DE1241709B - Electrophotographic recording material - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

G03g

German class: 57 e - 1/06

Number: 1 241709

File number: E 21900IX a / 57 e

Filing date: November 2, 1961

Open date: June 1, 1967

The invention relates to an electrophotographic recording material consisting of a layer support and a photoconductive layer having one dispersed in a binder, optionally sensitized zinc oxide.

It is known to add dyes to photoconductive zinc oxide layers in order to make them light a certain Sensitize the spectral range. The sensitivity range is related to the absorption spectrum of the dye used in each case. However, it has been shown that the Dyes can be divided into two classes, namely those that noticeably sensitize and those that which sensitize only weakly or not at all. Dyes that noticeably sensitize are those which have one or more carboxyl, phenolic hydroxyl or aromatic sulfhydryl groups. Only dyes with these groups become quite evident from the surface of the zinc oxide noticeably adsorbed. The limited number of effective sensitizing dyes include Phthalein dyes such as Rose Bengal and Fluorescein, as well as certain substituted ones Cyanine dyes. Even these sensitizing dyes, however, are not affected by zinc oxide fully adsorbed. As each of these sensitizing dyes only has a relatively narrow range of the spectrum, it is necessary to use several sensitizing dyes to obtain the Extend the sensitivity range to the entire visible spectrum. The production of layers, which contain several sensitizing dyes, however, is due to the different solubility properties the sensitizing dyes are not always easy. Also, in general receive strongly colored layers, which are also only relatively insensitive.

There is a need to check the sensitivity of zinc oxide layers in certain spectral ranges to reduce so that these layers z. B. can be handled in safety light. Layers that discharge quickly in the dark and cannot be used for normal use. It has has shown that particularly those layers that have a high concentration discharge rapidly in the dark contain sensitizing dye. As a result, it is not possible to use any of the zinc oxide layers Add quantities of sensitizing dye.

The object of the invention is to provide an electrophotographic recording material with a photoconductive Specify zinc oxide, the zinc oxide of which is modified in such a way that it is known Electrophotographic recording material

Applicant:

Eastman Kodak Company,

Rochester, N.Y. (V. St. A.)

Representative:

Dr.-Ing. W. Wolff and H. Bartels, patent attorneys,

Munich 22, Thierschstr. 8th

Named as inventor:
Norman Walter Blake,
Cornelia Cahill Natale,
Rochester, NY (V. St. A.)

Claimed priority:
V. St. v. America December 14, 1960
(75 753)

Lets sensitizing dyes sensitize over the entire range of visible light, that low intensity visible light can be used for image acquisition. Furthermore should a recording material with a ZnO binder layer can be given, its dark decay rate can be set as required during manufacture.

The object of the invention is based on an electrophotographic recording material, consisting of a layer support and a photoconductive layer with a zinc oxide dispersed in a binder, optionally sensitized, and is characterized in that it contains a zinc oxide which on its surface per mole 0.14 · IO- ⁵ to 7.2 · IO- ³ moles of a modifying agent.

These concentrations correspond to 1.8 x 10 ^-8 to 9.0 x 10 ^-5 moles, of modifier per gram of zinc oxide.

The recording material contains the modifier a Lewis acid, a reducing agent, or an ion-donating compound.

According to a particularly advantageous embodiment of the invention, the recording material contains as ion-supplying compound is an Al, Bi, Cr, Cu, Fe, Li, Mg, Ni, Sn or Ti compound.

The compounds can be bound to 10 to 100% on the surface of the zinc oxide. Also can multiple connections can be used at the same time. -

709 588/297

3 4

According to a preferred embodiment of the invention, additional modifiers are added

Application contains the recording material, based on components, for example one or more poly

on the weight of the total zinc oxide, 30 bis merisate and one or more sensitizing color

90 percent by weight modified zinc oxide. substances added to the slurry. The mixture

According to a further embodiment of the invention 5 can then be applied to a layer support

if the recording material contains a If a gaseous modifier,

effect of a gaseous modifying agent mo- for example hydrogen chloride or trimethylchloride

differentiated zinc oxide. silane, then dry zinc oxide powder is used

That for the production of the recording material in a closed vessel quickly stirred, whereupon Usable zinc oxide can, according to the French io, the gaseous modifier for a few minutes Process, the wet process or the America-long is fed slowly. The zinc niches can also Process be prepared provided that the oxide with a stream of an inert gas that with it is at least 98% pure. Suitable method is saturated with the vapor of the modifying agent, to produce such zinc oxides are brought into contact.

»A Volume-Charge Capacitor Model for 'Electrofax' 15 In some cases the modification

Layers, "J. A. Amick, RCA Review, Vol. 20, moderately violent with the zinc oxide, although more

Pp. 770 to 784, dated December 1959. than only the surface of the zinc oxide can react.

Suitable Lewis acids are described in the book by Unless the Reaction is Carefully Controlled, supra

W.F.Ludern and S. Zuffanti, »The Elec- can be a mixture of unmodified

tronic Theory of Acids and Bases ”, New York, 1946, 20 and from“ overmodified ”zinc oxide which

Pp. 15 to 17 and 43 to 46. is not particularly beneficial. Neither of that

Examples are: hydrogen sulphide, chlorine-modified as well as the "over-modified" zinc oxide

hydrogen, hydrogen fluoride, hydrogen bromide, sulfur compared to the normally modified zinc oxide

Feic acid, phosphoric acid, sulfur dioxide, sulfur have poorer properties. Must accordingly

trioxide, aluminum chloride, boron fluoride, zinc chloride, 25 highly reactive modifiers, such as chlorine

Zinc bromide, thionyl chloride, acetyl chloride, acetyl hydrogen and acid chlorides, like zinc oxide

bromide, trifluoroacetic acid, iodoacetic acid, thioglycol - are added to each zinc oxide particle

acid, benzoyl chloride, adipic acid chloride, adipine- uniform action of the modifier

acid bromide, terephthalic acid chloride, isophthalic acid. This can be achieved by

chloride, maleic anhydride, silicon tetrachloride, 30 that the zinc oxide continuously moves violently and that

Trichloromethylsilane, dichlorodimethylsilane, chlorotri modifier is slowly added,

methylsilane, trichlorophenylsilane, dichlorodiphenylsilane- The amount of modifier that is not Chlorotriphenylsilane, chlorodimethylphenylsilane. is agile to get with the percentage you want

or chloromethyldiphenylsilane. of the surface to react depends on the surface

Suitable reducing agents are: tannic acid, gene 35 of the zinc oxide used, those of zinc oxide tisic acid, pyrogallol, benzylaminophenol, ascorbic to zinc oxide can be different. The intrinsic acid, Tin (II) salts and compounds that have little of the modified zinc oxides can after at least as much as tin (II) chloride. certain test methods can be determined.

The invention achieves that the layers 40 produced under the length of the incident radiation for the discharge after charging have a particularly high sensitivity - a zinc oxide layer can thereby be determined. They also show a greatly reduced that a charged layer is exposed to a radiation spectrum with the dimensions of the dark decay rate of the applied solutions X-Y , especially at high sensitizing dye concentrations, the wavelength of the radiation spectrum. The layers (logarithm of exposure) of a stepwise direction (logarithm of exposure) made by using 45 changed along the X-direction and prepared along the Y-direction have a relative sensitivity which is subject to an intensity attenuation. Is reduced by a factor of at least 3. The entanglement of the charge image becomes a curve, the layers produced using reducing agents the effectiveness of the various light wavelengths have an increased dark decay rate. 50 indicates the discharge of the relevant shift,

A modifier belongs to the class of received. This curve is called the negative spectral Reducing agents as well as another class, so called sensitivity curve. For comparison predominates the effect obtained with reducing agents. purposes must always have the same conditions Represents a modifier or a Lewis acid. Uncolored, common zinc one is an ion-supplying compound, then 55 oxide predominates leads to layers A with a sensitivity of Effect resulting from the fact that the connection speed curve, as shown in FIG. 1 is shown, the one belongs to the class of ion-donating compounds. Has maximum at about 380 nm and after

The production of the modified zinc oxide can drop rapidly on either side, so that light of a wave occurs in the following way: The zinc oxide will cause too little discharge or no discharge at all in an inert solvent, for example toluene, for a length of 410 nm or higher. F i g. Figure 2 shows the emp-slurried so that the slurry contains a 5 to 5 sensitivity curve of an unmodified zinc-45% zinc oxide. At the same time, an amount of a modifying agent produced from oxide and sensitizing with crystal violet is added to a layer B. FIG. 3 shows the sensitivity, relatively small amount of a solvent, curve of a layer E, which has been dissolved with modified zinc oxide or toluene, for example acetonitrile, dimethylformamide, methanol or toluene sensitized with crystal violet. The zinc oxide slurry was made. In each case, 5 x 10 ~ ⁷ mole of mung is moved vigorously, whereupon the solution is used per gram of zinc oxide crystal violet. Is added dropwise as a modifier. Modifying agent served SO ₂ , ie a Lewis

acid. The relative efficiency with which the radiant energy absorbed by the zinc oxide covers the layer discharging can be derived from measurements of the relative sensitivity of the layer. The sensitivity a layer depends on two factors, namely, first, how much of the incident radiation energy the layer absorbs, and secondly, how effectively the absorbed radiation is used, to unload the layer. A comparison of the sensitivity curves of two different layers, which have identical absorption spectra, sets the efficiency of one layer compared to the other firm.

The relative sensitivity of the layers can also be determined as follows:

A layer is charged in the dark and placed in a sensitometer immediately behind a stepped gray wedge. Each level attenuates the light by about 25 ° / ₀ more than the previous level. Through the most permeable step, 1900 lux from a tungsten light source of 3000 ⁰ K fall on the layer. The layer is exposed for 3 seconds and then developed in the usual way. The step of the toner image on which no toner is retained indicates the relative sensitivity of the layer. This sensitivity is arbitrarily set at 20. The following levels have sensitivities of 25, 31, 49, 61, etc. The higher the number, the greater the relative sensitivity and the weaker the level, ie the less light is needed to discharge the layer. On this scale, non-sensitized zinc oxide layers have a sensitivity of approximately 60.

The property of zinc oxide layers to keep an applied charge in the dark can be determined by charging the zinc oxide layer and measuring its surface potential in the dark as a function of time. Measurement starts immediately after charging and continues for 3 minutes. The potential determined immediately after charging and after V ₂ , 1, 2 and 3 minutes is noted. The time after which the initial potential has dropped to half its value is also often used as a comparison value. It is necessary that the zinc oxide layer hold the charge in the dark until the layer is exposed and developed. If more than 3 minutes are required for the initial potential to drop to half its value, the charge storage capacity of the layer is sufficient. In the case of the unknown, non-sensitized zinc oxide layers, the time in which the initial potential drops by half is more than 3 minutes if the applied charge is negative. If the applied charge is positive, the initial potential drops by half in less than 15 seconds. As a result, such layers can only be charged positively with difficulty or not at all, although this is desirable in certain cases. In the case of layers sensitized with dyes, it was observed that the higher the concentration of the dye in the layer, the greater the lowering of the initial potential. At very high dye concentrations, the initial potential in the dark, even when negatively charged, often falls so rapidly that the layer is no longer suitable for xerographic purposes.

example 1

168 g of zinc oxide and 238 g of xylene were placed in a mixer fitted with a water cooling jacket. 90% of the zinc oxide particles were smaller than 0.4 μm. The most common particle size was 0.1 μm. 60 ml of xylene, in which SO _{2 was} dissolved as Lewis acid, were then added dropwise to the mixer with thorough stirring. After addition of the xylene for 10 minutes was further stirred, after which 8.4 x 10 ^-6 moles of crystal violet that was dissolved in 15 g of methanol, were added. The mixture was stirred for a further 5 minutes, after which 14.4 g of a solution of polysiloxane in toluene with 60% solids and 111.9 g of a mixed polymer solution of styrene and butadiene in toluene with 30% solids were added. The mixture was then stirred for a further 3 minutes. The mixture was then applied to paper in such a way that 0.09 m ² accounted for 3 g of dry layer. Further layers were produced without Lewis acid and without crystal violet. The layers were conditioned for 3 days at 21 ^° C. and 50% relative humidity. The relative sensitivities were then determined. The results obtained are shown in Table I.

Table I.

layer Moles of SO ₂ gSO ₂ crystal
violet Relative
Sensation
opportunity A. 0 0 no 60 B. 0 0 Yes 131 C. 0.75 · ΙΟ- ³ 4.8 · ΙΟ- ² Yes 790 D. 1.5 -ΙΟ- ³ 9.6 ΙΟ- ² Yes 3400 E. 2.25 · ΙΟ- ³ 14.4 · ΙΟ- ² Yes 4200 F. 3.0 x ³ ΙΟ- 19.2 ■ ΙΟ- ² Yes 1600 G 4,5 -ΙΟ- ³ 28.8 · ΙΟ " ² Yes 2000 H 6.0 -10- ³ 38.4 · ΙΟ- ² Yes 393 I. 9.0 -ΙΟ- ³ 57.6 · ΙΟ- ² Yes 192 J 2.5 -ΙΟ- ³ 16.0 · ΙΟ- ² no 122

The relative sensitivity curves of layers A, B and E are shown in FIGS. 1, 2 and 3 shown. The table shows that the optimum modification takes place when 2.25 · 10 ^-3 moles of SO _{2 were used} per 168 g of zinc oxide. Based on the reaction

ZnO + SO ₂

ZnSO ₃

this means that about 20% of the zinc oxide has reacted. By modifying the zinc oxide with SO ₂ , the sensitivity of the layer can be doubled even in the absence of dye. _{No SO 2 was} found in the liquid obtained by centrifuging the zinc oxide slurry after adding the SO ₂ but before adding the dye.

Example 2

The process described in Example 1 for the production of layers C to I was repeated, except that the Lewis acids listed in Table II below were used _{instead of SO 2.} Each Lewis acid was used in an amount between 0.3 x 10 " ³ and 1 x 3/4" ² moles. In cases where the Lewis acid did not dissolve sufficiently in xylene, methanol was used. Then the relative sensitivities of the layers were determined

■ true. In Table II are the amounts of modifying agents with which maximum sensitivities were obtained.

Layers corresponding to layer J of Example 1 were made using the optimal Amounts of Lewis acid produced, in each case an increase in sensitivity by a factor of 2 was determined.

Table II

optimal sensitization of 168 g of ZnO required amount of Lewis acid in moles

Lewis acid

Hydrogen chloride 4.5

Acetyl chloride 4.5

Adipyl chloride 2.25

Cyanuric chloride 2.25

Phenyltrichlorosilane 1.5

Dimethyldichlorosilane 2.25

Trimethylchlorosilane 4.5

Hydrogen fluoride 4.5

Zinc chloride 2.25

Sulfur trioxide 2.25

Sulfamic acid 4.5

ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³ ίο- ³

That there were reactions between the modifiers and the zinc oxide resulted from this, that in the liquid obtained by centrifuging the slurry after adding the modifier and before adding the dye no modifier could be detected.

Example 3

Following the procedure described in Example 1, layers were made with those listed in Table III Sensitizing dyes produced, however

ίο 4.5 x 10 ^-3 moles of hydrogen chloride and 5 x 10 ~ ⁷ moles of sensitizing dye per gram of zinc oxide were used in place of SO _2. Furthermore, layers were produced using unmodified zinc oxide.

The percentage of sensitizing dye adsorbed by zinc oxide was determined by the amount of the sensitizing dye present in the centrifuged liquid is determined became. The layers made with modified zinc oxide showed increased sensitivities, such as can be seen from Table III. The layers made with unmodified zinc oxide showed a little or no sensitivity in the spectral region absorbed by the sensitizing dye of light, apart from the sensitizing dyes cyanine blue-red, fluorescein, rose bengal (Color Index Number 45 440), Rhodamine B and the sensitizing dyes that have a carboxyl or contain a phenolic hydroxyl group.

Table III

Dye type Modified zinc oxide relative Unmodified zinc oxide relative % on ZnO Sensation % on ZnO Sensation adsorbed opportunity adsorbed opportunity Awareness Awareness Sensitizing dye dye, dye, Cyanine based on 4250 based on 2030 Cyanine added 2620 added 204 Triphenylmethane Awareness 995 Awareness 67 Triphenylmethane dye 2620 dye 83 Cyanine blue red 99 70 Quinaldine red Triphenylmethane 90 4250 20th 131 Malachite green Azo 60 164 + + 43 Lithosol blue 6 G + + + (Color index number 42025) Azo 250 23 Crystal violet Azo 75 204 + + 67 Amanil Black ROL + + + (Color index number 22580) Azo 204 17th p-methyl red Azo + 164 + + 43 Pontacyl blue black Sx Thiazine + 4250 + + 104 (Color index number 20470) Oxazine 500 131 Nigrosine Azine + 995 + + 131 Chrysoidin 4 Anthraquinone + 250 + + 83 Methylene blue Anthraquinone 90 164 + + 23 Chrome blue GCB + + + Phenosafranine Anthraquinone 90 315 + + 204 1,4-diaminoanthraquinone Anthraquinone 25th 164 + + 55 D&C violet base Phthalein + 791 + + 315 (Color index number 60725) Phthalein 3380 500 alizarin Phthalein 50 995 + + 627 Celanthrene red + + + Fluorescein Acridine 100 500 50 104 Rhodamine B + + + Rose Bengal 90 60 (Color index number 45440) Phosphine RN + + + (Color index number 46045)

+ A noticeable amount of dye was adsorbed.

+ + Little or no dye was adsorbed.

Table III (continued)

Dye type Modified zinc oxide relative Not modified Zinc oxide ° / o to ZnO Emfmd- % on ZnO ' adsorbed opportunity adsorbed Awareness Awareness Sensitizing dye dye, dye, relative Acridine based on 627 based on Sensation Nitro added 104 added opportunity Diphenylmethane Awareness 627 Awareness Thiazole dye 500 dye Acridine orange + + + 83 Naphthol yellow S + + + 43 Auramiri O. + + + 55 Thioflavine TG + + + 67 (Color index number 49005)

. + A noticeable amount of dye was adsorbed.

+ + Little or no dye was adsorbed.

For ρ iel 4

Following the procedure described in Example 1 using those listed in Table IV Modifier made different layers. To make the layers were no sensitizing dyes used. In those cases where the modifying agent is in xylene were not completely soluble, methanol, acetonitrile or dimethylformamide were used.

Table IV

Modifying agents

CuCl ₂

SnI _4,.

CuCl

BiI ₃ ...:; ■

NiCl ₂

MgCl ₂

Tetraisopropyl titanate

SnI ₂

LiCl

CrCl ₃

FeCl ₃

AlCl ₃

concentration

in moles per 56 g of ZnO

1·

1'

I ·

ίο- ³ ίο- * ίο- ⁴ ίο- ⁴ ίο- ³ ίο-. ³ ίο- ³ ίο- ⁴ ίο- ³ ίο- ³ ίο- ³ ίο- ³

Relative sensitivity

20 20 20 31 31 34 20 20 39 31 31 39

From Table IV it can be seen that the addition of the modifying agents increases the relative sensitivity compared with an unmodified zinc oxide layer.

Example 5

224 g of dry zinc oxide were placed in a vessel equipped with a stirrer. In the vessel was then slowly filled with 200 ml of gaseous hydrogen chloride at atmospheric pressure and 20 ° C introduced. After addition of the hydrogen chloride, 317.1 g of toluene, 20.9 g of methanol and 0.03 g of crystal violet dissolved in approximately 10 ml of methanol was added. The resulting mixture ■ was then mixed in a mixer for 10 minutes. Thereafter, 12 g of a polysiloxane resin solution were added in toluene at a solids content of 60% was added, followed by an additional minute was mixed. Finally, 96 g of a solution of a copolymer of styrene and butadiene were added in toluene with 30% solids, followed by another 2 minutes of mixing.

The suspension was then applied to paper. The recording material thus obtained had a sensitivity between 3400 and 5300.

B e i s ρ ie I 6

Zinc oxide was treated with hydrogen chloride as described in Example 5. Part of the zinc oxide was immediately mixed with a solvent, a binder and a dye and applied to a paper support. The sensitivity of the recording material obtained was 2600.

After 3 days, another portion of the modified zinc oxide was poured on in the same manner Layer support made of paper applied. The sensitivity of the recording material obtained was again 2600.

After 7 days another portion of the modified Zinc oxide applied to a layer of paper. The sensitivity of the recording material obtained was 2000.

Example 7

Following the procedure described in Example 1, various layers were formed, were being used in place of ³ SO ₂ 4,5-10- MoI Actylchlorid as a modifier. Cyanine blue red was used for sensitization. Layers made from unmodified zinc oxide produced a large dark decay at high cyanine blue-red concentrations. When using modified zinc oxide, increased sensitivities were obtained and the dark decay remained small despite high dye concentrations. The results obtained are shown in Table V. (A) denotes layers produced using unmodified zinc oxide and (b) denotes layers produced using modified zinc oxide. Furthermore means
V _{0 is} the initial potential of the applied charge

in volts,
V ₁ 1 ₂ the potential of the applied charge

half a minute in the dark in volts,
F _{3 is} the potential of the applied charge after 3 minutes in the dark in volts,

Tv 12 is the time after which the applied charge had dropped to half of its initial potential, in minutes.

709 588/297

Table V

ZnO Receive mi Kl / 2 T / 2V * T Mole 5 10- ' find- 1 v / i Cyanine blue red 5 10- ' lightly- 580 470 ⁵ U per gram 10 10- ' speed 365 325 310 10 10- ' 995 600 480 215 (a) 25 10- ' 1615 420 390 - Minutes (b) 25 10- ' 2030 370 220 340 - ■ (a) 3380 300 270 - Minutes (b) 2620 180 - (a) 8680 (b)

10

Examples ¹ p

168 g of zinc oxide and 238 g of xylene were placed in a mixer with a capacity of 11 and provided with a water cooling jacket; Then, with thorough mixing, 60 ml of xylene, containing 4.5 x 10 " ³ equivalents of hydrogen chloride, were slowly added. The slurry was mixed for 10 minutes, whereupon 5.1 g of methanol, the 0.02345 g of p-methyl red and 0.1 g. 0137 g of crystal violet dissolved was added and the mixture was stirred for an additional 5 minutes, after which 14.4 g of a 60% solids solution of polysiloxane in toluene was added and the mixture was stirred for an additional minute Then "111.9 g of a mixed polymer solution of styrene and butadiene with 30% solids were added and the mixture was stirred for a further 2 minutes, after which it was applied to a paper support and dried. The sensitivity of the recording material obtained was 2,600.
. If no hydrogen chloride was added during the production of the recording material, a material having a sensitivity of 100 or less was obtained.

Example 9

2017 g of toluene and 35 g of methanol were mixed together in a 3.8 l mixer. 2057.4 g of zinc oxide were then added over a period of 45 minutes. The mixer was held by a water jacket at a temperature of 37.8 ⁰ C. 154 g of this slurry were transferred to a mixer with a capacity of about 0.471, whereupon 4 g of methanol and then 54 g of an approximately 33.3% plastic solution were added, which consisted of 80 parts of a solution of a copolymer of styrene and butadiene in toluene with 60 % Solids, 10 parts of a polysiloxane solution in toluene with 30% solids, and 10 parts of a copal resin obtained by polymerizing the unsaturated residue obtained from the low-temperature cracking of petroleum. The slurry was stirred for 5 minutes and then applied to aluminum foil. The remainder of the zinc oxide slurry was modified by adding 2864 ml of gaseous hydrogen chloride. 154 g of this slurry were then treated as described: further.

The resulting recording materials were then exposed to a tungsten light source for 10 seconds irradiated by 40,000 lux. The irradiation was carried out through a step wedge that was in contact with the photoconductive layer was located. That way The conductivity image generated was then developed into a visible image as follows: A with a 1.0% aqueous manganese (II) nitrate solution of saturated cellulose sponge was several times passed over the photoconductive layer, with the sponge at a potential of + 60VoIt opposite the aluminum foil was held. It was then dried using an absorbent fabric. The electrolytically developed image was made by treating with a 5% i.gen silver nitrate solution made visible, whereupon the recording material was rinsed with water and blown dry. That Recording material made using the modified zinc oxide was found to be two to one four times more sensitive than the recording material produced using unmodified zinc oxide.

B e i s ρ i e 1 10

56 g zinc oxide were treated with ³ MoI 2-10 KOH in methanol. The modified zinc oxide was made into a layer with a binder. The layer had an initial potential V ₀

T
of 30 volts and a value ^of 30 seconds.

A layer made from zinc oxide that had not been pretreated with KOH had an initial potential

TV ₀ of 500 volts and a ~ - value of 3 minutes.

Example 11

56 g zinc oxide were treated with 2 x 10- ³ moles of hexamethylene diamine in methanol. The pre-treated zinc oxide was then treated with 1 x 10 ^-6 moles of a phthalein dye per gram of zinc oxide ten times. The sensitized zinc oxide was dispersed in a binder and made into a layer. The layer had a sensitivity of 1252, an initial potential of 260 volts and

T
a -γ value of 45 seconds. Without the addition of hexamethylenediamine, a layer with a sensitivity of 1252, an initial potential

T
of 550 volts and a - ^ - value of> 3 minutes.

Claims (5)

Patent claims: 1. An electrophotographic recording material comprising a layer support and a photoconductive layer with a dispersed in a binder, optionally sensitized ZnO, characterized in that it contains a ZnO on the surface thereof per mole 0,14-10- ⁶ to 7.2 -10- ³ mol of a modifier. 2. Recording material according to claim 1, characterized in that it is used as a modifying agent contains a Lewis acid, a reducing agent or an ion-donating compound. 3. Recording material according to claim 2, characterized in that it is used as ion-donating Compound contains an Al, Bi, Cr, Cu, Fe, Li, Mg, Ni, Sn or Ti compound. 4. Recording material according to claim 1, S, characterized in that it, based on the weight of the total ZnO, contains 30 to 90 weight percent modified ZnO. 5. Recording material according to claim 1, characterized in that it is a by action contains modified ZnO of a gaseous modifying agent. 1 sheet of drawings 709 588/297 5. 67 © Bundesdruckerei Berlin