JP2009217155A - Electrophotographic carrier, electrophotographic developer, developing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic carrier that prevents toner spent even when an image is formed at a high speed, facilitates accurate detection of a toner density in a developing device and gives stable picture quality for a long period of time, and to provide an electrophotographic developer containing the electrophotographic carrier, and a developing device and an image forming apparatus using the electrophotographic developer. <P>SOLUTION: The electrophotographic carrier comprises a core material and a resin coating layer containing a conductive material and exhibits a saturation magnetization of 63 to 93 emu/g, F1 expressed by formula (1) of 63 to 73 sec/(50 cm<SP>3</SP>) and F2 expressed by formula (2) of 24 to 28 Oe g/cm<SP>3</SP>, wherein the formulae are (1):F1=AD×FR and (2):F2=AD×Hc. In the formulae, AD, FR and Hc represent an apparent density (g/cm<SP>3</SP>), a fluidity (sec/50g) and a coercive force (Oe), respectively. The electrophotographic developer contains the above electrophotographic carrier, and the developing device and the image forming apparatus use the above electrophotographic developer. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic carrier, an electrophotographic developer, a developing device, and an image forming apparatus.

  A method of visualizing image information through formation of an electrostatic latent image by electrophotography or the like is currently used in various fields. In the electrophotographic method, an electrostatic latent image is formed on the surface of a photosensitive member (electrostatic latent image holding member) by charging and exposure processes, and an electrophotographic developer containing toner (hereinafter simply referred to as “developer”). ), The electrostatic latent image is developed into a toner image, and the image is visualized through a transfer and fixing process. The developer used here is a two-component developer composed of an electrophotographic toner (hereinafter sometimes simply referred to as “toner”) and an electrophotographic carrier (hereinafter sometimes simply referred to as “carrier”), and magnetic. There are one-component developers that are used alone, such as toner, but the two-component developer shares functions such as stirring, transporting, and charging of the developer, and functions are separated as a developer. For this reason, it is currently widely used for reasons such as good controllability.

  The carriers are generally classified into carriers having a resin coating layer on the surface and carriers not having a resin coating layer. However, when charging characteristics / developer life is considered, the resin-coated carrier Therefore, various resin-coated carriers have been developed and put into practical use.

  In recent years, an electrophotographic printing machine capable of ultra-high-speed on-demand printing has been studied to replace offset printing for printing newspapers and direct mail. As an approach in the electrophotographic system, attempts are being made to improve the actual number of printed sheets by increasing the speed as well as widening the paper.

Under such circumstances, a method has been proposed in which the resin coating layer of the carrier is formed into a two-layer coating to suppress toner spent and prevent printing deterioration during long-term use (see, for example, Patent Documents 1 to 3). .
On the other hand, regarding the fluidity of the toner, the fluidity indexes F1 and F2 are defined from the apparent density, fluidity, and holding power, and a high image quality and a long life are proposed (for example, see Patent Documents 4 and 5). .
JP-A-10-268777 JP 2006-330277 A JP 2007-57659 A JP 2002-357930 A JP 2005-181848 A

  As described above, attempts have been made to improve the actual number of printed sheets by increasing the speed. Generally, when printing is performed at high speed, the stress applied to the developer is proportional to the square of the printing speed. Therefore, it tends to be extremely large compared to a low speed machine. As for maintenance, it is necessary to make the developer replacement interval constant to some extent even when the speed is increased, and the higher the speed, the longer the life of the developer is required.

  For the purpose of optimizing the printing performance, the resin coating layer on the carrier surface uses a conductive material such as carbon black for adjusting the electric resistance. However, in a high-speed machine, a low softening point resin, a low melting point wax, etc. When a toner containing a low-melting-point component is used, the stress applied to the developer causes the low-melting-point component contained in the toner to be spent on the surface of the resin coating layer. This deteriorates and causes problems such as erroneous detection of the toner density detecting means using the magnetic permeability sensor, and deterioration of image quality due to a decrease in charge imparting ability and a decrease in fluidity.

In the carriers described in Patent Documents 1 to 3, when the resistance value is increased due to an increase in the resin coating amount, the print density is decreased, or the carrier having a small particle diameter is used with high definition. When the fluidity is remarkably lowered, there are problems such as adversely affecting the toner density detecting means.
In addition, in the carriers described in Patent Documents 4 and 5, since the stirring strength at the time of conveyance is strong in a high-speed machine, the developing surface is caused by developer spikes on the developer holder that causes toner spent or rotates at high speed. There is a problem that unevenness of sweeping, called a brush mark, is seen when the ink is abraded.

  In addition, if the fluidity of the carrier and the developer deteriorates as the definition becomes higher, a toner with lower chargeability and poor charging is generated due to lowering of the mixing property. Since aggregation and stagnation easily occur in the container, there arises a problem that it is difficult to detect an appropriate toner concentration by the sensor.

  This invention makes it a subject to achieve the following objectives. That is, the present invention is an electrophotographic apparatus that can accurately detect the toner concentration in the developing device without causing toner spent even when an image is formed at a high speed, and can provide a stable image quality over a long period of time. It is an object to provide a carrier, an electrophotographic developer containing the electrophotographic carrier, a developing device and an image forming apparatus using the electrophotographic developer.

The above problem is solved by the following means. That is,
The invention according to claim 1
A core material, and a resin coating layer containing a conductive material and covering the surface of the core material;
The saturation magnetization is 63 emu / g or more and 93 emu / g or less,
The first fluidity index F1 represented by the following formula (1) is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ) or less,
A second fluidity index F2 represented by the following formula (2) is 24 Oe · g / cm ³ or more and 28 Oe · g / cm ³ or less.
F1 = AD × FR (1)
F2 = AD × Hc (2)
In the formulas (1) and (2), AD represents the apparent density (g / cm ³ ), FR represents the fluidity (sec / 50 g), and Hc represents the coercive force (Oe) when a magnetic field of 3000 Oe is applied. Indicates.

The invention according to claim 2
The content of the conductive material is 20% by mass or less, the second resin coating layer covers the surface of the resin coating layer, and the coating amount of the resin coating layer with respect to 100 parts by mass of the core material is 1.9 mass. 2. The electrophotographic carrier according to claim 1, wherein the coating amount of the second resin coating layer with respect to 100 parts by mass of the core material is 0.4 parts by mass or less. It is.

The invention according to claim 3
An electrophotographic developer comprising a toner and the electrophotographic carrier according to claim 1.

The invention according to claim 4
A developer holder that rotates while holding the developer on the surface; and a developer transport supply path that includes a developer transport supply member that transports the developer and supplies the developer to the developer holder. The developer transported to the most downstream side in the transport direction of the developer transport supply path is taken in, the toner is further replenished by the toner replenishment mechanism, and the developer replenished with the toner is supplied. A developer agitation supply path having a developer agitation supply member that conveys the developer in a direction opposite to the conveyance direction of the developer conveyance supply path and supplies the developer conveyance member to the developer conveyance member; and in the developer agitation supply path A toner concentration detecting member for measuring the toner concentration of the developer of
The developer agitation supply member has a conveyance speed of 180 mm / sec or more,
A developing device, wherein the developer is the electrophotographic developer according to claim 3.

The invention according to claim 5
The developing device according to claim 4, wherein the developer conveying efficiency in the developer stirring supply path is 50% or more.

The invention according to claim 6
6. The developing device according to claim 4, wherein the developer conveyance amount in the developer stirring supply path is 730 g · m / sec or more. 7.

The invention according to claim 7 provides:
An electrostatic latent image holding member; a charging unit that charges the surface of the electrostatic latent image holding member; an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the electrostatic latent image holding member; A developing unit that develops the electrostatic latent image into a toner image with a developer; a transfer unit that transfers the toner image formed on the surface of the electrostatic latent image holding member to the surface of the transfer member; Fixing means for fixing the transferred toner image,
The process speed is 1000 mm / second or more,
The developing unit includes a developer holding member that rotates while holding the developer on the surface, and a developer conveying and supplying member that conveys the developer and supplies the developer to the developer holding member. The developer transport supply path and the developer transported to the most downstream side in the transport direction of the developer transport supply path, the toner is further replenished to the captured developer by a toner replenishment mechanism, and the toner is replenished The developer agitation supply path having a developer agitation supply member that conveys the developer thus developed in a direction opposite to the conveyance direction of the developer conveyance supply path and supplies the developer to the developer conveyance member, and the development A toner concentration detection member that measures the toner concentration of the developer in the developer agitation supply path, and the conveyance speed in the developer agitation supply member is 180 mm / sec or more,
The developer contains a toner, a core material, and a conductive material, and has a resin coating layer that covers the surface of the core material. The saturation magnetization is 63 emu / g or more and 93 emu / g or less. ) Is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ) or less, and the second fluidity index F2 represented by the following formula (2) is 24 Oe. An image forming apparatus comprising: an electrophotographic carrier having g / cm ³ or more and 28 Oe · g / cm ³ or less.
F1 = AD × FR (1)
F2 = AD × Hc (2)
In the formulas (1) and (2), AD represents the apparent density (g / cm ³ ), FR represents the fluidity (sec / 50 g), and Hc represents the coercive force (Oe) when a magnetic field of 3000 Oe is applied. Indicates.

According to the first aspect of the present invention, even when an image is formed at a high speed, the fluidity and agitation on the agitating portion with the toner and the developer holding member are good, and toner spent is not caused. It is possible to accurately detect the toner density at the toner, and further, the triboelectric charge with the toner is quick, the rising of the charge is good, and the carrier adheres by forming a uniform, non-biased and soft spike on the sleeve. It is possible to provide an electrophotographic carrier that can obtain a stable image quality over a long period of time without a brush mark.
According to the invention of claim 2, the charging behavior of the toner is more stable.

  According to the invention of claim 3, the toner density in the developing device can be accurately detected, the rising of the charge is good, and a uniform, non-biased and soft spike is formed on the sleeve. As a result, it is possible to provide an electrophotographic developer that can provide stable image quality over a long period of time without carrier adhesion or brush marks.

  According to the fourth aspect of the present invention, it is possible to provide a developing device that can be operated at high speed, can accurately detect the toner density in the developing device, and can obtain a stable image quality over a long period of time.

According to the fifth aspect of the invention, the sensitivity of the toner density detecting member is improved and a better image can be formed.
According to the sixth aspect of the present invention, it is possible to provide a developing device that can operate at a high speed and a high printing rate by stably supplying the developer to the developer holding member and can obtain a stable image over a long period of time. .

  According to the seventh aspect of the present invention, it is possible to provide an image forming apparatus that can be operated at a high speed, can accurately detect the toner concentration in the developing device, and can obtain a stable image quality over a long period of time.

An embodiment of the present invention will be described.
The electrophotographic carrier of the present embodiment (hereinafter sometimes referred to as “the carrier of the present embodiment”) includes a core material and a resin coating layer that contains a conductive material and covers the surface of the core material. The saturation magnetization is 63 emu / g or more and 93 emu / g or less, and the first fluidity index F1 represented by the following formula (1) is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ). The second fluidity index F2 represented by the following formula (2) is 24 Oe · g / cm ³ or more and 28 Oe · g / cm ³ or less.
F1 = AD × FR (1)
F2 = AD × Hc (2)
In the formulas (1) and (2), AD represents the apparent density (g / cm ³ ), FR represents the fluidity (sec / 50 g), and Hc represents the coercive force (Oe) when a magnetic field of 3000 Oe is applied. Indicates.

In addition, in this embodiment, the measuring method of each physical property value is as follows.
The apparent density AD is measured in accordance with “Apparent Density Test Method for Metal Powder” defined in JIS Z2504.
The fluidity FR is measured in accordance with “Metal powder fluidity test method” defined in JIS Z2502.
The coercive force Hc is read from a hysteresis curve obtained by applying a magnetic field 3000 oersted (Oe) using a BH tracer (manufactured by Riken Denshi Co., Ltd .: BHU-60 type).
The saturation magnetization is obtained from a hysteresis curve obtained by applying a magnetic field 3000 oersted (Oe) using a BH tracer (manufactured by Riken Denshi Co., Ltd .: BHU-60 type) in the same manner as the coercive force Hc. Can be read.

As a result of intensive studies on the stability of image density, resolution, carrier adhesion, background fogging due to poorly charged toner, and the like, the first fluidity index F1 is 63 sec / (50 · cm ³ ) to 73 sec / (50 · cm ³ ) and the carrier having the second fluidity index F2 of 24 Oe · g / cm ^{3 to} 28 Oe · g / cm ³ is high over a long period of time. I found that I could achieve better image quality.

The first fluidity index F1 indicates the fluidity per unit volume in the vicinity of the toner concentration detecting means provided in the stirring unit without the influence of the magnetic field. In the present embodiment, the first fluidity index F1 is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ) or less, and is 63 sec / (50 · cm ³ ) or more and 70 sec / preferably (50 · cm ³⁾ or ^{less, 63sec / (50 · cm 3} ) or more 66sec / (50 · cm ³⁾ and more preferably less. If the first fluidity index F1 is less than 63 sec / (50 · cm ³ ), the fluidity is too good, and the developer is biased. Therefore, the spikes on the developer holding member are uneven. Become. On the other hand, when the first fluidity index F1 exceeds 73 sec / (50 · cm ³ ), the fluidity is too bad, so that the developer transportability and the stirrability in the developer agitation supply member described later are deteriorated. The developer may be biased, and the toner and the carrier may not be sufficiently agitated, causing toner scattering and fogging. In addition, since the fluidity deteriorates, the stress due to agitation increases, causing a loss of life.If the bias is too small, the stress applied to the developer at the bias is increased and the life is impaired. Become.

The second fluidity index F2 indicates the fluidity per unit volume on the developer holder having the influence of a magnetic field. Further, the second fluidity index F2 also indicates the rise of the magnetic brush on the developer holding member and the length of the carrier chain (the degree of the carrier chain extending between the magnetic poles). The second fluidity index F2 is 24 Oe · g / cm ³ or more and 28 Oe · g / cm ³ or less, preferably 25 Oe · g / cm ³ or more and 27 Oe · g / cm ³ or less, More preferably, it is 25 Oe · g / cm ³ or more and 26 Oe · g / cm ³ or less. When the second fluidity index F2 is less than 24 Oe · g / cm ³ , the brush of the magnetic brush becomes sparse on the developer holder and sufficient developability cannot be obtained, and a carrier chain stands. The ears become stiff and good image quality cannot be obtained. On the other hand, when the second fluidity index F2 exceeds 28 Oe · g / cm ³ , the ears of the magnetic brush become dense, but the movement of the developer on the developer holding member is poor and the ears become uneven. Since the toner is not sufficiently supplied, the image quality is deteriorated. Further, toner scattering occurs. Furthermore, the adhesion of the carrier increases.

  In the carrier of this embodiment, the coercive force (Hc) is preferably 10 Oe or more and 12 Oe or less, more preferably 10 Oe or more and 11.6 Oe or less, and further preferably 10 Oe or more and 10.7 Oe or less. When the coercive force (Hc) is 10 Oe or more and 12 Oe or less, the developing brush becomes dense on the developer holding member, and developability does not deteriorate, and good fluidity on the developer holding member. In other words, sufficient toner is supplied, the developability is not lowered, and the carrier is not sufficiently loosened after leaving the developer holding member, and is not easily mixed with newly supplied toner.

  The carrier of this embodiment is characterized in that the saturation magnetization is 63 emu / g or more and 93 emu / g or less, preferably 63 emu / g or more and 83 emu / g or less, and more preferably 63 emu / g or more and 73 emu / g or less. Is more preferable. When the saturation magnetization is less than 63 emu / g, a phenomenon (carrier adhesion) in which the carrier itself adheres to the photosensitive drum, which is the electrostatic charge image carrier, as the distance from the magnetic pole on the developer carrier during printing becomes remarkable, If it exceeds 93 emu / g, due to the high magnetic force, a hard developer brush is formed in the development region, causing cracks and roughness, making it difficult to obtain a good image.

  The carrier of this embodiment preferably has a volume average particle size of 30 μm or more and 90 μm or less, and more preferably 60 μm or more and 80 μm or less. When the volume average particle size is less than 30 μm, carrier adhesion may easily occur, and when it exceeds 90 μm, image quality may be deteriorated.

  As the core material used in the carrier of the present embodiment, ferrite, magnetite, iron powder or the like can be used. In particular, manganese ferrite has a high magnetic force and is almost spherical, which is advantageous from the viewpoint of extending the life. . Iron powder has a high saturation magnetization and is preferable for carrier adhesion. However, since the brush ears are high and too hard, the toner transferred to the photoconductor is scraped off by the carrier brush or the iron powder is low. Since it is a resistor, a brush mark may be easily generated due to a leak of electric charge and the destruction of the electrostatic latent image on the photosensitive member.

Further, as an example of the ferrite, a structure represented by the following formula (3) is preferably exemplified.
(MO) _X (Fe ₂ O ₃ ) _Y (3)
In the formula (3), M represents at least one selected from the group consisting of Cu, Zn, Fe, Mg, Mn, Ca, Li, Ti, Ni, Sn, Sr, Al, Ba, Co, and Mo. X and Y indicate mol ratios and satisfy the condition X + Y = 100.

  In the formula (3), when M is Mn and the molar ratio X of MnO is less than 0.1 (10 mol%), the stability after the ferritization reaction may be deteriorated, and resistance may be increased due to stress or the like. It may change and developability may be inferior. On the other hand, when the molar ratio X of MnO exceeds 45 mol%, the shape is deteriorated, and the toner adheres to the surface of the carrier due to stress in the developing device, which may easily cause a resistance change due to filming.

  As the core material, it is necessary to increase the ratio of Fe and Mn in order to control the saturation magnetization to 63 emu / g or more and 93 emu / g or less.

  As the method for producing the core material, for example, appropriate amounts of metal oxides, metal carbonates, and metal hydroxides of each raw material are blended so that X and Y in the formula (3) have desired values, and water is added. , Pulverized and mixed for 1 hour to 20 hours in a wet ball mill, dried, and held at 700 ° C. to 1200 ° C. This is pulverized with a wet ball mill to a particle size of 5 μm or less. This slurry can be granulated and dried, held in a nitrogen atmosphere at 1000 ° C. or higher and 1500 ° C. or lower for 1 hour to 24 hours, and then crushed and further classified into a desired particle size distribution.

  Various resins can be used for the resin coating layer covering the surface of the core material as a resin which is one of the constituent components. Examples of the resin include fluorine resin, acrylic resin, epoxy resin, polyester resin, fluorine acrylic resin, acrylic-styrene resin, silicone resin, or acrylic resin, polyester resin, epoxy resin, alkyd resin, and urethane resin. Modified silicone resins and cross-linked fluorine-modified silicone resins. The resin coating layer is subject to great stress due to agitation in the developing device and collision with the doctor blade, and thus is easily peeled off and worn. In addition, the spent phenomenon in which the toner adheres to the carrier surface is likely to occur. For this reason, as the resin constituting the resin coating layer, the following general formula (I) and / or the following general formulas (I) and / or Or it is preferable that it is resin which has a structure represented by (II).

In the general formulas (I) and (II), R ¹ , R ² and R ³ are each independently a hydrogen atom, a halogen atom, a hydroxy atom, a methoxy group, an alkyl group having 1 to 4 carbon atoms, or a phenyl group. Indicates.

Examples of the resin having the structure represented by the general formulas (I) and (II) include the above-described straight silicone resin, organic modified silicone resin, and fluorine modified silicone resin.
Examples of the fluorine-modified silicone resin include, for example, a curable crosslinked fluorine obtained by hydrolyzing the structure represented by the above (I) and / or (II) and an organosilicon compound containing a perfluoroalkyl machine. Examples thereof include modified silicone resins.
Examples of the organic silicon compound containing a perfluoroalkyl _{machine, CF 3 CH 2 CH 2 Si} (OCH 3) 3, C 4 F 9 CH 2 CH 2 Si (CH 3) (OCH 3) 2, C 8 F 17 _{CH 2 CH 2 Si (OCH 3} ) 3, C 8 F 17 CH 2 CH 2 Si (OC 2 H 5) 3, (CF 3) 2 CF (CF 2) 8 CH 2 CH 2 Si (OCH 3) 3 , etc. Is mentioned.

  The resin coating layer contains a conductive material. Here, the conductive material includes a wide range of low-resistance materials with respect to the coating resin, but generally refers to a material made of metal, carbon, an inorganic metal compound, or the like. Specific examples of conductive materials include metals such as gold, silver and copper; carbon black; conductive metal oxides such as titanium oxide and zinc oxide; titanium oxide, zinc oxide, aluminum borate and titanic acid. And a composite system in which the surface of fine particles of potassium, tin oxide or the like is coated with a conductive metal oxide.

As the conductive material, carbon black is particularly preferable from the viewpoint of manufacturing stability, cost, and low electrical resistance. The type of carbon black is not particularly limited, but those having a DBP (dibutyl phthalate) oil absorption of 50 ml / 100 g or more and 300 ml / 100 g or less with good production stability are preferable. The average particle diameter of the conductive powder is preferably 0.1 μm or less, and the primary particle diameter is preferably 50 nm or less in consideration of dispersion in the resin. Further, the specific surface area is preferably 700 m ² / g or more because the conductivity is high, and a sufficiently low resistance can be obtained with a small addition amount. Kettin black (Lion) is the most suitable carbon black. preferable.

  The content of the conductive material in the resin coating layer varies depending on the type, but is preferably 5% by mass or more and 20% by mass or less, more preferably 8% by mass or more and 15% by mass or less, and more preferably 10% by mass or more. More preferably, it is 12 mass% or less. When the content of the conductive material in the resin coating layer is less than 5% by mass, the electrical resistance is high, and an image having a good density may not be obtained. If it exceeds 20 mass%, the electric resistance is low, so that charge injection fog may easily occur.

  If necessary, a charge control agent or a fluidity control agent may be added to the coating resin layer. Examples of charge control agents and fluidity control agents include conductive carbon, borides such as titanium boride, oxides such as titanium oxide, iron oxide, aluminum oxide, chromium oxide, and silicon oxide, various titanium coupling agents, Although various silane coupling agents etc. are mentioned, it is not specifically limited.

  The coating amount of the coating resin layer is preferably 1.9 parts by mass or more and 3.0 parts by mass or less, particularly 2.1 parts by mass or more and 2.4 parts by mass or less with respect to 100 parts by mass of the core material. . When the coating amount of the coating resin layer is less than 1.9 parts by mass with respect to 100 parts by mass of the core material, it is difficult to form a uniform coating layer on the carrier surface, and further, physical properties due to stress due to stress in the developing device May cause fluctuations. On the other hand, when the amount exceeds 3.0 parts by mass, the carriers may be aggregated and the resistance value may be increased to disturb the charging behavior of the toner.

  As a method for forming the resin coating layer by coating the core material with the coating resin as described above, for example, a brush coating method, a dry method, a spray drying method using a fluidized bed, a rotary drying method, a universal stirring method. Coating can be performed by a liquid immersion drying method using a machine. In order to increase the coverage, a fluidized bed method is preferred.

  The carrier of this embodiment preferably has a conductive resin content of 20% by mass or less and has a second resin coating layer that covers the surface of the resin coating layer. By having the second resin coating layer, it is possible to further extend the life of the carrier. The content of the conductive material in the second resin coating layer is preferably 1.0% by mass or less, and more preferably 0% by mass.

  The coating amount of the second resin coating layer with respect to 100 parts by mass of the core material is preferably 0.4 parts by mass or less, and preferably 0.2 parts by mass or more and 0.4 parts by mass or less. When the coating amount of the second resin coating layer with respect to 100 parts by mass of the core material exceeds 0.4 parts by mass, aggregation of carriers may occur, resistance may increase, and toner charging behavior may be easily disturbed. is there.

  A preferred embodiment of the second resin coating layer is the same as the preferred embodiment of the resin coating layer except that the content of the conductive material is 1.0% by mass or less.

  In the carrier of this embodiment, the coating amount of the resin coating layer with respect to 100 parts by mass of the core material is 1.9 parts by mass or more and 3.0 parts by mass, and the second resin coating layer with respect to 100 parts by mass of the core material The coating amount is preferably 0.4 parts by mass or less.

  As a method of forming the resin coating layer on the surface of the core material, it is preferable to perform baking after coating the surface of the core material with a resin for forming a resin coating layer. The baking may be either an external heating method or an internal heating method, and for example, a stationary or fluidized electric furnace, a rotary electric furnace, a burner furnace, or microwave baking may be used. The baking temperature varies depending on the resin to be used, but a temperature higher than the melting point or glass transition point is necessary. For thermosetting resins or condensation-crosslinking resins, it is necessary to raise the temperature sufficiently to advance curing. . For example, in the case of a silicone resin, it is preferable to maintain the material temperature at a temperature of 200 ° C. or higher and 300 ° C. or lower for about 30 minutes.

  Moreover, when forming said 2nd resin coating layer on the said resin coating layer surface, it is preferable to bake after coat | covering the said resin coating layer surface with resin for 2nd resin coating layer formation. The preferable aspect of baking is the same as the preferable aspect of baking at the time of forming the said resin coating layer.

The carrier of this embodiment is cooled after baking, and a carrier on which a resin coating layer is formed through pulverization and particle size adjustment is obtained.
In addition, after the crushing treatment, post-treatment is performed in order to sufficiently remove the surface of the resin coating layer (or the second resin coating layer), remove burrs, and dissolve the carrier particles aggregated by the resin coating. You can also. Any post-treatment method may be used as long as it can apply mechanical stress to the carrier particles, and a known method can be used. For example, a Nauter mixer, a ball mill, a vibro mill and the like can be mentioned, but the invention is not limited to these.

  Note that there are various methods for changing the degree of aggregation of the carrier described above. For example, there is a method of performing post-treatment by mechanical stress after coating and baking to release the aggregated particles. Further, the degree of aggregation can be changed by changing the amount of the coating agent sprayed per unit time. Furthermore, the drying rate of the coating agent can be changed depending on the type of the coating resin and the type of the diluent solvent, and the degree of aggregation can be changed accordingly.

  In addition, there are various methods for changing the degree of curing of the coating resin. For example, it can be changed depending on the curing temperature and the curing time, depending on the type of coating resin, the type of crosslinking agent and curing catalyst, and the amount added. Can be changed.

  Further, the coverage can be changed, for example, depending on the surface properties of the carrier core material, the shape of the carrier core material, the coating amount, the amount of coating agent sprayed per unit time, or the post-treatment conditions due to mechanical stress.

The first fluidity index F1 is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ) or less, and the second fluidity index F2 is 24 Oe · g / cm ³ or more and 28 Oe · g / cm ³ or less. As a control method, the apparent density and fluidity of the carrier are controlled by controlling the thickness of the resin coating layer. Controls the combination and mixing ratio of conductive materials. It is controlled by the firing temperature, holding time, and oxygen concentration. Examples include, but are not limited to, a method of performing oxidation treatment so as to obtain desired magnetic characteristics using various furnaces after firing.

  The method for controlling the first fluidity index F1 and the second fluidity index F2 will be described in detail. Regarding the F1 value, the surface area increases and the apparent density increases as the particle diameter of the core material decreases, but contrary to this. Therefore, the amount of fluctuation is small. However, in friction with the toner, the charging characteristics are likely to increase in proportion to the resin coating layer, so a method of reducing the thickness or increasing the amount of the conductive material of the first resin coating layer, which is the lower layer, is addressed. easy. In addition, as the particle size of the core material is reduced, the balance with saturation magnetization, which is a holding force, is lost and it is easy to cause problems such as rising of the carrier, but the magnetic properties are optimized without changing the material of the core material. In order to achieve this, the control method is easy to deal with by changing the firing temperature and time. Further, as a measure for finely improving charging characteristics and image quality, a method of changing the amount of catalyst used for resin coating is also used.

The electrophotographic developer of the present embodiment (hereinafter sometimes referred to as “developer of the present embodiment”) includes a toner and the carrier of the present embodiment described above.
Hereinafter, a toner used in the electrophotographic developer of the present embodiment (hereinafter, may be referred to as “toner used in the present embodiment”) will be described.
For the toner used in the exemplary embodiment, a known binder resin, various colorants, and the like can be used. As the toner used in the exemplary embodiment, the binder resin is preferably a polyester resin, and bisphenol A is used as a component on the alcohol side in view of excellent filming resistance to a carrier, and an alkylene oxide adduct thereof. The polyester resin containing resin containing is preferable. Moreover, even if the said polyester resin is used independently, resin other than polyester, such as styrene acryl, polyether polyol, urethane, and silicone, can also be used together 2 or more types as needed.

  In addition to the polyester resin, the binder resin in the toner used in the exemplary embodiment includes a polyolefin resin, a copolymer of styrene and acrylic acid or methacrylic acid, polyvinyl chloride, a phenol resin, an acrylic resin, and a methacrylic resin. , Polyvinyl acetate, silicone resin, modified polyester resin, polyurethane, polyamide resin, furan resin, epoxy resin, xylene resin, polyvinyl butyral, terpene resin, coumarone indene resin, petroleum resin, polyether polyol resin, etc. Can be used together.

  Examples of the colorant in the toner used in the exemplary embodiment include cyan colorants such as C.I. I. Pigment Blue 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 13, 15, 15: 1, 15: 2, 15: 3, 15: 4, 15: 6, 16, 17, 17, 23, 60, 65, 73, 83, 180, C.I. I. Vat cyan 1, 3 and 20, etc., bitumen, cobalt blue, alkali blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated products of phthalocyanine blue, fast sky blue, indanthrene blue BC cyan pigment, C.I. I. Cyan dyes such as solvent cyan 79 and 162 can be used.

  Examples of magenta colorants include C.I. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 41, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 60, 63, 64, 68, 81, 83, 87, 88, 89, 90 112, 114, 122, 123, 163, 184, 202, 206, 207, and 209, pigment violet 19 magenta pigments, C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 30, 49, 81, 82, 83, 84, 100, 109, 121, C . I. Disper thread 9, C.I. I. Basic Red 1, 2, 9, 9, 13, 14, 15, 17, 17, 18, 22, 23, 24, 27, 29, 32, 34, the same 35, 36, 37, 38, 39, 40, etc. Magenta dyes, etc., Bengala, Cadmium Red, Lead Tan, Mercury Sulfide, Cadmium, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red, Calcium Salt, lake red D, brilliant carmine 6B, eosin lake, rotamin lake B, alizarin lake, brilliant carmine 3B, and the like can be used.

Examples of yellow colorants include C.I. I. Yellow pigments such as CI Pigment Yellow 2, 3, 3, 15, 16, 17, 97, 180, 185, and 139 can be used.
Further, in the case of black toner, as the colorant, for example, carbon black, activated carbon, titanium black, magnetic powder, Mn-containing nonmagnetic powder, or the like can be used.

  Further, when used as a toner for photofixing described later, the color toner preferably contains an infrared absorber. The infrared absorber refers to a material having at least one strong light absorption peak in the near infrared region having a wavelength in the range of 800 nm to 2000 nm, and can be used as an organic material or an inorganic material. .

  Specific examples include known infrared absorbers such as cyanine compounds, merocyanine compounds, benzenethiol metal complexes, mercaptophenol metal complexes, aromatic diamine metal complexes, diimonium compounds, aminium compounds, nickel. Complex compounds, phthalocyanine compounds, anthraquinone compounds, naphthalocyanine compounds, and the like can be used.

  More specifically, nickel metal complex infrared absorber (Mitsui Chemical Co., Ltd .: SIR-130, SIR-132), bis (dithiobenzyl) nickel (Midori Chemical Co., Ltd .: MIR-101), bis [1,2 -Bis (p-methoxyphenyl) -1,2-ethylenedithiolate] nickel (manufactured by Midori Chemical Co., Ltd .: MIR-102), tetra-n-butylammonium bis (cis-1,2-diphenyl-1,2-ethylene Dithiolate) Nickel (Midori Chemical Co., Ltd .: MIR-1011), Tetra-n-butylammonium bis [1,2-bis (p-methoxyphenyl) -1,2-ethylenedithiolate] Nickel (Midori Chemical Co., Ltd .: MIR-1021), bis (4-tert-1,2-butyl-1,2-dithiophenolate) nickel-tetra-n-butylammo Um (Sumitomo Seika Chemicals Co., Ltd .: BBDT-NI), cyanine infrared absorbers (Fuji Photo Film Co., Ltd .: IRF-106, IRF-107), cyanine infrared absorbers (Yamamoto Kasei Co., Ltd., YKR2900) aminium, diimonium -Based infrared absorber (Nagase Chemtech Co., Ltd .: NIR-AM1, IM1), imonium compound (Nippon Carlit Co., Ltd .: CIR-1080, CIR-1081), aminium compound (Nippon Carlit Co., Ltd .: CIR-960, CIR-961) , Anthraquinone compounds (Nippon Kayaku Co., Ltd .: IR-750), aminium compounds (Nippon Kayaku Co., Ltd .: IRG-002, IRG-003, IRG-003K), polymethine compounds (Nippon Kayaku Co., Ltd .: IR) -820B), diimonium compounds (manufactured by Nippon Kayaku Co., Ltd .: IRG-022, IRG-023 , Dianine compound (Nippon Kayaku Co., Ltd .: CY-2, CY-4, CY-9), soluble phthalocyanine (Nippon Shokubai Co., Ltd .: TX-305A), naphthalocyanine (Yamamoto Kasei Co., Ltd .: YKR5010, Sanyo Dye Company) Sample 1), inorganic material system (manufactured by Shin-Etsu Chemical Co., Ltd .: ytterbium UU-HP, manufactured by Sumitomo Metals: indium tin oxide), and the like can be used.

  Furthermore, the toner used in the exemplary embodiment preferably contains a charge control agent, and nigrosine, quaternary ammonium salts, organometallic complexes, chelate complexes, and the like can be used. Further, silica, titanium oxide, barium titanate, fluorine fine particles, acrylic fine particles and the like can be used in combination as external additives. As the silica, commercially available products such as TG820 (manufactured by Cabot) and HVK2150 (manufactured by Clariant) can be used.

  Furthermore, the toner used in this embodiment preferably contains a wax, and examples of the wax include ester wax, polyethylene, polypropylene, or a copolymer of polyethylene and polypropylene, polyglycerin wax, microcrystalline wax, and paraffin wax. , Carnauba wax, sazol wax, montanic acid ester wax, deacidified carnauba wax, palmitic acid, stearic acid, montanic acid, brandic acid, eleostearic acid, valinalic acid and other unsaturated fatty acids, stearic alcohol, aralkyl alcohol, Saturated alcohols such as behenyl alcohol, carnauvyl alcohol, seryl alcohol, melyl alcohol, or long-chain alkyl alcohols having a long-chain alkyl group; Polyhydric alcohols such as bitol; Fatty acid amides such as linoleic acid amide, oleic acid amide, lauric acid amide; Methylene bis stearic acid amide, ethylene biscapric acid amide, ethylene bis lauric acid amide, hexamethylene bis stearic acid amide, etc. Unsaturated fatty acid amides such as, for example, saturated fatty acid bisamides, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, N, N′-dioleyl adipic acid amide, N, N′-dioleyl sebacic acid amide; -Aromatic bisamides such as xylene bis stearamide, N, N 'distearyl isophthalic acid amide; fatty acid metal salts such as calcium stearate, calcium laurate, zinc stearate, magnesium stearate (generally metal soaps) Waxes grafted with aliphatic hydrocarbon waxes using vinyl monomers such as styrene and acrylic acid; partially esterified products of fatty acids such as behenic acid monoglycerides and polyhydric alcohols; vegetable oils and fats And a methyl ester compound having a hydroxyl group obtained by hydrogenation or the like.

  As the toner used in the exemplary embodiment, a commonly used kneading and pulverizing method, wet granulation method, or the like can be used. Here, as the wet granulation method, suspension polymerization method, emulsion polymerization method, emulsion polymerization aggregation method, soap-free emulsion polymerization method, non-aqueous dispersion polymerization method, in-situ polymerization method, interfacial polymerization method, emulsion dispersion granulation The law etc. can be used.

  To prepare a toner by the kneading and pulverizing method, a binder resin, a colorant, a charge control agent, a release agent, etc. are melt-kneaded and uniformly dispersed by, for example, a pressure kneader, a roll mill, an extruder, etc. Thereafter, the toner is finely pulverized by a jet mill or the like, and classified by a classifier such as an air classifier to obtain a toner having a desired particle diameter. The constituent components include a thermoplastic binder resin, carbon black, a charge control agent, and the like, and may contain wax, magnetic powder, a viscosity modifier, and other additives as necessary.

  In addition, the toner used in the exemplary embodiment can be manufactured by polymerizing a colorant, an additive, and the like and a monomer that is a base of the binder resin in an aqueous medium. As the production method, there are a suspension polymerization method in which toner-sized particles are formed by a one-step reaction and the shape is spherical, and an emulsion polymerization method in which several polymerized fine particles are aggregated to form a toner size.

Further, when adding the infrared absorbent to the toner, in addition to the method of adding the infrared absorbent by dispersing it inside the toner, the infrared absorbent can be adhered or fixed to the surface of the toner.
Examples of the surface modification device for fixing the surface include a surfing system (manufactured by Nippon Pneumatic Kogyo Co., Ltd.), a hybridization system (manufactured by Nara Machinery Co., Ltd.), a kryptron cosmo series (manufactured by Kawasaki Heavy Industries, Ltd.), Surface reformer that gives impacts in high-speed air currents such as Inomizer System (Hosokawa Micron); Applied dry mechanochemical methods such as Mechano Fusion System (Hosokawa Micron), Mechano Mill (Okada Seiko) A surface modification device using a wet coating method of Disper Coat (manufactured by Nisshin Engineering Co., Ltd.), Coat Mizer (manufactured by Freund Sangyo Co., Ltd.), and the like can be used in appropriate combination.

  The toner used in the exemplary embodiment preferably has a weight average particle diameter of 5 μm or more and 13 μm or less.

The average circularity of each toner is preferably 0.9 or more, more preferably 0.960 or more, and the standard deviation of the circularity is preferably 0.040 or less, and 0.038 or less. More preferably.
The average circularity of the toner is equal to the peripheral length (peripheral length) of the projected image of the toner particles and the projected area of the toner particles in a water dispersion system using a flow type particle image analyzer (manufactured by Simex, FPIA2000). The circumference of the circle (circle equivalent circumference) is obtained and calculated by (circle equivalent circumference / perimeter).

On the other hand, when the toner is produced by the wet granulation method, it is preferable that the shape factor SF1 of the toner is in the range of 110 to 135.
The toner shape factor SF1 is obtained by taking toner particles dispersed on a slide glass or an optical microscope image of the toner into a Luzex image analyzer through a video camera, and obtaining the maximum length and projected area of 50 or more toners. It is obtained by calculating by (4) and obtaining the average value.
SF1 = (ML ² / A) × (π / 4) × 100 (4)
In the above formula (2), ML represents the absolute maximum length of the toner particles, and A represents the projected area of the toner particles.

In addition, the volume particle size distribution index GSDv of the toner used in the present embodiment is preferably 1.25 or less.
The volume average particle size and particle size distribution index of the toner are measured using a Coulter Multisizer-II type (Beckman-Coulter) and the electrolyte is ISOTON-II (Beckman-Coulter). did.
For the divided particle size range (channel), a cumulative distribution is drawn from the small diameter side for each of the volume and number, and the particle size at which the accumulation becomes 16% is determined as the volume average particle diameter D16v and the number average particle diameter. D16p is defined, and the particle size that is 50% cumulative is defined as a volume average particle size D50v (the volume average particle size of the toner described above indicates this) and a number average particle size D50p. Similarly, the particle size that is 84% cumulative is defined as the volume average particle size D84v and the number average particle size D84p. Using these, the volume average particle size distribution index (GSDv) is calculated as (D84v / D16v) ^1/2 .

  The toner concentration in the developer of the exemplary embodiment is preferably 1% by mass or more and 10% by mass or less, and more preferably 2% by mass or more and 6% by mass or less. The mixing of the toner and the carrier can be performed with a Nauta mixer or the like.

  The developing device according to the present embodiment includes a developer holder that rotates while holding the developer on the surface, a developer transport / supply member that transports the developer, and further supplies the developer to the developer holder. A developer transport supply path having a developer and a developer transported to the most downstream side in the transport direction of the developer transport supply path, and further supplying toner to the captured developer by a toner replenishment mechanism, A developer agitation supply path having a developer agitation supply member that conveys the developer replenished with toner in a direction opposite to the conveyance direction of the developer conveyance supply path, and supplies the developer to a developer conveyance member; A toner concentration detecting member that measures the toner concentration of the developer in the developer agitation supply path, wherein the developer agitation supply member has a conveyance speed of 180 mm / sec or more, and the developer is as described above. This is a developer for electrophotography of this embodiment. And wherein the door.

The developing device of this embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an example of a developing device according to the present embodiment as viewed from the axial direction of a developer holder.
A developing device 4 shown in FIG. 1 includes a developing roller 5 that is a developer holding body that supplies a developer to an electrostatic latent image holding body (not shown), and supplies the developer to the developing roller 5 while conveying the developer. 5 includes a developer conveyance supply path 40 having a conveyance supply screw (developer conveyance supply member) 41 that collects the developer from 5. Further, the developer transported to the downstream end of the developer transport supply path 40 is taken in, toner is supplied to the taken-in developer from the toner replenishing mechanism 44 as necessary, and the developer and toner are stirred. However, a developer agitation supply path 10 having an agitation screw 11 as a developer agitation supply member that conveys in a direction opposite to the developer conveyance supply path 40 is provided. The developer conveyance supply path 40 and the developer agitation supply path 10 are partitioned by a partition wall 43 that is a partition member. The developer conveyance supply path 40 and the developer agitation supply path 10 communicate with each other through openings at both ends in the axial direction of the partition wall 43, and the developer conveyance supply path 40 and the developer agitation supply path 10 are connected with the developer. Are circulated and conveyed by conveying them in the opposite direction. In addition, the conveyance supply screw 41 and the agitation screw 11 are provided with helical protrusions that protrude in a spiral shape in a direction orthogonal to the axial direction on the outer peripheral surface of the shaft.

  In the developing device 4 shown in FIG. 1, the supply of the developer to the developing roller 5 and the recovery of the developed developer are performed by the conveyance supply screw 41. The developed developer is in a state where the toner is consumed by development and the toner density is lower than that before development. Since the developer supply screw and the recovery screw are the same, and the supply conveyance path and the recovery conveyance path are the same, the developed recovered developer and the developer before development are agitated. The As a result, the toner density of the developer supplied to the developing roller 5 decreases toward the downstream side of the developer transport supply path 40 in the developer transport direction. In particular, in an image with a high printing rate, a decrease in toner density after development is larger than that before development, and a decrease in toner density downstream in the developer transport direction is large. In order to prevent such a decrease in toner density, toner is replenished by the toner replenishment mechanism 44 to the developer whose toner density has decreased on the downstream side in the developer transport direction.

  The toner supply by the toner supply mechanism 44 is based on the toner concentration by the toner concentration detection member that measures the toner concentration of the developer provided in the developer stirring supply path 10 that transports the developer while stirring the developer by the stirring screw 11. Performed from time to time.

The toner concentration detection member provided in the developer stirring supply path 10 will be described with reference to FIG.
FIG. 2 is a view of the developer agitation supply path and the developer transport supply path of the developing device shown in FIG. 1 as viewed from a direction perpendicular to the axial direction of the developer holder. A magnetic permeability sensor, which is a toner concentration detection member, is attached to point B below the stirring screw 11. On the other hand, point A is a toner replenishment position. In FIG. 2, arrows α and β indicate the traveling direction of the developer.

  The toner concentration detection member will be further described. At point A, the developer is conveyed in the direction of arrow α in the figure. When the toner is replenished, a peak in which the toner density increases with the movement of the replenished toner is observed. The peak at B at that time is as shown in FIG. The peak at the time is X, and the peak when the replenished toner goes around the developer agitation supply path 10 and the developer transport supply path 40 is Y. Further, the replenished toner repeats the circulation of the developer agitation supply path 10 and the developer transport supply path 40, so that the toner density is stabilized. FIG. 3 is a diagram showing a peak of toner density detected by the toner density detecting member.

  The developing device according to the present embodiment corresponds to a high-speed image forming apparatus, and has a developer agitation supply member (agitating screw 11) having a conveyance speed of 180 mm / sec or more. When the conveying speed of the developer agitation supply member is less than 180 mm / sec, the supply amount to the developer holder is insufficient, and the developer is biased, and therefore, the spikes on the developer holder are uneven. become. For this reason, this causes a problem such as a difference in image density between the near side and the far side of the developer holder. Here, the conveyance speed of the developer agitation supply member (agitating screw 11) is the product of the screw pitch (distance between the helical protrusions) M of the agitating screw 11 shown in FIG. It is obtained by calculating pitch M × screw rotation speed V). Since the unit of the conveyance speed of the developer agitation supply member is “mm / sec”, the unit in the formula of (screw pitch M × screw rotation speed V) is “mm”. When the unit of the screw rotation number is “rpm”, it is necessary to multiply by 60. The conveyance speed of the developer agitation supply member is preferably 180 mm / sec or more, and more preferably 200 mm / sec or more.

  Further, in the developing device of the present embodiment, the developer transport efficiency in the developer stirring supply path 10 is preferably 50% or more, and more preferably 60% or more. Here, the developer conveyance efficiency in the developer agitation supply path 10 is calculated by dividing the moving speed of the developer in the developer agitation conveyance path 10 by the conveyance speed of the developer agitation supply member and multiplying this value by one hundred. %.

  Here, the moving speed of the developer in the developer stirring and conveying path 10 is obtained by calculating the time difference between the peak X and the peak Y shown in FIG. It is obtained by dividing by the distance when making a round.

Further, the developing device of the present embodiment preferably has a developer conveyance amount of 730 g · m / sec or more in the developer stirring supply path 10 in terms of being compatible with a high-speed image forming apparatus, and more preferably 800 g · m / sec. More preferably. Here, the developer transport amount in the developer agitation supply path 10 is obtained as follows.
The developer transport amount was calculated by multiplying the developer amount contained in the developing device, the transport speed of the developer agitation supply member, and the developer transport efficiency.

As described above, the developing device of the present embodiment is capable of high speed and is characterized in that the conveying speed of the developer agitation supply member is 180 mm / sec or more. When a general developing device is operated at a high speed, the replenished toner is hardly diffused into the developer, and the toner density is difficult to stabilize. Furthermore, the fluidity of the carrier and the developer is deteriorated, and the toner with low charge and poor charge is generated due to the decrease in the mixing property. As a result, the charge distribution of the toner is widened and the image quality is deteriorated. Since the stagnation is likely to occur, there is a problem that it is difficult to detect an appropriate toner concentration by the toner concentration detecting member.
However, since the developing device of the present embodiment uses the developer of the present embodiment described above having specific fluidity, the toner concentration does not become difficult to stabilize, and the mixing property does not decrease. Defective toner is not generated, the toner charge distribution is widened and the image quality is lowered, and aggregation and stagnation in the developing device are likely to occur. Done.

  The image forming apparatus according to the present embodiment forms an electrostatic latent image on the surface of the electrostatic latent image holding member, charging means for charging the surface of the electrostatic latent image holding member, and the electrostatic latent image holding member. An electrostatic latent image forming unit; a developing unit that develops the electrostatic latent image into a toner image with a developer; and the toner image formed on the surface of the electrostatic latent image holding member is transferred to the surface of the transfer target. A transfer unit; and a fixing unit that fixes the toner image transferred to the transfer target. The process speed is 1000 mm / second or more, and the developing unit rotates while holding the developer on the surface. A developer holding body, a developer carrying supply path having a developer carrying supply member for carrying the developer and supplying the developer to the developer holding body, and a carrying direction of the developer carrying supply path The developer transported to the most downstream side of is taken in, to the incorporated developer, A developer that further replenishes toner by a toner replenishment mechanism, conveys the developer replenished with toner in a direction opposite to the conveyance direction of the developer conveyance supply path, and supplies the developer to a developer conveyance member A developer agitation supply path having an agitation supply member; and a toner concentration detection member for measuring the toner concentration of the developer in the developer agitation supply path, wherein the conveying speed in the developer agitation supply member is 180 mm / sec. or longer, and the developer is the developer of the present embodiment described above.

  The image forming apparatus according to the present embodiment can cope with an ultra-high speed process, and the process speed is preferably 1000 mm / sec or more, and more preferably 1500 mm / sec or more. Here, the process speed is the conveyance speed of the printing medium, and is mainly the case where the mechanism in the image forming apparatus indicates the circumferential rotational speed of the surface of the electrostatic latent image holding member.

Hereinafter, an example of the image forming apparatus according to the present exemplary embodiment will be described with reference to the drawings. FIG. 5 is a schematic configuration diagram illustrating a basic configuration of an example of the image forming apparatus according to the present exemplary embodiment.
The image forming apparatus shown in FIG. 5 includes an electrostatic latent image holding body 12, a charging unit 14, an electrostatic latent image forming unit 16, a developing unit 18, a transfer unit 20, a cleaning unit 22, a charge eliminating unit 24, and a fixing unit 26. . The developing unit 18 is the developing device of the present embodiment described above.

  In the image forming apparatus shown in FIG. 5, the surface of the electrostatic latent image holding body 12 is sequentially placed around the electrostatic latent image holding body 12 along the rotation direction (direction of arrow A) of the electrostatic latent image holding body 12. The charging means 14 for charging, the electrostatic latent image forming means 16 for forming an electrostatic latent image on the surface of the electrostatic latent image holding body 12 according to the image information, and the developer of the present embodiment on the formed electrostatic latent image. Developing means 18 to be supplied, drum-like transfer means 20 that contacts the surface of the electrostatic latent image holding body 12 and can be driven to rotate in the direction of arrow B as the electrostatic latent image holding body 12 rotates in the direction of arrow A; A cleaning unit 22 that comes into contact with the surface of the electrostatic latent image holding body 12 and a static elimination unit 24 that neutralizes the surface of the electrostatic latent image holding body 12 are arranged.

  In the gap between the electrostatic latent image holding body 12 and the transfer means 20, a recording medium (transfer object) 50 conveyed in the arrow C direction by a conveying means (not shown) from the opposite side of the arrow C direction can be inserted. A fixing unit 26 having a built-in heating source (not shown) is arranged on the electrostatic latent image holding body 12 in the direction of arrow C. The fixing unit 26 is provided with a pressure contact portion 32. Further, the recording medium 50 that has passed through the gap between the electrostatic latent image holding member 12 and the transfer means 20 can be inserted through the pressure contact portion 32 in the direction of arrow C.

As the electrostatic latent image holding member 12, for example, a photosensitive member or a dielectric recording member can be used.
As the photoreceptor, for example, a photoreceptor having a single layer structure or a photoreceptor having a multilayer structure can be used. As the material of the photoconductor, an inorganic photoconductor such as selenium or amorphous silicon, an organic photoconductor, or the like can be considered.

  Examples of the charging means 14 include a contact charging device using a conductive or semiconductive roller, brush, film, rubber blade, etc., a non-contact type charging device such as corotron charging or scorotron charging using corona discharge, etc. Any known means can be used.

As the electrostatic latent image forming means 16, for example, any conventionally known means capable of forming a signal capable of forming a toner image at a desired position on the surface of the recording medium in addition to the exposure means can be used.
As the exposure means, for example, a conventionally known exposure means such as a combination of a semiconductor laser and a scanning device, a laser scanning writing device comprising an optical system, or an LED head can be used. In order to realize a preferable mode of producing a uniform and high-resolution exposure image, it is preferable to use a laser scanning writing device or an LED head.

  Specifically, as the transfer unit 20, for example, a conductive or semiconductive roller, brush, film, rubber blade, or the like to which a voltage is applied is used, and the electrostatic latent image holding member 12 and the recording medium 50 are used. A charged toner particle is formed by corona charging the back surface of the recording medium 50 with a means for transferring a toner image composed of charged toner particles, a corotron charger using a corona discharge, or a scorotron charger. Conventionally known means such as a means for transferring a toner image comprising the above can be used.

  A secondary transfer unit can also be used as the transfer unit 20. That is, although not shown, the secondary transfer unit is a unit that transfers the toner image to the intermediate transfer member and then secondary-transfers the toner image from the intermediate transfer member to the recording medium 50.

  Here, a cleaning blade is used as the cleaning means 22. Moreover, as the static elimination means 24, a tungsten lamp, LED, etc. are mentioned, for example.

As the fixing unit 26, for example, a heat fixing device that fixes a toner image by heating and pressurization including a heating roll and a pressure roll, an optical fixing device that heats and fixes a toner image by light irradiation with a flash lamp or the like, and the like. Available.
The material forming the roll surface such as a heating roll or a pressure roll is preferably, for example, a material excellent in releasability with respect to the toner, silicon rubber, fluorine resin, or the like for the purpose of preventing the toner from adhering.

  The recording medium 50 is not particularly limited, and conventionally known media such as plain paper and glossy paper can be used. A recording medium having a base material and an image receiving layer formed on the base material can also be used.

  Next, image formation using the image forming apparatus shown in FIG. 5 will be described. First, as the electrostatic latent image holding body 12 rotates in the direction of arrow A, the surface of the electrostatic latent image holding body 12 is charged by the charging unit 14, and the electrostatic latent image holding body 12 surface is charged with the electrostatic latent image. An electrostatic latent image corresponding to the image information is formed by the image forming means 16, and the developing means 18 is formed on the surface of the electrostatic latent image holding body 12 on which the electrostatic latent image is formed according to the color information of the electrostatic latent image. A toner image is formed by supplying the developer P of this embodiment.

  Next, the toner image formed on the surface of the electrostatic latent image holding body 12 is brought into contact with the electrostatic latent image holding body 12 and the transfer unit 20 as the electrostatic latent image holding body 12 rotates in the arrow A direction. Move to the department. At this time, the recording medium 50 is inserted through the contact portion in the direction of arrow C by a paper conveyance roll (not shown), and the electrostatic latent image is transferred by the voltage applied between the electrostatic latent image holder 12 and the transfer means 20. The toner image formed on the surface of the image carrier 12 is transferred to the surface of the recording medium 50 at the contact portion.

  The toner remaining on the surface of the electrostatic latent image holding body 12 after the toner image is transferred to the transfer unit 20 is removed by the cleaning blade of the cleaning unit 22 and the charge is removed by the charge removing unit 24.

  The recording medium 50 having the toner image transferred onto the surface in this way is conveyed to the pressure contact portion 32 of the fixing unit 26 and passes through the pressure contact portion 32 to be pressed by a built-in heating source (not shown). The surface of the section 32 is heated by the heated fixing means 26. At this time, an image is formed by fixing the toner image on the surface of the recording medium 50.

In addition, as an image forming apparatus according to the present exemplary embodiment, an image forming apparatus including an optical fixing device (flash fixing device) as a fixing unit is also a preferable mode.
Hereinafter, as an example of the image forming apparatus according to the present exemplary embodiment, an image forming apparatus including the light fixing device will be described with reference to the drawings.
FIG. 6 is a schematic configuration diagram showing a basic configuration of another example of the image forming apparatus according to the present embodiment, and illustrates a toner image formed with toner obtained by adding black to three colors of cyan, magenta, and yellow. .

  In FIG. 6, 61a to 61d are charging means, 62a to 62d are electrostatic latent image forming means, 63a to 63d are photosensitive members (electrostatic latent image holding members), 64a to 64d are developing means, and 50 is from the roll medium 65. Recording medium (transfer object) fed in the direction of the arrow, 120 is a cyan developing unit, 130 is a magenta developing unit, 140 is a yellow developing unit, 150 is a black developing unit, 70a to 70d are transfer rolls (transfer means), 71, Reference numeral 72 denotes a roll, 80 denotes a transfer voltage supply means, and 90 denotes an optical fixing device (fixing means).

  The image forming apparatus shown in FIG. 1 includes a developing unit (toner image forming unit) for each color indicated by reference numerals 120, 130, 140, and 150 including a charging unit, an exposure unit, a photoconductor, and a developing unit, and a recording medium 50. Rolls 71 and 72 which are arranged in contact with each other and convey the recording medium 50, and transfer rolls 70a and 70b which are arranged so as to be in contact with the opposite side through the recording medium 50 so as to press the photoreceptor of each developing unit. 70c, 70d, transfer voltage supply means 80 for supplying voltage to these three transfer rolls, and the side of the recording medium 50 in contact with the photoconductor passing through the nip portion between the photoconductor and the transfer roll in the direction of the arrow in the figure And an optical fixing device (fixing means) 90 for irradiating light.

  The cyan developing unit 120 has a configuration in which a charging unit 61a, an exposing unit 62a, and a developing unit 64a are arranged around the photosensitive member 63a in a clockwise direction. Further, the transfer roll 70a faces the surface of the photoconductor 63a from the position where the developing unit 64a of the photoconductor 63a is disposed to the position where the charging unit 61a is arranged clockwise. Has been placed. Such a configuration is the same for the developing units of other colors. In the image forming apparatus of the present embodiment, the developer containing cyan toner is stored in the developing unit 64a of the cyan developing unit 120, and the developing unit of the other developing unit has light corresponding to each color. A developer containing toner for fixing is stored.

  Next, image formation using this image forming apparatus will be described. First, in the black developing unit 150, the surface of the photosensitive member 63d is uniformly charged by the charging unit 61d while rotating the photosensitive member 63d in the clockwise direction. Next, the surface of the charged photoreceptor 63d is exposed by the exposure means 62d, so that a latent image corresponding to the yellow component image of the original image to be copied is formed on the surface of the photoreceptor 63d. Further, the black toner stored in the developing means 64d is applied on the latent image to develop it to form a black toner image. This process is similarly performed in the yellow developing unit 140, the magenta developing unit 130, and the cyan developing unit 120, and a toner image of each color is formed on the surface of the photosensitive member of the developing unit.

  The toner images of the respective colors formed on the surface of the photoreceptor are sequentially transferred onto the recording medium 50 conveyed in the direction of the arrow by the action of the transfer potential by the transfer rolls 70a to 70d, and recorded so as to correspond to the original image information. A full-color laminated toner image is formed by being laminated on the surface of the medium 50 in the order of cyan, magenta and yellow from the top layer.

  Next, the laminated toner image on the recording medium 50 is conveyed to the optical fixing device 90, where it is irradiated with light from the optical fixing device 90, melted, and optically fixed on the recording medium 50 to form a full-color image. It is formed.

Here, the optical fixing device 90 will be described.
The light source used for the optical fixing device 90 includes a normal halogen lamp, a mercury lamp, a flash lamp, an infrared laser, and the like, and it is optimal because it can save energy by fixing the flash lamp instantaneously. Preferably emission energy of the flash lamp is in the range of 1.0 J / cm ² or more 7.0J / cm ² or less, and more preferably 2J / cm ² or more 5 J / cm ² or less.

Here, the emission energy per unit area of the flash light indicating the lamp intensity of xenon is expressed by the following formula (5).
S = ((1/2) × C × V ² ) / (u × L) × (n × f) (5)
In the above formula (5), n is the number of lamps that emit light at once (f), f is the lighting frequency (Hz), V is the input voltage (V), C is the capacitor capacity (F), u is the process transport speed (cm) / S), L represents the effective light emission width of the flash lamp (usually the maximum paper width, cm), and S represents the energy density (J / cm ² ).

The light fixing method is preferably a delay method in which a plurality of flash lamps emit light with a time difference. This delay system is a system in which a plurality of flash lamps are arranged, each lamp is delayed by about 0.01 ms to 100 ms and light is emitted, and the same portion is illuminated a plurality of times. As a result, the light energy can be divided and supplied to the toner image with a single light emission, so that the fixing conditions can be made mild and both void resistance and fixability can be achieved.
Here, when flash emission is performed on the toner a plurality of times, the emission energy of the flash lamp indicates the total amount of emission energy given to the unit area for each emission.

In the present embodiment, the number of flash lamps is preferably in the range of 1 to 20, more preferably in the range of 2 to 10. The time difference between the plurality of flash lamps is preferably in the range of 0.1 msec to 20 msec, and more preferably in the range of 1 msec to 3 msec.
Furthermore, once emission energy of light emitted in one flash lamp is preferably 0.1 J / cm ² or more 1 J / cm ² or less in the range, 0.4 J / cm ² or more 0.8 J / cm ² or less Is more preferable.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples. In the following description, “part” means “part by mass”.
(Preparation of carrier C-1)
Silicone resin (KR9706) containing carbon black (Ketjen Black EC600JD) as conductive particles on the surface of the fired ferrite particles (Mn—Mg—Sr ferrite, average particle size = 65 μm) in toluene is added to toluene. Dilution was carried out and the obtained diluted product was coated on the ferrite particles using a fluidized bed coating apparatus to prepare Carrier C-1 on which a resin coating layer was formed. In addition, the coating amount with respect to 100 parts of core materials of the resin coating layer is as shown in Table 1. Further, the apparent density AD, the fluidity FR, the coercive force Hc, and the saturation magnetization measured by the above-described method are represented by the first fluidity index F1 represented by the above equation (1) and the second fluid represented by the above equation (2). It is shown in Table 1 together with the fluidity index F2.

(Production of carriers C-2 to C10)
In the preparation of carrier C-1, the firing temperature and firing time of the ferrite particles were changed as appropriate, and the coating amount of the silicone resin containing 10% by mass of carbon black was the coating amount with respect to 100 parts of the core material of the resin coating layer. Carriers C-2 to C10 were produced in the same manner as in the production of the carrier C-1, except that the values were adjusted to the values described in 1. The apparent density AD, the fluidity FR, the coercive force Hc, and the saturation magnetization measured by the above-described method are the first fluidity index F1 represented by the equation (1) and the second fluid represented by the equation (2). It is shown in Table 1 together with the fluidity index F2.

(Production of carriers C-11 to C15)
In the preparation of carrier C-1, the firing temperature and firing time of the ferrite particles were changed as appropriate, and the coating amount of the silicone resin containing 10% by mass of carbon black was the coating amount with respect to 100 parts of the core material of the resin coating layer. A resin coating layer is formed by adjusting so as to have a value described in 1. Further, a silicone resin obtained by removing carbon black from a silicone resin containing 10% by mass of carbon black is diluted in toluene, and a fluidized bed coating apparatus is used. Then, the obtained dilution was coated on the ferrite particles on which the resin coating layer was formed, to prepare carriers C-11 to C15 on which the second resin coating layer was formed. In addition, the coating amount with respect to 100 parts of core materials of the resin coating layer and the second resin coating layer is as shown in Table 1. Further, the apparent density AD, the fluidity FR, the coercive force Hc, and the saturation magnetization measured by the above-described method are represented by the first fluidity index F1 represented by the above equation (1) and the second fluid represented by the above equation (2). It is shown in Table 1 together with the fluidity index F2.

As a binder resin, 85 parts by weight of a polyester resin made from a propylene oxide adduct of bisphenol A (FN 118, manufactured by Kao Corporation), as a colorant, 10 parts by weight of carbon black (Black Pearls L, manufactured by Cabot Corporation), a nigrosine dye (Orient Chemical) N-13) 1 part by weight and 4 parts by weight of propylene wax (Biscol 550P, Sanyo Chemical Co., Ltd.) were added and melt kneaded with a pressure kneader at 160 ° C. for 30 minutes to obtain a toner mass. The toner lump was pulverized, and 0.5 parts by weight of silica (TG820F manufactured by Cabot) was externally added to the toner using a high-speed stirrer (Henschel mixer) to prepare a toner.
This toner and each of the carriers C1 to C15 were mixed so that the toner concentration was 4.5% by mass to prepare a developer.

<Examples 1 to 10, Comparative Examples 1 to 5>
The developer including the carrier shown in Table 1 was subjected to a printing test using an actual machine using a high-speed printer F6760D (manufactured by Fujitsu), and the following evaluation was performed. The results are shown in Table 1. The developing means provided in the high-speed printer F6760D has the same structure as the developing device shown in FIGS. 1 and 2, the developer agitation supply member conveying speed is 209 mm / sec, and the developer conveying efficiency. Was 55%, and the developer conveyance amount was 805 g · m / sec. The high-speed printer F6760D was operated at a process speed of 1200 mm / second or more.

<Evaluation>
(Controllability of toner density detection member)
The toner density fluctuation width of the toner density detecting member when 1000 images with a printing rate of 4% were continuously printed was measured and evaluated according to the following criteria.
A: The toner density fluctuation width of the toner density detecting member is less than 0.1 v.
A: The toner density fluctuation width of the toner density detecting member is 0.1 v or more and less than 0.3 v.
X: The toner density fluctuation width of the toner density detecting member is 0.3 v or more.

(Print density)
The print density when 1000 images having a printing rate of 4% were continuously printed was measured using a 939 Spectrodentitometer (X-Rite) and evaluated according to the following criteria.
A: The print density exceeds 1.4.
○: Print density exceeds 1.2 and is 1.4 or less.
X: Print density is 1.2 or less.

(Granularity)
Graininess when 1000 images with a printing rate of 4% were continuously printed was evaluated according to the following criteria by visual judgment using a panel.
A: Good.
○: Normal.
X: It is bad.

(Example 11)
In Example 9, a printing test was performed in the same manner as in Example 9 except that the developer conveyance efficiency was changed to 60%, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

Example 12
In Example 9, a printing test was performed in the same manner as in Example 9 except that the developer transport amount was changed to 914 g · m / sec, and the same evaluation as in Example 1 was performed. The results are shown in Table 1.

FIG. 3 is a cross-sectional view of an example of the developing device of the present embodiment as viewed from the axial direction of the developer holding member. FIG. 2 is a diagram of a developer agitation supply path and a developer transport supply path of the developing device shown in FIG. 1 as viewed from a direction perpendicular to the axial direction of the developer holder. FIG. 6 is a diagram illustrating a peak of toner density detected by a toner density detecting member. It is a figure which shows the screw pitch of the stirring screw 11. FIG. 1 is a schematic configuration diagram illustrating a basic configuration of an example of an image forming apparatus according to an exemplary embodiment. It is a schematic block diagram which shows the basic composition of the other example of the image forming apparatus of this embodiment.

Explanation of symbols

4 Developing device 5 Developing roller 10 Developer stirring supply path 11 Stirring screw 12 Electrostatic latent image holding body 14 Charging means 16 Electrostatic latent image forming means 18 Developing means 20 Transfer means 22 Cleaning means 24 Static eliminating means 26 Fixing means 120 Cyan development Unit 130 Magenta development unit 140 Yellow development unit 150 Black development unit

Claims (7)

A core material, and a resin coating layer containing a conductive material and covering the surface of the core material;
The saturation magnetization is 63 emu / g or more and 93 emu / g or less,
The first fluidity index F1 represented by the following formula (1) is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ) or less,
A carrier for electrophotography, wherein the second fluidity index F2 represented by the following formula (2) is 24 Oe · g / cm ³ or more and 28 Oe · g / cm ³ or less.
F1 = AD × FR (1)
F2 = AD × Hc (2)
In the formulas (1) and (2), AD represents the apparent density (g / cm ³ ), FR represents the fluidity (sec / 50 g), and Hc represents the coercive force (Oe) when a magnetic field of 3000 Oe is applied. Indicates.   The content of the conductive material is 20% by mass or less, the second resin coating layer covers the surface of the resin coating layer, and the coating amount of the resin coating layer with respect to 100 parts by mass of the core material is 1.9 mass. 2. The electrophotographic carrier according to claim 1, wherein the coating amount of the second resin coating layer with respect to 100 parts by mass of the core material is 0.4 parts by mass or less. .   An electrophotographic developer comprising a toner and the electrophotographic carrier according to claim 1. A developer holder that rotates while holding the developer on the surface; and a developer transport supply path that includes a developer transport supply member that transports the developer and supplies the developer to the developer holder. The developer transported to the most downstream side in the transport direction of the developer transport supply path is taken in, the toner is further replenished by the toner replenishment mechanism, and the developer replenished with the toner is supplied. A developer agitation supply path having a developer agitation supply member that conveys the developer in a direction opposite to the conveyance direction of the developer conveyance supply path and supplies the developer conveyance member to the developer conveyance member; and in the developer agitation supply path A toner concentration detecting member for measuring the toner concentration of the developer of
The developer agitation supply member has a conveyance speed of 180 mm / sec or more,
A developing device, wherein the developer is the electrophotographic developer according to claim 3.   The developing device according to claim 4, wherein the developer conveying efficiency in the developer stirring supply path is 50% or more.   The developing device according to claim 4, wherein a developer conveyance amount in the developer agitation supply path is 730 g · m / sec or more. An electrostatic latent image holding member; a charging unit that charges the surface of the electrostatic latent image holding member; an electrostatic latent image forming unit that forms an electrostatic latent image on the surface of the electrostatic latent image holding member; A developing unit that develops the electrostatic latent image into a toner image with a developer; a transfer unit that transfers the toner image formed on the surface of the electrostatic latent image holding member to the surface of the transfer member; Fixing means for fixing the transferred toner image,
The process speed is 1000 mm / second or more,
The developing unit includes a developer holding member that rotates while holding the developer on the surface, and a developer conveying and supplying member that conveys the developer and supplies the developer to the developer holding member. The developer transport supply path and the developer transported to the most downstream side in the transport direction of the developer transport supply path, the toner is further replenished to the captured developer by a toner replenishment mechanism, and the toner is replenished The developer agitation supply path having a developer agitation supply member that conveys the developer thus developed in a direction opposite to the conveyance direction of the developer conveyance supply path and supplies the developer to the developer conveyance member, and the development A toner concentration detection member that measures the toner concentration of the developer in the developer agitation supply path, and the conveyance speed in the developer agitation supply member is 180 mm / sec or more,
The developer contains a toner, a core material, and a conductive material, and has a resin coating layer that covers the surface of the core material. The saturation magnetization is 63 emu / g or more and 93 emu / g or less. ) Is 63 sec / (50 · cm ³ ) or more and 73 sec / (50 · cm ³ ) or less, and the second fluidity index F2 represented by the following formula (2) is 24 Oe. An image forming apparatus comprising: an electrophotographic carrier having a g / cm ³ or more and 28 Oe · g / cm ³ or less.
F1 = AD × FR (1)
F2 = AD × Hc (2)
In the formulas (1) and (2), AD represents the apparent density (g / cm ³ ), FR represents the fluidity (sec / 50 g), and Hc represents the coercive force (Oe) when a magnetic field of 3000 Oe is applied. Indicates.

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