DE2108939B2 - Electrophotographic recording material - Google Patents

Description

■ 40

The invention relates to an electrophotographic recording material having a photoconductor-binder layer.

The known arrangements (see. US-PS 31 21 006, 3121007, 30 37 861, 3165 405, etc.) have the common disadvantage that the surface of the photoconductor layer during the image formation Is exposed to environmental influences. In particular with cyclic recording, there are frictional influences, chemical influences, heat effects and multiple light effects as a result of the cyclical application on. These effects have a gradual deterioration in the electrical properties of the photoconductive ones Layer resulting in surface defects and scratches on the recording material on the images be reproduced. Furthermore, local areas of permanent conductivity are formed which are not electrostatic Can store more charge, and there is also a high level of dark discharge.

In addition to the problems noted above, these photoconductive layers are required to the photoconductor either makes up the entire layer, as is the case with vitreous selenium, or that preferably a high proportion of photoconductive material is present in a binder.

In that a photoconductive layer consists entirely or for the most part of photoconductive material must exist, the physical properties are in particular of a drum-shaped or tape-shaped recording material further restricted because, for example, the flexibility and the adhesion of the photoconductor on a layer substrate is primarily determined by the physical properties of the photoconductor are, but not by the binder, which is preferably only present in a small proportion is.

In US-PS 30 41 166 is a recording material described which has a layer of photoconductive material covered with a relatively thick layer of plastic is covered and applied to a substrate. However, it does not list any plastics that enable such a function; the examples given are limited to such structures where a photoconductor is used for the top layer. By the FR-PS 15 77 855 is a for special purposes Serving, composite electrophotographic recording material known, in particular for Reflective imaging with polarized light is suitable. When the polarized light on the white Background of a document to be copied falls, so it is depolarized, through the layer structure reflected and absorbed by the dichroic photoconductive material.

From DE-AS 10 68 115 is an electrophotographic Recording material known, the photoconductor layers made of poly-N-vinylcarbazole, if necessary among other photoconductive substances.

In view of the special training and the limited application possibilities of the known Recording material there is a need for a generally applicable recording material that has acceptable photoconductor properties and in addition has exceptional physical strength and has flexibility so that even with rapid and cyclical use without increasing deterioration the recording properties as a result of wear, chemical influences and light aging can be.

The object of the invention is therefore an electrophotographic recording material of the type mentioned at the beginning Kind that an effective generation of charge carriers by exposure to light as well as the transport such a load carrier enables.

This object is achieved by a recording material of the type mentioned, which is characterized by combining 0.5 to 5, preferably 0.1 to 1.0, parts by volume of a p-type photoconductor per 100 Volume parts of the binder layer with a p-type binder in the photoconductor-binder layer.

The photoconductive particles must be able to generate defect electrons when excited by light and inject them into the electrically active binder. A transparent binder can be used as a binder organic, polymeric or non-polymeric binder can be provided, which absorbs the radiation of the respective applied radiation area is not absorbed, but is active in the sense that it is the injection by light excitation generated holes from the photoconductive particles and allows them transported further. In a preferred embodiment of the invention they are photoconductive Particles dispersed in the binder.

The p-type binder should be used for irradiation applied wavelength range does not act as a photoliter.

One embodiment of the recording material according to the invention has a layer support, for example made of an electrically conductive material, and a binder layer applied thereon. the Bark middle layer can, for example, contain particles of trigonal selenium within a transparent, polymeric Contain layer that enables the injection of defect electrons and their transport. The transparent, p-conductive binder enables the advantage of an extremely low photoconductor content to be used, as was previously not possible with known recording material. It can also certain binders are used which have a high efficiency in terms of charge carrier injection and have their transport. Furthermore, a recording material according to the invention can be cyclic be applied repeatedly. One such application is, for example, xerography, in which usually a recording cycle consists of charge, optical projection and image development The recording method can, for example, be designed in such a way that the free surface of the binder layer uniformly electrostatically charged and irradiated with image-wise distributed activating radiation which is absorbed by the photoconductive particles and which the binder does not absorb, so that holes generated by light excitation in the photoconductive particles enter the binder are injected and transported in it and a latent electrostatic image on the free surface arises.

The invention is described below with reference to the exemplary embodiments shown in the figures, as well as their Properties described. It shows

F i g. 1 is a graph of photosensitivity of the electric field for a p-side binder alone and in conjunction with one Photoconductor,

F i g. 2 shows a representation similar to FIG. 1 for a second p-type binder,

F i g. 3 is a graph of the absorption spectrum of polyvinyl carbazole;

F i g. 4 is a graphic representation of the absorption spectrum of pyrene,

Fi g. 5 the sensitivity spectra of three photoconductive ones Fabrics,

F i g. 6 the absorption spectrum of perylene,

F i g. 7 shows an embodiment of a recording medium according to the invention,

F i g. 8 a graphical representation of the discharge properties of a recording material according to the invention with positive and negative corona charging,

F i g. 9 is a graph showing the discharge characteristics of another embodiment of a recording material according to the invention for positive and negative corona charging and

F i g. 10 shows the properties of a recording material according to the invention with repeated cyclical Use and different irradiation wavelengths.

A photoconductor is a material whose electrical conductivity is achieved by electromagnetic absorption Radiation increases noticeably within a wavelength range. This definition is therefore necessary because a large number of aromatic, organic compounds exist that are known or believed to exist when exposed to strongly absorbed ultraviolet radiation

tion, x-rays or gamma rays show photoconductivity. The photoconductivity of organic Fabric is a common phenomenon. Show practically all strongly conjugated organic compounds a certain degree of photoconductivity when suitable conditions are set. Most of these organic substances are primarily sensitive to ultraviolet radiation. However, this is becoming commercial only marginally used; the sensitivity of these substances to short wavelengths is great for copying Not particularly suitable for writing or for color reproduction. Since the organic compounds so mainly show photoconductivity when excited by short-wave radiation, must be emphasized be that in the context of the invention only those substances are referred to as photoconductors that actually have a show corresponding sensitivity in the wavelength range that contributes to their function as Recording material is to be used.

The p-conductive binding agent is a non-photoconductive material which enables an injection of defect electrons or holes generated by light excitation from the photoconductive layer of at least 10% with fields of approx. 2 × 10 ⁵ volts / cm. The binder also enables the charge carriers to be transported over at least 10 ^-3 cm with a field of no more than approx. 10 ⁶ volts / cm. In addition, it is transparent to radiation of the wavelength range used.

The binder, which is arranged according to the invention on the photoconductive layer, is to be referred to as an insulator insofar as an applied electrostatic charge is not discharged in the absence of radiation, at least not at a rate that would allow the generation and storage of an electrostatic latent image prevented. This means that the specific resistance of the material should be at least about 10 ¹⁰ ohm · cm.

As can be seen from the above, most p-type binders show a side effect also a photoconductivity, if they can absorb radiation, the wavelength of which is used electronic excitation is suitable. Such behavior at short wavelengths outside the Spectrum for the photoconductor used is immaterial for the function of the recording material. It is known that radiation must be absorbed in order to stimulate photoconductivity, but since it is permeable the p-type bonding agent is assumed for the radiation used, it can be the photosensitivity of the recording material in the radiation range used do not significantly influence.

The reason that the p-type binder must be transparent arises from the fact that under all practical conditions the effectiveness of the photoinjection from the photoconductor into the binder as a result of radiation absorbed by the photoconductor, the binding agent's own light sensitivity in every wavelength range, be it visible or invisible, by far exceeds. This is shown in FIGS. 1 and FIG. 2, which compares the dependence of the injection sensitivity of the selenium photoconductor in FIG Connection with typical p-conductive binders and the own photoconductivity of two binders, Polyvinyl carbazole and polyvinyl pyrene from electric field, respectively, at wavelengths of high sensitivity shows. The curves for polyvinyl carbazole and polyvinyl pyrene in FIG. 1 and 2 are obtained with samples of 20 μm Starch on an aluminum beam. after the in

Example 1 given method is prepared. The curves for the layer structure of the same materials with a 0.4 μm thick glassy selenium layer between the p-conducting binder and the layer support correspond to those in FIG. 9 and result from the method according to Example 3. The structure shown in FIG. The curves shown in 1 and 2 represent the xerographic gain G as a function of the applied field. The xerographic gain is calculated from the initial discharge speed using the following formula:

(dJTdM r _ = 0
(eldl,) ~ " ■

Here / is the incident photon flux, d is the thickness of the layer, ε is the dielectric constant and e is the electronic charge. A xerographic gain with the value 1 results if one charge carrier per photon is excited and moved through the layer. From Fig. 1 and 2 it can be seen that the inherent photoconductivity of the active materials at the wavelength of their peak absorption (ultraviolet excitation) gives a gain which is significantly lower than that of the two-phase structure with effective photoconductive substances. In the case of layer structures with thin selenium layers and suitable active materials, gains of approx. 0.7 are possible with a field of approx. To ⁶ volts / cm, with an excitation wavelength in the visible spectrum (400 to 800 nm) being used. 3 and 4 also show that the above-mentioned p-type binders show at most a negligible discharge when they are irradiated with a light wavelength which is used in xerography and is, for example, 400 to 800 nm. The improvement in performance possible with a two-phase structure can best be realized if the p-type binder is transparent to the radiation in an area in which the photoconductor is to be used. Any absorption of this desired radiation by the binder prevents this radiation from acting on the photoconductive layer, that is to say at a point where it is to be used. It follows from this that advantageously only those p-conductive binders should be used which are permeable in the wavelength range in which the photoconductor has its main sensitivity and is therefore to be used.

Use cases where complete transmission in the visible range of the spectrum for the p-type binding agent is not required, for example, the selective recording are narrower band Radiations, e.g. B. of lasers, the evaluation of spectral patterns and possibly colored xerography such as B. the reproduction of color-coded forms.

In the F i g. 3, 4 and 6 is the well-known absorption effect of the active substances polyvinyl carbazole, pyrene and perylene. Fig.5 shows the xerographic Sensitivity spectra for three typical combinations of photoconductor and p-conducting binder. The sensitivity for a combination of amorphous selenium and polyvinyl carbazole is for a 0.4 μΐη strong layer of amorphous selenium shown on a 20μπι thick layer of polyvinyl carbazole is arranged. In a polyvinyl carbazole binder, the X form are metal-free phthalocyanine and trigonal selenium with a concentration of approx. 30: 1 (volume fraction phthalocyanine) and approx. 100: 1 (volume fraction trigonal selenium). The binder structures with the X-shape metal-free phthalocyanine and trigonal selenium in polyvinyl carbazole are described in more detail elsewhere. Both Binder layers have a thickness of approx. 20 μm. As shown in FIGS. 3, 4, 5 and 6 are shown, are certain combinations of p-type binders with different photoconductors are particularly good for the selective use of the sensitivity spectrum suitable.

In FIG. 7, a recording material 10 is shown in plate form, which is on a layer support 11 a make coat 12 contains. The substrate 11 is preferably made of a conductive material. Suitable materials are, for example, aluminum, steel, Brass or the like. The substrate can be rigid or flexible and have any suitable thickness. For example it can be designed as a flexible band or sleeve, as a sheet, strip, plate, cylinder and drum. Of the Layer support can consist of several components, for example a thin conductive layer can be provided, furthermore a thin and conductive layer can be provided on a plastic base Layer of aluminum or copper iodide can be provided; finally, glass can also be used is covered with a thin and conductive layer of chromium or tin oxide.

The binder layer 12 contains photoconductive particles 13, which are random and without orientation in the Binder 14 are dispersed. The photoconductive particles can be made from any suitable inorganic or organic photoconductors and mixtures of such photoconductors. To the inorganic substances include inorganic crystalline compounds and inorganic photoconductive glasses. Typical inorganic crystalline compounds are cadmium sulfoselenide, cadmium selenide, cadmium sulfide and mixtures these substances. Typical inorganic photoconductive glasses are amorphous selenium and also selenium alloys like selenium tellurium and selenium arsenic. Selenium can also be used in a crystalline form, known as trigonal selenium is known. Typical organic photoconductive substances are phthalocyanine pigment substances, for example the X-form metal-free phthalocyanine, described in US Pat. No. 3,357,989, metal phthalocyanines such as copper phthalocyanine, quinacridones, substituted 2,4-diaminotriazines, described in US-PS 34 45 227, triphenodioxazines, described in US-PS 34 42 781, and polynuclear aromatic Quinones. The above-mentioned photoconductors are only examples of substances that can be used Do not limit the number of possible substances in any way. The size of the photoconductive particles is not particularly critical, but particularly good results are shown with particles with a size of 0.01 to 1.0 μm.

As already stated, the photoconductive material is used in a non-oriented arrangement. This is to be understood as meaning that the pigment substance or the photoconductive material with regard to the stimulating electromagnetic radiation is isotropic, d. that is, it is the same for each polarization of the exciting radiation Way sensitive. The p-type binder 14 can be any suitable transparent organic polymer or contain non-polymeric material that has a transport

of the injected and generated by light excitation and given off by the photoconductive pigment Makes defect electrons so that they can selectively discharge the layer surface. Polymers with these properties contain repeatedly occurring units of a polynuclear aromatic hydrocarbon, which can also contain foreign atoms, for example nitrogen, oxygen or sulfur. Typical polymers are polyvinyl carbazole (PVK), poly-1-vinyl pyrene (PVP), and polymethylene pyrene N-substituted polymeric acrylic acid amides of pyrene. Typical non-polymer substances are carbazole, N-ethylcarbazole, N-phenylcarbazole, pyrene, tetraphene, 1-acetylpyrene, 2,3-Benzochrysen, 6,7-Benzopyrene, 1-Bromopyrene, 1-Ethylpyrene, 1-Methylpyrene, Perylene, 2-Phenylindole, Tetracene, picene, 1,3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenathrene, triphenylene, 1,2,5,6-dibenzanthracene, 1,2,3,4-dibenzanthracene,

2,3-benzopyrene, 2,3-benzchrysen, anthraquinone, dibenzothiophene and naphthalene. Besides these substances are suitable mixtures of active polymeric substances and / or active non-polymeric substances can also be used.

Any suitable polymer whose repeating unit is the appropriate aromatic hydrocarbon such as B. contains carbazole and enables the injection of defect electrons and their transport, can be used. The polymers used for the photoconductor binder layer are made by the Invention not restricted. Polyesters, polysiloxanes, polyamides, polyurethanes and epoxy resins and copolymers in block form, random form, or compound form (with the aromatic repeating unit) are various examples of the p-type Polymers that can be used as binders. Furthermore, suitable mixtures of active polymers with inactive Polymeric or non-polymeric substances can be used.

The photoconductor binder layer is generally transparent or non-absorbent in at least one pronounced part of the spectrum between approx. 400 and 800 nm. In this range it enables injection and the transport of holes with radiation of a corresponding wavelength through the Photoconductor particles were generated.

An upper limit of the volume concentration of the photoconductor is determined by various factors: 1. Through a stage at which the physical properties of the polymer are greatly deteriorated, 2. through a stage in which there is pronounced charge carrier transport through mutual contact of the particles takes place, and 3. through a stage in which, when using conductive pigments such as z. B. trigonal selenium an excessively strong scattering of holes occurs during the charge. the The latter two factors often lead to a deterioration in the repeated cyclical application possibility. To achieve the best combination of physical and electrical properties, the The maximum proportion of photoconductor particles should not be more than approx. 5 percent by volume of the binder layer. A the lower limit for the photoconductive particles is about 0.1 volume percent of the binder layer required to ensure that the light absorption coefficient has a value sufficient for the generation of charge carriers. To one accordingly To achieve equivalent discharge rates with both types of charging, it is necessary with a volume filling to work where the middle child ring ticfc des

• π

Light is close to the middle of the layer. For the two embodiments shown in FIGS. 8 and 9 of Photolciter binder layers with the X-shape of metal-free phthalocyanine and trigonal selenium in one Polyvinyl carbazole layer results in an equivalent discharge in the range of approx. 1 part by volume of phthalocyanine in 84 parts by volume and approx. 1 part by volume of trigonal selenium in 190 parts by volume. It should be noted that these values depend on the respective layer thickness. They also show that even with positive Charging a steady increase in the rate of discharge with an increasing proportion of photoconductors is because the light absorption coefficient is increased. Even with shares in the order of 1 Percentage by volume, the performance is still very high.

From the above it can be seen that a critical proportion of the photoconductor from 0.1 to 5 Volume percent is required to take advantage of the invention. The preferably The range with regard to optimal mechanical properties is between 0.1 and 1.0 percent by volume Photoconductor portion.

The thickness of the photoconductor binder layer is not particularly critical. Layer thicknesses from 2 to ΙΟΟμπι show satisfactory results, preferably a layer thickness of 5 to 50 μm is used for particularly good results.

Another embodiment of the in FIG. The arrangement shown in Figure 7 is with a barrier layer at the interface provided between the substrate and the binder layer. The barrier prevents the injection of Charge carriers from the support into the photoconductive layer. Any suitable barrier material can be used. Typical such materials are nylons, epoxy resins and alumina.

The p-type binder can be any suitable polymeric or non-polymeric material with the required properties, preferably will polymeric substances are used because their physical properties, e.g. B. the flexibility, compared to the physical properties of non-polymer materials are better.

To the by the invention over the recording media according to US-PS 31 21 006 To demonstrate possible improvements, the following tests are carried out. Three typical Resin binders of the type described in US-PS 31 21 006 are tested one after the other to the Compare properties of these synthetic resins with the p-type binder of the present invention. Polystyrene, polyisobutyl methacrylate and a silicone resin are used as the resins. The test results show that these resin binders combined with a vitreous selenium layer are not practically useful Enable charge distribution. The polyisobutyl methacrylate resin and the silicone resin are with a Layer structure tested by first applying a thin nylon barrier layer of approx. 0.1 μm thickness on a 10 χ 10 cm aluminum support from a liquid solution using a known coating process is formed. A 1.0 μm thick layer of each Resin is then formed on the barrier layers of the two panels. A 0.5 μm thick layer Vitreous selenium is then formed on the resin layers by vacuum evaporation. According to the above A third plate is produced in the process Polystyrene is provided as a hard layer without a nylon coating.

The three plates are each tested by charging them to a known voltage and illuminating them. Then the residual stress is measured. If there is no charge transfer in the resin layer, the residual voltage can be calculated from the known properties of the synthetic resin, the thickness of the layers, the dielectric constant of the materials and the initial voltage. The calculated residual voltage should correspond to the measured residual voltage, with the exception of an experimental error, until the electrical flashover point of the plastic layer is reached. If one assumes that the initial field distribution is capacitive, the residual voltage K _rt is calculated. ₅ according to the following formula:

1 +

M ₂ "M",

If no charge is transported through the synthetic resin layer, the course of the experimentally determined residual voltage V _{res should be} proportional to the course of the voltage Vo (initial voltage), with the gradient being designed as follows:

k, I

In the above. Formula is k \ the dielectric constant of the resin, d \ the thickness of the resin layer, fo the dielectric constant of the selenium, d ₂ the thickness of the selenium layer. The initial voltage is Vo.

The experiments are carried out with a monochrome light source with a wavelength of 400 nm and an intensity of 2 χ ΙΟ ¹² photons / cmVsec. Each plate is charged with several selected voltages between about 0 and 100 volts (about 0 to 65 volts / micron). The residual voltage is not limited by the incident light, since a sufficient amount of light is available under all test conditions to generate a sufficient number of charge carriers in the selenium to reduce the field at the selenium layer to practically zero. The thickness of the layers is intentionally kept small, even if thin samples cause problems with regard to the measurement. This realizes the actual situation of the recording medium with a binder structure, in which the electrical properties of thin films made of plastic between the pigment particles are of influence. The results of these calculations and experiments are shown in Table I below:

Table I.

Electrical properties of layer structures

2.4 1.0 pitch calculated 2.7 i, o experimental 0.83 Polystyrene 0.77 (±) 0.01 0.82 Polyisobutyl 2.8 1.0 0.79 (±) 0.02 methacrylate 6th 0.5 0.81 Silicone resin 0.70 (±) 0.02 selenium

The values for the experimental slope are least squares method of the experimentally determined points calculated. The small normal error of the slopes shows that the ι Do not scatter individual points significantly in relation to the best straight line. The comparison between the experimental and the calculated or theoretical slopes must be carried out afterwards. Although the experimental and the calculated

do not exactly match in slopes, correspond however, they do well with each other when all faults are taken into account. Although the random errors of the measurements are small (i.e., the standard error of the slope), there can also be large systematic errors because

ι -, it is difficult to measure the layer thickness properly.

From the experimental data presented in Table I it can therefore be concluded that one negligible charge transfer occurs in the three resin layers, even if their thickness is only 1 μm

. '(ι is what for field strengths up to approx. 45 volts / micron is applicable. At field strengths above approx. 45 volts / micron, these thin layers show a dielectric breakdown. This experimental test does not show whether the charge shift is due to an inability to

> i would take the injected defect electrons out of the vitreous selenium or a very low penetration depth or a poor transport capacity for the load carrier. If all error limits are taken into account, one can safely say

jo be that these plastics are used as insulators among the Conditions of the tests carried out take effect, d. H. the charge doesn't get from the selenium into the either Layer injected or after injection it is not transported through the layer at the specified field strengths.

j-j To the advantages of the invention over the known arrangements with combinations of at least two or more photosensitive substances according to the U.S. Patents 3,121,007 and 3,037,861 will be shown further Tescs carried out. During use, absorbs that provided according to the invention p-type binders a part of the incident radiation, so the recording medium is less sensitive, regardless of whether it consists of particles dispersed in a binder or a

• Has n particularly photo-injecting layer. Except one A decrease in the discharge sensitivity leads to the utilization of the photoconductive properties of the p-type Binder cause serious problems in continuous use of the recording material, for example

ι »in a cyclically working reproduction machine. It is normally desired that the recording material have stable or stable electrical properties during the cyclical application has to be a corresponding structure of other components of the

ή to enable the machine, for example the developing device, the exposure device and the underground control. These conditions cannot are kept essentially constant so it becomes difficult and even impossible to obtain a reliable one

To build a working automatic copier machine, which does not require constant warning and adjustment work. To this critical error of the invention To show recording material only for a wavelength range in which the charge carriers with

h5 are generated on the photoconductor and for which the p-type binder is transparent, the following test is carried out.
A recording material with a quartz

Base produced on which a conductive tin oxide layer is provided. On top of the tin oxide layer is a 0.1 .mu.m thick barrier layer formed from epoxy resin, on which a 0.5 μm thick layer of amorphous selenium is generated by vacuum evaporation. Then a 10 μm thick coating is made on the selenium layer Polyvinyl carbazole formed. To the dependence of the maximum efficiency of the recording material of the permeability of the p-type bonding agent for the radiation used will show the the following test carried out:

The plate is charged to a negative voltage of approx. 200 volts and with four different Wavelengths tested by irradiating them through the surface of the polyvinyl carbazole layer. When irradiated, the recording material shows a characteristic electrical discharge curve. the xerographic sensitivity of the recording material can be assessed by the slope of the The discharge curve at the moment of lighting is determined graphically, d. H. the value

dV
d7

at r = 0.

The slope is normalized to the thickness of the sample and an irradiance of 1 χ 10 ¹² photons / cnWsec. This calculation gives the discharge sensitivity listed in Table II below.

Table II

Dependence of the discharge rate on the

Absorption by polyvinyl carbazole

wavelength Kl (-u / -) '= ⁰ (nm) (Volt) (Volts / sec) 400 205 157 355 185 83 334-337 200 75 315-318 200 45 272-274 195 49

As can be seen from Table II, for 400 nm, for which the polyvinyl carbazole is practically transparent, the Discharge sensitivity

/ dV \

UT) ι =

quite high. However, when exposed to wavelengths of 355 nm or less, some charge carriers become is generated in the polyvinyl carbazole and the sensitivity is substantially reduced.

To avoid the critical influence of the continuous and repeated use of the recording material show and the requirement of the transparency of the p-type bonding agent for the radiation used To clarify, further tests will be carried out. A 1Ox 10 cm aluminum support is initially with a 0.2 μm thick epoxy layer as Provided barrier layer, then a 0.5 μm thick Layer of vitreous selenium formed on the barrier layer by vacuum evaporation, on which a 12 μΐη strong polyvinyl carbazole layer is applied. This plate is then placed on a 20 cm aluminum drum Diameter drawn up and charged to a negative voltage of 900 volts. Then she will with Irradiated light to obtain a contrast potential of 200 volts -).

The plate is then erased to a negative voltage of 40 V or less by using a Quartz iodine lamp is irradiated. Then it is charged again to a negative voltage of 900 V. Of the

The cycle is then repeated with a peripheral speed of the drum of approx. 15 cm / sec. For all tests, the initial voltage is set to 900 V by setting the corona current at the start of the test. The experiments are carried out with radiations of 400, 345 and 253.7 nm wavelength. In each case, the radiation intensity is set at the beginning so that 200 V contrast potential is generated. The test results are shown in FIG. 10 shown.
As shown in FIG. 10, the structure is stable in its electrical properties for more than 1000 cycles at a wavelength of 400 nm, for which the polyvinyl carbazole is transparent and does not act as a photoconductor. At a wavelength of 345 and 253.7 nm, their radiation through the polyvinyl carbazole layer

2ί is strongly absorbed and in which the polyvinyl carbazole layer acts as a photoconductor, the initial voltage drops when the recording material is used cyclically: from, and extrapolation shows that the recording material will probably after about 10,000

jo cycles no longer accepts charge. Outside the range of these experiments, the potential drops Irradiation proportional to the drop in the initial voltage, creating a constant contrast potential results. The development of such an image is true

ü possible the potential change with constant contrast however, leads to difficulties in development and background control, so that such Application in automatic electrophotographic reproduction machines is disadvantageous.

■ κι In the following examples, percentage values relate to the weight, unless stated otherwise.

Example I.

It is a recording material with binder

• Γ) structure of the type shown in Fig. 7 with no oriented photoconductive particles made from the X-shape metal-free phthalocyanine, which in a Polyvinyl carbazole binder (PVC) with a weight ratio of 48 parts PVC to 1 part

in photoconductive pigment particles (volume ratio 60: 1) are available. The recording medium is formed as follows: 31 g of a 16.7% strength Polyvinyl carbazole solution are formed by adding an equivalent amount of poly-N-vinyl carbazole, in 180 g Toluene and 20 g of cyclohexanone are dissolved. This solution becomes 0.25 g of the X-form metal-free Phthalocyanine and 10 g of toluene added. This mixture is made with steel shot for about 15 to 60 minutes milled long until a well-dispersed suspension is obtained

«Ι results. Then a layer is made on an aluminum backing formed using a coating device. The final layer thickness according to Air drying at U0 ° C for 1 to 24 hours is 25 μιτι.

Example Il

Three record carriers are prepared according to the procedure described in Example I. with the

13th

Difference that the phthalocyanine concentration is as follows Has proportions:

a) Weight ratio 72: 1 (volume ratio 90: 1) of PVC to phthalocyanine for a Layer thickness of approx. 20 μm;

b) Weight ratio 24: 1 (volume ratio 30: 1) of PVC to phthalocyanine for a Layer thickness of approx. 20 μίτΐ;

c) Weight ratio 96: 1 (volume ratio 120: 1) of PVC to phthalocyanine for a Layer thickness of approx. 20 μίτι.

Example III

Three recording media are produced according to the method described in Example I, with the The difference is that a polynuclear, aromatic quinone is used instead of the phthalocyanine. This pigment is present in the following proportions:

a) weight ratio
30: 1) from PVK
Layer thickness of approx.

b) weight ratio
60: 1) from PVK
Layer thickness of approx.

c) weight ratio
72: 1) by PVK
Layer thickness of approx

24: 1 (volume ratio to pigment for a

13 μπί;

48: 1 (volume ratio to pigment substance with a 15 μm;

72: 1 (volume ratio to pigment for a

14 μm.

IV

example

Two recording media are generated according to the example! described method produced with the The difference is that trigonal selenium is used as a pigment in the following proportions:

a) Weight ratio 24: 1 (volume ratio: 1) of PVC to trigonal selenium for a Layer thickness of about 30 μm;

b) Weight ratio 48: 1 (volume ratio: 1) of PVC to trigonal selenium for a Layer thickness of approx. 12 μm.

Example V

A recording medium is produced according to the method described in Example I, with the difference that that as a pigment cadmium sulfoselenide with a weight ratio of 24: 1 (volume ratio : 1) from PVC to cadmium sulfoselenide is used. The layer thickness is approximately 10 μm.

Table III

Example VI

A recording medium is produced according to the method described in Example I, with the sub) it was decided that trigonal selenium with a weight ratio of 24: 1 (volume ratio 96: 1) is used by PVC to trigonal selenium. The layer thickness is approximately 10 μm. Furthermore is a 0.2 μm thick nylon barrier layer on the surface of the in the binder layer and at the interface between Binder and pad provided. The nylon barrier is created by dipping the panel in a Nylon solution formed in methyl alcohol.

^r> Example VIl

A recording medium is produced according to the method described in Example I, with the difference that that as a pigment trigonal selenium with a 2Ii weight ratio of 24: 1 (volume ratio 96: 1) is used by PVC to trigonal selenium. The layer thickness is approx. 9 μm.

Example VIII

2 ") A record carrier is made according to the method described in Example I. Process described, with the difference that as a pigment trigonal selenium with a Weight ratio of 6: 1 (volume ratio 24: 1) of PVC to trigonal selenium is used. the

in layer thickness is about 10 μm.

Each of the recording media described in Examples I to VIII has excellent electrical properties Properties that are shown by good charge absorption capacity and good photosensitivity.

η The profit or the maximum efficiency for seven of the recording media formed according to the preceding examples are listed in Table III.

The recording media listed in Table III are electrostatically applied to a positive voltage

4Ii of the specified field strength (a field strength of 50 × 10 ⁴ volts / cm corresponds to a voltage of 50 × 10 ⁴ volts for every centimeter of the layer thickness), for which purpose a corona discharge device is used. Each sample is then matched with a

• π single-color light source exposed, its wavelength is close to the peak absorption of the particular photoconductive pigment used. The resulting Discharge (voltage over time) is registered. From this data, the xerographic gain

in calculated according to the formulas given above will.

plate

from example

wavelength
(nm)

1'hutoncnliuU (Pholons / cm ² / sck)

1: 1. IcId (l () ⁴ V / cm)

Profit or achievement

(per iihsorhicrtcs Photon collected Charge carrier)

A.o.

Hh

IVii

IV ü

IVb

VIII

620
620
620
4 (K)
4 (X)
4 (K)
4 (K)

6.5 10 ''
(1.5 -10 "
8.0-10 '
.1, X- I0 ¹ ·
2.0- K) ¹ '
5. ¹ J- K) ¹ '
5.'I- K) ¹ '

50
50

8-95
10-70
25th
30th
30th

0.26
0.23
0.35
0.25
0.20
0.22
(UK

In addition to the tests listed in Table IU, three of the record carriers become an image reproduction subjected. The plate from Example IVa is electrostatically charged positively to about 800 volts, including a Corona discharge device is used. Then she will use a white light pattern with a Exposed quartz iodine lamp, which is provided with a filter that suppresses all radiation below 400 nm, whereby the charge in the irradiated areas is selectively dissipated. That generated electrostatic latent image is then developed using liquid development, which is electrostatic negatively charged toner particles dispersed in kerosene are moved across the latent image. the Electrostatically charged areas of the latent image attract the toner particles and create a visible one Image. This toner image is then transferred to a sheet of paper and on that to form a permanent one Fixed pressure.

The plate from Example VI is provided with an image according to the method described above, in doing so, however, it is charged to a voltage of approx. 500 volts.

The plate from Example V is also made using the method described above with an image provided, however, it is charged to a voltage of 500 volts, then the development with a Toner performed according to the cascading process. Each of these three plates produces an excellent Reproduction of an original image.

In order to illustrate the properties of the recording media according to the invention with regard to cyclical and repeated use, the disks from Examples I, HIa and IVa are used cyclically. First, they are electrostatically charged in the dark with a field strength of approx. 30 volts / μΐη of the binder strength. The plates I, IHa and IVa are then exposed to light wavelengths of 620, 400 and 400 nm, a photon flux of about 2 χ ΙΟ ¹² photons / cm / sec being generated for the discharge. Each plate is then illuminated with white light to remove any residual charge. This entire cycle is repeated 200 times for plates I and IVa and 250 times for plate IHa. Each panel shows excellent charge acceptance and light discharge capacity at the end of this cycling test. The initial voltage, contrast voltage and residual voltage at the end of the test are practically the same as after the first cycle.

Example IX

Vitreous selenium grains having a purity of 99.999% are enclosed in a quartz tube and placed in a vacuum chamber in which a pressure of approx IQ ⁵ Torr prevails The selenium is treated at 100 ⁰ C for about 16 hours to get it from the

ίο glassy state in the crystalline trigonal form to convert.

A mixture of 1 part by volume of trigonal selenium and 1 part by volume of poly-1-vinylpyrene (PVP) is dispersed in 100 parts of reagent chloroform. This mixture is ground in a paint mill for 1 hour with steel balls 3 mm in diameter until the selenium particles have a maximum size of do not have more than about 1 μm. Then so much PVP is added until the ratio of PVP to selenium is 24: 1.

This mixture is ground for about 30 minutes and placed on three aluminum alloy pads as a layer applied, the dry thickness of which is 25 μm. Each pad is 0.2 μm thick Provided epoxy barrier layer on which the binder mixture is applied.

Each of these plates is electrically tested. All plates show good electrical discharge capacity.
In the context of the invention, a transparent

jo te pad in the form of a with a thin, conductive Layer of aluminum or tin oxide provided plastic carrier can be used, so that a Exposure of the recording medium can take place through the substrate. Furthermore, an electrical insulating pad can be used. In this case the charge is on the record carrier applied by the insulating substrate and the surface of the recording medium simultaneously with opposite polarity can be charged by double corona discharge. Other amendments an insulating or missing base can be provided, the recording medium or the plate is placed on a conductive base and then the surface of the recording medium being charged. After the image generation, the recording medium can then be removed from the conductive substrate be removed.

In addition 6 sheets of drawings

Claims (4)

Patent claims: 1. Electrophotographic recording material with a photoconductor binder layer, characterized by combining 0.5-5, preferably 0.1-1.0 parts by volume of one p-photoconductor per 100 parts by volume of the binder layer with a p-conductive binder in the Photoconductor binder layer. 2. Recording material according to claim 1, characterized in that the binder is poly-I-vinylpyrene, Polymethylene pyrene, poly-N-pyrenylacrylamide, Carbazole, N-ethylcarbazole, N-phenylcarbazole, Pyrene, tetraphene, 1-acetylpyrene, 2,3-benzchrysene, 6,7-benzopyrene, 1-bromopyrene, 1-ethylpyrene, 1-methylpyrene, perylene, 2-phenylindole, Tetracene, picene, 1,3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenanthrene, triphenylene, 1,2,5,6-dibenzantfiracene, 1,2,3,4-dibenzanthracene, 2,3-Benzopyrene, 2,3-Benzchrysen, Anthraquinone, Dibenzthiophene and / or Naphthalene contains. 3. Recording material according to claim 1, characterized in that it is used as a photoconductor vitreous selenium, a selenium alloy, triogonal selenium, cadmium sulfoselenide or the X-form of contains metal-free phthalocyanine. 4. Electrophotographic process for the production of a charge image, in which an electrophotographic Evenly electrostatic recording material with a photoconductor binder layer charged and then imagewise with radiation which is absorbed by the photoconductor particles and is not absorbed by the binder, is exposed, characterized in that a Recording material according to claim 1 is used. in