JPH10301317A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of an image noise and to form a satisfactory image by interposing a 2nd undercoat layer contg. an azo pigment in a resin between an undercoat layer and a photosensitive layer. SOLUTION: At least an undercoat layer contg. titanium dioxide dispersed in a resin and a photosensitive layer contg. a phthalocyanine type electric charge generating material are formed on an electrically conductive substrate and a 2nd undercoat layer contg. an azo pigment in a resin is interposed between the undercoat layer and the photosensitive layer to obtain the objective electrophotographic photoreceptor 1. The azo pigment may be selected from among various azo pigments such as monoazo, bisazo, trisazo and polyazo pigments. The resin in which the azo pigment is contained is, e.g. a (co) polymer of a vinyl compd. such as styrene, vinyl acetate, vinyl chloride, acrylic ester or ethyl vinyl ether, polyvinyl acetal, polycarbonate, polyester, polyamide or cellulose ether.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used for an electrophotographic apparatus such as a copying machine or a printer, and more particularly, to a method in which at least titanium oxide is dispersed in a resin on a conductive support. An electrophotographic photoreceptor provided with an undercoat layer and a photosensitive layer containing a phthalocyanine-based charge generation material is characterized in that a decrease in sensitivity is suppressed.

[0002]

2. Description of the Related Art Conventionally, when an image is formed in an electrophotographic apparatus such as a copying machine or a printer, an electrophotographic method in which a photosensitive layer is generally formed on a surface of a conductive support made of a conductive material such as aluminum. A photoreceptor was used.

In forming an image using such an electrophotographic photoreceptor, the surface of the photoreceptor is charged by a charging device, and then the surface of the photoreceptor is exposed by an appropriate exposure means. The electrostatic latent image is formed on the photoreceptor by irradiating light corresponding to the image information, the electrostatic latent image is developed with toner, and the toner image thus developed is transferred to a transfer member such as transfer paper. To form an image.

In recent years, laser beam printers, digital copiers and the like have received particular attention with remarkable progress in digital signal data processing systems. The image forming methods used in these devices include:
A toner image is formed on the part irradiated with light such as a laser beam for the purpose of effectively utilizing light or increasing the resolution,
A reversal developing method in which a toner image is not formed on an unexposed portion is employed.

[0005] However, in the reversal development method, when charge injection from the conductive support to the photosensitive layer occurs in an unexposed portion,
The surface charge microscopically disappears or decreases, and is formed where a toner image should not be originally formed, and image noise called "black spots" is generated. This black spot is a state in which the toner is locally attached to a white background, so that the black portion is very conspicuous as compared with a case where the black portion is white, and the image quality is remarkably reduced.

As a method for solving such a problem, an undercoat layer has been provided between a conductive support and a photosensitive layer.

Here, in addition to those using various resins such as polyamide, polyvinyl alcohol, polyvinyl butyral, methylcellulose, polyurethane, casein, epoxy and phenol, such undercoat layers have recently been used. As disclosed in JP-A-1-206358 and the like, titanium oxide having a high dielectric constant is dispersed in a resin in the undercoat layer to improve the blocking property in the undercoat layer, and the conductive layer can be used as a photosensitive layer. There has been proposed a device that suppresses the injection of electric charge into the device.

However, when the undercoat layer containing titanium oxide in the resin is provided between the conductive support and the photosensitive layer, the generation of black spots is improved, but the static electricity of the photosensitive body is reduced. May adversely affect the electrical characteristics. Phthalocyanine compounds have sensitivity in the long wavelength range, and are widely used as charge generation materials for photoreceptors such as laser beam printers and digital copiers of the reversal development type using long wavelength light such as lasers and LEDs as a light source. However, on the other hand, phthalocyanine-based charge generating materials have the property of being easily affected by an electric field. That is, in an electrophotographic photoreceptor in which an undercoat layer containing titanium oxide is provided between a conductive support and a photosensitive layer, when a phthalocyanine-based charge generation material is used as a charge generation material in the photosensitive layer, There is a problem that the sensitivity is reduced.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in an electrophotographic photosensitive member used in an electrophotographic apparatus such as a copying machine or a printer.

That is, according to the present invention, there is provided an electrophotographic photoreceptor having an undercoat layer containing titanium oxide in a resin between a conductive support and a photosensitive layer as described above.
In particular, even when a phthalocyanine-based charge-generating material that is easily affected by an electric field is used as the charge-generating material in the photosensitive layer, the sensitivity in the photosensitive layer does not decrease and good image formation without image noise can be performed. It is an object of the present invention to provide an electrophotographic photoreceptor.

In the case where the undercoat layer containing titanium oxide in the resin is provided between the conductive support and the photosensitive layer as described above, the influence of an electric field as a charge generating material in the photosensitive layer is reduced. When a phthalocyanine-based charge generating material that is susceptible to light is used, the cause of the decrease in sensitivity in the photosensitive layer has been examined.In the undercoat layer containing titanium oxide in the resin as described above, the work function is small. It is considered that the electric field acting on the interface with the photosensitive layer is weakened, whereby the quantum efficiency of the charge generation material is reduced, and as a result, the sensitivity of the photosensitive layer is reduced.

The inventor has conducted intensive studies based on such considerations, and has completed the present invention.

[0013]

According to the electrophotographic photoreceptor of the present invention, in order to solve the above-mentioned problems, an undercoat layer having at least titanium oxide dispersed in a resin is provided on a conductive support. In an electrophotographic photoreceptor having a photosensitive layer containing a phthalocyanine-based charge generating material, a second undercoating wherein an azo pigment is contained in a resin between the undercoating layer and the photosensitive layer. A layer was provided.

Here, like the electrophotographic photosensitive member of the present invention, an undercoat layer in which titanium oxide is dispersed in a resin,
Providing a second undercoat layer containing an azo pigment between the photosensitive layer containing a phthalocyanine-based charge generating material,
Since the work function of the second undercoat layer is smaller than that of the undercoat layer in which the titanium oxide is dispersed in the resin, the electric field acting on the interface between the second undercoat layer and the photosensitive layer causes the titanium oxide to disperse. The electric field is larger than the electric field acting on the interface between the undercoat layer and the photosensitive layer, so that the quantum efficiency of the phthalocyanine-based charge generation material is increased and the sensitivity is improved.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an electrophotographic photosensitive member according to an embodiment of the present invention will be specifically described.

The electrophotographic photoreceptor according to the present invention comprises, as described above, an undercoat layer in which at least titanium oxide is dispersed in a resin, and a photosensitive layer containing a phthalocyanine-based charge generation material, on a conductive support. Is formed, and a second undercoat layer containing an azo pigment in a resin is provided between the undercoat layer and the photosensitive layer.

Here, in the electrophotographic photoreceptor of the present invention, a foil or plate of copper, aluminum, gold, silver, platinum, iron, palladium, nickel or the like is formed into a sheet or a drum as a conductive support. Formed, these metals are attached to a plastic film or the like by vacuum evaporation, electroless plating, or the like, or a layer of a conductive compound such as a conductive polymer, indium oxide, or tin oxide is formed of paper, a plastic film, or the like. Those formed by coating or vapor deposition on a support such as glass can be used.

In providing an undercoat layer in which titanium oxide is dispersed in a resin on the conductive support, the titanium oxide has any structure such as rutile type and anatase type. The particle size of the undercoat layer to be formed is usually 1 μm or less, which is smaller than the thickness of the undercoat layer to be formed, preferably 0.2 to 0.4 μm to improve the dispersibility in resin. To use

Examples of the resin for dispersing the titanium oxide include strong adhesion to a conductive support, sufficient solvent resistance, and good dispersibility of fine powder. Any one can be used as long as it satisfies the conditions of conventionally known polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinyl imidazole, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, gelatin, polyamide and the like. Can be used. Furthermore, thermoplastic resins such as general polyester resin, acrylic resin, vinyl acetate resin, vinyl chloride-vinyl acetate resin, polyvinyl butyral resin, alkyd resin, melamine resin, urethane resin, epoxy resin, silicone resin, phenol resin, A thermosetting resin such as a saturated polyester resin can be used. Among these, phenol resins, unsaturated polyester resins, acryl-melamine resins, urethane resins, epoxy resins, and the like are particularly preferable from the viewpoint of adhesiveness and coatability. However, in order to provide the above-described second undercoat layer on the undercoat layer, a resin in which the resin in the undercoat layer does not dissolve in the coating liquid for the second undercoat layer is used. The undercoat layer is sufficiently cured by using a phenolic resin.

When the undercoat layer as described above is provided, if the film thickness is small, the injection of charges from the conductive support to the photosensitive layer cannot be sufficiently blocked, but the thickness becomes large. If the amount is too high, the charge generated in the photosensitive layer at the time of static elimination is suppressed from flowing to the conductive support through the undercoat layer, and the residual potential in the photosensitive layer becomes high. ４4 μm, preferably 1-3 μm.

In providing a second undercoat layer containing an azo pigment in a resin between the undercoat layer and the photosensitive layer, monoazo, bisazo, trisazo, polyazo, etc. may be used as the azo pigment. Various azo pigments can be used.

Examples of the resin containing such an azo pigment include polymers of vinyl compounds such as styrene, vinyl acetate, vinyl chloride, acrylates, methacrylates, vinyl alcohol and ethyl vinyl ether. Polymers, polyvinyl acetals, polycarbonates, polyesters, polyamides, polyurethanes, cellulose esters, cellulose ethers, phenoxy resins, silicon resins, epoxy resins, and the like can be used, or a mixture of these can be used. In addition, it is preferable to use a polyvinyl acetal resin as this resin from the viewpoint of uniformly dispersing the above-mentioned azo pigment and improving the adhesion to the undercoat layer and the like.

When the azo pigment is contained in the resin as described above, if the content of the azo pigment is small, the residual potential is increased. On the other hand, if the content of the azo pigment is too large, the adhesion is reduced. It is preferable to add the azo-based pigment in a range of 5 to 200 parts by weight based on 100 parts by weight of the resin because of poor properties.

In providing such a second undercoat layer, if the thickness thereof is small, the electric field at the interface with the photosensitive layer cannot be sufficiently increased by the second undercoat layer.
While the quantum efficiency of the phthalocyanine-based charge generation material contained in the photosensitive layer cannot be sufficiently improved, if the film thickness is too large, the charging performance of the photosensitive layer is reduced. 0.1 to 2 μm, preferably 0.2 to 1 μm.

When a photosensitive layer is provided on the second undercoat layer, a photosensitive layer containing a phthalocyanine-based charge generating material may be provided as described above. There is no particular limitation, and even if the photosensitive layer is a single-layer photosensitive layer containing the above-described charge generating material and the charge transport material, the charge generating layer and the charge transport material containing the above charge generating material are contained. The charge-transporting layer may be a function-separated type photosensitive layer in which the photosensitive layer is laminated, and a known method for producing such a photosensitive layer may be used. It is also possible to provide a protective layer, etc.

Here, examples of the charge transport material include anthracene derivatives, pyrene derivatives, carbazole derivatives, tetrazole derivatives, metallocene derivatives, phenothiazine derivatives, pyrazoline compounds, hydrazone compounds, styryl compounds, styrylhydrazone compounds, enamine compounds, Butadiene compounds, distyryl compounds,
Oxazole compounds, oxadiazole compounds, thiazole compounds, imidazole compounds, triphenylamine derivatives, phenylenediamine derivatives, aminostilbene derivatives, triphenylmethane derivatives and the like can be used.

When the photosensitive layer is formed by incorporating the above-mentioned charge generation material or charge transport material into a binder resin, the binder resin used is an electrically insulating material, and is a thermoplastic resin known per se. Resins, thermosetting resins, photocurable resins, photoconductive resins, and the like can be used. Suitable binder resins include, for example, polyvinyl chloride, polyvinylidene chloride, and vinyl chloride-vinyl acetate copolymer. , Vinyl chloride-vinyl acetate-maleic anhydride copolymer, ethylene-vinyl acetate copolymer, polyvinyl butyral, polyvinyl acetal, polyester, phenoxy resin, (meth) acrylic resin, polystyrene, polycarbonate, polyarylate, polysulfone, Polyether sulfone, ABS
Thermoplastic resins such as resins, phenolic resins, epoxy resins, urethane resins, melamine resins, isocyanate resins, alkyd resins, silicone resins, thermosetting resins such as thermosetting acrylic resins, polyvinyl carbazole, polyvinyl anthracene, polyvinyl pyrene, etc. Examples thereof include photoconductive resins, but are not particularly limited to these.

[0028]

EXAMPLES Hereinafter, the electrophotographic photoreceptor according to the present invention will be specifically described with reference to examples, and in the case of the electrophotographic photoreceptor according to the example of the present invention, the improvement in sensitivity will be compared with the comparative example. To clarify.

(Example 1) In the electrophotographic photoreceptor of this example, a conductive substrate made of a cylindrical aluminum tube having an outer diameter of 80 mm and a length of 350 mm was used.

When forming an undercoat layer on the conductive substrate, one part of phenolic resin (Retop PL2205 manufactured by Gunei Chemical Co., Ltd.) was added to 15 parts by weight of methanol.
0 parts by weight and dissolved in titanium oxide (Ishihara Sangyo Co., Ltd .:
CR90) was added thereto and dispersed in a sand mill for 1 hour to prepare a coating liquid for an undercoat layer. The coating liquid for an undercoat layer was applied on the above-mentioned conductive support, and the obtained mixture was heated at 130 ° C. At 1
After drying for an hour, an undercoat layer having a thickness of 2 μm was formed.

In this embodiment, when providing the second undercoat layer on the above-mentioned undercoat layer, 1 part by weight of butyral resin (Eslek BH-3 manufactured by Sekisui Chemical Co., Ltd.) is added to 100 parts by weight of tetrahydrofuran. Parts by weight, 1 part by weight of an azo pigment shown in Chemical Formula 1 below was added, and the mixture was dispersed in a sand mill for 5 hours to prepare a second undercoat layer coating solution. Apply the coating liquid for the above undercoat layer,
A second undercoat layer having a thickness of 0.3 μm was provided.

[0032]

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In forming a photosensitive layer on the second subbing layer, 1 part by weight of butyral resin (Eslek BX-1 manufactured by Sekisui Chemical Co., Ltd.) is dissolved in 100 parts by weight of tetrahydrofuran. M-type titanyl phthalocyanine (manufactured by Toyo Ink Mfg .: am-TiOP)
C) was added in an amount of 1 part by weight, and the mixture was dispersed in a sand mill for 5 hours to prepare a coating solution for a charge generation layer. The coating solution for a charge generation layer was applied on the second subbing layer. A charge generation layer having a thickness of 0.2 μm was formed.

Then, 100 parts by weight of methylene chloride were mixed with a polycarbonate resin (Panlite K-13, manufactured by Teijin Chemicals Limited).
(00) was dissolved in 15 parts by weight, and 10 parts by weight of a charge transporting material shown in the following chemical formula (2) was added and dissolved to prepare a coating solution for a charge transporting layer. This is coated on a layer, and dried at 100 ° C. for 45 minutes to form a charge transport layer having a thickness of 30 μm. A function-separated type electrophotographic photosensitive member in which a layer and a charge transport layer were laminated was obtained.

[0035]

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(Example 2) In the electrophotographic photoreceptor of this example, when forming the second subbing layer in the above-mentioned Example 1, the azo pigment shown in the following Chemical Formula 3 was used as the azo pigment. , And otherwise,
An electrophotographic photosensitive member was produced in the same manner as in Example 1 described above.

[0037]

Embedded image

(Example 3) In the electrophotographic photoreceptor of this example, when forming the second undercoat layer in the above-mentioned Example 1, the azo pigment shown in the following Chemical Formula 4 was used as the azo pigment. , And otherwise,
An electrophotographic photosensitive member was produced in the same manner as in Example 1 described above.

[0039]

Embedded image

Example 4 In this example, when forming the charge generation layer in Example 1 described above, τ-type phthalocyanine (TPH-278, manufactured by Toyo Ink Mfg. Co., Ltd.) was used as the charge generation material. Otherwise, an electrophotographic photosensitive member was produced in the same manner as in Example 1 described above.

(Comparative Example 1) In this comparative example, the second undercoat layer in Example 1 was not provided, and the other conditions were the same as in Example 1 above. The body was made.

Next, Example 1 manufactured as described above was used.
Each of the electrophotographic photoreceptors 1 to 4 and Comparative Example 1 was used, and as shown in FIG.
While rotating at m / sec, a voltage of −5 kV is applied to the charger 2 to corona-charge each electrophotographic photosensitive member 1, and the initial surface potential V of each electrophotographic photosensitive member 1 is adjusted.
₀ (V) is measured by the potential probe 3, and each of the electrophotographic photoreceptors 1 is exposed to light so that its initial surface potential V
Half-exposure exposure E1 / 2, which is the exposure required to reduce ₀ by half.
(Lux · sec) and each electrophotographic photoreceptor 1
, The residual potential Vr after irradiating 50 lux · sec light from the static eliminator 4 to perform static elimination, respectively.
(V) was measured, and each electrophotographic photoreceptor 1 was placed in the dark for 5 minutes.
Decay rate D of initial surface potential V ₀ when left for 2 seconds
DR5 (%) was determined and the results are shown in Table 1 below.

[0043]

[Table 1]

As a result, between the undercoat layer in which the titanium oxide is dispersed in the resin and the charge generation layer containing the phthalocyanine-based charge generation material, the second sublayer in which the azo-based pigment is contained in the resin. Each of the electrophotographic photoreceptors of Examples 1 to 4 provided with the subbing layer has a lower half-life exposure amount E1 / 2 as compared with the electrophotographic photoreceptor of Comparative Example 1 without such a second subbing layer. Thus, the sensitivity was improved and the rise in the residual potential Vr was reduced.

[0045]

As described in detail above, in the electrophotographic photoreceptor of the present invention, the undercoat layer in which titanium oxide is dispersed in a resin and the photosensitive layer containing a phthalocyanine-based charge generating material are used. Because the second undercoat layer containing an azo pigment was provided between the work layers, the work function of the second undercoat layer was smaller than that of the undercoat layer in which titanium oxide was dispersed in the resin.
The electric field acting on the interface between the second undercoating layer and the photosensitive layer is larger than the electric field acting on the interface between the undercoating layer and the photosensitive layer in which titanium oxide is dispersed, and the phthalocyanine-based charge generation material described above. , The sensitivity in the electrophotographic photoreceptor is improved, and the undercoat layer suppresses the occurrence of image noise even when used in the reversal development method, so that a good image can be obtained. .

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a state of examining characteristics of an electrophotographic photosensitive member of each embodiment and each comparative example of the present invention.

[Explanation of symbols]

 1. Electrophotographic photoreceptor

Claims (1)

[Claims] 1. An electrophotographic photoreceptor comprising a conductive support, on which an undercoat layer in which at least titanium oxide is dispersed in a resin and a photosensitive layer containing a phthalocyanine-based charge generating material are formed. An electrophotographic photoreceptor characterized in that a second undercoat layer containing an azo pigment in a resin is provided between the undercoat layer and the photosensitive layer.