JP2598100B2 - Electrophotographic photoreceptor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used for forming an electrostatic latent image in an electrophotographic device used as a copying machine or a printer, The present invention relates to an electrophotographic photosensitive member having excellent properties.

[Conventional technology]

Conventionally, CdS, ZnO, Ti has been used as an electrophotographic photoreceptor mounted on electrophotographic devices used as copiers and printers.
Inorganic photoconductors such as O, Se, Se-Te, and a-Si are known.
In recent years, with the expansion of the copier and printer markets, inexpensive and highly mass-producible organic photoconductors have been attracting attention, and their initial characteristics such as sensitivity have progressed beyond inorganic ones. . In addition, as a feature of the organic material, there is a wide range in which functions can be added by various chemical modifications, and there is an advantage that characteristics can be easily improved or optimized.

In a general form of the organic photoreceptor, a charge transporting material and a charge generating material, which are organic materials, are formed on a conductive substrate using a resin or the like. Further, in terms of characteristics, a function-separated type photosensitive layer in which a charge transport layer and a charge generation layer are separated and laminated is particularly excellent, and there are many practical examples. Further, in the organic photoreceptor, an intermediate layer is often provided between the conductive substrate and the photosensitive layer in order to improve adhesion between the conductive substrate and the photosensitive layer, control of charge injection property, and the like.

Although the organic photoreceptor has the features and advantages as described above, it is inferior to the inorganic photoreceptor in durability. Because it is more flexible than inorganic materials, it is vulnerable to physical abrasion and scratches. In addition, the chemical stability is lower than that of the inorganic material, and the effect of an active corona product such as ozone generated by a charging process during durability is particularly large. The organic photoconductive material and resin forming the organic photoreceptor are liable to undergo chemical changes such as oxidation, addition, and cleavage due to the active corona product. In the organic photoreceptor subjected to such a change, the sensitivity is reduced, the residual potential is accumulated, the carrier mobility is reduced, and the charging ability is reduced. When a corona product or a reaction complex of an organic photoreceptor and a corona product acts as a charge acceptor or a charge donor, sensitivity increases due to generation or injection of carriers, charging ability decreases, dark decay increases, etc. cause.

The deterioration of the organic photoconductor due to the corona product described above appears as an influence on the entire surface of the photoconductor while the corona product is generated during operation of the apparatus. Further, even when the apparatus is stopped, corona products such as NO _x and HNO ₃ remain in the corona charger and appear as partial deterioration of the photoconductor near the charger. In either case, the copy or print image fluctuates, but when the entire photoconductor is deteriorated, a change in the density of the entire image or image blur occurs.
This causes partial density unevenness and the like. The organic photoreceptor that has undergone such chemical deterioration must be replaced, and this is reflected as an increase in the running cost of a copier or a printer, and a decrease in serviceability and maintainability.

This fact conflicts with the inherent advantages of the organic photoreceptor, such as low cost and ease of handling, and various solutions have been proposed for this purpose. For example, JP-A-57
JP-A-122444 and JP-A-58-120260, in which a deterioration inhibitor is added to a photosensitive layer. However, neither method is a complete countermeasure, and a highly practical organic photoreceptor has not been obtained, particularly in an apparatus for copying or printing a graphic image or a photographic image requiring high image quality. Was.

[Problems to be solved by the invention]

The findings obtained from our study revealed the following facts. That is, as the reason that the corona product deteriorates the organic photoreceptor, the corona product itself, or a reactant generated between the organic material constituting the photosensitive layer and the corona product, the complex is an electron acceptor or Acting as an electron donor is included. When these electron acceptors or electron donors are generated or mixed in the organic photoreceptor, they exhibit carrier generation ability and injection property, so that the sensitivity of the photoreceptor changes, dark decay increases, charging ability decreases, etc. Cause Also,
It has been suggested that the generation and injection of carriers described above have a significant adverse effect particularly at the interface between the photosensitive layer and the conductive substrate.

An object of the present invention is to prevent deterioration of an organic photoreceptor caused by a corona product, and in particular, to prevent a decrease in charging ability and an uneven image due to an increase in carriers.

[Means for solving the problem]

Therefore, in order to effectively achieve the object of the present invention, a method of inactivating corona products that have entered at the interface between the photosensitive layer and the conductive substrate has been selected.

The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor having a conductive substrate and an organic photosensitive layer, wherein a layer of a compound represented by the following formula (1) or the compound is provided between the conductive substrate and the photosensitive layer. It is characterized by having an intermediate layer containing a compound.

In the above formula, X ₃ , X ₄ , X ₅ and X ₆ are each independently a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group,
An aralkyl group or a heterocyclic compound group, OH, NO ₂ , COOR (where R is a hydrogen atom, an alkyl group, an aryl group or an aralkyl group), (Where R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group, an aryl group or an aralkyl group), Cl, Br,
F or CN, Y is CH _{2 n} , CH = CH _n , _{-S -, - O-, CH 2} n SCH 2 n or CH _{2 n} OC
H _{2 n} , Each independently One of the characteristics of these nitrogen-containing heterocyclic compounds is that the unpaired electron pair on the nitrogen atom tends to delocalize in the ring structure having a conjugated double bond. Low. It has been found that such a compound is unlikely to become an electric charge trap, so that even if it is added between the conductive substrate and the photosensitive layer, a decrease in sensitivity and an increase in residual potential are small. Further, since it has a weak basicity or a weak donor property, it can be inactivated by forming a complex with an acid such as a corona product or an acceptor.

In the present invention, in order to provide a nitrogen-containing heterocyclic compound layer between the conductive substrate and the photosensitive layer, a film obtained by dissolving the nitrogen-containing heterocyclic compound in an appropriate organic solvent is formed by a coating method. A compound that is difficult to form a film by itself is applied and formed as an intermediate layer using an appropriate resin as a binder.

The amount of the nitrogen-containing heterocyclic compound to be introduced is 0.1 to 300 mg / m ² per unit area of the photoreceptor. Although this value depends on the electron density on the nitrogen atom of the compound, more preferably 1 to 100 m
g / m ² . If the amount is small, the ability to deactivate corona products or the like is insufficient. If the amount is large, adverse effects such as sensitivity deterioration and increase in residual potential occur.

When a film is formed as an intermediate layer together with a binder resin, the following binder resin is used. Polyester resin, polycarbonate resin, polyarylate resin, polyurethane resin, phenol resin, epoxy resin, alkyd resin,
Examples include melamine resin, polystyrene resin, polyvinyl butyral resin, polyamide resin, acrylic resin, styrene-butadiene copolymer, styrene-acryl copolymer, cellulose, modified cellulose resin, polyamino acid, casein, gelatin and the like. Further, the thickness of these intermediate layers is 0.01 to 10 μm, more preferably 0.1 to 3 μm.
Further, the intermediate layer may contain a conductive pigment, an antioxidant, a surfactant and the like.

The charge transporting material that can be used in the present invention is a polycyclic aromatic compound or a nitrogen-containing compound generally used for an organic photoreceptor, and includes a phenanthrene derivative, an anthracene derivative, a triphenylmethane derivative, a triphenylamine derivative, Carbazole derivatives, fluorenone derivatives,
Pyrazoline derivatives, hydrazone derivatives, triazole derivatives, oxazole derivatives, imidazole derivatives, oxadiazole derivatives, stilbene derivatives and the like,
Specifically, there are the following. In each formula, X is a hydrogen atom, an alkyl group, an aryl group, a haloalkyl group, or a halogen atom.

Charge generation materials that can be used in the present invention are those generally used in organic photoreceptors, and include phthalocyanine pigments, polycyclic quinone pigments, trisazo pigments, disazo pigments, azo pigments, indico pigments, quinacridone pigments, and athrenium salts. Dyes, squarylium dyes, cyanine dyes,
Examples include pyrylium dyes, thiopyrylium dyes, xanthene dyes, quinoneamine dyes, triphenylmethane dyes, styryl dyes, selenium, selenium / tellurium, amorphous silicon, cadmium sulfide, and the like, and specifically include the following: M: Al, Ca, Si, Sn, Ge, V, Cu, Co X: Cl, F, O Azo pigment (In the following formulas, X is H, F, Cl, Br, NO ₂ , CN, etc. , Ar is a substituted or unsubstituted aromatic ring, and R is an alkyl group, an aralkyl group, or a hydrogen atom) The electrophotographic photoreceptor of the present invention has a conductive substrate and a photosensitive layer. The photosensitive layer is basically composed of the charge transporting material and the charge generating material and a binder resin for forming them. The layer configuration includes a single-layer type and a laminated type, the latter being more common. In the case of a single-layer type, the charge transport material,
The charge generating material and the binder resin are mixed in an appropriate ratio. In the case of a stacked type, the charge transporting material and the charge generating material are separately formed with a binder resin and laminated to form a charge transporting layer and a charge generating layer. At this time, either layer may be formed on the conductive substrate side, but generally, the charge generation layer is formed first. The charge transport layer may further contain a charge generating material, and the charge generating layer may further contain a charge transport material.

As a binder resin for film formation, polyester resin,
Polyarylate resin, acrylic resin, acrylonitrile resin, methacrylic resin, polycarbonate resin, polyamide resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, phenol resin, polyurethane resin, styrene
Butadiene copolymers, styrene-acrylic copolymers and the like are used.

In the case of the multilayer type, the ratio of the charge generation material to the binder resin is
It is 0.5 / 1 to 10/1, preferably 1/1 to 5/1. The thickness of the charge generation layer is 0.01 to 5 μm, preferably 0.1 μm.
05 to 3μ. Similarly, the ratio of the charge transport material of the charge transport layer and the binder resin is 5/10 to 50/10, preferably 7/1.
0 to 30/10. The thickness of the charge transport layer is 5 to 50 μm, preferably 10 to 30 μm.

As the conductive substrate of the photoreceptor that can be used in the present invention, aluminum, iron, copper, zinc, nickel, chromium, titanium, metals such as indium and alloys thereof,
Plastics, paper, metal, or the like that has been subjected to conductive treatment can be used. As the conductive treatment, a method of vapor deposition of a conductive material, a method of containing or dispersing in a binder resin, and forming a film are common. As the conductive material contained and dispersed in the binder resin, powders of the above metals or alloys, powders of carbon, tin oxide, zinc oxide, antimony oxide, silicon oxide, and the like, conductive plastics, and the like are used. The conductive substrate may be in the form of a film, a sheet, a belt, a cylinder, a column, or the like.

As a film forming method in the electrophotographic photoreceptor of the present invention, a general coating method is used. That is, the photoreceptor material is dispersed or dissolved in an appropriate solvent together with a binder resin and the like, and used in a liquid state. These liquids are applied by spray coating, dip coating, blade coating, Meyer bar coating, roller coating,
The film is formed by a coating method such as spinner coating or curtain coating.

Example 1 Structural formula 9 parts by weight of a nitrogen-containing heterocyclic compound represented by the following formula, 91 parts by weight of a soluble polyamide (Toresin EF-30: manufactured by Teikoku Chemicals), 800 parts by weight of methanol and 400 parts by weight of isopropanol were dissolved by stirring.

The solution was spray-coated on a mirror-finished aluminum cylinder having a diameter of 80 mm, a length of 375 mm, and a thickness of 1.0 mm. After drying at 50 ° C. for 30 minutes, an intermediate layer having a thickness of 0.7 μ was obtained.

Next, the structural formula Is dispersed at 2,000 rpm at 25 ° C. by a sand mill using 1 mm diameter glass beads in an amount of 10 parts by weight of an azo pigment represented by the following formula, 20 parts by weight of a polycarbonate resin (bisphenol A type: molecular weight Mn = 13,000) and 1,000 parts by weight of cyclohexanone. 50
Time went. After washing with 500 parts by weight of cyclohexanone, removing glass beads and centrifuging at 10,000 rpm, 500 parts by weight of tetrahydrofuran, cyclohexanone 2
It was diluted with 00 parts by weight. This dispersion was spray-coated on the intermediate layer, and then dried at 70 ° C. for 10 minutes to form a 0.15 μ charge-generating layer.

In addition, the structural formula Were mixed and dissolved in 20 parts by weight of a styrene compound represented by the following formula, 25 parts by weight of a polycarbonate resin (bisphenol Z type: mn = 14,000), and 200 parts by weight of benzene. After dip coating this solution on the charge generation layer,
By drying for 0 minutes, a charge transporting layer having a film thickness of 17 μm was obtained, whereby a photosensitive drum was obtained.

Comparative Example 1 A photoconductor drum was obtained in the same manner as in Example 1 except that the intermediate layer did not contain the nitrogen-containing heterocyclic compound.

[Evaluation of characteristic fluctuation due to durability]

For durability, a Canon copier NP-3525 was used. NP-35
The photosensitive drum was set at 25 and driven, and the primary charging grid bias was adjusted by a potential measurement sensor arranged at the developing position so that the dark potential (Vd) of the photosensitive member became -800 V. Further, the voltage of the document reading halogen lamp was adjusted such that the light potential (Ve) of the photoconductor when using a solid white document was -100V.

After the initial setting described above, continuous durability of A4 size horizontal flow was performed every 10,000 using a solid white original. After endurance, Vd and Ve were measured again, and Ve was measured when the grid bias was readjusted to Vd = -800V.

As a result, in the photoconductor of Comparative Example 1, Vd was reduced by 40 V and Ve was reduced by 50 V. However, in the photoconductor of Example 1, Vd was reduced by 15 V and Ve was reduced by 10 V, indicating that there was little change in potential. . Also early
It was found that the amount of light required for setting Ve did not change much as compared with Comparative Example 1, and that the decrease in sensitivity was small, indicating that a good photoconductor was obtained. Table 1 summarizes the above results.

Before and after the durability test, a change in density of a halftone image and occurrence of image unevenness were evaluated. In Comparative Example 1, a decrease in image density and density unevenness after durability occurred, but in Example 1, a stable halftone image was obtained even after durability. The results are summarized in Table 1.

Example 2 Structural formula for intermediate layer A photosensitive drum was prepared and durable in the same manner as in Example 1 except that the nitrogen-containing heterocyclic compound represented by the following formula was used. The results are summarized in Table 1.

Example 3 The following thermosetting polyurethane was used as the intermediate layer. That is, 50 parts by weight of polyol (trifunctional polyether polyol type, Nipporan 800), 50 parts by weight of isocyanate (block isocyanate type, Coronate 2540), structural formula Was applied onto an aluminum cylinder by dip coating using a solution comprising 5 parts by weight of a nitrogen-containing heterocyclic compound represented by the following formula and 895 parts by weight of cyclohexanone, and treated at 150 ° C. for 60 minutes to obtain a 0.6 μm intermediate layer. Hereinafter, Example 1
A photoreceptor was prepared in the same manner as described above, and durability was performed. The results are summarized in Table 1.

Comparative Example 2 A photoconductor was prepared and durable in the same manner as in Example 1 except that the nitrogen-containing heterocyclic compound was not contained in the intermediate layer.
The results are summarized in Table 1.

Example 4 Structural formula An aluminum cylinder was dip-coated with a solution of 8 parts by weight of a nitrogen-containing heterocyclic compound represented by the following formula, 50 parts by weight of methanol, and 40 parts by weight of propanol, and dried at 100 ° C. for 10 minutes. The solid content attached to the aluminum cylinder was 75 mg / m ² . Thereafter, a photosensitive drum was prepared in the same manner as in the other examples, and durability was performed. The result is
It is summarized in the table.

Comparative Example 3 A photoconductor was prepared and durable in the same manner as in Example 1 except that the intermediate layer and the nitrogen-containing heterocyclic compound were not contained. The results are summarized in Table 1.

In the table, ○ indicates that no item in the table is found visually, × indicates that the item is clearly found in the table, XX indicates that the degree is worse, and Δ indicates that the item is not so obvious, even if it is not so obvious. Not being found means not being able to say.

〔The invention's effect〕

As summarized in Table 1 above, nitrogen-containing heterocyclic compounds, in particular, nitrogen-containing heterocyclic compounds having a nitrogen atom and a conjugated double bond in a ring structure are formed between the photosensitive layer and the conductive substrate. Or, by including it in the intermediate layer, there is no adverse effect such as carrier trapping due to electrons on the SP ₂ hybrid nitrogen atom,
In addition, a photoreceptor drum capable of preventing generation of an electron-accepting substance or an electron-donating substance between the photosensitive layer and the substrate at the time of durability and causing a decrease in potential or the like was obtained.

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Susumu Nagahara 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-63-125944 (JP, A) JP-A-58 JP 187931 (JP, A) JP-A-58-17450 (JP, A) JP-A-1-314253 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photoreceptor having a conductive substrate and an organic photosensitive layer, wherein a layer of the compound represented by the following formula (1) or the compound is contained between the conductive substrate and the photosensitive layer. An electrophotographic photoreceptor, comprising an intermediate layer. In the above formula, X ₃ , X ₄ , X ₅ and X ₆ each independently represent a hydrogen atom, an alkyl group, a substituted or unsubstituted aryl group, an aralkyl group or a heterocyclic compound group, OH, NO ₂ , COOR R is a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group), (Where R ₁ and R ₂ are each independently a hydrogen atom, an alkyl group, an aryl group or an aralkyl group), Cl, Br,
F or CN, Y is CH _{2 n} , CH = CH _n , _{-S -, - O-, CH 2} n SCH 2 n or CH _{2 n} OC
H _{2 n} , Each independently