US3836381A

US3836381A - Method of developing a dielectric pattern on a semiconductor surface using a two-component developer

Info

Publication number: US3836381A
Application number: US00294001A
Authority: US
Inventors: K Metcalfe; A Clements; C Wilson
Original assignee: SECRETARY SUPPLY AUSTRALIA
Current assignee: SECRETARY DEPARTMENT OF SUPPLY AU; SECRETARY SUPPLY AUSTRALIA
Priority date: 1972-10-02
Filing date: 1972-10-02
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17

Abstract

A method of developing a dielectric pattern on a semiconductor surface by using a two-component developer, each selective to a different polarity, comprising applying an electrical bias through the surface to deposit on the high dielectric areas of the pattern, a developer component which has a lower dielectric constant than the semiconductive surface to form a relatively insulating shield at the deposition areas. Then the bias polarity is reversed to deposit the other developer component on the unshielded areas, due to the higher dielectric constant at the unshielded area.

Description

United States Patent Metcalfe et a1.

METHOD OF DEVELOPING A DIELECTRIC PATTERN ON A SEMICONDUCTOR SURFACE USING A TWO-COMPONENT DEVELOPER Inventors: Kenneth A. Metcalfe, Lockleys;

Alwin S. Clements, Largs Bay; Clive W. Wilson, Oaklands Park, all of Australia The Commonwealth of Australia care of The Secretary, Department of Supply, Parkes, Canberra, Australia Filed: Oct. 2, 1972 Appl. N0.: 294,001

Assignee:

US. Cl. 1l7/17.5, 96/1 S, 96/1 D,

96/1 LY, 117/37 LE Int. Cl. G03g 13/08, 003g 13/10 Field of Search 117/17.5, 37 LE; 96/1 R, 96/1 8, 1 D, 1 LY; 355/10, 17; 204/181 References Cited UNITED STATES PATENTS 12/1959 Epstein 117/17.5

[ Sept. 17,- 1974 3,010,842 ll/l96l Ricker 117/37 LE 3,038,799 6/1962 Metcalfe et al. 96/1 R 3,078,231 2/1963 Metcalfe et al 252/621 3,081,263 3/1963 Metcalfe et a1 252/621 3,527,684 9/1970 York et 117/37 LE 3,563,734 2/1971 Shely 96/] R 3,589,895 6/1971 Ville 96/1 R 3,703,399 11/1972 Tanaka et al. 355/10 Primary ExaminerMichael Sofocleous Attorney, Agent, or FirmEric H. Waters 13 Claims, 2 Drawing Figures 7210 om 0006f)! Peale/oper Pfo/Aer {Aer/mole aDeposi/ed lower Dark X/OOSGCZ l METHOD OF DEVELOPING A DIELECTRIC PATTERN ON A SEMICONDUCTOR SURFACE USING A TWO-COMPONENT DEVELOPER This invention relates to a method and apparatus for developing electrostatic images.

BACKGROUND OF INVENTION In developing electrostatic images it is necessary to use marking particles which develop the field or the background of an electrostatic image.

It is well known that these marking particles can be in dry form or they can be suspended in a liquid.

The marking particles must be so applied to the surface that they can deposit according to the existing latent image and this applies whether they are in the form of a powder cloud or held on carrier particles which impart a triboelectric charge to the particles, or whether they are suspended in a liquid of high electric resistivity so that they are freely available to deposit on the image or non-image areas.

Certain advances in the art have greatly improved the resolution obtainable by developers, and this applies particularly to what are now commonly known as liquid developers, that is developer in which the marking particles are suspended in a carrier liquid having an electrical resistivity preferably in excess of ohm. centimeter and a dielectric constant less than 3, the particles preferably being controlled by utilising a wetting medium for the particles or on the particles or a medium attached to the particles to control the particle movement.

It is also known that the behaviour of particles in insulating liquids vary considerably according to the insulating nature of the particles and thus for instance particles which are readily polarisable tend to go down on a surface but are then rejected when repolarisation of the particle takes place due to contact, and it can be shown by demonstration that insulating particles will normally have a charge in a liquid which may be inherent charge but which is retained relatively tenaciously on the particles because of the inability of the particles to lose the charge readily, and therefore insulating particles when they are drawn down on to a latent image area, tend to attach themselves to the area much more permanently than particles which are conductive.

Thus it will be found that insulating particles will go down on to a surface because they are of opposite electrical sign to the surface to which they are attracted, and they will hold to that surface as long as the relative polarities remain on the particles and the surface, but there will be an exchange between the particles and the surface which will eventually reduce the force by means of which the particles are held to the surface, and particles can then escape from the surface unless held by other means.

On the other hand with more conductive particles which are more readily able to exchange charges with a surface, a particle of one polarity, when moving down on to a surface of opposite polarity, will exchange charges rapidly, and this tends to cause repelling of the more conductive particles at a fairly high rate and because their polarity is then changed, they will tend to go to an opposite polarity where exactly the same interchange will again take place and such particles therefore tend to move alternately between areas of opposite polarity. I

Thus by selecting particles of the required dielectric constant, a fairly extensive control of behaviour of developers is possible and for instance where controlled developers are used, it is customary to use a relatively insulating medium on the surface of more conductive pigment particles to control the behaviour of the pig ment particles in an electrical field, this type of developer generally being referred to as controlled developers, such developers achieving a higher resolution and less background contamination because of the more uniform deposition.

Another problem in connection with the art of developing electrostatic images is that the surfaces of photoconductors which are to be made image containing, require first to have a charge applied to the surface in the dark, which charge can then be modified by a light image or X-ray image or the like, the light or X-ray or other electromagnetic wave having the effect of causing the photoconductive medium to become conductive and thus bleed away the charges from those areas, leaving an image on the remaining areas where the electromagnetic waves have not caused the bleeding away of the charge.

It has been proposed by the applicants to effect development without charging, for the reason that it is extremely difficult and costly to provide mechanism for effecting uniform charging.

One of the greatest problems in achieving a uniform charge is that the corona or other charging device tends to be more effective on some areas of the photoconductive surface than other, partly due to the irregularities in the surface, and partly due to lateral flow which can take place when uneven charging results due to the somewhat erractic movement of particles in the methods of charging adopted.

it will thus be considered that charging, while it allows a relatively high voltage to be built up on insulator surface which contains a photoconductive medium or is formed by a photoconductive medium, this higher charge, although it can be more readily developed by marking particles because of its magnitude, is subject to irregularities due to the effects mentioned, and also as charge bleeding and lateral flow can take place between the time of producing the image and the application of the developer, certain defects are well known to exist in any system which utilises charging of an insulator surface.

SUMMARY OF INVENTION An object of the present invention is to provide an improved form of development in which charging is not resorted to, and in which photoconductive surfaces are not necessarily used, but rather an image is produced, by modifying semiconductive surface, by patterned electromagnetic waves and then developing the image so produced.

While it has been possible heretofore to develop such images by means of the more sensitive liquid developers which are now available, the image nevertheless has lower density, and a further object of this invention therefore is to provide a method in which density of development can be enhanced without resorting to charging of the surface before development.

The objects of the present invention are achieved by making use of the difference in characteristic of a relatively insulating medium or toner in relation to relatively more conductive toner particles, or particles having a different dielectric constant, that is using at least two materials carying in their dielectric properties, which may be the electrical insulating liquid and the marking particles, and causing the particles to deposit during two separate steps, comprising applying a first and then an opposite bias to the surface containing a dielectric image caused through exposure to electromagnetic waves or by pressure or thermal gradiants while that surface is in contact with the developer, the first bias being selected to drive down the more insulating medium to the surface, while preventing the conducting particles from moving to the surface. This causes the insulator to act as a control medium for further development in that when the more conductive substance is driven down toward the surface by the reversed bias the substance already in position will act as a dielectric control.

Thus for instance if a photoconductive or a semiconductor surface, which has been dark adapted, is subjected to a light image, or an image of other electromagnetic waves, or a pressure or thermal image, the dielectric constant of the surface will be selectively changed in the light struck areas to produce an image and if now a developer containing a substance of a low dielectric constant, and also toner particles which are of higher dielectric constant, is brought into contact with the modified surface, it is possible by applying one polarity to an electrode at or near the surface to drive down first the more insulating medium on to the surface which will remain on the surface on which it was deposited, and when the surface will have an enhanced dielectric pattern on it which can be developed by the material of higher dielectric constant, that is the toner material.

In the case of chargeless images," the ultimate result to that which can be obtained with pre-charged surfaces, excepting that where no charge has been involved, the definition is found to be better and faults are greatly reduced, and moreover this image is obtained in a much simpler manner because the whole of the somewhat difficult charging procedure is dispensed with.

DESCRIPTION OF DRAWINGS FIG. 1 is a diagrammatic side elevational view of apparatus for developing a dielectric pattern on a semiconductor surface, and

FIG. 2 shows the apparatus of FIG. 1 in a further stage of operation.

DETAILED DESCRIPTION FIG. 1 shows diagrammatically a base 1 supporting on it a membrane 2 having a semiconductor coating 3 on it. The area 4 is exposed to light while the area 5 is dark adapted, causing the area 4 to be of higher dielectric constant (more conductive) than the area 5. The roller 6 has a developer 7 on it which combines positive toner particles 8 with a lower dielectric component 9 such as a resin.

The negative charge on the roller 6 which has an insulating coating on it locks the positive particles 8 to it but allows the lower dielectric particles to be drawn down towards the base electrode 1 at the areas where the semiconductor coating has had its dielectric constant raised to be sufficiently conductive to hold the component 9 down at this area to form an insulating shield.

At the area 5 however, the semiconductor characteristic remains and no deposit takes place unless an excessive voltage is applied to the roller 6.

FIG. 2 shows diagrammatically how when the roller 6 is again passed over the semiconductor surface with a positive potential on it, the Toner particles 8 are forced off the roller when over the semiconductor area 5 as a field can extend through this if the voltage is sufficient but cannot extend through the insulator layer 9 previously deposited by the roller pass of FIG. 1 and thus no toner deposit occurs here.

The voltages required and the polarity of any particular developer particle can readily be achieved by experiment but examples are given as a guide later herein.

The invention is conveniently used with photoconductive layers on a membrane, but as said a semiconductor medium can also be used so that a differential exists where the areas of this are varied by light exposure of X-rays or pressure or thermal effects so a differential deposition of insulator on the first pass exists which then increases the differential for the second pass.

Thus the method will be seen to increase the dielectric constant differential at image and non-image areas and allows intensive deposition of developer to occurr by what can be termed an amplified differential effect."

By varying voltages, as well as time and polarity, close control of both the first and second deposition can occur.

Naturally, the medium of higher insulating value, that is lower dielectric constant, can be a particulate substance such as a resin, co-mingled with the toner particles in an insulating liquid.

If the medium of higher insulating value is a resin or the like, and if the background is not to be colored in spite of deposition, mainly at the first biasing, it should be a colorless medium, or it could be an opaque white in cases where the photoconductor base itself is dyesensitized, so as to cover the dye and give a white background.

In summing up the invention it will be realised that it consists in the use of a first bias applied to hold the more conductive toner particles away from the semiconductor surface and thereby allowing the more insulating medium to be deposited on the exposed areas, that is electromagnetically exposed or pressure exposed or thermally exposed areas which are then generally ofa higher dielectric effect the deposit taking place because of the control which can be exerted by the magnitude and duration of the first bias.

By controlling the second reversed bias, the toner particles can be forced down in the image areas but not where the insulator layer has been deposited.

It will be realised that the invention uses differential deposition of insulator and less insulator particles.

EXAMPLES OF COATINGS ON A SUPPORTING MEMBRANE Coatin l Mowrtal polyvinyl-butyral (B6OH) (Hoechst) Zinc oxide colloidal grade (Durham Chemicals) grams 350 grams The Mowital was taken up in 500 mls. acetone and 50 mls. methyl ethyl ketone, and ball milled with the zinc oxide.

This coating can be applied to either film, metal backing or paper.

Coatin 2 lso ordosol 4501/60 short oil alkyd resin (Jordan Chemicals) Zinc oxide (colloidal grade) (Durham) Rose Bengal (sensitiser dye) Toluol 158 grams 430 grams 1200 millilitres Developer lgal) Negative Black Developer grams 0 moor Carbon Black 300 grams Sunflower seed oil 500 grams B.P.V. oil (Viscostatic) These materials are ball milled together and dip coated on paper, metal, wood, or film base to form a photoconductive layer.

THE DEVELOPERS USED COMPRISED Developer 11.

A two colour developer which was used to demonstrate the principle involved as it permitted blue to be deposited on the background areas it" too high voltage 10 were used during the second stage but no background deposit of either blue or black occurred with correct yoltage.

(More conductive) (Meggitts) (British Petrolium) 200 grams alkyd resin (1352/60) Super Beckosol (Reichold Chemicals) 0.1 parts by weight of developer 1(a) were added to one part of the following developer 1(b) and 0.1 part of developer l(c) Developer lib) Copolymeric Blue Developer grams ostaperm Blue 1330 (HA8 Insulator) (Hoechst) 200 grams Styrene-butadiene copolymer e.g. Solprene 1205" (Phillips Imperial Chemical) 100 grams Vinyl toluene-acrylate copolymer e.g. Pliolite VTAC Australian Synthetic Rubber) These materials were ball milled together to form a coating composition. Cobalt and zinc naphtenate driers were added (0.5%

and 0.5% by wt. of solid resin).

Coatin 3 lso ordosol 3501/ short oil alkyd resin (Jordan Chemicals) Titanium dioxide Toluol 430 grams 150 grams 1200 millilitres These materials were ball milled together to form a coating composition. Cobalt and zinc naphthenate driers were added 45 (0.5% and 0.5% by wt. of solid resin).

Coatin 4 tyrene-5utadiene copolymer Esso polymer 200 (Buton 200) Zinc oxide Lead naphthenate Cobalt naphthenate Zirconium octoate Cerium octoate Solvent Alsol Toluol Hexyl acetate Ethyl acetate Butanol Pentoxone Disulphine Blue Acridine Orange Erythrosin B Sodium fluorescein 6% solution in mineral spirits 6% solution in mineral spirits 6% solution in mineral spirits 6% solution in mineral spirits 1% by wt. in methyl alcohol 1% by wt. in methyl alcohol 1% by wt. in methyl alcohol 150 grams 500 grams 1.0 gram 0.1 gram 1 gram 0.05 gram 900 millilitres 65 millilitres 10 millilitres l0 millilitres l0 millilitres 5 millilitres 2 millilitres 2 millilitres 2 millilitres 5 millilitres The copolymeric resins were taken up in Solvesso and subsequently milled with the blue pigment.

Lower dielectric component Developer 1(c) (Copolymeric suspension in lsopar E (Esso), and isogaraffinic hydrocarbon solvent),

lsopar 200 mls.

"Solprene 1205" 5 grams (solution of 1 gram of solid in 2 mls.)

"Pliolite VTAC" 5 grams (solution of 1 gram of solid in 2 mls.)

0.1 parts by wt.

The developer can be applied by a simple electrode or by two rollers one following after the other but with opposite bias.

Time of first bias 30 volts at 30 centimetres per second.

Reverse field bias 50 volts at 10 centimetres per second.

Similar times were involved in using a bias plate having a spacing of 2 millimetres from the surface being 10 developed. Additional developers follow:

Developer 2 First pass 30 volts at 20 centimeter per second Second pass 50 volts at 20 centimeter per second Developer 3 B/A/8 54 grams Hosterperm Blue B3G (Hoechst) 6l grams Solprene I205 32 grams VTAC. Dispersed in I mls. Esso I00 2000 mls. lsopar E First pass 50 volts at 20 centimeter per second Second pass 10 volts at 20 centimeter per second First pass 300 volts at 20 centimeter per second Second pass I00 volts at 20 centimeter per second Developer 40 grams Permanent yellow GG (Hoechst) I0 grams Solprene I205 7 grams VTAC Dispersed in I00 mls. Esso I00 2000 mls. lsopar E First pass I00 volts at l5 centimeter per second Second pass 50 volts at l5 centimeter per second Exam le 6 60 grams Graphtol Red I630 I0 grams Solprene I205 10 grams VTL Copolymer Dispersed in I00 mls. Esso I00 2000 mls. Isopar E First pass 50 volts at centimeter per second Second pass 20 volts at 20 centimeter per second Example 7 50 grams lsol Ruby Red 30 grams Brillfast Rose Red 20 grams Pale lowering Lithographic Varnish 200 grams Rhodene alkyd resin L42/70 Dispersed in I00 mls. Esso I00 2000 mls. lsopar E First pass 50 volts at IO centimeter per second Second pass 10 volts at 10 centimeter per second Example 8 50 grams lsol Ruby Red 30 grams Brillfast Rose Red I50 grams Alkyd Resin P470 l2 grams Beeswax l5 mls. Toluene dispersed in 100 mls. Esso I00 2000 mls. lsopar E First pass 20 volts at 10 centimeter per second Second pass 2 volts at I0 centimeter per second IDENTIFICATION OF TRADE MARKS AND TRADE NAMES MOWITAL B6OI-I, polyvinyl butyral resin, made by Hoechst, Germany; containing polyvinyl acetal 76-78 percent, polyvinyl acetate I percent and polyvinyl alcohol 18-21 percent.

ISOJORDOSOL 4501/60 short oil alkyd resin made by Jordan Chemicals BUTON 200, styrene-butadiene copolymer made by Esso SOLPRENE 1205, styrene-butadiene copolymer Phillips Petroleum Corp., U.S.A., a block copolymer of butadiene and styrene in the ratio /25 containing 97.5 percent of rubber hydrocarbon, A.S.T.M. No. I205 with majority of styrene molecules added as polystyrene at the end of a long chain of butadiene units.

SUPERBECKOSOL 1352/60, a semi-drying safflower oil isophthaIic-modified long oil alkyd resin with 59-61% non-volatile matter, acid value 3-6, oil length 60%, viscosity Gardner l-loldt Y-Z.

VINYLITE VYNW, a vinyl chloride-acetate resin, approximate composition vinyl chloride 97%, vinyl acetate 3%, and specific gravity 1.39,

PENTACITE P423 is a modified pentarethyritol ester resin with acid number 20-30.

PLIOLITE VT RESIN is a styrene/butadiene type copolymer rubber made by the Goodyear Corp., U.S.A. and prepared by the G.R.S. method in which the butadiene polymerises in the main by a 1,4-addition. Pliolite VT is a vinyl toluene/butadiene random copolymer rubber, soluble in mineral spirits.

PLIOLITE SSD is a styrene/butadiene copolymer, KB value 60, manufactured by Goodyear Corp., U.S.A.

PLIOLITE V.T.A.C. is a vinyl toluene/acrylate copolymer, KB value 36.

ESSO I00 Solvent is a hydrocarbon solvent supplied by Esso Chemicals Australia Limited, having an aromatic content of 98%, flash point of 108 F., and distillation range I59-l82 C.

MICROLITH Pigments comprise a pigment and a resinous carrier. Microlith Black pigment contains pure neutral carbon black together with a toluene soluble carrier resin such as Stabilite Ester 10 of the Hercules Powder Co., U.S.A.

MICROLITH BLUE 4GT comprises a stable phthalocyanine blue pigment with a greenish cast together with Stabilite Ester l resin.

MlCROLlTl-I GREEN GT comprises a medium shade of phthalocyanine green together with Stabilite Ester 10 resin, the microlith pigments are manufactured by Ciba Co., Switzerland.

Colour Index of the Pigments Microlith Blue Colour Index No. 74160 Microlith Green Colour Index No. 72455 ELVACITE RESIN is an acrylic resin manufactured by DuPont, Delaware, U.S.A.

Coates hydrocarbon dispersible flake black comprises pure carbon black together with ethyl hydroxy cellulose resin.

B.P.V. OIL synthetic automotive lubricating oil containing antioxidant ZDP," dialkyl zinc dithiophosphate in solution, made by British Petroleum Ltd.

KOHINOOR CARBON BLACK supplied by A. C.

Hattrick Ltd. Aust.

SUNFLOWER SEED OIL vegetable oil supplied by Meggitts Ltd., Australia.

HOSTAPERM BLUE B3G copper phthalocyanine blue, pure beta-form, made by Hoechst, C.l. pigment Blue 15, Colour Index No. 74160.

GRAPHTOL BLUE BLF, phthalocyanine blue, C.I.

pigment blue made by Sandoz.

PERMANENT YELLOW 66, extra, a diazo yellow pigment without lake forming groups, C1. pigment yellow 17, colour Index No. 21105.

BRILLFAST ROSE RED 4444, a red phosphotungsto molybolic acid toner.

ISOL RUBY RED BKS 7520 (KVK) a lithol ruby red C.I. Pigment Red 57, Agfa, Calcium lake.

PALE LOWERING LITHOGRAPHIC VARNISH a polymerized linseed oil varnish made by Meggitts Ltd., Australia, Polylin l/S, acid value 40-65 vis cosity 7.0-9.5 poises at 25 C, from alkali refined linseed oil.

RHODENE RESIN L42/70, a safflower oil modified alkyd resin made by Polymer Corporation, Australia, acid value 6-10, with 69-7l, percent solids, 64% oil length.

ISOPAR G a hydrocarbon liquid solvent with greater than 95% isoparaffinic content, and aromatics and olifins less than 1 percent, and remainder cyclo and normal paraffins, KB No. 27, final boiling point 177 C.

ISOPAR E a hydrocarbon liquid solvent with greater than 95% isoparaffinic content, aromatics and olifins less than 1 percent, with remainder cyclo and normal paraffins, KB Value 29, final boiling point 143C.

B550 100 is an aromatic hydrocarbon solvent with 98% aromatics, KB value 9, final boiling point 182C.

We claim:

I. The method of developing a dielectric pattern on a semiconductor surface which is uncharged but has its dielectric constant modified imagewise, comprising the steps of a. subjecting the semiconductor surface to a developer having at least a first and a second particulate developer component, said components varying in their dielectric constant and polarity, the first said developer component having a dielectric constant less than the unmodified semiconductor surface, b. effecting a first development by applying an electrical bias of one polarity selected to deposit the first said developer component to form a selective shield on the areas of high dielectric constant of the semiconductor due to the greater general conductivity at that area, and subsequently effecting a second development by reversing the polarity of the bias to deposit the second particulate developer component on the areas of the said surface where the first shielding developer has not been deposited and where thus the greater conductivity now exists due to the lower conductivity of the deposited shield.

2. The method of claim I wherein the semiconductor surface is supported on one biasing electrode and a second electrode is spaced from the said surface with the developer between the said surface and the said second electrode.

3. The method of claim I wherein the semiconductor surface is supported on one biasing electrode and the developer is carried on an applicator which is passed over the said surface in contact with the said surface and which forms the second electrode.

4. The method of claim 1 wherein the said developer comprises toner particles of a higher dielectric constant, and resin particles of a lower dielectric constant.

5. The method of claim 4 wherein the said resin particles are colorless.

6. The method of claim 4 wherein the said resin particles are colored.

7. The method of claim I wherein the first biasing is relatively longer than the second said biasing but of lower voltage.

8. The method of claim 1 wherein the semiconductor surface is a photoconductor and the dielectric constant is varied by the application of electromagnetic waves.

9. The method of claim I wherein the semiconductor surface comprises a resin including therein relatively conductive particles and the dielectric constant is varied by electrical impulses.

10. The method of claim 1 wherein the semiconductor surface is a dye-sensitized photoconductor of particulate form embedded in a resin, and the first said developer component is white to mask the color of the said photoconductor where toner particles are not deposited.

11. The method of claim 1 wherein the semiconductor surface comprises a resin including therein relatively conductive particles and the dielectric constant is varied by pressure.

12. The method of claim 1 wherein the semiconductor surface comprises a resin including therein relatively conductive particles and the dielctric constant is varied by thermal patterning.

113. The method of developing a dielectric pattern on a semiconductor surface wherein the semiconductor surface comprises a resin including therein particles more conductive than the said resin, and wherein the dielectric constant is varied patternwise comprising the steps of supporting the said semiconductor on one electrical biasing electrode and applying the developer by selective shield on the areas of higher dielectric constant of the semiconductor due to the greater general conductivity at that area, and subsequently effecting a second development by reversing the polarity of the bias to deposit the second developer component on the areas of the said surface where the first shielding developer has not been deposited and where thus the greater conductivity now exists due to the lower conductivity of the deposited shield on the other areas.

Claims

2. The method of claim 1 wherein the semiconductor surface is supported on one biasing electrode and a second electrode is spaced from the said surface with the developer between the said surface and the said second electrode.
3. The method of claim 1 wherein the semiconductor surface is supported on one biasing electrode and the developer is carried on an applicator which is passed over the said surface in contact with the said surface and which forms the second electrode.
4. The method of claim 1 wherein the said developer comprises toner particles of a higher dielectric constant, and rEsin particles of a lower dielectric constant.
5. The method of claim 4 wherein the said resin particles are colorless.
6. The method of claim 4 wherein the said resin particles are colored.
7. The method of claim 1 wherein the first biasing is relatively longer than the second said biasing but of lower voltage.
8. The method of claim 1 wherein the semiconductor surface is a photoconductor and the dielectric constant is varied by the application of electromagnetic waves.
9. The method of claim 1 wherein the semiconductor surface comprises a resin including therein relatively conductive particles and the dielectric constant is varied by electrical impulses.
10. The method of claim 1 wherein the semiconductor surface is a dye-sensitized photoconductor of particulate form embedded in a resin, and the first said developer component is white to mask the color of the said photoconductor where toner particles are not deposited.
11. The method of claim 1 wherein the semiconductor surface comprises a resin including therein relatively conductive particles and the dielectric constant is varied by pressure.
12. The method of claim 1 wherein the semiconductor surface comprises a resin including therein relatively conductive particles and the dielctric constant is varied by thermal patterning.
13. The method of developing a dielectric pattern on a semiconductor surface wherein the semiconductor surface comprises a resin including therein particles more conductive than the said resin, and wherein the dielectric constant is varied patternwise comprising the steps of supporting the said semiconductor on one electrical biasing electrode and applying the developer by means of an applicator which is passed over the said surface in contact with the said surface and which forms the second electrode, a said developer having at least two developer components carried in an insulating liquid, said components varying in their dielectric constant, one developer component having a dielectric constant less than the unmodified semiconductor surface, effecting a first development by applying a bias of one polarity selected to deposit the component of the developer with the lower dielectric constant to form a selective shield on the areas of higher dielectric constant of the semiconductor due to the greater general conductivity at that area, and subsequently effecting a second development by reversing the polarity of the bias to deposit the second developer component on the areas of the said surface where the first shielding developer has not been deposited and where thus the greater conductivity now exists due to the lower conductivity of the deposited shield on the other areas.