JP2637584B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having excellent durability without deteriorating image quality even when used repeatedly.

[Conventional technology]

The electrophotographic photoreceptor is required to have predetermined sensitivity, electrical physical properties, and optical characteristics according to the applied electrophotographic process, and further, for a photoreceptor to be used repeatedly, the photoreceptor The surface layer, that is, the layer most distant from the substrate, is subjected to direct electrical and mechanical external forces, such as corona charging, toner development, transfer to paper, and cleaning treatment, and therefore requires durability against them. Specifically, there is a demand for durability against abrasion and scratches on the surface due to sliding contact, and deterioration on the surface due to ozone generated during corona charging under high humidity. Further, there is a problem that toner is adhered to the surface layer due to repeated development and cleaning of the toner. To solve this problem, it is required to improve the cleaning property of the surface layer.

Various methods have been studied to satisfy the characteristics required for the surface layer as described above, and among them, it is particularly effective to provide a resin layer in which a fluororesin powder is dispersed on the surface.

By providing a resin layer in which a fluorine-containing resin powder is dispersed, scratches, surface cleaning properties, durability against abrasion, etc. are improved, and the water repellency and release properties of the photoreceptor surface are improved. It is also effective in preventing surface deterioration.

On the other hand, the electrophotographic photoreceptor, in addition to the physical impulse received from the process when used according to the applied electrophotographic process, fatigue due to repeated exposure, or ozone generated by corona discharge And nitrogen oxides. In particular, ozone and nitrogen oxides act directly on the charge transport material on the surface of the photoreceptor to lower the surface resistance and affect the image. In order to prevent this, it is effective to use a charge transporting substance having a high oxidation potential so that it does not easily react with the above-mentioned ozone or nitrogen oxide.

However, in particular, in the case of nitrogen oxides, in addition to acting on the photoreceptor in a gaseous state, it acts on the photoreceptor in the form of nitric acid in combination with moisture in the air.

Particularly near the corona charger, a large amount of HNO ₃ and HNO ₂ is generated, which adheres to the corona charger, moves onto the photoconductor while the machine is idle for a long time, and enters the photoconductor. In addition, since the charge reaches the substrate, the portion under the charger lowers in charging ability and changes in sensitivity, causing a phenomenon that electrophotographic characteristics differ from those of other portions.

In order to prevent such development from occurring, a substance that traps HNO ₃ , HNO _2, etc. in the photoreceptor, for example, a weakly basic substance having two pyridine rings is added to the photoreceptor, It is effective to inactivate HNO ₃ , HNO _2, etc., which have invaded the air.

Here, when the above two techniques are combined, an electrophotographic photoreceptor excellent in mechanical properties, surface lubricity, and moisture resistance should be completed.

However, in reality, good things are not always possible. This is because the fluororesin powder taken up here has extremely poor dispersibility when dispersed in the binder resin, and it is almost indispensable to use a surfactant or the like as a dispersing aid for uniform dispersion. It can be said that there is.

However, when both the surfactant and the compound having two pyridine rings are mixed in the same layer of the photoconductor, their interaction adversely affects the electrophotographic characteristics of the photoconductor,
For example, a decrease in sensitivity, an increase in residual potential, an increase in potential fluctuation due to durability, and the like are exerted.

[Problems to be solved by the present invention]

An object of the present invention is to avoid the above-mentioned drawbacks, that is, it has durability against the occurrence of surface abrasion and scratches due to rubbing during repeated use, has moisture resistance, and has a partial resistance to nitric acid or the like. An object of the present invention is to provide an electrophotographic photoreceptor which does not cause charging unevenness and sensitivity unevenness and thus does not cause image unevenness.

Another object of the present invention is to provide an electrophotographic photoreceptor having high quality in a repetitive electrophotographic process, particularly high sensitivity.

[Means for solving the problem]

As a result of repeated studies according to the object, the present inventors have found that a surface layer containing a fluorine-containing resin and the following general formula (1)
It has been found that the above-mentioned problems can be solved by providing an electrophotographic photosensitive member having a laminated structure with a photosensitive layer containing a compound represented by the following formula:

That is, the electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a conductive substrate, an organic photosensitive layer and a surface layer, wherein the photosensitive layer has a general formula (Wherein, X is -S -, - S-S - , - (CH 2) n -, or - (CH = _{CH) n} - and is, n in this case is an integer of 0, R ₁ and R ₂ hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms), and the surface layer is fluorine-containing. It is characterized by containing resin powder.

In the present invention, the surface layer contains a fluororesin powder and a binder, and as the fluororesin powder, ethylene tetrafluoride, ethylene trifluoride chloride, ethylene propylene hexafluoride, vinyl fluoride, vinylidene fluoride, Powders of polymers such as fluorinated ethylene dichloride, trifluoropropylmethyldichlorosilane, or copolymers of these, or copolymer resins with vinyl chloride are used as appropriate. Vinylidene resin powder is preferred. The molecular weight of the fluorine-containing resin and the particle size of the powder can be appropriately selected within a range that does not affect the uniformity of the formed coating film.

The content of the fluororesin powder in the surface layer is suitably from 1 to 50% by weight.

The binder resin used for dispersion may be any polymer as long as it is a film-forming polymer, but from the viewpoint of having a certain degree of hardness even if used alone and not hindering carrier transport, polymethacrylic acid ester , Polycarbonate, polyarylate, polyester, polysulfone,
Vinyl chloride monoacetate copolymer, polystyrene and the like are preferred.

This fluororesin powder dispersion layer need not necessarily be treated only as a protective layer. That is, this layer can contain a charge transporting substance or a charge generating substance and function as a part of the charge transporting layer, and has the same charge transporting agent / binder or charge generating agent / binder as the photosensitive layer below this layer. Can also be used. The amounts of the charge transporting substance and the charge generating substance to be contained can be appropriately selected depending on the performance of the photoreceptor.

Even when a charge transporting substance and a charge generating substance are contained, the effect of the fluororesin powder is sufficiently exhibited.

Specific examples of the compound having two pyridine rings contained in the photosensitive layer include those shown in Table 1.

In the present invention, the compound having two pyridine rings occupies 1 to 10% by weight of the photosensitive layer, and even if used alone, the effect can be sufficiently improved. It is also possible to use in combination with an inhibitor.

These antioxidants include phenol-based, aromatic amine-based, phosphorus-based, and sulfide-based antioxidants.

When the electrophotographic photoreceptor of the present invention is manufactured, a cylindrical cylinder or a film made of metal such as aluminum or stainless steel, paper, plastic, or the like is used as the substrate. An undercoat layer (adhesive layer) having a barrier function and an undercoat function can be provided on these substrates.

The undercoat layer improves the adhesiveness of the photosensitive layer, improves coating properties, protects the substrate, covers defects on the substrate, improves charge injection from the substrate,
It is formed to protect the photosensitive layer against electrical breakdown. Known materials for the undercoat layer include polyvinyl alcohol, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene acrylic acid copolymer, casein, polyamide, copolymerized nylon, glue, gelatin, and the like. These are dissolved in a suitable solvent and applied onto a substrate. Its film thickness is about 0.2 to 2.0 μm.

As the charge generating substance, pyrylium, thiopyrylium dye, phthalocyanine pigment, anthantrone pigment,
Dibenzopyrene quinone pigments, pyranthrone pigments, trisazo pigments, disazo pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanines, quinocyanines and the like can be used.

As the charge transport substance, pyrene, N-ethylcarbazole, N-isopropylcarbazole, N-methyl-N-
Phenylhydrazino-3-methylian-9-ethylcarbazole, NN-diphenylhydrazino-3-methylian-9-ethylcarbazole, NN-diphenylhydrazino-3-methylian-10-ethylphenothiazine, N.P.
N-diphenylhydrazino-3-methylian-10-ethylphenoxazine, P-diethylaminobenzaldehyde-NN-diphenylhydrazone, P-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone, P-pyrrolidinobenzaldehyde-NN- Diphenylhydrazone, 1,3,3-trimethylindolenine-α-aldehyde-NN-diphenylhydrazone, P-
Hydrazones such as diethylbenzaldehyde-3-methylbenzthiazolinone-2-hydrazone, 2,5-bis (P-diethylaminophenyl) -1,3,4-oxadiazole, 1-phenyl-3- (P- Diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [quinolyl (2)]-3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (2)] -3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazolin, 1- [6-methoxy-pyridyl (2)
-3- (P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1- [pyridyl (3)]-3- (P-diethylaminostyryl) -5-
(P-diethylaminophenyl) pyrazolin, 1- [repidyl (2)]-3- (P-diethylaminostyryl-
5- (P-diethylaminophenyl) pyrazolin, 1-
[Pyridyl (2)]-3- (P-diethylaminostyryl) -4-methyl-5- (P-diethylaminophenyl) pyrazolin, 1- [pyridyl (2)]-3- (α-
Methyl-P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazoline, 1-phenyl-3
-3 (P-diethylaminostyryl) -4-methyl-5
Pyrazolines such as-(P-diethylaminophenyl) pyrazolin, 1-phenyl-3- (α-benzyl-P-diethylaminostyryl) -5- (P-diethylaminophenyl) pyrazolin, and spiropyrazolin; 2- (P-diethylaminostyryl) -6-diethylaminobenzoxazole, 2- (P-diethylaminophenyl) -4
Oxazole-based compounds such as-(P-dimethylaminophenyl) -5- (2-chlorophenyl) oxazole;
Thiazole compounds such as-(P-diethylaminostyryl) -6-diethylaminobenzothiazole, triarylmethane compounds such as bis (4-diethylamino-2-methylphenyl) -phenylmethane, 1,1-bis (4- Polyarylalkanes such as NN-diethylamino-2-methylphenyl) heptane and 1,1,2,2-tetrakis (4-N, N-dimethylamino-2-methylphenyl) ethane can be used.

In the present invention, as a method for dispersing the fluorine-containing resin powder in the resin solution, a method such as a homogenizer, a ball mill, a vibration ball mill, a sand mill attritor, a roll mill, or the like is considered. As a procedure, a binder resin is dissolved in an organic solvent, a required amount of a fluorine-containing resin powder and a dispersing aid are mixed therein, and the mixture is dispersed by the above-described dispersion method. Should be mixed. When the charge-generating substance is a pigment, a dispersion of the charge-generating substance alone may be prepared separately, and if the conditions permit, the dispersion may be carried out simultaneously with the fluororesin powder.

As a method for applying the photosensitive layer, for example, a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method, a curtain coating method, or the like can be used. Here, especially when coating the surface layer in which the fluorine-containing resin powder is dispersed on the lower photosensitive layer, if the binder is the same resin, or if the binder is not the same, the solvent used for one is the other. In the case of dissolution, the dip coating method or the like may not be used, and in this case, the spray coating method or the like is suitable. The thickness of the surface layer after coating and drying can be set to an appropriate thickness depending on the purpose.
In particular, in a system containing a CT material, the surface layer also functions as a CT layer, so that the electrophotographic characteristics are not deteriorated even when applied thicker than a general protective layer or the like.

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

Example 1 A 5% methanol solution of a 6-66-610-12 quaternary polyamide copolymer resin was applied on an aluminum cylinder substrate having a diameter of 80 mm and a length of 360 mm by a dipping method to provide an undercoat layer having a thickness of 05 µm. Was.

Next, the structural formula Of a charge generating substance, 6 parts of a polyvinyl benzal resin and 60 parts of cyclohexanone were dispersed in a sand mill using 1 mmφ glass beads for 20 hours. To this dispersion, 120 parts of tetrahydrofuran was added and mixed, and this mixture was applied on an undercoat layer to form a 0.2 μm charge generation layer.

Next, the structural formula Is dissolved in 70 parts of a mixed solvent of monochlorobenzene and dichloromethane, and the compound represented by the structural formula 3 in Table 1 is further dissolved in a binder resin. And 3% of the total weight of the compound and the charge transporting material.

This solution is applied by dip coating on the charge generation layer,
It was dried with hot air at 120 ° C. to form a 17 μm-thick charge transport layer.

Next, 5 parts of a low molecular weight polytetrafluoroethylene powder having an average primary particle size of 0.3 μm and a fluorine-based comb-type graft polymer having a fluoroalkylate as a dispersing aid in a side chain.
5 parts and 5 parts of a bisphenol Z-type polycarbonate having a number average molecular weight of about 20,000 as a binder were mixed with 35 parts of monochlorobenzene, and dispersed in a ball mill for 50 hours.
To this dispersion, 52 parts of the above-mentioned charge transporting substance, 50 parts of polycarbonate, 700 parts of monochlorobenzene and 100 parts of dichloromethane are added, and the mixture is coated on the charge transport layer by an air spray coating device, dried at 120 ° C., and dried at 5 μm. Was formed. This photoconductor is referred to as Sample 1. Further, a sample having a charge transport layer having a thickness of 22 μm without applying the surface layer was designated as Sample 2. When preparing the coating solution for the surface layer of Sample 1, the amount of the solvent added later was 300 parts of monochlorobenzene and 5 parts of dichloromethane.
The compound represented by Structural Formula 3 in Table 1 was dissolved in an amount of 1 mol% of the added charge transporting substance and dissolved. This dispersion preparation was applied on the charge generation layer and dried at 120 ° C. to form a charge transport layer having a thickness of 22 μm. Sample 3 in which the compound represented by Structural Formula 3 was not added to the charge transport layer in Sample 3 is referred to as Sample 4.

These samples 1 to 4 were set in a dry-type plain paper copier, and conditions were set so that the dark part potential was 650 V and the light part potential was 130 V.
The image after 30,000 sheets of durability was evaluated by an electrophotographic process including corona charging, image exposure, dry toner development, toner transfer to plain paper, and cleaning with a rubber blade. The results were as follows.

Next, these photosensitive members after the endurance use were left in a copying machine for 24 hours, and the images were evaluated again. When the samples 1 to 3 were used, the same images as those before the standing were obtained. When the sensitivity of the portion facing the charger was increased and a halftone image was displayed, the portion became white as a band.

That is, only the sample 1 did not have any of the scratches, the fog on the white background, and the band-like white dropping state after the 30,000-sheet running.

Example 2 In Example 1, polyvinylidene fluoride powder was used as the fluorine-containing resin powder, and a fluoropolymer composed of a perfluoroalkyl group portion and an acrylic resin was used as the dispersing aid. Similar results were obtained with the indicated compounds.

Example 3 An aluminum cylinder of 80 mmφ × 360 mm was used as a base, and a 5% methanol solution of the polyamide resin used in Example 1 was dip-coated thereon to form an undercoat layer of 1 μm.

Next, the structural formula 1 part of the charge-generating substance and 10 parts of pisphenol Z-type polycarbonate added to 60 parts of monochlorobenzene were dispersed in a stainless steel ball mill for 72 hours, and further 6 parts of the charge transporting substance used in Example 1 Was added and dissolved. Further, the compound represented by the structural formula 9 in Table 1 was added to the solution in an amount of 5% of the total weight of the binder resin and the charge transporting substance. This solution was applied onto the undercoat layer by dip coating to form a 15 μm photosensitive layer.

Next, using a method similar to the method for preparing this photosensitive layer coating liquid, when dispersed in a stainless steel ball mill, 4 parts of polytetrafluoroethylene resin powder and a perfluoroalkyl group and styrene as a dispersing aid are used. 0.4 parts of a fluorine-based comb type graft polymer was simultaneously added and dispersed to prepare a liquid in which a charge transporting substance was dissolved. However, in this case, the compound represented by the structural formula 9 was not added. Monochlorobenzene was further added to this dispersion solution to form a solution having a solid fraction of 10%. The solution was applied on the photosensitive layer by a spray coating device and dried at 120 ° C. to form a 5 μm surface layer. The photoreceptor thus prepared is referred to as Sample 5.

Samples 6 and 5 which had a thickness of 20 μm when the photosensitive layer was provided and had no surface layer were used in Samples 6 and 5 in the photosensitive layer.
The sample to which no compound represented by was added was designated as Sample 7. Further, when the photosensitive layer is provided, the photosensitive layer contains both the polytetrafluoroethylene resin powder and the compound represented by the structural formula 9 as Sample 8.

The photoreceptors of Samples 5 to 8 were set on a plain paper copier in the same manner as in Example 1, and were subjected to corona charging, image exposure, dry toner development, transfer to plain paper, cleaning with a rubber blade, and strong exposure. An image output durability test was performed by the process of removing the surface potential. The image evaluation after 30,000 copies was as follows.

The residual potential of these photosensitive members after strong exposure was measured and was as follows.

Further, in the same manner as in Example 1, these photosensitive members were left in the machine for 48 hours, and an image was formed again.
The same image was obtained for sample 8 as before, but sample 7
With regard to (2), the portion corresponding to the corona charger was white and band-like in the halftone image.

〔The invention's effect〕

As described above, the electrophotographic photoreceptor of the present invention has good durability against repeated use, and does not cause partial unevenness in charging ability and sensitivity due to nitric acid or the like, and therefore does not cause image unevenness.

Claims (2)

(57) [Claims] 1. An electrophotographic photosensitive member having a conductive substrate, an organic photosensitive layer and a surface layer, wherein the photosensitive layer has a general formula (Wherein, X is -S -, - S-S - , - (CH 2) n -, or - (CH = _{CH) n} - and is, n in this case is an integer of 0, R ₁ and R ₂ hydrogen atom, an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms), and the surface layer is fluorine-containing. An electrophotographic photoreceptor containing a resin powder. 2. The electrophotographic photosensitive member according to claim 1, wherein said surface layer contains a charge transport material.