JP5081402B2 - Image forming apparatus and image forming method - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, or a facsimile. Specifically, an electrostatic latent image is formed by exposing the surface of a latent image carrier and developed with a two-component developer. The present invention relates to an image forming apparatus and an image forming method for obtaining a toner image.

  In this type of image forming apparatus, an electrostatic latent image formed on a photoconductor (latent image carrier) having a photoconductive photosensitive layer on its surface is developed with a developer by a developing device, thereby exposing the photoconductor. Some form a toner image on the body. As a developer used in the developing device, a two-component developer mainly composed of a toner and a magnetic carrier is widely used because colorization is easy. In the two-component developer, the toner and the magnetic carrier are frictionally charged by being agitated and mixed in the developing device, and the toner is electrostatically attached to the surface of the magnetic carrier due to the electrostatic charge generated thereby. The magnetic carrier to which the toner is attached is carried by a magnetic force on the surface of a developing sleeve (developer carrying member) in which a magnet is disposed, and is conveyed along with the rotation of the developing sleeve.

  The developing sleeve is disposed at a position facing the photoconductor, and conveys the two-component developer so that the carried two-component developer contacts the surface of the photoconductor. The toner on the developing sleeve moves to and adheres to the electrostatic latent image on the surface of the photosensitive member by an electric field generated by the electrostatic latent image on the photosensitive member and the voltage applied to the developing sleeve. As a result, a toner image is formed on the surface of the photoreceptor. Here, the absolute value of the potential difference between the potential of the image portion where the electrostatic latent image is formed and the potential of the developing sleeve is referred to as the developing potential, and the potential of the non-image portion where the electrostatic latent image is not formed and the potential of the developing sleeve. The absolute value of the potential difference from the potential is called the background potential. In general, if the development potential is increased, the developing ability is increased and the image density is easily increased, and if the background potential is increased, the stain on the non-image portion, so-called background stain, is easily suppressed.

  However, simply increasing the development potential or background potential will induce abnormal images. For example, in Patent Document 1, there is a problem in that the toner is fixed to the developing sleeve by increasing the background potential and the developing ability is lowered, and as a countermeasure, the developing potential, the background potential, and the toner particle size are in appropriate ranges. Has been proposed. Further, in Patent Document 2, a development potential, a background potential, and a developer are used to suppress a phenomenon in which the rear end portion of the toner image or the front end portion of the toner image corresponding to the upstream side or the downstream side in the surface movement direction of the latent image carrier is thinned. It has been proposed that the amount of developer on the carrier is in an appropriate range. Thus, the development potential and the background potential are important parameters in development.

JP 2002-244415 A Japanese Patent No. 3522080

In recent years, as a two-component developer, a developer in which the volume resistivity of a magnetic carrier is adjusted to about 10 ⁹ to 10 ¹¹ [Ωcm] has been used mainly for the purpose of improving the developing ability. The present inventors have studied a two-component developer using such a magnetic carrier. As shown in FIG. 1A, the downstream side of the photosensitive member surface moving direction A with respect to the image portion (hereinafter, “ We discovered a phenomenon in which the toner adheres to the non-image area adjacent to the “tip side”. Hereinafter, the abnormal image due to the toner adhering to the non-image portion is referred to as a “hat image”.

  Conventionally, measures against such hat images have not been studied. In the Japanese Patent Application No. 2006-131225, the present applicant has applied for an image forming apparatus capable of suppressing the generation of such a hat image, but the present inventors have further performed a detailed analysis on the hat image. The photosensitive member surface and the developing sleeve surface are moved in a rotating direction so that the two-component developer on the developing sleeve is in contact with the photosensitive member surface, and the surface moving speed of the photosensitive member (hereinafter referred to as “linear velocity”). In the image forming apparatus that employs the forward developing method in which the linear velocity of the developing sleeve is set faster than the developing sleeve, the developing potential, the background potential, the resistance of the magnetic carrier, and the time during which the two-component developer passes through the developing nip. It was clarified that a hat image is generated under the above conditions.

FIG. 13 is an enlarged schematic view of the vicinity of the development nip outlet in order to explain the mechanism in which a hat image is generated in an image forming apparatus of the forward development type.
When the surface of the photosensitive member and the surface of the developing sleeve are moved in a rotating direction, and the linear velocity of the developing sleeve is faster than the linear velocity of the photosensitive member, the toner T ₁ developed on the photosensitive member 40 is later Rubbed by the incoming carrier C. At this time, in the vicinity of the developing nip exit where the two-component developer is separated from the photoconductor 40, the distance between the photoconductor 40 and the developing sleeve 65 increases and the electric field is weakened. For this reason, as indicated by (1) in FIG. 13, most of the toner T ₁ on the photoreceptor 40 in the vicinity of the developing nip exit is scraped off by the carrier C when it is rubbed against the carrier C coming later. Adhere to. In general, the larger the amount of toner with a smaller charge amount, the more the toner is developed, and the more the amount scraped off by the carrier C increases. Therefore, when the charge amount of the toner T ₁ slid on the carrier C near the exit of the developing nip is small, as shown in (2) in FIG. 13, the carrier C is covered with an excessive amount of toner T ₂ . It becomes a state. When such a carrier C subsequently moves to the non-image portion, as shown in (3) in FIG. 13, the toner T ₂ excessively attached to the carrier C moves to the non-image portion, which is a hat image and Become. Since the carrier coated with excessive toner becomes easier to move the toner to the non-image portion, the amount of toner T _{3 that} moves to the non-image portion increases as the toner charge amount decreases.

  The hat image generation mechanism described above is based on the forward development method in which the surface of the photosensitive member and the surface of the developing sleeve are moved along with each other and the linear velocity of the developing sleeve is set higher than the linear velocity of the photosensitive member. However, a counter direction developing system in which the surface of the developing sleeve is moved in the counter direction with respect to the surface of the photosensitive member is also conventionally known. In this counter direction developing method, it is easy to take a relative speed difference between the photosensitive member and the developer on the developing sleeve larger than that in the forward direction developing method. Therefore, it is easy to increase the amount of toner supplied per unit time to the image portion on the photoconductor, and to easily realize high development efficiency. As a result, there is an advantage that it is easy to secure the image density of the highlight portion and the halftone portion, which are low contrast regions, and it is easy to improve the image gradation. In addition, in the forward development method, when there is a low density part immediately after the high density part, the rear end of the high density part tends to be darker than necessary. There is also an advantage that it does not occur in the development system.

As a result of further research by the present inventors, the volume resistivity of the magnetic carrier is adjusted to about 10 ⁹ to 10 ¹¹ [Ωcm] mainly for the purpose of improving the developing ability even in such a counter direction developing method. As shown in FIG. 1B, the toner adheres to the non-image part adjacent to the upstream side of the photosensitive member surface movement direction A (hereinafter referred to as “rear end side”) as shown in FIG. It was confirmed that a hat image was generated. This hat image is also generated according to the conditions of development potential, background potential, magnetic carrier resistance, and time for the two-component developer to pass through the development nip.

FIG. 14 is an enlarged schematic view of the vicinity of the developing nip outlet in order to explain the mechanism by which a hat image is generated in the counter direction developing type image forming apparatus.
When the surface of the developing sleeve is moved in the counter direction with respect to the surface of the photosensitive member, the toner T ₁ developed on the photosensitive member 40 is rubbed by the carrier C. At this time, in the vicinity of the developing nip exit where the two-component developer is separated from the photoconductor 40, the distance between the photoconductor 40 and the developing sleeve 65 increases and the electric field is weakened. Therefore, as indicated by (1) in FIG. 13, much of the toner T ₁ on the photoreceptor 40 in the vicinity of the developing nip exit is scraped off and reattached to the carrier C when it is rubbed against the carrier C. When the charge amount of the toner T ₁ slid on the carrier C in the vicinity of the developing nip exit is small, as shown in (2) in FIG. 13, the carrier C is covered with an excessive amount of toner T ₂ . It becomes a state. When such a carrier C subsequently moves to the non-image portion, as shown in (3) in FIG. 13, the toner T ₂ excessively attached to the carrier C moves to the non-image portion, which is a hat image and Become. Since the carrier coated with excessive toner becomes easier to move the toner to the non-image portion, the amount of toner T _{3 that} moves to the non-image portion increases as the toner charge amount decreases.

  The present invention has been made in view of the above background, and an object of the present invention is to provide an image forming apparatus and an image forming method capable of suppressing the generation of a hat image.

ここで、上記数１に示す式中の各記号は次のとおりである。
ε［Ｆ／ｍ］は、上記磁性キャリアの誘電率である。
ρ［Ω・ｍ］は、上記磁性キャリアの体積抵抗率である。
Ｔ［ｓｅｃ］は、上記現像剤担持体上の二成分現像剤が上記潜像担持体との接触領域を通過するのに要する時間であり、二成分現像剤が潜像担持体に接触する潜像担持体表面移動方向長さＮｉｐ［ｍ］を、現像剤担持体の表面移動速度（線速）Ｖｒ［ｍ／ｓｅｃ］で除した値（Ｎｉｐ／Ｖｒ）である。
ΔＶｒ［ｍ／ｓｅｃ］は、上記潜像担持体の表面移動速度（線速）Ｖｐｃ［ｍ／ｓｅｃ］と上記現像剤担持体の表面移動速度（線速）Ｖｒ［ｍ／ｓｅｃ］との相対速度差（Ｖｒ−Ｖｐｃ）である。
δ［ｍ］は、上記露光手段により露光される上記潜像担持体表面上の画像部に対して潜像担持体表面移動方向に隣接する非画像部と該画像部との境界でのエッジ効果が発生する領域の潜像担持体表面移動方向長さの１／ｅの距離である。
また、請求項２の発明は、表面移動する潜像担持体と、該潜像担持体の表面を露光することにより該表面に静電潜像を形成する露光手段と、該潜像担持体と対向する位置に配置され、トナー及び磁性キャリアを含む二成分現像剤が該潜像担持体の表面に接触するように該二成分現像剤を表面に担持して表面移動する現像剤担持体と、該潜像担持体と該現像剤担持体との間に所定の直流電圧を印加する電圧印加手段とを有し、該現像剤担持体の表面が該潜像担持体の表面に対してカウンター方向へ移動するように構成された画像形成装置において、上記潜像担持体表面上の画像部と上記現像剤担持体表面との電圧差の絶対値Ｖ１［Ｖ］に対する、該潜像担持体表面上の非画像部と該現像剤担持体表面との電圧差の絶対値Ｖ２［Ｖ］の比率が、上記数１に示す式を満たすように構成されていることを特徴とするものである。
また、請求項３の発明は、請求項１又は２の画像形成装置において、上記二成分現像剤中のトナーと磁性キャリアとの間の付着力が１０［ｎＮ］以下となり、該二成分現像剤中のトナー含有率が１０［％］以下となるように構成したことを特徴とするものである。
また、請求項４の発明は、請求項１、２又は３の画像形成装置において、上記二成分現像剤中のトナーの平均帯電量と同じ極性で、かつ、帯電量の絶対値ｑとトナー粒径Ｔｄとの比率（ｑ／Ｔｄ）が０．１［ｆＣ／μｍ］以下であるトナーの含有率が２０［％］以下となるように構成したことを特徴とするものである。
また、請求項５の発明は、請求項１、２、３又は４の画像形成装置において、上記二成分現像剤中の磁性キャリアの重量平均粒径が２０［μｍ］以上６０［μｍ］以下となるように構成したことを特徴とするものである。
また、請求項６の発明は、請求項１、２、３、４又は５の画像形成装置において、上記二成分現像剤中の磁性キャリアの体積抵抗率が１０⁹［Ω・ｃｍ］以上１０¹⁴［Ω・ｃｍ］以下となるように構成したことを特徴とするものである。
また、請求項７の発明は、請求項１、２、３、４、５又は６の画像形成装置において、上記潜像担持体と上記現像剤担持体との最小間隔が２００［μｍ］以上４００［μｍ］以下となるように構成したことを特徴とするものである。
また、請求項８の発明は、請求項１、２、３、４、５、６又は７の画像形成装置において、上記潜像担持体との対向領域における上記現像剤担持体上の現像剤担持量が３５［ｍｇ／ｃｍ²］以上５５［ｍｇ／ｃｍ²］以下となるように構成したことを特徴とするものである。
また、請求項９の発明は、請求項１、２、３、４、５、６、７又は８の画像形成装置において、上記二成分現像剤中の磁性キャリアに対するトナーの被覆率が５０［％］以上７０［％］以下となるように構成したことを特徴とするものである。
また、請求項１０の発明は、表面移動する潜像担持体と、該潜像担持体の表面を露光することにより該表面に静電潜像を形成する露光手段と、該潜像担持体と対向する位置に配置され、トナー及び磁性キャリアを含む二成分現像剤が該潜像担持体の表面に接触するように該二成分現像剤を表面に担持して表面移動する現像剤担持体と、該潜像担持体と該現像剤担持体との間に所定の直流電圧を印加する電圧印加手段とを有する画像形成装置で、該現像剤担持体の表面を該潜像担持体の表面に対して連れ回り方向へ移動させ、かつ、該現像剤担持体の表面移動速度（線速）Ｖｒ［ｍ／ｓｅｃ］を該潜像担持体の表面移動速度（線速）Ｖｐｃ［ｍ／ｓｅｃ］よりも速くて画像形成を行う画像形成方法において、上記潜像担持体表面上の画像部と上記現像剤担持体表面との電圧差の絶対値Ｖ１［Ｖ］に対する、該潜像担持体表面上の非画像部と該現像剤担持体表面との電圧差の絶対値Ｖ２［Ｖ］の比率が、上記数１に示す式を満たすようにしたことを特徴とするものである。
また、請求項１１の発明は、表面移動する潜像担持体と、該潜像担持体の表面を露光することにより該表面に静電潜像を形成する露光手段と、該潜像担持体と対向する位置に配置され、トナー及び磁性キャリアを含む二成分現像剤が該潜像担持体の表面に接触するように該二成分現像剤を表面に担持して表面移動する現像剤担持体と、該潜像担持体と該現像剤担持体との間に所定の直流電圧を印加する電圧印加手段とを有する画像形成装置で、該現像剤担持体の表面を該潜像担持体の表面に対してカウンター方向へ移動させて画像形成を行う画像形成方法において、上記潜像担持体表面上の画像部と上記現像剤担持体表面との電圧差の絶対値Ｖ１［Ｖ］に対する、該潜像担持体表面上の非画像部と該現像剤担持体表面との電圧差の絶対値Ｖ２［Ｖ］の比率が、上記数１に示す式を満たすようにしたことを特徴とするものである。 To achieve the above object, the invention of claim 1 comprises a latent image carrier that moves on the surface, and exposure means that forms an electrostatic latent image on the surface by exposing the surface of the latent image carrier; The two-component developer disposed on the surface facing the latent image carrier and carrying the two-component developer on the surface moves so that the two-component developer containing toner and magnetic carrier contacts the surface of the latent image carrier. A developer carrying member, and a voltage applying means for applying a predetermined DC voltage between the latent image carrying member and the developer carrying member, and the surface of the developer carrying member is the surface of the latent image carrying member. The developer carrying member moves in the direction of rotation with respect to the surface, and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrying member is the surface moving velocity (linear velocity) Vpc [m / sec] of the latent image carrying member. In the image forming apparatus set faster than [sec], the image portion on the surface of the latent image carrier and the development The ratio of the absolute value V2 [V] of the voltage difference between the non-image portion on the surface of the latent image carrier and the surface of the developer carrier to the absolute value V1 [V] of the voltage difference with the surface of the carrier is as follows. It is characterized by being comprised so that the type | formula shown to several 1 may be satisfy | filled.

Here, each symbol in the formula shown in the above equation 1 is as follows.
ε [F / m] is the dielectric constant of the magnetic carrier.
ρ [Ω · m] is the volume resistivity of the magnetic carrier.
T [sec] is the time required for the two-component developer on the developer carrier to pass through the contact area with the latent image carrier, and the latent time when the two-component developer contacts the latent image carrier. This is a value (Nip / Vr) obtained by dividing the length Nip [m] in the surface movement direction of the image carrier by the surface movement speed (linear velocity) Vr [m / sec] of the developer carrier.
ΔVr [m / sec] is a relative value between the surface moving speed (linear velocity) Vpc [m / sec] of the latent image carrier and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrier. It is a speed difference (Vr−Vpc).
[delta] [m], the edge effect at the boundary between the non-image portion and the image portion adjacent to the latent image bearing member surface moving direction with respect to the image portion on the latent image bearing member surface to be exposed by said exposure means Is a distance of 1 / e of the length in the moving direction of the surface of the latent image carrier.
According to a second aspect of the present invention, there is provided a latent image carrier that moves on the surface, an exposure unit that forms an electrostatic latent image on the surface by exposing the surface of the latent image carrier, and the latent image carrier. A developer carrier that is disposed at opposing positions and that carries the two-component developer on the surface so that the two-component developer including toner and magnetic carrier contacts the surface of the latent image carrier; Voltage application means for applying a predetermined DC voltage between the latent image carrier and the developer carrier, and the surface of the developer carrier is counter-directional with respect to the surface of the latent image carrier In the image forming apparatus configured to move to the surface of the latent image carrier, the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. The ratio of the absolute value V2 [V] of the voltage difference between the non-image area and the developer carrying member surface is And it is characterized in that it is configured to satisfy the equation shown in Equation 1.
The invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the adhesive force between the toner and the magnetic carrier in the two-component developer is 10 [nN] or less, and the two-component developer. It is characterized in that the toner content in the toner is 10% or less.
According to a fourth aspect of the present invention, in the image forming apparatus of the first, second, or third aspect, the polarity is the same as the average charge amount of the toner in the two-component developer, and the absolute value q of the charge amount and the toner particles The toner content is such that the ratio (q / Td) to the diameter Td is 0.1 [fC / μm] or less and 20 [%] or less.
According to a fifth aspect of the present invention, in the image forming apparatus of the first, second, third, or fourth aspect, the weight average particle size of the magnetic carrier in the two-component developer is 20 [μm] or more and 60 [μm] or less. It is characterized by comprising.
According to a sixth aspect of the present invention, in the image forming apparatus of the first, second, third, fourth or fifth aspect, the volume resistivity of the magnetic carrier in the two-component developer is 10 ⁹ [Ω · cm] or more and 10 ^14. It is characterized by being configured to be [Ω · cm] or less.
According to a seventh aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, fifth or sixth aspect, a minimum distance between the latent image carrier and the developer carrier is 200 [μm] or more and 400. It is characterized by being configured so as to be [μm] or less.
According to an eighth aspect of the present invention, in the image forming apparatus according to the first, second, third, fourth, sixth or seventh aspect, the developer carrying member on the developer carrying member in a region facing the latent image carrying member. The amount is set to 35 [mg / cm ² ] or more and 55 [mg / cm ² ] or less.
The invention according to claim 9 is the image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7 or 8, wherein the toner coverage with respect to the magnetic carrier in the two-component developer is 50%. ] 70 [%] or less.
Further, the invention of claim 10 comprises a latent image carrier that moves on the surface, exposure means for forming an electrostatic latent image on the surface by exposing the surface of the latent image carrier, and the latent image carrier. A developer carrier that is disposed at opposing positions and that carries the two-component developer on the surface so that the two-component developer including toner and magnetic carrier contacts the surface of the latent image carrier; An image forming apparatus having a voltage applying means for applying a predetermined DC voltage between the latent image carrier and the developer carrier, wherein the surface of the developer carrier is made to face the surface of the latent image carrier. And the surface moving speed (linear velocity) Vr [m / sec] of the developer carrying member is determined from the surface moving speed (linear velocity) Vpc [m / sec] of the latent image carrying member. In an image forming method for forming an image at a fast speed, the image portion on the surface of the latent image carrier The ratio of the absolute value V2 [V] of the voltage difference between the non-image portion on the surface of the latent image carrier and the surface of the developer carrier to the absolute value V1 [V] of the voltage difference from the surface of the developer carrier. , And satisfying the expression shown in the above equation (1).
Further, the invention of claim 11 comprises a latent image carrier that moves on the surface, exposure means for forming an electrostatic latent image on the surface by exposing the surface of the latent image carrier, and the latent image carrier. A developer carrier that is disposed at opposing positions and that carries the two-component developer on the surface so that the two-component developer including toner and magnetic carrier contacts the surface of the latent image carrier; An image forming apparatus having a voltage applying means for applying a predetermined DC voltage between the latent image carrier and the developer carrier, wherein the surface of the developer carrier is made to face the surface of the latent image carrier. In the image forming method in which the image is formed by moving the image in the counter direction, the latent image carrier with respect to the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. Absolute value V2 of voltage difference between the non-image area on the surface of the body and the surface of the developer carrying body Ratio of V] is characterized in that it has to satisfy the equation shown in Equation 1.

  The surface of the developer carrying member moves in a rotating direction with respect to the surface of the latent image carrying member, and the linear velocity Vr [m / sec] of the developer carrying member is the linear velocity Vpc [m / sec] of the latent image carrying member. As will be described later, both a forward developing method faster than [sec] and a counter developing method in which the surface of the developer carrying member moves in the counter direction with respect to the surface of the latent image carrying member are employed. The voltage difference between the non-image portion on the surface of the latent image carrier and the surface of the developer carrier relative to the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. When the ratio of the absolute value V2 [V] satisfies the expression shown in the above equation 1, the generation of a hat image is suppressed.

  As described above, according to the present invention, there is an excellent effect that the formation of a hat image can be suppressed.

  Hereinafter, the present invention is applied to a tandem type color laser copying machine (hereinafter simply referred to as “copying machine”) which is an image forming apparatus in which a plurality of photosensitive members as latent image carriers are arranged in parallel. A form is demonstrated.

[overall structure]
First, the basic configuration of the copying machine will be described.
FIG. 2 is a schematic configuration diagram of the copying machine according to the present embodiment. The copier includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is placed, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder (hereinafter referred to as ADF) 400 fixed on the scanner 300 is also provided.
The printer unit 100 forms an image including four sets of process cartridges 18Y, 18C, 18M, and 18K for forming an image of each color of yellow (Y), magenta (M), cyan (C), and black (K). A unit 20 is provided. Y, C, M, and K added after the numerals are the members for yellow, cyan, magenta, and black, respectively (the same applies hereinafter). In addition to the process cartridges 18Y, 18C, 18M, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a registration roller pair 49, a paper feed cassette 44, and a belt fixing type fixing as exposure means. A unit 25 and the like are disposed.

[Optical writing unit]
The optical writing unit 21 includes a light source (not shown), a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of a photoreceptor to be described later with laser light based on image data.

[Process cartridge]
FIG. 3 is an enlarged view showing a schematic configuration of the yellow process cartridge 18Y and the cyan process cartridge 18C among the process cartridges 18Y, 18C, 18M, and 18K. The other process cartridges 18M and 18K have the same configuration except that the toner colors are different from each other. In the figure, a process cartridge 18Y, which is an image generating unit that generates a toner image, includes a drum-shaped photoreceptor 40Y, a charger 60, a developing device 61, a drum cleaning device 63, a static eliminator 64, and the like.

  The charger 60 serving as a charging means opposes a photosensitive roller 40Y serving as a latent image carrier with a charging roller as a rotating charging member that is driven to rotate while a charging bias is being applied therebetween through a predetermined minute gap. . Then, with this minute gap, a discharge is generated from the charging roller to the photoconductor 40Y, and the photoconductor 40Y is uniformly charged. The reason why the charging roller is rotated is that the roller surface immediately after the discharge is retracted from the minute gap and the roller surface that has not been discharged is caused to enter the minute gap, thereby generating a stable discharge. As the charging rotating member, a charging drum, a roller-shaped charging brush, or the like can be used in addition to the charging roller. In this copying machine, the surface of the photoreceptor 40Y is uniformly charged to about −600 [V] by the discharge from the charging roller.

The surface of the photoreceptor 40Y subjected to the charging process is irradiated with the laser light L modulated and deflected by the optical writing unit (21). Then, the potential of the irradiation part (exposure part) is attenuated to about −150 to −500 [V]. By this attenuation, an electrostatic latent image for Y is formed on the surface of the photoreceptor 40Y. The formed electrostatic latent image for Y is developed by a developing device 61 as developing means to become a Y toner image.
In the photoreceptor 40Y, for example, a base tube made of aluminum or the like is coated with a photosensitive layer made of an organic photosensitive material that exhibits photosensitivity, and further a filler reinforcing charge having a thickness of 3.5 to 5.0 [μm] is further formed thereon. It is in the form of a drum coated with a transport layer. Instead of the drum shape, a belt shape may be adopted.

The developing device 61 includes a developing unit 67 and a stirring unit 66 in the casing 70. The developing portion 67 is provided with a developing sleeve 65 that exposes a part of the peripheral surface from the opening of the casing 70, a doctor blade 73, and the like.
The cylindrical developing sleeve 65 as a developer carrying member is made of a non-magnetic material, and the surface thereof is roughened to a 10-point average surface roughness Rz of about 10 to 12 [μm] by sandblasting or the like. is there. By this roughening, the developer conveying ability is enhanced. Instead of roughening, fine grooves may be provided on the surface. The developing sleeve 65 is rotated by driving means (not shown). Inside the developing sleeve 65 that is driven to rotate in this manner, the magnet roller 72 is fixed so as not to rotate around the sleeve. The magnet roller 72 has a plurality of magnetic poles divided in the circumferential direction. Due to the influence of these magnetic poles, a magnetic field is formed on the periphery of the developing sleeve 65.

  The stirring unit 66 of the developing device 61 is provided with two conveying screws 68, a toner concentration sensor (hereinafter referred to as “T sensor”) 71, and the like, and includes a magnetic carrier and negatively chargeable Y toner. A Y developer (not shown) is accommodated. The Y developer is agitated and conveyed in the depth direction in the figure by the two conveying screws 68 and is frictionally charged. During this agitation and conveyance, the surface of the developing sleeve 65 comes into contact with the axial direction thereof. Then, it is carried on the surface of the developing sleeve 65 due to the influence of the magnetic field extending from the sleeve surface toward the stirring portion 66, and is pumped up from the stirring portion 66 as the sleeve surface rotates. And it conveys to the position facing the doctor blade 73 with rotation of the sleeve surface. At this facing position, the Y developer is regulated in layer thickness when it passes through a doctor gap of about 500 [μm], which is the gap between the developing sleeve 65 and the doctor blade 73, and the frictional charging of the toner is promoted. .

  The Y developer that has passed through the doctor gap reaches the developing region facing the photoreceptor 40Y as the sleeve surface rotates. In this development region, the photoconductor 40Y and the development sleeve 65 are opposed to each other with a development gap of about 350 [μm]. On the surface of the sleeve in the developing region, the magnetic carrier in the Y developer rises and forms a magnetic brush by the magnetic force from the developing magnetic pole (not shown) of the magnet roller 72. The formed magnetic brush moves while the tip of the magnetic brush is rubbed against the photoconductor 40Y to attach Y toner to the electrostatic latent image for Y on the photoconductor 40Y. By this adhesion, a Y toner image as a toner image is formed on the photoreceptor 40Y. The charge amount of Y toner in the Y developer conveyed to the development area is −10 to −40 [μC / g], preferably −15 to −35 [μC / g]. The magnetic force of the magnetic pole of the magnet roller 72, the stirring performance, the doctor gap, etc. are set so as to be in this range.

The developer that has consumed Y toner by development returns to the developing device 61 as the developing sleeve 65 rotates. Then, it is separated from the sleeve surface under the influence of the repulsive magnetic field and gravity formed in the container, and returned to the stirring unit 66 disposed at a position lower than the developing unit 67.
A partition wall 69 is provided between the two conveying screws 68 in the stirring unit 66. By this partition wall 69, the inside of the stirring unit 66 is partitioned into two. Of the two conveying screws 68, the one disposed on the right side in the figure is driven to rotate by a driving means (not shown), and the developer is supplied to the developing sleeve 65 while being conveyed from the near side to the far side in the figure. To do. The developer conveyed to the far end in the figure passes through an opening (not shown) provided in the partition wall 69 and is transferred to the conveyance screw 68 on the left side in the figure. Then, after the conveying screw 68 is driven to rotate, the conveying screw 68 is conveyed from the front side to the front side in the drawing, and then passes through the other opening (not shown) provided in the partition wall 69 to the right side in the drawing. Return to top. In this way, the developer is circulated and conveyed in the stirring unit 66.

  A T sensor 71 including a magnetic permeability sensor is provided below the right conveying screw 68 in the drawing, and outputs a voltage having a value corresponding to the magnetic permeability of the Y developer conveyed thereon. Since the magnetic permeability of the developer shows a certain degree of correlation with the toner concentration, the T sensor 71 outputs a voltage having a value corresponding to the Y toner concentration. This output voltage value is sent to a control unit (not shown). The control unit includes a RAM or the like, and stores therein a Y Vtref that is a target value of the output voltage from the T sensor 71. In addition, data of M Vtref, C Vtref, and K Vtref, which are target values of output voltage from a T sensor (not shown) mounted in another developing device, is also stored. The Y Vtref is used for driving control of a Y toner supply device (not shown). Specifically, the control unit drives and controls a Y toner supply device (not shown) so as to bring the value of the output voltage from the Y T sensor 71 closer to the Y Vtref, thereby controlling the inside of the stirring unit 66 of the developing device 61. Y toner is replenished. By this replenishment, the Y toner concentration of the developer in the developing device 61 is maintained within a predetermined range. Similar toner replenishment control is performed for the developing devices of other process cartridges.

[Drum cleaning device]
The Y toner image formed on the Y photoconductor 40Y is intermediately transferred to an intermediate transfer belt 10 described later. The surface of the photoreceptor 40Y after the intermediate transfer is cleaned of the transfer residual toner by the drum cleaning device 63. The drum cleaning device 63 includes a fur brush, a collection roller 77, a scraper blade 78, a collection screw 79, a cleaning blade 75, and the like.
The fur brush 76 is a roller-like brush in which an infinite number of brushes made of acrylic carbon are planted on a core material. Then, the tip of countless raised brushes (not shown) is driven to rotate counterclockwise in the figure, which is the surface movement in the counter direction, at the portion facing the photoconductor 40Y so as to be slid sequentially on the photoconductor 40Y. The collection roller 77 is applied with a positive cleaning bias from a power source (not shown) while being driven to rotate counterclockwise in the figure, which is the surface movement in the counter direction at the portion facing the brush so as to contact the fur brush 76. receive. The transfer residual toner on the photoreceptor 40Y is scraped off by the brushing of the fur brush 76 and captured in the fur brush 76, and then electrostatically adheres to the surface of the collecting roller 77 under the influence of the cleaning bias. Collected. The collected transfer residual toner is scraped off from the roller surface by a scraper blade 78 in contact with the collection roller 77 and falls onto the collection screw 79. The collection screw 79 that is rotationally driven by a drive means (not shown) receives the transfer residual toner falling in this way and sends it to the toner recycling device 89.
The transfer residual toner that has not been completely captured by the fur brush 76 is scraped off by the cleaning blade 75 disposed downstream of the brush in the drum rotation direction and is captured by the fur brush 76. The cleaning blade 75 is made of an elastic material such as polyurethane rubber.

  In the Y process cartridge 18 </ b> Y, the photoreceptor 40 </ b> Y cleaned by the drum cleaning device 63 is neutralized by the neutralizer 64. Then, it is uniformly charged by the charger 60 and returns to the initial state. The series of processes as described above is the same for the other process cartridges (18C, M, K).

[Intermediate transfer unit]
FIG. 4 is an enlarged configuration diagram showing the image forming unit 20, the intermediate transfer unit 17, the secondary transfer device 22, the registration roller pair 49, and the fixing unit 25.
The intermediate transfer unit 17 includes the intermediate transfer belt 10 and a belt cleaning device 90. Further, the tension roller 14, the driving roller 15, the secondary transfer backup roller 16, the four intermediate transfer bias rollers 62 </ b> Y, 62 </ b> C, 62 </ b> M, 62 </ b> K, the three ground rollers 74, and the like are also provided.
The intermediate transfer belt 10 has a base layer, an elastic layer, and a surface layer (not shown) from the inside of the belt loop. The base layer is a layer containing, for example, a fluorine-based resin having a small elongation or a rubber material having a large elongation and a material that is difficult to stretch, such as canvas, or laminated. The surface layer is a layer made of a material having a low surface energy and exhibiting good releasability from the toner, such as a fluorine resin. The elastic layer is a layer made of an elastic material such as fluorine-based rubber or acrylonitrile-butadiene copolymer rubber, and is provided in order to exert a certain degree of elasticity on the entire belt.

  The intermediate transfer belt 10 is tensioned by ten rollers including a tension roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown). The four intermediate transfer bias rollers 62Y, C, M, and K are disposed so as to be in contact with the base layer side (inner peripheral surface side) of the intermediate transfer belt 10, respectively, and receive an intermediate transfer bias from a power source (not shown). . Further, the intermediate transfer belt 10 is pressed from the base layer side toward the photoreceptors 40Y, 40C, 40M, and 40K to form intermediate transfer nips. At each intermediate transfer nip, an intermediate transfer electric field is formed between the photoreceptor and the intermediate transfer bias roller due to the influence of the intermediate transfer bias. The above-described Y toner image formed on the Y photoconductor 40Y is intermediately transferred onto the intermediate transfer belt 10 due to the influence of the intermediate transfer electric field and nip pressure. On the Y toner image, the C, M, and K toner images formed on the C, M, and K photoconductors 40C, 40M, and 40K are sequentially superimposed and transferred. By this superimposing intermediate transfer, a four-color superposed toner image (hereinafter referred to as “four-color toner image”) as a multiple toner image is formed on the intermediate transfer belt 10.

In the intermediate transfer belt 10 as a belt member, a ground roller 74 is in contact with a portion located between the intermediate transfer nips from the base layer side. These grounding rollers 74 are made of a conductive material. Then, the current due to the intermediate transfer bias transmitted from the intermediate transfer bias rollers 62Y, 62C, 62M, and 62K to the belt at each intermediate transfer nip is prevented from leaking to other intermediate transfer nips and process cartridges.
The four-color toner image superimposed and transferred on the intermediate transfer belt 10 is secondarily transferred to a transfer sheet (not shown) at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 10 after passing through the secondary transfer nip is cleaned by a belt cleaning device 90 that sandwiches the belt with the driving roller 15 on the left side in the drawing. In the figure, as the belt cleaning device 90, an example in which the fur brush method and the cleaning blade method are used in the same manner as the drum cleaning device 63 described above is shown. However, either one of the methods may be used.

[Secondary transfer device]
Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers 23. Of the two stretching rollers 23, one roller arranged on the right side in the drawing has the intermediate transfer belt 10 and the paper conveying belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is sandwiched. By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 10 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. A secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown). By applying this secondary transfer bias, the four-color toner image on the intermediate transfer belt 10 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip. A next transfer electric field is formed. The transfer paper fed into the secondary transfer nip so as to synchronize with the four-color toner image on the intermediate transfer belt 10 by a registration roller pair 49 described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

[Registration roller pair]
A registration roller pair 49 is disposed upstream of the secondary transfer nip in the belt moving direction. A transfer sheet (not shown) fed into the printer unit 100 from a sheet feeding device 200 described later is sandwiched between rollers of the registration roller pair 49. On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 10 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip. Thereby, in the secondary transfer nip, the four-color toner image on the intermediate transfer belt 10 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper P on which a full-color image is formed in this way exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and then is sent from the paper transport belt 24 to the fixing unit 25.

[Fixing unit]
The fixing unit 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward one roller of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper conveying belt 24 is sandwiched therebetween. Of the two rollers in the belt unit, the roller that is pressed from the pressure roller 27 has a heat source (not shown) inside, and pressurizes the fixing belt 26 by the generated heat. The pressed fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.

  In FIG. 2 described above, the transfer paper P that has passed through the fixing unit 25 is discharged to the outside of the apparatus through a pair of paper discharge rollers 56 and stacked on the stack unit 57 or below the fixing unit 25. It is sent to the arranged paper reversing unit. When sent to the paper reversing unit, it is turned upside down and then conveyed again to the secondary transfer nip, and the four-color toner image is secondarily transferred to the other surface. Then, after passing through the fixing unit 25, it is discharged outside the apparatus. Whether the transfer paper P is sent from the fixing unit 25 to the paper discharge roller pair 56 or the paper reversing unit is determined by switching the paper transport path by the switching claw 55.

[Overall operation]
When a document (not shown) is copied, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.
When a copy start switch (not shown) is pressed after the document is set in this way, the document reading operation by the scanner 300 starts. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation. In the document reading operation, first, the first traveling body 33 and the second traveling body 34 start traveling together, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.

  In parallel with the document reading operation, each device in the process cartridges 18Y, 18C, 18M, and 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing unit 25 start driving. Then, based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, C, M, and K toner images are formed on the photoreceptors 40Y, 40C, 40M, and 40K. Is done. These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 10.

  Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer paper is separated one by one by the separation roller 45 and enters the paper feed path 46, and then fed to the paper feed path 48 in the printer unit 100 by the transport roller 47. In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the paper feeding roller 50 is selectively rotated and the transfer paper on the manual feed tray 51 is sent out, the separation roller 52 separates the transfer paper one by one and feeds it to the manual paper feed path 53 of the printer unit 100. To do. The transfer paper fed to the paper feed path 48 or the manual paper feed path 53 in the printer unit 100 is secondarily transferred with a four-color toner image via the registration roller pair 49 and the secondary transfer nip. Then, after passing through the fixing unit 25, it is discharged outside the apparatus.

[toner]
As the toner, it is desirable to use a toner obtained by further adding an additive or the like to base particles containing a binder resin and other materials such as a colorant, a charge control agent, and a release accelerator. About the said release accelerator, it is desirable to contain 1-15 weight part with respect to 100 weight part of binder resin, Preferably, 2-10 weight part of a release accelerator is contained. This is because if the content of the release accelerator is less than 1 part by weight, hot offset of the toner to the fixing belt 26 cannot be sufficiently suppressed. On the other hand, if the amount exceeds 15 parts by weight, the developing ability is reduced, the occurrence of abnormal images due to the agglomerated toner, the transferability is lowered, and the durability is lowered. When it is 2 to 10 parts by weight, a high-quality image with high image density in the solid part and good dot reproducibility can be obtained.

  A conventionally well-known thing can be used as said mold release accelerator. For example, low molecular weight polyethylene wax, low molecular weight polyolefin wax such as low molecular weight polypropylene, synthetic hydrocarbon wax such as Fischer-Tropsch wax, natural wax such as beeswax, carnauba wax, candelilla wax, rice wax, montan wax, Petroleum waxes such as paraffin wax and microcrystalline wax, higher fatty acids such as stearic acid, palmitic acid and myristic acid, metal salts of higher fatty acids, higher fatty acid amides, synthetic ester waxes, and various modified waxes thereof. These mold release accelerators can be used alone or in combination of two or more. In particular, when carnauba wax or synthetic ester wax is used, good releasability of toner from the fixing belt 26 and the photoreceptor can be obtained.

  The amount of the additive added to the toner is preferably 0.6 to 4.0 parts by weight, more preferably 1.0 to 3.6 parts by weight, based on 100 parts by weight of the base particles. It is. When the amount of the additive is less than 0.6 parts by weight, the contact with the magnetic carrier as the magnetic particles is insufficient due to an increase in the degree of aggregation between the toner particles due to poor fluidity of the toner. In addition, sufficient chargeability of the toner cannot be obtained in the developing device. In addition, transferability and heat-resistant storage stability are insufficient, and it is easy to cause background contamination and toner scattering. On the other hand, when the amount is more than 4.0 parts by weight, the fluidity is improved, but the cleaning of the photosensitive member due to chattering or turning of the cleaning blade or the like, and filming on the photosensitive member due to the additive released from the toner are likely to occur. . As a result, the durability of the cleaning member such as a cleaning blade or the photosensitive member to be cleaned is lowered, and the fixing property is also deteriorated. In particular, when the content is 1.0 to 3.6 parts by weight, a high-quality image with high image density in the solid part and good dot reproducibility can be obtained. The background stain is a phenomenon in which toner adheres to the non-image portion of the photoreceptor.

Conventionally known additives can be used as additives to be added to the toner. For example, oxides such as Si, Ti, Al, Mg, Ca, Sr, Ba, In, Ga, Ni, Mn, W, Fe, Co, Zn, Cr, Mo, Cu, Ag, V, and Zr, and complex oxidation Thing etc. are mentioned. In particular, silica, titania and alumina which are oxides of Si, Ti and Al are preferably used. In addition, about an additive, it is desirable to surface-treat according to the objectives, such as hydrophobization, a fluid improvement, and charging control.
There are various methods for measuring the additive content, but it is generally determined by fluorescent X-ray analysis. In this method, a calibration curve is prepared by fluorescent X-ray analysis for a toner having a known additive content, and the additive content is determined using this calibration curve.

  As the treatment agent used for the surface treatment of the toner, an organic silane compound or the like is preferable. Examples thereof include alkylchlorosilanes such as methyltrichlorosilane, octyltrichlorosilane, and dimethyldichlorosilane, alkylmethoxysilanes such as dimethyldimethoxysilane and octyltrimethoxysilane, hexamethyldisilazane, and silicone oil. As a method of surface treatment with a treating agent, there are a method of immersing an additive in a solution containing an organosilane compound and drying, a method of spraying and drying a solution containing an organosilane compound as an additive, and the like.

  The particle size of the additive added to the toner base particles is preferably 0.002 to 0.2 [μm] in terms of the average primary particle size from the viewpoint of imparting fluidity and the like, and particularly preferably, the particle size is 0.00. 005 to 0.05 [μm]. An additive having an average primary particle size smaller than 0.002 [μm] is likely to be aggregated because the additive is easily embedded in the surface of the base particle. Further, sufficient fluidity cannot be obtained, or filming on the photoreceptor or the like is likely to occur. These tendencies are particularly remarkable under high temperature and high humidity. In addition, if the average primary particle diameter is smaller than 0.002 [μm], the additives tend to agglomerate with each other, and this also makes it difficult to obtain sufficient fluidity. On the other hand, if the average primary particle size is larger than 0.2 [μm], sufficient chargeability cannot be obtained due to poor fluidity of the toner, which is likely to cause background contamination and toner scattering. On the other hand, if the average primary particle diameter is larger than 0.1 [μm], the surface of the photoreceptor is easily damaged, and filming and the like are likely to occur. The particle size of the additive can be determined by measuring with a transmission electron microscope.

  A conventionally well-known thing can be used as said binder resin. For example, polystyrene, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, acrylic resin, polyester resin, epoxy resin, polyol resin, Examples thereof include rosin-modified maleic resin, phenol resin, low molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, ketone resin, ethylene-ethyl acrylate copolymer, polybutyral, and silicone resin. You may use these individually or in combination of 2 or more types. Particularly preferred are polyester resins and polyol resins. The method for producing the binder resin is not particularly limited, and any of bulk polymerization, solution polymerization, emulsion polymerization, suspension polymerization and the like can be used.

（ｃ）３価以上の多価カルボン酸、その低級アルキルエステル、酸無水物、３価以上の多価アルコールの何れかから選ばれる少なくとも一種
（ｄ）エポキシ樹脂
（ｅ）２価フェノールのアルキレンオキサイド付加物又はそのグリシジルエーテル
（ｆ）エポキシ基と反応する活性水素を分子中に１個有する化合物
（ｇ）エポキシ基と反応する活性水素を分子中に２個以上有する化合物 Various types of polyester resins can be used. In particular, it is preferable to use those obtained by mixing the following (a) to (g).
(A) at least one selected from divalent carboxylic acids, lower alkyl esters thereof, and acid anhydrides (b) a diol component represented by the chemical formula

(C) at least one selected from trivalent or higher polyvalent carboxylic acids, lower alkyl esters thereof, acid anhydrides and trivalent or higher polyhydric alcohols (d) epoxy resins (e) alkylene oxides of dihydric phenols Adduct or its glycidyl ether (f) Compound having 1 active hydrogen in the molecule reacting with epoxy group (g) Compound having 2 or more active hydrogen in the molecule reacting with epoxy group

  Examples of (a) include terephthalic acid, isophthalic acid, sebacic acid, isodecyl succinic acid, maleic acid, fumaric acid, monomethyl, monoethyl, dimethyl, diethyl ester, phthalic anhydride, maleic anhydride, etc. . In particular, terephthalic acid, isophthalic acid, and dimethyl esters thereof are preferable in terms of blocking resistance and cost. These divalent carboxylic acids, their lower alkyl esters, and acid anhydrides greatly affect the fixability and blocking resistance of the toner. Although depending on the degree of condensation, if a large amount of aromatic terephthalic acid, isophthalic acid or the like is used, the blocking resistance is improved, but the fixing property is lowered. Conversely, if a large amount of sebacic acid, isodecyl succinic acid, maleic acid, fumaric acid or the like is used, the fixing property is improved, but the blocking resistance is lowered. Therefore, it is desirable to select these divalent carboxylic acids as appropriate according to other monomer composition, ratio and degree of condensation, and use them alone or in combination.

  Examples of the above (b) include polyoxypropylene- (n) -polyoxyethylene- (n ′)-2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (n) -2,2 -Bis (4-hydroxyphenyl) propane, polyoxyethylene- (n) -2,2-bis (4-hydroxyphenyl) propane and the like. In particular, polyoxypropylene- (n) -2,2-bis (4-hydroxyphenyl) propane satisfying 2.1 ≦ n ≦ 2.5, polyoxyethylene- (2.0 ≦ n ≦ 2.5) n) -2,2-bis (4-hydroxyphenyl) propane is preferred. Such a diol component has the advantage of improving the glass transition temperature and making it easier to control the reaction. In addition, it is also possible to use aliphatic diols such as ethylene glycol, diethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, neopentyl glycol, propylene glycol as the diol component. is there.

Examples of the trivalent or higher polyvalent carboxylic acid, its lower alkyl ester and acid anhydride in the above (c) include 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,3,5-benzenetricarboxylic acid. Acid, 1,2,4-cyclohexanetricarboxylic acid, 2,5,7-naphthylenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexa Tricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra (methylenecarboxy) methane, 1,2,7,8-octanetetracarboxylic acid, emporic trimer acid and their monomethyl, Examples include monoethyl, dimethyl, and diethyl ester.
Examples of the trihydric or higher polyhydric alcohol in the above (c) include sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose 1,2,4-butanetriol, 1,2,5-pentatriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane 1,3,5-trihydroxymethylbenzene and the like. The blending ratio of the trivalent or higher polyvalent monomer is suitably about 1 to 30 [mol%] of the whole monomer composition. This is because when it is less than 1 [mol%], the offset resistance of the toner is lowered and the durability is easily deteriorated. Further, if it exceeds 30 [mol%], the toner fixing property tends to deteriorate.
As for the above-described trivalent or higher polyvalent monomers, benzenetricarboxylic acids such as benzenetricarboxylic acid, anhydrides and esters of these acids are particularly preferable. When benzenetricarboxylic acids are used, both fixability and offset resistance can be achieved.
As the above-mentioned polyol resin, various types can be used, and it is particularly preferable to use those obtained by reacting the substances listed below.

  As said (d) epoxy resin, what was obtained by couple | bonding bisphenol, such as bisphenol A and bisphenol F, and epichlorohydrin is good. In particular, in order to obtain stable fixing characteristics and gloss, the epoxy resin is at least two or more bisphenol A type epoxy resins having different number average molecular weights, the low molecular weight component has a number average molecular weight of 360 to 2000, and a high molecular weight component. The number average molecular weight is preferably 3000 to 10,000. Further, it is preferable that the low molecular weight component is 20 to 50% by weight and the high molecular weight component is 5 to 40% by weight. When there are too many low molecular weight components, or when the molecular weight is lower than 360, there is a possibility that the gloss will be too high or the storage stability may be deteriorated. Further, when the amount of the high molecular weight component is too large, or when the molecular weight is higher than 10,000, the gloss may be insufficient or the fixability may be deteriorated.

上述した２価フェノールのアルキレンオキサイド付加物もしくはそのグリシジルエーテルについては、ポリオール樹脂に対して１０〜４０［重量％］の範囲で含有せしめることが好ましい。これよりも量が少ないとカールが増すなどの不具合が生ずるからである。また、ｎ＋ｍが７以上であったり量が多すぎたりすると、光沢が出すぎたり、さらには保存性の悪化の可能性があるからである。 As the alkylene oxide adduct of dihydric phenol in (e) above, for example, the following can be used. That is, it is a reaction product of ethylene oxide, propylene oxide, butylene oxide, or a mixture thereof and a bisphenol such as bisphenol A or bisphenol F. The resulting adduct may be used after glycidylation with epichlorohydrin, β-methylepichlorohydrin, or the like. In particular, diglycidyl ether of an alkylene oxide adduct of bisphenol A represented by the following chemical formula is preferred.

About the alkylene oxide adduct of the dihydric phenol mentioned above or its glycidyl ether, it is preferable to make it contain in the range of 10-40 [weight%] with respect to polyol resin. This is because if the amount is less than this, problems such as an increase in curl occur. Further, if n + m is 7 or more or too much, there is a possibility of excessive glossiness and further deterioration in storage stability.

  As the compound (f), monohydric phenols, secondary amines, carboxylic acids and the like can be used. Among these, the following are mentioned as monohydric phenols. That is, phenol, cresol, isopropylphenol, aminophenol, nonylphenol, dodecylphenol, xylenol, p-cumylphenol and the like. Secondary amines include diethylamine, dipropylamine, dibutylamine, N-methyl (ethyl) piperazine, piperidine and the like. Examples of carboxylic acids include propionic acid and caproic acid.

Examples of the compound (g) include dihydric phenols, polyhydric phenols, and polycarboxylic acids. Among these, examples of the dihydric phenols include bisphenols such as bisphenol A and bisphenol F. Examples of the polyhydric phenols include orthocresol novolacs, phenol novolacs, tris (4-hydroxyphenyl) methane, and 1- [α-methyl-α- (4-hydroxyphenyl) ethyl] benzene. Examples of polyvalent carboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, terephthalic acid, trimellitic acid, and trimellitic anhydride.
About the polyester resin and polyol resin mentioned above, if a high crosslinking density is given, it will become difficult to obtain transparency and glossiness. For this reason, it is preferable to provide non-crosslinking or weak crosslinking (THF insoluble content is 5% or less).

  Conventionally known dyes and pigments can be used as the colorant to be contained in the toner. Examples of yellow colorants include naphthol yellow S, Hansa yellow (10G, 5G, G), cadmium yellow, yellow iron oxide, ocher, yellow lead, titanium yellow, polyazo yellow, oil yellow, Hansa yellow, (GR , A, RN, R), Pigment Yellow L, Benzidine Yellow (G, GR), Permanent Yellow (NCG), Vulcan Fast Yellow (5G, R), Tartrazine Lake, Quinoline Yellow Lake, Anthrazan Yellow BGL, Benzimidazo Long yellow, isoindolinone yellow, etc. are mentioned. Also, red colorants include Bengala, Pangdan, Lead Zhu, Cadmium Red, Cadmium Mercury Red, Antimony Zhu, Permanent Red 4R, Para Red, Fire Red, Parachloro Ortho Nitroaniline Red, Resol Fast Scarlet. G, Brilliant Fast Scarlet, Brilliant Carmine BS, Permanent Red (F2R, F4R, FRL, FRLL, F4RH), Fast Scarlet VD, Belkan Fast Rubin B, Brilliant Scarlet G, Resol Rubin GX, Permanent Red (F5R, FBB), Brilliant Carmine 6B, Pigment Scarlet 3B, Bordeaux 5B, Toluidine Maroon, Permanent Bordeaux F2K, Helio Bordeaux BL, Bordeaux 10B, Bon Maroon Ito, Bon Maroon Medium, Eosin Lake, Rhodamine Lake B, Rhodamine Lake Y, Alizarin Lake, Thioindigo Red B, Thioindigo Maroon, Oil Red, Quinacridone Red, Pyrazolone Red, Polyazo Red, Chrome Vermilion, Benzidine Orange, Perinone Examples include orange and oil orange. Blue colorants include cobalt blue, cerulean blue, alkaline blue rake, peacock blue rake, Victoria blue rake, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue, indanthrene blue (RS, BC), indigo , Ultramarine, bitumen, anthraquinone blue, fast violet B, methyl violet lake, cobalt violet, manganese violet, dioxane violet, anthraquinone violet, chrome green, zinc green, chromium oxide, pyridiane, emerald green, pigment green B, naphthol green B, Examples include green gold, acid green lake, malachite green lake, phthalocyanine green, and anthraquinone green. Examples of black colorants include azine dyes such as carbon black, oil furnace black, channel black, lamp black, acetylene black, and aniline black, metal salt azo dyes, metal oxides, and composite metal oxides. . Examples of other colorants include titania, zinc white, litbon, nigrosine dye, and iron black. Any colorant can be used alone or in combination of two or more. About the content rate, normally 1-30 weight part with respect to 100 weight part of binder resin, Preferably 3-20 weight part is good.

  If necessary, a charge control agent or the like may be added to the toner. As such a charge control agent, conventionally known charge control agents can be used. For example, nigrosine dye, chromium-containing complex, quaternary ammonium salt and the like. These are properly used according to the polarity of the toner particles. In particular, in the case of a color toner, a colorless or light-colored toner that does not affect the color tone of the toner is preferable. For example, a salicylic acid metal salt or a metal salt of a salicylic acid derivative (Bontron E84, manufactured by Orient) is preferable. The charge control agents exemplified so far can be used alone or in combination of two or more. About the content rate, 0.5-8 weight part with respect to 100 weight part of binder resin, Preferably 1-5 weight part is good.

As a toner production method, a pulverization method, a polymerization method, a capsule method, and the like are known. An example of the grinding method is as follows.
(1) A binder resin, a colorant, a charge control agent, a release accelerator, a magnetic material, and the like are sufficiently mixed by a mixer such as a Henschel mixer.
(2) The mixture is sufficiently kneaded by a batch type two roll, a Banbury mixer, a continuous twin screw extruder, a continuous single screw kneader or the like. As continuous twin screw extruders, KTK type twin screw extruder manufactured by Kobe Steel, TEM type twin screw extruder manufactured by Toshiba Machine Co., Ltd. A KEX type twin screw extruder manufactured by Kurimoto Iron Works Co., Ltd. is known. Further, as a continuous type single-screw kneader, a bushing co-kneader or the like is known.
(3) The kneaded product is cooled, coarsely pulverized using a hammer mill or the like, and further pulverized by a fine pulverizer or a mechanical pulverizer using a jet stream. And it classifies to a predetermined particle size with a classifier using a swirling airflow or a classifier using the Coanda effect to obtain base particles.

An example of the polymerization method will be described as follows.
(1) A polymerizable monomer, a polymerization initiator (if necessary), a colorant and the like are granulated in an aqueous dispersion medium.
(2) The granulated monomer composition particles are classified to an appropriate particle size.
(3) The monomer composition particles having a prescribed inner particle diameter obtained by this classification are subjected to a polymerization reaction.
(4) After removing the dispersant by appropriate treatment, the polymerization product obtained by the polymerization reaction is filtered, washed with water and dried to obtain base particles.

An example of the capsule method is as follows.
(1) A resin, a colorant, and the like are kneaded with a kneader or the like to obtain a molten toner core material.
(2) The toner core material is placed in water and stirred vigorously to form a fine particle core material.
(3) The above core material fine particles are put in a shell material solution, and a poor solvent is dropped while stirring, and the surface of the core material is covered with the shell material and encapsulated.
(4) The capsules thus obtained are filtered and then dried to obtain base particles.

  Other additives different from the above-described additives may be added to the toner. Examples of such other additives include Teflon (registered trademark) that functions as a lubricant, zinc stearate, polyvinylidene fluoride, and the like. Further, cerium oxide, silicon carbide, strontium titanate and the like that function as an abrasive may be mentioned. In addition, zinc oxide, antimony oxide, tin oxide, and the like that function as a conductivity imparting material can be given.

Conventionally known magnetic carriers can be used as the magnetic carrier used in the developer. For example, magnetic powder such as iron powder, ferrite powder, nickel powder, glass beads, and the like. It is desirable to form a protective layer by covering these surfaces with a resin or the like.
Examples of the resin used for the protective layer include polyfluorocarbon, polyvinyl chloride, polyvinylidene chloride, phenol resin, polyvinyl acetal, acrylic resin, and silicone resin. Examples of the method for forming the protective layer include a method in which a resin is applied to the surface of the magnetic carrier by means such as spraying or dipping. About the usage-amount of resin, it is preferable to set it as 1-10 weight part with respect to 100 weight part of magnetic carriers. The thickness of the protective layer is preferably 0.02 to 2 [μm], particularly preferably 0.05 to 1 [μm], and more preferably 0.1 to 0.6 [μm]. . When the film thickness is thick, the fluidity of the carrier and the developer tends to decrease, and when the film thickness is thin, the film tends to be easily affected by film scraping over time.

  It is desirable to use a magnetic carrier having a weight average particle diameter of 20 to 60 [μm]. The mixing ratio of the toner and the magnetic carrier is suitably about 0.5 to 7.0 parts by weight of the toner with respect to 100 parts by weight of the magnetic carrier.

Magnetic carriers include metals such as iron, nickel and cobalt, alloys of these and other metals, magnetite, γ-hematite, chromium dioxide, copper zinc ferrite, manganese zinc ferrite and other oxides, manganese-copper-aluminum, etc. Ferromagnetic particles such as Heusler alloys can be used. The ferromagnetic particles may be coated with a resin such as styrene-acrylic, silicone, or fluorine. The material of the ferromagnetic material is desirably selected as appropriate in consideration of the charging property with the toner containing the release accelerator. In addition, a charge control agent, a conductive substance, or the like may be added to the resin that coats the ferromagnetic particles. Moreover, what disperse | distributed these magnetic body particles in resin, such as a styrene-acrylic type and a polyester type, may be used. The intensity of saturation magnetization of the ferromagnetic material is preferably 40 × 4π × 10 ^{−4 to} 90 × 4π × 10 ⁻⁴ [A / m] (40 to 90 [emu / g]). If it is less than 40 × 4π × 10 ⁻⁴ [A / m] (45 [emu / g]), the transportability is lowered due to the weak saturation magnetization, and the carrier adheres to the photoconductor. Because. On the other hand, if it exceeds 90 × 4π × 10 ⁻⁴ [A / m] (90 [emu / g]), the magnetic brush and scavenging effect become strong due to the strength of saturation magnetization, and the halftone portion This is because scavenging marks are generated and image quality is lowered.

An example of a method for manufacturing a magnetic carrier will be described as follows. That is, first, materials to be listed next are prepared.
-Core material: Cu-Zn ferrite particles (weight average diameter: 35 [μm]) 5000 parts by weight-Coating material: 450 parts by weight of toluene Silicone resin SR2400 (manufactured by Toray Dow Corning Silicone, nonvolatile content 50%) 450 parts by weight Aminosilane SH6020 (Toray Dow Corning / Silicone) 10 parts by weight Carbon black 10 parts by weight

  The mixture composed of toluene and the like listed above is stirred with a stirrer for 10 minutes to obtain a coating material. The coating material is put into a coating apparatus that sprays while forming a swirling flow in a fluidized bed provided with a rotating bottom plate disk and a stirring blade, and is applied to the core material. The obtained particles are baked in an electric furnace at 250 [° C.] for 2 hours to obtain a magnetic carrier on which a coat film having a thickness of about 0.5 [μm] is formed.

Next, the configuration of the photoreceptor in the present embodiment will be described.
FIG. 5 is an enlarged sectional view showing the photosensitive layer of the photoreceptor. Since the configuration of each device in each process cartridge is the same as described above, the following description will be made with the symbols Y, M, C, and K omitted.
In the figure, the photoreceptor 40 has a photosensitive layer coated on a conductive support (not shown). This photosensitive layer is composed of a charge generation layer 40a, a charge transport layer 40b, and a filler-reinforced charge transport layer 40c coated thereon, from the conductive support side to the surface side.

As the conductive support, for example, a conductive material having a volume resistivity of 10 ¹⁰ [Ω · cm] or less coated on a film or cylindrical plastic or paper by vapor deposition or sputtering can be used. . Examples of the conductive material to be coated include metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, and platinum, and metal oxides such as tin oxide and indium oxide. Also, instead of coating the conductive material, a metal plate made of aluminum, aluminum alloy, nickel, stainless steel, etc. is formed into a cylindrical shape by a method such as extrusion or drawing, and then a surface such as cutting, superfinishing, polishing, etc. You may use the pipe | tube which performed the process. In this copying machine, a drum-shaped photosensitive member is used. However, when a belt-shaped photosensitive member is used, an endless nickel belt disclosed in Japanese Patent Laid-Open No. 52-36016 is used as a conductive support. An endless stainless steel belt can also be used. In addition to this, a conductive powder dispersed in a suitable binder resin on a support made of plastic or paper may be used. In this case, examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc and silver, or metal oxide powder such as conductive tin oxide. It is done. The binder resin used simultaneously is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, Thermoplastic, thermosetting resin or photo-curing resin such as melamine resin, urethane resin, phenol resin, alkyd resin and the like can be mentioned. The conductive layer formed on the support can be provided by dispersing and applying these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, toluene and the like. In addition, a conductive layer is provided on a suitable cylindrical substrate by a heat-shrinkable tube containing the conductive powder in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, and Teflon. Can also be used as a conductive support.

  The charge generation layer 40a of the photosensitive layer is mainly composed of a charge generation material, a solvent, and a binder resin. If necessary, a binder resin may be contained. Further, any additive such as a sensitizer, a dispersant, a surfactant, and silicone oil may be contained. Either an inorganic material or an organic material can be used as the charge generation material. Among these, examples of inorganic materials include crystalline selenium, amorphous selenium, selenium-tellurium, selenium-tellurium-halogen, selenium-arsenic compounds, and amorphous silicon. As amorphous silicon, dangling bonds that are terminated with hydrogen atoms or halogen atoms, or those that are doped with boron atoms or phosphorous atoms are preferably used. On the other hand, organic materials include metal phthalocyanine, metal-free phthalocyanine and other phthalocyanine pigments, azulenium salt pigments, squaric acid methine pigments, azo pigments having a carbazole skeleton, azo pigments having a triphenylamine skeleton, and diphenylamine skeletons. Azo pigments, azo pigments having a dibenzothiophene skeleton, azo pigments having a fluorenone skeleton, azo pigments having an oxadiazole skeleton, azo pigments having a bis-stilbene skeleton, azo pigments having a distyryl oxadiazole skeleton, distyrylcarbazole skeleton Azo pigments, perylene pigments, anthraquinone or polycyclic quinone pigments, quinoneimine pigments, diphenylmethane and triphenylmethane pigments, benzoquinone and naphthoquinone pigments, cyanine and Methine pigments, indigoid pigments, and bisbenzimidazole pigments. These charge generation materials can be used alone or as a mixture of two or more.

  Examples of the binder resin that can be included in the charge generation layer 40a as necessary include polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, polyarylate, silicone resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, Poly-N-vinylcarbazole, polyacrylamide and the like can be mentioned. These binder resins can be used alone or as a mixture of two or more. A polymer charge transport material can also be used as the binder resin. Furthermore, you may add a low molecular charge transport material as needed. Such low molecular charge transport materials include electron transport materials and hole transport materials, and these include further low molecular charge transport materials and high molecular charge transport materials. Hereinafter, the polymer type charge transport material is referred to as a polymer charge transport material.

  Examples of the electron transporting material include chloranil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron accepting substances such as nitrodibenzothiophene-5,5-dioxide. These electron transport materials can be used alone or as a mixture of two or more.

  Examples of the hole transport material include oxazole derivatives, oxadiazole derivatives, imidazole derivatives, triphenylamine derivatives, 9- (p-diethylaminostyrylanthracene), 1,1-bis- (4-dibenzylaminophenyl) propane, Examples include styryl anthracene, styryl pyrazoline, phenylhydrazones, α-phenyl stilbene derivatives, thiazole derivatives, triazole derivatives, phenazine derivatives, acridine derivatives, benzofuran derivatives, benzimidazole derivatives, and thiophene derivatives. These hole transport materials can be used alone or as a mixture of two or more. In addition, the following polymer charge transport materials can be used. A polymer having a carbazole ring such as poly-N-vinylcarbazole, a polymer having a hydrazone structure exemplified in JP-A-57-78402, and a polysilylene heavy exemplified in JP-A-63-285552 A polymer having a triarylamine structure exemplified in JP-A-7-325409. These polymer charge transport materials can be used alone or as a mixture of two or more.

Known methods for forming the charge generation layer 40a include a vacuum thin film fabrication method and a casting method from a solution dispersion system. For the former method, vacuum deposition method, glow discharge decomposition method, ion plating method, sputtering method, reactive sputtering method, CVD method, etc. are used, and the above-mentioned inorganic materials and organic materials should be formed satisfactorily. Can do. Further, in order to provide the charge generation layer by the casting method, it can be formed as follows. That is, the inorganic or organic charge generating material described above is dispersed by a ball mill, attritor, sand mill or the like using a solvent such as tetrahydrofuran, cyclohexanone, dioxane, dichloroethane, or butanone together with a binder resin as necessary. Then, the dispersion is appropriately diluted and applied. For this application, a dip coating method, a spray coating method, a bead coating method, or the like may be used.
The thickness of the charge generation layer 40a provided as described above is suitably about 0.01 to 5 [μm], preferably 0.05 to 2 [μm].

  The charge transport layer 40b can be formed by dissolving or dispersing a mixture or copolymer mainly composed of a charge transport component and a binder component in an appropriate solvent, and applying and drying the mixture. The film thickness is suitably about 5 to 50 [μm], and about 5 to 30 [μm] is appropriate when resolving power is required.

  Examples of the binder component used for the charge transport layer 40b include the following polymer compounds. That is, polystyrene, styrene / acrylonitrile copolymer, styrene / butadiene copolymer, styrene / maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride / vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, Thermoplastics such as polyarylate resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, acrylic resin, silicone resin, fluororesin, epoxy resin, melamine resin, urethane resin, phenol resin, alkyd resin, or For example, a thermosetting resin. These polymer compounds can be used alone or as a mixture of two or more kinds, or can be used after being copolymerized with a charge transport material.

  Examples of the material that can be used as the charge transport material include the above-described low molecular electron transport materials, hole transport materials, and polymer charge transport materials. Moreover, it is also possible to add an appropriate antioxidant, a plasticizer, a lubricant, a UV absorber, a low molecular compound such as a low molecular charge transport material, or a leveling agent as necessary. When a low molecular charge transport material is used, the amount used is 20 to 200 parts by weight, preferably about 50 to 100 parts by weight per 100 parts by weight of the polymer compound. When a polymer charge transport material is used, a material in which the resin component is copolymerized at a ratio of about 0 to 500 parts by weight with respect to 100 parts by weight of the charge transport component is preferably used.

  Dispersing solvents that can be used in preparing the charge transport layer coating solution include ketones such as methyl ethyl ketone, acetone, methyl isobutyl ketone, and cyclohexanone, ethers such as dioxane, tetrahydrofuran, and ethyl cellosolve, and aromatics such as toluene and xylene. Group, halogens such as chlorobenzene and dichloromethane, and esters such as ethyl acetate and butyl acetate. These compounds can be used alone or as a mixture of two or more. The amount of the low molecular compound used is 0.1 to 200 parts by weight, preferably 0.1 to 30 parts by weight based on 100 parts by weight of the polymer compound, and the amount of the leveling agent used is 100 parts by weight of the polymer compound. On the other hand, about 0.001 to 5 parts by weight is appropriate.

  The filler-reinforced charge transport layer 40c includes at least a charge transport component, a binder resin component, and a filler, and has both charge transport properties and mechanical resistance. It also functions as a surface layer in which the above charge transport layer is functionally separated into two or more layers.

  Examples of the filler material used for the filler-reinforced charge transport layer 40c include inorganic materials, silica, titanium oxide, and alumina. Two or more of these may be mixed and used. In order to improve the dispersibility in the coating liquid and the coating film, the filler surface may be modified with a surface treatment agent. The filler material can be dispersed by a suitable disperser in a solvent mixed with a charge transport material or a binder resin. The average primary particle diameter of the filler material is preferably 0.01 to 0.8 [μm] from the viewpoint of the transmittance and wear resistance of the charge transport layer. As a coating method of the solution in which the filler material is dispersed, a dipping method, a spray coating method, a ring coating method, a roll coater method, a gravure coating method, a nozzle coating method, a screen printing method, or the like can be used. The film thickness of the filler-reinforced charge transport layer 40c is preferably 0.5 [μm] or more, more preferably 2 [μm] or more.

An undercoat layer may be provided between the conductive support and the photosensitive layer. This undercoat layer generally contains a resin as a main component. With regard to this resin, it is desirable to use a resin having high solvent resistance with respect to a general organic solvent, considering that the resin is applied to the charge transport layer 40b in a state of dispersion dispersed in a solvent. Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, epoxy resin, and the like. And a curable resin that forms a three-dimensional network structure.
To the undercoat layer, a fine powder pigment of a metal oxide such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, or indium oxide may be added in order to suppress moire and reduce the residual potential. Moreover, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, etc. can also be used. In addition, and those provided with Al2O3 at anodic oxidation, organic materials such as polyparaxylylene (parylene) or provided _{SiO 2, SnO 2, TiO 2} , ITO, an inorganic material such as CeO ₂ by a vacuum thin-film forming method Can also be used. The thickness of the undercoat layer is suitably larger than 0 [μm] and not more than 20 [μm], preferably 1 to 10 [μm].

Each layer described so far has an antioxidant, a plasticizer, a lubricant, an ultraviolet absorber, a low molecular charge transport material, in order to improve the environmental resistance, in order to prevent a decrease in sensitivity and an increase in residual potential, A leveling agent may be added.
The following can be illustrated as antioxidant which can be added to each layer.
(A) Phenol compound 2,6-di-t-butyl-p-cresol, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, n-octadecyl-3- (4′- Hydroxy-3 ′, 5′-di-tert-butylphenol), 2,2′-methylene-bis- (4-methyl-6-tert-butylphenol), 2,2′-methylene-bis- (4-ethyl-) 6-t-butylphenol), 4,4′-thiobis- (3-methyl-6-tert-butylphenol), 4,4′-butylidenebis- (3-methyl-6-tert-butylphenol), 1,1,3 -Tris- (2-methyl-4-hydroxy-5-t-butylphenyl) butane, 1,3,5-trimethyl-2,4,6-tris (3,5-di-t-butyl-4-hydroxy Benzyl) benzene, te Lakis- [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, bis [3,3′-bis (4′-hydroxy-3′-t-butyl) Phenyl) butyric acid] cricol ester, tocopherols and the like.
(B) Paraphenylenediamines N-phenyl-N′-isopropyl-p-phenylenediamine, N, N′-di-sec-butyl-p-phenylenediamine, N-phenyl-N-sec-butyl-p-phenylene Diamine, N, N′-di-isopropyl-p-phenylenediamine, N, N′-dimethyl-N, N′-di-t-butyl-p-phenylenediamine and the like.
(C) Hydroquinones 2,5-di-t-octylhydroquinone, 2,6-didodecylhydroquinone, 2-dodecylhydroquinone, 2-dodecyl-5-chlorohydroquinone, 2-t-octyl-5-methylhydroquinone, 2 -(2-octadecenyl) -5-methylhydroquinone and the like.
(D) Organic sulfur compounds Dilauryl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, ditetradecyl-3,3′-thiodipropionate, and the like.
(E) Organic phosphorus compounds Triphenylphosphine, tri (nonylphenyl) phosphine, tri (dinonylphenyl) phosphine, tricresylphosphine, tri (2,4-dibutylphenoxy) phosphine and the like.

The following can be illustrated as a plasticizer which can be added to each layer.
(A) Phosphate ester plasticizer Triphenyl phosphate, tricresyl phosphate, trioctyl phosphate, octyl diphenyl phosphate, trichloroethyl phosphate, cresyl diphenyl phosphate, tributyl phosphate, tri-2-ethylhexyl phosphate, Triphenyl phosphate etc.
(B) Phthalate ester plasticizers Dimethyl phthalate, diethyl phthalate, diisobutyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, diisooctyl phthalate, di-n-octyl phthalate, phthalate Dinonyl acid, diisononyl phthalate, diisodecyl phthalate, diundecyl phthalate, ditridecyl phthalate, dicyclohexyl phthalate, butyl benzyl phthalate, butyl lauryl phthalate, methyl oleyl phthalate, octyl decyl phthalate, dibutyl fumarate, dioctyl fumarate Such.
(C) Aromatic carboxylic acid ester plasticizers Trioctyl trimellitic acid, tri-n-octyl trimellitic acid, octyl oxybenzoate, and the like.
(D) Aliphatic dibasic ester plasticizer dibutyl adipate, di-n-hexyl adipate, di-2-ethylhexyl adipate, di-n-octyl adipate, adipic acid n-octyl-n-decyl , Diisodecyl adipate, dicapryl adipate, di-2-ethylhexyl azelate, dimethyl sebacate, diethyl sebacate, dibutyl sebacate, di-n-octyl sebacate, di-2-ethylhexyl sebacate, di-2 sebacate -Ethoxyethyl, dioctyl succinate, diisodecyl succinate, dioctyl tetrahydrophthalate, di-n-octyl tetrahydrophthalate and the like.
(E) Fatty acid ester derivatives butyl oleate, glycerin monooleate, methyl acetylricinoleate, pentaerythritol ester, dipentaerythritol hexaester, triacetin, tributyrin and the like.
(F) Oxyacid ester plasticizers Methyl acetyl ricinoleate, butyl acetyl ricinoleate, butyl phthalyl butyl glycolate, tributyl acetyl citrate and the like.
(G) Epoxy plasticizer Epoxidized soybean oil, epoxidized linseed oil, butyl epoxy stearate, decyl epoxy stearate, octyl epoxy stearate, benzyl epoxy stearate, dioctyl epoxy hexahydrophthalate, didecyl epoxy hexahydrophthalate, etc. .
(H) Dihydric alcohol ester plasticizers such as diethylene glycol dibenzoate and triethylene glycol di-2-ethylbutyrate.
(I) Chlorinated plasticizer Chlorinated paraffin, chlorinated diphenyl, chlorinated fatty acid methyl, methoxychlorinated fatty acid methyl and the like.
(J) Polyester plasticizer Polypropylene adipate, polypropylene sebacate, polyester, acetylated polyester and the like.
(K) Sulfonic acid derivatives p-toluenesulfonamide, o-toluenesulfonamide, p-toluenesulfoneethylamide, o-toluenesulfoneethylamide, toluenesulfone-N-ethylamide, p-toluenesulfone-N-cyclohexylamide and the like.
(L) Citric acid derivatives Triethyl citrate, triethyl acetylcitrate, tributyl citrate, tributyl acetylcitrate, tri-2-ethylhexyl acetylcitrate, acetylcitrate-n-octyldecyl, and the like.
(M) Others Terphenyl, partially hydrogenated terphenyl, camphor, 2-nitrodiphenyl, dinonylnaphthalene, methyl abietate and the like.

The following can be illustrated as a lubricant which can be added to each layer.
(A) Hydrocarbon compounds Liquid paraffin, paraffin wax, microwax, low-polymerized polyethylene and the like.
(B) Fatty acid compounds Lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid and the like.
(C) Fatty acid amide compounds Stearylamide, palmitylamide, oleinamide, methylenebisstearamide, ethylenebisstearamide and the like.
(D) Ester compounds Lower alcohol esters of fatty acids, polyhydric alcohol esters of fatty acids, fatty acid polyglycol esters, and the like.
(E) Alcohol compounds Cetyl alcohol, stearyl alcohol, ethylene glycol, polyethylene glycol, polyglycerol and the like.
(F) Metal soap Lead stearate, cadmium stearate, barium stearate, calcium stearate, zinc stearate, magnesium stearate and the like.
(G) Natural wax Carnauba wax, candelilla wax, beeswax, whale wax, ivotaro, montan wax and the like.
(H) Others Silicone compounds, fluorine compounds, etc.

The following can be illustrated as a ultraviolet absorber which can be added to each layer.
(A) Benzophenone series 2-hydroxybenzophenone, 2,4-dihydroxybenzophenone, 2,2 ′, 4-trihydroxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2,2′-dihydroxy-4- Such as methoxybenzophenone.
(B) Salsylates Phenyl salsylates, 2,4 di-t-butylphenyl 3,5-di-t-butyl 4-hydroxybenzoate, and the like.
(C) Benzotriazole series (2′-hydroxyphenyl) benzotriazole, (2′-hydroxy5′-methylphenyl) benzotriazole, (2′-hydroxy5′-methylphenyl) benzotriazole, (2′-hydroxy3) '-Tertiarybutyl 5'-methylphenyl) 5-chlorobenzotriazole (d) cyanoacrylate type ethyl-2-cyano-3,3-diphenyl acrylate, methyl 2-carbomethoxy 3 (paramethoxy) acrylate, and the like.
(E) Quencher (metal complex)
Nickel (2,2′thiobis (4-t-octyl) phenolate) normal butylamine, nickel dibutyldithiocarbamate, nickel dibutyldithiocarbamate, cobalt dicyclohexyldithiophosphate and the like.
(F) HALS (hindered amine)
Bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 1- [2- [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6 6-tetramethylpyridine, 8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,3,8-triazaspiro [4,5] undecane-2,4-dione, 4-benzoyloxy- 2,2,6,6-tetramethylpiperidine and the like.

  As shown in FIG. 3, the copying machine according to the present embodiment includes a developing bias power source (not shown) as a voltage applying unit that applies a developing bias to the developing sleeve 65 of the developing device 61. Further, a charging bias power source (not shown) as charging bias applying means for applying a charging bias to a charging roller as a rotating charging member of the charger 60 is also provided. Among these power sources, the development bias power source is configured to supply the developing sleeve 65 with a DC developing bias consisting of only a DC component. On the other hand, the charging bias power source is configured to supply an AC charging bias including at least an AC component to the charging roller. This copier employs a combination of AC charging and DC developing. In such a configuration, as shown in FIG. 1, deterioration of the photoreceptor 40 due to film scraping of the filler-reinforced charge transport layer 40c can be suppressed.

Next, it is a characteristic part of the present invention. A configuration and operation for suppressing a hat image will be described.
In the present embodiment, the developing sleeve 65 and the photosensitive member 40 are driven in the rotational direction, and the linear velocity of the developing sleeve 65 is set to be higher than the linear velocity of the photosensitive member 40. The developer on the sleeve 65 passes over the surface of the photoreceptor 40. In such a situation, a situation occurs in which the developer that has passed through the image portion faces a non-image portion adjacent to the image portion on the front end side. In this case, the developer tip portion faces the non-image portion while the charge that has moved to the developer tip portion while passing through the image portion is held in the developer tip portion. Thereby, the electric field formed in the non-image part changes according to the charge amount of the developer tip.

FIG. 6 is a graph showing the relationship between the electric field formed when the developer tip portion faces the non-image portion and the charge amount of the developer tip portion.
As shown in FIG. 6, if the charge amount of the developer tip facing the non-image portion is equal to or less than a predetermined value Q ₀ , the electric field formed in the non-image portion is in the direction in which the toner moves toward the developing sleeve 65. An electric field (hereinafter referred to as “reverse development direction electric field”). In this case, the toner adhering to the developer tip does not move to the non-image portion. However, when the charge amount of the developer tip facing the non-image part exceeds the predetermined value Q ₀ , the electric field formed in the non-image part becomes a development direction electric field, and the toner attached to the developer tip part is It moves to the non-image part. As a result, the toner that becomes a hat image adheres to the non-image portion, and a hat image is generated. Therefore, in order to prevent the generation of a hat image, it is important how to reduce the charge amount of the developer tip that has passed through the image portion to a predetermined value Q ₀ or less.

FIG. 7 shows the change in the charge amount of the developer when the developer moves from the image area to the non-image area.
The developer facing the image portion of the photoconductor 40 is subjected to a developing direction electric field in the direction in which the toner is directed to the photoconductor 40. As a result, as shown in FIG. The electric charge moves. As the resistance of the magnetic carrier is lower, or as the time during which the developer tip is opposed to the image portion is longer, more charges move to the developer tip. The charge amount Q [C / m ² ] moved at this time is such that the volume resistivity of the magnetic carrier is ρ [Ω · m], the dielectric constant of the magnetic carrier is ε [F / m], and the photosensitive member 40 and the development When the distance from the sleeve 65 (development gap) is d [m], the development potential is V1 [V], and the developer tip is the time t [sec] facing the image area, the following formula 2 is shown. It can be obtained from the formula.

From the relationship between the charge amount of the developer tip and the electric field formed in the non-image portion, the condition for preventing the electric field formed in the non-image portion from becoming the developing direction electric field is as shown in the following Equation 3. is there. The maximum value of the time t when the developer tip is facing the image portion is the time T [sec] when the developer tip is in contact with the photoconductor 40. This time T is the time when the developer is on the photoconductor. 40 is obtained from a value (Nip / Vr) obtained by dividing the length Nip [m] in the moving direction of the photosensitive member surface contacting 40 by the linear velocity Vr [m / sec] of the developing sleeve 65. Here, the value of Nip / Vr was used as the time t during which the developer tip portion faces the image portion.

Considering that the charge at the developer tip facing the non-image portion moves to the developing sleeve 65 side by the electric field in the reverse development direction, the following equation (4) is obtained from the equation (3). It is done. That is, if the expression shown in the following equation 4 is satisfied, a developing direction electric field is formed between the developer tip portion and the non-image portion when the developer tip portion that has passed through the image portion faces the non-image portion. It will not be done. This result applies not only to the forward development method but also to the counter development method.

  Here, the length of the non-image portion adjacent to the image portion on the front end side in the moving direction A of the photoconductor surface is the movement of the photoconductor surface in the region where the edge effect occurs at the boundary between the image portion and the non-image portion. When it is less than δ [m] which is 1 / e of the length in the direction A, a strong reverse electric field is formed in the entire non-image area due to the edge effect. For this reason, even if the exposure amount of the image region tip region is a normal exposure amount, a developing direction electric field is not formed between the non-image portion and the developer tip, and a hat image is not generated. . Therefore, when the length of the non-image portion adjacent to the front end side with respect to the image portion in the photosensitive member surface movement direction A is less than δ [m], it is not necessary to control the exposure amount. However, when the length of the non-image portion adjacent to the leading end side with respect to the image portion in the photosensitive member surface moving direction A is δ [m] or more, among the non-image portions, from the leading end of the image portion to the photosensitive member surface moving direction. In an area separated by δ [m] or more downstream, if the exposure amount as described above is not controlled, a developing direction electric field is formed between the area and the developer tip, and a hat image may be generated. Therefore, in the present embodiment, the exposure amount is controlled only when the length of the non-image portion adjacent to the leading end side with respect to the image portion in the photoreceptor surface movement direction A is δ [m] or more. Note that the exposure amount may be controlled regardless of whether or not the length of the non-image portion adjacent to the front end side with respect to the image portion in the photosensitive member surface movement direction A is δ [m] or more. .

The numerical value δ described above is a value determined by the electric field formed in the image portion and the electric field formed in the non-image portion, and can be obtained by the following calculation.
As shown in FIG. 8, the developing sleeve and the photosensitive member are arranged in a two-dimensional plane, the latent image charge density distribution is applied to the surface of the photosensitive member, the applied voltage is applied to the developing sleeve, and the developing sleeve and the photosensitive member are Calculate the electric field between. The electric field calculation method is a method of calculating the electric field by solving the Poisson equation by the difference method. Details of this method are described in "Simulation of development / transfer process by electric field analysis" (Masashi Kadenaga, Natsuki Kuribayashi, Masao Nakano: Workshop on simulation of electrophotographic technology, Japan Society of Mechanical Engineers, p33, 2005). Yes. The calculation method of the latent image charge density distribution is described in “Simulation of charging / line image formation process by discharge field analysis” (Yoshio Watanabe: Workshop on simulation of electrophotographic technology, Japan Society of Mechanical Engineers, p19, 2005). The method is used. An example of the electric field on the surface of the photoreceptor thus obtained is shown in FIG.

  As shown in FIG. 9, the numerical value δ is sufficiently large from the point where the electric field on the surface of the photoreceptor changes from the developing direction electric field to the reverse developing direction electric field, that is, the point where the electric field becomes zero, from the peak value of the reverse developing electric field and the image portion front. The distance to the point at which the difference from the reverse development electric field at a position far away is 1 / e is obtained. Under the standard conditions of the image forming apparatus used by the present inventors, the numerical value δ was 70 [μm]. The numerical value δ is a value that varies depending on the latent image charge distribution, the developing bias, the distance between the developing sleeve 65 and the photoreceptor 40, and the like.

[Evaluation Test 1]
The present inventors employ a forward development system in an evaluation tester including the printer unit 100 and the paper feeding device 200 shown in FIG. 2 and are referred to as a hat image evaluation test (hereinafter referred to as “evaluation test 1”). ) The conditions and evaluation results of this evaluation test 1 are as shown in Table 1 below.

In this evaluation test 1, the development time was controlled by changing the photosensitive member linear velocity and the developing sleeve linear velocity.
The following items were the same under the conditions in Table 1 above.
The thickness of the filler-reinforced charge transport layer 40c of the photoreceptor 40: 5.0 [μm]
・ Developing sleeve diameter: 25 [mm]
-Ten-point average roughness Rz of the developing sleeve surface: 10 [μm]
-Developer capacity in the developing device 61: 500 [g]
-Peak magnetic flux density in the normal direction on the sleeve surface by the developing magnetic pole: 120 [mT]
・ Development gap: 350 [μm]
Agent transport amount: 45 [mg / cm ² ]
-Weight average particle diameter of magnetic carrier: 35 [μm]
-Toner coverage on magnetic carrier: 60 [%]
-Volume average particle diameter of toner: 7.5 [μm]

The volume resistivity of the magnetic carrier was measured as follows.
A container made of a fluororesin containing two electrodes having a distance between electrodes of 1 [mm] and a surface area of 2 × 4 [cm ² ] is filled with a magnetic carrier, and a DC voltage of 1000 [V] is applied between both electrodes. Apply. Then, the direct current resistance was measured with a high resistance meter 4329A (4329A + LJK5HVLVWDQFHOHWHU manufactured by Yokogawa Hewlett-Packard Company). Thereafter, the volume resistivity calculated from the obtained resistance value was defined as the volume resistivity [Ω · cm] of the magnetic carrier.

The dielectric constant of the magnetic carrier was measured as follows.
In a state where a magnetic carrier is put into a cylindrical cell having an inner diameter of 18 [mm] to which an electrode is attached, and the magnetic carrier in the cell is pressed into a disk shape having a thickness of 0.65 [mm] and a diameter of 18 [mm], It measured with TR-10C type dielectric loss measuring device (Ando Electric Co., Ltd.). The frequency is 1 [kHz] and RATIO is 11 × 10 ⁻⁹ .

The toner charge amount distribution was measured as follows.
The toner charge amount and particle size are measured using a toner particle charge amount distribution measuring apparatus (E-Spart Analyzer: manufactured by Hosokawa Micron Corporation) using a laser Doppler velocimeter to obtain a charge amount distribution.
The details of this measuring method will be described. First, a developer is held on a developer holding stand formed of a magnet. Next, the developer held on the developer holding table is separated into a magnetic carrier and toner by an air gun (nitrogen gas), and only toner particles are sucked into the measuring section. The toner sucked and introduced into the measuring unit is sequentially measured for the charge amount to obtain a toner charge amount distribution. From the obtained charge amount distribution, the content ratio in which the ratio between the toner charge amount and the particle diameter falls within a certain range is obtained.

The adhesion distribution between the toner and the carrier was measured as follows.
In addition, the apparatus used for the measurement is a centrifugal separator: manufactured by Hitachi Koki Co., Ltd., CP100MX (maximum rotation speed: 100,000 rpm, maximum acceleration: 720,000 G, angle rotor P100AT2), microscope for image filing: digital microscope VK- 8510, image processing software: Image-ProPlus (Planetron).
FIG. 10 is an explanatory diagram of a measurement cell of the powder adhesion measuring apparatus.
The measurement cell 1 includes a sample substrate 2 having a sample surface 2a to which powder is adhered, a receiving substrate 3 having an adhesion surface 3a to which powder separated from the sample substrate 2 is adhered, and a sample surface 2a of the sample substrate 2 The spacer 4 is provided between the attachment surface 3 a of the receiving substrate 3. A method for measuring the adhesive force between the toner and the carrier using this apparatus will be described with reference to FIG. 11. First, the adhesive layer 11 is formed on the sample substrate 2. The adhesive layer 11 needs to be a uniform thin film on the order of 10 μm in order to facilitate the spread of carriers. The thin film was formed by attaching an adhesive on the sample substrate 2 and spreading the adhesive with a flat plate. Next, the carrier is spread on the adhesive layer 11. FIG. 11 shows an example of a state in which powder is adhered to the sample substrate 2. As shown in FIG. 11, an adhesive layer 11 is provided on the sample substrate 2, a carrier is spread over the adhesive layer 11, and the toner adheres on the carrier so that the toners do not contact each other (toner adhesion method) Will be described later). The reason why the carrier is spread is to prevent the toner from entering between the carriers and adhering to the adhesive layer 11. As shown in FIG. 11, when the carrier particle size is sufficiently larger than the thickness of the adhesive layer 11, the carrier may be one layer. Next, toner is deposited on the carrier. When a large amount of toner is deposited on the carrier, the separated toners come into contact with each other or are stacked, so that the particle size of each particle cannot be measured. For this reason, it is necessary to control the amount of toner adhering, and by adhering so that adjacent powders do not come into contact with each other, the centrifugally separated toner has no contact or lamination between powders, and the particle size of the toner is easy. Can be measured. As a method for attaching the toner, a method of spraying the toner on the carrier using compressed air or the like was used.

FIG. 12 is a partial cross-sectional view of the centrifugal separator.
The centrifugal separator 5 includes a rotor 6 that rotates the measurement cell 1 and a holding means 7. The rotor 6 has a hole shape in a cross section perpendicular to the rotation center axis 9 of the rotor 6, and has a sample setting portion 8 where the holding means 7 is set. The holding means 7 includes a rod-like portion 7a, a cell holding portion 7b provided on the rod-like portion 7a for holding the measurement cell 1, a hole portion 7c for pushing the measurement cell 1 out of the cell holding portion 7b, and the rod-like portion 7a as a sample. An installation fixing part 7d for fixing to the installation part 8 is provided. The cell holding unit 7b is configured such that when the measurement cell 1 is installed, the vertical direction of the measurement cell 1 is perpendicular to the rotation center axis 9 of the rotor.
Using this apparatus, the number of rotations is divided into 17 stages from 1000 [rpm] to 100000 [rpm], and the image of the receiving substrate used at each number of rotations is filed. Then, the filed image is applied to image processing software to count the number of toners, and finally an adhesion force distribution curve is created. From the obtained adhesive force distribution, the content ratio at which the adhesive force is a certain value or less is obtained.

但し、Ｘは各チャンネルにおける代表径、Ｖは各チャンネルの代表径における相当体積、ｆは各チャンネルにおける粒子個数である。 The volume average particle diameter of the toner was determined by a Coulter counter method.
Specifically, toner number distribution and volume distribution data measured by a Coulter Multisizer 2e type (manufactured by Coulter Inc.) were sent to a personal computer for analysis via an interface (manufactured by Nikka Kikai Co., Ltd.). More specifically, a 1% NaCl aqueous solution using primary sodium chloride is prepared as an electrolyte, and a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant in 100 to 150 [ml] of the aqueous electrolyte. Add 1-5 [ml]. Further, 2 to 20 [mg] of toner as a test sample is added thereto, and dispersion treatment is performed for about 1 to 3 minutes using an ultrasonic disperser. Then, 100 to 200 [ml] of the electrolytic aqueous solution is put into another beaker, and the solution after the dispersion treatment is added to the beaker so as to have a predetermined concentration, and then applied to the Coulter Multisizer 2e type. The aperture is 100 [μm], and the particle size of 50,000 toner particles is measured. As a channel, it is less than 2.00-2.52 [micrometer]; 2.52-less than 3.17 [micrometer]; 3.17-less than 4.00 [micrometer]; 4.00-5.04 [micrometer] Less than 5.04 to 6.35 [μm]; 6.35 to less than 8.00 [μm]; 8.00 to less than 10.08 [μm]; 10.08 to less than 12.70 [μm]; 12.70 to less than 16.00 [μm]; 16.00 to less than 20.20 [μm]; 20.20 to less than 25.40 [μm]; 25.40 to less than 32.00 [μm]; Using 13 channels of 00 to less than 40.30 [μm], toner particles with a particle size of 2.00 [μm] or more and 32.0 [μm] or less are targeted. Then, the volume average particle diameter of the toner was calculated from the following equation (5).

However, X is the representative diameter in each channel, V is the equivalent volume in the representative diameter of each channel, and f is the number of particles in each channel.

  About the thickness of the filler reinforcement | strengthening charge transport layer, it measured with the film thickness measuring apparatus (FISCHERSSCOPEMS) made from a Fischer Instruments company.

但し、Ｄは各チャネルに存在する粒子の代表粒径［μｍ］、ｎは各チャネルに存在する粒子の総数である。なお、チャネルとは、粒径分布図における粒径範囲を等分に分割するための長さを示すものである。また、各チャネルに存在する粒子の代表粒径としては、各チャネルに保存する粒子径の下限値とする。 The weight average particle size of the magnetic carrier was determined as follows.
The particle size distribution of the magnetic carrier is measured with a Microtrac particle size analyzer (Model HRA9320-X100, manufactured by Honeywell). The measurement conditions are set as follows.
-Particle size range: 100-8 [μm]
・ Channel length (channel width): [2μm]
-Number of channels: 46
-Refractive index: 2.42
Then, the weight average particle diameter of the magnetic carrier was calculated from the particle size distribution measured under such measurement conditions and the formula shown in the following equation (6).

Here, D is the representative particle size [μm] of particles existing in each channel, and n is the total number of particles existing in each channel. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram. Further, the representative particle size of the particles present in each channel is the lower limit value of the particle size stored in each channel.

但し、Ｄｃは磁性キャリアの重量平均粒径［μｍ］、Ｄｔはトナーの重量平均粒径［μｍ］、Ｗｔはトナーの重量［ｇ］、Ｗｃは磁性キャリアの重量［ｇ］、ρｔはトナーの真密度［ｇ／ｃｍ³］、ρｃは磁性キャリアの真密度［ｇ／ｃｍ³］である。 The toner coverage on the surface of the magnetic carrier was determined as follows.
Using the above-mentioned Microtrac particle size analyzer, the weight average particle size [μm] of the toner is measured in the same manner as the magnetic carrier. And the coverage was calculated | required from the formula shown in following Formula 7.

However, Dc is the weight average particle diameter [μm] of the magnetic carrier, Dt is the weight average particle diameter [μm] of the toner, Wt is the weight [g] of the toner, Wc is the weight [g] of the magnetic carrier, and ρt is the weight of the toner. True density [g / cm ³ ], ρc is the true density [g / cm ³ ] of the magnetic carrier.

About the agent conveyance amount, it calculated | required as follows.
First, a sampling tube in which a magnet is inserted into a nonmagnetic pipe is prepared. A part of the developer is collected by applying a collection tube to the developer carried on the surface of the developing sleeve 65 that has passed the restriction position by the doctor blade 73. Next, the magnet is pulled out from the sampling tube to remove the sampling developer, and its weight is measured. Then, the area of the sleeve portion where the developer has disappeared by sampling is obtained by image analysis based on the video image. Thereafter, the agent transport amount [mg / cm ² ] was calculated based on the area and the previously measured weight.

Next, the results of the hat image evaluation test will be described.
The hat image evaluation in this evaluation test 1 was performed in three stages: good (◯), bad (Δ), and very bad (×).
From the condition numbers 4, 5, 6, 8, 9, 10, 11, 14, and 16 in Table 1 above, the higher the development potential / background potential (hereinafter, “potential ratio”), the better the hat image evaluation. I understand.
Moreover, in the condition numbers 1, 2, and 3, no hat image was generated, and the evaluations were all good. Compared with other condition numbers, it can be seen that the higher the volume resistivity of the magnetic carrier, the different the potential ratio at which the hat image is generated.
Further, it can be seen from condition numbers 6, 7, 11, and 12 that the hat image evaluation becomes better as the development time becomes shorter.
In addition, it can be seen that a hat image is generated under the condition that does not satisfy the expression shown in the above equation 1 in all the condition numbers except the condition numbers 13 and 15. Considering these condition numbers 13 and 15, the content ratio of the toner charge amount to the particle size is −1.0 [fC / μm] or less and the content ratio of the toner carrier adhesion is 10 [nN] or less. It can be seen that generation of a hat image can be suppressed by lowering.

As described above, from the results of the evaluation test 1, it was confirmed that the hat image evaluation was “good” and the generation of the hat image was sufficiently suppressed when the expression shown in the above equation 1 was satisfied.
The result of this evaluation test is the case where the forward development method is adopted, but it has been confirmed that the same result is obtained even when the counter direction development method is adopted. In this evaluation test, the developer on the developing sleeve is brought into contact with the photosensitive member by fixing the linear velocity of the photosensitive member 40 to 125 [mm / sec] and adjusting the linear velocity of the developing sleeve. The time required to pass through the region was controlled, and the same conditions as those shown in Table 1 were realized.

[Evaluation Test 2]
Next, the present inventors adopted a forward development method in an evaluation test machine including the printer unit 100 and the paper feeding device 200 shown in FIG. While changing each of the conditions, a reference image was printed out, and an evaluation test (hereinafter referred to as “evaluation test 2”) for evaluating the image quality was performed. The “agent transport amount” in the following Table 2 is the developer amount per unit area on the surface of the developing sleeve 65 that passes through the position facing the doctor blade 73 and reaches the developing region.

In this evaluation test 2, the linear velocity ratio was adjusted by adjusting the linear velocity of the developing sleeve 65. The following items were the same under the conditions in Table 2 above.
The thickness of the filler-reinforced charge transport layer 40c of the photoreceptor 40: 5.0 [μm]
-Linear speed of the photoreceptor 40: 245 [mm / s]
The exposed portion potential (electrostatic latent image potential) of the photoreceptor 40: −150 to −500 [V]
The background potential of the photoreceptor 40: −600 [V] (however, condition numbers 14 and 15 are −650 V and −550 V, respectively)
-DC development bias: -500 [V]
・ Developing sleeve diameter: 25 [mm]
-Ten-point average roughness Rz of the developing sleeve surface: 10 [μm]
-Developer capacity in the developing device 61: 500 [g]
-Peak magnetic flux density in the normal direction on the sleeve surface by the developing magnetic pole: 120 [mT]
-Volume average particle diameter of toner: 7.5 [μm]

Table 3 below shows the relationship between the conditions shown in Table 2 above and the quality of the printout image.

  In Table 3 above, fine line character reproducibility, graininess (no graininess), gradation reproducibility, halftone solid portion (hereinafter referred to as “HT solid portion”), trailing edge fading, and character surrounding loss For, the printout image was subjectively evaluated by a plurality of examiners. Regarding carrier adhesion and background contamination, the amount of magnetic carrier attached to the surface of the photoreceptor 40 and the amount of toner attached to the background portion of the photoreceptor were evaluated visually. Each was evaluated in four grades: very good (◎), good (◯: within acceptable range), bad (Δ), and very bad (×). Note that the HT solid portion rear end fading is a phenomenon in which light density and white spots are generated at the rear end of the HT solid portion due to a phenomenon called toner drift. In addition, toner drift is a phenomenon in which the toner at the tip of the developer passes when the developer passes through a region facing the background of the photosensitive member before the developer reaches the region facing the latent image portion of the HT solid portion. It is a phenomenon that electrostatically drifts to the root side. Character missing is a phenomenon in which when a colored background of HT is formed around a character, the character surrounding part in the colored background is white.

Condition No. 14 shows that the use of a magnetic carrier having a volume resistivity of less than 10 ⁸ [Ω · cm] causes a very bad level of carrier adhesion. On the contrary, in the condition number 15, the use of the magnetic carrier having a volume resistivity exceeding 10 ¹⁴ [Ω · cm] resulted in a very poor level of graininess and lack of character periphery.
In Condition No. 16, the toner adhered to the surface of the developing sleeve 65 due to the development gap being too narrow. Due to this influence, a printout image that could be a sample could not be obtained. On the other hand, in condition number 17, the development gap was too wide, resulting in a very poor level of graininess and missing characters.

In addition, the present inventors have empirically found that when a magnetic carrier having a weight average particle diameter of less than 20 [μm] is used, carrier adhesion is easily caused. Moreover, it has also been empirically found that the use of particles having a weight average particle size exceeding 60 [μm] significantly deteriorates the graininess. It has also been empirically found that if the “linear velocity ratio” is set to less than 1.5, a sufficient amount of toner cannot be transported to the development area, resulting in insufficient image density. Further, it has also been empirically found that when the “linear velocity ratio” is larger than 2.5, the trailing edge blur of the HT solid portion is abruptly deteriorated because the toner that has drifted in the developer tip does not return in time. . It has also been found empirically that if the agent transport amount is set to less than 35 [mg / cm ² ], a sufficient amount of toner cannot be transported to the development area, resulting in insufficient image density. It has also been found empirically that if the agent conveyance amount is set to be greater than 55 [mg / cm ² ], toner adhesion to the photoreceptor is likely to occur rapidly. It has also been empirically found that if the coverage of the toner on the magnetic carrier is set to less than 50%, carrier adhesion and insufficient image density are likely to occur rapidly. In addition, it has been empirically found that if the coverage is set higher than 70 [%], ground contamination due to toner scattering is easily generated. If the background potential, which is the difference between the absolute value of the background potential (charging potential by the charging means) and the absolute value of the DC developing bias (the former> the latter), is set to less than 50 [V], the background stain will be caused suddenly. It has been found empirically that it becomes easier. Furthermore, it has also been empirically found that setting this difference larger than 150 [V] makes it easy to cause carrier adhesion and missing characters.

  The reason why the fine line character reproducibility is realized under the condition number 4 is considered to be because a magnetic carrier having a relatively high volume resistivity is used. Moreover, it is thought that the reason why excellent granularity is realized under the condition number 3 is that a magnetic carrier having a relatively small weight average particle diameter is used. In addition, it is considered that the excellent graininess is realized under the condition number 7 because the development gap is set relatively narrow. Moreover, it is considered that the reason why the excellent granularity is realized under the condition number 8 is that the linear velocity ratio is set relatively large. In addition, it is considered that the reason why excellent graininess is realized under the condition number 11 is that the toner coverage is set to be relatively high. Further, the reason why the image with no blurring of the HT solid portion rear end is realized under the condition number 9 is that the “linear velocity ratio” is set to be relatively small. Further, the reason why the image having no blurring of the rear end of the HT solid portion under condition number 11 is realized is that the toner coverage is set relatively high. Further, the reason why the image with no blurring of the rear end of the HT solid portion is realized under the condition number 13 is that the background potential is set to be relatively small. Further, the reason why an image having no missing characters in the condition number 5 is realized is that a magnetic carrier having a relatively low volume resistivity is used. In addition, it is considered that the reason why an image with no missing characters around the condition number 7 is realized is that the development gap is set relatively narrow. In addition, it is considered that the reason why the image having no missing characters around the condition number 8 is realized is that the linear velocity ratio is set to be relatively small. In addition, it is considered that the reason why the image having no missing characters around the condition number 13 is realized is that the background potential is set relatively small. Moreover, it is considered that the carrier adhesion is not caused in the condition numbers 2 and 4 because the magnetic carrier having a relatively high volume resistivity is used. Moreover, it is considered that the carrier adhesion does not occur in the condition number 9 because the linear velocity ratio is set to be relatively small. Moreover, it is considered that the carrier adhesion does not occur in the condition number 13 because the background potential is set to be relatively small. In addition, in the condition number 12, the background stain is not generated because the background potential is set to be relatively large.

As described above, in view of the result and the empirical rule of the evaluation test 2, in the image forming apparatus that satisfies the expression shown in the above equation 1, the following conditions (A) to (B) are used as the magnetic carrier in the developer used for this. It is preferable to satisfy.
(A) Weight average particle diameter: 20 to 60 [μm]
(B) Volume resistivity: 10 ⁹ to 10 ¹⁴ [Ω · cm]
According to the image forming apparatus having such a configuration, as long as the designated magnetic carrier is used, carrier adhesion due to the weight average particle size being too small and granular deterioration due to the weight average particle size being too large are suppressed. be able to. Further, it is possible to suppress the carrier adhesion due to the volume resistivity being too small, and the remarkable deterioration of the graininess and the loss of character periphery due to the volume resistivity being too large.

In the present copying machine, it is desirable that the following conditions (C) to (G) are satisfied in the image forming apparatus that satisfies the expression shown in Equation (1).
(C) Development gap setting: 200 to 400 [μm]
(D) Linear speed ratio: 1.2 to 2.5
(E) Amount of agent transported: 35 to 55 [mg / cm ² ]
(F) Toner coverage with respect to magnetic carrier: 50 to 70 [%]
(G) Background potential: 50 to 150 [V]
By satisfying the above condition (C), the toner adheres to the surface of the developing sleeve 65 due to the development gap being too narrow, and the marked deterioration of the graininess and the loss of characters around the characters is suppressed due to the development gap being too wide. Can do. Further, by satisfying the condition (D), it is possible to suppress the image density shortage due to the linear velocity ratio being too small, and the remarkable deterioration of the HT solid portion rear end blur due to the linear velocity ratio being too large. Further, by satisfying the above condition (E), it is possible to suppress insufficient image density due to an excessively small amount of agent transport, and toner adhesion to the photoreceptor due to an excessive amount of agent transport. In addition, by satisfying the above condition (F), it is possible to suppress image density shortage due to the toner coverage being too low and background contamination due to the toner coverage being too high. In addition, by providing the condition (G), it is possible to suppress the remarkable deterioration of the background stain due to the background potential being too small, and the significant deterioration of the carrier adhesion and the missing character surroundings due to the background potential being too large.

In this evaluation test 2, the agent conveyance amount was adjusted to 35 to 55 [mg / cm ² ] by setting the magnetic force and arrangement position of each magnetic pole in the magnet roller 72 and the width of the doctor gap. Yes. As described above, the combination of the magnet roller 72 and the doctor blade 73 functions as a developer carrying body amount adjusting unit that adjusts the agent carrying amount that is the developer carrying amount on the sleeve surface in the developing region.
Further, in this evaluation test 2, the toner coverage of the magnetic carrier with respect to the magnetic carrier is maintained by maintaining the toner concentration of the developer in the developing device 61 within a predetermined range by toner replenishment using the toner replenishing device described above. It is adjusted to 50 to 70 [%]. As described above, the combination of the toner replenishing device and the control unit for controlling the operation of the toner replenishing device functions as a coverage rate adjusting unit.

The result of this evaluation test 2 is the case where the forward development method is adopted, but it has been confirmed that the same result is obtained even when the counter direction development method is adopted. Conditions in this evaluation test are as shown in Table 4 below. In this evaluation test, the linear velocity of the photosensitive member 40 was fixed at 125 [mm / sec], and the linear velocity ratio was controlled by adjusting the linear velocity of the developing sleeve. The preferable linear speed ratio condition in the counter direction developing method is 0.5 to 1.5.

As described above, the copying machine as the image forming apparatus according to the present embodiment forms the electrostatic latent image on the surface of the photosensitive member 40 by exposing the surface of the photosensitive member 40 and the photosensitive member 40 as the latent image carrier that moves on the surface. The optical writing unit 21 serving as an exposure unit and the photosensitive member 40 are arranged at positions facing the photosensitive member 40, and the developer is carried on the surface so that the two-component developer containing toner and magnetic carrier contacts the surface of the photosensitive member 40. A developing sleeve 65 as a developer carrying member that moves on the surface and a developing bias power source as a voltage applying means for applying a predetermined DC voltage between the photosensitive member 40 and the developing sleeve 65. The surface moves in a rotational direction with respect to the surface of the photosensitive member 40, and the linear velocity Vr [m / sec] of the developing sleeve 65 is set faster than the linear velocity Vpc [m / sec] of the photosensitive member 40. Have . Then, the copying machine has an absolute value of a voltage difference between the non-image portion on the photosensitive member surface and the developing sleeve surface with respect to an absolute value V1 [V] of a voltage difference between the image portion on the photosensitive member surface and the developing sleeve surface. The ratio of V2 [V] is configured to satisfy the formula shown in the above equation (1). As described above, when this ratio satisfies the expression shown in the above equation 1, when the developer tip that has passed through the image portion faces the non-image portion, the distance between the developer tip and the non-image portion is as follows. Thus, the development direction electric field is not formed. As a result, when the developer tip that has passed through the image portion faces the non-image portion, the toner adhering to the developer tip can be prevented from moving to the non-image portion, and a hat image is formed. Can be suppressed.
Even if the surface of the developing sleeve 65 is configured to move in the counter direction with respect to the surface of the photosensitive member 40, this effect can be obtained in the same manner as long as it is configured so as to satisfy the equation (1). It is done.
In this embodiment, the adhesion between the toner in the two-component developer and the magnetic carrier is 10 [nN] or less, and the toner content in the two-component developer is 10 [%] or less. It is configured. Thereby, it is possible to perform good development while preventing the toner from being developed in the non-image portion adjacent to the leading end side of the image portion to form a hat image.
In this embodiment, the polarity is the same as the average charge amount of the toner in the developer, and the ratio (q / Td) between the absolute value q of the charge amount and the toner particle size Td is 0.1 [fC / [mu] m] or less, the toner content is 20 [%] or less. Thereby, it is possible to perform good development while preventing the toner from being developed in the non-image portion adjacent to the leading end side of the image portion to form a hat image.
In this embodiment, the weight average particle size of the magnetic carrier in the two-component developer is 20 [μm] or more and 60 [μm] or less. Thereby, it is possible to suppress carrier adhesion due to the weight average particle size being too small, and remarkable deterioration in graininess due to the weight average particle size being too large.
In this embodiment, the volume resistivity of the magnetic carrier in the two-component developer is configured to be 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less. As a result, it is possible to suppress the carrier adhesion due to the volume resistivity being too small, and the remarkable deterioration of the graininess and letter-proof missing due to the volume resistivity being too large.
In this embodiment, the minimum distance (development gap) between the photoreceptor 40 and the developing sleeve 65 is configured to be 200 [μm] or more and 400 [μm] or less. As a result, it is possible to suppress the toner from adhering to the surface of the developing sleeve 65 due to the development gap being too narrow, and the remarkable deterioration of the graininess and letter-proof surrounding loss due to the development gap being too wide.
In the present embodiment, the developer carrying amount (agent transport amount) on the developing sleeve 65 in the region facing the photoreceptor 40 is 35 [mg / cm ² ] or more and 55 [mg / cm ² ] or less. It is configured. As a result, it is possible to suppress insufficient image density due to an excessively small amount of agent transport, and toner adhesion to the photoreceptor due to an excessive amount of agent transport.
Further, in the present embodiment, the toner coverage with respect to the magnetic carrier in the two-component developer is configured to be 50% or more and 70% or less. As a result, it is possible to suppress insufficient image density due to the toner coverage being too low, and scumming due to the toner coverage being too high.

(A) is explanatory drawing which shows the phenomenon in which a toner adheres to the non-image part adjacent to the front end side of an image part, and a hat image is formed in a forward direction developing system. FIG. 5B is an explanatory diagram showing a phenomenon in which a hat image is formed by toner adhering to a non-image portion adjacent to the rear end side of an image portion in the counter direction development method. 1 is a schematic configuration diagram of a copier according to an embodiment. FIG. 2 is an enlarged view showing a schematic configuration of a yellow process cartridge and a cyan process cartridge in the copier. FIG. 2 is an enlarged configuration diagram illustrating an image forming unit, an intermediate transfer unit, a secondary transfer device, a registration roller pair, and a fixing unit in the copier. FIG. 2 is an enlarged sectional view showing a photosensitive layer of a photoreceptor in the copier. The graph showing the relationship between the electric field formed when the developer tip portion faces the non-image portion and the charge amount of the developer tip portion. The graph showing the change in the charge amount of the developer when the developer moves from the image portion to the non-image portion. FIG. 3 is a schematic diagram for explaining a model for calculating an electric field between a developing sleeve and a photosensitive member. The graph which shows an example of the calculation result of the same electric field. Explanatory drawing of the measurement cell of the powder adhesive force measuring apparatus used in order to obtain | require the adhesive force between a toner and a carrier. Explanatory drawing which shows an example of the state which made the powder adhere to the sample board | substrate of the measurement cell. FIG. 3 is a partial cross-sectional view of a centrifugal separator used for obtaining an adhesion force between a toner and a carrier. FIG. 3 is a schematic diagram in which a vicinity of a developing nip exit is enlarged in order to explain a mechanism in which a hat image is generated in a forward developing type image forming apparatus. FIG. 3 is a schematic diagram enlarging the vicinity of a developing nip outlet in order to explain a mechanism in which a hat image is generated in a counter direction developing type image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 18Y, 18C, 18M, 18K Process cartridge 20 Image forming unit 21 Optical writing unit 40Y, 40C, 40M, 40K Photoconductor 61 Developer 65 Developing sleeve 72 Magnet roller 100 Printer unit 200 Paper feeding device 300 Scanner 400 Automatic document feeder

Claims (11)

A latent image carrier that moves on the surface;
Exposure means for forming an electrostatic latent image on the surface by exposing the surface of the latent image carrier;
The two-component developer disposed on the surface facing the latent image carrier and carrying the two-component developer on the surface moves so that the two-component developer containing toner and magnetic carrier contacts the surface of the latent image carrier. A developer carrier;
Voltage application means for applying a predetermined DC voltage between the latent image carrier and the developer carrier;
The surface of the developer carrying member moves in a rotating direction with respect to the surface of the latent image carrying member, and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrying member is the latent image. In the image forming apparatus set faster than the surface movement speed (linear velocity) Vpc [m / sec] of the carrier,
The non-image portion on the surface of the latent image carrier and the surface of the developer carrier with respect to the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. An image forming apparatus, characterized in that the ratio of the absolute value V2 [V] of the voltage difference satisfies the following equation (1).

Here, each symbol in the formula shown in the above equation 1 is as follows.
ε [F / m] is the dielectric constant of the magnetic carrier.
ρ [Ω · m] is the volume resistivity of the magnetic carrier.
T [sec] is the time required for the two-component developer on the developer carrier to pass through the contact area with the latent image carrier, and the latent time when the two-component developer contacts the latent image carrier. This is a value (Nip / Vr) obtained by dividing the length Nip [m] in the surface movement direction of the image carrier by the surface movement speed (linear velocity) Vr [m / sec] of the developer carrier.
ΔVr [m / sec] is a relative value between the surface moving speed (linear velocity) Vpc [m / sec] of the latent image carrier and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrier. It is a speed difference (Vr−Vpc).
[delta] [m], the edge effect at the boundary between the non-image portion and the image portion adjacent to the latent image bearing member surface moving direction with respect to the image portion on the latent image bearing member surface to be exposed by said exposure means Is a distance of 1 / e of the length in the moving direction of the surface of the latent image carrier. A latent image carrier that moves on the surface;
Exposure means for forming an electrostatic latent image on the surface by exposing the surface of the latent image carrier;
The two-component developer disposed on the surface facing the latent image carrier and carrying the two-component developer on the surface moves so that the two-component developer containing toner and magnetic carrier contacts the surface of the latent image carrier. A developer carrier;
Voltage application means for applying a predetermined DC voltage between the latent image carrier and the developer carrier;
In the image forming apparatus configured such that the surface of the developer carrying member moves in a counter direction with respect to the surface of the latent image carrying member,
The non-image portion on the surface of the latent image carrier and the surface of the developer carrier with respect to the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. image forming apparatus has an absolute value ratio of V2 [V] of the voltage difference, characterized by being configured to satisfy the equation shown in 2 the number below.

Here, each symbol in the formula shown in Equation 2 is as follows.
ε [F / m] is the dielectric constant of the magnetic carrier.
ρ [Ω · m] is the volume resistivity of the magnetic carrier.
T [sec] is the time required for the two-component developer on the developer carrier to pass through the contact area with the latent image carrier, and the latent time when the two-component developer contacts the latent image carrier. This is a value (Nip / Vr) obtained by dividing the length Nip [m] in the surface movement direction of the image carrier by the surface movement speed (linear velocity) Vr [m / sec] of the developer carrier.
ΔVr [m / sec] is a relative value between the surface moving speed (linear velocity) Vpc [m / sec] of the latent image carrier and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrier. It is a speed difference (Vr−Vpc).
δ [m] is an edge effect at the boundary between the non-image portion and the image portion adjacent to the image portion on the surface of the latent image carrier exposed in the exposure unit in the moving direction of the latent image carrier. Is a distance of 1 / e of the length in the moving direction of the surface of the latent image carrier. The image forming apparatus according to claim 1 or 2,
The adhesive force between the toner and the magnetic carrier in the two-component developer is 10 [nN] or less, and the toner content in the two-component developer is 10 [%] or less. An image forming apparatus. The image forming apparatus according to claim 1, 2 or 3.
The same polarity as the average charge amount of the toner in the two-component developer, and the ratio (q / Td) between the absolute value q of the charge amount and the toner particle size Td is 0.1 [fC / μm] or less. An image forming apparatus configured to have a toner content of 20% or less. The image forming apparatus according to claim 1, 2, 3, or 4.
An image forming apparatus, wherein the weight average particle diameter of the magnetic carrier in the two-component developer is 20 [μm] or more and 60 [μm] or less. The image forming apparatus according to claim 1, 2, 3, 4 or 5.
An image forming apparatus, wherein the volume resistivity of the magnetic carrier in the two-component developer is 10 ⁹ [Ω · cm] or more and 10 ¹⁴ [Ω · cm] or less. The image forming apparatus according to claim 1, 2, 3, 4, 5 or 6.
An image forming apparatus, wherein a minimum distance between the latent image carrier and the developer carrier is 200 [μm] or more and 400 [μm] or less. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6 or 7.
An image in which the developer carrying amount on the developer carrying member in a region facing the latent image carrying member is 35 [mg / cm ² ] or more and 55 [mg / cm ² ] or less. Forming equipment. The image forming apparatus according to claim 1, 2, 3, 4, 5, 6, 7 or 8.
An image forming apparatus, wherein the coverage of the toner with respect to the magnetic carrier in the two-component developer is 50% or more and 70% or less. A latent image carrier that moves on the surface; an exposure unit that forms an electrostatic latent image on the surface by exposing the surface of the latent image carrier; and a position that faces the latent image carrier. A developer carrier that carries the two-component developer on the surface so that the two-component developer containing a magnetic carrier is in contact with the surface of the latent image carrier, and the latent image carrier and developer An image forming apparatus having a voltage applying means for applying a predetermined DC voltage to the carrier, and moving the surface of the developer carrier in a rotational direction with respect to the surface of the latent image carrier; and Image formation is carried out with the surface moving speed (linear velocity) Vr [m / sec] of the developer carrying member being higher than the surface moving velocity (linear velocity) Vpc [m / sec] of the latent image carrying member. In the method
The non-image portion on the surface of the latent image carrier and the surface of the developer carrier with respect to the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. image forming method is absolute value ratio of V2 [V] of the voltage difference, characterized in that so as to satisfy the expression shown in expression 3 below.

Here, each symbol in the formula shown in Equation 3 is as follows.
ε [F / m] is the dielectric constant of the magnetic carrier.
ρ [Ω · m] is the volume resistivity of the magnetic carrier.
T [sec] is the time required for the two-component developer on the developer carrier to pass through the contact area with the latent image carrier, and the latent time when the two-component developer contacts the latent image carrier. This is a value (Nip / Vr) obtained by dividing the length Nip [m] in the surface movement direction of the image carrier by the surface movement speed (linear velocity) Vr [m / sec] of the developer carrier.
ΔVr [m / sec] is a relative value between the surface moving speed (linear velocity) Vpc [m / sec] of the latent image carrier and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrier. It is a speed difference (Vr−Vpc).
δ [m] is an edge effect at the boundary between the non-image portion and the image portion adjacent to the image portion on the surface of the latent image carrier exposed in the exposure unit in the moving direction of the latent image carrier. Is a distance of 1 / e of the length in the moving direction of the surface of the latent image carrier. A latent image carrier that moves on the surface; an exposure unit that forms an electrostatic latent image on the surface by exposing the surface of the latent image carrier; and a position that faces the latent image carrier. A developer carrier that carries the two-component developer on the surface so that the two-component developer containing a magnetic carrier is in contact with the surface of the latent image carrier, and the latent image carrier and developer An image forming apparatus having a voltage applying means for applying a predetermined DC voltage to the carrier and moving the surface of the developer carrier in the counter direction with respect to the surface of the latent image carrier. In the image forming method of performing
The non-image portion on the surface of the latent image carrier and the surface of the developer carrier with respect to the absolute value V1 [V] of the voltage difference between the image portion on the surface of the latent image carrier and the surface of the developer carrier. image forming method is absolute value ratio of V2 [V] of the voltage difference, characterized in that so as to satisfy the expression shown in expression 4 below.

Here, each symbol in the formula shown in Equation 4 is as follows.
ε [F / m] is the dielectric constant of the magnetic carrier.
ρ [Ω · m] is the volume resistivity of the magnetic carrier.
T [sec] is the time required for the two-component developer on the developer carrier to pass through the contact area with the latent image carrier, and the latent time when the two-component developer contacts the latent image carrier. This is a value (Nip / Vr) obtained by dividing the length Nip [m] in the surface movement direction of the image carrier by the surface movement speed (linear velocity) Vr [m / sec] of the developer carrier.
ΔVr [m / sec] is a relative value between the surface moving speed (linear velocity) Vpc [m / sec] of the latent image carrier and the surface moving speed (linear velocity) Vr [m / sec] of the developer carrier. It is a speed difference (Vr−Vpc).
δ [m] is an edge effect at the boundary between the non-image portion and the image portion adjacent to the image portion on the surface of the latent image carrier exposed in the exposure unit in the moving direction of the latent image carrier. Is a distance of 1 / e of the length in the moving direction of the surface of the latent image carrier.

Images