JP2003029429A - Electrophotographic photoreceptor and image forming method and image forming apparatus each using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which suppresses black spots, stabilizes electrification ability in repetitive use and can give good image quality over a long period of time and to provide an image forming method and an image forming apparatus each using the photoreceptor. SOLUTION: In the electrophotographic photoreceptor obtained by stacking at least a charge generating layer and a charge transporting layer in order on a support, the charge generating layer contains an ethylene copolymer.

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 in copying machines, printers and the like, an image forming method and an image forming apparatus using the same.

[0002]

2. Description of the Related Art In recent years, with the development of electronic information devices, the demand for printers using semiconductor lasers or LEDs as light sources has increased, and the demand for high-speed, high-quality copying machines has also increased.

By the way, in the printing of a character image that is often used normally, the area of the character portion is at most about 5% and the rest is a white background. When printing out such a print, it would be extremely disadvantageous in view of the life of the laser light source if the light was applied to the portion corresponding to the white background as in the conventional analog copying machine. Therefore, in these printers, a so-called reversal development process is usually performed in which light is applied to a character corresponding portion to lower the surface potential of the character, and a bias is applied to increase the potential of the character corresponding portion to adhere toner when developing. It is being appreciated.

Generally, the photosensitive member undergoes potential fluctuations such as a decrease in electric resistance of the photosensitive member under a high temperature and high humidity environment and a decrease in charging property. In many cases, laser printers, which have come to be widely used at present, perform image formation by reversal development after digital exposure as described above. In this image forming method by reversal development, the deterioration of the charging property appears as an image fog. Therefore, if the charging property is deteriorated, the image quality is significantly deteriorated.

Further, this process has a drawback that black spot-like image defects (black spots) are likely to occur. What is the cause of black spots is that the electric potential of a minute area on the surface of the photoconductor drops,
In normal development (regular development), white spots are generated on a black background, and in this case, it is not very noticeable. However, in the reversal development, black spots (black spots) appear on a white background, so that the image is significantly impaired.

What causes black spots is a decrease in chargeability of a minute area on the surface of the photoconductor (in other words, a decrease in chargeability locally generated on the surface of the photoconductor), which is caused by a defect of the aluminum base of the photoconductor. It is considered that this is caused by injection of positive charges into the photosensitive layer, poor dispersion of the pigment, mixing of foreign matter, or the like. As described above, this part is not widely used in image formation by analog exposure and regular development, which have been widely adopted.
It becomes a white spot and hardly affects the quality. However, in the case of reversal development, black spot-like image defects (hereinafter also referred to as black spots) appear. Therefore, even if the chargeability of a minute area where image trouble does not occur in the regular development that has been widely performed until now, black spots are remarkably generated in the reversal development, and the image quality is remarkably deteriorated.

[0007]

The present invention has been made to solve the above problems.

That is, the object of the present invention is to suppress black spots,
An object of the present invention is to provide an electrophotographic photosensitive member capable of stabilizing the chargeability during repeated use and obtaining good image quality for a long period of time, an image forming method using the same, and an image forming apparatus.

[0009]

Means for Solving the Problems As a result of intensive studies made by the present inventors, the resistance of CGL can be reduced by adding an ethylene-based copolymer, which is a high-resistivity resin, to a charge generation layer (also referred to as CGL). It has been found that the above can be suppressed and the object of the present invention can be achieved.

The resin used for CGL may be used as a mixture with the resin of the present invention and another resin, for example, butyral resin which is a binder resin for CGL which has been often used conventionally. However, the content of ethylene-based copolymer is 5
If it is less than mass%, the effect will be reduced.

That is, the object of the present invention is achieved by adopting any one of the following constitutions.

[1] An electrophotographic photoreceptor comprising a support and at least a charge generation layer and a charge transport layer, which are laminated in this order, wherein the charge generation layer contains an ethylene copolymer. Photoconductor.

[2] The electrophotographic photosensitive member according to [1], wherein the content of the ethylene copolymer in the charge generation layer is 5% by mass or more.

[3] The electrophotographic photosensitive member according to [1], wherein the charge generating substance in the charge generating layer is titanyl phthalocyanine.

[4] An image forming method characterized by using the electrophotographic photosensitive member according to any one of [1] to [3] to form an image by a reversal development method.

[5] An image forming method characterized by forming an electrostatic latent image on the electrophotographic photosensitive member according to any one of [1] to [3] by a digital method.

[6] Using the electrophotographic photosensitive member according to any one of [1] to [3], charging, exposure, development, transfer,
An image forming apparatus characterized in that an image is formed by repeating separation and cleaning steps.

[0018]

DETAILED DESCRIPTION OF THE INVENTION The components and embodiments used in the present invention will be further described.

The ethylene copolymer used in the present invention is a copolymer resin produced by using an alkylene monomer such as ethylene and propylene and another monomer.

As the copolymerization component, for example, vinyl acetate, acrylic acid, methacrylic acid, acrylic acid ester,
Methacrylic acid ester, vinyl alcohol, vinyl chloride, vinylidene chloride, vinyl fluoride, acrylonitrile,
Examples thereof include vinyl acetal, maleic acid, maleic anhydride, hydroxystyrene, acrylamide and vinylpyrrolidone.

Among them, the preferred alkylene monomer is ethylene, and preferred copolymerization components include vinyl acetate, acrylic acid, methacrylic acid, maleic acid, acrylic acid ester and methacrylic acid ester.

In the ethylene-based copolymer, the proportion of the above-mentioned copolymerization component is 5 to 50% by mass of the whole (100% by mass).
It is desirable to be set to, and it is more desirable to set to 10 to 40 mass%. If the proportion of the copolymerization component is less than 5% by mass, the solubility, adhesiveness, coatability, etc. will be reduced, and if the proportion of the copolymerization component is more than 50% by mass, the blocking function will be greatly reduced.

As a measure of the molecular weight of this copolymer, MFR
(Melt flow rate according to JIS / K6730 / 1981) is preferably 2 to 500 g / 10 min.

The main ethylene-based copolymer is ethylene-vinyl acetate-methacrylic acid copolymer (ELVAX42).
60 DuPont) and ethylene-vinyl acetate copolymer (EVAFLEX 45X manufactured by Mitsui DuPont Polychemical).

As other examples of the ethylene-based copolymer resin, JP-A-3-48855 and JP-A-2-183 are cited.
There is a compound described in Japanese Patent No. 265.

The following resins may be mentioned as specific examples of such ethylene copolymers.

Sumitate HE-10 (Sumitomo Chemical Co., Ltd.) KA-10 KA-20 KA-31 KC-10 KE-10 Acrylift WH-302 WK-402 WM-506 Evaflex A-703 (Mitsui DuPont Polychemical Co., Ltd.) ) A-704 EV150 Yucaron A-200K (manufactured by Mitsubishi Chemical Corporation) A-210M A-210S A-220M A-500W A-510W Primacall 5980 (manufactured by Dow Chemical Co.) NUC-6570 6070 (manufactured by Nippon Unicar) MB -730 870 There are no particular restrictions on the other constituent elements of the photoreceptor of the present invention, and known ones can be used.

As the charge generating substance (CGM), for example, polycyclic quinone compound, condensed polycyclic compound, copper phthalocyanine, titanyl phthalocyanine crystal type, gallium phthalocyanine, metal-free phthalocyanine, etc. can be used. Among these, titanyl phthalocyanine is particularly preferable. Further, the number of compounds is not limited to one, and a plurality of compounds may be used together depending on the purpose.

The ratio of pigment to binder resin is 10/1 to
1/5 is preferable. The thickness of the charge generation layer is 0.2 to 5.0.
μm is preferable, and 0.5 to 3.0 μm is particularly preferable.

The layer structure of the electrophotographic photosensitive member of the present invention is not particularly limited as long as it functions as a so-called function separation type photosensitive member. That is, it is a photoreceptor in which an undercoat layer (UCL) is provided on a conductive substrate as needed, and a charge generation layer (CGL) and a charge transport layer (CTL) are provided in that order on the underlayer. A structure in which a protective layer (OCL) is applied on the top can be adopted.

Known techniques can be used for both the undercoat layer (UCL) and the charge transport layer (CTL).

As the binder resin contained in the undercoat layer (UCL), any resin such as polycarbonate resin, polyester resin, polystyrene resin, acrylic resin, polyvinyl chloride resin, polyvinyl butyral resin or polyamide resin can be selected. Alternatively, a so-called ceramic undercoat layer obtained by condensing a hydroxide of a metal such as zirconia, titanium or silane may be used.

Examples of the charge transport material contained in the charge transport layer (CTL) include triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds and butadiene compounds.

Typical charge transport materials are listed below.

[0035]

[Chemical 1]

[0036]

[Chemical 2]

[0037]

[Chemical 3]

[0038]

[Chemical 4]

As the binder resin contained in the charge transport layer, any resin such as polycarbonate resin, polyester resin, polystyrene resin, acrylic resin, polyvinyl chloride resin, polyvinyl butyral resin, polyamide resin can be selected.

The mass ratio of the charge transport material to the binder resin in the charge transport layer is preferably 3: 1 to 1: 3. The thickness of the charge transport layer is preferably 5 to 50 μm, particularly preferably 10 to 40 μm.

When the protective layer is added to the present invention, the thickness of the protective layer is preferably 0.1 to 10 μm, and particularly preferably 0.2 to.
It is 7 μm, more preferably 0.5 to 5 μm.

As the protective layer, well-known organic polymers such as polycarbonate and polyester can be used, and an inorganic polymer layer containing a so-called siloxane bond (silicon hard coat layer) may be used. Further, fine particles may be included if necessary.

Next, as a coating processing method for producing the electrophotographic photosensitive member of the present invention, dip coating, spray coating,
A coating method such as circular amount control type coating is used, but the coating process on the upper layer side of the photosensitive layer does not dissolve the lower layer film as much as possible, and in order to achieve uniform coating process, spray coating or circular amount control type ( A circular slide hopper type is a typical example. It is preferable to use a coating processing method such as coating. It is most preferable to use the circular amount regulating type coating processing method for the protective layer. The circular amount control type coating is described in detail, for example, in JP-A-58-189061.

Next, the image forming method and the image forming apparatus will be described. FIG. 1 shows the image forming method 1 according to the present invention.
FIG. 3 is a sectional view of an image forming apparatus as an example.

In FIG. 1, reference numeral 50 designates a photosensitive drum (photosensitive member) which is an image bearing member, and is a photosensitive member having an organic photosensitive layer coated on the drum, which is grounded and driven and rotated clockwise. 52
Is a scorotron charger, which applies uniform charging to the peripheral surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, in order to eliminate the history of the photosensitive member in the pre-image formation, the pre-charging pre-exposure unit 51 using a light emitting diode or the like may be used to remove the charge on the peripheral surface of the photosensitive member.

After uniformly charging the photosensitive member, the image exposing device 53 performs image exposure based on the image signal. The image exposure device 53 in this figure uses a laser diode (not shown) as an exposure light source. The photosensitive drum is scanned by the light whose optical path is bent by the reflecting mirror 532 through the rotating polygon mirror 531, the fθ lens, etc., and an electrostatic latent image is formed.

The electrostatic latent image is then developed by the developing device 54. Here, the reversal development process of the present invention is the charger 52.
The surface of the photoconductor is uniformly charged, and the image-exposed region, that is, the exposed portion potential (exposed region) of the photosensitive member is visualized by a developing process (means). On the other hand, the unexposed portion potential is not developed by the developing bias potential applied to the developing sleeve 541.

At the periphery of the photosensitive drum 50, a developing device 54 containing a developer composed of toner and carrier is provided, and development is carried out by a developing sleeve 541 containing a magnet and holding the developer and rotating. . Developing unit 54
The inside is composed of developer agitating / conveying members 544 and 543, a conveyance amount regulating member, and the like, and the developer is agitated and conveyed to be supplied to the developing sleeve, and the supply amount is controlled by the conveyance amount regulating member. . The amount of the developer conveyed varies depending on the linear velocity of the applied organic electrophotographic photoreceptor and the specific gravity of the developer, but is generally in the range of ^{20 to} 200 mg / cm ² .

The developer is not particularly limited, but, for example, a carrier in which the above-mentioned ferrite is used as a core and an insulating resin is coated around the core, a coloring agent such as carbon black which is mainly composed of the above-mentioned styrene acrylic resin, and a charge are charged. Colored particles consisting of a control agent and low molecular weight polyolefin,
The toner contains silica, titanium oxide and the like as external additives.

The developer has its layer thickness regulated by the transport amount regulating member and is transported to the developing zone for development. At this time, a DC bias is applied between the photosensitive drum 50 and the developing sleeve 541, and if necessary, an AC bias voltage is applied to develop. Further, the developer is developed in a state of being in contact with or non-contacting with the photoreceptor. The potential of the photoconductor is measured, for example, by providing a potential sensor 547 above the developing position as shown in FIG.

After the image formation, the recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 57 when the transfer timing is adjusted.

In the transfer area, the transfer electrode (transfer device) 58 provided on the peripheral surface of the photosensitive drum 50 operates in synchronization with the transfer timing, and the toner image is transferred to the recording paper P that has been fed. It

Next, the recording paper P is separated by a separating electrode (separator) 59.
The charge is removed by the toner, and the toner is separated from the peripheral surface of the photosensitive drum 50 and conveyed to the fixing device 60. The heat roller 601 and the pressure roller 602 heat and pressurize the toner to fuse the toner, and then the discharge roller 61 is used to external the device. Is discharged to.

On the other hand, the photosensitive drum 50 after separating the recording paper P removes and cleans the residual toner by the pressure contact of the blade 621 of the cleaning device 62, and again the pre-charging exposure unit 51.
After the charge is removed by the charger and the charger 52 is charged, the next image forming process starts.

Reference numeral 70 denotes a detachable process cartridge in which a photoconductor, a charger, a transfer device, a separator and a cleaning device are integrated.

The image forming method of the present invention is an electrophotographic copying machine,
It is generally applicable to electrophotographic image forming apparatuses such as laser printers, LED printers and liquid crystal shutter printers. Further, it can be widely applied to devices such as displays, recording, light printing, plate making and facsimiles to which electrophotographic technology is applied.

[0057]

EXAMPLES Next, the constitution and effects of the present invention will be explained in the form of examples, but of course the embodiments of the present invention are not limited to these.

<< Preparation of Photoreceptor 1 >><ConductiveSubstrate> An aluminum cylindrical tube having a diameter of 80 mm was cut by a lathe.

The machined cylindrical tube is washed with cleaning water containing a surfactant and then with pure water, and dried by blowing air in a clean room to remove foreign matters adhering to the cylindrical tube and 1 ”was produced.

<Formation of Intermediate Layer> Polyamide resin “CM8000” (manufactured by Toray) 10 parts by mass Titanium oxide “SMT500SAS” (manufactured by Teika) 20 parts by mass Methanol 80 parts by mass 1-butanol 20 parts by mass Methanol and 1-butanol Polyamide resin "CM8000" was dissolved in the mixed solution of, and titanium oxide "SMT500SAS" was mixed in the solution, and the mixed solution was dispersed with a sand grinder for 5 hours to prepare an intermediate layer coating solution.
This coating liquid is dip-coated on the above-mentioned "base 1", and the temperature is 100 ° C
"Middle layer 1" with a film thickness of 1.5 μm
Was formed.

<Formation of Charge Generation Layer> Y-type titanyl phthalocyanine compound 90 parts by mass Ethylene-vinyl acetate copolymer resin “EVAFLEX 45X” (manufactured by Mitsui DuPont Polychemical Co., Ltd.) 90 parts by mass Methyl ethyl ketone 1000 parts by mass Toluene 1000 parts by mass Methyl ethyl ketone The resin was dissolved in a mixed solution of toluene and toluene, and a Y-type titanyl phthalocyanine compound was mixed with this dissolved solution to prepare a mixed solution. This mixed solution was dispersed by a sand grinder for 10 hours to prepare a charge generation layer coating solution.
This coating solution was dip-coated on the "intermediate layer 1" to form a "charge generation layer 1" having a film thickness of 0.25 µm.

<Formation of Charge Transport Layer> 300 parts by weight of charge transport material Bisphenol Z-type polycarbonate “Z-200” (manufactured by Mitsubishi Gas Chemical Co., Inc.) 500 parts by weight 1,2-dichloroethane 4000 parts by weight Bisphenol in 1,2-dichloroethane A charge-transporting substance was dissolved in a solution in which Z-type polycarbonate “Z-200” was dissolved to prepare a coating solution for charge-transporting layer.

This coating solution is dip-coated on the "charge generation layer 1" and dried at 100 ° C. for 1 hour to give a film thickness of 25 μm.
The "charge transport layer 1" of m was formed to prepare the "photoreceptor 1".

<< Preparation of Photoreceptor 2 >> In the preparation of "Photoreceptor 1", ethylene-vinyl acetate copolymer resin EVAFLEX 45X of "charge generation layer 1" was replaced with ethylene-vinyl acetate-methacrylic acid copolymer resin " ELVAX426
"Photoreceptor 2" was prepared in the same manner as "Photoreceptor 1", except that it was changed to "0" (manufactured by DuPont).

<< Preparation of Photoreceptor 3 >> In the preparation of "Photoreceptor 1", ethylene-vinyl acetate copolymer resin EVAFLEX 45X of "charge generation layer 1" was replaced with butyral resin "ESREC BX-1" (manufactured by Sekisui Chemical Co., Ltd.). ) 45 parts by mass, ethylene-vinyl acetate copolymer resin "EVAFLEX 45X" 4
"Photoreceptor 3" was prepared in the same manner as "Photoreceptor 1" except that the amount was changed to 5 parts by mass.

<< Preparation of Photoreceptor 4 >> In preparation of "Photoreceptor 1", ethylene-vinyl acetate copolymer heavy resin EVAFLEX 45X of "charge generation layer 1" was replaced with butyral resin "ESREC BX-1" 70 parts by mass, ethylene. -"Photoreceptor 4" was prepared in the same manner as "Photoreceptor 1", except that the vinyl acetate copolymer resin "EVAFLEX 45X" was changed to 20 parts by mass.

<< Preparation of Photoreceptor 5 >> In the preparation of "Photoreceptor 1", the "photoreceptor 1" was used except that the support was changed to the "base 2" which was anodized and the "intermediate layer 1" was not provided. "Photoreceptor 5" was prepared in the same manner as "1".

<< Preparation of Photoreceptor 6 >> In the preparation of Comparative Example "Photoreceptor 1" other than the present invention, the ethylene-vinyl acetate copolymer resin EVAFLEX 45X of "Charge generation layer 1" was prepared.
A “photoreceptor 6” was prepared in the same manner as the “photoreceptor 1” except that the butyral resin “ESREC BX-1” was used.

<Evaluation> “Photoreceptors 1 to 1 produced as described above
6 ”is a reversal development type digital copying machine“ Konica ”
7060 "(manufactured by Konica) to form an image,
The black spots and the image quality after printing 10,000 sheets were visually evaluated.

Black spots are high temperature and high humidity (30 ° C, 80% R
When printing was performed under H), the degree of black spots generated on the white image was visually evaluated.

The image quality after printing 10,000 sheets was evaluated by visually observing whether the image sample produced after printing 10,000 sheets had defective image quality such as black spots and fog.

[0072]   Visual evaluation criteria     Black spot ○: No occurrence                               Δ: Occurs slightly, but practically no problem                               X: Occurred and there is a problem in practical use     Image quality after printing 10,000 sheets ○: No defects occurred                               Δ: A slight defect occurs, but there is no problem in practical use                               X: defective, practically problematic The characteristics of the photoconductors 1 to 6 are shown in Table 1.

[0073]

[Table 1]

It is understood that the photoconductors 1 to 5 in the present invention are good in both characteristics, but the photoconductor 6 other than the present invention has problems in both properties.

[0075]

INDUSTRIAL APPLICABILITY According to the present invention, an electrophotographic photosensitive member capable of suppressing black spots, stabilizing chargeability upon repeated use, and obtaining good image quality for a long period of time, and an image formation using the same. A method and an image forming apparatus can be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of an image forming apparatus as an example of an image forming method of the present invention.

[Explanation of symbols]

50 photoconductor drum (or photoconductor) 51 Pre-charge exposure unit 52 Charger 53 Image exposure device 54 Developer 541 Development sleeve 543,544 developer stirring and conveying member 547 potential sensor 57 Paper Feed Roller 58 transfer electrode 59 Separation electrode (separator) 60 fixing device 61 Paper ejection roller 62 cleaning device 70 Process cartridge

Claims (6)

[Claims] 1. An electrophotographic photosensitive member comprising at least a charge generation layer and a charge transport layer sequentially laminated on a support, wherein the charge generation layer contains an ethylene copolymer. body. 2. The electrophotographic photosensitive member according to claim 1, wherein the content of the ethylene-based copolymer in the charge generation layer is 5 or less.
An electrophotographic photosensitive member characterized by being at least mass%. 3. The electrophotographic photosensitive member according to claim 1, wherein the charge generating substance in the charge generating layer is titanyl phthalocyanine. 4. An image forming method using the electrophotographic photosensitive member according to claim 1 to form an image by a reversal development method. 5. An image forming method comprising forming an electrostatic latent image on the electrophotographic photosensitive member according to claim 1 by a digital method. 6. An image forming apparatus using the electrophotographic photosensitive member according to claim 1, wherein an image is formed by repeating charging, exposure, development, transfer / separation and cleaning steps. .