JP4201763B2 - Image forming method and image forming apparatus - Google Patents

Description

Provided are an image forming method and an apparatus which are excellent in productivity with less image defects by using a dry two-component or one-component developer. The present invention also relates to improvements in copying machines, printers, and facsimile machines using dry two-component or one-component developers.

  Conventionally, various methods are known for electrophotography, and generally, the surface of an image carrier (photosensitive member) is charged, and the charged image carrier is exposed to form an electrostatic latent image. Next, the electrostatic latent image is converted into a visible image using electrophotographic toner, and a toner image is formed on the image carrier. Further, the toner image is transferred to a transfer member and fixed by heating, pressure, or a combination thereof, whereby a recorded matter having an image formed on the transfer member is obtained. The toner remaining on the image carrier after the toner image transfer is cleaned by a known method such as a blade, a brush, or a roller.

  As a recent trend of electrophotographic technology, digitization and high image quality are demanded. For example, a high resolution image having a resolution of 1200 dpi or higher has been studied. In order to realize this, an image with higher definition than before has been studied. A formation method is desired. For toner and developer that visualizes a latent image, further particle size reduction is being studied and realized in order to form a high-definition image. For example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and the like have proposed various small particle size toners having a specific particle size distribution.

  However, as compared with the conventional toner, the toner having a small particle size cannot ignore the adhesion force between the toners or other members represented by the photoreceptor. The adhesive force affects almost all image forming processes of the electrophotographic apparatus and affects the image quality. However, image defects such as background stains in the developing process, voids in the transfer process and transfer dust, and cleaning residue in the cleaning process. The toner adhesion control is one of the important issues in the toner particle design because it is directly related to the generation mechanism of toner, and these effects are promoted by reducing the particle size of the toner.

  Taking a two-component developer as an example during the development process, a sufficiently large amount of toner once contacts (attaches) to the solid surface in the development nip, and the direction and magnitude of the Coulomb force due to the development electric field. Thus, it is finally determined whether it adheres to the photosensitive member side (development) or returns to the carrier side (scavenging). If the development electric field is constant, the direction and magnitude of the Coulomb force is determined by the charge amount of the toner particles, but the charge amount of the toner particles has a distribution and the behavior of the toner particles is different. In general, a development bias is applied to the development nip for the purpose of reducing background stains, and a large coulomb that is scavenged toward the carrier side for many normally charged toners existing on the background in the development nip. Since the force works, the background dirt is suppressed. However, for a small number of reversely charged toners present in the developer, the Coulomb force acts in the direction of adhering to the photoconductor side, so that the reversely charged toner adheres to the background portion. In addition, in the case of a weakly charged toner, the Coulomb force toward the carrier side is small, so that the toner tends to remain on the background without being scavenged by the carrier. Therefore, it has been considered that the background-stained toner on the photoreceptor is mainly composed of the reversely charged toner and the weakly charged toner contained in the developer on the background. It is predicted that this is mainly due to the reverse charging in the developer and the increase in the number of weakly charged toners due to the deterioration of the developer with time and insufficient mixing and stirring of the developer.

  Therefore, as a countermeasure against these problems, a means for reducing the reverse / weakly charged toner in the developer has been proposed in the past. For example, Patent Document 5 discloses the distribution area of the appropriate charged region in the toner particle charge amount distribution of the developer. By defining this, a system free from background stains in which the amount of reverse / weakly charged toner in the developer is regulated is disclosed and actually used in an electrophotographic apparatus.

  However, as a recent trend, toners with a smaller softening point have been developed in order to reduce the particle size of the toner for higher image quality and low energy fixing. A problem that cannot be solved simply by regulating the toner charge amount distribution in the developer, that is, when using a new toner, there is a problem that the background contamination is not improved only by the conventional measures as described above. As a result, control of toner adhesion has become an important issue.

  The transfer process is a process in which the toner is moved from the photosensitive member to the transfer member by an electrostatic force due to an electric field, and the transfer characteristics are determined by the relationship between the toner adhesion force and the electrostatic force due to the electric field. Control is an important factor in transcription design. In the case of using roller transfer or belt transfer, when the toner image on the photosensitive member is pressed against the transfer member, the toner is pressed onto the photosensitive member by reaction, and the adhesion force between the toner and the photosensitive member and the toner particles / The adhesion force between the toner particles is increased, and the toner tends to remain on the photosensitive member without being transferred to the transfer member. This phenomenon is particularly likely to occur at the center of a thin line portion where pressure is easily applied, and an image is lost. Therefore, in order to improve the void in the image, it is necessary to reduce the adhesion force between the toner and the photoreceptor and the adhesion force between the toner particles / toner particles or the pressure applied between the photoreceptor and the transfer body.

  The adhesion force between the toner and the photoconductor is classified into electrostatic adhesion force due to toner charging and other non-electrostatic adhesion force. The electrostatic adhesion force depends on the toner charge amount. It can be reduced by lowering the charge amount. However, if the charge amount of the toner is too small, there is a problem that the toner cannot be transferred by electrostatic force due to an electric field.

  Examples of reports relating to toner adhesion include Patent Document 6, Patent Document 7, Patent Document 8, and the like. However, in the above report example, the toner adhesion force is not classified into electrostatic adhesion force and non-electrostatic adhesion force. In Patent Document 9, the relationship between the non-electrostatic adhesion force of the toner and the image quality is examined, and the non-electrostatic adhesion force of the toner is regulated to a constant value. Although the non-electrostatic adhesion force of the toner varies depending on the particle size of the toner, Patent Document 9 does not define the relationship between the non-electrostatic adhesion force and the toner particle size.

In general, the adhesion force between toners or between toner / other members has a distribution. When the toner adhesion force distribution is wide and the toner adhesion force is too large or too small, an image defect is likely to occur. Therefore, it is necessary to sharpen the toner adhesion force distribution. In general, the adhesion of toner particles varies depending on the particle size. For this reason, in order to sharpen the toner adhesion distribution, it is necessary to sharpen the particle size distribution. However, in order to sharpen the particle size distribution, there are problems such as a higher pulverization accuracy than the conventional method or a strict classification accuracy required in the manufacturing process. For example, Patent Document 10, Patent Document 11, Patent Document Although measures are taken by various new manufacturing techniques at No. 12, etc., as a result, the manufacturing cost is increased. In addition, when conducting classification with strict accuracy, the amount of waste increases more than before. Therefore, in terms of environmental ecology, we will establish a control technique for adhesion distribution using a simple method other than sharpening the toner particle size distribution. The demand was growing.
Japanese Patent Laid-Open No. 1-112253 JP-A-2-284158 Japanese Patent Laid-Open No. 3-181952 JP-A-4-162048 JP 4-110861 A JP-A-5-333757 JP-A-6-167825 JP-A-6-167826 JP-A-8-305075 Japanese Patent Laid-Open No. 5-134455 JP-A-6-273978 JP 7-333890 A

An object of the present invention is to enable non-electrostatic adhesion between the toner particles and another member (adhesion not caused by toner charge), thereby enabling high-quality image formation without image defects. and to provide an image forming method, and an image forming apparatus using the electrophotographic toner over which high productivity that do not require such extreme classification treatment to promote the loss of raw materials.

The present inventors, in view of the above problems, the results of quantitative evaluation of the adhesion between the various electrophotographic toner particles and an electrophotographic photoreceptor by centrifugation, was studied the relation between the image defect, The present inventors have found that the above-mentioned image defects can be improved by using an electrophotographic toner that satisfies a condition with non-electrostatic adhesion, and have reached the present invention.

That is, the present invention relates to a latent image forming step for forming an electrostatic latent image on a photoconductor, a developing step for forming a toner image on the latent image on the photoconductor using an electrophotographic toner, and a formed toner. In an image forming method having a transfer step of transferring an image onto a transfer body, the toner is caused by charging of the toner among the adhesive force acting between the electrophotographic toner and the electrophotographic photoreceptor measured by a centrifugal separation method. With respect to the non-electrostatic adhesion force, the average of the non-electrostatic adhesion force to the toner particle group in which the particle size range in the electrophotographic toner is D ± d (μm) ( where d is 2 μm or less) When the value is Fne (D) (nN), the proportionality coefficient of the linear regression line in the graph plotted with the toner particle diameter D as the horizontal axis and Fne (D) as the vertical axis is 0.01 (nN / μm). ~ 5 (nN / μm) Standard deviation in the use logarithmic distribution is characterized by using a combination of 0.65 or less and the electrophotographic toner and the photosensitive member. Here, the non-electrostatic adhesion force between the electrophotographic toner and the electrophotographic photosensitive member is composed of van der Waals force, liquid cross-linking force, intermolecular force and the like.

  Further, the electrophotographic toner used in the present invention is subjected to external addition treatment with an external additive composed of fine particles having an average primary particle diameter of 1 nm to 100 nm, and the external additive is coated on the surface area per one toner particle. The area ratio average value is 8% to 100%. More preferably, the average primary particle diameter is 5 nm to 80 nm, and the coating area ratio of the external additive is 10% to 90%.

  Further, the external additive used in the present invention is characterized by containing at least one of silica, titania and alumina. Further, the organic fine particles are acrylic polymers, particularly polymethyl methacrylate. The external additive is characterized by being hydrophobized. Further, the present invention is characterized in that it is externally added by a mixing apparatus such as a V-type blender, mechano, fusion, etc., particularly a Henschel mixer.

The electrophotographic toner is a magnetic one-component toner. Furthermore, it is a non-magnetic toner constituting a magnetic two-component developer used together with a magnetic carrier.
The toner for electrophotography for use in the present invention, the volume average particle diameter of the electrophotographic toner is characterized in that 3μm~15μm is particularly 3Myuemu～10myuemu.

The image forming method of the present invention, in a binder resin, a colorant, a charge control agent, by blending a releasing agent, granulated to a suitable particle size, the toner obtained by adding an external additive It is characterized by using .

The present invention also provides a latent image forming means for forming an electrostatic latent image on a photosensitive member, a developing means for forming a toner image on the latent image on the photosensitive member, and transferring the formed toner image onto a transfer member. In the image forming apparatus having the transfer means, the above-described electrophotographic toner is used .

In addition, the photoreceptor in such an apparatus is an inorganic photoreceptor or a conductive support on which a charge generation layer, a charge transport layer of an organic material is formed, or a protective layer is further formed.

By controlling the non-electrostatic adhesion force (adhesion force not caused by toner charge) between the toner particles and the other members according to the present invention, it is possible to form a high-quality image without causing image defects, and It is possible to provide an image forming method and an image forming apparatus using an electrophotographic toner that is excellent in productivity and does not require an extreme classification process that promotes loss.

First, a method for measuring the adhesion force between the toner and the photoreceptor by the centrifugal separation method will be described.
As a method for measuring the adhesion force of toner, a method for estimating a force necessary for separating toner from an object to which toner adheres is generally used. As a method for separating the toner, a method using centrifugal force, vibration, impact, air pressure, electric field, magnetic field or the like is known. Among these, the method using centrifugal force is easy to quantify and has high measurement accuracy. Therefore, in the present invention, the centrifugal separation method is used as a method for measuring the adhesion force between the toner and the photoreceptor.

Hereinafter, a method for measuring toner adhesion by centrifugation will be described. IS & T NIP7 ^th p. 200 (1991) and the like are known.

First, an apparatus for carrying out toner adhesion measurement will be described.
1 and 2 are diagrams showing an example of a measurement cell and a centrifugal separator of a toner adhesion measuring device according to the present invention.

FIG. 1 is an explanatory diagram of a measurement cell of the toner adhesion measuring apparatus. In FIG. 1, reference numeral 1 denotes a measurement cell. The measurement cell 1 includes a sample substrate 2 having a sample surface 2a to which toner is adhered, and a receiving substrate 3 having an adhesion surface 3a to which toner separated from the sample substrate 2 is adhered. The spacer 4 is provided between the sample surface 2 a of the sample substrate 2 and the attachment surface 3 a of the receiving substrate 3.

FIG. 2 is a partial cross-sectional view of the centrifugal separator. In FIG. 2, reference numeral 5 denotes a centrifugal separator, and the centrifugal separator 5 includes a rotor 6 that rotates the measurement cell 1 and a holding member 7. The rotor 6 has a hole-shaped cross section perpendicular to the rotation center axis 9 of the rotor 6 and has a sample setting portion 8 where the holding member 7 is set. The holding member 7 includes a rod-like portion 7a, a cell holding portion 7b provided on the rod-like portion 7a for holding the measurement cell 1, a hole portion 7c for pushing the measurement cell 1 out of the cell holding portion 7b, and the rod-like portion 7a as a sample installation portion. 8 is provided with an installation fixing portion 7d to be fixed to 8. The cell holding unit 7b is configured such that when the measurement cell 1 is installed, the vertical direction of the measurement cell 1 is perpendicular to the rotation center axis 9 of the rotor.

Next, a method for measuring the non-electrostatic adhesion force of toner using the above apparatus will be described.
First, a photoconductor is directly formed on the sample substrate 2 or a part of the photoconductor is cut out and attached to the sample substrate 2 with an adhesive. Next, uncharged toner is deposited on the photoreceptor (sample surface 2 a) on the sample substrate 2. Next, as shown in FIG. 1, the sample substrate 2, the receiving substrate 3, and the spacer 4
The measurement cell 1 is configured using The cell holding of the holding member 7 is performed so that the sample substrate 2 is positioned between the receiving substrate 3 and the rotation center axis 9 of the rotor 6 when the holding cell 7 is placed on the sample setting portion 8 of the rotor 6. Installed in part 7b. The holding member 7 is installed on the sample installation unit 8 of the rotor 6 so that the vertical direction of the measurement cell 1 is perpendicular to the rotation center axis 9 of the rotor. The centrifugal separator 5 is operated to rotate the rotor 6 at a constant rotational speed. The toner adhering to the sample substrate 2 receives a centrifugal force corresponding to the rotational speed, and when the centrifugal force received by the toner is larger than the adhesive force between the toner and the sample surface 2a, the toner is separated from the sample surface 2a, and the adhering surface It adheres to 3a.

The centrifugal force F received by the toner is obtained from Equation (1) using the weight m of the toner, the rotational speed f (rpm) of the rotor, and the distance r from the central axis of the rotor to the toner adhesion surface of the sample substrate.
F = m × r × (2πf / 60) ² (1)

The weight m of the toner is obtained from Equation (2) using the true specific gravity ρ of the toner and the equivalent circle diameter d.
m = (π / 6) × ρ × d 3 (2)

From the expressions (1) and (2), the centrifugal force F received by the toner can be obtained from the expression (3).
^{F = (π 3/5400)} × ρ × d 3 × r × f 2 (3)

  After completion of the centrifugation, the holding member 7 is taken out from the sample setting portion 8 of the rotor 6, and the measurement cell 1 is taken out from the cell holding portion 7 b of the holding member 7. The receiving substrate 3 is replaced, the measurement cell 1 is installed on the holding member 7, the holding member 7 is installed on the rotor 6, and the rotor 6 is rotated at a higher rotational speed than the previous time. The centrifugal force received by the toner becomes larger than the previous time, and the toner having a large adhesion force separates from the sample surface 2a and adheres to the adhesion surface 3a.

  By performing the same operation by changing the set rotational speed of the centrifugal separator from a low rotational speed to a high rotational speed, the toner on the sample surface 2a is changed according to the magnitude relationship between the centrifugal force and the adhesive force received at each rotational speed. Moves to the attachment surface 3a.

  After centrifuging for all the set rotation speeds, the adhesion force of each toner is obtained using equation (3) by measuring the particle size of the toner adhered to the adhesion surface 3a of the receiving substrate 3 at each rotation speed. be able to.

  To measure the particle size and number of toners, the toner on the adhesion surface 3a is observed with an optical microscope, the image is input to an image processing device through a CCD camera, and the particle size of each toner is measured using the image processing device. be able to.

  FIG. 3 shows an example of a common logarithmic distribution of the non-electrostatic adhesion force Fne between the toner and the photoreceptor measured by the above method. As shown in FIG. 3, the non-electrostatic adhesion distribution is characterized by an average value Fav and a standard deviation σ. The average value Fav and the standard deviation σ vary depending on various conditions such as the average particle diameter, the particle diameter distribution, the shape, the constituent material, and the additive of the toner.

In the above measuring method, the particle size of each toner adhering to the adhering surface 3a of the receiving substrate 3 is measured, so that the average value of the non-electrostatic adhesion force for each particle size can be obtained. For this reason, the relationship between the measured particle diameter and the adhesive force can be obtained by a single adhesive force measurement.
The measured value is plotted with the arbitrary toner particle diameter D (μm) as the horizontal axis and the average value Fne (D) (nN) of each non-electrostatic adhesion force in the particle diameter range D ± 0.5 (μm) as the vertical axis. The plotted results are shown in FIG. Note that the average value Fne (D) in FIG. 4 is obtained by calculating the arithmetic average value A for the common logarithm of the non-electrostatic adhesion force with respect to the toner having a particle diameter in the range of D ± 0.5 (μm). (D) = 10 ^A

  As shown in FIG. 4, the average value Fne (D) of the non-electrostatic adhesion force at each particle size is proportional to the particle size D. The straight line in FIG. 4 is a primary regression line of measured values, and the proportionality coefficient of this primary regression line is K. Even with toners made using the same constituent materials, the average value Fav of the non-electrostatic adhesion force of the whole toner varies depending on the particle size distribution and average particle size of the toner. However, even if the number of toners for each particle size changes, the average value Fne (D) of the non-electrostatic adhesion force for each particle size does not change, so the proportional coefficient K is the toner particle size distribution, average particle size. Does not depend on. Therefore, by using the proportionality coefficient K, it is possible to compare the magnitude relationship of the toner adhesion without considering the difference in particle size distribution and average particle size. However, if the particle size range for obtaining the average value Fne (D) of non-electrostatic adhesion force is too wide, Fne (D) changes depending on the particle size distribution. It was found that d in d (μm) needs to be 2 μm or less.

  The present inventors measured non-electrostatic adhesion force for various toners and examined the relationship between the proportionality coefficient K and the standard deviation σ and the image. As a result, it has been found that by using a toner having a proportional coefficient K of 0.01 (nN / μm) to 5 (nN / μm), image defects such as background stains and voids can be improved. By setting the proportionality coefficient K to 5 (nN / μm) or less, the non-electrostatic adhesion force of the whole toner is sufficiently small, which is preferable in terms of image defects such as background stains and voids. Further, when the proportional coefficient K is 0.01 (nN / μm) or more, the non-electrostatic adhesion force of the whole toner is sufficiently large, which is preferable in terms of image defects such as transfer dust. Furthermore, it has been found that image defects such as background stains and voids can be further improved by using a toner having a standard deviation σ of 0.65 or less. When the standard deviation σ exceeds 0.65, the non-electrostatic adhesive force distribution is wide, the toner having an excessively large or too small adhesive force increases, and image defects are likely to occur.

  The non-electrostatic adhesion force between the toner and the photoreceptor is composed of van der Waals force, liquid cross-linking force, intermolecular force, etc., but these forces are the geometric structure of the contact area between the toner and the photoreceptor. Depends on. In particular, the magnitude of the radius of curvature of the toner surface in the contact area with the photoreceptor is an important factor that determines the magnitude of non-electrostatic adhesion. Since the coating of the surface of the toner base particles (toner particles to which no external additive is added) with an external additive can greatly change the radius of curvature of the toner surface, an effective means for controlling non-electrostatic adhesion force Become. As a result of measuring the proportionality coefficient K for various toners, the present inventors found that the proportionality coefficient K depends on the constituent material, shape, etc. of the toner, and in particular, greatly depends on the coverage of the external additive on the toner surface. I found it. The external additive coverage is defined by the area of the external additive in the surface area of the toner base particles, and can be measured by image analysis of an electron micrograph of the toner. The inventors of the present invention have a tendency that the proportionality coefficient K decreases as the external additive coverage increases, and saturates at a certain external additive coverage or more. It has been found that it varies depending on the shape, the particle size of the external additive and the material. Therefore, the external additive coverage at which the proportionality coefficient K is 0.01 (nN / μm) to 5 (nN / μm) varies depending on the shape of the toner, the particle size of the external additive, the material, and the like.

In addition, as a result of measuring the standard deviation σ for various toners, the present inventors greatly depended on the external additive coverage, and the adhesion distribution is not limited to the control of the particle size distribution of the toner. It was found that it can be controlled by the agent coverage. The standard deviation σ tends to decrease as the external additive coverage increases, and the dependence of the standard deviation σ on the external additive depends on the shape of the toner, the particle size and material of the external additive, and the standard deviation σ ratio As described below, the coating ratio of the external additive with a value of 0.65 or less can be achieved by the shape of the toner, the particle size and material of the external additive, and the like.

  As a condition that the proportionality coefficient K is 0.01 (nN / μm) to 5 (nN / μm) and the standard deviation σ is 0.65 or less, the present inventors have an average primary particle diameter of 1 nm to 100 nm. It has been found that it is particularly preferable that fine particles of preferably 5 nm to 80 nm are used as the external additive and the external additive coverage is 8% to 100%, preferably 10% to 90%. When the average value of the primary particle diameter of the external additive is less than 1 nm, the external additive is buried in the toner base particles, so that the effect of the external additive is lost. In addition, when the average value of the primary particle diameter of the external additive exceeds 100 nm, the external additive is easily separated from the toner base particles, and the constituent members of the image forming apparatus such as the photoreceptor are damaged by the separated external additive. Cheap. If the coverage is less than 8%, it is difficult to make the proportionality coefficient K 5 (nN / μm) or less, and it is difficult to make the standard deviation σ 0.65 or less in the case of a toner having a wide particle size distribution. turn into. On the other hand, when the coverage of the external additive exceeds 100%, the external additive is easily separated from the toner, and the photoreceptor and the like are easily damaged.

  The external additive coverage of the toner is determined by carrying out the means described below for conditions such as the additive amount, particle size, specific gravity, toner particle size, specific gravity, shape, external addition method, and external addition conditions. Can be achieved. For example, when the amount of the external additive added is increased, the area of the external additive on the toner base particles increases with the number of external additives, and the external additive coverage increases. If the amount of external additive added is too small, the external additive coverage will not be 8% or more. If the amount of the external additive added is too large, the amount of the external additive not attached to the toner increases, and this external additive tends to damage the photoconductor and the like.

  The area of the external additive on the toner base particles is proportional to the area occupied by one external additive and the number of external additives. As the primary particle size of the external additive increases, the weight of one external additive increases, so the number of external additives contained in a constant weight of external additive decreases. Further, the area occupied by one external additive increases as the primary particle diameter of the external additive increases. When the amount of the external additive is the same, the external additive having a smaller particle size has a larger external additive coverage than the case where an external additive having a larger particle size is used. For this reason, when using an external additive having a small particle size, the external additive coverage can be increased to 8% or more with a smaller amount than when using an external additive having a large particle size.

When a constant weight of an external additive is added to a constant weight of toner base particles, the external additive coverage is determined by the ratio of the external additive area to the total surface area of each toner base particle. As the toner base particle size increases, the weight of one toner base particle increases, so the number of toner base particles contained in a constant weight of toner base particle decreases. Further, the surface area of one toner base particle increases as the particle size of the toner base particle increases. The total surface area of a constant weight of toner base particles is proportional to the number of toner base particles and the surface area of one toner base particle. When the external additive addition amount is the same, the smaller the toner base particle size, the smaller the external additive coverage. In addition, the surface area of the toner base particles is larger in the case of the toner particles having the same particle size than the pulverized toner having irregularities on the surface and the irregular shape of the toner particles. Is small and the external additive coverage is large. Therefore, in the case of a spherical toner, the external additive coverage can be increased to 8% or more with a smaller amount of external additive added than that of the irregular toner.

  When the external additive is externally added to the toner base particles, the primary particles of the external additive are often adhered in an aggregated state on the toner base particles. Since the area of the external additive on the toner base particles depends on the aggregation state of the external additive, the external additive coverage varies depending on the aggregation state of the external additive. Even if the conditions of the external additive and the toner base particles are the same, the state of aggregation of the external additive on the toner base particles varies depending on the external addition method and external addition conditions. Also, the adhesion strength between the external additive and the toner base particles differs depending on the external addition method and the external addition conditions. If the adhesion strength is weak, the external additive is easily separated from the toner base particles, and the photoreceptor and the like are easily damaged. . For this reason, in order to obtain an appropriate external additive coverage and adhesion strength, it is necessary to adjust the external additive conditions according to the conditions of the toner base particles and the external additive. As described above, various conditions must be adjusted in order to set the external additive coverage of the toner to 8% to 100%.

As the external additive used in the present invention, known organic fine particles and inorganic fine particles are used. The organic fine particle is not particularly limited, but an acrylic polymer, particularly polymethyl methacrylate is preferable. The inorganic fine particles are not particularly limited, but silica, alumina, or titania is preferably used. In the case of these inorganic fine particles having hygroscopicity, those subjected to a hydrophobization treatment are preferably used in consideration of environmental stability. The hydrophobic treatment can be performed by reacting the hydrophobic treatment agent with the fine powder at a high temperature. There is no restriction | limiting in particular as a hydrophobization processing agent, For example, a silane coupling agent, silicone oil, etc. can be used.

  As an external addition method of the external additive used in the present invention, a known external addition method using various mixing apparatuses such as a V-type blender, a Henschel mixer, and a mechano-fusion can be used. In particular, a method using a Henschel mixer. Is preferably used. When mixing and stirring the toner base particles and the external additive with a Henschel mixer, the rotational speed of the rotating blades can be adjusted to adjust the adhesion strength between the external additive and the toner base particles and the state of aggregation of the external additive on the toner base particles. It is necessary to set the rotation time appropriately. The appropriate rotation speed and rotation time of the rotating blades depend on various conditions of the toner base particles and the external additive.

  The particle diameter of the electrophotographic toner of the present invention is preferably 3 μm to 10 μm in volume average particle diameter. If the volume average particle size of the toner is less than 3 μm, the proportion of fine powder toner having a particle size of 1 μm or less that tends to cause image defects increases, and if the volume average particle size exceeds 10 μm, a demand for high image quality of electrophotographic images is required. It is difficult to cope with.

  As the electrophotographic toner of the present invention, toners having various configurations can be used. As an example of a suitable toner, additives such as a colorant, a charge control agent, and a release agent (offset prevention agent) are blended in a binder resin, granulated to an appropriate particle size, and an external additive. Can be added.

The toner for electrophotography of the present invention can be used alone as a magnetic toner that is used as a magnetic one-component toner, but can be used alone as a non-magnetic one-component developer, or a magnetic two-component together with a magnetic carrier. The toner is preferably used as a nonmagnetic toner constituting a developer.

  Binder resins include styrenes such as styrene and chlorostyrene, monoolefins such as ethylene, propylene, butylene and isobutylene, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate, and methyl acrylate. , Esters of α-methylene aliphatic monocarboxylic acids such as ethyl acrylate, butyl acrylate, octyl acrylate, dodecyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dodecyl methacrylate, Homopolymers and copolymers of vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether, vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and vinyl isopropenyl ketone can be exemplified. Particularly 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 a polymer, polyethylene, and polypropylene. Further examples include polyester, polyurethane, epoxy resin, silicone resin, polyamide, modified rosin, paraffin wax and the like.

  Colorants include carbon black, aniline blue, calcoil blue, chrome yellow, ultramarine blue, duPont oil red, quinoline yellow, methylene blue chloride, copper phthalocyanine, malachite green oxalate, lamp black, rose bengal, titanium oxide, C. 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 12, C.I. I. Pigment yellow 17, C.I. I. Pigment blue 15: 1, C.I. I. And CI Pigment Blue 15: 3. The colorant is used in a ratio of 1 to 30 parts by weight with respect to 100 parts by weight of the binder resin.

  There are two types of charge control agents for positive charge control and negative charge control depending on the charge polarity of the toner. Examples of charge control agents for controlling positive charge include oil-soluble dyes such as nigrosine base (CI5045), organic compounds having basic nitrogen atoms, such as basic dyes, aminopyrines, pyrimidine compounds, polynuclear polyamino compounds, aminosilanes, Includes fillers surface-treated with the above compounds. Examples of charge control agents for controlling negative charges include oil-soluble dyes such as oil black (CI26150), Bontron S, and Spiron black; charge control resins such as styrene-styrene sulfonic acid copolymers; compounds containing carboxy groups (For example, alkyl salicylic acid metal chelates), metal complex dyes, fatty acid metal soaps, resin acid soaps, naphthenic acid metal salts, and the like. The charge control agent is used in a proportion of 0.1 to 10 parts by weight, preferably 0.5 to 8 parts by weight, based on 100 parts by weight of the binder resin.

  Examples of the mold release agent include aliphatic hydrocarbons, aliphatic metal salts, higher fatty acids, fatty acid esters or partially saponified products thereof, silicone oil, and various waxes. The release agent is used at a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

The toner base particles are prepared by homogenously pre-kneading each of the above components with a dry blender, Henschel mixer, ball mill, etc., for example, using a kneading device such as a Banbury mixer, roll, uniaxial or biaxial extrusion kneader. The mixture is uniformly melt-kneaded and then kneaded, cooled and pulverized, and classified as necessary. In addition, it can also be produced by various polymerization methods such as suspension polymerization, dispersion polymerization and emulsion polymerization, and well-known production methods such as a microcapsule polymerization method and a spray drying method. Further, the external additive and the toner base particles are mixed by a mixing device such as a Henshur mixer, a V-type blender, or a hybridizer, and the external additive is fixed on the surface of the toner base particles.

Next, the electrophotographic photoreceptor used in the practice of the present invention will be described.
As the electrophotographic photoreceptor of the present invention, those in which a charge generation layer and a charge transport layer are formed on a conductive support, and those in which a protective layer is formed on the charge transport layer are used. As the conductive support, the charge generation layer, and the charge transport layer, any known ones can be used.

Also, the surface of the photoconductor is uneven due to the surface properties of the conductive support, the formation conditions of the photoconductor, etc. If the period of the unevenness is sufficiently larger than the toner particle size, the non-static state between the toner and the photoconductor The effect on electrical adhesion is small. When the unevenness period is about the same as the toner particle size, the contact area is small when the toner comes into contact with the convex part, so the non-electrostatic adhesive force is small. The adhesive force is increased, and the distribution of the non-electrostatic adhesive force is widened. When the unevenness period is smaller than the toner particle size, the contact area with the toner is small, so that the non-electrostatic adhesion is reduced. However, it is difficult to form such unevenness. For this reason, it is preferable that the surface of the photosensitive member has a period of unevenness sufficiently larger than the toner particle diameter.

  The material for the electrophotographic photoreceptor of the present invention may be an inorganic photoreceptor material such as selenium and its alloys, amorphous silicon, or an organic photoreceptor material.

When using an organic photoreceptor material, examples of the charge generating pigment include X-type metal-free phthalocyanine, π-type metal-free phthalocyanine, τ-type metal-free phthalocyanine, ε-type copper phthalocyanine, α-type titanyl phthalocyanine, and β-type titanyl. Phthalocyanine pigments such as phthalocyanine, disazo / trisazo pigments, anthraquinone pigments, polycyclic quinone pigments, indigo pigments, diphenylmethane, trimethylmethane pigments, cyanine pigments, quinoline pigments, benzophenone, naphthoquinone pigments, perylene pigments, fluorenone Pigments, squarylium pigments, azurenium pigments, perinone pigments, quinacridone pigments, naphthalocyanine pigments and porphyrin pigments can be used. The amount of these charge generating pigments that can be used in combination with the organic acceptor compound in the entire photosensitive layer is 0.1 to 40% by weight, preferably 0.3 to 25% by weight.

  Also, known organic hole transport materials can be used, such as compounds having a triphenylamine moiety in the molecule, hydrazone compounds, triphenylmethane compounds, oxadiazole compounds, carbazole compounds, pyrazoline compounds. Examples thereof include compounds, styryl compounds, butadiene compounds, polysilane compounds whose linear main chain is made of Si, and polymer donor compounds such as polyvinyl carbazole. The amount of the hole transporting material in the entire photosensitive layer is 10% by weight or more, preferably 20 to 60% by weight.

  In addition, as the binder for the photosensitive layer, polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, Addition polymerization resins such as melamine resins, polyaddition resins, polycondensation resins, and copolymer resins containing two or more of these repeating units, such as vinyl chloride-vinyl acetate copolymer, vinyl chloride-acetic acid Mention may be made of vinyl-maleic anhydride copolymer resins. The amount of these binders in the entire photosensitive layer is 20 to 90% by weight, preferably 30 to 70% by weight.

  In addition, an undercoat layer can be provided between the photosensitive layer and the conductive substrate for the purpose of improving the chargeability. As these materials, in addition to the binder material, known materials such as polyamide resin, polyvinyl alcohol, casein, and polyvinylpyrrolidone can be used.

  In order to produce an organic photoconductor, a photosensitive layer forming solution prepared by dissolving the above materials in an organic solvent or dispersing them with a ball mill, ultrasonic wave or the like is used to prepare a substrate by a known method such as dipping, blade coating, spray coating or the like. The protective layer may be formed by the above-mentioned known method after coating on and forming and drying the photosensitive layer.

As the conductive substrate that can be used in the present invention, a known substrate can be used, and a metal plate such as aluminum, nickel, copper, and stainless steel, a metal drum or a metal foil, a thin film of aluminum, tin oxide, and copper iodide is applied. Alternatively, an attached plastic film or glass can be used.
Next, the image forming method and the image forming apparatus of the present invention will be described in detail with reference to the drawings.

  The image forming method of the present invention comprises a latent image forming step for forming an electrostatic latent image on a photosensitive member, a developing step for forming a toner image on the latent image on the photosensitive member, and the formed toner image on a transfer member. A transfer step of transferring to the substrate.

  The image forming apparatus of the present invention includes a latent image forming unit that forms an electrostatic latent image on a photoconductor, a developing unit that forms a toner image on the latent image on the photoconductor, and the formed toner image on a transfer member. Has a transfer means for transferring to the surface.

  FIG. 5 is a schematic configuration diagram showing an example of the image forming apparatus of the present invention. In FIG. 5, around the photosensitive drum 21 which is an electrostatic latent image carrier, a charging device 22 for charging the drum surface, and exposure with a laser beam for forming a latent image on a uniformly charged surface. 23. A developing device 24 for forming a toner image by attaching charged toner to a latent image on the drum surface, a transfer device 28 for transferring the toner image on the formed drum to the recording paper, and fixing the toner on the recording paper. A fixing device 32, a cleaning device 36 for removing and collecting the residual toner on the drum, and a static elimination lamp 39 for removing the residual potential on the drum are arranged in this order.

First, the surface of the photosensitive drum 21 is uniformly charged by the charging roller 22. In the example of FIG. 5, the photosensitive drum 21 is charged using a charging roller, but corona charging such as corotron or scorotron may be used. Charging using a charging roller has the advantage of generating less ozone than using corona charging, but because the roller surface is contaminated with toner because it is in contact with the photoreceptor, a mechanism to clean the charging roller is required. become.

  The charged photosensitive drum 21 is irradiated with a laser beam 23 according to image information, and an electrostatic latent image is formed. It is also possible to detect the charging potential and the exposure part on the photosensitive drum 21 with a potential sensor and control the charging condition and the exposure condition.

Next, the developing device 24 forms a toner image on the photosensitive drum 21 on which the electrostatic latent image is formed. In the developing device 24, the developer is stirred and conveyed by the screw 25 and supplied to the developing sleeve 26. The developer supplied to the developing sleeve 26 is regulated by a doctor blade 27, and the amount of developer supplied is controlled by a doctor gap that is the distance between the doctor blade 27 and the developing sleeve 26. If the doctor gap is too small, the developer amount is too small and the image density becomes insufficient. Conversely, if the doctor gap is too large, the developer amount is excessively supplied and carrier adhesion occurs on the photosensitive drum 21. Problems arise. The developing sleeve 26 is provided with a magnet that forms a magnetic field so as to cause the developer to rise on the peripheral surface, and the developer is placed on the developing sleeve 26 so as to follow a normal magnetic line of force emitted from the magnet. A magnetic brush is formed with a chain. The developing sleeve 26 and the photosensitive drum 21 are disposed so as to be close to each other with a certain gap (developing gap) therebetween, and a developing region is formed in a portion facing both. The developing sleeve 26 is formed of a non-magnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape, and is rotated by a rotation driving mechanism (not shown). The magnetic brush is transferred to the developing area by the rotation of the developing sleeve 26. A developing voltage is applied to the developing sleeve 26 from a developing power source (not shown), and the toner on the magnetic brush is separated from the carrier by a developing electric field formed between the developing sleeve 26 and the photosensitive drum 21, Is developed on the electrostatic latent image. An alternating current may be superimposed on the development voltage. The development gap can be set to 0.25 mm to 1.5 mm when the developer particle size is about 5 to 30 times and the developer particle size is 50 μm. If it is wider than this, it is difficult to obtain a desired image density. Further, the doctor gap needs to be the same as or slightly larger than the development gap. The drum diameter and drum linear speed of the photosensitive drum 21 and the sleeve diameter and sleeve linear speed of the developing sleeve 26 are determined by restrictions such as the copying speed and the size of the apparatus. The ratio of the sleeve linear velocity to the drum linear velocity needs to be 1.1 or more in order to obtain a necessary image density. It is also possible to control the process conditions by installing a sensor at a position after development and detecting the toner adhesion amount from the optical reflectance. In the example of FIG. 5, a two-component development system in which development is performed by a magnetic brush composed of a carrier and toner is used, but the present invention is not limited to the two-component development system, and the toner formed on the developing sleeve A one-component development system in which the thin layer is developed on the photoreceptor with an electric field may be used.

For the carrier constituting the magnetic brush, magnetic powder such as iron powder , ferrite powder , resin particles in which magnetic particles are dispersed, and magnetic powder whose surface is coated with resin to control electric characteristics are preferable. used. As a carrier constituting the magnetic brush, the photosensitive drum 21 is used.
In order to reduce damage to the surface, spherical particles are preferably used, and those having an average particle size of 150 μm or less are preferable. If the average particle diameter of the carrier is too large, the radius of curvature is large even when the carriers are arranged in the close-packed state, the area not in contact with the photosensitive drum 21 increases, and a toner image is dropped or missing. On the other hand, if the average particle size is too small, when an AC voltage is applied, the particles easily move and exceed the magnetic force between the particles, and the particles are scattered and cause carrier adhesion. The average particle diameter of the carrier is particularly preferably 30 μm or more and 100 μm or less. Furthermore, if the volume resistivity of the carrier is too low, charges are injected into the carrier when a developing voltage is applied, causing carrier adhesion to the photosensitive drum 21 or dielectric breakdown of the photosensitive member. However, it is necessary to use a carrier of 10 ³ Ωcm or more.

The toner image formed on the photosensitive drum 21 is conveyed to a transfer nip where the photosensitive drum 21 and the transfer belt 29 are in contact with each other. At the same time, the recording paper conveyed from a paper supply tray (not shown) enters the transfer nip. A transfer voltage having a polarity opposite to that of the toner is applied to the bias roller 30 in contact with the transfer belt 29 by a transfer power supply (not shown). The toner image formed on the photosensitive drum 21 is transferred onto a recording sheet by a transfer electric field acting between the transfer belt 29 and the photosensitive drum 21. In the example of FIG. 5, a transfer roller may be used as a transfer member instead of the transfer belt, but the transfer belt has an advantage that a transfer nip can be widened compared to the transfer roller. In the example of FIG. 5, a transfer system using a transfer belt is used, but a corona transfer system in which a corona charge having a polarity opposite to that of the toner is applied from the back surface of the paper to charge and transfer the paper may be used. Compared to the corona transfer method, the transfer method that applies the transfer voltage to the transfer belt or the transfer roller is easier to separate from the photoconductor because of less charging of the paper, and has the advantage of not causing image defects due to separation discharge during separation. However, the belt and the roller are easily contaminated with toner, so that a cleaning mechanism is required, and there is also a drawback in that an image is easily lost as described above.

  The recording paper attached to the photosensitive drum during transfer is separated from the photosensitive drum 21 by the separation claw 31. The recording paper on which the unfixed toner image is placed is applied with a certain amount of heat and pressure by the fixing roller 33 and the pressure roller 34, and the toner is fixed on the recording paper. In order to keep the fixing temperature constant, a thermistor (not shown) is in contact with the fixing roller 33 to control the temperature of the fixing heater 35. A fixing method using a fixing roller has high thermal efficiency, excellent safety, can be miniaturized, and has a wide range of applications from low speed to high speed.

  On the other hand, the toner remaining on the photosensitive drum 21 without being transferred is removed by the cleaning blade 37 and recovered by the toner recovery device 38. Although the cleaning blade is used in the example of FIG. 5, a fur brush method in which the brush is rotated at a high speed to remove the toner may be used. Since the cleaning blade method has a high toner removing capability and can be configured simply, it can be made small and inexpensive.

The photosensitive drum 21 from which the residual toner has been removed is initialized by the charge eliminating lamp 39 and used for the next image forming process.
The example of FIG. 5 is a black and white image forming apparatus using one photosensitive drum and one developing device, but the present invention is not limited to a black and white image forming apparatus, and one photosensitive drum and a plurality of developing devices, Alternatively, it can be applied to a color image forming apparatus using a plurality of photosensitive drums and a developing device.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
First, the irregular toner base particles used in the examples will be described. All parts shown below are based on weight.

Polyester resin (weight average molecular weight 250,000) 80 parts Styrene-methyl methacrylate copolymer 20 parts Acid value rice wax (acid value 15) 5 parts Carbon black (manufactured by Mitsubishi Chemical Industries, # 44)
8 parts Metal-containing monoazo dye 3 parts

  The mixture having the above composition is sufficiently stirred and mixed in a Henschel mixer, heated and melted at a temperature of 130 to 140 ° C. for about 30 minutes with a roll mill, cooled to room temperature, and then the kneaded product obtained using a hammer mill is about 1 mm to Coarsely pulverize to 2 mm, finely pulverize with a jet mill, and classify the resulting fine powder to have a volume average particle size of 4.1 μm (toner base particle A), 7.2 μm (toner base particle B), 9.1 μm. An irregular toner mother particle (toner mother particle C) was obtained. In addition, toner base particles (toner base particles D) having a narrow volume average particle size of 7.2 μm with a narrow particle size distribution were prepared by changing the classification conditions. The toner particle size distribution was measured by dispersing the toner in an electrolytic aqueous solution to which a neutral surfactant was added and using a particle size measuring device TA-II manufactured by Coulter. FIG. 6 shows the particle size distribution of toner base particle B, and FIG.

Next, production examples of toners used in examples, reference examples (of which the standard deviation exceeds 0.65) and comparative examples will be described.
( Reference Example 1)
Hydrophobic silica (Cabot TS-720) having an average primary particle size of 14 nm is used as an external additive. The toner base particles A and the silica (silica A) are added, and the amount of silica A added is 0% of the toner weight. The toner was prepared by blending to 6 wt% and mixing with a Henschel mixer. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 2)
Toner mother particles A and silica A were blended so that the amount of silica A added was 0.8% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 3)
Toner mother particles A and silica A were blended so that the amount of silica A added was 1.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

Example 4
Toner mother particles A and silica A were blended so that the amount of silica A added was 2.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2500 rpm, and the rotation time was 5 minutes.

(Example 5)
Toner mother particles A and silica A were blended so that the amount of silica A added was 4.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 3000 rpm, and the rotation time was 5 minutes.

( Reference Example 6)
Toner mother particles B and silica A were blended so that the amount of silica A added was 0.3% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 7)
Toner mother particles B and silica A were blended so that the amount of silica A added was 0.4% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 8)
Toner mother particles B and silica A were blended so that the amount of silica A added was 1.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

Example 9
Toner mother particles B and silica A were blended so that the amount of silica A added was 2.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2500 rpm, and the rotation time was 5 minutes.

(Example 10)
Toner mother particles B and silica A were blended so that the amount of silica A added was 3.0% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 3000 rpm, and the rotation time was 5 minutes.

(Example 11)
Toner mother particles C and silica A were blended so that the amount of silica A added was 0.2% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 12)
Toner mother particles C and silica A were blended so that the amount of silica A added was 0.3% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 13)
Toner mother particles C and silica A were blended so that the amount of silica A added was 0.7% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 14)
Toner mother particles C and silica A were blended so that the amount of silica A added was 1.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Example 15)
Toner mother particles C and silica A were blended so that the amount of silica A added was 2.5% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2500 rpm, and the rotation time was 5 minutes.

(Comparative Example 1)
Toner mother particles A and silica A were blended so that the amount of silica A added was 0.3% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Comparative Example 2)
Toner mother particles B and silica A were blended so that the amount of silica A added was 0.1% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Comparative Example 3)
Toner mother particles C and silica A were blended so that the amount of silica A added was 0.1% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

For the toners of the above-mentioned Examples , Reference Examples and Comparative Examples, the external additive coverage and non-electrostatic adhesion were measured and copied by the methods described below.
(Measurement of external additive coverage)
The toner was adhered to the observation substrate for an electron microscope, the observation substrate to which the toner was adhered was coated with gold, and the surface of the toner was observed with an electron microscope (Hitachi, Ltd., scanning electron microscope S-4500). An image obtained by magnifying the toner surface to 30,000 times is taken into a personal computer, and the area of the external additive is measured using image processing software (Image-Pro Plus manufactured by Media Cybernetics), and the area of the external additive with respect to the area of the toner surface image The external additive coverage was determined by calculating the ratio of Table 1 shows the results of measuring the external additive coverage.

(Measurement of adhesion by centrifugation)
Ball milling 0.4 parts by weight of a bisazo pigment of the following structural formula (4) together with 4 parts by weight of a 5% by weight tetrahydrofuran solution of butyral resin (S-LEC BL-S Sekisui Chemical Co., Ltd.) and 7.6 parts by weight of tetrahydrofuran. After milling, tetrahydrofuran was added to dilute to 2% by weight to prepare a coating solution for forming a charge generation layer. This photosensitive solution was applied on a PET film having a thickness of 75 μm in which aluminum was vapor-deposited to a thickness of 100 nm using a doctor blade and dried to form a charge generation layer.

Next, 6 parts by weight of a hole transport material of the following structural formula (5) and 9.0 parts by weight of cyclohexylidene bisphenol polycarbonate (Z Polyca, Teijin Chemicals TS2050) as a photosensitive binder resin are dissolved in 67 parts by weight of tetrahydrofuran. This was applied onto the charge generation layer with a doctor blade and dried to provide a charge transport layer having a thickness of 20 μm to produce an organic photoreceptor.

  The PET film on which the organic photoconductor was formed was cut into a disk shape having a diameter of 7.8 mm, and attached to a sample substrate used for centrifugation using a plastic adhesive. Uncharged toner was scattered by compressed air to adhere the toner onto the organic photoreceptor.

  The non-electrostatic adhesion force between the toner and the photosensitive member was measured by the above-described centrifugal separation method, and the proportionality coefficient K and the standard deviation σ were obtained. Table 1 shows the measurement results of the proportionality coefficient K and the standard deviation σ.

The apparatus and measurement conditions used for the adhesion force measurement are as follows.
Centrifugal separator: Hitachi Koki CP100α (Maximum rotation
Number: 100,000 rpm,
Maximum acceleration: 800,000g)
Rotor: Hitachi Koki angle rotor P100AT
Image processing device: Interquest Hyper70
0
Sample substrate and receiving substrate: a disk with a diameter of 8 mm and a thickness of 1.5 mm, the material is aluminum Spacer: a ring with an outer diameter of 8 mm, an inner diameter of 5.2 mm, a thickness of 1 mm, and the material is aluminum. Holding material: diameter 13 mm, length It is a 59mm cylinder, and the material is the distance from the central axis of the aluminum rotor to the toner adhesion surface of the sample substrate: 64.5mm
Set rotation speed f: 1000, 1600, 2200,
2700, 3200, 5000,
7100, 8700, 10000,
15800, 22400,
31600, 50000,
70700, 86600,
100,000 (rpm)

(Copy test)
The toners of Examples , Reference Examples and Comparative Examples are mixed with Ricoh's Imagio MF3550 (two-component development type monochrome copying machine) carrier so that the toner concentration is 2.5% by weight, and a two-component developer. Was made. For each developer, continuous copying of 50,000 sheets was carried out using Imagio MF3550 manufactured by Ricoh. In the copying test, the photoconductor material used for the measurement of the adhesion force was formed on an aluminum photoconductor drum (φ60 mm) by an immersion method, and used as a photoconductor drum of Imagio MF3550 (manufactured by Ricoh Co., Ltd.). Using. The main copying conditions are shown below.

Copy speed: 35 CPM
Photoconductor linear velocity: 180 mm / s
Pixel density: 400 dpi
Photoconductor surface potential: -150V to -950V
Development voltage: -550V

  For the initial image after changing the developer and the image after continuous copying of 50,000 sheets, the background stain and the void image were evaluated. When the developer was changed, the photoconductor was changed to an unused product at the same time.

A four-level evaluation sample for each evaluation item was prepared, and the copy image and the photoreceptor surface were observed visually and by a CCD microscope camera (Keyence Corporation hypermicroscope), and compared with the evaluation sample, and the four-level evaluation sample was evaluated. Table 1 shows the evaluation results of the copy test. The evaluation at each stage represents the following states.
4: No problem 3: Almost no problem 2: Some problem 1: Problem

In Table 1, Reference Example 1 , Example 2 to Example 5 are toner base particles A having an average particle diameter of 4.1 μm, and Reference Examples 6, Example 7 to Example 10 are toner base particles having an average particle diameter of 7.2 μm. B, Examples 11 to 15 show the results when the amount of additive added to the toner base particles C having an average particle diameter of 9.1 μm is changed. As shown in Table 1, the external additive coverage varies depending on the combination of the particle size of the toner base particles and the amount of external additive added. Examples 2 to 5, Example 7 to Example 10, and Examples 12 to 15 have an external additive coverage of 8% or more, a proportionality coefficient K of 5 (nN / μm) or less, and a standard deviation σ. Was 0.65 or less, and there was no image defect at the initial stage and after copying 50,000 sheets, and a good copy image could be formed. Also, Reference Example 1, Reference Example 6, in the case of Reference Example 11, in the external additive coating ratio than 8%, although it standard deviation σ is 0.65 or more, proportional coefficient K is 5 (nN / μm) or less Although the evaluation of the copying test was lower than that of the other examples, an image having almost no problem was obtained. On the other hand, in Comparative Examples 1 to 3, the proportionality coefficient K was 5 (nN / μm) or more and the standard deviation σ was 0.65 or more, and image defects occurred at the initial stage and after copying 50,000 sheets. .

( Reference Example 16)
Toner mother particles D and silica A were blended so that the amount of silica A added was 0.2% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 17)
Toner mother particles D and silica A were blended so that the amount of silica A added was 0.3% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 18)
Toner mother particles D and silica A were blended so that the amount of silica A added was 1% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Comparative Example 4)
Toner mother particles D and silica A were blended so that the amount of silica A added was 0.1% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

For the toners of Comparative Example 16 , Example 17 to Example 18, and Comparative Example 4, the external additive coverage and non-electrostatic adhesion were measured and copied by the above-described methods, and the results are shown in Table 2. Show.

Table 2 shows the results when the additive amount of the external additive was changed for the toner base particles D having a volume average particle size of 7.2 μm and a narrow particle size distribution. In Example 17, the external additive coverage was 8% or less, but the proportionality coefficient K was 5 (nN / μm) or less and the standard deviation σ was 0.65 or less. No good copy image could be formed. In the case of Example 13, since the particle size distribution of the toner base particles is sharp, the adhesion distribution is also sharp, and it is considered that the standard deviation σ is 0.65 or less even when the external additive coverage is 8% or less. In the case of Example 14, the external additive coverage was 8% or more, the proportionality coefficient K was 5 (nN / μm) or less, and the standard deviation σ was 0.65 or less. There was no defect and a good copy image could be formed. In the case of Reference Example 16, the standard deviation σ is 0.65 or more, but the proportionality coefficient K is 5 (nN / μm) or less, and the evaluation of the copy test is lower than the other examples, but there is almost no problem. An image was obtained. On the other hand, in the case of Comparative Example 4, the external additive coverage was 8% or less, the proportionality coefficient K was 5 (nN / μm) or more, and the standard deviation σ was 0.65 or more. An image defect occurred after copying.

(Example 19)
Hydrophobic silica (RY-50, manufactured by Nippon Aerosil Co., Ltd.) having an average primary particle size of 40 nm is used as an external additive, and toner base particles B and the silica (silica B) are added. A toner was prepared by blending to 1.0 wt% and mixing with a Henschel mixer. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Example 20)
Toner mother particles B and silica B were blended so that the amount of silica B added was 2.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2500 rpm, and the rotation time was 5 minutes.

(Example 21)
Toner mother particles B and silica B were blended so that the amount of silica B added was 3.0% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 3000 rpm, and the rotation time was 5 minutes.

(Comparative Example 5)
Toner mother particles B and silica B were blended so that the amount of silica B added was 0.3% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Comparative Example 6)
Toner mother particles B and silica B were blended so that the amount of silica B added was 0.8% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

  The toners of Examples 19 to 21, Comparative Example 5 and Comparative Example 6 were subjected to the measurement of external additive coverage and non-electrostatic adhesion and the copying test by the above-mentioned methods. The results are shown in Table 3. Show.

Table 3 shows the results when the external additive addition amount of hydrophobic silica having an average primary particle size of 40 nm is changed with respect to the toner base particles B having a volume average particle size of 7.2 μm. Compared with the results of Reference Example 6 and Examples 10 to 10 in which toner base particles B and hydrophobic silica having an average primary particle diameter of 14 nm are combined, it is necessary to obtain a constant external additive coverage. It can be seen that the amount of external additive added and the values of proportionality coefficient K and standard deviation σ vary depending on the primary particle diameter of the external additive. In all of Examples 19 to 21, the external additive coverage was 8% or more, the proportionality coefficient K was 5 (nN / μm) or less, and the standard deviation σ was 0.65 or less. There was no image defect after copying, and a good copied image could be formed. On the other hand, in the case of Comparative Example 5 and Comparative Example 6, the external additive coverage was 8% or less, the proportionality coefficient K was 5 (nN / μm) or more, and the standard deviation σ was 0.65 or more. An image defect occurred.

( Reference Example 22)
Hydrophobic titanium oxide having an average primary particle diameter of 15 nm (Taika MT150A) is used as an external additive, and toner mother particles B and the titanium oxide (titanium oxide A) are added. The toner was blended so as to be 0.3% by weight and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 23)
Toner mother particles B and titanium oxide A were blended so that the amount of titanium oxide A added was 0.4% by weight of the amount of toner, and agitated and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 24)
Toner mother particles B and titanium oxide A were blended so that the amount of titanium oxide A added was 1.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Example 25)
Toner mother particles B and titanium oxide A were blended so that the amount of titanium oxide A added was 2.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2500 rpm, and the rotation time was 5 minutes.

(Example 26)
Toner mother particles B and titanium oxide A were blended so that the amount of titanium oxide A added was 3.0% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 3000 rpm, and the rotation time was 5 minutes.

(Comparative Example 7)
Toner mother particles B and titanium oxide A were blended so that the amount of titanium oxide A added was 0.1% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

Comparative Example 22 , Example 23 to Example 26, Toner of Comparative Example 7 ・ BR> “Measurement of external additive coverage and non-electrostatic adhesive force by the above methods, copy test, The results are shown in Table 4.

Table 4 shows the results when the external additive addition amount of hydrophobic titanium oxide having an average primary particle diameter of 14 nm is changed with respect to the toner base particles B having a volume average particle diameter of 7.2 μm. . Compared with the results of Reference Example 6, Example 7 to Example 10 in which the toner base particles B and hydrophobic silica having an average primary particle diameter of 14 nm are combined, the values of the proportional coefficient K and the standard deviation σ are externally added. It can be seen that it varies depending on the material of the agent. In all of Examples 23 to 26, the external additive coverage was 8% or more, the proportionality coefficient K was 5 (nN / μm) or less, and the standard deviation σ was 0.65 or less. There was no image defect after copying, and a good copied image could be formed. In the case of Reference Example 22, the external additive coverage is 8% or less and the standard deviation σ is 0.65 or more, but the proportionality coefficient K is 5 (nN / μm) or less, which is a copy than the other examples. Although the evaluation of the test was low, an image with almost no problem was obtained. On the other hand, in Comparative Example 7, the proportionality coefficient K was 5 (nN / μm) or more and the standard deviation σ was 0.65 or more, and an image defect occurred at the initial stage and after copying 50,000 sheets.

Next, spherical toner base particles used in Examples and the like will be described.
Monomer Styrene 20 parts n-Butyl acrylate 17.8 parts Carbon black (Mitsubishi Chemical Corporation:
MA-100) 1 part Charging agent (manufactured by Orient Chemical Co., Ltd .:
E-84) 0.3 part Initiator: ADVN 1 part Aqueous dispersion medium Ion-exchanged water 150 parts Polyvinyl alcohol 5.2 parts

  The monomer and the aqueous dispersion medium were placed in a stirring tank and suspended at 9500 rpm for 10 minutes with a homogenizer (manufactured by Tokushu Kika Kogyo Co., Ltd.). The suspension was polymerized while being stirred in a hot water bath at 60 ° C. for 8 hours. After completion of the polymerization, the mixture was allowed to stand overnight and allowed to settle naturally, and this was subjected to reprecipitation treatment with ion-exchanged water, then passed through a # 150 mesh to remove aggregates, and further subjected to centrifugal sedimentation. This was filtered and dried under reduced pressure to obtain spherical toner base particles (toner base particles E) having a volume average particle diameter of 7.3 μm.

(Example 27)
Toner mother particles E and silica A were blended so that the amount of silica A added was 0.2% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 28)
Toner mother particles E and silica A were blended so that the amount of silica A added was 0.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 29)
Toner mother particles E and silica A were blended so that the amount of silica A added was 1.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Example 30)
Toner mother particles E and silica B were blended so that the amount of silica B added was 0.5% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 31)
Toner mother particles E and silica B were blended so that the amount of silica B added was 1.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Example 32)
Toner mother particles E and silica B were blended so that the amount of silica B added was 2.5% by weight of the toner amount, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2500 rpm, and the rotation time was 5 minutes.

(Example 33)
Toner mother particles E and titanium oxide A were blended so that the amount of titanium oxide A added was 0.2% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 34)
Toner mother particles E and titanium oxide A were blended so that the amount of titanium oxide A added was 0.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Example 35)
Toner mother particles E and titanium oxide A were blended so that the amount of titanium oxide A added was 1.5% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 2000 rpm, and the rotation time was 5 minutes.

(Comparative Example 8)
Toner mother particles E and silica A were blended so that the amount of silica A added was 0.1% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Comparative Example 9)
Toner mother particles E and silica B were blended so that the amount of silica B added was 0.3% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

(Comparative Example 10)
Toner mother particles E and titanium oxide A were blended so that the amount of titanium oxide A added was 0.1% by weight of the amount of toner, and stirred and mixed with a Henschel mixer to prepare a toner. The rotation speed of the mixing blade of the Henschel mixer was 1500 rpm, and the rotation time was 5 minutes.

  The toners of Examples 27 to 35 and Comparative Examples 8 to 10 were subjected to the measurement of the external additive coverage and the non-electrostatic adhesion and the copying test by the above-described methods. The results are shown in Table 5. Show.

In Table 5, with respect to spherical toner base particles E having a volume average particle size of 7.3 μm, Examples 27 to 29 are hydrophobic silica having an average primary particle size of 14 nm, and Examples 30 to 32. Shows hydrophobic silica having an average primary particle diameter of 40 nm, and Examples 33 to 35 show the results when the additive amount of the hydrophobic titanium oxide having an average primary particle diameter of 15 nm is changed. Yes. Compared with the results for the irregular toner base particles B having a volume average particle size of 7.2 μm, the amount of additive added necessary to obtain a constant external additive coverage, the value of proportionality coefficient K and standard deviation σ It can be seen that this varies depending on the shape of the toner base particles. In any of the examples, the external additive coverage was 8% or more, the proportionality coefficient K was 5 (nN / μm) or less, and the standard deviation σ was 0.65 or less. And a good copy image could be formed. In contrast, in Comparative Examples 8 to 10, the external additive coverage was 8% or less, the proportionality coefficient K was 5 (nN / μm) or more, and the standard deviation σ was 0.65 or more. An image defect occurred after copying 50,000 sheets.
As mentioned above, although the Example of this invention was described, this invention is not limited to these Examples.

Explanatory drawing of the measurement cell in the powder adhesive force measuring apparatus which concerns on this invention. The partial cross section side view of the centrifuge of the powder adhesive force measuring apparatus which concerns on this invention. FIG. 4 is a diagram showing a non-electrostatic adhesion distribution between toner and a photoreceptor. FIG. 6 is a diagram illustrating a relationship between an average value Fne of a non-electrostatic adhesion force between a toner and a photoreceptor and a toner particle diameter D. 1 is a schematic configuration diagram showing an example of an image forming apparatus of the present invention. FIG. 6 is a view showing a particle size distribution of toner base particles B. FIG. 6 is a view showing a particle size distribution of toner base particles D.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Measurement cell 2 Sample substrate 2a Sample surface 3 Receiving substrate 3a Adhesion surface 4 Spacer 5 Centrifugal device 6 Rotor 7 Holding member 7a Rod-like part 7b Cell holding part 7c Hole part 7d Installation fixing part 8 Sample installation part 9 Rotation center axis 21 Photosensitive Body drum 22 Charging roller 23 Exposure 24 Developing device 25 Screw 26 Developing sleeve 27 Doctor blade 28 Transfer device 29 Transfer belt 30 Bias roller 31 Separating claw 32 Fixing device 33 Fixing roller 34 Pressure roller 35 Fixing heater 36 Cleaning device 37 Cleaning blade 38 Toner recovery device 39 Static elimination lamp

Claims (19)

A latent image forming step for forming an electrostatic latent image on the photosensitive member, a developing step for forming a toner image using electrophotographic toner on the latent image on the photosensitive member, and the formed toner image on the transfer member. In an image forming method having a transfer step of transferring, the toner is applied non-electrostatically, which is not caused by toner charging, among the adhesive force acting between the electrophotographic toner and the electrophotographic photosensitive member measured by a centrifugal separation method. Regarding the adhesion force, the average value of the non-electrostatic adhesion force to the toner particle group in which the particle diameter range in the electrophotographic toner is D ± d (μm) ( where d is 2 μm or less) is Fne (D). (NN), the proportional coefficient of the linear regression line in the graph plotted with the toner particle diameter D as the horizontal axis and Fne (D) as the vertical axis is 0.01 (nN / μm) to 5 (nN / μm). To the common logarithmic distribution of non-electrostatic adhesion Image forming method standard deviation is characterized by using a combination of 0.65 or less and the electrophotographic toner and the photosensitive member that. External addition treatment is performed with an external additive composed of fine particles having an average primary particle diameter of 1 nm to 100 nm, and the average value of the coating area ratio of the external additive to the surface area per toner particle is 8% to 100%. The image forming method according to claim 1, wherein the toner is used. The image forming method according to claim 2, which is an external additive composed of fine particles having an average primary particle diameter of 5 nm to 80 nm. 4. The image forming method according to claim 2, wherein the average value of the coating area ratio of the external additive to the surface area per toner particle is 10% to 90%. The image forming method according to claim 1, wherein the external additive contains at least one of silica, titania, and alumina. The image forming method according to claim 1 which is organic fine particles of the external additive Gapo polymethyl methacrylate. The image forming method according to claim 5, wherein the external additive is subjected to a hydrophobic treatment. The image forming method according to claim 1, wherein the external additive is externally added using a mixing device. The image forming method according to claim 8, wherein the external additive is externally added by a Henschel mixer. The electrophotographic toner is a magnetic - The image forming method according to any one of claims 1 to 9 which is a component toner. The image forming method according to claim 1, wherein the toner for electrophotography is a nonmagnetic toner constituting a magnetic two-component developer used together with a magnetic carrier. The image forming method according to any one of claims 1 to 11, volume average particle diameter of the electrophotographic toner is characterized in that it is a 3Myuemu～15myuemu. 13. The image forming method according to claim 12, wherein the volume average particle diameter of the electrophotographic toner is 3 μm to 10 μm. The toner according to any one of claims 1 to 13, wherein a toner is prepared by blending a colorant, a charge control agent, and a release agent in a binder resin, granulating to an appropriate particle size, and adding an external additive. The image forming method described . The image forming method according to claim 1, wherein the photoconductor is an inorganic photoconductor. The image forming method according to any one of claims 1 to 14, wherein the photoconductor is formed by forming a charge generation layer and a charge transport layer of an organic material on a conductive support, or further forming a protective layer.   An image having latent image forming means for forming an electrostatic latent image on the photosensitive member, developing means for forming a toner image on the latent image on the photosensitive member, and transfer means for transferring the formed toner image onto the transfer member. 16. An image forming apparatus using the electrophotographic toner according to claim 1 in the forming apparatus. The image forming apparatus according to claim 17 , wherein the photoconductor is an inorganic photoconductor. On the photosensitive member is electrically conductive support, a charge generation layer of an organic material, a charge transport layer is formed, or a protective layer in which is formed according to claim 17 the image forming apparatus according.

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