SU449515A3 - Electrophotographic element - Google Patents

Description

(54) ELECTROPHOTOGRAPHIC ELEMENT

one

The invention relates to xerography, P in particular to an electrophotographic element.

An electrophotographic element is known with a photoreceptor component containing compatible photosensitive and active transporting materials.

The disadvantages of the known electrophotographic element are significant wear, low resistance to the action of chemical reagents and heat and light fatigue, leading to deterioration of the electrical characteristics of the photoconductive layer and the appearance of surface defects.

The purpose of the invention is to increase the resistance to wear, chemical attack and light fatigue and increase the effective injection of photogenerated charges from a photosensitive material - achieved by using a bisbenzimidazole pigment as a photosensitive material, and as an active transporting material - a transporting charge material that

does not absorb radiation with a wavelength of 400O-6500 I.

It is desirable that the photoreceptor component contains a bisbenzimidazole pigment dispersed in the active binding transporting material and has a layered structure containing a layer of bisbenzimidazole pigment and a layer of active transporting material located above it.

The thickness of the simple layer of bisbenzimidazole pigment is usually 0.05 to 20 microns, and the thickness is active; transporting layer 5 - 1OO microns.

The ratio of the thickness of the layer of active transporting material to the thickness of the layer of photoconductor is most often in the range of 2: 1-2-2: 1.

The bisbenzimidazole pigment can be obtained by reacting 1,4,5,8-naphthalene tetracarboxylic acid with aryle or heterocyclic diamine.

Cis and trans isomers of the reaction product of 1,4,5,8 naphthalene tetracarboxylic acid with ofphenylene diamine can be used as bisbenzimidazole pium. Examples of active transporting materials are carrier materials, such as carbazole, N - apkylcarbazole, such as 1 - ethyl- or N1 .1zopropylcarbazole, N - phenylcarbazole, tetraphenylpyrene, 1-alkylpyrene, such as 1-methyl- or 1-ethylpyrene , perylene, chrysene, anthracene, tetracene, tetrafen, fluorene, imyopeHOH, phenylindole, polyvinylcarbazole, polyvinylpyrene, 2-phenylnaphthalene, azapiren. acetylpyrene, -v h-o and / l 2,3-benzochrizene, 3,4-benzopyrene, 1,4-. bromine pyrene, polyvinyl tetralen, polyvinylperylene and polyvinyl tetrafen, as well as transporting electrons of the materrdpy, for example 2,4,7- trinitro-9-fluorenone, 2,4,5-7-tetranitro fluorenone, dinitroantratsen, dinitroakridin tetratsianpiren, 1dinitroantrahinon and poly-dimensional materials based on them such gpoliefiry, polysiloxanes, polyamides, polyurethanes, epoxides, block, graft or disordered dannye copolymers. The proposed electrophotographic element containing pigment and active. A transporting material capable of supporting the injection and transportation of photogenerated charges has a high efficiency of photogeneration of charge carriers and the ability to inject charge into the transporting material. The pigments used have a low sensitivity to radiation with a wavelength for which the active transporting material is substantially transparent. An active trailing material must support the injection of holes or electrons and should not absorb radiation with a wavelength to which the photoconductor is sensitive. Electron-vapor pairs are generated by the photosensitive pigment, then electrons are introduced into the active transporting material and transported through it. Bisbenzimidazole pigments are used in combination with active electrostatic materials capable of transporting holes or electrons for the manufacture of sensitive xerographic or icic or electrophotographic elements. Bisbenzimidazole pigments are effective when combined with materials transporting electrons. The most useful are the bis-zimidazoles of the general formula obtained by the known guide. X N P- / VC-: K, V,. / Trans - tCs-ouep c-isomer PP where K and K, „are the same or 2, alkyl, substituted alkyl, aryl, substituted aryl, halogen, nitro and / or amino. and a. Group; fl 1-4, form a condensed aroma such as benzene, naphtha or quinoline ring,. The hue or tone of the composition and the sensitivity spectrum depend on the structure of the pigments used, and the unchanged cis and trans isomers of the bisbenzimidazole pigments give optimal results. In addition to bis-benzimidazole pigments 1X), sensitizers, enhancers, synergents or other modifiers can be introduced into the composition. The proposed bisbenzimidazole pigments are well matched with a majority of active transporting materials and have an optimum sensitivity to radiation with a wavelength of 4000 - 6500 A, for which the active transporting material must be sufficiently transparent. In contrast, many well-known photoconductors do not combine well with the active transporting materials used and do not efficiently inject photogenerated charges into the surrounding or surrounding active transporting matrix. This procedure requires the use of half of the order of 5. Yu in / cm, which is almost unacceptable. The proposed pigments are applied with transporting materials in relatively small quantities in a xerographic photoreceptor of either a layered structure or a binder based structure. The proposed electrophotographic element is an electrically conducting substrate and a layer of a photoconductor, coated on top with an active transporting material. The photoconductor layer (trans-isomer of the bisbenzim-unsubstituted dazole pigment) may be coated. a relatively thick layer of electron-accepting material, such as 2, J4,7-trinitro-9-fluorenone, which is capable of supporting injection and transport of electrons. The properties of pigments and their compatibility with active transporting material allow using relatively thin layers of them without losing their effectiveness. On -fig. 1 shows an electrophotographic element comprising a rigid or flexible metal substrate 1 (brass, aluminum, gold, platinum, steel); a thickness, in the form of a sheet, tape or cylinder; a photoconductive single layer 2 containing a bisbenimidazole pigment and a sufficiently transparent active transport layer 3. j The substrate can also be made from paper, metallized paper, plastic foxed, coated with a thin layer of copper oxide j or aluminum, or glass coated with a THIN layer of chromium or tin oxide. | In some gizmos, it may be non-conducting or completely absent. The thickness of the photoconductive layer O, O5: 2Q, O microns. When the thickness of the layer is more than 20 microns, the pigment content in the lamina increases. If the thickness is less than 0, the thickness of the layers is 1 s & ineffective in the absorption of radiation. Usually, the pigment is dispersed in the matrix matrix. The matrix material can be any suitable organic substance used for such purposes, including inert matrix or binder materials. The concentration of the photoconductor depends on the type of binder used and is usually 5-99% of the volume of the photoconductive layer. When using an electron-inert binding material in combination with pigments to ensure contact between frequencies, it is necessary that the volume ratio between the photoconductor and the electron-inert binding material is at least 25%. The most suitable layers with a thickness of 0.2-0.5 microns. Since the pigments used are optimally sensitive to radiation with a wavelength of 4OOO65OQ A, exposure to a light source with such an emission wavelength interval causes the pigment to function with maximum efficiency with respect to the absorption of incident radiation. generation and generation of charge carriers. The thickness of the active transport layer is not critical, but it is determined by the amount of electrostatic charges needed to induce a field sufficient; to achieve the desired degree of injection and transport of electrons. It is usually 5-1OO microns. When using a layered structure (see Fig. 1) with a transparent substrate, exposure can be realized through the substrate without transmitting light through the layer of the active transporting mother; rial In this case, it is not required that; the active material was non-absorbent in the wavelength region used. In cases where full transparency is not required from the active material, the proposed element can be used to selectively record narrowband radiation emitted, for example, by lasers, recognize spectral patterns, color code duplication and color xerography. The transporting layer 3 may also contain a transport charge d material dispersed in a suitable inert binder, such as polystyrene, silicone resins, polycarbonates, polyacrylates and poly-OK - acrylates, poly-butyl methacrylates, iefirakrilaty and polyether methacrylates, chlorinated rubber, vinyl polymers and copolymers (nolivinilhlorid or polyvinyl acetate), cellulose esters such as nitrocellulose or ethylcellulose, and alkyd resins. In addition, blends of such resins, whether or not containing plasticizers, can be used to improve the adhesives and flexibility of the coating. FIG. Figure 2 shows the photoreceiver1) 11th layer consisting of pigment particles 4 contained in the active transport of the first matrix on the basis of the binder 5. Optimal results are obtained when the content of the photoconductive pigment is from 0.1 to 5% relative to the volume of the active transporting layer pa based binder. Optimal results are obtained when the layers are 2-10 O microns thick, preferably 5-50 microns, and the sizes of the photosensitive particles O, O 1-1.0 microns. Although the layered structure (Fig. 1) differs from the photoreceptor based on the binder (Fig. 2), the function between the photo sensitive and active transporting materials is the same. A plate based on a binder is charged with charges of the same sign as that of the generated charges, which can be transported with active transporting material. When used as a bonding material transporting electrons, the plate is negatively charged, while using a material transporting the first hole, it is positive. A blocking layer may be placed at the interface between the photoreducer and the I receptor, which serves primarily to reduce potential leakage in the absence of activating radiation. In addition, the blocking layer helps to establish an electric field across the photoreceptor after charging. Any suitable blocking layer with a thickness of 0.1-1 microns may be used, for example, a layer of nylon, epoxy resin, alumina NIN oxide and various types of insulating resins (including polystyrenes, butadiene polymers and copolymers, polyacrylates and polymethacrylates, vinyl and alkyd resins and cellulose based resins). The resistivity of the active transporting material must be at least equal to 10–10 ohm-cm. In order to obtain optimum results, the total resistivity of the photoreceptor in the absence of activating radiation or injection of charges from photoconductive pigments should be 10 ohm-cm. FIG. Figure 3 shows the charged positive electron transport layer structure. The activating radiation (arrows 6) penetrates through the transport layer into the pigment layer, generating an electron-hole pair. The electron and hole are then separated in an electric field and the electron passes through the interface into an active transport layer, which is propelled by electrostatic attraction to the surface and neutralizes the positive charge there. Since only the photogenerated electrons can move in the electrically accepting transporting layer, large changes in the magnitude of the Noise potential can take place only when the electric field in the layered structure can cause the generated electrons to move from the photoconductor layer to the charged surface. Therefore, in the layered structure (Fig. 1), the photoreceptor from the electron transporting material should be positively charged, and: the photoreceptor from the transporting material is 9 negative. The opposite picture takes place when a layer based on a binder is used (Fig. 2). {Example 1. The aluminum substrate is coated at room temperature; a nylon layer thickness of about 2 microns was sprayed in a vacuum with a layer of trans-isomer of bisbenzimidazole (Endofast Orange Toner) about 8 microns thick, 17% polyf4-vinylcarbazole solution in 18O g of toluene and 2O g of cyclohexanone was applied to the formation of a layer thickness of 7 microns and the photoreceptor formed by air at 110 ° C for 2-24 hours. EXAMPLE 2 Analogously to Example 1, a plate was made using the cis isomer of unsubstituted bisbenzimidazole (Bot deux RRN) as a pigment. The plates obtained are charged with a negative corona discharge (up to a potential of 500 V), exposed to monochromatic light corresponding to the sensitivity of each pigment, using a tungsten lamp with an interference filter p with a bandwidth of 10O A and a maximum transmittance A. The initial voltage and the resulting discharge are measured in VQ, recorded with a DC probe connected to an electrometer for measuring voltages as a function of time. From the experiments, a xerographic maximum ij or gain factor (G), and a threshold field E (the field that gives the smallest recorded discharge) are obtained. From the magnitude of the initial discharge rate, it is possible to calculate the gain G, plotting the dependence of the initial xerographic gain G on the value of the applied field and using the formula:

9

p (dV / dT) T-0

  Ce3d / 6)

3 .., i, is the incident photon flux;

 - layer thickness; - dielectric constant e - electron charge.

A xerographic gain of one is observed when one carrier is excited per incident photon. The test results shown in the table show that both plates exhibit a good xerographic maximum gain (over 35%); the pigments used require the use of a relatively low threshold field (less than 2.5 V / micron), which allows them to be used in known xerographic machines; high discharge rates confirm an increase in the effective injection of generated charges from a layer containing bisbenzimidazole pigments. The dispersion of charge on charged surfaces graphically illustrates the efficiency of injection of charge carriers into the active transport layers of each plate.

When conducting similar experiments with an electron transporting photoreceptor containing the proposed pigments, the surface is charged with a rinsing charge and it is found that their xerographic properties are similar to the xerographic properties of materials transporting dfs (see table), i.e. they have acceptable xerographic gains and relatively low threshold fields.

Subject invention

Claims (9)

1. An electrophotographic element having a photoreceptor component comprising a compatible photo sensitive and active transport mat & characterized in that. 1O In order to increase the resistance to wear, chemical attack, light fatigue and increase the effective injection of 1 photogenerated charges from photosensitive material, the latter used bisbenzimidazole pigment, and: as an active transporting material - transporting charge; material that does not absorb radiation | with a wavelength of 4000 - 6500. 2. Element pop. 1, distinguished by the fact that the photoreceptor {component contains bisbenzimidazole ; :: pigment dispersed in active bonding transporting material. t 3. The element according to claim 1, wherein the photoreceptor component has a layered structure containing a layer of bisbenzimidazole pigment and a layer of active transporting material located above it. 4. The element according to claims 1–3, which means that the simple layer of bisbenzimidazole pigment is O, O5–20 microns thick, and the active transporting layer layer - thickness of 5-10 O microns. 5. The element according to p. 3 or p. 4, about tl and i is due to the fact that the ratio of the thickness of the active transporting material layer to the thickness of the photoconductor layer is maintained in the interval 2: 1 - 2OO: 1. 6, Element according to claims 1-5, about tl and h and lo. u and with the fact that bisbenzimidazole pigment can be obtained by the interaction of 1,4,5,8-naphthal and ntetracarboxylic acid with arylene or heterocyclic diamine. i 7. Element, in accordance with Clause 6, of tl and h a i 45 y and with the fact that, as a bis-bi-imidazole pigment, it is used} 1ene transisomer of the product of the interaction 1,4,5,8- ; naphthalenetetracarboxylic acid with o-phenylenediamine. 50 I 8. The element according to claim 6, which is based on the fact that the cyo-isomer I of the product of the interaction of 1,4,5,8-naphthalene tetracarboxylic acid with o-phenylenediamine is used as the bisbenzim of the dazole pigment. AND 9. The element according to claims 1-8, about tl and h ayush and the fact that as a transporting material used is a hole transporting material, such as carbazole, N -alkylcarbazole (such as N-ethyl or H- izopropilkarbazol), N - enilkarbazol, tetrafenilpiren, 1-alkilpiren (such as 1- methyl-1 etilpiren) perylene, chrysene, anthracene, tetracene, tetrafen, fluorene, non fluore-, phenylindole, polyvinylcarbazole, polivinilpiren, 2-phenylnaphthalene, azapiren. 12 acetylpyrene, 2, -benzochrizene, 3g4 benzopyrene, 1,4-bromopyrene, polyvinyl tetralen, polyvinyl perylene and polyvinyl tetrafen. 1O. An element according to claims 1-8, which is an example of the fact that an electron transporting material, for example 2,4,7-trinitro-9-fluorenone, is used as the active transporting material. 2,4,5,7-tetranitrofluorenone, dinitroanthracene, dicitroacridine, tetracyanopyrene, dinitroanthraquinone and polymeric materials based on them. 1 FIG. 2 fpuz.3