JPH01266548A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, and more particularly, to an electrophotographic photoreceptor having a photosensitive layer with excellent durability and no deterioration in image quality due to repeated use.

[Conventional technology]

In recent years, many electrophotographic photoreceptors using organic compounds as photoconductors have been developed. Most of those that have been put into practical use have a form in which the photoconductor is functionally separated into a charge-generating material and a charge-transporting material.

Electrophotographic photoreceptors using such organic photoconductors are expected to further improve electrophotographic properties such as sensitivity and photoresponsivity due to the flexibility of material design, and are also easy to form into films and have high productivity. is characterized by

An electrophotographic photoreceptor is repeatedly subjected to various image forming processes in an electrophotographic apparatus, and during this process, the photoreceptor is required to exhibit stable characteristics. However, electrophotographic photoreceptors using organic photoconductors as described above have the disadvantage that, when used repeatedly, image quality deterioration such as a decrease in image density due to a decrease in charging ability and image blurring due to a decrease in surface resistance occurs. There is.

The cause of these deteriorations is thought to be largely influenced by corona discharge. That is, when a photoreceptor is used in a copying machine, it is constantly exposed to an atmosphere of corona discharge, and as copies are repeatedly made, organic photoconductivity is caused by active substances such as ozone No. and nitric acid generated by corona discharge. It is thought that the body is subject to deterioration. In particular, electrophotographic photoreceptors using organic photoconductors are often used with negative charging, but in the case of negative corona charging, the amount of ozone generated is greater than that of positive charging. This is one of the factors that makes it more susceptible to deterioration than other photoreceptors.

In addition, after copying is completed, the part of the photoreceptor directly below the corona charger that has stopped rotating deteriorates, and the charging ability of that part deteriorates significantly, a phenomenon called dormant memory. considered to be an influence.

Conventionally, methods for preventing such deterioration of electrophotographic photoreceptors have been disclosed in Japanese Patent Application Laid-open Nos. 57-122444 and 1983.
Various additives such as antioxidants, ultraviolet absorbers, and photodegradation inhibitors are added as described in JP-A No. 8-120260, JP-A-61-156131, JP-A-62-105151, etc. It is proposed to do so.

However, none of these are practically sufficient for preventing deterioration of the electrophotographic photoreceptor, and the dark potential (VO),
In other words, it is insufficient to suppress a decrease in charging potential. Furthermore, by adding an additive, the additive itself acts as a trapping agent for the movement of charges, causing an increase in the bright area potential (VL), which actually worsens the electrophotographic characteristics. There are also disadvantages.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an electrophotographic photoreceptor that prevents deterioration due to active substances such as ozone, nitric acid, etc., and does not cause any adverse effects on electrophotographic characteristics.

A further object of the present invention is to provide an electrophotographic photoreceptor that has high potential stability (and can always maintain high quality images) even after repeated use.

[Means for solving problems]

The present inventors investigated the factors of such photoreceptor deterioration, and
As a result of repeated studies on improvement methods, we found that by adding two specific compounds to the photosensitive layer containing an organic photoconductor,
The present inventors have discovered that a photoreceptor can be obtained that has a sufficient deterioration prevention effect and does not adversely affect other electrophotographic properties, and has completed the present invention.

That is, the present invention provides an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, in which the photosensitive layer has the general formula (1) % formula % 1 to 10 alkyl group or carbon number 2 ~10 alkenyl groups. ] and General Formula (II) [However, x3 and X4 represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] An electrophotographic photoreceptor characterized by containing a compound represented by the following.

The present invention will be explained in detail below.

The additive in the present invention is a phenol derivative having two hindered phenol groups, which is known as a radical scavenger or antioxidant for plastics, rubber, etc.
Phosphites known as hydroperoxide decomposers are used at the same time.

Each of these compounds alone has a small effect, but
The mechanism of preventing deterioration by using these two types of compounds at the same time is currently unclear, but it may be due to the interaction between the hindered phenol group and the phosphite group, or due to ozone and the accompanying active substances. It is thought that this has a synergistic effect on preventing deterioration of the photosensitive layer.

The compound represented by the general formula (1) in the present invention includes 2,2'-methylene-bis-(4-methyl-6-t-
butylphenol), 2,2'-methylene-bis-(
4-ethyl-6-t-amylphenol), 2-t-butyl-6-(3'-t-amyl-5'-methyl-2'-
hydroxybenzyl)-4-methylphenol, 2
, 2'-methylene-bis-(4-ethyl-6-t-butylphenol), 2-t-butyl-6-(3'-t-amyl-5'-ethyl-2'-hydroxybenzyl)
-4-methylphenol, 2-t-butyl-6-(3'
-t-amyl-5'-isopropyl-2'-hydroxybenzyl)-4-butenylphenol, etc. In particular, R1 and R2 in general formula (I) have 1 carbon number.
-5 alkyl groups or C2-5 alkenyl groups are preferred.

Further, as the compound represented by the general formula (II) in the present invention, phosphonosacide [1,1-biphenyl-4
, 4'-diylbistetrakis [2,4-bis(butyl)phenyl] ester], phosphonosacide (1,
1'-biphenyl-4,4'-diylbistetrakis[2,4-bis(t-amyl)phenyl]ester]
, phosphonosacide [1,1-biphenyl-4,4'
-diylbistetrakis (2,4-bismethylphenyl) ester], phosphonosacide (1,1'-biphenyl-4,4' -diylbistetrakis (2゜4-bisethylphenyl) ester), phosphonosacide [1,
1'-biphenyl-4,4'-diylbistetrakis (2,4-bispropylphenyl) ester], phosphonosacide [1,1'-biphenyl-4゜4'-diylbistetrakis (2,4-bisbutenyl) phenyl) ester], etc. In particular, X3 and X4 in general formula (II) are preferably an alkyl group having 1 to 5 carbon atoms or an alkenyl group having 2 to 5 carbon atoms.

The total amount of these compounds added is in the range of 0.5 to 20%, preferably 2 to 15%, based on the total weight of the photosensitive layer, and the mixing ratio is 0.1:1 to 1:0. .1, preferably 0.3:1 to l:0.3.

If the total amount added is less than 0.5%, the deterioration prevention effect will be insufficient, and if it exceeds 20%, problems such as decreased sensitivity and increased residual potential will likely occur.

The photosensitive layer containing an organic photoconductor in the present invention is a single-layer photoconductor in which a charge-generating material and a charge-transporting material are mixed in a functionally separated manner, or a charge-generating layer containing a charge-generating material and a charge-transporting material. It takes the form of a laminated photoreceptor, etc., which has charge transport layers laminated together.

Examples of charge-generating materials include pyrylium, thiopyrylium dyes, phthalocyanine pigments, anthoanthrone pigments,
Organic photoconductors such as perylene pigments, dibenzpyrenequinone pigments, vilanthrone pigments, azo pigments, indigo pigments, and quinacridone pigments are used.

As charge transport materials, pyrazoline type, hydrazone type,
Stilbene type, triphenylamine type.

Benzidine series, oxazole series, indole series.

Organic photoconductors such as carbazole compounds are used.

In the case of a single-layer type photoreceptor, the charge-generating material and charge-transporting material described above are dissolved or dispersed in a suitable binder resin, and a layer is formed on the conductive support by coating. On the other hand, as a laminated type,
1) Charge generation layer on the conductive support.

There are two types: one in which a charge transport layer is laminated in this order, and the other in which (2) a charge transport layer and a charge generation layer are laminated in this order. In the case of l), the charge generation layer may be formed by dispersing or dissolving the charge generation material in a binder resin and a solvent and applying it, vapor deposition,
There are methods such as sputtering.

The film thickness is preferably 5 μm or less, particularly 0.01 to 3 μm. In this case, an inorganic photoconductor such as selenium or amorphous silicon can also be used.

The charge transport layer is formed by dissolving the above-mentioned charge transport material in a binder resin having film-forming properties and laminating it on the charge generation layer. Film thickness is 5-4
0 μm1, particularly preferably 8 to 35 μm.

In this case, the additive of the present invention is preferably included in the charge transport layer.

On the other hand, when a charge generation layer is laminated on the charge transport layer, both layers can be formed by applying the above-mentioned organic photoconductor together with a binder resin. At this time, it is preferable that a charge transport material is also contained in the charge generation layer. In this case, the additive is preferably contained in the charge generation layer or both the charge generation layer and the charge transport layer.

Examples of the conductive support include known ones, such as cylindrical or belt-shaped aluminum, iron, copper, or metal-deposited plastic films. Further, an intermediate layer such as an adhesive layer, a barrier layer, a smooth layer, etc. may be provided between the support and the photosensitive layer, if necessary.

The electrophotographic photoreceptor of the present invention can be applied to photoreceptors of various devices to which electrophotography is applied, such as ordinary copying machines, laser beam printers, LED printers, LCD printers, and CRT printers.

〔Example〕

Next, the present invention will be specifically explained using examples.

Example 1 Conductive support with a diameter of 80 mm and a length of 360 mm
Using an aluminum cylinder, a 5% methanol solution of polyamide resin (trade name: Amilan CM, -8000, manufactured by Toshi Co., Ltd.) was applied by dipping to form a 0.5 μm thick undercoat layer.

Next, 10 parts (parts by weight, the same applies hereinafter) of the trisazo pigment having the following structural formula, 6 parts of polyvinyl butyral resin (S-LEC BL-3。 manufactured by Tsukigi Chemical Co., Ltd.), and 50 parts of cyclohexanone were mixed in a sand mill apparatus using glass beads. Dispersed.

100 parts of methyl ethyl ketone was added to this dispersion and applied onto the undercoat layer to form a charge generation layer with a thickness of 0.2 μm.

Next, 10 parts of a stilbene compound having the following structural formula, 1 part of polycarbonate resin (Panlite L-1250 manufactured by Ondai Kasei)
0 parts, 50 parts of dichloromethane, 10 parts of monochlorobenzene
A charge transport layer coating solution was prepared. 2.
2'-methylene-bis-(4-methyl-6-t-butylphenol) (MBP-1): and phosphonosacide (1,1-biphenyl-4°4'-diylbistetrakis[2,4-bis(t- butyl) phenyl] ester]
(P-EPQ-1) 0.4 parts and 2 parts of Ni-Bu (IRGAFOS P-EPQFF: manufactured by Nippon Ciba Geigy) were added at a mixing ratio of 1:1, and the above-mentioned product was added at a mixing ratio of 0.5:1. A charge transport layer having a thickness of 18 .mu.m was formed by coating the above charge generation layer with the above-mentioned charge-generating layer and the above-mentioned charge-transporting layer at a mixing ratio of 1:0.5. The photoreceptors manufactured in this way were each photoreceptor 1. 2.3.4.5 and 6.

Furthermore, as a comparative sample, photoreceptor 7 without additives
, photoreceptor 8 to which 0.4 parts and 2 parts of MBP-1 were added alone,
9, and 0.4 parts of P-EPQ-1 alone.

Two parts of photoreceptor 10.11 were each prepared.

These photoreceptors were installed in an electrophotographic copying machine, and their characteristics were evaluated as follows. First, the dark potential (VO) and bright potential (VL) of the photoreceptor were set to -650V.

The conditions for the latent image were set to -150V.

The image exposure amount at that time was determined and used as the initial sensitivity. Next 5.0
After continuous copying of 00 sheets, the potential was measured, and the rate of decrease in V and the increase in VL were determined. Thereafter, the photoreceptor was left in a copying machine, and the surface potential was measured after 10 hours. At this time, mark the part of the photoreceptor that was located directly under the corona charger while it was left to stand, and check the difference (△VO) from other parts.
I asked for

Further, photoreceptors were manufactured with various additive mixing ratios and amounts added, and similar evaluations were conducted. The results are shown in Table 2. The amounts added in the table are based on the added photosensitive layer, that is,
Here, it is the weight ratio to the weight of the charge transport layer.

As is clear from Tables 1 and 2, the present invention 2
Photoreceptors containing various types of additives in the photosensitive layer exhibit a small decrease in dark area potential and are excellent in preventing deterioration during repeated electrophotographic processes, and in particular, the area directly under the corona charger is extremely susceptible to deterioration. It is small. Furthermore, there is no adverse effect on electrophotographic properties such as an increase in bright area potential due to the addition of additives.

On the other hand, in a photoreceptor that does not contain additives, a significant decrease in dark area potential is observed due to deterioration, and the portion directly below the corona charger is also severely deteriorated.

Furthermore, when one of these is added, the deterioration is somewhat improved compared to a photoreceptor in which no addition is made, but it cannot be said to be sufficient compared to the present invention.

Example 2 As a charge-generating material, 10 parts of a disazo pigment having the following structural formula, 6 parts of polyvinyl butyral resin (Eslec BX-1, manufactured by Block Chemical Co., Ltd.), and 50 parts of cyclohexanone were dispersed in a sand mill device using glass beads.

100 parts of tetrahydrofuran was added to this dispersion and coated on the same conductive support and undercoat layer as in Example 1.
．． A charge generation layer having a thickness of 2 μm was formed.

Next, as a charge transport material, 8 parts of a benzcarbazole compound having the following structural formula, styrene-acrylic copolymer resin (Estyrene MS-20
0, Nippon Steel Chemical Co., Ltd.) 10 parts, 2.2'-methylene-
Bis-(4-ethyl-6-t-amylphenol) (M
BP-2): and phosphonosacide (1,1'-biphenyl-4゜4'-diylbistetrakis [2,4-
bis(t-amyl)phenyl]ester](P-EPQ
-2) 0.72 parts of Ni-Am at a mixing ratio of 1:l and 15 parts of dichloromethane.

A solution dissolved in 45 parts of monochlorobenzene was applied onto the charge generation layer to form a charge transport layer with a thickness of 18 μm.

This will be referred to as a photoreceptor 19.

On the other hand, for comparison, a photoreceptor 20 to which MBP-2 and P-EPQ-2 were not added was manufactured. In addition, as a comparison sample, the additives shown in Table 3 were used alone or in a mixture (mixing ratio 1/
1) The photoreceptor used in Example 1 was manufactured in the same manner.

Table 3 Characteristics of these photoreceptors were evaluated in the same manner as in Example 1. Also early V. +vL and -650V respectively.

The amount of light at -150V was also measured. These results are shown in Table 4.

As shown in Table 4, the photoreceptor containing the additive of the present invention has small potential fluctuations and is excellent in preventing deterioration. On the other hand, it can be seen that other additives or different combinations do not provide a sufficient deterioration prevention effect or have serious adverse effects.

Example 3 A subbing layer was coated on a conductive support in the same manner as in Example 1. Next, 15 parts of a stilbene compound having the following structural formula, polycarbonate resin (Panlite L-1250: manufactured by Teijin Chemicals)
10 parts, 50 parts of dichloromethane, 1 part of monochlorobenzene
A 15 μm thick charge transport layer was formed by coating the undercoat layer with a 0 part solution.

Next, 4 parts of the disazo pigment having the following structural formula, 7 parts of the above stilbene compound, 10 parts of the above polycarbonate resin, and the MBP-1, P-EPQ-1 part ratio of 1/1 were reduced to 0.
．． A coating material dispersed and dissolved in 63 parts of dichloromethane, 150 parts of dichloromethane, and 50 parts of monochlorobenzene was spray coated on the charge transport layer to form a charge generation layer with a thickness of 5 μm. This will be referred to as a photoreceptor 35.

On the other hand, a photoreceptor 36 to which MBP-1 and P-EPQ-1 were not added was manufactured.

These photoreceptors are positively charged to V. =+650V.

Setting was made so that vL=+150v, and the following evaluation was performed in the same way as in the conventional case. The results are shown in Table 4.

Example 4 A subbing layer was coated on a conductive support in the same manner as in Example 1.

Next, 1 part of a disazo pigment having the following structural formula, 10 parts of the benzcarbazole compound used in Example 2, 10 parts of polycarbonate resin (Panlite L-1250 manufactured by Kijin Kasei), 2-t-butyl-6-(3'- t-Amyl-5'-methyl-2'-hydroxybenzyl)-4
-Methylphenol (MBP-3): and phosphonosacide [l, 1-biphenyl-4゜4'-diylbistetrakis[2,4-bis(methyl)phenyl]ester] (P-EPQ-3): mixed with H3 A paint obtained by dispersing and dissolving 0.3 parts in 60 parts of dichloromethane and 20 parts of monochlorobenzene at a ratio of 1/1 was applied onto the above-mentioned undercoat layer to produce a photosensitive layer with a thickness of 16 μm. This will be referred to as a photoreceptor 37. On the other hand, for comparison, MBP-3/
A photosensitive layer to which P-EPQ-3 is not added is manufactured, and this is used as a photoreceptor 38.

These photoreceptors were evaluated in the same manner as in Example 3, and the results are also listed in Table 5.

Table 5 Example 5 Compounds shown in Table 6 were used as additives at a mixing ratio of 1/1.
A photoreceptor was produced in the same manner as in Example 1 except for the addition amount of 10%. These results are shown in Table 7.

Table 6 Example 61 Photoreceptors 2.7 and 19 produced in Examples 1 and 2 were copied an additional 45,000 times after the 5,000 copies in the characteristic evaluation described above.

As a result, for photoreceptors 2 and 19 containing additives, there was no deterioration in image quality compared to the initial state even after running 50,000 sheets (images with stable high contrast and no unevenness were obtained. Comparative sample photoreceptor 17, to which no additives were added, showed a noticeable decrease in image density after approximately 15,000 sheets were used.Furthermore, due to the potential drop that occurred when the image was left at rest after copying was completed, the image density became extremely uneven. This resulted in many images.

〔Effect of the invention〕

As explained above, according to the present invention, which is a photoreceptor containing a combination of specific additives, deterioration of the photoreceptor due to active substances such as ozone can be prevented without adversely affecting electrophotographic characteristics. It has excellent potential stability in a corona discharge environment and can always form stable, high-quality images.

Claims (2)

[Claims] (1) In an electrophotographic photoreceptor having a photosensitive layer containing an organic photoconductor on a conductive support, the photosensitive layer has the general formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [However, X_1 and X_2 has ▲ mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ has mathematical formulas, chemical formulas, tables, etc. ▼
and R_1 and R_2 represent H, an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms. [However, X_3 and X_4 represent an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms. ] An electrophotographic photoreceptor characterized by containing a compound represented by the following. (2) The electrophotographic photoreceptor according to claim 1, wherein the photosensitive layer has a laminated structure of a charge generation layer and a charge transport layer.