US3884684A - Electrostatic developing process employing a porous photoconductive member - Google Patents

Abstract

A method for electrostatically printing, employing a photosensitive plate comprising a conductive substrate having fine pores distributed uniformly over the surface thereof and a liquid-repellent photoconductive layer coating the surface of the substrate except the part of the pores. An electrostatic latent image is formed on the photoconductive layer, and a liquid developer is supplied from the back side of the photosensitive plate. Next, a voltage is applied between the plate and an opposing electrode contacting a paper to be printed, disposed in an opposing relation to the plate so that the latent image is developed and transferred to the paper.

Description

United States Patent [1 1 [111 3,884,684

Ohno et a1. May 20, 1975 [54] ELECTROSTATIC DEVELOPING PROCESS 3,245,381 4/1966 Bremeisen et al. 96/1 LY EMPLOYNG A POROUS 3,285,741 11/1966 Gesierich et a1. 96/1 R PHOTOCONDUCTIVE MEMBER 3,776,723 12/1973 Royka et al. 96/1 LY [75] Inventors: Genji Ohno, Yokohama; Eiichi Inoue, Tokyo. both of Japan Primary Examiner-Norman G. Torchin Assistant Examiner.lohn R. Miller [73] Assignee: Research and Development Laboratories of Ohm) Co, Ltd" Attorney, Agent, or Fzrm-Staas and Halsey Kanagawa, Japan [22] Filed: Apr. 23, 1973 211 Appl. No; 353,799 [57] ABSTRACT Related Application Data 7 v A method for electrostatically printing, employing a [62] Division of Se o 33,5 a c 0, 97 atphotosensitive plate comprising a conductive substrate 3,776,630 having fine pores distributed uniformly over the surface thereof and a liquid-repellent photoconductive Forelgn Appllcatlon Pllol'lty Dam layer coating the surface of the substrate except the Mar. 29, 1971 Japan 46-17940 part of the pores. An electrostatic latent image is formed on the photoconductive layer, and a liquid de- [52] US. Cl 96/1 LY; 117/37 LE veloper is supplied from the back side of the photo- [51] Int. Cl G03g 13/10 sensitive plate. Next, a voltage is applied between the [58] Field of Search 96/1 LY; 1 17/37 LE; plate and an opposing electrode contacting a paper to 355/10 be printed, disposed in an opposing relation to the plate so that the latent image is developed and trans- [56] References Cited ferred to the paper.

UNITED STATES PATENTS 3,220,833 11/1965 McFarlane 118/637 X 11 Claims, 12 Drawing Figures 3 |0 4 |2 POTENTIAL 2O ':-T*" -T- =i- 8\ SOURCE .i I. i.

arr! PATENTED HAYZO i375 SHEET 10F 2 Fl G. I

FIG. 5

POTENTIAL SOURCE POTENTIAL SOURCE POTENTIAL SOURCE PATENTEU I 3,884,684

SHEET 20F 2 POTE IAL 80 CE I 1 1 I I OTENTIAL SOURCE POTENTIAL 8, SOURCE ELECTROSTATIC DEVELOPING PROCESS EMPLOYING A POROUS PHOTOCONDUCTIVE MEMBER CROSS-REFERENCE TO RELATED APPLICATIONS The present application is a division of United States application Ser. No. 233,547, filed Mar. 10, 1972, which was issued Dec. 4, 1973 as U.S. Pat. No. 3,776,630.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to an electrostatic printing method wherein liquid developers are used.

2. Description of the Prior Art Conventional electrostatic printing methods of the prior art require that an electrostatic latent image be formed on an electrophotographic plate and that colored fine particles be supplied to be electrostatically attracted to the latent image so that image development is carried out and the colored fine particles are electrostatically transferred to a print paper. In the above method, a photoconductive, photosensitive selenium plate (or other space discharge type of photosensitive plate including an insulating layer formed on the surface of a photoconductive layer), may be used as the electrophotographic sensitive plate. The colored finelydivided particles may be suspended in a highresistance, low dielectric constant carrier liquid.

Among the known conventional methods, dry developing methods have the following defects: vl) the developer particles are apt to be scattered 2) the developing unit is complex, and 3) the resolving power is inadequate. The known liquid developing methods have the following defects: 1) the liquid developers may have objectionable odors and be poisonous; and 2) the voltages required may cause fires due to discharges.

SUMMARY OF THE INVENTION An object of this invention is to provide an electrostatic printing method, wherein a positive image can be reproduced from both positive and negative originals by a liquid developing method without danger of fire, odor and poison.

In accordance with the teachings of this invention, a photosensitive plate comprises a conductive substrate with fine pores distributed uniformly over the entire surface of the substrate; the surface of said substrate is coated except the part of the pores, by a photoconductive layer which is repellent against liquid developers. One surface of the photosensitive plate is exposed to a light image to form an electrostatic latent charge thereon corresponding to the light image. Next, a liquid developer is applied to the other side of the photosensitive plate and a DC. voltage is applied between the photosensitive plate and an opposing electrode arranged near the photosensitive plate. The opposing electrode contacts a paper to be printed so that the latent image on the photosensitive plate can be developed and transferred to the paper.

The opposing electrode may be previously attached to the print paper or may be designed as a Separate member from the paper to provide an electrode surface disposed to contact the back side of the paper and to apply a voltage thereto.

According to a significant feature of this invention, the surface of the photosensitive layer is liquidrepellent and hence, the contamination of the printed image thereby is minimized and the optimum print can be reproduced by adjusting the applied voltage. Another significant feature of the invention is that a positive print can be made from both positive and negative originals by changing the polarity of the applied voltage. A still further feature of this invention is that the developer comprises water as the carrier and hence, the developer is not objectionable in odor, poisonous and does not present a fire hazard.

BRIEF DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, preferred embodiments are disclosed in the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 shows the contact angle of a liquid drop on a liquid-repellent insulating film when the film is uncharged;

FIG. 2 shows the same insulating film as shown in FIG. 1, except that the film is charged;

FIG. 3 shows a cross-sectional view of a photosensitive plate according to this invention;

FIG. 4 shows a perspective view of the photosensitive plate shown in FIG. 3;

FIGS. 5 to 8 show apparatus for producing latent images in various embodiments of this invention;

FIGS. 9 and 10 show illustrative embodiments of the electrostatic printing apparatus according to this invention; and

FIGS. 11A and 11B show the illustrative embodiment of a developer supply unit to be incorporated into the apparatus of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THIS INVENTION Referring to FIG. 1, when a liquid drop is placed on an uncharged surface of a liquid-repellent insulating film 1, the contact angle is more than and the liquid drop does not wet the film surface. In contrast, as shown in FIG. 2, if the film is charged (indicated by a broken line), the contact angle 0 is decreased to a value less than 90 and the liquid drop wets the film surface. This phenomenon depends on the liquid-repellent property of the film surface, the kind of liquid and the applied voltage. For instance, when a water drop is placed on a 3-fluoroethylene chloride resin film, the contact angle is 108 before it is charged and decreases to 56 to wet the film surface when it is charged by 500V.

In FIGS. 3 and 4, a conductive substrate 3 has a large number of fine pores 5 uniformly distributed over the surface. A part 5 of the substrate where no pores exist is coated by a liquid-repellent photoconductive layer 4. Thus, the photosensitive plate includes the substrate 3 and the photoconductive layer 4. The size of the fine pores 5 is determined by the resolution required in the 'printed matter. For example, the pore size may be 10 to 1., preferably 30 to 50;! The space between pores is determined by the kinds of paper and ink used and is selected to permit the developer in one pore to spread and contact the developer in an adjacent pore upon transfer and printing; the space is preferably 10 to 100g.

The thickness of the liquid-repellent photoconductive layer 4 is selected to be in the range of 3 to 400;.t, preferably 3 to 100g. If the thickness is less than 3g, contamination may be induced by non-uniformity of the pores and roughness of the paper. If the thickness is more than 400 the effect of the latent charge upon the developer is reduced and development is not sufficiently carried out. If the size of pores is less than 10p, they are often plugged up by impurities contained in the developer, and if the size is over 400a, a uniform image is not obtained. If the space between pores is less than 10p. or more than 10011., the accuracy of image is not good.

Such finely porous substrate can be easily made by conventional methods of making a porous metal filter. A metal plate such as copper, having a 5 to lOOu thickness, may be photoeteched so that pores are formed over the entire surface of the metal plate. Alternatively, a mesh can be used as a substrate of the photosensitive plate.

A coating containing a mixture of photoconductive particles and a resin solution is applied to the porous substrate 3 by an electrostatic painting method (the substrate 3 having been used as an electrode) to a predetermined thickness so that a photoconductive layer 4 is formed on the surface of the substrate 3. Alternatively, a solution of the particles charged in a polarity opposite to that of the substrate are electrodeposited onto the substrate by spray coating. If an inorganic photosemiconductor such as amorphous selenium is used as photosensitive material, the layer can be easily formed by vacuum deposition under suitable voltages.

In order to obtain the liquid-repellent photoconductive layer, liquid-repellent resins, such as polyethylene, polystyrene, alkyd resin, silicone varnish or 3- fluoroethylene chloride resin are used as a binder for the photoconductive material. Next, the photoconductive material is mixed with the binder (see Example 1, for a binder-type photoconductive layer). Alternatively, a film of the above mentioned liquid-repellent resins may be formed on the photoconductive layer (see Example 2); this layer may be formed by vacuum deposition on the inorganic semiconductor. Thus, a liquid-repellent photoconductive photosensitive plate having fine pores over the surface is obtained. Other known photoconductive layers, if they are porous and liquid-repellent, may be used in this invention.

FIGS. 5 and 6 show a unit for development used in this invention. In FIG. 5, a conductive substrate 10 has fine pores 4 distributed uniformly over the entire surface of the substrate 10. A liquid-repellent photoconductive layer 12 coats the surface except for the exposed pores 14. A photoconductive photosensitive plate 20 comprises the substrate 10 and the layer 12. An electrostatic image of charges indicated by the numeral 15 is formed on the surface of the plate by a conventional method, and an aqueous liquid developer 13 is supplied to the back side of the plate 20. The contact angle of the liquid developer being less than 90 with respect to the substrate 10 and more than 90 with respect to the photoconductive layer 12, the developer wets and enters into the pores 4 until it reaches the interface between the substrate 10 and the layer 12. An electrode 17 which provides a contact surface to a paper to be printed, is arranged to oppose the plate 20 as shown. A DC voltage is applied between the substrate l0 and the electrode 17 by a potential source 18, so as that the polarity of the substrate 10 is the same as that of the charge of the latent image 15 and the polarity of the opposing electrode 17 is opposite. An electric field is formed between the plate 20 and the electrode 17', the resulting field is much stronger through the portion of the plate 20 where the latent image is present than in the part where the image does not exist. Accordingly, the liquid developer does not exude through the pores to the surface of those portions of the plate 20 where no latent image exists due to repulsing influence of the liquid-repellent layer. Where the image exists, however, electrostatic polarization or induction is caused under the influence of the latent image charge and the applied voltage, so that the contact angle is decreased and the liquid developer wets the internal surfaces of the pores in the layer. As a result, the liquid penetrates through the pores of the layer to the surface of the plate 20. Thus, the exuded developer may be contacted, absorbed and transferred to a print paper 16 so that a positive image can be obtained in correspondence with the image of electrostatic charges.

Next, if the electrostatic voltage is applied so as that the polarity of the electrode 17 is the same as that of the charge of the latent image 15 and the polarity of the substrate 10 of the plate 20 is opposite, the electric field between the plate 20 and electrode 17 is decreased where the latent image exists and increased where the latent image does not exist.

If the applied voltage is properly adjusted, the field where the latent image exists, assumes a minimum value so that electrostatic polarization or induction of the liquid developer in the pores cannot occur and the field does not drive the liquid developer to the electrode 17. In contrast, where no image exists, the liquid is electrostatically polarized or induced in the pores due to the electric field, and the contact angle is decreased so that the liquid developer is attracted to the electrode 17. Thus, in a similar manner as discussed above, an inverse image of the electrostatic charge image is transferred and printed onto the paper 16. The value of the electrostatic voltage for developing the electrostatic charge latent image according to this invention depends on the developing speed and on the kinds of the electrostatic latent image, the charge, the liquid-repellent layer and the developer. Experiments indicate that a voltage of O to 2000 V (preferably 0 to 1500 V) is required when the electrostatic latent image is a positive one. If the voltage exceeds 2000 V, the image becomes blurred due to creeping discharge. When the latent image is a negative one, the voltage should be in the order of 20 to 2000 V, preferably 30 to 1500 V.

FIGS. 7 and 8 show a unit for developing a latent image according to this invention. If a large amount of material remains on the photoconductive layer of the photosensitive plate, the influence of the exposure remains for a long time after exposure (i.e., preexposure fatigue). Under such conditions, electrostatic printing can be carried out due to the conductivity resulting from irradiation of light without electrostatic charge. In FIG. 7, the liquid developer is supplied from the back side of the photosensitive plate 20, whose photoconductive layer 12 is formed on the surface of a finely porous conductive substrate 10 and contains trapping material, such as a low grade polymer including carboxylic acid or diphenyl picryl hydrazyl, and has a property of pre-exposure fatigue. Next, an electrostatic voltage is applied between the conductive substrate of the photosensitive plate 20, and the electrode 17 which opposes the plate and provides a contact surface to apply a voltage from source 18 to the paper to be printed. The field between the plate 20 and the opposing electrode is much more intensive where the plate has been irradiated than where the plate 17 has not been radiated, becuse the capacitance and conductivity of irradiated portions are increased thereby. Accordingly, the liquid developer does not exude through the pores to the surface of the plate due to inhibiting influence of the non-irradiated portion of the liquid-repellent layer. Where the layer has been irradiated, the developer is electrostatically polarized or induced under the intensive field to be attracted to the opposing electrode, and exuded to the surface of the plate 20 because the contact angle of the developer with the pores surface is decreased. Thus, the exuded developer may be contacted, absorbed and transferred to the a printing member such as paper 16 so that a reverse image can be obtained.

If the photoconductive layer has little or no preexposure fatigue effect, development can be carried out at the same time as the irradiation of the light image. In FIG. 8, the liquid developer is supplied to the back side of the photosensitive plate 20 composed of a finely porous conductive substrate 10 and a liquidrepellent photoconductive layer 12 formed on the substrate. A transparent paper or absorbent member to be printed is placed on a transparent opposing electrode 17, which is disposed near and opposed to the photosensitive plate and has a transparent conductive layer 21 such as NESA layer (tin dioxide transparent conductive film). The light image is irrediated onto the back side of the plate 20 through the transparent plate 12, and simultenously an electrostatic voltage is applied between the conductive substrate 10 of the photosensitive plate 20 and the transparent opposing electrode 17. A reverse image is obtained on the printing member paper by the same process as shown in FIG. 7. The voltage for development should be in the range of 30 to 2000 V, preferably 30 to 1500 V. If it is less than 30V, the intensity of the field is too weak to obtain uniform development, and if the voltage exceeds 2000 V, the image obtained becomes blurred.

Because of the principle of this invention mentioned above, it is not always necessary for the developer of this invention to have a high electric resistance and a low dielectric constant.

Developers used in this invention are liquid and include coloring agents, contact angle adjusting agents, and viscosity adjusting agents. The liquid used in the developer of this invention has a contact angle not less than 90 with respect to uncharged surface of the photoconductive, photosensitive plate and less than 90 on the electrostatic latent image of the plate to thereby wet the surface. If the liquid-repellent material is made of polyethylene, polystyrene, 4-fluoroethylene, 3- fluoroethylene chloride, silicone varnish or akyd resin; water glycerol or ethylene glycol may be used as the developer solvent.

The coloring agent may be added to a solution, suspension or mixture of these aforementioned components. When water is used, water-soluble dyes such as malachite green, methyl violet, victoria blue and Persian orange are used. If a small amount of ethyl alcohol is contained as a contact angle adjusting agent, alcohol soluble dyes such as pigment green and carmine F8 are used.

A finely divided organic pigment such as carbon black and phthalocyanine may be dispersed into liquid by a suitable dispersing agent and is used as suspended coloring agent.

Contact angle adjusting agents are used for obtaining optimum contact angle in relation with the liquidrepellent property of the photoconductive photosensitive plate and the desired printing speed. Suitable contact agents are prepared by mixing two liquids having different surface tensions or utilizing a small amount of surface activator.

Viscosity adjusting agents are used for adjusting the fluidity of ink in relation with the printing speed. Liquid-soluble resins, for example, polyvinyl alcohol, dextrin, gelatin or methylol melamine, are used when the liquid is water. Viscosity adjusting agents may also serve to fix the coloring agent to the paper when the developer has dried.

FIG. 9 shows an emobidment of this invention wherein a cylindrical photoconductive photosensitive plate is used. A cylindrical plate is composed of a v conductive substrate 31 having fine pores over the entire surface and a liquid-repellent photoconductive layer 32 arranged on the substrate 32. After a latent image is formed on the surface of the plate 30 by an electrostatic latent image forming unit 41 the plate 30 is rotated in the direction of the arrow A as shown by a driving unit (not shown), and a developer 33 is applied onto its back side from a developer supply unit 42 which is disposed within a supply of the developer 33 and contact the inside surface of the plate as shown in FIG. 9. The developer can be discharged in numerous ways, for example, in a manner shown in FIGS. 11A and 11B. That is, the developer flows down to the inner surface of the plate by means of the axis of the cylindrical plate. The developer may be applied before or at the same time as the development and transfer.

The cylindrical plate 30 supplied with the developer is further rotated to an absorbent conductive roll 37, where the plate 30 comes into contact with a paper which is supplied by the roll 37. An electrostatic voltage is applied between the plate 30 and the roll 37 by a source 38, and the liquid developer supplied to the back side of the plate is exuded to the surface of the plate in the form of a positive or negative image of an original picture. The developer exuded in the form of the image is at once transferred to a paper to be printed. The printed paper is deposited to a receiver 44.

After printing, the processed part of the plate is erased by a latent image erasing unit 35 and cleaned by a cleaning unit 36. Again a latent image is formed by the latent image forming unit 41 to be continuously printed.

FIG. 10 shows the other embodiment of this invention wherein a photoconductive photosensitive plate in the form of a flexible, endless belt 30a is used. Similar elements are identified by corresponding numbers in FIGS. 9 and 10.

EXAMPLE 1 A photosensitive liquid was prepared of the following components:

Zinc oxide 100g Bromophenol blue (l% solution) l.5cc Fluorescein (1% solution) l.5cc Rose bengal (1% solution) l.5cc Styrene-butadiene copolymer 30g Toluene 60cc Brass particles (grain size 40y.) were press-sintered to form a 5 mm thick finely porous substrate. The surface of the substrate was polished to serve as an electrode. A photosensitive liquid is sprayed onto the polished surface by a nozzle. A 1 KV voltage is applied between the nozzle and the substrate. The photosensitive liquid is sprayed from the nozzle in the form of charged particles with a polarity opposite to that of the substrate. Thus, the liquid is electrodeposited to 30p. thickness onto the plate, and after drying, silicone varnish was electrodeposited thereon to an average thickness in the order of in the same manner as the photosensitive liquid.

The resultant photoconductive photosensitive plate was given a negative electrostatic charge latent image by conventional means, such as 9 KV corona discharging unit.

A liquid developer composed of the following components was supplied to the back side of the plate:

Methylene blue 6g Polyvinyl alcohol (8% solution) 50cc Glycerol Sec Water 50cc The plate was carried to oppose a paper placed on an opposing electrode; then, a 300V electrostatic voltage was applied between the conductive substrate of the photosensitive plate and the opposing electrode, the former being negative and the latter positive. A distinct blue positive image was printed on the paper corresponding with the original.

EXAMPLE 2 The process was performed in the same manner as in Example 1, except that the plate was placed at a positive voltage, the opposing electrode being negative, and the voltage therebetween being 450V. A distinct negative image was obtained.

EXAMPLE 3 A 100p. thick, brass plate was photoetched to produce fine pores having a diameter in the order of 40p. and a density of 225 pores per mm? The photosensitive liquid of Example 1 was sprayed and electrodeposited at lKV onto this conductive plate to provide a photosensitive layer with a thickness of 35 1. after drying.

Dilute silicone varnish (1% solution) was coated on the dried layer by air blown from the back side. A negative electrostatic latent image was formed on the surface of this photosensitive plate in correspondence with the original by a conventional method; then the plate was moved to oppose a paper placed on the opposing electrode.

Next, a liquid developer composed of the following components was supplied to the back side of the photosensitive plate:

Carbon black 7g -Continued Victoria blue 0. 15g Gelatin 2g Glycerol 15g Water cc A 280V electrostatic voltage was applied between the plate and the opposing electrode, the former being negative and the latter positive. A distinct blue-black positive image was obtained in correspondence with the original. When a 530V electrostatic voltage was applied in reverse polarity, the negative image was obtained.

EXAMPLE 4 Charged, liquid particles of a photosensitive liquid composed of the following components were electrodeposited to the surface of a stainless steel mesh (250 mesh):

Zinc oxide 100g Bromphenol blue (1% solution) 200 Rose bengal 1% solution) 2cc Diphenyl picryl hydrazyl 0.4g Styrene-butadiene copolymer 40g Toluene 60cc Victoria blue 3g Persian orange 5 g Dextrin 8g Glycerol 8g Water lOOcc A 480V electrostatic voltage was applied between the plate and the opposing electrode, and a distinct negative image was obtained.

EXAMPLE 5 A photosensitive plate was prepared by forming the liquid-repellent photoconductive layer of Example 1 on the mesh of Example 4. The developer of Example 3 was supplied to the back side of the plate, and the plate was then disposed adjacent to a transparent film placed on a conductive NESA film formed on a transparent glass plate. A light image was irradiated from the back side of the glass plate, as shown in FIG. 8, and at the same time a 500V electrostatic voltage was applied between the photosensitive plate and the conductive layer of the glass plate. A blue-black negative image was obtained in correspondence with the original.

EXAMPLE 6 A liquid developer was prepared of the following components:

Zinc oxide 50g Silicone varnish (resin 50g Rose bengal (2% methanol solution) cc Thinner lSOcc A 100p. thick copper plate was photo-etched to provide fine pores having a diameter in the order of 40p. and a density of 140 pores per mm*. The prepared photosensitive liquid developer was electrodeposited on the surface of this plate by a spary nozzle disposed at lKV. The thickness of the developer was 40p. after drying. Development and transfer was carried out at 600V, the photosensitive plate being positive and the opposing electrode negative. A distinct negative image was obtained in correspondence with the original.

Numerous modifications and adaptations of the system of the invention will be apparent to those skilled in the art and thus it is intended by the dependent claims to cover all such modifications and adaptations as fall within the true spirit and scope of the invention.

What is claimed is:

l. A method for electrostatic developing which comprises the steps of:

forming a latent electrostatic image on a composite transfer member comprising an electrically conductive substrate having a surface coated with a thin photoconductive layer, said transfer member having uniformly distributed fine pores disposed therethrough, and said photoconductive layer being repellent to aqueous liquids;

applying to said composite transfer member opposite said photoconductive layer a developer liquid comprising toner in an aqueous carrier to provide developer liquid in the pores of said substrate adjacent said photoconductive layer, said aqueous developer liquid establishing a contact angle with said photoconductive layer in said pores of greater than advancing an absorbent printing member in contact with the photoconductive member bearing the latent electrostatic image;

applying a DC. voltage between the electrically conductive substrate of the composite transfer member and electrode means adjacent the printing member on opposite side from said transfer member to decrease the contact angle of said aqueous liquid developer in said pores to less than 90;

flowing aqueous liquid developer through said pores onto said printing member in selected areas corresponding to the latent electrostatic image; and

separating said printing member from said transfer member.

2. The method of claim 1, wherein the photoconductive layer consists essentially of an inorganic photosemiconductor and a water-repellent organic resin.

3. The method of claim 1, wherein said transfer member comprises a cylindrical member comprising said substrate and said photoconductive layer.

4. The method of claim 1, wherein said transfer member comprises a continuous, flexible belt comprising said substrate and said photoconductive layer.

5. The method of claim 1, wherein said photoconductive layer comprises a liquid-repellent resin binder and a photoconductive material.

6. The method of claim 1, wherein said photoconductive layer comprises a first layer having a liquid repellent property and a second layer having a photoconductive property.

7. The method of claim 1, wherein said photoconductive layer has a thickness in the range of about Sp. to 400;.

8. The method of claim 7, wherein said pores have a diameter in the range of about 10p. to p.

9. The method of claim 1, wherein said pores are uniformly spaced from each other by a distance in the range of about 10p. to 100p" 10. The method of claim 1, wherein the voltage applied to the substrate is of the same polarity as that of the electrostatic charges of the latent image.

11. The method of claim 1, wherein the voltage applied to the substrate is of an opposite polarity to that of the electrostatic charges of the latent image.

Patent Noa 13 884, 684

EQHN

Dated May 20, 1974 Inventor(s) GENJI OHNO AN D ElICHl INOUE It is certified that error appears in the above-identified patent:

Q and that said. Letters Patent are hereby corrected as shown below:

Column 5, line 10, change "becuse" to because Column 5, line 21, delete "a"n 6 Column 5, line 36, change "irradiated to irradiated Column 5, line 38, change "simulteneously to simultaneously Column 5, line 62, change "akyd" to alkyd Column 5, line 67, change "Water-soluble" to -hydrophilic --Q Column 6, line 23, change emoloidnnent to embodiment "0 Column 6, line 43, change "a" to an absorbent Column 9, line 10, change "spary" to spray Q X mic thaa sixteenth a 0? September 1975 [SEAL] 5 Arresz:

RUTH (I. MASON C. MARSHALL DANN Azresring Officer Commissioner oj'Paienrs and Trademarkx

Claims (11)

1. A METHOD FOR ELECTROSTATIC DEVELOPING WHICH COMPRISES THE STEPS OF: FORMING A LATENT ELECTROSTATIC IMAGE ON A COMPOSITE TRANSFER MEMBER COMPRISING AN ELECTRICALLY CONDUCTIVE SUBSTRATE HAVING A SURFACE COATED WITH A THIN PHOTOCONDUCTIVE LAYER, SAID TRANSFER MEMBER HAVING UNIFORMLY DISTRIBUTED FINE PORES DISPOSED THERETHROUGH, AND SAID PHOTOCONDUCTIVE LAYER BEING REPELLENT TO AQUEOUS LIQUID, APPLYING TO SAID COMPOSITE TRANSFER MEMBER OPPOSITE SAID PROTOCONDUCTIVE LAYER A DEVELOPER LIQUID COMPRISING TONER IN AN AQUEOUS CARRIER TO PROVIDE DEVELOPER LIQUID IN THE PORES OF SAID SUBSTRATE ADJACENT SAID PHOTOCONDUCTIVE LAYER, SAID AQUEOUS DEVELOPER LIQUID ESTABLISHING A CONTACT ANGLE WITH SAID PHOTOCONDUCTIVE LAYER IN SAID PORES OF GREATER THAN 90*, ADVANCING AN ABSORBENT PRINTING MEMBER IN CONTACT WITH THE PHOTOCONDUCTIVE MEMBER BEARING THE LATENT ELECTROSTATIC IMAGE, APPLING A D.C. VOLTAGE BETWEEN THE ELECTRICALLY CONDUCTIVE SUBSTRATE OF THE COMPOSITE TRANSFER MEMBER AND ELECTRODE MEANS ADJACENT THE PRINTING MEMBER ON OPPOSITE SIDE FROM SAID TRANSFER MEMBER TO DECREASE THE CONTACT ANGLE OF SAID AQUEOUS LIQUID DEVELOPER IN SAID PORES TO LESS THAN 90*, FLOWING AQUEOUS LIQUID DEVELOPER THROUGH SAID PORES ONTO SAID PRINTING MEMBER IN SELECTED AREAS CORRESPONDING TO THE LATENT ELECTROSTATIC IMAGE, AND SEPARATING SAID PRINTING MEMBER FROM SAID TRANSFER MEMBER

2. The method of claim 1, wherein the photoconductive layer consists essentially of an inorganic photosemiconductor and a water-repellent organic resin.

3. The method of claim 1, wherein said transfer member comprises a cylindrical member comprising said substrate and said photoconductive layer.

4. The method of claim 1, wherein said transfer member comprises a continuous, flexible belt comprising said substrate and said photoconductive layer.

5. The method of claim 1, wherein said photoconductive layer comprises a liquid-repellent resin binder and a photoconductive material.

6. The method of claim 1, wherein said photoconductive layer comprises a first layer having a liquid repellent property and a second layer having a photoconductive property.

7. The method of claim 1, wherein said photoconductive layer has a thickness in the range of about 3 Mu to 400 Mu .

8. The method of claim 7, wherein said pores have a diameter in the range of about 10 Mu to 100 Mu .

9. The method of claim 1, wherein said pores are uniformly spaced from each other by a distance in the range of about 10 Mu to 100 Mu .

10. The method of claim 1, wherein the voltage applied to the substrate is of the same polarity as that of the electrostatic charges of the latent image.

11. The method of claim 1, wherein the voltage applied to the substrate is of an opposite polarity to that of the electrostatic charges of the latent image.

Images