JP5046908B2 - Electrophotographic photosensitive member and image forming apparatus using the same - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member and an image forming apparatus using the same. More specifically, the present invention relates to an electrophotographic photosensitive member that can be written with light having a short wavelength and an image forming apparatus using the same.

An electrophotographic image forming apparatus plays a part in a high-speed information processing system and its progress has been remarkable in recent years. Various methods are known as electrophotographic methods. Among them, the electrophotographic method using light as a recording probe improves the quality and reliability of print output in combination with the quality improvement of the light source itself. It is remarkable. Therefore, this method is used not only as a normal printer but also in a copying machine, and its importance is increasing more and more. Therefore, demand for image forming apparatuses using this method is expected to continue to grow.
In recent years, the above printer or copying machine is expected to have high image quality including colorization. In order to achieve high image quality, the diameter of the exposure light is reduced, and the resulting high-definition latent image / development on the photosensitive layer constituting the electrophotographic photosensitive member and the high-definition are stably brought about. It is desired to provide a photoconductor that can be used.

  To reduce the diameter of the exposure light, it is effective to shorten the oscillation wavelength of the light source. For example, when a short-wavelength laser whose oscillation wavelength is about half that of a conventional near-infrared laser (LD) is used as the light source, a laser beam spot on the photosensitive layer as shown by the following formula (1): The diameter can be considerably reduced in theory. Therefore, shortening the oscillation wavelength is very advantageous for increasing the writing density or resolution of the latent image.

d∝ (π / 4) (λf / D) (1)
In the formula, d represents the spot diameter on the photosensitive layer, λ represents the wavelength of the laser beam, f represents the focal length of the fθ lens, and D represents the lens diameter.
Techniques for shortening the oscillation wavelength of the light source include, for example, JP-A-9-240051 (Patent Document 1), JP-A-2000-47408 (Patent Document 2), and JP-A 2000-105479 (Patent Document 3). Etc. are described.
Japanese Patent Laid-Open No. 9-240051 JP 2000-47408 A JP 2000-105479 A

However, there are some problems in using a light shorter than the oscillation wavelength of a light source used in the past to form an image stably on the photosensitive layer.
First, the oscillation wavelength of a conventional light source is longer than 450 nm. Therefore, when writing on the photosensitive layer from the surface side, the exposure light source can be used even when the charge transport material used in the charge transport layer in the photosensitive layer is yellow. However, with a short wavelength laser, even when the charge transport material is yellow, the exposure light is blocked and the photosensitivity is lowered. In addition, the exposure light promotes the deterioration of the charge transport material itself. As a result, the function of the electrophotographic photoreceptor itself is degraded, and it becomes difficult to form an image stably on the photosensitive layer. Accordingly, it is necessary to use a charge transport material that is optically nearly colorless.

Next, compared with the absorption of light in the near infrared region and the accompanying charge generation process, those with respect to light with a short wavelength are greatly different in the interaction between a substance and light. That is, even if the same charge generating material is used, the energy of light having a short wavelength is clearly larger than the energy of light in the current near infrared region. The excess energy may have a secondary effect on the charge generating material during the process leading to the generation of carriers by light. Although the detailed process is not clear, it is cited as a problem for stability as a photoreceptor.
The past efforts to increase the resolution by using a short wavelength laser are described in the above-mentioned publication, but have not yet achieved both an increase in the resolution and the securing of stability as a photoreceptor.

で示される化合物を含有し、前記結晶型のオキソチタニルフタロシアニンが、Ｘ線回折スペクトルにおいて、ブラッグ角（２θ±０．２°）９．４°又は９．７°に最大回折ピークを示し、かつ少なくとも７．３°、９．４°、９．７°及び２７．３°に回折ピークを示すことを特徴とする電子写真感光体が提供される。 The inventors of the present invention use a charge generation material having a specific structure in the photosensitive layer, so that even when short-wavelength light is used as a writing light source, the dot reproducibility and durability are excellent, and the lifetime is long. The present inventors have found that an electrophotographic photosensitive member with high resolution and high image quality can be provided, and have reached the present invention.
Thus, according to the present invention, an electrophotographic photoreceptor having a photosensitive layer on a conductive substrate, the electrophotographic photoreceptor being writable by light having an oscillation wavelength in a wavelength range of 360 to 420 nm. The photosensitive layer is a crystalline form of oxotitanyl phthalocyanine ,
The following chemical formula (1)

Containing in compound represented by the crystal form of titanyl phthalocyanine, in the X-ray diffraction spectrum, the maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) 9.4 ° or 9.7 °, and There is provided an electrophotographic photosensitive member characterized by exhibiting diffraction peaks at least at 7.3 °, 9.4 °, 9.7 ° and 27.3 °.

  According to the invention, there is provided a semiconductor laser having an electrophotographic photosensitive member and means for charging, exposing, developing, transferring and cleaning the photosensitive member, wherein the exposing means has an oscillation wavelength in a wavelength range of 360 to 420 nm. Is provided as a writing exposure light source, and the electrophotographic photosensitive member is the above-mentioned electrophotographic photosensitive member.

According to the present invention, an electrophotographic photosensitive member capable of stably forming an excellent sensitivity characteristic and a high-resolution image by combining oxotitanylphthalocyanine having a specific structure and light having an oscillation wavelength of 360 to 420 nm. And an image forming apparatus using the same.
Further, when the photosensitive layer is a laminated type, it is possible to provide an electrophotographic photosensitive member capable of stably forming more excellent sensitivity characteristics and a high resolution image.
Furthermore, since the charge transport layer in the laminated photosensitive layer has a specific thickness, it is possible to provide an electrophotographic photoreceptor capable of stably forming more excellent sensitivity characteristics and high-resolution images.

Furthermore, by adding an inorganic filler to the outermost surface layer of the photosensitive layer, it is possible to provide an electrophotographic photosensitive member capable of stably forming more excellent sensitivity characteristics and high-resolution images.
Furthermore, when the photosensitive layer contains the compound represented by the chemical formula (1), it is possible to provide an electrophotographic photosensitive member capable of stably forming more excellent sensitivity characteristics and high-resolution images.

An electrophotographic photoreceptor (also simply referred to as a photoreceptor) and an image forming apparatus of the present invention will be described.
The photoconductor may have either a laminated type photoconductor or a single layer type photoconductor. FIG. 1A shows a multilayer photoreceptor, and FIG. 1B shows an example of a single-layer photoreceptor. In the figure, 1 is a conductive substrate (conductive support), 2 is a charge generation material, 3 is a charge generation layer, 4 is a charge transport material, 5 is a charge transport layer, 7 is a binder resin (binder resin), 20 And 21 denote a photosensitive layer.

(Multilayer photoconductor)
First, the laminated photoreceptor will be described. The multilayer photoreceptor has a photosensitive layer in which a charge generation layer containing a charge generation material and a charge transport layer containing a charge transport material are laminated on a conductive substrate (hereinafter also referred to as a substrate).
The material constituting the substrate is not particularly limited as long as it has conductivity. Examples thereof include metals and alloy materials such as aluminum, copper, brass, zinc, nickel, stainless steel, chromium, molybdenum, vanadium, indium, titanium, gold, and platinum. Other examples include polyester films deposited or coated with aluminum, aluminum alloys, tin oxide, gold or indium oxide, paper and metal films, plastics and papers containing conductive particles, and plastics containing conductive polymers. .

These materials can be used after being processed into a cylindrical shape, a columnar shape, or a thin film sheet shape. In particular, when each layer is applied and formed on the substrate by a dip coating method as described later, a cylindrical shape is preferable.
The formation method of each layer laminated | stacked on a base | substrate is not specifically limited. For example, each layer can be formed by a dip coating method. The dip coating method is a method of forming a layer by immersing a substrate in a coating tank filled with a coating solution containing a material and then pulling it up at a constant speed or an arbitrarily changed speed. Since this dip coating method is relatively simple and excellent in terms of productivity and cost, it is frequently used in the production of electrophotographic photoreceptors.

In forming the photosensitive layer on the substrate, the substrate and the photosensitive layer are coated for the purpose of covering the substrate with scratches and unevenness, preventing deterioration of charging properties during repeated use, and improving charging characteristics in a low temperature / low humidity environment. An undercoat layer may be provided between them.
Conventionally usable materials for the undercoat layer include polyamide, copolymer nylon, polyvinyl alcohol, polyurethane, polyester, epoxy resin, phenol resin, casein, cellulose, gelatin, and the like. In particular, alcohol-soluble copolymer nylon can be suitably used.

  When the dip coating method is used as a method for forming the undercoat layer, first, the above material is dispersed in water and various organic solvents, particularly water, methanol, ethanol, butanol alone, or various mixed solvents, and the undercoat layer is used. A coating solution is prepared. Various mixed solvents include mixed solvents of water and alcohols, mixed solvents of two or more alcohols, mixed solvents of acetone and dioxolane and alcohols, chlorinated solvents such as dichloroethane, chloroform and trichloroethane, and alcohols. And a mixed solvent.

  In addition, the coating solution for the undercoat layer may be prepared by using zinc oxide, titanium oxide, oxidation, for the purpose of adjusting the volume resistivity of the undercoat layer and improving the repetitive aging characteristics in a low temperature / low humidity environment. Inorganic pigments such as tin, indium oxide, silica, and antimony oxide may be dispersed. Dispersion can be performed using a disperser such as a ball mill, a dyno mill, or an ultrasonic oscillator. If the ratio of the inorganic pigment in the undercoat layer is in the range of 30 to 95% by weight, the above improvement can be further achieved.

Next, the undercoat layer coating solution prepared as described above is applied to the substrate surface using a dip coating apparatus. The thickness of the undercoat layer can be applied to be about 0.1 to 5 μm after drying.
On the undercoat layer, the charge generation layer can be formed by dip coating a coating solution for charge generation layer. The coating solution for the charge generation layer is mainly composed of a charge generation material that generates a charge when irradiated with light, and may contain a known binder resin, plasticizer, and sensitizer as necessary.

  As a charge generating material, the X-ray diffraction spectrum shows a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 9.4 ° or 9.7 °, and at least 7.3 °, 9.4 °, 9 Oxo titanyl phthalocyanine crystals exhibiting clear diffraction peaks at .7 ° and 27.3 ° (see FIG. 2—the vertical axis represents the absorption intensity and the horizontal axis represents the diffraction angle) can be used. The photoconductor containing the specific crystal type oxo titanyl phthalocyanine can provide high-sensitivity and high-quality images even with exposure light having an oscillation wavelength in the wavelength range of 360 to 420 nm. In addition, since the potential stability with respect to repeated use is excellent, the occurrence of background fog and the like in the electrophotographic process using reversal development can be greatly reduced. This electrical stability can be obtained not only by a near infrared laser (780 nm) but also by a short wavelength laser (for example, a GaN-based semiconductor laser having an oscillation wavelength at 405 nm).

  FIG. 3 shows a spectral transmission absorption spectrum of the specific oxotitanyl phthalocyanine (the vertical axis represents absorption efficiency and the horizontal axis represents wavelength). The sensitivity of the photoreceptor is largely dependent on the absorption efficiency of the charge generation material found in this absorption spectrum. From FIG. 3, the absorbance is relatively flat in the existing near-infrared region (about 780 nm). It can be seen that the wavelength range of 360 to 420 nm is not necessarily larger than that in the existing near-infrared region, and although there is absorption, the wavelength dispersion is large.

However, the reason why stable sensitivity can be obtained when the specific oxotitanyl phthalocyanine is used in the wavelength range of 360 to 420 nm is presumed as (1) to (3) below.
(1) In charge generation materials (particularly phthalocyanine materials), it is presumed that the charge generation process proceeds as follows. That is, excitons generated by absorption (usually having excess energy) are intrinsically separated into electrons and holes through a thermal relaxation process. Since the excitation light in the wavelength range has a short wavelength, it has excessive energy in the first place. From this excess energy state to electron-hole separation, charge can be trapped in various secondary processes. On the other hand, a path where free carriers are efficiently generated through the surplus energy can be considered. Although the details are not clear, it seems that this latter process is dominant in the charge generating material of the present invention.

(2) The diffusion length of the generated excitons greatly depends on the crystal structure, that is, the packing state of the constituent molecules. Therefore, even with the same molecular structure, the packing state, packing imperfection, that is, the existence probability of lattice defects and the anisotropy of the particle shape as a crystallite influence the diffusion length of excitons. As shown in the following specific evaluation results, it is largely due to the difference in electrophotographic characteristics that are observed even with the same titanyl phthalocyanines.
(3) The stability of the laser as the excitation light source is improved. The thermal drift of the laser oscillation wavelength has become very small recently. For this reason, the influence of wavelength dispersion on the photoreceptor characteristics can be relatively suppressed.

  When the wavelength of the excitation light source is longer than 420 nm, the absorption coefficient is small, and it is difficult to ensure sufficient charge generation efficiency. On the other hand, when the thickness is less than 360 nm, it is difficult to secure a “transparent” charge transport material, which will be described later, and there are restrictions on the binder resin that is a constituent material of the photoreceptor. As a result, the selection of the constituent material of the photoreceptor becomes very difficult.

  The specific crystal form of oxotitanyl phthalocyanine can be obtained, for example, by the following method. First, o-phthalodinitrile, titanium tetrachloride, and α-chloronaphthalene as raw materials are reacted by a known method to obtain a crude product. The crude product is subjected to hot washing in an organic solvent such as methanol until the pH is 6 to 7, thereby obtaining intermediate crystals. By milling the intermediate crystal, the specific crystal form of oxotitanyl phthalocyanine can be obtained.

  The specific crystal form of oxotitanyl phthalocyanine may be used in combination with other charge generation materials. Other charge generation materials include phthalocyanine pigments that differ in crystal form from specific crystal forms of oxotitanyl phthalocyanine, perylene pigments such as azo pigments, perylene imide, and perylene anhydride, and polycyclic quinone series such as quinacridone and anthraquinone And pigments, squalium dyes, azurenium dyes, thiapyrylium dyes, and the like. Examples of phthalocyanine pigments that differ in crystal form from a specific crystal form of oxotitanyl phthalocyanine include α-type, β-type, Y-type, amorphous metal phthalocyanine containing oxotitanyl phthalocyanine, metal-free phthalocyanine, halogenated metal-free phthalocyanine, etc. Can be mentioned. As the azo pigment, an azo pigment having a carbazole skeleton, a styryl stilbene skeleton, a triphenylamine skeleton, a dibenzothiophene skeleton, an oxadiazole skeleton, a fluorenone skeleton, a bis-stilbene skeleton, a distyryl oxadiazole skeleton, a distyryl carbazole skeleton, etc. Is mentioned.

By using together with other charge generating materials, it is possible to easily adjust the light attenuation curve of the photosensitive layer to a desired curve. As a result, the degree of freedom is widened and superior in designing the image forming process.
Binder resins include melamine resin, epoxy resin, silicone resin, polyurethane, acrylic resin, vinyl chloride-vinyl acetate copolymer resin, vinyl chloride-vinyl acetate-maleic anhydride copolymer resin, vinyl chloride-vinyl acetate-polyvinyl alcohol. Examples include copolymer resins, polycarbonates, phenoxy resins, phenol resins, polyvinyl butyral, polyarylate, polyamide, and polyester.

  Solvents for dissolving these binder resins include ketones such as acetone, methyl ethyl ketone and cyclohexanone, esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran, dioxane, dioxolane and dimethoxyethane, benzene, toluene and xylene. And aprotic polar solvents such as N, N-dimethylformamide and dimethyl sulfoxide.

  In particular, the coating solution for the charge generation layer is preferably composed of a specific crystalline oxotitanyl phthalocyanine crystal, a butyral resin as a binder resin, a silicone oil, and a mixed solvent of two or more non-halogen organic solvents. . The mixed solvent is most preferably a mixed solvent of dimethoxyethane and cyclohexanone.

As a method for producing the charge generation layer, there is a method in which a compound that is a charge generation material is directly formed by vacuum deposition, but generally a coating solution in which a charge generation material is dispersed in a binder resin solution is applied to a substrate. A method of forming a film is preferable. As a method for mixing and dispersing the charge generation material in the binder resin solution and a method for applying the charge generation layer coating solution, the same methods as those for the undercoat layer are used.
The ratio of the charge generation material in the charge generation layer is preferably in the range of 30 to 90% by weight. The thickness of the charge generation layer is preferably 0.05 to 5 μm, and most preferably 0.1 to 1.5 μm.

A charge transport layer is provided on the charge generation layer. The charge transport layer contains a charge transport material, a binder resin, a known plasticizer, a sensitizer, and the like as required, which have the ability to accept and transport the charge generated by the charge generation material.
Examples of the charge transport material include an electron donating substance and an electron accepting substance. Examples of the electron donating substance include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadi Azole derivatives, imidazole derivatives, 9- (p-diethylaminostyryl) anthracene, 1,1-bis (4-dibenzylaminophenyl) propane, styrylanthracene, styrylpyrazoline, pyrazoline derivatives, phenylhydrazones, hydrazone derivatives, triphenyl Examples thereof include amine compounds, triphenylmethane compounds, stilbene compounds, and azine compounds having a 3-methyl-2-benzothiazoline ring.

  Examples of the electron accepting substance include fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo [c] cinnoline derivatives, phenazine oxide derivatives, tetracyanoethylene, Examples include tetracyanoquinodimethane, bromanyl, chloranil, and benzoquinone.

  In particular, when a semiconductor laser having an oscillation wavelength of 360 to 420 nm is used as the exposure light source, an arylamine compound that does not absorb in the wavelength region of 360 nm or more is particularly preferable as the charge transport material. Specific examples of arylamine compounds include triphenylamine compounds.

As the binder resin constituting the charge transport layer, a material having compatibility with the charge transport material and having no absorption at 360 nm or more can be used. Examples include polycarbonate and copolymer polycarbonate, polyarylate, polyvinyl butyral, polyamide, polyester, epoxy resin, polyurethane, polyketone, polyvinyl ketone, polystyrene, polyacrylamide, phenol resin, phenoxy resin, polysulfone, and copolymer resins thereof. It is done. You may use these individually or in mixture of 2 or more types. Among them, resins such as polystyrene, polycarbonate, copolymer polycarbonate, polyarylate, and polyester have a volume resistivity of 10 ¹³ Ω or more, and are excellent in film formability and potential characteristics.

  Solvents for dissolving the binder resin include alcohols such as methanol and ethanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, ethers such as ethyl ether, tetrahydrofuran, dioxane and dioxolane, and aliphatic halogens such as chloroform, dichloromethane and dichloroethane. Aromatics such as hydrocarbons, benzene, chlorobenzene, and toluene can be used.

  The coating solution for the charge transport layer can be prepared by dissolving the charge transport material in the binder resin solution. The ratio of the charge transport material is preferably in the range of 30 to 80% by weight in the coating solution. As a method for mixing and dispersing the charge transport material in the binder resin solution and a method for applying the coating solution for the charge transport layer, the same methods as those for the undercoat layer are used.

The film thickness of the charge transport layer is preferably 10 to 30 μm, more preferably 10 to 20 μm, particularly preferably 10 μm or more and less than 20 nm. In the case of a charge transport layer thickness of 20 to 30 μm, which is usually applied, the electrostatic latent image spreads and the high-resolution latent image is generated because diffusion in the in-plane direction of carriers occurs in the charge transport layer even if the exposure light is reduced in diameter. Imaging may be hindered. In order to prevent this, as described above, it is desired to further reduce the thickness of the charge transport layer. A charge transport layer is usually formed on the charge generation layer, but the reverse is also possible.
Each layer on the substrate is preferably dried using a dryer such as hot air or far-infrared rays each time a coating layer for forming each layer is formed. The drying is preferably performed at 40 to 130 ° C. for about 10 minutes to 2 hours.

The photosensitive layer may contain one kind or two or more kinds of electron accepting substances and dyes. As a result, the sensitivity of the photoreceptor can be improved, and an increase in residual potential and fatigue during repeated use can be suppressed.
Examples of the electron acceptor include acid anhydrides such as succinic anhydride, maleic anhydride, phthalic anhydride and 4-chloronaphthalic anhydride, cyano compounds such as tetracyanoethylene and terephthalmalondinitrile, and 4-nitrobenzaldehyde. Aldehydes, anthraquinones such as anthraquinone and 1-nitroanthraquinone, and polycyclic or heterocyclic nitro compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitrofluorenone. These can also be used as chemical sensitizers.
Examples of the dye include pyrazoline, coumarin, and anthracene.

  Furthermore, the photosensitive layer may contain a known plasticizer to improve moldability, flexibility, and mechanical strength. Examples of the plasticizer include dibasic acid esters, fatty acid esters, phosphate esters, phthalate esters, chlorinated paraffins, and epoxy type plasticizers.

In addition, the photosensitive layer may be a leveling agent for preventing distorted skin such as polysiloxane, a phenolic compound for improving durability, a hindered amine compound, a hydroquinone compound, a tocopherol compound, paraphenylenediamine, if necessary. You may contain antioxidants, ultraviolet absorbers, etc., such as arylalkane and those derivatives, an amine compound, an organic sulfur compound, and an organic phosphorus compound.
In addition, an additive may be used to ensure the electrical stability of the photoreceptor. The photosensitive layer may further contain the following chemical formula (1) as an additive.

When the compound represented by the formula (1) is contained, the potential / image stability as the photoreceptor can be secured over a long period of time.
A filler may be added to the outermost surface layer for the purpose of suppressing wear deterioration of the surface of the photoreceptor caused by slid printing with a cleaning blade or the like. The outermost surface layer means the entire charge transport layer or the surface layer of the charge transport layer. The fillers that can be added are broadly classified into organic fillers and inorganic fillers centered on metal oxides. In general, organic fillers, mainly fluorine-based materials, are mainly used for the purpose of controlling the wettability of the photoreceptor surface and suppressing the adhesion of foreign materials, etc., and inorganic materials are used for the purpose of improving printing durability. Fillers are mainly used.

  As the inorganic filler, a material having high hardness as a material and easily dispersible in the binder resin can be suitably used. Examples thereof include oxides such as silicon oxide (silica), titanium oxide, zinc oxide, calcium oxide, and aluminum oxide (alumina), and nitride compounds such as silicon nitride and aluminum nitride. In addition, it is desirable to form the outermost surface layer in a state where the filler is more uniformly dispersed.

  As the inorganic filler, silicon oxide (silica) having a small difference from the refractive index of the medium is suitable as a result of considering light scattering in the system. Also, the filler particle diameter is preferably small in order to minimize light scattering and adverse effects on electrical carriers in the system. Specifically, those having a primary particle diameter of 100 nm or less are suitable.

(Single layer type photoreceptor)
Next, a single layer type photoreceptor will be described. As in the case of the multilayer type, the single-layer type photoreceptor is a pigment layer in which a charge generation material is formed in a photosensitive layer in which a charge generation material is dispersed in a binder resin or a charge transport layer including a charge transport material. The photosensitive layer dispersed in (1) is provided. The amount of the charge generating material dispersed in the photosensitive layer is preferably 0.5 to 50% by weight, more preferably 1 to 20% by weight. The film thickness of the photosensitive layer is preferably 5 to 50 μm, more preferably 10 to 40 μm. In this single layer type as well as the laminated type, the photosensitive layer has a plasticizer for improving film formability, flexibility, mechanical strength, an additive for suppressing residual potential, and improved dispersion stability. A dispersion aid for the coating, a leveling agent for improving the coating property, a surfactant, and other additives may be added. Further, an inorganic filler may be contained in at least the outermost surface layer of the photosensitive layer.

  The single layer type photoreceptor has an advantage that it can be used as a photoreceptor for a positively charged image forming apparatus that generates less ozone. In addition, since there is only one photosensitive layer to be applied, there is an advantage that the manufacturing cost and the yield are better than those of the stacked type.

(Image forming device)
Next, an image forming apparatus equipped with an electrophotographic photosensitive member will be described. The image forming apparatus of the present invention includes an electrophotographic photosensitive member and charging, exposing, developing, transferring, and cleaning means, and the exposing unit includes a semiconductor laser having an oscillation wavelength in a wavelength range of 360 to 420 nm. An electrophotographic photosensitive member provided as a writing exposure light source includes the electrophotographic photosensitive member. In the present invention, as long as at least the above configuration is provided, the configuration of the image forming apparatus is not particularly limited.

FIG. 4 is an arrangement side view showing a simplified configuration of the image forming apparatus. The image forming apparatus shown in FIG. 4 is a laser printer 30 equipped with the photoreceptor A of the present invention. Hereinafter, the configuration of the laser printer 30 and the image forming operation will be described with reference to FIG.
The laser printer 30 includes a photosensitive member A, a laser 31, a rotary polygon mirror 32, an imaging lens 34, a mirror 35, a corona charger 36 as a charging unit, a developing unit 37 as a developing unit, a transfer paper cassette 38, and a paper feed roller. 39, a registration roller 40, a transfer charger 41 as a transfer means, a separation charger 42, a conveyor belt 43, a fixing device 44, a paper discharge tray 45, and a cleaner 46 as a photosensitive member cleaning means. The laser 31, the rotating polygon mirror 32, the imaging lens 34, and the mirror 35 constitute an exposure unit 49.

  The photoreceptor A is mounted on the laser printer 30 so as to be rotatable in the direction of an arrow 47 by a driving unit (not shown). The laser beam 33 emitted from the laser 31 is repeatedly scanned in the longitudinal direction (main scanning direction) on the surface of the photoreceptor A by the rotary polygon mirror 32. The imaging lens 34 has f-θ characteristics, and the laser beam 33 is reflected by the mirror 35 to form an image on the surface of the photosensitive member A and expose it. By scanning and imaging the laser beam 33 as described above while rotating the photoconductor A, an electrostatic latent image corresponding to image information is formed on the surface of the photoconductor A.

The laser 31 is not particularly limited as long as it emits light having an oscillation wavelength of 360 to 420 nm. Usually, a semiconductor laser is used.
The corona charger 36, the developing device 37, the transfer charger 41, the separation charger 42, and the cleaner 46 are provided in this order from the upstream side to the downstream side in the rotation direction of the photosensitive member A indicated by an arrow 47.

  The corona charger 36 is provided upstream of the image forming point of the laser beam 33 in the rotation direction of the photoconductor A, and uniformly charges the surface of the photoconductor A. Therefore, the laser beam 33 exposes the surface of the photosensitive member A that is uniformly charged, and a difference occurs between the charge amount of the portion exposed by the laser beam 33 and the charge amount of the portion that is not exposed. Electrostatic latent image is formed.

  The developing unit 37 is provided on the downstream side in the rotation direction of the photosensitive member A with respect to the image forming point of the laser beam 33, supplies toner to the electrostatic latent image formed on the surface of the photosensitive member A, and converts the electrostatic latent image into toner. Develop as an image. The transfer paper 48 accommodated in the transfer paper cassette 38 is taken out one by one by the paper feed roller 39 and is given to the transfer charger 41 by the registration roller 40 in synchronism with the exposure to the photoreceptor A. The toner image is transferred onto the transfer paper 48 by the transfer charger 41. A separation charger 42 provided in the vicinity of the transfer charger 41 discharges the transfer paper on which the toner image has been transferred and separates it from the photoreceptor A.

  The transfer paper 48 separated from the photoreceptor A is transported to the fixing device 44 by the transport belt 43, and the toner image is fixed by the fixing device 44. The transfer paper 48 on which the image is formed in this manner is discharged toward the paper discharge tray 45. After the transfer paper 48 is separated by the separation charger 42, the photoreceptor A that continues to rotate further cleans foreign matters such as toner and paper dust remaining on the surface by the cleaner 46. The photosensitive member A whose surface has been cleaned by the cleaner 46 is neutralized by a neutralizing lamp (not shown) provided together with the cleaner 46 and then further rotated, and a series of image forming operations starting from the charging of the photosensitive member A is repeated. .

Since the surface free energy of the surface of the photoconductor A provided in the laser printer 30 is set within the above-mentioned preferable range, the toner for forming the toner image is transferred from the surface of the photoconductor A in the image formation by the laser printer 30. The transfer toner 48 is easily transferred onto the paper 48 and hardly generates residual toner, and paper dust or the like of the transfer paper 48 that is in contact with the transfer hardly adheres to the surface of the photoreceptor A.
Further, even if foreign matter such as toner and paper dust adheres to the surface of the photoconductor A, it is easily removed by a cleaning blade of a cleaner 46 provided for cleaning the surface of the photoconductor A after transferring the toner image.

  Accordingly, in the image forming apparatus according to the present invention, the polishing ability of the cleaning blade can be set weak, and the contact pressure of the cleaning blade with respect to the surface of the photoconductor A can be set small, so that the life of the photoconductor A is extended. Is done. Furthermore, since the surface of the photoreceptor A after cleaning does not adhere to foreign matters such as toner and paper dust and is always kept clean, it is possible to stably form an image with good image quality for a long period of time. is there.

  In other words, the laser printer 30 which is an image forming apparatus according to the present invention can stably form an image without deterioration in image quality over a long period of time in various environments. Further, since the life of the photosensitive member A is long and the cleaner 46 has a simple configuration, the image forming apparatus 30 with low cost and low maintenance frequency is realized. In addition, even if the photoconductor A is exposed to light, its electrical characteristics do not deteriorate, so that deterioration in image quality due to exposure of the photoconductor A to light during maintenance or the like can be suppressed.

  The laser printer 30 that is the image forming apparatus according to the embodiment of the present invention described above is not limited to the configuration shown in FIG. 4, as long as the photoconductor according to the present invention can be used. For example, other different configurations may be used as follows.

  That is, when the outer diameter of the photoreceptor is 40 mm or less, the separation charger 42 may not be provided. The photoconductor A may be integrated with at least one of the corona charger 36, the developer 37, and the cleaner 46 to form a process cartridge.

  For example, a process cartridge in which the photosensitive member A, the corona charger 36, the developing device 37, and the cleaner 46 are assembled, a process cartridge in which the photosensitive member A, the corona discharge device 36, and the developing device 37 are incorporated, and the photosensitive member A and the cleaner. 46, a process cartridge incorporating the photosensitive member A and the developing device 37, and the like.

By using such a process cartridge in which several members are integrated, maintenance management of the apparatus is facilitated.
Further, the charger is not limited to the corona charger 36, and a corotron charger, a scorotron charger, a sawtooth charger, a roller charger, or the like can be used.
As the developing device 37, at least one of a contact type and a non-contact type may be used. As the cleaner 46, a brush cleaner or the like may be used.

  Further, the static elimination lamp may be omitted by devising the timing of applying a high pressure such as a developing bias. That is, in particular, in the case where the diameter of the photoconductor is small, the low-speed low-end printer, or the like, it is possible not to provide a static elimination lamp from the viewpoint of space saving.

Photosensitive layers are formed under various conditions on an aluminum conductive substrate having a diameter of 30 mm, and the photoconductors prepared as examples and comparative examples are evaluated.
Example 1
7 parts by weight of titanium oxide (TTO55A: manufactured by Ishihara Sangyo Co., Ltd.) and 13 parts by weight of copolymer nylon (CM8000: manufactured by Toray Industries, Inc.) were added to a mixed solvent of 159 parts by weight of methyl alcohol and 106 parts by weight of 1,3-dioxolane, The undercoat layer coating solution was prepared by dispersing for 8 hours in a paint shaker. The coating solution was filled in a coating tank, the conductive substrate was immersed and pulled up, and then naturally dried to form an undercoat layer having a layer thickness of 1 μm.
The charge generation material was manufactured by the following method.

  40 g of o-phthalodinitrile, 18 g of titanium tetrachloride, and 500 ml of α-chloronaphthalene were reacted by heating and stirring at 200 to 250 ° C. for 3 hours in a nitrogen atmosphere. Subsequently, after cooling to 100-130 degreeC, it filtered by hot, and wash | cleaned with 200 ml of (alpha) -chloronaphthalene heated at 100 degreeC, and obtained the dichlorotitanium phthalocyanine crude product.

  This crude product was washed with 200 ml of α-chloronaphthalene and then with 200 ml of methanol at room temperature, and further subjected to hot washing in 500 ml of methanol for 1 hour. After filtration, the obtained crude product was repeatedly subjected to hot washing in 500 ml of water until the pH reached 6-7. Then, it dried and the oxo titanyl phthalocyanine intermediate crystal was obtained. Further, the intermediate crystal was mixed with methyl ethyl ketone, milled with a glass bead having a diameter of 2 mm by a paint conditioner device (manufactured by Red Level), washed with methanol, and dried to obtain a crystal. The X-ray diffraction spectrum of the obtained crystal is shown in FIG. The obtained crystals have major diffraction peaks at Bragg angles (2θ ± 0.2 °) of 7.3 °, 9.4 °, 9.7 ° and 27.3 °, of which 9.4 ° and 9 ° It can be seen that it is a crystalline oxotitanyl phthalocyanine exhibiting a maximum diffraction peak in a peak bundle overlapped by 7 °.

  1.8 parts by weight of the oxotitanyl phthalocyanine crystals obtained here, 1.2 parts by weight of butyral resin (manufactured by Sekisui Chemical Co., Ltd .: ESREC BX-1), polydimethylsiloxane-silicone oil (manufactured by Shin-Etsu Chemical Co., Ltd .: KF- 96) 0.06 parts by weight, 87.3 parts by weight of dimethoxyethane, and 9.7 parts by weight of cyclohexanone (mixing ratio = 90/10) are mixed and dispersed by a paint shaker to form a coating solution for a charge generation layer. Adjusted. This coating solution was applied onto the above-described undercoat layer by the same dip coating method as in the case of the undercoat layer, and naturally dried to form a charge generation layer having a layer thickness of 0.3 μm.

  5 parts by weight of an arylamine compound represented by the following structural formula (2) as a charge transporting substance, 4.4 parts by weight of polycarbonate (GH503: manufactured by Idemitsu Kosan Co., Ltd.), 3.6 parts by weight of polycarbonate (TS2040: manufactured by Teijin Chemicals Ltd.) The charge transport layer coating solution was prepared using 49 parts by weight of tetrahydrofuran as a solvent. This coating solution was applied onto the above-described charge generation layer by a dip coating method and dried at 120 ° C. for 1 hour to form a charge transport layer having a layer thickness of 20 μm, thereby obtaining a photoreceptor.

Example 2
In the same manner as in Example 1, an undercoat layer and a charge generation layer were formed. Next, a photoreceptor was prepared in the same manner as in Example 1 except that 0.13 parts by weight of IRGANOX 1010 (manufactured by Ciba Specialty Chemicals) was further added to the charge transport layer coating solution.

Example 3
In the same manner as in Example 1, an undercoat layer and a charge generation layer were formed. Next, a photoconductor was prepared in the same manner as in Example 1 except that 0.13 parts by weight of Sanol LS-440 (manufactured by Sankyo Lifetech Co., Ltd.) was further added to the charge transport layer coating solution.
Example 4
In the same manner as in Example 1, an undercoat layer and a charge generation layer were formed. Next, a photoreceptor was produced in the same manner as in Example 1 except that 0.13 parts by weight of the following structural formula (1) was added to the charge transport layer coating solution.

Example 5
A photoconductor was prepared in the same manner as in Example 4 except that the thickness of the charge transport layer was 24 μm.
Example 6
A photoconductor was prepared in the same manner as in Example 4 except that the thickness of the charge transport layer was 27 μm.
Example 7
A photoconductor was prepared in the same manner as in Example 4 except that the thickness of the charge transport layer was 30 μm.

Example 8
In the same manner as in Example 1, an undercoat layer and a charge generation layer were formed. Next, 1.65 parts by weight of two kinds of polycarbonates, GH503 (manufactured by Idemitsu Kosan) and TS2040 (manufactured by Teijin Chemicals) and 3.3 parts by weight of silica particles (TS-610: manufactured by Cabot Specialty Chemicals) are added in tetrahydrofuran. Mixed to 66 parts by weight. The mixture was dispersed in a ball mill for 5 hours using ZrO ₂ beads (φ3 mm) as a medium to prepare a primary dispersion coating solution for a charge transport layer. At this stage, the silica particles are uniformly dispersed, and the dispersion state corresponding to the primary particle diameter (about 17 nm) is maintained using a particle size distribution analyzer: UPA-150 (manufactured by Nikkiso Co., Ltd.). confirmed.

  Next, 100 parts by weight of the compound of the above structural formula (2) as a charge transport material, two kinds of polycarbonates, GH503 (made by Idemitsu Kosan) and TS2040 (made by Teijin Chemicals) are respectively 86.4 parts and 70.4 parts by weight. Was dissolved in 1172 parts by weight of tetrahydrofuran. A total amount of the primary dispersion coating liquid for the charge transport layer was mixed with this solution and stirred for 15 hours to prepare a secondary dispersion coating liquid for the charge transport layer. This coating solution was applied onto the charge generation layer by a dip coating method and dried at 120 ° C. for 1 hour to form a charge transport layer having a layer thickness of 20 μm, whereby a photoreceptor of Example 5 was produced.

Comparative Example 1
A photoconductor was prepared in the same manner as in Example 4. However, in the evaluation, a semiconductor laser having an oscillation wavelength of 780 nm was used as the exposure light source.
Comparative Example 2
An oxytitanium phthalocyanine having a strong peak at a Bragg angle (2θ ± 0.2 °) of 27.2 ° obtained from an X-ray diffraction spectrum of a crystal obtained according to the production example disclosed in JP-A-2000-105479 A photoconductor of Comparative Example 2 was produced in the same manner as in Example 4 except that it was used as a charge generation material.

Comparative Example 3
The X-ray diffraction spectrum of the crystal obtained in accordance with the production example disclosed in JP-A No. 64-17066 shows Bragg angles (2θ ± 0.2 °) of 9.5 °, 9.7 °, 11. The photoreceptor of Comparative Example 2 in the same manner as in Example 4 except that oxytitanium phthalocyanine having strong peaks at 6 °, 14.9 °, 24.0 °, and 27.3 ° was used as the charge generation material. Was made.
Comparative Example 4
The X-ray diffraction spectrum of the crystal obtained according to the production example disclosed in JP-A-5-188614 has strong peaks at Bragg angles (2θ ± 0.2 °) of 9.6 ° and 27.3 °. A photoreceptor of Comparative Example 2 was produced in the same manner as in Example 4 except that the oxytitanium phthalocyanine having was used as the charge generation material.

(Evaluation)
The photosensitive member described in Example 1-8 and Comparative Example 1-4 manufactured as described above is used as a process cartridge for an image forming apparatus of a color composite machine MX-4500N manufactured by Sharp Corporation together with a charging member (a scorotron charger). A semiconductor laser having an oscillation wavelength of 405 nm was used as an image exposure light source, and writing was performed by an image exposure apparatus including a collimator lens, an aperture, a cylinder lens, a polygon mirror, an fθ lens, a barrel toroidal lens, and a reflection mirror. . However, the photoconductor shown in Comparative Example 1 was written using a semiconductor laser having an oscillation wavelength of 780 nm as an exposure light source.

Two-component development (toner with a volume average particle diameter of 6.5 μm) is performed for development, a transfer belt (a toner image is directly transferred to a transfer paper) is used as a transfer member, and a semiconductor laser of 780 nm is used for static elimination light. Used, the entire surface of the photoreceptor was neutralized by light irradiation. Using a chart with a writing rate of 6%, 50,000 sheets were printed intermittently with 5 sheets (the test environment is 25 ° C.-50% RH).
The photoreceptor characteristics were evaluated as follows before and after printing 50,000 sheets.

<Evaluation of photoreceptor electrical characteristics>
The potential at the time of solid image printing: VL (−V) was measured using Model-334 (manufactured by Trek), and used as a photoconductor sensitivity index.
VL <100 [V]: No problem in actual use VL ≧ 100 [V]: There is a problem in actual use because it affects the image density

<Evaluation of dot reproducibility>
A halftone image (one dot image) was formed, and the dot formation state was evaluated with respect to dot reproducibility, dissipated state, and contour sharpness with the following ranking.
◎: Good dot reproducibility, no dissipation, and excellent sharpness of the outline ○: Although there is some deterioration in the above three items, there is no problem in actual use △: Any of the three items is in actual use Problem x: 2 or more items out of 3 are actually unusable

<Evaluation of dirt>
A white solid image was output, and rank evaluation was performed visually from the number and size of black spots generated on the background. In addition, about the evaluation rank, it was set as the following ranking.
◎: No black spots appearing on the background part ○: Black spots appearing on the background part are present, but there is no problem in actual use △: Black spots appearing on the background part are scattered and present in actual use Problem level ×: There are a lot of black spots that occur on the background, and it cannot be used in practice.

<Evaluation of printing durability>
The film thickness of the photoconductor before and after the actual shooting test was measured using an optical interference type film thickness measuring device (F20: manufactured by Filmmetrics), and the amount of film slip was calculated from the difference from the rotation number of the photoconductor drum.
A summary of the evaluation results of this test is shown in Table 1.

In Example 1-8, in which the specific oxotitanyl phthalocyanine used in the present invention and a semiconductor laser having an oscillation wavelength of 405 nm as an exposure light source were combined, good characteristics were exhibited both before and after actual shooting. In particular, in Examples 4 and 5 to which a specific compound (chemical formula (3)) was added, a stable image could be formed even after actual shooting. Furthermore, by using the photoreceptor to which a specific filler was added in Example 8, good characteristics in terms of printing durability were also obtained.
On the other hand, in comparison examples 1-4 using the above-described exposure light source or charge generation material having no specific crystal type as compared with the examples, characteristics due to the large dot diameter or instability of sensitivity The deterioration was seen.

1 is a schematic cross-sectional view of an electrophotographic photosensitive member of the present invention. 1 is an X-ray diffraction spectrum diagram of an oxotitanyl phthalocyanine crystal that can be used in the present invention. It is a spectrum transmission absorption spectrum of the charge generation layer using the oxo titanyl phthalocyanine crystal of the present invention. 1 is a schematic view of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive base | substrate (conductive support body) 2 Charge generating material, 3 Charge generating layer 4 Charge transport material, 5 Charge transport layer, 7 Binder resin (binder resin)
20, 21 Photosensitive layer, A photoconductor, 16 Intermediate layer 30 Laser printer (image forming apparatus), 31 Laser 32 Rotating polygon mirror, 33 Laser beam, 34 Imaging lens 35 Mirror, 36 Corona charger, 37 Developer, 38 Transfer paper cassette 39 Paper feed roller, 40 Registration roller, 41 Transfer charger 42 Separation charger, 43 Conveyor belt, 44 Fixing device, 45 Paper discharge tray 46 Cleaner, 47 Arrows, 48 Transfer paper, 49 Exposure means

Claims (5)

An electrophotographic photosensitive member having a photosensitive layer on a conductive substrate, wherein the electrophotographic photosensitive member is a photosensitive member writable by light having an oscillation wavelength in a wavelength range of 360 to 420 nm, and the photosensitive layer is A crystalline form of oxotitanyl phthalocyanine ,
The following chemical formula (1)

Containing in compound represented by the crystal form of titanyl phthalocyanine, in the X-ray diffraction spectrum, the maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) 9.4 ° or 9.7 °, and An electrophotographic photosensitive member characterized by exhibiting diffraction peaks at least at 7.3 °, 9.4 °, 9.7 °, and 27.3 °. 2. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer has a laminate in which at least a charge generation layer and a charge transport layer are laminated in this order from the conductive substrate side. The said photosensitive layer has a laminated body which laminated | stacked at least the charge generation layer and the charge transport layer in this order from the said electroconductive base | substrate side, The said charge transport layer has a thickness of 25 micrometers or less. Electrophotographic photoreceptor. The electrophotographic photosensitive member according to claim 1, wherein the photosensitive layer includes an outermost surface layer to which an inorganic filler is added. An electrophotographic photosensitive member, and means for charging, exposing, developing, transferring, and cleaning the photosensitive member, and the exposing unit includes a semiconductor laser having an oscillation wavelength in a wavelength range of 360 to 420 nm as a writing exposure light source, and An image forming apparatus, wherein the electrophotographic photosensitive member is the electrophotographic photosensitive member according to any one of claims 1 to 4 .

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