SU463275A3 - Electrophotographic element - Google Patents

Description

(54) ELECTROPHOTOGRAPHIC ELEMENT

one

This invention relates to xerography and concerns a new photosensitive element.

In xerography, a xerographic element, made in the form of a plate containing a photoconductive insulating layer, is used to form an image by first uniformly electrostatically charging its surface, then exposing it with activating electromagnetic radiation to selectively dissipate the charge in the illuminated areas of the photoconductive layer while simultaneously maintaining the latent electrostatic images in unexposed areas and its occurrence by the deposition of electrically ground electroscu particles on the surface of the photoconductive insulating layer to form a visible image.

Known photoconductive layers for xerography can be simple homogeneous layers of the same material, for example, vitreous amorphous selenium, or complex, containing photoconductors and other material.

When exposing the known photonic conducting layers, the photoconductivity in the layered structure is accompanied by charge transport over the volume of the photoconductive layer, which

It is observed, for example, in the case of the use of vitreous selenium and other homogeneous layered structures. In layers containing photoconductive substances and bonding (inactive inactive electrically insulating polymeric resins), photoconductivity, or charge transport, is achieved due to the high content of photoconductive pgment, which ensures contact of photoconductive particles.

In the case when the photoconductive particles are dispersed in the photoconductive matrix, photoconductivity arises due to the generation of charge carriers in the photoconductive

the matrix, as well as in the particles of the photoconductive pgmept.

A disadvantage of known materials is that their photoconductive surface during operation is exposed to the environment, in particular, it perceives abrasion, multiple chemical, thermal and light effects. This causes a gradual deterioration.

electrical characteristics of the photoconductive layer, which causes the appearance of defects and scratches on the surface, localized areas of stable conductivity, which

unable to sustain an electrostatic charge, and to a high dark discharge.

In addition, in such photoconductive layers, the photoconductor must be either 100% of the weight of the entire layer, as in the case of using a layer of vitreous selenium, or contained in a high concentration in the binder-based structure. The requirement for the photoconductive layer to consist of or solely of a photoconductor material limits the physical characteristics of the base plate, drum or tape, such as flexibility and adhesion of the photoconductive layer to the substrate, since these indicators are determined mainly by the physical properties of the photons. (resin) or matrix material, which in such cases should be contained in a layer in a smaller amount.

In order to increase resistance to wear, chemical and light effects, in the proposed electrophotographic element a photoconductive layer is used, which has the ability to generate electrons under the action of light, and a transparent active transporting layer that can transfer injected electrons and does not absorb radiation with such wavelengths which photoconductor is sensitive.

In the proposed electrophotographic element, it is advisable to use an active electron transporting layer containing phthalic anhydride, tetrachlorophthalic anhydride, benzyl, mellitic anhydride, di- (tricyanobenzene), picryl chloride, 2,4-dinitrochlorobenzene, 2,4-dinitrobrombenzene, 4-nitrobiphenyl, 4 -dinitrobiphenyl, 2,4,6-trinitroanisole, trichlorotrinitrobenzene, trinitrotoluene, 4,6-dichloro-1,3-dinitrobenzene, 4,6-dibromo, 3-dinitrobenzene, ".-dinitrobenzene, chlororanyl, bromoanil, aromatic or heterocyclic, orchemical, or heterocyclic, orchemical, or alterative connection, having e at least one substituent such as nitro, sulfo, carboxy or cyano, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetraiitrofluorenone, trinitroanthracene, dinitroacridene, tetracyanopyrene, dinitroanthraquinone, and use a photoconductive layer containing a photoconductor dispersed in a binder in a concentration of 5-99%.

It is also preferable to use a photoconductive layer with a single layer of photoconductor; It is desirable to use a photoconductive layer comprising, as a photoconductor material, an X-or p-form phthalocyanine pigment containing no metal. A photoconductive layer with a thickness of 0.05–20.0 microns and a transport layer with a thickness of 5 to 100 microns can be used. It is advisable to use an active transparent transport layer that does not absorb from

radiation with a wavelength of 4200-8000 A.

In the proposed electrophotographic element, it is desirable to maintain the ratio of the thickness of the transporting layer to the thickness of the photoradiating layer from 2: 1 to 200: 1.

It is advisable to apply the photoconductive layer on the support substrate.

A blocking layer can be introduced into the proposed electrophotographic element between the substrate and the photoconductive layer.

The electron transporting active layer contains the electron transporting material in such a concentration as is necessary for transporting electrons injected from the photoconductive layer.

The photoconductor is a material that is sensitive to light of certain wavelengths, the conductivity of which significantly increases according to the absorbed electromagnetic radiation; organic compounds with a large number of conjugated bonds are suitable.

An electrophotographic sensitive plate can be prepared, for example, from aromatic or heterocyclic electron acceptors, which facilitate the transport of photogenerated electrons from the photoconductive layer under the influence of an electric field.

The use of active transporting material enables the use of specific portions of the electromagnetic spectrum for selective xerographic copying.

Electroactive materials can be used in color xerography for copying individual colors in successive ways and producing a color print.

FIG. Figure 1 shows the proposed xerographic plate.

The plate includes a rigid or flexible substrate 1 or a mechanical carrier made of metal (brass, aluminum, gold, platinum, steel, etc.) in the form of a sheet, tape, cylinder, etc., which may have a thin plastic layer. As a substrate, you can use paper with a metallic layer, sheets of plastic coated with a thin layer of aluminum or copper oxide, glass coated with a thin layer of chromium or tin oxide. The substrate must be somewhat electrically conductive or have a conductive surface and be strong enough. In some cases, however, it should not be conductive or may be completely absent.

The plate also includes a photoconductive monolayer or unitary layer 2, which contains photoconductive particles capable of generating electrons under the action of light and injecting them into the active matrix material.

The photoconductive layer based on the binder contains photoconductive particles in the electron-active matrix or layer 3 of the active transporting material. The photoconductive particles can be any suitable inorganic or organic photoconductor that generates hole – electron pairs. Typical inorganic photoconductive materials are inorganic crystalline compounds and inorganic photoconductive glasses, such as cadmium sulfide, cadmium sulfoselenide, cadmium selenide, zinc sulfide, zinc oxide and mixtures thereof, amorphous selenium, and selenium alloys such as selenium tellurium and selenium. Mouse K. Selenium can also be used in its hexagonal crystalline form, commonly called trigonal selenium. Typical organic photonic conductors are phthalocannine pigments (for example, metal-free X-form phthalocyanine), metal phthalocyanine pigments (for example, copper phthalocyanine), bisbenzimidazole, perylene, quinacridine, indigoid, and multi-quinone quinone pigments.

The photoconductive monolayer 2 can have any suitable thickness suitable for carrying out its functions in a xerographic plate to form an image, mainly 0.08-20.0 microns. With a thickness of more than 25 microns, there is a tendency for an undesirable buildup in the layer of residual pigment during operation, and with a thickness of less than 0.05 microns, the layers ineffectively absorb radiation. They prefer to use layers with a thickness of 0.2-5.0 microns, since in these cases the photoconductor functions to the maximum.

The proposed electrophotographic

the element allows the use of a minimum amount of photonic conductor in the photoconductive insulating binder.

The active transporting layer 3 contains an electron transporting material. (Aromatic or heterocyclic electron-withdrawing material) capable of both supporting the injection of electrons from the photoconductor w, its layer, and transporting them under the action of the applied field.

The active transporting matrix material must be transparent to the area of the electromagnetic spectrum at intervals

about

LENGTH waves from 4200 to 8000 A, since most of the suitable photoconductors are sensitive to light with such a wavelength.

The active transporting layer 2 contains an aromatic or heterocyclic electron-withdrawing substance capable of transporting negative charge carriers, mainly phthalic anhydride, tetrachlorophthalic anhydride, benzyl, mellitic anhydride, with L4L (tricyanobenzene, picryl chloride, 2,4-dinitrochloro benzene). dinitrobromobenzene, 4-nitrobiphenyl, 4,4-dinitrobiphenyl, 2,4,6-trinitroanizole, trichlorotrinitrobenzene, trinitro-o-toluene, 4,6-dichloro-1,3-dinitrobenzene, 4,6-dibromo-1,3- dinitrobenzene, p-dinitrobenzene, chloranil, bromanil and mixtures thereof.

Aromatic and heterocyclic compounds with more than one T (3 substituents such as a nitro, sulfo, carboxy or cyano group are particularly characteristic of their ability to transport electrons. It is preferable to use 2,4,7-trinitro-9- due to the excellent electron transforming properties fluorenone (TNP), 2,4,5,7-tetranitrofluorenone, trinitroanthracene, dinitroacridine, tetracyanopyrene and dinitroanthraquinone. Various polymers, for example polyethers, polysiloxanes, polyamides, polyurethanes and olnepoksidy, as well as block, graft random copolymer containing aromatic moieties.

The active transporting material must be transparent so that a sufficient amount of radiation from the source passes through it and that layer 2 can function as a generator

electrons. In this case, a sufficient amount of activating radiation reaches the photoconductive layer and causes discharging of the charged active transporting photoreceptor. Full transparency of the active material is not required for selective recording of narrow band radiation (e.g. laser radiation), for recognition of spectral patterns, color code duplication and color xerography.

Layer 3 may also contain a charge transporting material dispersed in sufficient concentration in a suitable inert binder to ensure contact of the particles, thus making it possible to achieve efficient transport of charge from the photoinjecting pigments through the layer.

Typical polymeric binders are polystyrene, silicone resins (resins DC-80, DC-804, and DC-896 from Dow Corning Corporation), Lexan-Polycarbonate from General Electric Co., acrylic and methacrylic ester polymers (Acryloid A10 and acryloid B72), full-sized essential

acromic n-acrylic acid derivatives produced by Room and Haas, polymerised butylt-hecrylates, chlorinated rubber, vinyl polymers and copolymers, cellulose esters and ethers (ethylcellulose,

nitrocellulose, etc.), alkyd resins produced by General Electric Co., etc. In addition, mixtures of such resins with plasticizers can be used to improve adhesion, flexibility and formability of coatings.

Tricresyl phosphate, dioctyl phthalate and the like are used as plasticizers.

The resistivity of the active matrix material should be at least 10 ohm-cm. In order to obtain optimal results, it is desirable that the resistivity of the active matrix material be such that the total resistance of the photoreceptor in the absence of

the activating illumination or charge injection of photoconductive pigments would be equal to l; om-see

In order to achieve efficient injection and transportation of electrical cables, active tractive layers 5–100 µm thick are used with a ratio of the crowd of the active transporting layer to the thickness of the photoconductive layer equal to 2: 1 to 200: 1.

FIG. Figure 2 shows another modification of the layered structure of the electrophotographic element. In this case, the photoconductive layer 1 contains a binder and dispersed in it crystalline particles of the photons. The binder may be any suitable organic substance used for such purposes, including inert binding materials. The concentration of the photo-diffusing material is varied depending on the type of binder used in the range of from 5 to 99% with respect to the volume of the photoconductive layer. If the inert binder is used with a photoconductive material,; then, in order to achieve the contact of the particles, it is necessary that the photoconductor material is at least 25% by volume relative to the inert binder.

A photoconductive layer with a thickness of 0.05-20 microns, generally 0.3-5 microns, can be used.

The most satisfactory results are obtained when the photoconductor particles in the binder-based layer have dimensions from 0; 01 to 1.0 microns.

Alternatively, the structure of the electrophotographic element may include a block-layer 4 (see FIG. 3) at the interface of the photo-receptor sub-plate. The blocking layer serves primarily to reduce potential leakage in the absence of activating radiation. In addition, it contributes to the establishment of an electric field after the charging stage. You can use a blocking layer with a thickness of 0.1 - 1 microns.

Nylon, enoxide resin, alumina and insulating resins of various types are suitable for forming such a layer, including polystyrene, butadiene polymers and copolymers, acrylic and methacrylic polymers, vinyl, alkydia and cellulose resins.

Thus, the proposed electrophotographic plate includes a photoinjecting pigment, photogenerating charge carriers upon excitation with radiation with a certain wavelength interval, and introduces photogenerated charge carriers into the adjacent active transporting material.

In addition, it contains a transparent active transporting material that provides radiation to the photo-injecting pigment, accepts photogenerated charge carriers from a photosensitive material, and actively transports these carriers to the oppositely charged surface or substrate for neutralization. This is graphically shown in FIG. four.

The xerographic material was negatively charged using a corona discharge.

The activating radiation (shown in Figs. 4-6 by arrows 5) penetrates through the transparent transport layer and reaches the photoconductive layer, thus creating an electron-hole pair. The electric and hole are then separated by the applied field and injected through the interface into the active transporting layer, into which the photogenerated electron is transported using electrostatic attraction forces through the active transporting layer system to the surface, where it neutralizes the positive charge previously applied to the corona.

bit

Since only photogenerated electrons can move in such a transport layer, large changes in the magnitude of the surface potential

can be observed only when the electric field in the layered structure is able to move the photogenerated electrons from the photoconductive layer through the active matrix layer to the charged top surface.

Therefore, to achieve optimal results, it is necessary that the active matrix layer is positively charged.

FIG. 5 depicts an electrographic

a plate of a known type in which the sensitizing pigment 6 is dispersed in the layer 3 of the photoconductive binder material in order to increase the sensitivity of the material.

Light creates photogenerated holes and electrons in the electrophotographic layer either in the photonic binding material or in the pigment material depending on the incident radiation.

Since the majority of charge carriers occurs near the surface of the photoinsulating element or on the surface, the transport of charges does not pose serious problems. Therefore, in part A, the light causes

photogeneration of an electron and a hole in a photoconductor, and in part B - photoheprisation in a pigment.

In order for the pigment to provide the effect of increasing the sensitivity of the electrophotographic element, it is necessary

relatively high concentration in the bed and

finding the pas above the surface or near the surface of the phototrector.

Photogeneration (see Fig. 4) occurs

Exclusively in the photoconductive layer is a photoparticle of the ppx particles, the active transporting material is sufficiently transparent for the incident radiation, and the photoconductor material is well protected by the active layer, active matrix binding, and the photoconductor may not be on or near the photoreceptor material.

FIG. 5 shows that a significant amount of it is necessary for the pigment to function in the material on or near the surface.

FIG. 6 depicts a photoreceptor in which the photosensitive pigment 6 is dispersed in an inert polymeric material 3 in two different concentrations.

Since no photogeneration occurs in the polymer binder, it is usually necessary that the photoconductive pigment or dye be present in sufficient concentration or ensure the geometric proximity of the particles to maintain injection of charges throughout the binder based system.

In Part A, where there is a high concentration of pigment, light creates a photogenerated hole-electron pair, which is then transported to a positively charged surface. At the same time, in Part B, where the pigment concentration is insufficient to ensure the proximity of the particles, the incident light creates a hole-electron pair, which is trapped due to the inability of the binder-based system to transport photogenerated charges to other pigment particles or to the charged surface.

In addition, because of the need for particles to contact in an inert binder structure (according to FIG. 6), problems arise with resolution, since the geometry of the particles may not correspond to the direction of propagation of the incident light, thereby causing irregular scattering Yes.

When the two-layer configuration (layer based on a bonding conductor — and an active transporting material) is strong enough to form a self-supporting element (referred to as “film”), you can eliminate the physical basis or carrier element and replace it with any device well known in the art. the plane previously created by the base layer. During operation, the grounded plane creates a source of image charges with both fields.

The deposition of an insulating two-layer structure based on a binder according to the invention of sensitizing charges of the desired polarity causes the same charges in the grounded plane of opposite polarity to migrate to the interface at the photoconductive insulating layer. Without this, the capacitance of the insulating element would be such that it would not be able to absorb enough charge to sensitize the layer to a xerographically useful potential. An electrostatic field arises between the deposited charges on one side of the xerographic two-layer element and the induced charges (from a grounded plane) on the other side. This creates a voltage in the xerographic element such that when (in the photoconductive layer) the electron is excited by a photon in the conduction band, as a result of which a hole-electron pair is created, the charges migrate under the action of this field, creating a latent electrostatic image. Therefore, if a physically grounded plane is excluded, then it can be replaced by deposition on opposite sides of a two-layer xerographic insulating film at the same time as electrostatic charges of opposite polarity. Thus, if positive electrostatic charges are placed on one side of the film using a corona charge, the simultaneous deposition of negative charges on the other side

films also using corona charging will create an induced, i.e. equivalent, grounded plane inside the film body, as if charges of opposite polarity were applied to the interface, being from a truly grounded plane. Such an artificial grounded plane makes it possible to perceive a sensitizing charge suitable for use and at the same time provides

charge migration under the action of an applied field when exposed to activating radiation. Further, the term “conductive base” should be understood both as a physical base and “artificial, described above.

The physical form of the xerographic active transport plate on the basis of the binder can be made arbitrarily, as required by the designer, in the form of a plane, a sphere, a cylinder, etc. The plate can be flexible or rigid.

Example 1. A plate with a photosensitive layer structure similar to that shown in FIG. 1, made by coating the aluminum substrate, put a dip into 3% Zytel nylon (Du Pont) solution in denatured alcohol to form a blocking layer with a thickness of 0.2 microns, drying

within 30 minutes by vacuum deposition of a layer of amorphous selenium (thickness 1 micron) on a blocking layer, cooled to 0 ° C and deposition in vacuum on an amorphous selenium layer (by evaporation of a 2,4,7-trintro-9-fluorenone) layer with a thickness of 10 micron The plate is then placed in an Xerox model D xerographic machine. A copy of the original is obtained by positively charging the plate to a value of 800 volts and exposing the original

radiation with an interval of wavelengths from 4200

about

TO 6500 A. The image produced on the plate is developed and transferred to paper, as a result of which a copy of the original of excellent quality is obtained, which by this indicator is comparable to the copy obtained using a conventional electrophotographic plate with amorphous selenium. An active transporting photoreceptor is used to produce a plurality of horses, and its surface is easily cleaned. Example 2. An electrophotographic plate was fabricated in Example 1, but on a blocking layer and an anhydrous layer of 2 microns of metal-free phthalocyanine (organic pigment) | 3-shape was made by immersing the substrate with a blocking layer in a solution of phthalocyanine pigment in dioxane and dichloromethane and substance for several hours. After the substance in vacuum, a layer of dinitroacridenum with a thickness of 20 microns is applied (see Example 1) to form an active transporting superlayer. The electrophotographic plate is used to obtain copies of good quality (see example 1). Example 3. 10 g of a lexicol polycarbonate resin is dissolved in a mixture of 40 g of dioxane and 40 g of dichloromethane, 10 g of 2,4,7-trnitro-9-fluorenone are added to the solution and the solution is mixed until the dissolution of the components is complete. A layered structure is prepared as described in example 1 by immersing a substrate with a blocking layer in a copper phthalocyanine composite and a solvent to form a layer 3 microns thick. Then, on a layered plate with a phthalocyanine layer a layer (10 microns thick) is formed (by immersion in a solution with 2,4,7-trinitro-9-fluorenone and lexan), the plate is dried for 24 hours and used to make copies of good quality, as in the example 1. The subject matter of the invention is 1, an electrophotographic element having an electrical conductor of a chuy substrate, a photoconductive layer with a photoconductor and an active transporting layer, made of organic material, covering the photoconductor of the 1ci layer, characterized in that, in order to increase wear resistance, The effects of photochemics and light are the effects of the photoconductive layer, which has the ability to generate electrons under the action of light, and a transparent active transporting layer capable of transporting the injected electrons and not absorbing radiation with wavelengths to which the photoconductor is sensitive. 2. Element no. 1, characterized in that it utilizes an active electron transporting layer containing phthalic anhydride, tetrachlorophthalic anhydride, benzyl, mellitic anhydride, di-cyanobenzene, picryl chloride, 2,4-dinitrochloro-beisole, 2,4-dinitrobrombenzene, 4- nitrobiphenyl, 4,4-dinitrobiphenyl, 2,4,6-trinitroanisol, trichlorotrinitrobenzene, trinitrotoluene, 4,6-dichloro-1,3 dinitrobenzene, 4,6-dibromo-1,3-dinitrobenzene, p-dinitrobenzene, chloroyl, bromoanil, an aromatic or heterocyclic organic compound having at least one such a substituent such as nitro, sulfo, carboxy or cyano, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitrofluorenone, trinitro anthracene, dinitroacridene, tetracyanopyrene, dinitroanthraquinone. 3. An element according to claim 1 or 2, characterized in that it uses a photoconductive layer containing a photoconductor dispersed in a binder at a concentration of 5-99%. 4. The element according to claim 1 or 2, of which is that it uses a photoconductive layer with a single layer of photoconductor. 5. An element according to claim 4, characterized in that the photoconductive layer includes phthalocyanine pigment of the X- or p-form as a photoconductive material, which does not contain metal. 6.Item but nn. 1-5, characterized in that it uses a photoconductive layer with a thickness of 0.05-20.0 microns and a transporting layer of a wavelength, another 5-100 microns. 7.Item on PP. 1-6, characterized in that the active translucent transport layer is used in the letters, not ABSORPTION and radiation e of a wavelength of 4200-8000 A. 8. Element according to claims. 1-7, characterized in that in it the ratio of the thickness of the transnorting layer to the thickness of the photoconductive layer is maintained from 2: I to 200: 1. 9. The element according to claims. 1-8, which differs in that the photon-conducting element is deposited on the support substrate. 10. Elemept according to claim 9, of which is HI, and with the fact that a blocking layer is inserted between the substrate and the photoconductive layer.