JPH0524507B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an electrophotographic photoreceptor, and more specifically, an electrophotographic photoreceptor characterized by containing a novel hydrazone compound in a photosensitive layer formed on a conductive substrate. Regarding. [Prior Art] Conventionally, photosensitive materials for electrophotographic photoreceptors (hereinafter also referred to as photoreceptors) have been made of inorganic photoconductive substances such as selenium or selenium alloys, or resins containing inorganic photoconductive substances such as zinc oxide or cadmium sulfide. organic photoconductive materials such as poly-N-vinylcarbazole or polyvinylanthracene, phthalocyanine compounds or bisazo compounds, or organic photoconductive materials dispersed in a binder; Dispersed in adhesives, etc. are used. In addition, a photoreceptor must have the function of retaining surface charge in the dark, the function of receiving light and generating charge, and the function of receiving light and transporting charge, but these functions can be achieved in one layer. A so-called single-layer type photoreceptor with multiple functions, and a layer with functionally separated layers: a layer that mainly contributes to charge generation, a layer that contributes to surface charge retention in the dark and charge transport during light reception, are laminated. There is a laminated type photoreceptor. For example, the Carlson method is applied to image formation by electrophotography using these photoreceptors. Image formation in this method involves charging the photoreceptor in a dark place by corona discharge,
Formation of an electrostatic latent image such as characters or pictures on a document by exposure to light on the surface of a charged photoreceptor, development of the formed electrostatic latent image with toner, and transfer of the developed toner image to a support such as paper. This is done by transferring and fixing, and after the toner image has been transferred, the photoreceptor is charged with electricity, residual toner is removed,
After photo-static neutralization, etc., it is reused. In recent years, electrophotographic photoreceptors using organic materials have been put into practical use due to their advantages such as flexibility, thermal stability, and film-forming properties. For example, a photoreceptor made of poly-N-vinylcarbazole and 2,4,7-trinitrofluoren-9-one (U.S. Pat.
3484237), a photoreceptor whose main component is an organic pigment (described in JP-A-47-37543), a photoreceptor whose main component is a eutectic complex consisting of a dye and a resin (described in JP-A-47-37543), a photoreceptor whose main component is a eutectic complex consisting of a dye and a resin 47-10735). Furthermore, many new hydrazone compounds have also been put into practical use. [Problems to be Solved by the Invention] As mentioned above, organic materials have many advantages that inorganic materials do not have, but there is still no material that fully satisfies all the characteristics required for electrophotographic photoreceptors. At present, this has not been achieved, and there have been problems in particular with respect to photosensitivity and characteristics during repeated and continuous use. The present invention has been made in view of the above points, and by using a new organic material that has never been used as a charge transporting substance in the photosensitive layer, copying with high sensitivity and excellent repeatability can be achieved. The purpose of the present invention is to provide electrophotographic photoreceptors for machines and printers. [Means for solving the problems] In order to achieve the above object, according to the present invention,
A photoreceptor for electrophotography has a photosensitive layer containing at least one type of hydrazone compound represented by the following general formula (). [In the formula (), R ₁ represents an aryl group which may have a substituent, and R ₂ , R ₃ , R ₄ , R ₅ and R ₆ each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, It represents a hydroxy group, a nitro group, an allyl group, an aryl group which may have a substituent, or an aralkyl group, and n represents 0 or 1. ] [Function] There is no known example of using a hydrazone compound represented by the above general formula () in a photosensitive layer. In order to achieve the above objective, the present inventors conducted numerous experiments on these hydrazone compounds while conducting intensive studies on various organic materials. We have discovered that the use of a specific hydrazone compound represented by the above general formula () as a charge transporting substance is extremely effective in improving electrophotographic properties, and we have developed a photoreceptor with high sensitivity and excellent repeatability. I was able to obtain it. [Example] The hydrazone compound of the general formula () used in the present invention can be synthesized by a conventional method. That is, it can be obtained by condensing aldehydes or carbonyl compounds with hydrazines in a suitable organic solvent such as alcohol, using a small amount of acid as a condensing agent if necessary. Specific examples of the hydrazone compound represented by the general formula () thus obtained are as follows. The photoreceptor of the present invention contains the above-mentioned hydrazone compound in the photosensitive layer.
It can be used as shown in FIG. 2 or 3. 1, 2, and 3 are conceptual cross-sectional views of different embodiments of the photoreceptor of the present invention, in which 1 is a conductive substrate, 20, 21, and 22 are photosensitive layers, 3 is a charge-generating material, 4 is a charge generation layer, 5 is a charge transport material, 6 is a charge transport layer, and 7 is a coating layer. FIG. 1 shows a photosensitive layer 20 on a conductive substrate 1 in which a charge generating substance 3 and a hydrazone compound as a charge transporting substance 5 are dispersed in a resin binder.
(a configuration commonly referred to as a single-layer photoreceptor). FIG. 2 shows a photosensitive layer 21( The structure is usually referred to as a laminated photoreceptor). A photoreceptor having this configuration is normally used in a negative charging system. FIG. 3 shows the reverse layer structure of FIG. 2,
Usually used with positive charging method. In this case, it is common to further provide a coating layer 7 to protect the charge generation layer 4. The reason why the laminated photoreceptor has two types of layer configurations is that even if a photoreceptor with the layer configuration shown in Figure 2 is used in a positive charging system, there is currently no charge transporting material that is compatible with this. This is because it has not been found. At present, when applying a positive charging method to a laminated type photoreceptor, it is necessary to use a photoreceptor having the layer structure shown in FIG. The photoreceptor shown in FIG. 1 can be produced by dispersing a charge generating substance in a solution containing a charge transporting substance and a resin binder, and applying this dispersion onto a conductive substrate. The photoreceptor shown in Figure 2 is produced by vacuum-depositing a charge-generating substance on a conductive substrate, or by coating and drying a dispersion obtained by dispersing particles of a charge-generating substance in a solvent or resin binder, and then It can be produced by applying a solution containing a charge transporting substance and a resin binder to a substrate and drying the solution. The photoreceptor shown in Figure 3 is produced by coating a conductive substrate with a solution containing a charge-transporting substance and a resin binder and drying it, and then vacuum-depositing a charge-generating substance thereon, or by depositing particles of the charge-generating substance in a solvent. Or apply a dispersion obtained by dispersing it in a resin binder,
It can be produced by drying and further forming a covering layer. The conductive substrate 1 serves as an electrode for the photoreceptor and at the same time serves as a support for other layers, and may be cylindrical, plate-shaped, or film-shaped, and may be made of aluminum, stainless steel, nickel, etc. It may also be made of metal, glass, resin, or the like, which has been subjected to conductive treatment. The charge generation layer 4 is formed by applying a material in which particles of the charge generation substance 3 are dispersed in a resin binder as described above, or by a method such as vacuum deposition, and generates charges by receiving light. . In addition to the high charge generation efficiency, the ability to inject the generated charges into the charge transport layer 6 and the coating layer 7 is also important, and it is desirable that the charge is less dependent on the electric field and can be easily injected even in a low electric field. Examples of charge generating substances include phthalocyanine compounds such as metal-free phthalocyanine and titanyl phthalocyanine, various azos, quinones,
Indigo pigments, dyes such as cyanine, squarylium, azulenium, and pyrylium compounds, and selenium or selenium compounds are used.
A suitable material can be selected depending on the light wavelength range of the exposure light source used for image formation. Since the charge generation layer only needs to have a charge generation function, its thickness is determined by the light absorption coefficient of the charge generation substance.
It is 5 μm or less, preferably 1 μm or less. The charge generation layer is mainly composed of a charge generation substance, and it is also possible to use a charge transporting substance added thereto. As a resin binder, polycarbonate, polyester, polyamide, polyurethane,
Epoxy, silicone resin, polymers and copolymers of methacrylic acid esters, etc. can be used in appropriate combinations. The charge transport layer 6 is a coating film in which a hydrazone compound represented by the general formula () as an organic charge transport substance is dispersed in a resin binder, and serves as an insulating layer in the dark to retain the charge on the photoreceptor and prevent light During reception, it functions to transport charges injected from the charge generation layer. As the resin binder, polycarbonate, polyester, polyamide, polyurethane, epoxy, silicone resin, polymers and copolymers of methacrylic acid ester, etc. can be used. The coating layer 7 has the function of receiving and retaining the charge of corona discharge in a dark place, and has the ability to transmit the light to which the charge generation layer is sensitive, and transmits the light upon exposure, and the charge generation layer It is necessary to neutralize and eliminate the surface charges by injecting the generated charges. As the coating material, organic insulating film-forming materials such as polyester and polyamide can be used. In addition, these organic materials and glass resin,
It is also possible to use a mixture of inorganic materials such as SiO ₂ and materials that reduce electrical resistance such as metals and metal oxides. The coating material is not limited to organic insulating film forming materials, and may also be formed using inorganic materials such as SiO ₂ or metals, metal oxides, etc. by methods such as vapor deposition and sputtering. As mentioned above, it is desirable that the coating material be as transparent as possible in the wavelength region where the charge generating substance absorbs maximum light. The thickness of the coating layer itself depends on the composition of the coating layer, but it can be set arbitrarily within a range that does not cause adverse effects such as an increase in residual potential when used repeatedly and continuously. Hereinafter, specific examples of the present invention will be described. Example 1 50 parts by weight of metal-free phthalocyanine (manufactured by Tokyo Kasei) ground for 150 hours in a ball mill and the above compound No. 1
Add 100 parts by weight of the hydrazone compound shown by 100 parts by weight to polyester resin (trade name Byron 200: manufactured by Toyobo).
A coating solution was prepared by kneading the parts by weight and a tetrahydrofuran (THF) solvent in a mixer for 3 hours, and the coating solution was applied onto an aluminum-deposited polyester film (Al-PET), which is a conductive substrate, using a wire bar method, and then dried. A photoreceptor having the structure shown in FIG. 1 was prepared by forming a photoreceptor layer so as to have a subsequent thickness of 15 μm. Example 2 First, α-type metal-free phthalocyanine is used as a starting material, and a non-magnetic case containing α-type metal-free phthalocyanine and a Teflon piece as a working piece is placed between two linear motors placed opposite each other to crush it. LIMMAC (Linear Induction Motor)
Mixing and Crashing: Processing (manufactured by Fuji Electric)
This was carried out for 20 minutes to form a fine powder. 1 part by weight of this finely powdered sample and 50 parts by weight of DMF (N,N-dimethylformamide) solvent were subjected to ultrasonic dispersion treatment.
Thereafter, the sample and DMF were separated and filtered, dried, and processed for metal-free phthalocyanine. Next, 100 parts by weight of the hydrazone compound represented by Compound No. 2 was added to tetrahydrofuran (THF).
A coating liquid made by mixing 700 parts by weight of a liquid dissolved in 100 parts by weight of polymethyl methacrylate polymer (PMMA: manufactured by Tokyo Kasei) in 700 parts by weight of toluene was applied to a wire on an aluminum vapor-deposited polyester film substrate. Applied using the bar method, the film thickness after drying is
A charge transport layer was formed to have a thickness of 15 μm. On the thus obtained charge transport layer, 50 parts by weight of the above-treated metal-free phthalocyanine, 50 parts by weight of polyester resin (trade name: Vylon 200, manufactured by Toyobo Co., Ltd.), and 50 parts by weight of PMMA were mixed together with THF solvent for 3 hours. A photoreceptor corresponding to the structure shown in Fig. 3 was prepared by kneading it with a machine to prepare a coating solution, and applying it using a wire bar method to form a charge generation layer with a film thickness of 1 μm after drying. Created. However, no coating layer not directly related to the present invention was provided. Example 3 The composition of the photosensitive layer of Example 1 was as follows: 50 parts by weight of metal-free phthalocyanine, 100 parts by weight of a hydrazone compound represented by Compound No. 3, 50 parts by weight of polyester resin (trade name: Vylon 200, manufactured by Toyobo), and 50 parts by weight of PMMA. A photoreceptor was produced by forming a photosensitive layer in the same manner as in Example 1, except that the following parts were changed. Example 4 In Example 3, chlorodiane blue, which is a bisazo pigment as shown in JP-A-47-37543, was used instead of the metal-free phthalocyanine,
Otherwise, a photosensitive layer was formed in the same manner as in Example 1 to produce a photoreceptor. The electrophotographic properties of the photoreceptor thus obtained were measured using an electrostatic recording paper tester "SP-428" manufactured by Kawaguchi Electric. The surface potential V _s (volts) of the photoreceptor is + in the dark.
This is the initial surface potential when a 6.0 kV corona discharge is performed for 10 seconds to positively charge the surface of the photoreceptor, and the surface potential V _d (volt ), then irradiate the surface of the photoconductor with white light with an illuminance of 2 lux, find the time (seconds) until V _d is halved, and find the half-attenuation exposure amount E _1/2 (lux seconds). did. Further, the surface potential when white light with an illuminance of 2 lux was irradiated for 10 seconds was defined as the residual potential V _r (volt). In addition, when a phthalocyanine compound is used as a charge-generating substance, high sensitivity with long wavelength light can be expected, so the electrophotographic characteristics when using monochromatic light with a wavelength of 780 nm were also measured at the same time. That is, measure up to V _d in the same way, then irradiate with 1 μW monochromatic light (780 nm) instead of white light to find the half-attenuation exposure (μJ/cm ² ), and expose this light for 10 seconds. The residual potential V _r (volts) when the body surface was irradiated was measured. The measurement results are shown in Table 1.

[Table] As seen in Table 1, Examples 1, 2, 3,
Photoreceptor No. 4 has no difference in half-attenuation exposure or residual potential, and exhibits good characteristics in terms of surface potential.
In addition, for long wavelength light of 780 nm, Examples 1 and 2 in which a phthalocyanine compound was used as a charge generating substance,
Photoreceptor No. 3 shows excellent electrophotographic properties. Example 5 On an aluminum plate with a thickness of 500 μm, selenium was vacuum-deposited to a thickness of 1.5 μm to form a charge generation layer, and then a hydrazone compound 100 represented by Compound No. 4 was deposited.
700 parts by weight of tetrahydrofuran (THF) and 100 parts by weight of polymethyl methacrylate polymer (PMMA: manufactured by Tokyo Kasei) were dissolved in 700 parts by weight of toluene.
A coating liquid made by mixing parts by weight with a dissolved liquid is applied using the wire bar method, and the film thickness after drying is 20 μm.
A charge transport layer was formed in such a manner that a photoreceptor having the structure shown in FIG. 2 was produced. To this photoreceptor-
When electrophotographic characteristics were measured using 6.0kV corona charging for 0.2 seconds, _Vs = -700V, _Vr = -60V,
A good result was obtained with E _1/2 = 4.2 Lux·sec. Example 6 Metal-free phthalocyanine 50 treated in Example 1
Weight parts, polyester resin (product name: Vylon)
200: Toyobo) 50 parts by weight, PMMA 50 parts by weight
The coating solution was prepared by kneading with THF solvent for 3 hours using a mixer, and then coated on an aluminum support with a thickness of about 1 μm.
A charge generation layer was formed. Next, hydrazone compound 100 shown as compound No. 5
Part by weight, polycarbonate resin (Panlite L-
1250) 100 parts by weight, 0.1 parts by weight of silicone oil
Mix 700 parts by weight of THF and 700 parts by weight of toluene,
Coat it on the charge generation layer to a thickness of about 15μm,
A charge transport layer was formed. The thus obtained photoreceptor was subjected to corona charging of -6.0 kV for 0.2 seconds in the same manner as in Example 5, and its electrophotographic characteristics were measured. As a result, _Vs = -760V,
A good result was obtained with E _1/2 = 4.6 Lux·sec. Example 7 A photosensitive layer was formed for each of Compounds No. 6 to No. 32 in the same manner as in Example 4, and a photoreceptor was prepared.
Table 2 shows the results of measuring the half-attenuation exposure using ``428''. A corona discharge of +6.0 kV was performed for 10 seconds in a dark place to positively charge the material, and the half-attenuation exposure amount E _1/2 (lux seconds) was shown when white light with an illuminance of 2 lux was irradiated.

【table】

〔Effect of the invention〕

According to the present invention, since a hydrazone compound represented by the general formula () is used as a charge transporting substance on a conductive substrate, a photoreceptor with high sensitivity and excellent repeatability even in positive and negative charging can be obtained. can be obtained. In addition, suitable charge-generating substances can be selected depending on the type of exposure light source. For example, by using phthalocyanine compounds and certain bisazo compounds, it is possible to obtain photoreceptors that can be used in semiconductor laser printers. I can do it. Furthermore, if necessary, it is possible to provide a coating layer on the surface to improve durability.

[Brief explanation of drawings]

FIGS. 1, 2, and 3 are conceptual sectional views showing different embodiments of the photoreceptor of the present invention. 1... Conductive substrate, 3... Charge generating substance, 4...
...Charge generation layer, 5...Charge transport material, 6...Charge transport layer, 7...Coating layer, 20, 21, 22...
photosensitive layer.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor characterized by having a photosensitive layer containing at least one type of hydrazone compound represented by the following general formula (). [In the formula (), R ₁ represents an aryl group which may have a substituent, and R ₂ , R ₃ , R ₄ , R ₅ and R ₆ each represent a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, It represents a hydroxy group, a nitro group, an allyl group, an aryl group which may have a substituent, or an aralkyl group, and n represents 0 or 1. ]