JPH03240067A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To exhibit stable performance with less fluctuation in potential by providing the synergistic effect of the inactivation of the corona product by a nitrongenous heterocyclic compd. and the charge trap removal by arom. sulfonic acid compd. CONSTITUTION:The nitrogenous heterocyclic compd. contg. nitrogen in the conjugate structure of a ring and the arom. sulfonic acid compd. are introduced at the boundary of a photosensitive layer and a conductive base body. Since the electron density on this nitrogen atom is lower than in the case of on the ordinary nitrogen atom, the influence in the degradation in the sensitivity on the photosensitive layer and the influence of the increase in residual potential are lessened even if these compds. are interposed between the conductive substrate and the photosensitive layer. These compds. can be inactivated by forming complexes with acidic materials, etc., such as, corona products. The arom. sulfonic acid compd. is made to coexist in this nitrogen atom, by which the trapped charges are rapidly and effectively released. The stable performance with the less fluctuation in the potential is exhibited by the synergistic effect thereof.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an electrophotographic photoreceptor that forms an electrostatic latent image in an electrophotographic device used as a copying machine or a printer, and particularly relates to an electrophotographic photoreceptor that has excellent durability and stability. Related to electrophotographic photoreceptors.

[Prior Art] Conventionally, inorganic CdS, ZnO, TiOa, Se, 5e-Te have been used as electrophotographic photoreceptors installed in electrophotographic devices used as copying machines or printers.
and α-Si are known. In recent years, with the expansion of the copier or printer market, organic photoreceptors, which are inexpensive and can be mass-produced, have begun to attract attention, and their initial characteristics such as sensitivity have improved to the point that they exceed those of inorganic photoreceptors.

In addition, one of the characteristics of organic materials is that a wide variety of functions can be added by introducing various functional groups.

Furthermore, it has the advantage that characteristics can be easily improved and optimized.

The general form of an organic photoreceptor is that a charge transporting material and a charge generating material, which are organic materials, are formed into a film using a film-forming resin or the like on a conductive substrate. In terms of characteristics, a functionally separated photosensitive layer in which a charge transport layer and a charge generation layer are separately laminated is particularly excellent and has many practical applications. In addition, in organic photoreceptors,
In order to improve the adhesion between the conductive substrate and the photosensitive layer and the ability to control charge injection, various intermediate layers are often interposed between the conductive substrate and the photosensitive layer.

Organic photoreceptors, which have the above features and advantages, are inferior to inorganic photoreceptors in that they lack durability. Since organic photosensitive materials are more flexible than inorganic materials, they are more susceptible to physical wear and damage. In addition, their chemical stability is still lower than that of inorganic materials, and they are particularly susceptible to deterioration by active corona products such as ozone generated by the charging process during durability tests. The organic photoconductive materials and resins forming the organophotoreceptor are susceptible to chemical changes such as oxidation, addition, decomposition, or deterioration by the active corona products described above. In an organic photoreceptor that has undergone such changes, a decrease in sensitivity, an accumulation of residual potential, a decrease in carrier mobility, a decrease in charging ability, etc. occur. In addition, when a corona product or a reaction product or a complex between an organic photoreceptor and a corona product acts as a charge donor or a charge donor, they may cause increased sensitivity, decreased charging ability, and This causes an increase in dark decay, etc.

The deterioration of the organic photoreceptor due to the corona products described above appears as an effect on the entire surface of the photoreceptor since corona products are generated when the apparatus is in operation. In addition, even when the equipment is stopped, the corona charger is equipped with NO, HN.
Since corona products such as O, etc. remain, this appears as partial deterioration of the photoreceptor near the charger. In any case, deterioration of the photoreceptor causes fluctuations in the copied or printed image, but when the entire surface of the photoreceptor deteriorates, it causes density changes and blurring of the entire image, while when it partially deteriorates, it causes local density unevenness, etc. will occur. Organic photoreceptors that have undergone such chemical deterioration must be replaced, which results in an increase in the running cost of the copying machine or printer and a decrease in serviceability or maintainability.

This fact is a problem that cancels out the inherent advantages of organic photoreceptors, such as low cost and ease of handling, and a number of countermeasures have been proposed to overcome this problem.

For example, JP-A No. 57-122444 or JP-A No. 5
As shown in Japanese Patent No. 8-120260, there is a method of adding a deterioration inhibitor to the photosensitive layer. However, it is not a perfect countermeasure, especially in devices that copy or print graphic images and photographic images that require high image quality.
A highly practical organic photoreceptor had not yet been obtained.

[Problems to be Solved by the Invention] The present invention aims to prevent the deterioration of an organic photoreceptor caused by corona products, and particularly aims to prevent a decrease in charging ability and image unevenness due to an increase in carriers. .

[Means for Solving the Problems] According to the findings obtained from research by the present inventors, the following facts were found.

That is, during the deterioration of the organic photoreceptor due to the corona product, the corona product itself or a reactant or complex formed between the organic material constituting the photosensitive layer and the corona product becomes an electron acceptor or an electron donor. The fact is that it can sometimes act as a

When the electron acceptor or electron donor is generated and mixed into an organic photoreceptor, they exhibit carrier generation and injection functions, resulting in changes in photoreceptor sensitivity, increase in dark decay, and decrease in charging ability. This may cause deterioration, etc.

Furthermore, it has been suggested that the above-mentioned adverse effects caused by the generation and injection of carriers are particularly severe when corona products penetrate into the interface between the photosensitive layer and the conductive substrate.

Therefore, in order to effectively achieve the object of the present invention, the present inventors have selected a method of inactivating corona products that have entered the interface between the photosensitive layer and the conductive substrate. Specifically, both a nitrogen-containing heterocyclic compound containing nitrogen in the conjugated structure of the ring and an aromatic sulfonic acid compound were introduced into the interface between the photosensitive layer and the conductive substrate.

The general concept of the nitrogen-containing heterocyclic compound is as shown in Group A and Group AA below, and examples of the basic skeleton thereof are also as shown below.

Specific examples of aromatic sulfonic acid compounds are shown in Group B below.

A characteristic of these nitrogen-containing heterocyclic compounds is that the unpaired electron pair on the nitrogen atom in the conjugated ring structure tends to be delocalized, so the electron density on this nitrogen atom is lower than that on the normal nitrogen atom. It may be lower than that. Since such a compound is less likely to become a charge trap, it has been found that even if it is interposed between the conductive substrate and the photosensitive layer, it has little influence on the photosensitive layer by reducing sensitivity or increasing residual potential. Furthermore, since it exhibits weak basicity or weak donor properties, it can form a complex with acidic substances such as corona products or acceptors to inactivate them.

However, the shallow charge trapping by nitrogen atoms is disadvantageous in terms of high-speed processing and repeatability.

After extensive investigation, we discovered that the coexistence of an aromatic sulfonic acid compound is extremely effective as a means to quickly release the charges trapped in nitrogen atoms.

In the present invention, in order to interpose the nitrogen-containing heterocyclic compound and the aromatic sulfonic acid compound between the conductive substrate and the photosensitive layer, the nitrogen-containing heterocyclic compound and the aromatic sulfonic acid compound are formed into a film by coating the compound as a solution in a suitable organic solvent, for example. Compounds that are difficult to form into a film alone can be coated or formed into a film in the form of a stabilizing layer using a suitable resin as a binder.

The amount of the nitrogen-containing heterocyclic compound introduced is usually 0.1 to 300 mg/m'' per unit area of the photoreceptor. This value also depends on the electron density on the nitrogen atom of the compound and the dissociation constant of the aromatic sulfonic acid. It depends, but preferably 1 to 100 B/m”
If the amount is less than this, the ability to inactivate corona products etc. will be insufficient.

If the amount is more than this, problems such as deterioration of sensitivity and increase in residual potential will occur.

The amount of aromatic sulfonic acid introduced at the same time is usually 0.1 to 3
00 mg/m'', but the proportion to the nitrogen-containing heterocyclic compound is chosen in the range 30-200%, preferably 50-150%, based on the weight of the latter.

When forming a stabilizing layer together with a binder resin, the following binder resins are preferably used: polyester resin, polycarbonate resin, polyacrylate resin, polyurethane resin, phenol resin, epoxy resin, alkyd resin, Melamine resin, polystyrene resin, polyvinyl butyral resin, polyamide resin, acrylic resin, styrene-butadiene copolymer, styrene-acrylic copolymer,
These include cellulose, modified cellulose resin, polyamino acids, casein, and gelatin.

The thickness of these stabilizing layers is usually 0.001-1 Ou, preferably 0.1-3 μm. Further, the stabilizing layer may further contain a conductive pigment, an antioxidant, a surfactant, or the like.

The stabilizing layer in the photoreceptor of the present invention is the center of improvement, and one of the stabilizing layers is the following nitrogen-containing heterocyclic compound A.
Or AA.

Heterocycle that may have a aryl group or a substituent; -0H1-NO
,, -GOOR (where R represents a hydrogen atom, an alkyl group, an aralkyl group, or an aryl group), 1 -N (where R1 and R2 are a hydrogen atom, an alkyl group,
aralkyl group or aryl group), -Cf, -Br, -
F, -CN, and Z represent an alkylene group, an alkenylene group, an aryl group, a nitrogen atom, an oxygen atom, and a sulfur atom, and two or more Z's coexisting may be different from each other.

Here, Y is an alkylene group, an alkenylene group, an arylene group, an oxygen atom, and a sulfur atom; Zl and zM are one or more of the groups defined in Group A and may be different from each other.

The basic skeletons of compounds belonging to Group A are as follows.

The basic skeleton of the compound belonging to the AA group is one in which two or more nitrogen-containing heterocyclic compounds belonging to the A group are bonded together via an intermediate group -Y-. An example is shown below. (Here, n is usually a number of 1 to 10, preferably 1 to 6, and more preferably 1 to 4.) Among these, preferred are A++, AA+, AAs, AA4. It is AAs.

The other of the stabilizing layers in the photoreceptor of the present invention is an aromatic carboxylic acid belonging to Group B below. As shown in the following example, the basic skeleton is a fused ring such as a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, or a pyrene ring, or a diphenyl ring in which two or more of these rings are directly bonded, or a hydrocarbon group. It has a structure in which one or more sulfonic acid groups are bonded to an aromatic nucleus whose basic structure is diphenylalkane or the like formed by bonding.

(Here, n is a natural number, preferably 1-2.

) A substituent may be bonded to this basic skeleton. Examples of substituents include the following. Two or more of these may coexist: alkyl group, aralkyl group, amino group, substituted amino group,
Aryl group, halogen atom, hydroxyl group, alkoxy group, nitro group or cyano group.

Examples of aromatic sulfonic acid compounds belonging to Group B are shown below.

Preferred aromatic sulfonic acids belonging to Group 8 are as follows: toluenesulfonic acid, isopropylbenzenesulfonic acid, naphthalenesulfonic acid.

The charge transport material used in the present invention may be polycyclic aromatic compounds or nitrogen-containing compounds that are commonly used in organic photoreceptors, and specifically, phenanthrene derivatives such as those listed below,
Examples include anthracene derivatives, triphenylmethane derivatives, triphenylamine derivatives, carbazole derivatives, fluorenone derivatives, pyrazoline derivatives, hydrazone derivatives, triazole derivatives, oxazole derivatives, imidazole derivatives, oxadiazole derivatives, and stilbene derivatives.

The charge generating materials used in the present invention are as follows: phthalocyanine pigments, polycyclic quinone pigments, bisazo pigments,
Disazo pigments, azo pigments, indigo pigments, quinacridone pigments, azulenium salt dyes, squalirium dyes, cyanine dyes, pyrylium dyes, thiopyrylium dyes, xanthine dyes, quinone amine dyes, triphenylmethane dyes, styryl dyes, selenium, selenium-tellurium, amorphous silicon (α-5L), cadmium sulfide, and the like.

The photoreceptor in the present invention consists of a conductive substrate and a photosensitive layer. The basic components of the photosensitive layer are the charge transporting material, the charge generating material, and a binder resin for forming them into films.

The layer structure can be divided into a single layer type and a laminated type, with the latter being more common. In the case of a single layer type, the charge transport material, charge generation material and binder resin are mixed in an appropriate ratio. On the other hand, in the case of a laminated type, the charge transport material and the charge generation material are each formed into films using a binder resin, and then they are laminated to form a laminate of the charge transport layer and the charge generation layer. −
let

At this time, any layer may be formed on the conductive substrate side, but it is common to form the charge generation layer first. Further, the charge transporting layer may also contain a charge generating material, and the charge generating layer may also contain a charge transporting material.

Examples of binder resins for film formation include polyester resins, polyarylate resins, acrylic resins, acrylonitrile resins, methacrylic resins, polycarbonate resins, polyamide resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, phenolic resins, and polyurethane resins. , styrene-butadiene copolymer, styrene-acrylic monomer copolymer, and the like.

In the case of a laminated type, the ratio of the charge generating material to the binder resin is 0.
The ratio is from 5/1 to 10/1, preferably from 1/ to 5/1.

Further, the thickness of the charge generation layer is 0.01 to 5 μm, preferably 0.05 to 3 μm. Similarly, the ratio of the charge transport material and the binder resin in the charge transport layer is 5/10 to 50/10.
However, it is preferably 7/10 to 30/10. Further, the thickness of the charge transport layer is 5 to 50 um, preferably 10 um.
~30 μm.

Examples of the conductive substrate constituting the photoreceptor used in the present invention include aluminum, iron, copper, zinc, nickel,
Metals such as chromium, titanium, and indium, alloys thereof, plastics, glass, etc., which have been subjected to conductive treatment can be used. As the conductive treatment, a method of vapor depositing a conductive material, a method of forming a film by including or dispersing the conductive material in a binder resin, etc. are common.

As the conductive material to be contained or dispersed in the binder resin, powders of the above-mentioned metals or alloys, powders of carbon, tin oxide, zinc oxide, antimony oxide, silicon oxide, etc., conductive plastics, etc. are used.

The shape of the conductive substrate may be a film, a sheet, a belt, a cylinder, a cylinder, or the like.

As a film forming method used to create the photoreceptor in the present invention, a general coating method can be used.

That is, the photoreceptor material can be used in a liquid form by dispersing or dissolving it in a suitable solvent together with a binder resin or the like. These liquids can be formed into films by coating methods such as spray coating, dip coating, blade coating, Meyer bar coating, roller coating, spinner coating, and curtain coating.

Example 1 Nitrogen-containing compound a+9 parts by weight, aromatic sulfonic acid al''A
A+m b+=8. - Me b + 3 parts by weight was added to soluble polyamide [trade name Niresin E
F-30 (manufactured by Teikoku Kagaku)] 1100 parts by weight Methanol 9
00 parts by weight and 400 parts by weight of Improper Tool were stirred and dissolved.

Diameter 80 mrH x Length 355 m 1ll x Thickness 1.0 m
The above solution was applied by dip coating onto a mirror-finished aluminum cylinder of 1.5 mm, and after drying at 50° C. for 30 minutes, a stabilizing layer with a thickness of 1.2 μm was created.

Next, 10 parts by weight of the following azo pigment, Et: ethyl group polycarbonate resin (bisphenol A type: molecular weight M
20 parts by weight (n = 13,000) and 1000 parts by weight of cyclohexanone were mixed and dispersed at 25°C at 2000 revolutions/min for 50 hours in a sand mill using glass beads having a diameter of 1a+m. The contents were washed out with 500 parts by weight of cyclohexanone, the glass beads were removed, and after a centrifugal sedimentation treatment at 10,000 rpm, 500 parts by weight of tetrahydrofuran and 2 parts by weight of cyclohexanone were added.
00 parts by weight. This fraction was spray-coated onto the stabilizing layer and dried at 70° C. for 10 minutes to form a charge generation layer with a thickness of 0.15 μm.

Furthermore, 20 parts by weight of the following stilbene compound, Me: methyl group polycarbonate resin (bisphenol type 2: Mar
= 14,000) and 200 parts by weight of benzene were mixed and dissolved. After coating this solution by dip coating on the charge generation layer, drying at 110°C for 80 minutes,
A charge transport layer having a thickness of 17 μm was created to obtain a photoreceptor drum.

Comparative Example 1 A photoreceptor drum was obtained in the same manner as in Example 1 except that the stabilizing layer contained neither the nitrogen-containing heterocyclic compound nor the aromatic sulfonic acid.

<Evaluation of property fluctuation by durability test> A copying machine [trade name: NP-3525 (manufactured by Canon)] was used for the durability test.

After the photoreceptor drum is installed in the copying machine, the copying machine is driven, and the primary charging grid is measured so that the dark potential of the photoreceptor becomes -800V by the potential measurement sensor placed at the development position. Bias adjusted. moreover,
The bright potential (Vβ) of the photoconductor when using a solid white original is -1
The voltage of the halogen lamp for reading the original was adjusted so that the voltage was 00V.

After the above initial settings, a continuous durability test of A4 size sideways printing was conducted using solid white originals for up to 10,000 sheets. After the durability test, Vd and v4 were measured again, and Vd =
Vβ was measured when the grid bias was readjusted to −800V.

As a result, in the photoconductor of Comparative Example 1, the Vd decreased by 40V.
, the range of decrease in Vff reached 50V, but in the photoreceptor of Example 1, the range of decrease in Vd was IOV and the range of decrease in VJ2 was 5V, indicating that the potential fluctuation was small. Also,
It was found that the amount of light required for the initial V4 setting also changed only slightly to medium than in Comparative Example 1, and there were fewer peaks in which the sensitivity decreased. In other words, it can be said that a good photoreceptor was obtained.

The above results are shown in Table 1.

In addition, before and after the durability test, changes in density of halftone images and occurrence of image unevenness were evaluated. In Comparative Example 1, a decrease in image density and density unevenness occurred after durability use, but in Example 1, a stable halftone image was obtained even after durability use. The results are shown in Table 1.

Example 2 A photoreceptor drum was prepared in the same manner as in Example 1, except that 6 parts by weight of the following nitrogen-containing heterocyclic compound az and 3 parts by weight of an aromatic sulfonic acid compound ba were used for the stabilizing layer, and durability evaluation was performed. Ta. The results are shown in Table 1.

ai"Air bi"B+ +-
Me Example 3 A photoreceptor drum was prepared in the same manner as in Example 1, except that 7 parts by weight of the following nitrogen-containing heterocyclic compound am and 5 parts by weight of aromatic sulfonic acid compound bs were used in the stabilizing layer, and durability evaluation was conducted. I did this. The results are shown in Table 1.

as"As+ bs"B*+ Example 4 The same photosensitive material as in Example 1 was used except that 47 parts by weight of the nitrogen-containing heterocyclic compound a and 5 parts by weight of the aromatic sulfonic acid compound A below were used in the stabilizing layer. A body drum was created and its durability was evaluated. The results are shown in Table 1.

a4=AAx* b4=B1 +-
Me Example 5 A photoreceptor drum was prepared in the same manner as in Example 1 except that 7 parts by weight of the nitrogen-containing heterocyclic compound am and 5 parts by weight of the aromatic sulfonic acid compound b below were used in the stabilizing layer. We conducted an evaluation. The results are shown in Table 1.

as=AA+g bs”B41 Example 6 The following thermosetting polyurethane was used as the stabilizing layer: 150 parts by weight of polyol [trifunctional polyether polyol type: trade name: Niraporan 800 (manufactured by Nippon Polyurethane Co., Ltd.]; Incyanate [blocked isocyanate type; trade name Coronate 2507 (manufactured by Nippon Polyurethane Co., Ltd.]) 550 parts by weight A solution consisting of 8.7 parts by weight of the following nitrogen-containing heterocyclic compound, 5 parts by weight of aromatic sulfonic acid compound t)s, and cyclohexanone was added to the above solution. A stabilizing layer with a thickness of 1.1 um was created by dip coating onto an aluminum cylinder and treating at 150° C. for 60 minutes.

Other than that, a photoreceptor drum was prepared in the same manner as in Example 1, and durability evaluation was performed. The results are shown in Table 1.

am"AA+m bs"Bj+Comparative Example 2 The same procedure as in Example 6 was carried out except that the nitrogen-containing heterocyclic compound and the aromatic sulfonic acid compound were not included.

Example 7 A photoreceptor drum was prepared in the same manner as in Example 6, except that 8 parts by weight of the following nitrogen-containing heterocyclic compound ay and 4 parts by weight of an aromatic sulfonic acid compound were used in the stabilizing layer, and durability evaluation was conducted. I did this. The results are shown in Table 1.

ar=As+-Et bt=B+
+ -Mea8°A7+ ba=Bz-iPr i-Pr: Isopropyl group Example 8 Example 6 except that 8 parts by weight of the following nitrogen-containing heterocyclic compound am and 5 parts by weight of the aromatic sulfonic acid compound ba were used in the stabilizing layer. A photoreceptor drum was prepared in the same manner and its durability was evaluated. The results are shown in Table 1.

Table [Effects of the Invention J] The photoreceptor of the present invention has a synergistic effect of inactivation of corona products by the nitrogen-containing heterocyclic compound and removal of charge traps by the aromatic sulfonic acid, resulting in less potential fluctuation. Demonstrates stable performance.

Claims (2)

[Claims] (1) In an organic photoreceptor comprising an electrically conductive substrate and a photosensitive layer containing at least a charge generating material and a charge transporting material present on the surface of the organic photoreceptor, a stabilizing layer is provided between the electrically conductive substrate and the photosensitive layer. An electrophotographic photoreceptor comprising a layer containing a nitrogen-containing heterocyclic compound and an aromatic sulfonic acid compound. (2) The electrophotographic photoreceptor according to claim 1, wherein the stabilizing layer is composed of at least two layers: a layer made of a nitrogen-containing heterocyclic compound and a layer made of an aromatic sulfonic acid compound. .