JPS602658B2 - Contaminant-free photoconductive insulation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates generally to improved photoconductors of the CdX-n (CdC03) type (where X is sulfur or selenium, 0<nmi4); In photoconductors, photoconductive materials are extremely stable, which makes them particularly useful as electrophotographic plates when embedded in an insulating binder.

[Description of prior art]

Previously, some electrophotographic components had chemical formulas. CdX-n (CdC03) It has been made from the substance represented by .

Here, X is sulfur or selenium, 0<nmi4. Such photoconductive materials and their manufacturing methods are published in 197 P.O.
US Pat. No. 3,494,78y, issued June 29, 1971, and US Pat. No. 3,589,928, issued June 29, 1971. The problem with U.S. Pat. ) is cadmium sulfur and the rest are cadmium oxide and possibly cadmium carbonate. The cadmium sulfide in this case has been found to be primarily alpha or hexagonal in crystal structure with a crystallite size of approximately 400 Angstroms. This material is not suitable as a photoconductive material for use in electrophotography. Said second U.S. Patent No. 3
, 589 928, CdS-n (C
discloses several methods for making dC03).

However, photoconductive layers prepared according to this patent have been found to have unstable electrical properties. It is clear that the new photoconductor produced according to the method of this patent has a relatively high charge retention capacity, but the charge retention capacity deteriorates considerably when it is exposed to the atmosphere for a day or more. It means putting it away. Such deterioration severely limits the utility of such electrophotographic plates. All of the methods disclosed in this patent contain undesirable ionic contaminants in the precipitate that are not volatilized by the subsequent steps. These ionic,
That is, salt-forming contaminants are believed to be responsible for the instability of electrical properties observed when exposed to the surrounding atmosphere for several days. SUMMARY OF THE INVENTION A primary object of the present invention is to provide an improved photoconductive material having the chemical formula C0-n (CdC03).

Here, X is sulfur or selenium or a mixture thereof, and n has a value of 0<nmin4. In one aspect of the invention, the CdX-n (CdC03) photoconductive material excludes all unwanted extraneous ions and the CdX-n (CdC03) photoconductive material
It is manufactured by a method that includes only the desired dopants, such as optionally added dopants for activation of the material.

In another feature of the invention, the photoconductive material is free of contaminants of the group consisting of sodium, chlorine, sulfates, bromine, calcium and nitrates, except for small amounts of e.g. chlorine optionally added as co-activators. .

In still other features of the invention, the light guide material comprises copper chloride;
Silver chloride, sulfated steel, silver sulfate, nitrate steel activated with a dopant selected from the group consisting of silver nitrate, copper ammonia complex, silver ammonia collar, steel carbonate dissolved in ammonia and silver carbonate dissolved in ammonia. Ru.

In still other features of the invention, the photoconductive insulating material is prepared by dispersing pure cadmium carbonate particles in water and reacting sulfide or selenide with the dispersed cadmium carbonate particles to convert a portion of the cadmium carbonate into cadmium sulfide or cadmium carbonate. It is produced by converting cadmium selenide to cadmium selenide, separating the reaction product from water, and volatilizing the reaction product and the remaining water and ionic contaminants, if present. The reaction product is free of ionic contaminants, ie, salts, and contains only the activator dopant, which is not readily volatilized at shrimp temperatures.

In yet another feature of the invention, pure cadmium carbonate particles dispersed in water are reacted with sulfide or selenide by passing hydrogen sulfide or hydrogen selenide or a mixture thereof through the water.

In yet another feature of the invention, the reaction of the sulfide or selenide with the dispersed cadmium carbonate is accelerated by adding ammonia to the water.

Other features and advantages of the invention will become apparent upon reading the following detailed description taken in conjunction with the accompanying drawings.

[Description of preferred embodiments]

Improved stable CdX-n (CdC03) material (X is sulfur or selenium or a mixture thereof, n is 0<nmi4
) is manufactured by a method that excludes all undesired extraneous ions and contains only those desired, such as optionally added dopants to activate the Cucumber material.

Improved photoconductive materials are manufactured according to one or more of the following methods. Example 1 Cadmium carbonate of reagent purity as starting material (this can be used, for example, in Morristown, New Jersey, USA).
stown), Allied Chemical Substances
Allied Chemical
al. Specialty ChemicalsDMsi
on) is used.

The following mixture is placed in a ceramic grinding collar with a volume of 1.13 liters.

CdC03, reagent purity 120 min 5/9
Aqueous solution containing CuCl2.20/desc.
9AgC of 96 shouts 5.

The aqueous solution containing 318 9NH3 / 96' deionized water and 480' was mixed by a ball mill for approximately 18 hours, then transferred to a 1 liter beaker prepared with a magnetic stirrer; placed on the vessel.

At this point 60 minutes of 30% NH3 solution is added. Hydrogen sulfide is then pumped into the stirred suspension through a molten glass bubbler at a rate of above 47±5 per minute for 3.5 hours.

During this step, some of the cadmium carbonate is converted to cadmium sulfide, but no absorption of foreign ions takes place. At the end of its conversion, the suspension is manufactured by, for example, International Equipment Co., USA (InterMti
oMIEquipmentCo. ), and the resulting cake (solids) is washed with deionized water in the centrifuge for approximately 18 minutes.

The centrifuge is rotated until most of the deionized water is removed from the cake. The cake is then dried in an oven, ground into pieces and sifted through a filter used in the kitchen. The resulting powder is heated to 200°C with nitrogen flow.
Shrimp is grilled in an oven for 24 to 4 hours. CdS-
The molar ratio of CdC03 is approximately 1:1. A photoconductive layer using the material thus produced is produced as follows. The next mixture is placed in a ceramic grinding collar with a volume of 0.24 liters. CdS-CdC0
3 14 taacryloid AT
150 (50%) 20 Yen (thermosetting acrylic resin) SC-100 18 Yen (
(High-boiling aromatic hydrocarbon solvent) These mixtures are approximately 1
Axial time milled and then wire wound Aya (MayerR
od) is used to coat the conductive layer (aluminum, aluminized polyester, or tin oxide coated glass).

The material applied to the conductive layer is then dried at 70° C. and 1 hour at 150 qC to create a durable photoconductor. The thickness of the coating thus dried is typically 25 mm, but may range from 15 to 65 mm. The weight ratio of binder solvent to pigment can typically vary from 0.8:1 to 2:1 depending on the properties required for a given application. A 4-length ratio gives high photoconductive speed, while a large ratio provides a smooth and long layer.

Example 2 This is the same as Example 1 except that the silver-containing dopant solution is omitted.

Example 34 This is the same as Example 1 and Example 2 except that the amount of dopant solution is less as follows.

CdC03, reagent purity 120 min 5/9
Aqueous solution containing CuC12/pan20/'
24 [deionized water]
280 Secretion Example 5 - Instead of using CdC03 of 8 reagent purity, start the reaction using a solution of cadmium nitrate or cadmium acetate and then obtain CdC03 by dilution using (N ratio) 2C03. I can do it.

The salts absorbed in such precipitates are ammonium nitrate or ammonium acetate, both of which can be volatilized by condensing CdC03 at approximately 200° C. to 250° C. The CdCQ thus purified is then processed as in Examples 1-4. Example 9-16 This is the same as Example 1-8 except that hydrogen selenide is pumped into the suspension of CdC03 instead of 2S and cadmium selenide is produced instead of cadmium sulfide.

Examples 17-32 This is similar to Examples 1-16 except that no NH3 solution is added, which in Examples 1-16 was added only to promote the reaction between sulfide or selenide ions and CdC03. is the same as

Examples 17-32 produce lower photoconductivity but less photocurrent, making photoconductors with these properties valuable for certain applications. Example 33-40 This is Example 1 except that ammonium sulfide or ammonium selenide is added to the suspension instead of 2S.
-8.

Example 41-80 This method uses a group consisting of silver chloride, steel sulfate, silver sulfate, steel nitrate, silver nitrate, copper ammonia body, silver ammonia body, and copper carbonate dissolved in ammonia, instead of CuC12 and AgC03. Same as Example 1-40 except that selected activators are added.

Testing of the photoconductor is accomplished by corona precharging and then measuring the surface potential drop during light irradiation (1 footcandle, 3 seconds).

Referring to FIG. 1, curve A illustrates the performance of an improved photoconductive layer prepared according to Example 1 above. This performance is reproducible every day and remains unchanged even after several months of storage. Curve B-1 in FIG.
9 represents an undoped photoconductor manufactured according to the example of Ball No. 9 928. It can be seen from this curve that the photoconductor based on the above-mentioned US patent is much slower than the improved material according to the invention of FIG. Curve B-2 represents the initial performance of a material made according to the example of U.S. Pat. No. 3,589,928, except that the dopants were added in the amounts described in Example 1 herein. It is something. This curve B-2 is as fast as the improved material of curve A. However, when left for 6 days, the performance deteriorated from curve B-2 to curve B-3. Moreover, the charge retention ability has decreased to approximately 60% of its initial value. Performance can be restored by reheating the material for 30 to 60 minutes at 150 pm, but then the charge retention capacity is again reduced to an unacceptable value. Examples 3-4 where a small amount of dopant was used
The material has a somewhat slower speed than curve A in FIG. 1, but its performance is still constant over time.

The photoconductive material of the invention prepared according to Example 1-80 is:
A cadmium carbonate component having a crystallite size in the range of 300 to 400 angstroms, and a C-like component having a crystallite size of 50 angstroms or less and having a predominantly cubic or even 8-crystal structure. have.

The material is free of ionic contaminants except dopants.
To explain in more detail, sodium, chloride, sulfate,
Free of undesirable contaminants: topotassium bromide and nitrates. Here, "not included" means that the weight ratio is 0.
The content should be 5% or less, and more preferably 0.1% or less. If pure starting material is used, the amount of any contaminants becomes insignificant. These and other ionic contaminants absorb water from the air, causing photoconductor performance to deteriorate over time. In other words, it is thought that speed and charging capacity are adversely affected. All sodium and potassium salts and N ratios S04, NH4CI are particularly undesirable. When CdC03 is used as the starting material, ionic contaminants such as sodium, chloride, sulfate, bromide, potassium and nitrate are present at a weight ratio of 0.1
% or less, preferably 0.05% or less.

The method described in the example of converting and centrifuging the photoconductive material is such that the activator (chlorinated steel or silver chloride) is removed to avoid further contamination. With respect to the activator, the stoichiometry of chloride should not be greater than the metal element of the activator so that the adverse effects of chloride are minimized. The shrimp step, which is preferably carried out within a temperature range of 150°C to 250qo, is effective in further removing volatile residual ionic impurities, such as ammonium carbonate, which may not be completely removed by cleaning. There is.

However, it has been confirmed that certain sulfates are formed when the competition is carried out in air. A typical amount of sulfate is 1 by weight after 2 hours of teriyakiing at 200 qC in air.
%, 2% after 2 hours of 25000 phosphorus. The presence of sulfates is surprising considering the relatively low temperatures of shrimp roasting. Normally, CdS does not undergo much oxidation by air below 30030. The fine crystallite CdS within the photoconductor of the present invention may be responsible for the surprisingly slow oxidation rate. Photoconductors made from said materials even when fired at 200° C. in air are disclosed in U.S. Pat. No. 3,58
Although it showed much better long-term stability than that made according to the method of No. 9,928, it is still observed that the properties change over time.

By carrying out the molding in an inert atmosphere, sulfate formation can be avoided and a photoconductive powder almost free of ionic contaminants is obtained.

1 when even the slightest change in the properties of the photoconductor is not allowed.
It is preferable to spend time in such a protective atmosphere. By inert atmosphere is meant a gas that neither oxidizes nor reduces the photoconductive powder. Included in this definition are, but are not limited to, nitrogen and all noble gases (ie, elements in group 0 of the periodic table). Referring to FIG. 3, a method of electrophotography using an electrophotographic member utilizing the photoconductive material of the present invention is illustrated. In FIG. 3a, the charge retentive surface of the electrophotographic plate 11 is, for example, -4. The chick is precharged by a corona discharge operating at V to have a surface potential of, for example, -1250V. The plate (photoconductive layer) 11 has a thickness of approximately 25 microns and is either relatively rigid, such as aluminum, aluminum treated polyester or tin oxide coated glass, or very flexible. It is placed on a certain conductive layer 12. As shown in FIG. 3b, the photoconductive layer 11 is then exposed to a photon image produced, for example, by directing light through the transparency 13 toward the photoconductive layer. Meanwhile, the conductive layer 12 behind is grounded.
Exposure is also accomplished by optically projecting an opaque original onto the photoconductive layer. Upon exposure, the surface charges on the portions irradiated with light are dissipated, and a charge image corresponding to the portions of the charge-retaining surface of the plate 11 that are not irradiated with light is formed. The charge retentive layer 14 of the recording medium, e.g. a conductive paper coated with a transfer material, is then brought into light contact with the charge image retentive surface of the plate 11, as shown in FIG. 3c. . A transfer potential is applied between the conductive backing 15 of the recording medium and the conductive layer 12 of the plate 11 to transfer the charge image from the plate 11 to the charge retention layer 14 of the recording medium. Next, as shown in FIG. 3d, an electrophotographic toner in which the charge particles are charged with an opposite sign is sprinkled to develop the charge image-bearing surface of the recording medium. The toner may be dry or dispersed in an insulating liquid vehicle. Instead of transferring the charge to dielectric-coated paper as described above, the charge image on the photoconductive layer is developed by methods well known in the art;
It can also be transferred to regular paper. Some of the advantages of the photoconductor disclosed herein are as follows.

It is physically very strong and highly resistant to abrasion or physical handling.

It is aluminized and is flexible enough to be pressed onto a plastic film base used as a copy machine belt. It is resistant to petroleum solvents used as carriers in liquid toners and therefore can be utilized in the transfer of colored images.

It has characteristics that can be used even in Fujion.

It can withstand physical abrasion performed to further remove dirt after transfer of the colored image. Charging can be achieved using either positive or negative corona. Also, although the chemical formula CdX-n(CdC03) (X is sulfur or selenium, n is a value of 0<nmin4) is used in this specification, x may also be a mixture of sulfur and selenium, and this mixture are CdS and CdSe
The separate phase is of course defined in the present invention as containing sulfoselenide.

[Brief explanation of drawings]

Figure 1 depicts the charging and discharging of a material for electrophotography, which is a feature of the present invention, and is a diagram in which the surface potential (volts) is plotted against the time (seconds) after charging. 2
Figures are similar to Figure 1 depicting the charging and discharging curves of three different conventional photoconductive materials; Figure 3 depicts an electrophotographic method using photoconductive materials according to the present invention; This is a schematic process flow diagram. 11... Plate (light guide fog layer), 12... Guide turtle layer, 13... Transparent image, 14... Charge retention layer, 15... Conductive adhesive layer. . FIG.・FIG FIG. 30 FIG. 3b FIG. 3c FIG. Sd

Claims (1)

Claims: 1. A time-stable photoconductive material for multicopy photocopying equipment having improved resolution and substantially reduced hygroscopicity, wherein said photoconductive material has the chemical formula CdX
-n (CdCO_3), is a material that is substantially free of ionic contaminants except for the dopant, which is an activator.
X is sulfur or selenium or a mixture thereof;
n has a value of 0<n≦4, and the CdX particles mainly have crystallites having a diameter of 50 angstroms or less and having a mainly cubic or β crystal structure as a constituent component. 2. A photoconductive material as claimed in claim 1, wherein the ionic contaminants belong to the group consisting of sodium, chlorine, sulfate, bromine, potassium and nitrate. 3. The photoconductive material according to claim 1, wherein the dopant is dissolved in copper chloride, silver chloride, copper sulfate, silver sulfate, copper nitrate, silver nitrate, copper ammonia complex, silver ammonia complex, or ammonia. Materials belonging to the group consisting of copper carbonate dissolved in ammonia and silver carbonate dissolved in ammonia. 4. The photoconductive material according to claim 1, wherein the chemical formula is CdX-n (CdCO_3), and n satisfies 0<n≦4. 5. The photoconductive material according to claim 1, wherein the ionic contaminants, excluding the activator dopant, are 0.02% or less of the weight of the photoconductive material. 6. The photoconductive material according to claim 1, wherein the ionic contaminants, excluding dopants that are activators, are 0.1% or less of the weight of the photoconductive material. 7. A method of making a time-stable photoconductive material for multicopy photocopying equipment with improved resolution and substantially reduced hygroscopicity, comprising: a. dispersing cadmium carbonate particles in water; b reacting sulfide or selenide or a mixture thereof with dispersed cadmium carbonate particles to convert a portion of the cadmium carbonate to cadmium sulfide or cadmium selenide; c
separating the reaction product from the water; d burning the reaction product in an inert atmosphere to volatilize residual water and ionic contaminants; and e removing the dopant as an activator and increasing the firing temperature. a step of keeping salts, which are contaminant ions that are not easily volatilized, from being included in the reaction product;
the photoconductive material is a material represented by the chemical formula CdX-n (CdCO_3) and is substantially free of ionic contaminants except for dopants as activators;
X is sulfur or selenium or a mixture thereof;
n has a value of 0<n≦4, and the CdX particles mainly have crystallites having a diameter of 50 angstroms or less and having a mainly cubic or β crystal structure as a constituent component. 8. The method described in claim 7,
A method in which the ionic contaminants free of reaction products belong to the group consisting of sodium, chlorine, sulfate, bromine, potassium and nitrate. 9. The method described in claim 7, wherein the reaction product is dissolved in copper chloride, silver chloride, copper sulfate, silver sulfate, copper nitrate, silver nitrate, copper ammonia complex, silver ammonia complex, or ammonia. activating with a dopant which is an activator selected from the group consisting of silver carbonate dissolved in ammonia and copper carbonate dissolved in ammonia. 10 The method according to claim 7, wherein the cadmium carbonate particles dispersed in water have a diameter of 3.
A method comprising as a constituent cadmium carbonate crystallites within the range of 00 to 400 angstroms. 11. The method of claim 7, wherein the ionic contaminants, excluding the activator dopant, are 0.02% or less of the weight of the photoconductive material. 12. The method of claim 7, wherein the ionic contaminants, excluding activator dopants, are less than 0.1% of the weight of the photoconductive material. 13. The method according to claim 7, wherein the step of reacting sulfide or selenide with dispersed cadmium carbonate comprises adding hydrogen sulfide or hydrogen selenide or a mixture thereof to the water. A method that includes a feeding step. 14. The method according to claim 7, comprising the step of adding ammonia to the water to promote the reaction of cadmium carbonate with sulfide or selenide. 15. The method of claim 7, wherein the step of reacting sulfide or selenide with dispersed cadmium carbonate comprises adding ammonium sulfide or ammonium selenide or a mixture thereof to the water. A method including the step of adding. 16. The method according to claim 7, wherein the baking temperature is within the range of 150°C to 250°C. 17. The method of claim 7, comprising: embedding the resulting photoconductive material in an electrically insulating binder to form a photoconductive electrophotographic member. 18. A method as claimed in claim 7, including the step of embedding the resulting photoconductive material in an insulating binder on a conductive substrate to form a photoconductive electrophotographic member. the method of. 19. A photoconductive insulating material comprising an electrically insulating binder and fine particles of a photoconductive material dispersed within the binder, the photoconductive material having improved resolution;
A time-stable material for multicopy photocopying equipment with substantially reduced hygroscopicity and having the chemical formula CdX-n (Cd
CO_3) is a material substantially free of ionic contaminants except for the activator dopant, where X is sulfur or selenium or a mixture thereof, and n is 0.
A photoconductive insulating material having a value of <n≦4, wherein the CdX particles mainly have crystallites having a diameter of 50 angstroms or less and having a mainly cubic or β-crystalline structure as a constituent component. 20. The photoconductive insulator according to claim 19, wherein the ionic contaminant is sodium, chlorine,
Photoconductive insulating materials belonging to the group consisting of sulfates, bromine, potassium and nitrates. 21. The photoconductive insulator according to claim 19, wherein the dopant is copper chloride, silver chloride, copper sulfate, silver sulfate, copper nitrate, silver nitrate, copper ammonia complex, silver ammonia complex, or ammonia. A photoconductive insulating material belonging to the group consisting of dissolved copper carbonate and silver carbonate dissolved in ammonia. 22. The photoconductive insulator according to claim 19, wherein the chemical formula is CdS-n (CdCO_3
), and 0<n≦4. 23. The photoconductive insulator according to claim 19, wherein the ionic contaminants excluding dopants that are activators are 0.02% or less of the weight of the photoconductive insulating material excluding the binder. However, photoconductive insulating material. 24. The photoconductive insulating material according to claim 19, wherein the ionic contaminants excluding the activator dopant are 0.1% or less of the weight of the photoconductive insulating material excluding the binder. However, photoconductive insulating material. 25. A photoconductive insulating material according to claim 19, wherein the photoconductive insulating material is formed by embedding the photoconductive material in an insulating binder on a conductive substrate.