JPH07175270A - Magnetic substance dispersed resin carrier - Google Patents

Abstract

PURPOSE:To obtain a carrier for an electrophotographic developer faithfully developing an electrostatic latent image and giving a faithful image of an original while preventing the sticking of the carrier to an electrostatic latent image carrier and excellent in resolution, highlight reproducibility and thin line reproducibility. CONSTITUTION:When fine particles of a magnetic substance are dispersed in a bonding resin to obtain a magnetic substance dispersed resin carrier, an oriented liq. crystal-like polymer is contained in the bonding resin and the fine particles are allowed to satisfy (major axis size)/(minor axis size) >1. The objective magnetic substance dispersed resin carrier is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic substance dispersion type resin carrier for electrophotography, which is mixed with a toner to form an electrostatic image developer.

[0002]

2. Description of the Related Art U.S. Pat. No. 2,29 as an electrophotographic method
Various methods are described in Japanese Patent No. 7,691, Japanese Patent Publication No. 42-23,910 and Japanese Patent Publication No. 43-24,748. In all of these methods, an electrostatic latent image is formed by irradiating the photoconductive layer with a light image corresponding to the original, and the electrostatic latent image is developed using colored fine powder called toner, and the necessary Accordingly, the toner image is transferred onto a transfer material such as paper and then fixed by heating, pressurizing, solvent vapor or the like to obtain a copy.

In the step of developing the electrostatic latent image, toner particles charged to a polarity opposite to that of the ordinary latent image are attracted by electrostatic attraction and attached to the electrostatic latent image (reversal). In the case of development, a toner having a triboelectric charge of the same polarity as the latent image charge is used.) Generally, the method of developing such an electrostatic latent image with toner is roughly classified into a small amount of toner on a medium called a carrier. There are a method of using a so-called two-component developer dispersed and a method of using a so-called one-component developer of toner alone without using a carrier.

Although the electrophotographic method has reached a satisfactory level as a document copy, a digital image processing and an alternating electric field application at the time of development are applied to an output image of a full-color image required by the development of computers and high-definition. Various techniques have been used to achieve high image quality and high quality. Furthermore, further improvement in image quality and quality is desired in the future.

Conventionally, to output a full-color image,
A two-component developer is used. In general, the carrier that constitutes such a two-component developer is a conductive carrier typified by iron powder and the surface of iron powder, nickel, ferrite, or the like is coated with an insulating resin, or magnetic fine particles are coated with an insulating resin. It is roughly classified into a so-called insulating carrier in which the resistance is increased by dispersing it inside. When an alternating electric field is applied to measure high image quality, if the resistance of the carrier in the developer is low, the carrier leaks the latent image potential and a good image cannot be obtained. is necessary. Therefore, when the core material of the carrier is conductive, it is preferable to cover the surface with an insulating resin or the like before use. In addition, ferrite or magnetic material-dispersed resin fine particles having a high resistance to some extent are preferably used as carriers.

In general, iron powder has a high magnetic force. When iron powder is used as a carrier in a developer, the magnetic brush of the developer becomes hard in the developing area where the toner in the developer develops a latent image. It is not possible to obtain a high-quality image because of the sharp edges and the sharpness. Therefore, in order to reduce the magnetic force of the carrier and achieve high image quality, a ferrite or resin carrier is preferably used. In order to form a high-quality image, in JP-A-59-104,663, ferrite particles having a saturation magnetization value of carrier of 50 emu / g or less are used to obtain a good image without peeling. Although it has been proposed that a carrier with a small saturation magnetization value can be used, the fine line reproducibility is improved, but as the distance from the magnetic pole increases, the carrier on the electrostatic latent image carrier (for example, photoconductor drum) is increased. The phenomenon in which is attached (attachment of carrier) becomes remarkable. Further, in the case of a magnetic substance dispersion type resin carrier, the fact that the specific gravity is small is disadvantageous in the carrier adhesion.

Further, Japanese Examined Patent Publication (Kokoku) No. 4-3868 discloses that a so-called hard ferrite having a coercive force of 300 gauss or more is used as a carrier. However, this is a system for making full use of hard ferrite having a high coercive force as a carrier, and an increase in the size of the device cannot be avoided. In order to realize a compact high-quality color copier, it is preferable to use a developer carrier that uses a fixed magnetic core, and the hard ferrite carrier with a high coercive force is rather self-aggregating, which makes it easier to transport the developer. Becomes worse.

Further, JP-A-2-88,429 proposes to use a hard ferrite composed of a magnet-plumbite phase containing a spinel phase and a lanthanoid element as a carrier.
Since the hard ferrite has conductivity, it is not preferable in a developing system using an alternating electric field for obtaining a high-quality image because electric charge leaks through the carrier and disturbs the development. Therefore, the carrier used in the developing system using the alternating electric field needs to have an electric resistance of a certain level or more. As described above, sufficient developer carriers have not yet been obtained that can prevent carrier adhesion to the electrostatic latent image carrier while simultaneously satisfying high image quality, particularly highlight reproducibility.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic developer carrier which solves the above-mentioned conventional problems. Another object of the present invention is to
Development that is faithful to the original, that is, develops the electrostatic latent image faithfully while preventing the carrier from adhering to the electrostatic latent image carrier, and has excellent high resolution, high highlight reproducibility and high fine line reproducibility. It is to provide a drug carrier. Another object of the present invention is to provide a developer carrier which does not leak the latent image potential by the carrier even in the development of an alternating electric field and obtains a good developed image quality. Another object of the present invention is to provide a developer carrier for a small-sized developing device using a fixed magnetic core type developer carrying member for obtaining a high quality image. Still another object of the present invention is to provide a developer carrier capable of maintaining high image quality for a long period of time.

[0010]

The above object can be achieved by the present invention described below. That is, the present invention is a magnetic substance-dispersed carrier obtained by dispersing magnetic fine particles in a binder resin, wherein the binder resin of the carrier contains an oriented liquid crystalline polymer, and the above magnetic fine particles are used. A magnetic substance-dispersed resin carrier characterized by using a magnetic substance having a major axis / minor axis> 1 as a magnetic substance dispersed particle carrier, wherein the magnetic substance fine particles are at least 30% oriented,
The magnetic intensity (σ _1,000 ) in the magnetic field of 1,000 oersted after magnetically saturated is 30 to 150 emu / c.
m ³ and magnetic field 0 oersted, the strength of magnetization (remanent magnetization: σr) is 25 emu / cm ³ or more, the coercive force is less than 300 oersted, and the strength of magnetization further satisfies the following formula: The average particle size of the resin carrier and carrier particles is 5 to 100 μm, the bulk density is 3.0 g / cm ³ or less, and the content of the magnetic substance contained in the magnetic substance dispersion type carrier is 30 to 99% by weight. The magnetic substance-dispersed resin carrier described above, and the magnetic substance-dispersed resin carrier having a specific resistance of 10 ⁸ to 10 ¹³ Ω · cm.

[Equation 2] [Wherein σ _1,000 represents the strength of carrier magnetization (emu / g) in a magnetic field of 1,000 oersteds, σ
₃₀₀ indicates the strength (emu / g) of carrier magnetization in a magnetic field of 300 Oersted. ]

[0012]

The carrier of the present invention improves the various drawbacks of the conventional carrier and prevents the carrier from adhering to the electrostatic latent image bearing member while faithfully developing the original, that is, developing the electrostatic latent image faithfully. It is considered that the high image quality can be maintained for a long period of time due to the following reasons.

In order to faithfully develop the latent image, it is important to weaken the carrier magnetization in the magnetic field at the developing pole. This is because the magnetic strength of the carrier is weak, and the magnetic brush of the developer carrier is short, dense and soft, so that faithful development of the latent image can be achieved. By making the magnetic brush short, dense and soft in this way, the development efficiency is particularly improved in the development in which an alternating electric field that vibrates the developer is applied to the development section, and higher quality and faithful development can be performed. . Generally, the strength of the magnetic field at the developing pole is about 1,000 Oersted, so
The magnetic properties of the carrier of the present invention are also targeted for the strength of magnetization (σ _1,000 ) in a magnetic field of 1,000 oersted, and the value is 30 to 150 emu / cm ³ , preferably 30.
~150emu / cm ³ was.

Another advantage of the present invention is that the deterioration of the image quality can be prevented and the initial high quality image can be maintained, by using such a carrier having a low magnetic force, a fixed magnet is included. When a developer carrier is coated with a two-component developer, the magnetic coupling between the carriers as magnetic brushes in the vicinity of the regulation member is weak, and since the ears are soft, they do not share much with the toner. Further, since the resin carrier is lighter in weight than the conventional iron / ferrite carrier, the load due to stirring in the developing device is small, the deterioration of the developer is significantly reduced, and a high quality image can be maintained for a long time.

Further, as a result of a detailed study, carrier adhesion to the electrostatic latent image carrier is likely to occur when the magnetic field strength is 0 to 300 Oersted, and when the carrier magnetization strength is high to some extent. It turned out to be absent or unlikely. Further, the carrier adhesion to the electrostatic latent image carrier depends on the developing bias condition, and when developing by an alternating electric field, when the carrier has an electric charge, the carrier is transferred to the electrostatic latent image carrier as compared with the DC electric field. The magnetic force is required to hold the carrier on the developer carrying member. Therefore, in order to suppress the carrier adhesion to the electrostatic latent image carrier, it is considered necessary to have a certain degree of magnetization in the magnetic field. The carrier of the present invention is shown in FIG. 2 (the needle-shaped particles 22 show a magnetic substance and are oriented with respect to the direction of the magnetic field. Further, the angle ± 15 ° for showing the orientation degree is shown. Is shown in the figure), the strength of the residual magnetization is enhanced by performing a treatment for orienting 30% or more of the magnetic fine particles 22 dispersed in the binder resin 21 of the carrier in the uniaxial direction. It was As a result, as shown in the hysteresis curve of FIG. 1, the magnetization intensity (σ _1,000 ) in the magnetic field of 1,000 oersteds was 30 to 150 emu / cm ^3.
And although it is smaller than the conventional carrier, 0-300
It became a resin carrier with strong magnetization in Oersted, and was able to achieve high image quality and prevention of carrier adhesion to the electrostatic latent image carrier at the same time.

Another feature of the carrier binder resin of the present invention is that a resin having so-called liquid crystallinity, that is, a liquid crystal polymer that exhibits molecular orientation not only in the solid state but also in the molten state is used. By using a liquid crystal polymer as the binder resin of the magnetic substance-dispersed resin carrier of the present invention, it is possible to more easily perform injection molding or orient molecules and magnetic substances in a magnetic field. Therefore, it becomes possible to form a magnetic substance dispersion type resin carrier having better magnetic characteristics as compared with the case of using a conventional binder resin. By using the polymer matrix, which is the above-mentioned oriented liquid crystal polymer, as the binder resin, the bulk elastic modulus can be remarkably increased, and thus high-strength, highly durable and long-life carrier particles and a developer composition are provided. It becomes possible to do. Further, the binder resin has excellent solvent resistance as compared with conventional resin resins and can be easily coated with a carrier, and as a result, a desired triboelectric charge level can be imparted to the carrier.

In general, a magnetic material having a large residual magnetization has a large coercive force and becomes a hard ferrite such as a so-called permanent magnet. That is, when a magnetic material having a large remanent magnetization is used for the magnetic substance in the carrier, as described above, a poor mixing property with the toner due to self-aggregation and a poor developer transporting property are likely to occur. A large and special developing device having such a developer carrying member is required. The present invention does not use such a general magnetic material such as hard ferrite for the magnetic substance in the carrier, but uses magnetic substance fine particles having a low coercive force such that the coercive force is less than 300 Oersted, Even a small-sized developing device using a fixed magnetic core type developer carrying member provides a carrier having a good mixing property with toner and a developer transporting property.

The magnetic properties of the carrier particles of the present invention are required to be as follows. That is, the magnetization intensity (σ _1,000 ) in the magnetic field of 1,000 oersted after magnetically saturated is 30 to 150 emu / cm ³ , and in order to achieve higher image quality, it is 30 to 100 emu / cm ³ . Something is preferable. When it is higher than 150 emu / cm ^3, the density of the magnetic brush of the developer carrier at the developing pole is the same as the conventional one, and it becomes difficult to obtain a high quality image.
If it is less than ³⁰ emu / cm ³ , the magnetic restraining force is reduced, so that the carrier adheres to the electrostatic latent image carrier.

The strength of remanent magnetization is 25 emu / cm.
Must be ³ or higher. If it is less than 25 emu / cm ³ , in particular, in a developing system using a large contrast potential for high image quality or using an alternating electric field with a large amplitude, carrier adhesion to the electrostatic latent image bearing member is likely to occur, and development In the subsequent transfer process, the carrier-adhered portion causes a transfer failure, which makes it difficult to obtain a high-quality image.

Further, it is necessary that the coercive force is less than 300 Oersted. When it is 300 oersteds or more, the carrier itself is self-aggregated, so that the mixing property with the toner is poor, and particularly in the developer carrier containing a fixed magnet, the carrier can easily move on the developer carrier. As a result, the transportability of the developer is deteriorated and the coat state of the developer on the developer carrier is deteriorated, so that it is difficult to obtain a high quality image.

Further important in the carrier of the present invention is the strength of magnetization in the vicinity of a magnetic field of 0 to 300 Oersted. That is, it is necessary to perform a treatment for orienting 30% or more of the magnetic fine particles dispersed in the binder resin of the carrier of the present invention, and further satisfy the following formula.

[0022]

[Equation 3] [In the formula, σ _1,000 represents the strength of carrier magnetization (emu / g) in a magnetic field of 1,000 Oersted, and σ ₃₀₀
Indicates the strength of carrier magnetization (emu / g) in a magnetic field of 300 Oersted. ]

It is more preferable that the value on the left side of the above formula is 0.30 or less. Here, the hysteresis curve of FIG. 1 will be described. When it exceeds 0.40, it is difficult to prevent carrier adhesion to the electrostatic latent image bearing member while achieving high image quality, which is one of the objects of the present invention. That is, if a value that satisfies σ _1,000 is taken, high image quality can be achieved, but the carrier adhesion is likely to occur. Further, if a value that satisfies σ ₃₀₀ is taken, it is possible to prevent the carrier adhesion, but σ
_When the value of _1,000 becomes large, it becomes difficult to obtain a high quality image as in the present invention.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The orientation degree of the magnetic substance dispersed in the binder resin of the carrier of the present invention is defined by the orientation probability of the magnetic substance having the shape anisotropy used in the present invention,
Field Emission Scanning Electron Microscope (FE-SE
M) S-800 (manufactured by Hitachi, Ltd.) was used to measure the orientation of the magnetic fine particles in the carrier cross section by statistically processing. Specifically, 100 or more shape-anisotropic magnetic materials used in the present invention are randomly extracted from 10 randomly extracted carrier cross-sectional photographs, and the magnetic field direction The ratio of those facing the range of ± 15 ° was calculated. The carrier cross section sample is
After the carrier is dispersed and solidified in the epoxy resin in a parallel magnetic field, the plastic embedding sample is microtome F.
It was created by cutting with C4E (manufactured by REICHERT-JUNG). For example, FIG. 2 shows an example schematically showing a cross section of a carrier in which a needle-shaped magnetic material is dispersed.

The magnetic characteristics of the carrier in the present invention are measured using a DC magnetization BH characteristic automatic recording device BHH-50 (manufactured by Riken Denshi Co., Ltd.). Generally, the developing pole in the developing device has a magnetic field of 1,000 oersted, and in the present invention, the magnetic characteristic of the carrier is a magnetic field of 10 kilo-oersted. Carrier magnetization intensity at (σ _1,000 , σ ₃₀₀ and σ
r) and the coercive force of the carrier are obtained. Regarding the magnetic characteristics in the present invention, after the sample is loosely put in a cylindrical plastic container, strong packing is performed in a state where a magnetic field of 10 kilo Oersted is applied and fixed, and the magnetic characteristics in that state are measured. The measured value in this state is used as the magnetic characteristic of the present invention. The volume of the sample holder at that time is 0.
It is 332 cm ³ , and the strength of magnetization per unit volume is obtained from this.

In order to achieve the above-mentioned magnetic characteristics which are the characteristics of the carrier of the present invention, a magnetic material dispersed in the carrier is a metal oxide magnetic material of 1 μm or less, for example, Ba.
Hexagonal plate-like magnetic material such as series ferrite, Sr series ferrite and Pb series ferrite, or γ-Fe ₂ O ₃ series, C
An acicular magnetic substance such as o-based ferrite and acicular magnetite alone is mixed, and particles having these shape anisotropies are mixed,
Alternatively, particles having shape anisotropy and a soft magnetic material such as soft ferrite can be mixed and used. It is one of the features of the present invention that the magnetic material is mechanically or magnetically oriented along the molecular orientation of the liquid crystal polymer which is the binder resin of the carrier by injection molding or the like. As the orientation means at this time, in addition to kneading in a magnetic field or injection molding, a method of cooling in a magnetic field after kneading can be mentioned, or they can be used in combination.

By taking the composition of the carrier and the orientation form of the magnetic substance in the carrier as described above, the magnetization intensity (σ _1,000 ) in the magnetic field of 1,000 oersted after magnetic saturation is 30 to 150 emu / It is possible to easily obtain a carrier having a magnetic property of cm ³ and a residual magnetization σr of 25 emu / cm ³ or more and a coercive force of less than 300 Oersted. The content of the magnetic substance with respect to the total amount of the carrier of the present invention is 30% by weight to 99% by weight, preferably 50% by weight or more. If it is less than 30% by weight, the above-mentioned desired magnetic properties as a carrier cannot be obtained, and it becomes difficult to control the specific resistance of the carrier. Further, if the content of the magnetic material exceeds 99% by weight, the adhesiveness between the magnetic material and the binder resin becomes poor.

Further, the carrier of the present invention can easily achieve the characteristic magnetic characteristics of the present invention by being used after being magnetically saturated. Examples of the magnetic saturation method include exposing carrier particles to a magnetic field of 10 kilo Oersted with a DC electromagnet.

The specific resistance of the carrier of the present invention is 10 ⁸ to 10
^It is preferably in the range of ¹³ Ω · cm. 10 ⁸ Ω · cm
When the amount is less than the above, a developing method in which a bias voltage is applied causes a current to leak from the developer carrying member to the surface of the photosensitive member in the developing region, and it is difficult to obtain a good image. On the other hand, if it exceeds 10 ¹³ Ω · cm, a charge-up phenomenon is caused under a condition such as low humidity, which tends to cause image deterioration such as low density, poor transfer or fog.

The measuring device shown in FIG. 3 was used for measuring the specific resistance of the carrier of the present invention. That is, the cell C is filled with the carrier to be measured, the electrodes 31 and 32 are arranged in contact with the filled carrier 37, a voltage is applied between the electrodes, and the current flowing at that time is measured by the ammeter 34,
The specific resistance was calculated from the value. In the above measuring method,
Since the carrier is powder, the filling rate may change and the specific resistance may change accordingly, so caution is required.
The specific resistance measurement conditions in the present invention are as follows: the contact area between the filled carrier and the electrode is about 2.3 cm ² , and the thickness (d) is about 1 m.
m, the load of the upper electrode 32 is 275 g, and the applied voltage is 10
It was set to 0V.

The average particle size of the carrier particles of the present invention is 5 to
The range is preferably 100 μm, more preferably 20 to 8
It is 0 μm. If it is less than 5 μm, the carrier tends to adhere to the electrostatic latent image carrier. On the other hand, when the thickness exceeds 100 μm, the magnetic brush of the carrier at the developing pole becomes coarse, and it is difficult to obtain a high quality image. The particle size of the carrier of the present invention was determined by randomly extracting 300 or more particles with an optical microscope and measuring the horizontal Feret diameter measured by an image processing analyzer Luzex3 (manufactured by Nireco) as the particle size of the carrier particles.

The bulk density of the carrier of the present invention is 3.0 g /
cm ³ or less is preferable. When it exceeds 3.0 g / cm ³ , the rotation of the developer carrier causes the centrifugal force applied to each carrier particle to be larger than the force of magnetically retaining the carrier on the carrier, and carrier scattering is likely to occur. Become. The bulk density of the carrier of the present invention is measured according to JIS-Z-250.
According to the method described in 4.

Examples of the binder resin used as the core material of the carrier of the present invention include all commonly known liquid crystal polymers such as a main chain type liquid crystal polymer, a side chain type liquid crystal polymer and a composite type liquid crystal polymer. Examples of the main chain type liquid crystal polymer mentioned here include wholly aromatic polyester. Examples of the monomer used for the wholly aromatic polyester include the following structural formulas (1) to (8) as an aromatic diol, the following structural formulas (9) to (15) as an aromatic dicarboxylic acid, and the following structural formulas as a hydroxycarboxylic acid. There are formulas (16) to (20) and their acid halides, and one or more of these monomers can be polymerized and used. Examples of the side chain type liquid crystal polymer include a vinyl type polymer having a mesogen group, polysiloxane, polypeptide, polyphosphazene or polyethylimine. As a composite type liquid crystal polymer,
For example, it can be obtained by further bonding a mesogenic group to the mesogenic group or the bent chain of the above main chain type liquid crystal polymer.

[0034]

[Chemical 1] [Wherein R represents a linear or branched alkylene group having 1 to 10 carbon atoms, an O atom, an S atom, an arylene group or a halogenated alkylene group, and X and Y represent a halogen atom or an alkyl group. X'represents a hydrogen atom, a halogen atom or an alkyl group, and Z represents a hydroxyl group or a halogen atom. ]

The sphericity of the carrier of the present invention is preferably 2 or less. That is, since the carrier of the present invention is a resin carrier, it is light, and since the share of the developer is reduced, one effect of the present invention is that deterioration of the developer is suppressed and high image quality can be maintained for a long period of time. The closer the carrier shape is to the spherical shape, the more advantageous the expression. Further, the closer the carrier is to the spherical shape, the more it tends to improve the fluidity as a developer.
Other development characteristics are also excellent. Therefore, in the developer capable of achieving and maintaining high image quality, it is preferable that the sphericity of the carrier has the above value.

The sphericity of the carrier of the present invention is measured by the field emission scanning electron microscope (FE-SEM) S.
-800 [Hitachi, Ltd.] randomly extracts 300 or more carriers, and image processing analysis device Luze
x3 (manufactured by Nireco Corp.) is used to obtain the shape factor derived by the following equation.

[0037]

[Equation 4] [In the formula, MX LNG represents the maximum diameter of the carrier, and A
REA represents the projected area of the carrier. ] Here, the sphericity means that the closer it is to 1, the closer it is to a sphere.

As a method for producing the carrier of the present invention, the binder resin and the magnetic fine particles are mixed in a desired quantitative ratio and, for example, a heating and melting mixing device such as a three-roll or an extruder is used. The mixture is kneaded at a temperature and the magnetic fine particles are oriented mechanically, magnetically or in combination during injection molding. After cooling the kneaded product, the particles obtained after pulverization and classification are collided with a plate at a high speed, and the surface is heat-melted by the energy to perform a spheroidizing treatment. By carrying out such a spheroidizing treatment, the sphericity of the carrier as described above can be satisfied.

Further, the carrier of the present invention may be used by coating the surface of carrier particles with an arbitrary resin, if necessary, in order to control the specific resistance or improve the durability. As the resin to be coated, a known appropriate resin can be used. For example, it can be used by coating with an acrylic resin, a fluorine resin, a silicon resin, or the like. As a method of resin-coating the core material of the carrier of the present invention, considering that the core material is made of resin, a treatment method in which the coating resin is rapidly coated so that the core materials do not adhere to each other is preferable. . That is, a treatment method is preferred in which conditions such as selection of a solvent that dissolves the coating resin, treatment temperature and treatment time are sufficiently controlled, and coating and drying are simultaneously performed in such a manner that the core material is always allowed to flow.

The toner used with the carrier of the present invention has a weight average particle size of 1 in order to obtain a higher quality image.
˜20 μm, more preferably 4˜
It is 10 μm. The weight average particle diameter of the toner is measured by
It can be carried out by various methods, but in the present invention, it is carried out by a Coulter counter.

In order to obtain a higher quality image, the cohesion of the toner used with the carrier of the present invention is preferably low, preferably 30% or less. The measurement of the degree of aggregation used in the present invention is performed by the following method. Powder tester [manufactured by Hosokawa Micron Co., Ltd.], 60 mesh from the top, 1
Three sieves were set in order of 00 mesh and 200 mesh, 5 g of the weighed toner was gently placed on the sieve, and vibration was applied for 15 seconds at a voltage of 17 V to weigh the toner remaining on each sieve. Is measured and the degree of aggregation is calculated according to the following formula.

[0042]

[Equation 5]

In order to reduce the degree of aggregation of the toner, it is preferable to use a fluidity improver such as silica, titanium oxide or alumina internally or externally added to the toner, and a fluidity improver having hydrophobicity is added to the outside. It is more preferable to add.

[0044]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples. These do not limit the invention in any way. In addition,% and parts in the following formulations represent% by weight and parts by weight, unless otherwise specified.

Example 1

[Chemical 2] Polymer having the above structural unit 30% 3% Zn-doped γ-Fe ₂ O ₃ 70% (horizontal ferret diameter: major axis = 1.0 μm, minor axis = 0.1
4 μm)

The above materials were sufficiently premixed with a Henschel mixer, melt-kneaded with a three-roll mill, the magnetic material in the binder resin was oriented by an injection molding machine, and further slowly cooled in a magnetic field, and after cooling. It was crushed to obtain a powder having a diameter of about 2 mm. Then, it was pulverized to a particle size of about 50 μm by an air jet pulverizer. Further, the obtained finely pulverized product was put into MechanoMill MM-10 (manufactured by Okada Seiko Co., Ltd.) and mechanically spheroidized. The pulverized finely pulverized particles were further classified to obtain a core material of a magnetic material-dispersed resin carrier. The particle diameter of the obtained core material is 42 μm, and the specific resistance is 3.0 × 10 ^10.
It was Ω · cm. As a result of cross-section observation by FE-SEM, the degree of orientation of the magnetic fine particles was 78%. The surface of the core material of the above magnetic substance-dispersed resin carrier was coated with a styrene-2-ethylhexyl methacrylate (50/50) copolymer by a fluidized bed coating method to obtain a magnetic substance-dispersed resin carrier of the present invention. . Table 1 collectively shows each physical property of the obtained carrier.

On the other hand, polyester resin obtained by condensing propoxylated bisphenol and fumaric acid 100 parts Phthalocyanine pigment 5 parts Di-tert-butylsalicylic acid chromium complex salt 4 parts After sufficiently pre-mixing the above materials with a Henschel mixer The mixture was melt-kneaded three times with a three-roll mill, cooled, and coarsely pulverized with a hammer mill to a particle size of about 1 to 2 mm.
Then, it was pulverized by an air jet pulverizer. Further, the obtained finely pulverized product was classified to have a negatively chargeable cyan powder (toner) having a weight average diameter of 8.2 μm.
Got 100 parts of the cyan toner and 0.4 part of silica fine powder hydrophobized with hexamethylzinlazan were mixed by a Henschel mixer to prepare a cyan toner having silica fine powder on the toner particle surface.

The carrier was magnetized in a magnetic field of 10 kilo Oersted and then mixed with the cyan toner in an N / N environment at a toner concentration of 5% to prepare a developer. An image output test was carried out using a modified machine of the full-color laser copying machine CLC-500 (manufactured by Canon Inc.) using the developer. FIG. 4 is a schematic diagram of the developing area portion of the developing device and the photoconductor drum at this time. The distance between the developer carrying member 42 and the developer regulating member 44 is 400 μm, and the process speed is 350 m.
m / sec, the peripheral speed ratio between the developer carrying member 42 and the photosensitive drum 40 was 1.4: 1, and the distance between the developer carrying member 42 and the photosensitive drum 40 was 500 μm. Further, the developing conditions were a magnetic field strength of the developing electrode of 1,000 oersted, an alternating electric field of 2,000 V _PP and a frequency of 3,000 Hz.

As a result of the image output test, the density of the solid image was as high as 1.50, there was no roughness, and the reproducibility of the halftone portion and the line image portion was good. Further, despite the high speed rotation of the developer bearing member, carrier adhesion to the electrostatic image portion or non-electrostatic image portion due to carrier scattering and carrier development was not recognized. Further, after the developing device was idly rotated at a speed of 200 rpm for 30 minutes, an image forming test was conducted. As a result, there was no particular problem with the image quality after idling, and no carrier adhesion was observed in the image area and non-image area. The ears of the magnetic brush of the developer carrier were dense, and the reproducibility of solid area density, halftone area and line image area was good. The above test results are summarized in Table 2.

Example 2

[Chemical 3] Polymer having the above structural unit 30% γ-Fe ₂ O ₃ 70% (horizontal ferret diameter major axis 0.9 μm uniaxial 0.12
μm)

The above materials were granulated in the same manner as in Example 1 to obtain a core material of a magnetic material dispersed carrier. The average particle diameter of the obtained core material was 41 μm, and the specific resistance was 2.0 × 10 ⁹ Ω.
It was cm. The core material was coated with the same resin as in Example 1 in the same manner as in Example 1 to obtain a magnetic substance-dispersed resin carrier of the present invention. Table 1 shows each physical property of the obtained carrier. When the carrier was tested in the same manner as in Example 1, good results were obtained as in Example 1. The above test results are summarized in Table 2.

Example 3

[Chemical 4] Polymer having the above structural unit 30% 3% Zn taup γ-Fe ₂ O ₃ 70% (horizontal ferret diameter major axis = 1.0 μm, uniaxial = 0.1
4 μm)

The above materials were melt-kneaded in the same manner as in Example 1, the magnetic material was mechanically oriented by an injection molding machine, and after cooling, pulverization, classification and spheronization were performed in the same manner as in Example 1, A core material of a magnetic material dispersed carrier was obtained. The average particle diameter of the obtained core material is 45 μm, and the specific resistance is 1.2 × 1.
It was ⁰⁹ Ω · cm. The core material was coated with the same resin as in Example 1 in the same manner as in Example 1 to obtain a magnetic substance-dispersed resin carrier of the present invention. Table 1 shows each physical property of the obtained carrier. When the carrier was tested in the same manner as in Example 1, good results were obtained as in Example 1. The above test results are summarized in Table 2.

Comparative Example 1 Fe ₂ O ₃ 50 mol% ZnO 25 mol% CuO 25 mol%

The above materials were weighed and mixed using a ball mill. The mixed powder was calcined and then ground. The crushed sample was made into a slurry, and the slurry was granulated with a spray dryer to sinter the granulated powder. The obtained sintered powder is classified by an air classifier, and the average particle size is 48 μm.
The carrier core material was obtained. The obtained core material had a substantially spherical shape, and the specific resistance was 5.2 × 10 ⁹ Ω · cm. The core material was coated with the same resin as in Example 1 in the same manner as in Example 1 to obtain a carrier of Comparative Example. Table 1 shows each physical property of the obtained carrier. Example 1 using the above carrier
As a result of the same test as the above, no carrier adhesion on the electrostatic image part or the non-electrostatic image part occurred, but the spikes of the magnetic brush of the developer carrier were rough, and the initial image had rough lines and lines on the halftone part. Caused a disturbance. or,
Image deterioration was observed after the 30-minute durability test. The above test results are summarized in Table 2.

Example 4

[Chemical 5] Polymer having the above structural unit 30% Ba ferrite (flat) 25% (mol% Fe ₂ O ₃ : ZnO: BaO = 70: 15:
15) (Ferre diameter in horizontal direction: 1.2 μm, thickness direction: 0.1 μm)
m) Cu-Zn ferrite of 40% _{(mol% Fe 2 O 3: CuO:} ZnO = 60: 20:
20) (Horizontal ferret diameter: 1.4 μm)

The above materials were melt-kneaded in the same manner as in Example 1, injection-molded, the melt was poured into a mold, and exposed to a magnetic field to magnetically separate the magnetic particles in the binder. After being oriented to, and cooled, pulverization, classification and spheronization were carried out in the same manner as in Example 1 to obtain a core material of a magnetic substance dispersion type carrier. The average particle size of the obtained core material is 46μ.
m, and the specific resistance was 9.7 × 10 ⁹ Ω · cm.
The core material was coated with the same resin as in Example 1 in the same manner as in Example 1 to obtain a magnetic substance-dispersed resin carrier of the present invention. Table 1 shows the physical properties of the obtained carrier. When the carrier was tested in the same manner as in Example 1, good results were obtained as in Example 1. The above test results are summarized in Table 2.

Example 5

[Chemical 6] Polymer having the above structural unit 30% Sr ferrite (plate-like) 15% (molar ratio Fe ₂ O ₃ : SrO: CaO = 80: 17:
3) (Ferre diameter in horizontal direction: 1.1 μm, thickness direction: 0.1 μm)
m) Cu-Zn ferrite of 55% (molar ratio _{Fe 2 O 3: CuO: ZnO} = 60: 15:
25) (Ferre diameter in the horizontal direction: 1.3 μm)

The above materials were melt-kneaded in the same manner as in Example 1 and then granulated in the same manner as in Example 4 to obtain a core material of a magnetic material dispersed carrier. The average particle size of the obtained core material is 47 μm.
And the specific resistance was 1.4 × 10 ¹⁰ Ω · cm. The core material was coated with the same resin as in Example 1 in the same manner as in Example 1 to obtain a magnetic substance-dispersed resin carrier of the present invention. Table 1 shows the physical properties of the obtained carrier. When the carrier was tested in the same manner as in Example 1, good results were obtained as in Example 1. The above test results are summarized in Table 2.

Example 6

[Chemical 7] Polymer having the above structural unit 30% 3% Zn-doped γ-Fe ₂ O ₃ 70%

The above materials were melt-kneaded in the same manner as in Example 1 and then granulated in the same manner as in Example 4 to obtain a magnetic material-dispersed resin carrier. The average particle size of the obtained carrier was 46 μm, and the specific resistance was 2.6 × 10 ¹⁰ Ω · cm. or,
As a result of cross-section observation by FE-SEM, the degree of orientation was 73%. Table 1 shows the physical properties of the carrier. When the same test as in Example 1 was performed on the carrier, Example 1 was performed.
Good results were obtained as well. The above test results are summarized in Table 2.

[0062]

[Table 1] -Part 1

[0063]

[Table 1] -Part 2

[0064]

[Table 1] -Part 3

[0065]

[Table 2] Excellent: ◎ Good: ○ Acceptable: △ Not acceptable: ×

[0066]

As described above, according to the present invention, the strength of the magnetization of the carrier at the developing pole is weakened, and the liquid crystallinity having a higher order structure in which the molecules of the carrier are uniformly aligned as the binder resin of the carrier. By using a resin that exhibits a high mechanical strength of the carrier and at the same time more orienting the magnetic substance dispersed in the carrier, as a result, the remanent magnetization is raised and the coercive force is not increased, resulting in high image quality at half It was possible to obtain a magnetic substance-dispersed resin carrier having good reproducibility of the tone portion and the line image portion. Further, in addition to the high durability due to the light load, which is a characteristic of the resin carrier, it was possible to obtain a carrier that does not adhere to the electrostatic latent image carrier.

[0067]

[Brief description of drawings]

FIG. 1 is a schematic diagram schematically showing a magnetic characteristic curve (hysteresis curve). In the figure, the numerical value shown in the frame is the value of (σ ₁₀₀₀ −σ ₃₀₀ ) / σ ₁₀₀₀ .

FIG. 2 is a schematic view schematically showing a cross section of a carrier of the present invention.

FIG. 3 is a schematic view schematically showing an electric resistance measuring device.

FIG. 4 is a schematic view schematically showing a developing device and a photosensitive drum.

[0068]

[Explanation of symbols]

 21: Binder resin 22: Needle-like magnetic material 31: Lower electrode 32: Upper electrode 33: Insulator 34: Ammeter 35: Voltmeter 36: Constant voltage device 37: Carrier 38: Guide ring

40: photosensitive drum 41: developing container 42: developer carrier 43: fixed magnetic core 43a to e: magnetic pole 44: developer regulating member 45: carrier returning member 46: toner 47: developer 48: toner replenishment Roller 49: Developer transport roller 50: Developer stirring roller

Claims (4)

[Claims] 1. A magnetic substance-dispersed carrier in which magnetic fine particles are dispersed in a binder resin, wherein the binder resin of the carrier contains an oriented liquid crystalline polymer, and the magnetic fine particles are used as the magnetic fine particles. A magnetic substance-dispersed resin carrier, wherein a magnetic substance having a major axis / minor axis> 1 is used. 2. In a magnetic substance dispersion type carrier, at least 30% of magnetic substance fine particles are oriented, and the magnetic strength (σ _1,000 ) in a magnetic field of 1,000 oersted after magnetic saturation is 30 to 150 emu / cm ³ , magnetic strength at 0 oersted magnetic field (remanent magnetization: σr)
Is 25 emu / cm ³ or more, the coercive force is less than 300 Oersted, and the strength of magnetization further satisfies the following formula: The magnetic material-dispersed resin carrier according to claim 1. [Equation 1] [Wherein σ _1,000 represents the strength of carrier magnetization (emu / g) in a magnetic field of 1,000 oersteds, σ
₃₀₀ indicates the strength (emu / g) of carrier magnetization in a magnetic field of 300 Oersted. ] 3. The carrier particles have an average particle diameter of 5 to 100 μm.
m, the bulk density is 3.0 g / cm ³ or less, and the content of the magnetic substance contained in the magnetic substance-dispersed carrier is 30 to
The magnetic substance-dispersed resin carrier according to claim 1, which is 99% by weight. 4. The carrier has a specific resistance of 10 ⁸ to 10 ¹³ Ω.
The magnetic substance-dispersed resin carrier according to claim 1, which has a size of cm.