DE2654096A1 - METHOD OF SMOOTHING AN IMAGE SURFACE - Google Patents

Description

XEROX CORPORATION Rochester, New York, USA

Method for smoothing an image surface

The invention relates to electrostatography. More special the invention relates to improvements in the field of electrostatographic imaging surfaces *

In the field of electrostatographic copying technology, as originally disclosed by Carlson in US Pat. No. 2,297,691 and further described in US Pat Many related patents, an electrostatographic imaging surface (imaging surface), which is a photoconductive Containing insulating layer, initially an even electrostatic charge is given to its entire surface to make sensitive «The surface then becomes a picture

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activating electromagnetic radiation, such as light, X-rays or the like. The radiation selectively distributes the charge in the exposed areas of the photoconductive insulator while a charge pattern remains in the unexposed areas. The charge pattern is then developed and visualized by adding a finely divided marking material (known in the art as "toner") on the surface of the photoconductive Insulating layer is deposited. When reusable photoconductive insulating material is used, it becomes visible Image formed by the toner transferred to a second surface, such as a sheet of paper, and fixed there to create a permanent visible reproduction of the original image. Where not reusable Photoconductive insulating materials are used, the toner particles are directly in place on the Fixed surface of the non-reusable insulating material. This becomes the transferring step of the above Procedure eliminated.

Such a charge pattern can also be created by a liquid Developer ". In one of the known methods of developing in a liquid state, a charge pattern manufactured. on an image surface and developed through a fluid development process. Here the liquid developer is attached to the charge pattern by a Applicator offered. It has a surface that has raised areas (so-called lands) and depressions (so-called valleys) owns. It contains the liquid developing agent between the raised parts. By the electrostatic Forces in the charge pattern becomes the liquid developer Dragged to the image area in an image configuration. *

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^; A preferred method of liquid development of electrostatic charge patterns is disclosed in British Patent No. 880597. In this method, the imaging surface can be a cylindrical body, which is cyclically imaged with a charge pattern. This is developed and the developed image is transferred to a device which receives the record. The image surface is then cleaned in order to be prepared for subsequent cycles of this type.

Imaging areas that are either for toner development or liquid development of charge patterns are desirably composed of photoconductive insulating layers, that are rigid enough to support a developed image. With cyclical use (as described above), it may be desirable to use imaging surfaces that are somewhat pliable and that are easily cleaned can be. In any case, the surface of the layer should be sufficiently smooth so that the quality of the developed image is not spoiled. Examples of such imaging surfaces are described in US patents No. 3 552 848, 3 621 248, 3 685 989, 3 697 265 and> 752 691.

Although they are usually able to produce good pictures, can use the imaging surfaces that have been used so far has yet to be improved in various ways. It has been found that imaging surfaces have defects in the surface, which can be recognized in the form of hills or other protruding areas. They can be up to about 100 microns above the imaging surface stand out. Such defects are likely to be formed during the placement process that is used to apply the photoconductive material to the substrate. They are often found on imaging surfaces that

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are used in both the toner process and the liquid charge pattern development process.

Surface defects of this type usually do not have an adverse effect on the quality of toner-processed Images. However, they affect the quality of charge patterns much less favorably, which evolves in a fluid manner became. In the case of the liquid development of charge patterns on such an imaging surface the surface defects have at least 2 undesirable defects in the developed image. The liquid developer collects in the form of a circle around the defect, so that it is transferred as a circle to the image-receiving surface. This is what experts call a "halo effect". A second undesirable deficiency appears after some copies have been made by the liquid development process, that is described in British Patent 88o 597. If the applicator for the liquid Developer rotates in contact with the imaging surface, he will have a tendency to counteract the imperfections hit on the imaging surface. The larger of the imperfections and those that have a steep profile, are sometimes broken off, leaving a roughened area or hollow on the image surface. The rough spot or hollow has a tendency to collect liquid developer, which then acts as an undesirable stain appears on the developed image. This occurs regardless of whether the image remains on the imaging surface or is transmitted to an image receiver.

In our pending UK patent application (our reference R 024-75) it has been suggested that the troublesome

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To reduce surface defects by having the Imaging surface in contact with a smoothing agent brings. The smoothing agent leaves the defects. cold flow away and in this way reduces their height to less than about 5 microns. This method - as has been found - gives satisfactory results in the most cases where you can find a metallic or metal-like Material used for the image surface. However, if surface defects that have a sharp profile with If they come into contact with a smoothing agent, they are often broken off with the formation of undesirable seams Areas or cavities as described above. It has also been found that this method does not give satisfactory results when used in conjunction with non-metallic photoreceptors, which are less compatible with the cold flow process, is used. It is therefore an object of the invention to provide a method for Reducing the surface defects on an imaging surface, so that the undesirable defects, 'the caused by them, at least largely avoided.

In accordance with the invention, a method has been provided for the reduction of surface defects on imaging surfaces, which includes the following steps:

a) Generation of relative movement between the image surface and an abrasive or abrasive agent which is pressed against the image surface during the Surface and abrasive are separated by a fluid bearing, and

b) Maintaining this movement until those defects are less than approximately in size 5 microns down,

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The invention will. well. in more detail and based on the Drawings described.

FIG. 1 shows, schematically and in cross section, a greatly enlarged point on an imaging surface that has surface defects.

Fig. 2 shows schematically and in cross section an arrangement for carrying out the method according to the invention, in which a hydrodynamic fluid support layer (fluid bearing) is used.

3 and 4 show, schematically and in cross-section, alternative ones Means for applying and measuring a liquid to the imaging surface in order to create a hydrodynamic Form support layer.

Fig. 5 shows, schematically and in cross section, yet another Means for forming a hydrodynamic support (bearing).

Fig. 6 shows schematically and in cross section an arrangement for carrying out the "method according to the invention, wherein a hydrostatic liquid prop is used.

By referring specifically to FIG. 1, the imaging surface 1, which contains the conductive substrate 2, can be seen. The photoconductive insulating layer 3 is applied to the substrate. Surface defects 4 and 4a are on the upper surface of layer 3 shown. They are typical of surface defects that occur when layer 3 occur on the substrate 2. Fig. 1 also shows the cavity 5, which is typical of surface defects, which occur when a surface defect such as defect 4a is caused by the action of a liquid developer applicator or

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torn off by a flattening agent (as above described).

As suggested earlier, a thin intermediate layer, which is not shown here, are placed between the layer 3 and the substrate 2, in order to increase the electrical properties of the imaging surface and the adhesion of layer 3 to improve ^the substrate. 2

Substrate 2 can be made of any conventional material that is electrically conductive, such as e.g. Brass, aluminum, steel or the like. Fabrics. Substrate can be flexible or rigid and can be in the form of a belt or belt, cylinder, or .a plate.

The layer j5 can be made of any photoconductive ' Isolating means are formed. The photoconductive cover layer can ei thalten a photoconductor, which is in a insulating binder is dispersed, a solution of a photoconductor and binder, or it can consist of a homogeneous photoconductive material. When used in the dispersed phase, the photoconductive layer can generally consist of an organic or inorganic photoconductive material in an insulating Binder is dispersed. Any suitable photoconductive material can be used in the practice of the invention will. Typical inorganic photoconductive materials are sulfur, selenium, zinc sulfide, zinc oxide, zinc-cadmium sulfide, Zinc magnesium oxide, cadmium selenide, zinc silicate, calcium strontium sulfide, Cadmium sulfide, mercury (2) iodide, mercury (2) oxide, mercury (2) sulfide, indium trisulfide, Gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, Antimony trisulfide, cadmium sulfoselenide and mixtures of these compounds.

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Typical organic photoconductors are: triphenylamine; 2,4-bis (4,4'-diethylaminophenyl) -1,3,4-oxadiozole ; N-isopropylcarbozene; Triphenylphyrrole; 4,5-diphenylimidazolidione, 4,5-diphenylimidazolidinthione; 4,5-bis (4 'aminophenyl) imidazolidinone; 1,5-dicyanonaphthalene; 1,4-dicyanonaphthalene; Aminophthalonitrile; Nitrophthalodinitrile; 1,2,5 * δ-tetraazacyclooctatetraene- (2,4,6,8); 2-mercaptobenzothiazol-2-phenyl-4-diphenylidene-oxazolone; 6-hydroxy-2,3-dic, methoxyphenyl) benzofuran; 4-dimethylaminobenzylidene benzhydrazide; 3-benzylidene aminocarbazole; Polyvinyl carbazole; (2-nitrobenzylidene) -p-bromoaniline 2,4-diphenylquinazoline; 1,2,4-triazine-1,5-diphenyl-j5-methyl-pyrazoline j 2- (4'-dimethylamino phenyl) benzoxazole; 3-aminocarbazolj phthalocyanines and mixtures of these compounds.

Any suitable binding material can be incorporated into the photoconductive insulating layer 3 if so desired will. Typical binding materials are similar to those disclosed in U.S. Patents 3,121,006 and 3,121,007. The particular binding material you use will depend on the nature of the photoconductive pigment you use, to make the photoconductive layer. If required, the "binding material that comes with the photoconductive Compound used to be an insulator to the extent that an electrostatic charge is on the photoconductive Layer to be worn. can, at least in the absence of lighting. The binding material will be firmly attached to the base of the Conductive substrate 2 connected and is an effective dispersant for the photoconductive pigment. Pernerhin the binding material should be selected so that it is relatively inert in the presence of the photoconductive Link. Typical non-photoconductive organic binders

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are polystyrene, epoxy resins such as the epon resins commercially available from Shell Chemical Company, Epoxy-phenolic compounds, epoxy novolaks, silicone resins, such as DC 801, DC 804, and DC 996, which are commercially available are from Dow Corning Corp., polysulfone, acrylic and methacrylic polyester, such as Acryloid AlO and Acryloid B-72, polymerized ester derivatives of acrylic and alpha acrylic acids, as are all commercially available from Röhm and Hass Company, Lucite, a polymerized Butyl methacrylate, which is commercially available from E.I. duPont de Nemours and Company, vinyl polymers and copolymers such as polyvinyl chloride, polyvinyl acetate, and mixtures thereof Links.

If the binding material is itself photoconductive then it can a homogeneous layer of the bonding agent can be used as layer 3. If the binding material is photoconductive, it is preferred that the resistivity of the binder

I ^
is at least 10 ^ ohm cm in order to satisfactorily meet the requirements of the resulting photoconductive insulating plate. Typical photoconductive binders are selenium, sulfur, polyvinyl carbazole, anthracene, resinous charge transfer complexes such as those disclosed in U.S. Patents 3,4o8,183, 3,4o8,184, 3,4o8,182, 3,4o8 Ιδ ^ β, and mixtures of these compounds.

Besides the application of photoconductive materials and Binders disclosed above can be the layers 3 of a photoconductive based on a glass binder Make the plate as described in U.S. Patent 3,151,982.

Although the method according to the invention is useful in connection with imaging surfaces, the photoconductive Containing layers made from any of the materials described above, one has 709828/0 8 A 5

but observed that the present process works better and worse on more brittle materials on more plastic materials. The more brittle materials appear to be flattened more quickly by abrasion or abrasion, while the materials of a more plastic character tend to undergo deform under the pressure of the abrasive and then at least partially regain their original shape, thereby flattening by the abrasive becomes a heavier task.

In the typical image area that Pig. I illustrated layer 3 is approximately 60 microns deep. It has been observed that defects such as 4, 4a and 5 are large are enough to cause an undesirable halo effect and to give blotches in the developed image. It is generally observed that defects such as 4 and 4a are greater than about 5 microns in height are capable of causing printing defects, such as halo effects, and also breaking away from layer 3 causing defects that lead to stains on the developed print.

If we now refer more specifically to FIG. 2, which shows part of a cylindrical imaging surface 6, then recognizes one that the image area 6 contains a photoconductive layer, as it was described as layer 3 in. FIG. For use in the liquid development of charge patterns it must be made smooth. You should be aware that the image surface is flat, curved, or curved. can be curved in any way. In other words, the cylindrical imaging area β is only as an exemplary embodiment has been chosen.

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The reduction of surface defects on the cylindrical image surface 6 is achieved by the abrasive or abrasive agent 7, which is pressed against the cylindrical image surface 6 and yet is kept from it by the hydrodynamic fluid bearing 8. A hydrodynamic liquid support 8 can be created between the abrasive 7 and the cylindrical imaging surface 6 when the rotation of the image surface in the direction indicated by the arrow brings the liquid 9 between the image surface and the abrasive.

To be useful in the invention, the abrasives should 7 be hard enough to abrade or sand off the appropriate photoreceptor materials without harming yourself to become. The agent should be hard enough and have a sufficiently roughened surface to remove the surface defects, which are normally found to be abraded and reduced to a size of less than reduce about 5 microns without tearing them out and without completely penetrating the liquid prop, thereby affecting the smooth parts of the photoconductive surface would. The abrasive or abrasive means is preferably somewhat flexible so that it conforms to the general Adjusts the contours of the image area.

Any suitable abrasive material can be used. Typical Agents that are useful are steel, nickel, and chrome foils. Particularly good results are obtained with nickel foil which has a surface roughness of from about to about 20 microns / inch (2.5 cm) "center line average" (CLA) has. Such a film is made with a total thickness of 0.08 l cm (0.032 inch) used. Typically it exists

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of 8 layers of 0.010 cm (0.004 inch) film, although 3 outer layers of film and one 0.038 cm (0.015 inch) thick support material is also useful

have proven.

Abrasives that have a surface roughness greater than about 20 microns / 2 cm (inch) break-as found sometimes through the liquid backing layer, tearing the smooth photoconductor surface. On the other hand, a surface roughness of less than about 6 microns / 2.5 cm (inch) (CLA) is less effective in their smoothing effect.

The abrasive 7 can be pressed against the imaging surface to be smoothed with any suitable pressure. Typically the pressure will range from about 0.028 to 0.60 kg / cm ² (0.4 to about 8.5 lbs./in ² ). When pressing

below about 0.028 kg / cm, a reduced smoothing effect has been observed, while an undesirable abrasion has been observed of the smooth photoreceptor surface can take place when the pressure is greater than about 0.60 kg / cm.

The fluid 9 * that is used to create a hydrodynamic To create liquid prop 8 can be any suitable fluid. Typically the fluid is a liquid, which has a viscosity of 100 cps to 300 cps 25 ° C. At viscosities greater than about 300 cps at -25 ° C, the liquid prop 8 begins, the abrasive 7 and the cylindrical imaging surface β to separate so much that no smoothing effect occurs. Liquids, which have a viscosity as low as that of water (1 cps at 25 ° C) can be used; she however, require so high speeds for the movement of the image surface that they are undesirable. Good results are achieved by using an oil such as a mineral oil,

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that has a viscosity of about 200 cps. at 25 ° C. Such a viscosity allows a hydrodynamic fluid support between the imaging surface and the To create abrasives using speeds for the movement of the image surface that is easily mastered can be.

The image surface that you want to smooth, like the cylindrical one Image surface 6, can be moved past the abrasive 7 at any suitable speed, to create a hydrodynamic liquid proppant 8 and to make the image surface smooth. Typically becomes the imaging surface on the abrasive at a speed of up to approx. 5,600 cm (2200 inches) moves past per minute. A preferred speed is about 2116 cm (850 inches) per minute because of this Speed is compatible with the preferred liquid for the formation of a liquid prop between the Abrasives and the picture surface.

Although not necessary, the abrasive 7 can be vibrated during the smoothing operation, to improve the reduction or lessening of surface defects on the photoreceptor. Vibrations are in the generally achieved by using the abrading or sanding device oscillate at right angles to the direction of movement of the screen at frequencies up to approximately 10,000 Hz.

Referring to Fig. 3, one sees a method of applying the liquid to the imaging surface, such as the cylindrical imaging surface 6 in Fig. 2. In Fig. 2, the cylindrical imaging surface 6 has been rotated in the direction of the arrow through the bath 14, where it receives a coating of the liquid 9. The applied liquid is evenly distributed on the cylindrical image surface 6

and to a uniform thickness through the 709 8 28/0 8A5

direction 15 measured. After applying with Ab-r measurement, the liquid layer 9 forms the hydrodynamic liquid support 8 between the image surface and the abrasive 7.

Any suitable means can be used to measure the thickness of the liquid 9 on the image area β. Typically the sizing means 15 is a blade such as a wiper or a scraper. It can also be an absorbent His roller / the sizing means 15 is shown in Fig. 3 as a wiper.

Referring now more specifically to FIG. 4, we show an alternative means of applying the liquid 9 to the cylindrical imaging surface 6. In FIG. K , the liquid 9 is applied to the surface by means of an opening or nozzle 16 and then spread and measured of the area by the measuring means 15, as described in connection with FIG. 3. The opening or nozzle 16 can be any suitable device for applying a stream of liquid 9 to the image surface 6. Typically it can be a nozzle for applying liquid 9 under pressure to the surface or a mouth-like opening to apply the liquid 9 to the surface bring to.

Referring now specifically to FIG. 5, we show here yet another means of creating a hydrodynamic liquid support 8 - between the abrasive 7 • and the cylindrical imaging surface 6. Here the Liquid 9 is applied directly to the support surface area by means of the nozzle 16. In this embodiment, the Liquid is not metered onto the support zone by a separate means, and therefore the flow of liquid is 9 from the nozzle 1β preferably carefully maintained at a constant speed.

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Referring now specifically to Fig. 6, we show an apparatus for use in the method of the invention which uses a hydrostatic liquid prop 10 to separate abrasive Ja from the flat image surface 11 to be smoothed.

The hydrostatic liquid prop 10 is produced in this exemplary embodiment by forcing a liquid under pressure through the passage 12 in the abrasive Ya so that the abrasive 7a is separated from the flat imaging surface 11. Any suitable fluid can be used. Typically such fluids are gases, water and oils which have a viscosity up to 1000 cps at 25 ° C. The embodiment shown in FIG. 3 is suitable for gases since there is no minimum viscosity requirement for the fluid as long as it is pushed through the passage 12 with sufficient force to keep the abrasive Ja away from the flat image surface 11.

The functional surface 13 of the abrasive Yes. should have the same abrasion characteristics as those described in connection with the abrasive or abrasive agent 7 of FIG. Furthermore, the abrasive 7a of FIG. 6 can be made to oscillate like the abrasive 7 of FIG. 2. Although this is not a preferred embodiment, the abrasive can be yes. optionally including a cutting edge 17 for cutting off surface defects of the image surface while the abrasive means 7a is moved in relation to the image surface. Optionally, the abrasive material such as the abrasive Yes. can only be used with a grinding edge 17, without a roughened functional surface. The use of a grinding edge such as the grinding edge is not preferred because of the shear force thus generated

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sometimes large enough to remove the surface defect from the Tear off the image surface and in this way create an undesirable hole (as described above).

The flat imaging surface 11 does not need to be moved in order to form the hydrostatic liquid support 10. However, the surface 11 relative to the abrasive 7a. move while the surface 6 is moved relative to the abrasive 7.

The method described herein with reference to Figures 2-6 is useful to at least substantially Dimensions of surface defects on imaging surfaces such as those that do shown in Fig. 1 to reduce in size to less than about 5 microns. This applies to both Inorganic as well as organic picture surfaces, whereby one can almost completely tear or spoil the Avoids imaging surface.

Specific embodiments of the invention are described above been. It will be understood, however, that various modifications can be made by those skilled in the art without departing from the scope of the invention as defined in the claims.

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Claims (22)

Claims 1. A method for reducing surface defects on an imaging surface, characterized in that that it includes the following steps: a) the generation of a relative movement between an imaging surface and an abrasion or Abrasive that is pressed against that image surface while the surface and the abrasive or Abrading media are separated by a liquid prop and b) maintaining such a movement until the defects are reduced in size to less than about 5 microns. 2. The method according to claim 1, characterized in that g e characterization η e t that the imaging surface includes a photoconductive material coated on a conductive substrate. 3. The method according to claim 1, characterized in eh-η e t that the imaging surface is a drum. '4. Method according to claim 1, characterized et that the imaging surface is a flexible sleeve (sleeve) is. 5. The method according to claim 1, characterized in, that the abrasive or abrasive is a metal foil is. 709828/0848 ORIGINAL INSPECTED 6. The method according to claim 5 *, characterized in that that the foil is a nickel foil having a surface roughness of about 6 to about 20 microns per Inch C.L.A. Has. 7. The method of claim 1 characterized in that the abrasive is pressed against the imaging surface at a pressure of from about 0.028 to about 0.60 kg / cm (0.4 to about 8.5 lbs / in ² ). 8. The method according to claim 1, characterized in that that the relative movement between the imaging surface and the abrasive by moving the imaging surface is produced. 9. The method according to claim 8, characterized in that that the imaging surface relative to the abrasive at a speed up to about 560 cm (2,200 inches) / minute. 10. The method according to claim 1, characterized in that that the relative movement between the imaging surface and the abrasive by oscillating the abrasive in a plane at right angles to the Direction of movement of the surface is generated. 11. The method according to claim 10, characterized in that that the abrasive oscillates at a frequency of up to about 10,000 Hz. 12. The method according to claim 1, characterized in, that the fluid bearing is a hydrostatic support layer. 709828/0846 -19- 13. The method according to claim 12, characterized in that the hydrostatic support by Application of a gas is formed, 14. The method according to claim 1, characterized in that the liquid support is a hydrodynamic Prop is. 15. The method according to claim Vi, characterized in that the hydrodynamic support is formed by applying a liquid which
has a viscosity no greater than about 1000 cps at 25 ° C. 16. The method according to claim 15 *, characterized in that the liquid is an oil. 17. The method according to claim 15, characterized in that the liquid is applied to the imaging surface and then to a practically even thickness prior to contact with the abrasive spread out by measuring. will. 18. The method according to claim I7, characterized in that the liquid by a wiping " blade is spread out. 19. The method according to claim I7, characterized in that the liquid is applied to the imaging surface by means of a bath. -20- 709828 / 084S 265A096 -ν ■ 20. The method according to claim 17, characterized in that the liquid is applied to the imaging surface by means of a nozzle. 21. The method according to claim 15, characterized in that the liquid is directly between applied to the imaging surface and the abrasive will. 22. The method according to claim 21, characterized in that the liquid by means of a Nozzle is applied. 709828/0845