JP3149100B2 - 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 having the same, and more particularly, to reduce the contact energy between the surface of the photosensitive member and a developer, a cleaning blade, a deposit, a contaminant, etc. having a low surface energy. The present invention relates to an electrophotographic photosensitive member that realizes high image quality and an electrophotographic apparatus having the same.

[0002]

2. Description of the Related Art Conventionally, inorganic materials such as zinc oxide, selenium, and cadmium sulfide have been known as photoconductive materials used in electrophotographic photosensitive members. Organic polyvinyl carbazole, phthalocyanine, azo pigments, and the like have attracted attention for their advantages such as high productivity and no pollution. Recently, new materials with improved disadvantages have been devised, and in particular, the photoconductive properties are surpassing those of inorganic materials.

In an electrophotographic process of a copying machine, a laser beam printer, or the like, an electrophotographic photosensitive member is repeatedly subjected to actions such as charging, exposure, development, transfer, cleaning, and static elimination. Various durability and stability such as electrical are required. The surface energy of the photoreceptor is also an important factor for the interaction between a contact material such as a developer, a transfer material, a corona product, and a cleaning blade and the photoreceptor surface.

On the other hand, since the organic photoconductive material does not have a film-forming property by itself, it is generally formed with a binder resin. Therefore, it is no exaggeration to say that physical properties such as surface energy are almost limited by the selection of the binder resin. However, binder resins satisfying photoconductive properties and mechanical strength are considerably limited, and a sufficiently low surface energy surface has not been obtained.

[0005]

The electrophotographic processes that are most involved in the physical properties of the photoreceptor are cleaning and transfer. In recent years, as the developer becomes finer, the cleaning is required to have higher and higher precision. In addition, it is advantageous to employ blade cleaning in order to realize a simpler device configuration along with space saving of the device.
The blade cleaning has a simple configuration in which a plate-like elastic member such as polyurethane is abutted on the photoconductor in the generatrix direction. However, in such a case, a large contact energy is generated between the photoconductor and the blade, which promotes abrasion of the photoconductor and lowers durability.

To cope with this, it is effective to improve the mechanical strength of the photoreceptor and to reduce the contact energy due to a decrease in the photoreceptor surface energy. In the former case, it is generally considered to increase the molecular weight of the binder resin and use a curable binder resin. However, a high molecular weight binder resin causes a viscosity increase of a coating material in a coating step, which is a main method for manufacturing an organic photoreceptor, and therefore, there is a limit to polymerization. Further, the curable binder resin has adverse effects such as deterioration of the photoconductive properties due to the reaction deterioration of the organic photoconductive material at the time of curing, the formation of impurity levels due to unreacted functional groups and by-products of the polymerization initiator, and the like. The reality is that it has not reached a practical level.

As the latter method, use of a low surface energy compound such as a fluorine-based compound or a silicon-based compound has been considered, but there is no material that satisfies the film forming property and the compatibility alone. Therefore, means for dispersing the fluorine-based or silicon-based compound in the photosensitive layer has been tried. However, these fine particles or these phase-separated compounds scatter and reflect the light incident on the photosensitive layer to form a faithful latent image. In some cases. In particular, in a process using a dot-shaped minute latent image such as a laser, an LED, or a liquid crystal shutter controlled by a digital signal, which has been frequently used in recent years, this effect is large and causes a reduction in image uniformity.

On the other hand, with regard to transfer, it has become difficult to perform high-efficiency transfer as the particle size of the developer is reduced, and a photoreceptor surface with higher transfer efficiency has been desired. Implementation was difficult. As a result, the image quality is disturbed due to poor transfer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic photosensitive member having improved durability and stability by improving surface properties such as surface energy without deteriorating electrophotographic characteristics, and an electrophotographic apparatus having the same. is there.

[0010]

That is, the present invention relates to an electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the surface layer of the photoreceptor has a fluorine atom-containing compound and the following general formula (1):

[0011]

Embedded image (Wherein R ₁ , R ₂ and R ₃ represent a hydrogen atom or a methyl group, provided that R ₁ , R ₂ and R ₃ are simultaneously a hydrogen atom.
Never. An electrophotographic photosensitive member comprising a resin containing a repeating structural unit of poly (n-methyl) styrene (n = α, β, 2,3,4)

Further, the present invention relates to an electrophotographic apparatus having an exposure means for forming a dot-shaped electrostatic latent image on an electrophotographic photosensitive member, wherein the photosensitive member has a photosensitive layer on a conductive support. Wherein the surface layer of the photoreceptor has a fluorine atom-containing compound and the following general formula (1):

[0013]

Embedded image (Wherein R ₁ , R ₂ and R ₃ represent a hydrogen atom or a methyl group, provided that R ₁ , R ₂ and R ₃ are simultaneously a hydrogen atom.
Never. An electrophotographic apparatus comprising a resin containing a repeating structural unit of poly (n-methyl) styrene (n = α, β, 2,3,4) represented by the following formula:

The fluorine atom-containing compound is mainly composed of carbon-
It preferably contains a fluorine bond, and the weight ratio of fluorine atoms preferably occupies 30 to 80% of the atoms constituting the compound. The fluorine atom is not only the van der Waals radius second only to the hydrogen atom but also the atom having the highest electronegativity, and further has the feature that the interaction between the outermost electron and the nucleus is strong and the polarizability is small. Therefore, the carbon-fluorine bond has features such as a short interatomic distance, a high bond energy, and a covalent bond with a small polarizability. As a result, the fluorine-containing compound is
Since it is thermally, chemically and electrically stable and has a small intermolecular cohesion, the surface energy is low and the refractive index of light tends to be small. The photosensitive layer in which the fluorine atom-containing compound is uniformly dispersed reflects the small intermolecular cohesion of the fluorine atom-containing compound and gives a surface with a remarkably low energy. Therefore, it is possible to significantly reduce the contact energy between the surface of the photoconductor and a developer, a cleaning blade, or the like that comes into contact with the surface, and the shaving of the photoconductor due to the cleaning load is suppressed. Further, the photoreceptor having a low energy surface obtained by the present invention significantly enhances the transfer efficiency of the developer and enables a high-quality copy image without transfer failure or the like. However, as described above, the fluorine atom-containing compound has a remarkably low intermolecular cohesion and poor compatibility with the photosensitive material or resin constituting the photosensitive layer, and is therefore contained in the photosensitive layer in a dispersed state. In such a case, if the apparent particle size of the fluorine atom-containing compound is so large that the fluorine atom-containing compound is strongly agglomerated, the light image incident on the photosensitive layer is scattered, which may hinder the formation of a faithful latent image. . In particular, in a process using a dot-shaped minute latent image such as a laser, an LED, or a liquid crystal shutter controlled by a digital signal, which has been frequently used in recent years, this effect is large and causes a reduction in image uniformity. Then, when various resins having different dispersibility of the fluorine atom-containing compound were examined, the resin of the layer containing the fluorine atom-containing compound in the photosensitive layer of the present invention was at least poly (n-) represented by the following general formula (1).
It has been found effective to use a resin containing a repeating structural unit of (methyl) styrene (n = α, β, 2.3.4).

[0015]

Embedded image In the formula, R ₁ , R ₂ and R ₃ represent a hydrogen atom or a methyl group. Provided that R ₁ , R ₂ and R ₃ are simultaneously hydrogen atoms
Never.

Specific examples of the fluorine atom-containing compound include:
Tetrafluoroethylene, hexafluoropropylene,
Trifluoroethylene, chlorotrifluoroethylene,
Polymers such as vinylidene fluoride, vinyl fluoride, and perfluoroalkyl vinyl ether, and copolymers thereof are used. Further, a fluorine atom-substituted ferrene,
Graphite-structured fluorocarbon, fluorine-substituted oils and the like are also used. Further, an inorganic fluoride or the like is also used.
When the fluorine atom-containing compound is a solid fine powder, the particle size is preferably in the range of 0.005 to 2.5 μm, and in the case of a polymer, the molecular weight is preferably in the range of 3,000 to 10,000,000. A more preferable range of the particle size is 0.01 to
The range is 0.7 μm. In the case of a fluorine atom-containing compound as a solid fine powder, the compound is dispersed as a photosensitive layer composition together with the polystyrene resin having the above structure. Examples of the dispersion method include a sand mill, a ball mill, a roll mill, a homogenizer,
Nanomizer, paint shaker, ultrasonic wave, etc. are used. At the time of dispersion, a fluorine-based surfactant, a graft polymer, a coupling agent, or the like may be additionally used. The content of the fluorine atom-containing compound is preferably 5 to 75% by weight of the layer to be contained.

The photosensitive layer of the present invention has a single layer or a laminated structure. In the case of a single-layer structure, generation and movement of photocarriers are performed in the same layer. In the case of a stacked structure, a charge generation layer that generates photocarriers and a charge transport layer in which carriers move are stacked. The surface layer may be formed on either the charge generation layer or the charge transport layer. Single layer photosensitive layer
A thickness of 100 μm is preferred, more preferably 10-6
0 μm. The charge generating material and the charge transporting material preferably contain 20 to 80% by weight, more preferably 30 to 70% by weight.
% By weight. In the laminated photoreceptor, the thickness of the charge generation layer is preferably from 0.001 to 6 μm, more preferably from 0.01 to 2 μm. The amount of charge generating material is preferably from 10 to 100% by weight, more preferably from 40 to 100% by weight. The thickness of the charge transport layer is preferably 5 to 100.
μm, more preferably 10 to 60 μm. The amount of charge transport material is preferably 20-80% by weight, more preferably 30-70% by weight. As the charge generating material used in the present invention, a phthalocyanine pigment, a polycyclic quinone pigment, an azo pigment, a perylene pigment, an indigo pigment, a quinacridone pigment, an azulhenium salt dye, a squarylium dye,
Cyanine dye, pyrylium dye, thiopyrylium dye,
Xanthene dyes, quinone imine dyes, triphenylmethane dyes, styryl dyes, selenium, selenium-tellurium, amorphous silicon, cadmium sulfide, and the like. Examples of the charge transport material used in the present invention include pyrene compounds, carbazole compounds, hydrazone compounds, N, N-
Dialkylaniline compounds, diphenylamine compounds,
Examples include triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, stilbene compounds, and the like.

In the electrophotographic photosensitive member of the present invention, a protective layer may be laminated on the photosensitive layer. The thickness of the protective layer is preferably 0.01 to 20 μm, more preferably 0.1 to 1 μm.
0 μm. The protective layer includes the above-described charge generation material or charge transport material, iron, copper, nickel, aluminum, titanium, tin, antimony, indium, lead, zinc, gold,
Metals such as silver and oxides, nitrides, salts, and alloys thereof, and conductive materials such as carbon may be contained. The conductive support used in the electrophotographic photoreceptor of the present invention is iron, copper,
Nickel, aluminum, titanium, tin, antimony,
Metals and alloys such as indium, lead, zinc, gold, and silver, or oxides, carbons, and conductive resins thereof can be used. The shapes include a cylindrical shape, a belt shape, and a sheet shape. The conductive material may be molded, but may be applied as a paint or may be deposited. An undercoat layer may be provided between the conductive support and the photosensitive layer. The undercoat layer is mainly made of a binder resin, but may contain the conductive material or the acceptor. As the binder resin for forming the undercoat layer, polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, polyamideimide, polysulfone, polyallylether, polyacetal, nylon, phenolic resin, acrylic resin The method for producing the electrophotographic photoreceptor of the present invention, which includes silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, butyral resin, and the like, employs methods such as vapor deposition and coating. For coating, a bar coater, knife coater, roll coater, attritor, spray, dip coating, electrostatic coating, powder coating and the like are used.

[0019]

The present invention will be described below with reference to examples. [Example 1] 5 parts by weight of conductive titanium oxide (tin oxide, antimony oxide coat, average primary particle size 0.4 μm), high resistance titanium oxide (alumina coat, average primary particle size 0.4 μm)
m) 5 parts by weight, phenol resin precursor (resole type) 1
0 parts by weight, 10 parts by weight of methanol, and 10 parts of butanol
After the weight part was dispersed in a sand mill, it was applied by dip coating to an aluminum cylinder having an outer diameter of 80 mm and a length of 360 mm, and cured by heating to provide a conductive layer having a volume resistance of 5 × 10 ⁹ Ωcm and a thickness of 20 μm. Next, 3 parts by weight of a methoxymethylated nylon (30% methoxymethylated drug) represented by the following compound 1 <Compound 1>

[0020]

Embedded image 6/66/610/12 quaternary copolymer nylon 9 parts by weight,
And 150 parts by weight of isopropanol were mixed and dissolved, followed by dip coating on the conductive layer to provide a 1 μm undercoat layer. Next, 10 parts by weight of an azo pigment of the following compound 2, <Compound 2>

[0021]

Embedded image Poly (vinyl acetate-vinyl alcohol-vinyl benzal) copolymer of the following compound 3 (molecular weight: 8,000
0) 5 parts by weight, <Compound 3>

[0022]

Embedded image And 700 parts by weight of cyclohexanone were dispersed in a sand mill, and this dispersion was applied by dip coating on the undercoat layer.
A 0.05 μm charge generation layer was obtained.

10 parts by weight of a triphenylamine compound of the following compound 4, <Compound 4>

[0024]

Embedded image Compound 5 polycarbonate resin (bisphenol Z,
(Molecular weight Mw 25000) 10 parts by weight, <Compound 5>

[0025]

Embedded image 50 parts by weight of monochlorobenzene and dichloromethane 2
5 parts by weight were dispersed by a sand mill, and the resulting charge generation layer was applied by dip coating and dried with hot air to provide a 20 μm charge transport layer.

3 parts by weight of polytetrafluoroethylene fine particles (average primary particle size 0.22 μm, molecular weight Mw 400,000, emulsion polymerization product), 7 parts by weight of poly (α-methyl) styrene (molecular weight Mw 45,000) of the following compound 6 , <Compound 6>

[0027]

Embedded image Monochlorobenzene 150 parts by weight, dichloromethane 50
Parts by weight were dispersed by a sand mill, spray-coated on the charge transport layer and dried with hot air to provide a 1.5 μm protective layer.

Comparative Example 1 A photoreceptor was obtained in the same manner as in Example 1, except that a polycarbonate resin of the following compound 7 (Polycarbo Z, molecular weight 25,000) was used as the protective layer resin. <Compound 7>

[0029]

Embedded image

[Comparative Example 2] In Example 1, the photosensitive member without the protective layer was used as the photosensitive member of Comparative Example 2.

<Dispersibility of Fluorine Atom-Containing Compound> The surface states of the protective layers of Example 1 and Comparative Example 1 were observed with an electron microscope. As shown in FIG. 1, in Example 1, a state in which polytetrafluoroethylene particles were uniformly dispersed was observed, but in Comparative Example 1, the polytetrafluoroethylene particles were aggregated, and the apparent particle size was reduced. Example 1
It is observed that the size is considerably larger than that of.

<Scattered Image of Laser Spot> The protective layers of Example 1 and Comparative Example 1 were similarly formed on a slide glass, and a semiconductor laser (wavelength: 672 nm, spot diameter: 35 × 65 μm) was applied from the surface to the interface between the protective layer and the glass. From 20μ
Irradiation was performed after focusing on the rear side, and a laser spot image 20 μm rearward from the interface between the protective layer and the glass was observed from the back surface using an objective lens. Spot image is CCD on objective lens
Connected camera and output video. As shown in FIG. 2, the protective layer of Example 1 reproduced a spot image almost equivalent to an aerial image, but the protective layer of Comparative Example 1 was granular due to scattering of laser light due to aggregation of polytetrafluoroethylene fine particles. The spot image was disturbed in nature, and it was presumed that this also had an effect on the actual image. The evaluation of the image will be described later.

<Contact Angle> The contact angle of the photoreceptor surface to pure water was compared with a drop-type contact angle meter (manufactured by Kyowa Interface Science). As a result, the contact angles of the photoreceptors of Example 1 and Comparative Example 1 were as large as 108 degrees and a low energy surface was obtained, whereas Comparative Example 2 was as small as 79 degrees and a low energy surface was not obtained.

<Image> Image evaluation was performed using the electrophotographic apparatus shown in FIG. This electrophotographic apparatus can be used as an output device such as a copying machine, a printer, a facsimile, and the like. The image forming process is basically performed in the order of charging, exposure, development, transfer, cleaning, and charge elimination. First, a charge is applied to the surface of the photoreceptor 1 by a charger 3 such as a corotron or a scorotron, and then a reading device such as a CCD is used.
Alternatively, a small light image in the form of dots is irradiated onto the photoconductor from a light source 5 such as a laser, an LED, or a liquid crystal shutter controlled by information processing such as a computer and a digital image signal sent from the storage medium 4. The light image generates charge carriers in the photoreceptor and erases the surface charge of the photoreceptor to form a minute electrostatic latent image in the form of dots.
After the electrostatic latent image is formed, it is developed by the developing device 6. The image developed by the developer is transferred to a transfer material such as transfer paper in a transfer step. In order to transfer the developer from the photoreceptor onto the transfer material, a corotron, a scorotron, a conductive brush, a conductive roller, or the like is mainly used by an electrostatic force having a polarity opposite to that of the developer. At the same time, a pressure member may be used in combination to impart a transfer effect by pressure. The residual developer after the transfer is removed by cleaning. As a cleaning method, along with space saving of the device,
In order to realize a simpler device configuration, it is desirable to employ the blade cleaning 9. The blade cleaning has a simple configuration in which a plate-like elastic member such as polyurethane is abutted on the photoconductor in the generatrix direction. The blade cleaning contact direction is the forward direction with the blade tip facing the photoconductor rotation direction, the counter direction with the blade tip facing in the opposite direction to the rotation direction of the photoconductor, and the case where the photoconductor and the blade are perpendicular. There is. Further, not only a single blade but also a plurality of blades can be used in combination. Further, a cleaning brush, a web, a magnetic brush, and the like may be additionally used. Spot diameter 3 on the electrophotographic apparatus
An image was evaluated by mounting a semiconductor laser of 5 × 65 μm and a wavelength of 672 nm. The output of the semiconductor laser was controlled as a 400 dpi dot-like output by pulse width modulation, and a halftone solid image of 0.3 was output by a reflection type Macbeth densitometer. In the photoconductors of Example 1 and Comparative Example 2, a uniform and smooth halftone image was obtained. On the other hand, in the photoconductor of Comparative Example 1, an uneven image was formed, and the laser spot was disturbed due to scattering. Seemed to be.

<Transfer Efficiency> The transfer efficiency of each photosensitive member was measured using the electrophotographic apparatus shown in FIG. The measurement was performed by measuring the developer after transfer on the transfer material and the developer remaining after transfer on the photoreceptor as reflection densities using a reflection type Macbeth densitometer. The photoconductors of Example 1 and Comparative Example 1 exhibited high transfer efficiencies of 94% and 95%, respectively, due to the effect of the low energy surface, whereas the photoconductor of Comparative Example 2 had a low transfer efficiency of 83%.

<Load Torque> Using the electrophotographic apparatus shown in FIG. 3, the load torque at the time of driving each photosensitive member was measured. The measurement was performed by monitoring the current of the photosensitive drum motor when the apparatus was driven, and the result was converted into torque. Example 1
The photoreceptor of Comparative Example 1 had a small load torque due to the effect of the low energy surface, whereas the photoreceptor of Comparative Example 2 had a large load torque.

<Durability of Actual Machine> Each photosensitive member was durable using the electrophotographic apparatus shown in FIG. When the durability of 20,000 sheets was performed, the photoreceptor of Comparative Example 2 became unusable due to significant white background image fog at 13,000 sheets, but the photoreceptor of Example 1 was good after 20,000 sheets. Image. Further, the amount of abrasion of the photoconductor after the endurance was remarkably smaller in the sample of Example 1 than in Comparative Example 1. Further, transfer failure after 1,000 sheets was examined under the same conditions. Evaluation was performed on a halftone image having a reflection density of 0.6 after 1,000 sheets. The photoconductor of Comparative Example 2 was unevenly uneven due to poor transfer. However, the photoconductor of Example 1 had a uniform height. It was a high quality halftone image. No transfer failure occurred in the photoreceptor of Comparative Example 2, but roughness due to scattering was still observed.

Example 2 A photoconductor was prepared in the same manner as in Example 1, except that a poly (4-methyl) styrene resin of the following compound 8 (molecular weight Mw: 45,000) was used as the protective layer resin. <Compound 8>

[0039]

Embedded image In the polytetrafluoroethylene fine particles dispersed in the resin of Compound 8, no aggregation of the particles was observed, and almost no scattering of the laser spot was observed. A lower energy surface was realized than the measurement of the contact angle, showing good transfer efficiency and low load torque. A uniform and smooth halftone image was obtained, and a good image was maintained without causing fogging or transfer failure even in durability.

[0040]

According to the present invention, the photoreceptor of the present invention comprises a poly (n-methyl) styrene resin (n = α, β,
By dispersing the particles in (2, 3, 4), the fluorine-containing compound fine particles can be dispersed without causing any aggregation, so that light scattering between the two phases is prevented, and faithful latent image reproduction and uniform image reproduction are realized. . Further, in order to provide a low energy surface, it was possible to maintain a high uniform transfer efficiency and a good uniform image free from transfer failure even after durability. Furthermore,
The drive load torque has been reduced, and a photoconductor without durable fog has been realized.

[Brief description of the drawings]

FIG. 1 is an electron micrograph of the surfaces of Example 1 and Comparative Example.

FIG. 2 shows laser spot images of Example 1 and Comparative Example 1.

FIG. 3 is an electrophotographic apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 2 Transfer electrification 3 Primary electrification 4 Storage medium, reading device 5 Light source 6 Developing device 7 Feeding 8 Fixing 9 Cleaning blade

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-123063 (JP, A) JP-A-63-43162 (JP, A) JP-A-4-284459 (JP, A) JP-A-5- 257315 (JP, A) JP-A-5-181299 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/00-5/16

Claims (6)

(57) [Claims] 1. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the surface layer of the photoreceptor has a fluorine atom-containing compound, and a compound represented by the following general formula (1): (Wherein R ₁ , R ₂ and R ₃ represent a hydrogen atom or a methyl group, provided that R ₁ , R ₂ and R ₃ are simultaneously a hydrogen atom.
Never. An electrophotographic photosensitive member comprising a resin containing a repeating structural unit of poly (n-methyl) styrene (n = α, β, 2,3,4) 2. The electrophotographic photoreceptor according to claim 1, wherein the fluorine atom-containing compound has a fluorine atom weight ratio of 30 to 80%. 3. The electrophotographic photosensitive member according to claim 1, wherein the fluorine atom-containing compound is one or a mixture of two or more compounds selected from a compound in which a graphite structure is substituted with a fluorine atom and a compound in which a hydrocarbon is substituted with a fluorine atom. body. 4. The electrophotographic photosensitive member according to claim 1, wherein said fluorine atom-containing compound is fine particles having an average particle diameter of 0.003 to 2.5 μm. 5. An electrophotographic apparatus having an exposure means for forming a dot-shaped electrostatic latent image on an electrophotographic photosensitive member, wherein the photosensitive member has a photosensitive layer on a conductive support. The surface layer of the photoreceptor has a fluorine atom-containing compound and the following general formula (1): (Wherein R ₁ , R ₂ and R ₃ represent a hydrogen atom or a methyl group, provided that R ₁ , R ₂ and R ₃ are simultaneously a hydrogen atom.
Never. An electrophotographic apparatus comprising a resin containing a repeating structural unit of poly (n-methyl) styrene (n = α, β, 2,3,4) represented by the following formula: 6. An exposure means for forming a dot-shaped electrostatic latent image, the exposure means comprising:
The electrophotographic apparatus according to claim 5, wherein the spot diameter is not more than m.