect to the plastic frame is set to 10 ° and FL
Was 50 mm.

Example 9 Example 5 was repeated except that the control electrode faced the toner delivery means.

Example 10 Example 6 was repeated except that the control electrode faced the toner delivery means.

Example 11 Example 7 was repeated except that the control electrode faced the toner delivery means.

Example 12 Example 8 was repeated except that the control electrode faced the toner delivery means.

In Examples 13-16, a printhead structure according to the second aspect of the invention, illustrated schematically in FIG. 7, is used.

Example 13 In Example 13 according to the second aspect of the present invention, a printhead structure having control electrodes on both sides of sheet A of the printhead structure was produced. Sheet A of plastic material is 1
It was 25 μm thick and had 8 μm thick copper control electrodes on each side. Sheet B of printhead structure is 50
8 μm thick continuous copper layer (shield electrode) which is a μm thick polyimide layer and faces the toner delivery means.
Was included. The other parameters were the same as those used in Example 5.

Example 14 Example 13 was repeated except that a 50 μm thick polyimide film without a continuous copper layer was used as the second sheet of plastic material (sheet B).

Example 15 8 μ as a second sheet of plastic material (sheet B)
Example 13 was repeated except that a 50 μm thick polyimide film with m continuous copper layers was used. The copper side of the second sheet of plastic material faced the counter electrode.

Example 16 Example 13 was repeated except that a 50 μm thick polyimide film with a continuous copper layer of 8 μm thickness on each side was used as the second sheet of plastic material (sheet B).

It was possible to print an image with good density and sharpness regardless of which printhead structure (described in the examples above) was used. The contrast (or the power supply needed to obtain good contrast) could be optimized by proper localization of the continuous electrodes in the second sheet of plastic material of the printhead structure. . In Example 1, as compared with Example 2, good image homogeneity was obtained, but the image contrast was low.

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

1. Insulating material (102), the insulating material (1
02) A printhead structure for a DEP (Direct Electrostatic Printing) device comprising a slit (103) as a printing aperture formed by the two sides (SA and SB) and a control electrode (102a). A printhead structure, characterized in that only one of the two sides forming the slit carries a control electrode.

2. The printhead structure of claim 1, wherein control electrodes (102a) are on both sides of the one side having control electrodes.

3. The control electrodes on both sides are control electrodes (1
02a) printhead structure according to claim 2, arranged to have exactly one pair (one on each side) in the registration device.

4. The printhead structure of claim 3 wherein the pairs of control electrodes (one on each side) are connected in pairs on both sides by metal vapor deposition through slits (103).

5. The printhead structure of claim 2, wherein the control electrodes on both sides are staggered.

6. The printhead structure of any of claims 1-5, wherein one of the two sides opposite the side having the control electrode has a shield electrode.

7. A DEP device comprising a reverse electrode (105), a toner feeding means (101) and the print head structure according to any one of 1 to 6 above.

8. (I) the slit aperture has two sides defined by two ends (A and B) formed by at least one sheet of insulating material, namely side A (SA) and side B (SB). And
(Ii) The insulating material has a formula of 0.1 GPa < YM < 10 Gpa.
It has an elastic modulus (Young's modulus, YM) that satisfies
i) the ends A and B with respect to each other are of the formula 0 ° < α <45
The DEP device according to 7 above, which is placed at an angle α that satisfies °.

9. The elastic modulus is expressed by the formula 2GPa < YM < 8Gp.
8. The DEP device according to 8 above, which satisfies a.

10. The DEP device according to any one of 7 to 9 above, wherein the angle α satisfies the expression 0 ° < α <20 °.

11. The insulating material contains both limits 5
DEP device according to any of claims 7 to 10, having a thickness between 0 and 200 μm.

12. The slit is realized by installing two separate sheets of insulating material to form side A (SA) and side B (SB) of the slit.
11. The DEP device of any one of 11.

13. DEP of any of the above 8-12, wherein the sides A and B have a free unsupported length (FL) equal to or greater than 20 mm.
apparatus.

[Brief description of the drawings]

1 is a schematic representation of the essential features of a DEP device.

FIG. 2 is a schematic representation of a printhead structure of a prior art DEP device.

FIG. 3 is a schematic representation of a printhead structure according to the first aspect of the present invention.

FIG. 4 is a schematic representation of a printhead structure according to a second aspect of the invention.

FIG. 5 is a schematic representation of a printhead structure according to a third aspect of the present invention.

FIG. 6D incorporating a printhead structure according to the present invention
3 is a schematic representation of a particular aspect of an EP device.

FIG. 7D incorporating a printhead structure according to the present invention
3 is a schematic representation of another particular aspect of an EP device.

[Explanation of symbols]

 101 sending-out means 102 insulating material 102a control electrode 103 slit 105 reverse electrode

Claims (2)

[Claims] 1. A printhead structure for a DEP (Direct Electrostatic Printing) device comprising an insulating material, a slit as a printing aperture formed by two sides of the insulating material and a control electrode. And only one of the two sides forming the slit carries a control electrode. 2. A DEP device comprising a reverse electrode, a toner delivery means and the printhead structure of claim 1.