Electrophotographic photoconductor, method of manufacturing the same, and electrophotographic device including the same
11073771 · 2021-07-27
Assignee
Inventors
Cpc classification
G03G5/047
PHYSICS
International classification
G03G5/06
PHYSICS
G03G5/05
PHYSICS
Abstract
An electrophotographic photoconductor includes a conductive substrate; and a photosensitive layer provided on the conductive substrate and containing a charge generation material, a hole transport material, a first electron transport material, from 3% by mass to 40% by mass of a second electron transport material, a resin binder, and an inorganic oxide filler surface-treated with a silane coupling agent. In a dipole-dipole force component (a Hansen solubility parameter), the first electron transport material and the silane coupling agent have a difference of ΔSPa<2.50; the second electron transport material and the silane coupling agent have a difference of ΔSPb<2.50; and the first electron transport material and the second electron transport material have a difference of 0.30<ΔSPc<1.00. In a London dispersion force component (a Hansen solubility parameter), the resin binder and the silane coupling agent have a difference of ΔSPd<2.00.
Claims
1. An electrophotographic photoconductor, comprising: a conductive substrate; and a photosensitive layer provided on the conductive substrate and containing a charge generation material, a hole transport material, a first electron transport material, a second electron transport material, a resin binder, and an inorganic oxide filler surface-treated with a silane coupling agent, wherein the first electron transport material and the silane coupling agent have a difference ΔSPa in a dipole-dipole force component, that is a Hansen solubility parameter, between the first electron transport material and the silane coupling agent that satisfies a relationship of ΔSPa<2.50, wherein the second electron transport material and the silane coupling agent have a difference ΔSPb in a dipole-dipole force component, that is a Hansen solubility parameter, between the second electron transport material and the silane coupling agent that satisfies a relationship of ΔSPb<2.50, wherein the first electron transport material and the second electron transport material have a difference ΔSPc in a dipole-dipole force component, that is a Hansen solubility parameter, between the first electron transport material and the second electron transport material that satisfies a relationship of 0.30<ΔSPc<1.00, wherein the resin binder and the silane coupling agent have a difference ΔSPd in a London dispersion force component, that is a Hansen solubility parameter, between the resin binder and the silane coupling agent that satisfies a relationship of ΔSPd<2.00, and wherein the second electron transport material is present in an amount ranging from 3% by mass to 40% by mass with respect to combined content of the first electron transport material and the second electron transport material.
2. The electrophotographic photoconductor according to claim 1, wherein the first electron transport material and the second electron transport material are selected from compounds represented by general formulas (ET1) and (ET2) as follows: ##STR00014## where R.sub.1 and R.sub.2 are the same or different and each represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or an alkyl halide group, R.sub.3 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or an alkyl halide group, where R.sub.4 to R.sub.8 are the same or different and each represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, an aralkyl group which may have a substituent, a phenoxy group which may have a substituent, an alkyl halide group, a cyano group, or a nitro group with a condition that two or more groups may be combined to form a ring, and each substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or an alkyl halide group; and ##STR00015## where R.sub.9 and R.sub.10 are the same or different and each represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or an alkyl halide group, and each substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or an alkyl halide group.
3. The electrophotographic photoconductor according to claim 2, wherein the inorganic oxide filler has a primary particle size ranging from 1 nm to 300 nm.
4. The electrophotographic photoconductor according to claim 2, wherein the photosensitive layer consists of a single layer containing the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler.
5. The electrophotographic photoconductor according to claim 4, wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in a total solid content of the photosensitive layer, and wherein the inorganic oxide filler is present in a content F (% by mass) in the total solid content of the photosensitive layer that is smaller than the combined content E (% by mass) of the first electron transport material and the second electron transport material, and the content F satisfies a relationship of 2≤F≤15.
6. The electrophotographic photoconductor according to claim 1, wherein the first electron transport material and the second electron transport material are compounds represented by structural formulas (A1) and (A2) as follows: ##STR00016##
7. The electrophotographic photoconductor according to claim 6, wherein the inorganic oxide filler has a primary particle size ranging from 1 nm to 300 nm.
8. The electrophotographic photoconductor according to claim 6, wherein the photosensitive layer consists of a single layer containing the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler.
9. The electrophotographic photoconductor according to claim 8, wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in a total solid content of the photosensitive layer, and wherein the inorganic oxide filler is present in a content F (% by mass) in the total solid content of the photosensitive layer that is smaller than the combined content E (% by mass) of the first electron transport material and the second electron transport material, and the content F satisfies a relationship of 2≤F≤15.
10. The electrophotographic photoconductor according to claim 1, wherein the inorganic oxide filler has a primary particle size of from 1 nm to 300 nm.
11. The electrophotographic photoconductor according to claim 10, wherein the photosensitive layer consists of a single layer containing the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler.
12. The electrophotographic photoconductor according to claim 11, wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in a total solid content of the photosensitive layer, and wherein the inorganic oxide filler is present in a content F (% by mass) in the total solid content of the photosensitive layer that is smaller than the combined content E (% by mass) of the first electron transport material and the second electron transport material, and the content F satisfies a relationship of 2≤F≤15.
13. The electrophotographic photoconductor according to claim 1, wherein the photosensitive layer consists of a single layer containing the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler.
14. The electrophotographic photoconductor according to claim 13, wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in a total solid content of the photosensitive layer, and wherein the inorganic oxide filler is present in a content F (% by mass) in the total solid content of the photosensitive layer that is smaller than the combined content E (% by mass) of the first electron transport material and the second electron transport material, and the content F satisfies a relationship of 2≤F≤15.
15. The electrophotographic photoconductor according to claim 1, wherein the photosensitive layer includes a charge transport layer and a charge generation layer layered disposed in that order on the conductive substrate, and the charge generation layer contains the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler.
16. The electrophotographic photoconductor according to claim 15, wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in a total solid content of the charge generation layer, and wherein the inorganic oxide filler is present in a content F (% by mass) in the total solid content of the charge generation layer that is smaller than the combined content E (% by mass) of the first electron transport material and the second electron transport material, and the content F satisfies a relationship of 2≤F≤15.
17. The electrophotographic photoconductor according to claim 16, wherein the hole transport material is present in a content H (% by mass) in a solid content of the charge generation layer, and wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in the solid content of the charge generation layer that is larger than the content H (% by mass) of the hole transport material, and the combined content E and the content H satisfy 1.5≤E/H≤10.0.
18. The electrophotographic photoconductor according to claim 15, wherein the hole transport material is present in a content H (% by mass) in a solid content of the charge generation layer, and wherein the first electron transport material and the second electron transport material are present in a combined content E (% by mass) in the solid content of the charge generation layer that is larger than the content H (% by mass) of the hole transport material, and the combined content E and the content H satisfy 1.5≤E/H≤10.0.
19. A method of manufacturing an electrophotographic photoconductor according to claim 1, comprising: providing a coating solution containing the charge generation material, the hole transport material, the first electron transport material, the second electron transport material, the resin binder, and the inorganic oxide filler surface-treated with a silane coupling agent; dip coating the conductive substrate into the coating solution to provide a coating; and drying the coating to forming the photosensitive layer.
20. An electrophotographic device comprising the electrophotographic photoconductor according to claim 1.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1)
(2)
(3)
(4)
(5)
(6)
DETAILED DESCRIPTION OF THE INVENTION
(7) Hereinafter, specific embodiments of the electrophotographic photoconductor of the present invention will be described in detail with reference to the drawings. The present invention is not limited at all by the following description.
(8)
(9)
(10) The conductive substrate 1 serves not only as an electrode of the photoconductor but also as a support for each layer constituting the photoconductor, and may have any shape such as a cylindrical shape, a plate shape, and a film shape. Examples of a material of the conductive substrate 1 include metals such as aluminum, stainless steel, and nickel, and materials obtained by performing a conductive treatment on the surface of glass, resin, and the like.
(11) The undercoat layer 2 is made of a layer mainly composed of a resin or a metal oxide film such as alumite, and may have a layered structure of an alumite layer and a resin layer. The undercoat layer 2 is provided as necessary for the purpose of controlling charge injection from the conductive substrate 1 to the photosensitive layer, covering defects on the surface of the conductive substrate 1, and improving the adhesiveness between the photosensitive layer and the conductive substrate 1. Examples of a resin material used for the undercoat layer 2 include insulating polymers such as casein, polyvinyl alcohol, polyamide, melamine, and cellulose, and conductive polymers such as polythiophene, polypyrrole, and polyaniline, which may be used singly or in combination as appropriate. Further, these resins may contain a metal oxide such as titanium dioxide or zinc oxide when used.
(12) Positively Charged Single-Layered Photoconductor
(13) In the positively charged single-layered photoconductor, the single-layered photosensitive layer 3 is a photosensitive layer formed on the undercoat layer 2. The single-layered photosensitive layer 3 is a single-layered positively charged photosensitive layer which is a single layer mainly containing a charge generation material, a hole transport material, and an electron transport material and resin binder. The photosensitive layer 3 further contains an inorganic oxide filler surface-treated with a silane coupling agent.
(14) Examples of a charge generation material include X-type metal-free phthalocyanine, α-type titanyl phthalocyanine, β-type titanyl phthalocyanine, Y-type titanyl phthalocyanine, γ-type titanyl phthalocyanine, and amorphous-type titanyl phthalocyanine, which may be used singly or in combination as appropriate. A suitable substance can be selected according to the light wavelength range of an exposure light source used for image formation. From the viewpoint of increasing the sensitivity, titanyl phthalocyanine having high quantum efficiency is optimal.
(15) Examples of a hole transport material include various hydrazone compounds, styryl compounds, diamine compounds, butadiene compounds, indole compounds, and the like, which may be used singly or in combination as appropriate. However, a styryl compound having a triphenylamine skeleton is suitable in terms of cost and performance.
(16) An electron transport material includes first and second electron transport materials. The first and second electron transport materials may be selected from the group consisting of, for example, succinic anhydride, maleic anhydride, dibromo succinic anhydride, phthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic anhydride, pyromellitic acid, trimellitic acid, trimellitic anhydride, phthalimide, 4-nitrophthalimide, tetracyanoethylene, tetracyanoquinodimethane, chloranil, bromanil, o-nitrobenzoic acid, malononitrile, trinitrofluorenone, trinitrothioxanthone, dinitrobenzene, dinitroanthracene, dinitroacridine, nitroanthraquinone, dinitroanthraquinone, thiopyran compounds, quinone compounds, benzoquinone compounds, diphenoquinone compounds, naphthoquinone compounds, anthraquinone compounds, stilbenequinone compounds, azoquinone compounds, naphthalenetetracarboxylic diimide compounds, and the like.
(17) The first electron transport material and the second electron transport material are preferably selected from an azoquinone compound represented by general formula (ET1) below and a naphthalenetetracarboxylic diimide compound represented by general formula (ET2) below. Further, a naphthalenetetracarboxylic diimide compound represented by general formula (ET2) below is preferable as a first electron transport material, and an azoquinone compound represented by general formula (ET1) below is preferable as a second electron transport material. A naphthalenetetracarboxylic diimide compound contributes to potential stability in environmental changes. An azoquinone compound contributes to suppression of ghost images.
(18) ##STR00004##
where R.sub.1 and R.sub.2 are the same or different and each represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or an alkyl halide group, R.sub.3 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group which may have a substituent, a cycloalkyl group, an aralkyl group which may have a substituent, or an alkyl halide group, R.sub.4 to R.sub.8 are the same or different and each represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, an aralkyl group which may have a substituent, a phenoxy group which may have a substituent, an alkyl halide group, a cyano group, or a nitro group with a condition that two or more groups may be combined to form a ring, and each substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or an alkyl halide group.
(19) ##STR00005##
where R.sub.9 and R.sub.10 are the same or different and each represent a hydrogen atom, a halogen atom, a cyano group, a nitro group, a hydroxyl group, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an ester group, a cycloalkyl group, an aralkyl group which may have a substituent, an allyl group, an amide group, an amino group, an acyl group, an alkenyl group, an alkynyl group, a carboxyl group, a carbonyl group, a carboxylic acid group, or an alkyl halide group, and each substituent represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a hydroxyl group, a cyano group, an amino group, a nitro group, or an alkyl halide group.
(20) Specific examples of an electron transport material such as a naphthalenetetracarboxylic diimide compound or an azoquinone compound are represented by, for example, structural formulas A1 to A18 below. Suitable examples of the first electron transport material and the second electron transport material include a combination of a compound selected from the group consisting of compounds represented by structural formulas A1, A12, A13, A14, and A15 and a compound selected from the group consisting of compounds represented by structural formulas A2 and A11. In addition, it is also preferable that the first electron transport material and the second electron transport material are a combination of compounds represented by structural formulas (A1) and (A2).
(21) ##STR00006## ##STR00007## ##STR00008## ##STR00009##
(22) Examples of a resin binder that can be used for the single-layered photosensitive layer 3 include polycarbonate resins such as bisphenol A, bisphenol Z, bisphenol A-biphenyl copolymer, and bisphenol Z-biphenyl copolymer, polyphenylene resin, polyester resin, polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl alcohol resin, vinyl chloride resin, vinyl acetate resin, polyethylene resin, polypropylene resin, acrylic resin, polyurethane resin, epoxy resin, melamine resin, silicone resin, polyamide resin, polystyrene resin, polyacetal resin, polyarylate resin, polysulfone resin, methacrylate polymer, and copolymers thereof. Further, resins of the same type having different molecular weights may be used in combination.
(23) Specific examples of a preferable resin binder include polycarbonate resins having repeating units, such as bisphenol Z and bisphenol Z-biphenyl copolymer, represented by the following structural formulas (B1) to (B4).
(24) ##STR00010##
(25) The weight average molecular weight of a resin binder is preferably from 5,000 to 250,000, more preferably from 10,000 to 200,000 in GPC (gel permeation chromatography) analysis in terms of polystyrene.
(26) The inorganic oxide filler surface treated with a silane coupling agent is a material in which a silane coupling agent is attached to the surface of an inorganic oxide filler.
(27) Examples of the inorganic oxide filler include fine particles mainly composed of silica as well as fine particles mainly composed of alumina, zirconia, titanium oxide, tin oxide, zinc oxide, or the like. These fine particles may have a hydroxyl group on the surface thereof when used, and when the fine particles are directly mixed into a coating liquid, the fine particles tend to aggregate with each other.
(28) The primary particle size of the inorganic oxide filler is in a range of preferably from 1 nm to 300 nm, more preferably from 5 nm to 100 nm, still more preferably from 10 nm to 50 nm. When the primary particle size of the inorganic oxide filler is less than 1 nm, the dispersion state may be uneven due to aggregation. On the other hand, when the primary particle size of the inorganic oxide filler exceeds 300 nm, light scattering may increase and image loss may occur. The primary particle size is a number average diameter measured using a scanning microscope capable of directly observing the surface shape of particles.
(29) Fine particles containing silica as a main component are preferable as the inorganic oxide filler. As a method of producing silica fine particles, a method of producing water glass as a raw material, which is called a wet method, a method of reacting chlorosilane or the like in a gas phase, which is called a dry method, a method of using an alkoxide, i.e., a silica precursor as a raw material, and the like have been known. Examples of such silica fine particles include YA010C manufactured by Admatechs Company Limited.
(30) Surface treatment of the inorganic oxide filler with a silane coupling agent causes hydroxyl groups on the surface of the inorganic oxide filler and the silane coupling agent to bind to each other, thereby reducing cohesiveness between inorganic oxide filler particles.
(31) Specific examples of the silane coupling agent include compounds represented by the following structural formulas C1 to C5:
(32) ##STR00011##
(33) In a case in which a large amount of a dissimilar metal is present as an impurity in the inorganic oxide filler, defects caused by the metal at sites different from the sites of an ordinary oxide result in fluctuations in the charge distribution on the surface, which improves the cohesiveness of the filler starting from those sites and eventually causes an increase in aggregates in the coating liquid and the photosensitive layer during surface treatment. It is therefore preferable that the filler has high purity. It is preferable that the content of a metal other than the metal elements constituting the filler is controlled to 1000 ppm or less for each metal.
(34) Meanwhile, in order to sufficiently react a surface-treating agent to improve the activity on the silica surface, it is preferable to add a very small amount of a different metal. The surface-treating agent reacts with a hydroxyl group present on the surface of silica. However, in a case in which silica contains a trace amount of a different metal, reactivity of a silanol group (hydroxyl group) adjacent to the different metal present on the silica surface is improved due to the influence of the difference in electronegativity between metals. Since this hydroxyl group has high reactivity with the surface-treating agent, it reacts with the surface-treating agent more strongly than other hydroxyl groups, and when remaining, it causes aggregation. After the reaction with the surface-treating agent, the surface-treating agent reacts with other hydroxyl groups, and due to the effects of the surface-treating agent and the effects of reducing the bias of the surface charge due to the dissimilar metal on the surface, the cohesiveness between silica particles is expected to be greatly improved. In an embodiment of the present invention, in a case in which the inorganic oxide contains a trace amount of a different metal, the reactivity of the surface-treating agent becomes more favorable, and as a result, the dispersibility is improved due to surface treatment, which is preferable. It can be said that the improvement in the cohesiveness when the above-described dissimilar metal is present in a large amount as an impurity and the improvement in the dispersibility by including a very small amount of a different metal are based on different mechanisms.
(35) Regarding silica, the addition of aluminum in a range of 1000 ppm or less is preferable for surface treatment. The amount of aluminum in silica can be adjusted using a method described in JP2004-143028A, JP2013-224225A, or the like. The adjustment method is not particularly limited as long as the amount can be controlled in a desired range. Specifically, as a method of more preferably controlling the amount of aluminum on the silica surface, for example, the following method is available. There is a method in which first, when producing silica fine particles, after growing the silica particles in a shape smaller than the target silica particle size, the amount of aluminum on the silica surface is controlled by, for example, adding aluminum alkoxide serving as an aluminum source. There are also an method in which silica fine particles are put in a solution containing aluminum chloride to coat the surfaces of silica fine particles with the aluminum chloride solution, and the particles are dried to and fired, a method in which a mixed gas of an aluminum halide compound and a silicon halide compound is reacted, and the like.
(36) In addition, it is known that the structure of silica is such that a plurality of silicon atoms and oxygen atoms are connected cyclically to form a network-like bonding structure. When aluminum is contained, the number of atoms constituting the cyclic structure of silica becomes larger than that of ordinary silica due to the effect of mixing aluminum. Due to this effect, steric hindrance present when the surface treatment agent reacts with the hydroxyl group on the aluminum-containing silica surface is reduced as compared to the ordinary silica surface, and the reactivity of the surface-treating agent is improved, resulting in surface-treated silica having improved dispersibility as compared to when the same surface treatment agent is reacted with ordinary silica.
(37) Here, in order to maintain the effects of the embodiment of the present invention, silica obtained by a wet method is more preferable for controlling the amount of aluminum. Further, the content of aluminum with respect to silica is preferably 1 ppm or more in consideration of the reactivity of the surface-treating agent.
(38) The form of the inorganic oxide is not particularly limited. However, in order to reduce cohesiveness and achieve a uniform dispersion state, the sphericity of the organic oxide is preferably 0.8 or more, more preferably 0.9 or more.
(39) When using an organic oxide for a charge transport layer of a photoconductor where high resolution is expected, it is preferable to consider the effects of α-rays derived from a material added to the charge transport layer. For example, taking a semiconductor memory element as an example, the memory element holds the type of data to be stored depending on whether or not electric charges are stored, while on the other hand, the size of the stored charges also decreases with miniaturization, and the type of data changes due to charges that would vary with α-rays emitted from the outside, resulting in unexpected changes in data. Further, since the magnitude of the current flowing through the semiconductor element also becomes small, the current (noise) generated by α-rays becomes relatively large as compared with the magnitude of the signal, which may cause malfunction. Considering the influence on the movement of charges in the charge transport layer of the photoconductor in the same manner as the above phenomenon, it is more preferable to use a material that generates less α-rays as a material constituting a film. Specifically, it is effective to reduce the concentrations of uranium and thorium in an organic oxide. Preferably, the concentration of thorium is 30 ppb or less and the concentration of uranium is 1 ppb or less. A method of reducing the amounts of uranium and thorium in an inorganic oxide is described in, for example, JP2013-224225A. However, the method is not limited as long as the concentrations of these elements can be reduced.
(40) A combination of an electron transport material, a resin binder, and a silane coupling agent used for a single-layered photosensitive layer 3 preferably satisfies a specific relationship with respect to Hansen solubility parameters. A difference ΔSPa in a dipole-dipole force component that is a Hansen solubility parameter between a first electron transport material and a silane coupling agent satisfies a relationship of ΔSPa<2.50. A difference ΔSPb in a dipole-dipole force component that is a Hansen solubility parameter between a second electron transport material and a silane coupling agent satisfies a relationship of ΔSPb<2.50. A difference ΔSPc in a dipole-dipole force component that is a Hansen solubility parameter between a first electron transport material and a second electron transport material satisfies a relationship of 0.30<ΔSPc<1.00. Further, a difference ΔSPd in a London dispersion force component that is a Hansen solubility parameter between a resin binder and a silane coupling agent satisfies a relationship of ΔSPd<2.00.
(41) By selecting materials satisfying such relationships, compatibility among the electron transport material, the resin binder, and the silane coupling agent, and in particular, sufficient compatibility between the first electron transport material and the second electron transport material can be achieved in the single-layered photosensitive layer 3, allowing dispersibility of the inorganic oxide filler to be improved. The high dispersibility also makes it possible to sufficiently reduce the abrasion amount on the surface of the photoconductor, and at the same time, to ensure favorable electrical characteristics and image characteristics.
(42) Regarding the Hansen solubility parameter of the silane coupling agent, ΔSPa and ΔSPb are preferably ΔSPa≤2.40 and ΔSPb≤2.40, and ΔSPd is ΔSPd<1.90. The smaller they are, the more preferable they are.
(43) Regarding the Hansen solubility parameters of the first electron transport material and the second electron transport material, ΔSPc is in a range of 0.30<ΔSPc<1.00, preferably 0.30<ΔSPc<0.80, still more preferably 0.30<ΔSPc<0.60. When ΔSPc is 0.30 or less, great compatibility between the first electron transport material and the second electron transport material makes it impossible to obtain sufficient effects in terms of filler dispersibility even selecting a silane coupling agent that satisfies ΔSPa and ΔSPb. When ΔSPc is 1.00 or more, compatibility between two types of electron transport materials is insufficient, resulting in a decrease in dispersibility at the molecular level and formation of charge traps. Thus, ghost reduction effects cannot be obtained sufficiently. In the case of ΔSPc<0.60, excellent ghost reduction effects can be obtained.
(44) The content of each material relative to the solid content of the single-layered photosensitive layer 3 is as follows. The content of a charge generation material is preferably from 0.1% to 5% by mass, more preferably from 0.5% to 3% by mass. The content of a hole transport material is preferably from 3% to 60% by mass, more preferably from 10% to 40% by mass. The content of an electron transport material is preferably from 1% to 50% by mass, more preferably from 5% to 20% by mass. The content of an inorganic oxide filler surface-treated with a silane coupling agent is preferably from 2% to 15% by mass. The content of a resin binder is preferably from 20% to 80% by mass, more preferably from 30% to 70% by mass. The content of a resin binder may be preferably from 20% to 90% by mass, more preferably from 30% to 80% by mass relative to the solid content of the photosensitive layer 3 excluding an inorganic oxide filler.
(45) The ratio of the contents of the electron transport material and the hole transport material may be in a range of from 1:1 to 1:4, preferably in a range of from 1:1 to 1:3. From the viewpoint of the transport balance between holes and electrons, a ratio in this range is preferable in sensitivity characteristics, charging characteristics, and fatigue characteristics. The ratio of the content of the second electron transport material to the content of the first electron transport material and the second electron transport material is desirably in a range of from 3% by mass to 40% by mass. When the content of the second electron transport material is not in a range of from 3% by mass to 40% by mass, the improvement of electron injectability becomes insufficient, and ghost suppression effects cannot be sufficiently obtained.
(46) In addition, regarding the solid content of the single-layered photosensitive layer 3, when the content of the inorganic oxide filler is F (% by mass) and the content of the first electron transport material and the second electron transport material is E (% by mass), the content F is preferably smaller than the combined content E. When the content F is equal to or larger than the combined content E, the improvement of electron injectability of the electron transport material becomes insufficient, and the effect of suppressing ghost may not be obtained.
(47) Further, the ratio of the content E2 (% by mass) of the second electron transport material to the content F (% by mass) of the inorganic oxide filler is preferably in a range of from 1/15 to 20. When the amount is other than this ratio, the electron injectability becomes insufficient, and the effect of suppressing ghost may not be obtained.
(48) The film thickness of the single-layered photosensitive layer 3 is preferably in a range of from 12 to 40 μm, more preferably from 15 to 35 μm, and still more preferably from 20 to 30 μm from the viewpoint of ensuring practically effective performance.
(49) The single-layered photosensitive layer 3 may contain a deterioration inhibitor such as an antioxidant or a light stabilizer for the purpose of improving environmental resistance and stability against harmful light, if desired. Examples of a compound used for such purpose include chromanol derivatives such as tocopherol, esterified compounds, polyarylalkane compounds, hydroquinone derivatives, etherified compounds, dietherified compounds, benzophenone derivatives, benzotriazole derivatives, thioether compounds, phenylenediamine derivatives, phosphonates, phosphites, phenol compounds, hindered phenol compounds, linear amine compounds, cyclic amine compounds, hindered amine compounds, and the like.
(50) The single-layered photosensitive layer 3 may contain a leveling agent such as silicone oil or fluorine-based oil for the purpose of improving the leveling property of a formed film and imparting lubricity. In addition to the inorganic oxide filler surface-treated with a silane coupling agent, fine particles of metal oxide such as calcium oxide, metal sulfates such as barium sulfate and calcium sulfate, fine particles of metal nitride such as silicon nitride or aluminum nitride or particles of fluorine resin such as tetrafluoroethylene resin, fluorine-based comb-type graft polymer resin, or the like may be further contained for the purpose of adjusting the film hardness, reducing the coefficient of friction, imparting lubricity, or the like. Furthermore, if necessary, other known additives can be contained within a range that does not significantly impair electrophotographic properties.
(51) Positively Charged Multi-Layered Photoconductor
(52) In the case of a positively charged multi-layered photoconductor, a multi-layered photosensitive layer 6 includes a charge transport layer 4 and a charge generation layer 5. The charge transport layer 4 and the charge generation layer 5 are layered in that order on a conductive substrate 1. In the positively charged multi-layered photoconductor, the charge transport layer 4 contains a hole transport material and resin binder, the charge generation layer 5 contains a charge generation material, a hole transport material, a first electron transport material, a second electron transport material, an inorganic oxide filler surface-treated with a silane coupling agent, and resin binder. A undercoat layer 2 may be provided between the conductive substrate 1 and the charge transport layer 4.
(53) As the hole transport material and the resin binder in the charge transport layer 4, the same materials as those described for the single-layered photosensitive layer 3 can be used. The content of the hole transport material in the charge transport layer 4 is preferably from 10% to 80% by mass, more preferably from 20% to 70% by mass relative to the solid content of the charge transport layer 4. The content of the resin binder in the charge transport layer 4 is preferably from 20% to 90% by mass, more preferably from 30% to 80% by mass relative to the solid content of the charge transport layer 4. The film thickness of the charge transport layer 4 is preferably in a range of from 3 to 50 μm, and more preferably in a range of from 15 to 40 μm in order to maintain a practically effective surface potential.
(54) As the charge generation material, the hole transport material, first electron transport material, the second electron transport material, the inorganic oxide filler surface-treated with a silane coupling agent, and the resin binder in the charge generation layer 5, the same materials as those described for the single-layered photosensitive layer 3 can be used.
(55) In the case of a positively charged multi-layered photoconductor, a combination of an electron transport material, a resin binder, and a silane coupling agent used for a charge generation layer 5 preferably satisfies a specific relationship the same as that for a single-layered photosensitive layer 3 with respect to the Hansen solubility parameter.
(56) The content of each material relative to the solid content of the charge generation layer 5 is as follows. The content of a charge generation material is preferably from 0.1% to 5% by mass, more preferably from 0.5% to 3% by mass. The content of a hole transport material is preferably from 1% to 30% by mass, more preferably from 5% to 20% by mass. The content of an electron transport material is preferably from 5% to 60% by mass, more preferably from 10% to 40% by mass. The content of an inorganic oxide filler surface-treated with a silane coupling agent is preferably from 2% to 15% by mass. The content of a resin binder is preferably from 20% to 80% by mass, more preferably from 30% to 70% by mass.
(57) The ratio of the content of the second electron transport material to the content of the first electron transport material and the second electron transport material is desirably in a range of from 3% by mass to 40% by mass.
(58) Regarding the solid content of the charge generation layer 5, when the content of the inorganic oxide filler is F (% by mass), the combined content of the first electron transport material and the second electron transport material is E (% by mass), and the content of the hole transport material is H (% by mass), the content F is preferably smaller than the combined content E, and the combined content E is preferably greater than the content H (% by mass). Further, the ratio of the content E2 (% by mass) of the second electron transport material to the content F (% by mass) of the inorganic oxide filler is preferably in a range of from 1/15 to 20.
(59) By controlling the contents within these ranges, electron injectability is improved, and the balance of the charge transfer with the hole transport material is also improved, so that the effect of suppressing ghost is more effectively obtained.
(60) The ratio of the combined content E (% by mass) of the electron transport material to the content H (% by mass) of the hole transport material is preferably 1.5≤E/H≤10.0, which means that H:E may be in a range of from 1:1.5 to 1:10, more preferably from 1:2 to 1:10. An electron transport material includes first and second electron transport materials. Even when the content of the electron transport material relative to the hole transport material is large, it is possible to suppress crystallization in the photosensitive layer using the above-described first and second electron transport materials, thereby sufficiently dispersing the filler.
(61) The film thickness of the charge generation layer 5 can be the same as that of the single-layered photosensitive layer 3 of the single-layered photoconductor. The film thickness is preferably in a range of from 3 to 100 μm, more preferably in a range of from 5 to 40 μm.
(62) Further, as with the single-layered photosensitive layer 3, the multi-layered photosensitive layer 6 can contain a deterioration inhibitor such as an antioxidant or a light stabilizer, a leveling agent, and the like, if desired.
(63) Method of Manufacturing Photoconductor
(64) A method of manufacturing a photoconductor according to the embodiment of the present invention includes a step of forming a photosensitive layer using a dip coating method when manufacturing the above-described electrophotographic photoconductor.
(65) The method of manufacturing a single-layered photoconductor is illustrated in
(66) The method of manufacturing a multi-layered photoconductor includes a step of forming a charge transport layer on a conductive substrate and a step of forming a charge generation layer. The step of forming a charge transport layer includes: dissolving an arbitrary hole transport material and a resin binder in a solvent to prepare a coating liquid for forming a charge transport layer; and a step of applying the coating liquid to the outer periphery of a conductive substrate by a dip coating method via an undercoat layer as required; and a step of drying the coating liquid. Next, the sequence of steps in
(67) The step of preparing a coating liquid containing an inorganic oxide filler surface-treated with a silane coupling agent may include: a step of dispersing a charge generation material and the like in a solvent to prepare a coating liquid A; and a step of dispersing the inorganic oxide filler surface-treated with a silane coupling agent in the coating liquid A to prepare a coating liquid B.
(68) Examples of a solvent used for forming a photosensitive layer can include: halogenated hydrocarbons such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, and chlorobenzene; ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, dioxane, dioxolane, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether; and ketones such as acetone, methyl ethyl ketone, and cyclohexanone. Such a solvent can be appropriately selected from the viewpoints of solubility, liquid stability, and coating performance of various materials.
(69) Here, the type of solvent used for preparing the coating liquid, coating conditions, drying conditions, and the like can also be appropriately selected according to an ordinary method, and are not particularly limited.
(70) Electrophotographic Device
(71) An electrophotographic device according to the embodiment of the present invention includes with the above-described photoconductor, and thus, expected effects can be obtained by applying the electrophotographic device to various machine processes. Specifically, sufficient effects can be obtained also in charging processes such as a contact charging method using a charging member such as a roller or brush and a non-contact charging method using a charging member such as corotron or scorotron and development processes such as a contact development method and a non-contact development method using non-magnetic one-component, magnetic one-component, two-component development methods (developers) and the like.
(72) The electrophotographic device of the embodiment of the present invention includes the above-described electrophotographic photoconductor, and can be an electrophotographic device for tandem color printing at a printing speed of 20 ppm or more. Further, the electrophotographic device according to another embodiment of the present invention can be an electrophotographic device including the above-described electrophotographic photoconductor and having a printing speed of 40 ppm or more. It is considered that space charges easily accumulate in devices where photoconductors are heavily used, such as high-speed machines that require high charge transport performance in the photosensitive layer and tandem color machines that are greatly affected by discharge gas, especially those with short time between processes. In such an electrophotographic device, since ghost images are easily generated, the application of the present invention is more useful. In particular, in a tandem-type electrophotographic device for color printing or an electrophotographic device having no discharging member, ghost images are likely to occur, and therefore, the application of the present invention is useful.
(73)
(74)
EXAMPLES
(75) Hereinafter, specific embodiments of the present invention will be described in more detail using the Examples. The present invention is not limited by the following Examples unless it exceeds the gist thereof.
(76) Example of preparing positively charged single-layered photoconductor
Example 1
(77) As a conductive substrate, a 0.75-mm thick aluminum tube cut to have a diameter φ of 30 mm× a length of 244.5 mm and a surface roughness (Rmax) of 0.2 μm was used. The conductive substrate had an alumite layer on the surface.
(78) Single-Layered Photosensitive Layer
(79) A single-layered photosensitive layer was formed according to the compounding amounts shown in Table 1 below. A coating liquid A was prepared by dissolving a compound represented by structural formula (HT1) below as a hole transport material, a compound represented by the structural formula (A1) described above as a first electron transport material, a compound represented by the structural formula (A2) described above as a second electron transport material, and a polycarbonate resin having a repeating unit represented by the structural formula (B1) described above as a resin binder in tetrahydrofuran, adding titanyl phthalocyanine represented by structural formula (CG1) below as a charge generation material, and performing dispersion treatment with a sand grind mill. As an inorganic oxide filler surface treated with a silane coupling agent, a surface-treated silica was prepared by surface-treating silica manufactured by Admatechs Company Limited (YA010C; aluminum content: 500 ppm) with a silane coupling agent represented by the structural formula (C1) described above. The surface-treated silica was mixed and dispersed in the coating liquid A to prepare a photosensitive layer coating liquid B in which the filler was dispersed. The coating liquid B was applied to the above-described conductive substrate by a dip coating method, and dried at a temperature of 100° C. for 60 minutes to form a single-layered photosensitive layer having a film thickness of about 25 μm, thereby obtaining a positively charged single-layered photoconductor.
(80) ##STR00012##
Examples 2 to 15 and Comparative Examples 1 to 9
(81) A single-layered photosensitive layer was formed in the same manner as in Example 1 except that the type and amount of each material were changed according to the conditions shown in Table 1 below, thereby obtaining the positively charged single-layered photoconductors of Examples 2 to 15 and Comparative Examples 1 to 9. The structural formulas of the materials used in the Comparative Examples are shown below.
(82) ##STR00013##
(83) Example of preparing positively charged multi-layered photoconductor
Example 16
(84) As a conductive substrate, a 0.75-mm thick aluminum tube cut to have a diameter φ of 30 mm× a length of 254.4 mm and a surface roughness (Rmax) of 0.2 μm was used. The conductive substrate had an alumite layer on the surface.
(85) Charge Transport Layer
(86) A coating liquid C was prepared by dissolving a compound represented by the structural formula (HT1) described above as a hole transport material and a polycarbonate resin having a repeating unit represented by the structural formula (B1) described above as a resin binder in tetrahydrofuran. The coating liquid C was applied to the above-described conductive substrate by a dip coating method, and dried at 100° C. for 30 minutes, thereby forming a charge transport layer having a film thickness of 10 μm. The contents of the hole transport material and the resin binder with respect to the solid content of the charge transport layer were each 50.0% by mass.
(87) Charge Generation Layer
(88) A charge generation layer was formed according to the compounding amounts shown in Table 2 below. A coating liquid D was prepared by dissolving a compound represented by the structural formula (HT1) described above as a hole transport material, a compound represented by the structural formula (A1) described above as a first electron transport material, a compound represented by the structural formula (A2) described above as a second electron transport material, and a polycarbonate resin having a repeating unit represented by the structural formula (B1) described above as a resin binder in tetrahydrofuran, adding titanyl phthalocyanine represented by the structural formula (CG1) described above as a charge generation substance, and performing dispersion treatment with a sand grind mill. As an inorganic oxide filler surface treated with a silane coupling agent, a surface-treated silica was prepared by surface-treating silica manufactured by Admatechs Company Limited (YA010C; aluminum content: 500 ppm) with a silane coupling agent represented by the structural formula (C1) described above. The surface-treated silica was mixed and dispersed in the coating liquid D to prepare a charge generation layer coating liquid E in which the surface-treated silica was dispersed. A coating liquid E was applied to the above-described charge transport layer by a dip coating method, and dried at a temperature of 110° C. for 30 minutes to form a charge generation layer having a film thickness of 15 μm, thereby obtaining a positively charged multi-layered photoconductor having a photosensitive layer having a film thickness of about 25 μm.
Examples 17 to 32 and Comparative Examples 10 to 20
(89) A charge generation layer was formed in the same manner as in Example 16 except that the type and amount of each material were changed according to the conditions shown in Table 2 below, thereby obtaining the positively charged multi-layered photoconductors of Examples 17 to 32 and Comparative Examples 10 to 20.
(90) Evaluation of Positively Charged Single-Layered Photoconductors
(91) The single-layered photoconductors of Examples 1 to 15 and Comparative Examples 1 to 9 were each integrated into a commercially available printer HL5200DW manufactured by Brother Industries, Ltd. to evaluate each photoconductor under three environments of 10° C.-20% (LL, low temperature and low humidity), 25° C.-50% (NN, normal temperature and normal humidity), and 35° C.-85% (HH, High temperature and high humidity). The results are shown in Table 3 below.
(92) Evaluation of Electrical Characteristics
(93) The electrical characteristics of the photoconductor obtained in each of the Examples and Comparative Examples were evaluated by the following method using a process simulator (CYNTHIA91) manufactured by GENTEC. For the photoconductors of Examples 1 to 15 and Comparative Examples 1 to 9, the surface of each photoconductor was charged to +650 V by corona discharge in a dark place under the environment at a temperature of 22° C. and a humidity of 50%, and the surface potential V0 immediately after charging was measured. Subsequently, after leaving each photoconductor in a dark place for 5 seconds, the surface potential V5 was measured, and the potential retention rate Vk5(%) 5 seconds after charging was obtained according to the following calculation formula (1):
Vk5=V5/V0×100 (1).
(94) Next, using a halogen lamp as a light source, each photoconductor was irradiated with exposure light of 1.0 μW/cm.sup.2, which was dispersed at 780 nm using a filter, for 5 seconds after when the surface potential became +600 V, and the residual potential on the photoconductor surface 5 seconds after exposure was evaluated as Vr5 (V).
(95) Evaluation of Abrasion Resistance
(96) For the photoconductor obtained in each of the Examples and the Comparative Examples, 10,000 sheets of A4 paper were printed, the film thickness of the photosensitive layer before and after printing was measured, and the average abrasion amount (μm) after printing was evaluated. The average abrasion amount is a value obtained by measuring the film thickness at four points obtained by rotating the position of the center (130 mm from the end) of the photoconductor in the longitudinal direction by 90° in the circumferential direction and averaging the values.
(97) Evaluation of Ghost Image
(98) The halftone (1on2off) image shown in
(99) Evaluation of Environmental Stability of Print Density
(100) A solid pattern of 25 mm×25 mm square was formed on A4 paper under three environments of LL, NN and HH, and the print density was measured using a Macbeth densitometer in each environment. The difference between the minimum and maximum values of print density in the three environments was calculated. The results were classified into “⊚” with a print density of less than 0.1, “◯” with a print density of from 0.1 to less than 0.2, “Δ” with a print density of from 0.2 to less than 0.4, or “x” with a print density of 0.4 or more.
(101) Evaluation of Positively Charged Multi-Layered Photoconductor
(102) The positively charged multi-layered photoconductors of Examples 16 to 32 and Comparative Examples 10 to 20 were each integrated into a commercially available printer HL3170CDW manufactured by Brother Industries, Ltd. to evaluate each photoconductor under three environments of 10° C.-20% (LL, low temperature and low humidity), 25° C.-50% (NN, normal temperature and normal humidity), and 35° C.-85% (HH, High temperature and high humidity). The results are shown in Table 4 below.
(103) Evaluation of Electrical Characteristics
(104) The electrical characteristics of the photoconductor obtained in each of the Examples and Comparative Examples were evaluated by the following methods using a process simulator (CYNTHIA91) manufactured by GENTEC. For the photoconductors of Examples 16 to 32 and Comparative Examples 10 to 20, the surface of each photoconductor was charged to +650 V by corona discharge in a dark place under the environment at a temperature of 22° C. and a humidity of 50%, and the surface potential V0 immediately after charging was measured. Subsequently, after leaving each photoconductor in a dark place for 5 seconds, the surface potential V5 was measured, and the potential retention rate Vk5(%) 5 seconds after charging was obtained according to the following calculation formula (1):
Vk5=V5/V0×100 (1).
(105) Next, using a halogen lamp as a light source, each photoconductor was irradiated with exposure light of 1.0 μW/cm.sup.2, which was dispersed at 780 nm using a filter, for 5 seconds after when the surface potential became +600 V, and the residual potential on the photoconductor surface 5 seconds after exposure was evaluated as Vr5 (V).
(106) Evaluation of Abrasion Resistance
(107) For the photoconductor obtained in each of the Examples and the Comparative Examples, 10,000 sheets of A4 paper were printed, the film thickness of the photosensitive layer before and after printing was measured, and the average abrasion amount (μm) after printing was evaluated. The average abrasion amount is a value obtained by measuring the film thickness at four points obtained by rotating the position of the center (130 mm from the end) of the photoconductor in the longitudinal direction by 90° in the circumferential direction and averaging the values.
(108) Evaluation of Ghost Image
(109) The halftone (1on2off) image shown in
(110) Evaluation of Environmental Stability of Print Density
(111) A solid pattern of 25 mm×25 mm square was formed on A4 paper under three environments of LL, NN and HH, and the print density was measured using a Macbeth densitometer in each environment. The difference between the minimum and maximum values of print density in the three environments was calculated. The results were classified into “⊚” with a print density of less than 0.1, “◯” with a print density of from 0.1 to less than 0.2, “Δ” with a print density of from 0.2 to less than 0.4, or “x” with a print density of 0.4 or more.
(112) TABLE-US-00001 TABLE 1 Charge Hole First electron Second electron generation transport transport transport material material material material Resin binder Inorganic filler Con- Con- Con- Con- Con- Pri- Si- Con- tent tent tent tent tent mary lane tent (% (% (% (% (% Filler par- cou- (% Mate- by Mate- by Mate- by Mate- by Mate- by mate- ticle pling by rial mass) rial mass) rial mass) rial mass) rial mass) rial size agent mass) ΔSPa ΔSPb ΔSPc ΔSPd Example 1 CG1 0.9 HT1 22.5 A1 19.4 A2 2.2 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 2 CG1 0.9 HT1 22.5 A1 15.2 A2 6.4 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 3 CG1 0.9 HT1 22.5 A1 13 A2 8.6 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 4 CG1 1.0 HT1 23.8 A1 20.4 A2 2.3 B1 47.5 Silica 10 nm C1 5.0 1.85 1.35 0.50 1.72 Example 5 CG1 0.9 HT1 21.2 A1 18.3 A2 2.1 B1 42.5 Silica 10 nm C1 15.0 1.85 1.35 0.50 1.72 Example 6 CG1 0.9 HT1 22.5 A1 19.4 A2 2.2 B1 45.0 Silica 10 nm C2 10.0 0.88 0.38 0.50 1.85 Example 7 CG1 0.9 HT1 22.5 A1 19.4 A2 2.2 B2 45.0 Silica 10 nm C4 10.0 0.25 0.75 0.50 1.62 Example 8 CG1 0.9 HT1 22.5 A1 19.4 A2 2.2 B4 45.0 Silica 10 nm C4 10.0 0.25 0.75 0.50 0.91 Example 9 CG1 0.9 HT1 22.5 A1 19.4 A7 2.2 B1 45.0 Silica 10 nm C2 10.0 0.88 1.80 0.92 1.85 Example 10 CG1 0.9 HT1 22.5 A1 19.4 A7 2.2 B2 45.0 Silica 10 nm C4 10.0 0.25 0.67 0.92 1.62 Example 11 CG1 0.9 HT1 22.5 A1 19.4 A8 2.2 B1 45.0 Silica 10 nm C2 10.0 0.88 1.75 0.87 1.85 Example 12 CG1 0.9 HT1 22.5 A1 19.4 A11 2.2 B1 45.0 Silica 10 nm C1 10.0 1.85 2.48 0.63 1.72 Example 13 CG1 0.9 HT1 22.5 A2 19.4 A11 2.2 B1 45.0 Silica 10 nm C1 10.0 1.85 2.48 0.63 1.72 Example 14 CG1 0.9 HT1 22.5 A5 13.6 A8 8.6 B1 45.0 Silica 10 nm C2 10.0 0.84 1.75 0.91 1.85 Example 15 CG1 0.9 HT1 22.5 A5 13.6 A8 8.6 B3 45.0 Silica 10 nm C4 10.0 0.29 0.62 0.91 1.98 Comparative CG1 1.0 HT1 25.0 A1 24 — — B1 50.0 — — — — — — — — Example 1 Comparative CG1 0.9 HT1 22.5 A1 19.5 A2 2.1 B1 55.0 — — — — — — — — Example 2 Comparative CG1 0.9 HT1 22.5 A1 21.6 — — B1 45.0 Silica 10 nm C1 10.0 1.85 — — 1.72 Example 3 Comparative CG1 0.9 HT1 22.5 A1 6.5 A2 15.1 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 4 Comparative CG1 0.9 HT1 22.5 A1 11.5 A3 10.1 B1 45.0 Silica 10 nm C6 10.0 2.81 4.02 1.21 3.10 Example 5 Comparative CG1 0.9 HT1 22.5 A1 11.5 A5 10.1 B1 45.0 Silica 10 nm C6 10.0 2.81 2.85 0.04 3.10 Example 6 Comparative CG1 0.9 HT1 22.5 A3 11.5 A4 10.1 B1 45.0 Silica 10 nm C7 10.0 2.63 1.44 1.19 2.02 Example 7 Comparative CG1 0.9 HT1 22.5 A4 11.5 A8 10.1 B1 45.0 Silica 10 nm C4 10.0 0.76 0.62 0.14 2.13 Example 8 Comparative CG1 0.9 HT1 22.5 A4 11.5 A8 10.1 B2 45.0 Silica 10 nm C4 10.0 0.76 0.62 0.14 1.62 Example 9
(113) TABLE-US-00002 TABLE 2 Charge Hole First electron Second electron generation transport transport transport material material material material Resin binder Inorganic filler Con- Con- Con- Con- Con- Pri- Si- Con- tent tent tent tent tent mary lane tent (% (% (% (% (% Filler par- cou- (% Mate- by Mate- by Mate- by Mate- by Mate- by mate- ticle pling by rial mass) rial mass) rial mass) rial mass) rial mass) rial size agent mass) ΔSPa ΔSPb ΔSPc ΔSPd Example 16 CG1 0.9 HT1 4.5 A1 38.2 A2 1.4 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 17 CG1 0.9 HT1 4.5 A1 29.7 A2 9.9 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 18 CG1 0.9 HT1 4.5 A1 23.8 A2 15.8 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 19 CG1 1.0 HT1 4.8 A1 31.2 A2 10.5 B1 47.5 Silica 10 nm C1 5.0 1.85 1.35 0.50 1.72 Example 20 CG1 0.9 HT1 4.3 A1 22.4 A2 14.9 B1 42.5 Silica 10 nm C1 15.0 1.85 1.35 0.50 1.72 Example 21 CG1 0.9 HT1 4.5 A1 29.7 A2 9.9 B1 45.0 Silica 10 nm C2 10.0 0.88 0.38 0.50 1.85 Example 22 CG1 0.9 HT1 4.5 A1 29.7 A2 9.9 B2 45.0 Silica 10 nm C4 10.0 0.25 0.75 0.50 1.62 Example 23 CG1 0.9 HT1 4.5 A1 29.7 A2 9.9 B4 45.0 Silica 10 nm C4 10.0 0.25 0.75 0.50 0.91 Example 24 CG1 0.9 HT1 4.5 A1 29.7 A7 9.9 B1 45.0 Silica 10 nm C2 10.0 0.88 1.80 0.92 1.85 Example 25 CG1 0.9 HT1 4.5 A1 29.7 A7 9.9 B2 45.0 Silica 10 nm C4 10.0 0.25 0.67 0.92 1.62 Example 26 CG1 0.9 HT1 4.5 A1 29.7 A8 9.9 B1 45.0 Silica 10 nm C2 10.0 0.88 1.75 0.87 1.85 Example 27 CG1 0.9 HT1 4.5 A1 29.7 A11 9.9 B1 45.0 Silica 10 nm C1 10.0 1.85 2.48 0.63 1.72 Example 28 CG1 0.9 HT1 4.5 A2 29.7 A11 9.9 B1 45.0 Silica 10 nm C1 10.0 1.85 2.48 0.63 1.72 Example 29 CG1 0.9 HT1 4.5 A5 29.7 A8 9.9 B1 45.0 Silica 10 nm C2 10.0 0.84 1.75 0.91 1.85 Example 30 CG1 0.9 HT1 4.5 A5 29.7 A8 9.9 B3 45.0 Silica 10 nm C4 10.0 0.29 0.62 0.91 1.98 Comparative CG1 1.0 HT1 5.0 A1 44.0 — — B1 50.0 — — — — — — — — Example 10 Comparative CG1 1.0 HT1 5.0 A1 42.5 A2 1.5 B1 50.0 — — — — 1.85 — — 1.72 Example 11 Comparative CG1 0.9 HT1 4.5 A1 38.2 A3 1.4 B1 45.0 Silica 10 nm C6 10.0 2.81 4.02 1.21 3.10 Example 12 Comparative CG1 0.9 HT1 4.5 A1 38.2 A5 1.4 B1 45.0 Silica 10 nm C6 10.0 2.81 2.85 0.04 3.10 Example 13 Comparative CG1 0.9 HT1 4.5 A3 38.2 A4 1.4 B1 45.0 Silica 10 nm C7 10.0 2.63 2.85 1.19 2.02 Example 14 Comparative CG1 0.9 HT1 4.5 A4 38.2 A8 1.4 B1 45.0 Silica 10 nm C4 10.0 0.76 1.44 0.14 2.13 Example 15 Comparative CG1 0.9 HT1 4.5 A1 38.2 A8 1.4 B2 45.0 Silica 10 nm C4 10.0 0.76 0.62 0.14 1.62 Example 16 Comparative CG1 0.9 HT1 4.5 A1 19.8 A2 19.8 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 17 Comparative CG1 0.9 HT1 4.5 A1 15.8 A2 23.8 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 18 Comparative CG1 0.9 HT1 4.5 A1 7.9 A2 31.7 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 19 Example 31 CG1 0.9 HT1 21.6 A1 21.8 A2 0.7 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Example 32 CG1 0.9 HT1 21.6 A1 16.9 A2 5.6 B1 45.0 Silica 10 nm C1 10.0 1.85 1.35 0.50 1.72 Comparative CG1 0.7 HT1 3.5 A1 15.3 A2 10.5 B1 35.0 Silica 10 nm C1 35.0 1.85 1.35 0.50 1.72 Example 20
(114) TABLE-US-00003 TABLE 3 Abrasion Electrical characteristics resistance Potential Residual Average retention potential abrasion Evaluation of rate Vk5 Vr5 amount Evaluation of print density (%) (V) (μm) ghost image stability Example 1 92.4 26 2.5 ⊚ ⊚ Example 2 92.1 27 2.8 ⊚ ⊚ Example 3 92.5 27 2.7 ⊚ ⊚ Example 4 92.8 24 3.6 ⊚ ⊚ Example 5 91.6 28 2.0 ⊚ ⊚ Example 6 92.3 29 3.1 ⊚ ⊚ Example 7 92.4 22 2.7 ⊚ ⊚ Example 8 93.1 23 2.9 ⊚ ⊚ Example 9 92.3 24 2.5 ◯ ⊚ Example 10 92.5 26 3.1 ◯ ⊚ Example 11 92.2 22 2.9 ◯ ⊚ Example 12 91.9 25 3.4 ◯ ⊚ Example 13 92.4 25 2.5 ◯ ⊚ Example 14 91.8 23 2.7 ◯ ⊚ Example 15 92.1 25 3.1 ◯ ⊚ Comparative 76.1 29 9.4 X X Example 1 Comparative 73.7 24 7.4 ◯ ◯ Example 2 Comparative 77.5 86 6.6 X X Example 3 Comparative 88.7 54 3.2 X Δ Example 4 Comparative 78.8 78 7.1 X X Example 5 Comparative 70.5 94 8.6 X X Example 6 Comparative 68.4 91 9.1 Δ X Example 7 Comparative 76.4 83 7.5 Δ X Example 8 Comparative 71.6 88 7.1 Δ Δ Example 9
(115) TABLE-US-00004 TABLE 4 Abrasion Electrical characteristics resistance Potential Residual Average retention potential abrasion Evaluation of rate Vk5 Vr5 amount Evaluation of print density (%) (V) (μm) ghost image stability Example 16 92.8 19 1.8 ⊚ ⊚ Example 17 92.4 21 1.9 ⊚ ⊚ Example 18 92.6 22 2.2 ⊚ ⊚ Example 19 92.4 22 2.1 ⊚ ⊚ Example 20 92.6 18 2.7 ⊚ ⊚ Example 21 92.1 26 1.5 ⊚ ⊚ Example 22 93.5 30 2.0 ⊚ ⊚ Example 23 92.4 24 2.3 ⊚ ⊚ Example 24 92.3 26 2.1 ◯ ⊚ Example 25 92 25 2.2 ◯ ⊚ Example 26 92.5 26 2.0 ◯ ⊚ Example 27 92.2 21 1.8 ◯ ⊚ Example 28 92.7 29 2.4 ◯ ⊚ Example 29 92.3 22 2.2 ◯ ⊚ Example 30 92.6 19 2.2 ◯ ⊚ Comparative 73.6 30 7.1 X X Example 10 Comparative 71.4 24 6.8 ⊚ ⊚ Example 11 Comparative 69.4 67 6.1 X X Example 12 Comparative 72.6 76 5.9 X X Example 13 Comparative 70.9 85 4.9 Δ X Example 14 Comparative 74.9 73 6.4 Δ X Example 15 Comparative 76.8 81 5.7 Δ Δ Example 16 Comparative 83.4 41 2.1 Δ Δ Example 17 Comparative 79.1 35 2.1 Δ X Example 18 Comparative 78.8 41 2.3 Δ X Example 19 Example 31 67.9 46 2.0 ◯ Δ Example 32 69.4 43 1.9 ◯ Δ Comparative 65.7 83 3.7 X Δ Example 20
(116) As is apparent from the results in Tables 3 and 4 shown above, favorable abrasion resistance, favorable electrical properties of a photoconductor, and reduced generation of ghost images were confirmed for the photoconductors of Examples 1 to 32 in which a combination of two types of electron transport materials that satisfies the above-described Hansen solubility parameter, a resin binder, and an inorganic oxide filler surface-treated with a silane coupling agent was used for the photosensitive layer, compared with the photoconductor of each of the Comparative Examples in which a combination different therefrom was used. In each of the Examples, favorable results were also obtained for the environmental stability of print density.
(117) Based on the results of the Example, it was found that a naphthalenetetracarboxylic diimide compound, an azoquinone compound, bisphenol Z or bisphenol Z-biphenyl copolymer, silica fine particles, a compound represented by the structural formula C1, C2, or C4 are particularly suitable as a first electron transport material, a second electron transport material, a resin binder, an inorganic oxide filler, and a silane coupling agent, respectively.
DESCRIPTION OF SYMBOLS
(118) 1 Conductive substrate; 2 Undercoat layer; 2A Alumite layer; 2B Resin layer; 3 Single-layered photosensitive layer; 4 Charge transport layer; 5 Charge generation layer; 6 Multi-layered photosensitive layer; 7, 8 Photoconductor; 21, 31 Charging member; 22 High voltage power supply; 23, 33 Image exposure member; 24 Developing unit; 241 Developing roller; 25 Paper feeding member; 251 Paper feeding roller; 252 Paper feeding guide; 26 Transfer charger (direct charging type); 27 Cleaning device; 271 Cleaning blade; 28 Discharging member; 32 Power supply; 34 Developing member; 35 Transfer member; 36 Cleaning member; 60, 70 Electrophotographic device; and 300 Photosensitive layer.