JP3221593B2 - Electrophotographic photoreceptor and electrophotographic apparatus - Google Patents

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 and an electrophotographic apparatus using the photosensitive member.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member basically comprises a support and a photosensitive layer formed on the support. But,
Covering defects of the support, improving the coating properties of the photosensitive layer, improving the adhesion between the photosensitive layer and the support, protecting the photosensitive layer from electrical breakdown, improving the chargeability, injecting charge from the support into the photosensitive layer It is effective to provide an intermediate layer between the photosensitive layer and the support for the purpose of improving the image quality. Therefore, the intermediate layer in the electrophotographic photoreceptor is required to have many functions such as covering properties, adhesive properties, mechanical strength, appropriate conductivity and electrical barrier properties.

Conventionally, the following types of intermediate layers have been proposed. (I) A resin thin film containing no conductive filler. (Ii) A resin thin film containing a conductive filler. (Iii) The thin film of (i) is laminated on the thin film of (ii).

[0004] The thin film (i) contains no conductive filler and therefore has a high electric resistance, and must be thick to cover defects on the support. Therefore, it has a disadvantage that the residual potential at the initial stage and at the time of repeated use becomes high. For practical use of the thin film (i), defects on the support are reduced and the thickness of the intermediate layer is extremely reduced. Need to be thinner.

On the other hand, the thin films of the above (ii) and (iii) have an advantage that an appropriate conductivity can be imparted by dispersing the conductive filler. Electrical characteristics such as resistance and dielectric constant change, which greatly affects potential characteristics and image characteristics. Further, if the dispersibility of the filler is poor, the surface smoothness of the film is deteriorated, which causes a coating defect. Further, if the dispersion of the filler is poor, the adhesion to the support and the mechanical strength are also reduced.

Until now, as conductive fillers for the intermediate layer, metals (JP-A-58-18154), metal oxides (JP-A-54-151843), and metal nitrides (JP-A-1-118848) have been used. Gazette) has been reported.

[0007]

However, a conventional electrophotographic photosensitive member using a conductive filler as a filler for an intermediate layer has a large environmental dependency such as temperature and humidity.
It has been difficult to produce a photoreceptor having constantly stable potential characteristics and image characteristics in all environments from low temperature and low humidity to high temperature and high humidity. For example, under low temperature and low humidity conditions that cause an increase in the resistance of the intermediate layer, when the photoreceptor is used repeatedly, charges are accumulated in the intermediate layer, and the residual potential and the light portion potential increase. On the other hand, under high temperature and high humidity, which causes a decrease in the resistance of the intermediate layer, the electrical barrier capability of the intermediate layer was reduced, carrier injection from the support was accelerated, and a decrease in the dark area potential upon repeated use was observed. As a result, in addition to the decrease in image density under high temperature and high humidity, in the case of an electrophotographic printer that performs reversal development, unnecessary black spots (black spots) appear on the image and fogging easily occurs. .

The reason why the characteristics of the photoreceptor change due to a change in environment is considered to be that the dispersibility of the conductive filler is poor. That is, it is considered that a local change in resistance occurs due to a decrease in the dispersibility of the conductive filler in the intermediate layer, so that the potential characteristics and image characteristics are easily affected by environmental changes.

It is an object of the present invention to provide an electrophotographic photosensitive member having stable potential characteristics and image characteristics in all environments from low temperature and low humidity to high temperature and high humidity, and an electrophotographic apparatus using the photosensitive member. Can be provided.

[0010]

That is, the present invention relates to an electrophotographic photoreceptor having an intermediate layer and a photosensitive layer on a conductive support in this order, wherein the intermediate layer comprises barium sulfate fine particles having a coating layer. Containing powder, and forming the coating layer
An electrophotographic photoreceptor formed of aluminum .

Further, the present invention provides the above electrophotographic photosensitive member,
A charging unit for charging the photoconductor, an image exposure unit for performing image exposure on the charged photoconductor to form an electrostatic latent image,
Developing means for developing the photoreceptor on which the electrostatic latent image is formed with toner.

The electrophotographic photosensitive member of the present invention has an intermediate layer and a photosensitive layer on a support in order from the support side. The intermediate layer contains, as a filler, a powder composed of barium sulfate fine particles having a conductive coating layer.

The barium sulfate fine particles have very excellent dispersibility. Further, since the refractive index of the barium sulfate fine particles is substantially equal to the refractive index of the binder resin, the light transmittance of the intermediate layer does not decrease.

In the present invention, a barium sulfate fine particle is provided with a conductive coating layer so as to have an appropriate specific resistance as a filler. As the coating layer, a coating layer formed of a metal is used.

[0015] Aluminum is used as the metal.

The average particle size of the barium sulfate fine particles having a coating layer is 0.05 to 1.0 μm, and more preferably 0.07 to 0.7 μm.
μm is preferred. In the present invention, the average particle size of the fine particles is a value measured by a centrifugal sedimentation method.

In general, when the average particle size of the filler is small, dispersion becomes difficult and reaggregation is liable to occur. However, the filler used in the present invention is excellent in dispersibility. The content of the filler is preferably 1.0 to 90% by weight, more preferably 5.0 to 80% by weight based on the intermediate layer.

The binder resin used in the intermediate layer of the present invention includes, for example, phenol resin, polyurethane, polyamide, polyimide, polyamideimide, polyamic acid, polyvinyl acetal, epoxy resin, acrylic resin,
Melamine resin or polyester is preferred. These resins may be used alone or in combination of two or more. These resins have good adhesiveness to the support, improve the dispersibility of the filler used in the present invention, and have good solvent resistance after film formation. Among the above resins, phenol resins, polyurethanes and polyamic acids are particularly preferred.

The intermediate layer can be formed, for example, by dipping or applying a solvent using a Meyer bar or the like.

In order to improve the dispersibility of the filler, the surface of the filler may be treated with a treating agent such as a coupling agent (such as a silane coupling agent or a titanium coupling agent) or silicone oil. Moreover, you may make the said processing agent contain in the binder of an intermediate | middle layer.

The thickness of the intermediate layer is preferably 0.1 to 30 μm, more preferably 0.5 to 10 μm. The volume resistivity of the intermediate layer 10 ¹³ [Omega] cm or less, more 10 ¹² [Omega] cm or less 10Ω
cm or more is preferred. In the present invention, the volume resistivity is obtained by applying an intermediate layer to be measured on an aluminum plate, further forming a gold thin film on the intermediate layer, and setting a current value flowing between both electrodes of the aluminum plate and the gold thin film to _p. It was determined by measuring with an A meter.

The intermediate layer may contain a filler made of powder such as zinc oxide or titanium oxide in addition to the powder made of barium sulfate fine particles having a coating layer. Further, a leveling agent may be added to enhance the surface properties of the intermediate layer.

The photosensitive layer of the present invention may be a single layer or a laminated structure comprising at least a charge generation layer and a charge transport layer.

When the photosensitive layer is a single layer, a charge generating substance and a charge transporting substance are contained in the same layer, and photo carriers are generated and moved in the same layer.

When the photosensitive layer has a laminated structure, the charge generating layer containing the charge generating substance and the charge transporting layer containing the charge transporting substance may be stacked in the order of the charge generating layer and the charge transporting layer from the support side. And vice versa.

Examples of the charge generating substance include azo pigments (eg, monoazo, bisazo, trisazo, etc.), metal and non-metallic phthalocyanine pigments, indigo pigments (eg, indigo, thioindigo, etc.), and quinone pigments (eg, anthantrone. , Pyrenequinone, etc.), perylene pigments (eg, perylene anhydride, perylene imide, etc.), squalium pigments, pyrylium, thiopyrylium salts, triphenylmethane pigments and the like. Further, an inorganic material such as selenium, selenium-tellurium, or amorphous silicon can also be used as the charge generating substance.

The charge transport material includes an electron transport material and a hole transport material. Examples of the electron transporting material and the hole transporting material include 2,4,7-trinitrofluorenone,
4,5,7-tetranitrofluorenone, chloranil,
And tetracyanoquinodimethane. Examples of the hole transport material include polycyclic aromatic compounds (eg, pyrene, anthracene, etc.), heterocyclic compounds (eg, carbazole, indole, imidazole, oxazole, thiazole, oxadiazole, pyrazole, pyrazoline, thiadiazole, triazole, etc.), Hydrazone-based compounds (eg, p-diethylaminobenzaldehyde-N, N-diphenylhydrazone, N, N-diphenylhydrazino-3-methylidene-9-ethylcarbazole, etc.), styryl-based compounds (eg, α-phenyl-4 ′)
-N, N-diaminostilbene, 5- [4- (di-p-
Tolylamino) benzylidene] -5H-dibenzo [a,
d] dicycloheptene), benzidine compounds, triarylamine compounds and the like.

When the photosensitive layer is a single layer, the thickness of the photosensitive layer is 5
To 100 μm, more preferably 10 to 60 μm. The single photosensitive layer preferably contains a charge generating substance and a charge transporting substance in an amount of 10 to 70% by weight, more preferably 20 to 70% by weight.

When the photosensitive layer has a laminated structure, the thickness of the charge generation layer is preferably 0.001 to 5 μm, more preferably 0.05 to 2 μm, and the thickness of the charge transport layer is 1 to 40 μm, and more preferably 10 to 40 μm.
-30 μm is preferred. The charge generating layer preferably contains a charge generating substance in an amount of 10 to 100% by weight, more preferably 40 to 100% by weight. The charge transport layer contains 2 charge transport materials.
The content is preferably 0 to 80% by weight, more preferably 30 to 70% by weight.

The electrophotographic photoreceptor of the present invention can be obtained by forming a film on a support by combining a material used for the photosensitive layer with a vacuum deposition or an appropriate binder resin.

As the binder resin for the photosensitive layer, for example, polyvinyl acetal, polycarbonate, polystyrene, polyester, polyacetate, polymethacrylate, acrylic resin, cellulose resin and the like are preferably used.

Depending on the kind of the material for the photosensitive layer, free carriers may be injected from the intermediate layer into the photosensitive layer, which lowers the charging ability of the photosensitive member and greatly affects image characteristics.
In such a case, if necessary, a barrier layer having an electric barrier property (for example, a suitable resin thin film) is provided between the intermediate layer and the photosensitive layer to effectively suppress the injection of the free carrier. be able to. As a barrier layer,
For example, water-soluble resins such as polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acids, methylcellulose, ethylcellulose, polyglutamic acid, casein, starch, polyamide, polyimide, polyamideimide, polyamic acid, melamine resin, epoxy resin, polyurethane, and polyglutamic acid ester And the like. In particular, polyamide is preferred as the barrier layer in terms of coating properties, adhesion, solvent resistance, electrical barrier properties, resistance, and the like. As the polyamide, a low-crystalline or non-crystalline copolymer nylon which can be applied in a solution state is suitable. The thickness of the barrier layer is 0.1 to 2 μm
m is preferred.

In the electrophotographic photosensitive member of the present invention, a protective layer may be provided on the photosensitive layer. The protective layer is mainly composed of a resin. As a material constituting the protective layer, for example, polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamide imide, polysulfone, polyallyl ether, polyacetal, nylon, phenol resin, acrylic resin, Examples include silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, and butyral resin. The thickness of the protective layer is 0.05 to 15 μm,
10 μm is preferred.

The support may be a metal or alloy such as aluminum, aluminum alloy, copper, titanium, stainless steel, or a polymer material such as polyethylene terephthalate, polybutylene terephthalate, phenolic resin, polypropylene, or polystyrene, or a hard paper. It can be manufactured using materials. The shape of the support is cylindrical,
A belt shape or a sheet shape is preferred. When the material constituting the support has a high volume resistance, it is necessary to conduct a conductive treatment. The conductive treatment can be performed by forming a conductive thin film on the support or dispersing a conductive substance in the support.

The electrophotographic photoreceptor of the present invention is widely used not only for electrophotographic copying machines but also for electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, facsimile machines, and laser plate making. be able to.

The electrophotographic photoreceptor according to the present invention can realize stable potential characteristics and good image formation in all environments from low temperature and low humidity to high temperature and high humidity.

Next, an electrophotographic apparatus provided with the electrophotographic photosensitive member of the present invention will be described. FIG. 1 shows a schematic configuration of a transfer type electrophotographic apparatus using the drum type photoreceptor of the present invention. In the figure, reference numeral 1 denotes a drum type photoconductor of the present invention,
It is driven to rotate around the shaft 1a in the direction of the arrow at a predetermined peripheral speed. The photosensitive member 1 is uniformly charged at a predetermined positive or negative potential on its peripheral surface by a charging means 2 during the rotation process, and then, in an exposure section 3, a light image exposure L (slit exposure or Laser beam scanning exposure). As a result, an electrostatic latent image corresponding to the exposure image is sequentially formed on the peripheral surface of the photoconductor. The electrostatic latent image is then developed with toner by a developing unit 4, and the developed toner image is transferred by a transfer unit 5 between a photosensitive unit 1 and a transfer unit 5 from a paper supply unit (not shown) in synchronization with the rotation of the photosensitive unit 1. The recording material P is sequentially transferred onto the surface of the taken and fed recording material P. Recording material P after image transfer
Is separated from the photoreceptor surface, introduced into the image fixing means 8 and subjected to image fixing to be printed out of the apparatus as a copy. The surface of the photoreceptor 1 after the image transfer is cleaned and cleaned by removing the untransferred toner by the cleaning unit 6, subjected to a charge removal process by the pre-exposure unit 7, and used repeatedly for image formation. As the uniform charging means 2 for the photoreceptor 1, a corona charging device is generally widely used. Also, the corona transfer means is generally widely used for the transfer device 5. As an electrophotographic apparatus, a plurality of components such as the above-described photoreceptor, developing means, and cleaning means are integrally connected as an apparatus unit, and this unit is configured to be detachable from the apparatus body. You may. For example, the photoreceptor 1 and the cleaning means 6 may be integrated into one apparatus unit, and may be configured to be detachable using a guide means such as a rail of the apparatus body. At this time, the above-described device unit may be provided with a charging unit and / or a developing unit. When the electrophotographic apparatus is used as a copying machine or a printer, the light image exposure L uses reflected light or transmitted light from the original, or reads the original, converts it into a signal, and scans the laser beam according to this signal. Or by driving a light emitting diode array or a liquid crystal shutter array.

[0038]

The present invention will be described below with reference to examples. (Example 1) 120 parts by weight of a powder composed of barium sulfate fine particles having an aluminum coating layer, and 70 parts by weight of a resol-type phenol resin (Plyofen J-325, manufactured by Dainippon Ink and Chemicals, solid content 70%); A solution consisting of 100 parts by weight of 2-methoxy-1-propanol was dispersed in a ball mill for about 20 hours. The average particle size of the filler contained in this dispersion was 0.25 μm.

The dispersion prepared in this manner was treated with an outer diameter of 30.
mm, an aluminum cylinder having a length of 360 mm (surface roughness R _max 5 μm) was applied by an immersion method.
By heating and curing at 0 ° C for 30 minutes, the thickness is 10 μm
Was formed. Surface roughness R _max of the intermediate layer at this time
Was 0.8 μm. Incidentally, the roughness R _{ma x}
Is based on JIS B0601.

Next, a copolymerized nylon resin (Amilan CM)
(8000, manufactured by Toray) A solution prepared by dissolving 10 parts by weight of a mixed solution of 60 parts by weight of methanol and 40 parts by weight of butanol was applied onto the intermediate layer by dip coating, and dried by heating at 90 ° C. for 10 minutes to obtain a layer having a thickness of 0.5 μm. Was formed.

Next, a solution consisting of 4 parts by weight of an oxytitanium phthalocyanine pigment, 2 parts by weight of a polyvinyl butyral resin (BX-1, manufactured by Sekisui Chemical Co., Ltd.) and 34 parts by weight of cyclohexanone was dispersed in a sand mill for 8 hours, and then 60 parts by weight of tetrahydrofuran To prepare a dispersion for the charge generation layer. This dispersion was applied onto the above barrier layer by dip coating, and dried by heating at 80 ° C. for 10 minutes to form a charge generation layer. The thickness of the charge generation layer was 0.2 μm.

Next, 50 parts by weight of a triarylamine compound represented by the following structure:

[0043]

[Outside 1] A solution prepared by dissolving 50 parts by weight of a polycarbonate resin (Iupilon Z-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.) in 400 parts by weight of monochlorobenzene was applied onto the charge generating layer by dip coating, and dried by heating at 120 ° C. for 1 hour to a thickness of 20 μm Was formed.

The electrophotographic photoreceptor of the present invention thus prepared is mounted on a forward-developed electrophotographic copying machine.
The charging-exposure-development-transfer-cleaning process was repeated in a 0.8 second cycle. Low temperature and low humidity (15 ° C., 15% RH) and high temperature and high humidity (30 ° C.,
The electrophotographic properties were evaluated under an environment of 85% RH). As a result, as shown in Table 1, this photoconductor may form a large difference between the dark portion potential (V _D ) and the bright portion potential (V _L ) at both low temperature and low humidity and high temperature and high humidity. As a result, sufficient contrast could be obtained. Further, when images were continuously printed on 10,000 sheets of recording paper, the dark potential and the bright potential hardly changed in any environment, and an image of extremely excellent image quality was stably obtained.

[0045]

(Example 2) The intermediate layer of Example 1 was replaced with an intermediate layer formed by using the following coating solution, and the others were the same as in Example 1.
An electrophotographic photoreceptor was prepared in the same manner as described above. 150 parts by weight of barium sulfate fine particles having an aluminum coating layer 70 parts by weight of polyester polyurethane (Nipporan 2304, manufactured by Nippon Polyurethane) 100 parts by weight of 2-methoxy-1-propanol The printer was mounted on a reversal-developing electrophotographic printer, and a charging-exposure-development-transfer-cleaning process was repeated at a cycle of 6 seconds. The electrophotographic characteristics of this photoreceptor were evaluated under low temperature and low humidity (15 ° C., 15% RH) and high temperature and high humidity (30 ° C., 85% RH). As a result, as shown in Table 2, this photoreceptor can form a large difference between the dark portion potential (V _D ) and the bright portion potential (V _L ) even at low temperature, low humidity, and high temperature and high humidity. Sufficient contrast was obtained. Furthermore, when images were continuously output on 5000 sheets of recording paper, both the dark potential and the bright potential hardly changed in any environment, and extremely excellent image quality free of unnecessary black spot images and fog Was obtained stably.

[0047]

(Comparative Examples 1 and 2)
The electrophotographic photoreceptors of Comparative Examples 1 and 2 were prepared in the same manner as in Example 1 except that the intermediate layer was formed using the following coating liquid.

Each of the electrophotographic photosensitive members thus produced was evaluated in the same manner as in Example 1. As a result, as shown in Table 3, in any of the photoconductors, a large difference can be initially formed between the dark portion potential (V _D ) and the bright portion potential (V _L ), and a sufficient contrast can be obtained. However, when images were continuously formed on 10,000 sheets of recording paper, all of the electrophotographic photoreceptors showed a decrease in the dark area potential and an increase in the light area potential in a low-temperature and low-humidity environment.

The powder made of titanium oxide fine particles having a coating layer of tin oxide of the coating liquid, antimony-containing comparative example 1 (ECTT-1, manufactured by Titan Kogyo)
150 parts by weight-75 parts by weight of the same resole type phenol resin as in Example 1-60 parts by weight of methyl cellosolve-15 parts by weight of methanol

The coating liquid of Comparative Example 2 and the powder comprising antimony-containing tin oxide fine particles (T-
1, manufactured by Mitsubishi Materials Corporation) 100 parts by weight-70% by weight of the same polyester polyurethane as in Example 2-80 parts by weight of 2-methoxy-1-propanol

[0052]

[Outside 2]

[Brief description of the drawings]

FIG. 1 is a side view showing an example of an electrophotographic apparatus using the electrophotographic photosensitive member of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electrophotographic photoreceptor 2 Charging means 3 Exposure part 4 Developing means 5 Transfer means 6 Cleaning means 7 Pre-exposure means 8 Image fixing means

Continuation of the front page (56) References JP-A-6-208238 (JP, A) JP-A-6-250430 (JP, A) JP-A-6-19174 (JP, A) JP-A-6-27707 (JP) JP-A-61-110153 (JP, A) JP-A-60-111255 (JP, A) JP-A-3-1311862 (JP, A) JP-A-5-210260 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 5/00

Claims (5)

(57) [Claims] 1. An electrophotographic photoreceptor having an intermediate layer and a photosensitive layer on a conductive support in this order, wherein the intermediate layer contains a powder of barium sulfate fine particles having a coating layer, and the coating layer An electrophotographic photoreceptor characterized in that is formed of aluminum . 2. The binder resin of the intermediate layer is selected from the group consisting of phenolic resin, polyurethane, polyamide, polyimide, polyamideimide, polyamic acid, polyvinyl acetal, epoxy resin, acrylic resin, melamine resin and polyester. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor is used. 3. A phenol resin as the binder resin,
3. The electrophotographic photosensitive member according to claim 2, wherein a member selected from the group consisting of polyurethane and polyamic acid is used. 4. The electrophotographic photosensitive member according to any one of claims 1 to 3 having a barrier layer between the intermediate layer and the photosensitive layer. 5. An electrophotographic photoreceptor according to claim 1, a charging unit for charging the photoreceptor, and image exposure of the charged photoreceptor to form an electrostatic latent image. An electrophotographic apparatus comprising: an image exposing unit; and a developing unit that develops the photoconductor on which an electrostatic latent image is formed with toner.