JP4700535B2 - Electrophotographic carrier, electrophotographic developer, electrophotographic carrier, and manufacturing method of carrier core material - Google Patents

Description

  The present invention relates to a method for classifying magnetic particles, resin-coated magnetic particles, or electrophotographic carrier particles containing a magnetic material prepared by a polymerization method, a method for producing electrophotographic carrier particles, and classification The present invention relates to an electrophotographic carrier core material, an electrophotographic carrier using the classified particles, and an electrophotographic developer using the carrier.

Electrophotographic development methods include a one-component development method mainly composed of toner and a two-component development method using a developer obtained by mixing a carrier and toner.
The two-component development method uses a carrier and has a wide frictional charging area for the toner, so the charging characteristics are more stable than the one-component method, which is advantageous for obtaining high image quality over a long period of time. Two-component developers are widely used because of their high toner supply capacity.

In recent years, a development system capable of faithfully developing a latent image has become an important issue in order to cope with resolution enhancement, highlight reproducibility improvement, and colorization. For this reason, various proposals have been made in terms of both process conditions and developer (toner, carrier). In terms of process, it is effective to make the developing gap close, to make the photoconductor thin, and to reduce the writing beam diameter, but there are still significant problems in terms of cost and reliability.
It is known that the reproducibility of dots is greatly improved by using a toner having a small particle diameter as a developer. However, a developer containing a toner having a small particle diameter causes scumming or lack of image density. There remains a problem to be solved.
In the case of a full color toner with a small particle size, a resin with a low softening point is used in order to obtain a sufficient color tone, but the spent amount to the carrier is increased and the developer is deteriorated as compared with the case of a black toner. As a result, toner scattering and background staining are likely to occur.

On the other hand, various proposals have been made for the use of small particle size carriers.
That is, Patent Document 1 proposes a magnetic carrier having an average particle size of less than 30 μm, which is composed of ferrite particles having a spinel structure. This is a carrier that is not resin-coated, and is used under a low development electric field, and has a short development life because it has poor development capability and is not resin-coated.

Further, in Patent Document 2, in an electrophotographic carrier having carrier particles, the carrier has a 50% average particle size (D50) of 15 to 45 μm and contains 1 to 20% of carrier particles smaller than 22 μm. 3% or less of carrier particles smaller than 16 μm, 2 to 15% of carrier particles of 62 μm or more, and 2% or less of carrier particles of 88 μm or more, Specific surface area S1 of the carrier measured by the air permeation method, and specific surface area S2 of the carrier calculated by the following formula: S2 = {(6 / ρ) × D ₅₀ } × 104 (ρ is the specific gravity of the carrier) However, there is described an electrophotographic carrier characterized by satisfying the condition of 1.2 ≦ S1 / S2 ≦ 2.0.

These small particle size carriers are known to have the following advantages.
That is,
(1) Since the surface area per unit volume is large, sufficient frictional charge can be given to each toner, and the generation of low charge amount toner and reverse charge amount toner is small. As a result, the background stains are less likely to occur, the toner around the dots is less dusty and blurred, and the dot reproducibility is improved.
(2) Since the surface area per unit volume is large and scumming is less likely to occur, the average charge amount of the toner can be reduced and a sufficient image density can be obtained. Accordingly, the small particle size carrier can make up for the disadvantages when using the small particle size toner, and at the same time is particularly effective in drawing out the advantages of the small particle size toner.
(3) The small particle size carrier has a feature that a dense magnetic brush is formed and an ear mark is hardly generated in an image.
However, as the particle size of the carrier decreases, the magnetic binding force rapidly decreases at a ratio of the cube of the particle size, and the carrier adhesion is very likely to occur, in the form of carrier particles or cut magnetic brushes. Adhere to. As a result, the conventional small particle size carrier becomes a source of scratches on the photoreceptor and fusing roller, and has a very large problem in practical use.
Further, when the carrier particle size is reduced, the frictional force between the particles is increased, and the torque of the developing sleeve is increased, so that the sleeve surface is easily scraped or the toner is fixed. When these occurred, the amount of developer pumped up on the sleeve varied, and image density variation occurred.

When examining the carrier adhering to the small particle size carrier, the carrier on the small particle size side has an overwhelmingly high ratio. Thus, various methods for sharply classifying the particle size distribution have been proposed. Among them, classification with a sieve can be classified sharply compared with centrifugal force and pneumatic classification methods, and the necessary particles in the particle size distribution can be recovered with high yield.
However, it is known that the classification method using a sieve makes it difficult to classify into a sharp particle size distribution when the particle diameter is small, that is, when the mass per one is small.

  As a method for solving such a problem, a high-quality image is obtained, and it is highly durable and hardly causes carrier adhesion. The weight average particle diameter Dw is 25 to 45 μm, and the particle diameter is 44 μm or less. The content ratio is 70 wt% or more, the content ratio of particles having a particle size of 22 μm or less is 7 wt% or less, and the ratio Dw / Dp of the weight average particle diameter Dw to the number average particle diameter Dp is 1-1. In order to produce an electrophotographic developer carrier in the range of 30, ultrasonic vibration is applied to the wire mesh of the sieving machine, vertical acceleration is applied to the particles, and small diameter particles of less than 22 μm are efficiently and sharply formed. A cutting technique has been proposed (see, for example, Patent Document 3).

According to this method, since vertical acceleration is given to the particles, even particles having the same particle size behave substantially like masses, that is, particles having a large true specific gravity, and can efficiently pass the mesh material. it can. Patent Document 3 further describes the use of an ultrasonic transducer with a resonance ring in order to improve the efficiency of sieving.
However, when using a mesh material with a small mesh opening on the sieve machine, the mesh material is thin and low in strength (the thread is thin). If used for a long time, the edge of the mesh material will be broken by the weight of the carrier, and unclassified There is a problem that the fine particles are mixed in the product as they are, and the fine powder content increases.
Further, in the case of particles having a shape close to a sphere and small surface irregularities, it is difficult to maintain the classification performance even if a vibration sieve using an ultrasonic vibrator with a resonance ring is used. The reason is clogging of the mesh.
When the shape is close to a sphere and the surface irregularities are reduced, the contact area between the wire of the mesh and the particles is increased, the resistance to pass through the mesh is increased, and the mesh is easily clogged.
When the particle size is reduced, the clogging tends to be further amplified.

When the clogging of the mesh material occurs, it is very difficult to remove the spherical material because the spherical particles are embedded in the opening, and the mesh material needs to be replaced.
Although some mesh materials are knitted with resin yarn, stainless steel is usually used. This is because in the case of a mesh material knitted with resinous yarn, the rigidity of the yarn is small, so that ultrasonic waves are not effectively transmitted to the mesh material and classification is not possible at all.

On the other hand, if the mesh of the stainless steel mesh is fine, the manufacturing cost becomes extremely high.
As a result, there is a big problem that the manufacturing cost of the core material and the coat carrier is increased.

JP 58-144839 (Claims, page 1, right column, lines 17 to 20) Japanese Patent No. 3029180 (Claim 1, page 8, right column, lines 12 to 29) JP 2001-209215 A

  Therefore, the main object of the present invention is not to cause such problems, that is, high image quality (especially good graininess), no carrier adhesion, low development torque, and therefore low toner spent and good durability. In addition, there is provided a small particle size electrophotographic carrier particle having a sharp particle size distribution with little variation in the amount of pumping, little image density variation, and a method for efficiently producing the electrophotographic carrier particle at low cost. Is an offer.

As a result of intensive studies by the present inventors to solve the above problems, the present inventors have a specific particle size distribution with a small particle size and a small content ratio of the small particle size, and the shape of the particle is almost spherical. In addition, electrophotographic carrier particles having a smooth surface are classified into the following electrophotographic carrier particle classification method, classified electrophotographic carrier core material, electrophotographic carrier using the classified particles, In addition, the present inventors have found that the problem can be solved by an electrophotographic developer using the carrier.
That is, the following specific achievement means were found.
That is, the above-mentioned problems include the following core material for an electrophotographic carrier of the present invention, an electrophotographic carrier, a method for producing the electrophotographic carrier, a method for producing a core material for the electrophotographic carrier, and the electrophotography. This is achieved by an electrophotographic developer using a carrier for the use.
(1) “The weight average particle diameter Dw is 22 to 32 μm, and the ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw is 1 <Dw / Dp <1.20, which is smaller than 20 μm. The content of particles is 0 to 7% by weight, the content of particles smaller than 36 μm is 90 to 99.8% by weight, the shape factor SF1 is 100 to 107 , and SF2 is 100 to 110 , and is made of Mn ferrite. A core material for an electrophotographic coated carrier characterized by that;
(2) “Core material for electrophotographic coated carrier according to item (1) above, wherein the content of particles having a particle diameter of less than 20 μm is 0 to 5% by weight”;
(3) The core for an electrophotographic coated carrier according to (1) or (2), wherein the magnetization when a magnetic field of 1000 oersted is applied is 40 to 150 emu / g Material ";
(4) “A core material for an electrophotographic coated carrier classified by using a vibratory sieving machine equipped with an oscillator including an ultrasonic vibrator, wherein at least two sheets are provided on the ultrasonic vibrator as the vibratory sieving machine. The mesh material was closely stacked and installed, and the vibration received by the lower mesh material from the ultrasonic transducer was transmitted to the upper mesh material and supplied to the uppermost mesh material. The core for an electrophotographic coated carrier according to any one of (1) to (3), wherein the core is obtained by passing through a step of classifying the core material for the coated carrier. Material ";
(5) "The classification is characterized in that, as at least two mesh materials, a mesh material with a small mesh is installed on the upper side and a mesh material with a large mesh is installed on the lower side. The core material for an electrophotographic coated carrier according to item (4) above;
(6) The item (4) or the item (5), wherein a bending elastic modulus of at least one kind of mesh material having a small mesh installed on the upper side is 1 to 10 GPa. A core material for an electrophotographic coated carrier according to claim 1;
(7) “As the vibration sieving machine, a resonance member fixed to a mesh material is used, ultrasonic vibration is transmitted to the resonance member to resonate, and then the classification is transmitted to the uppermost mesh material surface. The core material for an electrophotographic coated carrier according to any one of (4) to (6) above, wherein the core material is obtained through a step of
(8) "the paragraph (1) to said second (7) electrophotographic coated carrier to form a resin coating layer on the electrophotographic coated surface of the carrier core material according to any one of Items";
(9) “The electrophotographic coated carrier according to item (8) , wherein the resin coating layer has a thickness of 0.03 to 0.8 μm”;
(10) “A developer for electrophotography, which basically comprises a coated carrier for electrophotography according to the item (8) or the item (9) and a toner.
(11) “A method for producing a core material for an electrophotographic coated carrier comprising a step of classifying a core material for an electrophotographic coated carrier using a vibrating screen with an oscillator having an ultrasonic vibrator , wherein the vibrating screen As a machine, at least two mesh materials are closely stacked on the ultrasonic vibrator, and the vibration received by the lower mesh material from the ultrasonic vibrator is applied to the upper mesh material. Telling, by classifying the core material supplied on the uppermost mesh material, the weight average particle diameter Dw is 22 to 32 μm, and the ratio Dw / Dp of the number average particle diameter Dp and the weight average particle diameter Dw is 1 <Dw / Dp <1.20, the content of particles having a particle size smaller than 20 μm is 0 to 7% by weight, the content of particles smaller than 36 μm is 90 to 99.8% by weight, and the shape factor SF1 is 100 to 107 and, Method for producing an electrophotographic coating core material for a carrier F2 is characterized by obtaining a core material for electrophotographic coated carrier comprising a Mn ferrite is 100 to 110 ";
(12 ) The item (11), wherein as the at least two mesh materials, a mesh material having a small mesh is installed on the upper side and a mesh material having a large mesh is installed on the lower side. A process for producing a core material for an electrophotographic coated carrier according to claim 1;
(13) The item (11) or the item (12), wherein a bending elastic modulus of at least one kind of mesh material having a small mesh installed on the upper side is 1 to 10 GPa. A process for producing a core material for an electrophotographic coated carrier according to claim 1;
(14) “As the vibration sieving machine, a resonance member fixed to a mesh material is used, ultrasonic vibration is transmitted to the resonance member to resonate, and then transmitted to the uppermost mesh material surface. The manufacturing method of the core material for an electrophotographic coated carrier according to any one of (11) to (13) above ;
(15) The item (11) to the item (14), wherein the core material for an electrophotographic coated carrier has a content of particles having a particle size of less than 20 μm in an amount of 0 to 5% by weight. Or a method for producing a core material for an electrophotographic coated carrier according to any one of the items] ;
(16) The items (11) to (15), wherein the magnetization of the core material for a coated carrier for electrophotography when a magnetic field of 1000 oersted is applied is 40 to 150 emu / g. A method for producing a core material for an electrophotographic coated carrier according to any one of "
(17) “A resin coating layer is formed on the surface of the coated carrier core material obtained by the method for producing a coated carrier core material according to any one of (11) to (16)”. method of manufacturing electrophotographic coating career characterized. "

As will be apparent from the following detailed and specific description, according to the present invention, two or more meshes are closely stacked on the ultrasonic transducer, and the function of supporting the load of each mesh and the function of sieving are provided. By separating the functions, it is more preferable that the elastic modulus of the upper mesh be smaller than that of the lower mesh. Photo carrier particles can be produced at low cost.
According to the present invention, by using a carrier having a specific narrow range of particle size distribution and a small particle size, the uniformity of highlights at high image density is good, the background is less stained, and It is possible to provide a carrier and a developer that hardly cause carrier adhesion. In addition, the carrier of the present invention has the characteristics that the carrier adhesion hardly occurs, the particle shape is close to a true sphere, and the surface is smooth, so that the development torque is small, the durability is good, and the pumping is performed. It is possible to provide a carrier with little fluctuation in image density and little fluctuation in image density.
That is, according to the present invention, it is possible to efficiently produce particles for a small particle size electrophotographic carrier that are close to a sphere and have a sharp particle size distribution with few surface irregularities, and have a small development torque and a low toner torque. Particles for electrophotographic carrier with low particle size, good durability, and high image quality, good graininess, less carrier adhesion and sharp particle size distribution In addition, it is possible to efficiently produce a carrier for small particle size electrophotography having a sharp particle size distribution, with high image quality and good graininess, hardly causing carrier adhesion, and with high image quality and granularity. The electrophotographic two-component developer having good properties and hardly causing carrier adhesion can be obtained.

The best mode for carrying out the present invention will be described below.
The particles for an electrophotographic carrier having a sharp particle size distribution in the present invention are classified into the particles for an electrophotographic carrier using an oscillating sieve equipped with an oscillator equipped with an ultrasonic vibrator. On the ultrasonic transducer, at least two meshes are closely stacked and installed, and more preferably, a mesh having a bending elastic modulus of 1 to 10 GPa is installed on the uppermost side, and the ultrasonic vibration It can be manufactured by transmitting the vibration received by the lower mesh from the child to the upper mesh and classifying the particles supplied on the uppermost mesh.
An electrophotographic carrier coated with a resin is prepared by forming a resin film on the surface of the magnetic particles of the core material to produce resin film particles, and then classifying the resin-coated particles with the above vibration sieve. Thus, a sharp particle size distribution can be obtained.

  When there are two mesh materials to be stuck to each other, it is preferable to set the mesh material with a small opening on the upper side and a larger lower side, and the mesh material with a small opening has a classification function and has a large opening. The mesh material receives vibration directly from the ultrasonic transducer and transmits the vibration to the upper mesh material, and has the function of substantially supporting the weight of the carrier. When classifying with a vibration sieve, the upper mesh The load on the material is reduced, it can withstand long-term use, and the life can be greatly extended.

As the lower mesh material, it is desirable to use a material having a wire diameter and an opening of, for example, knitted with a thick thread, which efficiently transmits ultrasonic vibrations and is less likely to be worn or cut. Further, the opening is preferably larger than the maximum particle diameter of the particles.
For example, when classifying an electrophotographic carrier having a weight average particle diameter Dw of 22 to 32 μm, it is sufficient that the mesh of the lower mesh material is 62 μm (250 mesh) or more.
On the other hand, since ultrasonic vibration is difficult to be transmitted if the wire diameter of the mesh material becomes too large, in the case of an electrophotographic carrier having a Dw of 22 to 32 μm, an opening of about 104 μm (150 mesh) is particularly preferable.

Further, the material of the lower mesh material is preferably a bending elastic modulus of 50 GPa to 500 GPa having a high strength in order to efficiently transmit the vibration energy of ultrasonic waves, and is particularly preferably metallic.
The mesh material is supported on the lower side and has a classification function on the upper side, and may have a structure of two or more layers. The mesh material on the upper side only needs to have an opening corresponding to the particle size to be classified. Since the lower mesh material is installed, an upper mesh material having a large opening ratio can be used.

In addition, as a vibration sieve machine with an ultrasonic oscillator used in the classification method of the present invention, when a resonance member fixedly installed on a mesh material is used, ultrasonic vibration is transmitted to the entire screen via the resonance ring. Communicating, transmitting uniform vibration to the mesh, and efficiently sieving the material on the mesh.
The ultrasonic vibration that vibrates the mesh material can be obtained by supplying a high-frequency current to the converter and converting it into ultrasonic vibration. The converter in this example consists of a PZT vibrator.
In order to vibrate the mesh material by ultrasonic vibration, the ultrasonic vibration generated by the converter is transmitted to the resonance member fixedly installed on the mesh material, the resonance member resonates by the ultrasonic vibration, and The mesh fixed to the resonance member is vibrated.
In this case, the frequency for vibrating the mesh material is 20 to 50 kHz, preferably 30 to 40 kHz.
The shape of the resonance member may be a shape suitable for vibrating the mesh material, and is usually a ring shape. The vibration direction for vibrating the mesh material is preferably a vertical direction.

FIG. 1 is a conceptual diagram for explaining an example of a vibration sieving machine with an ultrasonic oscillator used in the classification method of the present invention.
In FIG. 1, reference numeral (1) is a vibration sieve, (2) is a cylindrical container, (3) is a spring, (4) is a base (support), and (5) is a mesh material of two or more layers adhered to each other. A mesh with a large opening is installed on the lower side, (6) is a resonance member (in this case, ring-shaped), (7) is a high-frequency current cable, (8) is a converter, and (9) is a ring-shaped frame Indicates.
In order to operate the vibratory sieve with an ultrasonic oscillator (circular sieve) shown in FIG. 1, first, a high frequency current is supplied to the converter (8) via the cable (7). The high-frequency current supplied to the converter (8) is converted into ultrasonic vibration.
The ultrasonic vibration generated in the converter (8) vibrates the resonant member (6) to which the converter (8) is fixed and the ring-shaped frame (9) provided in the vertical direction in the vertical direction. Due to the vibration of the resonance member (6), the mesh member (5) fixed to the resonance member (6) and the frame (9) vibrates in the vertical direction.
A commercial product can be used as the vibration sieve machine equipped with an ultrasonic oscillator, and for example, “Ultrasonic” (product name) manufactured by Sakae Sangyo Co., Ltd. is available.

In addition, the particles to which the classification method of the present invention is applied may be completely unclassified, or those that have been subjected to a pneumatic / mechanical classification treatment. The side, coarse powder side, or both sides can be classified (classified and left).
In particular, when applied to the classification of the coarse powder side particles, the distribution is sharper than that of a classification method such as a pneumatic method, so that the target particles can be obtained in a high yield, which is preferable.

  The upper mesh can be made by knitting a thin wire rod or by making a hole with a laser or etching. However, since the carrier has a substantially spherical shape, clogging is likely to occur when the hole shape is circular. Therefore, a fibrous mesh knitted with various materials is more preferable. Furthermore, the material of the upper mesh is preferably a material having an appropriate elastic modulus and a bending elastic modulus in the range of 1 to 10 GPa.

If the elastic modulus of the upper mesh is made smaller than the elastic modulus of the lower mesh, the shape of the upper mesh opening is slightly deformed due to vibration transmitted from the lower mesh, and the mesh is less likely to be clogged. , Can improve the efficiency of classification.
When the flexural modulus of the upper mesh is larger than 10 GPa, the mesh opening is less deformed and clogging is likely to occur, and the classification efficiency is lowered. If the flexural modulus is less than 1 GPa, the upper mesh absorbs the vibration of the lower mesh, and the mesh shape changes greatly, so that the classification efficiency decreases.

The material is not particularly limited as long as the flexural modulus is in the range of 1 to 10 GPa. However, it is preferable to use a resin as a material because of superior manufacturing costs. The cost advantage of the resin mesh is more conspicuous as the mesh has a smaller mesh size. For example, a nylon mesh having a mesh size of about 20 μm has a cost per unit area of about 20 compared to a stainless steel mesh. It only takes about a minute.
The mesh material on the upper side with a small mesh opening and moderate elasticity will not have enough strength if the mesh is not installed on the lower side, so the life of the mesh will be shortened and it will be used as a mesh material for ultrasonic vibration sieves. Not suitable for use. Therefore, by using a mesh having a sufficient strength that is a flexural modulus of 50 GPa to 500 GPa in combination with the lower mesh, the classification accuracy and efficiency become very good.

The mesh material made of resin is not particularly limited in terms of the manufacturing method and material other than the flexural modulus. As long as the mesh material can be produced, a known resin such as a nylon resin, a polyester resin, an acrylic resin, or a fluorine resin can be used.
Among these, nylon resins are excellent mesh materials in terms of durability and chemical resistance, and polyester resins are preferable materials in terms of durability and weather resistance.
Commercially available nylon mesh or polyester mesh may be used, for example, SEFAR (Switzerland) NYTAL series or PETEX series.
Further, when these resins are knitted in a fibrous form, they may be used only for either warp or weft.

A mesh made of a material having a flexural modulus of 10 GPa or less may have insufficient strength unless a mesh is installed on the lower side, and may not be suitable for use as a mesh for an ultrasonic vibration sieve. However, it has been confirmed that by using the double sticking method as described above, sufficient strength and durability can be provided, and classification accuracy and efficiency are very good.
The measurement of the flexural modulus of the mesh material can be performed according to ASTM (American Society for Testing and Materials) D790. The value of the flexural modulus in the present invention is also measured according to ASTM D790.

  In addition, the magnetic particles (core material) or resin-coated magnetic particles, which are electrophotographic carrier particles classified by the classification method of the present invention, have a sharp particle size distribution and a weight average particle size Dw of 22. In the case of ˜32 μm, the content of particles smaller than 36 μm is 90 to 99.8% by weight, the content of particles having a particle size smaller than 20 μm is 7% by weight or less, and the weight average particle size Dw and the number average particle size When the ratio Dw / Dp to Dp is 1-1.20, the shape factor SF1 is 100-120, and the SF2 is 100-120, excellent characteristics as a carrier for an electrophotographic developer can be obtained, and the graininess, And soiling is good.

The smaller the weight average particle diameter Dw, the better the graininess (highlight image uniformity), but carrier adhesion is likely to occur. When carrier adhesion occurs, the graininess decreases. On the other hand, as the weight average particle diameter Dw is larger, carrier adhesion is less likely to occur. However, if the toner concentration is increased in order to obtain a high image density, scumming tends to increase.
The carrier adhesion here means a phenomenon in which the carrier adheres to the image portion or the background portion of the electrostatic latent image. As the electric field strength increases, the carrier adheres more easily. However, since the electric field strength of the image area is weakened by developing the toner, the carrier adhesion is less likely to occur compared to the background area.
When the weight average particle diameter Dw is 22 to 30 μm, even if the toner concentration is high, the background is hardly stained and an image with extremely good graininess can be obtained.
Further, the content of particles smaller than 36 μm is 90 to 99.8% by weight, the content of particles having a particle size smaller than 20 μm is 7% by weight or less, more preferably 5% by weight or less, and the weight average particle diameter Dw. It has been found that carrier adhesion is not a problem when the ratio Dw / Dp of the number average particle diameter Dp is 1-1.20, preferably 1-1.18.

  As the carrier particle size decreases, the frictional force between the particles increases, the carrier fluidity is poor, and the torque of the developing sleeve increases, but in the case of a small particle carrier, the carrier shape and surface smoothness also increase. A big influence. That is, if SF1 is greater than 120, the carrier shape deviates from the true sphere. Further, when SF2 is larger than 120, the surface unevenness increases. In each state, the torque of the developing sleeve increases, toner sticking to the sleeve and sleeve surface scraping become significant, the pumping amount changes, and the image density fluctuates. In addition, the toner spent on the carrier increases, causing a decrease in the developer charge amount.

SF1 and SF2 are more preferably 100 to 115 and 100 to 110, respectively.
When the carrier approaches a true sphere and the surface unevenness is small, the magnetic brush in the developing region becomes more uniform, and thus carrier adhesion is improved.
In addition, if the unevenness is large, the thickness of the coating resin varies depending on the location, and the charge amount and resistance are likely to be non-uniform, which affects durability over time and carrier adhesion.
The carrier shape factors SF1 and SF2 mean the following.
SF1 and SF2 indicating the shape factor are, for example, 100 carrier particle images that have been magnified 300 times using FE-SEM (S-800) manufactured by Hitachi, Ltd., and the image information is obtained via the interface. For example, it is introduced into an image analysis apparatus (Luzex AP) manufactured by Nireco and analyzed, and the values obtained from the following equations are defined as shape factors SF1 and SF2.
In the formula, L is the absolute maximum length of the particle (the length of the circumscribed circle), P is the peripheral length of the particle, and A is the projected area of the particle. The shape factor SF1 indicates the degree of roundness of the toner particles, and the shape factor SF2 indicates the degree of unevenness of the toner particles.

円（球形）から離れるとＳＦ１は値が大きくなる。表面の凹凸の起伏が激しくなるとＳＦ２の値も大きくなる。→それぞれの値は、真円（球）に近づくにつれて１００に近い値となる。

The value of SF1 increases as the distance from the circle (spherical) increases. When the unevenness on the surface becomes severe, the value of SF2 also increases. -> Each value becomes a value close to 100 as it approaches a perfect circle (sphere).

As the material for the core particles constituting the carrier of the present invention, conventionally known various magnetic materials are used.
The carrier core material particles used in the present invention have a magnetic moment of 40 emu / g or more, more preferably 50 emu / g or more when a magnetic field of 1000 oersted (Oe) is applied. The upper limit is not particularly limited, but is usually about 150 emu / g. If the magnetic moment of the carrier core particles is smaller than the above range, carrier adhesion tends to occur, which is not preferable.

The magnetic moment can be measured as follows. A BH tracer (BHU-60 / manufactured by Riken Denshi Co., Ltd.) is used, and 1.0 g of carrier core particles are packed in a cylindrical cell and set in an apparatus. The magnetic field is gradually increased and changed to 3000 Oersted, then gradually reduced to zero, and then the opposite magnetic field is gradually increased to 3000 Oersted.
Furthermore, after gradually reducing the magnetic field to zero, a magnetic field is applied in the same direction as the first. In this way, the BH curve is illustrated, and the magnetic moment of 1000 oersted is calculated from the figure.

Examples of the core particles having a magnetic moment of 40 emu / g or more when a 1000 oersted magnetic field is applied include, for example, ferromagnetic materials such as iron and cobalt, magnetite, hematite, Li-based ferrite, Mn—Zn-based ferrite, Cu -Zn ferrite, Ni-Zn ferrite, Ba ferrite, Mn ferrite and the like.
In this case, the ferrite is a sintered body generally represented by the chemical formula of the following formula (1).

但し、ｘ＋ｙ＋ｚ＝１００ｍｏｌ％であって、Ｍ、Ｎはそれぞれ、Ｎｉ、Ｃｕ、Ｚｎ、Ｌｉ、Ｍｇ、Ｍｎ、Ｓｒ、Ｃａなどでの金属原子あり、２価の金属酸化物と３価の鉄酸化物との完全混合物から構成されている。

However, x + y + z = 100 mol%, and M and N are metal atoms such as Ni, Cu, Zn, Li, Mg, Mn, Sr, and Ca, respectively. Divalent metal oxide and trivalent iron oxidation It is composed of a complete mixture with the product.

A smooth core material in which SF1 of electrophotographic carrier particles is nearly spherical with SF1 of 100 to 120 and SF2 of 100 to 120 is obtained by firing conditions, heat treatment, adjustment of the composition, and the like.
For example, as described in US2003 / 0209820A1, the surface can be smoothed and spheroidized by exposing the pulverized amorphous ferrite particles or the raw material for ferritization reaction to plasma.
By combining the former method, ferrite particles having a smoother surface and close to a true sphere can be obtained.

  In addition, particles having good fluidity are transported quickly by a feeder using vibration. Since particles that are close to a true sphere and have good surface smoothness have good fluidity, for example, when an electromagnetic feeder is used, it is possible to select particles having different fluidity depending on the difference in conveying speed. By repeatedly passing through the electromagnetic feeder, particles having good surface smoothness and close to a true sphere can be obtained.

Of the particles for an electrophotographic carrier applied as an object of the classification method of the present invention, resin-coated magnetic particles are produced by forming a resin layer on the surface of the core material particles.
As the resin for forming the resin layer, various conventionally known resins used for carrier production can be used. In the present invention, the following resins may be used alone or in combination of two or more.

  Silicone resin, polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer Polymer, styrene-maleic acid copolymer, styrene-acrylic acid ester copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-acrylic) Acid octyl copolymer, styrene-phenyl acrylate copolymer, etc.) Styrene-methacrylate copolymer (styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate copolymer) Coalescence, styrene-methacrylic acid phenolic Copolymers, etc.) Styrene resins such as styrene-α-chloroacrylic acid methyl copolymer, styrene-acrylonitrile-acrylic acid ester copolymer, epoxy resin, polyester resin, polyethylene resin, polypropylene resin, ionomer resin, polyurethane resin , Ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyamide resin, phenol resin, polycarbonate resin, melamine resin and the like.

  In particular, examples of silicone resins suitable as a carrier coating resin include the following. KR271, KR272, KR282, KR252, KR255, KR152 (manufactured by Shin-Etsu Chemical Co., Ltd.), SR2400, SR2406 (manufactured by Toray Dow Corning Silicone), and the like. Suitable modified silicone resins include epoxy-modified silicone, acrylic-modified silicone, phenol-modified silicone, urethane-modified silicone, polyester-modified silicone, and alkyd-modified silicone.

By including an aminosilane coupling agent in the resin coating layer made of the above-described silicone resin, a carrier having good durability can be obtained.
Examples of the aminosilane coupling agent used in the present invention include the following. The content is preferably 0.001 to 30% by weight.

As a method for forming the resin layer on the surface of the carrier core material particles, a known method such as a spray drying method, a dipping method, or a powder coating method can be used. In particular, a method using a fluidized bed type coating apparatus is effective for forming a uniform coated film.
The thickness of the resin layer formed on the surface of the carrier core particles is usually 0.02 to 1 μm, preferably 0.03 to 0.8 μm.

  The carrier of the present invention can be a so-called resin-dispersed carrier having a form in which magnetic powder is dispersed in a known resin such as a phenol resin, an acrylic resin, or a polyester resin.

In the carrier of the present invention, the resistivity (LogR · cm) is preferably 11.0 to 16.0, more preferably 12.0 to 15.0.
When the resistivity of the carrier is lower than 11.0, when the developing gap (the closest distance between the photosensitive member and the developing sleeve) becomes narrow, charges are induced in the carrier and carrier adhesion is likely to occur. When the linear velocity of the photosensitive member and the linear velocity of the developing sleeve are large, a tendency of deterioration is observed.
On the other hand, when the value is larger than 16.0, charges having a polarity opposite to that of the toner are likely to be accumulated, and the carrier is easily charged to cause carrier adhesion.
The carrier resistivity can be adjusted by adjusting the resistance of the coating resin on the core particles and controlling the film thickness.

The carrier core material resistance resistance LogR, Ωcm is preferably 6.0 to 11.0.
If it is lower than 6.0, inductive carrier adhesion is likely to occur due to non-uniformity of the carrier coating film, or, when used for a long time, due to abrasion of the coating film.
When the core material resistance is greater than 11.0, the developing ability of the carrier tends to decrease.

The carrier resistivity can be measured by the following method.
As shown in FIG. 2, a cell (11) made of a fluororesin container containing electrodes (12a) and (12b) having a distance between electrodes of 2 mm and a surface area of 2 × 4 cm is filled with a carrier (13), A DC voltage of 100 V is applied, DC resistance is measured by a high resistance meter 4329A (4329A High Resistance Meter; manufactured by Yokogawa Hewlett-Packard Co., Ltd.), and an electrical resistivity LogR (Ωcm) is calculated.
When filling the carrier resistance, fill the cell until it overflows, and after tapping the entire cell 20 times, use a non-magnetic horizontal spatula on the top surface of the cell along the top edge of the cell. Scrape flatly in one operation. No pressure is required during filling.

Further, in order to adjust the carrier resistance, the conductive fine powder can be added to the coating resin layer and used.
As the conductive fine particles, conductive ZnO, metal or metal oxide powder such as Al, _{SnO 2,} TiB 2 doped with SnO ₂ or the various elements that have been prepared in a variety of ways, _ZnB 2, M
borides such oB _2, silicon carbide, polyacetylene, polyparaphenylene, poly (para - phenylene sulfide) polypyrrole, a conductive polymer such as polyethylene, furnace black, acetylene black, carbon black such as channel black.
For these conductive fine powders, use a dispersing machine that uses media such as a ball mill or bead mill, or a stirrer equipped with blades that rotate at high speed after the conductive fine powder has been added to the solvent or coating resin solution used for coating. Can be uniformly dispersed.

  In the present invention, the weight average particle diameter Dw in the carrier and the carrier core material is calculated based on the particle diameter distribution (relationship between the number frequency and the particle diameter) of the particles measured on the basis of the number. The weight average particle diameter Dw in this case is represented by the following formula (2).

前記式中、Ｄは各チャネルに存在する粒子の代表粒径（μｍ）を示し、ｎは各チャネルに存在する粒子の総数を示す。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、本発明のキャリアの場合には、２μｍの長さを採用した。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粒径の下限値を採用した。

In the above formula, D represents the representative particle size (μm) of particles present in each channel, and n represents the total number of particles present in each channel. The channel indicates a length for equally dividing the particle size range in the particle size distribution diagram, and in the case of the carrier of the present invention, a length of 2 μm is adopted. Further, as the representative particle size of the particles existing in each channel, the lower limit value of the particle size stored in each channel was adopted.

  In the present invention, the number average particle diameter Dp of the carrier and the carrier core material particles is calculated based on the particle diameter distribution of the particles measured on the basis of the number. The number average particle diameter Dp in this case is represented by the following formula.

前記式中、Ｎは計測した全粒子数を示し、ｎは各チャネルに存在する粒子の総数を示し、Ｄは各チャネル（２μｍ）に存在する粒子粒径の下限値を示す。

In the above formula, N represents the total number of particles measured, n represents the total number of particles present in each channel, and D represents the lower limit of the particle size present in each channel (2 μm).

As a particle size analyzer for measuring the particle size distribution of the carrier, a Microtrac particle size analyzer (model HRA 9320-X100: manufactured by Honewell) was used. The measurement conditions are as follows.
(1) Particle size range: 100-8 μm
(2) Channel length (channel width): 2 μm
(3) Number of channels: 46
(4) Refractive index: 2.42

In the present invention, such sharp electrophotographic carrier particles having a particle size distribution obtained by the classification method of the present invention include both magnetic particle core material and resin-coated magnetic particles. Therefore, the following three cases are included as modes to which the classification method of the present invention is applied.
(1) The carrier core material classified by the classification method of the present invention is coated with a resin to produce an electrophotographic developer carrier having a sharp particle distribution.
(2) After preparing resin-coated magnetic particles formed by coating a carrier core material with a resin, the resin-coated magnetic particles are classified by the classification method of the present invention to provide a developer for electrophotography having a sharp particle distribution. Make a carrier.
(3) The carrier core material classified by the classification method of the present invention is coated with a resin to produce resin-coated magnetic particles, and the resin-coated magnetic particles are further classified by the classification method of the present invention. An electrophotographic developer carrier having a sharp particle distribution is prepared.
In particular, when the resin-coated magnetic particles are used as an electrophotographic carrier, there is an extremely excellent effect that the granularity is good and the carrier adhesion hardly occurs.

The bulk density of the carrier is 2.1 g / cm ³ or more, preferably 2.35 g / cm ³ or more, more preferable to be ^{2.35g / cm 3 ~2.50g / cm 3} , preferably carrier adhesion prevention . A core material having a low bulk density is porous or has large surface irregularities.

If the bulk density is small, even if the magnetization (emu / g) of 1 KOe is large, the substantial magnetization value per particle is small, which is disadvantageous for carrier adhesion.
To increase the bulk density, it is possible to increase the firing temperature. However, it is preferable that the core material is less than 2.60 because the core materials are easily fused to each other and are not easily crushed. Therefore, usually 2.10 g / cm ³ or more, preferably a 2.10~2.60g / cm ^3, more preferably ^{2.35g / cm 3 ~2.60g / cm 3} , more preferably 2.35 ˜2.50 g / cm ³ .

According to the metal powder-apparent density test method (JIS-Z-2504), the carrier according to the present invention has a bulk density of 25 cm ³ made of stainless steel, which is allowed to flow naturally from an orifice having a diameter of 2.5 mm. After pouring the carrier into the cylindrical container until it overflows, the upper surface of the container is scraped flat with a single operation along the upper edge of the container using a non-magnetic horizontal spatula.
If it is difficult to flow with an orifice with a diameter of 2.5 mm, the carrier naturally flows out from the orifice with a diameter of 5 mm. By this operation, the weight of the carrier per cm ^{3 is} obtained by dividing the weight of the carrier flowing into the container by the volume of the container 25 cm ³ . This is defined as the bulk density of the carrier.

The charge amount of the developer can be measured by the following method. This is shown in FIG.
A certain amount of developer is put into a conductive container (blow-off cage) (15) having a metal mesh at both ends. The mesh (made of stainless steel) has a mesh size between the toner and the carrier (particle size 20 μm), and is set so that the toner passes between the meshes. Compressed nitrogen gas (1 kgf / cm ² ) is blown from the nozzle (14) for 60 seconds, and when the toner is ejected from the gauge (15), the cage (15) has the opposite polarity to the charge of the toner (17). Left carrier (16).
The charge amount Q and the mass M of the protruding toner are measured, and the charge amount per unit mass is calculated as the charge amount Q / M. The toner charge amount is expressed in μc / g. The cage (15) is grounded via a capacitor, and an electrometer (18) is connected in parallel with the capacitor.

Next, the developer is produced by mixing the resin-coated magnetic particles obtained by the classification method of the present invention with a toner. The toner will be described.
The toner used in the present invention contains a colorant, fine particles, a charge control agent, a release agent and the like in a binder resin mainly composed of a thermoplastic resin. Can be used. This toner can be an amorphous or spherical toner prepared by various toner production methods such as a polymerization method and a granulation method. Either magnetic toner or non-magnetic toner can be used.

  The toner used in the present invention contains a colorant, fine particles, a charge control agent, a release agent and the like in a binder resin mainly composed of a thermoplastic resin. Can be used. This toner can be an amorphous or spherical toner prepared by various toner production methods such as a polymerization method and a granulation method. Either magnetic toner or non-magnetic toner can be used.

As the binder resin for the toner, the following can be used alone or in combination.
Styrene binder resins such as polystyrene, polyvinyltoluene and other styrene and substituted homopolymers, styrene-p-chlorostyrene copolymers, styrene-propylene copolymers, styrene-vinyltoluene copolymers, styrene-acrylic Acid methyl copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate copolymer, styrene-butyl methacrylate Copolymer, styrene-α-chloromethacrylic acid methyl copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene -Isoprene copolymer, styrene- Styrene copolymers such as oleic acid copolymers and styrene-maleic acid ester copolymers; acrylic binders such as polymethyl methacrylate and polybutyl methacrylate, and in addition, polyvinyl chloride, polyvinyl acetate, polyethylene , Polypropylene, polyester, polyurethane, epoxy resin, polyvinyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, aliphatic or aliphatic hydrocarbon resin, aromatic petroleum resin, chlorinated paraffin, paraffin wax Etc.

Further, the polyester resin can further reduce the melt viscosity while ensuring the stability during storage of the toner, as compared with the styrene-based or acrylic-based resin. Such a polyester resin can be obtained, for example, by a polycondensation reaction between an alcohol and a carboxylic acid.
Examples of the alcohol include diols such as polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-propylene glycol, neopentyl glycol, 1,4-butenediol, , 4-Bis (hydroxymethyl) cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylenated bisphenol A and other etherified bisphenols, which are saturated or unsaturated having 3 to 22 carbon atoms Divalent alcohol units substituted with a hydrocarbon group, other divalent alcohol units, sorbitol, 1,2,3,6-hexanetetrol, 1,4-sorbitan, pentaesitol, dipentaes Tolu, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, tri Mention may be made of trihydric or higher alcohol monomers such as methylolethane, trimethylolpropane and 1,3,5-trihydroxymethylbenzene.

  Examples of the carboxylic acid used to obtain the polyester resin include monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid, maleic acid, fumaric acid, mesaconic acid, citraconic acid, terephthalic acid, cyclohexanedicarboxylic acid, and succinic acid. Acids, adipic acid, sebacic acid, malonic acid, divalent organic acid monomers in which these are substituted with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms, anhydrides of these acids, lower alkyl esters and Dimer from linolenic acid, 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1, 2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl 2-methylenecarboxypropane, tetra (methylenecarboxyl) methane, 1,2,7,8-octanetetracarboxylic acid embol trimer acid, anhydrides of these acids, etc. The body can be mentioned.

  Epoxy resins include polycondensates of bisphenol A and epochrohydrin, such as epomic R362, R364, R365, R366, R367, R369 (above, Mitsui Petrochemical Co., Ltd.), Epototo YD-011, YD-012, YD-014, YD-904, YD-017 (above, manufactured by Tohto Kasei Co., Ltd.) Epochs 1002, 1004, 1007 (above, manufactured by Shell Chemical Co., Ltd.) Things.

  Examples of the colorant used in the present invention include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, phthalocyanine blue, Hansa Yellow G, rhodamine 6G lake, calco oil blue, chrome yellow, quinacridone, and benzidine yellow. Conventionally known dyes and pigments such as rose bengal, triallylmethane dyes, monoazo dyes, disazo dyes, and dyes can be used alone or in combination.

  The developer toner in the present invention can be made into a magnetic toner by containing a magnetic material in a toner raw material such as a resin binder. As the magnetic material, ferromagnetic powders such as iron and cobalt, fine powders such as magnetite, hematite, Li-based ferrite, Mn-Zn-based ferrite, Cu-Zn-based ferrite, Ni-Zn ferrite, and Ba ferrite can be used.

  For the purpose of sufficiently controlling the triboelectric chargeability of the toner, so-called charge control agents such as metal complex salts of monoazo dyes, nitrohumic acid and its salts, salicylic acid, naphthoic salts, dicarboxylic acid Co, Cr, Fe, etc. , A quaternary ammonium compound, an organic dye, and the like can be contained.

Furthermore, a release agent may be added to the toner used in the present invention as necessary.
As the release material, low molecular weight polypropylene, low molecular weight polyethylene, carnauba wax, microcrystalline wax, jojoba wax, rice wax, montanic acid wax and the like can be used alone or in combination, but are not limited thereto. is not.

Additives can be added to the toner. In order to obtain a good image, it is important to impart sufficient fluidity to the toner.
As the external additive, general hydrophobized inorganic fine particles can be used in addition to the inorganic fine particles, but the average particle size of the hydrophobized primary particles is 1 to 100 nm, more preferably 5 nm to 70 nm. It is desirable to include inorganic fine particles. Moreover, it is preferable that the specific surface area by BET method is 20-500 m < ² > / g.

Any known one can be used as long as the conditions are satisfied. For example, silica fine particles, hydrophobic silica, fatty acid metal salts (such as zinc stearate and aluminum stearate), metal oxides (such as titania, alumina, tin oxide, and antimony oxide), fluoropolymers, and the like may be contained.
Particularly suitable additives include hydrophobized silica, titania, titanium oxide, and alumina fine particles. As silica fine particles, there are HDK H 2000, HDK H 2000/4, HDK H 2050EP, HVK21, HDK H 1303 (Clariant Japan) and R972, R974, RX200, RY200, R202, R805, R812 (Nippon Aerosil). . Further, as titania fine particles, P-25 (Nippon Aerosil), STT-30, STT-65C-S (above Titanium Industry), TAF-140 (Fuji Titanium Industry), MT-150W, MT-500B, MT-600B MT-150A (taker above). Particularly, the hydrophobized titanium oxide fine particles include T-805 (Nippon Aerosil), STT-30A, STT-65S-S (above Titanium Industry), TAF-500T, TAF-1500T (above Fuji Titanium Industry), MT -100S, MT-100T (above Taka), IT-S (Ishihara Sangyo), etc.
In order to obtain hydrophobized inorganic fine particles, silica fine particles, titania fine particles, and alumina fine particles, hydrophilic fine particles are treated with a silane coupling agent such as methyltrimethoxysilane, methyltriethoxysilane, or octyltrimethoxysilane. Can be obtained. The electrophotographic developer in the present invention is "consisting essentially of" an electrophotographic carrier and a toner, which excludes the addition of such external additives as fluidity improvers and charge control agents. Means not.

In the toner used in the present invention, the weight average particle diameter Dt is 9.0 to 3.0 μm, preferably 7.5 to 3.5 μm. The ratio of the toner to the carrier is 2 to 25 parts by weight, preferably 3 to 20 parts by weight, per 100 parts by weight of the carrier.
The toner particle size was measured using a Coulter counter (manufactured by Coulter Counter).

[Image forming equipment]
4 and 5 show an example of an image forming apparatus using the developer of the present invention. The apparatus of this example includes, in order, around the electrostatic charge image carrier (20), a charging means (32), an exposure means (33), a developing means (40), a transfer means (50), a cleaning means (60), The neutralization means (70) is provided, and the image receiving medium sheet (80) onto which the toner image has been transferred by the transfer means (50) is introduced into a fixing means (not shown). The cleaning means (60) has a waste toner storage means (62) and a cleaning blade (61). The developing means (40) faces the electrostatic charge image carrier (20) with a development interval, rotates in the same direction as the electrostatic charge image carrier (20), and moves the developer brush to the electrostatic charge image carrier (20). ), A magnetic sleeve (41) to be supplied to the toner, a two-component developer stirring means (47) basically composed of the carrier (23) and toner (21) of the present invention, and a toner to the stirring means (47). Toner supply means (45) for supplying is provided. The magnetic sleeve (41) is housed in a housing (46) having an openable / closable window (43), and the stirring means (47) is housed in a housing (44) integrated therewith. The toner supply means (45) includes a toner agitation means (48) for releasing aggregated toner and a toner supply roller (49).
FIG. 6 shows another example of an image forming apparatus using the developer of the present invention. In this apparatus, around the endless belt-shaped charge image carrier (20) suspended between the drive roller (24a) and the tension roller (24b), a charging means (32), an exposure means (33), Developing means (40) using the two-component developer of the present invention, transfer means (50), pre-cleaning exposure means (26) located on the back surface of the charge image carrier (20), cleaning blade (61) and cleaning brush (The cleaning means including 64 and the static elimination means (70) are provided.
FIG. 7 shows an example of the process cartridge of the present invention. The process cartridge of the present invention has the charge image carrier (20) and the developing means (40) using the two-component developer of the present invention, and also includes the charging means (32) and the cleaning means. The process cartridge of this example can be mounted on and removed from the image forming apparatus, but the charge cartridge (32) and the two-component developer of the present invention are sequentially disposed around the charge image carrier (20). It has a developing means (40) to be used and a cleaning blade (61) as a cleaning means.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited to these examples. Moreover, a part represents a weight part.
(Toner Production Example 1)
Polyester resin 100 parts Quinacridone-based magenta pigment 3.5 parts Fluorine-containing quaternary ammonium salt 4 parts The above components are thoroughly mixed in a blender, melt-kneaded in a twin-screw extruder, allowed to cool, and then milled And then finely pulverized with a jet airflow fine pulverizer and further classified with an air classifier to obtain toner base particles having a weight average particle diameter of 5.7 μm.
Further, 1.2 parts of hydrophobic silica fine particles (R972: manufactured by Nippon Aerosil Co., Ltd.) were added to 100 parts of the toner base particles, and mixed with a Henschel mixer to obtain a toner I.

(Core production example 2)
The carrier core material I (Mn ferrite, 57 emu / g / SF1 = 115, SF2 = 115) shown in Table 1 was supplied onto the stainless steel mesh at a rate of 1 Kg / min for classification.
The vibration sieve used has the structure shown in FIG. 1 and is a 70 cmφ stainless mesh (635 mesh, 20 μm aperture, 25% porosity) supported by a frame (9) (single affixed) ( 5) is a sieving device (1) in which a resonance ring (6) is attached as a resonance member by direct contact, and a vibrator (8) for oscillating a 36 kHz ultrasonic wave is provided on the ring (6).
The stainless mesh (5) is disposed in a cylindrical container (2) supported by a base (4) via a spring (3). A vibration motor (not shown) is installed in the base (4), and high-frequency current generated by driving the motor is sent to the vibrator (8) attached to the resonance ring (6) via the cable (7), and ultrasonic waves are generated. It oscillates.
The ultrasonic vibration vibrates the resonance ring (6), and the vibration causes a vibration in the vertical direction of the entire mesh surface (5). Particles on the fine powder side of the carrier core material supplied on the 193 GPa stainless mesh (5) in the cylindrical container (2) are subjected to a sieving process and are removed at the lower part of the cylindrical container (2) under the mesh.
This classification operation was repeated to obtain a carrier core material II shown in Table 1 from above the mesh.
As a result of classification, the ratio of particles less than 20 μm in the carrier core material could be reduced to 9.8%. Table 1 shows the particle size distribution, SF1, and SF2 of the carrier core material II.
After the experiment, the degree of clogging of the stainless mesh was examined. As a result, the porosity was 10%, that is, 15% clogging occurred.

(Core material production example 3)
In the vibrating screen shown in FIG. 1, two or more meshes represented by reference numeral (5) have the following configuration.
That is, a stainless steel mesh with a mesh size of 104 μm (150 mesh) was installed on the lower side, and a nylon mesh with a mesh size of 20 μm (a porosity of 14%) was laminated on the upper side in close contact with the stainless steel mesh. The material used for the nylon mesh (nylon-66) has a flexural modulus of 2.7 GPa.
The lower stainless steel mesh is directly subjected to vibration from the ultrasonic vibrator, but the nylon mesh is installed in close contact with the stainless steel mesh, so the ultrasonic vibration is transmitted efficiently and the particles to be classified are nylon mesh. Classified.
Using this vibrating screen, a carrier core material I (Mn ferrite, 57 emu / g / SF1 = 115, SF2 = 115) shown in Table 1 is supplied onto a nylon mesh at a rate of 1 Kg / min. In the same manner as in No. 2, classification treatment was performed to obtain a carrier core material III shown in Table 1 on the mesh.
As a result of classification, the ratio of particles less than 20 μm in the carrier core material could be reduced from 26.0% to 6.1%. Table 1 shows the particle size distribution, SF1, and SF2 of the carrier core material III.
The nylon mesh after the experiment was hardly clogged, and the open area ratio was maintained at 13% or more (that is, less than 1% clogging).

(Core material production example 4)
Core material production example 3 except that polyethersulfone having an opening of 20 μm (opening ratio of 14%) and a flexural modulus of 2.6 Gpa is used instead of a nylon mesh having an opening of 20 μm (opening ratio of 14%). In the same manner as above, the core material was classified to obtain a carrier core material IV. As a result of classification, SF1 and SF2 are shown in Table 1.
Clogging after the experiment was less than 1%.

(Core material production example 5)
Core material production example 3 except that ultra-high molecular weight polyethylene having an opening of 20 μm (opening ratio of 14%) and a flexural modulus of 0.9 Gpa is used instead of the nylon mesh having an opening of 20 μm (opening ratio of 14%). In the same manner as above, the core material was classified to obtain a carrier core V. As a result of classification, SF1 and SF2 are shown in Table 1.
Clogging after the experiment was 3%.

(Core material production example 6)
Example of core material production, except that instead of nylon mesh with 20 μm mesh (14% aperture), GF30% reinforced polyethylene terephthalate with 20 μm mesh (14% aperture) and 11.0 Gpa flexural modulus is used. The core material was classified in the same manner as in No. 3 to obtain a carrier core VI. As a result of classification, SF1 and SF2 are shown in Table 1. Clogging after the experiment was 4%.

(Core material production example 7)
The carrier core material I of Table 1 (Mn ferrite, 57 emu / g / SF1 = 115, SF2 = 115) was supplied at a rate of 0.3 Kg / min. Classification was performed to obtain a carrier core VII shown in Table 1. Clogging after the experiment was less than 1%.

(Core material production example 9)
The core material was classified in the same manner as in Carrier Production Example 3 except that the carrier core material VIII shown in Table 1 was used, and the carrier core IX shown in Table 1 was obtained. Clogging after the experiment was about 3%.

<Carrier Production Examples 1-6>
In a silicone resin (SR2411: manufactured by Toray Dow Corning Silicone), 5% of carbon (made by Lion Akzo, Ketjen Black EC-DJ600) is dispersed for 60 minutes using a ball mill. The liquid was diluted to obtain a dispersion having a solid content of 5%.
An aminosilane coupling agent (NH ₂ (CH ₂ ) ₃ Si (OCH ₃ )) was further added to and mixed with this dispersion by 3% with respect to the solid content of the silicone resin to obtain a dispersion.
Using a fluidized bed type coating apparatus, using carrier core materials I to VI shown in Table 1,
On the surface of each 5 kg particle, the above dispersion is applied at a rate of about 30 g / min in an atmosphere of 100 ° C., and further heated at 200 ° C. for 2 hours to form a resin-coated carrier having a thickness of about 0.30 μm. A to F were obtained. The film thickness was adjusted depending on the amount of the coating solution.
Table 2 shows the particle size distributions of the carriers A to F, SF1 and SF2.

<Carrier Production Example 7>
In the vibrating screen shown in FIG. 1, two or more meshes represented by reference numeral (5) have the following configuration.
Specifically, a stainless steel mesh having a mesh size of 104 μm (150 mesh) was placed on the lower side, and a nylon mesh having a mesh size of 20 μm was adhered to the stainless steel mesh on the upper side. The material used for the nylon mesh (nylon-66) has a flexural modulus of 2.7 GPa.
The lower stainless steel mesh is directly subjected to vibration from the ultrasonic vibrator, but the nylon mesh is installed in close contact with the stainless steel mesh, so the ultrasonic vibration is transmitted efficiently and the particles to be classified are nylon mesh. Classified.
Using this vibrating screen, the carrier A obtained in Carrier Production Example 1 shown in Table 2 is supplied on a nylon mesh at a rate of 1 Kg / min, and classified in the same manner as in Core Material Production Example 3. To get carrier G.
Table 2 shows the carrier G particle size distribution, SF1, and SF2.
The clogging after the experiment in the carrier G classification was less than 1%.

<Carrier Production Example 8>
In the vibrating screen shown in FIG. 1, as two meshes used for the mesh portion of two or more layers represented by reference numeral (5), the mesh is 104 μm (150 mesh) stainless mesh on the lower side, and the mesh is on the upper side. A 32 μm polyester mesh (21% porosity) was installed.
The carrier G prepared in Carrier Production Example 7 was classified in the same manner as Carrier Production Example 7 to obtain a resin-coated carrier H.
Table 2 shows the carrier G particle size distribution, SF1, and SF2.
The clogging after the experiment in the carrier H classification was less than 1%.
However, the coarse powder side is the removed carrier, and the resin-coated carrier F is collected under the stainless steel mesh (5) in the cylindrical container (2).

(Manufacture and evaluation of developer)
Using 10 parts of the toner I obtained in Toner Production Example 1 and 100 parts of Carrier A to Carrier J obtained in Carrier Production Examples 1 to 10, the developer was prepared by stirring for 10 minutes with a mixer.
An image was formed using the obtained developer, and the image quality (background stain, graininess) and carrier adhesion margin test were performed.
The image was created using Imagio Color 4000 (Ricoh Digital Color Copier / Printer Combined Machine) under the following development conditions.
Development gap (photosensitive member-developing sleeve): 0.35 mm
Doctor gap (Development sleeve-Doctor): 0.65mm
Photoconductor linear velocity 200mm / sec
(Developing sleeve linear velocity / photosensitive member linear velocity) = 1.80
Writing density: 600 dpi
Charging potential (Vd): -600V
Potential after exposure of the portion corresponding to the image portion (solid document) (V1): -150V
Development bias: DC component-500 V / AC bias component: 2 KHZ
-100V to -900V, 50% duty

The test methods employed in the following image forming examples are as follows.
(1) Uniformity of highlight portion: Granularity (brightness range: 50 to 80) defined by the following formula was measured on transfer paper, and the numerical value was replaced with a rank as shown below.
Granularity = exp (aL + b) ∫ (WS (f)) ^1/2 VTF (f) df
L: Average brightness f: Spatial frequency (cycle / mm)
WS (f): brightness fluctuation power spectrum VTF (f): visual spatial frequency characteristics a, b: coefficient

Rank ◎ (very good): 0 or more and less than 0.1 ○ (good): 0.1 or more and less than 0.2 △ (available): 0.2 or more and less than 0.3 x Defect (unacceptable level): 0 .3 or more

(2) Background stain: The stain on the background portion of the image was visually evaluated. The symbols in the table are
A: Very good,
○: Good,
Δ: Usable,
X: Defect (x is an unacceptable level).

(3) Carrier adhesion: If carrier adhesion occurs, it may cause damage to the photosensitive drum and the fixing roller, leading to a reduction in image quality. Even if carrier adhesion occurs, only a part of the carrier is transferred to the paper, and therefore, evaluation was performed by transferring it from the photosensitive drum with an adhesive tape.
An image pattern of 2 dot lines (100 lpi / inch) is created in the sub-scanning direction, developed by applying −400 V as a DC bias component, and the number of carriers attached between the 2 dot line lines (area 100 cm ² ). The evaluation was performed by transferring with an adhesive tape and visually observing the number.
The symbols in Table 3 are as follows.
◎: Very good ○: Good △: (Can be used)
×: Defect (unacceptable level)

(4) Soil after 50K run:
A running evaluation of 50,000 sheets was performed using a character image chart with an image area ratio of 6% while supplying magenta toner I used for initial image formation. The background of the background under the above development conditions was evaluated for rank according to the same criteria as (2).
Table 1 shows the core material production example, Table 2 shows the carrier production example, and Table 3 shows the quality evaluation results in each example, reference example, and comparative example.

  According to the present invention, it is possible to provide a method for efficiently producing a small particle size electrophotographic carrier having high image quality, particularly good granularity, hardly causing carrier adhesion, and having a sharp particle size distribution. An electrophotographic two-component developer can be obtained.

An explanatory structural view of a vibration sieving machine with an ultrasonic oscillator in the present invention is shown. It is the figure which showed the perspective view of the resistance measurement cell used for the measurement of the electrical resistivity of the carrier in this invention. FIG. 6 is a diagram illustrating a method for measuring the charge amount of a developer. 1 is a diagram illustrating an example of an image forming apparatus using a developer according to the present invention. FIG. 5 is a diagram illustrating a developing unit in the image forming apparatus of FIG. 4. It is a figure which shows another example of the image forming apparatus using the developing agent of this invention. It is a figure which shows one example of the process cartridge example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vibrating sieve machine 2 Cylindrical container 3 Spring 4 Base 5 Mesh of two or more layers 6 Resonant ring 7 Cable 8 Converter (vibrator)
9 ring-shaped frame 11 cell 12a electrode 12b electrode 13 carrier 14 nozzle 15 cage 16 carrier 17 toner 18 electrometer 20 electrostatic charge image carrier 21 toner 23 carrier 24a drive roller 24b tension roller 26 pre-cleaning exposure means 32 charging means 33 exposure means 40 developing means 41 magnetic sleeve 42 housing 43 window 44 housing 45 toner supply means 46 housing 47 stirring means 48 toner stirring means 49 toner supply roller 50 transfer means 60 cleaning means 61 cleaning blade 62 waste toner storage means 64 cleaning brush 70 neutralizing means 80 Image receiving media sheet

Claims (17)

Content of particles having a weight average particle diameter Dw of 22 to 32 μm and a ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw of 1 <Dw / Dp <1.20, smaller than 20 μm Is 0 to 7% by weight, the content of particles smaller than 36 μm is 90 to 99.8% by weight, the shape factor SF1 is 100 to 107 , SF2 is 100 to 110 , and is made of Mn ferrite. An electrophotographic coated carrier core material. 2. The core material for an electrophotographic coated carrier according to claim 1 , wherein the content of particles having a particle size of less than 20 μm is 0 to 5% by weight. The core material for an electrophotographic coated carrier according to claim 1 or 2 , wherein magnetization when a magnetic field of 1000 oersted is applied is 40 to 150 emu / g. An electrophotographic coated carrier core material classified using a vibratory sieve equipped with an oscillator having an ultrasonic vibrator, wherein at least two mesh members are provided on the ultrasonic vibrator as the vibratory sieve. An electrophotographic coated carrier supplied on the uppermost mesh material by transmitting the vibration received by the lower mesh material from the ultrasonic vibrator to the upper mesh material, using a product that is closely stacked and installed. The core material for an electrophotographic coated carrier according to any one of claims 1 to 3, wherein the core material is obtained by undergoing a step of classifying the core material. The classification is characterized in that at least two mesh materials are used in which a mesh material with a small mesh is installed on the upper side and a mesh material with a large mesh is installed on the lower side. 4. The core material for an electrophotographic coated carrier according to 4 . The core material for an electrophotographic coated carrier according to claim 4 or 5 , wherein a bending elastic modulus of at least one kind of material of the mesh material having a small mesh installed on the upper side is 1 to 10 GPa. As the vibration sieving machine, a resonance member fixed on a mesh material is used, and ultrasonic vibration is transmitted to the resonance member to resonate, followed by a classification process transmitted to the uppermost mesh material surface. The core material for an electrophotographic coated carrier according to any one of claims 4 to 6 , wherein the core material is an electrophotographic coated carrier according to any one of claims 4 to 6 . It claims 1 to 7 electrophotographic coated carrier to form a resin coating layer on the surface of the core material for electrophotographic coated carrier according to any one of. The electrophotographic coated carrier according to claim 8 , wherein the resin coating layer has a thickness of 0.03 to 0.8 μm. 10. An electrophotographic developer comprising the electrophotographic coated carrier according to claim 8 or 9 and a toner. A manufacturing method of an electrophotographic coating core material for a carrier, comprising the step of classifying the core material for electrophotographic coated carrier using a vibrating screen classifier equipped with an oscillator comprising an ultrasonic vibrator, as the vibrating screen machine, the Using an ultrasonic transducer in which at least two mesh materials are closely stacked and installed, the vibration received by the lower mesh material from the ultrasonic transducer is transmitted to the upper mesh material, By classifying the core material supplied on the mesh material on the side, the weight average particle diameter Dw is 22 to 32 μm, and the ratio Dw / Dp of the number average particle diameter Dp to the weight average particle diameter Dw is 1 <Dw / Dp <1.20, the content of particles having a particle size smaller than 20 μm is 0 to 7% by weight, the content of particles smaller than 36 μm is 90 to 99.8% by weight, and the shape factor SF1 is 100 to 107 , And SF2 is 1 Method for manufacturing a core material for electrophotographic coated carrier, characterized in that to obtain an electrophotographic coating core material for a carrier consisting of Mn ferrite is 0-110. 12. The electrophotographic coated carrier according to claim 11 , wherein the at least two mesh materials are one in which a mesh material having a small mesh is installed on the upper side and a mesh material having a large mesh is installed on the lower side. Manufacturing method for core material . The core material for an electrophotographic coated carrier according to claim 11 or 12 , wherein a bending elastic modulus of at least one kind of mesh material having a small mesh installed on the upper side is 1 to 10 GPa. Method. As the vibration sieve machine, according to claim 11 in which the resonant member is used as fixedly installed on the mesh material, ultrasonic vibration is resonated by transmitting a resonant member, and then characterized to convey the uppermost mesh material surface The manufacturing method of the core material for electrophotographic coated carriers in any one of thru | or 13 . The core for electrophotography coated carrier, for electrophotography coated carrier according to any one of claims 11 to 14 content of the particles having a 20μm smaller particle size characterized in that it is a 0 to 5 wt% Manufacturing method of core material . 1000 magnetization of Oersted core material for electrophotographic coated carrier when a magnetic field is applied of an electrophotographic coated carrier wick according to any one of claims 11 to 15, characterized in that a 40~150emu / g A method of manufacturing the material . The claims 11 to 16 Electrophotographic coating career, characterized in that the surface of the resulting coated core material for a carrier than the method of manufacturing a core material for electrophotographic coated carrier to form a resin coating layer according to any one of the method of production.

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