JP2661073B2 - Photoconductive layer and manufacturing method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used for an electrophotographic copying machine, an optical printer and the like. 2. Description of the Related Art In electrophotographic photoreceptors, a function-separated electrophotographic photoreceptor in which carrier generation by photoexcitation and carrier transport are composed of different materials is widely used. As described above, by selecting materials according to functions, an excellent photoconductor having high sensitivity electrophotographic characteristics is provided. In addition, the optimum combination has been studied from a wide range of materials in various aspects such as mechanical strength, thermal stability, printing durability, environmental resistance, and manufacturing cost. Representative examples of such material combinations include amorphous selenium and polyvinyl carbazole, methyl squaric acid and triaryl pyrazoline, diane blue and oxadiazole, perylene pigment and oxadiazole,
There are bisazo pigments and styriananthracene. Japanese Patent Application Laid-Open No. 54-1436 discloses an amorphous layer.
No. 45 proposes a function-separated type photoreceptor using an organic semiconductor material, and JP-A-56-24355 proposes a function-separated type photoreceptor using an inorganic semiconductor material. We have also proposed a function-separated photoconductor in which a charge transport layer is composed of a layer mainly composed of amorphous carbon and a charge generation layer is composed of amorphous silicon. By the way, there is also a method in which the carrier generation and the carrier transport are made of different materials and are made of different layers. For example, there is a phthalocyanine-based organic semiconductor that has recently attracted attention because of its high sensitivity at long wavelengths. (Japanese Patent Application Laid-Open No. Sho 62-184463) The carrier transporting material is important in both the lamination and the single layer, and both satisfy the contradictory properties of retaining charge and transporting charge at the same time. Must. Among various materials, PPS (poly-P-
(Phenylene sulfide) has been proposed as a material having high hole mobility and excellent heat resistance. (Japanese Patent Laid-Open No. 60-5935
However, PPS usually has high resistance and requires some means to improve the mobility by some method. Problems to be Solved by the Invention In order to realize higher sensitivity in a function-separated type electrophotographic photoreceptor, a charge transport material having a smaller dielectric constant and a higher mobility and a higher charge generation ability are required. A combination of charge generating materials is desirable. However, even if the required conditions are satisfied, carrier injection between the two must be performed efficiently. It must also sufficiently satisfy the charge receiving ability, abrasion resistance, environmental resistance, and the like required in the electrophotographic process. PPS is known as an insulator having excellent heat resistance and mechanical strength and high electric resistance, and is used as a plastic agent and a sealing material. On the other hand, the use of a conductive material has attracted attention, and it is well known that the addition of an electron-accepting material significantly improves the conductivity. At this time, the mobility was also improved, and application to the charge transport material of the electrophotographic photoreceptor was expected. However, since the electric resistance was lowered by the increase of the carrier concentration, it was improved without having the required charge receiving ability. Was desired. JP-A-60-59353 discloses performing thinning and forming a transport layer by a vacuum deposition method of PPS.
Generally, in this state, the mobility is small, and both the sensitivity and the residual potential are poor. In addition, the high charge generation ability of the charge generation material requires, of course, good carrier injection efficiency into the charge transport material. Further, it is desirable that the formation method be performed at low cost. Means for Solving the Problems In a photoconductive layer composed of a charge generating material that generates carriers by photoexcitation and a charge transporting material that transports the carriers, the charge transporting material has P-phenylene, and S
A linear compound polymer having an atom and an O atom bonded to the S atom is included. Function In the case of a function-separated type photoconductive layer in which the charge generation layer and the charge transport layer are separated and stacked, the charge generation from the carrier generation to the carrier transport layer is performed through a planar interface. Carriers in the layer must reach the interface. Further, the charge generation layer desirably has a high quantum efficiency with respect to incident light, and it is desired to set the film thickness as thick as possible. Therefore, the carrier traveling distance must be long, and at least the thickness of the charge generation layer is required. In order to reduce this condition, functional separation is adopted. In general, the film thickness is often set to 1 μm or less. For this reason, the overall light absorption efficiency often remains low. On the other hand, when the charge generating material and the charge transporting material are mixed in the same layer, the limit on the film thickness is determined by the carrier traveling distance of the charge transporting material, and the charge generating material is included to sufficiently absorb incident light. It is possible to make it. However, carrier transfer at the grain boundary between the charge generating material and the charge transporting material differs depending on the combination and material processing. By the way, when the charge transporting material is a polymer, the movement of the carrier is performed by hopping conduction between electron orbits along the main chain direction of the polymer, and the mobility of the carrier has a large overlap between adjacent orbits. As the hopping probability increases, the hopping probability increases. In a polymer having a structure having P-phenylene in the main chain direction and having an S atom in the para position, when the S atom is in a neutral state, the adjacent P-phenylene spatially has a π-electron orbit in a perpendicular direction. And the mobility is small. However, when positively charged and ionized by the O atom to which the S atom is added, the spatial twist of P-phenylene is eliminated, the π electron orbit is arranged in the same plane, and the mobility is improved with the increase of the hopping probability. It is planned. On the other hand, various electron-accepting additives are known, but when the amount of addition is increased in order to increase the mobility, the mobility starts to decrease after a certain amount. This phenomenon is because the main chain structure of PPS is destroyed by the oxidizing action of the added electron acceptor, and the number of cross-linked structures having a structure that newly acts as a carrier trap increases. At this time, the electric resistance also decreases due to the increase in the carrier concentration, and the charge holding ability is degraded. Therefore, it is necessary to ionize the para-S atom without destroying the main chain structure of the PPS. This can be realized by O atoms. Further, by adding a small amount of another electron acceptor from this state, the effect of improving the mobility without significantly increasing the carrier concentration is improved. Therefore, by forming the charge transport material and the charge generation material in the same layer, a photoconductive layer having high charge generation efficiency can be formed. Example FIG. 1 schematically shows a cross section of an example of a basic electrophotographic photosensitive member according to the present invention. The electrophotographic photoreceptor shown in the figure has a photoconductive layer 2 containing a charge transfer material and a charge generating material on a support 1 as an electrophotographic photoreceptor, and the photoconductive layer 2 has a free surface on one hand. Three. Further, the photoconductive layer in the present invention may be used as a charge generation layer, and may be combined with another charge transport layer to form a layered function-separated electrophotographic photoconductor. At this time, the thickness of the charge transfer layer may be 5 to 50 μm, preferably 10 to 25 μm, and the thickness of the photoconductive layer may be 0.2 to 10 μm, preferably 0.5 to 5 μm. In the present invention, the conductive support may be coated with a metal material, for example, aluminum, or a metal material. In the present invention, in order to further improve the electrophotographic characteristics, in the figure, a barrier is provided between the support 1 and the photoconductive layer 2 to effectively prevent carriers injected into the photoconductive layer 2 from the support 1. A layer may be provided. Materials for forming the barrier layer include Al ₂ O ₃ , BaO, BaO ₂ ,
BeO, Bi ₂ O ₃ , CaO, CeO ₂ , Ce ₂ O ₃ , La ₂ O ₃ , Dy ₂ O ₃ , Lu
₂ O ₃ , Cr ₂ O ₃ , CuO, Cu ₂ O, FeO, PbO, MgO, SrO, Ta ₂ O ₃ ,
ThO ₂ , ZrO ₂ , HfO ₂ , TiO ₂ , TiO, SiO ₂ , GeO ₂ , SiO, GeO
Or metal nitrides such as TiN, AlN, SnN, NbN, TaN, GaN, or metal carbides such as WC, SnC, TiC, or insulators such as SiC, SiN, GeC, GeN, BC, BN, etc. Organic compounds having heat resistance, such as polyimide, polyamide imide, and polyacrylonitrile are used. Further, a surface coating layer is formed on the free surface 4 in the figure in order to improve the cleaning property, the wear resistance or the corona resistance. Materials suitable for the surface coating layer include Si _x O _1-x , Si _x C _1-x , Si _x N _1-x , Ge _x O _1-x , Ge
_x C _1-x , Ge _x N _1-x , B _x N _1-x , B _x C _1-x , Al _x N _1-x (0 <x <
1) Inorganic substances such as carbon and a layer containing hydrogen or halogen in them. When the main material of the charge transport material is directly formed on the substrate surface by a vacuum deposition method from a powder, an ion cluster beam method, or the like,
The charge generating materials may be mixed in advance, or may be separate evaporation sources. Also, the method of extruding the powder into a film by extrusion and fusing it to the substrate surface may be performed by previously mixing the charge generating material. At this time, a predetermined amount of an electron-accepting additive may be mixed in advance. I ₂ , Br ₂ , Cl ₂ , ICl, IB
r, (NO ₂ ) BF ₄ , (NO ₂ ) PF ₆ , (NO ₂ ) SbF ₆ , HClO ₄ , H ₂ S
O ₄ , HNO ₃ , HSO ₄ ⁻ , AgClO ₄ , Fe (ClO ₄ ), BF ₃ , FeCl ₃ , F
_{eBr 3, AlCl 3, InCl 3} , InI 3, ZrCl 4, HfCl 4, TeCl 4, TeB
_{r 4, TeI 4, SnCl 4} , SnI 4, SeCl 4, TiCl 4, TiI 4, FeC
^{_{I 4 -, AlCl 4 -,}} AsF 5, SbF 5, NbCl 5, NbF 5, TaCl 5, Ta
_{I 5, McCl 5, ReF 6} , IrCl 6, InF 6, UF 6, OsF 6, XeF 6, TeF
_6, SF _6, SeF there is a _{6, WF 6, WCl 6,} ReF 7 and the like. Binders that may be included in the photoconductive layer include phenolic resins, area resins, melamine resins, epoxy resins,
Silicon resin, vinyl chloride-vinyl acetate copolymer, butyral resin, xylene resin, urethane resin, polycarbonate resin, polyacrylate resin, saturated polyester resin, phenoxy resin and the like are used. Non-single crystals such as Se, SeTe, As ₂ Se ₃ , CdS, etc. containing chalcogen elements, silicon,
There is amorphous or the like made of a combination of germanium, carbon and the like. As the organic semiconductor of the charge generating material, (1) a phthalocyanine pigment (referred to as Pc), for example, a metal-free Pc, XPc (X = C
u, Ni, Co, TiO, Mg, Si (OH) ₂ , etc.), AlClPcCl, Ti
OClPcCl, InClPcCl, InClPc, InBrPcBr and the like. Further, (2) azo dyes such as monoazo dyes and disazo dyes,
(3) Penylene pigments such as penylene anhydride and penylene imide; (4) indigoid dyes; (5) quinacridone pigments; (6) polycyclic quinones such as anthraquinones and pyrenequinones; and (7) cyanine dyes. , (8) xanthene dye, (9) charge transfer complex such as PVK / TNF, (10)
Eutectic complexes formed from a beryllium salt dye and a polycarbonate resin, and (11) an azurenium salt compound. Example 1 PPS (poly p-phenylene sulfide) was used as a charge transporting material, and a phthalocyanine-based compound was used as a charge generating material from organic semiconductors. In addition, a vacuum deposition method was used as a film forming method. After placing the mirror-polished aluminum substrate in a vacuum furnace and evacuating it to 1.0 × 10 ^-5 Torr or less, PPS as the charge transporting material and phthalocyanine compound as the charge generating material were separately separated from the two evaporation sources at each temperature. Evaporated to form a film. At this time, each weight ratio can be made variable by controlling the film forming speed. The studied phthalocyanine compounds include titanyl phthalocyanine, chloroindium phthalocyanine, chloroindium phthalocyanine monochloride, magnesium phthalocyanine,
χ-type metal-free phthalocyanine, ε-type copper phthalocyanine 6
There are different types. When the respective weight ratios were changed, there was an optimum value for the charging potential and the sensitivity when the film thickness was constant at 30 μm. For example, in the case of titanyl phthalocyanine, the ratio between the charge generating material and the charge transporting material is 20% and 80%, respectively. The electrophotographic characteristics are 6.0kV corona charging, the charging potential is 1200V, and the sensitivity to white light source is 0.71xs. And a good value. The long wavelength sensitivity near 800 nm is 0.5 μJ / cm ^{2 for} titanyl phthalocyanine and 0.1 for chloroindium phthalocyanine.
7μJ / cm ^2, chloro indium phthalocyanine monochloride is 0.4μJ / cm ^2, magnesium phthalocyanine 0.3μJ
/ cm ² and high sensitivity that can be used for printers that use semiconductor lasers as light sources. Example 2 A film-shaped aluminum substrate was mirror-polished.
PPS (poly p-phenylene sulfide) was attached. At this time, a film prepared by mixing MgPc (magnesium phthalocyanine) as a charge generating material with PPS powder in advance by 15% by weight and extruding the film was used. Next, the fluororesin sheet was wound from above the film and heated in a heat treatment furnace to fuse the PPS film onto the aluminum substrate. The heating temperature is 290 ° C, which is higher than the melting temperature of PPS, 285 ° C, and the heating atmosphere is in the air. After the substrate was taken out of the heat treatment furnace, the fluororesin sheet was removed, placed again in the heat treatment furnace, and subjected to a heat treatment in an oxygen atmosphere. The heating temperature was controlled within the range of 285 ° C. to 350 ° C., and the heat treatment time was kept constant for 3 hours. After this processing,
The thickness of the PPS film was 10 to 25 μm. When these electrophotographic photoreceptors were corona-charged at 6.0 kV, a charge transport layer having a thickness of 20 μm was able to obtain a surface potential of +1500 V and was exposed to white light.
The residual potential was +50 V or less, and the half-life exposure amount was 1.01 × · s or less, showing very excellent electrophotographic characteristics. When the composition of this electrophotographic photosensitive member was analyzed, the composition ratio of O atoms to C atoms contained in the charge transport material was 12 atm%. As a comparison, heat treatment after fusion of PPS film was 0.1 Torr
Performed under the following reduced pressure, and the number of O atoms is 1 atm%
The following charge transport materials were obtained. The characteristics of this electrophotographic photoreceptor were inferior, with a residual potential of +400 V or more and a half-life exposure of 1501 × s or more. Further, when the number of O atoms in the film was changed to 50 atm% by the heating time of the heat treatment in the oxygen atmosphere,
Up to tm%, the residual potential was +50 V or less, showing electrophotographic characteristics with no practical problem. Example 3 When forming a photoconductive layer, TCNQ (7,
7,8,8, -tetracyanoquinodimethane) was added. An azurenium salt compound was used as the charge generating material in an amount of 5% by weight based on the PPS powder as the raw material. The synthesis of the azulenium salt was as follows. 1,4-dimethyl-
7-Isopropylazulene and P-dimethylaminocinnamaldehyde are dissolved in tetrahydrofuran and acid (HX,
X = ClO ₄ , BF ₄ , Br, I) are reacted while cooling to 10 ° C. or less, the solution is dried at 60 ° C., and the azulenium salt compound 1- (P-dimethylaminocinnamylidene) -5-
Isopropyl-3,8-dimethylazurenium salt was obtained.
This and the above-mentioned charge transport material were mixed with a butyral resin, dispersed in butyl acetate, coated with 30 μm, and dried at 70 ° C. After drying, a heat treatment was performed in an oxygen atmosphere in the same manner as in Example 2. The azulenium salt has excellent photoconductivity in a wavelength range from 400 to 900 nm, and particularly has a sensitivity peak at a long wavelength of 700 nm or more and can be applied to a printer using a semiconductor laser as a light source.
Among the above four types of azurenium salts, those containing I (iodine) as an acid are 0.71 × s 800 nm against white light.
Showed good sensitivity to 0.4 μJ / cm ² with respect to red light. Example 4 CdS, which is an inorganic material, was studied as a charge generating material. The photoconductive layer was composed of the charge generation material CdS, the binder polyurethane and PPS in the same manner as in Example 3. Furthermore, a function-separated electrophotographic photoreceptor in which this layer was used as a charge generation layer and the charge transport layer was composed of PPS alone was also evaluated. 20% by weight CdS, 60% PPS, 20% polyurethane
% As single layer, 25μm thickness, PPS film 2 when laminated
2.0 μm was formed on 0 μm. When the electrophotographic characteristics of this sample were evaluated, the former single layer film was 3.01xs against white light, and the latter laminated film was 4.01xs
And the sensitivity was good in both cases. Effect of the Invention In a photoconductive layer composed of a charge generating material that generates carriers by photoexcitation and a charge transporting material that transports the carriers, the charge transporting material has P-phenylene, and S
By containing a linear compound polymer having atoms, an electrophotographic photosensitive member having high sensitivity and low residual potential can be obtained. Further, the photoconductive layer can be formed by fusing, coating, and vapor-depositing a polymer, so that an inexpensive electrophotographic photosensitive member can be provided. Further, since the charge transporting material is a heat-resistant thermosetting polymer, the charge transporting material has excellent stability and printing durability.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of an electrophotographic photosensitive member using a photoconductive layer according to an embodiment of the present invention. 1 ... Support, 2 ... Photoconductive layer, 3 ... Free surface.

Claims (1)

(57) [Claims] At least, in a photoconductive layer including a charge generation material that generates carriers by photoexcitation and a charge transport material that transports the carriers, the charge transport material has P-phenylene, has an S atom in a para position, and has an O atom. Comprises a linear compound polymer bonded to the S atom. 2. The photoconductive layer according to claim 1, wherein the charge generating material is an inorganic material. 3. 2. The photoconductive layer according to claim 1, wherein the charge generating material is an organic material. 4. 2. The photoconductive layer according to claim 1, wherein the photoconductive layer contains a resin as a binder. 5. 2. The photoconductive layer according to claim 1, wherein the ratio of the number of O atoms to the number of C atoms in the linear compound polymer of the charge transport material is 1 to 35 atm%. 6. The weight ratio of the charge transport material in the photoconductive layer is 10 to 9
2. Photoconductive layer according to claim 1, characterized in that it is 9.5%, preferably 50-95%. 7. The weight ratio of the charge generation material in the photoconductive layer is 0.5 to 9
2. The photoconductive layer according to claim 1, wherein the content is 0%, preferably 5 to 50%. 8. 2. The photoconductive layer according to claim 1, wherein an electron acceptor is added to the photoconductive layer. 9. The photoconductive layer according to claim 1, wherein the charge generating material is a phthalocyanine compound. 10. At least, a charge generation material that generates carriers by photoexcitation, and a photoconductive layer including a charge transport material that transports the carriers, the charge transport material having P-phenylene, having an S atom in the para position, In the method for producing a photoconductive layer containing a linear compound polymer in which an O atom is bonded to the S atom, the step of forming the photoconductive layer includes a heat treatment in an atmosphere containing oxygen. A method for producing a photoconductive layer. 11. 11. The method for producing a photoconductive layer according to claim 10, wherein a heating temperature of the heat treatment in an atmosphere containing oxygen is in a range of 200 to 350 ° C.