JPH02139574A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having high photostability and superior photosensitive characteristics such as chargeability, sensitivity, etc., by incorporating a specified hindered amine as photostabilizer into a protective layer. CONSTITUTION:The title electrophotographic sensitive body is constituted of a charge transfer layer, a charge generating layer, and a protective layer laminated on an electroconductive base body in the described order, wherein the protective layer contains at least one kind of hindered amines selected from hindered amines expressed by the formula I-III(wherein each R1-R4 is each independent 1-4C alkyl group; R5 is an H atom or an alkyl group; R is a group expressed by the formula IV). In the formula IV, each R11-R14 is 1-4C alkyl group which is independent on each other; R15 is an H atom or an alkyl group. An electrophotographic sensitive body having high photostability, and photosensitive characteristics such as chargeability, sensitivity, etc., is thus obtd. because a specified hindered amine is contained in a protective layer as photostabilizer.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having excellent charging characteristics and photostability after repeated exposure.

<Prior art> In recent years, organic photoreceptors, in which the photosensitive layer is separated into two layers, a charge transport layer and a charge generation layer, and laminated on a conductive substrate, have attracted attention because of their large degree of freedom in functional design. Bathing. Such laminated photoreceptors include positively charged type and negatively charged type depending on their laminated structure.

However, many charge transport materials are of the hole transport type, and
In order to impart durability to the surface, it is common to use a negatively charged electrophotographic photoreceptor having a structure in which a charge generation layer is provided on a conductive base material, and a charge transport layer is further provided thereon.

Negatively charged type 8! Layered electrophotographic photoreceptors have excellent sensitivity and the like because holes can move easily.

However, when negatively charged, ozone is likely to be generated, causing problems in terms of environmental hygiene, such as respiratory disorders. Another problem is that it is necessary to use toner of positive polarity, although it is generally difficult to produce toner of positive polarity.

Therefore, we developed a multilayer structure for positive charging, in which a charge generation layer containing a charge generation substance that generates holes and electrons during exposure is used as a surface layer, and a charge transport layer that transports holes to a conductive substrate is arranged below the surface layer. Various electrophotographic photoreceptors have been proposed.

However, positively charged laminated photoreceptors have the disadvantage that the photoreceptor easily deteriorates because the surface layer is a charge-generating layer containing a charge-generating material that is fragile against exposure to light and external electrical and mechanical forces. .

For this reason, various photoreceptors have been proposed in which a protective layer is further laminated on top of a positively charged laminated photosensitive layer to improve wear resistance. Products containing antioxidants have also appeared to improve stability.

For example, a thermosetting or photocurable resin and one or more of various antioxidants such as phenols, diamines, hydroquinones, organic sulfur compounds, and organic phosphorous compounds are dissolved in a solvent. One in which a protective layer is formed using a coating liquid for a protective layer (see JP-A-63-18354), and one in which hindered amines are dispersed as an antioxidant in a charge transport layer (JP-A-133-206757).
(see Publication No. 2003), etc. have been proposed.

<Problems to be Solved by the Invention> By the way, in the case of a laminated type organic photoreceptor, there are major restrictions on the solvent used for each layer because the influence on the lower layers must be taken into consideration. In particular, only solvents with low polarity such as alcohols can be used as solvents for the protective layer.

However, among the antioxidants (including deterioration inhibitors) used in the above-mentioned conventional electrophotographic photoreceptors, there are many that have low solubility or low compatibility with solvents of low polarity. In many cases, it is actually difficult to incorporate these into the protective layer in an amount sufficient to produce effective effects.

Further, even if the solubility in a solvent is good, there are some that do not show a significant addition effect or that have an adverse effect on the photosensitive characteristics.

This is because the performance of antioxidants cannot be determined for sure until they are actually used.

The present invention has been made in view of the above circumstances, and its purpose is to provide a protective layer with an antioxidant that has excellent solubility or compatibility with solvents and has a high addition effect. The object of the present invention is to provide an electrophotographic photoreceptor that has excellent photostability and excellent photosensitive properties such as chargeability and sensitivity.

Means and Effects for Solving the Problems> An electrophotographic photoreceptor according to the present invention for achieving the above objects comprises a charge transport layer, a charge generation layer and a protective layer laminated in this order on a conductive base material. In the electrophotographic photoreceptor, the protective layer contains at least one selected from hindered amines represented by the following general formulas (1) to (3).

CH, -Coo-R CH2-Coo-R However, in the above general formulas (1) to (3), R1-R4 are each independent alkyl group having 1 to 4 carbon atoms, R5 is a hydrogen atom or an alkyl group, R6 represents a hydrogen atom or an alkyl group, and R represents a group represented by the following general formula (4). When R5 is an alkyl group, it preferably has 1 to 3 carbon atoms, and when R6 is an alkyl group, it preferably has 1 to 12 carbon atoms. Here, in the following general formula (4), R1+""
RI4 is each independent alkyl group having 1 to 4 carbon atoms, R15
represents a hydrogen atom or an alkyl group.

Since the electrophotographic photoreceptor according to the present invention contains a specific hindered amine as a light stabilizer in the protective layer, which has excellent solubility and exhibits an excellent deterioration prevention effect, it has excellent light stability over a long period of time. show.

The present invention will be explained in more detail below.

The hindered amines represented by the above general formulas (1) to (3) are all known substances that are already commercially available. The fact that it can be used suitably is something that was discovered for the first time as a result of intensive research by the present inventors.

The above-mentioned light stabilizer can be added in a commonly used ratio as long as it does not adversely affect the physical properties and photosensitivity characteristics of the protective layer. 0.1 to 5 per 100 parts by weight of adhesive resin
0 parts by weight is preferable, and 1 part by weight to 20 parts by weight are more preferable.

This is because if the amount is less than 0.1 part by weight, no significant effect can be obtained, and if it exceeds 50 parts by weight, a decrease in sensitivity and an increase in residual potential occur.

The protective layer is formed by applying the above-mentioned protective layer coating liquid onto the photosensitive layer and then curing the coating liquid.

The binder resin suitable for use with the above-mentioned light stabilizer is not particularly limited as long as it is a resin that is cured by light or heat. Examples include thermosetting acrylic resins, silicone resins, epoxy resins, urethane resins, phenol resins, polyesters, melamine resins, etc., and these binder resins are usually contained in the protective layer coating solution in an amount of 50% by weight or more. In addition,
When alcohols are used as a solvent in consideration of the influence on the lower layer, epoxy resins, melamine resins, etc. are unsuitable, and it is preferable to use silicone resins. Additionally, this silicone resin is generally stable against heat and light.
Furthermore, it is recommended for its excellent electrical properties.

In addition, in order to maintain good charging properties, the above-mentioned binder resin has an electrical resistance value of 1. Q X 10-8~5, OX
10-8 Ω'''''Cff1-' is preferable2,
OX 10"-8~4.OX 10-'Ω-'811
1-' is more preferred.

In addition, in order to improve the coating properties and prevent cracks from occurring in the protective layer, thermoplastic resin was used as the protective layer.
It may be contained in an amount less than ffi amount%. As such thermoplastic resin, conventionally known thermoplastic resins such as vinyl chloride resin, vinyl acetate resin, polypropylene, and methacrylic resin can be used.

The coating solution for the protective layer is prepared by dissolving or dispersing the above-mentioned light stabilizer and binder resin in a solvent.

Examples of solvents for preparing the coating solution include alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; aliphatic hydrocarbons such as n-hexane, octane, and cyclohexane; and aromatic hydrocarbons such as benzene, toluene, and xylene. ; Halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene; Ethers such as dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, and diethylene glycol dimethyl ether; Ketones such as acetone, methyl ethyl ketone, and cyclohexanone; Various solvents include esters such as ethyl acetate and methyl acetate; dimethylformamide; and dimethyl sulfoxide.

Note that in consideration of the influence on the lower layer, it is preferable to use weakly polar alcohols. These solvents may be used in combination or as a mixture of two or more.

In addition, in order to improve coating properties, surface smoothness, light resistance, etc., surfactants, leveling agents, plasticizers,
It may also contain an ultraviolet absorber or the like. Furthermore, a conductivity imparting agent may be included in order to facilitate charge injection into the lower layer, and a predetermined amount of a PH adjuster may be added to the coating liquid.

The pH adjuster can be used regardless of whether it is an organic acid or an inorganic acid. In the case of the silicone resin coating liquid, it is preferable to adjust the pH value within the range of 5.0 to 6.5. This is because if the pH value exceeds 6.5, the stability of the silanol contained in the silicone resin coating solution deteriorates, and if the pH value is less than 5.0, the charging characteristics after repeated exposure will deteriorate. This is because it is difficult to obtain an electrophotographic photoreceptor with excellent properties. Preferred acids include acetic acid, formic acid, hydrochloric acid, benzoic acid, oxalic acid, chloroacetic acid, citric acid, glycolic acid, maleic acid, malonic acid, and the like.

In mixing and preparing the coating solution for the protective layer, conventionally used methods such as various conventionally used mixing means such as mixers, ball mills, paint shakers, sand mills, attritors, and ultrasonic dispersers can be used. The coating solution may be applied onto the photosensitive layer using conventional coating methods such as dip coating (
Dipping method) Spray coating, spin coating,
This can be done using various methods such as roller coating, blade coating, curtain coating, bar coating, etc.

The protective layer usually has a thickness of 0.1 to 10 μm, preferably 2 to 10 μm.
Formed on 5 capes.

The electrophotographic photoreceptor according to the present invention is similar to conventionally known laminated photoreceptors except for the protective layer, and can use the same structure and materials as the conventional ones.

First, the photosensitive layer will be explained.

A positively charged laminated photosensitive layer is first formed by coating a charge transport layer on a conductive base material using a charge transport layer coating solution containing a charge transport material, a binder resin, and if necessary a solvent. A charge generation layer is formed by applying a charge generation layer coating liquid containing a charge generation material, a binder resin, and, if necessary, a solvent, on the charge transport layer.

As charge transport materials, fluorenone compounds such as chloranil, tetracyanoethylene, 2,4.7-dolinitro-9-fluorenone, nitrated compounds such as 2,4°8-trinidrothioxanthone and dinitroanthracene,
Hydrazone compounds such as N,N-diethylaminobenzaldehyde, N,N-diphenylhydrazone, N-methyl-3-carbazolylaldehyde F, N,N-diphenylhydrazone, 2,5-di(4-dimethylaminophenyl) Oxadiazole compounds such as -1,3,4-oxadiazole, styryl compounds such as 9-(4-diethylaminostyryl)anthracene, carbazole compounds such as N-ethylcarbazole, 1-phenyl-3-( p
-Pyrazoline compounds such as -dimethylaminophenyl)pyrazoline, 2-(p-diethylaminophenyl) -4
- Oxazole compounds such as (p-dimethylaminophenyl)-5-(2-chlorophenyl)oxazole, isoxazole compounds, thiazole compounds such as 2-(p-diethylaminostyryl)-6-dinithylaminobenzothiazole, Amine derivatives such as triphenylamine, 4,4'-bis[N-(3-methylphenyl)-N-phenylaminocodiphenyl, stilbene compounds, thiadiazole compounds, imidazole compounds, pyrazole compounds, indole compounds , nitrogen-containing cyclic compounds such as triazole compounds, fused polycyclic compounds, succinic anhydride, maleic anhydride, dibromomaleic anhydride, poly-N-vinylcarbazole, polyvinylpyrene,
Examples include polyvinylanthracene and ethylcarbazole-formaldehyde resin. Note that photoconductive polymers such as poly-N-vinylcarbazole can also be used as a binder resin, which will be described later. These charge transport materials may be used alone or in combination of two or more.

In addition, as the charge generating material, various conventionally known materials,
For example, selenium, selenium-tellurium, amorphous silicon, pyrylium salts, azo compounds, disazo compounds,
Trisazo compounds, anthanthrone compounds, phthalocyanine compounds, indigo compounds, triphenylmethane compounds, thren compounds, toluidine compounds,
Examples include pyrazoline compounds, perylene compounds, and quinacridone compounds, and these may be used alone or in combination of two or more.

As the binding resin (binder), styrene polymer,
Styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, acrylic polymer, styrene-acrylic copolymer, ethylene-vinyl acetate copolymer, polyvinyl chloride, vinyl chloride Vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, etc., as well as epoxy Examples include various polymers such as photocurable resins such as acrylate and urethane acrylate, and these may be used alone or in combination of two or more.

When forming the charge transport layer, the ratio of the charge transport material and the binder resin may be selected as appropriate. Typically, charge transport material 10
30 to 500 parts by weight of the binder resin or the like is used relative to 0 parts by weight. The charge transport layer may be formed to have an appropriate thickness.

Usually, the film is formed to have a thickness of about 2 to 100 μm.

Furthermore, when forming the charge generation layer, a binder resin may be used in combination, or the charge generation material may be directly formed on the charge transport layer using a film forming method such as vapor deposition or sputtering without using a binder resin. You may.

When forming a charge generation layer using a binder resin, the binder resin is usually used in an amount of 1 to 300 parts by weight per 100 parts by weight of the charge generating material. The charge generation layer may be formed to have an appropriate thickness. Usually, it is formed to have a film thickness of about 0601 to 5 μm.

In preparing and manufacturing the coating liquid for the charge generation layer and the coating liquid for the charge transport layer, an appropriate organic solvent is used as necessary to improve coating properties depending on the type of resin contained in each layer. The solvent can be appropriately selected from among the above-mentioned solvents used in preparing the coating solution for the protective layer.

In addition, the photosensitive layer contains terphenyl, halonaphthoquinones,
Various additives may be included, such as conventionally known sensitizers such as acenaphthylene, plasticizers, ultraviolet absorbers, deterioration inhibitors such as antioxidants, and the like. Further, an intermediate layer may be formed between the charge generation layer and the charge transport layer to facilitate charge transfer between the two layers. In the preparation of the coating liquid for the charge generation layer or the coating liquid for the charge transport layer, the above-described conventional mixing means and coating method used in the preparation of the coating liquid for the protective layer can be used.

The conductive base material on which the photosensitive layer consisting of the charge transport layer, charge generation layer, etc. is laminated may be aluminum,
Single metals such as aluminum alloys, copper, soot, platinum, gold, silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, and brass, and the metals listed above or their metal oxides. Examples include a glass substrate and a plastic substrate on which a film is formed by means such as vapor deposition. The shape of the conductive base material may be either sheet-like or drum-like.

<Example> Hereinafter, the present invention will be explained in more detail based on examples.

A. Preparation of Photoreceptor Sample (Example 1) An electrophotographic photoreceptor having a laminated photoreceptor layer was prepared using an aluminum drum as a conductive base material.

Formation of Charge Transport Layer 100 parts of polyarylate (manufactured by Unitika, trade name rU-100J) as a binder resin and 100 parts by weight of diethylaminobenzaldehyde diphenylhydrazone as a charge transport material were stirred and mixed with 900 parts by weight of dichloromethane to transport charges. Prepare a coating solution and apply it to an aluminum drum (diameter 78 mI, length 340 m),
By drying and curing with hot air at a temperature of 90° C. for 30 minutes, a charge transport layer having a thickness of 20 μm was formed.

91. Formation of charge generation layer Next, 50 parts by weight of polyvinyl acetate (manufactured by Nippon Gosei Kagaku Co., Ltd., trade name: rYS-NJ) as a binder resin, and dibromoanthanthron ClC1 (manufactured by ClC1) as a charge generation material 8
0 parts by weight and metal-free phthalocyanine (BASF
Co., Ltd.) and 2,000 parts by weight of diacetone alcohol were placed in a ball mill and stirred and mixed for 24 hours to prepare a charge generation coating solution. This charge generation coating liquid was applied onto the charge transport layer by a dipping method, and then heated at a temperature of 110°C for 30 minutes.
This was heated and cured for 0 minutes to form a charge generation layer with a thickness of 0.5 μm.

Formation of protective layer 100 parts by weight of silicone resin (containing 80% by weight of methylmethoxysilane and 20% by weight of glycidoxymethyltrimethoxysilane, manufactured by Toshiba Silicone Co., Ltd., trade name "Tosguard 510J") as a binder resin raw material, isopropanol 300 parts by weight of heavy fi, 1 part by weight of triethylamine as a curing catalyst, 50 parts by weight of antimony-doped tin oxide fine powder (manufactured by Sumima Cement Co., Ltd.) as a conductivity imparting agent, hindered amine (manufactured by Sankyosha, trade name rc10-440J general formula) In (1), a coating solution for a protective layer consisting of 10 parts by weight of R1-R4: methyl group, R5: methyl group, R6: C12H25 is coated on the charge generation layer, and 1 By heating and curing for a period of time, the thickness of the film increases.2.
A 5 μm protective layer was formed to prepare an electrophotographic photoreceptor sample (1).

(Example 2) The hindered amine (trade name rc10-440J) 1
In place of 0 parts by weight, hindered amine (manufactured by Adeka Argus Chemical Co., Ltd., trade name rLA-57J, in the general formula (4) of R in general formula (1), R11 to R14: methyl group, R15
Sample (2) was prepared in the same manner as in Example 1 except that 10 parts by weight of hydrogen atoms were used.

(Example 3) The hindered amine (trade name rc10-4404) 1
Instead of 0 parts and 2 parts, hindered amine (manufactured by Sankyo Co., Ltd., trade name "Sanol LS-770J," in general formula (3),
R1-R4: methyl group, R5: hydrogen atom) 1
Sample (3) was prepared in the same manner as in Example 1 except that 0 parts by weight was used.

(Example 4) The hindered amine (trade name rc10-440J) 1
Instead of 0 parts by weight, hindered amine (manufactured by Sankyo Co., Ltd., trade name "Sanol LS-765J," in general formula (3),
Sample (4) was prepared in the same manner as in Example 1, except that 10 parts by weight (R1-R5: methyl group) was used.

(Example 5) Polyurethane resin (manufactured by Kansai Paint Co., Ltd., product name "Rethane PG-
Sample (5) was prepared in the same manner as in Example 1 except that 100 parts by weight of 80J) was used. (Comparative Example 1) Comparative sample (1) was prepared in the same manner as in Example 1 except that no hindered amine was added.

(Comparative Example 2) Comparative sample (2) was prepared in the same manner as in Example 5 except that no hindered amine was added.

(Comparative Example 3) Instead of hindered amine (product name rc10-440J), hindered amine (manufactured by Ciba Geigy, product name rc
Il1MAssORB 944L D J , Poly [
[6-(1,1,3,3-tetramethylbutyl)imino-1,3,5-triazine-2,4-diyl][(2,
2,6,6-tetramethyl-4-piperidyl)imino]
Hexamethylene [[2,2,6゜6-tetramethyl-4
Comparative sample (3) was prepared in the same manner as in Example 1 except that 10 parts by weight of -piperidyl)imino]]) was used.

B. Photoreceptor performance test Above samples (1) to (5) and comparative samples (1) to (3)
The performance tests shown in (a) to (d) below were conducted.

(a) Photosensitive characteristics and initial surface potential Using a drum sensitivity tester (manufactured by Dientic Co., Ltd., trade name [Dientic Cynthia 30MJ), each photoreceptor is positively charged, and the photosensitive characteristics and surface potential are determined under the following conditions. The results are shown in the table.

Exposure time: 60 ms light
Source: Halogen lamp exposure Intensity: 0.92 mmW
/ aj In the table, Vl (V) indicates the initial surface potential Vi (V) of the photoreceptor when the photoreceptor is charged under the above conditions, and E l/2 (μJ / cd) is the surface potential It shows the half-reduced exposure amount calculated from the exposure time required for V1m to become 1/2 of the initial surface potential V1m. Also, V in the table
r, p, and (V) are determined as 11FJ, with the surface potential after 0.4 seconds elapsed from the start of exposure as a residual potential.

(b) Surface potential after repeated exposure
C-111J), and the electrophotographic process was repeated 500 times, and the surface potential of the photoreceptor at that time V 500s, p
, (V) was measured, and the difference from the initial surface potential V1m of the photoreceptor was calculated as Δv(v).The charging characteristics after repeated exposure were examined, and the results are shown in the table.

(e) Surface potential after light irradiation
The surface potential vP was measured after irradiation with light for 10 minutes and standing still for 30 seconds. The results are shown in the table.

(d) Appearance of photoreceptor The appearance of each photoreceptor was visually observed to determine the presence or absence of abnormalities. Those with no abnormality were evaluated as O, and those with pinholes were evaluated as x.

The results are shown in the table.

(Hereafter, blank space) As shown in the table, samples (1) to (5) according to the present invention showed no abnormality in appearance, whereas
Comparative samples (1) and (2) both had abnormalities in appearance. That is, because the dispersibility of the hindered amine used in the resin was poor, the hindered amine aggregated, and the charge was easily removed from the aggregated portions, resulting in pinholes in the photoreceptor.

In addition, all of the samples (1) to (5) according to the present invention exhibit excellent photosensitive properties, such as excellent charging properties after repeated exposure and small decrease in surface potential after light irradiation. I understand. On the other hand, Comparative Samples (1) to (3) all exhibited greater decreases in surface potential after repeated exposure and in surface potential after light irradiation than Samples (1) to (5).

In particular, it can be seen that both comparative samples (1) and (2) have significantly lowered surface potentials on both surfaces to the extent that they cannot be put to practical use, and photodeterioration is severe.

From the above, it can be seen that all of the samples (1) to (5) according to the present invention have excellent sensitivity and charging characteristics, as well as excellent photostability after repeated electrophotographic processes. There was found.

<Effects of the Invention> As detailed above, the electrophotographic photoreceptor according to the present invention has the following features:
Since the protective layer contains a specific hindered amine as a light stabilizer, the present invention exhibits excellent and unique effects such as excellent light stability.

Claims (1)

[Claims] 1. In an electrophotographic photoreceptor in which a charge transport layer, a charge generation layer, and a protective layer are laminated in this order on a conductive base material, the protective layer has the following general formulas (1) to (3). An electrophotographic photoreceptor comprising at least one selected from hindered amines represented by the following formulas. ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(2) ▲There are mathematical formulas, chemical formulas, tables, etc.▼...(3) However, the above general formula (1) ~(3), R_1 to R_4 are each independent alkyl group having 1 to 4 carbon atoms, R_5 is a hydrogen atom or an alkyl group, R_6 is a hydrogen atom or an alkyl group, and R is a group represented by the following general formula (4). represents. However, in the general formula (4), R_1_1 to R_1_4 each represent an independent alkyl group having 1 to 4 carbon atoms, and R_1_5 represents a hydrogen atom or an alkyl group. ▲There are mathematical formulas, chemical formulas, tables, etc.▼…(4)