JP4040650B2 - Electrophotographic photosensitive member, process cartridge, and electrophotographic apparatus - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member, a process cartridge, and an electrophotographic photosensitive member. More specifically, the present invention has a support and a photosensitive layer formed on the support, and the photosensitive layer contains a specific high molecular weight charge transport material. The present invention relates to an electrophotographic photoreceptor to be contained, a process cartridge having the electrophotographic photoreceptor, and an electrophotographic apparatus.

  Electrophotographic technology is widely used and applied in the fields of copiers and printers because of its immediacy and high quality images.

  One typical example of an image holding member used in an electrophotographic apparatus is an electrophotographic photosensitive member. Photoconductive materials used in electrophotographic photoreceptors include inorganic photoconductive materials typified by selenium, cadmium sulfide, and zinc oxide, but in recent years they are non-polluting, highly productive, and easy to design materials. In addition, organic photoconductive substances are being developed extensively from the viewpoint of future potential.

  The electrophotographic photosensitive member is naturally required to have various characteristics such as electrical, mechanical and optical characteristics according to the applied electrophotographic process. Especially for electrophotographic photoreceptors that are used repeatedly, electrical and mechanical forces such as charging, exposure, development, transfer, and cleaning are repeatedly applied directly or indirectly, so durability is required. Is done.

  In an organic electrophotographic photosensitive member using an organic photoconductive substance, it is usual to form a coating film by dissolving or dispersing the organic photoconductive substance in a binder resin. The coating film is formed by dissolving or dispersing the organic photoconductive substance and the binder resin in a solvent and then applying and drying.

  Examples of the binder resin include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, materials such as polycarbonate, polyester, polyarylate, polysulfone, phenoxy resin, epoxy resin, silicone resin, and copolymers thereof. It is used.

  Although the organic electrophotographic photoreceptor has many advantages such as excellent mass productivity and low price, it satisfies all the requirements for an electrophotographic photoreceptor. There is room for improvement.

  With regard to the functionality and characteristics of electrophotography, an electrophotographic photoreceptor superior to inorganic electrophotographic photoreceptors has been produced, but with respect to other characteristics, particularly durability in organic electrophotographic photoreceptors. Further improvements are desired.

  As one method for improving the durability of an organic electrophotographic photoreceptor, the use of various binder resins having excellent mechanical strength has been proposed, but even if the binder resin itself has excellent mechanical strength, it has a low molecular weight. Since the charge transport material is mixed and used, the original film strength of the binder resin cannot be fully utilized, and sufficient durability in wear resistance and scratch resistance has not been obtained.

  In order to make use of the inherent film strength of the binder resin, the amount of the charge transport material to be added may be reduced, but in that case, a problem arises that the electrophotographic sensitivity is lowered and the residual potential is increased, Neither film strength nor electrophotographic characteristics have been achieved at the same time.

  For the purpose of improving the decrease in film strength due to the addition of a low molecular weight charge transport material, the use of a high molecular weight charge transport material is disclosed in JP-A Nos. 64-9964 (Patent Document 1) and JP-A-2-282263 (Patent Document 2). ), JP-A-3-221522 (Patent Document 3), JP-A-8-208820 (Patent Document 4), and the like.

  However, many of them do not always have sufficient wear resistance, and even when they have a certain degree of film strength, they have drawbacks such as a very high manufacturing cost and not suitable for practical use.

  Also, from the viewpoint of wear resistance or cost of the electrophotographic photosensitive member, when these high molecular weight charge transport materials are used in combination with an insulating resin, the compatibility between the binder resin and the high molecular weight charge transport materials is poor. In some cases, an electrophotographic photosensitive member giving good image quality cannot be produced, or the wear resistance is deteriorated.

As another type of high molecular weight electron transport material, a high molecular weight electron transport material having a repeating structural unit of triphenylamine (International Publication No. WO99 / 32537 (Patent Document 5)) has been proposed. Since the high molecular weight electron transport material having this structure has good compatibility with the insulating resin, it has high mechanical strength and high mobility.
JP-A 64-9964 JP-A-2-282263 JP-A-3-221522 JP-A-8-208820 International Publication Number WO99 / 32537

  By improving the durability of the electrophotographic photosensitive member, it becomes necessary to provide stable characteristics even when the electrophotographic photosensitive member is repeatedly used over a long period of time. The characteristic that it is difficult to cause oxidative deterioration due to ozone and active oxygen during charging is required.

  However, the high molecular weight electron transport material disclosed in the above-mentioned publication (International Publication Number: WO99 / 32537) has high mechanical strength, but easily undergoes oxidative degradation, and there are cases where characteristic fluctuations are large during repeated use. there were.

  Accordingly, an object of the present invention is to provide an electrophotographic photosensitive member having high mechanical strength as an electrophotographic photosensitive member and having stable characteristics in repeated use. Specifically, by incorporating a high-molecular-weight electron transport material having high stability in electrophotographic photosensitive member properties that hardly deteriorates even in long-term use into the photosensitive layer of the electrophotographic photosensitive member, The object is to achieve a long life and to obtain stable characteristics even in repeated use.

  Another object of the present invention is to provide a process cartridge and an electrophotographic apparatus having such an electrophotographic photosensitive member.

  As a result of intensive investigations for improving the above problems, the present inventors have reached the present invention.

That is, in the present invention, the photosensitive layer contains a high molecular weight charge transport material having a repeating structural unit represented by the following formula (22) or (31) :
The high molecular weight charge transport material has a weight average molecular weight (Mw) of 1500 or more;
The energy level of the highest occupied molecular orbital by the semiempirical orbital calculations of the high molecular weight charge-transporting material _{(E HOMO),} characterized in that at most -8.3 [eV] or -8.0 [eV] Electronic It is a photographic photoreceptor.

(In formula (22), R ²²⁰¹ , R ²²⁰² , R ²²⁰³ , R ²²⁰⁴ , R ²²⁰⁵ , R ²²⁰⁶ , R ²²⁰⁷ , R ²²⁰⁸ , R ²²⁰⁹ , R ²²¹⁰ And R ²²¹¹ Each independently represents hydrogen, a substituted or unsubstituted alkyl group, or an electron-withdrawing group. A ²²⁰¹ Represents a group 16 element. )

(In formula (31), R ³¹⁰¹ , R ³¹⁰² , R ³¹⁰³ , R ³¹⁰⁴ and R ³¹⁰⁵ are each independently hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted group, Represents an alkoxy group or an electron-withdrawing group, Z ³¹⁰¹ represents a substituted or unsubstituted divalent heterocyclic group, d represents an integer of 1 or more, provided that when d is 2 or more, 2 Z ³¹⁰¹ above may be the same or different.)
The present invention also provides a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member.

As described above, in the present invention, the energy level (E _HOMO ) of the highest occupied orbital of the high molecular weight electron transport material was determined by semiempirical molecular orbital calculation.

  In the present invention, “semi-empirical molecular orbital calculation” means “structure optimization calculation using semi-empirical molecular orbital calculation using PM3 parameters”.

  In the molecular orbital method, the wave function used in the Schrödinger equation is approximated by a slater determinant or Gaussian determinant consisting of molecular orbitals represented by linear combinations of atomic orbitals. By using field approximation, various physical quantities can be calculated as total energy, wave functions, and expected values of wave functions.

  The semi-empirical molecular orbital method shortens the calculation time by approximating the time-consuming integral calculation using parameters using various experimental values when calculating the molecular orbital by field approximation.

  In the calculation in the present invention, since the calculation target is a high molecular weight substance, the number of atoms to be calculated is large, and thus a semi-empirical molecular orbital method that reduces the calculation time is adopted. The PM3 parameter set was used as a semi-empirical parameter, and calculation was performed using a semi-empirical molecular orbital calculation program MOPAC.

As described above, the energy level (E _HOMO ) of the highest occupied orbital of the high molecular weight electron transport material can be obtained using the semi-empirical molecular orbital calculation program.

By using a high molecular weight electron transport material having a specific highest occupied orbit energy level (E _HOMO ) as a charge transport material and having a specific repeating structural unit, it has high mechanical strength, Furthermore, it is possible to provide an electrophotographic photosensitive member that does not cause chemical deterioration even after repeated use and has stable electrophotographic characteristics.

^R 2201 in the above above formula ^{(22), R 2202, R} 2203, R 2204, R 2205, R 2206, R 2207, R 2208, R 2209, the alkyl group of ^{R 2210} and ^{R 2211 (R 2201 ~R} 2211) the methyl group, an ethyl group, a propyl group, and examples of the electron withdrawing group, fluorine, chlorine, bromine, trifluoromethyl group, a fluorophenyl group, and the like. among these, methyl group, ethyl group, full Tsu group, a trifluoromethyl group is preferable.

Examples of the substituent that these alkyl groups may have include a methyl group, an ethyl group, a propyl group, a phenyl group, fluorine, and a trifluoromethyl group. Among these, a methyl group and a phenyl group are preferable.

Examples of the group 16 element of A ^{2201 in} the above formula (22) include oxygen, sulfur, selenium, and tellurium. Among these, oxygen and sulfur are preferable.

R in the above formula (31) ³¹⁰¹ , R ³¹⁰² , R ³¹⁰³ , R ³¹⁰⁴ And R ³¹⁰⁵ (R ³¹⁰¹ ~ R ³¹⁰⁵ ) Alkyl groups include methyl group, ethyl group, propyl group, etc., aryl groups include phenyl group, naphthyl group, etc., and alkoxy groups include methoxy group, ethoxy group, etc. Examples of the electron-withdrawing group include fluorine, chlorine, bromine, trifluoromethyl group, and fluorophenyl group. Among these, methyl group, ethyl group, phenyl group, methoxy group, fluorine, and trifluoromethyl group are preferable.

Examples of the substituent that these alkyl group, aryl group, and alkoxy group may have include a methyl group, an ethyl group, a propyl group, a phenyl group, fluorine, and a trifluoromethyl group. Among these, a methyl group, A phenyl group is preferred.

Z in the above formula (31) ³¹⁰¹ Examples of the divalent heterocyclic group include a pyridylene group, a dibenzofuranylene group, and a dibenzothiophenylene group, and among these, a pyridylene group is preferable.

Examples of the substituent that these heterocyclic groups may have include hydrogen, methyl group, ethyl group, propyl group, phenyl group, methoxy group, ethoxy group, fluorine, chlorine, bromine, trifluoromethyl group, and fluorophenyl group. Among these, hydrogen, a methyl group, an ethyl group, and a trifluoromethyl group are preferable.

Also, high-molecular weight charge-transporting material having a repeating structural unit of represented by the above following formula (22) or (31) more preferably has further also repeating structural unit represented by the following formula (23).

In the above formula (23), R ²³⁰¹ , R ²³⁰² , R ²³⁰³ , R ²³⁰⁴ , R ²³⁰⁵ , R ²³⁰⁶ , R ²³⁰⁷ , R ²³⁰⁸ , R ²³⁰⁹ , R ²³¹⁰ , R ²³¹¹ , R ²³¹² and R ²³¹³ (R ^{2301 to} R ²³¹³⁾ are each independently hydrogen, substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, substitution or unsubstituted alkoxy group, or shows the electron-withdrawing group.

In the above formula (23), R ²³⁰¹ , R ²³⁰² , R ²³⁰³ , R ²³⁰⁴ , R ²³⁰⁵ , R ²³⁰⁶ , R ²³⁰⁷ , R ²³⁰⁸ , R ²³⁰⁹ , R ²³¹⁰ , R ²³¹¹ , R ²³¹² and R ²³¹³ (R ^{2301 to} R ²³¹³ ) includes an alkyl group such as a methyl group, an ethyl group, and a propyl group, examples of the aryl group include a phenyl group and a naphthyl group, and examples of the alkoxy group include a methoxy group and an ethoxy group. Examples of the electron withdrawing group include fluorine, chlorine, bromine, trifluoromethyl group, and fluorophenyl group, and among these, methyl group, ethyl group, phenyl group, methoxy group, fluorine, and trifluoromethyl group are preferable. .

Examples of the substituent that these alkyl group, aryl group, and alkoxy group may have include a methyl group, an ethyl group, a propyl group, a phenyl group, fluorine, and a trifluoromethyl group. Among these, a methyl group, A phenyl group is preferred .

The following, specific examples of the high molecular weight charge-transporting material having a structural unit represented by the formula (22).

Among these , ( 22-9), (22-10), (22-11), (22-12), (22-14), (22-15), (22-16), (22-17) ) Is preferred .

The following, specific examples of the high molecular weight charge transporting material having the structure unit represented by the structural unit and the formula (23) represented by the above formula (22).

Among these , ( 25-5), (25-6), (25-7), (25-8), (25-10), (25-11), (25-12), (25-13) ) Is preferred.

  Specific examples of the high molecular weight charge transporting material having the structural unit represented by the above formula (31) are given below.

  Among these, (31-1), (31-2), (31-5), (31-10), (31-11), and (31-12) are preferable.

Specific examples of the high molecular weight charge transporting material having the structural unit represented by the above formula (31) and the structural unit represented by the above formula ( 23 ) will be given below.

Among these, (33-1), (33-2), (33-3), (33-5), and (33-7) are preferable .

In upper Symbol the specific examples, n and m are each an integer of 1 or more.

The polymer charge transport materials described above have a maximum occupied orbit energy level (E _HOMO ) of −8.3 [eV] or more and −8.0 [eV] or less according to semi-empirical orbit calculation, and have a weight average. When the molecular weight (Mw) satisfies the characteristics of 1500 or more, an electrophotographic photosensitive member that has the desired high mechanical strength and can stably exhibit the characteristics of the electrophotographic photosensitive member even when used for a long time can be provided. .

By the above calculation method, the energy level (E _HOMO ) of the highest occupied molecular orbital of the high molecular weight charge transport material can be easily obtained using a semi-empirical molecular orbital calculation program.

The value of the energy level (E _HOMO ) of the highest occupied orbit calculated by the molecular orbital method indicates the chemical reactivity inherent to the object.

  Since the high molecular weight charge transport material used in the electrophotographic photoreceptor of the present invention has the above-mentioned specific repeating structural unit, the entire molecule constitutes a phenyl group, in particular, a main chain via an unshared electron pair on nitrogen. The π-conjugated system spreads in a pseudo manner on the phenyl group.

  Such a structure in which the π-conjugated system spreads is generally a structure in which charge transport ability (mobility) is increased.

However, since the energy level (E _HOMO ) of the highest occupied orbit is increased as an adverse effect of improving mobility, it becomes sensitive to chemical reactions, such as ozone, active oxygen, or NOx generated by discharge during charging. It becomes easy to react with active chemical species, and as a result, deterioration of the electrophotographic photosensitive member and deterioration of electrophotographic characteristics occur.

Therefore, in order to improve the durability of the electrophotographic photosensitive member and not cause deterioration of the characteristics even during repeated use, the energy level of the highest occupied orbit of the high molecular weight charge transporting material having the specific repeating structural unit (E _HOMO ) needs to be lower than a certain value.

For chemical modification of high molecular weight charge transport materials, the energy level (E _HOMO ) of the highest occupied orbital should be low, but in order to function as a charge transport material for electrophotographic photoreceptors, charge generation It is important that charge transfer occurs between the material and the charge transport material, and the extremely low energy level of the highest occupied orbit (E _HOMO ) creates an energy gap with the charge generating material, and the electrophotographic photoreceptor. Therefore, it is necessary to appropriately control the energy level (E _HOMO ) of the highest occupied trajectory.

When the energy level (E _HOMO ) of the highest occupied orbit by semi-empirical molecular orbital calculation is in the range of −8.3 [eV] or more and −8.0 [eV] or less, the electrophotographic photosensitive member is excellent. Without impairing the characteristics, it has become possible to improve the durability of the electrophotographic photoreceptor and to suppress the deterioration of the characteristics of the electrophotographic photoreceptor due to repeated use.

  Although the expression mechanism of the potential fluctuation evaluated in the present invention has not been elucidated in detail, it can be considered as follows.

  Potential fluctuation during repeated use, which is evaluated as deterioration of the characteristics of the electrophotographic photosensitive member, is due to material deterioration due to chemical modification due to ozone, active oxygen, NOx, etc. generated during the electrophotographic process, mainly charging of the electrophotographic photosensitive member. It is known to be attributed.

Used in the electrophotographic photoreceptor of the present invention, the highest occupied molecular orbital energy level (E _HOMO) at low and high molecular weight charge transport material having the specific repeating structural units, the highest occupied molecular orbital energy level (E _HOMO ) Is clearly superior to the potential fluctuation during repeated use, compared with not lowering.

This means that by reducing the energy level (E _HOMO ) of the highest occupied orbit, the activity is reduced against chemical reaction and chemical modification, it is difficult to be modified, and the characteristics of the charge transport material can be demonstrated over a long period of time. Which indicates that.

  In order to achieve the improvement of the mechanical strength of the electrophotographic photosensitive member, which is one of the objects of the present invention, the molecular weight of the high molecular weight charge transporting material having the specific repeating structural unit is important. .

  In order to improve the mechanical strength of the electrophotographic photosensitive member, the weight average molecular weight (Mw) of the high molecular weight charge transport material having the specific repeating structural unit must be 1500 or more.

On the other hand, the weight average molecular weight (Mw) of the high molecular weight charge transport material of the charge transport material having the specific repeating structural unit is preferably 6000 or less, and more preferably 4000 or less. If the weight average molecular weight (Mw) is too large, the compatibility with the binder resin may be deteriorated, and the energy level (E _HOMO ) of the highest occupied orbit by semi-empirical orbit calculation is −8.3 [ eV] or more and −8.0 [eV] or less becomes difficult.

  In order to improve the mechanical strength of the electrophotographic photosensitive member, the average value of the number of repetitions of the specific repeating structural unit (the number of repeating structural units) is preferably 6 or more.

On the other hand, the average value of the number of repetitions of the specific repeating structural unit is preferably 20 or less. If it exceeds 20, the compatibility with the binder resin may deteriorate, and the energy level (E _HOMO ) of the highest occupied orbit by semi-empirical orbit calculation is −8.3 [eV] or more and −8.0. [EV] It becomes difficult to make it below.

  The relationship between molecular weight improvement and mechanical strength is not clear in detail, but generally there is a correlation between the molecular weight improvement and the glass transition point (Tg), and as the molecular weight increases, Tg increases. From these results, it is speculated that the glass transition point increased with the increase in the molecular weight of the high molecular weight charge transport material, and as a result, the mechanical strength was improved.

  On the other hand, the higher the molecular weight, the greater the mechanical strength. However, as the number of iterations increases, the energy level of the highest occupied orbit in the molecular orbital calculation described above increases and causes chemical degradation such as oxidation. It is important to determine the structure of a molecule that achieves both chemical stability and chemical stability, and the calculation method of the energy level of the highest occupied orbit by semiempirical molecular orbital calculation is effective in that respect.

The formula (22) or the high molecular weight charge-transporting material having a structural unit represented by (31), the structural unit represented by the above formula to the total structural units of the high molecular weight charge-transporting substance in the molecule (22) or (31) The ratio of is taken arbitrarily as long as the energy level (E _HOMO ) of the highest occupied orbit by semi-empirical molecular orbital calculation is in the range of −8.3 [eV] or more and −8.0 [eV] or less. Can do.

  Furthermore, within the range, it can be used so as to be optimal from the viewpoints of solubility in a solvent and compatibility with a resin.

In order to develop a high charge transport function, it is preferable that the molecular weight of the high molecular weight charge transport material is as large as possible. Therefore, the molecular weight of the high molecular weight charge transport material is preferably as large as possible as long as E _HOMO is in a range satisfying −8.3 [eV] or more and −8.0 [eV] or less.

Further, indicated by the high molecular weight charge-transporting material having the other repeating structural units, such as repeating structural unit represented by the repeating structural units and the formula shown above following formula (22) (23), the equation (31) high molecular weight charge-transporting substance having the other repeating structural units, such as repeating structural unit represented by the repeating structural units and the above equation (23) means to be a copolymer.

  The copolymerization form may be any of random copolymerization, block copolymerization, and alternating copolymerization. Among them, the random copolymerization and alternating copolymerization forms are preferable because they do not cause charge localization in the molecule.

  In order to sufficiently obtain the effects of the present invention, the high molecular weight charge transport material used in the electrophotographic photosensitive member of the present invention contains the above-mentioned specific repeating structural unit in the molecule with respect to all repeating structural units. It is preferably 80% or more, more preferably 90% or more.

  Hereinafter, the structure of the electrophotographic photosensitive member used in the present invention will be described.

  The photosensitive layer of the electrophotographic photoreceptor of the present invention includes a single layer type photosensitive layer containing a charge generating material and a charge transporting material in a single layer, a charge transporting layer containing a charge transporting material, and a charge generating material. Either a function-separated type (laminated type) photosensitive layer that is functionally separated into a charge-generating layer is acceptable, but from the viewpoint of electrophotographic characteristics, a function-separated type (laminated type) is preferable. The function separation type (lamination type) laminated in the order of the transport layer is more preferable. Hereinafter, the expression “functionally separated type (laminated type)” means a layer in which a charge generation layer and a charge transport layer are laminated in this order from the support side.

  The high-molecular-weight charge transport material used in the electrophotographic photoreceptor of the present invention has at least a charge when the photosensitive layer of the electrophotographic photoreceptor is a functional separation type (laminated type) having a charge generation layer and a charge transport layer. Used in the transport layer with an insulating binder resin.

  The support used in the electrophotographic photosensitive member of the present invention may be any one as long as it has conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc, stainless steel in the form of a drum or a sheet. Examples include a molded product, a laminate of a metal foil such as aluminum or copper on a plastic film, and a product obtained by evaporating aluminum, indium oxide, tin oxide, or the like on a plastic film.

  When the image input such as LBP is laser light, a conductive layer may be provided for the purpose of preventing interference fringes due to scattering or covering a scratch on the support.

  This can be formed by dispersing conductive particles such as carbon black and metal particles in a binder resin.

  The film thickness of the conductive layer is preferably 5 μm or more and 40 μm or less (5 to 40 μm), and more preferably 10 μm or more and 30 μm or less (10 to 30 μm).

  Further, an intermediate layer having an adhesive function may be provided on the support or the conductive layer.

  Examples of the material for the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane. These are dissolved in an appropriate solvent and applied.

  The film thickness of the intermediate layer is preferably 0.05 μm or more and 5 μm or less (0.05 to 5 μm), and more preferably 0.3 μm or more and 1 μm or less (0.3 to 1 μm).

  In the case of the function separation type (laminated type) photosensitive layer, a charge generation layer is formed on the support, the conductive layer or the intermediate layer.

  The charge generation layer comprises a homogenizer, an ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a charge generation material together with a binder resin and a solvent in an amount of 0.3 to 4 times (0.3 to 4 times) of the charge generation material. It is formed by dispersing well by a method such as a roll mill and a liquid collision type high-speed disperser, and applying and drying the dispersion.

  The thickness of the charge generation layer is preferably 5 μm or less, more preferably 0.1 μm or more and 2 μm or less (0.1 to 2 μm).

  As the charge generation material, those generally known can be used, for example, selenium-tellurium, pyrylium, metal phthalocyanine, metal-free phthalocyanine, anthrone, dibenzpyrenequinone, trisazo, cyanine, disazo, monoazo, indigo. And pigments such as quinacrine.

  These pigments have a binder resin and solvent weight of 0.3 to 4 times (0.3 to 4 times), homogenizer, ultrasonic dispersion, ball mill, vibration mill, sand mill attritor, roll mill, liquid collision type high speed dispersion A well-dispersed dispersion is obtained using a machine. In the case of a functional separation type (laminated type) photosensitive layer, a charge generation layer is obtained by applying this solution and drying.

  In the case of a function separation type (laminated type) photosensitive layer, a charge transport layer is formed on the charge generation layer.

  The charge transport layer is prepared by dissolving the high molecular weight charge transport material and an insulating binder resin in a solvent to form a coating solution, coating the solution on the charge generation layer, and drying.

  The ratio of the high molecular weight charge transporting material to the binder resin (high molecular weight charge transporting material / binder resin) in the coating solution is preferably in the range of 1/10 to 12/10 (1/10 to 12/10) by mass ratio. From the viewpoint of charge transport characteristics of the electrophotographic photosensitive member or strength of the charge transport layer, a range from 2/10 to 10/10 (2/10 to 10/10) is more preferable.

  As the binder resin, any resin can be used as long as it is usually used for the photosensitive layer (charge transport layer). However, from the viewpoint of resin permeability and film forming property, the photosensitive layer (charge transport layer). ) Is a surface layer of an electrophotographic photoreceptor, polycarbonate or polyarylate resin is preferable from the viewpoint of wear resistance.

  The viscosity average molecular weight (Mv) of the polycarbonate resin is preferably 20,000 or more and 80,000 or less (20,000 to 80,000).

  Below, the specific example of polycarbonate resin is shown.

  The weight average molecular weight (Mw) of the polyarylate resin is preferably 50,000 or more and 200,000 or less (50000-200000), and more preferably 80000 or more and 150,000 or less (80000-150,000) in terms of strength, productivity, and the like. preferable.

  Below, the specific example of polyarylate resin is shown.

  Furthermore, in order to improve productivity, it is possible to blend polyarylate resin with polyarylate resin or polycarbonate resin of other structure. In order to efficiently express the effect of mixing, the mixing ratio is preferably in the range from 5/95 to 95/5 (5/95 to 95/5), and from 20/80 to 80/20. More preferably, it is in the range (20/80 to 80/20).

  Further, an antioxidant, a heat stabilizer, an ultraviolet absorber, and a plasticizer can be added to the charge transport layer as necessary.

  When the charge transport layer is a surface layer of an electrophotographic photosensitive member, a lubricant or fine particles may be used as necessary. Examples of the lubricant or fine particles include polytetrafluoroethylene fine particles, silica fine particles, and alumina fine particles.

  The film thickness of the charge transport layer is preferably 5 μm or more and 40 μm or less (5 to 40 μm), and preferably 15 μm or more and 30 μm or less (15 to 30 μm).

  Further, as a surface layer of the electrophotographic photoreceptor, a layer for protecting the photosensitive layer, that is, a protective layer may be separately provided on the photosensitive layer.

  The resin used for the protective layer is preferably a high molecular weight thermoplastic resin, thermosetting resin or photocurable resin, and more preferably a high molecular weight polycarbonate resin, polyarylate resin, phenol resin, acrylic resin or epoxy resin. preferable.

  Further, for the purpose of reducing the residual potential or improving the film strength, conductive particles or a lubricant may be contained.

  The method for forming the protective layer can be cured by heat, light or electron beam, and may contain a polymerization initiator or an antioxidant as necessary.

  In the step of forming each layer of the electrophotographic photoreceptor, examples of the solvent to be used include chlorobenzene, tetrahydrofuran, 1,4-dioxane, toluene, xylene, and the like. A single solvent or a plurality of solvents may be used.

  Further, as the coating method, a conventionally known method such as a dip coating method, a spray coating method, or a bar coating method can be used.

  FIG. 1 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having the electrophotographic photosensitive member of the present invention.

  In FIG. 1, reference numeral 1 denotes a drum-shaped electrophotographic photosensitive member of the present invention, which is rotationally driven around a shaft 2 in a direction indicated by an arrow at a predetermined peripheral speed. In the rotating process, the electrophotographic photosensitive member 1 is uniformly charged with a predetermined positive or negative potential on its peripheral surface by the primary charging unit 3, and then from an exposure unit (not shown) such as slit exposure or laser beam scanning exposure. The exposure light 4 is received. In this way, electrostatic latent images are sequentially formed on the peripheral surface of the electrophotographic photosensitive member 1.

  The formed electrostatic latent image is then developed with toner by the developing means 5, and the developed toner developed image is transferred between the electrophotographic photosensitive member 1 and the transfer means 6 from a paper supply unit (not shown). The image is sequentially transferred by the transfer means 6 to the transfer material 7 fed in synchronization with the rotation of 1.

  The transfer material 7 that has received the image transfer is separated from the surface of the electrophotographic photosensitive member, introduced into the image fixing means 8, and subjected to image fixing to be printed out as a copy (copy).

  After the image transfer, the surface of the electrophotographic photosensitive member 1 is cleaned by the removal of the toner remaining after the transfer by the cleaning unit 9, and is further subjected to charge removal processing by the pre-exposure light 10 from the pre-exposure unit (not shown). Used repeatedly for image formation. When the primary charging unit 3 is a contact charging unit using a charging roller as shown in FIG. 1, pre-exposure is not always necessary.

  In the present invention, a plurality of components such as the above-described electrophotographic photosensitive member 1, primary charging unit 3, developing unit 5, and cleaning unit 9 are integrally coupled as a process cartridge. May be configured to be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. For example, at least one of the primary charging unit 3, the developing unit 5 and the cleaning unit 9 is integrally supported together with the electrophotographic photosensitive member 1 to form a cartridge, and can be attached to and detached from the apparatus main body using guide means such as the rail 12 of the apparatus main body Process cartridge 11.

  Further, when the electrophotographic apparatus is a copying machine or a printer, the exposure light 4 is a reflected light or transmitted light from the original, or the original is read by a sensor and converted into a signal, and a laser beam performed in accordance with this signal. The light is emitted by scanning, driving the LED array, driving the liquid crystal shutter array, and the like.

  The electrophotographic photoreceptor of the present invention can be used not only in electrophotographic copying machines but also widely in electrophotographic application fields such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

  Hereinafter, the present invention will be described in more detail with reference to examples.

  In the examples, “part” means “part by mass”.

  The evaluation will be described.

As described above, the energy level (E _HOMO ) of the highest occupied molecular orbital of the high molecular weight electron transport material was calculated by performing structural optimization calculation using semiempirical molecular orbital calculation using PM3 parameters.

Evaluation of durability and characteristic fluctuations due to repeated use of an electrophotographic photosensitive member using a high molecular weight electron transporting material is based on the Canon Co. GP40 (contact charging method) image exposure amount on the surface of the electrophotographic photosensitive member. The evaluation was performed using an evaluator modified so that the amount of light was 0.6 μJ / cm ² .

  Evaluation of durability characteristics by repeated use of the electrophotographic photosensitive member is performed by copying 20000 sheets in an intermittent mode in which A4 size plain paper is stopped once for each copy, and then measuring the film thickness of the electrophotographic photosensitive member. The amount of wear was measured.

  Further, the light portion potential (Vl) was measured before durability evaluation (light portion potential) and after copying 20000 sheets, and the difference was evaluated as the light portion potential fluctuation.

  The surface potential of the electrophotographic photosensitive member was measured at the developing device position by exchanging the jig and the developing device fixed so that the potential measuring probe was positioned 180 mm from the upper end of the electrophotographic photosensitive member. Further, sebum was adhered to the surface of a new electrophotographic photosensitive member and left for 72 hours, and the presence or absence of a solvent crack was observed by microscopic observation (100 times). Ten observation points were observed, and “O” indicates that no cracks were observed at all observation points, and “X” indicates occurrences at the observation points.

(Examples 2-6, 2-7, 2-11, 2-12, 2-16, 2-17, 2-21, 2-22, 2-26, 2-27, 2-29, 2-30 3-1, 3-2, 3-3, 3-4, 3-5, 3-6, 3-7, 3-8 and 3-9 )
The electrophotographic photosensitive member of each example was produced as follows.

A coating composed of the following materials was applied on an aluminum cylinder having a diameter of 30 mm and a length of 357 mm by a dip coating method and thermally cured at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm. .
Conductive pigment: SnO ₂ coated treated barium sulfate 10 parts Resistance adjusting pigment: Titanium oxide 2 parts Binder resin: Phenol resin 6 parts Leveling material: Silicone oil 0.001 part Solvent: Methanol / methoxypropanol = 2/8 20 parts Next Further, on this conductive layer, a solution prepared by dissolving 3 parts of N-methoxymethylated nylon and 3 parts of copolymer nylon in a mixed solvent of 65 parts of methanol and 30 parts of n-butanol is applied by a dip coating method and dried. Thus, an intermediate layer having a thickness of 0.5 μm was formed.

  Next, 4 parts of hydroxygallium phthalocyanine having strong peaks at diffraction angles 2θ ± 0.2 ° of 7.4 ° and 28.2 ° in the X-ray diffraction spectrum of CuKα, polyvinyl butyral (trade name: ESREC BX-1, 2 parts of Sekisui Chemical Co., Ltd. and 60 parts of cyclohexanone were dispersed in a sand mill apparatus using glass beads having a diameter of 1 mm for 4 hours, and then 100 parts of ethyl acetate was added to prepare a dispersion for charge generation layer. This was applied onto the intermediate layer by a dipping method to form a charge generation layer having a thickness of 0.2 μm.

  Next, 6 parts of the high molecular weight charge transporting material shown in the following table (evaluation and results) and 10 parts of the binder resin shown in the following table are dissolved in a mixed solvent of 30 parts of monochlorobenzene and 70 parts of dichloromethane, A coating solution for charge transport layer was prepared. This was applied onto the charge generation layer by an immersion method and dried at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 25 μm.

  Thus, the electrophotographic photosensitive member of each example was produced.

(Comparative Examples 0-1 , 0-2, 3-1, 3-2, 3-3 and 3-4 )
In the examples, the high molecular weight charge transport materials were changed to those having repeating structural units represented by the following formula (7) or those shown in the following table (evaluation and results), respectively, Similarly, the electrophotographic photosensitive member of each comparative example was produced in the same manner as in the examples except that the materials were changed to those shown in the table below.

  Below, the result of evaluation of each Example and each comparative example is shown.

  In the table below, “number of structural units” (n or m) means the average number of structural units, “molecular weight (Mw)” means weight average molecular weight (Mw), and “crack” means Means the presence or absence of solvent cracks.

  It can be seen that the comparative example causes chemical deterioration due to the photosensitive process of the electrophotographic photosensitive member, and causes a large fluctuation in the bright portion potential, as compared with the example.

  Furthermore, it can be seen that the examples are superior in durability (mechanical strength and wear resistance) during repeated use as compared with the comparative examples.

  When the same binder resin is used for the charge transport layer, the wear resistance of each of the binder resins is improved as compared with the comparative example.

  Moreover, the result which can suppress a solvent crack by using a high molecular weight charge transport material is shown.

1 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus having the electrophotographic photosensitive member of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrophotographic photosensitive member of this invention 2 Axis 3 Primary charging means 4 Exposure light 5 Developing means 6 Transfer means 7 Transfer material 8 Image fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Rail

Claims (7)

In an electrophotographic photoreceptor having a support and a photosensitive layer formed on the support,
The photosensitive layer contains a high molecular weight charge transport material having a repeating structural unit represented by the following formula (22) or (31) :
The high molecular weight charge transport material has a weight average molecular weight (Mw) of 1500 or more;
The energy level of the highest occupied molecular orbital by the semiempirical orbital calculations of the high molecular weight charge-transporting material _{(E HOMO),} characterized in that at most -8.3 [eV] or -8.0 [eV] Electronic Photoconductor.

(In the formula (22), R ²²⁰¹ , R ²²⁰² , R ²²⁰³ , R ²²⁰⁴ , R ²²⁰⁵ , R ²²⁰⁶ , R ²²⁰⁷ , R ²²⁰⁸ , R ²²⁰⁹ , R ²²¹⁰ and R ²²¹¹ are each independently hydrogen, substituted or absent A substituted alkyl group or an electron-withdrawing group is represented. A ²²⁰¹ represents a group 16 element.)

(In formula (31), R ³¹⁰¹ , R ³¹⁰² , R ³¹⁰³ , R ³¹⁰⁴ and R ³¹⁰⁵ are each independently hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted group, Represents an alkoxy group or an electron-withdrawing group, Z ³¹⁰¹ represents a substituted or unsubstituted divalent heterocyclic group, d represents an integer of 1 or more, provided that when d is 2 or more, 2 Z ³¹⁰¹ above may be the same or different.) The electrophotographic photosensitive member according to claim 1 , wherein the high molecular weight charge transport material further has a repeating structural unit represented by the following formula (23).

(In the formula (23), R ²³⁰¹ , R ²³⁰² , R ²³⁰³ , R ²³⁰⁴ , R ²³⁰⁵ , R ²³⁰⁶ , R ²³⁰⁷ , R ²³⁰⁸ , R ²³⁰⁹ , R ²³¹⁰ , R ²³¹¹ , R ²³¹² and R ²³¹³ are each independently hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, substitution or unsubstituted alkoxy group, or an electron withdrawing group.) Said photosensitive layer, an electrophotographic photosensitive member according to claim 1 or 2, wherein a surface layer of the electrophotographic photosensitive member. The electrophotographic photosensitive member according to claim 3 , wherein the photosensitive layer contains polycarbonate. Said photosensitive layer, an electrophotographic photosensitive member according to claim 3 or 4 containing a polyarylate. 6. The electrophotographic photosensitive member according to claim 1 and at least one means selected from the group consisting of a charging means, a developing means, and a cleaning means are integrally supported and detachably attached to the main body of the electrophotographic apparatus. Process cartridge characterized by being. The electrophotographic photosensitive member according to any one of claims 1-5, a charging means, an exposure means, the electrophotographic apparatus, characterized in that it comprises a developing means and transfer means.

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