JPH061385B2 - Electrophotographic photoreceptor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a photoconductor for electrophotography, and more specifically, a layer (hereinafter, referred to as charge generation substance) containing a substance that generates a charge carrier when irradiated with light (hereinafter, referred to as a charge generation substance). Called charge generation material)
And a layer (hereinafter, referred to as a charge carrier layer) containing a substance (hereinafter, referred to as a charge carrier substance) that receives a charge carrier generated by the charge generation layer and carries the carrier (hereinafter, referred to as a charge carrier layer).

2. Description of the Related Art Conventionally, as electrophotographic photoreceptors, there are inorganic ones using selenium and its alloys, or photoreceptors in which dye-sensitized zinc oxide is dispersed in a binder resin.
For organic compounds, 2,4,7-trinitro-9
A typical example is one using a charge transfer complex of -fluorene (hereinafter referred to as TNF) and poly-N-vinylcarbazole (hereinafter referred to as PVK). However, it is also true that these photoconductors have many advantages and, at the same time, have various drawbacks. For example, selenium photoconductors that are widely used at present have difficult manufacturing conditions, are expensive to manufacture, are difficult to process into a belt because they are not flexible, and are sensitive to heat and mechanical shock. Therefore, handle with care. In addition, the zinc oxide photoconductor can be manufactured by applying it to a support using inexpensive zinc oxide, so the cost is low, but generally the sensitivity is low, the surface smoothness, hardness, tensile strength, abrasion resistance, etc. However, there are many problems in durability as a photoreceptor for a plain paper copying machine, which is usually used repeatedly. Further, the photoconductor using the charge transfer complex of TNF and PVK has low sensitivity and is not suitable as a photoconductor for a high speed copying machine.

In recent years, extensive research has been conducted in order to eliminate the drawbacks of these photoconductors, and in particular, various organic photoconductors have been proposed. Above all, a laminated type photoreceptor in which a thin film of an organic pigment is formed on a conductive support (charge generation layer) and a layer (charge transfer layer) mainly containing a charge transfer substance is formed on the conductive support is a conventional organic material-based one. Compared with the photoconductor, the photoconductor is generally attracting attention as a photoconductor for a plain paper copying machine because of its high sensitivity and stable charging property, and some of them have been put to practical use.

As a conventional laminated photoreceptor of this type, (1) one using a perylene derivative for the charge generation layer and one using an oxadiazole derivative for the charge carrier layer (see US Pat. No. 3,871,882), (2) charge generation layer As, using an organic amine as a solvent, using the one coated with chlordian blue,
The one using a pyrazoline derivative for the charge carrier layer (Japanese Patent Laid-Open No. Sho 5)
2-55643 and JP-A-52-72231), and (3) a triphenylamine-based trisazo pigment (see JP-A-53-132347) as a charge generation layer in a dispersion medium such as tetrahydrofuran. The charge-transporting layer is coated with a dispersion-coated dispersion solution,
Those using bis (4-diethylaminophenyl) -1,3,4-oxadiazole or TNF are known.

However, it is a fact that even in this type of laminated type photoreceptor, the conventional one has many advantages and various drawbacks.

For example, the photoconductor using the perylene derivative and the oxadiazole derivative described in (1) above has low sensitivity for a higher-speed copying machine or the like, although there is practically no problem. Further, the perylene derivative, which is a charge generating substance that controls the spectral sensitivity of the photoconductor, has a drawback that it is not suitable as a photoconductor for a color copying machine because it does not absorb in the entire visible range.

Further, although the photoreceptor using the chlordian blue and the pyrazoline derivative shown in (2) has relatively good sensitivity in the experiments of the present inventors, it is generally handled as a coating solvent for forming the charge generation layer. Since it is necessary to use a difficult organic amine (for example, ethylenediamine), there are many drawbacks in producing a photoreceptor.

Further, the photoreceptor shown in (3) is a proposal by the present inventors, these photoreceptors, as a method for forming a charge generation layer, a pigment dispersion liquid (fine particles fine particles dispersed in an organic solvent Although a binder resin may be added) on the support, it has an advantage that it can be easily formed, but it has a slightly low sensitivity and is not sufficient as a photoreceptor for a high speed copying machine.

On the other hand, in recent years, there is an increasing demand for photoconductors for laser printers, and development of high-sensitivity photoconductors in the wavelength range of semiconductor lasers in particular is desired, but the photoconductors described above have extremely high sensitivity to these semiconductor lasers. The reality is that it is too low for practical use.

The mechanism of formation of an electrostatic latent image in a laminated type photoreceptor of this type is that when the photoreceptor is charged and then irradiated with light, the light passes through the transparent charge transport layer and is absorbed by the charge generating substance in the charge generating layer. , The light-generating charge-generating substance generates charge carriers, which are injected into the charge-transporting layer and move in the charge-transporting layer according to the electric field generated by charging,
It is believed that an electrostatic latent image is formed by neutralizing the charge on the surface of the photoreceptor. Therefore, the charge generating substance used for this type of photoconductor is required to efficiently generate the charge carriers upon irradiation with light for image formation.

On the other hand, the charge carrier substance is required to be transparent to the light used, capable of maintaining a desired charging potential, and capable of promptly transporting the charge carrier generated by the charge generating substance when irradiated with light. It

Objective In view of the above points, the present inventors have the object of developing a laminated photoconductor that is highly sensitive, yet exhibits almost flat sensitivity over the entire visible range and the wavelength range of a semiconductor laser, and that is easy to manufacture. As a result of intensive studies on a large number of charge generating substances and charge carrier substances, the characteristics of the charge generating substance of the trisazo pigment represented by the following general formula (1) are significantly different depending on the type and position of the substituent R. It has been found that the trisazo pigments of which R and R are as shown below have particularly excellent characteristics, and that the characteristics of the photoconductor are very different depending on the combination of the charge generating substance and the charge carrier substance. By virtue of these specific combinations, a photoreceptor having excellent photoreceptor characteristics was obtained, and the above object was achieved.

The object of the present invention is to laminate a charge generation layer containing a charge generation material having an extremely excellent charge carrier generation ability and a charge transfer layer containing a charge transportation material showing excellent performance when used together with the charge generation material, By giving a sufficient charging potential in a dark place and dissipating the surface charge rapidly during exposure, even if these steps are repeated in the copying process in which charging, exposure, development, transfer and cleaning are repeated, no problem occurs. An object is to provide a laminated electrophotographic photosensitive member whose characteristics do not change.

Structure The electrophotographic photosensitive member of the present invention is a laminated electrophotographic photosensitive member provided with a charge generating layer and a charge transport layer on a conductive support, the charge generating layer is represented by the general formula (1) (However, R is Represents ) Containing a trisazo pigment represented by the general formula (2) (In the formula, R ₁ , R ₂ and R ₃ may be the same or different and each represents hydrogen, a lower alkyl group, a lower alkoxy group, a phenyl group, a phenoxy group or a chlorine atom). It is characterized by including.

Here, specific examples of the lower alkyl group for R ₁ , R ₂ and R ₃ in the general formula (2) include a methyl group, an ethyl group, a propyl group and a butyl group. In addition, specific examples of the lower alkoxy group include a methoxy group, an ethoxy group, a propoxy group, a butoxy group and the like.

The triphenylamine compound represented by the general formula (2) as described above is a known compound, for example, Earl. F. Nelson and Earl. N. Adams, Jay. AM. Seem Em. SOS. ，
(R.F. Nelson and R.N.Adam
S.J. Am. Chem. Soc. ,) 90 3,925
(1968) and the like to facilitate manufacture.

On the other hand, the trisazo pigment represented by the general formula (1) used in the charge generation layer of the present invention is a known substance, for example, as described in JP-A-5-
It is manufactured by the method described in 7-195767.

Next, specific examples of the trisazo pigment represented by the general formula (1) and specific examples of the triphenylamine compound represented by the general formula (2) obtained as described above are shown in Table-1 and Table-2, respectively.
Shown in.

The present invention will now be described in more detail with reference to the drawings.

The attached drawing is an enlarged cross-sectional view of an electrophotographic photosensitive member showing an embodiment of the present invention. This photoconductor is configured by providing a photoconductive layer 44 including a charge generation layer 22 and a charge transport layer 33 on a conductive support 11.

Here, as the conductive support, a metal plate made of aluminum, nickel, chromium or the like, a metal drum or a metal foil; a plastic film provided with a thin layer of aluminum, tin oxide, indium oxide, chromium, palladium or the like; a conductive material Paper or plastic film coated with or impregnated with is used.

The charge generation layer is a fine particles of the specific trisazo pigment represented by the general formula (1) by means of a ball mill or the like,
It is formed by applying a liquid dispersed in a suitable solvent or, if necessary, a dispersion liquid in which a binder resin is dissolved, on a conductive support. The charge generation layer thus formed is further subjected to surface finishing by a method such as buffing or adjustment of the film thickness, if necessary. Examples of the binder resin used here include polyester resin, butyral resin, ethyl cellulose, epoxy resin, phenoxy resin, acrylic resin, vinylidene chloride resin, polystyrene resin, polybutadiene resin, and copolymers thereof. These are used alone or in a mixed state of two or more kinds.

The thickness of the charge generation layer is 0.01 to 5 μm, preferably 0.05 to 2
μm, and the proportion of trisazo pigment in this layer is 10
~ 100% by weight, preferably 30-95% by weight. If the thickness of the charge generation layer is 0.01 μm or less, the sensitivity is poor, and if the thickness is 5 μm or more, the electric potential is poorly held. Further, if the proportion of the trisazo pigment in the charge generation layer is 10% by weight or less, the sensitivity becomes poor.

The charge transport layer is formed by applying a solution of the above-mentioned triphenylamine compound represented by the general formula (2) and a binder resin in a suitable solvent such as tetrahydrofuran to the charge generation layer. Examples of the binder resin used here include polycarbonate resin, polyester resin, polystyrene resin, polyurethane resin, epoxy resin, phenoxy resin, acrylic resin, silicone resin and copolymers thereof. These are used alone or in a mixed state of two or more kinds.

Further, various additives can be added to the charge transport layer for the purpose of improving flexibility or durability. Additives used for this purpose include halogenated paraffin, dialkyl phthalate, silicone oil and the like.

The proportion of the triphenylamine compound contained in the charge carrier layer is 10 to 80% by weight, preferably 25 to 75% by weight, and the film thickness thereof is 2 to 100 μm, preferably 5 to 40 μm. When the proportion of the triphenylamine compound in the charge transport layer is 10% by weight or less, the sensitivity is poor, and when it is 80% by weight or more, the layer becomes brittle or the layer becomes cloudy due to crystal precipitation, which is not preferable. Further, when the thickness of the charge transport layer is 5 μm or less, the retention of the potential is poor, and when it is 40 μm or more, the residual potential becomes high.

In the photoreceptor of the present invention, if necessary, a barrier layer may be provided between the conductive layer and the charge generation layer, an intermediate layer may be provided between the charge generation layer and the charge transport layer, and an overcoat layer may be provided on the charge transport layer. it can.

Effect With the above-mentioned constitution, the laminated electrophotographic photoreceptor of the present invention is easy to manufacture as compared with the conventional laminated electrophotographic photoreceptor, as will be apparent from Examples and Comparative Examples described later, and can be repeatedly used. It also has excellent properties such as stable characteristics and high sensitivity in the wavelength range of semiconductor lasers (about 800 nm).

Example 1 1 part by weight of a trisazo pigment represented by the formula (1-1) in Table 1, 19 parts by weight of tetrahydrofuran, and 6 parts by weight of a 5% by weight tetrahydrofuran solution of polyvinyl butyral resin (XYHL; manufactured by Union Carbide Plastic Company). The parts were thoroughly crushed with a ball mill. Next, this pulverized mixture was taken out, and 104 parts by weight of tetrahydrofuran was added and diluted while stirring slowly. Apply this solution on a polyester film with aluminum vapor deposited with a doctor blade with a wet gap of 35 μm.
After drying at 5 ° C. for 5 minutes, a 1.0 μm thick charge generation layer was formed. In the charge generation layer, 10 parts by weight of a triphenylamine photoconductor represented by the structural formula (2-7), 10 parts by weight of a polycarbonate resin (Panlite K-1300; manufactured by Teijin Chemicals Ltd.), silicone oil (KF-50). (Made by Shin-Etsu Chemical Co., Ltd.) 0.002 parts by weight and a solution of 80 parts by weight of tetrahydrofuran are applied with a doctor blade with a wet gap of 200 μm, and the mixture is applied at 80 ° C. for 2 minutes, then 100
By drying at 5 ° C. for 5 minutes, a charge transport layer having a thickness of 23 μm was formed, and photoconductor No. 1 was produced.

Examples 2 to 10 The following photoconductors were produced in exactly the same manner as in Example 1 except that the trisazo pigments and triphenylamine compounds shown in the table below were used.

Examples 11 to 15 Exactly the same as Example 1 except that the polyvinyl butyral resin of Example 1 was changed to a polyester resin (Vylon 200; manufactured by Toyobo Co., Ltd.) and the trisazo pigment and the triphenylamine compound shown in the following table were used. The following photoconductor was prepared.

Comparative Example 1 N, N′-dimethylperylene-3 as a charge generating substance,
4,9,10-Tetracarboxylic acid diimide was vacuum-deposited on an aluminum plate under the conditions of a vacuum degree of 10 ⁻⁵ mmHg, an evaporation source temperature of 350 ° C., and an evaporation time of 3 minutes to form a charge generation layer. Then, on this charge generation layer, 5 parts by weight of 2,5-bis (4-diethylaminophenyl) -1,3,4-oxadiazole, 5 parts by weight of a polyester resin (Polyester Adhesive 49000 manufactured by DuPont) and Apply a solution consisting of 90 parts by weight of tetrahydrofuran and 120 ° C
Was dried for 10 minutes to form a charge transport layer having a thickness of about 10 μm, and comparative photoconductor No. 1 was produced.

Comparative Example 2 As a charge generating substance, 1.08 part by weight of benzidine-based pigment, Chlordian Blue, was added to ethylenediamine 24.4.
It was dissolved in 6 parts by weight, 20.08 parts by weight of n-butylamine was added to this solution with stirring, and 54.36 parts by weight of tetrahydrofuran was further added to prepare a charge generation layer coating solution. Next, this coating solution was applied onto a polyester film on which aluminum was vapor-deposited using a doctor blade, and the temperature was adjusted to 5 at 80 ° C.
After drying for a minute, a charge generation layer having a thickness of about 0.5 μm was formed.
1-phenyl-3- (4-diethylaminostyryl) -5 (4-diethylaminophenyl) is formed on the charge generation layer.
-A solution consisting of 1 part by weight of pyrazoline, 1 part by weight of a polycarbonate resin (Panlite K-1300; Teijin Kasei Co., Ltd.), and 8 parts by weight of tetrahydrofuran is applied with a doctor blade, and the solution is applied at 80 ° C for 2 minutes and then 100 parts. By drying at 5 ° C. for 5 minutes to form a charge transport layer having a thickness of 20 μm, comparative photoconductor No. 2 was prepared.

Comparative Example 3 4,4 ′, 4 ″ -Tris [2-hydroxy-3- (2-
Methoxyphenylcarbamoyl) -1-naphthylazo]
Triphenylamine (2 parts by weight) and tetrahydrofuran (98 parts by weight) were pulverized and mixed in a ball mill, and the resulting dispersion was coated on an aluminum vapor-deposited polyester film with a doctor blade and air-dried to form a 1 μm-thick charge generation layer. did. On the other hand, a mixture of 2 parts by weight of 2,5-bis (4-diethylaminophenyl) -1,3,4-oxadiazole, 2 parts by weight of a polycarbonate resin (Panlite L; Teijin Chemicals Ltd.) and 46 parts by weight of tetrahydrofuran. To obtain a solution, which is applied onto the charge generation layer with a doctor blade and dried at 120 ° C. for 10 minutes to form a charge transport layer having a thickness of 10 μm.
O.3 was created.

Comparative Example 4 1 part by weight of a polyester resin (manufactured by DuPont, polyester adhesive 49000) and 4,4 ′, 4 ″ -tris [2-hydroxy-3, which is a triphenylamine pigment.
-(2,5-Dimethoxyphenylcarbamoyl) -1-
1 part by weight of naphthylazo] triphenylamine and 26 parts by weight of tetrahydrofuran are ground and mixed in a ball mill,
The obtained dispersion was applied onto a polyester film vapor-deposited on aluminum using a doctor blade and dried at 100 ° C. for 10 minutes to obtain a comparative photoreceptor No. 4 having a photosensitive layer having a thickness of 7 μm.

Comparative Example 5 10 parts by weight of polyester resin, 10 parts by weight of 2,4,7-trinitro-9-fluorenone, a trisazo compound in which R is a 2-methyl-4-methoxyphenyl group in the general formula (1) of the present invention (special 2 parts by weight of the trisazo compound disclosed in Kai 53-132347) and 198 parts by weight of tetrahydrofuran are pulverized and mixed in a ball mill, and the obtained dispersion is applied onto a polyester film on which aluminum is vapor-deposited using a doctor blade. And 100 ℃
Was dried for 10 minutes to prepare a comparative photoconductor NO. 5 having a photoconductive layer having a thickness of 10 μm.

With respect to the photoconductors NO.1 to NO.15 and the comparative photoconductors NO.1 to NO.5 produced as described above, an electrostatic copying paper test apparatus (SP428 type manufactured by Kawaguchi Electric Co., Ltd.) was used. hand,
-(Or +) Corona discharge of 6 KV is carried out for 20 seconds to be negatively or positively charged, then left in a dark place for 20 seconds, the surface potential Vpo (volt) at that time is measured, and then the surface is measured by a tungsten lamp. Illuminance 4.5lux
And the surface potential is 1 / Vpo
The time (sec) until 2 is obtained, and the exposure amount E1 / 2 (lux / se
c) was calculated.

Further, the following measurements were carried out in order to examine the sensitivity of each photoconductor to long-wavelength light.

First, each photoconductor was charged by corona discharge in the dark, and then dispersed on the monochromator at 800 nm.
Irradiation with monochromatic light of μw / cm ² . Next, the time (sec) until the surface potential decays to 1/2 is calculated (at this time, the attenuation of the surface potential due to dark decay was corrected), and the exposure dose (μw
sec / cm ² ) to obtain the optical attenuation rate (volt · cm ² · μ
w ⁻¹ · sec ⁻¹ ) was calculated. Table of these results
5 shows.

As is clear from the results shown in Table 5, the laminated photoconductor of the present invention has higher sensitivity in the visible range than the comparative photoconductors NO.1 to NO.5 and is extremely high in the wavelength range (800 nm) of the semiconductor laser. It can be seen that it has excellent sensitivity. Further, since it is not necessary to use the organic amine used when the comparative photoconductor NO.2 acts in the production, it is advantageous in production. Further, the photoconductors No. 1 to No. 15 of the present invention were mounted on an electrophotographic copying machine (M-10 manufactured by Ricoh Co., Ltd.),
The image output was repeated 10,000 times. As a result, clear images were obtained from all the photoconductors.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an electrophotographic photosensitive member showing an embodiment of the present invention. 11 ... Conductive support 22 ... Charge generation layer 33 ... Charge transport layer 44 ... Photosensitive layer

Claims (1)

[Claims] 1. A laminate-type electrophotographic photosensitive member comprising a conductive support and a charge generation layer and a charge transport layer provided on the conductive support, wherein the charge generation layer has the general formula (1). (However, R is Of the general formula (2), which contains a trisazo pigment represented by (In the formula, R ₁ , R ₂ and R ₃ may be the same or different and each represents hydrogen, a lower alkyl group, a lower alkoxy group, a phenyl group, a phenoxy group or a chlorine atom). An electrophotographic photosensitive member comprising: