CS204964B2 - Method of electrostatic picturing - Google Patents

Abstract

1281235 Transferring electrostatic latent images RANK XEROX Ltd 24 July 1969 [26 July 1968] 37323/69 Heading G2H An imaging process for producing multiple copies comprises forming a latent electrostatic image on a photo-conductive plate insulating layer 22 having a light fatigued resistivity in the range from 10<SP>8</SP> to 10<SP>13</SP> ohm-cm, and contacting the image surface with the uniformly charged surface. of an insulating layer 35, increasing the field between surfaces and then separating the surfaces to transfer selectively transfer charges between the surfaces to produce an electrostatic image on the insulating layer conforming to that on the photo-conductive layer 22. A potential is applied to the layer 35 by a corona device 24, Fig. 5 such that air breakdown decends in the air-gap between layers 35 and 22 which modifies the negative charge on the layer 35. Due to persistent conductivity of exposed areas of the layer 22 the negative charges in the exposed areas will be dissipated and the original image on the layer 22 will be recovered. The insulating layer may be, for example, of cellulose acetate, ethyl cellulose, polystyrene, polyethylene, polyvinyl chroride, insulating paper or polytetrafluoroethylene. Examples of photo-conductive materials are lead oxide, zinc oxide, cadmium sulphide, and arsenic selenium alloy. The latent image formed on the layer is developed in known manner e.g. g. in a rocking tray, Fig. 6 (not shown) and then heat fixed. Multiple copies may be formed on separate insulating layers without reimaging the photoconductive layer.

Description

The invention relates to an electrical imaging method in which a first electric charge pattern is formed on the surface of a photoelectrically conductive insulating member, then a uniform electrostatic charge is applied to the surface of the insulating substrate, the polarity of the electrostatic charge being the polarity of the charge pattern. contacting the photoelectric conductive member with the image bearing surface, and the electric field between the two surfaces is then increased.

A method and a corresponding electrophotographic apparatus are already described in which an electrostatic charge is applied to the surface of a photoelectrically conductive insulating layer and this charge is selectively dispersed by exposure to the light and shadow pattern to be recorded. This selective charge dispersion gives an electrostatic-latent image corresponding to the pattern with which the photoelectrically conductive layer is exposed. The electrostatic latent image thus formed usually serves to deposit the electroscopic marking particles by electrostatic attraction, thereby producing a visible image or pattern of the electroscopic substance that corresponds to the latent image. This image can then be fixed directly in place or transferred to the secondary surface.

The above procedure gives excellent copies and is widely used. However, the photoelectrically conductive insulation layer described above is subject to considerable wear as it typically comes into contact with a relatively abrasive dye-carrier composition and must be stripped of the remaining dye particles after each cycle. Thus, the photoelectrically conductive materials suitable for the reusable system have been limited to materials having a hard, tough surface that resists abrasion. Thus, in some cases, it is desirable to perform the deposition or deposition of the electroscopic eyepiece at a location remote from the photosensitive surface, either on the end print bearing member or on another surface, thereby eliminating the deterioration of the photoelectrically conductive surface and simplifying the process by eliminating the need. cleaning the photoelectrically conductive insulator after each cycle.

A method has also been developed whereby an electrostatic latent image formed previously on an insulating surface, for example a photoelectrically conductive insulating surface, can be transferred to a second surface of the insulating surface

204984 by bringing the second surface into contact or in close proximity. and that an intense electric field is formed between the two surfaces. · After separation, it has been established that a transmission has taken place. electrical charges between the two surfaces in the direction determined by the attached field to form a use. This procedure is very successful, ultimately leading to the dispersal of the originally created latent image due to charge transfer, thus limiting the procedure to a single display system.

It is therefore an object of the present invention to provide a new electrostatic imaging system that overcomes the above drawbacks and allows the photoelectrically conductive insulation layer to be reused and multiple copies made. This procedure should be based on the transfer of electric charge and the image development should be performed at a location remote from the photoelectrically conductive insulation layer. Finally, the original electrostatic pattern should be maintained in its original state.

All of these advantages are achieved according to the invention by:. by using a material having a high specific light-fatigue resistance of up to ΙΟ ¹⁷ proιη for the photoelectric conductive element, an increase in the electric field between the two surfaces is performed above the discharge threshold within the air gap between these surfaces, thereby creating a second electrostatic charge pattern the configuration and polarity of which are the same as the first electrostatic charge pattern while maintaining the first charge pattern, and finally the photoelectrically conductive member and the insulating substrate. separated from each other, and, and - the above steps, except for creation. first electrostatic. the patterns repeat at least · twice.

. ·. Image created as follows. Dielectric substrate. is called -. on · . . spot by electroscopic particles,. commonly referred to as &quot; particles &quot; again - either ·. stabilize on this substrate, or. - se ·. The surface is transferred to the secondary surface, such as. · Paper -. copy, and · attach to it. - ·. The original carrier member on which he stayed. . · Retained - 'latent. The image can then be again. used up. - to create. the required number. copies.

According to. In a preferred embodiment of the invention, the specific resistance to the light-fatigue material of the conductive member ranges from 1010 to 1035 µm.

According to a further embodiment of the invention, the electrical increase is increased. field is done - by applying electric. - cartridges · na. - the surface of the insulating substrate - and / or the photoelectrically conductive member.

The invention is. further. shown in the accompanying drawings. .

Giant. 1. shows the formation of a uniform charge on the surface photoelectrically. conductive plates; Fig. 2 shows exposing the charged plates; -'- according to Fig. 1 --světelným · · ^'· pattern in order to create ... · / · pattern of electrostatic charge; Fig. 3 shows a preliminary charging of the transfer sheet according to the invention; FIG. shows a layered formation formed by contacting a pre-charged transfer surface with a support member supporting the original electrostatic. picture; Fig. 5 shows schematically the subsequent formation of an image on the transfer substrate; Fig. 6 shows the development of an electrostatic latent. . image created on the transmit. listě; Fig. 7 shows the fusing of the induced powder image on the surface of the fuse to produce a continuous printing.

On . Figures 1 and 2 show a commonly used technique for generating an electrostatic latent image. on electrophotographic plate. In FIG. 1, an electro-photographic plate 20 is shown which comprises a conductive substrate 21 on the surface of which a photoelectric conductive insulating layer is applied.

22. A uniform electrostatic charge is applied to the surface of the feteelectrically conductive layer 22 by any suitable technique in the dark.

23. The TJ shown, for example, is a charging unit shown as a unit unit 24. The coil unit 24 is connected to a high voltage source 25, which in turn is earthed. After the uniform charge has been applied to the surface of the photoelectrically conductive layer 22, it is. this. charged. layer. 22 selectively exposes an electromagnetic activating radiation source 30 as shown in FIG.

2. The activating radiation source 30 casts a light and shadow pattern corresponding to the recorded optical image 31 onto the surface of the photoelectrically conductive plate 20. with the help of · the system. · Lenses. . 32. · · Pr. exposure. · Electrostatic charge, · applied. on . photoelectrically conductive. layers ..22, disperses · - on areas · affected. The light 22 leaves a charge pattern on the sheets where the light does not strike the layer 22. ···. <. · _{; ;} ·;

. In accordance with the nature of the invention, it requires a new procedure. use of new · photoelectrically conductive - insulating material · with controlled fatigue. Application - for - procedure. according to the invention. is therefore . fetoelectrically · conductive · - material such that it is exposed to light when exposed to light. fatigue by light.

Under fatigue. light means that the exposure to light will expire for a longer period of time. - the period before. Light induced conductivity of exposed. fetoelectrically · conductive surfaces. material disappears, or before it -. conductivity. - these exposed areas. it essentially returns to the original conductivity of the feteelectrically conductive material, i.e. the time period elapses longer than the phetoelectrically. - conductive - material - in ·. basically ·. it will return - to its - the original, specific · resistance - behind · the-darkness. Thus, the conductivity of the photoelectrically conductive material in the areas affected by the activation. radiation lasts for longer periods of time, so charge-of-image corresponding to. light pattern - persists for some time.

This persistent conductivity of the photo-electrically conductive material is used in a manner that gives a unique procedure for electrostatic imaging. Any suitable photoelectrically conductive insulating material which may be used may be used. meets the requirements of the invention. Typical photoelectrically conductive insulation. materials - include whole. a number of inorganic photoelectrically conductive -pigments, such as lead oxide, zinc oxide, cadmium sulfide, cadmium sulfoselenide, dispersed in binders, halogen-containing piglet, - alloy preparation. ..arsenu - and,. selenium, and s-cast iron preparations. - organic photoelectrically conductive pigments, such as polyvinylcarbazole with an admixture of trmitrofluorenone, phthalocyanine and its polymorphs. Desirably, in the light-free state, the specific resistance of the photovoltaic cell concerned is present. . of a conductive material in the dark greater than about 10 ¹⁷ µm, and that the - specific resistance - in the light-tired state is about 10-101 µm, for optimum results.

Any suitable substrate 21 for the photoelectrically conductive layer 22 may be used for the purposes of the invention. The substrate material 21 will preferably have less electrical resistance than the photoelectrically conductive layer 22, so that it will act as a ground when electrostatically the charged layer 22 is exposed to light. Such - typical - materials include - aluminum, - brass, conductive glass _; copper, zinc, paper and - any suitable - - plastic - - substrate or p. - with - - conductive properties. As a photoelectrically conductive substrate 21, other non-conductive materials may also be used, for example. - thermoplastic - resins. However, when used, it is necessary to charge both sides of the photoconductive plate.

Giant. 3 shows the pre-charge of the transfer sheet 35. The transfer sheet 35 is supported on a grounded metal plate 36 and a high-voltage ion source 37 is fed over the sheet, fed by an energy source 38, and to deposit a uniform charge on the surface of the transfer sheet 35. The charging unit 37 is similar. corotron - unit 24 -. as used in Figure 1. the photoelectric conductive layer 22 in FIG. 1 and the transfer sheet 35 in FIG. 3 are the same. For example, if the electrostatic latent image has a positive electrical polarity, then the surface of the transfer sheet 35 will be charged to a DC positive electrostatic charge.

Any transferable or insulating material may be used as the transfer sheet 35 of the present invention. Typical materials include cellulose acetate, ethylcellulose. lose, polystyrene, polyethylene, polyvinyl chloride, insulating paper, polytetrafluoroethylene, polyvinyl fluoride, polymethane, polycarbonate and other similar insulating materials. Although not the best results, they provide non-moisture sensitive plastic coatings, it has also been found that coatings - sensitive - in moisture can also be used. such as - is - gelatin and - casein.

As shown in FIG. 4, a uniformly pre-charged sheet 35 is brought into actual contact with the photo-electrically. a conductive, image-bearing layer 22 by its conductive grounded substrate 36. Dielectric. transfer sheet 35. it is positioned in contact with the image-bearing surface of the photoelectrically conductive layer 22, from which it is virtually only separated. very small air - gap. While the photoconductive imaging member 20 is in contact with the carrier. 35, the potential is brought. on the back - side of the transmission-. Within the air gap separating the respective surfaces, a puncture occurs in those regions which correspond to those regions of the photoconductive layer 22 which do not carry the image. Electric. - emphasis - air leads -. to reduce the negative charge in the case shown in the drawing, o-br. 5, on the dielectric band or by transmitting the sheet 35 at locations corresponding to the non-image regions of the photoelectrically conductive layer 22; as a result of a positive - air burst charge, which is schernattically represented here by positive charges 43. The respective - negative burst charge - initially settles on the surface - photorltrically conductive layer - 22 as shown and indicated by the rings. 41..

However, due to the persistence of the conductivity of the photoelectrically conductive layer 22 in the exposed areas, the conductivity of the photoelectrically conductive layer 22 is reduced. The negative charge dispersed on it dissipates and the original latent image is recovered. The entire procedure can then be repeated.

An image, which has the same meaning, as the original latent image, will be received on the dirt transfer sheet. Although the invention is interpreted as - air breakthrough and - transmission. The charge in the surface contact may be a charge transfer. caused when the surfaces approach each other,. or - after their separation.

Giant. 6 illustrates a method of inducing -electrostatic. - image. . FIG. wherein the sheet 35 is received in the developing well opening. 44, which is clamped. onto the substrate 36. The well 44 then flips over here a. there, so that the powder builder 4 wraps in cascade over the surface-image as indicated. As the developing mixture moves in cascade over the area of the sheet 35, the powder particle attaches more color to the areas of the latent image and forms a powder image on the sheet.

Giant. 7 shows the final step in printing completion. The transfer sheet 35 carrying the powder image 42 is placed in a furnace 45 heated by the electrical member 46 to a temperature above the melting point of the dye. The powder image melts on the surface of the transfer sheet 35 and the completed steady dome can be removed.

Any suitable developing techniques can be used for the purposes of the invention. Typical developing procedures used in conjunction with electrostatic imaging include magnetic brush developing, cascade developing, sliding developing, touch developing, powder cloud developing and liquid developing. Similarly, any suitable fixation techniques, such as heat melting as shown above, can be used. However, other fixing techniques, such as steam melting and layered fixing, may also be used.

To illustrate the other features of the invention, several examples of embodiments thereof will be given below, but the invention is not limited thereto. Parts and percentages are by weight unless otherwise stated.

Example 1

The electrographic paper is pre-charged with a negative voltage of 7700 volts by a laboratory corotron unit powered by a high-voltage power source. The zinc oxide paper sheet 22 is charged to a voltage of about 1100 volts using a similar corotron unit. A transparent positive control sheet is placed on a charged zinc oxide paper 22 and exposed to a 75 watts bulb. For paper with zinc oxide, an illumination of about 21.52 lx.s is required. The charged surface of the electrographic transfer sheet 35 is contacted with the image surface of the zinc oxide paper 22 so that the dielectric surface is adjacent to the photoelectrically conductive surface 22. The back surface of the transfer sheet 35 is negatively charged to a potential of 5200 volts using a laboratory corotron unit. The electrographically transfer sheet 35 is then detached from the zinc oxide paper 22 and the image formed on the transfer sheet 35 is developed with a magnetic brush developing system as described above. The polarity of the dye used in the developing system is positive. The second sheet of electrographic paper is pre-charged as above and brought into contact with the image photoelectrically conductive layer 22. Then, further operations are performed and a second image is developed. The procedure was repeated four times for

With proving multiple copying capabilities of the entire system.

Example 2

The procedure of Example 1 was repeated except that the electrographic paper was replaced with polyethylene impregnated paper. Similar results were obtained.

Example 3

The procedure of Example 1 was repeated except that the zinc oxide paper was replaced by polyvinylcarbazole, admixed with trinitrofluoronone, placed on an aluminum substrate. Although the same voltages were used as in Example 1, their polarities were reversed. Negative images on various separately used sheets of electrographic paper were obtained using a developing agent with negative dye polarity.

Example 4

The process of Example 3 was repeated except that paper impregnated with polyethylene was used instead of electrographic paper.

Although quite specific conditions and materials are included in the examples, they can be replaced by any of the other materials mentioned above with similar results. In addition to the steps used to carry out the process of the invention, other steps may be employed. For example, the electrostatic display system of the invention can be adapted for use in conjunction with semitone imaging. Additional materials may be added to the developer, photoelectrically conductive material, and transfer sheet to emphasize, support, or otherwise favor the desired properties of the materials. For example, the spectral sensitivity of photoelectrically conductive plates prepared and used in connection with the invention may be adjusted by the addition of photosensitizing dyes. It is within the ability of one of ordinary skill in the art to formulate additional options based on the teachings of the invention.

Claims (3)

SUBJECT An electrostatic imaging method in which a first electric charge pattern is formed on the surface of a photoelectrically conductive insulating member, then applying a uniform electrostatic charge to the surface of the insulating substrate, the polarity of the electrostatic charge. the electrostatic charge is the same as the polarity of the charge pattern, whereupon the uniformly charged surface of the substrate is contacted with the imaging surface of the photoelectrically conductive member and the electric field between the two surfaces is increased, characterized in that specific fatigue resistance up to 1017 Ωιη, the increase in the electric field between the two surfaces is performed above the discharge threshold within the air gap between these surfaces, creating a second electrostatic charge inventive pattern whose configuration and polarity are the same as the first electrostatic charge and the photoelectrically conductive member and the insulating substrate are separated from each other, and the steps are repeated at least twice except for forming the first electrostatic charge pattern. 2. Method according to claim 1, characterized in that the specific resistance of the conductive member material fatigue -in light is from 1O10 to about 10 ¹⁵ nm. 3. Method according to claim 1 or 2, characterized in that the increase in the electric field is carried out by applying an electric charge to the surface of the insulating substrate and / or the photoelectrically conductive element.