JP2008233373A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which maintains high transfer efficiency even when adopting a developer of small particle size and an image carrier of thin film and reduces scattering and re-transfer. <P>SOLUTION: A potential absolute value of a photoreceptor drum is controlled to be 200 V or less after development and before transfer, is controlled to be 100 V or less after transfer unit passage of sheet material and the outside diameter of the photoreceptor drum is set to be 20 to 40 mm. The developer includes a binder resin and particles of colorant, and further includes inorganic fine particles on the surface of particles of colorant, of which the average particle size is 30 to 300 nm and the content of the particle of particle size of 600 nm or more or the content of the number of aggregations is 1% or less. The weight average particle size of the developer is 3.0 to 7.0 μm; the circularity is 0.940 to 0.975 and the degree of aggregation is 50 to 70%. Among the distance L (mm) between a contact nip center of an intermediate transfer body and an image carrier and a contact nip center of a primary transfer means and the intermediate transfer body, the degree G (%) of aggregation and the outer diameter D (mm) of the photoreceptor drum, the following relation holds: 0.3<L≤(0.1×G-4.5)×D/30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and specifically to an image forming method used for a recording method using an electrophotographic method or an electrostatic recording method. In particular, in an image forming apparatus used for a copying machine, a printer, a facsimile machine, etc., in which an electrostatic latent image formed on an electrostatic latent image carrier is developed with toner and then transferred onto an intermediate transfer member to form an image. It is suitable for application.

  In general, in an image forming apparatus that records an image on a recording medium such as paper, such as a copying machine, a printer, or a facsimile, an electrophotographic system is employed as a system for recording the image on the recording medium.

  In recent years, a copying apparatus has been adopted not only as a copying machine for office processing for copying a manuscript but also as an information output device linked to another information processing machine by introducing digital technology. The copying apparatus is also employed as a copying machine or a printer that is an output device for creating a new original document because it is easy to process and edit image information due to its multi-function.

  Further, as demands from the market, higher speed, higher image quality, smaller and lighter weight, and higher reliability have been strictly pursued. In order to satisfy such a demand, a tandem type apparatus in which image forming units are arranged in parallel has become mainstream.

  In particular, in such a tandem type image forming apparatus, image formation is performed by transferring each color toner image onto a transfer medium as a developer image from a photoreceptor carrying each color toner image. Make it. For this reason, it is necessary to suppress the occurrence of image disturbance due to flickering at the time of transfer, color balance change such as each color density and secondary color, and color unevenness due to retransfer.

  In order to solve these problems, an image forming apparatus has been proposed in which a pressing member to which a bias is applied is disposed upstream or downstream of the transfer unit in the transfer unit (for example, Patent Document 1). Furthermore, the use of an amorphous silicon photoconductor has been proposed in order to reduce the particle size of toner as a developer, reduce the thickness of the photoconductor, and achieve high durability and high reliability in order to improve image quality.

  Amorphous silicon photoconductors have a high surface hardness, a high sensitivity to light of relatively long wavelengths corresponding to semiconductor lasers and LEDs, etc., and long life without deterioration due to repetition. Used in printers and printers.

That is, in the case of the OPC photoconductor that is usually used most widely, the life of the photoconductor is overwhelmingly short with respect to the life of the apparatus main body. Therefore, it is necessary to replace about 5 photoconductors until the mechanical life is reached. At this time, it takes time for the service person to replace the OPC photosensitive member. On the other hand, when an amorphous silicon photoconductor is used, the photoconductor first assembled in the machine can be used continuously until the end of the mechanical life, so that there is an advantage that it is not necessary to replace the photoconductor. ing.
JP 2004-246323 A

  However, in the technique described in Patent Document 1, since the configuration in which the push-up member is further installed in the vicinity of the transfer unit is adopted, it is difficult to reduce the size of the entire apparatus.

  In addition, there is a problem of reducing the particle size of the toner due to the demand for higher image quality. That is, as the particle size of the toner becomes smaller, the electrostatic force acting between the photoreceptor and the toner against the electrostatic force for transferring the toner image as the developer image from the surface of the photoreceptor when transferring is non-electrostatic. The ratio of the strong adhesion increases. Furthermore, since the amount of charge per unit weight of the appropriate toner increases as the particle size of the toner is reduced, the electrostatic adhesion between the photoconductor and the toner increases, and the transferability is significantly reduced. .

  In addition, due to the demand for higher speed, the transfer bias output required for electrostatic transfer increases by increasing the speed of image formation, so-called process speed. For this reason, the probability of occurrence of re-transfer in which the dust generated near the transfer portion or the toner transferred to the transfer medium is reversely transferred back to the photoconductor is increased.

  Furthermore, if a thin film photoconductor or an amorphous silicon photoconductor is used to improve the image quality, the dielectric constant or capacitance of the photoconductor itself increases. Then, transfer efficiency, which is transferability in a macroscopic sense, and electrostatic adsorption force of toner in contact with the drum surface in a microscopic sense are increased.

  Accordingly, in order to obtain good transferability in the image forming apparatus, a larger transfer bias is required. However, as described above, there is a problem that when the transfer bias is increased, flyback and retransfer are likely to occur.

  Further, in order to reduce the size of the entire apparatus, the diameter of the photosensitive drum to be used has been reduced. At present, the drum having a diameter of about 30 mm is mainly used. Since the width of the transfer nip is narrowed by reducing the diameter of the drum, there is no room for installing the push-up member.

  Accordingly, an object of the present invention is to provide an image forming apparatus having high reliability while reducing the size, increasing the speed and improving the image quality without adding a member. A further object of the present invention is to provide an image forming apparatus that has high transfer efficiency and is less subject to repetitive transfer and retransfer even when a small particle size developer or a thin film image carrier is employed. It is to provide.

In order to achieve the above object, the present invention provides:
A substantially cylindrical image carrier;
Charging means for charging the image carrier;
An electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier charged by the charging unit;
Developing means for developing the electrostatic latent image with a developer;
In an image forming apparatus having a transfer unit that transfers a developed developer image to a sheet material,
The absolute value of the potential on the image carrier is 200 V or less after development by the developing unit and before transfer by the transfer unit,
The absolute value of the potential of the image carrier after the sheet material has passed through the transfer means is 100 V or less,
The outer diameter of the circle in the cylindrical shape of the image carrier is 20 mm or more and 40 mm or less,
The developer is
Particles composed of at least a binder resin and a colorant;
The surface of the particles includes inorganic fine particles having an average primary particle size of 30 nm to 300 nm and a content of particles or aggregates having a particle size of 600 nm or more and 1% or less, and a weight average of the developer The particle size is 3.0 μm or more and 7.0 μm or less, and the circularity is 0.940 or more and 0.00.
975 or less, and the degree of aggregation is 50% or more and 70% or less,
The transfer means includes
An intermediate transfer member to which at least a developer image on the image carrier is transferred;
Primary transfer means for bringing the intermediate transfer member into contact with the image carrier and transferring the developer image on the image carrier to the intermediate transfer member;
The primary transfer means is
Arranged on the upstream side or the downstream side in the traveling direction of the intermediate transfer member from the image carrier,
L (mm) is a distance between the center of the contact nip between the intermediate transfer member and the image carrier and the center of the contact nip between the primary transfer unit and the intermediate transfer member in the traveling direction of the intermediate transfer member;
The degree of aggregation is G (%),
When the outer diameter of the circle in the cylindrical shape of the image carrier is D (mm),
0.3 <L ≦ (0.1 × G−4.5) × D / 30
It is characterized by having the following relationship.

  According to the present invention, the image forming apparatus can be downsized, and the speed and quality of the image forming apparatus can be increased. Even when a developer having a small particle diameter or a thin-film image carrier is employed, the image forming apparatus has high transfer efficiency. , Tobiri and re-transfer can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings of the following embodiments, the same or corresponding parts are denoted by the same reference numerals.

  Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a quadruple tandem type image forming apparatus according to a first embodiment of the present invention.

  As shown in FIG. 1, the image forming apparatus has four image forming stations Pa that respectively form yellow (Y), magenta (M), cyan (C), and black (BK) toner images as image forming means. , Pb, Pc, Pd. In each of the image forming stations Pa to Pd, photosensitive drums 1a, 1b, 1c, 1d having substantially cylindrical shapes, charging rollers 2a, 2b, 2c, 2d, and exposure devices 3a, 3b, 3c, 3d are provided as process units. And developing devices 4a, 4b, 4c, and 4d. The image forming stations Pa to Pd are provided with primary transfer rollers 53a, 53b, 53c, and 53d and cleaning devices 6a, 6b, 6c, and 6d, respectively. Below the image forming stations Pa to Pd, the intermediate transfer belt 51, the secondary transfer inner roller 56, the secondary transfer outer roller 57, the paper feed cassette 8, the pickup roller 81, the transport roller 82, the fixing device 7, and the intermediate transfer belt. A cleaner 60 is provided.

  After the surfaces of the photosensitive drums 1a to 1d are uniformly charged by the charging rollers 2a to 2d, electrostatic latent images are formed on the surfaces by exposure by the exposure devices 3a to 3d according to image signals. The electrostatic latent images on the respective photosensitive drums 1a to 1d are developed as toner images as developers by the developing devices 4a to 4d. The primary transfer bias is applied to the primary transfer rollers 53a to 53d from the toner images on the photosensitive drums 1a to 1d by a primary transfer bias application power source (not shown). Thus, the toner images are sequentially primary-transferred and superimposed on the intermediate transfer belt 51 rotating in the direction of the arrow in FIG. Note that toner (transfer residual toner) that is not transferred to the intermediate transfer belt 51 and remains on the photosensitive drums 1a to 1d is removed by the cleaning devices 6a to 6d.

The four-color toner images primarily transferred onto the intermediate transfer belt 51 are applied with a secondary transfer bias between the secondary transfer inner roller 56 and the secondary transfer outer roller 57, so that the paper is formed at the secondary transfer nip portion. And the like are collectively transferred onto the recording material P as a sheet material. The recording material P is supplied from the inside of the paper feed cassette 8 to the secondary transfer nip portion by a pickup roller 81, a conveyance roller 82, and the like. Note that toner (transfer residual toner) that is not transferred to the recording material P and remains on the intermediate transfer belt 51 is removed and collected by the intermediate transfer belt cleaner 60.

  In the fixing device 7, the toner image on the recording material P is heated and pressed by a fixing roller 71 having an inner heater 73 and a pressure roller 72 pressed against the toner, and is fixed on the surface. As a result, a four-color full-color image is formed.

(Transfer part)
Next explained is a transfer portion according to the first embodiment of the invention. FIG. 2 shows an enlarged view of the photosensitive drum 1, the intermediate transfer belt 51, and the primary transfer roller 53. FIG. 2 is a diagram in the case where the primary transfer roller 53 is arranged so as to be shifted to the upstream side along the traveling direction of the intermediate transfer belt 51.

  As shown in FIG. 2, the intermediate transfer belt 51 is moved to the transfer portion in synchronization with the rotation of the photosensitive drum 1 (in the direction of the arrow in FIG. 2). The intermediate transfer belt 51 is pressed against the photosensitive drum 1 from the opposite side to the photosensitive drum 1 by the primary transfer roller 53. Thus, before contacting the surface B of the photosensitive drum 1 vertically below the center of the photosensitive drum 1, that is, the center of the contact nip between the intermediate transfer belt 51 and the photosensitive drum 1, the portion A in FIG. A contact nip is formed at the center by the intermediate transfer belt 51 and the primary transfer roller 53. Thereafter, the intermediate transfer belt 51 contacts along the curvature of the surface of the photosensitive drum 1, passes through point B at the center of the contact nip between the intermediate transfer belt 51 and the photosensitive drum 1, and then gradually from the surface of the photosensitive drum 1. Spaced apart.

  The center B of the contact nip between the photosensitive drum 1 and the intermediate transfer belt 51 is the center of the contact nip when the primary transfer roller 53 is not pressed against the intermediate transfer belt 51. The center A of the contact nip between the intermediate transfer belt 51 and the primary transfer roller 53 is the center of the contact nip when the primary transfer roller 53 is pressed against the photosensitive drum 1 via the intermediate transfer belt 51. .

  To obtain the distance L (mm) between the center A of the contact nip between the primary transfer roller 53 and the intermediate transfer belt 51 and the center B of the contact nip between the photosensitive drum 1 and the intermediate transfer belt 51, The method is adopted.

  That is, first, a toner image is uniformly developed on the photosensitive drum 1. Thereafter, the photosensitive drum 1 and the intermediate transfer belt 51 are brought into contact without pressing the primary transfer roller 53. In this case, the toner adhering to the intermediate transfer belt 51 adheres linearly in the longitudinal direction of the photosensitive drum 1, and thus this toner is measured (nip center A). Similarly, the toner adhering linearly to the intermediate transfer belt 51 in the longitudinal direction of the photosensitive drum 1 when the primary transfer roller 53 is pressed to bring the photosensitive drum 1 into contact with the intermediate transfer belt 51 is measured. (Nip center B). Then, the interval between the “stripes” of these two toners is measured. Note that when the two linear toners are too close to each other and cannot be observed, the width of both is set to L. Further, although the center A of the contact nip between the primary transfer roller 53 and the intermediate transfer belt 51 is on the back surface side with respect to the photosensitive drum 1, for the sake of convenience, the opposite side of the intermediate transfer belt 51 at point A (A ′ on the drawing) ).

As described above, the center A of the contact nip between the photosensitive drum 1 and the intermediate transfer belt 51 and the contact nip B between the intermediate transfer belt 51 and the primary transfer roller 53 are shifted from each other by a distance L (mm). . Note that, by this arrangement, first, the contact roller width of the intermediate transfer belt 51 and the photosensitive drum 1 can be widened by slightly shifting the transfer roller position. Second, not only the electrostatic force in the vertical direction due to the transfer electric field but also a slight speed difference between the photosensitive drum 1 and the intermediate transfer belt 51 occurs with respect to the toner, which assists the transfer of the toner. Third, the shape of the gap formed by the surface of the photosensitive drum 1 and the surface of the intermediate transfer belt 51 at the entrance and exit to the transfer unit can be changed.

Specifically, for example, when the primary transfer roller 53 is disposed on the upstream side, the intermediate transfer belt 51 and the photosensitive drum 1 are formed on the transfer inlet side as compared with the case where the primary transfer roller 53 is not moved upstream. The angle increases. As a result, the range of voids where transfer distortion tends to occur is narrowed. Further, as will be described later, the surface resistance value Rs (Ω / cm ²⁾ of the intermediate transfer belt 51.
) Is as high as 10 ¹² to 10 ¹⁵ (Ω / cm ² ), so that the range in which the transfer electric field acts does not expand, but concentrates on the contact area in transfer. Further, after the development of the photoconductor, the potential before the transfer is suppressed to a low level of 200 V or less, so that the toner flying on the photoconductor drum 1 that causes torriness is suppressed.

Further, since the toner T on the photosensitive drum 1 is transferred according to the transfer charge, the amount of charge on the photosensitive drum 1 becomes important. Specifically, the absolute value | Q | of the charge amount Q (× 10 ⁻³ C / kg) on the photosensitive drum 1 is preferably 20 ≦ | Q | ≦ 50. Furthermore, even if the potential before transfer is 200 V or less as described above, if the photosensitive drum 1 is charged due to the effect of transfer charging, the retransfer that occurs downstream in the rotation direction of the photosensitive drum 1 deteriorates. Therefore, the potential after transfer is desirably 100 V or less. The photoreceptor drum 1 that achieves these conditions is preferably a thin film photoreceptor, and more preferably an amorphous silicon photoreceptor.

  Furthermore, since the aggregation degree G (%) of the toner T is as high as 50 to 70%, the toner T is difficult to fly individually according to the electric field. In addition, the contact area between the photosensitive drum 1 and the intermediate transfer belt 51 is expanded, and the time for which the transfer electric field is applied becomes longer, so that the transfer efficiency can be improved.

  On the other hand, when the primary transfer roller 53 is disposed on the downstream side, the toner image on the photosensitive drum 1 is transferred to the photosensitive drum 1 and the intermediate transfer belt 51 by the tension of the intermediate transfer belt 51 on the transfer entrance side. Sandwiched. As a result, the toner particles T in the toner image are aggregated individually. Subsequently, when the closest transfer portion between the primary transfer roller 53 and the intermediate transfer belt 51 is reached, the transfer pressure and the transfer electric field reach a peak, and the aggregated toner image is drawn toward the intermediate transfer belt 51. Thereafter, similarly to the case where the primary transfer roller 53 is moved upstream, the angle formed between the photosensitive drum 1 on the transfer outlet side and the intermediate transfer belt 51 is increased, so that a gap region where retransfer occurs is generated. It becomes smaller and retransfer is suppressed.

  There is a method of shifting the contact position of the primary transfer roller 53 upstream and downstream of the intermediate transfer belt 51, which is more effective than the case where neither method is shifted. First, transfer efficiency is particularly improved when shifted to the upstream side, and retransfer is particularly improved when shifted to the downstream side. Therefore, depending on the configuration, performance, and characteristics of various devices, the primary transfer roller 53 is set upstream. It is desirable to use either one of them or downstream. Note that it is desirable to shift the primary transfer roller 53 to the upstream side of the intermediate transfer belt 51 when comprehensively determining the toner usage rate and the influence on the image.

  According to the first embodiment, since it relates to the shape of the transfer nip composed of the photoconductor drum 1, the intermediate transfer belt 51, and the primary transfer roller 53, the outer diameter of the cross-sectional circle in the cylindrical shape of the photoconductor drum 1 (hereinafter referred to as the following) The smaller the outer diameter), the smaller the optimum inter-nip distance L. Further, as the toner aggregation degree G (%) increases, the toughness or the like decreases due to the aggregation property between the toners, so that the allowable range itself of the inter-nip distance L increases.

  Further, as the value of the inter-nip distance L approaches 0, the effect of the configuration of the shape in the transfer nip formed by the photosensitive drum 1, the intermediate transfer belt 51, and the primary transfer roller 53 becomes difficult to be revealed. Therefore, it is not desirable for the value of the distance L between nips to be 0.3 mm or less. However, in this case, as the value of L approaches 0, the influence of the outer diameter of the photosensitive drum disappears. Therefore, the absolute value of the potential on the photosensitive drum 1 is preferably 200 V or less after development and before transfer, and 100 V or less after transfer.

The outer diameter D (mm) of the photosensitive drum 1 is
20 (mm) ≦ D (mm) ≦ 40 (mm)
The aggregation degree G (%) of the toner is
50 (%) ≦ G (%) ≦ 70 (%)
It is.

The transfer means includes at least an intermediate transfer belt 51 (also referred to as an intermediate transfer member) to which a toner image on the photosensitive drum 1 is transferred, and the intermediate transfer belt 51 in contact with the photosensitive member to transfer the toner image on the photosensitive drum 1. Primary transfer means for transferring to the intermediate transfer belt 51 is included. The primary transfer unit is disposed upstream or downstream of the photosensitive drum 1 along the traveling direction of the intermediate transfer belt 51. The distance L (mm) between the contact nip center between the intermediate transfer member and the photosensitive drum 1 and the contact nip center between the primary transfer unit and the intermediate transfer member along the traveling direction of the intermediate transfer belt 51 is as follows. Satisfy the formula.
0.3 ≦ L ≦ (0.1 × G−4.5) × D / 30
When the distance L (mm) satisfies this relationship, it is possible to obtain a high-quality image with high transfer efficiency and almost no occurrence of flickering and retransfer.

(Secondary transfer part)
In FIG. 1, an intermediate transfer unit 5 as a secondary transfer unit is disposed below each of the photosensitive drums 1a to 1d. The intermediate transfer unit 5 includes an intermediate transfer belt 51, primary transfer rollers 53a to 53d, an intermediate transfer belt driving roller 55, a secondary transfer inner roller 56 (secondary transfer counter roller), a secondary transfer outer roller 57, and a tension roller. 58 and an intermediate transfer belt cleaner 60.

  The toner images of the respective colors formed on the photosensitive drums 1a to 1d are sequentially transferred onto the intermediate transfer belt 51 as described above, and then conveyed to the secondary transfer portion as the belt rotates. On the other hand, by this time, the transfer material P taken out from the paper feed cassette 8 is supplied to the transport roller 82 via the pickup roller 81. In the secondary transfer portion, the above-described toner image is transferred onto the transfer material P by a secondary transfer bias applied between the secondary transfer inner roller 56 and the secondary transfer outer roller 57. The transfer residual toner on the intermediate transfer belt 51 is removed and collected by the intermediate transfer belt cleaner 60.

The primary transfer roller 53a is composed of a core metal having an outer diameter φ of 8 mm and a conductive urethane sponge layer having a thickness of 4 mm. The resistance value of the primary transfer roller 53a is about 10 ⁵ Ω (23 ° C./60
% RH). Further, the resistance value of the primary transfer roller 53a is determined by applying a voltage of 100V to the core metal while pressing the primary transfer roller 53a against a grounded opposing roller with a load of 500 g and rotating it at a peripheral speed of 50 mm / s. It is obtained from the relationship of the current measured by applying.

  The primary transfer rollers 53a to 53d are pressed against the respective photosensitive drums 1a to 1d with a pressing force P (N / m). Here, the pressing force P (N / m) is preferably 5 N / m or more and 20 N / m or less, that is, 5 to 20 N / m.

  When the pressing force P is less than 5 N / m, the pressing force of the intermediate transfer belt 51 to the photosensitive drum 1 becomes small, and the contact state between the intermediate transfer belt 51 and the photosensitive drum 1 is not stable, so that the transferability is lowered. To do. On the other hand, if the pressing force P is greater than 20 N / m, the toner image is highly pressed against the photosensitive member during transfer, the contact area between the toner and the photosensitive drum 1 is increased, and the transferability is lowered.

Further, the secondary transfer inner roller 56 includes a cored bar having an outer diameter of φ16 mm and a conductive urethane solid layer having a thickness of 7 mm. The resistance value of the secondary transfer inner roller 56 is measured by rotating the secondary transfer inner roller 56 at a peripheral speed of 50 mm / s with respect to the ground under a load of 500 g and applying a voltage of 100 V to the core metal. It is obtained from the relationship of the measured current. Here, the resistance value of the secondary transfer inner roller 56 was about 10 ⁵ Ω in an environment of a temperature of 23 ° C. and a humidity of 50%.

The secondary transfer outer roller 57 is composed of a core metal having an outer diameter of φ16 mm and a conductive EPDM sponge layer having a thickness of 7 mm. The resistance value of the secondary transfer outer roller 57 is measured by rotating the secondary transfer outer roller 57 at a peripheral speed of 50 mm / s with respect to the ground under a load of 500 g and applying a voltage of 2000 V to the core metal. It is obtained from the relationship of the measured current. Here, the resistance value of the secondary transfer outer roller 57 was about 10 ⁸ Ω in an environment of a temperature of 23 ° C. and a humidity of 50%.

The intermediate transfer belt 51 is made of a dielectric resin such as polycarbonate (PC), polyethylene terephthalate (PET), or polyvinylidene fluoride (PVDF). In the first embodiment, PI having a volume resistivity of 10 ⁹ Ω · cm and a thickness t = 90 μm.
(Polyimide) resin is used. As the intermediate transfer belt 51, polyimide resin, polyamideimide resin, polyetherimide resin, polyarylate resin, aromatic polyester resin, wholly aromatic polyamide resin, or the like can be used. Moreover, it is also possible to mix and use these. In order to use these resins as the intermediate transfer belt 51, it is necessary to add various conductive materials to the resin in order to obtain semiconductivity. Specifically, inorganic compounds such as carbon black, aluminum, nickel, tin oxide and potassium titanate, conductive polymers represented by polyaniline and polypyrrole, and the like are used. Particularly from the viewpoint of resistance control and resistance reduction, it is important to uniformly disperse various conductive materials. Therefore, when carbon black or the like is used, it is necessary to appropriately select a carbon black having good dispersibility and a dispersion method. Moreover, when using conductive polymer etc., it is desirable to melt | dissolve in the same thing as the solvent in which the resin raw material is melt | dissolved. The content of these various conductive materials can be appropriately selected according to the type of the conductive material, but is preferably about 5 to 50% by weight, more preferably 7 to 40% by weight with respect to the resin. When this content is less than 5% by weight, the uniformity of the electrical resistance is lowered, and the surface resistivity may be greatly lowered during durable use. On the other hand, if it exceeds 50% by weight, it becomes difficult to obtain a desired resistance value, and further, it becomes brittle as a molded product.

The intermediate transfer belt 51 thus manufactured has a surface resistance value Rs in the range of 10 ¹² Ω / cm ^{2 to} 10 ¹⁵ Ω / cm ² , that is, 10 ¹² Ω / cm ² ≦ Rs ≦ 10 ¹⁵ Ω / Desirably, it is cm ² . This is because when the surface resistance value Rs is lower than 10 ¹² Ω / cm ² , toner dust (spattering / flying) may occur and the image quality may become coarse, while on the other hand, when the surface resistance value Rs is higher than 10 ¹⁵ Ω / cm ^2. This is because the charge during transfer remains on the belt and image unevenness may occur.

In particular, in an image forming apparatus or the like, when a toner image is transferred from the photosensitive drum 1 serving as an image holding member to the intermediate transfer belt 51, the electric field formed by the intermediate transfer belt 51 acting as an insulator. Effectively acts on the toner. On the other hand, the static electricity possessed by the toner T transferred to the intermediate transfer belt 51 may greatly affect the transfer efficiency and the image. Therefore, if the intermediate transfer belt 51 can maintain a slight electrical conductivity, static electricity can be discharged to the ground via the intermediate transfer belt 51 before transfer to a recording paper or the like, and the influence of static electricity on the transfer is reduced. Is done. In this case, the surface resistance Rs is preferably 10 ¹² to 10 ¹⁵ Ω / cm ² .

The volume resistance value Rv of the intermediate transfer belt 51 is 10 ⁸ Ω · cm or more and 10 ¹³ Ω · cm or less, that is,
10 ⁸ Ω · cm ≦ Rv ≦ 10 ¹³ Ω · cm
It is desirable that This is because when Rv is lower than 10 ⁸ Ω · cm, transfer charges are diffused and the occurrence of tobits tends to occur. On the other hand, when Rv is higher than 10 ¹³ Ω · cm, charging of the intermediate transfer belt 51 in multiple transfer is performed. This is because the transfer bias becomes high due to the excessively high value, and the retransfer is deteriorated.

  Next, a method for measuring the volume resistivity and the surface resistance value of the intermediate transfer belt 51 according to the first embodiment of the present invention will be described.

(Measuring machine)
Resistance meter: Super high resistance meter R8340A (manufactured by Advantest)
Sample box: Document box TR42 for ultra-high resistance measurement (manufactured by Advantest)
The main electrode had a diameter of 25 mm, the guard ring electrode had an inner diameter of 41 mm, and an outer diameter of 49 mm.

(Measurement sample)
The intermediate transfer belt is cut into a circle having a diameter of 56 mm. After cutting, an electrode is provided on one surface with a Pt—Pd vapor deposition film on one surface, and a main electrode with a diameter of 25 mm and a guard electrode with an inner diameter of 38 mm and an outer diameter of 50 mm are provided on the other surface with a Pt—Pd vapor deposition film. The Pt—Pd vapor-deposited film can be obtained by performing a vapor deposition operation for 2 minutes using mild sputtering E1030 (manufactured by Hitachi, Ltd.). The sample after the vapor deposition operation is used as a measurement sample.

(Measurement condition)
Measurement atmosphere: temperature 23 ° C, humidity 55% RH
The measurement sample is left in advance in an environment of 23 ° C. and 55% RH for 12 hours or more.
Measurement mode: Discharge 10s, charge and measure 30s
Applied voltage: 100V
The surface resistivity measurement is based on JIS-K6911. After obtaining good contact between the electrode and the belt surface by using conductive rubber as an electrode, an ultra-high resistance resistance meter (R8340 manufactured by Advantest) is used. Measured.

(Image carrier)
FIG. 3 shows a cross section of an electrophotographic photosensitive member as an image carrier according to the first embodiment. The photoreceptor drum 1 used in the first embodiment preferably has an outer diameter of 20 mm or more and 40 mm or less. If the outer diameter of the photosensitive drum 1 is smaller than 20 mm, it is advantageous for miniaturization, but the charging roller member as a charging member around the photosensitive drum 1 also has a smaller diameter, and the charging nip between the two becomes smaller. Charging properties such as potential and charging uniformity are reduced. Further, when the outer diameter is smaller than 20 mm, the number of rotations of the photosensitive drum 1 in image formation increases, so that the load on the photosensitive member increases, and problems such as scraping and scratches may occur and the life may be shortened. is there. On the other hand, if the outer diameter of the photosensitive drum 1 is larger than 40 mm, the above-mentioned problem does not occur. However, it is difficult to reduce the size of the apparatus itself, and it is a slight factor that causes torsion and retransfer before and after the transfer nip. The void area is increased.

The photosensitive drum 1 is also required to have the following characteristics. In other words, the torsion or retransfer at the time of transfer occurs when a strong electric field is formed in the gap before and after the transfer nip when the transfer electric field is applied. In order to prevent this problem, it is preferable that the absolute value of the dark portion potential on the photosensitive drum 1 after development and before transfer is 200 V or less, and after transfer, 100 V or less.

  According to the knowledge of the present inventor, when the absolute value of the dark portion potential on the photosensitive drum 1 before the transfer is 200 V or more, the toner particles forming the toner image on the photosensitive member by the electric field of the gap before the transfer Individually fly to the intermediate through the gap. On the other hand, when the dark portion potential of the photoconductor after transfer is 100 V or more, the electric field downstream of the transfer nip acts strongly, and a part of the toner image once transferred onto the intermediate body is reversely transferred to the photoconductor. So-called retransfer occurs. In order to set such a potential, a thin film photoconductor having a large electrostatic capacity of the photoconductor or an amorphous silicon photoconductor having a high dielectric constant of the photoconductor constituting material itself is optimal.

  Further, in the present invention, it is preferable to perform reversal development in which the charging polarity of the photoconductor is opposite to the transfer charging polarity. This is because amorphous silicon photoconductors have low chargeability when subjected to reverse polarity charging, i.e., transfer charging, so that a large potential is not generated, and the occurrence of repetitive transfer and retransfer due to the generated potential is reduced. It is. The amorphous silicon photoreceptor will be described below. FIG. 3 shows the electrophotographic photosensitive member according to the first embodiment.

  As shown in FIG. 3A, the electrophotographic photosensitive member as the image carrier according to the first embodiment is formed on a conductive substrate 301 made of a conductive material such as aluminum (Al) or stainless steel. A conductive layer 302 and a surface protective layer 303 are sequentially stacked. The conductive substrate 301 is most commonly aluminum (Al), but is not necessarily limited thereto. That is, as the conductive substrate 301, a metal or an alloy thereof, for example, stainless steel can be used. Further, as examples of metals, specifically, chromium (Cr), molybdenum (Mo), gold (Au), indium (In), niobium (Nb), tellurium (Te), vanadium (V), titanium ( Ti), platinum (Pt), lead (Pd), iron (Fe), and the like.

  Further, as shown in FIG. 3B, functional layers such as a lower charge injection blocking layer 304, an upper charge injection blocking layer 305, a charge injection layer, and an antireflection layer can be provided as necessary. Specifically, a lower charge injection blocking layer 304, an upper charge injection blocking layer 305, and the like are provided, and positively charged and negatively charged by selectively injecting group I-III elements and group IV elements as impurities. The charge polarity such as can be controlled. The substrate shape may be a desired one according to the driving method of the electrophotographic photosensitive member. The base material is generally a conductive material such as Al or stainless steel described above, but it is also possible to use a conductive base material deposited on an insulating base such as plastic or ceramic.

  As the photoconductive layer 302, for example, an amorphous material (a-Si (H, X)) containing, for example, silicon atoms (Si atoms) and hydrogen atoms (H atoms) or halogen atoms is mainly used. The film thickness of the photoconductive layer 302 is preferably set to 15 to 50 μm, for example, in view of manufacturing costs. Further, in order to improve the characteristics, as shown in FIG. 3B, a plurality of layers of a lower photoconductive layer 306 and an upper photoconductive layer 307 can be formed.

  The surface protective layer 303 is generally a non-single crystal material (preferably containing a carbon (C) atom, and optionally a hydrogen atom or a halogen atom) based on a silicon atom (Si atom). A-SiC (H, X) which is an amorphous material) is used.

The surface protective layer 303 is a non-single crystal material (preferably an amorphous material) a-SiN containing Si atoms as a base, nitrogen atoms, and optionally containing hydrogen atoms or halogen atoms.
(H, X) may be used. Further, the surface protective layer 303 is made of non-single-crystal carbon (preferably amorphous carbon) aC (H, X) containing C atoms as a base and containing hydrogen atoms or halogen atoms as necessary. In addition, by continuously changing the interface between the photoconductive layer 302 and the surface protective layer 303 and providing an antireflection layer, it is possible to suppress the interface reflection of the portion. Although an a-Si photoconductor has been described as an example, it can be applied to a thinned organic photoconductor (OPC) or a photoconductor in which a protective layer is formed on the OPC.

(A-Si photosensitive film forming apparatus)
Next, the a-Si photoconductor film forming apparatus and the amorphous silicon photoconductor forming method configured as described above will be described. The a-Si photosensitive member is formed by a plasma chemical vapor deposition (plasma CVD) method using a high-frequency power of an RF band (13.56 MHz) or a VHF band (50 to 450 MHz) that has been widely used conventionally. FIG. 4 shows a plasma CVD apparatus. This plasma CVD apparatus is an apparatus system for forming an electrophotographic photoreceptor using amorphous silicon as a base material using high-frequency power in the VHF band.

  As shown in FIG. 4, the system of the plasma CVD apparatus includes a deposited film forming apparatus 400 provided with at least a cylindrical substrate 401, a reaction vessel 402, a gas pipe 417, and a cathode 414. The reaction vessel 402 is configured so that the inside thereof can be depressurized while containing the cylindrical substrate 401. The gas pipe 417 is for supplying a source gas into the reaction vessel 402. In addition, electric power for decomposing the source gas is introduced by the cathode 414. In addition, the plasma CVD apparatus is provided with a source gas supply system 404 that supplies source gas into the reaction vessel 402, an exhaust system 405 that exhausts the inside of the reaction vessel 402, and a power supply system 406 that supplies power to the cathode 414. Yes.

  FIG. 5 shows a top view of a deposited film forming apparatus 400 as an example of an a-Si photosensitive film forming apparatus. As shown in FIGS. 4 and 5, a cylindrical substrate 401 is installed on a substrate support 403 containing a heater in a reaction vessel 402. Subsequently, the gas in the reaction vessel 402 is exhausted through the exhaust port 419 by the exhaust pump 407. After evacuation is completed until the pressure in the reaction vessel 402 reaches a desired degree of vacuum, for example, an inert gas such as helium (He) gas or argon (Ar) gas is supplied into the reaction vessel 402 at a predetermined flow rate. The The inert gas is supplied by a mass flow controller (MFC) in the source gas supply system 404. By adjusting the exhaust speed of the exhaust pump 407 in this way, the inside of the reaction vessel 402 can be controlled to a desired pressure. After the internal pressure of the reaction vessel 402 is set to a desired pressure, the cylindrical substrate 401 is heated to a desired temperature by a heater built in the substrate support 403. The cylindrical substrate 401 is maintained at a desired temperature necessary for forming the deposited film even during the formation of the deposited film.

After the heating process is completed by the above procedure, a deposited film forming process is performed. In the deposited film process, first, the inert gas in the reaction vessel 402 is exhausted by the exhaust pump 407. Thereafter, the exhaust valve 408 is closed and the main exhaust valve 409 is opened. Then, the opening of the throttle valve 410 is fully opened, and the inside of the reaction vessel 402 is exhausted to a vacuum degree of, for example, 1 × 10 ⁻³ Pa by the main exhaust pump 412 via the oil diffusion pump 411. Subsequently, each source gas is supplied into the reaction vessel 402 by the source gas supply system 404. At this time, each source gas is supplied at a predetermined flow rate by a mass flow controller installed in each supply pipe. In this way, the internal pressure of the reaction vessel 402 is controlled to a desired pressure by adjusting the opening speed of the throttle valve 410 to adjust the exhaust speed.

When the internal pressure of the reaction vessel 402 is stabilized, power is supplied from the power source 413 to the cathode 414 via the matching box 415, and glow discharge is generated in the reaction vessel 402. By this discharge energy, the source gas introduced into the reaction vessel 402 is decomposed, and a predetermined deposited film is formed on the cylindrical substrate 401. In order to improve the uniformity of the deposited film in the circumferential direction of the substrate, it is effective to rotate the cylindrical substrate 401 at a predetermined speed by the motor 416 via the driving unit 418 during the formation of the deposited film. By this operation, unevenness in the circumferential direction of the amorphous silicon photoreceptor can be easily reduced within an allowable range. When the deposited film has grown to the desired thickness, the supply of power applied to the cathode 414 is stopped, and the supply of the source gas from the source gas supply system 404 is stopped, thereby completing the formation of the deposited film. . Then, it is possible to form a deposited film having a multilayer structure by repeating the same operation a plurality of times.

(toner)
Next, the toner used for the two-component developer in the first embodiment of the present invention will be described. Specifically, the toner includes toner particles containing at least a binder resin and a colorant, an external additive, and silica particles. Here, the silica particles have a number average particle diameter of 50 nm or more, and 0.5 parts by mass or more is added to 100 parts by mass of the toner particles. As the binder resin that can be used in the first embodiment, a known resin can be used as the binder resin for toner, and preferably a resin selected from the following (a) to (f): is there.
(A) Polyester resin (b) Hybrid resin having polyester unit and vinyl polymer unit (c) Mixture of hybrid resin and vinyl polymer (d) Mixture of polyester resin and vinyl polymer e) Mixture of hybrid resin and polyester resin (f) Mixture of polyester resin, hybrid resin and vinyl polymer

When a polyester resin is used as the binder resin, a polyhydric alcohol and a polyvalent carboxylic acid, a polyvalent carboxylic acid anhydride, a polyvalent carboxylic acid ester, or the like can be used as the polyester monomer. Among polyester resins, the following resins are preferable as color toners because they have good charging characteristics. That is, a bisphenol derivative represented by the following general formula (a) is used as a diol component, and a carboxylic acid component containing a divalent or higher carboxylic acid, an acid anhydride thereof, or a lower alkyl ester thereof as an acid component. Is a polyester resin obtained by condensation polymerization. Examples of the carboxylic acid component include fumaric acid, maleic acid, maleic anhydride, phthalic acid, terephthalic acid, trimellitic acid, and pyromellitic acid.

In the binder resin contained in the toner according to the first embodiment, the “hybrid resin” is a resin in which a vinyl polymer unit and a polyester unit are chemically bonded. Specifically, it is a resin formed by a transesterification reaction between a polyester unit and a vinyl polymer unit obtained by polymerizing a monomer having a carboxylic acid ester group such as (meth) acrylic acid ester. The hybrid resin is preferably a graft copolymer or block copolymer having a vinyl polymer as a trunk polymer and a polyester unit as a branch polymer. In addition, the “polyester unit” in the first embodiment indicates a portion derived from polyester, and the “vinyl polymer unit” indicates a portion derived from a vinyl polymer. As a polyester-type monomer which comprises a polyester unit, the polyhydric carboxylic acid component and polyhydric alcohol component which are used for a polyester resin are mentioned. Examples of the vinyl monomer constituting the vinyl polymer unit include a monomer having a vinyl group used in the vinyl polymer. And in 1st Embodiment of this invention, it is desirable to use the hybrid resin containing the monomer which reacts with the component of each unit in at least one of a vinyl-type polymer unit and a polyester unit.

  Furthermore, the following are mentioned as a coloring agent used in 1st Embodiment of this invention. That is, as the colorant for black toner, a color toner that has been toned to black using carbon black, yellow, magenta, and cyan toner colorants is used. In addition, as a colorant when used as a color toner, known dyes and pigments can be used. In addition, although it is possible to use a pigment alone as the colorant, it is preferable to use a dye and a pigment together in order to improve the sharpness from the viewpoint of the image quality of a full-color image. Specifically, the amount of the colorant used is preferably 0.1 to 15 parts by mass, more preferably 0.5 to 12 parts by mass, and most preferably 3 to 100 parts by mass of the binder resin. -10 parts by mass.

  In the first embodiment, a releasing agent can be added to the toner particles. Although a commercially available release agent can be used, the following materials can also be mentioned. That is, aliphatic hydrocarbon waxes such as low molecular weight polyethylene, low molecular weight polypropylene, low molecular weight alkylene copolymers, microcrystalline wax, paraffin wax, and Fischer-Tropsch wax can be used. Moreover, as a release agent, oxides of aliphatic hydrocarbon waxes such as oxidized polyethylene wax or block copolymers thereof can be used. Furthermore, waxes mainly composed of fatty acid esters such as ester waxes such as behenyl behenate and stearyl stearate, carnauba wax, and montanic acid ester wax can also be used. Moreover, what deoxidized one part or all part of fatty acid esters, such as deoxidized carnauba wax, can also be used. In the first embodiment, the charge amount is preferably adjusted by using a charge control agent for the toner. As the charge control agent, known ones can be used. In particular, a metal compound of an aromatic carboxylic acid that is colorless, has a high toner charging speed, and can stably maintain a constant charge amount is desirable.

  Next, a toner manufacturing method will be described. That is, first, a binder resin and a release agent, a colorant such as a pigment and a dye, and other additives as necessary are sufficiently mixed by a mixer such as a Henschel mixer or a ball mill. Next, the mixture is melted and mixed using a heat kneader such as a heating roll, a kneader, and an extruder, and the obtained kneaded product is cooled. Thereafter, the kneaded product is coarsely pulverized by a pulverizing means, and finely pulverized and classified by an appropriate pulverizing / classifying means. Thereby, toner particles are manufactured. Here, as the fine pulverizer, the above-described pulverizer can be used. In the case where an airflow type pulverizer such as a jet mill is used, it is difficult to obtain toner having a desired circularity. Therefore, when using an airflow type pulverizer, it is necessary to reduce the processing amount to lower the pulverization pressure and perform soft pulverization, or to perform a surface modification treatment step after pulverization. Therefore, from the viewpoint of improving the toner production efficiency, it is desirable to use a mechanical pulverizer as the pulverizing means. Examples of this mechanical pulverizer include Hosokawa Micron Co., Ltd. pulverizer inomizer, Kawasaki Heavy Industries, Ltd. pulverizer KTM, Turbo Industry Co., Ltd. turbo mill, and the like. Are preferably used.

It is also possible to perform spheronization after pulverization. That is, for example, a mechano-fusion system (manufactured by Hosokawa Micron) or a hybridization system (manufactured by Nara Machinery Co., Ltd.) can be used. These apparatuses employ a method in which the toner is pressed against the inside of the casing by a centrifugal force by a blade rotating at high speed, and a mechanical impact force is applied to the toner by a force such as a compressive force or a frictional force. Then, inorganic and organic fine particles are externally added to the colored particles obtained as described above.

  Next, silica particles as a kind of inorganic fine particles having a number average particle diameter of 50 nm or more employed in the first embodiment of the present invention will be described.

  As described above, the addition of silica particles having a number average particle diameter of 50 nm or more and the presence of this silica on the surface of the toner particles can improve the transferability and can be achieved by standing in a high humidity environment for a long time. It is possible to prevent a decrease in charging. The silica particles used in the first embodiment have a number average particle diameter of 50 nm or more, preferably 80 to 200 nm, more preferably 100 to 150 nm. According to the knowledge of the present inventor, when the number average particle diameter is smaller than 50 nm, not only the improvement in transferability is suppressed, but also there is a tendency that the charge is lowered due to long-term standing in a high humidity environment. . On the other hand, when the number average particle diameter exceeds 200 nm, the adhesion of the silica particles to the toner particles is deteriorated, which may easily cause a charging failure or contamination around the developing device. The addition amount is 0.5 parts by mass or more and 2.0 parts by mass or less, and preferably 0.7 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the toner particles. That is, according to the knowledge of the present inventor, when the addition amount is less than 0.5 parts by mass with respect to 100 parts by mass of the toner particles, the transfer effect and the effect of preventing the decrease in charge due to long-term standing in a high humidity environment are suppressed. Is done. On the other hand, when the addition amount exceeds 2.0 parts by mass with respect to 100 parts by mass of the toner particles, the silica particles cannot adhere to the toner particles, which may easily cause charging failure and contamination around the developing device.

  Further, as the toner employed in the first embodiment of the present invention, from the viewpoint of improving the image quality, a fluidity improver is externally added to the toner particles separately from the silica particles having a number average particle diameter of 50 nm or more. It is preferable that As the fluidity improver, silicate fine powder, titanium oxide fine powder, aluminum oxide fine powder and the like are desirable. Furthermore, it is more desirable that it is hydrophobized by a hydrophobizing agent which is a silane coupling agent, silicone oil or a mixture thereof. In general, the flowability improver is used in an amount of 0.5 to 5 parts by mass with respect to 100 parts by mass of the toner particles.

  Since the inorganic fine particles are attached to the outer periphery of the toner, they function as a spacer between the photoreceptor and the toner. As a result, the fluidity of the toner is ensured and the transferability is maintained by maintaining a minute gap between the photoreceptor and the toner. Based on this effect, the size required to be held on the surface of the toner by van der Waals force is important as a characteristic required for the inorganic fine particles. Thereby, the number average particle diameter is preferably 30 nm or more and 300 nm or less. When the number average particle diameter is less than 30 nm, the function as a spacer between the toner and the photoreceptor or between the toners becomes insufficient. On the other hand, when the number average particle diameter is larger than 300 nm, the influence of electrostatic force, etc. on the adhesion force to the toner increases, and the probability that the toner does not adhere to the toner stably and is released increases. However, the function as a spacer becomes unstable, which is inappropriate.

In addition, the inorganic fine particles are not necessarily present as primary particles on the surface of the colored particles, and may be present as aggregates. Even in this case, the content ratio as the number of aggregates having a particle diameter of 600 nm or more is desirably 1% or less (1 number% or less). Further, when an aggregate having a particle diameter of 600 nm or more is contained, the aggregate behaves as one particle even if the primary particle diameter is 200 nm or less, which is not preferable for the same reason as described above. In the first embodiment, the particle size of the perovskite inorganic fine particles was determined by measuring 100 particle sizes from a photograph taken at a magnification of 50,000 with an electron microscope. As shown in FIG. 7, the particle diameter was determined as (a + b) / 2, where a is the longest side of the primary particles and b is the shortest side. Further, the inorganic fine particles may be those which satisfy such a condition, but more preferably those having perovskite crystals. Furthermore, in this perovskite type abrasive particle,
More preferably, strontium titanate, barium titanate and calcium titanate are preferable, and strontium titanate fine powder is particularly desirable. By subjecting the perovskite inorganic fine particles to surface treatment, aggregation between toners, inorganic fine particles and toner, or inorganic fine particles and separation from the toner can be reduced.

  Further, the number of carbon atoms of the fatty acid or fatty acid metal salt for surface treatment of the perovskite type inorganic fine particles is preferably 8 or more and 35 or less, and more preferably 10 or more and 30 or less.

When the number of carbon atoms of the fatty acid or fatty acid metal salt exceeds 35, the adhesion between the surface of the perovskite-type inorganic fine particles and the fatty acid or fatty acid metal salt deteriorates, and peeling occurs or durability decreases due to long-term use. To do. Furthermore, peeled fatty acids and fatty acid metal salts are not preferable because they cause fogging. On the other hand, when the number of carbon atoms of the fatty acid or fatty acid metal salt is less than 8, the adhesion improvement of the fine particles having the specific surface area of 100 m ² / g or more and 350 m ² / g or less becomes insufficient, which is not preferable.

  Further, the treatment amount of the fatty acid or fatty acid metal salt is preferably 0.1% by mass or more and 15% by mass or less, and more preferably 0.5% by mass or more and 12% by mass or less with respect to the parent body. . According to the knowledge of the present inventors, the surface treatment of the perovskite-type abrasive particles is performed using a treatment agent such as a silicone oil, a silane coupling agent, or a titanium coupling agent used to improve the hydrophobicity of the external additive. When done, the above mentioned adhesion improvement was not seen. This is because fatty acids and fatty acid metal salts have excellent releasability and improve adhesion, whereas silicone oil, silane coupling agents or titanium coupling agents have excellent hydrophobic properties, but release properties. This is thought to be due to inferior moldability.

When the perovskite inorganic fine particles are externally added to the toner, the specific surface area of the perovskite inorganic fine particles subjected to the treatment according to the present invention is preferably 45 m ² / g or less. This is to prevent an influence on the development process in a high-humidity environment due to moisture absorption of the inorganic fine powder, for example, a decrease in toner charge amount. By making the specific surface area 45 m ² / g or less in this way, the absolute amount of water adsorbed on the surface of the inorganic fine particles can be reduced, so that the influence on the toner charge imparted by frictional charging can be reduced. Become. In addition, the specific surface area employ | adopted by this embodiment is measured using BET multipoint method using the autosorb 1 (made by Yuasa Ionics).

Further, in order to prevent adhesion of fine particles having a specific surface area of 100 m ² / g or more and 350 m ² / g or less to the surface of the perovskite type inorganic fine particles in a low humidity environment, the contact angle of the inorganic fine particles treated with this invention with water is The angle is preferably 110 ° or more and 180 ° or less.

Hereinafter, a method for measuring the contact angle of inorganic fine particles with water will be described. That is, first, perovskite-type inorganic fine particles are pressed by a tablet molding machine at a pressure of 300 KN / cm ² to obtain a sample having a diameter of 38 mm. During molding, NP-Transparency TYPE-D was sandwiched between the molding machine and the sample. The sample is left at 23 ° C. and 100 ° C. for 2 minutes, and then returned to room temperature. Thereafter, the contact angle is measured by a roll material contact angle meter CA-X roll type (manufactured by Kyowa Interface Chemical Co., Ltd.). The measurement is performed 20 times for one sample, and an average value of 18 measurement values excluding the maximum value and the minimum value is adopted.

  The perovskite inorganic fine particles employed in the first embodiment are obtained by adding strontium hydroxide to a titania sol dispersion obtained by adjusting the pH of a hydrous titanium oxide slurry obtained by hydrolyzing a titanyl sulfate aqueous solution. Then, it can be synthesized by heating to the reaction temperature. Here, the titania sol having good crystallinity and particle size can be obtained by setting the pH of the hydrous titanium oxide slurry to 0.5 to 1.0.

  In order to remove ions adsorbed on the titania sol particles, it is desirable to add an alkaline substance such as sodium hydroxide to the titania sol dispersion. At this time, in order to prevent sodium ions and the like from being adsorbed on the surface of the hydrous titanium oxide, it is desirable that the pH of the slurry should not be 7 or higher, that is, neutral to acidic. The reaction temperature is preferably about 60 ° C. to 100 ° C., and in order to obtain a desired particle size distribution, the temperature rising rate is preferably 30 ° C./hour or less, and the reaction time is 3 to 7 hours. desirable.

  The inorganic fine particles formed as described above are obtained as perovskite crystals having a substantially cubic or cuboid particle shape. As described above, when the particle shape is approximately cubic or rectangular parallelepiped, it is difficult to be embedded in the toner surface, and the function as a spacer can be maintained. Further, as the inorganic fine particles, it is desirable to add 0.5 to 2.0 parts by mass of the toner resin with respect to 100 parts by mass. When the amount of the inorganic fine particles added is less than 0.5 parts by mass, the effect as the spacer particles on the toner surface and the rubbing effect due to the particle size distribution and shape are reduced. On the other hand, when the amount of the inorganic fine particles added is more than 2.0 parts, the release from the toner increases and the development is adversely affected, or the degree of aggregation as the toner is excessively increased.

  In addition, the toner used in the image forming apparatus according to the first embodiment preferably has a weight average particle size in the range of 3.0 μm or more and 7.0 μm or less. This is because when the weight average particle size is less than 3.0 μm, toner aggregation becomes remarkable, the influence of non-electrostatic adhesion becomes too great, and there are problems in how to use such as transfer efficiency, density decrease, and fog increase. This is because it occurs. On the other hand, if the thickness exceeds 7.0 μm, reproduction of a fine dot latent image or fine line becomes insufficient, and it becomes difficult to achieve a high resolution / high definition development method.

(Measurement of toner particle size)
Next, measurement of the toner particle diameter will be described. In the first embodiment, the weight average particle diameter of the toner was measured using Coulter Multisizer II (manufactured by Coulter Inc.). That is, first, an interface for outputting the number distribution and volume distribution and a personal computer are connected to the Coulter Multisizer II, and a 1% NaCl aqueous solution is prepared using first grade sodium chloride as the electrolyte. Here, ISOTON R-II (manufactured by Coulter Scientific Japan) or the like can be used. As a measuring method, 0.1 to 5 ml of a surfactant as a dispersant, preferably alkylbenzene sulfonate, is added to 100 to 150 ml of an electrolytic aqueous solution, and then 2 to 20 mg of a measurement sample is added. The electrolyte in which the sample is suspended is dispersed for about 1 to 3 minutes with an ultrasonic disperser, and the volume and number of toners of 2 μm or more are measured using a 100 μm aperture as an aperture with a Coulter Multisizer. Measure distribution and number distribution. Then, a weight-based weight average particle diameter obtained from the volume distribution according to the present invention, with the representative value of each channel as the representative value for each channel, is obtained.

(Measurement of average circularity of toner)
Next, the average circularity of the toner is measured. The average circularity of the toner is measured using a flow type particle image measuring device “FPIA-2100 type” (manufactured by Sysmex Corporation), and is calculated using the following equation.

  The “particle projected area” is an area of a binarized toner particle image. The “peripheral length of the projected particle image” is defined by the length of the contour line obtained by connecting the edge points of the toner particle image. The measurement uses the perimeter of the particle image when image processing is performed at an image processing resolution of 512 × 512 (pixels of 0.3 μm × 0.3 μm). Further, in the first embodiment, the circularity is an index indicating the degree of unevenness of the toner particles, and is 1.000 when the toner particles are completely spherical, and becomes a smaller value as the surface shape becomes more complicated. .

Further, the average circularity Cave. Which means the average value of the circularity frequency distribution is calculated from the following equation, where ci is the circularity (center value) at the division point i of the particle size distribution and m is the number of measured particles. .

  In the first embodiment, for example, a flow type particle image analyzer “FPIA-2100” is used as a measuring device. This measuring apparatus first calculates the circularity of each particle, then calculates the average circularity and the circularity standard deviation. Divide into 01 equally divided classes. Then, the average circularity and the circularity standard deviation are calculated using the center value of the division points and the number of measured particles.

  As a specific measuring method, first, for example, about 10 ml of ion exchange water from which impure solids and the like are removed in advance is prepared in a container, and a surfactant, preferably an alkylbenzenesulfone, is used as a dispersant in the ion exchange water. Add the acid salt. Thereafter, 0.02 g of a measurement sample is further added and dispersed uniformly. As a means for dispersing, an ultrasonic disperser “Tetora150 type” (manufactured by Nikka Ki Bios) is used, and a dispersion treatment is performed for 2 minutes to obtain a dispersion for measurement. At this time, a cooling process is appropriately performed so that the temperature of the dispersion does not exceed 40 ° C. Further, in order to suppress the variation in circularity, the installation environment is controlled to 23 ± 0.5 ° C. so that the in-machine temperature of the flow type particle image analyzer is 26 to 27 ° C. Automatically adjusts the focus using latex particles having a particle size of 2 μm every 2 hours.

  The flow type particle image measuring device described above is used for measuring the circularity of the toner particles. Then, the dispersion concentration is readjusted so that the toner particle concentration at the time of measurement is 3000 to 10,000 particles / μl, and 1000 or more toner particles are measured. After the measurement, the average circularity of the toner particles is obtained using this data by excluding data with an equivalent circle diameter of less than 2 μm. The average circularity of the toner used in the first embodiment is desirably 0.940 or more and 0.975 or less. If the average circularity is less than 0.940, the unevenness of the toner shape increases, and inorganic fine particles that should act as spacer particles enter the recesses of the toner, reducing its effect, and transfer efficiency is likely to decrease. Become. On the other hand, when the average circularity is larger than 0.975, the shape of the toner itself becomes close to a circle (sphere), and the inorganic fine particles are easily released from the toner. The toner preferably has a degree of aggregation of 50% to 70%. That is, when the degree of aggregation is lower than 50%, the binding force between the toners is reduced and the toner tends to scatter. On the other hand, if the degree of aggregation exceeds 70%, the adhesive force with the photoconductor increases excessively and affects transferability, and a part of the toner image is not transferred and remains on the photoconductor, resulting in voids. The developability will decrease.

(Measurement method of toner cohesion)
Further, a powder tester PT-D manufactured by Hosokawa Micron, which will be described later, is used for measuring the toner aggregation degree. First, a 100 mesh sieve, a 200 mesh sieve, and a 400 mesh sieve are set on the powder tester vibrating table of this apparatus. Thereafter, 5.0 g of toner is gently put on a 100 mesh sieve and is vibrated for 15 seconds at an amplitude of 0.5 mm and a frequency of 50 Hz. Note that the measurement is performed in an environment of a temperature of 23 ° C. and a humidity of 60% RH, and toner that is sufficiently aged in this environment is used for the measurement.

Then, the weight of toner on each sieve is measured, and the degree of toner aggregation is calculated based on the following equation.
Aggregation degree 1 = (toner weight on 60 mesh sieve / 2.0) × 100
Aggregation degree 2 = (toner weight on 100 mesh sieve / 2.0) × (3/5) × 100
Aggregation degree 3 = (weight of toner on 200 mesh sieve / 2.0) × (1/5) × 100
Aggregation degree G (%) = aggregation degree 1 + aggregation degree 2 + aggregation degree 3

(Career)
Next, the magnetic carrier used in the first embodiment will be described. The magnetic carrier used here is a coated magnetic carrier in which a carrier core is coated with a coating material. As the carrier core, for example, metal particles such as surface oxidized or unoxidized iron, nickel, copper, zinc, cobalt, manganese, chromium, rare earth, alloy particles thereof, oxide particles, and ferrite can be used. Further, as the core of the coated magnetic carrier, a magnetic material dispersion type carrier in which magnetic fine particles are dispersed in a binder resin is also preferable. With respect to the magnetic fine particles constituting the core of such a coated magnetic carrier, the same material as that of the core of the coated magnetic carrier described above can be used, and the number average particle diameter is 0.05 to 1.0 μm. Things are desirable.

  Examples of the resin used for the binder resin constituting the core of the magnetic material dispersion type carrier include all vinyl resins obtained by polymerizing vinyl monomers. In addition to the vinyl resin obtained by polymerization from a vinyl monomer, the following resins may be mentioned as the binder resin constituting the core. That is, non-vinyl condensation resins such as polyester resin, epoxy resin, phenol resin, urea resin, polyurethane resin, polyimide resin, cellulose resin, polyether resin, or a mixture of these non-vinyl condensation resin and vinyl resin. is there.

  In the magnetic carrier according to the first embodiment, as the coating resin for the coating material for coating the core of the coated magnetic carrier, a general insulating resin used for carrier coating can be used. Examples of the styrene resin, acrylic resin, and monoolefin monomer include resins polymerized from ethylene, propylene, butylene, isobutylene, and the like.

  Examples of vinyl monomers include vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; vinyl ethyl ether and vinyl methyl ether. Examples of vinyl monomers include resins polymerized from vinyl ethers, vinyl ketones, unsaturated fatty acid dicarboxylic acids, and the like. Here, examples of vinyl ethers include vinyl butyl ether. Examples of vinyl ketones include vinyl methyl ketone, vinyl hexyl ketone, and vinyl butyl ketone. Examples of unsaturated aliphatic dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, and dihydromuconic acid.

As other resins used for the coating material, polyester resins, polyurethane resins, polyamide resins, silicone resins, epoxy resins, fluororesins, phenol resins, melamine resins, and the like can be used. As these resins, monomers obtained by polymerizing monomers alone or in combination of two or more, or a combination of a plurality of resins can be used. Moreover, various crosslinking agents can also be added and used as needed.

（ｍは０〜１０の整数、好適には、ｍ＝４〜９）
なお、この発明における磁性キャリアの物性については特に限定されないが、磁性キャリアは被覆磁性キャリアのコート材のコート量を少なめにしつつ、磁性キャリア全体の抵抗率を少し高めに設計するのが好ましい。 The resin used for the coating material is preferably a fluorine-containing acrylic resin. Specifically, for example, a coated magnetic carrier coated with a polymer or copolymer of (meth) acrylic acid ester having a perfluoroalkyl unit shown below is particularly desirable.

(M is an integer of 0-10, preferably m = 4-9)
The physical properties of the magnetic carrier in the present invention are not particularly limited, but it is preferable that the magnetic carrier is designed to have a slightly higher resistivity of the entire magnetic carrier while reducing the coating amount of the coating material of the coated magnetic carrier.

(Charging means)
Next, the charging roller 2 (charging rollers 2a to 2d) as charging means according to the first embodiment will be described. The charging unit is not necessarily limited to the charging roller. However, according to the method of contact charging means such as a charging roller, the electrical load and the mechanical load on the photosensitive member are large as compared with the non-contact charging method such as corona charging. As a result, the surface of the photoreceptor is rapidly deteriorated and the transferability becomes severe, so that the effects of the present invention are likely to appear remarkably.

The charging roller 2 as a flexible contact charging member which is a charging means in the first embodiment is formed by providing a middle resistance layer of rubber or foam on a cored bar. This medium resistance layer is formulated with a resin such as urethane, for example, conductive particles such as carbon black, a sulfurizing agent or a foaming agent, and is formed into a roller shape on a core metal, and then the surface is polished. . Here, it is important that the charging roller 2 as a contact charging member functions as an electrode. That is, it is necessary to have a sufficiently low resistance in order to ensure sufficient contact with the charged body by providing elasticity and to charge the moving charged body. On the other hand, it is necessary to prevent voltage leakage when there is a low breakdown voltage defect portion such as a pinhole in the member to be charged. When an electrophotographic photosensitive member is used as the member to be charged, it is desirable to use a resistor having a resistance value of about 10 ⁴ to 10 ⁷ Ω in order to obtain sufficient charging property and leakage resistance. In the embodiment, a resistor having a resistance value of, for example, 10 ⁶ Ω is used.

  Further, regarding the hardness of the charging roller 2, if the hardness is too low, the shape is not stable, and the contact property with the member to be charged is deteriorated. On the other hand, if the hardness of the charging roller 2 is too high, it becomes difficult to secure a charging nip portion between the charging roller 2 and the micro contact property with respect to the surface of the charging member. Therefore, the hardness of the charging roller 2 is preferably 25 degrees or more and 60 degrees or less in Asker C hardness. In addition, Asker C hardness shows the value measured with the durometer (spring type hardness meter) prescribed | regulated to SRIS0101 (Japan Rubber Association standard).

The material of the charging roller 2 is not limited to an elastic foam. Specifically, examples of the material of the charging roller 2 include ethylene propylene diene copolymer synthetic rubber (EPDM), urethane, nitrile rubber (NBR), and silicone rubber. Further, a rubber material in which a conductive material such as carbon black or metal oxide is dispersed for adjusting resistance in IR or the like can be given. Furthermore, examples of the material for the elastic body include those obtained by foaming the above-described substances. Note that the resistance can be adjusted using an ion conductive material without dispersing the conductive substance. Further, the charging roller 2 is disposed in pressure contact with the photosensitive drum 1 as a member to be charged with a pressing force of 19.6 N (2 kgf) against elasticity. In this embodiment, a charging portion having a width of several mm is formed.

Here, the resistance value of the charging roller 2 is measured as follows. That is, first, the photosensitive drum 1 of the printer is replaced with an aluminum drum. Thereafter, a voltage of 100 V is applied between the aluminum drum and the core of the charging roller 2. The current value flowing at this time is measured. Thereby, the resistance value of the charging roller 2 is obtained. The resistance value of the charging roller 2 according to the first embodiment obtained as described above was 5 × 10 ⁶ Ω. This resistance was measured in an environment at a temperature of 25 ° C. and a humidity of 60%.

  Further, the charging roller 2 described above is driven to rotate as the photosensitive drum 1 rotates. The charging roller 2 is controlled by a constant current (frequency Vpp is about 1.4 kVpp) with a frequency of 2 kHz and a total current of 1800 μA from a charging high-voltage power source, and the photosensitive member potential is determined by a superimposed DC bias.

(Information writing means)
The image forming apparatus includes exposure devices 3a to 3d (hereinafter, exposure device 3) as electrostatic latent image forming means for forming electrostatic latent images on the surfaces of the charged photosensitive drums 1a to 1d. In the first embodiment, the exposure apparatus 3 is a laser beam scanner using a semiconductor laser, for example. The exposure device 3 outputs a laser beam modulated in accordance with an image signal sent from a host processing device such as an image reading device (not shown) to the printer. By the output of the laser light, the surface of the rotating photosensitive drum 1 that is uniformly charged is subjected to laser scanning exposure (image exposure) at an exposure position (exposure portion). As a result of laser scanning exposure, the potential of the portion irradiated with the laser light on the surface of the photosensitive drum 1 is lowered, and a bright portion potential VL is formed on the surface of the rotating photosensitive drum 1, corresponding to the image information. An electrostatic latent image is sequentially formed. In the first embodiment, the laser exposure apparatus is adopted as the information writing means, but other methods using light emitting diodes (LEDs) can be adopted.

(Development means)
The developing device 4 is provided to face the electrostatic latent image corresponding to the image on each photosensitive drum 1. The electrostatic latent image is rubbed with a magnetic brush to form respective color toner images on the photosensitive drum 1.

  The developing device used for this development has four developing devices: a yellow developing device, a magenta developing device, a cyan developing device, and a black developing device. The inside of each developing device includes, for example, a developer carrying member, a developing tank that contains a two-component developer, a replenishing agent container that contains a replenishing agent, and a replenisher from the replenishing agent container to the developing tank. At least replenisher supply means for supplying. FIG. 6 shows a schematic configuration of the developing devices 4a to 4d in FIG. In FIG. 6, the flow of conveyance until the two-component developer in the developing device 4 is developed will be described by taking the yellow developing device 4a as an example.

Inside the developing sleeve 4a6 as the developer carrying member, a fixed magnet roll 4a8 is provided, and a predetermined magnet gap is provided between the photosensitive drum 1a (not shown in FIG. 6) as the image carrying member. Driven and rotated while maintaining the development interval. The regulating member 4a7 has magnetism, and is pressed against the developing sleeve 4a6 with a predetermined load with no developer interposed therebetween, or is arranged with a predetermined interval between the developing sleeve 4a6 and the like. Various forms are adopted. The pair of developer agitating / conveying members 4a3 and 4a4 has a screw structure, conveys and circulates the two-component developer in opposite directions, and sufficiently agitates and mixes the toner and the magnetic carrier to form a two-component developer. It acts to deliver to the sleeve 4a6.

  Moreover, the magnet roll 4a8 may be composed of, for example, four magnets having the same magnetic force in which N poles and S poles are alternately arranged at equal intervals. Further, as the magnet roll 4a8, a repulsive magnetic field is formed in a portion in contact with a scraper (not shown), and in order to facilitate the peeling of the two-component developer, one pole is lost and the five poles are used. What was included in the state fixed inside may be used.

  The two developer agitating / conveying members 4a3 and 4a4 described above are members that also serve as agitating members that rotate in directions opposite to each other. The developer agitating / conveying members 4a3 and 4a4 are members for conveying the replenisher replenished from the replenisher container 4a9 to the developing sleeve 4a6 in the developing tank 4a5 by the thrust of the agitating screw. The developer agitating / conveying members 4a3 and 4a4 are homogeneous two-component developers that are triboelectrically charged by the mixing action of the toner and the magnetic carrier, and the two-component developers are placed on the peripheral surface of the developing sleeve 4a6. It is a member attached in a layered manner. The two-component developer on the surface of the developing sleeve 4a6 forms a uniform layer by the dual-structure regulating member 4a7 containing a nonmagnetic material and a magnetic material provided to face the magnetic pole of the magnet roll 4a8. The uniformly formed developer layer develops an electrostatic latent image on the peripheral surface of the photosensitive drum 1 as an image carrier in the development region, thereby forming a toner image.

As the charge amount of the toner according to this embodiment, the charge amount on the photoreceptor before transfer is important. The charge amount is 20 × 10 ⁻³ C / kg or more and 50 × 10 ⁻³ C / kg or less, that is, if the charge amount is Q (× 10 ⁻³ C / kg), 20 ≦ Q ≦ 50 Is desirable. When the charge amount Q (× 10 ⁻³ C / kg) is lower than 20, the reproducibility of the electrostatic latent image on the photosensitive member starts to deteriorate, and it is reversely charged by the transfer bias and is easily retransferred. At the time of fixing after being transferred to the toner image, the toner image is easily broken. On the other hand, when the charge amount Q (× 10 ⁻³ C / kg) is larger than 50, the electrostatic attraction force with the latent image on the photosensitive member is too strong and the transferability is lowered.

  Generally, the charge amount of the toner can be adjusted depending on the material by using an appropriate charge control agent for the toner material, and the material of the developer carrier or the contact of the developer regulating member with the developer carrier. By adjusting the pressure and the like, the ability to impart triboelectric charge to the developer can be controlled.

(Measurement method of toner charge amount on photoconductor)
A method for measuring the charge amount of the toner on the photoreceptor will be described. The triboelectric charge amount on the electrostatic latent image carrier is determined using a suction type Faraday cage method. FIG. 8 shows a suction type Faraday gauge.

  The developer recovery device used in this suction type Faraday cage method has a suction device section for sucking air, and a Faraday gauge connected to the suction device section as a recovery device section for recovering the developer. . As shown in FIG. 8, the collecting device section includes an outer cylinder 502 having a suction port for sucking the developer on the photosensitive drum 1 and an inner cylinder having a cylindrical filter paper 504 for collecting the sucked developer. 501.

Alternatively, the day gauge has a coaxial double cylinder structure. Further, the inner cylinder 501 and the outer cylinder 502 are insulated from each other while being fixed by an insulating member 503. If a charged body having a charge amount Q is put in the inner cylinder 501, it becomes equivalent to the presence of a metal cylinder having an amount of electricity Q by electrostatic induction. This induced charge is expressed as “KEITHLEY 616 DIGITAL ELECTROMETER
To measure. The charge amount is obtained by dividing the charge amount Q by the toner weight M in the inner cylinder 501.

In order to perform the suction recovery of the developer on the electrostatic latent image carrier using this developer recovery apparatus, the following method can be specifically adopted.

  First, a latent toner image having a VL potential is developed on the photosensitive drum 1 from the developer holder. Until the toner image is transferred onto the transfer paper, the developer recovery device is in a stopped state. After the toner image is transferred onto the transfer paper, the developer on the photosensitive drum 1 is moved in the longitudinal direction from one end to the other end of the developing sleeve while pressing the suction port against the surface of the developing sleeve using the developer collecting device described above. And the sucked developer is collected by the cylindrical filter paper 504. Then, the mass of the cylindrical filter paper 504 from which the developer has been collected is measured, and the value obtained by subtracting the mass of the cylindrical filter paper 504 before the collection from the mass of the collected cylindrical filter paper 504 is taken as the mass of the collected developer. At this time, the charge amount of the developer collected on the cylindrical filter paper 504 of the inner cylinder 501 electrostatically shielded from the outside is measured, and the charge amount is obtained from these charge amount and mass.

(Cleaner means)
As shown in FIG. 1, each image forming unit of the image forming apparatus includes a cleaning device 6 (cleaning devices 6 a, 6 b, 6 c) as a cleaner unit downstream of the primary transfer roller 53 in the rotation direction of the photosensitive drum 1. , 6d). The cleaning device 6 is provided with a cleaning blade (not shown). For example, a contact pressure of 0.15 N / cm in a counter direction with respect to the rotation direction of the surface of the photosensitive drum 1 and a contact angle of 25 °. To remove residual toner on the photosensitive drum 1. Here, the cleaning blade is an elastic body mainly composed of urethane. Further, when the cleaning blade is used as described above, the transfer residual toner, particularly the inorganic fine particle strontium titanate contained in the blade edge portion is blocked and strong rubbing occurs. In this case, when an amorphous silicon photoconductor or a high-hardness thin film photoconductor for extending the life is used, an image flow that is likely to occur under high temperature and high humidity can be prevented by this rubbing effect.

  Examples based on the embodiments of the present invention will be specifically described below. The present invention is not limited to the following examples. First, examples of the photoreceptor, developer, and inorganic fine particles of the present invention will be shown. In addition, the part in a following example represents a mass part.

(Example of photoconductor production)
An a-Si type photosensitive material comprising a charge injection blocking layer, a photoconductive layer, and a surface layer on a mirror-finished aluminum cylinder using an apparatus for manufacturing an electrophotographic photosensitive member by a high frequency plasma CVD method using a VHF band. The body was made.

(Toner Production Example 1)
(First kneading step)
C. I. Pigment Blue 15: 3: 3 parts by mass Polyester resin: 40 parts by mass First, these raw materials were charged into a kneader-type mixer and heated without pressure while being mixed. The material itself was melted and kneaded for 30 minutes at a temperature of 100 ° C., then cooled and pulverized simply to obtain a pulverized kneaded product.

(Second kneading step)
Kneaded pulverized product in the first step: 43 parts by mass Polyester resin: 40 parts by mass Copolymer: 20 parts by mass Wax A (normal paraffin, DSC peak temperature: 76 ° C., Mn: 580):
4 parts by weight Aluminum compound of di-tert-butylsalicylic acid (charge control agent):
2 parts by mass Premixed with a Henschel mixer according to these prescriptions, melt-kneaded at a material temperature of 130 ° C. with a twin screw extrusion kneader, coarsely crushed to about 1 to 2 mm using a hammer mill after cooling, and air The particle size is set to 15 μm or less by a jet type fine pulverizer. Further, the obtained finely pulverized product was classified by a multi-division classifier to obtain toner particles having a weight average particle size of 6.0 μm.

(Production example of inorganic fine particles)
First, hydrous titanium oxide obtained by hydrolyzing a titanyl sulfate aqueous solution is washed with pure water until the electric conductivity of the filtrate reaches 2200 μS / cm. NaOH is added to this hydrous titanium oxide slurry, and the sulfate radical (anion) adsorbed is washed as SO ₃ until it becomes 0.24% by mass.

Next, hydrochloric acid is added to the hydrous titanium oxide slurry to adjust the pH of the slurry to 1.0 to obtain a titania sol dispersion. NaOH is added to this titania sol dispersion, the pH of the dispersion is 6.0, and washing is performed by decantation using pure water until the electrical conductivity of the supernatant becomes 120 μS / cm. And when the obtained hydrous titanium oxide was analyzed by X-ray diffraction, only the peak of anatase TiO ₂ was shown.

533 g (0.6 mol) of metatitanic acid having a water content of 91% obtained as described above was added to SU.
Place in S reaction vessel. Nitrogen gas was blown in and left for 20 minutes to replace the inside of the reaction vessel with nitrogen gas. Further, 183.6 g (0.66 mol) of Sr (OH) ₂ .8H ₂ O (purity 95.5%) was added, and distilled water was further added to obtain 0.3 mol / l (in terms of SrTiO ₃ ), SrO / TiO. A slurry with a ₂ molar ratio of 1.10 was prepared.

  In a nitrogen atmosphere, this slurry was heated to 90 ° C. at 18 ° C./hour and reacted at the boiling point for 3 hours. After the reaction, after cooling to 40 ° C., the supernatant is removed under a nitrogen atmosphere, and the operation of adding 2.5 (l) pure water and decanting is repeated twice, washed, and then filtered with Nutsche. went. The obtained cake was dried in the atmosphere at 110 ° C. for 4 hours.

  The strontium titanate having a cubic or rectangular parallelepiped shape obtained as described above is an inorganic fine particle.

To 100 parts by mass of the toner particles described above, the following materials were externally added using a Henschel mixer to obtain toner 1 in Table 1.
Untreated silica particles (number average particle size: 120 nm): 1.0 part by mass Hydrophobic titanium oxide treated with n-C ₄ H ₉ Si (OCH ₃ ) ₃ (BET specific surface area: 110 m ² / g): 1 Part by weight Rectangular solid strontium titanate as inorganic fine particles: 1.0 part by weight The toner 1 has a circularity of 0.960 and an aggregation degree G (%) of 59%. Similarly, as shown in Table 1, toners 2 to 9 were prepared by changing the circularity of the toner and the external addition amount of strontium titanate. The aggregation degree G (%) of the toner at that time is as shown in Table 1.

(Evaluation methods)
Evaluation of transfer efficiency, flickering, and retransfer is performed by modifying the photoreceptor CRG of the iRC3200 (Canon copier) and the periphery of the transfer at a temperature of 24 ° C. and a humidity of 50% RH. In addition, an amorphous silicon drum is used as the photosensitive drum 1, and the toner of Table 1 is used as the toner, and evaluation is performed by outputting an image under an NL environment (23 ° C./5% RH).

  As evaluation criteria, in the transfer efficiency, 95% or more is OK, and less than 95% is NG. In addition, with regard to flickering and retransfer, OK and NG are judged at a visually acceptable level. These three items of transfer efficiency, fly-over, and re-transfer were all expressed as rank A, and at least one item as NG as rank B.

(Experiment 1)
In the following experiment, the outer diameter of the photosensitive drum is 30 mm, the weight average particle diameter is 6.0 μm, the pre-transfer potential is 180 V, and the post-transfer potential is 80 V. Table 2 shows the results of image evaluation performed by changing the distance L (mm) between the center of the contact nip between the intermediate transfer member and the photosensitive drum and the center of the contact nip between the primary transfer unit and the intermediate transfer member. Show.

  In Table 2, the sign of the displacement amount L is positive when the intermediate transfer member is displaced upstream in the traveling direction and negative when it is displaced downstream. From Table 2, the A rank is evaluated when the toner aggregation degree G of the toners 1 to 4 is in the range of 59 to 68% and the distance L between the contact nips is in the range of 0.4 to 2.0 mm. It turns out that it is. In addition, even within this range, it can be seen that the range of the distance L increases as the degree of aggregation G (%) increases.

(Experiment 2)
In Experiment 2, the outer diameter of the photosensitive drum is 20 mm, the weight average particle diameter is 4.5 μm, the pre-transfer potential is 150V, and the post-transfer potential is 100V. Image evaluation is performed by changing the distance L (mm) between the center of the contact nip between the intermediate transfer member and the photosensitive drum and the center of the contact nip between the primary transfer unit and the intermediate transfer belt along the traveling direction of the intermediate transfer member. The results are shown in Table 3.

  From Table 3, the A rank evaluation is that the toner aggregation degree G of toners 1 to 4 is in the range of 59 to 68%, the contact nip center between the intermediate transfer member and the photosensitive drum, the primary transfer means and the intermediate transfer. It can be seen that the distance L from the center of the contact nip with the body is in the range of 0.9 to 1.5 mm. Further, even within this range, it can be seen that the allowable range of the distance L is increased as the degree of aggregation G (%) is further increased. In Experiment 2 (the outer diameter of the photosensitive drum is 20 mm), the range of the distance L is narrower than Experiment 1 (the outer diameter of the photosensitive drum is 30 mm).

(Experiment 3)
In Experiment 3, the outer diameter of the photosensitive drum is 40 mm, the weight average particle diameter is 6.8 μm, the pre-transfer potential is 180 V, and the post-transfer potential is 110 V. Image evaluation was performed by changing the distance L (mm) between the center of the contact nip between the intermediate transfer member and the photosensitive drum and the center of the contact nip between the primary transfer unit and the intermediate transfer belt along the traveling direction of the intermediate transfer member. The results are shown in Table 4.

  From Table 4, the A rank is evaluated when the toner aggregation degree G of the toners 1 to 4 is in the range of 59 to 68% and the above-described contact nip center distance L is in the range of 0.5 to 3.0 mm. It can be seen that this is the case. Even within such a range, the range of the distance L increases as the degree of aggregation G (%) increases. That is, in Experiment 3 (the outer diameter of the photosensitive drum is 40 mm), the range of the distance L is wider than Experiment 1 (the outer diameter of the photosensitive drum is 30 mm).

  The results of the above experiments 1 to 3 are evaluated for each outer diameter D (mm) of the photosensitive drum as a graph of the toner aggregation degree G (%) and the distance L (mm) between the two contact nip centers described above. FIG. 9 shows an extracted portion of rank A.

From the graph shown in FIG. 9, the range in which the outer diameter D of the photosensitive drum is 20 mm and rank A is within the range of the brick-like pattern (vertical and horizontal line pattern) in FIG.
L = 0.3, G = 50, G = 70, L = (0.1 × G−4.5) × 20/30
It is within the range surrounded by the straight line. The range where the outer diameter D of the photosensitive drum is 30 mm and rank A is as follows:
L = 0.3, G = 50, G = 70, L = (0.1 × G−4.5) × 30/30
It is within the range surrounded by the straight line. Similarly, the range in which the outer diameter D of the photosensitive drum is 40 mm and the evaluation is rank A is as follows:
L = 0.3, G = 50, G = 70, L = (0.1 × G−4.5) × 40/30
It is the range surrounded by.

  That is, from the graph shown in FIG. 9, in the region where the evaluation is rank A, the toner aggregation degree G is in the range of 50 to 70%, the nip distance L is 0.3 mm or more, and the outer diameter D ( It can be seen that the region is surrounded by a straight line with mm) as a parameter.

In other words, from the above experimental results, the transfer efficiency is 95% or more, and the fly and re-transfer are visually acceptable levels.
50 ≦ G ≦ 70, 0.3 ≦ L ≦ (0.1 × G−4.5) × D / 30
It can be seen that

  As mentioned above, although embodiment of this invention was described concretely, this invention is not limited to the above-mentioned embodiment, The various deformation | transformation based on the technical idea of this invention is possible. For example, the numerical values given in the above embodiment are merely examples, and different numerical values may be used as necessary.

1 is a cross-sectional view schematically showing an image forming apparatus according to an embodiment of the present invention. It is a basic diagram which shows the principal part of the transfer means by embodiment of this invention. 1 is a cross-sectional view showing an electrophotographic photosensitive member according to an embodiment of the present invention. 1 is a longitudinal sectional view showing an amorphous silicon photosensitive film forming apparatus according to an embodiment of the present invention. It is a cross-sectional view showing an amorphous silicon photoconductor film forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view schematically showing a developing device according to an embodiment of the present invention. It is the schematic of the long side and short side in the particle size measurement of inorganic fine powder. FIG. 2 is a schematic diagram for explaining a toner charge amount measuring device on a photosensitive drum according to an embodiment of the present invention. It is the graph which integrated the result of Experiment 1 thru | or 3 by embodiment of this invention.

Explanation of symbols

1, 1a, 1b, 1c, 1d Photosensitive drum 2, 2a, 2b, 2c, 2d Charge roller 3, 3a, 3b, 3c, 3d Exposure device 4, 4a, 4b, 4c, 4d Developer 4a3, 4a4 Developer Agitating and conveying member 4a5 Developing tank 4a6 Developing sleeve 4a7 Restricting member 4a8 Magnet roll 4a9 Replenisher container 5 Intermediate transfer unit 6, 6a, 6b, 6c, 6d Cleaning device 7 Fixing device 8 Feed cassette 15 Pigment blue 51 Intermediate transfer belt 53 , 53a, 53b, 53c, 53d Primary transfer roller 55 Intermediate transfer belt drive roller 56 Secondary transfer inner roller 57 Secondary transfer outer roller 58 Tension roller 60 Intermediate transfer belt cleaner 71 Fixing roller 72 Pressure roller 73 Heater 81 Pickup roller 82 Conveyor roller 100 Toner particles Child 301 Conductive substrate 302 Photoconductive layer 303 Surface protective layer 304 Lower charge injection blocking layer 305 Upper charge injection blocking layer 306 Lower photoconductive layer 307 Upper photoconductive layer 400 Deposited film forming apparatus 401 Cylindrical substrate 402 Reaction vessel 403 Supporting substrate Body 404 Raw material gas supply system 405 Exhaust system 406 Power supply system 407 Exhaust pump 408 Exhaust valve 409 Main exhaust valve 410 Throttle valve 411 Oil diffusion pump 412 Main exhaust pump 413 Power source 414 Cathode 415 Matching box 416 Motor 417 Gas pipe 418 Drive unit 419 Exhaust port 501 Inner cylinder 502 Outer cylinder 503 Insulating member 504 Filter paper

Claims (10)

A substantially cylindrical image carrier;
Charging means for charging the image carrier;
An electrostatic latent image forming unit that forms an electrostatic latent image on the image carrier charged by the charging unit;
Developing means for developing the electrostatic latent image with a developer;
In an image forming apparatus having a transfer unit that transfers a developed developer image to a sheet material,
The absolute value of the potential on the image carrier is 200 V or less after development by the developing unit and before transfer by the transfer unit,
The absolute value of the potential of the image carrier after the sheet material has passed through the transfer means is 100 V or less,
The outer diameter of the circle in the cylindrical shape of the image carrier is 20 mm or more and 40 mm or less,
The developer is
Particles composed of at least a binder resin and a colorant;
The surface of the particles includes inorganic fine particles having an average primary particle size of 30 nm to 300 nm and a content of particles or aggregates having a particle size of 600 nm or more and 1% or less, and a weight average of the developer The particle size is 3.0 μm or more and 7.0 μm or less, the circularity is 0.940 or more and 0.975 or less, and the aggregation degree is 50% or more and 70% or less,
The transfer means includes
An intermediate transfer member to which at least a developer image on the image carrier is transferred;
Primary transfer means for bringing the intermediate transfer member into contact with the image carrier and transferring the developer image on the image carrier to the intermediate transfer member;
The primary transfer means is
Arranged on the upstream side or the downstream side in the traveling direction of the intermediate transfer member from the image carrier,
L (mm) is a distance between the center of the contact nip between the intermediate transfer member and the image carrier and the center of the contact nip between the primary transfer unit and the intermediate transfer member in the traveling direction of the intermediate transfer member;
The degree of aggregation is G (%),
When the outer diameter of the circle in the cylindrical shape of the image carrier is D (mm),
0.3 <L ≦ (0.1 × G−4.5) × D / 30
An image forming apparatus having the following relationship:   The image forming apparatus according to claim 1, wherein the primary transfer unit is disposed upstream of the image carrier in the traveling direction of the intermediate transfer member.   The image carrier has a photoconductive layer made of a non-single crystal material containing at least one of a hydrogen atom and a halogen atom based on a silicon atom formed on the surface of a conductive substrate. The image forming apparatus according to 1 or 2.   4. The image forming apparatus according to claim 1, wherein a transfer charging polarity supplied to the primary transfer unit is opposite to a charging polarity of the image carrier. 5. The absolute value of the charge amount of the developer on the image carrier is 20 × 10 ⁻³ C / kg or more and 50 × 10 ⁻³ C / kg or less. The image forming apparatus described.   6. The image forming apparatus according to claim 1, wherein the inorganic fine particles contained in the developer are strontium titanate fine powder having a perovskite crystal.   The image forming apparatus according to claim 1, wherein the content of the inorganic fine particles contained in the developer is 0.5 part by mass or more and 2.0 parts by mass or less. The volume resistivity of the intermediate transfer member is from 10 ⁸ Ω · cm to 10 ¹³ Ω · cm, and the surface resistance of the intermediate transfer member is from 10 ¹² Ω / cm ^{2 to} 10 ¹⁵ Ω / cm ^2. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   9. The image according to claim 1, wherein a pressing force of the primary transfer unit to the image carrier through the intermediate transfer member is 5 N / m or more and 20 N / m or less. Forming equipment.   The image forming apparatus according to claim 1, wherein the charging unit is a contact charging unit.

Images