JPH0548911B2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrophotographic photoreceptor.

[Prior art]

Conventionally, there have been many configurations of laminated organic photoreceptors in which a charge generation layer is laminated as a lower layer of a charge transport layer. Currently, most of the charge transport layers commonly found have hole transport properties, so
It is necessary to use a photoreceptor having such a configuration with a negative charge. For this reason, it has had various drawbacks that impact the photoreceptor, such as generation of high concentration ozone due to negative charging and uneven charging of Kontron. In order to eliminate this drawback, a charge generation layer is laminated as an upper layer of a charge transport layer and used for positive charging, and in order to further improve mechanical strength, deterioration, etc., a low resistance surface protection layer is laminated as the top layer. was attempted. However, a photoreceptor with such a structure does not have sufficient chargeability and only has a low contrast potential, or even if it has sufficient chargeability,
The residual potential is high due to insufficient light attenuation, and the charge level and residual potential fluctuate due to changes in temperature and humidity.
It had various drawbacks, such as changes in charge level and residual potential during repeated use, and a large decrease in sensitivity compared to before the surface protective layer was applied.

[Purpose of the invention]

The purpose of the present invention is to provide an electrophotographic photoreceptor that does not have such drawbacks, that is, to prevent a decrease in charging potential, a high residual potential, the influence of temperature and humidity, and a decrease in sensitivity, and to reduce the charging level and residual potential during repeated use. An object of the present invention is to provide a stable electrophotographic photoreceptor.

[Structure of the invention]

The object of the present invention can be achieved by using a specific squaric acid derivative as the material for the charge generation layer. A further object of the present invention is to provide a low-resistance surface protective layer made of fine particles of a specific conductive metal oxide dispersed in an insulating resin on a charge generation layer using a specific squaric acid derivative. It can be achieved.

The present invention is an electrophotographic photoreceptor in which a charge transport layer, a charge generation layer, and a low resistance surface protection layer are sequentially laminated on a conductive support, and the charge generation layer has the following general formula (). A squaric acid derivative expressed by , electrical resistance ¹⁰⁹ Ω・cm or less,
This is an electrophotographic photoreceptor characterized by particles having an average particle size of 0.3 μm or less.

Supports with conductive surfaces used in the present invention include drums and sheets of metals such as aluminum, copper, iron, zinc, and nickel, or aluminum, copper, gold, silver, platinum, palladium, titanium, and nickel-chromium. , stainless steel, metal vapor deposition such as copper-indium, conductive metal compounds (e.g.
In ₂ O ₃ , SnO ₂ ) vapor deposition, metal foil laminates, or carbon black, conductive metal compounds (e.g.
In ₂ O ₃ , Sb ₂ O ₃ −SnO ₂ , SnO ₂ , TiOx) powder, metal powder, etc., are dispersed in a binder resin and coated to make the surface conductive. Paper, plastic and glass etc. are used.

In the charge transport layer used in the present invention, charge transport materials include pyrene, N-ethylcarbazole, N-isopropylcarbazole, 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole, 1 -Phenyl-3-(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[pyridyl-(2)]-3-
(P-diethylaminostyryl)-5-(P-diethylaminophenyl)pyrazoline, 1-[quinolyl-(2)]-3-(P-diethylaminostyryl)
-5-(P-diethylaminophenyl)pyrazoline, triphenylamine, N,N'-diphenylN-N'-bis(3-methylphenyl)-[1,1'-
biphenyl]-4,4'-diamine, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, 4,4'-benzylidene-bis(N,
N'-diethyl-m-toluidine, poly-N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polypynylanthracene, polyvinylacridine poly-9-vinylphenylanthracene, pyrene-formaldehyde resin, ethyl Examples include calsol to formaldehyde resins. These charge transport materials can be used alone or in combination of two or more. Charge transport materials are not limited to those described here. As the binder resin used for the charge transport layer, general-purpose resins such as acrylic resin, methacrylic resin, polystyrene, polyester, polyarylate, polysulfone, and polycarbonate, and hole-transporting polymers such as poly-N-vinylcarbazole are used. Can be used. Note that an adhesive layer may be provided between the conductive support and the charge transport layer.

The charge generation layer used in the present invention uses the above-mentioned squaric acid derivative as a charge generation material, and disperses it in a binder resin in an amount of, for example, 5% to 90% by weight, preferably 20% to 50% by weight. It is something. The particle size of squaric acid derivatives is
A suitable range is 0.02 μm to 3 μm, preferably 0.05 μm to 1 μm. Various binder resins for the charge generation layer include polyvinyl butyral, polyvinyl acetate, polyester, polycarbonate, phenoxy resin, acrylic resin, polyacrylamide, polyamide, polyvinylpyridine resin, casein, polyvinyl alcohol, and poly-N-vinylcarbazole. Resins are used.

The low-resistance surface protective layer used in the present invention is a layer in which fine particles of a conductive metal oxide are dispersed in an insulating resin.
Fine particles with an average particle diameter of 0.3 μm or less, preferably 0.1 μm or less and exhibiting white, gray, or blue-white color at 10 ⁹ Ωcm or less are suitable, such as antimony oxide, tin oxide, titanium oxide, indium oxide, and tin oxide. Examples include a single particle such as a solid solution of antimony and antimony oxide, a mixture thereof, a mixture of these metal oxides in a single particle, or a coating thereof. Among them, tin oxide and antimony, a solid solution of antimony oxide, or tin oxide are preferably used because they can lower the electrical resistance and make the protective layer substantially transparent (Japanese Patent Laid-Open No. 57 −30847
No., JP-A-57-128344).

The protective layer is desirably constructed so that its electrical resistance is 10 ⁹ to ^{10 14} Ω·cm. Electrical resistance is 10 ¹⁴ Ω・
When the residual potential exceeds 10 9 Ω·cm, the residual potential increases, resulting in a copy with a lot of fog, and when it becomes below 10 ⁹ Ω·cm, the image becomes blurred and the resolution decreases. The protective layer must also be constructed so as not to substantially block the passage of light used for imagewise exposure. If the particle size of the conductive metal oxide used is too large, the protective layer becomes opaque, resulting in desensitization and a decrease in image density.
The particle size is determined by the wavelength of the light used for image exposure (0.42~
It is desirable to use particles having a particle size of 0.8 μm or less, preferably one half or less, that is, 0.3 μm or less, preferably 0.1 μm or less. As the insulating resin, it is desirable to use an electrically insulating transparent resin whose electrical resistance does not easily change due to changes in humidity or temperature. Examples of insulating resins include condensation resins such as polyamide, polyurethane, polyester, epoxy resin, polyketone, and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene, and polyacrylamide. It is preferably used in terms of stability. The fine particles of conductive metal oxide are 20% to 60% by weight of the insulating resin.
It is desirable to disperse up to % by weight. If it is less than 20% by weight, the electrical resistance will be 10 ¹⁴ Ω·cm or more, and if it is more than 60% by weight, the film strength of the protective layer will be significantly reduced. Dispersion is therefore preferably carried out in the range 30% to 50% by weight.

Further, a charge injection blocking auxiliary layer may be further provided between the low resistance surface protective layer and the charge generation layer. Examples of the auxiliary layer forming material include coupling agents such as silane coupling agents and titanium coupling agents, organometallic compounds such as organic zirconium compounds and organic titanium compounds, and general-purpose resins such as polyester and polyvinyl butyral.

The appropriate thickness of each layer is 5 μm to 40 μm for the charge transport layer, preferably 8 μm to 30 μm, and the appropriate thickness for the charge generation layer.
5μm or less, preferably 0.1μm to 3μm, low resistance surface protective layer 0.5μm to 20μm, preferably 1μm to 10μm
is appropriate.

〔Example〕

Examples of the present invention are shown below.

Example 1 A photoreceptor was prepared by sequentially laminating a charge transport layer, a charge generation layer, and a surface protection layer made of the following materials by spray coating on a PET substrate on which aluminum was vapor-deposited.

Charge transport layer Polycarbonate resin 50 parts by weight (20μ) (Teijin: Pyrite) 1-phenyl-3-(P-diethylaminostyryl)-5-
(P-diethylaminophenyl)pyrazoline
50 parts by weight Charge generation layer Squaric acid derivative (1μ) (Structural formula ()) 4.0 parts by weight Polyester resin (DuPont: Adhesive 49000) 60 parts by weight Surface protective layer Tin oxide powder 40 parts by weight (2μ) Polyurethane resin 60 parts by weight Using a commercially available electrostatic copying paper testing device (Kawaguchi Electric: Electrostatic Paper Analyzer SP-428), this photoreceptor was positively charged by +7kV corona discharge, and left in a dark place for 1 second. After that, the surface potential V _DDP was measured, and tungsten light of 5 lux was irradiated for 3 seconds, and the amount of light E1/2 required for V _DDP to be halved during that time was determined. Furthermore, after this,
The residual potential RP was determined by irradiating 200 lux light for 0.5 seconds to further attenuate it. Continuously perform this measurement.
Perform 1000 times, 1st cycle and 1000th cycle
Cycle stability was expressed by using the difference between V _DDP and RP as ΔV _DDP (C) and ΔRP (C). Also, similar measurements were carried out at 10℃.
The difference between V _DDP and RP in the first cycle was calculated as ΔV _DDP under 20%RH environment and 30℃, 80%RH environment.
Environmental safety was expressed as (E) and ΔRP(E).

Each measured value in this example is shown below.

V _DDP : 1000V E1/2: 1.0 Lux・sec RP: 80V ΔV _DDP (C): 100V ΔRP(C): 30V ΔV _DDP (E): 70V ΔRP(E): 30V In other words, sufficient chargeability and high It can be said that it has high sensitivity, excellent cycle stability, and environmental safety.

Comparative Example 1 A photoreceptor was prepared in the same manner as in Example 1 except that β-type copper phthalocyanine was used instead of the squaric acid derivative in the charge generation layer in Example 1, and the same measurements were performed. The value was shown.

V _DDP : 650V E1/2: 10.5 Lux・sec RP: 80V ΔV _DDP (C): 300V ΔRP(C): 30V ΔV _DDP (E): 200V ΔRP(E): 50V Low chargeability, cycle, environment This indicates that there is a problem with both stability.

Comparative Example 2 Instead of the surface protective layer in Example 1, the thickness
Example 1 except that 1μ of methyl cellulose was provided.
A photoreceptor was prepared in the same manner as above, and the same measurements were performed, and it showed the following characteristics.

V _DDP : 900V E1/2: 1.1 Lux・sec RP: 90V ΔV _DDP (C): 180V ΔRP(C): 50V ΔV _DDP (E): 310V ΔRP(E): 70V In particular, there is a problem with environmental stability. It shows.

Example 2 The surface protective layer in Example 1 was made of tin oxide-antimony oxide solid solution/polyurethane resin = 35/65
A photoreceptor was produced and measured in the same manner as in Example 1, except that (parts by weight) was changed, and it showed the same stable characteristics as the photoreceptor of Example 1.

V _DDP : 970V E1/2: 1.2 Lux・sec RP: 75V ΔV _DDP (C): 120V ΔRP(C): 40V ΔV _DDP (E): 80V ΔRP(E): 30V [Effects of the Invention] According to the present invention Thus, an electrophotographic photoreceptor having excellent charging properties, sensitivity, cycle stability, and environmental stability can be obtained.

[Brief explanation of the drawing]

1 to 4 are sectional views of specific examples of the electrophotographic photoreceptor of the present invention. DESCRIPTION OF SYMBOLS 10... Low resistance surface protective layer, 11... Charge generation layer, 12... Charge transport layer, 13... Conductive support, 14... Conductive metal oxide, 15... Charge generation material, 20... Adhesive layer, 30...Charge injection blocking auxiliary layer.

Claims (1)

[Claims] 1. A charge transport layer, a charge generation layer,
An electrophotographic photoreceptor in which low-resistance surface protective layers are sequentially laminated, the charge generation layer having the following general formula () A squaric acid derivative expressed by , electrical resistance ¹⁰⁹ Ω・cm or less,
An electrophotographic photoreceptor characterized by having particles having an average particle size of 0.3 μm or less.