JP2004348152A - Electrophotographic method and electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic method using a photoreceptor of high sensitivity which does not cause a decrease in the electrification property or an increase in the residual potential when the photoreceptor is repeatedly used for a long time, and to provide an electrophotographic apparatus using a photoreceptor of high sensitivity which does not cause the decrease in the electrification property or the increase in the residual potential when the photoreceptor is repeatedly used for a long time. <P>SOLUTION: The electrophotographic method is carried out by repeatedly subjecting a photoreceptor comprising at least a charge generating material and a charge transporting material to at least electrification, exposure, development, transfer, cleaning and discharge. The method is characterized in that as a charge transport material, a charge transport material having the absorption spectrum in a charged state in a near IR region is used, and at least one emission wavelength region in one kind or a plurality of irradiation light for the photoreceptor differs from the absorption peak wavelength of the charge transporting material in a charged state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electrophotographic method and an electrophotographic apparatus, and in particular, to an electrophotographic method and an electrophotographic apparatus which are excellent in stability, in which the chargeability of a photoreceptor does not decrease even after repeated use and the residual potential does not increase.

  As the electrophotographic method, the Carlson process and other various deformation processes are known, and are widely used in electrophotographic devices such as copying machines and printers. In these electrophotographic methods, an organic photoreceptor using an organic photosensitive material has been used in recent years from the viewpoint of cost, mass productivity, and pollution-free properties.

  Examples of the organic photosensitive material include a photoconductive resin represented by polyvinyl carbazole (PVK), a charge transfer complex type represented by PVK-TNF (2,4,7-trinitrofluorenone), and a phthalocyanine-binder. Known are pigment dispersion type, function-separated type using a combination of a charge generation material and a charge transport material, and in particular, functionally separated organic photoreceptors have high sensitivity and high-speed response comparable to inorganic photoreceptors. Organic photoreceptors, which are at the center of practical application and have a charge-generating material that absorbs mainly from the visible part to the near-infrared part and a charge-transporting material that mainly absorbs in the ultraviolet, are known. And useful.

  In a function-separated type organic photoreceptor, when the photoreceptor whose surface is charged is exposed, light passes through the transparent charge transport layer and is absorbed by the charge generation material in the charge generation layer. The charge generating material absorbs light to generate charge carriers. The generated charge carriers are injected into the charge transport layer, and move in the charge transport layer along the electric field generated by the charge, thereby neutralizing the surface charge of the photoconductor. As a result, an electrostatic latent image is formed on the surface of the photoconductor.

  However, although the function-separated type organic photoreceptor has high sensitivity and high-speed response, when used repeatedly and continuously, the chargeability is reduced and the residual potential is increased, so that there is a problem in durability.

  On the other hand, Japanese Patent Application Laid-Open No. 55-67778 (Patent Document 1) discloses that when the light excluding the wavelength range absorbed by the charge transport layer is used as the irradiation at the time of the image exposure processing and at the time of the static elimination exposure processing, it is repeatedly used. In this case as well, it is described that a decrease in chargeability is suppressed, a rise in residual potential is reduced, and fatigue over time in photosensitive characteristics is slightly improved. Further, Japanese Patent Application Laid-Open No. 63-4264 (Patent Literature 2) discloses that irradiation of a photoconductor at the time of image exposure processing has a longer wavelength than light having a peak wavelength on the longest wavelength side absorbed by the charge generating material. It is disclosed that the use of light prevents a decrease in chargeability and a rise in residual potential, thereby improving the durability of the photoconductor. However, even with these methods, the change with time of the photoreceptor characteristics cannot be sufficiently suppressed, and there is still a problem in durability.

  Japanese Patent Application Laid-Open No. 57-8550 (Patent Document 3) discloses that in a photoreceptor using a specific disazo pigment, light having a wavelength range of 460 to 700 nm is used as exposure for all or a part of exposure processing. It is described that by doing so, the electrostatic fatigue of the photoreceptor is reduced and a high quality image is obtained. However, the durability of the photoreceptor was insufficient even by the above technique.

  The cause of the electrostatic fatigue phenomenon of the photosensitive member as described above has not been clarified, and no decisive measures have been taken against it. As long as the photoreceptor fatigue phenomenon during repeated use remains one of the factors that hinders high durability of the photoreceptor, a highly durable and highly sensitive photoreceptor that does not cause a reduction in chargeability and fluctuation in residual potential even after repeated use. The use of the body is not complete. Therefore, further improvement in this regard has been strongly desired.

JP-A-55-67778 JP-A-63-4264 JP-A-57-8550

  A first object of the present invention is to provide an electrophotographic method using a highly sensitive photoreceptor in which the chargeability does not decrease and the residual potential does not increase when repeatedly used for a long time. A second object of the present invention is to provide an electrophotographic apparatus using a highly sensitive photoreceptor which does not decrease in chargeability and does not increase in residual potential when used repeatedly for a long period of time.

  The present inventors have conducted intensive studies from the viewpoint of photochemical reaction and deterioration of the charge transporting material with respect to the decrease in chargeability of the photoreceptor caused by repeated use and the increase in the residual potential during exposure. In the photoreceptor, it has been found that the light absorption of the charge transport material in the charged state is closely related to the electrostatic fatigue (reduction in chargeability and increase in residual potential) of the photoreceptor, and completed the present invention. Was.

  That is, the electrostatic fatigue of the function-separated organic photoreceptor has been regarded as a phenomenally irreversible reaction, but very few studies have analyzed it. With respect to such an electrostatic phenomenon, the present inventor has considered that it is appropriate to approach from an irreversible reaction involving an organic material as long as the material used for the photoreceptor is an organic substance.

  As described above, in the function-separated type organic photoreceptor, when the photoreceptor whose surface is charged is exposed, the irradiated light is not absorbed by the charge transporting material of the charge transporting layer, and the charge of the charge generating layer is not absorbed. Absorbed by generated material. The charge-generating material that has absorbed the light generates charge carriers, which are injected into the charge-transporting layer, move between the charge-transporting materials along the electric field generated by the charging, and neutralize the surface charge of the photoreceptor. Sum up. As a result, an electrostatic latent image is formed on the surface of the photoconductor.

  The phenomenon of charge transfer through the charge transport layer is based on a hopping conduction mechanism that transfers charge from molecules of the charge transport material in the charged state to molecules of the charge transport material in the adjacent uncharged (neutral) state. Further, in this charged state, when the charge transport material is a hole transport material, it is in a cation radical state, and when the charge transport material is an electron transport material, it is in an anion radical state.

  An uncharged charge transport material generally does not have light absorption in the visible light region, but when it becomes charged, it becomes light absorbing from the visible light region to the near infrared light region. The charged state of the cation radical state or the anion radical state is more unstable than the uncharged state so that it cannot be isolated. Unstable charge-transporting materials have light absorption from the visible light region to the near-infrared light region, so they absorb light when repeatedly exposed, causing electronic transitions, and gradually becoming irreversible. It is highly probable that the compound will decompose and degrade the charge transport function.

  From this point of view, we repeatedly studied the relationship between the light absorption of the charge state of the charge transport material and the chargeability and residual potential due to the repeated use of the function-separated photoreceptor using the charge transport material. The present invention has been achieved in that an increase in potential and the like can be effectively prevented.

  Accordingly, the present invention relates to (1) an electrophotographic method for repeatedly performing at least charging, exposure, development, transfer, cleaning, and charge elimination on an electrophotographic photosensitive member composed of at least a charge generation material and a charge transport material. As the charge transporting material, a charge transporting material having an absorption spectrum in a charged state in the near-infrared region, and at least one emission wavelength range of one or a plurality of irradiation lights on the photoreceptor is in a charged state of the charge transporting material. An electrophotographic method characterized in that the wavelength is different from the absorption peak wavelength. ", (2)" One or more of the irradiation light to the photoreceptor substantially contains the absorption light in the charged state of the charge transport material. (3) "Electrophotographic method according to (1) above," wherein one or more of the irradiation light to the photoreceptor is coherent light. (4) The electrophotographic method according to (1) or (2), wherein the irradiation light is at least one of image exposure and static elimination exposure. Of electrophotography. "

  The present invention also provides (5) an electrophotographic photosensitive member composed of at least a charge generating material and a charge transporting material, a charging unit, an exposing unit, a developing unit, a transferring unit, a cleaning unit, and a discharging unit. In the electrophotographic apparatus, the charge transporting material uses a charge transporting material having an absorption spectrum in a charged state in a near infrared region, and at least one emission wavelength of one or a plurality of irradiation lights on the photoconductor. Wherein the region has a wavelength different from the absorption peak wavelength of the charge-transporting material in the charge-transporting material. " (5) The electrophotographic apparatus according to the above (5), which does not substantially contain absorbed light in a charged state. ", (7)" Electrophotography means that one or more of the exposure means is coherent light. It provides an electrophotographic apparatus. "According to (5) or (6) to symptoms.

  According to the electrophotographic method and the electrophotographic apparatus of the present invention, the wavelength range of exposure to the photoreceptor does not have or is reduced in the wavelength range in which the charge-transporting substance in the charged state is absorbed. When repeatedly used, it is possible to effectively prevent electrostatic fatigue of the photoconductor, that is, a decrease in the charged potential and an increase in the residual potential.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram illustrating an example of the electrophotographic method and an example of the electrophotographic apparatus of the present invention. In this electrophotographic apparatus, a static elimination exposure section (2), a charging charger (3), and an eraser (4) are arranged close to the upper surface of a drum-shaped photoconductor (1) and along the circumference in a counterclockwise direction. ), Image exposure section (5), developing unit (6), pre-transfer charger (7), transfer charger (10), separation charger (11), separation claw (12), pre-cleaning charger (13), fur brush (14) A cleaning brush (15) is sequentially attached. Further, a registration roller (8) for feeding the transfer paper (9) between the photoreceptor (1), the transfer charger (10) and the separation charger (11) is provided. The photoreceptor (1) comprises a drum-shaped conductive support and a photosensitive layer in close contact with the upper surface thereof, and rotates counterclockwise.

  In the electrophotographic method using the above electrophotographic apparatus, the photoreceptor (1) rotates counterclockwise, is positively or negatively charged by the charger (3), and is further charged by the eraser (4). After the residual toner is cleaned, an electrostatic latent image is formed on the photoconductor (1) by exposure from the image exposure unit (5).

  In the developing unit (6), toner is adhered to the photoreceptor (1) to develop the electrostatic latent image, and the charging state of the toner image is adjusted by the pre-transfer charger (7). ), The toner image is transferred to the transfer paper (9), the electrostatic adhesion between the photoconductor (1) and the transfer paper (9) is eliminated by the separation charger (11), and the transfer paper ( 9) is separated from the photoreceptor (1). After the transfer paper (9) is separated, the surface of the photoconductor (1) is cleaned by the pre-cleaning charger (13), the fur brush (14) and the cleaning brush (15). This cleaning can also be performed by removing the remaining toner with only the cleaning brush (15).

  When image exposure is performed by applying positive or negative charge to the photoconductor, a positive or negative electrostatic latent image is formed on the photoconductor. If this is developed with a negatively or positively charged polarity toner, a positive image is obtained. Conversely, if this is developed with a positively or negatively charged polarity toner, a negative image is obtained. A known method can be applied to such development. Also, static elimination can be performed by applying a known method.

  In this example, the conductive support is shown as a drum, but a sheet or an endless belt can be used. As the pre-cleaning charger, known charging means such as a corotron, a scorotron, a solid state charger (solid state charger), a charging roller and the like can be used. Although the above-mentioned charging means can be usually used for the transfer charger and the separation charger, a charger in which the transfer charger and the separation charger are integrated as shown in FIG. 1 is efficient and preferable. As the cleaning brush, a known brush such as a fur brush or a mag fur brush can be used.

  As a light source used in the image exposure section and the charge removal exposure section, a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), an electroluminescence (EL), and the like are used. be able to. In the present invention, light from a normal light source is transmitted through various filters such as a sharp cut filter, a band pass filter, a near-infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter to obtain a desired wavelength range. Of light can be applied. Such a light source or the like can be used in an exposure section such as a pre-image exposure section, a pre-transfer exposure section, and a pre-cleaning exposure section shown in FIG.

  As described above, the photoreceptor used in the electrophotographic apparatus of the present invention receives a plurality of types of exposure. That is, the charge transport material that has been irradiated with the light in the image exposure unit is then irradiated with light in, for example, the charge removal exposure unit. That is, the light irradiated to the photoreceptor does not include the wavelength spectrum absorbed by the charge-transporting material in the charged state, or the greater the amount of light that does not include the wavelength spectrum absorbed by the charged charge-transporting material, The chargeability of the photoreceptor does not decrease, the residual potential does not increase, and the durability is improved. Therefore, in the present invention, such light is employed in at least one type of exposure unit, and is preferably employed in the image exposure unit and / or the charge removal exposure unit.

  FIG. 2 is a schematic diagram illustrating another example of the electrophotographic method and another example of the electrophotographic apparatus of the present invention. In this example, the belt-shaped photoreceptor (21) is driven by drive rollers (22a) and (22b), is charged by a charger (23), is exposed by an image exposure unit (24), and is developed (shown). ), A series of image operations including a transfer by a transfer charger (25), a pre-cleaning exposure by a pre-cleaning exposure unit (26), a cleaning by a cleaning brush (27), and a charge removal exposure by a charge removal exposure unit (28). It is repeated. In this case, the exposure of the exposed portion before cleaning is performed from the conductive support side of the photoconductor (21). Of course, in this case, the conductive support is translucent.

  The electrophotographic method and the electrophotographic apparatus illustrated above are merely examples of the embodiments of the present invention, and other embodiments are of course possible. For example, in FIG. 2, the exposure before cleaning can be performed from the photosensitive layer side, and the exposure of the image exposure section and the charge removal exposure section can also be performed from the conductive support side.

  Further, the irradiation light employed in the present invention is used in at least one type of exposure unit. For example, in the example of FIG. 2, as the light irradiation step, image exposure, pre-cleaning exposure, and static elimination exposure are illustrated, but in addition, pre-transfer exposure, pre-exposure of image exposure and other known light irradiation steps or An apparatus may be provided, and the photoconductor may be irradiated with the light of the present invention in at least one step. In particular, it is preferable to irradiate such light in the image exposure section or the charge removal exposure section.

  The electrophotographic means of the present invention as described above may be fixedly incorporated in an apparatus such as a copying machine, a facsimile, a printer, or the like, or may be incorporated in such an apparatus in the form of a process cartridge. A process cartridge is a single device (part) including a series of electrophotographic methods or electrophotographic devices that incorporate a photoconductor and includes a charging unit, an exposing unit, a developing unit, a transferring unit, a cleaning unit, and a discharging unit. , Can be incorporated in other devices.

  FIG. 3 is a cross-sectional view illustrating the concept of an electrophotographic photosensitive member composed of a charge generation material and a charge transport material used in the present invention. This is provided with a single-layer photosensitive layer (33) containing a charge generating substance and a charge transporting substance as main components on a conductive support (31). 4 and 5 are cross-sectional views showing the concept of another electrophotographic photosensitive member used in the present invention. Here, a charge generating layer (35) mainly composed of a charge generating substance and a charge transporting layer (37) mainly composed of a charge transporting substance are laminated on a conductive support (31) to constitute a photoreceptor. You.

As the conductive support (31), those exhibiting a conductivity of 10 ¹⁰ Ωcm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, silver, gold, platinum, tin oxide, indium oxide, etc. Metal oxides coated on film or cylindrical plastic or paper by vapor deposition or sputtering, or plates of aluminum, aluminum alloy, nickel, stainless steel, etc. A tube or the like whose surface has been treated by polishing or the like can be used.

Next, the photosensitive layer will be described. The photosensitive layer may be a single layer or a laminate. For convenience of explanation, a case where the photosensitive layer is composed of a charge generation layer (35) and a charge transport layer (37) will be described first.
The charge generation layer (35) is a layer containing a charge generation material as a main component. Inorganic and organic materials are used for the charge generating material, and typical examples thereof include monoazo pigments, disazo pigments, trisazo pigments, perylene pigments, perinone pigments, quinacridone pigments, quinone condensed polycyclic compounds, and squaric acid compounds. Dyes, phthalocyanine pigments, azurenium salt dyes, selenium, selenium-tellurium, selenium-arsenic alloys, amorphous silicon, and the like are used.

The charge generating materials are used alone or in combination of two or more.
The charge generation layer (35) of the present invention may use a binder resin in combination. As the binder resin, polyamide, polyurethane, polyester, epoxy resin, polyketone, polycarbonate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polyacrylamide and the like are used.

The charge generation layer (35) is obtained by dispersing the charge generation material together with a suitable binder resin using a suitable solvent such as tetrahydrofuran, cyclohexanone, dioxane, 2-butanone, or dichloroethane using a ball mill, an attritor, a sand mill, or the like. It can be formed by coating.
The thickness of the charge generation layer (35) is suitably about 0.01 to 5 μm, and preferably 0.1 to 2 μm.

The charge transport layer (37) is composed of a charge transport material and, if necessary, a binder resin. The charge transporting layer (37) can be formed by dissolving or dispersing the charge transporting material and a binder resin in a suitable solvent, and applying and drying this. If necessary, a plasticizer, a leveling agent, and the like can be added.
In the present invention, a charge transporting material having an absorption spectrum in a charged state in the near infrared region is used as the charge transporting material.

The charge transport materials include a hole transport material and an electron transport material.
Examples of the electron transporting material include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitroxanthone, 2,4,4 8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, 3, Known electron-accepting substances such as 5-dimethyl-3 ′, 5′-ditertiarybutyl-4,4′-diphenoquinone are exemplified.

Examples of hole transport materials include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, and triaryl Other known materials such as a methane derivative, a 9-styrylanthracene derivative, a pyrazoline derivative, a divinylbenzene derivative, a hydrazone derivative, an indene derivative, and a butadiene derivative are used.
These charge transport materials are used alone or in combination of two or more.

  As the binder resin used as required, polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer Coalescence, polyvinyl acetate, polyvinylidene chloride, polyarylate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol Thermoplastic or thermosetting resins such as resin and alkyd resin are exemplified.

As the solvent, tetrahydrofuran, dioxane, toluene, 2-butanone, monochlorobenzene, dichloroethane, methylene chloride and the like are used.
The thickness of the charge transport layer (37) is suitably from 5 to 100 μm.
In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer (37). As the plasticizer, those used as plasticizers for general resins such as dibutyl phthalate and dioctyl phthalate can be used as they are. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, and polymers or oligomers having a perfluoroalkyl group in a side chain are used.

Next, the case where the photosensitive layer has a single-layer structure (33) will be described. Also in this case, a function-separated type material composed of a charge generation material and a charge transport material is used.
That is, it can be formed by dissolving or dispersing the charge generating material and the charge transporting material in a suitable solvent together with a binder resin, if necessary, and applying and drying this. If necessary, a plasticizer, a leveling agent and the like can be added.
Further, a photosensitive layer in which a hole transporting material is added to a eutectic complex formed from a pyrylium-based dye or bisphenol A-based polycarbonate can also be used as a single-layer photosensitive layer.

In the electrophotographic photoreceptor of the present invention, an undercoat layer can be provided between the conductive support (31) and the photosensitive layer. Known undercoat layers can be used. The thickness of the undercoat layer is suitably from 0 to 5 μm.
In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. As the protective layer, a known layer is provided by a known method. The thickness of the protective layer is suitably about 0.5 to 10 μm.

Next, the relationship between the irradiation light to the photoreceptor and the absorption light in the charged state of the charge transport material will be described.
As described above, the photoirradiation step on the photoreceptor includes image exposure, pre-cleaning exposure, pre-transfer exposure in addition to static elimination exposure, pre-exposure of image exposure, and other known steps. Can also be used.
Irradiation light to the photoreceptor used in the present invention must basically contain a light component in a wavelength range absorbed by the charge generation material in the photosensitive layer (otherwise, no photocarrier is generated). Conventionally, research and development have been focused on how to efficiently irradiate light in the wavelength range absorbed by the charge generating material.
However, in most cases, the charge transport material has light absorption in the visible to near-infrared region in a charged state, and may partially overlap the light absorption wavelength of the charge generation material. Therefore, it is almost impossible to absorb light only in the charge-generating material without absorbing light in the charge-transporting material at all. Accordingly, the present invention provides a light irradiation method in which the amount of light absorbed in the charged state of the charge transport material is reduced or light is not absorbed as much as possible. Needless to say, when there is no overlap portion, it is best to irradiate light in that wavelength range.
Hereinafter, irradiation light to a photoreceptor composed of a charge transporting material having an absorption spectrum in a charged state in the near infrared region as the charge transporting material in the present invention will be described in detail with reference to FIGS.
FIG. 6 is a diagram schematically showing an absorption spectrum of a charge transport material in a charged state. There are two absorption peaks at wavelengths λ _A and λ _B.
FIG. 7 schematically shows a spectral range of light irradiated on the photoconductor. Of the half value (I _max / 2) wavelength of the peak value (I _max ) of the irradiation intensity, the shorter wavelength side is λ ₁ and the longer wavelength side is λ ₂ . In the electrophotographic method of the present invention, when the photoreceptor using the charge transport material shown in FIG. 6 is irradiated with light using the light shown in FIG. 7, (1) λ ₂ ≦ λ _A , ( Good results can be obtained by irradiating light in any of the following relations: 2) λ ₁ ≧ λ _A and λ ₂ ≦ λ _B , and (3) λ ₁ ≧ λ _B.
FIG. 8 schematically shows an irradiation light spectrum region having a threshold wavelength with respect to light irradiated on the photoconductor. The half-value (I _S / 2) the wavelength of the light intensity threshold (I _S) and lambda _3. When light is irradiated to the photoreceptor using the charge transport material shown in FIG. 6 using the light of FIG. 8, in the electrophotographic method of the present invention, light irradiation is performed while maintaining the relationship of λ ₃ ≧ λ _B. Good results are obtained. Note that, in the case of a similar continuous light and having a light-emitting component on the shorter wavelength side than the threshold value, contrary to FIG. 8, a method of irradiating light in a relationship of λ ₃ ≦ λ _A is the present invention, and The result is obtained.
On the other hand, as described above, a better result can be obtained if the charge transport material in the charged state is not absorbed as much as possible without reducing the irradiation light amount to the charge generation material. Such a light irradiation method can be easily realized when the light half width (λ ₂ −λ ₁ ) of the irradiation light is small, for example, in the case of coherent light.
FIG. 9 shows an absorption spectrum in the charged state of the charge transporting material similar to FIG. 6, but the half values λ _a , λ _b and λ _c , λ _{d of} two absorption peaks are defined.
When the light shown in FIG. 7 is irradiated on the photoconductor shown in FIG. 9, (1) λ ₂ ≦ λ _a , (2) λ ₁ ≧ λ _b and λ ₂ ≦ λ _c , (3) λ ₁ ≧ λ Irradiation with any of the relations _d and _d gives better results than the above case.
When the light shown in FIG. 8 is applied to the photoreceptor shown in FIG. 9, when the light is applied in the relationship of λ ₃ ≧ λ _d, a better result can be obtained as compared with the case described above. Note that, in the case of a similar continuous light, which has a light-emitting component on the shorter wavelength side than the threshold, contrary to FIG. 8, a method of irradiating light in _a relationship of λ ₃ ≦ λ _a is the present invention, and The result is obtained. Further, the absorption light of the present invention is substantially free is 7 described above in the charge state of the charge transport material, and lambda _b of FIG exposure conditions (e.g., so as not to further light absorption than the conditions of FIG. 8 9 (irradiating coherent light to a wavelength having a minimum absorption between λ _c ). In this state, better results can be obtained.

  A method for measuring the light absorption spectrum of the charge transport material in the charged state will be described. The upper and lower surfaces of the photosensitive layer or the charge transporting layer are sandwiched between two electrodes, and a dark current or a photocurrent is applied by applying a voltage between the electrodes, and the transmitted light absorption or reflected light is absorbed using a normal spectrophotometer. Measure.

  Further, another simple spectrum measuring method can be applied. That is, the charge transport material is dissolved in an organic solvent such as acetonitrile, methylene chloride, dimethylformamide and the like together with an unrelated salt (supporting electrolyte) such as tetraethylammonium perchlorate and tetrabutylammonium perchlorate, and then electrolyzed. The state is a cation radical state or an anion radical state. In this case, when the charge transporting material is a hole transporting material, the charge transporting material is oxidized at the anode to form a cation radical state, and when the electron transporting material is reduced at the cathode, it is converted to an anion radical state. This method is to measure the transmitted light absorption of an electron transporting material in a solution state in a cation radical state or an anion radical state using an ordinary spectrophotometer.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. The present invention is not limited at all by the following examples. In the examples, “parts” means “parts by weight”.

(Example 1)
On the surface of an aluminum cylinder, a coating liquid for an undercoat layer, a coating liquid for a charge generation layer, and a coating liquid for a charge transport layer comprising the following components were sequentially applied, and then dried and exposed to light. The body was made.
(1) Undercoat layer coating solution Alcohol-soluble nylon 5 parts Methanol 50 parts Isopropanol 20 parts (2) Charge generation layer coating solution 5 parts of charge generating material represented by the following chemical structural formula

ポリビニルブチラール ３部
テトラヒドロフラン ２００部
４−メチル−２−ペンタノン ９０部
（３）電荷輸送層用塗工液
次の化学構造式で表す電荷輸送物質 ８部

Polyvinyl butyral 3 parts Tetrahydrofuran 200 parts 4-methyl-2-pentanone 90 parts (3) Coating solution for charge transport layer 8 parts of charge transport material represented by the following chemical structural formula

ポリカーボネート １０部
塩化メチレン ８０部

Polycarbonate 10 parts
80 parts of methylene chloride

The light absorption spectrum of the charge generating material of Example 1 and the charge transporting material in the charged state was measured according to the method described above, and the light absorption wavelength region of the charge generating material was 400 nm to 680 nm. The absorption spectrum of the charge transporting material in the charged state (cation radical state) was as shown in FIG. In FIG. 10, λ _A = 474 nm, λ _B = 952 nm, λ _a = 425 nm, λ _b = 554 nm, λ _c = 840 nm, and λ _d = 1025 nm. Therefore, from the wavelength range of light absorption of the used charge generating substance, the irradiation light to the photoreceptor needs to include at least the wavelength range of 400 nm to 680 nm.

The electrophotographic apparatus shown in FIG. 1 was manufactured using a tungsten lamp (white light) as a light source of the image exposure unit and a tungsten lamp as a light source of the charge removal exposure unit. Further, a wavelength cutting filter was combined with each light source, and the half-value wavelengths of the image exposure and the charge removal exposure were set to λ ₁ = 480 nm and λ ₂ = 940 nm. Also, in an electrophotographic apparatus, when the photoreceptor is rotated and the electronic latent image of the image is rotated immediately before the developing unit, a surface voltmeter probe is provided on the surface of the photoreceptor so that the surface potential of the photoreceptor can be measured. Inserted.

(Examples 2 to 5 and Comparative Examples 1 to 4)
An electrophotographic apparatus was manufactured in the same manner as in Example 1 except that the wavelength cutoff filter for the light source in the static elimination exposure unit was changed. Further, in the electrophotographic apparatus, when the photoreceptor was rotated and the electronic latent image of the image was immediately before the developing unit, the surface potential of the exposed portion and the unexposed portion of the photoreceptor was measured. These results are shown in Table 1 as the half-value wavelength of the static elimination exposure, the surface potential after copying one sheet, and the surface potential after copying 10,000 sheets.

(Examples 6 to 11)
In Example 4, an electrophotographic apparatus was prepared in the same manner as in Example 4 except that a wavelength cut filter was added to the light source of the image exposure unit, and the surface potential of the exposed portion and the non-exposed portion was reduced. It was measured. These results are shown in Table 2 as the half-value wavelength of the image exposure, the half-value wavelength of the charge removal exposure, the surface potential after copying one sheet, and the surface potential after copying 10,000 sheets.

(Example 12)
An electrophotographic apparatus was manufactured in the same manner as in Example 10, except that the light source in the charge exposing unit was changed to a light emitting diode. The light emitting diode has an emission spectrum having a peak wavelength of 630 nm, and half-value wavelengths of 610 nm and 645 nm. Table 3 shows the surface potential of the photoreceptor measured in Example 12 after copying one sheet and after copying 10,000 sheets.

(Example 13)
An electrophotographic apparatus was manufactured in the same manner as in Example 12, except that the light source of the image exposure section was changed to a helium-neon laser, and the image exposure was performed using a polygon mirror. The emission wavelength of the helium-neon laser is 632.8 nm. Table 3 shows the surface potential of the photoreceptor measured in Example 13 after copying one sheet and after copying 10,000 sheets.

(Example 14)
On the surface of the electroformed nickel belt, a coating liquid for an undercoat layer, a coating liquid for a charge generation layer, and a coating liquid for a charge transport layer, comprising the following components, were sequentially applied and dried. And a photoreceptor was prepared.
(1) Coating liquid for undercoat layer 5 parts titanium dioxide powder 4 parts alcohol-soluble nylon 4 parts 50 parts methanol 20 parts isopropanol (2) coating liquid for charge generation layer
Oxytitanium phthalocyanine 4 parts Polyvinyl butyral 1 part Cyclohexanone 150 parts Tetrahydrofuran 100 parts (3) Coating solution for charge transport layer 9 parts of charge transport material represented by the following chemical structural formula

ポリカーボネート １０部
テトラヒドロフラン ８０部

Polycarbonate 10 parts Tetrahydrofuran 80 parts

When the light absorption spectrum of the charge generating substance of Example 14 and the charge transporting substance in a charged state was measured according to the method described above, the wavelength range of light absorption of the charge generating substance was 540 nm to 880 nm. FIG. 11 shows the absorption spectrum of the charge transport material in the charged state (cation radical state). In FIG. 11, λ _A = 497 nm, λ _B = 1022 nm, λ _b = 555 nm, and λ _c = 826 nm. λ _a is not displayed, it is λ _d is impossible to measure. Therefore, from the wavelength range of light absorption of the used charge generating substance, it is necessary that the exposure to the photoreceptor includes at least a wavelength range of 540 nm to 880 nm.

A semiconductor laser having a light absorption wavelength of 780 nm (image exposure was performed using a polygon mirror) was used as a light source of the image exposure unit, and a tungsten lamp was used as a light source of the charge removal exposure unit. The electrophotographic apparatus shown was manufactured. However, no pre-cleaning exposure was provided. Further, a half-wavelength of the charge elimination exposure was set to λ ₁ = 510 nm and λ ₂ = 810 nm by combining a wavelength cut filter with the light source of the charge elimination exposure unit. In an electrophotographic apparatus, a probe of a surface voltmeter was inserted into the surface of the photoconductor so that the surface potential of the photoconductor could be measured when the photoconductor rotated and the electronic latent image of the image came immediately before the developing unit. .

(Examples 15 to 18 and Comparative Examples 5 to 8)
An electrophotographic apparatus was manufactured in the same manner as in Example 14, except that the wavelength cutoff filter for the light source in the charge eliminating exposure unit was changed. In an electrophotographic apparatus, when the photoreceptor rotates and an electronic latent image of an image comes immediately before a developing unit (not shown in FIG. 2), the surface potential of an exposed portion and a non-exposed portion of the photoreceptor is measured. did. Table 4 shows the half-value wavelength of the static elimination exposure, the surface potential after copying one sheet, and the surface potential after copying 10,000 sheets.

(Example 19)
An electrophotographic apparatus was manufactured in the same manner as in Example 14, except that the light source of the charge exposing unit was changed to a light emitting diode. The emission spectrum of the light emitting diode has a peak wavelength of 840 nm, and the half-value wavelengths are 820 nm and 860 nm. Table 5 shows the surface potential of the photoreceptor measured in Example 19 after copying one sheet and after copying 10,000 sheets.
(Example 20)
An electrophotographic apparatus was manufactured in the same manner as in Example 14, except that the light source of the charge exposing unit was changed to a light emitting diode. The emission spectrum of the light emitting diode has a peak wavelength of 630 nm, and the half-value wavelengths are 620 nm and 645 nm. Table 5 shows the surface potentials of the photoreceptor after copying one sheet and after copying 10,000 sheets measured in Example 20.

(Example 21)
A coating solution for an undercoat layer, a coating solution for a charge generation layer, and a coating solution for a charge transport layer were sequentially coated and dried on an aluminum cylinder to prepare a laminated photoreceptor.
(1) Undercoat layer coating solution Alcohol-soluble nylon 5 parts Methanol 50 parts Isopropanol 20 parts (2) Charge generation layer coating solution 5 parts of charge generating material represented by the following chemical structural formula

ポリビニルブチラール ２部
テトラヒドロフラン ２００部
４−メチル−２−ペンタノン ９０部
（３）電荷輸送層用塗工液
次の化学構造式で表す電荷輸送物質 ８部

Polyvinyl butyral 2 parts Tetrahydrofuran 200 parts 4-methyl-2-pentanone 90 parts (3) Coating liquid for charge transport layer 8 parts of charge transport material represented by the following chemical structural formula

ポリカーボネート １０部
塩化メチレン ８０部

Polycarbonate 10 parts Methylene chloride 80 parts

The charge generation material used for this photoreceptor absorbs light of 400 nm to 780 nm. FIG. 12 shows an absorption spectrum of a charged state (cation radical) of the charge transporting material used for the photoreceptor.
From FIG. 12, it can be seen that λ _A = 480 nm, λ _B = 1264 nm, λ _a = 432 nm, λ _b = 522 nm, λ _D = 1039 nm, and λ _d = 1560 nm. On the other hand, in consideration of the absorption light wavelength range of the used charge generating material, the irradiation light to the present laminated photoreceptor needs to include at least light having a wavelength of 400 nm to 780 nm. As is clear from FIG. 12, the charge transport material used has very weak absorption between 550 and 780 nm, and light irradiation in this range applies light to the charge transport layer material as much as possible. It can be saved.

The electrophotographic photoreceptor was mounted on the electrophotographic apparatus shown in FIG. 1, and the image exposure light source was light of 460 to 640 nm (by a combination of a tungsten lamp and a filter). As a process for irradiating light of λ ₁ = 530 nm and λ ₂ = 1020 nm in a half range, a probe of a surface voltmeter was inserted so that the surface potential of the photoconductor immediately before development could be measured.

(Examples 22 to 25 and Comparative Examples 9 to 12)
An electrophotographic process similar to that of Example 21 was performed, except that the wavelength range of the static elimination light in Example 21 was changed to that shown in Table 6 by changing the wavelength cut filter.
Using each of the electrophotographic processes of Examples 21 to 25 and Comparative Examples 9 to 12, a copy test was repeatedly performed, and the surface potentials of the image-exposed portion and the non-exposed portion on the photoreceptor immediately before development were measured. The results are shown in Table 6.

(Example 26)
A coating liquid for an undercoat layer, a coating liquid for a charge generation layer, and a coating liquid for a charge transport layer comprising the following components are sequentially coated and dried on an electroformed nickel belt to form a laminated photoreceptor. Was prepared.
(1) Undercoat layer coating liquid Titanium dioxide powder 5 parts Alcohol-soluble nylon 4 parts Methanol 50 parts Isopropanol 20 parts (2) Charge generation layer coating liquid Oxytitanium phthalocyanine (Y-type crystal form) 4 parts Polyvinyl butyral 1 Part Cyclohexanone 150 parts Tetrahydrofuran 100 parts (3) Coating solution for charge transport layer 8 parts of charge transport material represented by the following chemical structural formula

ポリカーボネート １０部
テトラヒドロフラン ８０部

Polycarbonate 10 parts Tetrahydrofuran 80 parts

The charge generation material used for this photoreceptor absorbs light of 540 nm to 880 nm. FIG. 13 shows the absorption spectrum of the charged state (cation radical) of the charge transporting material used for this photoreceptor.
In FIG. 13, it can be seen that λ _A1 = 534 nm, λ _A2 = 579 nm, and λ _B = 1138 nm. With the same treatment as in the case of FIG. 12, λ _a = 483 nm, λ _b = 597 nm, λ _c = 1026 nm, and λ _d = 1248 nm are defined. On the other hand, in consideration of the absorption light wavelength range of the used charge generation material, the irradiation light to the present laminated photoreceptor needs to include at least light having a wavelength of 540 nm to 880 nm.

  The electrophotographic photoreceptor thus formed is mounted on the electrophotographic apparatus shown in FIG. 2 (however, there is no pre-cleaning exposure), and the image exposure light source is a 780 nm semiconductor laser (image writing with a polygon mirror), and the light is used as static elimination light. A process using a light emitting diode having an emission peak at 810 nm (half emission value is in the range of 790 to 830 nm) was used, and a probe of a surface electrometer was inserted so that the surface potential of the photoconductor immediately before development could be measured.

(Example 27)
An electrophotographic process was performed in the same manner as in Example 26, except that the static elimination light was changed to a light emitting diode having a light emission peak at 630 nm (half-emission value in the range of 610 to 645 nm).

(Comparative Example 13)
An electrophotographic process similar to that of Example 26 was performed, except that the static elimination light was changed to a tungsten lamp (white light).
Using each of the electrophotographic processes of Examples 26 and 27 and Comparative Example 13, a repetitive copy test was performed, and the surface potentials of the image-exposed portion and the non-exposed portion on the photoreceptor immediately before development were measured. It was shown to.

(Example 28)
A coating solution for an undercoat layer, a coating solution for a charge generation layer, and a coating solution for a charge transport layer were sequentially coated and dried on an aluminum cylinder to prepare a laminated photoreceptor.
(1) Undercoat layer coating solution Alcohol-soluble nylon 5 parts Methanol 50 parts Isopropanol 20 parts (2) Charge generation layer coating solution 5 parts of charge generating material represented by the following chemical structural formula

ポリビニルブチラール ３部
テトラヒドロフラン ２００部
４−メチル−２−ペンタノン ９０部
（３）電荷輸送層用塗工液
次の化学構造式で表す電荷輸送物質 ８部

Polyvinyl butyral 3 parts Tetrahydrofuran 200 parts 4-methyl-2-pentanone 90 parts (3) Coating solution for charge transport layer 8 parts of charge transport material represented by the following chemical structural formula

ポリカーボネート １０部
塩化メチレン ８０部

Polycarbonate 10 parts Methylene chloride 80 parts

The charge generation material used for this photoreceptor absorbs light of 400 nm to 680 nm. FIG. 14 shows an absorption spectrum of the charge transport material (cation radical) used in the photoconductor.
From FIG. 14, the peak wavelength, λ _A = 403 nm, λ _B = 624 nm, and λ _c = 819 nm are defined. From the figure, the half-value wavelength λ _b = 442 nm corresponding to λ _A (λ _a does not extend to the measurement), the half-value wavelength λ _c = 527 nm corresponding to λ _B , λ _d = 680 nm, and the half-value wavelength λ _e corresponding to λ _c = 771 nm and λ _f = 826 nm are obtained. On the other hand, in consideration of the absorption light wavelength range of the used charge generating material, the irradiation light to the present laminated photoreceptor needs to include at least light having a wavelength of 400 nm to 680 nm.

  The above electrophotographic photoreceptor is mounted on the electrophotographic apparatus shown in FIG. 1, the image exposure light source is a tungsten lamp (white light), and a light emitting diode having an emission peak at 670 nm as a neutralization light (half emission value is in the range of 650 to 690 nm). And a probe of a surface voltmeter was inserted so that the surface potential of the photoconductor immediately before development could be measured.

(Example 29)
An electrophotographic process was performed in the same manner as in Example 28 except that the static elimination light was changed to an argon ion laser (emission wavelength: 514.5 nm).
(Comparative Example 14)
An electrophotographic process was performed in the same manner as in Example 28, except that the static elimination light was changed to a light emitting diode having a light emission peak at 810 nm (half emission value was in the range of 610 to 645 nm).
Using each of the electrophotographic processes of Examples 28 and 29 and Comparative Example 14, a copy test was repeatedly performed, and the surface potentials of the image-exposed portion and the non-exposed portion on the photoreceptor immediately before development were measured. It was shown to.

1 is an example of a schematic diagram illustrating an electrophotographic method and an electrophotographic apparatus of the present invention. It is another example of the schematic explaining the electrophotographic method of this invention, and an electrophotographic apparatus. FIG. 2 is a cross-sectional view illustrating the concept of an organic photoconductor used in the present invention. FIG. 4 is another cross-sectional view illustrating the concept of the organic photoconductor used in the present invention. FIG. 4 is still another sectional view illustrating the concept of the organic photoreceptor used in the present invention. FIG. 3 shows a schematic diagram of a light absorption spectrum having two absorption peaks in a charge transport material in a charged state. FIG. 3 is a schematic diagram showing a spectrum of light having two absorption peaks irradiating a photoconductor and a half-value wavelength thereof. FIG. 4 is a schematic diagram showing an emission spectrum having a threshold wavelength in irradiation light to a photoconductor and a half-value wavelength of the threshold. FIG. 7 is a schematic diagram showing a light absorption spectrum of a charge transporting substance in a charged state similar to FIG. 6 and respective half-value wavelengths of two absorption peaks in the spectrum. 4 is a light absorption spectrum of a charged state charge transporting substance used in Examples 1 to 13. It is a light absorption spectrum of the charge transport material of the charge state used in Examples 14-20. It is a light absorption spectrum of the charge transport material of the charged state used in Examples 21-25. It is a light absorption spectrum of the charge transport material of the charged state used in Examples 26-27. It is a light absorption spectrum of the charge transport material of the charged state used in Examples 28-29.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 photoreceptor 2 static elimination exposure unit 3 charging charger 4 eraser 5 image exposure unit 6 developing unit 7 pre-transfer charger 8 registration roller 8
9 Transfer Paper 10 Transfer Charger 11 Separation Charger 12 Separation Claw 13 Charger Before Cleaning 14 Fur Brush 15 Cleaning Brush 21 Photoconductor 22a Driving Roller 22b Driving Roller 23 Charging Charger 24 Image Exposure Unit 25 Transfer Charger 26 Exposure Before Cleaning Part 27 cleaning brush 28 static elimination exposure part 31 conductive support 33 single photosensitive layer 35 charge generation layer 37 charge transport layer

Claims (7)

In an electrophotographic method in which at least charging, exposure, development, transfer, cleaning, and charge elimination are repeatedly performed on an electrophotographic photosensitive member composed of at least a charge generation material and a charge transport material, an absorption spectrum in a charged state as the charge transport material is obtained. Using a charge transport material in the near-infrared range, and that at least one emission wavelength range of one or more irradiation light to the photoconductor is different from the absorption peak wavelength of the charge state of the charge transport material. A characteristic electrophotographic method. 2. The electrophotographic method according to claim 1, wherein one or more of the irradiation light to the photoreceptor does not substantially include absorption light in a charged state of the charge transport material. 3. The electrophotographic method according to claim 1, wherein one or more of the irradiation light to the photoreceptor is coherent light. The electrophotographic method according to claim 1, wherein the irradiation light is at least one of image exposure and static elimination exposure. In an electrophotographic apparatus including at least an electrophotographic photosensitive member composed of a charge generation material and a charge transport material, a charging unit, an exposure unit, a development unit, a transfer unit, a cleaning unit, and a charge removal unit, An absorption spectrum in a charged state uses a charge transporting material in the near infrared region, and at least one emission wavelength range of one or a plurality of irradiation lights on the photoreceptor has a charge state of the charge transporting material. An electrophotographic apparatus, wherein the wavelength is different from the absorption peak wavelength. 6. The electrophotographic apparatus according to claim 5, wherein one or a plurality of light beams applied to the photoconductor does not substantially include absorbed light in a charged state of the charge transport material. 7. An electrophotographic apparatus according to claim 5, wherein one or more of the exposure means is coherent light.

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