JP3239704B2 - Photoconductor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic photoreceptor, and more particularly to a photoreceptor having a surface protective layer on a photosensitive layer.

[0002]

2. Description of the Related Art In general, a protective layer is formed on the surface of a photosensitive layer, particularly on the surface of a photosensitive layer having an organic photosensitive layer in order to prevent scratches and improve durability. The photosensitive member is repeatedly charged → image exposed. Therefore, in order to prevent charge accumulation on the surface or inside of the protective layer, the protective layer needs to have low insulation. However, if the conductivity is too high, the transfer of charges in the horizontal direction occurs, causing image blur. Conversely, if the conductivity is too low, the charge accumulates, causing fog on the image. Therefore, the conductivity of the protective layer must be controlled to an appropriate value, and the conductivity must be stable against external influences such as temperature and humidity.

The protective layer must be satisfactory in mechanical strength in order to prevent damage from a toner cleaning blade or the like.

Further, the protective layer should not be colored by a substance added for lowering the insulation, and should not adversely affect the spectral sensitivity of the photoreceptor.

[0005] From such a viewpoint, a protective layer in which conductive fine particles are dispersed in a binder resin is used. For example, JP-A-56-138742 discloses a protective layer in which tin oxide doped with antimony as conductive fine particles is dispersed in a resin.

[0006]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and is directed to a novel layer in which tantalum-doped tin oxide which is non-polluting and excellent in safety is dispersed as conductive fine particles in a resin. As an outermost surface layer of the photoreceptor.

It is another object of the present invention to provide a photoreceptor having excellent photoreceptor characteristics such as sensitivity, capable of forming a good image without image blur, fogging, etc., and having excellent repetition characteristics and durability.

[0008]

That is, the present invention provides a layer containing a fine powder of tantalum-doped tin oxide in a resin (hereinafter referred to as a layer containing tin fine powder).
(Referred to as "dispersion layer") on the outermost surface.

The tantalum-doped tin oxide (SnO ₂ ) used in the present invention contains 0.1% of tantalum metal in tin oxide.
10 to 10% by weight. The doping can be performed by forming a solid solution of tin oxide and tantalum, or by coating tantalum on the tin oxide surface. Alternatively, doping may be performed by fusing tantalum to tin oxide.

In the present invention, the dispersibility of the coating liquid is further improved by using a material obtained by doping tin oxide with tantalum and then performing a surface treatment with a coupling agent such as a silane coupling agent or a titanium coupling agent. A coating film can be formed uniformly. Further, the moisture resistance can be further improved by the coupling treatment.

The tantalum-doped tin oxide has an average particle size of 2 μm.
Or less, preferably 1 μm or less, more preferably 0.3 to
The thing of 1.0 μm is used. If the particle size is too large, the cleaning property due to toner slippage is reduced. If the particle size is too small, it is difficult to uniformly disperse the particles in the layer, which may cause cleaning failure.

The dispersion layer contains tantalum-doped tin oxide in an amount of 5 to 70% by weight, preferably 7 to 40% by weight of the entire dispersion layer. If the amount is too small, abrasion resistance and scratch resistance become insufficient, and the residual potential of the photoreceptor increases.
If the amount is too large, fine irregularities are formed on the surface of the surface protective layer after the formation, the toner cleaning property is reduced, and there is a problem that the toner passes through. In addition, there is a problem in that the photosensitive characteristics are deteriorated due to a decrease in light transmittance, and the mechanical strength is further reduced.

A photosensitive layer is formed below the dispersion layer. The photosensitive layer is formed by appropriately selecting a known material such as a charge generation material, a charge transport material, a binder resin, and the like, and a stacked photosensitive layer in which a charge transport layer is laminated on the charge generation layer, and a charge transport layer. The present invention can be applied to any photosensitive layer such as a so-called reverse-layered photosensitive layer having a charge generation layer provided thereon and a so-called single-layered photosensitive layer having both a charge generation function and a charge transport function.

Further, not only organic photosensitive layers but also inorganic materials such as zinc oxide, cadmium sulfide, selenium alloys and amorphous silicon alloys may be used.

Hereinafter, a case where a photoreceptor having a structure in which a charge generation layer, a charge transport layer, and a dispersion layer of the present invention are sequentially laminated on a conductive support as the photoreceptor of the present invention will be described.

As the support, copper, aluminum, iron,
A conductive material such as nickel or the like, which is made of a sheet or a drum, is used. Further, the above-mentioned metal was vacuum-deposited on a resin film or the like, a layer obtained by electroless plating, or a conductive polymer, a layer of a conductive compound such as indium oxide or tin oxide was similarly provided on paper or a resin film by coating or vapor deposition. The thing etc. are used.

A charge generation layer is formed on the support. The charge generating layer is formed by vacuum-depositing the charge generating material, or
Dissolve in an appropriate solvent and apply, or apply a coating solution prepared by dispersing the pigment in an appropriate solvent or a solution in which a binder resin is dissolved if necessary to form a charge generation layer by applying and drying, Further, a solution containing a charge transport material and a binder resin is applied thereon and dried to form a charge transport layer.

Examples of the charge generating material used in the photoreceptor of the present invention include bisazo pigments, triarylmethane dyes, thiazine dyes, oxazine dyes, xanthene dyes, cyanine dyes, styryl dyes, pyrylium dyes. Organic substances such as dyes, azo dyes, quinacdrine dyes, indigo pigments, perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indathrone pigments, squarylium pigments, and phthalocyanine pigments are exemplified. In addition, any material that absorbs light and generates charge carriers with extremely high efficiency can be used.

The charge transporting materials used in the above photoreceptors include hydrazone compounds, pyrazoline compounds, styryl compounds, triphenylmethane compounds, oxadiazole compounds, carbazole compounds, stilbene compounds, enamine compounds and oxazole compounds. , A triphenylamine compound, a tetraphenylbenzidine compound, an azine compound and the like can be used.

The binder resin used in the production of the above-mentioned photoreceptor is electrically insulating, and is measured by 1 × 10 ¹²
It is desirable to have a volume resistance of Ω · cm or more. For example, a binder such as a thermoplastic resin, a thermosetting resin, a photocurable resin, or a photoconductive resin known per se can be used. Specifically, saturated polyester resin, polyamide resin, acrylic resin, ethylene-vinyl acetate resin, ion-crosslinked olefin copolymer (ionomer), styrene-
Thermoplastic resins such as butadiene block copolymer, polycarbonate, vinyl chloride-vinyl acetate copolymer, cellulose ester, polyimide, and styrene resin; epoxy resin, urethane resin, silicone resin, phenol resin, melamine resin, xylene resin, alkyd resin , A thermosetting resin such as a thermosetting acrylic resin; a photocurable resin; a photoconductive resin such as polyvinyl carbazole, polyvinyl pyrene, polyvinyl anthracene, and polyvinyl pyrrole;
Use in combination of more than one species.

When the charge transporting material is a polymeric charge transporting material that can be used as a binder, it is not necessary to use another binder resin.

The photoreceptor of the present invention can be used together with a binder resin together with a plasticizer such as halogenated paraffin, polychlorinated biphenyl, dimethylnaphthalene, dibutylphthalate, O-terphenyl, chloranil, tetracyanoethylene, 2,4,7,
An electron-withdrawing sensitizer such as trinitrofluorenone, 5,6-dicyanobenzoquinone, tetracyanoquinodimethane, tetrachlorophthalic anhydride, 3,5-dinitrobenzoic acid, methyl violet, rhodamine B, cyanine dye, pyrylium salt And sensitizers such as thiapyrylium salts.

In the dispersion layer on the outermost surface of the photoreceptor, fine powder of tin oxide doped with tantalum is dispersed in a resin solution described later, and this solution is applied on the charge transport layer and dried to form a dispersion layer. After the application, drying is preferably performed at a temperature in the range of 60 to 120 ° C. As the resin constituting the dispersion layer, any solvent can be used as long as it satisfies conditions such as sufficient solvent resistance and good dispersibility of the fine powder.
Conventionally known polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinylimidazole, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, casein, gelatin, polyamide and the like can be used. In addition, general polyester resins, acrylic resins, vinyl acetate resins, vinyl chloride-vinyl acetate resins, thermoplastic resins such as polyvinyl butyral resins, alkyd resins, melamine resins, urethane resins, epoxy resins, silicone resins, phenol resins, etc. A thermosetting resin or the like can be used. In particular, of these,
Polyester resin, acryl-melamine resin, urethane resin, and the like are preferable in view of durability, electrostatic characteristics, and coatability.

As a method of applying a dispersion layer on a support,
The coating can be performed by using a coating method such as a dip coating method, a spray coating method, a spinner coating method, a wire bar coating method, a blade coating method, a roller coating method, and a curtain coating method.

The thickness of the dispersion layer is 7 μm or less, preferably about 1 to 5 μm. The dispersion layer of the present invention can be formed relatively thick, and as a result, the durability of the photoconductor is improved.

Although the case where the charge generation layer, the charge transport layer and the dispersion layer of the present invention are sequentially formed on the support has been described above, the present invention can be similarly applied to a photoreceptor having another structure. An appropriate modification may be performed according to the form of the photoconductor.

Since the dispersion layer can be formed relatively thick as described above, the present invention is most effective for a photoreceptor having the above-mentioned dispersion layer formed on an organic photosensitive layer, particularly in terms of improvement in durability.

The photoreceptor of the present invention may be provided with an undercoat layer below the photosensitive layer in order to improve the chargeability, image quality, adhesiveness and the like. Examples of the material of the undercoat layer include a resin such as an ultraviolet curable resin, a room temperature curable resin, and a thermosetting resin, a mixed resin in which a resistance adjusting material is dispersed in the resin, a metal oxide, a metal sulfide, and the like. For example, a vacuum thin film material formed into a thin film by a vapor deposition method, an ion plating method, or the like, an amorphous carbon film, an amorphous silicon carbide film formed by a plasma polymerization method, or the like can be used.

[0029]

【Example】

Example 1 1 part by weight of τ-type metal-free phthalocyanine, 0.5 part by weight of polyvinyl butyral, and 50 of tetrahydrofuran (THF)
It was dispersed by a sand mill together with parts by weight. The resulting phthalocyanine-based dispersion has a thickness of 0.3 μm after drying.
Was applied on an aluminum drum to form a charge generation layer.

The following formula:

Embedded image A coating solution prepared by dispersing 10 parts by weight of a distyryl compound represented by the following formula and 12 parts by weight of a polycarbonate resin (TS2020, manufactured by Teijin Chemicals Ltd.) in 180 parts by weight of tetrahydrofuran was applied onto the charge generation layer and dried to form a film having a thickness of 22 μm.
m of the charge transport layer was formed.

Tantalum-doped tin oxide (SnO ₂ )
(Pastran TYPE-VI, manufactured by Mitsui Kinzoku Mining) 40
A coating liquid in which 70 parts by weight of a polyurethane resin solution (Rethane 4000, manufactured by Kansai Paint Co., Ltd.) was dispersed in 70 parts by weight was applied onto the charge transport layer so that the film thickness after drying was 2 μm, and was dried. Produced.

Example 2 1 part by weight of τ-type metal-free phthalocyanine, 0.5 part by weight of polyvinyl butyral, 50 parts of tetrahydrofuran (THF)
It was dispersed by a sand mill together with parts by weight. The resulting phthalocyanine-based dispersion has a thickness of 0.3 μm after drying.
Was applied on an aluminum drum to form a charge generation layer.

The following formula:

Embedded image A benzyl diphenyl compound represented by the following formula and 10 parts by weight of a polycarbonate resin (Panlite K-1300, manufactured by Teijin Chemicals Ltd.) are dispersed in 180 parts by weight of dichloromethane, and the coating solution is coated on the charge generating layer and dried. Thus, a charge transport layer having a thickness of 25 μm was formed.

Tantalum-doped tin oxide (SnO ₂ )
(Pastran TYPE-VI, manufactured by Mitsui Kinzoku Mining) 30
A coating solution obtained by dispersing 60 parts by weight of an acrylic resin solution (G-4663A, manufactured by Nortape Industries) in an amount of 60 parts by weight on the charge transporting layer so that the film thickness after drying is 3 μm is dried and dried. Was prepared.

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1, except that the surface protective layer did not contain tantalum-doped tin oxide.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 2, except that tin oxide powder not doped with tantalum was used.

Each of the photoreceptors of Examples 1 and 2 and Comparative Examples 1 and 2 obtained as described above was used as a printer (SP101;
(Minolta Co., Ltd.), and a printing durability test of 5000 (5K) sheets was performed. The initial surface potential (V ₀ (V)) and the surface potential of each photoreceptor at the initial stage and after 5K were reduced to half of the initial surface potential. Exposure required to carry out (hereinafter, half-exposure) E
_1/2 (erg / cm ² ), the decay rate DDR ₁ (%) of the initial potential when left in the dark for 1 second was measured, and the images were visually observed and ranked as follows. Further, the shaving amount of the surface protective layer after 5K sheets was also measured, and ranked as follows.

Image evaluation: 〇: No fog or image blur was observed. ×: Although the density was low, fog or image blur was observed.

Abrasion amount: 〇: When the abrasion amount is 1 μm or less ×: When the abrasion amount is more than 1 μm

The above results are summarized in Table 1 below.

[0041]

[Table 1]

[0042]

According to the present invention, by including tantalum-doped tin oxide in the outermost surface layer of the photosensitive layer, photoreceptor characteristics such as sensitivity can be stabilized for a long time even if it is used repeatedly, and durability and safety can be improved. A photoreceptor having excellent properties can be obtained.

Continuation of front page (56) References JP-A-6-345430 (JP, A) JP-A-7-133374 (JP, A) JP-A-6-35220 (JP, A) JP-A-62-242958 (JP) JP-A-59-223445 (JP, A) JP-A-63-254463 (JP, A) JP-A-57-30847 (JP, A) JP-A-4-504388 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 5/00

Claims (3)

(57) [Claims] 1. A photoreceptor having on its outermost surface a layer containing tantalum-doped tin oxide fine powder in a resin. 2. The method according to claim 1, wherein said fine powder of tantalum-doped tin oxide is flat.
Tantalum-doped tin oxide fine powder with an average particle size of 2 μm or less
Of fine powder of tantalum-doped tin oxide in the layer containing the solid
2. The composition according to claim 1, wherein the amount is 5 to 70% by weight.
Photoconductor. 3. The tantalum-doped tin oxide fine powder is
Characterized by being surface-treated with a coupling agent
The photoconductor according to claim 1 or 2, wherein