CA1057589A - Doctored, fabric liquid development applicator in arcuate moving contact with imaging surface - Google Patents

Abstract

Abstract of the Disclosure An image is developed on an imaging surface using a novel method and apparatus. A fabric developer applicator is loaded with a liquid developer the the applicator surface is doctored so that portions thereof that will contact the imaging surface are substantially free from liquid developer. The applicator and imaging surface are brought into arcuate moving contact which is maintained through a nip width providing sufficient time for the developer to be drawn from the applicator toward the imaging surface in response to an electric field.

Description

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, The present inv~ntion relates generally to polar liquid development.

The formation and development of images on the surface of photoconductor materials by electrostatic means is well known. The basic xerographic process, as taught by C F Carlson in U~S. Patent 2,297,691 involves placing a uniform electrostatic charge on a photoconductive insulating layer exposing the layer to a light-and-shadow image to dissipate the charge on the areas of the layer exposed to the light, and developing the resulting electro-static latent imgage by depositing on the image a finely-divided marking material referred to in the art as "toner". The toner will normally be attracted to those areas of the layer which retain a charge, thereby forming a toner image corresponding to the electrostatic latent image. This powder image may then be transferred to a support surface such as paper. The transferred image may subsequently be permanently affixed to a support surface as by heat. Instead of latent image formation by uniformly charging the photoconductive layer and then exposing the layer to a light-and-shadow image, one may form the latent image by directly charging the layer in image configuration. The powder image may be fixed to a photoconductive layer if elimination of the powder image transfer step is desired. Other suitable means such as solvent or overcoating treatment may be substituted for the foregoing heat fixing steps.
Several methods are known for applying a developer to an electrostatic latent image to be developed. One

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development method as disclosed by E N Wise in U.S. Patent 2,618,552 is known as "cascade" development. Another method of developing electrostatic images is the "magnetic brush" process as disclosed for example in U.S. Patent 2,874,063. Still another development technique is the "powder cloud" process as disclosed by C F Carlson in U.S. Patent 2,221,776.
An additional dry development system involves developing an electrostatic latent image with a powdered developer material, the powder having been uniformly applied to the surface of a powder applicator. The latent image is brought close enough to the developer powder applicator so that the developer powder is pulled from the powder applicator to the charge bearing image in image configuration.
The latent image and powder applicator may desirably be brought in contact including contact under pressure to affect development. The powder applicator may be either smooth surfaced or patterned so that the developer powder is carried in the depressed portions of the patterned surface.
Exemplary of this system are the techniques disclosed by H G Greig in U.S. ~atent 2,811,465.
Liquid development may also be employed in the development of electrostatic latent images. In conventional liquid development, more commonly referred to as electro-phoretic development, an insulating liquid vehicle having finely divided solid material dispersed therein contacts the imaging surface in both charged and uncharged areas.
Under the influence of the electric field associated with the charged image pattern the suspended particles migrate ~0s~s8g toward the charged portions of the imaging surface separating out of the insulating liquid. This electrophoretic migration of charged particles results in the deposition of the charged particles on the imaging surface in image confi-guration.
An additional liquid technique for developing electrostatic latent images in the liquid development process disclosed by R W Gundlach in U.S. Patent 3,084,043 hereinafter referred to as out-of-contact liquid development.
In this method, an electrostatic latent image is developed or made visible by presenting to the imaging surface a liquid developer on the surface of a developer dispensing member having a plurality of raised portions defining a substantially regular patterned surface a plurality of portions depressed below the raised portions. The depressed portions contain a liquid developer which is maintained out of contact with the electrostatographic imaging surface.
When the raised areas of the developer applicator are brought into contact with an imaging surface bearing an electrostatic latent image, the developer creeps up the sides of raised portions in contact only with the charged area of the imaging surface, and is deposited thereon.
This technique is to be distinguished from conven-, tional liquid development wherein there is an electrophoretic movement of charged particles suspended in a liquid carrier vehicle to the charged portion of the image bearing surface.
That is, the charged particles under the influence of an applied electric field migrate to the charged portion of the image bearing surface while the liquid substantially remains on the applicator surface and serves only as a carrier medium.

~)57589 In out-of-contact liquid development, the liquid phase actively takes part in the development of the image since the entire liquid developer is attracted to the charged portions of the image bearing surface. Furthermore, in out-of-contact liquid development, unlike conventional liquid development, the developer liquid contacts only the charged portions of the image bearing surface.
It has been proposed that one of the co-operating surfaces be deformable, having a hardness of from about 30 to about 9O (Shore A durometer) while retaining the functional integrity of its operative surface.
The use of a deformable surface when at least one of such surfaces is arcuate, provides substantially uniform contact and a substantially uniform nip width between the surfaces.
Such an arrangement in effect compensates for a range of dimensional irregularities in the non-deformable surface so that substantially uniform density is achieved in the final copy.
A further liquid development technique is that referred to as "wetting development" or selective wetting described in U.S. Patent 3,285,741. In this technique an aqueous developer uniformly contact the entire imaging surface and due to the selected wetting and electrical properties of the developer substantially only the charged areas of the normally hydrophobic imaging surface are wetted by the developer. The developer should be realtively conductive having a resistivity generally from about 10 to 10 ohm-cm 105751~9 and have wetting properties such that the wetting angle measured when placed on the photoconductor surface is smaller than 90 at the charged areas and greater than 90 in the uncharged areas.
In a compact electrostatographic copying device employing polar liquid development techniques, to which this invention relates, the imaging surface and the liquid developer applicator are desirahly small diameter cylinders or the like, to facilitate the cooperative movement of the surfaces in contact during development in a confined space.
Such moving contact between the imaging surface and the applicator resulting in the transfer of liquid developer from the applicator to the photoreceptor occurs at development speeds ranging generally from about two to about 70 inches per second.
Such polar liquid development systems have demo-nstrated good capability in producing developed copies of satisfactory quality. However, when employed in specific commercial embodiments, certain deficiencies may be noted.
Difficulties are freguently encountered with regard to copy quality and particularly with regard to image density, re-solution, undesirably high background and strobbing.
Frequently areas of the original image which have the same density have areas of varying density in the developed image and final copy. When such density variations are large, the developed copies are generally less pleasing to the eye, and of poor copy quality. The difficulties encountered in achieving satisfactory density are believed to be due in part to the varying lengths of time during which 105'7589 the applicator is in developing contact with the imaging member. Such time variations are thought to be caused at least in part by irregularities in the surface of the imaging member and the developer applicator so that when they are in moving developing contact, certain portions of the imaging member are in developing contact with the applicator longer than are others.
It has been proposed that the density could be made to be more-uniform by machining the imaging surface and the developer applicator surface, so that there is uniform contact along the line of axial tangency between the applica-tor and the imaging surface at all times during their co-operative action. However, such machining is dependent cri~;c~l A upon aritial~ tolerances and is expensive and time consuming.
High background and strobing may also causeelectrostatographic copies to be generally poor. High background is said to exist whenever a distracting amount of developer is deposited in non-image areas of the imaging surface. An improved means for avoiding high background at high speeds is needed.
Strobing occurs whenever light or dark streaks occur in bands across the surface of the image area, generally perpendicular to the direction of travel of the record receiving means through the electrostatographic copying device. Strobing is believed to be caused by high frequency changes in machine development speeds whenever a small nip width between the applicator and the imaging surface is encountered in an electrostatographic development system.
Such machine speed changes are typified, for example, by those resulting from gearing imperfections.

Difficulties are experienced in transporting liquid developers to a development station from remote developer reserviors. Generally, liquid developer applicators take ~he form of rollers which rotate so that their circum-ference moves through a liquid developer bath from which liquid developer which remains on the surface of the roller is moved to a point in the path of the rollers' rotation which may be opposite the developer bath. If the liquid developer is sought to be m0ved to a further point, a series of rollers may be necessary. Other liquid developer appli-cators take the form for example, of solid belts having raised areas not wetted by the developer and depressions which are wetted by the developer, such as the belt described in U.S. Patent 3,084,043.
U.K. Patent 987,766 describes a developer applicator which is a rubber roller covered with a mesh fabric. The same patent describes, as an applicator, a nylon fabric lvstv(~er.e, cushion filled with po~yclyrene beads. Both of these applicators are described as being used for bringing the entire imaging surface into line contact with the liquid developer and not for use in out-of-contact liquid develop-ment as described in U.S. Patent 3,084,043.
U.K. Patent 1,024,505 describes applicators for use with aqueous liquid developers and hydrophobic imaging surfaces wherein a charge pattern on the hydrophobic charge carrier changes the contact angle on the aqueous developer so that the developer adheres only to the charged portions of the normally non-wettable surface. The applicators described are fabrics capable of holding an aqueous liquid developer in lUS7S8~
a capillary recess, parallel glass plates having a capillary space between helically grooved and patterned hard rollers.
Contact between the applicator and the imaging surface is not described.
According to one aspect of this invention there is provided an electrostatographic development apparatus which comprises a fabric applicator having a pattern of interlocking fibers capable of maintaining their functional integrity during flexing, an imaging surface, a means for loading said applicator with liquid developer, a means for doctoring said applicator such that the lands are free from developer and a means for maintaining the applicator in arcuate moving contact with the imaging surface such that the applicator presents a liquid developer to the imaging surface for out of contact development of charge patterns thereon with the proviso that said fabric applicator has a ~ thickness of from about 40 to 200 microns and mesh openi~gs ; of from about 30 to 240 microns.
According to another aspect of this invention there is provided the process of developing an image on an imaging surface which comprises loading a fabric developer applicator with a liquid developer, said applicator having a pattern of interlocklng fibers capable of maintaining their functional integrity during flexing, doctoring the applicator surface so that the portions thereof which will contact the imaging surface are substantially free from liquid developer, bringing the fabric liquid developer applicator and the imaging surface into arcuate moving contact and maintaining said contact through a nip width which provides sufficient time for the liquid developer to be drawn from the applicator toward the imaging surface responsive to an electric field

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lV5~5~39 for out of contact development of charge patterns on said imaging surface with the proviso that said fabric applicator has a thickness of from about 40 to 200 microns and mesh openings of from about 30 to 240 microns.

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The fabric applicator may be employed in ~ny suitable development configuration. It may, for example, be employed as a belt or as a covering on a cylindrical member which are capable of achieving moving, arcuate contact with the imaging surface.
Development may be accomplished in any suitable manner with the fabric applicator. Typically the fabric applicator is maintained in moving contact with the imaging surface for a time sufficient to allow the liquid developer to move from the applicator to the imaging surface to achieve development on the imaging surface to achieve development on the imaging surface responsive to a charge patterns. When the imaging surface and the applicator are in moving contact at increased speeds, the applicator preferably remains in contact with the imaging surface for increased distances to provide a sufficient time of presentation for the liquid developer to move from the applicator to the imaging surface.
Moving contact between the fabric and the imaging surface may be achieved in any suitable manner. Typically the fabric is placed around a soft back up roll or is in the form of a belt arcuately positioned around two or more positioning members, such as rollers, and urged against an arcuate imaging surface.
The fabric developer applicator may be loaded with liquid developer by any suitable means. Typical of such means are developer supply rollers or like devices which are coated with liquid developer and then placed into contact with ~057~8~

the fabric applicator. In another embodiment, the fabric applicator may be loaded by immersion in a liquid developer reservior.
The fabric applicator may then be doctored, which is the process of removing liquid developer from the portions of the fabric which will touch the imaging surface during moving contact. The doctoring may be by any suitable means.
Typical doctoring means include doctor blades, wiper blades, doctor rollers and the like.
If desirable, the fabric applicator or the backing rollers with which it is used may be electrically conductive.
An electrically conductive path from the developing nip to ground is desirable to achieve satisfactory development, particularly when the development system is used to develop more than one image. It is believed that the charge pattern on the imaging surface induces a charge of about an equal intensity and opposite polarity on the surface of the liquid developer by which the liquid developer is drawn from the app~icator to the imaging surface. Repeated development i8 believed to result in a buildup in the developer of charges like that on the imaging surfaces, and the path to ground reduces such a buildup by supplying a source of balancing charges. A conductive path to earth may be through the developer itself or through a conductive backing roller at the nip.
Alternatively, the applicator or backing roller may be conductive to facilitate a bias between the applicator and the imaging surface at the nip. Such a bias is lOS75B5~
optionally used to enhance the development of charge patterns.
For example, a bias may be applied to inhibit the otherwise normal movement of the liquid developer from the applicator to the imaging surface so that tne developer must overcome the bias in order to be attracted to the imaging surface.
Such a bias helps provide a clean background on the finished copy. A bias may also be applied in the direction of the movement of the developer in order to aid the movement of the developer.
Any suitable liquid developer may be employed with the developer applicator of this invention. Typical such liquid developers are those capable of having a charge induced on their surface by the charge pattern sought to be developed or of being attracted by a charge pattern or an electric field. Such typical developers may have a resistivity of from about 10 to about 1015 ohms cm.
The electrostatographic development apparatus described above produces clear copies with sharp images, uniform density, low background and minimal strobing effects.
The apparatus is easily and inexpensively ~abricated.
An electrostatographic development apparatus according to the invention will now be described by way of example with reference to the accompanying drawings wherein:-Fig. 1 shows in enlarged cross-section, the doctoring of a fabric applicator roller and the contacting of the applicator and an imaging surface.
Fig. 2 shows in enlarged cross-section, a fabric liquid developer applicator wherein the filaments which comprise the fabric are welded at each point of crossing.
Fig. 3 shows schematically an embodiment of the 1~5758~
electrostatographic development apparatus of the present invention.
Fig. 4 shows schematically an alternative embodi-ment of the electrostatographic development apparatus of the present invention.

Referring more specifically now to Fig. 1, there is shown in enlarged cross-section a portion of the fabric applicator 4, which has been previously loaded with liquid developer in a manner not shown, moving past doctor blade 6 in such a way that the edge portion of the fibers 10 of the fabric which are contacted by the doctor blade 6 are wiped clean of liquid developer 2.
The fabric applicator is loaded with a liquid developer in a manner not shown. Doctor blade 6 in Fig. 1 works in cooperative motion with the fabric applicator 4 so that the lands, the portions of the fabric applicator 4 which will contact the imaging surface 7 are substantially free from the liquid developer 2. Any suitable blade configuration and material may be used. Typical of such materials are metals and elastomers. Elastomer blades are preferred because they are pliable and resilient and thei~
wiping action, which substantially frees the lands of liquid developer, also wipes the top portions of the valleys free from liquid developer, so that the developer is contained in the lowest portions of the valleys. Such doctoring helps to maintain the liquid developer out of contact with the imaging member during contact.

lOS'7589 After doctoring, the fabric applicator 4 presents the liquid developer 2 to the imaging member 7, so that the liquid developer may be drawn from the fabric applicator to the imaging surface responsive to an electrostatic field __ such as an electrostatic latent image which is previously formed on imaging member 7 in a conventional manner such as by the uniform charging and imagewise exposure of a photoconductor.
While Fig. 1 has been described with reference to the development of an electrostatic latent image on a photoconductive insulating layer, development may be achieved on any suitable imaging surface in response to an electro-static field. Well known methods for creating such a field include the use of pin electrodes, latent conductivity patterns and electrostatic latent images. In the pin elec~rode method, a field is established between the appli-cator and the selected members of a group of pins in such a way that the liquid developer is drawn from the applicator toward the selected members. The imaging member may intercept the movement of the developer. Latent conductivity patterns are normally created by the exposure of a photoconductive insulating layer to an imagewise pattern of radiation.
The pattern of conductivity thus created controls the strength of an external transfer field applied between the fabric applicator and the imaging member such that the liquid developer is drawn toward the imaging member responsive to the pattern of conductivity in the photoconductive member.
Alternatively, an electrostatic latent image may be formed by charging an imaging member, such as imaging member 7 in ~ 14 -10575~9 Fig. 1, through a mask to place a charge pattern thereon, The liquid developer 2 on the fabric applicator 4 below the level of the edge portion of the fabric is maintained in the spaces between the fibers 10. In Fig. 1, the fabric applicator 4 is seen to be moving in arcuate contact with the imaging surface to achieve nip 11.
The developer free portions of the fabric appli-cator 4 fuction as lands and, the spaces between the fibers 10 function as valleys, when the fabric applicator 4 contacts the imaging surface 7 in the development method described in U.S.A. Patent 3,084,043 mentioned above. That is, charge patterns carried on the imaging surface 7 attract the liquid developer 2 from the valleys or interstices of the fibers 10 of the fabric applicator 4 so that the charge patterns are developed on the imaging surface 7.
The fabric applicator 4 may have any suitable pattern of interlocking fibers capable of maintaining their int~q rl ty A functional intcg~ct~ during flexing. Typically, the fabrics are formed from knitted or woven fibers or from non-woven fibers. Any suitable such fibers may be used to form the typical fabric applicator 4. Typically the fibers may be synthetic fibers such as, polyamids, polyesters or metal fibers although other materials may also be employed.
Preferably, the fabric is formed from synthetic fibers because of the conductive path to earth thus provided.
The fabric may be of any suitable thickness.
Typically, the thickness is from about 65 to about 185 microns. Fabric thicknesses greater than about 185 microns tend to provide image resolution which is generally sufficiently _ 15 ~

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lacking in detail to be considered of poor quality. The fiber size which is typical of fabric thicknesses greater than about 185 microns produces a screen pattern of such coarseness that the image resolution lacks sufficient detail to be considered of good quality. Fabric thicknesses of less than about 65 microns provide density of the developed image which, although regular, is considered to be poor. This occurs because fabric thicknesses of less than about 65 microns have valleys or intersticies which are capable of holding a lesser amount of liquid developer and therefore the images formed are of a lower density.
To obtain images of good density and resolution, the fabric thickness is preferably from about 75 to about 125 microns. Optimum image density and resolution is achieved with a fabric thickness of about 100 microns which provides crisp images having a resolution of about 8 line pairs per minute. Such an optimum fabric thickness provides image resolution which is sharp in detail and densities which are sufficiently dark to be pleasing to the eye.
Any suitable mesh openings may be used in the fabric applicator. Typically, the mesh openings range from about 30 to about 240 microns. Fabrics having mesh openings of less than about 30 microns provide a reduced amount of liquid developer available for development.
Mesh openings of greater than about 240 microns provide developed images which are sufficiently lacking in detail and resolution to be consi~redpoor. Greater density is generally accompanied by decreasingly satisfactory resolution, and improved density is generally associated with decreasingly satisfactory density. To obtain images of good density and l(~S75~9 resolution, the mesh openings in the fabric applicator are preferably from about 40 to about 130 microns. The optimum mesh opening of about 75 microns provides the most satisfactory balance between image resolution and density.
In Fig. 1, the fabric applicator 4 is in moving contact with the imaging surface 7 along nip 11. The width of the nip 11 allows time for the liquid developer to move from the applicator to the surface of the imaging member.
The width of the nip may be of any suitable size. Typically, for individual specific embodiments, the nip is increased or decreased in width as the cooperative speed of the fabric applicator and the imaging surface is increased or decreased so as to continue to provide a time of contact between the fabric applicator and the imaging surface sufficient to allow movement of the developer from the valleys of the applicator to the imaging surface. Typically, nip widths may range from about 0.2 mm to about 30 cm when used with a liquid developer having a viscosity of about 800 cps. Such a nip width range is useful whenever the applicator and the imaging surface are moving at development speeds of from about 2 to about 70 inches per~second. A preferred range of nip widths for use in connection with developer at speeds of cooperative movement between the fabric applicator and the imaging surface of about 5 inches per second is from about 0.5 mm to about 5 cm. It will be apparent to one skilled in the art that the required nip width will vary within these limits as the viscosity of the liquid developer is changed.
liquid developer of any suitable viscosity may ~0~75~9 be used with the fabric applicator of the present invention.
Typical viscosities range from about 10 to about 3000 cps.
Developers having viscosities of less than about 10 cps may be difficult to doctor properly or to hold in the fabric applicator during development. With developers having viscosities of greater than about 3,000 cps, generally stronger transfer fields are desirable to cause the liquid developer to be attracted from the applicator valleys to the imaging surface during the development step. To obtain adequate transfer of the liquid developer at a broad range of development speeds, a preferred developer viscosity is from about 500 to about 1000 cps. At the preferred nip width, described above, the preferred developer viscosity is from about 700 to about 900 cps. Such a preferred viscosity provides good transfer of developer from the applicator to the imaging surface while the applicator and the imaging surface in contact.
The use of a wide nip which is enabled by the fabric applicator may also minimize strobing caused by high frequency variations in speeds. Wide nips tend to avexage out high frequency changes in the time span during which the developer is presented to the imaging member so that the strobin~
caused thereby is minimized.
The fabric applicator 4 will be compliant with gross variations and imperfections in the surface of the imaging member 7, thereby maintaining the liquid developer 1 out of contact with the imaging surface 7, but uniformly and consistently close to the imaging surface to achieve development. Thus, in spite of such impe~fections and ~OS7~
gross variations in the surface of the imaging member, sub-stantially uniform density and satisfactory image resolution is achieved.
Referring more specifically now to Fig. 2, there is shown in enlarged cross-section an alternative embodiment of fabric applicator 4 wherein fibers 10 are welded at each point of crossing to obtain increased dimentional stability of the applicator. In Fig. 2 the fibers ~0 are depicted as steel, and welding is the appropriate means for attaching them together at each point of crossing. When other fibers, such as polyamids or polyesters are used, other convenient means for tacking the monofilament may be glued or melted together at each point of crossing or the fabric may be electroplated in order to effect the tacking.
The method of operation of the development system shown in Fig. 2 is the same as in the development system of Fig. 1.
Referring more specifically now to Fig. 3 there is shown in schematic cross-section a portion of an electrostatoyraphic copying deYice, wherein an embodiment of the electrostatographic development system of the prese~t invention is utilized. A fabric applicator 4 in the form of an endless belt is used to carry liquid developer 2 from r~servo~ ~
a the developer roE~or 3 past the doctoring means 6 to the developing station 1, where the fabric applicator 4 is urged against the imaging member 7 by resilient back up roller S in order to achieve nip 11 around the central point of contact between the fabric applicator 4 and the imaging member 7. The resilient backup roller 5 may be of any suitable hardness and material to provide a suitable nip for any development speed.

1~575~a In Fig. 3, the liquid developer 2 is relatively conductive and the path from the development station 1 to ground is through the developer and the developer reser-vior, which is grounded. However, if a more resistive devel-oper is used, the path to ground may be through the fabric applicator 4 or through the backup roller 5.
In Fig. 3, the fabric applicator 4 picks up liquid developer 2 as the applicator moves through the developer rocor~Yor 3. The liquid developer 2 is maintained in the fabric applicator as it moves toward the development station 1. As the developer loaded fabric moves, past the doctor blade 6, the portions of the fabric which will be in actual contact with the imaging surface are wiped substantially clean of liquid developer, leaving the intersticies between the fibers of the fabric applicator 4 filled with liquid developer 2. When the fabric applicator

4 is pressed into developing contact with imaging member 7 through nip 11 at development station l, the liquid developer 2 is dPawn toward the imaging member 7 by an electrostatic latent image created in the conventional manner such as by first charging the imaging member 7, which in this example is depicted as photoreceptor drum having a photoconductive insulating coating on a conductive substrate, in the dark with a corotron 8 and then exposing the charged surface to imagewise radiation at imaging station 9~
Referring more specifically now to Fig. 4, there is shown a portion of an alternative configuration of an electrostatographic development apparatus of the present invention. In Fig. 4, the liquid developer 2 is loaded l~)S75~

onto the fabric applicator 4 in the same manner as is described in Fig. 3 and is transported from the developer reservior 3 past the doctoring means 6 to the imaging station 1, where the liquid developer 2 is presented to the imaging surface 7 along nip 11 for development of a charge pattern on the imaging surface 7 as described in connection with Fig. 3. The large nip 11 shown in Fig. 4 is useful for high development speeds as discussed above. In fig. 4 an electrical bias is created to resist the transfer o liquid developer 2 from the fabric applicator 4 to the imaging surface 7 in order to help provide clean background areas as discussed above.
The following non-limiting examples are provided for the purpose of further exemplifying useful embodiments of the invention.
EXAMPLE I
In an electrostatographic copying device, similar to that partially shown in fig. 3, the imaging surface is a photoconductive selenium layer on a conductive backing, and the resilient backup ~oller i9 of soft rubber suitable for forming a nip at the development station of about 2 cm.
The doctor blade is an elastomer material. The liquid developer is liquid paraffin pigmented with about 10 weight per cent carbon black, and has a viscosity of about 800 cps.
The fabric applicators used are woven from steel fibers and have applicators' mesh openings range from about 30 to about 240 microns. The device is operated in the manner described above in connection with Fig. 3 at a development speed of about 5 inches per second so that an image is developed on 1~5~51~5~
the imaging surface. The developed image is inspected as the thickness of the fabric applicator is changed, and its characteristics are noted in the chart below:

Fabric Applicator Thickness Imaqe Characteristics 45 micronsGood resolution - poor density 65 micronsGood resolution - satisfactory density 75 micronsGood resolution - good density 100 microns " " " "
125 microns " " " "
185 micronsSatisfactory resolution - good density 200 micronsPoor resolution - good density.

EXAMPLE II
In the electrostatographic copying device of Example I, the fabric thickness is maintained at about 100 microns and the size of the mesh openings in the fabric applicator are varied as shown in the chart below, and the characteristics of the images thus achieved are also noted:

Mesh Openinq Size maqe Cha acteristics 15.,microns Good resolution - poor density 30 microns .Good resolution - satisfactory density 40 microns Good resolution - good density 75 microns "' " " "
130 microns " " "' "
240 micronsSatisfactory resolution - good density 300 micronsPoor resolution - good density lOS~S~
EXAMPLE III
In the electrostatographic copying device of Example 1, the fabric thickness is maintained at about 100 microns and the mesh opening size is maintained at about 75 microns. The fabric applicator used in this Example is woven from polyamid fibers. The nip width and the development speed are varied as shown in the chart below.
The characteristics of the developed images are also noted in the chart below:

Image NiP WidthDeveloPment Speed Characteristics 50 cm70 in/sec Excessive developer transferred 30 cm70 " " Good 25 cm70 " " Fair - reduced density 20 cm70 " " Poor - reduced density 10 cm5 " " Excessive developer transferred

5 cm5 " " Good 1 mm5 " " Good 0.5 mm5 " " Good 0.25mm5 " " Poor - reduced density 1 mm~2 " " Excessive developer transferred 0.2 mm2 " '" Good 0.1 mm2 " " Poor - reduced density While this invention has been described with reference to some specific embodiments, other modifications of the present invention will occur to those skilled in the art upon reading of the present description, which modifications are intended to be included within the scope of this invention.

Claims (30)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An electrostatographic development apparatus which comprises a fabric applicator having a pattern of interlocking fibers capable of maintaining their functional integrity during flexing, an imaging surface, a means for loading said applicator with liquid developer, a means for doctoring said applicator such that the lands are free from developer and a means for maintaining the applicator in arcuate moving contact with the imaging surface such that the applicator presents a liquid developer to the imaging surface for out of contact development of charge patterns thereon with the proviso that said fabric applicator has a thickness of from about 40 to 200 microns and mesh openings of from about 30 to 240 microns.

2. The apparatus of claim 1, wherein the fabric applicator is woven.

3. The apparatus of claim 1, wherein the fabric applicator is knitted.

4. The apparatus of claim 1, wherein the filaments of the fabric of said fabric applicator are tacked at each point of crossing.

5. The apparatus of claim 1, wherein the fabric of said fabric applicator comprises filaments of a composition selected from the group consisting of metals, polyamides and polyesters.

6. The apparatus of claim 1, wherein the fabric of said fabric applicator has a thickness of from about 75 to about 125 microns.

7. The apparatus of claim 1, wherein said fabric has mesh openings of from about 40 to about 130 microns.

8. The apparatus of claim 1, wherein said fabric applicator is maintained in arcuate moving contact with the imaging member across a nip width of from about 0.2 mm to about 30 cm.

9. The apparatus of claim 8, wherein said fabric applicator is maintained in arcuate moving contact with the imaging member across a nip width of from about 0.5 mm to about 5 cm.

10. The apparatus of claim 1, wherein said fabric applicator is maintained in contact with said imaging surface by a resilient means.

11. The apparatus of claim 10, wherein the resilient member provides a path to ground from the nip.

12. The apparatus of claim 1, wherein said fabric applicator is a fabric belt urged against the imaging surface by guiding roller means.

13. The apparatus of claim 1, wherein said fabric applicator is sufficiently conductive to define a path to ground from said imaging surface.

14. The apparatus of claim 1, wherein said liquid developer is sufficiently conductive to define a path to ground from said imaging surface.

15. The apparatus of claim 1, wherein an electrical field is provided between the fabric applicator and the imaging surface.

16. The process of developing an image on an imaging surface which comprises loading a fabric developer applicator with a liquid developer, said applicator having a pattern of interlocking fibers capable of maintaining their functional integrity during flexing, doctoring the applicator surface so that the portions thereof which will contact the imaging surface are substantially free from liquid developer, bringing the fabric liquid developer applicator and the imaging surface into arcuate moving contact and maintaining said contact through a nip width which provides sufficient time for the liquid developer to be drawn from the applicator toward the imaging surface responsive to an electric field for out of contact development of charge patterns on said imaging surface with the proviso that said fabric applicator has a thickness of from about 40 to 200 microns and mesh openings of from about 30 to 240 microns.

17. The method of claim 16, wherein the fabric applicator is woven.

18. The method of claim 16, wherein the fabric applicator is knitted.

19. The method of claim 16, wherein the filaments of the fabric of said fabric applicator are tacked at each point of crossing.

20. The method of claim 16, wherein the fabric of said fabric developer applicator comprises filaments of a composition selected from the group consisting of metals, nylon and polyesters.

21. The method of claim 16, wherein the fabric applicator has a thickness of from about 75 to about 125 microns.

22. The method of claim 16, wherein the fabric applicator has mesh openings of from about 40 to about 130 microns.

23. The method of claim 16, wherein the nip width is from about 0.2 mm to about 30 cm.

24. The method of claim 23, wherein the nip width is from about 0.5 mm to about 5 cm.

25. The method of claim 16, wherein the fabric liquid developer applicator is maintained in arcuate moving contact with the imaging surface by means of a resilient member.

26. The method of claim 25, wherein the resilient member provides a path to ground from the imaging surface.

27. The method of claim 16, wherein the fabric applicator is a fabric belt which is urged against an arcuate imaging member by guiding rollers.

28. The method of claim 16, wherein the loaded fabric applicator is sufficiently conductive to define a path to ground from the imaging surface.

29. The method of claim 16, wherein the liquid developer is sufficiently conductive to define a path to ground from the imaging surface.

30. The method of claim 16, wherein an electrical field is provided between the liquid developer applicator and the imaging surface.