JP5266991B2 - Electrophotographic photosensitive member and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor causing no transfer memory phenomenon for a long period of time, avoiding degradation of image quality by decrease in uniformity of charging, and thereby having high durability, and to provide an image forming apparatus using the photoreceptor. <P>SOLUTION: The electrophotographic photoreceptor has a photosensitive layer on a conductive support, wherein the photosensitive layer contains a compound (A) having a structure expressed by general formula (1) by 0.04 to 3.0 mass% with respect to a charge transporting substance. In the formula, R<SB>1</SB>to R<SB>4</SB>represent hydrogen atoms or alkyl groups or aryl groups which may have a substituent; and R<SB>5</SB>and R<SB>6</SB>represent hydrogen atoms or alkyl groups or aryl groups which may have a substituent. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an electrophotographic photosensitive member and an image forming apparatus using the same.

  In recent years, there are increasing opportunities for the use of electrophotographic image forming apparatuses in both the monochrome printing field and the color printing field. In both fields of black-and-white printing and color printing, there is a strong demand for stable and high-quality images from the beginning to the end of use of an electrophotographic photoreceptor (hereinafter sometimes referred to simply as a photoreceptor). .

As a measure for this, in the process of transferring the toner image from the photoreceptor, a transfer current is applied more strongly in order to perform sufficient transfer at high speed. However, in the conventional photoconductor, when the transfer current is increased, a chargeability difference is generated in the image area and the non-image area in the photosensitive layer due to the current application during transfer, and the image density in the next cycle is affected. A so-called transfer memory is likely to occur (see, for example, Patent Document 1). In particular, since it becomes conspicuous with the fatigue of the photoreceptor, it has been very difficult to improve the durability while maintaining the image quality.
Japanese Patent Laid-Open No. 2007-10962

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

  That is, an object of the present invention is to provide an electrophotographic photosensitive member that has no transfer memory for a long period of time and does not cause image quality deterioration due to a decrease in charging uniformity, and therefore has a high durability, and an image forming apparatus using the same. There is to do.

  As a result of diligent study, the present inventor, as a method for solving the problem, by adding an appropriate amount of a compound containing a quinone methide structure represented by the general formula (1) to the charge transport material, the generation of a transfer memory can be achieved. It became clear that durability could be improved while suppressing, and the present invention was achieved.

(1)
On a conductive support an electrophotographic photosensitive member having a photosensitive layer, the photosensitive layer, a compound A having a structure represented by the following general formula (1) is, the charge transporting substance 0.04 to 3 is added so as to be 2.0 mass%, the compound B having a structure represented by the following general formula (2), it is added so as to be 0.5 to 15 wt% of the charge-transporting substance, and An electrophotographic photoreceptor , wherein a mass ratio (A / B) between the compound A and the compound B is in a range of 0.05 to 0.20 .

(In general formula (1), R _{1 to} R ₄ represent hydrogen and an alkyl group which may have a substituent, R ₅ and R ₆ represent hydrogen and an alkyl group which may have a substituent, Represents an aryl group.)

(In General Formula (2), R _{7 to} R ₁₀ represent hydrogen and an alkyl group which may have a substituent. R ₁₁ and R ₁₂ represent hydrogen and an alkyl group which may have a substituent, Represents an aryl group.)
( 2 )
The electrophotographic photosensitive member according to (1) , wherein the compound A is represented by the following general formula (3).

(Shown in the general formula (3), R _{1 3} is hydrogen, an alkyl group which may have a substituent .R ₁₄ is hydrogen, an alkyl group optionally having a substituent, an aryl group .)
( 3 )
The electrophotographic photoreceptor according to (1) or (2), wherein the electrophotographic photoreceptor is a negatively charged photoreceptor.

( 4 )
In an image forming apparatus having an exposure unit that forms an electrostatic latent image using a writing light source on an electrophotographic photosensitive member after a charging step, and a developing unit that visualizes the electrostatic latent image into a toner image.
An image forming apparatus using the electrophotographic photosensitive member according to any one of (1) to ( 3 ) as the electrophotographic photosensitive member.

  According to the present invention, it is possible to provide an electrophotographic photosensitive member having no transfer memory for a long period of time, causing no deterioration in image quality due to a decrease in charging uniformity, and therefore having a high durability, and an image forming apparatus using the same. .

  It is not clear why the configuration of the present invention makes it possible to improve the durability without causing image quality degradation due to the transfer memory, chargeability reduction, and the like, which are the problems of the present invention.

  However, it is clear that the object of the present invention can be achieved by bringing the quinone methide compound used in the present invention into a state where it is already contained in the photosensitive layer at the beginning of production, for example, by including it in a coating solution for preparing the photosensitive layer. It is a true fact.

  The quinone methide compound is a compound that is generated even in the process of deterioration of the hindered phenolic antioxidant, but it was very difficult to control the deterioration state and to make it exist in the appropriate concentration range inside the photosensitive layer.

  In particular, the compound A having the structure represented by the general formula (1) is preferably a structure having a t-butyl group at the ortho position. Furthermore, the compound B having the structure represented by the general formula (2) is contained in an amount of 0.5 to 15% by mass with respect to the charge transporting substance, and the mass ratio (A / B) of the compounds A and B is 0.05. More preferably, it is used in the range of ˜0.20.

[Compounds A and B used in the present invention]
Specific examples of the compound A represented by the general formula (1) include the following.

  These representative synthesis examples are shown below.

Example Compound A1 (Synthesis of 2,6-di-tert-butyl 4-methylene-2,5-cyclohexadien-1-one (Bull. Chem. Soc. Jpn., 64, 1434-1436) That is, 2,6-di-t-butyl-4-methylphenol B1 (10 g) was added to 2.5 equivalents of cobalt (III) acetate solution and stirred at 70 ° C. for 48 hours under a nitrogen stream. After completion of the reaction, the residue was purified by column chromatography to obtain 0.87 g (yield: 8.8%) of the target compound A1.

Synthesis of Exemplified Compound A2 (2,6-di-t-butyl 4-ethylene-2,5-cyclohexadien-1-one) 2,6-di-t-butyl-4-methylphenol B1 (10 g) Exemplified Compound A2 was synthesized in the same manner as Exemplified Compound A1, except that it was changed to 1,6-di-t-butyl-4-ethylphenol B2 (11 g).

Synthesis of Exemplary Compound A3 (4-benzylidene-2,6-di-t-butyl-2,5-cyclohexadien-1-one) 2,6-di-t-butyl-4-methylphenol B1 (10 g) Except for changing to 4-benzyl-2,6-di-t-butyl-phenol B3 (11 g), 1.14 g (yield 8.3%) of Exemplified Compound A2 was synthesized by the same synthesis method as Exemplified Compound A1. did.

  Specific examples of the compound B represented by the general formula (2) include the following.

  Compound A is preferably present in the photosensitive layer, particularly in the charge transport layer, and exhibits a particularly remarkable effect on a negatively charged photoreceptor. However, the charge transport layer and the second charge transport layer functioning as a protective layer on the charge transport layer may be laminated and contained in the second charge transport layer.

  The abundance of Compound A and Compound B in the photosensitive layer can be measured as follows.

  The photosensitive layer is peeled off from the conductive support, and the additive inside the photosensitive layer is extracted with acetone. After acetone was removed under reduced pressure, the extract was dissolved in acetonitrile, and the abundance ratio of compounds A and B to the charge transport material was measured using high performance liquid chromatography.

  The measuring equipment and conditions are as follows.

Equipment: Hitachi High-Performance Liquid Chromatograph System LaChrom Elite
Column: ODS
Column temperature: 40 ° C
Outflow solution: acetonitrile Flow rate: 1 ml / min
Detector: Diode Array Detector (multispectra)
Hereinafter, the structure of the organic photoreceptor of the present invention will be described.

[Configuration of photoconductor]
The configuration of the organophotoreceptor of the present invention is not particularly limited as long as it has the surface layer described above, and examples thereof include the following configurations.
1) A structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support. 2) A charge generation layer, a first charge transport layer and a second charge transport layer are formed as a photosensitive layer on a conductive support. 3) A structure in which a single layer containing a charge transport material and a charge generation material is formed as a photosensitive layer on a conductive support 4) A charge transport layer and a charge generation layer as a photosensitive layer on a conductive support Sequentially laminated structure 5) Structure in which a surface protective layer is further formed on the photosensitive layer of the photosensitive body of the above 1) to 5) The surface layer of the photosensitive body in the present invention is a layer in which the photosensitive body is in contact with the air interface. In the case where only a single-layer type photosensitive layer is formed on the conductive support, the photosensitive layer is a surface layer, and the single-layer or multi-layer type photosensitive layer and the surface protective layer are formed on the conductive support. When laminated, the surface protective layer is the outermost surface layer. In the present invention, the configuration 1) or 2) is most preferably used.

  Note that, regardless of the configuration of the photoreceptor of the present invention, an undercoat layer (intermediate layer) may be formed on the conductive support prior to the formation of the photosensitive layer.

  The charge transport layer means a layer having a function of transporting charge carriers generated in the charge generation layer by photoexposure to the surface of the organic photoreceptor, and the specific detection of the charge transport function is carried out between the charge generation layer and the charge transport layer. It can be confirmed by laminating a transport layer on a conductive support and detecting optical conductivity.

  Next, the layer structure of the organic photoreceptor will be described focusing on the structure of 2) above.

[Conductive support]
The conductive support used for the photosensitive member may be either a sheet or a cylinder, but a cylindrical conductive support is more preferable for designing an image forming apparatus compactly.

  Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity is within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. A support is preferred. Exceeding the range of straightness and shake makes it difficult to form a good image.

As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ωcm or less at room temperature. The conductive support of the present invention is most preferably an aluminum support. As the aluminum support, one in which components such as manganese, zinc, silicon, magnesium and the like are mixed in addition to the main component aluminum is also used.

[Middle layer]
In the present invention, it is preferable to provide an intermediate layer between the conductive support and the photosensitive layer.

  The intermediate layer used in the present invention preferably contains N-type semiconductor particles. The N-type semiconductive particle means a particle whose main charge carrier is an electron. That is, since the main charge carrier is an electron, the intermediate layer containing the N-type semiconductive particles in the insulating binder effectively blocks hole injection from the support, and from the photosensitive layer. It has the property of being less blocking against electrons.

As the N-type semiconductor particles, titanium oxide (TiO ₂ ) and zinc oxide (ZnO) are preferable, and titanium oxide is particularly preferably used.

  As the N-type semiconductor particles, fine particles having a number average primary particle size in the range of 3.0 to 200 nm are used. Particularly, 5 nm to 100 nm is preferable. The number average primary particle diameter is a measured value as an average diameter in the ferret direction by image analysis by magnifying fine particles 10,000 times by observation with a transmission electron microscope, observing 100 primary particles randomly. N-type semiconducting particles having a number average primary particle size of less than 3.0 nm are difficult to uniformly disperse in the intermediate layer binder, and tend to form aggregated particles. Is likely to occur. On the other hand, N-type semiconducting particles having a number average primary particle size larger than 200 nm tend to make large irregularities on the surface of the intermediate layer, and the dot image tends to deteriorate through these large irregularities. In addition, the N-type semiconductive particles having a number average primary particle size larger than 200 nm are likely to precipitate in the dispersion and easily generate aggregates. As a result, the dot image tends to deteriorate.

  The titanium oxide particles have anatase, rutile, brookite, and amorphous forms as crystal forms. Among them, the rutile type titanium oxide pigment or the anatase type titanium oxide pigment has a rectifying property of charge passing through the intermediate layer. In other words, the mobility of electrons is increased, the charging potential is stabilized, the residual potential is prevented from increasing, and the dot image is prevented from deteriorating, which is most preferable as the N-type semiconductor particles of the present invention. .

  N-type semiconductive particles are preferably surface-treated with a polymer containing methylhydrogensiloxane units. The molecular weight of the polymer containing the methyl hydrogen siloxane unit is 1000 to 20000, and the surface treatment effect is high. As a result, the rectifying property of the N-type semiconductor particles is improved, and the N-type semiconductor particles are contained. By using the intermediate layer, the occurrence of black spots is prevented and there is an effect on the reproducibility of good dot images.

The polymer containing methylhydrogensiloxane units - a structural _{unit, - (HSi (CH 3)} O)
Copolymers of other structural units (other siloxane units) are preferred. As other siloxane units, dimethylsiloxane units, methylethylsiloxane units, methylphenylsiloxane units, diethylsiloxane units, and the like are preferable, and dimethylsiloxane is particularly preferable. The proportion of methylhydrogensiloxane units in the copolymer is 10 to 99 mol%, preferably 20 to 90 mol%.

  The methylhydrogensiloxane copolymer may be any of a random copolymer, a block copolymer, a graft copolymer, etc., but a random copolymer and a block copolymer are preferred. In addition to methylhydrogensiloxane, the copolymerization component may be one component or two or more components.

  The intermediate layer coating solution prepared for forming the intermediate layer used in the present invention is composed of a binder resin, a dispersion solvent and the like in addition to the N-type semiconductive particles such as the surface-treated titanium oxide.

  The ratio of the N-type semiconductive particles in the intermediate layer is preferably 1.0 to 2.0 times in terms of the volume ratio of the intermediate layer to the binder resin (when the volume of the binder resin is 1). By using the N-type semiconducting particles of the present invention at such a high density in the intermediate layer, the rectification of the intermediate layer is enhanced, and the increase in residual potential and dot image degradation are effective even when the film thickness is increased. Therefore, a good organic photoreceptor can be formed. Further, such an intermediate layer preferably uses 100 to 200 parts by volume of N-type semiconductive particles with respect to 100 parts by volume of the binder resin.

  On the other hand, the binder resin in which these particles are dispersed to form the layer structure of the intermediate layer is preferably a polyamide resin in order to obtain good dispersibility of the particles, but the polyamide resin shown below is particularly preferable.

Moreover, it is preferable that the said intermediate | middle layer is an insulating layer substantially. Here, the insulating layer has a volume resistance of 1 × 10 ⁸ or more. The volume resistance of the intermediate layer and the protective layer of the present invention is preferably 1 × 10 ⁸ to 10 ¹⁵ Ω · cm, more preferably 1 × 10 ⁹ to 10 ¹⁴ Ω · cm, still more preferably 2 × 10 ⁹ to 1 ×. 10 ¹³ Ω · cm. The volume resistance can be measured as follows.

Measurement conditions: According to JIS: C2318-1975.
Measuring instrument: Hiresta IP manufactured by Mitsubishi Yuka
Measurement conditions: Measurement probe HRS
Applied voltage: 500V
Measurement environment: 30 ± 2 ℃, 80 ± 5% RH
(Photosensitive layer)
The photosensitive layer configuration of the photoreceptor of the present invention may be a single layer photosensitive layer configuration in which a charge generation function and a charge transport function are provided on one layer on the intermediate layer. By adopting the generation layer, the increase in residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable to employ a charge generation layer (CGL) on the intermediate layer and a charge transport layer (CTL) thereon.

  The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.

(Charge generation layer)
In the organic photoreceptor of the present invention, a charge generating material known as a charge generating material (CGM) can be used. For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, as the CGM in which the effect of the present invention appears remarkably and the residual potential increase due to repeated use can be reduced, for example, oxytitanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to the Cu—Kα line. Pigments are preferred.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.3 μm to 2 μm.

(Charge transport layer)
The charge transport layer contains a charge transport material (CTM) and a binder resin that disperses and forms a CTM. Other substances may contain additives such as antioxidants as necessary.

  As the charge transport material (CTM), a known hole transport property (P-type) charge transport material (CTM) is preferably used. For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer.

  The binder resin used for the charge transport layer (CTL) may be either a thermoplastic resin or a thermosetting resin. For example, polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and these resins A copolymer resin containing two or more of the repeating unit structures. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Of these, polycarbonate resins are most preferred because of their low water absorption and good CTM dispersibility and electrophotographic characteristics.

  The ratio of the binder resin to the charge transport material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  The total thickness of the charge transport layer is preferably 10 to 40 μm. If the total film thickness is less than 10 μm, image unevenness is likely to occur, and if it exceeds 40 μm, the residual power is likely to increase, and the sharpness tends to deteriorate. Further, the thickness of the charge transport layer serving as the surface layer is preferably 0.5 to 10 μm.

[Preparation of photosensitive layer]
Solvents or dispersion media used to form layers such as intermediate layers, charge generation layers, and charge transport layers include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone , Methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, Tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cello Lube, and the like. Although this invention is not limited to these, Solvents friendly to global environment, such as tetrahydrofuran and methyl ethyl ketone, are used preferably. These solvents may be used alone or as a mixed solvent of two or more.

  Next, as a coating processing method for producing the organic photoreceptor, a coating processing method such as dip coating or spray coating is used in addition to the ride hopper type coating apparatus. For forming the surface layer of the present invention, it is most preferable to use a circular slide hopper type coating apparatus.

  Among the above coating liquid supply type coating apparatuses, the coating method using a slide hopper type coating apparatus is most suitable when the above-described dispersion using a low boiling point solvent is used as the coating liquid, and is a cylindrical photoconductor. In this case, the coating is preferably performed using a circular slide hopper type coating apparatus described in detail in JP-A No. 58-189061 and the like.

  In the coating method using a circular slide hopper type coating apparatus, the slide surface end and the base material are arranged with a certain gap (about 2 μm to 2 mm), so that the base material is not damaged, and layers having different properties are multilayered. Even in the case of forming, it can be applied without damaging the already applied layer. Furthermore, when multiple layers with different properties and dissolved in the same solvent are formed, the time in the solvent is much shorter compared to the dip coating method, so that the lower layer component hardly elutes to the upper layer side, and the coating tank Can be applied without elution.

[Image formation neglected]
Next, the image forming apparatus according to the present invention will be described.

  The image forming apparatus according to the present invention includes an exposure unit that forms an electrostatic latent image on a photoconductor using a writing light source, and a developing unit that visualizes the electrostatic latent image into a toner image.

  As the photoreceptor, a photoreceptor formed by adding the compound of the present invention to the photosensitive layer is used.

  The image forming apparatus according to the present invention is applicable to general image forming apparatuses such as a copying machine, a laser printer, an LED printer, and a liquid crystal shutter type printer as a light printing machine. The present invention can be widely applied to such devices.

  The image forming apparatus will be specifically described below.

  FIG. 1 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus in which a photoconductor according to the present invention can be used.

  An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D as a transfer paper transport unit. Yes.

  An automatic document feeder that automatically conveys the document is provided above the image reading unit A, and the document placed on the document placing table 11 is separated and conveyed by the document conveying roller 12 to the reading position 13a. Then, the image is read. The document that has been read is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 comprising the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including the two mirrors and the third mirror in the same direction at the speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the toner, developing means (developing process) 23, transfer conveying belt device 45 as a transferring means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and light neutralizing means (light slow charge). PCL (precharge lamp) 27 as a process is arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. As the photosensitive member 21, the organic photosensitive member according to the present invention is used, and the photosensitive member 21 is driven and rotated in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, an image based on an image signal called from the memory of the image processing unit B by an exposure optical system as an image exposure unit (image exposure step) 30 is used. Exposure is performed. The exposure optical system as the image exposure means 30 serving as a writing means uses a laser diode (not shown) as a light source, passes through a rotating polygon mirror 31, an fθ lens 34, and a cylindrical lens 35, and the optical path is bent by a reflection mirror 32 to perform main scanning. Therefore, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In one example of the present embodiment, the character portion is exposed to form an electrostatic latent image.

  In the image forming apparatus of the present invention, a semiconductor laser or a light emitting diode is used as an image exposure light source when an electrostatic latent image is formed on a photoreceptor. By using these image exposure light sources, the exposure dot diameter in the writing principal direction is narrowed down to 10 to 70 μm, and digital exposure is performed on the organic photoreceptor, so that it is 600 dpi (dpi: the number of dots per 2.54 cm) or more. A high-resolution electrophotographic image of 2500 dpi can be obtained.

The exposure dot diameter refers to the length of the exposure beam along the main scanning direction (Ld: measured at the maximum length) in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a solid scanner such as the scanning optical system and LED using a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot diameter according to the present invention is used.

  The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method according to the present invention, it is preferable to use a polymerized toner as a developer used in the developing unit. By using a polymer toner having a uniform shape and particle size distribution in combination with the organic photoreceptor according to the present invention, an electrophotographic image with better sharpness can be obtained.

  In the transfer paper transport section D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer paper storage means for storing transfer paper P of different sizes. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer paper P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer paper P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer paper P to be transferred, and then fed again. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 The toner image on the photosensitive member 21 is transferred to the transfer paper P while being transferred to the transfer conveyance belt 454 of the transfer conveyance belt device 45 by the transfer electrode 24 and the separation electrode 25 at the transfer position Bo. Is, transfer sheet P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.

  The above describes the state in which image formation is performed on one side of the transfer paper. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the transfer paper guide 177 is opened, and the transfer paper P is indicated by a broken arrow. Conveyed in the direction.

  Further, the transfer paper P is transported downward by the transport mechanism 178 and switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P becomes the leading end portion and transported into the duplex copying paper supply unit 130. The

  The transfer paper P is moved in a paper feed direction by a conveyance guide 131 provided in the double-sided copy paper supply unit 130, the transfer paper P is re-fed by the paper supply roller 132, and the transfer paper P is guided to the conveyance path 40. .

  Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer paper P, fixed by the fixing unit 50, and then discharged onto the paper discharge tray 64.

  As an image forming apparatus according to the present invention, the above-described photosensitive member and components such as a developing unit and a cleaning unit are integrally coupled as a process cartridge, and this unit is configured to be detachable from the apparatus main body. May be. In addition, a process cartridge is formed by integrally supporting at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device together with a photosensitive member, and a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of an apparatus main body.

  FIG. 2 is a cross-sectional configuration diagram showing an example of a color image forming apparatus in which the photoconductor according to the present invention can be used.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a feeding unit. It comprises a paper conveying means 21 and a fixing means 24. A document image reading device SC is disposed above the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit (charging step) 2Y, an exposure unit (exposure step) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A unit (developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (primary transfer step), and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk include charging means 2Y, 2M, 2C, and 2Bk that rotate around the photosensitive drums 1Y, 1M, 1C, and 1Bk, and image exposure means 3Y, 3M, 3C and 3Bk, rotating developing means 4Y, 4M, 4C and 4Bk, and cleaning means 5Y, 5M, 5C and 5Bk for cleaning the photosensitive drums 1Y, 1M, 1C and 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of toner images formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. explain.

  The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 5Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning means 5Y or the cleaning blade 5Y) is simply disposed, and a yellow (Y) toner image is formed on the photosensitive drum 1Y. In the present embodiment, in the image forming unit 10Y, at least the photosensitive drum 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 5Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photosensitive drum 1Y. In this embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The image exposure means 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y, and forms an electrostatic latent image corresponding to the yellow image. As the exposure means 3Y, the exposure means 3Y includes an LED in which light emitting elements are arrayed in the axial direction of the photosensitive drum 1Y and an imaging element (trade name; Selfoc lens), or A laser optical system or the like is used.

  As an image forming apparatus according to the present invention, the above-described photosensitive member and components such as a developing device and a cleaning device are integrally combined as a process cartridge (image forming unit), and this image forming unit is installed in the apparatus main body. On the other hand, it may be configured to be detachable. In addition, at least one of a charging device, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge (image forming unit), which is detachable from the apparatus main body. A single image forming unit may be detachable using guide means such as a rail of the apparatus main body.

  The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. A transfer material P as a transfer material (a support for carrying a fixed final image: for example, plain paper, a transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and a plurality of intermediates. After passing through rollers 22A, 22B, 22C, 22D and registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto a transfer material P to transfer a color image all at once. The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing unit 24, is sandwiched between paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a transfer support for a toner image formed on a photosensitive member such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

  On the other hand, after the color image is transferred to the transfer material P by the secondary transfer roller 5b as the secondary transfer means, the residual toner is removed by the cleaning means 6b from the endless belt-shaped intermediate transfer body 70 in which the transfer material P is separated by curvature. The

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5b.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b. Consists of.

  FIG. 3 is a cross-sectional configuration diagram showing an example of a color image forming apparatus in which the photoconductor according to the present invention can be used.

  This color image forming apparatus has a charging unit, an exposure unit, a plurality of developing units, a transfer unit, a cleaning unit, and an intermediate transfer unit around the photoreceptor.

  Reference numeral 1 denotes a rotary drum type photoconductor that is repeatedly used as an image forming body, and is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed.

  In the rotation process, the photoreceptor 1 is uniformly charged to a predetermined polarity and potential by a charging means (charging process) 2, and then time-series electric digital of image information by an image exposure means (image exposure process) 3 (not shown). An electrostatic latent image corresponding to the yellow (Y) color component image (color information) of the target color image is formed by receiving image exposure by scanning exposure light or the like by a laser beam modulated in accordance with the pixel signal. The

  Then, the electrostatic latent image is developed with yellow toner as the first color by yellow (Y) developing means: developing step (yellow color developing device) 4Y. At this time, the second to fourth developing means (magenta developer, cyan developer, black developer) 4M, 4C, and 4Bk are turned off and do not act on the photosensitive member 1. The first color yellow toner image is not affected by the second to fourth developing units.

  The intermediate transfer member 70 is stretched by rollers 79a, 79b, 79c, 79d, and 79e, and is driven to rotate in the clockwise direction at the same peripheral speed as the photosensitive member 1.

  The yellow toner image of the first color formed and supported on the photosensitive member 1 is applied to the intermediate transfer member 70 from the primary transfer roller 5a in the process of passing through the nip portion between the photosensitive member 1 and the intermediate transfer member 70. The intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 70 by the electric field formed by the primary transfer bias.

  The surface of the photoreceptor 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer body 70 is cleaned by the cleaning device 6a.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black (black) toner image are sequentially superimposed and transferred onto the intermediate transfer body 70 to correspond to the target color image. A superimposed color toner image is formed.

  The secondary transfer roller 5b is supported in parallel with the secondary transfer counter roller 79b so as to be separated from the lower surface portion of the intermediate transfer body 70.

  The primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photosensitive member 1 to the intermediate transfer member 70 has a polarity opposite to that of the toner and is applied from a bias power source. The applied voltage is, for example, in the range of +100 V to +2 kV.

  In the primary transfer process of the first to third color toner images from the photosensitive member 1 to the intermediate transfer member 70, the secondary transfer roller 5b and the intermediate transfer member cleaning means 6b can be separated from the intermediate transfer member 70. .

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred onto the transfer material P, which is the second image carrier, the secondary transfer roller 5b is brought into contact with the belt of the intermediate transfer member 70. At the same time, the transfer material P is fed from the pair of paper registration rollers 23 through the transfer sheet guide to the belt of the intermediate transfer body 70 to the contact nip with the secondary transfer roller 5b at a predetermined timing. A secondary transfer bias is applied to the secondary transfer roller 5b from a bias power source. By this secondary transfer bias, the superimposed color toner image is transferred (secondary transfer) from the intermediate transfer body 70 to the transfer material P which is the second image carrier. The transfer material P that has received the transfer of the toner image is introduced into the fixing means 24 and heated and fixed.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the following text, “part” means “part by mass”.

[Production of Photosensitive Example 1]
Photoreceptor Example 1 was prepared as follows.

Intermediate layer On the washed cylindrical aluminum support, the following intermediate layer coating solution was applied by a dip coating method and dried at 120 ° C. for 30 minutes to form an intermediate layer having a dry film thickness of 5 μm.

  The following intermediate layer dispersion is diluted twice with the same mixed solvent, and is allowed to stand overnight and then filtered (filter; rigesh mesh filter made by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 microns, pressure: 50 kPa). Produced.

(Preparation of intermediate layer dispersion)
Binder resin: (Polyamide resin N-1) 1.0 part Rutile titanium oxide (primary particle size 35 nm; titanium oxide pigment prepared by surface treatment with dimethylpolysiloxane having a hydroxyl group at the terminal and having a hydrophobicity of 33) 5.6 parts ethanol / n-propyl alcohol / tetrahydrofuran (THF) (= 45/20/30 mass ratio) 10 parts The above ingredients are mixed and dispersed in a batch system for 10 hours using a sand mill disperser. An intermediate layer dispersion was prepared.

Charge generation layer (CGL)
Charge generation material (CGM): oxytitanyl phthalocyanine (a titanyl phthalosine pigment having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray) 24 parts polyvinyl butyral resin “S-LEC BL-1” (manufactured by Sekisui Chemical Co., Ltd.) 12 parts 2-butanone / cyclohexanone = 4/1 (v / v) 300 parts The above composition is mixed, dispersed using a sand mill, and charged. A generation layer coating solution was prepared. This coating solution was applied by a dip coating method to form a charge generation layer having a dry film thickness of 0.5 μm on the intermediate layer.

Charge transport layer (CTL)
Charge transport material (4,4′-dimethyl-4 ″-(α-phenylstyryl) triphenylamine) 200 parts Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 300 parts Exemplary Compound A1 1.0 part Exemplary Compound B1 14 parts Tetrahydrofuran 1600 parts Toluene 400 parts Silicone oil (KF-96: manufactured by Shin-Etsu Chemical Co., Ltd.) 1.0 part was mixed and dissolved to prepare a charge transport layer coating solution, which was immersed on the charge generation layer. Coating was performed by a coating method, drying was performed at 110 ° C. for 70 minutes, and a charge transport layer having a dry film thickness of 26.0 μm was formed.

[Production of Photosensitive Examples 2 to 11 and Comparative Examples 1 to 4]
In the production of photoconductor Example 1, Photoconductor Example 2 , 3, and Photoreceptor Example 2 were prepared in the same manner as Photoreceptor 1 except that the types and amounts of Exemplified Compound A1 and Exemplified Compound B1 in the charge transport layer were changed as shown in Table 1 . 5, 6, 9, 10 and photoreceptor reference examples 4 , 7 , 8 , 11 and Comparative Examples 1 to 4 were produced.

[Evaluation]
Using the photoreceptor prepared above, image evaluation before and after printing with an actual machine was performed.

  As an image forming apparatus for image characteristic evaluation, a copying machine “Bizhub 920” (manufactured by Konica Minolta Business Technologies) was prepared.

The photoconductors prepared above were sequentially set in the image forming apparatus, and then 200,000 print-proof prints were performed using A4 plain paper (64 g / m ² ) in an environment of 20 ° C. and 50% RH.

  In the image evaluation, a character image (3 point, 5 point character) with a pixel rate of 7%, a human face photo (dot image including a halftone), a white solid image, and a black solid image are each equally divided into 1/4. The image sharpness of the original image, the presence or absence of fog in the halftone image, the solid black image density, and the transfer memory were each confirmed before and after printing.

The evaluation paper was a printed image obtained by printing on neutral paper (64 g / m ² ) of A4 size. Note that, as evaluation criteria, 合格 and ○ are acceptable and × is unacceptable (problematic).

(Image sharpness)
The sharpness of the image was evaluated by crushing the original image (3, 5 point character image) in a high temperature and humidity environment (30 ° C., 80% RH) and crushing the 3 point and 5 point character images.

Evaluation criteria ◎: 3 points and 5 points are clear and easily readable ○: 3 points are partially illegible, 5 points are clear and easily readable ×: 3 points are almost unreadable 5 points Is partially or completely unreadable (image fogging)
The image fog was evaluated based on the difference between the fog density of the plain image after printing 200,000 sheets and the blank paper density of plain paper (64 g / m ² ). In the present invention, the degree of fog generation was evaluated based on the type and content of the charge transport material used to form the charge transport layer.

  The white paper density of the transfer material is measured at 20 locations of A4 size, and the average value is defined as the white paper density.

  As for the fog density of the plain image after the completion of printing 200,000 sheets, 20 spots of A4 size are measured, and the average value is defined as the fog density. The density was measured using a reflection densitometer “RD-918 (manufactured by Macbeth)”.

Evaluation criteria A: Image fog is less than 0.003, good ○: Image fog is 0.003 or more and less than 0.010, practically no problem ×: Image fog density is 0.010 or more, practical problem Level that becomes.

(Image density)
Evaluation was performed under an environmental condition of 20 ° C. and 50% RH, and measurement was performed using RD-918 manufactured by Macbeth. The relative reflection density was measured with the paper reflection density set to “0”. When the residual potential increases in a large number of copies, the image density decreases. The measurement was performed on a solid black image portion after 200,000 copies.

A: Black solid image is higher than 1.2 (good)
○: Black solid image is 1.0 or more and 1.2 or less (no problem in practical use)
×: Black solid image is less than 1.0 (practical problem)
(Transfer memory)
The digital copying machine “Bizhub 920” is left in a high temperature and high humidity environment (HH: 30 ° C., 80% RH) for 24 hours, then placed in a low temperature and low humidity environment (LL: 10 ° C., 20% RH), and after 30 minutes, Copied. Copy original image of character image and halftone image, and judge by density difference between generated afterimages (ΔHD = historic afterimage and surrounding density difference) ◎: History afterimage density difference ΔHD is less than 0.02 (good)
○: History afterimage density difference ΔHD is 0.02 to 0.04 (no problem in practical use)
X: Density difference ΔHD of history afterimage is 0.05 or more (practical problem)
Table 2 shows the evaluation results.

As is apparent from Table 2, Examples 1 to 3, 5, 6, 9, 10 and Reference Examples 4 , 7 , 8 , and 11 using Example A of the compound A of the general formula (1) were used . 3, 5, 6, 9, and 10 and Reference Examples 4, 7, 8, and 11 "have satisfactory evaluation results for both the initial image and the image after printing 200,000 sheets, and satisfy the object of the present invention. On the other hand, the “comparative photoconductors 1 to 4” of Comparative Examples 1 to 4 cause the deterioration of the transfer memory and the reduction of the image density in the 200,000-printed images, and the object of the present invention cannot be achieved. I understand that.

1 is a cross-sectional configuration diagram illustrating an example of an image forming apparatus in which a photoconductor according to the present invention can be used. 1 is a cross-sectional configuration diagram illustrating an example of a color image forming apparatus in which a photoconductor according to the present invention can be used. 1 is a cross-sectional configuration diagram illustrating an example of a color image forming apparatus in which a photoconductor according to the present invention can be used.

Explanation of symbols

10Y, 10M, 10C, 10Bk Image forming unit 1Y, 1M, 1C, 1Bk Photoconductor 2Y, 2M, 2C, 2Bk Charging unit 3Y, 3M, 3C, 3Bk Exposure unit 4Y, 4M, 4C, 4Bk Developing unit

Claims (4)

On a conductive support an electrophotographic photosensitive member having a photosensitive layer, the photosensitive layer, a compound A having a structure represented by the following general formula (1) is, the charge transporting substance 0.04 to 3 Is added so as to be 0.0% by mass,
Compound B having a structure represented by the following general formula (2) is added so as to be 0.5 to 15% by mass with respect to the charge transporting substance,
An electrophotographic photoreceptor , wherein a mass ratio (A / B) between the compound A and the compound B is in a range of 0.05 to 0.20 .
(In general formula (1), R _{1 to} R ₄ represent hydrogen and an alkyl group which may have a substituent, R ₅ and R ₆ represent hydrogen and an alkyl group which may have a substituent, Represents an aryl group.)
(In General Formula (2), R _{7 to} R ₁₀ represent hydrogen and an alkyl group which may have a substituent. R ₁₁ and R ₁₂ represent hydrogen and an alkyl group which may have a substituent, Represents an aryl group.) The electrophotographic photoreceptor according to claim 1, wherein the compound A is represented by the following general formula (3) .
(In general formula (3), R ₁₃ represents hydrogen or an alkyl group which may have a substituent. R ₁₄ represents hydrogen, an alkyl group which may have a substituent or an aryl group.) The electrophotographic photosensitive member according to claim 1 or 2, wherein the electrophotographic photoreceptor is negatively charged photoreceptor. In an image forming apparatus having an exposure unit that forms an electrostatic latent image using a writing light source on an electrophotographic photosensitive member after a charging step, and a developing unit that visualizes the electrostatic latent image into a toner image.
An image forming apparatus using the electrophotographic photosensitive member according to claim 1 as the electrophotographic photosensitive member .