JP2007206349A - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method, with which an image with high resolution and high definition reproducibility can be formed for a long period of time from the initial use stage of a photoreceptor, even when the thickness of a photosensitive layer is made thick, and to provide an image forming apparatus, capable of forming the image with high resolution and high definition reproducibility over a long period of time, starting from the initial stage. <P>SOLUTION: The image forming method includes an exposure step and a charging step of forming an electrostatic latent image on an exposed electrophotographic photoreceptor, wherein exposure in the above steps is carried out at a charging potential V<SB>0</SB>(V) and an exposure dose Ex (mJ/m<SP>2</SP>), satisfying Formula (1). In the Formula (1), V<SB>M</SB>represents the surface potential (V) of the electrophotographic photoreceptor, when the electrophotographic photoreceptor charged to a potential V<SB>0</SB>is exposed to light energy Ex/2 (mJ/m<SP>2</SP>), which is half the energy giving a potential V<SB>L</SB>, V<SB>1/2</SB>represents a medium potential (V) between V<SB>0</SB>and V<SB>L</SB>, T represents the film thickness (μm) of the photosensitive layer and e is the base of natural logarithm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming method and an image forming apparatus.

  In electrophotographic image formation, a latent image is formed on a uniformly charged electrophotographic photosensitive member (hereinafter sometimes referred to as “photosensitive member”) using an exposure means, and the latent image is developed with toner or the like. The image is obtained by transferring the transferred image to the transfer object. Recently, the demand for image quality is increasing, and how to reproduce fine pixels (one dot line, etc.) clearly is not only a color copier / printer, but also a black-and-white copier / printer. Is also important. Therefore, there is a demand for an image forming apparatus with high resolution and high definition reproducibility.

As a technique for improving the resolution, for example, it has been proposed to reduce the thickness of the charge transport layer to 12 μm or less in a photoreceptor including a charge generation layer and a charge transport layer (see, for example, Patent Document 1). . In addition, as a technique for improving fine reproducibility, for example, 5 erg / cm ² (= 5 mJ / m ² ) or less for a photoreceptor including a charge generation layer containing a specific titanyl phthalocyanine crystal and a charge transport layer. There has been proposed a method of performing writing with the exposure energy (see, for example, Patent Document 2).

JP-A-8-234455 JP 2004-101886 A

  By the way, image forming apparatuses are also required to improve the image quality and reduce the running cost thereof, and there is an increasing demand for extending the life of replacement parts, in particular, extending the life of the photoreceptor. The photoreceptor is repeatedly used in the image forming apparatus, and the life thereof is usually affected by the amount of film abrasion of the photosensitive layer. Therefore, in order to extend the life of the photoreceptor, it is effective to set the film thickness of the photosensitive layer thick.

  However, in the conventional image forming apparatus, it is not always easy to achieve a long life and a high image quality at a high level by increasing the film thickness of the photosensitive layer for the following reason.

  That is, according to the study of the present inventor, when the film thickness of the photosensitive layer is set to a level at which a sufficient lifetime can be obtained, high resolution and high definition reproducibility can be obtained even if exposure is performed under the conditions described in Patent Document 2. It has been found that it is not always sufficiently maintained from the beginning to the long term.

  Therefore, the present invention has been made in view of the above circumstances, and even when the thickness of the photosensitive layer is set to be large, an image with high resolution and high definition reproducibility can be obtained from the initial use of the photoreceptor for a long period of time. And an image forming apparatus capable of forming an image with high resolution and high reproducibility from the initial stage over a long period of time.

  As a result of intensive studies to achieve the above-mentioned object, the present inventor conducted photosensitivity by controlling the charging potential and the exposure amount so as to satisfy specific conditions based on the film thickness of the photosensitive layer. Even when the thickness of the layer is set to be thick (specifically, 35 μm or more), it has been found that one dot line can be printed with high resolution and high reproducibility, and the present invention has been completed.

ここで、式（１）中、Ｖ_０は、露光前の電子写真感光体表面の帯電電位（Ｖ）を示し、Ｖ_Ｌは、電位Ｖ_０に帯電した電子写真感光体を光エネルギー量Ｅｘ（ｍＪ／ｍ^２）で露光したときの電子写真感光体の表面電位（Ｖ）を示し、Ｖ_Ｍは、電位Ｖ_０に帯電した電子写真感光体を、Ｖ_Ｌを得たときの光エネルギー量の半分Ｅｘ／２（ｍＪ／ｍ^２）で露光したときの電子写真感光体の表面電位（Ｖ）を示し、Ｖ_１／２は、Ｖ_０とＶ_Ｌとの中間電位（Ｖ）［Ｖ_１／２＝（Ｖ_０＋Ｖ_Ｌ）／２］を示し、Ｔは、感光層の膜厚（μｍ）を示し、ｅは、自然対数の底を示す。 That is, in the image forming method of the present invention, an electrophotographic photosensitive member having a conductive substrate and a photosensitive layer formed on the conductive substrate is charged, and the charged electrophotographic photosensitive member is exposed to electrophotography. An exposure process for forming an electrostatic latent image on the photoreceptor, a development process for developing the electrostatic latent image with a developer to form a toner image, and a transfer for transferring the toner image from the electrophotographic photoreceptor to a transfer medium. And a cleaning step for removing toner remaining on the electrophotographic photosensitive member after the transfer step, and charging in the charging step and exposure in the exposure step satisfy the relationship represented by the following formula (1) V ₀ (V) and exposure amount Ex (mJ / m ² ).

Here, in the formula (1), V ₀ denotes a charge potential of the electrophotographic photosensitive member surface before exposure (V), V _L is the electrophotographic photoreceptor charged to potential V ₀ which light energy Ex ( mJ / m ²⁾ shows the surface potential (V) of the electrophotographic photosensitive member when the exposure is, V _M is an electrophotographic photosensitive member charged to a potential V _0, the light energy amount when obtaining the V _L The surface potential (V) of the electrophotographic photosensitive member when exposed at half Ex / 2 (mJ / m ² ) is shown, and V _1/2 is an intermediate potential (V) between V ₀ and V _L [V _{1 / 2} = (V ₀ + V _L ) / 2], T represents the film thickness (μm) of the photosensitive layer, and e represents the base of the natural logarithm.

According to the image forming method of the present invention, the charging in the charging step and the exposure in the exposure step are performed with the charging potential V ₀ (V) and the exposure amount Ex (mJ / m ² ) satisfying the relationship of the above formula (1). As a result, even when the thickness of the photosensitive layer is set to be large, an image can be formed with high resolution and high definition reproducibility from the initial use of the photosensitive member over a long period of time. Therefore, by applying the image forming method of the present invention to an image forming apparatus including a photosensitive member having a photosensitive layer thickened (in particular, thickened to 35 μm or more), the life of the image forming apparatus can be increased. High image quality can be achieved at a high level, and further, running costs such as copying and printing can be reduced, and resources used for the photoreceptor can be effectively used.

The reason why the above-described effects are achieved by the present invention is presumed as follows. First, the reason why the resolution and fine reproducibility cannot be obtained when the photosensitive layer is a thick film in the conventional image forming method is that the distance from the place where the charge is generated during exposure to the surface of the photoreceptor is long, and the charge is generated. This is presumably because charge diffusion occurs at the time of diffusion of light incident on the layer or movement of charge. Note that if the exposure amount is increased so as to compensate for the diffused charge, the dot line becomes thicker, and conversely the resolution decreases. On the other hand, in the present invention, by performing charging and exposure with the charging potential V ₀ and the exposure amount Ex satisfying the above formula (1), the charge for diffusion is appropriately compensated without reducing the resolution. It is assumed that the fine reproducibility was sufficiently secured. The range represented by the above formula (1) changes according to the film thickness of the photosensitive layer, and is a case where the photosensitive layer is worn and the shape of the potential decay curve with respect to the diffusion of charges and the amount of light changes. In addition, by selecting a suitable charging potential and exposure amount, it is considered that an image can be formed with high resolution and high definition reproducibility over a long period from the initial use of the photoreceptor.

In the image forming method of the present invention, as the electrophotographic photosensitive member, the photosensitive layer of the electrophotographic photosensitive member includes a charge generation layer and a charge transport layer in this order from the conductive substrate side. In the photoreceptor, the distance from the outermost surface of the photosensitive layer to the interface between the charge generation layer and the charge transport layer is from 35 μm to 50 μm, and the capacitance of the photosensitive layer is from 56 pF / cm ^{2 to} 80 pF / cm ² It is preferable to use an electrophotographic photosensitive member having a half-exposure amount of 1 mJ / m ² or less.

  In the present invention, “half-exposure amount of electrophotographic photoreceptor” means that the surface of the photoreceptor is charged by charging the surface of the photoreceptor to a predetermined potential and then irradiating light having a wavelength used in the above exposure apparatus. It is defined as the amount of exposure necessary to halve the potential from the initial charging potential.

By using the electrophotographic photosensitive member and performing charging and exposure with the charging potential V ₀ and the exposure amount Ex satisfying the above formula (1), high resolution and high definition reproducibility can be obtained for a longer period of time and more reliably. Can form images

  In the image forming method of the present invention, as the electrophotographic photosensitive member, the photosensitive layer includes a charge generation layer and a charge transport layer in this order from the conductive substrate side. It is preferable to use one that contains one or more pigments of phthalocyanine and titanyl phthalocyanine.

  By combining the above electrophotographic photosensitive member, it is possible to form a higher quality image. The reason why such an effect is obtained is as follows. The above-mentioned pigment has high sensitivity and can generate charges with high efficiency. Therefore, the dependence on the strength of the electric field necessary for charge generation is small, and the potential can be shown linearly with respect to the amount of incident light. Although latent image formation can be expected, when the photosensitive layer is thickened, it has been difficult to obtain sufficient reproducibility of one dot line by the conventional image forming method. This is because when the photosensitive layer becomes thick, the light incident on the charge generation layer tends to scatter (this scattering becomes stronger in the particle dispersion type photosensitive layer), and the generated charge moves to the surface. In this case, it is considered that the long moving distance causes the latent image to be blurred due to charge scattering, and the phenomenon that the developing electric field is weakened by the thick film. On the other hand, according to the image forming method of the present invention, even when the photosensitive layer is thickened using the above-described pigment, the resolution of fine lines and the like is ensured while sufficiently ensuring the reproducibility of one dot line. Therefore, it is considered that image formation with higher quality could be achieved.

  In the image forming method of the present invention, as the electrophotographic photosensitive member, the outermost layer of the photosensitive layer includes one or more solid lubricants selected from fluorine-containing resin particles and silicon-containing resin particles. Is preferred. According to such an image forming method, it is possible to form a high-quality image over a longer period.

ここで、式（１）中、Ｖ_０は、露光前の電子写真感光体表面の帯電電位（Ｖ）を示し、Ｖ_Ｌは、電位Ｖ_０に帯電した電子写真感光体を光エネルギー量Ｅｘ（ｍＪ／ｍ^２）で露光したときの電子写真感光体の表面電位（Ｖ）を示し、Ｖ_Ｍは、電位Ｖ_０に帯電した電子写真感光体を、Ｖ_Ｌを得たときの光エネルギー量の半分Ｅｘ／２（ｍＪ／ｍ^２）で露光したときの電子写真感光体の表面電位（Ｖ）を示し、Ｖ_１／２は、Ｖ_０とＶ_Ｌとの中間電位（Ｖ）を示し、Ｔは、感光層の膜厚（μｍ）を示し、ｅは、自然対数の底を示す。 The present invention also provides an electrophotographic photosensitive member having a conductive substrate and a photosensitive layer provided on the conductive substrate, a charging device for charging the electrophotographic photosensitive member, and exposing the charged electrophotographic photosensitive member. An exposure apparatus for forming an electrostatic latent image in an exposure area; a developing apparatus for developing the electrostatic latent image formed in the exposure area with toner to form a toner image; and transferring the toner image from an electrophotographic photosensitive member An image forming apparatus including a transfer device that transfers to a medium, and a charging potential V ₀ (V) that satisfies a relationship represented by the following formula (1) based on a film thickness of the photosensitive layer obtained by a predetermined method: It further comprises a control device for obtaining the exposure amount Ex (mJ / m ² ) and controlling the charging potential on the surface of the electrophotographic photosensitive member and the exposure amount of the exposure device based on the values of the charging potential V ₀ and the exposure amount Ex. Image forming apparatus To provide.

Here, in the formula (1), V ₀ denotes a charge potential of the electrophotographic photosensitive member surface before exposure (V), V _L is the electrophotographic photoreceptor charged to potential V ₀ which light energy Ex ( mJ / m ²⁾ shows the surface potential (V) of the electrophotographic photosensitive member when the exposure is, V _M is an electrophotographic photosensitive member charged to a potential V _0, the light energy amount when obtaining the V _L The surface potential (V) of the electrophotographic photosensitive member when exposed at half Ex / 2 (mJ / m ² ) is shown, V _1/2 is the intermediate potential (V) between V ₀ and V _L, and T Indicates the film thickness (μm) of the photosensitive layer, and e indicates the base of the natural logarithm.

  The image forming apparatus of the present invention can form an image with high resolution and high reproducibility over a long period from the initial stage even when the film thickness of the photosensitive layer is set to be large by providing the control device. Therefore, according to the image forming apparatus of the present invention, it is possible to realize a long life and a high image quality at a high level, and further, it is possible to reduce running costs such as copying and printing and to effectively use resources used for the photoreceptor. It can be used.

The image forming apparatus of the present invention further includes a surface potential measuring device for measuring the surface potential of the electrophotographic photosensitive member, and the control device measures the electrophotographic photosensitive member before and after exposure measured by the surface potential measuring device. seeking to satisfy the relationship represented by the following formula (1) charging potential V ₀ which _(V) and the exposure amount Ex (mJ / m ²⁾ based on the thickness of the surface potential and the photosensitive layer of the charging potential V ₀ which and exposure It is preferable to control the charging potential on the surface of the electrophotographic photosensitive member and the exposure amount of the exposure apparatus based on the value of Ex.

Such an image forming apparatus includes the surface potential measuring device and the control device, so that a suitable charging potential V ₀ and exposure amount Ex can be obtained with higher accuracy, and an image can be obtained with high resolution and high definition reproducibility. It can be more reliably formed and has excellent environmental resistance.

  In the image forming apparatus of the present invention, the photosensitive layer includes a charge generation layer and a charge transport layer in this order from the conductive substrate side, and the charge generation layer is composed of hydroxygallium phthalocyanine and titanyl phthalocyanine. It is preferable that it contains one or more pigments. Thereby, an image forming apparatus with higher image quality can be realized.

  In the image forming apparatus of the present invention, the outermost layer of the photosensitive layer preferably contains one or more solid lubricants of fluorine-containing resin particles and silicon-containing resin particles. As a result, an image forming apparatus having a longer life can be realized.

In the image forming apparatus of the present invention, the photosensitive layer of the electrophotographic photoreceptor includes a charge generation layer and a charge transport layer in this order from the conductive substrate side. In the unused electrophotographic photoreceptor, The distance from the outermost surface of the photosensitive layer to the interface between the charge generation layer and the charge transport layer is 35 μm or more and 50 μm or less, and the electrostatic capacitance of the photosensitive layer is 56 pF / cm ² or more and 80 pF / cm ² or less. The half-exposure amount of the body is preferably 1 mJ / m ² or less.

The length of an image forming apparatus capable of forming an image with high resolution and high definition reproducibility by performing charging and exposure with the charging potential V ₀ and the exposure amount Ex satisfying the above formula (1) using the electrophotographic photosensitive member. The lifetime can be more reliably realized.

  According to the present invention, an image forming method capable of forming an image with high resolution and high definition reproducibility over a long period from the initial use of the photoreceptor even when the film thickness of the photosensitive layer is set thick, and from the initial stage An image forming apparatus capable of forming an image with high resolution and high definition reproducibility over a long period of time can be provided.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.

(Image forming device)
FIG. 1 is a schematic configuration diagram showing a preferred embodiment of an image forming apparatus according to the present invention. In the image forming apparatus 100 shown in FIG. 1, an electrophotographic photosensitive member 1 having a cylindrical shape and including a photosensitive layer 52 on a conductive substrate 51 is supported rotatably in the circumferential direction. A charging device 2, an exposure device 4, a developing device 5, a primary transfer roll (intermediate transfer member) 10, and a cleaning member 6 connected to the power supply unit 3 are arranged in this order along the rotation direction. Among these elements, the charging device 2, the primary transfer roll 10, and the cleaning member of the cleaning device 6 are disposed in contact with the outer peripheral surface of the photoreceptor 1 (surface of the photosensitive layer 52). Thus, charging of the photosensitive member 1 by the charging device 2 to which a predetermined voltage is applied by the power supply unit 3, exposure by the exposure device 4, development by the developing device 5, and primary of the toner image from the photosensitive member 1 to the primary transfer roll 10. The photosensitive member 1 is cleaned sequentially by the transfer and cleaning device 6. A power supply unit 15 is connected to the primary transfer roll, and a current having a predetermined current density is supplied to the photosensitive member 1 at the time of transfer. Further, a transfer roll 7 is disposed in contact with the primary transfer roll 10 on the side opposite to the photoreceptor 1, and the toner image transferred to the primary transfer roll 10 is supplied between the primary transfer roll 10 and the transfer roll 7. To the image output medium 9 to be transferred. The image output medium after the transfer is sent to the image fixing device 8, and the transferred toner image is fixed.

ここで、式（１）中、Ｖ_０は、露光前の電子写真感光体表面の帯電電位（Ｖ）を示し、Ｖ_Ｌは、電位Ｖ_０に帯電した電子写真感光体を光エネルギー量Ｅｘ（ｍＪ／ｍ^２）で露光したときの電子写真感光体の表面電位（Ｖ）を示し、Ｖ_Ｍは、電位Ｖ_０に帯電した電子写真感光体を、Ｖ_Ｌを得たときの光エネルギー量の半分Ｅｘ／２（ｍＪ／ｍ^２）で露光したときの電子写真感光体の表面電位（Ｖ）を示し、Ｖ_１／２は、Ｖ_０とＶ_Ｌとの中間電位（Ｖ）を示し、Ｔは、感光層の膜厚（μｍ）を示し、ｅは、自然対数の底を示す。 In addition, the image forming apparatus 100 shown in FIG. 1 includes a first potential measuring device 11 that measures the surface potential of the photoreceptor 1 after charging, and a second potential that measures the surface potential of the photoreceptor 1 after exposure. A measurement device 12, a first potential measurement device 11, a second potential measurement device 12, a power supply unit 3, and a control device 13 electrically connected to the exposure device 4 are provided. The control device 13 includes a CPU, a ROM, a RAM, a storage device, and the like (all not shown), and the surface potential of the photoreceptor measured by each potential measurement device according to a control program stored in the ROM or the like. A predetermined calculation process is performed based on the film thickness of the photosensitive layer 52 obtained by a predetermined method. Then, the CPU of the control device 13 charges the charging potential V ₀ (V) satisfying the relationship expressed by the following formula (1) based on the measured surface potential of the photosensitive member and the film thickness of the photosensitive layer obtained by a predetermined method. Then, the exposure amount Ex (mJ / m ² ) is obtained, and the voltage applied to the charging device 2 and the exposure amount of the exposure device 4 are varied by controlling the power supply unit 3 and the exposure device 4 based on the values of V ₀ and Ex.

Here, in the formula (1), V ₀ denotes a charge potential of the electrophotographic photosensitive member surface before exposure (V), V _L is the electrophotographic photoreceptor charged to potential V ₀ which light energy Ex ( mJ / m ²⁾ shows the surface potential (V) of the electrophotographic photosensitive member when the exposure is, V _M is an electrophotographic photosensitive member charged to a potential V _0, the light energy amount when obtaining the V _L The surface potential (V) of the electrophotographic photosensitive member when exposed at half Ex / 2 (mJ / m ² ) is shown, V _1/2 is the intermediate potential (V) between V ₀ and V _L, and T Indicates the film thickness (μm) of the photosensitive layer, and e indicates the base of the natural logarithm.

  Examples of the potential measuring device 11 and the potential measuring device 12 include, for example, those composed of a potential measuring probe and a surface potentiometer.

  Examples of the method for obtaining the film thickness of the photosensitive layer include a method of measuring the electrostatic capacitance of the photosensitive layer and calculating the film thickness of the photosensitive layer based on the electrostatic capacitance. In the image forming apparatus 100 shown in FIG. 1, (a) the current flowing from the charging device 2 to the photoconductor 1 is measured by the power supply unit 3, and the control device 13 causes the static electricity of the photoconductor to be measured based on the obtained inflow current amount. Or (b) a current flowing from the primary transfer roll 10 to the photosensitive member 1 is measured by the power supply unit 15, and the controller 13 determines the electrostatic capacitance of the photosensitive member based on the obtained inflow current amount. Can be calculated. In the present embodiment, from the viewpoint of accurately obtaining the capacitance of the photosensitive layer, (a) includes (c) the surface potential of the photoreceptor 1 by the first potential measuring device 11 or the second potential measuring device 12. It is preferable that the measurement is further combined, and the control device 13 calculates the capacitance of the photosensitive layer based on the inflow current amount and the surface potential.

  When calculating the electrostatic capacitance of the photosensitive layer from the relationship between the surface potential and the inflow current, specifically, the film thickness of the photosensitive layer can be obtained by the following method.

First, the charge Q is calculated from the inflow current I using the following formula (A).
Q = I / (W · Vp) (A)
[In formula (A), Q represents electric charge (C / mm ² ), I represents inflow current (A), W represents effective charge width (mm) of the charging device, and Vp (mm / sec) is Indicates the process speed of the photoreceptor. ]

From the charge Q and the surface potential V thus obtained, the capacitance C (F / mm ² ) is obtained using the following formula (B).
Q = CV (B)
[In formula (B), Q represents electric charge (C / mm ² ), V represents surface potential (V), and C represents electrostatic capacity (F / mm ² ). ]
Thereby, the electrostatic capacitance of the photoreceptor 1 can be obtained.

On the other hand, the capacitance C and the film thickness T of the photosensitive layer have the relationship of the following formula (C).
C = ε / T (C)
[In the formula (C), C represents the capacitance (F / mm ² ), T represents the film thickness (mm) of the photosensitive layer, and ε represents the dielectric constant (F / mm) of the photosensitive layer. ]

  Therefore, the film thickness T of the photosensitive layer can be obtained from the capacitance C by previously obtaining the dielectric constant ε inherent to the photosensitive layer.

  As another method for obtaining the film thickness of the photosensitive layer, for example, utilizing the fact that the wear of the photosensitive layer accompanying use is substantially proportional to the rotational speed of the photosensitive member, the number of cycles or the number of prints of the photosensitive member is used. And detecting the film thickness of the photosensitive layer at that time based on the correlation between the number of cycles or the number of prints and the film thickness of the photosensitive layer. In this case, a correlation between the number of cycles or the number of prints and the film thickness of the photosensitive layer is obtained in advance, and this is stored as a data table in the storage device or the like of the control device 13 so that the photosensitive layer is determined from the number of cycles or the number of prints. Can be obtained.

In the present embodiment, the control performed by the control device 13 is capable of causing the image forming process to proceed with the charging potential V ₀ (V) and the exposure amount Ex (mJ / m ² ) satisfying the above formula (1). Well, not particularly limited. Specific examples include the following control procedures.

First, the photosensitive layer is charged so that the charging potential becomes V ₁ (V), subsequently exposed with a reference exposure amount E _s (mJ / m ² ), and the surface potential V ₂ (V) of the photosensitive layer after exposure. Measure. Next, the photosensitive layer is charged so that the charging potential becomes V ₁ (V), subsequently exposed with an exposure amount of E _s / 2, and the surface potential V ₃ (V) of the exposed photosensitive layer is measured. . FIG. 7 shows an example of the relationship between the surface potential of the photosensitive layer and the exposure amount. The obtained V ₁ , V ₂ , V ₃ , (V ₁ + V ₂ ) / 2, and the film thickness of the photosensitive layer are respectively V ₀ , V _L , V _M , V _1/2 , Then, it is substituted for T, and the above-mentioned measurement is repeated until the exposure amount is changed until the relationship shown in the equation (1) is satisfied, and the exposure amount E (mJ / m ² ) for image formation is determined. Then, the progress of the image forming process in charging potential V ₁ and the exposure amount E at this time. Note that If changing the exposure amount does not satisfy the equation (1), by changing the V ₁ can determine the charge potential and the exposure value when the image is formed by repeating the above procedure.

  Although the image forming apparatus 100 includes two potential measuring devices, the surface potential of the photosensitive layer before and after exposure may be measured by one potential measuring device. In this case, the measurement can be performed by rotating the photosensitive member twice. Further, the place where the potential measuring device is arranged can be changed as appropriate. Further, it is possible to change to a mode in which the toner image on the photosensitive member is directly transferred to the image output medium 9 without providing the primary transfer roll 10.

  In the present invention, instead of controlling the charging potential and exposure amount based on the measured charging potential of the photosensitive layer as described above, the control device 13 sets the charging potential and exposure amount based on a data table prepared in advance. You may control. As the data table, for example, an experimentally obtained value representing the correlation between the film thickness of the photosensitive layer and the charging potential and the exposure amount that can satisfy the above formula (1) at the film thickness is cited. In this case, the control device 13 obtains a predetermined charging potential and exposure amount from the data table according to the film thickness of the photosensitive layer, and proceeds with image formation by controlling the charging potential and exposure amount based on these values. In the present embodiment, it is preferable to further use a calibration data table for calibrating the charged potential and the potential after exposure that vary depending on the environment (temperature, humidity, etc.) in which the apparatus is used. In this case, for example, the image forming apparatus further includes a temperature / humidity meter, so that the control device 13 can calibrate the charging potential and the exposure amount based on the temperature / humidity data.

  The film thickness of the photosensitive layer used for the control device 13 to control the charging potential and the exposure amount may be a value calculated by the above-described methods (a) to (c) or a combination thereof. It may be a value calculated based on the correlation between the number of cycles or the number of prints and the film thickness of the photosensitive layer. In the present embodiment, when combining the data table and the method for calculating the thickness of the photosensitive layer based on the correlation between the number of cycles or the number of prints and the thickness of the photosensitive layer, the potential of the image forming apparatus 100 is combined. The measuring device can be omitted.

  Next, components of the image forming apparatus 100 other than those described above will be described in detail.

(Electrophotographic photoreceptor)
First, a preferred example of the electrophotographic photoreceptor 1 provided in the image forming apparatus 100 will be described. 2 to 5 are schematic cross-sectional views each showing a preferred embodiment of the electrophotographic photosensitive member 1 according to this embodiment. The electrophotographic photosensitive member 1 is arranged in the stacking direction of the conductive substrate 51 and the photosensitive layer 52. And cut by a vertical plane.

  The electrophotographic photosensitive member 1 shown in FIG. 2 includes a conductive substrate 51, an undercoat layer 53, and a photosensitive layer 52 including a charge generation layer 54 and a charge transport layer 55. Further, in the electrophotographic photoreceptor 1 shown in FIG. 3, a conductive substrate 51, an undercoat layer 53, and a photosensitive layer 52 including a charge generation layer 54, a charge transport layer 55, and a protective layer 56 are sequentially laminated. It has a structure.

  In the electrophotographic photoreceptor 1 shown in FIG. 4, an undercoat layer 53 and an intermediate layer 57 are laminated in this order on a conductive substrate 51, and a photosensitive layer comprising a charge generation layer 54 and a charge transport layer 55 is further formed thereon. 52 is laminated. In addition, the electrophotographic photoreceptor 1 shown in FIG. 5 is a single-layer type photosensitive layer in which an undercoat layer 53 is provided on a conductive substrate 51 and a charge generation material and a charge transport material are included in the same layer. 52 is provided.

  Hereinafter, each element will be described based on the electrophotographic photosensitive member 1 shown in FIG.

  The conductive substrate 51 is made of a metal such as aluminum, copper, iron, zinc, nickel; aluminum, copper, gold, silver, platinum, palladium, titanium, nickel on a substrate such as a sheet, paper, plastic, glass, etc. -Deposited metal such as chromium, stainless steel, copper-indium; Deposited conductive metal compound such as indium oxide and tin oxide on the base; Laminated metal foil on the base; Carbon black, oxidized Indium, tin oxide-antimony oxide powder, metal powder, copper iodide and the like are dispersed in a binder resin and applied to the substrate to conduct a conductive treatment. Further, the shape of the conductive substrate 51 may be any of a drum shape, a sheet shape, and a plate shape.

  Examples of the undercoat layer 53 include those formed by containing a binder resin, metal oxide fine particles, and an acceptor compound.

  As the binder resin, any known one can be used as long as it can form a good film and can obtain desired characteristics. For example, an acetal resin such as polyvinyl butyral, a polyvinyl alcohol resin, Casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, Known polymer resin compounds such as a phenol resin, a phenol-formaldehyde resin, a melamine resin, and a urethane resin, a charge transporting resin having a charge transporting group, a conductive resin such as polyaniline, and the like can be used. Among these, resins that are insoluble in the coating solvent for the upper layer (in this embodiment, the charge generation layer 54) are preferably used, and phenol resins, phenol-formaldehyde resins, melamine resins, urethane resins, epoxy resins, and the like are particularly preferably used.

In order for the undercoat layer 53 to exhibit sufficient leakage resistance, the metal oxide fine particles preferably have a powder resistance of about 10 ² to 10 ¹¹ Ω · cm. Note that if the resistance value of the metal oxide fine particles is lower than the lower limit of the above range, sufficient leakage resistance is difficult to obtain, and if it is higher than the upper limit of this range, the residual potential tends to increase.

  In the present embodiment, it is preferable to use metal oxide fine particles such as tin oxide, titanium oxide, zinc oxide and zirconium oxide having the above resistance values. In particular, zinc oxide is preferably used. Further, two or more kinds of metal oxide fine particles having different surface treatments or different particle diameters can be used in combination.

As the metal oxide fine particles, those having a specific surface area of 10 m ² / g or more by the BET method are preferably used. Those having a specific surface area value of 10 m ² / g or less tend to cause a decrease in chargeability and tend to make it difficult to obtain good electrophotographic characteristics.

  The metal oxide fine particles can be subjected to a surface treatment as necessary. The surface treatment agent can be selected from known materials as long as desired characteristics such as a silane coupling agent, a titanate coupling agent, an aluminum coupling agent, and a surfactant can be obtained. In particular, silane coupling agents are preferably used because they give good electrophotographic characteristics. Furthermore, a silane coupling agent having an amino group is preferably used because it gives a good blocking property to the undercoat layer.

  Any silane coupling agent having an amino group can be used as long as it can obtain desired photoreceptor characteristics. Specific examples include γ-aminopropyltriethoxysilane, N-β- ( Aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, and the like. Although it is mentioned, it is not limited to these. Moreover, 2 or more types of silane coupling agents can also be mixed and used.

  Moreover, the silane coupling agent which has an amino group can be used in combination with another silane coupling agent. Other silane coupling agents include, for example, vinyltrimethoxysilane, γ-methacryloxypropyl-tris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycid. Xylpropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (amino Ethyl) -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, and the like. is not.

  As the surface treatment method, any known method can be used, but a dry method or a wet method can be used.

  When surface treatment is performed by a dry method, while stirring the metal oxide fine particles with a mixer having a large shearing force or the like, the silane coupling agent is dissolved directly or dissolved in an organic solvent, and the mixture is added to dry air or nitrogen gas. By spraying together, uniform surface treatment is performed. The dropping of the silane coupling agent and the spraying of the mixture are preferably performed at a temperature not higher than the boiling point of the solvent used. When dripping or spraying is performed at a temperature equal to or higher than the boiling point of the solvent, the solvent evaporates before being uniformly stirred, and the silane coupling agent tends to aggregate locally, making uniform treatment difficult. The surface-treated metal oxide particles can be further baked at 100 ° C. or higher. Baking can be carried out in an arbitrary range as long as the temperature and time allow the desired electrophotographic characteristics to be obtained.

  As a wet method, metal oxide fine particles are stirred in a solvent, dispersed using ultrasonic waves, a sand mill, an attritor, a ball mill, etc., added with a silane coupling agent solution, stirred or dispersed, and then the solvent is removed. It is processed uniformly by doing. The solvent can be removed by filtration or distillation. After removing the solvent, baking can be performed at 100 ° C. or higher. Baking can be carried out in an arbitrary range as long as the temperature and time allow the desired electrophotographic characteristics to be obtained. In the wet method, as a method for removing the metal oxide fine particle-containing water, a method of removing with stirring and heating in a solvent used for surface treatment, a method of removing by azeotropy with a solvent, or the like can be used.

  The amount of the silane coupling agent relative to the metal oxide fine particles in the undercoat layer 53 can be any amount as long as desired electrophotographic characteristics can be obtained. Further, the ratio between the metal oxide fine particles and the binder resin used in the undercoat layer 53 can be arbitrarily set as long as desired electrophotographic characteristics can be obtained.

  As the acceptor compound, any compound having a group capable of reacting with the metal oxide fine particles capable of obtaining desired properties can be used, but an acceptor compound having an anthraquinone structure is particularly preferably used. Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds and aminohydroxyanthraquinone compounds, and any of them can be preferably used. Furthermore, alizarin, quinizarin, anthralfin, purpurin, 1-hydroxyanthraquinone, 2-amino-3-hydroxyanthraquinone, 1-amino-4-hydroxyanthraquinone and the like are particularly preferably used.

  The content of the acceptor compound in the undercoat layer 53 can be arbitrarily set as long as the desired characteristics are obtained, but preferably used in the range of 0.01 to 20% by mass with respect to the metal oxide fine particles. It is done. More preferably, it is used in the range of 0.05 to 10% by mass relative to the metal oxide. If the content is less than 0.01% by mass, sufficient acceptor properties that contribute to the improvement of charge accumulation in the undercoat layer cannot be imparted, so that the sustainability deteriorates such as an increase in residual potential during repeated use. Cheap. On the other hand, if the content exceeds 20% by mass, aggregation of metal oxides is likely to occur, and when the undercoat layer is formed, the metal oxide cannot form a good conductive path in the undercoat layer and is repeatedly used. Sometimes, not only does the sustainability deteriorate, such as an increase in the residual potential, but it also tends to cause image quality defects such as black spots.

  The undercoat layer 53 can be formed using an undercoat layer forming coating solution obtained by dispersing each component constituting the above undercoat layer in a solvent. The mixing ratio of the metal oxide fine particles, the acceptor compound, and the binder resin in the coating solution for forming the undercoat layer can be arbitrarily set within a range in which desired electrophotographic photoreceptor characteristics can be obtained.

  Various additives can be used in the coating liquid for forming the undercoat layer in order to improve electrical characteristics, environmental stability, and image quality. As additives, quinone compounds such as chloranil and bromoanil, tetracyanoquinodimethane compounds, fluorenone compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2- (4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (4-naphthyl) -1,3,4-oxadiazole, Oxadiazole compounds such as 2,5-bis (4-diethylaminophenyl) 1,3,4-oxadiazole, xanthone compounds, thiophene compounds, 3,3 ′, 5,5′-tetra-t-butyl Electron transport materials such as diphenoquinone compounds such as diphenoquinone, electron transport pigments such as polycyclic condensation systems and azo systems, zirconium chelate compounds, titanium chelate compounds Well-known materials, such as a metal, an aluminum chelate compound, a titanium alkoxide compound, an organic titanium compound, a silane coupling agent, can be used.

  Although the silane coupling agent is used for the surface treatment of the metal oxide, it can also be used as an additive added to the coating solution. Specific examples of the silane coupling agent used here include vinyltrimethoxysilane, γ-methacryloxypropyl-tris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ- Glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (Aminoethyl) -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, γ-chloropropyltrimethoxysilane and the like.

  Examples of zirconium chelate compounds include zirconium butoxide, zirconium zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octoate, Zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, isostearate zirconium butoxide and the like.

  Examples of titanium chelate compounds include tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt , Titanium lactate, titanium lactate ethyl ester, titanium triethanolamate, polyhydroxy titanium stearate and the like.

  Examples of the aluminum chelate compound include aluminum isopropylate, monobutoxy aluminum diisopropylate, aluminum butyrate, diethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate) and the like.

  These compounds can be used alone or as a mixture or polycondensate of a plurality of compounds.

  As a solvent for adjusting the coating solution for forming the undercoat layer, known organic solvents such as alcohols, aromatics, halogenated hydrocarbons, ketones, ketone alcohols, ethers, esters, etc. It can be selected arbitrarily. More specifically, for example, methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-acetate Usual organic solvents such as butyl, dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, and toluene can be used. These solvents can be used alone or in combination of two or more. When two or more types are mixed and used, any combination can be used as long as the solvent can dissolve the binder resin as a mixed solvent.

  As a dispersion method, known methods such as a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker can be used.

  As a method for applying the coating solution for forming the undercoat layer, a normal method such as a blade coating method, a wire bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method is used. be able to.

  The undercoat layer is formed by drying the applied layer, but drying may be performed at a temperature at which the solvent can be evaporated to form a film.

  The undercoat layer 53 can be set to any thickness as long as desired characteristics can be obtained, but the thickness is preferably 15 μm or more, more preferably 15 μm or more and 30 μm or less. Preferably it is. If the thickness of the undercoat layer is less than 15 μm, it tends to be difficult to effectively prevent black spots caused by pinhole leakage, and if it exceeds 30 μm, the charge accumulated in the undercoat layer tends to be difficult. The amount increases, and the electrical characteristics as an electrophotographic photosensitive member tend to deteriorate.

  The surface roughness of the undercoat layer 53 is preferably adjusted to ¼n (n is the refractive index of the upper layer) to ½λ of the exposure laser wavelength λ used in order to prevent moire images. In order to adjust the surface roughness, particles such as a resin can be added to the undercoat layer. As the resin particles, silicone resin particles, cross-linked PMMA resin particles, and the like can be used. In addition, the undercoat layer can be polished to adjust the surface roughness. As a polishing method, buffing, sand blasting, wet honing, grinding, or the like can be used.

  The charge generation layer 54 includes a charge generation material or a charge generation material and a binder resin.

  Any charge generating material can be used as long as it is a conventionally known charge generating material, and among these, phthalocyanine pigments are preferably used. Furthermore, among the phthalocyanine pigments, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, dichlorotin phthalocyanine, oxotitanyl phthalocyanine, and metal-free phthalocyanine are more preferably used.

  The charge generation material can be subjected to a surface treatment in order to improve dispersibility. A coupling agent or the like can be used as the surface treatment agent, but is not limited thereto.

  As coupling agents, vinyltrimethoxysilane, γ-methacryloxypropyl-tris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane , Vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (aminoethyl) -γ- Examples include silane coupling agents such as aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, and γ-chloropropyltrimethoxysilane. Among these, vinyltriethoxysilane, vinyltris (2-methoxyethoxysilane), 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Silane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3- Aminopropyltrimethoxysilane, 3-mercaptopropyltrimethoxysilane, and 3-chloropropyltrimethoxysilane are preferred.

  In addition to coupling agents, zirconium butoxide, zirconium zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl acetoacetate butoxide, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octoate Organic zirconium compounds such as zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, and isostearate zirconium butoxide may be used in combination. Tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate ammonium salt, titanium lactate, titanium lactate Organic titanium compounds such as ethyl ester, titanium triethanolamate, polyhydroxy titanium stearate, aluminum isopropylate, monobutoxy aluminum diisopropylate, aluminum butyrate, diethyl acetoacetate aluminum diisopropylate, aluminum tris (ethyl acetoacetate) An organoaluminum compound such as can also be used.

  Examples of the binder resin include polyvinyl acetal resin, polyarylate resin, polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, and cellulose resin. Insulating resins such as urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinylpyrrolidone resin, and organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane. Among these, polyvinyl acetal resin and vinyl chloride-vinyl acetate copolymer are preferably used. These binder resins can be used alone or in combination of two or more. The blending ratio (mass ratio) of the charge generating material and the binder resin is preferably in the range of 10: 1 to 1:10, and more preferably in the range of 8: 2 to 3: 7.

  The charge generation layer 54 can be formed using a coating liquid in which a charge generation material and a binder resin are dispersed in a predetermined solvent. As the solvent, those capable of dissolving the binder resin, for example, alcohols, aromatics, halogenated hydrocarbons, ketones, ketone alcohols, ethers, esters and the like can be used. More specifically, methanol, ethanol, n-propanol, iso-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, Examples include dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like. These solvents can be used alone or in combination of two or more.

  In addition, as a method for dispersing the charge generation material and the binder resin in the solvent, a normal method such as a ball mill, a roll mill, a sand mill, an attritor, or an ultrasonic wave can be used.

  When the charge generation layer 54 is formed, a normal method such as a blade coating method, a Meyer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, or a curtain coating method can be used. .

  The thickness of the charge generation layer 54 thus obtained is preferably 0.05 to 0.5 μm, preferably 0.1 to 0.3 μm.

  The charge transport layer 55 includes a charge transport material and a binder resin.

  Examples of the charge transport material include oxadiazole derivatives such as 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1,3,5-triphenylpyrazoline, 1- [ Pyrazoline derivatives such as pyridyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminostyryl) pyrazoline, triphenylamine, tri (p-methyl) phenylamine, N, N′-bis ( Aromatic tertiary amino compounds such as 3,4-dimethylphenyl) biphenyl-4-amine, dibenzylaniline, 9,9-dimethyl-N, N′-di (p-tolyl) fluorenon-2-amine, N , N′-diphenyl N, N′-bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine and other aromatic tertiary diamino compounds 1,2,4-triazine derivatives such as 3- (4′-dimethylaminophenyl) -5,6-di- (4′-methoxyphenyl) -1,2,4-triazine, 4-diethylaminobenzaldehyde-1, Hydrazone derivatives such as 1-diphenylhydrazone, 4-diphenylaminobenzaldehyde-1,1-diphenylhydrazone, [p- (diethylamino) phenyl]-(1-naphthyl) -phenylhydrazone, 2-phenyl-4-styrylquinazoline, etc. Quinazoline derivatives, benzofuran derivatives such as 6-hydroxy-2,3-di (p-methoxyphenyl) benzofuran, α-stilbene derivatives such as p- (2,2-diphenylvinyl) -N, N′-diphenylaniline, enamines Derivatives, carbazole derivatives such as N-ethylcarbazole, poly- And hole transport materials such as N-vinylcarbazole and its derivatives. In addition, quinone compounds such as chloranil, bromoanil, anthraquinone, tetracyanoquinodimethane compounds, fluorenone compounds such as 2,4,7-trinitrofluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2 -(4-biphenyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (4-naphthyl) -1,3,4-oxadiazole, 2 Oxadiazole compounds such as 1,5-bis (4-diethylaminophenyl) -1,3,4-oxadiazole, xanthone compounds, thiophene compounds, 3,3 ′, 5,5′-tetra-t-butyl Electron transport materials such as diphenoquinone compounds such as diphenoquinone can also be used. Furthermore, a polymer having a group composed of the above compound in the main chain or side chain can also be used. These charge transport materials can be used alone or in combination of two or more.

  As the binder resin, an electric insulating film-forming resin is preferable. Examples of such resins include polycarbonate resin, polyarylate resin, polyester resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, chloride Vinylidene-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N -Carbazole, polyvinyl butyral, polyvinyl formal, polysulfone, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenol resin, polyamide, carboxy-methyl cellulose Vinylidene polymer wax chloride, polyurethane, and the like. These binder resins can be used individually by 1 type or in mixture of 2 or more types. The blending ratio (mass ratio) between the binder resin and the charge transport material can be arbitrarily set in any case, but it is preferable to set it while paying attention to a decrease in electrical characteristics and a decrease in film strength.

  The charge transport layer 55 is formed by applying a charge transport layer coating liquid containing the above material onto the charge generation layer 54 and drying it. The solvent used in the coating solution can be arbitrarily selected from known organic solvents as long as the desired electrophotographic photoreceptor characteristics can be obtained, but dioxane, tetrahydrofuran, methylene chloride, chloroform, chlorobenzene, toluene and the like are preferable. Used for. Moreover, these can be used individually by 1 type or in mixture of 2 or more types.

  The thickness of the charge transport layer 55 is preferably 5 to 50 μm, more preferably 10 to 50 μm. From the viewpoint of extending the service life, it is preferable to increase the thickness in order to compensate for film wear due to repeated use, and it is even more preferable to set the thickness of the charge transport layer 55 to 35 μm or more and 50 μm or less. If the thickness of the charge transport layer 55 exceeds 50 μm, it tends to be difficult to achieve both the reproduction of one dot and the ensuring of resolution.

  Additives such as an antioxidant and a light stabilizer may be added to the photosensitive layer 52 for the purpose of preventing deterioration of the photoreceptor due to ozone or oxidizing gas generated in the image forming apparatus or light or heat. it can.

  Examples of the antioxidant include hindered phenol, hindered amine, paraphenylenediamine, arylalkane, hydroquinone, spirochroman, spiroidanone and derivatives thereof, organic sulfur compounds, and organic phosphorus compounds.

  Examples of phenolic antioxidants include 2,6-di-t-butyl-4-methylphenol, styrenated phenol, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxy Phenyl) -propionate, 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2-t-butyl-6- (3′-tert-butyl-5′-methyl-2′-) Hydroxybenzyl) -4-methylphenyl acrylate, 4,4′-butylidene-bis- (3-methyl-6-tert-butylphenol), 4,4′-thio-bis- (3-methyl-6-tert-butylphenol) ), 1,3,5-tris (4-t-butyl-3-hydroxy-2,6-dimethylbenzyl) isocyanurate, tetrakis- [methylene-3- (3 ′, 5 ′,-di-t-butyl) − 4′-hydroxyphenyl) propionate] methane, 3,9-bis [2- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionyloxy] -1,1-dimethylethyl] -2 4,8,10-tetraoxaspiro [5,5] undecane and the like.

  Examples of hindered amine compounds include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionyloxy]- 2,2,6,6-tetramethylpiperidine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, dimethyl-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine succinate Polycondensate, poly [{6- (1,1,3,3-tetramethylbutyl) imino-1,3,5-triazine-2,4-diimyl} {(2,2,6,6-tetra Methyl-4-piperidyl) imino} hexamethylene {(2,3,6,6-tetramethyl-4-piperidyl) imino}], 2- (3,5-di-t-butyl-4-hydroxybenzyl)- 2-n-butylmalonate bis (1,2,2,6,6-pentamethyl-4-piperidyl), N, N′-bis (3-aminopropyl) ethylenediamine-2,4-bis [N-butyl- N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3,5-triazine condensate and the like.

  Examples of organic sulfur-based antioxidants include dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythritol-tetrakis. -(Β-laurylthiopropionate), ditridecyl-3,3′-thiodipropionate, 2-mercaptobenzimidazole and the like.

  Examples of the organophosphorus antioxidant include trisnonylphenyl phosfte, triphenyl phosfte, tris (2,4-di-t-butylphenyl) -phosfte and the like.

  The organic sulfur-based and organic phosphorus-based antioxidants are called secondary antioxidants, and a synergistic effect can be obtained by using them together with a primary antioxidant such as a phenol-based or amine-based antioxidant.

  Examples of the light stabilizer include benzophenone, benzotriazole, dithiocarbamate, and tetramethylpiperidine derivatives.

  Examples of the benzophenone light stabilizer include 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, and the like.

  Examples of the benzotriazole light stabilizer include 2- (2′-hydroxy-5′-methylphenyl) -benzotriazole, 2- [2′-hydroxy-3 ′-(3 ″, 4 ″, 5 ′, 6 ″). -Tetrahydrophthalimido-methyl) -5'-methylphenyl] benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2- (2'- Hydroxy-3′-t-butyl-5′-methylphenyl) -5-chlorobenzotriazole, 2- (2′-hydroxy-3 ′, 5 ′,-di-t-butylphenyl) benzotriazole, 2- ( 2'-hydroxy-5'-t-octylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5',-di-t-amylphenyl) benzotriazole And the like.

  Examples of other compounds include 2,4-di-t-butylphenyl-3 ', 5'-di-t-butyl-4'-hydroxybenzoate and nickel dibutyl-dithiocarbamate.

  The photosensitive layer 52 can contain at least one electron accepting substance for the purpose of improving sensitivity, reducing residual potential, and reducing fatigue during repeated use.

Examples of the electron accepting substance include succinic anhydride, maleic anhydride, dibromomaleic anhydride, phthalic anhydride, tetrabromophthalic anhydride, tetracyanoethylene, tetracyanoquinodimethane, o-dinitrobenzene, m-dinitrobenzene. , Chloranilquinone, dinitroanthraquinone, trinitrofluorenone, picric acid, o-nitrobenzoic acid, p-nitrobenzoic acid, phthalic acid and the like. Among these, fluorenone compounds, quinone compounds and, Cl-, CN-, NO 2 _- benzene derivatives having an electron attractive substituent, and the like are particularly preferable.

  Further, a solid lubricant or a metal oxide can be dispersed in the charge transport layer 55 which is the outermost layer of the photoreceptor 1 for the purpose of reducing wear. Solid lubricants include fluorine-containing resin particles (ethylene tetrafluoride, ethylene trifluoride chloride, ethylene tetrafluoride hexafluoropropylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride, and those And the like, and silicon-containing resin particles. Examples of the metal oxide include silica, alumina, titanium oxide, tin oxide and the like. When the solid lubricant is dispersed, the friction coefficient on the surface of the charge transport layer decreases, so that wear can be suppressed. Further, when the metal oxide is dispersed, the mechanical hardness of the charge transport layer is increased, so that wear can be suppressed. Further, since the fluorine-containing resin particles are hardly dispersed particles, dispersibility is improved by using a fluorine-containing polymer-based dispersion aid.

  Examples of the method for dispersing the solid lubricant and metal oxide in the coating solution for forming a charge transport layer include a roll mill, a ball mill, a vibrating ball mill, an attritor, a sand mill, a colloid mill, a paint shaker, a homogenizer, and a high-pressure treatment type homogenizer. A method is mentioned. In this dispersion, it is effective to make the dispersed particles 1.0 μm or less, preferably 0.5 μm or less.

  Further, a small amount of silicone oil can be added to the charge transport layer forming coating solution as a leveling agent for improving the smoothness of the coating film.

  In the photoreceptor 1 of this embodiment, the distance from the outermost surface of the photosensitive layer to the interface between the charge generation layer and the charge transport layer (the film thickness of the charge transport layer 55 in the photoreceptor 1) is 35 μm to 50 μm. Preferably there is. If the distance is less than 35 μm, the effect of extending the life tends to be difficult to obtain, and if it exceeds 50 μm, it tends to be difficult to achieve both the reproducibility and resolution of one dot.

Further, the capacitance per unit area from the outermost surface of the photosensitive layer to the interface between the charge generation layer and the charge transport layer is preferably 56 pF / cm ^{2 to} 80 pF / cm ² . If the capacitance is less than 56 pF / cm ² , the electric field at the time of charge transfer tends to be weak and scattering of the mobile charge tends to occur, and if it exceeds 80 pF / cm ² , the life of the photoreceptor is prolonged. It tends to be difficult to obtain the effect.

Furthermore, the half exposure amount of the photosensitive member 1 is preferably 0.4 mJ / ^{m 2} or more 1 mJ / ^{m 2} or less. If the half exposure amount is less than 0.4 mJ / m ² , the reproducibility of one dot line is ensured, but the resolution tends to decrease and the line tends to be crushed, and if it exceeds 1 mJ / m ^2. However, the amount of exposure light is insufficient, and it tends to be difficult to cope with high-speed printing and high-resolution printing. In the present embodiment, for example, an exposure amount (mJ / m ² ) necessary for attenuating the charging potential from −700 V to −350 V can be used as the half exposure amount of the photoreceptor.

In the present embodiment, by using the photoconductor 1 that satisfies all the above conditions and performing image formation with the charging potential V ₀ and the exposure amount Ex satisfying the above formula (1), high resolution and high performance can be achieved over a long period of time. An image can be more reliably formed with fine reproducibility.

  In the photoreceptor used in the present invention, an intermediate layer 57 may be provided between the undercoat layer 53 and the photosensitive layer 52 as shown in FIG. Thereby, an improvement in electrical characteristics, an improvement in image quality, an improvement in image quality maintenance, an improvement in adhesion of the photosensitive layer, and the like can be achieved.

  The constituent material of the intermediate layer provided for such purpose includes acetal resin such as polyvinyl butyral, polyvinyl alcohol resin, casein, polyamide resin, cellulose resin, gelatin, polyurethane resin, polyester resin, methacrylic resin, acrylic resin, polychlorinated resin. Polymer resins such as vinyl resin, polyvinyl acetate resin, vinyl chloride-vinyl acetate-maleic anhydride resin, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, melamine resin, zirconium, titanium, aluminum, manganese, silicon atom And organometallic compounds containing the above. These compounds can be used alone or as a mixture or polycondensate of a plurality of compounds. Among these, an organometallic compound containing a zirconium or silicon atom is preferable because it has excellent performance such as low residual potential, little potential change due to environment, and little potential change due to repeated use.

  Examples of organometallic compounds containing silicon atoms include vinyltrimethoxysilane, γ-methacryloxypropyl-tris (β-methoxyethoxy) silane, β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, and γ-glycid. Xylpropyltrimethoxysilane, vinyltriacetoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β- (amino Ethyl) -γ-aminopropylmethylmethoxysilane, N, N-bis (β-hydroxyethyl) -γ-aminopropyltriethoxysilane, γ-chloropropyltrimethoxysilane, and the like. Among these, vinyltriethoxysilane, vinyltris (2-methoxyethoxysilane), 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Silane, N-2- (aminoethyl) 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-phenyl-3-aminopropyl It is particularly preferable to use a silane coupling agent such as trimethoxysilane, 3-mercaptopropyltrimethoxysilane, or 3-chloropropyltrimethoxysilane.

  Zirconium-containing organometallic compounds include zirconium butoxide, zirconium zirconium acetoacetate, zirconium triethanolamine, acetylacetonate zirconium butoxide, ethyl zirconium acetoacetate, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, octanoic acid Zirconium, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, methacrylate zirconium butoxide, stearate zirconium butoxide, isostearate zirconium butoxide and the like.

  Examples of organometallic compounds containing titanium include tetraisopropyl titanate, tetranormal butyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate, titanium acetylacetonate, polytitanium acetylacetonate, titanium octylene glycolate, titanium lactate Ammonium salts, titanium lactate, titanium lactate ethyl ester, titanium triethanolamate, polyhydroxytitanium stearate and the like can be mentioned.

  Examples of the organometallic compound containing aluminum include aluminum isopropylate, monobutoxyaluminum diisopropylate, aluminum butyrate, diethyl acetoacetate aluminum diisopropylate, and aluminum tris (ethyl acetoacetate).

  When these intermediate layers are formed, an arbitrary film thickness can be set within a range where desired characteristics can be obtained. However, in addition to improving the coatability of the upper layer, these intermediate layers also play the role of an electrical blocking layer, so if the film thickness is too large, the electrical barrier becomes too strong, resulting in desensitization and repetition. May cause an increase in potential. Therefore, when forming the intermediate layer using the above-mentioned material, it is preferable to set the film thickness in the range of 0.1 to 5 μm.

  In the photoreceptor used in the present invention, the photosensitive layer 52 may have a protective layer 56 as the outermost layer of the photoreceptor, as shown in FIG.

Examples of the protective layer 56 include a cured film formed by including a compound represented by the following general formula (I).
F [−D−A] _b (I)
Here, in formula (I), F represents an organic group derived from a photofunctional compound, D represents a divalent group, and A represents -SiR ¹ _(3-a) (OR ² ) _a . Represents a substituted silicon group having a hydrolyzable group, and b represents an integer of 1 to 4. Here, R ¹ represents hydrogen, an alkyl group, or a substituted or unsubstituted aryl group, R ² represents hydrogen, an alkyl group, or a trialkylsilyl group, and a represents an integer of 1 to 3.

A substituted silicon group having a hydrolyzable group represented by A in the general formula (I), that is, -SiR ¹ _(3-a) (OR ² ) _a is a three-dimensional Si-O-Si by cross-linking reaction. It plays a role in forming bonds (inorganic glassy network).

  In general formula (I), F is an organic group having photoelectric characteristics, more specifically, photocarrier transport characteristics, and the structure of a photofunctional compound conventionally known as a charge transport material is used as it is. be able to. Specific examples of the organic group represented by F include triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted ethylene compounds, stilbene compounds, anthracene compounds, hydrazone compounds, and the like. Examples include a compound skeleton having a hole transporting property, and a compound skeleton having an electron transporting property such as a quinone compound, a fluorenone compound, a xanthone compound, a benzophenone compound, a cyanovinyl compound, and an ethylene compound.

ここで、一般式（ＩＩ）中、Ａｒ^１〜Ａｒ^４は、それぞれ独立に、置換あるいは未置換のアリール基を表す。Ａｒ^５は、置換あるいは未置換のアリール基又はアリーレン基を表す。Ａｒ^１〜Ａｒ^４のうち１〜４個は、−Ｄ−Ａで表される基との結合手を有する。Ｄ及びＡはそれぞれ上記一般式（Ｉ）中のＤ及びＡと同一の定義内容を示す。ｋは、０又は１を表す。 Preferable examples of the organic group represented by F include groups represented by the following general formula (II). When F is a group represented by the general formula (II), particularly excellent photoelectric characteristics and mechanical characteristics are exhibited.

Here, in general formula (II), Ar < ¹ > -Ar < ⁴ > represents a substituted or unsubstituted aryl group each independently. Ar ⁵ represents a substituted or unsubstituted aryl group or arylene group. 1-4 of Ar ^{1 to} Ar ⁴ have a bond with a group represented by -DA. D and A each have the same definition as D and A in the general formula (I). k represents 0 or 1.

Ar ^{1 to} Ar ⁴ in the general formula (II) are preferably any of the following formulas (II-1) to (II-7).

_{-Ar-Z 's -Ar-X} m (II-7)

In the above formulas (II-1) to (II-7), R ⁶ is substituted with a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms. Or a phenyl group, an unsubstituted phenyl group, or an aralkyl group having 7 to 10 carbon atoms, wherein R ^{7 to} R ⁹ are each independently a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. , A phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, or an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom. 1 represents one, Ar represents a substituted or unsubstituted arylene group, X represents a group represented by -DA in the general formula (I), and m and s each independently represent 0 or 1 , T each independently represents an integer of 1 to 3 .

  Here, as Ar in Formula (II-7), what is represented by following formula (II-8) or (II-9) is preferable.

In the above formulas (II-8) and (II-9), R ¹⁰ and R ¹¹ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, unsubstituted or a carbon number. A phenyl group substituted with 1 to 4 alkoxy groups, an aralkyl group having 7 to 10 carbon atoms or a halogen atom is shown, and t is an integer of 1 to 3.

Moreover, as Z 'in Formula (II-7), what is represented by either of following formula (II-10)-(II-17) is preferable.
_{- (CH 2) q - (} II-10)
_{- (CH 2 CH 2 O)} r - (II-11)

In the above formulas (II-10) to (II-17), R ¹² and R ¹³ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, unsubstituted or carbon number. 1 type selected from the group consisting of a phenyl group substituted with 1 to 4 alkoxy groups, an aralkyl group having 7 to 10 carbon atoms or a halogen atom, W represents a divalent group, and q and r are each independently Represents an integer of 1 to 10, and t independently represents an integer of 1 to 3.

W in the formulas (II-16) and (II-17) is preferably any one of divalent groups represented by the following (II-18) to (II-26).
—CH ₂ — (II-18)
_{-C (CH 3) 2 - (} II-19)
-O- (II-20)
-S- (II-21)
_{-C (CF 3) 2 - (} II-22)
—Si (CH ₃ ) ₂ — (II-23)

上記式（ＩＩ−２５）中、ｕは０〜３の整数を示す。

In said formula (II-25), u shows the integer of 0-3.

In general formula (II), Ar ⁵ is preferably an aryl group exemplified in the description of Ar ^{1 to} Ar ⁴ when k is 0. An arylene group excluding a hydrogen atom is preferred.

In the general formula (I), the divalent group represented by D plays a role of linking F that imparts photoelectric characteristics and A that is directly bonded to a three-dimensional inorganic glassy network, On the other hand, it imparts moderate flexibility to an inorganic glassy network that is brittle and plays a role of improving the toughness of the film. Examples of the divalent group represented by D, and _{specifically, -C n H 2n -, -} C n H 2n-2 -, - C n H 2n-4 - 2 divalent hydrocarbon group represented by (n represents an integer of 1~15), - COO -, - S -, - O -, - CH 2 -C 6 H 4 -, - n = CH -, - C 6 H 4 -C 6 H 4 -, A combination of these, or a substituent introduced.

  In general formula (I), b is preferably 2 or more. When b is 2 or more, the photofunctional organosilicon compound represented by the general formula (I) has two or more Si atoms, which facilitates formation of an inorganic glassy network and improves mechanical strength. Tend to.

  The compound represented by general formula (I) may be used individually by 1 type, and may be used together 2 or more types.

A compound represented by the following general formula (III) may be used in combination with the compound represented by the general formula (I) for the purpose of further improving the mechanical strength of the cured film.
B [-A] _n (III)
Here, in formula (III), A represents a substituted silicon group having -SiR ¹ _(3-a) hydrolyzable group represented by ^(OR _{2) a.} Here ^is the same as R 1, ^R 1 in ^{R 2} and a have the general formula (I), ^{R 2} and a. B represents an n-valent hydrocarbon group which may contain a branch, an n-valent phenyl group, or —NH—, or an n-valent group composed of a combination of two or more thereof, where n is 2 or more. Indicates an integer.

The compound represented by the general formula (III) is a compound having a substituted silicon group having a hydrolyzable group represented by A, that is, -SiR ¹ _(3-a) (OR ² ) _a . The compound represented by the general formula (III) forms a Si—O—Si bond by the reaction with the compound represented by the general formula (I) or the reaction between the compounds represented by the general formula (III). Thus, a three-dimensional crosslinked cured film is provided. When the compound represented by the general formula (III) and the compound represented by the general formula (I) are used in combination, the crosslinked structure of the cured film tends to be three-dimensional, and the cured film has an appropriate flexibility. Therefore, stronger mechanical strength can be obtained. Preferred examples of the compound represented by the general formula (III) are shown in Table 1.

  In addition to the compound represented by the general formula (I), another compound capable of crosslinking reaction may be used in combination. As such a compound, various silane coupling agents, commercially available silicone hard coat agents, and the like can be used.

  As silane coupling agents, vinyltrichlorosilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxy Silane, γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylmethyldimethoxysilane, N-β (aminoethyl) γ-aminopropyltriethoxysilane, tetramethoxysilane, methyltrimethoxysilane, Examples include dimethyldimethoxysilane.

  As a commercially available hard coat agent, KP-85, CR-39, X-12-2208, X-40-9740, X-4101007, KNS-5300, X-40-2239 (manufactured by Shin-Etsu Silicone), AY42-440, AY42-441, AY49-208 (manufactured by Toray Dow Corning) and the like.

  A fluorine-containing compound can be added to the protective layer 56 for the purpose of imparting surface lubricity. By improving the surface lubricity, the coefficient of friction with the cleaning member decreases, and the wear resistance can be improved. It also has the effect of preventing the adhesion of discharge products, developer, paper dust, etc. to the surface of the photoreceptor, which helps to improve the life of the photoreceptor.

  As the fluorine-containing compound, a fluorine atom-containing polymer such as polytetrafluoroethylene can be added as it is, or fine particles of these polymers can be added. In the case of a cured film formed of the compound represented by the general formula (I), it is desirable to add a fluorine-containing compound that can react with an alkoxysilane and configure it as a part of the crosslinked film. Examples of such fluorine-containing compounds include (tridecafluoro-1,1,2,2-tetrahydrooctyl) triethoxysilane, (3,3,3-trifluoropropyl) trimethoxysilane, 3- (heptafluoro Isopropoxy) propyltriethoxysilane, 1H, 1H, 2H, 2H-perfluoroalkyltriethoxysilane, 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane, 1H, 1H, 2H, 2H-perfluorooctyltri An ethoxysilane etc. are mentioned.

  The content of the fluorine-containing compound is preferably 20% by mass or less based on the total amount of the protective layer 56. When the content of the fluorine-containing compound exceeds 20% by mass, a problem may occur in the film formability of the crosslinked cured film.

  The protective layer 56 containing the above compound has sufficient oxidation resistance, but an antioxidant may be added for the purpose of imparting stronger oxidation resistance.

  Antioxidants are preferably hindered phenols or hindered amines, organic sulfur antioxidants, phosphite antioxidants, dithiocarbamate antioxidants, thiourea antioxidants, benzimidazole antioxidants. , Etc., may be used. As content of antioxidant, 15 mass% or less is preferable on the basis of the protective layer 56 whole quantity, and 10 mass% or less is further more preferable.

  Examples of the hindered phenol antioxidant include 2,6-di-t-butyl-4-methylphenol, 2,5-di-t-butylhydroquinone, N, N′-hexamethylene bis (3,5-di). -T-butyl-4-hydroxyhydrocinnamide, 3,5-di-t-butyl-4-hydroxybenzylphosphonate-diethyl ester, 2,4-bis [(octylthio) methyl] -o-cresol, 2 , 6-di-t-butyl-4-ethylphenol, 2,2'-methylenebis (4-methyl-6-t-butylphenol), 2,2'-methylenebis (4-ethyl-6-t-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 2,5-di-tert-amylhydroquinone, 2-tert-butyl-6- (3-butyl-2-hydroxy) Proxy-5-methylbenzyl) -4-methylphenyl acrylate, 4,4'-butylidene bis (3-methyl -6-t-butylphenol) and the like.

  Further, other additives used for forming a known coating film can be added to the protective layer 56, and known materials such as a leveling agent, an ultraviolet absorber, a light stabilizer, and a surfactant are used. be able to.

  The protective layer 56 is formed by applying a coating solution containing the above compound onto the charge transport layer 55 and heat-treating it. Thereby, the compound etc. which are represented by general formula (I) raise | generate a crosslinking hardening reaction three-dimensionally, and a firm cured film is formed. The temperature of the heat treatment is not particularly limited as long as it does not affect the lower layer, but is preferably room temperature to 200 ° C, more preferably 100 to 160 ° C.

  The crosslinking curing reaction may be performed without a catalyst, or an appropriate catalyst may be used. Catalysts include acid catalysts such as hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, trifluoroacetic acid, bases such as ammonia and triethylamine, organotin compounds such as dibutyltin diacetate, dibutyltin dioctoate, stannous oxalate, Examples thereof include organic titanium compounds such as tetra-n-butyl titanate and tetraisopropyl titanate, iron salts of organic carboxylic acids, manganese salts, cobalt salts, zinc salts, zirconium salts, and aluminum chelate compounds.

  Solvents used in the coating solution for forming the protective layer 56 are water, methanol, ethanol, n-propanol, i-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, acetic acid. Usual organic solvents such as methyl, n-butyl acetate, dioxane, tetrahydrofuran, methylene chloride, chloroform, dimethyl ether, and dibutyl ether can be used. These may be used singly or in combination of two or more. However, it is preferable to use a solvent that hardly dissolves the lower layer (the charge transport layer 55 in the photoreceptor shown in FIG. 3) to which this coating solution is applied. preferable.

  As a coating method of the coating liquid for forming the protective layer 56, a normal method such as a blade coating method, a Mayer bar coating method, a spray coating method, a dip coating method, a bead coating method, an air knife coating method, a curtain coating method, or the like is used. Can be used.

  The thickness of the protective layer 56 thus formed is preferably 0.5 to 20 μm, more preferably 0.5 to 5 μm.

  The charging device 2 is of a type (contact charging type) in which a conductive member (charging roll) is brought into contact with the surface of the electrophotographic photoreceptor 1 to charge the surface of the photoreceptor 1. In the present invention, a contactless charging device such as corotron or scorotron may be used instead of the contact charging device.

  As described above, the charging method used in the present invention is not particularly limited. However, in recent years, a contact charging method that generates less ozone and has a low environmental load tends to be used preferably. In general, the contact charging method has a weak charging ability as compared with non-contact charging methods such as scorotron and corotron, and is likely to be a problem particularly in an image forming apparatus that requires a high-speed response. When the charging ability is weak, the charge remaining in the photosensitive layer of the electrophotographic photosensitive member causes image quality defects such as ghost. However, according to the image forming apparatus of the present embodiment, even when the electrophotographic photosensitive member having the thickened photosensitive layer is combined with the contact charging method, the charging voltage and the exposure amount are controlled by the control device 13. It is suitably controlled and can sufficiently prevent the image quality defect as described above from the beginning of use for a long time.

  As the contact-type charging member, a member in which an elastic layer, a resistance layer, a protective layer and the like are provided on the outer peripheral surface of the core material is preferably used. The shape of the conductive member may be any of a brush shape, a blade shape, a pin electrode shape, a roller shape, and the like.

  As the material of the core material, a conductive material such as iron, copper, brass, stainless steel, aluminum, nickel, or the like is used. Also, a resin molded product in which conductive particles or the like are dispersed can be used.

  As the material of the elastic layer, a material having conductivity or semiconductivity, for example, a material in which conductive particles or semiconducting particles are dispersed in a rubber material can be used.

  Examples of rubber materials include EPDM, polybutadiene, natural rubber, polyisobutylene, SBR, CR, NBR, silicone rubber, urethane rubber, epichlorohydrin rubber, SBS, thermoplastic elastomer, norbornene rubber, fluorosilicone rubber, ethylene oxide rubber, chloroprene. Rubber, isoprene rubber, epoxy rubber or the like is used.

Examples of the conductive particles or semiconductive particles include carbon black, zinc, aluminum, copper, iron, nickel, chromium, titanium and other metals, ZnO—Al ₂ O ₃ , SnO ₂ —Sb ₂ O ₃ , In _2. Examples include metal oxides such as O ₃ —SnO ₂ , ZnO—TiO ₂ , MgO—Al ₂ O ₃ , FeO—TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO, and MgO. . These materials can be used individually by 1 type or in mixture of 2 or more types.

  Examples of the material of the resistance layer and the protective layer include those in which conductive particles or semiconductive particles are dispersed in a binder resin and the resistance is controlled. Examples of the binder resin include acrylic resin, cellulose resin, polyamide resin, methoxymethylated nylon, ethoxymethylated nylon, polyurethane resin, polycarbonate resin, polyester resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin, and PFA. Polyolefin resins such as FEP and PET, styrene butadiene resins, and the like are used. Examples of the conductive particles or semiconductive particles include carbon black, metal, and metal oxide similar to those of the elastic layer. Further, if necessary, an antioxidant such as hindered phenol and hindered amine, a filler such as clay and kaolin, and a lubricant such as silicone oil can be added.

  As a means to form layers such as elastic layer, resistance layer and protective layer, blade coating method, Meyer bar coating method, spray coating method, dip coating method, bead coating method, air knife coating method, curtain coating method, melt molding Method, injection molding method and the like can be used.

  When the photosensitive member is charged using these conductive members, a voltage is applied to the conductive member by the power supply unit 3. The applied voltage may be either a DC voltage or a DC voltage superimposed with an AC voltage. Good.

  As the exposure device 4, an optical system device that can expose a light source such as a semiconductor laser, an LED (light emitting diode), a liquid crystal shutter, or the like on the surface of the electrophotographic photoreceptor can be used. For color image formation, a surface-emitting laser light source capable of multi-beam output is also effective.

  As the developing device 5, for example, a general developing device that performs development by bringing a magnetic or non-magnetic one-component developer or two-component developer into contact or non-contact with each other can be used. Such a developing device is not particularly limited as long as it has the functions described above, and can be appropriately selected according to the purpose. For example, a known developing device having a function of attaching the one-component developer or the two-component developer to the photosensitive member 1 using a brush, a roller, or the like can be used.

  Examples of the toner used in the image forming apparatus according to the present embodiment include a toner including a binder resin and a colorant. Examples of the binder resin include homopolymers and copolymers such as styrenes, monoolefins, vinyl esters, α-methylene aliphatic monocarboxylic acid esters, vinyl ethers, and vinyl ketones. Typical binder resins include polystyrene, styrene-alkyl acrylate copolymer, styrene-alkyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer. Examples thereof include coalescence, polyethylene, and polypropylene. Furthermore, polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like can also be used.

  Examples of the colorant include magnetic powders such as magnetite and ferrite, carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, Lamp Black, Rose Bengal, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 57: 1, C.I. I. Pigment yellow 97, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. Pigment Blue 15: 3 can be cited as a representative example.

  The toner may be internally added or externally added with a known additive such as a charge control agent, a release agent, or other inorganic fine particles.

  Typical examples of the release agent include low molecular weight polyethylene, low molecular weight polypropylene, Fischer-Tropsch wax, montan wax, carnauba wax, rice wax, and candelilla wax.

  Known charge control agents can be used, but charge control agents such as azo-based metal complex compounds, metal complex compounds of salicylic acid, and resin types containing polar groups can be used.

  As other inorganic fine particles, small-diameter inorganic fine particles having an average primary particle size of 40 nm or less are used for the purpose of powder flowability, charge control, etc., and if necessary, larger diameters are used to reduce adhesion. Inorganic or organic fine particles may be used in combination. As these other inorganic fine particles, known ones can be used.

  In addition, the surface treatment of the small-diameter inorganic fine particles is effective because the dispersibility becomes high and the effect of increasing the powder fluidity increases.

  As a method for producing the toner used in the present invention, a polymerization method such as an emulsion polymerization aggregation method or a dissolution suspension method is preferably used because high shape controllability can be obtained. In addition, a manufacturing method may be performed in which the toner obtained by the above method is used as a core, and agglomerated particles are further adhered and heat-fused to give a core-shell structure. When an external additive is added, it can be produced by mixing the toner and the external additive with a Henschel mixer or a V blender. Further, when the toner is manufactured by a wet method, it can be externally added by a wet method.

  Examples of the primary transfer roll 10 include those in which an elastic layer and a surface layer are provided in this order on a cylindrical substrate. As the substrate, for example, a metal pipe formed from aluminum, stainless steel (SUS), copper, iron or the like is preferably used.

Examples of the material of the elastic layer include those having conductivity or semiconductivity, and those obtained by dispersing conductive particles or semiconducting particles in a rubber material. Examples of rubber materials include EPDM, polybutadiene, natural rubber, polyisobutylene, SBR, CR, NBR, silicone rubber, urethane rubber, epichlorohydrin rubber, SBS, thermoplastic elastomer, norbornene rubber, fluorosilicone rubber, ethylene oxide rubber, chloroprene. Rubber, isoprene rubber, epoxy rubber or the like is used. Examples of the conductive particles or semiconductive particles include carbon black, zinc, aluminum, copper, iron, nickel, chromium, titanium and other metals, ZnO—Al ₂ O ₃ , SnO ₂ —Sb ₂ O ₃ , In _2. Examples include metal oxides such as O ₃ —SnO ₂ , ZnO—TiO ₂ , MgO—Al ₂ O ₃ , FeO—TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO, and MgO. . These materials can be used individually by 1 type or in mixture of 2 or more types.

  Moreover, as a material for the surface layer, for example, fluororubber in which fluororesin fine particles are dispersed is preferably used.

  The primary transfer roll 10 is not limited to the three layers of the surface layer, the elastic layer, and the base material, and can be further multilayered.

  As the transfer roll 7, for example, a contact type transfer charger using a belt, a roller, a film, a rubber blade or the like, or a known transfer charger such as a scorotron transfer charger using a corona discharge or a corotron transfer charger. Can be mentioned.

  The cleaning device 6 is for removing residual toner adhering to the surface of the electrophotographic photosensitive member after the transfer process, and the electrophotographic photosensitive member thus cleaned is repeatedly used for the image forming process described above. . As the cleaning device, brush cleaning, roll cleaning, and the like can be used in addition to the cleaning blade. Among these, it is preferable to use the cleaning blade. Examples of the material for the cleaning blade include urethane rubber, neoprene rubber, and silicone rubber.

  Although not shown in FIG. 1, the image forming apparatus 100 may further include a static eliminator. As a result, when the electrophotographic photosensitive member is repeatedly used, the phenomenon that the residual potential of the electrophotographic photosensitive member is brought into the next cycle is prevented, so that the image quality can be further improved. Examples of the static eliminator include an erase light irradiation device.

  FIG. 6 is a schematic configuration diagram showing another preferred embodiment of the image forming apparatus of the present invention, and shows the internal configuration of a so-called tandem type digital color printer. Note that the image forming apparatus 200 can adopt the configuration of the image forming apparatus 100 as appropriate.

  As shown in FIG. 6, the image forming apparatus 200 includes three image forming units 120a, 120b, and 120c that form color toner images, and an image forming unit 120d that forms black toner images. The image forming units 120a, 120b, 120c, and 120d share the intermediate transfer belt 108 and are arranged substantially in parallel. The image forming units 120a, 120b, 120c, and 120d form a black-and-white image composed of only black toner or a color image including a color toner image. The image forming unit 120a has an electrophotographic photosensitive member 101a, and a developing device 102a, a charging device 103a, a cleaning blade 106a, and a transfer bias roll 104a are arranged along the outer periphery of the electrophotographic photosensitive member 101a. An intermediate transfer member 108 is disposed between the transfer bias roll 104a and the photosensitive member 101a. The intermediate transfer member 108 is an endless belt, and is circulated by a driving roller 114, a driven roller 115, and a tension roller 116. On the surface of the electrophotographic photosensitive member 101a and between the developing unit 102a and the charging unit 103a, a desired image exposure is performed by a ROS (Laser Output Scanner) 111 as an exposure device. . Therefore, when a yellow toner image is formed on the intermediate transfer member 108, the electrophotographic photosensitive member 101a is rotated, the surface of the photosensitive member 101a is charged by the charger 103a, and a desired image exposure is performed by the ROS 111. The toner is developed by the developing unit 103a, and an electric field is applied by the transfer bias roll 104a to transfer the yellow toner image to the intermediate transfer member. After the transfer, the yellow toner remaining on the surface of the electrophotographic photosensitive member 101a is removed by the cleaning blade 106a. Between the developing device 102a and the charger 103a, there is a potential measuring device 109a that measures the surface potential of the photoreceptor 101a after charging, and a potential measuring device 110a that measures the surface potential of the photoreceptor 101a after exposure. Has been placed. Further, the image forming apparatus 200 includes a control device 113 that is electrically connected to the potential measurement device 109a and the potential measurement device 110a. Further, the control device 113 is electrically connected to a power source unit (not shown) connected to the charger 103a and the ROS 111.

  The image forming units 120b, 120c, and 120d have substantially the same configuration as that of the image forming unit 120a except for the types of the electrophotographic photosensitive member and the toner, and their operations are the same as those of the image forming unit 120a. Accordingly, in the image forming units 120b, 120c, and 120d, constituent elements corresponding to the charger 103a, the developing device 102a, the cleaning blade 106a, the transfer bias roll 104a, the potential measuring device 109a, and the potential measuring device 110a of the image forming unit 120a. And b, c, d instead of a in the above reference numerals.

  Further, the image forming apparatus 200 transfers the toner image on the intermediate transfer body 108 by applying an electric field onto the paper tray 130 that stores the paper P as a transfer medium and the paper P sent out from the paper tray 130. A transfer roll 117 and a fixing device 118 that fixes the toner image transferred onto the paper P to the paper P are provided. The paper P is sandwiched between the secondary transfer roll 117 and the driven roll 114. Therefore, when an electric field is applied to the paper P by the secondary transfer roll 117, the toner image on the intermediate transfer member 108 is transferred onto the paper P, and the transferred toner image is fixed by the fixing device 118, and thus the black and white image or A color image will be obtained.

  In the image forming apparatus 200, in each of the image forming units 120a, 120b, 120c, and 120d, each process of charging, exposure, and development (reversal development) is performed as each photoconductor rotates, and Y, M, C, and K toner images are formed. These toner images are transferred onto the intermediate transfer belt 108 by a transfer process.

  In the image forming apparatus 200 as well as the image forming apparatus 100, the control device 113 is connected to a charger so that charging and exposure are performed at a predetermined charging potential and exposure amount based on the film thickness of the photosensitive layer. Controls the power supply and ROS.

  Examples of the intermediate transfer belt 108 include a belt having a base material formed by molding a resin material into a belt shape. As the resin material, a conventionally known resin can be used. For example, polyimide resin, polycarbonate resin (PC), polyvinylidene fluoride (PVDF), polyalkylene terephthalate (PAT), ethylenetetrafluoroethylene copolymer (ETFE) / PC, ETFE / PAT, PC / PAT blend materials, polyester, polyetheretherketone, polyamide and other resin materials, and resin materials mainly composed of these materials. Furthermore, an elastic material can be blended with these resin materials. Examples of the elastic material include polyurethane, chlorinated polyisoprene, NBR, chloropyrene rubber, EPDM, hydrogenated polybutadiene, butyl rubber, silicone rubber, and the like. Use a material obtained by blending one or more of these. Can do.

  If necessary, the resin material and the elastic material used for these base materials can be added in combination of one or more of a conductive agent having electron conductivity and a conductive agent having ion conductivity. As the conductive agent, a conductive polymer such as carbon black, metal oxide, or polyaniline can be used. As the intermediate transfer belt used in the present embodiment, it is preferable to use a polyimide resin in which the above-mentioned conductive agent is dispersed from the viewpoint of excellent mechanical strength.

  A belt made of a polyimide resin in which a conductive agent is dispersed is, for example, 5 to 20% by mass as a conductive agent in a solution of polyamic acid, which is a polyimide precursor, as described in JP-A-63-311263. After the carbon black is dispersed, the dispersion is cast on a metal drum and dried, and then the film peeled off from the drum is stretched at a high temperature to form a polyimide film. Can be produced.

  In the above-described film molding, a polyamic acid solution stock solution in which a conductive agent is dispersed is injected into a cylindrical mold, and the cylindrical mold is rotated at a rotational speed of 500 to 2000 rpm while being heated to 100 to 200 ° C., for example. Then, the film is formed into a film by a centrifugal molding method, and then the obtained film is demolded in a semi-cured state and covered with an iron core, and is subjected to a polyimide reaction (polyamide acid ring-closing reaction) at a high temperature of 300 ° C. or higher. ) Is allowed to proceed to be fully cured. In addition, the stock solution is cast on a metal sheet to a uniform thickness and heated to 100 to 200 ° C. to remove most of the solvent in the same manner as described above, and then gradually raised to a high temperature of 300 ° C. or higher. There is also a method of forming a polyimide film.

  The intermediate transfer belt 108 may further include a surface layer.

  The thickness of the intermediate transfer belt 108 can be appropriately selected according to the hardness of the material, but is preferably 50 to 500 μm, and more preferably 60 to 150 μm.

  In this embodiment, instead of using a belt-shaped intermediate transfer member, an intermediate transfer member having a drum shape may be used. In this case, a surface layer is formed on a cylindrical substrate formed of aluminum, stainless steel (SUS), copper, or the like, or an elastic layer is coated on the substrate as necessary, A surface layer can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples.

(Preparation of electrophotographic photoreceptor)
100 parts by mass of zinc oxide (manufactured by Teika, average particle diameter 70 nm, BET specific surface area value 15 m ² / g) is stirred and mixed with 500 parts by mass of tetrahydrofuran, and silane coupling agent (KBM603, manufactured by Shin-Etsu Chemical Co., Ltd.) 1.25 mass Part was added and stirred for 2 hours. Thereafter, tetrahydrofuran was distilled off under reduced pressure and baked at 120 ° C. for 3 hours to obtain a surface-treated zinc oxide pigment.

  60 parts by mass of the surface-treated zinc oxide pigment obtained above, 0.3 parts by mass of alizarin, 12 parts by mass of blocked isocyanate (Sumijoule BL3175, manufactured by Sumitomo Bayern Urethane Co., Ltd.) and butyral resin (ESREC BM-1, Sekisui Chemical Co., Ltd.) (Product made) 50 parts by mass of a resin solution obtained by dissolving 10 parts by mass in 90 parts by mass of methyl ethyl ketone was dispersed in a sand mill for 2.5 hours using 1 mmφ glass beads to obtain a dispersion. As a catalyst, 0.005 part by mass of dioctyltin dilaurate and 3 parts by mass of silicone resin particles (Tospearl 145, manufactured by GE Toshiba Silicone) were added to the resulting dispersion to obtain an undercoat layer forming coating solution. . This coating solution is applied onto an aluminum substrate (outer diameter 24 mmφ, length 257 mm, wall thickness 1 mm) by a dip coating method, dried and cured at 170 ° C. for 40 minutes, and an undercoat layer having a thickness of 25 μm is formed. Formed.

  Next, the Bragg angle (2θ ± 0.2 °) of the X-ray diffraction spectrum using the Cukα ray as the charge generation material is at least 7.5 °, 9.9 °, 12.5 °, 16.3 °. , 15 parts by mass of hydroxygallium phthalocyanine having diffraction peaks at 18.6 °, 25.1 ° and 28.3 °, vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Nihon Unicar Co., Ltd.) as a binder resin ) A mixture of 10 parts by mass and 300 parts by mass of n-butyl acetate was dispersed with a horizontal sand mill for 100 minutes using 1 mmφ glass beads to obtain a coating solution for forming a charge generation layer. This coating solution was dip-coated on the undercoat layer and dried at room temperature to form a charge generation layer having a thickness of 0.2 μm.

Next, 1 part by mass of tetrafluoroethylene resin particles, 0.02 part by mass of the fluorine-based graft polymer, 5 parts by mass of tetrahydrofuran, and 2 parts by mass of toluene were sufficiently stirred and mixed to obtain a tetrafluoroethylene resin particle suspension. . Next, 4 parts by mass of N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1 ′] biphenyl-4,4′-diamine, a bisphenol Z-type polycarbonate resin ( Viscosity average molecular weight 40,000) After mixing and dissolving in 6 parts by mass, tetrahydrofuran 23 parts by mass and toluene 10 parts by mass, after adding the tetrafluoroethylene resin particle suspension and stirring and mixing, a fine flow path is provided. Using a high-pressure homogenizer equipped with a through-type chamber (trade name LA-33S, manufactured by Nanomizer Co., Ltd.), the dispersion treatment with the pressure increased to 400 kgf / cm ² was repeated 6 times to obtain a tetrafluoroethylene resin particle dispersion. It was. Further, 0.2 parts by mass of 2,6-di-t-butyl-4-methylphenol was mixed to obtain a coating solution for forming a charge transport layer. This coating solution is applied onto the charge generation layer and dried at 135 ° C. for 40 minutes to form a 35 μm-thick charge transport layer. On the aluminum substrate, the undercoat layer, the charge generation layer and the charge transport layer are formed. An electrophotographic photosensitive member provided with a photosensitive layer was obtained.

(Capacitance of photosensitive layer and half exposure amount of photoreceptor)
About the electrophotographic photoreceptor obtained above, the electrostatic capacity of the photosensitive layer and the half exposure amount of the photoreceptor were determined by the following methods.

<Capacitance>
(1) First, the photosensitive member is charged by a charger.
(2) Next, the current value I (A) flowing from the charger to the photosensitive member is measured. Then, this current value flowed into the unit area (cm ² ) per second by the process speed: PS (mm / s) and the charging width of the charger (the length of the normal charging device): L (cm). It is converted into a current value, that is, a charge amount per unit area (Q / cm ² ).
(3) Next, the surface potential (V) of the photosensitive member charged in (1) not exposed is measured.
(4) Next, the electric charge (Q / cm ² ) obtained in ( ² ) and the surface potential (V) obtained in (3) are substituted into the relational expression of Q = CV, and the capacitance C is calculated. Ask.
Although the electrostatic capacity can be obtained by performing charging at one level, the accuracy can be improved by performing plural levels of charging and obtaining the average value of each electrostatic capacity obtained by the above relational expression. .

<Half exposure amount>
(1) First, the photosensitive member is charged by a charger.
(2) Next, the surface potential (V ₀ ) of the photosensitive member charged in (1) not exposed is measured.
(3) Next, the level of the exposure light amount is adjusted, and the surface potential of the photosensitive member exposed and attenuated with each exposure light amount is measured.
(4) Next, the amount of light at which the surface potential attenuated by exposure becomes approximately half of V ₀ is obtained, and the level of the exposure light that is exposed and attenuated at each exposure light amount is measured with a finer level of exposure light amount.
(5) From the measurement result of (4), the amount of exposure light necessary for the surface potential to be reduced to half of V ₀ is determined, and this is set as the half exposure amount (mJ / m ² ).

As a result of the above measurement, the capacitance of the photosensitive layer was 78.4 pF / cm ² , and the half-exposure amount of the photoreceptor was 0.9 mJ / m ² . The surface potential (V ₀ ) was set to −700 V when measuring the half exposure amount. That is, the half exposure amount is an exposure amount at which the surface potential is changed from −700V to −300V.

(Image formation test 1)
Example 1
The electrophotographic photoreceptor obtained above was mounted as a photoreceptor on a process cartridge of an image forming apparatus DocuCenter Color a450 (manufactured by Fuji Xerox Co., Ltd.). The DocuCenter Color a450 is modified so that the charging potential V ₀ of the photosensitive member, the surface potential after exposure (exposure potential) V _L , and the potential Vd applied to the developing sleeve can be adjusted to predetermined values. The surface potential after exposure (exposure potential) _VL is set to a predetermined value by adjusting the exposure amount.

Next, using the above image forming apparatus, the charging potential V ₀ of the photoconductor is set to −700 V and the surface potential _VL after exposure is set to −200 V, and the process speed is 250 mm / sec, 20 ° C., 40% RH. In this environment, a line image is printed on Fuji Xerox J paper with a resolution setting of 1200 dpi, and a pattern print is repeated that repeats not printing two lines after printing one dot line and one dot line. The image quality was visually evaluated based on the following evaluation criteria. The obtained results are shown in Table 2. Note that in order to perform image formation under the condition without fogging, Vd was adjusted so that the relationship of V ₀ -Vd = 150 V was maintained. Also, _{V 1/2} is the surface potential _{V M} of the photosensitive member when the exposure at half the light energy amount when obtaining the _{V L} which is an intermediate potential between -400 V, _{V 0} and _{V L} is an -450V , the value of _V 1/2 -V _M was calculated to -50V.
<1 dot line reproducibility>
G0: 1 dot line is not printed.
G1: 1 dot line is printed lightly.
G2: 1 dot line is printed.
G3: 1 dot line is printed darkly in any of vertical, horizontal and diagonal directions.
<Resolution>
G0: 1 dot line is not reproduced and resolution evaluation is impossible.
G1: Dot lines are not resolved, but are thickened and connected. Alternatively, the line is thickened and some points on the line are connected to the adjacent line, or the line is broken in some places.
G2: 1 dot line can be distinguished.
G3: 1 dot line is clearly resolved, and a line perpendicular to the process direction is also resolved.

(Example 2)
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photoconductor was set to −650 V and the surface potential _VL after exposure was set to −150 V. The obtained results are shown in Table 2. In Example 2, the surface potential V _M of the photosensitive member when exposed to half the light energy amount when V _L is obtained is −340 V, and V _1/2 that is an intermediate potential between V ₀ and V _L is − a _400V, the values of _V 1/2 -V _M was calculated to 60V.

(Example 3)
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photosensitive member was set to −600 V and the surface potential _VL after exposure was set to −100 V. The obtained results are shown in Table 2. In Example 3, the surface potential V _M of the photosensitive member when exposed to half the light energy amount when V _L is obtained is −270 V, and V _1/2 that is an intermediate potential between V ₀ and V _L is − a 350 _V, the value of _V 1/2 -V _M was calculated to -80 V.

Example 4
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photoconductor was set to −550 V and the surface potential _VL after exposure was set to −50 V. The obtained results are shown in Table 2. In Example 4, _{V 1/2} is the surface potential _{V M} of the photosensitive member when the exposure at half the light energy amount when obtaining the _{V L} which is an intermediate potential between -210V, _{V 0} and _{V L} is - a 300 _V, the value of _V 1/2 -V _M was calculated to -90 V.

(Example 5)
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photoconductor was set to −800 V and the surface potential _VL after exposure was set to −300 V. The obtained results are shown in Table 2. In Example 5, the surface potential V _M of the photosensitive member when exposed at half the amount of light energy when _VL is obtained is −520 V, and V _1/2 that is an intermediate potential between V ₀ and V _L is − a 550 _V, the value of _V 1/2 -V _M was calculated to -30 V.

(Comparative Example 1)
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photosensitive member was set to −700 V and the surface potential _VL after exposure was set to −250 V. The obtained results are shown in Table 2. In Comparative Example 1, the surface potential V _M of the photosensitive member when exposed at half the amount of light energy when V _L is obtained is −455 V, and V _1/2 that is an intermediate potential between V ₀ and V _L is − a _475V, the values of _V 1/2 -V _M was calculated to -20 V.

(Comparative Example 2)
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photosensitive member was set to −800 V and the surface potential _VL after exposure was set to −350 V. The obtained results are shown in Table 2. In Comparative Example 2, the surface potential V _M of the photosensitive member when exposed to half the light energy amount when V _L is obtained is −560 V, and V _1/2 that is an intermediate potential between V ₀ and V _L is − is 575 V. _However, the value of _V 1/2 -V _M was calculated to -15V.

(Comparative Example 3)
An image formation test was conducted in the same manner as in Example 1 except that the charging potential V ₀ of the photosensitive member was set to −450 V and the surface potential _VL after exposure was set to −50 V. The obtained results are shown in Table 2. In Comparative Example 3, the surface potential V _M of the photoreceptor when exposed at half the light energy amount when V _L is obtained is −100 V, and V _1/2 that is an intermediate potential between V ₀ and V _L is − a _250V, the values of _V 1/2 -V _M was calculated to -150 V.

(Image formation test 2)
(Example 6)
An image forming apparatus similar to that of Example 1 is prepared, and the charging potential V ₀ and the surface potential V _L change monotonously so that the initial values are −700 V, −200 V, and 100,000 sheets printed: −550 V and −65 V, respectively. Except for the above, 100,000 patterns were printed in the same manner as in Example 1. The image quality at that time was visually evaluated based on the above evaluation criteria. The image quality was good from the initial printing to when 100,000 sheets were printed. Table 2 shows the results when printing 100,000 sheets. In Examples 6, the surface potential V _M of the photosensitive member when the exposure at half the light energy amount when obtaining the print initial V _L is an intermediate potential between -400 V, V ₀ and V _L V _1/2 is -450 _V, the value of _V 1/2 -V _M was calculated to -50 V, the surface of the photosensitive member when the exposure at half the light energy amount when obtaining the _{V L} when 100,000 sheets voltage _{V M} is -297.5V, _{V 1/2} is the intermediate potential to _{V 0} and _{V L} are _-307.5V, the value of _V 1/2 -V _M was calculated to -10 V.

The film thickness T of the photoreceptor after printing 100,000 sheets was 14.2 μm. When the electrostatic capacity and half exposure amount of the photosensitive layer of this photoreceptor were measured, the electrostatic capacity was 196 pF / cm ² and the half exposure amount was 1.3 mJ / m ² .

(Comparative Example 4)
An image forming apparatus similar to that in Example 1 is prepared, and the charging potential V ₀ and the surface potential V _L change monotonously so that the initial values are −700 V, −200 V, and 100,000 sheets printed: −700 V and −250 V, respectively. Except for the above, 100,000 patterns were printed in the same manner as in Example 1. The image quality at that time was visually evaluated based on the above evaluation criteria. The image quality was good at the initial stage of printing, but the resolution was lowered by repeated printing. Table 2 shows the results when printing 100,000 sheets. In Comparative Example 4, the surface potential V _M of the photosensitive member when the exposure at half the light energy amount when obtaining the print initial V _L is an intermediate potential between -400 V, V ₀ and V _L V _1/2 is -450 _V, the value of _V 1/2 -V _M was calculated to -50 V, the surface of the photosensitive member when the exposure at half the light energy amount when obtaining the _{V L} when 100,000 sheets voltage _{V M} is -415V, _{V 1/2} is the intermediate potential to _{V 0} and _{V L} is _-475V, the value of _V 1/2 -V _M was calculated to -60 V.

  As shown in Table 2, in Examples 1 to 5 in which image formation was performed under the conditions satisfying the above formula (1), even when a photoconductor having a thickened photosensitive layer was used, it was sufficiently excellent. It was confirmed that an image can be formed with a reproducibility and resolution of one dot line. Furthermore, from the results of Example 6, it was confirmed that an image can be formed with a sufficiently excellent reproducibility and resolution of one dot line even after printing 100,000 sheets by performing image formation under the conditions satisfying the above formula (1). It was. Therefore, according to the present invention, it is possible to achieve both a long life and high image quality of the image forming apparatus at a high level.

On the other _{hand, {(V 1/2 -V M)} / (V 0 -V L)} value of ^{6.3 × 10 -4 e (T /} 8) 3.8 × 10 -3 e (T / 8) In Comparative Example 1 and Comparative Example 2 in which image formation was performed with a charging potential V ₀ and an exposure amount lower than 1, a dot line was not sufficiently reproduced, and charging exceeding 3.8 × 10 ⁻³ e ^{(T / 8)} In Comparative Example 3 and Comparative Example 4 in which image formation was performed with the potential V ₀ and the exposure amount, one dot line was reproduced, but so-called line thickening occurred and sufficient resolution could not be obtained.

1 is a schematic configuration diagram illustrating a preferred embodiment of an image forming apparatus of the present invention. 1 is a schematic cross-sectional view showing a preferred embodiment of an electrophotographic photosensitive member according to the present invention. It is. FIG. 6 is a schematic cross-sectional view showing another preferred embodiment of the electrophotographic photosensitive member according to the present invention. It is. FIG. 6 is a schematic cross-sectional view showing another preferred embodiment of the electrophotographic photosensitive member according to the present invention. It is. FIG. 6 is a schematic cross-sectional view showing another preferred embodiment of the electrophotographic photosensitive member according to the present invention. It is. It is a schematic block diagram which shows other suitable embodiment of the image forming apparatus of this invention. It is a figure which shows the relationship between the surface potential of a photoreceptor, and exposure amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrophotographic photosensitive member, 2 ... Charging device, 3 ... Power supply unit, 4 ... Exposure device, 5 ... Developing device, 6 ... Cleaning device, 7 ... Transfer roll, 8 ... Image fixing device, 9 ... Image output medium, 10 ... primary transfer roll, 11, 12 ... surface potential measuring device, 13 ... control device, 51 ... conductive substrate, 52 ... photosensitive layer, 53 ... subbing layer, 54 ... charge generation layer, 55 ... charge transport layer, 56 ... Protective layer, 57 ... intermediate layer.

Claims (4)

A charging step of charging an electrophotographic photosensitive member having a conductive substrate and a photosensitive layer formed on the conductive substrate; and exposing the charged electrophotographic photosensitive member to an electrostatic latent image on the electrophotographic photosensitive member An exposure process for forming the electrostatic latent image with a developer to form a toner image, a transfer process for transferring the toner image from the electrophotographic photosensitive member to a transfer medium, and the transfer And a cleaning step of removing toner remaining on the electrophotographic photosensitive member after the step,
Charge formation in the charging step and exposure in the exposure step are a charging potential V ₀ (V) and an exposure amount Ex (mJ / m ² ) satisfying a relationship represented by the following formula (1). Method.

Wherein (1), V ₀ represents the charging potential of the electrophotographic photosensitive member surface before exposure (V), V _L is the electrophotographic photoreceptor charged to potential V ₀ which light energy Ex ( mJ / m ²⁾ shows the surface potential (V) of the electrophotographic photosensitive member when the exposure is, V _M, the light energy when the electrophotographic photosensitive member charged to a potential V _0, which give the V _L The surface potential (V) of the electrophotographic photosensitive member when exposed at half the amount Ex / 2 (mJ / m ² ) is shown, and V _1/2 is an intermediate potential (V) between V ₀ and V _L. , T represents the film thickness (μm) of the photosensitive layer, and e represents the base of the natural logarithm. ] An electrophotographic photosensitive member having a conductive substrate and a photosensitive layer provided on the conductive substrate, a charging device for charging the electrophotographic photosensitive member, and exposing the charged electrophotographic photosensitive member to expose the exposed region. An exposure device for forming an electrostatic latent image; a developing device for developing the electrostatic latent image formed in an exposure region with toner to form a toner image; and a medium to which the toner image is transferred from the electrophotographic photosensitive member An image forming apparatus comprising:
Based on the film thickness of the photosensitive layer obtained by a predetermined method, a charging potential V ₀ (V) and an exposure amount Ex (mJ / m ² ) satisfying the relationship expressed by the following formula (1) are obtained, and the charging potential V An image forming apparatus, further comprising a control device that controls a charging potential on the surface of the electrophotographic photosensitive member and an exposure amount of the exposure device based on values of ₀ and the exposure amount Ex.

Wherein (1), V ₀ represents the charging potential of the electrophotographic photosensitive member surface before exposure (V), V _L is the electrophotographic photoreceptor charged to potential V ₀ which light energy Ex ( mJ / m ²⁾ shows the surface potential (V) of the electrophotographic photosensitive member when the exposure is, V _M, the light energy when the electrophotographic photosensitive member charged to a potential V _0, which give the V _L The surface potential (V) of the electrophotographic photosensitive member when exposed at half the amount Ex / 2 (mJ / m ² ) is shown, and V _1/2 is an intermediate potential (V) between V ₀ and V _L. , T represents the film thickness (μm) of the photosensitive layer, and e represents the base of the natural logarithm. ] A surface potential measuring device for measuring the surface potential of the electrophotographic photosensitive member;
Charge that satisfies the relationship represented by the following formula (1) based on the surface potential of the electrophotographic photosensitive member before and after exposure and the film thickness of the photosensitive layer measured by the surface potential measuring device. A potential V ₀ (V) and an exposure amount Ex (mJ / m ² ) are obtained, and a charging potential on the surface of the electrophotographic photosensitive member and an exposure amount of the exposure apparatus are controlled based on the values of V ₀ and Ex. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus. The photosensitive layer of the electrophotographic photoreceptor includes a charge generation layer and a charge transport layer in this order from the conductive substrate side,
In the unused electrophotographic photoreceptor, the distance from the outermost surface of the photosensitive layer to the interface between the charge generation layer and the charge transport layer is from 35 μm to 50 μm, and the capacitance of the photosensitive layer is 56 pF / cm ² or more 80 pF / cm ² or less, the image forming apparatus according to claim 2 or 3 half decay exposure amount of the electrophotographic photosensitive member is characterized in that at 1 mJ / ^{m 2} or less.

Images